Based on a phosphine-free route and the nucleation-doping strategy, Mn-doped CdSe nanocrystals (d-dots) with zinc-blende structure were successfully synthesized by facilely controlling the reaction temperature. The evolution of the UV-vis and PL spectra exhibited the distinctly different results for the nanocrystals synthesized at 160, 180 and 200 degrees C. The products were Mn:CdSe d-dots at 160 degrees C, but undoped CdSe nanocrystals at 200 degrees C. We proposed a possible mechanism that Mn ions were rapidly ejected from the host CdSe lattice if the doping temperature was too high. Combining with TEM and spectral results of the resulting nanocrystals, the mechanism was further confirmed powerfully by the annealing for the presynthesized and purified Mn: CdSe nanocrystals. (C) 2012 Elsevier B.V. All rights reserved.