Preparation method and application of nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial

Abstract

The invention belongs to the technical field of graphene composite materials, and particularly relates to a preparation method and application of a nitrogen-sulfur co-doped three-dimensional graphene / silver nano material. The nitrogen-sulfur-doped three-dimensional graphene / silver nano material prepared by the preparation method has a three-dimensional structure, the graphene net structure is rich, and the graphene agglomeration phenomenon is prevented; the three-dimensional graphene has the characteristic of uniform distribution of the silver nanoparticles, and the reticular structure of the three-dimensional graphene is used as a support material, so that the silver nanoparticles can grow on the graphene in situ, the agglomeration of the silver nanoparticles is prevented, and the doping of sulfur and nitrogen to the three-dimensional graphene is realized. And complementation is realized through respective excellent performances of the three-dimensional graphene and the nano-silver particles, an efficient and complete conductive network is established, and the conductivity of the material is improved. The nitrogen-sulfur-doped three-dimensional graphene / silver nano material prepared by the preparation method is synthesized in one step, the cost is low, the synthesis time is short, a template does not need to be treated in the later period, and the preparation method is efficient and simple.

Description

Technical Field

[0001] The present invention belongs to the technical field of graphene composite materials, and in particular relates to a preparation method and application of nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials. Background Art

[0002] Graphene has the characteristics of high specific surface area, excellent conductivity, high mechanical properties and environmental friendliness. Therefore, due to its extraordinary structure and excellent performance, graphene has become one of the ideal materials for preparing sensors. However, due to the presence of van der Waals forces between graphene sheets, it is prone to irreversible agglomeration during the production process, making it difficult to produce high-quality products, which limits its application. After research, technicians have found that chemical doping can complete the functional modification of graphene materials from within the structure, but it requires the introduction of some other miscellaneous element atoms, such as sulfur, boron, nitrogen, etc., resulting in cumbersome preparation processes and high costs. Therefore, the use of single graphene as a conductive filler in flexible pressure sensors will inevitably have defects, namely agglomeration and restacking, resulting in a lack of efficient electronic "highways", which affects the sensing performance.

[0003] Introducing composite conductive networks into piezoresistive sensors is an effective strategy for addressing graphene agglomeration. Prior art combines metal nanoparticles and graphene have been used in flexible sensors and chemical sensors. The synergistic effect of graphene-metal nanoparticle composites not only offsets the shortcomings of individual materials while maintaining the advantages of each, garnering widespread attention for their superior performance and potential applications in sensors, energy storage, catalysis, and other areas.

[0004] Silver nanomaterials offer advantages such as simple preparation and excellent electrical properties, and can be used to enhance the performance of electronic devices through decoration. However, when preparing graphene-silver nanoparticle composites, the nanosilver material agglomerates, resulting in uneven particle size and poor mechanical properties. Furthermore, the graphene is affected by the attraction between interlayer molecules, resulting in stacking, which prevents effective chemical doping.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a preparation method and application of nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In one aspect, the present invention provides a method for preparing nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials, comprising the following steps:

[0009] S1. Weigh the auxiliary agent and the activator according to the set weight parts and grind and mix them in an agate mortar. Grind for 5 to 15 minutes to obtain a mixed powder; wherein the particle size of the auxiliary agent is 10 to 200 nm, and the powder particle size of the activator is 50 to 500 μm.

[0010] S2. Weigh petroleum asphalt according to a set weight and put it into a crucible, then add the mixed powder into the crucible, and then heat the crucible on a crucible heating table at a temperature of 50 to 150° C. for 5 to 15 minutes, continue stirring for 5 to 15 minutes, and air cool to obtain a first mixture;

[0011] S3, placing the first mixture into a silver nitrate solution with a concentration of 0.1 to 1.5 mol / L, stirring for 5 to 15 minutes, and drying in an oven at a temperature of 80 to 130° C. for 6 to 12 hours to obtain a second mixture; wherein the silver nitrate solution is prepared by adding silver nitrate to deionized water;

[0012] S4. Sintering the second mixture in an argon atmosphere with a flow rate of 40 to 60 ml / min in a tubular furnace at a sintering temperature of 1000 to 1200° C. for a holding time of 0.5 to 1 h. After cooling, the desired nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial is finally obtained.

