A material with structural color and its preparation method and application

Abstract

The application belongs to the field of optics and nanomaterial self-assembly, and provides a material with structural color and a preparation method and application thereof. A polymer nanoring is used as an assembly unit, an easily volatile organic solvent is used as a dispersion medium, and a water vapor interface is used as an assembly interface. A self-assembly process induced by an interface surface tension gradient is used to make the nanoring array directionally arrange on the water surface. The nanoring has an outer diameter of 500-1000 nm and a thickness of 100-400 nm. Subsequently, LB film analyzer technology is used to controllably transfer the closely arranged nanoring array to a transparent substrate under suitable film forming pressure, film forming speed, film pulling speed and film pulling pressure to obtain a material with structural color. The structural color material prepared by the application has obvious structural color and angle correlation, and the structural color can be regulated by the size of the assembly unit, and is suitable for use in the fields of display, anti-counterfeiting, encryption and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optics and self-assembly of nanomaterials, and relates to a material with structural color and a preparation method and application thereof. BACKGROUND

[0002] Nanometer arrays with periodicity assembled by colloidal particles can interact with light to produce bright and colorful structural colors, also known as structural colors. Such structural colors are different from conventional pigments or dyes, and have the advantages of environmental friendliness, strong stability and insensitivity to light, thus playing an increasingly important role in the fields of anti-counterfeiting, display, encryption and the like.

[0003] According to the morphological characteristics of colloidal particles, nanometer arrays can be divided into nanosphere arrays and arrays of anisotropic nanoparticles with complex morphologies. Compared with nanosphere arrays, arrays of anisotropic nanoparticles with complex morphologies can improve the diversity of assembly methods and thus enhance the light regulation ability of nanometer arrays. Wang et al. reported in the article "Magnetic Assembly and Field-Tuning of Ellipsoidal-Nanoparticle-Based Colloidal Photonic Crystals" that an ordered assembly body assembled by ellipsoidal nanoparticles has different periodicities in different directions due to the asymmetry of the ellipsoidal structure, which is a feature that nanosphere assemblies do not have, thus significantly widening the adjustable range of reflected light. Song et al. reported in the article "Design and Self-Assembly of Polyhedron Particles to Construct Iridescent Structural Colors" that a nanometer array composed of polyhedral assembly units exhibits a shining metallic structural color due to the multi-directional scattering properties of the polyhedron, and this unique structural color has application potential in the field of anti-counterfeiting. The above studies show that it is necessary to further expand the types of anisotropic nanoparticle assemblies and study the influence of their structures on light transmission, both in the field of theoretical research and in the field of application. However, in general, the research in this regard is very limited, which is mainly attributed to the difficulty of the ordered assembly process of anisotropic nanoparticles with complex morphologies.

[0004] In the previous research work (CN112499615A), we reported a kind of anisotropic nano-polymer ring, nano-carbon ring and its preparation method. With long-chain fatty alcohol phase change material, surfactant, phenol, aldehyde and organic amine as raw materials, water as solvent, through low temperature polymerization, polymer ring with regular shape and adjustable cross section diameter was prepared. Since these nano-ring materials do not have periodic structure, they do not have structural color themselves. Based on the generation principle of structural color, periodic arrangement of nano-ring is expected to prepare new structural color materials, which is of great significance to expand the application performance and scene of structural color materials. However, for nano-ring with anisotropic morphology, the van der Waals force and electrostatic force it receives in the solution are not symmetrical, so it is necessary to more accurately control the orientation of nano-ring in order to prepare uniform and ordered nano-ring array. Due to the above challenges, there is no report on this aspect. SUMMARY

[0005] In view of the shortcomings of the prior art, the first object of the present application is to provide a material with structural color, which is composed of a transparent substrate and a single-layer nano-ring array uniformly covering the surface of the substrate. In the nano-ring array, the nano-rings are closely arranged in a "flat" manner, and the number of nano-rings per square millimeter is 800-2000. The structural color material can exhibit structural color changing with the observation angle under transmission condition.

