Nanoparticles and preparation and application of self-assembled three-dimensional non-close-packed photonic crystals

Abstract

The application relates to the field of nanomaterials and photonic crystal materials, in particular to a kind of nanoparticles and preparation and application of three-dimensional non-close-packed photonic crystal of self-assembly of the nanoparticles, the nanoparticles are colloidal nanoparticles with ionized phenolic hydroxyl on the surface, and the nanoparticles can be self-assembled into three-dimensional non-close-packed photonic crystal in the concentration range of 1 wt%-60 wt%. The application solves the problem that three-dimensional non-close-packed colloidal photonic crystal is difficult to realize self-assembly at low concentration. By adjusting the mass fraction of particles in solution, three-dimensional non-close-packed colloidal photonic crystal with rich colors can be self-assembled, and has wide application prospect in the fields of sensing, display and the like.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials and photonic crystal materials, and particularly to a nanoparticle and its preparation and self-assembly of a three-dimensional non-dense photonic crystal. Background Technology

[0002] With the rapid development of science and technology, three-dimensional non-dense colloidal photonic crystals with periodic structures have great application prospects in sensing, anti-counterfeiting, and display fields due to their tunable photonic bandgap and excellent optical properties. Typically, highly charged monodisperse nanoparticles self-assemble in solution to form non-dense three-dimensional structures due to electrostatic interactions between particles. However, current design strategies often limit the concentration of structural colors generated by particle self-assembly to above 15 wt% due to insufficient electrostatic repulsion between colloidal nanoparticles (Lee, et al, Adv. Mater. 2010, 22, 4973-4977; Song, et al, J. Mater. Chem. C, 2022, 10, 3114-3120). This often poses a significant obstacle in material design and application.

[0003] Therefore, designing three-dimensional colloidal photonic crystals with self-assembly properties over a wide concentration range is of great significance and remains a challenge. Summary of the Invention

[0004] In view of this, one of the objectives of the present invention is to provide a nanoparticle that achieves an ultra-high surface charge on the particle surface and can self-assemble at an ultra-low mass fraction.

[0005] The second objective of this invention is to provide a method for preparing nanoparticles that solves the technical problem of insufficient electrostatic repulsion between colloidal nanoparticles, making it difficult to achieve the self-assembly of three-dimensional non-densely packed photonic crystals at low concentrations.

[0006] The third objective of this invention is to provide a self-assembled three-dimensional non-densely packed photonic crystal, which is self-assembled from colloidal nanoparticles with a surface containing polyhydroxy compounds.

[0007] The fourth objective of this invention is to provide a method for preparing a self-assembled three-dimensional non-densely packed photonic crystal, which is simple, easy to implement and control.

[0008] The fifth objective of this invention is to provide an application of a self-assembled three-dimensional non-densely packed photonic crystal.

[0009] One of the technical solutions adopted to achieve the objective of this invention is: a nanoparticle, wherein the nanoparticle is a colloidal nanoparticle with ionized phenolic hydroxyl groups on its surface, and the nanoparticle can self-assemble into a three-dimensional non-close-packed photonic crystal in a concentration range of 1 wt%-60 wt%.

[0010] The nanoparticles of this invention, due to the large number of ionized phenolic hydroxyl groups on their surface, can self-assemble into three-dimensional non-densely packed self-assembled colloidal photonic crystals that produce structural colors within a low concentration range, compared to existing technologies.

[0011] Preferably, more than 10% of the phenolic hydroxyl groups modified on the surface of the nanoparticles are ionized.

[0012] Preferably, the average particle size of the colloidal nanoparticles is 5 nm-1 μm.

[0013] Preferably, the average particle size of the colloidal nanoparticles is 30 nm-1 μm.

[0014] Preferably, the colloidal nanoparticles have a PDI (polydispersity index) of 0-0.2, including silica nanoparticles, or oxides or sulfides of at least one of iron, cobalt, nickel, titanium, zinc, cerium, cadmium, aluminum, copper, molybdenum, vanadium, manganese, chromium, and tungsten on their surface or themselves.

