A gas-sensitive material of polyoxyethylene composite metal oxide and its application in flexible gas sensors

Abstract

This invention belongs to the field of gas sensor technology, and provides a gas-sensitive material composed of polyoxyethylene (PEO) composite metal oxide and its application in flexible gas sensors. The gas-sensitive material is formed by combining a metal oxide material with polyoxyethylene (PEO), wherein the metal oxide is any one of indium oxide, tungsten oxide, or copper oxide. This gas-sensitive material is composed of the metal oxide and polyoxyethylene, and is coated onto the surface of a flexible electrode to achieve specific gas detection. This flexible gas sensor features uniform material coating, resistance to material detachment after bending, and good long-term stability of sensing performance. The composite PEO material increases the adhesion between the sensitive material and the electrode and the uniformity of material distribution. After film formation, the flexible gas sensor is resistant to material detachment even after repeated bending, exhibiting stable performance and improving the long-term stability and repeatability of the flexible gas sensor.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a gas-sensitive material of polyoxyethylene composite metal oxide and its application in flexible gas sensors. Background Technology

[0002] Currently, semiconductor-based gas sensors have attracted widespread attention due to their simple fabrication and low cost. Some metal oxides, such as zinc oxide, tungsten oxide, tin oxide, indium oxide, and copper oxide, can be morphologically controlled to form specific nanostructures, such as nanowires, nanorods, nanosheets, nanofibers, and hollow microspheres, which can possess gas-sensitive properties and have shown good practical applications in the detection of harmful gases such as NO, CO, H2S, and NO2. However, these sensors typically achieve their sensing function by dissolving the metal oxide gas-sensitive material in alcohol or deionized water and coating it onto the electrode surface. This method, when used in flexible gas sensors, suffers from uneven coating and the risk of sensitive material detachment due to prolonged bending, thus affecting sensor performance. Therefore, addressing these issues and improving the long-term stability of flexible gas sensors is a crucial technology that urgently needs to be developed. Summary of the Invention

[0003] This invention addresses the problems and shortcomings mentioned in the background art by providing a gas-sensitive material composed of polyoxyethylene (PEO) composite metal oxide and its application in a flexible gas sensor. This gas-sensitive material is composed of a metal oxide and polyethylene oxide (PEO), and is coated onto the surface of a flexible electrode to achieve specific gas detection. This flexible gas sensor features uniform material coating, minimal material detachment after bending, and good long-term stability of sensing performance.

[0004] This invention is achieved by the following technical solution: a method for preparing a gas-sensitive material composed of polyoxyethylene (PEO) composite metal oxide, wherein a gas-sensitive material is formed by compositing a metal oxide material with polyoxyethylene (PEO), wherein the metal oxide is any one of indium oxide, tungsten oxide, or copper oxide; specifically including the following steps:

[0005] Add 5-10g of polyoxyethylene (PEO) powder to 100ml of deionized water and stir magnetically for 5 hours to form a PEO solution with a mass concentration of 5%-10%. Add metal oxide powder to the PEO solution and stir magnetically for 3 hours to form a metal oxide / 5%-10% PEO solution, which is the gas-sensitive material. The mass ratio of metal oxide material to PEO powder is 1:10-1:3.

[0006] Excessive PEO content reduces the sensitivity of metal oxides to gases, making it impossible to achieve highly sensitive sensing; while insufficient PEO content results in insufficient adhesion between the sensitive material and the flexible electrode of the substrate, leading to a decrease in the stability of the flexible sensor.

[0007] The present invention also provides a gas-sensitive material prepared using the method described above.

[0008] The present invention also provides a flexible gas sensor prepared using the aforementioned gas-sensitive material, wherein the flexible gas sensor is prepared by drop-coating the gas-sensitive material onto the surface of a flexible electrode at a drop volume of 0.1 ml / 100 mm. 2 The gas-sensitive material is baked on a hot plate at 60°C until the deionized water is completely evaporated and forms a film, which is the flexible gas sensor.

[0009] Furthermore, the flexible electrode is either a PI interdigitated flexible electrode or a PET interdigitated flexible electrode.

[0010] The present invention also provides the application of the flexible gas sensor in nitrogen dioxide gas detection.

