Naphthoquinone-based gas sensitive material, preparation method and application of naphthoquinone-based gas sensitive material in ammonia gas sensor

Abstract

The invention discloses a naphthoquinone-based gas sensitive material, a preparation method and application of the naphthoquinone-based gas sensitive material in an ammonia gas sensor, and belongs to the technical field of gas sensors. The material is composed of divalent metal ions such as copper, nickel and cobalt and a polysubstituted naphthoquinone organic ligand, forms a one-dimensional chain structure, has a high specific surface area, an ordered electron channel and excellent molecular recognition capability, and can detect toxic gases such as ammonia gas at room temperature with high sensitivity. Macroscopic preparation of the material can be realized through solvothermal one-step reaction. Compared with the prior art, the one-dimensional coordination structure and ligand site engineering synergistically improve the carrier transport and molecular recognition capability, can realize continuous, real-time and selective detection of ammonia gas under complex working conditions, and has the advantages of high yield, large-scale preparation and excellent device application prospect.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor materials, specifically relating to a naphthoquinone-based gas sensitive material, its preparation method, and its application in an ammonia sensor. Background Technology

[0002] Ammonia (NH3) is a crucial raw material and refrigerant in industries such as fertilizers, pharmaceuticals, fine chemicals, and refrigeration and air conditioning. It is highly irritating and volatile. Ammonia readily reacts with moisture in the air to form ammonia water, which is highly alkaline and corrosive, causing acute damage to the respiratory tract, eyes, and skin. It also corrodes metals such as copper and zinc and their alloys, leading to equipment failure and secondary accidents. High-concentration ammonia leaks can also cause regional environmental hazards and production shutdowns, resulting in significant economic losses. Due to ammonia's low odor threshold, easy diffusion, and diverse leakage scenarios (such as ammonia refrigeration rooms, urea and ammonium nitrate production, wastewater treatment, and livestock farming), continuous, real-time, sensitive, and selective detection of ammonia is crucial for early warning, occupational health protection, process safety, and environmental compliance monitoring. Existing detection methods include electrochemistry, metal oxide semiconductors, optics, and chromatography / mass spectrometry, but they often face problems such as insufficient selectivity, high energy consumption, large size / cost, or complex maintenance under complex operating conditions. There is an urgent need for new ammonia sensing materials and devices that combine low power consumption, high selectivity, and integrability.

[0003] Metal-organic frameworks (MOFs) are formed by the self-assembly of metal nodes and organic ligands. They possess ultra-high specific surface areas, designable pore structures, and abundant chemical functional sites, enabling the directional tuning of adsorption / recognition capabilities for specific gas molecules by controlling the valence state / coordination environment of the metal center, ligand functionalization, pore size, and surface polarity. Compared to traditional inorganic sensors, MOFs can achieve the enrichment and selective recognition of a variety of volatile molecules and small gases at room temperature or near room temperature. They also possess high programmability in structure and chemistry, facilitating the design of Lewis acidic / hydrogen-bonded acceptor sites for basic molecules such as ammonia. The high specific surface area and ordered pores result in rapid mass transfer and low detection limits. Although some traditional MOFs exhibit strong insulation, sensitivity to environmental humidity, and require optimization for long-term stability, through conductive design, post-synthesis modification, and device structure engineering (such as thin-film fabrication, interface coupling, and encapsulation), they show significant potential in terms of low power consumption, selectivity, and integrated manufacturability.

