Electrochemical sensor based on ion-selective membrane of silica/polyaniline nano-composites for selective determination of uranyl ions
Gagandeep Kaur, Harpreet Kaur, Susheel K. Mittal
Abstract
Life threatening impacts of uranium have necessitated its detection and determination in economically feasible way before it arrives in living bodies. Therefore, a new form of UO22+ ion-selective electrode has been fabricated based on membrane of silica/polyaniline core-shell nano-composites, in-spite of traditionally used ionophores, because of intrinsically conducting nature of polyaniline. For the synthesis of these nano-composites, silica has been extracted from rice straw in its cristobalite form, whereas the layer of polyaniline shell has been grafted on silica nanoparticles through in-situ chemical oxidative polymerization technique by cautiously maintaining the electro-active nature of these core-shell nano-composites. The chemical composition, purity, topography, morphology and surface polarity of this nano-composite assembly have been studied through various spectroscopic techniques such as, FT-IR, EDS, FESEM, UV–Vis, DLS and Raman spectroscopy. The results confirm that silica/polyaniline nano-composites have been synthesized with desired semi-cavities and electrostatic surface charge, which is responsible for binding with target cation, i.e., UO22+for its potentiometric determination in aqueous medium even in the presence of interfering metal ions. The designed potentiometric sensor has shown fast and stable linear response in concentration range of 1 × 10−6 to 1 × 10−2 M with the limit of detection of 1.4 × 10−7 M which is 100-folds lower than the detection limit calculated using spectrofluorometry. In addition to this, the proposed UO22+ion-selective electrode has been successfully employed as an indicator electrode for the determination of uranyl ions in complexometric titration and for the estimation of UO22+ions in real life based environmental sample, i.e., soil.