MXene / ZnO nanocomposite, preparation method and application thereof

Abstract

This invention belongs to the field of nanosensing and gas monitoring technology, and discloses an MXene / ZnO nanocomposite material, its preparation method, and its application. First, Ti3AlC2 is etched with hydrochloric acid and lithium fluoride to obtain multilayer two-dimensional MXene, which is then ultrasonically exfoliated and freeze-dried to obtain few-layer MXene. After alkalization treatment, the few-layer MXene is centrifuged and washed to obtain a composite structure of 1D / 2D-MXene. The 1D / 2D-MXene and zinc acetate dihydrate are added to a mixed solution of water and ethanol for a hydrothermal reaction. After centrifugation, washing, and vacuum drying, a multi-level 1D / 2D-MXene / 0D-ZnO nanocomposite structure composed of 0D-ZnO, 1D-MXene, and 2D-MXene is obtained. This multidimensional nanocomposite structure is suitable for preparing gas sensors for detecting low concentrations of nitrogen dioxide gas at room temperature. The nanocomposite material and sensor prepared by this invention exhibit excellent gas-sensing performance for nitrogen dioxide gas, with high sensitivity, enabling room temperature detection and showing great application potential.

Description

Technical Field

[0001] This invention belongs to the field of nanosensing and gas monitoring technology, specifically, it relates to a nano-zinc oxide microsphere and a novel Ti3C2T x Nanofiber composite materials and their preparation methods are disclosed. These composite materials can be used to detect extremely low concentrations (ppb level) of nitrogen dioxide gas at room temperature. Background Technology

[0002] Compared to other gas sensors, metal-oxide-semiconductor (MOS) sensors have been widely studied due to their advantages such as simple synthesis, high sensitivity, and low cost. However, MOS sensors typically operate at high temperatures, which not only requires higher energy consumption but also significantly reduces the sensor's stability and lifespan, and poses a fire hazard. Therefore, improving the gas sensing performance of MOS sensors at room temperature is a major challenge in the field of gas sensing.

[0003] Transition metal carbide MXene (Ti3C2T) x Accordion-like materials are a new type of two-dimensional layered material with unique physical properties such as a distinctive accordion-like shape, high specific surface area, and excellent mechanical properties. They also possess unique electronic properties such as high conductivity, high signal-to-noise ratio, and a variety of tunable surface functional groups. However, their practical applications are limited by problems such as easy oxidation in air and stacking between layers, which lead to low sensitivity and poor durability. Summary of the Invention

[0004] This invention addresses the technical problems of existing semiconductor metal oxide sensors, such as high operating temperature, insufficient sensitivity, high detection limit, and poor gas selectivity. It provides an MXene / ZnO nanocomposite material, its preparation method, and its application for detecting extremely low concentrations (ppb level) of nitrogen dioxide gas at room temperature.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] According to a first aspect of the present invention, an MXene / ZnO nanocomposite material is provided, which is obtained by the following preparation method:

[0007] S1. Under water bath conditions, Ti3AlC2 was etched in a mixed solution of hydrochloric acid and lithium fluoride. After the reaction, the sample was centrifuged, washed, and vacuum dried to obtain a multilayer two-dimensional MXene (Ti3C2T). x );

[0008] S2, The ultrasonic exfoliation is: ultrasonically exfoliating the powder obtained in S1 and freeze-drying it to obtain a few-layer MXene;

[0009] S3. The powder obtained in S2 is subjected to alkalization treatment;

[0010] S4. The powder obtained in S3 is centrifuged, washed and vacuum dried to obtain a composite structure 1D / 2D-MXene with one-dimensional MXene grown in situ on the surface of two-dimensional MXene.

[0011] S5. Add the powder obtained in S4 and zinc acetate dihydrate to a mixed solution of water and ethanol for hydrothermal reaction.

[0012] S6. The powder obtained in S5 is centrifuged, washed, and vacuum dried to obtain a multi-level 1D / 2D-MXene / 0D-ZnO nanocomposite structure composed of 0D-ZnO, 1D-MXene, and 2D-MXene.

