A responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material, a preparation method and application thereof

Abstract

The application discloses a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material, and is characterized in that biomass such as yacon peel is used as a carbon source, ethylenediamine is used as a nitrogen source, nitrogen-doped carbon quantum dots are prepared through a one-step hydrothermal method, the nitrogen-doped carbon quantum dots and hydrophilic polymers are uniformly dispersed in deionized water to obtain the responsive fluorescent carbon quantum dot composite material, and the ink prepared by using the composite material has the following characteristics: the printed pattern is invisible under natural light, can display cyan fluorescence under ultraviolet light, presents green phosphorescence after the ultraviolet light is removed, and can realize fluorescent / phosphorescent dual-mode anti-counterfeiting functions. 3+ In addition, the printed pattern can undergo fluorescence quenching under alkaline solution or Fe 3+ solution, realizes dynamic response anti-counterfeiting functions, and solves the problems that the existing carbon quantum dots have single light-emitting mode and are difficult to have dynamic response and dual-mode light-emitting functions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light-emitting materials, and more particularly to a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material, a preparation method thereof and an application thereof. BACKGROUND

[0002] Carbon quantum dots (CDs) are a new type of carbon nanomaterials, with a particle size generally less than 10 nm. They not only have good biocompatibility, optical stability, water solubility, etc., but also can realize other new anti-counterfeiting modes in addition to the ordinary static fluorescence anti-counterfeiting mode due to their wide raw material sources, small size, easy functionalization, and tunable optical properties. Compared with traditional anti-counterfeiting technologies, light functional materials with a stimulus response feature have obvious advantages in the field of anti-counterfeiting or information encryption.

[0003] At present, CDs synthesized using chemical reagents often have advantages such as high quantum yield and high uniformity, but the cost of the raw materials for synthesis is relatively high, and they also have certain toxicity. Using biomass materials as precursors for CDs can reduce production costs and reduce environmental pollution. For example, CN110194953A and CN106833630B propose to use biomass resources as carbon sources to prepare responsive fluorescent carbon quantum dots by a hydrothermal method, which can be applied to ion detection and fluorescent ink printing. This type of fluorescent carbon quantum dots has a wide range of raw materials, is environmentally friendly and sustainable, but the light-emitting mode and light-emitting color are relatively single, and they are easily imitated when used in the anti-counterfeiting field. CN114806554A discloses a phosphorescent carbon dot, which is obtained by a hydrothermal reaction using vitamin B1 and ethylenediamine as precursors, and also provides its application in anti-counterfeiting and information encryption as well as a LED lamp bead based on the phosphorescent carbon dot. CN114479833A discloses a nitrogen-doped carbon dot prepared by a microwave method using citric acid and urea as starting materials, and a room-temperature phosphorescent material prepared by combining the carbon dot with a solid matrix can realize multi-color and time-dependent multiple anti-counterfeiting. However, these phosphorescent carbon quantum dot materials do not have dynamic response anti-counterfeiting, and the cost of the carbon source is relatively high or has certain toxicity, which is difficult to popularize and apply due to its harm to the natural environment and human health. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material to solve the problems of single light-emitting mode and difficulty in combining dynamic response and dual-mode light-emitting of existing carbon quantum dots.

[0005] Another technical problem to be solved by the present application is to provide a preparation method and an application of the responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material.

[0006] The object of the present application is achieved by the following technical solutions:

[0007] A responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material is disclosed. The raw materials include nitrogen-doped carbon quantum dots and a hydrophilic polymer matrix, with a mass ratio of nitrogen-doped carbon quantum dots to hydrophilic polymer of 1:200,000-30,000. The nitrogen-doped carbon quantum dots are prepared using biomass as the carbon source and ethylenediamine as the nitrogen source. The biomass is any one of snow lotus peel, grapefruit peel, pomegranate peel, and kiwi peel. This invention prepares nitrogen-doped carbon quantum dots (N-CDs) using biomass such as snow lotus peel as the carbon source and ethylenediamine as the nitrogen source. The particle size distribution ranges from 1 to 5 nm, and it exhibits both metal ion and pH responsiveness. The prepared N-CDs have abundant amino, hydroxyl, and carboxyl groups on their surface, readily reacting with Fe. 3+ A chelate is formed, and electrons in the excited state of N-CDs are transferred to Fe. 3+ The N-CDs undergo deprotonation under acidic conditions, promoting non-radiative electron-hole recombination and leading to fluorescence quenching. Under acidic conditions, the prepared N-CDs exhibit high protonation, good carbon dot dispersion, and high fluorescence intensity; under alkaline conditions, the N-CDs deprotonate and aggregate, resulting in fluorescence quenching. Inks prepared using this composite material can achieve multi-mode information storage (static / dynamic, fluorescent / phosphorescent), showing broad application prospects in advanced anti-counterfeiting and information encryption.

