All-weather carbon nanodot-based self-cleaning coating and application

Abstract

The invention relates to the technical field of special functional coating materials. The invention relates to a self-cleaning coating, in particular to an all-weather carbon nanodot-based self-cleaning coating and application. The formed self-cleaning coating comprises the following raw material components: a main body coating and a carbon nanodot aqueous solution serving as a coating additive; wherein the carbon nanodot aqueous solution is prepared according to the following steps: 1) adding an auxiliary agent solution into a high-molecular polymer to obtain a precursor solution; 2) transferring the precursor solution into a reactor, and reacting for 1-24 hours under the condition of 100-500 DEG C; and 3) after the reaction is finished, cooling to room temperature, collecting reaction liquid, and separating and purifying to obtain the product. The high-molecular polymer is selected from a structure shown in the specification. According to the coating, the inherent antibacterial performance of the carbon nanodots and the performance of generating active oxygen through photosensitization are utilized, stable sterilization and disinfection are achieved under the light or dark environment, formaldehyde is efficiently degraded under the light condition, and the coating can be widely applied to the fields of buildings, medical treatment, food processing, transportation and the like and has important industrial application value.

Description

Technical Field

[0001] This invention relates to the field of special functional coating materials technology. More specifically, it relates to an all-weather carbon nanoparticle-based self-cleaning coating and its application. Background Technology

[0002] With increasing demands for environmental hygiene and air quality, coating materials with self-cleaning functions such as sterilization, disinfection, and pollutant degradation are in high demand in building decoration, medical environments, food processing, livestock and aquaculture, and transportation. Currently, most commercial self-cleaning coatings are based on photocatalytic materials (such as titanium dioxide and zinc oxide), but they have significant limitations: first, their function depends on light exposure, and they cannot perform sterilization and self-cleaning in the absence of light; second, most coatings only possess a single function, making it difficult to simultaneously achieve the synergistic effect of sterilization and disinfection with the degradation of harmful gases.

[0003] Carbon nanodots, as a novel zero-dimensional carbon-based nanomaterial, possess excellent properties such as small size (typically less than 100 nm), high chemical stability, good biocompatibility, and low toxicity. Studies have found that some carbon nanodots, under light conditions, can generate reactive oxygen species (ROS) through photoinduced energy or electron transfer, achieving pollutant degradation, sterilization, and degradation of toxic and harmful gases. Under dark conditions, some carbon nanodots can disrupt bacterial cell membranes through electrostatic interactions between their surface functional groups and bacterial surfaces, achieving a bactericidal effect. However, currently, no carbon nanodots have been reported to possess all-weather capabilities for pollutant degradation, sterilization, and degradation of toxic and harmful gases. Furthermore, the market for commercial coating products based on such carbon nanodots as additives for all-weather sterilization and formaldehyde photodegradation is currently untapped.

[0004] Therefore, developing a carbon nanoparticle-based self-cleaning coating that is simple to manufacture, highly compatible, can stably exert its bactericidal and disinfecting effects under both light and dark conditions, and can efficiently degrade formaldehyde under light conditions has significant market value. Summary of the Invention

[0005] Based on the above-mentioned shortcomings, the first objective of this invention is to provide an all-weather carbon nanoparticle-based self-cleaning coating.

[0006] A second objective of this invention is to provide an application of the self-cleaning coating described above in killing harmful pathogenic microorganisms or degrading toxic and harmful gases under light or in the dark.

