Glutaraldehyde gas sensor with low-concentration detection capability and preparation method of glutaraldehyde gas sensor

Abstract

The invention discloses a glutaraldehyde gas sensor with low-concentration detection capability and a preparation method thereof, and belongs to the technical field of gas sensors. The sensor is composed of a six-pin circular base, a gas sensitive film and a nickel-chromium alloy heating wire, the outer surface of an aluminum oxide ceramic tube and an annular Au electrode are coated with the gas sensitive film, the nickel-chromium alloy heating wire is arranged in the aluminum oxide ceramic tube, and the gas sensitive film is made of bismuth vanadate with a specific crystal face exposed through crystal face regulation and control. The sensor works at different temperatures through heating of the nichrome heating wire; according to an oxygen adsorption model, when the concentration of glutaraldehyde in an external environment is changed, the width of a space charge region on the surface of bismuth vanadate is changed, so that the resistance between the annular Au electrodes of the sensor is changed. The glutaraldehyde sensor based on crystal face regulation and control of bismuth vanadate can realize low-concentration detection of glutaraldehyde as low as 50ppb, is helpful for realizing concentration detection of glutaraldehyde gas in the disinfection field, and has the advantages of low cost, easiness in integration and packaging, suitability for standardized production and the like.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a glutaraldehyde gas sensor with low concentration detection capability and its preparation method. Background Technology

[0002] Glutaraldehyde possesses broad-spectrum antimicrobial capabilities and is a major chemical component of common disinfectants used in the medical, cosmetic, and livestock industries. A 2% glutaraldehyde disinfectant solution can kill various microorganisms within minutes to hours. Glutaraldehyde can evaporate along with water molecules, resulting in a certain concentration of glutaraldehyde gas in the air. Long-term exposure to glutaraldehyde gas can cause certain harm to the human body; at excessively high concentrations, it can even trigger contact dermatitis, asthma, and respiratory damage. The National Institute for Occupational Safety and Health (NIOSH) in the United States sets the exposure limit for glutaraldehyde gas in the air at 200 ppb. However, due to the long-chain aldehyde nature of glutaraldehyde, traditional MOS sensors (such as SnO2, WO3, and In2O3) rarely meet the low-concentration detection requirements of glutaraldehyde, primarily due to insufficient intrinsic reactivity. Furthermore, glutaraldehyde in disinfectants evaporates along with water vapor, leading to humidity interference in the detection environment. Ambient humidity competes for active sites on the surface of the MOS material, causing signal drift and decreased sensitivity. Therefore, improving the reactivity and resistance to humidity interference of materials is key to developing glutaraldehyde gas sensors.

[0003] In recent years, bismuth vanadate (BiVO4) materials have been increasingly used in gas sensing due to their good physical and chemical stability and easily tunable crystal structure, making them suitable for modification through crystal facet manipulation. Studies have shown that crystal facet manipulation is a common method for improving the gas sensing and catalytic performance of semiconductors. This is because the sensing and catalytic reaction mechanisms rely on redox reactions that occur when reactant molecules come into contact with the semiconductor surface. Crystal facet manipulation can improve the band structure, expose highly active crystal faces, and enhance reactant adsorption, thereby promoting surface oxidation reactions. Bismuth vanadate, as a highly promising gas-sensitive material, has an advantage in glutaraldehyde detection due to its tunable surface chemical properties. Specifically, the {010} crystal facet of BiVO4 is rich in unsaturated coordinated V0. 5+ The high content of oxygen vacancies and Lewis acidic sites in bismuth vanadate, as a highly active crystal facet, greatly promotes the chemical adsorption and reaction between glutaraldehyde molecules and reactive oxygen species, thereby improving sensor sensitivity. While the {021} and {111} crystal facets have lower reactivity, their surface adsorption strength for water molecules is weaker, effectively mitigating the competitive adsorption of water molecules on active sites and helping to improve the sensor's resistance to humidity interference. Therefore, this invention improves the gas-sensing performance of bismuth vanadate through crystal facet engineering to achieve gas detection of glutaraldehyde. Summary of the Invention

[0004] The purpose of this invention is to provide a glutaraldehyde gas sensor with low concentration detection capability and its preparation method.

