ZnO / ZnS / ZnSO4 nano composite material and gas sensor based on ZnO / ZnS / ZnSO4 nano composite material
By preparing ZnO/ZnS/ZnSO4 nanocomposite materials, the problems of high operating temperature, poor selectivity and stability of existing nitrogen dioxide gas sensors were solved, and high-sensitivity detection of nitrogen dioxide gas at low temperature was achieved, with good stability and selectivity.
Patent Information
- Application Number
- CN202511218778.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-28
- Publication Date
- 2025-12-26
AI Technical Summary
Existing nitrogen dioxide gas sensors based on simple oxides suffer from problems such as high operating temperature, poor selectivity, and poor stability.
A method for preparing ZnO/ZnS/ZnSO4 nanocomposites was adopted. ZnO hollow microspheres were prepared by solvothermal and hydrothermal methods, and then reacted with thioacetamide to form ZnO/ZnS nanocomposites. Finally, ZnS was partially converted to ZnSO4 by high-temperature annealing in air atmosphere to form a ternary composite material.
It achieves highly sensitive detection of nitrogen dioxide gas at relatively low operating temperatures, exhibits good stability and selectivity, and is suitable for monitoring low concentrations of nitrogen dioxide gas.
Smart Images
Figure CN121202178A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of composite material preparation technology, specifically relating to a ZnO / ZnS / ZnSO4 nanocomposite material and a gas sensor based thereon. Background Technology
[0002] Given the increasingly severe environmental challenges, monitoring toxic gases is crucial for preventing human exposure to nitrogen oxides (NOx). x ), sulfur oxides (SO x The impact of air pollution, including nitrogen dioxide (NO2) and ozone (O3), is crucial. Nitrogen dioxide is colorless and primarily produced by industry and automotive engines. When concentrations exceed 53 ppb (the level set by the U.S. Environmental Protection Agency), it causes numerous serious pollution and respiratory illnesses, including acid rain, photochemical smog, and respiratory irritation leading to emphysema. Therefore, developing inexpensive, compact, sensitive, and reliable gas sensors to monitor NO2 concentrations is essential for human health.
[0003] Various sensing technologies have been used to detect nitrogen dioxide gas, including optical, electrochemical, absorption spectroscopy, and resistive sensors. Among these applications, metal oxide-based resistive gas sensors are widely used due to their low cost, high sensitivity, small size, high integration, fast response, and good reliability. Therefore, various metal oxide semiconductors, such as n-type ZnO and SnO2, and p-type NiO and Co3O4, have been developed to achieve nitrogen dioxide sensing properties. ZnS, with a crystal structure similar to ZnO and abundant trapping surface states, sulfur vacancies, and interstitial sulfur lattice defects, has also been widely used in sensors. To date, various micro / nanomaterial heterojunctions have been synthesized for gas sensors, but the relatively low response and poor selectivity of these sensors have not been completely resolved. In fact, since the sensing mechanism of gas sensors based on micro / nanomaterials-multilayer heterojunctions has not been fully developed, there is still much room for further optimization of the structure, configuration, chemical composition and other properties of multilayer heterojunctions to further improve their gas sensing performance. Therefore, continued research on nitrogen dioxide gas sensors based on multilayer heterojunction composite materials has important scientific and practical significance. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing ZnO / ZnS / ZnSO4 nanocomposite materials and a gas sensor based thereon, so as to solve the shortcomings of existing nitrogen dioxide gas sensors based on simple oxides, such as high operating temperature, poor selectivity and stability.
[0005] To achieve its objectives, the present invention employs the following technical solution: This invention first discloses a method for preparing ZnO / ZnS / ZnSO4 nanocomposite materials, comprising the following steps: Step 1: ZnO hollow microspheres were prepared in methanol by a solvothermal method using Zn(CH3COO)2·2H2O, salicylic acid and polyvinylpyrrolidone as raw materials. Step 2: Using the ZnO hollow microspheres and thioacetamide as raw materials, prepare ZnO / ZnS nanocomposite materials by hydrothermal method; Step 3: The ZnO / ZnS nanocomposite material is annealed at high temperature in air to convert some of the ZnS in the ZnO / ZnS nanocomposite material into ZnSO4, thereby obtaining ZnO / ZnS / ZnSO4 nanocomposite material.
