Synthetic method of anti-reflection self-cleaning nano coating material

Abstract

The invention discloses a synthetic method of an anti-reflection self-cleaning nano coating material, and relates to the technical field of new materials.The method comprises the steps that a porous silicon dioxide loaded zinc oxide quantum dot and fluorosilane compounded ternary system is constructed through a sol-gel method; after in-situ embedding of a zinc source, carrying out hydrothermal treatment to form confinement quantum dots, and then grafting fluorosilane to obtain a precursor solution; the thickness of the obtained film layer is 110 + / -10 nm, the refractive index is 1.23, the light transmittance is increased by more than or equal to 3.8% when the film layer is 400-1100 nm, the film layer has photocatalytic degradation and super-hydrophobic self-cleaning capabilities, the adhesive force is 0 level, the wet heat and friction stability is excellent, the process is mild, the cost is low, and the film layer is suitable for photovoltaic, building and automobile glass. The invention aims to solve the problems of difficult cooperation of anti-reflection and self-cleaning performance, high cost and poor stability in the prior art.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a method for synthesizing an antireflective self-cleaning nano-coating material. Background Technology

[0002] In fields such as optical devices, photovoltaic energy conversion systems, and modern energy-efficient buildings, surface functionalization of transparent substrates has become a key step in improving overall performance. Among these, nano-coating materials that combine high light transmittance with self-cleaning capabilities have attracted widespread attention in recent years due to their ability to simultaneously reduce light energy loss and lower maintenance costs. An ideal functional coating not only needs to maintain excellent optical transmittance across a broad visible to near-infrared spectral range but also should possess reliable environmental durability, good substrate adhesion, and the ability to autonomously remove contaminants through hydrophobic or hydrophilic mechanisms. However, the inherent coupling difficulty between these two core functions—anti-reflection and self-cleaning—at the material design level often leads to compromises in existing technologies, making it difficult to achieve multi-objective synergistic optimization.

[0003] Specifically, early technological approaches focused on constructing photocatalytic self-cleaning systems. This involved dispersing photocatalytic nanoparticles such as titanium dioxide in a medium containing wetting and dispersing agents to form a stable slurry, which was then combined with organic resins or inorganic sols to prepare a coating liquid with self-cleaning and heat-insulating functions. This approach effectively solved surface contamination problems in specific applications and improved film uniformity through an inorganic-organic hybrid structure. However, its design logic, essentially driven by self-cleaning functionality, failed to systematically regulate the film's refractive index, making it difficult to achieve effective anti-reflection effects across a wide spectral range. More importantly, the organic components used were prone to photo-oxidation, yellowing, or cross-linking aging under long-term outdoor exposure, leading to a decrease in transmittance and failing to meet the extremely stringent optical stability requirements of applications such as photovoltaic glass.

[0004] Building upon this foundation, subsequent research attempted to introduce highly transparent conductive materials to balance anti-reflection and functionality. A polyethylene glycol-modified indium tin oxide nanosol was combined with a general self-cleaning component. While this achieved high average transmittance in the 400–1100 nm wavelength range and improved film wear resistance, its self-cleaning ability relied solely on the added component, failing to establish a synergistic physical or chemical mechanism with the intrinsic properties of indium tin oxide. Particularly noteworthy is the lack of a clear pathway for self-cleaning—neither its photocatalytic activity was confirmed, nor was a superhydrophobic micro / nano structure constructed, resulting in a lack of theoretical support and engineering reproducibility for actual self-cleaning efficiency. Furthermore, indium tin oxide itself relies on scarce and expensive indium, and its synthesis requires high-temperature, high-pressure, subcritical conditions, significantly increasing process complexity and manufacturing costs, severely limiting its feasibility for large-scale industrial applications.

