Flexible room temperature sensor and preparation method and application thereof

Abstract

The invention provides a flexible room temperature sensor as well as a preparation method and application thereof, and relates to the technical field of gas sensors. The flexible room temperature sensor provided by the invention comprises a flexible substrate, a flexible sensitive film covering the surface of the flexible substrate, and an interdigital electrode positioned on the surface of the sensitive material film, a sensitive material in the flexible sensitive film comprises a Cu-HHTP two-dimensional nanosheet or a Cu / Co-HHTP two-dimensional nanosheet; and the HHTP is 2, 3, 6, 7, 10, 11-hexahydroxy triphenyl. The flexible room temperature sensor provided by the invention has good adsorption capacity on ammonia gas at room temperature, and has relatively high electronic conductivity; the flexible room temperature sensor shows excellent ammonia gas sensitive characteristics (high sensitivity, high selectivity and high stability) at room temperature and good bending shape follow-up characteristics (zero drift of baseline resistance and no attenuation of sensitivity after multiple times of bending).

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, specifically to a flexible room temperature sensor, its fabrication method, and its application. Background Technology

[0002] The rapid development of flexible electronics technology has driven an urgent need for sensing technologies that integrate high sensitivity, room temperature operation, and mechanical adaptability. Ammonia (NH3) is a fundamental chemical in modern agriculture, refrigeration, and pharmaceutical industries, playing a crucial role in global industrial processes due to its high reactivity and versatility as a nitrogen source. However, ammonia exhibits acute toxicity, corrosiveness, and a low ignition threshold, making its detection critical. Gas sensors are devices capable of detecting and measuring the concentration of gases in the environment, widely used in industrial, medical, safety, and environmental fields. Chemi-resistive gas sensors are widely used due to their advantages of good selectivity and high sensitivity; however, most chemi-resistive gas sensors operate at high temperatures during normal operation. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a flexible room temperature sensor, its fabrication method, and its application. The flexible room temperature sensor provided by this invention exhibits excellent ammonia gas sensitivity characteristics at room temperature due to its low operating temperature.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a flexible room temperature sensor, comprising a flexible substrate, a flexible sensitive film covering the surface of the flexible substrate, and interdigitated electrodes located on the surface of the sensitive material film; the sensitive material in the flexible sensitive film includes Cu-HHTP two-dimensional nanosheets or Cu / Co-HHTP two-dimensional nanosheets, wherein the mass ratio of Cu to Co in the Cu / Co-HHTP two-dimensional nanosheets is 1-3:1-3; and the HHTP is 2,3,6,7,10,11-hexahydroxytriphenyl.

[0006] Preferably, the thickness of the flexible sensitive film is 50–80 nm;

[0007] The mass fraction of HHTP in the flexible sensitive membrane is 10-30%;

[0008] The mass ratio of Cu to Co in the Cu / Co-HHTP two-dimensional nanosheets is 1-3:1-3.

[0009] Preferably, the preparation method of the sensitive material includes the following steps: mixing a metal salt, a surfactant, an inorganic strong base, HHTP and water, and carrying out a polymerization reaction to obtain the sensitive material; the metal salt includes a mixed salt of copper salt and cobalt salt or a copper salt.

[0010] Preferably, the surfactant comprises sodium dodecyl sulfate and / or sodium dodecylbenzene sulfonate; the mass ratio of the metal salt to the surfactant is 3-7:2-4;

[0011] The inorganic strong base includes alkali metal hydroxides; the mass ratio of the metal salt to the inorganic strong base is 3-7:2-4;

[0012] The mass ratio of the metal salt to HHTP is 3-7:4-7.

[0013] Preferably, the polymerization reaction includes sequential ultrasonic polymerization and static polymerization;

[0014] The ultrasonic polymerization temperature is 40–60°C, the frequency is 0.02–1 MHz, and the time is 20–60 min.

[0015] The settling temperature is 20–30°C, and the settling time is 10–15 hours.

[0016] Preferably, the material of the interdigitated electrodes includes one or more of gold, silver and aluminum; the number of interdigitated electrodes is 2 to 5 pairs, the length is 10 to 20 mm, the width is 10 to 20 mm, the finger spacing is 1 to 2 mm, and the thickness is 0.5 to 1 μm.

[0017] Preferably, the flexible substrate is made of one or more of polyethylene terephthalate-polytetrafluoroethylene, polyimide, and polydimethylsiloxane.

[0018] The thickness of the flexible substrate is 0.5 to 5 mm.

[0019] The present invention also provides a method for fabricating the flexible room temperature sensor described in the above technical solution, comprising the following steps:

[0020] A flexible sensitive membrane is formed by suspending a sensitive material on the surface of a flexible substrate, thus obtaining a self-supporting flexible sensitive membrane.

[0021] Interdigitated electrodes were fabricated on the surface of the self-supporting flexible sensitive membrane to obtain a flexible room temperature sensor.

[0022] Preferably, the concentration of the sensitive material suspension is 0.5–8 mg / mL;

[0023] After obtaining the interdigitated electrode, the process further includes: replacing the composite film with the interdigitated electrode with acetonitrile and then drying it.

[0024] The present invention also provides the application of the flexible room temperature sensor described in the above technical solution or the flexible room temperature sensor prepared by the preparation method described in the above technical solution in the detection of ammonia.

