Langmuir-Blodgett films of phycobiliproteins .2. Photoelectrochemical property of R-phycoerythrin

Through an electrochemical cell deposited with R-phycoerythrin (R-PE) monolayer on SnO2 optically transparent electrode (SnO2 OTE), charge transport phenomenon and the photoelectrochemical behavior of R-PE have been investigated. The experimental results indicate that the cell is able to generate photocurrent; moreover, the signal increases apparently in the presence of electron donor or acceptor in the electrolyte solution, showing that the photocurrent of R-PE would originate from its charge transfer. Further comparative test showed that the photocurrent came from the photo-induced charge separation property of the chromorphores attached covalently to the apoprotein of R-PE. The photocurrent spectrum of R-PE LB films verified the above viewpoint, from which the mechanism of photo-induced charge transfer of R-PE is suggested. The quantum yield for photoelectric conversion of R-PE LB films was measured to be phi(520nm) = 3.4% and the photovoltage approached 400 mV. Moreover, the protein is stable for a long irradiation time. In addition, the effects of pH value of the electrolyte solution, the concentration of electron donor, the number of layers of R-PE LB films and the irradiation time on the photocurrent are studied.