Humidity sensor based on hydrogen-bonded organic framework material and preparation method thereof

Abstract

The application discloses a humidity sensor based on hydrogen bond organic framework material and a preparation method thereof, and comprises the following steps: (1) ultrasonic dissolving HOFs raw materials in a solvent, then adding deionized water, stirring, centrifuging, and obtaining a HOFs solution; (2) adding a metal cation solution and an adhesive solution into the HOFs solution in the step (1), and obtaining a HOFs composite solution; (3) depositing the HOFs composite solution in the step (2) on a prepared electrode substrate by using a drop casting method, and vacuum drying. The humidity sensor obtained by the application can cover a measurement range of 12%RH-91%RH, and the response time, sensitivity and stability under high humidity of the humidity sensor are obviously superior to those of an existing humidity sensor, and the humidity sensor is convenient for practical application and measurement.

Description

TECHNICAL FIELD

[0001] The application relates to a humidity sensor based on a hydrogen-bonded organic framework material and a preparation method, and belongs to the field of humidity sensors. BACKGROUND

[0002] A 'framework' material with high adjustability, designability and modifiability, extremely high specific surface area and pore volume, and good selectivity is one of ideal materials for manufacturing a humidity sensor. The 'framework' material mainly includes a metal organic framework (MOF), a covalent organic framework (COF), a hydrogen-bonded organic framework (HOF) and the like. The porous crystal material can be used for adsorbing and separating a gas, a catalyst, a magnetic material and an optical material due to the controllable pore structure and large specific surface area. The COF and the MOF also have related research and application in the humidity sensing field. However, the HOF synthesized by self-assembly of organic molecules through weak hydrogen bonds is ignored in the humidity sensing field. At present, the related application of the HOF in the humidity sensing field is very rare, mainly because the single HOF has the following problems: 1. The hydrogen bond in the HOF is relatively weak, and can be easily destroyed or changed in structure under certain humidity conditions, resulting in unstable performance of the material. 2. The HOF can not respond to the humidity change fast enough or the response degree is not obvious enough due to the structural and property characteristics. 3. The hydrogen-bonded organic framework material can have some difficulties in the processing and preparation process, for example, it is difficult to form a uniform film or structure, or the preparation process is complicated.

[0003] The humidity-sensitive voltage material is covered with a layer of humidity-sensitive material on a substrate, and when water vapor is adsorbed on the humidity-sensitive material, the potential difference through which the electrode is conducted by the humidity-sensitive material will change accordingly, so as to measure the humidity. The HOF material humidity sensor is based on the characteristic that the change of ion conductivity of the material adsorbing water molecules changes the potential between the two electrodes. The response recovery time, on-off ratio and high humidity stability of the existing humidity sensor made of other materials cannot be effectively guaranteed, especially in a high humidity environment (such as an environment with humidity greater than 70% RH, especially an environment with humidity greater than 90% RH), the stability and on-off ratio of the humidity sensor are urgent problems to be solved. SUMMARY

[0004] In view of the problems in the prior art, the application provides a humidity sensor based on a hydrogen-bonded organic framework material and a preparation method.

[0005] In order to achieve the above purpose, the application adopts a preparation method of a humidity sensor based on a hydrogen-bonded organic framework material, which comprises the following steps:

[0006] (1) ultrasonic dissolve HOFs raw materials in solvent, then add deionized water, stir, centrifuge, and obtain HOFs solution;

[0007] (2) add metal cation solution and adhesion agent solution to the HOFs solution of step (1), and obtain HOFs composite solution;

[0008] (3) adopt drop casting method to deposit the HOFs composite solution of step (2) on the substrate of prepared electrode, and vacuum dry.

[0009] As an improvement, the HOFs raw materials in step (1) adopt at least one of 4,4',4''-(1,3,5-triazine-2,4,6-triazyl) triphenylamine, 1,3,6,8-tetra-(p-aminophenyl)-pyrene, 1,2,4,5-tetra(4-carboxyphenyl) benzene.

