Preparation and Visual Anti-counterfeiting Application of Cellulose-Based Long-Lifetime Room Temperature Phosphorescent Carbon Quantum Dot Composite Coatings

Abstract

This invention relates to the field of room temperature phosphorescent coating technology, specifically to the preparation and visual anti-counterfeiting application of a cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating. The preparation method of the room temperature phosphorescent carbon quantum dot composite coating uses cellulose as the carbon source and rhodamine 6G, rhodamine B, sulfonyl rhodamine B, or riboflavin as the nitrogen source, to prepare carbon quantum dots through a hydrothermal reaction in an aqueous medium. After purification, the obtained carbon quantum dots are heat-treated with boric acid to obtain boric acid-modified carbon quantum dot powder. This powder is then compounded with sodium lignosulfonate and an aqueous acrylic emulsion to obtain a cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating. The coating can be applied by brushing, rolling, or spraying to form a room temperature phosphorescent coating, exhibiting adjustable color, long average phosphorescence lifetime, and excellent resistance to ultraviolet aging.

Description

Technical Field

[0001] This invention relates to the field of room temperature phosphorescent coating technology, specifically to the preparation and visual anti-counterfeiting application of a cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating. Background Technology

[0002] Room temperature phosphorescent coatings are a class of functional coating materials that continue to emit light even after the excitation source is removed at ambient temperature. Their luminescence principle stems from the electron transition to the triplet state after the phosphor is excited, and the electron slowly releases energy to return to the ground state through forbidden radiation. Applying this type of material to the surface of engineered wood products can endow traditional wood materials with dynamic optical responses and information storage capabilities, enabling them to spontaneously provide afterglow illumination in the dark. This not only creates unique decorative effects but also provides passive safety guidance in emergency evacuation scenarios, demonstrating significant practical value.

[0003] However, existing fluorescent functionalization technologies for wood-based panels face numerous bottlenecks: they rely on petroleum-based dyes or phosphors containing heavy metals, resulting in a heavy environmental burden; the processes are complex and often involve multiple steps, leading to high production costs; the luminescence properties are limited, mostly nanosecond-level transient fluorescence, and the color cannot be adjusted; the phosphorescent materials have poor interfacial compatibility with wood-based substrates, weak adhesion, and insufficient long-term stability, easily degrading after daily wiping and light aging. Furthermore, existing phosphorescent coatings are difficult to adapt to mainstream processes in wood-based panel production lines, such as roller coating and curtain coating, hindering their large-scale application.

[0004] Cellulose, as the most abundant natural polymer on Earth, possesses advantages such as regular chemical structure, renewability, and biodegradability. The regular structure of its hydroxyl groups provides the possibility for forming rigid luminescent networks, making it an ideal precursor for the preparation of green functional materials. Converting cellulose into carbon quantum dots (CQDs) and controlling their room-temperature phosphorescence properties through matrix engineering can solve the environmental and performance defects of traditional phosphorescent materials. However, in current technologies, cellulose-based carbon quantum dots exhibit low room-temperature phosphorescence efficiency, short afterglow time, and require improvement in dispersibility with resin matrices and coating stability. Therefore, developing a green, efficient, high-performance, and process-adaptable technology for preparing cellulose-based room-temperature phosphorescent carbon quantum dot coatings has significant scientific value and market prospects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a method for preparing a cellulose-based long-life, room-temperature phosphorescent carbon quantum dot composite coating and its application in visual anti-counterfeiting. This invention aims to overcome the deficiencies of existing technologies by providing a carbon quantum dot coating with long lifespan and tunable color room-temperature phosphorescence properties, prepared using cellulose as a green precursor through solvothermal carbonization, boric acid modification, and resin composite processes. This coating is not only environmentally friendly and simple to process, but also exhibits excellent compatibility with wood-based substrates, good mechanical properties, and long-term stability, making it widely applicable in high-end decoration, smart packaging, and information encryption anti-counterfeiting fields.

