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

该更新项目的主要重点是由固态和材料化学计划支持，旨在阐明等离子体场对重要的光化学和光物理系统（例如聚合物，掺杂和未掺杂的金属氧化物和蛋白质细菌视紫红质）的动力学的影响。 掺杂TiO 2最近在科学界引起了广泛关注，因为等离子体银和金纳米颗粒的使用极大地增强了材料的光催化和光电化学效率。细菌视紫红质是仅有的两种天然存在的光合系统之一，除了其重要的化学和生物学性质外，还被认为可用于太阳能转换和电子学。在所有这些材料中，强等离子体增强的局部电场对其基本动力学光诱导过程的影响知之甚少。 动力学可能涉及未知的激发态和中间体以及改变的动力学速率。将确定对太阳能和太阳能转换应用最重要的基本过程，并将使用胶体化学来合成新的贵金属纳米结构，选择性地增强物理事件的概率和/或动力学。该计划将建立在El-Sayed小组在等离子体、金属和半导体纳米结构、光谱学、催化、光化学和光生物学领域的广泛成就的基础上。非技术摘要拟议的工作旨在确定在基本水平上等离子体纳米颗粒和可用于太阳能和太阳能转换的材料之间的相互作用，从而可以阐明负责等离子体增强性能的机制。成功将为化学家，物理学家，材料科学家和工程师提供如何最好地将贵金属纳米颗粒纳入设备和催化系统的知识。所获得的知识将为胶体化学领域的科学家提供新的合成策略以及如何优化纳米颗粒的形状，尺寸，结构，组成和颗粒间排列以用于特定应用。学生、博士后研究员和初级科学家将获得化学、光谱学和纳米技术方面的宝贵多学科经验，为学术界或工业界的职业生涯做准备。金和银纳米结构引起的电场增强已经彻底改变了整个领域，如拉曼光谱学。虽然贵金属的成本非常高，但表面增强拉曼散射中的许多数量级的增强表明，在优化的系统中可能仅需要极少量的材料。充分利用等离子体效应，同时最大限度地降低成本，需要详细了解耦合到等离子体场的材料的静态和动态特性，以及可扩展的化学合成，避免昂贵和耗时的技术，如电子束光刻。这一奋进的成功将有助于更好地利用阳光作为能源，并减少生产重要工业产品（如氢气）所消耗的能源。由此产生的技术和经济增长虽然减缓了向环境中排放污染物和温室气体的速度，但将对全世界产生重大影响。

TECHNICAL SUMMARYThe main focus of this renewal project, supported by the Solid State and Materials Chemistry program, is to elucidate the effects of plasmonic fields on the dynamics of important photochemical and photophysical systems (e.g. polymers, doped and undoped metal oxides, and the protein bacteriorhodopsin). Doped TiO2 has attracted much recent attention in the scientific community because the use of plasmonic silver and gold nanoparticles has greatly enhanced the material's photocatalytic and photoelectrochemical efficiency. Bacteriorhodopsin is one of only two naturally-occurring photosynthetic systems and, in addition to its important chemical and biological properties, has been considered for applications in solar-energy conversion and electronics. In all of these materials there is little known about the effects of strong plasmon-enhanced local electric fields on their fundamental dynamical light-induced processes. The dynamics may involve unknown excited states and intermediates and altered kinetic rates. Fundamental processes most important to applications in photocatalysis and solar-energy conversion will be identified and colloidal chemistry will be used to synthesize new noble-metal nanostructures that selectively enhance the probabilities and/or dynamics of photophysical events. This program will build upon the El-Sayed group's extensive accomplishments in the areas of plasmonics, metal and semiconductor nanostructures, spectroscopy, catalysis, photochemistry, and photobiology.NON TECHNICAL SUMMARYThe proposed work seeks to determine at a fundamental level the interactions between plasmonic nanoparticles and materials that can be applied for photocatalysis and solar-energy conversion, so that the mechanisms responsible for plasmon-enhanced performance may be elucidated. Success will provide chemists, physicists, materials scientists, and engineers with knowledge on how best to incorporate noble-metal nanoparticles into devices and catalytic systems. The knowledge obtained will inform scientists in the field of colloidal chemistry on new synthesis strategies and how to optimize nanoparticle shape, size, structure, composition, and interparticle arrangement for particular applications. Students, postdoctoral fellows, and junior scientists will gain valuable multidisciplinary experience in chemistry, spectroscopy, and nanotechnology in preparation for careers in academia or industry.The electric field enhancement caused by gold and silver nanostructures has revolutionized entire fields such as Raman spectroscopy. Although the cost of noble metals is very high, the many orders-of-magnitude enhancement in surface-enhanced Raman scattering suggests that only extremely small amounts of material may be needed in optimized systems. Taking full advantage of plasmonic effects while minimizing cost requires a detailed understanding of the static and dynamical properties of materials coupled to plasmonic fields, as well as scalable chemical syntheses that avoid expensive and time-consuming techniques such as electron beam lithography. Success in this endeavor will help to better utilize sunlight as an energy source and reduce the energy consumed to produce important industrial products such as H2. The resulting technological and economic growth, while slowing the rate of releasing pollutants and greenhouse gases into the environment, will have a significant worldwide impact.