A Cu-BTC single crystal resistive humidity sensor and its preparation method

Abstract

The present invention discloses a Cu-BTC single crystal resistive humidity sensor and a preparation method, belonging to the field of MOFs material sensing. The Cu-BTC single crystal resistive humidity sensor of the present invention comprises a planar interdigitated electrode produced by ultrafast laser-induced processing of the Cu-BTC single crystal surface and unprocessed Cu-BTC single crystal material between the interdigitated fingers. The planar electrode is prepared by the following steps: S1: preparing a Cu-BTC single crystal sample with a length and width of the to-be-processed surface greater than or equal to 100 μm; S2: using an ultrafast laser processing device to perform ultrafast laser-induced processing on the Cu-BTC single crystal sample in step S1 under set laser processing parameters to obtain the planar interdigitated electrode; wherein the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8 mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the focused spot is 4 μm. The Cu-BTC single crystal resistive humidity sensor can detect humidity in the range of 5% to 90% RH, with a response time of up to 2 s and good selectivity, stability, and cyclability.

Description

Technical Field

[0001] The present invention relates to the field of MOFs material sensing, and in particular to a Cu-BTC single crystal resistive humidity sensor and a preparation method thereof. Background Art

[0002] With the continuous development of industries such as medical care, semiconductor manufacturing, biomedicine, and chemicals, sensing technology has become a key link in the operation of various industries. Humidity sensing, as an important branch of the sensing field, is of great significance in monitoring low, medium, and high humidity working scenarios. In the medical field, humidity sensors are used in equipment such as ventilators, sterilizers, and incubators to monitor the humidity conditions in the environment in real time; in the biomedicine and chemical fields, the humidity of gases under different atmospheres will interfere with the synthesis of organisms, drugs, and chemicals, so humidity sensors are needed for real-time monitoring; in the semiconductor manufacturing field, the manufacturing and packaging of electronic products and other production steps all need to be carried out in a specific humidity environment under monitoring.

[0003] The key to humidity sensing lies in the material's adsorption of water molecules. Existing humidity sensors generally use organic polymers, semiconductors, and metal oxide composites as humidity-sensitive materials, requiring significant effort from design to preparation. Metal-organic frameworks (MOFs), as coordination compounds with high surface area, high porosity, and metal active sites, possess unique advantages in adsorbing water molecules and transporting them within their pores. As a result, they have garnered increasing attention in the field of gas sensing in recent years.

[0004] Currently, the design of humidity sensors based on MOFs materials primarily focuses on MOF powders and MOF polycrystalline thin films. Thin-film devices are primarily composed of MOF powders, but the film-forming properties of MOF powders hinder the transmission of electrical signals, limiting the improvement of sensing performance. To obtain high-quality sensing films and powders, the particle size of the MOFs material must be controlled at the nanoscale. This makes the preparation of the sensitive material complex and technically challenging, making it difficult to preserve and integrate into miniaturized sensor devices. Summary of the Invention

[0005] The purpose of the present invention is to provide a Cu-BTC single crystal resistive humidity sensor and its preparation method. By inducing a planar electrical structure on the surface of the Cu-BTC single crystal through ultrafast laser processing, the intrinsic adsorption advantages of the Cu-BTC single crystal material and its stable properties in air are combined to easily realize the preparation of the Cu-BTC single crystal humidity sensor.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A Cu-BTC single crystal resistive humidity sensor consists of planar interdigitated electrodes produced by ultrafast laser-induced processing on the surface of a Cu-BTC single crystal, and unprocessed Cu-BTC single crystal material between the interdigitated electrodes. The planar interdigitated electrodes serve as the electrical structure, and the unprocessed Cu-BTC single crystal material between the interdigitated electrodes serves as the sensitive material.

[0008] Furthermore, the planar interdigitated electrodes are prepared by the following method:

[0009] S1: Prepare a Cu-BTC single crystal sample with a length and width of the processing surface greater than or equal to 100 μm;

[0010] S2: using an ultrafast laser processing device to perform ultrafast laser induced processing on the Cu-BTC single crystal sample in step S1 under set laser processing parameters to obtain a planar interdigitated electrode;

[0011] Among them, the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8 mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the laser focus spot diameter is about 4 μm.

