MXene composite sensor and preparation and application thereof, detection device and application thereof, and ammonia gas detection method

Abstract

The invention belongs to the technical field of gas sensors, and provides an MXene composite sensor and preparation and application thereof, a detection device and application thereof, and an ammonia gas detection method. According to the MXene composite sensor disclosed by the invention, a composite material formed by a conductive polymer (PEDOT: PSS) and MXene is taken as a sensitive film, and the binding force between the conductive polymer and MXene in the sensitive film is strong, so that the detection accuracy of the sensor is improved; functional groups such as-O and-OH are arranged on the surface of MXene, ammonia gas can be adsorbed, the interlayer spacing of MXene is increased by adding PEDOT: PSS, more active adsorption sites can be exposed, ammonia gas adsorption or ammonia gas desorption is accelerated, the response time and recovery time of the sensor are shortened, and the detection sensitivity is improved. Meanwhile, even under the condition of high humidity, the conductive polymer and the MXene are still well combined together, so that the humidity adaptability of the sensor is high.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a MXene composite sensor and its preparation and application, a detection device and its application, and an ammonia detection method. Background Art

[0002] Ammonia (NH3) is a key food and safety indicator, and its monitoring is crucial. Long-term exposure to high concentrations of NH3 can cause adverse effects such as skin irritation, eye damage, and respiratory distress. Consuming foods containing high concentrations of ammonia and biogenic amines can also cause adverse reactions such as headaches and hypotension. Furthermore, with the increasing importance of ammonia in respiratory disease diagnosis and environmental monitoring, the development of ammonia monitoring technology has become a key interdisciplinary research area.

[0003] In terms of gas sensing, MXene materials have quickly become a research hotspot due to their high affinity for gas molecules and rapid response capabilities. x MXene-based sensors have shown promise in gas sensing applications.

[0004] However, the existing Ti3C2T x The accuracy of MXene sensor detection is low. Summary of the Invention

[0005] In view of this, the present invention aims to provide a MXene composite sensor and its preparation and application, a detection device and its application, and an ammonia detection method. The MXene composite sensor provided by the present invention has high detection accuracy.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a MXene composite sensor, comprising interdigital electrodes and a sensitive film attached to the interdigital electrodes, wherein the material of the sensitive film is a conductive polymer / MXene composite material; The conductive polymer in the conductive polymer / MXene composite material is PEDOT:PSS.

[0007] Preferably, the MXene in the conductive polymer / MXene composite material is Ti3C2T x MXene; In the conductive polymer / MXene composite material, the mass ratio of MXene to conductive polymer is 1:(0.5-8); The thickness of the sensitive film is 5-20 μm.

[0008] Preferably, the parameters of the interdigital electrodes include: thickness of 2-20 μm, specification of 10-15 pairs of fingers, finger width of 50-80 μm, and finger spacing of 50-80 μm; The material of the interdigital electrodes is aluminum, gold, copper or silver.

[0009] Preferably, it further comprises a substrate, the interdigital electrodes are attached to the substrate, the substrate is a flexible substrate, and the material of the flexible substrate is polyimide, polyester resin or polydimethylsiloxane.

[0010] The present invention also provides a method for preparing the MXene composite sensor described in the above technical solution, comprising the following steps: A mixed system containing a conductive polymer and MXene is applied to an interdigitated electrode, and sequentially dried and oxidized to obtain the MXene composite sensor.

[0011] Preferably, in the mixed system containing the conductive polymer and MXene, the concentration of MXene is 0.1-1 mg / mL; The application method is drip coating; The drying comprises sequentially performing pre-drying and vacuum drying; The pre-drying temperature is 80-120°C and the time is 1-5 minutes; The vacuum drying pressure is -0.04~-0.08MPa, the temperature is 50~90℃, and the time is 1~2h; The oxidation time is 6 to 12 hours.

[0012] The present invention also provides a detection device, comprising a sensor, wherein the sensor is the MXene composite sensor described in the above technical solution or the MXene composite sensor prepared by the preparation method described in the above technical solution.

[0013] Preferably, it also includes an external power supply, a signal conditioning circuit, a main control and a terminal system.

[0014] The present invention also provides the use of the MXene composite sensor described in the above technical solution, or the MXene composite sensor prepared by the preparation method described in the above technical solution, or the detection device described in the above technical solution in ammonia detection.

