In order to achieve the highly efficient Tc-99m production from (MoO3)-Mo-100 by the Mo-100(n, 2n)Mo-99 reaction, we have developed a new protocol to synthesize nano-sized Mo particles, of which the size was controlled by the inner space of the liposomes. Calcium and molybdate ions were encapsulated into similar to 100 nm size liposomes. The liposome suspensions were then mixed and heated to promote the membrane fusion. As a result, the insoluble CaMoO4 nanoparticles precipitated inside the liposomes. The median particle diameter of 168 nm and average diameter of 169 +/- 56 nm (n = 109) were obtained from an SEM image, and the particles have a powellite-structure. The formation process of the particles was then examined. The formation of nano-sized CaMoO4 was observed by the high resolution TEM image and TEM image of negative-stained liposome. At the room temperature, the fusion of liposome did not occur significantly. These results suggest that nanocrystals of the CaMoO4 were likely formed in the liposomes because of the liposome fusion and aggregated during the drying processes of reaction solution. (C) 2018 Elsevier Inc. All rights reserved.