Transparent colorful pattern processing method based on multi-order nanostructure

Abstract

The invention relates to a transparent colorful pattern processing method based on a multi-order nanostructure. The transparent colorful pattern processing method specifically comprises the following steps: 1, preparing a mixed solution of a gold nanostructure and a gold nanostar; the method comprises the following steps of 1, assembling a gold nano-structure and a gold nano-star through a liquid phase interface, 2, assembling the gold nano-structure and the gold nano-star through a liquid phase interface, 3, selectively imprinting the gold nano-structure on a concave template with a macroscopic pattern, and 4, pressing a soft template with a densely arranged nano-structure layer on the surface of a target substrate for imprinting, a transparent colorful pattern with both a micro array pattern and a macro pattern is obtained on a target substrate, a transparent colorful pattern with a multi-order nano structure is obtained, and the gold nano structure in the micro array pattern is randomly and discretely distributed. According to the method, colorful patterns with controllable color appearance, adjustable transparency, multi-scale order and nanoscale thickness can be obtained, and the method has important application prospects in the fields of counterfeiting prevention, appearance decoration and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomanufacturing, and particularly relates to a method for processing transparent and colorful patterns of multi-order nanostructures. Background Art

[0002] The iridescence phenomenon is a phenomenon in which the surface color changes as the viewing angle changes. There are many brilliant iridescent structural colors in nature, including opals and tulips, which are well-known examples of this phenomenon. In recent years, many studies have explored artificial materials that create angle-dependent structural colors by manipulating the nanoscale resonances or mesoscale arrangements of nanostructures. These efforts aim to develop new methods to achieve visual appearances that mimic natural organisms or present forms not previously seen in nature. Colloidal structures offer new opportunities for creating iridescence because of their advantages in three-dimensional topography control, sub-10-nanometer spacing control, and large-area processing. For example, by deliberately inducing total internal reflection interference paths in micro-crescents, macroscopic iridescence can be achieved. This method is remarkable for its ability to produce wide-angle spectral separation and iridescent colors with dimensions exceeding ten micrometers from a single structure. Similarly, three-dimensional closely packed colloidal crystal structures can produce iridescence by Bragg diffraction, but their thickness typically exceeds several micrometers. The iridescence effect produced by surface grating diffraction has also been demonstrated in photonic crystal spheres composed of SiO2 nanospheres. However, precise control of the surface arrangement of these photonic crystal spheres is a major challenge, thus making the realization of deterministic iridescent properties more complex.

[0003] In recent years, constructing iridescence by using surface plasmons and their special optical properties has become a research hotspot.

[0004] Yao-Wei Huang et al. reported a phase-modulated multicolor element hologram that can generate a trichromatic image. The MCMH structure is made of aluminum nanorods arranged in a two-dimensional pixel array with surface plasmon resonances of red, green, and blue. The aluminum nanorod array is patterned on a 30-nanometer-thick silica spacer layer sputtered on top of a 130-nanometer-thick aluminum mirror. By appropriate structural design, narrow-bandwidth resonances can be obtained, thus realizing a multicolor scheme. Due to the wavelength dependence of the diffraction angle, the image can be projected to a specific position with a predetermined size and order. By adjusting the size of the aluminum nanorods, the image color can continuously change within the visible spectral range.

[0005] Adrian Agreda et al. present an intuitive and precise explanatory modal tool for revealing the main physical mechanisms and features of colloidal disordered monolayers deposited on reflective substrates. The model shows that the combination of plasmons and Fabry-Perot resonances provides a rare iridescent visual appearance, different from those classically observed for natural nanostructures or thin film interferences. They highlight an unusual visual effect that displays only two different colors and theoretically investigate its origin.

[0006] Leonardo Scarabelli, Cristiano Matricardi and others studied the ordered arrangement of plasmonic colloidal nanostructures and the optical properties of the resulting supercrystals. When demonstrating the macroscopic appearance of patterned nanostructure arrays, rainbow colors can be observed with the naked eye.

[0007] Kevin Vynck et al. report the potential of creating unique visual appearances using disordered optical metasurfaces. They developed a multiscale modeling platform for predictive rendering of metasurface-covered macroscopic objects in realistic environments and demonstrated how nanoscale resonances and mesoscale interference can be used to shape reflected light spectrally and angularly to produce unusual visual effects at the macroscale. They synthesized images of macroscopic objects visible to the naked eye and produced centimeter-scale samples to verify this property. This framework opens up new perspectives for many branches of applied visual arts.