[0006] The second object of the present application is to provide a preparation method of a material with structural color, and the principle of the preparation method is the self-assembly process of nano-ring induced by surface tension gradient.

[0007] The third object of the present application is to provide the application of a material with structural color in the fields of structural color material, anti-counterfeiting, display and encryption, etc.

[0008] Technical scheme of the present application:

[0009] A material with structural color is mainly composed of a transparent substrate and a single-layer nano-ring array uniformly covering the surface of the substrate. In the nano-ring array, the nano-rings are closely arranged in a "flat" manner, and the number of nano-rings per square millimeter is 800-2000. The structural color material can exhibit structural color changing with the observation angle under transmission condition.

[0010] A preparation method of a material with structural color, comprising the following steps:

[0011] ①Nano-ring is added to volatile organic solvent and ultrasonically oscillated to obtain a nano-ring dispersion liquid with a certain concentration;

[0012] (2) the preparation of the material with structural color by using the FLB2000A LB film analyzer: fill the aqueous ammonia solution with certain pH in the disc surface of the LB film analyzer as the sub-phase, then clamp the transparent substrate with the mechanical arm of the LB film analyzer and immerse it in the groove in the center of the disc surface; slowly drop a certain volume of the above-mentioned nanoring dispersion liquid into the aqueous ammonia solution; the addition of the organic solvent will cause the imbalance of the surface tension of the whole water surface, and the convection of the water surface will occur under the driving of the imbalance of the surface tension, and the nanorings will float on the water surface to form a loose "island-shaped" nanoring monolayer aggregate; set the parameters (film forming speed, film forming pressure, film pulling speed, film pulling pressure) of the LB film analyzer, then the LB film analyzer barriers at both ends of the disc surface start to move according to the set film forming speed and compress the nanoring aggregate floating on the water surface into a closely arranged nanoring array under the set film forming pressure. Then control the mechanical arm to pull the transparent substrate upwards at the set film pulling speed, and the barriers will slowly adjust the position to keep the pressure on the nanoring array at the set film pulling pressure, so that the nanoring array on the water surface is slowly transferred to the continuously elevated substrate. After the substrate completely leaks out of the water surface, the nanoring array is uniformly transferred to the substrate surface to obtain the material with structural color.

[0013] The nanoring has an outer diameter of 500-1000 nm and a thickness of 100-400 nm.

[0014] The volatile organic solvent is propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol or amyl alcohol, preferably butyl alcohol.

[0015] The mass fraction of the nanorings in the nanoring dispersion liquid is 0.5%-3.5%, preferably 2%.

[0016] The pH of the aqueous ammonia solution is between 7.1 and 11.0, preferably 10.0.

[0017] The certain volume of the nanoring dispersion liquid is 0.2-4 μL of the nanoring dispersion liquid per square centimeter of the disc surface.

[0018] The parameters of the LB film analyzer are as follows: the film forming pressure is 15-30 mN / m; the film forming speed is 1 mm / min-40 mm / min; the film pulling speed is 1 mm / min-40 mm / min; and the film pulling pressure is 15-30 mN / m.

[0019] The transparent substrate is glass, quartz, PDMS, PET, PP or the like, preferably glass and quartz.

[0020] The application discloses a material with structural color and a preparation method and application thereof. The structural color material is obtained by closely arranging a nanoring array on a transparent substrate through an LB film analyzer by means of a surface tension induced self-assembly method. The concentration of a suitable nanoring dispersion liquid, a solvent component, a pH of a subphase, a film forming speed, a film forming pressure, a film pulling speed and a film pulling pressure can avoid problems such as disordered accumulation, multi-layer overlapping and sparse arrangement of the nanoring array, and are the key to preparing a high-quality nanoring array. A better nanoring arrangement state is a prerequisite for obtaining bright structural color. The size of the nanoring can be further adjusted to adjust the properties of the structural color, and the material exhibits application potential in novel structural color materials. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A micro-morphology diagram of the nanoring assembly array prepared in the embodiment 1 of the application.

