阅读说明：本技术 一种气相聚合法制备聚邻甲氧基苯胺/氧化锌纳米阵列气敏元件的方法及应用 (Method for preparing poly (o-anisidine)/zinc oxide nano-array gas-sensitive element by gas-phase polymerization method and application ) 是由 徐英明 高蕊 霍丽华 程晓丽 张现发 于 2020-11-19 设计创作，主要内容包括：一种气相聚合法制备聚邻甲氧基苯胺/氧化锌纳米阵列气敏元件的方法及应用,它涉及一种制备氧化锌气敏元件的方法及应用。本发明主要解决现有聚合物/金属氧化物复合材料无法在高湿条件下进行低浓度氨气的检测,导致无法检测人体呼出气体中的氨气问题。制备方法：一、ZnO纳米棒阵列；二、气体扩散。本发明用于一种气相聚合法制备聚邻甲氧基苯胺/氧化锌纳米阵列气敏元件的方法及应用。(A method for preparing a poly-o-anisidine/zinc oxide nano-array gas sensor by a gas phase polymerization method and application thereof relate to a method for preparing a zinc oxide gas sensor and application thereof. The invention mainly solves the problem that the existing polymer/metal oxide composite material can not detect low-concentration ammonia gas under high humidity condition, so that the ammonia gas in the exhaled air of human body can not be detected. The preparation method comprises the following steps: firstly, ZnO nano-rod array; secondly, gas diffusion. The invention relates to a method for preparing a poly (o-anisidine)/zinc oxide nano-array gas-sensitive element by a gas-phase polymerization method and application thereof.)

1. A method for preparing a poly-o-anisidine/zinc oxide nano-array gas sensor by a gas phase polymerization method is characterized by comprising the following steps:

firstly, ZnO nanorod array:

adding zinc acetylacetonate and urea into a mixed solvent of methanol and water, uniformly mixing to obtain a mixed solution, dipping the sensor element into the mixed solution, keeping the temperature for 5-20 h under the condition that the temperature of a blast drying oven is 100-120 ℃, taking out the sensor element after the reaction is finished, and roasting for 1-2 h under the conditions that the air atmosphere and the temperature are 400-500 ℃ to obtain the ZnO nanorod array sensor element;

the mass percentage of the zinc acetylacetonate in the mixed solution is 1-10%; the molar ratio of the zinc acetylacetonate to the urea is 1 (1-2); the volume ratio of the formazan pure to the water is 1 (5-10);

secondly, gas diffusion:

soaking the ZnO nanorod array sensor element in an ammonium persulfate aqueous solution with the concentration of 0.1-0.5 mol/L for 5-30 s, taking out the sensor element, placing o-anisidine in an open container, then placing the container containing the o-anisidine and the sensor element in the same closed space, volatilizing the o-anisidine to the surface of the sensor element under the condition that the temperature is 1-10 ℃, and carrying out gas diffusion reaction for 10-60 min to obtain the poly-o-anisidine/zinc oxide nano array gas-sensitive element.

2. The method for preparing the gas-sensitive element of the poly (o-anisidine)/zinc oxide nanoarray by the gas-phase polymerization method according to claim 1, wherein the volume of the closed space in the second step is 1L to 8L.

3. The method for preparing a poly (o-anisidine)/zinc oxide nanoarray gas sensor by gas phase polymerization as claimed in claim 1, wherein the open area of the open container in the second step is 30cm²～100cm²。

4. The method for preparing the poly (o-anisidine)/zinc oxide nano-array gas sensor by the gas phase polymerization method according to claim 1, wherein 100 μ L to 400 μ L of o-anisidine is placed in an open container in the second step.

5. The method for preparing the poly (o-methoxyaniline)/zinc oxide nanoarray gas sensor by the gas phase polymerization method according to claim 1, wherein the sensor element is immersed in the mixed solution in the step one, and the temperature is kept for 8 to 20 hours under the condition that the temperature of an air-blast drying oven is 100 to 120 ℃.