[0025] This invention employs a flexible substrate and uses Cu-HHTP two-dimensional nanosheets (Cu metal neutral and single-ligand HHTP) and Cu / Co-HHTP two-dimensional nanosheets (Cu and Co bimetallic neutral and single-ligand HHTP) as sensing materials. These sensing materials exhibit a honeycomb lattice structure, demonstrating excellent ammonia adsorption capacity at room temperature and high electronic conductivity. By combining a flexible sensing film made from this material with a flexible substrate and designing an electrode with an interdigitated structure, the invention exhibits excellent ammonia sensing characteristics at room temperature (high sensitivity, high selectivity, and high stability), as well as good bending conformal characteristics (zero baseline resistance drift and no sensitivity attenuation after multiple bends). The flexible room temperature sensor provided by this invention can be easily placed in small, enclosed spaces and can accurately monitor the ambient ammonia concentration. Moreover, the sensitive material used in this invention has a unique nanoscale effect, which can effectively alleviate the influence of external forces on the flexible sensitive membrane, thereby reducing stress concentration and crack propagation, and thus significantly improving the mechanical properties of the flexible room temperature sensor. This enables efficient room temperature construction of the gas sensor, significantly improves the wearability and practical value of the gas sensor, and solves the inherent limitations of the rigid crystal structure of traditional bulk materials that cannot be bent.

[0026] Furthermore, this invention utilizes a surfactant-assisted solution synthesis method to prepare Cu-HHTP two-dimensional nanosheets and Cu / Co-HHTP two-dimensional nanosheets. The prepared sensitive materials have advantages such as high yield, high crystallinity, and large lateral dimensions. The aspect ratio of the sensitive materials is optimized. The sensitive materials with two-dimensional nanosheet structures have unique nanoscale effects, which can effectively alleviate the influence of external forces on flexible sensitive films, thereby reducing stress concentration and crack propagation, and thus significantly improving the mechanical properties of flexible room temperature sensors. Attached Figure Description

[0027] Figure 1 A schematic diagram of the fabrication process of a flexible room temperature ammonia sensor based on Cu / Co-HHTP;

[0028] Figure 2 TEM-EDS images of C1s (purple), O 1s (yellow), Cu 2p (cyan), and Co 2p (green) of Cu / Co-HHTP nanosheets;

[0029] Figure 3 The ultra-deep three-dimensional depth-of-field surface topography perspective view (a-e), surface height view (f-j), and 3D surface height view (k-o) of the continuous optical zoom function of the flexible room temperature ammonia gas sensor based on Cu / Co-HHTP-3:1-NS-x prepared in Examples 1 and 5 are shown, where x is 30, 40, 50, 60, and 70 from left to right.

[0030] Figure 4Plan view (a, c, e) and top view (b, d and f) of the system mechanical test of the Cu / Co(3:1)-HTP-NS-60 self-supporting flexible sensitive membrane underwent bending cycles of 60° (a~b), 90° (c~d) and 120° (e~f);

[0031] Figure 5 This is a schematic diagram of the gas dynamic testing system.

[0032] Figure 6 The figure shows the test results of the interdigitated electrode response values ​​of the flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheet sensitive material prepared in Example 1 at room temperature in atmospheres of 100 ppm ammonia, methane, acetone, CO2, CO, isoprene, n-butanol, H2, methanol, and SO2.

[0033] Figure 7 The curves show the change in resistance between the interdigitated electrodes over time for the ammonia sensors prepared in Examples 1-4 and Comparative Example 1 at room temperature during a cycle of being placed in a 100ppm NH3 atmosphere and then in an air atmosphere. Where a is Example 2, b is Example 1, c is Example 3, d is Example 4, and e is Comparative Example 1.

[0034] Figure 8 The curves show the function of NH3 gas concentration versus resistance between interdigitated electrodes for the flexible room-temperature ammonia gas sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheet sensitive material prepared in Example 1 at room temperature in an atmosphere of 1–500 ppm NH3.

[0035] Figure 9 The repeatability test curves of the flexible room temperature ammonia gas sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheet sensitive material prepared in Example 1 at room temperature in a 100ppm NH3 atmosphere after being bent at 120° 0, 20, 60 and 90 times. Detailed Implementation

[0036] This invention provides a flexible room temperature sensor, comprising a flexible substrate, a flexible sensitive film covering the surface of the flexible substrate, and interdigitated electrodes located on the surface of the sensitive material film; the sensitive material in the flexible sensitive film includes Cu-HHTP two-dimensional nanosheets or Cu / Co-HHTP two-dimensional nanosheets; the HHTP is 2,3,6,7,10,11-hexahydroxytriphenylene.

[0037] In this invention, the flexible substrate is preferably made of one or more of polyethylene terephthalate-polytetrafluoroethylene (PET-PTFE), polyimide (PI), and polydimethylsiloxane (PDMS). The thickness of the flexible substrate is preferably 0.5–5 mm, specifically 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm. The shape of the flexible substrate is preferably circular or square. The diameter of the circular substrate is preferably 40–50 mm, specifically 40 mm, 42 mm, 44 mm, 45 mm, 46 mm, 48 mm, or 50 mm; the side length of the square substrate is preferably 10–40 mm, specifically 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, or 40 mm.

[0038] In this invention, the mass ratio of Cu to Co in the Cu / Co-HHTP two-dimensional nanosheets is preferably 1-3:1-3, specifically 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 1:1.5, 2:1.5, 2.5:1.5, 1:2, 1.5:2, 1:2.5, 1.5:2.5, 2:2.5, 3:2.5, 1:3, 2:3, or 2.5:3. In this invention, the mass fraction of HHTP in the flexible sensitive membrane is preferably 10-30%, specifically 10%, 15%, 20%, 23.5%, 25%, or 30%. In this invention, the thickness of the flexible sensitive membrane is preferably 50-80 nm, specifically 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, or 80 nm.

