Preparation method and application of Rh-SnS / WS2 flower-like heterojunction nano material

Abstract

The invention relates to a preparation method and application of an Rh-SnS / WS2 flower-like heterojunction nano material, and belongs to the field of gas sensing, the Rh-SnS / WS2 flower-like heterojunction nano material is prepared by taking stannic chloride, sodium tungstate, sodium dodecyl benzene sulfonate, thiourea and oxalic acid as raw materials through a one-step hydrothermal method, and finally the SnS / WS2 flower-like heterojunction nano material uniformly modified by noble metal Rh is obtained through an impregnation method. The structure shows that the material is of a two-dimensional sheet-shaped self-assembled nano flower-shaped structure, the preparation process is simple, high-temperature tedious steps are not needed, the prepared Rh-SnS / WS2 flower-shaped heterojunction nano material has rapid response and recovery characteristics to nitrogen dioxide gas, the problems that traditional WS2 is poor in stability and slow in response and recovery time are effectively solved, and the preparation method is suitable for large-scale industrial production. The method has the characteristics of specific selectivity and low-temperature detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and in particular relates to a preparation method and application of a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial. Background Art

[0002] As industrial pollution worsens, NO2 has become one of the common pollutants. This gas is reddish-brown at room temperature and usually comes from automobile exhaust emissions and fossil fuel combustion. In addition to producing acid rain and photochemical smog that damage the ecological environment, it also poses a huge threat to human health. When the human body is exposed to NO2 for a long time, the respiratory system will be damaged to varying degrees, making it prone to diseases such as asthma, pneumonia, and bronchitis; in addition, this gas will also affect the cardiovascular system, thereby inducing a series of diseases such as increased heart rate, myocardial infarction, hypertension, and neurasthenia. The American Conference on Industrial Hygiene requires that the maximum threshold for human exposure to NO2 is only ≤5ppm, so based on this, it is very necessary to develop a type of sensor gas-sensitive material for rapid detection of NO2.

[0003] For gas detection, the most widely used material is metal oxide, but this material usually has a high operating temperature (>200℃), which increases power consumption, weakens stability, and has poor selectivity. In recent years, new two-dimensional TMD materials have gradually been applied to multiple fields. As a member of the TMD family, tungsten disulfide is connected between structures by weak van der Waals forces, has adjustable band gaps, and has large specific surface areas. These characteristics create conditions for low-temperature sensing, making it have great application potential in the field of gas sensing. However, traditional tungsten disulfide exhibits problems such as slow response recovery, low sensitivity, and poor stability when detecting NO2, so its modification is imperative. Summary of the invention

[0004] In order to solve the problems of slow response recovery time, low sensitivity and poor selectivity of sensors for detecting NO2 gas in the prior art, the present invention provides a preparation method and application of a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The invention discloses a method for preparing a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial. The method comprises the following steps: using tin tetrachloride, sodium tungstate, sodium dodecylbenzenesulfonate, thiourea and oxalic acid as raw materials, synthesizing SnS / WS2 flower-shaped heterojunction nanospheres through a one-step hydrothermal method, then mixing and impregnating the SnS / WS2 flower-shaped heterojunction nanospheres with RhCl3·3H2O, and vacuum drying to obtain the Rh-SnS / WS2 flower-shaped heterojunction nanomaterial.

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

[0008] Step 1: dissolve sodium tungstate, tin tetrachloride and thiourea in deionized water under continuous stirring to obtain solution A, then add sodium dodecylbenzene sulfonate to fully dissolve, then add oxalic acid and stir evenly to obtain solution B, perform hydrothermal reaction on solution B, cool after the reaction, centrifuge, wash and vacuum dry the product to obtain SnS / WS2 flower-shaped heterojunction nanospheres;

[0009] Step 2: Ultrasonically uniformly mix the SnS / WS2 flower-shaped heterojunction nanospheres and RhCl3·3H2O, fully impregnate them, and then vacuum dry them to obtain Rh-SnS / WS2 flower-shaped heterojunction nanomaterials.

[0010] Furthermore, in step 1, 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 dodecylbenzene sulfonate to sodium tungstate is 1:(1-4).

[0011] Furthermore, in step 1, the temperature of the hydrothermal reaction is 200-220° C., and the time is 18-26 hours.

[0012] Furthermore, in step 1, the vacuum drying temperature is 50-80° C. and the time is 8-18 hours.

[0013] Furthermore, in step 2, the mass concentration of RhCl3·3H2O is 0.3% to 0.6%, and the mass ratio of RhCl3·3H2O to SnS / WS2 flower-shaped heterojunction nanospheres is 0.3% to 4%.

[0014] Furthermore, in step 2, the immersion time is 10 to 24 hours, the vacuum drying temperature is 50 to 100° C., and the drying time is 12 to 30 hours.

