Nitrogen doping method of gamma-graphdiyne and application of nitrogen doping method

Abstract

The invention belongs to the technical field of nano materials, and particularly relates to a nitrogen doping method and application of gamma-graphdiyne. Graphdiyne oxide is prepared through a hydrothermal method, then melamine serves as a nitrogen source, graphdiyne oxide serves as a framework, in-situ doping of nitrogen elements and reduction of graphdiyne oxide are achieved at the same time through high-temperature calcination, and the gamma-graphdiyne is obtained. The method is simple and easy to implement, the processing period is short, the doping amount is easy to control, dangerous chemicals such as concentrated sulfuric acid and concentrated nitric acid are not involved, the production safety is greatly improved, and the prepared nitrogen-doped gamma-graphdiyne has the advantages of high purity, high specific surface area, nanoscale pore diameter and excellent wave absorbing performance, gas sensitivity and ferromagnetism.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a nitrogen doping method for γ-graphyne and its application. Background Technology

[0002] With the acceleration of industrialization and the continuous expansion of urbanization, electromagnetic radiation and air pollution have become increasingly serious problems, posing a global challenge to human health and the ecological environment. Human activities such as industrial production, vehicle exhaust, and fossil fuel combustion release large amounts of toxic and harmful gases into the atmosphere. These air pollutants not only directly harm human health but also cause environmental problems such as acid rain, photochemical smog, and the greenhouse effect, profoundly impacting ecosystems. Long-term exposure to polluted gases can lead to respiratory diseases, cardiovascular diseases, and even cancer, seriously threatening human life and health. Electromagnetic interference and signal leakage not only affect equipment performance but also significantly impact people's quality of life. For example, long-term exposure to electromagnetic radiation can cause irreversible damage, leading to various diseases such as childhood leukemia, fetal malformations, and unhealthy development in adolescents, as well as posing a cancer risk. Significant electromagnetic pollution can also affect plants, preventing normal growth, causing gene mutations, and even death. Furthermore, electromagnetic waves interfere with electronic devices, instruments, and communication signals, affecting their normal use. Therefore, developing multifunctional electronic materials that combine microwave absorption and gas sensing properties is of great significance. This means utilizing the absorption of electromagnetic waves by microwave absorbing materials to reduce the impact of electromagnetic interference on gas sensing performance, thus providing material support for improving the stability and reliability of gas sensors. At the same time, by utilizing the adsorption of gas molecules by gas sensing materials, the electromagnetic parameters of microwave absorbing materials can be controlled to achieve dynamic regulation of microwave absorption performance, providing a feasible path for developing intelligent tunable microwave absorbing materials.

[0003] While carbon-based materials are generally considered to possess microwave absorption properties and can be used as gas-sensitive materials, traditional carbon-based microwave absorbing materials lack magnetism. They typically require compositing with magnetic materials to balance their high electrical conductivity and achieve better impedance matching, which inevitably leads to complex fabrication processes and increased costs. Graphdiyne, composed of an all-carbon polymer with a two-dimensional planar network structure formed by conjugated benzene rings linked by 1,3-diyne bonds, possesses abundant carbon chemical bonds, a large conjugated system, wide interplanar spacing, excellent chemical stability, and semiconductor properties. Graphdiyne's unique electronic structure and natural porosity result in an extremely unbalanced charge distribution, making it a prime candidate for excellent microwave absorbing materials.

