CN112763559A - Gamma-polyglutamic acid based humidity sensor and preparation method thereof - Google Patents
Gamma-polyglutamic acid based humidity sensor and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of humidity sensitive elements and preparation thereof, and discloses a gamma-polyglutamic acid based humidity sensor and a preparation method thereof. The gamma-polyglutamic acid based humidity sensor comprises a sensitive device and a humidity sensitive layer arranged on the sensitive device, wherein the humidity sensitive layer is composed of gamma-polyglutamic acid or a composite sensitive material thereof, and the preparation method of the gamma-polyglutamic acid based humidity sensor comprises the following steps: preprocessing a sensitive device; preparing gamma-polyglutamic acid-based sensitive material dispersion liquid; and depositing a single-layer or multi-layer humidity sensitive layer on the sensitive device by using the prepared dispersion liquid, and drying and aging to obtain the humidity sensor. The humidity sensor obtained by utilizing the abundant hydrophilic functional groups and the anion characteristics of the gamma-polyglutamic acid has the advantages of high response, high speed, good repeatability and the like.
Description
Technical Field
The invention relates to the technical field of humidity sensitive elements and preparation thereof, in particular to a gamma-polyglutamic acid based humidity sensor and a preparation method thereof.
Background
The humidity has close relation with the fields of human life, production, animal and plant survival, scientific research and the like, and the environmental humidity has the same important significance as the environmental temperature.
The resistive humidity sensor can be classified into a semiconductor ceramic material base and a polymer base. Although the semiconductor type ceramic material has abundant micro-morphology, the ceramic material-based sensitive film is easy to fall off and is not resistant to bending, and the sensor has low accuracy and is not easy to integrate. The high molecular polymer not only has the soft material characteristic, but also can improve the flexibility characteristic of the sensor; and part of the high molecular polymer has abundant hydrophilic functional groups and has the potential of becoming a humidity sensitive material.
The resistance type high molecular polymer humidity sensor is mainly divided into two types, one is a dilatability organic humidity sensitive element, for example, the invention patent with the application number of 202010813831.6 discloses an asymmetric film type humidity sensor and a preparation method thereof. The graphene oxide and nano-cellulose dispersion liquid is subjected to suction filtration to obtain the composite film. Under the same humidity, the composite membrane deflects due to different degrees of moisture absorption and expansion; the sensor has different curvatures at different humidities. The other is a polyelectrolyte humidity-sensitive element. For example, patent application No. 201910240221.9 discloses a flexible humidity sensor with a fast response characteristic. The invention relates to a flexible humidity sensor based on imidazole ionic liquid. By introducing a layer of nanowire structure into the flexible substrate and adding ionic liquid into the nanowire structure, the response speed of the sensor can be improved. The polymer-based humidity sensor material has wide sources, is suitable for batch production, and is beneficial to developing a high-performance humidity sensor.
Disclosure of Invention
The invention aims to provide a gamma-polyglutamic acid based humidity sensor which is simple to prepare, high in response speed and good in linearity and a preparation method thereof.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a gamma-polyglutamic acid based humidity sensor comprises a sensitive device and a humidity sensitive layer arranged on the sensitive device, wherein the humidity sensitive layer is made of gamma-polyglutamic acid or a composite sensitive material thereof.
Further, the sensitive device is an interdigital electrode of a rigid substrate or a flexible substrate, a quartz crystal microbalance or a surface acoustic wave device.
Further, the rigid substrate is a rigid silicon-based substrate, a ceramic substrate or an aluminum oxide substrate, and the flexible substrate is flexible polyimide, polyethylene terephthalate, polyurethane, a cloth base or a paper base.
Furthermore, the number of the interdigital electrodes is 1-50 pairs, and the fork value interval of each pair of fork value electrodes is 5-500 mu m.
Further, the thickness of the humidity sensitive layer is 50 nm-500 μm.
Further, the composite sensitive material is gamma-polyglutamic acid composite metal oxide and/or carbon material and/or inorganic salt.
The invention also provides a preparation method of the gamma-polyglutamic acid based humidity sensor, which comprises the following steps:
s1, preprocessing a substrate of the sensitive device, including cleaning, drying and hydrophilic processing;
s2, preparing gamma-polyglutamic acid dispersion or gamma-polyglutamic acid-based composite sensitive material dispersion;
s3, depositing the sensitive material dispersion liquid on the sensor substrate to form a humidity sensitive layer;
and S4, drying and aging the sensitive device with the humidity sensitive layer.
