Conversion of carbon dioxide (CO₂) to value-added chemicals and fuels driven by low-grade renewable electricity is of significant interest since it serves the dual purpose of reducing atmospheric content of CO₂ by utilizing it as a feedstock and storing it in the form of high-energy-density fuels. In this regard, there are an increasing number of interesting developments taking place in the popular research focus area of electrochemical reduction of CO₂. This review first introduces the general principles of CO₂ electroreduction. Next, the latest progress relating to electrocatalytic materials and experimental and theoretical studies of the reaction mechanism has been discussed. Finally, the challenges and prospects for further development of CO₂ electroreduction have been presented.

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers, constructed with lightweight elements by covalent bonds. Owing to their low density, high thermal stability, and inherent porosity, COFs have many potential applications in gas adsorption, heterogeneous catalysis, energy storage, etc. This article reviews the latest progress in COFs, including their structural design, synthesis, purification, characterization methods, and applications in gas adsorption, catalysis, and photoelectricity. Finally, the prospects of COFs are also discussed.

本文总结了2012-2017年度化学科学三处（物理化学、理论化学）优秀青年科学基金项目的受理和资助情况，阐述了近年来该领域优秀青年科学基金项目人才队伍的申请和资助趋势，并对该类项目资助下取得的部分典型成果进行了简介。最后，对项目申请中存在的问题和应注意的事项进行了说明。

Lithium-sulfur (Li-S) batteries are promising electrochemical energy storage systems because of their high theoretical energy density, natural abundance, and environmental benignity. However, several problems such as the insulating nature of sulfur, high solubility of polysulfides, large volume variation of the sulfur cathode, and safety concerns regarding the lithium anode hinder the commercialization of Li-S batteries. Graphene-based materials, with advantages such as high conductivity and good flexibility, have shown effectiveness in realizing Li-S batteries with high energy density and high stability. These materials can be used as the cathode matrix, separator coating layer, and anode protection layer. In this review, the recent progress of graphene-based materials used in Li-S batteries, including graphene, functionalized graphene, heteroatom-doped graphene, and graphene-based composites, has been summarized. And perspectives regarding the development trend of graphene-based materials for Li-S batteries have been discussed.

Graphyne is a rapidly rising star material of carbon allotropes containing only sp and sp² hybridized carbon atoms forming extended two-dimensional layers. In particular, graphdiyne is an important member of graphyne family. With unique nanotopological pores, two-dimensional layered conjugated frameworks, and excellent semiconducting and optical properties, graphdiyne has displayed distinct superiorities in the fields of energy storage, electrocatalysis, photocatalysis, nonlinear optics, electronics, gas separation, etc. Therefore, the synthesis of high-quality graphdiyne is highly required to fulfill its potentially extraordinary applications. Furthermore, the development of a standardized and systematic set of characterization procedures is an urgent need, and would be based on intrinsic samples. However, there are still obvious barriers to synthesizing this new-born carbon allotrope that can be mainly considered as follows. The selection and stability of monomers is essential for synthesis. The synthesis process in solution also suffers from an annoying problem of the relatively free rotation possible about the alkyne-aryl single bonds, which leads to the coexistence and rapid equilibration of coplanar and twisted structures. Furthermore, the limited reaction conversion and side reactions also lead to a confusion of configuration.

In this review, we primarily focus on the state-of-the-art progress of the synthetic strategies for graphdiyne. First, we give a brief introduction about the structure of graphyne and graphdiyne. We subsequently discuss in detail the recent developments in synthetic methods that can mainly be divided into three aspects: total organic synthesis, on-surface covalent reaction, and polymerization in a solution phase. In particular, much progress in solution polymerization has been achieved since in-situ polymerization on Cu surface was reported in 2010. Liquid/liquid interface, gas/liquid interface, and surface template were also employed for confined reaction, and contribute significantly to the synthesis of a graphdiyne film. Through such strategies, graphdiyne with a well-defined structure and diverse morphologies could be achieved successfully. Finally, the opportunities and challenges for the synthesis of graphdiyne are prospected. A more rational design is desired in terms of monomer modification and reaction regulation.

In response to aggravated fossil resources consuming and greenhouse effect, CO₂ reduction has become a globally important scientific issue because this method can be used to produce value-added feedstock for application in alternative energy supply. Photoelectrocatalysis, achieved by combining optical energy and external electrical bias, is a feasible and promising system for CO₂ reduction. In particular, applying graphene in tuning photoelectrochemical CO₂ reduction has aroused considerable attention because graphene is advantageous for enhancing CO₂ adsorption, facilitating electrons transfer, and thus optimizing the performance of graphene-based composite electrodes. In this review, we elaborate the fundamental principle, basic preparation methods, and recent progress in developing a variety of graphene-based composite electrodes for photoelectrochemical reduction of CO₂ into solar fuels and chemicals. We also present a perspective on the opportunities and challenges for future research in this booming area and highlight the potential evolution strategies for advancing the research on photoelectrochemical CO₂ reduction.

Functional materials and devices that can efficiently store and convert energies have attracted a great deal of attention in recent years. The composites of layered double hydroxide and graphene (LDH/G) are important energy materials. They have excellent physical and chemical properties of both components. Furthermore, their performances in energy-related systems can be improved by increasing the electrical conductivity of LDHs by blending graphene and partly preventing the aggregation of graphene sheets using LDH nanostructures. Therefore, LDH/G composites can be used in various energy applications, particularly for developing high-performance supercapacitors and efficient electrocatalysts for electrochemical splitting of water. In this review, we summarize the recent advances on the synthesis of LDH/chemically modified graphene (CMG, e.g., graphene oxide, reduced graphene oxide and their derivatives) composites and their application in electrochemical energy storage and conversion. Furthermore, the challenges and future perspectives in this research field are also outlined.

Organic-inorganic perovskite solar cells (PSCs) have become one of the most promising solar cells, as the power conversion efficiency (PCE) has increased from less than 5% in 2009 to certified values of over 22%. In the typical PSC device architecture, hole transport materials that can effectively extract and transmit holes from the active layer to the counter electrode (HTMs) are indispensable. The well-known small molecule 2, 2', 7, 7'-tetrakis-(N, N-di-4-methoxy-phenyl amino)-9, 9'-spirobifluorene (spiro-OMeTAD) is the best choice for optimal perovskite device performance. Nevertheless, there is a consensus that spiro-OMeTAD by itself is not stable enough for long-term use in devices due to the sophisticated oxidation process associated with undesired ion migration/interactions. It has been found that spiro-OMeTAD can significantly contribute to the overall cost of materials required for the PSC manufacturing, thus its market price makes its use in large-scale production costly. Besides, another main drawback of spiro-OMeTAD is its poor reproducibility.

To engineer HTMs that are considerably cheaper and more reproducible than spiro-OMeTAD, shorter reaction schemes with simple purification procedures are required. Furthermore, HTMs must possess a number of other qualities, including excellent charge transporting properties, good energy matching with the perovskite, transparency to solar radiation, a large Stokes shift, good solubility in organic solvents, morphologically stable film formation, and others. To date, hundreds of new organic semiconductor molecules have been synthesized for use as HTMs in perovskite solar cells. Successful examples include azomethine derivatives, branched methoxydiphenylamine-substituted fluorine derivatives, enamine derivatives, and many others. Some of these have been incorporated as HTMs in complete, functional PSCs capable of matching the performance of the best-performing PSCs prepared using spiro-OMeTAD while showing even better stability.

In light of these results, we describe the advances made in the synthesis of HTMs that have been tested in perovskite solar cells, and give an overview of the molecular engineering of HTMs. Meanwhile, we highlight the effects of molecular structure on PCE and device stability of PSCs. This review is organized as follows. In the first part, we give a general introduction to the development of PSCs. In the second part, we focus on the introduction of the perovskite structure, device architecture, and relevant work principles in detail. In the third part, we discuss all kinds of molecular HTMs applied in PSCs. Special emphasis is placed on the relationship between HTM molecular structure and device function. Last but not least, we point out some existing challenges, suggest possible routes for further HTM design, and provide some conclusions.

The frequency of oil-spill accidents and industrial wastewater discharges have caused severe water pollution, not only resulting in huge economic losses but also threatening the ecological system. Recently, researchers have developed different types of materials with special wettability (such as superhydrophobicity or superoleophobicity) and used them successfully for oil-water separation. Superhydrophobic and superoleophobic surfaces can generally be obtained by designing the surface geometric micro-topography and chemical composition of solid materials. Endowing porous materials with reverse super-wettability to water and oil using various microfabrication technologies is the key to separate oil-water mixtures. In this review we initially identify the significance of fabricating oil/water-separating materials and achieving effective separations. Then, the typical theoretical principles underlying surface wettability are briefly introduced. According to the difference in surface wettabilities toward water and oil, we classify the current oil-water separating materials into three categories: (ⅰ) superhydrophobic/superoleophilic materials, (ⅱ) superoleophobic/ superhydrophilic materials, and (ⅲ) smart-response materials with switchable wettability. This review summarizes the representative research work for each of these materials, including their fabrication methods, principle and process of oil-water separation, and main characteristics and applications. Finally, existing problems, challenges, and future prospects of this fast-growing field of special wettability porous materials for the separation of oil-water mixtures are discussed.

Numerous real space functions have been purposed so far for unveiling chemically interesting molecular electronic structure characteristics, such as chemical bonds, lone pairs, and multicenter electronic conjugations. Among these analysis methods, electron localization function (ELF), Laplacian of electron density (∇²ρ), and deformation density (ρ_def) were widely employed in practical research work. It is well known that the analysis of total molecular electron density is not sufficient for revealing much information about the molecular electronic structure like the above-mentioned methods. However, in this work, using several instances and by comparing with the ELF, ∇²ρ, and ρ_def values, we show that it is possible to explore molecular electronic structure characteristics if one solely focuses on investigating the valence electron density distribution. It is found that for most cases, analysis of the very simple valence electron density conveys analogous information as ELF, ∇²ρ and ρ_def analyses, with additional advantage of reduced computational complexity. We hope that this work will bring chemists' attention to the high importance of valence electron density, which has been largely ignored for a long time. It should also be noticed that the valence electron density analysis is not free from drawbacks, and when this method is unable to provide an informative picture, one has to use other analysis methods.

Lithium-sulfur batteries are considered to be rather latest and high-performance storage batteries due to their high theoretical specific capacity (1675 mAh·g^-1), high energy density (2600 Wh·kg^-1), environmental friendliness, low cost, and safety. These features make them important in the field of mobile electric vehicles and portable devices. However, because of rapid capacity attenuation with poor cycle and rate performances, these batteries are far from ideal for commercial applications. This paper reviews the entire and latest studies in lithium-sulfur batteries. Cathodes, electrolyte, separators, and anodes protection are introduced in detail. The existing lithium-sulfur batteries defects and problems are analyzed. Finally, we provide some insights into the future direction and prospects of lithium batteries.

Radiation therapy kills tumor cells via focused high energy radiation, and has become one of the most common and effective clinical treatments for malignant tumors. However, some limitations restrict its clinical efficacy, including a requirement for elevated doses of radiation, side effects due to exposure of healthy tissue, and especially radioresistance of tumor cells. With the development of nanomedicine, multifunctional nanoradiosensitizers offer a new route to improve the efficiency of radiation therapy. In this paper, we summarize the main types of nanoradiosensitizers and their applications in radiation therapy, especially those that have currently entered clinical trials. We also summarize the main approaches to nanomaterials-based radiosensitization, and discuss the factors influencing their application. Finally, the challenges and prospects of multifunctional nanoradiosensitizers are presented.

Quantitative correlation of several theoretical electrophilicity measures over different families of organic compounds are examined relative to the experimental values of Mayr et al. Notably, the ability to predict these values accurately will help to elucidate the reactivity and selectivity trends observed in charge-transfer reactions. A crucial advantage of this theoretical approach is that it provides this information without the need of experiments, which are often demanding and time-consuming. Here, two different types of electrophilicity measures were analyzed. First, models derived from conceptual density functional theory (c-DFT), including Parr's original proposal and further generalizations of this index, are investigated. For instance, the approaches of Gázquez et al. and Chamorro et al. are considered, whereby it is possible to distinguish between processes in which a molecule gains or loses electrons. Further, we also explored two novel electrophilicity definitions. On one hand, the potential of environmental perturbations to affect electron incorporation into a system is analyzed in terms of recent developments in c-DFT. These studies highlight the importance of considering the molecular surroundings when a consistent description of chemical reactivity is needed. On the other hand, we test a new definition of electrophilicity that is free from inconsistencies (so-called thermodynamic electrophilicity). This approach is based on Parr's pioneering insights, though it corrects issues present in the standard working expression for the calculation of electrophilicity. Additionally, we use machine-learning tools (i.e., symbolic regression) to identify the models that best fit the experimental values. In this way, the best possible description of the electrophilicity values in terms of different electronic structure quantities is obtained. Overall, this straightforward approach enables one to obtain good correlations between the theoretical and experimental quantities by using the simple, yet powerful, interpretative advantage of c-DFT methods. In general, we observed that the correlations found at the HF/6-31G(d) level of theory are of semi-quantitative value. To obtain more accurate results, we showed that working with families of compounds with similar functional groups is indispensable.

Polymer solar cells (PSCs) with bulk heterojunction (BHJ) structures have seen rapid development in recent years. In comparison with their inorganic counterparts, PSCs have some advantages such as low cost, light weight, solution processability, and good mechanical flexibility. However, improvement of the power conversion efficiency (PCE) of PSCs is required for commercial applications. In order to achieve high-performance PSCs, active layers, including donor polymers and acceptors, are very important. Several design principles for conjugated donor polymers in PSCs have emerged, including optimization of the conjugated backbone, side-chains, and substituents. In the past few decades, various classes of electron-donating polymers have been reported for PSCs. Among them, quinoxaline (Qx) is a unique building block for the construction of different optoelectronic polymers because of its planar, rigid, and conjugated structure. Qx derivatives have proven interesting and have been widely employed in many fields. Qx-based conjugated polymers (or small molecules) can be easily modified to match with ball-like fullerene derivatives such as PCBM ([6, 6]-phenyl-C₆₁ or C₇₁-butyric acid methyl ester) or weak crystalline non-fullerene acceptors such as 2, 2'-[[6, 6, 12, 12-tetrakis(4-hexylphenyl)-6, 12, -dihydrodithieno[2, 3-d:2', 3'-d']-s-indaceno[1, 2-b:5, 6-b']dithiophene-2, 8-diyl]bis[methylidyne(3-oxo-1H-indene-2, 1(3H)-diylidene)]]bispropanedinitrile (ITIC). Herein, we synthesized a Qx-based polymer with asymmetric side-chains (TPQ-1). The molecular weight, optical properties, molecular energy levels, and mobilities of TPQ-1 were investigated. Furthermore, the blend morphologies and photovoltaic properties of TPQ-1 using a strong crystalline non-fullerene (NF) acceptor (o-IDTBR) were systematically explored. The photovoltaic performance of TPQ-1 and its symmetric side-chain counterpart, HFQx-T, was compared. The introduction of asymmetric side-chains led to a favorable phase separation when blended with o-IDTBR. As expected, the TPQ-1:o-IDTBR-based devices exhibited a high PCE of 8.6% after thermal annealing (TA). In contrast, the HFQx-T:o-IDTBR-based devices showed a moderate PCE of 5.7%, moreover, the PCE was decreased to 4.6% after TA treatment. More importantly, a low bandgap material, PTB7-Th, was specifically selected as a third component to mix with the TPQ-1:o-IDTBR blend to form highly-efficient ternary PSCs. At an optimal weight ratio (15%) of PTB7-Th addition, a PCE of 9.6% was achieved. In the systems that were investigated, TPQ-1 demonstrated significantly better photovoltaic properties than the HFQx-T-based devices. These results indicate that Qx-based polymers with asymmetric side chains have a bright future in photovoltaic devices.

ZnO has attracted extensive research in perovskite solar cells because of its high electron mobility, spectacular optical transparency, low-temperature processing, and ease of synthesis. Traditional electrode buffer layers used in perovskite solar cells have shown some drawbacks, such as high-temperature treatment, low transmittance, and complex fabrication procedures, which might not be fit for the further development of high-performance flexible perovskite solar cells. Here, we intend to give a systematic introduction to the fabrication and functions of ZnO electrode buffer layers (sol-gel method, pre-fabricated ZnO nanoparticle suspension, atomic layer deposition, spray pyrolysis, electrodeposition, chemical bath deposition, radio-frequency sputtering, metal organic chemical vapor deposition, and magnetron sputtering etc.). Particular attentions were paid to the understanding of the structure-property relations between the thickness, morphology, doping, and composition of ZnO electrode buffer layers and the performance of perovskite solar cells (open circuit voltage, current density, fill factor, power conversion efficiency, etc.). A perspective on the future development of ZnO electrode buffer layers and their applications in perovskite solar cells were also discussed in this review.

Solution-processable organic photovoltaic cells (OPVs) have attracted considerable interest.Over the past twenty years, fullerene and its derivatives have been predominately used as the electron acceptor materials to fabricate OPV devices.In recent few years, non-fullerene organic photovoltaic cells (NF-OPVs), consisting of polymers as the donors and the non-fullerene (NF) materials as the acceptors, have been developed rapidly, and the highest power conversion efficiencies of NF-OPVs exceed those of fullerene-based OPVs.In these NF-OPVs, both polymeric donor materials and NF acceptors play critical roles in achieving outstanding efficiencies, and hence, the molecular design of the polymer donors has been deemed a very important topic of research in the field.In this review, we will present an introduction of the specific requirements for polymer donors in NF-OPVs and summarize the recent progress related to polymer donors for the applications in highly efficient NF-OPVs.

Aerogels have been developed rapidly in recent years due to their excellent physicochemical properties and broad range of applications. However, most efforts have been devoted to traditional aerogel 3D monoliths, and particular requirements regarding the shape and size of the aerogels for some special uses have been neglected. Shaping aerogel into microspheres, that is, the fabrication of aerogel microspheres, may facilitate potential applications and extension of the range of applications of porous microspheres. Herein, we will present the fabrication and performance of various aerogel microspheres such as silica aerogel microspheres, cellulose aerogel microspheres, RF/carbon aerogel microspheres, and graphene aerogel microspheres. The current challenges and future developments of the aerogel microspheres are also discussed briefly in this review.

