Conductive Polymer nano-bioComposites (CPC): Chitosan-carbon nanoparticle a good candidate to design polar vapour sensors

Conductive Polymer nanoComposites (CPC) prepared from the dispersion of carbon nanoparticles into a chitosan biomatrix (Chit-CNP) have been successfully used to develop polar solvent vapours (water and methanol) sensors, by spray layer-by-layer process. Such CPC transducers give a quantitative response when exposed to water vapour that can be considered as a sorption isotherm and very well fitted with a Langmuir–Henry-Clustering (LHC) diffusion model. This model gives a new insight into understanding of chemo-electrical behaviour of CPC and appears to be helpful to optimise sensor design by tailoring transducer initial characteristics to suitable solvent vapour fraction measurement range. Moreover, Chit-CNP sensors selectivity allowed ranking vapours by relative response amplitude (Ar) in the following order: water > methanol > toluene. The origin of this selectivity was not found into χ12 the Flory–Huggins polymer/solvent interaction parameter but into δp, ɛr and d, respectively the polar component of solubility parameter, the dielectric permitivity and the molecules size of solvents. Surprisingly little influence of chitosan nature and treatment on chemo-electrical behaviour was found.