KR101327074B1 - Nanowire and method for manufacturing the same - Google Patents

Abstract

Nanowires and methods of making the same are disclosed. In the method of manufacturing a nanowire, a metal compound, a metal halogen catalyst, and a capping agent are added to a first solvent having a first reducing force and a second solvent having a second reducing force greater than the second reducing force to form a metal nanowire. Wherein the capping agent comprises a first capping agent comprising a polymer of a first molecular weight; And a second capping agent comprising a polymer of a second molecular weight greater than the first molecular weight.

Description

NANOWIRE AND METHOD FOR MANUFACTURING THE SAME

Embodiments relate to nanowires and methods for their preparation.

Background Art A transparent electrode using a transparent conductive material has been applied to various electronic products such as display devices, solar cells, and mobile devices. As a transparent conductive material for forming such a transparent electrode, research on nanowires, which are wire-shaped structures having a size of nanometer level, is being actively conducted.

Such nanowires may have excellent electrical conductivity, flexibility, and transmittance such that the transparent electrode may have excellent characteristics. However, the nanowires are easily aggregated in the reaction process to form nanoparticles, thereby decreasing the yield of the nanowires. In addition, when the length of the nanowires are made longer, the diameter becomes thicker, and when the diameter is thin, the length tends to be shorter, which makes it difficult to manufacture long and thin nanowires. Accordingly, there is a difficulty in practical use. In addition, a substance such as a catalyst used to promote the nanowire formation reaction remains on the surface of the nanowires, causing surface oxidation or corrosion, or lowering electrical conductivity.

The example is to provide a nanowire having a small diameter and a long length, and an improved aspect ratio and a method of manufacturing the same.

In the method of manufacturing a nanowire according to an embodiment, a metal compound, a metal halogen catalyst, and a capping agent are added to a first solvent having a first reducing power and a second solvent having a second reducing power greater than the first reducing power, and then heated to a metal. Forming nanowires.

In this case, the capping agent comprises a first capping agent comprising a polymer of the first molecular weight; And a second capping agent comprising a polymer having a second molecular weight different from the first molecular weight.

In one embodiment, the first solvent and the second solvent may be glycol.

In one embodiment, the first solvent may be ethylene glycol, and the second solvent may be propylene glycol.

In one embodiment, the volume ratio of the first solvent and the second solvent may be 1: 1 to 1: 4.

In one embodiment, the metal compound may be a silver compound.

In one embodiment, the polymer of the first molecular weight and the polymer of the second molecular weight may be polyvinylpyrrolidone.

In one embodiment, the first molecular weight is 40000 to 80000, the second molecular weight may be 240000 to 450000.

In one embodiment, the ratio of the polymer of the first molecular weight and the polymer of the second molecular weight may be 2: 1 to 8: 1.

By the nanowire manufacturing method according to the embodiment, the diameter is 30nm to 55nm, the length is 20㎛ to 60㎛, the aspect ratio is 363 to 2000, a nanowire comprising a metal can be provided. In this case, the metal may be silver (Ag).

In the nanowire manufacturing method according to the embodiment, the metal compound is reduced and metal nanowires are formed by using solvents having different reducing powers.

In particular, the second solvent having a relatively high reducing power may increase the length of the metal nanowires, and the first solvent having a relatively low reducing power may thinly form the metal nanowires.

That is, the metal nanowires may be formed to be thin and long by the first solvent and the second solvent. Accordingly, the nanowire manufacturing method according to the embodiment can provide a metal nanowire having a large aspect ratio.

In addition, the nanowire manufacturing method according to the embodiment uses a first capping agent including a polymer having a first molecular weight and a second capping agent including a polymer having a second molecular weight.

In this case, the length of the metal nanowires is increased by the second capping agent having a relatively large molecular weight, and the diameter of the metal nanowires may be thinned by the first capping agent having a relatively small molecular weight.

That is, the metal nanowires may be formed to be thin and long by the first capping agent and the second capping agent. Accordingly, the nanowire manufacturing method according to the embodiment can provide a metal nanowire having a large aspect ratio.

