WO3 / MXene nanocomposite film and wireless NFC trimethylamine sensor and preparation method and application thereof

Abstract

The present invention belongs to the technical field of nanomaterial sensors, and specifically relates to a WO3 / MXene nanocomposite film and sensor, as well as a preparation method and application thereof. The WO3 is a nano-granular structure, and the MXene is a multi-layer nano-sheet structure. The WO3 nanoparticles are uniformly adhered to the interlayers or surfaces of the multi-layer MXene nanosheets, so that there are gaps between the multi-layer MXene nanosheets, providing abundant reaction sites for gas adsorption. Preparation method: synthesis of WO3 nanoparticles; synthesis of multi-layer MXene nanosheets; synthesis of WO3 / MXene composite materials. The sensor is a solution of the WO3 / MXene composite material coated on a printed interdigitated electrode to form a uniform gas-sensitive film. The sensor is applied to a wireless non-contact trimethylamine (TMA) detection device. The present invention is used to detect TMA at room temperature, and has the advantages of fast response / recovery time, good stability and selectivity, and wireless non-contact detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterial sensors, and specifically relates to a WO3 / MXene nanocomposite film and sensor, and a preparation method and application thereof. Background Art

[0002] Trimethylamine (TMA) is a colorless gas that can easily form explosive mixtures in air. It can burn or explode violently under open flames or high temperatures, producing toxic fumes during thermal decomposition, posing a significant threat to human safety. Long-term exposure to TMA can cause severe irritation to the eyes, nose, and skin, and can even affect the nervous system. Furthermore, some people are unable to metabolize TMA and instead release it through breathing, urination, and sweating, which can cause a fishy odor in their urine. This condition is known as trimethylaminuria. Testing for TMA concentration in a patient's urine can be used to determine whether they have TMA. Interestingly, fresh fish contains trimethylamine oxide. However, after the fish dies, trimethylamine oxide is reduced to trimethylamine, which is responsible for the foul odor of decaying fish. Therefore, the freshness of fish can be determined by measuring TMA concentration. When TMA concentration exceeds 10 ppm, the fish is considered to be rotten. In summary, the development of TMA gas sensors is crucial for food spoilage detection and human health monitoring.

[0003] Selecting a gas-sensitive material that is sensitive to the target gas is a key factor in the preparation of high-performance gas sensors. In recent years, gas sensors based on metal oxide semiconductors (MOS) have developed rapidly due to their low cost, simple manufacturing, high sensitivity, and fast response. Among these metal oxides, tungsten oxide (WO3), as a typical n-type semiconductor material, is widely used in gas sensing and other fields due to its fast electron mobility. The gas-sensing mechanism of WO3 is mainly attributed to the adsorption and desorption of gas molecules on its surface. In addition, the morphology of the gas-sensitive material is also an important factor affecting the performance of gas sensors. In addition to constructing various forms of the same material through different preparation methods, the overall morphology can also be adjusted by doping other materials with excellent microstructures.

[0004] Furthermore, the novel two-dimensional material MXene has shown great potential in applications such as gas sensors and nanogenerators. Recent studies have demonstrated that doping MXene significantly improves gas sensing performance. On the one hand, due to its structural characteristics, MXene can form unique morphologies with other nanomaterials, promoting gas adsorption. On the other hand, when MXene comes into contact with metal oxide semiconductors, it forms a Schottky junction, which modulates the conductivity of the sensing material and improves gas sensing performance.

[0005] Therefore, there is an urgent need for a WO3 / MXene nanocomposite film and sensor that has good response and fast response / recovery time to trimethylamine gas, as well as excellent repeatability, selectivity and long-term stability, as well as a preparation method and application thereof. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention proposes a WO3 / MXene nanocomposite film and sensor and its preparation method and application to solve the problems involved in the background technology.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a WO3 / MXene nanocomposite film, wherein the WO3 has a nanogranular structure and the MXene has a multilayer nanosheet structure. The WO3 nanoparticles are uniformly adhered to the interlayers or surfaces of the multilayer MXene nanosheets, so that there are gaps between the multilayer MXene nanosheets, providing rich reaction sites for gas adsorption.

