KR102117783B1 - Preparation method of Ag nano wires by selective dealloying - Google Patents

Abstract

An object of the present invention is to provide a silver nanowire manufacturing method for easily manufacturing a silver nanowire with a simple process. The present invention relates to a silver nanowire manufacturing method using selective corrosion. In order to achieve the above object, the present invention provides the silver nanowire manufacturing method using the selective corrosion, which comprises: a first step of manufacturing a melt by melting Ag alloy; a second step of manufacturing an Ag alloy ribbon by spinning the melt; and a third step of immersing the Ag alloy ribbon in an alkali solution and maintaining the same for a certain period of time.

Description

Manufacturing method of silver nanowires using selective corrosion {Preparation method of Ag nano wires by selective dealloying}

The present invention relates to a method of manufacturing silver nanowires using selective corrosion, and more particularly, to a method of manufacturing silver nanowires by a simple method of adding an Ag alloy to an alkali solution.

Recently, transparent electrodes have been widely applied in accordance with diversification and development of eco-friendly energy devices such as mobile devices and solar cells, and indium tin oxide (ITO) having high light transmittance and excellent conductivity is mainly used as a transparent electrode material. Is becoming. However, indium tin oxide has a problem of being difficult to apply to a flexible electric device because it has natural ceramic properties. Accordingly, there is a need to develop a material that can replace indium tin oxide as a transparent electrode, and various alternative materials such as carbon nanotubes, graphene, conductive polymers, and metal nanowires have been developed.

Among them, metal nanowires have high conductivity, chemical stability, flexibility, and a very small size that is difficult to discriminate in the visible light region, and thus various fields such as large-area touch screen panels, thin film solar cells, flexible organic light emitting diodes, and transparent displays It is spotlighted as a new material that can be applied to. In particular, research on silver (Ag) nanowires having high permeability and high conductivity has been actively conducted. Silver nanowires are electric, magnetic, optical, chemical and biosensor fields, display devices, and solar due to their excellent electrical and thermal conductivity of silver (Ag) and optical properties and chemical stability that show the highest surface enhancement Raman efficiency in the visible region. It can also be used for transparent electrodes using conductive materials for various electronic products such as batteries and mobile devices.

Various methods have been proposed in the past as a method of manufacturing silver nanowires, for example, poly which induces wire formation in a polyol solvent such as propylene glycol (PG) heated in Korean Patent No. 10-1360688. Preparation of silver nanowires in the solution by adding a salt or purified salt containing sodium chloride (NaCl) as a catalyst and a vinylpyrrolidone (PVP) capping agent and a catalyst, followed by addition of a metal compound (silver precursor) The method is disclosed. In the case of the above manufacturing method, the reaction temperature is lowered by using a propylene glycol solvent having excellent reducing power, and the amount of the capping agent is reduced by using a solar salt or a purified salt as a catalyst, and there is an advantage in that wire formation can be facilitated. However, the manufacturing method, as well as lowering the content of the capping agent by the use of a catalyst, in order to prevent the aggregation of substances in the solvent to form a nanowire, not only the capping agent must be included, but also a solvent and sun salt or purified salt as a catalyst There is a problem in that it is not possible to completely remove the material or impurities formed by the nanowires obtained by use.

Korean Patent Publication No. 10-2015-0077601 discloses a nanowire manufacturing method that can improve the production efficiency of silver nanowires by using a lanthanum-based metal salt as an additive and suppress the generation of accompanying impurities and particles. It is. However, the manufacturing method uses only a lanthanum-based metal salt in place of the sun salt or purified salt containing sodium chloride (NaCl), and still uses a capping agent and a polyol solvent, which is also obtained from the obtained nanowire to the material or the material. There is a problem that the impurities formed by cannot be completely removed.

In addition, conventional silver nanowire manufacturing methods have difficulty in mass production of silver nanowires due to complicated synthesis conditions or complicated processes. Accordingly, the present inventors did not use a capping agent, a catalyst, or the like, and did not form impurities on the silver nanowires, and developed a method of manufacturing the silver nanowires with a simple process.