[0039] In this invention, the material of the interdigitated electrodes preferably includes one or more of gold, silver, and aluminum; the number of pairs of interdigitated electrodes is preferably 2 to 5, specifically 2, 3, 4, or 5 pairs; the length of the interdigitated electrodes is preferably 10 to 20 mm, specifically 10 mm, 12 mm, 14 mm, 15 mm, 16 mm, 18 mm, or 20 mm; the width of the interdigitated electrodes is preferably 10 to 20 mm, specifically 10 mm, 12 mm, 14 mm, 15 mm, 16 mm, 18 mm, or 20 mm; the finger spacing of the interdigitated electrodes is preferably 1 to 2 mm, specifically 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.8 mm, or 2 mm; the thickness of the interdigitated electrodes is preferably 0.5 to 1 μm, specifically 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm.

[0040] In this invention, the method for preparing the sensitive material preferably includes the following steps: mixing a metal salt, a surfactant, an inorganic strong base, HHTP and water, and carrying out a polymerization reaction to obtain the sensitive material; the metal salt includes a mixed salt of copper salt and cobalt salt or a copper salt.

[0041] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0042] In this invention, the metal salt preferably includes acetate and / or chloride; the copper salt preferably includes Cu(OAc)₂·H₂O and / or CuCl₂·2H₂O. In this invention, the cobalt salt preferably includes Co(OAc)₂·4H₂O and / or CoCl₂·6H₂O. In this invention, when the metal salt is a mixture of copper and cobalt salts, the mass ratio of the copper and cobalt salts is preferably 2–4:1–3, specifically 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 2:1.5, 2.5:1.5, 3.5:1.5, 4:1.5, 2:2, 2.5:2, 3:2, 3.5:2, 2:2.5, 3:2.5, 3.5:2.5, 4:2.5, 2:3, or 2.5:3.

[0043] In this invention, the surfactant preferably comprises sodium dodecyl sulfate (SDS) and / or sodium dodecylbenzenesulfonate (SDBS). In this invention, the mass ratio of the metal salt to the surfactant is preferably 3–7:2–4, specifically 3:2, 4:2, 5:2, 6:2, 7:2, 3:3, 4:3, 5:3, 7:3, 3:4, 5:4, 6:4, or 7:4.

[0044] In this invention, the inorganic strong base preferably comprises an alkali metal hydroxide, specifically NaOH and / or KOH. In this invention, the mass ratio of the metal salt to the inorganic strong base is preferably 3–7:2–4, specifically 3:2, 4:2, 5:2, 6:2, 7:2, 3:3, 4:3, 5:3, 7:3, 3:4, 5:4, 6:4, or 7:4.

[0045] In this invention, the mass ratio of the metal salt to HHTP is preferably 3-7:4-7, and may specifically be 3:4, 4:4, 5:4, 6:4, 7:4, 3:5, 4:5, 6:5, 7:5, 3:6, 4:6, 5:6, 7:6, 3:7, 4:7, 5:7 or 6:7.

[0046] In this invention, the mixing preferably includes: dissolving a metal salt and a surfactant in water to obtain a precursor salt solution; mixing the precursor salt solution with an aqueous solution of an inorganic strong base to obtain a precursor body fluid; and mixing the precursor body fluid with HHTP. In this invention, the concentration of the aqueous solution of the inorganic strong base is preferably 0.5–2 mg / mL, specifically 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, or 2 mg / mL.

[0047] In this invention, the polymerization reaction preferably includes sequential ultrasonic polymerization and static polymerization. In this invention, the ultrasonic polymerization temperature is preferably 40–60°C, specifically 40°C, 45°C, 50°C, 55°C, or 60°C; the ultrasonic polymerization frequency is preferably 0.02–1MHz, specifically 0.02MHz, 0.05MHz, 0.1MHz, 0.2MHz, 0.3MHz, 0.4MHz, 0.5MHz, 0.6MHz, 0.7MHz, 0.8MHz, 0.9MHz, or 1MHz; the ultrasonic polymerization time is preferably 20–60 min, specifically 20 min, 30 min, 40 min, 50 min, or 60 min. In this invention, the static polymerization temperature is preferably 20–30°C, specifically 20°C, 25°C, or 30°C; the static polymerization time is preferably 10–15 h, specifically 10 h, 11 h, 12 h, 13 h, 14 h, or 15 h.

[0048] After the polymerization reaction is completed, the present invention preferably further includes: solid-liquid separation, wherein the obtained solid components are sequentially subjected to water centrifugation washing, ethanol centrifugation washing, and ultrasonic dispersion in an ethanol-water solution to obtain a suspension of the sensitive material. In the present invention, the number of water centrifugation washings is preferably 2 to 4 times, specifically 2, 3, or 4 times. In the present invention, the number of ethanol centrifugation washings is preferably 2 to 4 times, specifically 2, 3, or 4 times. In the present invention, the volume ratio of ethanol to water in the ethanol-water solution is preferably 1:1 to 3, specifically 1:1, 1:1.5, 1:2, 1:2.5, or 1:3. In the present invention, the ultrasonic dispersion is preferably carried out in an ice-water bath, and the ultrasonic dispersion time is preferably 20 to 40 minutes, specifically 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes. In this invention, the concentration of the sensitive material suspension is preferably 4 to 8 mg / mL, specifically 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL, 6.5 mg / mL, 7 mg / mL, 7.5 mg / mL or 8 mg / mL.

