TiO2-WO3 core-shell nanowire as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of gas sensors, and particularly relates to a TiO2-WO3 core-shell nanowire as well as a preparation method and application thereof. The TiO2-WO3 core-shell nanowire prepared by using an electrostatic spinning method is used as a sensitive material, due to the formation of a core-shell structure, on one hand, TiO2 is in contact with WO3, and due to different work functions, electrons are directionally migrated, and a surface electron depletion layer is generated; and on the other hand, oxygen molecules in the air can extract electrons from the shell layer to form oxygen anions to further increase the width of a depletion layer, so that relatively thin shell layer electrons can be seriously depleted, the sensitivity of the sensor to triethylamine is further improved, the response / recovery time of the sensor is shortened, and the required working temperature of the sensor is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and in particular relates to a TiO2-WO3 core-shell nanowire and a preparation method and application thereof. Background Art

[0002] Triethylamine (TEA) is an organic volatile gas with a strong pungent odor. Long-term exposure to triethylamine can cause headaches, nausea, tears, and other conditions. In severe cases, it can cause dyspnea, pulmonary edema, and even death. In addition, seafood such as fish and shellfish release volatile substances such as triethylamine and trimethylamine during their deterioration and corruption. Detecting the concentration of triethylamine can be used as a chemical marker to monitor the freshness of seafood. Therefore, it is necessary to develop a high-performance triethylamine sensor. However, existing triethylamine gas sensors based on metal oxide semiconductors generally have problems such as low sensitivity and high operating temperature, which greatly limits their practical application range. Summary of the invention

[0003] The present invention aims to provide a triethylamine sensor based on TiO2-WO3 core-shell nanowires and a preparation method thereof. By using TiO2-WO3 core-shell nanowires as sensitive materials, the sensitivity of the sensor to triethylamine and the response / recovery speed can be improved, and the operating temperature required by the sensor can be reduced.

[0004] In order to solve the above-mentioned technical problems, this application provides the following technical solutions:

[0005] The present invention provides a method for preparing TiO2-WO3 core-shell nanowires, comprising the following steps:

[0006] S11: preparing a mixed solution I and a mixed solution II respectively; the mixed solution I is obtained by dissolving a tungsten source and a polymer substrate in a solvent A; the mixed solution II is obtained by dissolving a titanium source and a polymer substrate in a solvent B;

[0007] S12: coaxial electrospinning is performed with the mixed solution I as the outer phase and the mixed solution II as the inner phase to obtain a spinning sample;

[0008] S13: calcining the spun sample at 500-700° C. for 2-3 h to obtain the TiO2-WO3 core-shell nanowires.

[0009] Preferably, the tungsten source is selected from ammonium metatungstate (ammonium metatungstate hydrate), tungsten chloride (WCl6) or tungstic acid (H2WO4); the titanium source is selected from tetrabutyl titanate (C 16 H 36 O4Ti).

[0010] Preferably, acetic acid needs to be added to the mixed solution II to inhibit the hydrolysis of tetrabutyl titanate.

[0011] Preferably, the polymer substrate is selected from one or more of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and polyacrylonitrile (PAN); and the mass ratio of the polymer substrate to solvent A or solvent B is 1-2:10.

[0012] Preferably, the solvent A and the solvent B are independently selected from one or more of water, N,N-dimethylformamide (DMF), ethanol, acetic acid, methanol, isopropanol and n-butanol.

[0013] Preferably, the molar ratio of the titanium source to the tungsten source is 1:2-4.

[0014] Preferably, the molar ratio of the titanium source to the tungsten source is 1:3.5.

[0015] Preferably, in the step S12, during the coaxial electrospinning, the model of the coaxial electrospinning dedicated needle is 17G / 22G.

[0016] Preferably, in step S12, during coaxial electrospinning, the syringe advancement speed is 0.1-0.6 mL / h, the voltage is set to 5-20 kV, the receiving distance is set to 10-20 cm, and the ambient humidity is 10%-50% RH.

