Kinetically Driven Cadmium Chalcogenide Nanorod Growth Fed by Local Cluster Aggregates

Abstract

The process of symmetry breaking that leads to the formation of anisotropic, colloidal semiconductor nanocrystals is an important issue for understanding the physical mechanism of nucleation and growth. One-dimensional growth of nanorods is assumed to occur under reaction-limited control at a high concentration of monomer, which preferentially reacts at the crystal facet that has the highest energy and least passivation by surface ligands. In this study, it is shown that instead of assuming a homogeneous distribution of monomer in the reaction solution, the seeded growth of CdS nanorods on CdSe particles is driven by the formation of one-dimensional reaction intermediates that act as local monomer reservoirs. These result in heterogeneously distributed hotspots of the nucleating species that guarantees fast deposition and one-dimensional growth of the nanorod exclusively in one direction. Thus, performing anisotropic particle growth reactions under conditions that favor formation of transient, metastable intermediates lead to particles with a higher aspect ratio and better mechanistic reaction control.