阅读说明：本技术 磁场响应光子晶体防伪薄膜及其制备方法与应用 (Magnetic field response photonic crystal anti-counterfeiting film and preparation method and application thereof ) 是由 曹玉华 许佳晟 于 2020-12-19 设计创作，主要内容包括：本发明涉及一种磁场响应光子晶体防伪薄膜及其制备方法与应用。本发明通过采用十二烷基硫酸钠作为细乳化的乳化剂,通过在细乳液中挥发有机溶剂合成了粒径可调的超顺磁性纳米晶簇,用于制备构建光子晶体的磁性胶体纳米粒子。并通过修饰非离子聚合物和包覆二氧化硅合成了稳定、均一的磁性胶体纳米粒子,用于制备磁组装光子晶体。再采用琼脂糖水凝胶的作为薄膜材料,在磁场下固化形成磁响应光子晶体防伪薄膜。本发明制备的磁响应光子晶体防伪薄膜,可以在施加磁场后,瞬间显示防伪图案,当撤销磁场后,图案立即消失,实现防伪图案的快速显-隐。制备简单快速、成本较低、防伪响应快速,防伪图案可调控,可以作为防伪材料应用。(The invention relates to a magnetic field response photonic crystal anti-counterfeiting film and a preparation method and application thereof. The invention adopts sodium dodecyl sulfate as emulsifying agent for fine emulsification, and synthesizes superparamagnetic nano crystal cluster with adjustable particle size by volatilizing organic solvent in the fine emulsion, which is used for preparing magnetic colloidal nano particles for constructing photonic crystals. And the stable and uniform magnetic colloid nano particles are synthesized by modifying the nonionic polymer and coating the silicon dioxide, and are used for preparing the magnetic assembly photonic crystals. And then, agarose hydrogel is adopted as a film material, and the magnetic response photonic crystal anti-counterfeiting film is formed by curing under a magnetic field. The magnetic response photonic crystal anti-counterfeiting film prepared by the invention can display anti-counterfeiting patterns instantly after a magnetic field is applied, and the patterns disappear immediately after the magnetic field is cancelled, so that the anti-counterfeiting patterns are displayed and hidden quickly. The preparation is simple and rapid, the cost is low, the anti-counterfeiting response is rapid, the anti-counterfeiting pattern can be regulated and controlled, and the anti-counterfeiting material can be used as an anti-counterfeiting material.)

1. A preparation method of a magnetic field response photonic crystal anti-counterfeiting film is characterized by comprising the following steps:

(1) dispersing hydrophobic magnetic nanoparticles in an organic solvent to serve as an oil phase, dissolving an emulsifier in water to serve as a water phase, mixing the oil phase and the water phase, and then performing fine emulsification to obtain an oil-in-water type miniemulsion;

(2) evaporating the oil-in-water type miniemulsion under negative pressure to remove the organic solvent to obtain a magnetic nano crystal cluster, and then modifying the magnetic nano crystal cluster by using a water-soluble macromolecular compound;

(3) coating the modified magnetic nano crystal cluster with silicon dioxide by a sol-gel method, and then washing and magnetically separating for multiple times to obtain magnetic colloidal nano particles;

(4) the magnetic colloid nano particles are dispersed in a hydrogel solution and are solidified under a magnet forming a pattern to form the photonic crystal anti-counterfeiting film with the pattern capable of being displayed and hidden.

2. The method according to claim 1, wherein in step (1), the emulsifier is sodium lauryl sulfate or a C16-C22 alkyl trimethyl quaternary ammonium salt.

3. The preparation method according to claim 1, wherein the hydrophobic magnetic nanoparticles are oleic acid-modified ferroferric oxide, oleylamine-modified ferroferric oxide or lauric acid-modified ferroferric oxide.

4. The method according to claim 1, wherein the water-soluble macromolecule is polyvinylpyrrolidone, N-methylpyrrolidone, or hydroxycellulose.