[0017] Specifically, the preparation method of the TiO2-WO3 core-shell nanowires is as follows:

[0018] a1: Taking N,N-dimethylformamide as solvent, weigh 5 / 100-10 / 100 mass ratio of tungsten source (ammonium metatungstate hydrate) and 10 / 100-20 / 100 mass ratio of polyvinyl pyrrolidone, put them in a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution I;

[0019] a2: Taking a mixed solution of solvent ethanol and a small amount of acetic acid as a reference, weigh a titanium source (tetrabutyl titanate) in a mass ratio of 20 / 100-25 / 100 and polyvinyl pyrrolidone in a mass ratio of 10 / 100-20 / 100, place them in a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution II;

[0020] a3: prepare a syringe, the needle of which is a needle specially used for coaxial electrospinning;

[0021] a4: preparing a receiving roller, the receiving roller is used to receive the non-woven fabric membrane, and the receiving roller rotates at a speed of 200-500 r / min; transferring the mixed solution I and the mixed solution II into the syringe for electrospinning;

[0022] a5: After obtaining enough electrospinning samples, remove the non-woven fabric membrane and place it in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2-10°C / min, and after heating to 500-700°C, keep warm for 2-3 hours; after the temperature is naturally cooled, a TiO2-WO3 core-shell nanowire powder sample can be obtained.

[0023] The TiO2-WO3 core-shell nanowires of the present invention form a microstructure of the TiO2-WO3 core-shell nanowires due to the formation of the core-shell structure, increase the initial resistance of the gas-sensitive material and the reaction active sites on the surface, accelerate the adsorption and desorption of gas molecules, and use them in sensors to improve the sensitivity of the sensor to triethylamine, the response / recovery speed, and reduce the operating temperature required for the sensor.

[0024] The present invention also provides a TiO2-WO3 core-shell nanowire prepared by the above preparation method.

[0025] The present invention also provides a triethylamine sensor, which is prepared by the following steps:

[0026] S21: dispersing the TiO2-WO3 core-shell nanowires in water or ethanol, and grinding to obtain a mixed solution III;

[0027] S22: applying the mixed liquid III to the outer surface of a sensor carrier having a gas sensor function, and allowing the mixed liquid III to completely cover the electrodes of the sensor carrier, forming a sensitive material film on the outer surface, and obtaining a semi-finished product; the sensor carrier having a gas sensor function comprises an Al2O3 ceramic tube, annular gold electrodes arranged at both ends of the Al2O3 ceramic tube, and a platinum wire welded to the annular gold electrode;

[0028] S23: baking the semi-finished product under infrared light for 20-30 minutes and then calcining at 150-200° C. for 2-3 hours to obtain the triethylamine sensor.

[0029] Preferably, the volume ratio of the TiO2-WO3 core-shell nanowires to water or ethanol is 2-5:1.

[0030] Preferably, the thickness of the sensitive material film is 10-30 μm.

[0031] Preferably, a heating wire is further provided on the surface of the triethylamine sensor, and the heating wire is selected from a nickel-cadmium alloy coil running through the interior of the Al2O3 ceramic tube.

[0032] Preferably, the length of the Al2O3 ceramic tube is 4-4.5 mm, the inner diameter is 0.8-1.0 mm, the outer diameter is 1.2-1.5 mm, the width of the annular gold electrode is 0.5-1.0 mm; and the resistance of the nickel-cadmium alloy coil is 30-40Ω.

