A preparation method of a cross-shaped silver nanolattice based on twice stamping

Abstract

The application relates to the fields of plasmonic nanophotonics and micro-nano manufacturing technology, and discloses a preparation method of a cross-shaped silver nano dot array based on secondary stamping, which comprises the following steps: a nickel stamping template with a square periodic structure is used to stamp a first aluminum substrate, and anodic oxidation and phosphoric acid etching are carried out to form a cross-shaped cone anodic aluminum oxide template; the cross-shaped cone anodic aluminum oxide template is used to stamp a second aluminum substrate, and anodic oxidation is carried out at an oxidation voltage lower than that matched with the period of the cross-shaped stamping pit array to form a second anodic aluminum oxide structure with cross-shaped channels; a double-pass anodic aluminum oxide template is formed through supporting, aluminum removal and back etching, and the template is peeled off after silver is deposited on the back of the template to obtain a cross-shaped silver nano dot array. The application can realize the preparation of a large-area, period-consistent cross-shaped silver nano dot array without electron beam exposure, focused ion beam processing or complex photolithography process, and the preparation cost and process complexity are reduced.

Description

Technical Field

[0001] This invention relates to the fields of plasmonic nanophotonics and micro / nano fabrication technology, and particularly to a method for preparing a cross-shaped silver nanoarray based on secondary imprinting. Background Technology

[0002] Plasmonic nanolattices can support localized surface plasmon resonances with surface lattices, and have significant application value in fields such as nanolasers, metasurfaces, sensing, and nonlinear optics. Among them, cross-shaped and anisotropic metallic nanolattices have attracted widespread attention in recent years due to their high sensitivity to polarization and azimuth.

[0003] Currently, the fabrication of cross-shaped or complex symmetrical metal nanolattices mainly relies on electron beam lithography, focused ion beam lithography, or multi-step photolithography. However, these methods generally suffer from high costs, strong equipment dependence, limited effective processing area, and complex process steps, making it difficult to achieve centimeter-scale uniform structures. Furthermore, they still have shortcomings in repeatability and consistency, and it is difficult to achieve continuous control of structural depth and morphology while maintaining high structural symmetry.

[0004] Anodized aluminum oxide templates are widely used for fabricating periodic nanostructures due to their low cost, ability to prepare large areas, and adjustable structural periods. However, the pore structures formed by traditional anodized aluminum oxide templates naturally tend to be circular or hexagonal symmetrical structures, and directly obtaining cross-shaped or other higher-order symmetrical structures remains quite difficult, thus limiting their application in the fabrication of complex anisotropic metal nanolattices.

[0005] Therefore, how to achieve the fabrication of large-area, periodically consistent, and structurally symmetrical cross-shaped metal nanoarrays without electron beam exposure, focused ion beam processing, or complex photolithography processes, while taking into account fabrication cost, process complexity, and consistency of structural replication, remains a technical problem that needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of high cost, limited effective processing area and relatively simple structural form in the preparation of complex nanoarrays in the prior art, and to provide a method for preparing cross-shaped silver nanoarrays based on secondary imprinting. The method achieves the preparation of cross-shaped silver nanoarrays through secondary imprinting of cross-shaped cone anodic aluminum oxide templates, undervoltage anodizing, and construction and silver deposition of double-channel anodic aluminum oxide templates.

