Radiataive and Ultrafast Non-radiative Electronic Relaxation in Individual and Assembled Noble Metallic Nanopartiacles of Different Shapes

本项目旨在研究单个金纳米点和纳米棒的辐射和非辐射特性以及它们在溶液中的自组装特性。一个方面是测量溶液中以及不同液体和固体介质中的银和铜单个纳米颗粒的性质。第二个是检查具有不同形状的金、银或铜纳米颗粒的自组装形式的性质。将检查这些纳米粒子从溶液中自组装的不同方法。对于单个纳米颗粒，该项目将解决：1）电子-声子和声子-声子弛豫对金属原子质量的依赖性; 2）这些纳米颗粒溶解在其中的介质对电子-声子和声子-声子弛豫的影响;以及3）不同形状纳米颗粒的激光光热转化。由于金属纳米颗粒的紧密接近，它们能够通过等离子体共振电子耦合，与单个颗粒的光学性质相比，又改变了组装结构的光学性质。因此，拟议的研究将探索辐射和超快非辐射弛豫特性作为多粒子结构的粒子类型，大小和形状的函数。这在将金属纳米颗粒结合到固态器件中时非常重要。 通过使用时间分辨飞秒泵浦-探测瞬态光谱和显微镜，将检查单个粒子的组装结构的加热，冷却和结构转变的动力学。单个金属纳米粒子的电子动力学研究对于基础物理学和纳米技术的潜在应用都具有重要意义。了解电子能量转化为晶格声子以及热金属纳米颗粒与周围环境的相互作用对于未来可能的应用非常重要。这些领域对工业界具有高度兴趣，拟议的研究将培养这些学生为国家重大利益的材料科学和工程领域做出贡献。

This project aims to study radiative and nonradiative properties of individual gold nanodots and nanorods and their self-assembly properties from solution. One aspect is to measure properties for silver and copper individual nanoparticles in solution and in different liquid and solid media. The second is to examine the properties of self-assembled forms of either gold, silver, or copper nanoparticles having different shapes. Different methods for self-assembly of these nanoparticles from solution will be examined. For the individual nanoparticles, the project will address: 1) the dependence of electron-phonon and phonon-phonon relaxation on the atomic mass of the metal; 2) the effect of the medium in which these nanoparticles are dissolved on the electron-phonon and phonon-phonon relaxation; and 3) the laser photothermal transformation of nanoparticles of different shapes. Because of the close proximity of the metallic nanoparticles they are able to couple electronically via the plasmon resonance, changing in turn the optical properties of the assembled structures compared to those of the individual particles. Accordingly, the proposed research will explore radiative and ultrafast nonradiative relaxation properties as a function of the particle type, size and shape of the multi-particle structure. This is very important when incorporating metallic nanoparticles into solid-state devices. By using time-resolved femtosecond pump-probe transient spectroscopy and microscopy, the dynamics of heating, cooling and structural transformation will be examined for the assembled structures of the individual particles.%%%The study of the electron dynamics of individual metallic nanoparticles is of great importance to fundamental physics and for their potential use in nanotechnology. Understanding the electron energy conversion into lattice phonons and the interactions of the hot metallic nanoparticles with their surrounding environment is of great importance for possible future applications. These areas are of high interest to industry, and the proposed studies will train these students to contribute to materials science and engineering areas of significant national interest.