[0013] According to a second aspect of the present invention, a method for preparing MXene / ZnO nanocomposite materials is provided, comprising:

[0014] S1. Under water bath conditions, Ti3AlC2 was etched in a mixed solution of hydrochloric acid and lithium fluoride. After the reaction, the sample was centrifuged, washed, and vacuum dried to obtain a multilayer two-dimensional MXene (Ti3C2T). x );

[0015] S2. The powder obtained in S1 is ultrasonically exfoliated and freeze-dried to obtain few-layer MXene;

[0016] S3. The powder obtained in S2 is subjected to alkalization treatment;

[0017] S4. The powder obtained in S3 is centrifuged, washed and vacuum dried to obtain a composite structure 1D / 2D-MXene with one-dimensional MXene grown in situ on the surface of two-dimensional MXene.

[0018] S5. Add the powder obtained in S4 and zinc acetate dihydrate to a mixed solution of water and ethanol for hydrothermal reaction.

[0019] S6. The powder obtained in S5 is centrifuged, washed, and vacuum dried to obtain a multi-level 1D / 2D-MXene / 0D-ZnO nanocomposite structure composed of 0D-ZnO, 1D-MXene, and 2D-MXene.

[0020] Regarding the above-mentioned multi-level 1D / 2D-MXene / 0D-ZnO nanocomposite structures and their preparation methods:

[0021] Preferably, in S1, the water bath conditions are constant temperature at 50-80°C and stirring at 300-600 rpm.

[0022] Preferably, in S1, the concentration of hydrochloric acid is 7-10 mol / L.

[0023] Preferably, in S1, the mass ratio of Ti3AlC2 to lithium fluoride is 1:1.6 to 2.0.

[0024] Preferably, in S1, the etching reaction time is 24–36 h.

[0025] Preferably, in S2, the multilayer MXene is dispersed in deionized water and ultrasonically exfoliated for 30-60 minutes under a water bath at 50-80°C to obtain a few-layer MXene.

[0026] Preferably, in S3, the alkalization treatment involves adding a small layer of MXene to a 10–12 mol / L KOH solution and continuously stirring at 300–500 rpm for 18–30 hours under a water bath at 50–80°C.

[0027] Preferably, in S5, the mass ratio of 1D / 2D-MXene to zinc acetate is 1:(0.1~1.2).

[0028] Preferably, in step S5, the volume ratio of water to ethanol in the mixed solution is 1:(40-60).

[0029] Preferably, in step S5, the hydrothermal reaction is carried out in a polytetrafluoroethylene beaker under high pressure and closed environment, and kept at 110-160°C for 6-12 hours.

[0030] According to a third aspect of the present invention, an application of the above-described multilayer 1D / 2D-MXene / 0D-ZnO nanocomposite material is provided for the detection of low concentrations of nitrogen dioxide gas at room temperature.

[0031] According to a fourth aspect of the present invention, a gas sensor for detecting low concentrations of nitrogen dioxide at room temperature is provided, using the aforementioned multilayer 1D / 2D-MXene / 0D-ZnO nanocomposite material as the gas-sensitive material.

[0032] The beneficial effects of this invention are:

[0033] (I) This invention prepares a zinc oxide and 1D / 2D-MXene multidimensional composite material by combining liquid phase etching, alkali treatment and hydrothermal method. This material can detect extremely low concentrations (ppb level) of nitrogen dioxide gas at room temperature, which overcomes the disadvantage of traditional semiconductor metal oxide sensors that require high temperature operation, significantly reduces energy consumption, improves the stability and service life of the sensor, and reduces safety hazards.

[0034] (II) This invention effectively solves the problem of secondary stacking of existing MXene sheets by growing one-dimensional 1D-MXene in situ on the surface of two-dimensional 2D-MXene, thereby increasing the specific surface area of ​​the gas-sensitive response. At the same time, by growing zero-dimensional 0D-ZnO quantum dots in situ in the interlayer network structure of the 1D / 2D-MXene composite structure through hydrothermal method, the gas-sensitive sensitivity is significantly improved, ensuring the high room temperature response characteristics and long-term stability of the sensor in practical applications.

[0035] (III) By optimizing the preparation process parameters, such as controlling the amount of 1D / 2D-MXene, the concentration of zinc acetate, and the hydrothermal temperature, this invention achieves the effective composite of 0D-ZnO and 1D / 2D-MXene nanostructures, forming a multi-level nanocomposite structure with synergistic effect, which improves the sensitivity and response speed of the sensor.

