Alkali metal carboxylates as non-polar-facet ligands for the synthesis of colloidal quantum dots

Abstract

The impact of alkali metal carboxylates on the synthesis of colloidal quantum dots (CQDs) was investigated. Through a ligand removal experiment, we demonstrated that due to its high hydrophilic nature, sodium oleate dispersed in n-octadecene (ODE) with the formation of micelles with the help of other polar molecules, which resulted in reduced concentration of oleic acid and cadmium oleate both in the solution and on the surface of CQDs. These effects allow for control the size of CdSe CQDs in a wide range when synthesizing them by solely changing the amount of sodium oleate, under either cation-rich or anion-rich conditions. Additionally, enhanced ligand dynamics promote morphology transformation and suppress size deviation caused by different morphologies’ existence in CQDs synthesis. Alkali metal oleate not only stabilized anion-rich CdSe CQDs but also results in highly crystallized wurtzite structure of CdSe CQDs when synthesizing them with excess anions. Furthermore, under anion-rich synthetic condition, anisotropic growth can be realized, leading to nanorods and nanoplatelets based on the alkali metal ions used. Given their outstanding effects and widely applicable synthetic conditions, alkali metal carboxylates offer new possibilities for designing efficient methods for synthesizing CQDs.