CN110018204A - A kind of method of polyaniline carbonizatin method preparation high-performance gas sensor - Google Patents

Abstract

The invention relates to a preparation method of a gas sensor array based on carbonization of hydrochloric acid-doped polyaniline nano-powder. The device involved in this method is composed of 4 sensors, a ceramic substrate and 8 electrodes. The change of the semiconductor P and N types is simply caused by different carbonization times, and the difference in detection performance between the sensors is thus caused, and the difference is greatly reduced. Improved gas sensor sensitivity. Using the data processing method of radar fingerprint, it can realize rapid (27 seconds) identification and detection of ammonia water, formaldehyde, ethanol and water vapor at room temperature (25 ℃), which makes up for the low sensitivity and long recovery time of traditional polyaniline sensors. shortcoming. The preparation method of the sensor array involved in the present invention is simple, has the advantages of non-contact identification and detection at room temperature, and greatly enhances the practicability of the sensor array.

Description

A kind of method for preparing high performance gas sensor by polyaniline carbonization

technical field

The invention relates to the field of toxic gas detection, in particular to a method for identifiable detection of toxic atmosphere. The method improves its gas-sensing sensing characteristics by directly carbonizing polyaniline and realizes differential responses to various target gases.

Background technique

In recent years, my country's social economy has continued to develop, and the consumption of agricultural mineral resources has continued to increase. At the same time, a large amount of toxic and harmful gases has also been produced. However, my country's environmental protection started late, and the level of environmental protection awareness is not high. Therefore, people's daily life and production work The environment is getting worse and the air pollution is getting worse. A clean atmosphere is one of the most important conditions for people's survival and a necessary condition to ensure people's normal life and health. Toxic gases will invade the human body through various ways, causing various diseases and endangering health. For example, through direct contact with the skin, etc., intrusion into the human body through the respiratory system, and intrusion of contaminated food into the human body through the digestive system. The increasingly severe situation of air pollution has aroused the high attention of the public and the country, so the country has also issued a series of laws and regulations to prevent and control air pollution. The detection of formaldehyde, benzene series and other harmful gases released from home decoration and furniture and car interiors in daily life, as well as the detection of various harmful gas leaks in the industrial production process and the real-time monitoring of toxic and harmful gases at the scene of explosion accidents have become very important. important research topic. For example, the efficient early warning and real-time monitoring of various on-site polluting gases such as ammonia, formaldehyde and ethanol are also the basic work of environmental protection. Therefore, we are committed to finding a low-cost, high-response, and environmentally friendly gas detection sensor to detect various toxic and harmful gases. Ammonia and formaldehyde are harmful to human health. Formaldehyde is a toxic gas, it is colorless, soluble in water, and has a pungent odor. Formaldehyde is ubiquitous in everyday life, and it is often found in furniture, clothing and industrial production. Inhaling formaldehyde gas can cause burning sensations in the eyes, throat and even difficulty breathing. When the formaldehyde concentration is too high and inhaled for a long time, it can lead to more serious lung disease and even cancer. As early as October 27, 2017, formaldehyde appeared in the list of carcinogens published by the World Health Organization's International Agency for Research on Cancer. Ammonia is very important to life on earth, it is an important component of many foods and fertilizers, and it is also a direct or indirect component of all medicines. Ammonia has a wide range of uses, but it also has many dangerous properties. Ammonia is a toxic gas. The inhalation of ammonia gas will also endanger health. When inhaling high concentrations of ammonia gas, it will cause damage to the trachea, bronchial mucosa and even lungs. emphysema. Ammonia is also an important raw material for the manufacture of nitric acid, fertilizers, and explosives. Because of its strong explosiveness, it is likely to be used in terrorist attacks. Therefore, the detection and real-time monitoring of ammonia, a highly toxic gas, is very important in industry, agriculture, medical fields, and even in the field of social security hidden danger investigation. Therefore, we urgently need to create a more practical, more cost-effective and effective Gas sensors to detect these gases.