1 is a block diagram illustrating a process of manufacturing a silver nanowire according to an embodiment.
2 is a SEM photograph of the silver nanowires according to the embodiment.
Figure 3 is a SEM photograph of the silver nanowires according to Comparative Example 1.
Figure 4 is a SEM photograph of the silver nanowires according to Comparative Example 2.

In the method of manufacturing a nanowire according to an embodiment, a metal compound, a metal halogen catalyst, and a capping agent are added to a first solvent having a first reducing power and a second solvent having a second reducing power greater than the first reducing power, and then heated to a metal. It may include forming a nano wire.

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In this case, the capping agent comprises a first capping agent comprising a polymer of the first molecular weight; And a second capping agent including a polymer having a second molecular weight different from the first molecular weight.

The first solvent and the second solvent may be glycol.

The first solvent may be ethylene glycol, and the second solvent may be propylene glycol.

The volume ratio of the first solvent and the second solvent may be 1: 1 to 1: 4.

The metal compound may be a silver compound.

The polymer of the first molecular weight and the polymer of the second molecular weight may be polyvinylpyrrolidone.

The first molecular weight may be 40000 to 80000, and the second molecular weight may be 240000 to 450000.

The ratio of the polymer of the first molecular weight and the polymer of the second molecular weight may be 2: 1 to 8: 1.

By the nanowire manufacturing method according to the embodiment, the diameter is 30nm to 55nm, the length is 20㎛ to 60㎛, the aspect ratio is 363 to 2000, a nanowire comprising a metal can be provided. In this case, the metal may be silver (Ag).

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

1 is a block diagram illustrating a process of manufacturing a silver nanowire according to an embodiment. 2 is a SEM photograph of the silver nanowires according to the embodiment. Figure 3 is a SEM photograph of the silver nanowires according to Comparative Example 1. Figure 4 is a SEM photograph of the silver nanowires according to Comparative Example 2.

Referring to Figure 1, the nanowire manufacturing method according to the embodiment, heating the solvent (ST10), adding a capping agent to the solvent (ST20), adding a catalyst to the solvent (ST30), to the solvent The method may include adding a metal compound (ST40), adding a solvent at room temperature to the solvent (ST50), and purifying the nanowires (ST60). Not all of these steps are necessary and depending on the manufacturing method, some steps may not be performed and the order of each step may be changed. Each step described above will be described in more detail as follows.

In the step of heating the solvent (ST10), the solvent is heated to a reaction temperature suitable for the formation of the metal nanowires.

A polyol may be used as the solvent. Such polyols act as a mile reducing agent together with the role of a solvent for mixing different materials. Accordingly, the solvent may reduce the metal compound to form metal nanowires.

The solvent may be a mixture of at least two kinds of materials. For example, the solvent may include a first solvent and a second solvent. More specifically, the solvent may include a mixture of the first solvent and the second solvent.

The first solvent has a relatively low first reducing power. More specifically, the first solvent has a lower reducing power than the second solvent. Ethylene glycol etc. are mentioned as an example of the said 1st solvent.

The second solvent has a relatively high second reducing power. In more detail, the second solvent has a higher reducing power than the first solvent. In other words, the second reducing force is greater than the first reducing force. Here, the second reducing power is relatively higher than that of the first reducing power, and the first reducing power and the second reducing power may be low overall.

Examples of the second solvent include propylene glycol and the like. In addition, diethylene glycol, dipropylene glycol, 1,3-propanediol, glycerin, glycerol or glucose may be used as the first solvent and the second solvent.

The ratio of the first solvent and the second solvent may vary in various ways depending on the reaction temperature and the kind and properties of the metal compound. The volume ratio of the first solvent and the second solvent may be about 1: 1 to about 1: 4. For example, to form silver nanowires, when a mixture of ethylene glycol and propylene glycol is used as the solvent, the volume ratio of ethylene glycol and propylene glycol is from about 1: 1 to about 1: 4. Can be. More specifically, in the total mixed solvent, the proportion of ethylene glycol may be about 20 vol% to about 50 vol%, and the proportion of propylene glycol may be about 50 vol% to about 80 vol%.

