Slow colloidal growth of PbSe nanocrystals for facile morphology control

Abstract

We report growth of colloidal PbSe nanosheets via simple control of reaction para-meters. The approach involves slow injection of precursors with excess amounts of oleic acid. Retarded growth, due to both the slow supply of precursors and the surfeit of oleic acid, causes attachment of PbSe nanocrystals (NCs) through most reactive {110} planes into two-dimensional geometry. On the other hand, such attachment processes can be pre-vented by impurities, e.g., Cd chalcogenide (CdSe or CdS) NCs dispersed in chloroform. For instance, the slow injection of Pb and Se precursors into a reaction solution containing Cd chalcogenide NCs results in the growth of spherical PbSe NCs, as the Cd chalcogenide NCs hinder the PbSe nuclei from merging via {110} planes. Compared to conventional rapid-injection methods, PbSe NCs grow very slowly, which enables fine control of NC size. Cd chalcogenide clusters bound on the surface of PbSe NCs are responsible for both impeding nanosheet formation and slowing PbSe NC growth.