用密度泛函理论研究Lennard-Jones 流体在狭缝中的相平衡

用改进的基础度量理论(modified fundamental measure theory, MFMT)和密度Taylor展开分别表达过剩自由能中的短程作用和色散作用. 流体分子与狭缝壁之间的相互作用以10-4-3势能函数表达. 由巨势最小原理确定Lennard-Jones (LJ)流体在狭缝中的密度分布和过剩吸附量, 所得结果与分子模拟数据吻合良好. 根据平衡时两相温度, 化学势及巨势相等, 计算了LJ流体在狭缝中的相平衡.     

抗坏血酸锌的制备及标准生成焓测定

合成了一种新的补锌剂抗坏血酸锌,通过元素分析、红外光谱、热重、电导和化学分析确定了配合物的组成。用新型的具有恒定温度环境的反应热量计,在298·2K条件下分别测定了ZnO(s) C6H8O6(s)配位反应中反应物和生成物在2mol/L HCl溶液中的溶解焓,设计了一个新的热化学循环,得到固相配位反应焓。进而计算出配合物Zn(C6H7O6)2·4H2O(s)的标准生成焓:ΔfHm[Zn(C6H7O6)2·4H2O,s]=-3528·9±0·5kJ/mol。     

纳米羟基磷灰石制备及其对溶液中苯酚吸附的优化设计

采用化学沉淀法制备得到纳米羟基磷灰石(n-HAp)粉体,研究了n-HAp粉体对水溶液中苯酚的吸附性能,并初步探讨了其在粉体上的吸附机理,在低浓度(5~30mg/L)时的吸附符合Freundlich等温吸附模型。实验结果表明,n-HAp粉体对苯酚具有较好的吸附效果,2h可基本达到吸附平衡。利用正交设计实验探讨了粉体煅烧温度、吸附温度、吸附时间、溶液pH等因素对吸附效果的影响。正交实验结果统计分析表明,各种因素对吸附的影响程度依次为:溶液pH>煅烧温度>振荡温度>振荡时间。pH对吸附性能的影响最明显,强酸和强碱环境能有效提高n-HAp对苯酚的吸附量。     

Sensitive determination of phenols in environmental water samples with SPE packed with bamboo carbon prior to HPLC

Bamboo carbon, an inexpensive, readily available material, has attracted great attention in recent years because of adsorptive properties. In this paper, the potential of bamboo carbon as a SPE adsorbent for the determination of phenols, was investigated. Phenols are important environmental contaminants that may adversely affect human health. Parameters influencing extraction efficiency, including type of eluent, eluent volume, amount of adsorbent, as well as sample pH, volume, and flow rate were investigated and optimized. The optimized results exhibited excellent linear relationships between peak area and phenol concentrations over the range of 2.0–100 ng/mL, with precision between 2.2–7.2%. The LODs were 0.06–0.4 ng/mL for the eight phenols tested. The proposed method has been successfully applied to the analysis of several real‐world environmental water samples. These results indicate that bamboo carbon may be used as a novel SPE adsorbent for the concentration and determination of phenols in real environmental water samples.     

Anhydrous proton conducting membranes based on crosslinked graft copolymer electrolytes

A comb-like copolymer consisting of a poly(vinylidene fluoride-co-chlorotrifluoroethylene) backbone and poly(hydroxy ethyl acrylate) side chains, i.e. P(VDF-co-CTFE)-g-PHEA, was synthesized through atom transfer radical polymerization (ATRP) using CTFE units as a macroinitiator. Successful synthesis and a microphase-separated structure of the copolymer were confirmed by proton nuclear magnetic resonance (¹H NMR), FT-IR spectroscopy, and transmission electron microscopy (TEM). This comb-like polymer was crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification of the –OH groups of PHEA and the –COOH groups of IDA. Upon doping with phosphoric acid (H₃PO₄) to form imidazole–H₃PO₄ complexes, the proton conductivity of the membranes continuously increased with increasing H₃PO₄ content. A maximum proton conductivity of 0.015 S/cm was achieved at 120 °C under anhydrous conditions. In addition, these P(VDF-co-CTFE)-g-PHEA/IDA/H₃PO₄ membranes exhibited good mechanical properties (765 MPa of Young's modulus), and high thermal stability up to 250 °C, as determined by a universal testing machine (UTM) and thermal gravimetric analysis (TGA), respectively.     

Preparation of a Novel COOH Ion Implantation Sensor and Its Application

A novel ion implantation sensor (DNA/COOH/ITO) based on DNA immobilization in COOH/ITO probe was manufactured for the first time. The surface morphologies of the electrodes were characterized by X‐ray photoelectron spectroscopy (XPS), field‐emission‐scanning electron microscopy (FSEM) and electrochemical methods. In a 0.5 mol/L PBS solution, a sensitive oxidation peak of DNA on the COOH/ITO electrode was obtained by voltammetry. The electrochemical behavior of DNA was studied. And the oxidative peak potential of DNA was +0.400 V (vs. Ag/AgCl). Its peak current was proportional to the concentration of DNA over the range of 1.0×10^?8?1.0×10^?6 mol/L with a detection limit of 5.0×10^?9 mol/L (about 0.5 ng/mL). This sensor was applied to the direct detection of DNA samples.     

