Environmental photochemistry on semiconductor surfaces. Visible light induced degradation of a textile diazo dye, naphthol blue black, on TiO{sub 2} nanoparticles
- Universite du Quebec a Trois Rivieres (Canada)
- Indiana Univ. Northwest, Gary, IN (United States)
- ICI Canada Inc., McMasterville (Canada)
- Univ. of Notre Dame, IN (United States)
Visible light induced degradation of the textile diazo dye Naphthol Blue Black (NBB) has been carried out on TiO{sub 2} semiconductor nanoparticles. Diffuse reflectance transient absorption and FTIR techniques have been used to elucidate the mechanistic details of the dye degradation. The failure of the dye to degrade on insulator surfaces such as Al{sub 2}O{sub 3} or in the absence of oxygen further highlights the importance of semiconducting properties of support material in controlling the surface photochemical processes. The primary event following visible light excitation is the charge injection from the excited dye molecule into the conduction band of the semiconductor TiO{sub 2}, producing the dye cation radical. This was confirmed by diffuse reflectance laser flash photolysis. The surface-adsorbed oxygen plays an important role in scavenging photogenerated electrons, thus preventing the recombination between the dye cation radical and photoinjected electrons. Diffuse reflectance FTIR study facilitated identification of reaction intermediates and end products of dye degradation. By comparison with the degradation products from other azo dyes such as Chromotrope 2B and Chromotrope 2R we conclude that the NBB is degraded to a colorless naphthaquinone-like end product. 41 refs., 9 figs.
- OSTI ID:
- 263189
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 20; Other Information: PBD: 16 May 1996
- Country of Publication:
- United States
- Language:
- English
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