Design And Preparation Of High-Performance Noble Metal-Based Nanozymes And Its Application In Optical Analysis

Nanozymes are nanomaterials that can simulate the catalytic activity of natural enzymes.With many advantages that superior to natural enzymes,nanozymes have shown important application prospects in the fields of bioanalytical analysis,disease diagnosis and treatment,and environmental protection.Nanozymes can be divided into transition metal-based nanozymes,noble metal-based nanozymes,carbon-based nanozymes,etc.Compared with other types of nanozymes,noble metal-based nanozymes display higher catalytic activity and better stability,which has attracted extensive attention.However,compared with natural enzymes,the catalytic activity and selectivity of precious metal-based nanozymes still need to be improved,which greatly restrict their practical applications in medicine,biology and environment.The enzyme-like activity of nanozymes is mainly related to the structural parameters such as the surface modification,dimension,facets,and atom utilization ratio.Therefore,in order to further improve the enzyme-like activity and catalytic efficiency of nanozymes,we prepared three noble metal-based nanozymes by modifying surface,simultaneously regulating dimension and crystal face,and improving the atom utilization rate.Material characterization test and activity analysis are performed,and then the synthesized nanozymes were successfully used for optical analysis.The main research work is as follows:1.The catalytic reaction of nanozymes often occurs on the surface,so it is of great significance for the surface modification of nanozymes.We prepared the palladium nanocubes coated with dopamine（PDA-Pd/NCs）.By comparing the palladium nanocubes before and after modification,it was found that dopamine greatly improved its catalytic activity through induced accumulation and electron transfer effect.PDA-Pd/NCs can also catalyze the oxygen in the solution to generate reactive oxygen species（ROS）and thus oxidize 3,3’,5,5’-tetramethylbenzidine（TMB）.We confirmed that the ROS generated in this paper are superoxide radicals(O₂^·-)and singlet oxygen（¹O₂）.In the presence of acid phosphatase（ACP）,L-ascorbic acid-2-phosphate trisodium salt（AAP）is hydrolyzed to ascorbic acid,which can effectively inhibit the enzyme-like activity of PDA-Pd/NCs.Inspired by this,we established a colorimetric method to detect ACP.The detection range of ACP was 0.01–10 U/L,and the detection limit was 0.00081 U/L.Moreover,this method has been successfully applied to the selective determination of human serum.In addition,organophosphorus pesticides can inhibit the activity of ACP,thus restoring the color reaction of TMB.Based on this,we further detected the pesticide malathion.The linear range was 0–8μM,and the detection limit was 0.023μM.2.In order to expose more active sites for catalytic reaction,and thus improve the catalytic efficiency,two-dimensional palladium nanosheets grown in-situ on reduced graphene oxide（PdSP@rGO）were prepared by simultaneously regulating crystal surface and dimension.Compared with the two-dimensional palladium nanosheets with{111}and the three-dimensional palladium nanocubes with{100}exposed surfaces,this PdSP@rGO has higher catalytic activity.PdSP@rGO can catalyze the oxidation of TMB to blue oxidation state TMB（oxTMB）.However,thiocyanate（SCN^-）can be adsorbed on the surface of PdSP@rGO by binding with Pdatoms,blocking the active site of simulated oxidase,thus inhibiting the color reaction of TMB.Based on this principle,we designed a colorimetric detection method of SCN^-based on PdSP@rGO-TMB system.This method can sensitively detect SCN^-in the concentration range of 0.05–2.0μM,and the detection limit was 0.044μM.The recovery rate was also good in the test of actual samples.3.In order to solve the problems of low atom utilization rate,we prepared platinum monoatomic nanozyme（SA-Pt/CN）,which makes the best use of platinum atoms.Through characterization and analysis,we proved the successful preparation of SA-Pt/CN and its excellent oxidase-like activity.During the catalytic reaction,SA-Pt/CN can catalyze the oxygen in solution to generate ¹O₂ and hydrogen peroxide（H₂O₂）,which then can oxidize colorless TMB into blue oxTMB.Hydroquinone（HQ）,as a powerful reducing substance,will reduce oxTMB to colorless.Accordingly,we have realized the sensitive detection of HQ.The linear range of detection was 1–10μM,and the detection limit was 0.07μM.In the presence ofα-glucosidase（α-Glu）,arbutin will be hydrolyzed to HQ,which can effectively inhibit the color development of TMB.Therefore,we innovatively detectedα-Glu withα-Arbutin as substrate,and the linear range and detection limit were 0.01–8 U/m L and 0.0038 U/m L respectively.In addition,this method was also used to determineα-Glu in calf serum.