Method for fabricating core-shell structured copper nanowires having high aspect ratio

Abstract

The present invention relates to a method for fabricating core-shell structured copper nanowires having a high aspect ratio and, more specifically, provides a method for fabricating core-shell copper nanowires, the method comprising: a first step of preparing a first aqueous solution containing a copper precursor, alkylamine, and a halogen compound; and a second step of synthesizing copper nanowires by adding a reducing agent to the first aqueous solution.

Description

Method for manufacturing core-shell structured copper nanowires with a high aspect ratio

[0001] The present invention relates to a method for manufacturing a core-shell structured copper nanowire having a high aspect ratio and a copper nanowire manufactured therefrom.

[0002] Conventional conductive materials such as indium tin oxide (ITO), conductive polymers, carbon nanotubes, and graphene have played important roles in various application fields. However, active research is being conducted to explore new application possibilities by miniaturizing conductive metals such as copper, silver, nickel, and indium to nanoscale sizes to replace these materials. In particular, copper nanowires are attracting attention as a promising material to replace ITO due to their various advantages, including high conductivity, flexibility, transparency, and low cost, and have high potential for use in diverse fields such as low-emissivity windows, touch-sensitive control panels, solar cells, and electromagnetic shielding materials.

[0003] Copper nanowires oxidize when exposed to air for extended periods, forming copper oxides, which leads to a significant decrease in electrical conductivity. This degrades the stability of copper nanowires, thereby limiting their industrial applications. Furthermore, existing manufacturing methods, such as liquid-phase reduction and hydrothermal synthesis, have limitations in synthesizing nanowires with high aspect ratios. A high aspect ratio refers to a structure where the length is significantly greater than the thickness, and such a structure is essential for maximizing the electrical conductivity of nanowires. A low aspect ratio results in an increased number of contact points between nanowires, leading to reduced conductivity; this poses an obstacle to achieving desired performance in applications such as electronic devices.

[0004] Conventional liquid reduction methods have the problem of generating nanowires with low aspect ratios and non-uniform sizes and shapes, making it difficult to secure consistent electrical properties. Additionally, high concentrations of NaOH (15M) must be used, and synthesis temperatures above 100°C are required, which restricts the choice of solvent. These conditions increase manufacturing costs and require complex processes, resulting in poor cost efficiency. Furthermore, the use of high concentrations of NaOH accounts for a significant portion of the cost, which lowers overall economic viability.

[0005] In the case of hydrothermal synthesis, there is a problem in that high temperature and high pressure conditions are required, and synthesis takes at least 10 hours. This lowers process efficiency and acts as a factor causing difficulties in mass production. Furthermore, existing technologies require very high reaction temperatures when using ethylene glycol, and glucose, which has low reducing power, requires a long synthesis time of over 12 hours at 90°C, leading to reduced productivity and increased energy consumption. Additionally, hydrazine, which has high reducing power, still presents critical problems, such as the formation of irregular copper particles due to rapid reduction reactions and the danger of handling due to its high toxicity.

[0006] Therefore, there is a need for technology regarding methods to stably manufacture copper nanowires at low temperatures and short synthesis times. Furthermore, there is an urgent need for research and development on nanowires that can fundamentally resolve the oxidation problem of copper nanowires while simultaneously being energy and cost-efficient, possessing a high aspect ratio, and ensuring superior conductivity and mechanical properties.

[0007] The objective of the present invention is to provide a method for manufacturing core-shell copper nanowires suitable for industrial mass production, which can produce core-shell copper nanowires with excellent oxidation stability, uniform size and shape, and a high aspect ratio with a high yield, and can be synthesized with a relatively short reaction time even at low temperatures of 100°C or lower.

[0008] Another objective of the present invention is to provide a core-shell copper nanowire that has a uniform size and shape and a high aspect ratio, thereby reducing the number of contacts between copper nanowires to decrease resistance generated at the contacts, and provides a continuous path to form a percolation network with a small number of nanowires, thereby ensuring high conductivity.

[0009] To achieve the above-mentioned objective, the present invention provides a method for manufacturing core-shell copper nanowires comprising: a first step of preparing a first aqueous solution comprising a copper precursor, an alkylamine, and a halogen compound; and a second step of synthesizing copper nanowires by adding a reducing agent to the first aqueous solution.

[0010] According to one embodiment, in the second step, the synthesis temperature may be 30 to 90°C.

[0011] According to one embodiment, the copper precursor may be one or more selected from the group consisting of copper nitrate (Cu(NO3)2), copper sulfate (CuSO4), copper sulfite (CuSO3), copper acetate (Cu(CH3COO)2), copper chloride (CuCl2), copper bromide (CuBr2), copper iodide (CuI), copper phosphate (Cu3(PO4)2), and copper carbonate (CuCO3).