[0008] Furthermore, the biomass is preferably snow lotus peel.

[0009] Furthermore, the preparation steps of the nitrogen-doped carbon quantum dots include:

[0010] S1. Dry and grind the biomass into powder, and use the biomass and ethylenediamine as precursors and deionized water as dispersion medium to form a uniformly dispersed reaction solution.

[0011] S2. After subjecting the solution to be reacted to a hydrothermal reaction for a certain period of time, cool it to room temperature to obtain a suspension;

[0012] S3. Centrifuge, dialyze, and dry the suspension to obtain nitrogen-doped carbon quantum dot powder.

[0013] Furthermore, the mass ratio of biomass, ethylenediamine, and deionized water in S1 is 0.1-0.3:0.2-0.6:10.

[0014] Furthermore, the hydrothermal reaction temperature described in S2 is 160-200℃, and the reaction time is 4-10h.

[0015] Furthermore, the centrifugation speed described in S3 is 6000-8000 r / min, and the centrifugation time is 10-20 min.

[0016] Furthermore, the drying described in S3 is freeze drying, with a freeze drying temperature of -35 to -45°C and a time of 12-36 hours.

[0017] Furthermore, the dialysis described in S3 uses a dialysis bag with a molecular weight cutoff of 500-1000 Da, and the dialysis time is 24-48 hours.

[0018] Further, the hydrophilic polymer is any one of polyacrylic acid (PAA), polyethylene glycol (PEG), and polyvinyl alcohol (PVA). Preferably, the hydrophilic polymer is polyacrylic acid.

[0019] Further, the weight-average molecular weight of the hydrophilic polymer is 2000-5000. Preferably, the weight-average molecular weight of the hydrophilic polymer is 3000.

[0020] Furthermore, the preparation steps of the responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material include: dispersing a hydrophilic polymer in deionized water to prepare a polymer aqueous dispersion with a mass fraction of 20-30% at room temperature; then mixing the obtained nitrogen-doped carbon quantum dots and the hydrophilic polymer aqueous dispersion and stirring evenly at room temperature to obtain the responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material.

[0021] Furthermore, the responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material is used in anti-counterfeiting or information encryption.

[0022] Furthermore, according to the application of the above-mentioned responsive fluorescence / phosphorescence dual-mode carbon quantum dot composite material, the step is characterized by comprising:

[0023] S1. The prepared carbon quantum dot composite material is dispersed in a mixed solvent of deionized water and ethanol, and polyacrylic acid aqueous dispersion is added to adjust the viscosity. The mixture is stirred rapidly for 6 hours until it is uniformly mixed to obtain water-based fluorescent anti-counterfeiting ink.

[0024] S2. The water-based fluorescent anti-counterfeiting ink is used to print the desired pattern on the substrate by screen printing, gravure printing or inkjet printing, and then allowed to dry naturally.

[0025] Furthermore, the addition ratio of the carbon quantum dot composite material, PAA, and mixed solvent is 11:2 to 9:10-25.

[0026] Furthermore, the volume ratio of deionized water to ethanol in the mixed solvent is 3-4:1.

[0027] Furthermore, the solid content of the polyacrylic acid aqueous dispersion is 40-60%.

