Experimental Demonstration of Hydrophobicity Variation in Carbon Nanotubes by Surface Modifications

Surface modification of the carbon nanotubes is important for their application in various fields. In this study, multiwalled carbon nanotubes (MWCNTs) were grown on cobalt catalyst layer (3 nm thickness) sputtered on a silicon substrate using Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) system. The as-grown MWCNT layer was found to have a thickness of ∼5 μm and an average nanotube diameter ∼70 nm. The surface of as-grown nanotubes was modified by polyvinyl alcohol (PVA). The surface hydrophobicity has been estimated by measuring the static contact angles of water on nanotube surfaces before and after the modification by varying PVA concentration in the range of 1:10,000-5:10,000 (w/v). This functionalisation showed a dramatic change of the surface of nanotubes from highly hydrophobic to hydrophilic. The fictionalization of MWCNTs was confirmed further with electrochemical measurements.