Preparation method and application of rh-sns / WS2 flower-like heterojunction nanomaterial

Abstract

The application relates to a preparation method and application of Rh-SnS / WS2 flower-shaped heterojunction nanomaterials, and belongs to the field of gas sensing. The Rh-SnS / WS2 flower-shaped heterojunction nanomaterials are prepared by using tin tetrachloride, sodium tungstate, sodium dodecyl benzene sulfonate, thiourea and oxalic acid as raw materials through a one-step hydrothermal method. Finally, the SnS / WS2 flower-shaped heterojunction nanomaterials are uniformly modified by the noble metal Rh through an immersion method. The structure shows that the material presents a two-dimensional sheet-shaped self-assembled nanoflower structure. The preparation process is simple, and high-temperature complicated steps are not needed. The prepared Rh-SnS / WS2 flower-shaped heterojunction nanomaterials have rapid response and recovery characteristics for nitrogen dioxide gas. The problems of poor stability and slow response and recovery time of traditional WS2 are effectively solved. The Rh-SnS / WS2 flower-shaped heterojunction nanomaterials have the characteristics of selectivity, specificity and low-temperature detection.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a method for preparing and applying Rh-SnS / WS2 flower-like heterojunction nanomaterials. Background Technology

[0002] With industrial pollution worsening daily, NO2 has become a common pollutant. This gas, reddish-brown at room temperature, typically originates from vehicle exhaust emissions and fossil fuel combustion. Besides contributing to acid rain and photochemical smog that damage the environment, it poses a significant threat to human health. Long-term exposure to NO2 can damage the respiratory system to varying degrees, increasing susceptibility to asthma, pneumonia, and bronchitis. Furthermore, it can affect the cardiovascular system, potentially leading to rapid heartbeat, myocardial infarction, hypertension, and neurasthenia. The U.S. Industrial Hygiene Conference recommends a maximum threshold of ≤5 ppm for human exposure to NO2, making the development of rapid NO2 detection sensor materials essential.

[0003] For gas detection, metal oxides are the most widely used materials, but these materials typically have high operating temperatures (>200℃), which increases power consumption, weakens stability, and results in poor selectivity. In recent years, novel two-dimensional TMD materials have been gradually applied in various fields. Tungsten disulfide, as a member of the TMD family, has tunable band gaps and large specific surface areas due to its weak van der Waals forces connecting its structures, creating conditions for low-temperature sensing and giving it strong application potential in gas sensing. However, traditional tungsten disulfide exhibits slow response recovery, low sensitivity, and poor stability when detecting NO2, making its modification imperative. Summary of the Invention

[0004] To address the problems of slow response recovery time, low sensitivity, and poor selectivity in existing NO2 gas detection sensors, this invention provides a method for preparing and applying Rh-SnS / WS2 flower-like heterojunction nanomaterials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing Rh-SnS / WS2 flower-like heterojunction nanomaterials involves using tin tetrachloride, sodium tungstate, sodium dodecylbenzenesulfonate, thiourea, and oxalic acid as raw materials to synthesize SnS / WS2 flower-like heterojunction nanospheres via a one-step hydrothermal method. The SnS / WS2 flower-like heterojunction nanospheres are then mixed with and impregnated with RhCl3·3H2O, followed by vacuum drying to obtain the Rh-SnS / WS2 flower-like heterojunction nanomaterials.

[0007] Furthermore, the specific steps of the method are as follows:

[0008] Step 1: Sodium tungstate, tin tetrachloride and thiourea were dissolved in deionized water under continuous stirring to obtain solution A. Sodium dodecylbenzenesulfonate was then added and dissolved completely. Oxalic acid was then added and stirred until homogeneous to obtain solution B. Solution B was subjected to a hydrothermal reaction. After the reaction was completed, the solution was cooled, and the product was centrifuged, washed and vacuum dried to obtain SnS / WS2 flower-like heterojunction nanospheres.

[0009] Step 2: The SnS / WS2 flower-shaped heterojunction nanospheres and RhCl3·3H2O are ultrasonically mixed and thoroughly impregnated before vacuum drying to obtain Rh-SnS / WS2 flower-shaped heterojunction nanomaterials.

[0010] Furthermore, in step one, the molar ratio of sodium tungstate to oxalic acid is 1:(1-5), the molar ratio of tin tetrachloride to sodium tungstate is 1:(1-3), the molar ratio of oxalic acid to thiourea is 1:(2-4), and the molar ratio of sodium dodecylbenzenesulfonate to sodium tungstate is 1:(1-4).

