Gas sensor as well as preparation method and application thereof

Abstract

The invention discloses a gas sensor as well as a preparation method and application thereof. The gas sensor comprises a substrate, a Ti3C2Tx-MXene modified zinc oxide seed crystal layer, a zinc oxide layer and an interdigital electrode which are sequentially stacked. The preparation method comprises the following steps: 1) preparing the Ti3C2Tx-MXene modified zinc oxide seed crystal layer on the surface of the substrate; 2) preparing a zinc oxide layer on the surface of the Ti3C2Tx-MXene modified zinc oxide seed crystal layer; and 3) preparing an interdigital electrode on the surface of the zinc oxide layer. The gas sensor is suitable for ammonia gas detection, has the advantages of being high in reaction speed at normal temperature, stable in performance, easy to store, low in power consumption, low in cost, suitable for wearable equipment and the like, and is simple in preparation method, low in production cost and suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and particularly relates to a gas sensor, a preparation method thereof, and an application thereof. Background Art

[0002] Ammonia is a colorless gas with a strong pungent odor. Its large-scale emission can cause environmental problems and human health problems (for example: excessive emission of automobile exhaust can lead to the excessive formation of PM2.5 particles in the atmosphere, thus causing environmental pollution; some household cleaning products, decoration and painting agents, etc. will release ammonia, which will endanger human health). At the same time, ammonia is one of the endogenous exhaled gases in the human body and can be used as a diagnostic basis for diseases. Therefore, ammonia detection is of great importance.

[0003] A gas sensor is a sensor used to detect the concentration and composition of gases and is an ideal device for gas detection, monitoring, analysis, and alarm. Metal oxide semiconductors have the advantages of low preparation cost, wide material sources, stable chemical properties, semi-permanent use, and easy integration, and are widely used in the manufacture of gas sensors. Traditional metal oxide semiconductor ammonia gas sensors have a high response degree and are ideal devices for ammonia detection, with good application prospects. However, most traditional metal oxide semiconductor ammonia gas sensors have problems such as slow reaction speed, high working temperature, long response and recovery time, and are not suitable for wearable devices, resulting in great limitations in their practical applications.

[0004] Therefore, it is of great significance to develop a gas sensor suitable for ammonia detection, with a fast reaction speed at room temperature, stable performance, easy storage, low power consumption, low cost, and suitable for wearable devices. Summary of the Invention

[0005] The purpose of the present invention is to provide a gas sensor, a preparation method thereof, and an application thereof.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A gas sensor, which comprises a substrate, a Ti3C2T x -MXene modified zinc oxide seed layer, a zinc oxide layer, and interdigital electrodes stacked in sequence; the Ti3C2T x -MXene modified zinc oxide seed layer comprises zinc oxide seeds and Ti3C2T x -MXene; the zinc oxide layer comprises zinc oxide nanorods.

[0008] Preferably, the substrate is one of a glass substrate, a TZO substrate, an ITO substrate, and a silicon substrate.

[0009] Preferably, the zinc oxide seed crystal, Ti3C2T x -MXene in the Ti3C2T x -MXene modified zinc oxide seed layer has a mass ratio of 1:0.01 to 0.06.

[0010] Preferably, the thickness of the Ti3C2T x -MXene modified zinc oxide seed layer is 18 μm to 20 μm.

[0011] Preferably, the thickness of the zinc oxide layer is 1 μm to 2 μm.

[0012] Preferably, the interdigital electrode is composed of at least one of Au, Pt, Al, Cu, and Ag.

[0013] Preferably, the thickness of the interdigital electrode is 40 nm to 60 nm.

[0014] A method for preparing a gas sensor as described above includes the following steps:

[0015] 1) Disperse zinc salt, stabilizer, and Ti3C2T x -MXene in an organic solvent to form a dispersion, then coat the dispersion on the surface of the substrate and anneal to form a Ti3C2T x -MXene modified zinc oxide seed layer;

[0016] 2) Disperse zinc salt and alkaline compound in water to form a dispersion, then immerse the substrate treated in step 1) in the dispersion for hydrothermal reaction, and then take it out for drying and annealing to form a zinc oxide layer;

[0017] 3) Sputter electrode metal on the surface of the zinc oxide layer to form an interdigital electrode, and then anneal to obtain the gas sensor.

