Na-ion batteries are currently an emerging and low-cost energy storage technology, which have attracted enormous attention and research due to its promising potentiality for large-scale energy storage applications. As the key electrode materials for Na-ion batteries, non-graphite carbonaceous materials have been regarded as the best choice for practical application due to its high sodium storage activity, low-cost and non-toxicity. According to the current research, graphite materials are not suitable to be anode materials of Na-ion batteries for practical application due to its low sodium storage capacity in carbonate electrolytes. Hard carbons have a high capacity of ~300 mAh·g^-1 with low sodium storage potential and thus are suitable for practical applications. Soft carbons have a sodium storage capacity about 200 mAh·g^-1 with sodium storage potential below 1 V vs. Na⁺/Na. Soft carbons usually exhibit excellent rate performances and thus are suitable to be used as anode materials for power Na-ion batteries. Reduced graphene oxide (rGO) has a sodium storage capacity of about 220 mAh·g^-1 and excellent rate performances. A high sodium storage capacity can be obtained by doping heteroatoms and introducing defect sites in rGO. However, the low material density, high sodium storage potential and large irreversible capacity of rGO will restrict its practical application. Porous carbons have high capacities of 300-450 mAh·g^-1 with excellent rate performances because their developed porous structure can provide more defects as the active sites for sodium storage and shorten the diffusion path of Na⁺ to improve rate performances. Carbon nanowires/fibers have good flexibility due to their unique one-dimensional feature and stable sodium storage reversible capacity with good rate performance. These materials have advantages to be flexible electrodes for sodium-based flexible energy storage devices. By introducing N, S and other heteroatoms, heteroatom-doped carbons have more active sites for sodium storage and thus achieve higher sodium storage capacity. In summary, carbon materials with low graphitization degree are important development directions for anode materials of low cost Na-ion batteries. New carbon materials with unique microstructure and morphology have higher sodium storage capacity and rate capability, so they can be used as high power anode materials for sodium storage. Considering many factors, such as cycle life, energy density, power density and manufacturing cost, of practical application, hard carbon anodes is currently the best choice for practical application of Na-ion batteries. In the future, improving SEI stability, increasing Coulombic efficiency and improving electrical conductivity of hard carbon are urgent problems to be solved for practical application. Herein, the recent progress of carbonaceous anode materials is reviewed. The sodium storage mechanism and characteristics of carbon materials are summarized and discussed. Furthermore, the relationship between micro-structures and electrochemical performances, and remained problems of carbon anodes are discussed. This review will promote the development and understanding of carbon anode materials for sodium storage.

Nuclear magnetic resonance (NMR) is an effective and widely adapted technique that can be used for medical diagnosis and chemical analysis. However, its application has been limited by low sensitivity originating from the extremely low polarization of nuclear spins that follow a typical Boltzmann distribution. In principal, it is possible to break this Boltzmann distribution using different physical or chemical mechanisms to generate hyperpolarization and increase NMR sensitivity by several orders of magnitude. The crucial point of hyperpolarization is to transfer the polarization from highly polarized systems to nuclear spins. For example, the unpaired electrons in organic radicals or other systems exhibit much higher polarization than that of nuclear spins (~660 times higher than ¹H) under the same magnetic field. The high polarization of electrons at thermal equilibrium can be transferred to nuclear spins via microwave irradiation and hyperfine coupling. This hyperpolarization method is called dynamic nuclear polarization (DNP) and has been successfully and widely applied for the evaluation of the protein structure and the examination of nanomaterial surface chemistry. Electron spins can also be hyperpolarized using circularly polarized light (CPL) or nonpolarized light in some systems, and this polarization can be transferred to nuclear spins as well. These hyperpolarization methods are referred to as optical pumping (OP) and optical nuclear polarization (ONP), respectively. A common application of OP is the production of hyperpolarized noble gases, including hyperpolarized xenon-129, which can be used in magnetic resonance imaging of lungs or evaluation of porous structures. For ONP, the nitrogen-vacancy center in diamond is the most promising system that has demonstrated the ability to track the precession of a single spin. In addition, electrons can be polarized by certain chemical reactions as used in chemically induced dynamic nuclear polarization (CIDNP). CIDNP can be used to study the active sites of proteins and identify low-concentration intermediates that are formed during chemical processes. In addition to electrons, hydrogen molecules with unique spin state, i.e., parahydrogen, can be converted to hyperpolarized NMR signals via hydrogen addition reactions, which is known as parahydrogen induced polarization (PHIP). PHIP was originally used to understand the mechanisms of hydrogenation processes, but has recently become a promising hyperpolarization technique via the protocols of signal amplification by reversible exchange (SABRE). Herein, the basic mechanisms and potential applications of DNP, OP, CIDNP, and PHIP techniques are reviewed. These emerging hyperpolarization techniques have the potential to push the limits of NMR beyond current conceptions.

The National Natural Science Foundation of China (NSFC) is a vital government agency supporting basic research and people to create knowledge and meet major national needs, where a rigorous and objective merit-based peer review mechanism is the key to funding the most promising research proposals. This invited comment overviews some recent attempts aimed at bettering the academic evaluation environment at the Department of Chemical Science in 2019, through measures such as grouped panel committee meetings, standardized panel committee meeting procedures, and review process refinement to improve the project review at panel committee meeting levels.

Lithium-ion batteries have been widely used in portable electronic devices and electric vehicles because of their high energy density and long cycle life. Sodium-ion batteries have broad application prospects in the areas of large-scale electrochemical energy storage systems and low-speed electric vehicles because of their abundant raw materials, low resource cost, safety, and environmental friendliness. However, the development of sodium-ion batteries has been hindered by the low reversibility, sluggish ion diffusion, and large volume variations of the host materials. Suitable electrode materials with decent electrochemical performance must be primarily explored for the successful use of sodium-ion batteries. Since the electrochemical potential and specific capacities of cathode materials have a major impact on the energy densities of sodium-ion batteries, the development of cathode materials is critical. To date, various Na-insertable frameworks have been proposed, and some cathode materials have been reported to deliver reversible capacities approaching their theoretical values. Among them, transition metal oxides show a high reversible capacity and high working potential, but most of them still possess problems such as irreversible phase transition, air instability, and insufficient battery performance. Another type is the Prussian blue analogs. These materials exhibit a favorable operating voltage, cycling stability, and rate capability; however, the main obstacles to their practical application are the control of lattice defects, thermal instability, and low tap density. Polyanionic phosphates are the most promising cathode materials for sodium-ion batteries and have great research value and application prospects because of their stable framework structure, suitable operating voltage, and fast ion diffusion channels. However, their inherent defects, such as poor electronic conductivity and low theoretical energy density, considerably limit their practical applications. Researchers have conducted modification studies through bulk structure adjustment and micro-nano structural control with the goal of improving the performance of phosphate cathode materials and promoting the research and development of sodium-ion energy storage systems. This study reviews the recent advances in phosphate cathode materials for sodium-ion batteries, including orthophosphates, pyrophosphates, fluorophosphates, and mixed phosphate compounds. In this study, the intrinsic relationships among material composition, structure, and electrochemical properties are identified through analyses of the crystal structures, sodium storage mechanisms, and modification strategies of phosphate materials, thereby providing a reference for the continuous modification of polyanion phosphate cathode materials and exploration of high-voltage phosphate cathode materials. Some directions for future research and possible strategies for building advanced sodium-ion batteries are also proposed.

Sodium batteries have drawn increasing attention from multiple researchers owing to the abundant reserves and low cost of sodium resources. However, traditional sodium batteries based on organic solvent electrolyte systems have safety risks. Thus, the utilization of solid electrolyte materials instead of organic electrolytes could effectively resolve safety issues and ensure the safe performance of the battery. Solid sodium-ion battery is a promising energy storage device. The sodium ion solid-state electrolytes mainly includes Na-β-Al₂O₃, Na super ionic conductor (NASICON), sulfide, polymer, and borohydride. Inorganic solid electrolytes have the advantage of ionic conductivity compared with polymer solid electrolyte. This paper summarizes the research progress on three common inorganic sodium ion solid electrolytes: Na-β-Al₂O₃, NASICON, and sulfide. Research efforts have mainly focused on increasing ionic conductivity and interface stability. Na-β-Al₂O₃ has been successfully commercialized in high-temperature Na-S and ZEBRA batteries with molten electrodes. Pure β″-Al₂O₃ is difficult to prepare owing to its low thermodynamic stability. The synthesized β″-Al₂O₃ based on traditional solid-state reaction generally contains impurities such as β-Al₂O₃ and NaAlO₂ (around the boundaries). Further improvements are required to develop favorable methods for fabricating pure β″-Al₂O₃ with high production yield, low cost, and well-controlled microstructure. NASICON, one of the most promising ionic conductors for solid sodium-ion batteries, has attracted considerable attention for its high ionic conductivity at room temperature. The general method to enhance ionic conductivity is to increase the bottleneck size by introducing proper substituents. However, the substitution of synthetic elements could result in different optimal calcination temperatures, which would lead to a change in the density of ceramic sintering. β″-Al₂O₃ and NASICON have higher ionic conductivity at room temperature but cannot achieve good performance in the field of high power densities and long-term cycling owing to the poor interface contact with electrode materials. Because the high polarizability and large ionic radius of sulfur atoms weaken the interaction between skeleton and sodium ions, sulfide solid electrolytes often provide higher ionic conductivity at room temperature than analogous oxides. At the same time, sulfide solid electrolytes can be easily pressed into a mold at room temperature. However, sulfide electrolytes have low chemical stability in air because of hydrolysis by water molecules with the generation of H₂S gas, which should be handled in inert gas atmosphere. In conclusion, this review discusses the recent progress in different aspects of ionic conductivity and interface stability.

Project proposal review is the core of science foundation management. This article systematically overviews existing key issues in panel committee meetings in final reviews of scientific research grants, which are becoming an increasing concern in the science community. Moreover, it reassesses the importance and functionality of panel committee meetings, and accordingly provides suggestions and measures based on the "verification-rectification-and-selection" principle for further installation and improvement of the panel committee meeting mechanism.

All-solid-state sodium ion batteries (ASIBs) are important for future large-scale energy storage applications. ASIBs have come to occupy an important position in research on advanced secondary batteries in recent years owing to their advantages of abundance in resources, low cost, long lifetime, and high safety. As the key to the success of ASIBs, solid-state electrolytes such as polymers, oxide ceramics, and sulfide glass-ceramics have always attracted immense interest. Chalcogenide electrolytes for ASIBs have high room-temperature conductivity, high elastic modulus, and can be easily pressed into a mold at room temperature; hence, they are the research focus in ASIBs. This paper summarized recent studies on the structure and properties of chalcogenide electrolytes for ASIBs. These studies demonstrate the relationship between the phase structure and ionic conductivity of sulfide-based electrolytes and selenide-based electrolytes. Besides, arguments that the sodium vacancy in the crystal structure dominates ionic conduction, and creating a sodium vacancy via cation substitution is the principal strategy to increasing ionic conduction, are discussed. Further, the intrinsic chemical stability and interface stability between the electrode and electrolyte are highlighted. Based on the soft and hard acid and base theory, some studies adopted various anion/cation ion substitution strategies to improve the chemical stability of chalcogenide electrolytes in humid air. Particularly, the inconsistency in the electrochemical stability window of a representative chalcogenide electrode, Na₃PS₄, as measured by a semi-blocking electrode and calculated by first-principles, is compared. Additionally, to develop all-solid-state Na-S and Na-O₂ batteries with high capacity, the nonnegligible interface instability of the sulfide electrode against the sodium metal anode and feasible solutions are summarized. Next, the research progress on ASIBs using chalcogenide electrolytes is reviewed. Chalcogenide electrolytes are restricted by the electrochemical stability window and chemical compatibility with electrode materials; hence, they are expected to only be applicable to ASIBs using sulfur, sulfide, and organic matter as the cathode and Na-Sn alloy as the anode. However, these ASIBs have long cycling life (> 500 cycles), illustrating their potential applications in large-scale energy storage power stations. Finally, we comprehensively evaluate the ionic conductivity, stability against humid air, stability of the interface, electrochemical stability window, and ease of preparation of typical chalcogenide electrolytes, including Na₃PS₄, Na₃PSe₄, Na₃SbS₄, Na₃SbSe₄, Na₁₀SnPS₁₂, and Na₁₁Sn₂PS₁₂. Moreover, we highlight the challenges and propose possible solutions toward the development of chalcogenide electrolytes in future. Advanced technologies in fine synthesis, in situ characterization, and surface/interface modification are essential to overcome existing challenges and promote the development of chalcogenide-electrolyte-based ASIBs.

Sodium-ion batteries (SIBs) are promising candidates to replace lithium-ion batteries (LIBs) to meet the emergent requirements of various commercial applications. SIBs and LIBs are similar in many aspects, including their reduction potentials, approximate energy densities, and ionic semidiameters. Analogously, safety issues, including liquid leakage, high flammability, and explosiveness limit the usage of SIBs. All-solid-state batteries have the potential to solve the aforementioned problems. However, polycarbonates as promising solid electrolytes have been rarely exploited in all-solid-state SIBs. In addition, organic electrode materials, including non-conjugated redox polymers, carbonyl compounds, organosulfur compounds, and layered compounds, have been intensively investigated as part of various energy storage systems owing to their low cost, environmental friendliness, high energy density, and structural diversity. Nevertheless, the dissolution of small organic compounds in organic-liquid electrolytes has hindered its further applications. Fortunately, the utilization of solid polymer electrolytes combined with organic electrode materials is a promising method to prevent dissolution into the electrolyte and improve the cycling performance of SIBs. Thus, we proposed the utilization of a poly(propylene carbonate) (PPC)-based solid polymer electrolyte and cellulose nonwoven with a 3, 4, 9, 10-perylene-tetracarboxylicacid-dianhydride (PTCDA) cathode in an all-solid-state sodium battery (ASSS). The solid electrolyte significantly enhanced the safety of the SIB and was successfully synthesized via a facile method. The morphology of the as-prepared solid electrolyte was examined by electron scanning microscopy (SEM). Furthermore, the electrochemical performances of the PTCDA/Na battery with organic-liquid and solid electrolytes at room temperature were compared. The SEM results demonstrated that the solid polymer electrolyte and sodium bis(fluorosulfonyl)imide (NaFSI) were evenly distributed inside the pores of the nonwoven cellulose. The ionic conductivity of the composite solid polymer electrolyte (CSPE) at room temperature was 3.01 × 10^-5 S·cm^-1, suggesting that the CSPE was a promising candidate for commercial applications. In addition, the ASSS showed significantly improved cycling performance at a current density of 50 mAh·g^-1 with a high capacity retention of 99.1%, whereas the discharge capacity of the liquid PTCDA/Na battery was only 24.6mAh·g^-1 after 50 cycles. This indicated that the cycling performance of the PTCDA cathode in the SIB was largely improved by preventing the dissolution of the PTCDA cathode material in the electrolyte. Electrochemical impedance spectroscopy results demonstrated that the CSPE was compatible with the organic cathode electrode.

Lithium-ion batteries (LIBs) are widely used in cellphones, laptops, and electric cars owing to their high energy density and long operational lifetime. However, their further deployment in large-scale energy storage systems is restricted by the uneven distribution of lithium resources (~0.0017% (mass fraction, w) in the Earth's crust). Therefore, alternative energy storage systems composed of abundant elements are of urgent need. Recently, sodium-ion batteries (SIBs) have attracted significant attention and are considered to be a potential alternative for next-generation batteries owing to abundant sodium resources (~2.64% (w) of the Earth's crust), suitable potential (−2.71 V), and low cost. SIBs are similar to LIBs in terms of their physical and electrochemical properties. Previous studies have mainly focused on SIB storage materials, including hard carbon, alloys, and hexacyanoferrate, while the safety of SIBs remains largely unexplored. Similar to LIBs, the current electrolytes used in SIBs are mainly composed of flammable organic carbonate solvents (or ether solvents), sodium salts, and functional additives, which pose possible safety issues. Moreover, the chemical activity of sodium is much higher than that of lithium, leading to a higher risk of fire, thermal runaway, and explosion. To overcome this problem, herein we propose a fluorinated non-flammable electrolyte composed of 0.9 mol∙L⁻¹ NaPF₆ (sodium hexafluorophosphate) in an intermixture of di-(2, 2, 2 trifluoroethyl) carbonate (TFEC) and fluoroethylene carbonate (FEC) in a 7 : 3 ratio by volume. Its physical and electrochemical properties were studied by ionic conductivity, direct ignition, cyclic voltammetry, and charge/discharge measurements, demonstrating excellent flame-retarding ability and outstanding compatibility with sodium electrodes. The electrochemical tests showed that the Prussian blue cathode retained a capacity of 84 mAh∙g⁻¹ over 50 cycles in the prepared electrolyte, in contrast to the rapid capacity degradation in a flammable conventional carbonate electrolyte (74 mAh∙g⁻¹ with 57% capacity retention after 50 cycles). To test the practical application of the proposed electrolyte, a hard carbon anode was used and exhibited exceptional performance in this system. The enhancement mechanism was further verified by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning emission microscopy (SEM) investigations. Polycarbonate on the surface of the cathode played an important role for the studied electrolyte system. The polycarbonate may originate from FEC decomposition, which can enhance the ionic conductivity of the solid electrolyte interface (SEI) layer and reduce impedance. Hence, we believe that this proposed electrolyte may provide new opportunities for the design of robust and safe SIBs for next-generation applications.

Semitransparent organic solar cells (ST-OSCs) have attracted attention for use in building integrated photovoltaics because of their large range tunability in colors, transparency, and high efficiency. However, the development of semitransparent devices based on fullerene acceptors remained almost stagnant in the early period. This was due to the weak absorption of fullerene small molecules in the visible and near-infrared regions as well as the large non-radiative energy loss, resulting in drastic open-circuit voltage loss. In addition, the energy level and chemical structure of fullerene molecules cannot be easily regulated, and the strong aggregation characteristics of fullerenes greatly limit the development of OSCs. In contrast, the designability of the chemical structures and controllability of the energy levels of non-fullerene electron acceptors has encouraged researchers to explore high-performance organic solar cells while and simultaneously stimulating the development of ST-OSCs. In this review, the recent progress in non-fullerene small molecule acceptors for ST-OSCs is summarized. The article focuses on ST-OSCs from the aspects of device structures and active layers. In view of the semitransparent device structure, except for replacing the traditional electrodes with semitransparent electrodes, researchers have introduced suitable interface layers to regulate the absorption and reflection of sunlight. The interface layers mainly contain a reflective layer (evaporated on the top electrode to reflect near-infrared light); an anti-reflection layer (located below ITO (indium tin oxide)) to mitigate light reflection at the air-glass interface and thus enhance the absorption of sunlight); and an optical outcoupling layer (simultaneously increasing reflection and transmission). From the active layer, it is mainly divided into two categories. First, researchers have optimized the photovoltaic performance of semitransparent devices from the perspective of molecular structures, mainly by broadening the absorption window of non-fullerene small molecule acceptors, thus improving the crystallinity and charge mobility of small molecules, and regulating the stacking behavior and orientation of molecules in the films. Second, regarding the active layer processing, much effort has been undertaken to optimize the light absorption, morphology, and charge carrier transport channels of blended films.

Because of their high energy density and long cycle life, lithium-ion batteries (LIBs) have dominated the portable electronics market for over 20 years. However, with the increasing demand for large-scale energy storage systems for grid applications, the price of Li resources has increased owing to the low abundance of Li in Earth's crust and non-uniform distribution on the planet. Because Na has similar physical and chemical properties as Li and is an abundant natural resource, room-temperature sodium-ion batteries (SIBs) are expected to be among the most promising next-generation large grid energy storage devices. It is known that the cathode, anode, separator and electrolyte materials are the main components of batteries. Among these, Na-containing cathode materials are of critical importance. As a cathode material for SIBs, polyanion-type compounds have become a hot research topic owing to their versatile structural frameworks, high thermal stabilities, high ambient stabilities even in the charging state, small volume changes, tunable operating voltage by tuning the chemical environment of the polyanions, and high operating voltages owing to the inductive effects of the polyanionic groups (PO₄³⁻, SO₄²⁻, SiO₄⁴⁻, etc.). In particular, for Earth's abundant resources and inherent stability, polyanion-based compounds are suitable for large-scale stationary energy storage. Taking grid balancing into account, batteries with fast charge rates are in demand, which requires cathodes having high rate capability. However, despite the presence of ion diffusion channels in polyanion compounds, the electronic transport channels are blocked owing to the separation of the metal polyhedral and the strong electronegativity of the anions, leading to poor electron conductivity, which largely limits the rate capability of polyanion compounds. Therefore, it is crucial to understand the inherent limitation of the kinetics in terms of the structural aspects and to determine strategies for improving the rate capability. This review discusses the intrinsic reasons for the factors impacting ion diffusion based on the different structures of polyanion-type cathodes. From the perspectives of surface modification and morphology, strategies for enhancing the transport of sodium ions and electrons at the surface and interface are summarized and discussed. Then, from the standpoint of the hierarchical structures of materials to the design of a structural framework, which have been rarely reported, this review proposes schemes that intrinsically enhance the rate capability of polyanion compounds and provides a perspective on developments that can further improve the rate capability of cathode materials. This review provides suggestions for designing and optimizing high-rate polyanion-type and other kinds of cathodes from both academic and practical viewpoints.

The electrocatalytic activity of commercial Pt/C for ethanol oxidation is relatively low, and the C―C bond is difficult to break. Thus, the complete oxidation process is not easy, and the fuel utilization efficiency becomes considerably reduced. Increasing the temperature can increase the reaction rate and enhance the mass transport; therefore, a temperature-controlled electrode was used during our in situ FTIRS (Fourier Transform Infrared Spectroscopy) investigation. The temperature sensor was placed at a certain distance from the surface of the electrode; thus, the surface temperature needed to be corrected. The temperature was calibrated using the "potentiometric" measurement method, which was because the potential-temperature coefficient of the redox couple is constant under certain conditions, and the electrode surface temperature was obtained by potential conversion at different temperatures during the experiment. The experimental results showed that the relationship between the heating temperature, T_h, and the surface temperature, T_S, was T_S = 0.57T_h + 7.71 (30 ℃ < T_h ≤ 50 ℃) and T_S = 0.62T_h + 5.12 (50 ℃ < T_h ≤ 80 ℃), and according to error analysis, the maximum error was 1 ℃. The temperature-controlled electrode was applied to investigate the electrooxidation of ethanol using both in situ FTIRS and cyclic voltammetry using a commercial Pt/C catalyst at different temperatures. Clearly, based on the CV curve for the oxidation of ethanol, with increasing temperature, the overall oxidation current increased, and the onset potential and peak potential both negatively shifted, indicating that thermal activation allows the oxidation reaction to proceed easier. Electrooxidation of ethanol showed two positive oxidation peaks, and the ratio of the first peak current to the second peak current was used to qualitatively evaluate the selectivity of CO₂. Compared with at 25 ℃, the first peak current increased by 30% at 65 ℃, indicating that the high temperature was conducive to C―C bond cleavage. Comparing the in situ FTIRS recorded at 50 ℃, 35 ℃, and 25 ℃, we found that the onset potential of CO₂ on the commercial Pt/C catalyst was lower by 200 mV, indicating that Pt/C can provide oxygen-containing species at lower potentials at high temperature; however, the onset potentials of CH₃CHO and CH₃COOH did not change with temperature. The CO₂ selectivity was semi-quantitatively calculated by the area of CO₂ compared with the area of CH₃COOH from the FTIRS data. It was found that CO₂ had the highest selectivity at high temperature and low potential, indicating that high temperature is conducive to complete ethanol oxidation during CO₂ formation, possibly because both the ethanol bridge adsorption pattern and adsorbed OH (OH_ad) increased with temperature, enhancing subsequent CO_ad and OH_ad oxidation reactions. The low selectivity of CO₂ at the high potential was due to the adsorption of oxygen-containing species that occupied the surface-active site, blocking the adsorption of ethanol.