[0004] To further optimize the performance of graphodyne and expand its applications, researchers have begun exploring the use of heteroatoms (such as nitrogen, boron, and sulfur) to modulate the electrical, magnetic, and dielectric properties of the material. Nitrogen-doped graphodyne (N-GY) materials have attracted widespread attention in recent years due to their unique electronic structure and tunable band structure. The introduction of nitrogen atoms can not only adjust the conductivity and dielectric constant of γ-GY, but also enhance the multiple relaxation process by introducing additional defect states and polarization centers. Furthermore, nitrogen doping may introduce more heterointerfaces, promoting more interfacial polarization and further improving the material's electromagnetic wave loss capability. Simultaneously, the defects and vacancies formed during the doping process impart magnetism to graphodyne, balancing its high dielectric properties and improving its impedance matching characteristics. Therefore, nitrogen doping provides a new approach for the design of high-performance electromagnetic wave absorbing materials. A literature search revealed virtually no patents related to nitrogen-doped graphyne. Commonly used doping methods (such as ball milling) suffer from long preparation times, complex processes, and difficulties in industrial production. The inability to precisely control the nitrogen content leads to challenges in controlling the doping degree. Furthermore, the oxidation process involves hazardous chemicals such as concentrated sulfuric acid and concentrated nitric acid, posing significant safety risks. The resulting nitrogen-doped graphyne samples also exhibit low purity, low yield, high density, and numerous impurities, hindering the industrial-scale application of nitrogen-doped graphyne materials. Therefore, it is essential to prepare high-yield, highly crystalline magnetic nitrogen-doped graphyne materials for use as microwave absorbing materials.

[0005] Before the discovery of graphididyne, the electronic structure of all carbon materials was sp. 3 or sp 2 Carbon hybridization, such as fullerenes, carbon nanotubes, and graphene, is all composed of sp... 2 Hybridization is formed, while graphynylene is formed by sp hybridization and sp 2 Because of the hybridized carbon atoms, nitrogen doping technology for graphyne faces more possibilities and more challenges. Although patent documents with announcement numbers CN115974056B and CN103265019B introduce the preparation technology of nitrogen-doped graphene, they are difficult to provide inspiration for graphyne technology.

[0006] In addition, graphyne possesses characteristics such as large specific surface area, high interfacial reactivity, high room-temperature carrier mobility, excellent semiconductor properties, and abundant unsaturated bonds, making it an ideal raw material for preparing high-performance gas-sensitive materials. For example, the patent with announcement number CN113860298B significantly improves the NO2 gas-sensing performance of the material through thermal calcination. The patent with announcement number CN116253314B improves the yield of graphyne films by controlling the water-oil liquid phase interface, enabling the application of graphyne films in NH3 gas sensors. The patent with publication number CN118759002A achieves the production of NO gas-sensitive core materials by in-situ growing hydrogen on the surface of graphene monoacetylene films. However, the above patents all show high sensitivity to a single gas and cannot achieve high sensitivity to multiple gases. Furthermore, the development of graphyne gas-sensitive materials for formaldehyde, toluene, acetone, and ethanol is still lacking in current research. Therefore, broadening the gas-sensing spectrum of graphyne can meet the application requirements of gas sensors in complex environments, enabling the rapid and accurate detection of multiple gases simultaneously. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a nitrogen doping method for γ-graphyne and its application.

[0008] The technical solution of this invention: The first objective of this invention is to provide a nitrogen doping method for γ-graphyne, comprising the following steps: 1) Preparation of γ-graphyne dispersion: Weigh γ-graphyne (abbreviated as γ-GY) and place it in deionized water. Use ultrasonic dispersion and mechanical stirring to fully disperse γ-graphyne to obtain γ-graphyne dispersion. 2) Preparation of γ-graphyne oxide: An oxidant was added to the γ-graphyne dispersion, and after magnetic stirring, it was placed in a high-pressure reactor for hydrothermal reaction. After the hydrothermal reaction was completed, the mixture was naturally cooled and extracted to obtain a mixture. Then, the mixture was soaked in hydrochloric acid to remove the unreacted oxidant. After soaking, the precipitate was obtained by filtration. The precipitate was washed with deionized water until neutral and then dried to obtain γ-graphyne oxide. 3) Preparation of nitrogen-doped γ-graphyne: Melamine and γ-graphyne oxide are mixed evenly and calcined at high temperature under an inert gas atmosphere. After cooling to room temperature, nitrogen-doped γ-graphyne is obtained.

