Improved performance of Schiff based ionophore modified with MWCNT for Fe(ii) sensing by potentiometry and voltammetry supported with DFT studies

Abstract

A novel potentiometric and voltammetric sensor for creating a cationic response for Fe(II) is introduced. These methods were applied to produce an Fe(II) selective sensor based on (E)-3-((2-aminoethylimino)methyl)-4H-chromen-4-one (IFE). The influence of variables including the amount of ionophore, plasticizers, anion excluder and multiwalled carbon nanotubes (MWCNTs) on the performance of the potentiometric sensor were investigated. The sensor for Fe(II) improvised the dynamic linear range (1 × 10⁻⁷ to 1 × 10⁻¹ mol L⁻¹) with a slope of 27 mV per decade and a detection limit of 2.5 × 10⁻⁸ mol L⁻¹. Selectivity of the ion selective electrode improved after modification with MWCNTs. The reduction and oxidation properties of IFE were studied by voltammetric measurements. Differential pulse voltammetry was applied to the optimized electrode and a linear dynamic range from (9.9 × 10⁻⁷ to 2.9 × 10⁻⁵ mol L⁻¹) with a detection limit of 6.13 × 10⁻⁸ mol L⁻¹ was obtained. The composition and morphology of the modified ion selective electrode were characterized with scanning electron microscopy. The modified electrodes have good selectivity for Fe(II) ions over a number of metal ions. It was successfully applied for direct determination of Fe(II) ions in different real life samples. Theoretical calculations also supported the complexation behavior of Fe(II) with IFE.