Single quantum dots in silica spheres by microemulsion synthesis

A new method for the preparation of single quantum dots (QDs) in silica spheres has been developed. The work involves an oil-in-water microemulsion system with cyclohexane as the "oil" phase and Synperonic NP-5 as the surfactant. Reaction parameters such as reactant concentrations, time, and temperature were studied. The method resulted in smooth silica nanoparticles of good monodispersity and high luminescence with single QDs in the center. Elucidating the coating mechanism was attempted. Possible mechanisms include a phase transfer by ligand exchange and a surfactant-supported mechanism. In contrast to sol-gel based methods, this is a straightforward, simple "one-pot" synthesis for such particles. The resulting nanoparticles could be used for further silica growth and assembly of photonic structures, for biolabeling, or for other applications.