[0015] Furthermore, in step 2, the power of ultrasound is 200-400 W, the frequency is 20 kHz, and the time of ultrasonic dispersion is 10-60 min.

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

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

[0018] The present invention forms SnS / WS2 flower-shaped heterojunction nanospheres by a one-step hydrothermal method, which has simple steps and does not require high temperature and other complicated conditions. The SnS / WS2 heterojunction presents two-dimensional sheet-assembled self-assembled flower-shaped nanospheres with a large specific surface area, which provides more gas adsorption sites for NO2 adsorption. Through the catalytic effect of Rh, the minimum detection limit of the material for NO2 is only 500 ppb, and it has good sensing response characteristics.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention enhances the carrier transport efficiency by constructing a SnS / WS2 PP heterojunction, making up for the performance defects of traditional WS2 in detecting NO2. After the introduction of Rh modification, the material's oxygen adsorption sites are increased. Under the blessing of the precious metal spillover effect of Rh, the material's sensing performance for NO2 is enhanced.

[0021] 2. The preparation process of the two-dimensional material heterojunction described in the present invention is simple, does not require cumbersome high-temperature steps, and is low in cost. The obtained Rh-SnS / WS2 flower-shaped heterojunction nanomaterial has rapid response and recovery characteristics to NO2 gas, and the working temperature is lower than 200°C. It effectively solves the problems of poor stability and slow response recovery time of traditional WS2, and has the characteristics of selectivity, specificity and low-temperature detection.

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

[0023] The Rh-SnS / WS2 flower-shaped heterojunction nanomaterial prepared by the present invention is applied in the field of gas sensors. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0027] Figure 4 TEM image of the Rh-SnS / WS2 flower-shaped heterojunction nanomaterial prepared in Example 1;

[0028] Figure 5 This is the mapping image of the Rh-SnS / WS2 flower-shaped heterojunction nanomaterial prepared in Example 1;

[0029] Figure 6 The response and recovery characteristic curves of the materials prepared in Examples 2 to 5 to NO2 gas;

[0030] Figure 7 The response and recovery characteristic curves of the materials prepared in Examples 1, 5, 6 and 7 to NO2 gas;

[0031] Figure 8 This is a test chart of the selectivity of the materials prepared in Examples 1 and 5 to NO2 gas. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] Aiming at the problems of slow response recovery, low sensitivity and poor stability of traditional tungsten disulfide in detecting NO2, such as slow response recovery, low sensitivity and poor stability, constructing heterojunction and noble metal modification are relatively effective means. However, the construction of TMD heterojunction usually has complicated steps and high preparation temperature. In addition, tin sulfide, as a P-type semiconductor, has a structure similar to that of TMD material and a small band gap. The present invention proposes a strategy for preparing SnS / WS2 flower-shaped heterojunction nanostructure by a simple one-step hydrothermal method, which effectively improves the stability of tungsten disulfide sensors, and improves the sensitivity of the sensor to NO2 under the modification of noble metal Rh, and has fast response and recovery characteristics. The present invention mainly provides a preparation method and application of nanomaterials for rapid detection of NO2.

[0034] Specific implementation method 1: This implementation method describes a method for preparing a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial, using tin tetrachloride, sodium tungstate, sodium dodecylbenzenesulfonate, thiourea and oxalic acid as raw materials, and synthesizing SnS / WS2 flower-shaped heterojunction nanospheres by a one-step hydrothermal method, and then adding RhCl3·3H2O for ultrasonic uniform mixing, impregnation, and vacuum drying to obtain the Rh-SnS / WS2 flower-shaped heterojunction nanomaterial.

[0035] Specific embodiment 2: This embodiment describes a method for preparing a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial, which is specifically carried out in the following steps:

[0036] Step 1, preparation of SnS / WS2 flower-shaped heterojunction nanospheres: sodium tungstate, tin tetrachloride and thiourea are dissolved in deionized water under continuous stirring to form a uniform precursor solution, and SnS / WS2 heterojunction materials with different ratios are prepared by controlling the ratio of tungsten source to tin source, and then sodium dodecylbenzene sulfonate is added and stirred and fully dissolved by ultrasonic vibration, and then oxalic acid is added and stirred continuously, and a hydrothermal reaction is carried out at a specific temperature and time, and finally cooled, centrifuged and washed, and vacuum dried to obtain SnS / WS2 flower-shaped heterojunction nanospheres;

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

[0038] Specific implementation method three: This implementation method is a further supplementary explanation of specific implementation method two: 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 dodecylbenzene sulfonate to sodium tungstate is 1: (1-4).

[0039] Specific embodiment 4: This embodiment is a further supplementary explanation of specific embodiment 2: in step 1, the temperature of the hydrothermal reaction is 200-220° C., and the time is 18-26 hours.