[0018] Preferably, in step 1), the mass ratio of the zinc salt, stabilizer, and Ti3C2T x -MXene is 1:0.5 to 2:0.005 to 0.03.

[0019] Preferably, in step 1), the zinc salt is at least one of zinc acetate, zinc sulfate, and zinc nitrate.

[0020] Preferably, in step 1), the stabilizer is at least one of ethanolamine, monoisopropanolamine, morpholine, and ethylenediamine.

[0021] Preferably, in step 1), the organic solvent is at least one of ethanol, propylene glycol, and isopropanol.

[0022] Preferably, in step 1), the Ti3C2T x- MXene is prepared by a preparation method including the following steps: dispersing lithium fluoride (LiF) in dilute hydrochloric acid, adding Ti3AlC2 - MAX phase material for etching, centrifuging, taking the solid for washing, and then performing calcination to obtain Ti3C2T x - MXene.

[0023] Preferably, the mass ratio of the lithium fluoride to the Ti3AlC2 - MAX phase material is 1:0.5 - 2.

[0024] Preferably, the concentration of the dilute hydrochloric acid is 11 mol / L - 13 mol / L.

[0025] Preferably, the etching is carried out at room temperature (25°C ± 5°C), and the etching time is 48 h - 72 h.

[0026] Preferably, the annealing in step 1) is carried out under the condition of a temperature of 230°C - 270°C, and the annealing time is 40 min - 80 min.

[0027] Preferably, the molar ratio of the zinc salt to the alkaline compound in step 2) is 1:1 - 3.

[0028] Preferably, the zinc salt in step 2) is at least one of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride.

[0029] Preferably, the alkaline compound in step 2) is at least one of hexamethylenetetramine, potassium hydroxide, and sodium hydroxide.

[0030] Preferably, the hydrothermal reaction in step 2) is carried out under the condition of a temperature of 85°C - 95°C, and the reaction time is 3 h - 5 h.

[0031] Preferably, the drying in step 2) is carried out under the condition of a temperature of 50°C - 70°C, and the drying time is 20 min - 40 min.

[0032] Preferably, the annealing in step 2) is carried out under the condition of a temperature of 230°C - 270°C, and the annealing time is 20 min - 40 min.

[0033] Preferably, the annealing in step 3) is carried out under the condition of a temperature of 300°C - 400°C, and the annealing time is 5 min - 10 min.

[0034] An application of the gas sensor as described above in ammonia detection.

[0035] The beneficial effects of the present invention are as follows: The gas sensor of the present invention is applicable to ammonia detection, and has the advantages of fast reaction speed at room temperature, stable performance, easy storage, low power consumption, low cost, and suitability for wearable devices. Moreover, its preparation method is simple and the production cost is low, making it suitable for large-scale industrial production and application.

[0036] Specifically:

[0037] 1) The gas sensor of the present invention contains a Ti3C2T x -MXene modified zinc oxide seed layer (heterostructure layer). Ti3C2T x has a relatively high work function, strong adsorption and desorption capabilities for ammonia molecules, and Ti3C2T x -MXene can provide abundant adsorption sites, enhancing the gas-sensing response of the gas sensor to ammonia. Zinc oxide is widely available and has good gas-sensing properties. The synergistic effect of the two endows the gas sensor with excellent properties such as high carrier mobility, outstanding response-recovery time, and fast reaction speed at room temperature;

[0038] 2) Compared with a pure zinc oxide ammonia gas sensor, the gas sensor of the present invention has higher selectivity and stability, and its response to ammonia at different concentrations shows a good linear relationship, which is beneficial to practical applications;

[0039] 3) The gas sensor of the present invention is applicable to ammonia detection, and has the advantages of fast reaction speed at room temperature, stable performance, easy storage, low power consumption, low cost, etc., and is applicable to wearable devices, having a very broad application prospect;

[0040] 4) The preparation method of the gas sensor of the present invention has simple steps, low cost, strong operability, high repeatability, and low requirements for equipment, making it suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic structural diagram of the gas sensor of the present invention.

[0042] Figure 2 is a graph showing the response test results of the gas sensors of Examples 1 to 4 to ammonia at a concentration of 50 ppm at room temperature.

