Evolution of Aqueous-Phase CdTe Magic-Size Clusters from Their Precursor Compounds.

Abstract

Aqueous-phase semiconductor CdTe magic-size clusters (MSCs) have not been reported. Here, we report the first synthesis of aqueous-phase CdTe MSCs and propose that they evolve from their nonabsorbing precursor compounds (PCs). CdCl2 and Na2TeO3 are used as the respective Cd and Te sources, with l-cysteine as a ligand and NaBH4 as a reductant. When a 5 °C reaction mixture is dispersed in butylamine (BTA), CdTe MSCs evolve. We argue that the self-assembly of the Cd and Te precursors followed by the formation of the Cd-Te covalent bond inside each assembly results in one CdTe PC, which quasi-isomerizes to one CdTe MSC in the presence of BTA. At higher temperatures such as 25 °C, the PCs fragmentize, assisting the nucleation and growth of CdTe quantum dots. We introduce a novel synthetic approach to aqueous-phase CdTe PCs, which transform to CdTe MSCs in the presence of primary amines.