| My thesis work is focused on the application of spatially resolved microscopy and spectroscopy techniques to a variety of interesting organic and metallic systems. Single molecule spectroscopy (SMS) was first used to study the fluorescence properties of single DiIC12 molecules imbedded in polymer matrices. A statistical distribution of single molecule fluorescence spectra were acquired from poly(methyl methacrylate), poly(ethylene oxide), and polystyrene, analyzed using “center of mass” and “r.m.s. width” calculations, and compiled into distributions. The distributions reveal the presence of two classes of deviations in the fluorescence spectra. Class I deviations are characterized by narrow, well-resolved spectra with high-intensity (0–0) transitions and class II deviations have broad, washed-out vibronic structure with increased contributions from (0–1) and (0–2) transitions. PMMA has a large population of class I deviations while PEO contains a large population of class II deviations. We attribute class I deviations in PMMA to a rigid environment and class II deviations in PEO to a fluid environment.; We also apply SMS to a more complex luminescent system, the conjugated polymer MEH-PPV. Using fluorescence imaging, static and dynamic polarization modulation, and fluorescence spectroscopy, we characterize the solvent-dependent photophysical properties of single MEH-PPV chains. Chains cast from chloroform solvents exhibit clumpy fluorescence features, moderate polarization anisotropy, ensemble-like intensity trajectories, and broad fluorescence spectra. Chains cast from toluene are characterized by uniform fluorescence features, strong polarization anisotropy, discrete intensity fluctuations, and well-resolved vibronic structure. We attribute these phenomena to an open, extended chain conformation for MEH-PPV cast from chloroform and a compact, cylindrical structure for chains cast from toluene.; Nanosphere lithography was used to prepare tailored silver nanostructures for use as surface-enhanced Raman scattering (SERS) substrates. Due to the control over the nanocluster morphology and intercluster separation, these substrates are excellent candidates to replace current SERS substrates, where regions of high electromagnetic fields are randomly dispersed throughout the substrate. SERS spectra of rhodamine 6G adsorbed onto these nanoclusters show order of magnitude signal increases in comparison with amorphous metal films prepared under identical deposition conditions. We attribute these enhancements to increased fields at the sharp corners of these triangular nanoclusters. |