In recent years, measurement and detection technology based on resistive gas sensors has developed rapidly, providing new ideas and methods for gas detection. Doped polyaniline is generally used to detect strong acid and strong alkali gases, and the conductivity of polyaniline before carbonization is relatively poor, while high selectivity and low power consumption are two important indicators to measure the performance of resistance gas sensors. Polyaniline has higher selectivity and sensitivity, so as to realize the identification and detection of strong acid and alkali gases at room temperature.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a gas sensor array based on hydrochloric acid-doped polyaniline carbonized nano-powder. The device involved in this method is composed of 4 sensors, a ceramic substrate and 8 electrodes. The surface state and electron depletion layer are changed by simply using different time of carbonization, and the difference in detection performance between the sensors is caused. Using the data processing method of radar fingerprint, the identification and detection of ammonia water, formaldehyde, ethanol and water vapor can be realized at room temperature (25 ℃).

Described in the present invention is a method for preparing a gas sensor array based on hydrochloric acid-doped polyaniline carbonized nano-powder, and the specific operation is carried out according to the following steps:

Preparation of gas sensitive materials:

a. Dissolve ammonium persulfate and hydrochloric acid in 25 mL of deionized water in a molar ratio of 5:16;

b. Dissolve 5 mL of aniline in 400 mL of deionized water, and then slowly drop the solution obtained in step a into it, and stir for 19 hours at 25° C. in the dark; the obtained solution is ultrasonicated with deionized water and centrifuged for 6 times ;

c, drying the precipitate obtained in step b at a temperature of 25°C for about 24 hours to obtain a hydrochloric acid-doped polyaniline nano-powder;

d. Divide the hydrochloric acid-doped polyaniline nano-powder obtained in step c into four parts, take out three parts and put them into a chemical vapor deposition furnace respectively, and carbonize them for 1h, 3h and 5h under the protection of nitrogen gas.

Preparation of Resistive Gas Sensor Arrays:

e. Disperse the hydrochloric acid-doped polyaniline nano-powder obtained in steps c and d in deionized water and grind for 10 minutes to obtain 4 parts of hydrochloric acid-doped polyaniline nano-paste, which are then uniformly coated respectively. The first sensor, the second sensor, the third sensor and the fourth sensor were dried at room temperature for 24 hours to form a gas sensor array.

The nanostructured gas sensor array obtained by carbonizing hydrochloric acid-doped polyaniline has the purpose of detecting toxic atmospheres containing ammonia, formaldehyde, ethanol and steam, and after carbonization, the polyaniline P-type semiconductor will be changed into an N-type semiconductor. .

The purpose of the present invention is to provide a method for preparing a gas sensor array based on carbonized nano-powders of hydrochloric acid-doped polyaniline. The device involved in the method is composed of a first sensor, a second sensor, a third sensor and a fourth sensor, a ceramic substrate and 8 electrodes, and the surface state and electron depletion layer are changed simply by carbonization at different times. , and thus cause the difference of detection performance among the sensors, and enhance the sensitivity of the gas sensor. Using the data processing method of radar fingerprint, the identification and detection of ammonia water, formaldehyde, ethanol and water vapor can be realized at room temperature (25 ℃).

Description of drawings

1 is the scanning electron microscope images (a) to (d) of the present invention respectively corresponding to the hydrochloric acid-doped polyaniline without carbonization and after carbonization for 1, 3, and 5 hours;

2 is a graph showing the response curves of the sensor array to ammonia water and air at room temperature in the present invention, wherein the response curves corresponding to (a) to (d) correspond to the first sensor, the second sensor, the third sensor, the Four sensors;

3 is a graph showing the response curves of the sensor array to formaldehyde and air at room temperature in the present invention, wherein the response curves corresponding to (a) to (d) correspond to the first sensor, the second sensor, the third sensor, the Four sensors;

4 is a graph showing the response curves of the sensor array to ethanol and air at room temperature in the present invention, wherein the response curves corresponding to (a) to (d) correspond to the first sensor, the second sensor, the third sensor, the Four sensors;

5 is a response curve diagram of the sensor array in the present invention to saturated steam at room temperature, wherein the response curves corresponding to (a) to (d) correspond to the first sensor, the second sensor, the third sensor, the fourth sensor, respectively. sensor;

Fig. 6 is the radar fingerprint spectrum of ammonia water (a), formaldehyde (b), water vapor (c) and ethanol (d) in the present invention;

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments:

Example 1 A method for preparing high-performance gas sensor by polyaniline carbonization

The preparation method of polyaniline carbonization gas sensor material includes four stages: preparation of gas sensor material, preparation of gas sensor array, detection of target atmosphere by gas sensor array and identification and distinction of toxic gas.