完善评审机制是国家自然科学基金委新时代基金改革的重要任务之一。为切实落实该项改革任务，建立符合新时代科学基金资助导向的科学、公正、高效的评审机制，基金委化学部努力探索新的学科基金管理模式，尝试了在通信评审阶段由科学家与学科管理人员共同参与项目的分组、指派，共同完成同行评议专家遴选工作的新模式。本文分析了科学家参与同行评议专家遴选工作的利弊，探讨了如何更好的发挥科学家在同行评议专家遴选工作中的作用，建立学术共同体互信的基金评审机制。

The process that converts CO₂ to value-added chemical fuels or industrial feedstocks is called the electrochemical carbon dioxide reduction reaction (CO₂RR). When used in combination with renewable energy resources such as solar or wind, it represents one of the most promising strategies for transforming the intermittent renewable energy to chemical energy. However, because CO₂ molecules are thermodynamically stable, their electrochemical reduction is kinetically challenging. CO₂RR also has several different reaction pathways with a large spectrum of reduction products, making its selectivity problematic. It often requires the assistance of highly effective electrocatalysts with excellent activity, selectivity, and durability. Recently, palladium (Pd)-based nanomaterials have attracted considerable attention for CO₂RR. They can enable the selective production of formic acid or formate (HCOOH or HCOO^-) at near the theoretical equilibrium, as well as CO at a more negative potential. Unfortunately, the strong surface affinity of Pd toward CO often results in the deactivation of catalytic activity in the electrocatalytic process, in particular for formate production. Over recent years, extensive research effort has been invested into enhancing the electrochemical performances of Pd-based electrocatalysts. By controlling the size, morphology, and crystal surfaces of Pd nanocrystals, the distribution and structure of the atoms on the catalyst surface can be carefully engineered. For example, reducing the size of Pd nanoparticles has been found to significantly enhance the reaction activity and selectivity for the production of both CO and formate. The high-index crystal surfaces of Pd nanocrystals with low coordination numbers also generally show higher electrocatalytic activities. The design of Pd-based alloy nanostructures with tunable electronic structures represents another effective way to improve the electrochemical performance. Incorporation of non-precious metals can not only reduce the cost, but also effectively weaken the surface binding of CO. In addition, dispersing Pd nanoparticles on high-surface-area supports can increase the surface exposure of active sites and facilitate the formation of the electrochemical active phase. In this perspective, we provide an overview of the recent progress on nanostructured Pd-based catalysts for electrochemical CO₂ reduction. First, we briefly introduce the CO₂RR fundamentals as well as the reaction mechanism on Pd-based nanostructures. We then review a number of strategies to promote CO₂RR performance, including utilizing the size effect, morphology effect, alloy effect, core-shell effect, and support effect. Finally, we conclude with a perspective on the future prospects of Pd-based CO₂RR electrocatalysts, providing readers a snapshot of this rapidly evolving field.

Solvent molecules can significantly reduce the heat of detonation and stability of energetic metal-organic framework (EMOF) materials, and the development of solvent-free EMOFs has become an effective strategy to prepare high-energy density materials. In this study, a solvent-free EMOF, [Ag₂(DTPZ)]_n (1) (N% = 32.58%), was synthesized by reacting a high-energy ligand, 2, 3-di(1H-tetrazol-5-yl)pyrazine (H₂DTPZ), with silver ions under hydrothermal conditions, and it was structurally characterized by elemental analysis, infrared spectroscopy, X-ray diffraction, and thermal analysis. In 1, the DTPZ²⁻ ligands that adopted a highly torsional configuration bridged the Ag⁺ ions in an octadentate coordination mode to form a three-dimensional framework (ρ = 2.812 g∙cm⁻³). The large steric effect and strong coordination ability of DTPZ²⁻ effectively prevented the solvent molecules from binding with the metal centers or occupying the voids of 1. Moreover, the strong π-π stacking interactions [centroid-centroid distance = 0.34461(1) nm] between the tetrazole rings in different DTPZ²⁻ ligands provided a high thermal stability to the framework (T_e = 619.1 K, T_p = 658.7 K). Thermal analysis showed that a one-step rapid weight loss with intense heat release primarily occurred during the decomposition of 1, suggesting potential energetic characteristics. Non-isothermal thermokinetic analyses (based on the Kissinger and Ozawa-Doyle methods) were performed using differential scanning calorimetry to obtain the thermoanalysis kinetic parameters of the thermodecomposition of 1 (E_a = 272.1 kJ·mol⁻¹, E_o = 268.9 kJ·mol⁻¹; lgA =19.67 s⁻¹). The related thermodynamic parameters [enthalpy of activation (ΔH^≠ = 266.9 kJ·mol⁻¹), entropy of activation (ΔS^≠ = 125.4 J·mol⁻¹·K⁻¹), free energy of activation (ΔG^≠ = 188.3 kJ·mol⁻¹)], critical temperature of thermal explosion (T_b = 607.1 K), and self-accelerating decomposition temperature (T_SADT = 595.8 K) of the decomposition reaction were also calculated based on the decomposition peak temperature and extrapolated onset temperature when the heating rate approached zero. The results revealed that 1 featured good thermal safety, and its decomposition was a non-spontaneous entropy-driven process. The standard molar enthalpy for the formation of 1 was calculated to be (2165.99 ± 0.81) kJ·mol⁻¹ based on its constant volume combustion energy determined using a precise rotating oxygen bomb calorimeter. Detonation and safety performance tests revealed that 1 was insensitive to impact and friction, and its heat of detonation (10.15 kJ·g⁻¹) was higher than that of common ammonium nitrate explosives, such as octogen (HMX), hexogene (RDX), and 2, 4, 6-trinitrotoluene (TNT), indicating that 1 is a promising high-energy and insensitive material.

Thermal analysis (TA) is a technology that can be applied to evaluate the relationship between the physical properties of substances and temperature changes under programmed temperature control. It has been widely used in many fields and is particularly useful for determining the thermal stability and service life of polymers and other materials, the stability of drugs, and the danger of flammable and explosive materials. Simultaneously, the mechanism of dehydration, decomposition, and degradation of inorganic materials or dissociation of complexes can be studied and the decomposition rates of environmental pollutants can be estimated. Recently, TA kinetics has become the most extensively studied topic in TA research. The main purpose of kinetic analysis is to obtain the three kinetic triplets of a reaction process, namely, activation energy E_a, pre-exponential factors A, and and mechanism function f(a). For a solid-state reaction, many mathematical models and corresponding data processing methods can be used for the study of TA kinetics. These methods can be classified as either isothermal or non-isothermal methods and further divided into integral and differential methods in the form of the kinetic equation. These equations can be divided into a single scanning rate and multiple scanning rate methods (isoconversion method) by the operation method. The isoconversion method can calculate activation energies without the mechanism function, and the complexity of the reaction can be determined by the change in activation energy as a function of conversion rate. Therefore, the International Confederation for Thermal Analysis and Calorimetry (ICTAC) recommends the isoconversion method for processing TA data. Because of the limitation of traditional isoconversion methods, novel isoconversion methods have been proposed over the past 10 years. The relationship among the existing dynamic analysis methods must be complementary, instead of competitive, because the reliability of the analysis results can be improved only through complementarity. Further efforts to popularize modern integral and differential methods with equal conversion rates are essential. Herein, the progress in isoconversion method development is briefly introduced. A novel kinetic equation and seven new isoconversion methods are reviewed, and the characteristics and limitations of these methods are discussed. In addition, the development trends and prospects of TA kinetics research methods are highlighted. We suggest that the Arrhenius formula should be modified on the basis of the relationship between the rate constant and temperature. The rate equation that is more suitable for non-isothermal and heterogeneous reactions should be used. The mechanism of multi-step solid-state reactions should be studied in depth, and unified standards must be adopted for the study of thermal decomposition kinetics. This represents imminent and important progress in the study of TA kinetics.

Fuel cells, whose energy source can be hydrogen, formic acid, methanol, or ethanol, have received considerable attention in recent years because of their environmentally friendly characteristics. A high Pt loading is often required to achieve a practical power density in fuel cells, thus leading to high costs and limited applications. Meanwhile, the high Pt loading promotes aggregation during cycling under harsh electrocatalytic conditions, which reduces the surface area of the catalyst and leads to a decrease in catalytic activity. The formation of alloy or intermetallic nanocrystals via the addition of non-precious metals along with precious metals is one strategy to effectively reduce the cost. Due to the electronic and geometric effects introduced by the non-precious metals, the catalytic performance of these bimetallic nanocrystals can be retained or even improved. Compared to the metallic alloy nanocrystals, the intermetallic ones are more stable in critical catalytic conditions. Due to their highly ordered structures, Pt-based intermetallic nanocrystals are widely used as electrode materials for various electrocatalytic reactions in fuel cells, and they show high stability against oxidation and etching. PtCo intermetallic nanocrystals have attained performances that exceed the 2020 target of the U.S. Department of Energy (DOE) for Pt activity and stability for the cathode reaction of fuel cells (oxygen reduction reaction). Decreasing the size of intermetallic compounds to the nanometer scale can significantly increase their active site densities due to the large specific surface area. However, the preparation of intermetallic nanocrystals is more complicated than that of alloys. Therefore, to further improve the electrocatalytic properties of intermetallic nanocrystals, an in-depth study of the factors affecting the electrocatalytic properties of nanocrystals is necessary. This review summarizes recent advances in Pt-based intermetallic nanocrystals. First, we highlight the controlled synthesis strategies, including direct liquid-phase synthesis, the thermal annealing approach, and chemical vapor deposition. Of these strategies, direct liquid-phase synthesis is the most common approach to prepare the intermetallic nanocrystals. Second, the diverse potential applications of different electrocatalytic reactions are summarized. The reactions include the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and hydrogen oxidation reaction (HOR), as well as the oxidation reactions of formic acid (FAOR), methanol (MOR), and ethanol (EtOR). Of these reactions, ORR is the most important, and it has been widely studied. Some advanced characterization techniques and machine learning research based on density functional theory (DFT) are also mentioned. Finally, the challenges and the future perspectives of intermetallic nanocrystals are outlined.

Alcohols fuel electro-oxidation is significant to the development of direct alcohols fuel cells, that are considered as a promising power source for portable electronic devices. Currently, the catalyst was restricted by the serious poisoning effect and high cost of noble metals. Developing low-cost Pt alloy with high performance and anti-CO poisoning ability was highly desired. In this work, PtCo-NC catalyst was synthesized by combining Pt nanoparticles with ZIF-67 after annealing in the tube furnace and the in situ generated N-doped carbon from ZIF-67 was functionalized to support the PtCo alloy nanoparticle. The structure and morphology were probed by X-ray diffraction, scanning electron microscope and transmission electron microscope, and the electrochemical performance was evaluated for alcohols of methanol and ethanol oxidation in the acid electrolyte. Compared with the reference sample of Pt/C, several times performance enhancement for alcohols fuel oxidation was found on PtCo-NC catalyst as well as the good catalytic stability. Specifically, the peak current density of PtCo-NC was 79.61 mA∙cm⁻² for methanol oxidation, about 2.2 times higher than that of the Pt/C electrode (36.97 mA∙cm⁻²) and 2.5 times higher than that of the commercial Pt/C electrode (31.23 mA∙cm⁻²); it was 62.69 mA∙cm^–2 for ethanol oxidation, about 1.65 times higher than that of Pt/C catalyst (37.99 mA∙cm⁻²) and commercial Pt/C electrode (37.77 mA∙cm⁻²). These catalytic performances were also much higher than some analogous catalysts developed for alcohols fuel oxidation. A much higher anti-CO poisoning ability was demonstrated by the CO stripping voltammetry experiment, in which the CO_ad oxidation peak potential for PtCo-NC was 0.46 V, ca. 110 mV negative shift compared with Pt/C catalyst at 0.57 V. A strong electronic effect was indicated by the peak position shifting to the lower binding energy direction by 0.3 eV on PtCo-NC compared with Pt/C reference catalyst. According to the d-band center theory, the electron-enriched state of Pt will decrease the interaction strength of poisoning intermediates adsorbed on its surface; Moreover, according to the bifunctional catalytic mechanism, the presence of Co can form the adsorbed oxygen-containing species (―OH) more easily than Pt at low potentials, and this oxygen-species were helpful in the oxidation of CO_ad at neighboring Pt sites. The high catalytic performance for alcohols fuel oxidation could be due to the largely improved anti-CO poisoning ability and the synergistic effect between the in situ formed PtCo nanoparticles and the N-doped carbon support.

Sodium has the advantages of being an abundant resource and having a low cost; thus, sodium ion batteries are considered as one of the best candidates for replacing lithium ion batteries in the future. However, the radius of the sodium ion is larger than that of the lithium ion, and the de-intercalation of the sodium ion will seriously damage the crystal structure of most electrode materials during the charging and discharging process, which considerably limits its charge-discharge specific capacity, cycle performance, and rate performance. However, finding appropriate electrode materials is one of the difficulties in fabricating high-performance sodium ion batteries. Among the many candidate materials, vanadate materials can improve the stability of material structures by introducing cations to increase the coordination numbers of vanadium, thus improving the electrochemical performance of sodium ion batteries. In this paper, an in situ phase separation method to fabricate V₂O₅/Fe₂V₄O₁₃ nanocomposite materials is reported. First, we synthesized hydrated crystalline Fe₅V₁₅O₃₉(OH)₉·9H₂O nanomaterials using a water bath heating method; then, we in situ constructed two-phase nanocomposite V₂O₅ and Fe₂V₄O₁₃ from the single phase by further high-temperature treatment. The morphology, composition, and structure of the electrode materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FTIR), as well as other methods. The V₂O₅/Fe₂V₄O₁₃ nanocomposite materials were found to have a more stable structure, higher initial discharge capacity (342 mAh·g^-1 at a current density of 0.1 A·g^-1), longer cycle life, and better rate performance than V₂O₅ nanowires. Therefore, this research on V₂O₅/Fe₂V₄O₁₃ nanocomposite materials has broadened ability to develop new high-performance anode materials for sodium ion batteries.

In the past few decades, new energy industries have developed rapidly due to the threat of the depletion of non-renewable resources. Among them, the lithium-ion battery has attracted significant attention of various researchers. However, lithium-ion batteries are limited by the uneven distribution of lithium resources and high cost. Sodium, which is in the same periodic group as Lithium, can help alleviate the problems related to the limited development of lithium ion batteries owing to the shortage of lithium resources. Sodium ion batteries are cheap, with varying choice of electrolytes, and have relatively stable electrochemical performances. However, the radius of a sodium ion is larger than that of a lithium ion, leading to slow ion transportation as well as changes in the volume of the host material during the charging and discharging processes. Therefore, compared with existing lithium ion batteries, sodium ion battery anode materials are very limited. Moreover, most sodium ion battery electrode materials have low specific capacities and poor cycle retention rates. Among these, ternary metal oxides, which have two different cations and can reversibly react with sodium ions are promising high-capacity anode materials for sodium ion batteries. In this study, Ti₂Nb₂O₉ nanosheets are obtained by ion-exchange and chemical-delaminate methods. The carbon-coated Ti₂Nb₂O₉ nanosheets are obtained after hydrothermal coating with sucrose and calcination. From the thermogravimetric analysis (TG) curve, the carbon content in the composites is calculated to be approximately 8.0%. Owing to the rich reactive sites and a short ion transport pathway, the Ti₂Nb₂O₉/C electrode delivers a high reversible capacity of 265.2 mAh·g^-1 at a current density of 50 mA·g^-1. Even at a high current density of 500 mA·g^-1, the electrode exhibits an excellent electrochemical performance with a reversible capacity of 160.9 mAh·g^-1 after 200 cycles (capacity retention of 75.3%). Additionally, the Ti₂Nb₂O₉/C nanosheets exhibit high reversible capacities of 251.3, 224.6, 197.4, 176.3, and 156.5 mAh·g^-1 at the current densities of 100, 200, 500, 1000, and 2000 mA·g^-1, respectively. It is demonstrated through the use X-ray photoelectron spectroscopy (XPS) that the following process involving the transfer of four electrons occurs: Ti⁴⁺/Ti³⁺, Nb⁵⁺/Nb⁴⁺, during the charging and discharging process of the Ti₂Nb₂O₉ electrode in the voltage range of 0.01–3.0 V. The theoretical specific capacity of Ti₂Nb₂O₉ in this process is calculated to be 252 mAh·g^-1, corresponding to the electrochemical data. Overall, this study demonstrates that the Ti₂Nb₂O₉/C anode nanosheets have an excellent charge-discharge performance, cycle stability, and rate performance in sodium ion batteries, thereby providing a feasible choice for sodium ion battery anode materials.

The fast-growing demand for safe energy storages with high power and energy density drives the continuous improvement of rechargeable Li-ion batteries (LIBs). In situ characterization is a potential way to understand the mechanism (metaphases, diffusion, kinetics, inhomogeneity etc.) of battery under operation conditions. Solid-state nuclear magnetic resonance (SS-NMR) is very sensitive to the local environment of ¹H, ^{6, 7}Li, ¹¹B, ¹³C, ¹⁷O, ¹⁹F, ²³Na, and ³¹P isotopes, which are widely used in battery materials, regardless of their ordering degree. In addition to providing well-resolved spectra obtained under fast magic angle spinning (MAS), NMR can effectively serve as a non-invasive tool to capture the evolution of electrodes/electrolyte upon charge/discharge electrochemical cycling. Subsequently, in situ NMR and imaging (MRI) have been developed for extending toward temporal and spatial dimensions in working batteries. Complementarily, highly sensitive electron paramagnetic resonance (EPR) and imaging (EPRI) have been employed to track and map the redox of transition metals and oxygen species (O₂ⁿ⁻) within electrodes. The insights gained from in situ NMR/EPR and their imaging can serve as a guide for the structural design of energy storage materials and the fabrication of batteries with optimized performance. As such, this review summarizes the applications of both NMR and EPR in the field of battery community. In particular, we first introduce the combination of fast magic angle spinning and phase-adjusted sideband separation (pjMATPASS) to obtain highly resolved spectra for extreme broad signal mediated by unpaired electrons, which is usually found in battery materials, as well as isotope-oriented NMR to determine the Li pathway in the composite electrolyte by the aid of ⁶Li replacing ⁷Li in their transport pathway. Secondly, we introduce the combination of NMR/MRI measurement while battery under electrochemical cycling by (1) briefly summarizing the advantages and disadvantages of home-made cells (coin cell, bag cell, and cylindrical cell) developed for in situ NMR study; (2) using different isotopes for conducting in situ NMR on batteries: ⁷Li, ²³Na, and ³¹P spectra; and (3) performing in situ MRI on electrolytes and electrodes with and without chemical shift information (CSI, S-ISIS, and stray-field MRI). Furthermore, in situ EPR determines and quantifies the evolution of active Li microstructure, transition metals, and oxygen species together with in situ EPRI mapping of the concentration of the paramagnetic center within a functioning battery. Finally, we point out the limitations and perspective of in situ NMR and EPR for cycling batteries in real-time. This review will provide illuminating insights on the magnetic technologies in the battery community and pave a way for carrying out NMR/EPR on functional materials.

The growing demand for electric vehicles, communication devices, and grid-scale energy storage systems urgently calls for the development of rechargeable batteries. Although lithium-ion batteries have dominated the new energy market for decades, there are challenges limiting their development, such as the high cost of lithium, as well as the toxicity and flammability of the organic electrolyte. In recent years, aqueous zinc-ion batteries (ZIBs) have gained much attention due to their advantages of high safety, high capacity, low cost, and nontoxicity. Materials based on multivalent vanadium and manganese have shown great potential for application as cathodes that are compatible with the metallic zinc anode in ZIBs. However, the commercialization of ZIBs has been hindered by the choice of cathodes, since the cathode materials show unsatisfactory energy densities and suffer from severe structural collapse, dissolution of the electrode components, sluggish reaction kinetics and detrimental side reactions during cycling. This stalemate was broken when a Zn²⁺/H₂O co-inserted V₂O₅ (Zn_0.25V₂O₅·nH₂O) material was first reported in 2016, and it showed much higher cycling stability and capacity than those of V₂O₅. The Zn²⁺ and water molecules pre-intercalated into the interlayer served as pillars to maintain the crystal structure and increase the interplanar spacing, leading to high structural stability and fast Zn²⁺ diffusion. Since then, several guest ions (Li⁺, Na⁺, K⁺, Ca²⁺, NH₄⁺, PO₄^3-, N^3-, etc.) and molecules (H₂O, polyethylene dioxythiophene (PEDOT), polyaniline (PANI, etc.) have been widely used to improve the electrochemical performance of aqueous ZIB cathodes, especially with manganese-based and vanadium-based materials. It is demonstrated that pre-intercalation of the guest ions or molecules can effectively optimize the electronic structure, regulate the interplanar spacing, and improve the reaction kinetics of the host. The local coordination structure of the host with pre-intercalated guest ions/molecules directly influences the zinc-ion storage performance. For example, sodium vanadates with a tunneled structure generally show better cycling stability than those with a layered structure due to their stronger Na-O bonds, since the O atoms on their layer surfaces are only single-connected. Manganese dissolution could be greatly suppressed by intercalation of the large potassium ions into tunneled α-MnO₂, where solid K-O bonds act as pillars to be connected with Mn polyhedrons, and thus strengthen the structure. New mechanisms underlying reduction/displacement reactions could also be revealed in vanadates upon the introduction of Ag⁺ and Cu²⁺. Thus, we believe that guest pre-intercalation is a promising method for optimizing the zinc-ion storage performance of the appropriate cathodes and is worthy for further exploration. Here we have reviewed the recent advances in manganese-based and vanadium-based cathodes via the guest pre-intercalation strategy, discussed the related advantages and challenges. The future research direction for these two kinds of aqueous ZIB cathodes is also prospected.

Sodium-ion batteries (SIBs) have recently garnered considerable attention because of the greater abundance, wider distribution, and lower cost of Na compared to Li. However, the investigation is insufficient, mainly because Na⁺ is larger and heavier than Li⁺, thereby limiting the Na⁺ insertion and extraction ability from the host materials. Anodes with alloying reactions such as Sn, Ge, and Sb have been considered for SIBs owing to their high gravimetric and volumetric specific capacities. In this study, we devised a one-pot reaction strategy for the in-situ fabrication of a spherical porous nano-SnSb/C composite by employing aerosol spray pyrolysis, and subsequently applied it as an anode in SIBs. The products of spray pyrolysis generally feature three-dimensional spherical hierarchical structures, which are considered to be relatively stable and also act as high-packing-density electrode materials. Additionally, they can be easily handled during the fabrication of the electrode. By adjusting the precursor concentration of SnCl₂·2H₂O and SbCl₃, different sizes for SnSb nanoparticles (10 and 20 nm) were obtained. The crystal structures and morphologies of the as-prepared samples were characterized using X-ray diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. Thermal gravimetric analysis was carried out to analyze the carbon content of SnSb/C composites by using a TG-DSC analyzer with a heating rate of 5 ℃·min^-1 in air from 25 ℃ to 600 ℃. The specific surface areas of the microspheres were determined by Brunauer-Emmett-Teller analysis. X-ray photoelectron spectroscopy and Raman spectroscopy were used to investigate the studied materials. The micro-nanostructured composite is composed of SnSb nanoparticles (10 and 20 nm); moreover, the carbon content and size of SnSb nanograins could be controlled by altering the reaction conditions. Owing to its unique structure, the obtained nano-composite displays stable cycle performance and high rate capability as the anode for SIBs. The specific capacity of 10-SnSb/C was 722.1 mAh·g^-1 at the first cycle, and the coulombic efficiency of the first cycle was 86.3%. The 10-SnSb/C was stable at different current densities of 100, 1000, and 3000 mA·g^-1, and exhibited specific capacities of 607.7, 645.4 and 452.2 mAh·g^-1, respectively. The reversible capacity reached 623 mAh·g^-1 after 200 cycles at a current density of 1000 mA·g^-1, and the capacity retention rate was 95%. The outstanding performance of SnSb/C was due to its distinctive nanostructure, which could effectively improve the utilization rate of active materials, facilitate the transportation of Na⁺ ions, and prevent the nanoparticle pulverization/agglomeration upon prolonged cycling. The facile synthesis technique and good performance would shed light on the practical development of SnSb/C nanocomposites as high rate capability and long cycle life electrodes for SIBs.

As a type of layered material, layered double hydroxides (LDHs) exhibit high development potential and application prospects, and have been used widely in adsorbents, catalysts, ion exchangers, flame retardants, biology, sensing, medicine, and other fields. With the continued development in nanoscience and nanotechnology, it has been established that monolayer LDHs contain an abundance of exposed highly unsaturated coordination sites, and so display unexpected functionality. However, due to the higher charge density of the LDHs layers, the strong interactions between the layers, and the hydroxyl groups on the surface of the layers, the result is a compact stacking of the layers. Consequently, it is still a great challenge to synthesize high-quality monolayer LDHs. Despite various methods of preparing monolayer LDHs having been developed, which can generally be divided into top-down and bottom-up strategies, most of these approaches have used organic solvents, which take a long time to achieve the exfoliation of LDHs, or require special equipment. Furthermore, high costs and the low yields have prevented large-scale production of monolayer LDHs. With the rapid development of the national economy, the industrial preparation of monolayer LDHs has become an inescapable trend. The separate nucleation and ageing method for the preparation of nanostructured LDHs is a feasible method, the key features of which are a very rapid mixing and nucleation process in a colloid mill, followed by a separate ageing process. This method has been successfully applied to a pilot plant in China for the industrial-scale synthesis of LDHs materials. It should be noted that the particle size distribution of LDHs obtained by this method can be well controlled. Moreover, the synthesis operation is simple, and quick (with a short duration of only several minutes). Through new in-depth technology studies on two-dimensional layered materials, large-scale preparation, and industrial application of monolayer LDHs will certainly be increasingly realized, and ultimately transformed into economic benefits. In this review, we summarize the synthesis method of monolayer LDHs, describe the necessary characterization technologies that have been used to study monolayers LDHs nanosheets, such as X-ray diffraction, transmission electron microscopy, and atomic force microscopy. Then we discuss the applications in various fields, such as photocatalysis, electrocatalysis, batteries, supercapacitors, membrane materials, and biomedical fields. We further discuss the recent breakthroughs in the synthesis of monolayer and ultrathin LDHs and the advance of production scale-up of LDHs. Finally, the performance of monolayer/ultrathin LDHs is summarized to provide a basis for the ensuing design of high-performance monolayer LDHs.

