A TiO2-WO3 core-shell nanowire, its preparation method and application

Abstract

This invention belongs to the field of gas sensor technology, specifically relating to a TiO2-WO3 core-shell nanowire, its preparation method, and its application. This invention uses TiO2-WO3 core-shell nanowires prepared by electrospinning as the sensing material. Due to the formation of the core-shell structure, on the one hand, TiO2 and WO3 come into contact, and due to the difference in work function, electrons migrate in a directional manner, generating a surface electron depletion layer; on the other hand, oxygen molecules in the air extract electrons from the shell layer to form oxygen negative ions, further increasing the width of the depletion layer. Therefore, the relatively thin shell layer may be severely depleted of electrons, thereby improving the sensor's sensitivity to triethylamine and reducing the sensor's response / recovery time and required operating temperature.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a TiO2-WO3 core-shell nanowire, its preparation method, and its application. Background Technology

[0002] Triethylamine (TEA) is a volatile organic compound with a strong, pungent odor. Long-term exposure can cause headaches, nausea, and tearing; in severe cases, it can lead to respiratory distress, pulmonary edema, and even death. Furthermore, seafood such as fish and shellfish release volatile substances like triethylamine and trimethylamine during spoilage. Detecting triethylamine concentration can serve as a chemical marker for monitoring the freshness of seafood. Therefore, there is a need to develop high-performance triethylamine sensors. However, existing metal-oxide-semiconductor (MOS) based triethylamine gas sensors generally suffer from low sensitivity and high operating temperatures, significantly limiting their practical applications. Summary of the Invention

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

[0004] To address the aforementioned technical problems, this application provides the following technical solution:

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

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

[0007] S12: Coaxial electrospinning was performed with mixture I as the external phase and mixture II as the internal phase to obtain a spun sample;

[0008] S13: Calcine the spun sample at 500-700℃ for 2-3 hours 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 mixture II to inhibit the hydrolysis of tetrabutyl titanate.

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

[0012] Preferably, solvent A and 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 step S12, during coaxial electrospinning, the coaxial electrospinning needle is of model 17G / 22G.

[0016] Preferably, in step S12, during coaxial electrospinning, the syringe advance 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: Using N,N-dimethylformamide as a solvent, weigh 5 / 100-10 / 100 of the tungsten source (ammonium metatungstate hydrate) and 10 / 100-20 / 100 of the polyvinylpyrrolidone by mass into a container, stir at room temperature until the solutes are completely dissolved to obtain mixture I;

[0019] a2: Based on the mixture of solvent ethanol and a small amount of acetic acid, weigh 20 / 100-25 / 100 mass ratio of titanium source (tetrabutyl titanate) and 10 / 100-20 / 100 mass ratio of polyvinylpyrrolidone and place them in a container. Stir at room temperature until the solute is completely dissolved to obtain mixture II.

[0020] a3: Prepare a syringe, the needle of which is a coaxial electrospinning needle;

[0021] a4: Prepare the receiving roller, which is used to receive the nonwoven film. The receiving roller rotates at a speed of 200-500 r / min. Transfer the mixture I and mixture II into the syringe for electrospinning.

[0022] a5: After obtaining sufficient electrospun samples, remove the nonwoven fabric membrane and place it in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2-10℃ / min, and after heating to 500-700℃, it is kept at that temperature for 2-3 hours; after the temperature cools naturally, TiO2-WO3 core-shell nanowire powder samples can be obtained.

[0023] The TiO2-WO3 core-shell nanowires of this invention, due to the formation of the core-shell structure, form a microstructure of TiO2-WO3 core-shell nanowires, which increases the initial resistance and surface reactive sites of the gas-sensitive material, accelerates the adsorption and desorption of gas molecules, and when used in sensors, can improve the sensor's sensitivity to triethylamine, response / recovery speed, and reduce the operating temperature required by 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: Disperse the above TiO2-WO3 core-shell nanowires in water or ethanol, then grind them to obtain mixture III;

[0027] S22: The mixture III is coated on the outer surface of the sensor carrier with gas sensor function, and the mixture III completely covers the electrodes of the sensor carrier to form a thin film of sensitive material on the outer surface, thus obtaining a semi-finished product; the sensor carrier with gas sensor function includes an Al2O3 ceramic tube, an annular gold electrode disposed at both ends of the Al2O3 ceramic tube, and a platinum wire welded to the annular gold electrode.

