Synthesis Of Nanozymes And Their Applications In The Detection Of Aluminum Ions And Pyrophosphate

Nanozymes are a type of nanomaterials with enzyme-like characteristics.Compared with natural biological enzymes,nanozymes have the advantages of simple synthesis,good stability,and lower cost,and have attracted the attention of researchers in various fields.With continuous development of nanomaterials,nanozymes are also developing rapidly.More and more nanomaterials are used to simulate the activity of biological enzymes,such as oxidase-like enzymes,peroxidase-like enzymes,hydrolase-like enzymes and so on.Due to the advantages of easy modification,low preparation cost and relatively stable properties,nanozymes have been widely used in various aspects,such as analysis and detection,environmental protection,clinical diagnosis and treatment.Hence,the application of nanozymes is a growing area of research all over the world.This thesis mainly studies the effects of aluminum ion and pyrophosphate on the catalytic activity of nanozymes and substrate affinity.Based on inhibition effect of the analyte on the activity of the nanozymes,a novel method is developed for detection of aluminum ions and pyrophosphate.The specific work content is as follows:1.Cerium dioxide nanoparticles are prepared by stirring cerium nitrate and ammonium hydroxide for 24 h at room temperature,and find that this nanoparticles have enzyme-like properties.The catalytic activity of cerium dioxide nanoparticles as phosphatase-like enzymes is studied by using CDP-star,a chemiluminescent substrate of phosphatase.Several cerium dioxide nanoparticles with different surface ligands are synthesized,and their phosphatase activities are compared with cerium dioxide nanoparticles.At the same time,the phosphatase activity of cerium dioxide nanoparticles and natural phosphatase（ALP）under different p H values are investigated.Experimental results show that cerium dioxide nanoparticles exhibit strong phosphatase mimetic activity under neutral p H 7,while ALP has catalytic activity only under alkaline condition.It is found that aluminum ions can significantly inhibit the phosphatase activity of cerium dioxide nanoparticles.Based on this,a novel highly sensitive chemiluminescence method for detection of aluminum ions is developed on account of the phosphatase activity of cerium dioxide nanoparticles.The method has a linear response in the concentration range of 30 n M to 3.5μM,and the limit of detection（LOD）is 10 n M.The content of intracellular aluminum ions is of great significance for the study of the function and toxicity of aluminum ions in organisms.Cell proliferation assay（MTT assay）is used to evaluate the cytotoxicity of cerium dioxide nanoparticles,and aluminum ions in cells are detected by using this method.It can be seen that this chemiluminescence method has certain practicability in the detection of complex biological samples.2.Luminol-gallium nanoassemblies are prepared by one-pot synthesis.Luminol-gallium nanoassemblies are formed by small particles.Small particles are selfassembled together to form big irregular spheres or network nanoassemblies.A one-pot approach has been demonstrated for the synthesis of amorphous luminol-gallium nanoassemblies,which are formed by small particles with big irregular spheres or network nanoassemblies.The nanoassemblies can be stored stably for more than 1 month in a refrigerator at 4°C.Luminol-gallium nanoassemblies exhibit peroxidase-mimetic activity toward the oxidation of peroxidase substrate 3,3’,5,5’-tetramethylbenzidine（TMB）in the presence of hydrogen peroxide（H₂O₂）.The experimental results show that pyrophosphate can interact with luminol-gallium nanoassemblies and inhibit peroxidase mimicry activity of nanoassemblies.Hence,a novel sensitive colorimetric detection of pyrophosphate from0.5 to 15μM using luminol-gallium nanoassemblies is developed with the limit of detection of 62.4 n M In the analysis of real water samples from lake water and tap water,the practicability of this method for detecting pyrophosphate is studied.Recoveries of pyrophosphate in local lake water samples are in the range of 98.2%-102.6%and recoveries of pyrophosphate in tap water samples are in the range of 97.3%-101.3%.It can be seen that the colorimetric detection by using the peroxidase-like activity of the luminol-gallium nanoassemblies has relatively high accuracy.And this colorimetric sensor is expected to be applied to the quantitative detection of pyrophosphate in environmental samples.