[0015] The present invention also provides an ammonia detection method, comprising the following steps: Place the gas to be measured in contact with the sensor, wait until it reaches the saturation value, then introduce air, wait for the sensor to recover, and obtain the response value; Substituting the response value and humidity into a preset GA-BP humidity compensation neural network model to obtain a predicted ammonia concentration in the gas to be measured; The establishment parameters of the preset GA-BP humidity compensation neural network model include: the number of nodes in the input layer is 3, and the data in the input layer includes humidity, actual ammonia concentration and response value; the number of nodes in the output layer is 1, and the data in the output layer is the predicted ammonia concentration; The sensor is the MXene composite sensor described in the above technical solution, or the MXene composite sensor prepared by the preparation method described in the above technical solution, or the sensor in the detection device described in the above technical solution.

[0016] The present invention provides a MXene composite sensor.

[0017] The sensor provided by the present invention utilizes a composite material formed from a conductive polymer (PEDOT:PSS) and MXene as its sensitive film. The conductive polymer and MXene in this sensitive film strongly bond, improving the sensor's detection accuracy. The MXene surface has functional groups such as -O and -OH, which can adsorb ammonia. The addition of PEDOT:PSS increases the interlayer spacing of the MXene, exposing more active adsorption sites and accelerating ammonia adsorption and desorption. This shortens the sensor's response and recovery times, improving detection sensitivity. Furthermore, the conductive polymer and MXene maintain good bonding even in high humidity conditions. Therefore, the resulting sensor has strong humidity adaptability and maintains high accuracy and a long lifespan even in environments with a certain humidity.

[0018] Furthermore, the present invention uses a flexible substrate as a base, has strong flexibility, can be directly combined with clothes, skin, etc. to construct a wearable device, is easy to install, facilitates large-scale production and has a wide range of application scenarios.

[0019] The MXene composite sensor provided by the present invention has the following advantages: 1. The MXene composite sensor provided by the present invention has a sensitive film including PEDOT:PSS and MXene attached to the interdigital electrodes. It has a simple structure and is of great significance for the promotion of the sensor in the field of gas sensors.

[0020] 2. The MXene composite sensor of the present invention has a good correlation between its response value to ammonia and gas concentration. It has the advantages of sensitive gas response, low detection limit and wide detection range, which makes the sensor a basis for application in food safety, environmental monitoring and health monitoring.

[0021] 3. The MXene composite sensor of the present invention can maintain almost unchanged response value to low-concentration ammonia within 30 days, and the sensing detection process is repeatable, which can achieve long-term and stable detection of ammonia.

[0022] The present invention also provides a method for preparing the MXene composite sensor described in the above technical solution. The present invention adopts an in-situ polymerization method to attach a PEDOT:PSS / MXene composite material to the interdigital electrodes, and the preparation method is simple.

[0023] The present invention also provides a detection device, which has a small size.

[0024] The present invention also provides an ammonia detection method. The ammonia detection method of the present invention utilizes a preset GA-BP humidity compensation neural network model. GA-BP learns the response of the sensor under different humidity conditions, models the influence of humidity on the sensor, counteracts the interference of environmental variables, achieves accurate compensation for the influence of humidity, and improves the accuracy of the detection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the MXene composite sensor provided by the present invention; Figure 2 The preparation process and device diagram of the MXene composite sensor provided by the present invention; Figure 3 A system block diagram of the detection device provided by the present invention; Figure 4 This is the test process and device diagram for the sensor used solely for ammonia detection; Figure 5 Schematic diagram of the GA-BP humidity compensation neural network model; Figure 6 SEM image of the cross section of PEDOT:PSS / MXene composite material; Figure 7 XPS characterization images of MXene, PEDOT:PSS and PEDOT:PSS / MXene composites; Figure 8 EDS characterization of PEDOT:PSS / MXene composites; Figure 9 This is a physical picture of the MXene composite sensor obtained in Example 1; Figure 10 The test results of the MXene composite sensor obtained in Example 1 under different ammonia concentrations; Figure 11 This is the sensitivity curve of the MXene composite sensor obtained in Example 1; Figure 12 Response time and recovery time of the MXene composite sensor obtained in Example 1 under 50 ppm ammonia; Figure 13This is a comparison chart of the predicted and actual ammonia concentrations of the ammonia mixed gas optimized by the GA-BP humidity compensation neural network model under different concentrations and humidity conditions; Figure 14 This is the sensitive mechanism of the MXene composite sensor provided by the present invention in air and ammonia. DETAILED DESCRIPTION

[0026] The present invention provides a MXene composite sensor, comprising interdigital electrodes and a sensitive film attached to the interdigital electrodes, wherein the material of the sensitive film is a conductive polymer / MXene composite material; The conductive polymer is PEDOT:PSS.

