Graphene-based composite material as well as preparation method and application thereof

Abstract

The invention provides a graphene-based composite material as well as a preparation method and application thereof. The graphene-based composite material comprises reduced graphene, a first functional material and a second functional material, the first functional material comprises at least one of 1, 3, 5-benzenetricarboxylic acid, resorcinol, hydroquinone, catechol, 2, 5-dihydroxybenzoic acid, 1, 5-naphthalene disulfonic acid, 2, 6-sodium naphthalene disulfonate and anthraquinone-2-sodium sulfonate; the second functional material comprises at least one of metal, metal oxide and conductive polymer. A sensing element or a sensor prepared from the graphene-based composite material can realize integration of humidity and gas (such as formaldehyde and NO2) detection functions under light assistance, so that the space is greatly saved, and the detection efficiency is improved. Meanwhile, a sensing element or a sensor prepared from the graphene-based composite material has higher sensitivity and higher response speed, and a foundation is laid for preparing a commercialized humidity-sensitive and gas-sensitive collaborative detection sensor.

Description

Technical Field

[0001] The present invention belongs to the technical fields of composite materials and sensing detection, and particularly relates to a graphene-based composite material, a preparation method thereof, and an application thereof. Background Art

[0002] The measurement and control of humidity are of great significance in precision instruments, semiconductor integrated circuits, and component manufacturing factories. In addition, humidity sensing is also widely applied in fields such as weather forecasting, medical treatment, and food processing. When people breathe (inhale and exhale), the humidity of the gas changes. It can reflect the body's movement state and can also be used as one of the most important health indicators. Since humidity sensors are crucial for human production and daily life, there is an urgent need to develop reliable humidity sensors.

[0003] According to different output electric quantities, humidity sensors are further divided into resistive type, capacitive type, frequency type, etc. Resistive humidity sensors have the advantages of being reusable, low-cost, easy for large-scale production and miniaturization, and are one of the most widely studied humidity sensors at present. Various materials, such as ceramics, organic polymers, semiconductors, electrolytes, etc., have been widely studied as humidity sensing materials. Graphene has been widely studied and applied in resistive humidity sensors due to its large specific surface area, strong adsorption ability, and inherent flexible characteristics. However, graphene has poor hydrophilicity during the water absorption process and poor repeatability after water absorption, which limits its application.

[0004] In practical applications, it is necessary to accurately and efficiently detect humidity and distinguish the content of other harmful gases at high humidity. Moreover, in addition to the importance of humidity detection, in real life, the detection of harmful gases such as formaldehyde and NO2 is also very important.

[0005] However, traditional humidity sensors and gas (such as formaldehyde and NO2) sensors often work independently (that is, the humidity-sensitive element and the gas-sensitive element are fabricated separately and tested separately), which not only occupies a large space but also has low detection efficiency. At the same time, some existing detection means have difficulty guaranteeing the detection accuracy in complex environments, especially at high humidity, which will interfere with the monitoring of other target gases by the sensor and cannot meet the increasing high-precision detection requirements. Summary of the Invention

[0006] To solve the problems and deficiencies existing in the prior art, the present invention provides a graphene-based composite material, a preparation method and an application thereof. The sensing element or sensor prepared by using the graphene-based composite material can integrate the functions of humidity and gas (such as formaldehyde, NO2) detection under light assistance, greatly saving space and improving the detection efficiency. At the same time, the sensing element or sensor prepared by using the graphene-based composite material has higher sensitivity and faster response speed, laying a foundation for the preparation of commercial humidity and gas sensing co-detection sensors.

[0007] According to the first aspect of the present invention, there is provided a graphene-based composite material, comprising reduced graphene, a first functional material, and a second functional material; the first functional material comprises at least one of 1,3,5-benzenetricarboxylic acid, resorcinol hydroquinone, catechol, 2,5-dihydroxybenzoic acid, 1,5-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonate, sodium anthraquinone-2-sulfonate; the second functional material comprises at least one of a metal, a metal oxide, and a conductive polymer.

[0008] As mentioned in the background art, due to its large specific surface area, strong adsorption ability and inherent flexible characteristics, graphene has been widely studied and applied in resistive humidity sensors. Moreover, graphene has also been widely studied and applied in gas sensors for harmful gases such as formaldehyde and NO2. However, graphene has poor hydrophilicity during the water absorption process and poor repeatability after water absorption, which limits its application. Therefore, how to improve the hydrophilicity of graphene and the stability after water absorption is of great significance for obtaining highly sensitive and accurate humidity and gas sensors.

[0009] The graphene-based composite material designed by the present invention comprises reduced graphene, a first functional material (organic molecule) and a second functional material (metal or metal oxide or conductive polymer). Among them, reduced graphene has higher chemical stability and conductivity compared with graphene oxide, and can also ensure the original large specific surface area, strong adsorption ability and inherent flexible characteristics of graphene. As a sensor material, it is more conducive to ensuring the stability, detection accuracy and sensitivity of the sensor. However, the reaction activity of pure reduced graphene is not ideal in some environments, especially in a humid (high humidity) environment, which affects its detection performance for specific gases such as formaldehyde and NO2. At the same time, the sensitivity of pure reduced graphene for the detection of some trace substances may not meet the requirements.

[0010] Thus, a graphene-based composite material provided by the present invention has the above-mentioned first functional material (organic molecule) and the second functional material (metal or metal oxide or conductive polymer) modified on the surface of reduced graphene. First, the above-mentioned first functional material contains an aromatic cyclic conjugated structure and can undergo π-π interaction with graphene. Therefore, the above-mentioned first functional material can effectively modify graphene, improving the dispersibility and electron transport performance of graphene. Moreover, in addition to the conjugated structure, some of the organic molecules provided by the present invention also contain carboxyl groups, hydroxyl groups or charged functional groups. Since reduced graphene is usually obtained by reducing graphene oxide, the final reduced graphene still has some active groups such as hydroxyl groups and carboxyl groups. Therefore, the organic molecules can also bind to the reduced graphene in a non-covalent bond manner such as hydrogen bonds or electrostatic forces, thus further optimizing the dispersibility and electron transport performance of graphene. And the organic molecules have specific responses, so stable sensing in humidity sensing can be achieved. In particular, organic molecules with aromatic benzene rings or conjugated structures can further optimize the electron transport stability and sensitivity during the sensing process, so it is more conducive to improving the sensitivity and accuracy of material sensing. Secondly, the second functional material further improves the resistance stability of the graphene-based composite material, enabling it to have a more stable and more sensitive resistance response, that is, to have a higher sensitivity for humidity detection and gas (such as formaldehyde, NO2) detection.

