Nanocup discovery an 'accident'

Nikolay Mirin suddenly realized the nanocups he was throwing away could be useful. It led the Rice graduate student and his mentor, Professor Naomi Halas, to pursue research that could light the way toward high-powered optics, ultra-efficient solar cells and even cloaking devices.

Mirin and Halas have invented the first 3-D nano-antenna, a substance with the ability to bend light.

Nanocups are what they sound like: tiny cup-shaped particles. What makes them special is their ability to bend light. Halas and Mirin have found a way to make material incorporating nanocups that can bend it in a specific direction. They authored a paper published in Nano Letters that details how they isolated nanocups to create light-bending nanoparticles.

“The truth is, a lot of exciting science actually does fall in your lap by accident,” said Halas, Rice’s Stanley C. Moore Professor in Electrical and Computer Engineering and professor of chemistry and biomedical engineering. “The big breakthrough was being able to lift the nanocups off a structure and preserve their orientation. Then we could look specifically at the properties of these oriented nanostructures.”

In earlier research, Mirin had tried to make a thin gold film with nano-sized holes, when it occurred to him the knocked-out bits were worth investigating. Previous work on gold nanocups gave researchers a sense of their properties, but until Mirin’s revelation, nobody had found a way to lock ensembles of isolated nanocups while preserving their matching orientation.

To make light-bending material, the Rice researchers spread polystyrene or latex colloidal particles on a glass slide, evaporate a layer of gold at various angles on top of the particles, deposit a layer of elastomer on top and then, after curing, lift the slab from the substrate with the oriented nanocups embedded.

Mirin had manufactured a metamaterial, a substance that gets its properties from its structure and not its composition. Halas and Mirin found their new material particularly adept at capturing light from any direction and focusing it in one direction.

Redirecting scattered light means none of it bounces off the metamaterial back into the eye of an observer. That essentially makes the material invisible. “Ideally, one should see exactly what is behind an object,” said Mirin. A native of Russia, he came to Houston seven years ago after receiving his bachelor’s degree from Lomonosov Moscow State University.

Mike Williams, Rice News