A surface reduced graphene oxide fiber and its preparation method and application

Abstract

The present invention discloses a surface reduced graphene oxide fiber and a preparation method and application thereof. The surface reduced graphene oxide fiber of the present invention comprises a surface reduced graphene oxide film that has been folded and twisted, and the surface reduced graphene oxide film comprises a graphene oxide layer and a reduced graphene oxide layer that covers the graphene oxide layer. The preparation method of the surface reduced graphene oxide fiber of the present invention comprises the following steps: 1) preparing a graphene oxide film; 2) preparing a surface reduced graphene oxide film; 3) folding and twisting the surface reduced graphene oxide film. The surface reduced graphene oxide fiber of the present invention has a sensitive temperature warning function, a fast response speed, a short response time, and can provide a warning signal at a relatively low temperature, and is suitable for early warning of fires.

Description

Technical Field

[0001] The present invention relates to the technical field of fire warning, and in particular to a surface reduced graphene oxide fiber and a preparation method and application thereof. Background Art

[0002] Fires often cause huge losses of life and property to people, so fire warning is crucial. The speed of fire spread is usually measured in seconds, and every second is crucial. The slower the response to fire risks, the greater the possibility of causing tragic fires. At present, the commonly used smoke sensors in indoor areas have a long response time (>100s, even >300s) due to the transmission and enrichment process of smoke, and the sensitivity of infrared sensors is also low, and the response time is usually greater than 100s. The response time of these two types of sensors is too long to fully meet the requirements of practical applications. In addition, the ignition point of common indoor plastic materials, chemical textiles, paper, wood, etc. is generally within 500℃ (the lowest is only about 130℃), and most of the existing fire warning devices cannot provide warning signals at lower temperatures (<300℃) and without open flames.

[0003] Therefore, it is of great significance to develop a temperature-sensitive material with high sensitivity, short response time and the ability to provide early warning signals at lower temperatures. Summary of the invention

[0004] The purpose of the present invention is to provide a surface reduced graphene oxide fiber and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A surface reduced graphene oxide fiber comprises a folded and twisted surface reduced graphene oxide film; the surface reduced graphene oxide film comprises a graphene oxide layer and a reduced graphene oxide layer covering the graphene oxide layer.

[0007] Preferably, the thickness of the graphene oxide layer is 4 μm to 15 μm.

[0008] Further preferably, the graphene oxide layer has a thickness of 5 μm to 10 μm.

[0009] Preferably, the reduced graphene oxide layer has a thickness of 1 μm to 5 μm.

[0010] Further preferably, the reduced graphene oxide layer has a thickness of 2 μm to 5 μm.

[0011] Preferably, the graphene oxide layer comprises flake graphene oxide.

[0012] Preferably, the flake diameter of the flake graphene oxide is 5 μm to 45 μm.

[0013] More preferably, the flake diameter of the flake graphene oxide is 15 μm to 30 μm.

[0014] A method for preparing the surface-reduced graphene oxide fiber as described above comprises the following steps:

[0015] 1) preparing graphene oxide into a dispersion liquid, and then coating the dispersion liquid on a substrate to form a film, thereby obtaining a graphene oxide film;

[0016] 2) placing the graphene oxide film into a reducing agent solution for immersion to obtain a surface-reduced graphene oxide film;

[0017] 3) The surface-reduced graphene oxide film is rolled and twisted to obtain the surface-reduced graphene oxide fiber.

[0018] Preferably, the concentration of the dispersion in step 1) is 5 mg / g to 10 mg / g.

[0019] Preferably, the reducing agent solution in step 2) is a mixed solution consisting of hydroiodic acid, acetic acid solution and hypophosphorous acid solution.

[0020] Preferably, the soaking in step 2) is carried out at room temperature (25°C±5°C).

[0021] Preferably, the soaking time in step 2) is 1 h to 120 h.

[0022] Further preferably, the soaking time in step 2) is 1 h to 24 h.

[0023] An application of the surface reduced graphene oxide fiber as described above in fire warning.

[0024] A fire sensor comprises the surface-reduced graphene oxide fiber.

[0025] Preferably, the fire sensor also includes a fracture detection circuit.

[0026] Preferably, the fracture detection circuit is composed of a low-voltage DC power supply, a current-limiting resistor, a warning signal light and a thyristor.

[0027] The beneficial effects of the present invention are as follows: the surface-reduced graphene oxide fiber of the present invention has a sensitive temperature warning function, a fast response speed, a short response time, and can provide a warning signal at a relatively low temperature, and is suitable for early warning of fire.

