Preparation Of Zinc-oxide-based Fiber And Study On Its Gas Sensitive Property

In recently years,ZnO gas sensors play an important role in the detection of harmful gases such as H₂,NO_x,NH₃ and VOCs.One-dimensional nanofibers and core-shell materials have attracted most researchers to improve their gas sensing properties due to their remarkable electrical,catalytic and surface properties that can be adjusted to meet individual requirements.In this paper,uniaxial electrospinning was used to synthesize Ce-doped ZnO nanofibers.When Ce doping content is 2 mol%,due to Ce³⁺/Ce⁴⁺has less dispersion in ZnO,ZnO can nucleate normally and the sample crystallinity is improved.Since the addition of Ce³⁺and NO₃^-changed the conductivity and viscosity of precursor solution,the diameter of Ce-doped ZnO nanofibers obtained by electrospinning decreased,and it was confirmed that Ce was doped in ZnO nanofibers in the form of oxide.Compared with pure ZnO nanofiber,2 mol%Ce doped ZnO has the maximum response to 1 ppm acetone at 325°C,with a value of 22.20.In the concentration range of 2.0?10 ppm acetone,its sensitivity is increased by16.8 times compared with pure ZnO.After 30 days of stability test,2mol%Ce doped ZnO still maintained a high response to 2 ppm acetone.The gas sensitivity mechanism of Ce doped ZnO nanofibers to acetone can be attributed to its one-dimensional nanofiber structure and Ce doping increases the oxygen defect and improves adsorption capacity of ZnO.In this paper,coaxial electrospinning was used to synthesize ZnO@Ce O₂ core-shell composite nanofibers.The nanofibers are composed of two kinds of metal oxides with high Ce concentration on the surface.The core-shell structure was found by transmission electron microscopy and energy spectrum scanning.Compared with pure phase ZnO and Ce O₂ nanofiber gas sensors,ZnO@CeO₂ core-shell nanofibers have the best dynamic response-recovery curve for acetone in the range of 0.2?10 ppm at 370°C,and satisfy the linear relationship.At 370°C,the core-shell structure fiber has better selectivity to 1 ppm acetone,and its response value is 8.2.The mechanism of increasing gas sensitivity of ZnO@Ce O₂ core-shell heterostructure nanofibers to acetone can be attributed to its one-dimensional nanofiber structure and the synergistic effect of core-shell n-n heterostructure.In this paper,polyacrylonitrile based carbon nanofiber film(CFF)was fabricated by uniaxial electrospinning method after pre-oxidation and carbonization.CFF has good flexible folding ability and can be used as the electrode substrate of ZnO gas sensitive materials.At room temperature,the CFF gas sensor presents typical p-type semiconductor properties,and its response to 10 ppm ethanol is 2.20%.Then,the ZnO was successfully loaded on CFF by hydrothermal method.When the amount of ZnAc₂·2H₂O was 1.00 g,the device had a good selectivity for 10 ppm ethanol at room temperature.At 20 ppm of ethanol,the response was 33.21%,a nearly 50-fold increase compared to 1 ppm.At room temperature,oxygen molecules exist on the surface of ZnO loaded CFF devices in the form of physical adsorption,resulting in a small increase in the surface resistance of materials.Therefore,the gas-sensitive performance of ZnO loaded CFF is improved compared with that of CFF.In conclusion,the ZnO-based composite nanofiber gas sensor obtained by doping elements or creating heterostructures has a low detection limit and has potential application value in the field of diabetes diagnosis.In addition,the flexible carbon nanofiber film is used as the electrode substrate,and ZnO gas-sensitive material is loaded on CFF,which is a successful exploration for the preparation of flexible wearable gas sensor.