Schematic representation of a nanoantenna formed of two gold nanoparticles linked by a DNA double strand and supplied by a single quantum emitter. Credit: Busson, Rolly, Stout, Bonod, Bidault

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 Université have succeeded in
producing a nanoantenna from short strands of DNA, two gold
nanoparticles and a small fluorescent molecule that captures and emits
light. This easy-to-handle optical antenna is described in an article
published in Nature Communications. This work could in the longer term
lead to the development of more efficient light-emitting diodes, more
compact solar cells or even be used in quantum cryptography.

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-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 Fresnel 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.

Accelerated single photon emission from dye molecule driven nanoantennas assembled on DNA

Source: CNRS