Preparation method of novel multi-color carbon nanometer invisible anti-counterfeiting ink

Abstract

The present application relates to a kind of preparation method of novel multicolor carbon nano invisible anti-fake ink, to solve the technical problem of current paper information transmission insecurity, technical scheme is as follows: including the following steps: first, using sulfuric acid nile blue and salicylic acid as raw material, with anhydrous ethanol as solvent, by one-step solvothermal method, red fluorescent carbon dot powder is prepared, then the red fluorescent carbon dot powder is placed in centrifuge and centrifuged, the supernatant is taken, filtered with microporous filter membrane, then spin, evaporate, dry, after removing anhydrous ethanol, re-add secondary water, freeze-drying to obtain carbon dot powder, carbon dot powder is dissolved in organic solvent, carbon nano invisible anti-fake ink can be obtained.The present application can synthesize carbon dot powder in a short time by screening suitable precursor and using simple solvothermal method, carbon nano invisible anti-fake ink is prepared by dissolving in organic solvent, with low cost, high controllability, good repeatability, precursor diversity and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of anti-counterfeiting ink technology, specifically relating to a method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink. Background Technology

[0002] In recent years, counterfeiting has become a pervasive problem threatening individuals and society, potentially causing significant negative impacts on the public and even hindering economic growth through the circulation of illicit or counterfeit goods, documents, and currency. Therefore, counterfeiting carries serious environmental, health, economic, and social consequences. Developing a high-performance, economical, and traceable anti-counterfeiting product is therefore crucial. As human society continues to develop and information encryption methods evolve, the security of paper-based information transmission remains a significant challenge. Thus, employing high-tech solutions to prevent and stop counterfeiting and to encrypt information is of paramount importance.

[0003] To date, carbon quantum dots have been widely used as a high-quality new anti-counterfeiting ink for data encryption and storage due to their good biocompatibility, environmental friendliness, low cost and excellent resistance to photobleaching. As a fluorescent anti-counterfeiting material with excellent performance, carbon quantum dots have achieved considerable success in recent years.

[0004] Patent CN117384513A describes a fluorescent anti-counterfeiting security ink with carbon quantum dots and its preparation method. It mentions obtaining a water-soluble blue fluorescent product via a one-step hydrothermal method, which exhibits good stability and can be used as a fluorescent ink after dilution to a certain concentration. However, this carbon dot ink cannot achieve multi-color anti-counterfeiting, thus having certain limitations, and it cannot achieve secondary anti-counterfeiting. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems and provide a method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink includes the following steps:

[0008] Step 1) Red fluorescent carbon dot powder is prepared by a one-step solvothermal method using Nyl blue sulfuric acid and salicylic acid as raw materials and anhydrous ethanol as solvent.

[0009] Step 2) Place the red fluorescent carbon dot powder obtained in Step 1) into a centrifuge for centrifugation.

[0010] Step 3) Take the supernatant from the centrifugation, filter it with a microporous membrane, then rotate, evaporate and dry it to remove anhydrous ethanol, add secondary water again, freeze dry and obtain carbon dot powder.

[0011] Step 4) Dissolve the carbon dot powder obtained in step 3) in an organic solvent to obtain carbon nanotube invisible anti-counterfeiting ink.

[0012] Furthermore, in step 1), the mass ratio of Nyl Blue sulfate to salicylic acid is 1:10, and the mass ratio of salicylic acid to deionized water is 1:3.

[0013] Furthermore, in step 1), the synthesis temperature of the solvothermal method is 180℃, and the time is 4h to 8h.

[0014] Furthermore, in step 2), the centrifugation speed is 10,000 rpm and the centrifugation time is 10 min.

[0015] Furthermore, in step 3), the pore size of the microporous filter membrane is 0.22 μm, and the processing temperature for removing anhydrous ethanol is 40 °C.

[0016] Furthermore, any organic solvent can be used in step 4).

