An acetone sensor based on an ion-conducting metal-ion-organic framework and its preparation method.

Abstract

This application discloses an acetone sensor based on an ion-conducting copper ion-organic framework and its preparation method, belonging to the field of gas sensor technology. The sensor uses a glass substrate with indium tin oxide (ITO) interdigitated electrodes. The sensitive layer is an ion-conducting copper-based MOF thin film formed by the in-situ coordination reaction of tetrakis(4-aminophenyl)porphyrin and copper ions at the liquid-phase interface, constituting a capacitive gas sensor. In the preparation process, a ligand methanol solution and a copper nitrate solution are first prepared. After plasma cleaning of the substrate, the ligand solution is sprayed onto the copper salt solution interface to form an in-situ film, which is then vacuum dried to obtain the acetone sensor. This application has advantages such as simple process, low cost, high sensitivity, fast response, and good stability, making it suitable for large-scale production. It can be used for non-invasive detection of acetone in diabetic respiration, environmental monitoring, and industrial VOCs detection, showing promising application prospects.

Description

Technical Field

[0001] This application belongs to the field of gas sensor technology, specifically relating to an acetone sensor based on an ion-conducting metal ion-organic framework and its preparation method. Background Technology

[0002] The development of gas sensors capable of accurately detecting volatile organic compounds is of great significance in fields such as industrial safety control, environmental monitoring, and personal health management. Acetone, as a selective biomarker for diabetes, is a key indicator for diabetes diagnosis in human respiration: acetone concentrations in the breath of healthy individuals are below 1 ppm (0.3–0.9 ppm), while those in patients with type 1 and type 2 diabetes can reach ~2.2 ppm and ~1.7 ppm, respectively. Therefore, achieving highly sensitive acetone detection at the ppb level is crucial for the early diagnosis of diabetes.

[0003] Existing methods for acetone detection, such as chromatography, spectroscopy, electrophoresis, and chemiluminescence, generally suffer from drawbacks such as time-consuming sample preparation, long analysis cycles, expensive and bulky instruments, high power consumption, and the need for professional maintenance, failing to meet the requirements for real-time detection and timely early warning. Chemical sensors based on ion-conductive materials can operate at room temperature and exhibit excellent selectivity and stability. Selective adsorption of gas molecules can be achieved by controlling the types of active ions. However, existing ion-conductive gas sensors suffer from insufficient sensitivity, poor stability, cumbersome preparation processes, and high costs, making it difficult to simultaneously meet the demands for high sensitivity, fast response, ease of preparation, and low cost. Summary of the Invention

[0004] This application provides an acetone sensor based on an ion-conducting metal ion-organic framework and its preparation method, in order to solve the shortcomings of existing acetone detection methods, including low sensitivity, poor stability, expensive equipment, and cumbersome preparation process.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: an acetone sensor based on an ion-conducting metal ion-organic framework, a glass substrate with an indium tin oxide interdigitated electrode on its surface and a sensing layer coated on the substrate and the electrode.

[0006] The sensing layer is composed of an ion-conducting copper ion-organic framework thin film generated by in-situ coordination reaction of tetrakis(4-aminophenyl)porphyrin and copper ions; the sensor is a capacitive sensor, which realizes gas detection by detecting the capacitance change after acetone is adsorbed in the sensing layer.

[0007] Furthermore, the conductive channel length of the indium tin oxide interdigitated electrode is 90~110μm, the width is 900~1100μm, and the electrode thickness is 166~204nm.

[0008] Furthermore, the capacitance of the sensing layer changes under the action of acetone gas. The detection conditions are: an AC voltage of 2 V and a frequency of 400 Hz applied to the two ends of the interdigital electrodes, and the capacitance signal is read using an LCR meter.

[0009] Furthermore, the sensor exhibits a response rate of less than 20% to interfering gases such as ethanol, dimethyl carbonate, cyclohexane, and toluene, and has high selectivity for acetone.

[0010] Another technical solution adopted in this application is: a method for preparing an acetone sensor based on an ion-conducting metal ion-organic framework, comprising:

[0011] S1. Preparation of tetra(4-aminophenyl)porphyrin methanol solution;

[0012] S2. Prepare copper nitrate solution;

[0013] S3. Perform plasma cleaning on the glass substrate with indium tin oxide interdigitated electrodes for 6 min;

[0014] S4. Place the cleaned substrate into a copper nitrate solution, and then spray a tetrakis(4-aminophenyl)porphyrin methanol solution onto the liquid surface to generate a sensitive film in situ.

