A composite coating with light-conversion, super-hydrophobic and self-cleaning functions, preparation and application thereof

Abstract

The present invention discloses a composite coating with light conversion and super-hydrophobic self-cleaning functions, as well as its preparation and application. The method comprises the following steps: preparing a light conversion coating solution, an adhesion coating solution, and a super-hydrophobic self-cleaning coating solution; pulling or coating a pretreated substrate to obtain a substrate having a light conversion coating; pulling or coating the substrate having the light conversion coating to obtain a semi-cured adhesion coating; spraying the super-hydrophobic self-cleaning coating solution on the semi-cured adhesion coating, and curing and forming the coating to obtain a composite coating with light conversion and super-hydrophobic self-cleaning functions. The composite coating takes into account the performance of light wavelength conversion, high light transmittance, and self-cleaning. At the same time, the composite coating also has good light conversion anti-attenuation and self-cleaning stability. In addition, the composite coating is applicable to a variety of substrates and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of functional coatings and functional nanomaterial preparation, and more specifically to a composite coating with light conversion, super-hydrophobic and self-cleaning functions, and its preparation and application. Background Art

[0002] Short-wavelength, high-energy ultraviolet light in solar radiation can damage, age, or degrade animals, plants, plastics, rubber, and more, including humans. Therefore, it's often necessary to shield UV light or convert it into longer-wavelength, lower-energy light. Using light-conversion materials to convert UV light into usable visible light, thereby increasing sunlight utilization, is an effective solution to the UV problem and has broad applications in agriculture, building materials, solar cells, and other fields.

[0003] Existing reports indicate that carbon dots can be used as light-conversion materials to convert ultraviolet light into visible light, and thus be applied in the preparation of light-conversion films. However, the concentration quenching phenomenon of carbon dots severely limits their application. In addition, in practical applications, agricultural greenhouses, solar cells, and building materials are used outdoors for long periods of time, and the dust and dirt accumulated on the surface will block the penetration of sunlight, reduce the utilization of light energy, and seriously affect the efficiency and lifespan of the materials. Manual cleaning and maintenance are time-consuming, labor-intensive, and costly. Currently, there are no reports of membrane structures that can achieve both light conversion and self-cleaning functions. Therefore, in order to fill the scientific research gap and meet the application needs of today's society, it is urgent to develop a membrane structure that can achieve both light conversion and self-cleaning functions. Summary of the Invention

[0004] To address these shortcomings, the first objective of the present invention is to provide a method for preparing a composite coating with light-conversion and super-hydrophobic self-cleaning functions. This method first prepares a red-light-emitting carbon dot solution using green plants as a raw material and an alcohol-soluble polymer as a modifier. This solution is then applied to various substrates to form a light-conversion coating by pulling or coating. Next, an adhesion coating solution is used to form a semi-cured adhesion coating on the outside of the light-conversion coating. While the adhesion coating is still viscous and not fully cured, a super-hydrophobic self-cleaning coating is sprayed with a super-hydrophobic self-cleaning coating solution to form a super-hydrophobic self-cleaning coating. This coating is then fully cured to form a composite coating.

[0005] A second object of the present invention is to provide a composite coating with light conversion and super-hydrophobic self-cleaning functions, prepared using the above-described preparation method. The composite coating has light wavelength conversion capability, high light transmittance, super-hydrophobic self-cleaning ability, good light conversion resistance to attenuation, and self-cleaning stability. Furthermore, the sprayed polydimethylsiloxane and hydrophobic silica adhere firmly to the adhesive coating after curing, and the adhesive coating is also firmly cured with the inner light conversion coating, thereby ensuring the light transmittance and super-hydrophobic stability of the composite coating while achieving the effect of preventing the layers from separating.

[0006] The third object of the present invention is to provide an application of the composite coating described above in the preparation of agricultural greenhouses, building materials, and solar cells.

[0007] In order to achieve the above first object, the present invention adopts the following technical solutions:

[0008] The present invention discloses a method for preparing a composite coating with light conversion and super-hydrophobic self-cleaning functions, comprising the following steps:

[0009] 1) Prepare light-converting coating solution

[0010] The green plants are washed and ground, extracted with ethanol at room temperature, an alcohol-soluble polymer is added to the extract and ultrasonic treatment is performed to obtain a mixed raw material solution;

[0011] Transfer the mixed raw material solution to a high-pressure reactor, react at 120-200°C for 2-24 hours, centrifuge after the reaction, collect the supernatant, and refrigerate at 0-5°C for later use;

[0012] 2) Prepare adhesive coating solution

[0013] Dispersing the PDMS adhesive in a diluent to obtain an adhesion coating solution;

[0014] 3) Preparation of super hydrophobic self-cleaning coating solution

[0015] Dispersing PDMS adhesive and hydrophobic silica in a diluent to obtain a super-hydrophobic self-cleaning coating solution;

[0016] 4) Preparation of light-converting coating

[0017] The pretreated substrate is immersed in a light-converting coating solution, pulled, and then dried at 40-60° C. for 0.5-2 h to obtain a light-converting coating;

[0018] Alternatively, the light conversion coating solution is coated on the pretreated substrate, and then dried at 40-60° C. for 0.5-2 h to obtain the light conversion coating;

[0019] 5) Preparation of semi-cured adhesive coating

[0020] The substrate with the light-converting coating is immersed in the adhesive coating solution, pulled, and then heated at 50-60°C for 5-30 minutes to obtain a semi-cured adhesive coating;

[0021] Alternatively, the adhesion coating solution is applied to the substrate having the light-converting coating, and then heated at 50-60° C. for 5-30 minutes to obtain a semi-cured adhesion coating;

[0022] 6) Preparation of super hydrophobic self-cleaning coating

[0023] The super-hydrophobic self-cleaning coating solution is sprayed on the semi-cured adhesive coating and cured to obtain a composite coating with light-converting and super-hydrophobic self-cleaning functions.