[0033] The technical solution of the present invention has the following advantages over the prior art:

[0034] The present invention can prepare complete, continuous, uniformly sized one-dimensional TiO2-WO3 core-shell nanowires. Since the one-dimensional TiO2-WO3 core-shell nanowires have a large specific surface area, they can provide more adsorption sites, and the disordered interwoven and stacked nanowires make the gas-sensitive material have many pores inside, which is conducive to the rapid diffusion reaction of the gas and the adsorption and desorption of the target gas, and improves the response and response / recovery speed of the sensor. At the same time, the sensor in the technical solution of the present invention can be manufactured based on the existing commercially available tubular gas sensor as a carrier, and its device process is simple, the volume is small, and it is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 These are the SEM (scanning electron microscope) morphology images and TEM (transmission electron microscope) morphology images of the TiO2-WO3 core-shell nanowires prepared in Example 1, where (a) to (i) are SEM morphology images, and (j) to (m) are TEM morphology images.

[0036] Figure 2 This is the full XRD spectrum of the TiO2-WO3 core-shell nanowires prepared in Example 1.

[0037] Figure 3 (a) is the Ti characteristic XPS spectrum of the TiO2-WO3 core-shell nanowires prepared in Example 1, and (b) to (d) are the O1s spectra of pure WO3 nanowires, pure TiO2 nanowires and TiO2-WO3 core-shell nanowires, respectively.

[0038] Figure 4 This is a schematic diagram of the structure of the triethylamine sensor made based on TiO2-WO3 core-shell nanowires in Example 1.

[0039] Figure 5 The responses of the comparative sensor and the sensor of Example 1 to 100 ppm triethylamine at different operating temperatures.

[0040] Figure 6 Response-recovery curves of the comparative example sensor and the sensor of Example 1 to 100 ppm triethylamine at 130° C. and 220° C.

[0041] Figure 7 Response-recovery curves of the comparative sensor and the sensor of Example 1 to different concentrations of triethylamine at different operating temperatures.

[0042] Explanation of reference numerals: 1-Al2O3 ceramic tube, 2-semiconductor sensitive material layer, 3-annular gold electrode, 4-platinum wire, 5-heating wire. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0044] Example 1 Preparation of triethylamine sensor based on TiO2-WO3 core-shell nanowires

[0045] 1. Preparation method of TiO2-WO3 core-shell nanowires:

[0046] a1: Taking N,N-dimethylformamide as solvent, weigh 6 / 100 mass ratio of tungsten source (ammonium metatungstate hydrate) and 12 / 100 mass ratio of polyvinyl pyrrolidone into a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution I;

[0047] a2: Taking a mixed solution of solvent N,N-dimethylformamide, ethanol and acetic acid (N,N-dimethylformamide: ethanol = 1:1) as a reference, weigh a titanium source (tetrabutyl titanate) at a mass ratio of 21 / 100 and polyvinyl pyrrolidone at a mass ratio of 14 / 100, place them in a container, and stir at room temperature (25±5°C) until the solute is completely dissolved to obtain a mixed solution II;

[0048] a3: prepare a syringe, the needle of which is a needle specially used for coaxial electrospinning;

[0049] The model of the coaxial electrospinning needle is 17G / 22G;

[0050] The shell / core solution syringe advancing speed is 0.3 / 0.2 mL / h, the voltage is set to 10 kV, the receiving distance is set to 15 cm, and the ambient humidity is controlled at 30% RH;

[0051] a4: preparing a receiving roller, the receiving roller is used to receive the non-woven fabric membrane, and the receiving roller rotates at a speed of 400 r / min; transferring the mixed solution II into the syringe for electrospinning;

[0052] a5: After obtaining enough electrospinning samples, the non-woven fabric membrane is removed and placed in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2°C / min, and after heating to 550°C, the temperature is kept for 2 hours; after the temperature is cooled naturally, a powdered sample of TiO2-WO3 core-shell nanowires can be obtained;

[0053] 2. Preparation method of triethylamine sensor based on TiO2-WO3 core-shell nanowires:

[0054] b1: Prepare a sensor carrier with gas sensor function;

[0055] b2: mixing a powdered sample of TiO2-WO3 core-shell nanowires and deionized water in a ratio of 2:1, grinding the mixture, and preparing a paste-like mixed solution III containing TiO2-WO3 core-shell nanowires;