Further, in step S2, the solvent of the sensitive material dispersion liquid is deionized water, ethanol, acetone, or N-methylpyrrolidone.
Further, in step S3, the deposition process of the sensitive material dispersion liquid includes coating with a paint pen, spraying, spin coating, dropping, dipping or self-assembly.
Further, in step S3, the humidity sensitive layer is a single layer or a plurality of layers.
The invention has the following beneficial effects:
the invention provides a gamma-polyglutamic acid based humidity sensor and a preparation method thereof, and the humidity sensor with large response, high speed and good repeatability is developed by combining the hydrophilicity and anion characteristics of gamma-polyglutamic acid; the gamma-polyglutamic acid based humidity sensor has simple structure and simple process, and is beneficial to large-scale manufacture and popularization; due to the soft material characteristic of the gamma-polyglutamic acid, the method can be used for designing and preparing the flexible humidity sensor, and the bending resistance characteristic of the sensitive film and the adhesion of the sensitive film and the substrate are improved.
Drawings
FIG. 1 is a flow chart of the preparation of a gamma-polyglutamic acid based humidity sensor according to the present invention;
FIG. 2 is an infrared spectrum of gamma-polyglutamic acid according to the present invention;
FIG. 3 is a graph showing the real-time variation of the resistance-Relative Humidity (RH) of the gamma-polyglutamic acid based humidity sensor of the present invention;
FIG. 4 is a graph of the hysteresis of a gamma-polyglutamic acid based humidity sensor in accordance with the present invention;
FIG. 5 is a graph of the response time of a gamma-polyglutamic acid based humidity sensor in accordance with the present invention;
fig. 6 is a graph of 6 cycle response versus time for a gamma-polyglutamic acid based humidity sensor of the present invention at 0% and 50% RH switching.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and examples.
As shown in fig. 1, the method for preparing a γ -polyglutamic acid based humidity sensor provided by the present invention comprises the following steps:
(1) pretreating a substrate of a sensitive device, wherein the pretreatment comprises the treatment processes of cleaning, drying, hydrophilic treatment and the like;
(2) preparing gamma-polyglutamic acid dispersion or gamma-polyglutamic acid-based composite sensitive material dispersion;
(3) depositing the sensitive material dispersion liquid on the sensor substrate to form a humidity sensitive layer;
(4) and drying and aging the sensitive device with the humidity sensitive layer to obtain the gamma-polyglutamic acid based humidity sensor.
In the above method, the solvent for preparing the sensitive material dispersion in step (2) may be selected from deionized water, ethanol, acetone, N-methylpyrrolidone, or the like. The deposition process of depositing the sensitive material dispersion on the sensitive device substrate to form the humidity sensitive layer in step (3) includes, but is not limited to, coating with a paint pen, spray coating, spin coating, drop coating, dip coating or self-assembly process. It is noted that the humidity sensitive layer prepared by the above preparation method may be one layer or a plurality of layers. The solvent of the sensitive material dispersion liquid, the deposition process of the humidity sensitive layer and the layer number selection of the humidity sensitive layer can be selected and prepared according to the needs of designers.
Example 1
The sensing device selected in the embodiment is an interdigital electrode, the interdigital electrode is a gold electrode manufactured on a flexible Polyimide (PI) substrate, the interdigital distance of the interdigital electrode is 200 μm, the interdigital width of the interdigital electrode is 200 μm, and the electrode thickness of the interdigital electrode is 100 nm. In the embodiment, pure gamma-polyglutamic acid is selected as a humidity sensitive material, and a dropping coating process is adopted to prepare the gamma-polyglutamic acid based humidity sensitive layer, and the specific preparation steps are as follows:
(1) pretreating a PI substrate gold interdigital electrode, and cleaning with ionized water, acetone, alcohol and deionized water; after drying, carrying out ultraviolet hydrophilic treatment for 30 min;
(2) preparing gamma-polyglutamic acid dispersion liquid, wherein a solvent is deionized water, preparing the gamma-polyglutamic acid dispersion liquid with the concentration of 0.1mg/mL, and performing ultrasonic treatment for later use;
(3) preparing a humidity sensitive film on an interdigital electrode of a flexible PI substrate by a drop coating process; drying for 12 hours at the temperature of 60 ℃, and then circularly aging the sensor for 12 hours in a dry and wet environment to obtain the gamma-polyglutamic acid based humidity sensor.
