硫化氢在金属-有机骨架材料中吸附与分离的计算模拟

摘 要: 采用优化的DREIDING力场参数,通过巨正则系综蒙特卡洛(GCMC)模拟方法对天然气中的两种气体CH4和H2S在Cu6(BTTC)4(H2O)6·xS (1)和[(CH3)2NH2]3[(Cu4Cl)3(BTTC)8]·yS (2)两种金属有机骨架(MOFs)材料中的吸附与分离性能进行了比较研究.结果证明了聚合物2的吸附量和分离性能相比之下高于聚合物1,且两种材料的吸附机理存在差异,聚合物1中金属Cu和有机基团对于吸附两种气体没有明显的作用,主要分布在小孔道和大孔道;然而聚合物2中H2S和CH4主要吸附在有机基团、金属Cu和-Cl基团周围.则含有-Cl基团的聚合物2展现了优越的吸附能力和稳定性.总而言之,本文获得的结果可以应用于此类研究领域,因此在环境范围中吸附去除污染物可以产生更深层次定性和定量的作用.     

Photoluminescence quantum and surface states of excitons in ZnSe and CdS nanoclusters

The optical spectra of quantum dots (QDs) of CdS and ZnSe grown in borosilicate glass by the sol-gel method are obtained and analyzed. It is found that at concentrations of the two semiconductors x<0.06% the emission spectra are due to annihilation of free (internal) excitons in quantum states. The mean size of the quantum dots for a given concentration of ZnSe and CdS is calculated and found to be in good agreement with the X-ray data, and the exciton binding energy is calculated with allowance for the dielectric mismatch between the semiconductor and matrix. It is proposed that this mismatch may be the cause giving rise to the exciton percolation level that is observed in QD arrays for both systems at x>0.06%. The emission from the surface level of CdS QDs in the region ~2.7 eV, formed by the outer atoms with dangling bonds, is observed for the first time, as is the emission band from surface localized states. The relation between the position of the maximum of this band and the energy of the 1S state of the free exciton is established. It is shown that the properties of surface localized states are largely similar to the analogous properties of localized states of 3D (amorphous semiconductors, substitutional solid solutions of substitution) and 2D (quantum wells and superlattices) structures.     

Thermally evaporated CdS/CdTe thin film solar cells: Optimization of CdCl2 evaporation treatment on absorber layer

CdCl₂ treatment is crucial in the fabrication of highly efficient CdS/CdTe thin-film solar cells. This study reports a comprehensive analysis of thermal evaporated CdS/CdTe thin-film solar cells when the CdTe absorber layer is CdCl₂ annealed at temperatures from 340 to 440 °C. Samples were characterized for structural, optical, morphological and electrical properties. The films annealed at 400 °C showed better crystallinity with a cubic zinc blende structure having large grains. Higher refractive index, optical conductivity, and absorption coefficient were recorded for the CdTe films annealed at 400 °C with CdCl₂. Optimum photoactive properties for CdS/CdTe thin-film solar cells were also obtained when samples were annealed at 400 °C for 20 min with CdCl₂, and the best device exhibited V_OC of 668.4 mV, J_SC of 13.6 mA cm⁻², FF of 53.9% and an efficiency of 4.9%.     

The electrical properties of semiconductor/metal,semiconductor/liquid,and semiconductor/conducting polymer contacts

Critical comparisons are drawn between the basic electrical properties of semiconductor/metal, semiconductor/liquid, and semiconductor/conducting polymer junctions. A theoretical model is developed to describe the basic current-voltage properties of semiconductor contacts, with emphasis on the contrasts between ideal and observed behavior. Using the concepts from this model, the characteristics of a variety of semiconductor contacts are evaluated. The discussion focuses on the following semiconductors: Si, GaAs, InP, and II-VI compounds based on the Cd-(chalcogenide) materials.     

CdS/PAMAM与氨基酸作用研究及其在潜在指印显现中的应用

提出了以硫化镉/聚酰胺-胺树形分子(CdS/PAMAM)纳米复合材料显现潜在指印的新方法。傅里叶变换光谱研究了PAMAM G4.5外部酯端基与氨基酸中胺基之间的胺解反应,选用相对峰高比H_{1 267/1 735}来监测不同条件下的反应进程,并发现温度对于胺解反应的影响很大,90 ℃时胺解反应可在4h内显著进行,120 ℃时胺解反应速率在3 h后发生递减。将CdS/PAMAM作为指印显现试剂,在同等条件下与现有常规指印显现液对比,发现前者的荧光强度约为后者的65倍,荧光性能优势明显。确定使用加热压显法显现不同客体表面潜在指印的条件为120 ℃下反应0.5～3 h。使用优化后的条件对多种载体表面潜在指印进行显现,可以获得理想的显现效果。该显现方法具有简便、快速、灵敏、安全、经济等特点。     