[0056] b3: Cover the outer surface of the sensor carrier evenly and completely with the mixed liquid III, ensuring that the mixed liquid III completely covers the electrode to form a sensitive material film of about 20 μm;

[0057] b4: After the sensor carrier coated with the sensitive material film was baked under an infrared lamp for 20 minutes, the sensor carrier was calcined at 150°C for 3 hours to obtain a triethylamine sensor based on TiO2-WO3 core-shell nanowires;

[0058] b5: Pass the nickel-cadmium alloy coil through the interior of the sensor carrier as a heating wire to obtain a semi-finished sensor;

[0059] b6: The semi-finished sensor was welded and packaged according to the general indirect heating gas sensor to obtain a triethylamine sensor based on TiO2-WO3 core-shell nanowires with heating function.

[0060] Example 2

[0061] 1. Preparation method of TiO2-WO3 core-shell nanowires:

[0062] a1: Taking N,N-dimethylformamide as solvent, weigh 5 / 100 mass ratio of tungsten source (tungsten chloride (WCl6)) and 10 / 100 mass ratio of polyvinyl pyrrolidone into a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution I;

[0063] a2: Taking a mixed solution of solvent N,N-dimethylformamide, ethanol and acetic acid (N,N-dimethylformamide:ethanol=1:1) as a reference, weigh a titanium source (tetrabutyl titanate) in a mass ratio of 20 / 100 and polyvinyl pyrrolidone in a mass ratio of 10 / 100, place them in a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution II;

[0064] a3: prepare a syringe, the needle of which is a needle specially used for coaxial electrospinning;

[0065] The model of the coaxial electrospinning needle is 17G / 22G;

[0066] The shell / core solution syringe advancing speed is 0.3 / 0.2 mL / h, the voltage is set to 5 kV, the receiving distance is set to 10 cm, and the ambient humidity is controlled at 10% RH;

[0067] a4: preparing a receiving roller, the receiving roller is used to receive the non-woven fabric membrane, and the receiving roller rotates at a speed of 200 r / min; transferring the mixed solution II into the syringe for electrospinning;

[0068] a5: After obtaining enough electrospinning samples, the non-woven fabric membrane is removed and placed in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2°C / min, and after heating to 500°C, the temperature is kept for 2 hours; after the temperature is cooled naturally, a powdered sample of TiO2-WO3 core-shell nanowires can be obtained;

[0069] 2. Preparation method of triethylamine sensor based on TiO2-WO3 core-shell nanowires:

[0070] b1: Prepare a sensor carrier with gas sensor function;

[0071] b2: mixing a powdered sample of TiO2-WO3 core-shell nanowires and deionized water in a ratio of 2:1, grinding the mixture, and preparing a paste-like mixed solution III containing TiO2-WO3 core-shell nanowires;

[0072] b3: Cover the outer surface of the sensor carrier evenly and completely with the mixed liquid III, ensuring that the mixed liquid III completely covers the electrode to form a sensitive material film of about 10 μm;

[0073] b4: After the sensor carrier coated with the sensitive material film was baked under an infrared lamp for 20 minutes, the sensor carrier was calcined at 150°C for 2 hours to obtain a triethylamine sensor based on TiO2-WO3 core-shell nanowires;

[0074] b5: Pass the nickel-cadmium alloy coil through the interior of the sensor carrier as a heating wire to obtain a semi-finished sensor;

[0075] b6: The semi-finished sensor was welded and packaged according to the general indirect heating gas sensor to obtain a triethylamine sensor based on TiO2-WO3 core-shell nanowires with heating function.

