Humidity sensor based on hydrogen bond organic framework material and preparation method

Abstract

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

Description

Technical Field

[0001] The invention relates to a humidity sensor based on a hydrogen bond organic framework material and a preparation method thereof, belonging to the field of humidity sensors. Background Art

[0002] "Framework" materials with high adjustability, designability and modifiability, extremely high specific surface area and pore volume, and good selectivity are one of the ideal materials for making humidity sensors. "Framework" materials mainly include: metal organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen bonded organic frameworks (HOFs), etc. This type of porous crystalline material is often used for adsorption and separation of gases, catalysts, magnetic materials, optical materials, etc. due to its ability to control the structure of the pores and large specific surface area. COFs and MOFs have also been studied and applied in the field of humidity sensing. However, the application of HOFs, which are self-assembled by organic molecules through weak hydrogen bonds, in the field of humidity sensing has been ignored. At present, the application of HOFs in the field of humidity sensing is very rare, mainly because single HOFs have the following problems: 1. The hydrogen bonds in HOFs are relatively weak, and they may be easily damaged or undergo structural changes under certain humidity conditions, resulting in unstable material performance. 2. Due to the characteristics of their structure and properties, HOFs may not respond quickly enough to humidity changes, or the response degree is not obvious enough. 3. Hydrogen-bonded organic framework materials may have some difficulties in processing and preparation, such as difficulty in forming uniform films or structures, or complex preparation processes.

[0003] The humidity-sensitive voltage material is a layer of humidity-sensitive material covered on the substrate. When water vapor is adsorbed on the humidity-sensitive material, the potential difference of the electrode through the humidity-sensitive material will change accordingly, thereby achieving the purpose of measuring humidity. The HOFs material humidity sensor is based on the property that the material adsorbs water molecules to change the ionic conductivity and thus change the potential between the two electrodes. The response recovery time, switching ratio and high-humidity stability of existing humidity sensors made of other materials cannot be effectively guaranteed, especially in high-humidity environments (such as environments with humidity greater than 70% RH, especially environments with humidity greater than 90% RH). The stability and switching ratio of humidity sensors are urgent issues that need to be solved. Summary of the invention

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

[0005] In order to achieve the above object, the present invention adopts a method for preparing a humidity sensor based on a hydrogen-bonded organic framework material, comprising the following steps:

[0006] (1) Dissolve the HOFs raw material in a solvent by ultrasonication, add deionized water, stir, and centrifuge to obtain a HOFs solution;

[0007] (2) adding a metal cation solution and an adhesive solution to the HOFs solution of step (1) to obtain a HOFs composite solution;

[0008] (3) The HOFs composite solution of step (2) is deposited on the prepared electrode substrate by drop casting and then dried in vacuum.

[0009] As an improvement, the HOFs raw material in step (1) is at least one of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene, and 1,2,4,5-tetrakis(4-carboxyphenyl)benzene.

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

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

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

[0015] As an improvement, the adhesive solution in step (2) is a 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 made of Ti3C2T x -MXene electrode is made by electroplating and depositing metal Zn.

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

[0018] The principle of the present invention is:

[0019] As a porous network material interconnected by hydrogen bonds, HOFs materials have continuous and abundant hydrophilic sites. When sensing water molecules in the environment, they can quickly bind to and transport them, increasing ionic conductivity, which is manifested as a change in the potential difference between the two electrodes. By adding metal cations, since metal cations can act as pillars in the layered framework, they promote the diffusion of ions and the insertion of water molecules, thus significantly improving the ion transport performance. When HOFs composite materials are exposed to the environment, the HOFs molecular framework "supported" by metal cations exposes a large number of binding sites and pores to water molecules when sensing water molecules in the environment. At the same time, the addition of ions enriches the types and number of carriers used for conduction, greatly increasing ionic conductivity, manifested as an extremely high switching ratio, and also allows HOFs to get rid of a single structure, increasing the stability of HOFs to a certain extent. In addition, the addition of adhesives enhances the mechanical properties of HOFs, making it easy to form thin films and disperse evenly.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

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

[0022] (2) The present invention uses HOFs raw materials to be ultrasonically dissolved in DMF solvent, then poured into deionized water for stirring, and centrifugally collected to obtain a HOFs solution to manufacture a humidity sensor (such as a self-powered potential difference type). By combining the HOFs solution with a PVA aqueous solution and then adding metal cations, the humidity sensitivity of the HOFs composite material is significantly enhanced after treatment. Compared with the switch ratio of several thousand levels in existing research, the switch ratio of the present invention reaches 3w level; HOFs is used as the humidity sensitive element part of the humidity sensor, and the response recovery time is significantly reduced after treatment.

