A method for preparing a metal oxide inverse opal photonic crystal film

Abstract

The application discloses a preparation method of a three-dimensional ordered metal oxide inverse opal photonic crystal film. The method comprises the following steps: mixing polystyrene microspheres and corresponding solvents in proportion to obtain a microsphere emulsion for standby; under constant temperature environment conditions, a vertical deposition self-assembly method is adopted to obtain a large-area ordered photonic crystal template on a substrate, wherein by adjusting the mass of glycerol, the cracking phenomenon of the template can be reduced; on the basis of the photonic crystal template, a metal precursor solution is filled into the template pores, the template microspheres are removed, and finally an inverse opal photonic crystal film containing periodically arranged holes is obtained. The application can be used for the preparation of templates and inverse opals of all sizes of PS balls. The prepared photonic crystal template has the advantages of few structural defects, high ordered arrangement, low method cost, high repeatability and strong applicability, and the prepared high-quality photonic crystal film has stable structural color.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photonic crystal preparation, and particularly relates to a preparation method of a three-dimensional ordered metal oxide inverse opal photonic crystal film. BACKGROUND

[0002] Since Vevel successfully prepared three-dimensional ordered macroporous (3DOM) materials in the 1990s, ordered porous materials have attracted high attention of experts in chemistry, materials and physics, and become a new type of nano-structured material rapidly rising. Among them, the inverse opal crystal has received extensive attention due to its wide range of materials, easy realization of complete photonic band gap and functionalization of photonic band gap, and has broadened the application in the fields of optical devices, biological detection and photoelectric catalysis.

[0003] Although the inverse opal crystal has low cost and simple preparation, its micro-morphology depends on the quality of the template. At present, the commonly used method for preparing the inverse opal film is the physical self-assembly method, including spin coating, vertical deposition, drop coating, and limited growth. Among them, the crystal template is mainly grown by the vertical deposition self-assembly method under the joint action of surface tension and electrostatic repulsion between microspheres. In the early stage of the vertical deposition process, a meniscus interface is formed on the surface of the glass substrate, and when the emulsion evaporates, the PS microspheres reach the meniscus interface under the action of capillary force and self-assemble in a close-packed structure. Due to its ability to obtain well-oriented crystal domains, high-quality low-defect and thickness-controllable large-area photonic crystals, it has been widely adopted by many researchers. However, in the drying process, the relatively high surface tension inevitably leads to cracks perpendicular to the substrate, structural defects, and damage to the photoelectric structure, which limits the further application of the photonic crystal film in related fields. Therefore, it is increasingly important to find a more simple, green, low-cost and effective method to prevent the photonic crystal film from cracking. The present application can greatly reduce the shrinkage synergy of the microspheres by adding glycerol, adjust the wettability of the medium and the template, and thus reduce the occurrence of cracking of the photonic crystal film. However, excessive glycerol can significantly reduce the evaporation-driven flow, resulting in fewer PS particles transported before assembly, which reduces the thickness and quality of the assembled template. Therefore, the mass of glycerol needs to be properly adjusted. There are few literatures on related work. The photonic crystal template prepared by the present application has few structural defects, high order arrangement, low cost, high repeatability and strong applicability. SUMMARY

[0004] Based on the defects of the prior art, the first object of the present application is to provide a preparation method of a three-dimensional ordered metal oxide inverse opal photonic crystal film.

[0005] In order to achieve the above object, the technical scheme adopted by the present application is as follows: a preparation method of constructing three-dimensional ordered metal oxide inverse opal photonic crystal thin film, comprising the following sequential steps:

[0006] 1) mixing polystyrene microspheres with the same particle size and corresponding solvent in proportion, and vertically placing a substrate in the solvent, and drying the solvent and solidifying under constant temperature conditions by vertical deposition self-assembly method, to obtain an ordered photonic crystal template on the substrate;

[0007] Specifically, polystyrene microspheres with the same particle size and corresponding solvent are mixed in proportion, and the substrate is vertically placed in the mixed solution, and glycerol is further added in the mixed solution, and the moisture degree of the template surface is maintained by controlling the mass of glycerol, wherein the mass of glycerol added in every 20ml water is 0.1g-0.4g (preferably 0.2g-0.4g, more preferably 0.2g-0.3g); during the process of drying the solvent and solidifying under constant temperature conditions, the photonic crystal template is obtained on the substrate by vertical deposition self-assembly method using the capillary force at the meniscus; at this time, the contact surface is curved and a meniscus is formed due to the interaction force between liquid molecules and the interaction force between liquid and solid molecules.