[0008] Furthermore, the average diameter of the WO3 is about 100 nm.

[0009] The present invention also includes a method for preparing a WO3 / MXene nanocomposite film.

[0010] Synthesis of WO3 nanoparticles:

[0011] Na2WO4·2H2O was dissolved in a mixed solution containing ethylene glycol and deionized water. After cooling to room temperature, HCl was added to the solution under continuous stirring to form a yellow solution. The solution was transferred to an autoclave for reaction. After cooling to room temperature, the obtained product was washed with deionized water to remove impurities, dried, and calcined for 2 h to obtain pure yellow WO3 powder.

[0012] Synthesis of multilayer MXene nanosheets:

[0013] LiF and MAX powders were dissolved in HCl and stirred at room temperature to etch the aluminum layer. The lithium ions in the solution were washed with deionized water and ethanol. H2SO4 was added to the solution until the pH value reached 6. The product was ultrasonically treated in an ice bath and argon atmosphere. After centrifugation, a dark green supernatant of MXene was obtained.

[0014] Synthesis of WO3 / MXene composites:

[0015] WO3 powder was uniformly dispersed in deionized water to prepare a WO3 solution, and the WO3 solution and MXene solution were mixed and ultrasonically treated to obtain a WO3 / MXene composite material.

[0016] Further,

[0017] Said ①, the reaction temperature in the autoclave was 75 ℃, 12 h; drying temperature was 60 ℃, 10 h; calcination temperature was 450 ℃; HCl concentration was 12M;

[0018] In the above-mentioned step ②, the stirring reaction time is 48 hours;

[0019] Alternatively, the WO3 concentration in ③ is 0.01 g / mL.

[0020] Furthermore, the specific preparation steps include:

[0021] Synthesis of WO3 nanoparticles:

[0022] At 75°C, 0.66 g of Na2WO4·2H2O was dissolved in a mixed solution containing 10 mL of ethylene glycol and 25 mL of deionized water. After cooling to room temperature, 2.5 mL of 12.0 M HCl was added to the above solution under continuous stirring to form a yellow solution. The above solution was transferred to a 100 mL autoclave and heat-treated at 75°C for 12 h. After cooling to room temperature, the obtained product was washed with deionized water to remove impurities and then dried at 60°C for 10 h. Finally, it was calcined at 450°C for 2 h at a heating rate of 1°C / min to obtain pure yellow WO3 powder.

[0023] Synthesis of multilayer MXene nanosheets:

[0024] 2 g each of LiF and MAX powder was dissolved in 30 mL of 9 M HCl and stirred at room temperature for 48 hours to etch the aluminum layer. The lithium ions in the solution were washed with deionized water and ethanol. 2 M H2SO4 was added to the above solution until the pH value reached 6. The product was sonicated in an ice bath and argon atmosphere for 1 hour. After centrifugation at 3500 rpm for 1 hour, a dark green supernatant of MXene was obtained.

[0025] Synthesis of WO3 / MXene composites:

[0026] For the WO3 / MXene composites, the WO3 solution was prepared by uniformly dispersing 0.05 g of WO3 powder in 5 mL of deionized water, and the WO3 solution and 1 mL of MXene solution were mixed and ultrasonicated for 1 h to obtain the WO3 / MXene composites.

[0027] The present invention also includes a sensor based on a WO3 / MXene nanocomposite film, wherein a solution of the WO3 / MXene composite material is coated on a Cu / Ni printed interdigital electrode to form a uniform gas-sensitive film.