[0011] Secondly, the above-mentioned first functional material (organic molecule) can regulate the photothermal effect under the assistance of a light source, and combine with light assistance to effectively realize a high-performance sensor for complete gas detection. Through experience, it is known that the light source can cause certain damage to the material, and even burn when the light intensity is too high. Adding organic molecules helps to improve the overall stability and thermal conductivity of the graphene material, so as to protect the material from achieving a stable response to the target in a complex environment and realizing highly stable and sensitive sensing of gases (such as formaldehyde, NO2). At the same time, the second functional material can assist the first functional material to further optimize and regulate the photothermal effect under the assistance of a light source. For example, metals have a surface plasmon resonance effect, absorb light energy of a specific wavelength, and convert it into heat energy, thereby affecting the photothermal effect; metal oxides and conductive polymers also generate a photothermal effect when absorbing light energy, thus regulating the overall photothermal effect. And in addition to regulating the photothermal effect, the second functional material also has other important functions. For example, metals or metal oxides can serve as active sites and undergo specific chemical reactions with target gases (such as formaldehyde, NO), thereby improving the sensitivity of the sensor to the target gas.

[0012] In addition, it should be emphasized here that the graphene-based composite material provided by the present invention can achieve the collaborative detection of humidity and gases, effectively overcoming the limitations of traditional humidity sensors and gas sensors working independently, as well as the defect that gas sensors are greatly affected by humidity, and bringing a new solution to the detection work in related fields. That is, the sensor provided by the present invention can not only achieve sensitive detection of humidity, but also achieve sensitive detection of target gases (such as formaldehyde, NO) that are greatly affected by humidity. That is, at high humidity, it can still achieve high sensitivity detection of target gases (such as formaldehyde, NO), avoiding the influence of humidity on the detection of target gases (such as formaldehyde, NO).

[0013] Preferably, the mass ratio of reduced graphene, the first functional material, and the second functional material is (0.1 - 7):(10 - 300):(1 - 1000). Under the above ratio, the three materials can have better synergistic effects, that is, they can more fully exert the beneficial effects brought by the three materials, better take into account the comprehensive properties such as the stability and thermal conductivity of the graphene-based composite material, and make the graphene-based composite material exhibit higher sensing performance for humidity and gases.

[0014] Preferably, the mass ratio of reduced graphene, the first functional material, and the second functional material is (0.1 - 5):(10 - 200):(1 - 500). Preferably, the mass ratio of reduced graphene, the first functional material, and the second functional material is (0.1 - 5):(10 - 200):(1 - 200). Preferably, the mass ratio of reduced graphene, the first functional material, and the second functional material is (0.1 - 5):(10 - 200):(1 - 100). Preferably, the mass ratio of reduced graphene, the first functional material, and the second functional material is (0.1 - 5):(10 - 200):(1 - 50).

[0015] Preferably, the metal includes at least one of Au, Ag, Cu, Fe, Pt; the metal oxide includes at least one of titanium dioxide, zinc oxide, tin oxide, indium oxide, tungsten trioxide, copper oxide, iron(III) oxide, iron(II,III) oxide, molybdenum trioxide, cobalt(II,III) oxide, cerium oxide; the conductive polymer includes at least one of polyaniline, polypyrrole, polythiophene.

[0016] Preferably, the first functional material includes at least one of 1,3,5-benzenetricarboxylic acid and resorcinol.

[0017] Preferably, the second functional material includes at least one of Ag, zinc oxide, and polyaniline.

[0018] Preferably, the graphene-based composite material comprises reduced graphene, 1,3,5-benzenetricarboxylic acid, and Ag; or the graphene-based composite material comprises reduced graphene, 1,3,5-benzenetricarboxylic acid, and zinc oxide; the graphene-based composite material comprises reduced graphene, resorcinol, and polyaniline. Further optimizing the combination of various types of materials is more conducive to exerting the interaction between the materials, and thus can be more conducive to the detection sensitivity and accuracy of the graphene-based composite material to humidity and gases.

[0019] According to the second aspect of the present invention, a preparation method of the above-mentioned graphene-based composite material is provided. When the second functional material comprises a metal, the preparation method comprises the following steps: S11. Prepare a graphene oxide dispersion by using graphene oxide and water; S12. Mix the first functional material with water, then adjust the pH of the obtained solution to 6.8-7.2, then add the graphene oxide dispersion and a metal salt solution containing the metal thereto, and after mixing evenly, add a reducing agent solution thereto, and react at 85-95 °C for 0.5-2 h; S13. Filter and wash the mixed system after the reaction in S12 with water to obtain the graphene-based composite material. Through the above steps, a graphene-based composite material with good compounding of reduced graphene, the first functional material (organic molecule), and the metal can be obtained, and the obtained graphene-based composite material can realize the collaborative detection of humidity and gases, and has high detection sensitivity and accuracy.

[0020] Preferably, in S11, the concentration of the graphene oxide dispersion is 0.5-5 mg / L. Preferably, in S11, the concentration of the graphene oxide dispersion is 0.5-2 mg / L.

[0021] Preferably, in S12, the mass-volume ratio of the first functional material to water is 80-300 mg:40 mL. Preferably, in S12, the mass-volume ratio of the first functional material to water is 100-250 mg:40 mL.

[0022] Preferably, in S12, the pH is adjusted to 6.8-7.2 by using an alkaline solution; the alkaline solution comprises at least one of a sodium hydroxide solution and a potassium hydroxide solution. Preferably, the mass concentration of the alkaline solution is 7-15 wt%.

[0023] Preferably, in S12, the metal salt in the metal salt solution is at least one of chloroauric acid, silver chloride, silver nitrate, chloroplatinic acid, copper nitrate, and ferric chloride. Preferably, in S12, the concentration of the metal salt solution is 0.05-0.2 mol / L.

[0024] Preferably, in S12, the reducing agent in the reducing agent solution comprises at least one of hydrazine hydrate, sodium borohydride, ascorbic acid, and glucose.

[0025] Preferably, in S12, the mass ratio of graphene oxide, the first functional material, the metal salt, and the reducing agent is (1-10):(100-500):(10-100):(1-100). Preferably, in S12, the mass ratio of graphene oxide, the first functional material, the metal salt, and the reducing agent is (1-10):(100-500):(10-100):(1-50). Preferably, in S12, the mass ratio of graphene oxide, the first functional material, the metal salt, and the reducing agent is (1-10):(100-500):(10-100):(1-20). Preferably, in S12, the mass ratio of graphene oxide, the first functional material, the metal salt, and the reducing agent is (1-10):(100-500):(10-100):(1-10).

[0026] Preferably, in S12, when the reducing agent is hydrazine hydrate, the concentration of the reducing agent solution is 0.1-1 μL / mL.

