A method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors

Abstract

This invention discloses a method for preparing iridescent cuprous oxide nanoparticle photonic crystals. By controlling the crystal form of the cuprous oxide nanoparticles, monodisperse spherical particles are obtained, enabling them to self-assemble into a three-dimensional ordered photonic crystal structure, thereby producing a brilliant iridescent color. The method for preparing iridescent cuprous oxide nanoparticle photonic crystals uses polycrystalline monodisperse spherical cuprous oxide nanoparticles as the structural unit, and is synthesized through the following steps: 1) High molecular weight polyvinylpyrrolidone, trisodium citrate, and soluble divalent copper salt are dissolved in a mixed solvent of polyethylene glycol and water, and stirred until completely dissolved; 2) A strong alkaline solution is added dropwise to the solution prepared in step 1), and a reducing agent is rapidly added after vigorous stirring. The reaction is stopped after complete stirring; 3) The reaction product is separated, washed, and vacuum dried.

Description

Technical Field

[0001] This invention belongs to the field of photonic crystal preparation technology, specifically relating to a method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors. The method involves preparing photonic crystals through the self-assembly of high-refractive-index nanoparticles and obtaining structural colors with iridescent colors by controlling the particle crystal form. Background Technology

[0002] Structural colors are produced by the scattering, interference, or diffraction of visible light when it is incident on an object with a spatial period similar to its wavelength. Compared to pigment colors, structural colors have the advantages of being fade-resistant, having easily controllable colors, and producing vibrant hues. Photonic crystals are materials with periodically varying dielectric constants and refractive indices. They produce iridescent structural colors through the diffraction of visible light within their structure, and have excellent application prospects in the textile printing and dyeing industry.

[0003] To improve structural color fastness on textile substrates, adhesives are typically used to bond the structural building blocks of photonic crystals, such as nanospheres, together before attaching them to the textile substrate. However, conventional photonic crystal structures for textile substrate coloring tend to use polymers and inorganic materials with low refractive indices (refractive index n of 1.4–1.5). While the addition of adhesives improves structural color fastness, the refractive index difference becomes very small because the adhesive's refractive index is very close to that of the structural building blocks in the crystal structure. This results in a significant decrease in diffraction intensity, leading to a deterioration in color (Light: Science & Applications, 2022, 11, 316).

[0004] To obtain robust and vibrant iridescent colors on textile substrates, photonic crystals are required using structural building blocks with high refractive indices (n>2.0). Cuprous oxide is considered a promising material for photonic crystal fabrication due to its advantages such as high refractive index (n=2.7), simple synthesis, and low cost. Indeed, cuprous oxide nanoparticles have been used as structural building blocks to construct structural colors in the literature (CN109850932B; Nanoscale, 2020, 12, 3220; ACS Appl. Mater. Interfaces 2021, 13, 57796). However, research shows that because these cuprous oxide nanoparticles are single crystals, interfacial tension prevents them from forming perfectly spherical shapes; therefore, they cannot be tightly packed into photonic crystals with a three-dimensional ordered structure.

[0005] To date, the structural color of cuprous oxide nanoparticles is believed to be generated based on Mie scattering of individual nanoparticles (Advanced Materials 2015, 27, 7432). Therefore, this structural color does not possess the iridescent color characteristic of photonic crystals. Based on this, how to form photonic crystals from cuprous oxide nanoparticles to obtain brilliant iridescent colors is a technical problem that needs to be solved. Summary of the Invention

[0006] In view of the shortcomings of the above-mentioned background technology, the purpose of this invention is to provide a method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors. By controlling the crystal form of cuprous oxide nanoparticles, monodisperse spherical particles are obtained, which can self-assemble into a three-dimensional ordered photonic crystal structure, thereby producing a brilliant iridescent color.