[0012] According to one embodiment, the alkylamine may be a C10-20 alkyl amine.

[0013] According to one embodiment, the halogen compound may be one or more selected from the group consisting of sodium chloride (NaCl), sodium bromide (NaBr), potassium chloride (KCl), potassium bromide (KBr), and ammonium chloride (NH4Cl).

[0014] According to one embodiment, the reducing agent may be one or more selected from the group consisting of ascorbic acid, erythorbic acid, N-acetylcysteine, L-cysteine, cysteine ​​hydrochloride, and glutathione.

[0015] According to one embodiment, the alkylamine may be included in an amount of 0.5 to 10 moles per 1 mole of the copper precursor.

[0016] According to one embodiment, the halogen compound may be included in an amount of 0.5 to 5 moles per 1 mole of the copper precursor.

[0017] According to one embodiment, the reducing agent may be included in an amount of 1 to 6 moles per 1 mole of the copper precursor.

[0018] According to one embodiment, in the second step, the synthesis time may be 90 minutes or less.

[0019] According to one embodiment, the yield of the copper nanowires produced in the second step may be 70% or more.

[0020] According to one embodiment, after the second step, a third step of coating the surface of the manufactured copper nanowire with a conductive material may be further performed.

[0021] According to one embodiment, the conductive material may be one or more selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), nickel (Ni) and graphene.

[0022] According to one embodiment, the conductive material is silver, and the third step may be performed by dropping a coating solution containing a complex of silver and EDTA into a second aqueous solution containing copper nanowires prepared in the second step.

[0023] According to one embodiment, the second aqueous solution may further include one or more reducing agents selected from the group consisting of hydroquinone, ascorbic acid, glucose, and hydrazine.

[0024] The present invention can provide a copper nanowire with a surface coated with a conductive material, manufactured according to the core-shell copper nanowire manufacturing method described above.

[0025] The present invention provides a core-shell copper nanowire comprising a shell containing a conductive material and a core containing copper, having an average diameter of 100 to 500 nm, an average length of 20 to 55 μm, and an average aspect ratio of 100 to 500.

[0026] According to one embodiment, the conductive material may be silver (Ag).

[0027] According to one embodiment, the shell may have a thickness of 5 to 30 nm.

[0028] The method for manufacturing core-shell copper nanowires according to the present invention provides high energy efficiency and is highly suitable for industrial mass production as synthesis is possible at low temperatures with a relatively short reaction time. This manufacturing method has practical and economic advantages and is characterized by easy maintenance due to reduced burden on the reactor. Therefore, the manufacturing method of the present invention enables cost-effective and stable production.

[0029] Furthermore, the core-shell copper nanowires manufactured according to the present invention have uniform size and shape and a high aspect ratio. These structural characteristics can reduce the number of contact points between nanowires, thereby decreasing resistance at the contact points. Additionally, by forming a continuous path for electron movement, a percolation network can be constructed with a small number of nanowires, ensuring high conductivity. Moreover, the core-shell structure reduces the possibility of oxidation, providing a more stable product and maximizing usability in various industrial applications.

[0030] Figures 1 (a) and (b) are scanning electron microscope (SEM) images of copper nanowires prepared through Example 1.

[0031] FIG. 2(a) is a transmission electron microscope (TEM) image of a silver-coated core-shell copper nanowire prepared through Example 1, and FIG. 2(b) is a transmission electron microscope (TEM) EDS mapping image.

[0032] Figure 3 is a scanning electron microscope (SEM) image of copper nanowires prepared through Example 2.

[0033] Figure 4 is a scanning electron microscope (SEM) image of copper nanowires prepared through Example 3.

[0034] Figure 5 is a scanning electron microscope (SEM) image of a copper nanowire prepared through Comparative Example 1.

[0035] Figure 6 is a scanning electron microscope (SEM) image of copper nanowires prepared through Comparative Example 2.

[0036] Figure 7 is a scanning electron microscope (SEM) image of a plate-shaped copper nanostructure prepared through Comparative Example 5.

[0037] The core-shell structured metal nanowire of the present invention will be described in detail below with reference to the attached drawings. The drawings presented below are provided as examples to ensure that the concept of the present invention is sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the concept of the present invention. Unless otherwise defined, technical and scientific terms used herewith have the meanings commonly understood by those skilled in the art to which this invention pertains, and descriptions of known functions and configurations that could unnecessarily obscure the essence of the present invention are omitted in the following description and attached drawings.

