阅读说明：本技术 基于可印刷纳米复合材料的平面柔性室温气体传感器 (Planar flexible room temperature gas sensor based on printable nanocomposite ) 是由 李鸿鹏 闻杰 徐金勇 吴凯迪 张超 于 2020-11-03 设计创作，主要内容包括：本发明公开了一种基于可印刷纳米复合材料的平面柔性室温气体传感器,该传感器包含柔性衬底、导电层和气体敏感层,所述铺设于柔性衬底上的导电层为Au或Ag叉指电极；所述覆盖于导电层上的气体敏感层是Ag/TiO-2/Ti-3C-2T-(x)纳米复合材料涂层。本发明在Ti-3C-2T-(x)二维纳米片表面原位生成的Ag和TiO-2纳米颗粒可以有效阻止Ti-3C-2T-(x)二维纳米片的自堆叠,同时,Ag/Ti-3C-2T-(x)表面原位形成的TiO-2纳米颗粒确保了TiO-2-Ti-3C-2T-(x)和TiO-2-Ag异质结的生成,在Ag/TiO-2/Ti-3C-2T-(x)气体敏感材料内部构建了多重肖特基势垒,室温条件下对1 ppm丙酮的响应值高达77%,实现对低浓度丙酮的快速且高灵敏的检测,在智能医疗、可穿戴器件等领域具有巨大应用前景。(The invention discloses a planar flexible room temperature gas sensor based on a printable nanocomposite, which comprises a flexible substrate, a conducting layer and a gas sensitive layer, wherein the conducting layer laid on the flexible substrate is an Au or Ag interdigital electrode; the gas sensitive layer covered on the conductive layer is Ag/TiO 2 /Ti 3 C 2 T x A nanocomposite coating. The invention is in Ti 3 C 2 T x Ag and TiO generated in situ on surface of two-dimensional nanosheet 2 The nanoparticles can effectively prevent Ti 3 C 2 T x Self-stacking of two-dimensional nanoplates, simultaneously, Ag/Ti 3 C 2 T x Surface in situ formed TiO 2 The nano-particles ensure TiO 2 ‑Ti 3 C 2 T x And TiO 2 Formation of Ag heterojunctions in Ag/TiO 2 /Ti 3 C 2 T x Multiple Schottky barriers are built in the gas sensitive material at room temperatureThe response value to 1 ppm acetone under the condition reaches up to 77 percent, the rapid and high-sensitivity detection to the low-concentration acetone is realized, and the method has great application prospect in the fields of intelligent medical treatment, wearable devices and the like.)

1. The planar flexible room-temperature gas sensor is characterized by comprising a flexible substrate, a conductive layer and a gas sensitive layer, wherein the conductive layer laid on the flexible substrate is an Au or Ag interdigital electrode; the gas sensitive layer covered on the conductive layer is Ag/TiO₂/Ti₃C₂T _x A nanocomposite coating.

2. The sensor of claim 1, wherein the flexible substrate material comprises any one of polyethylene terephthalate and polyimide.

3. The sensor according to claim 1, wherein the number of interdigital pairs of Au or Ag interdigital electrodes is 5 to 20, the electrode width is 1 μm to 100 μm, and the electrode pitch is 1 μm to 100 μm.

4. The sensor of claim 1, wherein Ag/TiO₂/Ti₃C₂T _x The nano composite material coating is printed with Ag/TiO by spraying₂/Ti₃C₂T _x Aqueous dispersion of nanocomposite, wherein Ag/TiO₂/Ti₃C₂T _x The aqueous dispersion of the nanocomposite was prepared by the following steps:

1) taking Ti₃C₂T _x Adding deionized water to dilute, stirring, and adding AgNO dropwise₃Solution of AgNO₃With Ti₃C₂T _x The mass ratio of the Ag to the Ti is 0.1-0.4: 1, ultrasonic treatment is carried out for 10-15 min after full stirring reaction, the product is centrifuged at the rotating speed of 8000-10000 rpm and is repeatedly washed by deionized water, the centrifugal precipitate is re-dispersed in a proper amount of water, and ultrasonic treatment is carried out for 5-10 min to obtain the Ag/Ti with the concentration of 1-5 mg/mL₃C₂T _x An aqueous dispersion;

2) taking the above Ag/Ti₃C₂T _x Carrying out autoxidation reaction on the aqueous dispersion in an oven at the temperature of 80 ℃ for 4-24 h to obtain Ag/TiO₂/Ti₃C₂T _x An aqueous dispersion solution of a nanocomposite.