[0040] Specific implementation mode 5: This implementation mode is a further supplementary explanation of specific implementation mode 2: in step 1, the vacuum drying temperature is 50-80° C., and the time is 8-18 hours.

[0041] Specific implementation method six: This implementation method is a further supplementary explanation of 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 7: This implementation method is a further supplementary explanation of specific implementation method 2: in step 2, 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 eight: This implementation is a further supplementary explanation of specific implementation two: in step two, the immersion time is 10 to 24 hours, the vacuum drying temperature is 50 to 100° C., and the drying time is 12 to 30 hours.

[0044] Specific embodiment 9: This embodiment describes the application of a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial. The Rh-SnS / WS2 flower-shaped heterojunction nanomaterial is used as a new type of two-dimensional composite material in the field of gas sensors. The Rh-SnS / WS2 flower-shaped heterojunction nanomaterial is used to detect NO2 gas.

[0045] The content of the present invention is not limited to the content of the above-mentioned embodiments, and the purpose of the invention can also be achieved by combining one or several specific embodiments.

[0046] Embodiment 1:

[0047] A method for preparing a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial is specifically carried out according to the following steps:

[0048] Step 1: Preparation of SnS / WS2 flower-shaped heterojunction nanospheres: Dissolve 2.33mmol sodium tungstate, 1.17mmol tin tetrachloride and 16.5mmol thiourea in 30ml deionized water, stir for 30min until fully dissolved, add 1.1mmol sodium dodecylbenzene sulfonate, ultrasonically shake and stir for 30min, then add 7mmol oxalic acid, stir the mixed solution for 15min and transfer it to a 50ml reactor, react at 210℃ for 24h, and after natural cooling, centrifuge and wash alternately with anhydrous ethanol and deionized water three times each, finally dry the sample at 60℃ in a vacuum environment for 12h to obtain SnS / WS2 flower-shaped heterojunction nanosphere material with W:Sn being 2:1;

[0049] Step 2, preparation of Rh-SnS / WS2 flower-shaped heterojunction nanomaterials: Take 10 mg of the SnS / WS2 flower-shaped heterojunction nanosphere material prepared in step 1, then add 20 μL of 0.5wt% RhCl3·3H2O, so that the mass ratio of RhCl3·3H2O to SnS / WS2 flower-shaped heterojunction nanospheres is 1%, perform ultrasonic dispersion and uniform mixing at a power of 200 W for 30 minutes, immerse for 12 hours, and dry in a vacuum atmosphere at 60°C for 24 hours to obtain Rh-SnS / WS2 flower-shaped heterojunction nanomaterials.

[0050] Embodiment 2:

[0051] The difference between this embodiment and embodiment 1 is that in step 1, the amount of sodium tungstate used is 2.625 mmol, and the amount of tin tetrachloride used is 0.875 mmol, and a SnS / WS2 flower-shaped heterojunction nanosphere material with a W:Sn ratio of 3:1 is obtained. The other steps and parameters are the same as step 1 of embodiment 1, and step 2 is not implemented.

[0052] Embodiment 3:

[0053] The present embodiment is different from the embodiment 1 in that only step 1 is implemented to obtain the SnS / WS2 flower-shaped heterojunction nanosphere material with a W:Sn ratio of 2:1, and step 2 is not implemented.

[0054] Embodiment 4:

[0055] The difference between this embodiment and embodiment 1 is that in step 1, the amount of sodium tungstate used is 1.75 mmol, the amount of tin tetrachloride used is 1.75 mmol, and a SnS / WS2 flower-shaped heterojunction nanosphere material with a W:Sn ratio of 1:1 is obtained. The other steps and parameters are the same as step 1 of embodiment 1, and step 2 is not implemented.

[0056] Embodiment 5:

[0057] The difference between this embodiment and embodiment 1 is that in step 1, the amount of sodium tungstate used is 3.5 mmol, tin tetrachloride is not added, and WS2 flower-shaped nanospheres are obtained. The other steps and parameters are the same as step 1 in embodiment 1, and step 2 is not implemented.

[0058] Embodiment 6:

[0059] The difference between this embodiment and embodiment 1 is that in step 2, 10 μL of 0.5 wt % RhCl 3 · 3H 2 O is added so that the mass ratio of RhCl 3 · 3H 2 O to SnS / WS 2 is 0.5%. The other steps and parameters are the same as those in embodiment 1.

[0060] Embodiment 7:

[0061] The difference between this embodiment and embodiment 1 is that in step 2, 40 μL of 0.5 wt % RhCl 3 · 3H 2 O is added so that the mass ratio of RhCl 3 · 3H 2 O to SnS / WS 2 is 2%. The other steps and parameters are the same as those in embodiment 1.

