Preparation method of pH and metal ion response type carbon quantum dot fluorescent anti-forgery ink

Abstract

The invention belongs to the field of anti-forgery ink application, and particularly relates to a preparation method of pH and metal ion response type carbon quantum dot fluorescent anti-forgery ink. In order to solve the problems of poor compatibility between a nano fluorescent material and ink, instability of a nano material and the like, phenolphthalein and m-phenylenediamine are adopted as raw materials, carbon dot powder is synthesized in a short time by virtue of a simple one-step hydrothermal method and a NaOH regulator, the carbon dot powder is dissolved in deionized water, and glycerol is added to prepare the anti-counterfeiting ink.

Description

Technical Field

[0001] The invention belongs to the field of anti-counterfeiting ink applications, and in particular relates to a method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink. Background Art

[0002] With the rapid development of the market economy, the phenomenon of counterfeit and shoddy products is becoming increasingly serious. Especially in the food, medicine, cosmetics and luxury goods industries, counterfeit products not only pose a threat to the health and safety of consumers, but also have a serious impact on brand image and market order. Therefore, effective anti-counterfeiting measures are urgently needed to protect consumer rights and maintain market fairness. Traditional anti-counterfeiting technologies such as watermarks, laser engraving, barcodes and QR codes can prevent counterfeiting to a certain extent, but these methods are often complicated to operate and easy to be imitated or cracked. For example, the environmentally friendly laser holographic QR code anti-counterfeiting mark and production method based on burning white technology proposed by patent CN118629310A, the anti-counterfeiting mark includes release paper, glue layer, inkjet layer, PET polyester film layer, holographic information layer, aluminum coating layer and transparent protective layer arranged in sequence from bottom to top. Although this patent improves the reading rate and reading speed, this production method is too complicated, expensive and easy to be cracked.

[0003] As an emerging anti-counterfeiting method, anti-counterfeiting ink has a good application prospect. It can realize the authenticity identification of products by adding specific anti-counterfeiting materials to the ink. This method can not only be combined with printing technology to facilitate large-scale production, but also provide unique identification features visually. In addition, anti-counterfeiting ink technology can provide multi-level anti-counterfeiting effects, such as displaying different colors through illumination of different wavelengths of light, or revealing hidden information under specific conditions, thereby enhancing the anti-counterfeiting effect.

[0004] Carbon quantum dots are a nano-scale carbon material with unique fluorescent properties that can emit specific fluorescent signals. The anti-counterfeiting marks used to make them are more difficult to imitate and copy, which improves the safety and credibility of anti-counterfeiting products. In addition, carbon quantum dots can be used to prepare fluorescent inks of different colors and different fluorescent properties through different surface modifications and synthesis methods, and then anti-counterfeiting marks can be customized according to the needs of different products. For example, patent CN119144323A discloses a method for chemical oxidation to regulate the multi-color luminescence of carbon dots. By regulating the surface oxidation degree of hydrophobic fluorescent carbon dots, multi-color carbon dots with a peak wavelength of the emission spectrum between 420 and 620 nm and colors ranging from blue to red are prepared at an excitation wavelength of 365 nm. Although carbon quantum dots have a very broad application prospect in anti-counterfeiting inks, fluorescent nanomaterials may change color or decay after being exposed to light or ultraviolet rays for a long time, resulting in a reduced anti-counterfeiting effect. In addition, the compatibility of nano-fluorescent materials with inks is not good, and the nano-materials themselves are unstable. In order to solve these problems, it is necessary to further study and improve the performance of nanofluorescent materials, improve their photostability and chemical resistance, and find economical and environmentally friendly preparation methods to ensure better application effects in anti-counterfeiting inks. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink, comprising the following steps:

[0008] Step 1, using phenolphthalein and m-phenylenediamine as raw materials, using NaOH solution as solvent, ultrasonic treatment to fully dissolve, and then performing high temperature and high pressure reaction to obtain a crude N-CDs solution;

[0009] Step 2, centrifuging the crude N-CDs solution;

[0010] Step 3, taking the supernatant after centrifugation, filtering, dialyzing, and then freeze-drying to obtain brown N-CDs powder;

[0011] Step 4, dissolving the obtained N-CDs powder in deionized water, adding glycerin as a thickener, and mixing to form a uniform and viscous mixed liquid, namely, the N-CDs fluorescent ink anti-counterfeiting ink.

