Layer-by-layer assembled films of multi-walled carbon nanotubes with chitosan and cellulose nanocrystals

Chitosan solutions and cellulose nanocrystal suspensions were used to produce highly stable aqueous dispersions of multi-walled carbon nanotubes (MWCNTs). The different MWCNT dispersions, presenting positive and negative charges, were used to prepare multilayered hybrid thin films through electrostatic layer-by-layer (LBL) self-assembly. The MWCNTs are well dispersed and homogeneously distributed on each layer of chitosan and cellulose nanocrystals of the films. The nanotubes are densely packed in each multilayer, forming a random network. The surface of the LBL film exhibited a uniform and relatively smooth surface with a mean roughness value of ∼5.8±0.4nm. Electrochemical characterization revealed a decrease in two orders of magnitude in the film resistance as the number of bilayers increased from 5 to 20, which is a consequence of an increase in the amount of conductive material (MWCNT). The thin films with up to 20 bilayers exhibited transmittance higher than 90% in the visible range. The results presented in this work demonstrate the viability of the LBL technique for the deposition of active materials using the biopolymer pair chitosan/cellulose nanocrystals. The obtained films can be employed for the design of transparent and biocompatible carbon nanostructured based electrodes.