Gold nanocolloids with the controlled diameter ranging from 5.2 to 10.7 nm were in situ prepared by reduction of gold chloride trihydrate with sodium borohydride as reductant via the interaction between the gold naocolloids and the functional groups on the surface of polymer microsphere-stabilizer. The nature of such interaction was studied in detail by X-ray photoelectron spectroscopy (XPS). The effect of the functional groups on the catalytic activity of the gold nanocolloids was preliminarily investigated with the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride as reductant. (c) 2007 Elsevier Inc. All rights reserved.