Multi-color-changing fluorescent anti-counterfeiting super-hydrophobic composite film and preparation method thereof

Abstract

The invention relates to the technical field of fluorescent anti-counterfeiting detection, in particular to a fluorescent anti-counterfeiting super-hydrophobic composite film with multiple color changes and a preparation method of the fluorescent anti-counterfeiting super-hydrophobic composite film. The color change of the surface of the multi-color-change fluorescent anti-counterfeiting super-hydrophobic composite film can be realized by changing the excitation wavelength. According to the multi-color change, two different fluorescent dyes are blended and encapsulated to prepare a fluorescent anti-counterfeiting emulsion, and then the fluorescent anti-counterfeiting emulsion is sprayed on the surface of a polymer substrate to obtain the multi-color-change fluorescent composite film with the super-hydrophobic characteristic. The fluorescent anti-counterfeiting composite film prepared by the invention has the characteristic of multiple discoloration, and is strong in fluorescence signal and good in fluorescence performance stability.

Description

Technical Field

[0001] The invention relates to the technical field of fluorescent anti-counterfeiting detection, and in particular to a fluorescent anti-counterfeiting super-hydrophobic composite film with multiple color changes and a preparation method thereof. Background Art

[0002] As a global problem, counterfeiting and shoddy products pose a serious threat to people's health and economic property. The development of efficient and reliable anti-counterfeiting technology can effectively identify the authenticity of products and prevent counterfeiting, which is of great significance to the development of enterprises and the protection of consumer rights. As a new anti-counterfeiting technology, fluorescent anti-counterfeiting has the characteristics of simplicity and reliability. It has received close attention from scientists and entrepreneurs and is widely used in the fields of national economy and people's livelihood such as currency, food, and medicine. However, the current fluorescent anti-counterfeiting has a single color and is easy to be cracked and imitated. Therefore, the development of color-changeable multi-color fluorescent anti-counterfeiting technology has great basic research value and commercial application value.

[0003] A two-component fluorescent composite material refers to the introduction of a second component into a first-component fluorescent material. Through this strategy, the luminescence performance is effectively improved. However, the second component in the current two-component fluorescent material is considered to enhance the fluorescence intensity or broaden the luminescence range. There is energy transfer between the two components, and even if the excitation wavelength is changed, a single color of light is still emitted. On the other hand, whether it is a single-component fluorescent material or a two-component fluorescent material, its luminescence process is easily disturbed by the external environment, resulting in fluorescence quenching and a decrease in luminescence intensity. Organic fluorescent molecules have attracted much attention due to their adjustable structure and controllable luminescence range. However, organic luminescent materials have intramolecular rotation, which will cause a decrease in luminescence intensity. Summary of the invention

[0004] In order to solve the problems in the background technology, the present invention first provides a two-component fluorescent material, which can achieve the regulation of the color of the film surface by changing the excitation wavelength. Then the two-component fluorescent material is encapsulated to protect the fluorescent material from being disturbed by the external environment during the luminescence process. On the other hand, the multi-color-changing fluorescent capsules are synergistically combined with fluorinated surfactants and polydimethylsiloxane to prepare a multi-color-changing anti-counterfeiting luminescent composite film with stable superhydrophobic properties, further improving the stability of the fluorescent anti-counterfeiting composite film.

[0005] The present invention provides a multi-color-changing anti-counterfeiting super-hydrophobic film using these two fluorescent materials as luminescent substances and a preparation method thereof, which is prepared according to the following steps: (1) Preparation of fluorescent capsules 1) Dissolve sodium dodecyl sulfate, sodium bicarbonate and polyvinyl pyrrolidone in ultrapure water to prepare solution A; wherein the mass ratio of sodium dodecyl sulfate, sodium bicarbonate and polyvinyl pyrrolidone is 1:0.1-0.8:0.6-2.6; the preferred mass ratio is 1:0.3:1.2.

[0006] 2) Add a mixture of 7-amino-4-methylcoumarin, indocyanine green and styrene into dichloromethane to prepare solution B. The mass ratio of 7-amino-4-methylcoumarin, indocyanine green and styrene is 1:0.02-0.2:30-200, and more preferably 1:0.1:90-110.

