Tungsten disulfide / black phosphorene composite material and preparation method and application thereof

Abstract

The invention relates to a tungsten disulfide / black phosphorene composite material as well as a preparation method and application thereof, and belongs to the field of gas sensors. The preparation method of the tungsten disulfide / black phosphorene composite material comprises the following steps: carrying out hydrothermal reaction on black phosphorus nanosheets, tungsten chloride and thiourea in water, and carrying out solid-liquid separation to obtain a black precipitate; the tungsten disulfide / black phosphorene composite material prepared by the method takes a black phosphorene material as a substrate, tungsten disulfide nanosheets are compounded on the substrate in situ, and the construction of a heterogeneous interface between tungsten disulfide and black phosphorene can promote the rearrangement of an internal electronic structure of the material and improve the electrical properties and the ammonia gas adsorption / desorption performance of the material; therefore, the material can be used for rapid trace testing of ammonia gas at room temperature, and the detection concentration limit is as low as 100 ppb.

Description

Technical Field

[0001] The invention relates to a tungsten disulfide / black phosphorene composite material and a preparation method and application thereof, belonging to the field of gas sensors. Background Art

[0002] With the rapid development of industry, environmental pollution problems are becoming increasingly prominent, among which air pollution and detection have become an important topic of concern to more and more people. Ammonia is a gas with a wide range of sources and is irritating and harmful to the human body. Long-term exposure to an ammonia atmosphere will cause irreversible damage to the human body and even endanger life safety. The long-term exposure safety limit of indoor ammonia is 25ppm. Accurate and reliable detection of low-concentration ammonia is of great significance in ensuring environmental and personal safety.

[0003] The current ammonia monitoring technology mainly relies on semiconductor resistive gas sensors, whose response principle is to use the conductivity change caused by the reaction of gas molecules on the surface of semiconductor film to achieve quantitative detection of gas. The sensor is low-cost, simple to manufacture, fast in response, small in size, widely applicable, and easy to use.

[0004] The sensing material system of semiconductor resistive gas sensors is mainly concentrated on metal oxide semiconductor films. This type of sensor generally needs to work at a high temperature above 300°C, with high energy consumption, and long-term detection can easily cause equipment aging. Moreover, it is difficult to achieve a thermodynamic equilibrium state between metal oxides and the oxygen in the volatile external environment, which will affect the flow and distribution of oxygen vacancy defects inside the material, making it difficult to maintain the long-term stability of the sensor. Therefore, metal oxide gas sensors cannot detect gases at room temperature. Moreover, the sensitivity of this type of sensor is insufficient (>5ppm). The ammonia content in human exhaled gas is in the range of 0.05 to 5ppm, which is often used as the basis for diagnosing certain diseases. Obviously, general semiconductor ammonia sensors cannot detect low-concentration ammonia in the environment.

[0005] The Chinese invention patent application with application publication date of March 31, 2020 and application publication number CN110940705A discloses a polypyrrole-graphene nanocomposite gas-sensitive structural material, which uses reduced graphene oxide as a three-dimensional framework, and pyrrole monomer undergoes polymerization reaction on the surface of reduced graphene oxide to eventually form a uniform polypyrrole shell. The polypyrrole-graphene nanocomposite gas-sensitive structural material has a dynamic response to 300ppb and 660ppb ammonia at room temperature of 20°C, and its sensitivity to ammonia response is 1.16 and 1.86, respectively. Although the composite gas-sensitive structural material can detect ammonia at room temperature, the detection limit of ammonia is still high and the sensitivity is low, which makes it difficult to meet the high-sensitivity detection requirements of extremely trace ammonia. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a tungsten disulfide / black phosphorene composite material to solve the problem that existing gas-sensitive materials cannot effectively respond to extremely small amounts of ammonia.

[0007] The second object of the present invention is to provide a tungsten disulfide / black phosphorene composite material prepared by the above preparation method to solve the above problems.

[0008] The third object of the present invention is to provide an application of a tungsten disulfide / black phosphorene composite material in an ammonia sensor to solve the problem that the ammonia sensor in the prior art has a high detection limit and low sensitivity for ammonia at room temperature.

[0009] In order to achieve the above purpose, the first technical solution of the present invention is:

[0010] A method for preparing a tungsten disulfide / black phosphorene composite material comprises the following steps: subjecting black phosphorus nanosheets, tungsten chloride and thiourea to a hydrothermal reaction in water, and performing solid-liquid separation to obtain a black precipitate.