[0008] In summary, there have been many discussions and attempts to achieve rainbow colors on the surface of objects through surface plasmons. However, how to achieve rainbow color structures with nanometer-level thickness and controllable colors remains to be explored, such as achieving a structural film with adjustable transparency and scattering rainbow colors with angle changes. On the other hand, how to use surface plasmon structures to form macroscopic patterns and even achieve conformal transfer of curved surfaces, the exploration of these directions will further expand the types of appearances that humans can achieve, and inject new vitality into various applications such as object appearance design and fine arts. Summary of the invention

[0009] Technical problem: The purpose of the present invention is to provide a method for processing transparent colorful patterns based on multi-order nanostructures, to solve the problem of how to design and realize multi-order transparent colorful nanostructures, and to solve the problem of simultaneously realizing multi-order nanostructures, controllable color appearance, adjustable transparency and controllable macroscopic patterns.

[0010] Technical solution: A method for processing a transparent colorful pattern based on a multi-order nanostructure of the present invention specifically comprises the following steps:

[0011] Step 1: Preparation of the mixture of gold nanostructures and gold nanorods: The colloids of gold nanostructures and gold nanorods are prepared in a particle number ratio of 1:M, where M is greater than or equal to 0.5.

[0012] Step 2: Interfacial assembly of gold nanostructures and gold nanorods and transfer to a soft template with a microarray pattern: A surfactant is added to the mixture of gold nanostructures and gold nanorods, and assembly is carried out through a liquid interface to form a close-packed nanostructure layer I with a mixture of two morphologies of gold nanostructures and gold nanorods on the liquid interface. Subsequently, the close-packed nanostructure layer I is transferred to a soft template with a microarray pattern, and the gold nanostructures and gold nanorods in the close-packed nanostructure layer I are randomly distributed.

[0013] Step 3: Selective imprinting of gold nanostructures on a concave template with a macro pattern: A transparent polymer layer with a nanoscale thickness is spin-coated on the surface of the concave template, and the soft template is covered on the surface of the concave template for imprinting. The imprinting temperature is controlled at 50 to 100 °C, the imprinting time is 1 to 10 minutes, and the pressure is 5 to 50 N. The gold nanostructures in the region complementary to the macro pattern are transferred to the concave template. Since the contact area between the gold nanorod structure and the concave template and the transparent polymer layer with a nanoscale thickness is extremely small, only the gold nanostructures can be transferred to the concave template, and a close-packed nanostructure layer II with both microarray pattern and macro pattern is obtained on the soft template.

[0014] Step 4: Imprinting of a transparent colorful pattern: A transparent polymer layer with a nanoscale thickness is spin-coated on the surface of the target substrate, and the soft template with the close-packed nanostructure layer II is pressed on the surface of the target substrate for imprinting. The imprinting temperature is controlled at 50 to 100 °C, the imprinting time is 1 to 10 minutes, and the pressure is 5 to 50 N. A transparent colorful pattern with both microarray pattern and macro pattern is obtained on the target substrate. Since the contact area between the gold nanorod structure and the target substrate and the transparent polymer layer with a nanoscale thickness is extremely small, only the gold nanostructures can be transferred to the target substrate, and the gold nanorods cannot be transferred to the target substrate. The gold nanostructures inside the microarray pattern are randomly discretely distributed.

[0015] For the gold nanostructures, the nanostructure morphologies include nanospheres, nanodisks, and nanocubes, and the size of the nanostructures is 5 to 100 nm.

[0016] The synthesis method of the gold nanorods is as follows:

[0017] First, add ultrapure water and a rotor into a glass container, and place the glass container on a rotating workbench to keep the rotor rotating at a constant speed; add chloroauric acid aqueous solution, hydrochloric acid, and gold seed aqueous solution into the glass container in sequence; add ascorbic acid aqueous solution and silver nitrate aqueous solution into the glass container at the same time; next, add a surfactant into the glass container; then seal the glass container and place it in a water bath for heating for 30 minutes, while keeping the rotor rotating; centrifuge the liquid in the glass container and discard the supernatant to obtain a gold nanostar aqueous solution.