Example 2
The sensing device selected in the embodiment is a Quartz Crystal Microbalance (QCM) device, the upper and lower metal electrodes of the QCM device are silver electrodes, and the fundamental frequency of the QCM device is 9.98 MHz; in the embodiment, pure gamma-polyglutamic acid is selected as a humidity sensitive material, and the specific preparation steps are as follows:
(1) pretreating the QCM device, and cleaning with ionized water, acetone, alcohol and deionized water; after drying, carrying out plasma treatment for 20 min;
(2) preparing gamma-polyglutamic acid dispersion liquid, wherein a solvent is deionized water, preparing the gamma-polyglutamic acid dispersion liquid with the concentration of 0.1mg/mL, and performing ultrasonic treatment for later use;
(3) respectively spraying 0.2mL of dispersion liquid on two surfaces of the QCM device by a spraying process to prepare a humidity sensitive film; drying for 12 hours at the temperature of 60 ℃, and then circularly aging the sensor for 12 hours in a dry and wet environment to obtain the gamma-polyglutamic acid based humidity sensor.
Example 3
In the embodiment, a sensitive device is selected as an interdigital electrode, the interdigital electrode is a nickel-chromium-gold electrode on a flexible polyethylene glycol terephthalate (PEI) substrate, the interdigital distance of the interdigital electrode is 50 microns, the interdigital width is 50 microns, and the electrode thickness is 100 nm; in the embodiment, gamma-polyglutamic acid composite zinc oxide is used as a humidity sensitive material. The nanometer appearance of zinc oxide can provide more adsorption sites for water molecules. The gamma-polyglutamic acid-based humidity-sensitive composite film is prepared by adopting a spin coating process, and the specific preparation steps are as follows:
(1) pretreating the nickel-chromium-gold interdigital electrode of the PET substrate, and cleaning with ionized water, acetone, alcohol and deionized water; after drying, carrying out ultraviolet hydrophilic treatment for 10 min;
(2) preparing gamma-polyglutamic acid dispersion liquid, wherein a solvent is deionized water, preparing the gamma-polyglutamic acid dispersion liquid with the concentration of 0.5mg/mL, and performing ultrasonic treatment for later use; preparing zinc oxide dispersion liquid, wherein a solvent is deionized water, preparing the zinc oxide dispersion liquid with the concentration of 0.1mg/mL, and performing ultrasonic treatment for later use;
(3) spin-coating a layer of gamma-polyglutamic acid film on a PET substrate by a spin-coating process, and then spin-coating a layer of zinc oxide film on the gamma-polyglutamic acid film by utilizing the viscosity of the gamma-polyglutamic acid; and (3) repeatedly and sequentially spin-coating the gamma-polyglutamic acid and the zinc oxide layer to obtain the gamma-polyglutamic acid-based humidity-sensitive composite film.
(4) Drying for 12 hours at the temperature of 60 ℃, and then circularly aging the sensor for 12 hours in a dry and wet environment to obtain the gamma-polyglutamic acid based humidity sensor.
Test examples
Performance tests were performed on the basis of one of the γ -polyglutamic acid based humidity sensors prepared in example 1, and the performance tests were performed according to methods already disclosed in the art. The specific method comprises the following steps: the resistance signals of the above prepared sensors were tested using an AES-4SD device analyzer, and different Relative Humidity (RH) environments were obtained by the bubbling method and calibrated by a high precision humidity sensor, the test humidities including 0%, 28.8%, 41.1%, 60.8%, 72.0%, 79.3%, 84.5% and 91.5% RH.
The infrared spectrum of the gamma-polyglutamic acid sensitive layer in the present example is shown in FIG. 2. As can be seen from the figure, gamma-polyglutamic acid has abundant hydrophilic functional groups, such as amino, carboxyl and amido bonds.