[0006] This invention is achieved through the following technical solution: A method for preparing cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coatings includes the following steps: S1. Preparation of precursor solution: Add cellulose and nitrogen source to a beaker, add solvent, stir at room temperature for 10 min to obtain a homogeneous precursor solution; S2. Preparation of carbon quantum dots: The precursor solution obtained in step S1 was transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at a constant temperature of 180℃ for 4 h. After natural cooling, it was centrifuged at 10000 r / min for 15 min, filtered to remove residue, and dialyzed with a dialysis bag with a molecular weight cutoff of 1000 Da for 48 h, with water changed every 6 h, to obtain a pure carbon quantum dot solution. S3. Boric acid modification treatment: Take the carbon quantum dot solution obtained in step S2, add boric acid and deionized water, heat and stir at 50°C until the boric acid is completely dissolved, transfer to an evaporating dish, heat in an oven at 150°C for 2.5 h, evaporate the water and grind to obtain powdered modified carbon quantum dots; S4. Coating composite: Take the modified carbon quantum dot powder obtained in step S3, sodium lignosulfonate and water-based acrylic emulsion, stir at 4000 r / min for 30 min to obtain cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating.

[0007] Further, in step S1, the mass ratio of cellulose to nitrogen source is 1:3.

[0008] Further, in step S1, the nitrogen source is one of Rhodamine 6G, Rhodamine B, sulfonyl Rhodamine B, or riboflavin.

[0009] Further, in step S1, the ratio of cellulose to solvent is 0.01 g: 20 mL.

[0010] Furthermore, in step S1, the solvent is deionized water.

[0011] Furthermore, in step S3, the ratio of the carbon quantum dot solution, boric acid, and deionized water is 10 mL:1 g:10 mL.

[0012] Further, in step S4, the ratio of the modified carbon quantum dot powder, sodium lignosulfonate, and aqueous acrylic emulsion is 0.25 g:0.09 g:10 mL.

[0013] Furthermore, in step S4, the solid content of the aqueous acrylic emulsion is 40%-50%.

[0014] Furthermore, the present invention also provides a method for preparing a room temperature phosphorescent coating using the cellulose-based long-lifetime room temperature phosphorescent carbon quantum dot composite coating, comprising the following steps: (1) Substrate pretreatment: Sand the artificial board with sandpaper, wipe it with anhydrous ethanol to remove oil, and let it air dry naturally; (2) Coating preparation: The cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating was uniformly applied to the substrate surface in a "horizontal first and then vertical" manner using a wool brush. The coating thickness was controlled to be 50-80 μm. It was dried at 60℃ for 1 h for preliminary curing. After cooling to room temperature, it was applied once more and dried at 70℃ for 1.5 h. It was then allowed to cool naturally to room temperature to obtain a room temperature phosphorescent coating.

