CN113087942A

CN113087942A - Conductive ionic gel membrane, preparation method thereof and clean energy collecting device

Info

Publication number: CN113087942A
Application number: CN202110349926.1A
Authority: CN
Inventors: 邢孟秋; 叶海雁; 刘抗; 郭瀛军
Original assignee: Zhejiang Depp Medical Polytron Technologies Inc
Current assignee: Zhejiang Depp Medical Polytron Technologies Inc
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2021-07-09

Abstract

The invention provides a conductive ion gel film, a preparation method thereof and a clean energy collecting device, the conductive ion gel film according to the embodiment of the invention comprises the following components: a film matrix comprising a polyacrylic acid hydrogel and a conductive nanofiller dispersed in the polyacrylic acid hydrogel; and the polyaniline coating is formed on at least one side surface of the film matrix. According to the conductive ionic gel film disclosed by the embodiment of the invention, the polyacrylic acid hydrogel is used as a matrix, the conductive nano filler is dispersed in the matrix, the PAA hydrogel has excellent mechanical properties, the mechanical stress of the PAA hydrogel can be further improved by adding the conductive nano filler, and the film matrix has conductive performance, and on the basis, the polyaniline coating is formed on the surface of the film matrix and has excellent electrochemical properties after being combined with the PAA hydrogel, such as capacity and overall electrical properties can be improved, so that the conductive ionic gel film becomes a useful material of a plant wearable sensor.

Description

Conductive ionic gel membrane, preparation method thereof and clean energy collecting device

Technical Field

The invention relates to the technical field of intelligent agriculture, in particular to a conductive ionic gel film, a preparation method thereof and application thereof in a clean energy collecting device, a sensor and electronic skin.

Background

Along with global climate change and unsafe grain, great threat is brought to human beings. The growth of population and the increase in global food demand require higher agricultural productivity and efficiency, however, the application of large amounts of synthetic fertilizers can limit crop productivity on the one hand and also cause environmental problems. For example, nitrous oxide is one of the major gases emitted by agricultural activities, accounting for approximately half of the warming effect. There is therefore a need to reduce agricultural greenhouse gas emissions to reduce their impact on climate change.

For this reason, it is desired to develop intelligent agriculture that improves the quantity and quality of agricultural products in an eco-friendly manner. Sensing technology and light fertilizer are two technologies relied on by intelligent agriculture. In smart agriculture, it is known to use Light Emitting Diodes (LEDs) instead of traditional soil fertilizers. Light Emitting Diode (LED) lamps have a peak emission wavelength ranging from UV-C

To the infrared

By tuning the LED lights to a wavelength that matches the photoreceptors of a particular plant, the plant can achieve higher productivity. For example, red and blue LED lights greatly promote the growth of leafy vegetables, tomatoes, cucumbers and peppers. Despite the excellent performance in green agriculture, the large power consumption of LED boost systems limits their practical applications. Therefore, self-powered light fertilizer systems are needed to meet the large energy consumption.

On the other hand, our environment is flooded with clean energy such as air flow, sound and rain. These clean energy sources can be harvested by triboelectric nano-generators (TENG) and converted into electrical energy. By using triboelectric materials, mechanical energy can be converted into electrical energy, which drives light fertilizers, sensors or actuators. Recently triboelectric energy generators using different triboelectric polymers, including, for example, polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), have been developed to harvest clean energy. However, in order to improve the energy collection efficiency, such triboelectric materials (PVDF, PTFE, PET) need to be surface modified to increase the effective contact area. Special patterns such as nanowires and nanoparticles are commonly used for surface modification of triboelectric materials. However, in order to prepare these special patterns, high-cost, complicated techniques such as inductively coupled plasma dry etching are required.

Sensor technology is one of the most important components in intelligent agriculture. It requires deployment of various sensors integrated over a network. Plant wearable sensors, which facilitate site-specific monitoring of environmental conditions such as temperature, humidity and soil nutrient, as well as monitoring of plant growth rate, allow for precise management during cultivation and thereby improve efficiency and productivity. However, the real-time plant wearable sensor using the polymer tape and/or Polydimethylsiloxane (PDMS) as the base material has a limitation in the sensing range. For example, the wearable tape sensor shows that only 7% strain corresponds to a change in resistance. Whereas PDMS-based plant sensors have a linear dependence in the strain range of 25%.

On the other hand, a thin film sensor made of carbon material provides a method for monitoring ammonia gas, which is also a component of farm systems that need to be monitored. Existing thin film sensors, although having short response times and high sensitivity, have limited stretchability.

That is, all of the above materials used to make plant real-time wearable sensors and ammonia sensors have limited stretchability, and thus are not feasible for fast growing plants. Moreover, the electrodes of the sensors are usually made of expensive noble metals (Au, Ti). To mount these electrodes on the sensor, advanced techniques and equipment such as electron beams, high pressure steam, etc. are required.

Therefore, it is desirable to develop a plant wearable sensor for smart agriculture that is scalable, low-cost, and highly sensitive.

The conductive ionic gel membrane according to the embodiment of the invention can be used for cleaning energy collecting devices, sensors and electronic skins.

