Preparation method and application of SnO2-x thin film with oxygen vacancies

Abstract

The invention discloses a preparation method and application of a SnO2-x film with oxygen vacancies, and the method comprises the following steps: (S1) mixing (NH2) 2CO or alkali metal halide, SnCl4. 5H2O and metal powder in a solvent to form a mixed solution; and (S2) coating the mixed solution on a substrate, and carrying out solvothermal reaction to obtain the SnO2-x thin film with the oxygen vacancy. The SnO2-x thin film with the oxygen vacancy is used for detecting toxic gas such as NO2 under irradiation of visible light at room temperature, and the detection limit is as low as 1ppb; the response value (Ra / Rg is greater than or equal to 1000) to 100 ppm NO2, and the response time is less than or equal to 30 seconds; the selectivity on common interference gases such as CO, NH3 and H2 is greater than or equal to 100.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of gas sensing materials, and specifically relates to a preparation method and application of an SnO 2-x thin film with oxygen vacancies, and further relates to a preparation method of an SnO 2-x thin film with oxygen vacancies and its application in detecting trace toxic gases, such as nitro explosives or NO2, under visible light irradiation at room temperature. Background Art

[0002] In industrial activities and daily life, toxic gas pollutants continuously threaten global ecological security and human health. Taking nitrogen dioxide (NO2) as an example, its excessive emissions not only trigger environmental disasters such as photochemical smog, acid rain, and ozone layer depletion, but also directly lead to an increase in the concentration of PM2.5 and a sharp rise in the risk of respiratory diseases. Research shows that when the NO2 concentration exceeds 53 ppb, it can cause irreversible damage to the human cardiovascular system, liver and kidney functions, and skin barrier (WHO, 2021). At the same time, nitro explosives have irreplaceable strategic value in fields such as national defense, aerospace propulsion, and mining engineering. However, the terrorist threats caused by their illegal abuse have become a global governance problem. According to the statistics of the Action on Armed Violence (AOAV), there were more than 29,000 terrorist attacks globally from 2011 to 2021, causing more than 360,000 casualties, with civilians accounting for as high as 73%. Typical nitro explosives such as trinitrotoluene (TNT), trinitrophenol (TNP), and cyclotrimethylenetrinitramine (RDX), although widely used in the military field, pose severe challenges to detection due to the following characteristics: their saturated vapor pressures at room temperature are extremely low, such as 9.1 ppb for TNT, 0.97 ppb for TNP, and 4.9 ppt for RDX; they are extremely easy to adsorb and easily combine with environmental particulate matter to form stable complexes; they are also easily affected by interferents such as various co-existing volatile organic compounds (VOCs); high-temperature detection is dangerous, etc., making it difficult for many existing technologies and materials to achieve real-time online high-sensitivity detection at room temperature. As a typical mixed explosive system, the illegal circulation of the core components of ammonium nitrate explosives, ammonium nitrate (oxidizer) and urea nitrate (sensitizer precursor), has become a key node in the control of explosive raw materials. Therefore, trace detection of ammonium nitrate and urea nitrate can effectively trace and control the raw materials of nitro explosives. However, the current detection limits of gas sensors for NO2 mostly remain in the ppm range, making it difficult to meet the stringent requirements of environmental monitoring for ppb-level trace detection. Developing new sensing materials with high sensitivity (≤ppb), fast response / recovery (<30 s), excellent selectivity, and room temperature stability has become an urgent need in the fields of environmental safety and anti-terrorism explosion protection. Therefore, it is of great significance to prepare gas sensors with good comprehensive performance (stable, high sensitivity, fast response and recovery, room temperature detection, good selectivity) for efficient and accurate detection of trace gases.

