Synthesizing Semiconductor Photocatalysts with Vacancy Defects for Enhanced Color Switching

Stimuli responsive materials have found widespread applications as sensors, encryption devices, rewritable media, etc. The response of these materials/system to a multitude of stimuli such as light, mechanical force, temperature, solvents, electricity, and many more stimuli have found widespread academic interest. The discover and understanding of these different phenomena has led to the development of new devices and fundamental understanding of the material interactions underlying the responsive materials. A recently developed system based on the coupling of redox dyes with semiconductor photocatalysts offers promise as photochromic devices, but further understanding of the color changing kinetics and component interactions are still needed. In this dissertation, a novel approach is presented to develop defective semiconductors to act as the photocatalyst for the color switching of redox dyes. The defects help to act as internal electron donors to prevent degradation of the organic dyes and can help promote the photoreduction of dyes, resulting in enhanced color switching and high cyclability. Additionally, the mechanism underlying the color changing kinetics of the redox dyes are explored and manipulated to develop multi-color systems that respond to different parameters of applied light including wavelength, intensity and time of illumination and a final system that can be made to be responsive to multiple stimuli. The catalyst and redox studies provide important insight into the development of highly active photocatalysts and understanding into the kinetic mechanism underlying the reduction of redox dyes for potential use in functional color changing devices.