[0015] The oxides or sulfides of the metal elements selected in this invention are all rich in coordinating unsaturated metal ions and can coordinate or complex with phenolic hydroxyl groups, thus enabling the multifunctional modification of polyhydroxy compounds on their surfaces.

[0016] The second objective of this invention is achieved by a method for preparing the aforementioned nanoparticles, which involves treating colloidal nanoparticles modified with polyhydroxy compounds using an alkaline solution.

[0017] This invention involves treating colloidal nanoparticles modified with polyhydroxy compounds with an alkaline solution, resulting in nanoparticles that exhibit the properties of self-assembled three-dimensional non-dense photonic crystals over a wide concentration range (1 wt%-60 wt%).

[0018] Preferably, the method for preparing the colloidal nanoparticles modified with polyhydroxy compounds involves using a solvent containing polyhydroxy compounds to perform one or more surface modifications on the colloidal nanoparticles, and washing away the free polyhydroxy compounds in the system after the reaction is completed to obtain colloidal nanoparticles with polyhydroxy compounds modified on the surface.

[0019] Preferably, the solute in the alkaline solution includes at least one of hydroxide, borate, carbonate, bicarbonate, acetate, phosphate, and pH buffer.

[0020] Preferably, the pH of the alkaline solution is ≥7.4.

[0021] Preferably, the alkaline solution includes at least one of sodium hydroxide solution, sodium tetraborate decahydrate solution, sodium carbonate solution, sodium bicarbonate solution, sodium acetate solution, and sodium phosphate solution.

[0022] The alkaline solution includes at least one of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, sodium acetate solution, and sodium phosphate solution with a concentration of 0.05~0.2 mol / L, or sodium tetraborate decahydrate solution with a concentration of 0.026~0.262 mol / L.

[0023] Sufficient alkaline solution is used; after treatment, unreacted solutes are washed away.

[0024] The addition of alkaline solution makes it easier for the polyhydroxy compounds modified on the surface of colloidal nanoparticles to ionize, giving the colloidal nanoparticles an ultra-high surface charge, so as to achieve a thick electric bilayer and high electrostatic repulsion between particles. By adjusting the mass fraction of particles in the solution, they can self-assemble into three-dimensional non-dense colloidal photonic crystals with rich colors.

[0025] In addition, unlike other alkaline solutions, sodium tetraborate decahydrate has the following effects: when dissolved in water, it generates hydroxide ions, making the solution alkaline, which can promote the ionization of polyhydroxy compounds. At the same time, it generates free borate ions, which react with the hydroxyl groups on the polyhydroxy compounds to form BO covalent bonds, providing connection points for constructing multilayer polyhydroxy compound modifications. By changing the content of surface polyhydroxy compounds, the surface charge of particles can be dynamically adjusted, thereby further expanding the surface charge of particles and achieving excellent self-assembly performance.

[0026] When using sodium tetraborate decahydrate solution as an alkaline solution to treat colloidal nanoparticles modified with polyhydroxy compounds, an excess of polyhydroxy compounds needs to be added to the system after treatment.

[0027] Preferably, the polyhydroxy compound includes compounds containing phenolic hydroxyl groups.

[0028] Preferably, the polyhydroxy compound includes at least one of tannic acid, catechin, epigallocatechin gallate, epigallocatechin gallate, pyrogallol, dopamine, chlorogenic acid, neochlorogenic acid, and lignin compounds.

[0029] The third objective of this invention is achieved by the following technical solution: a self-assembled three-dimensional non-densely packed photonic crystal, which is prepared using the aforementioned nanoparticles.

[0030] The fourth objective of this invention is achieved by the following technical solution: a method for preparing the self-assembled three-dimensional non-dense photonic crystal, wherein the nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-60 wt%, and the nanoparticles self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

[0031] Preferably, the nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-30 wt%, and the nanoparticles self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

[0032] Preferably, the nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-20 wt%, and the nanoparticles self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

[0033] Preferably, the nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-15 wt%, and the nanoparticles self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

[0034] Preferably, the nanoparticles in the dispersion system will self-assemble into a three-dimensional non-close-packed photonic crystal due to electrostatic repulsion.