[0011] This invention uses a polymer PEO with high viscosity and good dispersion to synthesize a sensitive material with metal oxides, which is then coated onto a flexible electrode. This increases the adhesion between the sensitive material and the electrode and the uniformity of the material distribution, thereby improving the long-term stability and repeatability of the flexible gas sensor. Attached Figure Description

[0012] Figure 1 The flowchart shows the fabrication process of a flexible gas sensor. In the flowchart: 1-deionized water, 2-PEO solution, 3-metal oxide material, 4-flexible electrode;

[0013] Figure 2 The images show SEM comparisons of the morphology of pure indium oxide and indium oxide composite PEO material in Example 1. In the images: (a) and (b) are the morphology of pure indium oxide nanoparticles, and (c) and (d) are the morphology of indium oxide composite PEO material.

[0014] Figure 3 The image shows the dynamic response of the indium oxide composite PEO flexible gas sensor in Example 1 to nitrogen dioxide at room temperature.

[0015] Figure 4 This is a comparison chart of the mass change of the indium oxide composite PEO flexible gas sensor after bending in Example 1 and the mass change of the pure indium oxide flexible gas sensor after bending.

[0016] Figure 5 This is a graph showing the change and comparison of the response of the indium oxide composite PEO flexible gas sensor to 5 ppm nitrogen dioxide after bending, and the response of the pure indium oxide flexible gas sensor after bending, in Example 1.

[0017] Figure 6 This is a comparison chart of the long-term stability of the indium oxide composite PEO flexible gas sensor and the pure indium oxide flexible gas sensor in Example 1 to 10 ppm nitrogen dioxide gas.

[0018] Figure 7 The response of the indium oxide composite PEO flexible gas sensor in Example 1 to 10 ppm of different gases is shown.

[0019] Figure 8 The image shows the dynamic response of the indium oxide composite PEO flexible gas sensor in Example 1 to 1 ppm NO2 under different relative humidity conditions.

[0020] Figure 9 The images show a comparison of the morphology of pure tungsten oxide and tungsten oxide composite PEO material in Example 2. In the images, (a) and (b) show the morphology of pure tungsten oxide nanoparticles, and (c) and (d) show the morphology of tungsten oxide composite PEO material.

[0021] Figure 10 This is a comparison chart of the mass change of the tungsten oxide composite PEO flexible gas sensor after bending in Example 2 and the mass change of the pure tungsten oxide flexible gas sensor after bending.

[0022] Figure 11 This is a graph showing the change and comparison of the response of the tungsten oxide composite PEO flexible gas sensor to 20 ppm nitrogen dioxide after bending, and the response of the pure tungsten oxide flexible gas sensor after bending, in Example 2.

[0023] Figure 12 This is a comparison chart of the long-term stability of the tungsten oxide composite PEO flexible gas sensor and the pure tungsten oxide flexible gas sensor in Example 2 to the response of 20 ppm nitrogen dioxide gas.

[0024] Figure 13 This is a comparison chart of the mass change of the copper oxide composite PEO flexible gas sensor after bending in Example 3 and the mass change of the pure copper oxide flexible gas sensor after bending.

[0025] Figure 14 This is a graph showing the change and comparison of the response of the copper oxide composite PEO flexible gas sensor to 20 ppm nitrogen dioxide after bending, and the response of the pure copper oxide flexible gas sensor after bending, in Example 3.

[0026] Figure 15 This is a comparison chart of the long-term stability of the copper oxide composite PEO flexible gas sensor and the pure copper oxide flexible gas sensor in Example 3 in response to 20ppm nitrogen dioxide gas. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0029] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0031] Example 1: A method for fabricating a room-temperature nitrogen dioxide flexible gas sensor based on indium oxide composite PEO material, the specific method is as follows:

[0032] (1) Preparation of indium oxide nanomaterials: 0.45 g of indium nitrate (In(NO3)3·4.5 H2O) and 0.3 g of hexadecyltrimethylammonium bromide (C 19 H 42 Add BrN to 40 ml of diethylenetriamine (C4H) 13 In N3), a mixed solution was obtained by magnetic stirring at room temperature for 1 hour; then the mixed solution was placed in a reaction vessel and heated at 140 °C. o Heat at C for 12 hours; finally, at 500 o Indium oxide (In₂O₃) nanoparticles were obtained by calcination in a muffle furnace at C for 2 hours. The microstructure of these nanoparticles is shown in the attached figure. Figure 2 As shown in (a) and (b), the prepared indium oxide has a bipyramidal structure of varying sizes, with particle sizes ranging from 5 to 500 nm, and the nanoparticles are in a non-uniformly distributed aggregated state.

