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

Abstract

• Glu functionalized RGO-Au nanocomposites were synthesized as an electrochemical chiral sensor. • The electrochemical chiral sensor has high chiral recognition capability for Trp enantiomers. • Mechanism and binding thermodynamics were explained by UV–vis and DFT in detail. 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 (I L /I D ) 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.