As shown in fig. 3, a real-time resistance change curve of the γ -polyglutamic acid based humidity sensor at 28.8% -91.5% RH is shown. As can be seen from the figure, the humidity response range of the sensor is wide, and the response changes by more than three orders of magnitude under a high humidity state. Through calculation, the sensor has the characteristic of piecewise linearity, and the linearity is 0.9954 within the range of 28.8% -72.0% RH; linearity was 0.9957 in the range of 72.0% to 91.5% RH.
FIG. 4 shows a graph of the wet hysteresis of a gamma-polyglutamic acid based humidity sensor. The hysteresis of the sensor was calculated to be 3.0% RH.
Fig. 5 shows a response time curve for a gamma-polyglutamic acid based humidity sensor. As shown, the sensor has a fast response time of about 4s at 91.5% RH; the recovery time was approximately 43 s.
Fig. 6 shows 6 cyclic response-time plots of the gamma-polyglutamic acid based humidity sensor at 0% RH and 50% RH switching. As shown in the figure, the sensor can quickly reach a stable state after humidity switching, and shows good repeatability.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention, the scope of the present invention is defined by the appended claims, and all equivalent changes made by applying the contents of the description of the present invention should be embraced in the scope of the present invention.
Claims (10)
1. The gamma-polyglutamic acid based humidity sensor is characterized by comprising a sensitive device and a humidity sensitive layer arranged on the sensitive device, wherein the humidity sensitive layer is made of gamma-polyglutamic acid or a composite sensitive material thereof.
2. The gamma-polyglutamic acid based humidity sensor of claim 1, wherein the sensing device is an interdigital electrode of a rigid substrate or a flexible substrate, a quartz crystal microbalance or a surface acoustic wave device.
3. The γ -polyglutamic acid based humidity sensor according to claim 2, wherein the rigid substrate is a rigid silicon-based substrate, a ceramic substrate or an alumina substrate, and the flexible substrate is a flexible polyimide, polyethylene terephthalate, polyurethane, cloth-based or paper-based substrate.
4. The γ -polyglutamic acid based humidity sensor according to claim 2, wherein the number of the interdigital electrodes is 1 to 50 pairs, and the fork value spacing of each pair of the interdigital electrodes is 5 to 500 μm.
5. The γ -polyglutamic acid based humidity sensor according to claim 1, wherein the humidity sensitive layer has a thickness of 50nm to 500 μm.
6. The gamma-polyglutamic acid based humidity sensor according to claim 1, wherein the composite sensitive material is gamma-polyglutamic acid composite metal oxide and/or carbon material and/or inorganic salt.
7. A preparation method of a gamma-polyglutamic acid based humidity sensor is characterized by comprising the following steps:
s1, preprocessing a substrate of the sensitive device, including cleaning, drying and hydrophilic processing;
s2, preparing gamma-polyglutamic acid dispersion or gamma-polyglutamic acid-based composite sensitive material dispersion;
s3, depositing the sensitive material dispersion liquid on the sensor substrate to form a humidity sensitive layer;
and S4, drying and aging the sensitive device with the humidity sensitive layer.
8. The method as claimed in claim 7, wherein in step S2, the solvent of the sensitive material dispersion is deionized water, ethanol, acetone or N-methylpyrrolidone.
9. The method of claim 7, wherein the step S3, the sensitive material dispersion is deposited by a process selected from the group consisting of pen coating, spray coating, spin coating, drop coating, dip coating, and self-assembly.
10. The method of claim 7, wherein in step S3, the humidity sensitive layer is a single layer or multiple layers.
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| CN114166901A (en) * | 2021-12-06 | 2022-03-11 | 吉林大学 | Gold nanoparticle-loaded metal organic framework material, low-humidity sensor with gold nanoparticle-loaded metal organic framework material as sensing material and preparation method of low-humidity sensor |
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| CN109613071A (en) * | 2019-01-11 | 2019-04-12 | 电子科技大学 | The humidity sensor and preparation method thereof of wet sensitive composite membrane based on polylysine modification carbon-based material |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114166901A (en) * | 2021-12-06 | 2022-03-11 | 吉林大学 | Gold nanoparticle-loaded metal organic framework material, low-humidity sensor with gold nanoparticle-loaded metal organic framework material as sensing material and preparation method of low-humidity sensor |
| CN114166901B (en) * | 2021-12-06 | 2024-04-26 | 吉林大学 | Gold nanoparticle-loaded metal organic framework material, low-humidity sensor using same as sensing material and preparation method |
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