Anti-fake ink, preparation method and application thereof
By combining nitrogen-doped carbon quantum dot-silica composite particles with waterborne polyurethane and hydroxyethyl cellulose, the problems of fluorescence quenching and dispersion stability of carbon quantum dot anti-counterfeiting materials are solved, achieving high fluorescence intensity and environmental friendliness. This makes the materials suitable for dual verification functions and low-cost production of smart anti-counterfeiting packaging materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2026-05-20
- Publication Date
- 2026-07-24
AI Technical Summary
Existing carbon quantum dot anti-counterfeiting materials suffer from severe fluorescence quenching, poor dispersion stability, insufficient environmental friendliness, and limited functionality. Furthermore, their high production costs fail to meet the growing practical needs.
Anti-counterfeiting ink composed of nitrogen-doped carbon quantum dots-silica composite particles, water-based polyurethane, and hydroxyethyl cellulose forms Si-OC covalent bonds through sol-gel interaction, blocking π-π stacking. It also utilizes collagen liquid made from waste leather as a carbon source and a self-doped nitrogen source, combined with a water-based polyurethane-hydroxyethyl cellulose composite binder system, to achieve stable fluorescence emission and printing performance.
It achieves anti-counterfeiting functions such as high fluorescence stability, high fluorescence intensity, excellent resistance to photobleaching, and safety and environmental protection. It is suitable for use in intelligent anti-counterfeiting packaging materials and has dual verification functions and low-cost industrial production capabilities.
Smart Images
Figure CN122445221A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fluorescent anti-counterfeiting technology, specifically to an anti-counterfeiting ink, its preparation method, and its application. Background Technology
[0002] Carbon quantum dots (CQDs) possess excellent photoluminescence properties, good biocompatibility, and low toxicity, making them widely used in anti-counterfeiting materials. However, existing CQD anti-counterfeiting materials suffer from the following technical drawbacks: 1) Severe solid-state fluorescence quenching: Although CQDs exhibit good fluorescence properties in solution, their fluorescence is easily quenched due to π-π stacking in the solid state, severely limiting their application in inks; 2) Poor dispersion stability: CQDs have poor compatibility with organic binders, easily leading to agglomeration and sedimentation; 3) Insufficient environmental friendliness: Existing CQD fluorescent anti-counterfeiting inks mostly use solvent-based polyurethane systems, resulting in high VOC emissions, which does not align with the trend of green packaging; 4) Limited functionality: Traditional QR code anti-counterfeiting relies solely on the graphic itself, lacking optical concealment and dual verification mechanisms. Furthermore, the carbon sources currently used to prepare CQDs mainly include chemical reagents such as citric acid and ethylenediaminetetraacetic acid, or carbon materials such as graphene and carbon nanotubes. These chemical reagents are expensive and non-renewable, while these carbon materials lack functional dopant elements. In summary, existing CQD anti-counterfeiting materials cannot fully meet the growing practical needs, and their application is greatly limited.
[0003] Therefore, it is of great significance to develop a CQDs anti-counterfeiting material with high fluorescence stability, high fluorescence intensity, excellent resistance to photobleaching, safety and environmental protection, and low production cost. Summary of the Invention
[0004] The purpose of this invention is to provide an anti-counterfeiting ink, its preparation method, and its application.
[0005] The technical solution adopted in this invention is: An anti-counterfeiting ink comprising the following components by weight percentage: Waterborne polyurethane: 50%–55%; Hydroxyethyl cellulose: 1%–5%; Nitrogen-doped carbon quantum dot-silica composite particles: 1%–3%; Water: 37%–48%.
[0006] Preferably, the solid content of the waterborne polyurethane is 30% to 40%.
[0007] Preferably, the number-average molecular weight of the hydroxyethyl cellulose is 30,000 g / mol to 80,000 g / mol.
[0008] Preferably, the nitrogen-doped carbon quantum dot-silica composite particles consist of carrier silica particles and loaded nitrogen-doped carbon quantum dots.
[0009] Preferably, the nitrogen-doped carbon quantum dots in the nitrogen-doped carbon quantum dot-silica composite particles are ellipsoidal with a particle size ≤10nm and a height (i.e., thickness) distributed between 0.5nm and 1.6nm.