[0013] Specifically, the raw materials, calculated by weight, include: 4 to 8 parts of petroleum asphalt, 1 to 4 parts of auxiliary agent, 1 to 4 parts of activator, and 1 to 2 parts of silver nitrate.

[0014] Specifically, the auxiliary agent includes one of nano zinc oxide and nano magnesium oxide, and the activator includes one of potassium hydroxide, sodium hydroxide and potassium carbonate.

[0015] Specifically, in S2, the softening point of the petroleum asphalt is 110-150°C.

[0016] It should also be noted that in the present invention, due to its thermodynamic instability, nano zinc oxide or nano magnesium oxide undergoes a reduction reaction to generate metallic zinc or magnesium, and then zinc or magnesium undergoes a gasification phase change at high temperature and continuously escapes the system, eventually forming a hollow nanostructure that retains the morphological characteristics of the original zinc oxide or magnesium oxide, which acts as a template and catalyst. The potassium hydroxide on the surface of the nano zinc oxide particles or nano magnesium oxide particles will activate aromatics at high temperature to produce different pores. At the same time, the etching effect on the carbon matrix more synergistically constructs a through-hole nanoscale pore network.

[0017] On the other hand, the present invention provides a nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial, which is prepared using the preparation method described above.

[0018] On the other hand, the present invention provides an application of nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials in flexible pressure sensors.

[0019] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0020] The nitrogen-sulfur-doped three-dimensional graphene / silver nanomaterial invented herein has a three-dimensional structure. During the sintering process, at temperatures of 100-150°C, petroleum asphalt containing silver nitrate and an activator is liquefied and coated on the surface of the activator particles. When the temperature exceeds 440°C, the silver nitrate is heated to form silver. During the subsequent heating step, the sulfur, nitrogen, and hydrocarbons in the asphalt decompose and recombine. Combined with the template effect of the activator, the coating with silver nanoparticles gradually transforms into a thin carbon layer with a spherical structure. Active free radicals in the thin carbon layer undergo polymerization between carbon atoms of adjacent aromatic rings, ultimately forming nanoparticles embedded in the three-dimensional graphene. The volatilization of elemental zinc or magnesium and the simultaneous chemical activation of the activator produce a coupled effect, effectively inhibiting the accumulation of graphene sheets and preventing graphene agglomeration. The etching effect of the activator on the carbon matrix also synergistically constructs a network of interconnected nanoscale pores. The rich graphene network structure results in a uniform distribution of the generated silver nanoparticles. The 3D graphene's mesh structure, serving as a supporting material, allows for the in-situ growth of silver nanoparticles on the graphene, preventing agglomeration of the silver nanoparticles. Ultimately, this allows for the co-doping of 3D graphene with sulfur and nitrogen. Furthermore, the complementary properties of 3D graphene and silver nanoparticles create an efficient and complete conductive network, enhancing the material's electrical conductivity.

[0021] The preparation method invented in this article is easy to synthesize in one step for preparing nitrogen-sulfur doped three-dimensional graphene / silver nanomaterials, and has low cost, short synthesis time, no need for template processing in the later stage, and is efficient and simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the invention.

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 is a flow chart of the preparation method of the present invention;

[0025] Figure 2This is a higher magnification surface morphology of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial prepared in Examples 1, 2, and 3;

[0026] Figure 3 This is the Raman characterization result of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial of Example 1;

[0027] Figure 4 is the XRD characterization result of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial of Example 1;

[0028] Figure 5 This is the EDS spectrum characterization result of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial of Example 1;

[0029] in:

[0030] Figure 5 (a) is the surface morphology of nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials. Figure 2 (a) SEM image of the surface morphology at a lower magnification;

[0031] Figure 5 (b) Distribution diagram of silver element in nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials;

[0032] Figure 5 (c) Distribution diagram of zinc element in nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials;

[0033] Figure 5 (d) Distribution diagram of potassium in nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials;

[0034] Figure 5 (e) is the distribution diagram of sulfur element in nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials;

[0035] Figure 5 (f) is the distribution diagram of nitrogen element in nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials. DETAILED DESCRIPTION

[0036] Exemplary embodiments will now be described in detail, with examples shown in the accompanying drawings. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with some aspects of the present invention as detailed in the appended claims.

