Preparation method and application of a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide

Abstract

This invention relates to a method for preparing and applying a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide, belonging to the field of gas sensor technology. The invention discloses a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide and its application as a sensing material in a highly selective and sensitive flexible NO2 gas sensor. The invention utilizes a liquid-phase growth method, using SnSe2 nanosheets, ammonium tungstate, and diphenyldiselenoether as raw materials, and varying reaction conditions such as temperature, reaction time, and raw material content to prepare the ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide. Subsequently, these nanosheets are sprayed onto interdigitated electrodes and dried to form a film, thus preparing a chemielectric resistive gas sensor capable of detecting low concentrations of nitrogen dioxide gas at room temperature. It not only possesses high sensitivity and selectivity but can also be applied to flexible NO2 gas sensing.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, specifically to the preparation of tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets and the preparation and testing of flexible nitrogen dioxide gas sensor devices based on these heterostructure nanosheets. Technical Background

[0002] In recent years, two-dimensional (2D) materials, represented by metal sulfides (such as molybdenum disulfide, tin diselenide, and tungsten diselenide), have demonstrated excellent electrical, optical, and thermodynamic properties, making them promising for applications in catalysis, energy storage and conversion, and sensing. Currently, 2D materials have become a novel class of gas-sensitive materials, providing crucial active sensing material support for the development of highly sensitive and selective gas sensors. 2D materials possess abundant surface active sites, a large specific surface area, and unique gas adsorption capabilities, allowing them to exchange charge with adsorbed gas molecules at room temperature, thereby enhancing sensor sensitivity.

[0003] Tin diselenide, with its stable chemical structure and excellent photoelectric properties, is widely used in gas sensing. NO2 gas sensors using tin diselenide as the sensing material can operate at room temperature. NO2 gas molecules adsorb and desorb on the surface of the sensitive material; the sensing mechanism is based on the change in the sensor's electrical properties caused by charge transfer between the target gas molecules and the material surface. However, at room temperature, the adsorption / desorption rate of the target gas on the material surface is slow, leading to low sensor response and long response and recovery times.

[0004] Compared to single materials, constructing heterostructures, modifying functional groups, and doping with noble metals can effectively improve the performance of sensors operating at room temperature, resulting in high-sensitivity and selective room-temperature gas sensors. Crucially, different materials can form contact barriers at the heterojunction interface through heterostructure construction, exponentially increasing the sensor's electrical response signal. Combined with the synergistic effects between the heterostructure components, this effectively enhances the sensor's sensitivity and selectivity. Summary of the Invention

[0005] The objective of this invention is to disclose a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide and its application as a sensing material in a flexible NO2 gas sensor with high selectivity and high sensitivity. This invention utilizes a liquid-phase growth method, using SnSe2 nanosheets, ammonium tungstate, and diphenyldiselelenide as raw materials, and varying reaction conditions such as temperature, reaction time, and raw material content to prepare the tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets. Subsequently, these nanosheets are sprayed onto interdigitated electrodes and dried to form a film, thus fabricating a chemielectric resistive gas sensor capable of detecting low concentrations of nitrogen dioxide gas at room temperature. The 1T'-WSe2 / SnSe2 / SnSe composite material of this invention not only possesses high sensitivity and selectivity but can also be applied to flexible NO2 gas sensing.

[0006] To solve the technical problem of this invention, the proposed technical solution is as follows: a method for preparing tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets, comprising the following steps:

[0007] (1) Add tin diselenide nanosheets and ammonium tungstate to a three-necked flask containing a certain amount of octadecene and oleylamine in a certain proportion, evacuate at 110°C to 130°C for 20 to 40 minutes, then introduce nitrogen and continue heating to 280 to 320°C.

[0008] (2) During the heating process in the previous step, a certain amount of diphenyl diselenide was ultrasonically dissolved in a certain amount of oleylamine to prepare a selenium source;

[0009] (3) When the temperature of the solvent in the three-necked flask reaches between 280 and 320°C, the selenium source is immediately injected into the three-necked flask and reacted for 3 minutes, followed by rapid cooling under nitrogen.

[0010] (4) The product obtained by hot injection is centrifuged and washed several times with a mixture of n-hexane and ethanol to obtain tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets.

[0011] Preferably, in step (1), 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine are added to a three-necked flask, vacuumed at 120°C for 30 min, then nitrogen is introduced and the temperature is continued to rise to 300°C.