[0005] Ultimately, the two representative technical approaches revealed a deep-seated technical contradiction: the antireflection function relies heavily on the precise gradient design of the film's refractive index, typically requiring the use of low-refractive-index porous silica or fluoride systems; while the efficient self-cleaning function often necessitates the introduction of high-surface-energy photocatalytic materials or the construction of low-surface-energy hydrophobic structures. These two approaches inherently conflict in terms of material composition, microstructure, and interfacial characteristics. Forcing a composite approach can easily lead to phase separation, increased interfacial defects, or enhanced optical scattering, thereby weakening the overall performance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for synthesizing antireflective and self-cleaning nano-coating materials, so as to solve the technical problems in the prior art, such as difficulty in synergistic optimization of antireflective performance and self-cleaning function, high raw material cost, complex process and insufficient long-term stability.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for synthesizing an antireflective, self-cleaning nanocoating material, the method comprising the following steps: Step S1: First, mix tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid in a volume ratio of 1:4:2:0.05 and stir at a constant temperature of 25°C for 30 minutes to form an acidic hydrolysis precursor solution. Step S2: Subsequently, polyethylene glycol-2000 is added dropwise to the precursor solution as a structure directing agent, with the addition amount being 8% of the molar amount of tetraethyl orthosilicate. Stirring is continued for 2 hours to obtain a homogeneous and transparent silica sol. Step S3: Based on this, zinc acetate dihydrate is dissolved in anhydrous methanol to prepare a zinc source solution with a concentration of 0.15 mol / L. The solution is then added dropwise to the silica sol under a nitrogen protective atmosphere, with the dropping rate controlled at 1 mL / min. The system temperature is maintained at 40°C. After the addition is complete, the mixture is stirred for 4 hours to allow zinc ions to be embedded in situ into the silica network that is undergoing condensation. Step S4: After the reaction is complete, the resulting composite sol is aged in a 60°C oven for 12 hours to form a stable sol. Precursor gel.

[0008] Step S5: Perform ultrasonic-assisted hydrothermal treatment on the above gel: transfer it to a polytetrafluoroethylene-lined stainless steel reactor, add deionized water to adjust the solid content to 5 wt%, and keep it at 120℃ for 6 hours to promote the crystallization of embedded zinc species into zinc oxide quantum dots with an average particle size of 3.2±0.3 nm. This size is strictly controlled below the exciton Bohr radius to ensure that it has a strong ultraviolet absorption cross section without inducing visible light scattering. After the hydrothermal treatment is completed, cool it naturally to room temperature, centrifuge and wash it three times with anhydrous ethanol, and redisperse it in anhydrous ethanol to form a stable dispersion with a concentration of 3 wt%.

[0009] Step S6: Add tridecafluorooctyltrimethoxysilane to the above dispersion. The molar amount of the added silanol is 1.2 times the total amount of silanols in the silica framework. Reflux the reaction at 60°C for 4 hours to allow fluorosilane molecules to be covalently grafted onto the silica surface and the inner wall of the pores through hydrolysis and condensation reaction, forming a low surface energy modification layer with a gradient distribution. Step S7: After the reaction is complete, volatile components are removed by vacuum distillation to obtain the final antireflection self-cleaning nano-coating material precursor solution.

[0010] The precursor solution can be directly used in dip coating, spin coating, or spray coating processes to form a film on the surface of transparent substrates such as glass, quartz, or polymers. After film formation, heat treatment at 120°C for 30 minutes promotes further condensation and crosslinking of residual silanol groups, while simultaneously completing the complete curing of fluorosilanes, forming a dense and porous composite film structure. This film layer consists of a continuous silica network forming the main framework, with size-constrained zinc oxide quantum dots uniformly distributed inside. The surface and pore walls are modified with tridecafluorooctyltrimethoxysilane, forming a dual structure that combines micron-level roughness with nanoscale chemical heterogeneity.

[0011] The physical structure of the film is as follows: the thickness is 110±10 nm, the porosity is 38%–42%, the average pore size is 15–25 nm, and the refractive index at a wavelength of 550 nm is 1.23±0.02, which was measured by an ellipsometer and confirmed by fitting the Cauchy model. In the wavelength range of 400–1100 nm, the average transmittance improvement of the single-sided coated glass is not less than 3.8 percentage points and can reach up to 4.5 percentage points. Moreover, the transmittance curve is smooth and has no significant fluctuations, indicating that there is no obvious optical interference anomaly or scattering loss.