Phosphorene is a novel two-dimensional material that is more advanced than graphene. This material possesses excellent physical, chemical, and mechanical properties, which are useful for potential applications in a variety of electronic devices. Thus far, a comprehensive review on the latest fabrication methods, property tuning, and applications of phosphorene is lacking. Therefore, a comprehensive review of the synthetic methods, structures, properties, modification methods, and device applications of phosphorene has been presented. The preparation strategies of phosphorene including top-bottom and bottom-up methods have been introduced, followed by a summary of its structure and properties. The modification methods of phosphorene have also been discussed. Finally, the applications of phosphorene in electronic devices have been discussed in detail. Future prospects and potential research areas of phosphorene have also been presented in this review.

In recent years, deep eutectic solvents (DESs) have attracted considerable attention. They have been applied in many fields such as dissolution and separation, electrochemistry, materials preparation, reaction, and catalysis. The DESs are generally formed by the hydrogen bonding interactions between hydrogen-bond donors (HBDs) and acceptors (HBAs). Knowledge of the thermal stability of DESs is very important for their application at high temperatures. However, there have been relatively few studies on the thermal stability of DESs. Herein, a systematic investigation on the thermal stability of 40 DESs was carried out using thermal gravimetric analysis (TGA), and the onset decomposition temperatures (T_onset) of these solvents were obtained. The most important conclusion drawn from this work is that the thermal behavior of DESs is quite different from that of ionic liquids. The anions or cations of ionic liquids decompose first, followed by the decomposition of the opposite ion at elevated temperatures. On the other hand, the DESs generally first decompose to HBDs and HBAs at high temperatures through the weakening of the hydrogen bond interactions. Subsequently, the HBDs with relatively low boiling points or poor stabilities undergo volatilization or decomposition; the HBAs also undergo volatilization or decomposition but at a higher temperature. For example, the most commonly used HBA choline chloride (ChCl) begins to decompose at around 250 ℃. The hydrogen bond plays an important role in the thermal stability of DESs. It hinders the "escape" of molecules and requires greater energy to break than pure HBAs and HBDs, which causes the T_onset of DESs to shift to higher temperatures. Note that the thermal stability of HBDs has a crucial effect on the T_onset of DESs. The HBDs would decompose or volatilize first during TGA because of their relatively poor thermal stability or lower boiling points. The more stable the HBDs are, the greater would be the T_onset values of the corresponding DESs. Further, the effects of anions on HBAs, molar ratio of HBAs to HBDs, and heating rate in fast scan TGA have been discussed. As the heating rate increased, the TGA curves of DESs shifted to higher temperatures gradually, and the temperature hysteretic effect became prominent when the rate reached 10 ℃?min?1. From an industrial application point of view, there is an overestimation of the onset decomposition temperatures of DESs by T_onset, so the long-term stability of DESs was investigated at the end of the study. This study could help understand the thermal behavior of DESs (progressive decomposition) and provide guidance for designing DESs with appropriate thermal stability for practical applications.

Graphdiyne(GDY) is a new booming carbon material with a highly π-conjugatedstructure that consists of sp-and sp²-hybridizedcarbon atoms. Due to the diverse compositions of the carbon atoms, GDYs can bedivided into several forms based on their structure and periodicity. Until2010, γ-GDY has been successfully synthesized and becomes a new member of thecarbon family. Many researchers have subsequently devoted their attention tothe study of GDY. Compared to the traditional carbon materials, GDY exhibits aunique carbon network and electronic structure, thereby attracting considerableattention in a variety of fields. With the development of its syntheticchemistry, many types of GDY with different structures have been synthesizedand characterized. The characterization of their micromorphology is crucial forstudying the synthesis procedure and understanding the properties of GDYmaterials. At present, the developed method can characterize GDY morphology, crystal structure, and thechemical bonds of the carbon atoms. Specifically, the morphology and thicknessof GDY can be evaluated by scanning electron microscopy, transmission electronmicroscopy, and atomic force microscopy. The crystal structure can beinvestigated using X-ray diffraction and high-resolution transmission electronmicroscopy. The chemical bonding of the carbon atoms can be analyzed by Ramanspectroscopy, X-ray photoelectron spectroscopy, Fourier transforminfrared (FT-IR) spectroscopy, C-13 nuclear magnetic resonance (¹³C NMR), UV-visible (UV-Vis) absorption spectroscopy, etc. However, methods for therapid and nondestructive characterization of the highly crystalline graphdiyneare still absent, restricting the study of the intrinsic properties of GDY. Dueto the unique electronic and porous structure of GDY, it has been the focus ofextensive investigations in the field of catalysis. As a result of itsfavorable electronic structure and good capability for transferringphotoexcited electrons and holes, GDY can enhance light absorption andfacilitate the separation of photoexcited charge carriers in semiconductors andthereby significantly promote their photocatalytic performance. In addition, GDY can be modified using foreign elements, providing an ideal platform toprepare a highly active catalyst for the hydrogen evolution reaction, oxygenevolution reaction, oxygen reduction reaction, etc. Furthermore, GDY can besynthesized on arbitrary substrates in a three-dimensional nanosheet arraystructure, which can provide a large number of channels for the transfer ofelectrons and a large contact area with the reactant, which is beneficial inelectrocatalytic reactions. This review focused on the recent developments incharacterization methods as well as the photo and electrocatalysis applicationsof GDY, and elaborated the opportunities and challenges for the investigationof GDY in the future.

Electrochemicalenergy storage devices are becoming increasingly important in modern societyfor efficient energy storage. The use of these devices is mainly dependent onthe electrode materials. As a newly discovered carbon allotrope, graphdiyne(GDY) is a two-dimensional full-carbon material. Its wide interlayer distance(0.365 nm), large specific surface area, special three-dimensional porousstructure (18-C hexagon pores), and high conductivity make it a potentialelectrode material in energy storage devices. In this paper, based on thefacile synthesis method and the unique porous structure of GDY, theapplications of GDY in energy storage devices have been discussed in detailfrom the aspects of both theoretical predictions and recent experimentaldevelopments. The Li/Na migration and storage in mono-layered and bulk GDYindicate that GDY-based batteries have excellent theoretical Li/Na storagecapacity. The maximal Li storage capacity in mono-layered GDY is LiC₃(744 mAh∙g^-1). The experimental Li storage capacity of GDY issimilar to theoretical predictions. The experimental Li storage capacity of athick GDY film is close to that of mono-layered GDY' (744 mAh∙g^-1).A thin GDY film with double-side storage model has two-times the Li storagecapacity (1480 mAh∙g^-1) of mono-layered GDY. Powder GDY has lower Listorage capacity than GDY film. The maximal Na storage capacity in GDYcorresponds to NaC_5.14 (316 mAh∙g^-1), and mono-layeredGDY possesses higher theoretical Na storage capacity (NaC_2.57). Theexperimental Na storage capacity (261 mAh∙g^-1) is similar to itstheoretical value. Besides, GDY as electrode material, applied in metal-sulfurbatteries, presents excellent electrochemical performance (in Li-S battery: 0.1C, 949.2 mAh∙g^-1; in Mg-S battery: 50 mA∙g^-1, 458.9 mAh∙g^-1).This ingenious design presents a new way for the preparation of carbon-loadedsulfur. GDY electrode material is also successfully used in supercapacitors, including the traditional supercapacitor, Li-ion capacitors, and Na-ioncapacitors. The traditional supercapacitor with GDY as the electrode material showsgood double layer capacitance and pseudo-capacitance. Both Li-ion capacitor(100.3 W∙kg^-1, 110.7 Wh∙kg^-1) and Na-ion capacitor (300W∙kg^-1, 182.3 Wh∙kg^-1) possess high power and energydensities. Moreover, the effects of synthesis of GDY nanostructure, heattreatment of GDY, and atom-doping in GDY on the performance of electrochemicalenergy storage will be introduced and discussed. The results indicate that GDYhas great potential for application in different energy storage devices as anefficient electrode material.

The electronic structures, deformation potential, electron-phonon couplings (EPCs), and intrinsic charge transport of layered systems — the sp +sp² hybridized carbon allotropes, graphynes (GYs) and graphdiynes (GDYs), as well as sp² + sp³ hybridized structure with buckling, such as stanine — have been investigated theoretically. Computational studies showed that, similar to graphene, some GYs can possess Dirac cones (such as α-, β-, and 6, 6, 12-GYs), and that the electronic properties of GYs and GDYs can be tuned by cutting into nanoribbons with different widths and edge morphologies. Focusing on the features of Dirac cones, band structure engineering can provide a clue for tuning electronic transport in 2D carbon-based materials. Based on the Boltzmann transport equation and the deformation potential approximation (DPA), the charge carrier mobilities in GYs and GDYs were predicted to be as high as 10⁴–10⁵ cm²·V^-1·s^-1 at room temperature. Interestingly, due to lower EPC strength and longer relaxation time, the charge carrier mobility in 6, 6, 12-GY with double Dirac cones structure was found to be even larger than that of graphene at room temperature. The unique electronic properties and high mobilities of GYs and GDYs make them highly promising candidates for applications in next generation nanoelectronics. Additionally, through the full evaluation of the EPC by density functional perturbation theory (DFPT) and Wannier interpolation, the EPCs with different phonon branches and wave-vectors as well as charge carrier mobilities for graphene, GYs and stanene have been discussed. This showed that the longitudinal acoustic (LA) phonon scattering in the long wavelength limit is the main scattering mechanism for GYs and graphene, and thus the DPA is applicable. Due to stronger LA phonon scattering, the electron mobilities (∼10⁴ cm²·V^-1·s^-1) of α-GYs and γ-GYs were predicted to be one order of magnitude smaller than that of graphene at room temperature by full evaluation of the EPC. However, the DPA would fail if there was buckling in the honeycomb structure and the planar symmetry was broken (absence of σ_h), such as in stanene, where the inter-valley scatterings from the out-of-plane acoustic (ZA) and transverse acoustic (TA) phonons dominate the carrier transport process and limit the electron mobilities to be (2–3) × 10³ cm²·V^-1·s^-1 at room temperature. In addition to our calculations, others have also found that the main scattering mechanisms in layered systems with buckling, such as silicene and germanene, are ZA and TA phonons. Thus, these results give us new insights into the role of EPCs and the limitation of the DPA for carrier transport in layered systems. They also indicate that the carrier mobilities of systems without σ_h-symmetry can be improved by suppressing the out-of-plane vibrations, for example by clamping by a substrate.

With solar, wind, and other types of renewable energy incorporated into electrical grids and with the construction of smart grids, energy storage technology has become essential to optimize energy utilization. Due primarily to its abundance and low cost, aqueous rechargeable sodium-ion batteries (ARSBs) have received increasing attention in the field of electrochemical energy storage technology, and represent a promising alternative to energy storage in future power grids. However, because of the limitations of the thermodynamics of electrochemical processes in water, reactions in aqueous solution are more complicated compared to an organic system. Many parameters must be taken into account in an aqueous system, such as electrolyte concentration, dissolved oxygen content, and pH. As a result, it is challenging to select an appropriate electrode material, whose capacity, electrochemical potential, adaptability, and even catalytic effect may seriously affect the battery performance and hamper its application. Therefore, the development of advanced electrode materials, which can suppress side reactions of the battery and have good electrochemical performance, has become the focus of ARSB research. This paper briefly discusses the characteristics of ARSBs and summarizes the latest research progress in the development of electrode materials, including oxides, polyanionic compounds, Prussian blue analogues, and organics. This review also discusses the challenges remaining in the development of ARSBs, and suggests several ways to solve them, such as by using multivalent ions, hybridized electrolytes, etc., and speculates about future research directions. The studies and concepts discussed herein will advance the development of ARSBs and promote the optimization of energy utilization.

Vitamin E compounds are biologically active and are frequently used as antioxidants. The demand for Vitamin E compounds has increased significantly in recent years, and at present, more than 80% of the market demand for Vitamin E is fulfilled by its synthetic counterparts. Therefore, it is imperative to increase the production of Vitamin E. Vitamin E compounds contain tocopherol and tocotrienol derivatives, and α-tocopherol, which dominates the sound, is the most biologically active. This review covers the methods of preparation of α-tocopherol, focusing on the synthesis routes, chemical reactions, and corresponding catalysts. The synthesis of Vitamin E, including preparation of 2, 3, 5-trimethylhydroquinone (TMHQ), preparation of isophytol, and condensation of TMHQ and isophytol are discussed in detail. The disadvantages and issues related to the preparation methods are also included. In general, the preparation of TMHQ comprises three steps: (1) methylation of m-cresol to 2, 3, 6-trimethylphenol, (2) oxidation of 2, 3, 6-trimethylphenol to 2, 3, 5-trimethylbenzoquione (TMBQ), and (3) hydrogenation of TMBQ to TMHQ. Recently, a novel and attractive method using isophorone, which can be produced by self-condensation of acetone, as a source for synthesizing TMHQ has been developed. Among these procedures, it is important to attain high selectivity in the oxidative reactions, including oxidation of 2, 3, 6-trimethylphenol and isophorone (α-isophorone or β-isophorone), and to replace H₂O₂, a common oxidant, by oxygen or air. One of the methods of preparation of isophytol using citral as a source has been abandoned because of shortage of oil of litsea cubeba, which is a natural source of citral. Linalool, produced from 6-methyl-5-hepten-2-one, is a key intermediate in the main process of preparation of isophytol. Both BASF SE and Roche have developed effective methods for the preparation of 6-methyl-5-hepten-2-one, respectively. Semi-hydrogenation of alkynols plays a key role in the whole process. The selectivity, especially at high conversion is directly related to the profit; therefore, it is of great importance for industries. The condensation of TMHQ and isophytol is essentially a Friedel-Crafts alkylation reaction catalyzed by acids. Similar reactions include methylation of m-cresol. Bronsted acids are usually effective for these reactions; however, it is difficult to recover these catalysts from the homogeneous systems. Therefore solid acid has a great potential in this area and it is also a promising topic to reduce the loss of acid sites when using acid-immobilized catalysts. The supply of various sources of the reactants and the local policy need to be considered while choosing an appropriate method for the preparation of Vitamin E.

Graphdiyne features sp and sp² hybridized carbon atoms. The direct natural band gap and Dirac cone structure for graphdiyne are believed to originated from inhomogeneous π-bonding of differently hybridized carbon atoms and overlap of carbon 2p_z orbitals. The special electronic structures and pore structures of graphdiyne are responsible for its potential and important applications in the fields of information technology, electronics, energy, catalysis, and optoelectronics. Recent basic and applied research studies of graphdiyne have led to important results; as a result, graphdiyne has become a new research field for carbon materials. The high activity of acetylenic units in graphdiyne provides a good platform for chemical modification and doping. Several approaches have been developed to modify the band gap of graphdiyne, including invoking strain, BN-doping, preparing nanoribbons, and hydrogenation, leading to a new graphdiyne (GDY) or graphyne (GY) derivatives. In this review, we summarize the recent progress in nonmetallic heteroatom doping, especially by nitrogen, boron, or oxygen; by modifying metal atoms for tuning electronic/spintronic properties, enhancing water splitting performance, and applying dye-sensitized solar cells and catalysts; and by surface functionalization of graphdiyne via hydrogenation, hydroxylation, and halogenation to adjust the band gap. Hence, it can be surmised that the electronic structures of graphdiynes can be tuned for specific applications. These results suggest that graphdiynes can be more advantageous than grapheme for tailoring energy band gaps for application in nanoelectronics. We also discuss the influence of doping and functionalization on the electronic properties of graphdiyne and their effects on the synergistic enhancement of photoelectrocatalytic performance. We hope that the deep and wide application of these new materials in many fields such as energy transfer and storage, catalyst, electronics, gas separation, and spintronics will draw much attention and become a widely focused research direction.

Understanding the nature of the active sites and the relationship between the catalyst structure and its performance are fundamental aspects of heterogeneous catalysis. With the development of modern surface science techniques, atomically resolved surface structures of heterogeneous catalysts and their properties can be studied with ease. Combined with an in situ high pressure cell, model catalysis studies can provide convincing information about the relationship between the catalyst structure and its performance. In this mini-review, several case studies of model catalysts have been summarized, including those of the active surfaces for CO and alkane oxidation using the Pt group metals as catalysts, the active site of gold nanoparticles for CO oxidation, synergistic effects between VO_x and Pt for propane oxidation, promotional effects of Au in Pd-Au catalysts for vinyl acetate synthesis, structure-sensitivity of n-heptane dehydrocyclization on model oxide-supported Pt, as well as several significant improvements of the model catalysis techniques.

Sodium ion batteries (SIBs), a promising substitute for lithium ion batteries (LIBs), have attracted extensive attention due to the abundance and low cost of sodium resources. In addition, flexible sodium-ion batteries may be able to satisfy the demands of large-scale energy storage applications for portable, wearable, and flexible electronics. Compared to the development of cathode materials, the progress on anode materials has been relatively slow. Therefore, the exploration of low-cost anode materials with high Na⁺ storage capacity is very important. Herein, we present oxygen-deficient Na₂Ti₃O₇ nanobelts grown on carbon cloth (CC) as a promising novel flexible anode material for SIBs. Free-standing Na₂Ti₃O₇ nanobelts with oxygen vacancies were directly grown on CC through a simple hydrothermal and thermal reduction process. Benefiting from the improved conductivity and increased active sites after the introduction of oxygen vacancies, the new material exhibits a high reversible capacity of 100 mAh·cm^-2 at 200 mA·cm^-2, with almost 80% capacitance retention after 200 cycles. When the current density was increased to 400 mA·cm^-2, a high capacity of 69.7 mAh·cm^-2 was achieved, which is three times that of bare Na₂Ti₃O₇ nanobelts on CC. This 3D oxygen-deficient electrode can significantly promote the transport of Na⁺ ions and electrons, leading to remarkably improved electrochemical properties. Furthermore, this work constitutes a promising strategy to rationally design and fabricate novel Na₂Ti₃O₇-based anodes with enhanced capacitive behavior, which hold great promise for energy storage/conversion devices, facilitating the large-scale implementation of high-performance flexible SIBs.