[0012] Furthermore, in step 1, the molar ratio of phenolphthalein to m-phenylenediamine is 1:10, and the concentration of the NaOH solution is 0.01M.

[0013] Furthermore, in step 1, the ultrasonic treatment time is 10 minutes, and the temperature of the high temperature and high pressure reaction is 160° C. and the time is 8 hours.

[0014] Furthermore, the rotation speed of the centrifugal treatment in step 2 is 10000 rpm and the time is 10 min.

[0015] Furthermore, in step 3, the filtration is performed using a microporous filtration membrane with a pore size of 0.22 μm, the dialysis treatment is performed using a 500-1000 Da dialysis membrane for 3 days, and the freeze-drying time is 2 days.

[0016] Furthermore, the method also includes spraying NaOH solution and HCl solution on the N-CDs fluorescent anti-counterfeiting ink for acid-base treatment to obtain further advanced security ink.

[0017] Furthermore, the invention also includes adding cationic Hg to the N-CDs fluorescent ink anti-counterfeiting ink. 2+ , anion SO3 2- 、S2O3 2- , S 2- A further advanced security ink can be obtained by adding a stock solution.

[0018] The present invention also provides a carbon quantum dot fluorescent anti-counterfeiting ink prepared by the preparation method.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The present invention can synthesize carbon dot powder in a short time by screening suitable precursors and using a simple one-step hydrothermal method with the help of NaOH regulator, and dissolve it in deionized water to obtain carbon nano invisible anti-counterfeiting ink, which has low cost, high controllability and good repeatability;

[0021] 2. The carbon dots obtained by the present invention have excellent salt resistance, light stability and time stability;

[0022] 3. The carbon dots obtained by the present invention have a pH-sensitive luminescence effect, and the carbon dot inks prepared with different pH solutions have different fluorescence intensities;

[0023] 4. The anti-counterfeiting ink prepared by the carbon dots obtained in the present invention has pH-sensitive luminescence characteristics, so it can be applied to advanced security inks for encryption and decryption of handwritten information;

[0024] 5. The carbon dots obtained by the present invention can be fluorescently detected by Hg 2+ Selectively quenched, and the Hg 2 + The fluorescence quenching caused by it can therefore be achieved by adding different ions to the ink to achieve “turn-off-turn” encryption and decryption of invisible anti-counterfeiting inks.

[0025] 6. The anti-counterfeiting ink prepared with carbon dots obtained in the present invention exhibits different fluorescence properties when exposed to ultraviolet light on different paper substrates, further proving that the N-CDs have great application potential in anti-counterfeiting inks. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 In the figure, (a) is the TEM, HRTEM and particle size distribution diagram of N-CDs; (b) is the TGA and DTG diagram of N-CDs; (c) is the XRD diagram of N-CDs; (d) is the Raman spectrum of N-CDs; (e) is the infrared spectrum of N-CDs; (f) is the full XPS spectrum of N-CDs; (g) is the high-resolution C1s spectrum of N-CDs; (h) is the N1s spectrum of N-CDs; (i) is the O1s spectrum of N-CDs.

[0027] Figure 2 In the figure, (a) is the UV-visible absorption spectrum, excitation spectrum and emission spectrum of N-CDs; (b) is the 3D fluorescence spectrum of N-CDs; (c) is the emission spectrum of N-CDs under different excitations.

[0028] Figure 3 In the figure, (a) is a graph showing the effect of KCl concentration on the fluorescence intensity of N-CDs; (b) is a graph showing the effect of xenon lamp continuous irradiation time on the fluorescence intensity of N-CDs; (c) is a graph showing the effect of storage time on the fluorescence intensity of N-CDs; (d) is a graph showing the fluorescence emission spectra of N-CDs in different solvents.