[0028] Specifically:

[0029] 1) The surface-reduced graphene oxide fiber of the present invention can provide an early warning signal at a relatively low temperature (150° C.) and without an open flame, and is suitable for early warning of fire;

[0030] 2) The surface-reduced graphene oxide fiber of the present invention has a sensitive temperature warning function, can be used in places with high requirements for fire prevention, and has a high market value;

[0031] 3) The preparation process of the surface-reduced graphene oxide fiber of the present invention is simple and easy to operate, and the raw materials used are cheap, the production cost is low, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a flow chart for preparing the surface-reduced graphene oxide fiber.

[0033] Figure 2 The SEM images and line scanning energy spectrum images of the cross sections of the graphene oxide film and the surface-reduced graphene oxide film in Example 3.

[0034] Figure 3 This is a SEM image of the surface-reduced graphene oxide film after being rolled up in Example 3.

[0035] Figure 4 These are SEM images of the surface and cross-section of the surface-reduced graphene oxide fiber in Example 3.

[0036] Figure 5 Experimental setup and experimental circuit diagram for responsiveness testing.

[0037] Figure 6 This is a diagram of the appearance of the surface-reduced graphene oxide fiber in Example 3 during the response test under different temperature and flame conditions.

[0038] Figure 7 Schematic diagram of the structure of the test device for response time test.

[0039] Figure 8 This is a current-time relationship curve and response time statistical result diagram of the surface reduced graphene oxide fiber in Example 3 under different temperature and flame conditions.

[0040] Fig. 9 The current-time relationship curves of the surface-reduced graphene oxide film in Comparative Example 1 and the surface-reduced graphene oxide fiber in Comparative Example 2 at 200°C.

[0041] Fig.10 This is a graph showing the response time test results of the graphene oxide fiber in Comparative Example 3 and the surface-reduced graphene oxide fiber in Examples 1 to 5 at 200°C.

[0042] Fig.11 The response behavior of the surface-reduced graphene oxide fiber in Example 3 during voltage step and the current-time relationship curve at different voltages.

[0043] Fig.12 The temperature-time relationship curve of the surface-reduced graphene oxide fiber in Example 3 under different voltages.

[0044] Fig.13 These are appearance photos of the surface-reduced graphene oxide fibers in Example 3 after they were broken under different temperatures and flame conditions.

[0045] Fig.14 The XRD diagrams of the corresponding fracture products obtained after the surface-reduced graphene oxide fiber in Example 3 is fractured under different temperatures and flame conditions.

[0046] Fig.15 These are photos of the appearance of the surface-reduced graphene oxide fiber in Example 3 after breaking at different voltages.

[0047] Fig.16 These are XRD diagrams of the corresponding fracture products obtained after the surface-reduced graphene oxide fiber in Example 3 is fractured at different voltages. DETAILED DESCRIPTION

[0048] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0049] Embodiment 1:

[0050] A surface-reduced graphene oxide fiber, the preparation method of which comprises the following steps (the preparation flow chart is as follows Figure 1 shown):

[0051] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0052] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution, and then the graphene oxide film was placed in the reducing agent solution and soaked at room temperature for 1 hour, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0053] 3) The surface-reduced graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) and twisted to obtain the surface-reduced graphene oxide fiber.

[0054] Embodiment 2:

[0055] A surface-reduced graphene oxide fiber, the preparation method of which comprises the following steps:

[0056] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0057] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution, and then the graphene oxide film was placed in the reducing agent solution and soaked at room temperature for 3 hours, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0058] 3) The surface-reduced graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) and twisted to obtain the surface-reduced graphene oxide fiber.

[0059] Embodiment 3:

[0060] A surface-reduced graphene oxide fiber, the preparation method of which comprises the following steps:

[0061] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0062] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution, and then the graphene oxide film was placed in the reducing agent solution and soaked at room temperature for 5 hours, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0063] 3) The surface-reduced graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) and twisted to obtain the surface-reduced graphene oxide fiber.

[0064] Embodiment 4:

[0065] A surface-reduced graphene oxide fiber, the preparation method of which comprises the following steps:

[0066] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0067] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution, and then the graphene oxide film was placed in the reducing agent solution and soaked at room temperature for 12 hours, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0068] 3) The surface-reduced graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) and twisted to obtain the surface-reduced graphene oxide fiber.

