Photoelectrochemical study on photosynthetic pigments-sensitized nanocrystalline ZnO films

Hetero-structures formed by quantum-sized ZnO nanocrystals and photosynthetic pigments were prepared by adsorbing either chlorophyll a, carotenoids or their mixture onto a film of organic-capped ZnO nanoparticles. Photoelectrochemical measurements were comparatively performed on both bulk and nanocrystalline ZnO films after dye-covering in order to probe the photosensitization process occurring at the hetero-junction. The photoconversion process was found to be greatly enhanced at the nanocrystalline electrodes upon sensitization with a dye mixture. The sensitization process is discussed on the basis of the aggregation state of chlorophyll a, and of the specific photoprotective action played by carotenoids. (C) 2004 Elsevier B.V. All rights reserved.