A method for preparing a zinc stannate sensor sensitive to isopropanol

Abstract

A method for preparing a zinc stannate sensor sensitive to isopropanol belongs to the field of semiconductor material preparation technology. This invention aims to solve the problems of insufficient sensitivity, long response recovery time, and poor stability in existing zinc stannate gas sensors for isopropanol detection. The method includes: 1. Adding cobalt nitrate and 2-methylimidazole to methanol and stirring to dissolve; 2. Allowing to stand, centrifuging, filtering, and drying; 3. Sintering to obtain cobalt tetroxide; 4. Preparing a zinc stannate precursor mixed solution; 5. Hydrothermal reaction; 6. Sintering to obtain cobalt tetroxide heterojunction zinc stannate; 7. Adding cobalt tetroxide heterojunction zinc stannate and tetrachloroauric acid to deionized water and stirring to dissolve, then adding sodium citrate and stirring to dissolve; 8. Sintering to obtain gold-doped cobalt tetroxide heterojunction zinc stannate; 9. Preparing the sensor. This invention is used for preparing a zinc stannate sensor sensitive to isopropanol.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material preparation technology. Background Technology

[0002] Zinc stannate (ZnSnO3) is a ternary metal oxide with a perovskite structure. Its crystal structure exhibits a face-centered cubic arrangement with equal lattice parameters a, b, and c, and three facet angles α, β, and γ of 90°. In this structure, each cell contains four atoms, providing stability and homogeneity to the crystal. One characteristic of the face-centered cubic structure is its surface energy distribution, with the (110) facet having the highest surface energy, followed by the (100) facet, and the (111) facet having the lowest. This energy distribution is crucial for understanding how the crystal grows and stabilizes.

[0003] During crystal growth, the (111) facets, which have the lowest energy, are more likely to form because they represent the most energy-stable form in the crystal structure. In contrast, the (100) and (110) facets, with higher surface energy, gradually decrease or are covered by other facets during crystal growth; this is a natural tendency for crystals to reach their overall lowest energy state. Ultimately, zinc stannate tends to form a stable octahedral structure. This structural characteristic not only reflects the fundamental laws of crystal growth but also provides a solid theoretical foundation for the application of zinc stannate in fields such as gas sensors. Through this structural property, zinc stannate can exhibit high sensitivity and selectivity to specific gases, making it a promising candidate in gas-sensitive material research.

[0004] However, existing traditional zinc stannate gas sensors suffer from insufficient sensitivity, long response recovery time, and poor stability in isopropanol detection, limiting their application in demanding detection fields. For example, zinc stannate-based gas sensors exhibit low sensitivity and slow response / recovery speed for volatile isopropanol; furthermore, pure zinc stannate gas sensors suffer from low isopropanol response values ​​and poor response stability. Developing zinc stannate gas sensors with high sensitivity, fast response, and high stability is crucial for meeting market demands for high-performance gas detection technology. Summary of the Invention

[0005] The present invention aims to address the problems of insufficient sensitivity, long response recovery time, and poor stability of existing zinc stannate gas sensors for isopropanol detection, and to provide a method for preparing a zinc stannate sensor sensitive to isopropanol.

[0006] A method for preparing a zinc stannate sensor sensitive to isopropanol, comprising the following steps:

[0007] 1. Cobalt nitrate and 2-methylimidazole were added to methanol and stirred to dissolve, resulting in a mixed solution of precursors;

[0008] 2. Allow the precursor mixture solution to stand to form a precipitate, then centrifuge, filter and dry sequentially to obtain the precursor solid product;

[0009] 3. Grind and sinter the precursor solid product to obtain cobalt tetroxide;

[0010] 4. Add crystalline tin tetrachloride, zinc acetate, sodium hydroxide and cobalt tetroxide to deionized water and stir to dissolve, to obtain a mixed solution of zinc stannate precursor;

[0011] 5. The zinc stannate precursor mixture was subjected to hydrothermal reaction, followed by centrifugation, filtration and drying to obtain the solid zinc stannate product.