[0007] 3) Solution A and solution B are mixed, and after ultrasonic vibration at low temperature (0°C) for 10-30 minutes, potassium persulfate is added and reacted at a temperature of 50-100°C for 5-30 hours. The reaction product is separated by centrifugation and washed alternately with distilled water and ethanol for 3 times to obtain a multi-color fluorescent capsule. Furthermore, the mass ratio of sodium dodecyl sulfate, 7-amino-4-methylcoumarin and potassium persulfate is 30:10:5-50. It is further preferred that the reaction is preferably 80°C for 12 hours.

[0008] (2) Preparation of multi-color fluorescent anti-counterfeiting super-hydrophobic composite films 1) Adding multi-color fluorescent capsules, fluorinated surfactants and polydimethylsiloxane into tetrahydrofuran, and dispersing them evenly by ultrasonic vibration, a fluorescent anti-counterfeiting emulsion is obtained; wherein the mass ratio of the multi-color fluorescent capsules, fluorinated surfactants and polydimethylsiloxane is 1:0.5-2:0.05-0.5; and further optimized to 1:1:0.2.

[0009] 2) Spray the fluorescent anti-counterfeiting emulsion onto the polyimide substrate and dry it at 60-150° C. for 2-10 hours to obtain a fluorescent anti-counterfeiting super-hydrophobic composite film with multiple color changes. A further preferred reaction is: react at 120° C. for 5 hours.

[0010] Wherein, the fluorine-containing surfactant is one or more of perfluorohexyl ethyl sulfonic acid, hexafluoroisopropanol, and perfluorooctyl ethyl acrylate.

[0011] The structural formula of 7-amino-4-methylcoumarin is as follows:

[0012] The structural formula of indocyanine green is as follows:

[0013] 7-amino-4-methylcoumarin in the two-component fluorescent material is a blue fluorescent material with an emission spectrum of 375-480nm. Indocyanine green in the two-component fluorescent material is a near-infrared fluorescent material with an absorption peak near 780nm and a strongest excitation wavelength near 815nm. The emission spectrum of 7-amino-4-methylcoumarin and the absorption spectrum of indocyanine green have almost no overlap, which can effectively avoid energy transfer between the two. In addition, the polar functional groups between 7-amino-4-methylcoumarin and indocyanine green have hydrogen bond interactions, which can inhibit the rotation of the two molecules, enhance the charge transfer within the molecules, increase the intensity of the excited state oscillator, emit stronger fluorescence, and enhance the luminescence effect.

[0014] The above method has the following technical advantages: The core of the fluorescent capsule with multiple color changes prepared by the present invention is 7-amino-4-methylcoumarin and indocyanine green, which can effectively avoid energy transfer between multi-component fluorescent materials, thereby realizing multi-color anti-counterfeiting. The shell of the fluorescent capsule with multiple color changes prepared by the present invention is polystyrene, and this structure is conducive to protecting the luminescence process of the fluorescent dye from being disturbed by the external environment; the multi-color anti-counterfeiting luminescent composite film prepared by the present invention also has super-hydrophobic properties, which is conducive to further improving the stability of the fluorescent performance of the composite film; the present invention adopts a spray coating method to prepare an anti-counterfeiting super-hydrophobic composite film, which has simple equipment and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the optical absorption spectrum of 7-amino-4-methylcoumarin and indocyanine green.

[0016] Figure 2 Optical absorption spectrum of multi-color fluorescent capsules.

[0017] Figure 3 The fluorescence spectra of 7-amino-4-methylcoumarin at different excitation wavelengths.

[0018] Figure 4 Fluorescence spectra of indocyanine green at different excitation wavelengths.