[0024] In the present invention, in order to solve the problems existing in the prior art, the inventors finally obtained a method for preparing a composite coating with light conversion, super hydrophobic and self-cleaning functions as described above through a large number of experimental attempts. The method is divided into two stages: the preparation stage of the coating liquid and the preparation stage of the composite coating. In the first stage, biomass such as green plants is selected as raw materials, modified with alcohol-soluble polymers, and a modified red light-emitting carbon dot solution is obtained by a solvent thermal method as a light conversion coating solution; the introduction of alcohol-soluble polymers can increase the steric hindrance on the surface of the carbon dots, effectively avoiding the non-radiative energy release caused by excessive energy transfer between carbon dot nanoparticles, thereby realizing the solid-phase luminescence of the carbon dots. Secondly, an adhesion coating solution is prepared with PDMS adhesive, and then a super hydrophobic self-cleaning coating solution is prepared with PDMS adhesive and hydrophobic silica to provide the system with hydrophobicity and self-cleaning ability. After each coating liquid is prepared, the composite coating is prepared. The light-converting coating can be prepared on the substrate by pulling or coating. The light-converting coating can provide the composite coating with light wavelength conversion capability, efficiently converting the ultraviolet light in sunlight into red light, improving the utilization rate of sunlight, and promoting plant growth and development; the second layer of adhesive coating is also critical. A solution containing PDMS adhesive is used for preparation. By mastering the curing characteristics of PDMS adhesives of different concentrations, the curing conditions are adjusted to form a semi-cured adhesive coating. The so-called semi-cured adhesive coating refers to a solution containing PDMS adhesive that loses fluidity as the diluent evaporates, but still maintains a certain viscosity. The formation of this intermediate coating can utilize the adhesion force that exists when it is not fully cured to firmly adhere the light-converting coating and the super-hydrophobic self-cleaning coating. After complete curing, the three coatings are formed into one piece and are difficult to separate, which solves the problem of directly The super-hydrophobic self-cleaning coating formed on the light-converting coating is easy to fall off and separate. At the same time, the design of this intermediate state coating is related to the preparation of the super-hydrophobic self-cleaning coating by spraying. Since the super-hydrophobic self-cleaning coating is formed directly by pulling or coating, there will be problems of weak adhesion and decreased transmittance. Therefore, the spraying method selected in this application is used to prepare the super-hydrophobic self-cleaning coating. After testing, the adhesive coating and the super-hydrophobic self-cleaning coating are interactively bonded after complete curing. The total thickness of the two coatings is about 20 microns, which has little effect on transmittance. The super-hydrophobic self-cleaning coating formed by the third layer gives the composite coating excellent hydrophobicity and self-cleaning ability. The static water contact angle is up to 174°, and the rolling angle is less than 2°, which protects the integrity of the inner light-converting layer and improves the service life of the light-converting coating. At the same time, the self-cleaning performance can achieve the removal of impurities such as dust and falling sand on the surface of the composite coating, maintaining a high light transmittance.

[0025] Furthermore, the green plants include but are not limited to one or more of amaranth, spinach, chrysanthemum, bitter chrysanthemum, radish leaves, rapeseed, kale, fennel, lettuce, wood ear, water spinach, shepherd's purse, celery, ginkgo leaves, cypress leaves, clover, purslane, foxtail grass, morning glory leaves and Stephanotis chinensis;

[0026] The alcohol-soluble polymer has good dispersibility and film-forming properties, and can effectively disperse the formed red light-emitting carbon dots. The alcohol-soluble polymer includes polyethylene glycol and / or polyvinyl pyrrolidone; illustratively, the polyethylene glycol includes but is not limited to one or more of PEG-400, PEG-600, PEG-800, PEG-1000, PEG-1500, PEG-2000, PEG-3000 and PEG-4000, and the polyvinyl pyrrolidone includes but is not limited to one or more of PVP K15, PVP K30, PVP K60 and PVP K90.

[0027] Furthermore, the mass ratio of the green plants to the alcohol-soluble polymer is 10-20:1.

[0028] Furthermore, the concentration of the PDMS adhesive in the adhesion coating solution is 20-60 wt %.

[0029] Furthermore, the PDMS adhesive is selected from DOWSIL SYLGARD 184 PDMS. Commercially available DOWSIL SYLGARD 184 PDMS is used in a base (PDMS) to curing agent ratio of 10:1. The base exhibits a certain degree of adhesion in the presence of the curing agent. By understanding the curing characteristics of solutions containing PDMS adhesive at different concentrations and adjusting the curing conditions, the semi-cured adhesive coating required by the present invention is formed. Extensive experiments have shown that when the PDMS adhesive concentration is 40 wt%, complete curing takes approximately 2 hours at 60°C, while when the PDMS adhesive concentration is 50 wt%, complete curing takes approximately 1 hour at 60°C.

