Preparation method of antioxidant nano-copper particles based on metastable state of intermediate

Abstract

The invention discloses a preparation method of antioxidant nano-copper particles based on an intermediate metastable state, which comprises the following two steps: firstly, reacting copper salt with a first reducing agent and a pH regulator for 10-40 minutes in a first organic solvent of 70-130 DEG C to obtain copper-based intermediate particles of 20-25 nm; and then dispersing the intermediate in deionized water, adding a second reducing agent, a pH regulator and a coating agent, reacting at 70-130 DEG C for 20-60 minutes, so that the coating agent and copper atoms are deposited and synchronously bonded in situ under an alkaline condition to form a continuous coating layer with the thickness of 4-10nm, and finally obtaining the antioxidant nano-copper particles with the particle size of 30-40nm and high sphericity through epitaxial growth control. According to the preparation method, nucleation and growth processes are accurately regulated and controlled under mild conditions, and the nano-copper particles which are uniform in particle size, high in sphericity degree and long-acting in oxidation resistance are directly prepared.

Description

A method for preparing antioxidant copper nanoparticles based on intermediate metastable states Technical Field

[0001] This invention relates to the field of metal material preparation technology, and in particular to a method for preparing antioxidant copper nanoparticles based on intermediate metastable states. Background Technology

[0002] Compared to traditional metallic materials, metallic nanomaterials have garnered significant attention due to their unique chemical and physical properties. When material sizes reach the nanoscale, their optical, thermal, and electromagnetic properties undergo abrupt changes, leading to small-size effects, surface effects, and quantum size effects. Therefore, nanomaterials are primarily used in biosensors, catalysts, adsorbents, and electronic devices. Among these metallic nanomaterials, copper nanoparticles have increasingly attracted researchers' attention due to their substantial advantages in cost and specific surface area.

[0003] Currently, methods for synthesizing copper nanoparticles are mainly divided into physical and chemical methods. Physical methods mainly include mechanical ball milling, physical vapor deposition, and gas evaporation, while chemical methods mainly include liquid-phase chemical reduction, chemical deposition, electrochemical methods, and hydrothermal methods. Among these methods, compared to the high equipment costs and uncontrollable production processes of physical methods, liquid-phase chemical reduction is widely used due to its controllable particle size and simple process. However, the use of liquid-phase reduction in China faces problems such as complex processes and environmentally unfriendly synthesized materials. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention proposes a method for preparing antioxidant copper nanoparticles based on the metastable state of intermediates. By precisely controlling the nucleation and growth process under mild conditions, copper nanoparticles with uniform particle size, high sphericity, and long-lasting antioxidant properties are directly obtained.

[0005] This invention provides the following technical solution: a method for preparing antioxidant copper nanoparticles based on metastable intermediates, comprising the following steps: S1: intermediate seed preparation: at 70-130℃, copper salt is reacted in a first organic solvent in the presence of a first reducing agent and a first pH adjuster for 10-40 minutes to generate copper-based intermediate particles with a particle size of 20-25nm, which are then separated and purified for later use; S2: controllable growth and simultaneous coating: the copper-based intermediate particles obtained in step S1 are dispersed in an aqueous reaction system composed of deionized water, a second reducing agent, a second pH adjuster, and a coating agent with both dispersion and surface bonding functions are added, and the reaction is carried out at 70-130℃. 20-60 minutes; In the aqueous reaction system, under the alkaline environment provided by the second pH adjuster, the coating agent bonds in situ to the surface of copper particles while copper atoms are reduced and deposited, forming a continuous coating layer with a thickness of 4-10 nm. Furthermore, the reaction is controlled so that copper mainly grows epitaxially on the surface of the aforementioned intermediate particles, thereby obtaining antioxidant copper nanoparticles with a coating layer, a particle size of 30-40 nm, and high sphericity. The first organic solvent is one of polyethylene glycol, diethylene glycol, ethylene glycol, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, and dipropylene glycol methyl ether acetate. The coating agent is one of polyvinylpyrrolidone, octadecyl mercaptan, triethanolamine, and isopropanol.