[0012] Preferably, in step (2), while heating in the previous step, 12.5 mg of diphenyldiselelenide is ultrasonically dissolved in 1 mL of oleylamine to prepare a selenium source.

[0013] Preferably, the steps include the following:

[0014] (1) Take 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine and add them to a three-necked flask. Vacuum at 120 °C for 30 min, then introduce nitrogen and continue heating to 300 °C.

[0015] (2) While heating in the previous step, take 12.5 mg of diphenyldiselelenide and dissolve it in 1 mL of oleylamine by ultrasonication to prepare a selenium source;

[0016] (3) When the temperature in the three-necked flask reaches 300°C, immediately inject the selenium source into the three-necked flask and react for 3 minutes. After the reaction is completed, cool rapidly under nitrogen.

[0017] (4) The product is centrifuged and the centrifuged product is washed three to four times with n-hexane and ethanol (volume ratio of 1:3) to obtain tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets, which are then dispersed in n-hexane for later use.

[0018] To solve the technical problem of the present invention, another technical solution is proposed: tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets prepared by any of the methods described above.

[0019] To address the technical problem of this invention, another proposed technical solution is as follows: the application of the aforementioned tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets can be used in gas sensing materials and devices, and the steps are as follows:

[0020] (1) Take a certain amount of tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheet solution and spray it evenly on the gold interdigitated electrode, exposing only the two ends of the gold interdigitated electrode. Then, vacuum dry it at 60°C for one day to obtain a gas sensor that can be used to detect NO2 gas concentration.

[0021] (2) Connect the electrodes at both ends of the gas sensor to the data acquisition unit with wires and place them in the gas reactor. Use the gas control device to introduce pure nitrogen and NO2 gas of different concentrations from the inlet and discharge them from the outlet.

[0022] (3) The gas control device is adjusted and controlled to introduce nitrogen gas with a flow rate of 500 sccm before testing NO2 gas, and the baseline resistance R0 of the gas sensor is obtained.

[0023] (4) The flow rate of NO2 gas is controlled by a gas control device to be 500 sccm, and the concentration is gradually increased from 0.1 ppm to 200 ppm;

[0024] (5) At each NO2 gas concentration, when the sensor resistance reaches equilibrium and no longer changes with the introduction of NO2 gas, its response resistance is denoted as R. aThen, nitrogen gas at a flow rate of 1000 sccm is introduced to purge the sensor, causing the sensor resistance to return to the baseline resistance (R0).

[0025] (6) Convert the data into a response value based on ΔR / R0, where ΔR is the sensor resistance R when NO2 gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0 (ΔR = R a -R0);

[0026] (7) Plot ΔR / R0 against concentration. As the concentration of the gas to be measured increases, the resistance of the sensor changes more and the corresponding response is also greater.

[0027] To address the technical problem of this invention, another proposed technical solution is as follows: the application of the aforementioned tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets can be used in the field of flexible gas sensing, and the steps are as follows:

[0028] (1) A silver interdigitated electrode (11 mm long, 9 mm wide, and 0.43 mm between interdigitated fingers) was printed on a PET film (0.1 mm thick) using a high-precision 3D inkjet printer. A certain amount of tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheet solution was sprayed onto the printed flexible interdigitated electrode and then vacuum dried at 60 °C for one day to obtain a flexible NO2 gas sensor.

[0029] (2) Connect the electrodes at both ends of flexible gas sensors with different bending radii to the data acquisition device with wires and place them in the gas reactor. Use a gas control device to introduce pure nitrogen and NO2 gas of different concentrations from the inlet and discharge them from the outlet.

[0030] (3) The gas control device is adjusted and controlled to introduce nitrogen gas with a flow rate of 500 sccm before testing NO2 gas, and the baseline resistance R0 of the gas sensor is obtained.

[0031] (4) The flow rate of NO2 gas is controlled by a gas control device to be 500 sccm, and the concentration is gradually increased from 0.1 ppm to 200 ppm;

[0032] (5) At each NO2 gas concentration, when the sensor resistance reaches equilibrium and no longer changes with the introduction of NO2 gas, its response resistance is denoted as R. a Then, nitrogen gas at a flow rate of 1000 sccm is introduced to purge the sensor, causing the sensor resistance to return to the baseline resistance (R0).

