Mn-TiO2 / TiO2 homojunction film-based room-temperature nitrogen dioxide gas sensor and preparation method thereof

Abstract

The invention discloses a room-temperature nitrogen dioxide sensor based on a Mn-TiO2 / TiO2 homojunction thin film material and a preparation method of the room-temperature nitrogen dioxide sensor, and relates to the technical field of nitrogen dioxide gas detection. The preparation method comprises the following steps: S1, growing and preparing a Mn-TiO2 / TiO2 homojunction film gas sensitive material on an FTO (Fluorine-doped Tin Oxide) substrate through a two-step hydrothermal method; s2, sputtering a Pt electrode on the surface of the Mn-TiO2 / TiO2 homojunction film through magnetron sputtering to obtain a resistance type nitrogen dioxide sensor; the invention provides a room-temperature nitrogen dioxide sensor. The sensitivity and selectivity of TiO2 to nitrogen dioxide at room temperature are improved through Mn doping and homojunction construction; the advantages of p-type doping, construction of a homogeneous p-n junction and Pt electrode modification are combined, the response and working consistency of the TiO2 material at room temperature is greatly improved, and the method has important practical application value for further promoting the development of semiconductor gas sensitive devices.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen dioxide gas detection, and in particular to a room-temperature nitrogen dioxide gas sensor based on a Mn-TiO2 / TiO2 homojunction thin film and a preparation method thereof. Background Art

[0002] Gas sensors play an increasingly important role in many fields such as environmental monitoring, safety protection, industrial production and medical diagnosis. Nitrogen dioxide (NO2) is a typical air pollutant that poses significant risks to human health and the environment, and therefore has received widespread attention in environmental monitoring. In order to detect NO2, researchers have used a variety of materials, including metal oxides, sulfides, and their heterojunctions and homojunctions. Considering that NO2 has a certain corrosiveness, titanium dioxide (TiO2) has become an ideal material for NO2 gas sensing due to its excellent chemical and physical stability, high catalytic activity, non-toxicity and low-cost manufacturing feasibility. However, sensors based on intrinsic TiO2 materials have poor sensitivity to nitrogen dioxide at room temperature, which limits their effectiveness in practical applications.

[0003] Therefore, we proposed a room-temperature nitrogen dioxide gas sensor based on Mn-TiO2 / TiO2 homojunction thin film and its preparation method in order to solve the above-mentioned problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a room temperature nitrogen dioxide gas sensor based on Mn-TiO2 / TiO2 homojunction thin film and a preparation method thereof, so as to solve the problems existing in the current market raised by the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a room temperature nitrogen dioxide gas sensor of a Mn-TiO2 / TiO2 homojunction thin film and a preparation method thereof, comprising the following steps:

[0006] S1. Prepare Mn-TiO2 / TiO2 homojunction thin film gas-sensitive material on FTO substrate by a two-step hydrothermal method;

[0007] The method for preparing the Mn-TiO2 / TiO2 homojunction thin film comprises the following steps, specifically including:

[0008] Rutile TiO2 thin films were grown on FTO substrates using a hydrothermal method:

[0009] S1-1. Add different amounts of deionized water and anhydrous ethanol to a beaker according to the volume ratio of deionized water to anhydrous ethanol and stir for 5 minutes; add 30 mL of hydrochloric acid and stir for 5 minutes; finally, add 1 mL of TBOT and stir for 30 minutes;

[0010] S1-2. Place two cleaned FTO sheets with the conductive surface facing downward at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor, and transfer the reaction precursor solution in the beaker to the reactor; after sealing, place the reactor in a forced air drying oven and react at 150°C for 8 hours; after the reaction is completed and cooled to room temperature, remove the sample, rinse with deionized water, and soak in deionized water in a beaker for 3 hours;

[0011] S1-3. After the sample is dried, place it in a rapid annealing furnace and anneal it at 400°C in air for 20 minutes;

[0012] Anatase phase Mn-doped TiO2 thin film was grown on rutile phase TiO2 thin film by hydrothermal method:

[0013] S1-4. Take 37.5 mL of deionized water and 1.5 mL of anhydrous ethanol in a beaker and stir for 5 minutes; add 1329 μL of nitric acid and stir for 5 minutes; add 1 mL of TBOT and stir for 30 minutes; finally, add a certain amount of manganese nitrate according to the atomic ratio of Mn to Ti and stir for 30 minutes;

[0014] S1-5. Place the FTO film with rutile TiO2 thin film at a downward angle of 45° in a polytetrafluoroethylene hydrothermal reactor, and transfer the reaction precursor solution in the beaker to the reactor; after sealing, place the reactor in a forced air drying oven and react at 160°C for 12 hours; after the reaction is completed and cooled to room temperature, remove the sample, rinse it with deionized water, and then soak it in deionized water in a beaker for 3 hours;

[0015] S1-6. After the sample is dried, place it in a tubular annealing furnace and anneal it at 400°C in air for 1 hour;

[0016] S2. A resistive nitrogen dioxide gas sensor was obtained by sputtering a Pt electrode on the surface of a Mn-TiO2 / TiO2 homojunction film by magnetron sputtering.