[0015] Furthermore, the present invention also provides the application of the cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating in visual anti-counterfeiting.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing a cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating and its application in visual anti-counterfeiting. Using cellulose as a green precursor, a long-lifetime room-temperature phosphorescent carbon quantum dot coating with good mechanical properties and long-term stability is prepared through solvothermal carbonization, boric acid modification, and resin composite processes. The invention uses cellulose as the carbon source, and rhodamine 6G, rhodamine B, sulfonylrhodamine B, and riboflavin as nitrogen sources, with water as the solvent, to prepare nitrogen-doped carbon quantum dots via a one-pot hydrothermal carbonization reaction. The introduction of the nitrogen source can regulate the surface functional groups and electronic structure of the carbon quantum dots, providing a foundation for room-temperature phosphorescence performance. Centrifugation, filtration, and dialysis purification ensure the purity and dispersion stability of the carbon quantum dots. This invention modifies the obtained carbon quantum dots with boric acid to introduce boron-containing functional groups onto the material surface and regulate its surface chemical environment, thereby obtaining cellulose-based room-temperature phosphorescent carbon quantum dots with room-temperature phosphorescence properties. Through the interaction between boric acid and the hydroxyl groups on the carbon quantum dot surface, a rigid network structure is formed, further suppressing the nonradiative transition of the excited triplet state of the carbon quantum dots, significantly extending the phosphorescence lifetime and increasing the luminescence intensity, while simultaneously enhancing the compatibility of the carbon quantum dots with aqueous acrylic emulsions. The modified carbon quantum dots can exhibit different luminescence colors, including green, yellow, orange, and red. By adjusting the preparation and modification conditions, the luminescence performance can be controllably adjusted. This invention mixes the modified carbon quantum dots with an aqueous acrylic emulsion in an optimized ratio and achieves uniform dispersion through high-speed stirring. The aqueous acrylic emulsion not only has good film-forming properties and environmental friendliness, but its carboxyl and ester groups on the molecular chain can also form hydrogen bonds with the functional groups on the carbon quantum dot surface, constructing a rigid confined environment, stabilizing triplet excitons, and synergistically improving room-temperature phosphorescence performance. A uniform coating is formed on the surface of pretreated engineered wood panels through a two-coat process. Controlled curing temperature and time ensure a strong bond between the coating and the substrate, while preserving excellent room-temperature phosphorescence and mechanical properties. This invention uses natural cellulose as raw material, achieving high-value utilization of biomass resources. The preparation process uses water as the main medium, leaving no toxic solvent residues, complying with the dual-carbon strategy and environmental protection requirements. Through synergistic regulation of nitrogen doping and boric acid modification, the room-temperature phosphorescence lifetime of carbon quantum dots is achieved ≥9s, with adjustable phosphorescence color, far superior to traditional cellulose-based luminescent materials. Cellulose-based carbon quantum dots and wood-based substrates have a "homogeneous synergistic effect." Combined with boric acid modification and resin composite processes, the coating adhesion reaches Grade 1, without affecting the original decorative effect of the wood. The preparation process of this invention uses conventional equipment; the coating can be applied by brushing, rolling, or spraying. The curing conditions are mild, adaptable to existing engineered wood panel production lines, and suitable for large-scale production. The composite coating of this invention has a wide range of applications, combining long-life room-temperature phosphorescence and environmental responsiveness, and can be applied to high-end decoration, intelligent packaging freshness monitoring, and high-level information encryption and anti-counterfeiting fields. Attached Figure Description

[0017] Figure 1XPS images of the modified carbon quantum dots described in this invention; wherein, (a) is the XPS image of green room temperature phosphorescent carbon quantum dots, (b) is the XPS image of yellow room temperature phosphorescent carbon quantum dots, (c) is the XPS image of orange room temperature phosphorescent carbon quantum dots, and (d) is the XPS image of red room temperature phosphorescent carbon quantum dots. Figure 2 The following are the phosphorescence lifetime decay fitting curves of the modified carbon quantum dots described in this invention: (a) is the phosphorescence lifetime decay fitting curve of green room temperature phosphorescent carbon quantum dots, (b) is the phosphorescence lifetime decay fitting curve of yellow room temperature phosphorescent carbon quantum dots, (c) is the phosphorescence lifetime decay fitting curve of orange room temperature phosphorescent carbon quantum dots, and (d) is the phosphorescence lifetime decay fitting curve of red room temperature phosphorescent carbon quantum dots. Figure 3 These are comparison images of the appearance of the room temperature phosphorescent coating described in this invention before and after QUV accelerated aging. Figure 4 The curves showing the phosphorescence intensity variation of the room temperature phosphorescent coating described in this invention under different humidity conditions are shown. Figure 5 The application effect diagrams of the room temperature phosphorescent carbon quantum dot composite coating of the present invention are shown; wherein, (a) is the application effect diagram of the anti-counterfeiting label, and (b) is the application effect diagram of the clothing logo. Figure 6 The images show the luminescence effects of the carbon quantum dot solution, modified carbon quantum dot powder, and room-temperature phosphorescent carbon quantum dot composite coating described in this invention. (a) shows the luminescence effect of the carbon quantum dot solution under natural light, 254 nm and 365 nm ultraviolet light; (b) shows the luminescence effect of the modified carbon quantum dot powder under natural light, 254 nm ultraviolet light, 365 nm ultraviolet light, and after turning off 365 nm ultraviolet light; (c) shows the luminescence effect of the room-temperature phosphorescent carbon quantum dot composite coating under natural light and 365 nm ultraviolet light. Figure 7 The images show the luminescence effects of the room-temperature phosphorescent carbon quantum dot composite coating described in this invention on different substrates; where (a) is a wood chip, (b) is a cloth chip, (c) is a napkin, (d) is a weighing paper, and (e) is a filter paper. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. However, this invention is not limited to the following embodiments. It should be noted that, unless otherwise specified, all chemical reagents involved in this invention are purchased through commercial channels.