In order to explore their luminescence properties, a series of carbon nanodots were prepared by microwave heating by controlling the microwave power, reaction time, and pH value.The luminescence properties of carbon nanodots were characterized by their fluorescence excitation spectrum and emission spectrum.We present the transformation mechanism of glucose into carbon nanodots during the microwave heating process and the corresponding luminescence mechanism together with the analysis of functional group changes during the reaction as monitored with ultraviolet (UV) absorption and Fourier Transform Infrared (FT-IR) spectra.The results show that the optimal luminescence properties of carbon nanodots were obtained when the glucose was heated under a microwave heating power of 560 W for 2.5 min.When the carbon nanodots were excited with UV radiation with a wavelength of 370 nm, the strongest luminescence appeared at 451 nm.The wavelength of the strongest luminescence peak moved from 350 nm to higher wavelengths significantly, when the pH value was modified from acidic to alkaline, and was accompanied with a significant rise in luminescence peak intensity.We show that polycyclic aromatic hydrocarbons form in the reaction process, as evidenced by UV absorption and FTIR monitoring, indicating that microwave synthesis of carbon nanodots proceeds via polymerization and final carbonization of glucose.Carbon nanodots formed under different pH values exhibit a change in the ratio of carbon-to-carbon double bonds to carbon-to-oxygen double bonds.The optical bandgap and exciton binding energy of the carbon nanodots were also investigated comprehensively.

Solution-processed bulk-heterojunction organic solar cells (BHJ-OSCs), with their advantages of light weight, low cost, and easy fabrication, are a photovoltaic technology with practical potentials. In BHJ-OSCs, the exciton dissociation and charge transport are highly sensitive to the molecular packing pattern and phase separation morphology in the active layer. On the other hand, when using photovoltaic small molecules (SMs), the purity can be controlled due to their well-defined chemical structure, and therefore there is better reproducibility in device performance. Especially, the non-fullerene acceptors are easier to tune in their light absorption and energy level. Hence, there has been considerable interest in small non-fullerene SM organic solar cells (NF-SM-OSCs). Although these cells have the dual advantages of non-fullerene acceptor materials and SMs, the fabrication of high-efficiency cells still possess great challenges. For example, efficient photovoltaic SMs typically possess an acceptor-donor-acceptor (A-D-A) structure that causes intrinsic anisotropy, making it more complicated to modulate and control the morphology of the nanoscale active layer. In this article, we will summarize recent advances in high-performance NF-SM-OSCs, and present an introduction of the specific requirements for SM donors in the small NF-SM-OSCs. We first summarize our works on SM donors with the A-D-A structure. The trialkylthienyl-substituted benzodithiophene (TriBDT-T) unit is employed as the D-core unit, and the A end groups include rhodanine (RN), cyano-rhodanine (RCN), and 1, 3-indanone (IDO). The band gap (E_g) of these compounds is about 2.0 eV, with the low-lying highest occupied molecular orbital (HOMO) level of -5.51 eV. First, NF-SM-OSCs with DRTB-T and a non-fullerene acceptor (IDIC) were constructed. The morphology of the active layer was fine-tuned by solvent vapor annealing (SVA), leading to the formation of the desired interconnected nanoscale structure. Our results demonstrate that the molecular design of a wide band gap (WBG) donor to create a well-matched donor-acceptor pair with a low band gap (LBG) non-fullerene SM acceptor, as well as subtle morphological control, provides great potential to realize high-performance NFSM-OSCs. We also studied the molecular orientation optimization from the aspect of molecular design. We designed and synthesized a group of SM compounds having identical π-conjugated backbones and end groups with different alkyl chain lengths. Since these compounds have identical photoelectric properties, they allow us to focus on the significant influence of the end alkyl chains on the molecular orientation and intermolecular aggregation behavior in solid-state films. Characterization of the DRTB-T-CX films using 2D grazing incidence wide-angle X-ray scattering (GIWAXS) revealed an obvious transition of orientation from edge-on to face-on relative to the substrate when the end alkyl chain is lengthened. This demonstrates that the length of the end alkyl chain can be used to modify the molecular orientation. A DRTB-T-C4/IT-4F-based device achieved a maximum power conversion efficiency (PCE) of up to 11.24%, which is the best performance reported for state-of-the-art NF-SM-OSCs. On this basis, the challenges and prospects of NF-SM-OSCs are discussed.

As new types of carbon nanomaterials, carbon quantum dots (CQDs) have received widespread attention for their potential applications in optoelectronic device owing to their unique properties such as long hot-electron lifetime, high electron mobility, tunable bandgap, strong stable florescence, solution-processability, stability, non-toxicity, and low cost. Correspondingly, there has been several interesting developments in researches focusing on CQDs. In this review, we will present an update the on the latest research on the synthesis, morphology, structural characteristics, and optoelectronic properties of CQDs. The latter are determined by quantum confinement effect and surface defects. Using bottom-up synthesis methods, CQDs with higher crystallinity and less surface defects could be obtained by accurately designing the precursors and reaction conditions. The structures could be characterized by high-resolution transmission electron microscopy. Secondly, the latest progress on photoelectric devices, including light-emitting diodes (LEDs), solar cells (SCs), and photodetectors (PDs), are summarized in detail. CQDs-based LEDs are divided into photoluminescence (PL) and electroluminescence (EL) LEDs owing to their different excitation modes. Recently, PL LEDs leveled with developed QDs-based LEDs in both luminous efficiency and color rendering index (CRI). With the discovery of their bandgap emission, CQDs overcame carrier injection, which is determined by surface defects and molecule states, and presented excellent potential in EL applications. Moreover, their broad absorption in the ultraviolet-to-visible light range and high electron mobility make CQDs preferable for improving energy conversion efficiency of SCs and responsivity of PDs. Finally, we delineate current challenges on studying CQDs. Its indefinite fluorescence mechanism and structural characterizations limit the development of CQDs. Furthermore, large-scale synthesis methods for CQDs with high quantum yields and crystallinity are not yet established, which hinders their utility in optoelectronic devices. Moreover, CQDs with narrow emission bandwidth (full width at half maximum, FWHM ≤ 35 nm) still do not exist, which restrains their applications in display and laser. Hence, researches on CQDs-based optoelectronic applications are still in the first stages of development. We hope that this review will indicate future directions and encourage critical thinking to elicit new discoveries on CQDs from both fundamental and applied researches. Consequently, the potential of environment-friendly CQDs can be realized in optoelectronics and more areas.

Although a large variety of aromatic systems have been unveiled in the literature, justifying their origin of stability and understanding their nature of aromaticity is still an unaccomplished task. In this work, using tools recently developed by us within the density functional reactivity theory framework, where we employ simple density functionals to quantify molecular structural and reactivity properties, we examine the aromaticity concept from a different perspective. Using six quantities from the information-theoretic approach, namely, the Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, Onicescu information energy, information gain, and relative Rényi entropy, and four aromaticity descriptors, namely, the aromatic stabilization energy (ASE) index, the harmonic oscillator model of aromaticity (HOMA) index, the aromatic fluctuation (FLU) index, and the nucleus-independent chemical shift (NICS) index, we systematically examined the correlations between substituted fulvene derivatives fused with one, two, and three benzene rings. Among the 14 benzofulvene derivatives studied in this work, there were seven single-fused, four double-fused, and three triple-fused benzofulvene derivatives. Our results show that the aromaticity indexes are often well correlated with one another. The same is true for information-theoretic quantities. Moreover, these correlations are valid across all series of benzofulvene derivatives with different ring structures. The cross-correlations between information-theoretic quantities and aromaticity indexes were usually strong. However, two completely opposite patterns were observed; as a consequence, these correlations are not valid across all series of benzofulvene derivatives. The nature of these correlations depends on the nature of the ring structure. The two groups of systems, each obeying the same cross-correlation patterns, have a total number of 4n + 2 and 4n π electrons, respectively, which are in agreement with Hückel's rule of aromaticity and antiaromaticity. Compared with the results obtained for systems without a benzene fused ring, the correlation patterns of these quantities were always found to be the same, both with and without fused benzene rings. This suggests that, despite benzene's aromaticity, its fusion with a fulvene moiety does not modify the aromaticity and antiaromaticity of the fulvene ring. These results confirm that the fusion of benzene rings with a fulvene moiety has no influence on the aromatic nature of the fulvene moiety. Thus, the aromaticity and antiaromaticity of benzene-fused fulvene derivatives are solely determined by the fulvene moiety. These results should provide a new understanding of the origin and nature of aromaticity and antiaromaticity.

A lithium ion hybrid supercapacitor system with battery and supercapacitor characteristics has the potential to meet the increasing demand for an energy storage device with both high energy and power densities. In this work, orthorhombic Nb₂O₅ (T-Nb₂O₅) with three-dimensional (3D) flower-like structures was synthesized by a facile hydrothermal reaction and an annealing process. A lithium ion hybrid supercapacitor was constructed by using T-Nb₂O₅ as an anode and commercial activated carbon (AC) as a cathode. The electrochemical performance of these T-Nb₂O₅/AC hybrid capacitors was measured by cyclic voltammetry and galvanostatic charge/discharge tests. The results showed that the working voltage of the hybrid supercapacitor could reach 3.0 V in the organic carbonate electrolyte system. The as-assembled device showed impressive power density of 294 W·kg^-1 and energy density of 53.79 W·h·kg^-1 at a current density of 100 mA·g^-1 with a voltage range of 0.5-3.5 V. Moreover, it also showed excellent cycling stability with a retention of 73% after 1000 cycles at 200 mA·g^-1. These results demonstrate that this novel lithium ion hybrid supercapacitor based on T-Nb₂O₅ with 3D flower-like structures and AC is a promising candidate for high power density energy storage applications.

Microorganisms exploit extracellular electron transfer (EET) with external minerals during their growth. This process is accompanied by the conversion of chemical energy. Direct electron transfer (DET) from the microorganisms to solid electron acceptors via membrane-bound cytochrome c enzymes or conductive nanowires/pili has been reported. In previous studies, mediated electron transfer (MET) has also been demonstrated to occur through electrochemically active metabolites acting as redox mediators. The microorganisms with EET capabilities have been harnessed for bioelectrochemical systems (BESs) in the bioremediation of environmental contaminants and the production of biofuels and nanomaterials. Electron transfer at the electrode biofilm/solution interface is one of the core phenomena occurring in BESs. The study of the redox reactions occurring in the microenvironment of the biofilm should elucidate the mechanism of microbial EET, which will then help improve the electron transfer efficiency of BESs. The composition of a biofilm is complex and contains many redox secreta and extracellular polymeric substances. Therefore, the specific current generated from the DET or MET pathways cannot be solely detected using classic electrochemical methods. In the present study, the interfacial electron transfer of Shewanella oneidensis MR-1 on an ITO surface was investigated. Cyclic voltammetry (CV) was first applied to study the redox properties of Shewanella and its interaction with ferrocenylmethanol (FcMeOH), which served as an exogenous electron mediator. The cyclic voltammograms showed that the oxidation current of S. oneidensis MR-1 was dramatically enhanced in the presence of 0.01 mmol·L^-1 FcMeOH compared to a control, i.e. bacterium-free ITO. This can be explained by the ability of S. oneidensis MR-1 to reduce FcMeOH⁺ during the positive scan. These results also showed that FcMeOH was a good redox mediator and capable of transferring electrons between the electrode and the bacterial cells. In addition, using the penetration mode in scanning electrochemical microscopy, the current generated from the MET by FcMeOH was collected using a microelectrode. Examination of the approaching curve showed that the current started to increase when the tip was approaching the solution/biofilm interface, providing positive feedback for the FcMeOH-mediated electron transfer between the microelectrode and the bacterial cells. The electrode biofilm/solution microenvironment was also detected, showing the thickness of the solution/biofilm to be 500 μm and the thickness of the biofilm to be 1100 μm. This study indicates that scanning electrochemical microscopy can be used in studying microbial MET. It also provides insight into the electron transfer mechanism of the microbial metabolism from a physical chemistry perspective.

Magnetic nanoparticles (MNPs) have attracted great attention because of their unique physiochemical properties in emulsion preparation and demulsification.This paper summarizes the synthesis, structure, and significant properties of functional magnetic nanoparticles.The application of MNPs in emulsion preparation and demulsification is also reviewed.The processes through which MNPs disperse well in liquid and stably absorb on the oil-water interface leading to the formation of films are emphatically analyzed.More importantly, their magnetic response contributed to the change in interface properties, deformation, and migration of magnetically responsive droplets in the emulsion issummarized.Then, we summarize the effects of surface properties and behaviors of MNPs on emulsion stabilization or demulsification.This study provides a theoretical support for further applications of emulsions.Finally, we propose the crucial issues to be addressed in studying the application and effect of functional magnetic nanoparticles.

In the past decade, perovskite solar cells (Pero-SCs) have attracted a great deal of attention owing to their soaring power conversion efficiency (PCE), up to 22.7% in 2017. In p-i-n type Pero-SCs, one of the most commonly used hole transport layer (HTL) materials is poly(3, 4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT: PSS), which possesses a high coverage and an extremely smooth surface. However, the inferior electrical conductivity (or large series resistance) and lower work function (WF) of PEDOT:PSS relative to many other HTL materials limits the open-circuit voltages of Pero-SCs. Furthermore, the hygroscopic property and the acidic nature of PEDOT:PSS can readily cause the degradation of perovskite, and thereby affect the long-term stability of Pero-SCs. The abovementioned disadvantages can hinder the application of PEDOT:PSS in high-performance and stable Pero-SCs; therefore, many efforts have been made to modify PEDOT:PSS to prevent these disadvantages, for instance, adding various organic solvents, surfactants, salts, or acids to PEDOT:PSS as dopants. In this paper, we report a simple codoping method to modify PEDOT:PSS, i.e., employing L-3, 4-dihydroxyphenylalanine (DOPA) and dimethyl sulfoxide (DMSO) as codopants in PEDOT:PSS, and applying it as a HTL in p-i-n type Pero-SCs. Herein, DOPA and DMSO were mixed separately with PEDOT:PSS to obtain HTLs for comparison. The DMSO-doped PEDOT:PSS improved the conductivity of the PEDOT:PSS film, while the DOPA-doped PEDOT:PSS tuned the WF of the PEDOT:PSS film. Hence, codoping of DMSO and DOPA not only allows for a good match of the energy levels between PEDOT:PSS and the perovskite but also leads to an improvement in the conductivity of PEDOT:PSS. The champion PCE of the Pero-SCs increased from 13.35% to 17.54% after DOPA and DMSO were codoped in PEDOT:PSS. Owing to their aligned energy levels and enhanced charge transportation, the detailed photovoltaic parameters were greatly improved. Scanning electron microscope and X-ray diffraction were used to characterize the morphological change and crystallinity of the perovskite films. Morphological characterization also revealed that the density of grain boundaries in the perovskite films decreased, which should alleviate the charge recombination occurring in the photoactive layer. Both steady-state photoluminescence (PL) and time-resolved PL characterizations were carried out, and they indicated that nonradiative recombination increased for the perovskite films prepared on the doped PEDOT:PSS films. This result explains the improved short-circuit current density. Electrochemical impedance spectroscopy was employed to determine the resistances of the solar cells. The results are consistent with device performance and that reflected in the PL spectra.

Inorganic porous materials have been widely applied in the field of chemical industry, energy, environmental protection and other fields owing to their special physicochemical properties. In this paper, the current research progress on inorganic porous materials was summarized. The detailed preparation methods for macroporous, mesoporous, microporous materials and macro-mesoporous, macro-microporous, meso-microporous, macro-meso-microporous materials have been discussed in detail. The indoor and outdoor applications of inorganic porous materials for environmental protection were described and the application of inorganic porous materials in the field of removing mobile source pollution was particularly introduced. Finally, the existing problems about the preparation of inorganic porous materials were summarized and the future research directions for the preparation and application of inorganic porous materials were also prospected.

Water is an indispensable resource for all biological life on earth. It is crucial for the existence of human beings and civilizations have historically thrived around water bodies. However, there still remains an enormous cognitive gap about the abnormal properties of water, its influence in the field of physics, chemistry, and biology, and the underlying mechanism of its effect on natural processes. Hydroscience has gradually entered the arena for scientific discussion and transformed into a main research area. While the majority of water on earth exists as bulk water, it typically participates in different physical and chemical processes in the form of interface/confined water under both natural and scientific research conditions. Nanoconfined water generally exists in natural and synthetic nanoscale environments, and its distinction from bulk water is mainly reflected in its dynamic and thermodynamic properties. The existence of confined water also has a profound impact on the development of devices composed of nanomaterials and their applications in the fields of biology, environmental science, geology etc. In this paper, the hydrogen bond structure of nanoconfined water has been analyzed and its dynamic, thermodynamic, and electrical properties have been generalized. A summary of the different research methods and their corresponding developmental history, together with examples of the application potential of nanoconfined water in the fields of environmental and material science have been presented. A summary of the progress made and existing problems in the research area of confined water is given along with the prospects for future developments.