[0007] To solve the above-mentioned technical problems, the objective of this invention is achieved as follows:

[0008] A method for preparing iridescent cuprous oxide nanoparticle photonic crystals, wherein the structural unit is polycrystalline monodisperse spherical cuprous oxide nanoparticles, synthesized through the following steps:

[0009] 1) Dissolve high molecular weight polyvinylpyrrolidone, trisodium citrate and soluble divalent copper salt in a mixed solvent of polyethylene glycol and water, and stir until completely dissolved;

[0010] 2) Add the strong alkali solution dropwise into the solution prepared in step 1), stir vigorously, and then quickly add the reducing agent. Stop the reaction after it is complete under stirring.

[0011] 3) Separate the reaction products, wash and vacuum dry them.

[0012] Based on the above scheme and as a preferred embodiment of the above scheme: the number average molecular weight of the polyvinylpyrrolidone mentioned in step 1) is between 100,000 and 2,000,000.

[0013] Based on the above scheme and as a preferred option of the above scheme: the amount of polyvinylpyrrolidone used in step 1) is 5-20 grams per mole of copper.

[0014] Based on the above scheme and as a preferred embodiment of the above scheme: the molecular weight of the polyethylene glycol mentioned in step 1) is between 100 and 900.

[0015] Based on the above scheme and as a preferred embodiment of the above scheme: the ratio of polyethylene glycol and water in step 1) is 1:4 to 1:0.25.

[0016] Based on the above scheme and as a preferred embodiment of the above scheme: the strong alkaline solution in step 2) is sodium hydroxide, potassium hydroxide or cesium hydroxide; the reducing agent in step 2) is ascorbic acid, sodium ascorbate or hydrazine.

[0017] Based on the above scheme and as a preferred embodiment of the above scheme: the reaction temperature in step 2) is 0-50℃; the separation method in step 3) is centrifugation or filtration.

[0018] Based on the above scheme and as a preferred embodiment of the above scheme: the particle size of cuprous oxide nanoparticles is between 100-300 nanometers; the crystal domain size of cuprous oxide nanoparticles is less than 1 / 4 of the particle size.

[0019] Based on the above scheme and as a preferred option, the self-assembly of cuprous oxide nanoparticles is achieved by impregnation, printing or spraying.

[0020] A fabric with iridescent colors is made by bonding a composite of iridescent cuprous oxide nanoparticle photonic crystals and an adhesive to the fabric surface; the adhesive is polyacrylate, polyurethane, or polyvinyl butyral.

[0021] The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to the present invention has the following significant and beneficial technical effects compared to existing technologies:

[0022] This invention synthesizes cuprous oxide nanoparticles using a mixed solvent of water and polyethylene glycol, and stabilizes the generated nanoparticles with high molecular weight polyvinylpyrrolidone. Due to its large molecular weight, polyethylene glycol can effectively inhibit the growth of cuprous oxide single crystals, while high molecular weight polyvinylpyrrolidone acts as a weak flocculant, enabling single crystal particles to aggregate into larger particles.

[0023] The cuprous oxide nanoparticles prepared by the above method are spherical and can self-assemble and tightly pack into photonic crystals with a three-dimensional ordered structure, thus exhibiting a brilliant iridescent color. The use of an adhesive greatly improves the fastness of the obtained structural color on the fabric surface without reducing the brilliance of the iridescent color. Attached Figure Description

[0024] Figure 1 Scanning electron microscopy (SEM) images of cuprous oxide nanoparticles with different molar ratios of sodium citrate to copper acetate, and the relationship between average particle size, monodispersity index, and the molar ratio of sodium citrate to copper acetate. Specifically: (a) Molar ratio of sodium citrate to copper acetate: 0.7:1; (b) Molar ratio of sodium citrate to copper acetate: 0.8:1; (c) Molar ratio of sodium citrate to copper acetate: 1:1; (d) Molar ratio of sodium citrate to copper acetate: 1.2:1; (e) Molar ratio of sodium citrate to copper acetate: 1.3:1.

