Graphene quantum dot film, preparation method and application thereof

Abstract

This invention relates to the field of graphene quantum dot film technology, and discloses a graphene quantum dot film, its preparation method, and its applications. The film is composed of the following components: modified graphene quantum dots, inorganic nanoparticles, a polymer matrix, a dispersant, a crosslinking agent, and additives. Through the optimized integration of raw material design and preparation process, the graphene quantum dot film of this invention achieves a synergistic improvement in both microstructure and macroscopic performance. From a macroscopic perspective, the film's transmittance reaches a maximum of 91.3% at 550 nm, and its light absorption coefficient reaches 4.0 × 10⁻⁶. 4 cm ‑1 The material exhibits a maximum tensile strength of 48.6 MPa and an elongation at break of 4.5%, and maintains a high performance retention rate even after humid heat and ultraviolet light aging. These superior properties are attributed to the synergistic effect of modified graphene quantum dots, modified inorganic nanoparticles, and optimized polymer matrices, as well as the regulation of processes such as segmented ultrasonication-intermittent stirring and gradient curing.

Description

Technical Field

[0001] This invention relates to the field of graphene quantum dot film technology, and more particularly to a graphene quantum dot film, its preparation method, and its applications. Background Technology

[0002] With the rapid development of optoelectronic devices towards high performance, miniaturization, and high stability, more stringent requirements are being placed on the comprehensive performance of core functional materials. Graphene quantum dots, as a novel nanomaterial that combines the excellent conductivity of graphene with the unique optical properties of quantum dots, have shown broad application prospects in the field of optoelectronic devices, and functional thin film materials based on them have become a current research hotspot.

[0003] However, there are still many problems to be solved in the preparation and application of existing graphene quantum dot films. At the raw material level, traditional graphene quantum dots have limited surface active sites, poor compatibility with other components, and are prone to aggregation, resulting in non-uniform internal structure of the film, which directly affects optical performance and mechanical stability. Inorganic nanoparticles, as commonly used performance-enhancing components, have different surface hydrophobicity than polymer matrices, resulting in weak interfacial bonding forces, making it difficult to fully exert synergistic enhancement effects, and may even introduce defects due to poor dispersion.

[0004] In addition, existing thin film materials are not able to maintain their performance in complex environments. After aging processes such as damp heat and ultraviolet light, they are prone to phenomena such as decreased light transmittance and deterioration of mechanical properties, which cannot meet the requirements for long-term stable operation of optoelectronic devices.

[0005] Therefore, developing a graphene quantum dot film that achieves synergistic improvement in optical performance, mechanical performance, and stability through rational raw material design and optimized preparation process is of great significance for promoting its large-scale application in the field of optoelectronic devices. Summary of the Invention

[0006] To address the problems in the prior art, the present invention provides a graphene quantum dot film.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a graphene quantum dot film, characterized in that, by mass parts, it is made of the following components: 15-25 parts modified graphene quantum dots, 8-12 parts inorganic nanoparticles, 50-65 parts polymer matrix, 2-4 parts dispersant, 4-6 parts crosslinking agent, and 1.5-2.5 parts additives. The inorganic nanoparticles are titanium dioxide and zinc oxide composite particles modified with silane coupling agent KH-550, with a titanium dioxide to zinc oxide mass ratio of 2.5:1, a particle size of 80-150 nm, and the amount of silane coupling agent KH-550 being 5-7% of the mass of the inorganic nanoparticles. The thickness of the graphene quantum dot film is 100-400 nm.

[0008] As a further technical solution, the preparation method of the modified graphene quantum dots includes the following steps: Preparation of S1 precursor: Graphite powder, sodium nitrate, and concentrated sulfuric acid were mixed at a mass ratio of 1:0.5:50. Potassium permanganate was slowly added under ice bath conditions at 2-4℃, with a mass ratio of graphite powder to potassium permanganate of 1:3. After stirring for 2 hours, the temperature was raised to 35℃ and stirring was continued for 3 hours. Then, deionized water was slowly added, with a volume ratio of deionized water to concentrated sulfuric acid of 2:1. The temperature was raised to 95℃ and the reaction was carried out for 15 minutes. Hydrogen peroxide was added to reduce the remaining oxidant, with a mass ratio of hydrogen peroxide to graphite powder of 5:1. The mixture was centrifuged, washed with deionized water until the filtrate was neutral, and ultrasonically exfoliated at 300-400W power for 45 minutes to obtain a graphene oxide quantum dot dispersion. Centrifugation speed: 3000-4000 r / min; time: 10-15 min; S2 element doping: Add a mixed dopant of urea and ammonium fluoride to the graphene oxide quantum dot dispersion obtained in step S1. The mass ratio of urea to ammonium fluoride is 3:1, and the amount of dopant is 14-16% of the mass of the graphene oxide quantum dots. Adjust the pH of the system to 8.5 and perform a hydrothermal reaction at 120-130℃ for 12 hours. After cooling to room temperature, centrifuge, wash with deionized water, and vacuum dry to obtain nitrogen-fluorine co-doped graphene quantum dots. Centrifugation speed: 3000-4000 r / min; time: 10-15 min; S3 Surface Grafting: The nitrogen-fluorine co-doped graphene quantum dots obtained in step S2 were dispersed in anhydrous ethanol, and maleic anhydride-modified polyethylene glycol was added as a grafting monomer, with the amount of grafting monomer being 40% of the mass of the nitrogen-fluorine co-doped graphene quantum dots; azobisisobutyronitrile was added as an initiator, with the amount of initiator being 3-4% of the mass of the grafting monomer; the reaction was refluxed at 75°C for 7 hours; after the reaction was completed, the mixture was centrifuged and vacuum dried according to the parameters described in step S2, washed with anhydrous ethanol, and then vacuum dried to obtain grafted modified graphene quantum dots; S4 Plasma Activation: The grafted modified graphene quantum dots obtained in step S3 are placed in a plasma processor and activated at a power of 90-110W for 3-4 minutes to obtain the modified graphene quantum dots.

