Effect of ligands and growth temperature on the growth kinetics and crystal size of colloidal CdSe nanocrystals

Using trioctylphosphine (TOP) as the ligand of the Se source and oleic acid (OA) as the ligand of the Cd precursor, high-quality CdSe nanocrystals were synthesized in the noncoordinating solvent octadecene (ODE) with the standard airless techniques. The initial TOP : Se, OA : Cd and Cd : Se molar ratios are determinative factors for the growth kinetics, crystal size and size distribution of the as-synthesized CdSe nanocrystals. A large excess of OA, TOP and Se, were found necessary to achieve a narrow absorption profile. By simply changing the amount of the two ligands or the growth temperature, we are able to not only control the balance of the initial nucleation and the subsequent growth of CdSe nanocrystals, but also tune the crystal size and size distribution.