a. Dissolve ammonium persulfate and hydrochloric acid in 25 mL of deionized water in a molar ratio of 5:16;

b. Dissolve 5 mL of aniline in 400 mL of deionized water, and then slowly drop the solution obtained in step a into it, and stir at 25 °C for 19 h under dark conditions; the obtained solution is ultrasonicated with deionized water and centrifuged Separate 6 times;

c, drying the precipitate obtained in step b at a temperature of 25°C for about 24 hours to obtain a hydrochloric acid-doped polyaniline nano-powder;

a. Dissolve ammonium persulfate and hydrochloric acid in 25 mL of deionized water in a molar ratio of 5:16;

b. Dissolve 5 mL of aniline in 400 mL of deionized water, and then slowly drop the solution obtained in step a into it, and stir at 25°C for 19 h under dark conditions; the obtained solution is ultrasonicated with deionized water and centrifuged. 6 times;

c. Dry the precipitate obtained in step b at a temperature of 25 °C for about 24 hours to obtain polyaniline nano-powder doped with hydrochloric acid, take out a portion of it and put it in a chemical vapor deposition furnace, and carbonize it for 1 h under the protection of nitrogen gas. The temperature is set to 600℃;

a. Dissolve ammonium persulfate and hydrochloric acid in 25 mL of deionized water in a molar ratio of 5:16;

b. Dissolve 5 mL of aniline in 400 mL of deionized water, and then slowly drop the solution obtained in step a into it, and stir at 25 °C for 19 h under dark conditions; the obtained solution is ultrasonicated with deionized water and centrifuged Separate 6 times;

c. Dry the precipitate obtained in step b at a temperature of 25 °C for about 24 hours to obtain a polyaniline nano-powder doped with hydrochloric acid, take out a portion of it and put it into a chemical vapor deposition furnace, and carbonize it for 3 hours under the protection of nitrogen. Set to 600 ℃;

a. Dissolve ammonium persulfate and hydrochloric acid in 25 mL of deionized water in a molar ratio of 5:16;

b. Dissolve 5 mL of aniline in 400 mL of deionized water, and then slowly drop the solution obtained in step a into it, and stir at 25 °C for 19 h under dark conditions; the obtained solution is ultrasonicated with deionized water and centrifuged Separate 6 times;

c. Dry the precipitate obtained in step b at a temperature of 25 °C for about 24 hours to obtain polyaniline nano-powder doped with hydrochloric acid, take out a portion of it and put it in a chemical vapor deposition furnace, and carbonize it for 5 hours under the protection of nitrogen gas. The temperature is set to 600 ℃;

Preparation of gas sensor array:

The hydrochloric acid-doped polyaniline nano-powders obtained in step c in Examples 1-4 were dispersed in deionized water and ground for 10 minutes to obtain 4 parts of hydrochloric acid-doped polyaniline nano-powder pastes, which were then homogeneously The gas is coated on the first sensor, the second sensor, the third sensor and the fourth sensor, and dried at room temperature to form a gas sensor array.

Detection of target atmosphere by gas sensor array:

Detection of target atmosphere by gas sensor array:

Turn on the power of the Catherine meter, and test the resistance of the sensor array obtained in step d in ammonia water atmosphere and air under the bias voltage of 4 V at room temperature (temperature 25 ℃, relative humidity 25%). The response curve is from (a) to ( d) are carbonization 0h, 1h, 3h and 5h, respectively. It can be seen from the response curve that at room temperature, the response sizes of the hydrochloric acid-doped polyaniline resistive sensor array to 1000ppm ammonia water atmosphere reach -69.7%, 34831.5%, 81918.9% and 60609.4%, respectively; the response times are 1.4, 24.0, 25.9 and 22.9; recovery times were 7.2, 1.6, 0.9, and 1.8, respectively (Figure 3).

Turn on the power of the Catherine meter, and test the resistance of the sensor array obtained in step d in formaldehyde atmosphere and air under the bias voltage of 4 V at room temperature (temperature 25 °C, relative humidity 25%). The response curve is from (a) to ( d) are carbonization 0h, 1h, 3h and 5h, respectively. It can be seen from the response curve that at room temperature, the response sizes of the hydrochloric acid-doped polyaniline resistive sensor array to 1000ppm formaldehyde atmosphere reach -16%, 260.9%, 761.0% and 8191.9%, respectively; the response times are 11.0, 22.7, 24.8 and 14.8; recovery times were 10.3, 2.1, 2.7 and 1.2, respectively (Fig. 4).

