A Pt-WS2@BP nanoflower composite material, its preparation method and application

Abstract

The application discloses a Pt-WS2@BP nanoflower composite material and a preparation method and application thereof, and relates to the field of semiconductor gas sensing.The material is prepared by a one-step hydrothermal method, raw materials of which include sodium tungstate, thiourea and oxalic acid, and then is mixed with BP nanosheets and ultrasonically mixed with chloroplatinic acid, and vacuum drying is performed to obtain a noble metal Pt-loaded WS2@BP nanocomposite material, wherein the WS2 three-dimensional flower-like nanospheres have a flaky nanoflower structure, and the BP nanosheets have a nanosheet layer structure.The preparation process is simple, and the prepared Pt-WS2@BP nanoflower composite material has good response and recovery characteristics and excellent selectivity to nitrogen dioxide gas at low temperature.The prepared composite material can be used in the field of semiconductor gas sensing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor gas sensing. Background Technology

[0002] Nitrogen dioxide is a reddish-brown toxic and harmful gas at room temperature. Therefore, there is an urgent need for a sensor that can monitor nitrogen dioxide gas. Although traditional metal oxide semiconductor gas sensors have high sensitivity, they have poor selectivity and cannot effectively screen for specific gases. In addition, they usually operate at high temperatures.

[0003] Two-dimensional materials typically exhibit high electrical conductivity at room temperature, enabling low-temperature and even room-temperature sensing. Tungsten disulfide, a two-dimensional transition metal sulfide, possesses a layered structure similar to graphene. Its monolayer consists of three atomic layers: the top and bottom layers are sulfur atoms, with a tungsten atom layer sandwiched in between, forming a "sandwich" structure. This structure makes tungsten disulfide a promising candidate for applications in lubrication, electrical systems, and gas sensing. However, traditional methods for preparing tungsten disulfide are complex and costly. Summary of the Invention

[0004] To address the technical problems of poor selectivity and high operating temperature in the current field of gas sensing, this invention provides a Pt-WS2@BP nanoflower composite material, its preparation method, and its application.

[0005] A Pt-WS2@BP nanoflower composite material is first synthesized by a one-step hydrothermal method using sodium tungstate, thiourea, and oxalic acid as raw materials. WS2 three-dimensional flower-shaped nanospheres are then mixed with BP nanosheets, and H2PtCl6•6H2O (chloroplatinic acid) is added for ultrasonic homogenization. The mixture is then vacuum dried to obtain a Pt-supported WS2@BP nanocomposite material. The WS2 three-dimensional flower-shaped nanospheres exhibit a sheet-like nanoflower structure, while the BP nanosheets exhibit a nanosheet layer structure.

[0006] The preparation method of the Pt-WS2@BP nanoflower composite material is carried out according to the following steps:

[0007] Step 1: Preparation of WS2 nanoflower-like microspheres: Sodium tungstate was dissolved in deionized water under continuous stirring to form a homogeneous sodium tungstate solution. Thiourea was added and stirred continuously until dissolved. Sodium dodecylbenzenesulfonate was then added and ultrasonically vibrated and stirred until completely dissolved. Oxalic acid was added and stirred until dissolved. A hydrothermal reaction was carried out, followed by cooling, centrifugation and washing, and vacuum drying to obtain WS2 nanoflower-like microspheres.

[0008] Step 2: After grinding the black phosphorus crystals, they were placed in anhydrous ethanol for ultrasonic exfoliation, followed by centrifugation, washing, and vacuum drying to obtain BP nanosheets.

[0009] Step 3: Preparation of Pt-WS2@BP nanoflower composite material: The WS2 nanoflower-like microspheres prepared in Step 1 and the BP nanosheets prepared in Step 2 are mixed, and H2PtCl6•6H2O is added for ultrasonic homogenization. Then, the mixture is vacuum dried to obtain the Pt-WS2@BP nanoflower composite material.

[0010] The Pt-WS2@BP nanoflower composite material is used as a two-dimensional semiconductor composite gas-sensitive material in the field of semiconductor gas sensing.

[0011] This invention provides a simple method for preparing flower-shaped tungsten disulfide using a one-step hydrothermal method. Black phosphorus (BP) has a large specific surface area, which increases the adsorption sites for gas molecules. Therefore, the WS2@BP nanoflower composite material loaded with the noble metal Pt in this invention exhibits good response and recovery characteristics for NO2 at a working temperature of 50°C, down to 100 ppb. This invention mainly provides a method for preparing materials with good gas-sensing properties for NO2.

