In Situ Electrodeposited Gold Nanoparticles on Polyaniline-Modified Electrode Surface for the Detection of Dopamine in Presence of Ascorbic Acid and Uric Acid

In this study, in situ electrodeposition of gold nanoparticles (AuNPs) over polyaniline (PANI)-modified glassy carbon electrode (GCE) surface using linear sweep voltammetry (LSV) has been found to be more effective than cyclic voltammetry (CV). LSV prevents stripping of the Au atoms from the electrode surface, thus leading to an efficient loading of AuNPs on the PANI matrix. The reduction of Au over PANI-modified GCE occurs at 0.34 V and the amount of Au loaded using LSV for 15 linear sweep cycles is 54.75 × 10 −9 g. Various techniques are employed to characterize the modified electrode surface. Fourier transform infrared spectroscopic studies show that the electroreduction of Au increases the quinoid moieties in PANI, and the X-ray diffraction data reveals the average crystallite size of AuNPs as 65 nm. The field emission scanning electron microscopy and atomic force microscopy analysis indicate the dispersion of spherical AuNPs over the PANI matrix. The electrochemical studies show enhanced electrocatalytic activity of the modified electrode surface at neutral pH, suitable for sensing biomolecule, dopamine (DA) amidst the interferences, ascorbic acid (AA), and uric acid (UA). The oxidation of DA reported to occur in the range of 0.270 V to 0.361 V for PANI-AuNPs based electrodes at neutral pH is lowered to 0.168 V at the modified electrode surface prepared electrochemically in the present study. The peak-to-peak separation for DA-AA and DA-UA is 108 mV and 345 mV, respectively, with the working linear range of 20–100 μM and a detection limit of 16 μM for DA. Such enhanced electrocatalytic response is attributed to a synergistic interaction between the PANI film and electrodeposited AuNPs. Graphical Abstract