[0028] Further,

[0029] When the sensor is exposed to TMA, a large number of electrons will be released. During this process, the concentration of majority carriers will increase, resulting in a decrease in the resistance of the gas sensor. Due to the addition of MXene with a multilayer structure, WO3 nanoparticles obtain more attachment points, providing more reaction sites for gas reactions. The uniform distribution of WO3 nanoparticles between the layers and on the surface of the multilayer MXene nanosheets can provide a larger specific surface area, which is conducive to the diffusion and reaction of TMA on the sensor surface. MXene has conductive properties similar to those of metals. When in contact with WO3, a Schottky junction will be formed at the interface of WO3 and MXene, and electrons will be transferred from MXene to WO3. When TMA is introduced, more electrons will be released and the electron accumulation layer will become thicker, thereby reducing the resistance of the gas sensor and improving the response value of the sensor.

[0030] The present invention also includes a method for preparing a WO3 / MXene nanocomposite thin film sensor.

[0031] The solution of WO3 / MXene composite material was coated on the Cu / Ni printed interdigital electrode by spin coating to form a uniform gas-sensitive film. The prepared gas sensor was then dried at 60 °C for 4 h to enhance stability.

[0032] The present invention also includes the application of sensors based on WO3 / MXene nanocomposite films,

[0033] The sensor is applied to a wireless non-contact TMA detection device.

[0034] Further,

[0035] The TMA detection device includes a detection end and a target end, with an Arduino microcontroller as the controller;

[0036] The detection end is powered by a lithium-ion battery and includes a wireless power coil, an NFC data transmission module, and an OLED screen;

[0037] The target end is arranged in a closed gas environment and is provided with the sensor;

[0038] The detection end supplies power to the target end through a wireless coil, calls a sensor to detect the gas concentration in the current environment, and transmits the sensor data to the detection end through the NFC coil. When the detection end is far away from the target end, the target end has no power and is in a non-working state, and the display of the detection end shows "No device!". When the detection end approaches the target end, the target end is powered by the wireless power supply and starts working, detecting the concentration of trimethylamine gas in the environment and transmitting the data to the detection end for display.

[0039] The benefits of the WO3 / MXene nanocomposite film and sensor of the present invention, as well as their preparation methods and applications are as follows:

[0040] This invention fabricates a chemiresistive gas sensor based on a WO3 / MXene thin film for detecting TMA at room temperature. It exhibits fast response / recovery times and a high response (277.78) to 10 ppm TMA. It also exhibits good stability and selectivity. Because TMA has a pungent odor, which increases the difficulty of detecting it, this application proposes a wireless, contactless detection device based on near-field communication (NFC) that can detect TMA gas in a closed environment. The detection terminal does not require a power source; the detector only needs to operate outside a closed gas environment to monitor gas concentrations within it. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The manufacturing process of the sensor according to the embodiment of the present invention is as follows;

[0042] Figure 2 It is a sensor experimental test platform according to an embodiment of the present invention;

[0043] Figure 3 This is the SEM image of the WO3 / MXene film of the embodiment of the present invention:

[0044] Figure 4 (a) XRD patterns of pure WO3, pure MXene and WO3 / MXene films according to the present invention;

[0045] (b) is the measured spectrum of the WO3 / MXene film according to an embodiment of the present invention;

[0046] (c) C 1s spectrum of WO3 / MXene film according to an embodiment of the present invention;

[0047] (d) is the O 1s spectrum of the WO3 / MXene film according to an embodiment of the present invention;

[0048] (e) Ti 2p spectrum of WO3 / MXene film according to an embodiment of the present invention;

[0049] (f) W 4f spectrum of WO3 / MXene film according to an embodiment of the present invention;

[0050] Figure 5 (a) Resistance value of the gas sensor of WO3 / MXene film according to an embodiment of the present invention;

[0051] (b) Response of the WO3 / MXene thin film gas sensor under different TMA concentrations according to an embodiment of the present invention;

[0052] (c) Response of the pure WO3 gas sensor according to an embodiment of the present invention at different TMA concentrations of 1-10 ppm;

[0053] (d) Comparison of the responses of the gas sensors based on pure WO3 and WO3 / MXene thin films at 1-5 ppm TMA concentration according to an embodiment of the present invention;

[0054] (e) is the response concentration fitting curve of the gas sensor based on pure WO3 and WO3 / MXene film in the embodiment of the present invention;