[0012] Furthermore, step S1 includes the following steps:

[0013] S101: Synthesis of Cu-BTC single crystal materials;

[0014] S102: Soaking the synthesized Cu-BTC single crystal material in an organic solvent for a first predetermined time, then soaking it in anhydrous ethanol for a second predetermined time, and then placing the Cu-BTC single crystal material in a vacuum oven and drying it at a set activation temperature for a third predetermined time to obtain a Cu-BTC single crystal sample with a length and width of the to-be-processed surface both greater than or equal to 100 μm.

[0015] Furthermore, in step S102, the activation temperature is set in the range of 50°C-80°C, the first predetermined time is at least 72 hours; the second predetermined time is at least 72 hours; and the third predetermined time is at least 12 hours.

[0016] Furthermore, the organic solvent is DMF.

[0017] Furthermore, step S2 includes the following steps:

[0018] S201: placing a Cu-BTC single crystal sample on a glass slide with the surface to be processed facing upward;

[0019] S202: placing the glass slide in S201 on the ultrafast laser processing platform and positioning it, and adjusting the processing platform to focus the light spot;

[0020] S203: Setting the process parameters of the ultrafast laser processing system and performing laser-induced processing to obtain a planar interdigitated electrode; wherein the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8 mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the focused spot is approximately 4 μm.

[0021] Furthermore, in step S203 , when the scanning speed v is 200 μm / s≤v<280 μm / s, the processing power P is 3 mW≤P≤5 mW; when the scanning speed v is 280 μm / s≤v≤360 μm / s, the processing power P is 6 mW≤P≤8 mW.

[0022] Furthermore, the Cu-BTC single crystal resistive humidity sensor can be wired by bonding metal wires to the conductive areas of the planar interdigitated electrodes, enabling the assembly and integration of single crystal electronic devices. Specifically, high-viscosity conductive silver glue and micron-sized copper wires are bonded to the surface of the ultrafast laser-processed Cu-BTC single crystal.

[0023] The present invention has the following beneficial effects:

[0024] (1) The present invention uses ultrafast laser processing to form planar interdigitated electrodes on the surface of a Cu-BTC single crystal material. The planar interdigitated electrodes and the unprocessed Cu-BTC single crystal material between the interdigitated fingers form a Cu-BTC single crystal resistive humidity sensor. The Cu-BTC single crystal resistive humidity sensor based on the planar interdigitated electrodes can detect humidity in the range of 5% to 90% RH, with a response time of up to 2 s and good selectivity, stability, and cyclability.

[0025] (2) Compared with the existing MOFs powder and MOFs polycrystalline thin film humidity sensor devices, the Cu-BTC single crystal resistive humidity sensor of the present invention has simpler preparation steps and is easy to store. Moreover, under the same sensing performance, the single crystal sensor is easier to realize the miniaturized integration of MOFs sensor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the Cu-BTC single crystal resistive humidity sensor of the present invention;

[0027] Figure 2 This is an optical microscope image of the Cu-BTC single crystal resistive humidity sensor of the present invention;

[0028] Figure 3 Response-recovery curve of humidity sensing when the inter-finger spacing is 5 μm and the aspect ratio is 75:3 in Example 1;

[0029] Figure 4 This is the humidity sensing response-recovery curve of Example 2 when the inter-finger spacing is 10 μm and the aspect ratio is 75:3;

[0030] Figure 5 This is the humidity sensing response-recovery curve of Example 3 when the inter-finger spacing is 10 μm and the aspect ratio is 50:3;

[0031] Figure 6 Response-recovery curve of humidity sensing below 20% RH when the inter-finger spacing is 5 μm and the aspect ratio is 50:3 in Example 4;

[0032] Figure 7 Comparison of the sensing performance of the Cu-BTC single crystal resistive humidity sensors of Examples 1-4 at 70% RH;

[0033] Figure 8 The results of the cyclic test of the Cu-BTC single crystal resistive humidity sensor of Example 4 at 70% RH are shown;

[0034] Figure 9 Schematic diagram of the conductivity test of the external leads of the planar conductive structure on the surface of the Cu-BTC single crystal after laser processing;

[0035] Figure 10 for Figure 9 An enlarged view of the external leads.

