Super nanoparticles assemble

Chemists from the University of Florida have developed a technique for growing new materials from nanorods.

The study marks a breakthrough in the field, demonstrating how thermodynamic forces can manipulate nanoparticle growth into superparticles with exceptional precision. The research is described in Science.

Charles Cao, professor of chemistry at UF said: “Like putting oxygen atoms and hydrogen atoms together in a two-to-one ratio – the synergy gives you water, something with properties completely different from the ingredients themselves.”

The technique for making single nanorods is well established, but until now, it was unknown how to assemble them in a controlled manner. The researchers bathed individual fluorescent nanorods in a series of liquid compounds which reacted with hydrophobic regions on the rods, pushing them together to create a larger, more complex particle. They found that two different treatments yielded two different products.

“One treatment gave us something completely unexpected- these superparticles with a really sophisticated structure unlike anything we’ve seen before,” said Tie Wang, lead author of the study.

The other treatment resulted in a less complex structure that the researchers were able to grow into a small square of polarized film (about a quarter the size of a postage stamp).  The film could one day be used to increase the efficiency in polarized LED television and computer screens by up to 50 per cent.

“I don’t think anyone has been able to get them to self-assemble into superparticles like this before. They have achieved a tour-de-force in precision and control,” said Dmitri Talapin, an associate professor of chemistry at the University of Chicago.