[0008] 2) filling a metal precursor solution into the photonic crystal template pores by drop coating or immersion, and removing the template microspheres, to finally obtain an inverse opal photonic crystal thin film with a cubic close-packed structure.

[0009] The particle size of the polystyrene microspheres in step 1 is 200nm-800nm, the particle size A refers to the average particle size A, the particle size distribution is A-3 to A+3 (i.e. the particle size distribution is A±3nm), preferably the particle size distribution is A-1 to A+1 (i.e. the particle size distribution is A±1nm), more preferably the particle size distribution is A-0.2 to A+0.2 (i.e. the particle size distribution is A±0.2nm), and most preferably the particle size is the same (i.e. the particle size distribution is A±0nm); the solvent is water, and the polystyrene microspheres in the solution are 0.1wt%-0.3wt% of water.

[0010] The substrate in step 1 is FTO conductive glass with size of 1 cm x 1 cm to 1 cm x 3 cm. The FTO conductive glass is cleaned in deionized water, ethanol and acetone for 10 min to 15 min, respectively, and then dried by nitrogen flow. Then the glass is immersed in a solution of 70 °C to 85 °C (mass fraction of 30% to 35% H2O2, mass fraction of 25% to 28% NH4OH and H2O with volume ratio of 1:1:3 to 1:1:5, preferably 1:1:4 to 1:1:5, more preferably 1:1:4.5 to 1:1:5) for 2 h to 4 h (preferably 2 h to 3 h, more preferably 2 h to 2.5 h) to functionalize the surface of the substrate with hydroxyl groups. Finally, the substrate is immersed in a 3-(trihydroxysilyl)-propane sulfonic acid methanol solution with a concentration of 1 wt% to 3 wt% (preferably 1 wt% to 2 wt%, more preferably 1 wt% to 1.5 wt%) for 23 h to 25 h (preferably 23.5 h to 24.5 h) to functionalize the substrate with negative charges.

[0011] The temperature conditions of the temperature environment in step 1 are as follows: the drying temperature is 50 °C to 65 °C (preferably 50 °C to 60 °C, more preferably 53 °C to 56 °C), the drying time is 16 h to 22 h (preferably 16 h to 20 h, more preferably 16 h to 18 h), the curing temperature is 100 °C to 120 °C (preferably 105 °C to 110 °C, more preferably 108 °C to 110 °C), and the curing time is 10 min to 30 min (preferably 15 min to 30 min, more preferably 25 min to 30 min).

[0012] In step 1, the moisture level of the template surface is maintained by controlling the mass of glycerol added to 20 ml of water: 0.1 g to 0.4 g of glycerol is added to 20 ml of water.

[0013] In step 2, the method of filling the metal solution is as follows: the solution of metal oxide precursor is uniformly filled into the pores between the photonic crystal microspheres by drop coating or immersion, wherein the amount of solution dropped on the substrate surface per square centimeter is 100 μL to 300 μL (preferably 100 μL to 200 μL, more preferably 100 μL to 150 μL); when immersed, the substrate surface per square centimeter (according to the one side surface of the substrate) is immersed in 2 mL to 4 mL (preferably 2 mL to 3 mL, more preferably 2 mL to 2.5 mL) of the solution.

[0014] In step 2, the method of removing the template microspheres is as follows: the template microspheres are removed by calcination, the calcination temperature is 400 °C to 600 °C (preferably 400 °C to 550 °C, more preferably 450 °C to 550 °C), and the calcination time is 2 h to 4 h (preferably 2 h to 3 h, more preferably 2 h to 2.5 h).

