A WS 2 / MoO 3 Preparation method and application of composite multi-level nanomaterial
By preparing WS2/MoO3 composite multi-layer nanomaterials, the problem of WS2 material stacking and the problem of low response of existing materials at low temperatures are solved, and the ability to efficiently detect low concentrations of NH3 at room temperature is achieved.
Patent Information
- Application Number
- CN202210548041.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-05-18
- Publication Date
- 2025-05-27
- Estimated Expiration
- 2042-05-18
AI Technical Summary
In the prior art, when preparing WS2 materials, the products are easy to stack, which affects their usefulness. The existing mixed materials of WS2 and MoO3 are low in response at low temperatures and lack the ability to detect low concentrations of NH3.
The preparation method of WS2/MoO3 composite multi-layer nanomaterial was adopted. The WS2 powder and sodium molybdate were uniformly dispersed by ultrasonic method, and the concentrated hydrochloric acid was added to carry out hydrothermal reaction to form WS2/MoO3 composite multi-layer nanomaterial.
The problem of WS2 material stacking is solved, a multi-layer nanostructure is formed, which enhances gas-sensitive response and sensitivity, and can detect trace NH3 at room temperature.
Smart Images
Figure 220518152649 
Figure 220518152652 
Figure 220518152655
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of gas sensor materials, and specifically relates to a preparation method and application of a WS 2 / MoO 3 composite multi-level nanomaterial. Background Art
[0002] First, ammonia (NH 3 ) is the only alkaline gas in the air. It reacts with acidic gases in the environment to form ammonium salt aerosol particles, which further promotes the formation of secondary particles during the atmospheric haze pollution process and causes greater harm to environmental pollution. Second, the solubility of NH 3 is extremely high, and it is often adsorbed on the skin mucosa and conjunctiva. Inhaling a large amount of NH 3 in a short time poses a great threat to human health. According to the literature, the limit time for humans to tolerate 25 or 35 ppm NH 3 is 8 h / 15 min. Therefore, it is particularly important to develop a sensitive material that can efficiently, rapidly, and real-time detect low-concentration NH 3 .
[0003] In the prior art, the two-dimensional semiconductor material tungsten disulfide (WS 2 ) is considered a promising ammonia-sensitive material due to its Lewis acid surface characteristics and high conductivity. However, in the process of preparing WS 2 materials in the prior art, the pure WS 2 obtained by hydrothermal reaction will stack into blocks, greatly affecting its practicality. Summary of the Invention
[0004] Aiming at the above deficiencies existing in the prior art, the purpose of the present invention is to provide a preparation method of a WS 2 / MoO 3 composite multi-level nanomaterial to solve the problem of product stacking existing in the process of preparing WS 2 in the prior art.
[0005] To solve the above technical problems, the present invention adopts the following technical solutions:
[0006] A preparation method of a WS 2 / MoO 3 composite multi-level nanomaterial, comprising the following steps:
[0007] Step 1: Prepare WS 2 powder;
[0008] Step 2: Ultrasonically disperse WS 2The powder and sodium molybdate dihydrate are uniformly dispersed in water to form a homogeneous dispersion;
[0009] Step 3: Add concentrated hydrochloric acid to the dispersion obtained in Step 2 to obtain a precursor solution;
[0010] Step 4: Perform a hydrothermal reaction on the precursor solution obtained in Step 3 to obtain the WS 2 / MoO 3 composite multi-level nanomaterial.
[0011] The present invention also provides an application of a WS 2 / MoO 3 composite multi-level nanomaterial. The WS 2 / MoO 3 composite multi-level nanomaterial prepared by the preparation method of the WS 2 / MoO 3 composite multi-level nanomaterial can be used for ammonia detection.