[0011] Furthermore, in step one, the hydrothermal reaction is carried out at a temperature of 200–220°C for 18–26 hours.

[0012] Furthermore, in step one, the vacuum drying temperature is 50–80°C, and the time is 8–18 hours.

[0013] Furthermore, in step two, the mass concentration of RhCl3·3H2O is 0.3% to 0.6%, and the mass ratio of RhCl3·3H2O to SnS / WS2 flower-like heterojunction nanospheres is 0.3% to 4%.

[0014] Furthermore, in step two, the impregnation time is 10–24 h, the vacuum drying temperature is 50–100 °C, and the drying time is 12–30 h.

[0015] Furthermore, in step two, the ultrasonic power is 200–400W, the frequency is 20kHz, and the ultrasonic dispersion time is 10–60min.

[0016] An application of the Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared by the aforementioned preparation method is described, wherein the Rh-SnS / WS2 flower-like heterojunction nanomaterial is used as a gas sensor.

[0017] Furthermore, the Rh-SnS / WS2 flower-like heterojunction nanomaterial is used to detect NO2 gas.

[0018] This invention forms SnS / WS2 flower-like heterojunction nanospheres via a one-step hydrothermal method. The process is simple and does not require high temperatures or other complicated conditions. The SnS / WS2 heterojunctions present as two-dimensional sheet-like self-assembled flower-like nanospheres with a large specific surface area, providing more gas adsorption sites for NO2 adsorption. Through the catalytic effect of Rh, the material has a minimum detection limit of only 500 ppb for NO2, exhibiting excellent sensing response characteristics.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention enhances carrier transport efficiency by constructing a SnS / WS2 PP heterojunction, thus overcoming the performance defects of traditional WS2 in detecting NO2. After introducing Rh modification, the number of oxygen adsorption sites in the material is increased, and the noble metal spillover effect of Rh enhances the material's sensing performance for NO2.

[0021] 2. The preparation process of the two-dimensional heterojunction described in this invention is simple, requiring no high-temperature and cumbersome steps, and is low in cost. The resulting Rh-SnS / WS2 flower-like heterojunction nanomaterial exhibits rapid response and recovery characteristics to NO2 gas, and operates at temperatures below 200℃. This effectively solves the problems of poor stability and slow response recovery time of traditional WS2, and possesses selective specificity and low-temperature detection characteristics.

[0022] 3. The Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared by this invention still has a good response to low concentrations of NO2 and a single selectivity, providing a reliable candidate material for the rapid detection of low concentrations of NO2.

[0023] The Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared in this invention is applied in the field of gas sensors. Attached Figure Description

[0024] Figure 1 X-ray diffraction patterns of the samples prepared in Examples 1-5;

[0025] Figure 2 SEM image of the WS2 flower-like nanospheres prepared in Example 5;

[0026] Figure 3 SEM image of the SnS / WS2 flower-like heterojunction nanospheres prepared in Example 3;

[0027] Figure 4 This is a TEM image of the Rh-SnS / WS2 flower-like heterostructure nanomaterial prepared in Example 1;

[0028] Figure 5 Mapping image of the Rh-SnS / WS2 flower-like heterostructure nanomaterial prepared in Example 1;

[0029] Figure 6 The graphs show the response and recovery characteristics of the materials prepared in Examples 2-5 to NO2 gas.

[0030] Figure 7 The graphs show the response and recovery characteristics of the materials prepared in Examples 1, 5, 6 and 7 to NO2 gas.

[0031] Figure 8 The graphs show the selectivity of the materials prepared in Examples 1 and 5 to NO2 gas. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] To address the problems of slow response recovery, low sensitivity, and poor stability exhibited by traditional tungsten disulfide (TDS) sensors in NO2 detection, constructing heterojunctions and modifying them with noble metals are relatively effective methods. However, the construction of TMD heterojunctions is usually cumbersome and requires high preparation temperatures. Furthermore, tin sulfide, as a p-type semiconductor, has a similar structure to TMD materials but with a small band gap. This invention proposes a strategy to prepare SnS / WS2 flower-like heterojunction nanostructures using a simple one-step hydrothermal method, which effectively improves the stability of the tungsten disulfide sensor. Modification with the noble metal Rh enhances the sensor's sensitivity to NO2, resulting in rapid response and recovery characteristics. This invention mainly provides a method for preparing nanomaterials for rapid NO2 detection and their application.

