Graphene oxide / silver nanowire composite conductive film and preparation method and application thereof

Abstract

The invention relates to the technical field of nano thin film material preparation, in particular to a graphene oxide / silver nanowire composite conductive thin film and a preparation method and application thereof.The thin film is prepared according to the following method that a substrate is sequentially coated with a silver nanowire solution and a graphene oxide dispersion liquid, and a graphene oxide / silver nanowire flexible thin film is obtained; and performing laser irradiation on the graphene oxide / silver nanowire flexible thin film to sinter a silver nanowire contact point so as to obtain the laser reduction graphene oxide / silver nanowire composite conductive thin film. According to the method, the non-thermally dominant mechanism and the submicron spatial resolution of the ultrafast laser are utilized, the reduction degree of the graphene oxide is precisely regulated and controlled, the silver nanowire contact points are synchronously sintered, the contact resistance is remarkably reduced, and the method has remarkable advantages in the aspects of substrate compatibility and heterogeneous integration.

Description

Technical Field

[0001] This invention relates to the field of nanofilm material preparation technology, specifically to a graphene oxide / silver nanowire composite conductive film, its preparation method, and its application. Background Technology

[0002] With the rapid development of flexible electronic devices, wearable devices, and high-frequency communication technologies, transparent conductive films (TCFs), as core functional materials, are increasingly in demand in fields such as touch panels, flexible displays, smart window films, and 5G electromagnetic shielding. Traditional indium tin oxide (ITO) films, due to their high brittleness, scarcity of indium resources, and limitations in high-temperature, high-vacuum fabrication processes, cannot meet the mechanical stability and large-scale production requirements of flexible substrates. Therefore, silver nanowires (AgNWs), with their high conductivity, solution processability, and excellent flexibility, have become the mainstream material to replace ITO; however, their high contact resistance and susceptibility to oxidation severely restrict their practical applications. To overcome these bottlenecks, a composite system of graphene and AgNWs has emerged.

[0003] In the prior art, Chinese patent CN111029037A discloses a silver nanowire / graphene oxide composite transparent conductive film prepared by a solution method. This method improves the film's oxidation resistance and stability by coating the silver nanowire surface with a graphene oxide layer. However, the graphene oxide in this solution is an insulating material, making it difficult to effectively improve the electrical properties of the composite film. Chinese patent CN105869719A discloses a PET-graphene-silver nanowire composite transparent conductive film, its preparation method, and its applications. This method involves separately forming silver nanowires and graphene into films and then combining them to obtain the graphene-silver nanowire composite transparent conductive film. The graphene film is prepared using chemical vapor deposition (CVD), which requires etching it from a metal foil and then transferring it to the substrate surface. This process is complex and often causes mechanical damage to the graphene film, affecting the composite film's performance. Furthermore, while the graphene layer in this composite structure, positioned between the substrate and the silver nanowires, effectively reduces contact resistance, the metal nanowires still pose an exposure risk and may undergo localized oxidation with prolonged use, affecting stability. Therefore, existing applications of flexible transparent heating films using silver nanowires suffer from susceptibility to oxidation and insufficient stability.

[0004] The spin-coating method for the silver nanowire solution on the pretreated substrate is as follows: first, spin at a speed of 500 rpm to 700 rpm for 15 s to 25 s to make the silver nanowires evenly distributed on the substrate surface, and then spin-coat at a speed of 1500 rpm to 2000 rpm for 40 s to 60 s, and repeat spin-coating 1 to 5 times.

[0005] In a preferred embodiment of the present invention, the graphene oxide dispersion is prepared in the following manner: Graphite powder was added to concentrated sulfuric acid under ice bath conditions, then potassium permanganate was added, and the mixture was reacted in an oil bath. Water and hydrogen peroxide were then added, and the mixture was exfoliated after post-treatment to obtain graphene oxide, resulting in a graphene oxide dispersion. The concentration of the graphene oxide dispersion is 0.5 mg / mL to 3 mg / mL.

[0006] In a preferred embodiment of the present invention, the graphene oxide dispersion is spin-coated onto the surface of the silver nanowire flexible film by first rotating at a speed of 500 rpm to 700 rpm for 15 s to 25 s to make it uniformly distributed on the surface of the AgNWs / PET flexible film, and then spin-coating at a speed of 1500 rpm to 2000 rpm for 40 s to 60 s, and repeating the spin-coating once to five times.