The reaction temperature may be adjusted in various ways in consideration of the type and characteristics of the solvent and the metal compound. In particular, the reaction temperature may vary depending on the solvent used. For example, when the solvent comprises a mixture of ethylene glycol and propylene glycol, the reaction temperature may be about 110 ° C to about 160 ° C.

Next, in the step of adding a capping agent to the solvent (ST20), a capping agent for inducing wire formation is added to the solvent. If the reduction for forming the nanowire is made too fast, it is difficult to form a wire shape as the metals aggregate, such a capping agent serves to prevent the aggregation by properly dispersing the material in the solvent.

The capping agent may include a first capping agent and a second capping agent.

The first capping agent comprises a polymer of a first molecular weight. The second capping agent also includes a polymer of a second molecular weight that is greater than the first molecular weight. That is, the molecular weight of the first capping agent is smaller than the molecular weight of the second capping agent.

The same polymer may be used as the first capping agent and the second capping agent. Alternatively, different polymers may be used as the first capping agent and the second capping agent.

Examples of the polymer used as the first capping agent and the second capping agent may include polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylamide (PAA), and the like.

The first molecular weight polymer may have a weight average molecular weight of about 40000 to about 80000. The second molecular weight polymer may have a weight average molecular weight of about 240000 to about 450000.

In particular, the polymer of the first molecular weight and the polymer of the second molecular weight may be polyvinylpyrrolidone. More specifically, the first capping agent may be polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000, and the second capping agent may be polyvinylpyrrolidone having a weight average molecular weight of about 240000 to about 450000 have.

The mass ratio of the first capping agent and the second capping agent may be about 2: 1 to about 8: 1. In more detail, in the capping agent, the first capping agent may be about 70 wt% to about 90 wt%, and the second capping agent may be about 10 wt% to about 30 wt%.

In particular, the capping agent comprises polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000 and polyvinylpyrrolidone having a weight average molecular weight of about 240000 to about 450000 of about 2: 1 to about 8: 1. It can be included as a ratio. More specifically, in the capping agent, polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000 is about 70wt% to about 90wt%, polyvinylpyrrolidone having a weight average molecular weight of about 240000 to about 45000 May be from about 10 wt% to about 30 wt%.

The first capping agent comprises a polymer having a relatively small first molecular weight. Accordingly, metal nanowires having a thin diameter may be formed by the first capping agent. The second capping agent also includes a polymer having a relatively large second molecular weight. Accordingly, metal nanowires having a long length may be formed by the second capping agent. That is, the elongated metal nanowires may be formed by the first capping agent and the second capping agent.

For example, the polymer having the first molecular weight and the polymer having the second molecular weight may have a helical structure. In this case, the polymer having the second molecular weight may be extended in a spiral structure of a large diameter. In addition, the polymer having the first molecular weight may be shortly extended into a spiral structure of a small diameter. In this case, several molecules of the polymer having the first molecular weight may be disposed in one molecule of the polymer having the second molecular weight, thereby forming a complex. Such a composite has a small inner diameter and may have a long length. Elongated metal nanowires may be formed in such a composite.

Subsequently, in the step of adding the catalyst to the solvent (ST30), sun salt, purified salt or a halogen metal such as AgCl, PtCl ₂ , PdCl ₂ , AuCl ₃ is added as a catalyst. Such a catalyst has various metals or halogen elements to serve to promote reaction of seed formation and metal nanowire formation for forming metal nanowires.

Subsequently, in the step (ST40) of adding the metal compound to the solvent, the metal compound is added to the solvent to form a reaction solution.

In this case, the metal compound may be added to a solvent to which a capping agent and a catalyst are added while dissolved in a separate solvent. As a separate solvent, the same material or different materials as the solvent used for the first time may be used. And, the metal compound may be added after a certain time after the addition of the catalyst. This is to stabilize the temperature to an appropriate reaction temperature.

Here, the metal compound is a compound containing a metal for forming the metal nanowires to be manufactured. In order to form silver nanowires, AgCl, AgNO ₃ or KAg (CN) ₂ may be used as the metal compound.