[0009] Further, in step 1), the mass-to-volume ratio of γ-graphyne to deionized water in the γ-graphyne dispersion is 1 mg: 1-3 mL.

[0010] Further, in step 2), the amount of the oxidant is 1.5 to 2.5 times the mass of γ-graphyne. The oxidant is potassium permanganate.

[0011] Furthermore, in step 2), the conditions for the hydrothermal reaction are: temperature 180–200°C, time 2–5 h.

[0012] Furthermore, in step 2), the hydrochloric acid has a mass fraction of 37%.

[0013] Furthermore, in step 2), the soaking time is 36 to 60 hours.

[0014] Furthermore, in step 2), the drying process conditions are: temperature 70°C, time 24-36h.

[0015] Furthermore, in step 3), the mass ratio of melamine to γ-graphyne oxide is 20 to 35:1.

[0016] Furthermore, in step 3), the high-temperature calcination involves first heating the material from room temperature to 700–900°C, and then calcining it at a constant temperature for 2–4 hours. The heating rate is 5°C / min.

[0017] The second objective of this invention is to provide the application of nitrogen-doped γ-graphyne prepared by the above-described nitrogen doping method in the preparation of magnetic materials, radar stealth materials, electromagnetic shielding materials, or gas monitoring materials.

[0018] Beneficial effects: This invention employs a hydrothermal method to prepare graphyne oxide, then uses melamine as a nitrogen source and graphyne oxide as a framework, achieving in-situ nitrogen doping and reduction of graphyne oxide simultaneously through high-temperature calcination. The doping methods include sp carbon hybridization and sp... 2 Doping of carbon hybrid structures.

[0019] The nitrogen doping method of the present invention is simple and easy to implement, has a short processing cycle, and the doping amount is easy to control. It does not involve hazardous chemicals such as concentrated sulfuric acid and concentrated nitric acid, which greatly improves production safety.

[0020] The nitrogen-doped γ-graphyne prepared by the method of this invention has high purity, high specific surface area, nanoscale pore size, excellent wave absorption performance, gas sensitivity and ferromagnetism. This makes nitrogen-doped γ-graphyne suitable for the preparation of magnetic materials, radar stealth materials, electromagnetic shielding materials or gas monitoring materials, which will help promote its application in multiple fields such as electronic devices, electronic equipment, and environmental monitoring. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of step 1) in Example 1.

[0022] Figure 2 This is the process flow diagram for step 2) in Example 1.

[0023] Figure 3 The images are XRD patterns of the melamine samples added in Examples 1-4, with 200-350 mg added respectively.

[0024] Figure 4 The Fourier transform infrared spectrum of nitrogen-doped γ-graphyne in Example 1 is shown.

[0025] Figure 5 These are scanning electron microscope images of nitrogen-doped γ-graphyne from Example 1; the left image is at 500 nm magnification and the right image is at 200 nm magnification.

[0026] Figure 6 This is the XPS spectrum of nitrogen-doped γ-graphyne in Example 1.

[0027] Figure 7 This is the magnetization curve of nitrogen-doped γ-graphyne in Example 1.

[0028] Figure 8 This is the BET characterization diagram of nitrogen-doped γ-graphyne in Example 1.

[0029] Figure 9 This is the reflection loss diagram of nitrogen-doped γ-graphyne in Example 1.

[0030] Figure 10 This is a gas-sensing curve of nitrogen-doped γ-graphyne in Example 1.

[0031] Figure 11 This is a magnetic comparison between undoped graphyne and nitrogen-doped graphyne prepared in Example 1.