[0049] The present invention also provides a method for fabricating the flexible room temperature sensor described in the above technical solution, comprising the following steps:

[0050] A flexible sensitive membrane is formed by suspending a sensitive material on the surface of a flexible substrate, thus obtaining a self-supporting flexible sensitive membrane.

[0051] Interdigitated electrodes were fabricated on the surface of the self-supporting flexible sensitive membrane to obtain a flexible room temperature sensor.

[0052] This invention forms a flexible sensitive membrane on the surface of a flexible substrate by suspending a sensitive material, thereby obtaining a self-supporting flexible sensitive membrane. Specifically, a first sensitive material suspension can be vacuum filtered onto the surface of a flexible substrate and then freeze-dried to obtain a pre-formed membrane. A second sensitive material suspension can be vacuum filtered onto the surface of the pre-formed membrane and then freeze-dried to form a flexible sensitive membrane, thereby obtaining a self-supporting flexible sensitive membrane.

[0053] In this invention, the concentration of the sensitive material suspension is preferably 0.5–8 mg / mL, more preferably 0.5–2 mg / mL or 4–8 mg / mL, and may specifically be 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL, 6.5 mg / mL, 7 mg / mL, 7.5 mg / mL or 8 mg / mL.

[0054] In this invention, the concentration of the first sensitive material suspension is more preferably 4-8 mg / mL, and the concentration of the second sensitive material suspension is more preferably 0.5-2 mg / mL.

[0055] In this invention, the temperatures of the first freeze-drying and the second freeze-drying are preferably independently between -60 and -30°C, specifically -60°C, -55°C, -50°C, -45°C, -42°C, -40°C, -35°C, or -30°C; the times of the first freeze-drying and the second freeze-drying are preferably independently between 2 and 5 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours.

[0056] After obtaining the self-supporting flexible sensitive membrane, the present invention prepares interdigitated electrodes on the surface of the self-supporting flexible sensitive membrane to obtain a flexible room temperature sensor.

[0057] In this invention, the interdigitated electrodes are preferably prepared by vapor deposition. In this invention, the conditions for vapor deposition and the shape of the mask used are not particularly limited, as long as the aforementioned logarithmic and dimensional interdigitated electrodes can be obtained.

[0058] After obtaining the interdigitated electrodes, the present invention preferably further includes: replacing the composite film with the interdigitated electrodes with acetonitrile and then drying it to obtain a flexible room temperature sensor. In the present invention, the acetonitrile replacement is preferably acetonitrile immersion replacement, and the acetonitrile replacement time is preferably 12-72 hours, specifically 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 25 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 35 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 45 hours, 48 ​​hours, 50 hours, 52 hours, 55 hours, 56 hours, 58 hours, 60 hours, 62 hours, 64 hours, 65 hours, 68 hours, 70 hours, or 72 hours; during the acetonitrile replacement process, the acetonitrile is replaced every 8-20 hours (specifically 8 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, or 20 hours). In this invention, the drying temperature is preferably 50 to 100°C, specifically 50°C, 60°C, 70°C, 80°C, 90°C or 100°C; the drying time is preferably 8 to 24 hours, specifically 8 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0059] The present invention also provides the application of the flexible room temperature sensor described in the above technical solution or the flexible room temperature sensor prepared by the preparation method described in the above technical solution in the detection of ammonia.

[0060] To further illustrate the present invention, the following detailed description of the flexible room temperature sensor, its preparation method, and its application, in conjunction with embodiments, is provided but should not be construed as limiting the scope of protection of the present invention.

[0061] Example 1

[0062] The structure of a flexible room-temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets consists of a flexible substrate, a flexible sensitive membrane covering the surface of the flexible substrate, and gold interdigitated electrodes deposited on the surface of the flexible sensitive membrane. The flexible substrate is a flexible PET-PTFE filter membrane composed of a PTFE substrate and a PET support layer, with a diameter of 47 mm. The flexible sensitive membrane is made of Cu / Co-HHTP-3:1 two-dimensional nanosheets and has a thickness of 60 nm. The gold interdigitated electrodes consist of 3 pairs, each 15 mm long and 15 mm wide, with a 1 mm interdigitation distance and a thickness of 0.8 μm.

[0063] The preparation process of Cu / Co-HHTP-3:1 two-dimensional nanosheet sensitive material is shown in the flowchart below. Figure 138.1 mg Cu(OAc)₂·H₂O, 15.85 mg Co(OAc)₂·4H₂O, and 30 mg SDS were dissolved in 50 mL of deionized water to obtain a precursor salt solution. 30 mL of 1 mg / mL NaOH solution was added to the precursor salt solution to obtain a precursor solution. 60 mg HHTP was dissolved in the precursor solution to obtain a nanosheet precursor solution. The nanosheet precursor solution was ultrasonically reacted at 50 °C for 30 min, and then allowed to stand at 27 °C for 12 h to obtain a nanosheet precursor precipitate. The nanosheet precursor precipitate was first washed three times by centrifugation with deionized water, then washed three times by centrifugation with ethanol, and then dispersed in an ultrasonic ice bath with a 1:1 volume ratio of deionized water and ethanol for 30 min to obtain a 5 mg / mL Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension product, denoted as Cu / Co-HHTP-3:1-NS-60.

