MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction, its preparation method and application

Abstract

The application belongs to the technical field of nano material heterojunction, and particularly relates to a MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction and a preparation method and application thereof. The MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction comprises a substrate, an intermediate layer and an outer layer; wherein the substrate is a two-dimensional MXene nanosheet, the intermediate layer is a TiO2 nanoparticle; the outer layer is a ZnIn2S4 nanosheet; a metal-semiconductor interface is formed between the two-dimensional MXene nanosheet and the TiO2 nanoparticle; and a semiconductor heterojunction interface is formed between the TiO2 nanoparticle and the ZnIn2S4 nanosheet. The MXene / TiO2 / ZnIn2S4 heterojunction provided by the application exhibits excellent gas selectivity to triethylamine, has a high response value, a fast recovery speed, and excellent long-term stability and humidity interference resistance, and has a wide application prospect in actual production.

Description

Technical Field

[0001] This application belongs to the field of nanomaterial heterostructure technology, specifically relating to an MXene / TiO2 / ZnIn2S4 ternary integrated heterostructure, its preparation method, and its application. Background Technology

[0002] Resistive gas sensors based on semiconductor gas-sensitive materials are among the most widely used and representative types of gas sensors, demonstrating broad application potential in the detection of volatile organic compounds (VOCs). However, there is still a significant gap between their actual gas-sensing performance and theoretical predictions, as well as application requirements. Therefore, the development of high-performance VOCs gas sensing materials has become a research hotspot in the sensing field in recent years.

[0003] Gas sensors are widely used in various industrial and daily life fields, including chemical, metallurgical, environmental protection, medical, and food industries. Developing novel and efficient sensing materials is a current research focus in the field of gas sensors. In recent years, transition metal carbides / nitrides (MXenes) have gradually gained attention in the gas sensing field due to their excellent conductivity, tunable bandgap structure and surface properties, good mechanical properties, and hydrophilicity. However, research shows that although pure-phase MXenes exhibit some gas-sensitive response to certain environmental gases (such as ammonia and ethanol), their sensitivity is generally low, their recovery performance and selectivity are poor, and they are significantly affected by environmental humidity. Furthermore, the surface stability of MXenes is also a significant issue, especially in the presence of water and oxygen in the environment. These factors greatly limit the practical application of MXene materials in the field of gas sensing.

[0004] Constructing MXene / semiconductor nanocrystal heterojunctions using MXene as a matrix in combination with traditional semiconductor nanocrystals is one of the most common and important strategies for improving the gas-sensing performance of MXene. However, overall, the design of MXene / semiconductor nanocrystal heterojunction gas-sensing materials is still in its initial stage, and their gas-sensing performance still falls far short of theoretical values ​​and practical application requirements. The following key issues remain to be addressed: First, for MXene / semiconductor nanocrystal heterojunction gas-sensitive materials, the heterojunction interface between MXene and semiconductor nanocrystals significantly influences charge transfer behavior, thus affecting gas-sensing performance. However, in reality, most reported MXene / semiconductor nanocrystal heterojunction gas-sensitive materials exist almost entirely as non-uniform mixtures. In this case, it is difficult to form a robust and tightly connected heterojunction interface between MXene and semiconductor nanocrystals, making efficient charge transport challenging. Consequently, the charge signal generated during the gas-sensing reaction cannot be effectively converted into a resistance signal, which is a key factor hindering the improvement of gas-sensing performance in MXene / semiconductor nanocrystal heterojunction gas-sensitive materials. In fact, constructing an effective heterojunction interface requires considering both lattice matching and band matching. Lattice matching ensures the formation of a stable heterojunction interface, while band matching provides the driving force for charge transfer at the interface. In conclusion, constructing a robust and tightly connected heterojunction interface with excellent charge transport characteristics is crucial for improving the gas-sensing performance of MXene / semiconductor nanocrystal heterojunctions. Secondly, due to limitations in synthesis technology, most MXene substrates currently used for constructing MXene semiconductor nanocrystal heterojunctions are common accordion-shaped multilayer MXenes. In this case, the advantages of the large specific surface area and high surface activity of layered MXene materials are not only difficult to fully utilize, but also unfavorable for sufficient interfacial contact between semiconductor nanocrystals and MXene. Furthermore, in-depth research is needed on the interfacial charge transport mechanism and gas-sensing performance regulation of MXene semiconductor nanocrystal heterojunctions at the microscopic level. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction, its preparation method, and its application. Specifically, the following technical solution is adopted: In a first aspect, the present invention provides an MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction, wherein the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction comprises a substrate, an intermediate layer and an outer layer; The substrate is a two-dimensional MXene nanosheet, the middle layer is TiO2 nanoparticles, and the outer layer is ZnIn2S4 nanosheets. A metal-semiconductor interface is formed between the two-dimensional MXene nanosheets and the TiO2 nanoparticles; a semiconductor heterostructure interface is formed between the TiO2 nanoparticles and the ZnIn2S4 nanosheets. The loading of ZnIn2S4 nanosheets in the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction is 1 wt%~3 wt%.

[0006] In the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction constructed in this invention, the TiO2 nanoparticle layer is tightly embedded on the surface of the MXene nanosheets, and the ZnIn2S4 nanosheets further encapsulate the TiO2 nanoparticles. Specifically, the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction... 2 / The ZnIn2S4 heterojunction structure forms a robust heterostructure interface, achieving efficient multi-interface charge transfer characteristics, enabling the charge signal of the gas-solid reaction to be effectively converted into a resistance signal. Furthermore, the two-dimensional MXene nanosheets of this invention have a large specific surface area, significantly increasing the number of active sites and improving the gas adsorption activity on the material surface compared to accordion-shaped MXene. Therefore, under relatively low operating temperatures, the MXene / TiO2 / ZnIn2S4 heterojunction of this invention exhibits excellent gas selectivity for triethylamine with high response value and fast recovery speed. Among these, transition metal carbides / nitrides (MXenes) possess excellent conductivity, tunable bandgap structure and surface properties, good mechanical properties, and hydrophilicity.