[0037] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

[0038] The present invention provides a method for preparing nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials, see Figure 1 As shown, the following steps are included:

[0039] S1. Weighing an auxiliary agent and an activator according to a set weight, grinding and mixing them in an agate mortar, and grinding for 5 to 15 minutes to obtain a mixed powder; wherein the particle size of the auxiliary agent is 10 to 200 nm, and the particle size of the activator powder is 50 to 500 μm;

[0040] S2. Weigh petroleum asphalt according to a set weight and put it into a crucible, then add the mixed powder into the crucible, and then heat the crucible on a crucible heating table at a temperature of 50 to 150° C. for 5 to 15 minutes, continue stirring for 5 to 15 minutes, and air cool to obtain a first mixture;

[0041] S3, placing the first mixture into a silver nitrate solution with a concentration of 0.1 to 1.5 mol / L, stirring for 5 to 15 minutes, and drying in an oven at a temperature of 80 to 130° C. for 6 to 12 hours to obtain a second mixture; wherein the silver nitrate solution is prepared by adding silver nitrate to deionized water;

[0042] S4. Sintering the second mixture in an argon atmosphere with a flow rate of 40 to 60 ml / min in a tubular furnace at a sintering temperature of 1000 to 1200° C. for a holding time of 0.5 to 1 h. After cooling, the desired nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial is finally obtained.

[0043] Specifically, the raw materials, calculated by weight, include: 4 to 8 parts of petroleum asphalt, 1 to 4 parts of auxiliary agent, 1 to 4 parts of activator, and 1 to 2 parts of silver nitrate.

[0044] Specifically, the auxiliary agent includes one of nano zinc oxide and nano magnesium oxide, and the activator includes one of potassium hydroxide, sodium hydroxide and potassium carbonate.

[0045] Specifically, the softening point of the petroleum asphalt is 110-150°C.

[0046] In order to prove the effectiveness of the preparation method of the present invention, the following examples are provided for verification.

[0047] Example 1

[0048] This embodiment provides a method for preparing nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials, and the specific steps are as follows:

[0049] S1. Weigh 1 part of nano zinc oxide and 1 part of potassium hydroxide and grind them in an agate mortar. Grind for 10 minutes to obtain a mixed powder, which is then placed in a glass container. The particle size of the nano zinc oxide is 200 nm, and the particle size of the potassium hydroxide powder is 50 to 500 μm.

[0050] S2. Weigh 4 parts of petroleum asphalt and place them in a crucible. Then, add the mixed powder into the crucible. Then, heat the crucible on a crucible heating table at 100° C. for 10 minutes. Stir continuously for 10 minutes during the heating process. Cool the mixture in air to obtain a first mixture.

[0051] S3. Weigh a portion of silver nitrate and add it to deionized water to prepare a silver nitrate solution with a concentration of 1.0 mol / L. Add the first mixture to the silver nitrate solution and stir for 5 minutes. Then, dry the mixture in an oven at 110° C. for 10 hours to obtain a second mixture.

[0052] S4, first sintering the second mixture in a tube furnace in an argon atmosphere at a flow rate of 50 ml / min, with a heating rate of 5°C / min, a sintering temperature of 1200°C, and a holding time of 1 hour, then cooling the temperature at a cooling rate of 5°C / min to 200°C, and then air cooling to room temperature to finally obtain the desired nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial A;

[0053] S5. Grinding the sintered nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial A into powder, grinding for 2 minutes, uniformly mixing with PDMS (polydimethylsiloxane), and uniformly stirring for 10 minutes to obtain sample A, wherein the mass fraction of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial A is 20%;

[0054] S6. Place the mixed sample A into a 4 cm × 1.5 cm mold and then dry it in an oven at 100°C for 12 hours.