[0062] Figure 1X-ray diffraction patterns of the samples prepared in Examples 1 to 5 (Rh-SnS / WS2 flower-shaped heterojunction nanomaterials, 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, WS2 flower-shaped nanospheres). It can be seen from the figure that the samples prepared in Examples 1 to 5 are consistent with WS2 and the standard card (JCPDS no.08-0237), proving the successful preparation of WS2, and the (002) offset in the figure is mainly due to the increase in the SWS interlayer spacing, which is related to factors such as the bending, strain effect, and interlayer folding defects of the WS2 plate; and the samples prepared in Examples 1 to 4 are consistent with SnS and the standard card (JCPDS no.39-0354), proving the successful preparation of SnS / WS2 flower-shaped heterojunction nanospheres, and the characteristic peak of Rh is not found in the XRD diffraction spectrum due to the too low doping content;

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

[0064] Figure 3 This is the SEM image of the SnS / WS2 flower-shaped heterojunction nanospheres prepared in Example 3. From the image, we can see that SnS and WS2 are tightly combined to form a three-dimensional flower-shaped nanostructure assembled by two-dimensional nanosheets, creating more adsorption sites for NO2 gas adsorption.

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

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

[0067] For Examples 2 to 5, when the operating temperature is 79° C., the materials prepared by Examples 4 to 5 have 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 having the highest response.

[0068] For Examples 1, 5, 6 and 7, when the operating temperature is 157° C., the Rh-SnS / WS2 flower-shaped heterojunction nanomaterials prepared by Examples 1, 6 and 7 have fast response and recovery characteristics to NO2 gas, such as Figure 7As shown, Example 1 has the highest response, and the response and recovery to 64 ppm NO2 are only 6s and 33s;

[0069] Figure 8 The gas selectivity of the Rh-SnS / WS2 flower-shaped heterojunction nanomaterials prepared in Examples 1 and 5 and pure WS2 shows that both Examples 1 and 5 have good selectivity for NO2 gas, and the modification of Rh and the construction of SnS / WS2 flower-shaped heterojunction further improve their selectivity.

[0070] The above characterization and testing prove that the Rh-SnS / WS2 flower-shaped heterojunction nanomaterial prepared by the present 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] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial, characterized in that: SnS / WS2 flower-shaped heterojunction nanospheres were synthesized by a one-step hydrothermal method using tin tetrachloride, sodium tungstate, sodium dodecylbenzenesulfonate, thiourea and oxalic acid as raw materials. The SnS / WS2 flower-shaped heterojunction nanospheres were then mixed and impregnated with RhCl3·3H2O, and Rh-SnS / WS2 flower-shaped heterojunction nanomaterials were obtained after vacuum drying.

2. The preparation method according to claim 1, characterized in that: 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 dodecylbenzene sulfonate to fully dissolve, then add oxalic acid and stir to obtain solution B, perform hydrothermal reaction on solution B, cool after the reaction, centrifuge, wash and vacuum dry the product to obtain SnS / WS2 flower-shaped heterojunction nanospheres; Step 2: Ultrasonically uniformly mix the SnS / WS2 flower-shaped heterojunction nanospheres and RhCl3·3H2O, fully impregnate them, and then vacuum dry them to obtain Rh-SnS / WS2 flower-shaped heterojunction nanomaterials.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1, 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 dodecylbenzene sulfonate to sodium tungstate is 1:(1-4).

4. The preparation method according to claim 2, characterized in that: In step 1, the temperature of the hydrothermal reaction is 200-220° C., and the time is 18-26 hours.

5. The preparation method according to claim 2, characterized in that: In step 1, the vacuum drying temperature is 50-80° C. and the time is 8-18 hours.

6. The preparation method according to claim 2, characterized in that: In step 2, the mass concentration of RhCl3·3H2O is 0.3% to 0.6%, and the mass ratio of RhCl3·3H2O to SnS / WS2 flower-shaped heterojunction nanospheres is 0.3% to 4%.

7. The preparation method according to claim 2, characterized in that: In step 2, the immersion time is 10 to 24 hours, the vacuum drying temperature is 50 to 100° C., and the drying time is 12 to 30 hours.

8. The preparation method according to claim 2, characterized in that: In step 2, the power of ultrasound is 200-400W, the frequency is 20 kHz, and the time of ultrasonic dispersion is 10-60 minutes.

9. An application of a Rh-SnS / WS2 flower-shaped heterojunction nanomaterial prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The Rh-SnS / WS2 flower-shaped heterojunction nanomaterial is used as a gas sensor.

10. The use according to claim 9, characterized in that: The Rh-SnS / WS2 flower-shaped heterojunction nanomaterial is used for detecting NO2 gas.

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