[0015] The metal precursor in step 2) is one or more than two of tin tetrachloride, zinc nitrate hexahydrate, ferric chloride hexahydrate, bismuth nitrate pentahydrate and copper nitrate trihydrate; the metal precursor solution is a salt solution containing metal ions required, and the metal is one or more than two of tin, zinc, iron, bismuth and copper;

[0016] The mass concentration of tin tetrachloride ranges from 8% to 9% (preferably from 8% to 8.5%, more preferably from 8% to 8.3%) when preparing the tin dioxide inverse opal; the mass concentration of zinc nitrate hexahydrate ranges from 19% to 20% (preferably from 19.5% to 19.7%, more preferably from 19.5% to 19.6%) when preparing the zinc oxide inverse opal; the mass concentration of ferric chloride hexahydrate ranges from 0.8% to 1% (preferably from 0.8% to 0.95%, more preferably from 0.8% to 0.9%) when preparing the diiron trioxide inverse opal; the mass concentration of copper nitrate trihydrate ranges from 0.2% to 0.4% (preferably from 0.2% to 0.3%, more preferably from 0.25% to 0.3%) and the mass concentration of bismuth nitrate pentahydrate ranges from 1% to 2% (preferably from 1% to 1.5%, more preferably from 1% to 1.2%) when preparing the copper bismuthate inverse opal.

[0017] The solvent of the metal precursor solution is one or more than two of anhydrous ethanol, hydrochloric acid with a mass fraction of 36% to 38% and acetic acid with a mass fraction of 99.8% to 100%.

[0018] The present application can reduce the occurrence of template cracking by adjusting the mass of glycerol; the metal precursor solution is filled into the template pores on the basis of the photonic crystal template, the template microspheres are removed, and finally the inverse opal photonic crystal film containing periodically arranged holes is obtained. The present application can be used for the preparation of all size PS ball templates and inverse opals, and the prepared photonic crystal template has the advantages of few structural defects, high-order arrangement, low method cost, high repeatability, strong applicability, and the prepared high-quality photonic crystal film has stable structural color.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The present application can reduce the occurrence of template cracking by adjusting the mass of glycerol; the metal precursor solution is filled into the template pores on the basis of the photonic crystal template, the template microspheres are removed, and finally the inverse opal photonic crystal film containing periodically arranged holes is obtained. The present application can be used for the preparation of all size PS ball templates and inverse opals, and the prepared photonic crystal template has the advantages of few structural defects, high-order arrangement, low method cost, high repeatability, strong applicability, and the prepared high-quality photonic crystal film has stable structural color. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 (a) is a scanning electron microscope image of the 250nm PS ball inverse opal photonic crystal template prepared in Example 1 of the present application;Figure 1 (b) is a scanning electron microscope image of the tin dioxide inverse opal photonic crystal prepared in Example 1 of the present invention;

[0022] Figure 2 (a) A scanning electron microscope image of the 400nm PS sphere inverse opal photonic crystal template prepared in Example 2 of the present invention; Figure 2 (b) is a scanning electron microscope image of the zinc oxide inverse opal photonic crystal prepared in Example 2 of the present invention;

[0023] Figure 3 (a) is a scanning electron microscope image of the 600nm PS inverse opal photonic crystal template prepared in Example 3 of the present invention; Figure 3 (b) is a scanning electron microscope image of the ferric oxide inverse opal photonic crystal prepared in Example 3 of the present invention;

[0024] Figure 4 (a) is a scanning electron microscope image of the 800nm ​​PS inverse opal photonic crystal template prepared in Example 4 of the present invention; Figure 4 (b) is a scanning electron microscope image of the copper bismuthate inverse opal photonic crystal prepared in Example 4 of the present invention. Detailed Implementation

[0025] Other aspects, features, and advantages of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0026] Example 1