6. The method for preparing the poly (o-anisidine)/zinc oxide nanoarray gas-sensitive element by the gas-phase polymerization method according to claim 1, wherein in the step one, the poly (o-anisidine)/zinc oxide nanoarray gas-sensitive element is calcined for 1 hour under the conditions of air atmosphere and temperature of 450-500 ℃.

7. The method for preparing the gas-sensitive element of the poly (o-anisidine)/zinc oxide nano-array by the gas-phase polymerization method according to claim 1, wherein the mass percent of the zinc acetylacetonate in the mixed solution in the step one is 5-10%; the volume ratio of the formazan pure to the water in the step one is 1 (5-8).

8. The method for preparing the poly (o-methoxyaniline)/zinc oxide nano-array gas sensor by the gas-phase polymerization method according to claim 1, wherein in the second step, the ZnO nano-rod array sensor element is immersed in an ammonium persulfate aqueous solution with the concentration of 0.1-0.3 mol/L for 5-30 s.

9. The method for preparing the poly (o-anisidine)/zinc oxide nanoarray gas sensor by the gas phase polymerization method according to claim 1, wherein in the second step, o-anisidine is volatilized to the surface of the sensor element at a temperature of 2 ℃ to 10 ℃, and gas diffusion reaction is carried out for 40min to 60 min.

10. The application of the poly (o-anisidine)/zinc oxide nano-array gas sensor prepared by the method of claim 1, wherein the poly (o-anisidine)/zinc oxide nano-array gas sensor is used for detecting ammonia in human exhaled air.

Technical Field

The invention relates to a method for preparing a zinc oxide gas sensitive element and application thereof.

Background

Ammonia is a common air pollutant, colorless but irritatingA sexual odor. If NH exhaled by the human body₃NH content higher than that of healthy human body₃Levels (about 0.96ppm) may indicate that some kidney disease may be present in the body. NH exhaled by uremic patients is reported₃The content of the compound has obvious changes before and after dialysis, which is an important index for monitoring the kidney state of a patient. Therefore, there is a need to develop a gas sensor capable of rapidly detecting ammonia gas in real time for detecting ammonia gas exhaled by a human body, so as to realize preliminary screening of kidney diseases of the human body in the medical field.

At present, the reports of detecting ammonia gas by using a polymer/metal oxide composite material generally refer to an in-situ polymerization method for preparing the composite material and preparing a sensor for detecting high-concentration ammonia gas, the sensor element prepared by the in-situ polymerization method is easy to have the problems of uneven material thickness and the like, the subsequent treatment of the product is required, the operation is complex, and the method is not suitable for large-scale industrial production. And the polymer material widely used at present is polyaniline, the rigidity of a polyaniline chain is stronger, the acting force between chains is larger, the solubility is low, and the good moisture resistance is not achieved. The poor humidity interference resistance of the polymer sensor is the biggest problem existing at present, as is known, human body exhaled air contains more water vapor, the humidity reaches more than 70%, and the existing polymer/metal oxide composite material cannot detect low-concentration ammonia gas under high humidity conditions, so that the ammonia gas in the human body exhaled air cannot be detected.

Disclosure of Invention

The invention provides a method for preparing a poly-o-anisidine/zinc oxide nano-array gas sensor by a gas phase polymerization method and application thereof, aiming at solving the problem that the existing polymer/metal oxide composite material cannot detect low-concentration ammonia gas under high humidity condition, so that the ammonia gas in the exhaled air of a human body cannot be detected.

A method for preparing a poly-o-anisidine/zinc oxide nano-array gas sensor by a gas phase polymerization method comprises the following steps:

firstly, ZnO nanorod array:

adding zinc acetylacetonate and urea into a mixed solvent of methanol and water, uniformly mixing to obtain a mixed solution, dipping the sensor element into the mixed solution, keeping the temperature for 5-20 h under the condition that the temperature of a blast drying oven is 100-120 ℃, taking out the sensor element after the reaction is finished, and roasting for 1-2 h under the conditions that the air atmosphere and the temperature are 400-500 ℃ to obtain the ZnO nanorod array sensor element;

