Polythiophene/multiwalled carbon nanotubes/nitrate reductase deposited glassy carbon electrode (GCE/PTH/MWCNT/NR): a novel biosensor for the detection of nitrate in aqueous solution

Abstract In the present investigation, a novel biosensor (GCE/PTH/MWCNT/NR) based on the nanocomposite of polythiophene (PTH) and multiwalled carbon nanotube (MWCNT) immobilized by nitrate reductase (NR) was designed and made on a glassy carbon electrode (GCE). PTH and its composite with MWCNT were prepared by in situ oxidative polymerization. The structural features and surface morphologies of the composites were investigated by the standard analytical techniques, namely, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Measurements of the electrochemical performance and electrocatalytic activity of GCE/PTH/MWCNT/NR were carried out by cyclic voltammetry at different scan rates (20–100 mV s−1) in artificially polluted water containing nitrate ions. This laboratory-developed bio-electrode attained a maximum current density of 5.12 mAcm−2 at a scan rate of 100 mVs−1 for 8.0 mM sodium nitrate solution.