Aqueous synthesis of CdSe and CdSe/CdS quantum dots with controllable introduction of Se and S sources

A new and convenient route is developed to synthesize CdSe and core–shell CdSe/CdS quantum dots (QDs) in aqueous solution. The gaseous precursors, H2Se and H2S, generated on-line by reducing SeO32− with NaBH4 and the reaction between Na2S and diluted H2SO4, are used to form high-quality CdSe and CdSe/CdS QDs, respectively. The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield (3% and 20%) and narrow full-width-at-half-maximum (43 nm and 38 nm). The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals, and can be readily extended to the large-scale aqueous synthesis of QDs.