Trace identification of cysteine enantiomers based on an electrochemical sensor assembled from CuxS@SOD zeolite

The nonchiral sensor concept based on a sodalite (SOD) zeolite loaded CuxS (CuxS@SOD) catalyst is proposed as a sensing platform for chiral cysteine (Cys) determination. Chiral Cys is analyzed by the difference of binding capacity between CuxS catalysts. The observed current in amperometric i-t curve (A i-t C) is always positive for the L-cysteine (L-Cys), while it is negative for the D-cysteine (D-Cys). Under differential pulse voltammetry (DPV) method, the characteristic current peak for the CuxS@SOD moves to right (positive potential position) with the addition of L-Cys while it moves to left (negative potential direction) with the addition of D-Cys, respectively. Cyclic voltammetry (CV) is consistent with DPV and discusses the diffusion control mechanism. In this work, the ultra-trace determination of cysteine enantiomers reaches the limit of detection (LOD) of 0.70 fM and 0.60 fM by the highly efficient CuxS catalyst restrained in the nanosized SOD zeolite cages of the opening window pores, respectively. The sensor opens up a novel potential prospect for achiral composite in the field of chiral recognition through electrochemical methods with extra-low concentration. The sensor is generated by the combination of the CuxS and the Sodalite (SOD) structure zeolite. By using chronoamperometry method, the observed current value is always positive for the L-cysteine while the one for the D-cysteine is always negative. Under differential pulse voltammetry (DPV) method, the characteristic potential for the CuxS@SOD moves to right (positive potential direction) with the addition of L-cysteine while it moves to left (negative potential direction) with the addition of D-cysteine, respectively. The ultra-trace recognition towards cysteine enantiomers reaches the limit of detection (LOD) of 0.0007 pM and 0.0006 pM. And the pure L-cysteine, D-cysteine and the mixture can be found in the separate areas. [Display omitted]