One pot soap-free synthesis of fluorescent, magnetic composite particles with high monodispersity

Composite particles dually functionalized with fluorescent and magnetic properties were prepared in a one pot synthesis in soap-free emulsion polymerization combined with heterocoagulation. Styrene monomer dissolving a fluorescent component, pyrene, was used in the emulsion polymerization; whereas, the magnetic nanoparticles surface-modified with a silane coupling agent possessing a double bond were continuously supplied to the polymerization system. The polymerization was conducted with an amphoteric initiator at a weakly basic pH suitable for heterocoagulation between the magnetic nanoparticles and the polystyrene particles formed in the polymerization. The magnetic nanoparticles could be incorporated into the inside of polystyrene particles by the double bonds reacting with polymer radicals formed in the polymerization, accompanied with absorption of pyrene by the polystyrene particles. The present method prepared highly monodisperse, submicrometer-sized composite particles with the dual functions of fluorescent and magnetic properties.