CN110940705A - Polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristic and preparation method thereof - Google Patents
Polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristic and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristics and a preparation method thereof. The polypyrrole-graphene nano composite gas-sensitive material with the three-dimensional porous structure characteristic is formed by liquid-phase chemical polymerization of pyrrole monomers in a three-dimensional graphene frame, and is applied to an ammonia sensor and has high-sensitivity response to ppb-level ammonia gas at room temperature.
Description
Technical Field
The invention belongs to the technical field of gas sensors, and relates to a polypyrrole-graphene nano composite gas sensitive material with a three-dimensional porous structure characteristic and a preparation method thereof.
Background
Ammonia is an important raw material for manufacturing important industrial and agricultural products such as nitrogen fertilizers, nitric acid, explosives, medicines, rocket liquid fuels, plastics, resins and the like, is a basic raw material of modern chemical industry, and has a large amount of applications in the aspects of medicines, fertilizers, national defense and light industry. Ammonia gas is a toxic gas with pungent odor, and long-time exposure to the ammonia gas atmosphere can cause unrecoverable damage to a human body and even endanger life safety. The accurate and reliable detection of the low-concentration ammonia gas has important significance in the aspect of ensuring the environment and personal safety. Currently, the development of high-performance ammonia-sensitive sensors based on various nanocomposite systems is an important approach to realize high-sensitivity and reliable detection of ammonia gas and is continuously explored. The heterogeneous effect and the synergistic/coupling effect existing in the nano composite sensitive structure can generate better gas sensitive response than a pure phase nano gas sensitive structure; on the other hand, in order to meet the requirement of the sensor network on the power consumption performance of the sensor element, the response characteristic at low temperature, particularly room temperature, is another important performance index of the high-performance ammonia-sensitive sensor. The current research situation is that the room temperature sensitivity and the response recovery characteristic of the reported and developed ammonia sensor made of the nano composite sensitive material are not satisfied, and a novel nano composite sensitive system with high room temperature sensitivity must be researched and developed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a polypyrrole-graphene nano composite gas sensitive material with three-dimensional porous characteristics and a preparation method thereof.
The technical purpose of the invention is realized by the following technical scheme.
A polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristics and a preparation method thereof are disclosed, wherein reduced graphene oxide is used as a three-dimensional framework, pyrrole monomers are subjected to polymerization reaction on the surface of the reduced graphene oxide to form a uniform polypyrrole shell layer, and the polypyrrole-graphene nano composite gas sensitive structure material is prepared according to the following steps:
under the condition of continuous stirring, dropwise adding the suspended liquid of the uniformly dispersed reduced graphene oxide into the pyrrole polymerization reaction liquid, dropwise adding hydrochloric acid, and adjusting the pH value of the mixed solution to 1-3; and then dropwise adding a solution of an initiator into the mixed solution to initiate a reaction, so that a pyrrole monomer is subjected to a polymerization reaction on the surface of the reduced graphene oxide (nanosheet) to form a uniform shell layer of polypyrrole, and thus the polypyrrole-graphene nano composite gas sensitive structure material with the three-dimensional porous characteristic can be obtained, wherein:
(1) stirring by adopting mechanical or magnetic force at the rotating speed of 100 and 200 revolutions per minute;
(2) in the pyrrole polymerization reaction liquid, the molar ratio of Sodium Dodecyl Benzene Sulfonate (SDBS) to pyrrole monomer (Py) is (1-1.5): 3;
(3) the molar ratio of the initiator to the pyrrole monomer (Py) is (0.5-1): 6;
(4) the mass molar ratio of the reduced graphene oxide to the pyrrole monomer is (1-3): 1, the unit of mass is g, and the unit of mol is mmol;
(5) and dropwise adding the initiator solution into the mixed solution in a uniform dropwise manner for 1-5 min.
In the technical scheme, the concentration of hydrochloric acid is 1-5mol/L, and the pH of the mixed solution is adjusted to 2-3.
In the above technical solution, the rotation speed is 120-.
In the technical scheme, after the polymerization reaction is finished, centrifugally separating turbid liquid, centrifugally cleaning obtained solid twice by using deionized water respectively, and drying a wet sample at the temperature of 40-60 ℃ for 10-15 hours to obtain a PPy-rGO composite structure sample.
In the technical scheme, the reaction is carried out at the room temperature of 20-25 ℃.