[0043] Figure 3 is the SEM image and EDS energy spectrum diagram of the Ti3C2T x -MXene modified zinc oxide seed layer and zinc oxide layer in the gas sensor of Example 1.

[0044] Figure 4 is a graph showing the response-recovery test results of the gas sensor of Example 1 to ammonia at a concentration of 50 ppm at room temperature.

[0045] Figure 5 The graph shows the test results of the gas sensor of Example 1 for ammonia with a concentration ranging from 10 ppm to 500 ppm at room temperature. Detailed implementation manners

[0046] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0047] Example 1:

[0048] A gas sensor (the structural schematic diagram is as Figure 1 shown), which is composed of a substrate, a Ti3C2T x -MXene modified zinc oxide seed layer, a zinc oxide layer and interdigital electrodes stacked in sequence from bottom to top; the substrate is quartz glass; the Ti3C2T x -MXene modified zinc oxide seed layer is composed of zinc oxide seeds and Ti3C2T x -MXene, and the mass ratio of zinc oxide seeds to Ti3C2T x -MXene is 1:0.036; the thickness of the Ti3C2T x -MXene modified zinc oxide seed layer is 20 μm; the zinc oxide layer is composed of zinc oxide nanorods with a thickness of 1.5 μm; the interdigital electrodes are composed of aluminum with a thickness of 50 nm.

[0049] The preparation method of the above gas sensor is as follows:

[0050] 1) Add 1 g of zinc acetate dihydrate and 1 g of ethanolamine to 10 g of absolute ethanol, stir at 60 °C until completely dissolved, then add 36 mg of Ti3C2T x -MXene, ultrasonically treat for 30 min at 5 °C to prepare a dispersion liquid, then use a pipette to suck 125 μL of the dispersion liquid and spin-coat it on the surface of quartz glass (size specification: 1 cm × 1 cm × 0.5 mm) in two steps. The rotation speed of the first spin-coating is 500 r / min and the time is 5 s. The rotation speed of the second spin-coating is 1500 r / min and the time is 30 s. Then place the quartz glass on a heating table and heat it at 60 °C for 5 min. Repeat the above spin-coating and heating processes 3 times, and then anneal it in an air atmosphere at a temperature of 250 °C for 60 min to form a Ti3C2T x -MXene modified zinc oxide seed layer (thickness: 20 μm; mass ratio of zinc oxide seeds to Ti3C2T x -MXene is 1:0.036);

[0051] 2) Add 2.8756 g of Zn(NO3)2·6H2O and 1.4628 g of hexamethylenetetramine (C6H 12N4) Stir and dissolve it in 100 mL of deionized water to prepare a dispersion liquid. Then add the quartz glass treated in step 1) into a hydrothermal autoclave and immerse it with the dispersion liquid. React at 90 °C for 4 h, cool naturally to room temperature, take out the quartz glass, wash it with deionized water, dry it at 60 °C for 30 min, and then anneal it in an air atmosphere at 250 °C for 30 min to form a zinc oxide layer (with a thickness of 1.5 μm).

[0052] 3) Put Al grains with a purity of 99.99% into a tungsten boat and place it in an evaporation device. Then cover the surface of the zinc oxide layer of the quartz glass treated in step 2) with a mask plate and put it into the evaporation device. Then evacuate to below 8×10 -4 Pa, pass a 60 mA current and maintain it for 3 min, then increase the current to 180 mA at a rate of 15 mA / min to form interdigital electrodes (with a thickness of 50 nm). Then take out the quartz glass and anneal it in an air atmosphere at 350 °C for 5 min to obtain the gas sensor.

[0053] Note:

[0054] The quartz glass was pretreated before use. The pretreatment operations are as follows: Ultrasonically clean the quartz glass with acetone, absolute ethanol, and deionized water for 15 min each in turn, dry it, then place it in an ultraviolet box and pass oxygen for 2 min, and then keep it for 15 min after closing the air inlet device.

