Theoretical Insight into the Origin of Large Stokes Shift and Photophysical Properties of Anilido‐Pyridine Boron Difluoride Dyes

The geometric and electronic structures and photophysical properties of anilido‐pyridine boron difluoride dyes 1 – 4 , a series of scarce 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) derivatives with large Stokes shift, are investigated by employing density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations to shed light on the origin of their large Stokes shifts. To this end, a suitable functional is first determined based on functional tests and a recently proposed index—the charge‐transfer distance. It is found that PBE0 provides satisfactory overall results. An in‐depth insight into Huang–Rhys (HR) factors, Wiberg bond indices, and transition density matrices is provided to scrutinize the geometric distortions and the character of excited states pertaining to absorption and emission. The results show that the pronounced geometric distortion due to the rotation of unlocked phenyl groups and intramolecular charge transfer are responsible for the large Stokes shift of 1 and 2 , while 3 shows a relatively blue‐shifted emission wavelength due to its mild geometric distortion upon photoemission, although it has a comparable energy gap to 1 . Finally, compound 4 , which is designed to realize the rare red emission in BODIPY derivatives, shows desirable and expected properties, such as high Stokes shift (4847 cm^?1), red emission at 660 nm, and reasonable fluorescence efficiency. These properties give it great potential as an ideal emitter in organic light‐emitting diodes. The theoretical results could complement and assist in the development of BODIPY‐based dyes with both large Stokes shift and high quantum efficiency.     

Conformational analysis of N-aryl-N-(2-azulenyl)acetamides

Aromatic amides bearing 2-azulenyl group on the amide nitrogen were synthesized and their structures were investigated. The π-electron density of the N-aryl group was found to influence the cis-trans conformational preferences of these compounds in solution. X-ray crystallography revealed that the plane of the 2-azulenyl ring has a strong tendency to lie coplanar with the amide plane when the azulene group is located on the same side as the amide oxygen atom.     

Three Octacyanometallate‐Based LnIII–MV (Ln = La,Ce; M = Mo,W) Bimetallic Assemblies with a One‐Dimensional Rope‐Ladder Chain Structure

Three octacyanometallate‐based hetero‐bimetallic complexes, [Ln(H₂O)₄(CH₃CN)₂][M(CN)₈] · CH₃CN [Ln = La, M = Mo( 1 ), W( 2 ); Ln = Ce, M = W( 3 )], were synthesized and characterized structurally. Single‐crystal X‐ray analysis reveals that 1 – 3 are isomorphous and consist of infinite one‐dimensional (1D) 3,3 rope‐ladder chains, in which the 12‐membered puckered square Ln₂M₂(CN)₄ is the basic building unit. The 1D chains are further linked through interchain hydrogen bonds, resulting in a three‐dimensional (3D) supramolecular network.     

Enhanced photoactivity of CdS nanorods by MXene and ZnSnO3: Application in photoelectrochemical biosensor for the effect of environmental pollutants on DNA hydroxymethylation in wheat tissues

The photoactivity of CdS nanorods was greatly improved by amino functionalized accordion-like MXene and spherical ZnSnO₃. MXene possesses good electron transfer capability and ZnSnO₃ presents matched energy band with CdS, which deeply accelerate the electron transfer and prevent the recombination of photogenerated electron-hole pair, leading to a strong photoelectrochemical (PEC) response. Taking the merit of the improved photoactivity of CdS nanorods, a novel PEC biosensor was constructed for DNA hydromethylation detection based on immune recognition of target molecule, where 5-hydroxymethyl-2′-deoxycytidine triphosphate (5hmdCTP) was employed as detect target, CdS/MXene was used as photoactive material, and ZnSnO₃ was adopted as signal amplification unit. Under enzymatic covalent reaction of –CH₂OH of 5hmdCTP with –NH₂ of MXene, 5hmdCTP was specifically recognized and captured. Then, taking advantages of the covalent reaction between phosphate group of 5hmdCTP and ZnSnO₃, the signal amplification unit was captured. Under the optimum conditions, this PEC biosensor presents wide linear range of 0.008–100 nM and low detection limit of 4.21 pM (3σ). The applicability of the developed method was evaluated by investigating the effect of Cd²⁺ and perfluorohexane compound pollutant on 5-hydroxymethylcytosine content in the genomic DNA of the roots and leaves of wheat seedlings.     

