Preparation of thiolated polymeric nanocomposite for sensitive electroanalysis of dopamine

We report on the thiol-ene chemistry guided preparation of novel thiolated polymeric nanocomposite films of abundant anionic carboxylic groups for electrostatic enrichment and sensitive electroanalysis of cationic dopamine (DA) in neutral solution. Briefly, the thiol-ene nucleophilic reaction of a carboxylated thiol with oxidized polypyrrole (PPy), which was electrosynthesized on an Au electrode in the presence of solution-dispersed acidified multiwalled carbon nanotubes (MWCNTs), produced an a PPy–thiol–MWCNTs/Au electrode, and the PPy can be electrochemically overoxidized (OPPy) to form an OPPy–thiol–MWCNTs/Au electrode. The carboxylic groups of the polymeric nanocomposite film originate from the acidified MWCNTs, PPy-tethered carboxylated thiol, and OPPy. The carboxylated thiols examined are mercaptosuccinic acid (MSA) and thioglycolic acid, with β-mercaptoethanol as a control. Electrochemical quartz crystal microbalance, scanning electron microscopy, Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy were used for film characterization and process monitoring. Under the optimized condition, the differential pulse voltammetry peak current of DA oxidation at OPPy–MSA–MWCNTs/Au electrode is linear with DA concentration from 1.00×10–9 to 2.87×10–6 mol L−1, with a limit of detection of 0.4 nmol L−1, good anti-interferent ability and stability.

► Stripping electroanalysis of dopamine using thiol-ene chemistry of polypyrrole nanocomposite. ► Sub-nM detection limit of dopamine. ► Examination of polypyrrole thiolation by quartz crystal microbalance.