[0033] (2) Synthesis of indium oxide composite PEO material: 7g of PEO raw material powder was weighed and added to 100ml of deionized water, and magnetically stirred for 5h to form a 7% PEO solution. 1g of indium oxide nanomaterial powder was weighed and added to the 7% PEO solution, and magnetically stirred for 3h to form a 1% indium oxide / 7% PEO solution. (See attached diagram) Figure 2(a), (b), (c), and (d) show that the addition of PEO solution effectively improved the aggregation and inhomogeneity of indium oxide nanoparticles, resulting in a uniform nanoparticle structure, as shown in the attached diagram. Figure 2 As shown in (c) and (d).

[0034] (3) Fabrication of flexible gas sensor: The 1% indium oxide / 7% PEO solution from step (1) was drop-coated onto a PET flexible interdigitated electrode (10mm×10mm) using a pipette, with a drop volume of 0.1ml. The electrode was then baked on a hot plate at 60℃ for 15min to evaporate the deionized water. After cooling, an indium oxide composite PEO sensitive film with a thickness of about 100μm was formed on the surface of the flexible electrode, thus completing the fabrication of the flexible gas sensor.

[0035] (4) Sensing performance test of flexible gas sensor: The indium oxide composite PEO flexible gas sensor was tested for its sensitivity to nitrogen dioxide at room temperature. It was found that the indium oxide composite PEO flexible gas sensor showed good sensitivity to nitrogen dioxide gas with a concentration of 0.1-10 ppm and a complete response recovery process, as shown in the attached figure. Figure 3 As shown.

[0036] (5) Stability test of flexible gas sensor after bending: The indium oxide composite PEO flexible sensor and the pure indium oxide flexible sensor were bent multiple times, and the mass change of the flexible sensor was measured after 20, 40, 60, 80 and 100 bends. The material surplus rate was defined as (flexible sensor mass after bending - flexible electrode mass / initial flexible sensor mass - flexible electrode mass) × 100%.

[0037] Through append Figure 4 It can be seen that after 100 bends, the material remaining rate of the pure indium oxide flexible gas sensor is only 51%, while the material remaining rate of the indium oxide composite PEO flexible sensor is still 98% after 100 bends, indicating that the material loss of the flexible gas sensor is significantly improved after the composite PEO.

[0038] Appendix Figure 5 The graphs show the response changes of the indium oxide composite PEO flexible sensor and the pure indium oxide flexible sensor to 5 ppm nitrogen dioxide after bending 20, 40, 60, 80 and 100 times. It can be seen that the response value of the pure indium oxide flexible gas sensor decreases significantly after bending. After bending 100 times, the responsivity drops from the original 48 to 6.5. In contrast, the responsivity of the indium oxide composite PEO flexible sensor remains basically between 9.3 and 9.5 after bending, showing a highly stable characteristic.

[0039] (6) Long-term stability test of flexible gas sensors: Long-term stability tests were conducted on the indium oxide composite PEO flexible sensor and the pure indium oxide flexible sensor. The response of both to 10 ppm nitrogen dioxide was measured every 5 days for 95 days. The results are shown in the appendix. Figure 6 As shown in the figure, the response value of the pure indium oxide flexible gas sensor gradually decreases over time, dropping from an initial 88.5 to 39.4 after 95 days; while the response value of the indium oxide composite PEO flexible gas sensor fluctuates between 16.5 and 20.2. Therefore, the indium oxide composite PEO flexible gas sensor also has a greater advantage in long-term stability than the pure indium oxide flexible gas sensor.