[0027] Preferably, in S13, the filtration treatment is carried out by vacuum filtration. Preferably, the water washing treatment is carried out 2-5 times. The water washing is to completely remove the free first functional material (organic molecules), metal ions such as Na + or K + 、Ag + 、NO3 - and hydrazine hydrate, so as to avoid these materials from affecting the sensing performance of the finally prepared graphene-based composite material and its response performance to humidity or other gases.

[0028] Preferably, in S13, the product after water washing can be redispersed in water and freeze-dried for relevant characterizations such as electron microscopy and XRD. The temperature of the freeze-drying treatment is -60 to -50 °C, and the pressure is 1-10 Pa.

[0029] Preferably, in each of the above steps, the water used is deionized water.

[0030] According to the third aspect of the present invention, a method for preparing the above graphene-based composite material is provided. When the second functional material includes a metal oxide, the preparation method includes the following steps: S21. Prepare a graphene oxide dispersion by using graphene oxide and water; S22. Mix the first functional material with water, then adjust the pH of the obtained solution to 6.8 - 7.2, then add the graphene oxide dispersion thereto. After mixing evenly, add a reducing agent solution and react at 85 - 95 °C for 0.5 - 2 h. Filter and wash the obtained mixed system with water, and redisperse the obtained solid in water; S23. Continuously add the oxide to the dispersion obtained in S22, mix for 0.5 - 2 h, centrifuge and wash the obtained product with water to obtain the graphene-based composite material. Through the above steps, a graphene-based composite material with good composite of reduced graphene, the first functional material (organic molecule), and the metal oxide can be obtained, and the obtained graphene-based composite material can realize the synergistic detection of humidity and gas, and has high detection sensitivity and accuracy.

[0031] Preferably, in S21, the concentration of the graphene oxide dispersion is 0.5 - 5 mg / L. Preferably, in S21, the concentration of the graphene oxide dispersion is 0.5 - 2 mg / L.

[0032] Preferably, in S22, the mass-volume ratio of the first functional material to water is 80 - 300 mg:40 mL. Preferably, in S22, the mass-volume ratio of the first functional material to water is 100 - 250 mg:40 mL.

[0033] Preferably, in S22, the pH is adjusted to 6.8 - 7.2 by using an alkaline solution; the alkaline solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution. Preferably, the mass concentration of the alkaline solution is 7 - 15 wt%.

[0034] Preferably, in S22, the reducing agent in the reducing agent solution includes at least one of hydrazine hydrate, sodium borohydride, ascorbic acid, and glucose.

[0035] Preferably, in S22, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1 - 10):(10 - 500):(0.001 - 20). Preferably, in S22, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1 - 10):(10 - 500):(0.01 - 10). Preferably, in S22, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1 - 10):(10 - 500):(0.1 - 10). Preferably, in S22, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1 - 10):(10 - 300):(1 - 10). Preferably, in S22, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1 - 10):(10 - 200):(1 - 10).

[0036] Preferably, in S22, when the reducing agent is hydrazine hydrate, the concentration of the reducing agent solution is 0.1 - 1 μL / mL.

[0037] Preferably, in S22, the filtration treatment is carried out by vacuum filtration. Preferably, the water washing treatment is carried out 2 - 5 times.

[0038] Preferably, in S23, the input amount of the oxide is calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, and the oxide of (1 - 10):(10 - 500):(0.001 - 20):(1 - 1000). Preferably, in S23, the input amount of the oxide is calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, and the oxide of (1 - 10):(10 - 500):(0.01 - 10):(1 - 500). Preferably, in S23, the input amount of the oxide is calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, and the oxide of (1 - 10):(10 - 500):(0.1 - 10):(1 - 500). Preferably, in S23, the input amount of the oxide is calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, and the oxide of (1 - 10):(10 - 300):(1 - 10):(1 - 300). Preferably, in S23, the input amount of the oxide is calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, and the oxide of (1 - 10):(10 - 300):(1 - 10):(1 - 200).

[0039] Preferably, in S23, in the centrifugation treatment, the centrifugation speed is 6000 - 9000 rpm, and the centrifugation time is 3 - 10 minutes. Preferably, the water washing treatment is carried out 2 - 5 times.

[0040] Preferably, in each of the above steps, the water used is deionized water.

[0041] According to the fourth aspect of the present invention, there is provided a method for preparing the above-mentioned graphene-based composite material. When the second functional material includes a conductive polymer, the preparation method includes the following steps: S31. Prepare a graphene oxide dispersion using graphene oxide and water; S32. Mix the first functional material with water, then add the graphene oxide dispersion thereto. After mixing evenly, add a reducing agent solution and react at 85-95 °C for 0.5-2 h. Filter and wash the obtained mixed system with water, and dry to obtain a solid; S33. Disperse the solid in S32 in an acidic solution, then add a monomer thereto. After mixing for 0.5-2 h, add an initiator, and place the obtained mixture at -5-6 °C for reaction for 3-6 h. Then centrifuge and wash the obtained product with water to obtain the graphene-based composite material. Through the above steps, a graphene-based composite material with good compounding of reduced graphene, the first functional material (organic molecule), and the conductive polymer can be obtained, and the obtained graphene-based composite material can realize the synergistic detection of humidity and gas, and has high detection sensitivity and accuracy.

[0042] Preferably, in S31, the concentration of the graphene oxide dispersion is 0.5-5 mg / L. Preferably, in S31, the concentration of the graphene oxide dispersion is 0.5-2 mg / L.

[0043] Preferably, in S32, the mass-to-volume ratio of the first functional material to water is 80-300 mg:40 mL. Preferably, in S32, the mass-to-volume ratio of the first functional material to water is 100-250 mg:40 mL.

[0044] Preferably, in S32, use an alkaline solution to adjust the pH to 6.8-7.2; the alkaline solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution. Preferably, the mass concentration of the alkaline solution is 7-15 wt%.

[0045] Preferably, in S32, the reducing agent in the reducing agent solution includes at least one of hydrazine hydrate, sodium borohydride, ascorbic acid, and glucose.

[0046] Preferably, in S32, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1-10):(10-100):(1-100). Preferably, in S32, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1-10):(10-100):(1-50). Preferably, in S32, the mass ratio of graphene oxide, the first functional material, and the reducing agent is (1-10):(10-100):(1-10).

[0047] Preferably, when the reducing agent in S32 is hydrazine hydrate, the concentration of the reducing agent solution is 0.1-1 μL / mL.

[0048] Preferably, in S32, the filtration process is carried out by vacuum filtration. Preferably, the water washing process is carried out 2 to 5 times.