5. The sensor of claim 4, wherein Ti₃C₂T _x The colloid was prepared by the following steps: mixing Ti of 400 meshes₃AlC₂Slowly adding the powder into an etching solution containing LiF and 9 mol/L concentrated hydrochloric acid, and adding Ti₃AlC₂The mass ratio of the powder to the LiF is 0.9-1.1, and Ti₃AlC₂The mass volume ratio of the powder to the concentrated hydrochloric acid is 2 g: 30-50 mL, and the concentrated hydrochloric acid is dissolved in water at 40-60 DEG CStirring and reacting for 36 h in a bath, and after the reaction is finished, centrifuging the product at 3500 rpm and repeatedly washing the product with deionized water until the pH value of the supernatant is 6-7; then dispersing the washed product into deionized water, violently shaking for 30-60 min, centrifuging at 3500 rpm for 30-60 min, taking the upper layer solution to obtain Ti₃C₂T _x And (3) colloid.

6. The method of making a planar flexible room temperature gas sensor of any of claims 1-5, comprising the steps of:

1) the conducting layer is deposited on the flexible substrate through vacuum evaporation or magnetron sputtering;

2) repeatedly washing the flexible substrate with the conductive layer by using deionized water and absolute ethyl alcohol, drying, and sticking the region around the conductive layer by using a polyimide adhesive tape to carry out masking so that the spraying printing range is limited in the region where the conductive layer is located;

3) measuring Ag/TiO with concentration of 1-5 mg/mL₂/Ti₃C₂T _x Placing the aqueous dispersion of the nano composite material in a spray gun storage tank, uniformly spraying the aqueous dispersion on a flexible substrate with a conductive layer, wherein the spraying thickness is 50-200 nm, and drying the flexible substrate for 30-60 min at the temperature of 60-80 ℃ under a vacuum condition;

4) and removing the adhesive tape to obtain the required planar flexible room-temperature gas sensor.

7. Use of a planar flexible room temperature gas sensor according to any of claims 1 to 5 for gas detection.

Technical Field

The invention belongs to the technical field of gas sensors, and particularly relates to a Ag/TiO material₂/Ti₃C₂T _x A flexible room temperature gas sensor with plane bending deformation and nano composite material as a sensitive electrode and a preparation method thereof.

Background

Current medical research indicates that human exhaled breath contains a variety of volatile organic compounds and inorganic gases, which are closely related to human physical conditions. At present, ammonia gas (renal failure), acetone (diabetes) and other gases are used as biomarkers for diagnosing corresponding diseases. The concentration of these gases in the expired air of the patient is obviously higher than that of a healthy person, so that the expired air can be analyzed by using the gas sensor, and noninvasive diagnosis of various diseases can be realized.

The gas sensor is an induction device for detecting the existence and concentration change of gas in a certain range, and can realize accurate detection on the type and concentration change of the gas. With the rise of wearable devices and internet of things, the demand of the modern society for flexible room temperature gas sensors with high selectivity and high sensitivity is increasing. However, most are based on transition metal oxides (ZnO, SnO)₂Etc.) semiconductor gas sensors are fabricated on rigid substrates such as Indium Tin Oxide (ITO) coated glass or silicon wafers, and cannot be integrated into wearable electronics. In addition, the optimum operating temperature of the transition metal oxide based gas sensor is generally higher than 100 ℃, and the sensitivity is not high, and the response-recovery time is too long, which severely limits the integration thereof in the embedded monitoring system.

MXenes (especially Ti) as a novel class of transition metal carbo/nitrides₃C₂T _x ) Has excellent metalloid conductivity, hydrophilicity, adsorption property and surface functional group adjustability, and high mechanical strength, and can be used as a high-performance gas sensing material. Studies have shown that, compared to other two-dimensional materials (e.g., graphene, black phosphorus, transition metal disulfides, etc.),based on Ti₃C₂T _x Has an ultra-high signal-to-noise ratio (ACS Nano, 2018, 12, 986-₃C₂T _x The low response values of base gas sensors limit their large area applications in the sensor field.