[0009] As a further technical solution, in the element doping step, the vacuum drying temperature is 60-80℃, the pressure is 0.05-0.08MPa, and the time is 8-10h.

[0010] As a further technical solution, the initiator in the surface grafting step is azobisisobutyronitrile.

[0011] As a further technical solution, the polymer matrix is ​​a blend of PEG-2000 and chitosan, with a mass ratio of PEG-2000 to chitosan of 4:1.

[0012] As a further technical solution, the dispersant is sodium dodecylbenzenesulfonate; The crosslinking agent is glutaraldehyde; The adjuvant is antioxidant 1010.

[0013] The preparation method of graphene quantum dot films includes the following steps: (1) Preparation of composite slurry: According to the mass fractions, the modified graphene quantum dots and inorganic nanoparticles are added to deionized water. First, 60% of the dispersant sodium dodecylbenzene sulfonate is added, and ultrasonic dispersion is carried out using segmented ultrasonic-intermittent stirring mode to obtain a dispersion. The remaining 40% of the dispersant sodium dodecylbenzene sulfonate, polymer matrix, crosslinking agent glutaraldehyde, and auxiliary agent antioxidant 1010 are added to the dispersion. The mixture is stirred at 65°C for 2.5 h to obtain a uniform and stable composite slurry. (2) Substrate pretreatment: The substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 18 min each, and dried at 80℃ for 30 min. (3) Step-by-step coating: The composite slurry is coated onto the pretreated substrate in steps by spin coating. The spin coating speed is 2500-3500 r / min and the spin coating time is 40-50 s. After each layer is coated, it is pre-dried at 90℃ for 12 min. The coating is repeated 3-4 times until the film thickness reaches 100-400 nm. (4) Gradient curing: Place the coated substrate in a curing oven and heat it to 110-115℃ at a heating rate of 4-5℃ / min. Cure for 1.5h to remove moisture and organic solvents from the system. Then heat it to 145-155℃ at a heating rate of 4-5℃ / min and cure for 2.5h to promote the crosslinking reaction. Finally, cool it to 80℃ at a cooling rate of 4℃ / min, keep it at that temperature for 1h, and then let it cool naturally to room temperature. (5) Post-treatment: The cured film was irradiated with ultraviolet light with a wavelength of 254nm for 15min, and then kept at 100℃ for 30min for hydrophobic shaping to obtain the graphene quantum dot film.

[0014] As a further technical solution, in step (1), the segmented ultrasonic-intermittent stirring mode is specifically as follows: first, ultrasonically sonicate at 350-380W power for 12-13 minutes, then intermittently stir for 5 minutes, and then ultrasonically sonicate at 420-480W power for 12-13 minutes, then intermittently stir for 5 minutes.

[0015] As a further technical solution, in step (2), the substrate is a transparent conductive glass substrate.

[0016] The graphene quantum dot film described herein is applied in the field of optoelectronic devices.

[0017] The beneficial effects of this invention are: This invention modifies graphene quantum dots through a four-step process: precursor preparation, elemental doping, surface grafting, and plasma activation, optimizing their structure and performance at the microscopic level. In the precursor preparation process, by controlling the oxidation and ultrasonic exfoliation parameters, uniformly sized and well-dispersed graphene oxide quantum dots were obtained. Elemental doping introduces nitrogen and fluorine, which not only modulates the electronic structure of the graphene quantum dots and enhances their light absorption capacity but also improves their interaction with other components. Surface grafting of maleic anhydride-modified polyethylene glycol effectively improves the hydrophilicity and hydrophobicity of the graphene quantum dots, enabling them to form a stable interfacial bond with the polymer matrix. Plasma activation further increases the surface active sites, promoting subsequent synergistic effects with other components. Due to the above modification treatment, the graphene quantum dots can be uniformly dispersed in the film, avoiding agglomeration and significantly improving the film's transmittance and light absorption coefficient. It also enhances the stress transfer ability with other components, thus solving the problem of limited film performance caused by poor dispersion of traditional unmodified graphene quantum dots.

[0018] Regarding the raw material composition, the titanium dioxide-zinc oxide composite particles modified with silane coupling agent KH-550 exhibit strong interactions between the organic functional groups formed on their surface and the polymer matrix and modified graphene quantum dots. This enhances the dispersion stability of inorganic nanoparticles in the slurry and optimizes the optical and mechanical properties of the film through synergistic effects. The blend matrix of PEG-2000 and chitosan possesses both good film-forming properties and mechanical toughness, providing stable structural support for the film. The rational ratio of dispersants, crosslinking agents, and additives further promotes the synergistic effect of each component, improving the overall performance of the film. In terms of the preparation process, the segmented ultrasonic-intermittent stirring mode, through the combination of ultrasonic waves of different powers and intermittent stirring, achieves deep dispersion of each component in the composite slurry, avoiding local agglomeration problems. The gradient curing process, through stepwise heating and holding, first fully removes moisture and organic solvents from the system, then promotes the full crosslinking reaction, effectively alleviating internal stress in the film and improving structural density.

