If radio antennas amplify the signals from our mobile phones and televisions, the same principle can be applied to light. A major innovation!
For the first time CNRS andAix Marseille University have succeeded in making a nano-antenna from short strands of DNA, two gold nanoparticles and a small fluorescent molecule that captures and emits light.
This optical antenna, easy to handle and control, is described in an article published in Nature Communications of July 17, 2012. In the longer term, this work could lead to the development of more efficient light-emitting diodes, more compact solar cells or be used in quantum cryptography.
Since light is a wave, it should be possible to develop optical antennas capable of amplifying the light signal in the same way that the antennas of our televisions or cell phones pick up radio waves. Since light oscillates a million times faster than radio waves, it takes extremely small objects in the nanometre (nm) range to pick up these very fast light waves. This is why the optical equivalent of an elementary antenna (of the dipole type) is a quantum transmitter surrounded by two particles a thousand times smaller than a human hair.
For the first time, researchers from the Langevin and Fresnel Institutes1 have developed such a bio-inspired nano-antenna for light, simple and easy to handle. On short synthetic DNA strands (10 to 15 nm long), they grafted gold particles (36 nm in diameter) and a fluorescent organic dye. The fluorescent molecule acts as a quantum source that feeds photons to the antenna, while the gold nanoparticles amplify the interaction between the emitter and the light.
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In parallel, scientists have produced several billion copies of these pairs of particles (in solution) by controlling the position of the fluorescent molecule to the nanometre level, thanks to the DNA backbone. These characteristics go far beyond the possibilities offered by the classical lithography techniques currently used in the design of microprocessors.
In the longer term, such miniaturization could allow the development of more efficient light-emitting diodes and more compact sensors. These nano light sources could also be used in quantum cryptography.
(Source: CNRS / July 2012)