[0007] This invention aims to achieve large-area, periodically consistent, and regularly arranged cross-shaped silver nanoarrays, reducing fabrication costs and process complexity without requiring electron beam exposure, focused ion beam processing, or complex photolithography. Simultaneously, by adjusting process parameters such as etching, imprinting, and anodizing, the morphology of the cross-shaped anodized aluminum template and the cross-shaped channel structure can be controlled. This provides a simple and feasible technical solution for the fabrication of nanoarrays with polarization response and plasmon resonance characteristics, and is applicable to fields such as nanolasers, polarization modulation, metasurfaces, and optical sensing.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a cross-shaped silver nanoarray based on secondary imprinting includes the following steps: A first aluminum substrate is imprinted using a nickel imprinting template with a four-sided periodic structure, and the imprinted first aluminum substrate is anodized to form a first anodized aluminum template. The first anodized aluminum template is then etched with phosphoric acid to form a cross-shaped anodized aluminum template. The second aluminum substrate is imprinted with the cross-shaped anodized aluminum template to form a cross-shaped imprint pit, and anodizing is performed at an oxidation voltage lower than that matching the array period of the cross-shaped imprint pit to form a second anodized aluminum structure with cross-shaped channels. A polymethyl methacrylate support layer is spin-coated onto the surface of the second anodic aluminum oxide structure, the second aluminum substrate is removed, and the back side of the second anodic aluminum oxide structure is etched to form a double-through anodic aluminum oxide template with through-holes. After removing the polymethyl methacrylate support layer, the double-through anodized aluminum template is transferred to the substrate, and silver is deposited from the back side of the double-through anodized aluminum template, so that the silver is deposited on the surface of the substrate through the through-holes. The double-through anodized aluminum template is then peeled off to obtain a cross-shaped silver nanoarray.

[0009] Preferably, both the first aluminum substrate and the second aluminum substrate are obtained by cleaning and electrochemical polishing of high-purity aluminum sheets with a purity of 99.999%. The electrochemical polishing uses a mixed solution of perchloric acid and anhydrous ethanol as the polishing liquid. The cleaning includes ultrasonic cleaning of the corresponding aluminum sheets in sequence with anhydrous ethanol, deionized water and anhydrous ethanol, with each ultrasonic cleaning time being 7 minutes.

[0010] Preferably, the period of the nickel imprint template is 400 nm; the pressure for imprinting the first aluminum substrate is 5.0~6.0 MPa, and the holding time is 2 min; the anodizing voltage for forming the first anodic aluminum template is 160 V, the oxidation process is carried out in a low temperature environment of 3~5℃, the oxidation time is 1 h, and the maximum current limit during the oxidation process is 0.03 A.

[0011] Preferably, the first anodic aluminum oxide template is etched using a 5% phosphoric acid solution at a temperature of 55 °C for 17 min 40 s to form the cross-shaped anodic aluminum oxide template with a feature size of approximately 200 nm.

[0012] Preferably, when the cross-shaped anodized aluminum template is used to imprint the second aluminum substrate, the imprinting pressure is 2.2 MPa and the imprinting time is 2 min.

[0013] Preferably, the array period of the cross-shaped imprint pits is 400 nm, the oxidation voltage for anodizing the second aluminum substrate is 120 V, the oxidation process is carried out in a low-temperature environment of 3~5℃, and the oxidation time is 1 h.

[0014] Preferably, the second aluminum substrate is removed using a hydrochloric acid-copper chloride mixed solution to obtain an anodized aluminum film supported by the polymethyl methacrylate support layer.

[0015] Preferably, the back side of the anodic aluminum oxide film is etched using a 5% phosphoric acid solution at a temperature of 55 °C for 12 min to form the double-pass anodic aluminum oxide template; after removing the polymethyl methacrylate support layer with acetone, the double-pass anodic aluminum oxide template is transferred to the substrate.

[0016] Preferably, silver is deposited from the back side of the dual-channel anodic aluminum oxide template using magnetron sputtering. After deposition, the dual-channel anodic aluminum oxide template is peeled off with the aid of adhesive tape to obtain a cross-shaped silver nanoparticle array with a unit size of approximately 200 nm.

[0017] The beneficial effects of this invention are as follows: Compared with existing technologies, this invention first prepares a cross-shaped anodized aluminum template, and then uses the cross-shaped anodized aluminum template to perform a secondary imprinting on a second aluminum substrate, forming cross-shaped imprint pits on the surface of the second aluminum substrate. Subsequently, anodizing is performed at an oxidation voltage lower than that matching the array period of the cross-shaped imprint pits to form a second anodized aluminum structure with cross-shaped channels. A double-channel anodized aluminum template with through-channels is further constructed. By depositing silver from the back side of the double-channel anodized aluminum template and then peeling off the double-channel anodized aluminum template, a cross-shaped silver nanoparticle array can be formed on the substrate surface. The above preparation process does not require electron beam exposure, focused ion beam processing, or complex photolithography processes, and can achieve the preparation of large-area, periodically consistent cross-shaped silver nanoparticle arrays, thereby effectively reducing preparation costs and process complexity.