[0027] Figure 1 This is a schematic diagram of the structure of the MXene composite sensor provided by the present invention, Figure 1 The structure of the MXene composite sensor provided by the present invention is described in detail.

[0028] The MXene composite sensor provided by the present invention includes interdigital electrodes. In the present invention, the parameters of the interdigital electrodes include: the thickness is preferably 2 to 20 μm, specifically preferably 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm; the specification is preferably 10 to 15 pairs of fingers, specifically preferably The interdigital electrodes are preferably 10, 11, 12, 13, 14, or 15 pairs of fingers; the finger width is preferably 50-80 μm, more preferably 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm; the interdigital spacing is preferably 50-80 μm, more preferably 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm. In the present invention, the material of the interdigital electrodes is preferably a conductive material, and the material of the interdigital electrodes is further preferably aluminum (Al), gold (Au), copper (Cu), or silver (Ag), more preferably copper (Cu).

[0029] The MXene composite sensor provided by the present invention includes a sensitive film attached to the interdigital electrode, and the thickness of the sensitive film is preferably 5~20μm, specifically preferably 5μm, 10μm, 15μm or 20μm. In the present invention, the material of the sensitive film is a conductive polymer / MXene composite material. In the present invention, the conductive polymer in the conductive polymer / MXene composite material is PEDOT:PSS, and the weight average molecular weight Mw of the PEDOT:PSS is preferably 70000~90000. In the present invention, the MXene in the conductive polymer / MXene composite material is preferably a single-layer MXene; the MXene is specifically preferably Ti3C2T x MXene. In the conductive polymer / MXene composite material, the mass ratio of MXene to conductive polymer is preferably 1:(0.5-8), more preferably 1:(2-6), and more preferably 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, or 1:8. In the present invention, gas contact with the sensitive film causes a resistance effect in the sensitive film, which is used for gas concentration detection.

[0030] The MXene composite sensor provided by the present invention preferably further includes a substrate, the interdigitated electrodes are preferably attached to the substrate, the substrate is preferably a flexible substrate, and the material of the flexible substrate is preferably polyimide (PI), polyester resin or polydimethylsiloxane (PDMS).

[0031] In the present invention, the operating temperature of the MXene composite sensor is preferably 20-30°C, specifically preferably 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C.

[0032] In the present invention, the MXene composite sensor is preferably a resistive semiconductor sensor.

[0033] The present invention also provides a method for preparing the MXene composite sensor described in the above technical solution, comprising the following steps: A mixed system containing a conductive polymer and MXene is applied to an interdigitated electrode, and sequentially dried and oxidized to obtain the MXene composite sensor.

[0034] Figure 2 The preparation process and device diagram of the MXene composite sensor provided by the present invention are shown below. Figure 2 The preparation process of the present invention is described in detail.

[0035] In the present invention, the interdigitated electrodes are preferably prepared by chemical deposition, lithographic printing, screen printing, or inkjet printing. The present invention does not impose any specific restrictions on the parameters of the chemical deposition, lithographic printing, screen printing, or inkjet printing, as long as the interdigitated electrodes of the target size can be obtained.

[0036] In the present invention, in the mixed system containing a conductive polymer and MXene, the concentration of MXene is preferably 0.1 to 1 mg / mL, specifically preferably 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.36 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL.

[0037] In the present invention, the method for preparing the mixed system containing a conductive polymer and MXene preferably comprises the following steps: mixing a conductive polymer dispersion and a MXene dispersion, and sequentially performing magnetic stirring and ultrasonic dispersion to obtain the mixed system containing a conductive polymer and MXene.