[0007] This invention forms a robust heterojunction (MXene / TiO2 / ZnIn2S4) within an MXene-based ternary integrated heterojunction, achieving highly efficient multi-interface charge transfer characteristics, enabling the effective conversion of charge signals from gas-solid reactions into resistance signals. Furthermore, due to the 1D / 0D / 2D array structure design, the ternary MXene / TiO2 / ZnIn2S4 heterojunction not only possesses a large specific surface area for gas adsorption and reaction but also enhances the stability of the original MXene, providing important insights into the study of multi-interface charge transport mechanisms in resistive gas sensors.

[0008] As a further preferred embodiment, the specific surface area of ​​the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction is 20 m². 2 / g~50 m 2 / g; The MXene nanosheets have a lateral dimension of 2 μm to 10 μm, the TiO2 nanoparticles have a size of 5 nm to 10 nm, and the ZnIn2S4 nanosheets have a thickness of 10 nm to 50 nm.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction, comprising the following steps: Two-dimensional MXene nanosheets were obtained by using a water bath method combined with ultrasonic exfoliation of accordion-shaped MXene. TiO2 nanoparticles were grown in situ on the surface of the two-dimensional MXene nanosheets by high-temperature calcination to obtain the intermediate product MXene / TiO2 heterojunction. ZnIn2S4 nanosheets were further grown on the surface of the intermediate product MXene / TiO2 heterojunction using a water bath method to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0010] As a further preferred embodiment, the specific preparation method for obtaining two-dimensional MXene nanosheets by using a water bath method combined with ultrasonic exfoliation of accordion-shaped MXene includes the following steps: Lithium fluoride was dissolved in concentrated hydrochloric acid and stirred to obtain a reaction solution; Aluminum carbide was added to the reaction solution for a water bath reaction. After the reaction, the solution was washed with dilute hydrochloric acid and water in sequence, and then centrifuged. The solution was then subjected to ultrasonic exfoliation and reaction under an argon atmosphere. After the reaction, the solution was centrifuged, the supernatant was taken, frozen, and dried to obtain the two-dimensional MXene nanosheets.

[0011] As a further preferred embodiment, the molar ratio of lithium fluoride to aluminum carbide is 11~12:1; The concentration of the concentrated hydrochloric acid is 11 mol / L to 13 mol / L, and the concentration of the dilute hydrochloric acid is 1 mol / L. The ultrasonic power during ultrasonic ablation is 50W~80W.

[0012] In the above reaction process, lithium fluoride reacts with concentrated hydrochloric acid to generate hydrofluoric acid, and the concentration of hydrofluoric acid has a significant impact on the etching effect of the aluminum layer in aluminum carbide. When the concentration of hydrofluoric acid is too low, the aluminum layer cannot be effectively removed, making it difficult to obtain an MXene colloidal solution; conversely, if the concentration of hydrofluoric acid is too high, the specific surface area of ​​the obtained MXene sheets will decrease, and a large number of sheets will break down. Considering both etching efficiency and sheet integrity, the optimal amount of lithium fluoride is 3 g. This condition ensures that the aluminum layer is completely etched while maximizing the integrity of the MXene sheet structure.

[0013] As a further preferred embodiment, the specific preparation method for obtaining the intermediate product MXene / TiO2 heterojunction by in-situ oxidation growth of TiO2 nanoparticles on the surface of the two-dimensional MXene nanosheets through high-temperature calcination includes the following steps: The two-dimensional MXene was dissolved in sodium hydroxide solution and stirred continuously. After the reaction was completed, the sample was washed alternately with deionized water and ethanol, centrifuged, and freeze-dried to obtain a black sample powder. The black sample powder was placed in a muffle furnace and calcined at a high temperature of 300℃~380℃ for 2 h~6 h to obtain the intermediate product MXene / TiO2 heterojunction.

[0014] As a further preferred embodiment, the specific preparation method of further growing ZnIn2S4 nanosheets on the surface of the intermediate product MXene / TiO2 heterojunction using a water bath method to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction includes the following steps: Zinc chloride, indium chloride, and thioacetamide are dissolved in water, mixed, and stirred to obtain a reaction solution. The pH of the reaction solution was adjusted to 1-3 using nitric acid, and then the intermediate product MXene / TiO2 heterojunction was added for a water bath reaction. After the reaction was completed, the product was washed and dried to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0015] As a further preferred embodiment, the molar ratio of zinc chloride, indium chloride and thioacetamide is 1:1~3:1~4; The water bath reaction temperature is 40 ℃~100 ℃, and the reaction time is 1 h~3 h.

[0016] This invention obtains high-yield, large-lateral-size two-dimensional thin-layer Ti3C2Tx MXene nanosheets under relatively mild conditions through LiF-assisted low-temperature etching combined with ultrasonic exfoliation. A uniform TiO2 nanoparticle layer is then tightly coated onto the surface using in-situ oxidation technology, resulting in a two-dimensional thin-layer Ti3C2Tx / TiO2 nanoparticle heterojunction. Finally, a two-dimensional ZnIn2S4 nanosheet array is further deposited using liquid phase deposition technology, constructing a stable 2D / OD / 2D MXene@TiO2 / ZnIn2S4 integrated heterojunction material.

[0017] This invention investigates the gas-sensing properties of this heterojunction structure for some typical harmful environmental gases, especially VOCs. Through the design of an efficient multi-interface electron transport channel, the efficient conversion of charge signals generated during the gas-sensing reaction into resistance signals is achieved, thereby comprehensively improving the gas-sensing performance of MXene for triethylamine, a typical VOC. Based on the above results, using a combination of various spectroscopic techniques (including in-situ infrared characterization) and density functional theory-based calculations, key issues such as the adsorption of target gas molecules, changes in the electronic structure of the surface and interface during the gas-sensing process, and real-time changes in charge transfer, surface species, and adsorbed groups with the ambient atmosphere were studied in depth, elucidating the gas-sensing mechanism. This invention will not only greatly expand the application of MXene materials in the field of resistive gas sensors, but also provide important guidance for understanding the working mechanism of resistive gas sensors.

