In-Situ Construction Of Self-Supported Nanocrystalline/Conductive MOF Heterostructure For Electrochemical Sensing Of Hydrogen Peroxide

Hydrogen peroxide（H₂O₂）plays an important role in many physiological processes.However,overexpression of H₂O₂ in cells disrupts the redox balance in vivo,which can lead to diverse diseases such as cancer,inflammation,aging,and cardiovascular disease.Therefore,accurate and rapid detection of hydrogen peroxide is of great significance for human health management.Noble metal nanomaterials,transition metal oxides and sulfides have certain electrocatalytic properties for hydrogen peroxide.However,they tend to agglomerate in the process of preparation and catalysis,which will affect the catalytic performance.The high porosity,high specific surface area,high designability and adjustability of metal-organic frameworks make them better than carbon and zeolite as supporting matrix materials,which can effectively improve the dispersion of catalyst.However,most of the reported preparation methods for metal-based nanocrystalline/metal organic framework have the disadvantages such as complex steps,insufficient catalytic performance,poor controllability,poor universality and they are unable to be prepared as self-supporting electrode.In view of the shortcomings in the current preparation methods of nanocrystals/metal organic frameworks heterostructure,in this thesis,two-dimensional conductive Cu HHTP（2,3,6,7,10,11 hexahydroxytriphenyl copper）nanorod arrays on copper foam or carbon cloth are used as the research object.Through a series of methods,part of Cu HHTP are in-situ transformed into Cu based nanocrystalline,forming nanocrystalline/MOF heterostructure self-supporting electrode.At the same time,metal-based nanocrystals are converted in situ from uniform metal nodes in MOFs,which ensure their effective dispersion and controllability.The following main research results have been achieved in this thesis:（1）CuS NC@Cu HHTP/CF:Copper hydroxide nanorod arrays were in-situ grown on copper foam（CF）and used as templates to prepare Cu HHTP nanorod arrays.Part of Cu HHTP were vulcanized by thioacetamide to form CuS nanocrystals through solution infiltration method.The degree of vulcanization and the formation of CuS NC@Cu HHTP/CF can be effectively controlled through regulating the concentration of thioacetamide.The as prepared electrode was used as H₂O₂ sensor with a wide linear detection range（2μM～15 m M）,high sensitivity(5544.3μA m M^-1·cm^-2),the preparation method of catalytic materials is simple and can be manufactured on a large scale.（2）Cu₂O NC@Cu HHTP/CF:In order to avoid the negative effect of sulfur on the catalytic activity of CuS NC@Cu HHTP/CF in the electrochemical reaction,the Cu HHTP nanorods array on copper foam was directly reduced by electrochemical method,and part of Cu HHTP was destroyed in situ and converted into Cu₂O nanocrystals to obtain Cu₂O NC@Cu HHTP/CF heterostructure self-supporting electrode.It is found that the content and size of Cu₂O nanocrystals can be controlled by adjusting the reduction voltage and reduction time.The obtained Cu₂O NC@Cu HHTP/CF heterostructure self-supporting electrode showed higher sensitivity(8150.6μA·m M^-1·cm^-2)and lower detection limit（50 n M）than CuS NC@Cu HHTP/CF,and were successfully applied to the detection of H₂O₂ in serum and urine samples.（3）Cu Co₂O₄NC@Cu Co HHTP/CF:In order to further improve the stability of Cu₂O in catalytic materials for longer preservation,bimetallic oxide heterojunction was prepared.Cu Co HHTP bimetallic conductive MOF nanorods were prepared using copper hydroxide nanorods array and cobalt nitrate as precursor.Calcined in air at low temperature,partial Cu Co HHTP was destroyed and converted into bimetallic oxide.The components,contents and sizes of the bimetallic oxide can be regulated effectively.After optimization,the Cu Co₂O₄ NC@Cu Co HHTP/CF heterostructure self-supporting electrode exhibit a higher sensitivity(8853μA m M^-1cm²),lower detection limit（10 n M）,wider linear detection range（50 n M～6 m M）than Cu₂O NC@Cu HHTP/CF.What’s more,Cu Co₂O₄NC@Cu Co HHTP/CF is more stable in the air at room temperature,after 30 days of storage,it still retains 90.5%of the initial response current intensity.（4）Cu Pt NC@Cu HHTP/CC:In order to further improve the linear detection range of the sensor,noble metal Pt with better catalytic performance was introduced in this chapter.Through a mild thermal reduction strategy,part of the copper nodes in Cu HHTP are converted into Cu nanocrystals,and then Cu Pt alloy nanocrystals are uniformly assembled into Cu HHTP through an displacement reaction with potassium chloroplatinate to form Cu Pt NC@Cu HHTP/CC heterostructure self-supporting electrode.It is worth noting that the size and content of Cu Pt alloy nanoparticles can be effectively adjusted by adjusting the temperature of thermal reduction.Moreover,the composition of Cu Pt alloy nanocrystals can also be effectively regulated by changing the concentration of potassium chloroplatinate in the displacement reaction.Therefore,the detection performance of the sensor is also adjustable.Optimized Cu Pt NC@Cu HHTP/CC heterostructure self-supporting electrode exhibit a wider linear detection range（10 nm～6.66 m M）and a lower detection limit（5 n M）than Cu Co₂O₄ NC@Cu Co HHTP/CF.Therefore,Cu Pt NC@Cu HHTP/CC electrode can not only detect hydrogen peroxide in human serum and urine,but also successfully detect the content of hydrogen peroxide secreted by cells.We also discussed Fenton like electrocatalytic mechanism of Cu Pt NC@Cu HHTP/CC heterojunction in electrochemical detection of hydrogen peroxide.