5. The method according to claim 1, wherein in the step (1), the organic solvent is a low boiling point organic solvent.

6. The preparation method according to claim 1, wherein the mass concentration of the hydrophobic magnetic nanoparticles in the oil phase is 2.5-12.5%, and the mass concentration of the emulsifier is 0.075-0.2%.

7. The process according to claim 1, wherein in the step (1), the volume ratio of the oil phase to the aqueous phase is 1:10 to 16.

8. The method according to claim 1, wherein in the step (4), the hydrogel is agarose and has a mass concentration of 1 wt% to 1.5 wt%.

9. The magnetic field response photonic crystal anti-counterfeiting film prepared by the method of any one of claims 1 to 8.

10. The use of the magnetic field responsive photonic crystal security film of claim 9 in the field of security materials.

Technical Field

The invention relates to the technical field of magnetic response photonic crystals and anti-counterfeiting, in particular to a magnetic response photonic crystal anti-counterfeiting film and a preparation method and application thereof.

Background

With the development of society and the advancement of science and technology, the spreading ways and related fields of counterfeit products are more and more extensive, the market is seriously disturbed, and the problem of counterfeit phenomenon needs to be solved urgently. The anti-counterfeiting technology is a preventive technical measure for protecting enterprise brands and consumer interests, maintaining normal operation of enterprises and fighting against counterfeit products, and is widely applied to the fields of currency, certificates, medicines, food, cosmetics, cigarettes, wine, clothing, audio-visual products and the like. Although most of the current products can be protected by advanced anti-counterfeiting technologies such as fluorescence anti-counterfeiting, thermochromism, holographic patterns, watermarks and the like, economic losses caused by counterfeiting and faking are still increased year by year.

The photonic crystal is an ordered structure material formed by periodically arranging two or more media with different refractive indexes, a photonic forbidden band formed by the ordered structure can reflect light with specific wavelength, and due to the unique optical characteristic of the photonic crystal, the photonic crystal is widely researched in the fields of optical fibers, photovoltaic devices, infrared stealth, displays, color printing, sensors and the like. When the wavelength of the structural color is in the visible light region by adjusting the diffraction level interval, the light incidence angle and the refractive index of the medium, the structural color is generated. Unlike dyes and pigments, since the structural color of photonic crystals results from refraction, diffraction and dry radiation of light in the internal structure thereof, the structural color will always exist as long as the internal photonic band gap structure is not damaged or changed, and the cost is also low. In addition to the structural requirements, photonic crystals have lower material requirements and therefore more material types can be selected. And responsive materials can be introduced into the photonic crystal and patterns can be designed, so that the method has great application value in the anti-counterfeiting technical field.

The magnetic response photonic crystal is fixed in the hydrogel to prepare the magnetic response photonic crystal anti-counterfeiting film, and the obvious-hidden switch taking a magnetic field as an anti-counterfeiting pattern is realized. The magnetic response photonic crystal has the characteristic of quick assembly in a magnetic field, and the structural color of the magnetic response photonic crystal can be adjusted through the strength of the magnetic field and is quick in response. At present, the photonic crystal anti-counterfeiting film is mainly formed by stacking or printing polymers and silicon dioxide microspheres to form a photonic crystal structure, and needs longer time or precise equipment and instruments. In addition, the polymer is adopted as the film material of the photonic crystal, polymerization reaction is required, the preparation process is complicated, and the influence factors are large. Therefore, a photonic crystal anti-counterfeiting film which is simple to prepare, low in cost and quick in anti-counterfeiting response is developed.

Disclosure of Invention

In order to solve the technical problems, the invention develops a photonic crystal anti-counterfeiting film with magnetic field response. The invention combines the miniemulsion method and the sol-gel method to synthesize the colloidal nanoparticles with adjustable particle size and superparamagnetism, and takes the hydrogel as the substrate to prepare the photonic crystal anti-counterfeiting film with the visible-invisible pattern. When a magnetic field is applied, the anti-counterfeiting pattern is displayed, and after the magnetic field is canceled, the anti-counterfeiting pattern is hidden. The photonic crystal anti-counterfeiting thin film pattern is convenient to imprint, does not need polymerization reaction, and realizes the magnetic field identification of the anti-counterfeiting pattern.