[0012] The self-cleaning function is achieved through a dual mechanism: First, zinc oxide quantum dots generate electron-hole pairs under ultraviolet light irradiation with wavelengths less than 387 nm. Holes react with surface-adsorbed water molecules to generate hydroxyl radicals, while electrons react with oxygen to generate superoxide radicals. Both mechanisms synergistically degrade organic pollutants. Second, fluorosilane modification endows the membrane with a static water contact angle of 112°±3° and a roll-off angle of less than 8°, forming a weakly adhesive superhydrophobic surface that allows rainwater or condensate to easily roll off and carry away inorganic dust particles. These two mechanisms work synergistically under natural light and rainfall conditions to achieve full-spectrum removal of both organic and inorganic pollutants.

[0013] The adhesion between the film layer and the soda-lime glass substrate reached level 0 in the cross-cut test (according to GB / T 9286-2021). After 1000 hours of continuous damp heat aging test at 85℃ / 85%RH, the light transmittance decreased by no more than 0.5 percentage points, and the water contact angle changed by less than 5°, indicating that it has excellent environmental stability. After the gravel abrasion test (load 500 g, stroke 50 mm, 100 cycles), there were no visible scratches on the film layer, and the light transmittance retention rate was higher than 98%, proving that its mechanical durability meets the requirements for long-term outdoor use.

[0014] The synthesis method is carried out entirely under mild conditions of normal pressure and below 120°C, without the need for high-temperature sintering, high-pressure synthesis, or precious metal catalysts. Among the raw materials used, tetraethyl orthosilicate, zinc acetate, and tridecafluorooctyltrimethoxysilane are all commercially available industrial-grade chemicals. Zinc replaces scarce or high-cost elements such as indium and titanium in traditional schemes, reducing the overall cost of raw materials by more than 62% compared to the indium tin oxide system described in CN115746591B. The entire process involves only one sol preparation, one hydrothermal treatment, and one surface modification, making it simple and suitable for continuous roll-to-roll production.

[0015] The in-situ confined growth of zinc oxide quantum dots is a key technical feature of this invention: by controlling the timing of the introduction of the zinc source and the reaction temperature in the early stage of silica sol polycondensation, the zinc is encapsulated inside the nanopores during the formation of the silica network, rather than being simply physically mixed. This confinement effect not only inhibits the excessive growth of zinc oxide grains, ensuring that they are within the quantum size range to avoid light scattering, but also effectively isolates zinc oxide from direct contact with the external environment, preventing photocorrosion or agglomeration and deactivation in humid environments. At the same time, the high specific surface area of ​​the silica matrix provides sufficient grafting sites for fluorosilanes, while the hydrophobicity of fluorosilanes, in turn, protects the internal zinc oxide from moisture erosion, forming a self-reinforcing stability cycle.

[0016] The refractive index gradient of the film is determined by both the intrinsic properties and microstructure of the material: porous silica itself has a low refractive index, and its porosity and pore size distribution are precisely controlled by a polyethylene glycol template agent, making its refractive index close to the geometric average of air and glass (approximately 1.22); although zinc oxide quantum dots have a relatively high refractive index (approximately 2.0), their size is much smaller than the wavelength of visible light and their volume fraction is controlled below 7%, so their impact on the overall refractive index is negligible; the fluorosilane molecular layer is approximately 2–3 nanometers thick, with a refractive index of approximately 1.35, but since it only covers the inner surface of the pores, it does not change the effective refractive index of the main framework. Therefore, the entire film exhibits a uniform effective refractive index, achieving a smooth transition from air (n=1.0) to glass (n=1.52), minimizing Fresnel reflection loss.

[0017] The storage stability of the precursor solution was tested: after being stored at 25°C for 30 days under sealed and light-proof conditions, there was no precipitation, no stratification, and no significant change in viscosity (initial viscosity was 2.1 mPa·s, and after 30 days it was 2.3 mPa·s), indicating that it has good process window adaptability. In the spin coating process, a 110 nm thick film can be obtained when the rotation speed is set to 2000 rpm, with a thickness deviation of less than ±5 nm, proving that its film formation repeatability is excellent.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The coating material prepared by the synthesis method described in this invention is suitable for various transparent substrates such as photovoltaic module cover glass, building curtain wall glass, automotive windshields, and display panel protective layers. Under standard AM1.5G solar spectrum irradiation, the short-circuit current density of the coated photovoltaic glass is increased by 4.1%, and the energy conversion efficiency is relatively improved by 3.9%. After being exposed to simulated acid rain (pH=4.0) and salt spray (5% NaCl) environments for 500 hours, the film layer shows no corrosion or peeling, and the self-cleaning efficiency retention rate is higher than 90%. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall process flow for synthesizing the antireflective self-cleaning nano-coating material of the present invention. Detailed Implementation

[0020] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present invention and not to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the invention.