[0038] In the present invention, the concentration of the conductive polymer dispersion is preferably 4-6 mg / mL, specifically preferably 4 mg / mL, 5 mg / mL, or 6 mg / mL; the solvent of the conductive polymer dispersion is preferably one or more of water and ethanol. In the present invention, the method for preparing the conductive polymer dispersion preferably includes the following steps: diluting a commercially available conductive polymer system and ultrasonically dispersing it (referred to as the first ultrasonic dispersion) to obtain the conductive polymer dispersion. In the present invention, the concentration of the commercially available conductive polymer system is preferably 1-1.5 wt%, specifically preferably 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, or 1.5 wt%; the diluent for dilution preferably includes one or more of water and ethanol; and the first ultrasonic dispersion is preferably performed for 15 minutes.

[0039] In the present invention, the concentration of the MXene dispersion is preferably 0.5-2.5 mg / mL, specifically preferably 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, 2 mg / mL, or 2.5 mg / mL. The solvent of the MXene dispersion is preferably one or more of water, ethanol, and methanol. In the present invention, the method for preparing the MXene dispersion preferably includes the following steps: dispersing the MXene in a solvent and ultrasonically dispersing it (referred to as the second ultrasonic dispersion) to obtain the MXene dispersion. In the present invention, the solvent is preferably water, more preferably deionized water; and the second ultrasonic dispersion is preferably performed for 15 minutes.

[0040] In the present invention, the magnetic stirring speed is preferably 500-900 rpm, more preferably 500 rpm, 600 rpm, 700 rpm, 800 rpm, or 900 rpm; the time is preferably 0.5-1.5 hours, more preferably 1 hour. In the present invention, the ultrasonic dispersion power is preferably 70-90 W, more preferably 70 W, 75 W, 80 W, 85 W, or 90 W; the time is preferably 1-2 hours, more preferably 1.5 hours.

[0041] In the present invention, the application method is preferably drop coating. The present invention does not impose any specific limitation on the amount of drop coating, as long as a sensitive film of corresponding thickness can be obtained.

[0042] In the present invention, the drying preferably includes sequentially performing pre-drying and vacuum drying.

[0043] In the present invention, the pre-drying temperature is preferably 80-120°C, specifically 80°C, 90°C, 100°C, 110°C, or 120°C; the pre-drying time is preferably 1-5 minutes, specifically 1 minute, 2 minutes, 3 minutes, 4 minutes, or 5 minutes. In the present invention, the pre-drying is preferably carried out under normal pressure and air atmosphere. In the present invention, the pre-drying is preferably carried out on a heating table.

[0044] In the present invention, the vacuum drying pressure is preferably -0.04~-0.08MPa, specifically preferably -0.04MPa, -0.05MPa, -0.06MPa, -0.07MPa or -0.08MPa; the temperature is preferably 50~90℃, specifically preferably 50℃, 60℃, 70℃, 80℃ or 90℃; the time is 1~2h, specifically preferably 1h, 1.5h or 2h; the vacuum drying is preferably carried out in a vacuum drying oven.

[0045] In the present invention, the oxidation is preferably carried out at room temperature and pressure in an air atmosphere. In the present invention, the oxidation time is preferably 6 to 12 hours, specifically preferably 6 hours, 8 hours, 10 hours or 12 hours. In the present invention, the oxidation is preferably carried out in an oven.

[0046] In the present invention, the oxidation can oxidize the surface of the sensitive film. When the device is exposed to air, oxygen molecules capture electrons in the conduction band of the PEDOT:PSS / MXene composite material and adsorb onto the surface of the PEDOT:PSS / MXene composite material to form oxygen anions (O2 − (ads)). The trapped electrons will be released back to the surface and recombine with holes, resulting in a decrease in hole carrier concentration and therefore an increase in resistance.

[0047] The present invention also provides a detection device, comprising a sensor, wherein the sensor is the MXene composite sensor described in the above technical solution or the MXene composite sensor prepared by the preparation method described in the above technical solution.

[0048] Figure 3 This is a system block diagram of the detection device provided by the present invention, Figure 3 The detection device provided by the present invention is described in detail.

[0049] The detection device provided by the present invention includes a sensor, which is the MXene composite sensor described in the above technical solution or the MXene composite sensor prepared by the preparation method described in the above technical solution.

[0050] The detection device provided by the present invention preferably also includes an external power supply, a signal conditioning circuit, a main control and a terminal system.

