A transparent metal network electrode based on leaf vein structure and a preparation method and application thereof

Abstract

The application discloses a transparent metal network electrode based on leaf vein structure and a preparation method and application thereof. Firstly, the mesophyll of a natural plant leaf is removed through chemical treatment, and a fractal net-shaped leaf vein cellulose skeleton is reserved; then the leaf vein is immersed in a catalyst solution to load a catalytic active site; finally, the leaf vein is placed in a chemical plating solution to deposit metal, so that a flexible transparent network metal electrode is obtained. The high-pore topological structure and excellent flexibility of the natural leaf vein are ingeniously utilized, so that the limitation between the light transmittance and the thickness of traditional materials is broken without expensive micro-nano processing equipment, the balance between high light transmittance and ultra-low surface resistance is realized, and the prepared electrode has excellent mechanical stability and high electromagnetic shielding efficiency, and has a wide application prospect in electromagnetic protection of flexible electronics, wearable devices and transparent photoelectric windows.

Description

Technical Field

[0001] This invention belongs to the field of flexible electromagnetic shielding materials technology, and relates to a transparent metal network electrode based on leaf vein structure, its preparation method and application. Background Technology

[0002] With the explosive growth of wireless communication, the Internet of Things (IoT), and intelligent devices, electromagnetic pollution and interference (EMI) have become key challenges restricting the stable operation of modern electronic systems. This is especially true in scenarios where these devices function as optical windows, such as smartphone touchscreens, automotive windshields, and smart building windows. Developing transparent electromagnetic shielding materials that combine high light transmittance with excellent shielding effectiveness is therefore particularly urgent. Currently, mainstream technologies in this field still rely on traditional transparent conductive materials such as indium tin oxide (ITO). Although ITO possesses good optoelectronic properties, its high raw material costs, inherent brittleness, and complex vacuum deposition process make it difficult to meet the stringent requirements of next-generation flexible electronic devices that can be bent and folded. Meanwhile, while traditional metal films can provide excellent electromagnetic shielding, they often severely sacrifice transparency due to excessive light absorption and reflection, resulting in a persistent contradiction between high shielding and high light transmittance. To overcome this bottleneck, in recent years, the academic and industrial communities have turned their attention to leaf vein structures, which are widely found in nature. These natural fractal networks, with their multi-level branching topology, extremely high specific surface area, and excellent mechanical flexibility, have provided inspiration for constructing novel conductive frameworks.

[0003] However, despite the great potential shown by biomimetic leaf vein-based transparent electrodes, existing research still faces serious technical challenges in moving towards practical applications: First, performance synergy optimization is difficult, and existing solutions struggle to simultaneously achieve ultra-low surface resistivity, high visible light transmittance, and high electromagnetic shielding effectiveness (SE), often resulting in trade-offs; second, the flexibility mechanism is still imperfect, and some composite structures are prone to conductive network breakage under repeated bending, failing to fully utilize the natural flexibility of leaf veins; more critically, the trade-off between thickness and light transmittance remains significant, and increasing the metal load or film thickness in pursuit of higher shielding effectiveness often comes at the cost of transparency, and an effective way to overcome this physical bottleneck has not yet been found. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a transparent metal network electrode based on leaf vein structure, its preparation method, and its application. This solves the technical problems faced by existing flexible electromagnetic shielding materials, such as the difficulty in synergistically optimizing ultra-low surface resistance, high light transmittance, and high electromagnetic shielding effectiveness, insufficient flexibility and durability, and the inherent trade-off between increasing thickness and maintaining light transmittance.

[0005] This invention is achieved through the following technical solution: A method for fabricating a transparent metal network electrode based on a leaf vein structure includes the following steps: S1: Remove the leaf mesophyll from the plant leaves to obtain the leaf veins; S2: Immerse the leaf vein in a chemical plating catalyst solution to load the surface of the leaf vein with a catalyst, thereby obtaining a leaf vein loaded with a catalyst. S3: Immerse the leaf vein loaded with catalyst into the catalyst activation solution and carry out a reaction to obtain a leaf vein substrate loaded with metal catalyst particles. S4: The leaf vein substrate loaded with metal catalyst particles is immersed in a chemical metal plating solution to carry out a secondary reaction, thereby obtaining the transparent metal network electrode based on the leaf vein structure.

[0006] Preferably, step S1 specifically involves: placing the plant leaves in an aqueous solution containing NaOH and Na2CO3 for heating treatment, then adding H2O2 for treatment, removing the leaf mesophyll tissue by ultrasonication or water washing, and finally bleaching and drying with H2O2 aqueous solution again.

[0007] Preferably, the plant leaves include one of the following: Bodhi leaf, Magnolia leaf, Poplar leaf, and Rubber leaf.

[0008] Preferably, the chemical plating catalyst is ammonium tetrachloropalladate or palladium nitrate, with a concentration of 50~100 mmol / L.

[0009] Preferably, the catalyst activation solution is dimethylaminoborane or stannous chloride, with a concentration of 0.5~1 g / L.

[0010] Preferably, the reaction temperature of the primary reaction is 20~30 ℃ and the reaction time is 30~60 s.

[0011] Preferably, the electroless metal plating solution is one of the following: electroless copper plating solution, electroless nickel plating solution, electroless silver plating solution, electroless gold plating solution, electroless cobalt plating solution, electroless palladium plating solution, electroless lead plating solution, electroless tin plating solution, electroless zinc oxide plating solution, and electroless iron oxide plating solution.

[0012] Preferably, the reaction temperature of the secondary reaction is 30~100 ℃ and the reaction time is 10~200 min.

[0013] A transparent metal network electrode based on leaf vein structure is prepared by the above method.

