CN116575259A

CN116575259A - Preparation method of magnetic graphene cellulose composite material and flexible light-emitting device

Info

Publication number: CN116575259A
Application number: CN202310134054.6A
Authority: CN
Inventors: 张焕侠; 智一帆; 许佳; 何建磊
Original assignee: Hebei University of Science and Technology; Jiaxing University
Current assignee: Hebei University of Science and Technology; Jiaxing University
Priority date: 2023-02-20
Filing date: 2023-02-20
Publication date: 2023-08-11

Abstract

The invention discloses a preparation method of a magnetic graphene cellulose composite material and application thereof in a flexible light-emitting device,wherein the preparation method comprises Fe ₃ O ₄ Preparation of nanoparticles, amination of Fe ₃ O ₄ Preparing a nanoparticle and magnetic graphene cellulose composite material by a co-crosslinking method: adding covalent crosslinking magnetic graphene oxide into water to prepare covalent crosslinking magnetic graphene oxide dispersion liquid, and adopting Fe in the magnetic graphene oxide prepared by covalent crosslinking ₃ O ₄ Are all wrapped by graphene oxide; and (3) placing the cellulose filter paper into a covalent crosslinking magnetic graphene oxide solution, dipping under the regulation and control of a magnetic field, and drying and reducing. The magnetic field regulation and control enables the magnetic graphene cellulose composite material to have good electric conductivity. The composite material is used as an electrode, the dielectric layer, the luminescent layer and the ITO/PET substrate are combined together by layer-by-layer assembly through a spin coating process, and the preparation method is simple and quick and is easy to apply and suitable for mass production.

Description

Preparation method of magnetic graphene cellulose composite material and flexible light-emitting device

Technical Field

The invention relates to the technical field of graphene composite materials, in particular to a preparation method of a magnetic graphene cellulose composite material and a flexible light-emitting device.

Background

The polymer nano composite material is a composite material which takes polymer as a matrix continuous phase and nano filler as a disperse phase. Among them, the polymer as a matrix is an organic substance, and the nanoparticles, nanotubes, and the like as fillers are generally inorganic substances. The polymer nanocomposite is typically an organic-inorganic phase composite. There is a wider interfacial area between the filler and the matrix of the polymer nanocomposite. Thus, even at low concentrations (typically less than 5 vol%) the nanoscale filler can significantly improve the properties of the composite without adversely affecting the processability of the polymer.

The nano-level fillers of the polymer are mainly inorganic minerals, and the properties of the polymer can be greatly improved by dispersing the nano-level fillers as the fillers in the polymer. Or improving the original properties of the polymer such as tensile strength, elongation at break, wear resistance, thermal stability, rheological property and the like. Or brings new properties such as flame retardant property, water repellency, electric conductivity, heat conductivity, etc. The carbon nanofiller such as graphene, carbon nanotube, nano carbon fiber and the like is a research hot spot in the current scientific field, and the orientation of the nanoparticles in the polymer is often random.

With the rapid development of smart wearable devices in recent years, smart displays have become an integral part of smart wearable devices [100]. Organic Light Emitting Diode (OLED) schemes are currently commonly employed. In smart wearable devices, however, are typically manufactured with textile substrates. The fabric is rough in surface, the yarn interweaving has voids, and the flexibility of the fabric is provided by its deformation. OLED requires nanoscale flatness of the substrate, and fabrics can affect the uniformity of the OLED layer during fabrication. There are solutions to pre-deposit a smooth functional film on the fabric surface to reattach the fabric. However, there are still some problems that the OLED manufacturing process is complicated and the cost is high; the OLED luminescent material has a shorter service life than the other luminescent materials; in addition, the OLED and the textile substrate have flexibility, and the OLED and the textile substrate can be separated after being bent for a certain number of times; OLED materials are sensitive to air humidity and display problems.

Disclosure of Invention

The invention aims to provide a preparation method of a magnetic graphene cellulose composite material, wherein Fe3O4 in magnetic graphene oxide prepared by a covalent crosslinking method is wrapped by GO. The relative content of iron element in the magnetic graphene oxide is greatly increased, and the magnetism of the sample is sharply increased. The relative content of carbon elements is reduced, the oxygen-containing functional groups are reduced in the preparation, but the aromaticity thereof becomes greater.

Another object of the present invention is to produce a flexible light emitting device having excellent mechanical properties and stability. The light intensity is reduced from the initial 60.03lux to 58.92lux after bending for 500 times, and the flexible electroluminescent device still maintains the luminous brightness above 98%.

In order to solve the technical problems, the aim of the invention is realized as follows:

the preparation method of the magnetic graphene cellulose composite material comprises the following steps:

step one, fe ₃ O ₄ Preparation of nanoparticles: adding sodium hydroxide to removeAdding the mixture into ionized water, stirring and heating to 80 ℃ to obtain sodium hydroxide solution;

FeCl is added ₃ ·6H ₂ O、FeCl ₂ ·4H ₂ Adding O and hydrochloric acid into a sodium hydroxide solution, and uniformly mixing; and carrying out vacuum suction filtration for a set time in the presence of ammonia gas, washing until the pH value is 7, and drying to obtain Fe ₃ O ₄ A nanoparticle;

step two, aminating Fe ₃ O ₄ Nanoparticles: fe prepared in the last step ₃ O ₄ Dispersing the nano particles in 3-aminopropyl triethoxysilane, and then adding the nano particles into an organic solvent for uniform mixing; then heating in an oil bath, condensing and refluxing to finish the reaction; cleaning the product, vacuum filtering, and vacuum drying to obtain aminated Fe ₃ O ₄ And (3) nanoparticles.

Step three, preparing magnetic graphene oxide by a covalent crosslinking method: preparing a certain amount of graphene oxide into graphene oxide dispersion liquid; adding N-hydroxysuccinimide and 1-ethyl-3-dimethylaminopropyl carbodiimide hydrochloride into graphene oxide dispersion, stirring uniformly, and adding aminated Fe ₃ O ₄ The nano particles are uniformly stirred, and then the magnetic graphene oxide by the co-crosslinking method is obtained;