[0028] S23: The semi-finished product is baked under infrared light for 20-30 minutes and then calcined at 150-200℃ 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, the surface of the triethylamine sensor is further provided with a heating wire, which is selected from a nickel-cadmium alloy coil that runs through the interior of the Al2O3 ceramic tube.

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

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

[0034] This invention enables the fabrication of complete, continuous, and uniformly sized one-dimensional TiO2-WO3 core-shell nanowires. Due to their large specific surface area, these one-dimensional TiO2-WO3 core-shell nanowires provide more adsorption sites. Furthermore, the disordered, interwoven stacking of the nanowires creates numerous pores within the gas-sensitive material, facilitating rapid gas diffusion and adsorption / desorption of the target gas, thereby improving the sensor's response and response / recovery speed. Simultaneously, the sensor in this invention can be fabricated using existing commercially available tubular gas sensors as a carrier, resulting in a simple manufacturing process, small size, and suitability for mass production. Attached Figure Description

[0035] Figure 1 The images show the SEM (scanning electron microscope) 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 The image shows the full XRD pattern of the TiO2-WO3 core-shell nanowires prepared in Example 1.

[0037] Figure 3 (a) is the Ti characteristic XPS energy spectrum of 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 triethylamine sensor fabricated based on TiO2-WO3 core-shell nanowires in Example 1.

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

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

[0041] Figure 7 The response-recovery curves of the comparative sensor and the sensor in Example 1 to different concentrations of triethylamine at different operating temperatures are shown.

[0042] Explanation of reference numerals in the attached figures: 1-Al2O3 ceramic tube, 2-semiconductor sensitive material layer, 3-ring gold electrode, 4-platinum wire, 5-heating wire. Detailed Implementation

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

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

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

[0046] a1: Using N,N-dimethylformamide as a solvent, weigh 6 / 100 of the tungsten source (ammonium metatungstate hydrate) and 12 / 100 of the polyvinylpyrrolidone by mass and place them in a container. Stir at room temperature until the solutes are completely dissolved to obtain mixture I.

[0047] a2: Based on a mixture of solvents N,N-dimethylformamide, ethanol and acetic acid (N,N-dimethylformamide:ethanol = 1:1), weigh 21 / 100 of the titanium source (tetrabutyl titanate) and 14 / 100 of the polyvinylpyrrolidone and place them in a container. Stir at room temperature (25±5℃) until the solutes are completely dissolved to obtain mixture II;

[0048] a3: Prepare a syringe, the needle of which is a coaxial electrospinning needle;

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

[0050] The shell / core solution injector has an injection speed of 0.3 / 0.2 mL / h, a voltage of 10 kV, a receiving distance of 15 cm, and an ambient humidity of 30% RH.

[0051] a4: Prepare the receiving roller, which is used to receive the nonwoven film, and the receiving roller rotates at 400 r / min; transfer the mixture II into the syringe for electrospinning.

[0052] a5: After obtaining sufficient electrospun samples, remove the nonwoven fabric membrane and place it in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2℃ / min, and after heating to 550℃, it is kept at that temperature for 2h; after the temperature cools naturally, TiO2-WO3 core-shell nanowire powder samples 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 functionality;

[0055] b2: Mix TiO2-WO3 core-shell nanowire powder sample and deionized water in a ratio of 2:1, grind the mixture to obtain a paste-like mixture III containing TiO2-WO3 core-shell nanowires;

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

[0057] b4: After baking the sensor carrier coated with the sensitive material film 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 a nickel-cadmium alloy coil through the inside of the sensor carrier as a heating wire to obtain a semi-finished sensor product;

[0059] b6: The sensor semi-finished product was welded and packaged according to the general side-heated gas-sensitive element 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: Using N,N-dimethylformamide as the solvent, weigh 5 / 100 of the tungsten source (tungsten chloride (WCl6)) and 10 / 100 of the polyvinylpyrrolidone and place them in a container. Stir at room temperature until the solutes are completely dissolved to obtain mixture I.