Über die thermischen Eigenschaften von Heteropolysäuren des Typs H3+n[PVnMo12−nO40] · x H2O (n = 0, 1, 2, 3) II. Raman- und IR-spektroskopische Untersuchungen

On the Thermal Behaviour of Heteropoly Acids of the Type H_3+n[PV_nMo_12?nO₄₀] · x H₂O (n = 0, 1, 2, 3). II. Raman and Infrared Spectroscopic Investigations The investigation of de- and rehydratization of the heteropoly acids H_3+n[PV_nMo_12?nO₄₀] · x H₂O (n = 0, 1, 2, 3) shows typical changes in the region of valence and bridging vibrations in the Raman and infrared spectra, in particular during the existence of ?anhydrous”? forms. The time dependence of rehydratization is also demonstrated well with a special Raman sample technique.     

Localized surface plasmon resonance properties and biomedical applications of copper selenide nanomaterials

Nanomaterials with localized surface plasmon resonance (LSPR) locating in the near-infrared region have broad application prospects in the field of biomedicine. However, the biggest problem that limits the biomedical application of such nanomaterials lies in two aspects: First, the potential long-term in vivo toxicity caused by the metabolism of many nanomaterials with LSPR effect; Second, most of current nanomaterials with LSPR effect are difficult to achieve LSPR wavelength tunability in the near-infrared region to adapt to different biomedical applications. Copper selenide nanomaterials are composed of selenium and copper, which are necessary nutrient elements for human life. Because of the active and flexible chemical properties of selenium and copper, copper selenide nanomaterials can not only be effectively degraded and utilized in human body, but also be endowed with various physicochemical properties by chemical modification or doping. Recently, copper selenide nanomaterials have shown unique properties such as LSPR in the near-infrared region, making them attractive for near-infrared thermal ablation, photoacoustic imaging, disease marker detection, multimode imaging, and so on. Currently, to the best of our knowledge, there is no review on the LSPR properties of copper selenide nanomaterials and its biomedical applications. This review first discusses the relationship between the physicochemical properties and the LSPR of copper selenide nanomaterials and then summarizes the latest progress in the application of copper selenide nanomaterials in biological detection, diagnosis, and treatment of diseases. In addition, the advantages, and prospects of copper selenide nanomaterials in biomedicine are also highlighted.     

Meso-四(对-磺基苯基)卟啉光度法测定螺旋藻中的痕量锌

在pH=4．5的乙酸-乙酸钠缓冲介质中，锌和meso-四-（对磺基苯基）卟啉生成1：l的黄色配合物，λmax=421nm，ε=4.34×105L·mol-1·cm-1。该法可不经分离直接测定螺旋藻中的锌,结果满意。     

新型四硫代富瓦烯衍生物的合成及其性质的研究

合成了3个新的含有卤素取代基的四硫代富瓦烯衍生物及6个新的相关化合物。利用溶液的电子吸收光谱对四硫代富瓦烯衍生物的性质进行了研究。研究结果表明, 四硫代富瓦烯衍生物的分子中π轨道之间的能级差较小, 因而分子具有较高的稳定性。     

The underlying mechanism for reduction stability of organic electrolytes in lithium secondary batteries

Many organic solvents have very desirable solution properties, such as wide temperature range, high solubility of Li salts and nonflammability, and should be able but fail in reality to serve as electrolyte solvents for Li-ion or -metal batteries due to their reduction instability. The origin of this interfacial instability remains unsolved and disputed so far. Here, we reveal for the first time the origin of the reduction stability of organic carbonate electrolytes by combining ab initio molecular dynamics (AIMD) simulations, density functional theory (DFT) calculations and electrochemical stability experiments. It is found that with the increase of the molar ratio (MR) of salt to solvent, the anion progressively enters into the solvation shell of Li⁺ to form an anion-induced ion–solvent-coordinated (AI-ISC) structure, leading to a “V-shaped” change of the LUMO energy level of coordinated solvent molecules, whose interfacial stability first decreases and then increases with the increased MRs of salt to solvent. This mechanism perfectly explains the long-standing puzzle about the interfacial compatibility of organic electrolytes with Li or similar low potential anodes and provides a basic understanding and new insights into the rational design of the advanced electrolytes for next generation lithium secondary batteries.

