Semiconductor photocatalysts, which can harvest light energy to generate redox potentials, have received significant attention as a sustainable technological option for environmental remediation. One of the challenges for environmental application of photocatalysts is its relatively low efficiency of photosensitization by visible light, despite extensive research in the past. We herein propose a highly innovative approach to enhance the visible light utilization of semiconductor-based photocatalysis processes. Our approach aims at manipulating light to amplify the frequency based on a unique photoluminescence process called triplet-triplet annihilation based upconversion (TTA-UC). We successfully achieved green-to-blue TTA-UC in the aqueous phase through encapsulating a non-volatile, less-toxic oil phase containing a benchmark sensitizer (PtOEP) and acceptor (DPA) pair inside a rigid, spherical, and uniformly-sized polymer shell. The microcapsules had remarkable upconversion quantum yield (~28%) as well as photochemical stability to occur UC even after a few weeks of exposure to the ambient environment. We further demonstrated for the first time in literature UC-assisted photochemical production of hydroxyl radical on the selected photocatalyst (Pt/WO3) under sub-band-gap energy photon (532 nm) irradiation. Figure 1 shows optical and fluorescence microscope images of the microcapsules and schematic illustration of the newly developed UC/photocatalyst hybrid system.

Encapsulated triplet-triplet annihilation-based upconversion in the aqueous phase for sub-band-gap semiconductor photocatalysis

246th National Meeting (2013)

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