[0006] As an improvement, the copper salt is one of anhydrous copper chloride, copper sulfate pentahydrate, copper acetate monohydrate, and copper nitrate.

[0007] As an improvement, the first reducing agent and the second reducing agent are selected from one of sodium phosphite, ascorbic acid, and sodium borohydride, respectively.

[0008] As an improvement, ascorbic acid is L(+)-ascorbic acid.

[0009] As an improvement, the first pH adjuster and the second pH adjuster are selected from sodium hydroxide and sodium bicarbonate, respectively.

[0010] As an improvement, the concentration of copper salt in the reaction system is 0.1-5 mol / L.

[0011] As an improvement, the concentration of copper salt is 0.25-4 mol / L.

[0012] As an improvement, in step S2, the concentration of the second reducing agent in the reaction system is 0.1-1 mol / L, and the molar ratio of the second pH adjuster to the second reducing agent is (1-2.8):1.

[0013] As an improvement, the concentration of the coating agent in the reaction system is 0.025-1.25 mol / L.

[0014] As an improvement, the concentration of the coating agent is 0.1-1 mol / L.

[0015] As an improvement, the reaction temperatures for steps S1 and S2 are 100-120℃, respectively.

[0016] Compared with existing technologies, the advantages of this invention are as follows: This invention provides a method for preparing antioxidant copper nanoparticles based on metastable intermediates. Through its unique two-step liquid-phase chemical reduction design and precise synergy of various process parameters, significant technological advancements are achieved. Firstly, in a specific first organic solvent, by controlling the reaction conditions, copper-based intermediate particles with uniform size and a particle size of approximately 20-25 nm are preferentially generated as templates. This step effectively separates the nucleation and growth processes, laying the foundation for subsequent precise control. Subsequently, through the crucial step of transferring the intermediate to an aqueous phase system composed of deionized water, controllable epitaxial growth of copper is carried out in an alkaline environment using the intermediate as a seed. During this process, a specific coating agent is in situ bonded to the surface of copper atoms while they are deposited, simultaneously constructing a dense and continuous organic coating layer with a thickness of 4-10 nm. This coating layer not only effectively prevents the copper nucleus from contacting oxygen through physical isolation, but also, due to the reducing groups inherent in the selected coating agent, it can release a reducing atmosphere through thermal decomposition during subsequent high-temperature sintering, reducing the oxidized copper. This endows the copper nanoparticles with excellent, intrinsic antioxidant stability, enabling the direct preparation of highly stable copper nanoparticles in air. The entire process, through a seed-mediated growth mechanism, strictly limits new random nucleation, ensuring that the particle size of the final product is precisely controlled within the range of 30-40 nm, with an extremely narrow size distribution and high sphericity. The copper salts, reducing agents, pH adjusters, and coating agents used in each step are all common and non-toxic chemicals, meeting the requirements of green production. In summary, this invention innovatively combines the seed template method, controlled epitaxial growth, and in-situ synchronous functionalization coating. The various technical features work closely together to directly produce copper nanoparticles with small size, high uniformity, good sphericity, and long-lasting antioxidant properties in a one-step process under mild conditions without the need for inert gas protection. This successfully overcomes many difficulties of traditional methods in terms of yield, energy consumption, oxidation control, and industrial adaptability. Attached Figure Description

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 shows the intermediate particles and nano-copper particles prepared in Example 1 of the present invention; Figure 2 shows the XRD pattern of the nano-copper particles prepared in Example 1 of the present invention. Detailed Implementation

