Sesamum indicum Plant Extracted Microwave Combustion Synthesis and Opto-Magnetic Properties of Spinel Mn _x Co_1-x Al₂O₄ Nano-Catalysts

SpinelMn _x Co_1−x Al₂O₄ (x =0, 0.3 and 0.5) nanoparticles were synthesized using Sesamum indicum (S. indicum) plant extracted microwave-assisted combustion method. S. indicum plant extract simplifies the process, provides an alternative process for a simple, economical and environment friendly synthesis. The absence of surfactant/catalysts has led to a simple, cheap and fast method of synthesis of spinel nanoparticles. The as-synthesized spinel nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analysis, UV-Visible diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy, and vibrating sample magnetometer. The formation of spinel nanoparticles was confirmed by HR-SEM and HR-TEM and their possible formation mechanisms were also proposed. Powder XRD, FT-IR, SAED and EDX results confirmed the formation of pure and single cubic phase CoAl₂O₄ with well-defined crystalline. The optical property was determined by DRS and PL spectra. VSM measurements revealed that pure and Mn-doped CoAl₂O₄ samples have weak ferromagnetic behavior and the magnetization values increases with increasing the concentration of Mn²⁺ ions in the CoAl₂O₄ lattice. The sample Mn_0.5Co_0.5Al₂O₄ possessed higher surface area and smaller crystallite size than other samples, which led to enhance the performance toward the selective oxidation of benzyl alcohol into benzaldehyde.