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. This invention uses a suitable precursor and a simple solvothermal method to synthesize carbon dots in a short time. After a series of treatments, carbon dot powder is obtained and dissolved in an organic solvent to produce carbon nanotube invisible anti-counterfeiting ink. It has low cost, high controllability and good repeatability.

[0019] 2. The carbon dots obtained by this invention have excellent salt resistance, acid and alkali resistance, and photobleaching resistance, and also have high fluorescence and high quantum yield;

[0020] 3. The carbon dots obtained by this invention have a solvent effect, and inks prepared with different solvents have different color characteristics. Therefore, they can be used in different scenarios in the same industry for anti-counterfeiting differentiation.

[0021] 4. After the anti-counterfeiting ink prepared with carbon dots obtained by the present invention is written on a paper base, the fluorescence intensity of the anti-counterfeiting carbon dot ink on the paper base is not easily quenched in the air. That is, after a week, after the paper base is soaked in water for 30 minutes and dried, it still has a strong fluorescence intensity when irradiated under ultraviolet light. It has good compatibility and stability for future anti-counterfeiting ink application scenarios.

[0022] 5. The anti-counterfeiting ink formulated with carbon dots obtained in this invention can exhibit strong fluorescent anti-counterfeiting effects on different paper bases, and also has different color development effects under different ultraviolet light irradiation. Therefore, it has good prospects in multiple anti-counterfeiting aspects, and can also have the same anti-counterfeiting effect on paper with printed text. Therefore, it also has good prospects in the precision printing industry. Attached Figure Description

[0023] Figure 1 (A) is a TEM image of the R-CDs of the present invention;

[0024] Figure 1 (B) is a particle size distribution diagram of the R-CDs of the present invention;

[0025] Figure 2 (A) is the infrared spectrum of the R-CDs of the present invention;

[0026] Figure 2 (B) is the XPS full spectrum of the R-CDs of this invention;

[0027] Figure 2 (C) is the high-resolution C1s spectrum of the R-CDs of the present invention;

[0028] Figure 2 (D) is the N1s spectrum of the R-CDs of this invention;

[0029] Figure 2 (E) is the O1s spectrum of the R-CDs of the present invention;

[0030] Figure 2 (F) is the S2p spectrum of the R-CDs of this invention;

[0031] Figure 3 (A) shows the UV-Vis absorption spectrum of the R-CDs of the present invention and its fluorescence spectrum in ethanol;

[0032] Figure 3 (B) is the 3D fluorescence spectrum of the R-CDs of the present invention;

[0033] Figure 3 (C) shows the optimal fluorescence emission spectra of the R-CDs of the present invention in methanol, ethanol, acetone and tetrahydrofuran;

[0034] Figure 3 (D) is a graph showing the effect of NaCl concentration on the fluorescence intensity of R-CDs in this invention;

[0035] Figure 3 (E) is a graph showing the effect of pH value on the fluorescence intensity of R-CDs in this invention;

[0036] Figure 3 (F) is a graph showing the effect of continuous xenon lamp irradiation time on the fluorescence intensity of R-CDs in this invention;

[0037] Figure 4 These are color photographs of the R-CDs in different solvents (sunlight, 254nm UV lamp, 365nm UV lamp) in this invention.

[0038] Figure 5 is a photographic image of text written on stone paper with the隐形 anti-counterfeiting inks of different concentrations prepared from R-CDs of the present invention using absolute ethanol as the solvent, under different light irradiation (taking the characters "Shanxi University" as an example);

[0039] Figure 6 In the present invention, the 0.1 mg / ml multi-color anti-counterfeiting隐形 inks prepared with ethanol, petroleum ether, tetrahydrofuran and water as solvents respectively drawn on stone paper under irradiation of daylight, 254 nm ultraviolet lamp and 365 nm ultraviolet lamp and the photographic image of the written character "Xue";

[0040] Figure 7 is a photographic image of the characters "Cheng Gong" written on stone paper with 0.1 mg / ml multi-color anti-counterfeiting隐形 inks prepared with petroleum ether, tetrahydrofuran and water as solvents of the present invention under irradiation of daylight, 254 nm ultraviolet lamp and 365 nm ultraviolet lamp respectively;