[0004] One-dimensional conductive MOFs (1D MOFs) possess advantages such as high room temperature response, low power consumption, and easy arraying due to their chain conjugation and anisotropic channels. They have already been used in the detection of carbon monoxide. However, their application in ammonia sensing faces a series of problems that urgently need to be addressed. First, ammonia is a strong Lewis base, easily leading to strong coordination poisoning and hysteresis. Second, it competes with amines / alcohols / water for adsorption, and under humidity, it easily generates ammonia water, causing drift. Third, heating is often required to ensure reversible desorption, sacrificing low power consumption. Therefore, simply changing the target gas faces a systemic bottleneck of "reversibility—selectivity—power consumption." Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing naphthoquinone-based gas-sensitive materials.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a naphthoquinone-based gas-sensitive material, comprising, The metal ion solution was added dropwise to the organic ligand solution, concentrated ammonia was added, and the mixture was stirred to react. After the reaction was completed, the resulting black precipitate was washed, centrifuged, and dried to obtain the gas-sensitive material; The metal ion solution is one of the following: a solution containing cobalt ions, a copper ion solution, or a nickel ion solution. The organic ligand solution is a multi-substituted 1,4-naphthoquinone solution, and the structural formula of the multi-substituted 1,4-naphthoquinone is as follows: ; Wherein, R1 is a hydroxyl group, and R2 is any one or more of hydrogen, methyl, and fluorine atoms.

[0009] In a preferred embodiment of the preparation method described in this invention, the metal salt includes hydrated acetate, hydrated sulfate, and hydrated chloride. The solvent for the metal ion solution is dimethyl sulfoxide.

[0010] As a preferred embodiment of the preparation method described in this invention, the organic ligands include 5,8-dihydroxy-1,4-naphthoquinone (DHNQ), 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthoquinone (DHTMNQ), and 5,8-dihydroxy-2,3,6,7-tetrafluoro-1,4-naphthoquinone (DHTFNQ).

[0011] In a preferred embodiment of the preparation method described in this invention, the solvent of the organic ligand solution is dimethyl sulfoxide.

[0012] In a preferred embodiment of the preparation method described in this invention, the molar ratio of the ligand to the metal salt is 1 mmol : (0.5~2) mmol. The ratio of the amount of the metal salt to the volume of concentrated ammonia is 1 mmol: (2~4) mL.

[0013] In a preferred embodiment of the preparation method described in this invention, the volume ratio of the amount of metal salt in the metal ion solution to the volume of the solvent is 1 mmol: (30~50) mL, and the volume ratio of the amount of organic ligand in the organic ligand solution to the volume of the solvent is 1 mmol: (30~50) mL.

[0014] In a preferred embodiment of the preparation method described in this invention, the temperature of the stirring reaction is 20℃~60℃, and the stirring reaction time is 12 h~36 h.

[0015] Another objective of this invention is to overcome the shortcomings of the prior art and provide a naphthoquinone-based gas-sensitive material.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a naphthoquinone-based gas-sensitive material in the preparation of an ammonia sensor, wherein: the active layer of the ammonia sensor includes the gas-sensitive material; the active layer is a thin film or nanorod coating with a thickness of 1~10 μm.

[0017] Beneficial effects of this invention: (1) This invention provides a naphthoquinone-based gas-sensitive material, which constructs 1D conductive MOFs through naphthoquinone-based functional ligands to form ligand-electron cooperative recognition: naphthoquinone C=O and ortho-OH can construct multi-site hydrogen bond / acid-base pockets, enhancing the characteristic binding of ammonia and distinguishing it from VOCs; at the same time, its reversible π The coupling of the acceptor and the conductive chain amplifies the reversible conductivity modulation at room temperature, avoiding strong coordination poisoning; the polarity distribution and size sieving reduce moisture intrusion and improve moisture resistance stability; and the good film-forming properties of the material result in a dense, ultra-thin, low contact resistance thin film array, achieving milliwatt-level or even lower power consumption. This results in ammonia sensing performance that is fast and reversible at room temperature, with low drift, high selectivity, moisture resistance, long lifespan, and good batch consistency, which is substantially different from the existing traditional 1D MOFs and solves the key pain points in ammonia scenarios.

[0018] (2) The present invention provides a one-dimensional metal-organic framework gas-sensitive material with high specific surface area, ordered electron channels and good molecular recognition ability, which can achieve high sensitivity detection of ammonia at room temperature; combined with the powder synthesis method proposed in the present invention, the microstructure and gas sensing performance of the metal-organic framework material can be controlled, thereby improving the yield of the metal-organic framework material. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the gas-sensitive material preparation method of the present invention.