[0032] Figure 12 This is a response graph of nitrogen-doped γ-graphyne in Example 1 to different concentrations of ethanol. Detailed Implementation

[0033] Example 1 A nitrogen doping method for γ-graphyne includes the following steps: 1) Using potassium permanganate as an oxidant, γ-GY oxide was prepared by a hydrothermal method. The specific operation was as follows: First, weigh 60 mg of γ-graphyne sample and place it in 120 ml of deionized water. Sonicate the sample for 30 min while continuously stirring to ensure uniform dispersion in the deionized water, forming solution A. Simultaneously, weigh 120 mg of potassium permanganate and add it to solution A, forming solution B. Place solution B on a magnetic stirrer and stir for 10 min. Then, transfer solution B to a high-pressure reactor and perform a hydrothermal reaction at 180℃ for 3 h. After the reaction is complete and the mixture cools naturally, remove it and filter it to obtain mixture C. Soak mixture C in 37% concentrated hydrochloric acid for 48 h to remove unreacted potassium permanganate, forming solution D. Finally, after soaking, filter solution D to obtain a precipitate, wash it with deionized water until neutral, and dry it in a 70℃ oven for 28 h to obtain γ-GY oxide.

[0034] 2) Using melamine as the nitrogen source, nitrogen doping is carried out simultaneously during the reduction of γ-graphyne oxide through high-temperature calcination. The specific operation is as follows: First, weigh 10 mg of γ-graphyne oxide and then weigh 300 mg of melamine. Mix the two together and place them in a quartz boat. Place the quartz boat in a high-temperature tube furnace and, under the protection of Ar gas, raise the temperature from room temperature to 800°C at a rate of 5°C / min and maintain the temperature for 2 hours. Finally, after the reaction is completed and cooled to room temperature, N-GY powder can be obtained.

[0035] Example 2 1) Using potassium permanganate as an oxidant, γ-GY oxide was prepared by a hydrothermal method. The specific operation was as follows: First, weigh 50 mg of γ-graphyne sample and place it in 120 ml of deionized water. Sonicate the sample for 30 min while continuously stirring to ensure uniform dispersion in the deionized water, forming solution A. Simultaneously, weigh 110 mg of potassium permanganate and add it to solution A, forming solution B. Place solution B on a magnetic stirrer and stir for 10 min. Then, transfer solution B to a high-pressure reactor and perform a hydrothermal reaction at 180℃ for 3 h. After the reaction is complete and the mixture cools naturally, remove it and filter it to obtain mixture C. Soak mixture C in 37% concentrated hydrochloric acid for 40 h to remove unreacted potassium permanganate, forming solution D. Finally, after soaking, filter solution D to obtain a precipitate, wash it with deionized water until neutral, and dry it in a 70℃ oven for 26 h to obtain γ-GY oxide.

[0036] 2) Using melamine as the nitrogen source, nitrogen doping is carried out simultaneously during the reduction of γ-graphyne oxide through high-temperature calcination. The specific operation is as follows: First, weigh 10 mg of γ-graphyne oxide and then weigh 200 mg of melamine. Mix the two together and place them in a quartz boat. Place the quartz boat in a high-temperature tube furnace and, under the protection of Ar gas, raise the temperature from room temperature to 750°C at a rate of 5°C / min and maintain the temperature for 3 h. Finally, after the reaction is completed and cooled to room temperature, N-GY powder can be obtained.

[0037] Example 3 1) Using potassium permanganate as an oxidant, γ-GY oxide was prepared by a hydrothermal method. The specific operation was as follows: First, weigh 70 mg of γ-graphyne sample and place it in 130 ml of deionized water. Sonicate the sample for 30 min while continuously stirring to ensure uniform dispersion in the deionized water, forming solution A. Simultaneously, weigh 150 mg of potassium permanganate and add it to solution A, forming solution B. Place solution B on a magnetic stirrer and stir for 10 min. Then, transfer solution B to a high-pressure reactor and perform a hydrothermal reaction at 200℃ for 3 h. After the reaction is complete and the mixture cools naturally, remove it and filter it to obtain mixture C. Soak mixture C in 37% hydrochloric acid for 50 h to remove unreacted potassium permanganate, forming solution D. Finally, after soaking, filter solution D to obtain a precipitate, wash it with deionized water until neutral, and dry it in a 70℃ oven for 30 h to obtain γ-GY oxide.