In recent years, some efforts have been made by researchers to improve the gas sensing performance of MXenes. ZHao et al (InfoMat, 2019, 1, 407-416) use a low temperature polymerization method at Ti₃C₂T _x PANI nano-particles grow in situ on the nano-chip, and the prepared PANI/Ti₃C₂T _x The response of the nanocomposite to acetone at room temperature was about 20% (200 ppm). Yang et al (Sensors)&Actors b. Chemical, 2021, 326, 128828) use ultrasonic spray pyrolysis to prepare anti-agglomeration three-dimensional Ti₃C₂T _x the/ZnO wrinkled ball realizes the acetone sensing at room temperature, but has lower response value (about 2.5 percent and 100 ppm). Sun et al (Sensors)&Actors: b. Chemical, 2020, 304, 127274) using a solvothermal method on two-dimensional Ti₃C₂T _x On the nano-chip in-situ grows a one-dimensional W₁₈O₄₉Nanowires, W produced therefrom₁₈O₄₉/Ti₃C₂T _x The nanocomposites can detect low concentrations of acetone, but the response is only 11.6% (20 ppm) and their optimum operating temperature is up to 300 ℃.

Disclosure of Invention

The invention aims to provide a silver/TiO-based material₂/Ti₃C₂T _x A planar flexible room temperature gas sensor made of a nano composite material, a preparation method of the sensor and application of the sensor in acetone detection. The sensor obtained by the invention has the conventional Ti₃C₂T _x The base sensor has the highest acetone response and has good selectivity and mechanical flexibility. The preparation method is simple in preparation process, and the full water phase is green, environment-friendly and pollution-free, and can be prepared in large batch.

The invention provides a plane soft pieceThe gas sensor at the room temperature comprises a flexible substrate, a conducting layer and a gas sensitive layer, wherein the conducting layer laid on the flexible substrate is an Au or Ag interdigital electrode; the gas sensitive layer covered on the conductive layer is Ag/TiO₂/Ti₃C₂T _x A nanocomposite coating.

Preferably, the flexible substrate material includes any one of polyethylene terephthalate and polyimide.

Preferably, the interdigital pair number of the Au or Ag interdigital electrode is 5-20 pairs, the electrode width is 1-100 μm, and the electrode spacing is 1-100 μm.

Preferably, Ag/TiO₂/Ti₃C₂T _x The nano composite material coating is printed with Ag/TiO by spraying₂/Ti₃C₂T _x Aqueous dispersion of nanocomposite, wherein Ag/TiO₂/Ti₃C₂T _x The aqueous dispersion of the nanocomposite was prepared by the following steps:

1) taking Ti₃C₂T _x Adding appropriate amount of deionized water into the colloid for dilution, and adding AgNO dropwise under magnetic stirring₃Solution of AgNO₃With Ti₃C₂T _x The mass ratio of the Ag to the Ti is 0.1-0.4: 1, ultrasonic treatment is carried out for 10-15 min after full stirring reaction, the product is centrifuged at the rotating speed of 8000-10000 rpm and is repeatedly washed by deionized water, the centrifugal precipitate is re-dispersed in a proper amount of water, and ultrasonic treatment is carried out for 5-10 min to obtain the Ag/Ti with the concentration of 1-5 mg/mL₃C₂T _x An aqueous dispersion;

2) taking the above Ag/Ti₃C₂T _x Carrying out autoxidation reaction on the aqueous dispersion in an oven at the temperature of 80 ℃ for 4-24 h to obtain Ag/TiO₂/Ti₃C₂T _x An aqueous dispersion solution of a nanocomposite.

