Preparation and characterization of multifunctional polypyrrole–Au coated NiO nanocomposites and study of their electrocatalysis toward several important bio-thiols

Polypyrrole (PPy) and Au were co-deposited onto the surface of NiO nanoparticles to prepare multifunctional nanocomposites for electroanalysis applications. It is proposed that each component in NiO/PPy–Au nanocomposites plays a great role on their electrocatalytical performance where conductive PPy helps to immobilize the nanocomposites onto the electrode surface due to its outstanding adherence ability, NiO does to mediate the oxidation of thiols through the redox couple of Ni(OH)2/NiOOH, and Au does to the electron transfer of nanocomposites and the redox transformation between Ni(OH)2 and NiOOH due to its high conductivity. The obtained NiO/PPy–Au nanocomposites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, UV–vis spectroscopy and powder X-ray diffraction. The obtained NiO/PPy–Au nanocomposites could be easily immobilized onto the surface of glassy carbon electrodes. They exhibit excellent electrochemical property for the redox couple Ni(OH)2/NiOOH and high electrocatalytical oxidation toward some typical and important biological thiols such as cysteine, homocysteine and glutathione. Cysteine could be selectively detected at the applied potential of 0.15 V where the interfering of homocysteine and glutathione is somewhat low. The NiO/PPy–Au nanocomposite modified electrode also shows high electrochemical response to the produced thiocholine from the hydrolysis reaction of acetylcholinesterase.