Magneto-Optical and Catalytic Properties of Recyclable Spinel NiAl2O4 Nanostructures Using Facile Combustion Methods

Spinel nickel aluminate (NiAl (2) O (4)) nanospheres (NSPs) and nanoplatelets (NPLs) were successfully synthesized using a facile microwave combustion method (MCM) and conventional combustion method (CCM), respectively, using urea as the fuel. The as-prepared samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM) analysis. Powder XRD, FT-IR, EDX, and SAED results showed that the samples were pure phase spinel NiAl (2) O (4) nanocrystals without any other secondary phase impurity. UV-Vis DRS and PL spectroscopy results were used to calculate the energy band gap (E (g)) value of the samples which is 3.41 and 3.08 eV for NiAl (2) O (4) NSPs and NiAl (2) O (4) NPLs, respectively. VSM results of the NiAl (2) O (4) NPLs sample show lower M (s) (49.16 x 10 (-3) emu/g) values compared with the NiAl (2) O (4) NSPs sample (73.42 x 10 (-3) emu/g), which confirm that both the products have ferromagnetic behavior. NiAl (2) O (4) NSPs were found to have higher surface area than NiAl (2) O (4) NPLs, which in turn leads to the improved performance towards the selective oxidation of benzyl alcohol into benzaldehyde, with 100 % selectivity, and it was found that the NiAl (2) O (4) NSPs sample show higher conversion (96.25 %) than NiAl (2) O (4) NPLs (85.37 %). The as-prepared samples show high activity, good reusability, remarkable stability, and environmentally friendly materials for industrial and technological applications.