[0018] A method for preparing antioxidant copper nanoparticles based on metastable intermediates includes the following steps: S1: Intermediate seed preparation: At 70-130℃, copper salt is reacted in a first organic solvent in the presence of a first reducing agent and a first pH adjuster for 10-40 minutes to generate copper-based intermediate particles with a particle size of 20-25 nm, which are then separated and purified for later use; S2: Controlled growth and simultaneous coating: The copper-based intermediate particles obtained in step S1 are dispersed in an aqueous reaction system composed of deionized water, and a second reducing agent, a second pH adjuster, and a coating agent with both dispersion and surface bonding functions are added. The reaction is carried out at 70-130℃ for 20-60 minutes. In the aqueous reaction system, the coating agent, under the alkaline environment provided by the second pH adjuster, bonds in situ to the surface of copper particles while copper atoms are reduced and deposited, forming a continuous coating layer with a thickness of 4-10 nm. Furthermore, the reaction is controlled so that copper mainly grows epitaxially on the surface of the aforementioned intermediate particles, thereby obtaining antioxidant copper nanoparticles with a coating layer, a particle size of 30-40 nm, and high sphericity. The first organic solvent is one of polyethylene glycol, diethylene glycol, ethylene glycol, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, and dipropylene glycol methyl ether acetate. The coating agent is one of polyvinylpyrrolidone, octadecyl mercaptan, triethanolamine, and isopropanol.

[0019] The copper salt is one of anhydrous copper chloride, copper sulfate pentahydrate, copper acetate monohydrate, and copper nitrate.

[0020] The first reducing agent and the second reducing agent are selected from one of sodium phosphite, ascorbic acid, and sodium borohydride, respectively.

[0021] Ascorbic acid is L(+)-ascorbic acid.

[0022] The first pH adjuster and the second pH adjuster are selected from sodium hydroxide and sodium bicarbonate, respectively.

[0023] The concentration of copper salt in the reaction system is 0.1-5 mol / L.

[0024] The concentration of copper salt is 0.25-4 mol / L.

[0025] In step S2, the concentration of the second reducing agent in the reaction system is 0.1-1 mol / L, and the molar ratio of the second pH adjuster to the second reducing agent is (1-2.8):1.

[0026] The concentration of the coating agent in the reaction system is 0.025-1.25 mol / L.

[0027] The concentration of the coating agent is 0.1-1 mol / L.

[0028] The reaction temperatures for steps S1 and S2 are 100-120℃, respectively.

[0029] Example 1 is shown in Figures 1 and 2. An antioxidant copper nanoparticle preparation method based on intermediate metastable state includes the following steps: S1: intermediate seed preparation: In the reaction vessel, diethylene glycol is measured as the first organic solvent, L(+)-ascorbic acid is added as the first reducing agent, and stirred to dissolve it, so as to obtain a mixed solution with an ascorbic acid concentration of 0.1 mol / L.

[0030] Add copper acetate monohydrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 0.1 mol / L.

[0031] Then, sodium hydroxide was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium hydroxide was 0.1 mol / L.

[0032] The resulting mixture was placed in an oil bath and heated to 70°C with magnetic stirring. The mixture was then held at this temperature for 10 minutes. After the reaction was complete, the system became a milky white suspension.

[0033] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0034] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add L(+)-ascorbic acid as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.1mol / L.

[0035] Accurately weigh the copper-based intermediate particles obtained in the previous step, polyvinylpyrrolidone as a coating agent, and sodium hydroxide as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that the particles are fully dispersed and dissolved. At this point, the concentration of the coating agent polyvinylpyrrolidone in the system is 0.025 mol / L, and the concentration of sodium hydroxide is 0.1 mol / L.

[0036] The resulting mixture was placed in an oil bath and heated to 70°C with magnetic stirring, and then kept at this temperature for 20 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0037] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0038] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0039] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 30 nm, and the particle morphology is spherical.

[0040] Example 2 S1: Preparation of intermediate seed: In a reaction vessel, ethylene glycol was measured as the first organic solvent, sodium phosphite was added as the first reducing agent, and stirred to dissolve it, resulting in a mixed solution with a sodium phosphite concentration of 0.2 mol / L.

[0041] Add anhydrous copper chloride to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 0.15 mol / L.