[0014] The above-mentioned application of a transparent metal network electrode based on a leaf vein structure in the field of electromagnetic shielding.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for fabricating a transparent metal network electrode based on a leaf vein structure. This method overcomes the performance bottleneck of traditional flexible shielding materials by synergistically combining a biomimetic leaf vein hierarchical network structure with a chemical plating process. First, a high-efficiency electron transport channel is constructed using a hierarchical network of micron-sized main veins and nano-sized lateral veins formed by the self-assembly of natural leaf veins. This achieves ultra-low surface resistance with extremely low metal loading, avoiding the decrease in transmittance caused by traditional thick-film deposition and fundamentally resolving the inherent trade-off between thickness and transmittance. Second, a gradient growth strategy of catalyst pre-loading, activation, and chemical plating ensures that the metal layer grows uniformly and densely only along the leaf vein skeleton, forming a high aspect ratio conductive pathway. This significantly improves the conductivity per unit area and electromagnetic reflection / absorption efficiency, achieving synergistic optimization of high transmittance and strong shielding effectiveness. Simultaneously, the inherent bioflexibility of the leaf vein substrate and the strong interfacial bonding force of the chemically plated metal layer endow the electrode with excellent bending resistance and fatigue resistance, overcoming the defects of traditional metal meshes such as easy breakage and insufficient durability. This method eliminates the need for complex photolithography or high-temperature processes, enabling the low-cost fabrication of integrated electrodes that combine ultra-thinness, high transparency, low resistance, strong shielding, and high flexibility. It successfully breaks through the constraints of existing technologies on multiple performance indicators, providing an ideal electromagnetic shielding solution for flexible electronic devices.

[0016] Further, step S1 specifically involves: placing the plant leaves in an aqueous solution containing NaOH and Na2CO3 for heating treatment, followed by treatment with H2O2, removing the mesophyll tissue by ultrasonication or water washing, and finally bleaching and drying with an H2O2 aqueous solution again. Furthermore, the plant leaves include one of the following: Bodhi leaf, Magnolia leaf, Poplar leaf, and Rubber leaf, effectively expanding the universality of this solution.

[0017] Furthermore, the electroless plating catalyst is ammonium tetrachloropalladate or palladium nitrate, with a concentration of 50-100 mmol / L. Ammonium tetrachloropalladate and palladium nitrate can effectively initiate the subsequent chemical deposition reaction of the metal. A suitable concentration range can ensure that the catalyst forms a uniform and appropriately active catalytic layer on the leaf vein surface. If the concentration is too low, the catalytic activity is insufficient, resulting in uneven metal deposition and ineffective deposition; if the concentration is too high, it will affect the mechanical properties of the leaf vein and the quality of subsequent metal deposition.

[0018] Furthermore, the catalyst activation solution is dimethylaminoborane or stannous chloride, with a concentration of 0.5~1 g / L. Both dimethylaminoborane and stannous chloride can activate the chemical plating catalyst supported on the leaf veins, enhancing its catalytic activity. A suitable concentration range ensures effective activation, allowing more active sites to form on the catalyst surface and improving the efficiency and uniformity of subsequent metal deposition. Too low a concentration results in insufficient activation, failing to effectively enhance catalyst activity; too high a concentration leads to over-activation, affecting the quality of metal deposition.

[0019] Furthermore, the reaction temperature for the first reaction is 20-30 °C, and the reaction time is 30-60 s. A suitable reaction time ensures that the catalyst and activation solution react fully, allowing the catalyst to reach its optimal activation state and providing favorable conditions for subsequent metal deposition. A suitable reaction temperature can accelerate the reaction rate and improve activation efficiency, while avoiding damage to the leaf veins and catalyst due to excessively high or low temperatures, thus ensuring the stability and controllability of the activation process.

