A kind of purple phosphorus nanosheet field effect transistor gas sensor and its preparation and application

Abstract

The present application relates to a kind of purple phosphorus nanosheet field effect transistor gas sensor and its preparation and application.The preparation method of purple phosphorus nanosheet field effect transistor gas sensor includes: mechanical stripping method: two-dimensional purple phosphorus bulk crystal material is placed on adhesive tape and is repeatedly pasted, and the few-layer purple phosphorus nanosheet retained on adhesive tape is transferred to field effect transistor electrode;Liquid phase stripping method: purple phosphorus dispersion liquid is directly dropped on interdigital electrode area, after drying, single-layer purple phosphorus nanosheet field effect transistor gas sensor is obtained, and the prepared gas sensor can be used for detecting nitrogen dioxide in atmospheric environment and distinguishing nitrogen dioxide and nitrous oxide gas.Compared with prior art, the present application has the advantages of simple preparation process, cross response sensitivity, low operating cost and the like, and has important significance for the promotion of field effect transistor in the field of gas sensor and nitrogen oxide distinguishing detection.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, and in particular to a purple phosphorus nanosheet field-effect transistor gas sensor and its preparation and application. Background Technology

[0002] Nitrous oxide (N₂O) is a greenhouse gas with a global warming potential (GWP) 265 times greater than that of carbon dioxide. It primarily originates from natural emissions from nitrogen conversion processes by various nitrogen-producing bacteria in soil and oceans, as well as anthropogenic activities such as wastewater treatment and the combustion of biomass and biofuels. In the stratosphere, N₂O can be converted into NO and NO₂. NO is readily oxidized to NO₂ in the air, and the photolysis of NO₂ can trigger the formation of another greenhouse gas, O₃. Therefore, both N₂O and NO₂ have a detrimental impact on global warming. Although the concentration of N₂O in the atmosphere is much lower than that of NO₂, its greenhouse effect is largely overlooked because it can be oxidized to NO₂. Identification and analysis of NO₂ and N₂O will help monitor greenhouse gas (GHG) emissions, thereby achieving global carbon accounting targets. Furthermore, efficient detection of NO₂ and N₂O will contribute to a better understanding of nitrogen transformation pathways and geochemical processes, enabling comprehensive control of nitrogen dioxide and nitrous oxide emissions.

[0003] Existing optical and electrochemical analytical methods for detecting nitrogen oxides typically require expensive equipment and complex operations, have long detection times, relatively low sensitivity, and struggle to meet detection limits. Both NO2 and N2O gases are released into the atmosphere as byproducts or intermediates of ammonia oxidation. Due to their similar densities, solubilities, oxidizing properties, and the total number and types of atoms, few gas analysis methods or sensors can effectively distinguish between them. Therefore, developing a highly efficient detection method for NO2 and N2O gases with high sensitivity, high selectivity, and rapid response at room temperature is imperative.

[0004] In recent years, field-effect transistor (FET) based sensors have gained popularity due to their high compliance with ambient air quality standards (GB3095-2012, HJ633-2012) regarding NO. x The performance of FET gas sensors has attracted much attention due to their high detection requirements. The performance of FET gas sensors primarily depends on the channel material; their sensing mechanism involves the change in conductivity of the semiconductor channel before and after gas adsorption, giving FET sensors a fast response speed (detection time on the order of seconds) and excellent sensitivity. Currently, graphene, MoS2, black phosphorus, and Ti3C2T are among the most popular materials used in FET sensors. xTwo-dimensional (2D) nanomaterials have been used as semiconductor channel materials in FET gas sensors. Chinese patent application CN110186979A discloses a field-effect transistor (FET) for a high-sensitivity gas sensor, which uses small amounts of black phosphorus (BP), boron nitride (BN), and tungsten disilicate (WSe2) as the top gate, dielectric layer, and conductive channel, respectively. In this structure, the top gate uses BP, which has excellent gas adsorption capabilities, as the sensing material. However, this gas sensor does not perform discrimination analysis for nitrogen oxides (NOx). Furthermore, these materials exhibit poor anti-interference performance when detecting target gases, making them difficult to apply accurately in complex and variable atmospheric environments. This limits the development of FET sensors in gas detection and makes it difficult to eliminate NOx in practical applications. x Obstacles to performing differential detection.

