Engineering Noble-Metal Nanoparticles for Sensing and Imaging with Surface-Enhanced Raman Scattering

This research investigated the surface-enhanced Raman scattering: SERS) from Ag and Au nanoparticles with an aim to better understand the SERS mechanism and to implement this technique for single-molecule detection and imaging. In addition, SERS was used as a sensitive probe to study molecules confined to a nanoparticle\u27s surface. The first part of this work focused on measuring the SERS from different Ag and Au nanoparticles and determining how their structural and physical properties affect SERS. The effects of shape, size, and Au-Ag composition on SERS are determined using Ag nanocubes, Ag nanospheres, and Au-based nanocages. I also demonstrate several techniques used to study the SERS of single nanoparticles, one at a time, which has provided significant insight into the SERS effect. I then discuss the development of a new and simple way to create large SERS enhancements by taking advantage of the supporting substrate of a nanoparticle. In this technique, simply depositing a single Ag nanocube on a metal substrate can increase its SERS enhancements to levels capable of single-molecule detection. In the second part of this work I used SERS as a molecular probe to understand how glucose molecules interact at a nanocube\u27s surface, and as an optical thermometer to quantify the temperature change at the surface of a Au-based nanocage during the photothermal effect. The nanoparticles were coated with highly ordered self-assembled monolayers: SAMs), and then SERS was used to determine the structural and conformational changes in the SAMs as a result of perturbations from the environment. This allowed me to use SERS to directly probe the molecules on the nanoparticle\u27s surface. In the final part of this work, I used nanocubes and nanospheres in SERS imaging. The resolution, sensitivity, and penetration depth are determined for our Raman microprobe system. In addition, phantoms are used to generate SERS images of three-dimensional microstructures