[0018] This invention forms a cross-shaped cone anodized aluminum template by etching the first anodic aluminum template with phosphoric acid, causing corrosion and morphological evolution at the interface between adjacent channels. By adjusting the etching time, the morphology of the cross-shaped cone anodized aluminum template can be adjusted, providing a suitable template base for subsequent secondary imprinting and the formation of cross-shaped channels, which is beneficial for the replication and transfer of the cross-shaped structure.

[0019] This invention combines secondary imprinting with undervoltage anodizing. A cross-shaped imprint pit is formed on the surface of a second aluminum substrate using a cross-shaped anodized aluminum template. Anodizing is then performed using an oxidation voltage lower than that matching the array period of the cross-shaped imprint pits. This causes the oxidation process to preferentially occur along the cross-shaped imprint pits and their local high-field regions, thereby forming a second anodized aluminum structure with cross-shaped channels. This method is beneficial for improving the replication integrity and morphological consistency of complex anisotropic structures, and allows for the control of structural symmetry and channel morphology through appropriate process parameters.

[0020] The cross-shaped silver nanolattice obtained by the above preparation method has the characteristics of large area, consistent period and regular arrangement, which provides a simple and feasible technical solution for preparing nanolattices with polarization response and plasmon properties, and can be applied to fields such as nanolasers, polarization control, metasurfaces and optical sensing. Attached Figure Description

[0021] Figure 1 A schematic diagram of the process flow for forming a cross-shaped anodized aluminum template, including pretreatment of the first aluminum substrate, first imprinting, anodizing, and phosphoric acid etching. Figure 2 The images show scanning electron microscope (SEM) images of the periodic imprinted structure on the surface of the first aluminum substrate after the first imprinting and the first anodized aluminum template formed after anodizing. Figure 2 (a) shows the periodic imprint structure on the surface of the first aluminum substrate after the first imprinting. Figure 2 (b) shows the cross-sectional morphology of the first anodized aluminum template formed after anodizing; Figure 3 This is a schematic diagram of the structure of a cross-shaped anodized aluminum template; Figure 4 The image shows a scanning electron microscope (SEM) image of the cross-shaped anodized aluminum oxide template formed after phosphoric acid etching. Figure 4 (a) is a top view of a cross-shaped anodized aluminum template. Figure 4 (b) is a side view of the cross-shaped anodized aluminum template; Figure 5 This is a schematic diagram of the process flow for forming a second anodic aluminum oxide structure by using a cross-shaped cone anodic aluminum oxide template to perform secondary imprinting on a second aluminum substrate and by undervoltage anodizing. Figure 6 These are scanning electron microscope images of the structures obtained after secondary imprinting and undervoltage anodizing, in which... Figure 6 (a) shows the cross-shaped embossing pits on the surface of the second aluminum substrate after the second embossing. Figure 6 (b) is a top view of the second anodic aluminum oxide structure with cross-shaped channels formed after undervoltage anodizing. Figure 6 (c) is a cross-sectional view of the second anodic aluminum oxide structure; Figure 7 A schematic diagram of the process flow for spin coating of polymethyl methacrylate support layer, removal of second aluminum substrate, back etching, removal of polymethyl methacrylate support layer and transfer of double-channel anodized aluminum template; Figure 8 A scanning electron microscope image of the back side of a double-channel anodized aluminum template formed after back-side etching; Figure 9 A schematic diagram of the process flow for depositing silver from one side of the back of a double-channel anodic aluminum oxide template and peeling off the double-channel anodic aluminum oxide template to form a cross-shaped silver nano-array; Figure 10 A schematic diagram of the cross-shaped silver nano-dot array; Figure 11 Scanning electron microscope image of a cross-shaped silver nanoarray obtained after depositing silver from the back side of a double-pass anodic aluminum oxide template and then peeling off the template. Detailed Implementation