Disclosure of Invention

The inventor finds that the hydrogel has excellent tensile property and strength, is easy to manufacture, has high electrochemical activity and multiple functions, and is expected to be used for developing a plant wearable sensor. But triboelectric nanogenerators using hydrogels in smart agriculture systems have not been explored to date.

In view of the above, the present invention aims to provide a conductive ionic gel membrane which has high elasticity and excellent mechanical properties and is easy to prepare and applicable to a plant wearable sensor.

The invention also aims to provide a preparation method of the conductive ionic gel film.

It is still another object of the present invention to provide the use of the above conductive ionic gel membrane for cleaning energy harvesting devices, sensors, and electronic skins.

In order to solve the technical problems, the invention adopts the following technical scheme:

a conductive ionic gel membrane according to an embodiment of the first aspect of the present invention, comprising:

a film matrix comprising a polyacrylic acid hydrogel and a conductive nanofiller dispersed in the polyacrylic acid hydrogel;

and the polyaniline coating is formed on at least one side surface of the film matrix.

According to the conductive ionic gel film disclosed by the embodiment of the invention, the polyacrylic acid hydrogel is used as a matrix, the conductive nano filler is dispersed in the matrix, the PAA hydrogel has excellent mechanical properties, the mechanical stress of the PAA hydrogel can be further improved by adding the conductive nano filler, and the film matrix has conductive performance.

Further, the conductive nanofiller is reduced graphene oxide. Reduced Graphene Oxide (RGO) has a higher C/O ratio in the graphene structure than Graphene Oxide (GO), and thus has better conductivity than GO.

Further, the film matrix is formed by polymerizing acrylic acid monomer and a dispersion of reduced graphene oxide in water under the action of a cross-linking agent and an initiator, wherein the acrylic acid monomer: the mass ratio of the reduced graphene oxide is 5 (1-4). Specifically, reduced graphene oxide is dispersed in an aqueous solution of an acrylic monomer, and after the reduced graphene oxide is sufficiently dispersed, a cross-linking agent and an initiator are added to initiate polymerization of the acrylic monomer, so that a film matrix is formed. That is, the film matrix is a network of polyacrylic acid in which reduced graphene oxide particles are uniformly dispersed as a conductive nanofiller, forming a PAA-RGO composite hydrogel. Compared with the PAA hydrogel, the PAA-RGO composite hydrogel has better electrical properties, and the mechanical properties of the membrane matrix are further improved by adding RGO.

Further, the crosslinking agent includes an ionic crosslinking agent and a covalent crosslinking agent. That is, ionic crosslinks forming reversible ionic bonds by the ionic crosslinker, covalent crosslinks forming irreversible covalent bonds by the covalent crosslinker, and double network structures formed by ionic crosslinks and covalent crosslinks, so that the PAA-RGO composite hydrogel has excellent stretchability and strength.

Further, the ionic crosslinking agent is calcium chloride, the covalent crosslinking agent is N, N' -Methylene Bisacrylamide (MBA), and the initiator is Ammonium Persulfate (APS). That is, in the dispersion of acrylic acid monomer and reduced graphene oxide in water, calcium chloride is added to form ionic bonding between calcium ions and PAA, and irreversible chemical bonding is formed by adding MBA. With regard to the amount of calcium chloride, reference may be made to the amount of MBA, that is to say, it may be introduced in the 1:1 form. In addition, with respect to the amount of MBA and APS, the specific amount of the acrylic monomer used in the polymerization reaction can be referred to, and is not particularly limited herein.

Further, the thickness of the conductive ionic gel film is between 50 and 1000 microns. The conductive ionic gel film with the thickness is suitable for being applied to a plant wearable sensor.

The preparation method of the conductive ionic gel membrane according to the second aspect of the invention comprises the following steps:

step S1, providing an acrylic monomer;

step S2, adding conductive nano filler powder, a cross-linking agent and an initiator into the acrylic monomer to polymerize the acrylic monomer to obtain a film matrix;

step S3, coating aniline on at least one side surface of the film matrix, and polymerizing the aniline to form a polyaniline coating on the surface of the film matrix, so as to obtain the conductive ionic gel film.

That is, according to the method for preparing the conductive ionic gel film of the embodiment of the present invention, an acrylic monomer is first provided, then conductive nano filler powder, a cross-linking agent, and an initiator are introduced into the monomer, and after being sufficiently mixed, cross-linking polymerization is performed to obtain a conductive film substrate, and then aniline is coated on the surface of the film substrate to form a polyaniline coating layer, thereby further improving the electrical properties and sensitivity of the film substrate, and obtaining the conductive particle gel film having excellent tensile properties and strength, easy manufacturing, high electrochemical activity, and multiple functionalities.

Further, the conductive nano filler powder is reduced graphene oxide. As described above, reduced graphene oxide has better conductivity than graphene oxide. The reduced graphene oxide powder can be commercial powder, and preferably, the reduced graphene oxide powder is prepared by taking graphene oxide as a raw material through a hydrothermal conversion method.

Specifically, for example, graphene oxide powder is added to deionized water and dispersed for 1 hour by an ultrasonic homogenizer, and then the dispersion is placed in an autoclave and heated in an oven at 180 ℃ for 8 hours to perform hydrothermal conversion, thereby converting the graphene oxide powder into reduced graphene oxide powder. After that, the obtained product was taken out from the autoclave, filtered, washed, and freeze-dried to obtain RGO powder.

