Synthesis of Manganese Dioxide Nanoparticles Using Andrachne Aspera Root Extract for Antibacterial Activities

Abstract

This study presents a bio-fabrication technique for MnO2 nanoparticles utilizing Andrachne aspera root extract as a natural bio- agent. The phytochemicals inherent in the Andrachne extract perform a vital function in the bio-reduction of manganese ions and the steadying of the resultant tiny particles. The synthesized MnO2 nanoparticles were systematically distinguished through ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermal analysis (TGA/DTA). UV-Vis confirmed the formation of MnO2 nanoparticles by exhibiting characteristic absorption features, with the measured band gap of the fabricated nanoparticles determined to range between 2.6 for 2.1eV, and 2.8 and 1.2 eV. FTIR analysis indicated the functional groups from the Andrachne extract in nanoparticle capping and stabilization. XRD analysis revealed that the MnO2 nanoparticles possess a cubic face-centered phase structure, with crystallite sizes measured at 28.58 nm, 28.83 nm, and 25.83 nm corresponding to those synthesized with metal-to-bioextract ratios of 1:1, 2:1, and 1:2, respectively, and also the PH and concentration effect. The antibacterial efficacy of the produced MnO2 nanoparticles was assessed against Gram-positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria using the disc diffusion technique. The 2:1 MnO₂ sample synthesized using Andrachnes aspera root extract shows better antibacterial activity because this ratio optimizes the balance between phytochemical capping agents and MnO₂ nanoparticles. This leads to a smaller particle size, higher surface area, and stronger interaction with bacterial cell walls, enhancing oxidative stress and membrane disruption compared to other ratios. The nanoparticles demonstrated significant antibacterial activity, with inhibition zones increasing at higher nanoparticle concentrations. This is potentially due to a greater quantity of metallic precursors, potentially resulting in smaller and more reactive particles. These discoveries emphasize the capacity of biosynthesized MnO2 nanoparticles as efficient antimicrobial agents. Overall, this study establishes a green, low-cost, and scalable synthesis route for producing bio functional nanomaterials, with promising applications in biomedicine and environmental science.