From Nearly Monodispersed toward Truly Monosized Nanocrystals: Chemical Potential Well during Growth of Nanocrystals

An approach toward truly monosized nanocrystals based on a mechanism of the chemical potential well during crystal growth is presented. Nanocrystals are first grown to sizes corresponding to stable crystallographic configurations in a lower energy state, for example, the magic closed-shell structure. Second, the nanocrystals are treated by a quenching process to suspend the crystal growth, which can place the nanocrystals in the chemical potential well generated by the stable magic closed-shell structure. The last isothermal annealing provides a thermodynamic regime for the nanocrystals to adjust their sizes and morphology to the magic closed-shell structure, which finally narrows the size distribution. By this approach, size deviation of CdSe nanocrystals with 3.6 nm diameter is reduced about 45%. The final size deviation is limited by random temperature fluctuations from a heating source.