step four, preparing a magnetic graphene cellulose composite material by a co-crosslinking method: adding covalent crosslinking magnetic graphene oxide into water to prepare covalent crosslinking magnetic graphene oxide dispersion liquid; and (3) placing cellulose filter paper in a covalent crosslinking magnetic graphene oxide solution, dipping under the regulation and control of a magnetic field, taking out, drying, and reducing to obtain the co-crosslinking magnetic graphene cellulose composite material.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: in step one, 5g of sodium hydroxide was added to 250mL of deionized water and heated to 80℃in a heated magnetic stirrer, 6.75g of FeCl ₃ ·6H ₂ O, 2.48g FeCl ₂ Adding 4H2O, 25mL of deionized water and 0.83mL of hydrochloric acid into a sodium hydroxide solution respectively, mixing uniformly, filling into a three-necked flask, and adding ammonia gas Carrying out vacuum filtration under the protection of (1) for 1h, and washing the product with water and methanol in sequence until the pH value is 7; vacuum drying at 50deg.C to obtain Fe ₃ O ₄ And (3) nanoparticles.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: in step two, 1g of the Fe produced ₃ O ₄ The nanoparticles were dispersed in 5.4ml of 3-aminopropyl triethoxysilane; adding the mixture into a mixed solvent of methanol and toluene, uniformly mixing, adding the mixture into a three-neck flask, heating the mixture to 110 ℃ in an oil bath, and condensing and refluxing the mixture for 10 hours to complete the reaction; and (3) cleaning the product for 2-3 times by using methanol, repeatedly carrying out vacuum filtration, and carrying out vacuum drying at 50 ℃ to obtain the aminated Fe3O4 nano particles.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: in the third step, a certain amount of graphene oxide is taken and subjected to ultrasonic treatment for 10 hours to prepare graphene oxide dispersion liquid with the concentration of 0.6%; taking the aminated Fe prepared in the previous step ₃ O ₄ Nanoparticles in which graphene oxide dry powder is heavy and aminated Fe ₃ O ₄ The mass ratio is 85:15;

adding 0.001-0.1g EDC and 0.0001-0.01g NHS into 100mL of 0.6% GO solution at room temperature, stirring, adding Fe ₃ O ₄ And stirring the nano particles for 15-30min to obtain the magnetic graphene oxide by the covalent cross-linking method.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: in the fourth step, the prepared magnetic graphene oxide with the co-crosslinking method is mixed with a certain amount of water to prepare a magnetic graphene oxide dispersion with the concentration of 0.6%, cellulose filter paper is placed in a square container to be immersed in the magnetic graphene oxide dispersion with the co-crosslinking method, and a magnet is used for direction regulation;

soaking for 5-30min under the control of magnetic field, taking out, oven drying at 80-100deg.C for 20-60min, and repeatedly soaking and oven drying for multiple times; and reducing all the prepared products to prepare the magnetic graphene cellulose composite material.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: the reduction is to reduce the magnetic graphene oxide by using HI steam.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: the methanol and toluene were mixed in 50mL:50mL of the mixture.

The invention also relates to a flexible light-emitting device, which comprises the magnetic graphene cellulose composite material prepared by the preparation method, wherein one side of the magnetic graphene cellulose composite material is sequentially provided with a dielectric layer and a light-emitting layer; the side of the light-emitting layer far away from the dielectric layer is adhered to the ITO/PET substrate.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: the dielectric layer is BaTiO ₃ Mixing with PB glue according to a mass ratio of 0.8-1:1-1.5, and spin-coating the mixture on the magnetic graphene cellulose composite material at 500rpm for 60s by using a spin coater after uniformly stirring.

The above-mentioned scheme is based on and is a preferable scheme of the above-mentioned scheme: the luminescent layer is prepared from luminescent powder ZnS, cu and PB glue according to a mass ratio of 1-1.5:1.2-2, spin-coating the luminescent powder onto the dielectric layer at 500rpm for 60s by using a spin coater after uniformly stirring, wherein the thickness is 20-40 mu m, and drying and volatilizing the solvent at 80-100 ℃.

The beneficial effects of the invention are as follows: according to the preparation method of the magnetic graphene cellulose composite material and the flexible light-emitting device, fe3O4 in the magnetic graphene oxide prepared by a covalent crosslinking method is wrapped by graphene oxide. The relative content of iron element in the magnetic graphene oxide is greatly increased, and the magnetism of the sample is sharply increased. The relative content of carbon elements is reduced, the oxygen-containing functional groups are reduced in the preparation, but the aromaticity thereof becomes greater. And the parallel magnetic field regulation and control enables the magnetic graphene cellulose composite material to have good conductivity. The electrode, the dielectric layer, the luminescent layer and the ITO transparent electrode are combined together by layer-by-layer spin coating process on the ITO/PET substrate, the preparation method is simple and quick, and the method is easy to apply and suitable for mass production. The flexible light emitting device has excellent mechanical properties and stability. The light intensity is reduced from the initial 60.03lux to 58.92lux after bending for 500 times, and the flexible electroluminescent device still maintains the luminous brightness above 98%.

Drawings

FIG. 1 is a process flow diagram of a method for preparing a magnetic graphene cellulose composite material according to the present invention;

FIG. 2 is a structural characterization of the GO produced; where a-c are TEM images of GO at different multiples, d are SEM images of GO, and e is the EDS element distribution of GO.

FIG. 3 is an infrared spectrum, a Raman spectrum and an XRD spectrum of the prepared GO, wherein a is the infrared spectrum of GO; b is a raman spectrum of GO; c is the XRD spectrum of GO.

Fig. 4 is a scanning electron microscope, transmission electron microscope, scanning electron microscope, and EDS element profile of a magnetic field induced MCG. Wherein (a) and (b) are scanning electron microscope images of MCG induced by magnetic fields under different multiples; (c) MCG transmission electron microscopy; (d) MPG scanning electron microscopy; (e) EDS element profile.

Fig. 5 is an infrared spectrum, raman spectrum and XRD spectrum of MCG, wherein (a) MCG infrared spectrum; (b) MCG raman spectra; (c) XRD patterns of MCG.

FIG. 6 is a plot of sheet resistance versus number of MCG dispersion dips for an MrCG-CEL composite without magnetic field alignment and an MrCG-CEL composite with parallel magnetic field alignment.

FIG. 7 is a structural analysis diagram of MrCG-CEL. Wherein, (a) MCG-CEL, mrCG-CEL and XPS full spectrum as it is; (b) XPS C1s spectrum of MCG-CEL; (C) XPS C1s spectrum of MrCG-CEL; (d) Magnetic field induced MrCG-CEL, mrCG-CEL without magnetic field induction and original thermogravimetric image (e) rGO-CEL, GO-CEL, mrCG-CEL and MCG-CEL; (f) XRD test curves of MCG and GO; (g) XRD test curves for GO-CEL, unordered MCG-CEL, ordered MCG-CEL, and ordered MrCG-CEL. Fig. 8 is a schematic structural view of a flexible light emitting device;

FIG. 9 is a topographical view of a flexible light emitting device; wherein (a) a cross-sectional fluorescence image of the flexible electroluminescent device; (b) cross-sectional SEM images of flexible electroluminescent devices; (c) Device photographs of the working colors of the electroluminescent flexible light-emitting devices with MrCG-CEL electrodes with different resistances as substrates are changed from dark to bright; (d) cross-sectional view of the MrCG-CEL electrode; (e) a cross-sectional view of a dielectric layer attached to the MrCG-CEL electrode; (f) a cross-sectional view of a light-emitting layer attached to the dielectric layer; (g) ITO/PET transparent electrode cross-section.