[0069] Embodiment 5:

[0070] A surface-reduced graphene oxide fiber, the preparation method of which comprises the following steps:

[0071] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0072] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution, and then the graphene oxide film was placed in the reducing agent solution and soaked at room temperature for 24 hours, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0073] 3) The surface-reduced graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) and twisted to obtain the surface-reduced graphene oxide fiber.

[0074] Comparative Example 1:

[0075] A surface-reduced graphene oxide film, the preparation method of which comprises the following steps:

[0076] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0077] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution. The graphene oxide film was then placed in the reducing agent solution and soaked at room temperature for 5 h, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm).

[0078] Comparative Example 2:

[0079] A surface-reduced graphene oxide fiber, the preparation method of which comprises the following steps:

[0080] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film;

[0081] 2) 100 mL of 57% hydroiodic acid and 9 mL of 50% hypophosphorous acid solution were mixed, and then 250 mL of 99% acetic acid solution was added to prepare a reducing agent solution, and then the graphene oxide film was placed in the reducing agent solution and soaked at room temperature for 5 hours, then taken out and rinsed with water and ethanol, and then left at room temperature for 2 days to obtain a surface-reduced graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0082] 3) The surface-reduced graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) to obtain the surface-reduced graphene oxide fiber.

[0083] Comparative Example 3:

[0084] A graphene oxide fiber, the preparation method of which comprises the following steps:

[0085] 1) dispersing flake graphene oxide with a sheet diameter of 15 μm to 30 μm in water to prepare a dispersion with a concentration of 7 mg / g, and then coating the dispersion on a substrate to form a film to obtain a graphene oxide film (strip-shaped, with a size of 60 mm×10 mm);

[0086] 2) The graphene oxide film is rolled up (along the width direction, the folded width is about 1.8 mm) and twisted to obtain graphene oxide fibers.

[0087] Performance Testing:

[0088] 1) The cross-sectional scanning electron microscope (SEM) images and line scanning energy spectrum images of the graphene oxide film and the surface reduced graphene oxide film in Example 3 are as follows: Figure 2(a is a graphene oxide film, c is a line scanning energy spectrum at the dashed line in a, b is a surface reduced graphene oxide film, and d is a line scanning energy spectrum at the dashed line in b).

[0089] Depend on Figure 2 From a in , we can see that the thickness of the graphene oxide film is about 10 μm.

[0090] Depend on Figure 2 From b in the figure, we can see that the thickness of the surface reduced graphene oxide film is close to that of the graphene oxide film.

[0091] Depend on Figure 2 From the c in the figure, we can see that the distribution ratio of carbon and oxygen elements in the graphene oxide film remains roughly unchanged throughout the entire cross section.

[0092] Depend on Figure 2 From d in the figure, we can see that the carbon element distribution on the outside of the cross-section of the surface reduced graphene oxide film is significantly higher and lower on the inside. Correspondingly, the distribution of oxygen elements is exactly the opposite of the distribution of carbon elements, low on the outside and high on the inside. The depth of the area with high carbon elements on the outside is about 2μm, and the thickness of the area with low carbon elements in the middle is about 6μm.

[0093] 2) The scanning electron microscope (SEM) image of the surface-reduced graphene oxide film after rolling up in Example 3 is as follows: Figure 3 (a is a cross-sectional view, b is a partially enlarged view of the cross-sectional view).

[0094] Depend on Figure 3 It can be seen that the thickness of the surface reduced graphene oxide film is about 10 μm, the folded width is about 1.8 mm, and there are large gaps between the folded layers.

[0095] 3) The SEM images of the surface and cross section of the surface-reduced graphene oxide fiber in Example 3 are as follows: Figure 4 (a and b are surface images, c and d are cross-sectional images).

[0096] Depend on Figure 4 It can be seen that obvious spiral texture can be observed on the surface of the surface reduced graphene oxide fiber, and the surface is basically smooth; there are large gaps between the layers in the surface reduced graphene oxide fiber, and the layers are tightly squeezed against each other due to torsion, and the layers are greatly restricted.

[0097] 4) The surface-reduced graphene oxide fiber in Example 3 was placed under different temperatures (120°C, 150°C and 250°C; heated by a blast heating device calibrated by a thermocouple) and flame conditions (alcohol lamp) for responsiveness testing (the experimental device and experimental circuit diagram used are as shown in FIG. Figure 5 The appearance of the surface-reduced graphene oxide fiber during the test is shown in Figure 6 shown.

