Creating and Probing Optical and Material Nonlinearities in Single Nanoparticles, Dimers, Clusters and Arrays

芝加哥大学的Norbert Scherer由实验物理化学计划支持，对单个金属纳米颗粒材料进行最终结构功能(即非线性光学响应)测量的综合计划。这些材料是单一的银和金纳米球和纳米棒，以及在惰性表面自发形成的二聚体和它们的簇，允许进行透射电子显微镜和光学测量。将创建和研究扩展的一维和二维材料。研究目的如下：(1)提高已经发展到~10 nm的光学-空间相关方法的空间分辨率，以允许确定来自纳米粒子二聚体、簇和阵列的非线性信号的来源，(2)实现一系列非线性光学测量(例如倍频和双光子荧光干涉测量、三阶非线性散射干涉测量和SERS)，用于与来自单个纳米粒子特征的线性散射进行比较，以量化所产生的多粒子共振的局部场增强和动力学，(3)探索光子与一个或两个纳米粒子和一个光学陷阱之间的多体(或多点)相互作用，建立由俘获场产生的粒子之间的作用力以及作为非线性增强的单个光子与多个粒子的多点相互作用，以及(4)将前三个项目扩展到研究自组装的紧密堆积的纳米晶体单层阵列和由驻波光学陷阱产生的有序纳米棒阵列中的等离子体激元耦合和离域。这项研究的总体目标是提高对基于等离子体激元的光学和材料非线性的理解，并最终允许对其进行控制。该项目的长期动机是由纳米级光学器件的愿景所激发的。将实现的基础科学最终可能导致开发出更好的光学传感器和可调谐的反射镜。这项研究还可能导致开发用于在纳米尺度上研究生物结构和局部化学成分的探针。

Norbert Scherer of the University of Chicago is supported by the Experimental Physical Chemistry Program to carry out a comprehensive plan of definitive structure-function (i.e. nonlinear optical response) measurements of individual metal nanoparticle-based materials. These materials are single silver and gold nanospheres and nanorods and spontaneously formed dimers and clusters thereof on inert surfaces that allow TEM and optical measurement. Extended one and two-dimensional materials will be created and studied. Research aims are the following: (1) to improve the spatial resolution of the optical-spatial correlation method that has been developed to ~10 nm to allow determination of the origin of the nonlinear signals from nanoparticle dimers, clusters, and arrays, (2) to implement a range of nonlinear optical measurements (e.g. SHG and 2-photon fluorescence interferometry, third-order nonlinear scattering interferometry, and SERS) for comparison with linear scattering from single nanoparticle features to quantify the local field enhancements and dynamics of the multi-particle resonances created, (3) to explore the multi-body (or multi-point) interactions among photons and one or two nanoparticles and an optical trap, to establish the force between the particles resulting from the trapping field as well as the multi-point interaction of single photons with multiple particles observed as a nonlinear enhancement ,and (4) to extend the first three projects to the study of plasmon coupling and delocalization in self-assembled close-packed monolayer arrays of nanocrystals and in ordered nanorod arrays created by standing wave optical trapping. The overall goal of this research is to improve understanding of and ultimately allow control of plasmon-based optical and material nonlinearities.The longer-range motivations of this project are stimulated by the vision of nanoscale optical devices. The fundamental science that will be achieved could ultimately lead to the development of better optical sensors and reflective mirrors that are tunable. This research could lead as well to the development of probes for investigating biological structures and local chemical composition on the nano-scale.