[0022] Figure 2 A scattering spectrum of the nanoring assembly array prepared in the embodiment 1 of the application varying with a scattering angle.

[0023] Figure 3 A micro-morphology diagram of the nanoring assembly array prepared in the embodiment 2 of the application.

[0024] Figure 4 A scattering spectrum of the nanoring assembly array prepared in the embodiment 2 of the application varying with a scattering angle.

[0025] Figure 5 A micro-morphology diagram of the nanoring assembly array prepared in the comparative example 1 of the application.

[0026] Figure 6 A micro-morphology diagram of the nanoring assembly array prepared in the comparative example 2 of the application.

[0027] Figure 7 A micro-morphology diagram of the nanoring assembly array prepared in the comparative example 10 of the application. DETAILED DESCRIPTION

[0028] The specific embodiment of the application is further illustrated in combination with the drawings and technical solutions.

[0029] Embodiment 1

[0030] A preparation method of a material with structural color, specifically comprising the following steps:

[0031] ① 20 mg of polymer nanorings (an outer diameter of 850 nm and a thickness of 250 nm) are added into 1 mL of butanol and ultrasonically oscillated to obtain a 2wt% nanoring dispersion liquid;

[0032] (2) Preparation of the structural color material by using the FLB2000A LB film analyzer: Fill the NH4OH aqueous solution with pH = 10 in the disc surface of the LB film analyzer as the subphase, then clamp the glass slide with the mechanical arm of the LB film analyzer and immerse it in the groove in the center of the disc surface filled with water. Slowly drop 200 μL of the above-mentioned nanoring dispersion liquid on the water surface, i.e. drop 0.83 μL per square centimeter of the disc surface. Set the parameters of the LB film analyzer (film forming speed is 20 mm / min, film forming pressure is 20 mN / m, film pulling speed is 10 mm / min, film pulling pressure is 20 mN / m) and start the film forming operation, then the barriers at both ends of the disc surface start to move at the set film forming speed of 20 mm / min and compress the nanoring aggregates floating on the water surface into a closely arranged monolayer nanoring array at the set film forming pressure of 20 mN / m. Then control the mechanical arm to lift the glass slide upward at the set film pulling speed of 10 mm / min, while slowly adjust the position of the barriers to keep the pressure on the nanoring array stable at about 20 mN / m, so as to slowly transfer the nanoring array on the water surface to the continuously lifting glass slide. After the glass slide completely leaks out of the water surface, the nanoring array is uniformly transferred to the surface of the glass slide to obtain the structural color material.

[0033] Figure 1 Figure 1 is a scanning electron microscope (SEM) image of the nanoring array prepared in Example 1, from which it can be seen that the nanorings are closely arranged on the glass slide substrate in a "flat lying" manner.

[0034] Figure 2 Figure 2 is a scattering spectrum of the nanoring array prepared in Example 1 as a function of the scattering angle (the angle between the scattering angle and the normal direction of the array), it can be seen that as the scattering angle increases (the incident light and the scattered light are on both sides of the array, and the angle between the incident angle and the normal direction of the array is 0°), the scattering peak is always in the blue light region.

[0035] This ordered nanoring array has significant differences compared with the spherical array. First, the nanoring itself has two adjustable dimensions, i.e. the diameter and the thickness, so it has more adjustable dimensions and stronger controllability of optical properties compared with the nanosphere. Second, when the nanoring array is regarded as a kind of grating material, the cavity region inside and the gap region between the rings are periodically present, forming the effect of a complex grating, which is equivalent to the superposition of two layers of gratings with different structures. Theory shows that the complex grating can more effectively change the propagation path of light compared with the ordinary grating, thereby realizing a larger diffraction angle. Therefore, this kind of nanoring array may play a unique role in the fields of image display, signal transmission, etc. in the future.

[0036] Example 2

[0037] A method for preparing a material with structural color, which is different from example 1 in that the nanoring diameter is 970 nm and the thickness is 440 nm.

