Enhancing performances of colorimetric response of carboxymethylcellulose-stabilized silver nanoparticles: A fully eco-friendly assay for Hg2+ detection

Abstract

Although various methods have been reported for the analysis of hazardous Hg2+ ions in aqueous medium, development of environment-friendly colorimetric assays and enhancing their performances still remain a great challenge. Here, we propose a fully eco-friendly colorimetric assay for Hg2+ detection. The approach uses silver nanoparticles (Ag Nps) stabilized by carboxymethyl cellulose (CMC), obtained by carboxymethylation of cellulose waste isolated from Tunisian date palm petioles, as optical probe and NaCl as risk-free reagent. Preliminary investigations reveal high stability of the as-prepared colloidal suspension through ξ-potential measurements and UV–vis spectrophotometry as function of aging, pH, and ionic strength. The analytical applicability of CMC-stabilized Ag NPs to detect Hg2+ ions, using the feedback titration method proves several weaknesses including high detection limit (LOD) and limit of quantification (LOQ) as well as poor selectivity. The proposed strategy indicates that the sensitivity of the colorimetric assay was greatly influenced by the final concentration of NaCl in the test medium. An optimal NaCl concentration of 300mM improved all the colorimetric assay performances. Especially, the LOD and the LOQ values, commonly used as quality criterion for analytical method, were greatly enhanced and found to be around 5nM and 16nM, respectively, which are lower than the permissible authorized level (30nM) by the World Health Organization (WHO). Toward the purpose of practical application, the current developed fully eco-friendly colorimetric assay was successfully applied for analytical determination of Hg2+ ions and drinking-water safety.