The invention provides a preparation method of a magnetic field response photonic crystal anti-counterfeiting film, which comprises the following steps:

(1) dispersing hydrophobic magnetic nanoparticles in an organic solvent to serve as an oil phase, dissolving an emulsifier in water to serve as a water phase, mixing the oil phase and the water phase, and then performing fine emulsification to obtain an oil-in-water type miniemulsion;

(2) evaporating the oil-in-water type miniemulsion under negative pressure to remove the organic solvent to obtain a magnetic nano crystal cluster, and then modifying the magnetic nano crystal cluster by using a water-soluble macromolecular compound;

(3) coating the modified magnetic nano crystal cluster with silicon dioxide by a sol-gel method, and then washing and magnetically separating for multiple times to obtain magnetic colloidal nano particles;

(4) the magnetic colloid nano particles are dispersed in a hydrogel solution and are solidified under a magnet forming a pattern to form the photonic crystal anti-counterfeiting film with the pattern capable of being displayed and hidden.

Further, in the step (1), the emulsifier is Sodium Dodecyl Sulfate (SDS) or C16-C22 alkyl trimethyl quaternary ammonium salt.

Further, the hydrophobic magnetic nanoparticles are oleic acid-modified ferroferric oxide, oleylamine-modified ferroferric oxide or lauric acid-modified ferroferric oxide.

Further, the water-soluble macromolecule is polyvinylpyrrolidone, N-methyl pyrrolidone or hydroxy cellulose.

Further, in the step (1), the organic solvent is a low boiling point organic solvent.

Further, the low-boiling-point organic solvent is one or more of chloroform, ethyl acetate, n-hexane and cyclohexane.

Further, in the oil phase, the mass concentration of the hydrophobic magnetic nanoparticles is 2.5% -12.5%, and the mass concentration of the emulsifier is 0.075% -0.2%.

Further, in the step (1), the volume ratio of the oil phase to the water phase is 1: 10-16.

Further, the fine emulsification is ultrasonic fine emulsification for 1-5 min by an ultrasonic cell disruptor with the power of 120-72W.

Further, in the step (3), the silicon dioxide coating is performed in tetraethyl orthosilicate (TEOS).

Further, the dosage of the tetraethoxysilane is 0.3 to 3.0 percent.

Further, in the step (4), the hydrogel is agarose, and the mass concentration is 1 wt% -1.5 wt%.

The second purpose of the invention is to provide the magnetic field response photonic crystal anti-counterfeiting film prepared by the method.

The third purpose of the invention is to provide the application of the magnetic field response photonic crystal anti-counterfeiting film in the field of anti-counterfeiting materials.

By the scheme, the invention at least has the following advantages:

1. the invention synthesizes superparamagnetic nano crystal clusters with adjustable particle size by volatilizing organic solvent in miniemulsion, and is used for preparing magnetic colloidal nano particles for constructing photonic crystals.

2. The stable and uniform magnetic colloidal nanoparticles are synthesized by modifying the nonionic polymer and coating the silicon dioxide, and are used for preparing the magnetic assembly photonic crystals.

The invention adopts agarose hydrogel as a film material, and the magnetic response photonic crystal anti-counterfeiting film is formed by curing under a magnetic field.

4. The magnetic response photonic crystal anti-counterfeiting film prepared by the invention can display anti-counterfeiting patterns instantly after a magnetic field is applied, and the patterns disappear immediately after the magnetic field is cancelled, so that the anti-counterfeiting patterns are displayed and hidden quickly.