[0038] 2) Using melamine as the nitrogen source, nitrogen doping is carried out simultaneously during the reduction of γ-graphyne oxide through high-temperature calcination. The specific operation is as follows: First, weigh 10 mg of γ-graphyne oxide and then weigh 250 mg of melamine. Mix the two together and place them in a quartz boat. Place the quartz boat in a high-temperature tube furnace and, under the protection of Ar gas, raise the temperature from room temperature to 850°C at a rate of 5°C / min and maintain the temperature for 4 h. Finally, after the reaction is completed and cooled to room temperature, N-GY powder can be obtained.

[0039] Example 4 1) Using potassium permanganate as an oxidant, γ-GY oxide was prepared by a hydrothermal method. The specific operation was as follows: First, weigh 30 mg of γ-graphyne sample and place it in 65 ml of deionized water. Sonicate the sample for 30 min while continuously stirring to ensure uniform dispersion in the deionized water, forming solution A. Simultaneously, weigh 60 mg of potassium permanganate and add it to solution A, forming solution B. Stir solution B on a magnetic stirrer for 10 min. Then, transfer solution B to a high-pressure reactor and perform a hydrothermal reaction at 190℃ for 3.5 h. After the reaction is complete and the mixture cools naturally, remove it and filter it to obtain mixture C. Soak mixture C in 37% concentrated hydrochloric acid for 45 h to remove unreacted potassium permanganate, forming solution D. Finally, after soaking, filter solution D to obtain a precipitate, wash it with deionized water until neutral, and dry it in an oven at 70℃ for 30 h to obtain γ-GY oxide.

[0040] 2) Using melamine as the nitrogen source, nitrogen doping is carried out simultaneously during the reduction of γ-graphyne oxide through high-temperature calcination. The specific operation is as follows: First, weigh 10 mg of γ-graphyne oxide and then weigh 350 mg of melamine. Mix the two together and place them in a quartz boat. Place the quartz boat in a high-temperature tube furnace and, under the protection of Ar gas, raise the temperature from room temperature to 900°C at a rate of 5°C / min and maintain the temperature for 4 h. Finally, after the reaction is completed and cooled to room temperature, N-GY powder can be obtained.

[0041] Figure 3 The XRD patterns of the samples with 200-350 mg of melamine added in Examples 1-4 are shown in the figure. As can be seen from the figure, nitrogen-doped graphyne samples can be stably prepared under different contents of melamine.

[0042] Figure 4 The Fourier transform infrared spectrum is that of sample N-GY-300, in Example 1, which contained 300 mg of melamine. From... Figure 4 It can be known that 667cm -1 and 2341cm -1 The peak at 827 cm⁻¹ corresponds to the vibrational peak of the acetylene group (sp-C). -1 and 1624cm -1 The peak at that point corresponds to the benzene ring (sp). 2 The vibration peak of -C) is 1205 cm⁻¹. -1 The location corresponds to the CN vibration peak. Note that Example 1 achieved sp and sp... 2 Co-doping.

[0043] Figure 5These are scanning electron microscope images of nitrogen-doped γ-graphyne from Example 1; the left image is at 500 nm magnification, and the right image is at 200 nm magnification. The images show that the prepared sample exhibits a multi-folded, layered stacked structure.

[0044] Figure 6 The image shows the XPS spectrum of nitrogen-doped γ-graphyne in Example 1, proving that N was successfully incorporated and that there were no other impurities inside.

[0045] Figure 7 The image shows the magnetization curve of nitrogen-doped γ-graphyne in Example 1, indicating that nitrogen-doped γ-graphyne is ferromagnetic.

[0046] Figure 8 The image shows the BET characterization of the nitrogen-doped γ-graphyne from Example 1, indicating a specific surface area of ​​464.33 m². 2 / g, with an average pore size of 9.28nm.