[0005] The glutaraldehyde gas sensor of this invention comprises a six-legged circular base, a gas-sensitive thin film coated on the outer surface of an alumina ceramic tube and on a ring-shaped Au electrode, and a nickel-chromium alloy heating wire placed inside the ceramic tube. The gas-sensitive thin film is made of bismuth vanadate, with specific crystal faces exposed through crystal facet modulation. The sensor operates at different temperatures through heating by the nickel-chromium alloy heating wire. According to the adsorption oxygen model, when the concentration of glutaraldehyde in the external environment changes, the width of the space charge region on the surface of bismuth vanadate changes, which in turn leads to a change in the resistance between the ring-shaped Au electrodes of the sensor. By measuring the change in resistance between the ring-shaped Au electrodes, the sensitivity of the sensor can be calculated, thereby obtaining the relationship between the sensor sensitivity and the glutaraldehyde concentration, and establishing a glutaraldehyde gas concentration detection model.

[0006] The sensitivity of the sensor is defined as R. a / R g ×100%, where R a R is the initial resistance value between the annular Au electrodes of the sensor in air. g This represents the resistance between the annular Au electrodes of the sensor in the target gas. Response time (t) res The recovery time (t) is defined as the time it takes for the resistance between the annular Au electrodes of the sensor to change by 90% after the sensor has been transferred from air to the target gas. Similarly, the recovery time (t) rec The resistance value between the annular Au electrodes of the sensor is defined as the time it takes for the resistance value to recover to 90% of the changed value after the sensor is removed from the target gas and transferred back to the air.

[0007] The preparation method of the glutaraldehyde gas sensor with low concentration detection capability according to the present invention comprises the following steps: (1) Add 2.5~3.0g of bismuth nitrate pentahydrate to 20~30mL of 2mol / L dilute nitric acid and stir until completely dissolved to obtain bismuth nitrate acid solution; (2) Add 0.5~1.0g of ammonium metavanadate solid to 20~30mL of 2mol / L dilute nitric acid and stir until completely dissolved to obtain ammonium metavanadate acid solution; (3) Mix the bismuth nitrate solution and the ammonium metavanadate solution thoroughly; (4) Add 2.0~3.0g of urea to the mixed solution obtained in step (3), and then stir continuously at 85~95℃ for 20~30h; (5) After the reaction solution from step (4) has cooled to room temperature, wash the product alternately with deionized water and anhydrous ethanol, and then dry it at 55~65℃. (6) Calcine the sample obtained after drying in step (5) at 350~450℃ for 1.5~3.0h to obtain bismuth vanadate; (7) Mix the bismuth vanadate obtained in step (6) with deionized water and grind it into a uniform slurry. Then coat it evenly onto the surface of the alumina ceramic tube with two parallel and separate ring Au electrodes on the outer surface. Then place a nickel-chromium heating wire with a resistance of 30~40Ω inside the alumina ceramic tube. (8) The annular Au electrode and the nickel-chromium heating wire from step (7) are welded to a six-legged circular base through platinum wire leads to obtain a glutaraldehyde gas sensor with low concentration detection capability.

[0008] In step (5), the sample is dried in an oven; in step (6), the sample is calcined in a tube furnace with an air atmosphere; the alumina ceramic tube has a length of 3~5 mm, an outer diameter of 1.1~1.3 mm, and an inner diameter of 0.7~0.9 mm; the nickel-chromium alloy heating coil provides the working temperature for the sensor, and the resistance of the heating coil is 30~40 Ω; the width of the annular Au electrode is 0.7~0.9 mm, and the distance between the two annular Au electrodes is 1.7~1.9 mm; the thickness of the gas-sensitive film is 150~200 μm.

[0009] The glutaraldehyde gas sensor prepared by this invention, which has the ability to detect low concentrations, has the following advantages: (1) The method described in this invention avoids the harsh conditions of high temperature and high pressure preparation, has low equipment requirements, is safe to operate, and the raw materials are readily available and inexpensive; (2) The glutaraldehyde sensor based on crystal plane-controlled bismuth vanadate of the present invention can realize the detection of glutaraldehyde at a low concentration of 50 ppb, which helps to realize the concentration detection of glutaraldehyde gas in the field of disinfection and ensure the safety of staff. (3) The sensor described in this invention adopts a side-heated structure, which has the advantages of low cost, easy integration and packaging, and suitability for standardized production. Attached Figure Description