[0010] Preferably, the mass percentage of nitrogen-doped carbon quantum dots in the nitrogen-doped carbon quantum dot-silica composite particles is 20% to 25%.
[0011] Preferably, the nitrogen-doped carbon quantum dot-silica composite particles are prepared by a method including the following steps: dispersing nitrogen-doped carbon quantum dots with water to prepare a nitrogen-doped carbon quantum dot dispersion, adding nano-colloidal silica and then ultrasonically treating, followed by drying and grinding to obtain nitrogen-doped carbon quantum dot-silica composite particles.
[0012] Preferably, the nitrogen-doped carbon quantum dots are prepared by a method comprising the following steps: a) The waste leather is crushed, washed with ethanol, and dried to obtain fibrous material; b) The fibrous material was hydrolyzed using an alkaline method to obtain a collagen solution; c) The collagen solution was subjected to a hydrothermal reaction, followed by product separation, purification, and drying to obtain nitrogen-doped carbon quantum dots.
[0013] Preferably, the alkaline hydrolysis in step b) includes the following operation: dispersing the fibrous material and calcium oxide in water for hydrolysis (the purpose of which is to degrease and remove chromium).
[0014] Preferably, the alkaline hydrolysis in step b) is carried out at a temperature of 60℃~70℃ for 6h~8h.
[0015] Preferably, the hydrothermal reaction in step c) is carried out at a temperature of 140℃ to 180℃ for a reaction time of 8h to 12h.
[0016] Preferably, the mass fraction of the nitrogen-doped carbon quantum dot dispersion is 0.5% to 2.5%.
[0017] Preferably, the volume of the nano-colloidal silica accounts for 15% to 25% of the total volume of the nano-colloidal silica and the nitrogen-doped carbon quantum dot dispersion.
[0018] Preferably, the anti-counterfeiting ink is used at a shear rate of 0.133 s. -1 Under certain conditions, the viscosity ranges from 769 mPa·s to 32113 mPa·s, exhibiting pseudoplastic fluid characteristics.
[0019] A method for preparing the anti-counterfeiting ink as described above includes the following steps: Hydroxyethyl cellulose is dispersed in water, then waterborne polyurethane is added and mixed evenly. Nitrogen-doped carbon quantum dot-silica composite particles are then added and mixed evenly to obtain anti-counterfeiting ink.
[0020] A smart anti-counterfeiting packaging material, the surface of which contains a pattern made of the aforementioned anti-counterfeiting ink.
[0021] Preferably, the pattern is a QR code.
[0022] The beneficial effects of this invention are: the anti-counterfeiting ink of this invention can achieve intelligent anti-counterfeiting function of sunlight invisibility and ultraviolet color development. It has the advantages of high fluorescence stability, high fluorescence intensity, excellent anti-bleaching performance, suitable fluidity and viscosity, safety and environmental protection, etc. It is suitable for use in intelligent anti-counterfeiting packaging materials. Moreover, its preparation method is simple, the raw materials are widely available, and the production cost is low, making it suitable for large-scale industrial production and application.
