Phytobiogenic and Bacterial Synthesized Silver Nanoparticles: Structural Differences and Their Impact on Antimicrobial and Photocatalytic Performance

Abstract

Antimicrobial resistance and the persistence of synthetic dyes in water represent two pressing challenges that silver nanoparticles (AgNPs), as broad-spectrum biocides and visible-light plasmonic photocatalysts, can address simultaneously. Here, AgNPs were synthesized via two green biological platforms-Levisticum officinale leaf extract (phytobiogenic, Bi-AgNP) and Lacticaseibacillus rhamnosus supernatant (bacterial, Ba-AgNP)-to compare how synthesis-dependent structural differences govern antibacterial, antioxidant, and photocatalytic performance. Nanoparticles were characterized by UV-vis, FTIR, XRD, SEM-EDX, TEM, DLS, and zeta potential analysis. UV-vis confirmed SPR peaks at 418 nm (Ba-AgNP) and 420 nm (Bi-AgNP). Bi-AgNP showed a phenolic/flavonoid biocorona, high fcc crystallinity, and larger size (similar to 100-120 nm), whereas Ba-AgNP exhibited a protein/polysaccharide biocorona, lower crystallinity, and smaller size (similar to 60-80 nm). In both systems colloidal stability was predominantly steric (zeta approximate to -15 and -11 mV). Ba-AgNP displayed markedly higher antibacterial activity against E. coli, stronger DPPH scavenging (63% vs. 54% at 100 & micro;g/mL), and superior methylene blue degradation (similar to 98% at 120 min vs. similar to 86% at 150 min), with both following pseudo-first-order Langmuir-Hinshelwood kinetics. These findings demonstrate that the biosynthetic source critically shapes AgNP surface chemistry, crystallinity, and morphology, modulating their multifunctional outputs and providing a rational basis for application-specific biogenic AgNP design.