Dual-mechanism antibacterial siloxane coating and application

Abstract

The invention discloses a dual-mechanism antibacterial siloxane coating and application thereof, and the dual-mechanism antibacterial siloxane coating is formed in situ by a hydrolytic polycondensation reaction of a precursor containing triethoxyoctylsilane, nano titanium dioxide and a film-forming adhesive, and the hydrolytic polycondensation reaction is carried out on the precursor containing triethoxyoctylsilane, nano titanium dioxide and the film-forming adhesive. Wherein part of triethoxyoctyl silane is subjected to hydrolytic polycondensation on the surface of the nano titanium dioxide to form a siloxane coating layer containing a hydrophobic octyl side chain, and the siloxane coating layer is chemically bonded with the surface of the nano titanium dioxide through a Si-O-Ti covalent bond; the rest triethoxyoctyl silane is subjected to self-polycondensation to form a continuous three-dimensional siloxane network which is used as a film forming substrate of the coating; the film-forming adhesive is dispersed in the siloxane network; a siloxane coating layer containing a hydrophobic octyl side chain is constructed on the surface of nano titanium dioxide in situ, so that the coating is endowed with super-hydrophobicity, and a physical barrier is formed to inhibit microbial attachment; and bacteria are efficiently killed under ultraviolet irradiation, so that double protection of physical barrier and chemical sterilization is realized.

Description

Technical Field

[0001] This invention relates to the field of cultural heritage protection materials technology, specifically to a dual-mechanism antibacterial siloxane coating and its application. Background Technology

[0002] Stone artifacts, exposed to the natural environment for extended periods, are susceptible to moisture penetration, microbial erosion, and UV aging. Traditional protective agents such as acrylic resins and fluorocarbon materials, while waterproof, suffer from severely insufficient breathability. Industry data shows that the natural water vapor permeability of untreated limestone and other substrates is typically 800–1500 g / (m²). 2 • 24h), while after coating with traditional resins, the water vapor transmission rate drops sharply. Among them, acrylic resins (such as Paraaloid B-72) have dense cured films with a water vapor transmission rate of only 10–50 g / (m). 2 •24h); Although fluorocarbon resins have excellent weather resistance, their highly crystalline molecular structure results in poorer air permeability, with water vapor transmission rates often below 10 g / (m²). 2 Both (24h) have a water vapor exchange blocking rate of up to 90%–99%.

[0003] In recent years, nano-titanium dioxide has been widely studied for its excellent photocatalytic activity, self-cleaning properties and UV resistance, and is used for the preservation of cultural relics. However, in practical applications, titanium dioxide is difficult to disperse evenly on hydrophobic substrates due to its strong hydrophilicity, and it is prone to agglomeration, which reduces the effective specific surface area. The high recombination rate of hole pairs limits its antibacterial efficiency, and its strong oxidizing properties may cause potential damage to the organic components of cultural relics.

[0004] To address the aforementioned issues, researchers have attempted to modulate the interfacial properties of titanium dioxide through surface modification. Among these modifications, siloxane compounds have become ideal modification media due to their excellent film-forming properties, air permeability, and chemical compatibility with inorganic substrates. Triethoxyoctylsilane, as a typical long-chain alkylsilane, can form a three-dimensional siloxane network with hydrophobic side chains after hydrolysis and polycondensation, which can provide both physical barriers and anchor functional particles.

[0005] However, there are no reports in the existing technology of constructing a coating system with both physical barrier and chemical bactericidal mechanisms by synergistically combining siloxane-modified titanium dioxide with adhesives, and of successfully applying it to the protection of cultural relics. Summary of the Invention

[0006] The purpose of this invention is to provide a dual-mechanism antibacterial siloxane coating, its preparation method and application. This coating has superhydrophobic, self-cleaning, UV-resistant and long-lasting antibacterial properties, while maintaining good air permeability. It is suitable for green, safe and long-lasting protection of porous cultural relics surfaces.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A dual-mechanism antibacterial siloxane coating, which is formed in situ by a precursor comprising triethoxyoctylsilane, nano-titanium dioxide and a film-forming binder via a hydrolysis-condensation reaction; Among them, some of the triethoxyoctylsilanes undergo hydrolysis and condensation on the surface of nano-titanium dioxide to form a siloxane coating layer containing hydrophobic octyl side chains, which is chemically bonded to the surface of nano-titanium dioxide through Si–O–Ti covalent bonds. The remaining triethoxyoctylsilane self-condenses to form a continuous three-dimensional siloxane network, which serves as the film-forming matrix for the coating. The film-forming binder is dispersed in a siloxane network; Optionally, the coating may also include an additive selected from at least one of a dispersant, a leveling agent, or a defoamer.

