Preparation and formation mechanism of CdS nano-films via chemical bath deposition

CdS semiconductor nano-films were grown on ITO glass substrates by means of chemical bath deposition (CBD), with Cd(NO₃)₂ as Cd ion and (NH₂)₂CS as S ion sources. The concentration of Cd ions, deposition temperature, deposition time and post-treatment temperature have an impact on the formation of CdS nano-films. UV-vis absorption spectrum and atomic force microscope (AFM) images indicated that the change of concentration and post-treatment temperature may adjust the band-gap of CdS to obtain stable, homogeneous and compact films. Formation mechanism of the crystal nucleus and CdS film was also discussed. Active sites on the surface of ITO are critical to the formation of the crystal nucleus and a uniform and compact CdS nano-film. The active site and crystal nucleus are formed due to the comprehensive effect of electricity, thermodynamics and chemistry. __________ Translated from Journal of Jilin University (Science Edition), 2007, 45(1): 116–120 [译自: 吉林大学学报(自然科学版)]     

Hydration of ionic species studied by the reference interaction site model with a repulsive bridge correction

We have tested the reference interaction site model (RISM) for the case of the hypernetted chain (HNC) and the partially linearized hypernetted chain (PLHNC) closures improved by a repulsive bridge correction (RBC) for ionic hydrated species. We have analyzed the efficiency of the RISM/HNC+RBC and RISM/PLHNC+RBC techniques for decomposition of the electrostatic and the nonpolar hydration energies on the energetic and the enthalpic parts for polyatomic ions when the repulsive bridge correction is treated as a thermodynamic perturbation, and investigate the repulsive bridge effect on the electrostatic potential induced by solvent on solute atoms. For a number of univalent and bivalent atomic ions, molecular cations, and anions, the method provides hydration energies deviating only by several percents from the experimental data. In most cases, the enthalpic contributions to the free energies are also close to the experimental results. The above models are able to satisfactory predict the hydration energies as well as the electrostatic potential around the ionic species. For univalent atomic ions, they also provide qualitative estimates of the Samoilov activation energies.     

白色念珠菌N-肉豆蔻酰基转移酶中药物结合位点的MCSS分析

采用多拷贝同时搜寻方法(MCSS)分析得到了CaNMT活性位点的疏水区域、氢键结合位点和负电性区域. MCSS计算结果显示, CaNMT活性位点有两个疏水性比较强的区域: 一个由Tyr107, Tyr109, Val108, Phe117, Phe123, Ala127, Phe176和Leu337等残基组成; 另一个由Phe115, Phe240和Phe339组成. CaNMT活性位点发现有两个氢键作用区域, 其中Tyr119, His227, Asn392和Leu451是与已有抑制剂的氢键结合位点, Tyr107, Asn175, Thr211和Asp412是新发现的氢键结合位点, 而且在NMT家族中高度稳定, 它们对设计新结构类型的CaNMT抑制剂具有重要作用. Leu451是负电性兼氢键作用位点, 是抑制剂设计时所必需考虑的位点.     

钾改性氧化铝基羰基硫水解催化剂及其失活机理

天然气、油田伴生气、高炉煤气等化工生产过程中伴生COS气体,不仅会腐蚀管道和毒害催化剂,还会严重污染环境并危害人类健康。COS催化水解反应可在温和条件下高效的将COS脱除,是最具应用前景的COS脱除技术之一。碱金属元素因其具有独特的电子供体性质、表面碱性和静电吸附等特性,常被用作助催化剂以提高Al₂O₃的COS催化水解性能。近年来,以钾为助剂改性的Al₂O₃催化剂(K₂CO₃/Al₂O₃)在COS催化水解反应中得到广泛的应用,但由于负载在Al₂O₃上的K物种的组成复杂,目前研究者对K₂CO₃/Al₂O₃催化剂上COS水解机理的理解仍存在一定的困惑和争议。本论文通过湿法浸渍法合成出一系列钾盐和钠盐改性的Al₂O₃催化剂,并利用各类先进的表征技术对这些催化剂进行分析。活性测试表明,以K₂CO₃、K₂C₂O₄、NaHCO₃、Na₂CO₃和NaC₂O₄改性Al₂O₃催化剂均有助于COS的水解。其中K₂CO₃/Al₂O₃拥有最佳的COS水解性能,连续运行20 h后其COS转化率仍高于~93%,远远优于未改性的Al₂O₃ (~58%)。我们利用原位红外光谱和X射线光电子能谱探明了反应过程中催化剂的化学结构特征,阐明了H₂O分子在K₂CO₃/Al₂O₃上的水解作用机制。原位红外表明COS在K₂CO₃/Al₂O₃上的水解过程中形成了硫代碳酸氢盐中间产物。X射线光电子能谱表征证明催化剂的失活主要是因为催化剂表面积累了硫酸盐和单质硫。此外,我们还研究了水蒸气含量对COS水解性能的影响,研究发现,由于H₂O和COS分子在催化剂表面存在竞争吸附,过量的H₂O会引起催化活性的下降。上述研究表明,K₂CO₃/Al₂O₃催化剂上COS水解性能的提高主要是形成了HO-Al-O-K界面活性位。更为重要的是,所制备的催化剂都是在模拟工业工况条件下进行的,这为后续的工业应用提供了宝贵理论指导。本工作为理解助剂钾在Al₂O₃催化剂上COS水解活性的增强提供了新的见解,这为未来设计稳定高效的COS水解催化剂打开了新的发展方向。     