[0019] Figure 5 The fluorescence spectra of the fluorescent anti-counterfeiting emulsion prepared in Example 1 at different excitation wavelengths. DETAILED DESCRIPTION

[0020] In order to explain the present invention more clearly, the present invention is further described below in conjunction with embodiments. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0021] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. The experimental materials, reagents, etc. used in the following experimental examples can be obtained through commercial channels or known experimental methods. Embodiment 1:

[0022] (1) Preparation of fluorescent capsules 1) Dissolve 30 mg of sodium dodecyl sulfate, 9 mg of sodium bicarbonate and 36 mg of polyvinyl pyrrolidone in 30 mL of ultrapure water to prepare solution A; 2) Dissolve 10 mg of 7-amino-4-methylcoumarin and 1 mg of indocyanine green in 0.5 mL of dichloromethane and mix with 1.1 mL (1 g) of styrene to prepare solution B.

[0023] 3) Solution A and solution B were mixed, ultrasonically shaken at 0°C for 15 minutes, and then 20 mg of potassium persulfate was added and reacted at 80°C for 12 hours. The product was separated by centrifugation and washed alternately with distilled water and ethanol for 3 times to obtain multi-color fluorescent capsules.

[0024] (2) Preparation of multi-color fluorescent anti-counterfeiting super-hydrophobic composite films 1) Add 30 mg of multi-color fluorescent capsules, 30 mg of perfluorohexyl ethyl sulfonic acid, and 6 mg of polydimethylsiloxane into 20 mL of tetrahydrofuran, and disperse them evenly by ultrasonic vibration to obtain a fluorescent anti-counterfeiting emulsion; 2) Spray the fluorescent anti-counterfeiting emulsion onto the polyimide substrate (about 1mL / cm 2 ), and dried at 120 °C for 5 hours to obtain a fluorescent anti-counterfeiting super-hydrophobic composite film with multiple color changes.

[0025] Example 2: The difference between this example and Example 1 is that the fluorinated surfactant used in step (2) is hexafluoroisopropanol, and the other treatment methods are consistent with those in Example 1.

[0026] Example 3: This example differs from Example 1 in that the amount of styrene used in step (1) is 0.25 mL (0.2 g), and the other treatment methods are consistent with those in Example 1.

[0027] Example 4: This example differs from Example 1 in that the amount of styrene used in step (1) is 5 mL (4.5 g), and the other treatment methods are consistent with those in Example 1.

[0028] Example 5: The difference between this example and Example 1 is that the amount of potassium persulfate used in step (1) is 8 mg, and the other treatment methods are consistent with Example 1.

[0029] Example 6: The difference between this example and Example 1 is that the amount of potassium persulfate used in step (1) is 40 mg, and the other treatment methods are consistent with Example 1.

[0030] Example 7: The difference between this example and Example 1 is that the amount of the multi-color fluorescent capsule used in step (2) is 10 mg, and the other processing methods are consistent with Example 1.

[0031] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the luminescent material used in step (1) is 7-amino-4-methylcoumarin, and indocyanine green is not used, wherein the amount of 7-amino-4-methylcoumarin used is consistent with the amount of 7-amino-4-methylcoumarin used in Example 1, and the other processing methods are consistent with Example 1.

[0032] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the luminescent material used in step (1) is indocyanine green, and 7-amino-4-methylcoumarin is not used, wherein the amount of indocyanine green used is consistent with the amount of indocyanine green used in Example 1, and the other processing methods are consistent with Example 1.

[0033] Comparative Example 3: The difference between this comparative example and Example 1 is that the amount of perfluorohexylethylsulfonic acid used in step (2) is 10 mg, and the other treatment methods are consistent with Example 1.

[0034] Comparative Example 4: The difference between this comparative example and Example 1 is that the amount of polydimethylsiloxane used in step (2) is 2 mg, and the other processing methods are consistent with Example 1.

[0035] Comparative Example 5: The difference between this comparative example and Example 1 is that polydimethylsiloxane is not used in step (2), and the amount of perfluorohexylethyl sulfonic acid used is the sum of the masses of perfluorohexylethyl sulfonic acid and polydimethylsiloxane in Example 1, and the other processing methods are consistent with Example 1.