[0042] Then, sodium bicarbonate was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium bicarbonate was 0.4 mol / L.

[0043] The resulting mixture was placed in an oil bath and heated to 76°C with magnetic stirring. The mixture was then held at this temperature for 15 minutes. After the reaction was complete, the system became a milky white suspension.

[0044] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0045] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add sodium phosphite as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.2 mol / L.

[0046] Accurately weigh the copper-based intermediate particles obtained in the previous step, octadecyl mercaptan as a coating agent, and sodium bicarbonate as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that they are fully dispersed and dissolved. At this time, the concentration of the coating agent octadecyl mercaptan in the system is 0.1 mol / L, and the concentration of sodium bicarbonate is 0.4 mol / L.

[0047] The resulting mixture was placed in an oil bath and heated to 76°C with magnetic stirring, and then held at this temperature for 28 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0048] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0049] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0050] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 34 nm, and the particle morphology is quasi-spherical.

[0051] Example 3 S1: Preparation of intermediate seed: In a reaction vessel, polyethylene glycol was measured as the first organic solvent, sodium borohydride was added as the first reducing agent, and stirred to dissolve it, resulting in a mixed solution with a sodium borohydride concentration of 0.35 mol / L.

[0052] Add copper sulfate pentahydrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 1 mol / L.

[0053] Then, sodium hydroxide was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium hydroxide was 0.8 mol / L.

[0054] The resulting mixture was placed in an oil bath and heated to 80°C with magnetic stirring, and then kept at this temperature for 20 minutes. After the reaction was complete, the system became a milky white suspension.

[0055] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0056] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add sodium borohydride as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.35 mol / L.

[0057] Accurately weigh the copper-based intermediate particles obtained in the previous step, triethanolamine as a coating agent, and sodium hydroxide as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that they are fully dispersed and dissolved. At this time, the concentration of the coating agent triethanolamine in the system is 0.2 mol / L, and the concentration of sodium hydroxide is 0.8 mol / L.

[0058] The resulting mixture was placed in an oil bath and heated to 80°C with magnetic stirring, and then kept at this temperature for 38 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0059] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0060] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0061] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 38 nm, and the particle morphology is spherical.

[0062] Example 4 S1: Preparation of intermediate seed: In a reaction vessel, diethylene glycol butyl ether acetate was measured as the first organic solvent, and sodium phosphite was added as the first reducing agent. The mixture was stirred to dissolve the sodium phosphite and a concentration of 0.48 mol / L was obtained.

[0063] Add copper sulfate pentahydrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 1.8 mol / L.

[0064] Then, sodium bicarbonate was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium bicarbonate was 1.3 mol / L.

[0065] The resulting mixture was placed in an oil bath and heated to 95°C with magnetic stirring. The mixture was then held at this temperature for 25 minutes. After the reaction was complete, the system became a milky white suspension.

[0066] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0067] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add sodium phosphite as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.48 mol / L.

[0068] Accurately weigh the copper-based intermediate particles obtained in the previous step, isopropanol as a coating agent, and sodium bicarbonate as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that they are fully dispersed and dissolved. At this time, the concentration of the coating agent isopropanol in the system is 0.4 mol / L, and the concentration of sodium bicarbonate is 1.3 mol / L.

[0069] The resulting mixture was placed in an oil bath and heated to 95°C with magnetic stirring, and then kept at this temperature for 40 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0070] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0071] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0072] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 50 nm, and the particle morphology is spherical.

[0073] Example 5 S1: Preparation of intermediate seed: In a reaction vessel, diethylene glycol was measured as the first organic solvent, sodium borohydride was added as the first reducing agent, and stirred to dissolve it, resulting in a mixed solution with a sodium borohydride concentration of 0.56 mol / L.

[0074] Add copper acetate monohydrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 2.5 mol / L.

[0075] Then, sodium hydroxide was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium hydroxide was 1.6 mol / L.