[0003] In the prior art, traditional metal oxide semiconductor (such as SnO2) gas sensors usually need to work at high temperature (>200 °C), which has high energy consumption and potential safety hazards; at the same time, the sensor has low sensitivity and selectivity, resulting in reduced detection accuracy for nitro explosive atmospheres. Conventional preparation methods (such as sputtering, chemical vapor deposition) are costly and difficult to control the defect structure of the material. Sensitivity can be improved by doping (such as Ag, Co doping) or composite structures (such as SnO2 / rGO), but the process is complex and the selectivity is insufficient. Oxygen vacancy engineering has been proven to enhance gas sensing performance, but existing methods (such as hydrogen reduction, plasma treatment) are prone to damaging the film uniformity. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for preparing an SnO 2-x film with oxygen vacancies. The method uses a low-cost, one-step film-forming solvothermal method to directly synthesize an SnO 2-x transparent film with oxygen vacancies by regulating the chemical environment of the mixed solution, and combines visible light excitation to achieve high-sensitivity detection at room temperature.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing an SnO 2-x film with oxygen vacancies, the method comprising:

[0007] (S1) Mixing (NH2)2CO or alkali metal halide, SnCl4·5H2O and metal powder in a solvent to form a mixed solution;

[0008] (S2) Coating the mixed solution on a substrate and performing a solvothermal reaction to prepare the SnO 2-x film with oxygen vacancies.

[0009] According to an embodiment of the present invention, in step (S1), the metal powder is selected from one or more of titanium (Ti) powder, zirconium (Zr) powder, iron (Fe) powder, chromium (Cr) powder, aluminum (Al) powder, copper (Cu) powder, tin (Sn) powder, silver (Ag) powder, gold (Au) powder, or indium (In) powder, preferably tin powder.

[0010] According to an embodiment of the present invention, in step (S1), the alkali metal halide is selected from at least one of KBr, NaBr, KCl, NaCl, etc.

[0011] According to an embodiment of the present invention, in step (S1), the solvent is, for example, at least one of water or organic solvents, and the organic solvents are selected from at least one of ethanol, acetic acid, ammonia water, methanol, ethylene glycol, N,N-dimethylformamide, dimethyl sulfoxide, toluene, hydrochloric acid.

[0012] According to an embodiment of the present invention, in step (S1), the molar ratio of (NH2)2CO or alkali metal halide, SnCl4·5H2O and metal powder is 1-30:1-20:0.1-4, preferably 1-20:1:0.1-1, and more preferably 1-10:1:0.2-0.8.

[0013] In the present invention, the content of the solvent is not particularly limited as long as it can completely dissolve, partially dissolve or disperse each raw material.

[0014] For example, in step (S1), the dosage of KBr or (NH2)2CO is 0.01-20 mmol, preferably 3 mmol.

[0015] For example, in step (S1), the dosage of the solvent (such as water) is 0.01-50 mL, preferably 10 mL.

[0016] For example, in step (S1), the dosage of SnCl4·5H2O is 0.01-10 mmol, preferably 1 mmol.

[0017] For example, in step (S1), the dosage of the metal powder is 0.01-2 mmol, preferably 0.2 mmol.

[0018] According to an embodiment of the present invention, in step (S1), the preparation method of the mixed solution is as follows: dissolve the alkali metal halide in the solvent to obtain solution A, or dissolve (NH2)2CO in hydrochloric acid to obtain solution A; dissolve SnCl4·5H2O in an organic solvent to obtain solution B; mix solution A, solution B and the metal powder to obtain the mixed solution.

[0019] According to an embodiment of the present invention, in step (S2), the temperature of the solvothermal reaction is 120-220 °C, and the preferred reaction temperature is 150-200 °C.

[0020] According to an embodiment of the present invention, in step (S2), the time of the solvothermal reaction is 6-48 hours, preferably 12-48 hours.

[0021] According to an embodiment of the present invention, in step (S2), the substrate is one of ordinary glass (such as a glass slide), sapphire, Al2O3 substrate, silicon wafer, polytetrafluoroethylene substrate, quartz substrate, PDMS substrate, etc., and preferably ordinary glass, such as a glass slide.

[0022] According to an embodiment of the present invention, in step (S2), put the mixed solution and the substrate into the reaction device together, place the substrate obliquely in the reaction device, and at the same time immerse it in the solution to carry out the solvothermal reaction to obtain the SnO with oxygen vacancies. 2-xThin film.

[0023] According to an embodiment of the present invention, the method further includes step (S3): post-treatment steps such as washing and drying the obtained thin film. For example, ethanol washing is used. For example, the drying temperature is 60 - 150 °C, and the drying time is 12 - 48 hours, preferably drying at 120 °C for 12 hours.

