A photonic gel film with a double-layer hollow structure capable of controllable water permeation and color change, and its preparation method and application

Abstract

The present invention belongs to the technical field of polymer composite material preparation and discloses a double-layer hollow structure photonic gel film with controllable water permeation and color change, as well as its preparation method and application. The method comprises the following steps: preparing a three-dimensional PS-SiO2 photonic crystal and a three-dimensional SiO2 photonic crystal; calcining the three-dimensional PS-SiO2 photonic crystal at high temperature, filling the crystal with a polymer, and curing the crystal with ultraviolet light to obtain a hollow SiO2 structural color gel; curing the three-dimensional SiO2 photonic crystal with a polymer, and then etching the crystal with hydrofluoric acid to obtain an inverse opal gel; and bonding the hollow SiO2 structural color gel and the inverse opal gel to form a double-layer hollow structure photonic gel film with controllable water permeation and color change. The photonic gel film can be used in snowmelt warning indicators at large ski resorts, portable alcohol solubility detectors, or anti-counterfeiting identification labels for small commercial packaging.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer composite material preparation, and particularly relates to a photonic gel film with a double-layer hollow structure capable of controllable water permeation and color change, and a preparation method and application thereof. Background Art

[0002] Controllable water-permeable color-changing materials are a type of smart material that has the ability to adaptively respond to environmental changes. For example, by introducing components that react to liquid penetration (such as color-changing agents or sensitive compounds), these materials can undergo significant color changes when exposed to liquid. However, the long-term use of color-changing agents or sensitive compounds can cause damage to the environment, and also faces many material research and development issues, including achieving a stable and reversible color change mechanism, enhancing the contrast of color changes, and improving the stability and durability of materials.

[0003] Therefore, developing structural colors that do not rely on reaction color change and can continuously and reversibly change color is undoubtedly a preferred mode. Among them, three-dimensional hollow photonic crystals have attracted widespread attention due to their large pore structure. According to Bragg's law The diffraction wavelength λ can be adjusted by n eff to change, where λ is the diffraction wavelength, n eff is the effective refractive index, d is the interparticle distance, and θ is the angle measured relative to a vector perpendicular to the close-packed plane. This periodic appearance of low-refractive-index material within a high-refractive-index material is the fundamental characteristic of the color change. This is also due to the hollow structure's ability to accommodate a variety of liquids with varying refractive indices, enabling a wide range of color changes. Compared to the current color-changing behavior of single hollow photonic structures, the preparation and performance development of complex double-layer hollow structures for controllable water permeability are undoubtedly more versatile and practical.

[0004] Therefore, research on controllable water-transmitting color-changing materials aims to improve the efficiency and accuracy of fields such as information recognition and liquid detection, and enhance the safety and reliability of these applications through the intelligent response of the materials. Research on such materials not only promotes the development of intelligent sensing technology but also promotes innovation in areas such as high-performance optical materials and environmental monitoring equipment. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the primary purpose of the present invention is to provide a method for preparing a photonic gel film with a double-layer hollow structure and controllable water permeation and color change.

[0006] Another object of the present invention is to provide a double-layer hollow structure photonic gel film with controllable water permeation and color change prepared by the above-mentioned preparation method; the prepared photonic gel film is composed of three-dimensional photonic crystals and polymers, wherein the three-dimensional photonic crystals can be used but not limited to polystyrene-silica core-shell structure balls or monodisperse silica microspheres; wherein the polymer can be used but not limited to polyacrylic acid, polyhydroxyethyl methacrylate, polyethylene glycol diacrylate polymer and polymethyl acrylate.

[0007] The present invention achieves controllable color changes by collaboratively regulating water permeability through a variety of photonic crystals and polymers; this includes regulating the three-dimensional photonic crystal structure, regulating the degree of polymer cross-linking, and regulating the hydrophilicity of the polymer to collaboratively control the process of structural color change.

[0008] Another object of the present invention is to provide an application of the above-mentioned double-layer hollow structure photonic gel film with controllable water permeation and color change; the photonic gel film can be applied in the following aspects: 1. As a signal indicator for warning of snow melting in indoor ski resorts; 2. As a portable alcohol concentration detector; 3. As an anti-counterfeiting label for small commercial packaging for hiding information.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change, comprising the following steps:

[0011] (1) Initiating a polymerization reaction between styrene and an initiator at 60-80° C. to obtain polystyrene microspheres; reacting the obtained polystyrene microspheres with ammonia water and vinyl triethoxysiloxane to obtain polystyrene-silica core-shell nanospheres having polystyrene as a core and silica as a shell;

[0012] The thickness of the outer shell silica of the polystyrene-silica core-shell nanospheres is 19 to 60 nm, and the thickness is controlled by changing the volume ratio of ammonia water to vinyl triethoxysiloxane, wherein the volume ratio of ammonia water to vinyl triethoxysiloxane is (1.2 to 10): (0.45 to 3.75);

[0013] The polystyrene-silica core-shell microspheres were dispersed in an ethanol solvent, and then the polystyrene-silica core-shell nanospheres were assembled into neat face-centered cubic three-dimensional PS-SiO2 photonic crystals by self-assembly during ethanol solvent evaporation.