[0028] Compared with existing technologies, the beneficial effects are:

[0029] This invention prepares carbon quantum dot materials using biomass such as snow lotus peel as the main raw material. The prepared carbon quantum dots, composite materials of carbon quantum dots and hydrophilic polymers, and inks containing the composite materials all exhibit cyan fluorescence under ultraviolet light. Patterns printed with inks containing this carbon quantum dot composite material produce green phosphorescence and continue to emit light for 3 seconds after the ultraviolet light source is removed, achieving dual-mode anti-counterfeiting or information encryption using fluorescence / phosphorescence. Simultaneously, patterns printed with inks containing the carbon quantum dot composite material prepared in this invention also exhibit metal ion and pH responsiveness, showing resistance in Fe... 3+ Fluorescence quenching may occur in alkaline solutions, Fe 3+ The higher the concentration of the alkaline solution, the more significant the decrease in fluorescence. The printed pattern was then coated with Fe... 3+ Alternatively, an alkaline solution can quench the cyan fluorescence of the anti-counterfeiting pattern, achieving static / dynamic response anti-counterfeiting or information encryption, and providing multi-mode anti-counterfeiting functionality with stimulus-responsive characteristics.

[0030] The carbon quantum dot composite material described in this invention is inexpensive, readily available, natural, non-toxic, environmentally friendly, and sustainable. It enables the recycling of resources and provides an important approach for the preparation, performance regulation, and application research of biomass-based carbon quantum dot materials. It has significant social and economic value for the entire anti-counterfeiting industry. Attached Figure Description

[0031] Figure 1 This is a transmission electron microscope image of the carbon quantum dots obtained in Example 1;

[0032] Figure 2 This is a size distribution diagram of the carbon quantum dots obtained in Example 1;

[0033] Figure 3 This is the XPS image of the carbon quantum dots obtained in Example 1;

[0034] Figure 4 This is the FT-IR spectrum of the carbon quantum dots obtained in Example 1;

[0035] Figure 5 These are the excitation spectrum, emission spectrum, and UV-Vis absorption spectrum of the carbon quantum dots obtained in Example 1;

[0036] Figure 6 These are photographs of the carbon quantum dot aqueous dispersion obtained in Example 1 under natural light (left) and 365nm ultraviolet light (right);

[0037] Figure 7 The carbon quantum dots obtained in Example 1 are at different Fe concentrations 3+ Fluorescence intensity at the specified levels;

[0038] Figure 8 The fluorescence intensity of the carbon quantum dots obtained in Example 1 at different pH values;

[0039] Figure 9 These are photographs of the water-based carbon quantum dot anti-counterfeiting ink patterns from Examples 1, 2, and 3 under natural light and 365nm ultraviolet light.

[0040] Figure 10 These are photographs taken under 365nm ultraviolet light after the water-based carbon quantum dot anti-counterfeiting ink pattern from Example 1 has been sprayed with alkaline solution, and after spraying with Fe... 3+ Photograph of the aqueous solution under 365nm ultraviolet light.

[0041] Figure 11 These are photographs of the pattern printed with water-based carbon quantum dot anti-counterfeiting ink in Example 1 at 0s, 1s, 2s, and 3s after the ultraviolet light was turned off. Detailed Implementation

[0042] The following examples further explain and clarify the invention, but the specific examples do not limit the invention in any way. Unless otherwise specified, the methods and equipment used in the examples are conventional methods and equipment, and the raw materials used are all commercially available.

[0043] Example 1

[0044] This embodiment provides an application of a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material in anti-counterfeiting, the steps of which include:

[0045] S1. Preparation of nitrogen-doped carbon quantum dots

[0046] S11. Dry and grind the snow lotus peel into powder. Use 0.2g snow lotus peel powder and 0.27g ethylenediamine as precursors and 10g deionized water as dispersion medium, and sonicate for 15min to form a uniformly dispersed reaction solution.

[0047] S12. After reacting the solution to be reacted at 180℃ for 6 hours, the solution was cooled to room temperature to obtain a suspension;

[0048] S13. Transfer the suspension to a centrifuge and centrifuge at 8000 r / min for 10 min to remove solid residues from the solution. Dialyze the solution in deionized water for 24 h, with the molecular weight cutoff of the dialysis bag being 1000 Da. Change the deionized water every 6 h to remove unreacted small molecules. Then freeze the solution at -40℃ for 24 h to obtain nitrogen-doped carbon quantum dot powder.

[0049] S2. Preparation of carbon quantum dot composite materials

[0050] S21. Disperse 1 mg of N-CDs in deionized water to prepare an N-CDs aqueous solution with a concentration of 0.1 mg / mL at room temperature, and store at 4 °C.