[0030] Furthermore, the diluent includes but is not limited to one or more of n-hexane, petroleum ether, ethyl acetate and toluene.

[0031] Furthermore, in the superhydrophobic self-cleaning coating solution, the mass ratio of the PDMS adhesive, hydrophobic silica and diluent is 0.02-0.2:0.01-0.1:1; illustratively, the mass ratio of the PDMS adhesive, hydrophobic silica and diluent can be 0.02:0.01:1, 0.05:0.03:1, 0.1:0.01:1, 0.1:0.03:1, 0.1:0.05:1, 0.15:0.03:1, 0.15:0.05:1, 0.15:0.1:1, 0.2:0.05:1, 0.2:0.1:1, etc., or an interval formed by any two points thereof.

[0032] Further, the steps of pre-treating the substrate are:

[0033] The substrate is sequentially placed in water, ethanol and acetone solutions, ultrasonically cleaned for 10-30 minutes, then blown dry with high-purity nitrogen, and then subjected to oxygen plasma cleaning (plasma) for 3-10 minutes before use.

[0034] Furthermore, the specific steps of the pulling process in step 4 are as follows:

[0035] The pretreated substrate is placed in the light-converting coating solution, and after soaking for 10-90 seconds, it is pulled once at a rate of 0.5-5 mm / s, for a total of 1-20 times, and then dried at 40-60° C. for 0.5-2 hours to obtain a light-converting coating.

[0036] Furthermore, the specific steps of the pulling process in step 5 are as follows:

[0037] The substrate with the light-converting coating is immersed in the adhesive coating solution. After each immersion for 10-90 seconds, it is pulled once at a rate of 0.5-5 mm / s for a total of 1-20 times, and then heated at 50-60°C for 5-30 minutes to obtain a semi-cured adhesive coating.

[0038] Furthermore, in step 6, the spraying pressure is 0.1-0.3 MPa, the spraying distance is 10-25 cm, and the spraying time is 3-15 s.

[0039] Furthermore, in step 6, the curing temperature is 50-60° C., and the curing time is 0.5-2 h.

[0040] Furthermore, the substrate includes but is not limited to plastic agricultural film, architectural glass or photovoltaic glass.

[0041] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0042] The present invention discloses a composite coating with light conversion, super-hydrophobic and self-cleaning functions, wherein the composite coating is prepared by the preparation method described above;

[0043] Wherein, the composite coating comprises

[0044] Light conversion coating for converting the wavelength of ultraviolet light into red light;

[0045] A super-hydrophobic self-cleaning coating for protecting the light-converting coating and maintaining the light-converting effect of the light-converting coating; and

[0046] An adhesive coating for adhering and fixing the light-converting coating and the super-hydrophobic self-cleaning layer.

[0047] In order to achieve the third object, the present invention adopts the following technical solutions:

[0048] The present invention discloses an application of the composite coating described above in the preparation of agricultural greenhouses, building materials and solar cells.

[0049] The beneficial effects of the present invention are as follows:

[0050] The present invention discloses a composite coating with light-conversion, super-hydrophobic and self-cleaning functions, its preparation and application, which has the following advantages over the prior art:

[0051] 1. The present invention discloses for the first time a composite coating that can realize light conversion and super hydrophobic self-cleaning functions. It has excellent light conversion and attenuation resistance. After being soaked in water, subjected to high temperature and high humidity, and exposed to natural light, it still has a good light conversion effect. The composite coating consists of a light conversion coating, an adhesion coating, and a super hydrophobic self-cleaning coating. The light conversion coating can effectively absorb ultraviolet light in sunlight and convert it into red light, thus avoiding damage to facilities and equipment caused by high-intensity ultraviolet light. It emits red light of ~670nm, with a fluorescence quantum yield of up to 17%, achieving effective conversion of the incident spectrum. The adhesion coating can effectively absorb ultraviolet light in sunlight and convert it into red light, thus avoiding damage to facilities and equipment caused by high-intensity ultraviolet light. Before the coating is cured, based on the adhesion of the PDMS adhesive, the sprayed superhydrophobic self-cleaning coating solution is effectively combined with the semi-cured PDMS coating. The resulting superhydrophobic self-cleaning coating has good resistance to bending and 3M tape adhesion and peeling. The static water contact angle of the prepared superhydrophobic self-cleaning coating is as high as 174°, and the rolling angle is less than 2°. Surface impurities such as dust and falling sand can be easily carried away by water, and it has good self-cleaning function. In addition, the superhydrophobic self-cleaning layer can effectively protect the light-converting coating, increase the service life of the light-converting coating, and does not affect the light transmittance of the substrate.

[0052] 2. When preparing the light-converting coating, the present invention uses red-light-emitting carbon dots made from green plants and modified with an alcohol-soluble polymer. The introduction of the alcohol-soluble polymer increases steric hindrance on the carbon dot surface, effectively preventing non-radiative energy release caused by excessive energy transfer between carbon dot nanoparticles, thereby achieving solid-phase luminescence of the carbon dots.