[0020] Furthermore, the electroless metal plating solution is one of the following: electroless copper plating solution, electroless nickel plating solution, electroless silver plating solution, electroless gold plating solution, electroless cobalt plating solution, electroless palladium plating solution, electroless lead plating solution, electroless tin plating solution, electroless zinc oxide plating solution, and electroless iron oxide plating solution. The reaction temperature of the secondary reaction is 30~100 ℃, and the reaction time is 10~200 min. Different metal deposition reactions require different time and temperature conditions to ensure the full progress of the reaction and the quality of metal deposition. A suitable time and temperature range can control the rate and thickness of metal deposition, so that the metal layer is deposited uniformly and densely on the surface of the leaf vein, improving the performance of the composite material. If the time is too short or the temperature is too low, the metal deposition will be incomplete; if the time is too long or the temperature is too high, it may lead to an excessively thick and uneven metal layer, or even affect the structure and performance of the leaf vein. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 These are scanning electron microscope images and energy scattering spectra of the copper / leaf vein composite material prepared in Example 1 of this invention at different magnifications. Figure 2 The images shown are scanning electron microscope images and energy scattering spectra of the leaf veins deposited with metallic nickel obtained in Example 2 of the present invention at different magnifications. Figure 3 The images shown are scanning electron microscope images and energy scattering spectra of the surface of the leaf veins deposited with metallic silver obtained in Example 3 of the present invention at different magnifications. Figure 4 The images shown are scanning electron microscope images and energy scattering spectra of the leaf veins deposited with metallic gold obtained in Example 4 of this invention at different magnifications. Figure 5 These are scanning electron microscope images and energy scattering spectra of the leaf veins deposited with metallic cobalt obtained in Example 5 of the present invention at different magnifications. Figure 6 The images shown are scanning electron microscope images and energy scattering spectra of the surface of the leaf veins deposited with palladium obtained in Example 6 of the present invention at different magnifications. Figure 7 The images shown are scanning electron microscope images and energy scattering spectra of the surface of leaf veins deposited with metallic lead obtained in Example 7 of the present invention at different magnifications. Figure 8 The images shown are scanning electron microscope images and energy scattering spectra of the leaf veins deposited with metallic tin obtained in Example 8 of the present invention at different magnifications. Figure 9 The images shown are scanning electron microscope images and energy scattering spectra of the leaf veins deposited with zinc oxide metal oxide obtained in Example 9 of the present invention at different magnifications. Figure 10 This is an X-ray diffraction pattern of leaf veins deposited with metallic copper obtained in Example 1 of the present invention; Figure 11 This is an X-ray diffraction pattern of leaf veins deposited with metallic nickel obtained in Example 2 of the present invention; Figure 12 This is an X-ray diffraction pattern of the leaf veins deposited with metallic silver obtained in Example 3 of the present invention; Figure 13 This is an X-ray diffraction pattern of leaf veins deposited with metallic gold obtained in Example 4 of the present invention. Figure 14 This is an X-ray diffraction pattern of leaf veins deposited with metallic cobalt obtained in Example 5 of the present invention; Figure 15 This is an X-ray diffraction pattern of the leaf veins deposited with metallic palladium obtained in Example 6 of the present invention; Figure 16 This is an X-ray diffraction pattern of leaf veins deposited with metallic lead obtained in Example 7 of the present invention; Figure 17 This is an X-ray diffraction pattern of leaf veins deposited with metallic tin obtained in Example 8 of the present invention; Figure 18This is an X-ray diffraction pattern of leaf veins deposited with zinc oxide metal oxide obtained in Example 9 of the present invention. Figure 19 These are macroscopic photographs of leaf vein electrodes deposited with different metals or metal oxides, prepared in Examples 1-9 of this invention. Figure 20 Photographs of electrodes made by depositing copper and nickel on the natural leaf veins of four different plants (from left to right: Bodhi, Magnolia, Poplar, and Rubber). The first row shows the original leaf, the second row shows the extracted leaf vein structure, the third row shows the electroless copper plating, and the fourth row shows the electroless nickel plating. Figure 21 The hysteresis loops of the biomimetic leaf vein electrodes prepared in Embodiments 2 and 5 of the present invention; Figure 22 The flexibility test results are for the leaf vein copper electrode deposited for 60 min, prepared in Example 1 of this invention. Figure 23 The mechanical stability test results are for the leaf vein copper electrodes prepared in Examples 1, 10, 11 and 12 of this invention. Figure 24 The broadband electromagnetic shielding performance of the copper network electrodes prepared in Embodiments 1, 10, 11, and 12 of this invention is shown, wherein (ac) represents the SE of the copper network electrode in the X-band (8.2-12.4 GHz). T SE R with SE A ; (df) SE of copper network electrodes in the Ku band (12-18 GHz) T SE R with SE A ; Figure 25 The broadband electromagnetic shielding performance of different metal network electrodes prepared in Examples 1-8 of this invention is shown, wherein (ac) represents the SE of the copper network electrode in the X-band (8.2-12.4 GHz). T SE R with SE A ; (df) SE of copper network electrodes in the Ku band (12-18 GHz) T SE R with SE A ; Figure 26 This describes the broadband electromagnetic shielding performance of the copper network electrodes prepared in Embodiments 1 and 13-15 of the present invention, wherein (ac) represents the SE of the copper network electrode in the X-band (8.2-12.4 GHz). T SE R with SE A; (df) represents the SE of the copper network electrode in the Ku band (12-18 GHz). T SE R with SE A ; Figure 27 The shielding effect of the leaf vein copper electrode prepared in Embodiment 1 of the present invention on high-frequency WiFi signals is shown. (ab) is the monitoring interface of 2.4 GHz and 5 GHz WiFi signal strength received by the mobile phone in real time when the window is open; (cd) is the 2.4 GHz and 5 GHz WiFi signal strength received by the mobile phone in real time after the window is covered by the biomimetic leaf vein electrode. Figure 28 The shielding effect of the leaf vein copper electrode prepared in Embodiment 1 of the present invention on the cellular network call signal of a smartphone is shown in the figure. In the figure, a is when the window of the aluminum foil shielding box is open and b is when the window is completely covered by the biomimetic leaf vein network electrode. Figure 29 The shielding effect of the leaf vein copper electrode prepared in Embodiment 1 of the present invention on near-field wireless data transmission signals is shown in the figure. In the figure, a is the equivalent circuit diagram of the wireless transmission demonstration system, b is the brightness of the LED indicator when no shield is placed, and c is the brightness of the LED indicator after inserting the biomimetic metal network electrode between the coils. Figure 30 This is a real-world demonstration of how the leaf vein copper electrode prepared in Embodiment 1 of the present invention shields commercial wireless charging signals. In the embodiment, a is the state when the smartphone is placed on the wireless charging base and charging normally without obstruction, and b is the state when charging is performed after the biomimetic leaf vein electrode is inserted between the phone and the charging base. Detailed Implementation

[0023] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0024] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0025] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0026] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0027] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0028] This invention provides a method for fabricating a transparent metal network electrode based on a leaf vein structure, comprising the following steps: S1: Remove the leaf mesophyll from the plant leaves to obtain the leaf veins; Specifically, the step involves treating natural plant leaves with chemical reagents to remove the leaf mesophyll, i.e., non-fibrous components, leaving only the pure natural leaf vein structure with branching characteristics. The steps for removing leaf mesophyll specifically include: placing the plant leaves in an aqueous solution containing NaOH and Na2CO3 for heating treatment, then adding H2O2 for treatment, removing the leaf mesophyll tissue by ultrasonication or water washing, and finally bleaching and drying with H2O2 aqueous solution again.