[0021] This invention provides a method for synthesizing an antireflective, self-cleaning nanocoating material. The core of this method lies in constructing a ternary nanocomposite system consisting of a porous silica matrix loaded with modified zinc oxide quantum dots and combined with low surface energy fluorosilane molecules via a single sol-gel reaction pathway. The method includes the following specific steps: Step S1: Tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid are mixed in a volume ratio of 1:4:2:0.05 and stirred at a constant temperature of 25°C for 30 minutes to form an acidic hydrolysis precursor solution. Step S2: Polyethylene glycol-2000 is added to the precursor solution as a structure directing agent, and the amount added is 8% of the molar amount of tetraethyl orthosilicate. Stirring is continued for 2 hours to obtain silica sol. Step S3: Under a nitrogen protective atmosphere, a 0.15 mol / L zinc acetate dihydrate methanol solution is added dropwise to the silica sol at a rate of 1 mL / min, while maintaining the system temperature at 40°C. After the addition is complete, the mixture is stirred continuously for 4 hours to allow zinc ions to be embedded in situ into the silica network that is undergoing condensation. Step S4: The obtained composite sol is aged at 60°C for 12 hours to form... Precursor gel; the gel was transferred to a reaction vessel, deionized water was added to adjust the solid content to 5 wt%, and hydrothermal treatment was carried out at 120°C for 6 hours to crystallize the embedded zinc species into zinc oxide quantum dots with an average particle size of 3.2 ± 0.3 nm; Step S5: After hydrothermal treatment, centrifuge and wash three times with anhydrous ethanol, then redisperse in anhydrous ethanol to form a dispersion with a concentration of 3 wt%. Step S6: Add tridecafluorooctyltrimethoxysilane to the dispersion, the molar amount of which is 1.2 times the total amount of silanol groups in the silica framework, and reflux at 60°C for 4 hours to covalently graft fluorosilane molecules onto the surface and inner walls of the silica pores. Step S7: After the reaction is complete, volatile components are removed by vacuum distillation to obtain a precursor solution for the antireflective self-cleaning nano-coating material.

[0022] In one specific embodiment, an acidic hydrolysis precursor solution was first prepared: 10.0 mL of tetraethyl orthosilicate (TEOS, purity ≥98%, Sinopharm Chemical Reagent Co., Ltd.), 40.0 mL of anhydrous ethanol (purity ≥99.7%, Maclean's reagent), 20.0 mL of deionized water (resistivity ≥18.2 MΩ·cm), and 5.0 mL of a 0.1 mol / L hydrochloric acid aqueous solution were sequentially added to a 250 mL four-necked round-bottom flask. The mixture was placed on a thermostatic magnetic stirrer and stirred continuously at 300 rpm for 30 minutes at 25.0±0.5℃ to allow TEOS to fully hydrolyze and generate a silanol intermediate, forming a clear and transparent acidic hydrolysis precursor solution. Subsequently, polyethylene glycol-2000 (PEG-2000, average molecular weight 2000 g / mol, Aladdin reagent) was slowly added dropwise to the above precursor solution as a structure-directing agent. The amount added was calculated as 8% of the molar amount of TEOS, i.e., 0.86 g (corresponding to 0.04 mol TEOS), and the dropwise addition was completed within 5 minutes. After the dropwise addition was completed, the reaction was continued for 2 hours under the same temperature and stirring conditions to obtain a homogeneous, stable, and phase-separated silica sol. Its appearance was light blue and transparent, and its viscosity was 1.8 mPa·s (25℃, measured by rotational viscometer).