[0024] As an exemplary embodiment of the present invention, the SnO with oxygen vacancies 2-x The preparation method of the thin film is as follows:

[0025] (S1) Mix KBr, H2O, SnCl4·5H2O with metal powder, and ultrasonically treat for 30 - 240 minutes (power 50 - 200 W, frequency 10 - 40 kHz) to form a suspension;

[0026] (S2) Transfer the suspension to a polytetrafluoroethylene reaction kettle, use glass (such as a glass slide) as the substrate, and carry out solvothermal reaction;

[0027] (S3) After the reaction, naturally cool, wash the surface of the thin film with ethanol, and vacuum dry at 60 - 150 °C to obtain the SnO with oxygen vacancies 2-x Thin film.

[0028] The present invention also provides a SnO with oxygen vacancies prepared by the above method 2-x Thin film.

[0029] According to an embodiment of the present invention, in the SnO with oxygen vacancies 2-x thin film, the content of oxygen vacancies exceeds 10 mol%, for example, 11 - 30 mol%.

[0030] According to an embodiment of the present invention, the thickness of the SnO with oxygen vacancies 2-x thin film is 20 - 2000 nm, preferably 200 - 1000 nm.

[0031] According to an embodiment of the present invention, the visible light transmittance of the SnO with oxygen vacancies 2-x thin film is ≥ 80% (the wavelength of visible light is 400 - 800 nm), for example, 80 - 95%.

[0032] According to an embodiment of the present invention, the surface roughness Ra of the SnO with oxygen vacancies 2-x thin film is ≤ 5 nm, for example, 1 - 5 nm.

[0033] According to an embodiment of the present invention, the SnO with oxygen vacancies 2-x thin film can absorb visible light and has a band gap less than 3 eV.

[0034] The present invention also provides a chemiresistive sensor, which is prepared by using the above-mentioned SnO thin film with oxygen vacancies. 2-x

[0035] The present invention also provides a method for preparing a chemiresistive sensor, the method comprising:

[0036] Connecting electrodes to both ends of the SnO thin film with oxygen vacancies, 2-x heating, to prepare the chemiresistive sensor.

[0037] According to an embodiment of the present invention, the connecting of electrodes to both ends of the SnO thin film with oxygen vacancies specifically includes: connecting electrodes to both ends of the thin film to prepare a top electrode and a bottom electrode. For example, methods such as spraying, evaporation coating, drop coating, spin coating, etc. can be used to prepare the electrodes, and preferably, the electrodes are prepared by drop coating silver paste. 2-x

[0038] According to an embodiment of the present invention, the heating temperature is 50 - 220 °C, preferably 60 - 120 °C, and the heating time is 0.5 - 48 h, preferably 1 - 24 h.

[0039] The present invention also provides the application of the above-mentioned SnO thin film with oxygen vacancies 2-x or the above-mentioned chemiresistive sensor, which is applied to the detection of bulk gases or nitro explosive atmospheres.

[0040] Preferably, visible light is used as the light source for the detection of bulk gases or nitro explosive atmospheres.

[0041] Preferably, the wavelength of the visible light is 300 - 800 nm, for example, it can be one or several of 400, 420, 450, 475, 500, 520, 550, 570 nm, or it can also be a certain continuous band in the visible light band, preferably single wavelength 450 nm and continuous wavelength 400 - 800 nm.

[0042] According to an embodiment of the present invention, the bulk gas is an acidic toxic bulk gas, such as NO2, SO2 or CO2, preferably NO2.

[0043] According to an embodiment of the present invention, the nitro explosive is at least one of TNT, DNT, PA, RDX or its derivatives, preferably RDX and / or TNT.