[0036] (iv) The composite material prepared by this invention has excellent gas selectivity, has a specific recognition ability for nitrogen dioxide gas, and can effectively filter the influence of other interfering gases, thus ensuring the accuracy and reliability of the detection results.

[0037] (v) The preparation method of the present invention is simple and controllable, easy to operate, easy to scale up production, and has good repeatability and reproducibility, meeting the needs of industrial applications. Attached Figure Description

[0038] Figure 1 The zinc oxide microspheres of this invention and the novel Ti3C2T x Flowchart of nanofiber fabrication and its gas sensor;

[0039] Figure 2 This is a comparison of the responses of gas sensors prepared from the samples obtained in Examples 1-6 and Comparative Examples 1-2 to the same concentration of nitrogen dioxide gas under the same conditions.

[0040] Figure 3 The continuous dynamic response-recovery curves of 2D-MXene, 1D / 2D-MXene, and 1D / 2D-MXene / 0D-ZnO nanocomposite structures to different concentrations of nitrogen dioxide gas are shown.

[0041] Figure 4 Linear fitting relationship between the response of the gas sensor prepared from the 1D / 2D-MXene / 0D-ZnO nanocomposite structure (Example 5) to different concentrations of nitrogen dioxide gas (0.5-50ppm) and the gas concentration;

[0042] Figure 5Dynamic response-recovery curve of a gas sensor prepared from the sample of the 1D / 2D-MXene / 0D-ZnO nanocomposite structure (Example 5) to 8 ppm nitrogen dioxide gas at room temperature;

[0043] Figure 6 A gas sensor prepared from the sample of the 1D / 2D-MXene / 0D-ZnO nanocomposite structure (Example 5) is shown in a five-cycle sensitivity test of 10 ppm nitrogen dioxide gas at room temperature.

[0044] Figure 7 The graph shows the selectivity test results of 2D-MXene, 1D / 2D-MXene, and 1D / 2D-MXene / 0D-ZnO nanocomposite structures against various gases at 50 ppm at room temperature.

[0045] Figure 8 Long-term stability test graph of the gas sensor prepared from the sample obtained by 1D / 2D-MXene / 0D-ZnO nanocomposite structure (Example 5);

[0046] Figure 9 A schematic diagram illustrating the principle of a gas sensor for detecting nitrogen dioxide gas prepared from a sample obtained from a 1D / 2D-MXene / 0D-ZnO nanocomposite structure (Example 5). Detailed Implementation

[0047] The specific implementation of the present invention will be described in more detail below with reference to the accompanying drawings and embodiments, so as to better understand the solution of the present invention and the advantages of its various aspects. It should be noted that the specific implementation methods and embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0048] Figure 1 The zinc oxide microspheres of this invention and the novel Ti3C2T x The fabrication process of nanofibers and their gas sensors is shown in the following diagrams: Figure a shows the process of preparing few-layer 2D-MXene from raw material MAX (Ti3AlC2) through liquid phase etching and ultrasonic exfoliation; Figure b shows the process of preparing 1D / 2D-MXene from few-layer 2D-MXene through alkali treatment and then hydrothermally synthesizing 1D / 2D-MXene / 0D-ZnO nanocomposite structure with zinc acetate under appropriate conditions; Figure c shows the assembly of the sensing element and the gas-sensing test process.

[0049] like Figure 1 As shown, this invention provides a 1D / 2D-MXene / 0D-ZnO nanocomposite structure and its preparation method, comprising:

[0050] S1. Under water bath conditions, Ti3AlC2 was etched in a mixed solution of hydrochloric acid and lithium fluoride. After the reaction, the sample was centrifuged, washed, and vacuum dried to obtain a multilayer two-dimensional MXene (Ti3C2T). x ).

[0051] In some preferred embodiments of the present invention, the water bath conditions are constant temperature at 50-80°C and stirring at a speed of 300-600 rpm.

[0052] In some preferred embodiments of the present invention, the concentration of hydrochloric acid is 7-10 mol / L.

[0053] In some preferred embodiments of the present invention, the mass ratio of Ti3AlC2 to lithium fluoride is 1:1.6 to 2.0.

[0054] In some preferred embodiments of the present invention, the etching reaction time is 24 to 36 hours.

[0055] S2. The powder obtained in S1 is ultrasonically exfoliated and freeze-dried to obtain few-layer MXene.