[0027] (1) Preparation of a three-dimensional ordered inverse opal photonic crystal template: 0.04 g of polystyrene microspheres with a particle size of 250 nm (particle size distribution range of 247 nm to 253 nm) were dispersed in 20 ml of deionized water, and 0.3 g of glycerol was added and stirred to obtain a homogeneous emulsion; then, a flat FTO conductive glass plate with a length × width of 1 cm × 2 cm was washed in deionized water, ethanol and acetone for 15 min in sequence, and dried with nitrogen gas flow. Then, the glass was immersed in "alkaline piranha" (mass fraction of 30% H2O2, mass fraction of 25% to 28% NH4OH and H2O) at 80 °C. The substrate surface was functionalized with hydroxyl groups by immersing it in a 1:1:5 (volume ratio) solution for 2 hours. Then, the substrate was immersed in a 1 wt% 3-(trihydroxysilyl)-propanesulfonic acid methanol solution for 24 hours to functionalize it with a negative charge. The substrate was then placed vertically (with its surface perpendicular to the horizontal plane) in a container filled with the emulsion, ensuring the emulsion completely submerged it. It was dried at 55°C for 18 hours, allowing the solvent in the emulsion to gradually evaporate. The polystyrene microspheres in the emulsion reached the meniscus under capillary force, achieving a compact structure and self-assembling on the FTO conductive surface through microsphere interaction. Finally, the substrate was cured in a 110°C oven for 30 minutes to form a 15-layer template. Each layer consisted of a single layer of polystyrene microspheres laid flat to form a 250 nm thick film. The PS spheres in each layer were sequentially and tightly arranged. The 15 single-layer polystyrene microsphere films were stacked sequentially to form a highly ordered template with a smooth, crack-free surface.

[0028] Inverse opal photonic crystal template without glycerol addition during preparation (control group): The preparation process is the same as described above for preparing a three-dimensional ordered inverse opal photonic crystal template, except that glycerol is not added during the preparation process. Other steps are consistent with the above steps, forming a template with 13 layers. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the template surface accounts for approximately 6% of the surface area of ​​a 1cm × 2cm substrate.

[0029] (2) Preparation of three-dimensional ordered tin dioxide inverse opal photonic crystal: 2.8 g of tin tetrachloride and 25 mg of ammonium fluoride were dissolved in 40 mL of anhydrous ethanol to obtain a tin dioxide precursor solution. The three-dimensional ordered inverse opal photonic crystal template (substrate) prepared in step 1) was immersed in 5 mL of the tin dioxide precursor solution for 30 min to ensure that the emulsion submerged the substrate. The immersed substrate was removed from the beaker and placed vertically for 2 h to dry the sample. Finally, the sample was placed in a muffle furnace and calcined at 450 °C for 2 h. Each layer consisted of a monolayer composed of closely arranged spherical pores with a diameter of 250 nm, with tin dioxide separating adjacent pores. The monolayers were stacked sequentially to form a 15-layer inverse opal crystal film with a cubic close-packed structure. The morphology and size of the spherical pores were consistent with those of the PS spheres. The tin dioxide wall thickness between adjacent pores was approximately 60 nm to 100 nm, and the surface was smooth and crack-free.

[0030] Inverse opal photonic crystals were prepared using an inverse opal photonic crystal template without the addition of glycerol during the preparation process (comparison group): The process was the same as that described above for preparing three-dimensional ordered inverse opal photonic crystals, except that the substrate used was the inverse opal photonic crystal template without the addition of glycerol in step 1) of the comparison group. The other steps were the same as those described above, forming 13 layers of inverse opal. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the surface of the inverse opal accounted for approximately 6.5% of the surface area of ​​a 1cm × 2cm substrate.

[0031] Example 2

[0032] (1) Preparation of a three-dimensional ordered inverse opal photonic crystal template: 0.05 g of polystyrene microspheres with a particle size of 400 nm (particle size distribution range of 397 nm to 403 nm) were dispersed in 20 ml of deionized water, and 0.4 g of glycerol was added and stirred to obtain a homogeneous emulsion; then, a flat FTO conductive glass plate with a length × width of 1 cm × 2 cm was washed in deionized water, ethanol and acetone for 15 min in sequence, and dried with nitrogen gas flow. Then, the glass was immersed in "alkaline piranha" (mass fraction of 30% H2O2, mass fraction of 25% to 28% NH4OH and H2O) at 80 °C. The substrate surface was functionalized with hydroxyl groups by immersing it in a 1 wt% (volume ratio of 1:1:5) solution for 2 hours. Then, the substrate was immersed in a 1 wt% 3-(trihydroxysilyl)-propanesulfonic acid methanol solution for 24 hours to functionalize it with a negative charge. The substrate was then placed vertically (with its surface perpendicular to the horizontal plane) in a container filled with the emulsion, ensuring the emulsion completely submerged it. It was dried at 55°C for 18 hours, allowing the solvent in the emulsion to gradually evaporate. The polystyrene microspheres in the emulsion reached the meniscus under capillary force, achieving a compact structure and self-assembling on the FTO conductive surface through microsphere interaction. Finally, the substrate was cured in an oven at 110°C for 30 minutes to form an 11-layer template. Each layer consisted of a single layer of polystyrene microspheres laid flat, forming a 400 nm thick film. The PS spheres in each layer were sequentially and tightly arranged. The 11 layers of single-layer polystyrene microsphere films were stacked sequentially to form a highly ordered template with a smooth, crack-free surface.

