Quasi-solid medium for photoinduced charge separation

New quasi-solid was proposed as a medium for photoinduced charge separation. Photoinduced charge separation and hydrogen production with the new quasi-solid medium using polysaccharide has been investigated. The new medium is a quasi-solid polysaccharide containing a large quantity of water. This medium is tight and elastic solid, obtained by cooling an aqueous solution of a polysaccharide (agarose or κ-carrageenan in this paper) to room temperature after it was dissolved in water by heating. When the quasi-solid (agarose or κ-carrageenan) involving sacrificial electron donor ethylenediaminetetraacetate (EDTA), tris(2,2′-bipyridine)ruthenium complex ([Ru(bpy)3]2+) and methylviologen (MV2+) was irradiated with visible light, methylviologen cation radical (MV+) was formed. The formation rate of methylviologen cation radical in an agarose solid was faster than that in a κ-carrageenan one. Photoinduced hydrogen production was achieved with this system containing additionally proton reduction catalyst such as platinum black (Pt black), platinum oxide (PtO2), and ruthenium oxide (RuO2). The characteristics of this solid medium for photochemical reactions were discussed.