Sensitive colorimetric sensing of glutathione and H2O2 based on enhanced peroxidase mimetic activity of MXene@Fe3O4

The peroxidase-like activity of MXene@Fe 3 O 4 nanocomposites and the relevant colorimetric application have been investigated for the first time. According to a kinetic study, MXene@Fe 3 O 4 nanocomposites displayed higher peroxidase activity than their individual components, and the catalytic process followed a ping-pong mechanism. The improved peroxidase-like activity of the MXene@Fe 3 O 4 nanocomposites was obtained due to the synergetic impact of the Fe 3 O 4 and MXene phases, the huge ion-accessible interface, and quick electron transfer channels in the nanocomposites. In the presence of hydrogen peroxide (H 2 O 2 ), the MXene@Fe 3 O 4 nanocomposites can catalyze the reaction of the colorless substrate 3, 3, 5, 5-tetramethylbenzidine (TMB) into oxidized TMB which revealed a blue color at 652 nm. After the introduction of glutathione (GSH), the blue color was gradually fading owing to the hydroxyl radical scavenging effect of glutathione. A colorimetric detection platform based on the peroxidase-like activity of the MXene@Fe 3 O 4 nanocomposites was developed for H 2 O 2 and GSH with a detection limit of 0.4 μM and 0.5 μM, respectively. The calibration plot for glutathione detection is calculated by absorbance difference at 652 nm, which ranged from 0.5 to 10 μM with a detection limit of 0.2 μM. The recoveries of GSH with different concentrations ranged from 93.76 to 108.50% and the relative standard deviation from 0.30 to 5.96%. This work significantly extends the application of MXene@Fe 3 O 4 nanocomposites in the construction of colorimetric sensors and reveals a satisfactory result in real sample analysis. Graphical Abstract