[0005] Chinese patent CN112758918A discloses a purple phosphorus / graphene composite material sensor, realizing the application of purple phosphorus as a gas-sensitive material for the detection of carbon monoxide and nitrogen monoxide; however, the gas sensor disclosed in this invention has low sensitivity: the response to 500 ppm NO and CO only reaches 20-25% (only 0.04-0.05% response per ppm of gas); moreover, the sensor's anti-interference ability has not been confirmed, and it has only been tested in a few single gases, and UV or UV-vis-IR light is required to realize the gas desorption process, which is not conducive to the detection application in actual atmospheric environment. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a field-effect transistor gas sensor based on two-dimensional purple phosphorus nanosheets that is easy to prepare, has high detection sensitivity, good selectivity, and strong anti-interference ability, as well as its preparation and application, to solve the problem that existing gas detection devices are unable to perform the identification and analysis of nitrogen oxides.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] Purple phosphorus is a two-dimensional nanomaterial with semiconductor properties. Due to its larger bandwidth, higher hole mobility, and better thermal stability compared to black phosphorus, it has broad application prospects in the field of FET gas sensors. Utilizing the strong adsorption of nitrogen dioxide by purple phosphorus, this sensor has unique advantages and broad development prospects in the accurate detection of nitrogen dioxide over a wide concentration range and in the discrimination analysis of nitrogen oxides.

[0009] The concept is as follows:

[0010] A 300nm thick silicon dioxide layer is mounted on a silicon wafer to form a photolithography substrate. Gold interdigitated electrodes are formed on the top of the Si / SiO2 substrate using optical etching technology, which are used as source and drain electrode pairs.

[0011] In the gold interdigitated electrode region, purple phosphorus nanosheets are loaded as channel materials to connect adjacent source and drain electrode pairs by tape peeling or drop coating.

[0012] By connecting the source, drain, and silicon gate in the form of a back-gate field-effect transistor gas sensor, accurate detection of nitrogen dioxide over a wide concentration range and identification analysis of nitrogen oxides can be achieved.

[0013] The specific plan is as follows:

[0014] This invention provides a purple phosphorus nanosheet field-effect transistor gas sensor.

[0015] This field-effect transistor gas sensor comprises, from bottom to top, a silicon gate, a silicon dioxide layer, an interdigitated electrode region, and a purple phosphorus nanosheet layer. The interdigitated electrode region includes source and / or drain electrodes distributed in an interdigitated pattern. Simply put, this field-effect transistor gas sensor is formed by two interdigitated electrodes joined together, one serving as the source and the other as the drain, with the source and drain electrodes distributed in an interdigitated pattern. Adjacent source and drain electrodes are electrically connected through the purple phosphorus nanosheet layer.

[0016] Furthermore, the silicon dioxide layer is 300 nm thick.

[0017] Furthermore, both the source and drain electrodes are gold electrodes.

[0018] Furthermore, the width of the gold electrode is 1.9-2.1 μm, and the spacing between adjacent gold electrodes is 1.4-1.6 μm.

[0019] This invention also provides a method for fabricating a purple phosphorus nanosheet field-effect transistor gas sensor:

[0020] Process 1: Mechanical peeling method: The two-dimensional purple phosphorus block crystal material is placed on a transparent tape and repeatedly adhered and peeled to make it into a thinner nanosheet layer. Then, the few layers of purple phosphorus nanosheets retained on the tape are transferred to the interdigitated electrode region of the FET to obtain a field-effect transistor gas sensor based on few layers of purple phosphorus nanosheets.

[0021] Process 2: Liquid phase exfoliation method: The ultrasonically treated phosphorus dispersion is directly drop-coated onto the interdigitated electrode region of the FET. After drying, a field-effect transistor gas sensor based on a single layer of phosphorus nanosheets is obtained.

[0022] Furthermore, in process one, the number of times the adhesive is repeatedly applied is 5-8 times, preferably 6 times.

[0023] Furthermore, in process one, during the repeated application, the two-dimensional purple phosphorus block crystal material is manually pressed for 1-2 minutes at the location where it remains, left to stand for 4-6 minutes, and then the tape is slowly peeled off; even further, the pressing time is preferably 1 minute, and the standing time is preferably 5 minutes.

[0024] Furthermore, in Process 1, the entire material preparation process for mechanical stripping is carried out in a dry, sealed glove box filled with high-purity argon gas.

[0025] Furthermore, in process two, the ultrasonic time is 8-12 minutes, preferably 9 minutes; the ultrasonic environment is ultrapure water, and the ultrasonic frequency is 46KHz.

[0026] Furthermore, in process two, the entire liquid-phase exfoliation material preparation process is carried out in a dry, sealed glove box filled with high-purity argon gas.

[0027] Furthermore, in process two, the prepared single-layer purple phosphorus field-effect transistor sensor is annealed at 200-300℃ for 2-4 hours before use.

[0028] Furthermore, the annealing environment is an inert gas environment, preferably argon.

[0029] Furthermore, the annealing time is preferably 2 hours.