[0029] More specifically, the step of removing the mesophyll involves: placing the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heating it to 90 °C for 30 min; subsequently, adding H2O2 for further treatment, and removing the mesophyll tissue by ultrasonication or washing with water; finally, bleaching again with H2O2 aqueous solution and drying. The concentration of NaOH is 100 g / L, and the concentration of Na2CO3 is 50 g / L. Plant leaves include one of the following: Bodhi leaf, Magnolia leaf, Poplar leaf, and Rubber leaf. This method has strong applicability. S2: Immerse the leaf vein in a chemical plating catalyst solution to load the surface of the leaf vein with a catalyst, thereby obtaining a leaf vein loaded with a catalyst. The electroless plating catalyst is ammonium tetrachloropalladium or palladium nitrate, preferably ammonium tetrachloropalladium; the concentration is 50~100 mmol / L.

[0030] S3: Immerse the leaf vein loaded with catalyst into the catalyst activation solution and carry out a reaction to obtain a leaf vein substrate loaded with metal catalyst particles. The catalyst activation solution is dimethylaminoborane or stannous chloride, preferably dimethylaminoborane, with a concentration of 0.5~1g / L.

[0031] The reaction temperature of the first reaction is 20~30 ℃ and the reaction time is 30~60 s. During the reaction, the catalyst activation solution reduces the metal in the chemical plating catalyst into metal particles with high catalytic activity. S4: The leaf vein substrate loaded with metal catalyst particles is immersed in a chemical metal plating solution to carry out a secondary reaction, thereby obtaining the transparent metal network electrode based on the leaf vein structure.

[0032] The electroless metal plating solution is one of the following: electroless copper plating solution, electroless nickel plating solution, electroless silver plating solution, electroless gold plating solution, electroless cobalt plating solution, electroless palladium plating solution, electroless lead plating solution, electroless tin plating solution, electroless zinc oxide plating solution, and electroless iron oxide plating solution.

[0033] The electroless copper plating solution comprises copper sulfate pentahydrate (1-10 g / L), potassium sodium tartrate (1-15 g / L), disodium ethylenediaminetetraacetate (1-20 g / L), sodium hydroxide (1-15 g / L), 2,2-bipyridine (0.01-1 g / L), potassium ferrocyanide (0.01-1 g / L), and formaldehyde (1-20 mL / L). The reaction temperature is 25-40 °C, and the reaction time is 10-120 min.

[0034] The electroless nickel plating solution comprises nickel sulfate hexahydrate (20-50 g / L), sodium citrate (16-30 g / L), lactic acid (8-15 g / L), and dimethylaminoborane (0.2-1 g / L). The reaction temperature is 30-60 °C, the reaction time is 100-180 min, and the pH value is 7.5-10 (adjusted with ammonia).

[0035] The electroless silver plating solution comprises solution A: silver nitrate (30-60 g / L), solution B: sodium hydroxide (0.5-2 g / L), ammonia (50-100 mL / L), and solution C: tartaric acid (4-10 g / L), glucose (20-40 g / L), and ethanol (100-200 mL / L). The liquid volume ratio of solutions A, B, and C is 1:1:2, the reaction temperature is 40-80 °C, and the reaction time is 40-120 min.

[0036] The electroless gold plating solution comprises chloroauric acid (3-5 g / L), sodium hydroxide (0.4-1 g / L), hydroxylamine hydrochloride (6-20 g / L), disodium hydrogen phosphate (11-20 g / L), sodium thiosulfate pentahydrate (16-25 g / L), and sodium sulfite (40-50 g / L). The activation time is 30-60 s, the reaction temperature is 50-80 ℃, the reaction time is 40-120 min, and the pH value is 7.5-10 (adjusted with ammonia).

[0037] The electroless cobalt plating solution comprises cobalt sulfate (6-10 g / L), sodium hypophosphite (2.5-5 g / L), sodium citrate (12-20 g / L), and boric acid (1-5 g / L). The reaction temperature is 50-100 °C, the reaction time is 100-200 min, and the pH value is 8-11 (adjusted with sodium hydroxide).

[0038] The electroless palladium plating solution comprises palladium chloride (1~2 g / L), hydrochloric acid (1~5 ml / L), sodium hypophosphite (10~20 g / L), and ammonium chloride (10~20 g / L), with a pH value of 8~9 (the pH is adjusted with ammonia).

[0039] The electroless lead plating solution includes lead chloride (20~30 g / L), disodium ethylenediaminetetraacetate (30~60 g / L), sodium citrate (30~60 g / L), ammonium triacetate (38~76 g / L), and titanium trichloride (4.6~7.7 g / L).

[0040] In addition, during immersion in the electroless lead plating solution, the solution needs to be replaced after a period of reaction. After several replacements, metallic lead gradually coats the leaf vein fibers, forming a dense thin layer of lead metal. The reaction temperature is 50-80 ℃, the reaction time is 20-40 min, the number of replacements is 3-6, and the pH value is 8-10 (adjusted with ammonia).

[0041] The electroless tin plating solution comprises tin chloride (7.6~15.2 g / L), disodium ethylenediaminetetraacetate (15~30 g / L), sodium citrate (51~102 g / L), titanium trichloride (3~6 g / L), and aminetriacetic acid (20~40 g / L). The reaction temperature is 40~80 ℃, the reaction time is 100~200 min, and the pH value is 8~11 (adjusted with ammonia).