[0007] To achieve the first objective mentioned above, the present invention adopts the following technical solution: This invention discloses an all-weather carbon nanodot-based self-cleaning coating, the self-cleaning coating comprising the following raw material components: a main coating and an aqueous solution of carbon nanodots as a coating additive; The aqueous solution of carbon nanodots is prepared according to the following steps: 1) Add an auxiliary agent solution to a polymer to obtain a precursor solution; 2) Transfer the precursor solution to the reactor and react at 100-500℃ for 1-24 hours; 3) After the reaction is complete, cool to room temperature, collect the reaction solution, separate and purify it to obtain the aqueous solution of the carbon nanodots; The polymer is selected from the following structures: ; m and n are natural numbers from 0 to 10000, and m and n are not both 0 at the same time; Ar1 is selected from benzene, naphthalene, anthracene, pyrene, indole, thiophene, carbazole, rhodamine, fluorene, quinoline, cyano dyes, pyrrole, coumarin, fluorescein, or carbazole; X and Y are each independently selected from O, S, Se, N, or Si; Z, R1, R2, R3, and R4 are each independently selected from hydrogen, alkyl, hydroxyl, mercapto, carboxyl, amino, amide, cyano, alkenyl, alkynyl, aryl, ester, ether, quaternary ammonium salt, sulfonate, phosphate, or polyethylene glycol group with 1-18 carbon atoms.

[0008] In this invention, high molecular polymers are used as functional precursors, combined with hydrothermal carbonization technology, to prepare carbon nanodots with antibacterial properties and the ability to generate reactive oxygen species through photosensitization. These nanodots are then added to the coating formulation in a certain proportion, enabling the self-cleaning coating to achieve stable sterilization and disinfection in both light and dark environments (bacterial inhibition rate of ≥99% against common bacteria), and to efficiently degrade formaldehyde under light conditions (purification rate of ≥80% in 24 hours). Furthermore, the entire self-cleaning coating manufacturing process is simple, cost-effective, and the carbon nanodots have good compatibility with commercial coatings, are not easily detached, and can be mass-produced.

[0009] Furthermore, the mass concentration of the carbon nanodot aqueous solution is 1-5‰.

[0010] Furthermore, the mass ratio of carbon nanodots to the main coating is 1:5000-8000. For example, the mass ratio of carbon nanodots to the main coating can be 1:5000, 1:6000, 1:7000, 1:8000, etc.

[0011] Furthermore, the main coating is selected from commercially available coatings, including but not limited to water-based acrylic coatings, polyurethane coatings, epoxy resin coatings, and fluorocarbon coatings.

[0012] Furthermore, the polymer is selected from the following structures: 1) PT1, where n is an integer between 3 and 3000; 2) CPT1, where m is an integer between 3 and 3000, and n is an integer between 3 and 750; 3) CPT2, where m is an integer from 3 to 1000 and n is an integer from 3 to 5000; 4) PT2, where n is an integer between 3 and 3000.

[0013] Furthermore, the number-average molecular weight of the polymer is 10. 4 -10 5 Da has an absorption range of 400-800nm.

[0014] Furthermore, the auxiliary agent is selected from one of acidic compounds, basic compounds, and neutral compounds; preferably, the auxiliary agent is selected from one or more of hydrochloric acid, phosphoric acid, sodium hydroxide, potassium hydroxide, ammonia, sodium chloride, potassium chloride, and sodium bisulfate.

[0015] Furthermore, the concentration of the polymer in the precursor solution is 5-1000 ug / mL. For example, the concentration of the polymer in the precursor solution can be 5 ug / mL, 10 ug / mL, 50 ug / mL, 100 ug / mL, 200 ug / mL, 300 ug / mL, 400 ug / mL, 500 ug / mL, 600 ug / mL, 700 ug / mL, 800 ug / mL, 900 ug / mL, 1000 ug / mL, etc.

[0016] Furthermore, the concentration of the auxiliary agent solution is 0.1-1 M.

[0017] Furthermore, the particle size of the carbon nanodots is 2-200 nm.

[0018] Furthermore, the carbon nanodots are preferably positively charged carbon nanodots with a surface potential of 25-35 mV. In one specific embodiment, the positively charged carbon nanodots generate singlet oxygen under illumination, with a light intensity of 5-20 mW / cm². 2 When exposed to light for 24 hours, the antibacterial rate can reach 99%, the virus inactivation log value is greater than 4, and the formaldehyde degradation rate is over 80%. In another specific embodiment, the positively charged carbon nanodots on the surface are exposed to light intensity of 30-80 mW / cm². 2 When exposed to light for 10 minutes, the antibacterial rate can reach 99%, the virus inactivation log value is greater than 4, and the formaldehyde degradation rate is over 80%. Simultaneously, the positively charged carbon nanodots on their surface exhibit antibacterial properties even in the absence of light, achieving an antibacterial rate of over 99% after 24 hours.

