Date of Award

2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Specialization

Analytical Chemistry

Department

Chemistry

First Advisor

William B. Euler

Abstract

A three-layer fluorescence sensing platform is described. The sensor consists of an ultra-thin fluorophore layer of Rhodamine 6G (Rh6G) on top of a sub-micron polymer film of polymethyl methacrylate (PMMA) on top of a rigid glass support. Both fluorophore and polymer layers are prepared by spin-coating, a common industrial process for repeatable deposition of thin films of uniform thickness. First, we study the preparation of PMMA films. Using an accepted equation of state, we closely examine spin-coating dynamics and show that casting solution concentration and spin speed process parameters can be used to modulate the final thickness and surface morphology of dry PMMA films. Then, we apply the fluorophore layer. Using absorbance, excitation, and emission spectroscopy, we study the photophysics of Rh6G and demonstrate that interfacial roughness can help enhance fluorescence by disrupting the formation of weakly emissive dimer and aggregate absorbing species. Additionally, light trapping within the dielectric polymer layer can enhance fluorescence by promoting photon reabsorption at the polymer-fluorophore interface.

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