Silver quantum dots (QDs) embedded silica/PAAc hybrid nanoparticles were prepared by copolymerization of acrylic acid (AAc) onto gamma Methacryloxypropyltrimethoxysilane (NIPS) modified silica nanoparticles followed by reduction of the immobilized Ag+ ions to metallic Ag. The prepared hybrid nanoparticles were characterized using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The hybrid nanoparticles dispersed well in aqueous media and showed effective bactericidal activities. The results suggest that the hybrid nanoparticles have potential application as a water-soluble agent in many fields. (c) 2007 Elsevier B.V. All rights reserved.