[0035] Preferably, the solvent includes at least one of carbonates, carboxylic esters, ethers, alkanols, pyrrolidones, acetonitrile, dimethyl sulfoxide, deionized water, acetone, and N,N-dimethylformamide.

[0036] Preferably, the carbonates include at least one of cyclic carbonates (such as ethylene carbonate, propylene carbonate), chain carbonates (such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate), and fluorocarbonates; the carboxylic acid esters include at least one of γ-butyrolactone, ethyl acetate, and methyl formate; the ethers include at least one of tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxymethane, and 1,2-dimethoxyethane; the alkanols include at least one of methanol, ethanol, and isopropanol; and the pyrrolidones include at least one of N-methylpyrrolidone, 1-epoxy-2-pyrrolidone, N-octylpyrrolidone, 1-acetyl-2-pyrrolidone, 4-hydroxy-2-pyrrolidone, 2-pyrrolidone, and 1-methyl-2-pyrrolidone. The fluorocarbonates include fluorocyclic carbonates (such as fluoroethylene carbonate: fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl ethylene carbonate, fluoropropylene carbonate: trifluoromethyl propylene carbonate, etc.) and fluorochain carbonates (such as dimethyl fluorocarbonate, methyl ethyl fluorocarbonate, diethyl fluorocarbonate, etc.).

[0037] The fifth objective of this invention is achieved through the following technical solution: an application of the aforementioned nanoparticles or self-assembled three-dimensional non-dense photonic crystals in the fields of anti-counterfeiting, sensors, display technology, biomedicine, and smart windows.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. The nanoparticles of the present invention achieve ultra-high surface charge on the particle surface, solving the technical problem that the electrostatic repulsion between colloidal nanoparticles is insufficient and it is difficult to achieve self-assembly of three-dimensional non-dense photonic crystals at low concentrations. Self-assembly can occur at ultra-low mass fractions.

[0040] 2. The nanoparticle preparation method of the present invention modifies the particle surface by introducing polyhydroxy compounds, and under treatment with alkaline salt solution, the polyhydroxy compounds can be better ionized, resulting in an ultra-high surface charge on the particle surface. Compared with traditional colloidal photonic crystals, the nanoparticles prepared by the present invention achieve an ultra-high surface charge on the particle surface and can self-assemble in solutions with ultra-low mass percentages.

[0041] 3. The materials used in this invention are widely available, the preparation process is simple and fast, and it is easy to mass-produce. Attached Figure Description

[0042] Figure 1 Digital photographs of the three-dimensional non-densely packed self-assembled colloidal photonic crystals at different concentrations prepared in Example 1;

[0043] Figure 2 The Zeta potential diagrams in water are for Fe3O4 particles prepared in Example 2 that were not treated with alkaline salt solution and Fe3O4 particles treated with sodium tetraborate decahydrate solution.

[0044] Figure 3 This is a digital photograph of the three-dimensional non-dense-packed self-assembled colloidal photonic crystal prepared in Example 2, which generates color through self-assembly.

[0045] Figure 4 This is a digital photograph of the three-dimensional non-dense-packed self-assembled colloidal photonic crystal prepared in Example 3, which generates color through self-assembly.

[0046] Figure 5 This is a digital photograph of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 4, which generates color through self-assembly.

[0047] Figure 6 This is a digital photograph of the three-dimensional non-dense-packed self-assembled colloidal photonic crystal prepared in Example 5, which generates color through self-assembly.

[0048] Figure 7A digital photograph of the three-dimensional non-dense-packed self-assembled colloidal photonic crystal prepared in Example 6, showing the colors generated through self-assembly.

[0049] Figure 8 A digital photograph of the three-dimensional non-dense-packed self-assembled colloidal photonic crystal prepared in Example 7, showing the colors generated through self-assembly.

