Hydrothermal synthesis of Fe-doped ZnAl2O4 nanosheets: bandgap engineering and room temperature ferromagnetism.

In this study, well-separated Fe-doped ZnAl₂O₄ nanosheets were synthesized by a co-precipitation assisted hydrothermal method (220 °C). The as-synthesized nanosheets were characterized by X-ray diffraction, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV- diffuse reflectance spectroscopy and vibrating sample magnetometer studies. The diffraction patterns reveal that there is no noticeable effect of doped Fe ions on the crystal structure of ZnAl₂O₄. This also confirms the crystallinity and pure spinel structure formation. In addition, no characteristic diffraction peaks related to any impurity, cluster formation, or secondary phase of Fe were detected. The XPS spectra of Fe-doped ZnAl₂O₄ confirms the presence target elements such as Zn, Al, O, and Fe. It is also confirmed the existence of mixed oxidation states, i.e., Fe²⁺ and Fe³⁺, in the optimized sample ZAO-Fe-3 (i.e., 3% of Fe ions doped ZnAl₂O₄). TEM images of pure ZnAl₂O₄ show a micro-hexagonal structure, whereas the Fe-doped ZnAl₂O₄ exhibits nanosheet-like structure. DRS analysis confirms that Fe doping modifies the bandgap energy of ZnAl₂O₄ with increasing Fe content. The M–H hysteresis curves of Fe-doped ZnAl₂O₄ exhibited clear room temperature ferromagnetism. [ABSTRACT FROM AUTHOR]