Luminescent and Magnetoresponsive Multifunctional Chalcogenide/Polymer Hybrid Nanoparticles

Cadmium sulfide/magnetite/polymer multifunctional hybrid nanoparticles are prepared by crystallizing CdS in a controlled manner on the surface of phosphonate-functionalized polystyrene particles with a magnetic core. The supporting polymer magnetoresponsive nanoparticles are produced by a modified miniemulsion polymerization process: a first miniemulsion containing the core monomer (styrene) and a phosphonate-functionalized surface-active monomer is mixed with a second miniemulsion containing magnetite nanoparticles capped with oleic acid and the same surface-active monomer. The chalcogenide formation occurs in situ at the surface of the polymer particles by adding a precipitating agent (sodium sulfide) at a controlled rate. The phosphonate groups on the surface of the polymer particles have the ability to bind the cadmium ions and act as nucleating centers from which the controlled crystallization of CdS takes place. The resulting hybrid particles show a “raspberry-like” structure, with CdS nanocrystals surrounding the polymeric core. The superparamagnetic behavior of the initial iron oxide nanoparticles, without a recognizable blocking temperature, is retained in the final hybrids particles. The obtained hybrids show luminescence in the visible light with a maximum at 620 nm (2.00 eV).