[0055] (f) Response / recovery characteristic curves of the gas sensor based on pure WO3 and WO3 / MXene thin films to 2 ppm TMA in an embodiment of the present invention;

[0056] Figure 6 (a) Effects of different relative humidity (11-85% RH) on sensor performance according to an embodiment of the present invention;

[0057] (b) Long-term stability of the WO3 / MXene-based gas sensor according to an embodiment of the present invention when exposed to 2, 3, and 4 ppm TMA;

[0058] (c) Repeatability test of the WO3 / MXene-based gas sensor according to an embodiment of the present invention;

[0059] (d) Selectivity test of the WO3 / MXene-based gas sensor according to an embodiment of the present invention for various interfering gases;

[0060] Figure 7 (a) Schematic diagram of the sensing mechanism of the WO3 / MXene film exposed to air according to an embodiment of the present invention;

[0061] (b) Schematic diagram of the sensing mechanism of the WO3 / MXene film exposed to TMA according to an embodiment of the present invention;

[0062] (c) is the energy band structure diagram of the WO3 / MXene film exposed to air according to an embodiment of the present invention;

[0063] (d) is the energy band structure diagram of the WO3 / MXene film exposed to TMA according to an embodiment of the present invention;

[0064] Figure 8 This is a structural diagram of a wireless non-contact trimethylamine gas detection device according to an embodiment of the present invention;

[0065] Figure 9 (a) is the non-working state of the device according to the embodiment of the present invention (the target end is far away from the detection end);

[0066] (b) is the working state of the device according to the embodiment of the present invention (the target end is close to the detection end);

[0067] Figure 10 This is a block diagram of the gas-sensing characteristic test of the sensor according to the embodiment of the present invention;

[0068] Figure 11 This is a structural block diagram of a wireless trimethylamine gas detection device according to an embodiment of the present invention;

[0069] Figure 12 This is a circuit diagram of a wireless trimethylamine gas detection device according to an embodiment of the present invention; DETAILED DESCRIPTION

[0070] The specific implementation is further described below with reference to the accompanying drawings. Example 1:

[0071] WO3 / MXene nanocomposite film, Figure 3 The SEM image of WO3 / MXene film. Due to the negative charge of MXene and the positive charge of WO3, WO3 nanoparticles can be evenly adhered to the interlayer or surface of multilayer MXene nanosheets, and obvious gaps can be observed, providing rich reaction sites for gas adsorption, such as Figure 3 (ab) as shown. Figure 3 As shown in (cd), WO3 shows a nanogranular structure with an average diameter of about 100 nm, and MXene shows a multilayer nanosheet structure.

[0072] The crystal phase of the prepared samples was determined by XRD analysis. The XRD patterns of pure WO3, pure MXene and WO3 / MXene films are shown in Figure 2. Figure 4 (a) The three characteristic peaks of WO3 are located at 22.92 o , 23.48 o and 24.23 o The 2θ of MXene corresponds to the (002), (020) and (200) planes, which matches the standard diffraction card JCPDS 43-1035. The characteristic peaks of MXene appear at 6 o This indicates that pure WO3 and pure MXene were successfully synthesized. For the XRD pattern of WO3 / MXene film, all characteristic peaks of WO3 and MXene can be observed, which proves the successful preparation of WO3 / MXene film.