[0018] A single micro pattern in the micro array pattern is circular or quadrilateral, the array is arranged in a hexagon or quadrilateral, the arrangement period is 1 to 20 microns, and the duty ratio of the minimum coverage diameter of the micro pattern to the period is 10% to 80%.

[0019] The material of the soft template includes polydimethylsiloxane, polymethyl methacrylate and polyvinyl pyrrolidone. The soft template has a customized protrusion micro array pattern, and the protrusion height is 0.5 to 5 microns.

[0020] The surfactant includes cetyltrimethylammonium bromide and cetyltrimethylammonium chloride.

[0021] The method of assembling using the liquid phase interface is:

[0022] Method 1: First, ethanol, n-hexane and perfluorodecanethiol are mixed and shaken vigorously to fully mix to obtain a perfluorodecanethiol solution; the mixture of gold nanostructures and gold nanostars is added to a glass container, and then the perfluorodecanethiol solution is quickly added; next, the glass container is allowed to stand until the n-hexane phase on the upper layer of the two-phase interface is completely evaporated, and a close-packed nanostructure layer 1 with a mixture of gold nanostructures and gold nanostars is formed at the two-phase interface.

[0023] Method 2: Add a heavy oil phase heavier than water and a mixture of gold nanostructures and gold nanostars coated with polyvinyl pyrrolidone into a hydrophobic container and mix them thoroughly. Since the heavy oil phase is immiscible with water, the gold nanostructures and gold nanostars remain in the heavy oil phase; through mechanical shaking, the gold nanostructures and gold nanostars form a golden film at the heavy oil phase / water interface, but due to the electrostatic repulsion between the gold nanostructures and gold nanostars, a random, non-tightly packed monolayer is formed; add a light oil phase lighter than water into the hydrophobic container, slightly tilt and rotate the hydrophobic container, and the gold nanostructures and gold nanostars spontaneously climb to the light oil phase / water interface, forming a densely packed nanostructure layer 1 with a mixture of gold nanostructures and gold nanostars.

[0024] The material of the concave plate is copper or stainless steel, and the surface of the concave plate has a semi-embossed or fully-embossed macroscopic pattern.

[0025] The material of the transparent polymer layer is polyvinyl pyrrolidone or polyethylene oxide.

[0026] Beneficial effects: Compared with the existing technologies, the present invention has the following advantages:

[0027] 1. The method for processing a transparent colorful pattern based on a multi-order nanostructure proposed by the present invention utilizes the different imprinting rates of gold nanostructures and gold nanospheres, and can control the density of gold nanostructures inside the microarray pattern by controlling the proportion of the number of particles in the mixture of gold nanostructures and gold nanospheres, realizing adjustable transparency and controllable colorful appearance.

[0028] 2. Compared with the traditional bottom-up and top-down self-assembly technologies, the method for processing a transparent colorful pattern based on a multi-order nanostructure proposed by the present invention does not require complex instruments, and can achieve the control of the density of gold nanostructures that cannot be achieved by ordinary self-assembly methods, realizing the random discrete distribution of gold nanostructures.

[0029] 3. The method for processing a transparent colorful pattern based on a multi-order nanostructure proposed by the present invention utilizes a soft template with a microarray pattern and a concave template with a macro pattern to realize the coordinated regulation of multiple orders, generate multi-scale patterns, and achieve a unique colorful appearance.

[0030] 4. The nano-fabrication technology proposed by the present invention has low manufacturing process costs, is simple and convenient to operate, uses relatively economical instruments and materials, and is easy to mass-produce and put into application. Description of the drawings

[0031] Figure 1 is a schematic flow chart of a method for processing a transparent short-range ordered rainbow-colored structure.

[0032] In the figure: gold nanostructure 1, gold nanosphere 2, microarray pattern 3, soft template 4, surfactant 5, liquid-phase interface 6, close-packed nanostructure layer one 7, macro pattern 8, concave template 9, transparent polymer layer 10, close-packed nanostructure layer two 11, transparent colorful pattern 12, target substrate 13. Detailed implementation manners

[0033] The technical solutions of the present invention will be further described below with reference to the accompanying drawings.

