The Preparation And Analytical Application Of Doped Carbon-based Nano Mimetic Enzyme

In recent decades,nanozymes,as a substitute for natural enzymes,have received extensive attention from domestic and foreign scientists in various fields due to their multiple advantages,such as low cost,high activity and good stability.Among them,carbon-based nanozymes is becoming a hot spot in the research and exploration of nanozyme materials because of their unique electronic and geometric structure,good biocompatibility and tunable enzyme activity.However,the enzymatic catalytic properties of pure carbon nanoenzymes are still not very ideal.In this paper,we synthesized two kinds of carbon-based nanoenzymes with highly efficient enzyme activity by doping different metals and heteroatomic N on the carbon substrate.On this basis,we have developed a colorimetric sensing platform for detecting acid phosphatase(ACP)and a new method for detecting total antioxidant capacity(TAC)in beverages,respectively.The details are as follows:1.Ultra-thin carbon nitride(g-C₃N₄)nanosheets were prepared by high temperature calcination and ultrasonic exfoliation by using urea as carbon source and nitrogen source templates.Then,single-atom Pt-g-C₃N₄ was obtained from the reaction of g-C₃N₄nanosheets with H₂PtCl₆.The prepared single-atom Pt-g-C₃N₄ has good peroxidase-like(POD)properties,which can oxidize the typical substrate 3,3',5,5'-tetramethylbenzidine(TMB)in the presence of H₂O₂.The mechanism of the catalytic reaction of Pt-g-C₃N₄ is mainly attributed to the fact that Pt-g-C₃N₄ can activate H₂O₂ to produce·OH.Based on the POD-like properties of Pt-g-C₃N₄ and the reduction possibility of ascorbic acid(AA)from ACP hydrolyzes,we established a new ACP colorimetric sensing method.In the range of 0.5U/L-3.5 U/L,the ACP concentration showed a good linear relationship with the absorbance of the reaction system.The limit of detection(LOD)of this method was 0.19 U/L,and it had been successfully applied to the detection of ACP in human serum with the recovery of between 91.9%-101.4%.This colorimetric sensing method not only provided a new possibility for ACP biological detection and inhibitor drug screening,but also broadened the potential of single-atom carbon nitride materials in biological analysis.2.In this work,Fe(acac)₃,Zn²⁺and 2-methylimidazole were used as raw materials to synthesize Fe and N codoped carbon-based nanozymes(Fe-N-C)by hydrothermal method and high-temperature pyrolysis.Fe-N-C catalyst can rapidly oxidize TMB to oxidation state TMB in the presence of O₂ without the addition of H₂O₂.The experiment results shows that Fe-N-C has high-efficiency oxidase-like activity when the temperature of pyrolysis is at 800?.The further mechanism investigation indicated that the high catalytic activity of Fe-N-C-800 can be mainly attributed to the presence of carbon substrates with a large specific surface area and abundant FeN_x sites,which can promote the activation of O₂ into ¹O₂ to accelerate the oxidation process.Based on oxidase activity of Fe-N-C-800,we established a TAC sensor modeled on AA,and successfully applied in the TAC detection of commercial beverages.