[0012] 6. Grind and sinter the solid zinc stannate product to obtain cobalt tetroxide heterojunction zinc stannate;

[0013] 7. Add cobalt tetroxide, zinc stannate, and tetrachloroauric acid to deionized water and stir to dissolve. Then, sonicate the mixture, add sodium citrate and stir to dissolve. Finally, centrifuge, filter, and dry the mixture to obtain a solid product.

[0014] 8. Grind and sinter the solid product to obtain gold-doped cobalt tetroxide heterojunction zinc stannate;

[0015] 9. Dissolve and coat the gold-doped cobalt tetroxide heterojunction zinc stannate onto the electronic components of the gas sensor, dry it, and then calcine and age it to obtain the gold-doped cobalt tetroxide heterojunction zinc stannate gas sensor.

[0016] The beneficial effects of this invention are:

[0017] 1. In this invention, the heterostructure formed by gold-doped zinc stannate and cobalt tetroxide is key to improving gas-sensing performance. The doping of gold atoms not only optimizes the electronic structure of zinc stannate, thereby enhancing its adsorption capacity for gas molecules, but also lowers the activation energy required for the gas-sensing reaction. Simultaneously, cobalt tetroxide, as a material with high catalytic activity and a high specific surface area, further enhances the gas-sensing performance of the material through the heterostructure formed with zinc stannate. This heterostructure not only improves the material's adsorption capacity for gas molecules but also promotes electron transport, thereby increasing the sensor's response speed and sensitivity.

[0018] 2. This invention employs a hydrothermal method to prepare a gold-doped zinc stannate and cobalt tetroxide heterostructure. This method is simple, low-cost, and highly reproducible. Using a gold compound as a dopant, mixed with deionized water, achieves a uniform distribution of gold atoms within the zinc stannate lattice, thereby significantly improving the material's gas-sensing performance. This heterostructure enhances gas adsorption capacity and electron transport efficiency, improving the sensor's response speed and sensitivity, and providing a new and effective approach for the fabrication of high-performance gas sensors.

[0019] This invention relates to a method for preparing a zinc stannate sensor that is sensitive to isopropanol. Attached Figure Description

[0020] Figure 1 A comparison chart showing the sensitivity of the ZnSnO3 sensor prepared in the comparative experiment and the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 in the detection of isopropanol gas.

[0021] Figure 2 The repeatability test graph of the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 for isopropanol gas detection is shown.

[0022] Figure 3 The image shows the long-term performance of the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 for isopropanol gas detection.

[0023] Figure 4 The response-recovery time graph of the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 for isopropanol gas detection is shown.

[0024] Figure 5 The X-ray diffraction (XRD) patterns of Au-Co3O4@ZnSnO3 prepared in step eight of Example 1 and ZnSnO3 prepared in step three of the comparative experiment are shown.

[0025] Figure 6 Raman spectra of Co3O4 prepared in step three of Example 1, Au-Co3O4@ZnSnO3 prepared in step eight of Example 1, and ZnSnO3 prepared in step three of the comparative experiment.

[0026] Figure 7 For comparison, the microstructure diagram of ZnSnO3 prepared in step three of the experiment is shown.

[0027] Figure 8 This is a microstructure diagram of Au-Co3O4@ZnSnO3 prepared in step eight of Example 1. Detailed Implementation

[0028] Specific Implementation Method 1: This implementation method describes a method for preparing a zinc stannate sensor sensitive to isopropanol, which is carried out according to the following steps:

[0029] 1. Cobalt nitrate and 2-methylimidazole were added to methanol and stirred to dissolve, resulting in a mixed solution of precursors;

[0030] 2. Allow the precursor mixture solution to stand to form a precipitate, then centrifuge, filter and dry sequentially to obtain the precursor solid product;

[0031] 3. Grind and sinter the precursor solid product to obtain cobalt tetroxide;

[0032] 4. Add crystalline tin tetrachloride, zinc acetate, sodium hydroxide and cobalt tetroxide to deionized water and stir to dissolve, to obtain a mixed solution of zinc stannate precursor;

[0033] 5. The zinc stannate precursor mixture was subjected to hydrothermal reaction, followed by centrifugation, filtration and drying to obtain the solid zinc stannate product.

