New Nanoscale Belts Display Remarkable Plasmonic Traits

A group of physicists and nanotechnologists at the Rice University announces the discovery of a remarkable new material, which comes in the shape of gold nanorods. The tiny bars can be arranged as a belt, providing investigators with new and exciting ways of manipulating light.

There are countless potential applications for these new materials, the research team says. They could for example be used to create the next generation of highly advanced sensors, or to create new and improved medical devices at a nanoscale.

They have the most impact when they are arranged in nanobelts, as Rice expert Jason Hafner calls them. The researcher holds an appointment as an associate professor of physics and astronomy and of chemistry at the university.

[ADMARK=]He and his research group published additional details of the new materials in this week's online issue of the esteemed American Chemical Society journal Nano Letters. The scientist say that the nanoribbons can successfully be used in combination with gold nanorods and nanoshells.

When an optical manipulation device is constructed out of such materials, researchers gain the ability to tune its properties to such an extent that only light coming in at a particular wavelength is strongly absorbed. Additionally, the device can be made to re-emit the light in a single, specific direction.

The reason why this happens is because the new material contains surface plasmons, which are quanta of plasma oscillation that are created when “free electrons in a metal or doped dielectric interact strongly with light,” according to a Rice press release.

Whenever they are subjected to a light source, the plasmons begin a ripple-like oscillation, which then goes on to re-emit the stored energy as either light or heat. When researchers want to re-emit light, they can easily construct the manipulation device in such a way that the light beam goes in a certain direction.

“People have studied electrons moving the long way in these kinds of materials, but when they get too long the resonances detune out of the visible and the peaks become so broad that there's no sharp resonance anymore,” Hafner explains.

“We're going across the nanobelt, so length doesn't matter. The nanobelt could be a meter long and still show sharp plasmon resonance,” he goes on to say. Graduate students Lindsey Anderson, Courtney Payne and Yu-Rong Zhen were all involved in the study as coauthors.

Another coauthor was Rice professor of physics and astronomy and in electrical and computer engineering, Peter Nordlander. Funds for the research were provided by the US National Science Foundation (NSF) and the Robert A. Welch Foundation.