[0033] Inverse opal photonic crystal template with a small amount of glycerol added during preparation (control group): The preparation process is the same as described above for preparing a three-dimensional ordered inverse opal photonic crystal template, except that the amount of glycerol added during preparation is 0.05g. Other steps are the same as above, forming a template with 11 layers. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the template surface accounts for approximately 1.3% of the area of ​​a 1cm × 2cm substrate.

[0034] (2) Preparation of three-dimensional ordered zinc oxide inverse opal photonic crystal: 1.96 g of zinc nitrate hexahydrate was dissolved in 10 ml of ethanol and 150 μL of hydrochloric acid to obtain a zinc oxide precursor solution. The three-dimensional ordered inverse opal photonic crystal template (substrate) prepared in step 1) was immersed in the solution for 30 min to ensure that the emulsion submerged the substrate. After removal, it was vertically aged for 2 h. Finally, the sample was placed in a muffle furnace and calcined at 500 °C for 2 h. Each layer consisted of a monolayer composed of spherical pores with a diameter of 400 nm arranged in a tightly packed manner, with zinc oxide separating adjacent pores. The monolayers were stacked sequentially to form an 11-layer inverse opal crystal film with a cubic close-packed structure. The morphology and size of the spherical pores were consistent with those of the PS spheres. The zinc oxide wall thickness between adjacent pores was approximately 100 nm to 110 nm, and the surface was smooth and crack-free.

[0035] Inverse opal photonic crystals were prepared using an inverse opal photonic crystal template with a small amount of glycerol added during the preparation process (comparison group): The process was the same as that described above for preparing three-dimensional ordered inverse opal photonic crystals, except that the substrate used was the inverse opal photonic crystal template with 0.05g of glycerol added during the preparation process of the comparison group in step 1). The other steps were the same as those described above, forming an 11-layer inverse opal. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the surface of the inverse opal accounted for approximately 1.5% of the surface area of ​​a 1cm × 2cm substrate.

[0036] Application examples of inverse opal films: First, zinc oxide inverse opal photonic crystals were synthesized under two conditions: with 0.4 g of glycerol and with 0.05 g of glycerol, respectively, using the same method as described above. Then, photoelectrochemical water splitting tests were conducted in 0.5 M Na₂SO₄ solution using a three-electrode system (counter electrode: platinum sheet; reference electrode: Ag / AgCl; working electrode: the prepared zinc oxide inverse opal film) and a solar simulator equipped with an AM 1.5G filter and a 300W Xe lamp. The current density of the inverse opal with added glycerol was 0.46 mA / cm². 2 Adding 0.05g of glycerin resulted in a current density 0.24mA / cm² higher. 2 This is mainly because the anti-opal with 0.4g of glycerol added has a more ordered structure, no cracks, reflects more visible light, and has a better PEC water splitting ability.