[0050] Figure 9 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 8.

[0051] Figure 10 A digital photograph of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 9, showing the colors generated through self-assembly.

[0052] Figure 11 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 10.

[0053] Figure 12 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 11.

[0054] Figure 13 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 12.

[0055] Figure 14 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 13.

[0056] Figure 15 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 14.

[0057] Figure 16 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 15.

[0058] Figure 17 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 16.

[0059] Figure 18 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 17.

[0060] Figure 19 This is a digital photograph of the colors produced by the self-assembly of the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 18. Detailed Implementation

[0061] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0062] Unless otherwise specified, the methods described in the following examples are conventional; the reagents and materials described are commercially available unless otherwise specified.

[0063] The following specific embodiments further illustrate this solution.

[0064] Example 1

[0065] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 93 nm.

[0066] The preparation method includes the following steps:

[0067] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0068] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.262 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0069] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in propylene carbonate solutions of different volumes to obtain three-dimensional non-dense self-assembled colloidal photonic crystals with mass fractions of 17.19 wt%, 12.77 wt%, 8.449 wt%, 6.735 wt%, 4.188 wt%, 3.345 wt%, 2.505 wt%, and 1.667 wt%, respectively.

[0070] like Figure 1 The figures show three-dimensional non-densely packed self-assembled colloidal photonic crystals at different concentrations prepared in Example 1. It can be observed that the colloidal nanoparticles designed according to this invention can self-assemble into three-dimensional non-densely packed photonic crystals at low concentrations. Furthermore, by keeping the particle size constant, the color gradually redshifts with increasing concentration, and second-order diffraction phenomena are observed.

[0071] Example 2

[0072] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 137 nm.

[0073] The preparation method includes the following steps:

[0074] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0075] S2. Take 40 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.262 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0076] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 667 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 5 wt%.

[0077] In another preparation, without treatment with sodium tetraborate decahydrate solution, 40 mg of Fe3O4 colloidal nanoparticles with tannic acid surface modified were directly dispersed in a 667 μL propylene carbonate solution to obtain a dispersion with a mass fraction of 5 wt%.

[0078] To verify the performance improvement resulting from alkaline solution treatment, zeta potential testing was used. Figure 2 As shown in the figure, it is clear that compared with the untreated particles, the zeta potential of the particles treated with sodium tetraborate decahydrate increased by more than 20 mV, indicating that the surface charge was enhanced and the electrostatic repulsion between particles was increased. Figure 3 Figure a shows a three-dimensional non-densely packed self-assembled colloidal photonic crystal formed by the self-assembly of particles treated with sodium tetraborate decahydrate prepared in Example 2. The crystal is bright yellow-green in color. Figure 3 b represents particles obtained without treatment with sodium tetraborate decahydrate solution, which cannot undergo color development through self-assembly at this concentration.

[0079] Example 3

[0080] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 76 nm.

[0081] The preparation method includes the following steps:

[0082] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0083] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.2 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0084] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 1140 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 4.188 wt%.

[0085] like Figure 4 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 3, which is bright red in color.

[0086] Example 4

[0087] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 100 nm.

[0088] The preparation method includes the following steps:

[0089] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0090] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0091] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 340 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 12.77 wt%.

[0092] like Figure 5 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 4, which is bright green in color.

[0093] Example 5

[0094] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 120 nm.

[0095] The preparation method includes the following steps:

[0096] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0097] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.262 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0098] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 540 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 8.449 wt%.

[0099] like Figure 6 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 5, which is dark red in color.

[0100] Example 6

[0101] A three-dimensional non-densely packed self-assembled colloidal photonic crystal comprises Fe3O4 particles with catechin surface modified and an N-methylpyrrolidone solution; the Fe3O4 particles have a particle size of 120 nm.

[0102] The preparation method includes the following steps:

[0103] S1. Disperse the original Fe3O4 particles into an N-methylpyrrolidone solution with a concentration of 20 mg / mL catechin, sonicate them, and then wash them 1-2 times by centrifugation with N-methylpyrrolidone solution to remove free catechin in the system, so as to obtain Fe3O4 colloidal nanoparticles with catechin modified on the surface.