[0030] Furthermore, in process two, the mass concentration of the phosphorus dispersion is 0.1-0.3 mg / mL, preferably 0.2 mg / mL, and the drop volume is 0.8-1.2 μL / mm. 2 Preferably 1 μL / mm 2 .

[0031] This invention also provides an application of a purple phosphorus nanosheet field-effect transistor gas sensor, which involves connecting the source, drain, and silicon gate of the field-effect transistor gas sensor to a semiconductor analyzer that analyzes the electronic characteristics and sensing signals of the sensor, and then placing it in a detection gas environment. This enables accurate detection of nitrogen dioxide in the atmosphere over a wide concentration range and the differentiation analysis of nitrogen dioxide and nitrous oxide, thus efficiently monitoring greenhouse gas emissions. It is also suitable for portable and wearable instruments that monitor different types of gases in real time.

[0032] Furthermore, the sensing and detection methods specifically include:

[0033] A few-layer purple phosphorus field-effect transistor gas sensor, prepared by process one mechanical stripping, was placed in an air atmosphere until the current between the source and drain stabilized. Then, NO2 / air mixtures of different concentrations were introduced, and the changes in the current between the source and drain were monitored to reflect the response value R = (Ig-I0) / I0 of the field-effect transistor gas sensor to different concentrations of nitrogen dioxide, thus exploring the high selectivity of the few-layer purple phosphorus field-effect transistor gas sensor to NO2.

[0034] Where I0 is the stable current of the field-effect transistor gas sensor in an air atmosphere, and Ig is the peak current of the field-effect transistor gas sensor after NO2 / air mixture is introduced.

[0035] Similarly, the monolayer purple phosphorus field-effect transistor gas sensor prepared by the liquid phase stripping method was subjected to similar operations as described above. The difference is that different concentrations of NO2 / air mixture and N2O / air mixture were introduced into the detection environment to further explore the ability of the purple phosphorus sensor to identify and analyze nitrogen oxide gases.

[0036] Furthermore, the detection concentration of nitrogen oxide gas is 0.1-10 ppm.

[0037] When NO2 and N2O gases are introduced into the cavity containing the field-effect transistor gas sensor, the adsorption of nitrogen oxides by purple phosphorus causes changes in the electronic properties of the channel material. The resulting change in conductivity is reflected in the change in current between the source and drain electrodes. The purple phosphorus sensor exhibits high sensitivity to NO2 gas because the purple phosphorus nanosheets possess high adsorption energy and a short PN bond length when adsorbing NO2 gas; that is, purple phosphorus has a stronger adsorption capacity for NO2 than for N2O. Therefore, it can achieve accurate detection of NO2 over a wide concentration range and differentiate between the two nitrogen oxides. Simultaneously, purple phosphorus can stimulate electron transfer to spontaneously activate the decomposition reaction of N2O, resulting in a unique response mode for N2O, further demonstrating its application potential in the differential detection of nitrogen oxides.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] (1) Based on the strong adsorption effect of purple phosphorus on nitrogen oxides, this invention prepares purple phosphorus nanosheet channel materials of different thicknesses and applies them to field-effect transistors, which further improves the sensor's response speed, cross sensitivity, selectivity and anti-interference ability for NO2 detection.

[0040] (2) High detection sensitivity: The purple phosphorus nanosheet field-effect transistor gas sensor in this invention can achieve a response of more than 100% to 2 ppm NO2 (a response of ~50% per ppm NO2) and a response of 54.81% to 5 ppm N2O (a response of ~10% per ppm N2O). The detection limits for NO2 and N2O are 5.9 ppb and 0.788 ppb, respectively, which can realize trace detection of nitrogen oxide gas.

[0041] (3) Strong anti-interference ability: The purple phosphorus nanosheet field-effect transistor gas sensor prepared by this invention has extremely strong anti-interference ability. Selectivity tests were conducted on 9 reducing gases, 3 oxidizing gases and 6 mixed gases (which have a similar response to NO2 in mixed gas environment as to pure NO2 (22-23%)), proving that it has excellent anti-interference ability and highly competitive selectivity to NO2, and can accurately detect in complex and real atmospheric environments.

[0042] (4) Achieving the discrimination analysis of nitrogen oxides: The field-effect transistor gas sensor based on two-dimensional purple phosphorus nanosheets prepared in this invention achieved different response modes for the same concentrations of N2O and NO2 at room temperature. The sensitivities for 5ppm N2O and NO2 were 55% and 153%, respectively, meeting the requirements for the discrimination analysis of nitrogen oxides and realizing the discrimination analysis of NO. x Differentiation detection.