FIG. 10 is a graph showing the performance analysis of a composite material in which MrCG-CEL is arranged in four different directions without induction, parallel linear magnetic force line induction, parallel closed magnetic force line induction and vertical closed magnetic force line induction; wherein, (a) the schematic diagram is prepared without magnetic field induction of MrCG-CEL electrode; (b) Preparing a schematic diagram of a parallel linear magnetic line induced MrCG-CEL electrode; (c) Preparing a schematic diagram of parallel closed magnetic line induced MrCG-CEL electrode; (d) Preparing a schematic diagram of a vertical closed magnetic line induced MrCG-CEL electrode; (e) Four kinds of electrodes of MrCG-CEL are arranged in different directions to prepare an illuminance map of the flexible electroluminescent device; (f) Four kinds of flexible electroluminescent devices CIE1931 coordinate diagrams prepared by MrCG-CEL electrodes arranged in different directions; (g) Normalized spectrogram of flexible electroluminescent device prepared by four MrCG-CEL electrodes arranged in different directions

FIG. 11 is a graph showing the illuminance contrast of a flexible electroluminescent device prepared without inducing the MrCG-CEL electrode by a magnetic field and inducing the MrCG-CEL electrode by parallel linear magnetic lines under different driving voltages.

Fig. 12 is a graph comparing illumination data of a flexible light emitting device not aligned by magnetic field induction and a flexible light emitting device aligned by parallel linear magnetic field lines.

Fig. 13 shows the variation of illuminance of a flexible electroluminescent device arranged by induction of parallel linear magnetic lines with the number of bends.

Detailed Description

The invention will be further described with reference to the drawings and specific examples.

step one, fe ₃ O ₄ Preparation of nanoparticles: sodium hydroxide was added to deionized water and heated to 80 ℃ with stirring to obtain sodium hydroxide solution.

FeCl is added ₃ ·6H ₂ O、FeCl ₂ ·4H ₂ O andadding hydrochloric acid into a sodium hydroxide solution, and uniformly mixing; and carrying out vacuum suction filtration for a set time in the presence of ammonia gas, washing until the pH value is 7, and drying to obtain Fe ₃ O ₄ And (3) nanoparticles.

Step three, preparing magnetic graphene oxide by a covalent crosslinking method: preparing a certain amount of graphene oxide into graphene oxide dispersion liquid; adding N-hydroxysuccinimide and 1-ethyl-3-dimethylaminopropyl carbodiimide hydrochloride into graphene oxide dispersion, stirring uniformly, and adding aminated Fe ₃ O ₄ And (3) uniformly stirring the nano particles to obtain the magnetic graphene oxide by the co-crosslinking method.

Specifically, in step one, 5g of sodium hydroxide was added to 250mL of deionized water, heated to 80℃in a heated magnetic stirrer, and 6.75g of FeCl ₃ ·6H ₂ O, 2.48g FeCl ₂ Adding 4H2O, 25mL of deionized water and 0.83mL of hydrochloric acid into a sodium hydroxide solution respectively, uniformly mixing, filling into a three-neck flask, reacting for 1H under the protection of ammonia gas, performing vacuum filtration, and washing the product with water and methanol in sequence until the pH value is 7; vacuum drying at 50deg.C to obtain Fe ₃ O ₄ And (3) nanoparticles.

Specifically, in the second step,1g of the Fe prepared ₃ O ₄ The nanoparticles were dispersed in 5.4ml of 3-aminopropyl triethoxysilane; adding the mixture into a mixed solvent of methanol and toluene, uniformly mixing, adding the mixture into a three-neck flask, heating the mixture to 110 ℃ in an oil bath, and condensing and refluxing the mixture for 10 hours to complete the reaction; and (3) cleaning the product for 2-3 times by using methanol, repeatedly carrying out vacuum filtration, and carrying out vacuum drying at 50 ℃ to obtain the aminated Fe3O4 nano particles. The methanol and toluene were mixed in 50mL:50mL of the mixture.

Specifically, in the third step, a certain amount of graphene oxide is taken and subjected to ultrasonic treatment for 10 hours to prepare a graphene oxide dispersion liquid with the concentration of 0.6%; taking the aminated Fe prepared in the previous step ₃ O ₄ Nanoparticles in which graphene oxide dry powder is heavy and aminated Fe ₃ O ₄ The mass ratio is 85:15.

adding 0.001-0.1g EDC and 0.0001-0.01g NHS into 100mL of 0.6% GO solution at room temperature, stirring, adding Fe ₃ O ₄ And stirring the nano particles for 15-30min to obtain the magnetic graphene oxide by the covalent cross-linking method. In this example, 0.001g EDC and 0.0001g NHS were added and stirred well before Fe was added ₃ O ₄ The nanoparticles were stirred for 15min.

Furthermore, the reduction is to reduce the magnetic graphene oxide by using HI steam.

In the third step, the improved Humans method is adopted to prepare graphene oxide, the coprecipitation method is used to prepare magnetic graphene oxide, and the microscopic morphology and structure of the graphene oxide and the magnetic graphene oxide are analyzed through SEM, TEM, XRD and other instruments. The graphene is produced by Shanghai Ala Biochemical technology Co., ltd, and has carbon content of 99. 95% and particle size 8000 mesh. The experimental drugs used are shown in table 1.

Table 1 experimental medicine

The experimental apparatus and equipment used are shown in table 2.

Table 2 laboratory apparatus and equipment

The preparation of the graphene oxide comprises the following steps:

s1, pre-oxidizing graphite: adding 5g of potassium persulfate and 5g of graphite into a beaker, stirring, adding 50mL of concentrated sulfuric acid, stirring for 5min, adding 5.5g of phosphorus pentoxide, and uniformly stirring; heating to 80 ℃ and then heating for 5 hours; cooling to room temperature, and slowly adding 200mL of deionized water; and (3) standing, settling and layering, sucking the supernatant, repeatedly operating for four to five times, washing the supernatant until the pH value is neutral, and carrying out suction filtration, and drying for 24 hours at 50 ℃ to obtain the product of the preoxidized graphite.

S2, preparing graphene oxide: adding crushed ice into a heating magnetic stirrer to reduce the temperature to 0 ℃, adding 46mL of concentrated sulfuric acid and 1g of sodium nitrate into a beaker, stirring, reacting for 2 hours, adding 2g of the graphite pre-oxide prepared in the first step, and slowly adding 6g of KMnO ₄ The method comprises the steps of carrying out a first treatment on the surface of the After 2h of reaction at 0 ℃, removing crushed ice, raising the temperature to 45 ℃ and reacting for 30min; after the reaction is finished, 92mL of deionized water is added twice, wherein the first time of the quick addition and the second time of the slow addition are carried out; the reaction was continued for 30min. After cooling to room temperature, 280mL of deionized water and 10mL of 30% H2O2 solution are added to react for 15min from dark red to light yellow; after standing, washing with 5% hydrochloric acid, washing with water several times, and centrifuging to neutral pH. And freeze-drying for 24 hours by using a freeze dryer to obtain the graphene oxide.

