Preparation of a dual-photoresponsive anti-counterfeiting ink

Abstract

This invention provides a method for preparing a dual-photoresponsive anti-counterfeiting ink, specifically comprising: (1) mixing a carbon source with a nitrogen source, a modifier, and a solvent, and ultrasonically reacting the mixture for a period of time to obtain a carbon quantum dot precursor liquid; (2) pouring the carbon quantum dot precursor liquid obtained in step (1) into a tetrafluoroethylene liner of a stainless steel high-temperature and high-pressure autoclave, placing the autoclave in a forced-air drying oven, and reacting at high temperature for a period of time to obtain carbon quantum dot ink. The preparation method of this invention is simple; a carbon quantum dot ink with two photoresponsive effects can be prepared in a single solvothermal step, simplifying the preparation process and facilitating application. The handwriting written with the prepared dual-photoresponsive anti-counterfeiting ink emits strong green fluorescence under 365nm ultraviolet light irradiation, and the handwriting can be clearly displayed under 980nm infrared light, providing dual encryption and improving the anti-counterfeiting performance of the material.

Description

Technical Field

[0001] This invention relates to the field of anti-counterfeiting ink manufacturing technology, specifically to the preparation of a dual-photoresponsive anti-counterfeiting ink. Background Technology

[0002] With the rapid development of the commodity economy, an increasing number of counterfeit and substandard products have entered the market, negatively impacting economic and social stability. Counterfeit documents, currency, and pharmaceutical products can even threaten public security and harm consumers' health. Therefore, developing effective and easily identifiable anti-counterfeiting technologies is crucial. Currently used barcodes, QR codes, and laser holographic anti-counterfeiting technologies with dazzling effects are easily copied, offering only moderate anti-counterfeiting effectiveness. Photoresponsive anti-counterfeiting materials, however, are difficult to imitate, possessing accurate and easily identifiable anti-counterfeiting characteristics. They can be identified using readily available ultraviolet and infrared lamps, making them a hot research topic.

[0003] Currently, commonly used photoresponsive anti-counterfeiting materials mainly include inorganic photoluminescent materials, such as phosphors doped with rare-earth ions and phosphors doped with transition metal ions; semiconductor quantum dots, such as ZnO, Cd-containing quantum dots, and perovskite quantum dots, which are currently under extensive research; organic light-emitting materials; metal-organic framework materials; and carbon quantum dots. These materials can produce corresponding photoluminescence phenomena under excitation by 254nm ultraviolet light, 365nm ultraviolet light, or 980nm infrared light, as well as various wavelengths of light, providing a good anti-counterfeiting effect on product packaging. However, current photo-response anti-counterfeiting materials generally emit fluorescence under illumination of one or two or more wavelengths of light, resulting in a relatively simple photoresponse effect and weak anti-counterfeiting performance. For example, Chinese patent application CN112175449A discloses an ultra-stable, printable water-based fluorescent anti-counterfeiting ink and its preparation method. The water-based fluorescent anti-counterfeiting ink is prepared by the following method: 1) preparing a quantum dot aqueous solution; 2) preparing the water-based fluorescent anti-counterfeiting ink: adding water, ethanol, and ethylene glycol to the QDs / A / B quantum dot aqueous solution to dilute the quantum dots, and adjusting the pH of the solution to 6.0-10.0 with a pH adjuster to obtain the water-based fluorescent anti-counterfeiting ink. This quantum dot fluorescent ink has a low concentration, high fluorescence intensity, and strong storage stability. Under ordinary light, it is a pale yellow or pale red transparent liquid. The printed pattern is invisible under ordinary light, but a clear fluorescent pattern appears under 365nm ultraviolet light excitation, exhibiting high anti-counterfeiting and confidentiality properties. Another example is Chinese patent application CN106147398A, which discloses an anti-counterfeiting ceramic ink and its preparation method, belonging to the field of ceramic inks. Its components include: 30-45% by weight ceramic pigment, 45-65% by weight solvent, 5-20% by weight binder, 1-5% by weight film-forming resin, and 0.05-1% by weight anti-counterfeiting powder. The preparation method of the anti-counterfeiting ceramic ink includes the following steps: After thoroughly mixing and dispersing the ceramic pigment, solvent, binder, film-forming resin, and anti-counterfeiting powder, the mixture is ground and filtered to control the average particle size of the pigment to be 200-600 nm, with a maximum particle size less than 1000 nm, thus obtaining the anti-counterfeiting ceramic ink. The anti-counterfeiting powder is a powder with a sodium tungstate or sodium molybdate matrix and a small amount of yttrium, thulium, samarium, europium, dysprosium, erbium, or ytterbium added. This anti-counterfeiting ink can withstand a high temperature of 1300 degrees Celsius and generates infrared light after being excited by an infrared laser, which can be identified by an infrared detector to distinguish authenticity. However, there are no reports in the existing technology regarding anti-counterfeiting inks that simultaneously possess both blue and red light response effects. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a dual-light-responsive anti-counterfeiting ink. The preparation process is simple, and the resulting anti-counterfeiting ink exhibits both blue and red light response effects. The written characters emit strong green fluorescence under 365nm ultraviolet light irradiation, and the characters are clearly visible under 980nm infrared light. This dual encryption enhances the anti-counterfeiting performance of the material.