[0017] Preferably, in S1-1, the volume ratio of deionized water to anhydrous ethanol is 2:1.

[0018] Preferably, in said S1-4, the doping amount of Mn is 3at%.

[0019] Preferably, in S2, the relevant parameters during sputtering are: gas pressure of 1.0 Pa, sputtering power of 40 W, and sputtering time of 5 min.

[0020] The present invention also provides a room-temperature nitrogen dioxide gas sensor based on a Mn-TiO2 / TiO2 homojunction thin film, which is prepared using the above-mentioned preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a room-temperature nitrogen dioxide gas sensor, which improves the sensitivity and selectivity of TiO2 to nitrogen dioxide at room temperature by Mn doping and constructing a homojunction; combined with the advantages of p-type doping, constructing a homogeneous pn junction and Pt electrode modification, it greatly improves the response and working consistency of TiO2 materials at room temperature, and has important practical application value for further promoting the development of semiconductor gas sensing devices.

[0023] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a SEM photo of the Mn-TiO2 / TiO2 homojunction thin film material prepared by the present invention;

[0025] Figure 2 This is a physical picture of the room temperature nitrogen dioxide gas sensor based on the Mn-TiO2 / TiO2 homojunction thin film of the present invention;

[0026] Figure 3 This is a room temperature response diagram of the homojunction thin film material prepared by using deionized water and anhydrous ethanol in different volume ratios to nitrogen dioxide in the present invention;

[0027] Figure 4 This is a diagram showing the room temperature selectivity of the homojunction film prepared under the optimal ratio conditions of the present invention to various gases. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1:

[0030] The Mn-TiO2 / TiO2 homojunction thin film material was prepared by a two-step hydrothermal method. Figure 1 As shown, Figure 1 The SEM image of the prepared Mn-TiO2 / TiO2 homojunction thin film material is shown. As can be seen from the image, the film surface is uniform, without obvious cracks, and the Mn doping and homojunction structure are clearly visible:

[0031] According to the volume ratio of deionized water to anhydrous ethanol of 5:1, 25 mL of deionized water and 5 mL of anhydrous ethanol were added to the beaker and stirred for 5 minutes; 30 mL of hydrochloric acid was added and stirred for 5 minutes; finally, 1 mL of TBOT was added and stirred for 30 minutes;

[0032] Place two cleaned FTO sheets, conductive surface facing downward, at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor. Transfer the precursor solution from the beaker to the reactor. Seal the reactor and place it in a forced-air drying oven at 150°C for 8 hours. After the reaction is complete and cooled to room temperature, remove the sample, rinse it with deionized water, and soak it in deionized water in a beaker for 3 hours.

[0033] After the sample was dried at 60°C, it was placed in a rapid annealing furnace and annealed at 400°C in air for 20 min to obtain sample R-5TiO2;

[0034] Take 37.5mL of deionized water and 1.5mL of anhydrous ethanol in a beaker and stir for 5 minutes; add 1329μL of nitric acid and stir for 5 minutes; add 1mL of TBOT and stir for 30 minutes; finally, add 20μL of manganese nitrate at a doping ratio of 3at% and stir for 30 minutes;

[0035] Place the R-5TiO2 film sample face-down at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor. Transfer the precursor solution from the beaker to the reactor. After sealing, place the reactor in a forced-air drying oven at 160°C for 12 hours. After the reaction is complete and cooled to room temperature, remove the sample, rinse it with deionized water, and soak it in deionized water in a beaker for 3 hours.

[0036] After the sample was dried, it was placed in a tubular annealing furnace and annealed at 400 °C in air for 1 h to obtain sample A-Mn-TiO2 / R-5TiO2;

[0037] A resistive nitrogen dioxide gas sensor was fabricated by magnetron sputtering a Pt electrode onto the surface of an A-Mn-TiO2 / R-5TiO2 thin film. The sputtering parameters were: pressure of 1.0 Pa, sputtering power of 40 W, and sputtering time of 5 minutes.

