A novel synthesis of CdSe nanocrystals

A novel synthesis of CdSe nanocrystals is presented, which is based on the room temperature reaction between selenourea and cadmium nitrate triggered by the fast injection of a base. A long-chain thiol was employed for terminating the aggregation of the species created by the reaction, obtaining monodispersed particles that were heat-treated in pyridine at 145 degreesC to grow larger particles. TEM observations and optical absorption spectra indicate that the particle size depends on the synthesis parameters, while XRD shows the formation of CdSe nanocrystals with hexagonal crystal system. The analysis of the optical absorption spectra allows proposing a first, simple model for the formation and growth of the nanocrystals. The reaction mechanism seems to proceed through the formation of a cadmium-selenourea intermediate species.