[0033] (6) Convert the data into a response value based on ΔR / R0, where ΔR is the sensor resistance R when NO2 gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0 (ΔR = R a-R0);

[0034] (7) Plot ΔR / R0 against concentration. As the concentration of the gas to be measured increases, the resistance of the sensor changes more and the corresponding response is also greater.

[0035] To address the technical problem of this invention, another technical solution is proposed: a gas sensing material based on a two-dimensional transition metal chalcogenide heterostructure, wherein the gas sensing material of tungsten diselenide / tin diselenide heterostructure nanosheets is used to prepare the gas sensing material.

[0036] Beneficial effects:

[0037] This invention is the first to realize the composite of metallic tungsten diselenide and semiconductor tin diselenide / tin monoselenide, constructing a new material tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheet, which is then used as a gas-sensitive material in a flexible NO2 gas sensor with high sensitivity and good selectivity.

[0038] This invention utilizes a liquid-phase growth method with SnSe2 nanosheets, ammonium tungstate, and diphenyldiselenoether as raw materials. By varying reaction conditions such as temperature, reaction time, and raw material content, a novel ternary heterostructure nanosheet material of tungsten diselenoide / tin diselenoide / tin monoselenide is prepared. Subsequently, these nanosheets are sprayed onto interdigitated electrodes and dried to form a film, thus fabricating a chemielectric resistive gas sensor capable of detecting low concentrations of nitrogen dioxide gas at room temperature. The 1T'-WSe2 / SnSe2 / SnSe composite material of this invention not only exhibits high sensitivity and selectivity but can also be applied to flexible NO2 gas sensing.

[0039] like Figure 9 As shown in the figure, the response-concentration relationship curve of the chemielectric gas sensor based on 1T'-WSe2 / SnSe2 / SnSe nanosheets shows that the response of the 1T'-WSe2 / SnSe2 / SnSe sensor increases with the increase of NO2 concentration. Figure 9 The linear fitting graph of the sensor's response at NO2 concentrations of 0.1-0.4 ppm shows that the detection limit of the sensor for NO2 is calculated to be 73.5 ppb.

[0040] The 1T'-WSe2 sensor showed a response of 7.5% to 0.8 ppm NO2, while the SnSe2 sensor showed a response of 10%. However, the 1T'-WSe2 / SnSe2 / SnSe heterostructure nanosheets we prepared exhibited a response of 18.5% to 0.8 ppm NO2. This demonstrates that the sensing performance of the 1T'-WSe2 / SnSe2 / SnSe heterostructure nanosheets is superior to that of the single-component 1T'-WSe2 and SnSe2.

[0041] The data is converted into a response value based on ΔR / R0, where ΔR is the sensor resistance R when the target gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0 (ΔR = R a -R0), compare the response values ​​(ΔR / R0) of different target gases, and make the following... Figure 10 The bar chart shown illustrates this. By comparing the response values ​​of nitrogen dioxide, oxygen, acetone, ethanol, and ammonia at a concentration of 2 ppm, it can be found that the chemielectric resistive gas sensor based on 1T'-WSe2 / SnSe2 / SnSe nanosheets exhibits the strongest response and best selectivity to NO2. Attached Figure Description

[0042] Figure 1 SEM image of 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0043] Figure 2 EDS surface scan of the 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0044] Figure 3 EDS image of 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0045] Figure 4 The image shows the XRD pattern of the 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0046] Figure 5 XPS image of W 4f in 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0047] Figure 6 XPS image of Se 3d in 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0048] Figure 7 XPS image of Sn 3d in 1T'-WSe2 / SnSe2 / SnSe nanosheets in Example 1.

[0049] Figure 8 The image shows the response recovery curves for detecting different concentrations of NO2 gas using the 1T'-WSe2 / SnSe2 / SnSe nanosheet sensor in Example 4.

[0050] Figure 9 The graph shows the relationship between the response value and concentration of nitrogen dioxide gas detected by the 1T'-WSe2 / SnSe2 / SnSe nanosheet sensor in Example 4. The inset is a linear fitting graph of the sensor's response when the nitrogen dioxide concentration is 0.1-0.4 ppm.

[0051] Figure 10 This is a comparison chart of the response values ​​of NO2, oxygen, ammonia, acetone and ethanol at the same concentration (2ppm) based on the 1T'-WSe2 / SnSe2 / SnSe nanosheet sensor in Example 5.