[0019] Furthermore, the reactor includes, but is not limited to, a microwave reactor, an ultrasonic reactor, or a hydrothermal reactor.

[0020] Furthermore, the self-cleaning coating is prepared according to the following steps: The main coating is stirred and mixed evenly with an aqueous solution of carbon nanodots, then coated onto the surface of the substrate, and after curing, a self-cleaning coating is obtained.

[0021] Furthermore, the substrate is selected from one of the following: metal, glass, ceramic, wood, concrete, and plastic.

[0022] Furthermore, the thickness of the self-cleaning coating is 20-300 μm.

[0023] Furthermore, the curing temperature of the self-cleaning coating is 25-80℃, and the curing time is 2-3 hours.

[0024] Furthermore, the term "all-weather" refers to sunny (strong light), cloudy (weak light), and dark (no light) environments, where light includes, but is not limited to, sunlight and artificial light.

[0025] To achieve the second objective mentioned above, the present invention adopts the following technical solution: This invention discloses an application of the self-cleaning coating described above in killing harmful pathogenic microorganisms or degrading toxic and harmful gases under light or in the dark.

[0026] Furthermore, the self-cleaning coating can be applied in fields including but not limited to construction, medical, food processing, livestock / aquaculture, and transportation.

[0027] Furthermore, the application further includes: adding a system containing bacteria, fungi, or viruses to the surface of the self-cleaning coating, whereby the bacteria, fungi, or viruses are killed under visible light irradiation, wherein the intensity of the visible light irradiation is 5-80 mW / cm². 2 (e.g., 5mW / cm) 2 10mW / cm 2 20mW / cm 2 30mW / cm 2 40mW / cm 2 50mW / cm 2 60mW / cm 2 70mW / cm 2 80mW / cm 2 (etc.), light exposure time 0.5-24 hours (e.g. 0.5 hours, 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, etc.).

[0028] Furthermore, the application further includes: placing the self-cleaning coating in a formaldehyde-containing enclosed space, testing it according to the national standard JC / T1074-2021, and then placing it under visible light for a period of time to achieve the degradation of formaldehyde.

[0029] Furthermore, the area of ​​the self-cleaning coating is 0.25m² relative to the volume of the enclosed space. 2 1m 3 .

[0030] Furthermore, the application further includes: placing 0.25m 2 The self-cleaning coating is placed in 1m 3 In the enclosed space, the initial concentration of formaldehyde was 1.0 mg / m³. 3 When the self-cleaning coating is irradiated with visible light, the formaldehyde concentration in the enclosed space is approximately 0.99 mg / m³. 3 The formaldehyde degradation rate is over 80%.

[0031] Furthermore, the intensity of visible light irradiation is between 5-80 mW / cm². 2 (e.g., 5mW / cm) 2 10mW / cm 2 20mW / cm 2 30mW / cm 2 40mW / cm 2 50mW / cm 2 60mW / cm 2 70mW / cm 2 80mW / cm 2 (etc.), with light exposure time ranging from 0.5 to 24 hours (e.g., 0.5 hours, 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, etc.).

[0032] Furthermore, the application further includes: adding a system containing bacteria, fungi, or viruses to the surface of the self-cleaning coating and culturing it in a light-protected state to kill the bacteria, fungi, or viruses, wherein the culturing time is 6-24 hours.