[0073] The elemental composition and chemical state of the samples were analyzed by XPS. The measured spectrum of WO3 / MXene film is as follows: Figure 4 As shown in (b), this confirms the presence of W, O, C, and Ti elements in the WO3 / MXene film. Figure 4(c) shows the XPS spectrum of C 1s, which shows that four characteristic peaks appear at 281.97 eV, 284.85 eV, 286.32 eV, and 288.95 eV, corresponding to the c-Ti, cc, cO, and Oc=O bonds in MXene, respectively. Figure 4 (d) shows the XPS spectrum of O 1s. The three characteristic peaks appear at 530.00 eV, 531.60 eV, and 533.59 eV, corresponding to lattice oxygen (O L ), vacancy oxygen (O V ) and chemically adsorbed oxygen (O C ).exist Figure 4 In (e), the six characteristic peaks of Ti 2p are located at 454.11 eV, 455.01 eV, 457.57 eV, 459.53 eV, 460.52 eV, and 462.98 eV, corresponding to Ti-C 2p 3 / 2 、Ti(II)2p 3 / 2 、Ti(III)2p 3 / 2 、Ti-C 2p 1 / 2 、Ti(II)2p 3 / 2 、Ti(III)2p 3 / 2 The XPS spectrum of W 4f is as follows: Figure 4 As shown in (f), two peaks appear at 35.60 eV and 37.80 eV, which are attributed to W 4f 7 / 2 and W 4f 5 / 2 This indicates that the W element is at a valence of +6.

[0074] A method for preparing WO3 / MXene nanocomposite film:

[0075] Synthesis of WO3 nanoparticles: First, 0.66 g of Na2WO4·2H2O was dissolved in a mixture containing 10 mL of ethylene glycol and 25 mL of deionized water at 75°C. After cooling to room temperature, 2.5 mL of 12.0 M HCl was added to the solution with continuous stirring, forming a yellow solution. The solution was then transferred to a 100 mL autoclave and heat-treated at 75°C for 12 h. After cooling to room temperature, the resulting product was washed with deionized water to remove impurities and then dried at 60°C for 10 h. Finally, it was calcined at 450°C for 2 h at a heating rate of 1°C / min to obtain pure yellow WO3 powder.

[0076] Synthesis of multilayer MXene nanosheets: For MXene (Ti3C2T x ) synthesis, Ti3C2T xThe aqueous dispersion was obtained by etching Ti3AlC2 using LiF-HCl. First, 2 grams each of LiF and MAX powder were dissolved in 30 mL of 9 M HCl and stirred at room temperature for 48 hours to etch the aluminum layer. The lithium ions in the solution were cleaned with deionized water and ethanol. 2 M H2SO4 was added to the above solution until the pH reached 6. The product was sonicated in an ice bath and argon atmosphere for 1 hour. Finally, after centrifugation at 3500 rpm for 1 hour, a dark green supernatant of MXene was obtained.

[0077] Synthesis of WO3 / MXene composites: For the WO3 / MXene composites, a WO3 solution was prepared by uniformly dispersing 0.05 g of WO3 powder in 5 mL of deionized water. Next, the WO3 solution and 1 mL of MXene solution were mixed and sonicated for 1 h to obtain the WO3 / MXene composites. Example 2:

[0078] Sensor based on WO3 / MXene nanocomposite film: A solution of the WO3 / MXene composite material is coated on a Cu / Ni printed interdigital electrode to form a uniform gas-sensitive film.

[0079] Preparation method of sensor based on WO3 / MXene nanocomposite film: Spin coating is used to apply the WO3 / MXene composite material solution on the Cu / Ni printed interdigital electrode to form a uniform gas-sensitive film. The prepared gas sensor is then dried at 60°C for 4 hours to enhance stability. The manufacturing process of TMA gas sensor based on WO3 / MXene film is as follows: Figure 1 shown.

[0080] The experimental test platform of gas sensor for TMA sensing is as follows Figure 2 The prepared gas sensor was placed in a homemade test chamber. TMA was mixed with dry air via a mass flow controller to achieve a TMA concentration of 1-10 ppm. The sensor was connected to a Keysight 34470A to measure resistance at 25°C and 23% relative humidity.

