Nitrogen-rich carbon nitride gas sensitive material, gas sensitive sensor as well as preparation method and application of nitrogen-rich carbon nitride gas sensitive material and gas sensitive sensor

Abstract

The invention belongs to the technical field of nano material application, and particularly relates to a nitrogen-rich carbon nitride gas-sensitive material, a gas-sensitive sensor and a preparation method and application of the nitrogen-rich carbon nitride gas-sensitive material and the gas-sensitive sensor. The ammonia leakage in the environment or the ammonia content in the expired gas of the human body can be accurately detected; and harmful gases such as ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine, nitrogen dioxide and the like can be detected. The nitrogen-rich carbon nitride gas-sensitive material is prepared into a gas-sensitive sensor, and the gas-sensitive sensor has the advantages of high ammonia responsivity, good selectivity, good stability, strong anti-interference performance and the like at room temperature. The gas sensor does not need to be heated during use, a conventional gas sensor heating step is omitted, and the gas sensor can be directly placed in a normal-temperature environment for operation; and different substrate materials can be used for constructing rigid and flexible substrate sensors, and the application method is simple, easy to operate, good in effect and wide in application prospect.

Description

Technical Field:

[0001] The present invention belongs to the technical field of nanomaterial applications, and specifically relates to a nitrogen-rich carbon nitride gas-sensitive material, a gas sensor, a preparation method thereof, and an application thereof. Using the nitrogen-rich carbon nitride material as the sensitive material of the gas sensor, it can highly sensitively detect low-concentration ammonia in the environment and the ammonia content in human exhaled breath. Background Art:

[0002] Semiconductor gas sensors detect gas molecules by adsorbing reducing or oxidizing gases and changing the surface conductivity of the gas-sensitive material. Common gas-sensitive materials include metal oxides (such as tin dioxide, zinc oxide, and tungsten trioxide), and conductive polymers (such as polypyrrole and polythiophene). Based on the advantages of high sensitivity and good stability of metal oxide-based gas sensors, a certain temperature is required to overcome the adsorption reaction barrier, resulting in a relatively high operating temperature; gas sensors based on conductive polymers can work at low temperatures or even at room temperature, but their sensitivity is often low, making it difficult to meet the requirements for detecting low-concentration gases. The development of high-performance gas-sensitive materials and gas sensing technologies has important practical significance for achieving accurate detection of trace gases.

[0003] Nitrogen-rich carbon nitride (C 3 N 5 ) is a new type of covalent compound semiconductor material with a band gap of about 1.70 eV and excellent ability to absorb visible light. It is widely used in photocatalysis, oxygen reduction, piezoelectric catalysis, and adsorbents. In recent years, important progress has been made in the research on nitrogen-rich carbon nitride. For example, Chinese Patent CN202310536603.2 discloses a preparation method of surface co-modified graphitic carbon nitride and its application in photocatalytic hydrogen production. 3-Amino-1,2,4-triazole and potassium iodide are dissolved in deionized water, and after molten salt polymerization and tempering reaction, a mixed powder of potassium iodide and carbon nitride is obtained. Then, the mixed powder and tin chloride are dissolved in hydrochloric acid, and after hydrothermal reaction, graphitic carbon nitride co-modified with surface carboxyl and tin dioxide nanoparticles is prepared, which has strong visible light absorption ability and good stability. Chinese Patent CN202211314165.7 discloses a potassium-doped nitrogen-rich carbon nitride catalyst and its application in photocatalytic carbon dioxide to produce methane. Potassium element and 3-amino-1,2,4-triazole are dissolved in a water-ethanol mixed solvent in a certain proportion, and the crystal slurry obtained by hydrothermal reaction is annealed at 300°C to 700°C to obtain potassium-doped carbon nitride. The interaction between potassium and the -N=N- bond of nitrogen-rich carbon nitride slows down the recombination rate of photo-generated electrons and holes, thus showing stronger catalytic activity.

