Electrochemical activation of polyethyleneimine-wrapped carbon nanotubes/in situ formed gold nanoparticles functionalised nanocomposite sensor for high sensitive and selective determination of dopamine

An electrochemical sensor based on polyethyleneimine (PEI)–multiwalled carbon nanotubes (MWNTs)–gold nanoparticles (AuNPs) nanocomposite was constructed for determination of dopamine (DA). MWNTs–PEI–AuNPs nanocomposite combined the advantages of PEI-well dispersed MWNTs and in situ formed AuNPs, thus endowed with high stability and some special properties to the enzyme-free sensor. The formation of the material was characterized by scanning electron microscope, transmission electron microscope and energy-dispersive X-ray. Electrochemical activation of the modified sensor at a positive potential remarkably enhanced the signal due to some introduced fragmentation in the side wall of MWNTs–PEI–AuNPs. Another important conclusion which was not recognized before is that CVD–CNT with open end caps of CNT also can be electrochemically activated after coating with polyelectrolytes (PEs). The prepared sensor showed good performance for the determination of DA in a linear range from 50 to 4000 nM with a limit of detection of 6.56 nM and a sensitivity of 5.2 μA μM−1. It also exhibit high stability of at least 2 months and high selectivity of DA under the interferences of glucose, ascorbic acid, etc. due to the novel sensing materials and remarkable electrochemical activation. We also demonstrated the successful application of this sensor for the determination of dopamine in serum.