[0014] (2) Tetraethyl orthosilicate autonomously nucleates and grows at room temperature under the action of ammonia water to obtain solid silica nanostructured microspheres; the particle size of the solid silica nanostructured microspheres is 180-260 nm, and the particle size is controlled by changing the volume ratio of ammonia water to tetraethyl orthosilicate, which is (4-7.5):20;

[0015] Solid silica nanostructured microspheres are dispersed in an ethanol solvent, and then the ethanol solvent is evaporated to self-assemble the solid silica nanostructured microspheres into a neat face-centered cubic stacked three-dimensional SiO2 photonic crystal;

[0016] (3) calcining the three-dimensional PS-SiO2 photonic crystal obtained in step (1) at a high temperature of 500-600° C. in a muffle furnace for 8-12 hours to obtain a hollow SiO2 photonic crystal; filling the prepolymer monomer added with a photoinitiator into the hollow SiO2 photonic crystal, curing by ultraviolet exposure, embedding the prepolymer monomer and the hollow SiO2 photonic crystal, and peeling off the obtained polymer film to obtain a hollow SiO2 structural color gel;

[0017] (4) filling the prepolymer monomer added with a photoinitiator into the three-dimensional SiO2 photonic crystal obtained in step (2), curing by ultraviolet exposure, embedding and combining the prepolymer monomer and the three-dimensional SiO2 photonic crystal, peeling off the obtained polymer film, and etching the SiO2 with hydrofluoric acid having a volume percentage concentration of 4% to obtain an inverse opal gel;

[0018] (5) The hollow SiO2 structural color gel obtained in step (3) and the inverse opal gel obtained in step (4) are stacked together in two layers, and bonded under ultraviolet light using ethoxylated trimethylolpropane triacrylate and a photoinitiator in a mass ratio of 99:1 to obtain a double-layer hollow structure photonic gel film with controllable water permeability and color change.

[0019] The initiator in step (1) is potassium persulfate or ammonium persulfate.

[0020] The thickness of the outer shell silica in step (1) is the key to controlling the water permeability in the first step. The thickness of the silica is achieved by controlling the combined ratio of ammonia water and vinyl triethoxysiloxane. The thinner the outer shell silica, the shorter the water permeation process and the stronger the water permeability. Conversely, the thicker the outer shell, the longer the water permeation process and the weaker the water permeability.

[0021] In step (1), the three-dimensional PS-SiO2 photonic crystal is prepared by ultraviolet lithography to form a variety of but not limited to pattern labels such as "Chinese knot", "QR code" and other patterns, and then proceed to subsequent steps.

[0022] The calcination time in step (2) is 550° C. and the calcination time is 12 hours.

[0023] The prepolymer monomers in steps (3) and (4) are composed of polymer monomers and crosslinking agents in a mass ratio of 1:1 to 1:2. The polymer monomers are one or more of acrylic acid, hydroxyethyl methacrylate, polyethylene glycol diacrylate, and methyl acrylate. The order of hydrophilicity is from strong to weak: acrylic acid > hydroxyethyl methacrylate > polyethylene glycol diacrylate > methyl acrylate. This can regulate the different water permeability of the gel, which is a means of controlling the water permeability in the second step. The crosslinking agent is ethoxylated trimethylolpropane triacrylate. Preferably, the prepolymer monomers include acrylic acid, polyethylene glycol diacrylate, and ethoxylated trimethylolpropane triacrylate in a mass ratio of 1:4:5 to 1:4:10. Increasing and decreasing the crosslinking agent content is a means of controlling the water permeability in the third step.

[0024] The photoinitiator in step (3) and step (4) is 2-hydroxy-2-methyl-1-phenyl-1-propanone; the amount of the photoinitiator used is 2% to 3% of the mass of the polymer monomer in the prepolymer liquid monomer.

[0025] A photonic gel film with a double-layer hollow structure and controllable water permeation and color change is prepared by the above preparation method.