[0051] S22. Disperse 4.0g of PAA with a solid content of 50% (weight average molecular weight = 3000) in deionized water to prepare a PAA aqueous dispersion with a mass fraction of 20% at room temperature;

[0052] S23. Mix 1 mL of the obtained N-CDs aqueous solution and 10 g of the obtained PAA aqueous dispersion, and stir magnetically for 1 h at room temperature to obtain a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material.

[0053] S3. Anti-counterfeiting application

[0054] The prepared carbon quantum dot composite material was dispersed in 5 mL of deionized water and ethanol (V). 去离子水 V 乙醇 In a mixed solvent of 4:1, 14g of a 50% solids aqueous dispersion of polyacrylic acid (weight-average molecular weight of polyacrylic acid = 3000) was added to adjust the viscosity. The mixture was stirred rapidly for 6 hours until homogeneous to obtain water-based fluorescent anti-counterfeiting ink. The QR code pattern was then screen-printed on non-fluorescent paper and allowed to dry naturally.

[0055] Example 2

[0056] This embodiment provides an application of a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material in anti-counterfeiting, the steps of which include:

[0057] S1. Preparation of nitrogen-doped carbon quantum dots

[0058] S11. Dry and grind the snow lotus peel into powder. Use 0.1g snow lotus peel powder and 0.2g ethylenediamine as precursors and 10g deionized water as dispersion medium, and sonicate for 10min to form a uniformly dispersed reaction solution.

[0059] S12. After reacting the solution to be reacted at 160℃ for 10 hours, the solution was cooled to room temperature to obtain a suspension;

[0060] S13. Transfer the suspension to a centrifuge and centrifuge at 6000 r / min for 20 min to remove solid residues in the solution. Dialyze the solution in deionized water for 36 h, with the molecular weight cutoff of the dialysis bag being 1000 Da. Change the deionized water every 6 h to remove unreacted small molecules. Then freeze the solution at -35℃ for 36 h to obtain nitrogen-doped carbon quantum dot powder.

[0061] S2. Preparation of carbon quantum dot composite materials

[0062] S21. Disperse 1 mg of N-CDs in deionized water to prepare an N-CDs aqueous solution with a concentration of 0.1 mg / mL at room temperature, and store at 4 °C.

[0063] S22. Disperse 6.0g of polyacrylic acid (weight average molecular weight = 3000) with a solid content of 50% in deionized water to prepare a PAA aqueous dispersion with a mass fraction of 30% at room temperature;

[0064] S23. Mix 1 mL of the obtained N-CDs aqueous solution and 10 g of the obtained polyacrylic acid aqueous dispersion, and stir magnetically for 1 h at room temperature to obtain a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material.

[0065] S3. Anti-counterfeiting application

[0066] The prepared carbon quantum dot composite material was dispersed in 5 mL of deionized water and ethanol (V). 去离子水 V 乙醇 In a mixed solvent of 4:1, 4g of a 50% solids aqueous dispersion of polyacrylic acid (weight average molecular weight of polyacrylic acid = 3000) was added to adjust the viscosity. The mixture was stirred rapidly for 6 hours until it was uniformly mixed to obtain water-based fluorescent anti-counterfeiting ink. The ink ring pattern was then printed on non-fluorescent paper and allowed to dry naturally.

[0067] Example 3

[0068] This embodiment provides an application of a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material in anti-counterfeiting, the steps of which include:

[0069] S1. Preparation of nitrogen-doped carbon quantum dots

[0070] S11. Dry and grind the snow lotus peel into powder. Use 0.3g snow lotus peel powder and 0.6g ethylenediamine as precursors and 10g deionized water as dispersion medium, and sonicate for 20min to form a uniformly dispersed reaction solution.

[0071] S12. After reacting the solution to be reacted at 200℃ for 4 hours, the solution was cooled to room temperature to obtain a suspension;

[0072] S13. Transfer the suspension to a centrifuge and centrifuge at 7000 r / min for 15 min to remove solid residues from the solution. Dialyze the solution in deionized water for 48 h, with the molecular weight cutoff of the dialysis bag being 500 Da. Change the deionized water every 6 h to remove unreacted small molecules. Then freeze the solution at -45℃ for 12 h to obtain nitrogen-doped carbon quantum dot powder.