In recent years, organic solar cells (OSCs) have attracted increasing attention, and the power conversion efficiency (PCE) of OSCs has markedly improved. To enhance the photovoltaic properties of OSCs, it is important to develop the donor materials in the light-harvesting layer, which mainly include conjugated polymers and small molecules (SMs). Compared with polymeric materials, small-molecule materials have been widely investigated for their superior characteristics, such as well-defined molecular structures that can provide good batch-to-batch reproducibility. In this work, we synthesized three SM donor materials with theacceptor-donor-acceptor (A-D-A) structure by employing the trialkylthienyl-substituted benzodithiophene (TriBDT-T) unit as the D-core unit, and rhodanine (RN), cyano-rhodanine (RCN), and 1, 3-indanone (IDO) as the A end groups, respectively. The optical properties, molecular energy levels, and thermogravimetic characteristics of the three SMs were studied; moreover, the blend morphologies and photovoltaic properties of the devices by employing the non-fullerene (NF) acceptor, IT-4F, were systematically investigated. The results showed that 1) the three SMs exhibit good thermal stabilities as evinced by thermogravimetric analysis (TGA), and all decomposition temperatures exceeded 410 ℃; 2) They all exhibit strong and broad absorption in the visible light range (300–700 nm), and show similar molar extinction coefficients; 3) the HOMO levels are -5.47 eV, -5.54 eV, and -5.44 eV for RN, RCN, and IDO, respectively, implying the clear influence of the different end groups for the energy levels of the A-D-A-type SMs; the slight differences in the optical and electrochemical properties of the corresponding donor material could be attributed to the different electron-withdrawing ability of the A-type end groups. When studying the photovoltaic properties, interestingly, the RN:IT-4F blend was found to form fibrillar-like aggregates with appropriate size, and the corresponding devices exhibited desirable short circuit current (J_sc) and thus the highest PCE value of 9.25%; however, large-size aggregates were formed in the RCN:IT-4F and IDO:IT-4F blend films, resulting in a much lower J_sc and fill factor (FF), and the PCE of the corresponding devices were only around 6%. In summary, by introducing RN, RCN, and IDO as the A units, we synthesized a class of TriBDT-T based A-D-A type SMs. This study shows that terminal A units exert influence on the absorption spectra, molecular energy level, and morphologies after blending with the acceptor material, and hence, the corresponding devices exhibit significant differences in photovoltaic performance. This work also provides useful information for the molecular design of SM donor materials.

Lead acetate, which is highly soluble in dimethylformamide, was used to synthesize mixed halide perovskite CH₃NH₃PbBr_3-xCl_x (MA = CH₃NH₃, 0 ≤ x ≤ 3) nanocrystals (NCs). This method provides an approach to address the low solubility of lead halides, especially lead chloride. Different Br/Cl ratios in MAPbBr_3-xCl_x lead to various optical properties. The photoluminescence emission peak can be tuned from 399 to 527 nm. Their full-widths at half-maxima (FWHM) are about 20 nm. MAPbBr_3-xCl_x NCs have an average diameter of ~(11 ± 3) nm and have uniform dispersion in toluene. The MAPbBr₃ NCs have a long average recombination lifetime (τ_ave = 97.4 ns) and a photoluminescence quantum yield (PLQY) of up to 73%.

Deep eutectic solvents (DESs) are regarded as a new class of green solvents because of their unique properties such as easy synthesis, low cost, environmental friendliness, low volatility, high dissolution power, high biodegradability, and feasibility of structural design. DESs have been widely applied for the separation of mixtures as alternatives to conventional solvents. A DES usually consists of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). HBAs include amides, thiourea, amines, imidazole, azole, alcohols, acids and phenol. HBAs include quaternary ammonium salts, quaternary phosphonium salts, imidazolium-based salts, dication based salts, inner salts, and molecular imidazole and its analogues. Therefore, there are numerous DESs available for use in different applications. With an in-depth understanding of the common and novel properties of DESs, researchers have prepared and applied DESs to various types of separations. We first introduce the composition of DESs, including various HBDs and HBAs frequently used in the literature. Second, the properties of DESs, including phase diagrams, melting points, density, viscosity, and conductivity, are summarized. Third, recent applications of DESs in the separation of mixtures are reviewed, including the absorption of acidic gases (CO₂, SO₂ and H₂S), the extraction of bioactive compounds, extraction of sulfur-and nitrogen-containing compounds from fuel oils, extraction of phenolic compounds from oils, separation of mixtures of aromatic and aliphatic compounds, separation of alcohol and water mixtures, removal of glycerol from biodiesel, separation of alcohol and ester mixtures, removal of radioactive nuclear contaminants, and separation of isomer mixtures of benzene carboxylic acids. DESs are used in two ways for the separation of mixtures. (1) A DES prepared in advance is used as a solvent to separate a component from a mixture by selective dissolution or absorption of specific compound(s), such as the absorption of SO₂ using betaine+ethylene glycol DES. Here, DESs are used like traditional solvents. (2) A DES is formed in situ during the separation of mixtures by adding a HBA to a mixture containing one or more HBDs, such as the removal of phenol from an oil mixture using choline chloride, where a phenol+choline chloride DES is formed during the separation process and the formed DES does not dissolve in the oil phase. Although various DESs have been broadly developed for the separation of mixtures, research continues in the field of DESs, including analysis of the physicochemical properties of DES, especially during extraction or absorption, development of functional DESs for high-efficiency separations, development of efficient methods to regenerate DESs, and combined use of DESs with other techniques to improve separation processes. This article describes general trends in the development of DESs for separation and evaluates the problematic or challenging aspects of DESs in the separation of mixtures.

Flaky polyaniline-reduced graphene oxide (PANI-rGO) composites have larger specific capacitance due to the improved redox charge of PANI in the composites, fabricated by simultaneous reduction of PANI-GO. The structural and morphological analyses were carried out using scanning electron microscopy, UV-Vis spectroscopy, and thermogravimetry. The results showed that the composites are flaky in shape. PANI is uniformly coated on GO, and PANI-rGO has specific capacitance as high as 1069 F·g^-1 (1.71 F·cm^-2) at a current density of 20 A·g^-1, 5 times higher than PANI-GO; this is caused by the large surface and conductivity of the rGO in the composite.

Si-based anode materials in Li-ion batteries (LIBs) suffer from severe volume expansion/contraction during repetitive discharge/charge, which results in the pulverization of active materials, continuous growth of solid electrolyte interface (SEI) layers, loss of electrical conduction, and, eventually, battery failure. Herein, we present unprecedented low-content phosphorene (single-layer black phosphorus) encapsulation of silicon particles as an effective method for improving the electrochemical performance of Si-based LIB anodes. The incorporation of low phosphorene amounts (1%, mass fraction) into Si anodes effectively suppresses the detrimental effects of volume expansion and SEI growth, preserving the structural integrity of the electrode during cycling and achieving enhanced Coulombic efficiency, capacity retention, and cycling stability for Li-ion storage. Thus, the developed method can also be applied to other battery materials with high energy density exhibiting substantial volume changes.

The past decade has witnessed tremendous progress in the improvement of the electrocatalytic efficiency of the oxygen reduction reaction (ORR), which is important for the widespread adoption of fuel cells. This review provides an overview of the recent advances in the rational structural design and construction of Pt-based nanocatalysts to achieve higher ORR activity, with an emphasis on tuning the dimensionalities of Pt-based nanocrystals. The advantages and disadvantages of each dimensional catalyst have been discussed. In particular, we focus on a contemporary understanding of the structure-performance relationships based on the combined theoretical and experimental evidence, which can be further applied to guide the search for more exciting catalytic systems. The review concludes with a personal perspective for future research directions.

Organic-inorganic hybrid perovskites have attracted substantial attention due to their outstanding performance in solar energy conversion and optoelectronic applications. However, the poor stability of organic lead halide perovskites (APbX₃, A: organic cations; X: halide anions) hinders their practical application. Compositional engineering, optimizing the concentration of different A and/or X, is one of the most effective ways to enhance the stability of APbX₃. In particular, mixing formamidinium (FA) and methylammonium (MA) cations has been widely investigated. Here, we performed first-principles calculations to systematically investigate the structures and optical properties of FA_1-xMA_xPbI₃. We obtained several stable crystal structures of FA_1-xMA_xPbI₃ in the cubic phase for different ratios of FA and MA cations. By analyzing the structures of these mixed cation perovskites, we revealed that the lattice parameters decreased linearly with increasing concentration of MA cations, which was consistent with previous experimental results. For APbX₃ perovskites, the Goldschmidt tolerance factor has been shown to be an effective index for predicting the stability. The mixing of organic cations is an effective method for adjusting this factor and thus the stability of these perovskite materials. In this work, the formation energy difference (∆E) was calculated and our results showed that mixing of FA and MA cations could increase the thermodynamic stability compared to pure FAPbI₃ and MAPbI₃. FA_0.5MA_0.5PbI₃ was found to be the most stable of all composites investigated. Furthermore, the band gap decreased with increasing proportion of FA cations, indicating an effective strategy for extending the absorption range of organic-inorganic hybrid perovskites into the infra-red region of the solar spectrum. By analyzing the Pb―I bond lengths for different FA : MA ratios, we showed that the decrease of band gap mainly comes from the increase of the maximum valence band energy. In addition, the effective masses were similar, irrespective of the cation mixture, indicating that the mixing of organic cations does not affect the carrier transport mechanism in this material. Density of states (DOS) analysis revealed that the DOS of valence band edge increased with increasing proportion of FA cations, enhancing transitions between the valence and conduction bands. Finally, detailed analysis of the optical absorption coefficients of all composition was performed; the absorption spectra were blue shifted with increasing MA cation concentration. These results demonstrated the possibility of controlling the optoelectronic properties of organometallic lead halide perovskites by mixing FA and MA cations and hence, further improving the efficiency of perovskite solar cells.

Intrinsically conductive polymers are a class of exciting materials since they combine the advantages of both metals and plastics. But their application is limited due to the issues related to their electronic properties, stability and processibility. For example, although polyacetylene can have electrical conductivity comparable to metals, it degrades fast in air. Most of the conductive polymers in the conductive state, such as polypyrrole and polythiophene, cannot be dispersed in any solvent and cannot be turned to a melt. It is thus difficult to process them into thin films with good quality, while thin films with good quality are important for many applications. In terms of the materials processing, polyaniline (PANi) and poly(3, 4-ethylenedioxythiophene) (PEDOT) have gained great attention. PANi doped with some large cations can be dispersed in some toxic organic solvents, and poly(3, 4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) can be dispersed in water and some polar organic solvents. But the PANi and PEDOT:PSS films prepared from their solutions are usually low. Recently, great progress was made in improving the properties of intrinsically conductive polymers. The conductivity of PEDOT:PSS can be enhanced from 10^-1 S·cm^-1 to > 4000 S·cm^-1 through the so-called "secondary doping". The high conductivity together with the solution processibility enables the application of conductive polymers in many areas, such as electrodes and thermoelectric conversion. In addition, due to their electrochemical activity, conductive polymers or their composites with inorganic materials can have high capacity of charge storage. Conductive polymers can also be added into the electrodes of batteries, because they can facilitate the charge transport and alleviate the large volume change problem of silicon electrode of batteries. It has been demonstrated that conductive polymers can have important application in many areas, such as transparent electrode, stretchable electrode, neural interfaces, thermoelectric conversion and energy storage system. This article provides a brief review on the enhancement of the electrical conductivity of intrinsically conductive polymers and their application as electrodes and in thermoelectric conversion, supercapacitors and batteries.

As a new member of the carbon allotrope family, graphdiynes (GDs)consist of both sp-and sp²-hybridized carbon atoms, possessing unique π-conjugated carbon skeletons and expanded 18C-hexagonalpores in two dimensions. In contrast with the zero band gap graphene (GR), GDis a semiconductor with a direct band gap of 1.22 eV calculated according tothe density functional theory (DFT) using the HSE06 method; this makes it apotential semiconductor material that can supplant silicon in the integratedcircuit industry. Moreover, owing to the presence of diacetylenic linkagesbetween its hexagonal carbon rings, GD shows electron-deficient properties, which lead to its electron-accepting tendency. Graphdiynes exhibit unusualsemiconducting properties with excellent charge mobilities and electrontransport properties that are associated with its distinct topological andelectronic structures. Graphdiynes play the role of not only electron-acceptorsthat efficiently collect the electrons from other materials but also electron-donorsthat inject electrons into other systems, thus exhibiting excellentelectron-transfer enhancement characteristics. The unique electron-transferenhancement property of GDs inspired us to summarize the interactions betweenGDs and other materials including metal oxides, metal nano-particles, andorganic molecules. In this review paper, we first introduce the TiO₂/GDnanocomposite, because the linking of GDs and titania nanoparticles (P25) throughthe Ti—O—Cbond sets an important precedent for exploring the electron-transfer behaviors involvingGDs and the metal oxide. These results indicate that the GDs can act asacceptors of the photogenerated electrons in the TiO₂/GD system, effectively suppressing charge recombination and resulting in excellent photocatalyticproperties. Nevertheless, the GDs in CdSe quantum dots (QDs)/GD composites areable to collect photogenerated holes from the QDs and perform as promising hole-transfermaterials in the photoelectrochemical cell for water splitting. As a result, the interactions between GDs and various metal compounds should be explored todeeply understand the electron-transfer properties of GDs. Furthermore, GDs canbe also used as electron donors to reduce PdCl₄^2- toPd nanoparticles that can subsequently be used for the electroless depositionof highly dispersed Pd nanoparticles. Based on electrostatic potential surfaceanalysis over the Pt₂/GD, GDs can attract the electron cloud fromthe Pt nanoparticles and produce a positive polarization of the metal atomsurface. However, due to its large π-conjugated system, GD can alsocollect and transfer electrons from the electrode under a bias voltage, making ita new type of electrocatalyst material, especially for single-atom catalysts.The interactions between GDs and metal particles/clusters/atoms have attracted thebroad attention of the rapidly developing field of single-atom catalysis.Finally, research on the interactions between GDs and organic molecules, especially biomolecules, is still in its infancy and requires development. In summary, we overview the recent research progress on GD and its enhanced ability forelectron transfer in this review paper, including metal oxides/GD, metalnano-particles/GD, polymers/GD, and organic molecules/GD, from bothexperimental and theoretical perspectives, and emphasize the interactions andelectron-transfer enhancement properties. It is expected that this review canpromote the development and applications of GD chemistry.

Two new coordination polymers, namely, [[Zn₂(TTR4A)(L)₂]·DMF·4H₂O]_n (compound 1) and [[Co(TTR4A)Cl₂]·DMA·H₂O]_n (compound 2), have been synthesized under solvothermal conditions (TTR4A = tetrakis(1, 2, 4-triazol-ylmethylresorcin[4]arene), L = 4, 4'-biphenyldicarboxylic acid, DMF = N, N-dimethylformamide and DMA = N, N-dimethylacetamide). Crystal structures of the coordination compounds 1 and 2 were determined by single-crystal X-ray diffraction analyses, and further characterized by infrared spectra, elemental analyses, powder X-ray diffraction, and thermogravimetric analyses. In coordination compound 1, four L ligands bridge four adjacent Zn(Ⅱ) atoms to generate macrocyclic Zn₄L₄ units, which are further linked by the TTR4A ligands into a one-dimensional chain structure. In coordination compound 2, four 1, 2, 4-triazole groups of each TTR4A ligand bridge four Co(Ⅱ) atoms to form a two-dimensional layer structure. Furthermore, studies on the luminescent properties of compound 1 in solid state at room temperature reveal that it exhibits an intense emission peak. Luminescent-sensing detections for Fe³⁺, Cr₂O₇²⁻, and nitrobenzene solvents were also investigated by using compound 1 as the potential luminescent sensor.

White LEDs are considered the next-generation light source as they are environmentally friendly and have high efficiencies. Therefore, researches are being conducted to meet the performance requirements of phosphors, which are the crucial components of white LEDs. Eu²⁺ and Eu³⁺ ions have different electronic structures, which lead to distinct photoluminescence properties. The characteristic emissions of Eu²⁺ and Eu³⁺ originate from the 4f-4f and 4f-5d transitions, respectively. In order to combine their respective features, the research of mixed-valence Eu ions into single-phase phosphors has become a hot research topic in recent years. The mixed-valence Eu ion-doped phosphors have tunable luminescence properties because they possess the respective properties of Eu²⁺ and Eu³⁺. From their respective characters of Eu²⁺ and Eu³⁺, this paper mainly reviews the progress of mixed valence Eu(+2, +3) ion-activated single-component luminescent materials in recent years from three aspects: unbalanced substitution, crystal field regulation, and other systems. In addition, the respective photoluminescence properties of Eu²⁺ and Eu³⁺ and the luminescence performances and mechanisms of the mixed-valence Eu ion-activated phosphors have been summarized. The luminescence performances and mechanisms have been summarized as well. All the research works carried out in this field provide inspiration for the investigation of new phosphors.

MXene is a new group of electrocatalysts for two-dimensional hydrogen evolution reaction (HER). Its surfaces are often covered by hydrophilic O and OH mixed groups. To find the effect of the O and OH mixed groups on HER, we studied the HER activity for M₂XO_2-2x(OH)_2x (M=Ti, V; X=C, N) by first-principle calculations. Results indicate that HER activity is closely related to OH-occupied coverage (x). For Ti₂CO_2-2x(OH)_2x, excellent HER activity could be maintained when the OH-occupied coverage was not larger than 1/3. For Ti₂NO₂-2x(OH)_2x, V₂CO_2-2x(OH)_2x, and V₂NO_2-2x(OH)_2x, high HER activity was obtained when OH-occupied coverage reached 4/9, 1/3, and 5/9, respectively. Next, we analyzed the charge-transfer density and found that the charges on the oxygen groups were strongly affected by the OH-occupied coverage. Finally, we revealed the variation of HER activity that oxidizability of O groups is weakened with increasing OH-occupied coverage. In this paper, we propose a new method to obtain the optimal HER activity for M₂XO_2-2x(OH)_2x by adjusting the OH-occupied coverage of the surfaces, which is useful in industrial hydrogen production.

