Preparation of composite particles with magnetic silica core and fluorescent polymer shell

Dual functions of magnetic and fluorescent properties were created in composite particles that incorporated magnetite (Fe(3)O(4)) nanoparticles in particle cores of silica and fluorescent pyrene in particle shells of polystyrene. The Fe(3)O(4) nanoparticles were prepared with a conventional homogeneous precipitation method and surface modified with a coupling agent of carboxyethylsilanetriol. The silica particles incorporating Fe(3)O(4) nanoparticles were synthesized with a modified Stober method in which the Fe(3)O(4) nanoparticles were added to a system of tetraethylorthosilicate (TEOS)/ammonia/water/ethanol. Then, the magnetite/silica composite particles were coated with the pyrene/polystyrene shell in a soap-free emulsion polymerization, which was conducted in the presence of pyrene in a mixed solvent of water/ethanol. The composite particles prepared in the mixed solvent had both magnetic and fluorescent properties. The fluorescent spectrum of the particles with Fe(3)O(4) was very similar to that without Fe(3)O(4), indicating that the magnetic component within the core particles scarcely interfered with the fluorescent emission from the polymer shell.