Homogeneous and structurally controlled thin films of single-wall carbon nanotubes by the Langmuir-Blodgett technique

Abstract

Optically homogeneous thin films of chemically solubilized single-wall carbon nanotubes (SWNTs) have been realized by using the Langmuir-Blodgett technique. Deposition can be performed in a layer-by-layer fashion up to 25 layers, allowing for precise control of the film thickness. Absorption spectra of these LB films preserving all the essential spectral features characteristic of semiconducting and metallic SWNTs prove that no serious alteration of their electronic structures occurred during the chemical treatment and functionalization. Polarized absorption spectroscopy demonstrates that the tubes are strongly oriented in the dipping direction. Comparison with thin films prepared by horizontal lifting show that both compression on the water surface and flow during vertical deposition contribute to this high degree of tube orientation. AFM profiles of SWNT monolayers indicate that most tubes are isolated or in small bundles of 1-6 nm sizes.