ANTIMICROBIAL ASSESSMENT USING SYNTHESIZED BINARY METAL OXIDE NANOPARTICLES.

The growing global concern of antimicrobial resistance has fueled the hunt for alternative nanomaterials with therapeutic promise. This work used a green approach to create manganese– magnesium binary oxide (Mn–MgO) nanoparticles. Ficus exasperata leaf extract in alkaline environments (pH 9–10) act as a stabilizing and reducing agent. The nanoparticles' crystalline structure was validated by X-ray diffraction (XRD) examination, with distinctive peaks at 2θ values of 29.4°, 42.9°, and 62.0°, with an average crystallite size of 18 nm determined by the Debye–Scherrer equation. FTIR (Fourier Transform Infrared) spectrum showed notable peaks at 3339.69 cm⁻¹ (O–H stretching), 1543.11 cm⁻¹ (amide/aromatic C=C), and 1017.50 cm⁻¹ (C–O stretching), suggesting the existence of capping agents made of phytochemicals. Highly aggregated, irregular particles were found using scanning electron microscopy (SEM) that created a porous cluster structure. Energy Dispersive X-ray Spectroscopy (EDS) was used to verify the elemental composition; manganese (51.40 wt%), magnesium (35.00 wt%), and oxygen (5.20 wt%) were the primary elements. A primarily mesoporous structure was indicated by Brunauer–Emmett–Teller (BET) analysis, which showed a high specific surface area of 212.13 m²/g, a total pore volume of 0.106 cm³/g, and average pore diameters of 2.11 nm (BJH), 2.65 nm (DFT), and 3.04 nm (DA). A hybrid micro–mesoporous architecture was confirmed by the classification of the nitrogen adsorption–desorption isotherm as Type IV with an H3 hysteresis loop. There were no zones of inhibition (0 mm) against Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans when antimicrobial activity was assessed using the agar well diffusion method at doses ranging from 7.813 to 62.5 mg/mL. As a result, values for minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) were not determined. The Mn–MgO nanoparticles showed no discernible antibacterial activity despite having a large surface area and nanoscale crystallinity. This was probably caused by particle aggregation and surface passivation by phytochemical residues. These results demonstrate how important surface shape and accessibility are in influencing the bioactivity of green-synthesised nanoparticles.