An Electrochemical Sensor Based on Redox-Active Schiff Base Polymers for Simultaneous Sensing of Glucose and pH

Abstract

A novel redox-active Schiff base polymer (SBPPPDA-PDA) was prepared by condensation of p-phenylenediamine with 1,10-phenanthroline-2,9-dicarbaldehyde. The structure of SBPPPDA-PDA was investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherm, and powder X-ray diffraction and electrochemical techniques. The results showed that SBPPPDA-PDA had two-dimensional lamellar structure. The electrochemical properties of SBPPPDA-PDA were characterized by cyclic voltammetry, showing several pairs of redox peaks and good catalytic ability toward oxygen reduction. On the basis of the redox-active activity of SBPPPDA-PDA, an electrochemical pH sensor was proposed based on SBPPPDA-PDA with a linear range from 2 to 9 for pH detection. With nitrogen-containing skeleton and porous structure, SBPPPDA-PDA could be used as support to load glucose oxidase (GOD). Thus, a novel ratiometric electrochemical glucose sensor was further constructed by immobilizing GOD on SBPPPDA-PDA modified electrode. The results revealed that the reduction peak of O2 decreased with the gradual addition of glucose, while the response peak of SBPPPDA-PDA at about 0.15 V almost remained. The sensor based on GOD/SBPPPDA-PDA/SPE showed a rapid response, a linear range from 22.5 μmol/L–5 mmol/L and a lower detection limit of 7.56 μmol/L for glucose.