[0049] Preferably, in S33, the solid-liquid ratio of the solid to the acidic solution is 90 to 100 mg: 10 mL. Preferably, the H + concentration in the acidic solution is 0.5 to 2 mol / L. Preferably, the acidic solution includes hydrochloric acid solution.

[0050] Preferably, in S33, the input amounts of the monomer and the initiator are calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, the monomer, and the initiator being (1 to 10): (10 to 100): (1 to 100): (10 to 100): (1 to 50). Preferably, in S33, the input amounts of the monomer and the initiator are calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, the monomer, and the initiator being (1 to 10): (10 to 100): (1 to 50): (10 to 70): (1 to 50). Preferably, in S33, the input amounts of the monomer and the initiator are calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, the monomer, and the initiator being (1 to 10): (10 to 100): (1 to 20): (10 to 50): (1 to 20). Preferably, in S33, the input amounts of the monomer and the initiator are calculated based on the mass ratio of graphene oxide, the first functional material, the reducing agent, the monomer, and the initiator being (1 to 10): (10 to 100): (1 to 10): (10 to 50): (1 to 10).

[0051] Preferably, in S33, the initiator includes at least one of ammonium persulfate and potassium persulfate.

[0052] Preferably, in the centrifugation process of S33, the centrifugation speed is 1000 to 10000 rpm, and the centrifugation time is 5 to 20 minutes. Preferably, the water washing process is carried out 2 to 5 times.

[0053] Preferably, in each of the above steps, the water used is deionized water.

[0054] According to the fifth aspect of the present invention, a sensing element is provided, including an electrode and the above graphene-based composite material or a graphene-based composite material prepared by the preparation method of the above graphene-based composite material.

[0055] Preferably, the process of compounding the graphene-based composite material on the electrode surface includes at least one of sputtering, spraying, screen printing, and evaporation coating.

[0056] Preferably, the electrode includes interdigital electrodes.

[0057] According to the sixth aspect of the present invention, there is provided an application of the above-mentioned sensing element in the detection of humidity and gases, where the gases include at least one of formaldehyde and NO2.

[0058] According to the seventh aspect of the present invention, there is provided a sensor, including a light source and the above-mentioned sensing element.

[0059] According to the eighth aspect of the present invention, there is provided an application of the above-mentioned sensing element in the detection of humidity and gases, where the gases include at least one of formaldehyde and NO2; the light source includes at least one of infrared light and near-infrared light; the intensity of the light source is 1 - 1000 mW / cm 2 . By using infrared light or near-infrared light as the light source stimulation, the co-detection of humidity and gases (such as formaldehyde and NO2) can be achieved. That is, on a single sensor device, the detection of humidity can be realized, and the detection of gases (such as formaldehyde and NO2) can also be realized. For example, the humidity detection can be achieved without applying the light source. However, after applying the light source, if there are gases (such as formaldehyde and NO2) present, obvious response changes (such as changes in resistance in a resistive sensor) will occur. At this time, the responses to humidity and gases (such as formaldehyde and NO2) can be distinguished because the sensing element provided by the present invention can achieve the co-detection of humidity and gases (such as formaldehyde and NO2). And the intensity of the light source used needs to be within a specific range. If it is too small, the stimulation is insufficient and the responses to humidity and gases cannot be effectively distinguished. If it is too large, the sensitive material in the sensing element will be damaged, affecting the accuracy and sensitivity of the detection results, and even may seriously damage the sensitive material and the sensing performance cannot be achieved.

[0060] It should also be emphasized here that the sensing element or sensor device prepared from the graphene-based composite material provided by the present invention can still achieve good detection of gases (such as formaldehyde and NO2) under high humidity conditions under light source stimulation, that is, it can be unaffected by humidity and achieve accurate and stable testing of gases. The high humidity environment, for example, refers to a humidity ≥ 60%, that is, even under complex environments such as a humidity of 60%, high-precision and high-sensitivity detection of the target gas can still be achieved.

[0061] Preferably, the wavelength of the light source is 800 - 2500 nm.

[0062] In summary, compared with the prior art, the present invention has the following technical effects: (1) The modified reduced graphene composite material with the first functional material (organic molecule) and the second functional material (metal or metal oxide or conductive polymer) can not only ensure the characteristics of large specific surface area, strong adsorption capacity and inherent flexibility of graphene, but also highlight the specific response effect of organic molecules, enabling stable sensing in humidity or gas (such as formaldehyde, NO2) sensing. At the same time, the first functional material and the second functional material can further improve the stability and specific responsiveness of the graphene-based composite material, and optimize its detection sensitivity and accuracy for humidity and gas.

[0063] (2) Utilize the photothermal effect assisted by organic molecule-regulated light source, and combine with light assistance to effectively achieve a high-performance sensor for complete gas detection.

[0064] (3) Adopt a graphene-based composite sensing material with both high conductivity and high thermal conductivity and a unique light-assisted structure design, which can realize the collaborative detection application of humidity and gas in a complex environment, effectively overcome the limitations of traditional humidity sensors and gas sensors working independently, as well as the defect that gas sensors are greatly affected by humidity, and bring a new solution for the detection work in related fields. Description of the Drawings

[0065] Figure 1 SEM images of the TMA-rGO / Ag-2.5 sample in Example 1 and the TMA-rGO-100, TMA-rGO-150, TMA-rGO-200, and TMA-rGO-250 samples in Comparative Example 1;

[0066] Figure 2 Infrared spectra of the TMA-rGO-150 and TMA-rGO-200 samples in Comparative Example 1, the rGO sample in Comparative Example 4, and TMA;

[0067] Figure 3 XRD patterns of the TMA-rGO / Ag-2.5 sample in Example 1, the TMA-rGO-200 sample in Comparative Example 1, and Ag;

[0068] Figure 4 Microscope pictures of the TMA-rGO / Ag sample in Example 1 on the electrode;

[0069] Figure 5 Response curves of the TMA-rGO / Ag and TMA-rGO samples in Example 1 and Comparative Example 1 to different humidities;

[0070] Figure 6 Fitting curves of the sensitivities of the TMA-rGO / Ag and TMA-rGO samples in Example 1 and Comparative Example 1 changing with relative humidity;

[0071] Figure 7 It is the response curve of the TMA-rGO / ZnO composite material in Example 2 to 65% RH humidity under near-infrared light assistance;

[0072] Figure 8 It is the response curve of the TMA-rGO / ZnO composite material in Example 2 to 10 ppm NO2 under near-infrared light and 65% RH humidity;

[0073] Figure 9 It is the response curve of the rGO / ZnO composite material in Comparative Example 2 to 10 ppm NO2 under light illumination and 65% RH humidity;

