Assembly of CdSe nanoparticles into microspheres by a liquid droplet emulsion process

Abstract

Semiconductor CdSe nanoparticles assemble into micrometer-sized spheres ranging from <1 to 50 μm when precipitated from hexane by methanol under conditions of stirring. Both solid and hollow spheres may be formed and the type of sphere can be controlled by the solvent concentration. In addition, stir rate and nanoparticle concentration influence sphere size. Redissolving the spheres back into a nonpolar solvent gives nanoparticles with their original absorption and photoluminescence properties. Precipitating nanoparticles from other nonpolar solvents such as toluene and chloroform does not result in sphere formation.