Radiative and ultrafast non-radiative electronic relaxation in individual and assembled noble metallic nanoparticles of different shapes

技术综述：从El-Sayed小组和其他研究人员在等离子体纳米粒子领域的先前研究中可以清楚地看出，金和银纳米粒子的表面等离子体领域提供了许多新的和令人兴奋的方向。该领域的大量研究，特别是Schatz和Van Duyne小组的研究表明，这些领域如何依赖于纳米颗粒的大小和形状。人们还知道，纳米粒子之间的电场可以比单个纳米粒子的磁场强得多。金或银纳米粒子对的重叠场与它们的形状、大小、取向和分离的关系并没有得到同样的关注。位于佐治亚州理工学院微电子研究中心内的电子束光刻设施将被用来促进这些研究。纳米管、纳米棒、纳米立方体、纳米环和额外的纳米颗粒形状将通过自上而下的方法制备，并研究它们的尺寸、取向和颗粒间分离的函数。使用以前在El-Sayed群中已经很好地建立的DDA方法，将计算所有这些构型的消光、吸收和散射产额以及表面场强度。此外，还将研究针对不同构型计算的等离子体激元强度与纳米粒子对的各种光谱性质(吸收和散射)之间的相关性。还将研究与附近电子系统(分子和半导体)的光谱性质增强相关的等离子激元效应，如超热电子的吸收、荧光、非辐射弛豫和表面增强拉曼散射。根据观察到的表面等离子体共振对粒子间分离的依赖关系，将研究不同尺寸和形状的纳米粒子在不同距离范围内的生物和大分子间分离中的应用。观察到的定量SERS或荧光猝灭和增强也可以用于传感和诊断应用。非技术摘要：由等离子体纳米粒子对组成的纳米结构具有有趣的光学性质，因为纳米粒子之间存在非常强的近场耦合。这些特性已经开始影响许多领域，如用于增强传感器应用的场增强光谱学和等离子体共振传感，用于改进成像设备的纳米结构光学探针，以及用于能量传输应用的纳米光子波导和设备。对金属纳米粒子组装中等离子体共振耦合的基础研究将有助于表征和优化等离子体纳米结构的潜在应用。在拟议的支助期内，一项重要贡献将是通过与佐治亚理工学院微电子研究中心建立伙伴关系，维持在上一个支助期内建立的现有跨学科关系。作为国家纳米技术基础设施网络(NNIN)的成员，mIRC在促进跨学科伙伴关系方面发挥了重要作用。通过与信息和通信技术研究中心的合作并使用其中最先进的设备，建立了一个综合了科学基础和工程优化的多才多艺的研究人员网络，这导致了一些跨学科的出版物和会议发言。拟议的研究将对培训研究生和本科生以及纳米技术广泛领域的博士后研究人员产生教育影响，包括纳米制造、胶体化学、光学光谱学和电动力学。此外，El-Sayed小组一直吸引和接受聪明的NNIN和REU暑期本科生，他们在研究实验室环境中获得非凡经验的同时，为这项研究做出贡献。已经建立的伙伴关系将改善佐治亚理工学院为学生提供的令人印象深刻的教育和培训传统，为他们在学术界和工业界的纳米技术领域的职业生涯做好准备。

TECHNICAL SUMMARY:From previous studies of the El-Sayed group and other researchers in the plasmonic nanoparticle field, it is clear that the surface plasmon fields of gold and silver nanoparticles offer many new and exciting directions. A large volume of the studies in the field, especially those by the Schatz and Van Duyne groups, have shown how these fields depend on the nanoparticle size and shape. It is further known that the field between nanoparticles can be much stronger than the fields of individual nanoparticles. The dependence of the overlapping fields of pairs of gold or silver nanoparticles on their shape, size, orientation, and separation has not been given the same attention. The electron beam lithography facilities located within the Georgia Institute of Technology Microelectronics Research Center will be utilized to further these studies. Nanoprisms, nanorods, nanocubes, nanorings, and additional nanoparticle shapes will be fabricated by top down methods and studied as a function of their size, orientation, and interparticle separation. Using DDA methods, which have been previously well established in the El-Sayed group, extinction, absorption, and scattering yields as well as the surface field intensities will be calculated for all such configurations. Also, the correlation between the plasmonic field strength calculated for different configurations and the various spectroscopic properties of nanoparticle pairs (absorption and scattering) will also be studied. Plasmonic field effects associated with enhanced spectroscopic properties of nearby electronic systems (molecule and semiconductors) such as the absorption, fluorescence, non-radiative relaxation of hot electrons, and surface enhanced Raman scattering will also be investigated. From the observed dependence of the surface plasmon resonance on interparticle separation, nanoparticles of different sizes and shapes will be studied for nanoruler applications of different distance ranges for biological and macromolecular intersite separations. The observed quantitative SERS or fluorescence quenching and enhancement could also be used for sensing and diagnostic applications.NON-TECHNICAL SUMMARY:Nanostructures consisting of plasmonic nanoparticle pairs have interesting optical properties because of the very strong near-field coupling between the nanoparticles. These properties have already begun to impact a number of fields such as field-enhanced spectroscopy and plasmon resonance sensing for enhanced sensor applications, nanostructured optical probes for improved imaging devices, and nanophotonic waveguides and devices for applications in energy transport. Fundamental studies of the plasmon resonance coupling in metal nanoparticle assemblies will help characterize and optimize plasmonic nanostructures for potential applications. An important contribution during the proposed support period will be in maintaining the current cross-disciplinary relationships that have been established during the previous support period through partnerships with the Microelectronics Research Center (MiRC) at Georgia Tech. As a member of the National Nanotechnology Infrastructure Network (NNIN) the MiRC has been instrumental in catalyzing inter-disciplinary partnerships. Through collaboration with the MiRC and use of state-of-the-art equipment located therein, a versatile network of researchers has been developed that integrates scientific fundamentals and engineering optimization, which have led to several inter-discipline publications and conference presentations. There will be an educational impact of the proposed research on training of graduate and undergraduate students as well as postdoctoral researchers in the broad range of areas of nanotechnology including nanofabrication, colloidal chemistry, optical spectroscopy, and electrodynamics. In addition, the El-Sayed group has always attracted and accepted intelligent NNIN and REU summer undergraduate students to who contribute to this research while receiving exceptional experience in a research laboratory environment. The partnerships that have been established will improve upon the impressive tradition of education and training that Georgia Tech has provided to students to prepare them for careers in the field of nanotechnology, in both academia and industry.