[0004] Since chemical sensing is actually a heterogeneous surface catalysis process, excellent catalytic activity helps to achieve high gas-sensing performance. However, there is no relevant report on the use of nitrogen-rich carbon nitride materials as gas-sensing materials yet. Summary of the Invention:

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a nitrogen-rich carbon nitride gas-sensing material, a gas sensor, and its preparation method and application. The nitrogen-rich carbon nitride gas-sensing material is used as a sensitive element of the gas sensor to detect ammonia leakage in the environment and the ammonia content in human exhaled breath.

[0006] To achieve the above purpose, the present invention provides an application of a nitrogen-rich carbon nitride gas-sensing material in gas detection. The nitrogen-rich carbon nitride can detect gases at room temperature as a gas-sensing material.

[0007] Further, the nitrogen-rich carbon nitride gas-sensing material is prepared by calcining 3-amino-1,2,4-triazole. The material as a whole presents a blocky morphology and is assembled by two-dimensional sheet structure units.

[0008] Further, the nitrogen-rich carbon nitride contains abundant nitrogen vacancy defects.

[0009] Further, the gas is ammonia, ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine or nitrogen dioxide.

[0010] Further, the nitrogen-rich carbon nitride can have a linear response to ammonia with a concentration of 0.2 - 100 ppm at room temperature, and the sensitivity reaches 17.36 Res. / ppm. The nitrogen-rich carbon nitride has a sensitive response to ppb-level ammonia at room temperature, and the detection limit reaches 18 ppb.

[0011] The present invention also provides an application of the nitrogen-rich carbon nitride gas-sensing material in exhaled ammonia detection, which is used to detect the ammonia concentration in human exhaled breath, and distinguish healthy people from liver disease patients through the detected ammonia concentration difference.

[0012] The present invention also provides a gas sensor, the gas-sensing layer of which is a nitrogen-rich carbon nitride gas-sensing material.

[0013] The gas sensor is prepared by coating the nitrogen-rich carbon nitride gas-sensing material on a rigid substrate or a flexible substrate.

[0014] Further, the nitrogen-rich carbon nitride gas-sensing material can be coated on a rigid substrate such as a ceramic chip or a ceramic tube by methods such as spin coating, spraying, and doctor blading to make a traditional gas sensor, or can be deposited on the surface of a flexible substrate such as non-woven fabric, plastic film, and cellulose paper to make a flexible gas sensor.

[0015] The present invention also provides the application of the gas sensor in gas detection, which can detect the contents of ammonia, ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine and nitrogen dioxide, has high sensitivity and can resist cross-interference; preferably, it can be used for highly sensitive detection of ammonia at room temperature.

[0016] In one embodiment, the preparation method of the gas sensor is as follows: the nitrogen-rich carbon nitride gas-sensitive material is ground and mixed evenly with terpineol and then coated on a rigid substrate, and dried for 1 to 6 hours; then interdigital electrodes or lateral structure electrodes are fabricated by screen printing, and aged for 24 hours to obtain the gas sensor.

[0017] In one embodiment, the preparation method of the gas sensor is as follows: the nitrogen-rich carbon nitride gas-sensitive material is fully mixed evenly with absolute ethanol, sprayed on the surface of non-woven fabric and dried, then interdigital electrodes or lateral structure electrodes are screen printed, and aged for 24 hours to obtain the gas sensor.

[0018] Furthermore, the gas sensor can work at room temperature, and the response degree to 20 ppm ammonia is as high as 453.

[0019] The gas sensor shows a linear response in the ammonia concentration range of 0.2 to 100 ppm, and the sensor sensitivity is 17.36 Res. / ppm.

[0020] The gas sensor also responds to other harmful gases such as ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine and nitrogen dioxide, and the response degrees are all greater than 2.

[0021] Furthermore, the nitrogen-rich carbon nitride gas-sensitive material can also be used for detecting low-concentration ammonia in human complex exhaled breath, and has the advantages of high sensitivity and anti-cross-interference.

