Effects of Surface-Immobilization on Photobleaching of Xanthene Dye Photocatalysts

While organic photocatalysts provide increasingly versatile chemical pathways under mild conditions, their long-term stability remains understudied. Here, the photobleaching behavior of xanthene dye photocatalysts is investigated. Rose Bengal, Eosin Y, and fluorescein are studied when in solution, when grafted to glass beads, and when incorporated into polymer brushes that are tethered to glass beads. This provides a comparison between xanthene's stability as a homogeneous and as a heterogeneous photocatalyst. Photobleaching is investigated using UV–vis, diffuse reflectance UV–vis (DR UV–vis), and fluorescence microscopy. Xanthene dyes as homogeneous photocatalysts exhibit the highest photostability, while the grafted systems appeared to fade more rapidly. Notably, heterogenization appears to have different effects based on the photocatalyst system, and further altering the photocatalyst environment with reagents may improve stability.