Hollow Ag spheres with tunable sizes in a range of 74-167 nm were fabricated using a two-step synthesis including the creation of solid Ag2O particles and the reduction of these Ag2O particles in situ. Ag nanoclusters were generated by the reduction of Ag2O. Ag2O particles were as scaffolds to create Ag spheres. Namely, the reduction of Ag2O occurred firstly on the surface of the Ag2O particles. The H-2 was generated due to the hydrolysis of borohydride ions. The diffusion of H-2 and the further reduction of Ag2O particles resulted in the formation of a hollow part within Ag spheres. The average diameter of the hollow Ag spheres can be adjusted by varying the concentration of NaOH and NaBH4, the kinds of solvent, and reaction temperature. (c) 2013 Elsevier Ltd. All rights reserved.