Studies of Single Nanoparticle Systems by Localized Surface Plasmon Resonance Spectroscopy, Atomic Force Microscopy, Transmission Electron Microscopy, and Combinations Thereof

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The work presented here describes investigations into the optical properties of single silver nanoparticles. The contents of this thesis are divided into two parts: (1) single nanoparticle localized surface plasmon resonance (LSPR) spectroscopy and sensing and (2) approaches to combining LSPR spectroscopy with atomic force and transmission electron microscopies. Part I addresses the LSPR properties of two specific nanoparticle geometries: triangular nanoprisms and nanocubes. It was shown that the LSPR spectra for ensembles of these structures are inhomogenously broadened, and that the LSPR spectra of single nanoparticles are highly sensitive to details of their geometries. These geometric details play an important role in determining the utility of a nanoparticle as an environmental sensor. It was demonstrated that nanoprisms have a 1 nm per alkyl unit greater sensitivity to the binding of molecular adsorbates than truncated tetrahedral arrays despite being five times thinner, suggesting they will be excellent candidates for sensing large biomolecules. It was further shown, for the case of the nanocubes, that the energy of LSPR modes are not simply sensitive to their environments, but that the environment can actually affect the number of modes observed in a nanoparticle's LSPR spectrum. For the nanocube it was shown that this leads to two peaks: a narrow high energy peak and a broader low energy peak. A figure of merit has been defined for single nanoparticle sensors and nanocubes' high energy peaks were shown to have the highest value FOM measured to date. Part II addresses the ambiguity that persists in standard single nanoparticle LSPR studies due to the fact that no structural information is available to enlighten interpretations of nanoparticle spectra. This was done by correlating the LSPR spectra with atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements.

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  • 07/30/2018
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