[0064] Fabrication of a flexible room-temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets:

[0065] Take 60 mL of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension and filter the suspension onto a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer using a vacuum pump. Freeze-dry the filter membrane with the sensitive material at -42℃ for 3 h to obtain the pre-formed membrane.

[0066] The suspension was reconstituted with deionized water and ethanol at a volume ratio of 1:1 to a concentration of 1 mg / L. 20 mL of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension was taken and the pre-made membrane was subjected to repeated vacuum filtration twice. After vacuum freezing for 3 h, a self-supporting flexible sensitive membrane was obtained.

[0067] 0.15g of gold was evaporated onto the self-supporting flexible sensitive membrane. The mask used in this process was a three-pair interdigitated electrode with dimensions of 15mm in length, 15mm in width, and 1mm in finger spacing.

[0068] A self-supporting flexible sensing membrane covered with gold electrodes was immersed in acetonitrile for 48 hours, with the acetonitrile being replaced every 12 hours. The immersed flexible membrane was then dried under vacuum at 70°C for 12 hours to obtain a flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets.

[0069] Example 2

[0070] The structure of a flexible room-temperature ammonia sensor based on Cu-HHTP two-dimensional nanosheets consists of a flexible substrate, a flexible sensitive membrane covering the surface of the flexible substrate, and gold interdigitated electrodes deposited on the surface of the flexible sensitive membrane. The flexible substrate is a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer, with a diameter of 47 mm. The flexible sensitive membrane is made of Cu-HHTP two-dimensional nanosheets and has a thickness of 60 nm. The gold interdigitated electrodes have three pairs, a length of 15 mm, a width of 15 mm, a finger spacing of 1 mm, and a thickness of 0.8 μm.

[0071] Preparation of Cu-HHTP two-dimensional nanosheet sensitive material: 50.8 mg Cu(OAc)2·H2O and 30 mg SDS were dissolved in 50 mL of deionized water to obtain a precursor salt solution; 30 mL of 1 mg / mL NaOH solution was added to the precursor salt solution to obtain a precursor solution; 60 mg HHTP was dissolved in the precursor solution to obtain a nanosheet precursor solution; the nanosheet precursor solution was ultrasonically reacted at 50 °C for 30 min, and then the reaction system was allowed to stand at 27 °C for 12 h to obtain a nanosheet precursor precipitate; the nanosheet precursor precipitate was first washed three times by centrifugation with deionized water, then washed three times by centrifugation with ethanol, and then dispersed in an ultrasonic ice bath with a volume ratio of 1:1 deionized water and ethanol for 30 min to obtain a 5 mg / mL Cu-HHTP two-dimensional nanosheet suspension product.

[0072] Fabrication of a flexible room-temperature ammonia sensor based on Cu-HHTP two-dimensional nanosheets:

[0073] Take 60 mL of Cu-HHTP two-dimensional nanosheet suspension and filter the suspension onto a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer using a vacuum pump; freeze-dry the filter membrane with the sensitive material at -42℃ for 3 h to obtain the pre-formed membrane.

[0074] The suspension was reconstituted with deionized water and ethanol in a volume ratio of 1:1 to a concentration of 1 mg / L. 20 mL of Cu-HHTP two-dimensional nanosheet suspension was taken and the pre-made membrane was subjected to repeated vacuum filtration twice. After vacuum freezing for 3 h, a self-supporting flexible sensitive membrane was obtained.

[0075] 0.15g of gold was evaporated onto the self-supporting flexible sensitive membrane. The mask used in this process was a three-pair interdigitated electrode with dimensions of 15mm in length, 15mm in width, and 1mm in finger spacing.

[0076] A self-supporting flexible sensing membrane covered with gold electrodes was immersed in acetonitrile for 48 hours, with the acetonitrile being replaced every 12 hours. The immersed flexible membrane was then dried under vacuum at 70°C for 12 hours to obtain a flexible room temperature ammonia sensor based on Cu-HHTP two-dimensional nanosheets.

[0077] Example 3

[0078] The structure of a flexible room-temperature ammonia sensor based on Cu / Co-HHTP-1:1 two-dimensional nanosheets consists of a flexible substrate, a flexible sensitive membrane covering the surface of the flexible substrate, and gold interdigitated electrodes deposited on the surface of the flexible sensitive membrane. The flexible substrate is a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer, with a diameter of 47 mm. The flexible sensitive membrane is made of Cu / Co-HHTP-1:1 two-dimensional nanosheets and has a thickness of 60 nm. The gold interdigitated electrodes have three pairs, a length of 15 mm, a width of 15 mm, a finger spacing of 1 mm, and a thickness of 0.8 μm.

[0079] Preparation of Cu / Co-HHTP-1:1 two-dimensional nanosheet sensitive material: 25.4 mg Cu(OAc)₂·H₂O, 31.7 mg Co(OAc)₂·4H₂O, and 30 mg SDS were dissolved in 50 mL of deionized water to obtain a precursor salt solution; 30 mL of 1 mg / mL NaOH solution was added to the precursor salt solution to obtain a precursor solution; 60 mg HHTP was dissolved in the precursor solution to obtain a nanosheet precursor solution; the nanosheet precursor solution was ultrasonically reacted at 50 °C for 30 min, and then the reaction system was allowed to stand at 27 °C for 12 h to obtain a nanosheet precursor precipitate; the nanosheet precursor precipitate was first washed three times by centrifugation with deionized water, then washed three times by centrifugation with ethanol, and then dispersed in an ultrasonic ice bath with a volume ratio of 1:1 deionized water and ethanol for 30 min to obtain a 5 mg / mL Cu / Co-HHTP-1:1 two-dimensional nanosheet suspension product.