[0053] In summary, the composite coating with light conversion and super-hydrophobic self-cleaning functions prepared by the present invention has good light conversion and super-hydrophobic self-cleaning properties, and the composite coating has high light transmittance, high light conversion anti-attenuation and mechanical stability; the maximum temperature required for the preparation of the composite coating is 60°C, which can be met in an ordinary drying oven, and the drying time is short. Overall, the preparation method is simple, has low equipment requirements, is applicable to different substrates, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0055] Figure 1 Fluorescence excitation, emission spectra and fluorescence quantum yield in solution of the spinach leaf-based red-light emitting carbon dots modified with polyethylene glycol PEG-1000 prepared in Example 1 when dispersed in ethanol solution and in solid state.

[0056] Figure 2 Fluorescence excitation and emission spectra of the red-light-emitting carbon dots modified with polyvinylpyrrolidone (PVP) K30 prepared in Example 2 dispersed in an ethanol solution and in a solid state, as well as the fluorescence quantum yield in the solution.

[0057] Figure 3 Comparison of light transmittance between the sample prepared in Example 5 and the original polyethylene film; the insets are digital photos and photos under 365nm ultraviolet irradiation of the original polyethylene film and the polyethylene film with the composite coating, respectively.

[0058] Figure 4 The cross-sectional layer structure of the sample prepared in Example 5 and the rough structure of the composite coating surface tested using a scanning electron microscope S-4800 are shown;

[0059] in, Figure 4 a is the cross-sectional layer structure of the polyethylene film with composite coating. Figure 4 Figure b is the rough structure diagram of the composite coating surface.

[0060] Figure 5 These are the fluorescence excitation and emission spectra of the sample prepared in Example 5.

[0061] Figure 6 Comparison of solar radiation intensity of the original polyethylene film and the sample prepared in Example 5.

[0062] Figure 7 Water contact angle and sliding angle of the sample prepared in Example 5;

[0063] in, Figure 7 Where a is the water contact angle, Figure 7 b is the rolling angle.

[0064] Figure 8 The water contact angle of the sample prepared in Example 5 before and after 1000 bending and curling operations;

[0065] in, Figure 8 a in the middle is the water contact angle before 1000 bending and curling operations. Figure 8 b is the water contact angle after 1000 bending and curling operations.

[0066] Figure 9 The water contact angle of the sample prepared in Example 5 before and after 100 repeated adhesion and peeling of 3M tape;

[0067] in, Figure 9 a in the middle is the water contact angle before repeated adhesion and peeling of 3M tape 100 times. Figure 9 (b) is the water contact angle after 100 repeated adhesion and peeling of 3M tape.

[0068] Figure 10 Relative fluorescence intensity and water contact angle of the sample prepared in Example 5 after being immersed in water for 240 hours;

[0069] The relative fluorescence intensity is relative to the fluorescence intensity of the sample before immersion in water, with 0 h being set as 100%.

[0070] Figure 11 Relative fluorescence intensity and water contact angle of the sample prepared in Example 5 after 240 hours in a high temperature and high humidity environment (40°C, 80%);

[0071] The relative fluorescence intensity is the fluorescence intensity of the sample before constant temperature and humidity treatment, with 0 hour being 100%.

[0072] Figure 12 Comparison of water contact angles of the sample prepared in Comparative Example 1 before and after being adhered once with 3M tape;

[0073] in, Figure 12 a is the water contact angle before adhesion, Figure 12 b is the water contact angle after adhesion.

[0074] Figure 13 is the light transmittance of the sample prepared in Comparative Example 2.

[0075] Figure 14 is the relative fluorescence intensity of the sample prepared in Comparative Example 3 after being immersed in water for 240 hours;

[0076] The relative fluorescence intensity is relative to the fluorescence intensity of the sample before immersion in water, with 0 h being set as 100%.

[0077] Figure 15is the relative fluorescence intensity of the sample prepared in Comparative Example 3 after 240 hours in a high temperature and high humidity environment (40°C, 80%);

[0078] The relative fluorescence intensity is the fluorescence intensity of the sample before constant temperature and humidity treatment, with 0 hour being 100%. DETAILED DESCRIPTION

[0079] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0080] In addition, unless otherwise specified, the raw materials used in the present invention can be obtained commercially, and any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0081] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0082] The PDMS adhesives used in the various embodiments and comparative examples of the present invention are all commercially available DOWSIL (Dow Corning) SYLGARD 184 PDMS products, and are used in a mass ratio of PDMS main agent to curing agent of 10:1.

[0083] Example 1

[0084] Preparation of light-converting coating solution: Preparation of a spinach leaf-based solid-phase red light-emitting carbon dot solution, specifically implemented as follows:

[0085] 10 g of spinach leaves were weighed, washed, dried, and ground in a mortar. The leaves were then extracted by soaking in 40 mL of ethanol. 1 g of polyethylene glycol PEG-1000 was added to the extract and ultrasonicated to completely dissolve the polymer. The resulting mixed raw material solution was transferred to an autoclave and reacted at 150° C. for 7 hours. After the reaction, the mixture was naturally cooled to room temperature to obtain a crude product. The crude product was centrifuged at 10,000 rpm for 10 minutes to remove large particles. The supernatant was collected as the final product and stored in a 4° C. refrigerator for later use.

