Peroxidase mimic Cu-MOF nanosheet for highly sensitive colorimetric detection of cysteine

• Cu-MOF shows the highly oxidizing ability toward H2O2-TMB system to have the obviously color change. • Cys with different concentrations can reduce the color of the Cu-MOF, H 2 O 2 and TMB reaction system, the visual detection of Cys can be realized easily through the observable color fading by bare eyes without any instrumentation. • The colorimetric approach has a good response to Cys detection with a linear range of 0.2 to 2.8 mM and a detection limit of 0.03 mM. In the present work, a simple and sensitive colorimetric sensing strategy based on Cu-MOF nanosheet for the detection of cysteine (Cys) is developed. Cu-MOF can catalyze the color change of the H 2 O 2 -TMB detection system from colorless to blue, and produce an obvious UV absorption peak at 652 nm. In the presence of Cys, it can effectively inhibit the color development of H 2 O 2 -TMB. Under optimal conditions, the absorbance value at 652 nm and the Cys concentration range from 0.2 mM to 2.8 mM show a linear relationship. The detection limit of the sensor is 0.03 mM, and it can effectively distinguish Cys from 9 other amino acids and its metabolites. In addition, we also assessed the Cys content in milk, which has practical significance for detection.