Development of a dry process for coating metal nanoparticles on carbon nanotubes

Metal nanoparticles such as platinum (Pt) and gold (Au) decorated CNTs have been thoroughly investigated as electrode of fuel cells and chemical and biological sensors. In these applications, the size and the density of nanoparticles are very important, because the catalyst activation depends on the particle size and the deposition amount. We focused on a dry processing without solutions and attempted to fabricate metal nanoparticles on CNTs by sputtering. In this study, the effect of the crystallinity of CNTs surface on the morphology of Pt film deposited by sputtering process was investigated. To control the crystallinity of CNTs surface, the Ar plasma irradiation was applied to CNTs and the crystallinity of CNTs surface was analyzed by Raman spectroscopy. As results, the I-D/I-G ratio of CNTs surface increased with the Ar plasma irradiation time. This suggested that the crystallinity of CNTs was changed to amorphous carbon with increasing the plasma time. Furthermore, the morphology of Pt on as-received CNTs and plasma-treated CNTs was changed to island shape by annealing at 750 degrees C. As a result, the particle size on plasma-treated CNTs was smaller with increasing the plasma treatment time. This indicated that morphology of Pt on CNTs related to crystallinity of CNTs surface.