[0026] The above-mentioned double-layer hollow structure photonic gel film with controllable water permeation and color change is used in signal indicators for snowmelt warnings at large ski resorts, portable alcohol solubility detectors, or anti-counterfeiting identification labels for small commercial packages.

[0027] The above-mentioned double-layer hollow structural color gel with controllable water seepage and color change is used as a signal indicator for snowmelt warning in large ski resorts. Its characteristic is that the color of the structural color gel changes due to accumulated water caused by snowmelt, and the snowmelt time can be judged based on the different color labels.

[0028] The above-mentioned double-layer hollow structural color gel with controllable water permeation color change is used for a portable alcohol solubility detector. Its characteristics are: when a series of commercially available alcohol-containing products are dripped onto the structural color gel, different colors of different alcohols are displayed;

[0029] The above-mentioned double-layer hollow structural color gel with controllable water permeation color change is used for optical anti-counterfeiting identification of small commercial packaging labels. Its characteristics are: it becomes transparent when wet so that the hidden commercial anti-counterfeiting code information can be displayed, and different concentrations of solvents can be used as a corresponding encoding means.

[0030] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0031] This invention proposes a novel method for modulating the photonic bandgap (PBG) through a slow water infiltration process. This slow-infiltration, non-sensitive structural color indicator tag enables the temporal measurement of changing responses. Based on the stable periodic arrangement of hollow SiO2, the material exhibits a synergistic water permeation effect influenced by the triple factors of SiO2 thickness, gel hydrophilicity, and gel crosslinking. Importantly, a larger SiO2 thickness slows water permeation; more hydrophilic gels and gels with lower crosslinking tend to permeate more rapidly, and vice versa. Furthermore, the macroporous structure of an inverse opal gel is combined with the hollow SiO2 to produce a novel double-layer hollow structural color gel. This structural feature combines the dual permeation mechanisms of hollow SiO2 and inverse opal, making it effective for early warning of ice melt control in large venues such as indoor ski resorts and ice storage facilities. Clearly, the Bragg diffraction effect associated with slow permeation can provide enhanced time indication. In addition, by using solvents with low surface tension, such as ethanol and water, high-level anti-counterfeiting labels can achieve fast and reversible information encryption and decryption, playing a good role in protecting high-value goods and combating counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the preparation process of hollow structural color gel with controllable water permeation color change;

[0033] Figure 2 The QR code patterns of hollow SiO2 photonic crystals are colorless dry state, blue ethanol wet state (a), dry purple state, green ethanol wet state (b), colorless dry state with different SiO2 thickness, blue ethanol wet state (c), dry green state, orange ethanol wet state (d);

[0034] Figure 3 Digital photos of the structural color changes of four hollow SiO2 photonic crystal gels at different angles;

[0035] Figure 4 The structural color images of hollow SiO2 photonic crystals at different water infiltration stages (time-dependent);

[0036] Figure 5 Structural color reflectance spectrum of hollow SiO2 photonic crystal immersed for 3 hours;

[0037] Figure 6 Schematic diagram of the structural color change of a double-layer hollow structural color gel when immersed in water and ethanol, as well as the schematic process of hiding when dry and showing when wet;

[0038] Figure 7 Video contact angle test of inverse opal gel, corresponding to the contact angle values ​​under pure water, 5%, 10%, 15%, and 20% volume fraction alcohol concentrations;

[0039] Figure 8 A schematic diagram of the principle and process of a signal indicator for snowmelt warning used in large ski resorts;

[0040] Figure 9 This is a picture of the structural color display of a double-layer hollow structural color gel used in testing 3°, 5°, and 8° commercially available edible alcoholic beverages;

[0041] Figure 10 An ethanol concentration-dependent information display process applied to high-level encrypted anti-counterfeiting labels. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0043] The preparation process of one of the following examples ( Figure 1 ), the specific steps are as follows:

[0044] Step 1: Monodisperse polystyrene (PS) nanospheres are added to a reaction solution of mixed ammonia and vinyl triethoxysilane at a certain dispersion concentration of 3-5mL. According to the volume ratio of ammonia + vinyl triethoxysilane (1.2-10): (0.45-3.75), SiO2 thicknesses ranging from 19nm to 60nm can be obtained. After the reaction is completed, polystyrene-silica (PS-SiO2) core-shell structure microspheres of different particle sizes are obtained; the microspheres are dispersed in an ethanol solvent, and then the ethanol solvent is evaporated and self-assembled to assemble the polystyrene-silica core-shell nanospheres into neat face-centered cubic stacked three-dimensional PS-SiO2 photonic crystals;