In the above technical scheme, in the solution of the initiator, the solvent is water, and the initiator is Ammonium Persulfate (APS), potassium persulfate, or sodium persulfate.
In the technical scheme, sodium dodecyl benzene sulfonate is uniformly dispersed in deionized water in a pyrrole polymerization reaction solution, a pyrrole monomer is uniformly dispersed in absolute ethyl alcohol, and the two are mixed to form the pyrrole polymerization reaction solution, wherein if 0.1-0.8 mmol of Sodium Dodecyl Benzene Sulfonate (SDBS) is weighed, 80ml of deionized water is added, and the solution A is obtained by slow magnetic stirring for 5 min; weighing 0.3-2.4 mmol of pyrrole monomer (Py), pre-dissolving the pyrrole monomer (Py) in 1ml of absolute ethyl alcohol, and uniformly mixing to form a solution B; and (3) dropwise adding the solution B into the solution A under the condition of magnetic stirring, and continuing to magnetically stir for 20-30 min to form uniform pyrrole polymerization reaction liquid.
In the technical scheme, the suspension of the uniformly dispersed reduced graphene oxide is dropwise added into the pyrrole polymerization reaction solution, hydrochloric acid is dropwise added, the pH of the mixed solution is adjusted to 1-3, and the mixed solution is stirred for 1-2 hours to be uniformly mixed.
In the technical scheme, the solution of the initiator is dripped to initiate the reaction, the reaction temperature is 20-25 ℃, and the reaction time is 1-5 hours, preferably 2-4 hours.
In the above technical scheme, the reduced graphene oxide is prepared by a hydrothermal method: uniformly dispersing graphene oxide in deionized water, transferring the graphene oxide into a high-pressure reaction kettle lined with polytetrafluoroethylene, sealing, placing the reaction kettle in an oven, heating for hydrothermal reaction at the working temperature of 180-200 ℃, the reaction time of 10-15 hours, preferably 180-190 ℃, the reaction time of 12-15 hours, naturally cooling to the room temperature of 20-25 ℃, centrifugally separating black solid-liquid reactants in the reaction kettle, and centrifugally cleaning solids obtained by centrifugation for 2 times by using absolute ethyl alcohol and deionized water respectively. And finally, transferring the washed centrifugal product into 10ml of deionized water, and carrying out ultrasonic treatment for 10-15 min to obtain the uniformly dispersed reduced graphene oxide suspension.
In the above technical scheme, the purity of the chemical reagents used in each step is analytically pure AR.
In the technical scheme, in order to avoid the phenomena of local accumulation and uneven distribution of polypyrrole caused by increase of the using amount, the using amount of the pyrrole monomer is controlled to be less than 1.5mmol, such as 0.3-15 mmol.
The invention discloses a high-sensitivity ammonia sensor at room temperature based on a polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristics, wherein a platinum interdigital electrode is arranged on an alumina ceramic substrate, and a polypyrrole-graphene nano composite gas sensitive structure material coating with three-dimensional porous characteristics is arranged on the platinum interdigital electrode.
The invention provides a preparation method for forming a polypyrrole-graphene nano composite gas-sensitive material with three-dimensional porous structure characteristics by polymerizing pyrrole monomers in a three-dimensional graphene framework by using an optimized liquid-phase chemical process. The method firstly adopts an optimized liquid-phase chemical oxidation polymerization method based on an ethanol pre-dispersion technology to realize the uniform coverage of the organic polymer on the surface of the three-dimensional structure nano flaky graphene, and solves the problem that the heterogeneous and synergistic effects cannot be fully embodied due to the difficulty in forming a uniformly covered organic polymer shell layer film on the surface of a complex structure by the traditional polymerization process.
The invention aims to break through the performance indexes of the existing ammonia-sensitive sensor and explore a novel ammonia-sensitive sensing material with high-sensitivity and quick response to dilute ammonia gas at room temperature, and provides a preparation method of a polypyrrole-graphene nano composite gas-sensitive material with three-dimensional porous structure characteristics, which is formed by liquid-phase chemical polymerization of pyrrole monomers in a three-dimensional graphene framework. The ammonia sensor constructed by the three-dimensional porous polypyrrole-graphene nano composite gas-sensitive material prepared by the method has the characteristics of high room temperature sensitivity, instantaneous response and quick recovery when used for detecting ammonia gas, can be applied to a low-power consumption and high-sensitivity ammonia sensor, and realizes high-efficiency detection of ammonia gas in multiple fields, so that the method has very good development and application prospects.