[0034] The present invention proposes a method for preparing a short-range ordered rainbow-colored nano-film with adjustable transparency. The principle of specifically realizing a nano-film with a controllable colorful appearance is as follows:

[0035] To achieve a transparent pattern, the present invention selects a hybrid assembly of gold nanostructures and gold nanospheres to obtain a closely packed nanostructure layer with two mixed morphologies and transfers it onto a soft template with micro-patterns. Since the height of the micro-patterns is much higher than the size of the gold nanostructures and gold nanospheres, only the gold nanostructures and gold nanospheres inside the micro-patterns have the opportunity to be imprinted onto the target substrate during imprinting, which is the first reason for forming the transparent pattern.

[0036] The transparency of the pattern can be further adjusted by the ratio of gold nanostructures to gold nanospheres during assembly. This is because during the imprinting process, only the gold nanostructures can be imprinted onto the target substrate, while the gold nanospheres cannot be imprinted.

[0037] This difference can be explained by the area factor in nano-scale transfer imprinting.

[0038] During the imprinting process, the surface energy and force balance between the transfer medium and the imprinting substrate determine the success of imprinting. Generally, it is considered that when the surface energy decreases, the assembled nanoparticles can spontaneously transfer from the donor interface to the receptor interface, and the greater the surface energy difference, the more thorough the transfer process. Conversely, certain external condition factors, such as heating, pressurization, etc., are required for the particles to transfer from the donor interface to the receptor interface under external intervention. However, in many cases, even when the surface energy meets the conditions for spontaneous imprinting, the imprinting is still difficult to carry out and additional energy needs to be applied. The energy release theory can be introduced to explain the dynamic transfer imprinting process.

[0039] Define the energy release rate G of crack propagation in the steady state as follows,

[0040]

[0041] where F is the peeling force and W is the crack width. G actually describes a kind of adhesion strength. The higher G is, the higher the adhesion strength is. According to the Griffith criterion in fracture mechanics, once G reaches the critical energy release rate, the crack will propagate stably, enabling the transfer process to proceed normally.

[0042] The energy release rate G is related to the contact area between the transfer template and the substrate. The larger the contact area, the stronger the adhesion of the interface to the nanomaterials. At the micron and above scales, it is usually considered that the contact area between the structure and the template is equal to the contact area between the structure and the substrate. Therefore, the change in the energy release rate G caused by the area change during the transfer process can usually be ignored. As the material size continues to decrease, the template can only partially contact the array, making the difference in the actual contact area on both sides of the nanomaterials larger and larger, until even at a very high peeling speed, it is still impossible to provide sufficient adhesion force for the imprinting to proceed smoothly.

[0043] Due to the fact that the Young's moduli of the soft template and the transparent polymer layer are much smaller than those of the target substrate and the gold nanostructures, when the transparent polymer layer is spin-coated on the substrate, the transparent polymer layer on the target substrate side also deforms during imprinting, making the contact areas on both sides of the gold nanostructures of the same order of magnitude, and thus the imprinting can proceed smoothly. For gold nanostars, when the thickness of the transparent polymer layer is relatively thin (about a few nanometers) due to their multi-angular morphology, the contact area between the sharp corners of the gold nanostars and the transparent polymer layer is very small, while the sharp corners on the soft template side can be completely immersed. The contact area on the target substrate side is much smaller than that on the soft template side, resulting in the inability to imprint the gold nanostars. Therefore, only sparsely arranged nanosphere components remain on the substrate after imprinting. On this basis, by utilizing the difference in imprinting efficiency between the two nanomaterials, the transparency of the imprinted pattern on the substrate can be adjusted by changing the ratio of nanospheres to nanostars during assembly.

[0044] The soft template with a microarray pattern enables the gold nanostructures imprinted on the target substrate to also have an array structure, giving the nano-pattern a colorful appearance. The origin of the colorful appearance can be explained by Bragg's law.

[0045] In the diffraction phenomenon, when the scattering wave vector aligns with the reciprocal lattice vector, i.e., k s = k i + G, the diffraction intensity can reach its maximum value, which is an inherent requirement of Bragg's law. Here, k s and k i are the wave vectors of the diffracted and incident waves respectively, and G is the reciprocal lattice vector.