[0038] Example 2:

[0039] Mn-TiO2 / TiO2 homojunction thin film material was prepared by a two-step hydrothermal method:

[0040] According to the volume ratio of deionized water to anhydrous ethanol of 2:1, 20 mL of deionized water and 10 mL of anhydrous ethanol were added to the beaker and stirred for 5 minutes; 30 mL of hydrochloric acid was added and stirred for 5 minutes; finally, 1 mL of TBOT was added and stirred for 30 minutes;

[0041] Place two cleaned FTO sheets, conductive surface facing downward, at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor. Transfer the precursor solution from the beaker to the reactor. Seal the reactor and place it in a forced-air drying oven at 150°C for 8 hours. After the reaction is complete and cooled to room temperature, remove the sample, rinse it with deionized water, and soak it in deionized water in a beaker for 3 hours.

[0042] After the sample was dried at 60°C, it was placed in a rapid annealing furnace and annealed at 400°C in air for 20 min to obtain sample R-10TiO2;

[0043] Take 37.5mL of deionized water and 1.5mL of anhydrous ethanol in a beaker and stir for 5 minutes; add 1329μL of nitric acid and stir for 5 minutes; add 1mL of TBOT and stir for 30 minutes; finally, add 20μL of manganese nitrate at a doping ratio of 3at% and stir for 30 minutes;

[0044] Place the R-10TiO2 film sample face-down at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor. Transfer the precursor solution from the beaker to the reactor. After sealing, place the reactor in a forced-air drying oven at 160°C for 12 hours. After the reaction is complete and cooled to room temperature, remove the sample, rinse it with deionized water, and soak it in deionized water in a beaker for 3 hours.

[0045] After the sample was dried, it was placed in a tubular annealing furnace and annealed at 400 °C in air for 1 h to obtain sample A-Mn-TiO2 / R-10TiO2;

[0046] A resistive nitrogen dioxide sensor was fabricated by magnetron sputtering a Pt electrode onto the surface of an A-Mn-TiO2 / R-10TiO2 thin film. The sputtering parameters were: pressure of 1.0 Pa, sputtering power of 40 W, and sputtering time of 5 minutes.

[0047] Example 3:

[0048] Mn-TiO2 / TiO2 homojunction thin film material was prepared by a two-step hydrothermal method:

[0049] According to the volume ratio of deionized water to anhydrous ethanol of 1:1, 15 mL of deionized water and 15 mL of anhydrous ethanol were added to the beaker and stirred for 5 minutes; 30 mL of hydrochloric acid was added and stirred for 5 minutes; finally, 1 mL of TBOT was added and stirred for 30 minutes;

[0050] Place two cleaned FTO sheets, conductive surface facing downward, at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor. Transfer the precursor solution from the beaker to the reactor. Seal the reactor and place it in a forced-air drying oven at 150°C for 8 hours. After the reaction is complete and cooled to room temperature, remove the sample, rinse it with deionized water, and soak it in deionized water in a beaker for 3 hours.

[0051] After the sample was dried at 60°C, it was placed in a rapid annealing furnace and annealed at 400°C in air for 20 min to obtain sample R-15TiO2;

[0052] Take 37.5mL of deionized water and 1.5mL of anhydrous ethanol in a beaker and stir for 5 minutes; add 1329μL of nitric acid and stir for 5 minutes; add 1mL of TBOT and stir for 30 minutes; finally, add 20μL of manganese nitrate at a doping ratio of 3at% and stir for 30 minutes;

[0053] Place the R-15TiO2 film sample face-down at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor. Transfer the precursor solution from the beaker to the reactor. After sealing, place the reactor in a forced-air drying oven at 160°C for 12 hours. After the reaction is complete and cooled to room temperature, remove the sample, rinse it with deionized water, and soak it in deionized water in a beaker for 3 hours.

[0054] After the sample was dried, it was placed in a tubular annealing furnace and annealed at 400 °C in air for 1 h to obtain sample A-Mn-TiO2 / R-15TiO2;

[0055] A resistive nitrogen dioxide sensor was obtained by sputtering Pt electrodes on the surface of sample A-Mn-TiO2 / R-15TiO2 film by magnetron sputtering. Figure 2 The relevant parameters during sputtering are: gas pressure of 1.0 Pa, sputtering power of 40 W, and sputtering time of 5 min.

[0056] Mn p-type doping and the construction of a TiO2 homogeneous pn junction can improve the sensitivity to nitrogen dioxide and reduce the operating temperature. Combining catalytic modification of the Pt electrode with thin film materials can further increase the device's detection range and enhance its safety and stability.