[0008] Furthermore, the particle size of nano-titanium dioxide does not exceed 50 nm, preferably 1–30 nm, and the crystal form is anatase.

[0009] Furthermore, the film-forming binder is selected from at least one of fluorosilicone resin, silicone-acrylic emulsion, or low molecular weight hydroxyl-terminated polysiloxane, and its solid content is 10%–30%.

[0010] Furthermore, based on the total mass of the dry film coating, it contains: 3%–8% nano-titanium dioxide, all based on the mass of the titanium dioxide, the surface of which is modified with triethoxyoctylsilane; 5%–12% film-forming binder; and the balance being a siloxane network matrix formed by the hydrolysis and condensation of triethoxyoctylsilane.

[0011] Furthermore, the siloxane coating satisfies one or more of the following properties: The water contact angle after curing is ≥150°; Water vapor transmission rate ≥800g / (m 2 ·24h); Under ultraviolet light with a wavelength ≤400 nm, the bactericidal rate against Bacillus subtilis is ≥98% after 2 hours; where ultraviolet light with a wavelength ≤400 nm refers to the ultraviolet light region including UVA (315–400 nm) and UVB (280–315 nm), covering all wavelengths effective for photocatalytic reactions in the natural environment. The mold resistance level against Aspergillus niger reaches level 0 (according to GB / T 1741–2007, cultured for 28 days). After accelerated aging (QUV 500 h + 100 cycles of damp heat), the water contact angle retention rate is ≥95% and the water vapor transmission rate retention rate is ≥95%.

[0012] Furthermore, a method for preparing a dual-mechanism antibacterial siloxane coating includes the following steps: S1: Dissolve triethoxyoctylsilane in an alcohol / water mixed solvent and hydrolyze under acidic conditions for 0.5–4 hours to obtain a silanol solution; S2: Add nano-titanium dioxide powder to the silanol solution, control the mass ratio of triethoxyoctylsilane to nano-titanium dioxide to be (2:1) to (5:1), stir and react at 40–70℃ for 4–12 hours, so that the silanol condenses on the surface of titanium dioxide to form a siloxane coating layer, while some silanol self-condenses, to obtain a siloxane precursor dispersion containing modified titanium dioxide; S3: Add film-forming binder and additives to the dispersion, mix well to obtain coating precursor solution; S4: The precursor solution is applied to the surface of the substrate, and then hydrolyzed and polycondensed to form a siloxane coating.

[0013] Furthermore, in step S2, the reaction endpoint can be determined by online monitoring of the system viscosity change or pH stability. When the system viscosity remains constant (±5 mPa·s) at 60°C for more than 30 minutes, or the pH value rises back to 4.5–5.0, it indicates that the reaction is nearing completion. The use of a static mixer continuous flow reaction device can achieve uniformity and reproducibility in large-scale preparation.

[0014] Further, in step S1, the alcohol is ethanol or isopropanol, the molar ratio of water to triethoxyoctylsilane is (2-4):1, and the pH value is 3–5.

[0015] Furthermore, the application of a dual-mechanism antibacterial siloxane coating in the surface protection of cultural relics, which are porous inorganic cultural relics such as stone, pottery, and bricks, as well as organic composite cultural relics such as murals (artifacts such as painted murals may contain organic components such as animal binders).

[0016] Furthermore, the coating is applied to the clean, dry surface of the artifact in the form of a precursor solution by spraying, brushing, or dipping, and cured at room temperature and humidity for 24–72 hours to form a transparent protective film with a thickness of 0.5–5 μm.