[0006] Further, the specific method of step 1 is as follows: 0.3-0.4 g Zn(CH3COO)2·2H2O, 0.1-0.2 g salicylic acid and 0.04-0.05 g polyvinylpyrrolidone are added to 40-50 mL of methanol and stirred until uniformly mixed. Then, the clear solution is transferred to an autoclave and heated at 180-200℃ for 20-24 h. After the reaction is completed, it is naturally cooled to room temperature, and then washed with deionized water and anhydrous ethanol in sequence. The product is collected and dried under vacuum at 40-60℃. Finally, the sample is annealed at 450-500℃ for 2-3 h in air atmosphere to obtain ZnO hollow microspheres.
[0007] Further, the specific method for step 2 is as follows: 0.2-0.3 g of ZnO hollow microspheres and 0.005-0.03 g of thioacetamide are added to 35-50 mL of deionized water and stirred until homogeneous. The resulting mixture is then transferred to an autoclave and heated at 100-120℃ for 7-9 h. After the reaction is complete, the mixture is allowed to cool naturally to room temperature, washed successively with deionized water and anhydrous ethanol, and the product is collected and vacuum dried at 40-60℃ to obtain the ZnO / ZnS nanocomposite material. By controlling the amount of thioacetamide, the mass percentage of ZnS in the obtained ZnO / ZnS nanocomposite material can be adjusted.
[0008] Furthermore, in step 3, the high-temperature annealing temperature is 450-500℃ and the time is 2-3 hours.
[0009] This invention also discloses the application of the ZnO / ZnS / ZnSO4 nanocomposite material prepared according to the above method in a gas sensor. This gas sensor uses the ZnO / ZnS / ZnSO4 nanocomposite material as the gas-sensitive material for the detection of NO2 gas.
[0010] Compared with the prior art, the beneficial effect of the present invention is that it provides a sensor with good stability and selectivity, and can detect low concentrations of nitrogen dioxide gas, specifically in the following aspects: (1) The method for synthesizing ZnO / ZnS / ZnSO4 nanocomposite materials of the present invention is simple to operate and low in cost. Moreover, the nanocomposite materials prepared have relatively uniform bonding between the components and have excellent performance.
[0011] (2) In the nanocomposite material synthesized in this invention, ZnO / ZnS / ZnSO4 forms two heterojunctions, which significantly improves the performance of the gas sensor based on the composite material and overcomes the disadvantage of low NO2 response of single oxide and double oxide heterojunctions.
[0012] (3) Existing nitrogen dioxide gas sensors are usually made of oxide as the gas-sensitive sensing layer, which requires a high operating temperature to provide sufficient performance. Heating to a high temperature has disadvantages such as increased power consumption and equipment failure rate. In addition, such sensors still have problems such as poor selectivity and stability. This invention provides new materials and new methods for nitrogen dioxide gas sensors with lower operating temperatures, and has great potential in developing low-temperature detection of low-concentration nitrogen dioxide gas. Attached Figure Description
[0013] Figure 1 The images shown are SEM images of the ZnO hollow microspheres in Embodiment 1 of the present invention, where (a) and (b) correspond to different magnifications.
[0014] Figure 2 The images shown are SEM images of the ZnO / ZnS / ZnSO4-5 nanocomposite material in Example 1 of this invention, where (a) and (b) correspond to different magnifications.
[0015] Figure 3 The images show the XRD patterns of ZnO, ZnS, ZnO / ZnS, and ZnO / ZnS / ZnSO4 nanocomposites in Example 1 of this invention.