Direct methanol fuel cells (DMFCs), as one of the important energy conversion devices, are of great interest in the fields of energy, catalysis and materials. However, the application of DMFCs is presently challenged because of the limited activity and durability of cathode catalysts as well as the poisoning issues caused by methanol permeation to the cathode during operation. Herein, we report a new class of Rh-doped PdCu nanoparticles (NPs) with ordered intermetallic structure for enhancing the activity and durability of the cathode for oxygen reduction reaction (ORR) and achieving superior methanol tolerance. The disordered Rh-doped PdCu NPs can be prepared via a simple wet-chemical method, followed by annealing to convert it to ordered phases. The results of transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), power X-ray diffraction (PXRD) analysis and high resolution TEM (HRTEM) successfully demonstrate the formation of near-spherical NPs with an average size of 6.5 ± 0.5 nm and the conversion of the phase structure. The complete phase transition temperatures of Rh-doped PdCu NPs and PdCu are 500 and 400 ℃, respectively. The molar ratio of Rh/Pd/Cu in the as-synthesized Rh-doped PdCu NPs is 5/48/47. Benefitting from Rh doping and the presence of the ordered intermetallic structure, the Rh-doped PdCu intermetallic electrocatalyst achieves the maximum ORR mass activity of 0.96 A·mg^-1 at 0.9 V versus reversible hydrogen electrode (RHE) under alkaline conditions—a 7.4-fold enhancement compared to the commercial Pt/C catalyst. For different electrocatalysts, the ORR activities follow the sequence, ordered Rh-doped PdCu intermetallics > ordered PdCu intermetallics > disordered Rh-doped PdCu NPs > disordered PdCu NPs > commercial Pt/C catalyst. In addition, the distinct structure endows the Rh-doped PdCu intermetallics with highly stable ORR durability with unaltered half-wave potential (E_1/2) and mass activity after continuous 20000 cycles, which are higher than those of other electrocatalysts. Furthermore, the E_1/2 of the Rh-doped PdCu intermetallics decreases by only 5 mV after adding 0.5 mol·L^-1 methanol to the electrolyte, while the commercial Pt/C catalyst negatively shifts by 235 mV and a distinct oxidation peak can be observed. The results indicate that the ORR activity of the Rh-doped PdCu intermetallic electrocatalyst can be well maintained even in the presence of poisoning environment. Our results have demonstrated that Rh-doped PdCu NPs with ordered intermetallic structures is a potential electrocatalyst toward the next-generation high-performance DMFCs.

The development of high-performance supercapacitor electrode materials is imperative to alleviate the ongoing energy crisis. Numerous transition metals (oxides) have been studied as electrode materials for supercapacitors owing to their low cost, environmental-friendliness, and excellent electrochemical performance. Among the developed binary transition metal oxides, manganese cobalt oxides typically show high theoretical capacitance and stable electrochemical performance, and are widely used in the electrode materials of supercapacitors. However, the poor conductivity and active material utilization of manganese cobalt oxide-based electrode materials limit their potential capacitance application. Cotton is mainly composed of organic carbon-containing materials, which can be transformed to carbon fibers after calcination. The resultant carbonaceous material exhibits a large specific surface area and good conductivity. Such advantages could potentially suppress the negative effects caused by the poor conductivity and small specific surface area of manganese cobalt oxides, thereby improving the electrochemical performance. Herein, we firstly deposited manganese cobalt oxides on cotton by a simple hydrothermal method, yielding a composite of manganese cobalt oxides and carbon fibers via subsequent calcination, to improve the electrochemical performance of the electrode material. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and electrochemical characterizations were used to investigate the physical, chemical, and electrochemical properties of the prepared samples. The fabricated manganese cobalt oxides in the composite were uniformly dispersed on the carbon fiber surface, which increased the contact between the interface of the electrode material and electrolyte, and enhanced electrode material utilization. The electrode material was confirmed to have well contacted with the electrolyte during a contact angle test. Hence, a pseudo-capacitance reaction completely occurred on the manganese cobalt oxide material. Moreover, the addition of carbon fibers reduced the resistance of the material, resulting in excellent capacitive performance. The capacitance of the prepared composite was 854 F∙g^-1 at a current density of 2 A∙g^-1. The capacitance was maintained at 72.3% after 2000 cycles at a current density of 2 A∙g^-1. These results indicate that the manganese cobalt oxide and carbon fiber composite is a promising electrode material for high-performance supercapacitors. The findings presented herein provide a strategy for coupling with carbon materials to enhance the performance of supercapacitor electrode materials based on manganese cobalt oxides. Thus, novel insights into the design of high-performance supercapacitors for energy management are provided.

SSZ-13 zeolite with a chabazite (CHA) topology structure has important applications for methanol to olefin (MTO) conversion and selective catalytic reduction of nitrogen oxides (NO_x) by ammonia (NH₃-SCR) to reduce diesel engine exhaust emissions. It has been reported that the Al-rich SSZ-13 zeolite can be used to tune the selectivity of olefins in the MTO reaction, and significantly enhance NO conversions at lower temperatures in NH₃-SCR. Thus, the aluminum content and distribution as well as the corresponding acidity in SSZ-13 zeolite determine the catalytic performance of the zeolite for different catalytic reactions. Herein, quantum chemical computing using density functional theory (DFT) combined with multinuclear solid-state nuclear- magnetic-resonance (NMR) experiments were performed to investigate the correlation of Al location and Brønsted acidity of H-SSZ-13 zeolite with the Si/Al ratio varying from 5.8 to 25. The most favorable acid site in the 1Al model is O(1)―H in which a proton is bonded with the O(1) atom near the isolated Al atom of the zeolite framework. Nevertheless, energy differences were rather small when comparing the substitution energies of an Al atom replacing a Si atom in the zeolite framework with a proton located in different O sites. As the Si/Al ratio decreased, the Al-rich SSZ-13 zeolite contained more Al substitutions in its framework. This system exhibited the lowest substitution energy when two Al atoms were located at the diagonal of the same six-membered ring for the Al-Si-Si-Al (NNNN) sequence in the framework of the Al-rich SSZ-13 zeolite. However, for the Al-Si-Al (NNN) sequence, the most favorable distribution involved two Al atoms located in different six-membered rings of the double six-membered ring units (D6R). The proton affinities (PA), NH₃ desorption energies, and ¹H NMR chemical shifts after d3-acetonitrile adsorption were calculated in the most stable models to characterize the Brønsted acid strength of the SSZ-13 zeolite with different Si/Al ratios. All computing results suggested that the Al-rich SSZ-13 zeolite exhibited weaker Brønsted acid strength than that of the Si-rich counterpart due to the presence of Si(2Al) groupings with the NNN sequence in the framework. Quantitative ²⁹Si magic-angle spinning (MAS) NMR measurements after deconvolution demonstrated that the content of Si(2Al) groupings in the Al-rich SSZ-13 was > 43%. The ¹H MAS NMR experiments after d3-acetonitrile adsorption showed that the chemical shift of the bridging hydroxyls in the Al-rich SSZ-13 moved to the lower field, further confirming that it had a weaker Brønsted acid strength than the Si-rich counterpart.

The rapid development of batteries, especially lithium-ion batteries, has dramatically changed our daily lives. From portable electronics to electric vehicles and smart grids, batteries are extensively used in many fields and are difficult to be replaced in terms of their excellent energy and power densities. The advancement of battery technology requires the thorough understanding of electrochemical reaction mechanisms, which strongly depends on the collaboration of researchers from different fields. Magnetic resonance spectroscopy includes the important techniques of nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR), and the former is suitable for studying light elements commonly found in batteries including Li, Na, P and O, while the latter is suitable for studying heavier transition metals such as Co, Mn, Fe and V. In addition, NMR and EPR are capable of quantitatively analysis in a nondestructive manner regardless of sample crystallinity. Hence, NMR and EPR spectroscopies have allowed for significant research progress and have become increasingly important for battery research over the past three decades. Herein, we will provide our perspective of magnetic resonance methods and first summarize the main interactions and the Hamiltonian forms of solid-state NMR and EPR (dipole-dipole interaction, electric quadrupole interaction, chemical shift, and hyperfine interaction). Subsequently, we summarize the important and frequently-used methods of solid-state NMR and EPR spectroscopies and introduce their representative applications in metal ion battery research (mainly lithium- and sodium-ion batteries). Specifically, we introduce the basic principles and representative applications of (ⅰ) MQMAS (multiple-quantum magic angle spinning), (ⅱ) pjMATPASS (MAT = magic-angle turning, PASS = phase-adjusted sideband separation, and pj = projection), (ⅲ) WURST-CPMG (WURST = wide band uniform rate smooth truncation, CPMG = Carr-Purcell Meiboom-Gil), (ⅳ) 2D homonuclear correlation and exchange (2D EXSY), (ⅴ) 2D homonuclear correlation based on dipole coupling (i.e. RFDR), (ⅵ) perpendicular mode EPR, (ⅶ) parallel mode EPR, (ⅷ) in situ NMR, and (ⅸ) in situ EPR. In addition, we briefly introduce representative applications of 2D heteronuclear correlation (i.e. CP-HETCOR), pulsed field gradient NMR, spin-lattice relaxation (SLR), spin alignment echo (SAE), DFT calculations, and dynamic nuclear polarization (DNP). Previous reviews regarding the application of magnetic resonance technology in battery research are almost all reported in terms of the classification of battery materials. In other words, they are written from the perspective of applications in cathode, anode, and electrolyte research. Herein, we summarize from the perspective of solid-state NMR and EPR methods, which may be beneficial for the readers to fully understand the value of these important technologies. We believe this review can serve as a guide to solve challenges related to using solid-state NMR and EPR spectroscopies in battery research.

The assembly of two-component nanocrystals (NCs) such as metals, magnets, and semiconductors into binary nanocrystal superlattices (BNSLs) provides a fabrication route to novel classes of materials. BNSLs with certain structures can exhibit the combined and collective properties of their building blocks and are widespread in the fields of electronics and magnetic devices. As most studies have focused on combined two-component NCs of different sizes for self-assembling BNSLs, there are a few studies on single-component NCs of different sizes for the construction of BNSLs; this is especially true for Au NCs. Noble metallic Au NCs are an excellent candidate material because of their exceptional chemical stability, catalytic activity, process ability, and metallic nature; these characteristics provide them unique size-dependent optical and electronic properties as well as a wide variety of applications in sensing, imaging, electronic devices, medical diagnostics, and cancer therapeutics owing to their strong interactions with external electromagnetic fields. Therefore, it is important to develop a simple and efficient procedure to build BNSLs with different sizes of Au NCs. In our study, we synthesized monodispersed (size distribution < 10%) 6.0, 7.3, and 9.6 nm Au NCs using dodecanethiol-stabilized 3.7 nm Au NCs as seeds through a seed-growth method in oleylamine. The obtained Au NCs exhibited morphology and nanocrystallinity (single-domain and polycrystalline) similar to those of Au seeds. As the size of Au NCs increased from 3.7 to 6.0, 7.3, and 9.6 nm, the surface plasmon resonance peaks narrowed and indicated a red shift. The oleylamine-functionalized 6.0, 7.3, and 9.6 nm Au NCs were mixed with 3.7 nm Au NCs at certain concentration ratios. Au BNSLs with AB₂ (hexagonal AlB₂ structure), AB₁₃ (NaZn₁₃ structure), and AB (cubic NaCl structure) type were obtained through the solvent evaporation method. The (001) plane of the AlB₂-type structure, (001) plane of the NaZn₁₃-type structure, and (100) plane of NaCl-type structure superlattices were observed through transmission electron microscopy (TEM). The effective particle size ratios (γ= D_small/D_large) serve as the critical determining factor in the formation of the BNSLs. The effective particle size of NCs is equal to the sum of the metal core diameter and twice the thicknesses of the surface ligand. In our study, the effective particle size D_small (Au seed) is 5.7 nm; the effective particle sizes D_large (6.0, 7.3, and 9.6 nm Au NCs) are 9.0, 10.3, and 12.6 nm, respectively. The effective particle size ratios γ were therefore calculated to be 0.63, 0.55, and 0.45, respectively. The relevant space filling principle predicted the stability of the AlB₂, NaZn₁₃, and NaCl-type structures in the range of 0.482 < γ < 0.624, 0.54 < γ < 0.625, and γ < 0.458, respectively; the experimental results adequately matched the relevant space filling principle. The investigation of such a single nanocomponent as a building block is noteworthy with regard to the structures and properties of BNSLs as well as the potential development of novel meta-materials.

Lithium is a promising anode material for next-generation high-energy-density rechargeable batteries owing to its high specific capacity, low density, and low electrochemical reduction potential. However, dendrite growth during cycling impedes its practical application and causes safety hazards. Extensive research has been conducted to obtain dendrite-free safe Li anodes with an extended cycle life by electrolyte or anode surface modification. In previous studies, the symmetrical Li/Li cell test was widely applied to evaluate the effect of various Li anode modification methods on the cycle stability and Li deposition overpotential. However, a general criterion has not yet been established to identify the short circuit in Li/Li cells. Some researchers have even made incorrect conclusions based on the Li/Li cycling data. The most common misjudgment is the ignorance of short circuit signals and mixing up of soft short circuit and normal potential decrease caused by electrode activation. In some studies, the fractal voltage signals were attributed to the unstable activation process of the symmetrical cell. Therefore, this study uses an in situ optical cell to demonstrate that a short circuit caused by the contact of dendrites from two opposite electrodes can cause a sudden drop in cell voltage to certain extent. According to the reversibility of the voltage, the short circuit induced by dendrite growth can be classified into unrecoverable hard short circuits and recoverable soft short circuits. Typical short circuit data were summarized and described to establish a rule to determine the different types of short circuits. The voltage profiles provide characteristic signals to distinguish between the soft short circuit, hard short circuit, and cell activation processes in symmetrical cells. Furthermore, this study provides a reference for identifying dendrite growth and cell short circuits, which is important for confirming the practical effect of different modification methods.

Liquid marbles (LMs) are liquid droplets coated with a layer of lyophobic particles at the air-liquid interface. Since the pioneering work by Aussillous et al. in 2001, LMs have attracted significant attention owing to their facile fabrication, flexibility in the choice of the constituent particles and liquids, intriguing properties such as non-wetting and non-adhesive nature, satisfactory elasticity and stability, as well as promising applications in microfluidics, sensors, controlled release, and microreactors. The classical strategy for the preparation of LMs involves rolling a small volume of a droplet on a lyophobic powder bed for complete encapsulation of the liquid by the particles. In addition, various innovative methods, including electrostatic and coalescent approaches, have been developed for preparing special LMs with a complicated structure or morphology. Diverse materials such as water, surfactant solutions, liquid metals, reagents, blood, and even viscous adhesives have been employed as the internal liquid for the fabrication of LMs. Theoretically, any particulates such as lycopodium, polytetrafluoroethylene, Fe₃O₄, SiO₂, and graphite grains can be employed as the outer coating, but they are usually required to be lyophobic with sizes of less than hundreds of microns. The unique structure of the particle-covered droplet and the dual solid-liquid characteristics endow LMs with some unique and interesting properties, especially the non-wetting and non-adhesive nature. As the lyophobic coating particles restrain the internal liquid from contacting the substrate, LMs can move easily across either solid or liquid surfaces, neither wetting the substrate nor contaminating the internal liquid. An equally fascinating property of LMs is their satisfactory stability, which is necessary for most of their applications. The high stability of LMs stems from the protection of the coating powders and is embodied in both good mechanical stability (remaining intact after being released from a certain height or under a certain compression) and long lifetime (greatly suppressing the evaporation of the internal liquid). These extraordinary properties make LMs promising candidates for use in multitudinous fields, especially droplet microfluidics and microreactors. The potential application of LMs in microfluidics is ascribed to their non-wetting, non-adhesive nature and other features such as an ability to float on a liquid surface, coalescence, split, a small force of rolling friction, and response to external forces. Notably, LMs hold great promise for applications in microreactions, because they can create a confined reaction microenvironment, minimize reagent usage, facilitate unhindered gas exchange between the internal liquid medium and the surrounding environment, and allow the entry/exit of the reactants/products. We herein review the recent advances in LMs, such as manufacturing techniques, formation mechanisms, physical properties, and emerging applications. In particular, much attention is paid to the factors affecting the stability of LMs and the potential strategies to increase their stability. Moreover, this review discusses the challenges in the future development of LMs, suggests several possible ways of addressing these challenges, and forecasts the future development directions. We believe that this review can help researchers gain a better understanding of LMs and promote their further advances.

Partially reduced TiO₂ nanomaterials have attracted significant interest because of their visible-light activity for catalysis and photodegradation. Herein, we prepared a partially reduced anatase TiO₂ (Re-A-TiO₂) nanoparticle material using a fast combustion method, demonstrating good activity toward decomposing methyl orange under visible light irradiation. The surface structure of the prepared material, after being surface-selectively ¹⁷O-labeled with H₂¹⁷O (¹⁷O-enriched water), was studied via ¹⁷O and ¹H solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, and the obtained results were compared to those of non-reduced anatase TiO₂ (A-TiO₂). The EPR results showed that the concentrations of paramagnetic species (i.e., oxygen vacancies (OV) and Ti³⁺) in Re-A-TiO₂ were much higher than that in A-TiO₂, while the former was associated with a higher OV/Ti³⁺ ratio. The intensities of the EPR signals were significantly affected by the adsorbed water, and this phenomenon was explored in combination with ¹H NMR spectroscopy. The ¹H species on Re-A-TiO₂ appeared at larger chemical shifts, denoting the increased acidity of the sample, and these ¹H species on Re-A-TiO₂ were more difficult to remove than those on A-TiO₂. On the other hand, different features were observed for the signals arising from the two-coordinated oxygen atoms (μ₂-O) in ¹⁷O NMR, suggesting a typical anatase TiO₂(101) surface on A-TiO₂, but a more complex surface environment for Re-A-TiO₂. Furthermore, a larger amount of hydroxyl groups (OH) were observed on Re-A-TiO₂ compared to that on A-TiO₂, indicating a larger proportion of exposed (001) facets on Re-A-TiO₂. However, the μ₂-O signals broadened and became similar when the drying temperature was increased to 100 ℃, indicating a non-faceted anatase TiO₂ surface in such conditions. Based on the EPR and NMR results, a significant fraction of the OH species is believed to be formed from the reaction of the paramagnetic centers and adsorbed water molecules. The ¹H→¹⁷O cross polarization (CP) MAS and two-dimensional heteronuclear correlation (2D HETCOR) NMR spectra were used to verify the spatial proximity of the hydrogen and oxygen species, confirming the spectral assignments of a strongly adsorbed water and one type of surface OH species. In particular, the ¹H NMR signals at approximately 11 ppm were ascribed to the hydrogen species in the intramolecular hydrogen bond. In summary, this study investigated the paramagnetic species and surface structure of anatase TiO₂ materials by combining EPR along with ¹H and ¹⁷O solid-state NMR spectroscopy. The differences in the surface structures of Re-A-TiO₂ and A-TiO₂ should be closely related to their different properties toward the photodegradation of methyl orange.

Adlayer chemistry has been a significant subject of interest in physical chemistry over the past decades. Considerable attention has been paid to the development of high-performance film-based gas sensors, and tremendous progress has been achieved. Among the different analytical techniques, fluorescence provides a highly sensitive and selective method for detecting a wide variety of analytes. Film-based fluorescent sensors have emerged as one of the most promising candidates for chemical sensing and are being further developed into portable devices. Theoretically, relative signal changes including static and dynamic characteristics are significantly used to determine the sensing process; these characteristics are associated with surface absorption, the interaction between the analytes and sensing adlayer, as well as desorption kinetics in the absence and presence of the targeted gaseous analytes. As revealed earlier, there are a number of factors that determine the sensing behavior of a film, and the most important factors have been identified. Firstly, the suitability of the employed sensing fluorophore, which is important as it ultimately determines the effectiveness of a sensing process. Secondly, the structure of the fluorescent adlayer of the film; this is another important factor as it significantly determines the efficiency of mass transfer, which is necessary for efficient and reversible sensing. Finally, the chemical nature and surface structure of the substrate as these could affect the sensing performance of the film via the screening or enriching of analyte molecules. However, in situ, online, fast, and sensitive detection and discrimination of toxic and hazardous species via vapor sampling is a challenge that will persist for many years. By using the simultaneous interaction of multiple analytes with different sensing materials, the sensor array-based approach can recognize the overall change in the composition of complex mixtures, rather than just identifying their specific elements. The data-rich outputs of array-based sensing methods have recently been widely adopted by the analytical community due to their improved capabilities with statistical and cheminformatic approaches during analysis. Moreover, the community has recognized that numerous complex sensing challenges cannot be solved with conventional analytical tools.

In the past 20 years, our group has been committed to effectively research the formation of fluorescent sensitive films, optimization of sensing films, and fabrication of film-based fluorescent sensor arrays. A series of fluorescence sensitive thin-film materials have been developed, and high-performance fluorescence sensors have been successfully fabricated due to which a positive technological transformation has been achieved. Based on the recent progress in our group, this article briefly reviews the key points of the interactions between the gaseous analytes and adlayer. Moreover, their applications have also been addressed in the vapor phase detection of explosives, illicit drugs, and volatile organic contaminants based on the film-based fluorescent gas sensors. Further discrimination of the complex analytes was realized using a sensor array and pattern recognition strategy. It is strongly believed that our studies are the first to provide powerful fluorescent techniques for the efficient detection and discrimination of important or hazardous substances with remarkably different properties. Meanwhile, the large-scale production of our development demonstrates that interdisciplinary corporation and industry participation plays a vital role in converting laboratory techniques to a conceptual sensing system, which can manufacture commercial portable detectors. Furthermore, we offer insights on the future directions and challenges of film-based sensors in gas sensing.

Solid materials containing frustrated Lewis pairs (FLPs) as active sites have attracted much attention due to their ability to activate and transform small molecules. However, it is still highly challenging to precisely construct FLP sites on the surfaces of nanomaterials, thereby limiting the applications of these materials. Nanostructured ceria (CeO₂) is commonly employed as a catalyst or functional support, and exhibits both Lewis acid and basic properties as well as abundant and easily regulated surface defects, which originate from the reversible Ce³⁺/Ce⁴⁺ redox pair. When the Lewis acid and base sites of CeO₂ are independent of each other, the combined Lewis acid-base sites play a similar role to that of homogeneous FLP sites. Thus, the rich surface properties of nanostructured CeO₂ provide significant potential for the construction of solid FLPs.

Herein, we demonstrate that solid FLP sites can be successfully constructed on the surface of CeO₂(110) via the regulation of surface defect clusters, which can be used to create new Lewis acid sites composed of two adjacent Ce³⁺ atoms on the surface. Novel interfacial FLP sites can then be formed by combining these Lewis acid sites with neighboring surface lattice oxygens, which act as Lewis base sites. Porous CeO₂ nanorods (PN-CeO₂) with boundary surface defects were prepared by a special two-step hydrothermal process, and exhibited remarkable catalytic FLP properties. Hydrogen molecules could be effectively activated on the surface of PN-CeO₂ with a low activation energy of 0.17 eV via a heterolytic cleavage process. Hydrogenation of alkenes and alkynes to alkanes could then be realized by the activated hydrogen under mild reaction conditions.

PN-CeO₂ nanorods with FLP active sites were also able to activate CO₂ molecules effectively. Unlike in other solid FLP sites, CO₂ molecule activation was realized via a Lewis base site binding with the C atom while two Lewis acid sites bound the two O atoms, owing to the unique configuration of the FLP sites in PN-CeO₂. When combined with the epoxidation of olefins by "isolated" Ce³⁺ sites in PN-CeO₂, the FLP-inspired activated CO₂ could be used to transform olefins and CO₂ to cyclic carbonates through a selective tandem transformation route. In addition, density functional theory studies indicate that the FLP sites on CeO₂(110) can activate the C―H bond of CH₄ with activation energies as low as 0.63 eV, which can be attributed to the enhanced acidity and basicity of the FLP sites.

With this improved understanding of solid FLP sites constructed on ceria, we have also been able to summarize the challenges and prospects in this field, including their construction, characterization, and mechanism analysis.