the mass percentage of the zinc acetylacetonate in the mixed solution is 1-10%; the molar ratio of the zinc acetylacetonate to the urea is 1 (1-2); the volume ratio of the formazan pure to the water is 1 (5-10);

secondly, gas diffusion:

soaking the ZnO nanorod array sensor element in an ammonium persulfate aqueous solution with the concentration of 0.1-0.5 mol/L for 5-30 s, taking out the sensor element, placing o-anisidine in an open container, then placing the container containing the o-anisidine and the sensor element in the same closed space, volatilizing the o-anisidine to the surface of the sensor element under the condition that the temperature is 1-10 ℃, and carrying out gas diffusion reaction for 10-60 min to obtain the poly-o-anisidine/zinc oxide nano array gas-sensitive element.

The invention has the beneficial effects that:

(1) the synthesis method is simple, the o-anisidine is directly polymerized on the surface of the ZnO nanorod array sensor element by adopting a gas phase diffusion method to obtain the sensor element with uniform thickness, the preparation method is simple, the cost is low, and the industrial production is easy to realize.

(2) The poly-o-methoxyaniline/zinc oxide nano-array gas sensor prepared by the invention has excellent gas-sensitive performance, responds to 100ppm of ammonia gas by 8.88, has strong humidity interference resistance, can still respond to ammonia gas when the humidity reaches 80%, can effectively detect ammonia gas in exhaled gas of a human body, and can be used as an auxiliary means for judging the state of a kidney disease in the medical field.

(3) The electron-donating substituent methoxyl group is added on the basis of the aniline, so that the rigidity of a polymer chain is effectively reduced, the acting force between chains is reduced, the possible side reaction at the substitution position is effectively prevented, and the electron-donating substituent can reduce the oxidation potential of the aniline monomer and improve the activity. The method is favorable for improving the charge transmission capability of the surface of the polymer, so that the polymer has stronger humidity interference resistance.

(4) The method has the advantages that the selectivity of the sensor to ammonia gas is effectively improved for the composition of zinc oxide and poly-o-methoxyaniline, the zinc oxide nanorod array is directly grown on the sensor element in situ by adopting a hydrothermal method, the operation is simple, the sensor element does not need to be prepared secondarily, the method is suitable for large-scale production, and the nanorod array is uniformly dispersed and is favorable for gas diffusion. After the sensor is compounded with poly-o-methoxyaniline, room temperature sensing is realized, the response to ammonia gas after the sensor and poly-o-methoxyaniline are combined is far higher than that of a single substance, the moisture resistance is enhanced, and the sensor is an important factor for realizing detection of ammonia gas in exhaled gas of a human body.

The invention relates to a method for preparing a poly (o-anisidine)/zinc oxide nano-array gas-sensitive element by a gas-phase polymerization method and application thereof.

Drawings

FIG. 1 is a scanning electron microscope image of a ZnO nanorod array sensor element prepared at step one of the examples;

FIG. 2 is a scanning electron microscope image of the gas sensor with poly (o-anisidine)/zinc oxide nanoarrays prepared in the first example;

FIG. 3 is an XRD diagram of a gas sensor of a poly (o-anisidine)/zinc oxide nanoarray prepared in the first example;

FIG. 4 is a graph of the sensitivity of the gas sensor with poly (o-anisidine)/zinc oxide nanoarrays prepared in the first example for detecting different gases;

FIG. 5 is a graph showing the recovery of the gas sensor of the poly (o-anisidine)/zinc oxide nanoarray composite prepared in the first example from the response to low-concentration ammonia gas at room temperature;

FIG. 6 is a graph showing the recovery of the gas sensor of the poly (o-anisidine)/zinc oxide nanoarray composite material prepared in the first example from the response to high-concentration ammonia gas at room temperature;

FIG. 7 is a graph showing the recovery of the poly (o-anisidine)/zinc oxide nanoarray gas sensor prepared in example one from 1ppm ammonia gas at room temperature under different humidity environments, where 1 is humidity 90%, 2 is humidity 85%, 3 is humidity 80%, 4 is humidity 75%, 5 is humidity 70%, and 6 is humidity 60%;

FIG. 8 is a graph of the response of the gas sensor of the poly (o-anisidine)/zinc oxide nanoarray prepared in the first example to ammonia in the exhaled air of five volunteers at room temperature.