[0022] Compared with the prior art, the present invention first uses nitrogen-rich carbon nitride as a gas-sensitive material for gas detection, especially for the detection of low-concentration ammonia, and can accurately detect ammonia leakage in the environment or the ammonia content in human exhaled breath; it can also detect harmful gases such as ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine and nitrogen dioxide. The nitrogen-rich carbon nitride gas-sensitive material is made into a gas sensor, which has the advantages of high ammonia response degree, good selectivity, good stability and strong anti-interference at room temperature. The gas sensor does not need to be heated during use, omitting the conventional heating step of the gas sensor, and can be directly placed in a normal temperature environment for operation; and different substrate materials can be used to construct rigid and flexible substrate sensors, and its application method is simple, easy to operate, has good effects and broad application prospects. Description of the Drawings:

[0023] Figure 1 It is a low-magnification SEM image of the nitrogen-rich carbon nitride material prepared in Example 1 of the present invention.

[0024] Figure 2 High-magnification TEM image of the nitrogen-rich carbon nitride material prepared in Example 1 of the present invention.

[0025] Figure 3 XRD spectrum of the nitrogen-rich carbon nitride material after calcination in Example 1 of the present invention.

[0026] Figure 4 XPS survey spectrum of the nitrogen-rich carbon nitride material after calcination in Example 1 of the present invention.

[0027] Figure 5 Response curve of the gas sensor prepared in Example 2 of the present invention to 20 ppm ammonia.

[0028] Figure 6 Response data of the gas sensor prepared in Example 2 of the present invention to 20 ppm of different gases.

[0029] Figure 7 Response data of the gas sensor prepared in Example 2 of the present invention to 20 ppm ammonia at different bending angles.

[0030] Figure 8 Response data of the gas sensor prepared in Example 2 of the present invention to 20 ppm ammonia at different humidities.

[0031] Figure 9 Response degree change and sensitivity of the gas sensor prepared in Example 2 of the present invention to different concentrations of ammonia.

[0032] Figure 10 Response degree of the gas sensor prepared in Example 2 of the present invention to low-concentration ammonia and the detection limit (minimum detection concentration) of the sensor.

[0033] Figure 11 Detection results of the exhaled breath of different populations using the flexible gas sensor prepared in Example 3 of the present invention. Detailed implementation method:

[0034] The present invention will be further described below through specific examples in conjunction with the accompanying drawings.

[0035] Example 1:

[0036] This example relates to a preparation method of a nitrogen-rich carbon nitride gas-sensitive material, and the specific steps are as follows:

[0037] Put 2.0 g of 3-amino-1,2,4-triazole (C 2 H 4)Place it in an alumina crucible, keep the crucible semi-covered, then put the crucible into a muffle furnace and heat it at a heating rate of 5 °C / min to 500 °C, hold it at 500 °C for 3 hours, and naturally cool it to room temperature after the holding ends; then grind the obtained brown sample into powder, wash the brown powder by centrifugation with ethanol multiple times, and dry it at 60 °C to obtain a nitrogen-rich carbon nitride gas-sensitive material.

[0038] Characterize the obtained product as follows:

[0039] Observe the surface morphology of the prepared nitrogen-rich carbon nitride by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as Figure 1 and Figure 2 shown. From Figure 1 and Figure 2 it can be seen that the obtained product is a bulk nitrogen-rich carbon nitride assembled from two-dimensional sheet structure units.

[0040] Characterize the phase structure of nitrogen-rich carbon nitride by X-ray powder diffraction (XRD), and the results are shown in Figure 3 . Nitrogen-rich carbon nitride has two obvious diffraction peaks. A strong peak at 2θ = 13.4° is related to the (100) plane and belongs to the in-plane structural order. Another strong peak at 2θ = 27.7° belongs to the (002) plane and is the interlayer stacking peak of the aromatic system in graphite materials, which proves that the obtained product is nitrogen-rich carbon nitride.

[0041] Characterize the surface chemical composition of the synthesized nitrogen-rich carbon nitride by X-ray photoelectron spectroscopy (XPS), and the results are shown in Figure 4 . The XPS survey spectrum shows that the elemental composition is carbon, nitrogen, and oxygen. Among them, the oxygen element comes from the oxygen adsorbed by the material from the air. After analyzing the XPS spectrum, it is found that the molar content percentages of carbon and nitrogen in nitrogen-rich carbon nitride are 40.41% and 56.78%; after calculation, the molar content ratio of carbon and nitrogen elements is 1:1.41, which is less than the theoretical value of 1:1.6, proving that the synthesized material contains abundant nitrogen vacancy defects.