[0042] The electroless zinc oxide plating solution comprises zinc nitrate (4~9.47 g / L) and dimethylaminoborane (1~2.95 g / L). The reaction temperature is 50~80 ℃, and the reaction time is 80~120 min.

[0043] In summary, the reaction temperature of the secondary reaction is 30~100 ℃, and the reaction time is 10~200 min, preferably 15~60 min, more preferably 60 min. In this step, the leaf veins loaded with metal particles are immersed in the electroless metal plating solution. After a period of reaction, the metal in the electroless metal plating solution gradually coats the leaf vein fibers, forming a dense metal thin layer.

[0044] In addition, the present invention also discloses a transparent metal network electrode based on a leaf vein structure prepared by the above method.

[0045] The present invention also discloses the application of the above-mentioned transparent metal network electrode based on leaf vein structure in the field of electromagnetic shielding.

[0046] This invention proposes an innovative biomimetic leaf vein surface metallization process. By directly immersing the natural leaf vein skeleton (after removing the leaf mesophyll) in a catalyst solution, followed by chemical plating, a variety of metals are successfully deposited uniformly and densely on a complex three-dimensional leaf vein network, bringing a new breakthrough to the field of flexible transparent electromagnetic shielding materials. This method has significant cost and process advantages, completely avoiding the dependence on expensive micro-nano lithography equipment and high-vacuum deposition processes required by traditional transparent electrodes (such as ITO or metal meshes), and greatly reducing the overall fabrication cost.

[0047] In terms of process flow, this invention achieves significant simplification. After stripping non-cellulose components using basic chemical reagents, the abundant oxygen-containing functional groups, such as hydroxyl and carboxyl groups, inherent in the exposed leaf vein cellulose directly interact with catalyst ions (such as palladium ions) through strong coordination and electrostatic adsorption, firmly anchoring the catalytically active sites onto the multi-branched substrate. This mechanism cleverly eliminates the cumbersome and environmentally unfriendly pretreatment steps such as surface roughening or grafting modification in the traditional flexible polymer substrate metallization process, significantly shortening the production cycle and greatly improving process reproducibility and production efficiency.

[0048] Meanwhile, this invention exhibits remarkable material versatility and structural tunability. Without the need for complex metal precursor conductive inks, metal deposition with different electromagnetic properties, such as copper and nickel, can be easily achieved simply by changing the chemical plating solution composition or adjusting the deposition time. This greatly facilitates the preparation of leaf vein metal composite materials that incorporate different shielding mechanisms, such as "reflection-dominant" or "absorption-dominant." In terms of performance, the chemically deposited metal layer exhibits extremely strong adhesion to the cellulose substrate and excellent interfacial stability. Thanks to the superior fractal topology and flexibility of natural leaf veins, the formed transparent network metal electrode demonstrates excellent mechanical stability, maintaining ultra-low sheet resistance and a continuous conductive network even after repeated bending at extremely small radii of curvature. This characteristic perfectly meets the stringent requirements of next-generation flexible electronics for both optical transmittance and mechanical durability.

[0049] Furthermore, this process demonstrates irreplaceable application value in areas such as broadband electromagnetic protection and green flexible electronics. Its three-dimensional porous network induces multiple reflections and efficient attenuation of incident electromagnetic waves within the channels, achieving excellent electromagnetic shielding performance. Moreover, the low cost and eco-friendly properties of the natural plant template align perfectly with the current development trend of green and biodegradable electronic devices. In summary, this invention breaks through the traditional trade-off between light transmittance and metal layer thickness in transparent electrodes, providing an efficient approach to developing low-cost, high-transmittance, and highly shielded flexible composite materials. It is expected to achieve significant applications in several core areas, including electromagnetic protection for smart wearable devices, transparent optoelectronic windows, and flexible sensors, possessing broad market prospects and significant economic value.

[0050] In summary, this invention successfully achieves a perfect balance between optical and electrical properties. Through a unique fabrication method, it fully preserves the high porosity topological advantages of natural leaf veins, enabling the electrode to possess extremely high transmittance in the visible light band; for example, the transmittance of the magnolia leaf vein copper electrode can reach approximately 80%. Simultaneously, its conductivity is significantly improved compared to traditional metal thin films; only 60 minutes of deposition is required to reduce the sheet resistance of the copper leaf vein electrode to 0.09 Ω / sq, and the conductivity reaches as high as 4×10⁻⁶. 5 The S / m ratio fundamentally breaks the physical constraint that increased thickness in traditional materials inevitably leads to decreased light transmittance. In terms of mechanical properties, relying on the natural support network structure of the leaf veins and the dense metal layer formed by chemical plating, this electrode exhibits extremely superior flexibility and mechanical stability. Even after repeated bending at a limit bending radius of 4.39 mm, its resistivity fluctuation remains controlled within a slight range of ±5%, perfectly meeting the stringent requirements of future wearable devices and stretchable electronic components for dynamic deformation. More importantly, this invention provides a highly efficient and customizable electromagnetic shielding solution. The prepared copper-magnolia leaf vein electrode achieves a highly stable electromagnetic shielding performance (EMI SE) exceeding 25 dB across the entire frequency band. Thanks to the complex multi-level branched network structure of the leaf veins, this electrode exhibits extremely high absorption loss (SE). A The shielding mechanism, primarily based on a shielding density of approximately 17~20 dB, effectively reduces secondary reflection pollution of electromagnetic waves and avoids secondary interference. Furthermore, this fabrication process is highly customizable: on the one hand, by precisely controlling the metal deposition time during the electroless plating process, the thickness and porosity of the metal layer at the micro-nano scale can be linearly adjusted, thereby achieving precise control over the overall shielding strength; on the other hand, by depositing different types of metals such as copper and nickel, the differences in material conductivity and permeability can be utilized to specifically optimize the electromagnetic shielding performance and the dominant mechanism, thus meeting the customized protection needs of various flexible electronic devices in complex electromagnetic environments and providing a new technical path for the electromagnetic compatibility design of next-generation intelligent electronic devices.