[0034] Specific Implementation Method 1: This implementation method describes a method for preparing Rh-SnS / WS2 flower-like heterojunction nanomaterials. Using tin tetrachloride, sodium tungstate, sodium dodecylbenzenesulfonate, thiourea, and oxalic acid as raw materials, SnS / WS2 flower-like heterojunction nanospheres are synthesized by a one-step hydrothermal method. Then, RhCl3·3H2O is added for ultrasonic uniform mixing, impregnation, and vacuum drying to obtain Rh-SnS / WS2 flower-like heterojunction nanomaterials.

[0035] Specific Implementation Method Two: This implementation method describes a method for preparing Rh-SnS / WS2 flower-like heterostructure nanomaterials, specifically following these steps:

[0036] Step 1: Preparation of SnS / WS2 flower-like heterojunction nanospheres: Sodium tungstate, tin tetrachloride, and thiourea were dissolved in deionized water under continuous stirring to form a homogeneous precursor solution. SnS / WS2 heterojunction materials with different ratios were prepared by controlling the ratio of tungsten source to tin source. Sodium dodecylbenzenesulfonate was then added and stirred, and the solution was fully dissolved by ultrasonic vibration. Oxalic acid was then added and stirring was continued. A hydrothermal reaction was carried out at a specific temperature and time. Finally, the solution was cooled, centrifuged, washed, and vacuum dried to obtain SnS / WS2 flower-like heterojunction nanospheres.

[0037] Step 2: Preparation of Rh-SnS / WS2 flower-shaped heterojunction nanomaterials: Take the SnS / WS2 flower-shaped heterojunction nanospheres prepared in Step 1, then add a certain amount of RhCl3·3H2O for ultrasonic uniform mixing, and after thorough impregnation, dry under vacuum atmosphere to obtain Rh-SnS / WS2 flower-shaped heterojunction composite nanomaterials.

[0038] Specific Implementation Method 3: This implementation method is a further supplement to Specific Implementation Method 2: In step one, the molar ratio of sodium tungstate to oxalic acid is 1:(1-5), the molar ratio of tin tetrachloride to sodium tungstate is 1:(1-3), the molar ratio of oxalic acid to thiourea is 1:(2-4), and the molar ratio of sodium dodecylbenzenesulfonate to sodium tungstate is 1:(1-4).

[0039] Specific Implementation Method Four: This implementation method is a further supplement to Specific Implementation Method Two: In step one, the temperature of the hydrothermal reaction is 200-220℃ and the time is 18-26h.

[0040] Specific Implementation Method 5: This implementation method is a further supplement to Specific Implementation Method 2: In step one, the vacuum drying temperature is 50-80℃ and the time is 8-18h.

[0041] Specific Implementation Method Six: This implementation method is a further supplement to Specific Implementation Method Two: In step two, the mass concentration of RhCl3·3H2O is 0.3-0.6%, and the mass ratio of RhCl3·3H2O to SnS / WS2 is 0.3-4%.

[0042] Specific Implementation Method Seven: This implementation method is a further supplement to Specific Implementation Method Two: In step two, the ultrasonic power of the ultrasonic disperser is 200-400W, the frequency is 20kHz, and the ultrasonic dispersion time is 10-60min.

[0043] Specific Implementation Method Eight: This implementation method is a further supplement to Specific Implementation Method Two: In step two, the impregnation time is 10-24 hours, the vacuum drying temperature is 50-100°C, and the drying time is 12-30 hours.

[0044] Specific Implementation Method Nine: This implementation method describes the application of a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial. This Rh-SnS / WS2 flower-shaped heterojunction nanomaterial, as a novel two-dimensional composite material, is applied in the field of gas sensors. The Rh-SnS / WS2 flower-shaped heterojunction nanomaterial is used to detect NO2 gas.

[0045] The content of this invention is not limited to the above-described embodiments; one or more specific embodiments can be combined to achieve the purpose of the invention.

[0046] Example 1:

[0047] A method for preparing Rh-SnS / WS2 flower-like heterostructure nanomaterials, specifically comprising the following steps:

[0048] Step 1: Preparation of SnS / WS2 flower-like heterojunction nanospheres: 2.33 mmol sodium tungstate, 1.17 mmol tin tetrachloride and 16.5 mmol thiourea were dissolved in 30 ml deionized water and stirred for 30 min until fully dissolved. Then, 1.1 mmol sodium dodecylbenzenesulfonate was added, and the mixture was ultrasonically vibrated and stirred for 30 min. Then, 7 mmol oxalic acid was added, and the mixture was stirred for 15 min before being transferred to a 50 ml reactor and reacted at 210 °C for 24 h. After natural cooling, the mixture was washed three times each by centrifugation with anhydrous ethanol and deionized water. Finally, the sample was dried in a vacuum environment at 60 °C for 12 h to obtain SnS / WS2 flower-like heterojunction nanospheres with a W:Sn ratio of 2:1.