[0016] Figure 4 XPS spectra of ZnO, ZnO / ZnS-5, and ZnO / ZnS / ZnSO4-5 nanocomposites in Example 1 of this invention are shown, where: (a) is the overall spectrum; (b) is the Zn 2p spectrum; (c) is the S 2p spectrum. The ZnO / ZnS-A-N2 sample used for comparison in the figure was obtained by annealing ZnO / ZnS nanocomposite powder at 500℃ for 2 h in a nitrogen atmosphere; (d) is the high-resolution S 2p XPS spectrum of ZnO / ZnS-5; (e) is the high-resolution S 2p XPS spectrum of ZnO / ZnS / ZnSO4-5; and (f) is the high-resolution O 1s XPS spectrum of ZnO / ZnS / ZnSO4-5.
[0017] Figure 5 The images show the response curves of sensors based on ZnO, ZnS, ZnO / ZnS / ZnSO4-3, ZnO / ZnS / ZnSO4-5, ZnO / ZnS / ZnSO4-7, and ZnO / ZnS / ZnSO4-14 to 5 ppm NO2 at different temperatures in Embodiment 1 of the present invention.
[0018] Figure 6 The response of the sensors based on ZnO, ZnS, ZnO / ZnS-5 and ZnO / ZnS / ZnSO4-5 in Embodiment 1 of the present invention to different concentrations of NO2 (0.1 ~ 10 ppm) at 110℃.
[0019] Figure 7 The response-recovery curve of the sensor based on ZnO, ZnS, and ZnO / ZnS / ZnSO4-5 in Embodiment 1 of the present invention at 110°C to 5 ppm NO2.
[0020] Figure 8 This is a dynamic repeatability gas response diagram of the ZnO / ZnS / ZnSO4-5-based sensor in Embodiment 1 of the present invention at 110°C to 5 ppm NO2.
[0021] Figure 9 This is a bar chart showing the selectivity test of different gases at 110°C using the ZnO / ZnS / ZnSO4-5-based sensor in Embodiment 1 of the present invention.
[0022] Figure 10 This is a graph showing the long-term stability test of the ZnO / ZnS / ZnSO4-5-based sensor in Embodiment 1 of the present invention at 110°C.
[0023] Figure 11 This is a dynamic response diagram of the ZnO / ZnS / ZnSO4-5-based sensor in Embodiment 1 of the present invention at 110℃ to 100 ppb-10ppm NO2. Detailed Implementation
[0024] To more clearly illustrate the purpose, features, and advantages of this invention, the synthesis method of the ZnO / ZnS / ZnSO4 nanocomposite material and the fabrication and gas-sensing testing of a gas sensor based on this material will be described in detail below with reference to illustrations and implementation examples. The following content is merely an example and explanation of the innovative ideas of this invention. Any modifications, additions, or similar alternatives made by those skilled in the art to the specific implementations described herein, as long as they do not deviate from the innovative ideas or exceed the limits defined in these claims, should be considered within the scope of protection of this invention.
[0025] Example 1 In this embodiment, ZnO / ZnS / ZnSO4 nanocomposite materials were prepared according to the following steps: 1. Preparation of ZnO hollow microspheres 0.3 g Zn(CH3COO)2·2H2O, 0.1 g salicylic acid, and 0.04 g polyvinylpyrrolidone were added to 40 mL of methanol and stirred until homogeneous. The clear solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave and heated in an electric oven at 180 °C for 24 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, then washed several times with deionized water and anhydrous ethanol. The white product was collected and dried under vacuum at 60 °C for 12 h. Finally, the sample was annealed at 500 °C for 2 h in air to obtain ZnO hollow microspheres.
[0026] 2. Preparation of ZnO / ZnS nanocomposites 0.2 g of the ZnO hollow microspheres prepared in step 1 and 0.005-0.03 g of thioacetamide (TAA) were added to 35 mL of deionized water and stirred until homogeneous. The resulting mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave and heated at 100 °C for 7 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature and washed successively with deionized water and anhydrous ethanol. The product was collected and dried under vacuum at 40 °C to obtain the ZnO / ZnS nanocomposite material.
