| This work reveals that triangular silver nanoparticles have remarkable optical properties and that the enhanced sensitivity of their nanoenvironment can be used as a new class of optical sensors using localized surface plasmon resonance (LSPR) spectroscopy. The contents of thesis can be divided into two main subject areas: (1) the characterization and optimization of nanoparticles for the basic understanding of their optical properties and (2) the development, testing, and theoretical understanding of model biological assays and nonmodel assays for disease diagnosis. In the first half of this work, an improved understanding of the physical characteristics of noble metal nanoparticles is explored. Specifically, the realization that the sensitivity of these nanoparticles can be optimized for a given adsorbate is revealed. First, it is demonstrated that the short range (viz., 0--3 nm) distance dependence of the electromagnetic fields that surround these nanoparticles can be systematically tuned by changing their composition, size, and structure. Second, multilayer shells are assembled onto surface-confined noble metal nanoparticles to study the long range distance dependence. It is shown that this dependence (viz., 3--35 nm) is non-linear and has a tunable sensing range. Finally, methods to enhance the nanosensor's response based on interactions between the nanoparticle's plasmon resonance and the adsorbate's molecular resonance is revealed. In the remainder sections, we explore the use of these nanoparticles as biological sensors. First, the model system of biotin/streptavidin is confirmed to be highly specific with low nonspecific influences. Next, the demonstration of an immunoassay (biotin/anti-biotin) is performed. Finally, the LSPR nanosensor is shown to be a promising platform for the possible mechanistic understanding of Alzheimer's disease. |