[0052] Figure 11 The graph shows the relationship between the response value of the NO2 detection sensor and the concentration under different bending radii in Example 6, based on the flexible 1T'-WSe2 / SnSe2 / SnSe nanosheet gas sensor. Detailed Implementation

[0053] To better understand the present invention, the technical solution of the present invention will be specifically described below with reference to the accompanying drawings and specific embodiments.

[0054] Example 1: Preparation of 1T'-WSe2 / SnSe2 / SnSe complex by template method

[0055] (1) Take 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine and add them to a three-necked flask. Vacuum at 120 °C for 30 min, then introduce nitrogen and continue heating to 300 °C.

[0056] (2) While heating in the previous step, take 12.5 mg of diphenyldiselelenide and dissolve it in 1 mL of oleylamine by ultrasonication to prepare a selenium source;

[0057] (3) When the temperature in the three-necked flask reaches 300°C, immediately inject the selenium source into the three-necked flask and react for 3 minutes. After the reaction is completed, cool rapidly under nitrogen.

[0058] (4) The product is centrifuged and the solid part is washed three to four times with n-hexane and ethanol (volume ratio of 1:3) to obtain tungsten diselenide / tin diselenide nanosheets, which are then dispersed in n-hexane for later use.

[0059] The product 1T'-WSe2 / SnSe2 / SnSe in Example 1 was analyzed, as follows: Figure 1 As shown, the SEM image of 1T'-WSe2 / SnSe2 / SnSe is shown. The SEM image can demonstrate that the final 1T'-WSe2 / SnSe2 / SnSe is in the form of nanosheets.

[0060] like Figure 2 As shown in the EDS surface scan of 1T'-WSe2 / SnSe2 / SnSe nanosheets, the main distribution of W elements is consistent with that of Sn elements, and they are uniformly covered on the surface, indicating that 1T'-WSe2 is uniformly grown on the SnSe2 surface and encapsulates SnSe2.

[0061] like Figure 3As shown, the EDS spectrum of 1T'-WSe2 / SnSe2 / SnSe nanosheets indicates that the 1T'-WSe2 / SnSe2 / SnSe nanosheets are non-pure SnSe2 phases, with some SnSe2 being converted into SnSe. Calculations show that the relative content of SnSe2 is 49% and the relative content of SnSe is 51%, with a phase ratio of approximately 1:1.

[0062] like Figure 4 The XRD pattern of 1T'-WSe2 / SnSe2 / SnSe is shown. The peaks at 13.6° and 31.3° correspond to the (001) and (100) crystal planes of 1T'-WSe2, and the peaks at 14.4° and 30.7° correspond to the (001) and (011) crystal planes of SnSe2. The remaining peaks correspond to SnSe peaks. (PDF cards: 89-0234 and 89-2939)

[0063] like Figure 5 The XPS plot of W 4f in 1T'-WSe2 / SnSe2 / SnSe is shown. In the W 4f spectrum, the binding energies of the two peaks corresponding to 1T' (31.6 and 33.77 eV) are 0.72 eV lower than those of the two peaks corresponding to 2H (32.32 and 34.49 eV). The relative contents of the 1T' and 2H phases can be determined by the proportion of the peak areas corresponding to different phases in the W 4f band. Calculations show that the concentrations of the 1T' and 2H phases in 1T'-WSe2 / SnSe2 / SnSe are 66% and 34%, respectively.

[0064] like Figure 6 The figure shows the XPS plot of Se 3d in 1T'-WSe2 / SnSe2 / SnSe. In the Se 3d spectrum, the binding energies of the two peaks corresponding to 1T' (53.6 and 54.4 eV) are reduced by 1.1 eV compared to the two peaks corresponding to 2H (54.7 and 55.5 eV).

[0065] like Figure 7 The image shows the XPS plot of Se 3d in 1T'-WSe2 / SnSe2 / SnSe / SnSe. 4+ The two corresponding peaks (485.8 and 494.2 eV) are related to Sn. 2+ The corresponding two peaks (486.6 and 495.0 eV) show a decrease in binding energy of 0.8 eV. This was achieved by calculating Sn... 4+ Phase and Sn 2+ The peak area ratios corresponding to the phases, in 1T'-WSe2 / SnSe2 / SnSe, the relative contents of SnSe2 and SnSe are 47% and 53%, respectively, which are the same as the EDS results.

[0066] Example 2

[0067] (1) Take 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine and add them to a three-necked flask. Vacuum at 110 °C for 30 min, then introduce nitrogen and continue heating to 280 °C.