[0076] The resulting mixture was placed in an oil bath and heated to 100°C with magnetic stirring, and then kept at this temperature for 30 minutes. After the reaction was complete, the system became a milky white suspension.

[0077] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0078] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add sodium borohydride as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.56 mol / L.

[0079] Accurately weigh the copper-based intermediate particles obtained in the previous step, octadecyl mercaptan as a coating agent, and sodium hydroxide as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that they are fully dispersed and dissolved. At this time, the concentration of the coating agent octadecyl mercaptan in the system is 0.6 mol / L, and the concentration of sodium hydroxide is 1.6 mol / L.

[0080] The resulting mixture was placed in an oil bath and heated to 100°C with magnetic stirring, and then kept at this temperature for 40 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0081] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0082] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0083] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 42 nm, and the particle morphology is spherical.

[0084] Example 6 S1: Preparation of intermediate seed: In a reaction vessel, ethylene glycol was measured as the first organic solvent, and L(+)-ascorbic acid was added as the first reducing agent. The mixture was stirred to dissolve the ascorbic acid, resulting in a mixed solution with an ascorbic acid concentration of 0.64 mol / L.

[0085] Add copper acetate monohydrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 3.2 mol / L.

[0086] Then, sodium bicarbonate was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium bicarbonate was 2 mol / L.

[0087] The resulting mixture was placed in an oil bath and heated to 109°C with magnetic stirring, and then kept at this temperature for 35 minutes. After the reaction was complete, the system became a milky white suspension.

[0088] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0089] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add L(+)-ascorbic acid as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.64mol / L.

[0090] Accurately weigh the copper-based intermediate particles obtained in the previous step, polyvinylpyrrolidone as a coating agent, and sodium bicarbonate as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that the particles are fully dispersed and dissolved. At this point, the concentration of the coating agent polyvinylpyrrolidone in the system is 0.8 mol / L, and the concentration of sodium bicarbonate is 2 mol / L.

[0091] The resulting mixture was placed in an oil bath and heated to 109°C with magnetic stirring, and then kept at this temperature for 50 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0092] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0093] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0094] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 48 nm, and the particle morphology is spherical.

[0095] Example 7 S1: Preparation of intermediate seed: In a reaction vessel, diethylene glycol butyl ether was measured as the first organic solvent, and L(+)-ascorbic acid was added as the first reducing agent. The mixture was stirred to dissolve the ascorbic acid, resulting in a mixed solution with an ascorbic acid concentration of 0.72 mol / L.

[0096] Add copper nitrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 3.7 mol / L.

[0097] Then, sodium hydroxide was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium hydroxide was 2.3 mol / L.

[0098] The resulting mixture was placed in an oil bath and heated to 116°C with magnetic stirring, and then kept at this temperature for 40 minutes. After the reaction was complete, the system became a milky white suspension.

[0099] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0100] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add L(+)-ascorbic acid as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.72mol / L.

[0101] Accurately weigh the copper-based intermediate particles obtained in the previous step, triethanolamine as a coating agent, and sodium hydroxide as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that the solution is fully dispersed and dissolved. At this time, the concentration of the coating agent triethanolamine in the system is 0.09 mol / L, and the concentration of sodium hydroxide is 2.3 mol / L.

[0102] The resulting mixture was placed in an oil bath and heated to 116°C with magnetic stirring, and then kept at this temperature for 52 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0103] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0104] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0105] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 49 nm, and the particle morphology is spherical.

[0106] Example 8 S1: Preparation of intermediate seed: In a reaction vessel, polyethylene glycol was measured as the first organic solvent, sodium borohydride was added as the first reducing agent, and stirred to dissolve it, resulting in a mixed solution with a sodium borohydride concentration of 0.9 mol / L.

[0107] Add copper nitrate to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 4 mol / L.

[0108] Then, sodium bicarbonate was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium hydroxide was 2.6 mol / L.

[0109] The resulting mixture was placed in an oil bath and heated to 120°C with magnetic stirring, and then kept at this temperature for 45 minutes. After the reaction was complete, the system became a milky white suspension.

