Construction, characterization and application of locust bean gum/Phyllanthus reticulatus anthocyanin - based plasmonic silver nanocomposite for sensitive detection of ferrous ions

Abstract

Iron is a transition metal of tremendous eco-physiological significance. This work aimed at constructing a simple plasmonic Ag-nanocomposite (LBG/PRAg-NC) based on locust bean gum and Phyllanthus reticulatus anthocyanin in a sustainable manner for the optical detection of ferrous ions (Fe2+) in aqueous solution. LBG/PRAg-NC was prepared via a green chemistry route and thoroughly characterized for its physico-chemical and plasmonic attributes. Successful synthesis of LBG/PRAg-NC under room temperature with Phyllanthus reticulatus anthocyanin as reductant and locust bean gum as stabilizer was accomplished within 15 min. LBG/PRAg-NC exhibited small size (∼8.04 nm), spherically shaped nanosilver, with good colloidal dispersion, stability and prominent SPR absorption peak at 420 nm. XPS analysis revealed the existence of both Ag0 and Ag + species embedded in the biopolymer support. Furthermore, LBG/PRAg-NC was highly selective for Fe2+ as opposed to other interferents including Fe3+. The presence of Fe2+ engendered a redox oxidation of the analyte by the Ag+ species, prompting a rapid, concentration dependent increase in color and SPR absorption band intensity of LBG/PRAg-NC colloidal solution. In aqueous solution, the probe displayed a good linear range for Fe2+ (0.1–100 μM), and a low detection limit (LOD of 0.38 μM). The obtained detection limit is much lower than the guideline limit of Fe2+ content in drinking water, ∼5 μM. Additionally, the probe was successfully applied in determination of Fe2+ in aqueous solutions of apple juice, iron supplement tablet, and tap water, with commendable analytical performances. Therefore, our research findings demonstrate a facile, efficacious, cost-effective, and eco-friendly approach for the sustainable synthesis of plasmonic Ag-nanocomposites based solely on locust bean gum and Phyllanthus reticulatus anthocyanin. Importantly, these results validate the capacity of plasmonic Ag-nanocomposite constructed via green chemistry route as a simple, rapid, and selective probe for effective monitoring of trace amounts of Fe2+ in aqueous environment.