Polymer / ucnp self-assembly anti-counterfeiting device and preparation method

Abstract

The present disclosure provides a polymer / UCNPs self-assembly anti-counterfeiting device and a preparation method thereof. The method mixes a dispersion solution of UCNPs with a uniform polymer solution. A "sandwich" template method is used for directional induction self-assembly to form an anti-counterfeiting device with a set anti-counterfeiting pattern. The polymer effectively saves UCNPs and makes the UCNPs have certain viscosity. The patterning becomes simple and feasible, and the adhesion firmness with the attachments is increased. The UCNPs anti-counterfeiting luminescent pattern prepared by the present disclosure has the advantages of easy operation, cost saving, firm adhesion, good design of luminescent pattern, clear imaging and the like.

Description

Technical Field

[0001] This disclosure relates to the field of optical anti-counterfeiting, specifically to a polymer / UCNPs self-assembled anti-counterfeiting device and its preparation method. Background Technology

[0002] Anti-counterfeiting technology is crucial for both commerce and national public security, and has become a global and long-term issue, widely applied in currency, negotiable instruments, confidential documents, food, and pharmaceuticals. Currently, various anti-counterfeiting technologies have been developed, such as plasma technology, radio frequency identification (RFID), anti-counterfeiting inks, and laser holography. However, the high production costs of these technologies and the equipment required limit their practical application. Furthermore, with the rapid advancements in counterfeiting techniques, traditional anti-counterfeiting technologies can no longer meet the demands of modern anti-counterfeiting efforts.

[0003] Anti-counterfeiting labels based on luminescent materials have attracted widespread attention due to their low cost, good concealment, and ease of preparation. Researchers have studied traditional luminescent materials such as quantum dots and organic dyes. Results show that while these materials possess high luminescence intensity, they are unstable in harsh environments and, due to their single luminescent color, are easily copied, resulting in low reliability. UCNPs (upconversion nanoparticles), as an emerging luminescent material, possess characteristics such as high optical stability, long fluorescence lifetime, and low toxicity. Furthermore, the near-infrared source that excites upconversion luminescence is generally difficult for the general public to obtain, making upconversion anti-counterfeiting labels difficult to copy and identify, thus becoming a research hotspot in the field of contemporary security and anti-counterfeiting. Currently, researchers have fabricated upconversion nanoparticle anti-counterfeiting devices using photolithography, printing, and screen printing. These devices are almost invisible under visible light, but exhibit different colors of luminescence when excited by a 980nm laser.

[0004] Although breakthroughs have been made in anti-counterfeiting luminescent patterns based on upconversion nanomaterials, the equipment used is still complex, and in practical applications, printing and screen printing technologies are still mostly used, which have problems such as strong dependence on equipment and complex operation; large demand for upconversion nanoparticles, waste of materials, and high cost; and difficulty in designing anti-counterfeiting luminescent patterns, low resolution, poor adhesion, and easy peeling. Summary of the Invention

[0005] This disclosure addresses the shortcomings of existing technologies by providing a polymer / UCNP self-assembled anti-counterfeiting device and its preparation method. The preparation method is simple, allows for pattern design and easy transfer, and enables adjustment of the amount of UCNPs used, thus reducing costs.

[0006] The technical solution adopted in this disclosure is: A method for preparing a polymer / UCNP self-assembled anti-counterfeiting device, the method comprising the following steps: Select polymer; Prepare a mixed solution of the polymer and UCNPs, wherein the UCNPs account for 80%-40% of the polymer / UCNPs mixture by mass. Based on the shape of the anti-counterfeiting pattern of the polymer / UCNPs self-assembled anti-counterfeiting device to be prepared, a shape template of the anti-counterfeiting pattern is prepared; A superhydrophobic shape template for the anti-counterfeiting pattern; Select a target substrate and modify the target substrate with superhydrophilicity; Take the mixed solution and drop it between the shape template and the target substrate; The mixed solution is evaporated and shrunken, and the polymer pulls UCNPs to assemble on the target substrate to form an anti-counterfeiting pattern; Collect the anti-counterfeiting pattern.

[0007] Optionally, the polymer includes a water-soluble polymer or an oil-soluble polymer; and / or the UCNPs include water-soluble UCNPs or oil-soluble UCNPs.