[0110] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0111] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add sodium borohydride as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 0.9 mol / L.

[0112] Accurately weigh the copper-based intermediate particles obtained in the previous step, polyvinylpyrrolidone as a coating agent, and sodium bicarbonate as a second pH adjuster, and add them to the above reducing agent solution. Stir to ensure that the particles are fully dispersed and dissolved. At this point, the concentration of the coating agent polyvinylpyrrolidone in the system is 1 mol / L, and the concentration of sodium bicarbonate is 2.6 mol / L.

[0113] The resulting mixture was placed in an oil bath and heated to 120°C with magnetic stirring, and then kept at this temperature for 53 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0114] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0115] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0116] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 35 nm, and the particle morphology is spherical.

[0117] Example 9 S1: Preparation of intermediate seed: In a reaction vessel, dipropylene glycol methyl ether acetate was measured as the first organic solvent, and sodium phosphite was added as the first reducing agent. The mixture was stirred to dissolve the sodium phosphite and a sodium phosphite concentration of 1 mol / L was obtained.

[0118] Add anhydrous copper chloride to the above mixture and stir until completely dissolved. At this point, the concentration of copper salt in the system is 5 mol / L.

[0119] Then, sodium hydroxide was added to the system as the first pH adjuster and stirred to dissolve it. At this point, the concentration of sodium hydroxide was 2.8 mol / L.

[0120] The resulting mixture was placed in an oil bath and heated to 130°C with magnetic stirring, and then kept at this temperature for 45 minutes. After the reaction was complete, the system became a milky white suspension.

[0121] The suspension was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes to separate the solid precipitate. The precipitate was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 4 hours to obtain copper-based intermediate particles with a particle size of approximately 20-25 nm, which were then set aside for use.

[0122] S2: Controlled growth and synchronous coating: Take another reaction vessel, measure deionized water, add sodium phosphite as the second reducing agent, stir to dissolve, and obtain a reducing agent solution with a concentration of 1 mol / L.

[0123] Accurately weigh the copper-based intermediate particles obtained in the previous step, isopropanol as a coating agent, and sodium hydroxide as a second pH adjuster, and add them to the above reducing agent solution. Stir to fully disperse and dissolve them. At this time, the concentration of the coating agent isopropanol in the system is 1.25 mol / L, and the concentration of sodium hydroxide is 2.8 mol / L.

[0124] The resulting mixture was placed in an oil bath and heated to 130°C with magnetic stirring, and then kept at this temperature for 55 minutes. During the reaction, the solution gradually turned reddish-brown, indicating the formation of nano-copper particles.

[0125] After the reaction was complete, the resulting reddish-brown colloidal solution of copper nanoparticles was cooled to room temperature, transferred to a centrifuge tube, and centrifuged at 15,000 rpm for 5 minutes. The supernatant was discarded. The precipitate was washed with anhydrous ethanol, and the centrifugation-washing operation was repeated three times.

[0126] Finally, the obtained solid product was dried in a vacuum drying oven at 50°C for 6 hours to obtain antioxidant copper nanoparticles.

[0127] As shown in Table 2, the average particle size of the obtained antioxidant copper nanoparticles is 46 nm, and the particle morphology is spherical.

[0128] Examples 1 to 9 strictly follow the core framework of the two-step method of intermediate seed preparation and controlled growth and simultaneous coating as defined in the claims. Within the broad parameter range defined in the claims, the types of key raw materials and process conditions were systematically changed and verified, which together constitute a solid and coherent set of technical solution examples, fully demonstrating the feasibility, universality, predictability of technical effects and inventiveness of the present invention compared with the prior art.