Drawings
Fig. 1 is a scanning electron microscope photograph (right image) of three-dimensional reduced graphene oxide (left image) and polypyrrole polymer prepared in example 1 of the present invention.
FIG. 2 is a TEM photograph of polypyrrole-graphene (PPy-rGO) with three-dimensional porous characteristics prepared in example 1 of the present invention.
Fig. 3 is a scanning electron microscope photograph of polypyrrole-graphene (PPy-rGO) having three-dimensional porous characteristics prepared in example 1 of the present invention.
FIG. 4 is an XRD spectrum of PPy-rGO, PPy and rGO prepared according to the present invention.
FIG. 5 is a schematic view showing the structure of a gas sensitive test device used in the present invention,
FIG. 6 is a schematic structural diagram of a gas-sensitive sensor element composed of a PPy-rGO nano-structured material prepared by the present invention.
FIG. 7 is a graph showing the dynamic response of a PPy-rGO nano-structured gas-sensitive sensing element prepared by the method to 330ppb and 660ppb ammonia gas (room temperature 20 ℃, humidity 15%).
FIG. 8 is a graph of the dynamic response of a PPy-rGO nano-structured gas sensor prepared according to the present invention to 1ppm, 2ppm, 3ppm, 4ppm, 5ppm ammonia gas (room temperature 20 deg.C, humidity 15%).
Detailed Description
The raw materials used in the present invention are all commercially available chemical pure reagents, and the present invention will be further described in detail with reference to specific examples. Stirring by magnetic force at the rotation speed of 120-150 revolutions per minute, the concentration of hydrochloric acid is 5M, selecting ammonium persulfate as the initiator, and dropwise adding the solution of the initiator into the mixed solution in a uniform dropwise adding mode for 2 min.
Example 1
(1) Hydrothermal method for preparing reduced graphene oxide
Adding 0.6g of graphene oxide aqueous solution into 60ml of deionized water (the mass percent of the graphene oxide is 1 wt%, namely the mass of the graphene oxide/the mass of the deionized water), and magnetically stirring for 80min to obtain the graphene oxide aqueous solution with a certain concentration. Transferring the graphene oxide aqueous solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, sealing, and then placing the reaction kettle into an oven to heat for solvothermal reaction, wherein the operating temperature of the oven is 200 ℃, and the heating time is 15 h.
(2) Cleaning of reduced graphene oxide
And after the hydrothermal reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, taking out the reaction kettle, centrifugally separating black solid-liquid reactants in the reaction kettle, and setting the rotating speed of a centrifugal machine to be 5000 r/min. The solid obtained by centrifugation is respectively centrifugally cleaned for 2 times by absolute ethyl alcohol and deionized water. And finally, transferring the washed centrifugal product into 10ml of deionized water, and carrying out ultrasonic treatment for 15min to obtain a uniformly dispersed graphene suspension.
(3) Preparing pyrrole polymerization reaction liquid
0.2mmol of Sodium Dodecyl Benzene Sulfonate (SDBS) is weighed, 80ml of deionized water is added, and the mixture is magnetically stirred at a slow speed for 5min to obtain a sodium dodecyl benzene sulfonate solution. Weighing 0.6mmol of pyrrole monomer (Py) and pre-dissolving the pyrrole monomer (Py) in 1ml of absolute ethyl alcohol, uniformly mixing, dropwise adding the mixture into the reaction solution, continuously stirring for 30min, dropwise adding the graphene suspension liquid in the step (2) into the reaction solution, and dropwise adding concentrated hydrochloric acid to adjust the pH of the reaction solution to 2. Stirring by magnetic force for 1 h.
(4) Initiating the polymerization reaction
0.1mmol of Ammonium Persulfate (APS) as an oxidizing agent is weighed and sufficiently dissolved in 10ml of deionized water, and the solution is dropwise added into the reaction solution in the step (3). Stirring was continued for 4 h. After the reaction is finished, the product is centrifugally cleaned twice by deionized water and absolute ethyl alcohol respectively, and then is dried for 10-15 hours at the temperature of 40-60 ℃ to obtain a PPy-rGO nano composite structure sample.