The transmission electron microscope, the scanning electron microscope and the EDS element distribution are tested on GO, and as shown in fig. 2, a large number of folds exist on GO through an SEM image, a large number of folds exist on the edge of GO in a TEM image, and the waves exist on the surface of GO. Such folds are natural properties that are present in two-dimensional materials, consistent with those described in the related studies. The size of the prepared graphene oxide sheet layer is 10-15 mu m. In the research, the structure of the wrinkles is considered to be a relatively easily adsorbed substance and reacted site. As can be seen from an EDS energy spectrum, namely FIG. 2e, the carbon content of the prepared graphene oxide is the highest of all elements, and the mass ratio is 59.97%. The oxygen content was 40.03%, indicating a large number of oxygen-containing functional groups in GO.

Infrared, raman and XRD tests were performed on GO, and the test results are shown in figure 3. The infrared absorption spectrum is mainly used for judging functional groups possibly existing through the position of an absorption peak. GO is 3406cm ^-1 There appears a strong and broad absorption peak due to vibrations of-OH at the GO surface at 1725cm ^-1 The sharp peak at which is attributed to c=o in the-COOH group, 1620cm ^-1 Corresponds to the stretching vibration peak of C=C on the benzene ring-like structure in the graphene oxide. Vibration of carboxyl group (O-C=O), epoxy group (C-O) and alkoxy group (C-O) was 1401cm, respectively ^-1 、1202cm ^-1 1045cm ^-1 The graphene oxide is rich in oxygen-containing groups.

Raman spectra are often used to characterize the defect level and structural information of carbon materials. Carbon material in Raman spectrum at 1300cm- ¹ The peak formed here is called the D peak, which is caused by lattice vibration, and generally indicates disorder of the material, and the apparent appearance is that the surface of the material is wrinkled. At 1600cm ^-1 The peak appearing at this point is called the G peak, due to SP ² The degree of regularity of the material is generally evident from the vibration of the carbon atoms. Whereas the value of ID/IG is often used to characterize the extent of defects on the surface of the carbon-based material. As shown in the figure, it is evident that the Raman spectrum of the GO sample is 1350cm ^-1 And 1588cm ^-1 The two characteristic peaks are strong, and the D peak strongly indicates that the GO defect degree is large and corresponds to the GO of the prepared sample, and the D peak becomes weak if the GO is reduced to rGO. The G peak is a characteristic peak of GO, which strongly suggests that there is hybridized carbon atom formation. An ID/IG of 0.93 indicates a small defect density.

XRD is typically used to characterize the crystal structure on graphene oxide. The X-ray diffraction pattern of graphene oxide is shown in fig. 3. From this, it can be seen that there is a strong diffraction peak at about 10 °, and according to the related study, it can be known that GO belongs to the 001 crystal form. The curve is smooth at about 26 degrees without diffraction peak of graphite, which indicates that the graphite is completely oxidized in the preparation process of graphene oxide.

SEM and TEM were used to observe the magnetic graphene oxide MCG prepared using the covalent cross-linking method to characterize its microscopic morphology. Fig. 4 (a) and (b) are SEM topography of the orientation arrangement of the synthesized MCG under magnetic field induction and SEM topography of the synthesized MCG. Fig. 4 (d) is an SEM image of MCG without magnetic field induction. It can be seen that the MCGs are neatly arranged into I-type folds under the induction of the magnetic field, showing a pronounced groove structure. The micro-morphology of MCG is not masked and a clearly evident microstructure can be seen. In the TEM image of fig. 4 (c), the edges of MCG had relatively flat folds present, with some topographical features of GO. From the figure, fe can be seen ₃ O ₄ The particles are oriented under the action of a magnetic field by being wrapped by graphene oxide, and the same alignment effect can be confirmed from (a) of SEM image fig. 4. As can be seen from the EDS spectrum, i.e., (e) in FIG. 4, the prepared MCG has a carbon content of 44.66%, an oxygen content of 52.70% and an iron content of 2.64%. The mass ratio of C is decreased, O is increased, and Fe is increased, so that the mass ratio of the MCG is increased after the iron element is introduced in the preparation process of the MCG.

Fig. 5 (a) shows an infrared spectrum of MCG. MCG at 3575cm ^-1 There appears a strong and broad absorption peak due to vibration of-OH at the MCG surface at 1712cm ^-1 The sharp peak at which is assigned to c=o in the-COOH group at 1608cm ^-1 Corresponds to the stretching vibration peak of C=C on the benzene ring-like structure in the graphene oxide. Vibration of alkoxy (C-O) at 1027cm ^-1 At 588cm ^-1 The peak at this point is the strong vibrational peak of Fe-O, indicating the lattice absorption of iron oxide. Thus Fe ₃ O ₄ Nanoparticles have been successfully loaded on graphene. The strength of-OH, C= O, C-O was slightly reduced as compared with the functional group in the graphene oxide in FIG. 2-4 (a), 1608cm ^-1 The peak intensity of C-C at this point increased, indicating that the oxygen-containing groups were reduced during the synthesis of MCG.

Fig. 5 (b) shows a raman spectrum of MCG. It is evident that the Raman spectrum of the sample is 1346cm ^-1 And 1598cm ^-1 Two characteristic peaks are shown, corresponding to the D and G peaks, respectively. The intensity ratio (ID/IG) of the D and G peaks is related to the defect level of the graphene surface and the size of the sp2 hybridized domain. I2D/IG is often used to infer the number of graphene layers, with the number of graphene layers increasing and increasing as the ratio decreases. It can be seen in FIG. 5 (b) that the I2D/IG of GO is 0.29 and that of MCG in FIG. 5 (b) is 0.26. The thickness of the prepared MCG is increased. GO through Fe ₃ O ₄ The ID/IG value increased from 0.93 to 0.97 after the covalent crosslinking of MCG, indicating an increase in the defect structure of the MCG surface during covalent crosslinking. Although sp ² The hybrid domain increases but the size decreases. Indicating that the aromatization zones formed during the preparation are smaller but more numerous and that the MCG surface contains more defective structures.

