TiO2负载型催化剂及光催化还原CO2反应的表面光电压谱研究

半导体TiO₂作为光催化剂,已被广泛应用于光催化废水处理及光催化储能^[1,2]等方面的研究.人们不断开发高活性的新型光催化剂并对其反应机理进行了探索性研究^[3],希望通过表面负载Pd、Ru、Pt或Rh等贵金属的小岛式颗粒以传递光生电子(或光生空穴).     

对叔丁基杯[4]芳烃乙酸萃取模拟制革废水中的cr3+

对叔丁基杯[4]芳烃乙酸;萃取;反应机理;萃取热力学函数;影响因素     

不同形态双金属氢氧化物颗粒水分散体系及其稳定的Pickering乳液

采用共沉淀法制备了3种形态的MgAl双金属氢氧化物颗粒的水分散体系, 并以其为乳化剂制备了Pickering乳液. 比较了3种颗粒的分散体系及其稳定的Pickering乳液的性质. X射线衍射(XRD)和透射电子显微镜(TEM)表征结果表明, 低结晶度的颗粒以形状不规则、 结构疏松、 表面粗糙的絮状体形式分散于水中, 且颗粒尺寸随高速搅拌分散时间的延长而减小; 而良好结晶的颗粒以形状规则、 结构致密、 表面平滑的六角片存在于水中. Zeta电位测试表明, 3种颗粒在水中均带正电荷, NaCl可降低颗粒的Zeta电位而使其发生絮凝, 但良好结晶颗粒的分散体系在更高NaCl浓度时才出现明显沉淀. 分别采用3种双金属氢氧化物颗粒/NaCl水分散体系制备了水包油(O/W)型Pickering乳液, 并比较了乳液的稳定性. 结果表明, NaCl的引入在一定程度上可提高3类乳液的稳定性; 良好结晶颗粒稳定乳液的能力强于低结晶度的颗粒; 对于低结晶度颗粒, 大颗粒稳定乳液的能力比小颗粒更强.     

Aqueous Dispersions of Positively Charged Al/Mg Mixed Metal-Hydroxide Particles:Surface Chemistry and Rheological Properties

The solids concentration, pH and NaCl were found to have a very significant effect on the rheological properties of aqueous dispersions of positively charged Al-Mg mixed metal hydroxide particles (Al-Mg MMH). At low solids concentrations the flow curves of the dispersions at natural pH followed the Newtonian model very well in the observed range of shear rate, while at high solids contents the dispersions developed a yielding type of response, with yield stress increasing rapidly as solids concentration increases. The variation in rheological properties with pH and NaCl contents correlated well with the change in surface properties of Al-Mg MMH particles. Al-Mg MMH dispersions with maximum yield stress occurred near the isoelectric point (IEP) where the Zeta potential (or electrophoretic mobility) is zero. At the IEP, the shear yield stress decreased monotonously in magnitude as a function of the increasing NaCl concentration, which is in contrast to the increment in the yield stress observed below the DEP at NaCl concentrations less than 0.1 mol dm^-3. At low NaCl concentrations, significant shear yield stress differences exist at and below the IEP. By contrast, at high NaCl concentrations, almost identical shear yield stress versus NaCl results are obtained in both cases.     

Transition Between Solid-like and Liquid-like States in Soft Silica Suspensions

The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G“ were investigated. The results show that the suspension transforms from a liquid-like state to a solid-like state with increasing the volume fraction of silica. Such a solid-like state can be transformed back into a liquid-like state under the application of a larger stress. At the higher volume fraction, the larger critical stress is required to induce the transition from solid-like to liquidlike state. As the electrolyte concentration decreases or pH value increases, the inter-particle force increases,which causes the state transition to occur at a higher stress.     

ZnO纳米粒子自建场的形成及对其光电特性的影响

The effect of built-in field on the surface photovoltage(SPV) response of ZnO nanoparticles was investigated by means of surface photovoltage spectroscopy(SPS). From the results of in situ SPS in atmosphere and in vacuum, we suggest that the built-in field should be a main condition for producing SPV response. By comparison of SPS with PL in vacuum as well as in atmosphere, we deduce that by changing the ambience of ZnO, its functional properties can be modulated.     

Quantum Solitons and Localized Modes in a One-Dimensional Lattice Chain with Nonlinear Substrate Potential

In the classical lattice theory, solitons and localized modes can exist in many one-dimensional nonlinear lattice chains, however, in the quantum lattice theory, whether quantum solitons and localized modes can exist or not in the one-dimensional lattice chains is an interesting problem. By using the number state method and the Hartree approximation combined with the method of multiple scales, we investigate quantum solitons and localized modes in a one-dimensional lattice chain with the nonlinear substrate potential. It is shown that quantum solitons do exist in this nonlinear lattice chain, and at the boundary of the phonon Brillouin zone, quantum solitons become quantum localized modes, phonons are pinned to the lattice of the vicinity at the central position j=j₀.     

不同取代基卟啉衍生物敏化纳米TiO2多孔膜电极的光电性质研究

采用含有不同取代基的卟啉衍生物四羟基苯基卟啉(THPP)和四羧基苯基卟啉(TCPP)分别对纳米TiO2多孔膜电极进行敏化.对两种敏化电极进行了UV-Vis光谱、FTIR光谱和X射线光电子能谱(XPS)测试.结果表明,TiO2与TCPP的作用比与THPP的作用强.在相同浸泡条件下,TiO2电极吸附TCPP的量大于吸附THPP的量.将两种敏化电极分别组装成光电化学电池,从正背两个方向照射光电池,研究它们在不同照射方向下的光电流响应.从光电化学电池的I-V曲线计算TCPP敏化的光电化学池的总光电转换效率(η)为0.13%,而THPP敏化的光电化学电池的η为0.06%.     

卟啉衍生物π离子自由基二聚体的电子光谱研究

根据四甲基吡啶铜叶啉（CuTMPyP）的光谱电化学和部分质子化的5，10，15-三（4-羟基苯基）-20－（4-十六烷氧苯基）卟啉（P31）LB膜的荧光光谱，研究了卟琳衍生物离子自由基二聚体的电子光谱．电还原产生的CuTMPyP负离子自由基与基态分子通过SOMO’-LUMO作用形成面对面二聚体，在480nm处出现二聚体的Q带，在820nm处出现π*→π*带．质子化产生的P31正离子自由基与基态分子通过SOMO-HOMO作用形成面对面二聚体，在470～515nm处出现二聚体的Q带吸收，在710nm出现π→π带．与单体Q带相比这些Q带发生蓝移．     

TiO2纳米粒子的光催化活性与光伏响应特性研究

TiO2纳米粒子由于其具有良好的化学稳定性、耐光腐蚀性、宽带隙能和大的比表面积等特点而被广泛地应用到光催化降解有机污染物^[1,2]和光催化储能等方面。由于研究手段和研究方法的限制,详细了解催化剂表面光生电荷行为、光谱谱带与催化活性的关系比较困难,而这些关系将为制备高催化活性的光催化剂提供理论基础,由于光催化活性的高低与催化剂的表面性质直接相关,表面光电压谱（SPS）是研究固体材料表面物性和界面间电荷转移过程的有利手段^[3],其为控制光催化机理提供了新的手段。本文利用表面光电压谱方法对系纳米TiO2光催化剂进行了光伏响应测试,发现TiO2的晶型、粒径及表面吸附物对其光催化活性有很大影响。不同性质的表面吸附物可使催化剂表面呈现不同的导电特性,而使其光催化活性不同。利用能带理论和场效应原理对此进行了 合理的解释。