[0036] In the figure, 1: Unprocessed Cu-BTC single crystal material; 2: Planar interdigitated electrode conductive area; 3: Cu-BTC single crystal sample; 4: Planar interdigitated electrode DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and embodiments:

[0038] like Figures 1 to 10 As shown, the Cu-BTC single crystal resistive humidity sensor described in the present invention is composed of a planar interdigital electrode 4 produced by ultrafast laser induced processing on the surface of the Cu-BTC single crystal and an unprocessed Cu-BTC single crystal material 1 between the interdigital fingers, wherein the planar interdigital electrode 4 serves as an electrical structure and the unprocessed Cu-BTC single crystal material 1 between the interdigital fingers serves as a sensitive material.

[0039] The inventors unexpectedly discovered that by adjusting the laser processing parameters when performing laser-induced processing on the surface of a Cu-BTC single crystal using an ultrafast laser, planar interdigitated electrodes with good electrical properties can be produced. These planar interdigitated electrodes can be used as capacitive or resistive sensor devices.

[0040] As known to those skilled in the art, a resistive sensor consists of interdigitated electrodes and a sensitive material. In the Cu-BTC single crystal resistive humidity sensor of the present invention, the planar interdigitated electrodes 4 are produced by ultrafast laser processing on the surface of the Cu-BTC single crystal, while the sensitive material is the unprocessed Cu-BTC single crystal material 1 between the interdigitated electrodes. Because Cu-BTC single crystals can naturally adsorb water molecules, the planar interdigitated electrodes 4, after being laser-processed on their surface, can be combined with the unprocessed Cu-BTC single crystal material 1 to form a combination of electrodes and sensitive material, thus forming a resistive humidity sensor.

[0041] Specifically, the planar interdigitated electrode 4 is prepared by the following method:

[0042] S1: Prepare a Cu-BTC single crystal sample with a length and width of the processing surface greater than or equal to 100 μm;

[0043] S2: Using an ultrafast laser processing device to perform ultrafast laser induced processing on the Cu-BTC single crystal sample in step S1 under set laser processing parameters to obtain a planar interdigitated electrode 4.

[0044] In the present invention, step S1 includes the following steps:

[0045] S101: Synthesis of Cu-BTC single crystal materials;

[0046] S102: Soaking the synthesized Cu-BTC single crystal material in an organic solvent for a first predetermined time, then soaking it in anhydrous ethanol for a second predetermined time, and then placing the Cu-BTC single crystal material in a vacuum oven and drying it at a set activation temperature for a third predetermined time to obtain a Cu-BTC single crystal sample 3 having a length and width of a to-be-processed surface both greater than or equal to 100 μm.

[0047] In step S101, the method for synthesizing Cu-BTC single crystal material is not particularly limited, and conventional methods known in the art, such as the solvothermal method, can be used. In the present invention, the solvothermal method first dissolves a suitable copper ion-containing metal salt and an organic ligand in a solvent to form a mixture, then heats the mixture to an appropriate temperature in a reactor, and finally cools and centrifuges to obtain large-sized Cu-BTC crystals. During the heating process, the evaporation of the solvent and the coordination effect of the reactants lead to the formation of Cu-BTC crystals.

[0048] As used herein, "large size" means that the length and width of the surface to be processed of the synthesized Cu-BTC single crystal sample 3 are both greater than or equal to 100 μm. In other words, the length and width of the surface to be processed of the Cu-BTC single crystal sample 3 in the present invention are both greater than or equal to 100 μm to ensure subsequent laser-induced processing.

[0049] In the present invention, the copper ion-containing metal salt, organic ligand, and solvent are all well known to those skilled in the art and can be selected as needed. For example, the copper ion-containing metal salt can be copper nitrate; the organic ligand can be trimesic acid; and the solvent can be DMF, ethanol, or the like.