[0029] Figure 4 In the figure, (a) is the fluorescence emission spectra of N-CDs in solvents with different pH values; (b) is the fluorescence intensity diagram of N-CDs in solvents with different pH values; (c) is the UV-visible absorption spectra of N-CDs in solvents with different pH values.

[0030] Figure 5 In the figure, (a) shows the effect of different metal ions on the fluorescence intensity of N-CDs; (b) shows the effect of different concentrations of Hg 2+ Titration curve of fluorescence intensity of N-CDs; (c) is the fluorescence quenching degree of N-CDs and Hg 2+ The nonlinear fitting diagram of the concentration; (d) is the fluorescence quenching degree of N-CDs and Hg 2+ Linear fit plot of concentration.

[0031] Figure 6 In the equation (a), N-CDs+Hg 2+ Selectivity diagram of solution for anions; (b~d) are different concentrations <h2 style=";text-align:left;direction:ltr">SO3<h2 style=";text-align:left;direction:ltr"> 2- <h2 style=";text-align:left;direction:ltr"> 、 S2O3 2- , S 2- For N-CDs+Hg 2+ Fluorescence titration curve and linear fitting diagram;

[0032] Figure 7 N-CDs were injected into fountain pens as fluorescent inks and written on three different papers: non-fluorescent paper, stone paper and filter paper. The images were then irradiated under sunlight and under UV lamps of 254nm and 365nm.

[0033] Figure 8 The fluorescent anti-counterfeiting ink prepared by N-CDs using water as solvent was used to write poems on non-fluorescent A4 paper and photographs were taken under sunlight, 245nm ultraviolet lamp, spraying NaOH+245nm ultraviolet lamp, and spraying HCl+245nm ultraviolet lamp.

[0034] Fig. 9 N-CDs with water, Hg 2+ Carbon dot solution, containing Hg 2+ +SO3 2- Carbon dot solution, containing Hg 2+ +S2O3 2- Carbon dot solution, containing Hg 2+ +S 2 Photos of text written on filter paper using fluorescent anti-counterfeiting ink prepared with carbon dots solution as solvent under sunlight and 365nm light (taking "Carbon dots, Shanxi University SXU, 2023" as an example). DETAILED DESCRIPTION

[0035] In order to further illustrate the technical solution of the present invention, the present invention is further described below through embodiments.

[0036] A method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink comprises the following steps:

[0037] Step 1, 0.0318 g of phenolphthalein and 0.108 g of m-phenylenediamine are used as raw materials, dissolved in 20 mL of 0.01 M (pH = 12) NaOH solution, ultrasonically treated for 10 min to fully dissolve, then placed in a 50 mL polytetrafluoroethylene liner and sealed in a stainless steel high-pressure hydrothermal reactor, placed in an oven, and subjected to high temperature and high pressure reaction at 160 ° C for 8 h to obtain a crude N-CDs solution;

[0038] Step 2, placing the crude N-CDs solution in a centrifuge for centrifugation at 10,000 rpm for 10 minutes;

[0039] Step 3, taking the supernatant after centrifugation, filtering it with a microporous filter membrane with a pore size of 0.22 μm, dialyzing it with a 500-1000 Da dialysis membrane for 3 days, and then freeze-drying it for 2 days to obtain a brown N-CDs powder;

[0040] Step 4, dissolving the obtained N-CDs powder in deionized water, adding glycerin as a thickener, and mixing to form a uniform and viscous mixed liquid, namely, the N-CDs fluorescent ink anti-counterfeiting ink.

[0041] The structural characterization of the carbon dots prepared in step 3 is as follows Figure 1 As shown:

[0042] like Figure 1 As shown in the TEM image (a), the synthesized N-CDs have a quasi-spherical structure, good uniformity and dispersibility, and a lattice structure of 0.21 nm. The particle size is mainly distributed around 2.37 nm.