[0044] The present invention also provides a method for detecting a bulk gas or a nitro explosive atmosphere, the detection method comprising:

[0045] Powering on the above-mentioned chemiresistive sensor, applying a voltage, and detecting the bulk gas or nitro explosive vapor. ​​

[0046] Advantages of the present invention:

[0047] (1) The SnO thin film with oxygen vacancies prepared in this application 2-x has a nanoscale thickness, a uniform and smooth surface, and an optical bandgap less than 3 eV, greatly improving the absorption of the SnO thin film 2-x to visible light. The oxygen vacancies rich on the surface can selectively adsorb common acidic toxic bulk gases in the environment such as NO2, SO2 or CO2, or nitro explosive atmospheres, thereby improving the gas-sensing performance and selectivity of the gas, enabling it to detect bulk toxic gases, nitro explosives and nitro-containing explosive raw materials in real-time online with high sensitivity and high selectivity. The response value to 100 ppm of NO2 at room temperature exceeds 10 5 %. And the devices can be mass-produced, and the success rate of mass production exceeds 80%.

[0048] (2) The SnO thin film of this application 2-x is very stable, can be prepared by a one-step solvothermal method, and the raw materials and consumables used, such as glass substrates, are cheap and easy to mass-produce and obtain, making the cost of mass-producing devices very low, and the cost of each device is less than 1 yuan.

[0049] (3) The SnO thin film with oxygen vacancies of the present invention 2-x is used for the detection of toxic gases such as NO2 under room temperature visible light irradiation, and the detection limit is as low as 1 ppb; the response value to 100 ppm NO2 (R a / R g ≥1000), the response time ≤ 30 seconds; the selectivity to common interfering gases such as CO, NH3, H2, etc. ≥ 100. Description of the drawings

[0050] Figure 1 is the scanning electron microscope image of the uniform and transparent SnO thin film in Example 1; 2-x thin film;

[0051] Figure 2 is the cross-sectional view of the scanning electron microscope image of the uniform and transparent SnO thin film in Example 1; 2-x thin film;

[0052] Figure 3 is the PXRD of the uniform and transparent SnO thin film in Example 1; 2-x thin film;

[0053] Figure 4 is the absorption spectrum of the uniform and transparent SnO thin film in Example 1; 2-x thin film;

[0054] Figure 5 is the transmittance spectrum of the uniform and transparent SnO thin film in Example 1; 2-x thin film;

[0055] Figure 6 It is the scanning electron microscope image of the uniform and transparent SnO2 thin film in Comparative Example 1;

[0056] Figure 7 It is the XPS spectrum of the oxygen content in Example 1 and Comparative Example 1;

[0057] Figure 8 It is the scanning electron microscope image of the uniform and transparent SnO 2-x thin film in Example 2;

[0058] Figure 9 It is the scanning electron microscope image of the uniform and transparent SnO 2-x thin film in Example 3;

[0059] Figure 10 It is the scanning electron microscope image of the uniform and transparent SnO 2-x thin film in Example 4;

[0060] Figure 11 It is the scanning electron microscope image of the uniform and transparent SnO 2-x thin film in Example 5.

[0061] Figure 12 It is the scanning electron microscope image of the uniform and transparent SnO 2-x thin film in Example 6.

[0062] Figure 13 It is the device diagram of the chemiresistive sensor in Example 1 for detecting NO2 atmosphere;

[0063] Figure 14 It is the response-recovery curve of the chemiresistive sensor in Example 1 to 100 ppm NO2 atmosphere for five cycles.

[0064] Figure 15 It is the response-recovery curve of the chemiresistive sensor in Example 1 to different concentrations of NO2 atmosphere from 1 ppm to 100 ppm.

[0065] Figure 16 It is the response time of the chemiresistive sensor in Example 1 to 100 ppm NO2 atmosphere.

[0066] Figure 17 It is the response-recovery curve of the chemiresistive sensor in Example 1 to TNT atmosphere.

[0067] Figure 18 It is the response-recovery curve of the chemiresistive sensor in Comparative Example 1 to NO2 atmosphere. Detailed implementation manners

[0068] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for exemplarily illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0069] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by known methods.

[0070] Example 1

[0071] Synthesis of a SnO thin film material for detecting bulk toxic gases or nitro explosive atmospheres by a chemiresistive sensor, comprising the following steps: 2-x a. Take 357 mg (3 mmol) of KBr and dissolve it in 10 mL of deionized water, and ultrasonically mix it evenly to obtain solution A.

[0072] b. Take 350.6 mg of SnCl4·5H2O (1 mmol) and dissolve it in 60 mL of acetic acid, and ultrasonically mix it evenly to obtain solution B.

