Journal
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
Volume 217, Issue 1, Pages 157-163Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jphotochem.2010.10.003
Keywords
Photoisomerization; Azobenzene; Laser flash photolysis; Photoresponsive gel; Magnetite nanoparticles; Multifunctional materials
Categories
Funding
- EU
- Spanish Ministerio de Ciencia e Innovacion with FEDER [CSD2007-00010, MAT2007-61584, CTQ2009-11583, CTQ-2008-06720]
- Generalitat Valenciana
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The photochemistry of three azobenzenes representing contrasting photochemical behaviors is described in the present work. Thus, Methyl Orange (MO, 4-[[(4-dimethylamino)phenyl]-azo]benzenesulfonic acid sodium salt, hereinafter (1) and 4-hydroxyazobenzene-4'-sulfonic acid (2) undergo in water fast photochemical proton shift, with decays in the microsecond timescale. In contrast to the previous cases, azobenzene-4,4'-dicarboxylic acid (3) undergoes photoisomerization in water. This photochemical behavior allows the preparation of aqueous gels with Aerosil as gelating agent (5% weight) exhibiting high cyclability and photoreversible isomerization of the trans to cis (300 nm irradiation) and cis to trans (visible white light irradiation). Gels containing azobenzene 3 as photoresponsive molecule and well-dispersed magnetite (Fe3O4) nanoparticles exhibit simultaneously high photoresponse and magnetic properties. Photoisomerization of compound 3 in these gels leads to small but reliable changes (25 G coercive field) in the magnetic hysteresis loop of magnetite nanoparticles. This novel concept of optical modulation of magnetism in iron oxide nanoparticles paves the way for the study of new systems, with a stronger coupling between trans-cis photoisomerization and magnetic properties. (C) 2010 Elsevier B.V. All rights reserved.
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