[0038] Additionally, the singular form used in the specification and the appended claims may be intended to include the plural form unless specifically indicated otherwise in the context.

[0039] In this specification and the appended claims, terms such as "include" or "have" mean that the features or components described in the specification exist, and unless specifically limited, this does not preclude the possibility that one or more other features or components may be added.

[0040] A method for manufacturing a core-shell copper nanowire according to one embodiment of the present invention will be described in more detail below.

[0041] Copper nanowires suffer from a problem where their electrical conductivity deteriorates due to oxidation when exposed to air for extended periods. Existing synthesis methods include liquid reduction and hydrothermal synthesis, but these methods have limitations in synthesizing nanowires with high aspect ratios. Conventional liquid reduction methods produce nanowires with low aspect ratios and non-uniform shapes, and are cost-inefficient due to the need for high concentrations of NaOH and high temperatures. Hydrothermal synthesis, on the other hand, requires high temperature and pressure conditions and long reaction times; furthermore, the use of reducing agents with low or excessively high reducing power leads to reduced productivity and the synthesis of irregular shapes rather than nanowires, respectively.

[0042] To solve the above problem, the inventors of the present invention discovered that when copper nanowires are synthesized by adding a suitable reducing agent to an aqueous solution containing a copper precursor, an alkylamine, and a halogen compound, synthesis is possible within a short time even at a low temperature, and electrical performance can be maximized by having uniform size and shape and a high aspect ratio. Thus, the present invention was completed. This solves the problems of existing methods that relied on high temperature, high pressure, and long time, and enables the implementation of a core-shell copper nanowire manufacturing method that is economical, efficient, and suitable for mass production.

[0043] The present invention provides a method for manufacturing core-shell copper nanowires comprising: a first step of preparing a first aqueous solution comprising a copper precursor, an alkylamine, and a halogen compound; and a second step of synthesizing copper nanowires by adding a reducing agent to the first aqueous solution.

[0044] According to one embodiment, the first step may be a step of preparing a first aqueous solution by adding a copper precursor, an alkylamine, and a halogen compound to water (ultrapure water). The first aqueous solution may contain a copper precursor, an alkylamine, and a halogen compound in water (ultrapure water), and although the order of addition is not significantly limited, they may be added in the order of water, copper precursor, halogen compound, and alkylamine. The first step may be performed at 30°C or lower or at room temperature.

[0045] According to one embodiment, the copper precursor may include one or more selected from the group consisting of copper nitrate (Cu(NO3)2), copper sulfate (CuSO4), copper sulfite (CuSO3), copper acetate (Cu(CH3COO)2), copper chloride (CuCl2), copper bromide (CuBr2), copper iodide (CuI), copper phosphate (Cu3(PO4)2), and copper carbonate (CuCO3). Specifically, the copper precursor may include one or more selected from the group consisting of copper chloride (CuCl2) and copper nitrate (Cu(NO3)2).

[0046] According to one embodiment, the copper precursor may be included in the water at a concentration of 5 to 50 mM, 10 to 30 mM, or 10 to 20 mM. When the above range is satisfied, core-shell copper nanowires with excellent oxidation stability, uniform size and shape, and a high aspect ratio can be produced. When included at a concentration higher than the above range, the irregularity of the diameter may increase, which is undesirable.

[0047] According to one embodiment, the alkylamine may be an organic compound comprising an alkyl group and an amine group (-NH2), and specifically may include a straight-chain or branched-chain C3-50 alkyl amine, a straight-chain or branched-chain C7-30 alkyl amine, or a straight-chain or branched-chain C10-20 alkyl amine. More specifically, the alkylamine may be a straight-chain C10-15 alkyl amine. Non-limiting examples of the alkylamine may include any one or more combinations selected from the group consisting of dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, etc. When the carbon number within the above range is satisfied, synthesis can be performed with a relatively short reaction time even at low temperatures, thereby providing a manufacturing method suitable for industrial mass production. However, if the carbon chain length is shorter than the above range, the growth rate increases and the reaction time can be shortened, but this is undesirable as it may increase the irregularity of the shape and size of the nanowires.

[0048] According to one embodiment, the alkylamine may be included in an amount of 0.1 to 20 moles, 0.5 to 10 moles, or 2 to 4 moles per 1 mole of the copper precursor. When the above range is satisfied, core-shell copper nanowires having uniform size and shape and a high aspect ratio can be produced, and when the above range is exceeded, the irregularity of the shape of the copper nanowires may increase.