[0051] In the present invention, the external power supply is used to supply power to the sensor, signal conditioning circuit and main control respectively. In a specific embodiment of the present invention, the voltage of the external power supply is preferably 3.3V.

[0052] In the present invention, the signal conditioning circuit preferably includes an amplifier, an amplification factor selection and a 16-bit ADC.

[0053] In the present invention, the main control preferably includes a chip, preferably a Bluetooth chip, preferably a CH573F model; the CH573F preferably integrates BLE Bluetooth functionality and a UART interface. In the present invention, the chip's communication protocol is preferably IIC. In the present invention, the CH573F is used as the main control, which has low power consumption, a small size, and is easy to carry. It can also wirelessly transmit sensor signals to a terminal display. This not only improves the portability and real-time performance of detection, but also enables remote monitoring.

[0054] In the present invention, the terminal system preferably includes a computer or a mobile phone.

[0055] In the present invention, the sensor is connected to the signal conditioning circuit and the main control in sequence. In the present invention, the sensor and the signal conditioning circuit, and the signal conditioning circuit and the main control are preferably connected via wires.

[0056] In the present invention, the main control and the mobile phone are preferably connected wirelessly via BLE Bluetooth; the main control and the computer are preferably connected wired via a UART interface.

[0057] In the present invention, the signal conditioning circuit and the main control preferably adopt arc serpentine wiring and grid copper. In the present invention, the signal conditioning circuit and the main control adopt arc serpentine wiring and grid copper, which can make the flexible circuit board not easy to break and can be used for a long time.

[0058] In the present invention, since the MXene composite sensor is a resistive semiconductor sensor, and the resistance value of the resistive semiconductor sensor varies in a relatively large range of 100Ω~1MΩ; in order to ensure the reliability of the detection signal transmission of the MXene composite sensor, it is necessary to select the amplification factor according to the initial resistance. The signal conditioning circuit can amplify, filter, and collect the voltage signal, and the ammonia concentration can be accurately measured by the change in voltage. In the present invention, the voltage range after conditioning by the signal conditioning circuit is preferably 0~2.5V. The output signal after conditioning by the signal conditioning circuit is sampled by the ADC and then transmitted to the main control via the IIC communication protocol; the output signal is preferably an analog voltage signal. In the present invention, when the MXene composite sensor is placed in ammonia with a changing concentration, the main control calculates the real-time sensitivity of the MXene composite sensor based on the change in the collected voltage signal.

[0059] The detection device provided by the present invention can realize the wireless sensing performance of NH3, and has the functions of signal acquisition, conditioning, processing, wireless transmission, etc.; and is simple, portable and low in power consumption.

[0060] The present invention also provides the use of the MXene composite sensor described in the above technical solution, or the MXene composite sensor prepared by the preparation method described in the above technical solution, or the detection device described in the above technical solution in ammonia detection.

[0061] In the present invention, the fields of ammonia detection preferably include meat freshness detection, farm environment monitoring, respiratory health monitoring, wearable devices, chronic kidney disease detection devices and smart packaging.

[0062] The MXene composite sensor and detection device provided by the present invention provide a convenient and efficient solution for food quality assurance, disease diagnosis and environmental monitoring.

[0063] The present invention also provides an ammonia detection method, comprising the following steps: Place the gas to be measured in contact with the sensor, wait until it reaches the saturation value, then introduce air, wait for the sensor to recover, and obtain the response value; Substituting the response value and humidity into a preset GA-BP humidity compensation neural network model to obtain a predicted ammonia concentration in the gas to be measured; The establishment parameters of the preset GA-BP humidity compensation neural network model include: the number of nodes in the input layer is 3, and the data in the input layer includes humidity, actual ammonia concentration and response value; the number of nodes in the output layer is 1, and the data in the output layer is the predicted ammonia concentration; The sensor is the MXene composite sensor described in the above technical solution, or the MXene composite sensor prepared by the preparation method described in the above technical solution, or the sensor in the detection device described in the above technical solution.

[0064] The present invention brings the gas to be measured into contact with the sensor, waits for the gas to reach a saturation value, introduces air, waits for the sensor to recover, and obtains a response value.

[0065] In the present invention, the flow rate of the gas to be measured is preferably 100-500 sccm, and specifically preferably 100 sccm, 200 sccm, 300 sccm, 400 sccm or 500 sccm.

