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Research Letters in Physical Chemistry
Volume 2007 (2007), Article ID 18278, 5 pages
http://dx.doi.org/10.1155/2007/18278
Research Letter

Surface Photochemistry: Benzophenone as a Probe for the Study of Modified Cellulose Fibres

1Centro de Química-Física Molecular - Complexo Interdisciplinar, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, Lisboa 1049-001, Portugal
2Laboratório de Química Orgânica, Departamento de Engenharia Química, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emídio Navarro 1, Lisboa 1950-062, Portugal
3Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Portalegre, Lugar da Abadessa, APT 148, Portalegre 7301-901, Portugal
4Laboratoire Sciences des Matériaux et Environnement (LMSE), Faculté des Sciences de Sfax, BP 802-3018 Sfax, Tunisia
5Laboratoire ITODYS, Université Paris Diderot, CNRS, 75005 Paris, France

Received 18 July 2007; Accepted 27 October 2007

Academic Editor: Bern Kohler

Copyright © 2007 L. F. Vieira Ferreira et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This work reports the use of benzophenone, a very well characterized probe, to study new hosts (i.e., modified celluloses grafted with alkyl chains bearing 12 carbon atoms) by surface esterification. Laser-induced room temperature luminescence of air-equilibrated or argon-purged solid powdered samples of benzophenone adsorbed onto the two modified celluloses, which will be named C12-1500 and C12-1700, revealed the existence of a vibrationally structured phosphorescence emission of benzophenone in the case where ethanol was used for sample preparation, while a nonstructured emission of benzophenone exists when water was used instead of ethanol. The decay times of the benzophenone emission vary greatly with the solvent used for sample preparation and do not change with the alkylation degree in the range of 1500–1700 micromoles of alkyl chains per gram of cellulose. When water was used as a solvent for sample preparation, the shortest lifetime for the benzophenone emission was observed; this result is similar to the case of benzophenone adsorbed onto the “normal” microcrystalline cellulose surface, with this latter case previously reported by Vieira Ferreira et al. in 1995. This is due to the more efficient hydrogen abstraction reaction from the glycoside rings of cellulose when compared with hydrogen abstraction from the alkyl chains of the modified celluloses. Triplet-triplet transient absorption of benzophenone was obtained in both cases and is the predominant absorption immediately after laser pulse, while benzophenone ketyl radical formation occurs in a microsecond time scale both for normal and modified celluloses.