Sensitive Detection of Trace Vitamin C via Enzyme-like Catalysis of S Defect-Rich Ultrathin 2D MoS2: Comprehensive Innovative Experiments on Two-Dimensional Materials for Undergraduates

Enzyme-like catalysis is the use of artificial catalysts to catalyze chemical reactions, which has the characteristics of enzymatic catalysis, such as high selectivity, high efficiency, and mild reaction conditions. In recent years, 2D materials, thickness ranging from a single to several atomic layers, have become a hot research topic in the field of materials, while 2D materials happen to have enzyme-like catalysis property. Among them, 2H-MoS2 is easy to peel away to form the 2D structure due to covalent bonds between S–Mo–S in each layer and van der Waals forces between layers. Meanwhile, using a mechanical solid-phase chemical method to produce its S defect, the S defect can significantly improve the catalytic efficiency and achieve rapid catalytic oxidation of TMB (3,3,5,5-tetramethylbenzidine) for quantitative detection of trace ascorbic acid. The experiment described in this study is designed for senior undergraduates majoring in chemistry, materials, chemical engineering, catalysis, etc., as part of their training in comprehensive chemical experimentation. This experiment can introduce students to the synthesis of 2D materials, enzyme-like catalytic reactions, and the principles for the use of analytical instruments. Integrating this experiment into undergraduate teaching will (1) stimulate students to think about developing innovative detection methods answering to actual scientific and social needs; (2) familiarize the students with serious and rigorous scientific method through the process of exploring and optimizing detection methods; and (3) increase students' understanding of catalytic analysis and detection through exploration of innovative detection methods, thereby raising their practical skills to a high-level.