[0023] Specifically: 1) Solved the problem of solid-state fluorescence quenching of carbon quantum dots: This invention uses nano-colloidal silica as a dispersion matrix and forms a composite structure with Si-OC covalent bonds with nitrogen-doped carbon quantum dots through sol-gel interaction, thereby anchoring nitrogen-doped carbon quantum dots in the three-dimensional network of silicon matrix, effectively blocking π-π stacking between particles, overcoming the aggregation-induced fluorescence quenching effect, and realizing stable solid-state blue fluorescence emission; 2) High-value utilization of waste leather is realized: This invention uses collagen liquid made from waste leather produced by the leather industry as a carbon source and self-doped nitrogen source. It utilizes the nitrogen-containing amino acids such as glycine (>25%) and proline (about 13%) that are rich in leather to achieve self-doping of nitrogen elements without the need to add additional nitrogen-containing chemical reagents, thus realizing the resource utilization of waste leather, which is in line with the concept of circular economy. 3) Excellent environmental tolerance and storage stability: The nitrogen-doped carbon quantum dots in this invention maintain a fluorescence intensity of 97.62% in a 2.0 mol / L NaCl solution and a fluorescence intensity of 96.34% after 10 months of storage, demonstrating excellent salt resistance and long-term stability. The anti-counterfeiting ink containing nitrogen-doped carbon quantum dots maintains a fluorescence intensity of 91.09% after 10 hours of continuous irradiation with 365 nm ultraviolet light, exhibiting good resistance to photobleaching. 4) Excellent printing and film-forming properties: This invention uses a water-based polyurethane-hydroxyethyl cellulose composite binder system. By adjusting the mass fraction of hydroxyethyl cellulose, the anti-counterfeiting ink can exhibit typical pseudoplastic fluid characteristics. In particular, the anti-counterfeiting ink system containing 2wt% hydroxyethyl cellulose will undergo a viscoelastic transition at 31.6 rad / s. In the low-frequency region, viscous flow ensures printing transfer performance, and in the high-frequency region, elastic response ensures film-forming stability, meeting the process requirements of screen printing. 5) It realizes intelligent optical anti-counterfeiting function: The anti-counterfeiting ink of the present invention is colorless, transparent and invisible under sunlight, but exhibits bright blue fluorescence under 365nm ultraviolet light. It can be used to print invisible QR codes, thereby realizing the dual functions of optical concealed anti-counterfeiting and information traceability. Attached Figure Description
[0024] Figure 1 This is a SEM image of the nitrogen-doped carbon quantum dots from Example 1.
[0025] Figure 2 The image shows the AFM diagram of the nitrogen-doped carbon quantum dots in Example 1.
[0026] Figure 3 The images show the UV absorption, excitation, and emission spectra of the nitrogen-doped carbon quantum dots in Example 1.
[0027] Figure 4 The image shows a comparison of the excitation spectrum and fluorescence intensity of the nitrogen-doped carbon quantum dot-silica composite particles in Example 2.
[0028] Figure 5 XPS image of nitrogen-doped carbon quantum dot-silica composite particles N-CQDs@SiO2-20 in Example 2.
[0029] Figure 6 Comparison images of high-purity nanocolloidal silica, nitrogen-doped carbon quantum dots from Example 1, and nitrogen-doped carbon quantum dot-silica composite particles N-CQDs@SiO2-20 from Example 2 under sunlight and UV light.
[0030] Figure 7 The graph shows the flowability and viscosity test results of the anti-counterfeiting inks in Examples 3 to 7.
[0031] Figure 8 The storage modulus and loss modulus curves of the anti-counterfeiting ink in Example 4 are shown.
[0032] Figure 9 This is a screen printing effect diagram of the anti-counterfeiting ink of Example 4. Detailed Implementation
[0033] The present invention will be further explained and described below with reference to specific embodiments.
[0034] Example 1: A nitrogen-doped carbon quantum dot, the preparation method of which is as follows: a) The waste leather is cut and crushed, then washed with anhydrous ethanol and dried to obtain fibrous material; b) Disperse the fibrous material and calcium oxide in water with a mass ratio of fibrous material, calcium oxide and water of 25:1:600, and then hydrolyze at 60℃ for 7 hours. Centrifuge to remove solids to obtain collagen solution. c) Add the collagen solution to a high-pressure reactor and react at 160°C for 10 hours. Cool to room temperature, vacuum filter, and put the filtrate into a dialysis bag for dialyzing in deionized water. Freeze dry to obtain nitrogen-doped carbon quantum dots (denoted as N-CQDs).
[0035] Performance testing: The scanning electron microscope (SEM) image of the nitrogen-doped carbon quantum dots (N-CQDs) in this embodiment is shown below. Figure 1 As shown, the atomic force microscope (AFM) image is as follows. Figure 2 As shown, the ultraviolet absorption spectrum, excitation spectrum, and emission spectrum are as follows: Figure 3 As shown.
[0036] Depend on Figure 1 and Figure 2 It can be seen that nitrogen-doped carbon quantum dots are ellipsoidal with a particle size ≤10nm and a height distribution of 0.5nm to 1.6nm.