[0020] Figure 2 This is a schematic diagram illustrating the synthesis principle of the gas-sensitive material of this invention.

[0021] Figure 3 This is a scanning electron microscope (SEM) image of the gas-sensitive material powder obtained in Example 1 of the present invention.

[0022] Figure 4 This is a schematic diagram of the gas sensing performance test according to an embodiment of the present invention.

[0023] Figure 5 This is a schematic diagram of the gas-sensitive material sensor obtained in Embodiment 1 of the present invention responding to the concentration gradient of ammonia.

[0024] Figure 6 This is a schematic diagram of the cyclic response of the gas-sensitive material thin-film sensor obtained in Example 1 of the present invention to 50 ppm ammonia. Figure 7 This is a schematic diagram of the CuDHNQ-1 gas-sensitive material obtained in Example 1 of the present invention responding to the concentration gradient of ammonia. Figure 8 This is a schematic diagram of the cyclic response of the CuDHNQ-1 gas sensing material obtained in Example 1 of the present invention to 40 ppm ammonia. Figure 9 The images show SEM images of the gas-sensitive materials CuDHTMNQ (a) and CuDHTFNQ (b) obtained in Examples 3 and 4 of this invention. Detailed Implementation

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0026] The structural formula of the organic ligand 5,8-dihydroxy-1,4-naphthoquinone (DHNQ) in this embodiment of the invention is as follows: Purchased from Jilin Zhongke Science & Technology Co., Ltd., item number 475-38-7, molecular weight 190.15.

[0027] The structural formula of 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthoquinone (DHTMNQ) is: Purchased from Jilin Zhongke Science & Technology Co., Ltd., with a molecular weight of 246.26.

[0028] The structural formula of 5,8-dihydroxy-2,3,6,7-tetrafluoro-1,4-naphthoquinone (DHTFNQ) is: Purchased from Jilin Zhongke Science & Technology Co., Ltd., with a molecular weight of 262.12. Other raw materials are also ordinary commercially available products.

[0029] Example 1 Preparation of gas-sensitive material powder: (1) Weigh 38.0 mg (0.2 mmol) of DHNQ ligand, dissolve it in 8 mL of DMSO, stir thoroughly to dissolve it, and obtain DHNQ ligand solution; Weigh 39.9 mg (0.2 mmol) of copper acetate monohydrate, dissolve it in 8 mL of DMSO, and sonicate to disperse it, thus obtaining a divalent copper ion solution.

[0030] (2) Place the DHNQ ligand solution in a 50 mL beaker, add a magnetic stir bar, and slowly add the divalent copper ion solution dropwise into the DHNQ ligand solution while stirring; After the addition of divalent copper ion solution is completed, 0.6 mL of concentrated ammonia solution is added dropwise to the mixed solution, and the mixture is stirred at 50 °C for 24 h. After the reaction was completed, the resulting black precipitate was washed by alternating centrifugation with deionized water and ethanol at a speed of 8000 rpm for 10 min. After that, it was dried in an oven at 60℃ for 6 h to obtain 1D MOF material powder CuDHNQ-1.

[0031] Figure 1 This is a schematic diagram of the gas-sensitive material powder preparation method of the present invention, specifically as follows: A homogeneous precursor was obtained by mixing a divalent metal salt solution with a ligand solution. Concentrated ammonia was then slowly added dropwise to adjust the alkalinity of the system and induce metal-ligand coordination polymerization. The reaction was continuously stirred at 50 °C for 24 h to allow crystal nuclei to form and grow directionally along the chain direction to create a one-dimensional structure. After the reaction, the suspension was centrifuged, and the solid was collected and dried under vacuum to remove residual solvent and ammonia, ultimately yielding rod-shaped one-dimensional MOF materials.