[0076] Example 3

[0077] 1. Preparation method of TiO2-WO3 core-shell nanowires:

[0078] a1: Taking N,N-dimethylformamide as solvent, weigh 10 / 100 mass ratio of tungsten source (tungstic acid (H2WO4)) and 20 / 100 mass ratio of polyvinyl pyrrolidone into a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution I;

[0079] a2: Taking a mixed solution of solvent N,N-dimethylformamide, ethanol and acetic acid (N,N-dimethylformamide: ethanol = 1:1) as a reference, weigh a titanium source (tetrabutyl titanate) in a mass ratio of 25 / 100 and polyvinyl pyrrolidone in a mass ratio of 20 / 100, place them in a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution II;

[0080] a3: prepare a syringe, the needle of which is a needle specially used for coaxial electrospinning;

[0081] The model of the coaxial electrospinning needle is 17G / 22G;

[0082] The shell / core solution syringe advancing speed is 0.3 / 0.2 mL / h, the voltage is set to 20 kV, the receiving distance is set to 20 cm, and the environmental humidity is controlled at 50% RH;

[0083] a4: preparing a receiving roller, the receiving roller is used to receive the non-woven fabric membrane, and the receiving roller rotates at a speed of 500 r / min; transferring the mixed solution II into the syringe for electrospinning;

[0084] a5: After obtaining enough electrospinning samples, the non-woven fabric membrane is removed and placed in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 10°C / min, and after heating to 700°C, the temperature is kept for 3 hours; after the temperature is cooled naturally, a TiO2-WO3 core-shell nanowire powder sample can be obtained;

[0085] 2. Preparation method of triethylamine sensor based on TiO2-WO3 core-shell nanowires:

[0086] b1: Prepare a sensor carrier with gas sensor function;

[0087] b2: mixing a powdered sample of TiO2-WO3 core-shell nanowires and deionized water in a ratio of 5:1, grinding the mixture, and preparing a paste-like mixed solution III containing TiO2-WO3 core-shell nanowires;

[0088] b3: Cover the outer surface of the sensor carrier evenly and completely with the mixed liquid III, ensuring that the mixed liquid III completely covers the electrode to form a sensitive material film of about 30 μm;

[0089] b4: After the sensor carrier coated with the sensitive material film was baked under an infrared lamp for 30 minutes, the sensor carrier was calcined at 200°C for 3 hours to obtain a triethylamine sensor based on TiO2-WO3 core-shell nanowires;

[0090] b5: Pass the nickel-cadmium alloy coil through the interior of the sensor carrier as a heating wire to obtain a semi-finished sensor;

[0091] b6: The semi-finished sensor was welded and packaged according to the general indirect heating gas sensor to obtain a triethylamine sensor based on TiO2-WO3 core-shell nanowires with heating function.

[0092] Comparative Example 1 Preparation of triethylamine sensor based on TiO2 nanowires

[0093] 1. Preparation method of TiO2 nanowires:

[0094] a1: Taking a mixed solution of solvent N,N-dimethylformamide, ethanol and a small amount of acetic acid (N,N-dimethylformamide:ethanol=1:1) as a base, extract 21 / 100 mass ratio of tetrabutyl titanate into a container, stir at room temperature until the solute is completely dissolved, and obtain mixed solution I;

[0095] a2: Taking the mixed solution in step a1 as a reference, weigh polyvinyl pyrrolidone and add it to the second mixed solution at a mass ratio of 14 / 100, and stir at room temperature to finally obtain a transparent viscous solution, which is recorded as mixed solution II;

[0096] a3: Prepare a syringe with a needle specially designed for electrospinning;

[0097] The inner diameter of the needle used for electrospinning is 0.41 mm and the outer diameter is 0.71 mm;

[0098] The syringe advancement speed was 0.3 mL / h, the voltage was set to 10 kV, the receiving distance was set to 15 cm, and the ambient humidity was controlled at 30% RH;

[0099] a4: prepare a receiving roller, which is used to receive the non-woven membrane, and the receiving roller rotates at a speed of 400 r / min; transfer the mixed solution II into a syringe for electrospinning;