In particular, Ti₃C₂T _x The colloid was prepared by the following steps: mixing Ti of 400 meshes₃AlC₂Slowly adding the powder into an etching solution containing LiF and 9 mol/L concentrated hydrochloric acid, and adding Ti₃AlC₂The mass ratio of the powder to the LiF is 0.9-1.1, and Ti₃AlC₂The mass volume ratio of the powder to the concentrated hydrochloric acid is 2 g: 30-50 mL, the mixture is stirred and reacted for 36 hours in a water bath at the temperature of 40-60 ℃, and after the reaction is finished, the product is centrifuged at 3500 rpm and repeatedly washed by deionized water until the pH value of the supernatant is 6-7; dispersing the washed product in 60-70 mL of deionized water, violently shaking for 30-60 min, centrifuging at 3500 rpm for 30-60 min, and taking the upper solution to obtain Ti₃C₂T _x (wherein T represents a surface-linked-F, -OH, = O active functional group, and x represents the number of surface functional groups) colloid, and the concentration thereof is 5-10 mg/mL.

The preparation method of the planar flexible room temperature gas sensor comprises the following steps:

1) the conducting layer is deposited on the flexible substrate through vacuum evaporation or magnetron sputtering;

2) repeatedly washing the flexible substrate with the conductive layer by using deionized water and absolute ethyl alcohol, drying, and sticking the region around the conductive layer by using a polyimide adhesive tape to carry out masking so that the spraying printing range is limited in the region where the conductive layer is located;

3) measuring Ag/TiO with concentration of 1-5 mg/mL₂/Ti₃C₂T _x Placing the aqueous dispersion of the nano composite material in a spray gun storage tank, uniformly spraying the aqueous dispersion on a flexible substrate with a conductive layer, wherein the spraying thickness is 50-200 nm, and drying the flexible substrate for 30-60 min at the temperature of 60-80 ℃ under a vacuum condition;

4) and removing the adhesive tape to obtain the required planar flexible room-temperature gas sensor.

The invention provides an application of a planar flexible room temperature gas sensor in manufacturing of wearable equipment related to human health monitoring.

The invention provides an application of a planar flexible room-temperature gas sensor in gas detection, wherein the gas sensor adsorbs gas molecules to cause the resistance of the gas sensor to change so as to be used for detecting information such as human health conditions.

Further, the gas sensor shows excellent gas-sensitive performance to acetone gas under the condition of room temperature (25 ℃): has high selectivity and stability to acetone, has response value of up to 77% to 1 ppm acetone, and is suitable for non-destructive diagnosis of diabetes.

Furthermore, the gas sensor is connected to an information receiving and processing system such as a computer or mobile phone software in a wired or wireless mode to collect, detect and analyze data.

Compared with the prior art, the invention provides a planar flexible room temperature gas sensor, which has the following advantages:

1) the invention discloses a flexible gas sensor prepared by spray printing, which is prepared from two-dimensional Ti₃C₂T _x Nanosheet based direct reduction of Ag without the addition of a reducing agent⁺Method for preparing nano confined Ag/TiO by ion and solution autoxidation₂/Ti₃C₂T _x The nano composite material greatly improves the acetone sensing performance to improve Ti₃C₂T _x The gas sensitive properties of the base sensor provide a viable solution.

2) The sensor can work under the condition of room temperature, does not need to heat a device to high temperature for testing, and slows down the aging and damage of materials caused under the environment of higher temperature.

3) The invention discloses a flexible gas sensor prepared by spray printing, which is simple in preparation method and easy to operate. The preparation method is prepared by directly spraying the aqueous dispersion, has the advantages of low cost, no pollution, simplicity, convenience, environmental protection, easiness in batch preparation and the like, has certain mechanical flexibility, and is hopeful to be applied to wearable equipment.

Drawings

FIG. 1 shows Ag/TiO prepared by the present invention through autoxidation for 4 h₂/Ti₃C₂T _x Scanning electron microscopy of the nanocomposite.

FIG. 2 shows Ag/TiO prepared by the present invention from autoxidation reaction for 8 h₂/Ti₃C₂T _x Scanning electron microscopy of the nanocomposite.

FIG. 3 is a graph showing the selectivity of the prepared sensor to 1 ppm of nitrogen dioxide, hydrogen sulfide, isopropyl alcohol, ethanol and acetone gases.

FIG. 4 is a continuous gradient test plot of the prepared sensors for 1 ppm and 10 ppm acetone gas.

FIG. 5 is a graph showing the response cycle of the prepared sensor to 5 ppm acetone gas.

Detailed Description

The present invention will be further described with reference to the following specific examples, which are not intended to limit the scope of the present invention.