The XRD spectrum was used to reveal the crystal structure of MPG particles. As shown in FIG. 5 (c), diffraction peaks having 2.2℃and 35.6℃correspond to Fe, respectively, in the spectral lines of the MPG spectrum ₃ O ₄ The (220) crystal face and the (311) crystal face of the graphene sheet layer show that Fe3O4 loaded on the graphene sheet layer has a spinel crystal structure with a pure cubic structure [66 ] ]. (since the amount of supported Fe is relatively small, the role of Fe in this experiment is to orient GO, so that part of the crystal form of Fe is not apparent in XRD). From the figure, it can be seen that the MCG is shifted to the left as a whole compared to the XRD diffractogram of GO, and the impurity atoms increase or decrease the unit cell parameters, indicating that the unit cell parameters increase and the interplanar spacing increases, due to the doping of Fe in the sample.

Specifically, in the fourth step, the prepared magnetic graphene oxide with the co-crosslinking method is mixed with a certain amount of water to prepare a magnetic graphene oxide dispersion with the co-crosslinking method, the magnetic graphene oxide dispersion with the concentration of 0.6%, cellulose filter paper is placed in a square container and immersed in the magnetic graphene oxide dispersion with the co-crosslinking method, and a magnet is used for direction regulation;

soaking for 5-30min under the control of magnetic field, taking out, oven drying at 80-100deg.C for 20-60min, and repeatedly soaking and oven drying for multiple times; and reducing all the prepared products to prepare the magnetic graphene cellulose composite material. In this example, each time of immersion was conducted under the control of a magnetic field for 5 minutes, and the resulting solution was taken out and dried in an oven at 100℃for 30 minutes.

The cellulose filter paper used is Jiejie brand 202 model cellulose filter paper. And the experimental drugs used are shown in table 3.

Table 3 experimental drugs

The experimental apparatus and equipment used are shown in table 4.

Table 4 laboratory apparatus and equipment

And analyzing the conductivity of the magnetic graphene cellulose composite material. From fig. 6, it can be seen that the sheet resistance of the MrCG-CEL composite material is continuously reduced with the increase of the impregnation times, and the conductivity is gradually improved. Fang Zuxiao of the magnetic field induced MrCG-CEL composite material immersed the same number of times is the sheet resistance of the magnetic field induced MrCG-CEL composite material. The orientation arrangement of MrCG on cellulose fiber is explained to connect MrCG particles with each other to form a more compact and coherent network. This demonstrates that the oriented MrCG more effectively improves the conductive properties of the MrCG-CEL composite.

The probability of contact between adjacent MCGs is low due to the misalignment, thereby limiting the conductivity of the composite. Magnetic field induction overcomes this obstacle due to the interaction between the induced dipoles. In the present composite, the magnetic field induces alignment of the MCGs, which then creates attractive forces between the aligned MCGs, which increases the effective aspect ratio of the MCG polymer composite. This increased effective aspect ratio lowers the percolation threshold. Furthermore, the conductive path between MCGs may be located not only in the direction of the magnetic field, but also between the materials arranged by lateral contact. The connection of MCG to adjacent dots to form short chains is responsible for the relatively high conductivity of the composite material in the direction perpendicular to the orientation field.

In addition, it can be seen that the sheet resistance value is substantially unchanged after repeating the dipping and drying process 6 times, because the adsorption amount tends to be saturated as the number of dipping times increases, an effective arrangement and connection of the three-dimensional conductive network MCG is formed.

Structural analysis was performed by MrCG-CEL, see FIG. 7. The prepared samples were tested using an X-ray photoelectron spectrometer, and the magnetic field induced MCG-CEL, mrCG-CEL and XPS total spectra as they are shown in FIG. 7 (a). Obvious Fe 2p peak, C1s peak and O1s peak can be observed from XPS full spectrum, and the relative content of the Fe, C and O elements contained on the surface of the magnetic graphene is shown in Table 5. When the MCG is reduced to MrCG, the relative content of O element in the composite material is reduced from 30.87% to 14.70%, which shows that the oxygen-containing functional group is reduced in the reduction process. Aminated Fe ₃ O ₄ The grafting of the nanoparticles onto the cellulose paper substrate was confirmed by the presence of the Fe 2p peak in the full spectrum (fig. 7 (a)). The XPS C1s spectra of MCG-CEL and MrCG-CEL are shown in (b) and (C) of FIG. 7, and the result of XPS C1s of MrCG-CEL after reduction shows that four obvious fitting peaks are seen at 284.7eV, 285.5eV, 286.6eV and 287.6eV, corresponding to C= C, C-N, C =O and O=C-O. The reduced c=c (284.7 eV), C-N (285.5 eV) functional group content increased, c=o (286.6 eV) and o=c-O (287.6 eV) functional group content decreased compared to MCG-CEL before reduction (see XPS (b) and (C) in fig. 7 and tables 5 and 6), which further demonstrate effective chemical reduction and grafting success of Fe nanoparticles.

As shown in FIG. 7 (d), the composition of MrCG-CEL with or without magnetic field regulation was characterized by TGA under nitrogen atmosphere. For two MrCG-CEL samples with or without magnetic field regulation, low temperature can be observed<Slow weight loss at 100 ℃ (5.98 wt%) which can be attributed to residual or absorbed solvent loss. The two samples underwent a one-stage weight loss at 150 ℃ indicating decomposition and evaporation of various functional groups at different positions on MrGO and MCG. ThenThe weight loss of MrCG-CEL at 225 ℃ under the control of magnetic field and at 239 ℃ without the control of magnetic field is the weight loss generated by the decomposition of the base material according to the comparison with the original thermogravimetric curve. The weight loss phase that occurs at 293℃and around 313℃for the two samples, respectively, may be attributed to the Fe in MrCG and MCG ₃ O ₄ Decomposition of the nanoparticle coordinated-COO group. Similar results were also observed for the preparation of polymer/Fe 3O4 magnetic microspheres. When the temperature reached 750 ℃, the weight of both samples of MrCG-CEL remained at 32.1wt% and 22.3wt%, with little weight loss after this temperature. Meanwhile, the comparison is carried out according to the original shape without any treatment, and the original shape thermal weight curve is a typical cellulose paper thermal weight curve, and a great amount of weight loss is carried out at about 300 ℃, and the weight after the final decomposition is almost zero.

FIG. 7 (e) shows Raman spectra of rGO-CEL, GO-CEL, mrCG-CEL and MCG-CEL before and after reduction. It is evident that the four samples have Raman spectra at 1360cm ^-1 And 1600cm ^-1 Two characteristic peaks are shown, corresponding to the D and G peaks, respectively. The intensity ratio (ID/IG) of the D and G peaks is related to the defect level of the graphene surface and the size of the sp2 hybridized domain. The ID/IG ratio of MrCG-CEL after reduction was increased (1.22) relative to MCG-CEL (0.90); the increase in ID/IG value from 0.91 to 1.08 after chemical reduction of GO to rGO suggests an increase in defective structure on the surface of MrCG during reduction, while the sp2 hybridized domain increases, but the size decreases. Indicating that the aromatization zones formed during the reduction are smaller but more numerous and that the MrCG surface contains more defective structures.