[0051] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0052] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0053] Example 1 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is copper, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for further treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry. The leaves used are Bodhi leaves.

[0054] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0055] Step 3: Prepare the chemical copper plating solution and preheat it in an environment of 30 ℃ to allow the solution temperature to reach 30 ℃.

[0056] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylaminoborane. Immerse the leaf veins loaded with the chemical plating catalyst into the catalyst activation solution, activate for 30 seconds, remove and rinse with deionized water to obtain leaf veins loaded with metal particles, i.e., leaf veins loaded with activated catalyst. Step 5: The leaf veins loaded with metal particles were immersed in a chemical copper plating solution. After reacting at 25 °C for 60 min, metallic copper gradually deposited on the surface of the leaf veins, forming a dense thin layer of metallic copper. Scanning electron microscopy revealed that the metallic copper was composed of layered stacking.

[0057] Example 2 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is nickel, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0058] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0059] Step 3: Prepare the electroless nickel plating solution, adjust the pH to 8 with ammonia, and preheat it in an environment of 30 ℃ to bring the solution temperature to 30 ℃.

[0060] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate for 30 s, remove and rinse with deionized water to obtain leaf veins loaded with metal particles.

[0061] Step 5: The leaf veins loaded with metal particles were immersed in a chemical nickel plating solution and reacted at 60 °C for 120 min. Metallic nickel gradually deposited on the surface of the leaf veins, forming a dense thin layer of nickel. Scanning electron microscopy revealed that the nickel was composed of a granular stacked structure.

[0062] Example 3 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is silver. The specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0063] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0064] Step 3: Prepare the chemical silver plating solution and preheat it in an environment of 50 ℃ to allow the solution temperature to reach 50 ℃.

[0065] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate for 30 s, remove and rinse with deionized water to obtain leaf veins loaded with metal particles.

[0066] Step 5: The leaf veins loaded with metal particles were immersed in a chemical silver plating solution and reacted at 80 °C for 120 min. Metallic silver gradually deposited on the surface of the leaf veins, forming a dense silver layer. Scanning electron microscopy revealed that the silver was composed of a blocky, stacked structure.

[0067] Example 4 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is gold. The specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0068] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0069] Step 3: Prepare the chemical gold plating solution, adjust the pH to 8 with ammonia, and preheat it in an environment of 65 ℃ to bring the solution temperature to 65 ℃.

[0070] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate for 30 s, remove and rinse with deionized water to obtain leaf veins loaded with metal particles.

[0071] Step 5: The leaf veins loaded with metal particles were immersed in a chemical gold plating solution and reacted at 50 °C for 60 min. Gold gradually deposited on the surface of the leaf veins, forming a dense gold layer. Scanning electron microscopy revealed that the gold was composed of a granular stacked structure.

[0072] Example 5 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is cobalt, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0073] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0074] Step 3: Prepare the chemical cobalt plating solution, adjust the pH to 9 with sodium hydroxide, and preheat it in an environment of 80 ℃ to bring the solution temperature to 80 ℃.

[0075] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate for 30 s, remove and rinse with deionized water to obtain leaf veins loaded with metal particles.

[0076] Step 5: The leaf veins loaded with metal particles were immersed in a chemical cobalt plating solution and reacted at 100 °C for 200 min. Cobalt metal gradually deposited on the surface of the leaf veins, forming a dense thin layer. Scanning electron microscopy revealed that the cobalt metal was composed of layered stacks.

[0077] Example 6 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is palladium, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0078] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0079] Step 3: Prepare the electroless palladium plating solution, adjust the pH to 9 with ammonia, and preheat it in an environment of 60 ℃ to allow the solution temperature to reach 60 ℃.

[0080] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate them at 20 ℃ for 40 s, and then take them out and rinse them with deionized water to obtain leaf veins loaded with metal particles.

[0081] Step 5: The leaf veins loaded with metal particles were immersed in a palladium electroless plating solution. After reacting at 50 °C for 120 min, palladium gradually deposited on the surface of the leaf veins, forming a dense palladium thin layer. Scanning electron microscopy revealed that the metal plating consisted of a granular stacked structure.

[0082] Example 7 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is lead, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0083] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0084] Step 3: Prepare the chemical lead plating solution, adjust the pH to 9 with ammonia, and preheat it in an environment of 60 ℃ to bring the solution temperature to 60 ℃.

[0085] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate for 30 s, remove and rinse with deionized water to obtain leaf veins loaded with metal particles.

[0086] Step 5: The leaf veins loaded with metal particles were immersed in a chemical lead plating solution. After reacting at 60 °C for 20 min, metallic lead gradually deposited on the surface of the leaf veins, forming a dense thin layer of metallic lead. Scanning electron microscopy revealed that the metallic lead was composed of a granular stack.

[0087] Example 8 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is tin, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0088] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0089] Step 3: Prepare the chemical tin plating solution, adjust the pH to 9 with ammonia, and preheat it in an environment of 60 ℃ to bring the solution temperature to 60 ℃.

[0090] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate for 30 s, remove and rinse with deionized water to obtain leaf veins loaded with metal particles.

[0091] Step 5: The leaf veins loaded with metal particles were immersed in a chemical tin plating solution and reacted at 50 °C for 120 min. Metallic tin gradually deposited on the surface of the leaf veins, forming a dense thin layer of metallic tin. Scanning electron microscopy revealed that the metallic tin was composed of a granular stacked structure.