[0043] (5) This invention achieves rapid and efficient detection of target gases by using the strong chemical interaction between few-layer and single-layer purple phosphorus nanosheets generated by mechanical exfoliation and liquid-phase exfoliation methods and NO2. The high sensitivity of the sensor and its unique response mode to the two nitrogen oxide gases enable it to identify and detect NO2 and N2O gases in situ with a concentration range of 0.1 to 10 ppm, which helps to monitor greenhouse gas (GHG) emissions and achieve global carbon verification targets. Attached Figure Description

[0044] Figure 1 This is a scanning electron microscope image of the gold interdigitated electrode loaded with few-layer purple phosphorus nanosheets by mechanical exfoliation in Example 1.

[0045] Figure 2 This is a schematic diagram of the structure of a purple phosphorus nanosheet field-effect transistor gas sensor in Example 2;

[0046] Figure 3 This is a photograph of the interdigitated electrode in Example 2;

[0047] Figure 4 This is a comparison of the dynamic response of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor in Example 3 to different concentrations of NO2;

[0048] Figure 5 This is a graph showing the real-time response of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor to NO2 and the logarithmic relationship of the gas concentration in Example 4.

[0049] Figure 6 This is a comparison chart of the response signals of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor to different gases in Example 5;

[0050] Figure 7 The radar image shows the response signal of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor to NO2 in different interfering gases in Example 6.

[0051] Figure 8 The graph shows the response comparison of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor in Example 7 to distinguish and detect N2O and NO2.

[0052] Figure 9 This is a comparison of the dynamic response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor to 2ppm NO2 before and after annealing in Example 8.

[0053] Figure 10 This is a comparison of the dynamic response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor to 10 ppm N2O before and after annealing in Example 8.

[0054] Figure 11 The image shows the dynamic response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor in Example 9 to different concentrations of NO2.

[0055] Figure 12 The image shows the dynamic response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor in Example 9 to different concentrations of N2O.

[0056] Figure 13 The graph shows the relationship between the response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor to NO2 and its concentration in Example 10.

[0057] Figure 14 The graph shows the relationship between the response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor to N2O and its concentration in Example 10.

[0058] Figure 15 This is a comparison curve showing the response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor in Example 11 to distinguish between N2O and NO2.

[0059] Figure reference numerals:

[0060] 1-Silicon gate, 2-Silicon dioxide layer, 3-Source, 4-Phosphorus nanosheet layer, 5-Drain. Detailed Implementation

[0061] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0062] A method for fabricating a field-effect transistor gas sensor based on purple phosphorus nanosheets includes the following steps:

[0063] S1: At room temperature, place the two-dimensional purple phosphorus block crystal material on a transparent tape, fold and stick it repeatedly from both sides 5-8 times to make the material into a thinner nanosheet layer. Manually press the material retention position for 1 minute, and after standing for 5 minutes, slowly peel off the tape to transfer the few layers of purple phosphorus nanosheets to the electrode. The entire mechanical peeling material preparation process is carried out in a dry and sealed glove box filled with high-purity argon.

[0064] S2: At room temperature, sonicate a 0.2 mg / mL phosphorus dispersion in ultrapure water for 8-12 min, then spray at 0.8-1.2 μL / mm. 2 The amount of material was dropped onto the interdigitated electrode area and then dried in air at room temperature to obtain a single-layer purple phosphorus field-effect transistor sensor. The entire liquid-phase exfoliation material preparation process was carried out in a dry and sealed glove box filled with high-purity argon. Finally, the prepared purple phosphorus sensor was annealed at 200-300℃ (in argon) for 2-4 hours before use.

[0065] A field-effect transistor gas sensor based on purple phosphorus nanosheets includes a silicon gate 1, a silicon dioxide layer 2, an interdigitated electrode region, and a purple phosphorus nanosheet layer 4 arranged sequentially from bottom to top; wherein the interdigitated electrode region includes source electrodes 3 and / or drain electrodes 5 distributed in an interdigitated pattern, and adjacent source electrodes 3 and drain electrodes 5 form a set of interdigitated electrode pairs and are electrically connected through the purple phosphorus nanosheet layer 4.

[0066] Specifically, both source 3 and drain 5 are gold electrodes with an electrode width of 1.9-2.1 μm and a spacing of 1.4-1.6 μm between adjacent gold electrodes.

[0067] An application of a field-effect transistor gas sensor based on purple phosphorus nanosheets includes connecting the source 3, drain 5, and silicon gate 1 of the field-effect transistor gas sensor to a semiconductor analyzer that analyzes the electronic characteristics and sensing signals of the sensor, and then placing it in a detection gas environment. This enables accurate detection of NO2 over a wide concentration range in the atmospheric environment and the differentiation analysis of two nitrogen oxides.