[0042] Example 2:

[0043] This example relates to a preparation method of a gas sensor. Mix 1.00 g of the nitrogen-rich carbon nitride prepared in Example 1 with 10 mL of absolute ethanol according to a solid-liquid ratio of 1:10. After fully stirring and ultrasonic mixing evenly, add it to a spray gun and spray it on a flexible substrate such as seaweed fiber non-woven fabric, dry it for 1 - 6 h, then fabricate electrodes by screen printing. The electrodes are silver interdigital electrodes or transverse structure electrodes, and age for 24 h to obtain a flexible gas sensor.

[0044] Example 3:

[0045] This embodiment relates to a preparation method of a gas sensor. The nitrogen-rich carbon nitride obtained in Example 1 is ground and mixed evenly with terpineol, and then coated on a rigid substrate such as a ceramic sheet, dried for 1 to 6 hours, and then electrodes are fabricated by screen printing. The electrodes are silver interdigitated electrodes or lateral structure electrodes. After aging for 24 hours, a gas sensor is obtained.

[0046] Example 4:

[0047] This embodiment is an application test of the nitrogen-rich carbon nitride gas-sensitive material in gas detection. The gas sensors prepared in Example 2 or Example 3 are placed in a gas sensing test system to detect the gas sensitivity and selectivity. The specific steps are as follows:

[0048] The fabricated gas sensor is placed in a gas sensing test system, and air or the gas to be measured is introduced. The working voltage is kept constant at 3 V, and the working temperature is room temperature. The current values in air and the gas to be measured are measured respectively, and the response degree of the gas sensor to the gas to be measured is calculated (for reducing gases: resistance in air / resistance in gas; for oxidizing gases: resistance in gas / resistance in air). When the gas to be measured is 20 ppm ammonia, the response degree results are as Figure 5 shown. As Figure 5 can be seen, the gas sensor made of the nitrogen-rich carbon nitride gas-sensitive material has a maximum response degree of 453 to 20 ppm ammonia at room temperature operating temperature, a response time of 55 seconds, and a recovery time of 65 seconds. Using the above method, it is measured that the gas sensor responds to 20 ppm ethanol, methanol, isopropanol, triethylamine, acetone, nitrogen dioxide, and trimethylamine, and the response degrees are all greater than 2 ( Figure 6 ). This shows that in addition to having good selectivity, the gas sensor also has the ability to detect other harmful gases in the environment and is suitable for detecting the leakage of harmful gases in the environment. This is because the azo bonds in the nitrogen-rich carbon nitride increase the extension of the π network, providing a larger π-conjugated network, resulting in more electron transfer. The triazole-based nitrogen-rich carbon nitride prepared by the self-condensation of 3-amino-1,2,4-triazole provides a large number of gas adsorption sites by introducing abundant nitrogen vacancies, which is beneficial to the adsorption of gas on the material surface, improves the detection response degree, and is also beneficial to carry out at room temperature.

[0049] The gas sensor prepared in Example 2 is bent, and the response degree to ammonia (20 ppm) at different bending angles is measured. The results are as Figure 7 shown. As Figure 7 can be seen, the response degree change of the flexible gas sensor constructed by this gas-sensitive material is very small in the bent state, indicating that this method can be used for detecting harmful gases in a flexible scenario.

[0050] The responsiveness of the gas sensors in Example 2 or Example 3 to ammonia (20 ppm) at different humidities was measured, and the results are as follows Figure 8 shown. As can be seen from Figure 8

[0051] it, the responsiveness of the gas sensor decreases slightly with the increase of humidity, and the decreasing trend shows a linear relationship, indicating that the influence of humidity on the sensor is small, and it can be compensated and adjusted by linear correction.

