Synthesis Of Metal Oxide Semicondutctor Core-Shell Nanofibers And Its Application In Gas Sensing

With the continuous development and progress of society,people's demand for energy is increasing.The exploitation and combustion of fossil fuels and the air pollution caused by industrial waste are also more and more serious.In the face of the severe pollution situation and the people's desire for the healthy atmosphere,it is imminent to control the air pollution and reduce the emission of harmful gases.The gas sensor device as a component of the gas concentration and other information can be converted into the use of personnel,instrumentation,computers and other information,is widely used in real-time detection of harmful gases,is conducive to the people of atmospheric pollution control and self protection.Sensitive material is the core of the field of gas sensors.The research and development of sensitive materials for high performance is one of the main ways to improve the sensitive characteristics of gas sensors.In recent years,the vigorous development of nanotechnology has opened up new ideas and directions for the research and exploration of sensitive materials,and has also provided a powerful driving force for the development and innovation of gas sensors.This paper mainly studies the core-shell structure on the gas sensing properties of semiconductor sensitive materials for influence,design based on free electron diffusion between semiconductor heterostructure and reactive direction function,through the preparation of nano fibers with core-shell structure,the relationship between the gas sensing properties and free electron diffusion direction of nano fiber the in-depth study of the sensitive mechanism of heterojunction,the core-shell structure of semiconductor material sensitive gas sensing properties of ascension,the main work is as follows:?1?In this work,a core-shell heterostructure nanowires?NWs?have been synthesized via a coaxial electrospinning approach.SnO₂ and TiO₂ were chosen as the samples for the synthesis of the core-shell NWs.A comparative gas sensing study among the TiO₂/SnO₂ core-shell NWs,the SnO₂ NWs and the TiO₂ NWs were performed to demonstrate the excellent gas sensing properties.The sensors based on the TiO₂/SnO₂ core-shell NWs exhibited excellent sensing properties[quick response to acetone?2 s?,high response to acetone?13.7?and good selectivity]at 280 ^oC operating temperature.The enhanced sensing properties relies on the changes of adsorbed oxygen species and electron depletion layer on the surface,because the electrons flow to the surface resulting from differences in the work functions.?2?In this work,core-shell WO₃-SnO₂?CS-WS?nanofibers?NFs?have been successfully synthesized via a coaxial electrospinning approach.The structure and morphology characteristics of the resultant products were investigated by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,and X-ray photoelectron spectra?XPS?.To investigate the sensing mechanism of the CS-WS NFs,sensors based on SnO₂ NFs,WO₃ NFs,and SnO₂-WO₃ composite NFs were fabricated respectively,and their gas sensing properties were investigated by using CO,ethanol,toluene,acetone,and ammonia as the test gas.The enhanced ethanol sensing properties of CS-WS NFs compared with those of SnO₂ NFs were closely associated with the CS structure and its derivative effect.The approach proposed in this study may contribute to the realization of more sensitive metal oxide semiconductor?MOS?core-shell heterostructure sensors.?3?In this work,two types of core-shell heterostructure NFs,In₂O₃-SnO₂ core-shell NFs and SnO₂-In₂O₃ core-shell NFs were synthesized by a coaxial electrospinning method.To demonstrate the potential applications,gas sensors based on above two core-shell NFs were fabricated and their gas sensing characteristics were investigated by using TMA as the target gas.In order to explain the sensing behaviors,the SnO₂pristine NFs and In₂O₃ pristine NFs were also synthesized respectively by electrospinning and their gas sensing behaviors were investigated.The sensing mechanism could be illustrated by the differences of the gas sensing properties of the core-shell NFs and the pristine NFs.?4?SnO₂/Au-doped In₂O₃ core-shell?CS?nanofibers?NFs?were designed and synthesized through a facile coaxial electrospinning method.To investigate its potential application,commercial gas sensor was fabricated and its gas sensing properties were tested.The SnO₂/Au-doped In₂O₃ CS NFs sensor showed enhanced acetone gas sensing properties compared to the Au-doped In₂O₃ single NFs sensor counterpart.The SnO₂/Au-doped In₂O₃ CS NFs sensor exhibited a high response at300 ^oC,whereas Au-doped In₂O₃ NFs sensor showed a relative low response at 300^oC.Furthermore,the former sensors also showed a fast response speed and a good selectivity to acetone.In addition,the underlying mechanism for the enhanced acetone sensing properties of SnO₂/Au-doped In₂O₃ CS NFs sensor could be attributed to the catalytic activity of Au and the CS structure.The approach and results proposed in this study may contribute to the realization of more sensitive CS structure NFs sensors.Based on the above four parts,the relationship between the core shell structure and the direction of free electrons in the heterojunction and the gas sensing properties of metal oxide semiconductor nanofibers has been systematically studied.The gas sensing mechanism of core shell nanofibers has been deeply studied.