Microwave-assisted green synthesis of silver nanoparticles using turnip root (Brassica rapa subsp. Rapa) extract and their antibacterial efficacy

Abstract

Biosynthesised silver nanoparticles (AgNPs), especially those synthesised by plant extracts, are extensively utilised in the fields of pharmacy and medicine due to their ability to exhibit a wide range of biological functions. The current study is focused on the green synthesis of silver nanoparticles from various concentrated silver nitrate solutions using turnip root extract as a reducing and stabilising agent and to assess the in vitro antibacterial efficacy of these AgNPs. For the study, we employed microwave-assisted reduction to examine the impact of microwave energy on the resulting AgNPs in comparison to the conventional heating method. X-ray diffraction analysis revealed the crystalline nature of the as-prepared AgNPs, while field emission-scanning electron microscopy (FE-SEM) showed the majority of spherical-shaped AgNPs had an average grain size of 47.5 nm. Energy-dispersive x-ray spectroscopy (EDX) indicates the high weight percentage of the produced AgNPs than for extract residue, especially for the AgNPs that are prepared with microwave assistance. Fourier transform infrared spectroscopy (FTIR) was used to reveal the functional groups that are related to many phytochemical compounds, such as alkaloids, flavonoids, and terpenoids, which act as reducing and stabilizing agents. High zeta potential measures (−22.77 and −38.83 mv) approved the high stability of the synthesised AgNPs as higher zeta potentials typically correlate with greater stability. The antibacterial activity behaviour of the produced NPs against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria was significantly acceptable for both heating techniques, as observed from the measured inhibition zone.