光催化剂活性位点调控及其光还原CO2制C2 产物研究进展

工业发展与人类活动导致大气中CO₂浓度逐年升高, 引发一系列生态环境问题. 将CO₂光催化转化为高附加值化学物质不仅有利于缓解环境压力,也可以带来额外经济价值. 然而, 由于多电子利用效率低和C―C偶联动力学缓慢, 光还原CO₂制多碳产品面临产率低和选择性差等挑战. 光催化剂活性位点调控能够有效解决上述问题. 我们综述了近几年用于光还原CO₂催化剂表面活性位点设计的研究进展, 主要包括缺陷位点、 金属位点以及掺杂位点等, 从活性位点的角度为光还原CO₂催化剂设计提供新视角, 并对开发高效光催化剂具有启发意义.     

便携式X射线荧光光谱仪在污染场地中重金属检测的应用

为探究便携式X射线荧光光谱法(Portable X-ray fluorescence spectrometry method, PXRF)测定结果的不确定度, 应用PXRF法和传统实验室方法对湖南某典型有色金属污染场地及周边土壤中的重金属进行测定,通过建立线性回归模型对比分析两种方法的测定数据,探究了PXRF法测定数据的准确程度和置信区间。结果表明,PXRF法原位、异位测定值与传统实验室方法测定值均能呈现较好的线性相关性,As、Cu、Pb、Cd等元素的决定性系数(R2)均大于0.70,其检测数据质量均能达到定量水平;PXRF法与实验室方法测定值间比率的置信区间结果显示,Cd元素的准确性最好,其次为Pb、Cu、As,比率置信区间分别为(0.57, 1.89)、(0.38, 2.22)、(0.31, 2.25)、(0.20, 4.53)。由此可见,PXRF法是一种方便快捷且相对准确的土壤重金属现场检测方法,可广泛地应用于污染场地调查和土壤修复工程实践中。     

Optical response of the Cu2S2 diamond core in (NGuaS)2Cl2

Density functional theory (DFT) and time‐dependent DFT calculations are presented for the dicopper thiolate complex Cu₂(NGuaS)₂Cl₂ [NGuaS=2‐(1,1,3,3‐tetramethylguanidino) benzenethiolate] with a special focus on the bonding mechanism of the Cu₂S₂Cl₂ core and the spectroscopic response. This complex is relevant for the understanding of dicopper redox centers, for example, the Cu_A center. Its UV/Vis absorption is theoretically studied and found to be similar to other structural Cu_A models. The spectrum can be roughly divided in the known regions of metal d‐d absorptions and metal to ligand charge transfer regions. Nevertheless the chloride ions play an important role as electron donors, with the thiolate groups as electron acceptors. The bonding mechanism is dissected by means of charge decomposition analysis which reveals the large covalency of the Cu₂S₂ diamond core mediated between Cu and S‐S π and π* orbitals forming Cu‐S σ bonds. Measured resonant Raman spectra are shown for 360‐ and 720‐nm excitation wavelength and interpreted using the calculated vibrational eigenmodes and frequencies. The calculations help to rationalize the varying resonant behavior at different optical excitations. Especially the phenylene rings are only resonant for 720 nm. © 2016 Wiley Periodicals, Inc.     

Calibration of a compact XUV soft X‐ray monochromator with a digital autocollimator in situ

A digital autocollimator of resolution 0.1 µrad (0.02 arcsec) serves as a handy correction tool for calibrating the angular uncertainty during angular and lateral movements of gratings inside a monochromator chamber under ultra‐high vacuum. The photon energy dispersed from the extreme ultraviolet (XUV) to the soft X‐ray region of the synchrotron beamline at the Taiwan Light Source was monitored using molecular ionization spectra at high resolution as energy references that correlate with the fine angular steps during grating rotation. The angular resolution of the scanning mechanism was <0.3 µrad, which results in an energy shift of 80 meV at 867 eV. The angular uncertainties caused by the lateral movement during a grating exchange were decreased from 2.2 µrad to 0.1 µrad after correction. The proposed method provides a simple solution for on‐site beamline diagnostics of highly precise multi‐axis optical manipulating instruments at synchrotron facilities and in‐house laboratories.