| Gold nanoparticles have unique optical properties due to localized surface plasmon resonance. This phenomenon results from the collective oscillation of conduction electrons of metals with the incident light and is exhibited as strong absorption bands in the visible regions of the electromagnetic spectrum. Due to these unique optical properties, gold nanoparticles have been exploited in a variety of applications such as a colorimetric detection of DNA hybridization, biomolecular interaction assays, enhancement of fluorescence and Raman scattering, and chemical and/or biological sensors.; In the first part of the thesis, a colorimetric sensor was developed using gold nanospheres through a series of surface modification processes, in which a hybrid material was synthesized by incorporating gold nanoparticles with the biopolymer dextran. The interaction of this material with model proteins was examined to confirm specific molecular recognition. This material provided a simple and convenient colorimetric method for biospecific interaction analysis. Furthermore, they facilitated larger-than-monolayer coverage of nanoparticles as well as maintained surface mobility when grafted on a planar surface such that they retained the capability to aggregate and redisperse.; In the second part of the thesis, surface modification of rod-shaped gold nanoparticles was systematically investigated; particularly, the adsorption and displacement of the cationic surfactant, cetyltrimethylammonium bromide (CTAB) on model crystalline gold surfaces representing crystal facets on gold nanorods were studied. Adsorption of CTAB from aqueous media onto gold surfaces of different crystal orientations was studied by water contact angle measurements, and FT-IR spectroscopy. Displacement of adsorbed CTAB molecules with 16-mercaptohexadecanoic acid (MHDA) from planar gold surfaces was performed using various incubation times with MHDA. The displacement reaction was also studied by water contact angle measurements, and FT-IR spectroscopy. The displacement of CTAB with MHDA on gold is evident in the decreased water contact angle upon formation of carboxyl terminated surfaces. FT-IR spectra also show differences indicative of the displacement reactions. |