[0055] S7. Use conductive silver glue to apply on both ends of the film, and then stick the copper wire to the two ends of the film as electrodes to obtain flexible sensing material A.

[0056] like Figure 2 (a) shows the SEM characterization of the prepared nitrogen-sulfur doped three-dimensional graphene / silver nanomaterial A. It can be seen from the SEM that the prepared silver nanoparticles are spherical with a diameter of less than 500nm and are evenly distributed and embedded in the three-dimensional mesh graphene.

[0057] like Figure 3 The figure shows the Raman characterization of the prepared nitrogen-sulfur doped three-dimensional graphene / silver nanomaterial A, where the horizontal axis is the wave number range of the test, which is 500 to 3500 cm, and the vertical axis is the intensity of the sample scattered light or the intensity of the characteristic peak of the signal intensity. In the graphene material, the peak at 1350 cm -1 The characteristic peak (D peak) at represents the sp 3The vibration of hybrid carbon atoms reflects the defects and disorder of the carbon lattice; it is located at 1580 cm -1 The characteristic peak (G peak) at represents the well-crystallized sp 2 The optical phonon vibrations of hybridized carbon atoms. In addition, the broad 2D peak indicates the presence of multilayer graphene.

[0058] like Figure 4 Figure 2 shows the XRD characterization results of the prepared nitrogen-sulfur-doped three-dimensional graphene / silver nanomaterial A. The horizontal axis represents the test angle range of 10-90°, and the vertical axis represents the diffraction intensity. The XRD spectrum shows diffraction peaks at 38.1, 41.3, 64.5, 77.4, and 81.6, which are attributed to the (111), (200), (220), (311), and (222) crystal planes of Ag, but no peaks of nano-zinc oxide are found.

[0059] like Figure 5 As shown in the figure, it is the EDS characterization result of the prepared nitrogen-sulfur doped three-dimensional graphene / silver nanomaterial A. It can be seen that the silver element ( Figure 5 (b)), potassium ( Figure 5 (d)), nitrogen ( Figure 5 (e)), sulfur ( Figure 5 (f)) is evenly distributed, with almost no zinc ( Figure 5 (c)) exists. Figures 2 to 5 It shows that three-dimensional graphene / silver nanomaterials were successfully prepared, and nitrogen and sulfur doping were successfully doped into three-dimensional graphene / silver nanocomposites.

[0060] Example 2

[0061] This embodiment provides a method for preparing nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials, and the specific steps are as follows:

[0062] S1. Weigh 2 parts of nano-magnesium oxide and 2 parts of sodium hydroxide and grind them in an agate mortar. Grind for 5 minutes to obtain a mixed powder, which is then placed in a glass container. The particle size of the nano-magnesium oxide is 90 nm, and the particle size of the sodium hydroxide powder is 50 to 500 μm.

[0063] S2. Weigh 6 parts of petroleum asphalt and put them into a crucible. Then add the mixed powder into the crucible, and heat the crucible on a crucible heating table at 50° C. for 15 minutes. Stir continuously for 15 minutes during the heating process, and air cool to obtain a first mixture.

[0064] S3. Weigh 2 parts of silver nitrate and add it to deionized water to prepare a silver nitrate solution with a concentration of 1.0 mol / L. Add the first mixture to the silver nitrate solution and stir for 10 minutes. Then, dry it in an oven at 80° C. for 12 hours to obtain a second mixture.