[0017] Furthermore, the thickness of the siloxane coating is 1–5 nm.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention constructs an in-situ chemically anchored nanoscale siloxane coating layer, using Si–O–Ti covalent bonds to firmly lock nano-titanium dioxide within the siloxane network, achieving monodispersity of the particles. This coating layer of a specific thickness effectively limits the diffusion distance of highly oxidizing reactive oxygen species into the substrate while retaining photocatalytic activity. Compared to the problems of severe particle agglomeration and weak interfacial bonding caused by simple physical mixing processes in existing technologies, this invention reduces the oxidative damage rate of organic binders to cultural relics by more than 80% while maintaining a bacterial kill rate of >98%, truly achieving a perfect balance between efficient sterilization and the safety of the cultural relics themselves. 2. The three-dimensional network formed by long-chain alkylsiloxanes endows the coating with excellent superhydrophobicity and high air permeability; while blocking the penetration of water and pollutants, it ensures that cultural relics can breathe freely. In addition, the coating has all-weather protection capabilities with passive defense in the absence of light and active killing in the presence of light; compared with the defect of unmodified titanium dioxide, which cannot be evenly dispersed in a hydrophobic matrix due to its strong hydrophilicity, resulting in the failure of protective effectiveness, it significantly improves the long-term weather resistance and biological degradation inhibition ability of stone cultural relics in complex natural environments. 3. By designing a reversible chemical bond and a reprocessable structure with a flexible matrix, the coating maintains stable performance after undergoing rigorous aging tests and can be completely removed with mild chemical reagents, leaving no fluoride ion residue and not damaging the substrate. Compared with the drawbacks of traditional protective agents that are difficult to remove, easy to leave residues, or cause secondary damage after aging, this invention strictly conforms to the core principles of minimal intervention and reversibility in cultural relic protection. It is suitable for fragile cultural relics containing organic components and provides a green protection solution that can be engineered and scaled up. 4. By adopting a room temperature and humidity curing process, no high-temperature baking or special equipment is required, which reduces the construction threshold and energy consumption. The resulting coating is transparent and colorless, and does not change the original appearance and color of the cultural relics. At the same time, by flexibly adjusting the mass ratio of triethoxyoctylsilane to titanium dioxide, the degree of modification and film-forming performance can be precisely adjusted, making it suitable for the protection needs of cultural relics of different materials such as limestone, sandstone and painted murals, and has extremely high promotion and application value. Attached Figure Description

[0019] Figure 1 This is a SEM cross-sectional view of the coating of Embodiment 1 of the present invention, which maintains its complete structure after long-term exposure. Figure 2 This is a SEM cross-sectional image of the comparative coating of the present invention after long-term exposure, showing microbial penetration and biofilm accumulation. Figure 3 This is an overall flowchart of Embodiment 1 of the present invention; Figure 4 The graph shows the 2-hour bactericidal rate of Bacillus subtilis in the embodiments and comparative examples of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0022] In this invention, triethoxyoctylsilane is converted into silanol under acidic hydrolysis conditions. This silanol can undergo a condensation reaction with the hydroxyl groups on the surface of nano-titanium dioxide to form stable Si–O–Ti covalent bonds (formed by the condensation of silanol and hydroxyl groups on the titanium dioxide surface), thereby achieving surface modification of titanium dioxide. The formation of this chemical bond can be verified by conventional characterization methods in the art, for example: Fourier transform infrared spectroscopy was used for detection in the range of 940–960 cm⁻¹. -1 Characteristic absorption peaks attributable to Si–O–Ti bonds appear within the range; X-ray photoelectron spectroscopy analysis showed that the binding energy of Ti2p3 / 2 was negatively shifted by 0.2–0.5 eV compared to unmodified titanium dioxide, indicating an increase in the electron cloud density of Ti atoms and confirming the formation of Ti–O–Si bonds.

[0023] It should be noted that the silanols generated by the hydrolysis of triethoxyoctylsilane have high reactivity and preferentially undergo condensation reactions with the hydroxyl groups on the surface of titanium dioxide. When the surface hydroxyl groups tend to be saturated, the unreacted silanols form a continuous three-dimensional siloxane network through self-condensation. Therefore, by controlling the mass ratio of triethoxyoctylsilane to nano-titanium dioxide, preferably 2:1 to 5:1, the proportion of silanes used for surface modification and film formation network can be reasonably allocated to achieve in-situ integrated structure construction.

[0024] In addition, to improve the processing performance of the coating precursor solution, a small amount of additives can be added, including dispersant BYK-163, leveling agent TEGOGlide410, and defoamer BYK-028. The total amount of additives added is typically 0.1%–2% of the total mass of the precursor solution, of which the dispersant accounts for 0.1%–1%, the leveling agent accounts for 0.05%–0.5%, and the defoamer accounts for 0.01%–0.2%. This dosage range is sufficient to improve dispersibility and film uniformity without affecting the hydrophobicity and permeability of the coating.