[0008] Optionally, the polymer and the UCNPs are both oil-soluble or water-soluble.

[0009] Optionally, the water-soluble polymer includes polyvinyl alcohol (PVA), polyacrylic acid (PAA), waterborne polyurethane (WPU), or polyvinylpyrrolidone (PVP); and / or, the oil-soluble polymer includes polystyrene (PS), polymethyl methacrylate (PMMA), or polycarbonate (PC).

[0010] Optionally, the preparation of the mixed solution includes: Prepare a UCNPs solution with a concentration of 0.1 wt%-5 wt%. Prepare a polymer solution with a concentration of 0.1 wt%-5 wt%. The UCNPs solution is mixed with the polymer solution.

[0011] Optionally, the solvent of the UCNPs solution or polymer solution includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, chlorobenzene, toluene, tetrahydrofuran, dimethylformamide, chloroform, and chloroform.

[0012] Optionally, when the polymer and the UCNPs are water-soluble, a gasket is also included, in which the shape template is embedded.

[0013] Optionally, the mixed solution is allowed to evaporate and shrink at room temperature for about 48 hours to form an anti-counterfeiting pattern.

[0014] This disclosure also proposes a polymer / UCNPs self-assembled anti-counterfeiting device, which is prepared according to the method proposed in this disclosure.

[0015] Optionally, the anti-counterfeiting device displays an anti-counterfeiting pattern when excited by a laser of a specific wavelength.

[0016] Compared with the prior art, the beneficial effects disclosed in this disclosure are as follows: (1) This invention combines polymers with UCNPs, which effectively saves the amount of UCNPs used and reduces costs; at the same time, the addition of polymers is beneficial to the preparation of anti-counterfeiting patterns. (2) This disclosure provides a polymer / UCNPs self-assembled anti-counterfeiting device and its preparation method. The preparation method is simple, low cost, not limited by substrate material, has a strong connection with the substrate, and has high stability.

[0017] (3) The present disclosure provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device. According to different needs of actual applications, the pattern of the photomask can be adjusted to change the pattern of the silicon substrate to meet the anti-counterfeiting requirements of different items. (4) The present disclosure provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device, which realizes anti-counterfeiting application under low-power infrared laser light and has good application prospects in the field of optical anti-counterfeiting technology. Attached Figure Description

[0018] Figure 1 A scanning electron microscope image of UCNPs according to one embodiment of this disclosure; Figure 2 A fluorescence photograph and upconversion fluorescence emission spectrum of UCNPs according to one embodiment of this disclosure under 980 nm near-infrared light illumination; Figure 3 Fluorescence photographs of bar patterns with different UCNPs / polymer mass ratios according to one embodiment of this disclosure after irradiation with a 980nm laser; Figure 4 An optical diagram of a structured annular silicon pillar according to one embodiment of this disclosure; Figure 5 The polymer / UCNPs of one embodiment of this disclosure are assembled into a ring-shaped anti-counterfeiting pattern, and photographs are taken before and after emitting light under 980nm laser irradiation. Figure 6 The image shows a polymer / UCNPs assembled into the letter QLU anti-counterfeiting pattern according to one embodiment of this disclosure, before and after emitting light under 980nm laser illumination. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this disclosure. Furthermore, the technical features involved in the various embodiments of this disclosure described below can be combined with each other as long as they do not conflict with each other.

[0021] Example 1 A method for preparing a polymer / UCNP self-assembled anti-counterfeiting device, the method comprising the following steps: Select polymer; Prepare a mixed solution of the polymer and UCNPs, wherein the UCNPs account for 80%-40% of the polymer / UCNPs mixture by mass. Based on the shape of the anti-counterfeiting pattern of the polymer / UCNPs self-assembled anti-counterfeiting device to be prepared, a shape template of the anti-counterfeiting pattern is prepared; A superhydrophobic shape template for the anti-counterfeiting pattern; Select a target substrate and modify the target substrate with superhydrophilicity; Take the mixed solution and drop it between the shape template and the target substrate; The mixed solution is evaporated and shrunken, and the polymer pulls UCNPs to assemble on the target substrate to form an anti-counterfeiting pattern; Collect the anti-counterfeiting pattern.