[0036] Comparative Example 6: The difference between this comparative example and Example 1 is that perfluorohexyl ethyl sulfonic acid is not used in step (2), and the amount of polydimethylsiloxane used is the sum of the masses of perfluorohexyl ethyl sulfonic acid and polydimethylsiloxane in Example 1, and the other processing methods are consistent with Example 1.

[0037] Comparative Example 7: The difference between this comparative example and Example 1 is that the drying temperature of the fluorescent anti-counterfeiting super-hydrophobic composite film in step (2) is 70°C, and the other treatment methods are consistent with Example 1. Luminescence performance test: A fluorescence spectrometer (Hitachi, F-4500) was used with a test range of 200-900 nm. Luminescence performance.

[0038] Luminescence properties: Taking the fluorescence intensity of the composite film prepared in Example 1 (before stability test) at 834 nm as a benchmark, other luminescence properties are the ratio of the intensity of the measured fluorescence curve at 834 nm divided by the benchmark.

[0039] Color-changing performance test: Use light with wavelengths of 375nm and 810nm to irradiate the composite film respectively. If the composite film can show two colors respectively, it is considered to have color-changing performance.

[0040] Super hydrophobic performance measurement: The contact angle test was performed using a JC2000D1 contact angle tester. The volume of the test liquid was 5 μL. Five sites on the film surface were tested and the average value was calculated, which was the water contact angle of the sample. If the contact angle was greater than 150 o , which is a super hydrophobic surface.

[0041] Heat resistance test: heat the composite film to 70 o After keeping at C for 30 min, the water contact angle and color change performance were tested.

[0042] Friction resistance test: Under a load of 50 g, the composite film was dragged over 1200-grit sandpaper at a speed of 2 cm / s and a distance of 5 m. After the test, the water contact angle and luminescence performance were tested.

[0043] Bending resistance: After the composite film is folded 1000 times, the water contact angle and color change performance are tested.

[0044] The above test results are shown in Table 1 below: Table 1

[0045] As can be seen from Table 1, it can be seen from Examples 1-2 that the composite film prepared by this method not only has multiple color-changing properties for anti-counterfeiting, but also has super-hydrophobic properties, and also shows excellent stability. As can be seen from Example 1-2 compared with Example 3, the amount of styrene is too little, the capsule external structure is fragile, and the stability of the fluorescent anti-counterfeiting composite film is reduced. As can be seen from Example 1-2 compared with Example 4, the amount of styrene is too much, the capsule external structure is too thick, and the luminescence performance of the fluorescent anti-counterfeiting composite film is weakened. It can be seen that the amount of styrene used has an important impact on the performance of the fluorescent anti-counterfeiting composite film. As can be seen from Example 1-2 compared with Example 5-6, the amount of potassium persulfate is too little or too much, and it is impossible to effectively induce the full polymerization of styrene or cause the molecular weight of polystyrene to decrease, resulting in the luminescence performance and stability of the fluorescent anti-counterfeiting composite film. As can be seen from Example 1-2 compared with Example 7, the amount of fluorescent capsule is too little, which will cause the luminescence performance of the fluorescent anti-counterfeiting composite film to decrease. As can be seen from Examples 1-2 and Comparative Examples 1-2, compared to a single-component fluorescent substance as a luminescent material, the composite film prepared by this method has multiple color-changing characteristics, and the anti-counterfeiting effect is better. In addition, it can also be seen from Examples 1-2 and Comparative Example 2 that, compared to a single-component composite film with indocyanine green as a luminescent material, the hydrogen bond interaction in the composite film with two-component 7-amino-4-methylcoumarin and indocyanine green as luminescent materials weakens the intramolecular rotation of indocyanine, and the luminescent performance is better. As can be seen from Examples 1-2 and Comparative Examples 3-6, the amount of perfluorohexyl ethyl sulfonic acid and polydimethylsiloxane has an important impact on the super-hydrophobic properties and stability of the composite film. As can be seen from Examples 1-2 and Comparative Example 7, the curing temperature of polydimethylsiloxane will also have a great impact on the stability of the composite film.