The effect of inserting coordinatively unsaturated metal sites (CUS) into porous aromatic frameworks (PAFs) on their hydrogen storage capacity was investigated systematically by density functional theory and grand canonical Monte Carlo simulations. The results indicate that the maximum excess gravimetric uptake of hydrogen possible with PAF-302MgO₂_PBE100 is 7.97% (w) at 77 K. The total uptakes of hydrogen by PAF-302 and PAF-303 functionalized with 100% magnesium alkoxide at 77 K and 10 MPa were determined to be 9.9% (w) (65.9 g∙L^-1) and 15.0% (w) (50.5 g∙L^-1), respectively. These uptake values are 80% (64.8%) and 173% (26.3%), respectively, more than the gravimetric and volumetric targets set by the Department of Energy (DOE) of USA. They also exceed the targets set by NU-1101, presenting the highest measured performance of 9.9% (w) (46.6 g∙L^-1) under the same conditions. Even at 243 K and 10 MPa, the total gravimetric and volumetric uptakes of hydrogen in the former are up to 5.13% (w) and 34.19 g∙L^-1, which are about 93.3% and 85.5% of the targets set by DOE, respectively. By analyzing the isosteric heat of adsorption (Q_st), radial distribution function, and mass center probability density, it is found that increasing the length of the organic linkers of PAFs incorporated with CUS will result in decreasing volumetric surface areas in spite of the increase in void fractions, which is the root of trade-offs between the total gravimetric and volumetric H₂ uptake in porous materials. Additionally, CUS incorporation improves the affinity of PAF materials to H₂ molecules, resulting in an enhancement of the volumetric hydrogen storage capacity.

Carbon quantum dots (CQDs) are emerging as the new-generation light absorber for solar energy conversion. However, the low photosensitization efficiency of CQDs is one of the current bottlenecks impeding their large-scale practical applications in photocatalysis. Therefore, developing a facile approach for the engineering and functionalization of CQDs-based composites to improve the photosensitization efficiency of CQDs is highly desirable. On account of the abundant functional groups, especially oxygen-containing functional groups such as carbonyl, carboxyl, and hydroxyl present on their surface, CQDs can be readily combined with various organic molecules or polymers as a surface passivation component to reduce the nonradioactive surface recombination of photo-generated charge carriers, thus enabling the CQDs to exhibit strong photoluminescence in the visible and near-infrared spectral regions. Consequently, polymer passivation has been demonstrated as an ideal strategy to make it accessible for improving the sensitization efficiency of CQDs in photocatalytic applications. Branched polyethylenimine (BPEI) is one of polymers that contains a high density of amine groups and exhibits high electron mobility, which can be used as an electron injection material at the interface of nanomaterials. Besides, the BPEI polymer with amino groups exhibiting positive charge has been utilized for designing heterogeneous catalysts by an electrostatic self-assembly strategy. Therefore, BPEI is expected to modify the surface of inorganic oxides semiconductor to enhance the photosensitization efficiency of CQDs under visible light. However, to date, the study in this regard has been still unavailable. In this work, we developed a facile approach to engineer well-distributed CQDs via electrostatic interaction on BPEI passivated TiO₂ composites (BTC) as photocatalysts. The BTC composites with an optimal loading of 5% (w, mass fraction) CQDs outperformed the TiO₂/CQDs (TC) composite and referential BPEI/SiO₂/CQDs (BSC) composites for the photoreduction of 4-nitroaniline under visible light irradiation. The structure of the fabricated BTC composites was systematically investigated by the combined use of structural and spectral characterizations, demonstrating that the photosensitizer CQDs contacted well with the BPEI modified TiO₂ nanoparticles. The comparison characterizations revealed that BPEI facilitated the dissociation and transfer of excitons as an electron transfer channel. The as-prepared BTC composites benefited from the favorable interfacial contact and effective transfer of photo-generated charge carriers, and thus manifested superior photocatalytic activity to the TC composite. It is expected that this strategy would be extended to other wide band gap semiconductor photocatalyst systems and open up new possibilities in designing efficient CQDs-based semiconductor artificial light harvesting systems by interfacial optimization.

Molecular geometries, electronic structure, and infrared spectroscopy of a series of polyoxometalate (POM)-supported single atom catalyst (SACs) (M₁/POM (M = Ni, Pd, Pt, Cu, Ag, Au, POM = [PW₁₂O₄₀]^3-) have been studied based on density factional theory (DFT) combined with natural bond orbital (NBO) analysis method. The results show that Pt₁/POM has a higher reactivity for activation of N₂ relevant to the others. The interaction between the isolated Pt atom and N₂ arises from an orbital mixture, which is formed by the d_xz and d_yz orbital of Pt atom and the π* anti-bond orbit of N₂ molecule. The electron transfer from Pt atom to the nitrogen molecule leads to a weakened N≡N bond. The N≡N bond distance increases when compared with the free N₂ molecule. All results indicate an effective activation of the nitrogen molecules. For DFT-derived IR spectra, the four characteristic peaks of Keggin-type POM split into five because of introduction of the isolated metal atom.

Owing to their unique optical, electronic, magnetic, and surface plasmon resonance properties, nanomaterials have attracted significant attention for potential bioanalysis and biomedical applications. Aptamers are single-stranded oligonucleotides, which are generated by a procedure termed as SELEX (Systematic Evolution of Ligands by EXponential Enrichment) and typically demonstrate high affinity and selectivity toward their target molecules. As a result of their unique characteristics, aptamers are promising recognition units that can be conjugated with nanomaterials for cancer cell imaging, diagnosis, and cancer therapy. By integrating the recognition abilities of aptamers with the properties of nanomaterials, aptamer-conjugated nanomaterials can serve as extraordinary tools for bioimaging and cancer therapy. Recently, aptamer-conjugated nanomaterials have attracted significant attention in the field of specific cancer cell targeted therapy owing to their improved efficacy and lower toxicity. In this review, we summarize the progress achieved of aptamer-conjugated nanomaterials as nanocarriers for specific cancer cell diagnosis and targeted therapy. In addition to drug delivery for cancer therapy, the various achievements of the aptamer-conjugated nanomaterials in combination with other emerging technologies to improve the efficiency and selectivity of cancer therapy have also been reviewed.

A solid polymer electrolyte (SPE), composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and poly(ethylene oxide) (PEO), is prepared by a simple solution-casting method. The physicochemical and electrochemical properties of the NaTFSI/PEO ([EO]/[Na⁺]=15) SPE in terms of its phase transitions, crystallization, thermal stability, ionic conductivity, and anodic electrochemical stability are systematically investigated. We demonstrate that the NaTFSI/PEO SPE has a relatively high ionic conductivity (σ ≈ 10^-3 S·cm^-1) at 80℃, excellent electrochemical stability (4.86 V vs. Na⁺/Na), and thermal stability up to 350℃. More importantly, the NaTFSI-based SPE delivers not only excellent chemical and electrochemical stability with sodium metal, but also good cycling and rate performances in an Na|SPE|NaCu_1/9Ni_2/9Fe_1/3Mn_1/3O₂ cell.

Monodisperse Fe₃O₄ microspheres with tunable diameters and high magnetic saturation were synthesized by a solvothermal reduction method. It was found that the morphology and structure of the Fe₃O₄ microspheres could be tuned by simply altering the amount of the reactants such as ferric chloride, sodium acetate, water, and the reaction time. The Fe₃O₄ microspheres obtained via this method possessed high purity, crystallinity, and a nearly spherical shape. Furthermore, they were monodispersed and no aggregation was found. Such monodisperse Fe₃O₄ microspheres had tunable diameters of 400-700 nm and the fabrication time was only 2-4 h. The products showed high magnetic saturation values, and their yields were typically more than 94%.

In recent years, the development of perylene diimide derivative (PDI)-based non-fullerene organic solar cells has been extensively studied. These solar cells exhibit unique advantages such as complementary light absorption, tunable energy levels, excellent electron transport properties, and relatively low cost. However, the strong π-π stacking between the PDI molecules tends to induce an uncontrolled phase separation structure, large domain size, and an unmanageable mixed phase, leading to severe geminate and non-geminate recombination and restriction of the final power conversion efficiency of the non-fullerene-based systems. In this work, it was found that one of the most important parameters that helps regulate phase structure is the molecular diffusion rate. By tuning the thermal annealing and liquid-solid phase separation and blend ratio, the phase-separated structure could be adjusted. Further, the domain size of blend systems with different compatibilities was regulated by balancing the π-π and charge transfer interactions. In addition, the amount of the intermixed phase was controlled by tuning the solubility parameter difference (Δδ) between the solvent and the solute.

In the present work, we successfully synthesized ZnO nanorods under hydrothermal conditions, which have been utilized as the matrix to fabricate various noble metal (Pt, Pd, and Ru)-supported ZnO photocatalysts by subsequent reduction with ethylene glycol. In terms of systematic characterization, it was found that the Pt particles in the Pt/ZnO composite have small size with narrow size distribution, while the Pd particles in the Pd/ZnO composite have a larger size distribution due to aggregation. On the other hand, no Ru particles were practically observed in the Ru/ZnO composite. In the photodegradation of a methylene blue solution under UV light irradiation, both Pt/ZnO and Pd/ZnO exhibited significantly enhanced photocatalytic activity compared with the ZnO nanorods, whereas no noticeable increase of catalytic activity could be observed in the case of Ru/ZnO. Furthermore, the photocatalytic activity of the Pt/ZnO catalyst was higher than that of Pd/ZnO, due to its small-sized and uniform Pt particles. Therefore, noble metal particles with small size and high dispersion contribute to the enhancement of the photocatalytic performance of ZnO materials. After detailed investigation of various Pt/ZnO composites with different Pt loadings, it was demonstrated that the optimal Pt loading required to maximally improve the photocatalytic performance of ZnO nanorods corresponds to 3.2%.

For a better understanding of the cytotoxicity of polyethyleneimine (PEI), which has long been considered as the "golden standard" for polymeric gene delivery carriers, on the molecular basis, UV-Vis absorption, fluorescence, circular dichroism, dynamic light scattering and zeta-potential measurements were conducted to reveal the interaction between the PEI of average molecular weight 1.8 and 25 kDa (denoted as PEI1.8k and PEI25k, respectively) and human serum albumin (HSA). The effects of interactions on the conformation of HSA and its binding capability to the model compounds, 8-anilino-1-naphthalenesulfonic acid (ANS) and quercetin, were also evaluated. PEI was found to bind to HSA and induce an alteration in the secondary and tertiary structures of the protein and its binding capability toward small compounds. The complex formation with PEI resulted in a more compact and hydrophobic conformation of HSA, accompanying an increase in α-helix content in the case of PEI1.8k and PEI25k at low concentrations. The binding efficacy of ANS and quercetin to HSA was reduced by competitive binding with PEI, however increased by the conformational change of the protein. Higher-molecular-weight PEI was found to interact with HSA more favorably. It was also more efficient in perturbing the conformation and the binding capability of the protein.

A series of MnO_x-CeO₂ with different Mn contents was prepared using CeBTC-MOF as the sacrificial template. These constituted a new kind of porous crystalline materials assembled by cerium as metal ions and 1, 3, 5-benzenetricarboxylic acid as organic ligands. The composite oxides exhibited good redox properties and were tested as catalysts in the oxidation of toluene. To obtain insight into the structure-activity relationship of the catalysts, the samples were characterized using powder X-ray diffraction (XRD), nitrogen adsorption-desorption, thermogravimetric analysis (TG), elemental analysis (EA), inductively coupled plasma-optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H₂ temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), and UV-Vis diffuse reflectance spectroscopy. Studies of the CeBTC-MOF template showed that the metal-organic framework could be completely decomposed at a calcination temperature of 300 ℃. Therefore, CeBTC-MOF decomposed and generated CO₂ and H₂O during the calcination process. The gas molecule spilled out from the structure to form the interior void space. The spilling out could be controlled by varying the calcination temperature. This regulated the quantity and size of the interior void, which in turn made the surface area controllable. The secondary building unit of CeBTC-MOF was oxidized to nano-sized crystalline particles, which exhibited outstanding interfacial contact. SEM and TEM results showed that the composite oxides prepared by pyrolysis of the CeBTC-MOF template exhibited rod-shaped nanocrystalline particles. While introducing Mn into MOF, part of Mn entered the ceria lattice to form solid solution and the remaining Mn was dispersed on CeO₂ surface. The elemental mappings revealed a well-proportioned distribution of Mn, which confirmed the successful formation of bimetallic metal oxides using the MOF-template method. All the samples exhibited sizes and shapes similar to their parent MOFs. As for catalytic activity, all the composite oxides showed better performances than pure CeO₂ for catalytic oxidation of toluene. This could be attributed to higher concentration of oxygen vacancies, which was characterized by Raman spectroscopy. In addition, the XPS results indicated that Mn⁴⁺/(Mn²⁺+Mn³⁺), Ce⁴⁺/Ce³⁺, O_latt (lattice oxygen), and O_sur(surface oxygen) all participated in the redox process during catalytic oxidation of toluene, which helped elucidate the mechanism at a micro level.

Interestingly, the catalytic activity did not improve further when the Mn content of the composite oxides reached 5%. This could be ascribed to two different states of the dispersed Mn: monolayer dispersion state and crystalline phase. The strong interaction between ceria oxides and dispersed Mn species played an important role in affecting catalytic activity. The results showed the presence of a monolayer dispersion threshold (6.2%), confirmed by XPS characterization, which was in accordance with all the characterization results; it was proved that this threshold had a significant impact on the catalytic activity. When the dispersed Mn content was lower than the monolayer dispersion threshold, Mn reacted with the surface CeO₂ in the form of an incorporation model, leading to charge transfer and higher concentration of oxygen vacancies, which in turn effectively promoted the catalytic performance. When the dispersed Mn content exceeded the monolayer dispersion threshold, Mn₃O₄ was formed on the CeO₂ surface; this disrupted the promotion of catalytic activity, which explains the same catalytic activity of all the samples (5% MnO_x-CeO₂, 8% MnO_x-CeO₂, and 10% MnO_x-CeO₂).

This successful formation of bimetallic metal oxides using CeBTC-MOF template indicated that composite oxide synthesis was feasible using the MOF template method. To obtain high catalyst performance of these composite oxides, it was important to control the metal content at the level of the monolayer dispersion threshold.

Heterogeneous catalysts are usually synthesized by the conventional wet-chemistry methods, including wet-impregnation, ion exchange, and deposition-precipitation. With the development of catalyst synthesis, great progress has been made in many industrially important catalytic processes. However, these catalytic materials often have very complex structures along with poor uniformity of active sites. Such heterogeneity of active site structures significantly decreases catalytic performance, especially in terms of selectivity, and hinders atomic-level understanding of structure-activity relationships. Moreover, loss of exposed active components by sintering or leaching under harsh reaction conditions causes considerable catalyst deactivation. It is desirable to develop a facile method to tune catalyst active site structures, as well as their local chemical environments on the atomic level, thereby facilitating reaction mechanisms understanding and rational design of catalysts with high stability.

Atomic layer deposition (ALD), a gas-phase technique for thin film growth, has emerged as an alternative method to synthesize heterogeneous catalysts. Like chemical vapor deposition (CVD), ALD relies on a sequence of molecular-level, self-limiting surface reactions between the vapors of precursor molecules and a substrate. This unique character makes it possible to deposit various catalytic materials uniformly on a high-surface-area support with nearly atomic precision. By tuning the number, sequence, and types of ALD cycles, bottom-up precise construction of catalytic architectures on a support can be achieved.

In this review, we focus on the design and synthesis of supported metal catalysts using ALD. We first review strategies developed to precisely tailor the size, composition, and structures of metal nanoparticles (NPs) using ALD. Catalytic performances of these ALD metal catalysts are also discussed and compared to conventional catalysts. We highlight synthetic strategies for synthesis of metal single-atom catalysts and bottom-up precise synthesis of dimeric metal catalysts. Their impact on catalysis is discussed. We demonstrate that metal oxide ALD on metal NPs can enhance catalytic activity, selectivity, and especially stability. In particular, we show that site-selective blocking of metal NPs with an oxide overcoat improves selectivity and contributes to an understanding of the distinct functionalities of the low-and high-coordination sites in catalytic reactions on the atomic level. Next, we discuss an effective method to construct bifunctional catalysts via precisely-controlled addition of a secondary functionality using ALD. Finally, we summarize the advantages of ALD for the advanced design and synthesis of catalysts and discuss the challenges and opportunities of scaling up ALD catalyst synthesis for practical applications.

Development of electrocatalysts is one of the challenges in the development of the lithium-oxygen battery, especially the synthesis of catalysts with special pore structures and excellent bifunctional catalytic performance for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). In this article, a reduced graphene oxide-LaFeO₃ (RGO-LaFeO₃) nanocomposite electrocatalyst was synthesized by combining sol-gel and hydrothermal methods and using graphene oxide, lanthanum nitrate, ferric nitrate, and citric acid as raw materials. The prepared samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The results confirmed that the RGO-LaFeO₃ was composed of pure phase LaFeO₃ with a perovskite structure and RGO and that the LaFeO₃ nanoparticles were loaded uniformly on the RGO layer surface. In comparison with a LaFeO₃ nanoparticle (NP-LaFeO₃) catalyst, RGO-LaFeO₃ exhibited superior activity for both the ORR and the OER when it served as the cathode of a lithium-oxygen battery. The higher catalytic activity of the RGO-LaFeO₃ is attributed to the synergistic effect of the special three-dimensional electronic conductive structure of RGO and the intrinsic catalytic property of LaFeO₃. It was shown that the lithium-oxygen battery with the RGO-LaFeO₃ cathode can be cycled stably up to 36 reversible cycles under conditions of a limit discharge depth of 1000 mAh·g^-1 and a 100 mA·g^-1 current density for charge-discharge. The study illustrates that the RGO-LaFeO₃ bifunctional electrocatalyst is a promising candidate for the cathode in lithium-oxygen batteries.

