Abstract
A methyl parathion (MP) DNA biosensor was constructed using Au nanoparticles doped in polymeric film on nano-composite carbon paste electrode. The nano-composite carbon paste (NCCPE) was composed of ionic liquid (IL), graphene nanosheets, Pt nanoparticles and graphite. The carbon paste electrode surface was covered by polypyrrole (PPy) film. It was seen that the existence of Pt NPs causes a better electrochemically deposition of PPy on NCCPE surface. The film was then doped with Au nanoparticles, and then, it was modified by a dd-DNA. The characterization of the biosensor surface was studied by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) methods. The biosensor response was obtained by differential fast Fourier transformation continuous linear sweep voltammetry (DFFTCLSV) technique, in which the change of the charge under curve (in form of coulomb) in a specific potential range was calculated. The combination of nanoparticles and conducting polymeric layer catalyzed the electron transfer, which amplifies the biosensor sensitivity. The result shows that the biosensor response was proportional to analyte concentration in the range of 10 to 300 nM, with a detection limit of 13 nM. Experimental parameters which affect the sensitivity of the biosensors were studied. The biosensor showed good reproducibility, long-term storage stability and accuracy. (C) 2014 Elsevier B.V. All rights reserved.