[0012] Compared with the prior art, the present invention has the following beneficial effects:
[0013] 1. The present invention innovatively uses WS 2 as a material growth template, and sodium molybdate dihydrate is anchored and grown on it to form MoO 3 . During the composite process, on the one hand, MoO 3 prevents the stacking of WS 2 nanosheets. On the other hand, due to the steric effect, the growth of MoO 3 is only limited to narrow nanosheets, and finally a multi-level nanostructure is formed. The sensor device constructed with the WS 2 / MoO 3 composite multi-level nanomaterial can detect trace NH 3 at room temperature and has enhanced gas sensing response and high sensitivity.
[0014] 2. The present invention does not directly mix WS 2 with MoO 3 , but uses WS 2 as a growth template, and the precursor of MoO 3 is directly anchored and grown on it, realizing the tight combination between the two materials.
[0015] 3. The WS 2 / MoO 3 composite multi-level nanomaterial of the present invention has enhanced ammonia-sensing performance, mainly in the following two aspects: 1) The material prepared by the method of the present invention has a special multi-level structure, enabling the gas to fully contact the sensitive material; 2) p-type WS 2 and n-type MoO3 The coupling enables the contact interface of the two materials to form a p-n heterojunction, which can provide an additional resistance modulation mechanism, thereby enhancing the gas sensing performance. Description of the Drawings
[0016] Figure 1 is the SEM surface morphology diagram of WS in Example 1 2 nanomaterial.
[0017] Figure 2 is the SEM surface morphology diagram of WS in Example 1 2 / MoO 3 composite multi-level nanomaterial.
[0018] Figure 3 is the SEM surface morphology diagram of WS in the comparative example 2 and MoO 3 directly mixed to obtain WS 2 -MoO 3 nanomaterial.
[0019] Figure 4 is a schematic diagram of the ammonia detection system.
[0020] Figure 5 is WS 2 / MoO 3 sensor device, WS 2 sensor device and WS 2 -MoO 3 sensor device in real-time response change diagram under different concentrations of ammonia.
[0021] Figure 6 is WS 2 / MoO 3 sensor device, WS 2 sensor device and WS 2 -MoO 3 sensor device in concentration-response diagram under different concentrations of ammonia.
[0022] Figure 7 is WS 2 -MoO 3 sensor device in response bar chart to 3 ppm ammonia at different temperatures.
[0023] Among them: gas control system 1, test chamber 2, data acquisition system 3. Detailed Implementation Modes
[0024] The present invention will be further described below in conjunction with the drawings and embodiments.
[0025] I. Embodiments and Comparative Examples
[0026] Example 1
[0027] Step 1) Preparation of WS 2 powder: Thioacetamide and tungsten chloride with a mass ratio of 1.5:1 are uniformly dispersed in 80 ml of ultrapure water by sonication to form a homogeneous dispersion, which is placed in a reaction kettle. After reacting at 270 °C for 22 h, the reaction product is centrifuged and washed, and then vacuum dried at 60 °C for 12 h to obtain WS 2 nanomaterials.
[0028] Step 2) Preparation of WS 2 / MoO 3 composite multi-level nanomaterials: The WS 2 nanomaterials prepared in Step 1 and sodium molybdate dihydrate are uniformly dispersed in ultrapure water with a molar ratio of 1:0.8 and a volume ratio of 1:1. Then 1 ml of concentrated hydrochloric acid is added thereto. Hydrothermal reaction is carried out at 160 °C for 2 h, and then the reaction product is centrifuged and washed, and vacuum dried at 60 °C for 12 h to obtain WS 2 / MoO 3 composite multi-level nanomaterials.
[0029] Step 3) Preparation of WS 2 / MoO 3 sensor devices and WS 2 sensor devices: The WS 2 nanomaterials and WS 2 / MoO 3 composite multi-level nanomaterials obtained in Step 1 and Step 2 are respectively dissolved in the same volume of ultrapure water, and then the same volume of WS 2 solution and WS 2 / MoO 3 solution are respectively dropped onto the electrodes, and vacuum dried at 50 °C for 4 h to obtain WS 2 / MoO 3 sensor devices and WS 2 sensor devices.