The materials, reagents and the like used specifically and not shown in the examples are commercially available or may be obtained by a method known to those skilled in the art without specific description. The specific experimental procedures and operating conditions involved are generally in accordance with conventional process conditions and conditions as described in the manual or as recommended by the manufacturer.

In the present invention, the applicant proposed a method for directly reducing Ag without adding a reducing agent⁺Method for preparing nano confined Ag/TiO by ion and solution autoxidation₂/Ti₃C₂T _x A method of gas sensitive materials. Ti₃C₂T _x The two-dimensional nano-sheets have good water dispersibility, but the dried Ti is generated due to strong van der Waals force and hydrogen bond action between the two-dimensional nano-sheets₃C₂T _x The two-dimensional nanoplatelets are seriously aggregated, which causes the nanoplatelets to lose the advantage of large specific surface area and is not beneficial to gas sensing. At Ti₃C₂T _x Ag and TiO generated in situ on surface of two-dimensional nanosheet₂The nanoparticles can effectively prevent Ti₃C₂T _x Self-stacking of two-dimensional nanoplates, more importantly, Ag/Ti₃C₂T _x Surface in situ formed TiO₂The nano-particles ensure TiO₂-Ti₃C₂T _x And TiO₂Formation of Ag heterojunctions in Ag/TiO₂/Ti₃C₂T _x In gas-sensitive materialsMultiple Schottky barriers are constructed, and rapid and high-sensitivity detection of low-concentration acetone under the room temperature condition is realized. The gas sensor is mainly used for detecting acetone in the exhaled gas of a human body, is high in sensitivity, short in detection time and large in response value, and has a huge application prospect in the fields of intelligent medical treatment, wearable devices and the like.

The preparation method of the planar flexible room temperature gas sensor comprises the following steps:

1) the Au or Ag interdigital electrodes are deposited on the polyimide or polyethylene glycol terephthalate flexible substrate through vacuum evaporation or magnetron sputtering, the number of interdigital pairs of the electrodes is 5-20 pairs, the width of the electrodes is 1-100 mu m, and the electrode spacing is 1-100 mu m;

2) repeatedly washing the flexible substrate with the Au or Ag interdigital electrode with deionized water and absolute ethyl alcohol, drying, and sticking the region around the electrode with a polyimide adhesive tape to carry out masking, so that the spraying printing range is limited in the region where the interdigital electrode is located, and the error among sensors in each batch is reduced;

3) measuring Ag/TiO with concentration of 1-5 mg/mL₂/Ti₃C₂Placing the aqueous dispersion of the T nano composite material in a spray gun storage tank, uniformly spraying the aqueous dispersion on a flexible substrate with interdigital electrodes, wherein the spraying thickness is 50-200 nm, and drying the aqueous dispersion for 30-60 min at the temperature of 60-80 ℃ under a vacuum condition;

4) and removing the adhesive tape to obtain the required planar flexible room-temperature gas sensor.

Wherein, Ag/TiO₂/Ti₃C₂T _x The aqueous dispersion of the nanocomposite was prepared by the following steps:

1) mixing Ti of 400 meshes₃AlC₂Slowly adding the powder into an etching solution containing LiF and 9 mol/L concentrated hydrochloric acid, and adding Ti₃AlC₂The mass ratio of the powder to the LiF is 0.9-1.1, and Ti₃AlC₂The mass volume ratio of the powder to the concentrated hydrochloric acid is 2 g: 30-50 mL, and the powder is stirred and reacted for 36 hours in a water bath at the temperature of 40-60 ℃. After the reaction is finished, centrifuging the product at 3500 rpm and repeatedly washing the product with deionized water until the pH value of the supernatant is 6-7; then the water is washed cleanDispersing the product in 60-70 mL of deionized water, violently shaking for 30-60 min, centrifuging at 3500 rpm for 30-60 min, and taking the upper Ti layer₃C₂T _x (wherein T represents a surface-linked-F, -OH, = O active functional groups, and x represents the number of surface functional groups) colloid, and the concentration of the colloid is 5-10 mg/mL;

