2, Yonsei University, Seoul, , Korea (the Republic of)
The photosynthetic apparatus is substantially located in the thylakoids. There is interest in stimulating this apparatus and extract photoelectrons through attached electrodes and use them as electric power sources. The thylakoid membrane is however not a well conducting electrolyte. We present an experimental study on spinach derived thylakoids deposited on gold electrodes and on TiO2 electrodes. The dark currents and light currents are determined under illumination with light ranging from 625nm to 470 nm under various DC bias. The expermentally obtained photocurrents scale with wavelength generally in analogy to the UV-vis absorption spectra. The photoelectrochemical response suggests that there is a chromatic change of the thylakoid layer towards longer wavelengths which can be attributed to the adsorption of the thylakoids on the electrode, in contrast to thylakoids in solution. The impedance spectra give account of the stark electric blocking properties of the lipid layer, underlining the necessity to further "widen" the gates for electrons in the thylakoid membrane. At first sight, there seems to be no influence of the nature of the electrode material (metal vs. metal oxide) to the effectivitiy of the charge transfer.