Visible-light-induced photocatalysts Bi2MO6 (M = W Mo) nanocrystals have been successfully synthesized via a new-ultrasonic-assisted method. Laminar structured Bi2WO6 nanoplates with size of ca. 100 nm and Bi2MoO6 nanoparticles with size of ca. 150 nm were prepared via ultrasonic pretreatment followed by calcination at 500 degrees C. The photocatalytic activities of as-prepared Bi2MO6 were about 4-6 times higher than that of the products prepared by traditional solid-state reaction (SSR), which were evaluated by the degradation of RhB dye in water under visible light irradiation (lambda > 400 nm). It was found that ultrasonic irradiation played an important role in the formation of the nanomaterials with a smaller crystal size and larger surface area, which was beneficial to their photocatalytic activities. The present study suggested a promising method, as an effective improvement of traditional SSR-process, for the synthesis of other photocatalysts. (c) 2006 Elsevier B.V. All rights reserved.