[0034] 6. Grind and sinter the solid zinc stannate product to obtain cobalt tetroxide heterojunction zinc stannate;

[0035] 7. Add cobalt tetroxide, zinc stannate, and tetrachloroauric acid to deionized water and stir to dissolve. Then, sonicate the mixture, add sodium citrate and stir to dissolve. Finally, centrifuge, filter, and dry the mixture to obtain a solid product.

[0036] 8. Grind and sinter the solid product to obtain gold-doped cobalt tetroxide heterojunction zinc stannate;

[0037] 9. Dissolve and coat the gold-doped cobalt tetroxide heterojunction zinc stannate onto the electronic components of the gas sensor, dry it, and then calcine and age it to obtain the gold-doped cobalt tetroxide heterojunction zinc stannate gas sensor.

[0038] In step six of this specific embodiment, sintering mainly promotes the crystal transformation and phase purification of the precursor material through heat treatment, forming a cobalt tetroxide heterojunction zinc stannate structure with a specific crystal form. At the same time, it enhances the interfacial bonding between the two materials, forms a built-in electric field, promotes the separation and migration of charge carriers, improves the catalytic activity of the material, and thus optimizes the performance of the gas sensor.

[0039] In this specific embodiment, appropriate gold doping can significantly improve the gas-sensing performance of zinc stannate. This is because gold doping can promote the reactivity of the grain surface, improve the dispersion between grains, and form a uniform porous structure, thereby enhancing the adsorption capacity of gas molecules.

[0040] Furthermore, constructing metal-oxide heterostructures is also an effective strategy for improving gas-sensing performance. Heterostructures can generate built-in electric fields, promoting rapid separation of photogenerated carriers and extending carrier lifetime, thereby improving gas-sensing performance. The heterostructure formed by gold-doped zinc stannate and cobalt tetroxide increases the active sites in the material, thus optimizing gas-sensing performance.

[0041] In summary, this specific embodiment successfully prepared a material with excellent gas-sensing properties by precisely controlling the gold doping amount and constructing a heterostructure of zinc stannate and cobalt tetroxide. This material exhibits high sensitivity, rapid response, and good stability when detecting volatile isopropanol, providing a new approach for the fabrication of high-performance gas sensors.

[0042] The beneficial effects of this embodiment are:

[0043] 1. In this embodiment, the heterostructure formed by gold-doped zinc stannate and cobalt tetroxide is key to improving gas-sensing performance. The doping of gold atoms not only optimizes the electronic structure of zinc stannate, thereby enhancing its adsorption capacity for gas molecules, but also lowers the activation energy required for the gas-sensing reaction. Simultaneously, cobalt tetroxide, as a material with high catalytic activity and a high specific surface area, further enhances the gas-sensing performance of the material through the heterostructure formed with zinc stannate. This heterostructure not only improves the material's adsorption capacity for gas molecules but also promotes electron transport, thereby increasing the sensor's response speed and sensitivity.

[0044] 2. This embodiment employs a hydrothermal method to prepare a gold-doped zinc stannate and cobalt tetroxide heterostructure. This method is simple, low-cost, and highly reproducible. Using a gold compound as a dopant, mixed with deionized water, achieves a uniform distribution of gold atoms within the zinc stannate lattice, thereby significantly improving the material's gas-sensing performance. This heterostructure enhances gas adsorption capacity and electron transport efficiency, improving the sensor's response speed and sensitivity, and providing a new and effective approach for the fabrication of high-performance gas sensors.

