A plasmon-coupled dynamic non-copyable anti-counterfeiting label and its preparation method

Abstract

The present invention discloses a plasmon-coupled dynamic, non-copyable anti-counterfeiting label. The preparation method comprises the following steps: first, providing a photoresist layer on a silicon wafer substrate and patterning the wafer using photolithography; second, sequentially applying an aluminum film and a silver film by magnetron sputtering or thermal evaporation; third, dropwise adding a silver nanoparticle solution onto the silver film surface; the silver nanoparticles assemble onto the silver film in a random distribution through nonspecific adsorption and exhibit optical behavior response under detection light of a preset wavelength; and fourth, removing the photoresist layer on the silicon wafer substrate using an organic solvent, thereby producing a plasmon-coupled dynamic, non-copyable anti-counterfeiting label. The anti-counterfeiting label preparation method disclosed herein is simple, requires minimal equipment, and has a high detection speed, offering excellent development prospects in anti-counterfeiting.

Description

Technical Field

[0001] The present invention relates to the field of anti-counterfeiting labels, in particular to a plasmon-coupled dynamic non-copyable anti-counterfeiting label and a preparation method thereof. Background Art

[0002] Counterfeiting is a global problem that not only causes enormous economic losses but also poses a threat to individuals, businesses, and society as a whole. To address this growing counterfeiting market, highly secure information encryption based on the concept of physically unreplicable functions offers a reliable solution for anti-counterfeiting. A physically unreplicable function refers to a system with unique characteristics, each corresponding to a single input and a single output. The inherent, unique, and random nature of security labels stems from the uncertain nature of material processes, making them unclonable. To date, numerous security labels have been developed based on the inherent random nature of physically unreplicable functions. However, nearly all of these developed physically unreplicable functions utilize static encryption processes. Specifically, these labels are developed and manufactured based on static luminescent materials. Therefore, to further enhance the security of security labels, it is urgent to find new strategies for creating dynamic, physically unreplicable encryption systems, increasing the complexity of security labels and reducing the risk of cloning.

[0003] This invention utilizes self-assembly of silver nanoparticles and a silver film to achieve plasmon coupling, using this structure as an information carrier for pattern and spectral encoding. The result is a fluorescent, dynamically blinking, and non-replicable optical anti-counterfeiting label. The silver nanoparticles are dispersed onto the silver film through nonspecific adsorption, with Brownian motion causing them to distribute randomly during adsorption, thus ensuring the label's non-replicability. Under dark field conditions, the bright scattered light produced by the coupling of the metal nanoparticles and the metal film serves as a static code. Furthermore, under excitation with blue light (460 nm-495 nm), the plasmon structure formed by the coupling of the metal nanoparticles and the metal film exhibits distinct fluorescent blinking, which can serve as a dynamic code.

[0004] The anti-counterfeiting label of the present invention has various coding modes, excellent coding characteristics, a simple preparation method, low equipment requirements and a fast detection speed, and has excellent development prospects in anti-counterfeiting. Summary of the Invention

[0005] To further enhance the security of anti-counterfeiting labels, a new strategy is urgently needed to create a dynamic, physically unreplicable encryption system, increase the complexity of security labels, and reduce the risk of cloning. This invention combines silver nanoparticles with a silver film to achieve plasmon coupling, using this structure as an information carrier for pattern and spectral encoding. The result is a fluorescent, dynamically blinking, unreplicable optical anti-counterfeiting label.

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

[0007] A method for preparing a plasmon-coupled dynamic non-copyable anti-counterfeiting label, specifically comprising:

[0008] Step 1: a photoresist layer is provided on a silicon wafer substrate, and the silicon wafer is patterned using photolithography technology;

[0009] Step 2: depositing a layer of aluminum film and silver film on the patterned silicon wafer substrate by magnetron sputtering or thermal evaporation;

[0010] Step 3: Add the silver nanoparticle solution dropwise onto the surface of the silver film. The silver nanoparticles will assemble on the silver film in a random distribution through non-specific adsorption and will respond optically under the detection light of a preset wavelength.

[0011] Step 4: The photoresist layer on the silicon wafer substrate is removed by an organic solvent to produce a plasmon-coupled dynamic non-copyable anti-counterfeiting label.

[0012] As a further technical solution of the present invention, in step one, a required pattern is photoetched in the selected preset area.

[0013] As a further technical solution of the present invention, in step 2, before magnetron sputtering or thermal evaporation of the silver film, an aluminum film is provided as an adhesion layer, and the aluminum film can induce the formation of a silver film with a flat surface morphology and high stability.

[0014] As a further technical solution of the present invention, in step three, the detection light is output by a mercury lamp as a light source.

[0015] As a further technical solution of the present invention, in step three, the silver nanoparticles in the silver nanoparticle solution are in the shape of cubes, and have a particle size of 90-110 nm.

