Ammonia sensor based on copper ion organic framework and preparation method thereof

Abstract

The present application discloses an ammonia sensor based on a copper ion organic framework and a preparation method thereof, the method comprising: plasma cleaning a glass substrate with an indium tin oxide interdigital electrode for 6 minutes; adding a copper nitrate solution to the glass substrate with the indium tin oxide interdigital electrode to obtain a first solution; spraying a pyromellitic acid solution containing methanol onto the first solution, and a transparent film appears on the surface of the solution; then taking out the excess solution with a syringe, and then drying it under vacuum conditions at 80°C for 2 hours to completely remove the residual solvent, thereby obtaining an NH3 sensor based on an ion-conducting metal copper ion-organic framework. The sensor of the present application exhibits an excellent linear response to NH3, and has high sensitivity, good selectivity and fast response / recovery time, and solves the problems of low sensitivity, poor stability, expensive equipment, and cumbersome preparation process that most gas sensors have.

Description

Technical Field

[0001] The present application belongs to the technical field of smart home appliances, and specifically relates to an ammonia sensor based on a copper ion organic framework and a preparation method thereof. Background Art

[0002] Ammonia (NH3) is a colorless gas with a pungent odor, which is mainly released in the fields of explosives, plastics, textiles, pharmaceuticals, and industrial coolants. Even at low concentrations, NH3 can cause serious damage to human organ systems, such as the respiratory tract, skin, and lungs. When the human body is exposed to NH3 at concentrations above 500ppm, the respiratory system will be severely irritated; when exposed to high concentrations of NH3 (1000ppm or higher), it will cause water accumulation in the lungs; when exposed to extreme concentrations of NH3 (5000-10000ppm), it will even cause death. Therefore, various health agencies around the world have limited the minimum ammonia content in the workplace to 25ppm. In view of this, the establishment of rapid, sensitive, and accurate NH3 sensing and detection methods is of great significance to safeguard human health and environmental safety.

[0003] At present, the methods used for NH3 detection include colorimetry, electrochemical sensing, resistive sensing, etc. Resistive sensing has the advantages of high sensitivity and short response time. However, these methods still have disadvantages such as expensive equipment and complicated preparation process. Summary of the invention

[0004] The present application provides an ammonia sensor based on a copper ion organic framework and a preparation method thereof to solve the above-mentioned technical problems.

[0005] In order to solve the above technical problems, a technical solution adopted in the present application is: a method for preparing an ammonia sensor based on a copper ion organic framework, comprising the following steps:

[0006] Step S1. Plasma cleaning the glass substrate with the indium tin oxide interdigitated electrodes for 6 min;

[0007] Step S2. adding a copper nitrate solution to the glass substrate with the indium tin oxide interdigital electrodes to obtain a first solution;

[0008] Step S3. Spray a methanol-containing pyromellitic acid solution onto the first solution, and a transparent film appears on the surface of the solution; then remove the excess solution with a syringe, and then dry it under vacuum conditions at 80°C for 2 hours to completely remove the residual solvent, thereby obtaining an NH3 sensor based on an ion-conducting metal copper ion-organic framework.

[0009] Further, the method for preparing the copper nitrate solution in step S2 comprises:

[0010] Step S21. Dissolve 254.15 mg of pyromellitic acid in 10 mL of methanol solution to prepare a 0.2 mM methanol-containing pyromellitic acid solution;

[0011] Step S22. Stir the methanol-containing pyromellitic acid solution at room temperature for 12 hours to obtain a uniformly dispersed methanol-containing pyromellitic acid solution.

[0012] Further, the method for preparing the pyromellitic acid solution containing methanol in step S3 comprises:

[0013] Step S31. Dissolve 24.16 g of copper nitrate trihydrate in a deionized water solution to prepare a 0.1 M copper nitrate solution;

[0014] Step S32. Stir the copper nitrate solution at room temperature for 1 hour to obtain a uniformly dispersed copper nitrate solution.

[0015] Another technical solution adopted in the present application is: an ammonia sensor based on a copper ion organic framework, comprising a glass substrate and interdigital electrodes with indium tin oxide on the surface; wherein the interdigital electrodes are arranged on the surface of the glass substrate.

[0016] Furthermore, a sensing layer composed of a sensing material is drop-coated on the surfaces of the interdigital electrodes and the glass substrate; the sensing material includes the copper nitrate solution prepared above.

[0017] Furthermore, the length and width of the conductive channel in the interdigital electrodes are 100 μm and 1000 μm, respectively.

[0018] Furthermore, the thickness of the interdigital electrodes was 185 nm.