[0055] Ti3C2T x The preparation process of -MXene is as follows: Stir and dissolve 2 g of lithium fluoride in 40 mL of dilute hydrochloric acid with a concentration of 12 mol / L, then add 2 g of Ti3C2T x- MAX phase material, stir at room temperature for 48 h, centrifuge for 5 min, the rotation speed of the centrifuge is 4000 r / min. Then pour out the supernatant and add deionized water for washing and centrifuging. Repeat the washing and centrifuging operations 6 times. Then take the solid and add deionized water, ultrasonically disperse it at 5 °C for 60 min, centrifuge for 8 min, the rotation speed of the centrifuge is 4000 r / min. Then pour out the supernatant and add deionized water and shake well until the solid is completely dissolved in water. Then place it in an oven and bake at 45 °C for 60 h. Then place it in a muffle furnace for calcination. The calcination atmosphere is an air environment. The calcination is divided into two stages. The first stage: Heat from room temperature to 120 °C at a heating rate of 2 °C / min and keep it for 2 h. The second stage: Continue to heat from 120 °C to 280 °C at a heating rate of 2 °C / min and keep it for 2 h. Then cool with the furnace to room temperature to obtain Ti3C2T x -MXene.

[0056] Example 2:

[0057] A gas sensor, except that Ti3C2Tx - The zinc oxide seeds and Ti3C2T in the Ti3C2T x - MXene modified zinc oxide seed layer, except that the mass ratio of zinc oxide seeds to Ti3C2T

[0058] Example 3:

[0059] A gas sensor, except that the Ti3C2T x - The zinc oxide seeds and Ti3C2T in the Ti3C2T x - MXene modified zinc oxide seed layer, except that the mass ratio of zinc oxide seeds to Ti3C2T

[0060] Example 4:

[0061] A gas sensor, except that the Ti3C2T x - The zinc oxide seeds and Ti3C2T in the Ti3C2T x - MXene modified zinc oxide seed layer, except that the mass ratio of zinc oxide seeds to Ti3C2T

[0062] Performance test:

[0063] 1) Connect the two ends of the electrodes of the gas sensors of Examples 1 - 4 with heat - curing conductive silver paste to copper wires. The wires are connected to a Keithley 2400 digital source meter. The gas sensors are placed in a closed gas chamber. The digital source meter is remotely controlled by a computer. Pass 50 ppm ammonia gas into the gas chamber for testing. After the test, pass nitrogen gas for desorption, thus completing the entire response test process. The response test results of the gas sensors of Examples 1 - 4 to 50 ppm ammonia gas at room temperature are as Figure 2 shown.

[0064] It can be seen from Figure 2 that: The gas sensors of Example 2 and Example 4 have longer response / recovery times in an ammonia gas atmosphere with a concentration of 50 ppm. For the gas sensor of Example 3 in an ammonia gas atmosphere with a concentration of 50 ppm, the response time is 7 s and the recovery time is 10 s, and it cannot return to the baseline. While for the gas sensor of Example 1 in an ammonia gas atmosphere with a concentration of 50 ppm, the response time is 1.5 s, the recovery time is 2.5 s, and it can return to the baseline, having an extremely short response - recovery time.

[0065] 2) The Ti3C2T in the gas sensor of Example 1 x- SEM images and EDS spectra of the Ti3C2Tx-MXene modified zinc oxide seed layer and zinc oxide layer are as follows Figure 3 (Figure (a) is the SEM image and Figure (b) is the EDS spectrum).

[0066] It can be seen from Figure 3 that zinc oxide nanorod arrays grow on the surface of the Ti3C2Tx-MXene modified zinc oxide seed layer, and the zinc oxide nanorods are evenly distributed and have good orientation. x -MXene modified zinc oxide seed layer has zinc oxide nanorod arrays growing on its surface, and the zinc oxide nanorods are evenly distributed and have good orientation.

[0067] In addition, through the same tests, it is found that the microstructure of the Ti3C2Tx-MXene modified zinc oxide seed layer and zinc oxide layer in the gas sensors of Examples 2-4 is very similar to that of the gas sensor of Example 1. x -MXene modified zinc oxide seed layer and zinc oxide layer in the gas sensors of Examples 2-4 is very similar to that of the gas sensor of Example 1.

