Fabrication and properties of single wall carbon nanotubes and hyperbranched diazonium salt self-assembly multilayers

Acid treated single-wall carbon nanotubes (SWNTs) were fabricated into multlayers with a hyperbranched polymer of diazonium salt (DAS) using the layer-by-layer electrostatic adsorption technique. The fabrication process, multilayer thickness variation, multilayer surface morphology and the interaction between SWNTs and DAS were detected by UV-Vis absorption spectroscopy, ellipsometry, atomic force microscopy, scanning electron microscopy and Raman spectroscopy, respectively. Moreover, the nanomechanical properties of the multilayer film was measured by nanoindentation. All results show that SWNTs and DAS can be fabricated into multilayers. based on the cooperation of electrostatic attraction and chemical cross-linkage between SWNTs and DAS. Further, this cooperation endows the SWNTs/DAS multilayer films with outstanding nanomechanical properties. Their hardness and modulus may be as high as 2.0 GPa and 10.0 GPa, respectively. Finally, the SWNTs/DAS multilayer film can be peeled off from the substrate as a free-standing membrane.