[0074] Figure 10 It is the response curve of the resorcinol-rGO / polyaniline material in Example 3 to a humid environment and formaldehyde under light illumination;

[0075] Figure 11 It is the response curve of the polyaniline material in Comparative Example 3 to a humid environment and formaldehyde under light illumination;

[0076] Figure 12 It is the response curve of the TMA-rGO / Ag sample in Example 1 to a humid environment and formaldehyde with / without light illumination. Detailed implementation manners

[0077] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0078] Example 1

[0079] Synthesize the graphene-based composite material (1,3,5-benzenetricarboxylic acid (TMA) modified graphene / Ag composite material) of this example according to the following steps

[0080] S11. Prepare a graphene oxide dispersion (1 mg / mL) using graphene oxide and deionized water;

[0081] S12. Dissolve 200 mg of TMA in 40 mL of deionized water and stir. Add a NaOH solution (10 wt%) to adjust the pH to 7. Then add 5 mL of the graphene oxide dispersion (1 mg / mL) and 2.56 mL of silver nitrate (0.1 mol / L) and stir for 1 h. Add 10 mL of a hydrazine hydrate solution (0.5 μL / mL of water), and stir at 90 °C for another 1 h; wherein, the mass ratio of graphene oxide, TMA, silver nitrate, and hydrazine hydrate is 5:200:43.52:5.15;

[0082] S13. Finally, vacuum filtration is carried out, and the sample is rinsed three times with deionized water. The obtained sample is redispersed in 10 ml of deionized water, and the dried product is the graphene-based composite material, labeled as TMA-rGO / Ag (TMA-rGO / Ag-2.5 in the attached figure is also this substance). In the TMA-rGO / Ag of this example, the mass ratio of rGO, TMA, and Ag is 4.5:150:20.

[0083] Example 2

[0084] Synthesize the graphene-based composite material (1,3,5-benzenetricarboxylic acid (TMA)-modified graphene / zinc oxide composite material) of this example according to the following steps

[0085] S21. Prepare a graphene oxide dispersion (1 mg / mL) using graphene oxide and water;

[0086] S22. Dissolve 200 mg of TMA in 40 mL of deionized water and stir. Add 10 wt% NaOH solution to adjust the pH to 7. Then add 5 mL of the graphene oxide dispersion (1 mg / mL) to it. After stirring for 1 hour, add 10 mL of hydrazine hydrate solution (0.5 μL / mL of water), and stir for another 1 hour at 90 °C. Carry out vacuum filtration and rinse three times with deionized water. Redisperse the obtained sample (denoted as TMA-rGO) in 10 mL of deionized water;

[0087] S23. Continue to add 100 mg of zinc oxide to the dispersion obtained in S22 (the mass ratio of graphene oxide, TMA, hydrazine hydrate, and zinc oxide is 5:200:5.15:100), stir for 1 hour, centrifuge the product at 8000 rpm for 8 minutes, and wash it 3 times with deionized water. After drying, the graphene-based composite material is obtained, denoted as TMA-rGO / ZnO. In the TMA-rGO / ZnO of this example, the mass ratio of rGO, TMA, and ZnO is 4.5:150:90.

[0088] Example 3

[0089] Synthesize the graphene-based composite material (resorcinol-modified graphene / polyaniline composite material) of this example according to the following steps

[0090] S31. Prepare a graphene oxide dispersion (1 mg / mL) using graphene oxide and water;

[0091] S32. Dissolve 50 mg of resorcinol in 40 mL of deionized water with stirring. Then add 5 mL of graphene oxide dispersion (1 mg / mL) thereto. After stirring for 1 hour, add 10 mL of hydrazine hydrate solution (0.5 μL / mL of water). Stir for another 1 hour at 90 °C, perform vacuum filtration, rinse three times with deionized water, and dry to obtain resorcinol-modified reduced graphene oxide, denoted as resorcinol-rGO;

[0092] S33. Disperse the product in S32 in 10 mL of hydrochloric acid solution (1 mol / L), and then introduce 20 μL of aniline monomer into the above dispersion. After stirring for 1 h, add a certain amount of ammonium persulfate (APS) initiator (the mass ratio of graphene oxide, resorcinol, hydrazine hydrate, aniline monomer, and initiator is 5:50:5.15:20:5). Transfer the mixture solution to a refrigerator at 4 °C for polymerization for 3 - 6 hours. Finally, centrifuge and wash the product 3 times with deionized water, and perform freeze-drying treatment to obtain a graphene-based composite material, denoted as resorcinol-rGO / polyaniline. And in the resorcinol-rGO / polyaniline of this example, the mass ratio of rGO, resorcinol, and polyaniline is 4.5:38:18.

[0093] Comparative Example 1

[0094] In this comparative example, the TMA-rGO composite material was synthesized, and the specific steps are as follows:

[0095] Dissolve 100, 150, 200, and 250 mg of TMA in 40 mL of deionized water with stirring, add 10 wt% NaOH solution, adjust the pH of these solutions to 7, and then add 5 mL of graphene oxide dispersion (1 mg / mL) to these solutions respectively. After stirring for 1 hour, add 10 mL of hydrazine hydrate solution (0.5 μL / mL of water) to each of them respectively. Stir for another 1 hour at 90 °C, perform vacuum filtration, rinse three times with deionized water, and then disperse the obtained samples in 10 mL of deionized water respectively, denoted as TMA-rGO-100, TMA-rGO-150, TMA-rGO-200, and TMA-rGO-250.

[0096] Comparative Example 2

[0097] In this comparative example, the reduced graphene oxide / zinc oxide (rGO / zinc oxide) composite material was synthesized, and the specific steps are as follows:

[0098] Prepare a graphene oxide dispersion (1 mg / mL) using graphene oxide and water. Take 5 mL of the graphene oxide dispersion (1 mg / mL), stir for 1 hour, then add 10 mL of hydrazine hydrate solution (0.5 μL / mL water), and stir for another 1 hour at 90 °C. Filter under vacuum and rinse three times with deionized water. Redisperse the obtained sample (denoted as rGO) in 10 mL of deionized water. Add 100 mg of zinc oxide to 10 mL of the rGO dispersion (0.5 mg / mL), stir for 1 hour, centrifuge the product at 8000 rpm for 8 minutes, and wash 3 times with deionized water. After drying, obtain the rGO / ZnO composite material.

