(95f) Silica-Encapsulated Magnetite Nanoclusters as a Platform for Functional Core-Shell Particles

Chang, E. P., Massachusetts Institute of Technology
Bromberg, L., Massachusetts Institute of Technology
Suh, S. K., Massachusetts Institute of Technology
Hatton, T. A., Massachusetts Institute of Technology

Magnetic iron oxide nanoparticles are well-known for their superparamagnetic, contrast imaging and catalytic properties. Our work introduces novel silica-encapsulated magnetite core-shell structures as a platform technology for the synthesis of functionalized nanoparticles. These particles exhibit strong magnetic properties, chemical stability and dispersibility. Moreover, the silica shell provides sites for surface functionalization with a variety of organic ligands, for example, chelating or catalytic ligands. Two different methods are used to synthesize the magnetic cores. The first is a simple aqueous co-precipitation of iron chloride salts, producing aggregates of small polydisperse magnetite nanoparticles. The second involves the thermal decomposition of iron tri(acetylacetonate) followed by emulsion droplet solvent evaporation to form well-defined spherical clusters of monodisperse magnetite nanoparticles. Both methods produce magnetic cores on the order of 100 nm. The coating of both types of clusters by silica has been attained via a modified Stöber process; functionalized coatings are obtained through the additional hydrolysis of γ-glycidoxypropyltrimethoxysilane, aminopropyltrimethoxysilane and similar compounds. Such particles are promising in the area of environmental remediation, and specifically, the decontamination of water sources. We have explored the use of the particles in the catalytic decomposition of organophosphates and the recovery of methylmercury chloride from water. Our synthesis methods, physical characterization of the particles, and applications will be discussed.