The scanning electron microscope analysis result of the three-dimensional graphene nanosheet morphology obtained after the step (2) of example 1 is shown in fig. 1. The scanning electron microscope analysis result of the morphology of the PPy-rGO three-dimensional porous composite structure prepared in the step (4) in the embodiment 1 is shown in the left picture of FIG. 2, and it can be observed that polypyrrole is uniformly coated on a graphene nanosheet to form a three-dimensional loose porous structure. The transmission electron microscopy analysis of the composite structure is shown in the right panel of figure 2.
Example 2
(1) Hydrothermal method for preparing reduced graphene oxide
Adding 0.9g of graphene oxide aqueous solution into 60ml of deionized water (the mass percent of the graphene oxide is 1 wt%, namely the mass of the graphene oxide/the mass of the deionized water), and magnetically stirring for 80min to obtain the graphene oxide aqueous solution with a certain concentration. Transferring the graphene oxide aqueous solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, sealing, and then placing the reaction kettle into an oven to heat for solvothermal reaction, wherein the operating temperature of the oven is 180 ℃, and the heating time is 12 hours.
(2) Cleaning of reduced graphene oxide
And after the hydrothermal reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, taking out the reaction kettle, centrifugally separating black solid-liquid reactants in the reaction kettle, and setting the rotating speed of a centrifugal machine to be 5000 r/min. The solid obtained by centrifugation is respectively centrifugally cleaned for 2 times by absolute ethyl alcohol and deionized water. And finally, transferring the washed centrifugal product into 10ml of deionized water, and carrying out ultrasonic treatment for 15min to obtain a uniformly dispersed graphene suspension.
(3) Preparing pyrrole polymerization reaction liquid
0.1mmol of Sodium Dodecyl Benzene Sulfonate (SDBS) is weighed, 80ml of deionized water is added, and the mixture is magnetically stirred at a slow speed for 5min to obtain a sodium dodecyl benzene sulfonate solution. Weighing 0.3mmol of pyrrole monomer (Py) and pre-dissolving the pyrrole monomer (Py) in 1ml of absolute ethyl alcohol, uniformly mixing, dropwise adding the mixture into the reaction solution, continuously stirring for 30min, dropwise adding the graphene suspension liquid in the step (2) into the reaction solution, and dropwise adding concentrated hydrochloric acid to adjust the pH of the reaction solution to 2. Stirring by magnetic force for 1 h.
(4) Initiating the polymerization reaction
0.05mmol of oxidant Ammonium Persulfate (APS) is weighed and fully dissolved in 10ml of deionized water, and the solution is dropwise added into the reaction solution in the step (3). Stirring was continued for 5 h. After the reaction is finished, the product is centrifugally cleaned twice by deionized water and absolute ethyl alcohol respectively and then dried for 10 hours at the temperature of 60 ℃ to obtain a PPy-rGO nano composite structure sample.
Example 3
(1) Hydrothermal method for preparing reduced graphene oxide
Adding 0.6g of graphene oxide aqueous solution into 60ml of deionized water (the mass percent of the graphene oxide is 1 wt%, namely the mass of the graphene oxide/the mass of the deionized water), and magnetically stirring for 80min to obtain the graphene oxide aqueous solution with a certain concentration. Transferring the graphene oxide aqueous solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, sealing, and then placing the reaction kettle into an oven to heat for solvothermal reaction, wherein the operating temperature of the oven is 190 ℃, and the heating time is 10 hours.
(2) Cleaning of reduced graphene oxide
And after the hydrothermal reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, taking out the reaction kettle, centrifugally separating black solid-liquid reactants in the reaction kettle, and setting the rotating speed of a centrifugal machine to be 5000 r/min. The solid obtained by centrifugation is respectively centrifugally cleaned for 2 times by absolute ethyl alcohol and deionized water. And finally, transferring the washed centrifugal product into 10ml of deionized water, and carrying out ultrasonic treatment for 15min to obtain a uniformly dispersed graphene suspension.
(3) Preparing pyrrole polymerization reaction liquid
0.15mmol of Sodium Dodecyl Benzene Sulfonate (SDBS) is weighed, 80ml of deionized water is added, and the mixture is magnetically stirred at a slow speed for 5min to obtain a sodium dodecyl benzene sulfonate solution. Weighing 0.3mmol of pyrrole monomer (Py) and pre-dissolving the pyrrole monomer (Py) in 1ml of absolute ethyl alcohol, uniformly mixing, dropwise adding the mixture into the reaction solution, continuously stirring for 30min, dropwise adding the graphene suspension liquid in the step (2) into the reaction solution, and dropwise adding concentrated hydrochloric acid to adjust the pH of the reaction solution to 3. Stirring by magnetic force for 1 h.