[0099] Comparative Example 3

[0100] The following are the specific steps for synthesizing the polyaniline material in this comparative example:

[0101] Introduce 20 μL of aniline monomer into 10 mL of hydrochloric acid solution (1 mol / L), stir for 1 h, then add a certain amount of ammonium persulfate (APS) initiator (the mass ratio of aniline monomer to initiator is 20:5). Transfer the mixture solution to a refrigerator at 4 °C for polymerization for 3 - 6 hours. Finally, centrifuge and wash the product 3 times with deionized water, and perform freeze-drying treatment to obtain the polyaniline material.

[0102] Comparative Example 4

[0103] The following are the specific steps for synthesizing reduced graphene oxide in this comparative example:

[0104] Prepare a graphene oxide dispersion (1 mg / mL) using graphene oxide and water. Take 5 mL of the graphene oxide dispersion (1 mg / mL), stir for 1 hour, then add 10 mL of hydrazine hydrate solution (0.5 μL / mL water), and stir for another 1 hour at 90 °C. Filter under vacuum and rinse three times with deionized water. Redisperse the obtained sample (denoted as rGO) in 10 mL of deionized water.

[0105] Test and Analysis

[0106] 1. Morphology Analysis

[0107] Perform SEM analysis on the materials prepared in Example 1 and Comparative Example 1. As Figure 1 shown, from Figure 1 (a - d), it can be seen that there are aggregation and stacking phenomena in the morphologies of the TMA-rGO-100 and TMA-rGO-250 samples, that is, there are aggregation and stacking phenomena in the morphologies of the organic molecule TMA under a small amount and an excessive amount, while the morphology distributions of the TMA-rGO-150 and TMA-rGO-200 samples are good. And further from Figure 1As can be seen from (e), Ag nanoparticles are uniformly distributed in the TMA-rGO / Ag material, that is, in the TMA-rGO / Ag material, the three can achieve good uniform distribution, which is more conducive to improving the overall performance of the composite material, and is more conducive to its sensing performance for humidity and gaseous formaldehyde and NO2, improving sensitivity and accuracy.

[0108] 2. Infrared analysis

[0109] The TMA-rGO-150 and TMA-rGO-200 samples in Comparative Example 1, the rGO sample in Comparative Example 4, and TMA were subjected to infrared tests, and the results are as Figure 2 shown. As can be seen from Figure 2 compared with rGO, characteristic peaks of TMA appear in the TMA-rGO-150 and TMA-rGO-200 samples, reflecting the successful modification of graphene by the organic molecule TMA.

[0110] 3. XRD analysis

[0111] The TMA-rGO-200 sample in Comparative Example 1, the TMA-rGO / Ag-2.5 sample in the Example, and Ag were subjected to XRD tests, and the results are as Figure 3 shown. As can be seen from Figure 3 compared with TMA-rGO-200, the diffraction peaks of the TMA-rGO / Ag-2.5 composite material match the diffraction peaks of Ag, and the crystallinity is good.

[0112] 4. Electrode microscopy analysis

[0113] The TMA-rGO / Ag-2.5 sample (the dispersion before drying) in Example 1 was coated on the interdigital electrode and dried at 55 °C to obtain an electrode containing the sensing material, that is, the sensing element, and it was subjected to microscopy analysis. The results are as Figure 4 shown. As can be seen from Figure 4 it that TMA-rGO / Ag-2.5 spreads flatly on the electrode, is evenly distributed, and has a small amount of usage, can be prepared on a large scale, and the even distribution is more conducive to ensuring that the sensing material has better sensing stability and sensitivity.

[0114] 5. Humidity and / or gas (formaldehyde, NO2) test

[0115] (1) The TMA-rGO / Ag-2.5 sample in Example 1 and the TMA-rGO-200 sample in Comparative Example 1 (both are 10 μL of the dispersion before drying) were coated on the interdigital electrode and dried at 55 °C to obtain an electrode containing the sensing material, that is, the sensing element.

[0116] The humidity responsiveness tests were respectively carried out on the TMA-rGO / Ag-2.5 sensing element and the TMA-rGO-200 sensing element. The specific test method is as follows: Install the sensing element in a sealed test chamber, and connect the supporting detection circuit and data acquisition equipment. First, pass dry nitrogen and record the initial electrical signal of the sensing element. Adjust the flow rates of dry nitrogen and standard wet gas in proportion to obtain mixed gases with different humidities, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% relative humidity. Pass them into the test chamber at a specific flow rate and record the data. After each humidity point test, pass dry nitrogen to restore the sensing element to its initial state. Finally, calculate the response parameters of the sensing element, such as sensitivity, that is, the resistance change rate (ΔR / R a *100% = R g -R a / R a *100%), and plot the humidity-response curve.

[0117] The results are as Figure 5 shown. Comparing Figure 5 (a) and Figure 5 (b), when the relative humidity is between 10% - 90%RH, the humidity response performance of the TMA-rGO / Ag sample is superior to that of the TMA-rGO sample. The resistance change range of the TMA-rGO sample is between 12 - 145 MΩ (the resistance change of the electrode from dry (0%) to the most humid (90%) state. For example, the resistance of TMA-rGO at 0%RH is 145 MΩ, and the resistance at 90%RH is 12 MΩ.), while the resistance change range of the TMA-rGO / Ag sample is between 21 - 1500 MΩ, and the resistance change resolution is higher. Therefore, TMA-rGO / Ag has higher sensitivity and accuracy for humidity detection.

[0118] Furthermore, analyzing the sensitivity, the results are as Figure 6 shown. It can be seen from Figure 6 (a) and Figure 6 (b) that as the relative humidity increases, the sensitivities of both the TMA-rGO and TMA-rGO / Ag samples show an upward trend, and the overall curve fitting degree is high, indicating that the sensitivity of the samples is good. In particular, the humidity response range of TMA-rGO / Ag is wider, which is more conducive to practical detection applications.

[0119] (2) Coat the TMA-rGO / ZnO sample (take 10 μL of the dispersion before drying) in Example 2 on the interdigital electrode, and dry it at 55 °C to obtain the electrode containing the sensing material, that is, the sensing element.

[0120] The NO2 gas responsiveness test was carried out on the TMA-rGO / ZnO sensing element, and specifically, two processes were tested.

[0121] Among them, the first test process is as follows: Install the sensing element in the sealed test chamber, and connect the supporting detection circuit and data acquisition equipment. Record the initial electrical signal of the sensing element in a 20% RH atmosphere. Inject a certain amount of water onto the heating sheet. After volatilization, a 35% RH atmosphere is obtained and a response signal (7.8%) is obtained. After returning to the 20% RH atmosphere, the signal recovers. After irradiation with 980 nm light of 50 mW / cm 2 , a photocurrent (1.97 μA) is generated. Then inject water to make the humidity reach 65% RH. Due to the photo-assisted anti-humidity effect, the sensing element is not affected by humidity. After turning off the light source, the photocurrent disappears, but due to the influence of high humidity (65% RH), the current of the sensing element increases to 1.57 μA. Then inject 10 ppm NO2 gas. The gas sensitivity is only 1.07 under high humidity. After recovery, the signal of the sensing element returns to the most original state. Finally, calculate the response parameters of the sensing element, such as sensitivity (R a / R g = 1.07).