[0040] (7) Selectivity test of flexible gas sensor: The indium oxide composite PEO flexible gas sensor was exposed to 10 ppm of NO2 and other common air pollutants, such as ethanol (C2H5OH), isopropanol (C3H8O), ammonia (NH3), hydrogen sulfide (H2S), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2). The response values ​​are shown in the attached figure. Figure 7 As shown, the response of the indium oxide composite PEO flexible gas sensor under other interfering gases is less than 1.5, which is much lower than its response under NO2, confirming the excellent selectivity of the sensor for NO2.

[0041] (8) Humidity resistance test of flexible gas sensor: The indium oxide composite PEO flexible gas sensor was placed in environments with relative humidity (RH) of 20%, 33%, 43%, 59%, and 75%, respectively, and the response of the sensor to 1 ppm NO2 was measured, as shown in the attached figure. Figure 8 As shown, although the response value of the flexible gas sensor decreases with increasing humidity, it still reaches 2.63 at a relative humidity of 75%, with a retention rate of 89%, demonstrating that the sensor has good moisture resistance.

[0042] Example 2: A method for fabricating a highly stable flexible nitrogen dioxide gas sensor based on tungsten oxide composite PEO material. The specific method is as follows:

[0043] (1) Dissolve 0.5 g of sodium tungstate dihydrate (Na2WO4·2H2O) in 50 ml of deionized water and stir with a magnetic stirrer at room temperature. While stirring, add hydrochloric acid dropwise until the pH of the solution reaches 3. Transfer the resulting suspension to a stainless steel autoclave and heat at 150 °C for 24 hours. Then, allow it to cool naturally to room temperature. Centrifuge the cooled solution and wash it five times with deionized water to obtain the sample. Dry the sample at 60 °C for 12 hours to obtain tungsten oxide (WO3) nanomaterials, the microstructure of which is shown in the attached figure. Figure 9As shown in (a) and (b), the prepared tungsten oxide has a nanoparticle structure with a particle size between 5 and 100 nm, and the nanoparticles are in a non-uniformly distributed aggregated state.

[0044] (2) Synthesis of tungsten oxide composite PEO material: Weigh 5g of PEO raw material powder and add it to 100ml of deionized water. Stir magnetically for 5h to form a 5% PEO solution. Weigh 1g of the tungsten oxide nanomaterial powder prepared in step (1) and add it to the 5% PEO solution. Stir magnetically for 3h to form a 1% tungsten oxide / 5% PEO solution. (See attached diagram) Figure 9 In (a), (b), (c), and (d), the addition of PEO solution effectively improved the aggregation and inhomogeneity of tungsten oxide nanoparticles, resulting in a uniform nanoparticle structure, as shown in the attached diagram. Figure 9 As shown in (c) and (d).

[0045] (3) Fabrication of flexible gas sensor: The 1% tungsten oxide / 5% PEO solution from step (2) was drop-coated onto the PET flexible electrode using a pipette, with a drop volume of 0.1 ml / 100 mm. 2 The flexible gas sensor was then baked on a hot plate at 60°C for 15 minutes to evaporate the deionized water. After cooling, a tungsten oxide composite PEO sensitive film with a thickness of about 100 μm was formed on the surface of the flexible electrode, thus completing the fabrication of the flexible gas sensor.

[0046] (4) Stability test of flexible gas sensor after bending: Refer to the test method in Example 1, and the results are attached. Figure 10 and Figure 11 As shown in the figure, the pure tungsten oxide flexible gas sensor has a material retention rate of 60% after 100 bends, while the tungsten oxide composite PEO flexible sensor has a material retention rate of 90% after 100 bends, indicating a significant improvement in material loss. (See attached image.) Figure 11 The graphs show the response changes of the tungsten oxide composite PEO flexible gas sensor and the pure tungsten oxide flexible gas sensor to 20 ppm nitrogen dioxide after bending. It can be seen that the response value of the pure tungsten oxide flexible gas sensor decreases significantly after bending, dropping from 6.8 to 4.2 after 100 bends. In contrast, the response of the tungsten oxide composite PEO flexible sensor remains relatively stable between 2.8 and 3.2 after bending.