[0129] First, regarding the coverage of raw material types, the embodiments systematically employ all optional types defined in the claims. Specifically, the copper salts include copper acetate monohydrate, anhydrous copper chloride, copper sulfate pentahydrate, and copper nitrate; the reducing agents include L(+)-ascorbic acid, sodium phosphite, and sodium borohydride, which are used independently or in combination in the first and second steps in different embodiments; the first organic solvent uses polyethylene glycol, diethylene glycol, ethylene glycol, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, and dipropylene glycol methyl ether acetate, fully covering the types listed in the claims; the coating agents also include polyvinylpyrrolidone, octadecyl mercaptan, triethanolamine, and isopropanol. This comprehensive raw material combination verification shows that the successful implementation of the present invention does not depend on a specific single raw material, but is based on the synergy of the two-step process principle and specific functional material categories, such as coating agents that can bond in an alkaline aqueous phase.

[0130] Secondly, regarding the examination of process parameters, each embodiment underwent meaningful gradient changes within the broad range specified in the claims. The copper salt concentration varied from 0.1 mol / L to 5 mol / L, the coating agent concentration from 0.025 mol / L to 1.25 mol / L, the reaction temperature ranged from 70°C to 130°C, and the total reaction time was between 30 and 100 minutes. Despite the differences in specific parameters, all embodiments successfully achieved controllable preparation from copper salt to intermediate particles, and then to final nano-copper particles. Particularly noteworthy is that the average particle size of the final product ranged from 30 nm to 50 nm, and the morphology exhibited good spherical or near-spherical shapes. This result clearly demonstrates that by adjusting the process parameters in this method, the size of the final product can be effectively controlled at the nanoscale while maintaining excellent morphological consistency, verifying the adjustability and robustness of the method. The particle size of 50 nm obtained in Example 4 can be considered a natural result of more complete growth at higher reactant concentrations and temperatures; it remains at the nanoscale and exhibits good sphericity, further demonstrating the tolerance of the process.

[0131] Furthermore, the preparation processes of all embodiments are carried out in air without the need for inert atmosphere protection, and the chemicals used are all low-toxicity or common reagents. This collectively confirms the significant advantages claimed by the present invention, such as ease of operation, mild conditions, environmental friendliness, and suitability for industrial production.

[0132] In summary, this series of embodiments is not an isolated operational example, but rather an organic whole. Through systematic variable control, they collectively demonstrate that the technical solution protected by the claims can be implemented throughout its entirety, and that the desired small-sized, highly spherical, and excellent antioxidant copper nanoparticles can be stably obtained. This provides a sufficient and necessary empirical basis to support the novelty, inventiveness, and utility of this invention.

[0133] Table 1. Raw material composition and process parameters for Examples 1 to 9 Table 2. Particle size and morphology of Examples 1 to 9 The comparative example uses the method described in Example 1 of CN108031839B to prepare nano-copper powder, specifically as follows: A certain amount of naphthalenesulfonate formaldehyde condensate was added to deionized water until it was fully dissolved, resulting in a concentration of 5 g / L for the naphthalenesulfonate formaldehyde condensate. A certain amount of polyvinylpyrrolidone was added to the solution obtained in the above step and allowed to dissolve fully, resulting in a final concentration of 9 g / L for the polyvinylpyrrolidone. Copper sulfate pentahydrate was added to the solution obtained in the above step and stirred until it was fully dissolved, resulting in a final concentration of 10 mmol / L for the copper ions. The solution obtained in the above step was adjusted with 1 mol / L sodium hydroxide solution until the pH value of the solution was 10 ± 0.5. The solution obtained in the above step was heated to 50°C, and a 50% (w / w) hydrazine hydrate solution was added dropwise, resulting in a molar ratio of hydrazine hydrate to copper ions of 66:1. The solution was then maintained at this temperature for 150 min, yielding a reddish-brown nano-copper colloid. After the reaction was completed, the copper colloidal solution obtained in the above steps was sonicated at 40 MHz for 30 min, then centrifuged at 10000 rpm for 5 min to separate the precipitate. After drying, the copper nanoparticles coated with organic matter were obtained.