[0056] In some preferred embodiments of the present invention, ultrasonic exfoliation involves dispersing multiple layers of MXene in deionized water and ultrasonically exfoliating them for 30 to 60 minutes in a water bath at 50 to 80°C.

[0057] S3. The powder obtained in S2 is subjected to alkalization treatment.

[0058] In some preferred embodiments of the present invention, the alkalization treatment involves adding a few layers of MXene to a 10–12 mol / L KOH solution and stirring continuously at 300–500 rpm for 18–30 hours under a water bath at 50–80°C.

[0059] S4. The powder obtained in S3 is centrifuged, washed, and vacuum dried to obtain a composite structure 1D / 2D-MXene with one-dimensional MXene grown in situ on the surface of two-dimensional MXene.

[0060] S5. Add the powder obtained in S4 and zinc acetate dihydrate to a mixed solution of water and ethanol for hydrothermal reaction.

[0061] In some preferred embodiments of the present invention, the mass ratio of 1D / 2D-MXene to zinc acetate is 1:(0.1 to 1.2).

[0062] In some preferred embodiments of the present invention, the volume ratio of water to ethanol in the mixed solution is 1:(40-60).

[0063] In some preferred embodiments of the present invention, the hydrothermal reaction is carried out in a polytetrafluoroethylene beaker under high pressure and closed environment, and kept at 110-160°C for 6-12 hours.

[0064] S6. The powder obtained in S5 is centrifuged, washed, and vacuum dried to obtain a multi-level 1D / 2D-MXene / 0D-ZnO nanocomposite structure composed of 0D-ZnO, 1D-MXene, and 2D-MXene.

[0065] The 1D / 2D-MXene / 0D-ZnO nanocomposite material prepared above can be used for the detection of low concentrations of nitrogen dioxide gas at room temperature.

[0066] The 1D / 2D-MXene / 0D-ZnO nanocomposite material prepared above was used as a gas-sensitive material to prepare a gas sensor for detecting low concentrations of nitrogen dioxide at room temperature.

[0067] Specifically:

[0068] Example 1:

[0069] Step 1: Weigh 40 ml of 7 mol / L concentrated hydrochloric acid. Weigh 1.6 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (80℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 300 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 36 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. Dry the resulting precipitate under vacuum at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Take 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in an 80°C water bath, and then freeze-dried to obtain a few-layer Ti3C2T. x .

[0070] Step 2: Take 0.2g of the few-layer Ti3C2T prepared above. x The mixture was added to 60 ml of 10 mol / L KOH solution and stirred continuously at 300 rpm for 30 h in an 80°C water bath to obtain 1D / 2D-MXene(Ti3C2T). xAfter the reaction, the sample was centrifuged at 10,000 rpm and washed successively with deionized water and anhydrous ethanol. After vacuum drying, 0.2 g of the obtained 1D / 2D-MXene and 0.02 g of zinc acetate dihydrate were added to a polytetrafluoroethylene beaker containing a mixture of 1 mL of deionized water and 50 mL of ethanol. The mixture was stirred continuously at 300 rpm for 2 hours at room temperature, and then transferred to a high-pressure sealed reactor and kept at 110℃ under hydrothermal conditions for 6 hours. After the reaction, the sample was centrifuged and washed several times with deionized water and anhydrous ethanol at 12,000 rpm. The resulting precipitate was vacuum dried at 60℃ for 12 hours, finally yielding a multi-layered 1D / 2D-MXene / 0D-ZnO nanocomposite structure.

[0071] Example 2:

[0072] Step 1: Weigh 40 ml of 8 mol / L concentrated hydrochloric acid. Weigh 1.6 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (80℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 300 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 36 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. Dry the resulting precipitate under vacuum at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Take 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in an 80°C water bath, and then freeze-dried to obtain a few-layer Ti3C2T. x .