[0032] Figure 2 This is a schematic diagram illustrating the synthesis principle of the gas-sensitive material of the present invention. Specifically, using naphthoquinone diol (such as 2,5-dihydroxy-1,4-naphthoquinone) as a ligand, it is first deprotonated under alkaline conditions to generate a di-negative ligand, which then reacts with a divalent metal ion M. 2+ (e.g., Cu) 2 + Ni 2+ Coordination occurs between ligands; each ligand chelates with the metal via ortho-phenolic oxygen / carbonyl oxygen, and the metal center then bridges adjacent ligands with —M–O—, repeating this connection to achieve chain growth, ultimately constructing one-dimensional conductive MOFs composed of repeating "ligand–M–O" units. In this process, the reaction completes self-assembly under mild conditions, yielding a regular 1D chain structure.

[0033] Figure 3 The image shows a SEM image of the gas-sensitive material CuDHNQ-1 obtained in Example 1 of this invention. As shown in the figure, the obtained gas-sensitive material CuDHNQ-1 has a columnar morphology with a particle size of about 50-100 nm. The nano-sized particles are beneficial to increasing the specific surface area of ​​the material, thereby improving the gas-sensing performance of the material.

[0034] Figure 4 The image shows the XRD characterization of the gas-sensitive material CuDHNQ-1 obtained in Example 1 of this invention. Figure 4 The illustrations provide a graphical representation of the theoretical simulation model of the structure. For example... Figure 4 As shown, the diffraction peak positions of the obtained gas-sensitive material CuDHNQ-1 are highly consistent with the simulated XRD diffraction peak positions. Diffraction peaks corresponding to the (001), (100), and (010) crystal planes can be observed. The peaks are relatively sharp, indicating that the structure of the experimental sample is consistent with the modeled structure. It is a one-dimensional chain structure with an ordered crystal structure, regular atomic arrangement inside the crystal, and high purity.

[0035] Example 2 Fabrication of Gas Sensor: See schematic diagram of gas sensor interdigitated electrode and gas sensor fabrication. Figure 5 .

[0036] The interdigitated electrodes used to fabricate the sensor were manufactured using photolithography and microfabrication techniques, and their dimensions are 690 × 730 μm. 2The spacing is 20 μm, and the material is Ti and Au; The manufacturing process includes: continuously depositing a 20 nm Ti layer and a 180 nm Au layer on a patterned Si / SiO2 substrate; dispersing the prepared MOFs sensitive material in anhydrous ethanol; using a pipette to drop approximately 3 μL of the dispersion onto the interdigitated electrode; drying in a vacuum oven at 60 °C for 2 h; repeating this step until a 1–10 μm MOFs sensitive material film is uniformly deposited on the electrode surface.

[0037] See the schematic diagram for the gas sensing performance test. Figure 6 Specifically, the gas sensor is placed in the test chamber, and the target gas is introduced using a dynamic gas mixing method at room temperature. A constant operating voltage of 500 mV is applied between the sensor electrodes, and the current change of the sensor is detected using an Agilent 4156C semiconductor parameter analyzer under inert gas and target gas environments. Before introducing the target gas, dry compressed air (flowmeter 3) is used to purify the chamber to stabilize the baseline signal, and compressed air (flowmeter 2) is used as a carrier gas to dilute the target gas. The target gas is controlled by a mass flow controller (flowmeter 1).

[0038] The current difference between the sensor in dry air and the target gas is compared with the current in dry air (|Ia-Ig| / Ia×100%, where Ia is the current value in dry air and Ig is the current value in the target gas) to obtain the device's response value to the target gas. The response and recovery times are defined by reaching 90% saturation of the response and recovery curves.

[0039] Figure 7 This is a schematic diagram illustrating the concentration gradient response of the CuDHNQ-1 gas-sensitive material obtained in Example 1 of this invention to ammonia. The response of the sensor based on the CuDHNQ-1 gas-sensitive material prepared in Example 1 to ammonia concentrations of 2, 4, 8, 10, 20, 40, and 80 ppm was tested at room temperature. As shown in the figure, the sensor's response value to 80 ppm ammonia reached 144%. The lowest detectable ammonia concentration reached 2 ppm. With increasing ammonia concentration, the sensor's response value also increased.