[0037] Depend on Figure 3 It can be seen that nitrogen-doped carbon quantum dots emit blue fluorescence with a wavelength of 454 nm when excited by UV light with a wavelength of 365 nm, and the fluorescence quantum yield is 26.73%.
[0038] Example 2: A nitrogen-doped carbon quantum dot-silica composite particle, the preparation method of which is as follows: The nitrogen-doped carbon quantum dots (N-CQDs) of Example 1 were ultrasonically dispersed in water to prepare a 1% (w / w) nitrogen-doped carbon quantum dot dispersion. High-purity nano-colloidal silica was then added and ultrasonically treated for 30 min. The volume of the high-purity nano-colloidal silica accounted for 10%, 20%, 30%, 40%, and 50% of the total volume of the nitrogen-doped carbon quantum dot dispersion and the high-purity nano-colloidal silica, respectively. After drying and grinding, nitrogen-doped carbon quantum dot-silica composite particles were obtained (denoted as N-CQDs@SiO2-10, N-CQDs@SiO2-20, N-CQDs@SiO2-30, N-CQDs@SiO2-40, and N-CQDs@SiO2-50, respectively).
[0039] Performance testing: 1) The excitation spectra and fluorescence intensity comparison diagrams of the nitrogen-doped carbon quantum dot-silica composite particles (N-CQDs@SiO2-10, N-CQDs@SiO2-20, N-CQDs@SiO2-30, N-CQDs@SiO2-40 and N-CQDs@SiO2-50) in this embodiment are shown in the figure below. Figure 4 (a is the excitation spectrum, b is the fluorescence spectrum, and c is the actual image under sunlight and UV light with a wavelength of 365nm, respectively; nitrogen-doped carbon quantum dots are used as a blank control.)
[0040] Depend on Figure 4 It can be known that: a) Due to the low SiO2 content, N-CQDs@SiO2-10 can enhance fluorescence intensity, but direct contact still exists between the N-CQDs particles in the solid state, and the fluorescence retention rate is about 75%. b) Due to the excessively high SiO2 content, N-CQDs@SiO2-30 exhibits an internal filtering effect, causing the emitted light to be reabsorbed by the system itself, resulting in a decrease in fluorescence intensity of approximately 15% compared to N-CQDs@SiO2-20; c) The fluorescence intensity of N-CQDs@SiO2-50 decreased significantly.
[0041] In summary, the optimal volume ratio of nano-colloidal silica is 20%, which can effectively block π-π accumulation and avoid internal filtration effect.
[0042] 2) The X-ray photoelectron spectroscopy (XPS) spectrum of the nitrogen-doped carbon quantum dot-silica composite particles N-CQDs@SiO2-20 in this embodiment is shown below. Figure 5 (a is the full spectrum, b to d are the detailed spectra) as shown.
[0043] Depend on Figure 5 It can be seen that in addition to C, O and N, Si element (14.8 at%) was also detected in N-CQDs@SiO2-20, and a characteristic peak belonging to Si-OC bond appeared at 106.8 eV, confirming that N-CQDs are grafted onto the SiO2 surface through covalent bonds.
[0044] In addition, tests (using the same method as in Example 1) revealed that N-CQDs@SiO2-20 exhibited bright and stable blue fluorescence in the solid state, without aggregation-induced fluorescence quenching.
[0045] 3) Comparison images of high-purity nano-colloidal silicon dioxide, nitrogen-doped carbon quantum dots (N-CQDs) from Example 1, and nitrogen-doped carbon quantum dot-silica composite particles N-CQDs@SiO2-20 from this example under sunlight and UV light with a wavelength of 365nm are shown below. Figure 6 As shown.