[0104] S2. Take 60 mg of Fe3O4 particles with catechin surface modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then add an aqueous solution of catechin with a concentration of 20 mg / mL.

[0105] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 116 μL N-methylpyrrolidone solution to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 30 wt%.

[0106] like Figure 7 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 6, which is cyan in color.

[0107] Example 7

[0108] A three-dimensional non-densely packed self-assembled colloidal photonic crystal comprises Fe3O4 particles with dopamine surface-modified and an N-octylpyrrolidone solution; the Fe3O4 particles have a particle size of 137 nm.

[0109] The preparation method includes the following steps:

[0110] S1. Disperse the original Fe3O4 particles into an N-octylpyrrolidone solution with a concentration of 10 mg / mL dopamine. After sonication, wash the particles 1-2 times with N-octylpyrrolidone solution to remove free dopamine from the system, and obtain Fe3O4 colloidal nanoparticles with surface modified with dopamine.

[0111] S2. Take 60 mg of Fe3O4 particles with dopamine surface modified and disperse them in a 0.06 mol / L sodium tetraborate decahydrate solution, and then add an aqueous solution of dopamine with a concentration of 10 mg / mL.

[0112] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 75 μL N-octylpyrrolidone solution to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 40 wt%.

[0113] like Figure 8 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 7, which is blue in color.

[0114] Example 8

[0115] A three-dimensional non-densely packed self-assembled colloidal photonic crystal comprises Fe3O4 particles with surface modified with epigallocatechin and a 1-epoxy-2-pyrrolidone solution; the Fe3O4 particles have a particle size of 120 nm.

[0116] The preparation method includes the following steps:

[0117] S1. The original Fe3O4 particles were dispersed in a 1-epoxy-2-pyrrolidone solution with a concentration of 10 mg / mL epigallocatechin. After ultrasonic homogenization, the particles were centrifuged and washed 1-2 times with 1-epoxy-2-pyrrolidone solution to remove free epigallocatechin from the system, thus obtaining Fe3O4 colloidal nanoparticles with surface modified epigallocatechin.

[0118] S2. Take 100 mg of Fe3O4 particles with surface modified with epigallocatechin and disperse them in a 0.2 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of epigallocatechin with a concentration of 10 mg / mL.

[0119] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 1-epoxy-2-pyrrolidone solution with a volume of 83 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 50 wt%.

[0120] like Figure 9 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 8, which is purple in color.

[0121] Example 9

[0122] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 200 nm.

[0123] The preparation method includes the following steps:

[0124] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0125] S2. Take 100 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.026 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0126] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 56 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 60 wt%.

[0127] like Figure 10 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 9, which is dark purple in color.

[0128] Example 10

[0129] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 140 nm.

[0130] The preparation method includes the following steps:

[0131] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0132] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.262 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0133] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 2940 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 1.667 wt%.

[0134] like Figure 11 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 10. Due to the low mass fraction, the main spectral peak shifts to the infrared, and the observed color is the second-order diffraction produced by the photonic crystal, appearing green in the digital photograph.

[0135] Example 11

[0136] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 160 nm.

[0137] The preparation method includes the following steps:

[0138] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0139] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified and disperse them in a 0.05 mol / L sodium hydroxide solution;

[0140] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 540 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled magnetic photonic crystal with a mass fraction of 8.449 wt%.

[0141] like Figure 12 The image shows the three-dimensional non-densely packed self-assembled magnetic photonic crystal prepared in Example 11, which is bright yellow-green in color.

[0142] Example 12

[0143] A three-dimensional non-densely packed self-assembled magnetic photonic crystal includes Fe3O4 particles with tannic acid surface-modified and an N-methylpyrrolidone solution; the Fe3O4 particles have a particle size of 70 nm.