[0019] Example 1: A method for preparing a cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating, comprising the following steps: S1. Preparation of precursor solution: Take a 100 mL beaker, add 0.01 g cellulose and 0.03 g rhodamine 6G, add 20 mL deionized water, stir at room temperature for 10 min to obtain a homogeneous precursor solution; S2. Preparation of carbon quantum dots: The precursor solution obtained in step S1 was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor and reacted at 180℃ for 4 h. After natural cooling, it was centrifuged at 10000 r / min for 15 min, filtered to remove residue, and dialyzed with a dialysis bag with a molecular weight cutoff of 1000 Da for 48 h, with water changed every 6 h, to obtain a pure carbon quantum dot solution. S3. Boric acid modification treatment: Take 20 mL of the carbon quantum dot solution obtained in step S2, add 2 g of boric acid and 20 mL of deionized water, heat and stir at 50°C until the boric acid is completely dissolved, transfer to a 100 mL evaporating dish, heat in an oven at 150°C for 2.5 h, evaporate the water and grind to obtain powdered modified carbon quantum dots; S4. Coating composite: Take 0.25 g of modified carbon quantum dot powder obtained in step S3, 0.09 g of sodium lignosulfonate and 10 mL of waterborne acrylic emulsion with a solid content of 50%, stir at 4000 r / min for 30 min to obtain cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating.

[0020] This embodiment also provides a method for preparing a room temperature phosphorescent coating using the cellulose-based long-lifetime room temperature phosphorescent carbon quantum dot composite coating, including the following steps: (1) Substrate pretreatment: Select particleboard as the substrate, cut it into 10 cm × 10 cm × 5 mm specimens, polish it with 400 grit sandpaper, wipe the surface with anhydrous ethanol to remove oil, and let it air dry for 2 hours for later use. (2) Coating preparation: The cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating was uniformly applied to the substrate surface in a "horizontal first and then vertical" manner using a wool brush. The coating thickness was controlled to be 80 μm. It was initially cured by drying at 60℃ for 1 h. After cooling to room temperature, it was applied once more and dried at 70℃ for 1.5 h. It was then allowed to cool naturally to room temperature to obtain a room temperature phosphorescent coating.

[0021] This embodiment also provides the application of the cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating in visual anti-counterfeiting.

[0022] Example 2: A method for preparing a cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating, comprising the following steps: S1. Preparation of precursor solution: Take a 100 mL beaker, add 0.01 g cellulose and 0.03 g rhodamine B, add 20 mL deionized water, stir at room temperature for 10 min to obtain a homogeneous precursor solution; S2. Preparation of carbon quantum dots: The precursor solution obtained in step S1 was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor and reacted at 180℃ for 4 h. After natural cooling, it was centrifuged at 10000 r / min for 15 min, filtered to remove residue, and dialyzed with a dialysis bag with a molecular weight cutoff of 1000 Da for 48 h, with water changed every 6 h, to obtain a pure carbon quantum dot solution. S3. Boric acid modification treatment: Take 20 mL of the carbon quantum dot solution obtained in step S2, add 2 g of boric acid and 20 mL of deionized water, heat and stir at 50°C until the boric acid is completely dissolved, transfer to an evaporating dish, heat in an oven at 150°C for 2.5 h, evaporate the water and grind to obtain powdered modified carbon quantum dots; S4. Coating composite: Take 0.25 g of modified carbon quantum dot powder obtained in step S3, 0.09 g of sodium lignosulfonate and 10 mL of waterborne acrylic emulsion with a solid content of 40%, stir at 4000 r / min for 30 min to obtain cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating.

