"The content of high-aspect-ratio gold nanorods produced by today's best synthetic methods is only about 20 percent," said Rice University Assistant Professor Eugene Zubarev, who is leading the research.

"A nanoparticle's shape plays a crucial role in determining many of its physical and chemical properties, so when four out of five particles in a batch are the wrong shape, it's a tremendous impediment to practical applications and commercialization."

Zubarev and graduate student Bishnu Khanal's new purification method filters more than 99 percent of impurities from gold nanorods.

The nanorods studied by Zubarev and Khanal are about 25 nanometers in diameter and about 250 nanometers long. In comparison, a single gold atom is only about one third of a nanometer in diameter. That, the researchers explained, means the cross-section of each nanorod is made of just a few thousand gold atoms.

The research, funded by the National Science Foundation, appears in the Sept. 25 issue of the Journal of the American Chemical Society.