Further, the step S2 includes:

step S21, preparing reduced graphene oxide powder by taking graphene oxide as a raw material through a hydrothermal conversion method;

step S22, dispersing the reduced graphene oxide powder in water to obtain a suspension;

step S23 of dispersing the suspension in the acrylic acid monomer to obtain the dispersion;

and step S24, adding a cross-linking agent and an initiator into the dispersion liquid, and curing at 40-50 ℃ to form the film matrix.

That is, after obtaining RGO powder, it is dispersed in water to obtain a suspension, and then the suspension is added to an acrylic monomer to prepare a dispersion, and thereafter a crosslinking agent and an initiator are added, and thereafter the dispersion with the crosslinking agent and the initiator added is cured in a water bath at 40 to 50 ℃ for 20 minutes to obtain a PAA-RGO composite hydrogel, that is, a membrane substrate.

Further, in the suspension, the mass concentration of the reduced graphene oxide powder in the suspension is 3-20g/L, and the volume concentration of the acrylic acid monomer in the dispersion is 10-25%. That is, a suspension of reduced graphene oxide powder having a predetermined concentration is prepared, and then a dispersion of an acrylic monomer having a predetermined concentration is prepared using the suspension, wherein the mass ratio of the acrylic monomer to the reduced graphene oxide powder in the dispersion is 5 (1-4). For example, the dispersion is prepared by adding 4 times the volume of the suspension to an acrylic monomer, and thereafter, a crosslinking agent and an initiator are added. Reference is made to the above for the crosslinking agent, the initiator, and the amount thereof, which are not described in detail herein.

Further, the step S3 includes:

step S31, providing aniline monomer solution;

step S32, adding an initiator into the aniline monomer solution to obtain a premixed solution;

step S33, dipping the film substrate in the pre-mixed liquid to polymerize aniline monomer on the surface of the film substrate to form the polyaniline coating.

That is, after a PAA-RGO film matrix of a double cross-linked network is obtained, a polyaniline coating is provided on the film matrix to improve sensitivity and comprehensive electrical properties.

Preferably, in step S31, aniline monomer is added to 1M hydrochloric acid aqueous solution and mixed to obtain the aniline monomer solution. That is, the polyaniline can exhibit high conductivity by doping the polyaniline with protonic acid.

Specifically, the electrical activity of polyaniline results from the P-electron conjugated structure in the molecular chain: as the P electron system in the molecular chain expands, the P bonding state and the P-reverse bonding state form a valence band and a conduction band respectively, and the non-localized P electron conjugated structure can form a P type and an N type conduction state after doping. Different from the doping mechanism of other conducting polymers which generate cation vacancy under the action of an oxidant, the electron number is not changed in the doping process of polyaniline, but H is generated by the decomposition of doped protonic acid⁺And anions (such as chloride ions, sulfate radicals, phosphate radicals and the like) enter a main chain, and are combined with N atoms in amine and imine groups to form a polar ion and a dipole ion delocalized into a P bond of the whole molecular chain, so that the polyaniline has higher conductivity. The unique doping mechanism makes the doping and de-doping of polyaniline completely reversible, the doping degree is influenced by factors such as pH value and potential, and the like, and shows corresponding change of appearance color, and the polyaniline also has electrochemical activity and electrochromic property.

In addition, in step S32, the initiator may be ammonium persulfate. And in the step S33, the reaction temperature is controlled to be 0-10 ℃, the dipping time is 4-12 hours, and after the dipping is finished, the film substrate with the polyaniline coating formed on the surface is taken out and washed by deionized water, so as to obtain the conductive ion gel film.

As an example, for example: 300 μ L of aniline monomer was added to 50mL of 1M HCl solution with constant stirring in an ice-water bath, after which 375mg of APS was added and dissolved well. Then, the PAA-RGO composite hydrogel obtained in the above way is placed in the water, soaked for 8 hours, then taken out, and washed by water for several times to remove the residual aniline monomer and APS on the surface, thus obtaining the PAA-RGO-PANI conductive ionic gel film with a polyaniline coating (PANI, functioning as a nano composite electrode) formed on the surface.

As can be seen from the description, the preparation method has the advantages of simple process, controllable cost and relative environmental protection, and the obtained PAA-RGO-PANI conductive ionic gel membrane has high elasticity and excellent mechanical properties.

The clean energy collecting device comprises a polyimide film, the conductive ionic gel film and an aluminum foil which are sequentially laminated from top to bottom, wherein the conductive ionic gel film is connected with an open circuit device to collect the clean energy generated by the conductive particle gel film.

The sensor according to the invention comprises:

the conductive ionic gel film of any one of the above;

and a polyvinyl alcohol coating, a polydimethylsiloxane coating or a vaseline coating formed on the conductive ionic gel film.

Further, the sensor is a plant growth sensor or an ammonia gas detection sensor.

The electronic skin comprises the sensor.

