One-step synthesis and functionalization of hydroxyl-decorated magnetite nanoparticles

Magnetite nanoparticles covered by a layer of ω-hydroxycarboxylic acid were synthesized in one step by high-temperature decomposition of iron(III) ω-hydroxycarboxylates in tri- and tetra-ethylene glycol. The nanoparticles were characterized by TEM, XRD, IR, XPS and NMR techniques in order to show that they comprise a crystalline magnetite core and actually bear on the outer surface terminal hydroxy groups. The latter ones are convenient “handles” for further functionalization as opposed to the chemically-inert aliphatic chains which cover conventionally synthesized nanoparticles. This was shown by several examples in which the hydroxy groups on the nanoparticle surface were easily transformed in other functional groups or reacted with other molecules. For instance, the hydroxyl-decorated nanoparticles were made water soluble by esterification with a PEGylated acetic acid. The reactive behavior of the surfactant monolayer was monitored by degrading the nanoparticles with aqueous acid and isolating the surfactant for NMR characterization. In general, the reactivity of the terminal hydroxyl groups on the nanoparticle surface parallels that observed in the free surfactants. The reported hydroxyl-decorated magnetite nanoparticles can be thus considered as pro-functional nanoparticles, i.e., a convenient starting material to functionalized magnetic nanoparticles.

Conventional nanoparticles have a sluggish complexion since they interact with the environment by unflappable aliphatic chains. We managed to synthesize spirited magnetic nanoparticles which display alcoholic groups at the outer surface. These hydroxyl-decorated magnetite nanoparticles are a convenient starting material for further functionalization thanks to the synthetic flexibility of the hydroxyl group.Figure optionsDownload as PowerPoint slide