[0050] After synthesizing a Cu-BTC single crystal of appropriate size, it needs to be activated and dried. Specifically, the synthesized Cu-BTC single crystal is first immersed in an organic solvent for a predetermined time to remove unreacted metal ions and organic ligands from the synthesis process. In the present invention, N,N-dimethylformamide (DMF) can be selected as the organic solvent.

[0051] In order to completely remove unreacted metal ions and organic ligands during the synthesis process as much as possible, a relatively long soaking time is used in the present invention, that is, the first predetermined time is at least 72 hours. In addition, during the soaking period, the organic solvent needs to be replaced, preferably every 5 hours, to ensure complete removal of unreacted metal ions and organic ligands. For example, when the Cu-BTC single crystal material is soaked in DMF solvent for two days, the DMF solvent needs to be replaced three times a day to ensure the removal effect.

[0052] After soaking with the organic solvent, it is also necessary to soak with absolute ethanol for a second predetermined time to carry out solvent exchange. The purpose of solvent exchange is to remove the organic solvent such as DMF in the previous step. The second predetermined time is generally at least 72 hours.

[0053] Since the sensing performance of Cu-BTC single crystal materials lies in the adsorption of water molecules by Cu-BTC single crystals, during the material activation process, if the temperature is too low, the organic solvent in the Cu-BTC pores will not be completely removed, which will affect the adsorption of water molecules. If the temperature is higher than 80°C, the organic solvent in the pores will be removed more cleanly (and some coordinated water will be removed), and the adsorption of water by the activated Cu-BTC single crystal will be greatly increased. This adsorption will cause damage to the internal topological structure of the crystal, making it difficult to store and process in air. Therefore, to achieve optimal performance, the activation temperature in the present invention is preferably set at 50°C-80°C. In one embodiment of the present invention, 70°C is a very stable temperature, and the material activated at this temperature can be stably stored in air for more than six months.

[0054] Afterwards, the obtained Cu-BTC single crystal material is subjected to laser induced processing. Specifically, step S2 includes the following steps:

[0055] S201: placing the Cu-BTC single crystal sample 3 on a glass slide with the surface to be processed facing upward;

[0056] Before fixing the Cu-BTC single crystal sample 3 on a glass slide, the glass slide needs to be wiped with anhydrous ethanol to prevent dust or other impurities from affecting subsequent laser induced processing.

[0057] In the present invention, there is no particular limitation on the method for securing the Cu-BTC single crystal sample 3 to the glass slide, as long as the sample can be kept immobile during processing. For example, PI double-sided tape can be attached to one surface of the glass slide to adhere the Cu-BTC single crystal sample 3 to the glass slide.

[0058] S202: placing the glass slide in S201 on the ultrafast laser processing platform and positioning it, and adjusting the processing platform to focus the light spot;

[0059] The operations of positioning and adjusting the processing platform to focus the light spot are conventional operations known to those skilled in the art and will not be described in detail here.

[0060] S203: Setting the process parameters of the ultrafast laser processing system and performing laser-induced processing to obtain a planar interdigitated electrode; wherein the ultrafast laser wavelength is 1030 nm, the pulse width is 1.2-10 ps, ​​the processing power P is 3 mW≤P≤8 mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the focused spot is approximately 4 μm.

[0061] The inventors discovered that the absorption rate of Cu-BTC single crystal material for 1030 nm wavelength laser is approximately 70%, so the ultrafast laser wavelength used in the present invention is 1030 nm. In the present invention, the processing interval refers to the interval between two adjacent laser scanning paths. In the embodiments of the present invention, a processing interval of 1 μm is used. The inventors have discovered that when laser-induced processing is performed under the above-mentioned laser processing parameters, due to the short pulse time domain characteristics, high peak power energy output, and small spot size of the ultrafast laser, when the laser is irradiated onto the surface of the Cu-BTC single crystal material, induced processing of the material only occurs within the area affected by the laser spot, while other areas remain undamaged. Therefore, during the ultrafast laser ablation process, the organic ligand structure in the ablated area is pyrolyzed, generating an enveloping reducing atmosphere, which reduces the copper ions released by the ligand structure to copper atoms, forming carbon-based copper nanoparticles. The area not irradiated by the laser spot remains intact, i.e., the unprocessed Cu-BTC single crystal material 1. In the present invention, a 1 μm processing interval is used for line-by-line scanning processing. Under the action of laser spot irradiation, a planar interdigitated electrode 4 can be processed. The planar interdigitated electrode 4 is mainly composed of carbon-based copper nanoparticles and has good electrical properties. In the area not irradiated by the laser spot, that is, between the interdigitated fingers, there is unprocessed Cu-BTC single crystal material 1. Since Cu-BTC single crystal itself can absorb water, after the planar interdigitated electrode 4 is prepared on its surface by laser, it can be combined with the unprocessed Cu-BTC single crystal material 1 to produce a combination of electrode and sensitive material, thereby forming a resistive humidity sensor, such as Figure 1 and Figure 2 shown.

