AbstractsChemistry

This project aimed to produce Janus carbon nanotubes (CNTs) that have onehydrophobic and one hydrophilic end. These particles could then be manipulated intwo-phase polymer systems or at liquid-liquid interfaces enabling new routes to novelnanotube architectures.Vertically aligned arrays of MWNTs were grown on silicon wafers by an injectionCVD method using toluene as carbon source and ferrocene as catalyst. The lengths ofCNTs were found to be affected by the reaction time and the flowrate of carrier gas.The optimum growth conditions for aligned CNT arrays which could be masked were100 ml/min argon as carrier gas and a reaction time of 1 h.Partial masking which protected half the length of the CNT arrays has been used inorder to subsequently realise asymmetric functionalisation. It was not found possibleto partially mask the CNT arrays using polystyrene by various approaches. Howeverpartial masking was achieved by the thermal-impregnation of paraffin wax. It wasfound that impregnating at 90 ºC for 3 min led to wax masking the top half of thealigned CNTs, which was suitable for further modification. Theoretical models werealso considered to interpret the thermal-impregnation process of paraffin wax into theCNTs array.Two routes were proposed to selectively functionalise the masked nanotubes, namelyplasma treatment, and electrochemical oxidation. Decline of water contact angles andincrease of ID/IG ratio proved plasma treatment to be effective to functionalise alignedCNTs array. The paraffin wax on partially masked array was sacrificially etched byplasma and prevented CNT functionalisation. As a consequence, the wax-masked endof nanotubes remained hydrophobic, while the unmasked end became nearlyhydrophilic.Electrodes were prepared from the aligned CNT arrays for the electrochemicaloxidation. CV and Raman spectra indicated the formation of oxygen-containingfunctional groups on the CNTs. A constant potential of 1.4 V for 30 s was found to beefficient to electrochemically oxidise the CNTs. According to the contact anglemeasurements, the electrochemically oxidised sample could be considered as Januscarbon nanotubes, which are hydrophilic on one side and hydrophobic on the other.