Syntheses,Crystal Structures and Luminescent Properties of Three Inorganic‐Organic Hybrid Frameworks Constructed from 4,5‐Imidazoledicarboxylate

Three inorganic‐organic hybrid frameworks [Mn(HIMDC)(4,4′‐bipyo)_0.5(H₂O)]_n (1) , [Cd(H₂IMDC)₂(2,2′‐bipyo)] (2) and [Ca(HIMDC)(H₂O)₂·H₂O]_n (3) (H₃IMDC = 4,5‐imidazoledicarboxylate; 4,4′‐bipyo = 4,4′‐bipyridine‐N,N′‐dioxide; 2,2′‐bipyo= 2,2′‐bipyridine‐N,N′‐dioxide) have been hydrothermally synthesized and characterized by the elemental analyses, IR spectra, TG analysis and the single crystal diffraction. Both compounds 1 and 3 exhibit 2D layers while 2 is a monomer. It is noteworthy that compound 2 exhibits strong fluorescent emission in the solid state at room temperature.     

High-performance Flexible Symmetric Supercapacitor Based on Heterostructured PANI@MoS2 Nanocomposite Electrode

Three-dimensional (3D) heterostructured molybdenum disulfide (MoS₂) is used as base materials for aniline monomer in situ polymerization on its surface. It is found that the aniline addition has a remarkable effect on the energy storage of the final compounds due to the improvement of the conductivity and structure stability combined with the synergistic effect between the two types of species. The optimal compound of PANI@MoS₂-150 not only shows a high capacitance value of 801.4 F ⋅ g⁻¹ at a current density of 0.5 A ⋅ g⁻¹ but also provides a high retention rate of 77.4 % after 10,000 cycles. The capacitance fading may be due to the increase of the internal resistance analyzed by EIS. Furthermore, a flexible symmetric supercapacitor based on PANI@MoS₂-150 has also been fabricated and the specific capacitance reaches 105 F ⋅ g⁻¹ at a current density of 1 A ⋅ g⁻¹. Impressively, the capacitance retention is larger than 100 % undergoing 10,000 cycles. Besides, the highest energy density of 21 Wh ⋅ kg⁻¹ was obtained. Additionally, the fabricated symmetric supercapacitor demonstrates excellent flexibility.     

Revealing Capacity Degradation of Ge Anodes in Lithium-Ion Batteries Triggered by Interfacial LiH

The Germanium (Ge), as a fast-charging and high specific capacity (1568 mAh g⁻¹) alloy anode, is greatly hampered in practical application by poor cyclability. To date, the understanding of cycling performance degradation remains elusive. This study illustrates that, contrary to conventional beliefs, most of the Ge material in failed anodes still retains good integrity and does not undergo severe pulverization. It is revealed that capacity degradation is clearly correlated to the interfacial evolution of lithium hydride (LiH). Tetralithium germanium hydride (Li₄Ge₂H), as a new species derived from LiH, is identified as the culprit of Ge anode degradation, which is the dominant crystalized component in an ever-growing and ever-insulating interphase. The significantly increased thickness of the solid electrolyte interface (SEI) is accompanied by the accumulation of insulating Li₄Ge₂H upon cycling, which severely retards the charge transport process and ultimately triggers the anode failure. We believe that the comprehensive understanding of the failure mechanism presented in this study is of great significance to promoting the design and development of alloy anode for the next generation of lithium-ion batteries.     

Synergistic Metal-Nonmetal Active Sites in a Metal-Organic Cage for Efficient Photocatalytic Synthesis of Hydrogen Peroxide in Pure Water

Photocatalytic synthesis of hydrogen peroxide (H₂O₂) is a potential clean method, but the long distance between the oxidation and reduction sites in photocatalysts hinders the rapid transfer of photogenerated charges, limiting the improvement of its performance. Here, a metal-organic cage photocatalyst, Co₁₄(L−CH₃)₂₄ , is constructed by directly coordinating metal sites (Co sites) used for the O₂ reduction reaction (ORR) with non-metallic sites (imidazole sites of ligands) used for the H₂O oxidation reaction (WOR), which shortens the transport path of photogenerated electrons and holes, and improves the transport efficiency of charges and activity of the photocatalyst. Therefore, it can be used as an efficient photocatalyst with a rate of as high as 146.6 μmol g⁻¹ h⁻¹ for H₂O₂ production under O₂-saturated pure water without sacrificial agents. Significantly, the combination of photocatalytic experiments and theoretical calculations proves that the functionalized modification of ligands is more conducive to adsorbing key intermediates (*OH for WOR and *HOOH for ORR), resulting in better performance. This work proposed a new catalytic strategy for the first time; i.e., to build a synergistic metal-nonmetal active site in the crystalline catalyst and use the host–guest chemistry inherent in the metal-organic cage (MOC)to increase the contact between the substrate and the catalytically active site, and finally achieve efficient photocatalytic H₂O₂ synthesis.