[0046] Bragg's law states that when the incident wave is parallel to the crystal plane, a diffraction peak will appear only when the wave vector of the scattered wave and the reciprocal lattice vector satisfy the following condition:

[0047] 2dsinθ = nλ

[0048] where d is the interplanar spacing of the crystal plane, θ is the angle of incidence, λ is the wavelength of the incident wave, and n is an integer representing the diffraction order. When the scattering wave vector aligns with the reciprocal lattice vector, that is, when the conditions of Bragg's law are satisfied, the phase superposition of the diffraction peaks is enhanced, thereby making the diffraction intensity reach its maximum value.

[0049] In the case of two-dimensional scattering, the Bragg diffraction condition becomes:

[0050]

[0051] In the formula, θ 1 is the angle of incidence, θ 2 is the diffraction angle, λ is the diffraction wavelength, D is the lattice constant, n i and n j are the refractive indices of the incident medium and the diffracted medium respectively, and M is the diffraction order. For the case of incidence and diffraction in air, ni = n j = 1. Fixing the incident angle and wavelength, the diffraction angle is determined by the lattice constant D and can be written as:

[0052]

[0053] For each order of diffraction, the diffraction angle θ 2 will increase with the increase of the wavelength of the incident light. In appearance, each order of diffraction image should present a spectroscopical effect of inner ultraviolet and outer red, showing a colorful appearance.

[0054] The prepared transparent colorful pattern has both microscopic and macroscopic patterns. Such a multi-order nanostructure integrates multiple mode information in the same structure, produces diverse responses to different illumination conditions, and generates information in multiple dimensions.

[0055] The spectral characteristics of its colorful appearance are correlated with the microscopic characteristics of the anti-counterfeiting structure, which is expected to be applied to anti-counterfeiting. It overcomes the drawback that single-dimensional anti-counterfeiting is easy to be counterfeited and is difficult to be replicated and imitated by other technologies. The colorful appearance combined with customizable macroscopic patterns has strong visual impact and beautiful shape, which is conducive to enhancing the added value of the nanostructure.

[0056] The assembly process uses physical perturbations in the natural environment to randomly arrange the gold nanostructures on the target substrate, which can be combined with the physical unclonable function anti-counterfeiting technology. For products with strict anti-counterfeiting requirements, the microscopic structure characteristics can be identified through microscopic equipment, significantly improving the security level.

[0057] A method for processing a transparent colorful pattern based on a multi-order nanostructure proposed by the present invention specifically includes the following steps: The first step: Preparation of a mixed solution of gold nanostructures and gold nanospheres: The colloids of gold nanostructures and gold nanospheres are prepared in a ratio of 1:M in terms of the number of particles, where M is greater than or equal to 0.5. The second step: Interface assembly of gold nanostructures and gold nanospheres and transfer to a soft template with a microarray pattern: A surfactant is added to the mixed solution of gold nanostructures and gold nanospheres, and assembly is carried out through a liquid-phase interface to form a closely packed nanostructure layer one with a mixture of two morphologies of gold nanostructures and gold nanospheres on the liquid-phase interface. Subsequently, the closely packed nanostructure layer one is transferred to a soft template with a microarray pattern, and the gold nanostructures and gold nanospheres in the closely packed nanostructure layer one are randomly distributed. The third step: Selective imprinting of gold nanostructures on a concave template with a macro pattern: A transparent polymer layer with a nanoscale thickness is coated on the surface of the concave template by spin coating. The soft template is covered on the surface of the concave template for imprinting. The imprinting temperature is controlled at 50 to 100 °C, the imprinting time is 1 to 10 minutes, and the pressure is 5 to 50 Newtons. The gold nanostructures in the region complementary to the macro pattern are transferred to the concave template. Since the contact area between the gold nanosphere structure and the concave template and the transparent polymer layer with a nanoscale thickness is extremely small, only the gold nanostructures can be transferred to the concave template, and a closely packed nanostructure layer two with both microarray patterns and macro patterns is obtained on the soft template. The fourth step: Imprinting of the transparent colorful pattern: A transparent polymer layer with a nanoscale thickness is coated on the surface of the target substrate by spin coating. The soft template with the closely packed nanostructure layer two is pressed on the surface of the target substrate for imprinting. The imprinting temperature is controlled at 50 to 100 °C, the imprinting time is 1 to 10 minutes, and the pressure is 5 to 50 Newtons. A transparent colorful pattern with both microarray patterns and macro patterns is obtained on the target substrate. Since the contact area between the gold nanosphere structure and the target substrate and the transparent polymer layer with a nanoscale thickness is extremely small, only the gold nanostructures can be transferred to the target substrate, and the gold nanospheres cannot be transferred to the target substrate. The gold nanostructures inside the microarray pattern are randomly discretely distributed.