[0018] Thirdly, the present invention provides a gas sensor comprising the aforementioned MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0019] This invention constructs a semiconductor gas sensor by drop-coating on a gas-sensitive substrate, wherein the gas-sensitive substrate is an Al2O3 gas-sensitive substrate.

[0020] The aforementioned Al2O3 gas-sensitive substrate is a commercially available flat-plate Al2O3 gas-sensitive substrate. This substrate is composed of inexpensive and readily available Al2O3 and has two pairs of Pt interdigitated electrodes on its surface, one pair being heating electrodes and the other pair being resistance signal collection electrodes. Heating the substrate and collecting the resistance signal are very convenient, and the two pairs of electrodes do not interfere with each other. An MXene / TiO2 / ZnIn2S4 heterojunction is used as the gas-sensitive sensing layer for surface gas adsorption and gas-sensitive reactions.

[0021] Fourthly, the present invention provides the application of the above-mentioned gas sensor in the detection of triethylamine gas.

[0022] The beneficial effects of this invention are as follows: The MXene / TiO2 / ZnIn2S4 heterojunction provided by this invention possesses a large specific surface area, significantly increasing the gas adsorption activity on the material surface and enhancing the stability of the original MXene. This provides important insights into the study of multi-interface charge transport mechanisms in resistive gas sensors, offering structural advantages over traditional accordion-shaped multilayer MXene nanosheets. Furthermore, through the design of efficient multi-interface electron transport channels, the efficient conversion of charge signals generated during the gas-sensing reaction into resistance signals is achieved, thereby comprehensively improving the gas-sensing performance of MXene for triethylamine, a typical VOC gas. At relatively low operating temperatures, the MXene / TiO2 / ZnIn2S4 heterojunction exhibits excellent gas selectivity for triethylamine with high response values ​​and fast recovery speed. This invention demonstrates excellent long-term stability and resistance to humidity interference, showing broad application prospects in practical production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1The XRD patterns (a) of MXene, MXene / TiO2, ZnIn2S4, and MXene / TiO2 / ZnIn2S4 and the atomic structure diagrams (b) of MXene, MXene / TiO2, and MXene / TiO2 / ZnIn2S4 are shown.

[0025] Figure 2 The images shown are (a) and (b) SEM images of MXene nanosheets; (c) and (d) SEM images of MXene / TiO2 nanoparticles; (e) and (f) SEM images of MXene / TiO2 / ZnIn2S4 heterojunctions; (g)-(o) HRTEM and EDS elemental distribution images of MXene / TiO2 / ZnIn2S4 heterojunctions; and (p) a schematic diagram of the MXene / TiO2 / ZnIn2S4 heterojunction fabrication process.

[0026] Figure 3 The XPS spectra of MXene, MXene / TiO2, ZnIn2S4, and MXene / TiO2 / ZnIn2S4 are shown; (a) C 1s XPS spectrum; (b) Ti 2p XPS spectrum; (c) O 1s XPS spectrum; (d) Zn 2p XPS spectrum; (e) In 3d XPS spectrum; (f) S 2p XPS spectrum.

[0027] Figure 4 The following are nitrogen adsorption-desorption isotherms and pore size distribution curves for different samples: (a) MXene / TiO2 / ZnIn2S4; (b) ZnIn2S4; (c) MXene / TiO2; (d) MXene.

[0028] Figure 5 The response curves of MXene, MXene / TiO2, ZnIn2S4 and MXene / TiO2 / ZnIn2S4 to triethylamine at a concentration of 100 ppm at different temperatures are shown; (a) MXene, MXene / TiO2, ZnIn2S4 and MXene / TiO2 / ZnIn2S4 are shown; (b) MXene and MXene / TiO2 are shown.

[0029] Figure 6 The following shows the repeatability of different samples for 100 ppm triethylamine over several cycles at 300 °C; (a) MXene / TiO2 / ZnIn2S4; (b) ZnIn2S4; (c) MXene / TiO2; (d) MXene.

[0030] Figure 7The following are the dynamic sensing characteristics of different samples for different concentrations of triethylamine at 300℃: (a) MXene / TiO2 / ZnIn2S4; (b) ZnIn2S4; (c) MXene / TiO2; (d) MXene.

[0031] Figure 8 The following figures are shown: (a) the detection limit of MXene / TiO2 / ZnIn2S4 for triethylamine gas sensitivity; (b) the response-recovery time curve of MXene / TiO2 / ZnIn2S4 to 100 ppm triethylamine; and (c) the response of MXene / TiO2 / ZnIn2S4 to different types of volatile organic compound gases.

[0032] Figure 9 The following are shown: (a) the long-term stability of MXene / TiO2 / ZnIn2S4 response to 100ppm triethylamine and substrate resistance; (b) the response curves of MXene / TiO2 / ZnIn2S4 to 100ppm triethylamine and the changes in substrate resistance under different humidity conditions.

[0033] Figure 10 The images show the ultraviolet photoelectron spectra (UPS), Kubelka-Munk transform reflectance spectra derived from ultraviolet-visible (UV-Vis) absorption spectra of different samples, and Mott-Schottky curves; (a), (b), and (c) are the UPS, Kubelka-Munk transform reflectance spectra, and Mott-Schottky curves of ZnIn2S4, respectively; (d), (e), and (f) are the UPS, Kubelka-Munk transform reflectance spectra, and Mott-Schottky curves of MXene / TiO2, respectively.