[0030] Example 2
[0031] Step 1) Preparation of WS 2 powder: Thioacetamide and tungsten chloride with a mass ratio of 1.5:1 are uniformly dispersed in 80 ml of ultrapure water by sonication to form a homogeneous dispersion, which is placed in a reaction kettle. After reacting at 270 °C for 22 h, the reaction product is centrifuged and washed, and then vacuum dried at 60 °C for 12 h to obtain WS 2 nanomaterials.
[0032] Step 2) Preparation of WS 2 / MoO 3 composite multi-level nanomaterials: The WS2 The nanomaterials and sodium molybdate dihydrate are uniformly dispersed in ultrapure water, with a molar ratio of 1:1.5 and a volume ratio of 1:1. Then 1 ml of concentrated hydrochloric acid is added thereto. Hydrothermal reaction is carried out at 160 °C for 2 h, and then the reaction product is centrifuged and washed, and vacuum dried at 60 °C for 12 h to obtain WS 2 / MoO 3 composite multi-level nanomaterials.
[0033] Step 3) Preparation of WS 2 / MoO 3 Preparation of the sensor device: Dissolve the WS 2 / MoO 3 composite multi-level nanomaterials obtained in Step 2 in the same volume of ultrapure water as in Example 1, and then dropwise coat the same volume of WS 2 / MoO 3 solution on the electrode, and vacuum dry at 50 °C for 4 h to obtain WS 2 / MoO 3 sensor device.
[0034] Comparative example
[0035] Step 1) Preparation of WS 2 powder: Uniformly disperse thioacetamide and tungsten chloride with a mass ratio of 1.5:1 in 80 ml of ultrapure water by sonic wave ultrasonic method to form a uniform dispersion, and place it in a reaction kettle. After reacting at 270 °C for 22 h, centrifuge and wash the reaction product, and then vacuum dry at 60 °C for 12 h to obtain WS 2 nanomaterials.
[0036] Step 2) Preparation of MoO 3 nanomaterials: Uniformly disperse sodium molybdate dihydrate in ultrapure water, and then add 1 ml of concentrated hydrochloric acid thereto. The mass of sodium molybdate dihydrate and the volume of ultrapure water are the same as in Example 1. Hydrothermal reaction is carried out at 160 °C for 2 h, and then the reaction product is centrifuged and washed, and vacuum dried at 60 °C for 12 h to obtain MoO 3 nanomaterials.
[0037] Step 3) Preparation of WS 2 -MoO 3 nanomaterials: Dissolve the WS 2 nanomaterials and MoO 3 nanomaterials obtained in Step 1 and Step 2 directly in 1 part of ultrapure water. The dosage of WS 2 and the volume of ultrapure water are the same as in Example 1.
[0038] Step 4) Preparation of WS 2 -MoO 3 sensor device: The WS obtained in Step 32 -MoO 3 The nanomaterials were dissolved in the same volume of ultrapure water as in Example 1, and then the same volume of WS 2 -MoO 3 solution was drop-coated on the electrode and dried in vacuum at 50 °C for 4 h to obtain WS 2 -MoO 3 sensor device.
[0039] In the research of the present invention, it was found that in the prior art when preparing WS 2 nanomaterials, there were serious stacking problems in the obtained products. The SEM surface morphologies of WS 2 nanomaterials, WS 2 -MoO 3 nanomaterials and WS 2 / MoO 3 composite multi-level nanomaterials are shown in Figure 1 , Figure 2 and Figure 3 respectively. Figure 1 The serious stacking of individual WS 2 nanosheets in [reference] makes it form a very compact bulk structure.