“反胶团法”合成的CdS半导体纳米粒子的光谱性质研究

反相胶束是指由介于油和水界面的表面活性剂分子, 稳定、且均匀分散于连续油介质中的微液滴。它可以作为“微反应器”合成性能优良的CdS粒子。文章研究了反相胶束的W值(W=[水]/[表面活性剂])、[Cd2+]与[S2-]的比例和Cd2+和S2- 离子的起始浓度对CdS纳米粒子发光特性均有明显影响。回流处理可以对CdS纳米粒子的表面进行修饰,可以使CdS粒子的缺陷发光减弱并消失而显著增强激子发射,同时可增大粒径使激子发射峰位红移,体现了明显的量子限域效应; 所得材料的室温最大荧光量子效率高达11%。     

基于顶空及表面增强拉曼散射(SERS)结合的葱属植物挥发性物质研究

为了在常温下鉴定新鲜植物样品的挥发性物质,且避免繁杂前期样品的制备过程,将新鲜样品切细后置入顶空瓶中,用注射器抽取顶空瓶上方的挥发性物质注入用微波法制备的纳米银溶胶中,用R-3000便携式拉曼光谱仪进行SERS的测量。获得了葱属植物大蒜、韭菜、葱的挥发性物质的表面增强拉曼光谱(SERS)。大蒜的SERS谱中较强的峰出现在307,399,569,711,1 182,1 287,1 397,1 622 cm-1处。韭菜的SERS谱中最强的峰出现在672 cm-1,较弱的峰出现在274,412,575,1 185,1 289,1 396,1 618 cm-1处。葱的SERS谱中最强的峰出现在693 cm-1,次强峰出现在372,888,1 023 cm-1处,较弱的峰出现在1 088,1 211,1 322 cm-1。获得二烯丙基二硫(diallyl disulfide)、烯丙基甲基硫醚(allylmethyl sulfide)、1-丙硫醇(1-Propanethiol)的液态、气态的SERS谱。经对比研究得出：吸附在银表面的大蒜、韭菜、葱的主要挥发性物质分别是二烯丙基二硫(diallyl disulfide)、烯丙基甲基硫醚(allyl methyl sulfide)、1-丙硫醇(1-Propanethiol)。同是葱属植物但不同种大蒜、韭菜、葱其吸附在银表面的主要的挥发性物质不一样,吸附在银表面的各种葱的主要挥发性物质都是1-丙硫醇。该实验结果表明顶空与SERS结合,不需要复杂的提取过程,可直接用于新鲜植物的挥发性物质快速检测。     

基于荧光分析技术的大鼠肠灌流液中H_2S含量测定

荧光素汞在碱性条件下具有很强的荧光,H2S能与荧光素汞结合,使其荧光猝灭,据此建立了一种荧光法测定大鼠肠灌流液中H2S含量的方法。在0.1mol·L-1 NaOH溶液中,以Na2S作为H2S供体,荧光素汞浓度为5.0×10-5 mol·L-1,Na2S浓度为1.0×10-5 mol·L-1时,以498nm为激发波长,在522nm处测定此二元体系的荧光强度。结果表明,在4.0×10-7~2.0×10-6 mol·L-1范围内,H2S浓度与荧光强度的下降程度呈良好的负相关性,r=0.998 0,精密度实验RSD=4.59%(n=7),检出限3.5×10-8 mol·L-1,样品中H2S含量分别为1.01×10-6和1.15×10-6 mol·L-1,加标回收率为95.8%~101.0%。该方法操作简单,灵敏度高,稳定性好,可准确测定肠灌流液中H2S含量,为内源性H2S的测定提供了依据。     

The effect of solvent on the crystal structure and size distribution of cadmium sulfide nanocrystals

CdS nanocrystals with different structures were synthesized by the method of solution precipitation using thiourea and cadmium acetate as starting materials in different solvents: water, methanol and N,N-dimethylformamide (DMF). Our results show that the solvent has direct effect on the structure and size of the final nanoparticles. It was found that using DMF, as a solvent, results in producing smaller nanoparticles with the cubic structures, while using the other solvents gives rise to larger nanoparticles with the hexagonal structure. It was also found that using heat during washing the precipitate results in a more homogenous size distribution of CdS nanocrystals. On the basis of our experimental results we also suggest a critical structure transformation size.     

Effect of corona discharge on cadmium sulphide and lead sulphide films

This paper describes the effect of corona discharge on cadmium sulphide (CdS) and lead sulphide (PbS) films prepared using the chemical route. The property of films before and after exposure to corona has been described in detail. The electronic properties of the CdS and PbS films have been studied by current-voltage (I-V), capacitance-voltage (C-V) measurements. The structural properties and surface morphology were studied by using X-ray diffraction and scanning electron microscopy before and after exposing to Corona discharge. The films displayed the change in surface morphology after exposure to the corona discharge. It has been found that the films showed an increase in resistivity after exposure. This change in property has been attributed to modification in surface states. Time-dependent recovery indicated that room temperature annealing is sufficient to regain the normal resistivity of the films. The experiment was carried with the aim of studying the effect of the interaction of corona discharge on the semiconductor films and its subsequent effects.