[0068] During detection, when NO2 and N2O gases are introduced into the cavity equipped with the field-effect transistor gas sensor, the adsorption of nitrogen oxides by purple phosphorus causes changes in the electronic properties of the channel material. The resulting change in conductivity is reflected in the change in current between the source and drain electrodes. Purple phosphorus has a stronger adsorption capacity for NO2 than for N2O, thus enabling accurate detection of NO2 over a wide concentration range and the differentiation of the two nitrogen oxides. Simultaneously, purple phosphorus can stimulate electron transfer to activate the spontaneous decomposition reaction of N2O molecules, exhibiting different response modes to NO2 and N2O gases, thereby achieving the distinguishable detection of the two nitrogen oxides. The preferred detection concentration of nitrogen oxide gases is 0.1-10 ppm.

[0069] The sensing detection method specifically includes the following steps:

[0070] 1) The few-layer purple phosphorus field-effect transistor gas sensor, fabricated by mechanical stripping, was placed in an air atmosphere until the current between the source 3 and drain 5 stabilized; then, NO2 / air mixtures of different concentrations were introduced, and the change in current between the source 3 and drain 5 was monitored to reflect the response value R = (I0) of the field-effect transistor gas sensor to different concentrations of NO2. g -I0) / I0;

[0071] Where I0 is the stable current of the field-effect transistor gas sensor in an air atmosphere, I g The peak current of the field-effect transistor gas sensor after NO2 / air mixture is introduced;

[0072] 2) Similarly, the monolayer purple phosphorus field-effect transistor gas sensor prepared by liquid phase stripping was subjected to similar operations as in step 1). Here, different concentrations of NO2 / air mixture and N2O / air mixture were introduced into the detection environment to further explore the ability of the purple phosphorus sensor to identify and analyze nitrogen oxide gases.

[0073] The following embodiments are implemented based on the above-described technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0074] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0075] In the following embodiments, unless otherwise specified, the raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0076] Example 1

[0077] This embodiment provides a method for fabricating a field-effect transistor gas sensor based on purple phosphorus nanosheets, including process one or process two:

[0078] Process 1: Mechanical peeling method

[0079] S11: The surface of the gold interdigitated electrode is washed with acetone, isopropanol and deionized water in sequence to remove the organic layer on the surface, and then dried with high-purity argon gas.

[0080] S12: Mechanical Exfoliation: At room temperature, two-dimensional purple phosphorus bulk crystal material (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.: XF282-purple phosphorus crystal) was placed on 3M transparent tape. The tape was repeatedly folded and adhered from both sides 6 times to transform the material into a thinner nanosheet layer. The material was manually pressed at the retention position for 1 minute, and after standing for 5 minutes, the tape was slowly peeled off to transfer the few-layer purple phosphorus nanosheets to the washed gold interdigitated electrode. The entire mechanical exfoliation material preparation process was carried out in a sealed, dry glove box filled with high-purity argon. The scanning electron microscope image of the field-effect transistor gas sensor with the obtained few-layer purple phosphorus nanosheets is shown below. Figure 1 As shown;

[0081] Process 2: Liquid phase stripping method:

[0082] S21: The surface of the gold interdigitated electrode is washed with acetone, isopropanol and deionized water in sequence to remove the organic layer on the surface, and then dried with high-purity argon gas.

[0083] S22: Liquid-phase exfoliation: At room temperature, a 0.2 mg / mL phosphorus dispersion (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.: XF285-1-high concentration phosphorus dispersion) was sonicated in ultrapure water for 9 min at a sonication frequency of 46 kHz. 1 μL of the dispersion was then dropped onto the channel of the gold interdigitated electrode surface (the area of ​​the gold interdigitated electrode region is 0.1108 mm²). 2 After natural air drying, a field-effect transistor gas sensor with a single layer of purple phosphorus nanosheets was obtained. The entire liquid-phase exfoliation material preparation process was carried out in a sealed, dry glove box filled with high-purity argon. Finally, the prepared purple phosphorus sensor was annealed at 200℃ (in argon) for 2 hours before use, thus obtaining a field-effect transistor gas sensor with a single layer of purple phosphorus nanosheets.

[0084] Example 2

[0085] This embodiment provides a field-effect transistor gas sensor based on purple phosphorus nanosheets, the structure of which is as follows: Figure 2As shown, it includes a photolithography substrate (Si / SiO2 substrate) composed of a silicon gate 1 and a surface silicon dioxide layer 2, multiple source electrode pairs 3 and drain electrode pairs 5 formed on the top of the Si / SiO2 substrate using photolithography, and a purple phosphorus nanosheet layer 4 disposed in the interdigitated electrode region and used as a channel material to connect the source electrode 3 and drain electrode 5.