Republic of Korea Registered Patent No. 10-1360688 (Invention name: Nano wire and its manufacturing method, Applicant: Nanopixis Co., Ltd., LG Innotek Co., Ltd., registration date: February 03, 2014) Republic of Korea Patent Publication No. 10-2015-0077601 (Name of invention: Method for manufacturing metal nanowire and metal nanowire manufactured therefrom, Applicant: Samsung SDI Co., Ltd., Publication date: July 8, 2015) Republic of Korea Patent Publication No. 10-2015-0072518 (Invention name: Method of manufacturing metal nanowires, metal nanowires and electronic devices, Applicant: Samsung Fine Chemicals Co., Ltd., Publication date: June 30, 2015)

An object of the present invention is to provide a method of manufacturing silver nanowires that can easily produce silver nanowires by using a simple process without using a capping agent, a catalyst, etc., using selective corrosion.

In addition, another object of the present invention is to provide a silver nanowire that is manufactured through the above manufacturing method and does not form impurities.

In order to achieve the above object, the present invention is a step (step 1) of melting an Ag alloy to prepare a melt;

(Step 2) producing an Ag alloy ribbon by spinning the melt; And

(Step 3) characterized by providing a method for producing silver nanowires using selective corrosion, including; immersing the Ag alloy ribbon in an alkaline solution and maintaining it for a certain period of time.

In the first step, the Ag alloy is characterized in that the Ag-Cu alloy containing Cu in Ag, and the Cu may be included in 25 to 30 wt%.

In the second step, the Ag alloy ribbon may have a layered structure.

In step 3, the alkali solution is characterized in that it is sodium hydroxide, and the concentration of the sodium hydroxide may be 0.1 to 6M.

In addition, the Ag alloy ribbon in step 3 may be maintained by immersion in an alkaline solution for 6 to 25 hours.

The silver nanowires can be produced by a simple method of immersing the Ag alloy ribbon in an alkali solution through the method of preparing silver nanowires using selective corrosion provided by the present invention. Therefore, it is economical because silver nanowires can be easily mass-produced.

In addition, the present invention can provide silver nanowires that do not contain impurities through the manufacturing method.

1 is a flow chart for explaining a method of manufacturing silver nanowires using selective corrosion of the present invention.
2 is a phase equilibrium diagram of Ag / Cu.
Figure 3 is a scanning electron microscope (Scanning Electron Microscope; SEM) image showing the layered structure of the Ag alloy ribbon of the present invention.
4 is an atomic force microscope (AFM) image of silver nanowires according to NaOH concentration prepared according to an embodiment of the present invention.
5 is an atomic force microscope (AFM) image of a silver nanowire manufactured according to an embodiment of the present invention.
Figure 6 is an atomic force microscope (Atomic Force Microscope; AFM) image of the silver nanowires prepared according to an embodiment of the present invention.
Figure 7 is an atomic force microscope (Atomic Force Microscope; AFM) image of a silver nanowire prepared according to an embodiment of the present invention.

With reference to the accompanying drawings, specific embodiments of the present invention will be described in detail.

1 is a flow chart for explaining a method of manufacturing silver nanowires using selective corrosion of the present invention, FIG. 2 is a phase equilibrium diagram of Ag / Cu, and FIG. 3 is a scanning electron microscope image showing the filling structure of an Ag alloy ribbon. to be.

Details not necessary to understand the technical idea of the invention as a part not different from the prior art are excluded from the description, but the technical idea of the present invention and its protection scope are not limited thereto.

A method of manufacturing silver nanowires using selective corrosion of the present invention will be described in detail with reference to FIGS. 1 to 3.

First, an Ag alloy is melted to prepare a melt (step 1). At this time, the Ag alloy in the first step is characterized in that the Ag-Cu alloy containing Cu in Ag, and the Ag alloy preferably contains Cu in an amount of 25 to 30 wt%. More preferably, the Ag alloy may have a composition of 72 wt% Ag and 28 wt% Ag, which is a eutectic composition of the Ag-Cu alloy, as shown in FIG. 2, when the Ag alloy melt is cooled, the two-component metal At the same time, it is crystallized so that all of the Ag alloys have a lamellar structure. When the content of Cu in the Ag alloy exceeds 25 to 30 wt%, it is not preferable because the layered structure is not sufficiently formed or not formed at all, which makes it difficult to manufacture silver nanowires.