[0045] Step 2: Adding a combination of ammonia water and tetraethyl orthosilicate in a volume ratio of (4-7.5):20 to a pure water and ethanol system can obtain solid SiO2 nanostructured microspheres ranging from 180 to 260 nm; dispersing the solid silica nanostructured microspheres in an ethanol solvent, and then using the ethanol solvent to evaporate and self-assemble the solid silica nanostructured microspheres to assemble into a three-dimensional SiO2 photonic crystal with neat face-centered cubic stacking; the solvent (ethanol) evaporates and self-assembles to similarly assemble the solid SiO2 into a three-dimensional photonic crystal with neat face-centered cubic stacking;

[0046] Step 3: The three-dimensional PS-SiO2 photonic crystal obtained in step 1 is fully calcined at a high temperature of 500-600°C for 8-12 hours to obtain a hollow SiO2 photonic crystal. A prepolymer monomer of acrylic acid, polyethylene glycol diacrylate and ethoxylated trimethylolpropane triacrylate (with an additional photoinitiator of 2-3 v / v%) in a mass ratio of 1:4:5 to 1:4:10 is filled into the hollow SiO2 photonic crystal, and cured by ultraviolet exposure. The prepolymer monomer and the hollow SiO2 photonic crystal are embedded and combined. Replacing acrylic acid with an equal volume of hydroxyethyl methacrylate or methyl acrylate can also obtain a polymer material of the same color. The obtained polymer film is peeled off and taken out to obtain a hollow SiO2 structural color gel;

[0047] Step 4: As in step 3, a prepolymer monomer of acrylic acid, polyethylene glycol diacrylate and ethoxylated trimethylolpropane triacrylate (with an additional photoinitiator of 2-3 v / v%) in a mass ratio of 1:4:5 to 1:4:10 is filled into the three-dimensional SiO2 photonic crystal obtained in step 2, and cured by ultraviolet exposure. The prepolymer monomer and the three-dimensional SiO2 photonic crystal are inlaid and combined. The filling prepolymer monomer is the same as step 3. The obtained polymer film is peeled off and taken out, and SiO2 is etched with hydrofluoric acid with a volume percentage concentration of 4% to obtain an inverse opal gel;

[0048] Step 5: Stack the hollow SiO2 structural color gel obtained in step 3 and the inverse opal gel obtained in step 4 together in two layers, and use ethoxylated trimethylolpropane triacrylate and photoinitiator with a mass ratio of 99:1 to bond them under ultraviolet light to obtain a double-layer hollow structure photonic gel film with controllable water permeability and color change.

[0049] The present invention produces a double-layer hollow photonic gel film with controllable water permeation color change. Its structural features combine the dual water permeation mechanisms of hollow SiO2 structural color gel and inverse opal, making it effective for use as an early warning system for ice melt control in large venues such as indoor ski resorts and ice storage facilities. Furthermore, by using low-surface-tension solvents such as ethanol and water, high-level anti-counterfeiting labels can achieve rapid and reversible information encryption and decryption, playing an important role in protecting high-value goods and combating counterfeiting.

[0050] Example 1

[0051] This embodiment provides a method for preparing polystyrene (PS) and polystyrene (PS)-silicon dioxide (SiO2) photonic crystals, comprising the following steps:

[0052] Step 1: Styrene monomer is mixed with water under the emulsification of sodium lauryl sulfate to form a suspension. The amount of styrene used is 10-15g, preferably 15g, and the amount of sodium lauryl sulfate used is 80-120mg. Different addition amounts are selected according to different particle sizes. The experiment is designed to have three PS particle size ranges: 180nm, 200nm, and 220nm, corresponding to sodium lauryl sulfate amounts of 85mg, 100mg, and 115mg, respectively. Finally, the polymerization reaction is initiated by persulfate under the action of heat to obtain polystyrene (PS).

[0053] Step 2: Add the 180nm PS and 220nm PS reaction stock solutions obtained in the reaction to new deionized water, preferably in an amount of 3-5mL. Then, add 1.2mL+0.45mL~10mL+3.75mL of ammonia water (NH3·H2O)+vinyl triethoxysiloxane (TEOVS) in a mixed solvent of PS and deionized water, and react for 3-5h.

[0054] Step 3: Place the reaction solution in a centrifuge tube for centrifugal drying, and the obtained solid is dispersed in anhydrous ethanol under ultrasonication to form a dispersion (the dispersion concentration is preferably 1% mass volume ratio), and then insert a glass bottle into the dispersion and place it in a constant temperature and humidity environment for 3 days to obtain PS-SiO2 photonic crystals.

