Low-Temperature Synthesis of Oil-Soluble CdSe, CdS, and CdSe/CdS Core−Shell Nanocrystals by Using Various Water-Soluble Anion Precursors

Abstract

Colloidal CdSe and CdS quantum dots were synthesized at low temperatures (60−90 °C) by a two-phase approach at a toluene−water interface. Oil-soluble cadmium myristate (Cd-MA) was used as cadmium source, and water-soluble Na2S, thiourea, NaHSe, Na2SeSO3, and selenourea were used as sulfur and selenium sources, respectively. When a cadmium precursor in toluene and a selenium precursor in water were mixed, CdSe nanocrystals were achieved at a toluene−water interface in the range of 1.2−3.2 nm in diameter. Moreover, we also synthesized highly luminescent CdSe/CdS core−shell quantum dots by a two-phase approach using poorly reactive thiourea as sulfur source in an autoclave at 140 °C or under normal pressure at 90 °C. Colloidal solutions of CdSe/CdS core−shell nanocrystals exhibit a photoluminescence quantum yield (PL QY) up to 42% relative to coumarin 6 at room temperature.