Dielectrophoretic assembly and surface treatment of carbon nanomolecules

Abstract

This dissertation describes experimental studies on the surface treatment and functionalisation of carbon nanomolecules. For characerisation of the disaggregation state of single-walled carbon nanotube bundles, dielectrophoresis with Raman spectroscopy has been investigated. The presence of semiconducting nanotubes in the Raman spectrum following dielectrophoretic assembly indicates incomplete disaggregation. I show that this novel technique is a more effective measure than two existing conventional techniques: (a) optical absorption measurement and (b) the reduction of (10, 2) semiconducting nanotube peak in the Raman spectrum. Excimer lamp processing has been used for three applications: (i) preferential destruction of metallic nanotubes, (ii) nitrization of nanotubes and (iii) instantaneous removal of nanotube caps by ozonolysis. Preferential destruction was undertaken by ultraviolet irradiation in an argon atmosphere. The Raman spectrum after radiation reveals that more metallic nanotubes were destroyed than semiconducting nanotubes. The radial breathing mode peak intensity of (13, 4) metallic nanotubes dropped by about 67 %. Nitrization of carbon nanotubes was undertaken by dissociation of nitric oxide using excimer lamp irradiation. Spectroscopic studies by FTlR and XPS on the irradiated nanotubes suggest that nitric oxide was chemically functionalised on the surface of the nanotubes. The change of surface morphology of the nanotubes was shown by transmission electron microscopy. Removal of nanotube caps was done by excimer lamp induced ozonolysis. Contact angle measurement and electron microscopy on the nanotubes which had been irradiated for ten seconds showed that the end-caps had been removed. Electrophoresis has been utilised for fabrication of a glass-like carbon film. Raman spectroscopy and scanning electron microscopy has shown the presence of glass-like carbon. This fabrication can be done at room temperature, whereas most fabrication processes are undertaken by high temperature processes exceeding 1000 oC