[0073] c. After mixing solution A and solution B evenly, add 10 mL of ethanol and mix it evenly to obtain solution C.

[0074] d: Then add 0.2 mmol of tin powder to solution C and ultrasonicate for 2 hours. After the tin powder is dissolved, solution D is obtained.

[0075] e: Transfer the solution D in step d into a polytetrafluoroethylene liner, then obliquely place a glass sheet of appropriate size as a substrate, put it into a stainless steel autoclave, and place it in an oven at 200 °C for 12 h for reaction. After the reaction is completed, cool it naturally, take out the glass substrate with the SnO thin film grown on it, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO thin film. Its scanning electron microscope image and the cross-section of the thin film are as shown in and, where, a and b are the morphologies of the obtained SnO thin film material at different magnifications.

[0076] is the cross-sectional view of the obtained film, from which it can be seen that the thickness of the film is about 500 nm. 2-x 2-x 2-x Figure 1 Figure 1 and Figure 2 Figure 2 Figure 1 a and Figure 1 2-x 2-x Figure 1 Figure 2 Figure 2

[0077] 2-x 2-x Figures 3 - 5 Figures 3 - 5 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 Figure 3 [[ID2-x Material. As Figure 4 shown, it is the absorption spectrum of the thin film. From this, it is known that the optical band gap of the synthesized thin film is 2.78 eV, indicating that the thin film material prepared by the present invention can absorb visible light. At the same time, the synthesized thin film material is uniform and transparent. As Figure 5 shown, the transmittance of the thin film of the present invention > 85%, which greatly broadens the application scenarios of the thin film.

[0078] Comparative Example 1

[0079] The synthesis of a SnO2 thin film material for chemical resistive sensors to detect bulk toxic gases or nitro explosive atmospheres includes the following steps:

[0080] a. Take 357 mg (3 mmol) of KBr and dissolve it in 10 mL of deionized water, and ultrasonically mix it evenly to obtain solution A.

[0081] b. Take 350.6 mg of SnCl4·5H2O (1 mmol) and dissolve it in 60 mL of acetic acid, and ultrasonically mix it evenly to obtain solution B.

[0082] c. After mixing solution A and solution B evenly, add 10 mL of ethanol and mix it evenly to obtain solution C.

[0083] d: Transfer solution C into a polytetrafluoroethylene inner liner, then obliquely place a glass sheet of appropriate size as the substrate into a stainless steel autoclave, and place it in an oven at 200 °C for 12 h for reaction. After the reaction is completed, let it cool naturally, take out the glass substrate with the SnO2 thin film grown on it, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO2 thin film without oxygen vacancies. Its scanning electron micrograph is as Figure 6 shown, where Figure 6 a and Figure 6 b are the morphologies of the synthesized film at different magnifications respectively.

[0084] Figure 7 For Example 1 (i.e., SnO 2-x ) and Comparative Example 1 (i.e., SnO2), the XPS spectra of the oxygen content are used to analyze and compare the oxygen content and the types of active oxygen species of SnO2 and SnO 2-x . As can be seen from Figure 7 , compared with SnO2, the peak intensity of oxygen vacancies (O 2-x ) in the XPS O1s spectrum of SnO V is significantly enhanced, and the overall shifts +0.3 eV towards the higher binding energy direction. This directly confirms the enrichment of oxygen vacancies in the material, and this characteristic is closely related to its enhanced surface adsorption ability and charge transfer efficiency. In addition, SnO 2-xThe abundant oxygen vacancies in it lead to the narrowing of its band gap, which in turn causes the change of the absorption characteristics in the visible light region, manifested as the significant change of the macroscopic color of the material.

[0085] Example 2

[0086] Synthesis of a SnO thin film material for a chemiresistive sensor to detect bulk toxic gases or nitro explosive atmospheres, including the following steps: 2-x Synthesis of a thin film material for a chemiresistive sensor to detect bulk toxic gases or nitro explosive atmospheres, including the following steps:

[0087] a. Take 357 mg (3 mmol) of KBr and dissolve it in 10 mL of deionized water, and ultrasonically mix it evenly to obtain solution A.

