Zhendong Fu,Feng Guo,Jiahe Qiu,Runchi Zhang,Mingxu Wang,Liping Wang
2-Methylimidazole (MIM) is a classic organic ligand that shows excellent thermal stability and chemical robustness and is widely used in ZIFs. Recently, transformations of MOFs have been realized by using metals or ligands. In this study, we propose a new strategy—adjusting MIM by extending the alkyl chain length —to change the properties of related MOFs. Furthermore, we used copper as the metal core to replace zinc to mimic the active sites of laccases (electron transfer between copper and imidazole ring). As a result, the nanostructures transformed from nanoleaves to nanovesicles, which changed the Cu(II)/Cu(I) ratio from 3.7 to 1.7, as well as the lattice constant (decreased the diffraction angle) and enzyme-like activity (inhibition). In addition, we revealed that superoxidase anions were the main factors responsible for its laccase-like activity. We applied it to detect and discriminate phenolics. Laccase-mimicking activity was best at pH 7.0. When compared to protein laccase, the Cu-MeIm nanozyme had a greater Vmax at the same mass concentration. It was used to identify and distinguish phenolics. In the presence of Cu-MeIm nanozymes, the linear range is 0.1–2 mM and the detection limit of 2,4-DCP is 0.034 mM.
Dopamine (DA) is an important neurotransmitter; however, any excess or deficiency of DA will cause several diseases in humans. To monitor DA efficiently and conveniently, a Ag nanozyme strengthened by bioactive folic acid (FA@AgNPs) was developed by homogeneous redox assembly. After the microstructure and performance were characterized in detail, it was noted that the proposed FA@AgNPs possessed superior peroxidase-like activity due to the ultra-small Ag nanoparticles and multiple amino, hydroxyl, and aromatic rings in FA. FA@AgNPs accelerated the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) with a low Michaelis constant ( K m ) and high maximal reaction rate ( V max ). Importantly, the characteristic absorbance intensity of FA@AgNPs-TMB-H 2 O 2 at 652 nm ( A 652 ) was exclusively deteriorated in the presence of trace DA, accompanied by a visual color change from blue to colorless. Under the optimized conditions (pH 4.0, 300 μL 1.5 mM TMB, 300 μL 1.0 M H 2 O 2 and incubated for 30 min at room temperature), there expressed an excellent linear relationship between lg A 0 / A 652 and c DA from 1.0 ×10 −8 to 6.67×10 −6 mol/L with a low limit detection of 7.1×10 −10 mol/L (S/N=3). When applied for monitoring of DA in real fruit juice and pharmaceutical samples, the recovery was between 96.6% and 104.9%, with RSD less than 2.2%. The enhanced peroxidase-like activity of the FA@AgNP system and its selective recognition mechanism for DA are also proposed. Graphical abstract
危险品化学品经营许可证（带存储）