XRD spectra of MCG, GO and GO-CEL, unordered MCG-CEL, aligned MCG-CEL and aligned MrCG-CEL are shown in (f) and (g) of FIG. 7. XRD patterns were used to reveal the crystal structure of MCG particles and MrCG-CEL. In the spectral line of the MCG particles, diffraction peaks with 2 theta values of 30.2 degrees and 35.6 degrees respectively correspond to (220) crystal faces and (311) crystal faces of Fe3O4, which shows that Fe3O4 loaded on the graphene sheet layer has a spinel crystal structure with a pure cubic structure [66]. (since the amount of supported Fe is relatively small, the role of Fe in this experiment is to orient GO so that part of the crystal form of Fe is not apparent in XRD). As can be seen from (g) in FIG. 7, XRD spectra of MCG-CEL, MCG-CEL and MrCG-CEL are shifted to the left as a whole, compared with GO-CEL, because all of the three samples are doped with Fe, impurity atoms make cell parameters become larger or smaller, and if shifted to the left, it is interpreted that cell parameters become larger and interplanar spacings become larger. The main diffraction peaks of cellulose paper are located at 2θ=14.8, 16.6, 22.8 and 34.5, corresponding to the (101), (107), (002) and (040) crystal planes of cellulose i, respectively. The 101-type crystal plane of C is located at 2θ=11.1, and the sample after doping Fe is shifted left and the 001-type crystal plane of the reduced sample disappears in comparison with the four samples.

TABLE 5 elemental composition of magnetic field induced MCG-CEL and MrCG-CEL

TABLE 6 magnetic field induced bonding of the C element of MCG-CEL and MrCG-CEL

The invention also relates to a flexible light-emitting device, which comprises the magnetic graphene cellulose composite material 1 prepared according to the preparation method, wherein one side of the magnetic graphene cellulose composite material 1 is sequentially provided with a dielectric layer 2 and a light-emitting layer 3; the side of the luminescent layer 3 remote from the dielectric layer 2 is adhered to the ITO/PET substrate 4.

Further, the dielectric layer 2 is prepared by mixing BaTiO3 and PB glue according to a mass ratio of 0.8-1:1-1.5, and spin-coating the mixture on the magnetic graphene cellulose composite material at 500rpm for 60s by using a spin coater after uniformly stirring, wherein the thickness of the formed dielectric layer 2 is 40 mu m, and then drying the mixture at 100 ℃ for 2 hours to volatilize the solvent to prepare the magnetic graphene cellulose composite material. The dielectric layer 2 serves to prevent voltage breakdown of the device. In the embodiment, the mass ratio of BaTiO3 to PB glue is 1:1, mixing.

Further, the luminescent layer 3 is prepared from luminescent powder ZnS: cu and PB glue according to a mass ratio of 1-1.5:1.2-2, spin-coating the luminescent powder onto the dielectric layer 2 by using a spin coater at 500rpm for 60s after uniformly stirring, wherein the thickness is 20-40 mu m, and drying at 80-100 ℃ for 2 hours to volatilize the solvent. The light-emitting layer 3 is used for electroluminescence. In the embodiment, znS: cu and PB glue in the luminescent layer 3 are mixed according to a mass ratio of 1:1.5 mixing was carried out to a thickness of 40 μm and drying was carried out at 100℃for 2 hours.

The clean ITO/PET substrate conductive surface and the luminous layer are adhered to prepare the flexible electroluminescent device, and the structure of the flexible electroluminescent device is shown in figure 8.

The formed flexible light emitting device was analyzed. The structure and the photo of the flexible light-emitting device prepared by using the MrCG-CEL composite material are shown in figure 9. The device consists of an electrode formed by a flexible ITO/PET substrate and an MrCG-CEL composite material and a luminous layer sandwiched between the electrode and the luminous layer. The luminescent layer is prepared by embedding ZnS: cu phosphors doped with different metals into various flexible polymer matrices having different dielectric constants. As a prototype device, znS: cu phosphor was dispersed into Polyisobutylene (PB) to form a blue light emitting layer. The device is fabricated by a simple spin-on process, the detailed fabrication process being described in the experimental section. As shown in (b) of fig. 9, the layer-by-layer stacked structure of the obtained device was verified by Scanning Electron Microscope (SEM) photographing of a cross section of the sample, and the image also shows a clear interface and close contact between two adjacent layers ((d), (e), (f) and (g) of fig. 9). The cross-sectional fluorescence image of the flexible electroluminescent flexible light emitting device can be seen by (a) in fig. 9, and these results also show the layer-by-layer stack of the obtained device, with close contact between two adjacent layers. In fig. 9, (d) is a cross-sectional view of the MrCG-CEL composite electrode, and it can be seen from the figure that the root-root intersections of the fibers have numerous voids, which are beneficial to the adsorption of MCG and adhesion to the dielectric layer. FIG. 9 (e) is a cross-sectional view of a dielectric layer attached to an electrode of the MrCG-CEL composite, the dielectric layer having a thickness of about 50 μm. From the figure, it can be seen that the dielectric powder BaTiO3 is uniformly dispersed in the polyisobutylene, and is flatly coated on the MrCG-CEL composite material, and is tightly combined with the MrCG on the surface of the electrode. Fig. 9 (f) is a cross-sectional view of the light-emitting layer attached to the dielectric layer, showing an average diameter of about 25 μm ZnS: the Cu fluorescent powder is uniformly distributed in the PB glue, the thickness of the blue emitting layer is about 40 mu m, and the dielectric layer is the same as the adhesive used by the light emitting layer, so that the two layers are tightly combined due to the formation of chemical bonds. Fig. 9 (g) is a cross-sectional view of an ITO/PET transparent electrode, which is well interconnected as a top electrode in close contact with the light emitting layer.

Under an alternating electric field, the metal-doped ZnS phosphor emits light due to radiation relaxation of the luminescence center. When the bottom electrode has different resistances, the intensity and brightness of the emitted light are also different, as shown in fig. 9 (c). Fig. 9 (c) is a light emission real image of a flexible light emitting device prepared again by impregnating the MCG-loaded electrode once to six times, respectively. It can be seen that the brightness of the electrode gradually becomes bright from dark during operation, the resistance of the electrode prepared with small dipping times is larger after reduction, and the flexible light-emitting device is easy to break down under the same excitation voltage.