[0144] S1. Disperse the original Fe3O4 particles into an N-methylpyrrolidone solution with a concentration of 5 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with N-methylpyrrolidone solution to remove free tannic acid from the system, so as to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0145] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified and disperse them in a 0.2 mol / L sodium hydroxide solution;

[0146] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 240 μL N-methylpyrrolidone solution to obtain a three-dimensional non-densely packed self-assembled magnetic photonic crystal with a mass fraction of 17.19 wt%.

[0147] like Figure 13 The image shows the three-dimensional non-densely packed self-assembled magnetic photonic crystal prepared in Example 12, which is bright blue in color.

[0148] Example 13

[0149] A three-dimensional non-densely packed self-assembled magnetic photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 105 nm.

[0150] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 15 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0151] S2. Take 60 mg of Fe3O4 particles with tannic acid surface-modified and disperse them in a 0.2 mol / L sodium hydroxide solution;

[0152] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 340 μL to obtain a three-dimensional non-densely packed self-assembled magnetic photonic crystal with a mass fraction of 17.19 wt%.

[0153] like Figure 14 The image shows the three-dimensional non-densely packed self-assembled magnetic photonic crystal prepared in Example 13, which is bright green in color.

[0154] Example 14

[0155] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 93 nm.

[0156] S1. The above Fe3O4 particles were dispersed in a propylene carbonate solution with a concentration of 20 mg / mL tannic acid. After ultrasonic homogenization, the particles were centrifuged and washed 1-2 times with propylene carbonate solution to remove free tannic acid from the system, thus obtaining Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0157] S2. Take 60 mg of Fe3O4 particles with tannic acid surface modification and disperse them in a 0.1 mol / L sodium acetate solution. After washing twice with deionized water and ethanol, disperse them in a 690 μL propylene carbonate solution to obtain a three-dimensional non-close-packed self-assembled colloidal photonic crystal with a mass fraction of 6.74 wt%.

[0158] like Figure 15 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 14. It appears as a deep red color in the digital photograph.

[0159] Example 15

[0160] A three-dimensional non-densely packed self-assembled magnetic photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 93 nm.

[0161] S1. The above Fe3O4 particles were dispersed in a propylene carbonate solution with a concentration of 10 mg / mL tannic acid. After ultrasonic homogenization, the particles were centrifuged and washed 1-2 times with propylene carbonate solution to remove free tannic acid from the system, thus obtaining Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0162] S2. Take 60 mg of Fe3O4 particles with tannic acid surface modification and disperse them in a 0.1 mol / L sodium carbonate solution. After washing twice with deionized water and ethanol, disperse them in a 540 μL propylene carbonate solution to obtain a three-dimensional non-close-packed self-assembled colloidal photonic crystal with a mass fraction of 8.45 wt%.

[0163] like Figure 16 The image shows the three-dimensional non-densely packed self-assembled magnetic photonic crystal prepared in Example 15. It appears yellow in the digital photograph.

[0164] Example 16

[0165] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes SiO2 particles with tannic acid surface-modified and a propylene carbonate solution; the SiO2 particles have a particle size of 118 nm.

[0166] The preparation method includes the following steps:

[0167] S1. Disperse the original SiO2 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0168] S2. Take 40 mg of SiO2 particles with tannic acid surface-modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 15 mg / mL.

[0169] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 360 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 8.5 wt%.

[0170] like Figure 17 The image shows the three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 16. It is blue in color and exhibits crystallization.

[0171] Example 17

[0172] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes CeO2 particles with tannic acid surface-modified and a propylene carbonate solution; the CeO2 particles have a particle size of 132 nm.

[0173] The preparation method includes the following steps:

[0174] S1. Disperse the original CeO2 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0175] S2. Take 40 mg of CeO2 particles with tannic acid surface-modified, disperse them in a 0.1 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 20 mg / mL.

[0176] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 667 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 4.7 wt%.

[0177] like Figure 18 The image shows a three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 17, which is green in color.

[0178] Example 18

[0179] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 93 nm.

