A method for preparing a malleable inorganic nanolaminate material

Abstract

The application provides a preparation method of a shapeable inorganic nanocrystal superlattice. The method comprises the following steps: preparing inorganic nanocrystal superlattice powder with surface grafted organic ligands, soaking the powder in a poor solvent containing additional organic ligands, and standing and drying, so that the originally brittle superlattice powder is converted into a solid material with excellent plasticity. The application constructs a soft organic interface phase at the interface of nanocrystal particles under mild conditions, while the long-range ordered structure of the superlattice in nanoscale is completely retained. The obtained plastic material can be directly formed into a macroscopic block with a specific shape through simple mold pressing and the like, and can inherit the inherent functional characteristics (such as magnetic properties and optical properties) of nanocrystals. The method solves the key problem that high-performance nanocrystal superlattice materials are difficult to be non-destructively macro-formed, and provides a new material basis for the direct application of the nanocrystal superlattice materials in the fields of flexible electronics, miniaturized magnets, optical devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and nanotechnology, specifically relating to a method for preparing a plastic inorganic nanocrystalline superlattice material, and particularly to a method for transforming superlattice powder into a macroscopic plastic bulk through the swelling of organic molecules. Background Technology

[0002] Inorganic nanocrystalline superlattices are advanced materials with long-range ordered structures formed by the self-assembly of nanocrystals of uniform size and shape, acting as "artificial atoms." These materials not only retain the size dependence and physicochemical properties (such as magnetic, optical, and catalytic properties) of nanocrystals, but also exhibit unique collective effects and synergistic properties due to the periodic spatial arrangement of nanocrystals, demonstrating revolutionary potential in next-generation high-density information storage and high-efficiency energy conversion devices. To apply these superior nanoscale properties to macroscopic devices, nanocrystalline superlattices must be processed into macroscopic solids with specific shapes, sizes, and mechanical integrity. However, this faces a fundamental contradiction: nanocrystalline superlattices typically exist in the form of brittle powders, making direct macroscopic shaping difficult.

[0003] Current technologies, whether polymer potting, high-temperature sintering, or high-pressure compaction, cannot solve this fundamental problem. The polymer matrix isolates key interactions between nanocrystals, leading to the loss of ordered structure and blocking electron, phonon, or ion transport between nanocrystals, significantly weakening the collective functional properties of the superlattice. High-temperature processing easily destroys the intrinsic properties and ordered assembly of nanocrystals, causing their unique nanoscale effect to disappear; while high-pressure compaction often results in structural breakage and extreme brittleness, making it difficult to apply practically.

[0004] In summary, existing technologies cannot simultaneously achieve macroscopic shaping while fully preserving the long-range ordered structure and intrinsic functions of nanocrystals at the nanoscale. Therefore, developing a mild, non-destructive processing method to directly transform brittle inorganic nanocrystalline superlattice powders into highly ductile macroscopic solids with high structural integrity, while fully inheriting their nanoscale structure and properties, has become a critical technological bottleneck that urgently needs to be overcome in this field. This invention aims to overcome these shortcomings and provide a novel solution. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a malleable inorganic nano-superlattice material, so as to achieve the non-destructive preservation of the long-range ordered structure of the superlattice and its malleability on a macroscopic scale.

[0006] This invention provides a method for preparing a malleable inorganic nanocrystalline superlattice material, which can directly transform inorganic nanocrystalline superlattice powder into a malleable bulk material. This strategy can fully preserve the ordered nanoscale structure of the material while endowing it with macroscopic plasticity and forming and processing capabilities, including the following steps:

[0007] (1) Prepare colloidal nanoparticles, wherein the particles include magnetic, semiconductor or upconversion colloidal nanocrystal particles, dispersed in n-hexane to obtain a n-hexane solution of colloidal nanoparticles;

[0008] (2) Place the hexane solution of colloidal nanoparticles obtained in step (1) in an open container, dry it in air, and assemble it to obtain nanoparticle superlattice powder.

[0009] (3) Prepare an acetone solution containing small molecule ligands;

[0010] (4) Immerse the nanoparticle superlattice powder from step (2) in the acetone solution containing small molecule ligands obtained in step (3), and air dry to obtain an inorganic nano-superlattice material with solid plasticity.

[0011] (5) The plastic inorganic nano-superlattice material obtained in step (4) can be molded into a block inorganic nano-superlattice material of any shape.

[0012] In this invention, the colloidal particles mentioned in step (1) are any one of Fe3O4 particles, CdSe particles or NaYF4:Yb / Er particles;

[0013] In this invention, the concentration of colloidal particles in step (1) is 15-75 mg / mL, and the diameter of the particles is 3-25 nm.

