KR20160103773A - Method for manufacturing nanowire of core-shell structure and device comprising the nanowire of core-shell structure manufactured by the same - Google Patents

Abstract

Provided is a method for manufacturing a nanowire with a core-shell structure including the following steps: (step 1) manufacturing a mixed solution by manufacturing a dispersion solution including nanosilver wire and then adding a reducing agent and a pH adjusting agent to the dispersion solution; and (step 2) coating the surface of the nanosilver wire with gold by injecting precursors of gold (Au) into the mixed solution manufactured by step 1. According to the present invention, the method for manufacturing a nanowire with a core-shell structure can form a fine shell on the surface of the nanosilver wire in the solution in an easy manner and can minimize a consumption amount of gold by coating the surface with a fine and thin gold film. In addition, breakage of the nanosilver wire can be ultimately prevented by preventing migration of the nanosilver wire, which is a core. Furthermore, oxidation stability and chemical stability of the nanosilver wire can be enhanced. Moreover, when the nanowire with a core-shell structure manufactured by the method of the present invention is applied to a device, performance of the device can be maintained for a long period of time.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a nanowire of a core-shell structure, and a method of manufacturing a nanowire of a core-

The present invention relates to a method of manufacturing a nanowire of a core-shell structure and a device including the nanowire of the core-shell structure manufactured thereby. More particularly, the present invention relates to a method of manufacturing a core- core structure in which nanowires are formed with a shell of a thin gold film on a nanowire.

In general, nano structures are used for sensing and diagnosis of microelectronic devices, chemical or biomolecules, light-emitting displays, energy conversion and storage, catalysis catalysis, drug delivery, separation and optical storage, and the like.

Among the nanostructures, nanowires having a linear structure exhibit properties of nanostructures in the diametrical direction as well as properties possessed by the linear nanomaterials. Therefore, nanowires having a linear structure in many fields including electronic, chemical, biological, and biotechnological fields It plays an important role and is actively applied as a next generation material.

The formation of nanowires, which are nano / microstructures, can be performed by evaporation and condensation, physical vapor deposition, chemical vapor deposition, solvothermal and hydrothermal methods, It can be implemented in various ways as well. Of the various methods, polyol synthesis methods are widely used in the synthesis of nanowires, especially metal nanowires, which can be mass-produced and synthesized at a high yield. In particular, the synthesis of silver nanowires, which are used as transparent electrode materials, has reached commercialization level.

The silver nanowires fabricated in this way can be applied in various ways, but they are most widely used to replace transparent electrode materials. When the nanowire is replaced with a transparent electrode material, it can be applied to various devices such as a transparent electrode-based touch screen, an OLED, and an OPV. However, in order to completely replace indium tin oxide (ITO), which is a transparent electrode material, problems still remain to be solved.

When a transparent electrode is fabricated using nanowires, it is possible to fabricate an electrode having high transparency and low surface resistance, but the haze due to the thickness of the silver nanowire becomes a problem. In order to overcome this blurring problem, if the thickness of the silver nanowire is extremely reduced (20 nm to 50 nm), the cloudiness can be improved, but it causes another problem. Specifically, when the thickness of the nanowire is reduced to 20 nm to 50 nm or less, the problem is that the migration of silver or the phenomenon of oxidation is rapidly accelerated.

Particularly, in the case of silver nanowires having a fine thickness, ions may move even under a normal electric field or at a normal temperature. These ion movements can be caused by various causes, mainly due to ostwald ripening and ion migration at the intersections. The migration of these materials can lead to electrical breakdown or breakdown of insulation through growth.

Therefore, this phenomenon not only sharply reduces the lifetime of the electrode but also hinders the operation of the device or device including the silver nanowire.

Further, when a transparent electrode made of silver nanowires is applied to a multi-layered device such as an organic device and an energy device, lifetime and driving of the device are hindered due to chemical reaction of silver.

Among the above-described problems, a method for manufacturing silver nanowires coated with an oxidation-preventive layer to prevent oxidation of silver nanowires has been disclosed in Korean Patent Laid-Open Publication No. 10-2014-0011654. Although the prior art has introduced a shell structure for the purpose of preventing oxidation, an expensive ALD process is used instead of a solution process, and the thickness of the shell is thicker than 20 nm, which may degrade the performance of the nanowire .

The inventors of the present invention have been studying a method for preventing all of the degradation factors of silver nanowires while preparing a mixed solution containing a reducing agent and a pH adjusting agent in a silver nanowire dispersion and adding a gold precursor We have developed a method of manufacturing core-shell nanowires by coating gold on the surface of silver nanowires to prevent migration of the core nanowires as well as to ensure oxidation stability and chemical stability. And completed the present invention.

