| Natural enzymes have the advantages of high catalytic efficiency,substrate specificity and variety,so they are used in biology,medicine and other fields.However,natural enzymes also have some inherent defects,such as high cost,easy inactivation,difficult transportation and so on.Therefore,in recent years,artificial enzymes have been developed.Nano mimetic enzymes are a kind of artificial mimetic enzymes with both the unique properties of nanomaterials and catalytic function.Because of their high stability and low cost,they are widely used as substitutes for natural enzymes.Cuprous oxide has the advantages of low toxicity and good biocompatibility.It has been widely concerned because of its potential applications in photocatalysis,catalyst,adsorption,biosensor and other fields.Based on the unique advantages of porous nanomaterials,this thesis is devoted to the development of a simple and economic method for the synthesis of porous cuprous oxide with high activity of nano enzyme,and establish a rapid colorimetric detection method with broad application prospects in the fields of biological science,medical diagnosis and so on.The main research contents are as follows:(1)Synthesis of Porous Cu2O Nanosphere and Application as Nanozymes in Colorimetric Biosensing.In this work,for the first time,using sodium hypochlorite as a green oxidant,urea was oxidized to CO2 as carbon source to prepare the fineparticle crosslinked Cu-precursors,which could further reduce by sodium ascorbate into pure Cu2O nanospheres(NPs)with a porous morphology at room temperature.Interesting,our study reveals that introduction of an appropriate amount of MgCl2 into the raw materials can tunepore sizes and surface area,but has no influence on the phase purity of the resulting Cu2O NPs.Significantly,all the synthesized Cu2O NPs exhibited the intrinsic peroxidase-like activity with higher affinity towards both 3,3,5,5-tetramethylbenzidine(TMB)and H2O2 than Horseradish Peroxidase(HRP).The colorimetric detection of glucose based on the resulting porous Cu2O NPs presented the limit of detection(LOD)of 2.19 μM with a broad linear range from 1-1000 μM,much better than many recently reported composite-based nanozymes.Meanwhile,this nanozyme system was utilized to detect L-cysteine,exhibiting the LOD value as low as 0.81 μM within a linear range from 0 to 10 μM.More interesting,this sensing system shows high sensitivity and excellent selectivity in determining of glucose and L-cysteine,which is suitable for detecting serum samples with reliable results.Therefore,the present study not only develops a simple strategy to prepare Cu2O NPs with controllable porous structure,but also indicates its promising applications in bioscience,disease diagnosis.(2)Synthesis of Cu2O porous nanosheets and their multi enzyme catalytic properties.In this chapter,a new and simple solid-state grinding method was established to prepare porous Cu2O nanosheets.Two dimensional Cu2O nanosheets were prepared by grinding copper chloride with β-cyclodextrin and NaBH4 at room temperature and adding appropriate amount of water.Further,porous Cu2O nanosheets were obtained by using the solubility of β-cyclodextrin in water increasing with temperature.The whole experimental process was carried out at room temperature,which required less equipment and higher yield.It was found that Cu2O nanosheets exhibited high laccase mimetic and peroxidase mimetic activities due to the existence of multiple catalytic sites.The laccase activity was investigated by the color reaction of 4-AP with phenolic substrates.The results showed that Cu2O nanoplates had high laccase mimic activity and could efficiently oxidize phenolic substrates.It can be used for the quantitative determination of epinephrine with LOD of 16.5 μm in the concentration range of 0.25-2.5 mM.Moreover,Cu2O nanoplates had high peroxidase mimetic activity,and the Km value of TMB was 0.325 mM,which indicated that the prepared Cu2O nanoplates had good affinity for substrates.Cu2O nanosheets have broad application prospects in biosensor,disease diagnosis and treatment,and environmental protection due to their simple synthesis method and high catalytic activity... |
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