Credit: © 2008 Wiley

There are several ways to make stable, monodispersed nanocrystals, but most of these methods form particles that are only soluble in the reaction solution or chemically similar solvents. Researchers at Emory University and Georgia Institute of Technology have now reported a way to synthesize a variety of stable nanocrystals that can dissolve in both polar and nonpolar solvents.

Andrew Smith and Shuming Nie1 combined the nanocrystal precursor metal ion solutions with a solvent and an amphiphilic multidentate polymer — a polymer with multiple binding points, consisting of an oily chain with a charged group on one end — at elevated temperatures. The metal ion precursors bind to the charged part of the polymer and grow into a nanocrystal with an oily coating. The arrangement of the polymer, with the oily part facing outside, allows the nanocrystals to be soluble in any nonpolar solvent. When the nanocrystals are exposed to a polar solvent, any excess polymer in the reaction solution encapsulates the nanocrystals, thus making them soluble. The nanocrystals prepared in this way retain their characteristic optical properties when dissolved in any of the polar and nonpolar solvents.

The universal solubility of these nanocrystals is expected to have applications in biology, catalysis and devices.