The preparation and characterization of silver nanocrystals by chemical reduction of silver ions in the presence of aniline using hydrazine monohydrate (N2H4.H2O) or sodium citrate as the reducing agent are described. A high yield of aniline-derivatized hexagonal silver nanoparticles is obtained by the reduction of Ag2SO4 with N2H4.H2O. An alternative strategy is the reduction of Ag+ by citrate in the presence of aniline, by which the size and morphology of the Ag nanocrystals can be controlled to a certain degree by changing the concentration ratio of aniline to Ag+. It is believed that the amount of aniline added in the starting solutions for the preparation influences the morphology of the Ag nanoparticles. In addition, the long Ag nanorods with a high mean aspect ratio are prepared in the presence of aniline at a low concentration or o-anisidine. (C) 2003 Elsevier Science (USA). All rights reserved.