阅读说明：本技术 一种氨气气体传感器及其制备方法 (Ammonia gas sensor and preparation method thereof ) 是由 庞希贵 于 2020-12-30 设计创作，主要内容包括：本发明涉及气体传感器技术领域,尤其涉及一种氨气气体传感器及其制备方法。所述氨气气体传感器,包括：叉指电极；以及聚吡咯/Fe-3O-4复合膜层,所述聚吡咯/Fe-3O-4复合膜层形成在所述叉指电极的表面,其中,所述聚吡咯/Fe-3O-4复合膜层由Fe-3O-4纳米颗粒和吡咯单体经原位聚合得到。本发明以特定的Fe-3O-4纳米颗粒掺杂聚吡咯膜可以提高聚合物膜的表面积和热稳定性,同时提高了聚合物膜的孔隙度,使氨气在膜内的扩散速度增加,从而具有更短的响应时间。本发明经特定条件制得的Fe-3O-4纳米颗粒,固含量远高于传统方法,适合大批量生产,有利于氨气气体传感器实现规模化生产。(The invention relates to the technical field of gas sensors, in particular to an ammonia gas sensor and a preparation method thereof. The ammonia gas sensor includes: an interdigital electrode; and polypyrrole/Fe 3 O 4 Composite film layer of said polypyrrole/Fe 3 O 4 A composite film layer is formed on the surface of the interdigital electrode, wherein the polypyrrole/Fe 3 O 4 The composite film layer is made of Fe 3 O 4 The nano particles and the pyrrole monomer are obtained by in-situ polymerization. The invention uses specific Fe 3 O 4 The nano-particle doped polypyrrole film can improve the surface area and the thermal stability of the polymer film, and simultaneously improve the porosity of the polymer film, so that the diffusion speed of ammonia in the film is increased, and the response time is shorter. Fe prepared by specific conditions 3 O 4 The solid content of the nano particles is far higher than that of the traditional method, and the method is suitable for mass production and is beneficial to realizing large-scale production of the ammonia gas sensor.)

1. An ammonia gas sensor, comprising:

an interdigital electrode; and

polypyrrole/Fe₃O₄Composite film layer of said polypyrrole/Fe₃O₄The composite film layer is formed on the surface of the interdigital electrode,

wherein the content of the first and second substances,

the polypyrrole/Fe₃O₄The composite film layer is made of Fe₃O₄The nano particles and the pyrrole monomer are obtained by in-situ polymerization.

2. The ammonia gas sensor of claim 1, wherein the Fe₃O₄The mass ratio of the nanoparticles to the pyrrole monomers is 0.8-1.2: 1.

3. an ammonia gas sensor according to claim 1 or 2, wherein the Fe is₃O₄The solid content of the nano particles is more than 40 percent.

4. According to any one of claims 1 to 3The ammonia gas sensor, wherein the Fe₃O₄The particle size of the nano-particles is 10-20 nm.

5. An ammonia gas sensor according to any one of claims 1 to 4, wherein the Fe is Fe₃O₄The nano particles are prepared from ferrous salt and ferric salt by a coprecipitation method;

wherein the molar ratio of the ferrous salt to the ferric salt is 1: 2.

6. an ammonia gas sensor as defined in claim 5 wherein the Fe₃O₄The nanoparticles are prepared by a process comprising the steps of:

ferrous salt and ferric salt are dissolved in water, and alkaline substances and surface active agents are added under the anaerobic condition.

7. The ammonia gas sensor of claim 6, wherein the ferrous salt is FeSO₄·7H₂O；

And/or the iron salt is FeCl₃·6H₂O；

And/or the alkaline substance is ammonia water;

and/or the surfactant is oleic acid.

8. A method for producing an ammonia gas sensor according to any one of claims 1 to 7, characterized by comprising the steps of:

(1) mixing Fe₃O₄Dissolving the nano particles and pyrrole monomers in water, and uniformly dispersing by ultrasonic to obtain a mixed solution;

(2) and vertically suspending the interdigital electrode in the mixed solution, adding iron salt into the mixed solution, and carrying out in-situ polymerization reaction.

9. The preparation method according to claim 8, wherein the in-situ polymerization reaction is carried out at room temperature for 3-5 hours.

10. The method of manufacturing according to claim 8, further comprising: and after the in-situ polymerization reaction is finished, washing the interdigital electrode by using deionized water, and annealing the interdigital electrode at the temperature of 60-80 ℃ for 1.5-2.5 h.

Technical Field

The invention relates to the technical field of gas sensors, in particular to an ammonia gas sensor and a preparation method thereof.

Background

Ammonia gas is the only high-concentration alkaline gas in the atmosphere, has high activity, can react with acid gases such as nitric acid or sulfuric acid to form aerosol, and the smog formed by the aerosol can destroy the global greenhouse gas balance and is also an important reason for forming secondary particles in the atmospheric haze pollution process. The huge population base and the rapid economic and industrial development can cause the discharge of a large amount of ammonia in various industries, such as agricultural fertilizers, building materials, urban sewer excrement and the like. Ammonia gas has strong irritation, and can cause chronic rhinitis, pharyngitis, etc., and high concentration ammonia can burn skin, eyes, mucosa of respiratory organ, and even cause lung swelling and death by excessive inhalation. Therefore, the development of a convenient and durable ammonia gas sensitive material and a gas sensor having excellent performance is particularly important for protecting the atmospheric environment and human life.