[0034] Figure 11 The following are the in-situ Fourier transform infrared spectra of MXene / TiO2 / ZnIn2S4 heterostructure nanoparticles in a triethylamine atmosphere; (a) is the total in-situ Fourier transform infrared spectrum; (b) is the spectrum at 600-1600 cm⁻¹. -1 In-situ Fourier transform infrared spectra within the range; (c) shows the spectra in the range of 1500–2600 cm⁻¹. -1 In-situ Fourier transform infrared spectra within the range; (d) shows the spectra in the range of 2600–3100 cm⁻¹. -1 In-situ Fourier transform infrared spectra within the range. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] The following embodiments of the present invention provide an MXene / TiO2 / ZnIn2S4 heterojunction, the preparation process of which is as follows: Figure 2 As shown in p, firstly, the aluminum layer in aluminum carbide was etched with hydrofluoric acid using a water bath method, and then the accordion-shaped MXene was ultrasonically exfoliated to obtain two-dimensional MXene nanosheets. Using the MXene nanosheets as a substrate, TiO2 nanoparticles were grown in situ on their surface by high-temperature calcination to obtain an MXene / TiO2 heterojunction. Finally, ZnIn2S4 nanosheets were uniformly coated on the surface of the MXene / TiO2 heterojunction using a water bath method to obtain an MXene / TiO2 / ZnIn2S4 heterojunction.

[0037] Example 1 A ternary integrated heterojunction of MXene / TiO2 / ZnIn2S4 is prepared by the following steps: (1) Add 1g of lithium fluoride (LiF) and 40mL of concentrated hydrochloric acid (HCl) to a polytetrafluoroethylene autoclave and stir magnetically for 1.0 hour to obtain a reaction solution; slowly add 2g of aluminum carbide (Ti3AlC2MAX) to the reaction solution in small amounts several times, controlling the time to 10min, and finally keep the reaction solution in a water bath at a constant temperature of 35℃ for 24h. After the reaction, wash with dilute hydrochloric acid (HCl) and centrifuge; then wash with deionized water and centrifuge until the pH value is about 7. Then sonicate under an argon atmosphere for 2h at a power of 50W, and finally centrifuge for 60min, and take the upper dark green Ti3C2T X MXene colloids were freeze-dried to obtain MXene nanosheets.

[0038] (2) Weigh 100 mg of MXene nanosheets and dissolve them in 10 mL of sodium hydroxide solution (3 mol / L). React in a water bath at a constant temperature for 24 h. The reaction temperature is set at 60 °C. After the reaction is completed, wash the solution three times with deionized water and ethanol alternately. Freeze and dry the reaction solution. Finally, calcine the dried black powder at a high temperature of 300 °C for 2 h to obtain the MXene / TiO2 nanoparticle heterojunction.

[0039] (3) Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:1:2, mixed, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 0.5 mol / L nitric acid. Then, 150 mg of MXene / TiO2 nanoparticles were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 40°C in a water bath for 2 hours. After the reaction was completed, the product was washed and dried to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0040] Example 2 A ternary integrated heterojunction of MXene / TiO2 / ZnIn2S4 is prepared by the following steps: (1) Add 2g of lithium fluoride (LiF) and 40mL of concentrated hydrochloric acid (HCl) to a polytetrafluoroethylene autoclave and stir magnetically for 1.0 hour to obtain a reaction solution; slowly add 2g of aluminum carbide (Ti3AlC2MAX) to the reaction solution in small amounts several times, controlling the time to 15min, and finally keep the reaction solution in a water bath at a constant temperature of 35℃ and a reaction time of 36h. After the reaction is completed, wash with dilute hydrochloric acid (HCl) and centrifuge; then wash with deionized water and centrifuge until the pH value is about 7. Then sonicate under an argon atmosphere for 4h at a power of 60W, and finally centrifuge for 60min, and take the upper dark green Ti3C2T X MXene colloids were freeze-dried to obtain MXene nanosheets.

[0041] (2) Weigh 100 mg of MXene nanosheets and dissolve them in 10 mL of sodium hydroxide solution (3 mol / L). React in a water bath at a constant temperature for 24 h. The reaction temperature is set at 60 °C. After the reaction is completed, wash the solution three times with deionized water and ethanol alternately. Freeze and dry the reaction solution. Finally, calcine the dried black powder at a high temperature of 330 °C for 3 h to obtain the MXene / TiO2 nanoparticle heterojunction.

[0042] (3) Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:2:2, mixed, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 0.5 mol / L nitric acid. Then, 150 mg of MXene / TiO2 nanoparticles were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 60°C in a water bath for 2 hours. After the reaction was completed, the product was washed and dried to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0043] Example 3 A ternary integrated heterojunction of MXene / TiO2 / ZnIn2S4 is prepared by the following steps: (1) Add 3g of lithium fluoride (LiF) and 40mL of concentrated hydrochloric acid (HCl) to a polytetrafluoroethylene autoclave and stir magnetically for 1.0 hour to obtain a reaction solution; slowly add 2g of aluminum carbide (Ti3AlC2MAX) to the reaction solution in small amounts several times, controlling the time to 12min, and finally keep the reaction solution in a water bath at a constant temperature of 35℃ for 48h. After the reaction, wash with dilute hydrochloric acid (HCl) and centrifuge; then wash with deionized water and centrifuge until the pH value is about 7. Then sonicate under an argon atmosphere for 6h at a power of 70W, and finally centrifuge for 60min, and take the upper dark green Ti3C2T X MXene colloids were freeze-dried to obtain MXene nanosheets.

[0044] (2) Weigh 100 mg of MXene nanosheets and dissolve them in 10 mL of sodium hydroxide solution (3 mol / L). React in a water bath at a constant temperature for 24 h. The reaction temperature is set at 60 °C. After the reaction is completed, wash the solution three times with deionized water and ethanol alternately. Freeze and dry the reaction solution. Finally, calcine the dried black powder at a high temperature of 350 °C for 6 h to obtain the MXene / TiO2 nanoparticle heterojunction.