[0100] a5: After obtaining enough electrospinning samples, remove the non-woven fabric membrane and place it in a muffle furnace for calcination; set the muffle furnace to heat up at a rate of 2°C / min, heat to 550°C, and keep warm for 2 hours; after the temperature cools down naturally, a powdered TiO2 nanowire sample can be obtained;

[0101] 2. Preparation method of triethylamine sensor based on TiO2 nanowires:

[0102] b1: Prepare a sensor carrier with gas sensor function;

[0103] b2: mixing a powdered TiO2 nanowire sample and deionized water in a ratio of 2:1, grinding the mixture, and preparing a paste-like mixed solution III containing TiO2 nanowires;

[0104] b3: Cover the outer surface of the sensor carrier evenly and completely with the mixed liquid III, ensuring that the mixed liquid III completely covers the electrode to form a sensitive material film of about 20 μm;

[0105] b4: After the sensor carrier coated with the sensitive material film was baked under an infrared lamp for 20 minutes, the sensor carrier was calcined at 150°C for 3 hours to obtain a triethylamine sensor based on TiO2 nanowires;

[0106] b5: Pass the nickel-cadmium alloy coil through the interior of the sensor carrier as a heating wire to obtain a semi-finished sensor;

[0107] b6: The semi-finished sensor was welded and packaged according to the general indirect heating gas sensor to obtain a triethylamine sensor based on TiO2 nanowires with heating function.

[0108] Comparative Example 2 Preparation of triethylamine sensor based on WO3 nanowires

[0109] 1. Preparation method of WO3 nanowires:

[0110] a1: Taking N,N-dimethylformamide as solvent, weigh 13 / 100 mass ratio of ammonium metatungstate hydrate and place it in a container, and stir at room temperature until the solute is completely dissolved to obtain a mixed solution I;

[0111] a2: Taking N,N-dimethylformamide in step a1 as a reference, weigh polyvinyl pyrrolidone in a mass ratio of 14 / 100 and add it into the second mixed solution, stirring at room temperature to finally obtain a transparent viscous solution, which is recorded as mixed solution II;

[0112] a3: Prepare a syringe with a needle specially designed for electrospinning;

[0113] The inner diameter of the needle used for electrospinning is 0.41 mm and the outer diameter is 0.71 mm;

[0114] The syringe advancement speed was 0.3 mL / h, the voltage was set to 10 kV, the receiving distance was set to 15 cm, and the ambient humidity was controlled at 30% RH;

[0115] a4: prepare a receiving roller, which is used to receive the non-woven membrane, and the receiving roller rotates at a speed of 400 r / min; transfer the mixed solution II into a syringe for electrospinning;

[0116] a5: After obtaining enough electrospinning samples, remove the non-woven fabric membrane and place it in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2°C / min, and after heating to 550°C, keep the temperature for 2 hours; after the temperature is cooled naturally, a WO3 nanowire powder sample can be obtained;

[0117] 2. Preparation method of triethylamine sensor based on WO3 nanowires:

[0118] b1: Prepare a sensor carrier with gas sensor function;

[0119] b2: Mix the WO3 nanowire powder sample and deionized water in a ratio of 2:1, grind the mixture, and prepare a paste-like mixed solution III containing WO3 nanowires;

[0120] b3: Cover the outer surface of the sensor carrier evenly and completely with the mixed liquid III, ensuring that the mixed liquid III completely covers the electrode to form a sensitive material film of about 20 μm;

[0121] b4: After the sensor carrier coated with the sensitive material film was baked under an infrared lamp for 20 minutes, the sensor carrier was calcined at 150°C for 3 hours to obtain a triethylamine sensor based on WO3 nanowires;

[0122] b5: Pass the nickel-cadmium alloy coil through the interior of the sensor carrier as a heating wire to obtain a semi-finished sensor;

[0123] b6: The semi-finished sensor was welded and packaged according to the general indirect heating gas sensor to obtain a triethylamine sensor based on WO3 nanowires with heating function.

