KR101991964B1 - Method for Preparing Nanowire having Core-Shell Structure - Google Patents

Abstract

The present invention relates to a method of manufacturing a nanowire having a core-shell structure, the method comprising: preparing a dispersion of metal nanowires in which metal nanowires are dispersed in a polar solvent; Preparing a metal precursor solution by dissolving a metal precursor in a polar solvent; And mixing the metal nanowire dispersion and the metal precursor solution. The nanowire having a core-shell structure manufactured by this method has a high conductivity and a high resistance to the metal nanowire core while preventing oxidation of the core metal. It is possible to manufacture a nanowire electrode having excellent electrical properties and high transmittance by simultaneously satisfying the prevention of oxidation of metal and the high conductivity.

Description

[0001] The present invention relates to a nanowire having a core-shell structure,

The present invention relates to a method of manufacturing a nanowire having a core-shell structure. More particularly, the present invention relates to a metal shell having high electrical conductivity while preventing the core metal from being oxidized in the metal nanowire core by utilizing a phase transition phenomenon in which reactants are distributed to the organic phase and water phase, To a method of manufacturing a nanowire having a core-shell structure having transparency.

In general, a transparent conductive film is used as an essential component of electrical and electronic equipment such as a power source for a display device, an electromagnetic wave shielding film for an electric appliance, a transparent electrode for various display fields such as an LCD, an OLED, a FED, a PDP, a flexible display, Metal oxide conductive materials such as ITO (Indium-Tin oxide), ATO (Antimony-Tin Oxide) and AZO (Antimony-Zinc Oxide) are used as the transparent conductive film materials mainly used at present.

As a method for producing these transparent conductive film materials, a conductive metal such as silver, copper, nickel, indium or the like is formed on a transparent resin film film as a metal thin film by a sputtering method, an ion plating method, an ion beam assist method, a vacuum deposition method, Is generally used as a method for forming the gate insulating film. However, in these conventional methods, since the method becomes very complicated, there has been a problem of high cost and poor productivity.

On the other hand, in order to simultaneously improve the conductivity and transmittance required for the transparent conductive film material, the conductive metal is formed in the form of nanowire by reducing the size of the nanometer unit, thereby providing excellent conductivity and high transparency in electrode implementation.

However, when an electrode material is implemented by using copper (Cu) nanowire as the conductive metal nanowire, copper easily oxidizes upon contact with oxygen to form copper oxide, and the contact with oxygen is physically / chemically completely blocked The conductivity can not be ensured and it is not applicable as a transparent electrode.

There is, of course, a way to block the oxygen by clotting a generally known organic shell in the copper oxidation prevention method, but this organic material acts as a resistor and thus can not be applied to an electrode.

 On the other hand, when the silver (Ag) nanowire is applied to the conductive metal nanowire, it is disadvantageous in that it is impossible to control the thickness freely by the relatively high price and synthesis.

Therefore, development of an electrode material having an excellent conductivity and a high transmittance, which is still inexpensive in price, is desperately required.

Accordingly, the present inventors have found that by using a phase transition phenomenon in which reactants are distributed to an organic phase and a water phase, a metal nano wire, which is relatively inexpensive and vulnerable to oxidation, for example, copper nano wire is used as a core, In the case of manufacturing a nanowire having a core-shell structure in which a metal having conductivity is composed of a shell, a metal having conductivity, which is not an organic substance acting as a resistor, but a cost is inexpensive, Nanowires can be manufactured, and the present invention has been completed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a metal nanowire which is relatively inexpensive and vulnerable to oxidation using a phase transition phenomenon in which reactants are distributed to an organic phase and a water phase, And a method of manufacturing a nanowire having a core-shell structure in which a metal is constituted by a shell.

In order to solve the above problems,

Preparing a dispersion of metal nanowires in which metal nanowires are dispersed in a polar solvent;

Preparing a metal precursor solution by dissolving a metal precursor in a non-polar solvent; And

And mixing the metal nanowire dispersion and the metal precursor solution to form a nanowire having a core-shell structure.

In the method of manufacturing a nanowire having a core-shell structure according to the present invention, the polar solvent in which the metal nanowire is dispersed may include one or more selected from the group consisting of water, methanol, ethanol, isopropanol, DMSO, methylene chloride, Or more. The metal nanowire is preferably selected from the group consisting of copper, aluminum, zinc, and nickel.