[0040] Figure 8 This is a schematic diagram illustrating the cyclic response of the CuDHNQ-1 gas sensing material obtained in Example 1 of this invention to 40 ppm ammonia. The cyclic response performance of the CuDHNQ-1 gas sensing material-based sensor prepared in Example 1 to 40 ppm ammonia was tested at room temperature. After six response-recovery cycles, the sensor's response value remained above 71.2%, and the response time remained essentially unchanged, indicating that the sensor prepared in the aforementioned examples possesses good cyclic stability.

[0041] Example 3 The difference from Example 1 is that the DHNQ ligand in step (1) is replaced with DHTMNQ, and the 1D MOF material is CuDHTMNQ.

[0042] Example 4 The difference from Example 1 is that the DHNQ ligand in step (1) is replaced with DHTFNQ, and the 1D MOF material is CuDHTFNQ.

[0043] Figure 9 The images show SEM images of the gas-sensitive materials CuDHTMNQ (a) and CuDHTFNQ (b) obtained in Examples 3 and 4 of this invention. As shown in the figures, the obtained gas-sensitive materials CuDHTMNQ and CuDHTFNQ are partially columnar in shape, but compared to CuDHNQ-1, the morphology shows severe agglomeration.

[0044] Example 5 The difference from Example 1 is that copper acetate monohydrate in step (1) is replaced with nickel acetate tetrahydrate, and the 1DMOF material is NiDHNQ.

[0045] Example 6 The difference from Example 1 is that copper acetate monohydrate in step (1) is replaced with cobalt acetate tetrahydrate, and the 1DMOF material is CoDHNQ.

[0046] Example 7 The difference from Example 1 is that copper acetate monohydrate in step (1) is replaced with copper sulfate pentahydrate, and the 1DMOF material is CuDHNQ-2.

[0047] Example 8 The difference from Example 1 is that copper acetate monohydrate in step (1) is replaced with copper chloride dihydrate, and the 1DMOF material is CuDHNQ-3.

[0048] Example 9 The difference from Example 1 is that the volume of DMSO solvent in the divalent metal salt solution in step (1) is 6 mL, and the 1D MOF material is CuDHNQ-4.

[0049] Example 10 The difference from Example 1 is that the volume of DMSO solvent in the divalent metal salt solution in step (1) is 10 mL, and the 1D MOF material is CuDHNQ-5.

[0050] Example 11 The difference from Example 1 is that the mass of the organic ligand DHNQ in step (1) is 19.0 mg (0.1 mmol), and the 1D MOF material is CuDHNQ-6.

[0051] Example 12 The difference from Example 1 is that the mass of the organic ligand DHNQ in step (1) is 76.0 mg (0.4 mmol), and the 1D MOF material is CuDHNQ-7.

[0052] Example 13 The difference from Example 1 is that the volume of concentrated ammonia in step (2) is 0.4 mL, and the 1D MOF material is CuDHNQ-8.

[0053] Example 14 The difference from Example 1 is that the volume of concentrated ammonia in step (2) is 0.8 mL, and the 1D MOF material is CuDHNQ-9.

[0054] Example 15 The difference from Example 1 is that the stirring reaction temperature in step (2) is 20 °C, and the 1D MOF material is CuDHNQ-10.

[0055] Example 16 The difference from Example 1 is that the stirring reaction temperature in step (2) is 60 °C, and the 1D MOF material is CuDHNQ-11.

[0056] Example 17 The difference from Example 1 is that the stirring reaction time in step (2) is 12 h, and the 1D MOF material is CuDHNQ-12.

[0057] Example 18 The difference from Example 1 is that the stirring reaction time in step (2) is 36 h, and the 1D MOF material is CuDHNQ-13.

[0058] Table 1. Reaction parameters and performance parameters for each embodiment.

[0059] Note: The response value is the response of the metal-organic framework material to ammonia gas at a concentration of 40 ppm.