[0124] Effect evaluation 1

[0125] like Figure 1 As shown in (a) to (i), the prepared nanowires are randomly interwoven and stacked together, and the nanowires are complete, continuous, and uniform in size. From TEM images (j) to (m), it can be observed that the prepared core-shell nanowires have a complete, uniform, and continuous shell coating, and the shell layer is very thin and has similar thickness.

[0126] like Figure 2As shown, according to the standard JCPDS card 72-1465, the diffraction peaks of the obtained pure tungsten trioxide nanowires are consistent with the cubic phase of tungsten trioxide, with lattice constants of a = 7.3A, b = 7.53A and c = 7.68A. However, there are two phases coexisting in pure titanium dioxide nanowires, but there are significant differences in content. Obviously, the diffraction peaks from anatase titanium dioxide (JCPDS Card No. 89-4921) are sharp and strong, and dominate. In contrast, the proportion of rutile titanium dioxide (JCPDS Card No. 89-4920) is quite small. Titanium dioxide constitutes the main diffraction peak in TiO2-WO3 core-shell nanowires, and the position of the diffraction peak does not shift to the left or right, indicating that the doping process has not occurred. No diffraction peaks from other substances were detected in all products, indicating that their purity is high. However, the peak intensity of the core-shell nanowires is weakened and the half-peak width is increased, indicating that the crystallinity is reduced, which may be due to the mutual interference of the two crystallization processes.

[0127] like Figure 3 As shown in (a), the Gaussian fitting peaks in the figure belong to Ti 2p1 / 2 and 2p3 / 2 of the sensors of Comparative Example 1 and the embodiment. Although the peak positions of each group of peaks are different due to the different internal chemical environments of the materials, the splitting energy of the two groups of peaks in each material remains unchanged, i.e., 5.71 eV, which is consistent with the energy splitting value of tetravalent Ti. In general, the O1s peak can be divided into three Gaussian fitting components: lattice oxygen (O L ), oxygen vacancies (O V ) and chemically adsorbed oxygen (O C ). It is generally believed that O L It is stable and does not participate in electron transfer. V It can provide active sites for the reaction gas, and O C Directly participate in the redox reaction on the surface of the material. Figure 3 As shown in (b) to (d), the O C and O V The ratio is significantly higher than that of titanium dioxide nanowires and tungsten trioxide nanowires. C +O V The proportion of titanium dioxide nanowires is 27.24%, tungsten trioxide is 36.09%, and TiO2-WO3 core-shell nanowires is 47.34%. The results show that the core-shell structure can increase the O C and O V The gas sensing performance of the material is improved.

[0128] like Figure 4 As shown, the device consists of an Al2O3 ceramic tube 1, a semiconductor sensitive material 2, an annular gold electrode 3, a platinum wire 4 welded on the annular gold electrode, and a nickel-cadmium alloy coil 5.

[0129] like Figure 5 As shown, in the entire temperature test range, the response of the sensor of Example 1 (the response of the gas sensor is defined as its resistance R in air) a And the resistance value R in triethylamine gas g The ratio of ) is higher than that of the comparative example sensor. The optimal operating temperature of the comparative example 1 sensor is 180°C, the optimal operating temperature of the comparative example 2 sensor is 200°C, and the optimal operating temperature of the embodiment sensor is 130°C. At this time, the responses of the sensors of comparative example 1, comparative example 2 and embodiment 1 to 100ppm of triethylamine at their respective optimal operating temperatures are 2.7, 18.5 and 106, respectively. The response of the embodiment sensor is about 40 times that of the comparative example 1 device and 6 times that of the comparative example 2 device, and the operating temperature is lower, indicating that the formation of core-shell nanowires greatly improves the response of the sensor and reduces the required operating temperature of the sensor.