[0022] Specifically: Unrealized carbon nanotubes (UCNPs) are a class of rare-earth-doped nanomaterials that can convert low-energy near-infrared light into high-energy visible or ultraviolet light, and they are expensive. The self-assembled anti-counterfeiting device fabrication method proposed in this disclosure cleverly selects suitable polymers and combines them with UCNPs, effectively reducing the amount of UCNPs used and saving costs.

[0023] The appropriate polymer should be selected based on whether the UCNPs are water-soluble or oil-soluble; that is, water-soluble UCNPs should be paired with water-soluble polymers, and oil-soluble UCNPs should be paired with oil-soluble polymers. Examples of water-soluble polymers include polyvinyl alcohol (PVA), polyacrylic acid (PAA), waterborne polyurethane (WPU), or polyvinylpyrrolidone (PVP); examples of oil-soluble polymers include polystyrene (PS), polymethyl methacrylate (PMMA), or polycarbonate (PC).

[0024] like Figure 1-2As shown, UCNPs have particle sizes ranging from a few nanometers to several hundred nanometers, and their dispersion can be either monodisperse or polydisperse. The shapes of the nanoparticles can be regular or irregular. The structure and composition of UCNPs are not limited, and the wavelength of their emitted fluorescence color is not limited. Among them, monodisperse UCNPs have the same particle size, while polydisperse UCNPs have different particle sizes.

[0025] UCNPs and polymers can be formulated into solutions, wherein the solvent can be one or more of dimethyl sulfoxide, N-methylpyrrolidone, chlorobenzene, toluene, tetrahydrofuran, dimethylformamide, chloroform, and chloroform.

[0026] The UCNPs solution and the polymer solution are mixed according to a preset mass ratio, for example by ultrasonic mixing, to form a homogeneous mixed solution.

[0027] Polymers, as an effective means of controlling nanoparticle assembly, can be used to induce the controlled assembly of nanoparticles into regular structures. By mixing polymers and nanoparticles to form a binary system, a synergistic effect occurs between the two components. The polymer can pull the flow of UCNPs during dewetting, and the nanoparticles can easily embed into the polymer to form various patterned structures. As the solvent evaporates, the presence of the polymer can also act as a binder, making the adhesion between the pattern and the substrate stronger. Therefore, this embodiment studies a binary system composed of a polymer that easily forms regular patterns and UCNPs. Figure 3 The image shows fluorescence photographs of polymer / UCNP bar patterns with different UCNP mass ratios after irradiation with a 980nm laser. It can be seen that when the UCNP mass ratio is 100%, the UCNPs have poor flowability, which is not conducive to bar formation and results in poor anti-counterfeiting performance. When the UCNP content is 80%-40%, the bar formation effect is good, which is beneficial for anti-counterfeiting. The anti-counterfeiting effect is best when the UCNP content is 60%. While the bar formation effect is good when the UCNP mass ratio is 20% due to the high polymer content, the anti-counterfeiting effect is poor because of the low UCNP content. Therefore, a UCNP content of 80%-40% is suitable for both bar formation and anti-counterfeiting performance.

[0028] The main steps in preparing the shape template for the anti-counterfeiting pattern are as follows: (1) Select a substrate etching shape template. The feature size of the shape template is 1-10 micrometers, and the pattern can be designed as a closed or open pattern. For oil-soluble polymers / UCNPs, the substrate for the shape template can be ITO glass, silicon wafer, SiO2@Si silicon wafer with grown SiO2 nanolayers, a flat metal sheet, or a ceramic sheet. For water-soluble polymers / UCNPs, in addition to the above-mentioned substrates, polyacrylic acid (PAA) sheets and PMMA sheets can also be used. The shape template can be designed according to the requirements of the anti-counterfeiting pattern, and can be linear, rectangular, triangular, or other suitable geometric shapes, as well as combinations of letters and characters. In one embodiment, for example, the shape template is a ring-shaped silicon pillar template: in nitrogen-doped... <100> A 5-inch diameter, 500-micron thick silicon wafer is coated with photoresist. Using a pre-designed chromium-plated (Cr) quartz photoresist template, a laser direct-write device is used to irradiate and cure the photoresist. After baking and development, the unexposed areas of the silicon wafer surface are exposed. A fluorine-based reagent is used to perform deep reactive ion etching on the silicon wafer with the photoresist pattern for approximately 6 minutes. Finally, the substrate is stripped of the photoresist and cleaned with acetone and ethanol to obtain a ring-shaped silicon pillar template. Figure 4 As shown.