[0066] In the present invention, the sensor is the MXene composite sensor described in the above technical solution, or the MXene composite sensor prepared by the preparation method described in the above technical solution, or the sensor in the detection device described in the above technical solution. In the present invention, the sensor is the MXene composite sensor described in the above technical solution, or the MXene composite sensor prepared by the preparation method described in the above technical solution, or the sensor in the detection device described in the above technical solution.

[0067] In the present invention, when the sensor is used alone, it is preferred to place the sensor on an in-situ hot and cold analysis table in the test chamber, and adjust the test time and operating temperature. In the present invention, the test process and device diagram of the sensor used alone for ammonia detection are as follows: Figure 4 shown.

[0068] In the present invention, the operating temperature of the MXene composite sensor is preferably 20-30°C, specifically preferably 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C.

[0069] In the present invention, the humidity of the gas to be measured is preferably obtained by conventional technical means.

[0070] After obtaining the response value and humidity of the gas to be measured, the present invention substitutes the response value and humidity into a preset GA-BP humidity compensation neural network model to obtain the predicted concentration of ammonia in the gas to be measured.

[0071] In the present invention, the establishment parameters of the preset GA-BP humidity compensation neural network model include: the number of nodes in the input layer is 3, and the data of the input layer includes humidity, actual ammonia concentration and response value; the number of nodes in the output layer is 1, and the data of the output layer is the predicted ammonia concentration.

[0072] In the present invention, during the construction of the preset GA-BP humidity compensation neural network model, sensor output data response values ​​of a known ammonia gas mixture under different concentrations and humidity conditions are collected; multiple measurements are performed, and the response values ​​and the actual ammonia concentration are recorded to form a data set. The input data includes the response value, humidity, and the actual ammonia concentration, and the number of nodes in the input layer is determined to be 3. The output data is the predicted concentration of ammonia after compensation, and the number of nodes in the output layer is determined to be 1. The data containing the response value, humidity, and the actual ammonia concentration is fused through the GA-BP humidity compensation neural network model to obtain the preset GA-BP humidity compensation neural network data set.

[0073] In the present invention, the schematic diagram of the GA-BP humidity compensation neural network model is as follows Figure 5 As shown. A multi-parameter compensation method using the GA-BP humidity compensation neural network model is used for humidity compensation. In the present invention, the GA-BP humidity compensation neural network model combines the optimization capability of the genetic algorithm and the learning ability of the back propagation neural network, which can effectively improve the accuracy of the detection method under different humidity conditions.

[0074] In the present invention, a genetic algorithm-optimized back propagation neural network (GA-BP) learns the sensor's response under different humidity conditions, models the influence of humidity on the sensor, combats the interference of environmental variables, achieves accurate compensation for the influence of humidity, and improves the accuracy of the ammonia detection method.

[0075] The following detailed description of the MXene composite sensor provided by the present invention, its preparation and application, the detection device and its application, and the ammonia detection method are provided in conjunction with the embodiments. However, they should not be construed as limiting the scope of protection of the present invention.

[0076] Example 1 A MXene composite sensor 1) Two-dimensional material single layer Ti3C2T xMXene was dispersed in deionized water and ultrasonically dispersed for 15 minutes to obtain a MXene dispersion with a concentration of 0.5 mg / mL; a commercially available conductive polymer PEDOT:PSS (weight-average molecular weight of 70,000-90,000) system (concentration of 1.2 wt%) was diluted with deionized water and ultrasonically dispersed for 15 minutes to obtain a conductive polymer dispersion with a concentration of 5 mg / mL; 2 mL of 0.5 mg / mL MXene dispersion and 0.8 mL of 5 mg / mL conductive polymer solution were mixed according to a mass ratio of MXene to PEDOT:PSS of 1:4, and the mixture was magnetically stirred at 600 rpm for 1 hour, and then ultrasonicated at 75 W for 1.5 hours to obtain a mixed system containing conductive polymer and MXene, wherein the MXene concentration was 0.36 mg / mL.

