Enantiomeric covalent organic polymers-based electrodes for selective electrochemical recognition of cysteine enantiomers and detection of L-Cysteine

In this work two novel chiral sensing platforms were constructed from enantiomeric covalent organic polymers (R-CCOP and S-CCOP) prepared via a one-step solvothermal method, for the enantioselective recognition of L- and D-cysteine (Cys). The prepared materials were characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), nitrogen adsorption-desorption (BET), and X-ray diffraction (XRD). By integrating the chiral characteristics of R-(+)-1,1-bisnaphthyl-2,2-diamine/S-(-)-1,1-bisnaphthyl-2,2-diamine building blocks with the electrochemical behavior of large π-conjugated systems formed after polymerization, two types of electrochemical chiral sensing interfaces were constructed using glassy carbon electrodes (GCE) modified with R-CCOP and S-CCOP. These interfaces were employed for the electrochemical chiral recognition of Cys enantiomers. The results showed that R-CCOP/GCE exhibited the highest chiral recognition efficiency, with an enantioselectivity coefficient ( I L / I D ) of 2.86, while S-CCOP/GCE had a chiral recognition efficiency of 1.37. Density functional theory (DFT) calculations confirmed that both R-CCOP and S-CCOP demonstrated stronger recognition capabilities for L-Cys, with hydrogen bonding being the key factor in recognition. Additionally, the R-CCOP/GCE sensing interface exhibited a linear response within a concentration range of 5 µM to 500 µM for L-Cys, with a detection limit of 0.50 µM (S/ N  = 3) for L-Cys, along with good stability and reproducibility, making it an effective chiral sensing interface for the recognition of Cys enantiomers.