[0046] Depend on Figure 6 It is known that high-purity nano-colloidal silica exhibits no photoluminescence, and the fluorescence effect of N-CQDs is poor, with some N-CQDs even completely losing their fluorescence effect. However, N-CQDs@SiO2-20 exhibits a brighter, more stable, and more uniform fluorescence effect. The reason is that when high-purity nano-colloidal silica is used as a dispersion matrix and is physically blended and ultrasonically treated with N-CQDs dispersion, the hydroxyl and carboxyl functional groups on the surface of N-CQDs form hydrogen bonds or covalent bonds with the silanol on the surface of silica sol. The two form a three-dimensional network structure through sol-gel interaction, which maintains the optimal distance between N-CQDs, stabilizes the surface state of N-CQDs, restricts non-radiative transitions, and overcomes aggregation-induced fluorescence quenching.
[0047] Example 3: An anti-counterfeiting ink, the composition of which is shown in the table below: Table 1. Composition of an anti-counterfeiting ink
[0048] The preparation method of the above-mentioned anti-counterfeiting ink is as follows: Hydroxyethyl cellulose (HEC) was dispersed in water, then waterborne polyurethane (WPU) was added and stirred until homogeneous. Nitrogen-doped carbon quantum dot-silica composite particles were then added and ultrasonically treated for 40 minutes. Finally, vacuum defoaming was performed to obtain the anti-counterfeiting ink.
[0049] Example 4: An anti-counterfeiting ink, the composition of which is shown in the table below: Table 2 Composition of an anti-counterfeiting ink
[0050] The preparation method of the above-mentioned anti-counterfeiting ink is as follows: Hydroxyethyl cellulose was dispersed in water, then waterborne polyurethane was added and stirred until homogeneous. Nitrogen-doped carbon quantum dot-silica composite particles were then added and ultrasonically treated for 40 minutes. Finally, vacuum defoaming was performed to obtain the anti-counterfeiting ink.
[0051] Example 5: An anti-counterfeiting ink, the composition of which is shown in the table below: Table 3 Composition of an anti-counterfeiting ink
[0052] The preparation method of the above-mentioned anti-counterfeiting ink is as follows: Hydroxyethyl cellulose was dispersed in water, then waterborne polyurethane was added and stirred until homogeneous. Nitrogen-doped carbon quantum dot-silica composite particles were then added and ultrasonically treated for 40 minutes. Finally, vacuum defoaming was performed to obtain the anti-counterfeiting ink.
[0053] Example 6: An anti-counterfeiting ink, the composition of which is shown in the table below: Table 4. Composition of an anti-counterfeiting ink
[0054] The preparation method of the above-mentioned anti-counterfeiting ink is as follows: Hydroxyethyl cellulose was dispersed in water, then waterborne polyurethane was added and stirred until homogeneous. Nitrogen-doped carbon quantum dot-silica composite particles were then added and ultrasonically treated for 40 minutes. Finally, vacuum defoaming was performed to obtain the anti-counterfeiting ink.
[0055] Example 7: An anti-counterfeiting ink, the composition of which is shown in the table below: Table 5 Composition of an anti-counterfeiting ink
[0056] The preparation method of the above-mentioned anti-counterfeiting ink is as follows: Hydroxyethyl cellulose was dispersed in water, then waterborne polyurethane was added and stirred until homogeneous. Nitrogen-doped carbon quantum dot-silica composite particles were then added and ultrasonically treated for 40 minutes. Finally, vacuum defoaming was performed to obtain the anti-counterfeiting ink.
[0057] Performance testing: 1) The flowability and viscosity test results of the anti-counterfeiting inks in Examples 3-7 are shown in the figure below. Figure 7 As shown (a is the result of the flowability test, b is the result of the viscosity test; anti-counterfeiting ink without hydroxyethyl cellulose is used as a control, and hydroxyethyl cellulose is replaced with an equal mass of water).
[0058] Depend on Figure 7 It can be seen that the anti-counterfeiting ink without hydroxyethyl cellulose has a flowability of 45 mm, which is too fluid and prone to dripping during screen printing, resulting in insufficient clarity of the printed pattern edges. The anti-counterfeiting ink of Example 7 has a flowability of 7 mm, which is too low and has too high viscosity, making it difficult to transfer during screen printing and easily clogging the mesh. The anti-counterfeiting inks of Examples 3 to 5 have more suitable flowability and viscosity. Among them, the anti-counterfeiting ink of Example 4 can achieve a balance between flowability and printability.
