Synthesis of ultrafine, multicomponent particles using phospholipid vesicles

This paper reports that because of their unique properties of self-assembly and selective ion permeability across the lipid bilayers, phospholipid vesicles were used as reaction vessels for the synthesis of ultrafine, multicomponent ceramic particles containing Y, Ba, Cu, and Ag. Chemical inhomogeneities in the system were limited to the individual particle size (< 50 nm), which was a considerable improvement over particles prepared using bulk precipitation routes. The consistent barium deficiency was a serious problem that arose when attempting to control the stoichiometry of the multicomponent system. The authors experimental evidence suggests that chemical interactions between the barium cations and the vesicle-forming phospholipid may inhibit the precipitation of barium salts. In a parallel study, we performed consolidation studies on vesicle-precipitated Ag2O particles before and after the removal of the phospholipid molecules. Particle packing was greatly improved in the surfactant coated particles. This demonstrates the multifunctionality of this biomimetic system in which the vesicle membrane simultaneously acts as: a reaction cell for particle precipitation, an ion selective membrane that affects precipitation kinetics, a barrier to prevent spontaneous agglomeration of the ultrafine particles, and a lubricant dispersant that facilitates particle rearrangement during consolidation