[0098] Depend on Figure 6 It can be seen that the surface-reduced graphene oxide fiber in Example 3 will undergo significant volume expansion and will quickly break when subjected to a temperature of 150° C. or above or flame burning.

[0099] 5) The surface-reduced graphene oxide fiber in Example 3 was placed under different temperatures (120°C, 150°C, 200°C and 250°C; heated by a blast heating device calibrated by a thermocouple) and flame conditions (alcohol lamp) to test the response time (i.e., fiber breakage time: the time required for the current to start rising until the current decreases to zero) (the structural schematic diagram of the test device is shown in FIG. Figure 7 The current-time relationship curve and response time statistics obtained from the test are shown in the figure below. Figure 8 shown.

[0100] Depend on Figure 8 It can be seen that the surface-reduced graphene oxide fiber in Example 3 has a fire warning effect starting from a temperature of 150° C., and the response time becomes shorter and shorter as the temperature increases (the driving force for expansion increases).

[0101] 6) The surface-reduced graphene oxide film in Comparative Example 1 and the surface-reduced graphene oxide fiber in Comparative Example 2 were placed at 200° C. for a response time test (the test process is the same as above). The current-time relationship curve during the test process is as follows: Fig. 9 (a is the surface reduced graphene oxide film in Comparative Example 1, and b is the surface reduced graphene oxide fiber in Comparative Example 2).

[0102] Depend on Fig. 9 It can be seen that the current of the surface-reduced graphene oxide film in Comparative Example 1 did not show a decreasing trend at 200°C, and no breakage occurred; the surface-reduced graphene oxide fiber in Comparative Example 2 (only rolled up) had a longer response time at 200°C compared with the surface-reduced graphene oxide fiber in Example 3.

[0103] 7) The graphene oxide fiber in Comparative Example 3 and the surface-reduced graphene oxide fiber in Examples 1 to 5 (the reduction time of the graphene oxide film is 0h, 1h, 3h, 5h, 12h and 24h, respectively) were placed at 200°C for a response time test (the test process is the same as above). The test results are as follows: Fig.10 shown.

[0104] Depend on Fig.10 It can be seen that as the reduction time of graphene oxide film increases, the response time is basically close, all within 8s.

[0105] 8) The response behavior of the surface-reduced graphene oxide fiber in Example 3 during voltage step and the current-time relationship curves at different voltages are as follows: Fig.11 As shown (the experimental device used is as Figure 5 The temperature-time relationship curves of the reduced graphene oxide fibers under different voltages obtained by the HM300 infrared thermal imager (Guangzhou SAT Infrared Co., Ltd.) are shown in Fig.12 shown.

[0106] Depend on Fig.11 It can be seen that: as the voltage applied to the reduced graphene oxide fiber increases, the current passing through the reduced graphene oxide fiber also increases, but when the voltage rises to 4V, it drops to 0 in a short time. At this time, the reduced graphene oxide fiber breaks, indicating that the reduced graphene oxide fiber can respond to the sudden increase in voltage (the reduced graphene oxide fiber can respond to voltage changes, which may be caused by the Joule heat caused by the current); under the single voltage test condition, when the voltage is between 0.5V and 3V, the current increases slowly with time, but it does not break. When the voltage is higher than 4V, the reduced graphene oxide fiber will expand significantly and break. The higher the voltage, the shorter the time required to break. The corresponding response times at voltages of 4V, 6V and 10V are approximately 11s, 3s and 1s.

[0107] Depend on Fig.12 It can be seen that: when the voltage is lower than 1V, the temperature rise is not obvious; at a voltage of 3V, the temperature of the reduced graphene oxide fiber rises to about 130°C due to the Joule heat generated by the current, but it does not break; when the voltage is higher than 4V, the highest temperature that the infrared camera can capture is close to 156°C; as the voltage increases further, the rate of temperature rise of the reduced graphene oxide fiber accelerates, but it often breaks when it exceeds 150°C; the voltage response characteristics of reduced graphene oxide fibers provide new ideas for electrical fire early warning.

[0108] 9) The appearance photos of the surface-reduced graphene oxide fiber in Example 3 after being broken under different temperatures and flame conditions are as follows Fig.13 As shown (the experimental device used is as Figure 5 The corresponding X-ray diffraction (XRD) pattern of the fracture product (fracture point) is shown in Fig.14 shown.