The exploitation of high-performing stable oxygen reduction reaction (ORR) electrocatalysts is critical for energy storage and conversion technologies. The existing high-efficiency electrocatalysts applied to the ORR are mainly based on Pt and its alloys. Moreover, carrier catalysts are the most widely used in actual electrocatalysis. A suitable carrier not only improves the utilization rate of precious metals and the service life of the catalyst, but also serves as a co-catalyst to ameliorate the catalytic activity through a synergistic effect in the reaction. Therefore, research into Pt-based electrocatalysts mainly focuses on the precious metal Pt and the carrier. With the aim of improving the activity and durability of Pt-based catalysts for the ORR, one-dimensional porous titanium nitride (TiN) nanotubes with a large specific surface area as well as good conductivity, electrochemical stability, and corrosion resistance were prepared in this study, and then, Pt nanoparticles were deposited on the TiN-support by atomic layer deposition (ALD). ALD is a novel and simple method for the preparation of films or nanoparticles with fine control of the thickness or size, respectively. The results of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) experiments confirmed that the Pt nanoparticles obtained by ALD (ALD-Pt/TiN) were face-centered cubic (fcc) crystals with a uniform size and were highly dispersed on the surface of TiN. X-ray spectroscopy (XPS) measurements verified that the binding energy of Pt 4f in ALD-Pt/TiN was positively shifted by 0.33 eV with respect to that of the Pt/C catalyst, indicating strong electronic interactions between the ALD-Pt nanoparticles and the TiN carriers. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) analyses revealed that ALD-Pt/TiN possessed high activity for the ORR and favorable durability. The onset potential and diffusion-limiting current density of ALD-Pt/TiN were similar to those of commercial Pt/C, while the half-wave potential was 20 mV higher than that of commercial Pt/C, indicating better electrocatalytic performance of the designed material. Furthermore, the electrocatalytic mechanism and kinetics for ALD-Pt/TiN were investigated by rotating ring-disc electrode (RRDE) experiments. The results suggested that the electron transfer number of the ALD-Pt/TiN catalyst was about 3.93, indicating that the ORR on the electrode was dominated by an efficient four-electron pathway. At the same time, the peroxide content was only 5%. The results of accelerated durability testing (ADT) showed that ALD-Pt/TiN had better ORR stability than Pt/C. This excellent electrocatalytic performance was probably due to the high dispersibility of the Pt nanoparticles deposited by ALD, good conductivity and corrosion resistance of TiN, and strong interactions between ALD-Pt and the TiN support. This work provides a reliable strategy for the design of new electrocatalytic materials with high activity and stability. Future research will focus on the strong interactions between ALD-Pt and the TiN carriers.

The Li metal anode is considered the most promising anode for next-generation high energy density batteries owing to its high theoretical capacity and low electrode potential. The development of batteries with high energy density is essential to meet the growing demand for energy storage devices in the modern world. However, the Li metal anode has operational problems. The high activity of Li causes dendritic growth during the cycling process, which leads to the cracking of the SEI (solid-electrolyte interphase), increased side reactions, and formation of dead Li. Furthermore, if the growth of Li dendrites is left uncontrolled, it can penetrate the separator and create a short-circuit accompanied by thermal runaway. Additionally, the complete utilization of active Li is challenged by the infinite volume expansion of the Li anode. To improve the application scope of Li metal batteries, it is imperative to develop advanced strategies for inhibiting Li dendritic growth, enhancing the stability of the SEI, reducing the accumulation of dead Li, and buffering the volume expansion. Understanding the mechanisms and models of Li nucleation and growth provides insight into solving these problems. This review summarizes some of the important models of Li nucleation and growth such as the surface nucleating model, charge-induced model, SEI model, and deposition/dissolution model. These models aid comprehension of the Li nucleation and growth process under various conditions. This review also discusses the strategies explored in the literature for improving the electrodes (such as three-dimensional (3D) matrix), electrolyte, SEI, and separator to realize uniform deposition of Li and improved utilization of Li. The 3D matrix strategy for improving the electrode design explores various matrices including graphene-based, carbon fiber-based, porous metal-based, and powder-based for buffering the volume expansion and reducing the local current density. To improve the electrolyte, concentrated lithium salts and functional additives are employed to stabilize the SEI and inhibit dendritic growth by regulating the chemical composition of SEI and inducing the deposition of Li. With respect to improving the design of the SEI, strategies for the construction of inorganic or organic components with high ionic conductivity and stable structure are explored for even distribution of Li ions and to avoid SEI rupture. This can reduce electrolyte consumption and dead Li formation. The modification of the separator by functional nanocarbon layer can control the direction of dendritic growth, thereby preventing the penetration of dendrites into the separator and achieving a uniform Li deposition layer. Finally, all solid state Li metal batteries (ASSLMBs) are discussed that utilize ceramic and polymer electrolytes owing to high safety of the solid state electrolyte. Therefore, reducing the interfacial resistance and suppressing dendritic growth between the Li anode and the electrolyte is key for the practical applications of ASSLMBs. Overall, this review provides a summary and outlook for promoting the practical applications of Li metal batteries.

Biological systems can be regarded as complex and open thermodynamic systems. All processes involved in biological growth and metabolism are accompanied by material and energy exchange. During metabolism, energy in the organisms is released in the form of heat, i.e., metabolic heat, which is the basis for development in the field of biothermochemistry. The calorimetric method considers the thermal effects produced by the various forms of action as the research object, to reveal the law of energy change and quantitative energy conversion. Studying the thermodynamic processes of complex biological systems and related reactions through microcalorimetry and thermodynamic methods reflects the intrinsic laws of life-related processes macroscopically and intrinsically. With the tremendous development and progress in microcalorimetry in terms of the temperature measurement accuracy, stability of temperature control, automation, and multi-functionalization, calorimetry has been widely used in life sciences. It can be used to describe macroscopic processes such as ecosystems and biological evolution, observe organismal and cell growth, examine mitochondrial metabolism, and study problems at the molecular level, including enzymatic reactions and interactions between small molecules and biomacromolecules. Herein, the application of biomass calorimetry in the life sciences is reviewed. The status and progress of biomass calorimetry at different biological and structural levels, such as the ecosystem, biological, organ, cellular, subcellular, and molecular levels are introduced. For example, soil microbial metabolic activity is a universal index for evaluating soil quality. The growth and metabolism of organisms as well as the physical and chemical processes of substances in soil are often accompanied by heat release, which is usually a non-selective signal. The use of isothermal microcalorimetry to nonspecifically monitor and record soil microbial metabolic characteristics has promoted the study of microbial metabolism in complex soil systems. The application of calorimetry to the study of tissues and organs mainly involves the calorimetric study of isolated animal and plant tissues and organs. Calorimetry of animal and microbial cells is considered the most common application of calorimetry in life sciences research. It mainly involves the classification and identification of bacteria, their growth and metabolism, inhibition mechanisms of drugs on microbial growth, principles of kinetics, and the thermodynamic characteristics of microbial growth and metabolism. However, owing to the lack of specificity of biomass calorimetry and the lack of direct access to information at the molecular level, more applications of calorimetry combined with other analytical techniques (especially in biology, medicine, and pharmacy) are needed in the future.

Silicon is a promising anode material for lithium-ion batteries (LIBs) because of its natural abundance, high theoretical capacity, and relatively low working potential for lithium storage. However, two main obstacles exist that hinder its commercial application. One is the large volume variation during prolonged cycling, which causes irreversible cracking and disconnection of the active mass from the current collector and subsequently rapid decay of capacity of the electrode. The other is its poor intrinsic electronic conductivity, which seriously restricts its rate performance. To date, strategies to improve its cycling stability and rate capability include rational designs of different Si nanostructures and the incorporation of conductive agents. In this study, we present a novel and effective method to fabricate a Si/C composite. Through hydrogen bonding and the electrostatic interaction between graphene oxides (GO) and acidized chitosans (Cs), a hybrid hydrogel was fabricated in which silicon nanoparticles and carbon nanotubes were encapsulated in situ. Following freeze-drying and subsequent calcination, a three-dimensional porous silicon/carbon nanotube/graphene (Si-CNT@G) nanocomposite was obtained. The phase, structure, and morphology of the sample were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The results show that the silicon nanoparticles were uniformly distributed in the graphene network, which was interwoven with carbon nanotubes. The resultant Si-CNT@G nanocomposite featured a porous three-dimensional conductive carbonaceous support, providing short pathways for electrons, conductive transport highways for lithium ions, a sufficient interface for contact of the electrolyte and electrode, and an effective buffer matrix to alleviate structural change during discharge/charge cycling. Benefiting from these particular features, the as-prepared Si-CNT@G nanocomposite exhibited superior lithium storage performance with high specific capacity and excellent long-term cycling stability when evaluated as an anode material for LIBs. For example, a high discharge capacity of 673.7 mAh·g⁻¹ can be retained after 200 discharge/charge cycles at a current density of 500 mA·g⁻¹ in the potential range of 0.01–1.20 V, with a decent capacity retention of 97%. Even when at a current density of 2000 mA·g⁻¹, a high discharge capacity of 566.9 mAh·g⁻¹ can still be retained. In contrast, the discharge capacity of pure silicon nanoparticles, when tested under the same conditions, was practically nil. These results suggest that the Si-CNT@G nanocomposite is a promising anode material for high-performance LIBs.

Selective hydrogenation of dienes and alkynes to monoenes is an important topic of research in the fields of pharmacology and organic synthesis. Catalyst design plays a key role in this process, where a general principle involves controlling the steric diene adsorption by modifying the surface of the metal nanoparticles. For example, upon introducing Bi species into Rh nanoparticles, the resulting RhBi/SiO₂ showed 90% selectivity to 2-hexene, with 95% conversion of 1, 4-hexadiene under ambient conditions, because of the suppressed adsorption of the internal C＝C bond. However, the catalyst activity decreased remarkably; that is, the activity of the unmodified Rh/SiO₂ was about 27 times higher than that of RhBi/SiO₂. Controlled steric adsorption of the diene molecules could also be achieved by the constructing porous channels around the metal nanoparticles. For example, metal-organic framework (ZIF-8) or mesoporous silica (MCM-41) encapsulated noble metals showed high selectivity for the hydrogenation of terminal C＝C bonds. However, these catalysts had poor durability under the thermal/hydrothermal reaction/regeneration conditions. In contrast, zeolites have superior durability under harsh reaction conditions, but they are rarely used in semi-hydrogenation reactions. We recently found that metal nanoparticles fixed within zeolite crystals (e.g., ZSM-5 and Beta) efficiently catalyze the selective hydrogenation of molecules bearing multiple reducible groups. Thus inspired, we developed a catalyst by fixing Rh nanoparticles within zeolite crystals via an inter-zeolite transformation method. The Rh@CHA catalyst was synthesized by introducing Rh species into the parent Y zeolite (Rh@Y) and transformation of the Y zeolite to chabazite (CHA zeolite) under hydrothermal conditions. X-ray diffraction patterns, N₂ sorption isotherms, scanning/transmission electron microscopy images, and model reactions (hydrogenation of probe molecules) confirmed the successful fixation of the Rh nanoparticles inside the CHA zeolite crystals. As expected, the Rh@CHA catalyst was highly selective for the hydrogenation of dienes. For example, Rh@CHA showed a 2-hexene selectivity of 86.7%, with 91.2% conversion of 1, 4-hexadiene. In contrast, the generally supported Rh nanoparticle catalyst (Rh/CHA) showed a low 2-hexene selectivity of 37.2% under identical reaction conditions. Considering that Rh@CHA and Rh/CHA comprise the same CHA zeolite crystals and have similar Rh nanoparticle sizes, the remarkably high selectivity of Rh@CHA is assigned to the steric adsorption of dienes on the Rh surface controlled by the micropores of the CHA zeolite. This work demonstrates that a zeolite-fixed metal core-shell structure is a powerful tool for developing efficient catalysts to be used in diene hydrogenation.

Gold nanoparticles (AuNPs) have been widely applied in the biomedical field due to their tunable localized surface plasmon resonance (LSPR) properties, versatile surface modifiability, and favorable biocompatibility. With the in-depth study, individual AuNPs cannot meet the requirements for multifunctional biological applications. By combining AuNPs with other inorganic materials, material scientists and chemists have successfully prepared various gold-based nanocomposites (AuNCs), such as Au-metals, Au-semiconductors, Au-magnetic nanocomposites, etc. Furthermore, despite their compositions being the same, products with different topological morphologies (i.e. core@shell, yolk@shell, core-satellite, and Janus) can be fabricated by sophisticated chemistry. Based on their special collective properties and synergetic effects, multifunctional AuNCs have been proposed for tumor theranostic applications; their parts exhibit impressive imaging/therapeutic performances and present tremendous application perspectives for basic research and at a pre-clinical stage. For example, when Au is combined with porous drug carriers, its photothermal properties can promote drug release, which can be useful for developing intelligent drug delivery platforms. In addition, Au and magnetic material hybrids can be used in multimodal imaging and combination therapy, depending on the integration of its optical and magnetic properties. Moreover, when Au is combined with semiconductor material, either LSPR coupling effects or nonradiative energy transfer occurs between them, causing enhanced photothermal or photodynamic therapy. Therefore, in this review, we have highlighted the fabrication approaches of AuNCs including the one-step method, seed-mediated growth method, ex situ assembly method, etc. For the one-step method, we emphasize that Au and other components nucleate and grow concurrently, which is frequently employed for the preparation of Au based alloys. The key to synthesizing AuNCs by seed-mediated growth method is the degree of lattice matching between the different components and the interactions of their heterogeneous interfaces; if the crystal lattices are well-matched, AuNCs can be obtained by direct epitaxial growth. Furthermore, approaches including the introduction of a ligand/surfactant, intermediate layer, and molecular weak interactions into the heterogeneous interfaces can regulate the two components' interaction and fabricate various AuNCs. For the ex situ assembly method, prefabricated AuNPs and other nanoparticles can be assembled into AuCNs by electrostatic attraction, host-guest reaction, bio-recognition, covalent binding, etc. We also summarize the recent achievements of typical AuNCs (i.e. Au-MOF, Au-Fe₃O₄, and Au-Cu_2–xS) in tumor theranostic applications based on their collective properties and/or synergetic effects, respectively. Finally, the main problems and the future developments of this research field are also discussed.

Using solar energy to power evaporative processes has found various applications in desalination, wastewater treatment, and power generation among other fields. Due to its green-energy sources and energy-efficient conversions, it has gained increasing attention. However, as one of the oldest approaches, the application of solar evaporation is still limited by issues such as low evaporation efficiency, fouling, and the rapid degradation of solar absorbers. During solar evaporation processes, the solar absorbing materials are directly heated by sunlight and the generated heat is transferred to the water around the material. Within this process, in situ photo-thermal conversion is realized by absorber materials at the air-water interface. After the water is heated, it vapors continuously. Therefore, the material for solar absorption and photo-thermal conversion is key to improving the efficiency of solar evaporation processes. Currently, many approaches are being developed to achieve high-efficient solar evaporation, such as the photon management, nano-scale thermal regulation, the development of new photo-thermal conversion materials, and the design of efficient light-absorbing solar stiller. Carbon-based materials including carbon nanotubes, graphene, carbon black, graphite, etc. have broad light-absorption profiles over the entire solar spectrum, which makes them the outstanding photo-thermal conversion materials. Herein, we design a new structure and house-like solar still on the basis of carbon-based materials to achieve high light absorption, efficient photo-thermal conversion, and continuous desalination. We use the chemical vapor deposition (CVD) technique to fabricate a reticulated carbon-nanotube solar evaporation membrane. Stainless steel mesh (SSM) is used as a reticulated skeleton, providing porous structures and increasing the mechanical strength of the membrane. Then the carbon nanotubes (CNTs) are grown on the reticulated skeleton to function as solar conversion structures due to their wide range of light absorption capacities. The CVD grown CNTs reticulated membrane (CGRM) is fixed in a house-like device with a sloped ceiling to condense and collect water vapors ensuring the continuous desalination of water. Our experiments show that the fabricated CGRM is hydrophobic with an average contact angle of 133.4° for a 100.0 g·L^-1 NaCl solution, only allowing water vapors to pass through while rejecting salts. When the light intensity was 1 kW·m^-2, the surface temperature of the membrane increased rapidly and stabilized at 84.37 ℃. The salt rejection rate of the system could reach up to 99.92%.To perform a comparative study, we also prepared a mechanically-filled CNTs reticulated membrane (MFRM1, MFRM2) for solar evaporation tests, which showed an inferior performance to that of the growing structure of the CGRM. Therefore, it was determined that our system might provide a potential way to harvest freshwater readily with portable-type equipment.

As an excellent photoelectric material, metal halide perovskites have been rapidly developed in the photovoltaic field. The power conversion efficiency of solar cells based on perovskite materials now exceeds 24%, which is close to the conversion efficiency of silicon-based solar cells. However, organic-inorganic hybrid perovskite materials are sensitive to light, oxygen, and moisture, particularly when combined in the ambient environment, limiting their commercial application in perovskite devices due to their poor environmental stability. Therefore, a comprehensive understanding of the degradation mechanism is the key for development of an effective method to inhibit the degradation of perovskite materials. Herein, the photo-induced degradation process of CH₃NH₃PbI₃ films in air was studied by conventional optical and structural characterization methods, including ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray diffraction (XRD) and advanced transmission electron microscopy (TEM) equipped with a probe spherical aberration corrector. The CH₃NH₃PbI₃ films were first decomposed into hexagonal PbI₂ and amorphous phase, and subsequently oxidized to the amorphous phase under the combined effects of light and oxygen. The molecular formula of the amorphous phase was further confirmed as PbI_2−2xO_x (0.4 < x < 0.6) via X-ray energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Further analysis showed that the film degradation is mainly related to superoxide (O₂^•−) formed by combination of oxygen molecules and photoelectrons in the perovskite film. The organic part of the CH₃NH₃PbI₃ is oxidized by O₂^•− and CH₃NH₃PbI₃ is decomposed to form volatile products, such as CH₃NH₂ and I₂, then degraded into PbI₂, and oxidized to form the amorphous PbI_2−2xO_x. Therefore, during the initial degradation of film under light soaking in air, the degradation sites are mainly located at the interface between CH₃NH₃PbI₃ and air. Many pores were observed on the film surface due to the large loss of volatile decomposition products during the initial degradation. The films then converted to a honeycomb hollow morphology due to the continuous consumption of material under light soaking, reducing the mass of the film as well. Finally, the entire film was oxidized to form an amorphous structure. Herein, for the first time, we report that the formation of amorphous oxides is accompanied by the degradation of perovskite film. This study presents a new understanding of the photo-induced degradation mechanism of perovskite films in air and provides novel theoretical guidance to promote the long-term stability of perovskite solar cells.

Platinum (Pt) is recognized as an excellent cocatalyst which not only suppresses the charge carrier recombination of the photocatalyst but also reduces the overpotential for photocatalytic H₂ generation. Albeit of its good performance, the high cost and low abundance restricted the utilization of Pt in large-scale photocatalytic H₂ generation. Pt based transition metal alloys are demonstrated to reveal enhanced activities towards various catalytic reactions, suggesting the possibility to substitute Pt as the cocatalyst. In the present work, Pt was partially substituted with Co, Ni, and Fe and Pt-M (M = Co, Ni, and Fe)/g-C₃N₄ composites were constructed through co-reduction of H₂PtCl₆ and transition metal salts by the reductant of ethylene glycol. The crystal structure and valence states were measured by X-ray diffractometer (XRD) and X-ray photoelectron spectrometer (XPS), respectively. The higher degree of XRD peaks and larger binding energies for Pt 4f_5/2 and Pt 4f_7/2 after incorporating Co²⁺ ions indicated that Co was successfully introduced into the lattice of Pt and Pt-Co bimetallic alloys was attained through the solvothermal treatment. The morphology was subsequently observed by transmission electron microscope (TEM), which showed a good dispersion of Pt-Co nanoparticles on the surface of g-C₃N₄. Meanwhile, the shrinkage of lattice fringe after introducing cobalt salt further confirmed the presence of Pt-Co bimetallic alloys. The UV-Vis absorption spectra of g-C₃N₄ and Pt, Pt-Co deposited g-C₃N₄ were subsequently performed. It was found that the absorption edges were all consistent for all three samples as anticipated, implying that the band gap energy was maintained after hybridizing with Pt or Pt-Co alloys. Furthermore, the photocatalytic H₂ generation was carried out over the as-prepared composites with triethanolamine (TEOA) as sacrificial reagent. Under visible-light illumination, the1% (w) Pt_2.5M/g-C₃N₄ (M = Co, Fe, Ni) composites all exhibited higher or comparable activity towards photocatalytic H₂ generation when compared to 1% (w) Pt loaded counterpart. In addition, the atomic ratios of Pt/Co and the loading amount of Pt-Co cocatalyst were modified to optimize the photocatalytic performance, among which, 1% (w) Pt_2.5Co/g-C₃N₄ composite revealed the highest activity with a 1.6-time enhancement. Electrochemical impedance spectra (EIS) and photoluminescence (PL) spectra indicated that the enhancement might be attributed to improved charge transfer from g-C₃N₄ to Pt_2.5Co cocatalyst and inhibited charge carrier recombination in the presence of Pt_2.5Co cocatalyst. Therefore, the present study demonstrates the great potential to partially replace Pt with low-cost and abundant transition metals and to fabricate Pt based bimetallic alloys as promising cocatalysts for highly efficient photocatalytic H₂ generation.

Nanoparticles (NPs) are ideal building blocks for constructing functional materials and devices due to their unique optical, electronic, magnetic, and mechanical properties. The precise assembly and patterning of NPs to obtain ordered structures are vital to explore the special properties of NPs. The specific configurations of large-scale NP assemblies from two-dimensional (2D) NP patterns to one-dimensional (1D) NP arrays on substrates are considered the ideal platform for many technological devices, such as solar cells, magnetic memory, switching devices, and sensing devices, due to their unique transport phenomena and the cooperative properties of NPs in assemblies. Regulation with high-precision control over the orientation and spatial arrangement of nanoarchitecture is required to achieve the coupling and collecting between NPs and thereby translate the properties of the individual NPs to the functions of the macroscopic materials. Therefore, the development of effective methods to build and implement ordered nanocomposites has been accelerated considerably over the last decade. However, due to the complex physics and thermodynamics of the NP assembly, precise control over the orientation and spatial distribution of nanoassemblies with a large area and high homogeneity remains a challenge. In order to tune the position and shape of the NPs into desired structures, a series of strategies and methods have been proposed and developed. These strategies include manipulation of interparticle physical interactions, modification of NP surface chemistry, effect of external fields, utilization of physically or chemically patterned templates, and application of an inkjet printing technique to achieve the desired level of spatial and orientational control over the assembly of NPs. In this paper, we summarized the typical morphologies and the precise control of the architectures prepared by the NPs self-assembly. The particle density, particle size, and interparticle distance of the NP assemblies were strongly controlled. Then the bottom-up strategies for positioning NPs into desired structures with high resolution and considerable throughput were shown. In addition, we discussed the unique functions and diverse applications of the ordered NP assemblies. Both the strong surface plasmon resonance coupling and directional electron transport between particles were studied, which was of highly significance in the development of many technological devices and of great scientific interest. Finally, we investigated the challenges and opportunities of the precise assembly of NPs, which could provide insight and guidance for the future development of functional nanoassembly devices.

The considerable demand of robust solid-state nuclear magnetic resonance (NMR) sequences has been met by the development in solid-state NMR hardware and probe design, particularly for fast magic angle spinning (MAS). Fast MAS enhances spectral resolution, however, it makes many conventional methods unusable because of the need of significantly high radiofrequency (RF) field strength and the intrinsic inefficiencies under such condition. Dipolar-based homonuclear recoupling sequences are widely used for structural analysis, and radio-frequency driven recoupling (RFDR) is one of the most popular zero-quantum (ZQ) homonuclear recoupling sequence. Previous studies demonstrated that RFDR efficiency strongly depends on factors such as MAS frequency, resonance offset, RF field inhomogeneity, and chemical shift anisotropy (CSA). To alleviate these dependencies, different RFDR phase cycles have been proposed. To completely understand the principle of ZQ recoupling sequences and achieve uniform broadband homonuclear recoupling under fast MAS conditions, we herein utilize the theory of symmetry sequences and propose a series of RN_N ¹ (N ≥ 4, N is even) sequences with various phase cycles under both moderate and fast MAS conditions. We simulated the influence of MAS rate, resonance offset, RF field strength, RF mismatch, and heteronuclear decoupling on ZQ homonuclear polarization transfer efficiency. We verified the ZQ dipolar recoupling efficiencies of various RN symmetry sequences using U-¹³C, ¹⁵N-labeled L-histidine and microcrystalline U-¹³C, ¹⁵N-labeled dynein light chain (LC8) protein. The basic R4 sequence showed the worst broadband ZQ polarization transfer performance theoretically and experimentally, while the basic R6 sequence could efficiently achieve ZQ dipolar recoupling within moderate bandwidth. Under low to moderate MAS conditions, high-power ¹H decoupling could considerably enhance the polarization transfer efficiency, while homonuclear recoupling sans heteronuclear decoupling is recommended under fast MAS conditions. Super phase cycling enhanced ZQ polarization transfer efficiency and bandwidth and resulted in significantly reduced sensitivity to RF mismatch. RN_ixy3 and RN_ixy4 sequences with 6^*N and 8^*N phase cycling steps, respectively, were preferred. The R4_ixy3 sequence with fewer phase cycling steps showed comparable, or even slightly better, performance to the R4_ixy4 sequence. As shown in the simulations, by choosing proper RF field strengths, 1.5^*ω_r < ω₁ < 3^*ω_r, uniform broadband ZQ recoupling with R4_ixy3 or R4_ixy4 sequences could be achieved under fast MAS conditions, which would be significant for the accurate determination of spatial proximities and internuclear distances. By prolonging the mixing time, the RN ZQ scheme could provide more cross peaks, where medium- to long-range spatial correlations could be included; these correlations are essential for structural determination in complex systems.