[0010] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0011] Figure 1These are scanning electron microscope images obtained in Embodiment 1 and Comparative Examples 1-3 of the present invention; Figure 2 These are X-ray diffraction patterns of the gas-sensitive materials prepared in Example 1 and Comparative Examples 1-3 of this invention; Figure 3 This is a bar chart showing the sensitivity of the gas sensors prepared in Example 1 and Comparative Examples 1-3 of the present invention to 60 ppm glutaraldehyde at 290-330ºC as a function of temperature. Figure 4 The dynamic response curves of the gas sensors prepared in Example 1 and Comparative Examples 1-3 to 50 ppm glutaraldehyde at the optimal operating temperature are shown. Figure 5 The graph shows the repeatability test results of the gas sensors prepared in Example 1 and Comparative Examples 1-3 of this invention, which are the repeatability test results of 8 consecutive tests on 50 ppm glutaraldehyde at the optimal operating temperature. Figure 6 The results show the selective test results of the gas sensor prepared in Example 1 on glutaraldehyde, hydrogen sulfide (60 ppm), ethanol, hydrogen peroxide, methanol, ammonia and acetic acid (200 ppm) at the optimal operating temperature. Figure 7 The dynamic response curves of the gas sensors prepared in Example 1 and Comparative Example 1 to 50 ppm glutaraldehyde at the optimal operating temperature and different humidity levels are shown. Figure 8 This is the dynamic response curve of the gas sensor prepared in Example 1 to 50~5000 ppb glutaraldehyde at the optimal operating temperature. Detailed Implementation

[0012] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0013] Sources of reagents and instruments: CGS-8 Intelligent Gas Sensitive Analyzer: Purchased from Beijing Elite Technology Co., Ltd. Bismuth nitrate pentahydrate (molecular formula: Bi(NO3)3·5H2O) (purity 99.9%): purchased from Xilong Scientific Co., Ltd. Ammonium metavanadate (molecular formula: NH4VO3) (purity 98.95%), sodium chloride (molecular formula: NaCl) (purity: 99.99%), sodium dodecyl sulfate (purity 95%), urea (purity 99.5%): purchased from Aladdin Industrial Company, China; Anhydrous ethanol: purchased from Chengdu Kelong Chemical Reagent Factory; Nitric acid (68% by mass), ammonia (28% by mass): purchased from Beijing Chemical Reagent Co., Ltd. Electric thermostatic drying oven: purchased from Kangheng Instruments Co., Ltd.; Where no specific experimental steps or conditions are specified in the embodiments, the operation or conditions of conventional experimental steps described in the literature in this field can be followed; the raw materials or instruments used are all conventional products that can be obtained commercially, including but not limited to the raw materials or instruments used in the embodiments of this application.

[0014] Example 1: This embodiment provides a method for preparing a glutaraldehyde gas sensor with low concentration detection capability based on crystal plane-controlled bismuth vanadate, the steps of which are as follows: (1) Add 2.91g of solid bismuth nitrate pentahydrate to 25mL of dilute nitric acid (2mol / L) and stir to obtain bismuth nitrate acid solution; (2) Add 0.7g of ammonium metavanadate solid to 25mL of dilute nitric acid (2mol / L) and stir to obtain ammonium metavanadate acid solution; (3) Mix the bismuth nitrate solution and the ammonium metavanadate solution thoroughly; (4) Add 2.5g of urea to the mixed solution, and then stir the solution at 90℃ for 24h. (5) After cooling to room temperature, wash the product alternately with deionized water and anhydrous ethanol to thoroughly remove soluble ions and organic impurities, and then dry it in an oven at 60°C. (6) The dried sample was placed in a tube furnace and calcined for 2 hours to obtain the final product bismuth vanadate; (7) Mix the bismuth vanadate obtained in step (6) with a small amount of deionized water and grind it into a uniform slurry. Then, use a small brush to evenly coat the slurry onto the surface of the alumina ceramic tube with two parallel and independent ring Au electrodes on the outer surface. After the slurry dries, a gas-sensitive film is obtained on the surface of the alumina ceramic tube and the ring Au electrodes. Then, place a nickel-chromium alloy heating wire with a resistance of 35Ω inside the ceramic tube. (8) The ring-shaped Au electrode of the alumina ceramic tube and the nickel-chromium alloy heating wire are welded to a six-legged circular base through platinum wire leads to obtain a glutaraldehyde gas sensor with low concentration detection capability based on crystal plane regulation of bismuth vanadate.