5. The magnetic response photonic crystal anti-counterfeiting film disclosed by the invention is simple and rapid to prepare, low in cost, rapid in anti-counterfeiting response and adjustable in anti-counterfeiting pattern, and can be used as an anti-counterfeiting material.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following description is made with reference to the preferred embodiments of the present invention and the accompanying detailed drawings.

Drawings

FIG. 1 is a transmission electron microscope image of magnetic colloid nano-particles and a scanning electron microscope image of a magnetic response photonic crystal anti-counterfeiting film;

FIG. 2 is a latent-visible image of the anti-counterfeiting pattern of the magnetic response photonic crystal anti-counterfeiting film after the magnetic field is removed and when the magnetic field is applied.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1: preparation of magnetic response photonic crystal anti-counterfeiting film

The preparation method comprises the following specific steps:

(1) oleic acid modified ferroferric oxide (OA-Fe)₃O₄) The preparation of (1): preparation of OA-Fe by improved chemical coprecipitation method₃O₄The magnetic nanoparticles of (1). Firstly, 0.02mol of ferrous chloride and 0.02mol of ferric chloride are mixed and dissolvedMechanically stirring 200mL of ultrapure water, heating in a 90 ℃ water bath, sequentially adding 30mL of ammonia water as a precipitator and 1.5g of oleic acid as a modifier, introducing nitrogen in the whole process to remove oxygen, and reacting for 1 h; respectively washing the mixture for multiple times by using deionized water and absolute ethyl alcohol until the mixture is neutral, and then carrying out vacuum drying at the temperature of 45 ℃ to obtain OA-Fe₃O₄And (4) storing the magnetic nanoparticles at normal temperature in a sealing manner for later use.

(2) Fine emulsification: weighing 450mg of OA-Fe₃O₄Fully dispersing magnetic nanoparticles in a proper amount of low-boiling organic solvent chloroform to serve as an oil phase, dissolving 50mg SDS in 40mL of deionized water to serve as a water phase, and ultrasonically finely emulsifying for 4min by using an ultrasonic cell disruption instrument with the power of 240W to obtain an oil-in-water (O/W) type miniemulsion;

(3) coating with silicon dioxide: evaporating the organic solvent from the miniemulsion under reduced pressure at normal temperature, carrying out magnetic separation to obtain magnetic nano crystal clusters, dissolving 1.6g of polyvinylpyrrolidone (PVP) in 60mL of deionized water, adding 250mg of magnetic nano clusters, carrying out ultrasonic treatment for 5min, pouring 20mL of the solution into an alcohol-water solution (80mL of ethanol, 4mL of ammonia water and 0.9mL of TEOS) which is stirred for 30min in advance, continuing stirring for 40min, and carrying out magnetic separation and multiple water washing to obtain magnetic colloidal nanoparticles coated with silicon dioxide;

(4) magnetic response photonic crystal anti-counterfeiting film: boiling and dissolving 1 wt% of agarose in deionized water, adding 3mg/mL of the magnetic colloid nano particles, uniformly mixing, injecting the mixture between two clean glass sheets, assembling the mixture into photonic crystals under a pattern formed by a magnet, cooling, and solidifying to form a film to obtain the magnetically-responsive photonic crystal anti-counterfeiting film.

Example 2: preparation of magnetic response photonic crystal anti-counterfeiting film

The preparation method comprises the following specific steps:

(1) oleic acid modified ferroferric oxide (OA-Fe)₃O₄) The preparation of (1): preparation of OA-Fe by improved chemical coprecipitation method₃O₄The magnetic nanoparticles of (1). Firstly, mixing and dissolving 0.02mol of ferrous chloride and 0.02mol of ferric chloride in 200mL of ultrapure water, mechanically stirring, heating in a water bath at 90 ℃, sequentially adding 30mL of ammonia water as a precipitator and 1.5g of oleic acid as a modifier, introducing nitrogen in the whole process to remove oxygen, and reacting for 1 h; with deionized water andrespectively washing the mixture with absolute ethyl alcohol for multiple times until the mixture is neutral, and then drying the mixture in vacuum at 45 ℃ to obtain OA-Fe₃O₄And (4) storing the magnetic nanoparticles at normal temperature in a sealing manner for later use.