[0073] S2. Preparation of carbon quantum dot composite materials

[0074] S21. Disperse 1 mg of N-CDs in deionized water to prepare an N-CDs aqueous solution with a concentration of 0.1 mg / mL at room temperature, and store at 4 °C.

[0075] S22. Disperse 5.0g of PAA with a solid content of 50% (weight average molecular weight = 3000) in deionized water to prepare a PAA aqueous dispersion with a mass fraction of 20% at room temperature;

[0076] S23. Mix 1 mL of the obtained N-CDs aqueous solution and 10 g of the obtained PAA aqueous dispersion, and stir magnetically for 1 h at room temperature to obtain a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material.

[0077] S3. Anti-counterfeiting application

[0078] The prepared carbon quantum dot composite material was dispersed in 15 mL of deionized water and ethanol (V). 去离子水 V 乙醇 In a mixed solvent of 4:1, 3g of 50% solids polyacrylic acid aqueous dispersion (polyacrylic acid weight average molecular weight = 3000) was added to adjust the viscosity. The mixture was stirred rapidly for 6 hours until it was uniformly mixed to obtain water-based fluorescent anti-counterfeiting ink. The ink was then printed on non-fluorescent paper and allowed to dry naturally.

[0079] The carbon quantum dots synthesized in Example 1 were subjected to transmission electron microscopy (TEM), XPS, FT-IR, excitation, emission, and UV-Vis absorption spectroscopy. The results are as follows:

[0080] like Figure 1 The transmission electron microscope image shown in a-1b and Figure 2 It can be seen that the prepared carbon quantum dots are spherical in shape, well dispersed, and without agglomeration. The particle size of the carbon quantum dots is between 1.32 nm and 2.99 nm, with an average particle size of 1.88 nm. Furthermore, the carbon quantum dots form a good crystalline structure with a lattice spacing of 0.22 nm.

[0081] like Figure 3 As shown in the XPS image, carbon quantum dots mainly contain C, N and O elements, accounting for 74.71%, 6.41% and 18.88% respectively, indicating that carbon quantum dots have hydroxyl, carboxyl and amino groups.

[0082] like Figure 4 As shown in the FT-IR image, polar functional groups such as carbonyl, carboxyl, and amino groups are formed on the surface of the carbon quantum dots, thus giving the carbon quantum dots excellent water solubility.

[0083] like Figure 5 The excitation spectrum, emission spectrum, and UV-Vis absorption spectrum shown are as follows: Figure 6It is known that the optimal excitation wavelength for carbon quantum dots is 432 nm, and the strongest emission wavelength under optimal excitation is 527 nm. The carbon quantum dot solution appears pale yellow under natural light, but bright cyan under 365 nm ultraviolet light. The ultraviolet absorption curve shows an absorption peak at 335 nm, which can be attributed to the n→π transition of electrons in C=C and C=O. * Leap forward.

[0084] Example 4

[0085] This example provides different concentrations of Fe. 3+ The quenching effect of the solution on carbon quantum dots was determined by the following steps: 0.5 mL of the N-CDs aqueous solution prepared in Example 1 was taken and reacted with 1 mL of Fe solutions with concentrations of 100 μM, 500 μM, 1 mM, 5 mM, and 10 mM, respectively. 3+ After thoroughly mixing the solution and allowing it to stand for 10 minutes, perform a fluorescence test.

[0086] like Figure 7 As shown, with Fe 3+ As the concentration of Fe increased from 100 μM to 10 mM, the fluorescence intensity of carbon quantum dots gradually decreased, especially when Fe... 3+ The fluorescence intensity of carbon quantum dots decreased most significantly when the concentration increased from 100 μM to 5 mM, indicating that higher concentrations of Fe... 3+ It can effectively quench the fluorescence of carbon quantum dots.

[0087] Example 5

[0088] This embodiment provides the quenching effect of different pH values ​​on carbon quantum dots. The steps are as follows: Take 0.5 mL of the N-CDs aqueous solution prepared in Example 1, and mix it thoroughly with 1 mL of aqueous solutions with pH values ​​of 1, 4, 7, 10 and 13 respectively (prepared with NaOH and dilute HCl solution). After standing for 10 min, perform fluorescence testing.

[0089] like Figure 8 As shown, the fluorescence intensity of carbon quantum dots gradually decreases with increasing pH value, and the fluorescence intensity of carbon quantum dots is weakest at pH value of 13, indicating that alkaline solution can effectively quench the fluorescence of carbon quantum dots.