Drawings

FIG. 1 is a schematic structural view of a PAA-RGO-PANI conductive ionic gel membrane obtained at various stages in the process according to example 1 of the present invention;

FIG. 2 shows SEM images of a PAA hydrogel, a PAA-RGO composite hydrogel, and a PAA-RGO-PANI conductive ionic gel film, wherein (a) shows an SEM image of the PAA hydrogel and (b) shows an SEM image of the PAA-RGO (5mg/ml) composite hydrogel; (c) SEM images of PAA-RGO (10mg/ml) composite hydrogels are shown; (d) SEM images of PAA-RGO (15mg/ml) composite hydrogels are shown; (e) SEM images showing the surface of a PAA-RGO (15mg/ml) -PANI conductive ionic gel membrane;

FIG. 3 shows FTIR spectra of PAA hydrogel, PAA-RGO composite hydrogel, and PAA-RGO-PANI conductive ionic gel film samples;

FIG. 4 shows the results of dynamic mechanical property testing of PAA hydrogels and PAA-RGO-PANI conductive ionic gel film samples, where (a) is a plot of the storage modulus (G ') and loss modulus (G') of PAA; (b) curves for storage modulus (G ') and loss modulus (G') of PAA-RGO (5mg/ml) -PANI; (c) curves for storage modulus (G ') and loss modulus (G') of PAA-RGO (10mg/ml) -PANI; (d) curves of storage modulus (G ') and loss modulus (G') for PAA-RGO (15mg/ml) -PANI;

FIG. 5 shows a graph of mechanical properties of a PAA hydrogel, a PAA-RGO composite hydrogel, and a PAA-RGO-PANI conductive ionic gel film, wherein (a) shows the strain stress curves of PAA and PAA-RGO; (b) shows the strain stress curve of PAA-RGO-PANI; (c) the Young's modulus and toughness of PAA and PAA-RGO are shown; (d) the Young's modulus and toughness of PAA-RGO-PANI are shown;

fig. 6 is a schematic view showing a structure, a schematic view showing an operation principle, and a test result of the clean energy collecting apparatus according to embodiment 2 of the present invention, wherein (a) shows a schematic view showing a structure of the clean energy collecting apparatus; (b) a schematic diagram of the working principle of the clean energy collecting device is shown; (c) PAA-RGO (15mg/ml) -PANI collects the test results from the wind energy and shows a diagram;

FIG. 7 is a schematic view showing a plant growth sensor and the detection results according to example 3 of the present invention;

FIG. 8 is a graph showing the results of detection when ammonia gas is detected by the ammonia gas detecting sensor according to example 4 of the present invention, wherein (a) the result of measurement of an ammonia water concentration of 8.62 ppm; (b) the ammonia concentration was 93.7 ppm; (c) the ammonia concentration was 203 ppm; (d) a measurement result of an ammonia water concentration of 537 ppm;

fig. 9 is a schematic view illustrating an application scenario of the conductive ionic gel membrane according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.

A conductive ionic gel film and a method of preparing the same according to an embodiment of the present invention will be described first with reference to fig. 1.

Example 1 preparation of conductive Ionic gel films

(1) Preparation of PAA-RGO film matrix

1. Preparation of reduced graphene oxide powder

And adding the graphene oxide powder into deionized water at a ratio of 5mg/ml by using an ultrasonic homogenizer, and homogenizing for 1 hour until the graphene oxide powder is fully dispersed. And then, placing the dispersion liquid in an autoclave coated with Teflon, preserving the heat for 8 hours in an oven at 180 ℃, then carrying out solid-liquid separation, washing with deionized water, and carrying out freeze drying to obtain the reduced graphene oxide powder.

And dispersing the obtained reduced graphene oxide powder in deionized water at the ratio of 5mg/ml, 10mg/ml and 15mg/ml, and performing ultrasonic treatment to obtain a suspension for later use.

PAA-RGO membrane substrate

80ml of each of the suspensions prepared above at concentrations of 5mg/ml, 10mg/ml and 15mg/ml was added to 20ml of an acrylic monomer, and the mixture was sufficiently stirred to obtain a dispersion.

Then, 30. mu.L of an aqueous calcium chloride solution (30 mg/mL in concentration), 30. mu.L of an aqueous MBA solution (30 mg/mL in concentration) and 30. mu.L of an aqueous APS solution (300 mg/mL in concentration) were added to the dispersion and stirred uniformly, and the mixture was heated in a warm water bath at 40 to 50 ℃ for 20 minutes to cure the mixture, thereby obtaining a PAA-RGO composite hydrogel.

A composite hydrogel prepared using an RGO suspension at a concentration of 5mg/ml was designated as PAA-RGO (5mg/ml), a composite hydrogel prepared using an RGO suspension at a concentration of 10mg/ml was designated as PAA-RGO (10mg/ml), and a composite hydrogel prepared using an RGO suspension at a concentration of 15mg/ml was designated as PAA-RGO (15 mg/ml).

(2) Preparation of PAA-RGO-PANI conductive ionic gel membrane

After the film matrix is obtained, a polyaniline coating is further added on the surface of the film matrix so as to improve the sensitivity and the comprehensive electrical property of the film matrix.

The method comprises the following specific steps:

in an ice-water bath, 300. mu.L of aniline monomer was added to 50ml of 1M HCl while stirring, and the ice-water bath was kept stirring for 10min while 375mg of APS was dissolved with 10ml of 1M HCl and cooled to 0 ℃. The dissolved APS solution was added to the monomer solution of aniline to form a homogeneous premix. Thereafter, the PAA-RGO (5mg/ml), the PAA-RGO (10mg/ml) and the PAA-RGO (15mg/ml) obtained above were immersed in the above premix for 8 hours, respectively, to polymerize on the surface of the PAA-RGO film substrate to form a polyaniline coating.