[0023] This embodiment also provides a method for preparing a room temperature phosphorescent coating using the cellulose-based long-lifetime room temperature phosphorescent carbon quantum dot composite coating, including the following steps: (1) Substrate pretreatment: Select particleboard as the substrate, cut it into 10 cm × 10 cm × 5 mm specimens, polish it with 400 grit sandpaper, wipe the surface with anhydrous ethanol to remove oil, and let it air dry for 2 hours for later use. (2) Coating preparation: The cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating was uniformly applied to the substrate surface in a "horizontal first and then vertical" manner using a wool brush. The coating thickness was controlled at 50 μm. The coating was initially cured by drying at 60℃ for 1 h. After cooling to room temperature, the coating was repeated once and dried at 70℃ for 1.5 h. The coating was then allowed to cool naturally to room temperature to obtain a room temperature phosphorescent coating.

[0024] This embodiment also provides the application of the cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating in visual anti-counterfeiting.

[0025] Example 3: A method for preparing a cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating, comprising the following steps: S1. Preparation of precursor solution: Take a 100 mL beaker, add 0.01 g cellulose and 0.03 g sulfonyl rhodamine B, add 20 mL deionized water, stir at room temperature for 10 min to obtain a homogeneous precursor solution; S2. Preparation of carbon quantum dots: The precursor solution obtained in step S1 was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor and reacted at 180℃ for 4 h. After natural cooling, it was centrifuged at 10000 r / min for 15 min, filtered to remove residue, and dialyzed with a dialysis bag with a molecular weight cutoff of 1000 Da for 48 h, with water changed every 6 h, to obtain a pure carbon quantum dot solution. S3. Boric acid modification treatment: Take 20 mL of the carbon quantum dot solution obtained in step S2, add 2 g of boric acid and 20 mL of deionized water, heat and stir at 50°C until the boric acid is completely dissolved, transfer to a 100 mL evaporating dish, heat in an oven at 150°C for 2.5 h, evaporate the water and grind to obtain powdered modified carbon quantum dots; S4. Coating composite: Take 0.25 g of modified carbon quantum dot powder obtained in step S3, 0.09 g of sodium lignosulfonate and 10 mL of waterborne acrylic emulsion with a solid content of 45%, stir at 4000 r / min for 30 min to obtain cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating.

[0026] This embodiment also provides a method for preparing a room temperature phosphorescent coating using the cellulose-based long-lifetime room temperature phosphorescent carbon quantum dot composite coating, including the following steps: (1) Substrate pretreatment: Select particleboard as the substrate, cut it into 10 cm × 10 cm × 5 mm specimens, polish it with 400 grit sandpaper, wipe the surface with anhydrous ethanol to remove oil, and let it air dry for 2 hours for later use. (2) Coating preparation: The cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating was uniformly applied to the substrate surface in a "horizontal first and then vertical" manner using a wool brush. The coating thickness was controlled at 60 μm. After initial curing at 60℃ for 1 h, the coating was cooled to room temperature and then applied once more. After drying at 70℃ for 1.5 h, the coating was allowed to cool naturally to room temperature to obtain a room temperature phosphorescent coating.

[0027] This embodiment also provides the application of the cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating in visual anti-counterfeiting.

[0028] Example 4: A method for preparing a cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating, comprising the following steps: S1. Preparation of precursor solution: Take a 100 mL beaker, add 0.01 g cellulose and 0.03 g riboflavin, add 20 mL deionized water, stir at room temperature for 10 min to obtain a homogeneous precursor solution; S2. Preparation of carbon quantum dots: The precursor solution obtained in step S1 was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor and reacted at 180℃ for 4 h. After natural cooling, it was centrifuged at 10000 r / min for 15 min, filtered to remove residue, and dialyzed with a dialysis bag with a molecular weight cutoff of 1000 Da for 48 h, with water changed every 6 h, to obtain a pure carbon quantum dot solution. S3. Boric acid modification treatment: Take 20 mL of the carbon quantum dot solution obtained in step S2, add 2 g of boric acid and 20 mL of deionized water, heat and stir at 50°C until the boric acid is completely dissolved, transfer to a 100 mL evaporating dish, heat in an oven at 150°C for 2.5 h, evaporate the water and grind to obtain powdered modified carbon quantum dots; S4. Coating composite: Take 0.25 g of modified carbon quantum dot powder obtained in step S3, 0.09 g of sodium lignosulfonate and 10 mL of waterborne acrylic emulsion with a solid content of 50%, stir at 4000 r / min for 30 min to obtain cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating.

