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Stabilization of Monodisperse, Phase-Pure MgFe2O4 Nanoparticles in Aqueous and Nonaqueous Media and Their Photocatalytic Behavior

Kirchberg, Kristin, Becker, Anna, Bloesser, André, Weller, Tobias, Timm, Jana, Suchomski, Christian, Marschall, Roland
The Journal of Physical Chemistry C 2017 v.121 no.48 pp. 27126-27138
X-ray diffraction, betaine, citric acid, colloids, dispersions, energy conversion, ferrimagnetic materials, infrared spectroscopy, light scattering, magnesium, microwave treatment, nanocrystals, nanoparticles, oleic acid, photocatalysis, physical chemistry, polyvinylpyrrolidone, solar energy, stabilizers, thermogravimetry, transmission electron microscopy, ultraviolet-visible spectroscopy
Monodisperse, monocrystalline magnesium ferrite (MgFe₂O₄) nanoparticles were synthesized phase purely by fast nonaqueous microwave-assisted solution-phase synthesis. Colloidal stabilization of the nanocrystals in nonaqueous media was realized either in-situ during synthesis or postsynthetically by surface capping with oleylamine and oleic acid. Phase transfer to aqueous media was performed employing citric acid and betaine hydrochloride, resulting in agglomerate-free dispersions of citrate- or betaine-functionalized MgFe₂O₄ nanocrystals. Furthermore, a one-step synthesis of highly stable, water-dispersible colloids of MgFe₂O₄ was achieved using polyvinylpyrrolidone as stabilizer. Characterization of the as-synthesized and functionalized nanoparticles was performed employing X-ray diffraction, UV–vis and infrared spectroscopy, thermogravimetry, dynamic light scattering, and transmission electron microscopy. Special focus was laid on phase purity, which was thoroughly monitored using Raman microscopy/spectroscopy. Photocatalytic reactions were performed to evaluate the use of such highly stable ferrite colloids for solar energy conversion.