A series of multi-branched dithienylpyrrole (SNS) monomers with rigid phenyl (PhSNS) and biphenyl rings (BPhSNS) as bridges were designed and synthesized, and were fabricated to form cross-linked polymers (pPhSNS, pBPhSNS) by electrochemical polymerization. Cyclic voltammetry (CV) results showed that PhSNS and BPhSNS exhibited similar oxidative properties except for one new higher-potential oxidative peak appearing in the curves of PhSNS. Theoretical calculations indicated that it should be attributed to the different steric configuration between the two dithienylpyrrole (SNS) units in PhSNS. One SNS unit possessed a larger twist angle (40.2°) between thiophene and pyrrole rings than the other one (21.2°), which indicated that PhSNS possessed a relatively larger energy gap (~0.4 eV) between HOMO-1 and HOMO than BPhSNS, for which HOMO and HOMO-1 levels were of almost the same energy. However, both PhSNS and BPhSNS showed similar onset oxidation potentials. The CV curves of pPhSNS and pBPhSNS showed that they presented similar oxidative properties, which enabled their corresponding electrochemical polymers to exhibit similar electrochromic properties. The UV-vis spectra of the corresponding polymers showed that both pPhSNS and pBPhSNS possessed similar optical absorption and similar multicolor switching between yellow (-0.8 V), greyish-green (0.9 V) and gray (1.1 V) colors. Besides, pPhSNS and pBPhSNS showed fast switching times of 0.57 s and 0.93 s at 1100 nm, respectively and reasonable contrasts of 46% and 31% at 1100 nm, respectively. These investigations may help understand the relationship between structural configuration and the electrochemistry/electrochromic properties for polymer electrochromic (PEC) materials research.

Non-fullerene organic solar cells are of broad and current interest in the field of organic solar cells, and show promising application in high performance solar cells. When designing conjugated molecules as non-fullerene materials, several parameters, such as absorption, energy levels, charge transport, and crystallinity should be considered. Among them, absorption spectra are an important parameter that determine the efficiency of sun-light harvesting. In this work, we explore a new near-infrared electron acceptor naphthalenediimide-porphyrin (NDI-Por) by using electron-donating porphyrin as the core, and four NDI as end groups with ethynyl as linkers attached to the meso-position of porphyrin. This star-shaped molecule exhibits absorption spectra up to 900 nm. NDI-Por was incorporated into non-fullerene solar cells as an electron acceptor, and together with a wide-band gap polymer donor, an initial power conversion efficiency of 1.80% could be achieved. In particular, the solar cells exhibit a broad photo-response from 300 to 900 nm. Our results demonstrate that it is an efficient strategy to incorporate porphyrin into conjugated molecules to realize non-fullerene materials with near-infrared absorption spectra.

The increasing anthropogenic emission of CO₂ leads to global warming, to address which three strategies can be considered: (1) decrease fossil fuel consumption through increased utilization efficiency and lower per capita consumption; (2) replace fossil fuels with renewable energy sources like wind, tidal, solar, and biomass energies; (3) utilize CO₂ efficiently. Despite efforts to reduce energy use and increase the use of carbon-neutral biofuels, it seems that fossil fuels will continue to be a major energy source for the next few decades. Tremendous effort is therefore being focused on developing effective technologies for CO₂ capture and transformation. In particular, the transformation of CO₂ into fuels and chemicals via reduction with renewable hydrogen is a promising strategy for mitigating global warming and energy supply problems. The hydrogenation of CO₂, especially to C₂₊ hydrocarbons and oxygenates, has sparked growing interest. The C₂₊ species can be used as entry platform chemicals for existing value chains, thus providing more advantages than C₁ compounds. However, optimizing catalyst design by integrating multifunctionalities for both CO₂ activation and C-C coupling remains an ongoing challenge. Here, we provide a timely review on the recent progress that has been made in the hydrogenation of CO₂ to higher-order alkanes, olefins, and alcohols by various heterogeneous catalysts. The thermodynamics and kinetics, as well as possible reaction pathways for CO₂ hydrogenation, are discussed. The hydrogenation of CO₂ to hydrocarbons usually involves the initial generation of CO via a reverse water-gas shift (RWGS) reaction followed by hydrogenation of the CO intermediate. The RWGS reaction proceeds through a redox route and an associative pathway. "CH_x" insertion (carbide-type) and "CO" insertion are two proposed mechanisms for this Fischer-Tropsch-like synthesis. Fe-or Co-based catalysts have been widely used to catalyze the hydrogenation of CO₂ to C₂₊ hydrocarbons via the CO intermediate. C₂₊ hydrocarbons can also be obtained by combining CH₃OH synthesis with the methanol-to-hydrocarbon process (MTH). This reaction pathway has been realized over bifunctional systems comprising a CH₃OH synthesis catalyst and an MTH catalyst. Alternatively, CO₂ hydrogenation can occur via a RWGS reaction to the CO intermediate, and subsequent formation of higher alcohols from syngas. Higher alcohols (mostly CH₃CH₂OH) have been produced by using a hybrid tandem catalyst. Understanding of the activation mechanism, precise C-C coupling, and synergy control between the two active components requires further research. In the final part, we describe the future challenges and opportunities in heterogeneous catalysis of CO₂ hydrogenation. The combination of calculations (precise theoretical models) and experiments (in-situ spectroscopic techniques) will facilitate the design of advanced catalysts to achieve both high CO₂ conversion and C₂₊ product selectivity.

Au/TiO₂/MoS₂ plasmonic composite photocatalysts were synthesized via deposition-precipitation with urea. The photocatalytic activities of the prepared samples were evaluated by performing hydrogen production experiments under Xe lamp irradiation with a 10% (φ, volume fraction) glycerol aqueous solution as the sacrificial agent. The results showed that the optimal content of MoS₂ in the Au/TiO₂/MoS₂ composite is 0.1% (w, mass fraction) and the corresponding H₂ production rate was 708.85 μmol·h^-1, which was almost 11 times higher than that of TM6.0 with the strongest photocatalytic activity in the all binary TiO₂/MoS₂ composites. The enhanced photocatalytic activity of the ternary Au/TiO₂/MoS₂ composites is mainly due to the surface plasmon resonance of the supported Au nanoparticles absorbed on the TiO₂/MoS₂ layered composite, which show an intense absorption maximum centered around 550–560 nm and induce the photoexcitation of electrons. Meanwhile, the electrons excited by surface plasmon resonance of Au could be injected into the conduction band of TiO₂, and they were then transferred to the edges of MoS₂ for catalyzing the production of H₂.

Alloy metal nanoclusters (NCs), including bimetallic and multimetallic clusters, have recently emerged as a novel class of multifunctional nanomaterials. They are widely used in catalysis, optical sensing, and biological imaging due to their excellent physicochemical properties such as unique electronic structure, ultrasmall size, strong photoluminescence, and rich surface chemistry. Although much progress has been made in the development of NCs, a major challenge in the synthesis of the relevant multifunctional nanomaterial is to achieve the synthetic methodological breakthrough, especially for controlling the synthesis and structure of NCs with atomic precision. It is evident that by realizing controlled synthesis and structural regulation at the atomic scale, we can better understand and tune the fundamental properties of NCs for efficient use in various application areas; this could also shed light on the development of new functionalized nanomaterials. Most of the recent research on the controlled synthesis and structural characterization of metal clusters with atomic precision has focused on monometallic NCs, and significant progress has been realized with respect to alloy metal NCs. A number of synthetic strategies have been developed for synthesizing high-quality alloy NCs with well-defined compositions, sizes, and architectures. In this review, we have highlighted some recent advances in strategies for the precise synthesis of ligands-protected alloy metal NCs, especially thiolate-stabilized gold-based alloy NCs. We classified the synthetic strategies for alloy NCs into several strategies, which include one-pot synthesis, metal exchange, ligand exchange, chemical etching, intercluster reactions, surface motif exchange reaction, and in situ two-phase ligand exchange strategy. One-pot synthesis is facile and widely used as a synthetic strategy for monodisperse alloy NCs with well-defined compositions, sizes, architectures, and surface chemistries. However, the alloy NCs obtained through the one-pot strategy often exhibits a relatively somber fluorescence. Therefore, other synthesis strategies have been exploited that can fabricate alloy NCs exhibiting strong photoluminescence. Among them, the surface motif exchange reaction is expected to be extended to the fabrication of new binary alloy NCs with precise alloy sites to broaden the physicochemical properties of the NCs; intercluster reactions has been explored as an emerging and efficient strategy to fabricate atomically precise alloy NCs. It is noted that the two or multiple metal species incorporated in a single alloy NC usually show unexpected synergistic properties like adjustable electronic structures and strong photoluminescence. Such unique properties have rapidly motivated the research community to use alloy NCs in many applications such as catalysis, biosensors, and biomedicine.

Quantum dots (QDs) exhibit excellent properties, such as broad absorption, narrow emission, high photoluminescence quantum yields, tunable emission wavelength, and anti-photobleaching. As a result, QDs have important applications in biological imaging, tracking, and sensing. When QDs enter living systems, they first encounter proteins. The interactions between proteins and QDs significantly influence the structures and functions of the proteins, as well as the performance of the QDs in applications. Studies on the interactions between QDs and proteins can provide a theoretical basis for the design, efficient application, and safety evaluation of QDs. Herein we have summarized methods for characterizing the thermodynamics of QD-protein interactions, on the basis of previous work by both our group and others. We also highlight the thermodynamic mechanisms of the QD-protein interactions.

Understanding the energy band alignment across multiple layers in thin-film optoelectronic devices is extremely important because it governs elementary optoelectronic processes, such as charge carrier generation, separation, transport, recombination and collection. This monograph summarizes recent progress in visualization of energy band alignment in thin-film optoelectronic devices, such as organic solar cells (OSCs) and organic-inorganic perovskite photodetectors from our group by using scanning Kelvin probe microscopy (SKPM). Since active layers are enclosed by the top and bottom electrodes in vertically stacked devices, it is highly challenging to study the energy band alignment under operando conditions. Thus, cross-sectional SKPM has been developed to resolve this challenge. The results demonstrated that the interlayer was one of the most important factors for adjusting energy band alignment, determining device polarity and improving device performance. The characterization methods described in this monograph are poised to be widely applied to research in various thin-film optoelectronic devices, such as photovoltaic devices, photodetectors and light-emitting diodes (LEDs), especially those devices with tandem structures.

Research on gold nanoclusters is at the frontier of nanoscience and nanotechnology. The introduction of the first phosphine-protected gold nanocluster, Au₁₁(PPh₃)₇(SCN)₃ (where PPh₃ stands for triphenylphosphine and Ph stands for benzene), can be dated back to 1969. As research in the field progressed, many structures of phosphine-protected nanoclusters such as Au₅, Au₈, Au₁₃, and Au₃₉ were reported. However, the stability of these phosphine-protected nanoclusters was not satisfactory, which handicapped their research and application. In an attempt to find alternatives for phosphine-protected nanoclusters, thiolated gold nanoclusters have attracted extensive attention in recent years. So far, there has been great progress primarily owing to the development of wet-chemical synthesis techniques, among which the utilization of ligand-exchange has been proved to be very effective to synthesize thiolated gold nanoclusters. It can be easily understood that phosphine in gold nanoclusters can be exchanged with thiolate because the latter has stronger affinity for gold. However, we recently found that the reverse ligand-exchange, i.e., the exchange of thiolate with phosphine, can also take place. Some questions have naturally arisen: Is the reverse ligand-exchange only applicable to superatomic [Au₂₅(SR)₁₈]⁻ (SR: thiolate) nanoclusters? Can it occur in other thiolated gold nanoclusters? If so, is this reverse ligand-exchange also dependent on the starting nanoclusters? These intriguing issues have inspired us to conduct this work.

We investigated the reactions of PPh₃ with some thiolated gold nanoparticles, including [Au₂₃(SC₆H₁₁)₁₆]⁻, Au₂₄(SC₂H₄Ph)₂₀, Au₃₆(TBBT)₂₈ (where TBBT stands for 4-(tert-butyl) benzene-1-thiolate), Au₃₈(SC₂H₄Ph)₂₀, mixed nanoclusters, and 3 nm Au nanoparticles. Surprisingly, the experimental results showed that under the action of PPh₃, thiolated gold nanoclusters (or nanoparticles) with different compositions, structures, sizes, and protecting thiolates can be uniformly transformed to [Au₁₁(PPh₃)₈Cl₂]⁺ and then [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺. In other words, PPh₃ is a universal converter for these thiolated gold nanoparticles. However, gold nanoparticles that are protected by polyvinylpyrrolidone (PVP) or citrate and [Ag₂₅(SPhMe₂)₁₈]⁻ particles cannot be transformed to [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺ and [Ag₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺, respectively, under the same conditions, which indicated that the special reactivity with PPh₃ is unique to thiolated gold nanoparticles. Our preliminary investigation on a possible reaction path between thiolated gold nanoparticles and PPh₃ also revealed that the peeling process found in Au₂₅ nanoclusters may be applicable to the conversion of [Au₂₃(SC₆H₁₁)₁₆]⁻, but not other nanoclusters like Au₂₄(SC₂H₄Ph)₂₀ and Au₃₆(TBBT)₂₈.

Employing this special chemistry, we synthesized seven [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺ species with various ligands and investigated the effect of the ligand on the luminescence properties of [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺. We found that the luminescence quantum yields decreased in the following order: [Au₂₅(PPh₃)₁₀(SCH₂Ph-t-Bu)₅Cl₂]²⁺ (1.32 × 10⁻⁴) > [Au₂₅(PPh₃)₁₀(SCH₂Ph)₅Cl₂]²⁺ (8.23 × 10⁻⁵) > [Au₂₅(PPh₃)₁₀(SC₂H₄Ph)₅Cl₂]²⁺ (5.35 × 10⁻⁶) > [Au₂₅(PPh₃)₁₀(SC₁₂H₂₅)₅Cl₂]²⁺ (5.02 × 10⁻⁶) > [Au₂₅(PPh₃)₁₀(SPh-t-Bu)₅Cl₂]²⁺ (3.97 × 10⁻⁶) > [Au₂₅(PPh₃)₁₀(SC₆H₁₃)₅Cl₂]²⁺ (3.73 × 10⁻⁶) > [Au₂₅(PPh₃)₁₀(S-c-C₆H₁₁)₅Cl₂]²⁺ (1.53 × 10⁻⁶). Therefore, it can be concluded that SCH₂Ph-t-Bu is the best ligand, while S-c-C₆H₁₁ is the worse one for triggering luminescence from gold nanoparticles in the investigated thiolates.

Since such diversity in surface ligands is not found in other nanoclusters (e.g., [Au₂₅(SR)₁₈]⁻), the special chemistry between thiolated gold nanoparticles and PPh₃ provides excellent opportunities to investigate the effect of ligands on the properties of gold nanoparticles and to screen ligands for special applications.

In summary, in this work we reveal the unique chemistry of thiolated gold nanoparticles with PPh₃ and provide excellent opportunities for investigating ligand effects of gold nanoparticles and screening ligands for special applications.

The sintering condition was studied how to influence the performance of indium-zinc-oxide (IZO) target and thin film transistor (TFT) in this paper. IZO targets was prepared by hot-pressing sintering using mixed power (20% (w, mass fraction) In₂O₃), then fabricated TFT with above sintering targets. X-ray diffraction (XRD) patterns & scanning electron microscopy (SEM) images showed targets had good crystallinity and elements were uniformly distributed. The target was typical densification process with sintering temperature of 850 ℃. The volatilization of In₂O₃ undermined the densification of the target, with condition of 900 ℃-60 min. It can be seen that increase of sintering temperature and elongation of preserving time could inhibit the In₂O₃ volatilization, facilitated the sintering densification of IZO target and formed the InZnO_x crystal phase, thereby increased the density of the target. IZO TFTs′ performance showed the sputtering deteriorates the film quality with low-density target, and the grain of the high-density target was slightly abnormal, which resulted in deterioration of the film uniformity, all reduced the performance of TFT. Therefore, an appropriate high-density target was essential for the preparation of IZO-TFT."

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted significant attention owing to their high absorption coefficient and ambipolar charge transport properties. With only several years of development, the power conversion efficiency (PCE) has increased from 3.8% to 22.7%. In general, PSCs have two types of structural architecture: mesoporous and planar. The latter possesses higher potential for commercialization due to its simpler structure and fabrication process, especially the inverted planar structure, which possesses negligible hysteresis. In an inverted PSC, the electron transport materials (ETM) are deposited on a perovskite film. Only a few ETMs can be used for inverted PSCs as the perovskite film is easily damaged by the solvent used to dissolve the ETM. Furthermore, the energy levels of the ETM should be well aligned with that of the perovskites. Normally it is difficult to use inorganic ETMs as they require high temperatures for the annealing process to improve the electron conductivity; the perovskite film cannot sustain these high temperatures. To date, the fullerene derivative, [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM), is the most commonly used organic ETM for high efficiency inverted planar PSCs. However, the high manufacturing cost due to its complex synthesis retards the industrialization of the PSCs. Here, we introduce a fullerene pyrrolidine derivative, N-methyl-2-pentyl-[60]fullerene pyrrolidine (NMPFP), synthesized via the Prato reaction of C₆₀ directly with cheap hexanal and sarcosine. Then the NMPFP electron transport layer (ETL) was prepared by a simple solution process. The properties of the resulting NMPFP ETLs were characterized using UV-Vis absorption spectroscopy, cyclic voltammetry measurements, atomic force microscopy, and conductivity test. From the results of the UV-Vis absorption spectroscopy and cyclic voltammetry measurements, the LUMO level of NMPFP ETL was calculated to be 0.2 eV higher than that of the PCBM ETL. This contributes to a higher open-circuit photovoltage. In addition, the NMPFP film presented higher conductivity than the PCBM film. Thus, the photo-generated charge carriers in the perovskite films should be transported more efficiently to the NMPFP electron transport layer (ETL) than to the PCBM ETL. This was confirmed by the results of the steady-state photoluminescence spectroscopy. Finally, the NMPFP as an alternative low-cost ETL was employed in an inverted planar PSC to evaluate the device performance. The device made with the NMPFP ETL yielded an efficiency of 13.83% with negligible hysteresis, which is comparable to the PCBM counterpart devices. Moreover, since stability is another important parameter retarding the commercialization of PSCs, the stability of the PCBM and NMPFP base PSCs were investigated and compared. It was found that the NMPFP devices possessed significantly improved stability due to the higher hydrophobicity of the NMPFP. In conclusion, this research demonstrates that NMPFP is a promising ETL to replace PCBM for the industrialization of cheap, efficient and stable inverted planar PSCs.

