UV induced local heating effects in TiO2 nanocrystals

Thomas Berger; Oliver Diwald; Erich Knözinger; Martin Sterrer; John T. Yates Jr

doi:10.1039/B517107E

UV induced local heating effects in TiO₂nanocrystals

Thomas Berger,^a Oliver Diwald,*^a Erich Knözinger,^a Martin Sterrer^b and John T. Yates Jr^c

* Corresponding authors

^a Institut für Materialchemie, Technische Universität Wien, Veterinärplatz 1/GA, Wien A-1210, Austria
E-mail: odiwald@mail.zserv.tuwien.ac.at
Fax: +43-1-250773890

^b Department of Chemical Physics, Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, D-14195 Berlin, Germany

^c Surface Science Center, Department of Chemistry, University of Pittsburgh, Pittsburgh, USA

Abstract

When isolated TiO₂ nanocrystals are subjected to UV light at 77 K and pressures below 10⁻⁶ mbar, trapping of photogenerated hole centers occurs on the surface of the nanocrystals and can be tracked by time-resolved electron paramagnetic resonance spectroscopy. Irrespective of the selected UV irradiance used, the maximum concentration of trapped charges was found to be constant for a given number of nanocrystals (∼10¹⁵) and corresponds to one electron–hole pair per particle. On a time scale of seconds to minutes the dynamics for the trapping process depend on the number of photons with supra band gap energy. A local temperature rise of the TiO₂ nanocrystals was observed for irradiances above 1.55 mW cm⁻² (10¹⁵ photons cm⁻² s⁻¹). This is attributed to enhanced nonradiative recombination of photogenerated charge carriers via heat production and points to a substantial contribution of thermal chemistry in photocatalytic reaction cycles.

Article information

https://doi.org/10.1039/B517107E

Article type

Paper

Submitted

05 Dec 2005

Accepted

13 Feb 2006

First published

02 Mar 2006

Download Citation

Phys. Chem. Chem. Phys., 2006,8, 1822-1826

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UV induced local heating effects in TiO₂ nanocrystals

T. Berger, O. Diwald, E. Knözinger, M. Sterrer and J. T. Yates Jr, Phys. Chem. Chem. Phys., 2006, 8, 1822 DOI: 10.1039/B517107E

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