[0005] To achieve the above technical solution, the present invention provides a method for preparing a dual-photoresponsive anti-counterfeiting ink, which specifically includes the following steps:

[0006] S1, preparation of solvent,

[0007] N,N-dimethylamide and acetic acid were mixed and stirred in a 1:1 ratio to prepare a mixed solvent of N,N-dimethylamide and acetic acid for later use.

[0008] Preparation of S2, carbon quantum dot precursor fluid

[0009] Weigh an appropriate amount of carbon source and add it to the N,N-dimethylamide and acetic acid mixed solvent obtained in step S1. Stir with a glass rod to completely dissolve the carbon source. Then weigh an appropriate amount of nitrogen source and add it to the mixture. Stir with a glass rod to completely dissolve the nitrogen source. The mass ratio of carbon source to nitrogen source is 2:1-2. Then add an appropriate amount of acetonitrile to the mixture. After stirring evenly, place it in an ultrasonic cleaner and ultrasonically vibrate for 5-10 minutes to obtain carbon quantum dot precursor liquid.

[0010] S3. Preparation of anti-counterfeiting ink

[0011] The carbon quantum dot precursor liquid obtained in step S2 is poured into the tetrafluoroethylene liner of a stainless steel high-temperature and high-pressure reactor. The high-temperature and high-pressure reactor is placed in a forced-air drying oven and the temperature is set to 170-200℃. The reaction is carried out by solvothermal method for 2-4 hours. After cooling to room temperature, the pseudo ink is obtained.

[0012] Preferably, in step S2, the carbon source is one or a combination of citric acid, diammonium hydrogen citrate, triammonium citrate, and o-phenylenediamine, and the nitrogen source is one or a combination of urea, tris(hydroxymethyl)aminomethane, and NH3.

[0013] Preferably, the mass ratio of carbon source to nitrogen source added in step S2 is 2:1.

[0014] Preferably, in step S2, 2g of citric acid is weighed and added to 14ml of the N,N-dimethylamide and acetic acid mixed solvent obtained in step S1. The mixture is stirred with a glass rod until the citric acid is completely dissolved. Then, 1g of urea is weighed and added to the mixture. The mixture is stirred with a glass rod until the urea is completely dissolved. Then, 1ml of acetonitrile is added dropwise to the mixture. After stirring evenly, the mixture is placed in an ultrasonic cleaner and ultrasonically vibrated at 100W power for 5 minutes to obtain the carbon quantum dot precursor fluid.