[0011] The present invention is a pioneering invention, which uses black phosphorus nanosheets, tungsten chloride, and thiourea as raw materials to prepare a tungsten disulfide / black phosphorene composite material. The composite material uses black phosphorene material (i.e., black phosphorus nanosheets) as a substrate, and tungsten disulfide nanosheets are in-situ compounded on the substrate. The construction of the heterogeneous interface between tungsten disulfide / black phosphorene can promote the rearrangement of the internal electronic structure of the material, improve its electrical properties and its absorption / desorption performance of ammonia, so that the material can be used for rapid trace testing of ammonia at room temperature, with a detection concentration limit as low as 100ppb.

[0012] Preferably, the mass ratio of black phosphorus nanosheets to tungsten chloride is (20-50):198.

[0013] More preferably, the molar ratio of tungsten chloride to thiourea is 1:(10-20).

[0014] Preferably, the temperature of the hydrothermal reaction is 210-240° C., and the time is 20-30 hours.

[0015] Preferably, the black phosphorus nanosheets are prepared by an electrochemical method.

[0016] Further preferably, the electrochemical method uses platinum as the positive electrode, black phosphorus crystal as the negative electrode, and a solution of tetrabutylammonium tetrafluoroborate in propylene carbonate as the electrolyte; the voltage is 8 to 20 V. In the solution of tetrabutylammonium tetrafluoroborate in propylene carbonate, the concentration of tetrabutylammonium tetrafluoroborate is 0.01 to 0.1M.

[0017] Preferably, the amount of water used is 50-100 mL for every 20-50 mg of black phosphorus nanosheets.

[0018] The second technical solution of the present invention is:

[0019] The tungsten disulfide / black phosphorene composite material prepared by the above preparation method.

[0020] The tungsten disulfide / black phosphorene composite material obtained by the above method has a tungsten disulfide / black phosphorene heterogeneous interface structure and shows good sensitivity in the detection of trace ammonia.

[0021] The third technical solution of the present invention is:

[0022] Application of the above-mentioned tungsten disulfide / black phosphorene composite material in ammonia sensors.

[0023] The tungsten disulfide / black phosphorene composite material has a good response to trace ammonia at room temperature and can be used as a gas-sensitive material in ammonia sensors, thereby realizing rapid trace testing of ammonia at room temperature.

[0024] Preferably, the ammonia sensor is a room temperature ammonia sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The SEM images of the black phosphorus nanosheets and the tungsten disulfide / black phosphorene composite material of Example 1 of the present invention; wherein (a) is the SEM image of the black phosphorus nanosheets, and (b) is the SEM image of the tungsten disulfide / black phosphorene composite material;

[0026] Figure 2 This is the principle diagram of ammonia detection using a dynamic gas-sensitive test system;

[0027] Figure 3 Response curve of the tungsten disulfide / black phosphorene composite material of Example 1 of the present invention to different concentrations of NH3 at room temperature. DETAILED DESCRIPTION

[0028] Two-dimensional transition metal sulfide layered materials have the characteristics of suitable bandwidth, low cost and environmental protection, and are a kind of gas-sensitive materials with great application potential. Among them, tungsten disulfide is a relatively regular hexagonal plate-like crystal with good conductivity and large specific surface area. As a new type of two-dimensional material, black phosphorus has good electrical and optical properties and has great application prospects in gas detection. The porous structure and large specific surface area of ​​two-dimensional materials can improve the detection and stability of gases, but pure two-dimensional materials have low sensitivity and poor recovery reversibility, which greatly limits the application of two-dimensional materials in gas sensing.

[0029] The present invention uses highly conductive black phosphorene material as a substrate and, based on a hydrothermal synthesis strategy, in-situ synthesizes tungsten disulfide nanosheets on black phosphorene to construct a tungsten disulfide / black phosphorene heterostructure, and then constructs sensing electronic components on the interdigitated electrodes for the detection of ammonia gas at room temperature, thus achieving accurate and rapid detection of low-concentration ammonia at the ppb level.

[0030] When constructing an ammonia gas sensor, the tungsten disulfide / black phosphorene composite material is modified on the surface of the interdigitated electrode. The interdigitated electrode is a type of patterned microelectrode arranged like fingers, and by modifying its surface with a gas-sensitive material, it can be made into a gas sensor element that can work at room temperature.