[0051] The responsiveness to ammonia at different concentrations was measured, and the results are as follows Figure 9 and Figure 10 shown. It can be seen from Figure 9 that in the ammonia concentration test range of 0.5 ppm to 100 ppm, the responsiveness of the gas sensor of the present invention shows a linear relationship with the change of ammonia concentration. The sensitivity of the sensor is 17.36 Res. / ppm, and the lower detection limit of the sensor for ammonia can reach 18 ppb.

[0052] Example 5:

[0053] This example is an application test of nitrogen-rich carbon nitride materials in the detection of trace ammonia in human exhaled gas. After making a flexible gas sensor with nitrogen-rich carbon nitride as the gas-sensitive layer and placing it in a gas-sensing test system, the responsiveness to different ammonia in human exhaled gas was detected. The specific steps are as follows:

[0054] 1. Preparation of a flexible nitrogen-rich carbon nitride gas sensor: The flexible gas sensor is composed of a base layer, a gas-sensitive layer, and an electrode layer. The base layer is a flexible substrate such as non-woven fabric or paper sheet; the gas-sensitive layer is the prepared nitrogen-rich carbon nitride; the electrode layer is a silver interdigital electrode or a lateral structure electrode. The preparation steps of the gas sensor are as follows: The gas-sensitive material is coated on the substrate by spraying. Specifically, the nitrogen-rich carbon nitride prepared in Example 1 is fully stirred and ultrasonically mixed with absolute ethanol and then added to a spray gun and sprayed on a flexible substrate such as seaweed fiber non-woven fabric, and dried for 1 - 6 h; then the electrodes are made by screen printing and aged for 24 h to obtain a flexible nitrogen-rich carbon nitride gas sensor.

[0055] Figure 11 Figure 11 shown. As can be seen fromIt can be seen that the flexible gas sensor made of nitrogen-rich carbon nitride gas-sensitive material has significant differences in the response to the exhaled breath of 3 healthy people and liver disease patients (Patient 1, Patient 2) at room temperature. The response of liver disease patients is significantly higher than that of the healthy population, proving that the nitrogen-rich carbon nitride gas sensor can effectively detect low-concentration ammonia in human exhaled breath.

Claims

1. Application of a nitrogen-rich carbon nitride gas-sensitive material in gas detection.

2. The use of the nitrogen-rich carbon nitride gas-sensitive material according to claim 1 in gas detection, characterized in that: The nitrogen-rich carbon nitride has nitrogen vacancy defects.

3. The use of the nitrogen-rich carbon nitride gas-sensitive material in gas detection according to claim 1, characterized in that: The nitrogen-rich carbon nitride gas-sensitive material has an overall block-like morphology and is assembled from two-dimensional lamellar structural units.

4. The use of the nitrogen-rich carbon nitride gas-sensitive material in gas detection according to claim 1, characterized in that: The gas is ammonia, ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine or nitrogen dioxide.

5. The use of the nitrogen-rich carbon nitride gas-sensitive material in gas detection according to claim 1, characterized in that: It can respond linearly to ammonia gas with a concentration of 0.2 to 100 ppm at room temperature, with a sensitivity of 17.36 Res. / ppm.

6. The use of the nitrogen-rich carbon nitride gas-sensitive material in gas detection according to claim 1, characterized in that: It has a sensitive response to ppb-level ammonia at room temperature, with a detection limit of 18ppb.

7. Application of a nitrogen-rich carbon nitride gas-sensitive material in breath ammonia detection, characterized in that: It can be used to detect ammonia in human exhaled breath, and to distinguish healthy people from liver disease patients through the difference in detected ammonia concentration.

8. A gas sensor, characterized in that: The gas-sensitive layer is a nitrogen-rich carbon nitride gas-sensitive material.

9. The gas sensor according to claim 8, characterized in that: The gas sensor is prepared by coating a nitrogen-rich carbon nitride gas-sensitive material on a rigid substrate or a flexible substrate.

10. Application of the gas sensor according to any one of claims 8 to 9 in gas detection, characterized in that: It can detect the content of ammonia, ethanol, methanol, isopropanol, triethylamine, acetone, trimethylamine and nitrogen dioxide with high sensitivity and resistance to cross interference.

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