[0060] Examples 1 and 3-4 demonstrate the response values ​​of gas sensors to 40 ppm ammonia when the organic ligands are DHNQ, DHTMNQ, and DHTFNQ. It can be seen that the gas-sensing response performance of the sensing material varies depending on the organic ligand used. A comparison shows that when the R2 group is an electron-withdrawing group (fluorine group), the gas-sensing performance of the sensing material is stronger; when the R2 group is an electron-donating group (methyl group), the gas-sensing performance of the sensing material is weaker. This is because the electron-withdrawing group extracts electrons from the aromatic ring, thereby reducing the electron density of the entire ligand system. This makes the metal center more electron-deficient, enhancing the Lewis acidity of the metal center, thus making it easier to undergo coordination or charge transfer reactions with electron-donating gases (such as ammonia). Conversely, the electron-donating group pushes electrons towards the aromatic ring and the metal center, increasing the metal electron density and reducing its affinity for gas molecules (especially Lewis basic gases), thereby weakening the gas-sensing response.

[0061] Examples 1 and 5-6 demonstrate the response values ​​of the gas sensor to 40 ppm ammonia gas when the metal ions are copper, nickel, and cobalt ions. It can be seen that the sensing material using copper ions has a higher response, while the sensing materials using nickel and cobalt ions have lower responses. A possible reason is that Cu... 2+ It exhibits stronger Lewis acidity and is more likely to form stable coordinate bonds or undergo electron transfer with gas molecules (such as ammonia) in its coordination structure; while Ni 2+ Co 2+ Copper ions are relatively inert and have a weaker interaction with gas molecules, resulting in reduced adsorption capacity and poor sensing response. Preferably, copper ions are used as the metal site, which improves the performance of the gas sensor.

[0062] Examples 1 and 7-8 demonstrate the gas sensor's response to 40 ppm ammonia when the divalent metal salts include hydrated acetate, hydrated sulfate, and hydrated chloride. It can be seen that using different metal salts has little impact on the final response of the sensing material. Different types of divalent metal salts can be used depending on the specific application.

[0063] Examples 1 and 9-10 demonstrate the gas sensor's response to 40 ppm ammonia when the volume of the divalent metal salt solvent DMSO is 6 mL, 8 mL, and 10 mL. It can be seen that both excessive and insufficient DMSO volume reduce the gas sensor's response. Insufficient solvent volume leads to severe product aggregation, while excessive solvent volume results in a slower reaction. Preferably, 8 mL of DMSO solvent provides the best gas sensor performance.

[0064] Examples 1 and 11-12 demonstrate the gas sensor's response to 40 ppm ammonia when the mass of the organic ligand DHNQ is 19.0 mg, 38.0 mg, and 76.0 mg. It can be seen that when the mass of the organic ligand DHNQ is too small, the synthesis reaction is incomplete, resulting in a decreased gas sensor response; when the mass of the organic ligand DHNQ is too large, the improvement in gas sensor response is not significant, but it wastes the organic ligand. Preferably, the mass of the organic ligand DHNQ is 38.0 mg, at which point the gas sensor performs best without wasting resources.

[0065] In Examples 1 and 13-14, the response values ​​of the gas sensor to 40 ppm ammonia were shown when the volume of concentrated ammonia added was 0.4 mL, 0.6 mL, and 0.8 mL. It can be seen that both excessive and insufficient volume of concentrated ammonia reduce the gas sensor response. When the volume of concentrated ammonia is too small, the synthesis reaction requires an alkaline environment; insufficient ammonia leads to insufficient alkalinity, affecting the efficiency of hydrogen ion departure from the hydroxyl group, resulting in incomplete reaction and a reduced gas sensor response. When the volume of concentrated ammonia is too large, ammonium ions form complexes with metal ions, shielding some metal ions from participating in the synthesis reaction, causing incomplete reaction and a reduced gas sensor response. Preferably, a volume of 0.6 mL of concentrated ammonia results in the highest reaction efficiency and the best gas sensor performance.

[0066] Examples 1 and 15-16 demonstrate the response values ​​of the gas sensor to 40 ppm ammonia at reaction temperatures of 20 °C, 50 °C, and 60 °C. It can be seen that when the reaction temperature is too low, the synthesis reaction is incomplete, resulting in a decreased gas sensor response; when the reaction temperature is too high, the improvement in gas sensor response is not significant, but energy is wasted. Preferably, the reaction temperature is 50 °C, at which point the gas sensor performs best without wasting energy.