[0029] This embodiment also provides a method for preparing a room temperature phosphorescent coating using the cellulose-based long-lifetime room temperature phosphorescent carbon quantum dot composite coating, including the following steps: (1) Substrate pretreatment: Select particleboard as the substrate, cut it into 10 cm × 10 cm × 5 mm specimens, polish it with 400 grit sandpaper, wipe the surface with anhydrous ethanol to remove oil, and let it air dry for 2 hours for later use. (2) Coating preparation: The cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating was uniformly applied to the substrate surface in a "horizontal first and then vertical" manner using a wool brush. The coating thickness was controlled at 70 μm. It was initially cured by drying at 60℃ for 1 h. After cooling to room temperature, it was applied once more and dried at 70℃ for 1.5 h. It was then allowed to cool naturally to room temperature to obtain a room temperature phosphorescent coating.

[0030] This embodiment also provides the application of the cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating in visual anti-counterfeiting.

[0031] Experimental Example 1: Modified carbon quantum dots prepared in Examples 1-4 were used, namely yellow, orange, red, and green room-temperature phosphorescent carbon quantum dots. The chemical composition and functional groups of the modified carbon quantum dots were analyzed using X-ray photoelectron spectroscopy (XPS). The results are as follows: Figure 1 As shown.

[0032] Figure 1XPS spectra of modified carbon quantum dots prepared with different nitrogen sources are shown. (a) Green room-temperature phosphorescent carbon quantum dots prepared with riboflavin as the nitrogen source; (b) Yellow phosphorescent carbon quantum dots prepared with rhodamine 6G as the nitrogen source; (c) Orange room-temperature phosphorescent carbon quantum dots prepared with rhodamine B as the nitrogen source; and (d) Red room-temperature phosphorescent carbon quantum dots prepared with sulfonylrhodamine B as the nitrogen source. The full spectrum shows that the samples mainly contain C, N, O, and B elements, and the elemental ratios differ among the samples, indicating that their surface chemical compositions are not the same. High-resolution fine spectra further provide peak fitting results for C1s, N1s, and B1s for each sample. The C1s spectrum can be mainly decomposed into three peaks, corresponding to CC / C=C, CO, and C=O, respectively, indicating that the sample surface contains a carbon framework and oxygen-containing functional groups. The N1s spectrum can be decomposed into three peaks, corresponding to Pyridinic N, Pyrrolic N, and Graphitic N, indicating that nitrogen exists in multiple chemical environments. The B1s spectrum can be decomposed into two main peaks, corresponding to BN / C or BO, indicating that boron has been successfully introduced into the material and formed chemical bonds with oxygen or carbon / nitrogen. Figure 1 The results show that B, N, O and other elements were successfully introduced into the samples of Examples 1-4. The elemental composition and chemical state of the samples of different colors are different, which provides a structural basis for their different room temperature phosphorescence properties.

[0033] Experimental Example 2: The modified carbon quantum dots prepared in Examples 1-4 were subjected to fluorescence detection with an excitation wavelength of 365 nm. A fluorescence lifetime decay fitting curve was plotted, and the results are as follows. Figure 2 As shown.

[0034] Figure 2 The figures show the phosphorescence lifetime decay fitting curves for green, yellow, orange, and red room-temperature phosphorescent carbon quantum dots. The average phosphorescence lifetimes of the green, yellow, orange, and red samples are 10.6 s, 10.2 s, 10.6 s, and 9.7 s, respectively, indicating long-lifetime phosphorescence. All samples exhibit significant long-lasting afterglow, and the decay curves fit well with the multi-exponential model. All four samples maintain considerable phosphorescence emission after excitation light removal, and the decay behavior differs among the samples, indicating that different phosphorescence durations and emission colors can be achieved through material structure manipulation. These results further demonstrate that the prepared material possesses distinct room-temperature phosphorescence characteristics and can be used in applications requiring visualization of delayed luminescence.

[0035] Experimental Example 3: The room temperature phosphorescent coatings prepared in Examples 1-4 were used to compare the appearance of the coatings before and after 1000 hours of accelerated QUV aging under natural light. This was used to evaluate the UV aging resistance and long-term stability of the coatings of this invention. The results are as follows: Figure 3As shown.

