Sunday, November 21, 2010

Not only are these gold nanoparticles gorgeous to look at – they may one day act as microscopic powerhouses for molecular machines. Researchers at the Nano/Bio Interface Center at the University of Pennsylvania recently discovered a novel to way to generate solar power by shining light onto gold nanoparticles. The discovery has far-reaching implications in the realm of nanotechnology, and may open the door for everything from self-powering molecular circuits to super-efficient data storage.

To generate current the researchers first packed a bunch of light-sensitive gold nanoparticles together on a glass substrate and then exposed them to optical radiation (light). This knocks conductive electrons free from the gold particles, which run along the surface to create surface plasmons, which in turn induce an electrical current across the molecules.

The amount of electricity generated is minute, but the researchers believe that by optimizing size, shape, and orientation of the nanparticles they could create a current strong enough to power nano-sized circuits. Professor Bonnell, who participated in the experiment, said “If the efficiency of the system could be scaled up without any additional, unforeseen limitations, we could conceivably manufacture a 1A, 1V sample the diameter of a human hair and an inch long“.

Turning sunlight into electrical power is all but a new problem, but recent advancements made by researchers at the University of Pennsylvania have given a new twist to the subject. While not currently aimed at solar panel technology, their research has uncovered a way to turn optical radiation into electrical current that could lead to self-powering molecular circuits and efficient data storage.

Professor of materials science Dawn Bonnell and colleagues placed light-sensitive gold nanoparticles on a glass substrate, minimizing the distance between the nanoparticles. The team then stimulated conductive electrons with optical radiation to ride the surface of the gold nanoparticles, creating so-called "surface plasmons" that induce electrical current across molecules.

Under these conditions, surface plasmons were found to increase the efficiency of current production by a factor of four to 20. The size, shape and separation of the array of golden nanoparticles can be customized independently of the optical characteristics of the molecule, and optimization of these parameters could, the researchers say, produce enhancement factors of thousands, and the resulting electrical current could be easily transported to the outside world.

"If the efficiency of the system could be scaled up without any additional, unforeseen limitations, we could conceivably manufacture a 1A, 1V sample the diameter of a human hair and an inch long," Prof Bonnell explained.

The results may lead to better nano-sized circuits that can power themselves, potentially through sunlight. Another interesting application suggested by the researchers could be for data storage, where a photovoltaic circuit could encode bits using wavelengths of light rather than electrical charge.

The study, published in the current issue of the journal ACS Nano, was supported by the Nano/Bio Interface Center, National Science Foundation, the John and Maureen Hendricks Energy Fellowship and the US Department of Energy.