Magnetite (Fe3O4) and maghemite (γ-Fe2O3) nanocrystals have been extensively studied for decades due to their superparamagnetic behavior and potential applications in magnetic storage devices, catalysis, and medical diagnosis. As the ratio of Fe3+/Fe2+ determines the phase composition and magnetic properties of iron oxide nanocrystals, it is important to control the oxidation state of Fe. While Fe3O4 can be slowly oxidized to γ-Fe2O3 in air or more rapidly by applying heat or adding oxidants, the reduction of γ-Fe2O3 to Fe3O4 is relatively rare. We report reduction of colloidal γ-Fe2O3 nanocrystals by UV irradiation in the presence of a sacrificial reductant. Photoreduction is followed using UV/vis/NIR electronic absorption spectroscopy in combination with superconducting quantum interference device magnetometry. X-ray diffraction and transmission electron microscopy are used to monitor the crystal structure and size/shape of the nanocrystals, respectively. The effects of photoreduction on the crystal and electronic structures of the iron oxide nanocrystals will be discussed.

Photoreduction of iron oxide nanocrystals

2019 Fall National Meeting

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