[0068] 3) Connect the two ends of the electrodes of the gas sensor of Example 1 to copper wires with heat-curing conductive silver paste. The wires are connected to a Keithley 2400 digital source meter. The gas sensor is placed in a closed gas chamber. The digital source meter is remotely controlled by a computer. Ammonia with a concentration of 50 ppm is introduced into the gas chamber for testing. After the test, nitrogen is introduced for desorption, thus completing the entire response test process. The response-recovery test results of the gas sensor of Example 1 to ammonia with a concentration of 50 ppm at room temperature are as follows Figure 4 (Figure (a) is the main figure, and Figures (b) and (c) are partial enlarged figures).

[0069] It can be seen from Figure 4 that for the gas sensor of Example 1 in an ammonia atmosphere of 50 ppm, the response time is 1.5 s, the recovery time is 2.5 s, and it can recover to the baseline, having an extremely short response-recovery time.

[0070] In addition, through the same tests, it is found that the gas sensor of Example 3 also has an extremely short response-recovery time.

[0071] 4) Use the gas sensor of Example 1 to conduct a response test on ammonia with a concentration of 10 ppm - 500 ppm at room temperature. The test results are as follows Figure 5 as shown.

[0072] It can be seen from Figure 5 that for the gas sensor of Example 1, the response to ammonia with a concentration of 10 ppm - 500 ppm shows a logarithmic relationship, and it has good linearity below 100 ppm.

[0073] In addition, through the same tests, it is found that for the gas sensor of Example 3, the response to ammonia with a concentration of 10 ppm - 500 ppm shows an exponential relationship, and it has good linearity below 100 ppm.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A gas sensor, characterized in that, The composition includes a substrate, a Ti3C2T x -MXene modified zinc oxide seed layer, a zinc oxide layer and interdigital electrodes which are stacked in sequence; the Ti3C2T x -MXene modified zinc oxide seed layer includes zinc oxide seeds and Ti3C2T x -MXene; the zinc oxide layer includes zinc oxide nanorods.

2. The gas sensor according to claim 1, wherein: The ZnO seed crystal and Ti3C2T x -MXene in the ZnO seed layer modified by Ti3C2T x -MXene have a mass ratio of 1:0.01 to 0.

06.

3. The gas sensor according to claim 1 or 2, characterized in that: The Ti3C2T x -MXene modified zinc oxide seed layer has a thickness of 18 μm to 20 μm.

4. The gas sensor according to claim 1 or 2, characterized in that: The thickness of the zinc oxide layer is 1 μm to 2 μm.

5. The gas sensor according to claim 1 or 2, characterized in that: The thickness of the interdigital electrode is 40 nm to 60 nm.

6. A method for preparing a gas sensor according to any one of claims 1 to 5, characterized in that, It includes the following steps: 1) Disperse zinc salt, stabilizer and Ti3C2T x -MXene in an organic solvent to prepare a dispersion, then coat the dispersion on the surface of a substrate, and then perform annealing to form a Ti3C2T x -MXene modified zinc oxide seed layer; 2) Disperse a zinc salt and an alkaline compound in water to form a dispersion liquid, then immerse the substrate treated in step 1) in the dispersion liquid for hydrothermal reaction, and then take it out for drying and annealing to form a zinc oxide layer; 3) Sputter electrode metal on the surface of the zinc oxide layer to form an interdigital electrode, and then perform annealing to obtain the gas sensor.

7. The preparation method according to claim 6, characterized in that: Step 1) The mass ratio of the zinc salt, the stabilizer, and Ti3C2T x -MXene is 1:0.5-2:0.01-0.06; the zinc salt in Step 1) is at least one of zinc acetate, zinc sulfate, and zinc nitrate; the stabilizer in Step 1) is at least one of ethanolamine, monoisopropanolamine, morpholine, and ethylenediamine.

8. The preparation method according to claim 6, wherein: In step 2), the molar ratio of the zinc salt to the alkaline compound is 1:0.5 to 3; in step 2), the zinc salt is at least one of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride; in step 2), the alkaline compound is at least one of hexamethylenetetramine, potassium hydroxide, and sodium hydroxide.

9. The preparation method according to claim 6 or 8, characterized in that: The hydrothermal reaction in step 2) is carried out under the condition that the temperature is 85 °C to 95 °C, and the reaction time is 3 h to 5 h.

10. Application of a gas sensor according to any one of claims 1 to 5 in ammonia detection.

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