Immobilisation of PS I and PS II on Semiconducting Particles

Various types of photoelectrochemical cells using photosynthetic components have been described. In most cases, the device consisted either in two half cells separated by a photoactive membrane or in a photogalvanic cell containing chloroplasts or chromatophores. In some cases, the material was directly deposited onto the surface of an electrode. In such systems, irradiation of the coated electrode by visible light induces a photoeffect through the charge separation generated in the reaction centers and the subsequent charge transfer to the supporting electrode and the surrounding medium. Using thylakoid fragments deposited on the surface of an SnO2 electrode Ochiai et al.(1982) have shown that an anodic photoeffect can be generated upon irradiation. However, using the same support coated with reaction centers or with vesicles isolated from photosynthetic bacteria Seibert et al.(1982) obtained a photocathodic effect, However, the mechanisms of electrode sensitization is far from beeing understood. We report here on some first results concerning the immobilisation of photosystems on TiO2 powders as a first step in the study of the interactions of photoactive biological complexes with semiconducting particles. The photocatalytic properties of this material is now extensively studied (Kalyanasundaram 1983). Anatase powders can have high specific surface area (50–200 m2g-1), can be sensitized by various dyes, and have a conduction band well suited for the generation of H2 from water.