In the method for producing a nanowire having a core-shell structure according to the present invention, the non-polar solvent in which the metal precursor is dissolved is preferably at least one selected from the group consisting of xylene, toluene, benzene and hexane.

The metal precursor preferably has the following structure:

Formula 1

Wherein M is selected from the group consisting of Ag, Au, Ni, Zn, In, and Pt, and n is an integer of 0 to 23.

The metal nanowire dispersion preferably contains a dispersant selected from the group consisting of aliphatic amine, carboxylic acid, thiol, PVP, and PAA.

An amine may be further added to the metal precursor solution, and the amine is preferably an alkylamine having a linear or branched structure.

The metal nanowires are preferably dispersed in an amount of 1 to 30 wt% based on the total weight of the metal nanowire dispersion, and the metal precursor is preferably dispersed in an amount of 1 to 10 wt% based on the total weight of the metal precursor solution Do.

The metal nanowire dispersion and the metal precursor solution are preferably mixed at a weight ratio of 10: 1 to 1: 1.

A method of manufacturing a nanowire having a core-shell structure according to the present invention is a method of manufacturing a nanowire having a core-shell structure by using a phase transition phenomenon in which a reactive material is distributed to an organic phase and a water phase, And nanowires having a core-shell structure according to reduction can be synthesized.

In addition, the method according to the present invention can also be used to produce nanowires of a core-shell structure having a non-polar surface due to a density difference but varying in thickness depending on the selective adsorption of relatively non-polar metal particles on the surface of the metal nanowires present in the aqueous phase Can be manufactured.

The core-shell nanowire obtained by the method according to the present invention has a metal nanowire core that prevents oxidation of the core metal and has a high conductivity and does not act as a resistor. At the same time, making it possible to manufacture nanowire electrodes having excellent electrical properties and high transmittance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart showing a manufacturing process of a nanowire having a core-shell structure according to the present invention. FIG.
FIG. 2 is a schematic diagram illustrating a method of manufacturing a nanowire having a copper-silver core-shell structure according to an embodiment of the present invention.
3 is a SEM photograph of a nanowire having a copper-silver core-shell structure fabricated according to an embodiment of the present invention.
4 is a SEM photograph of a copper nanowire for comparison with a nanowire of a copper-silver core-shell structure according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a flowchart illustrating a manufacturing process of a nanowire having a core-shell structure according to the present invention.

Referring to FIG. 1, a method for manufacturing a nanowire having a core-shell structure according to the present invention includes the steps of: preparing a dispersion of metal nanowires in which metal nanowires are dispersed in a polar solvent; Preparing a metal precursor solution by dissolving a metal precursor in a non-polar solvent (S12); And mixing the metal nanowire dispersion and the metal precursor solution (S13).

In the step (S11) of preparing a metal nanowire dispersion in which the metal nanowires are dispersed in the polar solvent, the metal nanowires can be used which are generally used in this field, and a metal which is vulnerable to oxidation may be more effective have. Specifically, it may be selected from copper, aluminum, zinc, nickel and the like, and is most preferably copper nanowire.

The metal nanowires having a diameter in the range of 5 to 200 nm and a length in the range of 5 to 200? May have excellent electrical properties and high transmittance in the electrode implementation.

As the polar solvent in which the metal nanowires are dispersed, a polar solvent common in the field may be used, and preferably at least one selected from the group consisting of water, methanol, ethanol, isopropanol, DMSO, methylene chloride, and THF .

In this case, it is preferable that the metal nanowires are dispersed in the range of 1 to 30 wt% based on the total weight of the metal nanowire dispersion. Depending on the concentration of the dispersion, the degree of shelling can be controlled and proper concentration is very important for proper shelling.

When the metal nanowires are dispersed in the polar solvent, a dispersant such as aliphatic amine, carboxylic acid, thiol, PVP or PAA may be included in the range of 0.001 to 10 wt% based on the total weight of the metal nanowire dispersion . The even dispersion of the nanowires plays an important role in applying a uniform shell over the surface of the nanowire.

In the step (S12) of preparing a metal precursor solution in which a metal precursor is dissolved in the nonpolar solvent, the metal precursor may be prepared from a fatty acid.

The synthesis of the metal precursor prepared from the fatty acid according to the present invention is as follows:

Scheme 1

Wherein M is selected from the group consisting of Ag, Au, Ni, Zn, In, and Pt, and n is an integer of 0 to 23.

