LAUSR

Abstract A highly efficacious green reductant, Chromolaena odorata phenolic extract (COPE), was used for the biosynthesis of silver nanoparticles (AgNPs) and iron was further in situ deposited to form silver@zero valent iron nanoparticles (Ag@ZVI NPs). Phenolic compounds were extracted from Chromolaena odorata leaves using our carefully formulated method and was further validated by ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. COPE was then used as a green bio-resource for room temperature synthesis of AgNPs. After successful synthesis of AgNPs, ferric (III) chloride was then added to realize Ag@ZVI NPs. X-ray diffraction validated the growth of Fe0 on the (111) crystalline facet of AgNPs during the formation of Ag@ZVI NPs. The synthesized AgNPs and Ag@ZVI NPs are highly stable, spherical and dispersed, with demonstrable antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Vibrio parahaemolyticus, Staphylococcus aureus and Listeria monocytogenes. The minimum inhibitory concentration and minimum bactericidal concentration ranged from 1 to 4 μg/mL and 2–8 μg/mL, respectively. Additionally, the antioxidant studies were probed by the DPPH-RSA, ABTS-RSA and MCA, which all confirmed the ability of the biosynthesized nanomaterials to scavenge radicals. The colorimetric sensing ability of COPE AgNPs was tested against hydrogen peroxide (H2O2) by visual observation and UV–vis spectrophotometry. A wide linear range from 5 to 200 µM as well as a low detection limit of 1.46 µM H2O2 was achieved. The practicality of the AgNPs sensor towards H2O2 was successfully performed on water sample with reliable accuracy.