KR101163854B1 - Method for manufacturing metal nanotube and metal nanotube manufactured by the same - Google Patents

Abstract

Provided are a metal nanotube manufacturing method and a metal nanotube produced thereby.
Metal nanotube manufacturing method according to the present invention comprises the steps of growing a nanowire template on a substrate; Immersing the nanowire template grown on the substrate in a metal solution; Reducing metal ions of the metal solution to precipitate metal on the nanowire template; And dissolving the nanowire template by the solution pH reduced with the metal ion reduction, and removing the nanowire template with the growth of the nanotubes in the same process without the separate mold removal process. As such, economical metal nanotube production is possible. In addition, it is possible to produce nanotubes at a lower temperature than the prior art, and to enable the production of nanotubes of uniform shape and length.

Description

Method for manufacturing metal nanotube and metal nanotube manufactured by the same

The present invention relates to a method for producing a metal nanotube and a metal nanotube produced thereby, more specifically to remove the nanowire template with the growth of the nanotube without a separate mold removal process in the same process in the same vessel The present invention relates to a metal nanotube manufacturing method and a metal nanotube manufactured thereby, which enables economical metal nanotube production.

Metal nanotubes or nanostructures comprising them not only have a large specific surface area due to their nano size, but also in many fields such as solar cell or fuel cell field or storage medium field due to the increase of electron transport ability due to the tube shape. It is expected to be utilized.

In general, nanoparticles are prepared by a method of preparing nanoparticles from precursors, such as liquid phase synthesis or gas phase synthesis. The liquid phase synthesis may include a sol-gel method, and the vapor phase synthesis method may include spray pyrolysis and spray drying. Can be mentioned.

Through the above process, it is possible to obtain a nanoparticle of a fine size, in the case of a nanotube or a nanostructure comprising the same it is difficult to manufacture in a conventional method due to the specificity of the shape. That is, since a reaction in which particles are formed from a precursor is generally a reaction in which another phase is generated in one phase, the reaction proceeds in a direction in which the interfacial area is minimized to minimize the interfacial energy. As a result, the particles produced by the nanoparticle manufacturing method usually have a spherical shape, and it is common to obtain a structure in which these spherical particles are sintered in the form of grape clusters.

Thus, there was a need to rely on more specific methods to produce metal oxide nanotubes. Korean Patent Publication No. 10-2007-0045917, which is a patent document, discloses a method for producing manganese oxide nanotubes or nanorods using an anodized aluminum oxide template (hereinafter, a template). After adsorbing a manganese oxide precursor on a surface, the adsorbed manganese oxide precursor is oxidized, and then the template is removed, and a process for producing manganese oxide nanotubes is carried out through filtration, drying and sewage. The method summarizes the process of using a mold to form a nanomaterial in the form of a tube, forming a metal oxide tube on the outer surface of the mold, and then removing the mold again.

As described above, all of the prior art for producing nanostructures having a specific shape other than spherical shape, for example, a tube shape, have a problem that a process for manufacturing a mold is complicated and uneconomical. Furthermore, in order to recover and assemble the nanotubes grown on the surface of the mold, the mold must be removed in a separate process. According to the separate removal process of the mold, the manufacturing cost of the nanotube increases and the reliability of the process is also inferior. .

However, when the mold is not used, there is a problem that it is difficult to reliably manufacture a nanostructure having a certain shape.

Therefore, at the same time as the efficiency of the mold manufacturing / removal, nanostructure manufacturing method that can reliably manufacture the shape, such as nanotubes has not been disclosed yet.

Accordingly, the problem to be solved by the present invention is to provide a method for producing metal nanotubes, which can produce a metal nanotube of a uniform shape in a simple, economical process.

Another problem to be solved by the present invention is to provide a metal nanotube manufactured economically in a certain shape.

In order to solve the above problems, the present invention comprises the steps of growing a nanowire template on the substrate; Immersing the nanowire template grown on the substrate in a metal solution; Reducing metal ions of the metal solution to precipitate metal on the nanowire template; And dissolving the nanowire template by a solution pH which decreases with the reduction of the metal ion.