Referring to Reaction Scheme 1, the synthesis of the metal precursor according to the present invention is a synthesis of a metal precursor by reacting a metal salt with a fatty acid in the presence of an organic solvent and a base.

Specifically, in the present invention, the metal precursor is formed by dissolving a fatty acid in an organic solvent and adding a base to produce a fatty acid solution; Adding a metal salt solution to the fatty acid solution and reacting the mixture; And forming a metal precursor precipitate from the mixed solution.

In the step of dissolving the fatty acid in an organic solvent to prepare a fatty acid solution, examples of the fatty acid include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, At least one member selected from the group consisting of eicosanoic acid, docosanoic acid, 2-ethylhexanoic acid, 2-methylhexanoic acid, 2-methylheptanoic acid, 2-ethylheptanoic acid, 2-ethylhexanoic acid, oleic acid, linoleic acid, linolenic acid, Fatty acids.

Examples of the solvent include H ₂ O, CH ₂ CN, CH ₃ OH, CH ₃ CH ₂ OH, THF, DMSO, DMF, 1-methoxy-2-propanol, 2,2- Methyl-2-pentanone, and dibutyl ether.

With the base is _{KOH, NaOH, NH 3, NH} 2 CH 3, NH 4 OH, NH (CH 3) 2, N (CH 3) 3, NH 2 Et, NH (Et) 2, NEt 3 , and Ca (OH ) ≪ ₂ >).

In the step of dropping and reacting the metal salt solution in the fatty acid solution, the metal salt is first dispersed in a solvent to prepare a metal salt solution.

Then, the metal salt solution is dropped into the fatty acid solution and reacted. In this case, it is preferable that stirring accompanies vigorous stirring at the same time.

As the metal, a metal generally used in this field can be used, and it is preferable to have a high conductivity while being able to prevent the oxidation of the metal nanowire, and specifically, a group of Ag, Au, Ni, Zn, In and Pt Among these metals, noble metals such as Ag and Au are preferably selected, and Ag is most preferable. The metal salt may be a nitride, an oxide, a sulfide, or a halide, and is preferably used in the form of a nitride.

The metal salt solution is preferably added dropwise to the fatty acid solution at a rate of 500 ml to 1000 ml per hour, and the fatty acid solution and the metal salt solution are mixed in a weight ratio of 1: 1 to 5: 1. The reaction is preferably carried out at room temperature.

In the step of forming the metal precursor precipitate from the mixed solution, the mixed solution, to which the metal salt solution has been added, is further stirred for 1 minute to 30 minutes to form a precipitate.

In the step of separating the precipitate, the method of separating the precipitate may be removed by a general method in the field, and a method such as filtration or recrystallization may be used.

Then, the separated precipitate is washed with a solvent several times and dried to obtain a final metal precursor having the following structure.

Formula 1

Wherein M is selected from the group consisting of Ag, Au, Ni, Zn, In, and Pt, and n is an integer of 0 to 23.

As the solvent in which the metal precursor is dissolved, a nonpolar solvent is preferable, and it is preferable that at least one solvent is selected from the group consisting of xylene, toluene, benzene and hexane.

In this case, the metal precursor is preferably dispersed in the range of 1 to 10% by weight based on the total weight of the metal precursor solution. If the concentration of the metal precursor solution is too low, the shell may be inadequate to be coated. In addition, when the concentration is too high, metal particles other than shells can be formed, making it impossible to form a core-shell structure.

In addition, the amine may be added to the metal precursor solution in an amount of 0.1 to 10 wt% based on the total weight of the metal precursor solution. The amine serves to promote dissociation of the metal precursor. Thus, it is possible to control the shell reaction rate and the shell thickness by controlling the amount of amine.

The amine ionizes a metal precursor, such as a silver precursor, in a non-polar solvent as shown in the following reaction formula (2).

Scheme 2

Wherein X is hydrogen, alkyl having 1 to 6 carbon atoms or halogen, and n is an integer of 0 to 23.