[0049] According to one embodiment, the halogen compound is regularly arranged on a specific crystal plane of copper and can play an important role in helping the copper grow in a wire shape by controlling the distance between the copper and the alkylamine. The halogen compound may include one or more selected from the group consisting of sodium chloride (NaCl), sodium bromide (NaBr), potassium chloride (KCl), potassium bromide (KBr), and ammonium chloride (NH4Cl). If the halogen compound is not included, it may be synthesized in a shape other than a wire, which is undesirable.

[0050] According to one embodiment, the halogen compound may be included in an amount of 0.1 to 10 moles, 0.5 to 5 moles, or 2 to 3.5 moles per mole of the copper precursor. When the above range is satisfied, core-shell copper nanowires having uniform size and shape and a high aspect ratio can be produced; when the above range is less, they may be synthesized in a particle shape rather than a wire shape; and when the above range is exceeded, the irregularity of the shape of the copper nanowire may increase.

[0051] According to one embodiment, the second step is a step of synthesizing copper nanowires, and the synthesis reaction can be performed by adding a reducing agent to the first aqueous solution prepared above.

[0052] According to one embodiment, the reducing agent may have an absolute value of a standard reduction potential (E°) of 0.1 to 1.0 V, 0.1 to 0.7 V, or 0.2 to 0.5 V. When the above range is satisfied, the reaction time, temperature, and productivity intended in the present invention can be achieved, and core-shell copper nanowires having uniform size and shape and a high aspect ratio can be produced.

[0053] According to one embodiment, the reducing agent may include one or more selected from the group consisting of ascorbic acid, erythorbic acid, N-acetylcysteine, L-cysteine, cysteine ​​hydrochloride, and glutathione. Preferably, the reducing agent of the second step may not include glucose or hydrazine.

[0054] According to one embodiment, the reducing agent may be included in an amount of 0.1 to 15 moles, 0.5 to 10 moles, 1 to 6 moles, or 1.5 to 3 moles per mole of the copper precursor. When the above range is satisfied, core-shell copper nanowires with uniform size and shape and a high aspect ratio can be produced; when the above range is not satisfied, the reaction time becomes long and inefficient, and when the above range is exceeded, the irregularity of the shape of the copper nanowires may increase. In particular, the concentration of the reducing agent can be easily adjusted in accordance with the interaction with the reaction temperature, taking into account the reaction time.

[0055] According to one embodiment, in the second step, the synthesis temperature may be 20 to 100°C, 30 to 90°C, 35 to 70°C, or 40 to 60°C. Additionally, the synthesis time may be 4 hours or less, 3 hours or less, 2 hours or less, 90 minutes or less, 10 minutes to 80 minutes, or 30 minutes to 70 minutes. If the above range is exceeded, particularly if synthesis is performed at a temperature higher than the above range, the irregularity of the shape of the copper nanowires may increase, and if synthesis is performed at a temperature lower than the above range, the reaction time may become excessively long, resulting in insufficient production efficiency.

[0056] A method for manufacturing core-shell copper nanowires according to one embodiment can produce copper nanowires by adding a suitable reducing agent to the first aqueous solution described above, thereby enabling synthesis to be performed under conditions of a relatively short reaction time even at a lower temperature than conventional technology, and can produce core-shell copper nanowires with a high yield, making it suitable for mass production.

[0057] According to one embodiment, the yield of the copper nanowires produced in the second step may be 60% or more, 70% or more, or 75% or more.

[0058] According to one embodiment, the copper nanowires prepared in the second step may have an average diameter of 100 to 400 nm, 100 to 300 nm, 120 to 210 nm, 170 to 210 nm, or 170 to 190 nm. Additionally, the copper nanowires prepared in the second step may have an average length of 20 to 55 μm, 30 to 55 μm, 35 to 55 μm, or 40 to 55 μm. Furthermore, the copper nanowires prepared in the second step may have an average aspect ratio of 100 to 500, 150 to 350, or 200 to 300.

[0059] According to one embodiment, after the second step, a third step of coating the surface of the manufactured copper nanowire with a conductive material may be further performed. The third step may involve dropping a separately prepared coating solution into a second aqueous solution containing the copper nanowire manufactured in the second step.

[0060] According to one embodiment, the conductive material may include one or more selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), nickel (Ni), and graphene. Preferably, the conductive material may be silver.

[0061] According to one embodiment, the coating solution may include a silver-containing compound and a chelating agent. The coating solution may include a complex formed by the silver-containing compound and the chelating agent being chelated with each other.

[0062] According to one embodiment, the silver-containing compound may include silver and, if it can form a complex with the chelating agent, be not significantly limited, but the fluoroborate may include one or more selected from the group consisting of silver nitrate, silver oxide, and silver chloride.