In one embodiment of the present invention, the nanowire template is a metal oxide, and the nanowire template has increased solubility in the solution as the pH of the immersed solution is decreased. The nanowires may be ZnO nanowires.

In the method of manufacturing metal nanotubes according to the present invention, after the nanowire template growth step, an amine compound may be present on the surface of the nanowire, and the nanowire template is a metal precursor solution in a direction in which the nanowires on the substrate face downward. Can be immersed in.

The present invention to solve the above problems, the step of growing a ZnO nanowire template on a substrate by hydrothermal synthesis in a solution containing a zinc salt and an amine compound; Immersing the mold in a metal solution; Reducing the metal ions of the metal solution on the surface of the ZnO nanowire mold to precipitate; Dissolving and removing the ZnO nanowire template by the pH of the solution which decreases with the reduction of the metal ions; And collecting metal nanotubes deposited on the surface of the ZnO nanowire template.

The ZnO nanowire template growth, the step of immersing the substrate in an aqueous solution containing the zinc salt and the amine compound; And heating the solution, wherein the amine-based compound is bonded to the grown ZnO nanowire surface.

The amine-based compound acts as a reducing agent of the metal ions, and the ZnO nanowire template is more dissolved in the metal precursor solution as the pH is lowered. In addition, the precipitation of the metal and the removal of the ZnO nanowire template are performed in the same vessel.

The present invention provides a metal nanotube produced by the above method, in order to solve the above problems.

Metal nanotube manufacturing method according to the present invention can be carried out in the same container, the same process with the growth of nanotubes and the growth of nanotubes without a separate mold removal process, it is possible to manufacture economical metal nanotubes. In addition, it is possible to manufacture metal nanotubes of uniform shape and length compared to the prior art.

1 is a step diagram of a metal nanotube manufacturing method according to an embodiment of the present invention.
2 is an SEM image of ZnO nanowires grown on a silicon substrate in one embodiment of the present invention.
3 is a graph showing the increase in acidity (pH decrease) and the remaining ZnO content in the metal precursor solution over time.
4 is an SEM image of platinum nanotubes, FIGS. 5A to 5B are TEM images, and FIG. 6 is an EDS analysis result.
FIG. 7 is an SEM image of palladium nanotubes, and FIGS. 8A and 8B are TEM images.
9A and 9B are graphs of cross-sectional compositional components and HAADF-STEM-EDS mapping of palladium nanotubes, respectively.

Hereinafter, the present invention will be described in detail with reference to the drawings. The following embodiments are provided as examples to sufficiently convey the spirit of the present invention to those skilled in the art. Therefore, the present invention is not limited to the embodiments described below and may be embodied in other forms. In the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

1 is a step diagram of a metal nanotube manufacturing method according to an embodiment of the present invention.

Referring to FIG. 1, first, a nanowire used as a template in a substrate is manufactured and grown (S100). In one embodiment of the present invention, the nanowires are ZnO nanowires, which are metal oxides, synthesized and prepared by hydrothermal synthesis. The scope of the present invention is not limited to the above methods and materials, but should be at least grown and prepareable on a substrate, and should have the property of increasing solubility in the solution as the acidity of the solution increases.

The nanowires grown on the substrate are a template of a metal tube to be obtained in the present invention, and are grown on the substrate and then immersed in the metal precursor solution (S200). On the surface of the immersed nanowires, metal ions of the metal precursor solution are reduced to precipitate metals, and as a result, metal nanotubes having nanowires inserted therein are manufactured (S300). In one embodiment of the present invention, the metal material of the nanotubes was platinum and palladium, but any reducing metals fall within the scope of the present invention, and the scope of the present invention is not limited by the present embodiment.

