Morphology And Composition Regulation Of Metal Oxide-based Micro-nano Composite Structures And The Study Of Their Electrochemical Sensing Performances

Metal oxides have been widely used in various areas including biotechnology,chemical energy storage,adsorption,catalysis,electrochemical sensing,and so on,owing to their advantages such as easy preparation,low cost,controllable morphology,and excellent performance.However,the effects of morphology,size,and surface modification of metal oxides on their properties,especially on their electrochemical sensing performances,are still not available.Based on this,four kinds of metal oxides-based micro-nano composite structures were prepared,and their morphology and composition were regulated through the change of chemical parameters.The structure-activity relationship and inherent law between the morphology of this kind of material and sensing characteristic were explored,and versatile electrochemical sensing platform was constructed.The main contents of this paper are as follows:1.This work fabricated a kind of MnO₂ microspheres with controllably hollow structure,which have abundant pore structure,adjustable pore size,and big surface area compared with solid MnO₂,and their interior space can accommodate substantial guest molecules,so much better response signal for riboflavin was obtained.Then,a sensitive electrochemical sensor for riboflavin detection was fabricated after the combination of hollow MnO₂ microspheres and graphene oxide（GO）.Through the optimization of supporting electrolyte,amount of hollow MnO₂ modifier on electrode surface,accumulation time,and accumulation potential,the linear rage and limit of detection for riboflavin on this sensor are obtained as 0.030-15?mol/L and 3.0 nmol/L（S/N=3）,respectively.The method is applied to the analysis of riboflavin in food and biological samples,with recovery ranging from 95.1%to 106%.2.A series of Cu₂O crystals with well-controlled cubic（C-Cu₂O）,star-shaped（S-Cu₂O）,and octahedral（O-Cu₂O）structures were prepared by facile wet chemical method to explore the morphology-dependent electrocatalytic efficiency.When tested for the sensing of 4-aminophenol（4-AP）,4-chlorophenol（4-CP）,and 4-nitrophenol（4-NP）,it was found that the O-Cu₂O exhibited the best current signals,which are mainly because of its more exposed?111?facets and higher surface area.Further,O-Cu₂O crystals were homogeneously dispersed on graphene oxide（GO）surface to achieve a hierarchical reinforcement structure.The electrode modified by O-Cu₂O@GO showed high electrocatalytic activity toward the oxidation of 4-AP,4-CP,and 4-NP,and could realize the selective detection of phenolic compounds in ternary electrolyte solutions and industrial wastewater.This work is beneficial to morphology tailoring and provides novel way to improve the electrochemical property of oxide-based catalysts as the promising applications in electrochemical sensors.3.In this study,a facile solution approach was developed for the synthesis of a series of core-shell structured Ag@Cu₂O nanocrystals of various shapes including triangles,spheres,and cubes with well-defined stable heterojunctions.The electrooxidation of dopamine（DA）,uric acid（UA）,guanine（G）,and adenine（A）using these hybrids revealed morphology-dependent sensing properties,with activities and accumulation ability following the order,triangular Ag@Cu₂O>spherical Ag@Cu₂O>cubic Ag@Cu₂O.Further,we constructed a novel graphene oxide（GO）nanosheet-reinforced triangular Ag@Cu₂O ternary hetero-nanostructure.Such a hybrid with a three-dimensional interconnected hierarchical architecture is suitable for catalysis,since it not only leads to improved interfacial electron transfer,but also readily exposes the highly catalytic Ag@Cu₂O to the reactants.Therefore,more enhanced electrochemical activities were observed for the oxidation of DA,UA,G,and A.This study provides an efficient way to synthesize morphology-controlled Ag@Cu₂O heterogeneous catalysts for the fabrication of potential biosensors,and also opens up attractiveavenuesinthedesignofmultifunctionalternarynoble metal-semiconductor-carbon hybrids.4.Metal-Organic Frameworks（MOFs）materials have the advantages of adjustable pores and large specific surface area,etc.In this work,three kinds of novel core-shell materials consisting of CeO₂@ZIF-8,CeO₂@Mg-MOF-74,and CeO₂@HKUST-1were prepared with hollow CeO₂ as the core and MOFs with different compositions as the shell.The electrocatalytic oxidation effect of these three CeO₂@MOFs were investigated using two kinds of antiseptics including 2,4-dichloro-3,5-dimethylphenol（DCMX）and 4-chloro-3,5-dimethylphenol（PCMX）as targets.The results showed that CeO₂@ZIF-8 has the highest detection sensitivity for the two antiseptics,with linear range of 0.010-25 and 0.0080-30?mol/L,and limit of detection of 3.5 and 0.60 nmol/L for DCMX and PCMX,respectively.Finally,this sensor was applied for the determination of DCMX and PCMX in food and environmental samples successfully.