[0023] (3) The present invention also uses a quantitative drop casting method to deposit metal cations and HOFs. The humidity sensitive element obtained by the treatment has good contact and good stability, which is beneficial to improving the humidity response of the humidity sensor, thereby obtaining a humidity sensor with good humidity sensitivity and small hysteresis, and suitable for humidity testing over a wide range. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a humidity sensor according to Embodiment 1 of the present invention;

[0025] Figure 2 This is a scanning electron microscope image of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) of Example 1 of the present invention;

[0026] Figure 3 This is a response recovery time diagram of the humidity sensor according to Example 1 of the present invention;

[0027] Figure 4 Graphs showing different humidity responses of the humidity sensor of Example 1 of the present invention;

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

[0029] The following embodiments are further descriptions of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0030] Example 1

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

[0032] (1) 4,4',4''-(1,3,5-triazine-2,4,6-triyl) was dissolved in DMF solution by ultrasonication for 10 min, and then deionized water was added, stirred for 1 h, and centrifuged for 10 min to obtain a HOFs solution with a concentration of 5 mg / ml. In addition, 4,4',4''-(1,3,5-triazine-2,4,6-triyl) was scanned, and the scanning electron microscope image was as shown in the figure. Figure 2 Shown, indicating It is a densely stacked nanomaterial that meets the nanoscale size requirements of humidity-sensitive materials;

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

[0034] (3) Preparation of electrodes on PET substrate

[0035] (a) Soaking the PET substrate in ethanol and ultrasonically removing stains on the surface of the PET substrate element for 15 minutes;

[0036] (b) Using Ti3C2T x -MXene is coated on the filter paper and dried naturally at room temperature. A laser engraving machine is used to make a 15 mm*5 mm Ti3C2T x -MXene electrode (for Figure 1 MXene in the x -MXene electrode electroplating deposits metal Zn to form Zn@Ti3C2T x -MXene electrode (for Figure 1 Zn@MXene in );

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

[0038] (4) The HOFs composite solution in step (2) is quantitatively drop-casted on the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrodes, covering the interface between the electrode and the substrate, and drying in an oven at 60 °C for 1.5 h to obtain a humidity sensor with the structure shown in Figure 1 shown.

[0039] The performance test of the humidity sensor prepared in Example 1 was carried out:

[0040] ①Response recovery test

[0041] Actual measurement procedure: Use an air pump (gas cylinder) to divert gas (air), connect a pipe to the washing bottle in the water bath (long in and short out), and use the other pipe as the dry gas for the sensor to reduce humidity. Calibrate humidity: Use dry air to blow the hygrometer sensor probe to the lowest humidity (generally up to about 6% RH), then use wet air to blow the hygrometer to make the hygrometer display to the calibrated humidity (such as 10% RH), record the time required from the lowest humidity to the calibrated humidity, and calibrate the time for each humidity multiple times. Measure the humidity response recovery time of the humidity sensor: Perform experiments at various humidities according to the time recorded by the hygrometer calibration while keeping the room temperature constant and the pipeline airflow constant, and use software to record the data. Use drawing software to make a waveform of the data recorded at 98% RH humidity 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, analysis shows that the response recovery time of the humidity sensor prepared in Example 1 is at a relatively good level. The response recovery time of existing studies is generally 3-5s, while the response recovery time of this embodiment is less than 1s.

[0043] ② Different humidity response test

[0044] Under the condition of keeping the room temperature constant and the airflow in the pipeline constant, carry out the experiments of various humidity levels according to the time recorded by the calibration of the above hygrometer, and use software to record the data. Use drawing software to make waveforms and distinguish them by colors.

[0045] Test results such as Figure 4 As shown in the figure, it can be seen from the analysis that as the humidity increases from 12% RH (relative humidity) to 91% RH, the output current increases 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 to provide a good switching ratio.

[0046] ③More than 200 rapid dry-wet cycle tests under high humidity conditions

[0047] Under the condition of keeping the room temperature constant and the airflow in the pipeline constant, the experiment was repeated more than 200 times at a certain humidity at a certain time recorded by the calibration of the hygrometer, and the data was recorded using software. The data recorded at a fixed humidity was used to make a waveform using drawing software.

[0048] Test results such as Figure 5 As shown, analysis shows that the humidity sensor prepared in Example 1 has excellent operational stability after 200 dry-wet cycles, with extremely rapid response and recovery, and extremely small current attenuation, which can be almost ignored.

[0049] Example 2

[0050] A method for preparing a humidity sensor based on a hydrogen-bonded organic framework material comprises the following steps:

[0051] (1) Dissolve 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene in DMF solution by ultrasonication 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 1.5 M NaCl solution and 2 mL of 6 mg / mL PVA solution to 1 mL of the HOFs solution prepared in step (1) to obtain a HOFs composite solution;

[0053] (3) Preparation of electrodes on PET substrate

[0054] (a) Soaking the PET substrate in ethanol and ultrasonically removing stains on the surface of the PET substrate element for 15 minutes;

[0055] (b) Using Ti3C2T x -MXene is coated on the filter paper and dried naturally at room temperature. A laser engraving machine is used to make a 15 mm*5 mm Ti3C2T x -MXene electrode, then Ti3C2T x -MXene electrode electroplating deposits metal Zn to form Zn@Ti3C2T x -MXene electrodes;

[0056] (c) Cut the PET substrate into appropriate size, blow dry it with a nitrogen gun, and use double-sided tape to paste the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrodes, with a spacing of about 2 mm;

[0057] (4) The HOFs composite solution in step (2) is quantitatively drop-casted on the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrodes, and placed in an oven and dried at 60 °C for 2 h to obtain a humidity sensor with the structure shown in Figure 1 shown.