[0038] Figure 3 is a scanning electron microscope (SEM) image of the nanoring array prepared in example 2. As can be seen from the image, the nanorings are arranged directionally on the glass slide substrate.

[0039] Figure 4 is a scattering spectrum of the nanoring array prepared in example 2 as a function of scattering angle. It can be seen that as the scattering angle increases, the scattering peak position is red-shifted from the green region to the red region, which is significantly different from the structural color of the nanoring array of example 1. This is because as the size of the nanorings increases, the size of the periodic unit of the array increases, which will cause the red shift of the scattering peak according to the grating diffraction formula.

[0040] Example 3

[0041] A method for preparing a material with structural color, which is different from example 1 in that the concentration of the nanoring butanol dispersion is 1 wt%.

[0042] Example 4

[0043] A method for preparing a material with structural color, which is different from example 1 in that the solvent of the nanoring dispersion is isopropanol.

[0044] Example 5

[0045] A method for preparing a material with structural color, which is different from example 1 in that the pH of the sub-phase in the LB film analyzer is 8.

[0046] Example 6

[0047] A method for preparing a material with structural color, which is different from example 1 in that the volume of the nanoring dispersion added is 500 μL, i.e. 2.1 μL per square centimeter of the disc surface.

[0048] Example 7

[0049] A method for preparing a material with structural color, which is different from example 1 in that the transparent substrate is a PDMS film.

[0050] Example 8

[0051] A method for preparing a material with structural color, which is different from example 1 in that the film-forming pressure is 28 mN / m.

[0052] Comparative example 1

[0053] Comparative example 1 differs from example 1 in that the film-forming pressure of the LB film analyzer is 40 mN / m.

[0054] Figure 5 The scanning electron microscope (SEM) image of the nanoring array prepared in the present comparative example is shown in the figure. It can be seen from the figure that the nanoring array prepared in the present comparative example has obvious multi-layer stacking regions. This is because the pressure applied by the barrier is too large, causing the flexible nanoring array on the interface to break and stack with each other, forming a large number of irregular stacking structures.

[0055] Comparative Example 2

[0056] Comparative Example 2 differs from Example 1 in that the film-forming pressure of the LB film analyzer is 10 mN / m.

[0057] Figure 6 The scanning electron microscope (SEM) image of the nanoring array prepared in the present comparative example is shown in the figure. It can be seen from the figure that the nanoring array at this time is in the form of "island" scattered on the substrate in different numbers of nanorings. This is because the pressure applied by the barrier is too small, causing the nanorings dispersed on the water surface to fail to be closely connected into a large-scale monolayer array. The film-forming process is a pre-process of the film-removing process, and both of them together guarantee the ordering of the nanoring array. Therefore, the film-forming pressure needs to be adjusted within a suitable range, and both too large and too small are not conducive to the formation of high-quality nanoring arrays.

[0058] Comparative Example 3

[0059] Comparative Example 3 differs from Example 1 in that the film-removing pressure of the LB film analyzer is 40 mN / m.

[0060] The nanoring array structure obtained under this condition has a large number of disordered stacking regions. The effect of too large film-removing pressure is similar to that of too large film-forming pressure, both of which will cause the nanoring array to be stacked with each other due to too large compression force during the transfer to the substrate, resulting in disordered nanoring array.

[0061] Comparative Example 4

[0062] Comparative Example 4 differs from Example 1 in that the film-removing pressure of the LB film analyzer is 10 mN / m.

[0063] The nanoring array structure obtained under this condition is very sparse. The effect of too small film-removing pressure is similar to that of too small film-forming pressure, both of which will cause the nanoring array to fail to be closely connected into a large-scale monolayer array due to too small compression force during the transfer to the substrate, resulting in loose nanoring array structure. The film-removing pressure is a decisive factor affecting the quality of the nanoring array during the film transfer process, and both too large and too small will cause the ordering of the film transferred to the substrate to decrease.