[0081] Trimethylamine gas-sensing mechanism of the sensor:

[0082] TMA sensing mechanism of WO3 / MXene-based gas sensor Figure 7As shown in Figure 2, WO3 is a typical n-type semiconductor, with electrons as the primary charge carriers. During the adsorption and desorption of gas molecules, the WO3 / MXene material itself does not participate in the reaction. The gas-sensing properties of the sensor are primarily due to the oxygen ions on the surface of the gas-sensing material. Therefore, the gas-sensing mechanism in this work is essentially the change in resistance of the gas sensor when gas molecules adsorb or desorb on the surface of the gas-sensing material. Figure 7 (a) Schematic diagram showing the gas sensing mechanism when the gas sensor is placed in air. The reaction process can be explained by the following formula:

[0083] O2(gas) → O2(ads) (2)

[0084] O2(ads)+e - → O2 - (ads) (3)

[0085] 4(CH3)3N + 21O2 - (ads) → 2N2+ 12CO2 + 18H2O + 21e - (4)

[0086] like Figure 7 As shown in (b), when the sensor is exposed to TMA, a large number of electrons will be released. During this process, the concentration of majority carriers will increase, resulting in a decrease in the resistance of the gas sensor. This is consistent with the phenomenon that the resistance of the sensor shows a decrease with increasing TMA concentration during the test. In addition, there may be two reasons why MXene-doped WO3 has better sensor properties. First, due to the addition of MXene with a multilayer structure, WO3 nanoparticles (which could originally only be arranged on a plane) obtain more attachment points, providing more reaction sites for gas reactions. The uniform distribution of WO3 nanoparticles between the layers and on the surface of the multilayer MXene nanosheets can provide a larger specific surface area, which is obviously beneficial to the diffusion and reaction of TMA on the sensor surface. Secondly, the work function of MXene is 4.7 eV and the work function of WO3 is 5.25 eV. Since MXene has conductive properties similar to those of metals, when in contact with WO3, the interface of WO3 and MXene will form a Schottky junction, and electrons will be transferred from MXene to WO3 ( Figure 7 When TMA is introduced, more electrons are released and the electron accumulation layer becomes thicker, thereby reducing the resistance of the gas sensor and improving the sensor's response value.

[0087] The trimethylamine sensing characteristics of the sensor are:

[0088] Resistance changes of WO3 / MXene-based gas sensors at different TMA concentrations. Figure 5As shown in (a), the basic resistance of the gas sensor in air is about 90.9 MΩ. As the TMA concentration increases, the resistance of the sensor shows a clear downward trend. In order to study the gas sensing performance of the TMA gas sensor based on WO3 / MXene, the sensor response is defined as the sensor resistance in air (R a ) and the sensor resistance in the gas (R g ). The expression is shown in formula (1):

[0089] Response = R a / R g (1)

[0090] The responses of WO3 / MXene-based gas sensors at different TMA concentrations are shown in Figure 2. Figure 5 As shown in (b). With the increase of TMA concentration, the sensor response increases significantly. The corresponding response values ​​for 1, 2, 3, 4 and 5 ppm TMA concentrations are 1.96, 3.99, 10.07, 13.55 and 24.77, respectively. When the gas concentration increases to 10 ppm, the response value can reach 277.78. Compared with the WO3 / MXene-based gas sensor, the response of the pure WO3-based gas sensor at different TMA concentrations is shown in Figure 2. Figure 5 (c) As shown. The response of pure WO3-based gas sensor to TMA is relatively low. When the TMA concentration increases to 10 ppm, the response value only reaches 16.9. The response comparison of WO3 / MXene-based gas sensor and pure WO3-based gas sensor is shown in Figure 5 As shown in (d), the response of WO3 / MXene-based gas sensors is significantly higher than that of pure WO3-based gas sensors. The response concentration fitting curves of gas sensors based on pure WO3 and WO3 / MXene films are shown in Figure 5 (e) are shown as Y=0.04089e (X / 1.69187) +1.78103 and Y=2.39258e (X / 2.11357) -1.45849. The fitting coefficients are 0.99982 and 0.99993 respectively. Figure 5 (f) shows the response / recovery characteristics of gas sensors based on pure WO3 and WO3 / MXene film to 2 ppm TMA. Compared with the pure WO3-based gas sensor, the WO3 / MXene-based gas sensor has a faster response / recovery time of 2 s / 3 s.