[0055] Example 2

[0056] This embodiment provides a method for preparing a hollow SiO2 photonic crystal having a two-dimensional code pattern of different colors, comprising the following steps:

[0057] Step 1: According to the various PS-SiO2 photonic crystals obtained in Example 1, they are labeled as 180nm-NH3·H2O4 according to the experimental formula. mL +TEOVS 1.5 mL , 180nm-NH3·H2O6 mL +TEOVS 2.25mL or 220nm-NH3·H2O2 mL +TEOVS 0.75 mL , 220nm-NH3·H2O6 mL +TEOVS 2.25 mL Four PS-SiO2 photonic crystals with different core-shell ratios are represented.

[0058] Step 2: Place the above PS-SiO2 photonic crystals at 500-600℃ and heat them for 8-12h to preliminarily obtain hollow SiO2 photonic crystals. Adjust the heating time to obtain hollow SiO2 with different residual carbon amounts, preferably heating at 550℃ for 8h.

[0059] Step 3: Prepare a negative photoresist with a mass ratio of 99:1. Weigh ethoxylated trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenyl-1-propanone, then mix them by sonication to create a prepolymer solution for use in UV lithography.

[0060] Step 4: Fill the negative photoresist in the glass interlayer with a spacing of 0.14 cm, fully penetrate the PS-SiO2 photonic crystal, then use a black pattern baffle to cover the top of the glass sheet, and use ultraviolet lamp to irradiate. The ultraviolet exposure time is set to 3 to 5 seconds according to different ultraviolet lamp power settings.

[0061] Step 5: Use anhydrous ethanol to rinse the unpolymerized liquid, and use a surgical blade to remove the photoresist, leaving behind hollow silica with a pattern (such as a QR code). The color will be different under ethanol rinsing depending on the size of the photonic crystal.

[0062] Experimental results: Figure 2 As shown, 180nm-NH3·H2O4 mL +TEOVS 1.5 mL The obtained colorless photonic crystals showed blue color when wetted with ethanol ( Figure 2 a); 180nm-NH3·H2O6 mL +TEOVS 2.25 mL The purple photonic crystals were obtained, and they showed green under ethanol wetting ( Figure 2 b); 220nm-NH3·H2O 2mL +TEOVS 0.75 mL Colorless photonic crystals were obtained, and blue was obtained when wetted with ethanol, but Figure 2 The difference is that the hollow silica here is thinner and has stronger water permeability ( Figure 2 c); 220nm-NH3·H2O 6mL +TEOVS 2.25 mL Green photonic crystals were obtained, which showed orange under ethanol wetting ( Figure 2 d); the QR code pattern changes to different colors in the dry state and when soaked in ethanol.

[0063] Example 3

[0064] This embodiment provides a method for preparing a hollow SiO2 photonic crystal with a Chinese knot pattern and angle-dependent color change, comprising the following steps:

[0065] Step 1: The PS-SiO2 photonic crystals are treated using the preparation method in Example 2. The difference is that the preparation of hollow SiO2 photonic crystals of different colors depends on the adjustment of the combination ratio of 1.2mL+0.45mL~10mL+3.75mL of ammonia water (NH3·H2O) + vinyl triethoxysiloxane (TEOVS). The purple photonic crystals are preferably prepared with 4mLNH3·H2O+1.5mLTEOVS formula (180nmPS), the blue photonic crystals are preferably prepared with 6mLNH3·H2O+2.25mLTEOVS formula (180nmPS), the green photonic crystals are preferably prepared with 4mLNH3·H2O+1.5mLTEOVS formula (220nmPS), and the orange photonic crystals are preferably prepared with 6mLNH3·H2O+2.25mLTEOVS formula (220nmPS).

[0066] Step 2: The same operation process as steps 2, 3 and 4 described in Example 2 is adopted, except that the patterned photolithography template is replaced with a Chinese knot pattern.

[0067] Step 3: Use acrylic acid, polyethylene glycol diacrylate and ethoxylated trimethylolpropane triacrylate prepolymer monomers with a mass ratio of 1:4:5 to 1:4:10 (plus 2 to 3 v / v% photoinitiator) to fill the hollow SiO2 photonic crystal, cure it by UV exposure and completely peel off the polymer film.

[0068] Experimental results: Figure 3 As shown, the 420-600 nm hollow SiO2 gel exhibits regular color change behavior at a change angle of 0 to 60°, purple-colorless, blue-purple, green-blue, and orange-green.