[0045] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the molar ratio of cobalt nitrate to 2-methylimidazole in step one is 1:(2~10); and the molar ratio of cobalt nitrate to methanol in step one is 1 mol:(10~30) L. Everything else is the same as in Specific Implementation Method One.

[0046] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: in step two, the precursor mixture solution is allowed to stand for 15-30 hours to form a precipitate; the centrifugation, filtration, and drying described in steps two, five, and seven are specifically carried out as follows: centrifugation for 5-20 minutes at a speed of 3000-5000 r / min, followed by filtration under washing with detergent, and finally drying at a temperature of 40-100℃ for 8-24 hours; the detergent in step two is anhydrous ethanol; the detergents in steps five and seven are deionized water and anhydrous ethanol used alternately. Everything else is the same as in Specific Implementation Method One or Two.

[0047] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the sintering described in step three is specifically carried out as follows: The sample is placed in a tube furnace and heated to 300℃ to 700℃ at a heating rate of 0.6℃ / min to 1.5℃ / min, and then sintered at 300℃ to 700℃ for 60min to 150min. Everything else is the same as in Specific Implementation Methods One to Three.

[0048] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in the following ways: the molar ratio of crystalline tin tetrachloride to zinc acetate in step four is 1:(0.5~2); the molar ratio of crystalline tin tetrachloride to sodium hydroxide in step four is 1:(5~10); the molar ratio of crystalline tin tetrachloride to cobalt tetroxide in step four is 1:(0.01~0.1); and the molar ratio of crystalline tin tetrachloride to deionized water in step four is 1 mol:(5~20) L. Everything else is the same as in Specific Implementation Methods One to Four.

[0049] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the hydrothermal reaction described in step five is carried out as follows: The reactor is placed in a high-pressure reactor, and the temperature is increased to 100℃ to 200℃ at a rate of 3℃ / min to 10℃ / min. The hydrothermal reaction is then carried out for 12 to 20 hours at this temperature. Everything else is the same as in Specific Implementation Methods One to Five.

[0050] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the sintering described in step six is ​​specifically carried out as follows: The sample is placed in a muffle furnace and heated to 400°C to 500°C at a heating rate of 3°C / min to 10°C / min. Sintering is then performed at this temperature for 1 to 3 hours. Everything else is the same as in Specific Implementation Methods One to Six.

[0051] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the molar ratio of cobalt tetroxide heterostannate zinc to tetrachloroauric acid in step seven is 1:(0.001~0.01); the molar ratio of tetrachloroauric acid to sodium citrate in step seven is 1:(1~5); and the molar ratio of cobalt tetroxide heterostannate zinc to deionized water in step seven is 1 mol:(15~50) L. Everything else is the same as in Specific Implementation Methods One to Seven.

[0052] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the sintering described in step eight is specifically carried out as follows: The sample is placed in a muffle furnace and heated to 200°C to 400°C at a heating rate of 3°C / min to 10°C / min. Sintering is then performed at this temperature for 30 to 70 minutes. Everything else is the same as in Specific Implementation Methods One to Eight.

[0053] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: in step nine, gold-doped cobalt tetroxide heterojunction zinc stannate is dissolved in a solvent to obtain a slurry, which is then coated onto the electronic components of the gas sensor; the solvent is diethyl ether, methanol, or ethanol; the mass percentage of gold-doped cobalt tetroxide heterojunction zinc stannate in the slurry is 30% to 70%; the drying in step nine is specifically performed at a temperature of 60℃ to 120℃; the calcination in step nine is specifically performed at a temperature of 150℃ to 200℃ for 1 to 3 hours; and the aging in step nine is specifically performed at a current of 50mA to 120mA for 48 to 144 hours. The rest is the same as in Specific Implementation Methods One to Nine.

[0054] The beneficial effects of the present invention are verified using the following embodiments:

[0055] Example 1:

[0056] A method for preparing a zinc stannate sensor sensitive to isopropanol, comprising the following steps:

[0057] 1. Cobalt nitrate and 2-methylimidazole were added to methanol and stirred for 60 minutes at a temperature of 25℃ and a stirring speed of 400 r / min to obtain a precursor mixed solution.

