Build-up of single-walled carbon nanotube/cellulose nanocrystal multilayered thin films

National audienceSingle-walled carbon nanotubes (SWNTs) are one-dimensional nanostructures with unique properties such as high mechanical strength, electrical conductivity, and optical properties. Their integration into polymer composites systems have been well reported during the last decades. Principal limitation for transferring nanoscale properties of SWNTs to macro-scale devices is due to their insolubility in most solvents. Biopolymers, such as protein, peptides, nucleic acid or polysaccharides [1], are known to non-covalently disperse SWNTs in water and to allow the formation of robust nanocomposites with optimized properties using solution-based techniques. In this study, for the first time, we report the dispersion of SWNTs by cellulose nanocrytals (CNs). Cellulose possesses outstanding physical properties such as high mechanical resistance and low density, and moreover benefits from tremendous natural abundance. Cellulose occurs in vivo in plant cell walls in the form of slender microfibrils, which are combined with other biomacromolecules to form supramolecular assemblies where they act as reinforcer. Cellulose nanocrystals (CNs) are obtained from sulfuric acid hydrolysis of microfibrils that yields negatively charged short crystalline rods with a cross section between 3 and 20 nm and a length between 100 nm and several micrometers, depending on the biological origin. Highly concentrated SWNTs dispersions with long-time stability were obtained after ultrasonication in CNs colloidal suspensions. Similarly to CNs suspensions, SWNTs/CNs dispersions were used to elaborate multilayered thin films by the layer by layer [2] (lbl) method. Characterisation of the dispersion, growth pattern, Raman and optical properties of the films were investigated. Up to 8 bilayers films, ®150nm thick, have been obtained. These films exhibit a nice deep blue colour due to CNs optical properties. The presence of isolated SWNTs in each bilayer is attested by characteristic luminescence Raman signals. The lbl technique is a simple and versatile method for tuning composition and properties of nanostructured thin films. These films may be interesting for sensing applications