[0027] 3. Preparation of ZnO / ZnS / ZnSO4 nanocomposites The ZnO / ZnS nanocomposite powder obtained in step 2 was annealed at 500℃ for 2 h in air atmosphere to obtain ZnO / ZnS / ZnSO4 nanocomposite.
[0028] In step 2, the mass of thioacetamide was 0.006 g, 0.01 g, 0.014 g, and 0.028 g, respectively. The resulting ZnO / ZnS nanocomposites were labeled as ZnO / ZnS-3, ZnO / ZnS-5, ZnO / ZnS-7, and ZnO / ZnS-14, respectively. The resulting ZnO / ZnS / ZnSO4 nanocomposites were labeled as ZnO / ZnS / ZnSO4-3, ZnO / ZnS / ZnSO4-5, ZnO / ZnS / ZnSO4-7, and ZnO / ZnS / ZnSO4-14, respectively.
[0029] For comparison, this embodiment also prepared a pure ZnS nanomaterial sample. The specific method was as follows: 0.03 g of ZnO hollow microspheres and 0.06 g of TAA were added to 15 mL of deionized water, and then transferred to a 50 mL Teflon-lined stainless steel autoclave. The mixture was reacted at 200 °C for 7 h, washed and dried to obtain ZnS nanomaterials.
[0030] Figure 1 This is a scanning electron microscope (SEM) image of the ZnO hollow microspheres obtained in this embodiment. As can be seen from the image, the sample consists of spheres with an average diameter of approximately 1.5 μm and a smooth surface. Furthermore, Figure 1 The illustration in (a) shows a broken ZnO sphere, revealing that the spherical structure is hollow, meaning that ZnO is a hollow microsphere. Furthermore, the figure shows that the sample exhibits good dispersibility and uniform size.
[0031] Figure 2 The image shows a scanning electron microscope (SEM) image of the ZnO / ZnS / ZnSO4-5 nanocomposite material obtained in this embodiment. As can be seen from the image, the ZnO / ZnS / ZnSO4-5 largely retains its spherical structure. Closer observation reveals that the surface of this sample is rougher than that of hollow ZnO microspheres and consists of numerous uniformly sized nanocrystals of approximately 50 nm. It is noteworthy that such rough-surfaced hollow spheres not only provide abundant active sites for absorbing more gas molecules but also promote gas diffusion throughout the sensing material.
[0032] Figure 3 Typical X-ray diffraction (XRD) patterns of the ZnO, ZnS, ZnO / ZnS, and ZnO / ZnS / ZnSO4 nanocomposites obtained in this embodiment are shown. The diffraction peaks of the synthesized pure ZnO and ZnS, scaled to hexagonal wurtzite ZnO (JPCDS card number 36-1451) and cubic ZnS (JPCDS card number 05-0566), respectively, show almost complete overlap of their three pairs of peaks. For the ZnO / ZnS composite, with increasing TAA content, except for a peak appearing close to 28° corresponding to ZnS (111), the other peaks are almost identical to those of pure ZnO, indicating that these composites exist primarily as the ZnO phase.