[0015] The alumina ceramic tube is 5 mm long, has an outer diameter of 1.1 mm, and an inner diameter of 0.9 mm; the annular Au electrode is 0.7 mm wide, and the distance between the two annular Au electrodes is 1.7 mm; the gas-sensitive film is 150 μm thick.

[0016] The scanning electron microscope image of the gas-sensitive material obtained in step (6) of this embodiment is shown below. Figure 1 As shown in (a) above, its X-ray diffraction pattern is as follows: Figure 2 As shown; the SEM image shows that the bismuth vanadate material of Example 1 is an octahedron with mainly exposed {010}, {110}, {011}, and {111} crystal planes. The XRD pattern shows that the diffraction peaks of the material of Example 1 correspond to the diffraction peak distribution of monoclinic bismuth vanadate crystal (PDF#14-0688), proving that Example 1 is a monoclinic bismuth vanadate crystal.

[0017] Comparative Example 1: This comparative example provides a method for preparing a gas sensor: 4.80 g of bismuth nitrate pentahydrate and 1.17 g of ammonium metavanadate were dissolved in 55 mL and 20 mL of 2 mol / L dilute nitric acid, respectively, and then the two solutions were thoroughly mixed. 0.11 g of NaCl was added, and after the reaction was complete, the pH of the mixed solution was titrated to 2 with ammonia solution. After aging for 2 h, the solution was transferred to a high-pressure reactor with a polytetrafluoroethylene (PTFE) bottom and reacted at 200 °C for 24 h. After cooling to room temperature, the yellow solid was collected by centrifugation, washed several times with deionized water and ethanol, dried in an oven at 60 °C, and finally calcined in a tube furnace for 2 h to obtain the final product.

[0018] Preparation of the gas sensor: Followed steps (7) to (8) of Example 1. The scanning electron microscope image of the gas-sensitive material prepared in Comparative Example 1 is shown below. Figure 1 As shown in (b) above, its X-ray diffraction pattern is as follows: Figure 2 As shown, the SEM image of Comparative Example 1 shows that the bismuth vanadate material is a decahedron with mainly exposed {010}, {110}, and {011} crystal planes. The XRD pattern shows that the diffraction peaks of Comparative Example 1 correspond to the diffraction peak distribution of monoclinic bismuth vanadate crystal (PDF#14-0688), proving that Comparative Example 1 is a monoclinic bismuth vanadate crystal.

[0019] Comparative Example 2: This comparative example provides a method for preparing a gas sensor: 4.80 g of bismuth nitrate pentahydrate and 1.17 g of ammonium metavanadate were dissolved in 55 mL and 20 mL of 2 mol / L dilute nitric acid, respectively. The two solutions were then thoroughly mixed, and after complete reaction, the pH of the mixed solution was titrated to 2 with ammonia solution. After aging for 2 h, the solution was transferred to a high-pressure reactor with a polytetrafluoroethylene (PTFE) bottom and reacted at 200 °C for 24 h. After cooling to room temperature, the yellow solid was collected by centrifugation, washed several times with deionized water and ethanol, and dried in an oven at 60 °C. Finally, the dried sample was calcined in a tube furnace for 2 h to obtain the final product.

[0020] Preparation of the gas sensor: Followed steps (7) to (8) of Example 1. The scanning electron microscope image of the gas-sensitive material prepared in this comparative example is shown below. Figure 1 As shown in (c), its X-ray diffraction pattern is as follows: Figure 2 As shown in the SEM image, the bismuth vanadate material of Comparative Example 2 is also a decahedron with mainly exposed {010}, {110}, and {011} crystal planes, but the proportion of each crystal plane is different from that of Comparative Example 1. Furthermore, the XRD pattern shows that the diffraction peaks of the material of Comparative Example 2 correspond to the diffraction peak distribution of monoclinic bismuth vanadate crystal (PDF#14-0688), proving that Comparative Example 2 is a monoclinic bismuth vanadate crystal.

