| The overarching theme of this work is to understand how the localized surface plasmon resonance (LSPR) of metallic nanoparticles can be utilized for sensing applications. The work presented here describes the use of both nanoparticle arrays and single nanoparticles. Specifically, nanoparticle arrays demonstrate sensing capabilities for inhibin A, prostate specific antigen (PSA), gas and vapors, and the dye, Nile Red. A new wide-field imaging apparatus is developed to characterize multiple single nanoparticles simultaneously as well as correlate the nanoparticle structural details using transmission electron microscopy (TEM), ultimately to develop single nanoparticle sensors. From these studies, LSPR spectroscopy is shown to be a valuable tool for sensor development.;In the studies utilizing nanoparticle arrays, LSPR spectroscopy proves to be a feasible technique to detect inhibin A and PSA using a sandwich assay format. However, binding constants are determined to be several orders of magnitude lower than expected for PSA. It is hypothesized that the method to immobilize the capture antibody affected the affinity for PSA. Using a high resolution LSPR spectrometer, gas and vapor sensing on the basis of small refractive index (RI) changes is demonstrated. Nile Red is used to investigate the interaction between the polarity-dependent dye absorbance and the RI dependent LSPR of Ag nanoparticles.;A wide-field LSPR imaging method using a liquid crystal tunable filter is used to measure the scattering spectra of multiple Ag nanoparticles in parallel and the RI response of multiple single nanoparticles is determined. This method also provides the ability to characterize moving Ag nanoparticles by measuring the scattering spectra of the particles while simultaneously tracking their motion. Consequently, single particle diffusion coefficients are determined. As an example, several single Ag nanoprisms are tracked, the LSPR scattering spectrum of each moving particle is obtained, and the single particle diffusion coefficient is determined from its trajectory. Coupling diffusion information with spectral information in real time is a significant advance and addresses many scientific problems, fundamental and biological. |