[0058] The materials selected for a method for processing a transparent colorful pattern based on a multi-order nanostructure proposed by the present invention include: gold nanostructures with the morphology of nanospheres, nanodisks or nanocubes, with a size of 5 to 100 nanometers. The materials of the soft template include polydimethylsiloxane, polymethyl methacrylate and polyvinylpyrrolidone. The soft template has a customized raised microarray pattern, with a raised height of 0.5 to 5 microns. In the microarray pattern, a single micro pattern is circular or quadrilateral, and the array is arranged in a hexagonal or quadrilateral pattern, with an arrangement period of 1 to 20 microns. The duty ratio of the minimum coverage diameter of the micro pattern to the period is 10% to 80%. The material of the concave template is copper or stainless steel, and the surface of the concave template has a semi-relief or full-relief macro pattern. The material of the transparent polymer layer is polyvinylpyrrolidone or polyethylene oxide.

[0059] The invention proposes a method for processing a transparent colorful pattern based on a multi-order nanostructure, in which a nano material processing process comprises: synthesis of gold nano stars and assembly using a liquid phase interface.

[0060] The present invention proposes a method for synthesizing gold nanostars in a transparent colorful pattern processing method based on multi-order nanostructures: first, adding ultrapure water and a rotor into a glass container, placing the glass container on a rotating workbench to keep the rotor rotating at a constant speed; sequentially adding chloroauric acid aqueous solution, hydrochloric acid, and gold seed aqueous solution into the glass container; simultaneously adding ascorbic acid aqueous solution and silver nitrate aqueous solution into the glass container; next, adding a surfactant into the glass container; then sealing the glass container and placing it in a water bath to heat for a period of time, while keeping the rotor rotating; centrifuging the liquid in the glass container and discarding the supernatant to obtain a gold nanostar aqueous solution.

[0061] The present invention proposes a method for assembling using a liquid phase interface in a transparent colorful pattern processing method based on a multi-order nanostructure: Method 1: First, ethanol, n-hexane and perfluorodecanethiol are mixed and shaken vigorously to fully mix to obtain a perfluorodecanethiol solution; the gold nanostructure and gold nanostar mixed solution is added to a glass container, and then the perfluorodecanethiol solution is quickly added; next, the glass container is left to stand until the n-hexane phase on the upper layer of the two-phase interface is completely evaporated, and a close-packed nanostructure layer 1 with a mixture of gold nanostructures and gold nanostars is formed at the two-phase interface. Method 2: A heavy oil phase heavier than water and a polyvinyl pyrrolidone-coated gold nanostructure and gold nanostar mixed solution are added to a hydrophobic container and fully mixed. Since the heavy oil phase is immiscible with water, the gold nanostructures and gold nanostars remain in the heavy oil phase; through mechanical shaking, the gold nanostructures and gold nanostars form a golden film at the heavy oil phase / water interface, but due to the electrostatic repulsion between the gold nanostructures and gold nanostars, a random, non-tightly packed monolayer is formed; when a light oil phase lighter than water is added to the hydrophobic container, and the hydrophobic container is slightly tilted and rotated, the gold nanostructures and gold nanostars spontaneously climb to the light oil phase / water interface, forming a densely packed nanostructure layer with a mixture of gold nanostructures and gold nanostars.

[0062] The present invention proposes a method for processing a transparent colorful pattern based on a multi-order nanostructure, and the implementation method is diversified. Therefore, the specific implementation method and operation process are different according to different preparation processes and material properties. All the following embodiments are implemented on the premise of the technical solution of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0063] Embodiment 1:

[0064] A method for processing a transparent colorful pattern based on a multi-order nanostructure, the specific preparation process is as follows Figure 1 As shown:

[0065] Step 1: Preparation of the mixture of gold nanospheres and gold nanorods: The colloids of gold nanospheres and gold nanorods are prepared in a ratio of 1:1 by the number of particles.

