Entropy-driven adsorption of carbon nanotubes on (001) and (111) surfaces of CeO_2 islands grown on sapphire substrate

摘要

According to the aim to compose combinatorial material by adsorption of carbon nanotubes onto the structured CeO_2 surface the interaction of the armchair (5,5) and zigzag (8,0) nanotubes with the (001) and (111) surfaces of CeO_2 islands have been investigated by theoretical methods. The thermodynamics of the adsorption were studied at the low surface coverage region. The interaction energy between the nanotube and the different CeO_2 surfaces shows significant increase when the size of the interface reaches 7-8 unit cells of CeO_2 and it remains unchanged in the larger interface region. However, the entropy term of the adsorption is significantly high when the distances of CeO_2 islands are equal to 27 nm (adsorption of armchair (5,5) nanotube) or 32 nm (adsorption of zigzag (8,0) nanotube). This property supports adsorption of nanotubes onto CeO_2 surfaces which possesses a very specific surface morphology. A long-wave vibration of nanotubes was identified as background of this unexpected phenomenon. This observation could be applicable in the development of such procedures where the nanotube adsorption parallel to the surface is aimed to perform.