Preparation Of Hierarchical Structure Of Metal Oxides By Electrospinning Technology And Study On Gas-sensing Performances

In this paper,a series of hierarchical structure of metal oxides with the special morphology,controllable sizes and excellent performance are synthesized via one-step electrospinning technology combined with the subsequent calcination process,including hierarchical structure of SnO₂-based fibers in situ growth of particles on the surface,hierarchical structure of WO₃/ZnWO₄ fibers in situ growth of particles on the surface,hierarchical structure of In₂O₃ fibers in situ growth of octahedron-like particles on the surface,and In₂O₃ hierarchical structure consisting of single crystalline octahedral particles and polycrystalline fibers,which are used for gas-sensing studies such as ethanol,formaldehyde（HCHO）and triethylamine（TEA）.These materials in this paper show high selectivity,high response value,and high stability,and have broad application prospects in the fields of cosmetics quality evaluation,indoor air purification testing,and food safe storage.The specific research content of this paper is as follows:1.The hierarchical structure of SnO₂ fibers in situ growth of particles on the surface is prepared by one-step electrospinning technology combined with the subsequent calcination process.By introducing the Zn component to further optimize the morphology and phase composition of the hierarchical structure,the SnO₂/ZnO hierarchical structure is synthesized.Gas-sensing performance tests show that compared to SnO₂ porous fiber（13.2）and SnO₂hierarchical structure（119）,the response value of SnO₂/ZnO hierarchical structure at the optimal operating temperature of 260 ^oC for 100 ppm ethanol can reach up to 366.What’s more,SnO₂/ZnO hierarchical structure has excellent gas selectivity and long-term stability,and can be used for trace detection of ethanol in cosmetics,providing a novel method for cosmetic quality evaluation.Its enhanced gas-sensing mechanism can be attributed to a multi-level effective heterojunctions of the hierarchical microstructure.2.The tunable WO₃ nanofiber is prepared by one-step electrospinning technology combined with the subsequent calcination process.By introducing ZIF-8 nanoparticles into the spinning solution,the obtained precursor fibers are calcined at the high temperature to prepare the hierarchical structure of WO₃/ZnWO₄ fibers in situ growth of particles on the surface.The formation mechanism of the microstructure is mainly due to the combination of nucleation competition and crystal plane matching during heat treatment.Compared with pure WO₃ and WO₃/ZnWO₄-10%samples,WO₃/ZnWO₄-5%sample shows the largest specific surface area,about 268.57 m²/g,which indicates that the sample has the excellent absorption characteristic of the target gas.Gas-sensing performance tests show that at the optimal operating temperature of 220 ^oC,the gas-sensing response of the WO₃/ZnWO₄-5%hierarchical structure to 5ppm HCHO is about 44.5.The enhanced gas-sensing mechanism can be attributed to the synergistic effects of effective heterojunctions,large specific surface area,multiple reaction sites,and unique surface/interface electron transport.The WO₃/ZnWO₄hierarchical structure in-situ growth of WO₃ nanoparticles for efficient detection of low concentration HCHO confirms its broad prospects for indoor air purification testing.3.The hierarchical structure of In₂O₃ fibers in situ growth of octahedron-like particles on the surface is prepared by one-step electrospinning technology combined with the subsequent calcination process.By precisely adjusting the parameter of the calcination time,different typical microstructures can be obtained,such as tube-in-tube fibers,ribbon fibers and octahedron-like cascade architecture with 1D orientation.Under dynamic equilibrium conditions,In₂O₃ material usually terminate with{111}planes at low energy,and hence it is easy to obtain In₂O₃ octahedron-like structures.The appropriate precursor fiber was prepared by electrospinning technology,and the crystal growth habit was adjusted by rationally controlling the calcination process,thereby obtaining the In₂O₃ hierarchical structure in-situ growth of octahedron-like particles.Compared with other typical structures,the In₂O₃hierarchical structure shows the best gas-sensing performance to TEA at 40 ^oC,and the response value to 50 ppm TEA is about 87.8.It also shows excellent selectivity and long-term stability and can achieve the freshness detection of seafoods（shrimps）at near room temperature,revealing its great potential for food safety storage.4.In₂O₃ hierarchical microstructures consisting of single crystalline octahedral particles and polycrystalline fibers is prepared by one-step electrospinning technology combined with the subsequent calcination process.By accurately adjusting the indium source and heating rate,typical In₂O₃ fibers and In₂O₃ octahedral particles can be obtained.Compared with In₂O₃fibers（240 ^oC,12）and In₂O₃ octahedral particles（180 ^oC,24）,the In₂O₃ hierarchical structure has the highest gas response value of 47 for 5 ppm HCHO at the optimal operating temperature of 160 ^oC.Its enhanced gas-sensing performance is mainly due to the synergistic effect of the two structural units,namely improving reaction sites,special surface adsorption and unique electron transport.