[0091] In addition, since the gas sensor works at room temperature, we need to consider the effect of humidity on its gas sensing performance. The effect of different relative humidity (11-85%RH) on the sensor response was studied. Figure 6As shown in (a), as the relative humidity increases, the resistance of the WO3 / MXene-based gas sensor decreases accordingly, and the response also decreases. Therefore, humidity compensation may be required in practical applications to eliminate the humidity effect. In addition, the stability of the sensor is also an important indicator in practical applications. Through long-term stability tests and repeatability tests, we found that the prepared gas sensor has good stability. Figure 6 As shown in (b), after 30 days of testing every five days, the response of the gas sensor has almost no change. The repeatability of the gas sensor was tested by switching between air and 1ppm TMA four times. The response of the sensor can be completely restored to the initial state, indicating that the sensor has good repeatability ( Figure 6 (c)). Figure 6 (d) shows the selectivity of the gas sensor for five different gases (trimethylamine, ammonia, ethanol, nitrogen dioxide, and methane) at a concentration of 2 ppm. The results show that the gas sensor has the highest response value for TMA, indicating that the sensor has good selectivity for TMA. The WO3 / MXene-based gas sensor has a significant advantage in TMA sensing.

[0092] When detecting TMA at room temperature, the WO3 / MXene thin film gas sensor exhibits a higher response than the pure WO3-based gas sensor. This phenomenon is attributed to the unique morphology of the WO3 / MXene film and the formation of a Schottky junction between WO3 and MXene. Example 3:

[0093] The application of a sensor based on WO3 / MXene nanocomposite film is applied to a wireless non-contact TMA detection device. The wireless non-contact detection device also realizes the function of obtaining the gas concentration in the air chamber outside the closed air chamber, and has obvious application prospects.

[0094] Usually, TMA has a strong fishy smell, and the detector needs to wear a gas mask to detect in the TMA environment, which makes the detection difficult and inconvenient. Therefore, we developed a wireless non-contact TMA detection device, such as Figure 8 As shown in the figure, this device, based on the principles of wireless charging and NFC data transmission, consists of a detection end and a target end, with an Arduino microcontroller as the controller. The detection end is powered by a lithium-ion battery, making it convenient for mobile detection. It features a wireless power coil and NFC data transmission module for powering the target device and reading data. A 0.96-inch OLED screen displays current operating status and sensor data.

[0095] The target end is designed to be power-free and can be placed in a closed gas environment. It is equipped with the above-mentioned integrated TMA gas sensor. When the detection end is close to the target end, the detection end supplies power to the target end through the wireless coil, and calls the sensor to detect the gas concentration in the current environment. At the same time, the sensor data is transmitted to the detection end through the NFC coil. The working status of the device is as follows: Figure 9 As shown. When the detection end is far away from the target end ( Figure 9 (a)), the target end has no power and is in a non-working state, and the display of the detection end shows "No device!" When the detection end approaches the target end, the target end is powered by the wireless power supply and starts working, detecting the concentration of trimethylamine gas in the environment and transmitting the data to the detection end for display. Figure 9 (b) Shows the currently detected sensor resistance value and TMA concentration. Figure 10 Sensor gas-sensing characteristics test block diagram. Figure 11 This is the structural block diagram of the trimethylamine gas wireless detection equipment. Figure 12 This is the circuit diagram of the trimethylamine gas wireless detection device.

[0096] The device's innovation and excellence lies in its wireless, non-contact detection, offering unique advantages for detecting gases in specific confined environments. To use this device, the target terminal is simply placed within the confined environment, and the detector performs detection by holding the detector terminal outside the gas environment, close to the target terminal. The gas to be measured is introduced into a closed chamber, and the detector approaches the target terminal through the chamber wall to obtain information on the gas concentration within the chamber.

