Photoelectrochemical oxidation of a turn-on fluorescent probe mediated by a surface Mn~(II) catalyst covalently attached to TiO_2 nanoparticles

摘要

A manganese complex covalently attached to a TiO_2 electrode via a light-absorbing organic linker (L) was used in the photooxidation of 2',7'-dihydrodichlorofluorescein (H_2DCF). Significant and sustained photocurrent was observed upon visible-light illumination of the fully assembled anode in the presence of the substrate. The two-electron, two-proton oxidation of H_2DCF yields the fluorescent compound, 2',7'- dichlorofluorescein (DCF). Our studies suggest that the MnII-L-TiO_2 architecture is an effective photoanode for multielectron chemistry, as production of DCF under visible-light illumination exceeds yields observed for bare TiO_2 as well as Zn~(II)-L-TiO_2 anodes. The turn-on fluorescent behavior of H_2DCF upon oxidation makes it an excellent substrate for the study of new photoanodes. The high fluorescence quantum yield of DCF allows for nanomolar sensitivity and real-time monitoring of substrate oxidation.