Growth of Carbon Nanotubes on Metallic Substrate: Growth Mechanism and Electrochemical Applications

Abstract

This work reports the use of carbon nanotubes-modified silver (CNTs-Ag) electrode prepared by chemical vapor deposition (CVD) as indicating system in differential electrolytic potentiometry (DEP) for both redox and precipitation reactions. Characterization of CNTs-Ag electrode by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) showed the formation of aligned CNTs of a good degree of crystallinity and well-graphitized sheets. CNTs-Ag electrode was applied successfully for the determination of ascorbic acid in both pure form and in pharmaceutical and food samples along with in the determination of cyanide too down to quite low concentrations. CNTs-Ag electrode exhibited a fast and stable response and attained equilibrium in a short time. These good characteristics are attributed to the rapid heterogeneous electron transfer and high electrode surface area offered by CNTs. Additionally, modification of the Ag with CNTs grown via CVD method offers adhesion of the CNTs layers to the Ag surface and direct electrical contact better than the external modification methods commonly used such as casting the CNTs or mixing them with Nafion. Moreover, CVD method offers the chance to produce aligned CNTs that have better electrical properties than the randomly distributed ones. This work also proposed a CNTs growth mechanism by XPS depth profiling analysis. Figure 1