[0092] Example 9 This embodiment provides a method for preparing a biomimetic leaf vein-based transparent electrode, wherein the metal is zinc oxide, and the specific steps are as follows: Step 1: Place the plant leaves in a 500 mL aqueous solution containing 50 g NaOH and 25 g Na2CO3, and heat to 90 ℃ for 30 min; then add H2O2 for treatment, and remove the mesophyll tissue by ultrasonication or water washing; finally, bleach again with H2O2 aqueous solution and dry.

[0093] Step 2: Prepare a 100 mmol solution of ammonium tetrachloropalladium, a chemical plating catalyst, and immerse the leaf veins in it for 30 min to obtain leaf veins loaded with the chemical plating catalyst.

[0094] Step 3: Prepare the chemical zinc oxide plating solution and preheat it in an environment of 60 ℃ to allow the solution temperature to reach 60 ℃.

[0095] Step 4: Prepare a catalyst activation solution of 1 g / L dimethylammonium borane. Immerse the leaf veins that have adsorbed the chemical plating catalyst into the catalyst activation solution, activate them at 30 ℃ for 60 s, and then take them out and rinse them with deionized water to obtain leaf veins loaded with metal particles.

[0096] Step 5: The leaf veins loaded with metal particles were immersed in a chemical zinc oxide plating solution. After reacting at 60 °C for 100 min, zinc oxide gradually deposited on the surface of the leaf veins, forming a dense zinc oxide thin layer. Scanning electron microscopy revealed that the zinc oxide was composed of a granular stacked structure.

[0097] Example 10 The difference between this embodiment and Embodiment 1 is that the deposition time in step 5 is 45 minutes.

[0098] Example 11 The difference between this embodiment and Embodiment 1 is that the deposition time in step 5 is 30 minutes.

[0099] Example 12 The difference between this embodiment and Embodiment 1 is that the deposition time in step 5 is 15 minutes.

[0100] Example 13 The difference between this embodiment and Embodiment 1 is that the plant leaves are magnolia leaves.

[0101] Example 14 The difference between this embodiment and Embodiment 1 is that the plant leaves are poplar leaves.

[0102] Example 15 The difference between this embodiment and Embodiment 1 is that the plant leaves are rubber leaves.

[0103] Figures 1-9 The images shown are scanning electron microscope (SEM) images and energy scattering spectra of leaf vein materials deposited with different metals or metal oxides, prepared in Examples 1-9 of this invention, at different magnifications. Figures 1-9 It can be seen that the various metals and oxides deposited on the leaf vein surface using the method of the present invention all exhibit highly controllable growth characteristics. The metal coating achieves full coverage of the cellulose fiber network surface with submicron precision. The microstructure shows that the coating is dense and uniform with continuous grains and no obvious pores, cracks or island agglomeration.

[0104] Figures 10-18 These are X-ray diffraction patterns of leaf vein materials deposited with different metals or metal oxides, prepared in Examples 1-9 of this invention. Figures 10-18 It can be seen that the metal coating prepared by this method is pure, free of impurities, and has good crystallinity.

[0105] Figure 19 These are macroscopic photographs of leaf vein electrodes deposited with different metals or metal oxides, prepared in Examples 1-9 of this invention. These images effectively demonstrate that the process of this invention has high metal universality, enabling flexible patterning / overall deposition of various metal materials on complex biological templates, and the sample surface exhibits a uniform metallic luster.

[0106] Figure 20 The images show actual electrode samples made by depositing copper and nickel on the natural leaf veins of four different plants (from left to right: Bodhi, Magnolia, Poplar, and Rubber). The first row shows the original leaf, the second row shows the extracted leaf vein structure, the third row shows the electroless copper plating, and the fourth row shows the electroless nickel plating. These results verify that the present invention breaks through the limitation of a single substrate and has excellent process compatibility and reproducibility for plant leaf vein templates with different fractal structures and different porosities.

[0107] Figure 21 The hysteresis loops of the biomimetic leaf vein electrodes prepared in Examples 2 and 5 of this invention are shown. The test results indicate that by depositing specific ferromagnetic metals or oxides, the leaf vein electrodes are endowed with excellent macroscopic magnetic properties.

[0108] Figure 22 The results show the flexibility test results of the leaf vein copper electrode deposited for 60 minutes, prepared in Example 1 of this invention. Figure 23The mechanical stability test results of the leaf vein copper electrodes prepared in Examples 1, 10, 11 and 12 of this invention are shown in the figure. As can be seen from the figure, thanks to the excellent mechanical toughness of natural leaf veins and the strong interfacial bonding force of the metal coating, the electrode exhibits excellent flexible conductive stability with minimal resistance fluctuation under extreme bending fatigue test.

[0109] Figure 24 The broadband electromagnetic shielding performance of the copper network electrodes prepared in Embodiments 1, 10, 11, and 12 of this invention is shown, wherein (ac) represents the SE of the copper network electrode in the X-band (8.2-12.4 GHz). T SE R with SE A ; (df) SE of copper network electrodes in the Ku band (12-18 GHz) T SE R with SE A .

[0110] Figure 25 The broadband electromagnetic shielding performance of different metal network electrodes prepared in Examples 1-8 of this invention is shown, wherein (ac) represents the SE of the copper network electrode in the X-band (8.2-12.4 GHz). T SE R with SE A ; (df) SE of copper network electrodes in the Ku band (12-18 GHz) T SE R with SE A .