An object of the present invention is to provide a method of manufacturing a core-shell structure nanowire capable of preventing migration of silver nanowires and finally preventing shorting of silver nanowires.

In order to achieve the above object,

Preparing a dispersion containing silver nanowires, adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution (step 1); And

A gold (Au) precursor is injected into the mixed solution prepared in the step 1, and gold is coated on the surface of the silver nanowire (step 2).

In addition,

Preparing a dispersion containing silver nanowires, adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution (step 1); And

(Step 2) of injecting a gold (Au) precursor into the mixed solution prepared in step 1 to prepare a core-shell structure nanowire having a gold thin film formed on the silver nanowire surface (step 2) And a method for preventing such a problem.

Further,

A core-shell structure nanowire including a core made of silver nanowires and a shell made of a gold thin film manufactured by the above manufacturing method.

The core-shell structure nanowire manufacturing method according to the present invention can easily form a fine shell on the surface of silver nanowires in a solution state and can minimize the amount of gold used by finely coating the gold thin film. In addition, the core phosphor can prevent the migration of the nanowires and ultimately prevent shorting of the silver nanowires. Furthermore, it is possible to improve the oxidation stability and chemical stability of silver nanowires. Furthermore, when the nanowire of the core-shell structure manufactured by the manufacturing method according to the present invention is applied to a device, the performance of the device can be maintained for a long period of time.

FIG. 1 is a photograph of a nanowire produced in Example 1 and Comparative Example 2 according to the present invention observed by a scanning electron microscope (SEM); FIG.
FIG. 2 is a photograph of the silver nanowire prepared in Comparative Example 1, which was left in air for one week and observed with a scanning electron microscope (SEM); FIG.
FIG. 3 is a photograph of the nanowires prepared in Example 1 and Comparative Example 1 according to the present invention, left for one week in air and observed with a scanning electron microscope (SEM); FIG.
4 is a photograph of the nanowires prepared in Example 1 and Comparative Example 1 according to the present invention, left for 4 weeks in air and observed with an optical microscope;
5 is a graph illustrating changes in resistance of nanowires fabricated in Example 1 and Comparative Example 1 with time according to the present invention;
FIG. 6 is a photograph of the nanowire prepared in Example 1 and Comparative Example 1 according to the present invention, observed with naked eyes after exposure to hydrogen peroxide; FIG.
FIG. 7 is a photograph of a nanowire prepared in Example 1 and Comparative Example 1 according to the present invention, after exposure to hydrogen peroxide, by a scanning electron microscope (SEM). FIG.

The present invention

Preparing a dispersion containing silver nanowires, adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution (step 1); And

A gold (Au) precursor is injected into the mixed solution prepared in the step 1, and gold is coated on the surface of the silver nanowire (step 2).

Hereinafter, a method for manufacturing a core-shell structure nanowire according to the present invention will be described in detail for each step.

First, in the method of manufacturing a nanowire core-shell structure according to the present invention, step 1 is a step of preparing a dispersion containing silver nanowires, and then adding a reducing agent and a pH adjuster to the dispersion to prepare a mixed solution .

In the step 1, a dispersion containing silver nanowires is prepared, and a reducing agent for reducing action and a pH adjusting agent for adjusting pH are added to the dispersion to prepare a mixed solution.

Specifically, the dispersion of step 1 may be selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinylphenol (PVPh), polyvinyl alcohol (PVA) polyvinylsulfonic acid, polyvinylsulfate metal salt, polyvinylcarboxylic acid, And a polymer dispersing agent such as a polyvalent metal salt, polyvinyl pyridine (PVPy), and copolymers thereof. As a specific example, polyvinyl pyrrolidone can be used.

The reducing agent in step 1 may be selected from the group consisting of ascorbic acid, hydrazine, sodium borohydride, sodium triacetoxyborohydride, lithium aluminum hydride, Diisobutylaluminum hydride, phenyl hydrazine, cystein, fructose, ribose, galactose, tocopherol, and triethanolamine. amine) and the like can be used. As a specific example, ascorbic acid can be used for strong reducing action.

Further, the pH adjuster of step 1 may be an organic base or sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH) and tetramethyl ammonium hydroxide (TMAH) have. As a specific example, sodium hydroxide, which is one of inorganic bases, can be used as a pH adjusting agent.

In addition, the pH of the mixed solution in step 1 is preferably 9.5 or more, more preferably 9.5 to 12, and most preferably 9.5 to 10.5. If the pH of the mixed solution is less than 9.5 in the step 1, the reducing power of the reducing agent is not sufficiently exhibited and the galvanic substitution reaction of the gold precursor can not be inhibited, so that the silver nanowire as the core material is damaged, There is a problem.