[0036] Figure 3 These are comparative images of the appearance of the room-temperature phosphorescent coating of this invention before and after accelerated QUV aging. The left image shows the coating before aging, and the right image shows the coating after 1000 hours of accelerated QUV aging. As can be seen from the images, the coatings maintain good integrity before and after aging. No obvious cracking, chalking, blistering, or peeling was observed in any of the colored coatings after aging; only slight color differences were observed. The overall surface maintained good smoothness and uniformity. This demonstrates that the composite system constructed by boric acid-modified carbon quantum dots and water-based acrylic emulsion in this invention possesses excellent weather resistance and stability, effectively resisting structural degradation caused by ultraviolet radiation and ensuring the stability of phosphorescent performance and decorative effect during long-term use. The room-temperature phosphorescent coating of this invention exhibits certain weather resistance and environmental stability. The coating material provided by this invention is suitable for scenarios requiring long-term stability, such as anti-counterfeiting labels, packaging printing, and decorative coatings.

[0037] Experimental Example 4: The room temperature phosphorescent coating prepared in Example 2 was used to test its phosphorescence intensity under different humidity levels. The phosphorescence intensity variation curve was plotted, and the results are as follows: Figure 4 As shown.

[0038] Figure 4 The graphs show the phosphorescence intensity changes of the room-temperature phosphorescent coating in Example 2 under different relative humidity conditions. As the relative humidity increases from 30% to 90%, the phosphorescence intensity of the coating gradually decreases, with the most significant decrease occurring in the 60%-70% RH range. This phenomenon is mainly due to water molecules entering the coating and competing with the hydroxyl and amino groups on the carbon quantum dots and cellulose surface to form hydrogen bonds, disrupting the original rigid hydrogen bond network and causing phosphorescence quenching. The fact that changes in ambient humidity affect the phosphorescence intensity of the coating indicates that the material has certain humidity-responsive characteristics. This characteristic allows the material of this invention, in addition to being used as a room-temperature phosphorescent coating, to be further applied in fields such as environmental humidity sensing, intelligent displays, or dynamic anti-counterfeiting.

[0039] Experimental Example 5: The room-temperature phosphorescent carbon quantum dot composite coatings prepared in Examples 1-4 were used to write on the surfaces of coated paper and fiber fabrics, resulting in anti-counterfeiting labels and clothing logo samples, respectively. The pattern display effects were observed under natural light, 254 nm ultraviolet light, and 365 nm ultraviolet light, and the afterglow image was recorded after the 365 nm ultraviolet light was turned off. The results are as follows: Figure 5 As shown.

[0040] Figure 5This image shows the application effect of the room-temperature phosphorescent carbon quantum dot composite coating of this invention in anti-counterfeiting labels and clothing logos. The results show that the text and patterns formed on paper or flat substrates have high concealment under natural light, exhibit obvious multi-color luminescence effects under 254 nm and 365 nm ultraviolet light irradiation, and continue to emit different colors of room-temperature phosphorescence even after the 365 nm ultraviolet light is turned off. The anti-counterfeiting label can present different visual effects under natural light and ultraviolet light irradiation, possessing certain information hiding and identification functions. This coating can firmly adhere to the surface of fibrous fabrics, exhibiting good adhesion and decorative properties, and also demonstrates excellent multi-color luminescence and afterglow effects in clothing logo applications. This indicates that the room-temperature phosphorescent carbon quantum dot composite coating of this invention can be used in anti-counterfeiting labels and clothing logos, and is suitable for the field of visual anti-counterfeiting.

[0041] Experimental Example 6: The carbon quantum dot solution, modified carbon quantum dot powder, and room temperature phosphorescent carbon quantum dot composite coating prepared in Examples 1-4 of this invention were taken, and their luminescence properties were observed. The results are as follows: Figure 6 As shown.

[0042] Figure 6 The results showed that carbon quantum dot solutions prepared with different nitrogen sources exhibited significant multicolor fluorescence under 254 nm and 365 nm UV excitation; the solid sample of modified carbon quantum dot powder after boric acid modification continued to emit light even after the 365 nm UV light was turned off; the room-temperature phosphorescent carbon quantum dot composite coating system formed by combining modified carbon quantum dots with aqueous acrylic emulsion was uniformly dispersed and maintained good multicolor emission under UV excitation, indicating its suitability for preparing functional room-temperature phosphorescent coatings. The composite coating of this invention exhibits good operability and application adaptability at different processing stages.