[0015] Preferably, in step S3, the prepared carbon quantum dot precursor liquid is poured into the tetrafluoroethylene liner of a 20ml stainless steel high-temperature and high-pressure autoclave, the high-temperature and high-pressure autoclave is placed in a forced-air drying oven, the temperature is set to 180℃, and the reaction is carried out by solvothermal method for 3 hours. After cooling to room temperature, the pseudo ink is obtained.

[0016] The beneficial effects of the preparation and apparatus for a dual-photoresponsive anti-counterfeiting ink provided by this invention are as follows:

[0017] (1) The preparation method of the present invention is simple. Carbon quantum dot ink with two photoresponse effects can be prepared by a one-step solvothermal method, which simplifies the preparation process and is conducive to application.

[0018] (2) The handwriting written by the dual photoresponsive anti-counterfeiting ink prepared by the present invention can emit strong green fluorescence under 365nm ultraviolet light and can display clear handwriting under 980nm infrared light. The dual encryption improves the anti-counterfeiting performance of the material. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0020] Figure 2 These are comparative images of the appearance of Example 1, Comparative Example 1, and Comparative Example 2.

[0021] Figure 3 The images show comparisons of Example 1, Comparative Example 1, and Comparative Example 2 under illumination and 365nm ultraviolet light.

[0022] Figure 4 The images show comparisons of Example 1, Comparative Example 1, and Comparative Example 2 under 365nm ultraviolet light irradiation and 980nm infrared light irradiation, respectively. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0024] Example 1: Preparation of a dual photoresponsive anti-counterfeiting ink.

[0025] Reference Figure 1 As shown, the preparation of a dual-photoresponsive anti-counterfeiting ink specifically includes the following steps:

[0026] S1. Prepare a solvent using N,N-dimethylamide (solvent): acetic acid (modifier) ​​in a 1:1 ratio. Measure 7 ml of N,N-dimethylamide and 7 ml of acetic acid, and mix the N,N-dimethylamide and acetic acid.

[0027] S2. Weigh 2g of citric acid (carbon source) and add it to the mixture. Stir with a glass rod until the citric acid is completely dissolved. Then weigh 1g of urea (nitrogen source) and add it to the mixture. Stir with a glass rod until the urea is completely dissolved. Add 1ml of acetonitrile (solvent) to the mixture. Stir evenly and place it in an ultrasonic cleaner. Ultrasonicate at 100W power for 5 minutes to obtain carbon quantum dot precursor fluid.

[0028] S3. Pour the prepared carbon quantum dot precursor liquid into the tetrafluoroethylene liner of a 20ml stainless steel high-temperature and high-pressure reactor. Place the high-temperature and high-pressure reactor in a forced-air drying oven and set the temperature to 180℃. React for 3 hours using a solvothermal method. Cool down to room temperature and transfer the carbon quantum dot ink in the reactor liner to a light-proof glass sample bottle for later use.

[0029] Comparative Example 1

[0030] Photoresponsive anti-counterfeiting ink is prepared by the following method:

[0031] (1) Measure 20ml of deionized water, weigh 2.00g of citric acid, add citric acid to deionized water, stir with a glass rod to completely dissolve citric acid, stir evenly and place in an ultrasonic cleaner, sonicate at 100w power for 5min to obtain carbon quantum dot precursor fluid.

[0032] (2) Pour the prepared carbon quantum dot precursor liquid into the tetrafluoroethylene liner of the stainless steel high-temperature and high-pressure reactor, place the high-temperature and high-pressure reactor in a forced-air drying oven, set the temperature to 180℃, react by hydrothermal method for 3 hours, cool down to room temperature, and transfer the carbon quantum dot ink in the reactor liner to a light-proof glass sample bottle for later use.

[0033] Comparative Example 2

[0034] Photoresponsive anti-counterfeiting ink is prepared by the following method:

[0035] (1) Measure 14 ml of N,N-dimethylamide (solvent), weigh 2 g of citric acid and add it to the mixture. Stir with a glass rod to completely dissolve the citric acid. Then weigh 1 g of urea and add it to the mixture. Stir with a glass rod to completely dissolve the urea. Add 1 ml of acetonitrile to the mixture. Stir evenly and place it in an ultrasonic cleaner. Ultrasonicate at 100 W power for 5 min to obtain carbon quantum dot precursor fluid.