[0134] In the above preparation method, the total preparation time is 180 minutes. The longest preparation time of this invention is 100 minutes, resulting in higher synthesis efficiency and lower energy consumption. In Comparative Example 1, a water-soluble macromolecular material was added to enhance the antioxidant properties of the prepared copper nanoparticles. This material can be considered a coating agent or antioxidant. In this invention, the dispersant used serves both a dispersing function and a reducing and antioxidant effect, reducing the types of synthetic materials used and further lowering costs. Furthermore, Comparative Example 1 uses a one-step preparation method, while this invention employs a two-step method, relying on intermediates to ultimately obtain copper nanoparticles; the principles are completely different. Finally, the copper nanoparticles prepared in Comparative Example 1 have a particle size of approximately 80-100 nm, while the copper nanoparticles prepared in this invention have a particle size of only approximately 30-40 nm, significantly smaller than those prepared in Comparative Example 1, resulting in better performance and a superior synthesis method.

[0135] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A method for preparing antioxidant copper nanoparticles based on metastable intermediate states, characterized in that, Includes the following steps: S1: Intermediate seed preparation: At 70-130℃, copper salt is reacted in a first organic solvent in the presence of a first reducing agent and a first pH adjuster for 10-40 minutes to generate copper-based intermediate particles with a particle size of 20-25 nm. These particles are then separated and purified for later use. S2: Controlled growth and simultaneous coating: The copper-based intermediate particles obtained in step S1 are dispersed in an aqueous reaction system composed of deionized water. A second reducing agent, a second pH adjuster, and a coating agent with both dispersion and surface bonding functions are added. The reaction is carried out at 70-130℃ for 20-60 minutes. In the aqueous reaction system, the coating agent... In the alkaline environment provided by the pH adjuster, copper atoms are reduced and deposited simultaneously, while in situ bonding occurs on the surface of copper particles, forming a continuous coating layer with a thickness of 4-10 nm. Furthermore, the reaction is controlled so that copper mainly grows epitaxially on the surface of the aforementioned intermediate particles, thereby obtaining antioxidant copper nanoparticles with the coating layer, a particle size of 30-40 nm, and high sphericity. The first organic solvent is one of polyethylene glycol, diethylene glycol, ethylene glycol, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, and dipropylene glycol methyl ether acetate. The coating agent is one of polyvinylpyrrolidone, octadecyl mercaptan, triethanolamine, and isopropanol.

2. The method for preparing antioxidant copper nanoparticles based on intermediate metastable states according to claim 1, characterized in that, The copper salt is one of anhydrous copper chloride, copper sulfate pentahydrate, copper acetate monohydrate, and copper nitrate.

3. The method for preparing antioxidant copper nanoparticles based on intermediate metastable states according to claim 1, characterized in that, The first reducing agent and the second reducing agent are selected from one of sodium phosphite, ascorbic acid, and sodium borohydride, respectively.

4. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 3, characterized in that, The ascorbic acid is L(+)-ascorbic acid.

5. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 1, characterized in that, The first pH adjuster and the second pH adjuster are selected from sodium hydroxide and sodium bicarbonate, respectively.

6. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 1, characterized in that, The concentration of the copper salt in the reaction system is 0.1-5 mol / L.

7. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 6, characterized in that, The concentration of the copper salt is 0.25-4 mol / L.

8. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 1, characterized in that, In step S2, the concentration of the second reducing agent in the reaction system is 0.1-1 mol / L, and the molar ratio of the second pH adjuster to the second reducing agent is (1-2.8):

1.

9. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 1, characterized in that, The concentration of the coating agent in the reaction system is 0.025-1.25 mol / L.

10. The method for preparing antioxidant copper nanoparticles based on intermediate metastable states according to claim 1, characterized in that, The concentration of the coating agent is 0.1-1 mol / L.

11. The method for preparing antioxidant copper nanoparticles based on intermediate metastable state according to claim 1, characterized in that, The reaction temperatures for steps S1 and S2 are 100-120℃, respectively.

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