Exploration of synergism between a polymer matrix and gold nanoparticles for selective determination of dopamine

In this work, synergism between the conducting polymer matrix and gold nanoparticles is explored for dopamine sensing in the presence of excess ascorbic acid using poly (3,4-ethylenedioxythiophene) (PEDOT) in neutral phosphate buffer solutions (PBS 7.4). The electrodeposited thin films of PEDOT were characterized by atomic force microscopy (AFM) (and current sensing-AFM), and the incorporated Au nanoparticles by UV-Vis spectroscopy and electrochemical methods. Distinct “oxidized” and “reduced” regions of the polymer film were revealed in the CS-AFM. Electrochemical studies have shown that the catalytic oxidation of DA and AA on PEDOT modified electrodes can afford a peak potential separation of ∼230 mV. Further enhancement in the oxidation current for DA/AA oxidation was achieved by incorporation of Au nanoparticles in the PEDOT modified electrodes. The nanometer sized gold particles favour the nanomolar sensing of dopamine in the presence of excess of ascorbic acid (1.0 mM). The DA oxidation current increases linearly with DA concentration and the detection limit of DA is found to be ∼2 nM. Amperometric detection under stirred conditions is free from electrode fouling at lower concentrations of DA and is only slightly affected at concentrations beyond 20 μM. The combined effect of Au nanoparticles and the PEDOT matrix is based on the Aunano surrounded by a “hydrophobic sheath” tending to reside within these hydrophobic regions of PEDOT, increasing the DA oxidation current.