[0063] According to one embodiment, in addition to EDTA (ethylenediaminetetraacetic acid), the chelating agent may include one or more selected from the group consisting of DTPA (diethylenetriaminepentaacetic acid), citric acid, gluconic acid, NTA (nitrilotriaacetic acid), polyphosphate, glycine, TPA (triethanolamine), IDA (iminodiaacetic acid), and derivatives thereof.

[0064] According to one embodiment, the molar ratio of the silver-containing compound to the chelating agent may be 1:0.5 to 5, 1:0.8 to 3, or 1:1.0 to 1.5, and the weight ratio may satisfy 1:0.5 to 10, 1:1 to 7, or 1:1.5 to 5.

[0065] According to one embodiment, the concentration of the coating solution may be 0.01 to 1 M, specifically 0.01 to 0.8 M, more specifically 0.05 to 0.5 M, and even more specifically 0.1 to 0.3 M.

[0066] According to one embodiment, the conductive material is silver, and the third step may be performed by dropping a coating solution containing a complex of silver and EDTA (Ethylenediaminetetraacetic acid) into a second aqueous solution containing copper nanowires prepared in the second step.

[0067] According to one embodiment, the second aqueous solution may further comprise a reducing agent, specifically, the reducing agent is from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimellitic acid, suberic acid, azelaic acid, sebacic acid, brasilic acid, dodecanoic acid, maleic acid, fumaric acid, gluconic acid, traumatic acid, muconic acid, glutinic acid, citraconic acid, mesaconic acid, aspartic acid, glutamic acid, diaminopimelic acid, tartronic acid, arabinaric acid, saccharic acid, mesosalic acid, oxaloacetic acid, acetonid-dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, diphenic acid, tartaric acid, potassium sodium tartrate, ascorbic acid, hydroquinone, glucose, and hydrazine. It may include one or more selected. Specifically, the reducing agent of the second aqueous solution may include one or more selected from the group consisting of hydroquinone, ascorbic acid, glucose, and hydrazine.

[0068] According to one embodiment, the concentration of the reducing agent in the second aqueous solution may be 0.001 to 3 M, specifically 0.005 to 1 M, and more specifically 0.005 to 0.1 M.

[0069] According to one embodiment, the second aqueous solution may further include a chelating agent. The chelating agent is the same as described above and is therefore omitted.

[0070] According to one embodiment, the concentration of the chelating agent in the second aqueous solution may be 0.001 to 3 M, specifically 0.005 to 1 M, and more specifically 0.005 to 0.1 M.

[0071] According to one embodiment, the second aqueous solution may further comprise a reducing agent and / or a chelating agent. Alternatively, the second aqueous solution may comprise water, copper nanowires, and a chelating agent. Alternatively, the second aqueous solution may comprise water, copper nanowires, and a reducing agent. Alternatively, the second aqueous solution may comprise water, copper nanowires, a reducing agent, and a chelating agent.

[0072] According to one embodiment, the concentration of copper nanowires in the second aqueous solution may be 1 to 50 g / L, 3 to 20 g / L, or 5 to 10 g / L.

[0073] According to one embodiment, the third step may be to form a silver coating layer on the surface of copper nanowires by dropping a coating solution containing a complex into a second aqueous solution containing copper nanowires. The dropping may be performed at a rate of 0.1 to 500 ml / min, 1 to 100 ml / min, or 5 to 50 ml / min.

[0074] The present invention can provide a copper nanowire with a surface coated with a conductive material, manufactured according to the core-shell copper nanowire manufacturing method described above.

[0075] The present invention provides a core-shell copper nanowire comprising a shell containing a conductive material and a core containing copper, having an average diameter of 100 to 500 nm, an average length of 20 to 55 μm, and an average aspect ratio of 100 to 500. The core may be a copper nanowire prepared in the second step described above, and a detailed description is omitted as it is identical to that described above.

[0076] According to one embodiment, the core-shell copper nanowire may have an average diameter of 100 to 500 nm, 100 to 350 nm, 120 to 260 nm, 170 to 260 nm, or 170 to 240 nm. Additionally, the core-shell copper nanowire may have an average length of 20 to 55 μm, 30 to 55 μm, 35 to 55 μm, or 40 to 55 μm. Furthermore, the core-shell copper nanowire may have an average aspect ratio of 100 to 500, 120 to 350, 150 to 300, or 200 to 250. When the above range is satisfied, the dispersibility within the composition can be improved, and at the same time, the number of contacts between nanowires is effectively reduced, thereby reducing the resistance generated at the contacts and better providing a continuous path for electrons to move, allowing a percolation network to be formed with a small number of nanowires to secure high conductivity.

