Photoredox behavior of methylviologen doped in silica gel matrices

Citation
Y. Kotani et al., Photoredox behavior of methylviologen doped in silica gel matrices, J MAT CHEM, 10(12), 2000, pp. 2765-2768
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
JOURNAL OF MATERIALS CHEMISTRY
ISSN journal
0959-9428 → ACNP
Volume
10
Issue
12
Year of publication
2000
Pages
2765 - 2768
Database
ISI
SICI code
0959-9428(2000)10:12<2765:PBOMDI>2.0.ZU;2-T
Abstract
Silica gels doped with methylviologen (MV), which is a photoredox and photo chromic compound, have been prepared under both acidic and basic conditions . The oxidation process of the reduced species, MV+, formed by UV irradiati on of the gels, was investigated on the basis of UV absorption measurements . The magnitude of the absorption maximum of MV+ in the gels gradually decr eased with time after irradiation, as is observed for MV+ in solution, indi cating that the photoredox behavior of MV in the gel matrix is very similar to that in solution. The lifetime of MV+ increased with increasing microvi scosity around MV after gelation in the gels prepared under acidic conditio ns. The lifetime of MV+, however, reached a maximum and then gradually decr eased as the gel was aged, suggesting that the oxidation of MV+ to more sta ble MV2+ readily occurred due to the restriction of the diffusion of MV+ an d oxidized solvents. Moreover, the lifetime of MV+ in the gels prepared und er basic conditions reached a maximum at an earlier stage of gel aging than for the gels prepared under acidic conditions because the microviscosity a round the MV molecules at the gelation point under basic conditions was gre ater than that under acidic conditions.