Short cylindrical W18O49 mesocrystal material as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a short cylindrical W18O49 mesocrystal material, which comprises the following steps: S1, respectively dissolving tungsten chloride and oxalic acid in n-propyl alcohol according to a mass ratio of (3.5-4.5): 1, and stirring to obtain a mixed solution; s2, placing the mixed solution in a high-pressure kettle, carrying out heating reaction for 11-13 hours under the condition of 155-165 DEG C, and centrifuging and washing after the reaction is finished, so as to obtain a crude product; and S3, drying the crude product under a vacuum condition, so as to obtain the short cylindrical W18O49 mesocrystal material. The W18O49 mesocrystal material prepared by the invention has a short cylindrical structure and uniform particles; during preparation of the sensor material, metal doping and other treatments are not needed, so that the cost is greatly reduced; and the method has good sensitivity for NO2 gas detection, and the test conditions are mild.

Description

Technical Field

[0001] This invention belongs to the field of NO2 gas-sensitive materials technology, specifically relating to a short cylindrical W 18 O 49 Mesocrystalline materials, their preparation methods, and applications. Background Technology

[0002] With the advancement of industrialization and urbanization, nitrogen dioxide, as one of the major air pollutants, has attracted much attention in terms of monitoring technology. Traditional monitoring methods, such as gas chromatography-mass spectrometry, offer high accuracy but are expensive and complex to operate. Metal oxide semiconductor sensors, on the other hand, are low-cost and simple to manufacture, thus gaining significant interest.

[0003] While semiconductor metal oxide (SMO) gas sensors are widely used in gas detection, they also face numerous technical challenges and limitations. This is particularly true for tungsten oxide (TCO) NO2 gas sensors, where performance limitations are particularly pronounced, primarily in the following aspects: First, insufficient sensitivity and selectivity; many SMO materials respond to multiple gases, making it difficult to distinguish specific target gases. Second, high detection limits for low-concentration gases, limiting their application in trace detection scenarios. Third, high operating temperatures; most SMO sensors require heating to 200-400°C to achieve a good response, which increases power consumption, poses safety hazards, shortens sensor lifespan, and results in slow recovery speeds. Gas desorption is often slower than adsorption, affecting continuous detection efficiency. Furthermore, exposure to high-concentration gases can lead to "poisoning," resulting in even slower recovery, and changes in humidity and oxygen concentration during testing significantly affect the response signal.

[0004] Therefore, it is particularly important to develop a material that is suitable for NO2 gas adsorption and desorption, with mild detection conditions and high sensitivity. Summary of the Invention

[0005] In view of this, the present invention provides a short cylindrical W 18 O 49 Mesocrystalline materials can adapt well to the adsorption and desorption of NO2 gas, and the material synthesis and device design are easy to operate and control, with high detection sensitivity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A short cylindrical W 18 O 49 A method for preparing mesocrystalline materials, the method comprising the following steps: S1. Dissolve tungsten chloride and oxalic acid in n-propanol according to a mass ratio of (3.5~4.5):1, stir, and obtain a mixed solution; S2. Place the mixed solution in an autoclave and heat it at 155~165℃ for 11~13 hours. After the reaction is complete, centrifuge and wash to obtain the crude product. S3. The crude product is dried under vacuum to obtain short cylindrical W-shaped products. 18 O 49 Mesocrystalline materials.

[0007] Furthermore, in step S1, the mass ratio of tungsten chloride to oxalic acid is 4:1, and the mass-volume ratio of the mixture of tungsten chloride and oxalic acid to n-propanol is 1:(130~170).

[0008] In some specific embodiments, preferably, the mass-to-volume ratio of the mixture of tungsten chloride, oxalic acid, and n-propanol is 1:150.

[0009] Furthermore, the stirring conditions in step S1 are: 100~150 rpm and 2.5~3.5 h.

[0010] In some specific embodiments, preferably, the reaction conditions in step S2 are: temperature 150°C and time 12h.

