Significantly improved catalytic activity of copper nanocrystal by introducing Ti₃C₂T_X and arginine and...

Copper nanocrystal has been widely used as nanozyme for construction of optical sensing platforms because of low cost, special catalysis, and high stability. However, low catalytic activity limits further applications in bioanalysis. This study reports one way for improving the catalytic activity of copper nanocrystal by introducing Ti₃C₂T_X and arginine and serine-functionalized graphene quantum dot (RSGQD). Cu²⁺ was reduced by RSGQD to produce copper nanocrystal, which was immobilized on Ti₃C₂T_X sheet via π-π stacking and self-assembly. The resulted Ti₃C₂T_X/Cu-RSGQD shows a three-dimensional structure composing of small copper nanocrystals with an average particle size of 18.1 ± 1.7 nm and Ti₃C₂T_X sheets. The introduction of Ti₃C₂T_X and RSGQD improves the catalytic activity due to good conductivity of Ti₃C₂T_X and formation of Ti₃C₂T_X/RSGQD/Cu Schottky heterojunction. The peroxidase-like and oxidase-like specific activities reach 591.61 U mg^-1 and 105.2 U mg^-1. Based on the catalysis of Ti₃C₂T_X/Cu-RSGQD towards oxidation of 3,3',5,5'-tetramethylbenzidine into a blue product, a sensitive method was developed for colorimetric detection of H₂O₂. The absorbance linearly increases with increasing H₂O₂ concentration between 0 and 50 μM with a detection limit of 0.0032 μM (S/N = 3). The sensitivity is better than that of other reported analytical methods. It has been contentedly applied in colorimetric detection of H₂O₂ in food.