[0080] Fabrication of a flexible room-temperature ammonia sensor based on Cu / Co-HHTP-1:1 two-dimensional nanosheets:

[0081] Take 60 mL of Cu / Co-HHTP-1:1 two-dimensional nanosheet suspension and filter the suspension onto a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer using a vacuum pump. Freeze-dry the filter membrane with the sensitive material at -42℃ for 3 h to obtain the pre-formed membrane.

[0082] The suspension was reconstituted with deionized water and ethanol at a volume ratio of 1:1 to a concentration of 1 mg / L. 20 mL of Cu / Co-HHTP-1:1 two-dimensional nanosheet suspension was taken and the pre-prepared membrane was subjected to repeated vacuum filtration for two times. After vacuum freezing for 3 hours, a self-supporting flexible sensitive membrane was obtained.

[0083] 0.15g of gold was evaporated onto the self-supporting flexible sensitive membrane. The mask used in this process was a three-pair interdigitated electrode with dimensions of 15mm in length, 15mm in width, and 1mm in finger spacing.

[0084] A self-supporting flexible sensing membrane covered with gold electrodes was immersed in acetonitrile for 48 hours, with the acetonitrile being replaced every 12 hours. The immersed flexible membrane was then dried under vacuum at 70°C for 12 hours to obtain a flexible room temperature ammonia sensor based on Cu / Co-HHTP-1:1 two-dimensional nanosheets.

[0085] Example 4

[0086] The structure of a flexible room-temperature ammonia sensor based on Cu / Co-HHTP-1:3 two-dimensional nanosheets consists of a flexible substrate, a flexible sensitive membrane covering the surface of the flexible substrate, and gold interdigitated electrodes deposited on the surface of the flexible sensitive membrane. The flexible substrate is a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer, with a diameter of 47 mm. The flexible sensitive membrane is a Cu / Co-HHTP-1:3 two-dimensional nanosheet with a thickness of 60 nm. The gold interdigitated electrodes consist of 3 pairs, each with a length of 15 mm, a width of 15 mm, a finger spacing of 1 mm, and a thickness of 0.8 μm.

[0087] Preparation of Cu / Co-HHTP-1:3 two-dimensional nanosheet sensitive material: 12.7 mg Cu(OAc)2·H2O, 47.55 mg Co(OAc)2·4H2O, and 30 mg SDS were dissolved in 50 mL of deionized water to obtain a precursor salt solution; 30 mL of 1 mg / mL NaOH solution was added to the precursor salt solution to obtain a precursor solution; 60 mg HHTP was dissolved in the precursor solution to obtain a nanosheet precursor solution; the nanosheet precursor solution was ultrasonically reacted at 50 °C for 30 min, and then the reaction system was allowed to stand at 27 °C for 12 h to obtain a nanosheet precursor precipitate; the nanosheet precursor precipitate was first washed three times by centrifugation with deionized water, then washed three times by centrifugation with ethanol, and then dispersed in an ultrasonic ice bath with a volume ratio of 1:1 deionized water and ethanol for 30 min to obtain a 5 mg / mL Cu / Co-HHTP-1:3 two-dimensional nanosheet suspension product.

[0088] Fabrication of a flexible room-temperature ammonia sensor based on Cu / Co-HHTP-1:3 two-dimensional nanosheets:

[0089] Take 60 mL of Cu / Co-HHTP-1:3 two-dimensional nanosheet suspension and filter the suspension onto a PET-PTFE flexible filter membrane composed of a PTFE substrate and a PET support layer using a vacuum pump. Freeze-dry the filter membrane with the sensitive material at -42℃ for 3 h to obtain the pre-formed membrane.

[0090] The suspension was reconstituted with deionized water and ethanol at a volume ratio of 1:1 to a concentration of 1 mg / L. 20 mL of Cu / Co-HHTP-1:3 two-dimensional nanosheet suspension was taken and the pre-prepared membrane was subjected to repeated vacuum filtration for two times. After vacuum freezing for 3 hours, a self-supporting flexible sensitive membrane was obtained.

[0091] 0.15g of gold was evaporated onto the self-supporting flexible sensitive membrane. The mask used in this process was a three-pair interdigitated electrode with dimensions of 15mm in length, 15mm in width, and 1mm in finger spacing.

[0092] A self-supporting flexible sensing membrane covered with gold electrodes was immersed in acetonitrile for 48 hours, with the acetonitrile being replaced every 12 hours. The immersed flexible membrane was then dried under vacuum at 70°C for 12 hours to obtain a flexible room temperature ammonia sensor based on Cu / Co-HHTP-1:3 two-dimensional nanosheets.

[0093] Example 5

[0094] A flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was prepared according to the method of Example 1. The only difference from Example 1 was that the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension was replaced with 30 mL instead of 60 mL. The flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was obtained, and the sensitive material was designated as Cu / Co-HHTP-3:1-NS-30.

[0095] Example 6

[0096] A flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was prepared according to the method of Example 1. The only difference from Example 1 was that the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension was replaced with 40 mL instead of 60 mL. The flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was obtained, and the sensitive material was designated as Cu / Co-HHTP-3:1-NS-40.

[0097] Example 7

[0098] A flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was prepared according to the method of Example 1. The only difference from Example 1 was that the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension was replaced with 50 mL instead of 60 mL. The flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was obtained, and the sensitive material was designated as Cu / Co-HHTP-3:1-NS-50.