[0122] The results are as Figure 7 shown. It can be seen that for the TMA-rGO / ZnO composite material prepared in Example 2, when the humidity changes from 20% to 35% RH, the sensor current increases. After the humidity returns to 20% RH, the signal recovers. Under the assistance of near-infrared light, introducing a high-humidity (65% RH) atmosphere, the current change of the sensor is almost 0, indicating that it is not affected by humidity, which is conducive to realizing complete gas sensing. When the light source is turned off, the photocurrent disappears, and the current increases to 1.57 μA due to the influence of humidity. The sensitivity of 10 ppm NO2 under high humidity is only 1.07. This shows that under the assistance of the light source, testing NO2 under high humidity conditions has higher sensitivity.

[0123] The second test process is as follows: Install the sensing element in the sealed test chamber, and connect the supporting detection circuit and data acquisition equipment. Record the initial electrical signal of the sensing element in the original 20% RH atmosphere. After irradiation with 980 nm light of 50 mW / cm 2 , a photocurrent (2.91 μA) is generated. Then inject water to make the humidity reach 65% RH. Due to the photo-assisted anti-humidity effect, the sensing element is not affected by humidity. Then inject 10 ppm NO2 gas. Under photo-assistance, even when the humidity is as high as 65% RH, the gas sensitivity reaches 1.12. After turning off the light source, the signal of the sensing element returns to the most original 20% RH state. In a relatively dry atmosphere, inject 10 ppm NO2 gas, and the gas sensitivity is 1.13. The sensitivity calculation formula: R a / R g .

[0124] The results are as Figure 8As shown, it can be seen that for the TMA-rGO / ZnO composite sensing material prepared in Example 2, in a high-humidity environment (65% RH), the response value of the sensor to 10 ppm NO2 is 1.12, and in an indoor environment (20% RH), the response value of the sensor to 10 ppm NO2 is 1.13. This indicates that with light assistance, the sensor can achieve comparable sensitivity even under high humidity as in a relatively dry environment, that is, it can accurately detect NO2 in a high-humidity environment and achieve the co-detection of high-performance humidity and NO2.

[0125] In a resistive sensor, R a and R g represent the following meanings respectively: R a : the static resistance value, that is, the resistance value under initial conditions. R a g : the resistance value of the gas in the specified concentration of the gas to be measured.

[0126] (3) Coat the rGO / ZnO sample in Comparative Example 2 (take 10 μL of the dispersion before drying) on the interdigital electrode and dry it at 55 °C to obtain an electrode containing the sensing material, that is, the sensing element.

[0127] Perform NO2 gas responsiveness testing on the rGO / ZnO sensing element. The specific testing method is as follows: Install the sensing element in a sealed test chamber and connect the supporting detection circuit and data acquisition equipment. Record the initial electrical signal of the sensing element in the original 20% RH atmosphere. After being irradiated with 980 nm light at 50 mW / cm 2 , a photocurrent (~1.17 μA) is generated. Then inject moisture to make the humidity reach 65% RH. The sensing element is not affected by humidity, but due to light damage, the photocurrent gradually decreases. After injecting 10 ppm NO2 gas, no useful signal can be observed.

[0128] The results are as Figure 9 shown. It can be seen that for the rGO / ZnO composite material prepared in Comparative Example 2, the electrode is easily damaged under light irradiation and the signal is unstable. In a high-humidity environment (65% RH), the sensor has almost no response to 10 ppm NO2.

[0129] (4) Coat the resorcinol-rGO / polyaniline sample in Example 3 (take 10 μL of the dispersion before drying) on the interdigital electrode and dry it at 55 °C to obtain an electrode containing the sensing material, that is, the sensing element.

[0130] Perform formaldehyde gas responsiveness testing on the resorcinol-rGO / polyaniline sensing element. The specific testing method (photocurrent-gas-sensing signal coupling testing method) is as follows: Install the sensing element in a sealed test chamber and connect the supporting detection circuit and data acquisition equipment. Record the initial electrical signal of the sensing element in a 60% RH humid atmosphere. After being irradiated with 100 mW / cm2 After being irradiated with 980 nm light, a photocurrent of 2.25 μA is generated, the sensitivity is 5.8%, and the repeated test signal has almost no attenuation (5.6%). Then, 55 ppm of formaldehyde gas is injected. When there is no light, no signal is generated (i.e., there is no moisture-resistant sensing signal). After being irradiated with 100 mW / cm 2 After being irradiated with 980 nm light, a photocurrent of 2.23 μA is generated, the sensitivity is 4.8%, and the repeated test signal has almost no attenuation (4.9%). Sensitivity calculation formula: ΔR / R a *100% = R g -R a / R a *100%.

[0131] The results are as Figure 10 shown. It can be seen that for the resorcinol-rGO / polyaniline composite sensing material prepared in Example 3, in humid air, the photocurrent is 5.6% - 5.8%, and in 50 ppm of formaldehyde, the photocurrent is 4.8% - 4.9%, indicating that the sensor can achieve the co-detection of humidity and formaldehyde. Among them, "in humid air" means only humid air (humidity is 60% RH), and "in 55 ppm of formaldehyde" means there is both humid air and formaldehyde. After adding formaldehyde, the photocurrent signal changes significantly (weakens), so it can be considered that this signal is the change in the photocurrent signal caused by formaldehyde. Therefore, the co-detection of humidity and formaldehyde can be achieved on the same sensor device.

[0132] (5) Coat the polyaniline sample in Comparative Example 3 (take 10 μL of the dispersion before drying) on the interdigital electrode and dry it at 55 °C to obtain the electrode containing the sensing material, that is, the sensing element.

[0133] Perform the formaldehyde gas responsiveness test on the polyaniline sensing element. The specific test method is as follows: Install the sensing element in a sealed test chamber and connect the supporting detection circuit and data acquisition equipment. Record the initial electrical signal of the sensing element in a 60% RH humid atmosphere. After being irradiated with 100 mW / cm 2 After being irradiated with 980 nm light, a photocurrent of 1.37 μA is generated, the sensitivity is 3.7%, and the repeated test signal has almost no attenuation (3.6%). Then, 55 ppm of formaldehyde gas is injected. When there is no light, no signal is generated (i.e., there is no moisture-resistant sensing signal). After being irradiated with 100 mW / cm 2 After being irradiated with 980 nm light, a photocurrent of 1.37 μA is generated, the sensitivity is 3.6%. Sensitivity calculation formula: ΔR / R a *100% = R g -R a / R a *100%.