[0086] The silicon gate 1 has a thickness of 500 μm, the surface silicon dioxide layer 2 has a thickness of 300 nm, the source 3 and drain 5 are both gold interdigitated electrodes with a thickness of 50 nm, an electrode width L of approximately 2 μm, a spacing D between adjacent gold interdigitated electrodes of approximately 1.5 μm, a finger length of 0.8 mm, a total of 20 pairs of gold interdigitated electrodes, and an area of ​​0.1108 mm². 2 (like Figure 3 (As shown). By employing the mechanical exfoliation method and the liquid phase exfoliation method as described in Example 1, few-layer and single-layer purple phosphorus nanosheets were prepared, respectively, and used as channel materials to connect electrode pairs on corresponding materials to construct complete field-effect transistor sensors. Among them, the purple phosphorus nanosheets obtained by mechanical exfoliation have a layer thickness of approximately 7.8 nm, approximately 7 layers (1 layer is approximately 1.1 nm); the purple phosphorus nanosheets obtained by liquid phase exfoliation have a layer thickness of approximately 1.1 nm.

[0087] Example 3

[0088] This embodiment provides an application of a field-effect transistor gas sensor based on purple phosphorus nanosheets, used to evaluate the response of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor in Example 2 to different concentrations of NO2 gas (qualitative analysis). The evaluation method includes the following steps:

[0089] (1) Place the above-mentioned field-effect transistor gas sensor inside the sensor cavity, connect the source 3 and drain 5 at both ends of the gold interdigitated electrode to a semiconductor analyzer (Tektronix 2602 digital source meter) and apply a bias voltage V. ds =1V, while grounding silicon gate 1;

[0090] (2) High-purity air is introduced into the sensor cavity until the current between the source electrode 3 and the drain electrode 5 is stabilized, and the stable current I0 is recorded.

[0091] (3) High-purity air is introduced into the sensor cavity until the current between the source electrode 3 and the drain electrode 5 is stabilized at I0;

[0092] (4) Switch the high-purity air to a high-purity air / NO2 mixture of a set concentration and monitor the current I between the source electrode 3 and the drain electrode 5. ds Changes;

[0093] (5) Switch the high-purity air / NO2 mixture to high-purity air and monitor the current I between the source electrode 3 and the drain electrode 5.ds Changes;

[0094] (6) Steps (3) to (5) are repeated as one experimental stage. At the same time, the mixing ratio of high-purity air and NO2 in the mixed gas is adjusted by mass flow meter so that the NO2 concentration is constant in each experimental stage. Throughout the evaluation process, the test concentration of NO2 increases step by step (0.1 to 10 ppm).

[0095] With response value R = (I ds -I0) / I0=ΔI / I0, reflecting the sensor's response to different concentrations of NO2. The resulting real-time response-concentration comparison curve is shown in [reference needed]. Figure 4 As shown (the relative humidity of the detection environment inside the sensor cavity is 5%).

[0096] from Figure 4 As can be seen, introducing NO2 gas of different concentrations will cause the sensor's I... ds The current increases rapidly as the NO2 concentration increases. The measured response and recovery speeds of the sensor to 2ppm NO2 are 92s and 150s, respectively, with a sensitivity of approximately 26.4%. This indicates that the sensor has a fast response speed and high sensitivity, and the response value is positively correlated with the NO2 gas concentration. This suggests that the field-effect transistor gas sensor can be used for accurate detection of NO2 in a wide concentration range in the atmospheric environment.

[0097] Example 4

[0098] This embodiment specifically examines the relationship between the response of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor to different concentrations of NO2 and the gas concentration (quantitative detection) in Example 2. The specific process is as follows:

[0099] Take multiple of the above-mentioned field-effect transistor gas sensors and place them in their respective sensor cavities. Connect the source 3 and drain 5 at both ends of the gold interdigitated electrodes to a semiconductor analyzer and apply a bias voltage V. ds =1V and simultaneously ground the silicon gate 1; high-purity air is introduced into the sensor cavity, and after the signal stabilizes, the ratio of air to NO2 introduced into each cavity is controlled by a mass flow controller to keep the NO2 gas concentration in each sensor cavity at its respective set concentration (0.1~10ppm), and the current I of the two electrodes is monitored in real time. ds The changes were observed to reflect the sensor's response to different NO2 concentrations (same as in Example 3, with a relative humidity of 5% in the sensor cavity). The resulting real-time response-concentration logarithmic curves are shown below. Figure 5 As shown.

[0100] As can be seen from the figure, the response of the constructed few-layer purple phosphorus nanosheet field-effect transistor gas sensor to NO2 is linearly correlated with the logarithm of the gas concentration, with a detection limit as low as 22 ppb.