Owing to the unique physical, chemical, optical, and biological properties, plasmonic nanoparticles (PNPs) have been widely used in various research fields such as materials science, biology, and medicine. The optical properties of PNPs can be regulated by changing their composition, shape, and size, so that a suitable light-scattering probe can be screened by means of controllable synthesis. Real-time study of the dynamic behavior of PNPs at the single molecule level is of great significance for understanding the biological behaviors of living cells and tissues, fabricating functional nanomaterials, and developing new chemical biosensors. Starting from the traditional dark-field microscopy (DFM), we have developed a series of plasmonic light-scattering imaging techniques with high sensitivity, high temporal-spatial resolution, and high throughput through optimizing the assembly of light sources, detectors, and other optical components, and applied these techniques to single molecule detection, multi-particle sensing, single cell imaging, biological process tracing, and so on. Based on the PNPs with optical anisotropy, we have also developed a three-dimensional scanning imaging system for living cells and asupercontinuum laser light-sheet imaging system coupled with high-speed capillary electrophoresis system, advancing the study of single molecule spectroscopy. This paper will summarize the work on PNP single particle analysis and imaging in our research group during the past ten years, and put forward some new ideas for further development in this field.

Atomically precise nanoclusters form an important class of functional materials that have recently attracted research interest for their unique properties and easily tunable surface functionalities. Core-shell nanomaterials with precise structural information can be produced to better understand the structure–property relationships for different applications. Polyoxo-titanium clusters (PTCs) are such a kind of nanomaterial for different functional applications in catalysis, photovoltaics, ceramics, etc. However, the high bandgap of semiconductive PTCs is the limiting factor in their practical solar application in the visible region of sunlight. The development of PTCs with different surface-bound ligands is an emerging area of research in the design and synthesis of core-shell nanoclusters with reduced bandgaps. It has been extensively reported that the polynuclear growth of PTCs requires molecular-level water supply in reactions. Moreover, it is important to identify more environment-friendly synthetic methods. Deep eutectic-solvothermal (DES) synthesis is an emerging green method for the synthesis of different crystalline materials. The hygroscopic nature of DES should enhance the provision of water during polynuclear growth of nanoclusters. Hence, we chose to synthesize different kinds of PTCs using DES as solvent. Two nanoclusters, Zr-oxo (PTC-65) and Zr/Ti-oxo (PTC-66) clusters having surface-bound 1, 10-phenanthroline (1, 10-phn) and phenol ligands, were successfully synthesized using this approach; 1, 10-phn was employed as the precursor in the synthetic reaction, and phenol was not employed directly in the chemical reaction, but was supplied from the DES solvent used in the reaction. In the presence of chromophoric ligands, 1, 10-phn and phenol are believed to enhance the light absorption properties of the resulting functional nanomaterials. Their crystal structure revealed that they form core-shell mimics with Zr-oxo and Ti/Zr-oxo core units having surface-bound shell ligands. Based on their different structural characteristics, photocatalytic hydrogen evolution studies were performed on these two functional materials using an aqueous solution of H₂O (50 mL)/triethanol amine (10 mL). Interestingly, PTC-65 formed a turbid solution, whereas PTC-66 formed a clear solution. The possible reasons for their different dispersion behaviors are widely discussed, with emphasis on their structure–property relationships. This study provides a potential tool for the homogenization of Ti-O materials to improve their photocatalytic activities. Moreover, the success of our work confirms that deep eutectic-solvothermal synthesis can be an effective method for cluster preparation. Many other interesting polynuclear complexes like polyoxometalates, chalcogenides, and noble-metal clusters could be obtained by this synthetic methodology.

In this perspective, we review the chemical information encoded in electron density and other ingredients used in semilocal functionals. This information is usually looked at from the functional point of view: the exchange density or the enhancement factor are discussed in terms of the reduced density gradient. However, what parts of a molecule do these 3D functions represent? We look at these quantities in real space, aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology (QCT). Generalized gradient approximations (GGAs) provide information about the presence of chemical interactions, whereas meta-GGAs can differentiate between the different bonding types. By merging these two techniques, we show new insight into the failures of semilocal functionals owing to three main errors: fractional charges, fractional spins, and non-covalent interactions. We build on simple models. We also analyze the delocalization error in hydrogen chains, showing the ability of QCT to reveal the delocalization error introduced by semilocal functionals. Then, we show how the analysis of localization can help understand the fractional spin error in alkali atoms, and how it can be used to correct it. Finally, we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1, 3-interactions.

Multi-scale quantum-mechanical/molecular-mechanical (QM/MM) and large-scale QM simulation provide valuable insight into enzyme mechanism and structure-property relationships. Analysis of the electron density afforded through these methods can enhance our understanding of how the enzyme environment modulates reactivity at the enzyme active site. From this perspective, tools from conceptual density functional theory to interrogate electron densities can provide added insight into enzyme function. We recently introduced the highly parallelizable Fukui shift analysis (FSA) method, which identifies how frontier states of an active site are altered by the presence of an additional QM residue to identify when QM treatment of a residue is essential as a result of quantum-mechanically affecting the behavior of the active site. We now demonstrate and analyze distance and residue dependence of Fukui function shifts in pairs of residues representing different non-covalent interactions. We also show how the interpretation of the Fukui function as a measure of relative nucleophilicity provides insight into enzymes that carry out S_N2 methyl transfer. The FSA method represents a promising approach for the systematic, unbiased determination of quantum mechanical effects in enzymes and for other complex systems that necessitate multi-scale modeling.

Multifunctional theranostic agents that are responsive to external physical stimuli such as light, magnetic field, ultrasound, radiofrequency, and X-rays have been widely explored for their use in physical stimulus-responsive therapies for cancer.Encouraging results in many preclinical animal experiments have been obtained; thus, this innovative strategy has gained great attention.Owing to the nontoxicity of physical stimulus-responsive agents and treatment specificity under particular external stimuli, physical stimulus-responsive cancer therapies provide greatly reduced toxicity and enhanced therapeutic efficiency compared with conventional chemotherapeutic agents.When combining physical stimulus-responsive therapies with other traditional therapeutics, synergistic antitumor effects via various mechanisms can be achieved.In this review, we will summarize the recent developments in physical stimulus-responsive therapies and discuss the important roles of nanoscale theranostic agents in these novel treatment modalities.

Recently, preparation of carbon materials using biomass as precursors has received much attention owning to their merits of low cost, abundance, renewability, and environmental benignity. In this study, honeycomb-like porous gelatin was synthesized and subsequently used as the precursor to prepare activated carbon through carbonization followed by activation. The prepared activated carbon had a higher specific surface area (up to 3692 m²·g^-1) and supercapacitor performance than that of activated carbon derived from commercial gelatin. In a 6 mol·L^-1 KOH solution, the activated carbon prepared from porous gelatin through 600℃ carbonization and 700℃ activation delivered high specific capacitances of 357 and 227 F·g^-1 at current densities of 1 and 100 A·g^-1, respectively. In addition, after 7500 charge/discharge cycles at a current density of 10 A·g^-1, it showed 93.0% retention of the initial capacitance, demonstrating excellent cycling stability. Moreover, a symmetric supercapacitor was assembled, which delivered an energy density of 10.3, 9.7, and 8.2 Wh·kg^-1 at power densities of 250, 2500, and 25000 W·kg^-1, respectively. Furthermore, a capacity retention as high as 97.6% was achieved after 10000 cycles at 10 A·g^-1 using this symmetric supercapacitor. This work has demonstrated that the activated carbon derived from honeycomb-like porous gelatin has great potential for application in high-performance supercapacitors.

The growth and structural properties of ZnO thin films on both Au(111) and Cu(111) surfaces were studied using either NO₂ or O₂ as oxidizing agent. The results indicate that NO₂ promotes the formation of well-ordered ZnO thin films on both Au(111) and Cu(111). The stoichiometric ZnO thin films obtained on these two surfaces exhibit a flattened and non-polar ZnO(0001) structure. It is shown that on Au(111), the growth of bilayer ZnO nanostructures (NSs) is favored during the deposition of Zn in presence of NO₂ at 300 K, whereas both monolayer and bilayer ZnO NSs could be observed when Zn is deposited at elevated temperatures under a NO₂ atmosphere. The growth of bilayer ZnO NSs is caused by the stronger interaction between two ZnO layers than between ZnO and Au(111) surface. In contrast, the growth of monolayer ZnO NSs involves a kinetically controlled process. ZnO thin films covering the Au(111) surface exhibits a multilayer thickness, which is consistent with the growth kinetics of ZnO NSs. Besides, the use of O₂ as oxidizing agent could lead to the formation of sub-stoichiometric ZnO_x structures. The growth of full layers of ZnO on Cu(111) has been a difficult task, mainly because of the interdiffusion of Zn promoted by the strong interaction between Cu and Zn and the formation of Cu surface oxides by the oxidation of Cu(111). We overcome this problem by using NO₂ as oxidizing agent to form well-ordered ZnO thin films covering the Cu(111) surface. The surface of the well-ordered ZnO thin films on Cu(111) displays mainly a moiré pattern, which suggests a (3 × 3) ZnO superlattice supported on a (4 × 4) supercell of Cu(111). The observation of this superstructure provides a direct experimental evidence for the recently proposed structural model of ZnO on Cu(111), which suggests that this superstructure exhibits the minimal strain. Our studies suggested that the surface structures of ZnO thin films could change depending on the oxidation level or the oxidant used. The oxidation of Cu(111) could also become a key factor for the growth of ZnO. When Cu(111) is pre-oxidized to form copper surface oxides, the growth mode of ZnO_x is altered and single-site Zn could be confined into the lattice of copper surface oxides. Our studies show that the growth of ZnO is promoted by inhibiting the diffusion of Zn into metal substrates and preventing the formation of sub-stoichiometric ZnO_x. In short, the use of an atomic oxygen source is advantageous to the growth of ZnO thin films on Au(111) and Cu(111) surfaces.

ZnO is an ideal material for ultraviolet (UV) detection due to its wide direct-bandgap, high exciton binding energy, and high internal photoconductive gain.However, ZnO UV detectors have the disadvantages of slow response speed and low detectivity.Graphdiyne (GD) is a novel carbonaceous allotrope, and possesses excellent electronic performance in air.In this study, the metal-semiconductor-metal (MSM) structured lateral ZnO UV detectors were prepared, and GD was employed to modify the ZnO surface.The effects of GD deposited 1–3 times (viz.1T, 2T, and 3T GD) on the performance of ZnO ultraviolet detector were carefully investigated.The results show that the dark current of the bare ZnO detector is 24 μA under a bias of 10 V, while that of the graphdiyne-modified detector is ~0.34 μA (about two orders of magnitude reduction).The dark current remains almost the same for the 1T, 2T and 3T GD films.The photocurrents of 1–3T GD-modified detectors were 0.21, 0.32, 0.27 mA, respectively.The device modified with 2T GD displays the highest photocurrent, which is significantly enhanced in comparison to the unmodified device (0.08 mA) under a 365-nm UV radiation of 100 μW·cm⁻².Meanwhile, the responsivity and detectivity are improved remarkably.Under a bias of 10 V, the 2T-GD-modified detector displays high responsivity of 1759 A·W⁻¹ and detectivity of 4.23×10¹⁵ Jones.The detectivity is thus far the highest for ZnO UV detectors prepared by the sol-gel method.The improved performance of the GD-modified detector is attributed to the p-n junction formed between the GD and the ZnO film.At dark, the p-n junction is formed between the ZnO film and the GD, which greatly decreases the dark current of the detector.Under UV illumination, photogenerated holes accumulate in the GD, reducing electron-hole recombination; thus, the photocurrent is significantly increased.Furthermore, desorption and absorption of oxygen on the ZnO surface are much reduced due to the GD attached on the ZnO surface, thus improving the response speed of the detector.However, the intensive distribution of GD slightly hinders the UV absorption of ZnO thin films, reducing the responsivity of the detector.Careful optimization shows that the use of 2T GD gives the best output, and the corresponding ZnO UV detector exhibits very good performance.Overall, this study demonstrates that using GD can effectively improve the performance of ZnO UV detector.

2, 4-Dithiouracil is potentially an important photosensitizer for use in photodynamic therapy. Its photophysics when populated in the lowest excited state has been studied extensively. However, its higher light absorbing excited states and the corresponding reaction dynamics have not been investigated sufficiently. Herein, the resonance Raman spectroscopy and density functional theory were adopted to clarify the electronic transitions associated with the UV absorptions in the far-UV region and the short-time structural dynamics corresponding to the higher light absorbing excited states. The UV absorption spectrum in acetonitrile was deconvoluted into four bands:the moderate intense absorption band at 358 nm (f=0.0336) (A band), the intense broad absorption bands at 338 nm (f=0.1491), 301 nm (f=0.1795), and 278 nm (f=0.3532) (B, C, and D bands) respectively, on the basis of the relationship between the resonance Raman intensities and the oscillator strength f. The result was consistent with the predictions made using the time-dependent density functional theory calculations and the resonance Raman intensity patterns. Thus, the four bands resulted from the deconvolution are assigned as the S₀→S₂, S₀→S₆, S₀→S₇ and S₀→S₈ transitions, respectively. The resonance Raman spectra of the corresponding B, C, and D bands are assigned and the qualitative short-time structural dynamics are obtained. The major character in the short-time structural dynamics of 2, 4-dithiouracil in the S₈ excited state is that a non-adiabatic process via S₈(ππ^*)/S(nπ^*) curve-crossing, accompanied with ultrafast structural distortion, takes place in or near the Franck-Condon region, while the major character in the short-time structural dynamics in the S₇ and S₆ excited state appears in the multidimensional reaction coordinates, which are mostly along the C₅C₆/C₂S₈/C₄S₁₀/N₂C₃ bond lengths + C₄N₃H₉/N₁C₂N₃/C₂N₁C₆/C₆N₁H₇/C₅C₆H₁₂ bond angles for the S₇ excited state and the C₅C₆/N₃C₂/C₄S₁₀/C₂S₈ bond lengths + C₆N₁H₇/C₅C₆H₁₂/C₅C₆N₁/C₅C₆H₁₂/C₂N₁C₆/N₁C₂N₃/C₄N₃H₉/N₁C₂N₃ bond angles for the S₆ excited state.

Cu has been widely used as a substrate material for graphene growth. To understand the atomistic mechanism of growth, an efficient and accurate method for describing Cu-C interactions is necessary, which is the prerequisite of any possible large-scale molecular simulation studies. The semi-empirical density-functional tight-binding (DFTB) method has a solid basis from the density functional theory (DFT) and is believed to be a good tool for achieving a balance between efficiency and accuracy. However, existing DFTB parameters cannot provide a reasonable description of the Cu surface structure. At the same time, DFTB parameters for Cu-C interactions are not available. Therefore, it is highly desirable to develop a set of DFTB parameters that can describe the Cu-C system, especially for surface reactions. In this study, a parametrization for Cu-C systems within the self-consistent-charge DFTB (SCC-DFTB) framework is performed. One-center parameters, including on-site energy, Hubbard, and spin parameters, are obtained from DFT calculations on free atoms. Two-center parameters can be calculated based on atomic wavefunctions. The remaining repulsive potential is obtained as the best compromise to describe different kinds of systems. Test calculations on Cu surfaces and Cu-or C atom-adsorbed Cu surfaces indicate that the obtained parameters can generate reasonable geometric structures and energetics. Based on this parameter set, carbon dimerization on the Cu(111) surface has been investigated via molecular dynamics simulations. Since they are the feeding species for graphene growth, it is important to understand how carbon dimers are formed on the Cu surface. It is difficult to observe carbon dimerization in brute-force MD simulations even at high temperatures, because of the surface structure distortion. To study the dimerization mechanism, metadynamics simulations are performed. Our simulations suggest that carbon atoms will rotate around the bridging Cu atom after a bridging metal structure is formed, which eventually leads to the dimer formation. The free energy barrier for dimerization at 1300 K is about 0.9 eV. The results presented here provide useful insights for understanding graphene growth.

Over the past two decades, bulk heterojunction polymer solar cells (PSCs) have attracted significant attention owing to their potential applications in the mass fabrication of flexible device panels by roll-to-roll printing. To improve the photovoltaic performance of PSCs, much effort has been devoted to the optimization of properties of donor-acceptor (D-A) type polymer donor materials. Until now, the development of high-performance donor polymers is mainly dependent on the design and synthesis of binary polymers with a regular D/A alternating skeleton. Compared to binary polymers, random terpolymers with three different donor or acceptor monomer units possess synergetic effects of their inherent properties, such as optical absorption ability, energy levels, crystallinity, charge mobility, and morphological compatibility with the n-OS acceptors with suitable adjustment of the molar ratio of the three monomers. However, the irregularity in the polymer backbone of the random terpolymers may have an adverse effect on molecular packing, crystallinity, and charge mobility. Therefore, design and synthesis of high-performance terpolymers for PSCs is a challenging task. In this study, a series of wide bandgap random terpolymers PSBTZ-80, PSBTZ-60, and PSBTZ-40 based on alkylthiothienyl substituted benzodithiophene as the donor unit and two weak electron-deficient acceptor units of 5, 6-difluorobenzotriazole (FBTz) and thiazolothiazole (TTz) were designed and synthesized for PSC applications. The optical, electrochemical, molecular packing, and photovoltaic properties of the polymers were effectively modulated by varying the FBTz:TTz molar ratio. Therefore, the PSC based on PSBTZ-60 as the donor material and narrow bandgap small molecule 3, 9-bis(2-methylene-(3-(1, 1-dicyanomethylene)-indanone))-5, 5, 11, 11-tetrakis(4-hexyl-phenyl)-dithieno[2, 3-d:2', 3'-d']-s-indaceno[1, 2-b:5, 6-b']di thiophene) (ITIC) as the acceptor, processed using halogen-free solvents, exhibited high power conversion efficiency (PCE) of 10.3% with high open-circuit voltage (V_oc) of 0.91 V, improved short-circuit current density (J_sc) of 18.0 mA∙cm⁻², and fill factor (FF) of 62.7%, which are superior to those of PSCs based on binary polymers PSBZ (a PCE of 8.1%, V_oc of 0.89 V, J_sc of 14.7 mA∙cm⁻², and FF of 61.5%) and PSTZ (a PCE of 8.5%, V_oc of 0.96 V, J_sc of 14.9 mA∙cm⁻², and FF of 59.1%). These results indicate that random terpolymerization is a simple and practical strategy for the development of high-performance polymer photovoltaic materials.

