Time‐resolved chemiluminescence study of the TiO 2 photocatalytic reaction and its induced active oxygen species

The time‐resolved chemiluminescence (CL) method has been applied to study the TiO 2 photocatalytic reaction on a µs–ms timescale. The experimental set‐up for time‐resolved CL was improved for confirmation of the unique luminol CL induced by the photocatalytic reaction. The third harmonic light (355 nm) from an Nd:YAG laser was used for the light source of the TiO 2 photocatalytic reaction. Luminol CL induced by this reaction was detected by a photomultiplier tube (PMT) and a preamplifier was used for amplifying the CL signal. Experimental conditions affecting the photocatalytically induced CL were discussed in detail. The involvement of active oxygen species such as ·OH, O 2 ·− and H 2 O 2 in the CL was examined by adding their scavengers. It is concluded that ·OH was greatly involved in the CL on a µs–ms timescale, especially in time periods <100 µs after illumination of the pulse laser. On the other hand, CL generated by O 2 ·− began to increase after 100 µs and became dominant after 2.5 ms. A small part of the CL might be generated by H 2 O 2 on the whole µs–ms timescale. A CL reaction mechanism related with ·OH and dissolved oxygen was proposed to explain the photocatalytically induced luminol CL on a µs–ms timescale, especially in periods <100 µs. Copyright © 2006 John Wiley & Sons, Ltd.