[0029] (2) Superhydrophobic modification of annular silicon pillars: The annular silicon pillar template needs to be cleaned with ethanol and acetone before modification. The silicon pillar template is treated with a low-temperature plasma treatment instrument (oxygen atmosphere, background vacuum degree of 10 Pa, discharge power of 200 W, treatment time of 300 s) to activate its surface. Then it is placed in a vacuum oven, 5 μl of octadecylfluorosilane is added, and the vacuum environment is maintained at 80 °C for 12 hours to obtain an annular structured silicon pillar template with a superhydrophobic surface. The water contact angle can reach about 150°.

[0030] Select a target substrate for the self-assembly of the anti-counterfeiting pattern on the target substrate. The target substrate needs to be treated with superhydrophilic treatment. In this embodiment, for example, a low-temperature plasma treatment instrument is used (atmosphere is oxygen, background vacuum degree is 10 Pa, discharge power is 200W, and treatment time is 300s). After treatment, the surface of the target substrate becomes superhydrophilic with a water contact angle of 0°.

[0031] In this embodiment, for example, tetrahydrofuran is selected as the solvent to prepare polymer and UCNPs solutions respectively. The polymer is selected as PMMA, and a 2 wt% PMMA solution is prepared; a 2 wt% UCNPs solution is prepared; wherein the concentration of the polymer and UCNPs solution can be between 0.1 wt% and 5 wt%.

[0032] The PMMA solution and UCNPs solution are mixed thoroughly. 10 μl of the PMMA / UCNPs mixture is then dropped between a superhydrophobic ring-shaped silicon pillar template and a superhydrophilic target substrate, forming a "sandwich" structure. The lower substrate is the superhydrophobic structured silicon pillar template, the upper substrate is the superhydrophilic target substrate, and the PMMA / UCNPs mixture is in the middle. Utilizing the significant surface energy difference between the upper and lower substrates, the PMMA / UCNPs mixture does not penetrate into the template but remains in the gap between the template tip and the substrate. As the solvent evaporates, the liquid bridge moves upwards. Precise template control induces the liquid film to rupture, and the PMMA pulls the UCNPs to assemble onto the target substrate surface. After approximately 48 hours of evaporation and shrinkage, a regular anti-counterfeiting pattern is formed.

[0033] Acquiring Fluorescent Anti-counterfeiting Patterns: The prepared UCNPs ring-shaped anti-counterfeiting pattern was illuminated using a special 980 nm light source matched to the UCNPs. The UCNPs ring-shaped anti-counterfeiting pattern emitted bright fluorescence. The fluorescent anti-counterfeiting features were captured using a microscope, such as... Figure 5 As shown.

[0034] Example 2 A method for fabricating a polymer / UCNP self-assembled anti-counterfeiting device is provided. For water-soluble polymers / UCNPs, a spacer is needed inside the "sandwich" structure of the shape template and the target substrate. The specific process is as follows: Take a glass slide, for example, 2.5 cm × 2.5 cm, and place a pre-fabricated PDMS spacer on the glass slide. Place a superhydrophobic silicon substrate in the center of the PDMS spacer. Use a pipette to draw 10 μL of a homogeneous transparent solution of UCNPs and polymer, drop it onto the silicon substrate, and quickly cover it with a flat substrate. Next, place another 2.5 cm × 2.5 cm glass slide. After clamping the two glass slides together, a "sandwich" structure assembly system is formed.

[0035] Example 3 This experiment, referring to Example 1, provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device. The difference from Example 1 is that the shape template of the anti-counterfeiting pattern is etched with a triangular structured silicon pillar template; the assembly result is a UCNPs triangular anti-counterfeiting pattern.

[0036] Example 4 This experiment, referring to Example 1, provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device. The difference from Example 1 is that the shape template of the anti-counterfeiting pattern is etched with a square structured silicon pillar template; the assembly result is a square anti-counterfeiting pattern of UCNPs.