Detailed Description

The first embodiment is as follows: the method for preparing the poly-o-anisidine/zinc oxide nano-array gas-sensitive element by the gas-phase polymerization method comprises the following steps:

firstly, ZnO nanorod array:

adding zinc acetylacetonate and urea into a mixed solvent of methanol and water, uniformly mixing to obtain a mixed solution, dipping the sensor element into the mixed solution, keeping the temperature for 5-20 h under the condition that the temperature of a blast drying oven is 100-120 ℃, taking out the sensor element after the reaction is finished, and roasting for 1-2 h under the conditions that the air atmosphere and the temperature are 400-500 ℃ to obtain the ZnO nanorod array sensor element;

the mass percentage of the zinc acetylacetonate in the mixed solution is 1-10%; the molar ratio of the zinc acetylacetonate to the urea is 1 (1-2); the volume ratio of the formazan pure to the water is 1 (5-10);

secondly, gas diffusion:

soaking the ZnO nanorod array sensor element in an ammonium persulfate aqueous solution with the concentration of 0.1-0.5 mol/L for 5-30 s, taking out the sensor element, placing o-anisidine in an open container, then placing the container containing the o-anisidine and the sensor element in the same closed space, volatilizing the o-anisidine to the surface of the sensor element under the condition that the temperature is 1-10 ℃, and carrying out gas diffusion reaction for 10-60 min to obtain the poly-o-anisidine/zinc oxide nano array gas-sensitive element.

The beneficial effects of the embodiment are as follows:

(1) the synthesis method of the embodiment is simple, the o-methoxyaniline is directly polymerized on the surface of the ZnO nanorod array sensor element by adopting a gas phase diffusion method, the sensor element with uniform thickness is obtained, the preparation method is simple, the cost is low, and the industrial production is easy to realize.

(2) The poly-o-methoxyaniline/zinc oxide nano-array gas sensor prepared by the embodiment has excellent gas-sensitive performance, the response to 100ppm ammonia is 8.88, the humidity interference resistance is strong, the response to ammonia can be still realized when the humidity reaches 80%, the ammonia in the exhaled air of a human body can be effectively detected, and the poly-o-methoxyaniline/zinc oxide nano-array gas sensor can be used as an auxiliary means for judging the state of a kidney disease in the medical field.

(3) The embodiment adds the electron-donating substituent methoxyl group on the basis of the aniline, effectively reduces the rigidity of a polymer chain, reduces the acting force between chains, effectively prevents the side reaction possibly occurring at the substitution position, and the electron-donating substituent can also reduce the oxidation potential of the aniline monomer and improve the activity. The method is favorable for improving the charge transmission capability of the surface of the polymer, so that the polymer has stronger humidity interference resistance.

(4) The method has the advantages that the selectivity of the sensor to ammonia gas is effectively improved for the composition of zinc oxide and poly-o-methoxyaniline, the zinc oxide nanorod array is directly grown on the sensor element in situ by adopting a hydrothermal method, the operation is simple, the sensor element does not need to be prepared secondarily, the method is suitable for large-scale production, and the nanorod array is uniformly dispersed and is favorable for gas diffusion. After the sensor is compounded with poly-o-methoxyaniline, room temperature sensing is realized, the response to ammonia gas after the sensor and poly-o-methoxyaniline are combined is far higher than that of a single substance, the moisture resistance is enhanced, and the sensor is an important factor for realizing detection of ammonia gas in exhaled gas of a human body.

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the volume of the closed space in the second step is 1L-8L. The rest is the same as the first embodiment.

The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the open area of the open container in the step two is 30cm²～100cm². The other is the same as in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: in the second step, 100 mu L-400 mu L o-anisidine is placed in an open container. The others are the same as the first to third embodiments.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: in the first step, the sensor element is immersed in the mixed solution, and the temperature is kept for 8-20 h under the condition that the temperature of an air-blast drying oven is 100-120 ℃. The rest is the same as the first to fourth embodiments.