[0031] The principle of the ammonia gas sensor based on the above-mentioned tungsten disulfide / black phosphorene composite material for detecting room temperature ammonia is: when ammonia is adsorbed on the surface of the composite material, the ammonia molecules capture electrons from the surface of the composite material, and the resistance of the material increases. By detecting the change in resistance, the ammonia content can be obtained.

[0032] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0033] 1. Specific embodiments of the tungsten disulfide / black phosphorene composite material and its preparation method of the present invention are as follows:

[0034] Example 1

[0035] The preparation method of the tungsten disulfide / black phosphorene composite material of this embodiment adopts the following steps:

[0036] (1) Platinum wire was used as the positive electrode and black phosphorus crystal was used as the negative electrode, and placed in a propylene carbonate solution containing 0.01 M tetrabutylammonium tetrafluoroborate. A 20 V DC voltage was applied for 8 min to perform electrochemical stripping to obtain sponge-like black phosphorus.

[0037] (2) The sponge-like black phosphorus obtained in step (1) is ultrasonically dispersed for 15 minutes, and then centrifugally cleaned to obtain black phosphorus nanosheets. The obtained black phosphorus nanosheets have a thickness of 4-7 nm and a two-dimensional size of (1.8-2.5)×(1.1-1.7) μm.

[0038] (3) 20 mg of black phosphorus nanosheets were dispersed in 50 mL of deionized water solution, and WCl6 (198 mg) and thiourea (570.9 mg) were added at a molar ratio of 1:15. After stirring and mixing evenly, the solution was transferred to a polytetrafluoroethylene reactor and subjected to a hydrothermal reaction at 240 °C for 24 h.

[0039] (4) After the reaction is completed, the sample is cooled naturally, the cooled sample is centrifuged and cleaned, the black precipitate is collected, and it is dried in a vacuum drying oven at 60° C. to obtain a tungsten disulfide / black phosphorene composite material.

[0040] The black phosphorus nanosheets and tungsten disulfide / black phosphorene composite materials obtained in this example were characterized by microscopic morphology. Figure 1 shown.

[0041] in, Figure 1 (a) is the SEM image of black phosphorus nanosheets, which show a typical two-dimensional sheet structure. Figure 1 (b) is the SEM image of the tungsten disulfide / black phosphorene composite material. It can be seen that the tungsten disulfide nanosheets are evenly covered on the black phosphorus nanosheets, and the growth direction is perpendicular to the black phosphorus nanosheets.

[0042] Example 2

[0043] The preparation method of the tungsten disulfide / black phosphorene composite material of this embodiment adopts the following steps:

[0044] (1) Platinum wire is used as the positive electrode and black phosphorus crystal is used as the negative electrode, and placed in a propylene carbonate solution containing 0.05 M tetrabutylammonium tetrafluoroborate, and a DC voltage of 10 V is applied for 15 min to perform electrochemical stripping to obtain sponge-like black phosphorus;

[0045] (2) ultrasonically dispersing the sponge-like black phosphorus obtained in step (1) for 20 minutes, and then centrifugally washing to obtain black phosphorus nanosheets;

[0046] (3) 50 mg of black phosphorus nanosheets were dispersed in 100 mL of deionized water solution, WCl6 (198 mg) and thiourea (761.2 mg) were added at a molar ratio of 1:20, and after stirring and mixing, the solution was transferred to a polytetrafluoroethylene reactor and subjected to a hydrothermal reaction at 220 °C for 26 h;

[0047] (4) After the reaction is completed, the sample is cooled naturally, the cooled sample is centrifuged and cleaned, the black precipitate is collected, and it is dried in a vacuum drying oven at 60° C. to obtain a tungsten disulfide / black phosphorene composite material.