[0023] Based on this, prepare the zinc source solution: weigh zinc acetate dihydrate ( 3.28 g of zinc source solution (purity ≥99.0%, Sigma-Aldrich) was dissolved in 100 mL of anhydrous methanol (purity ≥99.9%, Bailingwei Technology) to prepare a clear solution with a concentration of 0.15 mol / L. This zinc source solution was transferred to a constant-pressure dropping funnel and connected to the aforementioned silica sol reaction system. Under a nitrogen atmosphere (flow rate 50 mL / min, after deoxygenation and dehydration treatment), the zinc source solution was added dropwise to the silica sol at a constant rate of 1.0 mL / min, while the temperature of the reaction system was raised to 40.0 ± 0.5 °C and maintained constant. The dropping process lasted approximately 100 minutes, during which the system remained transparent and no precipitate formed. After the dropping was completed, the reaction continued for 4 hours at 40 °C, under a nitrogen atmosphere and with stirring at 300 rpm, allowing zinc ions to be in situ embedded within the three-dimensional framework of the silica network during the condensation process, forming… Complex precursor.

[0024] After the reaction was completed, the resulting composite sol was transferred to a 100 mL glass petri dish and placed in a forced-air oven at 60.0±1.0℃ for 12 hours to promote further condensation of siloxane bonds and form a three-dimensional cross-linked network structure. Wet gel. The gel is a semi-transparent jelly with good mechanical integrity, showing no cracking or shrinkage.

[0025] Further, the wet gel was subjected to ultrasonic-assisted hydrothermal treatment: it was scraped into a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, and deionized water was added to adjust the solid content to 5.0 wt%, i.e., 19 mL of water per gram of dry gel. After sealing the reactor, it was placed in an electric heating drying oven at 120.0±2.0℃ for 6 hours. Under these hydrothermal conditions, the embedded zinc species underwent a hydrolysis-condensation-crystallization process, transforming into zinc oxide (ZnO) quantum dots. After the reaction was completed, it was allowed to cool naturally to room temperature (approximately 4 hours), the reactor was opened, and the product was removed. The resulting suspension was centrifuged at 8000 rpm for 10 minutes (centrifugal radius 15 cm), the supernatant was discarded, and the precipitate was washed three times with anhydrous ethanol to remove residual ions and organic byproducts. Finally, the washed product was redispersed in anhydrous ethanol to prepare a stable dispersion with a solid content of 3.0 wt%. Transmission electron microscopy (TEM, JEOL JEM-2100F, accelerating voltage 200 kV) showed that the obtained ZnO particles were spherical with an average particle size of 3.2 ± 0.3 nm (statistical sample size > 200). The size distribution was concentrated, and the particles were completely embedded in the amorphous silica matrix without obvious agglomeration or exposure. X-ray diffraction (XRD, Bruker D8 Advance, Cu Kα radiation) patterns showed weak and broad diffraction peaks at 2θ = 31.8°, 34.4°, and 36.3°, corresponding to the (100), (002), and (101) crystal planes of ZnO, respectively, confirming that it has a hexagonal wurtzite structure and moderate crystallinity, which is consistent with the characteristics of quantum dots.

[0026] As a preferred embodiment of the present invention, the above-mentioned 3.0 wt% of Add tridecafluorooctyltrimethoxysilane to the ethanol dispersion ( The FOTS (purity ≥97%, Dow Corning) was added at a molar amount 1.2 times the theoretical total amount of silanols (≡Si–OH) in the silica framework. Based on the initial amount of TEOS (0.04 mol) and the assumption that each Si atom corresponds to one –OH after complete hydrolysis, the theoretical number of silanols is 0.04 mol, therefore the amount of FOTS added is 0.048 mol, or 24.6 g. The mixture was transferred to a three-necked flask equipped with a reflux condenser and heated under reflux in an oil bath at 60.0±1.0℃ for 4 hours. During this time, FOTS molecules hydrolyzed to generate silanols, which then condensed with the silanols on the surface and inner walls of the silica pores to form ≡Si–O–Si≡ covalent bonds, achieving a strong grafting of fluorosilanes. The system remained homogeneous during the reaction, with no phase separation. After the reaction was completed, the mixture was distilled under reduced pressure at 60℃ and -0.095 MPa for 2 hours to remove unreacted FOTS, methanol byproducts, and some ethanol solvent, obtaining the final antireflective self-cleaning nano-coating material precursor solution. The solution was pale yellow and transparent, with a viscosity of 2.1 mPa·s at 25℃ and a solid content of approximately 4.5 wt%.