[0019] The beneficial effects of the present application are as follows: the sensor based on ion-conducting metal copper ion-organic framework of the present application shows excellent linear response to NH3, and has high sensitivity, good selectivity and fast response / recovery time. The sensor also shows excellent performances such as high transparency, high selectivity and high stability. And it solves the problems of low sensitivity, poor stability, expensive equipment and complicated preparation process existing in most gas sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of an embodiment of an ammonia sensor based on a copper ion organic framework of the present application;

[0021] Figure 2 is a capacitance curve diagram of gas detection by the copper ion organic framework-based ammonia sensor at different gas concentrations in Example 4;

[0022] Figure 3is the response function of the ammonia sensor based on the copper ion organic framework to the gas concentration in Example 5;

[0023] Figure 4 is a response recovery time diagram of the ammonia sensor based on the copper ion organic framework in Example 6 at a 35 ppm NH3 gas concentration;

[0024] Figure 5 It is the responsiveness of the ammonia sensor based on the copper ion organic framework in Example 6 to different volatile organic compounds at room temperature. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0027] The present application provides a method for preparing an ammonia sensor based on a copper ion organic framework, comprising:

[0028] Step S1. Plasma cleaning the glass substrate with the indium tin oxide interdigitated electrodes for 6 min;

[0029] Step S2. adding a copper nitrate solution to the glass substrate with the indium tin oxide interdigital electrodes to obtain a first solution;

[0030] Step S3. Spray the methanol-containing pyromellitic acid solution onto the first solution, and a transparent film appears on the surface of the solution; remove the excess solution with a syringe, and then dry it under vacuum conditions at 80°C for 2 hours to completely remove the residual solvent, thereby obtaining an NH3 sensor based on ion-conducting metal copper ion-organic framework.

[0031] The present application also provides a method for preparing the copper nitrate solution in step S2, comprising:

[0032] Step S21. Dissolve 254.15 mg of pyromellitic acid in 10 mL of methanol solution to prepare a 0.2 mM methanol-containing pyromellitic acid solution;

[0033] Step S22. Stir the methanol-containing pyromellitic acid solution at room temperature for 12 hours to obtain a uniformly dispersed methanol-containing pyromellitic acid solution.

[0034] The present application also provides a method for preparing the pyromellitic acid solution containing methanol in the above step S3, comprising:

[0035] Step S31. Dissolve 24.16 g of copper nitrate trihydrate in a deionized water solution to prepare a 0.1 M copper nitrate solution;

[0036] Step S32. Stir the copper nitrate solution at room temperature for 1 hour to obtain a uniformly dispersed copper nitrate solution.

[0037] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of an embodiment of an ammonia sensor based on a copper ion organic framework of the present application, the sensor includes a glass substrate and an interdigitated electrode with indium tin oxide on the surface; wherein the interdigitated electrode is arranged on the surface of the glass substrate. The surfaces of the interdigitated electrode and the glass substrate are drop-coated with a sensing layer composed of a sensing material; the sensing material includes the copper nitrate solution prepared as described above. The length and width of the conductive channel in the interdigitated electrode are 100μm and 1000μm, respectively. The thickness of the interdigitated electrode is 185nm. The sensing sensitive layer reacts after contacting NH3, and the capacitance value of the sensitive layer of the sensing material on the surface of the indium tin oxide planar interdigitated electrode changes, and the capacitance value is read out by an LCR tester (the AC voltage applied to both ends of the interdigitated electrode is 1V, 400Hz).

[0038] Example 1

[0039] 254.15 mg of pyromellitic acid solution was dissolved in 10 mL of methanol solution to prepare a 0.2 mM methanol-containing pyromellitic acid solution; the methanol-containing pyromellitic acid solution was then stirred at room temperature for 12 hours to obtain a uniformly dispersed methanol-containing pyromellitic acid solution.

[0040] Example 2

[0041] 24.16 g of copper nitrate trihydrate was dissolved in 1000 mL of deionized water to prepare a 0.1 M copper nitrate solution, and the solution was stirred at room temperature for 1 hour to obtain a uniformly dispersed copper nitrate solution.

[0042] Example 3

[0043] Preparation of an ammonia sensor based on a copper ion organic framework. The glass substrate with an indium tin oxide interdigital electrode (the length and width of the conductive channel are 100μm and 1000μm, respectively, and the electrode thickness is 185nm) was plasma cleaned for 5 minutes, and the glass substrate with the indium tin oxide interdigital electrode was added to the copper nitrate solution using a glass petri dish. Then, a methanol-containing pyromellitic acid solution was sprayed onto the glass substrate with the indium tin oxide interdigital electrode. A transparent film quickly appeared on the surface of the solution. Then, the excess solution was removed with a syringe. The obtained device was dried under vacuum conditions at 80°C for 2 hours to completely remove the residual solvent. Thus, an ammonia sensor based on a copper ion organic framework was obtained. Figure 1This is a schematic diagram of the structure of the sensor.

[0044] Example 4

[0045] This example studies the sensing characteristics of the NH3 sensor. The sensor prepared in Example 3 was placed under different NH3 gas concentrations for testing using an LCR tester from Tonghui Electronic Instrument Co., Ltd. The dynamic response characteristics of the NH3 sensor prepared in Example 3 under 1V, 400Hz AC voltage were tested. Figure 2 The results show that the sensor exhibits good capacitance dynamic response characteristics in the range of 35-700ppm, indicating that the sensor can effectively detect NH3.

