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Identification of Reactive Species in Photoexcited Nanocrystalline TiO₂ Films by Wide-Wavelength-Range (400−2500 nm) Transient Absorption Spectroscopy

Toshitada Yoshihara,^†^‡ Ryuzi Katoh,*^†^‡ Akihiro Furube,^†^‡ Yoshiaki Tamaki,^†^‡^§ Miki Murai,^†^‡ Kohjiro Hara,^†^‡ Shigeo Murata,^†^‡ Hironori Arakawa,^†^‡ and M. Tachiya^‡

Photoreaction Control Research Center (PCRC) and National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan

J. Phys. Chem. B, 2004, 108 (12), pp 3817–3823

DOI: 10.1021/jp031305d

Publication Date (Web): February 28, 2004

†

PCRC.

‡

AIST.

Corresponding author. E-mail: r-katoh@aist.go.jp.

NEDO Fellow.

Abstract

Reactive species, holes, and electrons in photoexcited nanocrystalline TiO₂ films were studied by transient absorption spectroscopy in the wavelength range from 400 to 2500 nm. The electron spectrum was obtained through a hole-scavenging reaction under steady-state light irradiation. The spectrum can be analyzed by a superposition of the free-electron and trapped-electron spectra. By subtracting the electron spectrum from the transient absorption spectrum, the spectrum of trapped holes was obtained. As a result, three reactive speciestrapped holes and free and trapped electronswere identified in the transient absorption spectrum. The reactivity of these species was evaluated through transient absorption spectroscopy in the presence of hole- and electron-scavenger molecules. The spectra indicate that trapped holes and electrons are localized at the surface of the particles and free electrons are distributed in the bulk.

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Published In Issue March 25, 2004
Received December 11, 2003

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Article

Identification of Reactive Species in Photoexcited Nanocrystalline TiO₂ Films by Wide-Wavelength-Range (400−2500 nm) Transient Absorption Spectroscopy