[0025] Example 1: Preparation of dual-mechanism antibacterial siloxane coating: 10g of triethoxyoctylsilane was dissolved in a mixture of 30mL ethanol and 5mL deionized water and hydrolyzed under acidic conditions (pH=3) for 2 hours to obtain a silanol solution. 5g of prepared anatase nano-titanium dioxide powder with a particle size of 20nm was added to a silanol solution. The mass ratio of triethoxyoctylsilane to nano-titanium dioxide was controlled at 3:1. The mixture was stirred at 60℃ for 8 hours to allow silanol to condense on the surface of titanium dioxide to form a siloxane coating layer. TEM observation showed that the coating layer thickness was about 3.5nm. At the same time, the remaining silanol self-condensed to obtain a siloxane precursor dispersion containing modified titanium dioxide. Add 8g of fluorosilicone resin (20% solid content) to the dispersion, along with 0.3g of polymeric dispersant (BYK-163) and 0.2g of polyether-modified siloxane leveling agent. Mix thoroughly to obtain the coating precursor solution.

[0026] The precursor solution was sprayed onto the surface of a limestone specimen and cured for 48 hours under normal temperature and humidity conditions to form a transparent siloxane coating with a thickness of approximately 2 μm.

[0027] Example 2: Low silane ratio coating: Example 1 was repeated, but the mass ratio of triethoxyoctylsilane to nano-titanium dioxide was adjusted to 2:1, while the other conditions remained unchanged; TEM observation showed that the coating layer was thin, with a thickness of about 1.2 nm.

[0028] Example 3: High silane ratio coating: Example 1 was repeated, but the mass ratio of triethoxyoctylsilane to nano-titanium dioxide was adjusted to 5:1, while the other conditions remained unchanged; TEM observation showed that the coating layer was thickened to approximately 4.8 nm.

[0029] Comparative example: 5g of untreated anatase nano-titanium dioxide powder (particle size approximately 20nm) was directly added to a silanol solution composed of 10g triethoxyoctylsilane, 30mL ethanol, 5mL deionized water, and acidic conditions (pH=3). After stirring and reacting at 60℃ for 8 hours, 8g of fluorosilicone resin (solid content 20%), 0.3g of dispersant (BYK-163) and 0.2g of leveling agent (TEGOGlide410) were added. After mixing evenly, the mixture was sprayed onto a limestone test piece and cured at room temperature for 48 hours to form a coating. However, due to the abundance of hydrophilic hydroxyl groups on the surface of nano-titanium dioxide, the silanols generated by the hydrolysis of triethoxyoctylsilane are difficult to bond efficiently with it without a catalyst or pre-reaction conditions. As a result, the titanium dioxide particles are only physically dispersed in the siloxane network without forming a chemical anchor. TEM observation shows that there is no continuous and dense siloxane coating layer on the particle surface, the thickness is less than 0.5 nm, and the distribution is uneven. At the same time, a large number of titanium dioxide particles undergo severe agglomeration, forming aggregates with a size of 200–500 nm.

[0030] After nano-titanium dioxide is coated with siloxane, the siloxane layer effectively passivates the dangling bonds and uncoordinated atoms on the titanium dioxide surface. Since these surface defect states are originally the main trapping traps and recombination centers for photogenerated carriers, their reduction directly cuts off the fast nonradiative recombination channel of electron-hole pairs. This mechanism significantly reduces the recombination rate of carriers and greatly prolongs the separation lifetime of photogenerated electrons and holes. As a result, the modified titanium dioxide not only retains strong photocatalytic activity, but also exhibits enhanced response in the visible light region (λ=400–550 nm). At the same time, the superhydrophobic surface (contact angle ≥150°) can effectively inhibit microbial attachment and biofilm formation, and still has passive protection capabilities even under no-light conditions. After being placed under a light source (K, spectral range 400–700 nm, without ultraviolet radiation) for 7 days, the coatings in Examples 1-3 still showed an inhibition rate of over 85% against Bacillus subtilis, which was significantly better than the comparative example.

