Green synthesis of silver nanoparticles using Diplazium esculentum extract: catalytic reduction of methylene blue and antibacterial activities

Abstract

A green approach for the biosynthesis of silver nanoparticles (AgNPs) was developed using Diplazium esculentum aqueous extract as green reductant. The bio-stabilized AgNPs were characterized by UV–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), and high-resolution transmission electron microscopy (HRTEM). The formation of AgNPs was indicated by the colour change and the absorption peak at 449 nm in the UV–Vis spectrum. FTIR spectral analysis suggested the possible biomolecules associated with the reduction of silver ions. The crystalline and face-centered cubic (fcc) structure of AgNPs was obtained by the XRD study. HRTEM analysis showed that the biosynthesized AgNPs composed of quasi-spherical, hexagonal, and ellipsoidal shapes with an average particle size of 23.385 ± 8.349 nm. The biosynthesized AgNPs exhibited good catalytic activity up to 91% reduction of Methylene blue (MB), which followed a reductive pathway rather than a photocatalytic route. The catalytic reduction follows a pseudo-first-order reaction with a rate constant of 0.1051 min-1. The disc diffusion technique (DDT) and minimal inhibitory concentration (MIC) results showed significant antibacterial capability against Gram-positive (Escherichia coli ATCC 11,229) and Gram-negative (Staphylococcus aureus ATCC 6538) bacteria.