Photodependent hydrogen evolution by photosystem I entrapped in hybrid organo-silicate glasses

Photosystem I (PSI) is a molecular photovoltaic structure that can generate a 1 v potential over a 6 nm distance after absorption of a photon. The use of the sol-gel technique to entrap and stabilize PSI complexes and produce a stable photo-dependent hydrogen evolution catalyst was presented. The spectrophotometric, photochemical, and photocatalytic characteristics of the immobilized enzyme were examined to evaluate the properties of the reaction centers as the sol-gels were dehydrated. The effect of the solvent particularly on their ability to perform electron transfer reactions was studied. The magnitude of the photochemical response of the immobilized samples was slightly greater than the native sample after immobilization and when the majority of the water had been removed (91.4%) after 29 days. However, the photochemical response decreased by ∼ 50%, compared to the native sample, during storage for 8 mo over dessicant in the dark. The intramolecular electron-transfer characteristics of PSI remained intact even after virtually all the solvent was removed. The ability to manipulate PSI in a solid-state environment was essential for the exploitation of its unique optoelectronic properties for photo-fuel cells, photovoltaics, and other bio-electronics applications. This is an abstract of a paper presented at the ACS Fuel Chemistry Meeting (Washington, DC Fall 2005).