Citrus sinensis zest-mediated silver nanoparticles for rapid dye removal and antimicrobial properties

Growing interest in sustainable and renewable nanotechnology has accelerated the development of green synthesis strategies that are both environmentally friendly and economically viable. In this study, we report a simple, low-cost, and eco-conscious approach for synthesizing silver nanoparticles (AgNPs) using an aqueous zest extract of Citrus sinensis (Cs), which naturally serves as both the reducing and stabilizing agent. The phytochemicals present in the extract-including ascorbic acid, phenolic acids, flavonoids, terpenoids, and polysaccharides-effectively reduce Ag⁺ ions to stable AgNPs. The formation of AgNPs was confirmed through UV-Vis spectroscopy, revealing a characteristic surface plasmon resonance peak at 420 nm. FESEM imaging demonstrated predominantly spherical nanoparticles with uniform crystallite morphology and rough surface features, while TEM analysis showed an average particle size of approximately 15 ± 5.3 nm. XRD patterns confirmed the polycrystalline nature of the particles with diverse d-spacings, and EDX analysis indicated high purity (93.91% Ag) of the synthesized material. Compared to previously reported green synthesized nanoparticle systems, the biosynthesized AgNPs displayed excellent catalytic activity, achieving dye removal efficiencies of 98.93% (within 18 min) for methyl orange (MO) and 92.15% (within 30 min) for methylene blue (MB) under mild conditions, highlighting the advantage of waste-derived plant extract-mediated synthesis. Moreover, they exhibited strong antibacterial activity, showing notable inhibition against Gram-negative bacteria (E. coli,Pseudomonas spp.,K. pneumoniae, andSalmonella spp.) compared with Gram-positive strains (S. aureus andB. cereus), as assessed by inhibition zone measurements.