Ag纳米粒子在TiO2四棱柱阵列上的可控生长及其SERS效应

采用水热法在导电玻璃FTO导电面上沉积TiO₂四棱柱阵列; 并以其为基体, 分别采用聚乙烯基吡咯 烷酮(PVP)还原Tollens试剂以及柠檬酸三钠(TSC)还原硝酸银溶液, 将Ag纳米粒子(AgNPs)沉积在TiO₂四棱柱阵列上形成TiO₂@AgNPs-PVP和TiO₂@AgNPs-TSC微纳结构作为表面增强拉曼散射(SERS)基底. 实验结果表明, Ag纳米粒子在TiO₂四棱柱阵列上的尺寸和分布可通过改变Tollens试剂的浓度和TSC还原硝酸银溶液的反应时间来调控, 进而优化基底的SERS灵敏度. TiO₂@AgNPs-PVP微纳结构对罗丹明6G(R6G)的检出限为10^-12 mol/L, 对低活性小分子三聚氰胺的检出限为0.01 mg/mL; TiO₂@AgNPs-TSC微纳结构对R6G的检出限为10^-10 mol/L, 对三聚氰胺的检出限为0.01 mg/mL. TiO₂@AgNPs-PVP和TiO₂@AgNPs-TSC微纳结构基底的SERS活性、 循环可回收性与还原剂种类紧密相关: 包覆在Ag纳米粒子上的PVP可以作为隔离层避免Ag纳米粒子直接接触, 防止电磁场耦合作用减弱, 增强基底的SERS活性; 同时, PVP是一种水性聚合物, 有较强的亲水性, 作为循环可回收SERS基底使用时, 吸附小分子物质清洗难度较大.

Controllable Growth of Silver Nanoparticles on TiO2 Tetragonal Prism Nanarrays and Its SERS Effect

The TiO₂ tetragonal prism array structure was deposited on the conductive surface of the conductive glass FTO by hydrothermal method. The silver nanoparticles（AgNPs） grew on the TiO₂ tetragonal prism by polyvinylpyrrolidone（PVP） reduced Tollens reagent to form TiO₂@AgNPs-PVP micro-nano structure， while the silver nanoparticles grew on the TiO₂ tetragonal prismby trisodium citrate（TSC） reduced silver nitrate to form TiO₂@AgNPs-TSC micro-nano structure. The as-prepared micro-nano structures could be used as the substrate for surface enhanced Raman scattering（SERS）. The results showed that the size and distribution of Ag NPs nanoparticles on the TiO₂ tetragonal prism array could be adjusted by the concentration of Tollens reagent and the reaction time of TSC to optimize the SERS substrate. The detection limits of the optimized TiO₂@AgNPs-PVP substrate for rhodamine 6G（R6G） and melamine are 10^-12 mol/L and 0.01 mg/mL， respectively. The optimized TiO₂@AgNPs-TSC micro-nano structure for R6G and melamine are 10^-10 mol/L and 0.01 mg/mL， respectively. In addition， the SERS activity and recyclability of TiO₂@AgNPs-PVP and TiO₂@AgNPs-TSC substrates were closely related to the types of reducing agents： the PVP coated on Ag nanoparticles could be used as an isolation layer to avoid direct contact with nanoparticles， which could prevent the quenching of electromagnetic field coupling to enhance the SERS activity of the substrate. However， the adsorbed small molecules（such as R6G） could not be cleaned when the TiO₂@AgNPs-PVP was used as a recyclable SERS substrate. It was attributed to the fact that the PVP was a water-based polymer with strong hydrophilicity.