The (a) of fig. 10 is not arranged by any magnetic field induction, the random non-directivity of the luminescence can be seen from the upper right embedded graph (the luminescence real image of the prepared device), and the non-directivity of the MCG distribution can be seen from the lower right embedded graph (the MrCG-CEL SEM graph). In FIG. 10, (b) is an arrangement induced by parallel linear magnetic lines, the light emission is directional, and the light emission is parallel along the direction of the magnetic field, the distribution of MCG is directional, GO on MCG is attached to cellulose fiber, fe ₃ O ₄ And the GO is arranged in a directional linear way. It is further embodied as electrode directivity on the flexible light emitting device. Fig. 10 (c) is a parallel closed magnetic field line induced arrangement, and it can be seen from the upper right embedded graph that the light emission has directivity, and the light emission is arc-shaped along the direction of the applied magnetic field, and from the lower right embedded SEM graph that the MCG thereon is distributed along the arc-shaped direction. In FIG. 10, (d) is a vertical closed magnetic field line induced arrangement, and it can be seen from the upper right embedded graph that the luminescence direction is a triangle-shaped concentrated region formed on the electrode by the magnetic field formed by the lower bar magnet, and the region has smaller resistance and brighter luminescence, and Fe can be seen from the lower right SEM image ₃ O ₄ Is attracted by a magnetic field to move downwards, namely the inside of the matrix, and the apparent morphology is observed to be different from the other three morphologies and is Fe ₃ O ₄ The surface is flat because of the attractive force underneath.

The luminescence data of the four flexible electroluminescent devices were tested by a remote SPIC-300 spectral color illuminometer, and (e) in fig. 10 is a graph showing the comparison of the illuminances of the four flexible electroluminescent devices when they were driven by a 3V voltage driver. The maximum illuminance of the parallel magnetic field induction arranged device can be seen from the graph, and corresponds to the data of the No. 2 position in the graph, and the illuminance reaches 64.74lux; secondly, the illuminance of the unordered device corresponding to the data of the No. 1 position in the graph reaches 59.15lux; the illuminance of the devices of the single-side divergent magnetic field induction arrangement and the lower divergent magnetic field induction arrangement are 40lux and 39.7lux respectively, which correspond to numbers 3 and 4 in the figure. Analysis suggests that firstly the resistance of the magnetic field arrangement region is small, so that a significant difference can be seen from the light emitting direction in the above real image, and secondly the electrode is arranged by the influence of the magnetic field in not all regions, and the unordered regions are still in the original unordered distribution, and the resistance is relatively large. All regions of the sample aligned in parallel magnetic fields are aligned by the magnetic field so that their resistance is relatively small. The difference in resistance results in a specific luminescence reversal. Fig. 10 (f) is a CIE1931 color graph of a flexible electroluminescent device prepared by arranging the MrCG-CEL electrodes in four different directions, and it can be seen that the arrow direction in the CIE graph moves from a blue light region to a blue dark region. Samples No. 4, no. 3, no. 1 and No. 2, respectively, along the direction of the arrow. The coordinate movement coincides with the trend of the light-emitting illuminance data in fig. 10 (e). FIG. 10 (g) is a normalized spectrum of a flexible electroluminescent device prepared by arranging MrCG-CEL electrodes in four different directions. First, the blue light wavelength was 440-470 nm, the sample No. 2 emission peak was 460nm, and the sample No. 1, no. 3 and No. 4 emission peaks were 466nm, 470nm and 487nm in this order. It can be seen that numbers 2, 1, 3 and 4 are gradually shifted towards the red wavelength. Secondly, it can be seen from the normalized intensity data in the normalized spectrogram that sample No. 2 has the highest spectral intensity, and then sample nos. 1, 3 and 4 are sequentially carried out. The method shows that the blue light excited by the flexible electroluminescent device prepared by parallel linear magnetic force line induced arrangement is brightest.

The flexible light-emitting device which is not arranged by magnetic field induction and the flexible light-emitting device which is arranged by parallel linear magnetic force line induction are driven to emit light under different driving voltages, and the illuminance is tested, and the data are shown in figure 11. It can be seen from the graph that the voltage increases from 1V to 12V, with a substantial increase in the illuminance of both devices. The illuminance of the two devices under the same driving voltage is compared, and the flexible light-emitting devices which are arranged by parallel magnetic field induction and are not arranged by magnetic field induction are better than the flexible light-emitting devices which are not arranged by magnetic field induction, which proves that the directional arrangement preparation electrode is effective for increasing the illuminance.

Fig. 12 (a, c, e) shows a comparison of illumination data of a flexible light emitting device which is not aligned by magnetic field induction and fig. 4 to 7 (b, d, f) show a flexible light emitting device which is aligned by parallel linear magnetic lines of force induction. The voltage was varied at a constant 50Hz frequency for flexible electroluminescent device driving to control its light emitting performance.

Fig. 12 (a) and 12 (b) are luminance graphs of two device flexible electroluminescent devices cycling five times at different voltages. The device is continuously electrified under different voltages for lighting for 1min, and then is stopped for 5s, the operation is repeated for five times. It can be seen that both devices remain stable at different voltages with little fluctuation in the illuminance values. And secondly, comparing the two devices under the same voltage, and finding that the illuminance of the flexible light-emitting devices which are arranged by parallel linear magnetic force lines in an induction way is higher than that of the flexible light-emitting devices which are not arranged by a magnetic field in an induction way. Fig. 12 (c) and 12 (d) are normalized electroluminescence spectra of the flexible light emitting device not aligned by the magnetic field induction and the flexible light emitting device aligned by the parallel linear magnetic force line induction at different driving voltages. From the graph, the brightness of the two light emitting devices increases along with the increase of the voltage, the wavelength of the light emitting peak of the sample subjected to magnetic field regulation is shifted from 489nm to 470nm, and the wavelength of the light emitting peak of the sample not subjected to magnetic field regulation is shifted from 488nm to 468nm, which shows that the light emitting devices are optically lightened along with the increase of the voltage under the condition that the voltage is increased and all the light emitting devices are shifted in the direction of short-wave blue light. Comparing (c) and (d) in fig. 12, it can be seen that, under the same input voltage, the normalized intensity of the flexible light emitting device performing parallel linear magnetic force line induced modulation is greater than that of the flexible light emitting device not subjected to magnetic field modulation. Fig. 12 (e) and 12 (f) are CIE1931 color charts of flexible light emitting devices not aligned by magnetic field induction and flexible light emitting devices aligned by parallel linear magnetic lines of force induction at different driving voltages. From which the color of the electroluminescent device can be directly observed as a function of the voltage. The luminous color of the electroluminescent device moves to the blue region along with the increase of the input voltage, and the blue region where the color coordinate value of the flexible luminous device which is arranged directionally under the same voltage is smaller is deeper. The illumination intensity of the flexible light-emitting devices which are arranged by parallel linear magnetic force lines under different voltages is higher than that of the flexible light-emitting devices which are not arranged by magnetic field induction, and the difference is obvious; in the light-emitting color, the light-emitting color areas where the two are basically consistent in light-emitting trend are basically consistent, and the blue area where the flexible light-emitting devices which are arranged in a directional manner are located is deeper.