[0058] The molar ratio of cobalt nitrate to 2-methylimidazole is 1:8; the molar ratio of cobalt nitrate to methanol is 1 mol: 25 L.

[0059] 2. The precursor mixture was allowed to stand for 24 hours to form a precipitate. Then, it was centrifuged for 10 minutes at a speed of 3000 r / min, rinsed with anhydrous ethanol, and filtered. Finally, it was dried at 80℃ for 12 hours to obtain the precursor solid product.

[0060] 3. Grind the precursor solid product, place it in a tube furnace, heat it to 500℃ at a heating rate of 1℃ / min, and then sinter it at 500℃ for 2 hours to obtain cobalt tetroxide (Co3O4).

[0061] IV. Add crystalline tin tetrachloride, zinc acetate, sodium hydroxide and cobalt tetroxide to deionized water, and stir for 20 minutes at a temperature of 25℃ and a stirring speed of 400 r / min to obtain a mixed solution of zinc stannate precursor.

[0062] The molar ratio of crystalline tin tetrachloride to zinc acetate is 1:1; the molar ratio of crystalline tin tetrachloride to sodium hydroxide is 1:10; the molar ratio of crystalline tin tetrachloride to cobalt tetroxide is 1:0.017; and the molar ratio of crystalline tin tetrachloride to deionized water is 1 mol:10 L.

[0063] 5. Place the zinc stannate precursor mixed solution in a high-pressure reactor and heat it to 140°C at a heating rate of 5°C / min. Perform a hydrothermal reaction at 140°C for 12 hours. Then, centrifuge at 3000 r / min for 10 minutes. Filter the solution under vacuum while rinsing with deionized water and anhydrous ethanol alternately. Finally, dry the solution at 80°C for 12 hours to obtain the solid zinc stannate product.

[0064] 6. Grind the solid zinc stannate product, place it in a muffle furnace, and heat it to 500°C at a heating rate of 5°C / min. Sinter it at 500°C for 2 hours to obtain cobalt tetroxide heterojunction zinc stannate (Co3O4@ZnSnO3).

[0065] 7. Add cobalt tetroxide, zinc stannate, and tetrachloroauric acid to deionized water. Stir for 10 min at 25°C and 400 r / min. Then sonicate for 10 min at 40 kHz. Add sodium citrate and stir for 60 min at 25°C and 400 r / min. Centrifuge for 10 min at 3000 r / min. Filter under vacuum while rinsing with deionized water and anhydrous ethanol alternately. Finally, dry at 80°C for 12 h to obtain a solid product.

[0066] The molar ratio of cobalt tetroxide heterojunction zinc stannate to tetrachloroauric acid is 1:0.003; the molar ratio of tetrachloroauric acid to sodium citrate is 1:3; and the molar ratio of cobalt tetroxide heterojunction zinc stannate to deionized water is 1 mol:30 L.

[0067] 8. Grind the solid product and place it in a muffle furnace. Heat the product to 350°C at a rate of 5°C / min. Sinter the product at 350°C for 60 min to obtain gold-doped cobalt tetroxide heterojunction zinc stannate (Au-Co3O4@ZnSnO3).

[0068] 9. Dissolve gold-doped cobalt tetroxide heterojunction zinc stannate in a solvent to obtain a slurry. Coat the slurry onto an Al2O3 ceramic tube and dry it at 80°C. Then calcine it at 200°C for 2 hours. After calcination, weld it onto the sensor base. Then age it for 120 hours at a current of 80mA to obtain the gold-doped cobalt tetroxide heterojunction zinc stannate gas sensor, namely Au-Co3O4@ZnSnO3 sensor.

[0069] The solvent is ethanol; the mass percentage of gold-doped cobalt tetroxide heterojunction zinc stannate in the slurry is 50%.