[0007] In a preferred embodiment of the present invention, the substrate is a PET or PI substrate.

[0008] Another object of the present invention is to provide a graphene oxide / silver nanowire composite conductive film prepared by any of the above-described preparation methods.

[0009] A third objective of this invention is to provide an application of the aforementioned graphene oxide / silver nanowire composite conductive film in flexible electronic devices.

[0010] Compared with the prior art, the beneficial effects of the present invention are: 1. The graphene oxide / silver nanowire composite conductive film of the present invention is prepared by an ultrafast laser irradiation process, namely: a silver nanowire solution and a graphene oxide dispersion are sequentially coated on a substrate to obtain a flexible graphene oxide / silver nanowire film; the flexible graphene oxide / silver nanowire film is then subjected to laser irradiation to sinter the silver nanowire contact points, thereby obtaining a laser-reduced graphene oxide / silver nanowire composite conductive film; wherein the laser irradiation process conditions are as follows: defocusing amount 0.5 mm~1.5 mm, energy density 0.1 J / cm³. 2 ~0.35 J / cm 2 The laser scanning speed is 50 mm / s to 250 mm / s, and the laser scanning line spacing is 15 μm to 20 μm.

[0011] The pulse duration of the laser is less than or equal to 10. -12The term "second" refers to ultrafast lasers. Within the ultrafast laser irradiation area, nonlinear optical absorption occurs first. Due to the low binding energy between the oxygen-containing groups and carbon atoms in graphene oxide, the chemical bonds are easily broken, the oxygen-containing groups are removed, and graphene oxide is reduced to form reduced graphene oxide. During ultrafast laser treatment, excited free electrons form plasmons on the material surface, creating "hot spots" at specific locations in the nanowire structure. Unlike the distribution in a single structure, these plasmon hot spots accumulate at discontinuities in the geometric structure. The highest point of ultrafast laser energy input is located at the nanowire nodes, while other parts maintain low energy input, achieving effective junctions in the nanowire network structure. Therefore, this invention utilizes the non-thermal dominant mechanism and submicron-level spatial resolution of ultrafast lasers to precisely control the degree of graphene oxide reduction and simultaneously sinter silver nanowire contact points, significantly reducing contact resistance and thus solving the problems of easy oxidation and insufficient stability, laying the foundation for improving the electrical performance of the composite film. Furthermore, this invention prepares a transparent conductive film, which has significant advantages in substrate compatibility and heterogeneous integration.

[0012] 2. This invention adjusts multiple laser-related parameters. The parameters of the laser equipment used for laser irradiation are as follows: wavelength 343 nm~1030 nm, pulse repetition frequency 50 kHz~1000 kHz, laser spot diameter 20 μm~50 μm, and pulse duration 100 fs~15 ps. The laser irradiation process conditions are as follows: defocusing amount 0.5 mm~1.5 mm, and energy density 0.1 J / cm³. 2 ~0.35 J / cm 2 The laser scanning speed ranges from 50 mm / s to 250 mm / s, and the laser scanning line spacing ranges from 15 μm to 20 μm. Precise control of the reduction depth and functional group removal of graphene oxide transforms it into reduced graphene oxide with higher conductivity. Simultaneously, the "non-thermal" process of ultrafast laser irradiation enables in-situ interconnection of silver nanowire contact points (atomic diffusion on the nanowire surface forms molten solder joints), reducing contact resistance without damaging the nanowires. Under ultrafast laser irradiation, the reduced graphene oxide and silver nanowire network interpenetrate, promoting interfacial bonding. The two-dimensional sheet structure of the reduced graphene oxide provides a continuous conductive substrate for the silver nanowires, while the one-dimensional structure of the silver nanowires fills the gaps between the graphene sheets, forming a highly efficient conductive network. The synergistic effect of these two components gives the composite film excellent conductivity, optical properties, and high flexibility, making it suitable for high-performance flexible electronic devices.

[0013] 3. The "cold processing" characteristic of ultrafast laser in this invention can significantly reduce the damage of thermal effects to materials, avoid warping caused by high-temperature processing, and is compatible with flexible substrates such as PET and PI, making it suitable for the manufacture of flexible electronic devices; the reduced graphene oxide coating on the silver nanowires acts as a protective barrier, improving the environmental stability of the composite transparent conductive film; the one-step laser reduction of GO / AgNWs composite film has submicron-level processing precision and non-thermal damage characteristics, which is advantageous in fields requiring precise control of micro-nano structures (such as flexible microelectronics, biosensing, and high-frequency electromagnetic shielding).