[0011] Furthermore, the centrifugation conditions were: 4000~6000 rpm for 3~5 min; Washing conditions: Wash 4-6 times alternately with ethanol and water.

[0012] Further drying conditions: vacuum degree 10~100kPa, temperature 60~70℃, for 18~22h.

[0013] In some specific embodiments, the preferred drying conditions are: vacuum degree 50 kPa, temperature 65°C, and time 20 h.

[0014] The short cylindrical W-shaped material prepared by the above method 18 O 49 Mesocrystalline materials.

[0015] The short cylindrical W-shaped material prepared by the above method 18 O 49 Application of mesocrystalline materials in NO2 gas detection.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The W prepared in this application 18 O 49Mesocrystalline materials have a short cylindrical structure and uniform particle size (260±10 nm in length and 120±10 nm in diameter). They do not require metal doping or other treatments during sensor material preparation, which greatly reduces costs. They also exhibit good sensitivity for NO2 gas detection under mild testing conditions (test temperature 90℃, sensitivity reaches 12.65 when NO2 concentration is 1 ppm; response time 13.3±2 s; recovery time 11.9±2 s). Attached Figure Description

[0017] Figure 1 In Embodiment 1 of the present invention, FCL_W 18 O 49 Electron microscope image.

[0018] Figure 2 In Embodiment 1 of the present invention, FCL_W 18 O 49 Transmission electron microscope image.

[0019] Figure 3 In Embodiment 1 of the present invention, FCL_W 18 O 49 EDS distribution map.

[0020] Figure 4 This is an electron microscope image of sample 2 in Comparative Example 1 of this invention.

[0021] Figure 5 This is an electron microscope image of sample 3 in Comparative Example 2 of this invention.

[0022] Figure 6 This is an electron microscope image of sample 4 in Comparative Example 3 of this invention.

[0023] Figure 7 FCL_W in Embodiment 1 and Comparative Examples 1-3 of the present invention 18 O 49 X-ray diffraction patterns of samples 2-4.

[0024] Figure 8 Electron microscope images of the samples prepared for comparative examples 4-7 of this invention; wherein, a and b are comparative examples 4, c and d are comparative examples 5, e and f are comparative examples 6, and g and h are comparative examples 7.

[0025] Figure 9 This is a schematic diagram of the gas sensor testing system of the present invention.

[0026] Figure 10 In Embodiment 1 of the present invention, FCL_W 18 O 49 The gas sensor's sensing characteristics at 90℃ and a NO2 concentration of 1ppm.

[0027] Figure 11 In Embodiment 1 of the present invention, FCL_W 18 O 49 The sensing characteristic curves of the gas sensor at an operating temperature of 90℃ and NO2 concentrations ranging from 50ppb to 40ppm.

[0028] Figure 12 In Embodiment 1 of the present invention, FCL_W 18 O 49 The gas sensor has a sensing sensitivity at an operating temperature of 90℃ and a NO2 concentration of 50ppb to 40ppm.

[0029] Figure 13 The graphs show the gas sensor detection results of the samples in Comparative Examples 2-4 of this invention; where ac represents the sensing characteristic curves of sample 2-4 at 90℃ and 1ppm NO2 concentration, and d represents the sensitivity corresponding to the sensing characteristic curve of sample 2-4. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and all reagents and consumables are commercially available products.

[0031] Example 1 This embodiment provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The specific steps of the method for producing mesocrystalline materials are as follows: S1. Dissolve 0.4g of tungsten chloride and 0.1g of oxalic acid in 75mL of n-propanol; then stir at 120rpm for 3 hours to obtain a mixed solution.

[0032] S2. First, transfer the mixed solution to a 100mL stainless steel autoclave and heat it at 160℃ for 12h. Then, centrifuge the obtained product at 4000rpm for 4min to obtain a precipitate. Next, wash the precipitate four times with ethanol and water alternately to obtain the crude product.

[0033] S3. The crude product is dried under a vacuum of 50 kPa and a temperature of 65°C for 20 hours to obtain short cylindrical W-shaped products. 18 O 49 Mesocrystalline materials (FCL_W) 18 O 49 ).

