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Posted: Jul 27, 2012
Bio-inspired nanoantennas for light emission
(Nanowerk News) Just as radio antennas amplify the signals of our mobile phones and televisions, the same principle can apply to light. For the first time, researchers from CNRS and Aix Marseille UniversitÚ have succeeded in producing a nanoantenna from short strands of DNA, two gold nanoparticles and a small fluorescent molecule that captures and emits light.
Schematic representation of a nanoantenna formed of two gold nanoparticles linked by a DNA double strand and supplied by a single quantum emitter.
Since light is a wave, it should be possible to develop optical antennas capable of amplifying light signals in the same way as our televisions and mobile phones capture radio waves. However, since light oscillates a million times faster than radio waves, extremely small nanometer (nm) sized objects are needed to capture such very rapid light waves. Consequently, the optical equivalent of an elementary antenna (of dipole type) is a quantum emitter surrounded by two particles a thousand times smaller than a human hair.
For the first time, researchers from the Langevin and Fresnel1 Institutes have developed such a bio-inspired light nanoantenna, which is simple and easy to handle. They grafted gold particles (36 nm diameter) and a fluorescent organic colorant onto short synthetic DNA strands (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 produced 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 miniaturization 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.
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