And then taking out, and washing the surface for 3 times by using deionized water to remove residual aniline monomer and APS on the surface to obtain the PAA-RGO-PANI conductive ionic gel film.

The conductive ionic gel film obtained using PAA-RGO (5mg/ml) was designated as PAA-RGO (5mg/ml) -PANI, the conductive ionic gel film obtained using PAA-RGO (10mg/ml) was designated as PAA-RGO (10mg/ml) -PANI, and the conductive ionic gel film obtained using PAA-RGO (15mg/ml) was designated as PAA-RGO (15mg/ml) -PANI.

Comparative example 1

In order to compare between the PAA hydrogel and the above-described conductive ionic gel according to example 1 of the present invention, the PAA hydrogel was prepared in the same manner as in example 1, except that 80ml of deionized water was directly added instead of the suspension.

FIG. 1 shows a schematic structural diagram of the membrane obtained at different stages in the process of making a PAA-RGO-PANI conductive ionic gel membrane according to example 1 of the present invention. That is, a double network cross-linked structure exists in the PAA-RGO-PANI conductive ionic gel membrane, one of the networks is from acrylic acid and ionic cross-linker (Ca)²⁺) With an ionic cross-linking between them, which acts as a dynamic, reversible cross-linking, the other network being caused by a covalent cross-linking agent (MBA) which causes in situ polymerization between the acrylic monomers.

The gels were evaluated for the following properties.

(a) Microstructure evaluation

To observe the microstructure, the different gels obtained at the above stages were freeze-dried, placed and gold-sprayed on slides, and then observed with a JEOL JSM-5900LV scanning electron microscope.

FIG. 2 shows SEM photographs of the PAA hydrogel of comparative example 1, and the PAA-RGO (5mg/ml), PAA-RGO (10mg/ml), PAA-RGO (15mg/ml) -PANI obtained in example 1, respectively.

Wherein (a) shows a PAA hydrogel with visible pore sizes of microns and a uniformly distributed porous structure; (b) to (d) shows the microstructure of the membrane matrix obtained from the RGO suspensions at different concentrations, it can be seen that the RGO nanofillers are uniformly distributed in the polymer matrix and that with increasing RGO concentration an increase in the RGO filler in the PAA matrix can be observed.

Further, it was found from (e) and (f) that PANI was uniformly formed on the PAA-RGO (15mg/ml) membrane substrate.

(b) Intermolecular interaction

In addition, to investigate the effect between the molecules in PAA, PAA-RGO, and PAA-RGO-PANI gels, FTIR tests were performed on lyophilized PAA, PAA-RGO (15mg/ml), and PAA-RGO (15mg/ml) -PANI, respectively, using a Thermo Nicolet iS10 FTIR spectrometer. The test results are shown in fig. 3. As can be seen from FIG. 3, 1697cm which is ascribed to the carbonyl group in the side chain of PAA was observed in the spectrum of the PAA hydrogel^-1(iii) a peak at (d); 1541cm from RGO can be observed in the PAA-RGO (15mg/ml) spectrum^-1(iii) a peak at (d); 1402cm derived from PANI can be observed in the PAA-RGO (15mg/ml) -PANI spectrum^-1Peak (benzene ring C ═ C stretch) and 1566cm^-1The peak at (quinone ring C ═ C stretch) indicates that PANI in PAA-RGO (15mg/ml) -PANI is in the emeraldine salt state.

(c) Evaluation of dynamic mechanical Properties

In addition, for the rheological characterization of the above hydrogels, samples of each of the above gels (diameter 8mm, thickness 1mm) were loaded on parallel plates with a diameter of 20 mm. In the oscillatory frequency experiment, the rheological characteristics of the samples were measured at a constant strain of 0.5% at 21 ℃ in the frequency range from 0.1 to 100rad s/1.

FIG. 4 shows the results of dynamic mechanical property testing of PAA hydrogel and PAA-RGO-PANI conductive ionic gel film samples, respectively, where (a) is a plot of the storage modulus (G ') and loss modulus (G') of PAA; (b) curves for storage modulus (G ') and loss modulus (G') of PAA-RGO (5mg/ml) -PANI; (c) curves for storage modulus (G ') and loss modulus (G') of PAA-RGO (10mg/ml) -PANI; (d) curves of storage modulus (G ') and loss modulus (G') for PAA-RGO (15mg/ml) -PANI. As can be seen, the storage modulus (G') is higher than the loss modulus (G ") in all samples, indicating the formation of a stable hydrogel. Furthermore, by comparison, the storage modulus (G') of the hydrogel can be increased from about 10KPa to about 63KPa by adding an amount of RGO, and increases with increasing RGO suspension concentration. In addition, the samples provided with PANI coatings showed higher storage modulus (G'). The results show that the dynamic mechanical properties of the device can be improved by adding the RGO nano-filler and the PANI coating.

(d) Evaluation of mechanical Properties

The mechanical properties of each of the above samples were measured using an Instron 5965 mechanical analyzer.