[0014] In this invention, the ligand grafting density of the colloidal particles in step (1) is 3-4 nm. -2

[0015] In this invention, the small molecule ligand in step (3) is any one of oleic acid, oleylamine, linoleic acid and other organic compounds similar to and compatible with the particle surface, and the concentration of the mixed solution is 20-60 mmol / L.

[0016] This invention provides a mild and efficient method for plasticizing inorganic nanocrystalline superlattices. Its beneficial effects are: while maintaining the long-range ordered structure of the superlattice at the nanoscale, it successfully transforms it from a brittle powder into a macroscopic plastic solid. The resulting material has convenient processability, thereby realizing the lossless transfer of microscopic functional properties (such as magnetic and optical properties) of the superlattice to the macroscopic scale. This completely solves the core problems of structural damage, performance isolation, or cumbersome processing in traditional methods (such as sintering and potting). Attached Figure Description

[0017] Figure 1 These are small-angle X-ray scattering (SAXS) images of the plastic superlattices obtained by expanding the Fe3O4 superlattice with oleic acid and oleylamine, respectively, in Example 1 of this invention.

[0018] Figure 2 This is the amplitude scan diagram of the plastic NaYF4:Yb / Er superlattice prepared in Example 2 of the present invention under a rotational rheometer.

[0019] Figure 3 This is a photograph of the CdSe bulk superlattice prepared in Example 3 of the present invention under a UV lamp. Detailed Implementation

[0020] The present invention will be further illustrated by the following examples.

[0021] Example 1:

[0022] 1. Preparation of Fe3O4 colloidal nanoparticles: 10.8 g of ferric chloride hexahydrate and 36.5 g of sodium oleate were dispersed in 80 mL of ethanol, 60 mL of water, and 140 mL of n-hexane, and refluxed in an oil bath at 80 °C for 4 h. After deionized water extraction and washing, the solvent was removed by rotary evaporation to obtain the precursor ferric oleate. 9 g of ferric oleate, 2 g of oleic acid, and 60 mL of octadecene were mixed and degassed under vacuum at 120 °C for 1 h, then the mixture was heated to 320 °C under N2 atmosphere and reacted for 1 h. After the solution cooled naturally, it was dispensed into four centrifuge tubes, and 5 mL of n-hexane, 20 mL of isopropanol, and 5 mL of ethanol were added to each tube, respectively. The tubes were centrifuged at 3500 r for 5 min. After discarding the supernatant, add 15 mL of n-hexane, 20 mL of isopropanol and 5 mL of ethanol, centrifuge at 3500 r for 5 min, and disperse the resulting precipitate with 15 mL of n-hexane to obtain Fe3O4 colloidal nanoparticles with a solid content of 75 mg / mL and a particle size of 13 nm.

[0023] 2. Take 200 μL of the above solution and add it dropwise into an open solid container. Let it stand and dry to obtain a superlattice powder with a face-centered cubic stacked structure.

[0024] 3. Disperse 10 μL of oleic acid and 10 μL of oleylamine separately in 1 mL of acetone, and sonicate to ensure uniform dispersion. The concentration is approximately 30 mmol / L.

[0025] 4. Take 500 μL of the above mixed solution to impregnate the obtained superlattice powder, and air dry for 1 hour. The superlattice will change from brittle to plastic.

[0026] 5. Superlattices can be molded into specific shapes using molds.

[0027] Figure 1The image shows small-angle X-ray scattering patterns of the assembled brittle superlattice and the superlattice transformed into a plastic one, indicating that the plastic superlattices expanded by oleic acid and oleylamine perfectly maintain the long-range ordered structure at the nanoscale.

[0028] Example 2:

[0029] 1. Preparation of NaYF4:Yb / Er colloidal nanoparticles: 0.8 mmol yttrium chloride hexahydrate, 0.18 mmol ytterbium chloride hexahydrate, 0.02 mmol erbium chloride hexahydrate, 6 mL oleic acid, and 15 mL octadecene were mixed and thoroughly degassed at 120 °C. The mixture was then heated to 150 °C under a N2 atmosphere to form a homogeneous solution. After cooling to room temperature, 6 mL of a methanol solution containing 2.5 mmol sodium hydroxide and 4 mmol ammonium fluoride was added, and the mixture was slowly heated to 120 °C to completely remove methanol. The mixture was then rapidly heated to 300 °C and reacted for 1 h. After the solution cooled naturally, it was dispensed into two centrifuge tubes, and 5 mL of n-hexane and 5 mL of ethanol were added. The products were separated by centrifugation at 5000 r for 5 min. The resulting precipitate was redispersed in 5 mL of n-hexane to obtain NaYF4:Yb / Er colloidal nanoparticles with a solid content of 15 mg / mL and a particle size of 25 nm.