[0036] (2) Pour the prepared carbon quantum dot precursor liquid into the tetrafluoroethylene liner of the stainless steel high-temperature and high-pressure reactor, place the high-temperature and high-pressure reactor in a forced-air drying oven, set the temperature to 180℃, react for 10h by solvothermal method, cool down to room temperature, and transfer the carbon quantum dot ink in the reactor liner to a light-proof glass sample bottle for later use.

[0037] Substrate performance testing

[0038] The performance of Example 1, Comparative Example 1 and Comparative Example 2, and the prepared carbon quantum dot inks were tested. The test items and methods are as follows:

[0039] 1. Ultraviolet light response of carbon quantum dot ink: The response of writing on carbon quantum dot ink under 365nm ultraviolet light was observed using a multifunctional dark box ultraviolet analyzer.

[0040] 2. Infrared response of carbon quantum dot ink: The response of the writing on carbon quantum dot ink under 980nm infrared light was observed using an FDD-500 infrared camera.

[0041] Experimental Results Analysis

[0042] from Figure 2 It can be seen that Example 1 (the dual photoresponsive ink prepared by the present invention) and Comparative Example 2 are brownish-black, while Comparative Example 1 prepared by the method of Comparative Example 1 is transparent.

[0043] Figure 3 The images show comparisons of Example 1, Comparative Example 1, and Comparative Example 2 under illumination and 365nm ultraviolet light. Figure 3 a is a photograph of the dual photoresponsive anti-counterfeiting ink prepared in Example 1 under lightbox illumination; Figure 3 b is a photograph of the dual photoresponsive anti-counterfeiting ink prepared in Example 1 under 365nm ultraviolet light in a light box; Figure 3 c is a photograph of the ink writing in comparison sample 1 under the lightbox illumination; Figure 3 d is a photograph of the ink writing in comparison sample 1 under 365nm ultraviolet light in a light box; Figure 3 e is a photograph of the ink writing in comparison sample 2 under the lightbox illumination; Figure 3 f is a photograph of the ink writing in comparison sample 2 under 365nm ultraviolet light in a lightbox. From Figure 3 As can be seen, the writing produced by the carbon quantum dot ink prepared in Example 1 of this invention emits a strong bright green fluorescence under 365nm ultraviolet light irradiation and is also clearly visible under illumination. The anti-counterfeiting ink prepared in Comparative Example 1 cannot display writing under illumination, but can display writing under 365nm ultraviolet light irradiation. Comparative Example 2 can also display writing under both illumination and 365nm ultraviolet light irradiation.

[0044] Figure 4 The images show comparisons of Example 1, Comparative Example 1, and Comparative Example 2 under 365nm ultraviolet light irradiation and 980nm infrared light irradiation, respectively. Figure 4 g is a magnified image of the handwriting of the dual photoresponsive anti-counterfeiting ink prepared in Example 1 under 365nm ultraviolet light; Figure 4 h is a magnified image of the handwriting of the dual photoresponsive anti-counterfeiting ink prepared in Example 1 under 980nm infrared light irradiation; Figure 4 i is a magnified image of the ink writing in comparison sample 1 under 365nm ultraviolet light; Figure 4 j is a magnified image of the ink writing in comparison sample 1 under 980nm infrared light illumination; Figure 4 k is a magnified image of the ink writing in comparison sample 2 under 365nm ultraviolet light; Figure 4 m is a magnified image of the ink writing in comparison sample 2 under 980nm infrared light. From Figure 4 It can be seen that the writing produced by the carbon quantum dot ink prepared in Example 1 of this invention emits strong bright green fluorescence under 365nm ultraviolet light irradiation and can also display clear writing under 980nm infrared light irradiation. The anti-counterfeiting ink prepared in Comparative Example 1 can display writing under 365nm ultraviolet light irradiation, but cannot display writing under 980nm infrared light irradiation. Comparing the data of Example 1 and Comparative Example 2, it can be seen that the addition of the modifier acetic acid has a decisive influence on the infrared response of the ink.

