Application of Chemiluminescent Probe to Monitoring Superoxide Radicals and Hydrogen Peroxide in TiO2 Photocatalysis

A chemiluminescent probe, luminol, was successfully applied to monitoring superoxide ions (O 2 •- ) and hydrogen peroxide (H 2 O 2 ) produced on photocatalytic reaction in aqueous TiO 2 suspension. Two chemiluminescent reactions were distinguished from the decay profile after the end of the irradiation, and the reaction mechanism was analyzed. The fast decay component gives information about O 2 •- and the slow one provides the amount of H 2 O 2 . The rate constant for the reaction of O 2 •- with luminol was found to be 1 × 10 4 M -1 s -1 . The amount of O 2 •- during the irradiation on TiO 2 in alkaline solution could be estimated to be on the order of 10 -13 M. Detection of H 2 O 2 in concentrations as small as 10 -9 M was demonstrated in the photocatalytic water oxidation.