[0043] like Figure 1 (b) TGA and DTG curves show that the weight loss of N-CDs before 169°C is 19.29%, which is due to the loss of water content. Decomposition occurs at 246.47-382.58°C, with a weight loss of 10.07%, which is the decomposition of organic matter. The stage between 415.87 and 736.21 is related to the combustion process of the skeleton, with a weight loss of 33.31%.

[0044] like Figure 1 As shown in the XRD pattern in (c), N-CDs have a typical broad peak near 26°, indicating that NCD has good crystallinity.

[0045] like Figure 1 As shown in the Raman spectrum in (d), the -1 Two characteristic G and D bands of N-CDs were observed at the 2 The plane vibration of the carbon part produces the D band and sp 3 The ordered G band is weaker than the disordered D band, and the G / D intensity ratio is 0.68, which reflects that N-CDs are partially disordered graphite-like structures.

[0046] like Figure 1 (e) is the Fourier transform infrared spectrum (FTIR) of N-CDs. -1 The peak at 1602 cm is attributed to the stretching vibration of OH / NH. -1 A sharp and strong peak at 1495 cm-1 corresponds to the stretching vibration of -C=O. -1 The peak at 840 cm represents the vibration of -C=C / -C=N bond. -1 The clear peak at is due to the out-of-plane bending vibration of the aromatic structure. These results indicate that N-CDs are more inclined to form hydrophilic carbon dots.

[0047] like Figure 1(f~i) XPS shows the chemical composition of N-CDs and the electronic structure of the elements. The full XPS spectrum shows three signals of C (74.68%), N (3.87%) and O (21.45%). The high-resolution C1s spectrum is fitted with three peaks at 284.1, 284.8 and 287.9 ​​eV, which are attributed to CC, CC / C=C and C=N. The N1s spectrum has three peaks near 398.6, 399.3 and 406.6 eV, corresponding to pyridinic N, amine nitrogen and graphitic N, respectively, indicating that the proportion of pyridinic N is much higher than that of other N-containing substances. The high-resolution O1s spectrum has two peaks, namely C=O (530.8 eV), CO (532.3 eV) and C-OH (533.3 eV).

[0048] The optical properties of the carbon dots prepared in step 3 are as follows Figure 2 As shown:

[0049] like Figure 2 As shown in (a-c), N-CDs show two absorption peaks at 289nm and 337nm. The absorption band near 289nm is attributed to the transient π electron cloud transition of the C=C bond in NCDs. The peak at 337nm is the n-π* transition of the surface functional groups of C=O, CN or C=N. The optimal excitation and emission wavelengths of N-CDs are 333nm and 432nm, respectively. In addition, when the excitation wavelength increases from 300nm to 340nm, the PL intensity first increases and then decreases, suggesting that N-CDs have the characteristics of being independent of the excitation wavelength. On the contrary, with the continuous increase of excitation, the PL emission gradually red-shifts from 430nm to 500nm, which may be related to the surface states associated with the functional groups and several different types of surface defect states.

[0050] The fluorescence intensity of the carbon dots obtained in step 3 is as follows Figure 3 As shown:

[0051] like Figure 3 As shown in (a), the fluorescence intensity of N-CDs remains relatively stable in KCl solutions of different concentrations (0-2 mol / L), indicating that N-CDs have good tolerance to salt concentration.

[0052] like Figure 3 As shown in (b), N-CDs were irradiated with a xenon lamp continuously for 60 min. The results showed that the N-CDs had good photostability.

[0053] like Figure 3 As shown in (c), the fluorescence intensity of N-CDs remains almost unchanged for up to 30 days, which further demonstrates that the N-CDs have good storage stability.

[0054] like Figure 3As shown in (d), the emission changes of N-CDs in different solvents. In the distilled water and ethanol environments with stronger polarity, the emission intensity is larger and the peak wavelength is slightly blue-shifted. At the same time, the emission intensity of N-CDs is significantly reduced in CCl4 and petroleum ether with weaker polarity. This indicates that the change of PL emission with solvent polarity may be attributed to the change of dipole moment caused by electron rearrangement on the surface of N-CDs.

