Transparent Foamlike 2D Networks of Nitrogen-Doped Multiwalled Carbon Nanotubes Obtained by Self-Assembly

Abstract

Organizing carbon nanotubes into true mono- layerstructuresishighlydesirable,butthishasbeendifficultdue to their low solubility and tendency to aggregate. Here, we introduce a novel procedure to fabricate monolayers of nitro- gen-doped carbon nanotubes (CNx) using a Langmuir trough. Doped nanotubes disperse well in the subphase and slowly get trapped by the air/water interface, self-organizing in a remark- able two-dimensionalfoamlikenetwork at lowsurface densities, as observed in situ by Brewster angle microscopy, with a thickness that corresponds to one layer. More compact films are easily obtained by compression. Atomic force microscopy (AFM) and scanning electron microscopy images of transferred films on solidsubstrates show thattheirfoamlike network structure is preserved. The transparencyofthe films was determined by optical reflectance in the UVvis region and their Raman spectra in different areas. The average thickness of these transferred films was measured by means of ellipsometry and AFM.