[0012] The beneficial effects of this invention.

[0013] The preparation process of this invention is simple, and the obtained Pt-WS2@BP nanoflower composite material has good response and recovery characteristics and excellent selectivity to nitrogen dioxide gas at low temperature.

[0014] The Pt-WS2@BP nanoflower composite material prepared by this invention still has a good response curve for low concentrations of nitrogen dioxide at an operating temperature of 50℃, and has good selectivity. It has a relatively singular recognition of nitrogen dioxide, providing a candidate material for low-temperature sensing.

[0015] The Pt-WS2@BP nanoflower composite material prepared by this invention is used in the field of semiconductor gas sensing. Attached Figure Description

[0016] Figure 1 The X-ray diffraction patterns of Pt-WS2@BP nanoflower composite materials prepared in Examples 1-3 are shown below.

[0017] Figure 2 The image shows a SEM image of the WS2 nanoflower-like microspheres prepared in Example 1; where Figure (a) is a magnified view of a portion of Figure (b).

[0018] Figure 3 Here is a SEM image of the BP nanosheets prepared in Example 1;

[0019] Figure 4 SEM image of Pt-WS2@BP nanoflower composite material prepared in Example 3;

[0020] Figure 5The EDS spectrum of the Pt-WS2@BP nanoflower composite material prepared in Example 3 is shown.

[0021] Figure 6 Sensitivity test graphs for Pt-WS2@BP nanoflower composite materials prepared in Examples 1-4;

[0022] Figure 7 Selectivity test results for NO2 gas on Pt-WS2@BP nanoflower composite materials prepared in Examples 3 and 4. Detailed Implementation

[0023] Specific Implementation Method 1: This implementation method describes a Pt-WS2@BP nanoflower composite material. The material is first synthesized using a one-step hydrothermal method with raw materials including sodium tungstate, thiourea, and oxalic acid. WS2 three-dimensional flower-shaped nanospheres are then mixed with BP nanosheets, and H2PtCl6•6H2O is added for ultrasonic homogenization. Vacuum drying yields the noble metal Pt-supported WS2@BP nanocomposite material. The WS2 three-dimensional flower-shaped nanospheres exhibit a sheet-like nanoflower structure, while the BP nanosheets exhibit a nanosheet layer structure.

[0024] Specific Implementation Method Two: This implementation method describes a method for preparing a Pt-WS2@BP nanoflower composite material, which is carried out according to the following steps:

[0025] Step 1: Preparation of WS2 nanoflower-like microspheres: Sodium tungstate was dissolved in deionized water under continuous stirring to form a homogeneous sodium tungstate solution. Thiourea was added and stirred continuously until dissolved. Sodium dodecylbenzenesulfonate was then added and ultrasonically vibrated and stirred until completely dissolved. Oxalic acid was added and stirred until dissolved. A hydrothermal reaction was carried out, followed by cooling, centrifugation and washing, and vacuum drying to obtain WS2 nanoflower-like microspheres.

[0026] Step 2: After grinding the black phosphorus crystals, they were placed in anhydrous ethanol for ultrasonic exfoliation, followed by centrifugation, washing, and vacuum drying to obtain BP nanosheets.

[0027] Step 3: Preparation of Pt-WS2@BP nanoflower composite material: The WS2 nanoflower-like microspheres prepared in Step 1 and the BP nanosheets prepared in Step 2 are mixed, and H2PtCl6•6H2O is added for ultrasonic homogenization. Then, the mixture is vacuum dried to obtain the Pt-WS2@BP nanoflower composite material.

[0028] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the molar ratio of sodium tungstate to thiourea in step one is 1:(4~5), the concentration of sodium tungstate is 0.1~0.15 mol / L, and the concentration of thiourea is 0.4~0.75 mol / L. Everything else is the same as in Specific Implementation Method 2.

[0029] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two or Three in that the concentration of sodium dodecylbenzenesulfonate after addition in step one is 0.03~0.04 mol / L. Everything else is the same as in Specific Implementation Method Two or Three.

[0030] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods Two to Four in that the concentration of oxalic acid after addition in step one is 0.2~0.3 mol / L. Everything else is the same as in Specific Implementation Methods Two to Four.

[0031] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods Two to Five in that the hydrothermal reaction temperature in step one is 200~220℃, and the reaction time is 24~26h. Everything else is the same as in Specific Implementation Methods Two to Five.

