An electrochemical chiral sensor based on glutamic acid functionalized graphene-gold nanocomposites for chiral recognition of tryptophan enantiomers

A novel chiral sensing platform via the glutamic acid (Glu) functionalized graphene-gold nanoparticles (RGO-Au/l-Glu and RGO-Au/d-Glu) synthesized via the one-step hydrothermal method is described for the enantioselective recognition of L- and d-tryptophan (Trp). The SEM, TEM, EDS, AFM, FTIR, and XRD characterization techniques showed that RGO-Au/l-Glu and RGO-Au/d-Glu chiral composite were successfully synthesized. By combining the chiral features of Glu and the excellent electrochemical behaviors of RGO-Au, two electrochemical chiral sensing interfaces constructed by RGO-Au/l-Glu and RGO-Au/d-Glu modified glassy carbon electrode (GCE) were constructed for electrochemical chiral recognition of Trp enantiomers. The results demonstrated that the RGO-Au/l-Glu/GCE showed the highest chiral recognition efficiency, the enantioselectivity coefficient (IL/ID) was 2.56. UV–vis absorption spectroscopy and density functional theory (DFT) calculations proved that RGO-Au/l-Glu had a strong binding ability with l-Trp. In addition, the chiral sensing interface had a linear response in the 1 mM to 5 mM Trp concentration range and a 0.28 mM detection limit (at S/N = 3) for l-Trp, and 0.86 mM to d-Trp, also had good stability and reproducibility, which can be used as an efficient chiral sensing interface for the recognition of Trp enantiomers.