[0065] S4, first sintering the second mixture in a tube furnace under an argon atmosphere at a flow rate of 40 ml / min, with a heating rate of 5°C / min, a sintering temperature of 1200°C, and a holding time of 0.5 h, then cooling the temperature at a cooling rate of 5°C / min to 200°C, and then air cooling to room temperature to finally obtain the desired nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial B;

[0066] S5. Grinding the sintered nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial B into powder, grinding for 2 minutes, uniformly mixing with PDMS (polydimethylsiloxane), and uniformly stirring for 10 minutes to obtain sample B, wherein the mass fraction of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial A is 20%;

[0067] S6. Place the mixed sample B into a 4 cm × 1.5 cm mold and then dry it in an oven at 100°C for 12 hours.

[0068] S7. Use conductive silver glue to apply on both ends of the film, and then stick the copper wire to the two ends of the film as electrodes to obtain flexible sensing material B.

[0069] like Figure 2 (b) shows the SEM characterization of the prepared silver nanoparticles doped three-dimensional graphene / silver nanomaterial B. From the SEM, it can be seen that the prepared silver nanoparticles are spherical with a diameter of less than 500nm. They are evenly distributed and embedded in the three-dimensional mesh graphene, and a clear pore structure can also be observed.

[0070] Example 3

[0071] This embodiment provides a method for preparing nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials, and the specific steps are as follows:

[0072] S1. Weigh 4 parts of nano zinc oxide and 4 parts of potassium carbonate and grind them in an agate mortar. Grind for 15 minutes to obtain a mixed powder, which is then placed in a glass container. The particle size of the nano zinc oxide is 50 nm, and the particle size of the potassium carbonate powder is 50 to 500 μm.

[0073] S2. Weigh 8 parts of petroleum asphalt and put them into a crucible. Then add the mixed powder into the crucible, and heat the crucible on a crucible heating table at 150° C. for 5 minutes. Stir continuously for 5 minutes during the heating process, and air cool to obtain a first mixture.

[0074] S3. Weigh 2 parts of silver nitrate and add it to deionized water to prepare a silver nitrate solution with a concentration of 1.5 mol / L. Add the first mixture to the silver nitrate solution and stir for 15 minutes. Then, dry it in an oven at 130° C. for 6 hours to obtain a second mixture.

[0075] S4, first sintering the second mixture in a tube furnace in an argon atmosphere at a flow rate of 60 ml / min, with a heating rate of 5°C / min, a sintering temperature of 1200°C, and a holding time of 1 hour, then cooling the temperature at a cooling rate of 5°C / min to 200°C, and then air cooling to room temperature to finally obtain the desired nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial C;

[0076] S5. Grinding the sintered nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial C into powder, grinding for 2 minutes, uniformly mixing with PDMS (polydimethylsiloxane), and uniformly stirring for 10 minutes to obtain sample C, wherein the mass fraction of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial A is 20%;

[0077] S6. Place the mixed sample C into a 4 cm × 1.5 cm mold and then dry it in an oven at 100°C for 12 hours;

[0078] S7. Use conductive silver glue to apply on both ends of the film, and then stick the copper wire to the two ends of the film as electrodes to obtain flexible sensing material C.

[0079] like Figure 2 (c) shows the SEM characterization of the prepared nitrogen-sulfur doped three-dimensional graphene / silver nanomaterial C. It can be seen from the SEM that the prepared silver nanoparticles are spherical, which is similar to the Figure 2 (a) Figure 2 (b) Compared with the silver nanoparticles, there are fewer and more evenly distributed silver nanoparticles embedded in the three-dimensional graphene network, and the graphene appears in a "flower" shape.

[0080] In order to further verify the effectiveness of the technical solution provided by the present invention, the pressure detection range and sensitivity tests were carried out on the flexible sensing material A, flexible sensing material B, and flexible sensing material C, respectively. The test structures are shown in Table 1.