[0027] The precursor solution can be directly used in various film-forming processes. In this embodiment, a functional film layer was prepared on a soda-lime glass substrate (size 25 mm × 25 mm × 1.1 mm, Fuyao Glass Industry Group) using spin coating. Before spin coating, the glass substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 10 minutes each, and then dried in an oven at 120°C for 30 minutes. The precursor solution was dropped onto the clean glass surface, and the spin coating speed was set to 2000 rpm, the acceleration time to 5 seconds, and the duration to 60 seconds. After spin coating, the sample was annealed on a hot plate at 120.0±2.0°C for 30 minutes to promote further condensation and crosslinking of residual silanol groups and complete the curing of FOTS, forming a dense and porous composite film layer.

[0028] Cross-sectional observation using a field emission scanning electron microscope (FE-SEM, Hitachi SU8010) revealed a film thickness of 110 ± 10 nm with good thickness uniformity (relative standard deviation < 4.5%). Nitrogen adsorption-desorption isotherm (BET, Micromeritics ASAP 2460) measurements showed a specific surface area of ​​285 m² / g, a porosity of 40.2%, and an average pore size of 20.3 nm, with the pore size distribution concentrated in the 15–25 nm range, exhibiting typical mesoporous characteristics. Ellipsometry (JA Woollam M-2000) at a wavelength of 550 nm yielded a refractive index of 1.23 ± 0.02, which was confirmed by fitting the Cauchy dispersion model (n(λ) = A + B / λ²), where A = 1.228 and B = 0.0012 μm².

[0029] Optical performance tests were performed on a PerkinElmer Lambda 950 UV-Vis-NIR spectrophotometer. Using uncoated soda-lime glass as a reference, the average transmittance increase of the single-sided coated glass was 4.2 percentage points in the wavelength range of 400–1100 nm, with the highest increase occurring at 550 nm, reaching 4.5 percentage points. The transmittance curves were smooth, without significant fluctuations or sharp peaks and valleys, indicating that the coating layer did not exhibit obvious optical interference anomalies, scattering losses, or absorption band interference.

[0030] The self-cleaning property is achieved through a dual mechanism. First, ZnO quantum dots in the film generate photogenerated carriers under ultraviolet light (λ < 387 nm): holes ( ) reacts with surface-adsorbed water to generate ·OH free radicals, electrons ( )and Reaction generation Free radicals. To verify the photocatalytic activity, the coated glass was immersed in a 10 mg / L aqueous solution of methylene blue (MB). Under irradiation with a 365 nm UV LED (10 mW / cm²), the MB degradation rate reached 92.3% within 90 minutes, and the kinetic constant k = Secondly, FOTS modification endows the film with superhydrophobic properties. The static water contact angle (DSA100, Krüss) was measured to be 112°±3°, and the roll-off angle was less than 8°, indicating that the surface has weak adhesion superhydrophobicity. In simulated rainfall experiments (spray rate 5 L / m²·min, lasting 5 minutes), the pre-spread carbon black and quartz dust (particle size 1–10 μm) were effectively rolled off and removed by water droplets, with a surface cleanliness recovery rate >95%.

[0031] The adhesion between the film layer and the substrate was evaluated according to GB / T 9286-2021 "Cross-cut test for paint and varnish films". A 1 mm × 1 mm grid was cut on the film surface using a multi-bladed cutting tool. After applying 3M 600 tape, it was quickly peeled off. No film peeling occurred, resulting in a rating of 0. Environmental stability testing was conducted in a constant temperature and humidity chamber (Weiss Technik): After aging at 85℃ / 85%RH for 1000 hours, the light transmittance decreased by only 0.3 percentage points, and the water contact angle decreased from 112° to 108°, a change of less than 5°. Mechanical durability was evaluated through a gravel abrasion test: under conditions of 500 g load, 50 mm stroke, and 100 cycles (referring to ISO 9211-4), no visible scratches were observed on the film surface, and the light transmittance retention rate was 98.7%.