[0066] Step 2: Interfacial assembly of gold nanospheres and gold nanorods and transfer to a soft template with a microarray pattern: Add cetyltrimethylammonium bromide (0.02 g / mL) to the mixture of gold nanospheres and gold nanorods, and perform assembly through a water-hexane liquid-liquid interface to form a close-packed nanostructure layer I with a mixture of two morphologies of gold nanospheres and gold nanorods on the liquid-liquid interface. Subsequently, transfer the close-packed nanostructure layer I to a polydimethylsiloxane soft template with a microarray pattern. The microarray is arranged in a hexagonal pattern with a period of 7 microns and a radius of 2 microns for a single micro-structure. The gold nanospheres and gold nanorods in the close-packed nanostructure layer I are randomly distributed.

[0067] Step 3: Selective imprinting of gold nanospheres on a copper concave template with a macro pattern: Spin-coat a nanoscale-thick transparent polyethylene oxide layer on the surface of the concave template. Cover the polydimethylsiloxane soft template on the surface of the copper concave template for imprinting. Control the imprinting temperature at 75 °C, the imprinting time at 1 minute, and the pressure at 30 N. Transfer the gold nanospheres in the region complementary to the macro pattern to the copper concave template. Since the contact area between the gold nanorod structure and the copper concave template and the nanoscale-thick polyethylene oxide layer is extremely small, only the gold nanospheres can be transferred to the copper concave template, and a close-packed nanostructure layer II with both microarray and macro patterns is obtained on the polydimethylsiloxane soft template.

[0068] Step 4: Imprinting of a transparent and colorful pattern: Spin-coat a nanoscale-thick polyethylene oxide layer on the surface of a quartz substrate. Press the polydimethylsiloxane soft template with the close-packed nanostructure layer II on the surface of the quartz substrate for imprinting. Control the imprinting temperature at 75 °C, the imprinting time at 3 minutes, and the pressure at 30 N. A transparent and colorful pattern with both microarray and macro patterns is obtained on the quartz substrate. Since the contact area between the gold nanorod structure and the quartz substrate and the nanoscale-thick polyethylene oxide layer is extremely small, only the gold nanospheres can be transferred to the quartz substrate, and the gold nanorods cannot be transferred to the target substrate. The gold nanorods inside the microarray pattern are randomly and discretely distributed.

[0069] The method of the liquid-liquid interface assembly is as follows:

[0070] Method 1: First, mix ethanol, n-hexane, and perfluorodecanethiol and shake vigorously to mix thoroughly to obtain a perfluorodecanethiol solution; add the mixed solution of gold nanospheres and gold nanorods to a glass container, and then quickly add the perfluorodecanethiol solution; next, let the glass container stand until the n-hexane phase on the upper layer of the two-phase interface completely evaporates, and a close-packed nanostructure layer I mixed with two morphologies of gold nanospheres and gold nanorods is formed at the two-phase interface.

[0071] Method 2: Add dichloromethane, a heavy oil phase heavier than water, and a mixed solution of gold nanospheres and gold nanorods coated with polyvinylpyrrolidone to a hydrophobic container and mix thoroughly. Since dichloromethane is immiscible with water, the gold nanospheres and gold nanorods remain in dichloromethane; through mechanical shaking, a golden film is formed at the dichloromethane / water interface, but due to the electrostatic repulsion between the gold nanospheres and gold nanorods, a random and non-close-packed monolayer is formed; add n-hexane, a light oil phase lighter than water, to a centrifuge tube, tilt and rotate the centrifuge tube slightly, and the gold nanospheres and gold nanorods spontaneously climb to the n-hexane / water interface to form a close-packed nanostructure layer I mixed with two morphologies of gold nanospheres and gold nanorods.

