Total Internal Reflection: Applications in Nonlinear Microscopy and Fluorescence Anisotropy

As technology advances to harness new energies and to create new cures, the sophistication of analysis grows not only in depth but in efficiency. Total internal reflection (TIR) has been coupled to microscopy leveraging its unique optical phenomenon on a breadth of topics. In this dissertation, the work presented will show how TIR was applied in two different instrumental analyses to evaluate two unique and complex systems. The first project features TIR paired with the transient absorption microscopy (TAM), a nonlinear optical technique, to gauge solvent mixing and diffusion in microreactors. Microreactors gained acclaim for their ability to produce high grade products while producing less waste and for their modular assembly that facilitates production. Major avenues of interest for microreactors range from pharmaceuticals to nanoparticles; however, microreactors need a quick and sensitive method in order to optimize the numerous reaction conditions: temperature, flow velocity, and reactant concentration. TIRTAM resolves these issues by measuring solvent mixing and diffusion in an on-line apparatus that allows for high throughput analysis. The second project employs TIR in tandem with fluorescence anisotropy to measure molecular dynamics in microemulsions. Microemulsions are thermodynamically stable mixtures composed of oil, water, and surfactant. The most well-known application for microemulsions is oil recovery, but an exciting, emerging application for microemulsions are acting as solutions for electron transfer in flow batteries which are intended for green energy storage. Before microemulsions can be used for such an application, the ideal composition needs to be identified. Measuring dynamic information from microemulsions can reveal structural knowledge that will aid in electron transfer, and TIR anisotropy can measure the surface versus conventional anisotropy that can only probe the bulk solution. Ascertaining surface dynamics can inform how microemulsions would be affected by electrode surfaces. These projects highlight the themes of versatility for TIR and functionality of the techniques. TIR’s capabilities have much promise and more can be gleaned and built from the work presented herein.