[0010] As an improvement, DMF is used as the solvent in step (1), ultrasonic for 10-20 min, stirring for 0.5-1.5 h, and centrifugation for 10-20 min.

[0011] As an improvement, the concentration of the HOFs solution in step (1) is 3-10 mg / mL.

[0012] As an improvement, the concentration of the metal cation solution in step (2) is 1.5-2.5 M, and the concentration of the adhesion agent solution is 3-10 mg / ml.

[0013] As an improvement, the volume ratio of the HOFs solution, the metal cation solution and the adhesion agent solution is (5-15):1:(15-25).

[0014] As an improvement, the metal cation solution in step (2) adopts at least one of sodium chloride solution, potassium chloride solution, magnesium chloride solution, zinc chloride solution, calcium chloride solution, and lithium chloride solution.

[0015] As an improvement, the adhesion agent solution in step (2) adopts PVA solution.

[0016] As an improvement, the electrode in step (3) is Ti3C2T x -MXene and Zn@Ti3C2T x -MXene electrode, the Zn@Ti3C2T x -MXene electrode is prepared by Ti3C2T x -MXene electrode is prepared by electrodeposition of metal Zn.

[0017] The second aspect of the application also provides a humidity sensor based on hydrogen-bonded organic framework material, which is prepared by the preparation method.

[0018] The principle of the present application is:

[0019] The HOFs material is a porous network material interconnected by hydrogen bonds, which has a continuous and abundant hydrophilic site. When it senses the water molecules in the environment, it can quickly combine and transport them, increasing the ionic conductivity, which is manifested as a change in the potential difference between two electrodes. By adding metal cations, the metal cations can act as pillars in the layered framework, promoting the diffusion of ions and the insertion of water molecules, thus significantly improving the ion transport performance. When the HOFs composite material is exposed to the environment, the HOFs molecular framework supported by metal cations senses the water molecules in the environment, exposing a large number of binding sites to water molecules and through pores, while the addition of ions enriches the carrier type and quantity for conduction, greatly increasing the ionic conductivity, which is manifested as a very high on-off ratio. At the same time, it also makes the HOFs get rid of the single structure, to some extent, increases the stability of the HOFs. In addition, the addition of the adhesive enhances the mechanical properties of the HOFs, making it easy to form a thin film and uniformly dispersed.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] (1) The present application uses metal cations to support the HOFs material, so that the HOFs composite material (metal cation / HOFs / adhesive) can quickly detect in an environment with frequent changes in humidity. The HOFs composite material with added metal cations not only quickly senses in the water absorption process, but also senses extremely quickly in the dehydration process. The humidity sensor can quickly and continuously detect in an environment with frequent changes in humidity, and the humidity measurement range can cover 12%RH-91%RH, especially suitable for humidity sensing detection in an environment with frequent changes in humidity.

[0022] (2) The present application uses HOFs raw material to be ultrasonically dissolved in DMF solvent, then poured into deionized water and stirred, and the HOFs solution is collected by centrifugation. The humidity sensor (such as self-powered potential difference type) is made by matching the HOFs solution with PVA aqueous solution and adding metal cations. After treatment, the humidity sensitivity of the HOFs composite material is significantly enhanced. Compared with the on-off ratio of several thousand levels in the existing research, the on-off ratio of the present application reaches 3w levels. After treatment, the HOFs as the humidity sensing element part of the humidity sensor makes the response recovery time significantly reduced.