[0045] (3) Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:2:1, mixed, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 0.5 mol / L nitric acid. Then, 150 mg of MXene / TiO2 nanoparticle array was immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 80°C in a water bath for 2 hours. After the reaction was completed, the product was washed and dried to finally obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0046] Example 4 A ternary integrated heterojunction of MXene / TiO2 / ZnIn2S4 is prepared by the following steps: (1) Add 4g of lithium fluoride (LiF) and 40mL of concentrated hydrochloric acid (HCl) to a polytetrafluoroethylene autoclave and stir magnetically for 1.0 hour to obtain a reaction solution; slowly add 2g of aluminum carbide (Ti3AlC2MAX) to the reaction solution in small amounts several times, controlling the time to 10min, and finally keep the reaction solution in a water bath at a constant temperature of 35℃ and a reaction time of 36h. After the reaction, wash with dilute hydrochloric acid (HCl) and centrifuge; then wash with deionized water and centrifuge until the pH value is about 7. Then sonicate under an argon atmosphere for 2h at a power of 80W, and finally centrifuge for 60min, and take the upper dark green Ti3C2T X MXene colloids were freeze-dried to obtain MXene nanosheets.

[0047] (2) Weigh 100 mg of MXene nanosheets and dissolve them in 10 mL of sodium hydroxide solution (3 mol / L). React in a water bath at a constant temperature for 24 h. The reaction temperature is set at 60 °C. After the reaction is completed, wash the solution three times with deionized water and ethanol alternately. Freeze and dry the reaction solution. Finally, calcine the dried black powder at a high temperature of 380 °C for 4 h to obtain the MXene / TiO2 nanoparticle heterojunction.

[0048] (3) Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:2:3, mixed, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 0.5 mol / L nitric acid. Then, 150 mg of MXene / TiO2 nanoparticles were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 100℃ in a water bath for 2 hours. After the reaction was completed, the product was washed and dried to finally obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction.

[0049] Comparative Example 1 An MXene nanosheet, the preparation method of which includes the following steps: 3g of lithium fluoride (LiF) and 40mL of concentrated hydrochloric acid (HCl) were added to a polytetrafluoroethylene autoclave, and the mixture was continuously stirred magnetically for 1 hour to obtain a reaction solution. 2g of aluminum carbide (Ti3AlC2MAX) was slowly added to the reaction solution in small batches over 15 minutes. The reaction solution was then kept at a constant temperature of 35℃ in a water bath for 24 hours. After the reaction, the mixture was washed with dilute hydrochloric acid (HCl) and centrifuged; then washed with deionized water and centrifuged until the pH value was approximately 7. The mixture was then sonicated under an argon atmosphere for 2 hours at a power of 60W, and finally centrifuged for 60 minutes. The upper dark green Ti3C2MAX layer was collected. X MXene colloids were freeze-dried to obtain MXene nanosheets.

[0050] Comparative Example 2 An MXene / TiO2 nanoparticle heterostructure is prepared by the following steps: 100 mg of MXene nanosheets were dissolved in 10 mL of sodium hydroxide solution (3 mol / L) and reacted in a water bath at a constant temperature of 60 °C for 24 h. After the reaction was completed, the mixture was washed three times with deionized water and ethanol, and then the reaction solution was frozen and dried. Finally, the dried black powder was calcined at a high temperature of 350 °C for 2 h to obtain the MXene / TiO2 nanoparticle heterostructure.

[0051] Comparative Example 3 A ZnIn2S4 powder, the preparation method of which includes the following steps: Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:1:2, mixed thoroughly, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 1 mol / L nitric acid. This reaction solution was then subjected to a water bath reaction, with the temperature maintained at 80°C for 2 hours. After the reaction, the product was washed and dried to obtain ZnIn2S4 powder.

[0052] Example 5 The specific results of characterization and performance testing of the materials obtained in Example 3 and Comparative Examples 1-3 are as follows: (1) The phase composition of the prepared sample was characterized by X-ray diffraction (XRD). The results are as follows: Figure 1 As shown in Figure a, the results indicate that Ti3C2MXene exhibits significant diffraction peaks at 2θ = 7.2°, 17.1°, 27.2°, 34.6°, 42.3°, and 61.0°, consistent with previous literature reports. After high-temperature calcination, the characteristic peaks of Ti3C2MXene significantly weakened, while new diffraction peaks appeared at 2θ = 25.6°, 38.1°, 48.1°, 54.3°, 55.3°, 62.9°, 68.22°, 70.78°, 75.62°, and 83.06°. These peak positions highly coincide with the standard card (JCPDS No. 21-1272) for anatase TiO2. The main diffraction peaks of pure ZnIn2S4 are consistent with the data in the standard card (JCPDS No. 65-2023). In the XRD pattern of the ternary MXene / TiO2 / ZnIn2S4 matrix, in addition to the characteristic peaks of MXene / TiO2, two diffraction peaks were observed at 2θ = 27.2° and 47.7°, which can be attributed to the main diffraction peaks of ZnIn2S4. Due to the relatively low crystallinity of ZnIn2S4 compared to the MXene / TiO2 matrix, the other ZnIn2S4 diffraction peaks were not significantly observed.

[0053] like Figure 1 As shown in b, no significant shift in the characteristic diffraction peaks of MXene and TiO2 was found in the XRD pattern of MXene / TiO2 / ZnIn2S4, indicating that ZnIn2S4 is grown in situ on MXene / TiO2 nanosheets rather than being doped inside the MXene / TiO2 crystal.

[0054] (2) The morphology of the prepared material was characterized by SEM and TEM.