[0062] In one embodiment of the present invention, in step S203, the scanning speed v and the processing power P can be adjusted accordingly. For example, when the scanning speed v is 200 μm / s ≤ v < 280 μm / s, the processing power P is 3 mW ≤ P ≤ 5 mW; when the scanning speed v is 280 μm / s ≤ v ≤ 360 μm / s, the processing power P is 6 mW ≤ P ≤ 8 mW.

[0063] In the present invention, it is also possible to adjust the laser processing path to realize planar interdigitated electrodes 4 with different structures, thereby obtaining different sensing characteristics. For example, by adjusting the interdigital spacing and the aspect ratio of the interdigitated fingers through different processing paths, the electrical characteristics of the planar interdigitated electrodes can be changed, thereby affecting the sensing characteristics. Specifically, by adopting different laser processing paths, the interdigital spacing of the planar interdigitated electrodes 4 obtained are 10 μm and 5 μm, respectively, and the aspect ratio of the interdigitated fingers are 50:3 and 75:3, respectively. As shown in the following embodiments and Figure 3-7 As shown, the sensing characteristics vary under different inter-finger spacing and interdigital aspect ratios.

[0064] In addition, in order to integrate the Cu-BTC single crystal resistive humidity sensor of the present invention into a micro single crystal electronic device, the lead can be made by bonding the planar interdigitated electrode conductive area 2 with a metal wire. Specifically, high viscosity conductive silver glue and micron-grade copper wire are bonded to the planar interdigitated electrode conductive area 2. Since both the conductive silver glue and the copper wire have good conductivity, after bonding and contacting the planar interdigitated electrode conductive area 2, they are connected to the external circuit through the wire, which can effectively transmit the electrical signal, and finally realize the dynamic transmission of the sensor resistance signal in the external circuit, and realize the signal output of the Cu-BTC single crystal resistive sensor. In order to verify the effectiveness of this bonding method, as shown in FIG. Figure 9 and Figure 10 As shown, the conductivity test of the external leads of the Cu-BTC single crystal surface planar conductive structure was carried out. Figure 9 The figure is a schematic diagram of the conductivity test of the external lead of the planar conductive structure on the surface of the Cu-BTC single crystal after laser processing. In the present invention, the planar conductive structure adopts the same process parameters as the processing of the interdigital electrode to process a complete, gapless planar conductive area on the surface of the Cu-BTC single crystal. This conductive area is exactly the same as the composition of the interdigital electrode and can be considered as the lead area of ​​the interdigital electrode. The lead test on this area can prove the effectiveness of the interdigital electrode lead. Figure 9 As shown, when high-viscosity conductive silver glue and micron-sized copper wire are bonded to the conductive structure laser-processed on the surface of Cu-BTC single crystal, there is a measurable and stable resistance value, indicating that this bonding method can lead out the planar electrical structure on the surface of Cu-BTC single crystal with a wire, thereby realizing the subsequent assembly and integration of single crystal electronic devices.

