ZnS:Ag nanocrystals with Ag doping concentrations of 1 at% was synthesized by using 3-mercaptopropionicacid (MPA) as stabilizer. A ZnS shell was formed on surface of the ZnS:Ag nanocrystals by the decomposition of Zn-MPA complex under microwave irradiation. The new ZnS shell passivated the nanocrystal surface and resulted in a significant enhancement of the photoluminescent quantum yield and photostability of the nanocrystals. Under optimum reaction conditions, quantum yield of the ZnS:Ag nanocrystals increased from 2.5 to 10.2% after the shell growth. (c) 2005 Elsevier B.V. All rights reserved.