[0077] 2) Using a pipette, 60 μL of the mixed system containing the conductive polymer and MXene obtained in step 1) was drop-coated onto an interdigitated electrode (10 μm thick, 15 pairs of fingers, 70 μm wide, 70 μm between fingers, and made of copper) and heated on a heating table at 80°C for 2 min. The device was then placed in a vacuum oven and heated at -0.05 MPa and 80°C for 1.5 h to obtain a device in which the thickness of the sensitive film was 10 μm.

[0078] 3) The device was placed under normal temperature, pressure and air conditions for 12 hours to obtain a MXene composite sensor.

[0079] Figure 6 is the SEM image of the cross section of the PEDOT:PSS / MXene composite material, as shown in Figure 6 As shown in the figure, pure MXene is stacked more tightly, and the addition of PEDOT:PSS increases the interlayer spacing of MXene, making the sensor more responsive to gas; the greater the change in response resistance, the easier it is to detect and the better the detection effect.

[0080] Figure 7 XPS characterization diagrams of MXene, PEDOT:PSS and PEDOT:PSS / MXene composite materials. Figure 7 As shown in the figure, the position and peak intensity of S2p and PEDOT:PSS do not change much, the position of Ti2p is the same as that of MXene, but the peak intensity becomes weaker, which is due to the doping of MXene in PEDOT:PSS.

[0081] Figure 8 EDS characterization of PEDOT:PSS / MXene composites. Figure 8 As shown, C, Ti, S, O and F elements are evenly distributed, among which the Ti element comes from MXene and the S element comes from PEDOT:PSS.

[0082] Figure 9 This is a physical picture of the obtained MXene composite sensor.

[0083] use Figure 4 The test system shown is used to test the MXene composite sensor obtained in Example 1, including the following steps: 1) Place the MXene composite sensor on the in-situ hot and cold analysis table in the test chamber and adjust the test time (2250s) and operating temperature (25°C). 2) Use a gas mixer to adjust ammonia and air to the required ammonia concentration (2ppm, 5ppm, 10ppm, 15ppm, 25ppm, 50ppm or 100ppm) and humidity (40RH%); 3) A mixed ammonia gas with a certain humidity was introduced into the test chamber at a flow rate of 500 sccm. When the saturation value was reached, the gas was switched back to the air environment, and the resistance of the MXene composite sensor returned to its initial state.

[0084] The results are as follows Figure 10 As shown by Figure 10 It can be seen that with the increase of NH3 concentration, the response of MXene composite sensor shows a monotonically increasing trend, and its lower detection limit can reach 2ppm and its upper limit can reach 1000ppm.

[0085] The sensitivity curve is drawn by recording the response of the MXene composite sensor at different ammonia concentrations, such as Figure 11 As shown in the figure, the sensitivity data can be divided into two linear intervals (0~100ppm and 100~1000ppm). By analyzing the sensitivity curve and calculating the detection limit (LOD) of the MXene composite sensor: LOD=3RMS / k, the calculated RMS is 0.56. Therefore, the theoretical LOD of the MXene composite sensor is 600ppb, which is even lower than the average threshold of human exhalation (960ppb).

[0086] The response time and recovery time of the MXene composite sensor to 50ppm NH3 at room temperature were tested. The response time and recovery time are the time required for the MXene composite sensor to reach 90% of the resistance change under adsorption and desorption conditions, respectively. The results are as follows: Figure 12 As shown. Figure 12 As shown in the figure, the MXene composite sensor exhibits fast response and recovery speed (101s / 40s).

[0087] Establishment of GA-BP humidity compensation neural network model: use Figure 4Collect sensor output data response values ​​for a known ammonia mixture under different concentrations and humidity conditions, perform multiple measurements, and record the response values. Combine the humidity, response values, and actual ammonia concentration to form a dataset. The input data includes humidity, actual ammonia concentration, and response values, so the number of nodes in the input layer is 3. The output data is the predicted ammonia concentration, so the number of nodes in the output layer is 1.

[0088] The comparison chart of the predicted and actual concentrations of ammonia gas mixtures optimized by the GA-BP humidity compensation neural network model under different concentrations and humidity conditions is as follows: Figure 13 As shown, Figure 13 In the figure, the upper figure is the training set prediction result diagram, and the lower figure is the test set prediction result diagram; Figure 13 The results show that after compensation using the GA-BP humidity compensation neural network model, the sensor's performance under different humidity conditions is significantly improved. The MXene composite sensor's response signal stability and accuracy are enhanced, making ammonia concentration measurements more reliable.