[0030] 2. Take 5 mL of the above solution and add it dropwise into an open solid container. Let it stand and dry to obtain a superlattice powder with a face-centered cubic packing structure.

[0031] 3. Disperse 30 μL of oleic acid in 3 mL of acetone and sonicate to ensure uniform dispersion. The concentration should be approximately 30 mmol / L.

[0032] 4. The superlattice powder obtained by impregnating the above mixed solution is air-dried for 4 hours, and the superlattice changes from brittle to plastic.

[0033] 5. Superlattices can be molded into specific shapes using molds.

[0034] Figure 2 The image shows the amplitude scan of the plastic NaYF4:Yb / Er superlattice under a rotational rheometer, indicating that the prepared material has plasticity.

[0035] Example 3:

[0036] 1. Preparation of CdSe colloidal nanoparticles: 316 mg of selenium powder and 3 mL of trioctylphosphine were mixed and dissolved at 60 °C to form a Se-TOP solution. 256 mg of cadmium oxide, 3.5 mL of oleic acid, and 40 mL of octadecene were mixed and heated to 170 °C to form a cadmium oleate solution. The solution was then cooled to 120 °C, 7 mL of oleylamine was added, and the mixture was degassed under vacuum for 1 h. This solution was heated to 270 °C under N2 and then rapidly injected into the above Se-TOP solution, reacting for 10 min. After the solution cooled naturally, it was evenly distributed into four centrifuge tubes, and 5 mL of n-hexane, 5 mL of methanol, and 30 mL of ethanol were added to each tube. The tubes were centrifuged at 5000 r for 5 min. The supernatant was discarded, and 10 mL of n-hexane and 30 mL of acetone were added. The tubes were centrifuged at 5000 r for 5 min, and the resulting precipitate was dispersed in 10 mL of n-hexane to obtain CdSe colloidal nanoparticles with a solid content of 50 mg / mL and a particle size of 3 nm.

[0037] 2. Take 3 mL of the above solution and add it dropwise into an open solid container. Let it stand and dry to obtain a superlattice powder with a face-centered cubic packing structure.

[0038] 3. Disperse 100 μL of oleic acid in 5 mL of acetone and sonicate to ensure uniform dispersion. The concentration should be approximately 60 mmol / L.

[0039] 4. The superlattice powder obtained by impregnating the above mixed solution is air-dried for 10 h, and the superlattice changes from brittle to plastic.

[0040] 5. Superlattices can be molded into specific shapes using molds.

[0041] Figure 3 The image shown is a physical image of the prepared CdSe bulk superlattice under a UV lamp, indicating that the prepared material is easy to process and can be mass-produced on a large scale.

Claims

1. A method for preparing a malleable inorganic nano-superlattice material, characterized in that: Includes the following steps: (1) Prepare colloidal nanoparticles, wherein the particles include magnetic, semiconductor or upconversion colloidal nanocrystal particles, dispersed in n-hexane to obtain a n-hexane solution of colloidal nanoparticles; (2) Place the hexane solution of colloidal nanoparticles obtained in step (1) in an open container, dry it in air, and assemble it to obtain nanoparticle superlattice powder. (3) Prepare an acetone solution containing small molecule ligands; (4) Immerse the nanoparticle superlattice powder from step (2) in the acetone solution containing small molecule ligands obtained in step (3), and air dry to obtain an inorganic nano-superlattice material with solid plasticity. (5) The plastic inorganic nano-superlattice material obtained in step (4) can be molded into a block inorganic nano-superlattice material of any shape.

2. The preparation method according to claim 1, characterized in that: The colloidal particles mentioned in step (1) are any one of Fe3O4 particles, CdSe particles, or NaYF4:Yb / Er particles.

3. The preparation method according to claim 1, characterized in that: The concentration of colloidal particles in step (1) is 15-75 mg / mL, and the diameter of the particles is 8-25 nm.

4. The preparation method according to claim 1, characterized in that: The ligand grafting density of the colloidal particles in step (1) is 3-4 nm. -2 .

5. The preparation method according to claim 1, characterized in that: The small molecule ligand in step (3) is any one of oleic acid, oleylamine or linoleic acid and similar compatible organic compounds on the particle surface, and the concentration of the mixed solution is 20-60 mmol / L.

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