[0019] The graphene quantum dot film of this invention achieves a synergistic improvement in both microstructure and macroscopic performance through the optimized integration of raw material design and preparation process. From a macroscopic perspective, the film's transmittance reaches a maximum of 91.3% at 550 nm, and its light absorption coefficient reaches 4.0 × 10⁻⁶. 4 cm -1The film exhibits a high tensile strength of 48.6 MPa and an elongation at break of 4.5%, maintaining high performance retention even after hygrothermal and UV aging. These superior properties are attributed to the synergistic effect of modified graphene quantum dots, modified inorganic nanoparticles, and an optimized polymer matrix, as well as the controlled use of processes such as segmented ultrasonic-intermittent stirring and gradient curing. This technical solution not only addresses the shortcomings of existing graphene quantum dot films in terms of optical properties, mechanical properties, and stability, but also features a simple and highly controllable fabrication process, making it suitable for industrial production. It meets the demands of the optoelectronic device field for high-performance functional films, providing strong support for the performance upgrade of optoelectronic devices. Attached Figure Description

[0020] Figure 1 This is a comparison chart of the 550nm transmittance of an example graphene quantum dot film and a comparative example. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a graphene quantum dot film, its preparation method, and its application. The graphene quantum dot film, by mass parts, is composed of the following components: 15-25 parts modified graphene quantum dots, 8-12 parts inorganic nanoparticles, 50-65 parts polymer matrix, 2-4 parts dispersant, 4-6 parts crosslinking agent, and 1.5-2.5 parts additives. The preparation method includes composite slurry preparation, substrate pretreatment, step-by-step coating, gradient curing, and post-treatment steps. The graphene quantum dot film can be applied in the field of optoelectronic devices.

[0023] I. Raw Material Description: Modified graphene quantum dots: prepared through precursor preparation, elemental doping, surface grafting, and plasma activation steps.

[0024] Inorganic nanoparticles: These are titanium dioxide and zinc oxide composite particles modified with silane coupling agent KH-550. The mass ratio of titanium dioxide to zinc oxide is 2.5:1, the particle size is 80-150 nm, and the amount of silane coupling agent KH-550 is 5%-7% of the mass of the inorganic nanoparticles.

[0025] Polymer matrix: a blend of PEG-2000 and chitosan, with a mass ratio of PEG-2000 to chitosan of 4:1.

[0026] Dispersant: Sodium dodecylbenzenesulfonate.

[0027] Crosslinking agent: glutaraldehyde.

[0028] Additive: Antioxidant 1010.

[0029] Substrate: A transparent conductive glass substrate.

[0030] The present invention does not impose any special restrictions on the source of the above-mentioned raw materials; commercially available products well known to those skilled in the art can be used.

[0031] II. Preparation of modified graphene quantum dots: Preparation of S1 precursor: Graphite powder, sodium nitrate, and concentrated sulfuric acid were mixed at a mass ratio of 1:0.5:50. Potassium permanganate was slowly added under ice bath conditions at 2-4℃, with a graphite powder to potassium permanganate mass ratio of 1:3. After stirring for 2 hours, the temperature was raised to 35℃ and stirring continued for 3 hours. Then, deionized water was slowly added, with a deionized water to concentrated sulfuric acid volume ratio of 2:1. The temperature was raised to 95℃ and the reaction was carried out for 15 minutes. Hydrogen peroxide was added to reduce the remaining oxidant, with a hydrogen peroxide to graphite powder mass ratio of 5:1. The mixture was centrifuged, washed with deionized water until the filtrate was neutral, and then ultrasonically exfoliated at 300-400W power for 45 minutes to obtain a graphene oxide quantum dot dispersion. The centrifugation speed was 3000-4000 r / min, and the time was 10-15 minutes.

[0032] S2 element doping: A mixed dopant of urea and ammonium fluoride was added to the graphene oxide quantum dot dispersion obtained in the precursor preparation step. The mass ratio of urea to ammonium fluoride was 3:1, and the amount of dopant was 14-16% of the mass of the graphene oxide quantum dots. The pH of the system was adjusted to 8.5, and the reaction was carried out hydrothermally at 120-130℃ for 12 hours. After cooling to room temperature, the mixture was centrifuged, washed with deionized water, and vacuum dried to obtain nitrogen-fluorine co-doped graphene quantum dots. The centrifugation speed was 3000-4000 r / min, and the time was 10-15 min. The vacuum drying temperature was 60-80℃, the pressure was 0.05-0.08 MPa, and the time was 8-10 h.

[0033] S3 surface grafting: Nitrogen-fluorine co-doped graphene quantum dots obtained from the elemental doping step were dispersed in anhydrous ethanol. Maleic anhydride-modified polyethylene glycol was added as a grafting monomer, with the amount of grafting monomer being 40% of the mass of the nitrogen-fluorine co-doped graphene quantum dots. Azobisisobutyronitrile was added as an initiator, with the amount of initiator being 3-4% of the mass of the grafting monomer. The reaction was refluxed at 75°C for 7 hours. After the reaction was completed, the quantum dots were centrifuged and vacuum dried according to the parameters described in the elemental doping step. After washing with anhydrous ethanol, they were vacuum dried to obtain grafted modified graphene quantum dots.

[0034] S4 plasma activation: The grafted modified graphene quantum dots obtained from the surface grafting step were placed in a plasma processor and activated at 90-110W power for 3-4 minutes to obtain the modified graphene quantum dots.

[0035] III. Methods for preparing graphene quantum dot films, including: (1) Preparation of composite slurry: Modified graphene quantum dots and inorganic nanoparticles were added to deionized water according to the specified mass ratio. First, 60% of sodium dodecylbenzenesulfonate, a dispersant, was added, and the mixture was ultrasonically dispersed using a segmented ultrasonic-intermittent stirring mode to obtain a dispersion. The remaining 40% of sodium dodecylbenzenesulfonate, a polymer matrix, glutaraldehyde (a crosslinking agent), and antioxidant 1010 were added to the dispersion, and the mixture was stirred at 65℃ for 2.5 hours to obtain a uniform and stable composite slurry. Specifically, the segmented ultrasonic-intermittent stirring mode involved: first, ultrasonication at 350-380W power for 12-13 minutes, followed by intermittent stirring for 5 minutes; then, ultrasonication at 420-480W power for 12-13 minutes, followed by intermittent stirring for 5 minutes.

[0036] (2) Substrate pretreatment: The transparent conductive glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 18 min each, and then dried at 80℃ for 30 min.

[0037] (3) Step-by-step coating: The composite slurry was applied to the pretreated substrate in steps using a spin coating method. Each spin coating was performed at a speed of 2500-3500 r / min and for 40-50 s. After each layer was coated, it was pre-dried at 90℃ for 12 min. The coating was repeated 3-4 times until the film thickness reached 100-400 nm.