[0070] Comparative experiment:

[0071] 1. Add crystalline tin tetrachloride, zinc acetate, and sodium hydroxide to deionized water and stir for 20 minutes at a temperature of 25°C and a stirring speed of 400 r / min to obtain a mixed solution.

[0072] The molar ratio of crystalline tin tetrachloride to zinc acetate is 1:1; the molar ratio of crystalline tin tetrachloride to sodium hydroxide is 1:10; and the molar ratio of crystalline tin tetrachloride to deionized water is 1 mol: 10 L.

[0073] 2. Place the mixed solution in a high-pressure reactor and hydrothermally react at 140℃ for 12 hours. After hydrothermal treatment, centrifuge at 3000 rpm for 10 minutes, then filter under vacuum while rinsing with deionized water and anhydrous ethanol alternately. Finally, dry at 80℃ for 12 hours to obtain the solid product.

[0074] 3. Grind the solid product and then place it in a muffle furnace and sinter it at 500℃ for 2 hours to obtain pure zinc stannate (ZnSnO3).

[0075] 4. Dissolve pure zinc stannate in a solvent to obtain a slurry. Coat the slurry onto an Al2O3 ceramic tube and dry it at 80°C. Then calcine it at 200°C for 2 hours. After calcination, weld it onto the sensor base and age it for 120 hours at a current of 80mA to obtain a pure zinc stannate gas sensor, i.e., a ZnSnO3 sensor.

[0076] The solvent is ethanol; the mass percentage of pure zinc stannate in the slurry is 50%.

[0077] Gas-sensing performance testing: The test was conducted using a static gas mixing method, during which the device was heated to 260℃ using a resistance wire. The sensitivity was calculated using the formula S=Ra / Rg, where Rg and Ra represent the resistance values ​​of the sensor when it reaches a stable state in the test gas and pure air, respectively. Figure 1 This is a comparison of the sensitivity of the ZnSnO3 sensor prepared in the comparative experiment and the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 in isopropanol gas detection. As shown in the figure, at a isopropanol concentration of 100 ppm, the sensitivity of the Au-Co3O4@ZnSnO3 gas sensor is approximately 90, while the sensitivity of the undoped pure zinc stannate sensor is approximately 25, demonstrating a significant performance improvement of about 3.6 times after doping.

[0078] Repeatability testing procedure: First, fix the gas sensor in the testing instrument and ensure the test environment is sealed. The test is conducted at a device temperature of 260℃. After 100 seconds, isopropanol gas at a concentration of 100 ppm is introduced into the test environment. This gas concentration is maintained until the end of the next 100 seconds. Then, the sealed cover is opened, exposing the sensor to outside air to purge residual gas and reset its state. This continuous process, from gas introduction to sensor exposure to air, is defined as a complete test cycle. Five consecutive test cycles are performed. Figure 2 The figure shows the repeatability test results of the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 for isopropanol gas detection. As can be seen from the figure, with an isopropanol gas concentration of 100 ppm, the material exhibits good stability in both sensitivity and response recovery curves after five cycles of testing. The sensitivity still reaches 87 after the fifth cycle. This result demonstrates that the gas-sensitive element prepared from Au-Co3O4@ZnSnO3 material possesses excellent repeatability in an isopropanol gas environment and can continuously and effectively detect gases.

[0079] Long-term performance testing process: The Au-Co3O4@ZnSnO3 gas sensor was tested 11 times over a 21-day period, with one test every other day, specifically on days 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, and 21 of the 21-day period. Each test constitutes one complete cycle of the above repeatable test. The device was kept in the air when not being tested, and isopropanol gas was introduced only during testing. Figure 3 The figure shows the long-term performance of the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 for isopropanol gas detection. As can be seen from the figure, after 11 tests over a period of 21 days, the isopropanol gas concentration was 100 ppm and the sensitivity was maintained at a high level (sensitivity of 82~93). This result indicates that the Au-Co3O4@ZnSnO3 material has good stability for isopropanol gas detection.