[0022] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0023] In one embodiment, the present invention proposes a method for preparing a cross-shaped silver nanoarray based on secondary imprinting, comprising the following steps: A first aluminum substrate is imprinted using a nickel imprinting template with a four-sided periodic structure, and the imprinted first aluminum substrate is anodized to form a first anodized aluminum template. The first anodized aluminum template is then etched with phosphoric acid to form a cross-shaped anodized aluminum template. The second aluminum substrate is imprinted with the cross-shaped anodized aluminum template to form a cross-shaped imprint pit, and anodizing is performed at an oxidation voltage lower than that matching the array period of the cross-shaped imprint pit to form a second anodized aluminum structure with cross-shaped channels. A polymethyl methacrylate support layer is spin-coated onto the surface of the second anodic aluminum oxide structure, the second aluminum substrate is removed, and the back side of the second anodic aluminum oxide structure is etched to form a double-through anodic aluminum oxide template with through-holes. After removing the polymethyl methacrylate support layer, the double-through anodized aluminum template is transferred to the substrate, and silver is deposited from the back side of the double-through anodized aluminum template, so that the silver is deposited on the surface of the substrate through the through-holes. The double-through anodized aluminum template is then peeled off to obtain a cross-shaped silver nanoarray.

[0024] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0025] Example 1: This example provides a method for preparing a cross-shaped silver nanoarray based on secondary imprinting, specifically including the following steps: (1) First, high-purity aluminum material was selected and cut into circular substrates with a diameter of 2 cm. These substrates were then subjected to ultrasonic cleaning in anhydrous ethanol, deionized water, and anhydrous ethanol, respectively, for 7 minutes each time, to remove oil and impurities from the aluminum surface. After cleaning, the substrates were removed and dried for later use. Then, electrochemical polishing was used to smooth the surface of the cleaned aluminum substrates. The polishing solution used was a mixture of perchloric acid and anhydrous ethanol, with a volume ratio of 1:7. After electrochemical polishing, a first aluminum substrate with low surface roughness, suitable for subsequent nanoimprinting, was obtained. Figure 1 As shown, this step provides a smooth substrate for the subsequent first imprint and anodizing.

[0026] (2) A nickel imprinting template with a tetragonal 400 nm periodic structure is used as an imprinting mold and covered on the surface of the first aluminum substrate obtained by the above treatment. Cold imprinting is performed under a pressure of 5.2 MPa and a holding time of 2 min, thereby forming a regular tetragonal periodic pit array on the surface of the first aluminum substrate. Figure 1 As shown, this step constructs the pre-formed morphological basis required for subsequent anodizing on the surface of the first aluminum substrate.

[0027] (3) The first aluminum substrate after imprinting in step (2) is subjected to anodizing treatment. The oxidation solution used is a mixed solution of phosphoric acid, ethylene glycol, and water, with a volume ratio of 1:200:400. Based on the empirical relationship between the anodizing period and the oxidation voltage, an oxidation voltage of 160 V is used to match the formation of a 400 nm periodic structure. The maximum current during the anodizing process is limited to 0.03 A. The oxidation process is carried out in a low-temperature environment of 3~5 ℃, and the oxidation time is controlled to 1 h, thereby forming a first anodized aluminum template with a corresponding tetragonal periodic channel structure on the first aluminum substrate. Figure 1 As shown, this step prepares a first anodic aluminum oxide template with a regular square arrangement.

[0028] (4) The first anodic aluminum oxide template obtained in step (3) was subjected to phosphoric acid etching in a 55 ℃ water bath. Specifically, 40 mL of a 5% (w / w) phosphoric acid aqueous solution was used as the etching medium and placed in a beaker. The phosphoric acid aqueous solution was preheated in a water bath for more than 30 min in advance to ensure a stable and uniform etching temperature. Subsequently, the first anodic aluminum oxide template was placed in the phosphoric acid aqueous solution for chemical etching for 17 min 40 s, so that the interface area between adjacent channels would undergo continuous corrosion and morphological evolution, thereby forming a cross-shaped anodic aluminum oxide template with a characteristic size of about 200 nm. After etching, the sample was immediately thoroughly cleaned with ultrapure water and dried to remove residual phosphoric acid and reduce the impact of acid residue on structural uniformity. Figure 1 As shown, this step achieves the morphological transformation from the first anodic aluminum oxide template to the cross-shaped cone anodic aluminum oxide template; as Figure 4 As shown, the feature size of the cross-shaped anodized aluminum template obtained in this embodiment is approximately 200 nm.