[0025] Figure 2 : Relationship between the average particle size of cuprous oxide nanoparticles under different molar ratios of sodium citrate and copper acetate;

[0026] Figure 3 Transmission electron microscopy image of cuprous oxide nanoparticles with a particle size of 212 nm.

[0027] Figure 4 Wide-angle X-ray diffraction pattern of cuprous oxide nanoparticles with a particle size of 212 nm.

[0028] Figure 5 (a) Scanning electron micrographs of cuprous oxide nanoparticles synthesized in an aqueous solution of ethylene glycol and (b) using low molecular weight polyvinylpyrrolidone.

[0029] Figure 6 Polyester fabric dyed with photonic crystals constructed from cuprous oxide nanoparticles of different particle sizes.

[0030] Figure 7 Photonic crystal structure constructed from cuprous oxide nanoparticles of different sizes and bonded to a textile substrate using a 3D microscope image.

[0031] Figure 8 Comparison of cuprous oxide nanoparticle photonic crystals bonded with polyvinyl butyral before and after water washing. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. In the following embodiments, unless otherwise specified, the reagents, materials and equipment used are commercially available, prepared by conventional methods, or commonly used in the industry. Unless otherwise specified, all percentages are in units of mass.

[0033] A method for preparing iridescent cuprous oxide nanoparticle photonic crystals, wherein the structural unit is polycrystalline monodisperse spherical cuprous oxide nanoparticles, synthesized through the following steps:

[0034] 1) Dissolve high molecular weight polyvinylpyrrolidone, trisodium citrate and soluble divalent copper salt in a mixed solvent of polyethylene glycol and water, and stir until completely dissolved; the water-soluble divalent copper salt is copper acetate, copper chloride or copper sulfate, etc.

[0035] 2) Add the strong alkali solution dropwise into the solution prepared in step 1), stir vigorously, and then quickly add the reducing agent. Stir for a certain period of time until the reaction is complete, and then stop.

[0036] 3) Separate the reaction products, wash and vacuum dry them.

[0037] Polycrystalline monodisperse spherical cuprous oxide nanoparticles were obtained.

[0038] The number average molecular weight of the polyvinylpyrrolidone mentioned in step 1 is between 100,000 and 2,000,000, preferably between 200,000 and 1,500,000, and more preferably between 500,000 and 1,500,000.

[0039] The amount of polyvinylpyrrolidone used in step 1) is 5-20 grams per mole of copper, preferably 10-15 grams. The molecular weight of the polyethylene glycol used in step 1) is between 100-900, preferably between 300-750. The ratio of polyethylene glycol to water in step 1) is 1:4-1:0.25, preferably 1:2-1:0.5.

[0040] The strong alkaline solution mentioned in step 2) is sodium hydroxide, potassium hydroxide, cesium hydroxide, or other similar solutions. The reducing agent mentioned in step 2) is ascorbic acid, sodium ascorbate, hydrazine, or other similar solutions.

[0041] The reaction temperature in step 2) is 0-50℃, preferably 20-30℃.

[0042] The separation method described in step 3) is centrifugation or filtration, including but not limited to these.

[0043] The particle size of cuprous oxide nanoparticles is between 100 and 300 nanometers; the crystal domain size of cuprous oxide nanoparticles is less than 1 / 4 of the particle size.

[0044] The diameter of cuprous oxide nanoparticles can be mainly controlled by the amount of trisodium citrate used; the particle size increases with the increase of the molar ratio of trisodium citrate to copper ions. Figure 1 ).

[0045] The self-assembly of cuprous oxide nanoparticles can be achieved through commonly used methods, such as impregnation, printing, or spraying, including but not limited to these.

[0046] The photonic crystals formed by the self-assembly of cuprous oxide nanoparticles can have their adhesion to fabric surfaces improved by compounding them with an adhesive, which can be polyacrylate, polyurethane, polyvinyl butyral, etc., including but not limited to these.