Anodized TiO₂ nanotube arrays are one of the key electrode materials for supercapacitors, because of their easy synthesis, controllable morphology, and environmentally friendly characteristics. In this paper, the multi-modification of TiO₂ nanotube arrays is presented. These modifications include the introduction of oxygen vacancies, and the modification of the arrays by metals, nonmetals, metal oxides and conductive polymers; these modifications provide scope to increase the electrochemical performance of the TiO₂ nanotube arrays. Recent advances of anodized TiO₂ nanotube arrays in supercapacitors are systematically summarized, providing guidance for the practical application of these arrays.

Rolling circle amplification (RCA) is a simple and efficient isothermal enzymatic reaction, which has developed as a novel technology in the field of nucleic acid amplification. Its product has a wide range of applications in the assembly and preparation of multi-functional materials. Here, we report the effects of reaction time and the concentrations of deoxyribonucleoside triphosphates (dNTPs), polymerase, and primer on the product of RCA. The RCA product was characterized by methods including agarose gel electrophoresis, ultraviolet spectroscopy, and transmission electron microscopy (TEM). The results showed that the length of the RCA product was significantly affected by the reaction time, especially when the reaction time was less than 30 min. With an increase of dNTPs concentrations, the concentration and chain length of the RCA product increased. However, while the concentrations of enzyme and primer had little effect on the length of the RCA product, they had a large effect on its concentration. It is worth noting that the content of the RCA product decreased significantly in the presence of excess enzyme concentration.

Organic solar cells (OSCs) have received widespread attention for their advantages of cheap, light, flexible characteristics and roll-to-roll printing technology. However, the efficiencies of OSCs are still lower than 50% of the theoretical Shockley-Queisser detailed-balance efficiency limit. Consequently, to further improve device performance, it is significant to develop molecular design strategies to lower the energy loss and enhance the utilization of absorbed photons. From the molecular design aspects, down-shifting energy levels is an effective way to lowering the energy loss in order to obtain a high open circuit voltage, and optimizing the morphology is an efficient approach to lowering the fill factor and current density loss. Introduction of fluorine atom in molecules is an effective molecular design strategy to realize both above-mentioned requirements. In this review, starting from the characteristics of fluorine atoms, we summarized the fluorination effects on adjusting molecular levels. Whether the fluorine attached to the donor units, acceptor units or π-bridge units, it could efficiently downshift the energy levels. However, fluorinating the molecular backbone affects the energy levels more significantly than fluorinating the side chains of the two-dimensional structures. The introduction of fluorine is also an effective approach to optimize molecular packing and morphology. Generally, whether the fluorine attached to the donor units, acceptor units or π-bridge units, it can effectively increase molecular coherence length, decrease π–π stacking distance, and enhance domain purity. However, there is a saturation of the fluorine on the backbone, further introduction of the fluorine can accelerate molecular aggregation and induce disorder. In addition, the position of fluorination is important. In this review, we also briefly discuss the fluorination strategy for representative and high-efficiency photovoltaic material designs, including small molecule, polymer, and non-fullerene OSCs, mainly focusing on improving efficiency by reducing the efficiency losses. Fluorination is advantageous only for OSCs with high HOMO energy levels or poor molecular packing; otherwise, it can compromise device performance. OSCs based on narrow band-gap non-fullerene acceptors with low energy loss show promise for highly efficient device performance. Fluorination provides an effective means to fine-tune energy levels and form ideal microstructures to further reduce the efficiency loss and achieve a breakthrough in device performance.

Nonadiabatic processes widely exist in photochemistry and photophysics. The theoretical treatment of nonadiabatic processes is an important challenge in theoretical chemistry. In nonadiabatic dynamics, the well-known "Born-Oppenheimer approximation" breaks down due to the involvement of strong nuclear-electronic coupled motions. Hence, the development of a theoretical framework is required for the proper treatment of nonadiabatic dynamics. The fewest-switches trajectory surface-hopping method developed by Tully is one of the most widely used methods in the treatment of nonadiabatic processes because of its rather simple numerical implementation. In this approach, the nuclear degrees of freedom are propagated on the potential energy surface of an electronic state using the classical equations of motion, while the electronic degrees of freedom are propagated along the same trajectory according to the time-dependent Schr?dinger equation. Nonadiabatic effects are included by allowing sudden hops between different potential energy surfaces. After averaging over many trajectories, a reasonable description of nonadiabatic dynamics is achieved at low computational cost. Particularly, when we combine the trajectory surface-hopping dynamics with on-the-fly molecular dynamics, it is possible to describe the nonadiabatic dynamics of realistic polyatomic molecular systems at a fully atomic level with all degrees of freedom included. After the introduction of hybrid multiscale methods, the simulation of photochemistry in solutions and in biological systems becomes possible. The simulation results provide important information concerning the nonadiabatic dynamics of realistic polyatomic systems, such as excited-state lifetime, major active molecular motions, reaction channels, and branching ratio. This review article summarizes some progresses in this field. After briefly introducing the basic theory of widely used fewest switches surface-hopping dynamics methods, we mainly focus on several numerical details in the implementation of on-the-fly fewest switches surface-hopping dynamics. The seamless combination of surface-hopping dynamics and electronic-structure calculations is emphasized in this review, rather than an exhaustive discussion of rigorous nonadiabatic dynamics theories. Numerical methods to estimate nonadiabatic coupling terms are discussed, which allow us to perform the trajectory surface-hopping calculations when the nonadiabatic coupling vectors are not available in the electronic structure calculations. Several important issues, such as decoherence corrections, diabatic or adiabatic representations, and initial sampling methods are discussed in detail. We also summarize the theoretical treatment of the nonadiabatic dynamics of some interesting molecular systems, which include the photostability of DNA, photo-isomerization of organic systems, photochemistry of transition metal complexes, and photovoltaics. Finally, we discuss the theoretical challenges of this direct dynamics approach and provide an outlook of this field from our personal perspective.

Since the successful synthesis of graphdiyne, graphynes have emerged as an active field in carbon materials research.Hydrogen-substituted graphyne, structurally similar to graphynes, is a kind of two-dimensional (2D) carbon-rich material composed of sp²-hybridized carbon and hydrogen from phenyl groups and sp-hybridized carbon from ethynyl linkages.The large pore size in the molecular structure of hydrogen-substituted graphyne aids the diffusion of ions and molecules.In this work, hydrogen-substituted graphyne was synthesized by a facile mechanochemical route.Calcium carbide (CaC₂) was employed as the precursor of sp-hybridized carbon and 1, 3, 5 tribromobenzene (PhBr₃) as that of sp²-hybridized carbon and hydrogen.Hydrogen-substituted graphyne was directly obtained via the cross-coupling reaction performed by ball milling under vacuum and the impurities were removed by dilute nitric acid and benzene.Mechanochemistry is a mature technology for the simple and high-yield synthesis of nanostructured materials.The composition of the as-prepared hydrogen-substituted graphyne was confirmed by Raman and ¹H solid-state nuclear magnetic spectroscopies.Energy-dispersive X-ray (EDX) spectrum and X-ray diffraction (XRD) patterns indicated that the purity and crystallinity of the prepared samples are high, which was further confirmed by the corresponding selected area electron diffraction (SAED) patterns.Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images illustrated that samples had nanosheet structure with a layer-to-layer distance of 0.35 nm.However, owing to the lack of a substrate, the nanosheets reunite to form irregular microparticles, as shown in the scanning electron microscopy (SEM) images.Twin structure was found in the as-prepared samples, which might be relevant to the mechanochemical process.The samples were used to prepare electrodes for the photoelectrochemical and electrochemical catalytic analysis.The open circuit potential under chopped irradiation of the electrode showed that the as-prepared hydrogen-substituted graphyne was a p-type semiconductor.The band gap was calculated to be 2.30 eV by UV-Vis diffused reflectance (UV-Vis DRS) spectroscopy.The electrocatalytic properties of the sample were determined using a three-electrode cell in a neutral solution (Na₂SO₄, 0.5 mol·L⁻¹).The onset overpotential for hydrogen evolution was −0.17 V; however, the Tafel slope was too large (1088.4 mV·dec⁻¹), which restricted application in electrocatalytic hydrogen evolution.On the other hand, the overpotential for oxygen evolution reaction was only 0.04 V and the Tafel slope was 70.0 mV·dec⁻¹, making applications in electrocatalytic oxygen evolution and photocatalysis possible.This strategy opens a new avenue for preparing graphyne with good electrochemical properties using readily available precursors under mild conditions.

The evolution of cesium iodide band gap as a function of pressure is studied in the range from 0 to 60 GPa. Within this range, two structural phase transitions occurred, and the band gap was affected by the compression pressure and structural rearrangement. The band gap estimation under pressure, as obtained by the density functional theory methods, successfully reproduced the experimental trend of the optical gap and electrical resistivity, namely, a general decreasing tendency, an early maximum, and a discontinuous peak around 40 GPa.

Herein, the synthesis of a series of titanium based nanocrystals using tetrabutyl titanate (TBT) as the titanium source and hydrofluoric acid (HF) as the fluorine source under solvothermal conditions has been described. The effect of the amount of HF on the structural evolution of the nanocrystals was studied. The catalytic performance of the as-prepared samples was measured by photocatalytic hydrogen evolution, photocatalytic RhB degradation, and chronoamperometric tests. The obtained results showed that anatase TiO₂ nanoparticles with exposed {101} facets were synthesized in the absence of HF. After the addition of a small amount of HF, the F^- ion adsorbed on the surface of the nanocrystal and decreased the surface energy of the {001} facets. Thus, sheet-shaped TiO₂ was formed with exposed {001} facets. Furthermore, the as-prepared sample showed an enhanced photocatalytic performance because of the increased charge separation efficiency, which was dependent on the surface heterostructure generated between the {101} and {001} facets. On further increasing the amount of HF, F^- ions started to enter the lattice and formed a new crystal phase. The as-prepared sheet-stacked sample was comprised of TiO₂ and TiOF₂ phases in both surface and bulk regions, which showed the decreased photocatalytic activity. With the addition of more HF, the F^- ion moved completely into the crystal lattice and the large particle structure of (NH₄)_0.3TiO_1.1F_2.1 was formed. Although the as-prepared (NH₄)_0.3TiO_1.1F_2.1 displayed a low photocatalytic activity because of an improper band gap structure, it could be used as a precursor for the synthesis of N, F doped titanium based semiconductors.

AlN-Fe nanocomposite thin films with different AlN-Fe ratio were prepared by pulsed laser deposition (PLD).They were investigated as new anode materials for lithium ion batteries for the first time.The AlN-Fe nanocomposite films with an AlN/Fe ratio of 2:1 show the best electrochemical performance.They exhibit a specific capacity of 510 mA·g^-1 after 100 cycles at a rate of 500 mA·g^-1.Further, the study of the electrochemical reaction mechanism of the AlN-Fe nanocomposite thin films with lithium reveals that AlN decomposes during the discharge process to form the LiAl alloy and Li₃N.During recharge, a part of Li₃N reacts with Fe to form Fe₃N, and the rest reacts with Al to form AlN.In subsequent cycles, all of Fe₃N, AlN, and Al react with Li reversibly, contributing to the reversible charge-discharge processes and to the superior electrochemical performance of AlN-Fe nanocomposite thin films.Thus, this study provides a new perspective to design advanced electrode materials for lithium-ion batteries.

The molten salt CO₂ capture and electrochemical transformation (MSCC-ET) process is a potentially efficient method for CO₂ utilization, which can convert CO₂ into value-added carbon and oxygen with a current density of 100–1000 mA cm^-2. The electrolytic carbon (EC) prepared through the MSCC-ET process is highly electrically conductive and forms flexible microstructures. These structures show excellent adsorption ability towards environmental pollutants and high energy storage capacity when used in supercapacitors. Although the morphology, structure, and application of EC prepared under different electrolysis conditions have been previously reported, their intrinsic electrochemical properties have not yet been elucidated. Powder microelectrodes (PMEs) are useful for studying the electrochemical kinetics of various powdery materials. In this study, we systematically investigated the electrochemical properties of ECs obtained using molten Li₂CO₃-Na₂CO₃-K₂CO₃ under different temperature and electrolysis voltage conditions by cyclic voltammetry (CV) with a carbon powder microelectrode in 10 mmol L^-1 Na₂SO₄. The electrochemical behavior of the EC obtained at 450 ℃ and a cell voltage of 4.5 V (450 ℃-4.5 V-EC) differs significantly from that of other carbon materials, i.e., multi-walled carbon nanotubes, graphene, graphite, and acetylene black. In addition to a much larger charging-discharging capacity, unusual hysteresis of the charge/discharge current response of ECs in the negative potential region (-0.6 to -0.2 V vs SCE) was observed. This phenomenon was eliminated by annealing the material under Ar at 550 ℃, demonstrating that the unique electrochemical behavior of ECs is closely related to the oxygen-containing groups on its surface. Furthermore, CVs of EC-PME were compared in solutions with different pH, Na₂SO₄ concentrations, and other ions. The pH of the solution did not affect the CVs, excluding a redox mechanism involving the surface functional groups. Hysteresis was weakened by a certain degree at slower potential sweep speeds (< 10 mV s^-1) or in higher concentrations of electrolyte (100 mmol L^-1 Na₂SO₄). The onset potential for discharging was negatively shifted in electrolytes with a larger cation ((NH₄)₂SO₄) and was unaffected by larger anions (Na₂S₂O₈). This indicates that the hysteresis is more likely related to the specific adsorption of cations, caused by the unique surface properties of EC. It should be noted that the specific surface area and oxygen concentration of EC can be adjusted by the electrolysis temperature and cell voltage. Generally, the Brunauer–Emmett–Teller (BET) specific surface area and oxygen content decrease with increasing temperature and the BET-area increases with increasing cell voltage. The CVs of ECs prepared at different cell voltages were similar, but the adsorption capacity decreased for those prepared at higher temperatures (550 and 650 ℃). Interestingly, the specific capacitance of the ECs is much higher at negative potentials (-0.6 to 0 V vs. SCE) than that at positive potentials (0 to 0.6 V vs. SCE). Therefore, it is anticipated that a better capacitance performance can be achieved when the ECs are used as a negative electrode material in supercapacitors.

In recent years, the successful preparation of single-layer graphene, MoS₂, and other two-dimensional materials has started a new era of two-dimensional materials.The potential applications of two-dimensional materials in emerging electronics have drawn widespread attention.Two-dimensional carbon materials, with their unique properties, have become the research hotspot of condensed matter physics, nanoelectronics, and biological medicine.The remarkable success in preparing graphene provides additional possibilities for developing sensitive biodevices and medicine systems.However, graphene is gapless and thus is unsuitable for building nanoelectronic devices or biosensors due to the too low on/off current ratio.More than 20 years ago, graphyne and its family (viz.graphdiyne, graphyne-3, etc.), as hypothetical C allotropes, were theoretically predicted to be semiconductors with a layered structure.Recently, graphdiyne was successfully synthesized on the surface of copper via a cross-coupling reaction using hexaethynylbenzene.Graphdiyne, as a new two-dimensional carbon material with semiconductor properties and a unique porous structure, is more advantageous than graphene for nanoelectronic and biosensing applications.As the first discovered semiconducting two-dimensional carbon material, with independent intellectual property rights in China, graphdiyne has great research significance.Compared with graphene, graphdiyne has a unique structure with larger pores composed of high π-conjugated acetylenic bonds, which may facilitate strong adsorption to biomolecules.Therefore, further research is needed to reveal how the physical properties of graphdiyne can be modulated effectively to meet the requirements of practical applications.The interaction between biological molecules and materials is an important subject of research in condensed matter physics and materials science.Detailed understanding of the interactions between graphdiyne and small molecules may facilitate the development of advanced biological applications such as biosensors for the detection of biomolecules and living cells, drug delivery systems, and cell imaging technologies.In sensitive analysis, the ultimate goal is to achieve reliable detection of trace amounts of molecules.In this work, first-principles calculations were employed to investigate the electronic structure of graphdiyne nanoribbons and the adsorption of graphdiyne to small molecules.To improve the chemical response of graphdiyne to single molecules, we considered modifying graphdiyne by doping 3d transition metal atoms.We chose Sc and Ti, which have the largest adsorption energies on graphdiyne, and studied the room-temperature stabilities of Sc-and Ti-doped graphdiyne and the possibility of using Sc-and Ti-doped graphdiyne as materials for molecular sensing.Finally, we investigated the interaction between graphdiyne and amino acid molecules and discovered that the dispersion force plays a large role in the interaction.The influence of amino acids on the electronic transport properties of graphdiyne was also studied, and the potential applications of graphdiyne to biosensors were investigated.

Heat-assisted magnetic recording (HAMR) is one of the promising ways to extend the magnetic recording area density to 1 Tb·in^-2 in hard disk drives (HDDs).High temperature induced by laser heating can cause carbon overcoat (COC) oxidation.Reactive molecular dynamics (MD) simulations are performed to investigate the oxidation process of silicon-doped amorphous carbon (a-C:Si) films for HAMR application.The atomic details of the structure evolution and oxidation process are investigated, and, the oxidation mechanism of the a-C:Si film is clarified.The effect of the duration of laser irradiation on the oxidation of the a-C:Si film is investigated.The oxidation occurs during heating and the beginning of cooling process.Both volume expansion during heating process and cluster of carbon atoms during cooling process increase the rate of sp² carbon.Because of the decrease in the amount of unsaturated silicon atoms and low diffusion coefficient of atomic oxygen, the oxidation rate of the a-C:Si film decreases with laser irradiation cycles.The molecular oxygen is the oxidant due to surface defect of a-C:Si film.The atomic strains break the O-O bonds in Si-O-O-Si linkages and rearrange the surface oxide layers, and process the oxidation of the a-C:Si film.