August 10, 2009

Scientists observe nanocrystal growth

U.S. scientists report the first real-time, direct observation of single nanocrystal growth in solution revealed much of what we thought we knew is wrong.

The researchers, led by Berkeley National Laboratory Director Paul Alivisatos and Ulrich Dahmen, director of the lab's National Center for Electron Microscopy, said their study showed that while some crystals in solution grow steadily in size via classical nucleation and aggregation, others grow via coalescence events, in which small crystals randomly collide and fuse together into larger crystals.

Coalescence events have been previously observed in flask synthesis of colloidal nanocrystals and has been considered detrimental for achieving monodisperse colloidal nanocrystals, Haimei Zheng, a chemist in Alivisatos' research group, said. In our study, we found that coalescence events are frequently involved in the early stage of nanocrystal growth and yet monodisperse nanocrystals are still formed.

The findings were reported in the journal Science.