[0065] The sensing principle of the Cu-BTC single crystal resistive humidity sensor of the present invention is as follows:

[0066] Humidity sensing performance depends primarily on the sensitive material's adsorption of water molecules. Cu-BTC single crystals, as a classic MOFs material, are not only easy to synthesize into single crystals with regular morphology and ease of processing, but also possess coordinated copper ions as hydrophilic active sites. The sensitive material of the Cu-BTC single crystal resistive humidity sensor of the present invention is the undamaged crystal portion between the fingers of a planar interdigitated electrode structure produced by laser-induced processing, i.e., unprocessed Cu-BTC single crystal material 1. When surrounding water molecules are adsorbed into the pores of the Cu-BTC single crystal material, most of the water molecules will first approach the Cu ion sites within the pores due to the greater adsorption energy of the Cu ion sites within the pores. As the number of adsorbed water molecules increases, the water molecules occupy most of the pores, and the atomic interactions generate hydrogen bonds, forming a continuous water film, which promotes proton conduction and improves the conductivity of the material between the fingers, reducing the resistance at this humidity and achieving a response effect. Therefore, the higher the humidity, the more the resistance decreases, and the faster the response speed will be within a certain humidity range. At the same time, since the adsorption of water by Cu-BTC single crystal is physical adsorption, the higher the humidity, the more water molecules are adsorbed, the longer the time required for desorption, and the slower the recovery.

[0067] The present invention is further illustrated by the following examples.

[0068] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0069] In addition, the materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified. Example

[0070] Example 1

[0071] S101: Based on the recipe in the literature [J. Am. Chem. Soc. 2016, 138, 36, 11449–11452], a Cu-BTC single crystal with a processing surface length and width of 100 μm was synthesized by solvothermal synthesis.

[0072] S102: The synthesized Cu-BTC single crystal material is soaked in DMF solvent for three days (DMF is replaced every 8 hours), and then soaked in anhydrous ethanol for at least three days to exchange the solvent. The Cu-BTC single crystal material is then placed in a vacuum oven and dried at 70°C for 12 hours to obtain a dried Cu-BTC single crystal sample with a length and width of the processing surface reaching 100 μm.

[0073] S201: Attach PI double-sided tape to a glass slide wiped with anhydrous ethanol, and use pointed tweezers to place the above-mentioned Cu-BTC single crystal sample with intact and regular morphology on the double-sided tape surface for fixation, with the surface to be processed facing upwards;

[0074] S202: placing the glass slide in S201 on the ultrafast laser processing platform and positioning it, and adjusting the processing platform to focus the light spot;

[0075] S203: Setting the following laser-induced processing parameters: an ultrafast laser wavelength of 1030 nm, a pulse width of 1.2 ps, a processing power of 5 mW, a scanning speed of 200 μm / s, a processing interval of 1 μm, and a focused spot of approximately 4 μm, and then performing laser-induced processing to obtain a planar interdigitated electrode; the planar interdigitated electrode serves as an electrical structure, and the unprocessed Cu-BTC single crystal material between the interdigitated fingers serves as the sensitive material, together forming a Cu-BTC single crystal resistive humidity sensor, wherein the interdigitated finger spacing is 5 μm and the aspect ratio is 75:3.

[0076] Example 2

[0077] A Cu-BTC single crystal resistive humidity sensor was prepared in the same manner as in Example 1, except that the interdigital spacing was 10 μm and the aspect ratio was 75:3.

[0078] Example 3

[0079] A Cu-BTC single crystal resistive humidity sensor was prepared in the same manner as in Example 1, except that the interdigital spacing was 10 μm and the aspect ratio was 50:3.

[0080] Example 4

[0081] A Cu-BTC single crystal resistive humidity sensor was prepared in the same manner as in Example 1, except that the interdigital spacing was 5 μm and the aspect ratio was 50:3.

[0082] Experimental Example 5

[0083] 1. Sensing performance test

[0084] The sensing performance of the Cu-BTC single crystal resistive humidity sensors of Examples 1-4 was tested.

[0085] Specifically, first, dry air at about 3% RH is introduced to recover the resistance. When the resistance stabilizes, the humidity to be measured is introduced, and then dry air at 3% RH is introduced again to recover. The response-recovery curve under different humidity conditions is tested cyclically. The test platform is a micro-probe platform. The probe physically contacts the electrode and performs dynamic gas distribution in a closed chamber. The test results are as follows: Figure 2-5 shown.