[0080] Figure 4 The figure shows the response-recovery time of the Au-Co3O4@ZnSnO3 sensor prepared in Example 1 for isopropanol gas detection. As can be seen from the figure, in an environment with an isopropanol gas concentration of 100 ppm, the response time of this material is 23.4 s and the recovery time is 8.2 s.

[0081] Figure 5 The X-ray diffraction (XRD) patterns of Au-Co3O4@ZnSnO3 prepared in step eight of Example 1 and ZnSnO3 prepared in step three of the comparative experiment are shown. The sintered samples exhibit significant broadening of the XRD diffraction peaks, a phenomenon typically associated with reduced crystallinity. Compared to the XRD pattern of pure zinc stannate, the Au-Co3O4@ZnSnO3 XRD pattern shows a sharpening of the main peak at 32°, and a new diffraction peak is observed at 37°. Both changes are attributed to the formation of the Co3O4@ZnSnO3 heterostructure. No independent diffraction peaks for gold (Au) were observed in the XRD patterns, possibly due to the excessive broadening of the diffraction peaks masking them, making them difficult to distinguish in the patterns.

[0082] Figure 6 The Raman spectra of Co3O4 prepared in step three of Example 1, Au-Co3O4@ZnSnO3 prepared in step eight of Example 1, and ZnSnO3 prepared in step three of the comparative experiment are shown. The characteristic Raman peak of cobalt tetroxide is located at 194 cm⁻¹. -1 482cm -1 522cm -1 618cm -1 And 691cm -1Comparing the spectral data of cobalt tetroxide prepared in step three of Example 1 with the standard Raman spectrum of cobalt tetroxide, no obvious impurity characteristic peaks were observed, confirming that the cobalt tetroxide prepared in step three of Example 1 has high purity. By comparing the Raman spectra of Au-Co3O4@ZnSnO3 and pure ZnSnO3, it can be clearly observed that Au-Co3O4@ZnSnO3 exhibits a peak at 482 cm⁻¹. -1 and 522cm -1 The appearance of an additional Raman peak confirms the successful preparation of the Co3O4@ZnSnO3 heterostructure. Furthermore, the Raman peaks of the Au-Co3O4@ZnSnO3 sample exhibit a slight frequency shift compared to pure ZnSnO3, a change attributed to lattice distortion and electronic structure adjustments introduced by gold (Au) doping. These observations demonstrate that gold doping affects the Raman spectral properties of the material, thus confirming the successful synthesis and structural characteristics of the Au-Co3O4@ZnSnO3 composite material.

[0083] Figure 7 For comparison, the microstructure diagram of ZnSnO3 prepared in step three of the experiment is shown. Figure 8 This is a microstructure diagram of Au-Co3O4@ZnSnO3 prepared in step eight of Example 1; Figure 7 In pure ZnSnO3, the grain surface exhibits a smooth texture and distinct edges; however, the grain dispersion and size distribution show a certain degree of heterogeneity. In contrast, Figure 8 The Au-Co3O4@ZnSnO3 composite material exhibits more significant grain decomposition on its surface, leading to increased surface roughness and consequently higher specific surface area. Furthermore, the grain dispersion of this composite material is significantly improved, forming a uniform porous structure, which is highly beneficial for enhancing gas adsorption performance.

Claims

1. A method for preparing a zinc stannate sensor sensitive to isopropanol, characterized in that... It is done in the following steps:

1. Cobalt nitrate and 2-methylimidazole were added to methanol and stirred to dissolve, resulting in a mixed solution of precursors; The molar ratio of cobalt nitrate to 2-methylimidazole is 1:(2~10); the molar ratio of cobalt nitrate to methanol is 1 mol:(10~30) L; 2. Allow the precursor mixture solution to stand to form a precipitate, then centrifuge, filter and dry sequentially to obtain the precursor solid product; 3. Grind the precursor solid product and place it in a tube furnace. Heat the temperature to 300℃~700℃ at a heating rate of 0.6℃ / min~1.5℃ / min. Then sinter at 300℃~700℃ for 60min~150min to obtain cobalt tetroxide.