[0033] Figure 4 XPS images of ZnO, ZnO / ZnS-5, and ZnO / ZnS / ZnSO4-5 nanocomposites obtained in different steps of this embodiment. Figure 4 As shown in the full spectrum of (a), only three peaks (Zn, O, and C) exist in ZnO, while the peaks corresponding to Zn, O, S, and C are clearly visible in the spectra of ZnO / ZnS-5 and ZnO / ZnS / ZnSO4-5. The C peak is the standard peak in XPS, and the appearance of the S peak proves that the S element has been successfully modified into the ZnO surface. Figure 4 (b) The high-resolution Zn 2p spectra of ZnO, ZnO / ZnS-5, and ZnO / ZnS / ZnSO4-5 show that the peak at 1021.2 eV in pure ZnO and ZnO / ZnS-5 belongs to the Zn 2p peak. 3 / 2The peak at 1044.8 eV belongs to Zn 2p 1 / 2 Compared to the binding energy of pure ZnO, the Zn 2p (2p) bonding energy in the ZnO / ZnS / ZnSO4-5 composite material is higher. 3 / 2 and 2p 1 / 2 The binding energy of Zn 2p shifted by 0.6 eV, but Zn 2p 3 / 2 and Zn 2p 1 / 2 The difference between the spin orbitals is the same as that of Zn 2p in ZnO, which is 23 eV. This indicates that Zn has the same chemical state in ZnO, ZnO / ZnS and ZnO / ZnS / ZnSO4-5. Figure 4 (c) shows the high-resolution S 2p spectra of ZnO, ZnO / ZnS-5, ZnO / ZnS / ZnSO4-5, and ZnO / ZnS-A-N2. The ZnO / ZnS-A-N2 sample used for comparison was obtained by annealing ZnO / ZnS-5 nanocomposite powder at 500 °C for 2 h under a nitrogen atmosphere. ZnO / ZnS and ZnO / ZnS-A-N2 show a characteristic peak at 161 eV, while ZnO / ZnS / ZnSO4-5 shows peaks at both 161 eV and 168 eV, indicating the presence of two chemical states of S on its surface. Figure 4 (d) The high-resolution S 2p spectrum of ZnO / ZnS-5 shows that the S 2p peak at 161 eV can be decomposed into two peaks at 161.7 eV and 162.9 eV, which belong to the S 2p peaks, respectively. 3 / 2 and S 2p 1 / 2 Spectral lines, which also prove S 2− The existence of. For example... Figure 4 (e) The high-resolution S 2p spectrum of ZnO / ZnS / ZnSO4-5 shows that ZnO / ZnS / ZnSO4-5 has two peaks at 161 eV and 168 eV, which belong to the S 2p spectrum, respectively. 2- and S 6+ (SO4) 2- This means that after ZnO / ZnS-5 was annealed in air at 500℃ for 2 hours, the ZnS in ZnO / ZnS not only transformed into SO2 and ZnO, but also generated some sulfates. However, the XRD pattern of the ZnO / ZnS / ZnSO4-5 composite material did not show any SO4. 2- The presence of related crystalline phases may be due to the interaction between the material surface and SO4. 2- The related products have low crystallinity or form related SO4. 2- The presence of too few salt phases, below the detection limit of XRD, results in the absence of relevant peaks. For example... Figure 4As shown in (f), the O 1s of ZnO / ZnS / ZnSO4-5 was divided into three peaks: 530.4 eV, 531.3 eV, and 532.3 eV. These peaks correspond to lattice oxygen, lattice defect oxygen, and surface-adsorbed oxygen species in the ZnO lattice, respectively. From the above results, it can be seen that ZnS and ZnSO4 were successfully modified onto the surface of ZnO. In other words, this embodiment successfully synthesized a ZnO / ZnS / ZnSO4 ternary composite material.
[0034] 4. Manufacturing of gas-sensitive elements The powders of the prepared pure ZnO hollow microspheres, pure ZnS nanomaterials, ZnO / ZnS-5 nanocomposite materials, or ZnO / ZnS / ZnSO4 nanocomposite materials were dispersed in ethanol to form a paste, which was then coated onto the surface of an alumina substrate with a pair of Au interdigitated electrodes. To improve the stability and repeatability of the sensor, the fabricated sensor was aged in air at 240°C for 7 days.
[0035] 5. Gas Sensitivity Performance Test The gas-sensing performance of the sensor was studied using an automated gas mixing and testing system. This system uses two mass flow meters (MFCs) to distribute the concentration of the target gas, controlling the ratio of the target gas to high-purity air (99.999% purity) carrier gas in the gas preparation chamber. The response of the gas sensor is defined as the ratio of the sensor's resistance (Rg) in a given concentration of target gas to its resistance (Ra) in pure, dry air (S=Rg / Ra). The response time / recovery time is the time required for the sensor to recover from its initial / saturated state to 90% of the total resistance change during the response / recovery process. During the testing of the sensor's gas-sensing performance, the target gas was always dry.