[0043] Experimental Example 7: The room-temperature phosphorescent carbon quantum dot composite coatings prepared in Examples 1-4 were coated onto the surfaces of wood chips, cloth, paper towels, weighing paper, and filter paper, respectively. The states under sunlight, 254 nm and 365 nm ultraviolet light, and ultraviolet light removal were observed. The results are as follows: Figure 7 As shown.

[0044] Figure 7 The results showed that when the coating was applied to the surfaces of wood chips, cloth, napkins, weighing paper, and filter paper, it exhibited significant multicolor luminescence under 254 nm and 365 nm ultraviolet light excitation. Even after the 365 nm ultraviolet light was turned off, persistent afterglow was still observed on the surfaces of each substrate. This indicates that the coating of the present invention has excellent substrate adaptability, film-forming properties, and long-life room temperature phosphorescence characteristics, and can be widely used in wood, textiles, and various paper-based materials. The coating also demonstrates good substrate compatibility and photosensitivity.

[0045] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating, characterized by, Includes the following steps: S1. Preparation of precursor solution: Take a beaker, add cellulose and nitrogen source, add solvent, stir at room temperature to obtain a homogeneous precursor solution; S2. Preparation of carbon quantum dots: The precursor solution obtained in step S1 was transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at a constant temperature of 180°C for 4 h. After natural cooling, the solution was centrifuged, filtered to remove residue, and dialyzed to obtain a pure carbon quantum dot solution. S3. Boric acid modification treatment: Take the carbon quantum dot solution obtained in step S2, add boric acid and deionized water, heat and stir at 50°C until the boric acid is completely dissolved, transfer to an evaporating dish, heat in an oven at 150°C for 2.5 h, evaporate the water and grind to obtain powdered modified carbon quantum dots; S4. Coating composite: Take the modified carbon quantum dot powder obtained in step S3, sodium lignosulfonate and water-based acrylic emulsion, stir, and prepare cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating.

2. The preparation method of the cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating according to claim 1, characterized in that, In step S1, the mass ratio of cellulose to nitrogen source is 1:

3.

3. The method for preparing the cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating according to claim 2, characterized in that, In step S1, the nitrogen source is one of Rhodamine 6G, Rhodamine B, sulfonyl Rhodamine B, or riboflavin.

4. The method for preparing the cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating according to claim 3, characterized in that, In step S1, the ratio of cellulose to solvent is 0.01 g: 20 mL.

5. The method for preparing the cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating according to claim 4, characterized in that, In step S3, the ratio of the carbon quantum dot solution, boric acid, and deionized water is 10 mL:1 g:10 mL.

6. The method for preparing the cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating according to claim 5, characterized in that, In step S4, the ratio of the modified carbon quantum dot powder, sodium lignosulfonate, and aqueous acrylic emulsion is 0.25 g:0.09 g:10 mL.

7. The method for preparing the cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating according to claim 6, characterized in that, In step S4, the solid content of the aqueous acrylic emulsion is 40%-50%.

8. A method for preparing a room-temperature phosphorescent coating using a cellulose-based long-lifetime room-temperature phosphorescent carbon quantum dot composite coating prepared by any one of claims 1-7, characterized in that, Includes the following steps: (1) Substrate pretreatment: Sand the artificial board with sandpaper, wipe it with anhydrous ethanol to remove oil, and let it air dry naturally; (2) Coating preparation: The cellulose-based long-life room temperature phosphorescent carbon quantum dot composite coating is uniformly applied to the surface of the substrate, the coating thickness is controlled at 50-80 μm, dried and cured, cooled to room temperature, and then coated once more, dried, and naturally cooled to room temperature to obtain a room temperature phosphorescent coating.

9. The application of a cellulose-based long-life room-temperature phosphorescent carbon quantum dot composite coating prepared by the method of any one of claims 1-7 in visual anti-counterfeiting.

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