4. Add crystalline tin tetrachloride, zinc acetate, sodium hydroxide and cobalt tetroxide to deionized water and stir to dissolve, to obtain a mixed solution of zinc stannate precursor; The molar ratio of crystalline tin tetrachloride to zinc acetate is 1:(0.5~2); the molar ratio of crystalline tin tetrachloride to sodium hydroxide is 1:(5~10); the molar ratio of crystalline tin tetrachloride to cobalt tetroxide is 1:(0.01~0.1); and the molar ratio of crystalline tin tetrachloride to deionized water is 1 mol:(5~20) L.

5. Place the zinc stannate precursor mixed solution in a high-pressure reactor and heat it to 100℃~200℃ at a heating rate of 3℃ / min~10℃ / min. Under the condition of 100℃~200℃, perform hydrothermal reaction for 12h~20h. Then, centrifuge, filter and dry in sequence to obtain solid zinc stannate product.

6. Grind the solid zinc stannate product and place it in a muffle furnace. Heat the furnace to 400℃~500℃ at a heating rate of 3℃ / min~10℃ / min. Sinter the product at 400℃~500℃ for 1h~3h to obtain cobalt tetroxide heterojunction zinc stannate.

7. Add cobalt tetroxide, zinc stannate, and tetrachloroauric acid to deionized water and stir to dissolve. Then, sonicate the mixture, add sodium citrate and stir to dissolve. Finally, centrifuge, filter, and dry the mixture to obtain a solid product. The molar ratio of cobalt tetroxide heterostannate zinc to tetrachloroauric acid is 1:(0.001~0.01); the molar ratio of tetrachloroauric acid to sodium citrate is 1:(3~5); the molar ratio of cobalt tetroxide heterostannate zinc to deionized water is 1mol:(15~50)L.

8. Grind the solid product and place it in a muffle furnace. Heat the product to 200℃~400℃ at a heating rate of 3℃ / min~10℃ / min. Sinter the product at 200℃~400℃ for 30min~70min to obtain gold-doped cobalt tetroxide heterojunction zinc stannate.

9. Dissolve and coat the gold-doped cobalt tetroxide heterojunction zinc stannate onto the electronic components of the gas sensor, dry it, and then calcine and age it to obtain the gold-doped cobalt tetroxide heterojunction zinc stannate gas sensor.

2. The method for preparing a zinc stannate sensor sensitive to isopropanol according to claim 1, characterized in that... In step two, the precursor mixture solution is allowed to stand for 15-30 hours to form a precipitate. The centrifugation, filtration, and drying described in steps two, five, and seven are carried out as follows: centrifugation is performed at a speed of 3000-5000 r / min for 5-20 minutes, followed by filtration under washing with detergent, and finally drying is performed at a temperature of 40-100℃ for 8-24 hours. The detergent in step two is anhydrous ethanol. The detergents in steps five and seven are deionized water and anhydrous ethanol used alternately.

3. The method for preparing a zinc stannate sensor sensitive to isopropanol according to claim 1, characterized in that... In step nine, gold-doped cobalt tetroxide heterojunction zinc stannate is dissolved in a solvent to obtain a slurry, which is then coated onto the electronic components of the gas sensor. The solvent is diethyl ether, methanol, or ethanol. The mass percentage of gold-doped cobalt tetroxide heterojunction zinc stannate in the slurry is 30% to 70%. The drying in step nine is specifically performed at a temperature of 60°C to 120°C. The calcination in step nine is specifically performed at a temperature of 150°C to 200°C for 1 to 3 hours. The aging in step nine is specifically performed at a current of 50 mA to 120 mA for 48 to 144 hours.

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