2) taking 5-10 mL of the Ti₃C₂T _x Adding a proper amount of deionized water into the colloid for dilution, and dropwise adding 5-10 mL of AgNO under magnetic stirring₃Solution of AgNO₃With Ti₃C₂T _x The mass ratio of the Ag to the Ti is 0.1-0.4: 1, ultrasonic treatment is carried out for 10-15 min after full stirring reaction, the product is centrifuged at the rotating speed of 8000-10000 rpm and is repeatedly washed by deionized water, the centrifugal precipitate is re-dispersed in a proper amount of water, and ultrasonic treatment is carried out for 5-10 min to obtain the Ag/Ti with the concentration of 1-5 mg/mL₃C₂T _x An aqueous dispersion;

3) taking 5-10 mL of the Ag/Ti₃C₂T _x Carrying out autoxidation reaction on the aqueous dispersion in an oven at the temperature of 80 ℃ for 4-24 h to obtain Ag/TiO₂/Ti₃C₂T _x An aqueous dispersion solution of a nanocomposite.

Example 1

(1) Two-dimensional Ti₃C₂T _x Preparing a nano sheet: under magnetic stirring, adding Ti of 400 meshes₃AlC₂The powder was slowly added to an etching solution containing 2 g LiF and 9 mol/L concentrated hydrochloric acid, and reacted for 36 h with magnetic stirring at 350 rpm in a water bath at 50 ℃. After the reaction is finished, centrifuging the product at 3500 rpm and repeatedly washing the product with deionized water until the pH value of the supernatant is 6-7; then dispersing the washed product in 60-70 mL of deionized water, violently shaking for 30 min, centrifuging at 3500 rpm for 30 min, and taking the upper Ti layer₃C₂T _x (wherein T represents a surface-linked-F, -OH, = O active functional group, and x represents the number of surface functional groups) colloid, the concentration of which is 5 mg/mL, is put into a refrigerator for low-temperature storage and standby.

（2）Ag/TiO₂/Ti₃C₂T _x Preparing a nano composite: 5 mL of Ti prepared in step (1) was taken₃C₂T _x Adding 20 mL of deionized water into the colloid, diluting to 1 mg/mL, and dropwise adding 0.02 mol/L AgNO under magnetic stirring₃Solution of AgNO₃With Ti₃C₂T _x The mass ratio of the components is 0.17:1, ultrasonic treatment is carried out for 10 min after full stirring reaction, the product is centrifuged at the rotating speed of 8000 rpm and is repeatedly washed by deionized water, the centrifugal precipitate is re-dispersed in a proper amount of water, and ultrasonic treatment is carried out for 5-10 min to obtain Ag/Ti with the concentration of 1 mg/mL₃C₂T _x An aqueous dispersion. 10 mL of the above Ag/Ti₃C₂T _x Autoxidation reaction of the aqueous dispersion in an oven at 80 ℃ for 4 h to obtain Ag/TiO₂/Ti₃C₂T _x Aqueous dispersion of nanocomposite, in which Ag/TiO₂/Ti₃C₂T _x The scanning electron micrograph of the nanocomposite is shown in FIG. 1.

(3) Preparing an Au interdigital electrode: au interdigital electrodes with the thickness of 50 nm (the number of interdigital pairs is 10 pairs, and the electrode width and the electrode spacing are both 50 mu m) are evaporated on the polyimide film by using a mask.

(4) Preparing a planar flexible gas sensor: and (4) repeatedly washing the flexible polyimide substrate with the Au interdigital electrode, which is manufactured in the step (3), with deionized water and absolute ethyl alcohol, drying, and sticking the area around the electrode with a polyimide adhesive tape to perform masking. Measuring the Ag/TiO prepared in the step (2) with proper concentration₂/Ti₃C₂And (3) putting the aqueous dispersion solution T into a spray gun storage tank, uniformly spraying the aqueous dispersion solution T on a flexible substrate with interdigital electrodes, wherein the spraying thickness is 100 nm, and drying for 60 min at 60 ℃ under a vacuum condition. And removing the adhesive tape to obtain the required planar flexible room-temperature gas sensor.

(5) And (3) testing gas-sensitive performance: the ratio of the resistance difference value | Δ R | of the sensor in the target gas and the air to the resistance value in the air (| Δ R |/R |)_air100%) is the response of the sensor to the concentration of the target gas.

