Surface Properties of Carbon Nanotubes Adsorbed at an Air-Water Interface

Particles of appropriate size and wettability adsorb strongly at fluid-fluid liquid interfaces, lowering the interfacial energy and thereby stabilizing emulsions and foams. In the present work, we investigated the surface properties of both functionalized and non-functionalized carbon nanotubes (CNTs) at an air-water interface. Our findings indicated that both types of CNTs adsorbed strongly at the air-water interface, leading to an increase in surface pressure. The surface elastic modulus was calculated upon compression, and the Volmer equation of states has been applied to model and understand the surface pressure data. The CNT-decorated interface was studied both optically (in situ) and with electron microscopy after performing Langmuir-Schaefer deposition. Both types of CNTs showed some degree of orientational ordering upon compression. At high surface coverage, CNTs formed a layer which wrinkled upon further compression. The corresponding compressional modulus was calculated from the wavelength of the undulations. The findings may have implications on the development of more stable emulsions and the production of CNT thin films with controllable packing density and orientational ordering. This work is supported by NSF CAREER award #1253613.