Gold nanoparticle/nickel oxide/poly(pyrrole-N-propionic acid) hybrid multilayer film: Electrochemical study and its application in biosensing

The present study describes the fabrication of Indium Tin Oxide /gold nanoparticles/nickel oxide/poly(PyrroleN-propionic acid) (ITO/GNPs/NiO/poly(PPA)) multilayered film, and its modification with Tyrosinase (Ty). The ITO/GNPs/NiO/poly(PPA) electrode was fabricated by sequential electrochemical assembly onto ITO substrate which electrochemical deposition provides a facile, inexpensive technique for synthesis of multilayered film within the adherent morphology with controllable film thickness. Cyclic voltammetry (CV), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), scanning electron microcopy (SEM), and atomic force microcopy (AFM) were used to characterize the film assembly processes. The properties of a semiconductor/electrolyte interface were investigated based on the Mott-Schottky (M-S) approach for the modified electrodes, with the flat band potential (E^sub FB^) according to the potential intercept and the carrier density (N^sub D^) according to the linear slopes. The N^sub D^ and E^sub FB^ of ITO/GNPs/NiO/poly(PPA) were obtained as 2.48.10^sup 21^ cm^sup -3^ and 0.26 V, respectively. Tyrosinase was immobilized using carbodiimide coupling reaction. The bioelectrode was characterized by FTIR-ATR, SEM, AFM, electrochemical impedance spectroscopy (EIS). A Randles equivalent circuit was introduced for modeling the performance of impedimetric biosensing for the detection of the dopamine (DP) and the interface of bioelectrode/electrolyte. The EIS of the ITO/GNPs/NiO/poly(PPA)-Ty exhibited significant changes in the charge transfer resistance (R^sub CT^) value toward the detection of dopamine over a linear range of 80 µM to 0.2 mM with a limit of detection (LOD) of 5.46 µM.