[0047] The cuprous oxide nanoparticles prepared by the above method can self-assemble into a tightly packed photonic crystal with a three-dimensional ordered structure, thus obtaining a brilliant iridescent color. The use of an adhesive greatly improves the fastness of the obtained structural color to the fabric surface, while the brilliance of the iridescent color is basically not reduced.

[0048] The color-generating effect of cuprous oxide nanoparticle photonic crystals was tested using black polyester fabric as the textile substrate.

[0049] Before self-assembly, the polyester fabric undergoes hydrophilic modification through plasma treatment, as follows: First, the polyester fabric is ultrasonically cleaned and cut to an appropriate size. A water-repellent treatment solution is prepared and the fabric is impregnated for 30 minutes. The fabric is then rolled dry using a horizontal roller, dried at 90°C, and finally baked at 160°C for 3 minutes to ensure that the fabric is hydrophobic on both sides.

[0050] After ironing the hydrophobic fabric with an electric iron, the fabric is treated with a cold plasma modification device with a power of 30-120w, a duration of 20-100s, and a vacuum degree of 30Pa.

[0051] Spraying method is adopted: the compressor pressure is set to 0.5 PSI and the spray gun nozzle diameter is 0.2 mm; the spraying process is: spraying time 10 s and spraying distance 10 cm.

[0052] To evaluate the stability of the photonic crystal color-generating structure, the photonic crystal structure-colored textiles were subjected to ultrasonic washing using an adhesive. Specifically, the textiles were washed using an ultrasonic oscillator with an ultrasonic frequency of 120 kHz, an ultrasonic power of 120 W, and an ultrasonic time of 10 min.

[0053] Example 1:

[0054] Dissolve 50g of polyethylene glycol with a number average molecular weight of 750 in 250mL of deionized water to obtain an aqueous solution of polyethylene glycol.

[0055] Weigh 2.00 g of polyvinylpyrrolidone with a number average molecular weight of 250,000, 0.30 g of copper acetate monohydrate (1.5 mmol), and different amounts of trisodium citrate dihydrate (1.05, 1.2, 1.5, 1.8, 1.95 mmol) into a beaker, and dissolve these compounds in an aqueous solution of polyethylene glycol using a magnetic stirrer.

[0056] Dissolve 0.32g of ascorbic acid in 15mL of deionized water to prepare a reducing agent solution.

[0057] Under 25°C water bath conditions, 20 mL of 0.5 M sodium hydroxide solution was rapidly added dropwise to the obtained copper oxide precursor solution with vigorous stirring. After stirring for 10 min, 15 mL of 2% ascorbic acid aqueous solution was added. The reaction was stopped after stirring for 60 min, and the product was obtained by centrifugation at 5000 r / min for 5 min. The product was washed three times with a mixture of water and ethanol to remove excess ligands and then vacuum dried for later use.

[0058] Scanning electron microscope image of cuprous oxide nanoparticles ( Figure 1The results show that the obtained particles have good monodispersity (dispersion index PDI≤0.08) and can self-assemble into a three-dimensional ordered photonic crystal structure.

[0059] Through transmission electron microscopy (TEM) Figure 3 Studies have shown that the particles synthesized using this method are spherical and have a polycrystalline structure.

[0060] Figure 4 These are the wide-angle X-ray diffraction patterns of these particles. Analyzing them using the Scherrer equation, we can obtain a crystal domain size D of 21 nanometers, which is 1 / 10 of the particle size.

[0061] D = Kλ / (βcosθ)

[0062] Where K is a constant; λ is the X-ray wavelength; β is the full width at half maximum (FWHM) of the diffraction peak; and θ is the diffraction angle.

[0063] Example 2:

[0064] Dissolve 50g of ethylene glycol in 250mL of deionized water to obtain an aqueous solution of ethylene glycol. This is different from the polyethylene glycol in Example 1.

[0065] Weigh 2.00 g of polyvinylpyrrolidone with a number average molecular weight of 250,000, 0.30 g of copper acetate monohydrate (1.5 mmol), and 0.51 g of trisodium citrate dihydrate (1.8 mmol) into a beaker, and dissolve these compounds in an aqueous solution of ethylene glycol using a magnetic stirrer.