[0029] (5) Using the cross-shaped anodized aluminum template with a feature size of approximately 200 nm obtained in step (4) as a secondary imprinting mold, another aluminum substrate obtained after the same cleaning and electrochemical polishing treatment as in step (1) is imprinted. The imprinting pressure of the secondary imprinting is controlled at 2.2 MPa, and the imprinting time is 2 min. Since aluminum material has a certain degree of ductility, and the cross-shaped anodized aluminum template has a large contact friction during the imprinting process, if the imprinting pressure is too high, it is easy to cause damage to the periodic structure or cross-shaped morphology on the surface of the second aluminum substrate, and the cross-shaped anodized aluminum template and the second aluminum substrate are not easy to separate after imprinting; if the imprinting pressure is too low, it is difficult to obtain a clear and complete imprinted structure. After multiple experiments and optimizations, 2.2 MPa is the more suitable imprinting condition. With the cross-shaped anodized aluminum template structure remaining intact, the cross-shaped anodized aluminum template can be repeatedly used for multiple imprints, and a clear cross-shaped imprint pit is formed on the surface of the second aluminum substrate. Figure 5As shown, this step enables the replication of the morphology of the cross-shaped anodized aluminum template onto the surface of the second aluminum substrate.

[0030] (6) The second aluminum substrate after the second imprinting in step (5) is subjected to anodizing to form cross-shaped channels. The anodizing solution used is still a mixed anodizing solution prepared by phosphoric acid, ethylene glycol and water in a volume ratio of 1:200:400. The anodizing voltage and the array period usually satisfy an empirical relationship. Where P is the array period in nm and U is the anodizing voltage in V. For a prefabricated structure with an array period of 400 nm, the corresponding oxidation voltage is approximately 160 V. This step sets the actual oxidation voltage to 120 V, which is lower than the oxidation voltage corresponding to the 400 nm array period, thus constituting undervoltage anodizing.

[0031] Unlike the precursor morphology formed by imprinting with a nickel imprinting template with a square periodic structure, the prefabricated structure formed on the surface of the second aluminum substrate in step (5) is a cross-shaped imprint pit. Its surface potential distribution and local oxidation behavior differ from the conventional circular precursor structure. Therefore, this embodiment uses an oxidation voltage of 120 V for undervoltage anodizing. The oxidation process is carried out in a low-temperature environment of 3~5 ℃ for 1 h, allowing the anodizing process to preferentially proceed along the cross-shaped imprint pit and its local high-field region, thereby gradually transforming the cross-shaped imprint pit into a cross-shaped channel, forming a second anodic aluminum oxide structure with cross-shaped channels. Figure 5 , Figure 6 As shown, this step realizes the transformation from a cross-shaped imprint pit to a second anodic aluminum oxide structure with cross-shaped channels.

[0032] (7) A polymethyl methacrylate (PMMA) support layer is spin-coated onto the surface of the second anodic aluminum oxide structure obtained in step (6). The spin-coating parameters are a rotation speed of 110 r / min and a spin-coating time of 20 s. The PMMA support layer is formed by multiple spin-coating processes, wherein a dilute PMMA solution is first spin-coated three times, the dilute PMMA solution being prepared by 0.5 g of PMMA and 15 mL of dichloromethane; then a concentrated PMMA solution is spin-coated two times, the concentrated PMMA solution being prepared by 1 g of PMMA and 20 mL of dichloromethane. After spin-coating, the surface is dried at 60 ℃ for 5 min to enhance the bonding tightness between the PMMA support layer and the second anodic aluminum oxide structure. Figure 7 As shown, this step provides the necessary support for the subsequent removal of the second aluminum substrate and film transfer.

