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Proceedings Paper

Interfacial charge transfer dynamics in small molecule-modified TiO2 nanoparticles
Author(s): Shankar Varaganti; Edwin Mghangha; Jameel A. Hasan; Guda Ramakrishna
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Paper Abstract

Direct molecule-semiconductor interfacial charge transfer interactions have received considerable research attention for their applications in various fields. In this study, the dynamics of molecule-TiO2 interfacial charge transfer complexes is monitored with femtosecond fluorescence upconversion and transient absorption. Small molecules (catechol, dopamine, benzhydroxamic acid, acetyl acetonate and salicylate)-modified TiO2 nanoparticles are prepared and the complexation is followed with optical absorption measurements. Although little visible luminescence is observed from these molecule- TiO2 nanoparticles, ultrafast emission in broad range of wavelengths is detected with fluorescence upconversion which is ascribed to the interfacial charge transfer emission. The charge transfer emission arose out of the radiative recombination of the electrons in the conduction band of TiO2 with holes in the molecule. Femtosecond fluorescence anisotropy measurements have shown that the interfacial charge-transfer excitation is mostly a localized one for catechol, dopamine and benzhydroxamate modified TiO2 nanoparticles. However, the possibility of delocalized charge-transfer excitations is observed for salicylate and acetyl acetonate-TiO2 nanoparticles. The decay of the charge transfer emission is ascribed to the relaxation of the localized states to delocalized states in the TiO2 conduction band. Transient absorption measurements have shown long-lived charge separation in the case of surface-modified TiO2 nanoparticles. Further measurements on the influence of charge-transfer excitations on the interfacial electron transfer in surface-modified TiO2 nanoparticles are being carried out.

Paper Details

Date Published: 27 August 2010
PDF: 10 pages
Proc. SPIE 7758, Physical Chemistry of Interfaces and Nanomaterials IX, 775802 (27 August 2010); doi: 10.1117/12.861980
Show Author Affiliations
Shankar Varaganti, Western Michigan Univ. (United States)
Edwin Mghangha, Western Michigan Univ. (United States)
Jameel A. Hasan, Western Michigan Univ. (United States)
Guda Ramakrishna, Western Michigan Univ. (United States)

Published in SPIE Proceedings Vol. 7758:
Physical Chemistry of Interfaces and Nanomaterials IX
Oleg V. Prezhdo, Editor(s)

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