Simultaneous determination of ascorbic acid, dopamine, uric acid and hydrogen peroxide based on co-immobilization of PEDOT and FAD using multi-walled carbon nanotubes

Abstract

A simple method was used to synthesize active hybrid composites containing multi-walled carbon nanotubes (MWCNTs), poly(3,4-ethylenedioxythiophene) (PEDOT) and flavin adenine dinucleotide (FAD). The MWCNT/PEDOT–FAD hybrid composite had good electrocatalytic properties for ascorbic acid, dopamine, uric acid and hydrogen peroxide compared with PEDOT, PEDOT–FAD, MWCNT/PEDOT and PEDOT–FAD/MWCNT. It had a linear concentration range of 4 × 10⁻⁴ to 8 × 10⁻³ M for ascorbic acid, 6 × 10⁻⁶ to 7.5 × 10⁻⁵ M for dopamine and 2 × 10⁻⁶ to 4 × 10⁻⁵ M for uric acid. The sensitivities were 36 μA mM⁻¹ cm⁻² for ascorbic acid, 5154 μA mM⁻¹ cm⁻² for dopamine and 14 286 μA mM⁻¹ cm⁻² for uric acid. The detection limits were 4 × 10⁻⁴ M for ascorbic acid, 6 × 10⁻⁶ M for dopamine and 2 × 10⁻⁶ M for uric acid (S/N = 3). It also showed good electrocatalytic reduction of H₂O₂ with a linear concentration range of 5 × 10⁻⁴ to 9 × 10⁻³ M, a sensitivity of 52 μA mM⁻¹ cm⁻² and a detection limit of 5 × 10⁻⁴ M (S/N = 3). We report here a simple method of synthesizing the active species on the surface of the electrodes for the simultaneous determination of ascorbic acid, dopamine, uric acid and H₂O₂. This hybrid could be used to develop multifunctional biosensors.