Polysaccharide-assisted incorporation of multiwalled carbon nanotubes into sol-gel silica matrix for electrochemical sensing

For the in situ incorporation of multiwalled carbon nanotubes (MWCNTs) into sol-gel silica matrix for electrochemical sensing, a water-soluble carboxymethylchitosan derivative having pendant pyrene moieties (CMCSPy) was prepared and used. It was found that such a modified polysaccharide could act both as the stabilizing agent for preparing colloidally stable dispersion of MWCNTs in an aqueous system and the accelerating agent for inducing rapidly the sol-gel transition of water-soluble siliceous precursor, tetrakis(2-hydroxyethyl)orthosilicates (THEOS). By dissolving directly THEOS in aqueous MWCNT dispersions stabilized by CMCSPy, the gel matrices incorporated with well-dispersed MWCNTs could be obtained in mild conditions. Moreover, the incorporation of MWCNTs could shorten the time interval for the gel formation and enhance the gel strength, as confirmed by rheological analyses. By electrochemical experiments, it was found that the as-prepared gel matrix with MWCNTs could be used to construct the amperometric hydrogen peroxide biosensor with an improved response due to the favorable electrochemical characteristics of the incorporated MWCNTs.