Development of pivalic acid conjugated Nafion modified glassy carbon electrode for sensitive detection of Cu(II) by electrochemical approach

Abstract

In this work, pivalic acid (pivH) molecule is employed for an electrochemical sensing of copper cations in an aqueous medium. For sensitive as well as selective potential sensor application, pivH was fabricated onto a glassy carbon electrode (GCE) facilitated by adhesive conducting binder, nafion, so as make it selective and effective electrochemical probe (pivH/Nafion/GCE) towards specific heavy metal cations. This newly fabricated pivH/Nafion/GCE reveals enhance electrochemical activity toward copper ions in the presence of other interfering heavy metal cations in phosphate buffer solution (PBS) of pH=7. The calibration plot was linear (r² = 0.9879) across broad linear dynamic range (LDR) spanning Cu²⁺ concentration from 0.1 nM to 0.01 M. The sensitivity and detection limit was found to be 0.0212 × 10⁻² µAµM⁻¹cm⁻² and 0.014 nM, respectively. So, this newly fabricated GCE as selective electrochemical probe offers a sensitive as well as selective detection of Cu²⁺ cations in real environmental samples using a novel electrochemical, current–potential (I-V), approach, for the first time. Further, we explored pivalic acid for the preparation of new di-nuclear copper complex, [Cu₂(piv)₄(pivH)₂] (where piv = pivalate; pivH=pivalic acid) and characterized by Fourier transform infrared spectroscopy (FTIR) spectroscopy, elemental analysis and single crystal X-ray diffractometry. Density functional theory (DFT) calculations were carried out to confirm the interactions and these calculations well-support to experimental data. In case of deprotonated form of pivH, Molecular Electrostatic Potential (MEP) analysis exhibits electrostatic potential equals to −148.4 kcal/mol which suggest about the strong interaction of –COOH with copper centers. Similarly, interaction energies, the quantum theory of atoms in molecules (QTAIM) study and Natural Bond Orbital (NBO) analysis also favor to experimental work. Thus, this novel study demonstrates an excellent approach for highly selective and sensitive detection of Cu²⁺ cations in short response time with low detection limit and good reproducibility by using I-V method based on newly designed pivH/Nafion/GCE as selective Cu²⁺ cationic electrochemical sensor. The experimental data was compactable with theoretical calculations.