[0032] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Two to Six in that: in step two, the ultrasonic ablation process is carried out in ice water at 0°C, with an ultrasonic frequency of 20kHz, a power of 400W, and a ablation time of 6 hours. Everything else is the same as in Specific Implementation Methods Two to Six.

[0033] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods Two to Seven in that the amount of WS2 nanoflower-shaped microspheres used in step three is 10-40% of the mass of BP nanosheets. Everything else is the same as in Specific Implementation Methods Two to Seven.

[0034] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Two to Eight in that the mass concentration of H2PtCl6•6H2O added in step three is 0.2~0.3%. Everything else is the same as in Specific Implementation Methods Two to Eight.

[0035] Specific Implementation Method 10: This implementation method describes the application of a Pt-WS2@BP nanoflower composite material, which is used as a two-dimensional semiconductor composite gas-sensitive material in the field of semiconductor gas sensing.

[0036] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.

[0037] Example 1:

[0038] This embodiment describes a method for preparing a Pt-WS2@BP nanoflower composite material, which is carried out according to the following steps:

[0039] Step 1: Preparation of WS2 nanoflower-like microspheres: Under continuous stirring, 7 mmol of sodium tungstate was dissolved in 60 mL of deionized water and stirred for 15 min to form a homogeneous sodium tungstate solution. 33 mmol of thiourea was added and stirred continuously for 10 min. Then, 2.2 mmol of sodium dodecylbenzenesulfonate was added, ultrasonically vibrated and stirred for 15 min. After complete dissolution, 14 mmol of oxalic acid was added and stirred for 15 min. The solution was then transferred to a 100 mL reactor for hydrothermal reaction. The hydrothermal reaction temperature was controlled at 210 °C and the reaction time was 24 h. The solution was then naturally cooled and washed three times each with anhydrous ethanol and deionized water by centrifugation. Finally, the solution was vacuum dried at 60 °C for 12 h to obtain WS2 nanoflower-like microspheres.

[0040] Step 2: Grind 20mg of black phosphorus crystals and disperse them in 30mL of anhydrous ethanol. Stir well and place in an ice-water environment at 0℃. Perform low-temperature ultrasonic cycling for 6h using an ultrasonic cell disruptor with an ultrasonic frequency of 20kHz and a power of 400W. Then wash with anhydrous ethanol and deionized water three times each by alternating centrifugation and dry under vacuum at 50℃ for 12h to obtain BP nanosheets.

[0041] Step 3: Preparation of Pt-WS2@BP nanoflower composite material: 10 mg of WS2 nanoflower-shaped microspheres prepared in Step 1 and 0.1 mg of BP nanosheets prepared in Step 2 were mixed, and 20 μL of H2PtCl6•6H2O was added for ultrasonic homogenization for 15 min. Then, the mixture was vacuum dried at 50 °C for 12 h to obtain Pt-WS2@BP nanoflower composite material.

[0042] Example 2:

[0043] The difference between this embodiment and Embodiment 1 is that in step three, the amount of WS2 nanoflower-shaped microspheres used is 10 mg, and the amount of BP nanosheets used is 0.2 mg. Everything else is the same as in Embodiment 1.

[0044] Example 3:

[0045] The difference between this embodiment and Embodiment 1 is that in step three, the amount of WS2 nanoflower-shaped microspheres used is 10 mg, and the amount of BP nanosheets used is 0.3 mg. Everything else is the same as in Embodiment 1.

[0046] Example 4:

[0047] The difference between this embodiment and Embodiment 1 is that BP nanosheets were not added. Everything else is the same as in Embodiment 1.

[0048] Figure 1The X-ray diffraction patterns of Pt-WS2@BP nanoflower composite materials prepared in Examples 1-3 are shown in the figure. As can be seen from the figure, the prepared WS2 is consistent with the standard card (JCPDS no. 08-0237), which proves that the WS2 was successfully prepared. The shift of (002) in the figure is mainly due to the increase of the interlayer spacing of SWS, which is related to the bending of the WS2 plate, strain effect, interlayer folding defects and other factors. The BP is consistent with the standard card (JCPDS no. 73-1358), which proves that the composite material is doped with black phosphorus BP. The characteristic peak of Pt was not found in the XRD diffraction pattern due to the low doping content.

[0049] Figure 2 The image shows a SEM image of the WS2 nanoflower-like microspheres prepared in Example 1; where Figure (a) is a magnified view of a portion of Figure (b).