[0069] Example 4

[0070] This embodiment provides a test and judgment result of the water seepage process of a hollow SiO2 structural color gel, including the following steps:

[0071] Step 1: Preparation of hollow SiO2 photonic crystals as described in Example 3, preferably the orange preparation scheme 6mL NH3·H2O formula (220nmPS).

[0072] Step 2: Prepare a gel material with controllable water permeability. Experimentally, prepolymer solutions with varying water permeability were prepared. Polymerizable monomers including acrylic acid, hydroxyethyl methacrylate, polyethylene glycol diacrylate, and methyl acrylate were selected for the experiment. Water permeability tests revealed that the hydrophilic swelling ability ranked from strongest to weakest in the order of acrylic acid > hydroxyethyl methacrylate > polyethylene glycol diacrylate > methyl acrylate.

[0073] Step 3: The combination ratio is preferably a gel material with slow water permeability and certain anti-swelling properties. In actual comparison, three gels were used: acrylic acid co-polyhydroxyethyl methacrylate, acrylic acid co-polyethylene glycol diacrylate, and acrylic acid co-polymethyl acrylate. Comparison of any combination ratios revealed a combination ratio of acrylic acid to polyethylene glycol diacrylate and crosslinker ethoxylated trimethylolpropane triacrylate of 1:4:5 to 1:4:10 (mass ratio) (with 2-3 v / v% photoinitiator added) as the preferred combination ratio for slow permeation gel.

[0074] Step 4: Through the measurement of portable fiber optic spectrometer, the experiment was designed to study the water permeation and structural color change process of hollow SiO2 structural color gel within 3 hours, and the influence of gel hydrophilicity and cross-linking degree on gel water permeability was measured by data comparison.

[0075] Experimental results: Filling orange hollow SiO2 photonic crystals with acrylic acid, polyethylene glycol diacrylate and crosslinker ethoxylated trimethylolpropane triacrylate prepolymer monomers in a mass ratio of 1:4:5 to 1:4:10 yielded a gel that slowly changes color upon water permeation. This material possesses both a certain water permeability and anti-swelling properties, and can change color upon water permeation over a long period of time. Using less hydrophilic hydroxyethyl methacrylate and methyl acrylate will greatly weaken this permeation process. Figure 4 As shown in the figure, as the water immersion process progresses, the original reflectance spectrum value of the gel is 643nm, and it goes through an intermediate process of 688nm and reaches a stable result of 700nm. Figure 5 The structural color reflectance spectroscopy results after three hours of immersion also prove the occurrence of three processes.

[0076] Example 5

[0077] This embodiment provides a method for preparing a double-layer hollow structure color gel and a method for detecting water seepage, comprising the following steps:

[0078] Step 1: Preparation of the inverse opal structure. Ammonia, tetraethyl orthosilicate, and deionized water were dispersed in 200 mL of anhydrous ethanol at a mass ratio of 4:20:30 to 7.5:20:30. The mixture was stirred at high speed for 90 seconds, followed by a reaction at 300 rpm for 3 hours to synthesize monodisperse SiO2 nanoparticles. The resulting SiO2 was then prepared into SiO2 photonic crystals using the same method as in Step 3 of Example 1.

[0079] Step 2: Use the combination ratio of acrylic acid, polyethylene glycol diacrylate and ethoxylated trimethylolpropane triacrylate of 1:4:5 to 1:4:10 (mass ratio) (plus photoinitiator 2 to 3 v / v%) described in Example 4 to fill the SiO2 photonic crystal and cure it under ultraviolet light.

[0080] Step 3: Remove the polymer film and soak it in a 4% (volume fraction) hydrofluoric acid solution for 5 hours. Experiments using SiO2 with different particle sizes can produce inverse opal gels with various structural colors (such as purple, green, and yellow).

[0081] Step 4: Combine the inverse opal gel obtained in step 3 with any of the hollow SiO2 gels in Examples 2 and 3. Use UV light bonding with ethoxylated trimethylolpropane triacrylate and photoinitiator at a ratio of 99:1 (mass ratio) for application in water seepage identification in multiple scenarios.