Specifically, each hydrogel sample was subjected to a tensile test at a speed of 10mm/min until breaking. All samples were 2.5cm (length) by 2.0cm (width) by 2.5mm (thickness). All samples were tested in triplicate for a total of 30 samples.

Young's modulus was calculated as the slope of the initial linear region on the stress-strain curve, and toughness was calculated as the area under the strain-stress curve. The results are shown in FIG. 5.

FIG. 5 shows a graph of mechanical properties of a PAA hydrogel, a PAA-RGO composite hydrogel, and a PAA-RGO-PANI conductive ionic gel film, wherein (a) shows the strain stress curves of PAA and PAA-RGO; (b) shows the strain stress curve of PAA-RGO-PANI; (c) the Young's modulus and toughness of PAA and PAA-RGO are shown; (d) the Young's modulus and toughness of PAA-RGO-PANI are shown.

As shown in FIG. 5 (a), the PAA hydrogel has an ultimate tensile strength of 300. + -. 5.86KPa and a strain to failure of 900. + -. 5.67%; when 5mg/ml RGO was added, the strength of the hydrogel increased significantly from 300. + -. 5.86KPa to 430. + -. 7.64 KPa; as RGO concentration further increases, i.e. the amount of incorporation into the PAA hydrogel increases, the mechanical strength further increases; when the RGO concentration was doubled, i.e., 10mg/ml, the mechanical stress of the hydrogel showed a tensile strength of 550. + -. 9.41 KPa; the tensile strength of the PAA-RGO hydrogel reached 800. + -. 10.36KPa when the RGO concentration was increased to 15mg/ml RGO. However, as the RGO concentration was increased from 5mg/ml to 15mg/ml, the strain of the gel decreased from 900. + -. 5.67% to 800. + -. 6.89%.

Further, as can be seen from (b) in fig. 5, the tensile strength was also significantly increased after the polyaniline was formed on the PAA-RGO hydrogel, which had a tensile strength of 630 ± 8.75KPa and a strain to failure of 803 ± 7.89%; the tensile strength of the PAA-RGO (10mg/ml) -PANI hydrogel is 780 +/-9.34 KPa, and the failure strain is 745 +/-5.56 percent; the PAA-RGO (15mg/ml) -PANI hydrogel has a tensile strength of 1050 + -8.34 KPa and a strain to failure of 659 + -5.78%.

As shown in FIG. 5 (c), the Young's modulus of the PAA hydrogel sample was 26.98. + -. 1.61MPa, and the toughness was 1.15. + -. 0.15MJ m^-3(ii) a The Young's modulus increased from 105.63 + -4.84 MPa to 306.27 + -5.26 MPa as the amount of RGO in the PAA hydrogel increased from 5mg/ml to 15 mg/ml; toughness showed a similar increasing trend from 1.59 + -0.05 MJ m^-3To 3.85 +/-0.34 MJ m^-3. The results indicate that RGO as a nanofiller incorporated into hydrogels can effectively enhance the tensile strength and Young's modulus of PAA-RGO hydrogels, but to reduce strain.

As can be seen from (d) of FIG. 5, the Young's modulus increased from 149.17 + -7.71 MPa to 464.33 + -5.69 MPa and the toughness increased from 1.82 + -0.15 MJ m after the PANI layer was provided^-3Increased to 4.53 + -0.27 MJ m^-3。

Taken together, PANI can increase the mechanical strength and young's modulus of the hydrogel, but can reduce strain. In general, the conductive ionic gel product according to the embodiment of the invention has excellent mechanical properties in terms of stress, strain and toughness, and can be used for manufacturing electrical equipment applicable to green agricultural systems.

(d) Electrochemical performance

Each of the hydrogels obtained above was sandwiched between two aluminum foils as current collectors and sealed by a sealing film to prevent moisture from evaporating, thereby assembling a Supercapacitor (SC).

Electrochemical properties of the assembled SC were studied using an electrochemical workstation.

At 10⁵To 10^-2Frequency of Hz, alternating current amplitude of 10mV and zeroThe Electrochemical Impedance Spectroscopy (EIS) test was performed.

Constant current charge and discharge (GCD) measurements were performed at a constant current of 5mA from 0 to 0.8V.

At a rate of 0.002 to 1V s^-1The Cyclic Voltammetry (CV) curve was recorded from 0 to 0.8V.

The capacitance of a single electrode in SC is calculated from the discharge slope after IR drop based on the GCD curve by the following formula.

C＝2IΔt/(ΔV-V_IR)

Wherein I is a discharge current; Δ t represents the time span of a full discharge; Δ V is the potential change after full discharge; v_IRIndicating a potential drop during the initial discharge phase, which is mainly due to the intrinsic resistance of the electrode material and the resistance of the electrolyte.

The results are shown in Table 1 below.

It can be seen from table 1 that the samples containing RGO nanofillers exhibit better electrical properties than the samples without RGO nanofillers. The electrical properties improved significantly as the amount of RGO nanofiller increased from 5mg/ml to 15 mg/ml. In addition, when the PAA-RGO sample was coated with PANI, the electrical performance was further improved. This is because, for example, RGO nanofillers are uniformly distributed in the porous structure of PAA-RGO-PANI nanocomposites, which results in extremely high specific surface area and ultra-low density, which makes it possible to support a large number of nanosized conductive fillers (RGOs). In addition, the porous structure enables a larger contact area when triboelectrification occurs, thereby providing a large number of electrons on the surface of the PAA-RGO-PANI nanocomposite during the triboelectrification process.