(4) Initiating the polymerization reaction
0.05mmol of oxidant Ammonium Persulfate (APS) is weighed and fully dissolved in 10ml of deionized water, and the solution is dropwise added into the reaction solution in the step (3). Stirring was continued for 1 h. After the reaction is finished, the product is centrifugally cleaned twice by deionized water and absolute ethyl alcohol respectively and then dried for 15 hours at the temperature of 40 ℃ to obtain a PPy-rGO nano composite structure sample.
Example 4
(1) Hydrothermal method for preparing reduced graphene oxide
Adding 0.9g of graphene oxide aqueous solution into 60ml of deionized water (the mass percent of the graphene oxide is 1 wt%, namely the mass of the graphene oxide/the mass of the deionized water), and magnetically stirring for 80min to obtain the graphene oxide aqueous solution with a certain concentration. Transferring the graphene oxide aqueous solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, sealing, and then placing the reaction kettle into an oven to heat for solvothermal reaction, wherein the working temperature of the oven is 200 ℃, and the heating time is 12 hours.
(2) Cleaning of reduced graphene oxide
And after the hydrothermal reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, taking out the reaction kettle, centrifugally separating black solid-liquid reactants in the reaction kettle, and setting the rotating speed of a centrifugal machine to be 5000 r/min. The solid obtained by centrifugation is respectively centrifugally cleaned for 2 times by absolute ethyl alcohol and deionized water. And finally, transferring the washed centrifugal product into 10ml of deionized water, and carrying out ultrasonic treatment for 15min to obtain a uniformly dispersed graphene suspension.
(3) Preparing pyrrole polymerization reaction liquid
0.3mmol of Sodium Dodecyl Benzene Sulfonate (SDBS) is weighed, 80ml of deionized water is added, and the mixture is magnetically stirred at a slow speed for 5min to obtain a sodium dodecyl benzene sulfonate solution. Weighing 0.9mmol of pyrrole monomer (Py) and pre-dissolving the pyrrole monomer (Py) in 1ml of absolute ethyl alcohol, uniformly mixing, dropwise adding the mixture into the reaction solution, continuously stirring for 30min, dropwise adding the graphene suspension liquid in the step (2) into the reaction solution, and dropwise adding concentrated hydrochloric acid to adjust the pH of the reaction solution to 1. Stirring by magnetic force for 1 h.
(4) Initiating the polymerization reaction
0.075mmol of Ammonium Persulfate (APS) as an oxidizing agent is weighed and fully dissolved in 10ml of deionized water, and the solution is dropwise added into the reaction liquid in the step (3). Stirring was continued for 3 h. After the reaction is finished, the product is centrifugally cleaned twice by deionized water and absolute ethyl alcohol respectively and then dried for 12 hours at the temperature of 50 ℃ to obtain a PPy-rGO nano composite structure sample.
Example 5
(1) Hydrothermal method for preparing reduced graphene oxide
Adding 7g of graphene oxide aqueous solution into 60ml of deionized water (the mass percent of the graphene oxide is 1 wt%, namely the mass of the graphene oxide/the mass of the deionized water), and magnetically stirring for 80min to obtain the graphene oxide aqueous solution with a certain concentration. Transferring the graphene oxide aqueous solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, sealing, and then placing the reaction kettle into an oven to heat for solvothermal reaction, wherein the operating temperature of the oven is 200 ℃, and the heating time is 10 hours.
(2) Cleaning of reduced graphene oxide
And after the hydrothermal reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, taking out the reaction kettle, centrifugally separating black solid-liquid reactants in the reaction kettle, and setting the rotating speed of a centrifugal machine to be 5000 r/min. The solid obtained by centrifugation is respectively centrifugally cleaned for 2 times by absolute ethyl alcohol and deionized water. And finally, transferring the washed centrifugal product into 10ml of deionized water, and carrying out ultrasonic treatment for 15min to obtain a uniformly dispersed graphene suspension.