[0086] 200 μL of the prepared PEG-modified carbon dot solution was transferred and diluted to 5 mL with ethanol. The excitation spectrum of the carbon dot solution was measured by FLS1000 transient / steady-state fluorescence spectrometer, and the emission range was 330-410 nm, while the emission range was 650-750 nm, indicating that the carbon dot solution can effectively absorb ultraviolet light and emit red light, with excellent light conversion performance. After the carbon dot solution was dried, the test showed that the solid state still had high photoluminescence performance, indicating that the PEG-modified carbon dots have the properties of anti-aggregation quenching and solid-phase luminescence ( Figure 1 ).

[0087] Example 2

[0088] Preparation of light-converting coating solution: Preparation of a solid-phase red light-emitting carbon dot solution based on amaranth leaves, the specific implementation steps are as follows:

[0089] 10 g of amaranth leaves were weighed, washed, dried, and crushed in a mortar. The leaves were then soaked and extracted with 40 mL of ethanol. 0.5 g of polyvinylpyrrolidone K30 was added to the extract and ultrasonically treated to completely dissolve the polymer. The obtained mixed raw material solution was transferred to a high-pressure reactor and reacted at 160° C. for 10 hours. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a crude product. The obtained crude product was centrifuged at 10,000 rpm for 10 minutes to remove large particles. The supernatant was collected as the final product and placed in a 4° C. refrigerator for later use.

[0090] Similarly, 200 μL of the prepared PVP-modified carbon dot solution was transferred and diluted to 5 mL with ethanol. The excitation spectrum of the carbon dot solution was measured by FLS1000 transient / steady-state fluorescence spectrometer, and the emission range was 330-410 nm. The red light was also emitted in the range of 650-750 nm, indicating that the carbon dot solution also has the properties of ultraviolet absorption and red light emission. After the carbon dot solution was dried, the solid state was tested and found to have high photoluminescence properties, indicating that the carbon dots modified with PVP also have the properties of anti-aggregation quenching and solid-phase luminescence ( Figure 2 ).

[0091] Example 3

[0092] Preparation of light-converting coating solution: Preparation of a rapeseed leaf-based solid-phase red light-emitting carbon dot solution, the specific implementation steps are as follows:

[0093] 10 g of rapeseed leaves were weighed, washed, dried, and ground in a mortar. The leaves were then soaked and extracted with 40 mL of ethanol. 1.5 g of polyethylene glycol PEG-600 was then added to the extract and ultrasonically treated to completely dissolve the polymer. The resulting mixed raw material solution was transferred to a high-pressure reactor and reacted at 180° C. for 6 hours. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a crude product. The crude product was centrifuged at 12,000 rpm for 12 minutes to remove large particles. The supernatant was collected as the final product and placed in a 4° C. refrigerator for later use.

[0094] Example 4

[0095] Preparation of light-converting coating solution: Preparation of a solid-phase red light-emitting carbon dot solution on the base of Setaria viridis leaf, the specific implementation steps are as follows:

[0096] 10 g of Setaria officinalis leaves were weighed, washed, dried, and ground in a mortar. The leaves were then soaked and extracted with 40 mL of ethanol. 1 g of polyvinylpyrrolidone (PVP) K60 was added to the extract and ultrasonically treated to completely dissolve the polymer. The resulting mixed raw material solution was transferred to an autoclave and reacted at 120° C. for 24 hours. After the reaction, the mixture was naturally cooled to room temperature to obtain a crude product. The crude product was centrifuged at 12,000 rpm for 15 minutes to remove large particles. The supernatant was collected as the final product and stored in a 4° C. refrigerator for later use.

[0097] Example 5

[0098] A method for preparing a light-converting, super-hydrophobic, self-cleaning composite coating on a polyethylene plastic film, the specific implementation steps are as follows:

[0099] 1) Ultrasonic cleaning of polyethylene film with water, ethanol, and acetone for 10 minutes, followed by drying with high-purity nitrogen, followed by oxygen plasma cleaning for 6 minutes before use;

[0100] 2) placing the prepared polyethylene film in the solid-phase red light-emitting carbon dot solution prepared in Example 1, soaking for 60 seconds, pulling the film once at a rate of 1 mm / s, for a total of 15 times, and then drying the film at 40°C for 2 hours to obtain a light-converting coating;

[0101] 3) The substrate with the light-converting coating was placed in a solution containing 40% by mass of a PDMS adhesive. The substrate was then pulled up at a rate of 5 mm / s for 10 seconds each, for a total of two pull-ups. The substrate was then heated at 60°C for 15 minutes to obtain a semi-cured adhesive coating.

[0102] 4) Finally, a superhydrophobic self-cleaning coating solution of n-hexane, PDMS adhesive, and hydrophobic silica in a mass ratio of 100:10:3 was ultrasonically treated for 30 minutes and then sprayed on the semi-cured adhesive coating at a spraying pressure of 0.3 MPa, a spraying distance of 15 cm, and a spraying time of 10 seconds. The coating was then cured at 60°C for 2 hours to obtain a light-converting, superhydrophobic, self-cleaning composite coating on a polyethylene film substrate.