In the past few decades, lithium-ion batteries (LIBs) have dominated the market of rechargeable batteries and are extensively applied in the field of electronic devices (e.g., mobile phones and computers). However, lack of lithium resources, high cost of lithium as well as toxic and flammable organic electrolytes significantly hinder further development and large-scale application of LIBs. Therefore, it is necessary to develop next-generation green rechargeable batteries to replace LIBs. Recently, aqueous zinc-ion batteries (AZIBs) have been considered as energy storage devices with substantial development prospects for future large-scale storage systems owing to their high safety performance, low production cost, abundant zinc resources, and environmental friendliness. Typically, we use zinc metal as the anode with neutral or weakly acidic aqueous electrolyte (pH: 3.6–6.0). However, cathode materials have high requirements for AZIBs while considering the charge effect of multivalent metal ions. Currently, one of the research emphases is to develop suitable zinc ion intercalation cathode materials with stable structures and high capacities. Among all types of cathode materials, vanadium-based compounds have the advantages of low cost and high reversible capacity. Additionally, their structure is variable, mainly including layered, tunneled and natrium super ionic conductor (NASICON) structure. Therefore, vanadium-based compounds have clear application possibility in AZIBs. However, there are still several significant problems. In particular, vanadium-based compounds generally have poor conductivity and low voltage platform. Electrochemical performance can be significantly improved mainly by pre-inserting metal ions or water molecules, optimizing the electrolyte, and controlling morphology of nanomaterials (nanosheets, nanospheres, etc.). In addition, the zinc storage mechanism in vanadium-based compounds is more complicated and controversial, including Zn²⁺ intercalation/deintercalation mechanism, co-insertion mechanism, and conversion reaction mechanism. Moreover, different materials usually exhibit different electrochemical properties and energy storage mechanisms. In this review, we comprehensively describe the energy storage mechanisms of vanadium-based compounds and discuss the application as well as development status of vanadium-based materials in AZIBs. Further, several strategies for improving their performance are proposed, including structural design (e.g., pre-insertion of metal ions or water molecules), morphology control (e.g., carbon coating), and electrolyte optimization (e.g., adjustment of composition and concentration). In particular, pre-insertion of metal ions or water molecules in the original structure can effectively solve these problems of low ion diffusion rate, poor conductivity, and structural instability, thereby achieving excellent electrochemical performance. Moreover, the application of a high-concentration electrolyte is a simple and effective strategy that can not only significantly widen the electrochemical stability window of the aqueous electrolyte but also suppress the dissolution of vanadium, thereby effectively improving energy density and cycling stability for AZIBs. Accordingly, the future development direction of AZIBs and their vanadium-based cathode materials is further prospected, aiming at designing high-performance electrode materials for AZIBs.

Particle-stabilized dispersions such as emulsions, foams and bubbles are catching increasing attentions across a number of research areas. The adsorption mechanism and role of these colloidal particles in stabilizing the oil-water or gas-water interfaces and how these particles interact at interfaces are vital to the practical use of these dispersion systems. Although there have been intensive investigations, problems associated with the stabilization mechanisms and particle-particle interactions at interfaces still remain to explore. In this paper, we first systematically review the historical understanding of particle-stabilized emulsions or bubbles and then give an overview of the most important and well-established progress in the understanding of particle-stabilized systems, including emulsions, foams and liquid marbles. The particle-adsorption phenomena have long been realized and been discussed in academic paper for more than one century and a quantitative model was proposed in the early 1980s. The theory can successfully explain the adsorption of solid particles onto interface from energy reduction approaches. The stability of emulsions and foams can be readily correlated to the wettability of the particles towards the two phases. And extensive researches on emulsion stability and various strategies have been developed to prepared dispersion systems with a certain trigger such as pH and temperature. After that, we discuss recent development of the interactions between particles when they are trapped at the interface and highlight open questions in this field. There exists a huge gap between theoretical approaches and experimental results on the interactions of particles adsorbed at interfaces due to demanding experimental devices and skills. In practice, it is customary to use flat surfaces/interfaces as model surfaces to investigate the particle-particle at interfaces although most of the time interfaces are produced with a certain curvature. It is shown that the introduction of particles onto interfaces can generate charges at the interfaces which could possibly account for the long range electrostatic interactions. Finally, we illustrate that particle-stabilized dispersions have been found wide applications in many fields and applications such as microcapsules, food, biomedical carriers, and dry water. One of the most investigated areas is the microencapsulation of actives based on Pickering emulsion templates. The particles adsorbed at the interface can serve as interfacial stabilizers as well as constituting components of shells of colloidal microcapsules. Emulsions stabilized by solid particles derived from natural and bio-related sources are promising platforms to be applied in food related industries. Emulsion systems stabilized by solid particles of the w/w (water-in-water) feature are discussed. This special type of emulsion is attracting increasing attentions due to their all water features. Besides of oil-water interface, particle stabilized air-water interface share similar stabilization mechanism and several applications reported in the literature are subsequently discussed. We hope that this paper can encourage more scientists to engage in the studies of particle-stabilized interfaces and more novel applications can be proposed based on this mechanism

The human brain comprises over 100 billion neurons that communicate with each other via electrical activities called action potentials. Sensory perception, cognition, and behavior all emerge from these activities. Neuroengineering is a developing interdisciplinary field that employs knowledge from neurobiology, electrical and electronic engineering, materials science and engineering, computer science, and many others. Neuroengineering aims to develop tools for understanding the mechanism of brain function at the circuit level, and to further the development of neuromodulation strategy and neuroprosthetics for motor, sensory, and mental rehabilitation from disabilities and illnesses.

For high spatial and temporal resolution interfacing with neurons in the brain, implantable multielectrode arrays (MEAs) are a key member of the family of neuroengineering devices, which are designed and fabricated for in vivo electrophysiology, deep brain stimulation, and brain-computer interfaces (BCIs). On the one hand, action potential recording from MEAs can indicate the subject's mental state and movement intentions, thus enabling the BCI technology to control external motor restoration devices such as robotic arms. On the other hand, neural stimulation electrodes can modulate abnormal neural activity and treat disorders like Parkinson's disease, epilepsy, and depression. The physical and chemical properties of the electrodes, nanofabrication of arrays, and electrode–tissue interface materials are all important research subjects in translational neuroscience studies, and the utilization of nanomaterials and nanodevices continuously improves neural electrode technologies.

At present, neural interface technology is confronting numerous challenges and opportunities, especially for in vivo neural circuit analysis, neuroelectronic medicine, and functional neuromodulation. The development of neural interface devices eagerly demands super-high-density, mesoscopic recording, minimal invasion, biosignal stability, and wireless interfacing. Achievement of these next-generation neural interface technology capabilities requires collaboration between neuroscientists, neurosurgeons, material scientists, microelectronic engineers, and many others.

A human brain is composed of a large number of interconnected neurons forming a neural network. To study the functional mechanism of the neural network, it is necessary to record the activity of individual neurons over a large area simultaneously. Brain-computer interface (BCI) refers to the connection established between the human/animal brain and computers/other electronic devices, which enables direct interaction between the brain and external devices. It plays an important role in understanding, protecting, and simulating the brain, especially in helping patients with neurological disorders to restore their impaired motor and sensory functions. Neural electrodes are electrophysiological devices that form the core of BCI, which convert neuronal electrical signals (carried by ions) into general electrical signals (carried by electrons). They can record or interfere with the state of neural activity. The Utah Electrode Array (UEA) designed by the University of Utah is a mainstream neural electrode fabricated by bulk micromachining. Its unique three-dimensional needle-like structure enables each electrode to obtain high spatiotemporal resolution and good insulation between each other. After implantation, the tip of each electrode affects only a small group of neurons around it even allowing to record the action potential of a single neuron. The availability of a large number of electrodes, high quality of signals, and long service life has made UEA the first choice for collecting neuronal signals. Moreover, UEA is the only implantable neural electrode that can record signals in the human cerebral cortex. This article mainly serves as an introduction to the construction, manufacturing process, and functioning of UEA, with a focus on the research progress in fabricating high-density electrode arrays, wireless neural interfaces, and optrode arrays using silicon, glass, and metal as that material of construction. We also discuss the surface modification techniques that can be used to reduce the electrode impedance, minimize the rejection by brain tissue, and improve the corrosion resistance of the electrode. In addition, we summarize the clinical applications where patients can control external devices and get sensory feedback by implanting UEA. Furthermore, we discuss the challenges faced by existing electrodes such as the difficulty in increasing electrode density, poor response of integrated wireless neural interface, and the problems of biocompatibility. To achieve stability and durability of the electrode, advancements in both material science and manufacturing technology are required. We hope that this review can broaden the scope of ideas for the development of UEA. The realization of a fully implantable neural microsystem can contribute to an improved understanding of the functional mechanisms of the neural network and treatment of neurological diseases.

Peptide-based supramolecular colloids are assembled systems based on weak interactions between peptides (such as hydrogen bonding, electrostatic forces, hydrophobic effects, π–π interactions, and van der Waals forces), spontaneously formed in a bottom-up manner. Peptide-based supramolecular colloids have ordered molecular arrangements and regular structures, with characteristics of both traditional colloids and supramolecular systems. Constructing functional supramolecular colloids via weak intermolecular interactions assists in understanding the process of biomolecular self-assembly in vivo and provides an effective strategy for designing supramolecular materials with excellent performance. Peptides, consisting of several amino acids, are elegant building blocks in supramolecular chemistry as well as colloid and interface chemistry because of their biological origin, clear composition, low immunogenicity, structural programmability, excellent biosafety, and high biodegradability. Based on the approach of supramolecular self-assembly, peptides can be manipulated to form multiscale and multifunctional colloidal systems, which have widespread applications in medicine, catalysis, energy, nanotechnology, and other fields. However, the realization of precise control of the structures and functions of these supramolecular colloids through peptide design and intermolecular interactions regulation remains an important issue to be addressed. To study the assembly process and physicochemical mechanism of supramolecular colloids at the molecular scale, and to explore the relationship between colloidal structure and function, the construction and functionalization of supramolecular colloids must be achieved. This work is a systematic summary of the assembly mechanism, structures, and functions as well as the state of the art of peptide-based supramolecular colloids with emphasis on the regulation of intermolecular interactions and structure-function relationships. The research progress of peptide-based supramolecular colloids in the following fields is summarized herein: i) biomimetic photosynthesis, including light capture and charge separation; and ii) tumor phototherapies, including photothermal therapy (PTT) and photodynamic therapy (PDT). Currently, it is feasible to induce functional enhancement of peptide colloids via supramolecular assembly. The most important aspect is to design the primary structure of the peptide building block, to precisely control the weak interactions between peptide molecules and rationally optimize the self-assembly process, and control the size and structure of the assemblies. Follow-up studies should focus on the design of molecular precursors, the combination of basic research and practical application of peptide-based supramolecular colloids will be essential. The advantages of peptide-based supramolecular colloids, including their ordered organization, flexible structures, and versatile functions, will open up novel avenues for various applications of supramolecular colloids in fields such as green energy and medicine. It is hoped that this review will provide inspiration and broaden ideas to further drive the development and application of supramolecular colloids.

In this study, pure Bi₂MoO₆ was synthesized via a solvothermal method. A ZnCuAl-layered double hydroxide (LDH)/Bi₂MoO₆ (denoted as LDH/Bi₂MoO₆) nanocomposite was synthesized via a steady-state co-precipitation route using Bi₂MoO₆ as the matric material. LDH was deposited on the surface of Bi₂MoO₆ with a close contact interface. The specific surface area of the resulting LDH/Bi₂MoO₆ composite increased up to 19.1 m²∙g⁻¹ owing to the stacking arrangement between LDH and the Bi₂MoO₆ nanosheets, resulting in the generation of a large number of reactive sites. In addition, the light absorption region of the LDH/Bi₂MoO₆ composite was larger than those of pure LDH and Bi₂MoO₆ because of the formation of a heterojunction structure and the possible quantum size effect. The photocatalytic performance of the as-prepared samples was evaluated by carrying out the degradation of rhodamine B (RhB) using them under visible light irradiation. Compared to pure LDH and Bi₂MoO₆, the LDH/Bi₂MoO₆ nanocomposite exhibited enhanced photocatalytic activity for the degradation of RhB. With an increase in the LDH content, the photocatalytic activity of the LDH/Bi₂MoO₆ composite first increased and then decreased. Although the addition of an optimum amount of LDH was beneficial for the generation of electron-hole pairs, excessive LDH on the surface of Bi₂MoO₆ decreased the visible light absorption ability of both the components, thus reducing photocatalytic activity of the composite. This indicates that an appropriate LDH:Bi₂MoO₆ molar ratio is necessary for obtaining LDH/Bi₂MoO₆ composites with excellent photocatalytic activity. Furthermore, the LDH/Bi₂MoO₆ composite showed high photocatalytic stability and reusability. The structure of the LDH/Bi₂MoO₆ composite remained almost unchanged even after four photodegradation cycles. The enhanced photocatalytic performance of the composite can be attributed to the combined effect of its heterojunction structure and high specific surface area, which are beneficial for effective separation of photogenerated charge carriers and the availability of a large number of active sites for photocatalysis. It was found that •OH and O₂^•− were the main reactive species, while e⁻ and h⁺ contributed little to the photodegradation process. The generation, transfer, and separation of photoinduced electrons and holes in the composites were investigated by transient photocurrent responses, electrochemical impedance spectroscopy Nyquist plots, and photoluminescence measurements. The results showed that the heterojunction structure of the composites played a key role in enhancing their photocatalytic activity. A possible photodegradation mechanism was proposed for the composite. This study will provide a facile approach for the preparation of LDH- and/or Bi₂MoO₆-based nanocomposites. The LDH/Bi₂MoO₆ nanocomposite prepared in this study showed huge potential to be used as a visible-light photocatalyst for degrading environmental pollutants.

In recent years, aqueous sodium-ion batteries (ASIBs) have experienced rapid development, and a series of cathode materials for ASIBs has been widely reported. Among these, Na_0.44MnO₂ possesses the most promising prospects due to its low cost, non-toxic nature, simple synthesis, and structural stability. However, the reported capacity of Na_0.44MnO₂ in aqueous electrolyte was ~40 mAh·g⁻¹ (less than its theoretical capacity of 121 mAh·g⁻¹), which limits its practical applications. Recently, we developed a novel alkaline Zn-Na_0.44MnO₂ dual-ion battery using Na_0.44MnO₂ as the cathode, a Zn metal sheet as the anode, and a 6 mol L⁻¹ NaOH aqueous solution as the electrolyte. In this system, the Na_0.44MnO₂ electrode presented excellent electrochemical performance with high reversible capacity (80.2 mAh·g⁻¹ at 0.5C) and outstanding cycling stability (73% capacity retention over 1000 cycles at 10C) in alkaline aqueous electrolyte. When the negative potential window was extended to 0.3 V, the Na_0.44MnO₂ electrode delivered an incredibly high capacity of 345.5 mAh·g⁻¹, which far exceeded the theoretical capacity, but the cycling performance was extremely poor. In that study, X-ray diffraction (XRD) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) analyses revealed that de-intercalation of Na⁺ and formation of Mn(OH)₂ occurred during the discharge process, but the detailed electrochemical mechanism and structural evolution of this process remained unclear. In this study, we used ICP-AES to analyze the elemental composition of discharge products at different discharge depths and found that a small amount of Na⁺ ions extracted from Na_0.44MnO₂ electrode since Discharge-120 (corresponding to the discharge capacity of 120 mAh·g⁻¹), and the extraction rate increased gradually with increasing discharge depth. Scanning electron microscope (SEM) and XRD analyses were also carried out to characterize the morphology and phase changes of Na_0.44MnO₂ electrode during discharge. The results show that the discharge of Na_0.44MnO₂ electrode in the voltage range 1.95–0.3 V could be divided into the three following steps: (1) the potential range above 1.0 V: Na⁺ ions de-intercalate reversibly into the tunnel structure of Na_0.44MnO₂; this discharge mechanism is consistent with that in non-aqueous and neutral aqueous sodium ion batteries. (2) The initial platform region at 1.0 V: in this step, protons (H⁺) began to insert into the Na⁺-vacancies in Na_xMnO₂, and the tunnel structure of Na_xMnO₂ was still maintained. (3) Subsequent slope region: when the Na⁺-vacancies in the tunnel structure were fully occupied by protons, further intercalation led to intensification of charge repulsion in the crystal structure. Thus, the tunnel structure collapsed to form a new Mn(OH)₂ phase, accompanied by the release of Na⁺ from the structure. H⁺ has a smaller radius than Na⁺; therefore, it could insert into the smaller vacancies in Na_0.44MnO₂, resulting in higher specific capacity. However, the insertion of H⁺ will also cause structural damage, which seriously worsens the cycling stability of the Na_0.44MnO₂ electrode.

In the last thirty years, Gemini surfactants with various structures have been designed, synthesized, and demonstrated to show superior physicochemical properties. However, the utilization of non-degradable surfactants, including these Gemini surfactants, poses a threat to the environment; hence, degradable Gemini surfactants are desirable. Herein, biodegradable cationic Gemini surfactants with amide or ester groups in the hydrophobic chains or the spacer were synthesized. A monomeric surfactant containing an amide group and a Gemini surfactant with amide groups both in the hydrophobic chains and the spacer were synthesized for comparison. The effects of amide group location on the aggregation behavior of Gemini surfactants were studied systematically. The differences between the Gemini surfactants with amide groups and Gemini surfactants with ester groups were evaluated by comparing their aggregation behavior and hydrogen bonding formation. The Gemini surfactants with amide groups (C₁₂A-C_n-AC₁₂) in the chains showed much larger exothermic ΔH_mic and more negative ΔG_mic values than those of the corresponding monomeric surfactant C₁₂A; besides, their critical micelle concentration (cmc) was more than one order of magnitude lower than that of C₁₂A. The amide groups located in the hydrophobic alkyl chains promoted hydrogen bonding formation and self-assembly of the Gemini surfactants C₁₂A-C_n-AC₁₂. Moreover, ¹H NMR spectra revealed that the co-effect of a short spacer and hydrogen bonding leads to slow exchange of the C₁₂A-C₂-AC₁₂ molecules between the monomer and the aggregate. For the Gemini surfactant series C₁₂-AC_nA-C₁₂, the amide groups notably increased the spacer length, and largest cmc value and smallest exothermic ΔH_mic value were observed for C₁₂-AC₂A-C₁₂ instead of C₁₂-AC₆A-C₁₂. In C₁₂-AC₁₂A-C₁₂, the spacer was long and sufficiently flexible to adopt a "U"-shaped conformation above the cmc, and it acted as the hydrophobic part of the surfactant, as confirmed by ¹H NMR spectra. Among the Gemini surfactant with amide groups in both the spacer and the hydrophobic alkyl chains, C₁₂A-AC₆A-AC₁₂ had a smaller cmc and I₁/I₃ ratio as well as more exothermic ΔH_mic values than those of C₁₂A-C₆-AC₁₂ and C₁₂-AC₆A-C₁₂. ¹H NMR spectra indicated that an ester-alcohol structural equilibrium exists during aggregation for the Gemini surfactants with ester groups. In addition, the Gemini surfactants with ester groups formed water-mediated hydrogen bonds in the aggregates. This water-mediated hydrogen bonding between ester groups was weaker than the direct hydrogen bonding between amide groups. Therefore, the Gemini surfactants with ester groups, C₁₂E-C₆-EC₁₂ and C₁₂-EC₆E-C₁₂, exhibited lower surface activity, a larger micelle ionization degree, higher micropolarity, and smaller exothermic ΔH_mic and less negative ΔG_mic values than their counterparts with amide groups, C₁₂A-C₆-AC₁₂ and C₁₂-AC₆A-C₁₂.

Energy components used in solid rocket propellants are beneficial for improving the energy performance, and their thermal decomposition characteristics significantly affect the combustion properties of the propellants. As a kind of energetic material with both high energy and low sensitivity (impact and friction), 5, 5'-bistetrazole-1, 1'-diolate (TKX-50) can effectively improve the energy and safety characteristics of solid propellants. Burning catalyst is another important component of solid propellants, which can significantly improve the burning rate of the propellant and reduce the pressure exponent. Among various burning catalysts, nanoscale transition metal oxides can promote the thermal decomposition of the energetic component, thus enhancing the combustion properties of the solid propellant. However, the catalytic effects of nanoscale transition metal oxides with different morphologies on the thermal decomposition of TKX-50 have rarely been studied. Based on the excellent catalytic activity of Fe₂O₃ for TKX-50 thermal decomposition, nano-Fe₂O₃ particles with spherical and tubular microstructures were used for TKX-50 thermal decomposition. The Fe₂O₃ nanoparticles were successfully fabricated via the solvothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. The XRD, FT-IR, and XPS results confirmed the successful fabrication of spherical and tubular Fe₂O₃ samples. The SEM and TEM images showed that the spherical Fe₂O₃ samples are composed of agglomerated Fe₂O₃ nanoparticles with an average particle size of 110 nm. In addition, the average diameter and length of hollow tubular Fe₂O₃ nanoparticles are 120 nm and 200 nm, respectively. The catalytic activities of spherical and tubular Fe₂O₃ for TKX-50 decomposition were studied by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) methods. The DSC and TG-DTG curves showed that both tubular and spherical Fe₂O₃ could effectively promote TKX-50 thermal decomposition. The first thermal decomposition peak temperature (T_FDP) of TKX-50 was reduced by 36.5 K and 26.3 K in the presence of tubular and spherical Fe₂O₃, respectively, at 10 K·min⁻¹. The activation energy (E_a) of TKX-50, determined by the iso-conversional method, was significantly reduced in the presence of both tubular and spherical Fe₂O₃. The results indicated that the microstructure of the catalyst has a significant effect on its catalytic performance for TKX-50 thermal decomposition, and that tubular Fe₂O₃ with hollow microstructure possesses better catalytic activity than spherical Fe₂O₃. The excellent catalytic activity of tubular Fe₂O₃ can be attributed to the hollow microstructure, which has more active sites for TKX-50 thermal decomposition.

Atomic-scale characterization of the atomic structure as well as molecular adsorption on an alloy surface plays a vital role in elucidating the catalytic mechanism of effective catalysts. Au-Cu alloy nanoparticles have important applications in catalyzing CO oxidation and CO₂ reduction. However, the atomic-scale properties of Au-Cu alloy surfaces are rarely investigated. In particular, the physical and chemical properties of singly-dispersed doping atoms, either Au in Cu or vice versa, as well as their influence on the overall surface properties, have not been studied in detail. In response, we first prepared low-coverage bimetallic Au/Cu(111) and Cu/Au(111) films, which were then annealed at high temperature to realize single atomically-dispersed Au/Cu(111) and Cu/Au(111) surface alloys (SA). We characterized the surface structures and adsorption properties by low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS). For the SA-Au/Cu(111) system, we found that Au atoms can be incorporated in both the skin and subsurface layer of the Cu(111) substrate. These species can be readily distinguished from the topography contrast in STM. Moreover, STS measurements showed clear differences between the electronic states of doped Au atoms and the Cu host. In particular, we found that Au in the skin layer was strengthened while the subsurface Au showed weakened filled states at approximately −0.5 eV compared with the Cu(111) surface, which corresponds to the characteristic Shockley state of an Au surface. These altered electronic properties at the sites of doped atoms are also reflected by changes in the interactions with probe molecules. Adsorption experiments showed that Au atoms in the top surface prevented the binding of CO molecules, causing various adsorption vacancies in the CO adlayer. In contrast, the subsurface Au atoms had little influence on surface binding with CO molecules. For the SA-Cu/Au(111) system, we found that Cu atoms tend to aggregate into small clusters in the subsurface region of the Au(111) substrate. Only few Cu atoms can be stabilized at the elbow positions of the reconstructed top surface of Au(111). Adsorption experiments showed that only Cu atoms in the skin layer can adsorb CO molecules at liquid nitrogen temperature, while the subsurface Cu atoms cannot. On the other hand, the Au atoms around the doped Cu atoms do not seem to be influenced at all, possibly because of the weak effect of Cu. These experimental results provide details on the atomistic aspects of Au-Cu alloy surfaces, which can improve our understanding of the catalytic mechanism of Au-Cu alloy catalysts.