[0015] S5. Remove excess solution and dry the device under vacuum at 80°C for 2 hours to obtain the acetone sensor.

[0016] Furthermore, the method in step S1 includes:

[0017] Dissolve 650-700 mg of tetra(4-aminophenyl)porphyrin in 9-11 mL of methanol solution to prepare a 0.18-0.22 mM tetra(4-aminophenyl)porphyrin solution containing methanol.

[0018] A tetra(4-aminophenyl)porphyrin solution containing methanol was stirred at room temperature for 12 h to obtain a uniformly dispersed tetra(4-aminophenyl)porphyrin methanol solution.

[0019] Furthermore, the method in step S2 includes:

[0020] Dissolve 23-25 ​​g of copper nitrate trihydrate in a deionized aqueous solution to prepare a 0.09-0.11 M copper nitrate solution;

[0021] The copper nitrate solution was stirred at room temperature for 1 h to obtain a uniformly dispersed copper nitrate solution.

[0022] The beneficial effects of this application are as follows: This application uses copper ions and tetrakis(4-aminophenyl)porphyrin to construct an ion-conductive MOF sensitive membrane in situ, which differs from traditional resistive oxides and ordinary MOF materials, achieving highly sensitive acetone recognition at room temperature. The capacitive detection mechanism of this application features fast response, high sensitivity, low detection limit, and strong selectivity for interfering gases, meeting the needs for accurate acetone detection in diabetic respiration. This application uses in-situ one-step film formation at the liquid-phase interface, eliminating the need for high-temperature calcination and complex post-processing, resulting in a short process, mild conditions, and good repeatability. Both the raw materials and the substrate are commercially available conventional materials, requiring low equipment specifications and a simple process, suitable for industrial mass production. This application can operate at room temperature, is compact, and consumes low power, making it suitable for various scenarios such as non-invasive medical diagnosis, environmental monitoring, and industrial safety. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the acetone sensor based on an ion-conducting copper ion-organic framework in Example 3 of this application;

[0024] Figure 2 This is a capacitance curve of the sensor in Embodiment 4 of this application for gas detection at different gas concentrations;

[0025] Figure 3 It is the response function of the acetone sensor based on the ion-conducting copper ion-organic framework in Example 5 of this application to the gas concentration;

[0026] Figure 4 This is a response recovery time diagram of the sensor in Example 6 of this application at a concentration of 120 ppm acetone gas;

[0027] Figure 5 This is a response analysis graph of the acetone sensor in Example 6 of this application to different volatile organic compounds at room temperature. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0029] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0030] This application provides an acetone sensor based on an ion-conducting metal-organic framework, comprising a glass substrate with indium tin oxide interdigitated electrodes and a sensing layer coated on the substrate and electrodes. The sensing layer is composed of an ion-conducting copper-organic framework thin film formed by an in-situ coordination reaction between tetrakis(4-aminophenyl)porphyrin and copper ions. The sensor is a capacitive sensor, detecting gas by detecting the capacitance change after acetone adsorbs in the sensing layer. The sensor exhibits a response of less than 20% to interfering gases such as ethanol, dimethyl carbonate, cyclohexane, and toluene, and high selectivity for acetone.

[0031] The indium tin oxide interdigitated electrode has a conductive channel length of 90–110 μm, a width of 900–1100 μm, and a thickness of 166–204 nm. The sensing layer exhibits a capacitance change under the influence of acetone gas. The detection conditions are: an AC voltage of 2 V applied across the interdigitated electrode at a frequency of 400 Hz, and the capacitance signal is read using an LCR meter.

[0032] This application also provides a method for preparing an acetone sensor based on an ion-conducting metal ion-organic framework, comprising:

[0033] S1. Preparation of tetrakis(4-aminophenyl)porphyrin methanol solution, the specific steps are as follows:

[0034] S11. Dissolve 650-700 mg of tetra(4-aminophenyl)porphyrin in 9-11 mL of methanol solution to prepare a 0.18-0.22 mM tetra(4-aminophenyl)porphyrin solution containing methanol.

[0035] S12. Stir the tetra(4-aminophenyl)porphyrin solution containing methanol at room temperature for 12 h to obtain a uniformly dispersed tetra(4-aminophenyl)porphyrin methanol solution.

