Abstract

SPEARMINT-MEDIATED GREEN SYNTHESIS OF TETRAGONAL MNO2 NANOPARTICLES WITH ENHANCED ANTIMICROBIAL AND ANTIOXIDANT PROPERTIES

Khan Kadir Rafik, Pratiksha Shrichand Rathod, Neha Samreen Gulam Dastageer, Momin Nishat Parveen*

Abstract

Manganese dioxide nanoparticles (MnO2 NPs) were successfully synthesized using a green approach with spearmint plant leaf extract. The synthesized nanoparticles were characterized using various spectroscopic techniques, including Fourier-transform infrared spectroscopy (FT-IR), ultravioletvisible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and energydispersive X-ray (EDX) spectroscopy. XRD analysis revealed the tetragonal crystalline structure of the MnO2 NPs with an average crystallite size of 24 nm. SEM images showed roughly spherical nanoparticles with diameters ranging from 25 to 146 nm, while HRTEM indicated an average particle size of 34 nm. FT-IR spectra confirmed the presence of Mn-O bonds, and EDX analysis verified the elemental composition of the nanoparticles. The biosynthesized MnO2 NPs exhibited strong antimicrobial activity against various bacterial strains, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumoniae, with zones of inhibition ranging from 12 to 16 mm. However, the nanoparticles showed no antifungal activity against Aspergillus niger. In addition, the MnO₂ nanoparticles showed high antioxidant activity, where Mn2 (95.20%) and Mn1 (95.06%) were more effective than ascorbic acid 1 (94.15%) and ascorbic acid 2 (92.14%) in DPPH radical scavenging activity. These findings suggest that green-synthesized MnO2 NPs sing spearmint plant leaf extract have potential applications as antimicrobial and antioxidant agents.

Keywords: Green synthesis MnO2 NPs, Antimicrobial and Antioxidant properties analysis.