Abstract
Graphene oxide (GO) coated electrodes provide an excellent platform for enzymatic glucose sensing, induced by the presence of glucose oxidase and an electrochemical transduction. Here, we show that the sensitivity of GO layers for glucose detection redoubles upon blending GO with chitosan (GO+Ch) and increases up to eight times if covalent binding of chitosan to GO (GO−Ch) is exploited. In addition, the conductivity of the composite material GO−Ch is suitable for electrochemical applications without the need of GO reduction, which is generally required for GO based coatings. Covalent modification of GO is achieved by a standard carboxylic activation/amidation approach by exploiting the abundant amino pendants of chitosan. Successful functionalization is proved by comparison with an ad-hoc synthesized control sample realized by using non-activated GO as precursor. The composite GO−Ch was deposited on standard screen-printed electrodes by a drop-casting approach. Comparison with a chitosan-GO blend and with pristine GO demonstrated the superior reliability and efficiency of the electrochemical response for glucose as a consequence of the high number of enzyme binding sites and of the partial reduction of GO during the carboxylic activation synthetic step.
Highlights
Chitosan (Ch, scheme 1) is a natural cationic polysaccharide, deriving from shrimp shells and characterized by abundant –OH and –NH2 groups
X-ray photoelectron spectroscopy (XPS) was performed on Graphene oxide (GO), GO–Cl, Ch and GO−Ch samples; the spectra are reported in figure 1 and figure S3 in ESI, whereas the abundance of the different functional groups, defined on the basis of the binding energy of the different functional groups, are reported in table S2 in ESI
Electrochemical measurements performed at GO−Ch modified screen-printed electrodes (SPE) show the electrocatalytic effect induced by the presence of the coating toward oxygen reduction: the voltammogram registered in atmospheric conditions, i.e. in the presence of oxygen, exhibits a reduction peak at −0.4 V significantly shifted at less negative potentials with respect to that obtained at the pristine, carbon-based, electrode surface
Summary
Fabrizio Poletti , Laura Favaretto, Alessandro Kovtun , Emanuele Treossi, Franco Corticelli, Massimo Gazzano, Vincenzo Palermo2,4,5 , Chiara Zanardi and Manuela Melucci. Abstract attribution to the Graphene oxide (GO) coated electrodes provide an excellent platform for enzymatic glucose sensing, author(s) and the title of the work, journal citation induced by the presence of glucose oxidase and an electrochemical transduction. +Ch) and increases up to eight times if covalent binding of chitosan to GO (GO−Ch) is exploited. The conductivity of the composite material GO−Ch is suitable for electrochemical applications without the need of GO reduction, which is generally required for GO based coatings. Covalent modification of GO is achieved by a standard carboxylic activation/amidation approach by exploiting the abundant amino pendants of chitosan. Comparison with a chitosan-GO blend and with pristine GO demonstrated the superior reliability and efficiency of the electrochemical response for glucose as a consequence of the high number of enzyme binding sites and of the partial reduction of GO during the carboxylic activation synthetic step
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