[0016] As a further technical solution of the present invention, in step 4, the organic solvent is isopropyl alcohol, which can well preserve the patterned nanoparticle-metal film coupling system with unique optical response.

[0017] Based on the above preparation method, the present invention provides a plasmon-coupled dynamic non-copyable anti-counterfeiting label, which includes light absorbed and scattered by nanoparticles under dark field as static encryption; and the fluorescent flashing phenomenon of plasmons under blue light excitation as dynamic encryption.

[0018] By adopting the above-mentioned technical solution, the present invention has the following beneficial effects compared with the prior art: silver cubic nanoparticles are non-specifically adsorbed on the silver film to form a dynamic optical anti-counterfeiting label information element, and the metal nanoparticle and metal film coupling system constructed by the present invention has multiple optical responses. The bright scattered image generated by the randomly distributed nanoparticles in the dark field is used as a static physical non-replicable functional code, and the fluorescent flashing image that changes with time is used as a dynamic code. Such a security label realizes multiple optical anti-counterfeiting encryption. In addition, the dynamic encrypted information can be converted into binary data, and the static scattered light is mainly yellow and green, which can be stored as "1" and "0" respectively; similarly, the bright (ON) and gray (OFF) states of the dynamic fluorescent flashing can be converted into "1" and "0" respectively. According to the optical response of the metal nanoparticle and metal film coupling system constructed according to the present invention, according to the calculation formula, the number of theoretical capacities can reach 2 900 . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a simplified flow chart of a method for preparing a plasmon-coupled dynamic non-copyable anti-counterfeiting label according to the present invention;

[0020] Figure 2 This is a schematic diagram of the components of a plasmon-coupled dynamic non-copyable anti-counterfeiting label of the present invention;

[0021] Figure 3 It is a schematic diagram of dark field scattering and dynamic multi-color fluorescence multiple optical responses of a plasmon-coupled dynamic non-copyable anti-counterfeiting label of the present invention;

[0022] Figure 4 Figure a shows the encryption mechanism of a plasmon-coupled dynamic, non-copyable anti-counterfeiting label of the present invention, in which dark-field scattering is used as static encoding and fluorescent flashing is used as dynamic encoding; b is a schematic diagram of the conversion of dynamic optical response into binary data; and c is the theoretical encoding capacity.

[0023] Figure 5 Figure a is a dark-field image of a plasmon-coupled dynamic non-replicable anti-counterfeiting label of the present invention, with an exposure time of 1 s; b is a fluorescence image of the anti-counterfeiting label changing with time, with an exposure time of 3 s; c is a dark-field scattering spectrum of a single particle; Figure 5 d is the dynamic fluorescence spectrum of a single particle changing with time. DETAILED DESCRIPTION

[0024] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and are not intended to be exhaustive. All other embodiments obtained by those of ordinary skill in the art without creative effort are intended to fall within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the present invention provides a method for preparing a plasmon-coupled dynamic non-copyable anti-counterfeiting label, which includes:

[0026] Step 1: a photoresist layer is provided on a silicon wafer substrate, and the silicon wafer is patterned using photolithography technology;

[0027] Step 2: A layer of aluminum film and silver film is formed on the patterned silicon wafer substrate by magnetron sputtering or thermal evaporation, wherein the aluminum film serves as an adhesion layer, which can induce the formation of a silver film with a flat surface morphology and high stability;

[0028] Step 3: Add a solution of silver cubic nanoparticles (particle size 90-110 nm) onto the surface of the silver film. The silver nanoparticles will assemble on the silver film in a random distribution through non-specific adsorption and will respond optically under the detection light of a preset wavelength.

[0029] Step 4: The photoresist layer on the silicon wafer substrate is removed by an organic solvent (isopropyl alcohol), thereby producing a dynamic, non-replicable anti-counterfeiting label coupled with plasmons.

[0030] In this solution, the detection light in step three is output by a mercury lamp as a light source.

[0031] In this solution, the organic solvent in step 4 is isopropyl alcohol, which can well preserve the patterned nanoparticle-metal film coupling system with unique optical response.

[0032] Figure 2 This is a schematic diagram of the components of a plasmon-coupled dynamic non-copyable anti-counterfeiting label of the present invention. The synthesis steps are as follows: Figure 1 As shown, silver cubic nanoparticles are non-specifically adsorbed on the silver film to form dynamic optical anti-counterfeiting label information elements.

[0033] Figure 3 This diagram illustrates the dark-field scattering and dynamic multicolor fluorescence multiple optical responses of a plasmon-coupled, dynamic, non-copyable anti-counterfeiting label. When observing the sample using a multifunctional microscope, silver nanoparticles produce strong light scattering in dark-field mode. Simultaneously, fluorescence flashes can be observed under blue light excitation, driven by the fluorescence generated by the silver clusters formed by the illumination.