[0049] Step 2: Preparation of Rh-SnS / WS2 flower-like heterojunction nanomaterials: Take 10 mg of the SnS / WS2 flower-like heterojunction nanospheres prepared in Step 1, and then add 20 μL of 0.5 wt% RhCl3·3H2O to make the mass ratio of RhCl3·3H2O to SnS / WS2 flower-like heterojunction nanospheres 1%. Perform ultrasonic dispersion and uniform mixing at 200 W for 30 min, impregnate for 12 h, and dry in a vacuum atmosphere at 60 °C for 24 h to obtain Rh-SnS / WS2 flower-like heterojunction nanomaterials.

[0050] Example 2:

[0051] The difference between this embodiment and Example 1 is that in step one, the amount of sodium tungstate is 2.625 mmol and the amount of tin tetrachloride is 0.875 mmol, resulting in SnS / WS2 flower-like heterojunction nanospheres with a W:Sn ratio of 3:1. All other steps and parameters are the same as in step one of Example 1, but step two is not performed.

[0052] Example 3:

[0053] The difference between this embodiment and Embodiment 1 is that only step one is implemented to obtain SnS / WS2 flower-like heterojunction nanospheres with a W:Sn ratio of 2:1, and step two is not implemented.

[0054] Example 4:

[0055] The difference between this embodiment and Example 1 is that the amount of sodium tungstate and tin tetrachloride used in step one is 1.75 mmol, and the amount of tin tetrachloride used is 1.75 mmol, resulting in SnS / WS2 flower-like heterojunction nanospheres with a W:Sn ratio of 1:1. All other steps and parameters are the same as step one of Example 1, but step two is not performed.

[0056] Example 5:

[0057] The difference between this embodiment and Example 1 is that the amount of sodium tungstate used in step one is 3.5 mmol, tin tetrachloride is not added, and WS2 flower-shaped nanospheres are obtained. All other steps and parameters are the same as step one in Example 1, and step two is not performed.

[0058] Example 6:

[0059] The difference between this embodiment and Embodiment 1 is that in step two, 10 μL of 0.5 wt% RhCl3·3H2O is added to make the mass ratio of RhCl3·3H2O to SnS / WS2 0.5%. All other steps and parameters are the same as in Embodiment 1.

[0060] Example 7:

[0061] The difference between this embodiment and Example 1 is that in step two, 40 μL of 0.5 wt% RhCl3·3H2O is added, so that the mass ratio of RhCl3·3H2O to SnS / WS2 is 2%. All other steps and parameters are the same as in Example 1.

[0062] Figure 1X-ray diffraction patterns of the samples prepared in Examples 1-5 (Rh-SnS / WS2 flower-shaped heterojunction nanomaterial, SnS / WS2 flower-shaped heterojunction nanospheres with a molar ratio of 1:3, SnS / WS2 flower-shaped heterojunction nanospheres with a molar ratio of 1:2, SnS / WS2 flower-shaped heterojunction nanospheres with a molar ratio of 1:1, and WS2 flower-shaped nanospheres). As can be seen from the figure, the samples prepared in Examples 1-5 are consistent with the WS2 standard card (JCPDS no. 08-0237), proving the successful preparation of WS2. The offset (002) in the figure is mainly due to the increase in the interlayer spacing of SWS, which is related to factors such as the bending of the WS2 plate, strain effect, and interlayer folding defects. The samples prepared in Examples 1-4 are consistent with the SnS standard card (JCPDS no. 39-0354), proving the successful preparation of SnS / WS2 flower-shaped heterojunction nanospheres. However, no characteristic peak of Rh was found in the XRD diffraction pattern due to the low doping content.

[0063] Figure 2 This is a SEM image of the WS2 flower-like nanospheres prepared in Example 5.

[0064] Figure 3 The image shows a SEM image of the SnS / WS2 flower-like heterojunction nanospheres prepared in Example 3. The image shows that SnS and WS2 are tightly bound together, forming a three-dimensional flower-like nanostructure assembled from two-dimensional nanosheets, which creates more adsorption sites for NO2 gas adsorption.