(3) Preparing pyrrole polymerization reaction liquid
0.8mmol of Sodium Dodecyl Benzene Sulfonate (SDBS) is weighed, 80ml of deionized water is added, and the mixture is magnetically stirred at a slow speed for 5min to obtain a sodium dodecyl benzene sulfonate solution. Weighing 2.4mmol of pyrrole monomer (Py) and pre-dissolving the pyrrole monomer (Py) in 1ml of absolute ethyl alcohol, uniformly mixing, dropwise adding the mixture into the reaction solution, continuously stirring for 30min, dropwise adding the graphene suspension in the step (2) into the reaction solution, and dropwise adding concentrated hydrochloric acid to adjust the pH of the reaction solution to 2. Stirring by magnetic force for 1 h.
(4) Initiating the polymerization reaction
0.4mmol of Ammonium Persulfate (APS) as an oxidizing agent is weighed and sufficiently dissolved in 10ml of deionized water, and the solution is dropwise added into the reaction solution in the step (3). Stirring was continued for 4 h. After the reaction is finished, the product is centrifugally cleaned twice by deionized water and absolute ethyl alcohol respectively and then dried for 13 hours at the temperature of 55 ℃ to obtain a PPy-rGO nano composite structure sample.
As shown in fig. 1 to 4, the nano composite structure material prepared by the present invention uses the three-dimensional porous structure graphene as the supporting framework to uniformly compound polypyrrole and maintain the three-dimensional porous structure, and shows the characteristic peak morphology of respective XRD, but it should be noted that in example 5, the polypyrrole forms a phenomenon of local stacking and non-uniform distribution as the amount of the polymeric reactant increases.
The PPy-rGO nano composite structure material is constructed into a gas sensor, firstly, an electrode substrate is prepared, an aluminum oxide ceramic wafer is sequentially placed in acetone solvent, absolute ethyl alcohol and deionized water to be respectively ultrasonically cleaned for 5-10min, oil stains and organic matter impurities on the surface are removed, and the gas sensor is placed in an infrared oven to be thoroughly dried. Platinum interdigital electrodes were formed on an alumina ceramic wafer with the aid of a template, as shown in FIG. 6, with a being 22mm, b being 1.2mm, and c being 1.5 mm. The adopted metal platinum target material has the mass purity of 9995 percent, argon with the mass purity of 99.999 percent is taken as working gas, and the background vacuum degree is 4-6 multiplied by 10-4Pa, preparing by adopting a radio frequency magnetron sputtering method, sputtering for 2min, and enabling the thickness of the film to be 80-120 nm. Then, the nano composite structure material prepared by the invention is diluted by 5ml of absolute ethyl alcohol and then is spin-coated on a prepared electrode substrate, and the nano composite structure material is dried for 10 hours at the temperature of 60 ℃ and then is subjected to gas sensitivity test. As shown in fig. 5, in the gas sensitive testing device 1 used in the present invention, an air inlet is used for introducing a trace amount of injection agent into a tested gas to be tested; 2 is a gas sensor element, which is connected with a platinum electrode through a probe and is connected with external detection equipment; 3 is a platform which can be heated and kept to the required temperature; 4, a built test sealed container with the capacity of 30L; 5, a mini fan for helping gas diffusion and enabling the gas to be uniformly dispersed in the cubic container; 6 is an air outlet; 7 is an electronic control instrument which can control and regulate the temperature; 8, UT70D resistance detection equipment of Ulidede company, displaying the resistance value at the joint of the probe in real time, and outputting the resistance value to computer equipment; 9 is a computer terminal for recording and displaying the measured resistance change; the gas sensor element is connected with UT70D resistance detection equipment of Ulidede company through a sensing element wire, and is used for displaying the resistance value of the probe junction in real time, and transmitting the corresponding resistance test value to a computer terminal, and all the resistance test values are collected and recorded into a table through the computer terminal.
