Self-assembled monolayer of poly(o-phenylenediamine)/silver core–shell hybrid-based enzyme-free impedimetric glucose sensor for blood samples

Abstract

A core–shell hybrid of poly(o-phenylenediamine)/silver was prepared by a simple single-step process and self-assembled on a glassy carbon electrode to design an enzyme-free electrochemical glucose sensor. The working electrode was fabricated by self-assembling a dimethyl sulfoxide (DMSO) solution of the prepared hybrid on a glassy carbon electrode. The electrochemical properties of the fabricated electrode were analyzed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in an aqueous potassium chloride electrolyte containing the [Fe(CN)₆]^3−/4− redox couple. The electrochemical sensing responses towards varying concentrations of glucose were studied by CV and EIS in the same redox electrolyte medium. The poly(o-phenylenediamine)/silver core–shell hybrid-based sensor was found to show a reliable response in the EIS experiment over the CV experiment. By analyzing the EIS sensing responses, the experimental limit of detection was determined to be 10 μL of ∼80 mg per dL glucose solution in 25 mL of 1 (M) KCl electrolyte containing the 10⁻³ M [Fe(CN)₆]^3−/4− redox couple with a sensitivity of 298 Ω mg⁻¹ dL cm⁻². Excellent selectivity towards glucose was confirmed over various bioactive interfering biomolecules like ascorbic acid, dopamine, uric acid, lactose, fructose and sucrose. The glucose content in the human blood sample was verified by the designed sensor with almost 100% recovery.