l-Cysteine@Island-Like Co₃S₄ on Co₃O₄ Nanosheet Arrays Heterostructure: Electrochemical Chiral Sensing of l-Tryptophan

It is highly important to efficiently recognize and detect chiral molecules in drug development and life sciences. In this paper, an electrochemical chiral sensor for the detection of L -tryptophan ( l -Trp), based on l -cysteine ( l -Cys)@island-like Co 3 S 4 on Co 3 O 4 nanosheet arrays heterostructure/carbon paper ( l -Cys@Co 3 S 4 –Co 3 O 4 /CP), is presented. Co-MOF triangular nanosheets with a thickness of ∼200 nm are first grown on the CP. After calcination and partial sulfidation, the Co 3 S 4 –Co 3 O 4 heterostructure forms. Finally, l -Cys, as a chiral selector, is uniformly decorated on the heterostructure. The island-like heterostructure exhibits superior electrical conductivity and could potentially provide active sites for the absorption of l -Cys. The l -Cys@Co 3 S 4 –Co 3 O 4 /CP electrode is utilized for the electrochemical recognition and detection of L -tryptophan ( l -Trp) via a differential pulse voltammetry (DPV) method. It demonstrates a recognition efficiency of 1.50 and shows high sensitivity (0.33 μA·μM –1 ) and a low detection limit (0.021 μM) for l -Trp within the concentration range of 0.06–2 mM. The electrode has good anti-interference ability, reproducibility, and repeatability. Moreover, it exhibits good detection performance of l -Trp in biological samples, with recovery ranging from 96% to 105%, demonstrating excellent potential in clinical applications.