[0063] a2: Based on a mixture of solvents N,N-dimethylformamide, ethanol and acetic acid (N,N-dimethylformamide:ethanol = 1:1), weigh 20 / 100 of the titanium source (tetrabutyl titanate) and 10 / 100 of the polyvinylpyrrolidone into a container and stir at room temperature until the solutes are completely dissolved to obtain mixture II;

[0064] a3: Prepare a syringe, the needle of which is a coaxial electrospinning needle;

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

[0066] The shell / core solution injector has an injection speed of 0.3 / 0.2 mL / h, a voltage of 5 kV, a receiving distance of 10 cm, and an ambient humidity of 10% RH.

[0067] a4: Prepare the receiving roller, which is used to receive the nonwoven film, and the receiving roller rotates at 200 r / min; transfer the mixture II into the syringe for electrospinning.

[0068] a5: After obtaining sufficient electrospun samples, remove the nonwoven fabric membrane and place it in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 2℃ / min, and after heating to 500℃, it is kept at that temperature for 2h; after the temperature cools naturally, TiO2-WO3 core-shell nanowire powder samples 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 functionality;

[0071] b2: Mix TiO2-WO3 core-shell nanowire powder sample and deionized water in a ratio of 2:1, grind the mixture to obtain a paste-like mixture III containing TiO2-WO3 core-shell nanowires;

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

[0073] b4: After baking the sensor carrier coated with the sensitive material film 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 a nickel-cadmium alloy coil through the inside of the sensor carrier as a heating wire to obtain a semi-finished sensor product;

[0075] b6: The sensor semi-finished product was welded and packaged according to the general side-heated gas-sensitive element 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: Using N,N-dimethylformamide as a solvent, weigh 10 / 100 of the tungsten source (tungstic acid (H2WO4)) and 20 / 100 of the polyvinylpyrrolidone and place them in a container. Stir at room temperature until the solutes are completely dissolved to obtain mixture I.

[0079] a2: Based on a mixture of solvents N,N-dimethylformamide, ethanol and acetic acid (N,N-dimethylformamide:ethanol = 1:1), weigh 25 / 100 of titanium source (tetrabutyl titanate) and 20 / 100 of polyvinylpyrrolidone into a container and stir at room temperature until the solutes are completely dissolved to obtain mixture II;

[0080] a3: Prepare a syringe, the needle of which is a coaxial electrospinning needle;

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

[0082] The shell / core solution injector has an injection speed of 0.3 / 0.2 mL / h, a voltage of 20 kV, a receiving distance of 20 cm, and an ambient humidity of 50% RH.

[0083] a4: Prepare the receiving roller, which is used to receive the nonwoven film, and the receiving roller rotates at 500 r / min; transfer the mixture II into the syringe for electrospinning.

[0084] a5: After obtaining sufficient electrospun samples, remove the nonwoven fabric membrane and place it in a muffle furnace for calcination; the muffle furnace is set to a heating rate of 10℃ / min, and after heating to 700℃, it is kept at that temperature for 3 hours; after the temperature cools naturally, TiO2-WO3 core-shell nanowire powder samples 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 functionality;

[0087] b2: Mix TiO2-WO3 core-shell nanowire powder sample and deionized water in a ratio of 5:1, grind the mixture to obtain a paste-like mixture III containing TiO2-WO3 core-shell nanowires;

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

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

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

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

[0092] Comparative Example 1: Fabrication of a triethylamine sensor based on TiO2 nanowires

[0093] 1. Preparation method of TiO2 nanowires:

[0094] a1: Using a mixture of solvent N,N-dimethylformamide, ethanol and a small amount of acetic acid (N,N-dimethylformamide:ethanol = 1:1) as a reference, extract 21 / 100 of tetrabutyl titanate by mass and place it in a container. Stir at room temperature until the solute is completely dissolved to obtain mixture I.

[0095] a2: Based on the mixture in step a1, weigh polyvinylpyrrolidone into the second mixture at a mass ratio of 14 / 100, stir at room temperature, and finally obtain a transparent viscous solution, which is called mixture II.

[0096] a3: Prepare a syringe. The syringe needle is a special needle 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 advance speed is 0.3 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.

[0099] a4: Prepare the receiving roller, which is used to receive the nonwoven film. The receiving roller rotates at 400 r / min. Transfer mixture II into the syringe for electrospinning.

