The density functional theory and its extension to ensembles of excited states can be formalized as thermodynamics. However, these theories are not unique because one of their key quantities, the kinetic energy density, can be defined in several ways. Usually, the everywhere positive gradient form is applied; however, other forms are also acceptable, provided they integrate to the true kinetic energy. Recently, a kinetic energy density of the ground-state theory maximizing the information entropy has been proposed. Here, ensemble kinetic energy density, leading to extremum information entropy, is derived via constrained search. The corresponding ensemble temperature is found to be constant.
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-ylmethylresorcinarene), 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.
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.
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.
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.
The concept of resonance-assisted hydrogen bonds (RAHBs) highlights the synergistic interplay between the π-resonance and hydrogen bonding interactions. This concept has been well-accepted in academia and is widely used in practice. However, it has been argued that the seemingly enhanced intramolecular hydrogen bonding (IMHB) in unsaturated compounds may simply be a result of the constraints imposed by the σ-skeleton framework. Thus, it is crucial to estimate the strength of IMHBs. In this work, we used two approaches to probe the resonance effect and estimate the strength of the IMHBs in the two exemplary cases of the enol forms of acetylacetone and o-hydroxyacetophenone. One approach is the block-localized wavefunction (BLW) method, which is a variant of the ab initio valence bond (VB) theory. Using this approach, it is possible to derive the geometries and energetics with resonance shut down. The other approach is Edmiston's truncated localized molecular orbital (TLMO) technique, which monitors the energy changes by removing the delocalization tails from localized molecular orbitals. The integrated BLW and TLMO studies confirmed that the hydrogen bonding in these two molecules is indeed enhanced by π-resonance, and that this enhancement is not a result of σ constraints.