[0014] 4. The ultrafast laser processing used in this invention has an extremely low heat-affected zone. The process is a non-thermal-dominated mechanism. The pulse duration of the ultrafast laser (femtosecond to picosecond level) is much shorter than the thermal diffusion time of the material. The energy acts directly on the material through nonlinear absorption such as multiphoton absorption, with almost no thermal diffusion. This avoids substrate damage and reduces material thermal degradation. The silver nanowires are less likely to melt or break due to thermal effects, and the reduction process of graphene oxide is more controllable, avoiding excessive carbonization.

[0015] 5. In the preparation method of this invention, ethylene glycol is used as a solvent, and FeCl3, PVP, and AgNO3 solutions are added to it. The mixture is heated to obtain a silver nanowire solution. The silver nanowire solution is then spin-coated onto a pretreated substrate to obtain a flexible silver nanowire film. Graphite powder is added to concentrated sulfuric acid under ice bath conditions, followed by the addition of potassium permanganate. The mixture is reacted in an oil bath, and then water and hydrogen peroxide are added. After post-treatment, the graphene oxide is exfoliated to obtain a graphene oxide dispersion. This graphene oxide dispersion is then spin-coated onto the surface of the flexible silver nanowire film to obtain a graphene oxide / silver nanowire flexible film. The graphene oxide / silver nanowire flexible film is then laser-irradiated to obtain a laser-reduced graphene oxide / silver nanowire composite conductive film. This is a complete process flow with industrial production application value. Attached Figure Description

[0016] Figure 1 The transmission spectra of the AgNWs / PET, GO / AgNWs / PET, and RGO / AgNWs / PET films prepared in Example 1 are in the visible light range. Figure 2 The sheet resistance of the AgNWs / PET, GO / AgNWs / PET, and RGO / AgNWs / PET films prepared in Example 1; Figure 3 The relative change in sheet resistance of the thin film prepared in Example 1 when placed in air at room temperature; Figure 4 The relative change in sheet resistance of the thin film prepared in Example 1 during placement in water; Figure 5This is a SEM image of the AgNWs / PET film prepared in Example 1; Figure 6 This is a SEM image of the GO / AgNWs / PET film prepared in Example 1; Figure 7 The image shows a SEM image of the RGO / AgNWs / PET film prepared in Example 1. Detailed Implementation

[0017] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0019] Example 1 A method for preparing a graphene oxide / silver nanowire composite conductive film includes the following steps: (1) Using ethylene glycol as a solvent, prepare a 1.0 mmol / L FeCl3 solution and a 0.1 mol / L AgNO3 solution. Add 25 mL of ethylene glycol, 0.23 g of PVP (polyvinylpyrrolidone), 3 mL of FeCl3 solution, and 10 mL of AgNO3 solution sequentially to the reaction vessel. Stir the solution until homogeneous, and then stir at 160 ℃ for 1 h before stopping. After air cooling to room temperature, separate and wash the reaction product to remove excess PVP and ethylene glycol, which are non-conductive and non-volatile substances. Ethylene glycol and other non-conductive and non-volatile substances are considered impurities.

[0020] The product was collected by centrifugation: the original product solution was diluted with anhydrous ethanol, centrifuged at 5000 rpm, the supernatant was removed, anhydrous ethanol was added to redisperse the product, and the product was centrifuged 3 times to obtain silver nanowires (AgNWs), which were stored in anhydrous ethanol for later use.

[0021] Before spin coating, the silver nanowire solution was diluted to 2 mg / mL with anhydrous ethanol solution to obtain the AgNWs solution.