[0097] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a wireless NFC trimethylamine sensor containing a WO3 / MXene nanocomposite film, characterized by: In the WO3 / MXene nanocomposite film, WO3 has a nanoparticle structure and MXene has a multilayer nanosheet structure. The WO3 nanoparticles are evenly adhered to the interlayers or surfaces of the multilayer MXene nanosheets, creating gaps between the multilayer MXene nanosheets, providing abundant reaction sites for gas adsorption. The average diameter of the WO3 is 100 nm. The preparation method comprises: ①Synthesis of WO3 nanoparticles: At 75°C, 0.66 g of Na2WO4·2H2O was dissolved in a mixed solution containing 10 mL of ethylene glycol and 25 mL of deionized water. After cooling to room temperature, 2.5 mL of 12.0 M HCl was added to the above solution under continuous stirring to form a yellow solution. The above solution was transferred to a 100 mL autoclave and heat-treated at 75°C for 12 h. After cooling to room temperature, the obtained product was washed with deionized water to remove impurities and then dried at 60°C for 10 h. Finally, it was calcined at 450°C for 2 h at a heating rate of 1°C / min to obtain pure yellow WO3 powder. ②Synthesis of multilayer MXene nanosheets: 2 g each of LiF and MAX powder was dissolved in 30 mL of 9 M HCl and stirred at room temperature for 48 hours to etch the aluminum layer. The lithium ions in the solution were washed with deionized water and ethanol. 2 M H2SO4 was added to the above solution until the pH value reached 6. The product was sonicated in an ice bath and argon atmosphere for 1 hour. After centrifugation at 3500 rpm for 1 hour, a dark green supernatant of MXene was obtained. ③Synthesis of WO3 / MXene composite materials: For WO3 / MXene composites, WO3 solution was prepared by uniformly dispersing 0.05 g WO3 powder in 5 mL deionized water, and the WO3 solution and 1 mL MXene solution were mixed and ultrasonicated for 1 h to obtain WO3 / MXene composites; ④ The solution of WO3 / MXene composite material was coated on the Cu / Ni printed interdigital electrode by spin coating to form a uniform gas-sensitive film. The prepared gas sensor was then dried at 60°C for 4 hours to enhance stability.

2. A wireless NFC trimethylamine sensor containing a WO3 / MXene nanocomposite film, wherein the wireless NFC trimethylamine sensor is prepared according to the method of claim 1.

3. The wireless NFC trimethylamine sensor containing WO3 / MXene nanocomposite film according to claim 2, characterized in that: When the sensor is exposed to TMA, a large number of electrons will be released. During this process, the concentration of majority carriers will increase, resulting in a decrease in the resistance of the gas sensor. Due to the addition of MXene with a multilayer structure, WO3 nanoparticles obtain more attachment points, providing more reaction sites for gas reactions. The uniform distribution of WO3 nanoparticles between the layers and on the surface of the multilayer MXene nanosheets can provide a larger specific surface area, which is conducive to the diffusion and reaction of TMA on the sensor surface. MXene has conductive properties similar to those of metals. When in contact with WO3, a Schottky junction will be formed at the interface of WO3 and MXene, and electrons will be transferred from MXene to WO3. When TMA is introduced, more electrons will be released and the electron accumulation layer will become thicker, thereby reducing the resistance of the gas sensor and improving the response value of the sensor.

4. Application of a wireless NFC trimethylamine sensor containing a WO3 / MXene nanocomposite film according to any one of claims 2 to 3, characterized in that: The sensor is applied to a wireless non-contact TMA detection device.

5. The use of a wireless NFC trimethylamine sensor containing a WO3 / MXene nanocomposite film according to claim 4, characterized in that: The TMA detection device includes a detection end and a target end, with an Arduino microcontroller as the controller; The detection end is powered by a lithium-ion battery and includes a wireless power coil, an NFC data transmission module, and an OLED screen; The target end is arranged in a closed gas environment and is provided with the sensor; The detection end supplies power to the target end through a wireless coil, calls a sensor to detect the gas concentration in the current environment, and transmits the sensor data to the detection end through the NFC coil. When the detection end is far away from the target end, the target end has no power and is in a non-working state, and the display of the detection end shows "No device!". When the detection end approaches the target end, the target end is powered by the wireless power supply and starts working, detecting the concentration of trimethylamine gas in the environment and transmitting the data to the detection end for display.

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