[0089] The reason why the present invention uses PEDOT:PSS / MXene composite material as the sensitive film is that when the sensor is exposed to air, oxygen molecules capture electrons in the conduction band of the PEDOT:PSS / MXene composite material and adsorb onto the surface of the PEDOT:PSS / MXene composite material to form oxygen anions (O2 − (ads)). The captured electrons will be released back to the surface and recombine with holes, resulting in a decrease in hole carrier concentration and therefore an increase in resistance. After the introduction of the target molecule (i.e., NH3), the adsorbed NH3(g) reacts with O2 − (ads) reaction, releasing electrons back to the composite conduction band. Therefore, the sensor resistance decreases as the width of the electron depletion layer decreases. After the absorbed NH3 is replaced by air, the surface of the PEDOT:PSS / MXene composite material is restored by O2(ads), restoring the resistance of the sensor to its initial value. The sensitive mechanism diagram is as follows Figure 14 shown.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A MXene composite sensor, characterized in that: It includes interdigital electrodes and a sensitive film attached to the interdigital electrodes, wherein the material of the sensitive film is a conductive polymer / MXene composite material; The conductive polymer in the conductive polymer / MXene composite material is PEDOT:PSS.

2. The MXene composite sensor according to claim 1, characterized in that The MXene in the conductive polymer / MXene composite material is Ti3C2T x MXene; In the conductive polymer / MXene composite material, the mass ratio of MXene to conductive polymer is 1:(0.5-8); The thickness of the sensitive film is 5-20 μm.

3. The MXene composite sensor according to claim 1, characterized in that The parameters of the interdigital electrodes include: thickness of 2-20 μm, specification of 10-15 pairs of fingers, finger width of 50-80 μm, and finger spacing of 50-80 μm; The material of the interdigital electrodes is aluminum, gold, copper or silver.

4. The MXene composite sensor according to claim 1, characterized in that It also includes a substrate, the interdigital electrodes are attached to the substrate, the substrate is a flexible substrate, and the material of the flexible substrate is polyimide, polyester resin or polydimethylsiloxane.

5. The method for preparing the MXene composite sensor according to any one of claims 1 to 4, characterized in that: The following steps are involved: A mixed system containing a conductive polymer and MXene is applied to an interdigitated electrode, and sequentially dried and oxidized to obtain the MXene composite sensor.

6. The preparation method according to claim 5, characterized in that In the mixed system containing the conductive polymer and MXene, the concentration of MXene is 0.1-1 mg / mL; The application method is drip coating; The drying comprises sequentially performing pre-drying and vacuum drying; The pre-drying temperature is 80-120°C and the time is 1-5 minutes; The vacuum drying pressure is -0.04~-0.08MPa, the temperature is 50~90℃, and the time is 1~2h; The oxidation time is 6 to 12 hours.

7. A detection device, characterized in that: The invention comprises a sensor, wherein the sensor is the MXene composite sensor according to any one of claims 1 to 4 or the MXene composite sensor prepared by the preparation method according to any one of claims 5 to 6.

8. The detection device according to claim 7, characterized in that It also includes external power supply, signal conditioning circuit, main control and terminal system.

9. Use of the MXene composite sensor according to any one of claims 1 to 4, or the MXene composite sensor prepared by the preparation method according to any one of claims 5 to 6, or the detection device according to any one of claims 7 to 8 in ammonia detection.

10. A method for detecting ammonia, characterized in that: The following steps are involved: Place the gas to be measured in contact with the sensor, wait until it reaches the saturation value, then introduce air, wait for the sensor to recover, and obtain the response value; Substituting the response value and humidity into a preset GA-BP humidity compensation neural network model to obtain a predicted ammonia concentration in the gas to be measured; The establishment parameters of the preset GA-BP humidity compensation neural network model include: the number of nodes in the input layer is 3, and the data in the input layer includes humidity, actual ammonia concentration and response value; The number of nodes in the output layer is 1, and the data in the output layer is the predicted concentration of ammonia; The sensor is the MXene composite sensor according to any one of claims 1 to 4, or the MXene composite sensor prepared by the preparation method according to any one of claims 5 to 6, or the sensor in the detection device according to any one of claims 7 to 8.

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