[0033] (8) After spin-coating the polymethyl methacrylate (PMMA) support layer, the second aluminum substrate is removed using a hydrochloric acid-copper chloride mixture. The hydrochloric acid-copper chloride mixture is prepared by mixing 3.4 g of anhydrous copper chloride, 100 mL of ultrapure water, and 100 mL of hydrochloric acid. Treatment at room temperature for approximately 10 minutes can completely remove the second aluminum substrate, thus obtaining an anodized aluminum film supported by the PMMA support layer. Figure 7 As shown, this step completes the separation of the anodic aluminum oxide film from the second aluminum substrate.

[0034] (9) After removing the second aluminum substrate, the sample is fixed onto a thin glass slide using thin adhesive tape, with the back side of the anodic aluminum oxide film facing upwards. It is then placed in an etching solution for back-side etching. The back-side etching solution used is still a 5% (w / w) phosphoric acid solution, with an etching temperature of 55 °C and an etching time of 12 min, thereby expanding the channels on the back side of the anodic aluminum oxide film to form a double-channel anodic aluminum oxide template. After the back-side etching is completed, the sample is immersed in 55 °C ultrapure water for cleaning to remove residual phosphoric acid etching solution from the surface and to help prevent the anodic aluminum oxide film from drying and cracking.

[0035] After forming the double-channel anodized aluminum template, the polymethyl methacrylate (PMMA) support layer covering the template is immersed in acetone solution for 30 minutes to completely dissolve it. The resulting double-channel anodized aluminum template is then transferred, with the back side facing up, onto a glass slide as a substrate for later use. Figure 7 , Figure 8 As shown, this step enables the construction of a double-through anodized aluminum template with through-holes and the transfer of the double-through anodized aluminum template.

[0036] (10) Silver was deposited from the back side of a dual-channel anodic aluminum oxide template using magnetron sputtering. Specifically, the back side of the dual-channel anodic aluminum oxide template was positioned facing the silver target, and deposition was performed using the silver target. The deposition parameters were set as follows: output current 161 mA, operating temperature 21 °C, output voltage 382 V, and output power 101 W. During deposition, silver was deposited onto the substrate surface through the through-channels of the dual-channel anodic aluminum oxide template. After deposition, the dual-channel anodic aluminum oxide template was removed using tape-assisted peeling, thereby forming a cross-shaped silver nanoparticle array on the substrate surface. Figure 9 As shown, this step completes the process of silver deposition from the back side of the double-channel anodic aluminum oxide template and the stripping of the double-channel anodic aluminum oxide template; as Figure 10 and Figure 11 As shown, this embodiment ultimately yields a cross-shaped silver nanoparticle array with a unit size of approximately 200 nm.

[0037] In this embodiment, by controlling the phosphoric acid etching time of the first anodic aluminum oxide template to 17 min 40 s, a cross-shaped pyramidal anodic aluminum oxide template with a feature size of approximately 200 nm was prepared. Subsequently, the cross-shaped pyramidal anodic aluminum oxide template was used to perform a second imprinting on the second aluminum substrate, followed by undervoltage anodizing, construction of a double-channel anodic aluminum oxide template, silver deposition, and peeling off of the double-channel anodic aluminum oxide template, ultimately obtaining a cross-shaped silver nanoparticle lattice with a unit size of approximately 200 nm. This demonstrates that the above process can effectively replicate and transfer the cross-shaped pyramidal anodic aluminum oxide template structure to a cross-shaped silver nanoparticle lattice.

[0038] Example 2: This embodiment provides a method for preparing a cross-shaped silver nanoarray based on secondary imprinting. The preparation steps and other process conditions are the same as in Example 1, except that in step (2), a nickel imprinting template with a tetragonal 400 nm periodic structure is used as the imprinting mold to perform cold imprinting on the first aluminum substrate obtained after cleaning and electrochemical polishing. The imprinting pressure is set to 5.0 MPa, and the holding time is 2 min. After imprinting, a regular tetragonal periodic pit array is formed on the surface of the first aluminum substrate, providing a pre-formed morphological basis for the subsequent anodizing to form the first anodic aluminum template.

[0039] Subsequently, following steps (3) to (10) in Example 1, the following processes were performed sequentially: anodizing, phosphoric acid etching, secondary imprinting, undervoltage anodizing, spin coating of polymethyl methacrylate support layer, removal of the second aluminum substrate, construction of the double-pass anodized aluminum template, silver deposition, and stripping of the double-pass anodized aluminum template, ultimately obtaining a cross-shaped silver nano-array on the substrate surface.