[0036] S2. Preparation of copper nitrate solution; specific steps are as follows:

[0037] S21. Dissolve 23-25 ​​g of copper nitrate trihydrate in a deionized aqueous solution to prepare a 0.09-0.11 M copper nitrate solution;

[0038] S22. Stir the copper nitrate solution at room temperature for 1 h to obtain a uniformly dispersed copper nitrate solution.

[0039] S3. Perform plasma cleaning on the glass substrate with indium tin oxide interdigitated electrodes for 6 min;

[0040] S4. Place the cleaned substrate into a copper nitrate solution, and then spray a tetrakis(4-aminophenyl)porphyrin methanol solution onto the liquid surface to generate a sensitive film in situ.

[0041] S5. Remove excess solution and dry the device under vacuum at 80°C for 2 hours to obtain the acetone sensor.

[0042] Example 1

[0043] A 0.2 mM tetra(4-aminophenyl)porphyrin solution was prepared by dissolving 675 mg of tetra(4-aminophenyl)porphyrin in 10 mL of methanol solution. The methanol-containing tetra(4-aminophenyl)porphyrin solution was then stirred at room temperature for 12 h to obtain a uniformly dispersed methanol-containing tetra(4-aminophenyl)porphyrin solution.

[0044] Example 2

[0045] 24.16 g of copper nitrate trihydrate was dissolved in 1000 mL of deionized water to prepare a 0.1 M copper nitrate solution. The solution was then stirred at room temperature for 1 h to obtain a uniformly dispersed copper nitrate solution.

[0046] Example 3

[0047] An acetone sensor based on an ion-conducting copper ion-organic framework was fabricated. A glass substrate with indium tin oxide (ITO) interdigitated electrodes (conductive channel length and width 100 μm and 1000 μm, electrode thickness 185 nm) was plasma-cleaned for 5 min. The ITO-equipped glass substrate was then immersed in a copper nitrate solution in a glass culture dish. A tetrakis(4-aminophenyl)porphyrin solution containing methanol was then sprayed onto the ITO-equipped glass substrate, and a transparent film quickly appeared on the solution surface. Excess solution was then removed using a syringe. The resulting device was dried under vacuum at 80 °C for 2 h to completely remove residual solvent. Thus, the acetone sensor based on an ion-conducting copper ion-organic framework was obtained. Figure 1 This is a schematic diagram of the sensor's structure.

[0048] Example 4

[0049] To investigate the sensing characteristics of the acetone sensor, the sensor prepared in Example 3 was tested under different acetone gas concentrations using an LCR meter from Tonghui Electronic Instruments Co., Ltd. The dynamic response characteristics of the acetone sensor prepared in Example 3 under a 2 V, 400 Hz AC voltage were tested, as shown below. Figure 2 As shown in the figure. The results indicate that the sensor exhibits good capacitive dynamic response characteristics in the range of 30-300 ppm, demonstrating that the sensor can effectively detect acetone.

[0050] Example 5

[0051] To further investigate the sensitivity of the acetone sensor prepared in Application Example 3, the sensor was fitted with multiple detection results of acetone in the concentration range of 30-300 ppm, and a curve with high linearity was obtained. Figure 3 The concentration of acetone can be determined by tracing back the sensor's response magnitude. The small error at each data point, within the allowable error range, indicates good consistency between devices and repeatability in detecting different acetone gas concentrations. Furthermore, the sensor's lowest detection limit is 0.144 ppm.

[0052] Example 6

[0053] The response-recovery curve of the acetone sensor prepared in Example 3 to an acetone gas concentration of 120 ppm at 2 V and 400 Hz AC voltage is shown below. Figure 4 As shown in the figure, response / recovery time is one of the important indicators for evaluating the performance of a gas sensor. Under this definition, when the gas sensor detects a gas concentration of 120 ppm acetone, the time required for the capacitance value to reach 90% of the total capacitance change is defined as the response / recovery time. The results show that the sensor's response time is 3.5 s and its recovery time is 6.5 s, indicating that the sensor has good sensitivity.

[0054] Example 7

[0055] To further investigate the selectivity of the acetone sensor prepared in Application Example 3, this sensor was used to detect several common chemical gases, including ethanol, dimethyl carbonate, cyclohexane, and toluene. The acetone gas sensor, under a 2 V, 400 Hz AC voltage, exhibited the following response to interfering gases and acetone: Figure 5 As shown, their real-time response curves are integrated. The results show that the sensor has a responsivity of 83.9% at 240 ppm NH3 gas, which is more than four times that of other gases (< 20%). This indicates that the sensor has high selectivity for acetone and can accurately identify acetone in complex environments without interference from other common chemical gases.