[0058] Example 3

[0059] A method for preparing a humidity sensor based on a hydrogen-bonded organic framework material comprises the following steps:

[0060] (1) Dissolve 1,2,4,5-tetrakis(4-carboxyphenyl)benzene in DMF solution by ultrasonication for 20 min, then add deionized water, stir for 1.5 h, and centrifuge for 20 min to obtain a HOFs solution with a concentration of 8 mg / ml;

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

[0062] (3) Preparation of electrodes on PET substrate

[0063] (a) Soaking the PET substrate in ethanol and ultrasonically removing stains on the surface of the PET substrate element for 15 minutes;

[0064] (b) Using Ti3C2T x-MXene is coated on the filter paper and dried naturally at room temperature. A laser engraving machine is used to make a 15 mm*5 mm Ti3C2T x -MXene electrode, then Ti3C2T x -MXene electrode electroplating deposits metal Zn to form Zn@Ti3C2T x -MXene electrodes;

[0065] (c) Cut the PET substrate into appropriate size, blow dry it with a nitrogen gun, and use double-sided tape to paste the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrodes, with a spacing of about 2 mm;

[0066] (4) The HOFs composite solution in step (2) is quantitatively drop-casted on the Ti3C2T x -MXene electrode and Zn@Ti3C2T x -MXene electrodes, and placed in an oven and dried at 70 °C for 2 h to obtain a humidity sensor with the structure shown in Figure 1 shown.

[0067] The humidity sensor obtained by the present invention has a measurement range covering 12% RH-91% RH, and its response time, sensitivity and stability under high humidity are significantly better than those of existing humidity sensors, as shown in Table 1, and is convenient for practical application and measurement.

[0068] Table 1 Performance comparison between the humidity sensor prepared in Example 1 of the present invention and the existing humidity sensor

[0069]

[0070] The present invention uses HOFs raw materials through ultrasonic, stirring, and centrifugal treatment to obtain a HOFs solution, which can be directly used for the preparation of a humidity sensor. In the present invention, HOFs are mixed by adding a solution such as sodium chloride (NaCl) to form a HOFs composite material as a humidity-sensitive component in a humidity sensor. In addition, in addition to the detailed components (such as electrodes) mentioned in the present invention, other functional components can also be set in the humidity sensor according to actual needs.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a humidity sensor based on a hydrogen-bonded organic framework material, characterized in that: The following steps are involved: (1) Dissolve the HOFs raw material in a solvent by ultrasonication, add deionized water, stir, and centrifuge to obtain a HOFs solution; (2) adding a metal cation solution and an adhesive solution to the HOFs solution of step (1) to obtain a HOFs composite solution; (3) The HOFs composite solution of step (2) is deposited on the prepared electrode substrate by drop casting and then dried in vacuum.

2. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 1, characterized in that: The HOFs raw material in step (1) is , at least one of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene and 1,2,4,5-tetrakis(4-carboxyphenyl)benzene.

3. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 1, characterized in that: In the step (1), DMF is used as the solvent, ultrasonication is performed for 10-20 min, stirring is performed for 0.5-1.5 h, and centrifugation is performed for 10-20 min.

4. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 1, characterized in that: The concentration of the HOFs solution in step (1) is 3-10 mg / mL.

5. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 4, characterized in that: 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.

6. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 5, characterized in that: The volume ratio of the HOFs solution, the metal cation solution and the adhesive solution is (5-15):1:(15-25).

7. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 1, characterized in that: The metal cation solution in step (2) is at least one of a sodium chloride solution, a potassium chloride solution, a magnesium chloride solution, a zinc chloride solution, a calcium chloride solution, and a lithium chloride solution.

8. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 1, characterized in that: The adhesive solution in step (2) is a PVA solution.

9. The method for preparing a humidity sensor based on a hydrogen-bonded organic framework material according to claim 1, characterized in that: The electrode in step (3) is Ti3C2T x -MXene and Zn@Ti3C2T x -MXene electrode, the Zn@Ti3C2T x -MXene electrode made of Ti3C2T x -MXene electrode is made by electroplating and depositing metal Zn.

10. A humidity sensor based on hydrogen-bonded organic framework material, characterized in that: The method is prepared by the method according to any one of claims 1 to 9.

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