Next, the molten alloy is spun to prepare an Ag alloy ribbon (step 2). In the second step, the Ag alloy ribbon is characterized in that it has a lamellar structure in which Ag and Cu are layered on top of each other, and may be preferably manufactured using a melt spinning method to reduce the interlayer spacing. In more detail, an Ag alloy ribbon having a narrower interlayer spacing than a layered structure of an existing alloy metal can be manufactured by rapidly cooling the Ag alloy melt by contacting it with a rotating high-speed wheel surface. At this time, the high-speed rotating wheel in contact with the Ag alloy melt may use a conventional wheel known in the art, for example, a copper wheel or the like. Here, the rotational speed of the high-speed rotating wheel may be 500 to 1500 rpm, and the diameter of the wheel may be 20 to 30 cm. When the above-described conditions are satisfied, an alloy ribbon having a thin thickness and a microstructure can be formed while the melt contacting the surface of the wheel is rapidly cooled. Particularly, when the rotational speed of the wheel is less than 500 rpm, the interlayer spacing is wide, making it difficult to form silver nanowires. If it exceeds 1500 rpm, the residual stress of the alloy ribbon increases due to the rapid cooling rate, which makes it difficult to manufacture silver nanowires. not.

Finally, the Ag alloy ribbon is immersed in an alkaline solution and kept for a certain period of time (step 3). In the above step 3, the alkali solution is characterized in that it is sodium hydroxide (NaOH). Selective corrosion is a method of dissolving a single metal by using an electrolyte in an alloy of two metals with a difference in reactivity. When the alloy is immersed in a solvent, a highly reactive metal is dissolved and a less reactive metal is rearranged atomically. do. That is, when the Ag alloy ribbon is immersed in a sodium hydroxide solution, copper reacts as shown in Reaction Scheme 1 and disappears.

[Scheme 1]

Cu + NaOH → Cu (OH) ₂ (↓) + Na

At this time, since the Ag alloy ribbon of the present invention has a layered structure in which Ag and Cu are layered as shown in FIG. 3, copper is lost through the reaction, and thus silver nanowires can be automatically generated.

The concentration of sodium hydroxide in step 3 is preferably 0.1 to 6M, and more preferably 3 to 6M. When the concentration of sodium hydroxide is less than 0.1M, the selective corrosion reaction proceeds very quickly, making it unsuitable for the production of silver nanowires. If it exceeds 6M, the atomic movement is not smooth due to the dense atoms, which may interfere with selective corrosion. Therefore, it is difficult to manufacture silver nanowires, which is undesirable.

In addition, the Ag alloy ribbon in step 3 is preferably maintained by immersion in an alkaline solution for 6 to 25 hours. When the immersion time is less than 6 hours, silver nanowires are not sufficiently generated, and when it exceeds 25 hours, the effect of silver nanowires generation over time is negligible, which is not economical and thus undesirable.

In addition, the step 3 is preferably performed at 15 ~ 45 ℃. When the operating temperature is less than 15 ° C, the silver nanowire formation reaction does not occur sufficiently, and when it exceeds 45 ° C, the selective corrosion reaction proceeds very quickly, which is undesirable because it is unsuitable for silver nanowire production.

The silver nanowires manufactured through the method of manufacturing silver nanowires using selective corrosion of the present invention may have a diameter of 60 to 80 nm and a length of 3 to 10 μm.

Therefore, the present invention can easily produce silver nanowires by a simple method of immersing a layered structure Ag alloy ribbon in an alkali solution, and thus does not contain impurities because it does not require a separate capping agent or catalyst. It is characterized by being able to provide silver nanowires.

Hereinafter, a preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, it is provided to sufficiently convey the spirit of the present invention to those skilled in the art so that the contents introduced herein are thorough and complete.

Silver nanowire manufacturing

1. Preparation of silver nanowires according to NaOH concentration

First, the Ag-Cu alloy ribbon having a layered structure was prepared by melting Ag into Cu at 28wt% and rapidly cooling it by contacting Ag and Cu melts on the surface of a copper wheel (diameter 25 cm, thickness 4 cm) rotating at a speed of 1000 rpm. Did.

Subsequently, the Ag-Cu alloy ribbons prepared above were immersed in 3M, 5M, 7M, and 10M sodium hydroxide solutions at a temperature of 25 ° C for 24 hours each. Then, the surface was observed by an atomic force microscope (Atomic Force Microscope; AFM), and the results are shown in FIG. 4.

Referring to FIG. 4, silver nanowires were observed in 3M and 5M sodium hydroxide solutions, and a large amount of uniformly shaped silver nanowires were observed in 5M sodium hydroxide solution. Silver nanowires were not observed in the 7M and 10M sodium hydroxide solution, which increases the atomic density in the aqueous solution as the concentration of the solution increases, which decreases the dissolution rate of Cu and the diffusion rate of Ag. It is confirmed that it is because a spherical shape was formed.