[0041] Figure 8 In the present invention, a cross shape is used to represent the anti-counterfeiting carbon dots with ethanol, shape is used to represent the anti-counterfeiting carbon dots with petroleum ether, represents the anti-counterfeiting carbon dots with tetrahydrofuran; the three kinds of anti-counterfeiting inks are coated on different positions of the same discarded bank card, and the photographic images are obtained under irradiation of daylight and 254 nm ultraviolet lamp respectively;

[0042] Figure 9 is a photographic image of different characters written with anti-counterfeiting carbon dots on light yellow A4 paper printed with the character "Ying" in the present invention under irradiation of daylight and 254 nm ultraviolet lamp respectively;

[0043] Figure 10 The above-mentioned Figure 7 paper sheets, after being stored for 1 day and 7 days respectively, are then soaked in water for half an hour, dried, and then irradiated under daylight, 254 nm ultraviolet lamp and 365 nm ultraviolet lamp respectively to obtain the photographic images.

[0044] wherein: R-CDs represents red fluorescent carbon dots. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the accompanying drawings and examples.

[0046] PREPARATION OF MULTI-COLOR CARBON NANO INVISIBLE ANTI-COUNTERFEITING INKS

[0047] A preparation method of a novel multi-color carbon nano invisible anti-counterfeiting ink, comprising the following steps:

[0048] Step 1) Using 7.3 mg Nell Blue sulfuric acid and 70 mg salicylic acid as raw materials, the mixture was fully dissolved in 20 mL of anhydrous ethanol and then transferred to a 50 mL hydrothermal reactor. The mixture was reacted at 180 °C for 4 h to obtain red fluorescent carbon dot powder.

[0049] Step 2) Place the red fluorescent carbon dot powder obtained in Step 1) into a centrifuge and centrifuge at 10,000 rpm for 10 min;

[0050] Step 3) Take the supernatant from the centrifugation, filter it with a microporous membrane with a pore size of 0.22 μm, then rotate, evaporate and dry it at 40 °C. After removing anhydrous ethanol, add deionized water again, freeze dry and obtain R-CDs powder.

[0051] Step 4) Dissolve the carbon dot powder obtained in step 3) in methanol, ethanol, acetone and tetrahydrofuran respectively to obtain different carbon nanotube invisible anti-counterfeiting inks.

[0052] In step 1), Nell Blue sulfate and salicylic acid can also be any other combination with a mass ratio of 1:10, and the amount of secondary water added should be adjusted accordingly based on a mass ratio of salicylic acid to secondary water of 1:3.

[0053] The synthesis time for the solvothermal method in step 1) can also be any value between 4h and 8h.

[0054] The carbon dot powder in step 4) can also be dissolved in any other organic solvent.

[0055] like Figure 1 As shown, the morphology and size-related information of R-CDs were obtained using transmission electron microscopy (TEM). Figure 1 As shown in A, the synthesized R-CDs exhibit a quasi-spherical structure, good uniformity and dispersibility, and a lattice structure of 0.23 nm. Figure 1 B indicates that the particle size distribution of R-CDs is 2.62 ± 0.09 nm.

[0056] Structural characterization of red fluorescent carbon dots

[0057] like Figure 2 A represents the functional group information contained in R-CDs, 3425.96cm -1 The broad absorption peaks around 2923.60 cm⁻¹ are attributed to the stretching vibration of NH / OH. -1 The absorption peak at 1522.68-1772.65 cm⁻¹ is due to the stretching vibration of CH₄. -1 The sharp peak indicates the presence of C=C, C=N, and C=O functional groups on the surface of R-CDs, 1315.10 cm⁻¹. -1The absorption peak at 1110.21 cm⁻¹ is due to the stretching vibration of CN. -1 The peak value at 779.32 cm⁻¹ represents the stretching vibration of CO. -1 For the stretching vibration of CS;

[0058] Figure 2 B indicates that R-CDs are composed of four elements: C, N, O, and S. Characteristic peaks of S2p, C1s, N1s, and O1s were found at 168.05 eV, 284.22 eV, 398.85 eV, and 531.68 eV, respectively. The contents of C, N, O, and S elements were calculated to be 71.48%, 5.28%, 21.25%, and 1.99%, respectively.