[0100] a5: After obtaining sufficient electrospun samples, remove the nonwoven fabric membrane and place it in a muffle furnace for calcination; set the heating rate of the muffle furnace to 2℃ / min, heat to 550℃, and hold for 2 hours; after the temperature cools naturally, TiO2 nanowire powder samples can be obtained.

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

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

[0103] b2: Mix TiO2 nanowire powder sample and deionized water in a ratio of 2:1, grind the mixture to obtain a paste-like mixture III containing TiO2 nanowires;

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

[0105] b4: After baking the sensor carrier coated with the sensitive material film 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 a nickel-cadmium alloy coil through the inside of the sensor carrier as a heating wire to obtain a semi-finished sensor product;

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

[0108] Comparative Example 2: Fabrication of a Triethylamine Sensor Based on WO3 Nanowires

[0109] 1. Preparation method of WO3 nanowires:

[0110] a1: Using N,N-dimethylformamide as the solvent, weigh out 13 / 100 mass ratio of ammonium metatungstate hydrate and place it in a container. Stir at room temperature until the solute is completely dissolved to obtain mixture I.

[0111] a2: Based on N,N-dimethylformamide in step a1, weigh polyvinylpyrrolidone into the second mixture at a mass ratio of 14 / 100, stir at room temperature, and finally obtain a transparent viscous solution, which is called mixture II.

[0112] a3: Prepare a syringe. The syringe needle is a special needle 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 advance speed is 0.3 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.

[0115] a4: Prepare the receiving roller, which is used to receive the nonwoven film. The receiving roller rotates at 400 r / min. Transfer mixture II into the syringe for electrospinning.

[0116] a5: After obtaining sufficient electrospun samples, remove the nonwoven fabric membrane and place it in a muffle furnace for calcination; set the heating rate of the muffle furnace to 2℃ / min, heat to 550℃, and hold for 2 hours; after the temperature cools naturally, WO3 nanowire powder samples can be obtained.

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

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

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

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

[0121] b4: After baking the sensor carrier coated with the sensitive material film 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 a nickel-cadmium alloy coil through the inside of the sensor carrier as a heating wire to obtain a semi-finished sensor product;

[0123] b6: The sensor semi-finished product was welded and packaged according to the general side-heated gas-sensitive element 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. As can be observed from TEM images (j) to (m), the prepared core-shell nanowires have a complete, uniform, and continuous outer shell coating, which is very thin and of similar thickness.

[0126] like Figure 2As shown, according to 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 α = 7.3 Å, β = 7.53 Å, and β = 7.68 Å. However, two phases coexist in the pure titanium dioxide nanowires, but with significant differences in content. Clearly, the diffraction peaks from anatase titanium dioxide (JCPDS Card No. 89-4921) are sharp and strong, dominating the composition. In contrast, rutile titanium dioxide (JCPDS Card No. 89-4920) accounts for a relatively small proportion. In TiO2-WO3 core-shell nanowires, titanium dioxide constitutes the main diffraction peaks, and the peak positions do not shift to the left or right, indicating that no doping process occurred. No diffraction peaks from other substances were detected in any of the products, indicating high purity. However, the weakened peak intensity and increased half-peak width of the core-shell nanowires indicate a decrease in crystallinity, which may be due to mutual interference between the crystallization processes of the two phases.

[0127] like Figure 3 As shown in (a), the Gaussian fitted peaks in the figure belong to Ti 2p1 / 2 and 2p3 / 2 of the sensors in Comparative Example 1 and the Example. 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. Generally speaking, the O1s peak can be divided into three Gaussian fitted components: lattice oxygen (O L ), oxygen vacancy (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 reacting gases, while O C It directly participates in the redox reaction on the material surface. For example... Figure 3 As shown in (b) to (d), the O of TiO2-WO3 core-shell nanowires C and O V The proportion is significantly higher than that of titanium dioxide nanowires and tungsten trioxide nanowires. Calculation O C +O V The proportions of the constituent elements were as follows: titanium dioxide nanowires accounted for 27.24%, tungsten trioxide for 36.09%, and TiO2-WO3 core-shell nanowires for 47.34%. The results indicate that the core-shell structure can increase the oxygen content. C and O V The proportion of [amount] increases the gas-sensitive properties of the material.