[0023] (3) The present application also uses a quantitative drop-casting method to deposit metal cations and HOFs. The treated humidity sensing element has good contact and good stability, which is beneficial to improve the humidity response of the humidity sensor, so as to obtain a humidity sensor with good humidity sensitivity and small humidity hysteresis, and suitable for humidity testing in a wide range. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Structure diagram of the humidity sensor of Example 1 of the present application;

[0025] Figure 2 SEM image of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) of Example 1 of the present application;

[0026] Figure 3 Response recovery time diagram of the humidity sensor of Example 1 of the present application;

[0027] Figure 4 Different humidity response diagram of the humidity sensor of Example 1 of the present application;

[0028] Figure 5 Fast wet-dry cycle curve of the humidity sensor of Example 1 of the present application under high humidity conditions for more than 200 times. DETAILED DESCRIPTION

[0029] The following examples are further illustrations of the present application and are not intended to limit the present application in any way. Any changes or modifications that one can make to the present application based on the spirit of the present application should be within the scope of the present application.

[0030] Example 1

[0031] A method for preparing a humidity sensor based on hydrogen-bonded organic framework material, comprising the following steps:

[0032] (1) Dissolve 4,4',4''-(1,3,5-triazine-2,4,6-triyl) in DMF solution for 10 min under ultrasonic, then add deionized water, stir for 1 h, and centrifuge for 10 min to obtain a HOFs solution with a concentration of 5 mg / ml; in addition, scan 4,4',4''-(1,3,5-triazine-2,4,6-triyl) and the SEM image is as shown in Figure 2 , which shows that it is a stacked dense nanomaterial, which meets the nanoscale size requirement of humidity-sensitive materials;

[0033] (2) Add 100 uL of NaCl solution with a concentration of 2M and 2 mL of PVA solution with a concentration of 5 mg / mL to 1 mL of the HOFs solution of step (1) to obtain a HOFs composite solution (HOF@PVA in Figure 1 );

[0034] (3) Prepare electrodes on a PET substrate

[0035] (a) Soak the PET substrate in ethanol for 15 minutes with ultrasonic to remove the stains on the surface of the PET substrate element;

[0036] (b) Use Ti3C2T x -MXene to coat the filter paper, dry naturally at room temperature, use a laser engraving machine to make a 15 mm*5 mm Ti3C2T x -MXene electrode (as Figure 1 in MXene), and then use Ti3C2T x -MXene electrode to electrodeposit metal Zn to form Zn@Ti3C2T x -MXene electrode (as Figure 1 Zn@MXene in MXene);

[0037] (c) Cut the PET substrate to the appropriate size, then dry it with a nitrogen gun, and use double-sided tape to stick the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrode with a spacing of about 2 mm;

[0038] (4) Use a pipette to quantitatively drop-cast the HOFs composite solution of step (2) between the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrode, covering the interface between the electrode and the substrate, and place it in an oven at 60°C for 1.5h to obtain a humidity sensor, the structure of which is shown in Figure 1 .

[0039] The humidity sensor prepared in Example 1 was tested for performance:

[0040] ① Response recovery test

[0041] Actual measurement procedure: Use a gas pump (gas cylinder) to split the gas (air), one pipe is connected to the gas washing bottle in the water bath (long in and short out), and the other pipe is used as a dry gas for the sensor to reduce humidity. Calibrate the humidity: use dry air to blow the humidity sensor probe to the lowest humidity (generally to about 6% RH), then use wet air to blow the humidity meter to make the humidity meter show the calibrated humidity (such as 10% RH), record the time required from the lowest humidity to the calibrated humidity, and do this multiple times to calibrate the time of each humidity. Measure the humidity response recovery time of the humidity sensor: keep the room temperature constant and the pipe flow constant, and perform experiments at each humidity according to the recorded time of the humidity meter calibration, and use software to record the data. The data recorded at 98% RH humidity is used to make a waveform using drawing software and calculate the rise time and fall time of the waveform, which is the response recovery time of the humidity sensor.

[0042] The test results are as follows:Figure 3 As shown in the analysis, the response recovery time of the humidity sensor prepared in Example 1 is at a relatively excellent level. The response recovery time of the current research is generally 3-5 s, while the response recovery time of the present embodiment is less than 1 s.