[0088] b. Take 350.6 mg of SnCl4·5H2O (1 mmol) and dissolve it in 60 mL of acetic acid, and ultrasonically mix it evenly to obtain solution B.

[0089] c. After mixing solution A and solution B evenly, add 10 mL of ethanol and mix it evenly to obtain solution C.

[0090] d: Then add 0.025 mmol of tin powder to solution C and ultrasonically mix for 2 hours. After the tin powder is dissolved, solution D is obtained.

[0091] e: Transfer the solution D in step d into a polytetrafluoroethylene liner, then obliquely place a glass sheet of appropriate size as a substrate, put it into a stainless steel autoclave, and place it in an oven at 200 °C for 12 h for reaction. After the reaction is completed, let it cool naturally, and take out the glass substrate with the SnO thin film grown on it, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO thin film, the scanning electron microscope image of which is as shown in 2-x The scanning electron microscope image of which is as shown in 2-x thin film, the scanning electron microscope image of which is as shown in Figure 8 as shown, where Figure 8 a and Figure 8 b are the morphologies of different parts of the obtained film respectively.

[0092] Example 3

[0093] Synthesis of a SnO thin film material for a chemiresistive sensor to detect bulk toxic gases or nitro explosive atmospheres, including the following steps: 2-x Synthesis of a thin film material for a chemiresistive sensor to detect bulk toxic gases or nitro explosive atmospheres, including the following steps:

[0094] a. Take 357 mg (3 mmol) of KBr and dissolve it in 10 mL of deionized water, and ultrasonically mix it evenly to obtain solution A.

[0095] b. Take 350.6 mg of SnCl4·5H2O (1 mmol) and dissolve it in 60 mL of acetic acid, and ultrasonically mix it evenly to obtain solution B.

[0096] c. After mixing solution A and solution B evenly, add 10 mL of ethanol and mix them evenly to obtain solution C.

[0097] d: Then add 0.05 mmol of tin powder to solution C and sonicate for 2 hours. After the tin powder is dissolved, solution D is obtained.

[0098] e: Transfer solution D in step d into a polytetrafluoroethylene liner, then obliquely place a glass slide of appropriate size as the substrate inside a stainless-steel autoclave, and put it into an oven at 200 °C for 12 h for reaction. After the reaction is completed, let it cool naturally, and then take out the glass substrate with SnO 2-x thin film, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO 2-x thin film, and its scanning electron micrograph is as Figure 9 shown, where Figure 9 a and Figure 9 b are the morphologies of different magnifications and different regions of the film respectively.

[0099] Example 4

[0100] Synthesis of a SnO 2-x thin film material for chemical resistive sensors to detect bulk toxic gases or nitro explosive atmospheres, including the following steps:

[0101] a. Dissolve 357 mg (3 mmol) of KBr in 10 mL of deionized water and sonicate to mix evenly to obtain solution A.

[0102] b. Dissolve 350.6 mg of SnCl4·5H2O (1 mmol) in 60 mL of acetic acid and sonicate to mix evenly to obtain solution B.

[0103] c. After mixing solution A and solution B evenly, add 10 mL of ethanol and mix them evenly to obtain solution C.

[0104] d: Then add 0.8 mmol of tin powder to solution C and sonicate for 2 hours. After the tin powder is dissolved, solution D is obtained.

[0105] e: Transfer solution D in step d into a polytetrafluoroethylene liner, then obliquely place a glass slide of appropriate size as the substrate inside a stainless-steel autoclave, and put it into an oven at 200 °C for 12 h for reaction. After the reaction is completed, let it cool naturally, and then take out the glass substrate with SnO 2-x thin film, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO 2-x thin film, and its scanning electron micrograph is as Figure 10 shown, where Figure 10 a and Figure 10 b are the morphologies of different magnifications and different regions of the film respectively.

[0106] Example 5

[0107] Synthesis of a SnO thin film material for a chemiresistive sensor to detect a bulk toxic gas or nitro explosive atmosphere, comprising the following steps: 2-x

[0108] a. Take 357 mg (3 mmol) of KBr and dissolve it in 10 mL of deionized water, and ultrasonically mix it evenly to obtain solution A.