[0040] To solve this problem, the present invention considered introducing a metal oxide semiconductor material to form a new composite nanomaterial with the two, which might solve this problem. For this purpose, the present invention adopted the introduction of MoO 3 , but it was found after further research that although MoO 3 also has gas sensitivity for detecting NH 3 , its excellent gas sensing performance usually needs to be achieved at high temperatures, which undoubtedly limits the low-temperature and low-power consumption application prospects of the sensor device. After experiments, it was found that if WS 2 and MoO 3 were directly mixed, the working temperature of the obtained composite material was still high, and its gas sensing performance needed to be achieved at a relatively high temperature. Moreover, the response was extremely low and it lacked the ability to detect low-concentration NH 3 . At the same time, simple physical mixing did not well solve the serious stacking problem of WS 2 nanomaterials. As can be seen from Figure 2 , after directly mixing WS 2 nanomaterials and MoO 3 nanomaterials, the stacking problem was not alleviated, and the mixed product still had a relatively large bulk structure. Therefore, it was necessary to rethink the combination method of the two. For WS 2 nanomaterials and MoO 3In the continuous research on the method of combining nanomaterials, an unexpected discovery of the present invention is that the composite material obtained by the above method can surprisingly well solve the above technical problems. From Figure 3 it can be seen that the WS 2 / MoO 3 composite multi-level nanomaterials prepared by the method of the present invention exhibit an obvious multi-level structure. Almost all WS 2 nanosheets are dispersed, indicating that the presence of MoO 3 successfully prevents the agglomeration of WS 2 ; at other positions except for WS 2 nanosheets, no separate MoO 3 nanomaterials are observed, indicating that MoO 3 and WS 2 achieve tight binding. This fluffy multi-level structure can improve gas accessibility and expose more active sites, thereby enhancing the gas-sensing performance of the material.
[0041] II. Applications
[0042] The WS 2 / MoO 3 composite multi-level nanomaterials prepared by the preparation method of the present invention can be used for ammonia detection. Deposit the WS 2 / MoO 3 composite multi-level nanomaterials on the surface of the electrode to obtain a WS 2 / MoO 3 sensor device; the WS 2 / MoO 3 sensor device realizes the detection of ammonia through the relative change in resistance before and after its contact with ammonia. The preparation method of the WS 2 / MoO 3 sensor device includes the following steps: uniformly disperse the WS 2 / MoO 3 composite multi-level nanomaterials in ultrapure water, drop-coat them on the interdigital electrode, and vacuum dry at 50 °C for 4 h to obtain the WS 2 / MoO 3 sensor device. 2 / MoO 3 sensor device.
[0043] Taking the WS 2 nanomaterials and WS 2 -MoO 3 nanomaterials prepared in Example 1 and the comparative example as control examples, compared with the WS 2 / MoO 3Compare the performance of composite multi - level nanomaterials. WS 2 nanomaterials and WS 2 -MoO 3 The nanomaterials are prepared by the above - mentioned method to obtain WS 2 sensor devices and WS 2 -MoO 3 sensor devices, and compare the performance with WS 2 / MoO 3 sensor devices.
[0044] As Figure 4 shown in the schematic diagram of the ammonia detection system, it includes a gas control system 1, a test chamber 2, and a data acquisition system 3. When in use, the concentration of the target gas is controlled by the gas control system 1 constructed by a commercial flowmeter. At a fixed flow rate, the concentration of the target gas can be adjusted by adjusting the flow rate ratio of the target gas and dry air. In the test chamber 2, WS 2 sensor devices, WS 2 -MoO 3 sensor devices and the WS 2 / MoO 3 sensor devices of the present invention are placed side by side. There are ports at both ends of the test chamber, which are the inlet and outlet respectively. There is a data acquisition interface at the upper end of the test chamber. The signal output ends of the WS 2 sensor devices, WS 2 -MoO 3 sensor devices and WS 2 / MoO 3 sensor devices are connected to the data acquisition system 3. In the control experiment, Keithley 2700 (a multi - channel acquisition system that can collect multiple groups of data simultaneously) is used as the data acquisition system, and the resistance values of the WS 2 sensor devices, WS 2 -MoO 3 sensor devices and WS 2 / MoO 3 sensor devices are monitored in real - time and collected.
