Eco-friendly synthesis of silver nanoparticles with dual metal sensing and antimicrobial potentials

Abstract

In this study, silver nanoparticles (AgNPs) were green synthesized using an aqueous stem extract of Phyllanthus amarus ( P. amarus ) as a natural reducing and stabilizing agent. The synthesized nanoparticles demonstrated crystalline nature, with a morphology structure predominantly spherical and with particle sizes ranging from 10.02 to 28.50 nm. The developed silver nanoparticles exhibited excellent colorimetric sensing performance toward Pb²⁺, Cd²⁺, and As³⁺, producing distinct SPR shifts and visible colour changes upon metal-ion interaction. Analytical validation showed good linearity with coefficients of determination (R²) of close to unity (R² > 0.9) for Pb²⁺, Cd²⁺, and As³⁺. The sensor achieved low limits of detection (LOD) of 1.665, 1.021, and 1.399 µg L⁻¹ and limits of quantification (LOQ) of 5.047, 3.094, and 4.241 µg L⁻¹ for Pb²⁺, Cd²⁺, and As³⁺, respectively, demonstrating its suitability for trace-level heavy metal monitoring. The developed S-AgNPs also possess excellent optical selectivity toward Pb²⁺, Cd²⁺, and As³⁺ even in the presence of common coexisting ions, highlighting their potential application as a rapid and reliable colorimetric nanosensor for monitoring toxic heavy metals in environmental water samples. Furthermore, the nanoparticles exhibited potent antibacterial activity against Escherichia coli and Staphylococcus aureus , with inhibition zones of 25.0 ± 0.4 mm and 21.0 ± 0.6 mm, respectively, accompanied by low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. These findings demonstrate that P. amarus stem-mediated silver nanoparticles are promising eco-friendly multifunctional nanomaterials with dual applications as sensitive colorimetric sensors for toxic heavy metals and effective antimicrobial agents for environmental and biomedical applications.