[0077] According to one embodiment, the conductive material may include silver (Ag). Specific descriptions and examples of compounds are omitted as they are the same as those described above.

[0078] According to one embodiment, the shell may have a thickness of 1 to 50 nm, 5 to 30 nm, 10 to 25 nm, or 10 to 20 nm. The thickness of the shell can be measured by analyzing transmission electron microscope (TEM) EDS mapping images. In the case of core-shell copper nanowires having a thickness within the above range, superior electrical properties can be achieved.

[0079] According to one embodiment, the core-shell copper nanowire may have excellent length uniformity. As an example of a method for evaluating the uniformity, methods such as full-width at half maximum (FWHM), standard deviation, coefficient of variation, length histogram analysis, and length-diameter ratio distribution analysis may be used, but are not limited thereto. When the full-width at half maximum, which is the width measured at half the maximum height, is obtained by analyzing the distribution of the number of core-shell copper nanowires relative to their length, the full-width at half maximum may be 10 μm or less, 7 μm or less, 5 μm or less, or 2 μm or less. In this case, the distribution may be obtained according to a conventional method or a known method, and, for example, may be analyzed using an SEM operating software program from an SEM image, but is not limited thereto.

[0080] Hereinafter, the core-shell structured metal nanowire according to the present invention will be described in more detail through examples. However, the following examples are merely for reference to explain the present invention in detail, and the present invention is not limited thereto and can be implemented in various forms.

[0081] Furthermore, unless otherwise defined, all technical and scientific terms have the same meaning as generally understood by one of the art to which the present invention pertains. The terms used in the description herein are merely for the purpose of effectively describing specific embodiments and are not intended to limit the present invention.

[0082]

[0083]

[0084] [Example 1]

[0085] Fabrication of copper nanowires

[0086] Add 5,000 ml of water (ultrapure water) to a 5,000 ml four-necked flask, attach a stirrer, and while stirring, use copper(II) nitrate (Cu(NO3)) as a copper precursor 2·20g of 3H2O (Samjeon Soonyak Industrial Co., Ltd.) and 14g of sodium chloride (NaCl, Samjeon Soonyak Industrial Co., Ltd.) as a halogen compound were added. Subsequently, 58ml of dodecylamine (Dodecylamine, Samjeon Soonyak Industrial Co., Ltd.) molten with alkylamine was added and stirred for 5 minutes to prepare the first aqueous solution. 33g of ascorbic acid (Samjeon Soonyak Industrial Co., Ltd.) as a reducing agent was added to the prepared first aqueous solution, and the temperature was raised to 50℃. The reaction was carried out at 50℃ with stirring at 60RPM for a reaction time of approximately 60 minutes until the solution turned dark red. After the reaction was completed, the temperature was slowly cooled to room temperature and washed, and then dried in a vacuum oven (JEIO Tech, OV-12) at 25℃ for 24 hours.

[0087] The length, diameter, and aspect ratio of the copper nanowires obtained after drying were measured and recorded in Table 1 below, and Scanning Electron Microscope (SEM, COXEM, EM-30AXN) images of the prepared copper nanowires are shown in Figures 1 (a) and (b).

[0088] Fabrication of core-shell copper nanowires

[0089] At room temperature, 1.9 L of ultrapure water, 12.94 g of hydroquinone (Samjeon Soonyak Co., Ltd.), and 5.635 g of EDTA-2Na were added to a 3,000 ml four-necked flask and stirred. Then, 15 g of the copper nanowires prepared above were dispersed in a reactor to prepare a second aqueous solution. In a separate 1 L beaker, 655 ml of ultrapure water was placed, and 13.3 g of silver nitrate (AgNO3) and 29.2 g of EDTA-2Na were mixed to form a complex. The coating solution containing the complex was added dropwise to the reactor at a rate of 10 ml / min and reacted. After the reaction was completed, the metal nanowires separated using filter paper were washed with 2 L of water (ultrapure water) and dried at room temperature for 24 hours to obtain thin, uniformly silver-coated core-shell structured copper nanowires.

[0090] The synthesized silver-coated core-shell copper nanowires were confirmed to have an average length of 47 μm and an average diameter of 215 nm, and a transmission electron microscope image of the silver-coated copper nanowires is shown in Fig. 2(a), and a TEM-EDS analysis image is shown in Fig. 2(b).