Molecular electronics is an important field for the application of nanotechnologies with an ultimate goal of building functional devices using single molecules or molecular arrays to realize the same functionality as macroscopic devices. To attain this goal, reliable techniques for measuring and manipulating electron transfer processes through single molecules are essential. There are various techniques and many environmental factors influencing single-molecule electronic conductance measurements. In this review, we first provide a detailed introduction and classification of the current well-accepted techniques in this field for measuring single-molecule conductance. All available techniques are summarized into two categories: the fixed junction technique and break junction technique. The break junction technique involves repeatedly forming and breaking molecular junctions by mechanically controlling a pair of electrodes moving into and out of contact in the presence of target molecules. Single-molecule conductance can be determined from the conductance plateaus that appear in typical conductance decay traces when molecules bind two electrodes during their separation process. In contrast, the fixed junction technique is to fix the distance between a pair of electrodes and measure the conductance fluctuations when a single molecule binds the two electrodes stochastically. Both techniques comprise different application methods and have been employed preferentially by different groups. Specific features of both techniques and their intrinsic advantages are compared and summarized in Section 4.

Next, we systematically summarize the factors affecting the molecular conductance during the course of measurements, which are the focus of the current academic community in the field. As shown in the middle of the image above, the electrode, anchoring group, and target molecule are the three key elements in constructing a single-molecule junction. The contact geometry between the molecule and the electrode and the associated coupling strength can profoundly affect the conductance characteristics of single molecules. The properties of anchoring groups can determine whether a molecule is primarily transported by electrons or holes. A good selection of electrode materials can improve the yield of single-molecule junctions and facilitate strong electronic couplings with the target molecules. The conductance characteristics of saturated and conjugated molecules are quite different due to their diverse band gaps. Moreover, various substituents can be modified onto the backbone of the molecules, which can raise or lower the energy level of the frontier orbitals of molecules to different degrees, thereby affecting the conductance properties of target molecules. In addition to these factors for the key elements, the investigated molecules can be measured in a variety of environments, including organic solvents, high vacuum, aqueous solution, ionic liquids, or the atmosphere, and the work function of the metal contact may change in different environments. The change in work function can change the gap between the electrode Fermi energy and the frontier orbital of a target molecule, influencing the measured conductance. Additionally, both the electrical field orientation and the bias values applied have a significant effect on the molecular structures and thus their conductance characteristics. Temperature can also affect the charge transport when hopping dominates the transport mechanism. Meanwhile, pH affects the interactions between H⁺/OH^- and the anchoring groups, which indirectly induces a change in the tunneling barrier.

In this review, the influencing factors are comprehensively illustrated from two perspectives: internal factors (anchoring group, electrode, and target molecule) and external factors (voltage, temperature, solvent, pH value, and others). In addition, new approaches for modulating the molecular conductance (modulation of energy levels, light or heat stimulation, and others) that have been developed in recent years are reviewed, and investigations of chemical reactions at the single-molecule level using these methods are highlighted. Finally, the potential applications of these techniques and correlated modulating approaches are summarized and a prospective is provided for the field of single-molecule electronics.

Materials such as metals, semiconductors, and oxides are attractive at nanometer scales due to the physical and chemical property differences with their bulk counterparts as induced by the quantum confinement effect and large surface-to-volume ratios. In particular, heterogeneous nanostructures consisting of semiconductors and noble metals are extremely important because of the synergistic effects occurring at the interfaces between their noble metal and semiconductor domains; these often equip the heterogeneous nanostructures with improved properties compared to those of isolated individual components. Thus far, heterogeneous nanostructures have garnered a considerable research interest, and tremendous development in achieving high degree control over these nanostructures with respect to their domain size, morphology, and composition has been realized. Their immense application potential in optics, catalysis, imaging, and biomedicine render them a field full of original innovation possibilities. Herein, we demonstrate a phenomenon observed in core-shell nanostructures composed of noble metals and silver sulfide (Ag₂S): the inside-out migration of noble metals in Ag₂S nanoparticles. We prepare core-shell nanostructures with noble metals and Ag₂S residing at the core and shell regions, respectively, through various synthetic strategies including seed-mediated growth and galvanic replacement reactions followed by sulfidation. We then characterize the core-shell nanostructures before and after aging them in toluene at room temperature (e.g. 25 ℃) for a period of time up to 72 h. In contrast to the reported diffusion of Au from the outside to the inside of InAs or PbTe nanoparticles, which results in an Au core encapsulated by an amorphous InAs or PbTe shell, the noble metals (Au, Ag, Pd, or Pt) in core-shell nanostructures with noble metals and Ag₂S residing at the core and shell regions, respectively, are found to diffuse from the inside to the outside through the Ag₂S shell. Thus, heterogeneous nanodimers consisting of the corresponding noble metal and Ag₂S are formed. Observations using an electron transmission microscope confirm that the inside-out migration of noble metals in Ag₂S is carried out in a holistic manner. Due to the apparent interface mismatch between face-centered cubic noble metals and monoclinic Ag₂S crystal phases, defects such as vacancies must exist at these interfaces. This makes the migration of noble metals in Ag₂S possible by either a vacancy/substitutional mechanism or by the self-purification mechanism that occurs intrinsically in nanoscale semiconductors. As the migration rate of noble metals in Ag₂S increases with the decrease in the size of the noble metal core and the radius of noble metal atoms, the inside-out migration rates of Ag, Pd, and Pt in Ag₂S are found to be much higher than that of Au because of their smaller particle sizes or atom radii. This scientific phenomenon can be effective in the development of synthetic routes for heterogeneous nanostructures that might not be obtained by conventional methods.

Biological assemblies with specific function or pathogenicity are widespread within organisms; however, their insolubility, amorphous properties, and large size are the major obstacles for structure determination via solution NMR spectroscopy and X-ray crystallography. In contrast, solid-state NMR (ssNMR) spectroscopy is not limited by the solubility or crystallinity of the sample and is a potent method to determine the structure of protein assemblies at atomic resolution. High magnetic field, fast magic-angle spinning (MAS), isotope labeling schemes, and improved methodology in ssNMR have enabled resonance assignment and restraints in structure determination among protein assemblies. This review first discusses methods of obtaining structural restraints by ssNMR. Optimization of sample preparation is an effective approach to increase homogeneity in the conformation, thus also improving the resolution of ssNMR spectra. Furthermore, the resolution of ¹³C spectra can be further improved by using ¹³C sparse labeling strategies with selective labeling of carbon sources during protein expression. Structure characterization by ssNMR is based on structural restraints via multidimensional experiments correlating resonance between ¹³C and ¹⁵N. Protein secondary structure can be ascertained through chemical shifts involving ¹³Cα, ¹³Cβ, ¹³C', and ¹⁵N. The backbone torsion angle can be predicted using TALOS+ based on these chemical shifts. Site-specific structural restraints are accessible from 2D experiments such as ¹³C-¹³C, e.g., proton-driven spin diffusion (PDSD), dipolar-assisted rotational resonance (DARR), proton-assisted recoupling (PAR) and ¹³C-¹⁵N, e.g., transferred-echo double-resonance (TEDOR), rotational-echo double-resonance (REDOR). An additional issue is to distinguish inter-molecular and intra-molecular restraints. Preparations of mixed labeled samples (e.g., 50% ¹³C uniformly labeled subunits and 50% uniformly ¹⁵N labeled subunits) have yielded abundant structural restraints from ssNMR data, facilitating high-resolution structural analysis. Further, hybrid approaches based on ssNMR are discussed. Electron microscopy (EM) is a suitable method to investigate structural features including the diameter of the protein assemblies, which is "invisible" through ssNMR analysis. Scanning transmission electron microscopy (STEM) can help determine the mass-per-length parameters (MPL) of unbranched fibrils, thus confirming the number of subunits in a layer of fibrils. Cryo-EM is a powerful technique to describe the molecular envelope of protein assemblies. Cryo-EM potentially yields the density map and long-range symmetry parameters, while ssNMR provides atomic-level structural details; hence, Cryo-EM and ssNMR are highly complementary methods. X-ray diffraction can help determine the distance (4.5–4.7 Å, 1 Å = 0.1 nm) along the fibril axis between adjacent polypeptide chains in β-strand conformation, generally referred to as the "cross-β" structure. Rosetta has simulated the protein structure in accordance with structural data obtained from protein data bank (PDB) with the same peptide sequence. On combining ssNMR with those methods, more abundant structural information may be obtained, thus shortening the structural calculation cycle. Finally, a detailed description of the ssNMR structural data on amyloid-β (Aβ) fibrils and T3SS needles are provided as examples. Various structural characteristics of Aβ40/Aβ42 were reported by several groups, including the trimeric or dimeric conformations, parallel or antiparallel, in-register or out-of-register arrangements of the β-strands, demonstrating the structural polymorphism of Aβ40/Aβ42. Atomic-resolution structures of T3SS needles were analyzed on the basis of high-resolution spectra, using ¹³C sparse-labeled and ssNMR-Cryo-EM-Rosetta hybrid approaches, indicating that hybrid approaches based on ssNMR are a powerful tool to determine the high-resolution structure of protein assemblies.

The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo₂O₄) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo₂O₄ nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo₂O₄ products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo₂O₄ electrode materials were studied and the area capacitance was found to be 1.26 C·cm^-2 at a current density of 1 mA·cm^-2. Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA·cm^-2) were achieved. It was found that the Ni foam supporting the NiCo₂O₄ nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the as-synthesized NiCo₂O₄ nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh·cm^-3 at 1.56 and 4.5 W·cm^-3, respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo₂O₄ nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems.

The regulation of supramolecular chirality has applications in various aspects including asymmetric catalysis, chiral sensing, optical materials and smart devices. Additionally, it provides opportunities for the simulation of important activities in living organisms and the clarification of their mechanisms. Herein, we synthesized a chiral gelator SQLG (styrylquinoxalinyl L-amino glutamic diamide) containing a π-conjugated headgroup by introducing the quinoxaline-derived moiety into L-glutamic diamide-based amphiphile via two simple condensation steps. SQLG self-assembled into nanofibers through multiple intermolecular interactions, including π–π stacking, hydrogen bonding and van der Waals interaction, leading to gelation of various organic solvents ranging from nonpolar to polar ones. Chirality transfer from the chiral center to the supramolecular level was observed when organogels formed, which manifested itself in circular dichroism (CD) spectra. The organogels formed in polar solvents such as N, N-dimethylformamide (DMF) and nonpolar solvents such as toluene exhibited opposite signals of supramolecular chirality, attributed to different hydrogen bonding strengths and thus two different types of gelator stacking modes of the gelators which was confirmed by infrared spectroscopy (IR) and X-ray diffraction (XRD). Circular polarized luminescence (CPL) denotes left-handed or right-handed circularly polarized light with different intensities emitted by the chiral luminescent system, and it characterizes the chirality of the excited state, which finds potential application in fields such as 3D optical displays, optical data storage, polarization-based information encryption and bioencoding. Owing to the strong fluorescence and supramolecular chirality, the toluene gel emitted right-handed circular polarized luminescence upon excitation, while the gel formed in DMF did not exhibit CPL emission because of its relatively weak fluorescence. Furthermore, the organogels responded rapidly and distinctly to the stimulus of acid due to the proton-accepting sites in the quinoxaline skeleton. Utilizing NMR spectroscopy, we found that the two nitrogen atoms in the quinoxaline moiety could be protonated upon acidification. During the process, intramolecular charge transfer (ICT) was significantly strengthened and the driving forces of self-assembly underwent remarkable changes, resulting in the collapse of the yellow transparent organogel into a red dispersion. Meanwhile, transformation from nanofibers to nanospheres was observed using a scanning electron microscope (SEM). With change in stacking modes in the supramolecular assembly, a complete inversion of the CD signal was detected. The CPL signal was found to be switched off, which along with the other changes of the system could subsequently be recovered by neutralization of the entire system. Therefore, we constructed a chiroptical switch with multiple stimuli-responsiveness through the introduction of an acid-sensitive π-conjugated moiety into the L-glutamic diamide-based chiral amphiphile.

The micelles of zwitterionic betaine surfactant, SB3-12, have good biocompatibility and smaller negative charge density on the surface due to the electrostatic neutralization on the polar head that consists of two opposite charges. However, the available charge density on the micellar surface is essential for its application as a drug carrier owing to either the increased binding to cells or its favorable delivery into some specific organs under physiological conditions. This also facilitates the selective solubilization of drug molecules, depending on the interaction between the surfactant headgroup and drug molecule. When an anionic sodium dodecyl sulfate (SDS) is incorporated into SB3-12 micelles, the negative charge density of the micellar surface (from the sulfonic groups) can be continuously adjusted with a negative-positive order of the zwitterionic headgroup, where the electrostatic interaction occurs with the positively charged quaternary ammonium in the inner layer of the micellar polar region. Accordingly, positive micelles with adjustable charge density could be obtained if a cationic surfactant is incorporated into the micelles of the zwitterionic surfactant with a positive-negative headgroup. Using isothermal titration calorimetry, it is determined that a strong synergistic interaction occurs between SB3-12 and SDS, followed by a significant decrease in the mixed critical micelle concentration (CMC) and micellization enthalpy, which is mainly caused by weak electrostatic interaction. The synergistic effect is similar to that in the case of oppositely charged surfactant mixtures; however, the mixtures of zwitterionic and ionic surfactants do not form catanionic precipitates even at an equimolar ratio. When rutin, a model drug, is added to the SB3-12/SDS solution mixture, both SDS and the negatively charged rutin, obtained from the dissociation of the hydrogen of 7-hydroxyl group of rutin, can together interact with SB3-12 forming mixed micelles. The dissolved rutin molecules do not change the mixed CMC and the solubility of rutin is approximately constant when the composition of the mixed surfactants is in the range of 0.5 < x_SB3-12 < 1; however, these can significantly enhance the electrostatic interaction between the mixed micelle and rutin molecule as x_SB3-12 decreases. This can possibly allow the controlled release of rutin. UV-visible absorption spectroscopy and ¹H NMR spectroscopy reveal that in SB3-12 micelles, the A ring of rutin is located near the positively charged quaternary ammonium group of SB3-12, and the B ring is located between the oppositely charged headgroups of SB3-12. In SDS micelles, the B ring is located on the palisade layer and the A ring and disaccharide are exposed to the aqueous phase. For the mixed SB3-12/SDS micelles, as the molar fraction of SDS increases, the electrostatic attraction toward the A ring weakens. The role of ionic surfactant in adjusting the surface charge density of the zwitterionic surfactant micelles allows the fine-tuning of the physical and chemical properties of polar micellar region, thereby exhibiting the potential for selective solubilization and controlled release of drugs.

Dynamic regulation of self-assembly is of vital importance in chemistry, biology and material science thanks to its great potential for development of smart materials and devices. Polyoxometalates (POMs) are a class of functional inorganic nanoclusters, which has become one of the excellent building blocks for supramolecular self-assemblies, especially when covalently or non-covalently modified by organic species. As typical stimuli-responsive functional clusters, the POMs could be photochemically or electrochemically reduced to mixed-valence states, of which the structural integrity remains even after encountering stepwise multi-electron redox process. The intriguing photochromism of the POMs in different states exhibits distinct photophysical properties, which motivates us to exploit the dynamic self-assemblies of POM-based complexes. The divalent Lindqvist-type hexamolybdate cluster [Mo₆O₁₉]^2- is one of the least negative-charged POMs, which is the ideal building blocks to construct novel assembly structures. Based on this motivation, herein, a single chain surfactant-encapsulated polyoxometalate (POM) complex (ODTA)₂[Mo₆O₁₉] was prepared by simple counterion replacement of Lindqvist-type (TBA)₂[Mo₆O₁₉] with octadecyltrimethylammonium (ODTA) in acetonitrile solution. The structure of the POM complex was confirmed by ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and elemental analysis. The solution of complex (ODTA)₂[Mo₆O₁₉] in the mixed solvents of acetonitrile and isopropanol with the volume ration of 4 to 1 exhibited reversible photochromism upon alternate UV light irradiation and air exposure. Upon UV light irradiation, the light yellow transparent solution of (ODTA)₂[Mo₆O₁₉] turned into blue quickly. The new broad absorption band appearing at ca.751 nm assigned to the Mo^V → Mo^VI intervalence charge-transfer (IVCT) transition, indicated the formation of reduced POM, as revealed by UV-Vis absorption spectra. After exposed to air, the blue solution was bleached. The alternate photochromism could be conducted for multiple cycles. Helical self-assembled morphology of (ODTA)₂[Mo₆O₁₉] was formed in acetonitrile/isopropanol, characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods. More interestingly, morphology transformation of the complex from helical strips to spherical assemblies occurred accompanied by photochromism occurrence. The morphology evolution during the photochromism process experienced from shortened helical strips through sea urchin-like aggregates to spherical assemblies. Most significantly, the helical assemblies could be recovered again after air oxidation, implying the reversible morphology transformation driven by redox stimulus. The redox-modulated reversible self-assembly is driven by the variation of electrostatic attraction between organic cations and inorganic anions as well as the electrostatic repulsion between inorganic ionic clusters, proved by X-ray photoelectron spectroscopy (XPS) and ¹H NMR spectra. The results will contribute to better understanding the mechanism of dynamic assemblies and inspire the precise fabrication of advanced smart materials.

Separation and recycling of catalysts are crucial for realizing the objectives of sustainable and green chemistry but remain a great challenge, especially for enzyme biocatalysts. In this work, we report a new solvent-induced reversible inversion of Pickering emulsions stabilized by Janus mesosilica nanosheets (JMSNs), which is then utilized as a strategy for the in situ separation and recycling of enzymes. The interfacial active solid particle JMSNs is carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption experiments, Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA).The JMSNs are demonstrated to show order-oriented mesochannels with a large specific surface area, and the hydrophobic octylgroup is selectively modified on one side of the nanosheets. Furthermore, the inversion is found to be a fast process that is strongly dependent on the interfacial activity of the solid emulsifier JMSNs. Such a phase inversion is also a general process that can be realized in various oil/water phasic systems, including ethyl acetate-water, octane-water, and cyclohexane-water systems. By carefully analyzing the capacity of JMSNs with different surface wettabilities for phase inversion, a triphase contact angle (θ) close to 90° and a critical oil-water ratio of 1 : 2 are identified as the key factors to achieve solvent-induced phase inversion via a catastrophic phase inversion mechanism. Importantly, this reversible phase inversion is suitable for the separation and recycling of enzyme biocatalysts that are sensitive to changes in the reaction medium. Specifically, during the reaction, the organic substrates are dissolved in the oil droplets and the water-soluble catalysts are dispersed in the water phase, while a majority of the product is released into the upper oil phase and the enzyme catalyst is confined inside the water droplets in the bottom layer after phase inversion. The perpendicular mesochannels of JMSNs provide a highly accessible reaction interface, and their excellent interfacial activity allows for more than 10 rounds of consecutive phase inversions by simply adjusting the ratio of oil to water in the system. Using the enzymatic hydrolysis kinetic resolution of racemic acetate as an example, our Pickering emulsion system shows not only a 3-fold enhanced activity but also excellent recyclability. Because no sensitive chemical reagents are used in this phase inversion process, the intrinsic activities of the catalysts can be preserved even after seven cycles. The current study provides an alternative strategy for the separation and recycling of enzymes, in addition to revealing a new innovative application for Janus-type nanoparticles.

High-performance solid propellants are very important for the development of modern weapons. Aside from their high energy and high burning rate, safety performance is regarded as the most important factor that should be considered whenever a new solid propellant recipe is formulated. Therefore, exploring a new type of combustion catalyst that can improve both catalytic activity and reduce the sensitivity of the energetic component is significant. Traditionally, transition metals or metal oxides are used as a combustion catalyst for accelerating the thermal decomposition of energetic components. However, the existing problem of these catalysts is the aggregation of particles accompanied by poor surface area. Coupling metal oxides with graphene is a promising approach to obtain a binary composite with stable structure and large specific surface area. In this work, rod-like and granular Fe₂O₃ nanoparticles were synthesized using a hydrothermal method. Then, the two as-prepared Fe₂O₃ nanoparticles were coupled with graphene sheets using an interfacial self-assembly method, which can effectively prevent the aggregation of Fe₂O₃ particles and simultaneously increase the active sites that participate in the reaction. X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the phase states and chemical compositions of the prepared samples. The morphology and internal structures were further demonstrated through scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption tests. Both phase analysis and structure identification indicate that the prepared Fe₂O₃/G has high purity and high surface area. The catalytic performance of the prepared Fe₂O₃ and Fe₂O₃/G in the thermal decomposition of hexanitrohexaazaisowurtzitane (CL-20) was evaluated based on thermal gravimetric analysis-infrared spectroscopy (TGA-IR) and differential scanning calorimetry (DSC) tests. The non-isothermal decomposition kinetics of CL-20, Fe₂O₃/CL-20, and Fe₂O₃/G/CL-20 were further studied by DSC. The results reveal the excellent catalytic activity of Fe₂O₃/G in the thermal decomposition of CL-20, which is attributed to the presence of abundant pore structure and large surface area. The reaction mechanisms of the exothermic decomposition process of CL-20, Fe₂O₃/CL-20, and Fe₂O₃/G/CL-20 were obtained by the logical choice method, and the composites all followed same mechanism function model as CL-20. Through comparison, the rod-like Fe₂O₃ coupled with graphene was found to have the best catalytic activity in the thermal decomposition of CL-20. Thus, the rod-like Fe₂O₃ and its Fe₂O₃/G composite were used to investigate their influence on the impact sensitivity of CL-20 by fall hammer apparatus. The results show that rFe₂O₃/G can effectively decrease the impact sensitivity of CL-20 compared with pure CL-20 and rFe₂O₃/CL-20. Therefore, rFe₂O₃ coupled with graphene not only promotes the thermal decomposition but also improves the safety performance of CL-20.

Biological systems can be regarded as complex and open thermodynamic systems. All processes involved in biological growth and metabolism are accompanied by material and energy exchange. During metabolism, energy in the organisms is released in the form of heat, i.e., metabolic heat, which is the basis for development in the field of biothermochemistry. The calorimetric method considers the thermal effects produced by the various forms of action as the research object, to reveal the law of energy change and quantitative energy conversion. Studying the thermodynamic processes of complex biological systems and related reactions through microcalorimetry and thermodynamic methods reflects the intrinsic laws of life-related processes macroscopically and intrinsically. With the tremendous development and progress in microcalorimetry in terms of the temperature measurement accuracy, stability of temperature control, automation, and multi-functionalization, calorimetry has been widely used in life sciences. It can be used to describe macroscopic processes such as ecosystems and biological evolution, observe organismal and cell growth, examine mitochondrial metabolism, and study problems at the molecular level, including enzymatic reactions and interactions between small molecules and biomacromolecules. Herein, the application of biomass calorimetry in the life sciences is reviewed. The status and progress of biomass calorimetry at different biological and structural levels, such as the ecosystem, biological, organ, cellular, subcellular, and molecular levels are introduced. For example, soil microbial metabolic activity is a universal index for evaluating soil quality. The growth and metabolism of organisms as well as the physical and chemical processes of substances in soil are often accompanied by heat release, which is usually a nonselective signal. The use of isothermal microcalorimetry to nonspecifically monitor and record soil microbial metabolic characteristics has promoted the study of microbial metabolism in complex soil systems. The application of calorimetry to the study of tissues and organs mainly involves the calorimetric study of isolated animal and plant tissues and organs. Calorimetry of animal and microbial cells is considered the most common application of calorimetry in life sciences research. It mainly involves the classification and identification of bacteria, their growth and metabolism, inhibition mechanisms of drugs on microbial growth, principles of kinetics, and the thermodynamic characteristics of microbial growth and metabolism. However, owing to the lack of specificity of biomass calorimetry and the lack of direct access to information at the molecular level, more applications of calorimetry combined with other analytical techniques (especially in biology, medicine, and pharmacy) are needed in the future.

