Single-Layer Graphene Oxide-Amino-β-Cyclodextrin/Black Phosphorus Nanosheet Composites for Recognition of Tyrosine Enantiomers

A stable and effective chiral electrochemical sensor was designed to selectively identify tyrosine (Tyr) enantiomers by square wave voltammetry (SWV). Single-layer graphene oxide (SGO) and amino-β-cyclodextrin (NH₂-βCD) were integrated through an amidation reaction and then assembled with black phosphorus nanosheets (BPNSs) with a puckered orthorhombic layered structure to construct a chiral composite, which was used to modify a glassy carbon electrode to obtain a chiral electrochemical sensor (SGO-NH₂-βCD/BPNSs/GCE). Compared with the previously reported results, the covalent coupling and self-assembly methodologies for the preparation of SGO-NH₂-βCD/BPNSs/GCE greatly improved its recognition efficiency for Tyr enantiomers. SGO-NH₂-βCD/BPNSs/GCE showed a relatively higher affinity for d-Tyr with a lower oxidation peak potential and a higher oxidation peak current. Due to the different steric hindrances, the selective formation of hydrogen bonds among the hydroxyl/carboxyl groups of SGO-NH₂-βCD/BPNSs and the amino/carboxyl/phenolic hydroxyl groups of d-Tyr derived from the more suitable intermolecular distances, and the P–O interaction between SGO-NH₂-βCD/BPNSs and the phenolic hydroxyl/carboxyl groups of Tyr, better identification efficiency (ΔE_p = E_D – E_L = 36 mV and I_D/I_L = 1.94/ΔI = 8.89 μA) could be observed. Importantly, the concentrations of Tyr enantiomers had a good linear relationship with the peak currents, and the percentages of d-Tyr in racemic Tyr mixtures could be predicted at SGO-NH₂-βCD/BPNSs/GCE, confirming its ability in detection and quantitative analysis of Tyr enantiomers.