[0038] (4) Gradient curing: Place the coated substrate in a curing oven and heat it to 110-115℃ at a heating rate of 4-5℃ / min, and cure for 1.5h to remove moisture and organic solvents from the system; then heat it to 145-155℃ at a heating rate of 4-5℃ / min, and cure for 2.5h to promote the full crosslinking reaction; finally, cool it to 80℃ at a cooling rate of 4℃ / min, hold it at that temperature for 1h, and then let it cool naturally to room temperature.

[0039] (5) Post-processing: The cured film was irradiated with ultraviolet light at a wavelength of 254 nm for 15 min, and then kept at 100 °C for 30 min for hydrophobic shaping to obtain the graphene quantum dot film.

[0040] The graphene quantum dot film provided by this invention, through specific raw material ratios and preparation processes, exhibits excellent optical properties, mechanical properties, and stability, meeting the requirements for use in the field of optoelectronic devices. At the same time, the preparation method is simple to operate, highly controllable, and suitable for industrial production.

[0041] To further illustrate the present invention, the following detailed description is provided through the examples and comparative examples.

[0042] Example 1: (I) Preparation of modified graphene quantum dots: Preparation of S1 precursor: Graphite powder, sodium nitrate, and concentrated sulfuric acid were mixed at a mass ratio of 1:0.5:50. Potassium permanganate was slowly added under ice bath conditions at 2℃, with a mass ratio of graphite powder to potassium permanganate of 1:3. After stirring for 2 hours, the temperature was raised to 35℃ and stirring was continued for 3 hours. Then, deionized water was slowly added, with a volume ratio of deionized water to concentrated sulfuric acid of 2:1. The temperature was raised to 95℃ and the reaction was carried out for 15 minutes. Hydrogen peroxide was added to reduce the remaining oxidant, with a mass ratio of hydrogen peroxide to graphite powder of 5:1. The mixture was centrifuged at 3000 r / min for 10 minutes, washed with deionized water until the filtrate was neutral, and ultrasonically exfoliated at 300W power for 45 minutes to obtain a graphene oxide quantum dot dispersion.

[0043] S2 element doping: A mixed dopant of urea and ammonium fluoride was added to the above graphene oxide quantum dot dispersion. The mass ratio of urea to ammonium fluoride was 3:1, and the amount of dopant was 14% of the mass of the graphene oxide quantum dots. The pH of the system was adjusted to 8.5, and the hydrothermal reaction was carried out at 120℃ for 12 h. After cooling to room temperature, the mixture was centrifuged at 3000 r / min for 10 min, washed with deionized water, and vacuum dried at 60℃ and 0.05 MPa for 8 h to obtain nitrogen-fluorine co-doped graphene quantum dots.

[0044] S3 Surface Grafting: Nitrogen-fluorine co-doped graphene quantum dots were dispersed in anhydrous ethanol, and maleic anhydride-modified polyethylene glycol was added as a grafting monomer, with the amount of grafting monomer being 40% of the mass of nitrogen-fluorine co-doped graphene quantum dots; azobisisobutyronitrile was added as an initiator, with the amount of initiator being 3% of the mass of grafting monomer; the reaction was refluxed at 75℃ for 7h; after the reaction was completed, the mixture was centrifuged at 3000r / min for 10min, and vacuum dried at 60℃ and 0.05MPa for 8h. After washing with anhydrous ethanol, the mixture was vacuum dried again to obtain grafted modified graphene quantum dots.

[0045] S4 Plasma Activation: Grafted modified graphene quantum dots were placed in a plasma processor and activated at 90W power for 3 minutes to obtain modified graphene quantum dots.

[0046] (II) Preparation of Inorganic Nanoparticles: Titanium dioxide and zinc oxide were mixed at a mass ratio of 2.5:1 to obtain composite particles with a particle size of 80 nm. Silane coupling agent KH-550 was added at 5% of the mass of the composite particles, and the mixture was stirred to modify the particles, thus obtaining inorganic nanoparticles.

[0047] (III) Preparation of graphene quantum dot films: Preparation of composite slurry: 15 parts by mass of modified graphene quantum dots and 8 parts by mass of the above inorganic nanoparticles were added to deionized water. 60% of the dispersant sodium dodecylbenzenesulfonate was added first, and ultrasonic dispersion was carried out using a segmented ultrasonic-intermittent stirring mode. Specifically, ultrasonication was performed at 350W power for 12 minutes, followed by intermittent stirring for 5 minutes, and then ultrasonication was performed at 420W power for 12 minutes, followed by intermittent stirring for 5 minutes to obtain a dispersion. The remaining 40% of the dispersant sodium dodecylbenzenesulfonate, 50 parts of the polymer matrix (PEG-2000 to chitosan mass ratio 4:1), 4 parts of the crosslinking agent glutaraldehyde, and 1.5 parts of the auxiliary antioxidant 1010 were added to the dispersion. The mixture was stirred at 65℃ for 2.5 hours to obtain a uniform and stable composite slurry.

[0048] Substrate pretreatment: The transparent conductive glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 18 min each, and then dried at 80℃ for 30 min.

[0049] Stepwise coating: The composite slurry was coated onto the pretreated substrate in steps using a spin coating method. Each spin coating speed was 2500 r / min and the spin coating time was 40 s. After each coating layer, it was pre-dried at 90℃ for 12 min. The coating was repeated 3 times to achieve a film thickness of 100 nm.

[0050] Gradient curing: Place the coated substrate in a curing oven and heat it to 110°C at a heating rate of 4°C / min, and cure for 1.5h to remove moisture and organic solvents from the system; then heat it to 145°C at a heating rate of 4°C / min, and cure for 2.5h to promote the full crosslinking reaction; finally, cool it to 80°C at a cooling rate of 4°C / min, hold it at that temperature for 1h, and then let it cool naturally to room temperature.

