Ashley N. Rice, firstname.lastname@example.org PARIS – A bio-inspired light nanoantenna comprising two gold nanoparticles, short DNA strands and a tiny fluorescent molecule that can capture and emit light could pave the way to the development of highly efficient LEDs and ultracompact solar cells and could even find use in quantum cryptography. Light is a wave, so it should be possible to develop optical antennas that can amplify light signals in the same way that televisions and mobile phones capture radio waves. But because light oscillates 1 million times faster than radio waves, nanoscale objects are needed to capture the very fast light waves. Therefore, the optical counterpart of a basic antenna (of dipole type) is a quantum emitter surrounded by two nanoparticles 1000 times smaller than a human hair. Scientists at CNRS and Aix Marseille Université, also in France, have developed a simple, user-friendly optical antenna by embedding a fluorescent organic coolant and 36-nm-diameter gold particles into short artificial DNA strands. The fluorescent molecules behave like a quantum source, providing photons to the antenna, while the interaction between the light and the emitter is amplified by the gold nanoparticles. They produced several billion replicas of these particle pairs (in solution) in parallel via control of the fluorescent molecule positions with nanometric accuracy, thanks to the DNA backbone. Schematic representation of a nanoantenna formed of two gold nanoparticles linked by a DNA double strand and supplied by a single quantum emitter. Courtesy of ©Busson, Rolly, Stout, Bonod, Bidault. “I believe our dimers made of DNA will find applications in the sensitive monitoring of DNA or RNA which are smaller than proteins and more difficult to measure,” Sébastien Bidault, a CNRS researcher at the Institut Langevin’s Optical Antennas and Sensing group, told BioPhotonics. “The interesting thing about our technique is that the antennas are purified in solution and therefore very easy to handle and graft on different types of substrates, while, with lithography, the antennas are fixed on a given substrate.” And, because their technology does not require cleanroom equipment or high-temperature processes, it is cost-effective. These characteristics extend beyond the possibilities offered by existing lithography techniques used to design microprocessors. “Optical antennas could have wide applications in systems where a small piece of material absorbs or emits light: sensing, thin solar cells or detectors,” Bidault said. “For a detector, an optical antenna will allow the photodiode to be smaller (faster detector) and only interact with specific light polarizations or colors. For a sensor, the antenna allows strong interaction of light with a smaller piece of matter, making the system more sensitive.” Although it will take about five to 10 years for sensors to be developed, Bidault is confident that the technology will be useful for many applications. “Our specific bio-templated systems will mostly have a strong impact in biosensing, while detectors or solar cells will rely on lithography more than self-assembly,” he said. “However, our specific study should have a general impact on the field of optical antennas as it describes the simplest working antenna geometry.” The study appeared in Nature Communications (doi: 10.1038/ncomms1964).