[0134] The results are as Figure 11As shown, it can be seen that for the polyaniline sample prepared in Comparative Example 3, in humid air, the photocurrent is 3.6% - 3.7%, and in 55 ppm formaldehyde, the photocurrent is 3.6%, indicating that the synergistic detection effect of the sensor on humidity and formaldehyde is not obvious. That is, after adding formaldehyde, the current signal does not change significantly, and the synergistic detection effect on humidity and formaldehyde is not obvious.

[0135] (6) Coat the TMA-rGO / Ag sample (take 10 μL of the dispersion before drying) in Example 1 on the interdigital electrode and dry it at 55 °C to obtain the electrode containing the sensing material, that is, the sensing element.

[0136] Perform the formaldehyde gas responsiveness test on the TMA-rGO / Ag sensing element. The specific test method is as follows: Install the sensing element in a sealed test chamber and connect the supporting detection circuit and data acquisition equipment. Record the initial electrical signal of the sensing element in a 50% RH humid atmosphere, inject moisture to make the humidity reach 65% RH, and the response of the sensing element is 14.3%. After the humidity is restored to 50% RH, the signal is restored. After irradiation with 808 nm light of 1000 mW / cm 2 , a photocurrent (0.013 μA) is generated. Then inject moisture to make the humidity reach 65% RH. Due to the light-assisted anti-humidity effect, the sensing element is not affected by humidity. Then inject 80 ppb formaldehyde gas. Even at a humidity as high as 65% RH under light assistance, the gas sensitivity reaches 5.1%. After turning off the light source, the signal of the sensing element is restored to the 65% RH state. At high humidity, inject 80 ppb formaldehyde again. Due to the absence of light, no signal is generated (i.e., no anti-humidity sensing signal). At a relatively dry humidity, inject 80 ppb formaldehyde again. Due to the absence of light, no signal is generated (i.e., no anti-humidity sensing signal). The sensitivity calculation formula: ΔR / R a *100% = R g -R a / R a *100%.

[0137] The results are as Figure 12 shown. For the TMA-rGO / Ag sample prepared in Example 1, when the humidity changes from 50% RH to 65% RH, the sensitivity is 14.3%; under light irradiation, it has an anti-humidity effect. Under light assistance, even in a high-humidity environment (65% RH), the response value of the sensor to 80 ppb formaldehyde reaches 5.1%; without light assistance, in an indoor environment (50% RH) and at high humidity (65% RH), the sensor has no response to 80 ppb formaldehyde. It shows that the sensor can achieve the synergistic detection of humidity and formaldehyde and has high-efficiency gas sensing ability.

[0138] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A graphene-based composite material, characterized in that: It includes reduced graphene, a first functional material, and a second functional material; The first functional material includes at least one of 1,3,5-benzenetricarboxylic acid, resorcinol, hydroquinone, catechol, 2,5-dihydroxybenzoic acid, 1,5-naphthalenedisulfonic acid, sodium 2,6-naphthalenedisulfonate, and sodium anthraquinone-2-sulfonate; The second functional material includes at least one of a metal, a metal oxide, and a conductive polymer.

2. The graphene-based composite material according to claim 1, wherein: The mass ratio of the reduced graphene, the first functional material, and the second functional material is (0.1 - 7):(10 - 300):(1 - 1000).

3. The graphene-based composite material according to claim 1, wherein: The metal includes at least one of Au, Ag, Cu, Fe, and Pt; The metal oxide includes at least one of titanium dioxide, zinc oxide, tin oxide, indium oxide, tungsten trioxide, copper oxide, iron(III) oxide, iron(II,III) oxide, molybdenum trioxide, cobalt(II,III) oxide, and cerium oxide; The conductive polymer includes at least one of polyaniline, polypyrrole, and polythiophene.

4. A method for preparing the graphene-based composite material according to any one of claims 1 to 3, wherein when the second functional material includes the metal, the preparation method includes the following steps: S11. Prepare a graphene oxide dispersion using graphene oxide and water; S12. Mix the first functional material with water, then adjust the pH of the resulting solution to 6.8 - 7.2, then add the graphene oxide dispersion and a metal salt solution containing the metal thereto, mix evenly, and then add a reducing agent solution, and react at 85 - 95 °C for 0.5 - 2 h; S13. Filter and wash the reaction mixture in S12 with water to obtain the graphene-based composite material.

5. A method for preparing the graphene-based composite material according to any one of claims 1 to 3, wherein when the second functional material includes the metal oxide, the preparation method includes the following steps: S21. Prepare a graphene oxide dispersion using graphene oxide and water; S22. Mix the first functional material with water, then adjust the pH of the resulting solution to 6.8 - 7.2, then add the graphene oxide dispersion thereto, mix evenly, add a reducing agent solution, react at 85 - 95 °C for 0.5 - 2 h, filter and wash the resulting mixture with water, and redisperse the obtained solid in water; S23. Continue to add the oxide to the dispersion obtained in S22, mix for 0.5 - 2 h, centrifuge and wash the obtained product with water to obtain the graphene-based composite material.

6. A method for preparing the graphene-based composite material according to any one of claims 1 to 3, wherein when the second functional material includes the conductive polymer, the preparation method includes the following steps: S31. Prepare a graphene oxide dispersion using graphene oxide and water; S32. Mix the first functional material with water, then add the graphene oxide dispersion thereto. After mixing evenly, add the reducing agent solution and react at 85-95 °C for 0.5-2 h. Filter and wash the obtained mixed system with water, and dry to obtain a solid. S33. Disperse the solid in S32 in an acidic solution, then add a monomer thereto. After mixing for 0.5-2 h, add an initiator, and place the obtained mixture at -5-6 °C for reaction for 3-6 h. Then centrifuge and wash the obtained product with water to obtain the graphene-based composite material.

7. A sensing element, characterized in that: Comprising an electrode and the graphene-based composite material according to any one of claims 1-3, or the graphene-based composite material prepared by the preparation method of the graphene-based composite material according to any one of claims 4-6.

8. Application of the sensing element according to claim 7 in humidity and gas detection, wherein the gas comprises at least one of formaldehyde and NO2.

9. A sensor, characterized in that: Comprising a light source and the sensing element according to claim 7.

10. Application of the sensor according to claim 9 in humidity and gas detection, wherein the gas comprises at least one of formaldehyde and NO2; the light source comprises at least one of infrared light and near-infrared light. The intensity of the light source is 1 to 1000 mW / cm 2 .

Images