[0059] 2) The storage modulus (G') and loss modulus (G'') curves of the anti-counterfeiting ink in Example 4 are shown below. Figure 8 As shown.
[0060] Depend on Figure 8 It can be seen that: at a shear rate of 0.133 s⁻¹ -1 Under certain conditions, the viscosity of the anti-counterfeiting ink is 4500 mPa·s, while at a shear rate of 100 s⁻¹, the viscosity is higher. -1 Under the given conditions, the viscosity of the anti-counterfeiting ink is 850 mPa·s, exhibiting typical pseudoplastic fluid characteristics; dynamic angular frequency scanning shows that the storage modulus G' and loss modulus G'' intersect at 31.6 rad / s, indicating that the anti-counterfeiting ink exhibits predominantly viscous behavior in the low-frequency region and predominantly elastic behavior in the high-frequency region.
[0061] 3) The anti-counterfeiting ink of Example 4 was screen-printed onto the surface of double-ring qualitative filter paper to form a pattern. The pattern was then observed under sunlight and UV light with a wavelength of 365nm. The resulting screen-printed effect is shown in the image below. Figure 9 As shown.
[0062] Depend on Figure 9 It can be seen that the pattern is colorless and invisible under sunlight, but exhibits bright blue fluorescence under UV light, and the pattern has high fineness. In addition, after continuous UV light irradiation for 10 hours, the fluorescence intensity retention rate is 91.09%.
[0063] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. An anti-counterfeiting ink, characterized in that, The components include the following percentages by mass: Waterborne polyurethane: 50%–55%; Hydroxyethyl cellulose: 1%–5%; Nitrogen-doped carbon quantum dot-silica composite particles: 1%–3%; Water: 37%–48%.
2. The anti-counterfeiting ink according to claim 1, characterized in that: The solid content of the waterborne polyurethane is 30% to 40%.
3. The anti-counterfeiting ink according to claim 1, characterized in that: The number-average molecular weight of the hydroxyethyl cellulose is 30,000 g / mol to 80,000 g / mol.
4. The anti-counterfeiting ink according to any one of claims 1 to 3, characterized in that: The nitrogen-doped carbon quantum dot-silica composite particles consist of carrier silica particles and loaded nitrogen-doped carbon quantum dots.
5. The anti-counterfeiting ink according to claim 4, characterized in that: The nitrogen-doped carbon quantum dots in the nitrogen-doped carbon quantum dot-silica composite particles are ellipsoidal with a particle size ≤10nm and a height distribution of 0.5nm to 1.6nm.
6. The anti-counterfeiting ink according to claim 4, characterized in that: The nitrogen-doped carbon quantum dot-silica composite particles contain 20% to 25% nitrogen-doped carbon quantum dots by mass.
7. The anti-counterfeiting ink according to claim 4, characterized in that: The nitrogen-doped carbon quantum dot-silica composite particles are prepared by a method including the following steps: dispersing nitrogen-doped carbon quantum dots with water to prepare a nitrogen-doped carbon quantum dot dispersion, adding nano-colloidal silica and then ultrasonically treating it, followed by drying and grinding to obtain nitrogen-doped carbon quantum dot-silica composite particles.
8. The anti-counterfeiting ink according to claim 7, characterized in that: The nitrogen-doped carbon quantum dots are prepared by a method including the following steps: a) The waste leather is crushed, washed with ethanol, and dried to obtain fibrous material; b) The fibrous material was hydrolyzed using an alkaline method to obtain a collagen solution; c) The collagen solution was subjected to a hydrothermal reaction, followed by product separation, purification, and drying to obtain nitrogen-doped carbon quantum dots.
9. A method for preparing anti-counterfeiting ink as described in any one of claims 1 to 8, characterized in that, The process includes the following steps: dispersing hydroxyethyl cellulose in water, adding waterborne polyurethane and mixing evenly, then adding nitrogen-doped carbon quantum dot-silica composite particles and mixing evenly to obtain anti-counterfeiting ink.
10. A smart anti-counterfeiting packaging material, characterized in that, The surface contains a pattern made of the anti-counterfeiting ink as described in any one of claims 1 to 8.