[0066] Dissolve 0.32g of ascorbic acid in 15mL of deionized water to prepare a reducing agent solution.

[0067] Under 25°C water bath conditions, 20 mL of 0.5 M sodium hydroxide solution was rapidly added dropwise to the obtained copper oxide precursor solution with vigorous stirring. After stirring for 10 min, 15 mL of 2% ascorbic acid aqueous solution was added. The reaction was stopped after stirring for 60 min, and the product was obtained by centrifugation at 5000 r / min for 5 min. The product was washed three times with a mixture of water and ethanol to remove excess ligands and then vacuum dried for later use.

[0068] Scanning electron microscope image of the obtained cuprous oxide nanoparticles ( Figure 5 a) shows that the obtained particles are not spherical, and therefore cannot self-assemble into a three-dimensional ordered photonic crystal structure. Analysis of the wide-angle X-ray diffraction patterns of these particles using the Scherrer equation reveals that the crystal domain size and particle size are similar, indicating that these particles are single crystals.

[0069] Example 3:

[0070] Dissolve 50g of polyethylene glycol with a number average molecular weight of 500 in 250mL of deionized water to obtain an aqueous solution of polyethylene glycol.

[0071] Weigh 2.00 g of polyvinylpyrrolidone (NA) with a molecular weight of 56,000, 0.30 g of copper acetate monohydrate (1.5 mmol), and 0.51 g of trisodium citrate dihydrate (1.8 mmol) into a beaker, and dissolve these compounds in an aqueous solution of ethylene glycol using a magnetic stirrer. Dissolve 0.32 g of ascorbic acid in 15 mL of deionized water to prepare a reducing agent solution.

[0072] Under 25°C water bath conditions, 20 mL of 0.5 M sodium hydroxide solution was rapidly added dropwise to the obtained copper oxide precursor solution with vigorous stirring. After stirring for 10 min, 15 mL of 2% ascorbic acid aqueous solution was added. The reaction was stopped after stirring for 60 min, and the product was obtained by centrifugation at 5000 r / min for 5 min. The product was washed three times with a mixture of water and ethanol to remove excess ligands and then vacuum dried for later use.

[0073] Scanning electron microscope image of the obtained cuprous oxide nanoparticles ( Figure 5 b) shows that the obtained particles are not spherical, and therefore cannot self-assemble into a three-dimensional ordered photonic crystal structure. Analysis of the wide-angle X-ray diffraction patterns of these particles using the Scherrer equation reveals that the crystal domain size and particle size are similar, indicating that these particles are single crystals.

[0074] Table 1

[0075]

[0076] This invention innovatively replaces the monomer ethylene glycol with polyethylene glycol and adds high molecular weight polyvinylpyrrolidone as a weak flocculant, thereby obtaining spherical cuprous oxide nanoparticles with a polycrystalline structure and achieving wash-resistant structural color with iridescent effect on textiles.

[0077] Due to its large molecular weight, polyethylene glycol can effectively inhibit the growth of cuprous oxide single crystals, while high molecular weight polyvinylpyrrolidone is a weak flocculant that can aggregate single crystal particles into larger particles.

[0078] Dyed fabrics: Example 4

[0079] At room temperature, 2% (solid content) cuprous oxide nanoparticles of different sizes were ultrasonically dispersed in anhydrous ethanol. This dispersion was then added to a spray gun system and sprayed onto a polyester fabric. The coated textile was dried in an oven at 160°C for 1 minute, resulting in a densely ordered photonic crystal color-forming structure, and the fabric exhibited a distinct iridescent color. Figure 6 ).

