Self-assembled monolayers of pyridylthio-functionalized carbon nanotubes used as a support to immobilize cytochrome c.

Self-assembled monolayers (SAMs) of pyridylthio-functionalized multiwalled carbon nanotubes (pythio-MWNTs) have been constructed on the gold substrate surface, which were used as a support to immobilize cytochrome c (Cyt c). The assembly processes of the SAMs and adsorption of Cyt c were monitored by using quartz crystal microbalance (QCM). Based on the frequency change of the QCM resonator, the surface coverage for the SAMs of pythio-MWNTs was estimated to be about 5.2 μg/cm2, and that of the Cyt c adsorbed was about 0.29 μg/cm2. For the gold electrode modified by the SAMs of pythio-MWNTs-Cyt c, a quasi-reversible redox wave was recorded with the cathodic and anodic potentials at about -0.55 and -0.28 V vs Ag/AgCl, respectively. Compositions and morphologies of the SAMs before and after immobilization of Cyt c were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy.