β-Cyclodextrin dinuclear copper supported on graphene/polypyrrole nanocomposites as an electrochemical sensor for enantioselectivity recognition of tryptophan enantiomers

Electrochemical chiral recognition has gained much of attention as an efficient method for enantiomeric recognition. Herein, a chiral sensing platform via β-cyclodextrin dinuclear copper (Cu-β-CD) as a chiral selector supported on graphene/polypyrrole (RGO/Ppy) nanocomposites were fabricated for recognition of tryptophan (Trp) enantiomers. Cu-β-CD with additional chiral sites improves recognition efficiency, and the addition of the conducting polymer Ppy enhances the electrical conductivity of the nanocomposite and addresses the agglomeration effect of graphene (RGO). In addition, the composition and morphology of the materials were analyzed by transmission electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The mechanism of chiral recognition was evaluated by water contact angle experiments and UV–Vis absorption spectroscopy. And the battery of chiral recognition experiments revealed that the chiral sensing platform RGO/Ppy/Cu-β-CD/GCE provides excellent recognition of the Trp enantiomer with an enantioselectivity coefficient of 3.24. It also exhibits outstanding stability and reproducibility, with a minimum line of detection (LOD) of 0.37 mM and 1.05 mM for L-Trp and D-Trp, respectively. With these results, the RGO/Ppy/Cu-β-CD/GCE chiral sensing platform has provided a feasible approach for the electrochemical chiral recognition of Trp enantiomers.