[0082] Since the ratio of acrylic acid to polyethylene glycol diacrylate to ethoxylated trimethylolpropane triacrylate is 1:4:5 to 1:4:10, an inverse opal gel material with a hydrophilic contact angle of 30° at an ethanol concentration of 5% is obtained, Figure 6 Experimental results demonstrate the successful fabrication of a solvent-selective anti-counterfeiting label with both revealing and concealing capabilities. Increasing the amount of ethoxylated trimethylolpropane triacrylate increases the crosslinking degree of the gel, and the structural color gel exhibits enhanced resistance to deformation during wetting. Because water permeation through the hollow structure of the inverse opal gel is dependent on pore size and the surface tension of the permeating solution, the structural color typically blurs when immersed in pure water. However, the addition of alcohol rapidly transparentizes the gel, revealing the underlying pattern.

[0083] Example 6

[0084] This embodiment provides a double-layer hollow structural color gel for use in a large ski resort snowmelt warning indicator, a portable alcohol solubility detector, and an anti-counterfeiting identification label for small commercial packaging, including the following instructions:

[0085] Application 1: Artificial ski resorts must maintain an indoor environment below -20°C. However, due to the influence of the temperature of the venue area and the indoor atmospheric pressure, partial melting of ice and snow is inevitable. Therefore, in order to better monitor the degree of ice and snow freezing in the venue and ensure a good consumption experience for skiers, we propose to use double-layer hollow structural color gel as an indicator to measure the degree of ice and snow melting, which can serve as a technical indicator of whether the snow in the venue needs a certain scale of maintenance ( Figure 8), and if inverse opal is used as an indicator, its water response speed is too fast, and it is impossible to judge whether maintenance is needed. In the conceptual diagram, a tag with an arbitrary pattern (Chinese knot in the figure) is placed in an area with high indoor temperature or low-lying area. As a color indicator for fixed-point monitoring, it can play a good role in judging whether the ice and snow have melted and how long the ice and snow have melted. First, the controllable infiltration tag is designed as 4 sets of parallel data. Every time the site indicator is measured, the staff needs to use a mobile phone to scan and read the tag. The optical image captured by the camera is then quickly decomposed into RGB images by the mobile phone. Each color point in the image is scanned and integrated, and then a set of RGB output values ​​for the structural color tag is obtained. The law of change of RGB values ​​over time is used to calculate the water penetration time. This can not only play a role in snow melting, but also avoid the trouble and inconvenience of spectral analysis of the specific penetration state of water.

[0086] Application 2: The wort concentration of beer is one of the important indicators for measuring beer quality. It indicates the sugar content of the wort in the raw materials at the beginning of fermentation. Specifically, the wort concentration can be divided into three levels: 1. Low-concentration beer: the wort concentration is 6°-8°, and the alcohol content is also the lowest, generally around 2%; 2. Medium-concentration beer: the wort concentration is 10°-12°, and the alcohol content is around 3.5%. This is the main variety of mid-to-high-end industrial beer production in my country; 3. High-concentration beer: the wort concentration is 12°-20°, and the alcohol content is close to 5%. It is internationally recognized that beer above 12° is a high-end beer. This type of beer has a long brewing cycle, is resistant to storage, and has a mellow taste. A double-layer hollow structural color gel is used as an indicator to distinguish beers of different concentrations. By Figure 7 The hydrophilic contact angle is >30°, and the theoretical calculation shows that the neck angle of the inverse opal gel is 30°. When the alcohol concentration increases, the contact angle gradually decreases, proving that the solvent wettability is stronger. Figure 9 As shown, an alcohol concentration test was carried out using a cocktail of the same brand sold on the market. The experimental results preliminarily proved that when the alcohol solubility was 3%, the hollow structure was not completely infiltrated and the structural color (yellow-green) did not disappear. When the alcohol solubility was 5%, the structural color (yellow-green) showed signs of disappearing. When the alcohol concentration was 8%, the structural color (yellow-green) completely disappeared and became colorless. Therefore, a portable alcohol solubility detector was proved to be effective.

[0087] Application three: QR code anti-counterfeiting technology is used to ensure the authenticity and integrity of goods or documents. Its main functions include: verifying authenticity, tracking and tracing, preventing tampering, and simplifying the verification process. The QR code can contain a unique identification code or information. By scanning the QR code, the user can verify whether the product is genuine and avoid buying fakes. Secondly, the QR code can record the production and transportation process of the product, help track the source and circulation path of the product, and increase the transparency of the supply chain. In terms of security performance, by encrypting or embedding digital signatures, the QR code can prevent information from being tampered with and ensure that the displayed information is consistent with the actual situation. Figure 10 As shown, the use of the QR code anti-counterfeiting feature in the identification process uses a transparent display authentication principle, which can effectively prevent the occurrence of QR code theft and counterfeiting. The anti-counterfeiting concept is hidden at the bottom of the fuzzy structural color of the inverse opal, and the QR code can be selectively displayed by wetting with a solvent. This strategy plays a key role in protecting product information and improving the level of security authentication.