[0033] The beneficial effects of this invention are as follows: Compared with the prior art, the present invention has the following advantages: 1) All-weather sterilization and disinfection: The coating uses carbon nanodots as the core functional material to achieve antibacterial and antiviral effects through the synergistic effect of photoactive oxygen and surface properties. It does not rely on light and can effectively kill common pathogenic microorganisms, including but not limited to Staphylococcus aureus, Escherichia coli and Candida albicans, in both light and dark environments, with an antibacterial rate of ≥99%. 2) Also possesses photocatalytic formaldehyde degradation function: Under visible light irradiation (sunlight or lamplight), the carbon nanodots in the coating generate highly oxidizing reactive species such as singlet oxygen, which can rapidly degrade formaldehyde in the air. Under visible light irradiation (intensity ≥5mW / cm²), 2 (24 hours), formaldehyde degradation rate ≥80%; 3) Coating compatible with a variety of commercial coatings: The core functional material, carbon nanoparticles, has strong affinity and high compatibility with a variety of commercial coatings such as water-based acrylic coatings, polyurethane coatings, epoxy resin coatings, and fluorocarbon coatings. It does not require significant adjustments to the original formula of commercial coatings, making it easy to promote and apply in industrial applications. Attached Figure Description

[0034] Figure 1 The diagram shows the ESR of singlet oxygen generated by the coating prepared in Example 1 of the present invention under visible light (greater than 420 nm) illumination.

[0035] Figure 2 The fluorescence spectrum of the eluent after 10 rinsings is shown for the coating prepared in Example 1 of the present invention.

[0036] Figure 3 A schematic diagram of the bactericidal effect of the coating obtained in Example 1 of the present invention under light irradiation.

[0037] Figure 4 This diagram illustrates the virus inactivation effect of the coating prepared in Example 1 of the present invention under light conditions.

[0038] Figure 5 This diagram illustrates the bactericidal effect of the coating obtained in Example 1 of the present invention under no-light conditions. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0041] Example 1 Preparation of carbon nanodot aqueous solution: 50 mg of the carbon nanodot precursor polymer PT2 was diffused into a sodium hydroxide solution (containing 50 mL of water and 10 μL of 1 M sodium hydroxide), and solubilized by ultrasound to form a precursor solution. The precursor solution was transferred to a stainless steel reactor and reacted at 180 °C for 12 hours. After the reaction was complete, the mixture was cooled to room temperature, separated, and purified to obtain an aqueous solution of carbon nanodots (mass fraction of carbon nanodots: 0.1%).

[0042] The PT2 structure is as follows, where n is an integer from 3 to 3000: PT2 Preparation of a carbon nanoparticle-based self-cleaning coating: 24g of water-based acrylic paint was mixed with 4g of an aqueous solution of carbon nanoparticles (0.1% carbon nanoparticle mass fraction, 4mg), and stirred at 5000r / min for 1 hour to obtain a coating slurry. The slurry was then applied to the surface of a 50cm×50cm plastic substrate (polyethylene) and cured at 60℃ for 2 hours to obtain an all-weather carbon nanoparticle-based self-cleaning coating with a thickness of 220μm. Testing showed that the carbon nanoparticles and the paint were highly compatible, and no carbon nanoparticles detached after 10 washes.

[0043] The carbon nanoparticle-based self-cleaning coating prepared in this embodiment produces a singlet oxygen ESR diagram under visible light (greater than 420 nm) illumination, showing characteristic signals of singlet oxygen (such as...). Figure 1 (As shown).

[0044] The carbon nanoparticle-based self-cleaning coating prepared in this embodiment was rinsed 10 times with phosphate buffer solution (flow rate 200 mL / min, single rinse time 10 s). No fluorescence of the carbon nanoparticles was detected in the eluent, indicating that the carbon nanoparticles did not detach from the coating due to rinsing, demonstrating high stability (e.g., ...). Figure 2 (As shown).