[0022] (2) Add 3 g of graphite powder to 70 mL of concentrated sulfuric acid (commercially available 98% concentrated sulfuric acid) stirred in an ice bath. Under vigorous stirring, slowly add 9 g of potassium permanganate to lower the temperature of the suspension below 20 °C. Transfer the reaction system to a 40 °C oil bath and stir for 30 min. Then add 150 mL of water and stir at 95 °C for 15 min. Add another 500 mL of water, and then slowly add 15 mL of 30% hydrogen peroxide dropwise until the color of the solution changes from dark brown to yellow. Filter and wash with a 1:10 hydrochloric acid aqueous solution to remove metal ions. Dry the obtained solid in air and dilute to 600 mL to form an oxidized graphite ink dispersion. Finally, the graphene oxide dispersion was purified by dialysis with a molecular weight cutoff of 8000 Da for one week to remove the remaining metals. The resulting graphene oxide dispersion was diluted, allowed to stand overnight, and then sonicated for 30 min to exfoliate it into graphene oxide. The unexfoliated graphite was then removed by centrifugation at 3000 rpm for 40 min to obtain a graphene oxide dispersion. Before spin coating, the graphene oxide dispersion was diluted to 1 mg / mL to obtain a GO dispersion.

[0023] (3) The 20 mm × 20 mm PET substrate was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min, and then treated with nitrogen plasma etching device for 1 min to remove surface impurities and improve its hydrophilicity. It was then adsorbed on a benchtop spin coater to obtain the pretreated PET substrate.

[0024] (4) Take 10 μL of a 2 mg / mL AgNWs solution and drop it evenly onto the pretreated PET substrate. Prepare an AgNWs film using a two-step spin-coating method. First, spin-coat at 500 rpm for 20 s to distribute it evenly on the substrate surface, then spin-coat at 2000 rpm for 60 s to thin it. Repeat this process twice to obtain a two-layer AgNWs film. Dry the AgNWs film on a constant temperature heating platform at 60℃ for 2 min to obtain an AgNWs / PET flexible film.

[0025] (5) Take 5 μL of 1 mg / mL GO dispersion and spin-coat it at 500 rpm for 20 s to distribute it evenly on the surface of the AgNWs / PET flexible film. Then spin-coat it at 2000 rpm for 60 s to thin it. After that, dry it on a constant temperature heating platform at 60℃ for 2 min. Repeat this process twice to obtain a two-layer GO film, thus obtaining the GO / AgNWs / PET flexible film.

[0026] (6) The laser equipment used for laser irradiation is a high-power ultrafast fiber laser system. The laser equipment parameters are: wavelength 1030 nm, pulse repetition frequency (f) 50 kHz, laser spot diameter 20 μm, pulse duration 269 fs, maximum pulse energy 165 μJ, and beam quality (M 2 The laser pulse stability is no greater than 1% RMS (Resonance Momentum) and below 1.3. In this embodiment, the laser irradiation process conditions are as follows: the GO / AgNWs / PET film is adsorbed onto the sample stage, the laser is focused on the sample surface, a defocusing depth of 1 mm is set, and the sample is irradiated with a laser energy density of 0.2 J / cm². 2 The laser scanning speed was 100 mm / s and the laser scanning line spacing was 17 μm, resulting in a laser-reduced graphene oxide / silver nanowire composite transparent conductive film (RGO / AgNWs / PET).

[0027] Results Analysis The sheet resistance and transmittance of the obtained samples were tested to evaluate their optical and electrical properties.

[0028] Figure 1 The transmission spectra of the AgNWs / PET, GO / AgNWs / PET, and RGO / AgNWs / PET films prepared in Example 1 are shown in the visible light range. The average transmittance of the AgNWs / PET film in the visible light range (400-800 nm) is 91.26%. After spin-coating with GO dispersion, the average transmittance in the visible light range decreased to 88.7%, which is related to the brown color of the GO aqueous dispersion. After laser irradiation, the average transmittance in the visible light range decreased to 86.08%, which is related to the partial recovery of the π electron system in the GO layer, indicating that GO has been reduced to RGO.

[0029] Figure 2 The sheet resistance of the AgNWs / PET, GO / AgNWs / PET, and RGO / AgNWs / PET films prepared in Example 1 is shown. The sheet resistance of the laser-reduced graphene oxide / silver nanowire composite transparent conductive film is significantly reduced, indicating that the composite structure formed by the reduced graphene oxide and silver nanowires effectively improves the conductivity of the film while maintaining high transmittance. The results show that the RGO / AgNWs / PET film prepared in step (6) has excellent photoelectric properties. T =86.08%, R s =11.5 Ω / sq).

[0030] The samples were placed in air and water respectively, and the changes in the electrochemical performance of the samples were tested at regular intervals.

