Carbonyl groups anchoring for the water dispersibility of magnetite nanoparticles

Magnetite nanoparticles, which were synthesized by using diethylene glycol (DEG) as both solvent and reductant, displayed excellent hydrophilicity and water dispersibility. The influences of the amount of carboxymethyl-dextran sodium salt and NaOH on nanoparticles dispersibility were evaluated in terms of zeta potentials, concentration variation under centrifugal field, Fourier transform infrared, and X-ray photoelectron spectra, respectively. The results showed that the water dispersibility is not related to the amount of carboxymethyl-dextran, but depends on that of NaOH. Further evaluation revealed that DEG was partially oxidized with the assistance of NaOH, and thanks to the resultant carbonyl groups, the flexible oxidized DEG chains were anchored on the nanoparticles surface, which provides sufficient protection and high water-dispersibility of the as-prepared magnetite nanoparticles. Furthermore, we suggest that the binding between carbonyl groups and nanoparticles is related to the electron-withdrawing effect. The current study may provide more selectiveness of modifying molecules for magnetite nanoparticles.