Fabrication And Gas Sensing Properties Of Zinc Oxide And Carbon Quantum Dots-based Composite Material

With the development of industrial science and technology,people's quality of life has been greatly improved,but at the same time,people's negative impact on highly developed industry is not expected enough,and the prevention is unfavorable.The resulting environmental pollution seriously threatens the safety of human production and life.The urgent needs of people's production and life and the guidance of national policies have promoted gas sensors to become an important scientific research direction.The design and preparation of gas-sensitive materials with excellent performance is of great significance for the construction of high-performance gas sensors.The important factors that determine the performance of gas sensors are the design and development of sensitive materials,and the improvement of the performance of sensitive materials.With the development of materials science,the preparation of sensitive materials and strategies for improving the performance of sensitive materials have been continuously studied.In the selection of sensitive materials,metal oxide semiconductor gas sensors have received extensive attention from scientific researchers for their advantages of low cost,easy operation,low power consumption and high sensitivity.This paper mainly focuses on the application and performance optimization of metal oxide semiconductor materials represented by zinc oxide?ZnO?and carbon quantum dot materials?CQDs?in the direction of gas sensing.ZnO sensitive materials with excellent performance are prepared by adjusting the microscopic morphology of metal oxide materials and ZnO/CQDs composite materials are prepared by doping CQDs with excellent physical and chemical properties to achieve the design and development of high-performance sensitive materials.And through the preparation of a variety of metal oxide composite materials doped with carbon quantum dots,the study of carbon quantum dot doping on the sensitization of composite materials under UV excitation at room temperature is attempted to solve the current problem of excessively high working temperature of metal oxide sensitive materials.The main research contents of this paper are summarized as follows:1.Constructed a ZnO sensor with excellent H₂S gas sensitivity.First,lettuce-like ZnO gas-sensitive materials were prepared by a one-step hydrothermal method,and the materials were characterized by X-ray diffraction?XRD?and scanning electron microscopy?SEM?,and the composition,structure,crystallographic information and information of lettuce-like ZnO were determined.Morphology.The formation of lettuce-like morphology of ZnO was discussed,and conditions optimization experiments were carried out on the preparation method.The gas sensitivity performance of lettuce-like ZnO was tested by the laboratory self-made gas sensitivity test system.Lettuce-like ZnO exhibits a high H₂S response at a lower working temperature,as well as excellent H₂S selectivity and rapid response recovery.The lettuce-like ZnO sensitive material has a unique lettuce-like microspherical appearance and a large specific surface area,which makes the material have excellent H2S adsorption efficiency,which is one of the reasons why the sensor has a fast response and recovery time.Compared with other similar work,the lettuce-like ZnO sensor has the advantages of fast response speed and high sensitivity.In addition,the sensitive mechanism of lettuce-like ZnO was studied.2.Constructed a zinc oxide/carbon quantum dot?ZnO/CQDs?composite sensor for NO detection.First,ZnO with flower-like structure was synthesized by hydrothermal method,and then carbon quantum dots were introduced by co-mixing mechanical grinding.This doping method avoids the surface functional groups of CQDs from being destroyed during high temperature reaction.The materials were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and thermogravimetric analysis?TGA?,and the morphology,crystal structure and composition of ZnO/CQDs materials were determined.At the same time,we have also conducted a detailed study on the gas-sensitive properties of composite materials.The ZnO/CQDs composite sensitive material has excellent NO selectivity and rapid response recovery speed.Compared with ZnO without CQDs,the sensitivity of the ZnO/CQDs composite material to NO gas has been greatly improved.In addition,the sensitive mechanism of ZnO/CQDs composites is also discussed.3.Two kinds of zinc oxide/carbon quantum dots?ZnO/CQDs-1,ZnO/CQDs-2?composite sensitive materials,tin dioxide/carbon quantum dots?Sn O₂/CQDs?composite sensitive materials and nickel oxide-zinc oxide are constructed/Carbon quantum dots?NiO-ZnO/CQDs?composite sensitive materials,and several composite sensitive materials doped with carbon quantum dots are prepared into sensor devices.These composite materials were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,and transmission electron microscope?TEM?to determine the morphology,crystal structure and composition of the composite materials.We conducted a detailed study on the gas sensitivity characteristics of composite materials doped with carbon quantum dots through the darkroom-UV excitation gas sensing test system built in the laboratory.We have also studied the room temperature sensitization mechanism of carbon quantum dots on metal oxide composites under UV excitation.In summary,understand the relationship between the properties and sensitive properties of carbon quantum dots and metal oxide/carbon quantum dot composites,adjust the microscopic morphology of the materials to prepare ZnO sensitive materials,and introduce carbon quantum dots doping to prepare ZnO/CQDs Composite materials and research on the gas-sensing properties of different metal oxide composite materials doped with carbon quantum dots have realized the controllable preparation of sensitive materials.Researching and discussing the sensitive mechanism of gas sensing can achieve purposeful improvement of the gas sensitivity of sensitive materials.In this paper,the research of metal oxide semiconductor materials and carbon quantum dot materials represented by zinc oxide in the gas-sensing direction has strong practical application value,and it provides new ideas for improving the performance of sensitive materials and enhancing the sensitivity of materials.Methods and research ideas.