[0031] Figure 3The figure shows the relative change in sheet resistance of the film prepared in Example 1 when placed in air at room temperature. As can be seen from the figure, after 180 days, the relative change in sheet resistance of the AgNWs / PET film (∆) is... R s / R s0 The sheet resistance of the RGO / AgNWs / PET film reached 1.43, and was relatively stable (∆). R s / R s0 =0.12).

[0032] Figure 4 The figure shows the relative change in sheet resistance of the film prepared in Example 1 during water placement. As can be seen from the figure, after 48 hours of placement, the relative change in sheet resistance of the AgNWs / PET film (∆) is... R s / R s0 The sheet resistance of the RGO / AgNWs / PET film reached 2.48, and was relatively stable (∆). R s / R s0 =0.3), indicating that the environmental stability of the laser-reduced graphene oxide / silver nanowire composite transparent conductive film is significantly improved.

[0033] Figure 3 and Figure 4 This was used to evaluate whether the film was easily oxidized and whether it was stable. The results from these two figures show that the film of this invention is not easily oxidized in both air and water, exhibiting good stability.

[0034] Figure 5 The image shows the SEM image of the AgNWs / PET film prepared in step (4) of Example 1. It can be seen from the image that the AgNWs are dispersed on the substrate surface in a random arrangement and the contact between the nanowires is loose.

[0035] Figure 6 The image shows the SEM image of the GO / AgNWs / PET film prepared in step (5) of Example 1. It can be seen that the GO layer on the surface of AgNWs uniformly covers the silver nanowires and the substrate.

[0036] Figure 7The image shows a SEM image of the RGO / AgNWs / PET film prepared in step (6) of Example 1. After ultrafast laser irradiation, the GO in the GO / AgNWs / PET film is reduced to continuously conductive RGO, while the contact points of the silver nanowires (AgNWs) are effectively interconnected (welded). A crack-free, fully coated, and tight bond is achieved between the RGO layer and the silver nanowires, and the integrity of the film is not compromised. Furthermore, the transformation of the silver nanowire network from a three-dimensional structure to a two-dimensional structure, the increased contact area of ​​the nanoconnectors, the continuously conductive RGO layer, and the gapless tight bond between them significantly improve the electrical properties and environmental stability of the RGO / AgNWs / PET film.

[0037] in addition, Figure 2 The reduction of the resistance of the medium block, and Figure 7 The changes in the morphology and network structure of the silver nanowires can indirectly reflect the low contact resistance of the thin film obtained in Example 1 of this invention.

[0038] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. For example, in the inventive concept of this invention, "the parameters of the laser equipment used for laser irradiation are as follows: wavelength 343 nm~1030 nm, pulse repetition frequency 50 kHz~1000 kHz, laser spot diameter 20 μm~50 μm, pulse duration 100 fs~15 ps," and "the process conditions for laser irradiation are as follows: defocusing amount 0.5 mm~1.5 mm, energy density 0.1 J / cm²." 2 ~0.35 J / cm 2The laser scanning speed is 50 mm / s to 250 mm / s, and the laser scanning line spacing is 15 μm to 20 μm. The concentration of the silver nanowire solution is 0.5 mg / mL to 3 mg / mL. The concentration of the graphene oxide dispersion is 0.5 mg / mL to 3 mg / mL. The spin-coating method for the silver nanowire solution on the pretreated substrate is as follows: first, rotate at 500 rpm to 700 rpm for 15 s to 25 s to uniformly distribute the silver nanowires on the substrate surface, then spin-coat at 1500 rpm to 2000 rpm for 40 s to 60 s, repeating the spin-coating 1 to 5 times. The spin-coating method for the graphene oxide dispersion on the surface of the silver nanowire flexible film is as follows: first, rotate at 500 rpm to 700 rpm for 15 s to 25 s to uniformly distribute the graphene oxide dispersion on the surface of the AgNWs / PET flexible film, then spin-coat at 1500 rpm to 2000 rpm for 40 s to 60 s. The values ​​within the range of "s, repeated spin coating 1 to 5 times" can all be used to prepare graphene oxide / silver nanowire composite conductive films. Furthermore, all of these values ​​allow for precise control of the reduction degree of graphene oxide and simultaneous sintering of the silver nanowire contact points, significantly reducing contact resistance and thus solving the problems of easy oxidation and insufficient stability. This demonstrates significant advantages in substrate compatibility and heterogeneous integration. Several exemplary embodiments are provided below to support the above-mentioned value ranges.