[0056] The raw materials and the glass substrate with indium tin oxide interdigitated electrodes used in this application are commercially available. The raw materials are low-cost, high-yield, and structurally consistent, making them suitable for large-scale production. The acetone sensor fabricated in this application has a simple manufacturing process, is small in size, and is suitable for industrial mass production.

[0057] This application fully utilizes the characteristics of the empty electron orbitals of metal ions, enabling them to interact effectively with chemical substances. Metal-organic framework compounds, due to their ultra-high specific surface area, high porosity, and abundant active sites, have wide applications in gas separation, ion exchange, and sensors. Ion conduction-metal-organic framework sensors can detect target gases through a variety of ions, and at room temperature, various interaction modes can be formed between ions and gas molecules, including redox processes involving charge transfer, reversible weak coordination interactions without charge transfer, and irreversible strong coordination interactions. Therefore, it is expected to create intelligent gas sensors with high selectivity and high sensitivity at room temperature.

[0058] The sensor described in this application exhibits excellent linear response to acetone, along with high sensitivity (38.9% for 120 ppm acetone), good selectivity, and fast response / recovery time (3.5 s / 6.5 s). The sensor also demonstrates superior performance, including high transparency, high selectivity, and high stability. Furthermore, it addresses the problems of low sensitivity, poor stability, expensive equipment, and cumbersome preparation processes found in some gas sensors.

[0059] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. An acetone sensor based on an ion-conducting metal ion-organic framework, characterized in that, The sensor has a glass substrate with indium tin oxide interdigitated electrodes and a sensing layer coated on the substrate and electrodes. The sensing layer is composed of an ion-conducting copper ion-organic framework thin film generated by in-situ coordination reaction of tetrakis(4-aminophenyl)porphyrin and copper ions; the sensor is a capacitive sensor, which realizes gas detection by detecting the capacitance change after acetone is adsorbed on the sensing layer.

2. The acetone sensor based on an ion-conducting metal ion-organic framework according to claim 1, characterized in that, The conductive channel of the indium tin oxide interdigitated electrode has a length of 90~110μm, a width of 900~1100μm, and an electrode thickness of 166~204nm.

3. An acetone sensor based on an ion-conducting metal ion-organic framework according to claim 1, characterized in that, The capacitance value of the sensing layer changes under the action of acetone gas. The detection conditions are: an AC voltage of 2 V and a frequency of 400 Hz applied to the two ends of the interdigital electrodes, and the capacitance signal is read using an LCR meter.

4. An acetone sensor based on an ion-conducting metal ion-organic framework according to claim 1, characterized in that, The sensor exhibits a response rate of less than 20% to ethanol, dimethyl carbonate, cyclohexane, and toluene, but high selectivity to acetone.

5. A method for preparing an acetone sensor based on an ion-conducting metal ion-organic framework, characterized in that, include: S1. Preparation of tetra(4-aminophenyl)porphyrin methanol solution; S2. Prepare copper nitrate solution; S3. Perform plasma cleaning on the glass substrate with indium tin oxide interdigitated electrodes for 6 min; S4. The cleaned substrate is placed in the copper nitrate solution, and then the tetrakis(4-aminophenyl)porphyrin methanol solution is sprayed onto the liquid surface to generate a sensitive film in situ; S5. Remove excess solution and dry the device under vacuum at 80°C for 2 hours to obtain the acetone sensor.

6. The method according to claim 5, characterized in that, The method of step S1 includes: Dissolve 650-700 mg of tetra(4-aminophenyl)porphyrin in 9-11 mL of methanol solution to prepare a 0.18-0.22 mM tetra(4-aminophenyl)porphyrin solution containing methanol. The tetra(4-aminophenyl)porphyrin solution containing methanol was stirred at room temperature for 12 h to obtain a uniformly dispersed tetra(4-aminophenyl)porphyrin methanol solution.

7. The method according to claim 5, characterized in that, The method of step S2 includes: Dissolve 23-25g of copper nitrate trihydrate in a deionized aqueous solution to prepare a 0.09-0.11 M copper nitrate solution; The copper nitrate solution was stirred at room temperature for 1 h to obtain a uniformly dispersed copper nitrate solution.

8. The method according to claim 5, characterized in that, In step S4, the tetra(4-aminophenyl)porphyrin undergoes a coordination complexation reaction with copper ions in the copper nitrate solution at the interface to form a continuous, transparent ion-conducting copper ion-organic framework film.

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