[0059] C1s spectrum as follows Figure 2 As shown in Figure C, four peaks were found that belong to C=O (288.3eV), CN (285.9eV), CS (284.8eV) and CC / C=C (284.1eV), respectively;

[0060] N1s spectrum as follows Figure 2 D shows three peaks: pyridine N (398.8 eV), amino N (399.5 eV), and graphitic N (401.6 eV);

[0061] O1s high-resolution XPS spectrum as follows Figure 2 E shows that the O element mainly exists in the form of C-OH / COC (533.5 eV) and C=O (531.7 eV);

[0062] S2p spectrum as follows Figure 2 The F-display indicates that the S element exists primarily in two forms: S2p3 / 2 (168.0 eV) and S2p1 / 2 (169.1 eV).

[0063] Optical properties of red fluorescent carbon dots

[0064] Figure 3 A and Figure 3 B represents the fluorescence and UV-Vis absorption spectra of R-CDs. The strong absorption peak at 235 nm in the UV-Vis absorption spectrum may be due to the π-π* transition in the sp2 domain, the absorption peak at 305 nm may be due to the n-π* transition of C=N and C=O bonds, and the peak at 548 nm may originate from the surface functional groups of R-CDs. The fluorescence spectrum shows that the optimal excitation and emission of R-CDs are 545 nm and 621 nm, respectively.

[0065] Depend on Figure 3C indicates that the optimal emission peaks of R-CDs in methanol, ethanol, acetone, and tetrahydrofuran are 625 nm, 621 nm, 604 nm, and 593 nm, respectively. R-CDs have only one fluorescence emission center and exhibit wavelength independence. Using cresol violet as a standard, the quantum yields of R-CDs in different solvents were measured as follows: water 3.12%, methanol 40.90%, ethanol 57.63%, acetone 67.38%, and tetrahydrofuran 79.37%.

[0066] exist Figure 3 In D, the fluorescence changes of R-CDs under different NaCl concentrations were tested, and the results showed that the fluorescence intensity of R-CDs was stable under different salt concentrations.

[0067] exist Figure 3 In E, the pH stability of R-CDs was tested using a prepared BR buffer solution, and it was found that the fluorescence intensity of R-CDs remained basically unchanged within the pH range of 2-12.

[0068] Figure 3 F indicates that the fluorescence intensity of R-CDs did not change significantly under continuous xenon lamp irradiation for 120 min;

[0069] In summary, R-CDs exhibit wavelength independence and good resistance to salt, acids, alkalis, and photobleaching.

[0070] Color changes of red fluorescent carbon dots in different solvents

[0071] like Figure 4 As shown, the color of the carbon dots changes with the solvent. Under sunlight, the solution displays a variety of colors, including purple, red, plum, orange, pink, and transparent, laying the foundation for the development of multi-color inks. The colors under 254nm and 365nm ultraviolet lamps are significantly different from those under sunlight, laying the foundation for the development of double-layer anti-counterfeiting inks.

[0072] Test results of multicolor carbon nanotube invisible anti-counterfeiting ink with ethanol as solvent on filter paper and stone paper

[0073] like Figure 5 As shown, R-CDs solutions of 0.1, 0.2, 0.5, and 1 mg / ml were prepared respectively. When the ink was applied to non-fluorescent stone paper with a brush, no obvious traces were found under sunlight. The red characters appeared under 254nm ultraviolet light. Under 365nm ultraviolet light, the 0.1 and 0.2 mg / ml solutions also left no traces, while the 0.5 and 1 mg / ml solutions showed slight red traces. By switching between sunlight at 254nm and 365nm, the function of multiple invisible anti-counterfeiting inks was achieved.

