Facile polymerization of β-cyclodextrin functionalized graphene or graphene oxide nanosheets using citric acid crosslinker by in situ melt polycondensation for enhanced electrochemical performance

Abstract

In this study, we report a facile, environmental friendly route to synthesize water-insoluble β-cyclodextrin (β-CD)/graphene oxide (GO) or reduced graphene oxide (rGO) nanocomposite hydrogels. These nanocomposite hydrogels were synthesized by in situ melt polymerization; first, the β-CD was covalently bound to GO to produce β-CD/GO, and then β-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 β-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 β-CD polymer/rGO (CDP-CT/rGO) gels have higher equilibrium swelling ratios than the corresponding β-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 β-CD, GO or rGO nanosheets, polyester and poly(carboxylic acid).