Fabrication and characterization of cytochrome c-immobilized polyaniline/ multi-walled carbon nanotube composite thin film layers for biosensor applications

Cytochrome c (Cyt c)-immobilized thin films of electropolymerized polyaniline (PANI)/carboxylated multi-walled carbon nanotube (cMWCNT) composite on a glassy carbon (GC) electrode were prepared and applied for trace level detection of hydrogen peroxide. The chemical structure, elemental analysis and surface morphology of the prepared thin films were respectively examined by Fourier-transform infrared spectroscopy, energy dispersive X-ray spectroscopy and scanning electron microscopy. Their electrochemical properties were characterized using, electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry techniques. The formal potential, average surface coverage, electron transfer rate constant, and charge transfer coefficient of (-9)(-2)(-1)(the prepared electrodes were calculated to be -0.35 V, 3.1 x 10)( mol cm)(, 3.01 s)(, and 0.37, respectively.) The modified electrode was highly sensitive for hydrogen peroxide detection with a sensitivity of 97.6 nA mu M-1 and a detection limit of 0.2 mu mol L-1 in a linear response range of 2-600 mu mol L-1. According to the obtained results, the proposed PANI/cMWCNT composite thin film could facilitate direct electron-transfer between the GC electrode surface and the redox center of Cyt c, indicating a promising application in next-generation biosensors.