Single-wall carbon nanotube dispersions stabilised with N-trimethyl-chitosan

We report the noncovalent complexation of a biocompatible low substituted N-trimethyl chitosan (TMC), a cationic chitosan derivative, onto the graphitic surface of single-walled carbon nanotubes (SWCNTs). TMC was synthesized and characterized by 1H-NMR. A yield between the range of 34% and 56% was obtained with a degree of substitution of 19.7%. SWCNTs dispersed in TMC resulted in stable dispersions, which were further characterized by Atomic Force Microscopy (AFM) Raman Spectroscopy and ζ-potential. AFM and Raman spectroscopy studies confirmed that smaller diameter SWCNTs are preferentially dispersed by TMC molecules resulting in stable dispersions. In addition TMC coated CNTs have a high ζ-potential over a wide range of pH (2-12) exceeding values from 35 mV (pH 2) up to 10 mV (pH 12) respectively. The presence of TMC induces electrostatic repulsions which stabilize the CNTs against van der Waals attractions resulting in stable dispersions. Such complexes may have potential applications in nanomedicine