[0103] Performance Testing

[0104] Figure 3A comparison of the light transmittance of the polyethylene film with the composite coating obtained in Example 5 and a polyethylene film without the composite coating (referred to as the original polyethylene film) shows that the light transmittance of the polyethylene film with the composite coating is only 2% lower than that of the original polyethylene film, demonstrating that the composite coating has excellent light transmittance. The insets show digital photographs of the original polyethylene film and the polyethylene film with the composite coating, as well as photographs of each under 365nm UV light. This demonstrates that the polyethylene film with the composite coating maintains light transmittance comparable to that of the original film while also exhibiting excellent red light emission properties.

[0105] Figure 4 Figures a and b are respectively the cross-sectional layer structure of the polyethylene film with the composite coating obtained in Example 5 and the rough structure of the composite coating surface tested using a scanning electron microscope S-4800. Figure 4 The cross-sectional layer structure in (a) shows that the selected polyethylene substrate has a thickness of 85 μm, and the prepared composite coating is evenly distributed on both sides of the substrate, with a total thickness of 25 μm on one side. Figure 4 Figure b shows that the sprayed superhydrophobic self-cleaning coating is tightly combined with the middle adhesion layer and forms a rough micro-nano structure, which is conducive to the formation of a superhydrophobic surface.

[0106] Figure 5 The fluorescence excitation and emission spectra of the polyethylene film with the composite coating in Example 5 were tested using an FLS1000 transient / steady-state fluorescence spectrometer. The results showed that the film had high ultraviolet absorption performance and high fluorescence emission at 650-750 nm.

[0107] Figure 6 The solar radiation intensity of the original polyethylene film and the polyethylene film with the composite coating of Example 5 was tested under sunlight using a handheld plant lighting spectrum detector UPRtek PG-200N, indicating that the composite coating has good light conversion performance.

[0108] Figure 7 Figures a and b show that the light-converting, superhydrophobic, self-cleaning composite coating has a water contact angle of up to 174° and a sliding angle of less than 2°.

[0109] Figure 8 In the figure, a and b are the water contact angles of the prepared composite coating before and after 1000 bending and curling operations (both greater than 160°), indicating that it has excellent superhydrophobic mechanical stability.

[0110] Figure 9 In the figure, a and b are the water contact angles of the prepared composite coating before and after 100 repeated adhesions of 3M tape (both greater than 160°), which further illustrates that the composite coating has excellent superhydrophobic mechanical stability.

[0111] The polyethylene film with the composite coating of Example 5 was immersed in water to simulate rainy weather in a natural environment to study the light attenuation resistance and superhydrophobic stability of the polyethylene film with the composite coating; Figure 10 It was shown that the composite coating still maintained 90% of the fluorescence emission intensity and excellent superhydrophobicity WCA>160° after being immersed in water for 240 hours.

[0112] The polyethylene film with the composite coating of Example 5 was placed in a constant temperature and humidity chamber at 40°C and 80% humidity to simulate the stability of the polyethylene film with the composite coating in a high temperature and high humidity environment. Figure 11 It shows that after 240 hours, the composite coating still maintains more than 90% of the fluorescence emission intensity and superhydrophobicity WCA>160°.

[0113] Example 6

[0114] A method for preparing a light-converting, super-hydrophobic, self-cleaning composite coating on a commercially available glass substrate, the specific implementation steps are as follows:

[0115] 1) The glass substrate was ultrasonically cleaned with water, ethanol, and acetone for 10 minutes, then dried with high-purity nitrogen, and then cleaned with oxygen plasma for 10 minutes before use;

[0116] 2) placing the prepared glass substrate in the solid-phase red light-emitting carbon dot solution prepared in Example 2, soaking for 30 seconds, pulling once at a rate of 1 mm / s, for a total of 10 times, and then drying at 40°C for 2 hours to obtain a light-converting coating;

[0117] 3) The substrate with the light-converting layer was placed in a solution containing 50% by mass of a PDMS adhesive. The substrate was soaked for 30 seconds and then pulled up at a rate of 5 mm / s twice. The substrate was then heated at 60°C for 20 minutes to obtain a semi-cured adhesive coating.

[0118] 4) Finally, a superhydrophobic self-cleaning coating solution of n-hexane, PDMS adhesive, and hydrophobic silica in a mass ratio of 100:15:5 was ultrasonically treated for 30 minutes and then sprayed on the semi-cured adhesive coating at a spraying pressure of 0.25 MPa, a spraying distance of 15 cm, and a spraying time of 15 seconds. The coating was dried and cured at 60°C for 2 hours to obtain a light-converting, superhydrophobic, self-cleaning composite coating on a glass substrate.