[0099] Example 8

[0100] A flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was prepared according to the method of Example 1. The only difference from Example 1 was that the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension was replaced with 70 mL instead of 60 mL, and a flexible room temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheets was obtained. The sensitive material was designated as Cu / Co-HHTP-3:1-NS-70.

[0101] Comparative Example 1

[0102] An NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensing material uses highly conductive bimetallic Co / Cu-HHTP as the sensing material.

[0103] Preparation of highly conductive bimetallic Co / Cu-HHTP sensitive material: 9.98 mg Co(OAc)2·H2O, 8 mg Cu(OAc)2·H2O and 13 mg HHTP were dissolved in a mixed solvent of 1 mL deionized water and 1 mL N,N-dimethylformamide, and sonicated for 15 min. The solution was then placed in an 85℃ constant temperature oven for 12 h to obtain a dark brown product solution. The dark brown solution was first washed twice by centrifugation with deionized water, and then washed three times by centrifugation with methanol. After washing, the solution was allowed to air dry naturally at room temperature to obtain a black powder product. The black powder product was soaked in acetonitrile for 48 h, with the acetonitrile being replaced every 12 h. The soaked product was then placed in a 70℃ vacuum oven for 12 h to obtain the highly conductive bimetallic Co / Cu-HHTP sensitive material.

[0104] Fabrication of the NH3 gas sensor:

[0105] The PI substrate with gold interdigitated electrodes (15 pairs of interdigitated electrodes, each 10mm × 10mm in size; the distance between the interdigitated electrodes of two adjacent gold electrodes is 50μm) was fixed along its four sides with adhesive tape and stacked to a height of 2000μm. 1.5mg of highly conductive bimetallic Co / Cu-HHTP sensitive material was taken and mixed evenly with 300μL of isopropanol to form a slurry. 10μL of the slurry was taken with a pipette and dropped 5 times onto the surface of the interdigitated electrodes fixed with adhesive tape to completely cover the gold electrodes, resulting in a 30μm thick sensitive material film.

[0106] The PI substrate coated with the sensitive material film was dried in a vacuum oven at 70°C for 12 hours to obtain an NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensitive material.

[0107] Test Example 1

[0108] 1. Elemental Analysis

[0109] The Cu / Co-HHTP NSs prepared in Examples 1 and 3-4 were subjected to atomic-scale elemental analysis using scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray spectroscopy (EDS). The results are shown in the figure. Figure 2 It can be seen that Cu, Co, C, and O elements are uniformly distributed throughout the Cu / Co-HHTPNSs sample. The signal intensity increases with increasing Co content.

[0110] 2. Three-dimensional surface morphology

[0111] Using an ultra-deep three-dimensional microscope with continuous optical zoom, Cu / Co-HHTP-3:1-NS-x (where x represents the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension used, in mL, x = 30, 40, 50, 60 or 70; by adjusting the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension, self-supporting flexible sensitive films of different thicknesses can be prepared) can be captured along the Z-axis. No physical slicing is required, and the collected images can be superimposed to generate height maps, providing an intuitive three-dimensional surface morphology.

[0112] Figure 3The images show perspective views (a-e), surface height views (f-j), and 3D surface height views (k-o) of the ultra-deep three-dimensional depth-of-field surface morphology of the flexible room-temperature ammonia gas sensor based on Cu / Co-HHTP-3:1-NS-x prepared in Examples 1 and 5, where x represents 30, 40, 50, 60, and 70 from left to right. It can be seen that as the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension increases, the surface cracks of the sensitive material film gradually improve, becoming smoother and more uniform. When the amount of Cu / Co-HHTP-3:1 two-dimensional nanosheet suspension reaches 70 mL, the sensitive material film becomes too thick, leading to surface material fracture and detachment. Therefore, the Cu / Co-HHTP-3:1-NS-60 film was determined to have the best bending performance as a self-supporting flexible sensitive film.

[0113] 3. Mechanical testing

[0114] A dual-clamp vertical tension bending test system was adopted, in which the lower clamp is fixed to the base and the upper clamp is connected to a programmable displacement platform. The U-shaped bending of the film is achieved by controlling the vertical displacement (Δy) of the upper clamp. The bending angle (θ) is determined by the geometric relationship between the displacement Δy and the initial clamp spacing (d0): θ = 2arctan(Δy / d0). Initial clamp spacing (d0): 15.0 mm; vertical displacement (Δy): 8.7 mm, 15.0 mm, 26.0 mm (corresponding to bending angles θ = 60°, 90°, 120°); displacement speed: 5 mm / s.

[0115] Figure 4 The system mechanical test results of the Cu / Co-HHTP-3:1-NS-60 self-supporting flexible sensitive membrane underwent bending cycles of 60° (a~b), 90° (c~d), and 120° (e~f). It can be seen that the self-supporting flexible sensitive membrane has good flexibility and stable mechanical properties under different bending angles.

[0116] 4. Gas dynamic testing

[0117] Figure 5 This is a schematic diagram of a gas dynamic testing system, which consists of a mass flow controller (MFC), a test chamber, a DC power supply, and a multimeter.