2. Manufacturing of silver nanowires according to the cooling rate when manufacturing alloys

Copper wheels rotating at a rate of 500, 1000, 1500, 2000, 3000 rpm after melting 72 wt% Ag and 28 wt% Ag to compare the silver nanowire manufacturing effect according to the cooling rate during alloy manufacturing (diameter 25 cm, thickness 4 cm ) The Ag-Cu alloy ribbon having a layered structure was prepared by rapidly cooling by contacting each surface.

Subsequently, the Ag-Cu alloy ribbon prepared above was immersed in 5M sodium hydroxide solution for 24 hours at a temperature of 25 ° C. Then, the surface was observed by an atomic force microscope (Atomic Force Microscope; AFM).

As a result, silver nanowires were observed from the Ag-Cu alloy prepared at a cooling rate of 500 to 1500 rpm, but when the cooling rate exceeded 1500 rpm, no silver nanowires were generated as shown in FIG. 5. This is confirmed because the residual stress of the ribbon was increased due to the cooling rate being too fast.

In addition, the Ag-Cu (Cu 28wt%) alloy prepared at a cooling rate of 500 rpm was immersed in 0.1M and 0.5M sodium hydroxide solution for 24 hours, and then the surface was observed by an atomic force microscope. As a result, silver nanowires were generated. In particular, as shown in FIG. 6, it was confirmed that a number of silver nanowires were generated when immersed in a 0.5M sodium hydroxide solution.

3. Manufacturing silver nanowires according to temperature

In order to compare the silver nanowire production effect according to the temperature when immersing the sodium hydroxide solution, first, Ag is dissolved in Cu to 28wt%, and then Ag and Cu are rotated on the surface of a copper wheel (diameter 25cm, thickness 4cm) that rotates at a rate of 1000 rpm. The Ag-Cu alloy ribbon having a layered structure was prepared by rapid cooling by contacting the melt, and then the Ag-Cu alloy ribbon prepared above was immersed in a 4M sodium hydroxide solution at 40 ° C. for 6 hours. Then, the surface was observed by an atomic force microscope (Atomic Force Microscope; AFM), and the results are shown in FIG. 7.

Referring to FIG. 7, it was confirmed that a small amount of silver nanowires were found at a temperature of 40 ° C.

Ag: Cu
(wt%) Wheel rotation speed
(rpm) NaOH concentration
(M) Temperature
(℃) Whether silver nanowires are produced 72:28 500 0.1 25 △ 72:28 500 0.5 25 ○ 72:28 500 5 25 ○ 72:28 1000 3 25 ○ 72:28 1000 5 25 ○ 72:28 1000 7 25 × 72:28 1000 10 25 × 72:28 1500 5 25 ○ 72:28 2000 5 25 × 72:28 3000 5 25 × 72:28 1000 4 40 △ ○: Multiple silver nanowires
△: Small amount of silver nanowires
×: No silver nanowires were generated

Therefore, it is possible to easily manufacture silver nanowires by simply immersing an Ag alloy ribbon having a layered structure in a sodium hydroxide solution, wherein the wheel speed is 500 to 1500 rpm when manufacturing the layered alloy ribbon. When immersed in a sodium hydroxide solution, the concentration of sodium hydroxide is 0.1 to 6M, and the reaction temperature is preferably 15 to 45 ° C.

Claims (7)

(Step 1) preparing a melt by melting the Ag alloy;
(Step 2) producing an Ag alloy ribbon by spinning the melt; And
(Step 3) immersing the Ag alloy ribbon in an alkali solution and maintaining it for a certain period of time; a method for manufacturing silver nanowires using selective corrosion. According to claim 1,
In the first step, the Ag alloy is Ag-Cu, silver nanowire manufacturing method using selective corrosion. According to claim 2,
The Ag alloy is a method of manufacturing silver nanowires using selective corrosion, characterized in that Cu contains 25 ~ 30wt%. According to claim 1,
The method of manufacturing silver nanowires using selective corrosion, characterized in that the Ag alloy ribbon in the second step has a layered structure. According to claim 1,
The method of manufacturing silver nanowires using selective corrosion, characterized in that the alkali solution in the third step is sodium hydroxide (NaOH). The method of claim 5,
The concentration of the sodium hydroxide is 0.1 ~ 6M method of manufacturing silver nanowires using selective corrosion. According to claim 1,
In step 3, the Ag alloy ribbon is immersed in an alkaline solution for 6 to 25 hours, and is maintained.

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