[0037] Example 5 This experiment, referring to Example 1, provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device. The difference from Example 1 is that the shape template for the anti-counterfeiting pattern is etched with a structured silicon pillar template of the letters "QLU"; the assembled result is a UCNPs "QLU" letter anti-counterfeiting pattern, such as... Figure 6 As shown.

[0038] Compared with the prior art, the beneficial effects of this disclosure are as follows: (1) This invention combines polymers with UCNPs, which effectively saves the amount of UCNPs used and reduces costs; at the same time, the addition of polymers is beneficial to the preparation of anti-counterfeiting patterns. (2) This disclosure provides a polymer / UCNPs self-assembled anti-counterfeiting device and its preparation method. The preparation method is simple, low cost, not limited by substrate material, has a strong connection with the substrate, and has high stability.

[0039] (3) The present disclosure provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device. According to different needs of actual applications, the pattern of the photomask can be adjusted to change the pattern of the silicon substrate to meet the anti-counterfeiting requirements of different items. (4) The present disclosure provides a method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device, which realizes anti-counterfeiting application under low-power infrared laser light and has good application prospects in the field of optical anti-counterfeiting technology.

[0040] The embodiments described above are merely preferred embodiments of this disclosure. These preferred embodiments do not exhaustively describe all details, nor do they limit this disclosure to the specific implementations described. Various modifications and improvements made to the technical solutions of this disclosure by those skilled in the art without departing from its spirit should fall within the protection scope defined by the claims of this disclosure.

Claims

1. A method for preparing a polymer / UCNPs self-assembled anti-counterfeiting device, characterized in that, The preparation method includes the following steps: Select polymer; Prepare a mixed solution of the polymer and UCNPs, wherein the UCNPs account for 80%-40% of the polymer / UCNPs mixture by mass. Based on the shape of the anti-counterfeiting pattern of the polymer / UCNPs self-assembled anti-counterfeiting device to be prepared, a shape template of the anti-counterfeiting pattern is prepared; A superhydrophobic shape template for the anti-counterfeiting pattern; Select a target substrate and modify the target substrate with superhydrophilicity; Take the mixed solution and drop it between the shape template and the target substrate; The mixed solution is evaporated and shrunken, and the polymer pulls UCNPs to assemble on the target substrate to form an anti-counterfeiting pattern; Collect the anti-counterfeiting pattern.

2. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 1, characterized in that: The polymer includes water-soluble polymers or oil-soluble polymers; and / or, the UCNPs include water-soluble UCNPs or oil-soluble UCNPs.

3. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 2, characterized in that: Both the polymer and the UCNPs are oil-soluble or water-soluble.

4. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 2, characterized in that: The water-soluble polymer includes polyvinyl alcohol (PVA), polyacrylic acid (PAA), waterborne polyurethane (WPU), or polyvinylpyrrolidone (PVP); and / or, the oil-soluble polymer includes polystyrene (PS), polymethyl methacrylate (PMMA), or polycarbonate (PC).

5. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 1, characterized in that: The preparation of the mixed solution includes: Prepare a UCNPs solution with a concentration of 0.1 wt%-5 wt%. Prepare a polymer solution with a concentration of 0.1 wt%-5 wt%. The UCNPs solution is mixed with the polymer solution.

6. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 5, characterized in that: The solvent of the UCNPs solution or polymer solution includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, chlorobenzene, toluene, tetrahydrofuran, dimethylformamide, chloroform, and chloroform.

7. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 1, characterized in that: When the polymer and the UCNPs are water-soluble, a gasket is also included, and the shape template is embedded in the gasket.

8. The method for preparing the polymer / UCNPs self-assembled anti-counterfeiting device according to claim 1, characterized in that: The mixed solution evaporates and shrinks at room temperature to form an anti-counterfeiting pattern.

9. A polymer / UCNPs self-assembled anti-counterfeiting device, characterized in that, The anti-counterfeiting device is prepared according to any one of claims 1-8.

10. The polymer / UCNPs self-assembled anti-counterfeiting device according to claim 9, characterized in that, When excited by a laser of a specific wavelength, the anti-counterfeiting device displays an anti-counterfeiting pattern.

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