[0065] Figure 4 This is a TEM image of the Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared in Example 1.

[0066] Figure 5 The image shows a mapping of the Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared in Example 1. It can be seen that W, Sn, S, and Rh elements are uniformly distributed in the Rh-SnS / WS2 flower-like heterojunction nanomaterial.

[0067] For Examples 2-5, when the operating temperature is 79°C, the materials prepared in Examples 4-5 all exhibit good response and recovery characteristics to NO2 gas, such as... Figure 6 As shown, WS2 exhibited baseline drift, and the introduction of SnS improved this problem, with Example 3 showing the highest response.

[0068] For Examples 1, 5, 6, and 7, when the operating temperature is 157°C, the Rh-SnS / WS2 flower-like heterojunction nanomaterials prepared in Examples 1, 6, and 7 exhibit rapid response and recovery characteristics to NO2 gas. Figure 7As shown, Example 1 had the highest response, with a response and recovery of only 6s and 33s for 64ppm NO2.

[0069] Figure 8 The gas selectivity of the Rh-SnS / WS2 flower-like heterojunction nanomaterials prepared in Examples 1 and 5 compared to pure WS2 is shown. It can be seen that both Examples 1 and 5 have good selectivity for NO2 gas, and the modification of Rh and the construction of SnS / WS2 flower-like heterojunction further improve their selectivity.

[0070] The above characterization and testing demonstrate that the Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared in this invention has a high responsiveness to low-concentration NO2 gas, and achieves rapid response and recovery. It can accurately identify NO2 in a variety of gases with high selectivity, providing a reliable candidate material for the rapid detection of low-concentration NO2.

[0071] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing Rh-SnS / WS2 flower-like heterostructure nanomaterials, characterized in that: SnS / WS2 flower-like heterojunction nanospheres were synthesized via a one-step hydrothermal method using tin tetrachloride, sodium tungstate, sodium dodecylbenzenesulfonate, thiourea, and oxalic acid as raw materials. The SnS / WS2 flower-like heterojunction nanospheres were then mixed with and impregnated with RhCl3•3H2O, followed by vacuum drying to obtain Rh-SnS / WS2 flower-like heterojunction nanomaterials. The specific steps of the method are as follows: Step 1: Dissolve sodium tungstate, tin tetrachloride and thiourea in deionized water to obtain solution A. Then add sodium dodecylbenzenesulfonate and dissolve it completely. After that, add oxalic acid and stir evenly to obtain solution B. Perform a hydrothermal reaction on solution B. After the reaction is completed, cool it, centrifuge, wash and vacuum dry the product to obtain SnS / WS2 flower-like heterojunction nanospheres. Step 2: Mix SnS / WS2 flower-shaped heterojunction nanospheres and RhCl3•3H2O by ultrasonication, and then vacuum dry after thorough impregnation to obtain Rh-SnS / WS2 flower-shaped heterojunction nanomaterials. In step one, the molar ratio of sodium tungstate to oxalic acid is 1:(1-5), the molar ratio of tin tetrachloride to sodium tungstate is 1:(1-3), the molar ratio of oxalic acid to thiourea is 1:(2-4), and the molar ratio of sodium dodecylbenzenesulfonate to sodium tungstate is 1:(1-4). In step two, the mass concentration of RhCl3•3H2O is 0.3% to 0.6%, and the mass ratio of RhCl3•3H2O to SnS / WS2 flower-like heterojunction nanospheres is 0.3% to 4%.

2. The preparation method according to claim 1, characterized in that: In step one, the hydrothermal reaction is carried out at a temperature of 200–220°C for 18–26 hours.

3. The preparation method according to claim 1, characterized in that: In step one, the vacuum drying temperature is 50~80℃ and the time is 8~18h.

4. The preparation method according to claim 1, characterized in that: In step two, the impregnation time is 10-24 hours, the vacuum drying temperature is 50-100°C, and the drying time is 12-30 hours.

5. The preparation method according to claim 1, characterized in that: In step two, the ultrasonic power is 200~400W, the frequency is 20kHz, and the ultrasonic dispersion time is 10~60min.

6. The application of a Rh-SnS / WS2 flower-like heterojunction nanomaterial prepared by the preparation method according to any one of claims 1-5, characterized in that: The Rh-SnS / WS2 flower-like heterojunction nanomaterial is used as a gas sensor.

7. The application according to claim 6, characterized in that: The Rh-SnS / WS2 flower-like heterojunction nanomaterial is used to detect NO2 gas.

Images