Microwave-Assisted Synthesis and Assembly of Hyperbranched Supra Quantum Dot CdE (E = S, Se, Te) Nanocrystals

Abstract

Dichalcogenides are alternatives for synthesis of nanometal chalcogenides, which provides a variety of precursors with different reactivities. Using disulfide, diselenide, and ditelluride and their mixtures, metal chalcogenide nanocrystals (NCs) in which structures vary from spherical NCs with diameters of ∼4 nm to large, hyperbranched NCs with diameters approaching 200 nm are synthesized. Study of the effects of the reaction temperature, concentration and ratio of reactants shows that hyperbranched supra quantum dots (HSQDs) form in three steps: nucleation, aggregation, and kinetically controlled growth. By tuning the concentration of precursors and reaction temperature, both aggregation and growth can be modulated and tetrapod NCs with arms of tunable length and thickness can be prepared. The more reactive precursor forms small NCs, which work as a platform for formation of the arms from the less reactive precursor, providing controlled growth on the more reactive facets. By controlling the precursor ratio, the composition of the HSQDs can be controlled.