Controllable Preparation Of Ru Nanoenzymes And Their Peroxidase-like Properties

Natural enzymes have very high activity and specificity,but the cost is high,the stability is low,recovery and storage difficulties,it is necessary to develop natural enzyme replacement materials.Nanozyme is a kind of nano-material with enzyme-like activity,which has the advantages of economy,high stability,large-scale preparation and enzyme catalytic function,the catalytic activity is limited.Therefore,single-atom nanomaterials with bio-enzyme-like active centers and full exposure of active sites（100%atomic utilization）have become the most promising artificial enzymes,also known as single-atom enzymes.However,there are few studies on the structure-activity relationship between the composition,size and coordination environment of single-atom enzymes and their activity.Therefore,the design and synthesis of high catalytic activity and selectivity of single-atom enzymes is the key to achieve low-cost nanoenzyme scale applications.In this thesis,Ru-based single-atom nanoenzyme was used as the main enzyme to control the size and coordination environment of the active metal Ru,so as to realize the controllable preparation of Ru like peroxidase with high activity,selectivity and stability.The relationship between the size,coordination environment and catalytic performance of metal nanoparticles was revealed by structural characterization and comparative experiments.The specific research contents are as follows:（1）By using the method of impregnation combined with high temperature annealing in reducing atmosphere,by adjusting the amount of metal precursor,Ru nanoparticles with three sizes of single-atom,cluster（1.2 nm）and particle（3.2 nm）were loaded on nitrogen-doped carbon（NC）substrates.The results of colorimetric analysis and enzymatic chemical kinetics showed that the single-atom structure had higher peroxidase activity,stronger affinity for TMB and catalytic efficiency than the cluster and particle structure.This is because when the same number of Ru atoms are added in the catalytic reaction,the single-atom structure can expose the most active Ru-N-C sites,the cluster structure is next,and the particle structure is the least.Subsequently,we applied it to ascorbic acid detection and found that Ru/NC with single-atom structure had high selectivity and low detection limit（0.027μM）.The structure-activity relationship between the size of metal particles and their peroxidase activity has been explored in this work.（2）In order to further enhance the catalytic activity of Ru-based single-atom nanoenzyme,ammonium chloride was introduced into the nitrogen-doped carbon loaded with metal precursors.During high temperature annealing,the decomposition of ammonium chloride provides NH₃atmosphere,which regulates the coordination environment of Ru-N.Compared with pure ammonia atmosphere treatment,hydrogen chloride etching treatment and untreated Ru/NC with single-atom structure,the samples with ammonium chloride showed higher peroxidase activity.The results of elemental analysis and XPS showed that the addition of NH₄Cl significantly increased the N content in the catalyst,especially the content of pyridine nitrogen,so the Ru-N-C formed showed higher catalytic activity,this is consistent with the conclusions reported in the literature.In addition,ascorbic acid detection showed that Ru/NC-NH₄Cl had high selectivity and lower detection limit（0.0018μM）than Ru/NC.This work explored the structure-activity relationship between the coordination environment of active metals and the peroxidase activity,and provided some ideas for further improving the activity of nanoenzymes.