[0080] Photonic Crystal Bonding Adhesive: Example 5

[0081] At room temperature, 4% (based on solids content) of cuprous oxide nanoparticles with a particle size of 205 nm and a dispersion index (PDI) of 0.07 and 2.5% of the binder polyvinyl butyral were dispersed in anhydrous ethanol, followed by ultrasonic treatment for 15 min to prepare a structural color-generating spraying solution. This spraying solution was then sprayed onto polyester fabric, and the coated textile was dried in a 160°C oven for 1 min to obtain a blue photonic crystal color-generating structure with good stability and a densely ordered particle arrangement. Figure 7 a1). After ultrasonic washing, the structural color of the structured colored textiles did not diminish, and the photonic crystal structure did not detach. Figure 8 ).

[0082] Photonic Crystal Bonding Adhesive: Example 6

[0083] At room temperature, 5% (based on solids content) of cuprous oxide nanoparticles with a particle size of 223 nm and a dispersion index (PDI) of 0.03 and 3% of the binder polyvinyl butyral were dispersed in anhydrous ethanol, followed by ultrasonic treatment for 15 min to prepare a structural color-generating spraying solution. This spraying solution was then sprayed onto polyester fabric, and the coated textile was dried in a 160°C oven for 1 min to obtain a green photonic crystal color-generating structure with good stability and a dense, ordered particle arrangement. Figure 7 a2). After ultrasonic washing, the structural color of the structured textiles did not diminish, and the photonic crystal structure did not detach.

[0084] Photonic Crystal Bonding Adhesive: Example 7

[0085] At room temperature, 2% (based on solids content) of cuprous oxide nanoparticles with a particle size of 274 nm and a dispersion index (PDI) of 0.04, along with 3% of the binder polyvinyl butyral, were dispersed in anhydrous ethanol, followed by ultrasonic treatment for 15 min to prepare a structural color-generating spraying solution. This solution was sprayed onto polyester fabric, and the coated textile was dried in a 160°C oven for 1 min to obtain a red photonic crystal color-generating structure with good stability and a densely ordered particle arrangement. Figure 7 a3). After ultrasonic washing, the structural color of the structured textiles did not diminish, and the photonic crystal structure did not detach.

[0086] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors, characterized in that: Cuprous oxide nanoparticles, whose structural unit is a polycrystalline monodisperse spherical structure, were synthesized and prepared through the following steps: 1) Dissolve high molecular weight polyvinylpyrrolidone, trisodium citrate and soluble divalent copper salt in a mixed solvent of polyethylene glycol and water, and stir until completely dissolved; The number average molecular weight of the polyvinylpyrrolidone mentioned in step 1) is between 100,000 and 2,000,000; 2) Add the strong alkali solution dropwise into the solution prepared in step 1), stir vigorously, and then quickly add the reducing agent. Stop stirring after the reaction is complete. 3) Separate the reaction products, wash and vacuum dry them.

2. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The amount of polyvinylpyrrolidone used in step 1) is 5-20 grams per mole of copper.

3. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The molecular weight of the polyethylene glycol mentioned in step 1) is between 100 and 900.

4. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The ratio of polyethylene glycol to water in step 1) is 1:4 to 1:0.

25.

5. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The strong alkaline solution mentioned in step 2) is sodium hydroxide, potassium hydroxide, or cesium hydroxide; the reducing agent mentioned in step 2) is ascorbic acid, sodium ascorbate, or hydrazine.

6. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The reaction temperature in step 2) is 0-50℃; the separation method in step 3) is centrifugation or filtration.

7. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The particle size of cuprous oxide nanoparticles is between 100 and 300 nanometers; the crystal domain size of cuprous oxide nanoparticles is less than 1 / 4 of the particle size.

8. The method for preparing cuprous oxide nanoparticle photonic crystals with iridescent colors according to claim 1, characterized in that: The self-assembly of cuprous oxide nanoparticles can be achieved through impregnation, printing, or spraying.

9. A fabric with rainbow colors, characterized in that: The iridescent cuprous oxide nanoparticle photonic crystals described in any one of claims 1 to 8 are compounded and adhered to the surface of the fabric using an adhesive; the adhesive is polyacrylate, polyurethane, or polyvinyl butyral.

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