Deposition of Au colloids on plasmachemically modified carbon nanofibers

The surface properties of fishbone (FB) carbon nanofibers (CNFs) were altered. This was achieved by H2O-plasma treatment (FB-plasma) and oxidation in HNO3 (FB-HNO3). By zeta-potential measurements, the surfaces of as-grown and acid treated CNFs were found to be negatively charged at all pHs. Meanwhile, basic entities were introduced by H2O-plasma treatment, indicated by an isoelectric point of pH 4.6. Ultraviolet–visible measurements indicated the successful deposition of negatively charged Au colloids on FB-plasma, and incomplete deposition on FB-HNO3. The nature of the basic sites accommodating colloid deposition is discussed based on X-ray photoelectron spectroscopy (XPS) results. The XPS study indicated significant differences in the type and amount of surface groups. Also, a variation in the fraction of defect and/or edge sites was found. The possible sites responsible for colloid immobilization are discussed based on the XPS results. Plasma treatment is demonstrated as a simple and effective procedure for altering the surface characteristics of CNFs.