Synthesis and Characterization of Cu-Adenine Oxidase-like Nanozyme and Application for Phenol Detection: A Comprehensive Experiment for Undergraduates

Nanozyme, a class of nanomaterials with enzyme-like properties, is a new concept that has appeared in the textbook of enzyme engineering. Due to the tunable catalytic activities, low cost and robustness to harsh environments, oxidase-like nanozymes have exhibited various applications in sensing and imaging fields. At the undergraduate level, it is of great importance to introduce these concepts (nanozyme, oxidase-like nanozyme and catalytic kinetics) and applications (constructing a visual sensor) to chemistry curricula. Herein, a simple, rapid, and safe method is introduced to synthesize Cu-Adenine nanozyme through Cu2+ coordinating with adenine in water at 70 °C for 20 min. With 2,4-dichlorophenol (2,4-DP) as a substrate and 4-aminoantipyrine (4-AP) as a chromogenic agent, Cu-Adenine nanozyme catalyzes the oxidation of 2,4-DP to oxidized 2,4-DP and further couples with 4-AP, exhibiting an absorption peak at 505 nm. The intensity of the absorption peak is dependent on the O2 concentration, demonstrating that Cu-Adenine is an oxidase-like nanozyme. After investigating the catalytic kinetics, a visual sensor based on Cu-Adenine nanozyme is designed for correctly detecting 2,4-DP in seawater, river water and sewage. As a comprehensive experiment for third-year undergraduate student at Beijing Normal University, the experiment provides students with a perspective for understanding oxidase-like nanozyme, catalytic kinetics, and successfully construct a visual sensor to detect environmental pollutant (2,4-DP is also a kind of pollutant). Importantly, this experiment spans from coordinate chemistry and synthetic chemistry to biological chemistry, physical chemistry, environmental chemistry and analytical chemistry, creating a concise interdisciplinary laboratory experience.