TABLE 1 electrochemical Properties of the various samples

Next, an application example of the conductive ionic gel according to the embodiment of the present invention is exemplarily given.

Example 2 clean energy Collection device

As shown in fig. 6 (a), using an aluminum foil as a current collector, the lyophilized conductive ionic gel (5cm × 5cm × 0.5cm) obtained in example 1 above was disposed thereon, and thereafter a polyimide film (PI) was assembled thereon, to obtain a three-layer sandwich-structured clean energy collecting device. The LED lamp can be powered by connecting the LED lamp with an open circuit.

As shown in (b) of FIG. 6, in the initial stage, the PI surface or the PAA-RGO-PANI nanocomposite surface has no charge. Tribocharging occurs when the PI is brought into contact with the PAA-RGO-PANI nanocomposite due to an external force (mechanical squeezing or air vibration). PI is a triboelectric material with a strong potential to pick up electrons on its surface (negative charge), whereas PAA-RGO-PANI nanocomposites have a strong ability to lose surface electrons (positive charge). Thus, the contact between the PI surface and the PAA-RGO-PANI surface creates a negative charge on the PI surface and a positive charge on the PAA-RGO-PANI surface. At the same time, negative charges are induced in the aluminum foil, and the charges generated in the three layers eventually reach an equilibrium state. During the contact phase, the electrostatic potential increases and more charge can be retained in the system, driving electrons from ground to the aluminum foil. Thus, open circuit voltage (Voc) and short circuit current (Isc) can be generated by a cyclic "contact release" process.

When the surfaces of the two materials begin to separate (pressure release phase), the electrostatic potential between the PI and PAA-RGO-PANI nanocomposites decreases. The generated charge cannot be stored by the system and therefore the electrons on the aluminum foil flow to ground.

Therefore, it can be used for collecting clean energy.

FIG. 6 (c) shows the results of wind energy collection using PAA-RGO (15mg/ml) -PANI. As can be seen, the Isc can be maintained at 7.96. + -. 2.48. mu.A under continuous wind stimulation (1600 rpm fan speed).

In addition, although the results are not shown in the present disclosure, experiments have demonstrated that the clean energy harvesting device of the present invention can be used to harvest acoustic energy, mechanical energy (moderate to heavy rainfall or heavy snow).

EXAMPLE 3 plant growth sensor

The conductive ionic gel film of the present invention can be used for a plant growth sensor due to its excellent mechanical properties, electrical properties, and sensitivity.

Preparing a plant growth sensor:

polyvinyl alcohol (PVA) was coated on the aluminum film by spin coating to serve as a hydrophilic medium so that the PAA-RGO hydrogel could be uniformly crosslinked. And thereafter dried.

After drying, a mask was placed on the PVA coated aluminum foil by spin coating.

After that, the gaps of the mask were filled with the suspensions obtained in example 1 at various concentrations, respectively, and crosslinked at 40 to 50 ℃.

After crosslinking, the PVA layer was rinsed away with deionized water and then a PANI coating was placed thereon in the manner described in example 1.

Finally, PDMS (polydimethylsiloxane) was spin coated over the PAA-RGO-PANI to stabilize the sensor.

The sensor thus obtained had dimensions of 3.5 cm. times.0.5 cm. times.350 μm as shown in FIG. 7 (c).

The prepared sensor was attached to aloe leaves for growth testing. In which the calculated growth rate of aloe leaves by length measurement is shown in fig. 7 (a), and the corresponding resistance record is shown in fig. 7 (b). Wherein c1, c2, c3 respectively show the test results of the naturally growing 3-piece aloe samples, and T1, T2, T3 respectively show the test results of the 3-piece aloe samples under the irradiation of the LED lamp.

It can be seen that the plant growth sensor of the present invention shows a significant corresponding resistance change as a plant grows, and thus has high sensitivity.

In addition, experiments show that the sensor of the invention has a linear relationship between resistance and strain when the strain is less than 25%, so that the plant growth sensor of the invention can be used for growth monitoring when the strain is below 25%.

EXAMPLE 4 Ammonia gas detection sensor

The conductive ionic gel film can also be used for ammonia gas detection sensors.

Samples of ammonia detection sensors were prepared as follows:

each of the gel samples prepared in example 1 above was cut into a specific size (1 cm. times.1 cm. times.0.5 cm), air-dried to remove excess surface liquid, and then placed in a sealed plastic chamber containing 2 ml of ammonia gas at various concentrations. The hydrogel samples were connected to a wireless multimeter using copper wires prior to sealing the chamber.

And (3) ammonia gas testing:

data was recorded using a processor in the form of resistance changes once every 2 seconds. The test was performed when the resistance readings reached equilibrium.

FIG. 8 is a graph showing the results of detection when ammonia gas is detected by the ammonia gas detecting sensor according to example 4 of the present invention, wherein (a) the result of measurement of an ammonia water concentration of 8.62 ppm; (b) the ammonia concentration was 93.7 ppm; (c) the ammonia concentration was 203 ppm; (d) the ammonia concentration was 537 ppm.