[0068] (2) While heating in the previous step, take 12.5 mg of diphenyldiselelenide and dissolve it in 1 mL of oleylamine by ultrasonication to prepare a selenium source;

[0069] (3) When the temperature in the three-necked flask reaches 280°C, immediately inject the selenium source into the three-necked flask and react for 3 minutes. After the reaction is completed, cool rapidly under nitrogen.

[0070] (4) The product is centrifuged and the solid part is washed three to four times with n-hexane and ethanol (volume ratio of 1:3) to obtain tungsten diselenide / tin diselenide nanosheets, which are then dispersed in n-hexane for later use.

[0071] Example 3

[0072] (1) Take 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine and add them to a three-necked flask. Vacuum at 130 °C for 30 min, then introduce nitrogen and continue heating to 320 °C.

[0073] (2) While heating in the previous step, take 12.5 mg of diphenyldiselelenide and dissolve it in 1 mL of oleylamine by ultrasonication to prepare a selenium source;

[0074] (3) When the temperature in the three-necked flask reaches 320°C, immediately inject the selenium source into the three-necked flask and react for 3 minutes. After the reaction is completed, cool rapidly under nitrogen.

[0075] (4) The product is centrifuged and the solid part is washed three to four times with n-hexane and ethanol (volume ratio of 1:3) to obtain tungsten diselenide / tin diselenide nanosheets, which are then dispersed in n-hexane for later use.

[0076] Example 4: Application of the 1T'-WSe2 / SnSe2 / SnSe sensor – Testing NO2 gas

[0077] (1) Take the 1T'-WSe2 / SnSe2 / SnSe solution prepared in Example 1 and spray it evenly on the gold interdigital electrode, exposing only the electrodes at both ends of the gold interdigital electrode. Then, vacuum dry it at 60°C for one day to obtain a chemical resistance gas sensor that can be used to detect the NO2 gas concentration.

[0078] (2) Connect the electrodes at both ends of the gas sensor to the data acquisition unit (Agilent 34972A) with wires and place it in the gas reactor. Use the gas control device to introduce NO2 gas of different concentrations from the inlet and discharge it from the outlet. Collect the resistance value of the sensor during the test through the data acquisition unit.

[0079] (3) The gas control device is adjusted and controlled to introduce nitrogen gas with a flow rate of 500 sccm before testing NO2 gas, and the baseline resistance R0 of the gas sensor is obtained.

[0080] (4) The flow rate of NO2 gas is controlled by a gas control device at 500 sccm, and the concentration is gradually increased from 0.1 ppm to 20 ppm;

[0081] (5) At each NO2 gas concentration, when the sensor resistance reaches equilibrium and no longer changes with the introduction of NO2 gas, its response resistance is denoted as R. a Then, nitrogen gas at a flow rate of 1000 sccm is introduced to purge the sensor, causing the sensor resistance to return to the baseline resistance (R0).

[0082] (6) Convert the data into a response value based on ΔR / R0, where ΔR is the sensor resistance R when NO2 gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0 (ΔR = R a -R0);

[0083] (7) Plot ΔR / R0 against concentration. As the concentration of the gas to be measured increases, the resistance of the sensor changes more and the corresponding response is also greater.

[0084] (8) After the resistance of a NO2 gas test concentration changes from the beginning to the equilibrium point, the next higher concentration is introduced, and steps (4) to (7) are repeated.

[0085] like Figure 8 As shown, the response-recovery curve of the chemielectric gas sensor based on 1T'-WSe2 / SnSe2 / SnSe nanosheets shows that the sensor's resistance decreases when NO2 gas is introduced, exhibiting a negative response. Therefore, as the NO2 concentration increases, the resistance change (ΔR = R) increases. a As the response value (ΔR / R0) of the 1T'-WSe2 / SnSe2 / SnSe sensor gradually decreases, the absolute value of the response value (|ΔR / R0|) gradually increases.

[0086] like Figure 9As shown in the figure, the response-concentration relationship curve of the chemielectric gas sensor based on 1T'-WSe2 / SnSe2 / SnSe nanosheets shows that the response of the 1T'-WSe2 / SnSe2 / SnSe sensor increases with the increase of NO2 concentration. Figure 9 The linear fitting graph of the sensor's response at NO2 concentrations of 0.1-0.4 ppm shows that the detection limit of the sensor for NO2 is calculated to be 73.5 ppb.