[0045] The antibacterial application of the carbon nanoparticle-based self-cleaning coating prepared in this embodiment under visible light irradiation: The coating prepared in this embodiment was cut into 5mm × 5mm pieces, placed in a 12-well plate, and then 200 μL of a 2 × 10⁻⁶ concentration was added dropwise. 5 CFU / mL E. coli solution, incubated for 30 minutes, with 50 mW / cm 2 Irradiation with visible light for 10 minutes, recorded as Figure 3 The results of experiments 1 and 3 were analyzed. The coating was then removed from the 12-well plate and rinsed 10 times with phosphate buffer solution (flow rate 200 mL / min, rinsing time 10 s per rinse). The resulting rinse solution was transferred to an agar plate containing culture medium. After 24 hours, the survival rate of *E. coli* was calculated using colony counting, denoted as _____. Figure 3 The results of experiment No. 2. Tests showed that only the coating + light exposure group achieved an antibacterial efficiency of 99%. Experiment No. 2 indicates that the carbon nanoparticles did not detach from the coating during rinsing, therefore the antibacterial efficiency is negligible.

[0046] The antiviral application of the carbon nanoparticle-based self-cleaning coating prepared in this embodiment under visible light irradiation: The coating prepared in this embodiment was cut into 5mm × 5mm pieces and placed in a 12-well plate. Then, 90 μL of influenza virus solution H1N1 was added, and the plate was incubated for 2 hours at a cold chain temperature (4°C) or room temperature. The solution was then treated with 25 mW / cm² solution. 2 Irradiate the virus solution with visible light for 10 minutes. After irradiation, serially dilute the virus solution and add 1% chicken red blood cell suspension. Incubate at 37°C for 10 minutes and record the hemagglutination titer. Then, serially dilute the virus solution and inoculate it into a cell monolayer. Incubate at 37°C for 72 hours. Calculate the virus infection titer using the Reed-Muench method. A log value of virus inactivation greater than 5 is considered a control. A log value of virus inactivation less than 1 is negligible. Figure 4 As shown.

[0047] The application of the carbon nanoparticle-based self-cleaning coating prepared in this embodiment in the degradation of formaldehyde under fluorescent light irradiation: Referring to the JC / T1074-2021 standard, under a 14W fluorescent lamp, a 50cm×50cm self-cleaning coating was placed in an environment with an initial formaldehyde concentration of 1mg / m³. 3 Volume is 1m 3 In a sealed chamber (testing environment temperature 20℃, relative humidity 55%), formaldehyde concentration was tested for 24 hours. The results showed that the formaldehyde concentration decreased to 0.17 mg / m³. 3 The formaldehyde degradation rate is 82%.

[0048] The antibacterial application of the carbon nanoparticle-based self-cleaning coating prepared in this embodiment under light-protected conditions: The coating prepared in this embodiment was cut into 5mm × 5mm pieces and placed in a 12-well plate. Then, 200 μL of a solution with a concentration of 2 × 10⁻⁶ was added dropwise. 5 The coating was incubated with CFU / mL Candida albicans phosphate buffer solution in the dark for 24 hours, followed by rinsing the coating 10 times with phosphate buffer solution. The rinse solution was transferred to an agar plate containing culture medium. After 24 hours, the survival rate of Candida albicans was calculated by colony counting. A coating without carbon nanodots was used as a control. The tests showed that only the coated group achieved an antibacterial efficiency of 99% (e.g., ...). Figure 5 (As shown).

[0049] Example 2 Preparation of carbon nanodots: The carbon nanodot precursor polymer CPT1 (50 mg) was diffused into an ammonia solution (containing 50 mL of water and 10 μL of 1 M ammonia solution), and solubilized by ultrasound to form a precursor solution. The precursor solution was transferred to a microwave reactor and reacted at 110 °C for 1 hour. After the reaction was complete, the mixture was cooled to room temperature, separated, and purified to obtain an aqueous solution of carbon nanodots (mass fraction of carbon nanodots: 0.1%).