 As such, when the metal compound is added to the solvent to which the capping agent and the catalyst are added, the reaction occurs and the formation of the metal nanowires begins.

In the present embodiment, the capping agent may be added by 60 to 500 parts by weight based on 100 parts by weight of a metal compound such as AgCl, AgNO ₃ or KAg (CN) ₂ . When the capping agent is added in less than 60 parts by weight, the agglomeration phenomenon cannot be prevented sufficiently. In addition, when the capping agent is added in excess of 500 parts by weight, metal nanoparticles such as spherical and cubic shapes may be formed, and the capping agent may remain on the manufactured metal nanowires to reduce electrical conductivity.

And the catalyst may be added by 0.005 to 30 parts by weight based on 100 parts by weight of the metal compound. If the catalyst is added at less than 0.005 parts by weight, the reaction cannot be sufficiently promoted. When the catalyst is added in excess of 30 parts by weight, the reduction of silver proceeds rapidly to generate silver nanoparticles, or to increase the diameter of the nanowire and to shorten the length thereof. It may lower the conductivity.

Subsequently, in the step of further adding a solvent at room temperature to the reaction solution (ST50), a solvent at room temperature is further added to the solvent at which the reaction is started. The solvent at room temperature may use the same material or different materials as the solvent used for the first time. For example, polyols such as ethylene glycol and propylene glycol may be used as the solvent at room temperature.

The temperature of the solvent may be increased during the reaction by continuously heating the solvent to maintain a constant reaction temperature. As described above, by adding a solvent at room temperature to the solvent at which the reaction is started, the temperature of the solvent is temporarily lowered. The temperature can be kept more constant.

Further adding the solvent at room temperature (ST50) may be performed once or several times in consideration of the reaction time, the temperature of the reaction solution.

Subsequently, the step of purifying the nanowires (ST60) is to collect and collect the metal nanowires in the reaction solution.

More specifically, when acetone, which is a nonpolar solvent than water, is added to the reaction solution, the metal nanowires are precipitated under the solution by the capping agent remaining on the surface of the metal nanowires. This is because the capping agent dissolves well in the solvent but does not dissolve in acetone, but aggregates and precipitates. Subsequently, the supernatant solution is discarded to remove some of the capping agent and the formed nanoparticles.

When the distilled water is added to the remaining solution, the metal nanowires and the metal nanoparticles are dispersed, and when acetone or the like is added, the metal nanowires are precipitated and the metal nanoparticles are dispersed in the upper solution. Subsequently, the supernatant solution is discarded to remove some of the capping agent and the metal nanoparticles formed by aggregation. This process is repeated to collect the metal nanowires and store them in distilled water. By storing the metal nanowires in distilled water, it is possible to prevent the metal nanowires from reaggregating.

As described above, in the method of manufacturing nanowires according to the embodiment, a metal compound is reduced by using a first solvent having a different reducing power and the second solvent to form a metal nanowire.

In particular, the second solvent having a relatively high reducing power may increase the length of the metal nanowires, and the first solvent having a relatively low reducing power may thinly form the metal nanowires. That is, the metal nanowires may be formed to be thin and long by the first solvent and the second solvent. Accordingly, the nanowire manufacturing method according to the embodiment can provide a metal nanowire having a large aspect ratio.

In addition, the nanowire manufacturing method according to the embodiment uses a first capping agent comprising a polymer having the first molecular weight and a second capping agent comprising a polymer having the second molecular weight.

At this time, the length of the metal nanowires is increased by the second capping agent having a relatively large molecular weight, and at the same time, the diameter of the metal nanowires may be thinned by the first capping agent having a relatively small molecular weight. have.

That is, the metal nanowires may be formed to be thin and long by the first capping agent and the second capping agent. Accordingly, the nanowire manufacturing method according to the embodiment can provide a metal nanowire having a large aspect ratio.

For example, the metal nanowires formed according to the embodiment may have a diameter of about 55 nm or less and a length of about 30 μm or more. In more detail, the metal nanowires formed according to the embodiment may have a diameter of about 30 nm to about 55 nm, and may have a length of about 20 μm to about 60 μm.

