(351e) Functional Magnetic Nanoclusters for Chemical, Biological, Medical and Environmental Applications

Magnetic nanoparticle suspensions have been the focus of numerous studies over the past forty years, both for fundamental studies and for practical applications. Current research activity focuses on the use of such nanoparticles as recoverable separation media in chemical, environmental and biological processing, as contrast agents in magnetic resonance imaging, and as focusable drug delivery agents, while also finding use in a range of other medical applications. The first part of this presentation will provide an overview of the properties of these magnetic nanoparticle suspensions, and delineate the experimental and theoretical work ongoing in this area.

Our primary interest has been in the use of functionalized magnetic nanoparticles for the selective separation of proteins from aqueous solutions, or for the recovery of hydrophobic compounds from contaminated water sources. For these applications, recovery of the particles is accomplished using high gradient magnetic separation (HGMS) concepts. Individual nanoparticles are too small (~10 nm) to be captured effectively in HGMS columns, but theoretical analyses indicate that clusters on the order of 70 to 100 nm can readily be trapped in these devices. We have developed methods for the controlled formation of stable clusters of these particles that are sufficiently large (~70-100 nm) to be captured by HGMS, without compromising the adsorptive capacity provided by the large surface areas of these nanoparticles.

Applications in the environmental area include the use of multifunctional polymers attached to the magnetite nanoparticles to provide both a hydrophobic solubilizing environment and a hydrophilic stabilizing corona similar to those observed in block copolymer micelles. We have also developed methods for sorbing (e.g., adsorption and chemisorption) and catalyzing the hydrolysis of organophosphate compounds (e.g., pesticides, chemical warfare agents) at a neutral pH. The functionalized magnetite particles, which serve as nano-sized particulate carriers with powerful α-nucleophiles immobilized on their surfaces, are colloidally stable at neutral pH, are readily recovered from aqueous suspensions by HGMS, and can be recycled with no loss of catalytic activity.

The second part of this presentation will provide an overview of the experimental approaches we have taken to optimize the synthesis and functionalization of magnetic nanoclusters, demonstrate their use in chemical, biological and environmental applications, and detail the theoretical analysis of HGMS systems.