The kinetic and mechanistic investigation of interfacial electron transfer process in semi-heterogeneous photocatalytic system (porphyrin dye + TiO<SUB>2</SUB>/Re(I))
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We report a collisional electron-injection process in the semi-hetero hybrid photocatalytic system consisting of non-anchored porphyrins and TiO2/Re(I) nanoparticles. The net hetero-collisional electron transfer from the non-anchored fluorescent porphyrin sensitizer to the TiO2 catalytic particles was a major event during the initial stage of the catalysis. According to in situ UV‒vis absorption spectroscopy and mass analysis of dye solution filtered after photolysis, the initially added porphyrin dye is found to experience a photomodification accompanied by a breakage of π‒conjugation. With the structural identification of deformed porphyrin species, two acetyl- or ethyl-group modified porphyrins were prepared, and this modification elevated the excited-state energy levels, consequently shortening the activity delay at the early stage of photolysis. Thus, chemical modification had a favorable effect on the photosensitizing and electron transportation abilities of the dye.