[0119] Comparative Example 1

[0120] After the polyethylene substrate is pulled up and the light-converting coating is directly sprayed with the super-hydrophobic self-cleaning coating, the specific implementation steps are as follows:

[0121] 1) The polyethylene film was ultrasonically cleaned with water and ethanol for 10 minutes, then dried with high-purity nitrogen, and then cleaned with oxygen plasma for 10 minutes before use;

[0122] 2) placing the prepared polyethylene film in the solid-phase red light-emitting carbon dot solution prepared in Example 1, soaking for 60 seconds, pulling the film once at a rate of 1 mm / s, for a total of 15 times, and then drying the film at 40°C for 2 hours to obtain a light-converting coating;

[0123] 3) Then, a super hydrophobic self-cleaning coating solution of n-hexane, PDMS adhesive, and hydrophobic silica in a mass ratio of 100:15:5 was ultrasonically treated for 30 minutes and then directly sprayed onto a polyethylene film with a light-converting layer. The spraying pressure was 0.3 MPa, the spraying distance was 15 cm, the spraying time was 10 seconds, and the coating was dried and cured at 60°C for 2 hours to obtain a light-converting, super hydrophobic self-cleaning composite coating on the polyethylene film.

[0124] Performance Testing

[0125] After testing, the sample prepared in Comparative Example 1 has comparable fluorescence emission performance compared to the polyethylene film with light-converting, super-hydrophobic self-cleaning composite coating prepared in Example 5; however, the super-hydrophobic self-cleaning layer prepared by this method is very unstable compared to the super-hydrophobic self-cleaning layer in Example 5, and falls off after being adhered once with 3M tape, resulting in the disappearance of super-hydrophobic performance. Figure 12 The results showed that after one adhesion with 3M tape, the water contact angle decreased from 156° of super hydrophobicity to 71°, which was similar to the original polyethylene film, indicating that the sprayed super hydrophobic layer had been completely adhered.

[0126] Comparative Example 2

[0127] 1) Ultrasonic cleaning of polyethylene film with water, ethanol, and acetone for 10 minutes, followed by drying with high-purity nitrogen, followed by oxygen plasma cleaning for 6 minutes before use;

[0128] 2) placing the prepared polyethylene film in the solid-phase red light-emitting carbon dot solution prepared in Example 1, soaking for 60 seconds, pulling the film once at a rate of 1 mm / s, for a total of 15 times, and then drying the film at 40°C for 2 hours to obtain a light-converting coating;

[0129] 3) The substrate with the light-converting coating was placed in a solution containing 40% by mass of a PDMS adhesive. The substrate was then pulled up at a rate of 5 mm / s for 10 seconds each, for a total of two pull-ups. The substrate was then heated at 60°C for 15 minutes to obtain a semi-cured adhesive coating.

[0130] 4) Finally, a superhydrophobic self-cleaning coating solution of n-hexane, PDMS adhesive, and hydrophobic silica with a mass ratio of 100:10:3 was ultrasonically treated for 30 minutes, and then pulled onto the semi-cured adhesive coating. The solution was soaked for 10 seconds and pulled once at a speed of 5 mm / s, and then cured at 60°C for 2 hours to obtain a light-converting, superhydrophobic self-cleaning composite coating on a polyethylene film substrate.

[0131] Performance Testing

[0132] According to the light transmittance test, the sample prepared in Comparative Example 2 has a light transmittance of only about 20% (e.g. Figure 13 ), which is much lower than that of the original polyethylene film and cannot meet the practical application.

[0133] Comparative Example 3

[0134] A physical pressing composite film of a polyethylene film with a light-converting coating and a PDMS layer with a super-hydrophobic self-cleaning coating, the specific steps are as follows:

[0135] 1) Ultrasonic cleaning of polyethylene film with water, ethanol, and acetone for 10 minutes, followed by drying with high-purity nitrogen, followed by oxygen plasma cleaning for 6 minutes before use;

[0136] 2) placing the prepared polyethylene film in the solid-phase red light-emitting carbon dot solution prepared in Example 1, soaking for 60 seconds, pulling the film once at a rate of 1 mm / s, for a total of 15 times, and then drying the film at 40°C for 2 hours to obtain a polyethylene film with a light-converting coating;

[0137] 3) Place another new polyethylene substrate in a solution containing 60% PDMS adhesive by mass, soak for 30 seconds, and pull it up once at a rate of 1 mm / s for a total of two times. Then heat it at 60°C for 15 minutes to obtain a semi-cured adhesive coating.

[0138] 4) Finally, a superhydrophobic self-cleaning coating solution of n-hexane, PDMS adhesive, and hydrophobic silica with a mass ratio of 100:10:3 was ultrasonically treated for 30 minutes and then sprayed on the semi-cured adhesive coating with a spraying pressure of 0.3 MPa, a spraying distance of 15 cm, and a spraying time of 10 seconds. The coating was then cured at 60°C for 2 hours, and the cured superhydrophobic self-cleaning PDMS layer was peeled off on the polyethylene film substrate to obtain a superhydrophobic self-cleaning PDMS layer.

[0139] 5) The super-hydrophobic self-cleaning PDMS layer and the polyethylene film with the light-converting layer in step 2) are pressed under a weight of 10 kg for 12 hours to obtain a light-converting, super-hydrophobic self-cleaning composite polyethylene film.

[0140] Performance Testing

[0141] The sample prepared in Comparative Example 3 was immersed in water for testing. It was found that the sample was dispersed into two layers after immersion in water, namely the light-converting polyethylene layer and the super-hydrophobic PMDS layer. That is, the adhesion between the composite coatings after physical pressing was poor, and they were separated after immersion in water. Similarly, after 240 hours of water immersion, the fluorescence intensity of the composite film decreased by 50% compared with that before immersion (such as Figure 14 ), its resistance to fluorescence decay is significantly lower than that of the sample prepared in Example 5.

