Syringe pump-assisted synthesis of water-soluble cubic structure Ag2Se nanocrystals by a cation-exchange reaction

Water-soluble cubic structure Ag2Se (alpha-Ag2Se) nanocrystals smaller than 5 nm can be obtained by cation-exchange reaction at room ternperature, using water-dispersed ZnSe nanocrystals as precursors, which is achieved by controlling the injection speed of AgNO3 solutions via a syringe pump in the presence of the stabilizer of trisodium citrate. Meanwhile, the thermal stability of the product Ag2Se nanocrystals is Studied. The results show that the mean sizes and shapes of the precursor ZnSe and product Ag2Se nanocrystals are similar, and Se anion sublattices between them are topotaxial. In addition, no phase transition is observed for the product Ag2Se (cubic structure) nanocrystals below 180 degrees C. The present synthetic method based on cation-exchange reactions can also be applied to the syntheses of PbSe and CuSe nanocrystals. (c) 2008 Elsevier Inc. All rights reserved.