Photochemical formation of chromium (V) in dichromated materials: a quantitative and comparative approach

Michel Bolte; Christine Pizzocaro; Christophe Lafond

doi:10.1117/12.323477

25 September 1998 Photochemical formation of chromium (V) in dichromated materials: a quantitative and comparative approach

Michel Bolte, Christine Pizzocaro, Christophe Lafond

Author Affiliations +

Proceedings Volume 3417, Photopolymer Device Physics, Chemistry, and Applications IV; (1998) https://doi.org/10.1117/12.323477
Event: Lasers and Materials in Industry and Opto-Contact Workshop, 1998, Quebec, Canada

Abstract

We have been working on dichromated photosensitive materials for several years. After investigating the photochemical process in various systems, it appears that the chemical structure of the polymeric matrix plays an essential role in the progress of the reaction that takes place upon irradiation by the laser beams. If the primary photochemical process is always the electron transfer from the matrix to the metallic cation giving rise to chromium (V) and a macroradical, the fate of chromium (V) in the system strongly depends on the chemical structure of the polymer. In dichromated poly(acrylic acid) DCPAA, chromium (V) is an unstable species only detectably by ESR spectroscopy upon irradiation: it disappears after stopping the irradiation very fast. On the contrary, chromium (V) is surprisingly stable in poly(vinyl alcohol) and in gelatin. The first spectral evolution corresponds to the only reduction of chromium (VI) into chromium (V) as evidenced by the presence of an isosbestic point. The subsequent reduction of chromium (V) is a very slow process: the complete transformation into chromium (III) is only achieved after several days. As a result, we were able to estimate the UV-visible spectrum of chromium (V) in the matrix and for the first time, it was possible to quantitatively follow the formation of this species and to draw some conclusion about the complexation sites in gelatin.

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Michel Bolte, Christine Pizzocaro, and Christophe Lafond "Photochemical formation of chromium (V) in dichromated materials: a quantitative and comparative approach", Proc. SPIE 3417, Photopolymer Device Physics, Chemistry, and Applications IV, (25 September 1998); https://doi.org/10.1117/12.323477

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