[0064] Comparative Example 5

[0065] The difference between Comparative Example 5 and Example 1 is that the film formation speed of the LB film analyzer is 45 mm / min.

[0066] The nano-ring array structure obtained under this condition has a large number of disordered stacking regions. The film formation speed is too large (45 mm / min), which can cause the nano-rings floating on the water surface to be quickly connected and stacked. In this process, the interaction force of the local regions of the entire nano-ring array is easily unbalanced, which can increase the number of disordered stacking regions of the obtained nano-ring array and affect the order of the nano-ring array.

[0067] Comparative Example 6

[0068] The difference between Comparative Example 6 and Example 1 is that the film formation speed of the LB film analyzer is 0.5 mm / min.

[0069] The nano-ring array structure obtained under this condition has a large number of disordered stacking regions. When the film formation speed is too small (0.1 mm / min), the barrier compression process becomes very slow. The nano-rings can be gradually immersed in the water phase from the interface in a long standing process. Part of the nano-rings dispersed in the sub-phase can also be pulled to the glass slide surface, which can reduce the order of the nano-ring array.

[0070] Comparative Example 7

[0071] The difference between Comparative Example 7 and Example 1 is that the film formation speed of the LB film analyzer is 50 mm / min.

[0072] The nano-ring array structure obtained under this condition is very sparse. When the film formation speed is too large (60 mm / min), the nano-ring array does not have sufficient time to contact the substrate for transfer, which can result in a sparse nano-ring array structure.

[0073] Comparative Example 8

[0074] The difference between Comparative Example 8 and Example 1 is that the film formation speed of the LB film analyzer is 0.1 mm / min.

[0075] The nano-ring array structure obtained under this condition has a large number of disordered stacking regions. When the film formation speed is too small (0.1 mm / min), the time for preparing a sample of one glass slide is about 50 min. The nano-rings can be gradually immersed in the water phase from the interface in a long standing process. Part of the nano-rings dispersed in the sub-phase can also be pulled to the glass slide surface, which can reduce the order of the nano-ring array.

[0076] Comparative Example 9

[0077] The difference between Comparative Example 9 and Example 1 is that the concentration of the nano-ring dispersion liquid is 0.2 wt%.

[0078] The nano-ring array structure obtained under this condition has a large number of disordered accumulation regions. It is known from Comparative Example 2 that the dispersed nano-rings on the water surface exist in an "island-like" structure. When the concentration of the nano-ring dispersion is too low (0.2 wt%), the nano-rings cannot form this more stable "island-like" structure during solvent evaporation, but are more dispersed alone. Therefore, they are easily submerged into the sub-phase during the subsequent solvent evaporation-induced disturbance process, and more defects are generated during the subsequent barrier compression process due to the more points of interaction between the rings than between the "islands".

[0079] Comparative Example 10

[0080] Comparative Example 10 differs from Example 1 in that the concentration of the nano-ring dispersion is 4.5 wt%.

[0081] Figure 7 The scanning electron microscope (SEM) image of the nano-ring array prepared in this comparative example shows that there are many irregular accumulations in the local area. This is because when the concentration of the nano-ring dispersion is too high, a large number of nano-rings are arranged on the water surface at the same time, and the high density causes each nano-ring to connect with other nano-rings before reaching an equilibrium state, resulting in a large number of disordered accumulation regions.

[0082] Comparative Example 11

[0083] Comparative Example 11 differs from Example 1 in that the sub-phase is an HCl aqueous solution with pH = 4.

[0084] The disordered accumulation regions of the nano-ring array obtained under this condition are significantly increased, because pH is a key factor affecting the surface potential of the nano-ring. When pH = 4, the surface potential of the polymer nano-ring is close to 0, and the electrostatic repulsion between the nano-rings is very weak, so the nano-rings are easily agglomerated during the arrangement process.

[0085] Comparative Example 12

[0086] Comparative Example 12 differs from Example 1 in that the sub-phase is an aqueous ammonia solution with pH = 12.