[0031] Comparing the data of Example 1 and the comparative example, it can be seen that the sterilization rate of the comparative example (80.5%) is significantly lower than that of Example 1 (99.2%) (relative decrease of 18.7%). This performance gap is not a linear decrease, but is caused by a dual nonlinear decay mechanism caused by microstructural defects. In the comparative example, titanium dioxide is severely agglomerated, and the particle size increases dramatically from a monodisperse 20nm to 200–500nm. According to the specific surface area formula of spheres (S=6 / ρd), under the same mass concentration, the theoretical specific surface area of ​​500nm agglomerates is only 1 / 25 (i.e. 4%) of that of a 20nm single particle. This means that more than 95% of the titanium dioxide particles in the coating of the comparative example are wrapped inside the agglomerates and cannot directly contact the bacterial cell wall or water and oxygen molecules in the environment, resulting in an order-of-magnitude decrease in the density of effective catalytic active sites. This is the primary geometric factor that prevents the sterilization rate from breaking through the 85% bottleneck.

[0032] Explanation of the above coating test methods Thickness of the siloxane coating on titanium dioxide surface: cross-sectional observation by transmission electron microscopy (TEM), average value of multiple particles; Static water contact angle of the coating surface: determined according to GB / T30447–2013 or ISO19403-2:2017; Size of nano-titanium dioxide aggregates: Dynamic light scattering (DLS) or field emission scanning electron microscopy (FE-SEM) Water vapor transmission rate g / (m 2 • 24h): Determined according to GB / T17146–2015 (desiccant method, 23±1℃, 0%→90%RH); 2-hour sterilization rate against Bacillus subtilis: according to ISO 27447:2009, UV wavelength ≤400nm (main peak 365nm), light intensity 1.0mW / cm² 2 Measurement; Anti-mold grade against Aspergillus niger: Graded according to GB / T 1741–2007, after 28 days of cultivation; Accelerated aging test: 500 hours of QUV ultraviolet aging (UVA-340 lamp), 100 cycles of 60℃ / 95% RH damp heat cycling; Reworkability test: Wipe locally with 0.5 wt% ammonium fluoride aqueous solution for 5 minutes, and observe the removal effect and substrate damage.

[0033]

[0034] As shown in the table above, this invention constructs a siloxane coating layer with a thickness of 1.2–4.8 nm on the surface of titanium dioxide through in-situ hydrolysis and condensation reaction of triethoxyoctylsilane and nano-titanium dioxide, and forms stable Si–O–Ti covalent bonds, which effectively inhibits the aggregation of nanoparticles (aggregate size <50 nm) and achieves its uniform dispersion in the hydrophobic siloxane network. Correspondingly, the resulting coating also possesses excellent superhydrophobicity (water contact angle ≥150°) and high water vapor transmission rate ≥830 g / (m²). 2 It exhibits high-efficiency photocatalytic antibacterial properties (sterilization rate ≥98.7% in 2 hours) and strong inhibitory effects on common biological deterioration factors of cultural relics such as Aspergillus niger and lichens. In contrast, the comparative method, which uses physical mixing, does not form a chemically bonded coating structure, resulting in severe agglomeration of titanium dioxide (200–500 nm). This not only damages the coating uniformity but also significantly reduces hydrophobicity, breathability, and antibacterial efficiency (sterilization rate of only 82.0%), failing to achieve the synergistic protective effect of physical barrier and photocatalytic oxidation.

[0035] The above results fully demonstrate that only by forming a siloxane coating layer of a specific thickness (1–5 nm) through in-situ chemical modification can the photocatalytic antibacterial activity of nano-titanium dioxide be fully utilized while ensuring superhydrophobicity and high air permeability, thereby achieving long-term, safe, and green protection for porous cultural relics. It should be noted that this invention, by precisely controlling the thickness of the siloxane coating layer (1–5 nm), effectively limits reactive oxygen species (·OH, O2) while retaining the photocatalytic activity of titanium dioxide. - The diffusion distance of the coating layer is such that when the coating layer thickness is ≥1.2 nm, the degradation rate of adjacent organic matter (such as gelatin film) is reduced by more than 80% (refer to ISO 105-X12 color fastness test), while the killing efficiency of bacteria attached to the surface is still >98%, which is suitable for painted cultural relics containing organic binders.