[0091]

[0092] [Example 2]

[0093] In Example 1 above, copper chloride (II) (CuCl₂) instead of copper nitrate (II) 2· 14g of 2H2O (Samjeon Soonyak Industrial Co., Ltd.) was used, and the procedure was performed in the same manner as in Example 1, except that 6g of sodium chloride was used instead of 14g. Scanning electron microscope images of the prepared copper nanowires are shown in Figure 3. The silver-coated copper nanowires synthesized according to Example 2 were confirmed to have an average length of 35 μm and an average diameter of 160 nm.

[0094]

[0095] [Example 3]

[0096] The procedure was carried out in the same manner as in Example 1, except that 50 ml of hexadecylamine (Sigma-Aldrich) was used as the alkylamine instead of dodecylamine, and the reaction was carried out for 3 hours instead of 60 minutes. Scanning electron microscope images of the prepared copper nanowires are shown in Figure 4. The silver-coated copper nanowires synthesized according to Example 3 were confirmed to have an average length of 39 μm and an average diameter of 231 nm.

[0097]

[0098] [Comparative Example 1]

[0099] At room temperature, 267 mL of ultrapure water and 800 g of a 50% sodium hydroxide (NaOH, Samjeon Soonyak Industrial Co., Ltd.) solution were added to a 1000 mL four-necked flask and stirred. After cooling the reactor, which had heated up due to the exothermic reaction, so that the temperature did not exceed 50°C, copper(II) nitrate (Cu(NO3)2· 1.267 g of 3H2O (Samjeon Soonyak Industrial Co., Ltd.) dissolved in 10 ml of ultrapure water and 1.4 ml of ethylenediamine (Samjeon Soonyak Industrial Co., Ltd.) were added sequentially to a reactor. 0.95 ml of hydrazine (Samjeon Soonyak Industrial Co., Ltd.) was added, and the temperature was raised to 70°C. The mixture was stirred and reacted at 70°C for 60 minutes to obtain synthesized copper nanowires.

[0100] In addition, a scanning electron microscope image of the fabricated copper nanowire is shown in Fig. 5.

[0101]

[0102] [Comparative Example 2]

[0103] The above Example 2 was performed in the same manner as Example 2, except that 800g of glucose (Glucose, Samjeon Soonyak Industry) was added as a reducing agent to the first aqueous solution and the temperature was raised to 90℃ and reacted for 12 hours.

[0104]

[0105] [Comparative Example 3]

[0106] The above Example 1 was performed in the same manner as Example 1, except that 2.5 ml of hydrazine (Hydrazine, Samjeon Soonyak Industry) was added as a reducing agent to the first aqueous solution.

[0107]

[0108] [Comparative Example 4]

[0109] The above Example 1 was performed in the same manner as Example 1, except that 56 ml of oleylamine (Oleylamine, Sigma-Aldrich) was used instead of alkylamine and the reaction was carried out for a reaction time of 5 hours.

[0110]

[0111] [Comparative Example 5]

[0112] The procedure was carried out in the same manner as Example 2, except that 90 ml of butylamine (Samjeon Soonyak Industrial Co., Ltd.) was used as the alkylamine instead of dodecylamine, and 44 g of ascorbic acid (Samjeon Soonyak Industrial Co., Ltd.) was added as a reducing agent to the first aqueous solution and the reaction was carried out by raising the temperature to 70°C. Scanning electron microscope images of the prepared copper nanostructures are shown in Figure 7. As seen in Figure 7, it was confirmed that they exhibit a plate-like shape.

[0113]

[0114] [Evaluation Example 1] Measurement of average diameter, average length, and average aspect ratio of nanowires

[0115] The average diameter, average length, and average aspect ratio of the copper nanowires prepared in the examples and comparative examples were measured and recorded in Table 1 below. The average diameter, average length, and average aspect ratio were analyzed by obtaining SEM images using a SEM (COXEM) instrument and using the operating software program of the same instrument. In addition, the yield of the copper nanowires obtained for each example and comparative example was recorded in Table 1 below.

[0116] Copper Nanowire Average Diameter [nm] Average Length [㎛] Average Aspect Ratio Yield [%] Example 1: 185 47 25 47 9.5 Example 2: 130 35 26 9 7 6.8 Example 3: 201 39 19 47 5.5 Comparative Example 1: 200 4.5 22 7 4.1 Comparative Example 2: 192 10 5 25 7.9 Comparative Example 3: Particle form not nanowire Comparative Example 4: 173 12 6 9 4 4.3 Comparative Example 5: Plate form not nanowire

[0117] As shown in Table 1 above, it was confirmed that according to the manufacturing method of one embodiment, core-shell copper nanowires with a high aspect ratio can be produced at a lower temperature and within a shorter time than conventional methods with a high yield. Examples 1 to 3 showed a significantly improved aspect ratio compared to Comparative Examples 1, 2, and 4, and in particular, Comparative Examples 3 and 5 could not be produced in a wire shape.