The sensitive materials of the existing ammonia gas sensor are mainly classified into four types: metal oxides, carbon tubes, graphene, and polymers. Among them, the conductive polymer has unique advantages as the sensitive layer of the gas sensor: the conductive polymer can act at room temperature, is different from inorganic metal oxide, has strong interaction with gas analyte at room temperature, and can give out identifiable signals without high temperature; secondly, the property is easy to adjust, and the physicochemical property of the conductive polymer can be adjusted by introducing branched chains or copolymerizing different macromolecules; thirdly, the detection limit of the conductive polymer is low, the detection limit of the conductive polymer to gas analytes with strong activity can reach 1ppm, and inert analytes only need a few ppm; the device is easy to prepare, the preparation process of the device taking the conductive polymer as the sensitive material is relatively simple, and the conductive polymer inherits the good mechanical property of the polymer and is suitable for most mechanical manufacturing technologies.

The organic/inorganic composite material based on the conductive polymer has the advantages of both organic and inorganic materials, and can generate a plurality of excellent characteristics through the synergistic effect, the nanometer size effect, the large specific surface area and the strong interface interaction of the organic and inorganic materials.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide an ammonia gas sensor; the invention also aims to provide a preparation method of the ammonia gas sensor.

Specifically, the invention provides the following technical scheme:

an ammonia gas sensor comprising:

an interdigital electrode; and

polypyrrole/Fe₃O₄Composite film layer of said polypyrrole/Fe₃O₄The composite film layer is formed on the surface of the interdigital electrode,

wherein the content of the first and second substances,

the polypyrrole/Fe₃O₄The composite film layer is made of Fe₃O₄NanoparticlesAnd pyrrole monomer through in-situ polymerization.

In the prior art, polypyrrole is mostly adopted to be formed on the surface of an interdigital electrode to form an ammonia gas sensor, however, when the ammonia gas sensor is used for detection, the gas diffusion speed is slow, the response time is long, and the conductivity is low. The invention discovers that polypyrrole/Fe is formed on the surface of the interdigital electrode₃O₄The composite film layer can ensure that the obtained ammonia gas sensor has higher conductivity, and Fe₃O₄The nanoparticles can improve the porosity of polypyrrole, and in the practical application process, the diffusion of the gas to be detected can be accelerated, so that the response time is shortened.

It has also been found that Fe is used₃O₄Nanoparticle doped polypyrrole films can increase the porosity of polymer films, but Fe₃O₄The doping of the nanoparticles reduces the sensitivity of the polymer film to ammonia to some extent. Based on the above, the invention further explores and discovers that the Fe can be adjusted₃O₄The doping amount of the nano particles can obtain the response time as short as possible under the condition of not sacrificing the sensitivity as much as possible; namely when said Fe₃O₄The mass ratio of the nanoparticles to the pyrrole monomers is 0.8-1.2: 1 hour, the obtained ammonia gas sensor can achieve both high sensitivity and fast response time.

In order to further improve the sensitivity of the ammonia gas sensor and accelerate the response time, the invention is used for Fe₃O₄The nanoparticles are optimized as follows:

preferably, the Fe₃O₄The solid content of the nano particles is more than 40 percent.

Preferably, the Fe₃O₄The particle size of the nano-particles is 10-20 nm.

Preferably, the Fe₃O₄The nano particles are prepared from ferrous salt and ferric salt by a coprecipitation method;

wherein the molar ratio of the ferrous salt to the ferric salt is 1: 2.

the invention discovers that ferrous salt and ferric salt are adopted to carry out copolymerization under specific molar ratioPrecipitation of the resulting Fe₃O₄The solid content of the nano particles is more than 40 percent, which is beneficial to industrial production.

Preferably, the Fe₃O₄The nanoparticles are prepared by a process comprising the steps of:

ferrous salt and ferric salt are dissolved in water, and alkaline substances and surface active agents are added under the anaerobic condition.

Preferably, the ferrous salt is FeSO₄·7H₂O；

Preferably, the iron salt is FeCl₃·6H₂O；

Preferably, the alkaline substance is ammonia;

preferably, the surfactant is oleic acid.

Aiming at the coprecipitation system of the invention, when the ferrous salt is FeSO₄·7H₂O, the ferric salt is FeCl₃·6H₂O, when the alkaline substance is ammonia water and the surfactant is oleic acid, Fe is obtained₃O₄The solid content of the nano-particles is more than 40%, the particle size is 10-20 nm, and the Fe₃O₄The nanoparticles are water soluble.