[0050] Figure 3 Here is a SEM image of the BP nanosheets prepared in Example 1;

[0051] Figure 4 The image shows a SEM image of the Pt-WS2@BP nanoflower composite material prepared in Example 3. The image shows that BP nanosheets are intercalated in the middle of WS2 nanospheres and have good dispersion, which greatly increases the specific surface area of ​​the material and provides more adsorption sites for NO2 gas adsorption, thereby improving its gas-sensing performance.

[0052] Figure 5 The image shows the EDS spectrum of the Pt-WS2@BP nanoflower composite material prepared in Example 3, which contains only four elements: W, S, P, and Pt, and no other impurity elements.

[0053] For Examples 1-4, when the operating temperature is 50°C, the nanomaterials prepared in Examples 1-4 all exhibit good response and recovery characteristics to NO2 gas concentrations of 0.1-32 ppm. Figure 6 The images show sensitivity test results for the Pt-WS2@BP nanoflower composite materials prepared in Examples 1-4. The sample in Example 4 exhibited baseline drift; this was gradually improved by incorporating BP nanosheets, as shown below. Figure 6 Examples 1-4 are shown in the examples, with example 3 having the highest gas-sensitive response.

[0054] Figure 7 The selectivity test charts for NO2 gas prepared by Pt-WS2@BP nanoflower composite materials in Examples 3 and 4 show that the samples in Examples 3 and 4 have good selectivity for NO2 gas, especially the sample in Example 3 after adding BP, which has good selectivity and high sensitivity.

[0055] The above tests demonstrate that the Pt-WS2@BP nanoflower composite material prepared in this invention exhibits high sensitivity and good response recovery for NO2 gas at lower operating temperatures, and can accurately identify it with single selectivity, thus providing a candidate material for the field of low-temperature semiconductor gas sensing.

[0056] The above descriptions are preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any substitutions and transformations made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a Pt-WS2@BP nanoflower composite material, characterized in that... This method is specifically carried out in the following steps: Step 1: Preparation of WS2 nanoflower-like microspheres: Sodium tungstate was dissolved in deionized water under continuous stirring to form a homogeneous sodium tungstate solution. Thiourea was added and stirred continuously until dissolved. Sodium dodecylbenzenesulfonate was then added and ultrasonically vibrated and stirred until completely dissolved. Oxalic acid was added and stirred until dissolved. A hydrothermal reaction was carried out, followed by cooling, centrifugation and washing, and vacuum drying to obtain WS2 nanoflower-like microspheres. The concentration of sodium dodecylbenzenesulfonate after addition is 0.03~0.04 mol / L; Step 2: After grinding the black phosphorus crystals, they were placed in anhydrous ethanol for ultrasonic exfoliation, followed by centrifugation, washing, and vacuum drying to obtain BP nanosheets. Step 3: Preparation of Pt-WS2@BP nanoflower composite material: The WS2 nanoflower-like microspheres prepared in Step 1 and the BP nanosheets prepared in Step 2 are mixed, and H2PtCl6•6H2O is added for ultrasonic uniform mixing. Then, the mixture is vacuum dried to obtain the Pt-WS2@BP nanoflower composite material. The amount of WS2 nanoflower-like microspheres used in step three is 10-40% of the mass of BP nanosheets; The mass concentration of H2PtCl6•6H2O added in step three is 0.2~0.3%.

2. The preparation method of the Pt-WS2@BP nanoflower composite material according to claim 1, characterized in that In step one, the molar ratio of sodium tungstate to thiourea is 1:(4~5), the concentration of sodium tungstate is 0.1~0.15 mol / L, and the concentration of thiourea is 0.4~0.75 mol / L.

3. The preparation method of the Pt-WS2@BP nanoflower composite material according to claim 1, characterized in that The concentration of oxalic acid after its addition in step one is 0.2~0.3 mol / L.

4. The preparation method of the Pt-WS2@BP nanoflower composite material according to claim 1, characterized in that The hydrothermal reaction temperature in step one is 200~220℃, and the reaction time is 24~26h.

5. The preparation method of the Pt-WS2@BP nanoflower composite material according to claim 1, characterized in that The ultrasonic ablation process described in step two is carried out in ice water at 0°C, with an ultrasonic frequency of 20kHz, a power of 400W, and a ablation time of 6 hours.

6. An application of a Pt-WS2@BP nanoflower composite material, wherein the Pt-WS2@BP nanoflower composite material is prepared by the preparation method of claim 1, characterized in that... The Pt-WS2@BP nanoflower composite material is used as a two-dimensional semiconductor composite gas-sensitive material in the field of semiconductor gas sensing.

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