[0040] Example 3: This embodiment provides a method for preparing a cross-shaped silver nanoarray based on secondary imprinting. The preparation steps and other process conditions are the same as in Example 1, except that the imprinting pressure of the first imprinting in step (2) is different.

[0041] Specifically, in step (2), a nickel imprinting template with a tetragonal 400 nm periodic structure is used as the imprinting mold to cold imprint the first aluminum substrate obtained after cleaning and electrochemical polishing. The imprinting pressure is set to 6.0 MPa, and the holding time is 2 min. After imprinting, a regular tetragonal periodic pit array is formed on the surface of the first aluminum substrate, providing a pre-fabricated morphological basis for the subsequent anodizing to form the first anodic aluminum template.

[0042] Subsequently, following steps (3) to (10) in Example 1, the following processes were performed sequentially: anodizing, phosphoric acid etching, secondary imprinting, undervoltage anodizing, spin coating of polymethyl methacrylate support layer, removal of the second aluminum substrate, construction of the double-pass anodized aluminum template, silver deposition, and stripping of the double-pass anodized aluminum template, ultimately obtaining a cross-shaped silver nano-array on the substrate surface.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a cross-shaped silver nanoarray based on secondary imprinting, characterized in that, Includes the following steps: A first aluminum substrate is imprinted using a nickel imprinting template with a four-sided periodic structure, and the imprinted first aluminum substrate is anodized to form a first anodized aluminum template. The first anodized aluminum template is then etched with phosphoric acid to form a cross-shaped anodized aluminum template. The second aluminum substrate is imprinted with the cross-shaped anodized aluminum template to form a cross-shaped imprint pit, and anodizing is performed at an oxidation voltage lower than that matching the array period of the cross-shaped imprint pit to form a second anodized aluminum structure with cross-shaped channels. A polymethyl methacrylate support layer is spin-coated onto the surface of the second anodic aluminum oxide structure, the second aluminum substrate is removed, and the back side of the second anodic aluminum oxide structure is etched to form a double-through anodic aluminum oxide template with through-holes. After removing the polymethyl methacrylate support layer, the double-through anodized aluminum template is transferred to the substrate, and silver is deposited from the back side of the double-through anodized aluminum template, so that the silver is deposited on the surface of the substrate through the through-holes. The double-through anodized aluminum template is then peeled off to obtain a cross-shaped silver nanoarray.

2. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 1, characterized in that, Both the first aluminum substrate and the second aluminum substrate are obtained from high-purity aluminum sheets through cleaning and electrochemical polishing.

3. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 2, characterized in that, The period of the nickel imprinting template is 400 nm; when the nickel imprinting template is used to imprint the first aluminum substrate, the imprinting pressure is 5.0~6.0 MPa.

4. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 1, characterized in that, The first anodic aluminum oxide template is etched using a phosphoric acid solution to form the cross-shaped anodic aluminum oxide template.

5. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 4, characterized in that, When the second aluminum substrate is imprinted using the cross-shaped anodized aluminum template, the imprinting pressure is 2.2 MPa and the imprinting time is 2 min.

6. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 1, characterized in that, The array period of the cross-shaped imprint pits is 400 nm, and the oxidation voltage for anodizing the second aluminum substrate is 120 V.

7. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 1, characterized in that, The second aluminum substrate was removed using a hydrochloric acid-copper chloride mixed solution to obtain an anodized aluminum film supported by the polymethyl methacrylate support layer.

8. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 7, characterized in that, The back side of the anodic aluminum oxide film is etched with phosphoric acid to form a double-through anodic aluminum oxide template with through-holes; After removing the polymethyl methacrylate support layer, the double-channel anodized aluminum template is transferred to the substrate.

9. The method for preparing a cross-shaped silver nanoarray based on secondary imprinting according to claim 1, characterized in that, Silver was deposited from the back side of the dual-channel anodic aluminum oxide template using magnetron sputtering. After deposition, the template was peeled off with the aid of adhesive tape to obtain a cross-shaped silver nanoarray.

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