[0130] like Figure 6 (a) and Figure 6 As shown in (b), when the comparative example sensor and the sensor of Example 1 are at 130°C and the triethylamine gas concentration is 100ppm, the response times of Comparative Example 1, Comparative Example 2 and the embodiment are 27s, 19s and 132s respectively, and the recovery degrees in about 20 minutes are 21%, 10% and 52% respectively. Although the response time is slightly delayed, the embodiment device shows a faster recovery speed and higher response. When the operating temperature of the embodiment sensor is 220°C, the recovery time is 133s, and the recovery speed is faster than the optimal working degree performance. Therefore, in practical applications, different requirements for response value and response / recovery speed can be achieved by regulating the temperature of the sensor.

[0131] like Figure 7 (a) and Figure 7 As shown in (b), when the working temperature of the embodiment device is 130°C, its response increases with the increase of triethylamine concentration. In the entire test concentration range, the response to triethylamine remains leading, especially when the triethylamine concentration is greater than 20ppm. According to the formula, the minimum detection concentration of triethylamine for the device of Example 1 at the optimal working temperature is 40.86ppb, which is much lower than 363.93ppb of Comparative Example Device 1 and 287.15ppb of Comparative Example Device 2, indicating that the embodiment device has better gas concentration discrimination ability and low detection limit.

[0132] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing TiO2-WO3 core-shell nanowires, characterized in that: The steps include: S11: preparing a mixed solution I and a mixed solution II respectively; the mixed solution I is obtained by dissolving a tungsten source and a polymer substrate in a solvent A; the mixed solution II is obtained by dissolving a titanium source and a polymer substrate in a solvent B; S12: coaxial electrospinning is performed with the mixed solution I as the outer phase and the mixed solution II as the inner phase to obtain a spinning sample; S13: calcining the spun sample at 500-700° C. for 2-3 h to obtain the TiO2-WO3 core-shell nanowires.

2. The preparation method according to claim 1, characterized in that The tungsten source is selected from ammonium metatungstate, tungsten chloride or tungstic acid; the titanium source is selected from tetrabutyl titanate.

3. The preparation method according to claim 1, characterized in that: The polymer substrate is selected from one or more of polyvinyl pyrrolidone, polyvinyl alcohol and polyacrylonitrile; the mass ratio of the polymer substrate to solvent A or solvent B is 1-2:

10.

4. The preparation method according to claim 1, characterized in that: The solvent A and the solvent B are independently selected from one or more of water, N,N-dimethylformamide, ethanol, acetic acid, methanol, isopropanol and n-butanol.

5. The preparation method according to claim 1, characterized in that: The molar ratio of the titanium source to the tungsten source is 1:2-4.

6. The preparation method according to claim 1, characterized in that: In the step S12, during coaxial electrospinning, the syringe advancement speed is 0.1-0.6 mL / h, the voltage is set to 5-20 kV, the receiving distance is set to 10-20 cm, and the ambient humidity is 10%-50% RH.

7. A TiO2-WO3 core-shell nanowire prepared by the preparation method according to any one of claims 1 to 6.

8. A triethylamine sensor, characterized in that The triethylamine sensor is prepared by the following steps: S21: dispersing the TiO2-WO3 core-shell nanowires according to claim 7 in water or ethanol, and grinding to obtain a mixed solution III; S22: applying the mixed liquid III to the outer surface of a sensor carrier having a gas sensor function, and allowing the mixed liquid III to completely cover the electrodes of the sensor carrier, forming a sensitive material film on the outer surface, and obtaining a semi-finished product; the sensor carrier having a gas sensor function comprises an Al2O3 ceramic tube, annular gold electrodes arranged at both ends of the Al2O3 ceramic tube, and a platinum wire welded to the annular gold electrode; S23: baking the semi-finished product under infrared light for 20-30 minutes and then calcining at 150-200° C. for 2-3 hours to obtain the triethylamine sensor.

9. The triethylamine sensor according to claim 8, characterized in that: The thickness of the sensitive material film is 10-30 μm.

10. The triethylamine sensor according to claim 8, characterized in that: A heating wire is also provided on the surface of the triethylamine sensor.

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