[0086] Figure 3This is the humidity sensing test curve for Example 1 with an interdigital spacing of 5 μm and an aspect ratio of 75:3. Within the 7% RH to 30% RH range, the resistance value changes significantly with humidity, increasing from 4.5% to 98.7%. This indicates that the Cu-BTC single-crystal humidity sensor has high sensitivity below 30% RH. Within the 30% RH to 80% RH range, the resistance value does not change significantly with humidity. At high humidity conditions of 80% RH, increasing humidity results in a significant change at 90% RH, reaching 99.9%. Within the 7% RH to 40% RH range, the response speed increases with increasing humidity. Within the 60% RH to 80% RH range, the response speed remains unchanged, remaining essentially at 6 s. Furthermore, the recovery time is faster at low humidity, but gradually increases with increasing humidity.

[0087] Figure 4 This is the humidity sensing test curve for Example 2, with an interdigital spacing of 10 μm and an aspect ratio of 75:3. Within the 5% RH to 20% RH range, the resistance responds significantly to humidity, increasing from 3.3% to 99.1%. This indicates that the Cu-BTC single-crystal humidity sensor with these structural parameters is more sensitive below 20% RH. Within the 20% RH to 70% RH range, the resistance change is not significant. The response speed increases with increasing humidity, reaching as fast as 6 seconds.

[0088] Figure 5 This is the humidity sensing test curve of Example 3 when the inter-finger spacing is 10 μm and the aspect ratio is 50:3. From 5%RH to 30%RH, the response changes greatly, indicating that the structural parameters have a high sensitivity below 30%RH. In the range of 30%RH to 80%RH, the response resistance does not change by an order of magnitude, and it can be considered that the response under humidity in this range is basically stable. When the humidity rises to 90%RH, the response continues to increase. In the range of 5%RH to 80%RH, the response speed becomes faster with increasing humidity, the fastest response time is 2 s, and the recovery time becomes longer with increasing humidity.

[0089] Figure 6 This is the humidity sensing test response curve of Example 4 under low humidity (below 20% RH) when the inter-finger spacing is 5 μm and the aspect ratio is 50:3. This structural parameter is also relatively sensitive to low humidity, but compared with the sensing performance of other structural parameters, the response and recovery time of this sensing performance are slower.

[0090] like Figure 7This figure compares the sensing performance of the Cu-BTC single crystal resistive humidity sensors of Examples 1-4 at 70% RH. As can be seen from the figure, the Cu-BTC single crystal resistive humidity sensors with different structural parameters all exhibit good sensing characteristics. Specifically, the sensing performance when the interdigital spacing is larger is better than that when the interdigital spacing is smaller.

[0091] 2. Repeatability test

[0092] In a 70% RH environment, the Cu-BTC single crystal resistive humidity sensor of Example 4 was subjected to a cyclic test. Figure 8 As shown in the figure, when undergoing cyclic testing under the same conditions, the Cu-BTC single crystal resistive sensor can return to its initial resistance value under dry gas, and the response resistance and response time are at the same order of magnitude each time, showing good stability and repeatability.

[0093] Based on the above embodiments and accompanying drawings, it is obvious that the Cu-BTC single crystal resistive humidity sensor of the present invention can respond quickly to humidity due to the good electrical properties of the planar interdigitated electrodes. The humidity detection range can reach 5% to 90% RH, the response time can be as fast as 2 s, and it has good selectivity, stability and cyclability.

[0094] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A Cu-BTC single crystal resistive humidity sensor, characterized by: The Cu-BTC single crystal resistive humidity sensor is composed of planar interdigital electrodes produced by ultrafast laser-induced processing on the surface of a Cu-BTC single crystal, and unprocessed Cu-BTC single crystal material between the interdigital electrodes. The planar interdigital electrodes serve as the electrical structure, and the unprocessed Cu-BTC single crystal material between the interdigital electrodes serves as the sensitive material. The Cu-BTC single crystal resistive humidity sensor is wired by bonding metal wires to the conductive areas of the planar interdigital electrodes. Wherein, the planar interdigitated electrode is prepared by the following method: S1: Prepare a Cu-BTC single crystal sample with a length and width of the processing surface greater than or equal to 100 μm; S2: using an ultrafast laser processing device to perform ultrafast laser induced processing on the Cu-BTC single crystal sample in step S1 under set laser processing parameters to obtain a planar interdigitated electrode; Among them, the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the laser focus spot diameter is 4 μm.

