(458j) The Surface Pressure and Microstructure of Carbon Nanotubes at an Air-Water Interface

Interface-driven assembly of particles has been demonstrated by a number of authors (1). The corresponding physics is intriguing and fairly well documented for micron-size particles with a moderate aspect ratio (<10) (2). Carbon nanotubes (CNTs) are rolled cylinders of graphene sheets with an aspect ratio exceeding 50 and their interfacial behavior remains largely unexplored. In the present work, we investigated the surface pressure and interfacial assembly of both functionalized and non-functionalized CNTs at an air-water interface (3). Firstly, our findings indicated that both types of CNTs adsorbed strongly at the air-water interface, leading to an increase in surface pressure. Volmer equation of states (4) has been applied to model and understand the surface pressure data. Secondly, the CNT-decorated interface was studied both in situoptically and with electron microscopy after performing Langmuir-Schaefer deposition. Both types of CNTs showed some degree of orientational ordering upon compression. To quantify the degree of orientation for each type of CNTs, the scalar order parameters were calculated from the electron micrographs. 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.

References

1. Pieranski, P., Two-dimensional interfacial colloidal crystals. Phys. Rev. Lett., 45(7), 569-572 (1980).
2. Lewandowski, E.P. et al., Orientation and self-assembly of cylindrical particles by anisotropic capillary interactions. Langmuir, 26(19), 15142-15154 (2010).
3. Vora, S. R. et al., Surface pressure and microstructure of carbon nanotubes at an airâ??water interface. Langmuir, 31(16), 4663 - 4672 (2015).
4. Fainerman, V.B. et al., Surface-pressure isotherms of monolayers formed by microsize and nanosize particles. Langmuir, 22(4), 1701-1705 (2006).