Salicylaldehyde based Schiff base: synthesis, characterisation and application for selective electrochemical detection of Cu2+ in real samples

Abstract

ABSTRACT A simple salicylaldehyde-based Schiff base 2,2'-((1,3-phenylenebis(azanylylidine))bis(methanylylidene))dipehnol (PAMD) was synthesised by condensation reaction between salicylaldehyde and benzene-1,3-diamine (2:1 ratio) and characterised by spectral techniques such as NMR, FTIR and HRMS, followed by investigation for its spectroscopic behaviour towards diverse metal ions using UV and fluorescence studies. PAMD was found to exhibit sensitivity towards Cu2+ only. The receptor PAMD was then explored for its electrochemical behaviour using cyclic voltammetry, which displayed an irreversible anodic peak at 1.00 V due to imine group. Furthermore, PAMD was subjected to differential pulse voltammetry, which exhibited a sensitive response for Cu2+ in the linear range of 0–3.8 μM with lowest detection limit of 0.03 μM. The complexation between PAMD and Cu2+ was also supported by large values of binding constant (1.3 × 105 M−1) and negative free energy change (ΔG∘ = -29.2 kJmol−1) obtained from Benesi–Hildebrand equation. The carbon paste electrode (CPE) modified with PAMD displayed a Nernstian response to Cu2+ in the concentration range from 1.0 × 10−6 to 1.0 × 10−1 M and lowest detection limit of 4.0 × 10−7 M. The PAMD-CPE was successfully applied for determination of Cu2+ content in real samples such as groundwater, soil, and food grains (wheat and rice).