[0032] To quantify the process economy and technical advantages of this invention, comparative examples are provided. Comparative Example 1 uses the indium tin oxide (ITO)-based antireflective self-cleaning membrane preparation method disclosed in CN115746591B: and As a precursor, a film was prepared by sol-gel process, high-temperature sintering (550℃, 2 h), and fluorination. Comparative Example 2 contains only porous components. An antireflection membrane (without ZnO and FOTS). Comparative Example 3 is a physically blended ZnO nanoparticle (20 nm particle size) and... Sol-gel post-coating film formation (unrestricted growth). All comparative examples were performed on the same substrate and under the same testing conditions.

[0033] The performance comparison data is summarized in the table below:

[0034] As shown in the table, this invention significantly outperforms the comparative example in terms of improved transmittance, self-cleaning efficiency (balancing hydrophobicity and photocatalysis), environmental stability, and cost control. Particularly noteworthy is that Comparative Example 3, due to its excessively large ZnO particle size (20 nm > 1 / 10 of the visible light wavelength), exhibits significant Mie scattering, leading to a decrease in transmittance. Furthermore, its unconfined growth makes it prone to aggregation and deactivation in humid and hot environments, resulting in poor stability. In contrast, this invention, through in-situ confined growth, ensures that ZnO is at the quantum size (< exciton Bohr radius 2.34 nm), retaining a high ultraviolet absorption cross-section while avoiding visible light scattering.

[0035] Further analysis of the refractive index gradient mechanism of the film: porous The framework exhibits a low effective refractive index due to its porosity of 40.2% (theoretical calculation value ≈ 1.22, based on the Lorenz-Lorenz equation). Although ZnO quantum dots have a high intrinsic refractive index (n ≈ 2.0), their volume fraction is only 6.8% (converted from the Zn / Si molar ratio of 0.08 and density), and their size is much smaller than the visible light wavelength (3.2 nm << 400 nm), so their impact on the overall refractive index is negligible. The FOTS molecular layer is approximately 2.5 nm thick (confirmed by XPS depth profiling) with a refractive index of approximately 1.35, but it only covers the inner surface of the pores and does not change the effective optical constant of the main framework. Therefore, the film layer as a whole exhibits a uniform effective refractive index of 1.23, achieving impedance matching from air (n=1.0) to glass (n=1.52) and minimizing Fresnel reflection loss.

[0036] The storage stability of the precursor solution was also tested: after 30 days of storage at 25℃, in the dark, and under sealed conditions, the solution remained clear and transparent, without precipitation or stratification; the viscosity increased from the initial 2.1 mPa·s to 2.3 mPa·s with a change rate of <10%, indicating good process window adaptability. In roll-to-roll continuous production simulation, a slotted coating head was used to coat a PET base film (188 μm thick) at a speed of 5 m / min, followed by online drying at 120℃ for 30 seconds. The resulting film thickness was 108 nm, with a 4.0% increase in transmittance and a water contact angle of 110°, proving that this process is suitable for large-scale manufacturing of flexible substrates.

[0037] In photovoltaic applications, the coating of this invention is applied to the cover glass of a monocrystalline silicon solar cell (156mm × 156mm). Under standard AM1.5G solar spectrum (1000 W / m², 25℃), the short-circuit current density (Jsc) of the coated module increases from 38.2 mA / cm² to 39.8 mA / cm², an increase of 4.1%; the energy conversion efficiency (η) increases from 22.1% to 22.96%, a relative improvement of 3.9%. In simulated acid rain (… After being exposed to salt spray (5% NaCl, 35℃) for 500 hours, the membrane showed no corrosion or peeling, the MB degradation rate remained at 91.5%, the water contact angle remained at 109°, and the self-cleaning efficiency remained at >90%.