Accordingly, the metal nanowires formed according to the embodiment may have an aspect ratio of about 363 or more. In more detail, the metal nanowires formed in accordance with an embodiment may have an aspect ratio of about 363 to about 2000.

Therefore, the metal nanowires formed according to the present embodiment may have high optical and electrical properties when used in electrodes or the like. That is, the metal nanowire itself according to the present embodiment may be configured as an electrode in a network structure. At this time, since the metal nanowires according to the present embodiment are thin and long, the transmittance and transparency can be increased, and the resistance can be reduced.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the examples are only for illustrating the present invention, and the present invention is not limited thereto.

Example

Ethylene glycol and propylene glycol were mixed at a ratio of about 1: 2 to form about 2000 ml of solvent. The solvent is heated to about 130 ° C., dissolved by adding 57 g polyvinylpyrrolidone (molecular weight 40000-80000) and 10 g polyvinylpyrrolidone (molecular weight 240000-450000), followed by 0.75 g KBr and 2.25 g AgCl Was added. After about 1 hour and 30 minutes, about 22 g of AgNO ₃ is dissolved in 1000 ml of a mixture of ethylene glycol and propylene glycol (a ratio of about 1: 2) and mixed into a polyvinylpyrrolidone, KBr, and a mixed solution of a solvent. Added. After that, the reaction was continued for about 1 hour and 30 minutes to complete formation of the silver nanowires.

12000 ml of acetone was added to the reaction solution, and the upper solution containing ethylene glycol, propylene glycol, and silver nanoparticles was discarded.

1000 ml of distilled water was added to disperse the agglomerated silver nanowires and silver nanoparticles. Then, 4000 ml of acetone was added, and then the upper layer solution in which ethylene glycol and propylene glycol and silver nanoparticles were dispersed was discarded. This process was repeated three times and stored in 1000 ml of distilled water.

Comparative Example  One

Molecular weight using 67.0 g of polyvinylpyrrolidone (molecular weight 44000-58000) as the point and capping agent without using propylene glycol as a solvent (including additionally added solution) and ethylene glycol alone It proceeded under the same conditions as the experimental example except that no polyvinylpyrrolidone of 280000-360000 was used.

Comparative Example  2

It proceeded under the same conditions as in Comparative Example 1, except that only 2000 ml of propylene glycol was used without using ethylene glycol as a solvent.

result

As shown in Table 1 below and FIGS. 2 to 4, in the case of Comparative Example 1, the length was shorter than that of the Experimental Example, and in the case of Comparative Example 2, it was derived to have a thicker diameter than the Experimental Example. That is, in the experimental example, the elongate silver nanowire was formed.

Length diameter Experimental Example 35 탆 50 nm Comparative Example 1 15 탆 50 nm Comparative Example 2 30 μm 80 nm

Features, structures, effects, and the like described in the above description are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (14)

Adding a metal compound, a metal halide catalyst and a capping agent to a first solvent having a first reducing power and a second solvent having a second reducing power greater than the first reducing power and heating to form a metal nanowire,
The capping agent
A first capping agent comprising a polymer of a first molecular weight; And
A second capping agent comprising a polymer of a second molecular weight,
The first molecular weight is 40000 to 80000, and the second molecular weight is 240000 to 450000 nanowire manufacturing method. The method of claim 1, wherein the first solvent and the second solvent are glycol. The method of claim 2, wherein the first solvent is ethylene glycol and the second solvent is propylene glycol. The method of claim 3, wherein the volume ratio of the first solvent and the second solvent is 1: 1 to 1: 4. The method of claim 1, wherein the metal compound is a silver compound.   The method of claim 1, wherein the metal halide catalyst is AgCl or KBr. The method of claim 1, wherein the polymer of the first molecular weight and the polymer of the second molecular weight are polyvinylpyrrolidone. delete The method of claim 1, wherein the ratio of the polymer of the first molecular weight and the polymer of the second molecular weight is 2: 1 to 8: 1. The method of claim 1, wherein the metal nanowires have a diameter of 30 nm to 55 nm and the metal nano wires have a length of 20 μm to 60 μm. delete delete delete delete

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