[0087] The disordered accumulation regions of the nano-ring array obtained under this condition are significantly increased, because the ammonia concentration is high at this time, although the surface potential of the nano-ring increases with increasing pH, but the disturbance caused by the evaporation of ammonia gas is large, which is not conducive to the assembly of the nano-rings.

[0088] Comparative Example 13

[0089] Comparative Example 13 differs from Example 1 in that the solvent in the nano-ring dispersion is ethanol.

[0090] The nano-ring array structure obtained under this condition has a large number of disordered accumulation regions. This is because ethanol is completely miscible with water, part of the nano-ring ethanol dispersion liquid added dropwise evaporates on the water surface, drives the nano-ring to float on the water surface under the action of surface tension, and the other part is miscible with water, resulting in direct dispersion of the nano-ring in the sub-phase. During the film drawing process, part of the nano-ring dispersed in the sub-phase is also drawn to the surface of the glass slide, resulting in a decrease in the order of the nano-ring array.

[0091] Comparative Example 14

[0092] Comparative Example 14 and Example 1 differ in that the volume of the nano-ring dispersion liquid added dropwise is 6 μL per square centimeter of disc surface.

[0093] The nano-ring array structure obtained under this condition has a large number of disordered accumulation regions. This is because adding too much nano-ring dispersion liquid will cause the area of the single-layer arrangement of the nano-ring to be larger than the disc surface area, resulting in disordered accumulation of the nano-ring array.

Claims

1. A material having structural color, characterized in that, The material with structural color mainly consists of a transparent substrate and a monolayer of nanoring array uniformly covering the surface of the substrate; in the nanoring array, the nanorings are closely arranged in a "flat" manner, and the number of nanorings arranged per square millimeter is 800-2000; The nanorings have an outer diameter of 500-1000 nm and a thickness of 100-400 nm; The material with structural color is prepared by the following steps: ① adding nanorings into a volatile organic solvent and ultrasonically oscillating to obtain a nanoring dispersion liquid with a certain concentration; ② using a FLB2000A LB film analyzer to prepare the material with structural color: filling a certain pH aqueous ammonia solution in the disc surface of the LB film analyzer as a subphase, then clamping the transparent substrate with the mechanical arm of the LB film analyzer and immersing it into the groove in the center of the disc surface; slowly adding a certain volume of the nanoring dispersion liquid into the aqueous ammonia solution to form a loose "island-shaped" nanoring monolayer aggregate; setting the film forming speed, film forming pressure, film pulling speed and film pulling pressure of the LB film analyzer, then the LB film analyzer at both ends of the disc surface starts to move according to the set film forming speed and compresses the nanoring aggregate floating on the water surface into a closely arranged monolayer nanoring array under the set film forming pressure; then controlling the mechanical arm to pull the transparent substrate upward at the set film pulling speed, while slowly adjusting the position of the barrier to keep the pressure on the nanoring array at the set film pulling pressure, so that the nanoring array on the water surface is slowly transferred onto the continuously rising transparent substrate; after the transparent substrate completely leaks out of the water surface, the nanoring array is uniformly transferred to the surface of the transparent substrate to obtain the material with structural color; the volatile organic solvent is propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol or amyl alcohol; the mass fraction of nanorings in the nanoring dispersion liquid is 0.5%-3.5%; the pH of the aqueous ammonia solution is between 7.1 and 11.0; the certain volume of nanoring dispersion liquid is 0.2-4 μL of nanoring dispersion liquid per square centimeter of disc surface; the parameters of the LB film analyzer are as follows: film forming pressure is 15-30 mN / m; film forming speed is 1 mm / min-40 mm / min; film pulling speed is 1 mm / min-40 mm / min; film pulling pressure is 15-30 mN / m.

2. The material with structural color according to claim 1, characterized in that, the transparent substrate is glass, quartz, PDMS, PET or PP.

3. The material with structural color according to claim 1 is used in the fields of structural color materials, display, anti-counterfeiting and encryption.

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