[0088] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change, characterized in that The following steps are included: (1) Initiating a polymerization reaction between styrene and an initiator at 60-80° C. to obtain polystyrene microspheres; reacting the obtained polystyrene microspheres with ammonia water and vinyl triethoxysiloxane to obtain polystyrene-silica core-shell nanospheres having polystyrene as a core and silica as a shell; The thickness of the outer shell silica of the polystyrene-silica core-shell nanospheres is 19 to 60 nm, and the thickness is controlled by changing the volume ratio of ammonia water to vinyl triethoxysiloxane, wherein the volume ratio of ammonia water to vinyl triethoxysiloxane is (1.2 to 10): (0.45 to 3.75); The polystyrene-silica core-shell microspheres were dispersed in an ethanol solvent, and then the polystyrene-silica core-shell nanospheres were assembled into neat face-centered cubic three-dimensional PS-SiO2 photonic crystals by self-assembly during ethanol solvent evaporation. (2) Tetraethyl orthosilicate autonomously nucleates and grows at room temperature under the action of ammonia water to obtain solid silica nanostructured microspheres; the particle size of the solid silica nanostructured microspheres is 180-260 nm, and the particle size is controlled by changing the volume ratio of ammonia water to tetraethyl orthosilicate, which is (4-7.5):20; Solid silica nanostructured microspheres are dispersed in an ethanol solvent, and then the ethanol solvent is evaporated to self-assemble the solid silica nanostructured microspheres into a neat face-centered cubic stacked three-dimensional SiO2 photonic crystal; (3) calcining the three-dimensional PS-SiO2 photonic crystal obtained in step (1) at a high temperature of 500-600° C. in a muffle furnace for 8-12 hours to obtain a hollow SiO2 photonic crystal; filling the prepolymer monomer added with a photoinitiator into the hollow SiO2 photonic crystal, curing by ultraviolet exposure, embedding the prepolymer monomer and the hollow SiO2 photonic crystal, and peeling off the obtained polymer film to obtain a hollow SiO2 structural color gel; (4) filling the prepolymer monomer added with a photoinitiator into the three-dimensional SiO2 photonic crystal obtained in step (2), curing by ultraviolet exposure, embedding and combining the prepolymer monomer and the three-dimensional SiO2 photonic crystal, peeling off the obtained polymer film, and etching the SiO2 with hydrofluoric acid having a volume percentage concentration of 4% to obtain an inverse opal gel; (5) The hollow SiO2 structural color gel obtained in step (3) and the inverse opal gel obtained in step (4) are stacked together in two layers, and bonded under ultraviolet light using ethoxylated trimethylolpropane triacrylate and a photoinitiator in a mass ratio of 99:1 to obtain a double-layer hollow structure photonic gel film with controllable water permeability and color change.

2. The method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change according to claim 1, characterized in that: The initiator in step (1) is potassium persulfate or ammonium persulfate.

3. The method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change according to claim 1, characterized in that: The calcination temperature in step (3) is 550° C. and the calcination time is 12 h.

4. The method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change according to claim 1, characterized in that: The prepolymer monomers in step (3) and step (4) are composed of a polymer monomer and a cross-linking agent in a mass ratio of 1:1 to 1:2, the polymer monomer is one or more of acrylic acid, hydroxyethyl methacrylate, polyethylene glycol diacrylate and methyl acrylate; and the cross-linking agent is ethoxylated trimethylolpropane triacrylate.

5. The method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change according to claim 4, characterized in that: The prepolymer liquid monomers include acrylic acid, polyethanol diacrylate and ethoxylated trimethylolpropane triacrylate in a mass ratio of 1:4:5 to 1:4:

10.

6. The method for preparing a double-layer hollow photonic gel film with controllable water permeation and color change according to claim 1, characterized in that: The photoinitiator in step (3) and step (4) is 2-hydroxy-2-methyl-1-phenyl-1-propanone; the amount of the photoinitiator used is 2% to 3% of the mass of the polymer monomer in the prepolymer liquid monomer.

7. A photonic gel film with a double-layer hollow structure and controllable water permeation and color change, prepared by the preparation method according to any one of claims 1 to 6.

8. Application of the double-layer hollow photonic gel film with controllable water permeation and color change according to claim 7 in a signal indicator for snowmelt warning at a large ski resort, a portable alcohol solubility detector, or an anti-counterfeiting identification label for small commercial packaging.

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