[0074] Test results of multi-color carbon nano invisible anti-counterfeiting inks using ethanol, petroleum ether, tetrahydrofuran and water as solvents on stone paper

[0075] as shown in Figure 6 , 7 shown, under the premise that Figure 5 (it is known that the best anti-counterfeiting effect is achieved at a concentration of 0.1 mg / ml), the anti-counterfeiting inks with appropriate concentrations using petroleum ether and tetrahydrofuran as solvents were prepared, and photographed under natural light, 254 nm and 365 nm ultraviolet lamps respectively. It is found that the invisible ink can present different colors and different forms, has a multi-color anti-counterfeiting effect, and the anti-counterfeiting effect is better under 254 nm, with higher color development of carbon dots.

[0076] Test results of multi-color carbon nano invisible anti-counterfeiting ink on bank cards

[0077] as Figure 8 shown, taking scrapped bank cards as an example: the cross shape represents the anti-counterfeiting ink with ethanol solvent, the shape represents the anti-counterfeiting ink with petroleum ether solvent, and the shape represents the anti-counterfeiting ink with tetrahydrofuran solvent. Through testing the three anti-counterfeiting inks at different positions on the card, it is found that the secondary anti-counterfeiting effect can be achieved on bank cards.

[0078] Test results of multi-color carbon nano invisible anti-counterfeiting ink on A4 paper

[0079] as Figure 9 shown, taking an A4 image printed with the Chinese character "Ying" (meaning shadow) as an example, the anti-counterfeiting inks with different solvents were coated near the printed paper in a distinguishable manner, and it was found that the multi-color anti-counterfeiting effect was also achieved.

[0080] Stability test results of multi-color carbon nano invisible anti-counterfeiting ink

[0081] as Figure 10 shown, since water has a wide range of application scenarios in daily life, in order to detect whether water has a quenching effect on the ink based on stone paper and even filter paper as the medium, this example tests the Figure 7 shown paper samples with written characters that have been stored for 1 day and 7 days were soaked in tap water for half an hour and then dried, and irradiated under natural light, 254 nm and 365 nm ultraviolet lamps respectively. It is found that there is no obvious change in color and color development, indicating that the ink has good stability and still has the anti-counterfeiting function in a humid environment.

Claims

1. A method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink, characterized in that, Includes the following steps: Step 1) Red fluorescent carbon dot powder is prepared by a one-step solvothermal method using Nyl blue sulfuric acid and salicylic acid as raw materials and anhydrous ethanol as solvent. Step 2) Place the red fluorescent carbon dot powder obtained in Step 1) into a centrifuge for centrifugation. Step 3) Take the supernatant from the centrifugation, filter it with a microporous membrane, then rotate, evaporate and dry it to remove anhydrous ethanol, add secondary water again, freeze dry and obtain carbon dot powder. Step 4) Dissolve the carbon dot powder obtained in step 3) in an organic solvent to obtain carbon nanotube invisible anti-counterfeiting ink.

2. The method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink according to claim 1, characterized in that, In step 1), the mass ratio of Nyl Blue sulfate to salicylic acid is 1:10, and the mass ratio of salicylic acid to deionized water is 1:

3.

3. The method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink according to claim 1, characterized in that, In step 1), the solvothermal synthesis temperature is 180℃ and the time is 4h to 8h.

4. The method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink according to claim 1, characterized in that, In step 2), the centrifugation speed is 10,000 rpm and the centrifugation time is 10 min.

5. The method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink according to claim 1, characterized in that, In step 3), the pore size of the microporous filter membrane is 0.22 μm, and the processing temperature for removing anhydrous ethanol is 40 °C.

6. The method for preparing a novel multicolor carbon nanotube invisible anti-counterfeiting ink according to claim 1, characterized in that, The organic solvent used in step 4) can be any kind of organic solvent.

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