[0073] Step 2: Take 0.2g of the few-layer Ti3C2T prepared above. x The mixture was added to 60 ml of 10 mol / L KOH solution and stirred continuously at 300 rpm for 30 h in an 80°C water bath to obtain 1D / 2D-MXene(Ti3C2T). xAfter the reaction, the sample was centrifuged at 10,000 rpm and washed successively with deionized water and anhydrous ethanol. After vacuum drying, 0.2 g of the obtained 1D / 2D-MXene and 0.06 g of zinc acetate dihydrate were added to a polytetrafluoroethylene beaker containing a mixture of 1 mL of deionized water and 50 mL of ethanol. The mixture was stirred continuously at 300 rpm for 2 hours at room temperature, and then transferred to a high-pressure sealed reactor and kept at 120℃ under hydrothermal conditions for 8 hours. After the reaction, the sample was centrifuged and washed several times with deionized water and anhydrous ethanol at 12,000 rpm. The resulting precipitate was vacuum dried at 60℃ for 12 hours, finally yielding a multi-layered 1D / 2D-MXene / 0D-ZnO nanocomposite structure.

[0074] Example 3:

[0075] Step 1: Weigh 40 ml of 8 mol / L concentrated hydrochloric acid. Weigh 1.6 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (80℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 300 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 36 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. Dry the resulting precipitate under vacuum at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Take 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in an 80°C water bath, and then freeze-dried to obtain a few-layer Ti3C2T. x .

[0076] Step 2: Take 0.2g of the few-layer Ti3C2T prepared above. x The mixture was added to 60 ml of 10 mol / L KOH solution and stirred continuously at 300 rpm for 30 h in an 80°C water bath to obtain 1D / 2D-MXene(Ti3C2T). xAfter the reaction, the mixture was centrifuged at 10,000 rpm and washed successively with deionized water and anhydrous ethanol. After vacuum drying, 0.2 g of the obtained 1D / 2D-MXene and 0.10 g of zinc acetate dihydrate were added to a polytetrafluoroethylene beaker containing a mixture of 1 mL of deionized water and 50 mL of ethanol. The mixture was stirred continuously at 300 rpm for 2 hours at room temperature, and then transferred to a high-pressure sealed reactor and kept at 130℃ under hydrothermal conditions for 10 hours. After the reaction, the mixture was centrifuged and washed several times with deionized water and anhydrous ethanol at 12,000 rpm. The resulting precipitate was vacuum dried at 60℃ for 12 hours, finally yielding a multi-layered 1D / 2D-MXene / 0D-ZnO nanocomposite structure.

[0077] Example 4:

[0078] Step 1: Weigh 40 ml of 9 mol / L concentrated hydrochloric acid. Weigh 2.0 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (60℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 500 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 24 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. The resulting precipitate is vacuum dried at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Take 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in a 60°C water bath, and then freeze-dried to obtain few-layer Ti3C2T. x .

[0079] Step 2: Take 0.2g of the few-layer Ti3C2T prepared above. x The solution was added to 60 ml of 12 mol / L KOH solution and stirred continuously at 500 rpm for 24 h in a 50°C water bath to obtain 1D / 2D-MXene(Ti3C2T). xAfter the reaction, the mixture was centrifuged at 10,000 rpm and washed successively with deionized water and anhydrous ethanol. After vacuum drying, 0.2 g of the obtained 1D / 2D-MXene and 0.14 g of zinc acetate dihydrate were added to a polytetrafluoroethylene beaker containing a mixture of 1 mL of deionized water and 50 mL of ethanol. The mixture was stirred continuously at 500 rpm for 2 hours at room temperature, and then transferred to a high-pressure sealed reactor and kept at 140℃ under hydrothermal conditions for 10 hours. After the reaction, the mixture was centrifuged and washed several times with deionized water and anhydrous ethanol at 12,000 rpm. The resulting precipitate was vacuum dried at 60℃ for 12 hours, finally yielding a multi-layered 1D / 2D-MXene / 0D-ZnO nanocomposite structure.

[0080] Example 5:

[0081] Step 1: Weigh 40 ml of 9 mol / L concentrated hydrochloric acid. Weigh 2.0 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (60℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 500 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 24 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. The resulting precipitate is vacuum dried at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Take 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in a 60°C water bath, and then freeze-dried to obtain few-layer Ti3C2T. x .