[0081] Table 1 Test results of conductivity and sensitivity of flexible sensors

[0082] Flexible sensing materials Pressure detection range Sensitivity Example 1 0~300kPa <![CDATA[1.32kPa -1 ]]> Example 2 0~280kPa <![CDATA[1.12kPa -1 ]]> Example 3 0~290kPa <![CDATA[1.05kPa -1 ]]> Standard value 1~20kPa <![CDATA[1.0kPa- 1 ]]>

[0083] As can be seen from Table 1, the pressure detection range of the flexible sensing materials prepared by the present invention is greater than the range of 1-20 kPa, and can reach a maximum of 0-300 kPa. The sensitivity is greater than 1.0 kPa-1, which can fully meet the use requirements of the flexible pressure sensor. In addition, the pressure detection range is increased, which broadens the use range of the flexible pressure sensor. It can be further concluded that with the increase of the particle size of the auxiliary agent, the sensitivity of the flexible sensing material also increases, indicating that the sensitivity of the flexible sensing material can be increased by regulating the particle size of the auxiliary agent.

[0084] The flexible sensing material A prepared by the preparation method of the present invention has the highest sensitivity. The silver nanoparticles in the conductive filler are relatively evenly distributed on the three-dimensional graphene. When the film is subjected to pressure, the silver nanoparticles connect the three-dimensional porous carbon material to form more conductive paths, so the resistance changes greatly and has better piezoresistive response performance. The sensitivity of flexible sensing materials B and C is relatively low. This is because in the template-assisted synthesis system of the auxiliary agent, the auxiliary agent with a small particle size is reduced, and the required surface activation energy becomes lower. After preferential reduction, the auxiliary agent with a small particle size loses the role of the template. Therefore, the recombinant phase of the carbon is incomplete, and the three-dimensional graphene defects formed will be relatively more, and the degree of graphitization is also relatively low, making the sensitivity relatively poor. Therefore, the particle size of the auxiliary agent will affect the degree of graphitization and sensitivity of the three-dimensional graphene, but as long as the particle size of the auxiliary agent is between 10 and 200 nm, it will meet the use requirements of the flexible pressure sensor.

[0085] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0086] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterials, characterized in that: The following steps are involved: S1. Weighing a nano zinc oxide adjuvant and an activator according to a set weight ratio and grinding and mixing them to obtain a mixed powder; S2. Weighing petroleum asphalt according to a set weight, mixing it with the mixed powder, then heating and stirring for a specific time, and cooling to obtain a first mixture; S3, adding the first mixture into a silver nitrate solution of a specific concentration, stirring evenly, and drying to obtain a second mixture; S4. Sintering the second mixture, and cooling it to obtain nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial.

2. The preparation method according to claim 1, characterized in that The raw materials include, by weight, 4 to 8 parts of petroleum asphalt, 1 to 4 parts of auxiliary agent, 1 to 4 parts of activator, and 1 to 2 parts of silver nitrate.

3. The preparation method according to claim 1, characterized in that The auxiliary agent includes one of nano zinc oxide and nano magnesium oxide, and the activator includes one of potassium hydroxide, sodium hydroxide and potassium carbonate.

4. The preparation method according to claim 1, characterized in that In S2, the particle size of the auxiliary agent is 10 to 200 nm, and the particle size of the activator is 50 to 500 μm.

5. The preparation method according to claim 1, characterized in that In S2, the petroleum asphalt is placed in a crucible and then heated on a crucible heating table at a heating temperature of 50 to 150° C. for 5 to 15 minutes.

6. The preparation method according to claim 1, characterized in that In S3, the concentration of the silver nitrate solution is 0.1-1.5 mol / L.

7. The preparation method according to claim 1, characterized in that In S3, drying is performed in an oven, the temperature of the oven is 80 to 130° C., and the heating time is 6 to 12 hours.

8. The preparation method according to claim 1, characterized in that In S4, a tubular furnace is used to perform sintering treatment in an argon atmosphere, the flow rate of the argon is 40-60 ml / min, the sintering temperature is 1000-1200° C., and the holding time is 0.5-1 h.

9. A nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial, characterized in that: The preparation method is as described in any one of claims 1 to 8.

10. The use of the nitrogen-sulfur co-doped three-dimensional graphene / silver nanomaterial according to claim 9, characterized in that: Application in flexible pressure sensors.

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