[0055] The result is as follows Figure 2 As shown, Figure 2 a and 2b are SEM images of MXene nanosheets. It can be visually observed that the sample consists of a large array of monolayer lateral nanosheets. Figure 2 c and 2d are morphological characteristics of MXene / TiO2 nanoparticles. The sample consists of a large number of nanoparticles compactly embedded on the surface of MXene nanosheets. Figure 2 e and 2f represent the low- and high-magnification morphological features of the MXene / TiO2 heterostructure. It can be seen that, significantly different from the surface of the MXene / TiO2 nanoparticles, a thin layer of sheet-like ZnIn2S4 is uniformly coated on the surface of the MXene / TiO2 nanoparticles. Characterization was performed using HRTEM (...). Figure 2 Three distinct lattice fringes were clearly observed (g and 2h). Measurements and data comparisons revealed that these three lattice fringes correspond to the (103) crystal plane of MXene, the (101) crystal plane of TiO2, and the (102) crystal plane of ZnIn2S4. These data further confirm the successful formation of robust heterostructure interfaces between the three components in the MXene / TiO2 / ZnIn2S4 heterostructure array. The elemental energy distribution diagrams ( Figure 2 (i-2o) allows you to visually see that C, Ti, O, Zn, In, and S elements are evenly distributed in their respective regions.

[0056] (3) To further analyze the chemical state of the samples, X-ray photoelectron spectroscopy (XPS) was performed on MXene, MXene / TiO2, ZnIn2S4, and MXene / TiO2 / ZnIn2S4. Peak fitting of the XPS data of C element in the MXene sample showed that the energy at 281.98 eV, 284.73 eV, 286.55 eV, and 289.39 eV belonged to C–Ti, C–C, C–O, and OC=O, respectively, which is consistent with the literature. With the extension of high-temperature calcination time, the C-Ti peak intensity gradually weakened, which is due to the oxidation of Ti3C2MXene to TiO2 during the high-temperature process. Figure 3b presents the high-resolution energy spectra of the Ti 2p peak in different composite materials. For MXene nanosheets, the Ti 2p nuclear energy level is fitted to four doublets representing Ti 2p. 3 / 2 (455.58eV) and Ti2p 1 / 2 (461.21eV), while Ti 2p 3 / 2 The composition exhibits four peaks at 455.32 eV, 456.28 eV, 457.48 eV, and 459.43 eV, corresponding to Ti-C, Ti-F, Ti-O, and TiO2, respectively. After high-temperature calcination, the signals of Ti-C, Ti-F, and Ti-O decrease sharply, indicating their replacement by TiO2. It is readily apparent that the binding energies of 458.58 eV and 463.32 eV in the central sample are attributed to the 2p binding energy of Ti-O. 3 / 2 and Ti-O 2p 1 / 2 Compared to MXene / TiO2, the Ti-O 2p in the ternary composite... 3 / 2 and Ti-O 2p 1 / 2 Slight positive shifts occurred between each electron, and the binding energy is determined by the Coulomb interaction between the atomic nucleus and the outer electrons. Therefore, the change in binding energy reflects the change in electron density. Figure 3 c shows the high-resolution O 1s energy spectrum. In MXene / TiO2, the peaks at 530.14 eV and 531.94 eV are attributed to Ti-O bonds and chemisorbed oxygen (O2), respectively. c After the formation of the ternary heterojunction, the proportion of chemically adsorbed oxygen increases significantly, which is extremely beneficial for improving gas-sensing activity. Zn 2p energy dispersive spectroscopy of pure ZnIn2S4 and MXene / TiO2 / ZnIn2S4 (…) Figure 3 d) at 1022.01 eV (Zn 2p 3 / 2 ) and 1045.06 eV (Zn 2p 1 / 2 The characteristic peak appears at ( ), and the spin-orbit splitting energy is approximately 23.05 eV, confirming that Zn 2+ The presence of Zn 2p in the ternary MXene / TiO2 / ZnIn2S4 heterojunction. Compared to ZnIn2S4, Zn 2p in the ternary MXene / TiO2 / ZnIn2S4 heterojunction. 3 / 2 and Zn 2p 1 / 2 The peaks shifted positively by 0.06 eV and 0.05 eV, respectively, indicating that Zn atoms lost electrons and the electron density decreased. Figure 3 e shows the In 3d energy spectrum, with pure ZnIn2S4 at 445.05 eV (In 3d). 5 / 2 ) and 452.61 eV (In 3d 3 / 2 Characteristic peaks appear at ( ). In ternary heterostructures, both peaks show a slight positive shift, indicating a decrease in local electron density around the In atom. For example... Figure 3As shown in f, the S 2p of pure ZnIn2S4 3 / 2 and S 2p 1 / 2 The peaks are located at 161.78 eV and 163.02 eV, respectively. In the ternary heterojunction, these peaks exhibit small positive shifts of 0.04 eV and 0.01 eV, respectively. In summary, these results confirm the strong interfacial coupling and electronic interactions between MXene / TiO2 and ZnIn2S4, which are beneficial for promoting efficient charge transfer and separation within the heterojunction.

[0057] (4) In order to further analyze the microstructure of the sample, the specific surface area and pore size of the sample were determined by nitrogen adsorption-desorption isotherm test.

[0058] The result is as follows Figure 4 As shown, the N2 adsorption-desorption isotherms of MXene, MXene / TiO2, ZnIn2S4, and MXene / TiO2 / ZnIn2S4 all exhibit type IV isotherm characteristics, accompanied by an H3-type hysteresis loop, indicating the presence of mesoporous structures in the samples. Furthermore, the pore size distribution curves in the inset further confirm the presence of mesopores. Among them, ZnIn2S4 exhibits the largest specific surface area, which is attributed to the layered structure of the two-dimensional ZnIn2S4 nanosheets. Notably, a larger specific surface area provides abundant adsorption sites and surface active sites. The specific surface area of ​​MXene / TiO2 / ZnIn2S4 is 23.2614 m² / m³. 2 / g) was significantly higher than MXene (4.6509 m 2 / g) and MXene / TiO2 (11.4317 m 2 ( / g), which indicates that MXene / TiO2 / ZnIn2S4 has potential in gas sensing applications.