[0034] Comparative Example 1 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49The method for producing mesocrystalline materials is basically the same as that in Example 1, except that: in step S1, oxalic acid is changed to 0.05g, and in step S2, the reaction conditions are changed to heating at 150°C for 12h, while the rest remain unchanged, resulting in sample 2.

[0035] Comparative Example 2 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The method for producing mesocrystalline materials is basically the same as that in Example 1, except that oxalic acid in step S1 is removed, and the reaction conditions in step S2 are changed to heating at 190°C for 12 hours. All other conditions remain unchanged, and sample 3 is obtained.

[0036] Comparative Example 3 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The method for producing mesocrystalline materials is basically the same as that in Example 1, except that: in step S1, oxalic acid is changed to 0.05g, and in step S2, the reaction conditions are changed to heating at 210℃ for 24h. All other conditions remain unchanged, and sample 4 is obtained.

[0037] Comparative Example 4 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The method for producing mesocrystalline materials is basically the same as that in Example 1, except that in step S1, tungsten chloride is reduced to 0.2g, while the rest remain unchanged.

[0038] Comparative Example 5 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The method for producing mesocrystalline materials is basically the same as that in Example 1, except that in step S1, tungsten chloride is changed to 0.6g, while the rest remain unchanged.

[0039] Comparative Example 6 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The method for producing mesocrystalline materials is basically the same as that in Example 1, except that in step S1, tungsten chloride is changed to 0.8g, while the rest remain unchanged.

[0040] Comparative Example 7 This comparative example provides a short cylindrical W synthesized by a hydrothermal method. 18 O 49 The method for producing mesocrystalline materials is basically the same as that in Example 1, except that: in step S2, oxalic acid is changed to 0.05g, and the reaction conditions in step S2 are changed to heating at 190°C for 24h, while the rest remain unchanged.

[0041] The specific differences between the above embodiments and comparative examples are shown in Table 1.

[0042] Table 1. Differences between the Examples and Comparative Examples

[0043] Furthermore, in order to understand the specific performance of the products prepared in the above embodiments and comparative examples, the following experiments were also conducted: 1. Performance Characterization The obtained samples were analyzed for nanomaterial morphology details using field emission scanning electron microscopy (SEM: JEOL 6700F, manufactured by NEC Corporation) and transmission electron microscopy (TEN), and X-ray diffraction crystal structure analysis was performed using Panalytical (Empyrean, Netherlands). The results are shown in [Figure number missing]. Figure 1-7 .

[0044] in, Figure 1-3 The results are shown in the order described in Example 1, showing the materials prepared. Figure 1-3 It can be known that: Figure 1 The SEM image shows that the nanomaterial is 260±10 nm long and 120±10 nm in diameter. Figure 2 The TEM images of ad further verify W 18 O 49 Mesocrystalline materials have a short cylindrical structure. Figure 2 d shows a short cylindrical W 18 O 49 Mesocrystalline materials are composed of W atoms with a diameter of less than 10 nanometers. 18 O 49 It is formed by the self-assembly of fibers. Figure 2 The lattice spacing shown in the high-resolution TEM image is confirmed to be W. 18 O 49 Material, Figure 2 f further indicates that the material has a single-crystal structure; Figure 3 The EDS distribution plot shows its structure and purity.

[0045] Figure 4-6 The images shown in the order of comparative examples 1-3 are SEM images. Figure 4-6 It can be seen that as the synthesis temperature increases and the synthesis time increases, the end material will gradually exhibit agglomeration.

[0046] Figure 7 For Example 1 and Comparative Examples 1-3, FCL_W 18 O 49 The X-ray diffraction patterns of samples 2-4 show that all obtained samples are W. 18 O 49 Material.