[0109] b. Take 350.6 mg of SnCl4·5H2O (1 mmol) and dissolve it in 60 mL of acetic acid, and ultrasonically mix it evenly to obtain solution B.

[0110] c. After mixing solution A and solution B evenly, add 10 mL of ethanol and mix it evenly to obtain solution C.

[0111] d: Then add 0.2 mmol of copper powder to solution C and ultrasonically mix for 2 hours. After the copper powder is dissolved, solution D is obtained.

[0112] e: Transfer solution D in step d into a polytetrafluoroethylene liner, then obliquely place a glass sheet of appropriate size as a substrate inside a stainless steel autoclave, and place it in an oven at 200 °C for 12 h for reaction. After the reaction is completed, naturally cool it, and take out the glass substrate with the grown SnO 2-x thin film, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO 2-x thin film, the scanning electron micrograph of which is as Figure 11 shown.

[0113] Example 6

[0114] Synthesis of a SnO thin film material for a chemiresistive sensor to detect a bulk toxic gas or nitro explosive atmosphere, comprising the following steps: 2-x

[0115] a. Take 35 mg of SnCl4·5H2O (0.1 mmol) and dissolve it in 100 mL of deionized water, and ultrasonically mix it evenly to obtain solution A.

[0116] b. Take 92 mg of (NH2)2CO and dissolve it in 5 mL of hydrochloric acid, and ultrasonically mix it evenly to obtain solution B.

[0117] c. After mixing solution A and solution B evenly, solution C is obtained.

[0118] ​​d: Then transfer solution C into a polytetrafluoroethylene liner, and then obliquely place a glass sheet of appropriate size as a substrate into a stainless-steel autoclave. Place it in an oven and maintain the reaction at 200 °C for 12 h. After the reaction is completed, let it cool naturally, and then take out the glass substrate with SnO 2-x thin film, wash it with methanol, and dry it at 80 °C for 12 h to obtain a uniform and transparent SnO 2-x thin film. Its scanning electron microscope image is as shown in Figure 12 Figure

[0119] Example 7

[0120] Application of the above chemical resistive sensor for detecting bulk toxic gas NO2 in the formed film. The specific detection method is as follows:

[0121] S1. Connect the SnO 2-x thin film device in Example 1 to a gold wire with silver paste and place it at 80 °C for 2 h to obtain a chemical resistive sensor for detecting NO2;

[0122] S2. Connect the device to a Keithley source meter, introduce dry air, age it at 5 V for 12 h, and then use it for the detection of NO2;

[0123] S3. Use the Keithley source meter to monitor the current change caused by introducing NO2. The test device is as shown in Figure 13 Figure Figures 14 - 16 Figure Figure 14 is the response-recovery curve of the chemical resistive sensor in Example 1 to 100 ppm NO2 atmosphere for five cycles. As can be seen from Figure 14 , the response (R g / R a ) to 100 ppm NO2 is 4×10 4 , and it also has good cycling stability. As can be seen from Figure 15 , the device has an obvious response to NO2 from 1 ppm to 100 ppm, and the response value increases with the increase of concentration. At the same time, it is found that even when the concentration is as low as 1 ppm, there is an obvious response. As can be seen from Figure 16 , the response time of the device is 0.17 minutes.

[0124] Example 8

[0125] Application of the above chemical resistive sensor for detecting nitro explosive atmosphere. The specific detection method is as follows:

[0126] S1. Connect the SnO 2-x thin film device in Example 1 to a gold wire with silver paste and place it at 80 °C for 2 h to obtain a chemical resistive sensor for detecting nitro explosives;

[0127] S2. Connect the device to a Keithley source meter, introduce dry air, age it at 5 V for 12 h, and then use it for the detection of nitro explosive TNT;

[0128] S3. Load 2 g of TNT powder into a U-shaped glass tube, introduce dry air at both ends, heat it at 80 °C for 24 h to exhaust the adsorbed water vapor. Then seal it and pre-enrich it at room temperature for 48 h to obtain TNT vapor with a concentration of 0.97 ppb.