[0050] The CPT1 structure is as follows, where m is an integer from 3 to 3000, and n is an integer from 3 to 750: CPT1 Preparation of carbon nanoparticle-based self-cleaning coating: 24 g of commercially available water-based fluorocarbon coating was added to 4 g of carbon nanoparticle aqueous solution (carbon nanoparticle mass fraction of 0.1%, 4 mg), and stirred at 5000 r / min for 1 hour to obtain a coating slurry. The coating slurry was applied to the surface of a 50 cm × 50 cm glass substrate and cured at 60 °C for 2 hours to obtain an all-weather carbon nanoparticle-based self-cleaning coating with a thickness of 220 μm.

[0051] The testing procedures were the same as in Example 1. The results showed that the carbon nanoparticles and the coating had a strong affinity, and no carbon nanoparticles fell off after 10 washes. The coating showed a 99.5% inhibition rate against Escherichia coli under natural light conditions, and a 24-hour formaldehyde degradation rate of 80% under natural light conditions.

[0052] Example 3 Preparation of carbon nanodot aqueous solution: The carbon nanodot precursor polymer CPT2 (50 mg) was diffused into a hydrochloric acid solution (containing 50 mL of water and 10 μL of 1 M hydrochloric acid), and solubilized by ultrasound to form a precursor solution. The precursor solution was transferred to a stainless steel reactor and reacted at 170 °C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, separated, and purified to obtain an aqueous solution of carbon nanodots (carbon nanodot mass fraction of 0.1%).

[0053] The CPT2 structure is as follows, where m is an integer from 3 to 1000, and n is an integer from 3 to 5000: CPT2 Preparation of carbon nanoparticle-based self-cleaning coating: 24 g of commercially available waterborne polyurethane coating was added to 3 g of carbon nanoparticle aqueous solution (carbon nanoparticle mass fraction of 0.1%, 3 mg), and stirred at 5000 r / min for 1 hour to obtain a coating slurry. The coating slurry was applied to the surface of a 50 cm × 50 cm wood substrate and cured at 60 °C for 2 hours to obtain an all-weather carbon nanoparticle-based self-cleaning coating with a thickness of 120 μm.

[0054] The testing process was the same as in Example 1. The carbon nanoparticles and coating were highly compatible, and no carbon nanoparticles detached after 10 washes. Under no light conditions for 24 hours, the coating showed a 99.0% inhibition rate against Staphylococcus aureus; under natural light conditions, the inhibition rate against Staphylococcus aureus was 99.5% after 10 minutes; and the formaldehyde purification rate was 82% after 24 hours.

[0055] Example 4 Preparation of carbon nanodot aqueous solution: 50 mg of the carbon nanodot precursor polymer PT1 was diffused into a sodium hydroxide solution (containing 50 mL of water and 10 μL of 1 M sodium hydroxide), and solubilized by ultrasound to form a precursor solution. The precursor solution was transferred to a microwave reactor and reacted at 120 °C for 1 hour. After the reaction was complete, the solution was cooled to room temperature, separated, and purified to obtain an aqueous solution of carbon nanodots (mass fraction of carbon nanodots: 0.1%).

[0056] The PT1 structure is as follows, where n is an integer from 3 to 3000: PT1 Preparation of carbon nanoparticle-based self-cleaning coating: 16g of water-based epoxy resin coating was added to 2g of carbon nanoparticle aqueous solution (carbon nanoparticle mass fraction of 0.1%, 2mg), and stirred at 5000r / min for 1 hour to obtain a coating slurry. The coating slurry was applied to the surface of a circular metal substrate with a diameter of 50mm and cured at 60℃ for 2 hours to obtain an all-weather carbon nanoparticle-based self-cleaning coating with a thickness of 150μm.

[0057] The testing process was the same as in Example 1. The carbon nanoparticles and coating were highly compatible, and no carbon nanoparticles fell off after 10 rinsings. Under no light conditions, the coating showed a 96% inhibition rate against Staphylococcus aureus after 24 hours; under natural light conditions, the inhibition rate against Staphylococcus aureus was 99.5% after 10 minutes; and the formaldehyde purification rate was 80% after 24 hours.