[0043] 2. Different humidity response test

[0044] Under the condition of keeping the room temperature constant and the pipeline air flow constant, the experiments of different humidity were carried out according to the time recorded in the above humidity meter calibration, and the data were recorded by using software. The waveform was made by using drawing software and was color-coded.

[0045] The test results are shown in Figure 4 As shown in the analysis, with the increase of humidity from 12% RH (relative humidity) to 91% RH, the output current rises from 5 µA to 22 µA, the higher the humidity, the greater the output current, indicating that there is a good linear relationship between the output current and the relative humidity, and the initial current is small enough and the response current is large enough, providing a good on-off ratio.

[0046] 3. More than 200 times of rapid dry-wet cycle test under high humidity conditions

[0047] Under the condition of keeping the room temperature constant and the pipeline air flow constant, the experiment of repeating a certain determined humidity more than 200 times was carried out according to a certain time recorded in the humidity meter calibration, and the data were recorded by using software. The waveform was made by using drawing software.

[0048] The test results are shown in Figure 5 As shown in the analysis, the 200 times of dry-wet cycle of the humidity sensor prepared in Example 1 shows that the sensor has excellent running stability. The response and recovery are extremely rapid, and the current decay is extremely small, which can be ignored.

[0049] Example 2

[0050] A preparation method of a humidity sensor based on hydrogen-bonded organic framework material, comprising the following steps:

[0051] (1) ultrasonic dissolve 1,3,6,8-tetra-(p-aminophenyl)-pyrene in DMF solution for 15 min, then add deionized water, stir for 0.5 h, and centrifuge for 15 min to obtain a HOFs solution with a concentration of 4 mg / ml;

[0052] (2) add 100 µL of NaCl solution with a concentration of 1.5 M and 2 mL of PVA solution with a concentration of 6 mg / mL to 1 mL of the HOFs solution of step (1) to obtain a HOFs composite solution;

[0053] (3) Preparing electrodes on PET substrate

[0054] (a) Soaking the PET substrate in ethanol for 15 minutes under ultrasonic to remove stains on the surface of the PET substrate element;

[0055] (b) Coating the filter paper with Ti3C2T x -MXene at room temperature, and using a laser engraving machine to make a 15 mm*5 mm Ti3C2T x -MXene electrode, and then using Ti3C2T x -MXene electrode to electrodeposit metal Zn to form Zn@Ti3C2T x -MXene electrode;

[0056] (c) Cutting the PET substrate to the appropriate size, and then blowing dry with a nitrogen gun, and using double-sided tape to stick the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrode with a spacing of about 2 mm;

[0057] (4) Quantitatively dropping the HOFs composite solution of step (2) on the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrode, and placing it in an oven at 60°C for 2h to dry, to obtain a humidity sensor, the structure of which is shown in Figure 1 .

[0058] Example 3

[0059] A preparation method of a humidity sensor based on hydrogen-bonded organic framework material, comprising the following steps:

[0060] (1) Dissolving 1,2,4,5-tetrakis(4-carboxyphenyl) benzene in a DMF solution for 20 min under ultrasonic, and then adding deionized water, stirring for 1.5h, and centrifuging for 20 min to obtain a HOFs solution with a concentration of 8 mg / ml;

[0061] (2) Adding 100 µL of a NaCl solution with a concentration of 2 M and 2.5 mL of a PVA solution with a concentration of 8 mg / mL to 1.5 mL of the HOFs solution of step (1) to obtain a HOFs composite solution;

[0062] (3) Preparing electrodes on PET substrate

[0063] (a) Soaking the PET substrate in ethanol for 15 minutes under ultrasonic to remove stains on the surface of the PET substrate element;