[0118] In addition, to evaluate the uniformity of the length of the nanowires analyzed in the SEM image, a distribution plot showing the number according to length was obtained, and the Full-width at Half Maximum (FWHM) was calculated. As a result, all of Examples 1 to 3 showed a very narrow FWHM, and it was confirmed that this effect is a superior effect of the present invention that cannot be realized in conventional technology requiring high temperatures.

[0119] Through this, it was confirmed that the core-shell copper nanowires produced according to the manufacturing method of the present invention have excellent oxidation stability, very uniform length, size, and shape, and a high aspect ratio, and in particular, can be synthesized with a relatively short reaction time even at low temperatures of 100°C or lower, making them suitable for industrial mass production.

[0120] Although the present invention has been described above through specific details and limited embodiments, this is provided merely to aid in a more comprehensive understanding of the invention, and the invention is not limited to the above embodiments. Those skilled in the art can make various modifications and variations from this description.

[0121] Accordingly, the scope of the present invention is not limited to the described embodiments, and all things equivalent to or having equivalent variations to the claims set forth below, as well as the claims set forth below, shall be considered to fall within the scope of the concept of the present invention.

Claims

1. A first step of preparing a first aqueous solution comprising a copper precursor, an alkylamine, and a halogen compound; A method for manufacturing core-shell copper nanowires comprising: a second step of synthesizing copper nanowires by adding a reducing agent to the first aqueous solution.

2. In Paragraph 1, In the second step above, A method for manufacturing core-shell copper nanowires with a synthesis temperature of 30 to 90°C.

3. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the copper precursor is one or more selected from the group consisting of copper nitrate (Cu(NO3)2), copper sulfate (CuSO4), copper sulfite (CuSO3), copper acetate (Cu(CH3COO)2), copper chloride (CuCl2), copper bromide (CuBr2), copper iodide (CuI), copper phosphate (Cu3(PO4)2) and copper carbonate (CuCO3).

4. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the above alkylamine is a C10-20 alkyl amine.

5. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the above halogen compounds are one or more selected from the group consisting of sodium chloride (NaCl), sodium bromide (NaBr), potassium chloride (KCl), potassium bromide (KBr), and ammonium chloride (NH4Cl).

6. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the reducing agent is one or more selected from the group consisting of ascorbic acid, erythorbic acid, N-acetylcysteine, L-cysteine, cysteine ​​hydrochloride, and glutathione.

7. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the above alkylamine is included in an amount of 0.5 to 10 moles per 1 mole of the copper precursor.

8. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the above halogen compound is included in an amount of 0.5 to 5 moles per 1 mole of the copper precursor.

9. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the reducing agent is included in an amount of 1 to 6 moles per 1 mole of the copper precursor.

10. In Paragraph 1, In the second step above, A method for manufacturing core-shell copper nanowires with a synthesis time of 90 minutes or less.

11. In Paragraph 1, A method for manufacturing core-shell copper nanowires in which the yield of the copper nanowires produced in the second step above is 70% or higher.

12. In Paragraph 1, After the above second stage, A method for manufacturing core-shell copper nanowires by further performing a third step of coating the surface of the manufactured copper nanowires with a conductive material.

13. In Paragraph 12, A method for manufacturing core-shell copper nanowires in which the conductive material is one or more selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), nickel (Ni), and graphene.

14. In Paragraph 12, The above conductive material is silver, and A method for manufacturing core-shell copper nanowires, wherein the third step is performed by dropping a coating solution containing a complex of silver and EDTA into a second aqueous solution containing copper nanowires prepared in the second step.

15. In Paragraph 14, A method for manufacturing core-shell copper nanowires, wherein the second aqueous solution further comprises one or more reducing agents selected from the group consisting of hydroquinone, ascorbic acid, glucose, and hydrazine.

16. A core-shell copper nanowire manufactured according to the method for manufacturing a core-shell copper nanowire selected from any one of claims 12 to 15, the surface of which is coated with a conductive material.

17. It comprises a shell containing a conductive material and a core containing copper, Core-shell copper nanowires having a diameter of 100 to 500 nm, a length of 20 to 55 μm, and an aspect ratio of 100 to 500.

18. In Paragraph 17, The above conductive material is a core-shell copper nanowire made of silver (Ag).

19. In Paragraph 17, The above shell is a core-shell copper nanowire having a thickness of 5 to 30 nm.

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