In the wake of the sobering news that atmospheric carbon dioxide is now at its highest level in at least three million years, an important advance in the race to develop carbon-neutral renewable energy sources has been achieved. Scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have reported the first fully integrated nanosystem for artificial photosynthesis. While "artificial leaf" is the popular term for such a system, the key to this success was an "artificial forest."

"Similar to the chloroplasts in green plants that carry out photosynthesis, our artificial photosynthetic system is composed of two semiconductor light absorbers, an interfacial layer for charge transport, and spatially separated co-catalysts," says Peidong Yang, a chemist with Berkeley Lab's Materials Sciences Division, who led this research. "To facilitate solar water- splitting in our system, we synthesized tree-like nanowire heterostructures, consisting of silicon trunks and titanium oxide branches. Visually, arrays of these nanostructures very much resemble an artificial forest."

Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have discovered that DNA "linker" strands coax nano-sized rods to line up in way unlike any other spontaneous arrangement of rod-shaped objects. The arrangement -- with the rods forming "rungs" on ladder-like ribbons linked by multiple DNA strands -- results from the collective interactions of the flexible DNA tethers and may be unique to the nanoscale.

The research, described in a paper published online in ACS Nano, a journal of the American Chemical Society, could result in the fabrication of new nanostructured materials with desired properties. "This is a completely new mechanism of self-assembly that does not have direct analogs in the realm of molecular or microscale systems," said Brookhaven physicist Oleg Gang, lead author on the paper, who conducted the bulk of the research at the Lab's Center for Functional Nanomaterials.