[0118] When the operating temperature is room temperature (20-25℃), using Figure 5 The gas dynamic testing system shown demonstrates the interdigitated electrode response values ​​of the flexible room-temperature ammonia sensor based on Cu / Co-HHTP-3:1 two-dimensional nanosheet sensitive material prepared in Example 1 in an atmosphere of 100 ppm ammonia, methane, acetone, CO2, CO, isoprene, n-butanol, H2, methanol, and SO2 (high-purity air equilibrium). The interdigitated electrode response value is (Rg -R a ) / R a ×100%, where R g R is the resistance value of the sensor when it is placed in the test gas. a The resistance value of the sensor when placed in air is shown in the figure. Figure 6 As can be seen, the sensor prepared by the present invention has good selectivity for ammonia.

[0119] When the operating temperature is room temperature (20-25℃), using Figure 5 The gas dynamic testing system shown depicts the function curves of the interdigital electrode resistance versus time during one cycle of immersion in a 100 ppm NH3 atmosphere followed by an air atmosphere for the ammonia sensors prepared in Examples 1-4 and Comparative Example 1. The results are shown in the figure. Figure 7 In the examples, a represents Example 2, b represents Example 1, c represents Example 3, d represents Example 4, and e represents Comparative Example 1. It can be seen that the ammonia sensor prepared in Example 1 has the highest detection sensitivity for ammonia and the shortest response recovery time.

[0120] When the operating temperature is room temperature (20-25℃), using Figure 5 The gas dynamic testing system shown presents the function curves of NH3 gas concentration versus resistance change between interdigitated electrodes for the ammonia sensor prepared in Example 1 in NH3 atmospheres of 1ppm, 5ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 80ppm, 100ppm, 200ppm, 300ppm, 400ppm, and 500ppm. The results are shown in [Figure number missing]. Figure 8 It can be seen that the sensor sensitivity increases with the increase of NH3 concentration.

[0121] When the operating temperature is room temperature (20-25℃), using Figure 5 The gas dynamic testing system shown tested the ammonia sensor prepared in Example 1. Figure 4 Repeatability test curves of the mechanical system after being bent at 120° for 0, 20, 60, and 90 times in a 100ppm NH3 atmosphere are shown in the figure. Figure 9 As can be seen, the flexible sensor prepared by the present invention has good repeatability and good bending resistance, and can be used in flexible electronics and wearable devices.

[0122] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flexible room temperature sensor characterized in that, The device includes a flexible substrate, a flexible sensitive film covering the surface of the flexible substrate, and interdigitated electrodes located on the surface of the sensitive material film; the sensitive material in the flexible sensitive film includes Cu-HHTP two-dimensional nanosheets or Cu / Co-HHTP two-dimensional nanosheets, wherein the mass ratio of Cu to Co in the Cu / Co-HHTP two-dimensional nanosheets is 1-3:1-3; and the HHTP is 2,3,6,7,10,11-hexahydroxytriphenyl.

2. The flexible room temperature sensor of claim 1, wherein, The thickness of the flexible sensitive membrane is 50–80 nm; The mass fraction of HHTP in the flexible sensitive membrane is 10-30%; The mass ratio of Cu to Co in the Cu / Co-HHTP two-dimensional nanosheets is 1-3:1-3.

3. The flexible room temperature sensor of claim 1 or 2, wherein, The preparation method of the sensitive material includes the following steps: A sensitive material is obtained by mixing a metal salt, a surfactant, an inorganic strong base, HHTP, and water and carrying out a polymerization reaction; the metal salt includes a mixed salt of copper and cobalt salts or a copper salt.

4. The flexible room temperature sensor of claim 3, wherein, The surfactant includes sodium dodecyl sulfate and / or sodium dodecylbenzene sulfonate; the mass ratio of the metal salt to the surfactant is 3-7:2-4. The inorganic strong base includes alkali metal hydroxides; the mass ratio of the metal salt to the inorganic strong base is 3-7:2-4; The mass ratio of the metal salt to HHTP is 3-7:4-7.

5. The flexible room temperature sensor of claim 3 or 4, wherein, The polymerization reaction includes sequential ultrasonic polymerization and static polymerization; The ultrasonic polymerization temperature is 40–60°C, the frequency is 0.02–1 MHz, and the time is 20–60 min. The settling temperature is 20–30°C, and the settling time is 10–15 hours.

6. The flexible room temperature sensor of claim 1, wherein, The interdigitated electrodes are made of one or more of gold, silver, and aluminum; the number of interdigitated electrodes is 2 to 5 pairs, the length is 10 to 20 mm, the width is 10 to 20 mm, the finger spacing is 1 to 2 mm, and the thickness is 0.5 to 1 μm.

7. The flexible room temperature sensor of claim 1, wherein, The flexible substrate is made of one or more of polyethylene terephthalate-polytetrafluoroethylene, polyimide, and polydimethylsiloxane. The thickness of the flexible substrate is 0.5 to 5 mm.

8. Process for the preparation of a flexible room temperature sensor according to any one of claims 1 to 7, characterized in that, Includes the following steps: A flexible sensitive membrane is formed by suspending a sensitive material on the surface of a flexible substrate, thus obtaining a self-supporting flexible sensitive membrane. Interdigitated electrodes were fabricated on the surface of the self-supporting flexible sensitive membrane to obtain a flexible room temperature sensor.

9. The preparation method according to claim 8, characterized in that, The concentration of the sensitive material suspension is 0.5–8 mg / mL; After obtaining the interdigitated electrode, the process further includes: replacing the composite film with the interdigitated electrode with acetonitrile and then drying it.

10. The application of the flexible room temperature sensor according to any one of claims 1 to 7 or the flexible room temperature sensor prepared by the preparation method according to claim 8 or 9 in the detection of ammonia.

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