[0180] The preparation method includes the following steps:

[0181] S1. Disperse Fe3O4 particles with chlorogenic acid on the surface into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid. After sonication, wash the Fe3O4 colloidal nanoparticles with propylene carbonate solution by centrifugation 1-2 times to remove free tannic acid from the system, and obtain Fe3O4 colloidal nanoparticles with tannic acid and chlorogenic acid on the surface.

[0182] S2. Take 40 mg of Fe3O4 particles with surface modified with tannic acid and chlorogenic acid, disperse them in a 0.1 mol / L sodium tetraborate decahydrate solution, and then add an aqueous solution of tannic acid with a concentration of 20 mg / mL.

[0183] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 531 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 5.83 wt%.

[0184] like Figure 19 The image shows a three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in Example 18, which is red in color.

[0185] Example 19

[0186] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 30 nm.

[0187] The preparation method includes the following steps:

[0188] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0189] S2. Take 40 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0190] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 360 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 8.45 wt%.

[0191] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment has a reflection peak in the ultraviolet light, with a peak value of 384 nm.

[0192] Example 20

[0193] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes Fe3O4 particles with tannic acid surface-modified and a propylene carbonate solution; the Fe3O4 particles have a particle size of 1 μm.

[0194] The preparation method includes the following steps:

[0195] S1. Disperse the original Fe3O4 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain Fe3O4 colloidal nanoparticles with tannic acid modified on the surface.

[0196] S2. Take 40 mg of Fe3O4 particles with tannic acid surface-modified, disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0197] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 360 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 8.45 wt%.

[0198] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment has a reflection peak in the infrared, with a peak value of 2175 nm.

[0199] Example 21

[0200] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes ZnS particles with tannic acid surface-modified and a propylene carbonate solution; the ZnS particles have a particle size of 140 nm.

[0201] The preparation method includes the following steps:

[0202] S1. Disperse the original ZnS particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then wash them 1-2 times by centrifugation with propylene carbonate solution to remove free tannic acid from the system, so as to obtain ZnS colloidal nanoparticles with tannic acid modified on the surface.

[0203] S2. Take 40 mg of ZnS particles with tannic acid surface-modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 15 mg / mL.

[0204] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 160 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 17.19 wt%.

[0205] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment is green in color.

[0206] Example 22

[0207] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes CdS particles with tannic acid surface-modified and a propylene carbonate solution; the CdS particles have a particle size of 120 nm.

[0208] The preparation method includes the following steps:

[0209] S1. Disperse the original CdS particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain CdS colloidal nanoparticles with tannic acid modified on the surface.

[0210] S2. Take 40 mg of CdS particles with tannic acid surface-modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 12 mg / mL.

[0211] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 120 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 20 wt%.

[0212] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment is orange in color.

[0213] Example 23

[0214] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes TiO2 particles with tannic acid surface-modified and a propylene carbonate solution; the TiO2 particles have a particle size of 110 nm.

[0215] The preparation method includes the following steps:

[0216] S1. Disperse the original TiO2 particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain TiO2 colloidal nanoparticles with tannic acid modified on the surface.

[0217] S2. Take 40 mg of TiO2 particles with tannic acid surface-modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0218] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a propylene carbonate solution with a volume of 226 μL to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 12.77 wt%.

[0219] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment is red in color.

[0220] Example 24

[0221] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes CoO particles with tannic acid surface-modified and a propylene carbonate solution; the CoO particles have a particle size of 95 nm.

[0222] The preparation method includes the following steps:

[0223] S1. Disperse the original CoO particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then centrifuge and wash them 1-2 times with propylene carbonate solution to remove free tannic acid from the system, to obtain CoO colloidal nanoparticles with tannic acid modified on the surface.

[0224] S2. Take 40 mg of CoO particles with tannic acid surface modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 10 mg / mL.

[0225] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 160 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 17.19 wt%.

[0226] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment is blue in color.

[0227] Example 25

[0228] A three-dimensional non-densely packed self-assembled colloidal photonic crystal includes NiO particles with tannic acid surface-modified and a propylene carbonate solution; the NiO particles have a particle size of 140 nm.