FIG. 13 shows the variation of illuminance of a flexible electroluminescent device arranged by induction of parallel linear magnetic lines with bending times, a stepper is used to repeatedly bend a sample to be tested at a frequency of 1Hz, and the value of illuminance at different bending times is measured to characterize the stability of the device. Fig. 13 is a digital photograph of the embedded graph (a) and the embedded graph (b) before and after bending the flexible electroluminescent device in operation. It can be seen that the light is normally and uniformly emitted after bending. The driving was performed using a 3V ac driver. From the graph, the illuminance is stable in the process of bending 500 times, the illuminance is reduced from the initial 60.03lux to 58.92lux after bending, and the luminous brightness of the flexible electroluminescent device is still more than 98%. The result shows that the prepared flexible electroluminescent device has good mechanical fastness and strong bending stability. The remarkable stability of the flexible light emitting device can be attributed to the inherent flexible component of the polymer matrix, making it reliable in practical applications. The surface of the flexible electroluminescent device emits light uniformly and softly, and the flexible electroluminescent device has a flexible structure, so that the flexible electroluminescent device has good development potential and wide application prospect in the field of flexible wearable devices.

Abbreviations used herein are illustrated as follows: GO is graphene oxide; rGO is reduced graphene oxide; mrGO is magnetic reduced graphene; CEL is cellulose filter paper; MCG is covalent cross-linking magnetic graphene oxide; MCG-CEL is a covalent crosslinking magnetic graphene oxide cellulose composite material; mrCG-CEL is a magnetic graphene oxide cellulose composite material by a reduction covalent crosslinking method; GO-CEL is a graphene oxide cellulose composite material; the rGO-CEL is a reduced graphene oxide cellulose composite material.

The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention by one of ordinary skill in the art without undue burden. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims

1. The preparation method of the magnetic graphene cellulose composite material is characterized by comprising the following steps of:

step one, fe ₃ O ₄ Preparation of nanoparticles: adding sodium hydroxide into deionized water, stirring and heating to 80 ℃ to obtain sodium hydroxide solution;

step two, aminating Fe ₃ O ₄ Nanoparticles: fe prepared in the last step ₃ O ₄ Dispersing the nano particles in 3-aminopropyl triethoxysilane, and then adding the nano particles into an organic solvent for uniform mixing; then heating in an oil bath, condensing and refluxing to finish the reaction; cleaning the product, vacuum filtering, and vacuum drying to obtain ammonia Basified Fe ₃ O ₄ And (3) nanoparticles.

Step three, preparing magnetic graphene oxide by a covalent crosslinking method: preparing a certain amount of graphene oxide into graphene oxide dispersion liquid; adding N-hydroxysuccinimide and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride into graphene oxide dispersion, stirring uniformly, and adding aminated Fe ₃ O ₄ The nano particles are uniformly stirred, and then the magnetic graphene oxide by the co-crosslinking method is obtained;

2. The method of preparing a magnetic graphene cellulose composite material according to claim 1, wherein in step one, 5g of sodium hydroxide is added to 250mL of deionized water, heated to 80 ℃ in a heated magnetic stirrer, and 6.75g of FeCl is added ₃ ·6H ₂ O, 2.48g FeCl ₂ Adding 4H2O, 25mL of deionized water and 0.83mL of hydrochloric acid into a sodium hydroxide solution respectively, uniformly mixing, filling into a three-neck flask, reacting for 1H under the protection of ammonia gas, performing vacuum filtration, and washing the product with water and methanol in sequence until the pH value is 7; vacuum drying at 50deg.C to obtain Fe ₃ O ₄ And (3) nanoparticles.

3. The method for producing a magnetic graphene cellulose composite material according to claim 1, wherein in the second step, 1g of the produced Fe is mixed with ₃ O ₄ The nanoparticles were dispersed in 5.4ml of 3-aminopropyl triethoxysilane; adding the mixture into a mixed solvent of methanol and toluene, uniformly mixing, adding the mixture into a three-neck flask, heating the mixture to 110 ℃ in an oil bath, and condensing and refluxing the mixture for 10 hours to complete the reaction; washing the product with methanol for 2-3 times, and repeatedly vacuum-pumpingFiltering and vacuum drying at 50 ℃ to obtain the amination Fe3O4 nano-particles.

4. The preparation method of the magnetic graphene cellulose composite material according to claim 1, wherein in the third step, a certain amount of graphene oxide is taken and subjected to ultrasonic treatment for 10 hours to prepare graphene oxide dispersion liquid with the concentration of 0.6%; taking the aminated Fe prepared in the previous step ₃ O ₄ Nanoparticles in which graphene oxide dry powder is heavy and aminated Fe ₃ O ₄ The mass ratio is 85:15;

taking 100mL of 0.6% GO solution, adding 0.1-0.001g EDC and 0.01-0.0001g NHS at room temperature, stirring, adding Fe ₃ O ₄ And stirring the nano particles for 15-30min to obtain the magnetic graphene oxide by the covalent cross-linking method.

5. The method for preparing a magnetic graphene cellulose composite material according to claim 1, wherein in the fourth step, the prepared magnetic graphene oxide with a co-crosslinking method is prepared into a magnetic graphene oxide dispersion with a concentration of 0.6% by adding a certain amount of water, cellulose filter paper is placed in a square container, immersed in the magnetic graphene oxide dispersion with a co-crosslinking method, and direction adjustment and control are performed by using a magnet;

6. The method for preparing the magnetic graphene cellulose composite material according to claim 5, wherein the reduction is to reduce the magnetic graphene oxide by a co-crosslinking method by using HI steam.

7. The method of preparing a magnetic graphene cellulose composite material according to claim 3, wherein the methanol and toluene are mixed according to a ratio of 50mL:50mL of the mixture.

8. A flexible light-emitting device, characterized by comprising a magnetic graphene cellulose composite material (1) prepared by the preparation method according to any one of claims 1 to 7, wherein a dielectric layer (2) and a light-emitting layer (3) are sequentially arranged on one side of the magnetic graphene cellulose composite material (1); the side of the light-emitting layer (3) far away from the dielectric layer (2) is adhered to the ITO/PET substrate (4).

9. A flexible light emitting device according to claim 8, characterized in that the dielectric layer (2) is a film of BaTiO ₃ Mixing with PB glue according to a mass ratio of 0.8-1:1-1.5, and spin-coating the mixture on the magnetic graphene cellulose composite material at 500rpm for 60s by using a spin coater after uniformly stirring.

10. A flexible light-emitting device according to claim 8, characterized in that the light-emitting layer (3) is made of luminescent powder ZnS, cu and PB glue in a mass ratio of 1-1.5:1.2-2, spin-coating the luminescent powder onto the dielectric layer (2) at 500rpm for 60s by using a spin coater after uniformly stirring, wherein the thickness is 20-40 mu m, and drying and volatilizing the solvent at 80-100 ℃.