[0057] Figure 3 The response diagram of the homojunction material to nitrogen dioxide with different volume ratios of deionized water and anhydrous ethanol is shown in Figure 2. Figure 3 It can be seen that the optimal volume ratio of deionized water and anhydrous ethanol is 2:1. The present invention comprehensively solves the problem that TiO2 materials based on the existing technology are difficult to have a high response to nitrogen dioxide at room temperature. By modifying with Mn doping, constructing a homogeneous pn junction and modifying the Pt electrode, the preparation of a room temperature nitrogen dioxide gas sensor with fast response, high sensitivity and long-term stability can be achieved, such as Figure 4The figure shows the room-temperature selectivity of a homojunction thin film prepared using the optimal ratio (deionized water to anhydrous ethanol, 2:1 by volume) for various gases. The figure demonstrates the sensor's high selectivity for nitrogen dioxide and low response to other common gases, demonstrating its excellent anti-interference capabilities in practical applications. It holds broad application prospects in highly sensitive identification of toxic gases and the fabrication of novel array-type gas sensors.

[0058] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0059] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a room temperature nitrogen dioxide gas sensor based on Mn-TiO2 / TiO2 homojunction thin film material, characterized in that: The steps include: S1. Prepare Mn-TiO2 / TiO2 homojunction thin film gas-sensitive material on FTO substrate by a two-step hydrothermal method; S2. A resistive nitrogen dioxide gas sensor was obtained by sputtering a Pt electrode on the surface of a Mn-TiO2 / TiO2 homojunction film by magnetron sputtering.

2. The method for preparing a room-temperature nitrogen dioxide gas sensor based on a Mn-TiO2 / TiO2 homojunction thin film material according to claim 1, characterized in that: In step S1, the method for preparing the Mn-TiO2 / TiO2 homojunction thin film gas-sensitive material comprises the following steps: S1.

1. Growing a rutile TiO2 thin film on an FTO substrate using a hydrothermal method, specifically comprising: S1-1. Add different amounts of deionized water and anhydrous ethanol to a beaker according to the volume ratio of deionized water to anhydrous ethanol and stir for 5 minutes; add 30 mL of hydrochloric acid and stir for 5 minutes; finally, add 1 mL of tetrabutyl titanate and stir for 30 minutes; S1-2. Place two cleaned FTO sheets with the conductive surface facing downward at a 45-degree angle in a polytetrafluoroethylene hydrothermal reactor, and transfer the reaction precursor solution in the beaker to the reactor; after sealing, place the reactor in a forced air drying oven and react at 150°C for 8 hours; after the reaction is completed and cooled to room temperature, remove the sample, rinse with deionized water, and soak in deionized water in a beaker for 3 hours; S1-3. After the sample is dried, place it in a rapid annealing furnace and anneal it at 400°C in air for 20 minutes; S1.

2. Growing an anatase phase Mn-doped TiO2 film on a rutile phase TiO2 film using a hydrothermal method, specifically comprising: S1-4. Take 37.5 mL of deionized water and 1.5 mL of anhydrous ethanol in a beaker and stir for 5 minutes; add 1329 μL of nitric acid and stir for 5 minutes; add 1 mL of TBOT and stir for 30 minutes; finally, add a certain amount of manganese nitrate according to the atomic ratio of Mn to Ti and stir for 30 minutes; S1-5. Place the FTO film with rutile TiO2 thin film at a downward angle of 45° in a polytetrafluoroethylene hydrothermal reactor, and transfer the reaction precursor solution in the beaker to the reactor; after sealing, place the reactor in a forced air drying oven and react at 160°C for 12 hours; after the reaction is completed and cooled to room temperature, remove the sample, rinse it with deionized water, and then soak it in deionized water in a beaker for 3 hours; S1-6. After the sample is dried, place it in a tubular annealing furnace and anneal it at 400°C in air for 1 hour.

3. The method for preparing a room-temperature nitrogen dioxide gas sensor based on a Mn-TiO2 / TiO2 homojunction thin film material according to claim 2, characterized in that: In the S1-1, the volume ratio of deionized water to anhydrous ethanol is 2:

1.

4. The method for preparing a room temperature nitrogen dioxide gas sensor based on a Mn-TiO2 / TiO2 homojunction thin film material according to claim 2, characterized in that: In the above S1-4, the doping amount of Mn is 3 at %.

5. The method for preparing a room temperature nitrogen dioxide gas sensor based on a Mn-TiO2 / TiO2 homojunction thin film material according to claim 1, characterized in that: In S2, the relevant parameters during sputtering are: gas pressure of 1.0 Pa, sputtering power of 40 W, and sputtering time of 5 min.

6. A room temperature nitrogen dioxide gas sensor based on Mn-TiO2 / TiO2 homojunction thin film material, characterized in that: The method is prepared according to any one of claims 1 to 5.

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