[0021] Comparative Example 3: This comparative example provides a method for preparing a gas sensor: 2.91 g of bismuth nitrate pentahydrate, 0.7 g of ammonium metavanadate, and 0.6 g of sodium dodecyl sulfate were dissolved in 30 mL of 1.66 mol / L dilute nitric acid, respectively. These three substances were then mixed under stirring and stirred at room temperature for 2 h. The mixture was then transferred to an autoclave reactor with a polytetrafluoroethylene substrate and reacted at 150 °C for 4 h. After cooling to room temperature, the yellow solid was collected by centrifugation, washed repeatedly with deionized water and ethanol, and dried in an oven at 60 °C. Finally, the dried sample was calcined in a tube furnace for 2 h to obtain the final product.

[0022] Preparation of the gas sensor: Followed steps (7) to (8) of Example 1. The scanning electron microscope image of the gas-sensitive material prepared in this comparative example is shown below. Figure 1 As shown in (d) above, its X-ray diffraction pattern is as follows: Figure 2 As shown in the SEM image, the bismuth vanadate material of Comparative Example 3 is an octahedron with mainly exposed {120} and {021} crystal planes. The XRD pattern shows that the diffraction peaks of the material of Comparative Example 3 correspond to the diffraction peak distribution of monoclinic bismuth vanadate crystal (PDF#14-0688), proving that Comparative Example 3 is a monoclinic bismuth vanadate crystal.

[0023] Test Example 1: Measuring the response of a gas sensor to glutaraldehyde gas at different temperatures The gas-sensing performance of the device was tested using a CGS-8 intelligent gas sensitive analyzer at 290~330℃. First, the sensor was exposed to the air atmosphere for 8 minutes. Then, a specific concentration of the test gas was injected into the chamber through static gas mixing. After the gas reacted fully with the sensor, the device was exposed to the air atmosphere again to obtain the gas-sensing response.

[0024] like Figure 3As shown, the gas sensors prepared in Example 1 and Comparative Examples 1, 2, and 3 were tested for 60 ppm glutaraldehyde at 290~330℃. It can be seen that the sensitivity of the sensors obtained in Example 1 and Comparative Examples 1, 2, and 3 first increases and then decreases with the increase of temperature. This indicates that the optimal operating temperature of the sensors in Example 1 and Comparative Examples 1 and 2 is 310℃, and the optimal operating temperature of the sensor in Comparative Example 3 is 300℃. The sensitivity of the sensor obtained in Example 1 is significantly higher than that of the sensors obtained in the comparative examples.

[0025] Test Example 2: Gas Sensor Response to Glutaraldehyde Gas The gas-sensing performance of the device was tested using a CGS-8 intelligent gas sensitive analyzer at the optimal operating temperature. First, the sensor was exposed to the air atmosphere for 8 minutes. Then, a specific concentration of the test gas was injected into the chamber through a static gas mixing system. After the gas and sensor reacted fully, the device was exposed to the air atmosphere again, thus obtaining the gas-sensing response curve.

[0026] like Figure 4 As shown in (a) to (d), the gas sensors prepared in Example 1 and Comparative Examples 1, 2, and 3 were tested for 50 ppm glutaraldehyde at the optimal operating temperature. Calculations revealed the sensitivity of each sensor to 50 ppm glutaraldehyde. The sensor obtained in Example 1 exhibited the highest sensitivity at 4.1, followed by Comparative Example 1 at 3.73, Comparative Example 2 at 2.81, and Comparative Example 3 at 1.42. The different materials exhibit varying reactivity due to differences in the proportion of exposed crystal faces, resulting in different sensitivities when detecting glutaraldehyde. This demonstrates the feasibility of improving the gas-sensing performance of gas-sensitive materials through crystal facet modulation.

[0027] Test Example 3: Repeatability of the Gas Sensor's Response to Glutaraldehyde Gas Consistent with the conditions of Test Example 2, the gas sensors prepared in Example 1 and Comparative Examples 1, 2, and 3 were subjected to eight cycles of testing in a 50 ppm glutaraldehyde atmosphere at the optimal operating temperature.

[0028] like Figure 5 As shown in (a) to (d), it can be seen that the sensor prepared by the present invention has good repeatability and can achieve repeated testing multiple times, which has good practical application value.

[0029] Test Example 4: Selectivity of Gas Sensor for Glutaraldehyde Gas Consistent with the conditions of Test Example 2, the sensor prepared in Example 1 was tested against seven interfering gases, including glutaraldehyde, at the optimal operating temperature.