[0046] Combination Figure 1 and Figure 2 It can be seen that the fluorescent capsule contains two luminescent substances, 7-amino-4-methylcoumarin and indocyanine green. Figure 3 and Figure 4 It can be seen that even if the excitation wavelengths of the two luminescent substances, 7-amino-4-methylcoumarin and indocyanine green, are changed, the emission peaks of their fluorescence spectra will not change, indicating that using only one luminescent substance will not produce a multi-color anti-counterfeiting composite film. Figure 5 It can be seen that when 7-amino-4-methylcoumarin and indocyanine green are used at the same time, as the excitation wavelength red-shifts, the emission peak of the fluorescence spectrum also red-shifts accordingly, indicating that when different light is used to irradiate the composite film, the composite film will show different colors.

[0047] In summary, the composite film prepared by the present invention not only has super-hydrophobic and multiple color-changing properties, but also has excellent stability.

[0048] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A multi-color fluorescent anti-counterfeiting super-hydrophobic composite film, characterized in that: The multi-color fluorescent anti-counterfeiting super-hydrophobic composite film is prepared by blending multi-color fluorescent capsules and a hydrophobic modifier into a fluorescent anti-counterfeiting emulsion, which is sprayed on the surface of a polymer substrate to obtain a multi-color fluorescent composite film with super-hydrophobic properties; wherein the multi-color fluorescent capsules are prepared by encapsulating a mixture of 7-amino-4-methylcoumarin and indocyanine green in polystyrene.

2. The multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 1, characterized in that: The preparation method of the multi-color fluorescent capsules is as follows: (1) Dissolve sodium dodecyl sulfate, sodium bicarbonate and polyvinyl pyrrolidone in ultrapure water to prepare solution A; (2) adding a mixture of 7-amino-4-methylcoumarin and indocyanine green into dichloromethane to dissolve the mixture and then mixing the mixture with styrene to prepare solution B; (3) Solution A and solution B are mixed, and after ultrasonic oscillation at low temperature, potassium persulfate is added and heated for reaction. The reaction product is separated by centrifugation and washed to obtain a multi-color fluorescent capsule.

3. The multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 2, characterized in that: In step (1), the mass ratio of sodium dodecyl sulfate, sodium bicarbonate and polyvinyl pyrrolidone is 1:0.1-0.8:0.6-2.

6.

4. The multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 2, characterized in that: In step (2), the mass ratio of 7-amino-4-methylcoumarin, indocyanine green and styrene is 1:0.02-0.2:30-200.

5. The multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 2, characterized in that: In step (2), the mass ratio of 7-amino-4-methylcoumarin, indocyanine green and styrene is 1:0.1:90-110.

6. The multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 2, characterized in that: The mass ratio of sodium dodecyl sulfate, 7-amino-4-methylcoumarin and potassium persulfate is 30:10:5-50; the temperature of the heating reaction in step (3) is 50-100° C. and the time is 5-30 hours.

7. The method for preparing the multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 1, characterized in that: (1) Adding multi-color fluorescent capsules, fluorinated surfactants, and polydimethylsiloxane into tetrahydrofuran, and uniformly dispersing them by ultrasonic vibration to obtain a fluorescent anti-counterfeiting emulsion; (2) The fluorescent anti-counterfeiting emulsion is sprayed onto a polyimide substrate and heated and dried to obtain a fluorescent anti-counterfeiting super-hydrophobic composite film with multiple color changes.

8. The method for preparing the multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 7, characterized in that: The fluorinated surfactant in step (1) is one or more of perfluorohexyl ethyl sulfonic acid, hexafluoroisopropanol, and perfluorooctyl ethyl acrylate.

9. The method for preparing the multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 7, characterized in that: In step (1), the mass ratio of the fluorescent capsule, the fluorinated surfactant and the polydimethylsiloxane is 1:0.5-2:0.05-0.

5.

10. The method for preparing the multi-color fluorescent anti-counterfeiting super-hydrophobic composite film according to claim 7, characterized in that: In step (2), the drying temperature is 60-150° C. and the drying time is 2-10 hours.

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