[0036] To demonstrate that adding ZnS to the surface of ZnO microspheres and generating ZnSO4 composite materials are effective ways to enhance the gas sensing performance of ZnO-based gas sensors, the gas sensing performance of sensors based on ZnO, ZnS, ZnO / ZnS, and ZnO / ZnS / ZnSO4 materials was studied as follows.
[0037] (1) Sensor response performance test at different temperatures Measurements were performed on the gas response of sensors based on pure ZnO, ZnS, and ZnO / ZnS / ZnSO4 to 5 ppm NO2, at operating temperatures (T). w Temperatures ranged from 70 to 180°C (direct heating via a hot and cold plate) to explore the optimal addition amount of TAA and the optimal temperature range. w Value, such as Figure 5 As shown. The gas response of all sensors is related to T. w They all exhibit a volcanic-type correlation, meaning that although the optimal T values of different sensors...w The values may differ, but there always exists an optimal T that maximizes the gas response. w It can be observed that ZnO / ZnS / ZnSO4-5 exhibits the best response to 5 ppm NO2 at 110℃.
[0038] (2) Sensor response performance test at different concentrations Figure 6 The response of each sensor to different concentrations of NO2 (0.1 ~ 10 ppm) is shown at an operating temperature of 110℃. It can be seen that the response of all four sensors increases with increasing NO2 concentration, with the ZnO / ZnS / ZnSO4-5 sensor showing the highest response and a faster rate of increase than the ZnO, ZnS, and ZnO / ZnS-5 sensors.
[0039] (3) Response-recovery test under low concentration of target gas The NO2 gas concentration was set to 5 ppm in the dynamic gas distribution system operating interface, and the target gas was output. The response and recovery curves of ZnO, ZnS, and ZnO / ZnS / ZnSO4-5 sensors to 5 ppm NO2 at 110 ℃ were tested. The test results are as follows: Figure 7 As shown, the response and recovery times of the three sensors are 320 / 550 seconds, 270 / 570 seconds, and 370 / 460 seconds, respectively. Although the response time of ZnO / ZnS / ZnSO4-5 is longer than that of the other sensors, the time required for it to reach a certain response value (e.g., 10) (approximately 150 seconds) is much shorter than that of the other sensors, demonstrating excellent response to low concentrations of NO2.
[0040] (4) Repeatability testing The NO2 gas concentration was set to 5 ppm in the operation interface of the dynamic gas distribution system, the target gas was output, and the repeatability of the gas sensor's response to 5 ppm NO2 was tested. Figure 8 The resistance change graph of the ZnO / ZnS / ZnSO4-5 gas sensor under 5 ppm NO2 in 5 consecutive cycles at 110℃ is shown. The response did not degrade, indicating that the gas sensor has good repeatability.
[0041] (5) Selective testing The responses of ZnO, ZnS, and ZnO / ZnS / ZnSO₄⁻ sensors to various target gases were studied in detail at 110 °C. Interfering gases included 5 ppm NO, 100 ppm CO, 100 ppm H₂, 500 ppm ethanol, 500 ppm methanol, and 500 ppm acetone. Figure 9As shown, the ZnO / ZnS / ZnSO4-5 sensor exhibits a response of 65 to 5 ppm NO2 and an 8 to 5 ppm NO, indicating that at the same concentration, the response to NO2 is approximately 8.1 times that to NO. Furthermore, the ZnO / ZnS / ZnSO4-5 sensor also demonstrates a significantly greater response to 5 ppm NO2 than the other five gases, even though their concentrations are 20 or 100 times higher than NO2. Therefore, the ZnO / ZnS / ZnSO4-5 sensor exhibits excellent selectivity for NO2 compared to the other two sensors.
[0042] (6) Long-term stability test Tests were performed at 110℃ for 5 ppm NO2 gas, with the first four tests every 5 days, and then every 10 days thereafter, for a period of 40 days. Figure 10 As shown, after 40 days of testing, the ZnO / ZnS / ZnSO4-5 sensor exhibited relatively low T0 values. w It exhibits good long-term stability.