[0047] Figure 8 Electron microscope images of the samples prepared for Comparative Examples 4-7; where a and b are Comparative Examples 4, c and d are Comparative Examples 5, e and f are Comparative Examples 6, and g and h are Comparative Examples 7. Figure 8 It can be seen that when the amount of tungsten oxide reagent is small, the material is in a loose state; when the amount of tungsten oxide reagent increases, the material tends to agglomerate and form; the combination of oxalic acid and temperature has a certain influence on the morphology of the material.

[0048] The results above show that the material ratio, reaction temperature, and other parameters in this scheme have a significant impact on the final prepared material. When any one of these parameters is changed, it is impossible to obtain W particles with uniformity and a short cylindrical structure. 18 O 49 Mesocrystalline materials.

[0049] 2. NO2 gas detection The above materials are used to fabricate a detection sensor. A schematic diagram of the detection system is shown below. Figure 9 (A 4000-NMDOG intelligent gas-sensitive analysis system was used to analyze the gas-sensing performance of the gas sensor; the prepared gas sensor was placed in the test chamber via a test arm.) The specific preparation of the gas sensor is as follows: The prepared material was mixed with alcohol at a mass-to-volume ratio of 1:5, and ultrasonically dispersed to form a uniform slurry. A ceramic tube with an axial length of 4 mm and a bottom diameter of 1.5 mm was then used as a support device. Next, the slurry was uniformly coated onto the ceramic tube to design the gas sensor. The operating temperature of the gas sensor was adjusted by a nickel-chromium alloy coil inserted into the ceramic tube. The test results are shown below. Figure 10-13 .

[0050] Depend on Figure 10-13 It can be known that: FCL_W 18 O 49 The mesocrystalline material exhibits significantly higher reaction recovery rate and sensitivity compared to samples 2-4; FCL_W 18 O 49 At 90℃, the sensitivity of the gas sensor increases with increasing concentration, without any obvious saturation phenomenon.

[0051] Through the above series of investigations, it can be seen that the W prepared in this application 18 O 49 Mesocrystalline materials have a short cylindrical structure and uniform particle size; they do not require metal doping or other treatments when preparing sensor materials, which greatly reduces costs; and they have good sensitivity for NO2 gas detection and mild testing conditions.

[0052] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A short cylindrical W 18 O 49 The method for preparing mesocrystalline materials is characterized by, The preparation method includes the following steps: S1. Dissolve tungsten chloride and oxalic acid in n-propanol according to a mass ratio of (3.5~4.5):1, stir, and obtain a mixed solution; S2. Place the mixed solution in an autoclave and heat it at 155~165℃ for 11~13 hours. After the reaction is complete, centrifuge and wash to obtain the crude product. S3. The crude product is dried under vacuum to obtain short cylindrical W-shaped products. 18 O 49 Mesocrystalline materials.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of tungsten chloride to oxalic acid is 4:1, and the mass-volume ratio of the mixture of tungsten chloride and oxalic acid to n-propanol is 1:(130~170).

3. The preparation method according to claim 2, characterized in that, The mass-to-volume ratio of the mixture of tungsten chloride, oxalic acid, and n-propanol is 1:

150.

4. The preparation method according to claim 1, characterized in that, Stirring conditions in step S1: 100-150 rpm, 2.5-3.5 h.

5. The preparation method according to claim 1, characterized in that, The reaction conditions in step S2 are: temperature 150℃, time 12h.

6. The preparation method according to claim 5, characterized in that, Centrifugation conditions: 4000~6000 rpm, 3~5 min; Washing conditions: Wash 4-6 times alternately with ethanol and water.

7. The preparation method according to claim 1, characterized in that, Drying conditions: vacuum degree 10~100kPa, temperature 60~70℃, 18~22h.

8. The preparation method according to claim 7, characterized in that, Drying conditions: vacuum degree 50 kPa, temperature 65℃, time 20 h.

9. The short cylindrical W-shaped material prepared by the preparation method according to any one of claims 1-8 18 O 49 Mesocrystalline materials.

10. The short cylindrical W-shaped material prepared by the preparation method according to any one of claims 1-8 18 O 49 Application of mesocrystalline materials in NO2 gas detection.

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