[0111] Figure 26 This describes the broadband electromagnetic shielding performance of the copper network electrodes prepared in Embodiments 1 and 13-15 of the present invention, wherein (ac) represents the SE of the copper network electrode in the X-band (8.2-12.4 GHz). T SE R with SE A ; (df) represents the SE of the copper network electrode in the Ku band (12-18 GHz). T SE R with SE A .

[0112] Depend on Figures 24-26 It can be seen that the composite material of the present invention exhibits a strong shielding response over a wide frequency band, which not only enhances the overall shielding effectiveness (SE) T Excellent performance, and the absorption coefficient (SE) can be adjusted by controlling the type of metal and the size of the leaf vein grid. A ) and reflectance coefficient (SE) R Effective customization.

[0113] Figure 27The shielding effect of the leaf vein copper electrode prepared in Embodiment 1 of the present invention on high-frequency WiFi signals is shown in Figures a and b. Figures a and b show the real-time WiFi signal strength monitoring interface of the mobile phone when the window is open, respectively, for 2.4 GHz and 5 GHz. Figures c and d show the real-time WiFi signal strength of the mobile phone when the window is covered by the biomimetic leaf vein electrode, respectively. As can be seen from the figures, after the window is covered by the biomimetic leaf vein electrode, not only can the screen data be clearly read through the leaf vein, but the WiFi signal curve displayed on the screen also shows a significant decrease.

[0114] Figure 28 The shielding effect of the leaf vein copper electrode prepared in Embodiment 1 of the present invention on the cellular network call signal of a smartphone is shown in Figure a, where the window of the aluminum foil shielding box is in an open state, and Figure b shows the window being completely covered by the biomimetic leaf vein network electrode. As can be seen from the figures, when the window of the aluminum foil shielding box is in an open state, the mobile phone inside the box can receive external radio frequency signals and ring normally. However, when the window is completely covered by the biomimetic leaf vein network electrode, the electromagnetic leakage channel is blocked, and the mobile phone inside the box cannot receive external incoming call signals.

[0115] Figure 29 The shielding effect of the leaf vein copper electrode prepared in Embodiment 1 of the present invention on near-field wireless data transmission signals is shown in Figure a, which is the equivalent circuit diagram of the wireless transmission demonstration system, Figure b is the brightness of the LED indicator without a shield, and Figure c is the brightness of the LED indicator after inserting a biomimetic metal network electrode between the coils. As can be seen from the figures, when no shield is placed, the electromagnetic coupling of the transceiver coil is good and the LED indicator at the receiving end is bright. However, after inserting the biomimetic metal network electrode between the coils, the electromagnetic transmission path is blocked and the LED indicator dims significantly.

[0116] Figure 30 This is a real-world demonstration of the shielding of commercial wireless charging signals by the leaf vein copper electrode prepared in Embodiment 1 of the present invention. Figure a shows the state of a smartphone charging normally when placed on a wireless charging base without obstruction. Figure b shows the charging state after the bionic leaf vein electrode is inserted between the phone and the charging base. As can be seen from the figures, when the smartphone is charging normally on the wireless charging base, the screen displays the charging status. However, when the bionic leaf vein electrode is inserted between the phone and the charging base, the near-field electromagnetic induction is blocked, the phone cannot obtain power, and the phone screen turns off.

[0117] Depend on Figures 27-30 These intuitive and visual application scenarios fully demonstrate the enormous commercial application potential of this biomimetic transparent electrode in future flexible wearable devices, secure communication windows, and electromagnetic protection shells.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for fabricating a transparent metal network electrode based on a leaf vein structure, characterized in that, Includes the following steps: S1: Remove the leaf mesophyll from the plant leaves to obtain the leaf veins; S2: Immerse the leaf vein in a chemical plating catalyst solution to load the surface of the leaf vein with a catalyst, thereby obtaining a leaf vein loaded with a catalyst. S3: Immerse the leaf vein loaded with catalyst into the catalyst activation solution and carry out a reaction to obtain a leaf vein substrate loaded with metal catalyst particles. S4: The leaf vein substrate loaded with metal catalyst particles is immersed in a chemical metal plating solution to carry out a secondary reaction, thereby obtaining the transparent metal network electrode based on the leaf vein structure.

2. The method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, Step S1 specifically involves: placing the plant leaves in an aqueous solution containing NaOH and Na2CO3 for heating treatment, then adding H2O2 for treatment, removing the leaf mesophyll tissue by ultrasonication or water washing, and finally bleaching and drying with H2O2 aqueous solution again.

3. The method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, The plant leaves include one of the following: Bodhi leaf, Magnolia leaf, Poplar leaf, and Rubber leaf.

4. The method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, The electroless plating catalyst is ammonium tetrachloropalladate or palladium nitrate, with a concentration of 50~100 mmol / L.

5. A method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, The catalyst activation solution is dimethylaminoborane or stannous chloride, with a concentration of 0.5~1 g / L.

6. A method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, The reaction temperature for the first reaction is 20~30 ℃, and the reaction time is 30~60 s.

7. The method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, The electroless metal plating solution is one of the following: electroless copper plating solution, electroless nickel plating solution, electroless silver plating solution, electroless gold plating solution, electroless cobalt plating solution, electroless palladium plating solution, electroless lead plating solution, electroless tin plating solution, electroless zinc oxide plating solution, and electroless iron oxide plating solution.

8. A method for fabricating a transparent metal network electrode based on a leaf vein structure according to claim 1, characterized in that, The secondary reaction is carried out at a temperature of 30-100 °C for 10-200 min.

9. A transparent metal network electrode based on a leaf vein structure, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The application of the transparent metal network electrode based on leaf vein structure as described in claim 9 in the field of electromagnetic shielding.

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