Turn on the power of the Catherine meter, and test the resistance of the sensor array obtained in step d in water vapor and air at room temperature (temperature 25 °C, relative humidity 25%) under a bias voltage of 4 V. The response curve is from (a) to (d) are carbonization 0h, 1h, 3h and 5h, respectively. It can be seen from the response curve that at room temperature, the response sizes of the hydrochloric acid-doped polyaniline resistive sensor array to 1000ppm ethanol reach -27.9%, 9887.5%, 6813.6% and 18876.4%, respectively; the response times are 9.5, 20.5, and 24.9, respectively. and 23.5; recovery times were 10.3, 1.0, 1.4, and 1.7, respectively (Fig. 6).

Turn on the power of the Catherine meter, and test the resistance of the sensor array obtained in step d in ethanol atmosphere and air at room temperature (temperature 25 °C, relative humidity 25%) under a bias voltage of 4 V. The response curve is from (a) to ( d) are carbonization 0h, 1h, 3h and 5h, respectively. It can be seen from the response curve that at room temperature, the response sizes of the hydrochloric acid-doped polyaniline resistive sensor array to 1000ppm ethanol atmosphere reached -42.6%, 949.0%, 7409.6% and 3132.2%, respectively; the response times were 9.5, 22.9, 16.5 and 17.7; recovery times were 8.8, 0.8, 1.1 and 1.0, respectively (Figure 5).

Identification and distinction of toxic atmospheres:

The response size and response time of the first sensor, the second sensor, the third sensor and the fourth sensor in the sensor array to the four atmospheres are processed by the radar fingerprint analysis method, and the radar fingerprints of the four atmospheres are obtained. The spectrum can realize the distinction of four atmospheres, as shown in Figure 6;

The present invention can be more easily understood through the above-mentioned specific embodiments. The above-described embodiments are merely illustrative, and should not be construed as limiting the scope of the present invention.

Claims (5)

1. a preparation method of a gas sensor array based on the carbonization of hydrochloric acid-doped polyaniline to change the sensor P, N type and carbonization at different times to improve the sensitivity of the sensor, and the specific operation is carried out according to the following steps: Preparation of gas sensitive materials: Dissolve ammonium persulfate and hydrochloric acid in 25 mL of deionized water in a molar ratio of 5:16; Dissolve 5 mL of aniline in 400 mL of deionized water, then slowly drop the solution obtained in step a into it, and stir for 19 hours at 25°C in the dark; the obtained solution is ultrasonicated with deionized water and centrifuged for 6 times; drying the precipitate obtained in step b at a temperature of 20-600° C. for about 8-24 hours to obtain a hydrochloric acid-doped polyaniline nano-powder; Preparation of Resistive Gas Sensor Arrays: The hydrochloric acid-doped polyaniline nano-powder obtained in step c was divided into four parts, and three parts were taken out and put into a chemical vapor deposition furnace respectively, and carbonized under nitrogen protection for 1 h, 3 h and 5 h. 2. The hydrochloric acid-doped polyaniline nano-powders obtained in steps c and d are dispersed in deionized water and ground for 10 minutes to obtain 4 parts of hydrochloric acid-doped polyaniline nano-pastes, which are then uniformly coated respectively. The first sensor, the second sensor, the third sensor and the fourth sensor were dried at room temperature for 24 hours to form a gas sensor array. 3. a kind of preparation method of the gas sensor array based on hydrochloric acid-doped polyaniline carbonization according to claim 1, it is characterized in that the nano-powder after the hydrochloric acid-doped polyaniline carbonization obtained in step c is carbonized, its The carbonization temperature was 600°C. 4 . The method for preparing a nanostructured gas sensor array based on carbonization of hydrochloric acid-doped polyaniline according to claim 1 , wherein the temperature in step c is 24° C. and the reaction time is 24h. 5 . 5. The nanostructured gas sensor array obtained by carbonizing the hydrochloric acid-doped polyaniline obtained by the method of claim 1 has the purpose of detecting atmospheres containing ammonia, formaldehyde, ethanol and water vapor.