[0047] (5) Long-term stability test of flexible gas sensor: Refer to the test method in Example 1, and the results are attached. Figure 12 As shown in the figure, the response value of the pure tungsten oxide flexible gas sensor gradually decreases over time, dropping from an initial 6.8 to 4.0 after 95 days; while the response value of the tungsten oxide composite PEO flexible gas sensor fluctuates between 3.1 and 3.2, exhibiting better long-term stability.

[0048] Example 3: A method for fabricating a highly stable flexible nitrogen dioxide gas sensor based on copper oxide composite PEO material. The specific method is as follows:

[0049] (1) Synthesis of copper oxide composite PEO material: Weigh 6g of PEO raw material powder and add it to 100ml of deionized water. Stir magnetically for 5h to form a 6% PEO solution. Weigh 2g of copper oxide nanomaterial powder and add it to the 6% PEO solution. Stir magnetically for 3h to form a 2% copper oxide / 6% PEO solution.

[0050] (2) Fabrication of flexible gas sensor: The 2% copper oxide / 6% PEO solution from step (1) was drop-coated onto the PET flexible electrode using a pipette, with a drop volume of 0.1 ml / 100 mm. 2 The flexible gas sensor was then baked on a hot plate at 60°C for 15 minutes to evaporate the deionized water. After cooling, a copper oxide composite PEO sensitive film with a thickness of about 100 μm was formed on the surface of the flexible electrode, thus completing the fabrication of the flexible gas sensor.

[0051] (3) Stability test of flexible gas sensor after bending: Refer to the test method in Example 1, and the results are attached. Figure 13 and 14 As shown in the figure, the material retention rate of the pure copper oxide flexible gas sensor is only 36% after 100 bends, while the material retention rate of the copper oxide composite PEO flexible sensor is still 85% after 100 bends. This indicates that the material loss of the flexible gas sensor is significantly improved after incorporating PEO. (See attached image) Figure 14 The graphs show the response changes of the copper oxide composite PEO flexible gas sensor and the pure copper oxide flexible gas sensor to 20 ppm nitrogen dioxide after bending. It can be seen that the response value of the pure copper oxide flexible gas sensor decreases significantly after bending, dropping from 2.8 to 1.1 after 100 bends. In contrast, the response of the copper oxide composite PEO flexible sensor remains relatively stable between 1.7 and 1.9 after bending.

[0052] (4) Long-term stability test of flexible gas sensor: Refer to the test method in Example 1, and the results are attached. Figure 15 As shown in the figure, the response value of the pure copper oxide flexible gas sensor gradually decreases over time, dropping from an initial 2.8 to 1.2 after 95 days; while the response value of the copper oxide composite PEO flexible gas sensor fluctuates between 1.7 and 2.0, exhibiting better long-term stability.

[0053] In summary, Examples 1, 2, and 3 all demonstrate that composite PEO can effectively improve the material loss of flexible gas sensors after bending, and that PEO composite metal oxide flexible gas sensors have better stability than pure metal oxide flexible gas sensors.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible gas sensor fabricated using a gas-sensitive material, characterized in that: The gas-sensitive material is prepared by the following method: it is formed by combining common metal oxide nanomaterials with polyoxyethylene (PEO), wherein the metal oxide is either indium oxide or tungsten oxide. Specifically, the steps include the following: Add 5-10g of polyoxyethylene (PEO) powder to 100ml of deionized water and stir magnetically for 5 hours to form a PEO solution with a mass concentration of 5%-10%. Add metal oxide powder to the PEO solution and stir magnetically for 3 hours to form a metal oxide / 5%-10% PEO solution, which is the gas-sensitive material. The mass ratio of metal oxide material to PEO powder is 1:7-1:

5. The flexible gas sensor is constructed by drop-coating a gas-sensitive material onto the surface of a flexible electrode at a drop volume of 0.1 ml / 100 mm. 2 Bake on a hot plate at 60℃ for 15 minutes until the deionized water is completely evaporated and the gas-sensitive material forms a film, which is the flexible gas sensor.

2. The flexible gas sensor according to claim 1, characterized in that: The flexible electrode is either a PI interdigitated flexible electrode or a PET interdigitated flexible electrode.

3. The application of the flexible gas sensor according to claim 1 in nitrogen dioxide gas detection.

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