Example 2

(1) Two-dimensional Ti₃C₂T _x Preparing a nano sheet: under magnetic stirring, adding Ti of 400 meshes₃AlC₂The powder was slowly added to an etching solution containing 2 g LiF and 9 mol/L concentrated hydrochloric acid, and reacted for 36 h with magnetic stirring at 350 rpm in a water bath at 50 ℃. After the reaction is finished, centrifuging the product at 3500 rpm and repeatedly washing the product with deionized water until the pH value of the supernatant is 6-7; then dispersing the washed product in 60-70 mL of deionized water, violently shaking for 30 min, centrifuging at 3500 rpm for 30 min, and taking the upper Ti layer₃C₂T _x (wherein T represents a surface-linked-F, -OH, = O active functional group, and x represents the number of surface functional groups) colloid, the concentration of which is 5 mg/mL, is put into a refrigerator for low-temperature storage and standby.

（2）Ag/TiO₂/Ti₃C₂T _x Preparing a nano composite: 5 mL of Ti prepared in step (1) was taken₃C₂T _x Adding 20 mL of deionized water into the colloid, diluting to 1 mg/mL, and dropwise adding 0.02 mol/L AgNO under magnetic stirring₃Solution of AgNO₃With Ti₃C₂T _x The mass ratio of the components is 0.17:1, ultrasonic treatment is carried out for 10 min after full stirring reaction, the product is centrifuged at the rotating speed of 8000 rpm and is repeatedly washed by deionized water, the centrifugal precipitate is re-dispersed in a proper amount of water, and ultrasonic treatment is carried out for 5-10 min to obtain Ag/Ti with the concentration of 1 mg/mL₃C₂T _x An aqueous dispersion. 10 mL of the above Ag/Ti₃C₂T _x Autoxidation reaction of the aqueous dispersion in an oven at 80 ℃ for 8 h to obtain Ag/TiO₂/Ti₃C₂T _x Aqueous dispersion of nanocomposite, in which Ag/TiO₂/Ti₃C₂T _x The scanning electron micrograph of the nanocomposite is shown in FIG. 2.

(3) Preparing an Au interdigital electrode: au interdigital electrodes with the thickness of 50 nm (the number of interdigital pairs is 10 pairs, and the electrode width and the electrode spacing are both 50 mu m) are evaporated on the polyimide film by using a mask.

(4) Of flat flexible gas sensorsPreparation: and (4) repeatedly washing the flexible polyimide substrate with the Au interdigital electrode, which is manufactured in the step (3), with deionized water and absolute ethyl alcohol, drying, and sticking the area around the electrode with a polyimide adhesive tape to perform masking. Measuring the Ag/TiO prepared in the step (2) with proper concentration₂/Ti₃C₂And (3) putting the aqueous dispersion solution T into a spray gun storage tank, uniformly spraying the aqueous dispersion solution T on a flexible substrate with interdigital electrodes, wherein the spraying thickness is 100 nm, and drying for 60 min at 60 ℃ under a vacuum condition. And removing the adhesive tape to obtain the required planar flexible room-temperature gas sensor.

(5) And (3) testing gas-sensitive performance: the ratio of the resistance difference value | Δ R | of the sensor in the target gas and the air to the resistance value in the air (| Δ R |/R |)_air100%) is the response of the sensor to the concentration of the target gas. The gas sensor prepared by the step (4) shows excellent gas-sensitive performance to acetone gas under the condition of room temperature (25 ℃): has high selectivity and stability to acetone (figure 3), response value to 1 ppm acetone as high as 77 percent (figure 4), better reusability (figure 5) and suitability for nondestructive diagnosis of diabetes.

Example 3

(1) Two-dimensional Ti₃C₂T _x Preparing a nano sheet: under magnetic stirring, adding Ti of 400 meshes₃AlC₂The powder was slowly added to an etching solution containing 2 g LiF and 9 mol/L concentrated hydrochloric acid, and reacted for 36 h with magnetic stirring at 350 rpm in a water bath at 50 ℃. After the reaction is finished, centrifuging the product at 3500 rpm and repeatedly washing the product with deionized water until the pH value of the supernatant is 6-7; then dispersing the washed product in 60-70 mL of deionized water, violently shaking for 30 min, centrifuging at 3500 rpm for 30 min, and taking the upper Ti layer₃C₂T _x (wherein T represents a surface-linked-F, -OH, = O active functional group, and x represents the number of surface functional groups) colloid, the concentration of which is 5 mg/mL, is put into a refrigerator for low-temperature storage and standby.

