Nano-Cables Convert Light into Electricity

Via NewScientistTech.com -

Nanocables that convert light into electricity could one day be used to power nano-robots.

The cables are 16 nanometres in diameter and several micrometres long. They resemble the light-harvesting antennae used by some bacteria and transform light into electricity in a similar way to the semiconductors in solar panels, albeit on a much smaller scale.

"This is the first example of a photoconducting nanostructure," says Takanori Fukushita of the University of Tokyo, Japan, a member of the team that built the cables.

The hollow cables can grow up to several micrometres long. To build them, Fukushita and colleagues created a compound containing hexabenzocoronene (HBC), two carbon-12 chains, and trinitrofluorenone (TNF). They placed the compound in a solution of tetrahydrofuran and bubbled methane vapour though it, causing the compound to self-assemble into hollow cables.

The HBC, which sheds electrons when hit by light, formed the inside of the cable wall, and the TNF, which readily accepts electrons, coated the outside of the wall.

Each time a photon hits the cable from outside it passes through the outer layer and knocks an electron loose from the inner layer. This causes the electron to jump to the outer layer and leave behind a positively charged "hole". These separated charges can then generate a current.

To test the nanocables, the researchers placed one on a silicon surface and applied a voltage across it. When light was shone onto the surface, a current began flowing down the cable between two electrodes. When the light was switched off, the current stopped.

At the moment, the cables cannot produce usable electricity from sunlight alone, as current does not flow well through the outer layer of TNF. The next step, Fukushita says, is to modify the outer layer, perhaps by attaching carbon-60 molecules (buckyballs), so it acts as a semiconductor and allows more current to flow.

Once this has been achieved, the nanocables could be fitted to nano-sized robots or micro-machines and power their movements, suggests Franz Würthner at the University of Würzburg in Germany. Their similarity in size and function to the antennae used by bacteria for photosynthesis means it might also be possible to connect them to such organisms, creating hybrid devices, he says.

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Very interesting. Now if someone can just make cybernetic light-powered bateria to keep my car clean...