[0064] (b) Coating the filter paper with Ti3C2T x-MXene fills the filter paper room at room temperature, and uses a laser engraving machine to make 15 mm*5 mm Ti3C2T x -MXene electrode, and then use Ti3C2T x -MXene electrode, and then use Ti3C2T x -MXene electrode, and then use Ti3C2T

[0065] (c) cut the PET substrate to the appropriate size, and then use a nitrogen gun to blow dry, and use double-sided tape to stick Ti3C2T in parallel x -MXene electrode, and then use Ti3C2T x -MXene electrode, and then use Ti3C2T

[0066] (4) The HOFs composite solution of step (2) is quantitatively dropped and cast on Ti3C2T by using a pipette x -MXene electrode, and then use Ti3C2T x -MXene electrode, and then use Ti3C2T Figure 1

[0067] The humidity sensor obtained by the present application can cover a measurement range of 12%RH-91%RH, and has a response time, sensitivity and stability under high humidity that are obviously superior to those of existing humidity sensors, as shown in Table 1, and is convenient for practical application and measurement.

[0068] Table 1 Comparison of performance of humidity sensor prepared in Example 1 of the present application and existing humidity sensors

[0069]

[0070] The HOFs solution obtained by ultrasonic treatment, stirring and centrifugal treatment of HOFs raw materials can be directly used for the preparation of a humidity sensor. In the present application, HOFs is mixed with a solution of sodium chloride (NaCl) or the like to form a HOFs composite material, which is used as a humidity-sensitive component in the humidity sensor. In addition, in addition to the details of the components (such as the electrode) mentioned in the present application, other functional components can also be provided in the humidity sensor according to actual needs.

[0071] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, and any modifications, equivalent replacements or improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.​

Claims

1. A method for preparing a humidity sensor based on a hydrogen-bonded organic framework material, characterized by, The method comprises the following steps: (1) dissolving HOFs raw materials in a solvent by ultrasonic, then adding deionized water, stirring, centrifuging, and obtaining a HOFs solution; the HOFs raw materials are at least one of 4,4',4''-(1,3,5-triazine-2,4,6-triazyl) triphenylamine, 1,3,6,8-tetra-(p-aminophenyl)-pyrene, and 1,2,4,5-tetra(4-carboxylphenyl) benzene; (2) adding a metal cation solution and an adhesive solution to the HOFs solution of step (1) to obtain a HOFs composite solution; the metal cation solution is at least one of sodium chloride solution, potassium chloride solution, magnesium chloride solution, zinc chloride solution, calcium chloride solution, and lithium chloride solution; the adhesive solution is a PVA solution; (3) depositing the HOFs composite solution of step (2) on a prepared electrode substrate by drop casting, and vacuum drying.

2. The method of claim 1, wherein the method is characterized by: In step (1), DMF is used as the solvent, ultrasonic is performed for 10-20 min, stirring is performed for 0.5-1.5 h, and centrifuging is performed for 10-20 min.

3. The method of claim 1, wherein the method comprises: The concentration of the HOFs solution in step (1) is 3-10 mg / mL.

4. The method of claim 3, wherein the method is characterized by: In step (2), the concentration of the metal cation solution is 1.5-2.5 M, and the concentration of the adhesive solution is 3-10 mg / ml.

5. The method of claim 4, wherein the method further comprises the step of: 5-1) drying the HOF material at a temperature of 100-200 °C for 1-10 hours under vacuum. 5-2) repeating the step 5-1) for 1-10 times. The volume ratio of the HOFs solution, the metal cation solution, and the adhesive solution is (5-15):1:(15-25).

6. The method of claim 1, wherein the method is characterized by: The electrode of step (3) is Ti3C2T x - MXene and Zn@Ti3C2T x - MXene electrode, the Zn@Ti3C2T x - MXene electrode is made of Ti3C2T x - MXene electrode is prepared by electrodeposition of metal Zn.

7. A humidity sensor based on a hydrogen-bonded organic framework material, characterized in that The method is prepared by any one of claims 1-6.

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