Fabrication And Gas Sensitivity Of One-Dimensional Ordered TiO₂ And Sn Doped Nanowires

Titanium dioxide is an n-type metal oxide semiconductor with three crystalline phases:anatase,brookite and rutile,because of its unique mechanical,thermal and photoelectric properties,it has been applied in many fields,such as photocatalysis,solar cells and ultraviolet detectors.Similarly,titanium dioxide is an excellent gas sensing material,which can be used for the detection of various gases.Researchers have successfully prepared titanium dioxide nanomaterials by template method,hydrothermal method,anodic oxidation and other methods.Among them,one-dimensional titanium dioxide nanomaterials prepared by electrospinning have large specific surface area and draw ratio.In this paper,we fabricated one-dimensional ordered nanowires of titanium dioxide by electrospinning.The main research work is as follows:1.One dimensional order TiO₂ nanowires were prepared by electrospinning.The TiO₂ nanowires were annealed at 500℃,600℃,700℃and 800℃,respectively.Then the morphology,crystal structure and band gap of the TiO₂ nanowires were characterized by SEM,XRD,Raman and UV.Finally,the gas sensing properties of the TiO₂ nanowires to ethanol were tested.It was found that the sensitivity of all samples increased with the increase of ethanol concentration.At the same concentration,The sensitivities of the sensors fabricated by the nanowires annealed at 600℃are the highest,but the response speed is slower than that of the sample annealed at 800℃.This is because at 600℃,TiO₂ is a mixed-phase of anatase and rutile,which reducing the recombination of electrons and holes and reduces the energy loss of electrons during conduction.With the increase of annealing temperature,the grain size increases and the pore size increases,resulting in a decrease in sensitivity but a faster response speed.2.In order to improve the sensitivity of the TiO₂ sensor with annealing temperature of 800℃,we fabricated one-dimensional ordered TiO₂ nanowires with Sn doping of 0.5%,1%and 2%respectively.The gas sensitivity of Sn-doped TiO₂ gas sensor to ethanol was measured.It was found that at the same concentration,the sensitivity of 0.5%Sn doped nanowires to ethanol was the highest and better than the pure TiO₂,but the sensitivity decreases with the increase of Sn doping.At the same time,compared with pure TiO₂,the response time of Sn doping is longer.This is because Sn doping decreases grain size and pore size,although sensitivity increases,the response speed slows down.At the same time,Sn doping makes TiO₂ produce oxygen vacancies,which further improves the gas sensing properties.However,with the increase of Sn doping amount,Sn ions saturate in TiO₂,and excessive Sn ions adhere to the surface of TiO₂ in the form of SnO₂,occupying oxygen vacancies reduces the gas sensing characteristics.