[0038] In summary, the synthesis method described in this invention achieves porous structures by precisely controlling the timing of component introduction, reaction temperature, and template agent dosage during the sol-gel process. The synergistic construction of the framework, confined ZnO quantum dots, and FOTS modification layer. This ternary composite system simultaneously achieves broad-spectrum antireflection, dual-mode self-cleaning, and excellent environmental durability under a single, mild process route. Furthermore, the raw materials are inexpensive, and the process is simple and controllable, providing reliable technical support for the industrial application of transparent functional coatings in photovoltaics, construction, automotive, and display fields. Those skilled in the art can refer to the parameter ranges described in this embodiment (e.g., With reasonable adjustments to the volume ratio (1:3–5:1.5–2.5:0.03–0.07), PEG addition (6–10 mol%), Zn source concentration (0.1–0.2 mol / L), hydrothermal temperature (100–140℃), FOTS addition (1.0–1.5 times the amount of silanol), etc., high-performance antireflective self-cleaning nanocoating materials can be obtained.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing an antireflective, self-cleaning nano-coating material, characterized in that, Includes the following steps: Step S1: Tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid are mixed in a volume ratio of 1:4:2:0.05 and stirred at a constant temperature of 25°C for 30 minutes to form an acidic hydrolysis precursor solution. Step S2: Polyethylene glycol-2000 is added to the precursor solution as a structure directing agent, and the amount added is 8% of the molar amount of tetraethyl orthosilicate. Stirring is continued for 2 hours to obtain silica sol. Step S3: Under a nitrogen protective atmosphere, a 0.15 mol / L zinc acetate dihydrate methanol solution is added dropwise to the silica sol at a rate of 1 mL / min, while maintaining the system temperature at 40°C. After the addition is complete, the mixture is stirred continuously for 4 hours to allow zinc ions to be embedded in situ into the silica network that is undergoing condensation. Step S4: The obtained composite sol is aged at 60°C for 12 hours to form... Precursor gel; The gel was transferred to a reaction vessel, deionized water was added to adjust the solid content to 5 wt%, and hydrothermal treatment was carried out at 120°C for 6 hours to crystallize the embedded zinc species into zinc oxide quantum dots with an average particle size of 3.2 ± 0.3 nm. Step S5: After hydrothermal treatment, centrifuge and wash three times with anhydrous ethanol, then redisperse in anhydrous ethanol to form a dispersion with a concentration of 3 wt%. Step S6: Add tridecafluorooctyltrimethoxysilane to the dispersion, the molar amount of which is 1.2 times the total amount of silanol groups in the silica framework, and reflux at 60°C for 4 hours to covalently graft fluorosilane molecules onto the surface and inner walls of the silica pores. Step S7: After the reaction is complete, volatile components are removed by vacuum distillation to obtain a precursor solution for the antireflective self-cleaning nano-coating material.

2. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 1, characterized in that, The precursor solution is used to form a film on the surface of a transparent substrate such as glass, quartz, or polymer by dip coating, spin coating, or spray coating. After film formation, the film is heat-treated at 120°C for 30 minutes to form a composite film layer with a thickness of 110±10 nm, a porosity of 38%–42%, and an average pore size of 15–25 nm.

3. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 2, characterized in that, The composite film has a refractive index of 1.23±0.02 at a wavelength of 550 nm, and the average light transmittance improvement of the single-sided coated glass is not less than 3.8 percentage points in the wavelength range of 400–1100 nm.

4. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 2, characterized in that, The composite membrane has a static water contact angle of 112°±3°, a roll-off angle of less than 8°, and a degradation rate of methylene blue of not less than 92% after 90 minutes under ultraviolet light irradiation.

5. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 1, characterized in that, The zinc oxide quantum dots are completely embedded in the amorphous silica matrix, with a volume fraction controlled below 7%, and their size is strictly less than one-tenth of the wavelength of visible light.

6. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 1, characterized in that, The tridecafluorooctyltrimethoxysilane forms ≡Si–O–Si≡ covalent bonds with the silanol groups on the surface of silicon dioxide through a hydrolysis-condensation reaction. The graft layer has a thickness of 2–3 nanometers and covers the surface of the film and the inner wall of the pores.

7. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 1, characterized in that, After the precursor solution was stored at 25°C under sealed and light-protected conditions for 30 days, the viscosity change rate was less than 10%, there was no precipitation or stratification, and the solid content was 4.0–5.0 wt%.

8. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 2, characterized in that, The adhesion between the composite film and the soda-lime glass substrate reached level 0 in the cross-cut test. After 1000 hours of humid heat aging at 85℃ / 85%RH, the light transmittance decreased by no more than 0.5 percentage points, and the water contact angle changed by less than 5°.

9. The method for synthesizing the antireflective self-cleaning nano-coating material according to claim 2, characterized in that, The composite film layer, after being subjected to a 500 g load, a 50 mm stroke, and 100 cycles in a gravel abrasion test, maintained a light transmittance of over 98% and showed no visible scratches.

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