[0059] Example 6 The materials prepared in Example 3 and Comparative Examples 1-3 were tested for their performance in detecting triethylamine gas, as detailed below: Six test points were selected within a temperature range of 100℃ to 350℃, and each temperature test point was repeated several times. The response values ​​of MXene and MXene / TiO2 were low and fluctuated very little with increasing operating temperature. For ZnIn2S4, the response value was low and did not change much in the temperature range of 100℃ to 250℃, but reached a peak response value of about 10 at 300℃, after which the response value began to decrease with further increase in temperature. The MXene / TiO2 / ZnIn2S4 composite material showed a significantly different trend—its response value continued to increase with increasing operating temperature, reaching a peak of about 48 at 300℃, and began to decrease after exceeding the optimal operating temperature, with the curve exhibiting typical volcano-type sensor characteristics. Therefore, all subsequent tests were conducted at the optimal operating temperature of 300℃. The experimental results show that an appropriate amount of ZnIn2S4 can effectively improve the performance of MXene / TiO2. Therefore, by constructing a heterostructure, the gas-sensing performance of triethylamine was significantly improved, and 300℃ was selected as the optimal operating temperature in the subsequent gas-sensing tests.

[0060] The dynamic responses of different samples to triethylamine were recorded in continuous and repeated tests under a triethylamine atmosphere of 100 ppm. Figure 6 Each sample was tested repeatedly for 10 cycles under the same conditions. In any cycle, the introduction of triethylamine gas was observed to immediately cause a change in the material's resistance, which then tended to stabilize at a certain value. With the release of triethylamine and the introduction of air, the resistance eventually returned to its original value. Repeated testing over multiple cycles showed high stability. The construction of the heterostructure had a significant impact on the response to triethylamine gas. Compared with pure ZnIn2S4 (… Figure 6 b), MXene / TiO2 ( Figure 6 c) and MXene Figure 6 Compared to the response value of d), MXene / TiO2 / ZnIn2S4 ( Figure 6 a) The average response value increased significantly.

[0061] The dynamic sensing performance of each sensor was tested under different concentrations of triethylamine. Figure 7 The study found that MXene / TiO2 / ZnIn2S4 still showed a response to 10 ppm triethylamine. The response value also showed a significant upward trend with increasing triethylamine gas concentration. When the concentration reached 500 ppm, the response value almost saturated. Testing the dynamic sensing performance of other sensors clearly showed that the response value of ZnIn2S4 increased with increasing triethylamine concentration, but quickly reached saturation at 200 ppm, while MXene / TiO2 and MXene showed almost no response throughout the entire concentration range.

[0062] Figure 8The linear fit of MXene / TiO2 / ZnIn2S4 to different concentrations (from 10 ppm to 500 ppm) of triethylamine gas at 300°C is shown. According to the formula LOD = κσ / S (where κ is typically set to 3, σ represents the standard deviation of the measurement, and S represents the slope), the limit of detection (LOD) is approximately 697.2 ppb. Considering that the permissible safe emission limit for triethylamine in practical applications is 10 ppm, the obtained LOD fully meets the requirements of actual monitoring.

[0063] like Figure 8 As shown in b, the response / recovery curves are data extracted from one cycle of the MXene / TiO2 / ZnIn2S4 stability test data. Response time is defined as the time required for the sensor to reach 90% of its maximum resistance after exposure to a gas, while recovery time is the time required for the sensor to recover to 90% of its initial resistance after exposure to air. The test results show that the response time and recovery time are 60 seconds and 251 seconds, respectively. Furthermore, selectivity is another key parameter for evaluating gas sensors. Under the same test conditions, the response of MXene / TiO2 / ZnIn2S4 was tested by introducing 100 ppm of different common ambient gases (including methanol, ethanol, formaldehyde, acetaldehyde, acetic acid, formic acid, acetone, ethyl acetate, n-propanol, hydrogen sulfide, and nitrogen dioxide). The results show that MXene / TiO2 / ZnIn2S4 exhibits significant selectivity for triethylamine. Figure 8 c) Furthermore, MXene / TiO2 / ZnIn2S4 also exhibits excellent resistance to humidity interference and long-term stability against triethylamine. For example... Figure 9 As shown in Figure a, under relative humidity conditions of 20%–80%, it still maintains a response value of approximately 48 to triethylamine (100 ppm). To investigate whether it exhibits long-term stability to triethylamine, data were collected five times over 90–110 days. Under the same conditions, the response value of MXene / TiO2 / ZnIn2S4 to triethylamine showed minimal fluctuation within the allowable error range, demonstrating high stability. Figure 9 b) Example 7 To further elucidate the band structure arrangement of ZnIn2S4 and MXene / TiO2 in the formed heterostructure, a series of characterizations were performed (including UPS, UV-Vis absorption spectroscopy, and Mott Schottky test). The result is as follows Figure 10 As shown, Figure 10 a and Figure 10The test data from the UPS of d shows the distances from the Fermi level to the vacuum level for ZnIn2S4 and MXene / TiO2, i.e., work functions of 10.71 eV and 12.02 eV, respectively. Based on the UV-Vis absorption spectroscopy results, the band gaps for ZnIn2S4 and MXene / TiO2 are 2.46 eV, respectively. Figure 10 b) and 3.17 eV ( Figure 10 e). According to Mott Schottky tests, the conduction band of ZnIn2S4 is approximately -0.75 V ( Figure 10 c), while the valence band of MXene / TiO2 is approximately -0.59V ( Figure 10 f).

[0064] Example 8 To investigate the real-time gas-sensing behavior of triethylamine (TEA) on the surface of MXene / TiO2 / ZnIn2S4 heterojunction, in-situ Fourier transform infrared spectroscopy (FTIR) was performed.

