Graphene-carbon nanotubes modified graphite electrode for the determination of nicotinamide adenine dinucleotide and fabrication of alcohol biosensor

Through layer-by-layer adsorption (LBL) technique, the positively charged multiwalled carbon nanotubes (MWCNTs) and negatively charged graphene multilayer film were formed on graphite-poly(diallyldimethylammoniumchloride)-polystyrenesulphonate (Gr/PDDA/PSS) modified electrode. Due to large surface area and remarkable electrocatalytic properties of MWCNTs and graphene, the Gr/(PDDA/PSS-[MWCNTs-NH (3) (+) -graphene-COO-](5)) electrode exhibits potent electrocatalytic activity towards the electro-oxidation of nicotinamide adenine dinucleotide (NADH). A substantial decrease in the overpotential was observed at modified electrode, and the electrode showed high sensitivity to the electrocatalytic oxidation of NADH. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The diffusion coefficient was calculated by chronocoulometry. Chronoamperometric studies showed the linear relationship between oxidation peak current and the concentration of NADH in the range 25-250 mu M (R = 0.999) with the detection limit of 0.1 mu M (S/N = 3). Further, dopamine, uric acid, acetaminophen and hydrogen peroxide do not interfere in the detection of NADH. The ability of MWCNTs and graphene to promote the electron transfer between NADH and the electrode exhibits a promising biocompatible platform for development of dehydrogenase-based amperometric biosensors. Alcohol dehydrogenase (ADH) was casted on Gr/(PDDA/PSS-[MWCNTs-NH (3) (+) -graphene-COO-](5)) electrode; the resulting biosensor showed rapid and high sensitive amperometric response to ethanol with the detection limit of 10 mu M (S/N = 3).