[0101] Example 5

[0102] This embodiment uses the same method as in Example 4 to examine the response of the field-effect transistor gas sensor based on few-layer purple phosphorus nanosheets from Example 2 under different gas environments. A comparative chart of the sensor's detection selectivity for three oxidizing gases (oxygen, sulfur dioxide, and nitrogen dioxide), including NO2, and nine reducing gases (ethanol, triethylamine, formaldehyde, acetone, benzene, ammonia, hydrogen, carbon dioxide, and carbon monoxide) is obtained. Figure 6 The concentration of the gas to be tested was 2 ppm, the relative humidity of the detection environment inside the sensor cavity was 5%, and the calculation method of the response value R was the same as in Example 3.

[0103] As can be seen from the figure, the sensor did not respond significantly to other selected oxidizing and reducing gases (response values ​​ranged from 1.36% to 8.43%), but the response increased significantly when NO2 was introduced (approximately 26%), which was significantly higher than the other two oxidizing gases (sulfur dioxide and oxygen). This is due to the strong adsorption effect of purple phosphorus on NO2, which indicates that the constructed few-layer purple phosphorus nanosheet field-effect transistor gas sensor has a high recognition effect on NO2.

[0104] Example 6

[0105] This embodiment uses the same method as in Embodiment 5 to examine the response of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor from Embodiment 2 under detection environments where NO2 is mixed with different interfering gases. The radar image of the sensor's response signal to NO2 in the presence of interfering gases was obtained. Figure 7 The concentration of NO2 was 2 ppm, the concentration of interfering gas was set to 0.5 ppm, the relative humidity of the detection environment inside the sensor cavity was 5%, and the calculation method for the response value R was the same as in Example 3.

[0106] As can be seen from the figure, the sensor has a similar response (22-23%) to NO2 in a mixed gas environment as it does to pure NO2, indicating that the constructed few-layer purple phosphorus nanosheet field-effect transistor gas sensor has excellent anti-interference ability and highly competitive selectivity for NO2, and can accurately detect it in complex and realistic atmospheric environments.

[0107] Example 7

[0108] This embodiment uses the same method as in Embodiment 3 to examine the response of the few-layer purple phosphorus nanosheet field-effect transistor gas sensor in Embodiment 2 under two nitrogen oxide gas environments (discrimination analysis), and obtains a comparison diagram of the sensor's response modes to NO2 and N2O. Figure 8 The gas concentration was 2 ppm, the relative humidity of the detection environment inside the sensor cavity was 5%, and the calculation method for the response value R was the same as in Example 3.

[0109] As shown in the figure, the constructed few-layer purple phosphorus nanosheet field-effect transistor gas sensor exhibited different response modes for the same concentrations of N2O and NO2, with sensitivities of 18% and 26% for N2O and NO2, respectively. This meets the requirements for the discriminative analysis of nitrogen oxides and enables the detection of NO2O. x Differentiation detection.

[0110] Example 8

[0111] This embodiment examines the dynamic response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor in Example 2 to 2ppm NO2 and 10ppm N2O gases before and after annealing to study the effect of annealing on its response. The evaluation method is the same as in Example 3.

[0112] The prepared single-layer purple phosphorus sensors were divided into two categories: one category was kept in the air environment for later use, and the other category was annealed at 300℃ (in argon) for 2 hours before use.

[0113] With response value R = (I ds -I0) / I0=ΔI / I0, reflecting the sensor's response to NO2( under different annealing conditions) Figure 9 ) and N2O ( Figure 10 The response status of the sensor cavity (the relative humidity of the detection environment is 5%).

[0114] As can be seen from the figure, the sensor's response to NO2 and N2O gases is more stable after thermal annealing than before annealing. This is mainly due to the improved contact between the purple phosphorus nanosheets and the electrode.

[0115] Example 9

[0116] This embodiment is used to evaluate the dynamic response (qualitative analysis) of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor in Example 2 to different concentrations of NO2 and N2O gases. The evaluation method is the same as in Example 3.

[0117] Throughout the evaluation process, the test concentrations of NO2 and N2O increased sequentially in stages (0.1, 0.5, 2, 5, 10 ppm).

[0118] With response value R = (I ds-I0) / I0=ΔI / I0, reflecting the sensor's response to different concentrations of NO2 ( Figure 11 ) and N2O ( Figure 12 ), Figure 12 The response is low at concentrations of 0.1ppm and 0.5ppm, with values ​​of 0.043% and 0.057% respectively, so the two curves almost overlap and are difficult to distinguish in the figure. (The relative humidity of the detection environment inside the sensor cavity is 5%).

