|According to a research study published in Nature Communications, University of Melbourne and the National Institute of Standards and Technology in the US found that pairs of closely spaced nano particles made of gold can act as “optical antennas”.
These antennae concentrate the light shining on them into tiny regions located in the gap between the nano particles. The study was led by Professor Ken Crozier, a professor of Physics and Electronic Engineering at the University of Melbourne. Scientists have figured out the optimal gap needed between two gold nanoparticles to turn them into optical antennae. This geometry now determines the efficiency nanoparticle uses as a chemical sensor in sensing minute quantities of chemicals in air and water. The researchers coated the nanoparticles with molecules, and performed spectroscopy on them with a laser-based microscope. They measured the signal given off by the molecules as a function of the gap width. They found that as the gap width decreased, the signal increased until the gap width reached the atomic scale, after which the signal began to decrease—giving us the gap width that optimizes the signal from the molecules.