[0037] Example 3

[0038] (1) Preparation of a three-dimensional ordered inverse opal photonic crystal template: 0.02 g of polystyrene microspheres with a particle size of 600 nm (particle size distribution range of 597 nm to 603 nm) were dispersed in 20 ml of deionized water, and 0.3 g of glycerol was added and stirred to obtain a homogeneous emulsion; then, a flat FTO conductive glass plate with a length × width of 1 cm × 2 cm was washed in deionized water, ethanol and acetone for 15 min in sequence, and dried with nitrogen gas flow. Then, the glass was immersed in "alkaline piranha" (mass fraction 30% H2O2, mass fraction 25% to 28% NH4OH and H2O) at 80 °C. The substrate was functionalized with hydroxyl groups on its surface by immersing it in a 1:1:5 (volume ratio) solution for 2 hours. Then, it was immersed in a 1 wt% 3-(trihydroxysilyl)-propanesulfonic acid methanol solution for 24 hours to functionalize it with a negative charge. The substrate was then placed vertically (with its surface perpendicular to the horizontal plane) in a container filled with the emulsion, ensuring the emulsion completely submerged it. It was dried at 55°C for 20 hours, allowing the solvent in the emulsion to gradually evaporate. The polystyrene microspheres in the emulsion reached the meniscus under capillary force, achieving a compact structure and self-assembling on the FTO conductive surface through microsphere interaction. Finally, the substrate was cured in an oven at 110°C for 30 minutes to form an 8-layer template. Each layer consisted of a single layer of polystyrene microspheres laid flat, forming a 600 nm thick film. The PS spheres in each layer were sequentially and tightly arranged. The 8 layers of single-layer polystyrene microsphere films were stacked sequentially to form a highly ordered template with a smooth, crack-free surface.

[0039] Inverse opal photonic crystal template with a small amount of glycerol added during preparation (comparative group): The preparation process is the same as described above for preparing a three-dimensional ordered inverse opal photonic crystal template, except that the amount of glycerol added during preparation is 0.03g. Other steps are the same as above, forming a template with 8 layers. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the template surface accounts for approximately 1.5% of the area of ​​a 1cm × 2cm substrate.

[0040] (2) Preparation of three-dimensional ordered ferric oxide inverse opal photonic crystal: 0.07 g of ferric chloride hexahydrate was dissolved in 10 ml of ethanol solution to obtain a ferric oxide precursor solution. 200 μL of the precursor solution was uniformly dispersed on the surface of the substrate with the three-dimensional ordered inverse opal photonic crystal template prepared in step 1), and placed in an environment of 75 °C for 30 min for hydrolysis. Finally, the sample was placed in a muffle furnace and calcined at 450 °C for 2 h. Each layer consists of a monolayer composed of spherical pores with a diameter of 600 nm arranged in a tightly packed manner, with ferric oxide separating adjacent pores. The monolayers were stacked sequentially to form an inverse opal crystal film with a cubic close-packed structure of 8 layers. The morphology and size of the spherical pores were consistent with those of the PS spheres. The ferric oxide wall thickness between adjacent pores was approximately 85 nm to 140 nm, and the surface was smooth and crack-free.

[0041] Inverse opal photonic crystals were prepared using an inverse opal photonic crystal template with a small amount of glycerol added during the preparation process (comparison group): The process was the same as the preparation process for the three-dimensional ordered inverse opal photonic crystal described above, except that the substrate used was the inverse opal photonic crystal template with 0.03g of glycerol added during the preparation process of the comparison group in step 1): The other steps were the same as the steps above, forming an 8-layer inverse opal. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the surface of the inverse opal accounted for approximately 1.7% of the surface area of ​​a 1cm × 2cm substrate.

