Morphology control of CNT-TiO2 hybrid materials and rutile nanotubes

Carbon nanotube-inorganic hybrid materials are a new class of functional materials that has gained tremendous interest in recent years due to their exceptional optical, mechanical, electrical and thermal properties. The hydrophobicity of the carbon nanotubes's surface disfavours the adsorption of hydrophilic particles, thus limiting the quality and performance of the hybrid material. We demonstrate that using benzyl alcohol as a surfactant enables TiO2 to interact with the hydrophobic surface of pristine CNTs without the need of covalent functionalisation. The quality of the TiO2 coating is strongly affected by various reaction conditions, including the order of mixing, the choice of drying method, and the water concentration. Furthermore, the effect of heat treatment on the crystallisation of amorphous TiO2 to anatase and the phase transformation from anatase to rutile is discussed in detail. The key achievement of this work is the control of morphology and structure of the TiO2 coating and, after removal of the CNTs, of the rutile nanotubes, which also allows the production of the ideal CNT-TiO2 hybrid material for the desired photochemical, catalytic and sensor applications.