2. The Cu-BTC single crystal resistive humidity sensor according to claim 1, characterized in that: Step S1 includes the following steps: S101: Synthesis of Cu-BTC single crystal materials; S102: Soaking the synthesized Cu-BTC single crystal material in an organic solvent for a first predetermined time, then soaking it in anhydrous ethanol for a second predetermined time, and then placing the Cu-BTC single crystal material in a vacuum oven and drying it at a set activation temperature for a third predetermined time to obtain a Cu-BTC single crystal sample with a length and width of the to-be-processed surface both greater than or equal to 100 μm.

3. The Cu-BTC single crystal resistive humidity sensor according to claim 2, characterized in that: In step S102, the activation temperature is set in the range of 50°C-80°C, the first predetermined time is at least 72 hours, the second predetermined time is at least 72 hours, and the third predetermined time is at least 12 hours; and the organic solvent is DMF.

4. The Cu-BTC single crystal resistive humidity sensor according to claim 1, wherein: Step S2 includes the following steps: S201: placing a Cu-BTC single crystal sample on a glass slide with the surface to be processed facing upward; S202: placing the glass slide in S201 on the ultrafast laser processing platform and positioning it, and adjusting the processing platform to focus the light spot; S203: Setting process parameters of the ultrafast laser processing system, performing laser induced processing, and obtaining a planar interdigitated electrode; Among them, the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the focused spot is 4 μm.

5. The Cu-BTC single crystal resistive humidity sensor according to claim 4, characterized in that: In step S203 , when the scanning speed v is 200 μm / s≤v<280 μm / s, the processing power P is 3 mW≤P≤5 mW; when the scanning speed v is 280 μm / s≤v≤360 μm / s, the processing power P is 6 mW≤P≤8 mW.

6. A method for preparing the Cu-BTC single crystal resistive humidity sensor according to any one of claims 1 to 5, comprising the following steps: S1: Prepare a Cu-BTC single crystal sample with a length and width of the processing surface greater than or equal to 100 μm; S2: using an ultrafast laser processing device to perform ultrafast laser induced processing on the Cu-BTC single crystal sample in step S1 under set laser processing parameters to obtain a planar interdigitated electrode; Among them, the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the focused spot is 4 μm.

7. The preparation method according to claim 6, characterized in that: Step S1 includes the following steps: S101: Synthesis of Cu-BTC single crystal materials; S102: soaking the synthesized Cu-BTC single crystal material in an organic solvent for a first predetermined time, then soaking it in anhydrous ethanol for a second predetermined time, and then placing the Cu-BTC single crystal material in a vacuum oven at a set activation temperature and drying it for a third predetermined time to obtain a Cu-BTC single crystal sample having a length and a width of a to-be-processed surface both greater than or equal to 100 μm; Wherein, in step S102, the activation temperature is set in the range of 50°C-80°C, the first predetermined time is at least 72 hours; the second predetermined time is at least 72 hours; the third predetermined time is at least 12 hours; and the organic solvent is DMF.

8. The preparation method according to claim 6, wherein: Step S2 includes the following steps: S201: placing a Cu-BTC single crystal sample on a glass slide with the surface to be processed facing upward; S202: placing the glass slide in S201 on the ultrafast laser processing platform and positioning it, and adjusting the processing platform to focus the light spot; S203: Setting process parameters of the ultrafast laser processing system, performing laser induced processing, and obtaining a planar interdigitated electrode; Among them, the ultrafast laser wavelength is 1030 nm, the pulse width t is 1.2 ps≤t≤10 ps, ​​the processing power P is 3 mW≤P≤8mW, the scanning speed v is 200 μm / s≤v≤360 μm / s, the processing interval is 1 μm, and the focused spot is 4 μm.

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