[0042] Example 4

[0043] (1) Preparation of a three-dimensional ordered inverse opal photonic crystal template: 0.02 g of polystyrene microspheres with a particle size of 800 nm (particle size distribution range of 797 nm to 803 nm) were dispersed in 20 ml of deionized water, and 0.3 g of glycerol was added and stirred to obtain a homogeneous emulsion; then, a flat FTO conductive glass plate with a length × width of 1 cm × 2 cm was washed in deionized water, ethanol and acetone for 15 min in sequence, and dried with nitrogen gas flow. Then, the glass was immersed in "alkaline piranha" (mass fraction 30% H2O2, mass fraction 25% to 28% NH4OH and H2O) at 80 °C. The substrate surface was functionalized with hydroxyl groups by immersing it in a 1:1:5 (volume ratio) solution for 2 hours. Then, the substrate was immersed in a 1 wt% 3-(trihydroxysilyl)-propanesulfonic acid methanol solution for 24 hours to functionalize it with a negative charge. The substrate was then placed vertically (with its surface perpendicular to the horizontal plane) in a container filled with the emulsion, ensuring the emulsion completely submerged the substrate. It was dried at 55°C for 20 hours, allowing the solvent in the emulsion to gradually evaporate. The polystyrene microspheres in the emulsion reached the meniscus under capillary force, achieving a compact structure and self-assembling on the FTO conductive surface through microsphere interaction. Finally, the substrate was cured in an oven at 110°C for 30 minutes to form a 5-layer template. Each layer consisted of a single layer of polystyrene microspheres laid flat, forming a film layer with a thickness of 800 nm. The PS spheres in each layer were arranged sequentially and tightly. The 5 layers of single-layer polystyrene microsphere films were stacked sequentially to form a highly ordered template with a smooth, crack-free surface.

[0044] Preparation of an inverse opal photonic crystal template with added excess glycerol (control group): The preparation process is the same as described above for preparing a three-dimensional ordered inverse opal photonic crystal template, except that the amount of glycerol added during the preparation process is 0.6g. The other steps are the same as the above steps, forming a template with 3 layers. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the template surface accounts for approximately 0.5% of the area of ​​a 1cm × 2cm substrate.

[0045] (2) Preparation of three-dimensional ordered copper bismuthate inverse opal photonic crystal: 1 ml of 0.1 mol / L Bi(NO3)3·5H2O acetic acid solution and 4 ml of 0.0125 mol / L Cu((NO3)2·3H2O ethanol solution were ultrasonically dispersed and mixed evenly to obtain a copper bismuthate precursor solution. Then, 200 μL of the precursor solution was evenly dispersed on the surface of the substrate with three-dimensional ordered inverse opal photonic crystal template prepared in step 1), and then placed in a muffle furnace and calcined at 450 °C for 2 h. Each layer consists of a single layer of spherical pores with a diameter of 800 nm arranged in a tightly packed manner, with copper bismuthate separating adjacent pores. The single layers are stacked in sequence to form a three-layer inverse opal crystal film with a cubic close-packed structure. The morphology and size of the spherical pores are consistent with those of the PS spheres. The copper bismuthate wall thickness between adjacent pores is about 90 nm to 200 nm, and the surface is smooth and crack-free.

[0046] Inverse opal photonic crystals were prepared using an inverse opal photonic crystal template with excess glycerol added during the preparation process (comparative group): The process was the same as that described above for preparing three-dimensional ordered inverse opal photonic crystals, except that the substrate used was the inverse opal photonic crystal template with 0.6g of glycerol added during the preparation process of the comparative group in step 1): The other steps were the same as the above steps, forming a three-layered inverse opal. The area of ​​irregular cracks with a length × width of (1-10μm) × (0.1-0.4μm) on the surface of the inverse opal accounted for approximately 0.55% of the surface area of ​​a 1cm × 2cm substrate.

[0047] Application examples of inverse opal films: First, copper bismuthate inverse opal photonic crystals were synthesized under two conditions: with 0.3 g of glycerol and with 0.6 g of glycerol, using the same method as described above. Then, photoelectrochemical carbon dioxide reduction (PEC) tests were conducted in 0.1 M KHCO3 solution using a three-electrode system (counter electrode: platinum sheet; reference electrode: Ag / AgCl; working electrode: the prepared copper bismuthate inverse opal film) and a solar simulator equipped with an AM 1.5G filter and a 300W Xe lamp. The carbon monoxide Faraday efficiency of the inverse opal with 0.3 g of glycerol was 65%, which was 32% higher than that with 0.6 g of glycerol. This is mainly because the inverse opal with 0.3 g of glycerol has a more ordered structure, is free of cracks, reflects more visible light, has more layers, and contains more catalysts, thus exhibiting superior PEC carbon dioxide reduction capability.

[0048] Product characteristics: From Figures 1-4 It can be seen that the inverse opal photonic crystal template has few defects, a dense and uniform surface, and a highly ordered arrangement. The inverse opal has a three-dimensional ordered pore structure with pore size consistent with that of the PS sphere.