[0229] The preparation method includes the following steps:

[0230] S1. Disperse the original NiO particles into a propylene carbonate solution with a concentration of 10 mg / mL tannic acid, sonicate them evenly, and then wash them 1-2 times by centrifugation with propylene carbonate solution to remove free tannic acid in the system, so as to obtain NiO colloidal nanoparticles with tannic acid modified on the surface.

[0231] S2. Take 40 mg of NiO particles with tannic acid surface-modified and disperse them in a 0.15 mol / L sodium tetraborate decahydrate solution, and then continue to add an aqueous solution of tannic acid with a concentration of 20 mg / mL.

[0232] S3. The product from step S2 was washed twice with deionized water and ethanol, and then dispersed in a 120 μL solution of propylene carbonate to obtain a three-dimensional non-densely packed self-assembled colloidal photonic crystal with a mass fraction of 20 wt%.

[0233] The three-dimensional non-densely packed self-assembled colloidal photonic crystal prepared in this embodiment is red in color.

[0234] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0235] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A nanoparticle, characterized in that: The nanoparticles are colloidal nanoparticles with ionized phenolic hydroxyl groups on their surface. These nanoparticles can self-assemble into three-dimensional non-close-packed photonic crystals within a concentration range of 1 wt% to 60 wt%. They are prepared by treating the colloidal nanoparticles modified with polyhydroxy compounds with an alkaline solution.

2. The nanoparticles according to claim 1, characterized in that: The average particle size of the colloidal nanoparticles is 5 nm to 1 μm.

3. The nanoparticles according to claim 1, characterized in that: The colloidal nanoparticles have a PDI of 0-0.2 and include silica colloidal nanoparticles, or oxides or sulfides of at least one of iron, cobalt, nickel, titanium, zinc, cerium, cadmium, aluminum, copper, molybdenum, vanadium, manganese, chromium, and tungsten on their surface or in themselves.

4. The nanoparticles according to claim 1, characterized in that: The solute in the alkaline solution includes at least one of hydroxides, borates, carbonates, bicarbonates, acetates, phosphates, and pH buffers.

5. The nanoparticles according to claim 1, characterized in that: The polyhydroxy compounds include compounds containing phenolic hydroxyl groups.

6. A self-assembled three-dimensional non-densely packed photonic crystal, characterized in that: It is self-assembled from the nanoparticles according to any one of claims 1-5.

7. A method for preparing a self-assembled three-dimensional non-dense-packed photonic crystal as described in claim 6, characterized in that: The nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-60 wt%. The nanoparticles then self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

8. The method for preparing a self-assembled three-dimensional non-dense-packed photonic crystal according to claim 7, characterized in that: The nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-30 wt%. The nanoparticles then self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

9. The method for preparing a self-assembled three-dimensional non-dense-packed photonic crystal according to claim 7, characterized in that: The nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-20 wt%. The nanoparticles then self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

10. The method for preparing a self-assembled three-dimensional non-dense-packed photonic crystal according to claim 7, characterized in that: The nanoparticles are dispersed in a solvent to form a colloidal nanoparticle dispersion system with a concentration of 1 wt%-15 wt%. The nanoparticles then self-assemble to obtain the self-assembled three-dimensional non-dense photonic crystal.

11. A method for preparing a self-assembled three-dimensional non-dense-packed photonic crystal according to any one of claims 7-10, characterized in that: The solvent includes at least one of carbonates, carboxylic esters, ethers, alkanols, pyrrolidones, acetonitrile, dimethyl sulfoxide, deionized water, acetone, and N,N-dimethylformamide.

12. The application of a nanoparticle as described in any one of claims 1-5, or a self-assembled three-dimensional non-dense photonic crystal as described in claim 6, or a self-assembled three-dimensional non-dense photonic crystal prepared by the preparation method of claims 7-11, characterized in that: It is applied in fields such as anti-counterfeiting, sensors, display technology, biomedicine, and smart windows.

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