光阱中的胶体化学研究

To date, the research of colloidal chemistry is mostly focused on ensemble samples in solutions, which is suffered from many limitations. In-depth understanding of the mechanism asks for systematic studies on the basis of single particles. The concept of "Lab on a chip" is advanced recently and featured by many important characteristics, such as nanoscale, easy manipulation, selectivity, in-situ measurement, multifunctionality, and integration. In order to meet these requirements, we propose to develop an approach to colloidal chemistry study using the optical trap. Metal nanostructures, when trapped, is located at the center of the Gaussian beam with high power densities, which not only favors the study of the light-induced chemical reactions, but dramatically accelerates chemistry processes in the trap by elevating the temperature of the nanostructures through exciting their localized surface plasmon modes. The elevated temperature will also come up with many new phenomena that worth further investigating. Main topics in this project include oxidation and growth of gold nanostructures in the optical trap; coating of nanostructures and formation of core-shell structures in the optical trap; light-guided chemistry reactions; theoretical study on mechanics, thermal dynamics, and optics in the optical trap. Knowledge gained in the study will be of great significance not only in the synthesis of nanostructures but also in the development of functional materials and devices.

目前现有胶体化学的研究对象一般为集合溶液样品，实验研究受到诸多限制。深入的机理研究往往要求在单个纳米结构基础上进行的系统研究。纳米尺度，可操控性，可选择性，原位实时检测，多功能，集成化，即"芯片实验室"（Lab on a chip）是将来化学实验的发展趋势。为满足这方面的需求，我们提出基于光阱的胶体化学实验方法。光阱俘获的金属纳米结构，自然地处于其高斯光束的局域强光场中，不仅可以进行光致化学变化的研究，还可以结合其表面等离子共振热效应，得到远高于外界的反应温度，加速光阱中的化学过程，从而对胶体化学的一些新现象进行研究。本项目主要开展的研究方向包括：光阱中金纳米结构的氧化和生长；光阱中纳米结构的包覆及核壳结构的形成；光导向的胶体化学反应；光阱中力学、热学、光学的理论计算。研究成果对于纳米结构的合成及制备具有指导作用，对于纳米功能材料和器件的研制具有重要意义。

目前现有胶体化学的研究对象一般为集合溶液样品，实验研究受到诸多限制。深入的机理研究往往要求在单个纳米结构基础上进行的系统研究。纳米尺度，可操控性，可选择性，原位实时检测，多功能，集成化，即"芯片实验室"（Lab on a chip）是将来化学实验的发展趋势。为满足这方面的需求，本项目系统性的研究了金纳米棒的典型胶体化学反应过程和机理，开展了基于光阱的胶体化学过程光学检测方法的研究。具体包括金纳米棒的氧化机理，金-氧化物核壳结构的胶体化学合成机理，以及利用光阱的胶体化学过程光学检测方法实时观测金纳米棒自组装和包覆银壳层的反应动力学过程。实验观测银壳层的增强贡献可达5倍之多，结合电磁理论给出的不到2倍的值，实验确证了化学增强的机理。研究成果对于纳米结构的合成及制备具有指导作用，对于纳米功能材料和器件的研制具有重要意义。