[0087] Example 5: Application of 1T'-WSe2 / SnSe2 / SnSe sensor -- testing oxygen, ammonia, acetone, ethanol (1) Take a certain amount of the 1T'-WSe2 / SnSe2 / SnSe solution prepared in Example 1 and spray it evenly on the gold interdigitated electrode, exposing only the electrodes at both ends of the gold interdigitated electrode. Then, vacuum dry it at 60°C for one day to obtain a chemical resistance gas sensor that can be used to detect different target gases;

[0088] (2) Connect the electrodes at both ends of the gas sensor to the data acquisition unit (Agilent 34972A) with wires and place it in the gas reactor. Use the gas control device to introduce different target gases from the inlet and discharge them from the outlet. Collect the resistance value of the sensor during the test through the data acquisition unit.

[0089] (3) The gas control device is adjusted and controlled to introduce nitrogen gas with a flow rate of 500 sccm in front of the test target to obtain the baseline resistance R0 of the gas sensor.

[0090] (4) The flow rate of different target gases is controlled by a gas control device to be 500 sccm and the concentration is 2 ppm.

[0091] (5) When the resistance of the sensor no longer changes and reaches equilibrium as the target gas is introduced, its response resistance is denoted as R. a Then, nitrogen gas at a flow rate of 1000 sccm is introduced to purge the sensor, causing the sensor resistance to return to the baseline resistance (R0).

[0092] The data is converted into a response value based on ΔR / R0, where ΔR is the sensor resistance R when the target gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0 (ΔR = R a -R0), compare the response values ​​(ΔR / R0) of different target gases and generate a bar chart. Figure 10 By comparing the response values ​​of nitrogen dioxide, oxygen, acetone, ethanol, and ammonia at a concentration of 2 ppm, it can be found that the chemielectric resistive gas sensor based on 1T'-WSe2 / SnSe2 / SnSe nanosheets has the largest response and the best selectivity to NO2.

[0093] Example 6: Application of a flexible gas sensor based on 1T'-WSe2 / SnSe2 / SnSe—Testing the response to NO2 at different bending radii.

[0094] (1) Using a 3D printer, silver interdigitated electrodes (11 mm long, 9 mm wide, and 0.43 mm apart) were printed on a 0.1 mm thick PET film. A certain amount of 1T'-WSe2 / SnSe2 / SnSe solution prepared in Example 1 was sprayed onto the printed flexible interdigitated electrodes and then vacuum dried at 60 °C for one day to obtain a flexible NO2 gas sensor.

[0095] (2) Connect the electrodes at both ends of flexible gas sensors with different bending radii to the data acquisition unit (Agilent 34972A) with wires and place them in the gas reactor. Use the gas control device to introduce pure nitrogen and NO2 gas of different concentrations from the inlet and discharge them from the outlet.

[0096] (3) The gas control device is adjusted and controlled to introduce nitrogen gas with a flow rate of 500 sccm before testing NO2 gas, and the baseline resistance R0 of the gas sensor is obtained.

[0097] (4) The flow rate of NO2 gas is controlled by a gas control device at 500 sccm, and the concentration is gradually increased from 0.1 ppm to 0.8 ppm;

[0098] (5) At each NO2 gas concentration, when the sensor resistance reaches equilibrium and no longer changes with the introduction of NO2 gas, its response resistance is denoted as R. a Then, nitrogen gas at a flow rate of 1000 sccm is introduced to purge the sensor, causing the sensor resistance to return to the baseline resistance (R0).

[0099] (6) Convert the data into a response value based on ΔR / R0, where ΔR is the sensor resistance R when NO2 gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0 (ΔR = R a -R0);

[0100] (7) Plot ΔR / R0 against concentration. As the concentration of the gas to be measured increases, the resistance of the sensor changes more and the corresponding response is also greater.

[0101] (8) After the resistance of a NO2 test concentration changes from the beginning to the equilibrium point, the next higher concentration is introduced, and steps (4) to (7) are repeated.

[0102] like Figure 11As shown in the figure, the response-concentration relationship curves of the 1T'-WSe2 / SnSe2 / SnSe flexible sensor to NO2 at different bending radii are displayed. It can be seen from the graph that the smaller the bending radius, i.e., the greater the degree of bending, the higher the response value of the sensor. The higher the NO2 concentration, the greater the difference in response values ​​corresponding to different bending radii. This may be because after bending, the active material sprayed on the sensing electrode can expose more active surface, participating in the gas adsorption / desorption process and improving the sensor's sensitivity.