Furthermore, the concentration of the reducing agent in the mixed solution of step 1 is preferably 10 mM to 100 mM. If the concentration of the reducing agent is less than 10 mM in the mixed solution of step 1, there is a problem that a gold thin film is not formed on the surface of the nanowire when the gold precursor is introduced in a subsequent step. When the concentration is more than 100 mM, There is a problem that gold particles are formed due to a rapid reduction reaction before the gold precursor injected into the entire region of the dispersion is uniformly diffused.

Next, in the nanowire manufacturing method of the core-shell structure according to the present invention, step 2 is a step of injecting gold (Au) precursor into the mixed solution prepared in step 1 to coat gold on the silver nanowire surface .

In the step 2, a gold precursor is injected into the mixed solution prepared in the step 1 to coat gold on the surface of the silver nanowire to form a core- Shell structure of nanowires.

Specifically, the gold precursor of step 2 may be selected from the group consisting of HAuCl ₄ , AuCl ₃ , KAuCl ₄ , and Au (OH) ₃ .

In addition, the step 2 may be carried out at a temperature of 10 ° C to 40 ° C, and may be carried out with stirring for a time of 1 minute to 30 minutes.

Further, in step 2, the thickness of the gold coated on the surface of the silver nanowire is preferably 2 nm to 5 nm. By forming the fine thin film as described above, the use amount of gold can be minimized and migration of silver can be prevented. In addition, the oxidation stability and chemical stability of the silver nanowire can be secured.

Further,

Preparing a dispersion containing silver nanowires, adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution (step 1); And

(Step 2) of injecting a gold (Au) precursor into the mixed solution prepared in step 1 to prepare a core-shell structure nanowire having a gold thin film formed on the silver nanowire surface (step 2) And a method for preventing such a problem.

Hereinafter, a method for preventing the short-circuiting of the nanowire of the core-shell structure according to the present invention will be described in detail for each step.

First, in a method for preventing shorting of a nanowire according to the present invention, step 1 is a step of preparing a dispersion containing silver nanowires, and then adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution.

In the step 1, a dispersion containing silver nanowires is prepared, and a reducing agent for reducing action and a pH adjusting agent for adjusting pH are added to the dispersion to prepare a mixed solution.

Specifically, the dispersion of step 1 may be selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinylphenol (PVPh), polyvinyl alcohol (PVA) polyvinylsulfonic acid, polyvinylsulfate metal salt, polyvinylcarboxylic acid, And a polymer dispersing agent such as a polyvalent metal salt, polyvinyl pyridine (PVPy), and copolymers thereof. As a specific example, polyvinyl pyrrolidone can be used.

The reducing agent in step 1 may be selected from the group consisting of ascorbic acid, hydrazine, sodium borohydride, sodium triacetoxyborohydride, lithium aluminum hydride, Diisobutylaluminum hydride, phenyl hydrazine, cystein, fructose, ribose, galactose, tocopherol, and triethanolamine. amine) and the like can be used. As a specific example, ascorbic acid can be used for strong reducing action.

Further, the pH adjuster of step 1 may be an organic base or sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH) and tetramethyl ammonium hydroxide (TMAH) have. As a specific example, sodium hydroxide, which is one of inorganic bases, can be used as a pH adjusting agent.

In addition, the pH of the mixed solution in step 1 is preferably 9.5 or more, more preferably 9.5 to 12, and most preferably 9.5 to 10.5. If the pH of the mixed solution is less than 9.5 in the step 1, the reducing power of the reducing agent is not sufficiently exhibited and the galvanic substitution reaction of the gold precursor can not be inhibited, so that the silver nanowire as the core material is damaged, There is a problem.

Furthermore, the concentration of the reducing agent in the mixed solution of step 1 is preferably 10 mM to 100 mM. If the concentration of the reducing agent is less than 10 mM in the mixed solution of step 1, there is a problem that a gold thin film is not formed on the surface of the nanowire when the gold precursor is introduced in a subsequent step. When the concentration is more than 100 mM, There is a problem that gold particles are formed due to a rapid reduction reaction before the gold precursor injected into the entire region of the dispersion is uniformly diffused.

Next, in the method for preventing shorting of the nanowire according to the present invention, step 2 is a step of injecting a gold (Au) precursor into the mixed solution prepared in step 1 to form a core- Lt; RTI ID = 0.0 > nanowires < / RTI >

In the step 2, a gold precursor is injected into the mixed solution prepared in the step 1 to coat gold on the surface of the silver nanowire to form a core- Shell structure of nanowires.

