Formation of multilayer composite particles comprised of silica/vesicle/silica particles by heterocoagulation

The multilayer composite particles comprised of silica/PC (phosphatidylchol ine) vesicle/silica particles have been prepared by using the heterocoagula tion technique. The formation process is as follows: at first, large silica particles (2r = 1.5 mum) and PC vesicles (2r = 0.2 mum) were mixed at a de finite particle number ratio in 10(-4) M LaCl3 aqueous solution. The PC ves icle/silica composites were spontaneously formed by mutual electrostatic at traction. After removal of the excess PC vesicles from the system, the smal l silica particle (2r = 0.5 mum) suspension was added into the PC vesicle/s ilica composite dispersions to form the multilayer composite particles comp osed of small silica, PC vesicle, and core silica particles. The formation of multilayer composite particles was confirmed by the electrophoresis, dyn amic light scattering (DLS), and adsorption measurements of PC molecules. F inally, the existence of multilayers was confirmed directly using a special optical microscope.