In this paper, we report on the synthesis of size-dependent blue luminescent US nanocrystals by using a new nonhydrolytic single-source molecular method. The size of the synthesized US nanocrystals could be easily controlled by adjusting the ratio of reaction sources under inert atmosphere. The studies on the optical properties reveal an obvious size-dependent photoluminescence characteristic of the synthesized nanocrystals. (C) 2007 Elsevier Ltd. All rights reserved.