Specifically, the gold precursor of step 2 may be selected from the group consisting of HAuCl ₄ , AuCl ₃ , KAuCl ₄ , and Au (OH) ₃ .

In addition, the step 2 may be carried out at a temperature of 10 ° C to 40 ° C, and may be carried out with stirring for a time of 1 minute to 30 minutes.

Further, in step 2, the thickness of the gold coated on the surface of the silver nanowire is preferably 2 nm to 5 nm. By forming the fine thin film as described above, the use amount of gold can be minimized and migration of silver can be prevented. Thus, it is possible to prevent shorting of silver nanowires.

As described above, the core-shell structure nanowire manufacturing method and the nanowire short-circuit prevention method according to the present invention can prevent the migration of the core phosphor nanowire, thereby preventing the short-circuiting of the silver nanowire. Furthermore, it is possible to improve the oxidation stability and chemical stability of silver nanowires. Furthermore, when the nanowire of the core-shell structure manufactured by the manufacturing method according to the present invention is applied to a device, the performance of the device can be maintained for a long period of time.

Further,

A core-shell structure nanowire including a core made of silver nanowires and a shell made of a gold thin film manufactured by the above manufacturing method.

The core-shell structure nanowire according to the present invention is a core-shell structure nanowire in which a gold thin film as a shell material is uniformly coated on the surface of a silver nanowire as a core material so that migration of silver nanowires can be prevented However, oxidation stability and chemical stability are improved, so that the performance of the device can be maintained for a long time when it is applied to an electrode or the like.

Hereinafter, the present invention will be described in detail with reference to the following examples and experimental examples.

It should be noted, however, that the following examples and experimental examples are illustrative of the present invention, but the scope of the invention is not limited by the examples and the experimental examples.

Example 1 Nanowire Production of Core-Shell Structure 1

Step 1: 1.1 g of polyvinylpyrrolidine (PVP) was dissolved in 40 mL of distilled water, and 0.05 g of silver nanowire was added to prepare a silver nanowire dispersion.

Then, ascorbic acid, which is a reducing agent, was added to the prepared silver nanowire dispersion so as to have a concentration of 100 mM, and 200 mM sodium hydroxide (NaOH), which is a pH adjusting agent, was added thereto to prepare a mixed solution.

Step 2: 8 mL of a 0.1 mM aqueous solution of HAuCl ₄ as a gold precursor was slowly injected into the mixed solution prepared in step 1 at a rate of 40 L / min, stirred and reacted at room temperature for 10 minutes to form a core-shell structure Of nanowires were prepared.

≪ Comparative Example 1 > Preparation of nanowire 1

As a commercially available silver nanowire, SNW-006 product of EN & N Co., Ltd. was prepared.

≪ Comparative Example 2 &

Step 1: Silver nanowire 10 mg was added to 100 mL of distilled water to prepare a silver nanowire dispersion.

Step 2: The silver nanowire dispersion prepared in Step 2 was heated to a temperature of 99 ° C, stirred for 10 minutes while maintaining the temperature, and 3.3 ml of a 10 mM aqueous solution of HAuCl ₄ as a gold precursor And the mixture was stirred for another 10 minutes to prepare a core-shell structure nanowire.

<Experimental Example 1> Scanning electron microscope (SEM) and optical microscopic observation

The nanowires prepared in Example 1, Comparative Example 1 and Comparative Example 2 were observed under a scanning electron microscope (SEM) to examine the surface shape and migration phenomena of the core-shell structure nanowires produced by the manufacturing method according to the present invention. And an optical microscope, and the results are shown in Figs. 1 to 4. Fig.

As shown in FIG. 1, in the case of Comparative Example 2, which is a nanowire produced by a galvanic replacement method in which gold is coated on a nanowire, the gold thin film coated on the silver nanowire surface is not uniform, And it was confirmed that there is a problem that is difficult to do. In addition, the structure of the gold thin film formed by the shell is not only very uneven, but also the substitution (corrosion) occurs, so that the shape of the core phosphor nanowire is damaged.

On the other hand, in the case of Example 1, which is a core-shell structure nanowire fabricated by the manufacturing method of the present invention, it is confirmed that a shell made of a gold thin film with a very fine thickness is formed in the state where the core phosphor nanowire exists there was.

On the other hand, as shown in FIG. 2, in the case of Comparative Example 1, which is a silver nanowire having a minute thickness, it can be seen that ions move when a period of one week elapses under a normal state at room temperature. The migration of these ions can be caused by various causes, but mainly due to ostwald ripening and ion migration at the intersections. The migration of these materials causes electrical breakdown or insulation breakdown through growth .