Claims

1. A method for preparing a three-dimensionally ordered metal oxide inverse opal photonic crystal thin film, characterized in that, Includes the following steps: 1) Polystyrene microspheres are mixed with solvent water to obtain a mixed solution. The substrate is placed vertically in the mixed solution. Glycerin is also added to the mixed solution, with the mass of glycerin added per 20 ml of water being 0.1 g to 0.4 g. The solvent is dried and cured under constant temperature conditions. A photonic crystal template is obtained on the substrate by vertical deposition self-assembly using the capillary force at the meniscus. 2) The metal precursor solution is filled into the pores of the photonic crystal template by drop coating or impregnation, and the template microspheres are removed by calcination to obtain an ordered inverse opal photonic crystal film.

2. The preparation method according to claim 1, characterized in that: The polystyrene microspheres used in step 1) are polystyrene microspheres with a particle size of A, and the particle size range is 200nm~800nm. The particle size A refers to the average particle size A, and the particle size distribution is from A-3 to A+3, that is, the particle size distribution is the average particle size value A±3nm; the polystyrene microspheres in the mixed solution are 0.1wt%~0.3wt% of water.

3. The preparation method according to claim 1, characterized in that: In step 1), the substrate is FTO conductive glass. First, FTO conductive glass of 1cm×1cm~1cm×3cm is washed in deionized water, ethanol and acetone for 10min~15min respectively, and then dried with nitrogen gas. Then, the substrate is immersed in a solution of 70℃~85℃ with the following composition: 30%~35% H2O2, 25%~28% NH4OH and H2O in a volume ratio of 1:1:3~1:1:5 for 2h~4h to functionalize the hydroxyl groups on the substrate surface. Finally, the substrate is immersed in a 1wt%~3wt% 3-(trihydroxysilyl)-propanesulfonic acid methanol solution for 22h~25h to functionalize the substrate with negative charge.

4. The preparation method according to claim 1, characterized in that: The constant temperature environment conditions in step 1) are: drying temperature 50℃~65℃, drying time 16h~22h, curing temperature 100℃~120℃, and curing time 10min~30min.

5. The preparation method according to claim 1, characterized in that: In step 1), the ratio of solvent volume to the surface area of ​​one side of the substrate is 6.5~20 ml / cm². 2 .

6. The preparation method according to claim 1, characterized in that: The method for filling the metal precursor solution in step 2) is as follows: the metal precursor solution is uniformly filled into the pores in the middle of the photonic crystal microspheres by drop coating or dipping. The amount of the drop coating solution is 100μL~300μL per square centimeter of substrate surface; during immersion, each square centimeter of substrate surface should be immersed in 2mL~4mL of solution according to one side of the substrate surface.

7. The preparation method according to claim 1, characterized in that: The method for removing template microspheres in step 2) is as follows: the template microspheres are removed by calcination at a temperature of 400℃~600℃ for 2h~4h.

8. The preparation method according to claim 1 or 6, characterized in that: In step 2), the metal precursor is one or more of tin tetrachloride, zinc nitrate hexahydrate, ferric chloride hexahydrate, bismuth nitrate pentahydrate, and copper nitrate trihydrate; the metal precursor solution is a salt solution containing the desired metal ions, and the metal is one or more of tin, zinc, iron, bismuth, and copper. When preparing tin dioxide inverse opal, the mass concentration of tin tetrachloride ranges from 8% to 9%; when preparing zinc oxide inverse opal, the mass concentration of zinc nitrate hexahydrate ranges from 19% to 20%; when preparing ferric oxide inverse opal, the mass concentration of ferric chloride hexahydrate ranges from 0.8% to 1%; and when preparing copper bismuthate inverse opal, the mass concentration of copper nitrate trihydrate ranges from 0.2% to 0.4%, and the mass concentration of bismuth nitrate pentahydrate ranges from 1% to 2%.

9. The preparation method according to claim 8, characterized in that: The solvent for the metal precursor solution is one or more of the following: anhydrous ethanol, hydrochloric acid with a mass fraction of 36% to 38%, and acetic acid with a mass fraction of 99.8% to 100%.

Images