By theoretical and experimental evidence, the underlying mechanism for the enhanced reduction stability of the HMRE is revealed, suggesting that the interfacial stability of the electrolyte can be adjusted through the modulation of the anion-induced ISC structure.

The state-of-the-art electrolytes in Li-ion batteries (LIBs) are mostly based on 1.0 mol L⁻¹ LiPF₆/ethylene carbonate (EC)-based carbonate due to the surface passivation of the graphite anode by forming a stable solid electrolyte interphase (SEI). However, these electrolytes cannot operate well for new electrode materials and battery systems that are expected to have higher voltage, better safety and wider temperature range than current commercial LIBs.^1–3 For example, EC-based carbonate electrolytes are easily oxidized on a high voltage cathode at or above 4.3 V, resulting in depletion of electrolytes, gas evolution and low coulombic efficiency, which reduce the cycle life and create safety hazards for LIBs.⁴ These problems of the conventional electrolyte significantly hinder the development of new generation lithium batteries and limit these batteries for high voltage and/or high capacity applications and operation in a wide temperature range.To overcome these problems, great efforts have been devoted in recent years to the development of new electrolytes, such as solid state electrolytes,⁵ ionic liquids,^6–8 highly-concentrated electrolytes (HCEs),⁹ electrolyte stabilizing additive,^10–13 and so on. Among them, the HCEs or high-molar-ratio electrolytes (HMREs) of salt to solvent have received particular attention, owing to their unusual electrochemical stability, nonflammability, and good compatibility with a wide range of anode and cathode materials.^14–17 These desirable properties are apparently attributed to the solution structure of HCEs, where there exist almost no free solvent molecules, and the parasitic side reactions of solvents are thereby greatly reduced. Due to the lack of solvent molecules in HCEs, anions have to enter into the solvation shell of Li⁺, in order to meet the Li⁺ coordination number of 4–6, to form an ion–solvent-coordinated (ISC) structure.¹⁸ Several studies have shown that the unique ISC structure of HCEs leads to the shift of the lowest unoccupied molecular orbital (LUMO) from solvent to salt, which makes anions preferentially reduced or decomposed to produce a robust anion-derived SEI.^14,19 In recent years, the anion-derived SEI structure has been regarded as the “holy grail” of electrolyte chemistry for understanding the interfacial stability and compatibility of HCEs. However, recent studies have showed that some HCEs containing non-film-forming salts and solvents can still achieve excellent reversible Li⁺ insertion reactions.²⁰ Therefore, an intrinsic origin for the interfacial stability of HCEs still remains unrevealed. In our previous studies on HCEs or HMREs, their interfacial stability was found to depend predominately on the molar ratio (MR) of salt to solvent rather than the molar concentration.^2,21,22 Thus, the HMREs instead of the HCEs in the following study could more clearly describe the nature of electrolyte stability.In this work, we reveal the correlation between the solvation microstructures and the LUMO energy levels of typical ISC structures in the electrolytes at various MRs with non-film-forming lithium salt (LiClO₄) and organic carbonate solvents (PC, DMC, EMC and DEC) by ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) calculations. The choice of non-film-forming lithium salt and solvent in this study was aimed to exclude the contribution of the formation of the SEI film to the interfacial stability of the electrolytes. It is found from this study that the LUMO energy level of the ISC structure formed at a low MR is lower than that of pure solvent. With the