Porous niobium oxide (Nb2O5) nanoparticles have been successfully prepared without any surfactant assisting. They were characterized by X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the porous Nb2O5 nanoparticles are polycrystalline, the Brunauer-Emmett-Teller (BET) surface area is 12.09 m(2)/g and the average pore size is 3.4 nm. In addition, spherical and flake-like Nb2O5 samples were obtained and characterized. Possible explanations for the formation of Nb2O5 nanocrystals with different morphologies are discussed. (C) 2007 Elsevier Ltd. All rights reserved.