Further, as shown in Fig. 3, in the case of Comparative Example 1, it was confirmed that migration of silver nanowires occurred.

On the other hand, in the case of Example 1, which is a core-shell structure nanowire fabricated by the manufacturing method according to the present invention, migration of silver nanowires was delayed.

Further, as shown in Fig. 4, the nanowires of Comparative Example 1 and Example 1 were allowed to stand for 4 weeks, and then observed with an optical microscope. As a result, in Comparative Example 1, migration of silver nanowires as well as oxidation .

On the other hand, it was confirmed that the core-shell structure nanowire of Example 1 can delay the migration phenomenon and oxidation.

&Lt; Experimental Example 2 >

In order to confirm the change in resistance of the core-shell structure nanowire fabricated by the manufacturing method according to the present invention over time, the change in resistance of the nanowire fabricated in Example 1 and Comparative Example 1 with time was observed, The results are shown in Fig.

As shown in FIG. 5, the silver nanowires of Comparative Example 1 migrate and oxidize over time, so that the initial resistance value is significantly lost.

On the other hand, in the case of Example 1, which is the core-shell structure nanowire fabricated by the manufacturing method according to the present invention, the resistance change is much slower than that of Comparative Example 1, and it is confirmed that the initial resistance value can be maintained for a considerable period of time there was.

EXPERIMENTAL EXAMPLE 3 Analysis of Corrosion Characteristics

In order to confirm the corrosion characteristics of the core-shell structure nanowires manufactured by the manufacturing method according to the present invention, hydrogen peroxide (H ₂ O ₂ ) was applied to the nanowires prepared in Example 1 and Comparative Example 1, The morphology was observed with a naked eye and a scanning electron microscope (SEM), and the results are shown in FIG. 6 and FIG.

As shown in FIG. 6 and FIG. 7, it was confirmed that the silver nanowire of Comparative Example 1 changed its shape through abrupt etching and recombination when exposed to hydrogen peroxide.

On the other hand, in the case of Example 1, which is a core-shell structure nanowire fabricated by the manufacturing method according to the present invention, it can be confirmed that the initial nanowire shape is maintained by the shell made of the gold thin film.

Claims (10)

Preparing a dispersion containing silver nanowires, adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution (step 1); And
And a step (2) of injecting a gold (Au) precursor into the mixed solution prepared in step 1 to coat gold on the silver nanowire surface (step 2).
The method according to claim 1,
Wherein the dispersion of step 1 is selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinylphenol (PVPh), polyvinyl alcohol (PVA) polyvinylsulfonic acid, polyvinylsulfate metal salt, polyvinylcarboxylic acid, polyvinylcarboxylate metal salt, Polyvinylpyridine (PVPy), and copolymers thereof. 2. The method of claim 1, wherein the core-shell structure comprises at least one polymer dispersant.
The method according to claim 1,
The reducing agent in step 1 may be selected from the group consisting of ascorbic acid, hydrazine, sodium borohydride, sodium triacetoxyborohydride, lithium aluminum hydride, di Diisobutylaluminum hydride, phenyl hydrazine, cystein, fructose, ribose, galactose, tocopherol, and triethanol amine. Wherein the core-shell structure is at least one selected from the group consisting of a core-shell structure and a core-shell structure.
The method according to claim 1,
PH adjusting agent in step 1 is selected from the group consisting of an organic base or sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH) and tetra mekil ammonium hydroxide (tetra methyl ammonium hydroxide, TMAH) Wherein the core-shell structure is at least one inorganic base.
The method according to claim 1,
Wherein the pH of the mixed solution in step 1 is 9.5 or more.
The method according to claim 1,
Wherein the concentration of the reducing agent in the mixed solution of step 1 is 10 mM to 100 mM.
The method according to claim 1,
The gold precursor of step 2 is at least one selected from the group consisting of HAuCl ₄ , AuCl ₃ , KAuCl ₄ and Au (OH) ₃ . Of the core-shell structure.
The method according to claim 1,
Wherein the thickness of gold coated on the silver nanowire surface in step 2 is from 2 nm to 5 nm.
Preparing a dispersion containing silver nanowires, adding a reducing agent and a pH adjusting agent to the dispersion to prepare a mixed solution (step 1); And
(Step 2) of injecting a gold (Au) precursor into the mixed solution prepared in step 1 to prepare a core-shell structure nanowire having a gold thin film formed on the silver nanowire surface (step 2) How to prevent.
A nanowire of a core-shell structure comprising a core made of silver nanowires and a shell made of a gold thin film, the nanowire being manufactured by the manufacturing method of claim 1.

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