[0142] Similarly, the composite film prepared in the comparative example also had the phenomenon of composite coating delamination during the high temperature and high humidity treatment process, resulting in water vapor contacting the light conversion layer, and ultimately causing the fluorescent luminescence intensity of the composite film to drop to about 60% of the pre-treatment level after 240 hours of high temperature and high humidity treatment (e.g. Figure 15 ), and its stability under high temperature and high humidity is also significantly lower than that of the polyethylene film with light-converting, super-hydrophobic self-cleaning composite coating prepared in Example 5.

[0143] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a composite coating with light-conversion, super-hydrophobic and self-cleaning functions, characterized in that: The steps include: 1) Prepare light-converting coating solution The green plants are washed and ground, extracted with ethanol at room temperature, an alcohol-soluble polymer is added to the extract and ultrasonic treatment is performed to obtain a mixed raw material solution; Transfer the mixed raw material solution to a high-pressure reactor, react at 120-200°C for 2-24 hours, centrifuge after the reaction, collect the supernatant, and refrigerate at 0-5°C for later use; 2) Prepare adhesive coating solution Dispersing the PDMS adhesive in a diluent to obtain an adhesion coating solution; 3) Preparation of superhydrophobic self-cleaning coating solution Dispersing PDMS adhesive and hydrophobic silica in a diluent to obtain a super-hydrophobic self-cleaning coating solution; 4) Preparation of light-converting coating The pretreated substrate is immersed in a light-converting coating solution, pulled, and then dried at 40-60°C for 0.5-2 hours to obtain a light-converting coating; Alternatively, the light conversion coating solution is coated on the pretreated substrate, and then dried at 40-60° C. for 0.5-2 h to obtain the light conversion coating; 5) Preparation of semi-cured adhesive coating The substrate with the light-converting coating is immersed in the adhesive coating solution, pulled, and then heated at 50-60°C for 5-30 minutes to obtain a semi-cured adhesive coating; Alternatively, the adhesive coating solution is coated on the substrate having the light-converting coating, and then heated at 50-60° C. for 5-30 minutes to obtain a semi-cured adhesive coating; 6) Preparation of superhydrophobic self-cleaning coating The super-hydrophobic self-cleaning coating solution is sprayed on the semi-cured adhesive coating and cured to obtain a composite coating with light-converting and super-hydrophobic self-cleaning functions; The alcohol-soluble polymer includes polyethylene glycol and / or polyvinyl pyrrolidone.

2. The preparation method according to claim 1, characterized in that The green plants include one or more of amaranth, spinach, chrysanthemum, bitter chrysanthemum, radish leaves, rape, kale, fennel, lettuce, water spinach, shepherd's purse, celery, ginkgo leaves, cypress leaves, clover, purslane, foxtail grass, morning glory leaves and Stephanotis chinensis.

3. The preparation method according to claim 1, characterized in that The mass ratio of the green plants to the alcohol-soluble polymer is 10-20:

1.

4. The preparation method according to claim 1, characterized in that The concentration of the PDMS binder in the adhesion coating solution is 20-60 wt %.

5. The preparation method according to claim 4, characterized in that The PDMS adhesive is selected from DOWSIL SYLGARD 184 PDMS.

6. The preparation method according to claim 1, characterized in that The diluent includes one or more of n-hexane, petroleum ether, ethyl acetate and toluene.

7. The preparation method according to claim 1, characterized in that In the super-hydrophobic self-cleaning coating solution, the mass ratio of the PDMS adhesive, the hydrophobic white carbon black and the diluent is 0.02-0.2:0.01-0.1:

1.

8. The preparation method according to claim 1, characterized in that Step 4 The specific steps of the lifting process are: The pretreated substrate is placed in a light-converting coating solution, and after soaking for 10-90 seconds, it is pulled once at a rate of 0.5-5 mm / s for 1-20 times in total, and then dried at 40-60°C for 0.5-2 hours to obtain a light-converting coating.

9. The preparation method according to claim 1, characterized in that Step 5 The specific steps of the pulling process are: The substrate with the light-converting coating is immersed in the adhesive coating solution. After each immersion for 10-90 seconds, it is pulled once at a rate of 0.5-5 mm / s for a total of 1-20 times, and then heated at 50-60°C for 5-30 minutes to obtain a semi-cured adhesive coating.

10. The preparation method according to claim 1, characterized in that In step 6, the spraying pressure is 0.1-0.3 MPa, the spraying distance is 10-25 cm, and the spraying time is 3-15 s.

11. The preparation method according to claim 1, characterized in that In step 6, the curing temperature is 50-60°C and the curing time is 0.5-2 h.

12. The preparation method according to claim 1, characterized in that The substrate includes plastic agricultural film, architectural glass or photovoltaic glass.

13. A composite coating with light-conversion, super-hydrophobic and self-cleaning functions, characterized in that: The product is prepared by the preparation method according to any one of claims 1 to 12.

14. Use of the composite coating according to claim 13 in the preparation of agricultural greenhouses, building materials, and solar cells.

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