A solution chemistry method for transforming polycrystalline Ag spherical particles into single crystalline triangular Ag nanoplates has been developed. The synthesis consists of three consecutive steps: (1) the synthesis of Ag nanospheres by NaBH4 reduction of AgNO3 in the presence of sodium citrate: (2) the conversion of citrate-stabilized Ag nanospheres into SDS (sodium dodecyl sulfate)- stabilized Ag nanospheres, and (3) the aging of the SDS-stabilized Ag nanospheres in 0.01 M NaCl solution. Our study indicates that the shape evolved through a Ag nanoparticle dissolution- and re-deposition process; and demonstrated the critical role of SDS in the process: SDS regulates the dynamics in the dissolved O-2/Cl- etching of the Ag nanospheres and the reduction of the released Ag+ by citrate ions in the same solution. SDS also functions as a shape-directing agent to assimilate the Ag-0 atoms into single crystalline triangular Ag nanoplates. A model for the shape conversion is also proposed which provides the clue for the synthesis of anisotropic Ag nanoparticles with other shapes (rods, wires, cubes, etc.). (c) 2007 Elsevier Inc. All rights reserved.