[0051] Post-processing: The cured film was irradiated with ultraviolet light at a wavelength of 254nm for 15 minutes, and then kept at 100℃ for 30 minutes for hydrophobic shaping to obtain graphene quantum dot film.

[0052] Example 2: (I) Preparation of modified graphene quantum dots: Preparation of S1 precursor: Graphite powder, sodium nitrate, and concentrated sulfuric acid were mixed at a mass ratio of 1:0.5:50. Potassium permanganate was slowly added under ice bath conditions at 4℃, with a mass ratio of graphite powder to potassium permanganate of 1:3. After stirring for 2 hours, the temperature was raised to 35℃ and stirring was continued for 3 hours. Then, deionized water was slowly added, with a volume ratio of deionized water to concentrated sulfuric acid of 2:1. The temperature was raised to 95℃ and the reaction was carried out for 15 minutes. Hydrogen peroxide was added to reduce the remaining oxidant, with a mass ratio of hydrogen peroxide to graphite powder of 5:1. The mixture was centrifuged at 4000 r / min for 15 minutes, washed with deionized water until the filtrate was neutral, and ultrasonically exfoliated at 400 W for 45 minutes to obtain a graphene oxide quantum dot dispersion.

[0053] S2 element doping: A mixed dopant of urea and ammonium fluoride was added to the above graphene oxide quantum dot dispersion. The mass ratio of urea to ammonium fluoride was 3:1, and the amount of dopant was 16% of the mass of the graphene oxide quantum dots. The pH of the system was adjusted to 8.5, and the hydrothermal reaction was carried out at 130℃ for 12 h. After cooling to room temperature, the mixture was centrifuged at 4000 r / min for 15 min, washed with deionized water, and vacuum dried at 80℃ and 0.08 MPa for 10 h to obtain nitrogen-fluorine co-doped graphene quantum dots.

[0054] S3 Surface Grafting: Nitrogen-fluorine co-doped graphene quantum dots were dispersed in anhydrous ethanol, and maleic anhydride-modified polyethylene glycol was added as a grafting monomer, with the amount of grafting monomer being 40% of the mass of nitrogen-fluorine co-doped graphene quantum dots; azobisisobutyronitrile was added as an initiator, with the amount of initiator being 4% of the mass of grafting monomer; the reaction was refluxed at 75℃ for 7h; after the reaction was completed, the mixture was centrifuged at 4000r / min for 15min, and vacuum dried at 80℃ and 0.08MPa for 10h. After washing with anhydrous ethanol, the mixture was vacuum dried again to obtain grafted modified graphene quantum dots.

[0055] S4 Plasma Activation: Grafted modified graphene quantum dots were placed in a plasma processor and activated at 110W power for 4 minutes to obtain modified graphene quantum dots.

[0056] (II) Preparation of Inorganic Nanoparticles: Titanium dioxide and zinc oxide were mixed at a mass ratio of 2.5:1 to obtain composite particles with a particle size of 150 nm. Silane coupling agent KH-550 was added at 7% of the mass of the composite particles, and the mixture was stirred to modify the particles, thus obtaining inorganic nanoparticles.

[0057] (III) Preparation of graphene quantum dot films: Preparation of composite slurry: 25 parts by mass of modified graphene quantum dots and 12 parts by mass of the above inorganic nanoparticles were added to deionized water. 60% of the dispersant sodium dodecylbenzenesulfonate was added first, and ultrasonic dispersion was carried out using a segmented ultrasonic-intermittent stirring mode. Specifically, ultrasonication was performed at 380W power for 13 minutes, followed by intermittent stirring for 5 minutes, and then ultrasonication was performed at 480W power for 13 minutes, followed by intermittent stirring for 5 minutes to obtain a dispersion. The remaining 40% of the dispersant sodium dodecylbenzenesulfonate, 65 parts of the polymer matrix (PEG-2000 to chitosan mass ratio 4:1), 6 parts of the crosslinking agent glutaraldehyde, and 2.5 parts of the auxiliary antioxidant 1010 were added to the dispersion. The mixture was stirred at 65℃ for 2.5 hours to obtain a uniform and stable composite slurry.

[0058] Substrate pretreatment: The transparent conductive glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 18 min each, and then dried at 80℃ for 30 min.

[0059] Stepwise coating: The composite slurry was coated onto the pretreated substrate in steps using a spin coating method. Each spin coating speed was 3500 r / min and the spin coating time was 50 s. After each coating layer, it was pre-dried at 90℃ for 12 min. The coating was repeated 4 times to achieve a film thickness of 400 nm.

[0060] Gradient curing: Place the coated substrate in a curing oven and heat it to 115°C at a heating rate of 5°C / min, and cure for 1.5h to remove moisture and organic solvents from the system; then heat it to 155°C at a heating rate of 5°C / min, and cure for 2.5h to promote the full crosslinking reaction; finally, cool it to 80°C at a cooling rate of 4°C / min, hold it at that temperature for 1h, and then let it cool naturally to room temperature.

[0061] Post-processing: The cured film was irradiated with ultraviolet light at a wavelength of 254nm for 15 minutes, and then kept at 100℃ for 30 minutes for hydrophobic shaping to obtain graphene quantum dot film.

[0062] Example 3: (I) Preparation of modified graphene quantum dots: Preparation of S1 precursor: Graphite powder, sodium nitrate, and concentrated sulfuric acid were mixed at a mass ratio of 1:0.5:50. Potassium permanganate was slowly added under ice bath conditions at 3℃, with a mass ratio of graphite powder to potassium permanganate of 1:3. After stirring for 2 hours, the temperature was raised to 35℃ and stirring was continued for 3 hours. Then, deionized water was slowly added, with a volume ratio of deionized water to concentrated sulfuric acid of 2:1. The temperature was raised to 95℃ and the reaction was carried out for 15 minutes. Hydrogen peroxide was added to reduce the remaining oxidant, with a mass ratio of hydrogen peroxide to graphite powder of 5:1. The mixture was centrifuged at 3500 r / min for 12 minutes, washed with deionized water until the filtrate was neutral, and ultrasonically exfoliated at 350 W for 45 minutes to obtain a graphene oxide quantum dot dispersion.

