Time-Resolved Chemiluminescence of Luminol Induced by TiO2 Photocatalytic Reactions

Abstract

Abstract The time-resolved chemiluminescence (CL) of luminol in TiO2 photocatalytic reactions is reported. Third-harmonic light of 355 nm from a Q-switched Nd:YAG laser was used as a UV light source, and CL was collected in the perpendicular direction to the excitation light by two lenses. After eliminating the scattering light, the CL was detected by a PMT and recorded on a digital oscilloscope. It was found that the CL of luminol induced by the photocatalytic reaction increased with time after the illumination of a pulse laser, and reached the maximum value at about 40–60 μs, then slowly decreased with time. The time-resolved CL intensity increased greatly in an oxygen-bubbled TiO2 suspension, while it decreased greatly in a He-bubbled one. The total CL intensity increased linearly with the concentration of TiO2. Scavengers of active oxygen species of •OH, •O2− and H2O2 were added into the suspension for studying the involvement of the active oxygen species. The experimental results suggest that more than about 30% of CL might have been caused by H2O2 over the total time period, while the possibility of •OH involvement was small. On the other hand, the addition of a scavenger of •O2− had a small effect on the CL in time period of 0–0.7 ms, and decreased the CL after 0.7 ms.