[0045] Before testing the target gas, dry air is introduced for a period of time to stabilize the resistance values of the WS 2 sensor devices, WS 2 -MoO 3 sensor devices and WS 2 / MoO 3 sensor devices. When testing the target gas, the target gas is injected into the test chamber, and the target gas will react with the WS 2 sensor devices, WS 2 -MoO 3 sensor devices and WS2 / MoO 3 WS coated on the surface of the sensor device 2 nanomaterials, WS 2 -MoO 3 nanomaterials and WS 2 / MoO 3 The interaction of the composite multi-level nanomaterials causes a change in the resistance of the sensor device. The resistance changes of the sensor device under the target gas and in dry air are collected in real time by the data acquisition system and displayed in real time on the PC by the supporting software system. By analyzing the WS 2 sensor device, WS 2 -MoO 3 sensor device and WS 2 / MoO 3 resistance change of the sensor device in dry air and the target gas, its response to the target gas can be determined.
[0046] In this embodiment, the target gas is NH 3 .
[0047] The ammonia detection method of the present invention includes the following steps:
[0048] Step 1: Obtain the stable resistance value R of the WS 2 / MoO 3 sensor device, WS 2 sensor device and WS 2 -MoO 3 sensor device under dry air; g ;
[0049] Step 2: Introduce ammonia gas to act on the WS 2 / MoO 3 sensor device, WS 2 sensor device and WS 2 -MoO 3 sensor device;
[0050] Step 3: Simultaneously collect the stable resistance value R of the WS 2 / MoO 3 sensor device, WS 2 sensor device and WS 2 -MoO 3 sensor device under the action of ammonia gas; a ;
[0051] Step 4: Calculate the WS respectively according to the relative change of the resistance 2 / MoO 3 sensor device, WS 2 sensor device and WS 2 -MoO3 The response value of the sensor device, and its calculation formula is: (R g -R a ) / R a × 100%. Wherein, R g and R a respectively represent the stable resistance values of the sensor device under the action of ammonia gas and under dry air.
[0052] In the control experiment, in the same test environment (room temperature, 20 ± 5 °C), 0.2 ppm, 0.5 ppm, 1 ppm, and 3 ppm of NH 3 were successively and continuously introduced into the test chamber, and each response test included all steps in a method for detecting ammonia gas provided by the present invention. The test results are as Figure 5 shown. Obviously, compared with the WS 2 sensor device and the WS 2 -MoO 3 sensor device, the WS 2 / MoO 3 sensor device exhibits enhanced gas-sensing response, and different concentrations result in different responses. The gas response values of the WS 2 sensor device, the WS 2 -MoO 3 sensor device and the WS 2 / MoO 3 sensor device of the present invention corresponding to different NH 3 concentrations are as Figure 6 shown. In the range of 0.2 - 3 ppm of NH 3 , the WS 2 / MoO 3 sensor device of the present invention not only has an enhanced gas-sensing response but also shows a linear response change, and the response values of the WS 2 / MoO 3 sensor device of the present invention corresponding to 0.2 ppm, 0.5 ppm, 1 ppm, and 3 ppm of NH 3 are 22.7, 44.3, 42.4, and 52.8 times that of the WS 2 sensor device respectively, while the WS 2 -MoO 3 sensor device has no response to 0.2 ppm, 0.5 ppm, and 1 ppm of NH 3 , and the response value to 3 ppm of NH 3 is extremely low. And as Figure 7 shown, at 50 °C, the WS 2 -MoO 3 sensor device has the highest response to 3 ppm of NH 3 , but it is only 5.4%, far lower than that of the WS 2 / MoO 3 The response of the sensor device to 3 ppm of NH 3 at room temperature.
[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Those of ordinary skill in the art should understand that any modifications or equivalent replacements made to the technical solutions of the present invention without departing from the purpose and scope of the present technical solution shall be covered by the scope of the claims of the present invention.
Claims
1. A WS 2 / MoO 3 Preparation method of composite multi-level nanomaterial It is characterized in that It includes the following steps: Step 1: Prepare WS 2 nanosheets; Step 2: Ultrasonically disperse WS 2 powder and sodium molybdate dihydrate evenly in water to form a homogeneous dispersion; Step 3: Add concentrated hydrochloric acid to the dispersion obtained in Step 2 to obtain a precursor solution; Step 4: Hydrothermally react the precursor solution obtained in Step 3 to obtain the WS 2 / MoO 3 composite multi-level nanomaterial.