The amine may be an alkylamine having a straight chain or branched structure, and the size or structure of the alkylamine is not particularly limited, and it may be a primary to tertiary amine, a polyamine such as a monoamine, a diamine, do. For example, there can be mentioned amine compounds such as butylamine, hexylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadodecylamine, octadecylamine, cocoamine, tallowamine, hydrogenated tallowamine, oleylamine, Amines and stearylamines, secondary amines such as dicocoamine, dihydrogenated tallowamine and distearylamine, and secondary amines such as dodecyldimethylamine, didodecylmonomethylamine, tetradecyldimethylamine, Tertiary amines such as octadecyldimethylamine, cocodimethylamine, dodecyltetradecyldimethylamine, triethylamine and trioctylamine, and diamines such as naphthalene diamine, stearyl propylenediamine, octamethylenediamine and nonanediamine, . Of these amines, hexylamine, heptylamine, octylamine, decylamine, dodecylamine, 2-ethylhexylamine, 1,3-dimethyl-n-butylamine, 1-aminoundecane and 1- Do.

In the step (S13) of mixing the metal nanowire dispersion and the metal precursor solution, the copper nanowire dispersion may be added dropwise to the metal precursor solution or may be mixed simply by stirring.

In the mixing step (S13), the metal nanowire dispersion and the metal precursor solution are mixed at a ratio of 10: 1 to 1: 1 based on weight. The ratio of the metal precursor solution to the metal nanowire dispersion is very important in order to coat even shells and it is preferable to mix them in a ratio of 10: 1 to 1: 1 in order to apply a suitable shell.

The nanowires of the core-shell structure are synthesized by the distribution and reduction of the metal precursor according to the phase transition phenomenon in which the reaction material is distributed to the organic phase and the water phase according to the mixing of the metal nanowire dispersion and the metal precursor solution. In addition, as the reaction material is distributed and reduced, the rate of shelling reaction is controlled to obtain a uniform shell.

Here, the thickness of the shell in the nanowire of the core-shell structure is adjustable within the range of 5 to 50 nm. The thickness of the shell can be controlled according to the dispersion and dissolution state, solvent, concentration and mixing ratio of the metal nanowires and the metal precursor mentioned above.

FIG. 2 is a schematic diagram illustrating a manufacturing process of a nanowire having a copper-silver core-shell structure according to an embodiment of the present invention.

2, a dispersion in which copper nanowires 11 are dispersed in a polar solvent 10 is mixed with a silver precursor solution to which an amine obtained by dissolving a silver precursor 21 in a non-polar solvent 20 is added, The merchant forms a core-shell structure as the phase transition phenomenon occurs in which the reactants are distributed to the precursor solution and the aqueous copper nanowire dispersion. When metal copper is in contact with Ag + ions, a reaction occurs in which metal copper reduces Ag + ions by a standard reduction potential difference. However, such an oxidation-reduction reaction is very fast and leads to the formation of Ag particles rather than a shell on the copper surface, making it impossible to form a core-shell structure. However, since the Ag + ions 22 generated from the Ag precursor as in the present invention are distributed / reduced as the water phase due to the phase transition phenomenon, the Ag + ions in the copper nanowires existing in the water due to the difference in density have a nonpolar surface, The Ag nanoparticles thus obtained have a nonpolar surface and are thus selectively adsorbed on the surface of the copper nanowires to form nanowires 12 having a copper-silver core-shell structure ) Is obtained.

Scheme 3

Since the nanowire having the core-shell structure according to the present invention is composed of an anti-oxidized core metal and a metal shell having a high conductivity, it is possible to manufacture a nanowire electrode having excellent electrical properties and high transmittance.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited by the following examples.

Example 1

Synthesis of nanowires with Cu-Ag core-shell structure

In a 250 ml flask, 50 mg of copper nanowire having an average diameter of 80 nm and an average length of 80? Were dispersed in 100 ml of water as a polar solvent. Then, another 250 ml flask was charged with 20 mg of Ag orate dissolved in 50 ml of xylene, the non-polar solvent, and 1 mg of triethylamine was added. 50 ml of the copper nanowire dispersion was mixed with 10 ml of the Ag orolate solution, followed by shaking lightly. As the color of the copper nanowires changed from light red to gray over time, 20 mg of nanowires having a copper-silver core-shell structure were obtained.

Example 2

Synthesis of nanowires with Cu-Ag core-shell structure

In a 250 ml flask, 50 mg of copper nanowire having an average diameter of 80 nm and an average length of 80? Was dispersed in 100 ml of water as a polar solvent. Then, another 250 ml flask was charged with 20 mg of Ag orate dissolved in 50 ml of xylene, the non-polar solvent, and 5 mg of triethylamine was added. 50 ml of the copper nanowire dispersion was mixed with 10 ml of the Ag orolate solution, followed by shaking lightly. As the color of the copper nanowires changed from light red to gray over time, 20 mg of nanowires having a copper-silver core-shell structure were obtained.