[0030] like Figure 6 As shown, the gas sensor prepared in Example 1 has a significantly higher sensitivity to glutaraldehyde gas than the other six interfering gases, proving that the sensor prepared in this invention exhibits good selectivity for glutaraldehyde gas.

[0031] Test Example 5: The gas sensor's ability to resist humidity interference Consistent with the conditions of Test Example 2, the sensors prepared in Example 1 and Comparative Example 1 were subjected to gas-sensing tests at different humidity levels in a 50 ppm glutaraldehyde atmosphere at the optimal operating temperature.

[0032] like Figure 7 As shown in (a1) to (d2), the gas sensor prepared in Example 1 exhibits strong resistance to humidity interference in its gas-sensitive response to glutaraldehyde under different humidity conditions.

[0033] Test Example 6: Gas Sensor's Detection Capability for Low Concentrations of Glutaraldehyde Consistent with the conditions of Test Example 2, the sensor prepared in Example 1 was tested in an atmosphere of 50-5000 ppb glutaraldehyde at the optimal operating temperature.

[0034] like Figure 8 As shown, the gas sensor prepared in Example 1 exhibits a detection limit as low as 50 ppb for glutaraldehyde gas, demonstrating the sensor prepared in this invention's ability to detect low concentrations of glutaraldehyde gas.

[0035] Based on the above performance test results, the optimal operating temperature of the gas sensor prepared in Example 1 of this invention is 310ºC. At this optimal operating temperature, the sensitivity to 50ppm carbon dioxide gas is 4.1. It also exhibits good selectivity and repeatability, a certain degree of resistance to humidity interference, and the ability to detect low concentrations of glutaraldehyde. Compared to the comparative example, bismuth vanadate with exposed crystal facets does not perform as well as the sensor prepared in Example 1 of this invention in detecting glutaraldehyde gas. Therefore, this invention provides a method for preparing a glutaraldehyde gas sensor with low concentration detection capability based on crystal facet-controlled bismuth vanadate.

[0036] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a glutaraldehyde gas sensor having a low concentration detection capability, characterized by: The steps are as follows, (1) 2.5-3.0 g of bismuth nitrate pentahydrate is added to 20-30 mL of 2 mol / L dilute nitric acid, and stirred until completely dissolved to obtain a bismuth nitrate acid solution; (2) 0.5-1.0 g of ammonium metavanadate solid is added to 20-30 mL of 2 mol / L dilute nitric acid, and stirred until completely dissolved to obtain an ammonium metavanadate acid solution; (3) the bismuth nitrate acid solution and the ammonium metavanadate acid solution are mixed thoroughly; (4) 2.0-3.0 g of urea is added to the mixed solution obtained in step (3), and stirring is continued at 85-95 °C for 20-30 h; (5) after the reaction solution of step (4) is cooled to room temperature, the product is washed with deionized water and anhydrous ethanol alternately, and then dried at 55-65 °C; (6) the sample obtained after drying in step (5) is calcined at 350-450 °C for 1.5-3.0 h to obtain bismuth vanadate; (7) the bismuth vanadate obtained in step (6) is mixed with deionized water and ground into a uniform slurry, and then uniformly coated onto the surface of an alumina ceramic tube with two parallel and separate annular Au electrodes on the outer surface, and a nichrome heating wire with a resistance value of 30-40 Ω is placed inside the alumina ceramic tube; (8) the annular Au electrodes and the nichrome heating wire of step (7) are welded on a six-legged circular base through a platinum wire lead to obtain a glutaraldehyde gas sensor with low concentration detection capability.

2. The method of claim 1, wherein the sensor is capable of detecting low concentrations of glutaraldehyde. The length of the alumina ceramic tube is 3-5 mm, the outer diameter is 1.1-1.3 mm, and the inner diameter is 0.7-0.9 mm; the resistance value of the nichrome alloy heating coil is 30-40 Ω; the width of the annular Au electrode is 0.7-0.9 mm, and the distance between the two annular Au electrodes is 1.7-1.9 mm.

3. The method of claim 1, wherein the sensor is a glutaraldehyde sensor having a low concentration detection capability. The thickness of the gas sensitive thin film is 150-200 μm.

4. A glutaraldehyde gas sensor having a low concentration detection capability, characterized by: is prepared by the preparation method of any one of claims 1-3.

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