[0058] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An all-weather carbon nanoparticle-based self-cleaning coating, characterized in that, The self-cleaning coating comprises the following raw material components: a base coating and an aqueous solution of carbon nanoparticles as a coating additive; The aqueous solution of carbon nanodots is prepared according to the following steps: 1) Add an auxiliary agent solution to a polymer to obtain a precursor solution; 2) Transfer the precursor solution to the reactor and react at 100-500℃ for 1-24 hours; 3) After the reaction is complete, cool to room temperature, collect the reaction solution, separate and purify it to obtain the aqueous solution of the carbon nanodots; The polymer is selected from the following structures: ； m and n are natural numbers from 0 to 10000, and m and n are not both 0 at the same time; Ar1 is selected from benzene, naphthalene, anthracene, pyrene, indole, thiophene, carbazole, rhodamine, fluorene, quinoline, cyano dyes, pyrrole, coumarin, fluorescein, or carbazole; X and Y are each independently selected from O, S, Se, N, or Si; Z, R1, R2, R3, and R4 are each independently selected from hydrogen, alkyl, hydroxyl, mercapto, carboxyl, amino, amide, cyano, alkenyl, alkynyl, aryl, ester, ether, quaternary ammonium salt, sulfonate, phosphate, or polyethylene glycol group with 1-18 carbon atoms.

2. The self-cleaning coating according to claim 1, characterized in that, The mass concentration of the aqueous solution of carbon nanodots is 1-5‰; Preferably, the mass ratio of carbon nanodots to the main coating is 1:5000-8000.

3. The self-cleaning coating according to claim 1, characterized in that, The main coating includes one of water-based acrylic coating, polyurethane coating, epoxy resin coating, and fluorocarbon coating.

4. The self-cleaning coating according to claim 1, characterized in that, The polymer is selected from the following structures: 1) PT1, where n is an integer between 3 and 3000; 2) CPT1, where m is an integer between 3 and 3000, and n is an integer between 3 and 750; 3) CPT2, where m is an integer from 3 to 1000 and n is an integer from 3 to 5000; 4) PT2, where n is an integer between 3 and 3000.

5. The self-cleaning coating according to claim 1, characterized in that, The number average molecular weight of the polymer is 10. 4 -10 5 Da has an absorption range of 400-800nm.

6. The self-cleaning coating according to claim 1, characterized in that, The self-cleaning coating is prepared according to the following steps: The main coating is stirred and mixed evenly with an aqueous solution of carbon nanoparticles, then coated onto the surface of the substrate, and after curing, a self-cleaning coating is obtained. Preferably, the substrate is selected from one of metal, glass, ceramic, wood, concrete, and plastic; Preferably, the thickness of the self-cleaning coating is 20-300 μm.

7. The application of the self-cleaning coating as described in any one of claims 1-6 in killing harmful pathogenic microorganisms or degrading toxic and harmful gases under light and in the absence of light.

8. The application according to claim 7, characterized in that, The application further includes: adding a system containing bacteria, fungi, or viruses to the surface of a self-cleaning coating, whereby the bacteria, fungi, or viruses are killed under visible light irradiation, wherein the intensity of the visible light irradiation is 5-80 mW / cm². 2 Light exposure time is 0.5-24 hours.

9. The application according to claim 7, characterized in that, The application further includes: placing the self-cleaning coating in a formaldehyde-containing enclosed space and irradiating it under visible light for a period of time to degrade the formaldehyde; Preferably, the application further includes: placing 0.25m 2 The self-cleaning coating is placed in 1m 3 In the enclosed space, the initial concentration of formaldehyde was 1.0 mg / m³. 3 When exposed to visible light, the self-cleaning coating exhibits a formaldehyde degradation rate of over 80%. Preferably, the intensity of visible light irradiation is 5-80 mW / cm². 2 The light exposure time is 0.5-24 hours.

10. The application according to claim 7, characterized in that, The application further includes: adding a system containing bacteria, fungi, or viruses to the surface of a self-cleaning coating and culturing it in the dark to kill the bacteria, fungi, or viruses, wherein the culturing time is 6-24 hours.

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