As a preferred embodiment of the present invention, said Fe₃O₄The nanoparticles are prepared by a process comprising the steps of:

taking the molar ratio of 1: 2 FeSO₄·7H₂O and FeCl₃·6H₂Dissolving O in water, introducing nitrogen to remove oxygen, adding ammonia water and oleic acid at 65-75 ℃, reacting for 0.8-1.2 h, heating to 83-87 ℃, continuing to react for 25-35 min, washing, and drying to obtain Fe₃O₄And (3) nanoparticles.

The invention also provides a preparation method of the ammonia gas sensor, which comprises the following steps:

(1) mixing Fe₃O₄Dissolving the nano particles and pyrrole monomers in water, and uniformly dispersing by ultrasonic to obtain a mixed solution;

(2) and vertically suspending the interdigital electrode in the mixed solution, adding iron salt into the mixed solution, and carrying out in-situ polymerization reaction.

Preferably, the in-situ polymerization reaction is carried out for 3-5 hours at room temperature.

Preferably, the preparation method further comprises: and after the in-situ polymerization reaction is finished, washing the interdigital electrode by using deionized water, and annealing the interdigital electrode at the temperature of 60-80 ℃ for 1.5-2.5 h.

Preferably, the iron salt is FeCl₃·6H₂O。

The invention has the beneficial effects that:

(1) the invention uses specific Fe₃O₄The nano-particle doped polypyrrole film can improve the surface area and the thermal stability of the polymer film, and simultaneously improve the porosity of the polymer film, so that the diffusion speed of ammonia in the film is increased, and the response time is shorter.

(2) Fe prepared by specific conditions₃O₄The solid content of the nano particles is far higher than that of the traditional method, and the method is suitable for mass production and is beneficial to realizing large-scale production of the ammonia gas sensor.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1

This example provides an ammonia gas sensor, which comprises interdigital electrodes and polypyrrole/Fe₃O₄A composite film layer; wherein the polypyrrole/Fe₃O₄And the composite film layer is formed on the surface of the interdigital electrode.

The embodiment also provides a preparation method of the ammonia gas sensor, which comprises the following steps:

(1) 26.9g of FeSO₄·7H₂O and 18.4g FeCl₃·6H₂Dissolving O in 50mL of water, introducing nitrogen for 30min to remove oxygen, heating to 70 ℃, rapidly adding 50mL of ammonia water and 5g of oleic acid under high stirring speed, and reacting for 1 h; heating to 85 deg.C, maintaining for 30min, discharging excessive ammonia gas, washing the obtained product with ethanol for 1 time, washing with water for multiple times, and vacuum drying to obtain water soluble Fe₃O₄Nano meterParticles;

(2) 0.6g of said Fe₃O₄Dissolving the nano particles and 0.6g of pyrrole monomer in 100mL of water, and uniformly dispersing by ultrasonic to obtain a mixed solution;

(3) selecting 4-inch P-type silicon wafer (SiO)₂(300nm)/Si) is taken as a substrate, Au (100nm)/Ti (20nm) is taken as a parameter, and the interdigital electrode with the diameter of 7mm multiplied by 11mm is obtained by cutting after substrate cleaning, photoetching, sputtering and stripping according to the prior photoetching mask;

(4) respectively soaking the interdigital electrodes in ethanol and acetone, ultrasonically cleaning, vertically suspending the interdigital electrodes in the mixed solution, and adding FeCl into the mixed solution₃·6H₂O, stirring at room temperature, and reacting for 4 hours;

(5) and after the reaction is finished, taking out the interdigital electrode, cleaning the interdigital electrode by using deionized water, and annealing the interdigital electrode for 2 hours at 70 ℃.

Comparative example 1

This comparative example provides an ammonia gas sensor, differing from example 1 only in that: the ammonia gas sensor has different preparation methods; specifically, in the step (2), 0.4g of the Fe is added₃O₄Nanoparticles and 0.8g pyrrole monomer were dissolved in 100mL water.

Comparative example 2

This comparative example provides an ammonia gas sensor, differing from example 1 only in that: the ammonia gas sensor has different preparation methods; specifically, in the step (2), 0.8g of the Fe is added₃O₄Nanoparticles and 0.4g pyrrole monomer were dissolved in 100mL water.

Test example 1

The performance of the ammonia gas sensors of example 1 and comparative examples 1 to 2 was tested in this test example:

(1) during testing, the total gas flow is controlled at 200mL/min, the voltage of the electrochemical workstation is set to be 5V, 20min of air is firstly introduced to purge the cavity before testing to obtain a stable baseline, then 10min of ammonia gas is introduced, and finally 10min of air is introduced, and the process is circulated.

(2) And (3) test results: the ammonia gas sensor of example 1 had a response time to ammonia of 30 seconds and a recovery time of 170 seconds; the ammonia gas sensor of comparative example 1 had a response time to ammonia of 70 seconds and a recovery time of 260 seconds; the ammonia gas sensor of comparative example 2 had an uneven film surface and was not suitable as a gas sensor.

(3) From the results, it can be seen that: the ammonia gas sensor provided by the invention has short response time to ammonia gas and high response recovery speed, namely Fe₃O₄When the content accounts for 50% of the mass fraction of the composite film, the response effect is optimal.

Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.