30 Jul 2012

Optic antenna paves way to brighter LEDs

European researchers from the Centre national de la recherche scientifique and Aix Marseille Université, both in France, have fabricated a nano-antenna from short strands of DNA, two gold nanoparticles and a small fluorescent molecule that captures and emits light.

Claiming a world first, the researchers say the device paves the way to more efficient light-emitting diodes and compact solar cells.

Since light is a wave, it should be possible to develop optical antennas capable of amplifying light signals in the same way as mobile phones capture radio waves.

However, light oscillates a million times faster than radio waves and nanometre sized objects are needed to capture the very rapid light waves.

Consequently, the optical equivalent of an elementary antenna, is a quantum emitter surrounded by two particles a thousand times smaller than a human hair.

To develop such a device, the researchers first grafted 36nm diameter gold particles and a fluorescent organic colorant onto short synthetic DNA strands, some 10 to 15 nm long.

The fluorescent molecule acts as a quantum source, supplying the antenna with photons, while the gold nanoparticles amplify the interaction between the emitter and the light.

The scientists then went onto produce, in parallel, several billion copies of these pairs of particles, in solution by controlling the position of the fluorescent molecule with nanometric precision, thanks to the DNA backbone.

These characteristics go well beyond the possibilities offered by conventional lithography techniques currently used in the design of microprocessors.

In the longer term, such miniaturisation could allow the development of more efficient LEDs, faster detectors and more compact solar cells. These nanosources of light could also be used in quantum cryptography.

• Research is published in Nature Communications

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