[0082] Step 2: Take 0.2g of the few-layer Ti3C2T prepared above. x The solution was added to 60 ml of 12 mol / L KOH solution and stirred continuously at 500 rpm for 24 h in a 50°C water bath to obtain 1D / 2D-MXene(Ti3C2T). xAfter the reaction, the mixture was centrifuged at 10,000 rpm and washed successively with deionized water and anhydrous ethanol. After vacuum drying, 0.2 g of the obtained 1D / 2D-MXene and 0.18 g of zinc acetate dihydrate were added to a polytetrafluoroethylene beaker containing a mixture of 1 mL of deionized water and 50 mL of ethanol. The mixture was stirred continuously at 300 rpm for 2 hours at room temperature, and then transferred to a high-pressure sealed reactor and kept at 150℃ under hydrothermal conditions for 10 hours. After the reaction, the mixture was centrifuged and washed several times with deionized water and anhydrous ethanol at 12,000 rpm. The resulting precipitate was vacuum dried at 60℃ for 12 hours, finally yielding a multi-layered 1D / 2D-MXene / 0D-ZnO nanocomposite structure.

[0083] Example 6:

[0084] Step 1: Measure 40 ml of 10 mol / L concentrated hydrochloric acid. Weigh 2.0 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (60℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 500 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 24 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. Dry the resulting precipitate under vacuum at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Take 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in a 60°C water bath, and then freeze-dried to obtain few-layer Ti3C2T. x .

[0085] Step 2: Take 0.2g of the few-layer Ti3C2T prepared above. x The solution was added to 60 ml of 12 mol / L KOH solution and stirred continuously at 500 rpm for 18 h in a 50°C water bath to obtain 1D / 2D-MXene(Ti3C2T). xAfter the reaction, the sample was centrifuged at 10,000 rpm and washed successively with deionized water and anhydrous ethanol. After vacuum drying, 0.2 g of the obtained 1D / 2D-MXene and 0.22 g of zinc acetate dihydrate were added to a polytetrafluoroethylene beaker containing a mixture of 1 mL of deionized water and 50 mL of ethanol. The mixture was stirred continuously at 300 rpm for 2 hours at room temperature, and then transferred to a high-pressure sealed reactor and kept at 160℃ under hydrothermal conditions for 12 hours. After the reaction, the sample was centrifuged and washed several times with deionized water and anhydrous ethanol at 12,000 rpm. The resulting precipitate was vacuum dried at 60℃ for 12 hours, finally yielding a multi-layered 1D / 2D-MXene / 0D-ZnO nanocomposite structure.

[0086] Comparative Example 1:

[0087] Measure 40 ml of 9 mol / L concentrated hydrochloric acid. Weigh 2.0 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (60℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 300 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 24 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. The resulting precipitate is vacuum dried at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Weigh 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in a 60°C water bath, and then freeze-dried to obtain few-layer Ti3C2T. x .

[0088] Comparative Example 2:

[0089] Measure 40 ml of 9 mol / L concentrated hydrochloric acid. Weigh 2.0 g of LiF powder and 0.2 g of each of five portions of Ti3AlC2 powder onto different weighing papers. Pour the weighed concentrated hydrochloric acid into a polytetrafluoroethylene beaker. Under constant temperature water bath conditions (60℃), slowly add the weighed LiF powder to the hydrochloric acid solution. Stir continuously at 300 rpm for 30 minutes to ensure complete dissolution. Then, every five minutes, slowly add one portion of Ti3AlC2 powder to the mixture and stir continuously with a magnetic stirrer until complete dissolution. Etch for 24 hours. After the reaction is complete, centrifuge the resulting solution at 3500 rpm for 5 minutes. Add deionized water and centrifuge several times until the pH of the supernatant is greater than 6. The resulting precipitate is vacuum dried at 60℃ for 12 hours to obtain multilayer Ti3C2T. x Weigh 0.5g of the above multilayer Ti3C2T x Dispersed in 100 ml of deionized water, ultrasonically treated for 30 minutes in a 60°C water bath, and then freeze-dried to obtain few-layer Ti3C2T. x Take 0.2g of the few-layer Ti3C2T prepared above. x Add to 100 ml of 10 mol / L KOH solution and stir continuously at 500 rpm for 10 h in a 50 °C water bath to obtain 1D / 2D-MXene.

[0090] The samples prepared in Examples 1-6 and Comparative Examples 1-2 were weighed out at 10 mg each and added to a mortar. A small amount of ethanol was then added and the mixture was ground thoroughly. The powder was then drop-coated onto graphite interdigitated electrodes and dried at 40°C for 4 hours to obtain eight gas sensors for detection. The sensitivity of the sensor was defined as ΔR / Ra.

