【作者】 王明华；

【导师】 李则林；

【作者基本信息】 浙江师范大学 ， 物理化学， 2010， 硕士

【摘要】 金、钯等贵金属纳米粒子及其组装膜在光学、电子、磁学、催化等方面有着广泛的应用。近年来,贵金属纳米粒子的制备和在气-液、液-液两相界面上的组装倍受关注,各种方法层出不穷。因此发展界面组装新方法,制备二维和三维贵金属纳米粒子功能薄膜,具有重要意义。本文利用过量亚锡既作还原剂又作保护剂,分别制备了稳定的Au溶胶和Pd溶胶,并在气-液界面上得到了Au、Pd纳米粒子的自组装膜,研究了其成膜机理,考察了组装膜的表面增强拉曼散射效应和／或电催化活性。主要内容如下：1.酸性介质中,用过量亚锡还原氯金酸,得到以亚锡(SnCl3-形式)为保护剂的稳定金溶胶,该溶胶可在隔绝空气的条件下保存数月之久。但在与空气接触下陈化溶胶,则可在短时间内于气-液界面得到金纳米粒子组装而成的多孔结构超薄膜。拉曼光谱等实验证明,该界面组装过程涉及空气中的氧所导致的配体交换。即空气中的氧气氧化消耗溶液表面层的二价锡(Sn(Ⅱ)),引起溶液表面层的金纳米粒子发生SnCl3-和Cl-之间的配体取代,Cl-取代SnCl3-配体后,溶胶表面层中的金纳米粒子失稳,在气-液界面上自发组装成膜。另外,结合密度泛函理论(DFT)计算,对该配体变换机理进行了解释。2.该金纳米粒子组装薄膜表现出良好的SERS效应和电催化活性。以该组装膜为SERS基底,测定了吡啶、邻菲罗啉、烟酰胺的SERS光谱。另外,该组装膜在碱性溶液中对乙醇、葡萄糖、维生素C的电氧化有较好的催化活性。3.酸性介质中,过量的Sn(Ⅱ)加热还原氯化钯得到稳定的钯溶胶,持续加热陈化一定时间后,可在气-液界面获得Pd纳米粒子的组装膜。其机理可能涉及加热条件下Pd纳米粒子往气-液界面上的扩散与组装。将Pd纳米粒子组装成的超薄膜修饰在玻碳电极或光亮Pd电极上在碱性条件下对乙醇和甲酸的电催化氧化表现出较好活性。更多还原

【Abstract】 Nanopartices (NPs) and their assembly films of noble metals like gold and palladium have attracted a great deal of attention due to their broad application in such areas as optics, nanoelectronics, sensing, catalysis, and so forth. In recent years lots of efforts have being made to the preparation of noble metal NPs and their assembly at the interfaces of gas-liquid, liquid-liquid. Therefore it is of great significance to develop new interfacial assembly methods on fabricating two-and three-dimensional functional films of noble metal NPs. In this thesis, we prepared colloidal gold and palladium with excessive divalent tin Sn(Ⅱ) as both reductant and capping agent, made assembly films of the two kinds of NPs at the air-water interface, studied the assembly mechanisms, and showed the applications of the assembled films in surface-enhanced Raman scattering (SERS) and/or electrocatalysis. The main contents are summarized as follows:1. A gold colloid was synthesized by the reduction of AuCl4- with excessive divalent tin Sn(Ⅱ) in an acid medium, which was stable for months under airproof condition by the protection of Sn(Ⅱ)Cl3-. However, ultrathin nanoporous gold films were formed at the air-water interface by aging the colloid for some time under air contact. Experiments including Raman spectroscopy proved that the interfacial assembly process involves the ligand exchange induced by the O2 from the air, namely, the protective Sn(Ⅱ) species (mostly SnCl3-) of the gold colloid could be gradually replaced by Cl-in the solution while the strongly chemically adsorbed Sn(Ⅱ) species on the Au NPs at the superficial layer of the colloid was oxidized by the O2 from the air contact. The Au NPs become unstable and form assembly films at the air-water interface. In addition, density functional theory (DFT) calculations were used to explain the ligand exchange mechanism.2. The ultrathin nanoporous films of Au NPs display excellent SERS effect and good electrocatalytic activity. The SERS spectra of pyridine,1, 10-phenanthroline, nicotinamide etc. can be got easily by using the ultrathin nanoporous films of Au NPs as SERS substrates. And the modified glass carbon electrode by the assembled film of Au NPs shows better electrocatalytic activity toward the electrooxidation of ethanol, glucose, and ascorbic acid in alkaline solution.3. Stable Pd colloids were synthesized by the reduction of PdCl2 using excessive divalent tin Sn(Ⅱ) under heating in an acid medium. The assembled films of Pd NPs at the air-water interface could be obtained by aging the colloid for a while with continuous heating, involving diffusion of Pd NPs from the bulk colloid to the air-water interface with the help of heating. The modified smooth Pd or glassy carbon electrode by the assembled film of Pd NPs display good electrocatalytic activity toward the electrooxidation of ethanol and formic acid in alkaline solution.更多还原