[0063] S2 element doping: A mixed dopant of urea and ammonium fluoride was added to the above graphene oxide quantum dot dispersion. The mass ratio of urea to ammonium fluoride was 3:1, and the amount of dopant was 15% of the mass of the graphene oxide quantum dots. The pH of the system was adjusted to 8.5, and the hydrothermal reaction was carried out at 125℃ for 12 h. After cooling to room temperature, the mixture was centrifuged at 3500 r / min for 12 min, washed with deionized water, and vacuum dried at 70℃ and 0.065 MPa for 9 h to obtain nitrogen-fluorine co-doped graphene quantum dots.

[0064] S3 Surface Grafting: Nitrogen-fluorine co-doped graphene quantum dots were dispersed in anhydrous ethanol, and maleic anhydride-modified polyethylene glycol was added as a grafting monomer, with the amount of grafting monomer being 40% of the mass of nitrogen-fluorine co-doped graphene quantum dots; azobisisobutyronitrile was added as an initiator, with the amount of initiator being 3.5% of the mass of grafting monomer; the reaction was refluxed at 75℃ for 7h; after the reaction was completed, the mixture was centrifuged at 3500r / min for 12min, and vacuum dried at 70℃ and 0.065MPa for 9h. After washing with anhydrous ethanol, the mixture was vacuum dried again to obtain grafted modified graphene quantum dots.

[0065] S4 Plasma Activation: Grafted modified graphene quantum dots were placed in a plasma processor and activated at 100W power for 3.5 min to obtain modified graphene quantum dots.

[0066] (II) Preparation of Inorganic Nanoparticles: Titanium dioxide and zinc oxide were mixed at a mass ratio of 2.5:1 to obtain composite particles with a particle size of 115 nm. Silane coupling agent KH-550 was added at 6% of the mass of the composite particles, and the mixture was stirred to modify the particles, thus obtaining inorganic nanoparticles.

[0067] (III) Preparation of graphene quantum dot films: Preparation of composite slurry: 20 parts by mass of modified graphene quantum dots and 10 parts by mass of the above inorganic nanoparticles were added to deionized water. 60% of the dispersant sodium dodecylbenzenesulfonate was added first, and ultrasonic dispersion was carried out using a segmented ultrasonic-intermittent stirring mode. Specifically, ultrasonication was performed at 365W power for 12.5 min, followed by intermittent stirring for 5 min, and then ultrasonication was performed at 450W power for 12.5 min, followed by intermittent stirring for 5 min, to obtain a dispersion. The remaining 40% of the dispersant sodium dodecylbenzenesulfonate, 57.5 parts of the polymer matrix (PEG-2000 to chitosan mass ratio 4:1), 5 parts of the crosslinking agent glutaraldehyde, and 2.0 parts of the auxiliary antioxidant 1010 were added to the dispersion. The mixture was stirred at 65℃ for 2.5 h to obtain a uniform and stable composite slurry.

[0068] Substrate pretreatment: The transparent conductive glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 18 min each, and then dried at 80℃ for 30 min.

[0069] Stepwise coating: The composite slurry was coated onto the pretreated substrate in steps using a spin coating method. Each spin coating speed was 3000 r / min and the spin coating time was 45 s. After each coating layer, it was pre-dried at 90℃ for 12 min. The coating was repeated 3 times to achieve a film thickness of 250 nm.

[0070] Gradient curing: Place the coated substrate in a curing oven and heat it to 112°C at a heating rate of 4.5°C / min, and cure for 1.5 hours to remove moisture and organic solvents from the system; then heat it to 150°C at a heating rate of 4.5°C / min and cure for 2.5 hours to promote the full crosslinking reaction; finally, cool it to 80°C at a cooling rate of 4°C / min, hold it at that temperature for 1 hour, and then let it cool naturally to room temperature.

[0071] Post-processing: The cured film was irradiated with ultraviolet light at a wavelength of 254nm for 15 minutes, and then kept at 100℃ for 30 minutes for hydrophobic shaping to obtain graphene quantum dot film.

[0072] Comparative Example 1: All other conditions were exactly the same as in Example 3, except that the modified graphene quantum dots were replaced with ordinary graphene quantum dots that had not undergone precursor preparation, elemental doping, surface grafting, and plasma activation treatment.

[0073] Comparative Example 2: All other conditions were exactly the same as in Example 3, except that the inorganic nanoparticles were titanium dioxide and zinc oxide composite particles that had not been modified by the silane coupling agent KH-550 (titanium dioxide to zinc oxide mass ratio 2.5:1, particle size 115nm).

[0074] Comparative Example 3: Other conditions were exactly the same as in Example 3. During the preparation of the composite slurry, dispersion was carried out using only a single 450W power ultrasonic method for 25 minutes, without using a segmented ultrasonic-intermittent stirring mode.

[0075] Comparative Example 4: Other conditions were exactly the same as in Example 3. The temperature was directly raised to 150°C during the curing process and kept at a constant temperature for 4 hours. Gradient curing method was not used.

[0076] Performance testing experiments: Experiment 1: Optical performance test The optical properties of the graphene quantum dot films prepared in Examples 1-3 and Comparative Examples 1-4 were tested using a UV-Vis spectrophotometer. The test wavelength range was 300 nm-800 nm. The transmittance (at 550 nm) and light absorption coefficient (at 400 nm) of the films were recorded. The results are as follows. Table 1

[0077] The graphene quantum dot films in Examples 1-3 all exhibited transmittances exceeding 87% at 550 nm and light absorption coefficients reaching 3.8 × 10⁻⁶ at 400 nm. 4 cm -1 The above demonstrates excellent optical performance. Among them, Example 3 has the highest light transmittance, reaching 91.3%, and its light absorption coefficient is also at a high level, indicating that the optical performance is optimal when the parameters are taken at an intermediate value.