[0036] It is worth noting that in this invention, the 1–5 nm thickness of the siloxane coating layer refers to the molecular modification layer on the surface of the nano-titanium dioxide particles, while the overall coating thickness of 0.5–5 μm refers to the macroscopic protective film applied to the surface of the cultural relic. Although the two have different scales, they work synergistically. After reprocessability testing, SEM observation and ion chromatography analysis of the substrate revealed no residual fluoride ions or signs of calcium carbonate corrosion, confirming the safety of the cultural relic. In addition, the coating of this invention still has passive protection capabilities in low-light environments, and can be scaled up in engineering through online monitoring of process parameters (such as viscosity and pH), fully meeting the actual needs of cultural relic protection.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A dual-mechanism antibacterial siloxane coating, characterized in that, The coating is formed in situ by a precursor comprising triethoxyoctylsilane, nano-titanium dioxide and a film-forming binder via a hydrolysis-condensation reaction. Among them, some of the triethoxyoctylsilanes undergo hydrolysis and condensation on the surface of nano-titanium dioxide to form a siloxane coating layer containing hydrophobic octyl side chains, which is chemically bonded to the surface of nano-titanium dioxide through Si–O–Ti covalent bonds. The remaining triethoxyoctylsilane self-condenses to form a continuous three-dimensional siloxane network, which serves as the film-forming matrix for the coating. The film-forming binder is dispersed in a siloxane network; Optionally, the coating may also include an additive selected from at least one of a dispersant, a leveling agent, or a defoamer.

2. The dual-mechanism antibacterial siloxane coating according to claim 1, characterized in that, The particle size of nano-titanium dioxide is no more than 50 nm, and its crystal form is anatase.

3. The dual-mechanism antibacterial siloxane coating according to claim 1, characterized in that, The film-forming binder is selected from at least one of fluorosilicone resin, silicone-acrylic emulsion or low molecular weight hydroxyl-terminated polysiloxane, and its solid content is 10%–30%.

4. The dual-mechanism antibacterial siloxane coating according to claim 1, characterized in that, The coating contains, by total mass of dry film, 3%–8% nano-titanium dioxide (by mass of the titanium dioxide, whose surface is modified with triethoxyoctylsilane), 5%–12% film-forming binder, and the balance being a siloxane network matrix formed by hydrolysis and polycondensation of triethoxyoctylsilane.

5. The dual-mechanism antibacterial siloxane coating according to any one of claims 1 to 4, characterized in that, The siloxane coating meets one or more of the following properties: The water contact angle after curing is ≥150°; Water vapor transmission rate ≥800g / (m 2 ·24h); Under ultraviolet light with a wavelength ≤400nm, the bactericidal rate against Bacillus subtilis is ≥98% within 2 hours.

6. A method for preparing a dual-mechanism antibacterial siloxane coating as described in any one of claims 1–5, characterized in that, Includes the following steps: S1: Dissolve triethoxyoctylsilane in an alcohol / water mixed solvent and hydrolyze under acidic conditions for 0.5–4 hours to obtain a silanol solution; S2: Add nano-titanium dioxide powder to the silanol solution, control the mass ratio of triethoxyoctylsilane to nano-titanium dioxide to be (2:1) to (5:1), stir and react at 40–70℃ for 4–12 hours, so that the silanol condenses on the surface of titanium dioxide to form a siloxane coating layer, while some silanol self-condenses, to obtain a siloxane precursor dispersion containing modified titanium dioxide; S3: Add film-forming binder and additives to the dispersion, mix well to obtain coating precursor solution; S4: The precursor solution is applied to the surface of the substrate, and then hydrolyzed and polycondensed to form a siloxane coating.

7. The preparation method according to claim 6, characterized in that, In step S1, the alcohol is ethanol or isopropanol, the molar ratio of water to triethoxyoctylsilane is (2-4):1, and the pH value is 3–5.

8. The application of the dual-mechanism antibacterial siloxane coating according to any one of claims 1–5 in the protection of cultural relic surfaces, characterized in that, The cultural relics are porous inorganic relics made of stone, pottery, and bricks, as well as organic composite relics such as murals.

9. The application according to claim 8, characterized in that, The coating is applied to the clean, dry surface of the artifact in the form of a precursor solution by spraying, brushing, or dipping, and cured at room temperature and humidity for 24–72 hours to form a transparent protective film with a thickness of 0.5–5 μm.

10. The dual-mechanism antibacterial siloxane coating according to claim 1, characterized in that, The thickness of the siloxane coating is 1–5 nm.

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