[0067] In Examples 1 and 17-18, the response values ​​of the gas sensor to 40 ppm ammonia were shown at reaction times of 12 h, 24 h, and 36 h. It can be seen that when the reaction time is too short, the synthesis reaction is incomplete, resulting in a decreased gas sensor response; when the reaction time is too long, the improvement in gas sensor response is not significant, but energy is wasted. Preferably, the reaction time is 24 h, at which point the gas sensor performs best without wasting energy.

[0068] This invention constructs 1D conductive MOFs using naphthoquinone functional ligands, forming a ligand-electron cooperative recognition mechanism: naphthoquinone C=O and ortho-OH can construct multi-site hydrogen bonds / acid-base pockets, enhancing the characteristic binding to ammonia and distinguishing it from VOCs; its reversibility πThe receptor is coupled with the conductive chain, amplifying reversible conductivity modulation at room temperature and avoiding strong coordination poisoning; polarity distribution and size sieving reduce moisture intrusion and improve moisture resistance stability; good film-forming properties result in a dense, ultra-thin, low-contact-resistance thin-film array, achieving milliwatt-level or even lower power consumption. This results in ammonia sensing performance that is fast and reversible at room temperature, with low drift, high selectivity, moisture resistance, long lifespan, and good batch consistency, substantially different from existing traditional 1D MOFs and solving key pain points in ammonia scenarios.

[0069] Based on the above characteristics, naphthoquinone-based 1D MOF thin film devices are very suitable for building miniaturized, low-power and highly selective ammonia sensing systems.

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a naphthoquinone-based gas-sensitive material, characterized in that: include, The metal ion solution was added dropwise to the organic ligand solution, concentrated ammonia was added, and the mixture was stirred to react. After the reaction was completed, the resulting black precipitate was washed, centrifuged, and dried to obtain the gas-sensitive material; The metal ion solution is one of the following: a solution containing cobalt ions, a copper ion solution, or a nickel ion solution. The organic ligand solution is a multi-substituted 1,4-naphthoquinone solution, and the structural formula of the multi-substituted 1,4-naphthoquinone is as follows: ； Wherein, R1 is a hydroxyl group, and R2 is any one or more of hydrogen, methyl, and fluorine atoms.

2. The preparation method according to claim 1, characterized in that: The salts of the metal include hydrated acetate, hydrated sulfate, and hydrated chloride; The solvent for the metal ion solution is dimethyl sulfoxide.

3. The preparation method according to claim 1 or 2, characterized in that: The organic ligands include 5,8-dihydroxy-1,4-naphthoquinone (DHNQ), 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthoquinone (DHTMNQ), and 5,8-dihydroxy-2,3,6,7-tetrafluoro-1,4-naphthoquinone (DHTFNQ).

4. The preparation method according to claim 3, characterized in that: The solvent for the organic ligand solution is dimethyl sulfoxide.

5. The preparation method according to any one of claims 1, 2, and 4, characterized in that: The molar ratio of the ligand to the metal salt is 1 mmol : (0.5~2) mmol; The ratio of the amount of the metal salt to the volume of concentrated ammonia is 1 mmol: (2~4) mL.

6. The preparation method according to claim 5, characterized in that: The volume ratio of the metal salt in the metal ion solution to the solvent is 1 mmol: (30~50) mL, and the volume ratio of the organic ligand in the organic ligand solution to the solvent is 1 mmol: (30~50) mL.

7. The preparation method according to claim 1, characterized in that: The temperature of the stirring reaction is 20℃~60℃, and the stirring reaction time is 12 h~36 h.

8. The naphthoquinone-based gas-sensitive material prepared by any of the preparation methods described in claims 1 to 7.

9. The application of the naphthoquinone-based gas-sensitive material according to claim 8 in the preparation of an ammonia sensor.

10. The application as described in claim 9, characterized in that: The active layer of the ammonia sensor includes the gas-sensitive material; The active layer is a thin film or nanorod coating with a thickness of 1~10 μm.

Images