[0034] Figure 4 a is an encryption mechanism of a plasma-exciton coupled dynamic non-copyable anti-counterfeiting label of the present invention. The bright scattering image data generated by randomly distributed nanoparticles can be used as a static physical non-copyable code, and the fluorescence flashing image that changes with time can be used as a dynamic code. In addition, the purple spots represent the image of the nanoparticles in the dark field scattering mode, while the green and yellow spots represent the fluorescence flashing images. The dynamic physical non-copyable security label can realize a variety of anti-counterfeiting optical encryption, including dark field scattering and fluorescence flashing. The dynamic encryption information can be converted into binary data, and the bright (ON) and gray (OFF) states of the dynamic fluorescence flashing can be stored as "1" and "0", respectively. Similarly, the yellow and green emission colors can also be stored as "1" and "0", respectively (such as Figure 4 b). The theoretical encoding capacity of the dynamic fluorescent physical non-copyable tag can be expressed as c = r p To calculate, where r represents the number of color responses and p represents the number of pattern pixels. According to the optical response of the metal nanoparticle and metal film coupling system we constructed, the value of r is 2. When the resolution of the label image is 30×30 pixels, the theoretical capacity can reach 2 900 .

[0035] Figure 5 Figure a shows a dark-field image of a plasmon-coupled, dynamic, non-replicable anti-counterfeiting label. Metal nanoparticles are randomly distributed on the metal film, forming donut-shaped scattering points. The image shows that the nanoparticles primarily scatter blue and red light. Dark-field scattering is dependent on the nanoparticle's shape and size, the refractive index of the surrounding environment, and the distance between the nanoparticles and the film. Test results show that the scattering points of individual silver nanoparticles in the dark field have similar scattering colors and intensities, indicating that all nanoparticles have a similar plasmon resonance environment. Figure 5 Figure b shows the fluorescence image of the security label over time. From these four images, we can clearly see that the brightness of the particles changes significantly over time, with noticeable flickering. To gain a deeper understanding of the optical performance of the dynamic security label, we further measured the scattering and fluorescence spectra of individual particles. Figure 5 c is the dark-field scattering spectrum. The nanoparticles have a weak resonance peak at 450 nm and a strong resonance peak at 680 nm, which is consistent with the donut shape shown in the dark-field scattering image. Figure 5d is the fluorescence spectrum of the same particle collected under blue light excitation. As expected, the spectrum shows the emission intensity and peak position that vary with time. To eliminate background effects, all emission spectra are obtained by collecting the fluorescence signal from the particles and subtracting the fluorescence from nearby areas without particles. The dark line represents the dark state of fluorescent flashing, while the other lines represent the flashing bright state. It is worth noting that the emission positions of the bright state are not the same. The peak positions of dark green and dark orange, and the peak position of the dark yellow line are 526 nm, 536 nm and 564 nm, respectively. Through optical testing of dynamic non-copyable anti-counterfeiting labels, the coupled system of silver cubic nanoparticles and silver films we constructed exhibited unique optical properties, realizing high-security dynamic information encryption.

[0036] The above descriptions are only some embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a plasmon-coupled dynamic non-copyable anti-counterfeiting label, characterized by: Specifically include: Step 1: a photoresist layer is provided on a silicon wafer substrate, and the silicon wafer is patterned using photolithography technology; Step 2: depositing a layer of aluminum film and silver film on the patterned silicon wafer substrate by magnetron sputtering or thermal evaporation; Step 3: Add the silver nanoparticle solution dropwise onto the surface of the silver film. The silver nanoparticles will assemble on the silver film in a random distribution through non-specific adsorption and will respond optically under the detection light of a preset wavelength. Step 4: removing the photoresist layer on the silicon wafer substrate with an organic solvent, thereby producing a plasmon-coupled dynamic non-copyable anti-counterfeiting label; The dynamic non-copyable anti-counterfeiting label includes two encryption methods: dark field scattering and fluorescent flashing. The encrypted information can be converted into binary data. The bright and gray states of fluorescent flashing can be stored as "1" and "0" respectively. The yellow and green emission colors can also be stored as "1" and "0" respectively. The detection light is blue light, and the detection light is output by a mercury lamp as a light source; The silver nanoparticles in the silver nanoparticle solution are in the shape of cubes and have a particle size of 90-110 nm; The organic solvent is isopropyl alcohol.

2. The method for preparing a plasmon-coupled dynamic non-copyable anti-counterfeiting label according to claim 1, wherein: In step 1, a desired pattern is photoetched in the selected preset area.

3. The method for preparing a plasmon-coupled dynamic non-copyable anti-counterfeiting label according to claim 1, wherein: In step 2, before magnetron sputtering or thermal evaporation of the silver film, an aluminum film is provided as an adhesion layer, and the aluminum film induces the formation of a silver film with a flat surface morphology and high stability.

4. A plasmon-coupled dynamic non-replicable anti-counterfeiting label prepared by the preparation method according to any one of claims 1 to 3.

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