[0065] The result is as follows Figure 11 As shown in figure a, the infrared spectrum recorded the changes over a period of 0 to 60 minutes. (1295-1474 cm⁻¹) -1 -CH2 and -CH3 bending vibration bands within the range ( Figure 11 b) They remained largely unchanged throughout the process, indicating that these functional groups maintained structural integrity without significant bond breaking or rearrangement. It is worth noting that... Figure 11 c shows that triethylamine underwent partial oxidation at the surface of the heterojunction: 1557 cm⁻¹ -1 The enhanced absorption peak at 1618 cm⁻¹ originates from the NH bending vibration generated by TEA oxidation, a process possibly induced by hydroxyl or oxidized functional groups on the material surface; -1 The absorption peak at the interface corresponds to the CN stretching vibration. The heterojunction formed by TiO2 and ZnIn2S4 promotes hole migration and drives the oxidation reaction, while MXene enhances carrier transport efficiency. The synergistic effect of these three factors drives the excitation and conversion of the TEA. Infrared results clearly confirm the existence of a thermally induced surface oxidation reaction at the heterojunction. However, Figure 11 d is 2938.02 cm -1 (-CH2) and 2975.62 cm -1The stable stretching vibration peak of (-CH3) indicates that the main chain of most TEA molecules did not participate in the reaction and remained in a physically adsorbed state on the material surface. These results suggest that only a small portion of the surface-adsorbed molecules undergo oxidation under high TEA concentrations. The MXene / TiO2 / ZnIn2S4 heterojunction exhibits some selective chemical reactivity towards TEA, but the overall conversion efficiency remains limited under high concentration conditions. In conclusion, the gas-sensitive reaction of triethylamine on the heterojunction surface can lead to its mineralization and decomposition under catalysis.

[0066] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application 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 other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing an MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material, characterized in that, Includes the following steps: Two-dimensional MXene nanosheets were obtained by using a water bath method combined with ultrasonic exfoliation of accordion-shaped MXene. TiO2 nanoparticles were grown in situ by calcination at 300℃~380℃ on the surface of the two-dimensional MXene nanosheets to obtain the intermediate product MXene / TiO2 heterojunction material. ZnIn2S4 nanosheets were further grown on the surface of the intermediate product MXene / TiO2 heterojunction material using a water bath method to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material. The MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material includes a substrate, an intermediate layer, and an outer layer. The substrate is a two-dimensional MXene nanosheet, the middle layer is TiO2 nanoparticles, and the outer layer is ZnIn2S4 nanosheets; A metal-semiconductor interface is formed between the two-dimensional MXene nanosheets and the TiO2 nanoparticles; a semiconductor heterostructure interface is formed between the TiO2 nanoparticles and the ZnIn2S4 nanosheets. The loading of ZnIn2S4 nanosheets in the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material is 1 wt%~3 wt%; The specific surface area of ​​the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material is 20 m². 2 / g~50 m 2 / g; The MXene nanosheets have a lateral dimension of 2 μm to 10 μm, the TiO2 nanoparticles have a size of 5 nm to 10 nm, and the ZnIn2S4 nanosheets have a thickness of 10 nm to 50 nm. The specific preparation method for obtaining two-dimensional MXene nanosheets by combining water bath method with ultrasonic exfoliation of accordion-shaped MXene includes the following steps: Lithium fluoride was dissolved in concentrated hydrochloric acid and stirred to obtain a reaction solution; Aluminum carbide was added to the reaction solution for a water bath reaction. After the reaction, the solution was washed with dilute hydrochloric acid and water in sequence and centrifuged. Then, ultrasonic exfoliation and reaction were performed under an argon atmosphere. After the reaction, the solution was centrifuged, the supernatant was taken, frozen, and dried to obtain the two-dimensional MXene nanosheets. The molar ratio of lithium fluoride to aluminum carbide is 11~12:

1.

2. The preparation method according to claim 1, characterized in that, The concentration of the concentrated hydrochloric acid is 11 mol / L to 13 mol / L, and the concentration of the dilute hydrochloric acid is 1 mol / L. The ultrasonic power during ultrasonic ablation is 50W~80W.

3. The preparation method according to claim 1, characterized in that, The specific preparation method of obtaining the intermediate product MXene / TiO2 heterojunction material by in-situ oxidation growth of TiO2 nanoparticles on the surface of the two-dimensional MXene nanosheets through high-temperature calcination at 300℃~380℃ includes the following steps: The two-dimensional MXene was dissolved in sodium hydroxide solution and stirred continuously. After the reaction was completed, the sample was washed alternately with deionized water and ethanol, centrifuged, and freeze-dried to obtain a black sample powder. The black sample powder was placed in a muffle furnace and calcined at a high temperature of 300℃~380℃ for 2 h~6 h to obtain the intermediate product MXene / TiO2 heterojunction material.

4. The preparation method according to claim 1, characterized in that, The specific preparation method for further growing ZnIn2S4 nanosheets on the surface of the intermediate MXene / TiO2 heterojunction material using a water bath method to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material includes the following steps: Zinc chloride, indium chloride, and thioacetamide are dissolved in water, mixed, and stirred to obtain a reaction solution. The pH of the reaction solution was adjusted to 1-3 using nitric acid, and then the intermediate product MXene / TiO2 heterojunction material was added for a water bath reaction. After the reaction was completed, the product was washed and dried to obtain the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material.

5. The preparation method according to claim 4, characterized in that, The molar ratio of zinc chloride, indium chloride and thioacetamide is 1:1~3:1~4; The water bath reaction temperature is 40 ℃~100 ℃, and the reaction time is 1 h~3 h.

6. The MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material obtained by any of the preparation methods described in claims 1-5.

7. A gas sensor, characterized in that, Includes the MXene / TiO2 / ZnIn2S4 ternary integrated heterojunction material as described in claim 6.

8. The application of the gas sensor according to claim 7 in the detection of triethylamine gas.

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