Shape and phase control of colloidal ZnSe nanocrystals

Shape- and phase-controlled ZnSe nanocrystals are synthesized in hot mixtures of long-chain alkylamines and alkylphosphines. The variation in the rate of precursor addition, down to low and controlled levels, allows the nucleation, as well as the growth of the nanocrystals, to switch between the wurtzite and the zinc blend structures. Such a level of control leads to a variety of shapes, from spheres to rods to three-dimensional structures formed by rod sections interconnected through branching points. The temperature- and time-dependence of the chemical potentials for the monomer species in solution are the most relevant parameters involved in the growth mechanism.