[0055] The fluorescence intensity of the carbon dots prepared in step 3 in different pH solvents is as follows: Figure 4 As shown:

[0056] like Figure 4 As shown in (a-b), N-CDs showed the strongest fluorescence intensity when the pH value was 7. In acidic (pH = 2-7) and alkaline (pH = 7-12) environments, the fluorescence intensity decreased significantly, and the peak wavelength slightly red-shifted under acidic conditions, while no shift occurred under alkaline conditions, which may be caused by the protonation and deprotonation of the surface functional groups of N-CDs in strong acid-base environments.

[0057] like Figure 4 (c) The absorption spectra of N-CDs in different pH solutions show that in acidic solution, the peak at 336 nm disappears. On the contrary, the absorption of N-CDs in alkaline solution recovers and a new absorption peak appears at 554 nm.

[0058] The fluorescence intensity of the carbon dots prepared in step 3 in different concentrations of metal ions is as follows: Figure 5 As shown:

[0059] like Figure 5 As shown in (a), various metal ions can cause the fluorescence emission intensity of N-CDs to decrease, among which Hg 2+ The response was the most obvious.

[0060] like Figure 5 As shown in (b), different concentrations of Hg 2+ The emission spectrum in the presence of Hg 2+ As the concentration gradually increased from 0μM to 1000μM, the fluorescence intensity of the N-CDs solution showed a significant decreasing trend.

[0061] like Figure 5 As shown in (c), the Boltzmann equation is used to calculate the quenching degree F0-F and Hg 2+ The nonlinear fitting results of concentration, R 2 Calculated to be 0.99928.

[0062] like Figure 5As shown in (d), the relationship between fluorescence quenching efficiency and metal ion concentration is shown, with a linear range of 2.5 to 425 μM. According to the three-fold rule of standard deviation (SD) (LOD = 3SD / s, where s is the slope of the calibration curve), the detection limit is 0.978 μM.

[0063] The fluorescence intensity of the carbon dots prepared in step 3 in different anions and cations is as follows Figure 6 As shown:

[0064] like Figure 6 As shown in (a), Hg 2+ The fluorescence was quenched by adding SO3 2- 、S2O3 2- , S 2- The fluorescence of 2-Hydroxy-Sr-2+ anions can be obviously restored after ionization, while other anions cannot significantly restore the fluorescence, which indicates that reduced S ions have good selectivity for fluorescence recovery.

[0065] like Figure 6 As shown in (b~d), with the SO3 2- 、S2O3 2- , S 2- With the increase of concentration, the fluorescence intensity of N-CDs gradually increased. 2- In the concentration range of 0~150μM, S2O3 2- In the concentration range of 335-785 μM, S 2- In the concentration range of 30-530 μM, F0-F showed a good linear relationship with the concentration of sulfur-containing derivatives.

[0066] The application of the pH-responsive carbon quantum dot fluorescent anti-counterfeiting ink of this embodiment is as follows:

[0067] The test results of invisible anti-counterfeiting ink prepared by N-CDs solution on different paper bases are as follows: Figure 7 As shown:

[0068] N-CDs were injected into pens as fluorescent inks to observe the anti-counterfeiting effects on three different materials: non-fluorescent paper, stone paper, and filter paper. Under sunlight and 254nm and 365nm UV light boxes, no information written on the three types of paper could be seen under sunlight, but under 254nm UV light, green information could be observed on non-fluorescent paper and filter paper; under 365nm UV light, blue information could be observed on stone paper and filter paper. This different fluorescence characteristics emitted by different materials of paper and under different UV lights further proves that N-CDs have great potential in anti-counterfeiting applications.