[0078] The transmittance and light absorption coefficient of Comparative Example 1 were significantly lower than those of Example 3. This is because no modified graphene quantum dots were used. Ordinary graphene quantum dots have poor dispersion in the film and exhibit agglomeration, which affects the transmission and absorption of light. At the same time, the lack of modification treatments such as element doping and surface grafting resulted in poor compatibility between graphene quantum dots and other components, further reducing optical performance.

[0079] The optical performance of Comparative Example 2 is better than that of Comparative Example 1, but still lower than that of Example 3. This is because the inorganic nanoparticles have not been modified by the silane coupling agent KH-550, and their interfacial bonding with components such as the polymer matrix is ​​weak. Defects are easily generated in the film, which leads to increased light scattering, decreased light transmittance, and reduced light absorption efficiency.

[0080] In Comparative Example 3, due to the use of ordinary ultrasonic dispersion, the components in the composite slurry were not dispersed evenly, and some particles agglomerated, resulting in an uneven internal structure of the film. This increased the obstruction of light transmission, and the light transmittance was slightly lower than that of Example 3. Furthermore, the uneven dispersion also affected the light absorption coefficient.

[0081] Comparative Example 4 lacks a gradient curing step. The isothermal curing process prevents the moisture and organic solvents inside the film from being fully discharged, resulting in residual impurities forming defects. At the same time, the crosslinking reaction is insufficient, leading to inadequate film structure density, which in turn affects optical performance. Both the transmittance and light absorption coefficient are lower than those of Example 3.

[0082] Experiment 2: Mechanical property testing; The mechanical properties of the graphene quantum dot films prepared in Examples 1-3 and Comparative Examples 1-4 were tested using a universal testing machine. Samples with a width of 10 mm and a length of 50 mm were prepared, and the tensile rate was 5 mm / min. The tensile strength and elongation at break of the films were recorded, and the results are as follows: Table 2

[0083] The graphene quantum dot films of Examples 1-3 all exhibit tensile strengths higher than 42 MPa and elongation at break above 3.8%, demonstrating excellent mechanical properties. Example 3 shows the highest tensile strength at 48.6 MPa and an elongation at break of 4.5%, indicating that the film exhibits the best mechanical properties under the intermediate parameter values.

[0084] The tensile strength and elongation at break of Comparative Example 1 were much lower than those of Example 3, mainly because the unmodified graphene quantum dots had weak bonding forces with other components and could not effectively transfer stress, resulting in the film being prone to breakage during stretching and having poor mechanical properties.

[0085] In Comparative Example 2, the inorganic nanoparticles were not modified with silane coupling agents, resulting in poor compatibility with the polymer matrix and weak interfacial bonding. This made them prone to stress concentration under stress, leading to lower tensile strength and elongation at break compared to Example 3.

[0086] In Comparative Example 3, due to uneven dispersion of the composite slurry, there are weak areas inside the film. When subjected to stress, these areas are the first to break, resulting in a decrease in tensile strength and elongation at break, and the mechanical properties are not as good as those in Example 3.

[0087] Comparative Example 4 lacks a gradient curing step, resulting in uneven cross-linking density within the film and insufficient structural stability. Cracks are prone to propagate during stretching, thus its tensile strength and elongation at break are lower than those of Example 3, indicating poor mechanical properties.

[0088] Experiment 3: Stability Test; The graphene quantum dot films prepared in Examples 1-3 and Comparative Examples 1-4 were placed in a constant temperature and humidity chamber at 85°C and 85% relative humidity for 1000 hours of aging. The transmittance retention (at 550 nm) and tensile strength retention were then tested. Simultaneously, the films were irradiated with ultraviolet light at a wavelength of 254 nm for 500 hours, and the transmittance retention (at 550 nm) and tensile strength retention were also tested. The results are as follows: Table 3

[0089] The graphene quantum dot films of Examples 1-3, after 1000 hours of isothermal and humidity aging and 500 hours of UV irradiation, exhibited excellent stability with transmittance and tensile strength retention rates all exceeding 85%. Example 3 showed the highest retention rates: 90.2% transmittance and 91.5% tensile strength retention after isothermal and humidity aging, and 89.4% transmittance and 90.8% tensile strength retention after UV irradiation, indicating that the film prepared with the intermediate parameters had the best stability.

[0090] Comparative Example 1 showed the worst stability, with retention rates below 66% for all parameters. This was because unmodified graphene quantum dots are prone to oxidation and aggregation under harsh environments, leading to film structure damage and a sharp decline in performance. At the same time, their weak bonding with other components made them prone to interface separation during aging, further exacerbating performance degradation.

[0091] Comparative Example 2 showed better stability than Comparative Example 1, but still lower than Example 3. This is because the inorganic nanoparticles were not modified with silane coupling agent, and their interface with the polymer matrix was not strong. Under humid and hot conditions and ultraviolet light, voids and cracks were easily generated at the interface, leading to a decrease in film performance.

[0092] In Comparative Example 3, due to uneven dispersion of the composite slurry, there are defects in the internal structure of the film. During the aging process, these defects will gradually expand, resulting in a decrease in light transmittance and tensile strength retention, and the stability is not as good as in Example 3.

[0093] Comparative Example 4 lacks a gradient curing step, resulting in insufficient cross-linking reaction inside the film, inadequate structural density and stability, and susceptibility to degradation and damage under harsh environments. Therefore, its retention rates are all lower than those of Example 3, indicating poor stability.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A graphene quantum dot film, characterized in that, The product is composed of the following components by mass: 15-25 parts modified graphene quantum dots, 8-12 parts inorganic nanoparticles, 50-65 parts polymer matrix, 2-4 parts dispersant, 4-6 parts crosslinking agent, and 1.5-2.5 parts additives. The inorganic nanoparticles are titanium dioxide and zinc oxide composite particles modified with silane coupling agent KH-550, with a titanium dioxide to zinc oxide mass ratio of 2.5:1, a particle size of 80-150 nm, and the amount of silane coupling agent KH-550 being 5-7% of the mass of the inorganic nanoparticles. The thickness of the graphene quantum dot film is 100-400 nm.

