Thylakoid membranes were isolated from seven plant species. The isolated thylakoids were immobilized onto carbon paper electrodes and the photocurrent was measured. Spinach thylakoids showed the largest photocurrent, 80 +/- 10 mu A per mg protein and 430 +/- 60 mu A per mg chlorophyll. The electrodes were also tested in a bio-solar cell configuration. Open circuit voltages were the same regardless of the thylakoid source, and spinach thylakoid bio-solar cells had the largest currents. Exposure of the electrodes to diuron, a commonly used herbicide, showed that sensitivity varied by thylakoid source, with spinach having the highest sensitivity and green chard and beet greens having the lowest. (C) 2014 Elsevier Ltd. All rights reserved.