Siamese banana peel-mediated synthesis of silver nanoparticles and their broad-spectrum antibacterial activity

Abstract

Plant-mediated synthesis of silver nanoparticles (AgNPs) using agricultural by-products is not only a strategy to develop sustainable nanoparticle synthesis methods but also helps address environmental pollution caused by agricultural waste. In this study, Siamese banana peel (SBP) extract was used as a natural reducing and stabilizing agent for the synthesis of AgNPs. The effects of reaction time, AgNO3 solution concentration, and the volume ratio between the AgNO3 solution and banana peel extract on the formation of AgNPs were evaluated using UV-Vis spectroscopy via surface plasmon resonance (SPR). The physicochemical characteristics of AgNPs under optimal conditions were assessed via UV-Vis, FTIR, XRD, and HR-TEM analyses. Antibacterial activity was evaluated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against nine microbial strains, including Gram-positive and Gram-negative bacteria. The results showed that the suitable synthesis conditions included a reaction time of 120 minutes, an AgNO3 concentration of 2.0 mM, and an AgNO3 solution-to-extract volume ratio of 30 : 20 (v/v). Transmission electron microscopy (TEM) analysis revealed that the nanoparticles were predominantly spherical, well-dispersed, with sizes ranging within 28.3 ± 10.1 nm. XRD and selected area electron diffraction (SAED) analyses indicated that the AgNPs possessed a face-centered cubic (fcc) crystalline structure of metallic silver, whereas FTIR analysis confirmed the presence of phytochemical functional groups involved in nanoparticle formation and surface stabilization. The synthesized AgNPs exhibited antibacterial activity across all tested strains, with MIC/MBC ratios ranging from 2 to 4, demonstrating significant bactericidal efficacy under the experimental conditions.

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