2. The graphene quantum dot film as described in claim 1, characterized in that, The preparation method of the modified graphene quantum dots includes the following steps: Preparation of S1 precursor: Graphite powder, sodium nitrate, and concentrated sulfuric acid were mixed at a mass ratio of 1:0.5:

50. Potassium permanganate was slowly added under ice bath conditions at 2-4℃, with a mass ratio of graphite powder to potassium permanganate of 1:

3. After stirring for 2 hours, the temperature was raised to 35℃ and stirring was continued for 3 hours. Then, deionized water was slowly added, with a volume ratio of deionized water to concentrated sulfuric acid of 2:

1. The temperature was raised to 95℃ and the reaction was carried out for 15 minutes. Hydrogen peroxide was added to reduce the remaining oxidant, with a mass ratio of hydrogen peroxide to graphite powder of 5:

1. The mixture was centrifuged, washed with deionized water until the filtrate was neutral, and ultrasonically exfoliated at 300-400W power for 45 minutes to obtain a graphene oxide quantum dot dispersion. Centrifugation speed: 3000-4000 r / min; time: 10-15 min; S2 element doping: Add a mixed dopant of urea and ammonium fluoride to the graphene oxide quantum dot dispersion obtained in step S1. The mass ratio of urea to ammonium fluoride is 3:1, and the amount of dopant is 14-16% of the mass of the graphene oxide quantum dots. Adjust the pH of the system to 8.5 and perform a hydrothermal reaction at 120-130℃ for 12 hours. After cooling to room temperature, centrifuge, wash with deionized water, and vacuum dry to obtain nitrogen-fluorine co-doped graphene quantum dots. Centrifugation speed: 3000-4000 r / min; time: 10-15 min; S3 Surface Grafting: The nitrogen-fluorine co-doped graphene quantum dots obtained in step S2 were dispersed in anhydrous ethanol, and maleic anhydride-modified polyethylene glycol was added as a grafting monomer, with the amount of grafting monomer being 40% of the mass of the nitrogen-fluorine co-doped graphene quantum dots; azobisisobutyronitrile was added as an initiator, with the amount of initiator being 3-4% of the mass of the grafting monomer; the reaction was refluxed at 75°C for 7 hours; after the reaction was completed, the mixture was centrifuged and vacuum dried according to the parameters described in step S2, washed with anhydrous ethanol, and then vacuum dried to obtain grafted modified graphene quantum dots; S4 Plasma Activation: The grafted modified graphene quantum dots obtained in step S3 are placed in a plasma processor and activated at a power of 90-110W for 3-4 minutes to obtain the modified graphene quantum dots.

3. The graphene quantum dot film as described in claim 2, characterized in that, In the element doping step, the vacuum drying temperature is 60-80℃, the pressure is 0.05-0.08MPa, and the time is 8-10h.

4. The graphene quantum dot film as described in claim 2, characterized in that, The initiator used in the surface grafting step is azobisisobutyronitrile.

5. The graphene quantum dot film as described in claim 1, characterized in that, The polymer matrix is ​​a blend of PEG-2000 and chitosan, with a mass ratio of PEG-2000 to chitosan of 4:

1.

6. The graphene quantum dot film as described in claim 1, characterized in that, The dispersant is sodium dodecylbenzenesulfonate; The crosslinking agent is glutaraldehyde; The adjuvant is antioxidant 1010.

7. The method for preparing graphene quantum dot films according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of composite slurry: According to the mass fractions, the modified graphene quantum dots and inorganic nanoparticles are added to deionized water. First, 60% of the dispersant sodium dodecylbenzene sulfonate is added, and ultrasonic dispersion is carried out using segmented ultrasonic-intermittent stirring mode to obtain a dispersion. The remaining 40% of the dispersant sodium dodecylbenzene sulfonate, polymer matrix, crosslinking agent glutaraldehyde, and auxiliary agent antioxidant 1010 are added to the dispersion. The mixture is stirred at 65°C for 2.5 h to obtain a uniform and stable composite slurry. (2) Substrate pretreatment: The substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 18 min each, and dried at 80℃ for 30 min. (3) Step-by-step coating: The composite slurry is coated onto the pretreated substrate in steps using a spin coating method. The spin coating speed is 2500-3500 r / min and the spin coating time is 40-50 s. After each coating layer, pre-dry at 90℃ for 12 minutes, and repeat the coating 3-4 times until the film thickness reaches 100-400nm; (4) Gradient curing: Place the coated substrate in a curing oven and heat it to 110-115℃ at a heating rate of 4-5℃ / min. Cure for 1.5h to remove moisture and organic solvents from the system. Then heat it to 145-155℃ at a heating rate of 4-5℃ / min and cure for 2.5h to promote the crosslinking reaction. Finally, cool it to 80℃ at a cooling rate of 4℃ / min, keep it at that temperature for 1h, and then let it cool naturally to room temperature. (5) Post-treatment: The cured film was irradiated with ultraviolet light with a wavelength of 254nm for 15min, and then kept at 100℃ for 30min for hydrophobic shaping to obtain the graphene quantum dot film.

8. The preparation method according to claim 7, characterized in that, In step (1), the segmented ultrasonic-intermittent stirring mode is as follows: first, ultrasonically sonicate at 350-380W power for 12-13 minutes, then intermittently stir for 5 minutes, and then ultrasonically sonicate at 420-480W power for 12-13 minutes, then intermittently stir for 5 minutes.

9. The preparation method according to claim 7, characterized in that, In step (2), the substrate is a transparent conductive glass substrate.

10. The graphene quantum dot film as described in claim 1 is applied to the field of optoelectronic devices.

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