Upcycling Pomegranate Peel Waste for Comparative Green Synthesis of Silver Nanoparticles: Characterization and Biological Applications.

Pomegranate fruit peel was upcycled as a mediating agent for the comparative green synthesis of silver nanoparticles (AgNPs) utilizing facile (F), microwave (M), and autoclave (A) methodologies. XRD, SEM, TEM, and FTIR analyses revealed successful synthesis of AgNPs, with FTIR confirming polyphenol involvement in reduction and stabilization. The SEM micrographs indicated that all nanoparticles agglomerate into clusters. The TEM micrographs indicated that all nanoparticles are spherical, with varying particle sizes. In addition, the average particle size for AgNPs-A was 17.84 nm, 14.91 nm for AgNPs-F, and 14.23 nm for AgNPs-M. Furthermore, the obtained XRD patterns showed crystallinity across all methods, with the microwave route producing the smallest crystallite size (6.58 nm) as estimated by the Scherrer equation. It is important to note that the crystallite size estimated from XRD represents the coherent diffraction domain and is not directly equivalent to the particle size observed by TEM. The antimicrobial property of AgNPs-M was superior, especially against Staphylococcus aureus amongst other food-borne pathogens, with an inhibition zone of 22.6 mm at 5 mg/mL. This study provides insights into three green synthesis methods for AgNPs using pomegranate peel waste, offering a foundation for future studies on safety, stability, and application-oriented assessments.