基于表面等离激元催化反应现场构建分子结及谱学研究

The construction of the molecular device model and the development of characterization technique with high sensitivity have attracted considerable attention in the field of molecular electronic device. This project will attempt to develop the advantages of metal-molecule-metal and the surface enhanced Raman spectroscopy (SERS). By establishing the platform combined with the SERS detection and the molecular electronic measurements under the mechanically controllable break junction (MCBJ) control, the in situ construction and characterization of molecular junction will be investigated based on the plasmon induced catalysis as well as the exploration of the reaction mechanisms. The metal gap distance will be controlled by MCBJ technique for the formation of molecular through the link of the molecule produced by the plasmon catalyzed coupling reaction of two molecules attached the two sides of the metal gap. By controlling the amounts of molecule located in the gap, the conductance will be measured and made a statistics to obtain the single molecular conductance and the dynamics of single molecular catalysis reaction. By assisted with the huge ―hot spot effect in the metal gap, SERS was employed to investigate the molecular structure, reaction dynamics in the metal gap. The electric measurements will be associated with the in situ SERS detection. It will be beneficial to provide the experimental basis for the development of novel method in the construction of molecular junction based on plasmon induced catalysis, and SERS will be considered as one of powerful tolls for charactering the nature of the molecular junction. Finally, SERS combined with the molecular junction will be developed as a tool for exploring the mechanisms of plasmon induced catalysis with high spatial resolution and sensitivity.

分子器件模型构建及高灵敏度表征技术一直是分子电子学的研究热点。本项目结合分子电子学中金属-分子-金属模型异质结的优势以及SERS 光谱高灵敏度的特点， 通过构建基于机械可控裂结(MCBJ)技术的分子电子学测试以及SERS 检测的联用平台，开展基于等离激元催化偶联反应现场构筑分子结及等离激元诱导催化反应机理的研究。利用MCBJ 技术调控纳米金属间隙并采用等离激元诱导催化反应偶合两端分子形成分子结，开展电导的动态测量和统计，实现间隙内少数分子催化偶联反应过程的研究；借助间隙巨大的"热点"效应，采用SERS 光谱研究分子结内分子的微观结构，反应动力学等信息，并关联电学测量与SERS 测量结果，解析表面等离激元诱导催化反应机理，发展基于表面等离激元催化反应的现场构筑分子结的新方法，拓展SERS 技术成为分子电子学的高灵敏度表征工具。

本项目主要开展了金属-分子-金属（半导体）分子结的构筑、表征以及限域内电化学及等离激元催化反应机理的研究，深入探索了金属或金属-半导体纳米材料间隙内的 SERS 增强效应及限域内表面等离激元催化反应的性能。发展了通过有机偶联反应现场合成技术构筑了具有聚合物包裹层的金属-分子-金属分子结的新方法，通过SERS定位技术获得单个金属-分子-金属分子结的SERS光谱以及限域内少数分子的催化反应行为，表明限域内具备巨大的SERS增强效应及较常规粒子更强的SPR催化性能。修饰金纳米粒子单层膜构筑了金属-分子-金属分子结的二维阵列，利用动态技术调控了金纳米粒子间距，考察了纳米间隙限域内分子化学反应与间隙宽度及激发光之间的关系，优化和提升了限域内催化反应活性。通过引入半导体材料，构筑金属-分子-半导体（ZnO或TiO2）分子结，通过SPR及电化学调控，获得了Au/ZnO界面上增强的SPR反应，引入TiO2纳米粒子实现了电化学控制下SPR催化吡啶生成联吡啶的C-C偶联反应。发展了电化学-SPR联合催化有机物在金属纳米限域内的脱羧基和脱羟基反应，测定了不同电位和激光功率下的脱羧反应动力学参数，考察了同分异构体的脱羟基行为及效率与电化学和SPR的关系，为研究电场调控下限域内分子反应提供了新思路。构筑了单晶Au基底-分子-单晶Au片的分子结，通过调控外源纳米粒子SERS效应研究限域内分子的结构，为将分子结接入宏观电路测量电学行为提供了实验基础。通过以上研究发展了多种构筑异质分子结的新技术，更深入探索了纳米限域内SERS的复杂增强机理，关联分子结限域内的化学反应与分子结材料及外场效应（电学及光学效应）的关系，为限域化学反应的研究提供了简捷的研究模型，有望将SERS技术发展成为高度限域痕量化学反应以及金属异质分子结结构的高灵敏度研究工具。项目执行期间发表有标注的期刊论文24 篇；授权专利4件；应邀在国际学术会议上作邀请报告4 次，国内会议邀请报告4次，已毕业培养博士生2 名，硕士研究生12名。