[0103] Therefore, the 1T'-WSe2 / SnSe2 / SnSe composite material not only has high sensitivity and selectivity, but can also be applied to flexible NO2 gas sensing.

[0104] Comparative Example 1

[0105] The preparation method of the 1T'-WSe2 / SnSe2 / SnSe complex in this comparative example is basically the same as that in Example 1. The difference is that in step (3), the selenium source is immediately injected into the three-necked flask, the reaction time is changed from 3 min to 30 min, and the reaction is rapidly cooled under nitrogen after the reaction is completed. The reaction product is 1T'-WSe2 / SnSe. The possible reason is that SnSe2 is unstable at high temperature for a long time and is converted into SnSe. Therefore, the template SnSe2 nanosheets added in the initial stage of the reaction are completely converted into SnSe, resulting in the product being 1T'-WSe2 / SnSe.

[0106] Comparative Example 2

[0107] The preparation method of the 1T'-WSe2 / SnSe2 / SnSe complex in this comparative example is basically the same as that in Example 1, except that the amount of tin diselenide added in step (1) is adjusted to 20 mg; the reaction product is a mixture of 1T'-WSe2 and 1T'-WSe2 / SnSe2 / SnSe, in which most of the 1T'-WSe2 is in a free state, and only a small portion of 1T'-WSe2 grows on the surface of SnSe2 / SnSe nanosheets. The possible reason is that the amount of SnSe2 nanosheet template added is too small, which causes most of the 1T'-WSe2 to fail to grow on the surface of SnSe2 nanosheets.

[0108] Comparative Example 3

[0109] The testing methods for the 1T'-WSe2 sensor and SnSe2 sensor in this comparative example are basically the same as those in Example 4. The difference is that in step (1), the 1T'-WSe2 solution and SnSe2 solution are uniformly sprayed onto the gold interdigitated electrodes, exposing only the two ends of the gold interdigitated electrodes. Then, they are vacuum dried at 60°C for one day to obtain a chemical resistance gas sensor that can be used to detect the concentration of NO2 gas. The 1T'-WSe2 sensor has a response of 7.5% to 0.8ppm NO2, the SnSe2 sensor has a response of 10% to 0.8ppm NO2, while the 1T'-WSe2 / SnSe2 / SnSe heterostructure nanosheets we prepared have a response of 18.5% to 0.8ppm NO2. This shows that the sensing performance of the 1T'-WSe2 / SnSe2 / SnSe heterostructure nanosheets is superior to that of the single-component 1T'-WSe2 and SnSe2.

Claims

1. A method for preparing a ternary heterostructure nanosheet of tungsten diselenide / tin diselenide / tin monoselenide, characterized in that: The steps include the following: (1) Add tin diselenide nanosheets and ammonium tungstate to a three-necked flask containing a certain amount of octadecene and oleylamine in a certain proportion, evacuate at 110 ℃ to 130 ℃ for 20 to 40 min, then introduce nitrogen and continue heating to 280 to 320 ℃. (2) During the heating process in the previous step, a certain amount of diphenyldiselelenide was ultrasonically dissolved in a certain amount of oleylamine to prepare a selenium source; (3) When the temperature of the solvent in the three-necked flask reaches between 280 and 320 °C, the selenium source is immediately injected into the three-necked flask and reacted for 3 minutes, and then rapidly cooled under nitrogen. (4) The product obtained by hot injection is centrifuged and washed several times with a mixture of n-hexane and ethanol to obtain tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets.

2. The method of claim 1, wherein the method is characterized by: In step (1), 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine were added to a three-necked flask, and the flask was evacuated at 120 °C for 30 min. After that, nitrogen gas was introduced and the flask was heated to 300 °C.

3. The method of claim 1, wherein the method is characterized by: In step (2), while heating in the previous step, 12.5 mg of diphenyldiselelenide is ultrasonically dissolved in 1 mL of oleylamine to prepare a selenium source.

