Shedding light on surface-assembled photosynthetic systems

Abstract

The interfacing of biomolecules to nanostructures, electrode surfaces and/or optical components constitutes the new discipline of bioelectronics. It is based on electron transfer between a protein and an electrode, and can be monitored by amperometric techniques. The integration of biomolecules with electronics has strong potential for applications in a variety of functional devices, ranging from biosensors to solar cells. In this thesis we explore the possibilities of constructing a bio-electronic device for solar energy conversion by surface-assembly of photosynthetic pigment-protein complexes on a gold electrode. Optical excitation of the photosynthetic pigments gives rise to charge separation in the so-called reaction center complex. Energy conversion is completed by subsequent electron transfer to the electrode, generating a light-induced electric current. The data shows that light-harvesting complexes can be immobilized directly on a gold surface and on various SAM surfaces whilst retaining their full optical functionality. All energy transferring reactions still take place and are similar to those observed for the detergent-solubilized proteins. Furthermore it is shown that LH1 complexes exhibit a remarkable photostability, even under ambient conditions. These findings demonstrate the possibility of interfacing a fully functional energy transferring protein complex to a conducting substrate in the presence of oxygen, with the capacity of converting light into electrical energy.