[0109] Depend on Fig.13 It can be seen that: at 120°C, the surface reduced graphene oxide fiber only produced a slight expansion in the heated part and did not break; from other samples, it can be seen that the fracture was mainly due to the expansion of the heated part, and the surface reduced graphene oxide film that was originally twisted together has been completely unfolded; the fracture of the sample above 200°C showed obvious black, indicating the reduction of the internal graphene oxide.

[0110] Depend on Fig.14 It can be seen that the diffraction peak near 10° belongs to graphene oxide, and the diffraction peak near 24° belongs to reduced graphene oxide; when the temperature is 150°C, the graphene oxide peak is significantly weakened and shifted to the right, and the reduced graphene oxide peak begins to become broad, which indicates that the inner graphene oxide has undergone a certain reduction; as the temperature rises to above 200°C, the graphene oxide peak will further shift to the right and almost disappear, while the reduced graphene oxide peak is broader. The broadening of the reduced graphene oxide peak may be caused by the expansion of gas produced by thermal decomposition, which indicates that the graphene oxide inside the surface reduced graphene oxide has undergone a certain degree of reduction, that is, the oxygen-containing functional groups are removed, resulting in a decrease in the interlayer spacing to form reduced graphene oxide.

[0111] 10) The appearance photos of the surface-reduced graphene oxide fiber in Example 3 after breaking at different voltages are as follows Fig.15 As shown, the corresponding XRD pattern of the fracture product (fracture point) is as follows Fig.16 shown.

[0112] Depend on Fig.15 It can be seen that: when the voltage is 0.2V and 1V, no obvious change in the appearance of the surface reduced graphene oxide fiber was observed; when the voltage is 3V, the middle part of the surface reduced graphene oxide fiber expanded slightly but did not break; when the voltage exceeded 4V, the surface reduced graphene oxide fibers all broke significantly, and the reduced graphene oxide that was originally twisted and folded at the break expanded and unfolded visibly.

[0113] Depend on Fig.16 It can be seen that when the voltage is 0.2V and 1V, the XRD of the two products has no obvious change. Fig.12 Infrared thermal temperature measurement analysis shows that, in the absence of significant Joule heat, the applied voltage does not affect the structure of the surface reduced graphene oxide fiber; when the voltage is 3V, the 2θ angle belonging to the graphene oxide (001) shifts to the right, that is, the interlayer spacing of the graphene oxide decreases, which indicates that the inner layer of graphene oxide has undergone a certain reduction; when the voltage is further increased to 4V, 6V and 10V, it can also be observed that the respective graphene oxides (001) have shifted significantly to the right, and the reduced graphene oxide (002) has weakened significantly, which indicates that the increase in voltage causes the increase in current, and the resulting Joule heat can make the temperature inside the surface reduced graphene oxide fiber not too high (about 156°C), so the degree of reduction of the inner layer of graphene oxide is relatively slight.

[0114] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A surface-reduced graphene oxide fiber, characterized in that: The composition includes a surface reduced graphene oxide film that has been folded and twisted; the composition of the surface reduced graphene oxide film includes a graphene oxide layer and a reduced graphene oxide layer covering the graphene oxide layer; the thickness of the graphene oxide layer is 4μm to 15μm; the thickness of the reduced graphene oxide layer is 1μm to 5μm.

2. The surface-reduced graphene oxide fiber according to claim 1, characterized in that: The graphene oxide layer comprises flake graphene oxide.

3. The surface-reduced graphene oxide fiber according to claim 2, characterized in that: The flake diameter of the flake graphene oxide is 5 μm to 45 μm.

4. A method for preparing surface-reduced graphene oxide fibers according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) preparing graphene oxide into a dispersion liquid, and then coating it on a substrate to form a film, thereby obtaining a graphene oxide film; 2) placing the graphene oxide film in a reducing agent solution for immersion to obtain a surface-reduced graphene oxide film; 3) The surface reduced graphene oxide film is rolled and twisted to obtain the surface reduced graphene oxide fiber.

5. The preparation method according to claim 4, characterized in that: Step 2) The reducing agent solution is a mixed solution consisting of hydroiodic acid, acetic acid solution and hypophosphorous acid solution.

6. The preparation method according to claim 4 or 5, characterized in that: Step 2) The soaking is carried out at room temperature for 1 hour to 120 hours.

7. Use of the surface-reduced graphene oxide fiber as claimed in any one of claims 1 to 3 in fire warning.

8. A fire sensor, characterized in that: The invention comprises the surface-reduced graphene oxide fiber according to any one of claims 1 to 3.

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