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

[0129] like Figure 5 As shown, the response of the sensor in Example 1 (the response of the gas-sensitive element is defined as its resistance R in air) is measured across the entire temperature testing range. a With resistance R in triethylamine gas g The ratios of the values ​​of the core-shell nanowires in the example are all higher than those in the comparative example sensors. The optimal operating temperature of the comparative example sensor is 180°C, the optimal operating temperature of the comparative example sensor is 200°C, and the optimal operating temperature of the example sensor is 130°C. At this time, the responses of the sensors of comparative example 1, comparative example 2 and example 1 to 100 ppm triethylamine at their respective optimal operating temperatures are 2.7, 18.5 and 106, respectively. The response of the example sensor is about 40 times that of the device of comparative example 1 and 6 times that of the device of comparative example 2, and the operating temperature is lower. This indicates 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 sensor and the sensor of Example 1 are at 130°C and the triethylamine gas concentration is 100 ppm, the response times of Comparative Example 1, Comparative Example 2, and Example 1 are 27 s, 19 s, and 132 s, respectively, and the recovery rates after approximately 20 minutes are 21%, 10%, and 52%, respectively. Although the response time is slightly delayed, the device of Example 1 exhibits a faster recovery speed and higher response. When the operating temperature of the sensor of Example 1 is 220°C, the recovery time is 133 s, which is faster than the optimal operating performance. Therefore, in practical applications, different requirements for response value and response / recovery speed can be achieved by adjusting the temperature of the sensor.

[0131] like Figure 7 (a) and Figure 7 As shown in (b), when the operating temperature of the device in the examples is 130°C, its response increases with increasing triethylamine concentration. The response to triethylamine remains dominant throughout the entire test concentration range, especially when the triethylamine concentration is greater than 20 ppm. According to the formula, the device in Example 1 achieves a minimum detectable concentration of 40.86 ppb for triethylamine at its optimal operating temperature, significantly lower than the 363.93 ppb of Comparative Example 1 and the 287.15 ppb of Comparative Example 2, indicating that the device in the examples has better gas concentration discrimination capability and a lower detection limit.

[0132] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A triethylamine sensor, characterized in that, The triethylamine sensor is prepared by the following steps: S21: Disperse TiO2-WO3 core-shell nanowires in water or ethanol, then grind them to obtain mixture III; S22: The mixture III is coated on the outer surface of the sensor carrier with gas sensor function, and the mixture III completely covers the electrodes of the sensor carrier to form a thin film of sensitive material on the outer surface, thus obtaining a semi-finished product; the sensor carrier with gas sensor function includes an Al2O3 ceramic tube, an annular gold electrode disposed at both ends of the Al2O3 ceramic tube, and a platinum wire welded to the annular gold electrode. S23: The semi-finished product is baked under infrared light for 20-30 min and then calcined at 150-200℃ for 2-3 h to obtain the triethylamine sensor; The preparation method of the TiO2-WO3 core-shell nanowires includes the following steps: S11: Prepare mixture I and mixture II respectively; mixture I is obtained by dissolving a tungsten source and a polymer substrate in solvent A; mixture II is obtained by dissolving a titanium source and a polymer substrate in solvent B; S12: Coaxial electrospinning was performed with mixture I as the external phase and mixture II as the internal phase to obtain a spun sample; S13: Calcine the spun sample at 500-700℃ for 2-3 h to obtain the TiO2-WO3 core-shell nanowires; the tungsten source is selected from ammonium metatungstate, tungsten chloride, or tungstic acid; the titanium source is selected from tetrabutyl titanate; the polymer substrate is selected from one or more of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile; solvent A is selected from one or more of water, N,N-dimethylformamide, ethanol, acetic acid, methanol, isopropanol, and n-butanol; solvent B is selected from one or more of water, N,N-dimethylformamide, ethanol, methanol, isopropanol, and n-butanol and a mixture of acetic acid; the molar ratio of the titanium source to the tungsten source is 1:2-4; in step S12, during coaxial electrospinning, the syringe advance 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.

2. The triethylamine sensor as described in claim 1, characterized in that, The mass ratio of the polymer substrate to solvent A or solvent B is 1-2:

10.

3. The triethylamine sensor as described in claim 1, characterized in that, The thickness of the sensitive material film is 10-30 μm.

4. The triethylamine sensor as described in claim 1, characterized in that, The surface of the triethylamine sensor is also provided with a heating wire.

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