[0045] from Figure 2 , Figure 3 and Figure 4As can be seen, the writing produced by the carbon quantum dot ink prepared in Example 1 of this invention emits strong bright green fluorescence under 365nm ultraviolet light irradiation, and the writing is visible under 980nm infrared light, providing double encryption and improving the anti-counterfeiting performance of the material. In contrast, the carbon quantum dot ink prepared in Comparative Example 1 is a transparent suspension; the writing is not visible after drying, and it only emits weak fluorescence under 365nm ultraviolet light irradiation, but does not respond to infrared light. The writing produced by the carbon quantum dot ink prepared in Comparative Example 2 only emits green fluorescence under 365nm ultraviolet light irradiation, but does not respond to infrared light.

[0046] The above description is only a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in the embodiments and drawings. Therefore, any equivalent or modified embodiments made without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a dual light-responsive security ink, characterized in that Specifically comprising the following steps: S1, preparation of solvent, After mixing N,N-dimethylamide and acetic acid in a ratio of 1:1 and stirring evenly, an N,N-dimethylamide and acetic acid mixed solvent is prepared for standby; S2, preparation of carbon quantum dot precursor liquid, An appropriate amount of carbon source is weighed and added to the N,N-dimethylamide and acetic acid mixed solvent prepared in step S1, and a glass rod is used to stir until the carbon source is completely dissolved. Then, an appropriate amount of nitrogen source is weighed and added to the mixed solution, and a glass rod is used to stir until the nitrogen source is completely dissolved. The mass ratio of the carbon source to the nitrogen source is 2:

1. Then, an appropriate amount of acetonitrile is added dropwise to the mixed solution, and after stirring evenly, it is placed in an ultrasonic cleaning instrument for ultrasonic oscillation for 5-10 min to prepare a carbon quantum dot precursor liquid. S3, preparation of anti-fake ink, The carbon quantum dot precursor liquid prepared in step S2 is poured into the tetrafluoroethylene inner liner of a stainless steel high-temperature and high-pressure kettle, and the high-temperature and high-pressure kettle is placed in a forced air drying oven with a temperature setting of 170-200 ℃. After 2-4 h of solvothermal reaction, it is cooled to room temperature to obtain anti-fake ink. In step S2, the carbon source is one or a combination of citric acid, diammonium hydrogen citrate, triammonium citrate, and o-phenylenediamine, and the nitrogen source is one or a combination of urea, tris(hydroxymethyl) aminomethane, and NH3.

2. The method for preparing dual-photoresponsive anti-counterfeiting ink as described in claim 1, characterized in that: In step S2, 2 g of citric acid is weighed and added to 14 ml of the N,N-dimethylamide and acetic acid mixed solvent prepared in step S1, and a glass rod is used to stir until the citric acid is completely dissolved. Then, 1 g of urea is weighed and added to the mixed solution, and a glass rod is used to stir until the urea is completely dissolved. Then, 1 ml of acetonitrile is added dropwise to the mixed solution, and after stirring evenly, it is placed in an ultrasonic cleaning instrument for ultrasonic oscillation at a power of 100 w for 5 min to prepare a carbon quantum dot precursor liquid.

3. The method for preparing dual-photoresponsive anti-counterfeiting ink as described in claim 1, characterized in that: In step S3, the prepared carbon quantum dot precursor liquid is poured into the tetrafluoroethylene inner liner of a 20 ml stainless steel high-temperature and high-pressure kettle, and the high-temperature and high-pressure kettle is placed in a forced air drying oven with a temperature setting of 180 ℃. After 3 h of solvothermal reaction, it is cooled to room temperature to obtain anti-fake ink.

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