Tailoring the chemo-resistive response of self-assembled polysaccharide-CNT sensors by chain conformation at tunnel junctions Original Research Article

The performances of the e-noses used for the detection of toxic volatiles or anticipated diagnosis of diseases are closely related to the nanostructure of their conductive polymer composite (CPC) vapour sensors. It is attractive to be able to adjust a nanometric parameter such as the tunnel junctions’ gap between nanofillers in the percolated network of CPC sensors, to tune their macroscopic chemo-resistive properties, i.e., sensitivity and selectivity to organic vapours. Therefore, three types of transducers (multiwalled carbon nanotubes (CNTs), CNT functionalized by amylose, and CNT functionalized by amylopectine) were hierarchically assembled by spray layer by layer and exposed to water, methanol and toluene vapours. Amylose and amylopectine macromolecules, which have the same chemical nature but a different structure, linear and highly branched, are found (by atomic force microscopy) to adsorb in different conformations on CNT surface, helical and random, respectively. Interestingly, amylose is enhancing the sensitivity of CNT transducers to water by a factor 5, whereas amylopectine increases the sensitivity to toluene by a factor 1.5. These results suggest that changing the conformation of the polysaccharides adsorbed on CNT not only allows to tailor CPC chemo-resistive sensors sensitivity but also their selectivity by a specific orientation of chemical groups.