[0047] Figure 9 The diagram shows the reflection loss of nitrogen-doped γ-graphyne in Example 1, demonstrating that nitrogen-doped γ-graphyne has microwave absorption properties.

[0048] Figure 10 The graph shows the gas-sensing curves of nitrogen-doped γ-graphyne in Example 1, demonstrating that nitrogen-doped γ-graphyne exhibits good gas sensitivity to nitrogen dioxide, hydrogen, formaldehyde, toluene, acetone, and ethanol, indicating that nitrogen-doped γ-graphyne possesses excellent and broad-spectrum characteristics.

[0049] Figure 11 The magnetic properties of undoped graphyne and nitrogen-doped graphyne obtained in Example 1 are compared. It can be seen that the coercivity increases significantly after nitrogen doping.

[0050] In Example 1 of this invention, given that N-GY-300 exhibits good response to 100 ppm ethanol gas, ethanol gas was further selected and tested at different concentrations at 200°C to analyze its response, detection limit, and linearity. Based on the formula... Calculate and plot the trend of the sample resistance as follows: Figure 12 As shown, the response of the N-GY-300 sample generally increases with increasing ethanol concentration from 5 ppm to 500 ppm, exhibiting excellent sensitivity. With increasing ethanol concentration, the material adsorbs more ethanol, leading to an increase in carrier concentration, thus causing Rgas to gradually decrease. The N-GY-300 sample still shows a good response in a low concentration of 5 ppm ethanol, demonstrating its very small detection limit. It can respond to trace amounts of ethanol gas, making it highly practical.

[0051] Sensitivity (S) of N-GY-300 to different concentrations of ethanol

Claims

1. A nitrogen doping method for γ-graphyne, characterized in that, Includes the following steps: 1) Preparation of γ-graphyne dispersion: Weigh γ-graphyne and place it in deionized water. Use ultrasonic dispersion and mechanical stirring to fully disperse γ-graphyne to obtain γ-graphyne dispersion. 2) Preparation of γ-graphyne oxide: An oxidant was added to the γ-graphyne dispersion, and after magnetic stirring, it was placed in a high-pressure reactor for hydrothermal reaction. After the hydrothermal reaction was completed, the mixture was naturally cooled and extracted to obtain a mixture. Then, the mixture was soaked in hydrochloric acid to remove the unreacted oxidant. After soaking, the precipitate was obtained by filtration. The precipitate was washed with deionized water until neutral and then dried to obtain γ-graphyne oxide. 3) Preparation of nitrogen-doped γ-graphyne: Melamine and γ-graphyne oxide are mixed evenly and calcined at high temperature under an inert gas atmosphere. After cooling to room temperature, nitrogen-doped γ-graphyne is obtained.

2. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 1), the mass-to-volume ratio of γ-graphyne to deionized water in the γ-graphyne dispersion is 1 mg: 1-3 mL.

3. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 2), the amount of oxidant used is 1.5 to 2.5 times the mass of γ-graphyne; the oxidant is potassium permanganate.

4. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 2), the conditions for the hydrothermal reaction are: temperature 180-200℃, time 2-5h.

5. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 2), the hydrochloric acid has a mass fraction of 37%; the soaking time is 36-60 hours.

6. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 2), the drying process conditions are: temperature 70°C, time 24-36h.

7. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 3), the mass ratio of melamine to γ-graphyne oxide is 20 to 35:

1.

8. The nitrogen doping method for γ-graphyne as described in claim 1, characterized in that, In step 3), the high-temperature calcination involves first heating the material from room temperature to 700–900°C, and then calcining it at a constant temperature for 2–4 hours. The heating rate is 5°C / min.

9. The application of nitrogen-doped γ-graphyne prepared by the nitrogen doping method of any one of claims 1-8 in the preparation of magnetic materials, radar stealth materials, electromagnetic shielding materials or gas monitoring materials.

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