[0069] The color changes of invisible anti-counterfeiting ink prepared by N-CDs solution under different pH solvent treatments are shown in Figure 2. Figure 8As shown:

[0070] Based on the pH-sensitive luminescence properties of N-CDs, the N-CDs solution was studied for the encryption and decryption of handwritten information, and the potential of this material in advanced security inks was explored. The design information handwritten on non-fluorescent A4 paper was used as the first step of encryption using N-CDs solution as ink. Figure 8 As shown, the written information could not be observed under daylight conditions. Then, when green fluorescence was observed under a 254nm UV lamp, the information could be decrypted. During the second encryption process, NaOH solution was sprayed on the paper and the green fluorescence disappeared on the paper. Therefore, the encrypted information could not be observed either under daylight or under UV irradiation. For the second decryption, HCl solution was sprayed on the paper and then dried in air. Under a 254nm UV lamp, the green luminescent handwriting was restored. In addition, this fluorescence can also be quenched by acid and reduced by base. Therefore, this N-CDs has excellent application potential in data encryption.

[0071] The color changes of invisible anti-counterfeiting ink prepared by N-CDs solution under different ions are shown in Figure 2. Fig. 9 As shown:

[0072] Based on the fact that N-CDs fluorescence can be detected by Hg 2+ The "turn-off-turn" ion sensing can restore the fluorescence of carbon dots by quenching and recovering the fluorescence of carbon dots, which can realize information encryption and decryption. Use N-CDs solution as ink to write "Carbon dots, Shanxi University SXU, 2023" on filter paper, such as Fig. 9 As shown, the writing cannot be observed under sunlight, but green fluorescence can be observed under 365nm ultraviolet light. 2+ The solution was used as anti-counterfeiting ink to write "Carbon dots, Shanxi University SXU, 2023" on filter paper. The original green fluorescence disappeared at 365nm. When SO3 2- 、S2O3 2- , S 2 Then, the same words were written on the filter paper and the green fluorescence was restored under 365nm ultraviolet light. Therefore, N-CDs can achieve multiple anti-counterfeiting of writing by adding different ions.

[0073] The above shows and describes the main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0074] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink, characterized in that: The following steps are involved: Step 1, using phenolphthalein and m-phenylenediamine as raw materials, using NaOH solution as solvent, ultrasonic treatment to fully dissolve, and then performing high temperature and high pressure reaction to obtain a crude N-CDs solution; Step 2, centrifuging the crude N-CDs solution; Step 3, taking the supernatant after centrifugation, filtering, dialyzing, and then freeze-drying to obtain brown N-CDs powder; Step 4, dissolving the obtained N-CDs powder in deionized water, adding glycerin as a thickener, and mixing to form a uniform and viscous mixed liquid, namely, the N-CDs fluorescent ink anti-counterfeiting ink.

2. The method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink according to claim 1, characterized in that: In the step 1, the molar ratio of phenolphthalein to m-phenylenediamine is 1:10, and the concentration of the NaOH solution is 0.01M.

3. The method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink according to claim 1, characterized in that: The ultrasonic treatment time in step 1 is 10 minutes, and the temperature of the high temperature and high pressure reaction is 160° C. and the time is 8 hours.

4. The method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink according to claim 1, characterized in that: The rotation speed of the centrifugal treatment in step 2 is 10000 rpm and the time is 10 min.

5. The method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink according to claim 1, characterized in that: In step 3, filtration is performed using a microporous filtration membrane with a pore size of 0.22 μm, dialysis is performed using a 500-1000 Da dialysis membrane for 3 days, and freeze drying is performed for 2 days.

6. The method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink according to claim 1, characterized in that: It also includes spraying NaOH solution and HCl solution on the N-CDs fluorescent ink anti-counterfeiting ink for acid and alkali treatment.

7. The method for preparing a pH and metal ion responsive carbon quantum dot fluorescent anti-counterfeiting ink according to claim 1, characterized in that: The invention also includes adding cationic Hg to the N-CDs fluorescent ink anti-counterfeiting ink. 2+ , anion SO3 2- 、S2O3 2- , S 2- of stock solution.

8. A carbon quantum dot fluorescent anti-counterfeiting ink prepared by the preparation method according to any one of claims 1 to 7.

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