[0039] Example 2 A method for preparing a graphene oxide / silver nanowire composite conductive film includes the following steps: (1) Using ethylene glycol as a solvent, prepare a 1.0 mmol / L FeCl3 solution and a 0.1 mol / L AgNO3 solution. Add 25 mL of ethylene glycol, 0.23 g of PVP (polyvinylpyrrolidone), 3 mL of FeCl3 solution, and 10 mL of AgNO3 solution sequentially to the reaction vessel. Stir the solution until homogeneous, and then stir at 160 ℃ for 1 h before stopping. After air cooling to room temperature, separate and wash the reaction product to remove excess PVP and ethylene glycol, which are non-conductive and non-volatile substances. Ethylene glycol and other non-conductive and non-volatile substances are considered impurities.

[0040] The product was collected by centrifugation: the original product solution was diluted with anhydrous ethanol, centrifuged at 5000 rpm, the supernatant was removed, anhydrous ethanol was added to redisperse the product, and the product was centrifuged 3 times to obtain silver nanowires (AgNWs), which were stored in anhydrous ethanol for later use.

[0041] Before spin coating, the silver nanowire solution was diluted to 0.5 mg / mL with anhydrous ethanol solution to obtain the AgNWs solution.

[0042] (2) Add 3 g of graphite powder to 70 mL of concentrated sulfuric acid (commercially available 98% concentrated sulfuric acid) stirred in an ice bath. Under vigorous stirring, slowly add 9 g of potassium permanganate to lower the temperature of the suspension below 20 °C. Transfer the reaction system to a 40 °C oil bath and stir for 30 min. Then add 150 mL of water and stir at 95 °C for 15 min. Add another 500 mL of water, and then slowly add 15 mL of 30% hydrogen peroxide dropwise until the color of the solution changes from dark brown to yellow. Filter and wash with a 1:10 hydrochloric acid aqueous solution to remove metal ions. Dry the obtained solid in air and dilute to 600 mL to form an oxidized graphite ink dispersion. Finally, the graphene oxide dispersion was purified by dialysis with a molecular weight cutoff of 8000 Da for one week to remove the remaining metals. The resulting graphene oxide dispersion was diluted, allowed to stand overnight, and then sonicated for 30 min to exfoliate it into graphene oxide. The unexfoliated graphite was then removed by centrifugation at 3000 rpm for 40 min to obtain a graphene oxide dispersion. Before spin coating, the graphene oxide dispersion was diluted to 0.5 mg / mL to obtain a GO dispersion.

[0043] (3) The 20 mm × 20 mm PET substrate was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min, and then treated with nitrogen plasma etching device for 1 min to remove surface impurities and improve its hydrophilicity. It was then adsorbed on a benchtop spin coater to obtain the pretreated PET substrate.

[0044] (4) Take 10 μL of a 0.5 mg / mL AgNWs solution and drop it evenly onto the pretreated PET substrate. Prepare AgNWs films using a two-step spin-coating method. First, spin-coat at 600 rpm for 15 s to distribute the AgNWs evenly on the substrate surface, and then spin-coat at 1800 rpm for 40 s to thin the film. Repeat this process 5 times to obtain 5 layers of AgNWs film. Dry the AgNWs film on a constant temperature heating platform at 60℃ for 2 min to obtain AgNWs / PET flexible film.

[0045] (5) Take 5 μL of 0.5 mg / mL GO dispersion and spin-coat it at 600 rpm for 15 s to distribute it evenly on the surface of the AgNWs / PET flexible film. Then spin-coat it at 1800 rpm for 40 s to thin it. After that, dry it on a constant temperature heating platform at 60℃ for 2 min. Repeat this process 5 times to obtain a 5-layer GO film, thus obtaining the GO / AgNWs / PET flexible film.

[0046] (6) The laser equipment used for laser irradiation is a high-power ultrafast fiber laser system. The laser equipment parameters are: wavelength 343 nm, pulse repetition frequency (f) 50 kHz, laser spot diameter 20 μm, and pulse duration 500 fs. In this embodiment, the laser irradiation process conditions are as follows: the GO / AgNWs / PET film is adsorbed onto the sample stage, the laser is focused on the sample surface, a defocusing amount of 0.5 mm is set, and the sample is irradiated. The laser energy density is 0.1 J / cm². 2 The laser scanning speed was 50 mm / s and the laser scanning line spacing was 15 μm, resulting in a laser-reduced graphene oxide / silver nanowire composite transparent conductive film (RGO / AgNWs / PET).

