Shape Evolution and Control of Wurtzite CdSe Nanocrystals through a Facile One-Pot Strategy

The synthesis of one-dimensional (1D) CdSe nanocrystals (NCs) with hexagonal wurtzite (WZ) structures such as nanorods has been well developed over the past years. However, the shape modulation of WZ-CdSe with two-dimensional (2D)/three-dimensional (3D) morphologies remains challenging because of its intrinsic hexagonal unit and the involved ligands selectively binding to specific crystal facets. Here, we present a facile and general one-pot approach for the shape control of WZ-CdSe NCs without using pre-existing seeds. Interestingly, the low supersaturation in a drip injection mode enabled the control and formation of various shapes including the nanorods, long nanowires, and hexagonal platelets, compared to the traditional one-time injection. Such shape evolutions could be conveniently tuned by the parameters such as the temperature, growth time, and injection rates. The underlying growth mechanisms for the morphological evolution and control were discussed in the context of kinetic/thermodynamic factors. Our studies provide a fundamental understanding of shape modulations in polytypic compound NCs, offering great opportunities to tune the shape-size-property relationship for optoelectronic applications.