[0091] Figure 2 The responses of the gas sensors prepared in Examples 1-6 and Comparative Examples 1-2 to the same concentration of nitrogen dioxide at room temperature are demonstrated. Figure 2 As shown, with the increase of zinc oxide composite content, the sensitivity of each gas sensor for 50 ppm nitrogen dioxide gas showed a trend of first increasing and then decreasing. Among the eight sensors, Example 5 had the highest sensitivity, with a response value of 64.58%. Compared to 2D-MXene, which showed no significant response to nitrogen dioxide gas, 1D / 2D-MXene exhibited a weak response to 50 ppm nitrogen dioxide gas, with a response value of only 4.83%. Under the same nitrogen dioxide gas concentration conditions, the response value of the 1D / 2D-MXene / 0D-ZnO nanocomposite structure after incorporating 0D-ZnO reached 64.58%, and its sensitivity was improved by 13.37 times. This indicates that the construction of a multi-level structure significantly improved the sensing performance of nitrogen dioxide gas.

[0092] Figure 3The continuous dynamic response-recovery curves of 2D-MXene, 1D / 2D-MXene, and 1D / 2D-MXene / 0D-ZnO nanocomposite sensors to different concentrations of nitrogen dioxide gas are shown at room temperature. Figure 3 As shown, within the range of 500 ppb to 50 ppm, the response of the 1D / 2D-MXene / 0D-ZnO nanocomposite structure increases linearly with increasing nitrogen dioxide concentration, with responses of 4.07%, 7.38%, 46.46%, 60.4%, and 61.73% to nitrogen dioxide gas at concentrations of 0.5, 1, 5, 10, 30, and 50 ppm, respectively.

[0093] The response of the 1D / 2D-MXene / 0D-ZnO nanocomposite sensor to different concentrations of nitrogen dioxide gas was evaluated using linear regression analysis. The linear fitting relationship between the response and the gas concentration is as follows: Figure 4 As shown. The fitting model is the Langmuir adsorption model, and its linear equation is:

[0094]

[0095] The correlation coefficient (R) was 0.99754, indicating that the sensor's response to different concentrations of nitrogen dioxide gas has a good linear relationship with the gas concentration, and the response changes are more obvious for low concentrations of nitrogen dioxide gas (<10ppm).

[0096] Figure 5 The response-recovery curve of a gas sensor fabricated from a 1D / 2D-MXene / 0D-ZnO nanocomposite structure to 8 ppm nitrogen dioxide gas at room temperature. Figure 5 As shown, the 1D / 2D-MXene / 0D-ZnO nanocomposite structure has a response time of 230s and a recovery time of 1300s to 8ppm nitrogen dioxide gas.

[0097] At room temperature, a gas sensor fabricated using a 1D / 2D-MXene / 0D-ZnO nanocomposite structure was subjected to five consecutive dynamic response-recovery tests on 10 ppm nitrogen dioxide gas. The test results are as follows: Figure 6 As shown, after 5 cycles, the sensor's response to nitrogen dioxide gas remained essentially constant at around 60%, demonstrating good stability.

[0098] Figure 7The responses of 2D-MXene, 1D / 2D-MXene, and 1D / 2D-MXene / 0D-ZnO nanocomposite structures to a target gas of 50 ppm were shown at room temperature. The 1D / 2D-MXene / 0D-ZnO nanocomposite structure showed a response of 64.58% to 50 ppm nitrogen dioxide, while the responses to the same concentrations of triethylamine, butanone, ethanol, isopropanol, ammonia, acetone, and methanol were 7.3%, 0.1%, 0.2%, 0.5%, 0.7%, 0.2%, and 0.1%, respectively, indicating that the 1D / 2D-MXene / 0D-ZnO sensor exhibits significant selectivity for nitrogen dioxide.

[0099] To test the long-term stability of the sensor, a gas sensor fabricated using a 1D / 2D-MXene / 0D-ZnO nanocomposite structure was subjected to a continuous 30-day response test at room temperature against 10 ppm nitrogen dioxide gas. The results are as follows: Figure 8 As shown, the sensor's response fluctuates little over 30 days, demonstrating excellent long-term stability.