The gel sample PAA-RGO (15mg/ml) -PANI was used as an ammonia sensor and detected ammonia gas concentrations ranging from 8.62ppm to 537 ppm. From the test results, it was found that the higher the ammonia gas concentration, the larger the resistance change, and the shorter the time required to reach the equilibrium resistance. And exposure to 8.62ppm ammonia took 60 seconds to reach equilibrium.

FIG. 8 shows the results of PAA-RGO-PANI hydrogel ammonia sensors containing varying amounts of RGO (5mg/ml, 10mg/ml, 15mg/ml) detecting varying concentrations of ammonia. The results show that the better the conductivity of the PAA-RGO-PANI hydrogel, the higher the sensitivity, and the shorter the time required to reach a stable reading.

PAA-RGO-PANI has high sensitivity to ammonia because of absorbed NH₃The molecule will take a proton from the PANI backbone to form NH₄ ⁺Furthermore, the (electron donor) has an n-doping effect on the P-type PANI backbone. In particular, PAA-RGO-PANI hydrogels adsorb ammonia gas when exposed to it, forming protonated ammonium cations on PANI through acid-base interactions, thereby removing polarons and thus reducing the total amount and mobility of holes. As a result, the PAA-RGO-PANI hydrogel increased in resistance until equilibrium was reached. In addition, carbon materials (e.g., RGO) can provide synergistic effects to achieve excellent performanceAmmonia sensing performance of. Also, as the number of RGOs in the sensor increases, they achieve a higher sensing effect.

According to the test results, the ammonia gas detection sensor of the present invention can detect ammonia gas with a concentration ranging from 8.68ppm to 5000ppm or more. Sensitivity increases as RGO concentration increases from 5mg/ml to 15 mg/ml. A sensor with an RGO concentration of 15mg/ml can detect a lower concentration of 8.62ppm ammonia in 60 seconds.

The sensor can be used for plant electronic skin.

Fig. 9 shows an application scenario of the conductive ionic gel membrane according to an embodiment of the present invention.

As shown in the figure, in smart agriculture, a supercapacitor can be formed using the conductive ionic gel film according to the present invention to collect energy generated from clean energy such as sound energy, snow, rain, wind, etc., and convert it into electric energy to power LEDs and provide light fertilizers to plants. Further, the above-described plant growth sensor according to the present invention may also be used for monitoring the growth of plants, and the above-described ammonia gas detection sensor according to the present invention may also be used for monitoring ammonia gas in the environment.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A conductive ionic gel membrane, comprising:

2. The conductive ionic gel film of claim 1, wherein the conductive nanofiller is reduced graphene oxide.

3. The conductive ionic gel membrane of claim 2, wherein the membrane matrix is formed by polymerizing an acrylic monomer and a dispersion of reduced graphene oxide in water under the action of a cross-linking agent and an initiator, wherein the acrylic monomer: the mass ratio of the reduced graphene oxide is 5 (1-4).

4. The conductive ionic gel membrane of claim 3, wherein the crosslinker comprises an ionic crosslinker and a covalent crosslinker.

5. The conductive ionic gel membrane of claim 4, wherein the ionic crosslinker is calcium chloride, the covalent crosslinker is N, N' -methylenebisacrylamide, and the initiator is ammonium persulfate.

6. The conductive ionic gel film of claim 1, wherein the thickness of said conductive ionic gel film is between 50 μm and 1000 μm.

7. The preparation method of the conductive ionic gel film is characterized by comprising the following steps:

step S1, providing an acrylic monomer;

8. The preparation method according to claim 7, wherein the conductive nano filler powder is reduced graphene oxide, and the step S2 includes:

and step S24, adding a cross-linking agent and an initiator into the dispersion liquid, and curing at the temperature of 40-50 ℃ to form the film matrix.

9. The preparation method according to claim 8, wherein in the suspension, the mass concentration of the reduced graphene oxide powder in the suspension is 3-20g/L, and the volume concentration of the acrylic acid monomer in the dispersion is 10-25%.

10. The method for preparing a composite material according to claim 7, wherein the step S3 includes:

step S31, providing aniline monomer solution;

11. The production method according to claim 10,

in the step S31, an aniline monomer is added to a 1M hydrochloric acid aqueous solution and mixed to obtain the aniline monomer solution,

in the step S32, the initiator is ammonium persulfate,

in the step S33, the reaction temperature is controlled to be 0 to 10 ℃, the dipping time is 4 to 12 hours, and after the dipping is finished, the film substrate with the polyaniline coating formed on the surface is taken out and washed by deionized water, so as to obtain the conductive ion gel film.

12. A clean energy collecting device comprising a polyimide film, the conductive ionic gel film according to any one of claims 1 to 6, and an aluminum foil, which are sequentially laminated from top to bottom, wherein the conductive ionic gel film is connected to an open device to collect clean energy generated from the conductive ionic gel film.

13. A sensor, comprising:

the conductive ionic gel film of any one of claims 1 to 6;

14. The sensor of claim 13, wherein the sensor is a plant growth sensor or an ammonia gas detection sensor.

15. An electronic skin comprising the sensor of claim 14.