Ligand-mediated control of dislocation dynamics and resulting particle morphology of GdOCl nanocrystals.

While much progress has been achieved in the shape-controlled synthesis of nanocrystals, chemical strategies to define morphology remain primarily empirical. Here, a mechanistic study of the influence of different coordinating ligands on the kinetics and thermodynamics of crystal growth during the preparation of GdOCl by the non-hydrolytic condensation of GdCl3 and Gd(O (i) Pr)3 is reported. Growth using oleylamine, octadecylamine, trioctylamine, and didodecylamine yields 2D nanosheets with approximately square cross sections, whereas growth in trioctylphosphine oxide yields larger and thicker platelets. The nanostructures are characterized by the presence of spiral growth patterns and dislocations. Apart from preferential binding to specific crystallographic facets, the coordinating ligands are suggested to control the extent of supersaturation, thereby facilitating and tuning dislocation-mediated growth. Upon depletion of monomers, thermodynamic surface energy considerations become of paramount importance and the nanocrystals are reshaped via mass transport from edges to sides yielding their eventual equilibrium shapes. The mechanisms developed here are thought to be broadly generalizable to the ligand-directed growth of nanomaterials.