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 Co3S4 on Co3O4 nanosheet arrays heterostructure/carbon paper (l-Cys@Co3S4–Co3O4/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 Co3S4–Co3O4 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@Co3S4–Co3O4/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.