With the development of clean and sustainable energy sources, the demand for large-scale electrochemical energy storage systems has rapidly increased over the last few years. Rechargeable Na-ion batteries (NIBs), one of the most promising energy storage technologies, have received a great deal of attention. Titanium-based P2-type layered oxides are attractive candidates for NIB anode materials, owing to their suitable redox potential, low cost, air stability and high safety. The exposed large interlayers of P2 configuration provide facile channels for Na⁺ insertion/extraction when employed as electrode materials for room temperature, non-aqueous NIBs. In this paper, a novel P2-type Na_0.65Li_0.13Mg_0.13Ti_0.74O₂ is synthesized by a solid-state reaction method. An orthorhombic phase of Na_0.9Mg_0.45Ti_1.55O₂ is observed with the increase in calcination time. During the long calcination process, it is speculated that some lattice Na⁺ and Li⁺ of the previously formed P2 phase compound would be volatilized or extracted by O₂, forming a low Na-content orthorhombic phase based on the layered host structure. In particular, when the precursor was calcined at 1273 K for 24 h, a perfect biphasic hybrid composite was synthesized. The Na storage performance of the pure P2 compound and hybrid composite were evaluated respectively in sodium half cells with voltage range of 0.2–2.5 V. The P2-type electrode can deliver a reversible capacity of 85.1 mAh·g^-1 (theoretical capacity of approximately 108.5 mAh·g^-1), whereas, the sample with the orthorhombic phase shows an enhanced initial reversible capacity of 96.3 mAh·g^-1. Both of the curves are smooth with no observed plateau, indicating the good structural stability of the electrode during cycling. Thus, the hybrid composite exhibits better cycling performance (capacity retention of 89.7% vs. 84.4% for pure P2, after 400 cycles at current density of 1C) and better rate capability (56.6 mAh·g^-1 at 5C vs 47.1 mAh·g^-1 at 2C). These results can be attributed to the introduced second phase, which improves the electron and bulk ion conductivity and helps stabilize the structure. Therefore, this novel two-phase intergrowth composite could serve as a promising anode candidate for the large-scale energy storage application of NIBs. Moreover, this structural design strategy could be used for other layered oxides to improve their energy density and cycling stability.

Intermolecular interactions are the key to control the final structure and properties of polymers; however, molecular-level detection of complex interactions remains a challenge. In this study, a series of poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) solid films were prepared from aqueous solutions at different pHs. Multinuclear solid-state NMR (SSNMR) experiments, including one- and two-dimensional (1D and 2D) ¹H CRAMPS (Combined Rotation And Multiple Pulse NMR Spectroscopy) based on the continuous phase modulation technique, high-resolution ¹³C CPMAS (Cross-Polarization and Magic-Angle Spining), and ²³Na MQMAS (Multiple-Quantum MAS) experiments, were used to this in situ investigation of the structure and dynamics of these polymer blends. The ¹H CRAMPS experiments revealed different types of protons in the blends from the mutually hydrogen-bonded COOH groups, from the free COOH groups, the COOH groups bounded with water that undergo fast chemical exchange mutually, and the COOH groups interacting with PEO and from main chain groups. With increasing pH, most of these peaks decreased except for the main chain protons owing to the decrease in the hydrogen bonding interaction among PAA and PEO as well as water. These CRAMPS NMR techniques were also used to elucidate the molecular mobility of the different groups. Furthermore, 2D ¹H-¹H spin-exchange NMR experiments provided more detailed information about the interpolymer and water–polymer interactions. ¹H spin-diffusion experiments indicated the presence of phase separation in these blends, and the determined domain size of the mobile phase was approximately 17 nm. Two types of ²³Na sites were revealed by MQMAS experiment; in particular, the Na⁺ ionic location and interaction between individual polymers was revealed by ¹H detected ²³Na-¹H CP experiments, which showed that ²³Na is in the proximity of PAA instead of PEO. These SSNMR experimental results provide detailed information about the influence of hydrogen bonding interactions on the microcosmic structure and dynamics of PAA/PEO blends at the molecular level. The influence of different pH levels on the hydrogen bonding interactions, miscibility between PAA and PEO, microstructure, water–polymer interactions, and molecule mobility of individual compositions was clarified. Based on the above-mentioned NMR studies, we proposed a novel structural model of these PAA/PEO blends. This model successfully revealed the influence of pH on the microstructure and dynamics of PAA/PEO blends at the molecular level for the first time. Our results indicate that solid-state NMR is a powerful tool that can be used to study the complex interactions of multiphase polymer materials. Our research is of great significant to both the development of new methods to probe the weak interactions in polymers and the development of new polymer materials based on hydrogen bonding interactions.

Recently, MOF-derived metal oxides have been demonstrated as excellent semiconductor materials. Their derivatives can retain the high porosity and high specific surface area of the parent MOFs, effectively improving the adsorption capacity and mass transfer rate of reactive substances. Herein, UiO-67 was selected as the substrate due to its high hydrothermal stability and high specific surface area. Through the in situ growth of TiO₂ nanoparticles, a series of double metal composite catalysts (Zr_xTi/C) were produced after calcination at 400 ℃. The X-ray diffraction (XRD) patterns showed that the UiO-67 crystal structure of collapsed after calcination, forming a Zr-O-C/TiO₂ heterojunction. Energy-dispersive spectrometry (EDS) mapping images showed that Ti, Zr, and O were evenly distributed throughout the materials without obvious aggregation. Compared to conventional inorganic semiconductor materials, Zr_xTi/C heterojunction catalysts provided much higher BET surface area (317 m²·g^-1) for the effective enrichment of contaminants on the catalyst surface. Tetracycline was selected as a representative antibiotic to study photodegradation performance under a 300 W Xenon lamp. Among the obtained catalysts, the Zr_0.3Ti/C heterojunction catalyst exhibited the best photocatalytic efficiency, achieving 98% degradation within 30 min in a 10 mg·L^-1 tetracycline solution. Fluorescence spectra, electrochemical impedance spectroscopy, and transient photocurrent responses showed that the Zr_0.3Ti/C heterojunction catalyst exhibited the fastest charge-hole separation rate and a maximum photocurrent density of 8.75 μA·cm^-2, which was 2.64 and 3.71 times those of UiO-67 and UiO-67_0.3/TiO₂, respectively. The mechanism of tetracycline photodegradation was determined by UV-visible diffuse-reflectance absorption spectroscopy, Mott-Schottky plots, and electron spin resonance technology. A direct Z-scheme charge separation path was formed by the transfer and recombination of photoexcited e^- in the conduction band (CB) of Zr-O-C with h⁺ in the valence band (VB) of TiO₂, which effectively reduced the combination rate of e^- and h⁺ in Zr-O-C and TiO₂. The photodegradation rate constant of Zr_0.3Ti/C was 16 and 3.7 times those of TiO₂ and Zr-O-C, respectively, due to its large specific surface area and excellent tetracycline adsorption performance. Furthermore, the Zr-O-C/TiO₂ heterostructure exhibiting suitable energy level matching and containing highly conductive carbon material improved the separation and migration of electron-hole pairs. Mechanistic studies revealed that the three types of radicals, superoxide radicals (O₂^•-), hydroxyl radicals (•OH), and a small amount of holes (h⁺) simultaneously promoted tetracycline photodegradation. After five recycling tests, Zr_0.3Ti/C heterojunction catalyst maintained 91.2% removal efficiency for tetracycline, indicating good cycle stability. Combining the synergistic effects of adsorption and photodegradation, using bimetallic heterojunction composites with high specific surface area is promising for the photodegradation of environmental pollutants.

Wormlike micelles and low-molecular-weight hydrogels are composed of three-dimensional networks that endow them with viscoelasticity, but their viscoelastic properties are markedly different. The viscosity of wormlike micelles is attributed to a transient network, while that of gels is due to a stable network. Under certain conditions, wormlike micelles can undergo transition to gels with an increase in the density of the network. In our previous study, we found that the wormlike micelle formed by the ionic liquid-type surfactant 1-hexadecyl-3-octyl imidazolium bromide ([C₁₆imC₈]Br) without any additive has high viscoelasticity. The inclusion of a nonionic surfactant polyoxyethylene lauryl ether (Brij 30) is expected to enhance the viscoelasticity of [C₁₆imC₈]Br wormlike micelles via electrostatic shielding and strong hydrophobic interactions, which may be the driving factor for the wormlike micelle-to-gel structural transition. The morphology and viscoelasticity of [C₁₆imC₈]Br wormlike micelles with Brij 30 were studied as a function of concentration by rheological measurements and freeze-fracture transmission electron microscopy. The thermal stability and gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br gels were studied using rheology. The interaction between Brij 30 and [C₁₆imC₈]Br was studied by zeta potential measurements and nuclear magnetic resonance (NMR) spectroscopy. Upon the inclusion of Brij 30 into the [C₁₆imC₈]Br wormlike micelles, the viscoelasticity of the Brij 30/[C₁₆imC₈]Br samples first increased and then decreased with an increase in the Brij 30 concentration, at different initial concentrations of [C₁₆imC₈]Br. At a certain Brij 30 concentration, the Brij 30/[C₁₆imC₈]Br samples rheologically behaved as a gel. The maximum viscoelasticity of the [C₁₆imC₈]Br (4.06% (w))/Brij 30 gel was observed at a Brij 30/[C₁₆imC₈]Br molar ratio of 4.55. The viscoelasticity of the Brij 30/[C₁₆imC₈]Br gels was positively correlated with the activation energy of the gels. The gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br gels also increased first and then decreased with an increase in the Brij 30 concentration. The highest gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br (4.06% (w)) gel was observed at a Brij 30/[C₁₆imC₈]Br molar ratio of 2.93. The Brij 30 concentration had a notable impact on the viscoelasticity, thermal stability, and gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br gels. The zeta potential and ¹H NMR measurements revealed that the neutral Brij 30 molecules are inserted into the palisade layer of the [C₁₆imC₈]Br wormlike micelles via hydrophobic interactions. This decreased the electrostatic repulsion between the [C₁₆imC₈]Br headgroups, which in turn induced the rapid growth of wormlike micelles and the formation of a stiffer network structure. Finally, the wormlike micelles underwent a structural transition to gels. The obtained results would aid in better understanding the relationship between wormlike micelles and gels, and may be of potential value for industrial and technological applications.

Along with the promising applications of lanthanide doped upconversion nanomaterials in diverse fields such as biology, anti-counterfeiting, and lasering, the demand for multifunctional upconversion nanomaterials is increasing. One effective means of obtaining these nanomaterials is to fabricate upconversion nanomaterial-based heterostructures, which may provide superior properties as compared to the sum of the parts. However, obtaining heterostructured upconversion nanomaterials remains challenging mainly because of the crystal lattice mismatch between upconversion nanomaterials and other materials. Typically used strategies for synthesizing upconversion nanomaterial-based heterostructures are applicable only to limited types of materials. Alternatively, transformation of the intermediate layer is a promising strategy used to obtain these heterostructures. Nevertheless, this method remains in its infancy and, to date, only a few intermediate layers have been developed. New types of intermediate layers are therefore highly desirable. In this study, we show that amorphous Y(OH)CO₃ can be a promising candidate as an intermediate layer for fabricating upconversion nanoparticle-based heterostructures. As a proof-of-concept experiment, ligand-free NaGdF₄:Yb/Tm upconversion nanoparticles were first prepared as core nanoparticles. The Y(OH)CO₃ shell was then directly coated on the NaGdF₄:Yb/Tm upconversion nanoparticles in an aqueous solution using urea and Y(NO₃)₃, by a homogeneous precipitation approach. The thickness of the resulting Y(OH)CO₃ shell could be tuned by adjusting the amounts of either urea or Y(NO₃)₃. The as-coated Y(OH)CO₃ shell could be easily converted to YOF by heating at 300 ℃, yielding NaGdF₄:Yb/Tm@YOF core-shell heterostructured nanoparticles. In addition, we found that the NaGdF₄ core could be transformed to lanthanide oxide fluoride if the NaGdF₄:Yb/Tm@Y(OH)CO₃ core-shell nanoparticles were heated at 350 ℃. We also observed that treating the NaGdF₄:Yb/Tm@Y(OH)CO₃ core-shell nanoparticles at even higher temperatures (e.g., 400 ℃) produced aggregations of nanoparticles without regular morphologies. The transformation of the shell can be attributed to the decomposition of Y(OH)CO₃ and reactions between the Y(OH)CO₃ shell and NaGdF₄ core. Meanwhile, the transformation of the NaGdF₄ core at relatively high temperatures could be primarily due to the reactions between Y(OH)CO₃ and NaGdF₄. Notably, in this study, the core-shell structured nanoparticles, with either a Y(OH)CO₃ or YOF shell, maintained the photon upconversion properties of NaGdF₄:Yb/Tm upconversion nanoparticles. In addition, the method used here could be extended to the coating of other shells such as Tb(OH)CO₃ and Yb(OH)CO₃ on upconversion nanoparticles. Moreover, the NaGdF₄:Yb/Tm@Y(OH)CO₃ core-shell nanoparticles could be transformed to other nanoparticles with novel structures such as yolk-shell nanoparticles. These results can pave the way for preparing upconversion nanoparticle-based heterostructures and multifunctional composites, thus promoting new applications of upconversion nanoparticles.

The self-assembly of colloidal nanocrystals has emerged as a powerful strategy for the bottom-up fabrication of functional materials and nanodevices. Recently, the self-assembly of gold nanorods (GNRs) has attracted significant attention because of their unique plasmonic properties, but the realization of their adjustable self-assembly of GNRs through facile and effective approaches remains challenging. In this work, the controllable self-assembly of GNRs in aqueous solution was realized through the host-guest interactions of cyclodextrins (CDs) and the cetyltrimethylammonium bromide (CTAB) molecules adsorbed on the surface of the GNRs. The self-assembly of GNRs was readily achieved by the addition of aqueous α-CD solutions with varied concentrations into aqueous dispersions of CTAB-stabilized GNRs. At a relatively low α-CD concentration, slow aggregation of the GNRs occurred, resulting in their side-by-side assembly. This was revealed by the blue shift of the longitudinal surface plasmon resonance (LSPR) band in the absorption spectra and confirmed by transmission electron microscopy (TEM) observations. On the other hand, when a higher concentration of α-CD was added, fast aggregation of the GNRs occurred, resulting in their end-to-end assembly. This was revealed by the red shift in the LSPR band together with the TEM observations. If β-CD was employed instead of α-CD, the self-assembly of GNRs could also be induced, although a relatively higher concentration of β-CD was required to achieve the extent of aggregation similar to that induced by α-CD, indicating that the supramolecular host–guest interaction between CDs and the surfactant CTAB was crucial to the directed self-assembly of GNRs. Furthermore, the α-CD-induced assembly was inhibited on addition of excess CTAB, confirming that the supramolecular interaction of α-CD and CTAB played a key role in directing the self-assembly of the GNRs. Based on these experimental results, a possible mechanism for the α-CD-induced self-assembly of GNRs was proposed as follows: at a lower α-CD concentration, the gradual formation of the host-guest inclusion complex α-CD/CTAB led to the partial replacement of the highly charged CTAB bilayers adsorbed on the GNRs by the less charged complex, which resulted in a slow side-by-side assembly of the GNRs; at a higher α-CD concentration, the CTAB bilayers were quickly replaced by the α-CD/CTAB complex, and the CTAB molecules adsorbed at both ends of the GNRs were almost completely replaced, resulting in a fast end-to-end assembly of the GNRs. Additionally, on the basis of the hydrolysis of α-cyclodextrin catalyzed by α-amylase, the self-assembly of GNRs directed by the host-guest interaction could be used to realize the feasible detection of α-amylase in solutions. This self-assembly strategy mediated by the host-guest interaction may be extendable to other colloidal systems involving surfactants adsorbed on the surface of nanoparticles, and may open new avenues for the controllable self-assembly of non-spherical nanoparticles.

As the application of lithium-ion batteries in advanced consumer electronics, energy storage systems, plug-in hybrid electric vehicles, and electric vehicles increases, there has emerged an urgent need for increasing the energy density of such batteries. Lithium metal anode is considered as the "Holy Grail" for high-energy-density electrochemical energy storage systems because of its low reduction potential (-3.04 V vs standard hydrogen electrode) and high theoretical specific capacity (3860 mAh·g^-1). However, the practical application of lithium metal anode in rechargeable batteries is severely limited by irregular lithium dendrite growth and high reactivity with the electrolytes, leading to poor safety performance and low coulombic efficiency. Recent research progress has been well documented to suppress dendrite growth for achieving long-term stability of lithium anode, such as building artificial protection layers, developing novel electrolyte additives, constructing solid electrolytes, using functional separator, designing composite electrode or three-dimensional lithium-hosted material. Among them, the use of electrolyte additives is regarded as one of the most effective and economical methods to improve the performance of lithium-ion batteries. As a natural polyphenol compound, tannic acid (TA) is significantly cheaper and more abundant compared with dopamine, which is widely used for the material preparation and modification in the field of lithium-ion batteries. Herein, TA is first reported as an efficient electrolyte film-forming additive for lithium metal anode. By adding 0.15% (mass fraction, wt.) TA into the base electrolyte of 1 mol·L^-1 LiPF₆-EC/DMC/EMC (1 : 1 : 1, by wt.), the symmetric Li|Li cell exhibited a more stable cyclability of 270 h than that of only 170 h observed for the Li|Li cell without TA under the same current density of 1 mA·cm^-2 and capacity of 1 mAh·cm^-2 (with a cutoff voltage of 0.1 V). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and energy-dispersive X-ray spectroscopy (EDS) analyses demonstrated that TA participated in the formation of a dense solid electrolyte interface (SEI) layer on the surface of the lithium metal. A possible reaction mechanism is proposed here, wherein the small amount of added polyphenol compound could have facilitated the formation of LiF through the hydrolysis of LiPF₆, following which the resulting phenoxide could react with dimethyl carbonate (DMC) through transesterification to form a cross-linked polymer, thereby forming a unique organic/inorganic composite SEI film that significantly improved the electrochemical performance of the lithium metal anode. These results demonstrate that TA can be used as a promising film-forming additive for the lithium metal anode.

Peer review plays a crucial role in the fair and efficient allocation of high-quality research grants. This invited comment analyzes the fuzzy criteria and a possible bias in the peer review process, and explores the use of a potential approach based on fuzzy sets for tackling this challenge.

Lithium (Li) metal is considered a promising anode material for high energy density secondary Li metal batteries because it has the highest specific energy (3860 mAh·g^-1) and lowest redox potential (-3.04 V compared to standard hydrogen electrodes. However, the development of high-performance Li metal batteries is challenging. Firstly, Li dendrites tend to grow on the surface of Li metal foil, leading to a limited anodic coulombic efficiency (CE), poor cyclability, and even explosion hazards when an internal cell short circuit occurs. Moreover, Li metal suffers from serious surface stability problems and is easily corroded by electrolytes during cycling, further resulting in low CE, thus shortening the life cycle. We have developed a Li-carbon nanotube (Li-CNT) composite microsphere via a facile molten impregnation method. The Li-CNT composite's CNT framework can suppress volume changes during the charge/discharge process and help stabilize the solid electrolyte interphase (SEI), which is typically mechanically fragile. As a result, Li-CNT shows a high specific capacity (2000 mAh·g^-1) and can significantly suppress dendrite formation by reducing the current density, resulting in enhanced safety and cycling stability. However, the large specific surface area of the Li-CNT microspheres also enables increased reaction with the air and the electrolyte. A passivation layer is critical for the practical application of Li-CNT during the electrochemical cycling and manufacturing process. LiF is an important component of SEI in the liquid electrolyte system, and a uniform and dense LiF-rich SEI film can enable stable cycling. Moreover, LiF has been widely used as the preferred coating material to protect Li metal anodes through different methods. In this study, we improved the Li-CNT composite stability by constructing a uniform LiF-rich protecting layer on the surface through in situ polymerization of 4-fluorostyrene. The F functional group of 4-fluorostyrene, which is a lithiophilic group, reacts with the Li-CNT to produce a uniform LiF-rich layer on the surface of the Li-CNT via a facile and scalable liquid-phase reaction. The resulting passivation layer effectively suppresses the Li-CNT corrosion by the electrolyte and air, leading to better environmental and electrochemical stability. Consequently, after exposure to dry-air with a dew point -40 ℃ for 24 h, the specific capacity of the surface passivated Li-CNT is still as high as 1129 mAh·g^-1, corresponding to a capacity retention of 52.85%. When the surface passivated Li-CNT is paired with a LiFePO₄ cathode (the capacity ratio of cathode and anode is 1 : 6), a prolonged lifespan of over 280 cycles at 0.5C was reached, corresponding to a CE of 97.7%. The in situ polymerization passivation is simple and easy to be scale up; thus, it is a promising method for developing Li metal anodes towards the practical Li metal batteries.

In this work, light-responsive viscoelastic wormlike micelles based on cetyltrimethylammonium hydroxide (CTAOH) and cinnamic acid derivatives, including cinnamic acid (CA), 2-methoxycinnamic acid (2-MCA), 3-methoxycinnamic acid (3-MCA), 4-methoxycinnamic acid (4-MCA), 2, 3-dimethoxycinnamic acid (2, 3-DMCA), 2, 4-dimethoxycinnamic acid (2, 4-DMCA), 2, 3, 4-trimethoxycinnamic acid (2, 3, 4-DMCA), and 3, 4, 5-trimethoxycinnamic acid (3, 4, 5-DMCA), were prepared. The effects of the CA derivative structures, especially the position and number of methoxy moieties, on the formation of wormlike micelles were systematically determined. The CA derivatives facilitated the formation of long and entangled wormlike micelles. ¹H NMR results showed that the CA derivatives participated in the formation of wormlike micelles via insertion of the aromatic moieties into the aggregates. The number of methoxy moieties had a much stronger effect on the viscosity of the wormlike micelle solution than the position of this moiety. The larger the number of methoxy moiety, the smaller was the aggregate. Substituted methoxy moieties increased the steric hindrance between the surfactants and CA molecules, thus hindering the formation of large aggregates. However, the position of the methoxy moiety had a predominant effect on the UV-light-induced transition of the wormlike micelles. Specifically, the ortho-methoxy moiety in the CA molecules dramatically enhanced the efficiency of UV-light-induced trans-cis isomerization. For example, the 2-MCA/CTAOH, 3-MCA/CTAOH, and 4-MCA/CTAOH binary systems (90 mmol·L^-1/100 mmol·L^-1) were gel-like with similar viscosities of around 20 Pa·s, but after UV light irradiation, they were transformed into a fluid with lower viscosity because of the formation of smaller aggregates. However, the irradiation time required for the transition varied significantly, as suggested by the results of viscosity measurements and UV-Vis spectroscopy. The 2-MCA/CTAOH system underwent complete phase transition within 3 h, whereas continuous transitions were observed for the 3-MCA/CTAOH and 4-MCA/CTAOH systems upon irradiation for 24 h. ¹H NMR results suggested that the change in the configuration of MCA in the micelles before and after irradiation was the major cause of the abovementioned difference in the phase transition pattern. Initially, all the aromatic moieties of the trans-2-MCA molecules were deeply inserted into the hydrophobic cores of the micelles in a vertical manner, and the ionized carboxyl moiety was located in the palisade layer because of the electrostatic interactions between CTAOH and trans-2-MCA. In contrast, cis-2-MCA was inserted into the micelles in a horizontal manner, and some of the protons in the aromatic moiety were also transferred from the micellar core to the polar palisade layer. Accordingly, the CTAOH and cis-2-MCA molecules were packed loosely in the aggregates, thereby resulting in the formation of spherical micelles. Similar UV-light-induced transitions were observed for the 3-MCA/CTAOH and 4-MCA/CTAOH systems.

Solid-state Li metal batteries are considered promising next-generation energy storage systems due to its exceptional advantages in terms of safety and high energy density. The continuous process on the development of solid-state fast ionic electrolytes enables the solid-state battery to operate at room temperature. Among these, sulfide-based solid electrolytes have attracted significant attentions due to their extremely high ionic conductivity, excellent deformability, and mild low-temperature processability. However, the full demonstration of practical batteries remains challenging due to the slow lithium-ion transport kinetics at working solid-solid interfaces. The sluggish interfacial transport kinetics mainly result from the poor solid-solid contacts, resulting in poor battery performance. Especially for solid-state pouch cells, the high local current due to the poor contact is amplified by the high working current, leading to rapid failure. Constructing fast ion transport paths between the Li metal anode and solid electrolyte interface is key for the practical application of solid-state batteries. Here a simple protocol was developed to realize fast ionic transportation by wetting the solid electrolyte/Li metal anode interface with localized high salt concentration liquid electrolyte. First, 3.5 mmol lithium trifluoroalfonylimide (LiTFSI) was added into 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether (HFE) and dimethoxyethane (DME) mixed solvent, and stirred to obtain uniformly dispersed localized high-concentration liquid electrolyte, denoted as HFE-DME LiTFSI. The fluidity of liquid electrolyte ensures sufficiently conformal contacts between lithium anode and liquid electrolyte, as well as solid-state electrolyte and liquid electrolyte. Thus, fast ion transportation channels were constructed between the solid electrolyte and Li metal anode by wetting HFE-DME LiTFSI at a concentration of 3.0 μL·cm^-2. After liquid phase therapy, the interfacial resistance of solid-state Li|Li₄Ti₅O₁₂ (LTO) pouch cell rapidly reduced from 4366 to 64 Ω·cm^-2 and even lower than the cell that was pressed at 3 MPa in the assemble process (340 Ω·cm^-2). This suggests that the ion transport kinetics are significantly improved by liquid phase therapy. Therefore, the solid-state Li metal pouch cell with dimensions of 30 mm × 30 mm showed excellent cycling performances with specific capacities of 107 and 96 mAh·g^-1 at 0.1C and 0.5C, respectively. Furthermore, the solid-state Li-S pouch cell delivered capacities of 1100 and 932 mAh·g^-1 at 0.01C and 0.02C, respectively. This study demonstrates the effectiveness of the novel liquid phase therapy to construct fast ionic transportation channels, which providing an effective strategy for the practical application of solid-state Li metal pouch cells.

