| Enzyme-like catalysts,a class of nanomaterials showing enzyme-like characteristics,have engaged significant attentions due to the strong robustness under harsh conditions,low cost and easy mass preparation.Recently,following the development of nanotechnology,various catalysts with inherent peroxidase-,oxidase-,superoxide dismutase-and catalase-like activities have been constantly explored and applied in various fields covering biology,medicine,sensor,food and environmental industry.However,compared to natural enzymes,most reported nanomaterials such as metal oxides suffer from unsatisfactory activity,poor selectivity and unclear catalytic mechanism,due to the rich atomic composition and complex structural features.To promote the activity of enzyme-like catalysts,.several efforts such as size reduction,surface modification and composition optimization have been done but still far from satisfactory.In addition,these strategies may also bring some other disadvantages.For example,reducing size companys an increase in surface free energy,which inevitably leads to a rapid loss of activity.Therefore,effectively improving the catalytic activity of enzyme-like catalysts is still one of the biggest challenges.Herein,a series of methods for regulating the catalytic activity of enzyme-like catalysts were developed in this thesis.By systematically studying the relationship between enzyme-like activity and the surface exposed facets,it was found that changing the crystal facets can regulate the enzyme-like activity of catalysts.In addition,owing to the enzyme-like active sites and high atom utilization,the single-atom catalysts were applied to design enzyme-like catalysts with high activity and selectivity.The outlines are as follows:1.Facet Engineering of Nanoceria for Enzyme-Mimetic CatalysisCeO2 nanocrystals with different facets exposure are chosen as ideal carriers to investigate the relationship between crystal facet and peroxidase-like activity.We prepared fluorite cubic CeO2 nanocrystals in three different morphologies,including nanoctahedrons,nanocubes and nanorods.It is discovered that CeO2 nanorods dominantly exposing {110} facets show the highest peroxidase-like activity,followed by {100}-faceted CeO2 nanocubes and {111}-faceted CeO2 nanoctahedrons.On this basis,atom-dispersed Au was introduced into CeO2 nanorods.The obtained Au singleatom catalyst not only shows improved peroxidase-like activity,but also displays glucose oxidase-like activity,which successfully achieves enzyme-free colorimetric detection of glucose.2.Single Iron Site Enzyme-Like Catalyst for Ultrasensitive Glucose DetectionWe synthesized a single iron site enzyme-like catalyst(Fe SSN)via a supportsacrificed approach.The Fe SSN with well-defined coordination structure and dense active sites show outstanding peroxidase-like activity comparable to that of the native peroxidase HRP.Based on this,a simple and low-cost colorimetric biosensor was designed and successfully realized the visual assessment and rapid quantitative detection of glucose.3.Single Copper Sites Enzyme-Like Catalyst for Specific Phenols DetectionWe develop a facile solid migration strategy to access a flower-like single copper site enzyme-like catalyst(Cu SSN)via direct transformation of copper foam activated by 2-methylimidazole.With such high accessible active centers similar to natural polyphenol oxidase whose local structure is the aggregation of several CuN3 sites,the Cu SSN exhibits excellent activity and specificity to oxidize phenols but without peroxidase-like activity.Furthermore,the Cu SSN shows high sensitivity in colorimetric detection of epinephrine with a low detection limit of 0.10 μg mL-1,exceeding that of most previously reported enzyme mimic catalyst. |
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