[0047] Example 3 A method for preparing a graphene oxide / silver nanowire composite conductive film includes the following steps: (1) Using ethylene glycol as a solvent, prepare a 1.0 mmol / L FeCl3 solution and a 0.1 mol / L AgNO3 solution. Add 25 mL of ethylene glycol, 0.23 g of PVP (polyvinylpyrrolidone), 3 mL of FeCl3 solution, and 10 mL of AgNO3 solution sequentially to the reaction vessel. Stir the solution until homogeneous, and then stir at 160 ℃ for 1 h before stopping. After air cooling to room temperature, separate and wash the reaction product to remove excess PVP and ethylene glycol, which are non-conductive and non-volatile substances. Ethylene glycol and other non-conductive and non-volatile substances are considered impurities.

[0048] The product was collected by centrifugation: the original product solution was diluted with anhydrous ethanol, centrifuged at 5000 rpm, the supernatant was removed, anhydrous ethanol was added to redisperse the product, and the product was centrifuged 3 times to obtain silver nanowires (AgNWs), which were stored in anhydrous ethanol for later use.

[0049] Before spin coating, the silver nanowire solution was diluted to 3 mg / mL with anhydrous ethanol solution to obtain the AgNWs solution.

[0050] (2) Add 3 g of graphite powder to 70 mL of concentrated sulfuric acid (commercially available 98% concentrated sulfuric acid) stirred in an ice bath. Under vigorous stirring, slowly add 9 g of potassium permanganate to lower the temperature of the suspension below 20 °C. Transfer the reaction system to a 40 °C oil bath and stir for 30 min. Then add 150 mL of water and stir at 95 °C for 15 min. Add another 500 mL of water, and then slowly add 15 mL of 30% hydrogen peroxide dropwise until the color of the solution changes from dark brown to yellow. Filter and wash with a 1:10 hydrochloric acid aqueous solution to remove metal ions. Dry the obtained solid in air and dilute to 600 mL to form an oxidized graphite ink dispersion. Finally, the graphene oxide dispersion was purified by dialysis with a molecular weight cutoff of 8000 Da for one week to remove the remaining metals. The resulting graphene oxide dispersion was diluted, allowed to stand overnight, and then sonicated for 30 min to exfoliate it into graphene oxide. The unexfoliated graphite was then removed by centrifugation at 3000 rpm for 40 min to obtain a graphene oxide dispersion. Before spin coating, the graphene oxide dispersion was diluted to 3 mg / mL to obtain a GO dispersion.

[0051] (3) The 20 mm × 20 mm PET substrate was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min, and then treated with nitrogen plasma etching device for 1 min to remove surface impurities and improve its hydrophilicity. It was then adsorbed on a benchtop spin coater to obtain the pretreated PET substrate.

[0052] (4) Take 10 μL of a 3 mg / mL AgNWs solution and drop it evenly onto the pretreated PET substrate. Prepare an AgNWs film using a two-step spin-coating method. First, spin-coat at 700 rpm for 25 s to distribute it evenly on the substrate surface, and then spin-coat at 1500 rpm for 40 s to thin it. Repeat this process once to obtain a single-layer AgNWs film. Dry the AgNWs film on a constant temperature heating platform at 60℃ for 2 min to obtain an AgNWs / PET flexible film.

[0053] (5) Take 5 μL of 3 mg / mL GO dispersion and spin-coat it at 700 rpm for 25 s to distribute it evenly on the surface of the AgNWs / PET flexible film. Then spin-coat it at 1500 rpm for 40 s to thin it. After that, dry it on a constant temperature heating platform at 60℃ for 2 min. Repeat this process once to obtain a single-layer GO film, thus obtaining the GO / AgNWs / PET flexible film.

