Facile polymerization of b cyclodextrin functionalized graphene or graphene oxide nanosheets using citric acid crosslinker by in situ melt polycondensation for enhanced electrochemical performance
In this study, we report a facile, environmental friendly route to synthesize water insoluble b cyclodextrin (b CD)/graphene oxide (GO) or reduced graphene oxide (rGO) nanocomposite hydrogels. These nanocomposite hydrogels were synthesized by in situ melt polymerization; first, the b CD was covalently bound to GO to produce b CD/GO, and then b CD/rGO was obtained through in situ reduction of GO by hydrazine. These hybrid materials were polycondensed in the presence of melted citric acid (CT) as a crosslinker. The structures of the obtained macromolecules were characterized by ATR FTIR, Raman spectroscopy, TGA, DTG, DSC, DDSC, XRD, FE SEM, EDAX, and electrochemical impedance spectroscopy, and also by determining the amount of acidic groups and by adsorption of cationic methylene blue. These data have confirmed that b CD/GO or rGO was effectively polymerized using CT through ester linkages. Swelling ratio data shows the ability of these nanocomposites to absorb a large amount of water in their structures, and the b CD polymer/rGO (CDP CT/rGO) gels have higher equilibrium swelling ratios than the corresponding b CD polymer (CDP CT) and CDP CT/GO. The results of cyclic and differential pulse voltammetry electrochemical studies revealed that CDP CT/GO and CDP CT/rGO nanocomposite hydrogels exhibited higher electrochemical responses toward dopamine, tyrosine and uric acid (biomolecules) than unmodified CDP CT. In addition, CDP CT/rGO shows a higher response relative to CDP CT/GO, which is probably due to the restoration of the graphitic network after the reduction of GO. As a result, the improved electrochemical behaviors of these nanocomposites are due to a combination of the chemical properties of b CD, GO or rGO nanosheets, polyester and poly(carboxylic acid)