A novel Co, N-doped Ti(3)C(2)T(x) MXene-based nanozyme and Cu doped silicon quantum dots for colorimetric and fluorometric detection of gallic acid.

Herein, a novel TiCT MXene-based nanozyme (CoN-TiC) with remarkable peroxide-like activity was successfully synthesized. CoN-TiC can catalyze hydrogen peroxide (HO) to produce reactive oxygen species (ROS), which could oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into oxTMB with characteristic absorption peak at 650 nm. Cu doped silicon quantum dots (Cu-SiQDs) with excellent fluorescence property was used as the fluorescence probes. The fluorescence of Cu-SiQDs at 458 nm would be quenched by oxTMB due to inner filter effect. Gallic acid (GA) as a typical antioxidant had great free radical scavenging ability, it could inhibit the oxidization of TMB into oxTMB, so the fluorescence of Cu-SiQDs would be restored. Therefore, a colorimetric and fluorometric sensing platform that had dual output signals and self-correction function was strategically constructed for GA determination. This sensing system possessed excellent sensitivity with low limits of detection (LOD) of 0.12 μM (fluorescent method) and 0.20 μM (colorimetric method). Moreover, this proposed platform was successfully applied to detect GA in green tea samples.