[0054] (6) The laser equipment used for laser irradiation is a high-power ultrafast fiber laser system. The laser equipment parameters are: wavelength 532 nm, pulse repetition frequency (f) 1000 kHz, laser spot diameter 50 μm, and pulse duration 15 ps. In this embodiment, the laser irradiation process conditions are as follows: the GO / AgNWs / PET film is adsorbed onto the sample stage, the laser is focused on the sample surface, a defocusing amount of 1.5 mm is set, and the sample is irradiated. The laser energy density is 0.35 J / cm². 2 The laser scanning speed was 250 mm / s and the laser scanning line spacing was 20 μm, resulting in a laser-reduced graphene oxide / silver nanowire composite transparent conductive film (RGO / AgNWs / PET).

[0055] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0056] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A graphene oxide / silver nanowire composite conductive film, characterized in that, It was prepared according to the following method: A flexible graphene oxide / silver nanowire film was obtained by sequentially coating a silver nanowire solution and a graphene oxide dispersion on a substrate. The flexible graphene oxide / silver nanowire film was subjected to laser irradiation to sinter the silver nanowire contact points, thereby obtaining a laser-reduced graphene oxide / silver nanowire composite conductive film. The laser irradiation process conditions are as follows: defocusing amount 0.5 mm~1.5 mm, energy density 0.1 J / cm³. 2 ~0.35J / cm 2 The laser scanning speed is 50 mm / s to 250 mm / s, and the laser scanning line spacing is 15 μm to 20 μm. The pulse duration of the laser is less than or equal to 10. -12 Second.

2. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 1, characterized in that, Includes the following steps: The silver nanowire solution was spin-coated onto the pretreated substrate to obtain a flexible silver nanowire film. The graphene oxide dispersion was spin-coated onto the surface of the flexible silver nanowire film to obtain a graphene oxide / silver nanowire flexible film. The flexible graphene oxide / silver nanowire film was subjected to laser irradiation to obtain a laser-reduced graphene oxide / silver nanowire composite conductive film. The laser irradiation process conditions are as follows: defocusing amount 0.5 mm~1.5 mm, energy density 0.1 J / cm³. 2 ~0.35J / cm 2 The laser scanning speed is 50 mm / s to 250 mm / s, and the laser scanning line spacing is 15 μm to 20 μm; the pulse duration of the laser is 100 fs to 15 ps.

3. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 2, characterized in that, The parameters of the laser equipment used for laser irradiation are as follows: wavelength 343 nm~1030 nm, pulse repetition frequency 50 kHz~1000 kHz, and laser spot diameter 20 μm~50 μm.

4. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 2, characterized in that, The silver nanowire solution was prepared as follows: Using ethylene glycol as a solvent, FeCl3, PVP, and AgNO3 solutions were added, and the mixture was heated to react, resulting in a silver nanowire solution. The concentration of the silver nanowire solution ranges from 0.5 mg / mL to 3 mg / mL.

5. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 4, characterized in that, The spin-coating method for the silver nanowire solution on the pretreated substrate is as follows: first, spin at a speed of 500 rpm to 700 rpm for 15 s to 25 s to make the silver nanowires evenly distributed on the substrate surface, and then spin-coat at a speed of 1500 rpm to 2000 rpm for 40 s to 60 s, and repeat spin-coating 1 to 5 times.

6. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 2, characterized in that, The graphene oxide dispersion was prepared as follows: Graphite powder was added to concentrated sulfuric acid under ice bath conditions, then potassium permanganate was added, and the mixture was reacted in an oil bath. Water and hydrogen peroxide were then added, and the mixture was exfoliated after post-treatment to obtain graphene oxide, resulting in a graphene oxide dispersion. The concentration of the graphene oxide dispersion is 0.5 mg / mL to 3 mg / mL.

7. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 6, characterized in that, The spin-coating method for graphene oxide dispersion on the surface of silver nanowire flexible film is as follows: first, spin at a speed of 500 rpm to 700 rpm for 15 s to 25 s to make it uniformly distributed on the surface of the AgNWs / PET flexible film, and then spin-coat at a speed of 1500 rpm to 2000 rpm for 40 s to 60 s, and repeat spin-coating 1 to 5 times.

8. The method for preparing the graphene oxide / silver nanowire composite conductive film according to claim 2, characterized in that, The substrate is a PET or PI substrate.

9. The application of the graphene oxide / silver nanowire composite conductive film according to claim 1 in the fabrication of flexible electronic devices.

10. The application according to claim 9, characterized in that, Graphene oxide / silver nanowire composite conductive films are used in flexible electronic devices, including flexible transparent electrodes, flexible sensors, or flexible transparent heating films.

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