[0129] S4. Pass the vapor into the device in step S3, and use a Keithley source meter to monitor the current change caused after introducing TNT. The response-recovery curve of the chemiresistive sensor for the detection of TNT atmosphere is as Figure 17 shown, and the response to 0.97 ppb of TNT is 230%.

[0130] Comparative Example 2

[0131] The application of the above chemiresistive sensor is used for the detection of bulk toxic gas NO2 in the formed film. The specific detection method is as follows:

[0132] S1. Connect the SnO2 thin film device in Comparative Example 1 to a gold wire with silver paste and place it at 80 °C for 2 h; obtain a chemiresistive sensor for the detection of NO2;

[0133] S2. Connect the device to a Keithley source meter, introduce dry air, age it at 5 V for 12 h, and then use it for the detection of NO2;

[0134] S3. Use a Keithley source meter to monitor the current change caused after introducing NO2. The test device is as Figure 13 shown. Figure 18 Shown is the thin film synthesized without adding Sn powder, that is, SnO2 without oxygen vacancies. It has weak light absorption at 450 nm, so when tested with light at 450 nm, the response value is very low and it cannot recover. Therefore, visible light of 400 - 800 nm is used for testing. The response-recovery curve of the chemiresistive sensor for 100 ppm of NO2 atmosphere under visible light is as Figure 18 shown, and the response (R g / R a ) to 100 ppm of NO2 is 48.

[0135] Above, the embodiments of the present invention have been exemplarily described. However, the protection scope of the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of SnO thin film with oxygen vacancies, characterized in that, 2-x The method includes: ​ (S1) Mixing (NH2)2CO or an alkali metal halide, SnCl4·5H2O, and metal powder in a solvent to form a mixed solution; (S2) Coating the mixture on a substrate and performing a solvothermal reaction to obtain the SnO with oxygen vacancies 2-x thin film.

2. The method according to claim 1, wherein In step (S1), the metal powder is selected from one or more of titanium powder, zirconium powder, iron, chromium powder, aluminum powder, copper powder, tin powder, silver powder, gold powder, or indium powder; Preferably, in step (S1), the alkali metal halide is selected from at least one of KBr, NaBr, KCl, and NaCl; Preferably, in step (S1), the molar ratio of (NH2)2CO or the alkali metal halide, SnCl4·5H2O, and the metal powder is 1 - 30:1 - 20:0.1 - 4.

3. The method according to claim 1, characterized in that, In step (S2), the temperature of the solvothermal reaction is 120 - 220 °C, and the time of the solvothermal reaction is 6 - 48 hours; Preferably, in the SnO thin film with oxygen vacancies 2-x the content of oxygen vacancies accounts for more than 10 mol%.

4. The method according to claim 1, wherein The thickness of the thin film is 20 - 2000 nm; Preferably, the visible light transmittance of the thin film is ≥80%, and the wavelength of the visible light is 400 - 800 nm; Preferably, the surface roughness Ra of the thin film is ≤5 nm; Preferably, the thin film can absorb visible light and has a band gap of less than 3 eV.

5. SnO thin film with oxygen vacancies prepared by the method according to any one of claims 1-4 2-x thin film 6. A chemiresistive sensor, characterized in that, The chemiresistive sensor is prepared by using the SnO thin film with oxygen vacancies described in claim 5. 2-x ​ 7. The preparation method of the chemiresistive sensor according to claim 6, the method includes: At the SnO with oxygen vacancies 2-x Both ends of the thin film are connected to electrodes and heated to prepare the chemiresistive sensor.

8. Use of the SnO thin film with oxygen vacancies according to claim 5 or the chemiresistive sensor according to claim 6 for detecting a bulk gas or a nitro explosive atmosphere. 2-x ​ Preferably, visible light is used as a light source for detecting bulk gases or nitro explosive atmospheres.

9. The application according to claim 8, wherein The wavelength of the visible light is 300 - 800 nm; Preferably, the bulk gas is NO2, SO2, or CO2, and the nitro explosive is TNT, DNT, PA, RDX, or their derivatives.

10. A method for detecting a bulk gas or nitro explosive atmosphere, characterized in that, The detection method is as follows: Power on the chemiresistive sensor according to claim 6, apply a voltage, and detect bulk gases or nitro explosive vapors.

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