（2）Ag/TiO₂/Ti₃C₂T _x Preparing a nano composite: 5 mL of Ti prepared in step (1) was taken₃C₂T _x Adding 20 mL of deionized water into the colloid, diluting to 1 mg/mL, and dropwise adding 0.02 mol/L AgNO under magnetic stirring₃Solution of AgNO₃With Ti₃C₂T _x The mass ratio of the components is 0.39:1, ultrasonic treatment is carried out for 10 min after full stirring reaction, the product is centrifuged at the rotating speed of 8000 rpm and is repeatedly washed by deionized water, the centrifugal precipitate is re-dispersed in a proper amount of water, and ultrasonic treatment is carried out for 5-10 min to obtain Ag/Ti with the concentration of 1 mg/mL₃C₂T _x An aqueous dispersion. 10 mL of the above Ag/Ti₃C₂T _x Autoxidation reaction of the aqueous dispersion in an oven at 80 ℃ for 8 h to obtain Ag/TiO₂/Ti₃C₂T _x An aqueous dispersion solution of a nanocomposite.

(3) Preparing an Au interdigital electrode: au interdigital electrodes with the thickness of 50 nm (the number of interdigital pairs is 10 pairs, and the electrode width and the electrode spacing are both 50 mu m) are evaporated on the polyimide film by using a mask.

(4) Preparing a planar flexible gas sensor: and (4) repeatedly washing the flexible polyimide substrate with the Au interdigital electrode, which is manufactured in the step (3), with deionized water and absolute ethyl alcohol, drying, and sticking the area around the electrode with a polyimide adhesive tape to perform masking. Measuring the Ag/TiO prepared in the step (2) with proper concentration₂/Ti₃C₂And (3) putting the aqueous dispersion solution T into a spray gun storage tank, uniformly spraying the aqueous dispersion solution T on a flexible substrate with interdigital electrodes, wherein the spraying thickness is 100 nm, and drying for 60 min at 60 ℃ under a vacuum condition. And removing the adhesive tape to obtain the required planar flexible room-temperature gas sensor.

(5) And (3) testing gas-sensitive performance: the ratio of the resistance difference value | Δ R | of the sensor in the target gas and the air to the resistance value in the air (| Δ R |/R |)_air100%) is the response of the sensor to the concentration of the target gas.

The invention uses two-dimensional Ti₃C₂T _x Based on nanomaterials by direct reduction of Ag without addition of reducing agents⁺Method for preparing nano confined Ag/TiO by ion and solution autoxidation₂/Ti₃C₂T _x A nanocomposite material. At Ti₃C₂T _x Ag and TiO generated in situ on surface of two-dimensional nanosheet₂The nanoparticles can effectively prevent Ti₃C₂T _x Self-stacking of two-dimensional nanosheets, increasing two-dimensional Ti₃C₂T _x The interlayer distance and the specific surface area of the nanosheets are increased, and the Ag/TiO ratio is improved₂/Ti₃C₂T _x The contact area of the nano composite material and the gas to be detected; more importantly, Ag/Ti₃C₂T _x Surface in situ formed TiO₂The nano-particles ensure TiO₂-Ti₃C₂T _x And TiO₂Formation of Ag heterojunctions in Ag/TiO₂Ti₃C₂T _x Multiple Schottky barriers are constructed in the gas sensitive material, so that the measured gas molecules and Ag/TiO are greatly improved₂/Ti₃C₂T _x The combination efficiency of (a) and (b) realizes rapid and highly sensitive detection of low concentration acetone at room temperature.

The specific substances in the product components disclosed in the technical scheme of the invention can be implemented by the invention, and the technical effects are the same as those obtained in the examples, and the examples are not separately illustrated. Therefore, it is intended that all equivalents and modifications which do not depart from the spirit of the invention disclosed herein are deemed to be within the scope of the invention.