[0043] (7) Dynamic response test Dynamic response tests were conducted on NO2 gas at 110℃ within the range of 100 ppb-10 ppm. Figure 11 As shown, the ZnO / ZnS / ZnSO4-5 gas sensor exhibits good sensitivity to ppb-level NO2.
[0044] In summary, the ZnO / ZnS / ZnSO4-5 gas sensor excels in its excellent long-term stability, selectivity, and repeatability. For the detection of low concentrations of NO2 at 110°C, it also exhibits rapid response and recovery performance. These characteristics demonstrate the great potential of ZnO / ZnS / ZnSO4-5 composite materials in developing low-concentration NO2 gas detection technologies at lower temperatures.
[0045] The above description is merely a preferred embodiment of the present invention and does not imply any limitation thereof. Without departing from the spirit and principles of the present invention, those skilled in the art can make various modifications and improvements to the present invention, and all such modifications and improvements should be included within the scope of protection of the present invention.
Claims
1. A method for preparing ZnO / ZnS / ZnSO4 nanocomposite, characterized in that, The method comprises the following steps: Step 1: ZnO hollow microspheres are prepared by a solvothermal method in methanol using Zn(CH3COO)2·2H2O, salicylic acid and polyvinylpyrrolidone as raw materials; Step 2: ZnO / ZnS nanocomposites are prepared by a hydrothermal method using the ZnO hollow microspheres and thioacetamide as raw materials; Step 3: ZnO / ZnS / ZnSO4 nanocomposites are obtained by annealing the ZnO / ZnS nanocomposites at a high temperature in an air atmosphere.
2. The method for preparing ZnO / ZnS / ZnSO4 nanocomposite according to claim 1, characterized in that, The specific method of step 1 is as follows: 0.3-0.4 g Zn(CH3COO)2·2H2O, 0.1-0.2 g salicylic acid and 0.04-0.05 g polyvinylpyrrolidone are added into 40-50 mL methanol and stirred until mixed uniformly, and then the clear solution is transferred into an autoclave and heated at 180-200℃ for 20-24 h; after the reaction is completed, the natural cooling is performed to room temperature, and then the product is collected and dried in vacuum at 40-60℃; finally, the sample is annealed at 450-500℃ in an air atmosphere for 2-3 h to obtain ZnO hollow microspheres.
3. The method for preparing the ZnO / ZnS / ZnSO4 nanocomposite material according to claim 1, characterized in that, The specific method of step 2 is as follows: 0.2-0.3 g ZnO hollow microspheres and 0.005-0.03 g thioacetamide are added into 35-50 mL deionized water and stirred until mixed uniformly, and then the obtained mixture is transferred into an autoclave and heated at 100-120℃ for 7-9 h; after the reaction is completed, the natural cooling is performed to room temperature, and then the product is collected and dried in vacuum at 40-60℃ to obtain ZnO / ZnS nanocomposites.
4. The method for preparing ZnO / ZnS / ZnSO4 nanocomposite according to claim 1 or 3, characterized in that: In step 2, the mass percentage of ZnS in the obtained ZnO / ZnS nanocomposites is controlled by controlling the amount of thioacetamide.
5. The method for preparing the ZnO / ZnS / ZnSO4 nanocomposite material according to claim 1, characterized in that, In step 3, the high-temperature annealing is performed at a temperature of 450-500℃ for 2-3 h.
6. The ZnO / ZnS / ZnSO4 nanocomposites prepared by the preparation method in any one of claims 1-5.
7. The application of the ZnO / ZnS / ZnSO4 nanocomposites in claim 6 in a gas sensor.
8. A gas sensor, characterized by The gas sensor uses the ZnO / ZnS / ZnSO4 nanocomposites in claim 6 as a gas-sensitive material.
9. A gas sensor according to claim 8, characterised in that, The gas sensor is used for detecting NO2 gas.