2. The WS according to claim 1 2 / MoO 3 Method for preparing a composite multi-layer nanomaterial It is characterized in that In step 1, WS is prepared by the following method 2 nanosheets: (1) Uniformly disperse thioacetamide and tungsten chloride in water by ultrasonic method to form a uniformly dispersed reaction solution; wherein, the mass ratio of thioacetamide to tungsten chloride is (1:1) to (3:1); (2) Place the reaction solution in a reaction kettle and react at 200°C to 280°C for 20 h to 28 h; (3)The product after the reaction was repeatedly washed with absolute ethanol and ultrapure water, and WS 2 nanosheets were obtained after vacuum drying.
3. The WS according to claim 1 2 / MoO 3 Method for preparing a composite multi-level nanomaterial It is characterized in that In step 2, WS 2 and sodium molybdate dihydrate have a molar ratio of (1:0.77) to (1:2.22), and WS 2 and sodium molybdate dihydrate have a volume ratio of 1:
1.
4. The WS according to claim 1 2 / MoO 3 Preparation method of a composite multi-layer nano-material It is characterized in that In Step 3, the volume ratio of concentrated hydrochloric acid to the dispersion is 1:16, and the mass fraction is 36 wt% to 38 wt%.
5. The WS according to claim 1 2 / MoO 3 Method for preparing a composite multi-level nanomaterial It is characterized in that In Step 4, the temperature of the hydrothermal reaction is 100°C to 180°C, and the reaction time is 1 h to 5 h.
6. The WS according to claim 1 2 / MoO 3 Method for preparing a composite multi-level nanomaterial It is characterized in that Using WS 2 nanosheets as a template, sodium molybdate dihydrate is anchored and grown on the template to form MoO 3 to obtain the WS 2 / MoO 3 composite multi-level nanomaterial.
7. An application of WS 2 / MoO 3 composite hierarchical nanomaterial It is characterized in that The WS described in claim 1 2 / MoO 3 A composite multi-level nanomaterial is constructed on the surface of an electrode to form a sensor device, and trace ammonia is detected by obtaining the relative change in resistance before and after contacting ammonia.
8. The WS according to claim 7 2 / MoO 3 Application of the composite multi-level nanomaterial It is characterized in that Deposit the WS on the surface of the electrode 2 / MoO 3 composite multi-level nanomaterial to obtain WS 2 / MoO 3 sensor device; the WS 2 / MoO 3 sensor device realizes the detection of ammonia through the relative change of its resistance before and after contacting ammonia.
9. The WS according to claim 8 2 / MoO 3 Application of the composite multi-level nanomaterial It is characterized in that The WS 2 / MoO 3 The preparation method of the sensor device comprises the following steps: dispersing the WS 2 / MoO 3 composite multi-level nanomaterial uniformly in ultrapure water, drop-coating it on the interdigital electrode, and drying it in vacuum at 50 °C for 4 h to obtain the WS 2 / MoO 3 sensor device.
10. The WS according to claim 8 2 / MoO 3 Application of a composite multi-layer nanomaterial It is characterized in that The said WS 2 / MoO 3 The ammonia gas detection by the sensor device comprises the following steps: (1)Obtain WS 2 / MoO 3 The stable resistance value R of the sensor device under dry air g ; (2) Introduce ammonia gas and allow the ammonia gas to act on WS 2 / MoO 3 sensor device; (3)Collect WS 2 / MoO 3 The stable resistance value R of the sensor device under the action of ammonia a ; (4) Calculate WS based on the relative change in resistance 2 / MoO 3 The response value of the sensor device, and its calculation formula is: (R g -R a ) / R a ×100%; where R g and R a respectively represent the stable resistance values of the sensor device under the action of ammonia and in dry air.