increase of the MR, anions gradually enter into the first solvation shell of Li⁺ to form the anion-induced ISC (AI-ISC) structure, resulting in the increase of the LUMO energy level that enhances the reduction stability of the electrolyte. Also, it is revealed that the LUMO levels of ISC structures at different MRs are always situated at the coordinated solvent molecules, i.e., the strong reduction stability of HMREs is dominated by the modulation of solvent molecules rather than only the formation of the anion-derived SEI. Such a theoretical insight is further unequivocally evidenced by chemical compatibility experiments in this work. These findings reveal the origin of the greatly improved interfacial stability of HMREs and provide a mechanistic insight into the rational design of stable electrolytes for new generation alkali or alkaline metal based batteries.To investigate the specific ISC microstructures of the electrolytes with different MRs, AIMD simulations were first performed (see computational details in the ESI^†). Taking non-film-forming DEC solvent as an example, three types of electrolytes with MRs of LiClO₄ to DEC = 1 : 10, 1 : 5 and 1 : 2 are considered (Table S1^†). After long-time AIMD simulation, the representative images of the equilibrium structures are shown in Fig. 1a–c. To characterize the solution structures, the radial distribution function g(r) of the electrolyte with different MRs is analyzed (Fig. 1e–g), and the changes in the Li⁺ coordination number with the O atoms of solvents and anions are listed in Fig. 1d. In addition, it should be noted that the total coordination number of Li⁺ always remains around 4, which implies that the stable tetragonal solvation shell structure of Li⁺ does not change in the different MR electrolytes; meanwhile, both the coordination numbers of Li⁺ contributed by the solvent and anion change oppositely. This phenomenon can be corroborated experimentally through infrared spectroscopy (IR) because the C O bond of the carbonate group has a strong IR absorption in the carbonyl region (1650–1850 cm⁻¹) and its IR peak position shifts sensitively with its coordination environment. As shown in Fig. 1h, the IR band of carbonyl groups in pure DEC is located at ∼1741 cm⁻¹, which is shifted to ∼1710 cm⁻¹ in a LiClO₄/DEC (MR = 1 : 10) electrolyte due to the coordination of the O atom in C O with Li⁺. With the increase of the MR of Li⁺/DEC, its IR peak at ∼1741 cm⁻¹ gradually disappears, reflecting a gradual decrease in the number of free DEC molecules. In addition, the IR band of free ClO₄⁻ in a LiClO₄/DEC (MR = 1 : 10) electrolyte is located at ∼931 cm⁻¹, which is shifted to ∼942 cm⁻¹ in the 1 : 2 LiClO₄/DEC electrolyte due to the ionic association of Li⁺ and ClO₄⁻ (Fig. S1^†). Combining AIMD simulations and IR experiments, it can be concluded that with the increase of the MR of the electrolyte, the anions gradually enter into the solvation shell of Li⁺, which modulates the chemical stability of the electrolyte.Open in a separate windowFig. 1Snapshots of typical equilibrium trajectories from DFT-MD simulations: (a) 1 : 10 LiClO₄/DEC solution (2-LiClO₄/20-DEC), (b) 1 : 5 LiClO₄/DEC solution (3-LiClO₄/15-DEC) and (c) 1 : 2 LiClO₄/DEC solution (7-LiClO₄/14-DEC). (d) Typical ISC structure extracted from DFT-MD. (e–g) Radial distribution function of lithium–oxygen interaction (short dashed lines) and relationship between the coordination number and bond distances (full lines). (h) FTIR spectra of the carbonyl group in LiClO₄/DEC solution. Atom color: H, white; Li, purple; C, cyan; O, red; Cl, green.Coordination numbers (n(r)) of atom pairs of Li–O(DEC) and Li–O (ClO₄⁻) (cut-off length of r = 2.5 Å)

周岁内幼儿头发中锌钙含量的动态分析

对合肥市16671名1－12个月幼儿的发锌，钙含量进行了测定，并对测定值进行了统计分析。结果表明，锌，钙的含量随着月龄的增加呈直线递减。并给出了发锌，钙含量的趋势线方程，丰富了目前文献给出的发锌，钙的标准值，为及时准确判断周岁内幼儿微量元素锌，钙缺乏程度提出依据。