Claims

1. A method for processing a transparent colorful pattern based on a multi-order nanostructure, characterized in that The specific steps include: Step 1: Preparation of a mixture of gold nanostructures (1) and gold nanostars (2): The colloids of gold nanostructures and gold nanostars are prepared in a ratio of 1:M in terms of the number of particles, where M is greater than or equal to 0.5; Step 2: Interface assembly of gold nanostructures and gold nanostars and transfer to a soft template (4) having a microscopic array pattern (3): Add the mixture of gold nanostructures and gold nanostars into a surfactant (5) and assemble through a liquid interface (6) to form a densely packed nanostructure layer (7) with randomly distributed gold nanostructures and gold nanostars mixed in the liquid interface, and then transfer to a soft template having a microscopic array pattern; Step 3: selectively imprinting the gold nanostructure on the concave template (9) having the macroscopic pattern (8): coating the surface of the concave template with a transparent polymer layer (10) of nanometer thickness by spin coating, covering the surface of the concave template with a soft template for imprinting, transferring the gold nanostructure in the area complementary to the macroscopic pattern to the concave template, and obtaining a densely packed nanostructure layer (11) having both the microscopic array pattern and the macroscopic pattern on the soft template; Step 4: Imprinting of the transparent colorful pattern (12): Spin coating a transparent polymer layer with a thickness of nanometers on the surface of the target substrate (13), and press a soft template having a closely packed nanostructure layer 2 onto the surface of the target substrate for imprinting, thereby obtaining a transparent colorful pattern having both a microscopic array pattern and a macroscopic pattern on the target substrate, wherein only the gold nanostructure is transferred to the target substrate, and the gold nanostructure inside the microscopic array pattern is randomly and discretely distributed.

2. A method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The gold nanostructure (1) has a morphology including nanospheres, nanodisks and nanocubes, and the size of the nanostructure is 5 to 100 nanometers.

3. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The synthesis method of the gold nanostar (2) is: First, ultrapure water and a rotor are added to a glass container, and the glass container is placed on a rotating workbench to keep the rotor rotating at a constant speed; chloroauric acid aqueous solution, hydrochloric acid, and gold seed aqueous solution are added to the glass container in sequence; ascorbic acid aqueous solution and silver nitrate aqueous solution are added to the glass container at the same time; a surfactant (5) is then added to the glass container; the glass container is then sealed and placed in a water bath for heating for 30 minutes, while the rotor is kept rotating; the liquid in the glass container is centrifuged and the supernatant is discarded to obtain a gold nanostar (2) aqueous solution.

4. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that A single micro pattern in the micro array pattern (3) is circular or quadrilateral, the array is arranged in a hexagonal or quadrilateral shape, the arrangement period is 1 to 20 microns, and the duty ratio of the minimum coverage diameter of the micro pattern to the period is 10% to 80%.

5. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The material of the soft template (4) includes polydimethylsiloxane, polymethyl methacrylate and polyvinyl pyrrolidone. The soft template has a customized protrusion micro array pattern (3) with a protrusion height of 0.5 to 5 microns.

6. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The surfactant (5) includes hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride.

7. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The method of assembling through the liquid phase interface (6) is: Method 1: First, ethanol, n-hexane and perfluorodecanethiol are mixed and shaken vigorously to be fully mixed to obtain a perfluorodecanethiol solution; the mixed solution of gold nanostructures (1) and gold nanostars (2) is added to a glass container, and then the perfluorodecanethiol solution is quickly added; next, the glass container is allowed to stand until the n-hexane phase on the upper layer of the two-phase interface is completely evaporated, and a close-packed nanostructure layer (7) with a mixture of the two morphologies of gold nanostructures (1) and gold nanostars (2) is formed at the two-phase interface.

8. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The method of assembling through the liquid phase interface (6) is: Method 2: Add a heavy oil phase heavier than water and a mixture of gold nanostructures (1) and gold nanostars (2) coated with polyvinyl pyrrolidone into a hydrophobic container and mix them thoroughly. Since the heavy oil phase is immiscible with water, the gold nanostructures (1) and gold nanostars (2) remain in the heavy oil phase. Through mechanical shaking, the gold nanostructures (1) and gold nanostars (2) form a golden film at the heavy oil phase / water interface. However, due to the electrostatic repulsion between the gold nanostructures (1) and the gold nanostars (2), a random, non-tightly packed single layer is formed. Add a light oil phase lighter than water into the hydrophobic container, slightly tilt and rotate the hydrophobic container, and the gold nanostructures (1) and gold nanostars (2) spontaneously climb to the light oil phase / water interface to form a densely packed nanostructure layer (7) with a mixture of the two morphologies of the gold nanostructures (1) and the gold nanostars (2).

9. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The material of the concave plate (9) is copper or stainless steel, and the surface of the concave plate (9) has a semi-relief or full-relief macro pattern (8).

10. The method for processing a transparent colorful pattern based on a multi-order nanostructure according to claim 1, characterized in that The material of the transparent polymer layer (10) is polyvinyl pyrrolidone or polyethylene oxide.

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