The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: in the first step, the mixture is roasted for 1 hour under the conditions of air atmosphere and temperature of 450-500 ℃. The rest is the same as the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the mass percentage of the zinc acetylacetonate in the mixed solution in the step one is 5-10%; the volume ratio of the formazan pure to the water in the step one is 1 (5-8). The others are the same as the first to sixth embodiments.

The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: and in the second step, the ZnO nanorod array sensor element is immersed in an ammonium persulfate aqueous solution with the concentration of 0.1-0.3 mol/L for 5-30 s. The rest is the same as the first to seventh embodiments.

The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: and in the second step, under the condition that the temperature is 2-10 ℃, the o-anisidine volatilizes to the surface of the sensor element, and the gas diffusion reaction is carried out for 40-60 min. The other points are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: in the application of the poly (o-anisidine)/zinc oxide nano-array gas sensor, the poly (o-anisidine)/zinc oxide nano-array gas sensor is used for detecting ammonia in exhaled air of a human body.

The following examples were used to demonstrate the beneficial effects of the present invention:

the first embodiment is as follows:

a method for preparing a poly-o-anisidine/zinc oxide nano-array gas sensor by a gas phase polymerization method comprises the following steps:

firstly, ZnO nanorod array:

adding zinc acetylacetonate and urea into a mixed solvent of methanol and water, uniformly mixing to obtain a mixed solution, soaking the sensor element into the mixed solution, keeping the temperature for 8 hours under the condition that the temperature of a blast drying oven is 120 ℃, taking out the sensor element after the reaction is finished, and roasting for 1 hour under the conditions of air atmosphere and 500 ℃ to obtain a ZnO nanorod array sensor element;

the mass percentage of the zinc acetylacetonate in the mixed solution is 10%; the molar ratio of the zinc acetylacetonate to the urea is 1: 2; the volume ratio of the formazan pure to the water is 1: 5;

secondly, gas diffusion:

soaking the ZnO nanorod array sensor element in 0.1mol/L ammonium persulfate aqueous solution for 20s, taking out the sensor element, placing 224 mu L o-anisidine in an open container, then placing the container containing the o-anisidine and the sensor element in the same closed space, volatilizing the o-anisidine to the surface of the sensor element at the temperature of 2 ℃, and carrying out gas diffusion reaction for 40min to obtain the poly-o-anisidine/zinc oxide nanoarray gas-sensitive element.

And the volume of the closed space in the second step is 5L.

The open area of the open container in the step two is 80cm²。

Preparation of sensor element:

repeatedly washing the poly-o-anisidine/zinc oxide nano-array gas-sensitive element with deionized water and ethanol for 3 times, then naturally drying in the shade, and fixing the obtained sensor element on a sensor base for testing.

And (3) testing gas-sensitive performance:

at room temperature, testing the response capability of the poly-o-anisidine/zinc oxide nano-array gas-sensitive element to ammonia gas, wherein the ammonia gas is prepared by adopting a static gas distribution method, and the calculation method of the response of the sensor to target gas comprises the following steps: and S is Rg/Ra. Rg and Ra are the stable resistance values of the sensor after contact with the target gas and the stable resistance values in fresh air, respectively. The sensor needs to quickly and accurately identify target gas, as ammonia continuously responds on the surface of the poly-o-anisidine/zinc oxide nano array sensitive material, the overlong reaction time has no practical significance, and the response sensitivity of the poly-o-anisidine/zinc oxide nano array gas sensitive element and ammonia responding 100s is enough to realize real-time early warning of ammonia, so that the response time of the sensor is controlled to be 100 s. The recovery time is the time for the sensor resistance to reach 90% of the total resistance change after desorption of the target gas from the surface of the material.

FIG. 1 is a scanning electron microscope image of a ZnO nanorod array sensor element prepared at step one of the examples; as can be seen from the figure, the nanorod array is uniformly dispersed, has small size and diameter of about 50nm, has good dispersibility, is beneficial to the diffusion of gas molecules, and is the basis of excellent gas-sensitive performance of the sensor.

