Microwave Synthesis of Hematene and Other Two-Dimensional Oxides

With the emergence of graphene, the first two-dimensional (2D) material, many other 2D materials have been discovered and examined for novel applications. Various synthesis approaches have been employed for 2D Xenes, nitrides, carbide, and oxides to obtain high-quality and largequantity production. Among them, 2D oxides have gained researcher's attention for their magnetic, electronic, and catalytic properties. In this Article, we report single-step and scalable synthesis of hematene (a 2D atomic layer of iron oxide (Fe2O3)) and 2D metal oxides (2DMOs), e.g., chromium oxide, copper oxide, etc., by following a similar synthesis protocol. Metal chlorides dispersed in dimethylformamide (DMF) solvent immediately convert to the corresponding metal oxides upon microwave irradiation. Direct microwave solid-phase synthesis has also been explored and compared with liquid-phase microwave synthesis of hematene. Crystallographic structures of synthesized hematene were obtained by high-resolution transmission electron microscopy (HRTEM) and chemical identification was done by X-ray photoelectron (XPS) and Raman spectroscopy. In addition, magnetic measurements reveal the room-temperature ferromagnetic ordering of hematene with a saturation magnetization of 0.24 emu/g (at 300 K) and 1.08 emu/g (at 60 K). Field-cooled and zero-field cooled measurements clearly demonstrate a high Curie temperature of similar to 376 K. Versatility of the synthesis technique has been demonstrated by employing the same protocol to the successful synthesis of a variety of metal oxides. This synthesis route permits a simple, inexpensive, efficient, and scalable production of 2DMOs.