Flash photolysis observation of the absorption spectra of trapped positive holes and electrons in colloidal TiO₂

authored by

D. Bahnemann, A. Henglein, J. Lilie, L. Spanhel

Abstract

When a TiO₂ sol containing an adsorbed electron scavenger such as platinum or methyl viologen is flashed with a 347-nm laser, an immediate broad absorption with λ_max = 475 nm is observed. In acid solution the absorption decays within milliseconds. In alkaline solution it decays within microseconds, depending on the OH^- concentration, and OH^- ions are consumed in the process. In the presence of scavengers for positive holes the decay is faster, while oxygen does not have any effect. This absorption spectrum is attributed to excess positive holes trapped at the surface of the colloidal particles. When a TiO₂ sol containing an adsorbed scavenger for positive holes, such as polyvinyl alcohol or thiocyanate, is flashed, a broad absorption with λ_max = 650 nm is observed. It decays in the presence of electron scavengers. This spectrum is attributed to excess electrons trapped close to the surface of the colloidal particles.

External Organisation(s)

Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)

Type

Article

Journal

Journal of Physical Chemistry

Volume

88

Pages

709-711

No. of pages

3

ISSN

0022-3654

Publication date

1984

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Engineering, Physical and Theoretical Chemistry

Electronic version(s)

https://doi.org/10.1021/j150648a018 (Access: Unknown)