[0048] Example 3

[0049] The preparation method of the tungsten disulfide / black phosphorene composite material of this embodiment adopts the following steps:

[0050] (1) Platinum wire is used as the positive electrode and black phosphorus crystal is used as the negative electrode, and is placed in a propylene carbonate solution containing 0.1 M tetrabutylammonium tetrafluoroborate, and a DC voltage of 20 V is applied for 8 min to perform electrochemical stripping to obtain sponge-like black phosphorus;

[0051] (2) ultrasonically dispersing the sponge-like black phosphorus obtained in step (1) for 30 minutes, and then centrifugally washing to obtain black phosphorus nanosheets;

[0052] (3) 30 mg of black phosphorus nanosheets were dispersed in 80 mL of deionized water solution, WCl6 (198 mg) and thiourea (380.6 mg) were added at a molar ratio of 1:10, and after stirring and mixing, the solution was transferred to a polytetrafluoroethylene reactor and subjected to a hydrothermal reaction at 210 °C for 30 h;

[0053] (4) After the reaction is completed, the sample is cooled naturally, the cooled sample is centrifuged and cleaned, the black precipitate is collected, and it is dried in a vacuum drying oven at 60° C. to obtain a tungsten disulfide / black phosphorene composite material.

[0054] 2. Example of application of the tungsten disulfide / black phosphorene composite material of the present invention in an ammonia sensor

[0055] Example 4

[0056] The ammonia sensor of this embodiment is constructed by coating the tungsten disulfide / black phosphorene composite material of Example 1 on the surface of the interdigital electrode by a spin coating method. Specifically, 30 mg of tungsten disulfide / black phosphorene composite material and 500 μL of deionized water are mixed to form a coating liquid, and 5 μL of the coating liquid is coated on the interdigital electrode with an electrode size of 1 mm×1.5 mm.

[0057] Use Figure 2 The obtained dynamic gas-sensitive test system tests the ammonia detection performance of the ammonia sensor. During the test, the ammonia sensor constructed using the above method is placed in the test chamber. The specific test process is as follows: Use a dynamic gas-sensitive test system equipped with a high-precision gas mass flow manager to test the sensing performance of the electrode to be tested, and control the target gas concentration by adjusting the flow rate of the gas to be tested and the dry air, and keep the constant flow rate of the mixed gas at 100sccm. In the gas sensing experiment, a Keithley DMM6500 multimeter is used to record the resistance change of the sensor. The ratio of the resistance value in the ammonia atmosphere to the resistance value in the air is the response value of the sensor.

[0058] At room temperature, different concentrations of ammonia were tested, and the results are as follows: Figure 3 shown.

[0059] Depend on Figure 3 It can be seen that the tungsten disulfide / black phosphorene composite material responds to NH3 gas with a concentration of 0.1ppm (i.e. 100ppb) at room temperature, and the response sensitivity to NH3 gas above 1ppm continues to increase. For example, the response value for 2ppm NH3 reaches more than 18, showing a good detection effect for trace ammonia.

Claims

1. A method for preparing a tungsten disulfide / black phosphorene composite material, characterized in that: The following steps are involved: Black phosphorus nanosheets, tungsten chloride and thiourea are subjected to hydrothermal reaction in water, and solid-liquid separation is performed to obtain a black precipitate.

2. The method for preparing the tungsten disulfide / black phosphorene composite material according to claim 1, characterized in that: The mass ratio of black phosphorus nanosheets to tungsten chloride is (20-50):

198.

3. The method for preparing the tungsten disulfide / black phosphorene composite material according to claim 2, characterized in that: The molar ratio of tungsten chloride to thiourea is 1:(10-20).

4. The method for preparing the tungsten disulfide / black phosphorene composite material according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 210-240°C and the time is 20-30 hours.

5. The method for preparing the tungsten disulfide / black phosphorene composite material according to claim 1, characterized in that: The black phosphorus nanosheets are prepared by an electrochemical method.

6. The method for preparing the tungsten disulfide / black phosphorene composite material according to claim 5, characterized in that: The electrochemical method uses platinum as the positive electrode, black phosphorus crystal as the negative electrode, and tetrabutylammonium tetrafluoroborate propylene carbonate solution as the electrolyte; the voltage is 8-20V.

7. The method for preparing the tungsten disulfide / black phosphorene composite material according to claim 1, 2 or 3, characterized in that: The amount of water used for every 20 to 50 mg of black phosphorus nanosheets is 50 to 100 mL.

8. A tungsten disulfide / black phosphorene composite material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the tungsten disulfide / black phosphorene composite material as claimed in claim 8 in an ammonia sensor.

10. The use of the tungsten disulfide / black phosphorene composite material in an ammonia sensor as claimed in claim 9, characterized in that: The ammonia sensor is a room temperature ammonia sensor.

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