alpha-Bi2Mo3O12 nanoparticles were synthesized with water-in-oil (w/o) microemulsion consisted of water/cetyltrimethylamonium bromide, n-butanol/isooctane. By tuning the Bi/Mo ratio and pH value, controlled formation of alpha-Bi2Mo3O12 can be achieved. Low pH and high concentration of molybdenum was lead to the formation of alpha-Bi2Mo3O12. The pure phase of alpha-Bi2Mo3O12 can be prepared by calcination at 723 K. The resulted material was analyzed with different physicochemical methods which showed nearly spherical and uniform nanoparticles with size of about 100 nm. (C) 2012 Elsevier B.V. All rights reserved.