The American Vacuum Society’s (AVS) Plasma Science and Technology Division gave Hoffenberg the award for his work advancing the process to make these metal nanoparticles more sustainably and with higher purity. The 69^th AVS Symposium was held in Portland, Ore. in November.

While metal nanoparticles are increasingly important for high-tech applications and more sustainable industrial processes, they are difficult to produce at an industrial scale. The goal is to precipitate trillions of perfectly consistent iron particles, each smaller than a single SARS-CoV-2 virus. Conventional methods involve working with the metal salts in a liquid solution, which requires solvents and yields impure nanoparticles. Producing metal nanoparticles from the vapor can yield very consistent particle sizes and generates much less waste, according to Hoffenberg. But that process requires overcoming an energy barrier that is not well understood.

Hoffenberg, working with his co-advisers David Graves, professor of chemical and biological engineering, and Igor Kaganovich, a principal research physicist at the Princeton Plasma Physics Laboratory, identified a key factor in understanding the formation of iron nanoparticles from the vapor. As the vapor molecules zip around, they begin to bump into one another and cluster. But that clustering is not entirely random. Through atomic-resolution simulations, Hoffenberg showed that certain special clusters, called magic number clusters, complicate the thermodynamics in ways scientists had not previously appreciated. Understanding these complications is essential to produce consistent, pure and sustainable metal nanoparticles at scale.

Hoffenberg is a graduate student in chemical and biological engineering at Princeton and a Plasma Science and Technology Graduate Fellow. He earned his bachelor’s and master’s degrees from Johns Hopkins University.