[0090] The patterns printed with the water-based carbon quantum dot anti-counterfeiting inks prepared in Examples 1-3 were irradiated with natural light and 365nm ultraviolet light, respectively. Figure 9 As shown in a1-a3, no obvious traces were observed in the ink-printed patterns of Examples 1-3 under natural light. As shown in b1-b3, the ink-printed patterns of Examples 1-3 exhibited clear cyan fluorescent patterns under 365nm ultraviolet light irradiation. The patterns were full, with clear edge details, and had strong recognizability.

[0091] A pH=13 alkaline solution and a 10mM Fe solution were sprayed onto the ink-printed pattern, respectively. 3+ After being dissolved in water, under 365nm ultraviolet light irradiation, as... Figure 10 The alkaline treatment shown in c1-c3 and the Fe shown in d1-d3 3+ When images are treated with aqueous solutions, their fluorescence intensity is significantly reduced, and the patterns become blurry and difficult to distinguish, enabling dynamic response anti-counterfeiting and presenting a better anti-counterfeiting effect.

[0092] The ink-printed pattern in Example 1 was irradiated with 365nm ultraviolet light, such as... Figure 11 The images e1-e4 show photos taken at 0s, 1s, 2s, and 3s after the ultraviolet light was removed. At the moment of removal, the printed pattern is clearly visible and displays a green phosphorescence. After 3 seconds of ultraviolet light removal, the green phosphorescence pattern completely disappears, thus achieving a dual-mode anti-counterfeiting function of fluorescence and phosphorescence.

[0093] 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. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A responsive fluorescent / phosphorescent dual-mode carbon quantum dots composite material, characterized in that, The raw material comprises nitrogen-doped carbon quantum dots and a polyacrylic acid matrix, and the mass ratio of the nitrogen-doped carbon quantum dots to the polyacrylic acid is 1:20000-30000; the nitrogen-doped carbon quantum dots are prepared by taking yaoyou snow lotus peel as a carbon source and ethylenediamine as a nitrogen source, and have Fe 3+ / pH dual response fluorescent properties; the preparation steps of the nitrogen-doped carbon quantum dots comprise: S1. Dry and grind the yacon peel into powder, and form a uniformly dispersed reaction solution with the yacon peel and ethylenediamine as precursors and deionized water as a dispersion medium, the mass ratio of the yacon peel, ethylenediamine and deionized water being 0.1-0.3:0.2-0.6:10; S2. Hydrothermally react the reaction solution at 160-200℃ for 4-10h, and then cool to room temperature to obtain a suspension; S3. Centrifuge, dialyze and dry the suspension to obtain a nitrogen-doped carbon quantum dot powder. 2.The responsive fluorescent / phosphorescent dual-mode carbon quantum dots composite material of claim 1, wherein, The dialysis adopts a dialysis bag with a molecular weight cut-off of 500-1000 Da, and the dialysis time is 24-48 h.

3. The responsive fluorescent / phosphorescent dual-mode carbon quantum dots composite material according to claim 1, the preparation steps comprising: Disperse the polyacrylic acid in deionized water to prepare a polyacrylic acid water dispersion with a mass fraction of 20-30% at room temperature, then mix the obtained nitrogen-doped carbon quantum dots and the polyacrylic acid water dispersion, and stir uniformly at room temperature to obtain a responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material.

4. Application of the responsive fluorescent / phosphorescent dual-mode carbon quantum dot composite material of claim 1 in anti-counterfeiting or information encryption.

5. Use according to claim 4, wherein the step of Comprise: S1. Disperse the prepared carbon quantum dot composite material in a mixed solvent of deionized water and ethanol, add a polyacrylic acid water dispersion to adjust the viscosity, and stir rapidly for 6 h until mixed uniformly to prepare an aqueous fluorescent anti-counterfeiting ink; S2. Print the required pattern on a printing substrate by silk printing, intaglio printing or jet printing using the aqueous fluorescent anti-counterfeiting ink, and dry naturally.

6. Use according to claim 5, characterized in that, The addition ratio of the carbon quantum dot composite material, polyacrylic acid and mixed solvent is 11:2-9:10-25.

Images