FIG. 2 is a scanning electron microscope image of the gas sensor with poly (o-anisidine)/zinc oxide nanoarrays prepared in the first example; as can be seen from the figure, poly-o-methoxyaniline is compounded on the surface of the ZnO nanorod array, and meanwhile, a diffusion channel is reserved for gas molecules, so that the poly-o-methoxyaniline is an important factor for realizing room temperature sensing of the sensor.

FIG. 3 is an XRD diagram of a gas sensor of a poly (o-anisidine)/zinc oxide nanoarray prepared in the first example; as can be seen from the figure, the poly-o-anisidine/zinc oxide nano-array composite material has an amorphous carbon peak at 20 degrees and an obvious ZnO characteristic peak, which indicates that the material is the poly-o-anisidine/zinc oxide nano-array composite material.

FIG. 4 is a graph of the sensitivity of the gas sensor with poly (o-anisidine)/zinc oxide nanoarrays prepared in the first example for detecting different gases; as can be seen, the sensor has better selectivity to 100ppm ammonia gas at room temperature, and the response sensitivity reaches 8.88.

FIG. 5 is a graph showing the recovery of the gas sensor of the poly (o-anisidine)/zinc oxide nanoarray composite prepared in the first example from the response to low-concentration ammonia gas at room temperature; as can be seen from the figure, the sensor has good response recovery capability in the concentration range of 10 ppb-1000 ppb ammonia gas, and the lowest detection limit reaches 10 ppb.

FIG. 6 is a graph showing the recovery of the gas sensor of the poly (o-anisidine)/zinc oxide nanoarray composite material prepared in the first example from the response to high-concentration ammonia gas at room temperature; as can be seen from the graph, the response recovery time of 100ppm ammonia gas was 100s and 136s, respectively.

Fig. 7 is a graph showing the recovery of the poly (o-anisidine)/zinc oxide nanoarray gas sensor prepared in example one to 1ppm ammonia gas under different humidity environments at room temperature, where 1 is humidity 90%, 2 is humidity 85%, 3 is humidity 80%, 4 is humidity 75%, 5 is humidity 70%, and 6 is humidity 60%. As can be seen from the graph, the sensor has obvious electric signal response to ammonia gas when the ambient humidity is lower than 85%, and the response of the sensor becomes smaller with the increase of the humidity, but the ammonia gas in the environment with higher humidity can still be effectively captured.

FIG. 8 is a graph of the response of the gas sensor of the poly (o-anisidine)/zinc oxide nanoarray prepared in the first example to ammonia in the exhaled air of five volunteers at room temperature. Five volunteers were 18-40 years old and healthy. The sensor detected an ammonia response of about 1.10 in the expired air from five volunteers. According to C.H.Liu, H.L.Tai, P.Zhang, Z.B.Ye, Y.J.Su and Y, D.Jiang, Sensors and Actuators B,2017,246,85-95, it is known that the humidity of exhaled gas of a healthy human body is between 75% and 85%, and the concentration of ammonia gas in the exhaled gas is about 1ppm, FIG. 7 has tested a response recovery curve of the sensor to 1ppm of ammonia gas under different humidities, and the test result shows that the response of the sensor to 1ppm of ammonia gas is between 1.05 and 1.13 between 75% and 85%, so that the detection of the sensor to the actual exhaled gas of the human body is consistent with the experimental simulation value, which shows that the sensor can detect an actual sample, and the concentration of ammonia gas in the exhaled gas of a patient with kidney disease is higher, therefore, the poly-o-anisidine/zinc oxide nano-array sensor can realize the initial screening of kidney diseases of the human body.

From the above, the response of the sensor prepared in this embodiment to 100ppm ammonia gas is 8.88, the response recovery time is 100s and 136s, respectively, the lowest detection limit is 0.01ppm, the excellent moisture resistance of poly-o-anisidine enables the sensor to detect low-concentration ammonia gas in a high-humidity environment, the sensor also shows good performance for detecting an actual sample, the ammonia gas in the exhaled gas of a human body can be effectively identified, and the screening of kidney diseases in the medical field is expected to be realized.