Nervous system injury can disrupt communications between neurons, leading to loss of basic nerve functions and even paralysis. The clinical prognosis of nervous system injury is usually poor. This adversely affects the physical and mental health of patients and their families, and causes serious economic losses to the society. Due to slow and incomplete healing, the regenerative capacity of the nervous system is limited. Despite development of various biomedical treatment options such as, stem cell transplantation, neurotrophic factors and scaffold application, it is still very difficult to achieve adequate therapeutic effects that can benefit clinical practice. It is worth noting that nervous system components are closely related to electric fields (EFs), and a fundamental property of neurons is plasticity in response to endogenous and exogenous electrical stimulations. Electrical stimulation has been applied by researchers to induce nerve repair. This review summarizes the progress in research on EFs on neurons and applications of EFs in the treatment of peripheral nerve system and central nerve system injuries, focusing on the methods and effects of electrical stimulation. Research using direct, alternating, and pulsed EFs, with various parameters, has all demonstrated its positive effects on nerve healing and motor function recovery. Research on nanogenerators (NGs), a novel electrical stimulation technology that can convert mechanical energy into electrical energy, has achieved great progress in recent years. In biomedicine, NGs can collect the mechanical energy of human motion and convert it into electrical stimulations without requiring an external power supply, which can lead to significant innovations in electrical stimulation therapy. This review also discusses the recent applications of NGs in the treatment of nervous system diseases. NGs can be used to fabricate miniature, ultra-thin, flexible, and biodegradable healthcare devices according to different application scenarios such as in vivo or in vitro. NGs have enabled specific applications in deep brain stimulation, peripheral nerve stimulation, muscle stimulation, and sensory substitution to restore nervous system function. In order to apply electrical stimulation therapy in the clinical setting and improve the quality of life of patients with neurological injuries, further research into stimulation devices and their settings and parameters is highly desirable.

Perovskite solar cells (PSCs) have recently become one of the fastest-growing research fields. Furthermore, the PSCs that have a SnO₂ nanoparticle layer as an electron transport layer (ETL) have received extensive attention. The SnO₂-ETL layer can be prepared at a low temperature, which makes it suitable for flexible device development. However, the energy levels of the SnO₂ layer do not sufficiently match the energy levels of the perovskite light-absorbing layer, which largely affects the charge carrier extraction and reduces the open current–voltage (V_oc) of PSCs. Additionally, the interface between the ETL and perovskite layer always has defects, which cause charge recombination and affect the power conversion efficiency (PCE) of PSCs. Therefore, the interfacial engineering at the SnO₂/perovskite layer is crucial to address these issues. Researchers are looking for suitable passivation materials that could align the energy band and decrease the defect density. Halide materials, such as KCl and NH₄Cl, are promising solutions to solve these problems. However, the preparation process has to be explored, and the mechanism of halide ions at the interface is unclear. This study investigates the effects of SnO₂ surface halogenation on the photovoltaic performance of PSCs in depth. The SnO₂ surface was passivated using tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide (TBAB), and tetrabutylammonium iodide (TBAI) and the concentration gradient of the passivation solution was studied. Extensive characterization of the perovskite layers and PSC devices demonstrated the positive effects of SnO₂ surface halogenation on the SnO₂/perovskite interfacial properties. The causes of improved performance of the interfacial-engineered devices were studied using charge carrier dynamics. Interfacial engineering was further investigated by performing first-principles calculations based on density functional theory (DFT) to determine the energy, structure, charge density, density of states, work function, etc. Experiments and theoretical calculations proved that TBAC could be an optimal passivation material for the SnO₂ surface. Furthermore, the passivation effect became more apparent with the increase in solution concentration. TBAC could promote perovskite crystal growth, decrease defects at the interface, and increase the internal recombination resistance. Consequently, the photovoltaic performance of PSCs was improved. The halide ions on the SnO₂ surface could interact with Sn atoms, which increase the charge density and achieves high-efficiency charge extraction. This work shows the significance of improving the photovoltaic performance of PSCs along with providing physical principles for the interfacial engineering of PSCs toward achieving high efficiency.

Resveratrol is a natural polyphenol and phytoalexin with anti-inflammatory, anti-oxidant, anti-cancer, and neuroprotective effects. However, resveratrol exhibits low solubility, light sensitivity, poor absorption by oral administration, and short cycle time, which greatly limit its applications in medicine and the food industry. To overcome these limitations, a nano-resveratrol liposome (RES-Lip) was prepared. As a drug carrier, liposomes have many advantages such as good targeting properties, low toxicity, biocompatibility, and long-term sustained release. In liposomal studies, the oil-water (n-octanol-water) partition coefficient (P_o/w) is often used to predict the encapsulation and drug loading efficiencies. This method focuses on the lipophilicity of the drug, reflecting its hydrophobic action while ignoring the biological properties of the biofilm. The liposome-water partition coefficient (P_lip/w) reflects the structure of the biofilms and its interaction with drugs governed by factors including hydrophobicity, electrostatic forces, and hydrogen bonding. Herein, RES-Lip was successfully prepared using a rotary-evaporated film-ultrasonication method and subsequent characterization by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The effects of the membrane to material ratio (lecithin to cholesterol mass ratio m_PC : m_Chol = 5 : 1, 8 : 1, 10 : 1, and 12 : 1) and drug to lipid ratio (drug to lecithin mass ratio m_RES : m_PC = 1 : 25, 1 : 40, 1 : 50, and 1 : 60) of nano-resveratrol liposomes on the liposome-water partition coefficient (P_lip/w) were determined. Changes in the oil-water partition coefficient (lgP_o/w) and liposome-water partition coefficient (lgP_lip/w) as a function of pH were also determined. In addition, the Gibbs free energy between the drug and phospholipid bilayer membrane in RES-Lip was calculated. The results showed that RES-Lip adopted a spherical vesicle structure with a particle size of approximately 100 nm. When the membrane to material ratio was 10 : 1 and the drug to lipid ratio was 1 : 40, lgP_lip/w was maximized, indicating that the combined forces between RES and the phospholipid membrane were the highest at these ratios. The trends of lgP_o/w and lgP_lip/w as a function of pH were the same, indicating that the main interaction force between RES and the phospholipid membrane was the hydrophobic effect with secondary interaction forces of hydrogen bonding and electrostatic interaction. The Gibbs free energy between the RES and liposome membrane in RES-Lip was determined to be −17.07 kJ·mol⁻¹.

As opposed to nanoparticles, atomically precise metal clusters possess a well-defined surface and crystal structure, which aids in understanding the relationship between the structure and chemical reactivity at the atomic level. As an interesting subgroup of metal cluster compounds, heterometallic lanthanide-titanium oxo clusters (LnTOCs) have attracted extensive attention due to their interesting chemical properties. However, the controlled precise synthesis of LnTOCs remains a great challenge because of the intense hydrolysis of Ti⁴⁺ ions and the competitive coordination of Ln³⁺ ions. Owing to this synthetic difficulty, high-nuclearity LnTOCs are very rare, which obstructs further studies on their properties. Choosing the appropriate chelating ligands should be an effective strategy to synthesize LnTOCs because chelating ligands can reduce the degree of hydrolysis of Ti⁴⁺ ions. Herein, four new LnTOCs, formulated as [EuTi₆(μ₃-O)₃(OC₂H₅)₈(dtbsa)₆(Hdtbsa)]·(C₂H₅OH) (1), [EuTi₇(μ₃-O)₃(μ₂-OH)₂(OⁱPr)₉(dtbsa)₆(Hdtbsa)Cl]·(HOⁱPr)₃ (2), [EuTi₇(μ₃-O)₃(μ₂-OH)₂(OⁱPr)₈(dtbsa)₇(Hdtbsa)]·(HOⁱPr)₃ (3), and [LaTi₇(μ₃-O)₃(μ₂-OH)₂(OC₂H₅)₈(dtbsa)₇(Hdtbsa)]₂·(C₂H₅OH)₄ (4), were prepared by a solvothermal method via the reaction of 3, 5-di-tert-butylsalicylic acid (H₂dtbsa), rare-earth salts, and Ti(OⁱPr)₄. Single-crystal analysis showed that the heptanuclear compound 1 contains a EuTi₆ metal core featuring a trigonal prismatic structure, wherein Eu³⁺ is located at the center of the prism formed by six Ti⁴⁺ ions. The metal core structure of octanuclear compounds 2 and 3 can be viewed as the EuTi₆ unit in 1 connected to another Ti⁴⁺ on one side of the triangular prism. The metal framework of Ln₂Ti₁₄ in 4 can be regarded as a dimer of EuTi₇ in 2. UV-Vis diffuse reflectance spectra revealed that the band gaps of 1, 2, and 3 (2.35, 2.07, and 2.16 eV, respectively) are significantly smaller than that of anatase (3.2 eV). The results of photoelectric tests indicated that the three clusters show an obvious photoelectric response, and the charge separation efficiency of 1 and 2 was better than that of 3. In order to explore the applications of these compounds to photocatalysis, H₂ production by light-driven water splitting under irradiation by a 300 W Xe lamp (300–800 nm) in an aqueous methanol solution (20 mL, 10%) was attempted. The H₂ production rates for 1, 2, and 3 were 112, 106, and 87 μmol∙h^-1∙g^-1, respectively, which were higher than that obtained with the commercial P25. Powder X-ray diffraction (PXRD) spectra and thermogravimetry (TGA) profiles confirmed the optical and thermal stability of the three clusters. This work not only provides a chelating ligand strategy for the synthesis of LnTOCs but also reveals their light-driven photocatalytic activity stemming from the small band-gap.

Graphite phase carbon nitride (g-C₃N₄) has shown excellent potential when applied to photocatalytic hydrogen (H₂) generation upon exposure to visible light. However, the photocatalytic activity during hydrogen generation remains very low because of the high recombination rate of photogenerated electron-hole pairs and poor conductivity. Of the various strategies to improve H₂ generation efficiency, N vacancies have proven to be effective at increasing the photocatalytic performance of g-C₃N₄. However, creating a N vacancy is primarily dependent on the post-heating of g-C₃N₄ in air at an elevated temperature, which generates a high concentration of N vacancies and consequent decreased crystallinity of g-C₃N₄. Thus, as-produced g-C₃N₄ offers low photocatalytic efficiency owing to the high recombination rate of photogenerated electron-hole pairs. Currently, controlling the concentration of N vacancy in g-C₃N₄ is an immense challenge. Herein, we report an effective means of achieving controllable N vacancies in g-C₃N₄ via urea in-situ generated NH₃ at an elevated temperature. Specifically, g-C₃N₄ was first prepared with dicyandiamide as a precursor and subjected to rapid post-thermal treatment at 650 ℃ in a tubular furnace for 10 min, in which a desired amount of urea was mixed with g-C₃N₄ as the source material for NH₃. X-ray diffraction analysis showed increased crystallinity and an unchanged crystal structure as compared to pristine g-C₃N₄. X-ray photoelectron spectroscopy and elemental analysis verified the reduced levels of N-vacancy concentration with urea added as the NH₃ source when compared to the g-C₃N₄ post-heated in air without the addition of urea. In addition, UV-Vis spectra displayed an increased visible light absorption due to the generated N vacancies. Moreover, the specific surface area of g-C₃N₄ was progressively enlarged with an increase in the amount of urea added. The high crystallinity, low N-vacancy concentration, increased light absorption, and enlarged surface area translated into markedly increased photocatalytic H₂ generation. The highest H₂ generation rate from the optimized added amount of urea was 6.5 μmol·h^-1, which was three times higher than that when using a g-C₃N₄ sample thermally treated without urea addition. The H₂ generation enhancement was also the result of the increased separation efficiency of photogenerated electron-hole pairs as exemplified by the significantly decreased photoluminescence spectra and large transient photocurrent. The results of this study demonstrate the simultaneous production of highly crystalline g-C₃N₄ and controllable creation of N vacancy by in-situ generated NH₃ through thermal decomposition of urea. This study reveals the immense potential of NH₃ at controlling the N-vacancy concentration of g-C₃N₄ for increased photocatalytic H₂ generation.

The electrocatalytic CO₂ reduction reaction (CO₂RR) driven by renewable energy is an efficient approach to achieve the conversion and utilization of CO₂. In this context, CO₂RR has become an emerging research focus in the field of electrocatalysis over the past decade. While a large number of nanostructured catalysts have been developed to accelerate CO₂RR, the tradeoff between activity and selectivity usually renders the overall electrocatalytic performance very poor. Beyond catalyst design, rationally designing electrolyzers is also of substantial importance for improving the CO₂RR performance and achieving its scale-up for practical applications. To a large extent, the electrolyzer configuration determines the local reaction environment near an electrode by affecting the process conditions, thereby resulting in remarkably different electrocatalytic performances. To be techno-economically viable, the performance of CO₂ electrolyzers is expected to be at least comparable to that of the current state-of-the-art proton exchange membrane (PEM) water electrolyzers, with regard to their activity, selectivity, and stability. Researchers have made great progress in the development of CO₂ electrolyzers over the past few years, but they are also facing many issues and challenges. This review aims to provide an in-depth analysis of the research progress and status of current CO₂ electrolyzers including H-cell, flow-cell, and membrane electrode assembly cell (MEA-cell) electrolyzers. Herein, operation at industrial current densities (> 200 mA∙cm⁻²) is set as a basis when these electrolyzers are discussed and compared in terms of the four main figures of merit (current density, Faradic efficiency, energy efficiency and stability) that describe the CO₂RR performance of an electrolyzer. The advantages and drawbacks of each electrolyzer are discussed and highlighted with emphasis on the key achievements reported to date. Compared to conventional H-cell electrolyzers that work well in mechanistic studies, the newly developed electrolyzers using gas diffusion electrodes, both flow-cell and MEA-cell electrolyzers, are able to break the limitation of CO₂ solubility in water and acquire industrial current densities. Although flow-cell electrolyzers have achieved current densities exceeding 1 A∙cm⁻², they suffer from low energy efficiencies because of the significant iR drop and poor stability owing to the use of alkaline electrolytes. These issues can be overcome in the case of zero-gap MEA-cell electrolyzers with ion exchange membranes being as solid electrolytes. The anion exchange membrane (AEM)-based CO₂ electrolyzers are at the center of the current research, as they demonstrate promising activity and selectivity toward specific CO₂RR products and exhibit excellent stability for over thousands of hours in few cases. Meanwhile, the crossover of CO₂ and liquid products from the cathode to the anode through the membrane tends to lower the utilization efficiency of the CO₂ supplied to the AEM electrolyzers. MEA-cell electrolyzers using cation exchange membranes and bipolar membranes have also been explored; however, neither of them have shown satisfactory CO₂RR performance. The development of new polymer electrolyte membranes and ionomers would help address these problems. While issues and challenges still exist, MEA-cell electrolyzers hold the greatest promise for practical applications. As concluding remarks, research strategies and opportunities for the future have been proposed to accelerate the development of CO₂RR technology for practical applications and to deepen the mechanistic understanding behind improved performance. This review provides new insights into rational electrolyzer design and guidelines for researchers in this field.

Phosphate glass is widely used in optical applications; however, its generally low chemical stability and poor thermal mechanical properties hinder the application of phosphate glass to the rapidly evolving laser industry. The addition of a small amount of silicon can form a six-coordinate Si (Si⁽⁶⁾) network and improve the above-mentioned poor properties of phosphate glass. Therefore, it is important to characterize and understand the structural details of phosphosilicate glasses. It is difficult to investigate the glass structure because of its complicated and disordered characteristics. However, solid-state nuclear magnetic resonance (NMR) spectroscopy can provide detailed local structural information, regardless of the presence of its long-range order. To study the effect of alkaline earth metals on Si⁽⁶⁾ species formation, we prepared phosphosilicate glasses (2MO-3P₂O₅)_(1−x)·(SiO₂)_x (M = Ca, Sr, Ba) by conventional melt-quenching, and the glass structure was investigated by solid-state NMR and Raman spectroscopy. The ³¹P and ²⁹Si NMR spectra indicated that the glass networks consisted of P⁽²⁾ and P⁽³⁾ tetrahedrons linked via four- and six-fold coordinated silicon units (Si⁽⁴⁾ and Si⁽⁶⁾). The fraction of six-coordinated silicon Si⁽⁶⁾ decreased with increasing SiO₂ content. Similarly, the Raman spectra showed that the vibration band of the P＝O stretching mode in P⁽³⁾ linked with Si⁽⁶⁾ neighbors reduced as the silica content increased. The connectivities between various phosphorus species were probed by ³¹P one- and two-dimensional refocused INADEQUATE experiments. This experimental technique is based on homonuclear J-coupling and yields correlation peaks between nuclei engaged in P―O―P linkages (P⁽²⁾ and P⁽³⁾ units). The signals from isolated ³¹P nuclei are suppressed because of the absence of J-coupling, which precludes the formation of double quantum coherences. The results indicated the segregation of P⁽²⁾ and P⁽³⁾ units in the prepared glass, which were also compared with those in the previously reported Na₂O-P₂O₅-SiO₂ glasses. They differed from alkali phosphosilicate glasses, where each P⁽³⁾ unit exhibited a maximum average of one Si⁽⁶⁾―O―P⁽³⁾ linkage, and in the alkaline earth phosphosilicate glasses, the average was approximately 0.4–0.7. When the content of Si⁽⁶⁾ units reached its maximum, further increase in the SiO₂ content did not increase the Si⁽⁶⁾ content, and the surplus Si were present as Si⁽⁴⁾. Alkaline earth metal ions exhibit weaker stabilizing effects for Si⁽⁶⁾ species. Based on the results presented herein, we constructed sketches to illustrate the local structural organization of the glass. The relationships between the compositions and structures are important for glass composition and property design. It is important to improve the performance of phosphate glass by changing its composition, particularly for large laser device applications.

As an ideal negative electrode material for next-generation high-energy-density batteries, lithium (Li) metal has received extensive attention from the global research community. However, the safety hazards and short cycle life caused by the growth of Li dendrites have seriously hampered the application of Li metal batteries. Based on electrochemical phenomena and theory, this paper discusses the mechanism of dendritic growth, dead Li formation, and full battery failure from the perspective of concentration polarization. During the electrodeposition process, the consumption of Li ions on the surface induces concentration polarization. After the initial deposition, a relatively loose dendrite layer appears on the Li metal surface; the electrolyte can penetrate this dendrite layer to reach the dense Li metal surface. When the grown dendrites penetrate the concentration polarization layer, the interface concentration battery is short-circuited. In this case, the concentration difference battery tends to release all stored power and reach a potential balance between the high- and low-concentration regions, which causes the deposition of Li ions over the dendrites to reduce the ion concentration in the surrounding electrolyte. Meanwhile, the dissolution of Li ions that occurs at the roots of the dendrites increases the local ion concentration. This process accelerates the formation of a dead Li layer. A similar electrochemical process often occurs in columnar Li, as reported in other studies. When columnar Li is cycled several times, each Li column degenerates into a matchstick shape with a large head and thin neck. Therefore, eliminating concentration polarization is necessary for the application of columnar Li. Furthermore, in this work, concentration polarization and dendrite suppression in state-of-the-art porous host electrodes are analyzed. The larger specific surface area of the porous electrode greatly reduces the local current density on the electrode surface, which can reduce the interface concentration polarization and thus prevent dendrite growth. In charge-discharge cycling, a constant-voltage charging or shelving step is often inserted in each cycle in order to eliminate the influence of concentration polarization. However, if a dendritic layer has been formed on the Li metal surface after charging, in addition to the self-diffusion of ions, the self-discharge process of the interface concentration battery causes the detachment of the dendrite layer, thus resulting in the above-mentioned dead Li. Therefore, a larger amount of deposited Li yields a thicker Li dendritic layer, thus accelerating the capacity decay and failure of the battery, especially to those with high-capacity, high-voltage positive electrodes. The conclusions obtained in this paper can provide a theoretical basis for researchers to further explore Li metal protection strategies.

Marine organisms such as plants, algae or small animals can adhere to surfaces of materials that are submerged in ocean. The accumulation of these organisms on surfaces is a marine biofouling process that has considerable adverse effects. Marine biofouling on ship hulls can cause severe fuel consumption increase. Investigations on antifouling polymers are therefore becoming important research topics for marine vessel operations. Antifouling polymers can be applied as coating layers on the ship hull, protecting it against the settlement and growth of sea organisms. Polyethylene glycol (PEG) is a hydrophilic polymer that can effectively resist the accumulation of marine organisms. PEG-based antifouling coatings have therefore been extensively researched and developed. However, the inferior stability of PEG makes it subject to degradation, rendering it ineffective for long-term services. Zwitterionic polymers have also emerged as promising antifouling materials in recent years. These polymers consist of both positively charged and negatively charged functional groups. Various zwitterionic polymers have been demonstrated to exhibit exceptional antifouling properties. Previously, surface characterizations of zwitterionic polymers have revealed that strong surface hydration is critical for their antifouling properties. In addition to these hydrophilic polymers, amphiphilic materials have also been developed as potential antifouling coatings. Both hydrophobic and hydrophilic functional groups are incorporated into the backbones or sidechains of these polymers. It has been demonstrated that the antifouling performance can be enhanced by precisely controlling the sequence of the hydrophobic-hydrophilic functionalities. Since biofouling generally occurs at the outer surface of the coatings, the antifouling properties of these coatings are closely related to their surface characteristics in water. Therefore, understanding of the surface molecular structures of antifouling materials is imperative for their future developments. In this review, we will summarize our recent advancements of antifouling material surface analysis using sum frequency generation (SFG) vibrational spectroscopy. SFG is a surface-sensitive technique which can provide molecular information of water and polymer structures at interfaces in situ in real time. The antifouling polymers we will review include zwitterionic polymer brushes, mixed charged polymers, and amphiphilic polypeptoids. Interfacial hydration studies of these polymers by SFG will be presented. The salt effect on antifouling polymer surface hydration will also be discussed. In addition, the interactions between antifouling materials and protein molecules as well as algae will be reviewed. The above research clearly established strong correlations between strong surface hydration and good antifouling properties. It also demonstrated that SFG is a powerful technique to provide molecular level understanding of polymer antifouling mechanisms.

X-rays are widely used in many fields, including medical imaging, chemical structure analysis, and nondestructive examinations. However, long-term X-ray exposure is harmful to human health. Hence, radiation protection materials, especially wearable materials with outstanding performances, are in need of development. Lead (Pb) plates are commonly used as traditional radiation protection materials but have the disadvantages of heavy mass, toxicity, and poor wearability. Cement and alloy also are used to shield the X-ray, whereas application is limited by its heavy mass. In recent years, the wearable polymer based radiation protection was developed but has the defect which is low interfacial compatibility, resulting in poor shielding properties of the material. The K or L absorption edge of an element plays a major role in the attenuation of X-ray photon energy, and has a significant attenuation effect on X-ray photons with similar energy. As an alternative, it has been reported that the K absorption edge of rare earth (RE) elements is located in the range of 40–80 keV, which corresponds to the energy range of X-rays and medical X-ray energy range. Additionally, natural leather (NL) is an abundant natural biomass that is composed of multi-layered collagen fibers and contains amino (―NH₂), carboxyl (―COOH), and hydroxyl (―OH) groups. We believe that RE nanoparticles can be uniformly immobilized and stabilized by NL. In this study, we developed a novel strategy to prepare X-ray radiation protective materials by combining RE nanoparticles with NL. NL-based protective materials have the advantages of being lightweight and wearable while providing excellent protection. NL-based RE oxide nanoparticle composites (RE-NL) were successfully prepared by a "retanning" method and verified by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and transmission electron microscopy (TEM). X-ray protection tests showed that La-NL had the best shielding performance compared to the other tested RE oxide-loaded NLs owing to the small difference between the K-edge energy of La and the incident energy. Moreover, La_7.80-NL (La₂O₃ content of 7.80 mmol·cm^-3, 0.7 mm) showed better protection performance than a Pb plate with a high-Z elemental content (54.7 mmol·cm^-3, 0.25 mm) at 40–80 keV, confirming that the uniform distribution of RE oxides in NL provides enhanced X-ray shielding performance. The RE-NL also displayed a much better tensile strength, tear strength, and softness compared with polymer-based RE oxide composites. Meanwhile, it has the foldability and character of tailor. Therefore, the reported NL-based RE protective materials show promising potential for various scenarios requiring radiation protection.