Gold Nanoparticles and Quantum Dots: Their Optical Interaction and Application in A Hydrogel Modified Lateral Flow Sensing Device

The goal of this dissertation was to study the optical properties of gold nanoparticles (Au NP) and quantum dots (QD) and to use their unique properties in sensing applications. The first part of this dissertation focuses on studying the dipole coupling in a gold nanoparticle random array. A blue shift and narrowing of the extinction peak, when compared to the single particle and solution spectra, was observed when 120 nm Au NPs were randomly immobilized on a glass substrate. This was determined to be due to the long-range dipole coupling of the Au NPs in the array. The motivation behind the second project was to study the temperature dependent change in decay kinetics of aqueous phase quantum dots when in close proximity to 120 nm Au NP, using α-carboxy-ω-Thiol terminated Poly(N-isopropyl acrylamide) (PNIPAM) as a spacer. The structure of PNIPAM will expand or collapse based with a change in temperature, thus varying the interparticle distance between the QD and the Au NP. The temperature dependent decay kinetics of the system is studied by taking the fluorescence lifetime decay of the QD – PNIPAM – Au NP nanocomplex at different temperatures. The purpose of the third and final project was to develop of a novel lateral flow assay platform. In this work, Au NPs and QDs are captured by modifying the nitrocellulose membrane with a polymer hydrogel instead of using pre-printed biological probes. This unique modification of current lateral flow strips provides an alternate method of capturing the nanoparticle probes and introduces many possibilities to enhance the design of conventional lateral flow devices.