'Artificial Leaf' Produces Electricity

A water-based gel impregnated with photosensitive molecules and capped by electrodes effectively serves as an “artificial leaf,” mimicking a photosynthesis matrix to produce electricity (J. Mater. Chem., DOI: 10.1039/c0jm01820a). This biologically inspired class of “soft matter” photovoltaic devices, created by Hyung-Jun Koo and Orlin D. Velev of North Carolina State University and coworkers, is a potential low-cost, green alternative to silicon-based solar cells. The researchers first made a hydrogel from agarose, a natural polysaccharide typically used as a substrate in gel electrophoresis. They then added a combination of the photosensitive ionic dyes 9,10-dimethoxy-2-anthracenesulfonic acid and ruthenium trisbipyridine to capture light. The team showed that, when infused in the gel, natural molecules such as the plant pigment chlorophyll and the light-absorbing enzyme photosystem II generate electricity as well. The dye-containing gel was layered on a copper foil electrode coated with carbon black and graphite, which the researchers found to be an inexpensive substitute for a standard platinum electrode. They topped the gel with an indium tin oxide-coated plastic substrate, which served as the other electrode. The prototype biomimetic devices still require significant fine-tuning to improve efficiency and long-term stability, Velev says.