Polypyrrole is a conductive polymer with high intrinsic conductivity and good environmental stability, and has sensitivity to ammonia gas. The graphene has the characteristics of large specific surface area, high electron mobility, low electric noise, high electrical disturbance sensitivity to gas molecules and the like. The nano synergistic effect of the composite nano structure formed by compounding the graphene and the polypyrrole can lead to better gas-sensitive performance than that of pure-phase graphene or pure-phase polypyrrole. Based on the method disclosed by the invention, in the polypyrrole-graphene nano composite gas sensitive structure with three-dimensional porous characteristics, which is formed by uniformly compounding polypyrrole with three-dimensional stereo-structure graphene as a loading framework, the three-dimensional porous geometric characteristics ensure the extremely large gas adsorption surface and the rapid diffusion of gas in a composite structure sensitive element, and are beneficial to achieving high low-temperature gas sensitive sensitivity and rapid dynamic response and recovery; the three-dimensional high-conductivity graphene skeleton in the composite structure provides a continuous conductive path for electron transportation in the sensitive element, and due to the accumulation of pi-pi bonds between graphene and polypyrrole and the formation of H bonds, the rapid transportation of current carriers in the whole composite structure layer can be realized, and the rapid dynamic sensitive response is favorably obtained. In addition, the high structural stability of the three-dimensional composite sensitive layer can contribute to the high performance stability of the sensitive device. The sensor element constructed by the three-dimensional porous composite structure sensitive element formed by the method is particularly suitable for room temperature detection of ppb-level low-concentration ammonia gas. As shown in the attached FIGS. 7 and 8, the ammonia sensor of the present invention has dynamic response to 330ppb and 660ppb ammonia gas at room temperature, and the response sensitivity to ammonia gas is: 1.16 and 1.86, the element has extremely low detection limit on ammonia gas, and has dynamic response curves of 1ppm-5ppm ammonia gas, the sensitivity on ammonia gas is respectively 4.47, 7.91, 10.19 and 11.18, particularly, the response on 5ppm ammonia gas is extremely high, the sensor can achieve instantaneous response, and the response time is 1 s-3 s.
The preparation of the polypyrrole-graphene nano composite gas sensitive structure material with the three-dimensional porous characteristic can be realized by adjusting the process parameters according to the content of the invention, and the polypyrrole-graphene nano composite gas sensitive structure material shows the performance basically consistent with the performance of the polypyrrole-graphene nano composite gas sensitive structure material. The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.
Claims (10)
1. A polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristics is characterized in that reduced graphene oxide is used as a three-dimensional framework, pyrrole monomers are subjected to polymerization reaction on the surface of the reduced graphene oxide to form a uniform shell layer of polypyrrole, and the polypyrrole-graphene nano composite gas sensitive structure material is prepared according to the following steps:
under the condition of continuous stirring, dropwise adding the suspended liquid of the uniformly dispersed reduced graphene oxide into the pyrrole polymerization reaction liquid, dropwise adding hydrochloric acid, and adjusting the pH value of the mixed solution to 1-3; and then dropwise adding a solution of an initiator into the mixed solution to initiate a reaction, so that a pyrrole monomer is subjected to a polymerization reaction on the surface of the reduced graphene oxide to form a uniform shell layer of polypyrrole, and thus the polypyrrole-graphene nano composite gas sensitive structure material with the three-dimensional porous characteristic is obtained, wherein:
(1) stirring by adopting mechanical or magnetic force at the rotating speed of 100 and 200 revolutions per minute;
(2) in the pyrrole polymerization reaction liquid, the mol ratio of the sodium dodecyl benzene sulfonate to the pyrrole monomer is (1-1.5): 3;
(3) the molar ratio of the initiator to the pyrrole monomer is (0.5-1): 6;
(4) the mass molar ratio of the reduced graphene oxide to the pyrrole monomer is (1-3): 1;
(5) and dropwise adding the initiator solution into the mixed solution in a uniform dropwise manner for 1-5 min.
2. The polypyrrole-graphene nano composite gas-sensitive structural material with the three-dimensional porous characteristic according to claim 1, wherein the concentration of hydrochloric acid is 1-5mol/L, and the pH of the mixed solution is adjusted to 2-3; the rotating speed is 120-150 revolutions per minute; the reaction is carried out at room temperature of 20-25 ℃ for 1-5 hours, preferably 2-4 hours.
3. The polypyrrole-graphene nano composite gas sensitive structural material with the three-dimensional porous characteristic according to claim 1, wherein in a solution of an initiator, a solvent is water, and the initiator is ammonium persulfate, potassium persulfate, or sodium persulfate; in the pyrrole polymerization reaction liquid, sodium dodecyl benzene sulfonate is uniformly dispersed in deionized water, a pyrrole monomer is uniformly dispersed in absolute ethyl alcohol, and the two are mixed to form the pyrrole polymerization reaction liquid.