[0119] As shown in the figure, the single-layer purple phosphorus (32-235%) sensor exhibits an order of magnitude higher response to NO2 than the multi-layer purple phosphorus (10-35%) sensor. Importantly, it also demonstrates a significant response (0.043-114%) to different concentrations of NO2 gas, with a very rapid response speed, indicating that this field-effect transistor gas sensor can be used for sensitive detection of nitrogen oxides over a wide concentration range in the atmosphere.

[0120] Example 10

[0121] This embodiment examines the relationship between the response of the monolayer purple phosphorus nanosheet field-effect transistor gas sensor in Example 2 to different concentrations of NO2 and N2O and the gas concentration (quantitative detection), and the specific process is the same as in Example 4.

[0122] The obtained real-time response-concentration fitting curve is shown in the figure. Figure 13 (NO2) and Figure 14 As shown in (N2O).

[0123] As can be seen from the figure, the constructed monolayer purple phosphorus nanosheet field-effect transistor gas sensor shows a linear correlation between the response to NO2 and the gas concentration, with a detection limit as low as 5.9 ppb; the response to N2O also shows a linear correlation with the gas concentration, with a detection limit as low as 788 ppb.

[0124] Example 11

[0125] This embodiment uses the same method as in Example 3 to examine the response of the field-effect transistor gas sensor of monolayer purple phosphorus nanosheets under two nitrogen oxide gas environments (discrimination analysis), and obtains a comparison diagram of the sensor's response modes to NO2 and N2O. Figure 15 The gas concentration was 5 ppm, the relative humidity of the detection environment inside the sensor cavity was 5%, and the calculation method for the response value R was the same as in Example 3.

[0126] As shown in the figure, the constructed monolayer purple phosphorus nanosheet field-effect transistor gas sensor exhibits different response modes for the same concentrations of N2O and NO2, with sensitivities of 55% and 153% for N2O and NO2, respectively. This meets the requirements for the discriminative analysis of nitrogen oxides and enables the detection of NO2O. x Differentiation detection.

[0127] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An application of a purple phosphorus nanosheet field-effect transistor gas sensor, characterized in that, The aforementioned purple phosphorus nanosheet field-effect transistor gas sensor is used for qualitative and / or quantitative analysis of nitrogen dioxide in the atmospheric environment, as well as for the differentiation and analysis of nitrogen dioxide and nitrous oxide gases. The gas sensor is provided with a source electrode (3) and a drain electrode (5). The gas sensor also includes a purple phosphorus nanosheet layer (4), and the source electrode (3) and the drain electrode (5) are electrically connected through the purple phosphorus nanosheet layer (4); The method for preparing the gas sensor includes: Two-dimensional purple phosphorus bulk crystal material is placed on adhesive tape and repeatedly adhered and peeled to obtain few-layer purple phosphorus nanosheets. The few-layer purple phosphorus nanosheets are then transferred to the interdigitated electrode region of a field-effect transistor to obtain a field-effect transistor gas sensor based on few-layer purple phosphorus nanosheets. The number of times the adhesive is repeatedly applied is 5-8 times; When repeatedly applying the adhesive, manually press the position where the two-dimensional purple phosphorus block crystal material is retained for 1-2 minutes, let it stand for 4-6 minutes, and then slowly peel off the tape. The thickness of the few-layer purple phosphorus nanosheets is 6-9 nm.

2. An application of a purple phosphorus nanosheet field-effect transistor gas sensor, characterized in that, The aforementioned purple phosphorus nanosheet field-effect transistor gas sensor is used for qualitative and / or quantitative analysis of nitrogen dioxide in the atmospheric environment, as well as for the differentiation and analysis of nitrogen dioxide and nitrous oxide gases. The gas sensor is provided with a source electrode (3) and a drain electrode (5). The gas sensor also includes a purple phosphorus nanosheet layer (4), and the source electrode (3) and the drain electrode (5) are electrically connected through the purple phosphorus nanosheet layer (4); The method for preparing the gas sensor includes: An ultrasonically treated phosphorus dispersion was drop-coated onto the interdigitated electrode region of a field-effect transistor. After drying, a field-effect transistor gas sensor based on a single layer of phosphorus nanosheets was obtained. The purple phosphorene dispersion was subjected to ultrasonic treatment in an ultrapure water environment for 8-12 minutes. The mass concentration of the phosphorus dispersion is 0.1-0.3 mg / mL, and the amount dropped onto the interdigitated electrode region is 0.8-1.2 µL / mm. 2 ; The prepared monolayer purple phosphorus field-effect transistor sensor was annealed at 200-300 ℃ for 2-4 h before use.

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