[0046] Example 5

[0047] In order to further explore the sensitivity of the NH3 sensor prepared in Application Example 3, the sensor was fitted with multiple detection results of NH3 in the concentration range of 25-700ppm, and a curve with high linearity was obtained ( Figure 3 ). The concentration of NH3 can be traced back and determined by the response size of the sensor. The error of each data point is small and within the allowable error range, indicating good consistency between devices and repeatability in the detection of different NH3 gas concentrations. In addition, the minimum detection limit of the sensor is 0.7ppm.

[0048] Example 6

[0049] The response-recovery curve of the NH3 sensor prepared in Example 3 to NH3 gas concentration of 35ppm under 1V, 400Hz AC voltage is as follows: Figure 4 As shown. Response / recovery time is one of the important indicators for evaluating the performance of gas sensors. Under this definition, when the gas sensor is tested in an environment with a 35ppm NH3 gas concentration, the time required for the capacitance value to change by 90% of the total capacitance change is the response recovery time. The results show that the response time of the sensor is 12.5s and the recovery time is 63.5s, indicating that the sensor has good sensitivity.

[0050] Example 7

[0051] In order to further explore the selectivity of the NH3 sensor prepared in Application Example 3, the sensor was used to detect a variety of common chemical gases such as acetone, ethanol, dimethyl carbonate, cyclohexane and toluene. The response of the NH3 gas sensor to interfering gases and NH3 at 1V and 400Hz AC voltage is as follows: Figure 5As shown, their real-time response curves are integrated. The results show that the sensor has a response of 83.9% under 70ppm NH3 gas, which is more than four times the response to other gases (<20%), indicating that the sensor has high selectivity for NH3 and can accurately identify NH3 in a complex environment without interference from other common chemical gases.

[0052] This application makes full use of the characteristics of empty electron orbitals of metal ions, which enable them to interact effectively with chemical substances. Metal organic framework compounds have a wide range of applications in gas separation, ion exchange, and sensors due to their ultra-high specific surface area, high porosity, and abundant active sites. Ammonia sensors based on copper ion organic frameworks can detect target gases through a variety of ions, and a variety of interaction modes can be formed between ions and gas molecules at room temperature, including redox processes involving charge transfer, reversible weak coordination interactions that do not involve charge transfer, and irreversible strong coordination interactions. Therefore, it is expected to create smart gas sensors with high selectivity and high sensitivity at room temperature.

[0053] The ammonia sensor based on the copper ion organic framework prepared in this application shows an excellent linear response to NH3, and has high sensitivity (35ppmNH3: 13.9%), good selectivity and fast response / recovery time (12.5s / 63.5s). The sensor also shows excellent performance such as high transparency, high selectivity and high stability. It also solves the problems of low sensitivity, poor stability, expensive equipment and cumbersome preparation process in most gas sensors.

[0054] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An ammonia sensor based on a copper ion organic framework, characterized in that: The invention comprises a glass substrate and an interdigital electrode with indium tin oxide on the surface; wherein the interdigital electrode is arranged on the surface of the glass substrate; and the preparation method of the ammonia sensor comprises: Step S1. Plasma cleaning the glass substrate with the indium tin oxide interdigitated electrodes for 6 min; Step S2. Adding a copper nitrate solution to the glass substrate with the indium tin oxide interdigital electrodes; wherein the method for preparing the copper nitrate solution comprises: Step S21. Dissolve 24.16 g of copper nitrate trihydrate in a deionized water solution to prepare a 0.1 M copper nitrate solution; Step S22. Stirring the copper nitrate solution at room temperature for 1 h to obtain a uniformly dispersed copper nitrate solution; Step S3. Spraying a pyromellitic acid solution containing methanol onto the copper nitrate solution, and a transparent film appears on the surface of the solution; then taking out the excess solution with a syringe, and then drying it under vacuum conditions at 80° C. for 2 h to completely remove the residual solvent, thereby obtaining an NH3 sensor based on an ion-conducting metal copper ion-organic framework; wherein the method for preparing a pyromellitic acid solution containing methanol comprises: Step S31. Dissolve 254.15 mg of pyromellitic acid in 10 mL of methanol solution to prepare a 0.2 mM methanol-containing pyromellitic acid solution; Step S32. Stir the methanol-containing pyromellitic acid solution at room temperature for 12 h to obtain a uniformly dispersed methanol-containing pyromellitic acid solution.

2. The ammonia sensor based on a copper ion organic framework according to claim 1, characterized in that: The length and width of the conductive channel in the interdigital electrodes are 100 μm and 1000 μm, respectively.

3. The ammonia sensor based on a copper ion organic framework according to claim 1, characterized in that: The thickness of the interdigital electrodes is 185 nm.

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