Green synthesis of glucose-capped stable silver nanoparticles: a cost-effective sensor for the selective detection of Hg2+ ions in aqueous solutions

We, herein, report a unique, cost-efficient, and green method for the synthesis of glucose-capped silver nanoparticles (AgNPs) using Ocimum sanctum (tulsi) leaf extract for the detection of Hg2+ ions in water. The nanoparticles synthesized by the above-mentioned method were found to be highly stable. The higher stability of the glucose-capped nanoparticles may be due to the interaction of hydroxyl groups of carbohydrate molecules with the nanoparticles. The optical and structural properties of the nanoparticles were confirmed by different spectroscopic methods. The selective detection of Hg2+ ions by the AgNPs was studied by colorimetric analysis and optical absorption spectroscopy. The detection of Hg2+ ions was also investigated by fabricating an optical fiber using AgNPs. From the optical fiber-based experiments, the limit of detection (LOD) for Hg2+ ions using the sugar-capped AgNPs was found to be 2.8 ppb, which is better than that of many other sensors based on green AgNPs reported in the literature. The improvement in the value of LOD with sugar-capped AgNPs showed the impact of carbohydrates on the sensing abilities of AgNPs. The sensing ability of the AgNPs for Hg2+ ions was further verified by a nanoparticle-coated filter paper strip method.