(2) Fine emulsification: weighing 450mg of OA-Fe₃O₄Fully dispersing magnetic nanoparticles in a proper amount of low-boiling organic solvent chloroform to serve as an oil phase, dissolving 70mg SDS in 40mL of deionized water to serve as a water phase, and ultrasonically finely emulsifying for 4min by using an ultrasonic cell disruption instrument with the power of 360W to obtain an oil-in-water (O/W) type miniemulsion;

(3) coating with silicon dioxide: evaporating the organic solvent from the miniemulsion under reduced pressure at normal temperature, carrying out magnetic separation to obtain magnetic nano crystal clusters, dissolving 1.6g of polyvinylpyrrolidone (PVP) in 60mL of deionized water, adding 250mg of magnetic nano clusters, carrying out ultrasonic treatment for 5min, pouring 20mL of the solution into an alcohol-water solution (80mL of ethanol, 4mL of ammonia water and 0.6mL of TEOS) which is stirred for 30min in advance, continuing stirring for 40min, and carrying out magnetic separation and multiple water washing to obtain magnetic colloidal nanoparticles coated with silicon dioxide;

(4) magnetic response photonic crystal anti-counterfeiting film: boiling and dissolving 1.5 wt% of agarose in deionized water, adding 3mg/mL of the magnetic colloid nano particles, uniformly mixing, injecting the mixture between two clean glass sheets, assembling the mixture into photonic crystals under a pattern formed by magnets, cooling, and solidifying to form a film to obtain the magnetically-responsive photonic crystal anti-counterfeiting film.

Example 3:

the magnetic colloidal nanoparticles prepared in example 1 were observed under a transmission electron microscope, and the specific transmission electron microscope image is shown in fig. 1 a. It can be seen that the particles obtained have a regular spherical character and are uniform in particle size. The sample magnetic colloidal nanoparticles have good monodispersity. The magnetic response photonic crystal anti-counterfeiting film prepared in example 1 is observed under a scanning electron microscope, and a specific scanning electron microscope image is shown in fig. 1 b. It can be seen that the magnetic particles have chain-like structures in the agarose hydrogel, but because the agarose concentration is low, the hydrogel network has weak fixing ability to the particles, and when the magnetic field is removed, the particles originally arranged under the action of the magnetic field diffuse to the surroundings due to mutual repulsion of the solvolysis layers, so as to achieve the effect of hiding the pattern. When a magnetic field is applied, the particles restore the chain structure again to form structural color, and the particles without the magnetic field during curing can not form an ordered structure under the fixation of the hydrogel and the repulsion of the solvent layer, so that a special pattern appears.

Example 4:

the method for obtaining the obvious-hidden anti-counterfeiting pattern by applying the magnetic response photonic crystal anti-counterfeiting film comprises the following steps:

when the magnetic-response photonic crystal anti-counterfeiting film in example 1 is placed on a magnetic field, as shown in fig. 2b, a pattern with photonic crystal structural color appears in the film. When the magnetic field is removed, the pattern in the security film disappears as shown in fig. 2 a.

Comparative example 1:

according to the preparation method of example 1, except that when the agarose concentration in the specific preparation step is 0.5 wt%, after the particles and the agarose solution are cooled to form a film in a special magnetic field, the hydrogel network has weak immobilization effect on the magnetic colloidal nanoparticles, and when the magnetic field is applied, the structural color of the hydrogel changes integrally, and the anti-counterfeiting pattern cannot be displayed.

According to the preparation method of the embodiment 1, only when the concentration of the agarose is 3 wt% in the specific preparation steps, after the particles and the agarose solution are cooled to form a film on a special magnetic field, because the fixing effect of the agarose hydrogel network on the magnetic colloid nano particles is strong, the anti-counterfeiting pattern can not be hidden when the magnetic field is removed.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.