[0100] Figure 9 A schematic diagram illustrating the principle of a gas sensor for detecting nitrogen dioxide gas based on a 1D / 2D-MXene / 0D-ZnO nanocomposite structure is shown. Figure a illustrates the band structure of ZnO and MXene; Figures b and c show the energy levels of the heterojunction formed by the two materials and the electron conduction process in air (b) and nitrogen dioxide (c) environments, respectively; Figure d illustrates the sensing mechanism of the 1D / 2D-MXene / 0D-ZnO nanocomposite structure for nitrogen dioxide; Figure e illustrates the charge density distribution and charge transfer process of the 1D / 2D-MXene / 0D-ZnO nanocomposite structure for nitrogen dioxide. The pn junction composition creates a built-in electric field, i.e., an electron depletion layer (EDL), between the material phase interfaces. Due to the strong electronegativity of oxygen in air, oxygen molecules adsorb onto the surface of the 1D / 2D-MXene / 0D-ZnO composite material and react with electrons in its conduction band to form oxygen ions. At room temperature, the oxygen adsorbed on the material surface is mainly O2. - It exists in the form of... (e.g.) Figure 9 As shown, when the sensor is exposed to nitrogen dioxide gas, the adsorbed oxygen ions react with nitrogen dioxide molecules, further capturing electrons from the conduction band, widening the EDL and increasing the resistance, thus forming a gas-sensitive response.

[0101] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A method for preparing MXene / ZnO nanocomposites for low-concentration nitrogen dioxide detection at room temperature, characterized by, include: S1, etching Ti3AlC2 in a mixed solution of hydrochloric acid and lithium fluoride under water bath conditions, centrifugal cleaning and vacuum drying after reaction to obtain multi-layer two-dimensional MXene Ti3C2T x ; The concentration of hydrochloric acid is 7-10 mol / L, and the mass ratio of Ti3AlC2 to lithium fluoride is 1:1.6-2.0; the etching reaction time is 24-36 h. S2. The powder obtained in S1 is ultrasonically exfoliated and freeze-dried to obtain few-layer MXene; S3. The powder obtained in S2 is subjected to alkalization treatment; the alkalization treatment is to add a small layer of MXene to a 10~12 mol / L KOH solution and stir continuously at 300~500 rpm for 18~30 h under a water bath at 50~80 ℃. S4. The powder obtained in S3 is centrifuged, washed and vacuum dried to obtain a composite structure 1D / 2D-MXene with one-dimensional MXene grown in situ on the surface of two-dimensional MXene. S5. Add the powder obtained in S4 and zinc acetate dihydrate to a mixed solution of water and ethanol for hydrothermal reaction. S6. The powder obtained in S5 is centrifuged, washed, and vacuum dried to obtain a multi-level 1D / 2D-MXene / 0D-ZnO nanocomposite structure composed of 0D-ZnO, 1D-MXene, and 2D-MXene.

2. The method for preparing MXene / ZnO nanocomposite material for detecting low concentrations of nitrogen dioxide at room temperature according to claim 1, characterized in that, In S1, the water bath conditions are constant temperature at 50~80 ℃ and stirring at 300~600 rpm.

3. The method for preparing MXene / ZnO nanocomposite material for detecting low concentrations of nitrogen dioxide at room temperature according to claim 1, characterized in that, In S2, the ultrasonic ablation is performed by dispersing the multilayer two-dimensional MXene in deionized water and ultrasonically ablating it for 30-60 minutes in a water bath at 50-80 ℃.

4. The method for preparing MXene / ZnO nanocomposite material for detecting low concentrations of nitrogen dioxide at room temperature according to claim 1, characterized in that, In S5, the mass ratio of 1D / 2D-MXene to zinc acetate is 1:(0.1~1.2); the volume ratio of water to ethanol in the mixed solution is 1:(40~60).

5. The method for preparing MXene / ZnO nanocomposite material for detecting low concentrations of nitrogen dioxide at room temperature according to claim 1, characterized in that, In S5, the hydrothermal reaction is carried out in a high-pressure, closed environment and kept at 110~160 ℃ for 6~12 h.

6. An MXene / ZnO nanocomposite material for detecting low concentrations of nitrogen dioxide at room temperature, characterized in that, It is obtained by the preparation method of MXene / ZnO nanocomposite material as described in any one of claims 1-5.

7. A gas sensor for detecting low concentrations of nitrogen dioxide at room temperature, characterized in that, The MXene / ZnO nanocomposite material described in claim 6 for detecting low concentrations of nitrogen dioxide at room temperature is used as the gas-sensitive material.

Images