An effective trioctyl phos phi ne-trioctyl phosphine oxide-hexaclecylamine (TOP-TOPO-HDA) route was used to investigate the crystallization kinetics of CdSe nanocrystals. A new diffusion-controlled growth model was founded to simulate the CdSe nanocrystals (NCs) growth process. It was found that the population density of the CdSe NCs in solution remained constant during the early stage of the growth before ripening. About 28% of the Cd was consumed during nucleation. The concentration of Cd decreased after nucleation and the Cd monomer was almost exhausted after 300 s growth. The diffusion coefficient was found to be similar to 150 nm(2) /s. The apparent critical nucleus was estimated to be 1.64 nm by extrapolation of the modeling curve. (c) 2008 Elsevier B.V. All rights reserved.