4. The polypyrrole-graphene nano composite gas sensitive structural material with the three-dimensional porous characteristic of claim 1, wherein the reduced graphene oxide is prepared by a hydrothermal method: uniformly dispersing graphene oxide in deionized water, transferring the graphene oxide into a high-pressure reaction kettle lined with polytetrafluoroethylene, sealing, placing the reaction kettle in an oven, heating for hydrothermal reaction at the working temperature of 180-plus-200 ℃ for 10-15 hours, preferably at the working temperature of 180-plus-190 ℃ for 12-15 hours, and naturally cooling to the room temperature of 20-25 ℃.
5. A preparation method of a polypyrrole-graphene nano composite gas sensitive structure material with three-dimensional porous characteristics is characterized by comprising the following steps:
under the condition of continuous stirring, dropwise adding the suspended liquid of the uniformly dispersed reduced graphene oxide into the pyrrole polymerization reaction liquid, dropwise adding hydrochloric acid, and adjusting the pH value of the mixed solution to 1-3; and then dropwise adding a solution of an initiator into the mixed solution to initiate a reaction, so that a pyrrole monomer is subjected to a polymerization reaction on the surface of the reduced graphene oxide to form a uniform shell layer of polypyrrole, and thus the polypyrrole-graphene nano composite gas sensitive structure material with the three-dimensional porous characteristic is obtained, wherein:
(1) stirring by adopting mechanical or magnetic force at the rotating speed of 100 and 200 revolutions per minute;
(2) in the pyrrole polymerization reaction liquid, the mol ratio of the sodium dodecyl benzene sulfonate to the pyrrole monomer is (1-1.5): 3;
(3) the molar ratio of the initiator to the pyrrole monomer is (0.5-1): 6;
(4) the mass molar ratio of the reduced graphene oxide to the pyrrole monomer is (1-3): 1;
(5) and dropwise adding the initiator solution into the mixed solution in a uniform dropwise manner for 1-5 min.
6. The preparation method of the polypyrrole-graphene nano composite gas-sensitive structural material with the three-dimensional porous characteristic according to claim 5, wherein the concentration of hydrochloric acid is 1-5mol/L, and the pH of the mixed solution is adjusted to 2-3; the rotating speed is 120-150 revolutions per minute; the reaction is carried out at room temperature of 20-25 ℃ for 1-5 hours, preferably 2-4 hours.
7. The preparation method of the polypyrrole-graphene nano composite gas sensitive structural material with the three-dimensional porous characteristic according to claim 5, wherein in the solution of the initiator, the solvent is water, and the initiator is ammonium persulfate, potassium persulfate, or sodium persulfate; in the pyrrole polymerization reaction liquid, sodium dodecyl benzene sulfonate is uniformly dispersed in deionized water, a pyrrole monomer is uniformly dispersed in absolute ethyl alcohol, and the two are mixed to form the pyrrole polymerization reaction liquid.
8. The preparation method of the polypyrrole-graphene nano composite gas-sensitive structural material with the three-dimensional porous characteristic according to claim 5, wherein the reduced graphene oxide is prepared by a hydrothermal method: uniformly dispersing graphene oxide in deionized water, transferring the graphene oxide into a high-pressure reaction kettle lined with polytetrafluoroethylene, sealing, placing the reaction kettle in an oven, heating for hydrothermal reaction at the working temperature of 180-plus-200 ℃ for 10-15 hours, preferably at the working temperature of 180-plus-190 ℃ for 12-15 hours, and naturally cooling to the room temperature of 20-25 ℃.
9. A high-sensitivity ammonia sensor at room temperature based on a polypyrrole-graphene nano composite gas sensitive structural material with three-dimensional porous characteristics is characterized in that a platinum interdigital electrode is arranged on an alumina ceramic substrate, and a polypyrrole-graphene nano composite gas sensitive structural material coating with three-dimensional porous characteristics is arranged on the platinum interdigital electrode.
10. The application of the polypyrrole-graphene nano composite gas-sensitive structural material with the three-dimensional porous characteristic in detecting ammonia gas at room temperature according to one of claims 1 to 4, wherein the dynamic response to 330ppb ammonia gas and 660ppb ammonia gas at room temperature of 20 ℃ and humidity of 15% respectively has the following response sensitivities to ammonia gas: 1.16, 1.86, and the sensitivity to ammonia gas is 4.47, 7.91, 10.19 and 11.18 respectively, and the response time is 1 s-3 s.
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