Test Example 1

The copper-silver core-shell nanowires obtained in Example 1 were photographed by SEM and their structures were confirmed. Copper nanowires were photographed by SEM for comparison, and these photographs are shown in FIGS. 3 and 4, respectively. As can be seen from FIGS. 3 and 4, silver nanoparticles are attached to the surface of the copper nanowires to form a shell that completely encloses the copper nanowires and completely blocks exposure to the outside.

Test Example 2

The shell thicknesses of the nanowires having the copper-silver core-shell structure obtained in Examples 1 and 2 were measured through TEM, and the results are shown in Table 1 below.

 Shell Thickness (nm) Example 1 30 Example 2 50

From the above results, it was confirmed that the thickness of the shell of Example 2 in which the amount of triethylamine was increased was thick. It is believed that the shelling reaction progresses more rapidly as the amount of triethylamine increases and the shell thickness increases due to the increase in the size of the silver nanoparticles forming the shell.

Test Example 3

Copper nanowires for comparison with the copper-silver core-shell nanowires obtained in Example 1 were synthesized. Each of the obtained nanowires was spin-coated on a 2 cm x 2 cm glass substrate at 3000 rpm for 30 seconds, heated at 200 ° C for 10 minutes, dried and fired to form a transparent electrode. The sheet resistance and transmittance of each transparent electrode were measured by the following method, and the results are shown in Table 2 below.

Sheet resistance: BEGA (g) Measured using 4 point probe of RS8-1G model.

Transmittance: Average value measured by transmission through a wavelength of 400 to 800 nm using UV-spectroscopy of JASCO V-600 model was recorded.

division Sheet resistance Permeability Example 1 70Ω / □ 70% Example 2 60 Ω / □ 65% Copper nanowire 50,000 Ω / □ 30%

As can be seen from the above examples and test examples, it can be confirmed that the metal nanowire having a core-shell structure manufactured according to the method of the present invention is superior in terms of conductivity and transparency when a transparent electrode is realized. This indicates that the metal nanowires having a core-shell structure manufactured by the method according to the present invention can be applied as a transparent electrode material.

10: polar solvent
11: Copper nanowire
12: Copper-silver core-shell nanowire
20: Nonpolar solvent
21: Ag precursor
22: Ag + ion

Claims (11)

Preparing a dispersion of metal nanowires in which metal nanowires are dispersed in a polar solvent;
Preparing a precursor solution by dissolving a metal precursor in an organic phase non-polar solvent; And
And mixing the metal nanowire dispersion and the metal precursor solution to form a nanowire having a core-shell structure,
Phase transition occurs in the mixing step,
Wherein the metal precursor has a structure of the following formula 1:
Formula 1

Wherein M is selected from the group consisting of Ag, Au, Ni, Zn, In, and Pt, and n is an integer of 0 to 23), wherein X is hydrogen, an alkyl group having 1 to 6 carbon atoms, .
The method according to claim 1,
Wherein the polar solvent is at least one selected from the group consisting of water, methanol, ethanol, isopropanol, DMSO, methylene chloride, and THF.
The method according to claim 1,
Wherein the metal nanowire is at least one selected from the group consisting of copper, aluminum, zinc, and nickel.
The method according to claim 1,
Wherein the organic phase non-polar solvent is at least one selected from the group consisting of xylene, toluene, benzene and hexane.
delete The method according to claim 1,
Wherein the metal nanowire dispersion comprises a dispersant selected from the group consisting of aliphatic amines, carboxylic acids, thiols, PVP, and PAA.
The method according to claim 1,
Wherein an amine is further added to the metal precursor solution.
8. The method of claim 7, wherein the amine is a linear or branched alkylamine.
The method according to claim 1,
Wherein the metal nanowires are dispersed in an amount of 1 to 30 wt% based on the total weight of the metal nanowire dispersion.
The method according to claim 1,
Wherein the metal precursor is dissolved in an amount of 1 to 10 wt% based on the total weight of the metal precursor solution.
The method according to claim 1,
Wherein the metal nanowire dispersion and the metal precursor solution are mixed at a ratio of 10: 1 to 1: 1 on a weight basis.

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