Photogeneration of singlet oxygen by thionine molecular layer grafted on electrode surface from its diazonium salt

Abstract

article i nfo Thionine (Th) was electrochemically grafted to the glassy carbon (GC) surface from its corresponding diazonium salt to investigate it as a singlet oxygen source under light excitation. As confirmed by cyclic voltammetry data the Th molecules may form a monolayer structure in the reduction process carried out directly from the diazoti- zation reaction mixture without a time-consuming separation step. It was found that illuminated grafted Th at a level of monolayer coverage on GC surface is able to generate singlet oxygen at a constant rate. To determine ef- ficiency of the photogeneration process a singlet oxygen selective trap, 1,3-diphenylisobenzofuran (DPBF), was employed, which was monitored using UVVis spectroscopy. The progress of the trap decay was determined in terms of its half-life.