4. The method of claim 1, wherein the method is characterized by: The steps include the following: (1) Take 30 mg of tin diselenide, 5.1 mg of ammonium tungstate, 3 mL of octadecene and 2 mL of oleylamine and add them to a three-necked flask. Vacuum at 120 °C for 30 min, then introduce nitrogen and continue heating to 300 °C. (2) While heating in the previous step, 12.5 mg of diphenyldiselelenide was ultrasonically dissolved in 1 mL of oleylamine to prepare a selenium source; (3) When the temperature in the three-necked flask reaches 300 °C, the selenium source is immediately injected into the three-necked flask and reacted for 3 min. After the reaction is completed, the flask is rapidly cooled under nitrogen. (4) The product is centrifuged and the centrifuged product is washed three to four times with n-hexane and ethanol in a volume ratio of 1:3 to obtain tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets, which are then dispersed in n-hexane for later use.

5. Tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheets prepared by any of the methods described in claims 1-4.

6. Use of the ternary heterostructure nanosheets of tungsten diselenide / tin diselenide / tin monoselenide according to claim 5, characterized in that: The steps for applications in gas sensing materials and devices are as follows: (1) A certain amount of tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheet solution was uniformly sprayed onto the gold interdigitated electrode, exposing only the two ends of the gold interdigitated electrode. Then, it was vacuum dried at 60 °C for one day to obtain a gas sensor for detecting NO2 gas concentration. (2) Connect the electrodes at both ends of the gas sensor to the data acquisition unit with wires and place them in the gas reactor. Use the gas control device to introduce pure nitrogen and NO2 gas of different concentrations from the inlet and discharge them from the outlet. (3) The gas control device is used to regulate and control the flow of nitrogen gas at a flow rate of 500 sccm before testing NO2 gas, and the baseline resistance R0 of the gas sensor is obtained. (4) The flow rate of NO2 gas is controlled by a gas control device at 500 sccm, and the concentration is gradually increased from 0.1 ppm to 200 ppm; (5) At each NO2 gas concentration, when the resistance of the sensor no longer changes with the introduction of NO2 gas and reaches equilibrium, record its response resistance as R a ; then introduce nitrogen gas with a flow rate of 1000 sccm for purging, so that the resistance of the sensor returns to the baseline resistance R0; (6) converting the data into a response value according to ΔR / R0, where ΔR is the difference in sensor resistance R a from the baseline resistance R0; said ΔR = R a -R0; (7) Plot ΔR / R0 against concentration. As the concentration of the gas to be measured increases, the resistance of the sensor changes more and the corresponding response is also greater.

7. Use of the ternary heterojunction nanosheets of tungsten diselenide / tin diselenide / tin monoselenide according to claim 5, characterized in that: For use in flexible gas sensing, the steps are as follows: (1) A silver interdigitated electrode was printed on a PET film with a film thickness of 0.1 mm using a high-precision 3D inkjet printer. The electrode was 11 mm long and 9 mm wide, with a distance of 0.43 mm between the interdigitated fingers. A certain amount of tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure nanosheet solution was sprayed onto the printed flexible interdigitated electrode and then vacuum dried at 60 °C for one day to obtain a flexible NO2 gas sensor. (2) Connect the electrodes at both ends of flexible gas sensors with different bending radii to the data acquisition device with wires and place them in the gas reactor. Use a gas control device to introduce pure nitrogen and NO2 gas of different concentrations from the inlet and discharge them from the outlet. (3) The gas control device is used to regulate and control the flow of nitrogen gas at a flow rate of 500 sccm before testing NO2 gas, and the baseline resistance R0 of the gas sensor is obtained. (4) The flow rate of NO2 gas is controlled by a gas control device at 500 sccm, and the concentration is gradually increased from 0.1 ppm to 200 ppm; (5) At each NO2 gas concentration, when the sensor resistance no longer changes with the introduction of NO2 gas and reaches equilibrium, its response resistance is denoted as R. a Then, nitrogen gas at a flow rate of 1000 sccm was introduced to purge the sensor and bring the sensor resistance back to the baseline resistance R0. (6) Convert the data into a response value based on ΔR / R0, where ΔR is the sensor resistance R when NO2 gas is introduced. a The difference between the baseline resistance R0 and the baseline resistance R0; the ΔR = R a -R0; (7) Plot ΔR / R0 against concentration. As the concentration of the gas to be measured increases, the resistance of the sensor changes more and the corresponding response is also greater.

8. A gas sensing material based on two-dimensional transition metal chalcogenide heterostructure, characterized in that: The gas sensing material of the tungsten diselenide / tin diselenide / tin monoselenide heterostructure nanosheets according to claim 5 is used to prepare gas sensing materials.

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