The present inventors paid particular attention to the property that the acidity of the solution is increased with the reduction of metal ions, and using the nanowire template whose solubility in the solution increases as the acidity is increased, the nanowire template is removed without a separate mold removal process. Removed by increasing the acidity, thereby producing a metal nanotube (S400).

Hereinafter, the present invention will be described in detail through Examples and Experimental Examples.

Example  One

Nanowire  Manufacture of molds

Prior to fabricating metal nanotubes, ZnO nanowires used as templates for nanotubes were prepared on silicon substrates using a seeding process and hydrothermal synthesis.

First, the silicon substrate was immersed in a washing solvent (acetone / isopropanol / ethanol / deionized water), sonicated for 10 minutes in order and dried with nitrogen gas.

Next, as a seed for seed growth of ZnO nanowires, the ZnO nanoparticle solution dispersed in ethanol at a concentration of 30-50 nM is dropped on the substrate, and then evenly coated with 1 to 2 drops of the substrate. Dried. After repeating the above process 5-6, ZnO nanoparticles are evenly spread on the substrate, and the substrate was heated to a temperature of 100 ~ 150 ℃ to ensure that the seed ZnO nanoparticles are well attached to the substrate. Subsequently, Zn (NO ₃ ) _{2 to} 6H ₂ O, a metal salt, HMTA (hexamethyltetramine) and PEI (polyethyleneimine) are used to grow and manufacture ZnO nanowires on a substrate to which seed ZnO nanoparticles are attached. It was immersed in this precursor solution, heated at 95 ° C. for 2.5 hours, washed with deionized water and dried. In the seed coated substrate, ZnO nanowires grow by hydrothermal reaction. In particular, in the present invention, the amine compound which is initially bonded with zinc in the hydrothermal reaction is also used as a reducing agent for metal ion reduction, which will be described in more detail below.

2 is an SEM image of ZnO nanowires grown on a silicon substrate in one embodiment of the present invention.

Referring to FIG. 2, it can be seen that ZnO nanowires having a rod or wire shape are effectively grown on a silicon substrate.

Example  2

metal NANUTU  Produce

Platinum (Pt) and palladium (Pd) nanotubes were prepared in this example using ZnO nanowires prepared in Example 1 as templates. To this end, the silicon substrate of Example 1 is first inserted into a holder made of Teflon, fixed, immersed in a metal precursor solution, and then reacted at 90 ° C. for 1 hour. At this time, the size of the substrate is cut to 0.5cm in width, 1cm in length, but the scope of the present invention is not limited to the above numerical value. In this embodiment, the silicon substrate is immersed upside down so that the nanowires grown on the substrate face downward, in order to prevent the metal (platinum / palladim) nanoparticles produced by the reduction reaction from being deposited on the substrate.

In the present embodiment, the metal precursor solution is mixed with potassium tetrachloro platinate / palladate (K ₂ PtCl ₄ / K ₂ PdCl ₄ ) in distilled water and sonicated to form a 5 mM solution, and then capping reagent is added to the solution. Was prepared by adding 30 mM sodium citrate solution.

On the surface of the ZnO nanowires immersed in the metal precursor solution, metals are precipitated according to the reaction, and as a result, metal nanotubes having ZnO nanowires inserted therein are produced. In the present invention, the metal nanotubes are produced in a nanowire template. The principle is as follows.

First, amine-based compounds such as HMTA and PEI, which are used in the production of ZnO nanowires, which are templates, are bound and present on the surface of the template. The amine-based compound on the surface acts as a metal reducing agent in the immersed metal precursor solution, and as a result, platinum / palladium metal ions are reduced on the surface of the nanowires and precipitated in metal form on the surface of the nanowires. That is, the reduction of metal ions in the metal precursor solution proceeds on the surface of the nanowire template, resulting in a metal tube centered on the nanowire.

Example  3

Nanowire  Mold removal

In Example 2, the metal ions are reduced, thereby depositing the metal on the nanowire surface. According to the metal ion reduction, the acidity of the solution in which the nanowire template is immersed also increases. In this example, the pH before the reaction was 6.8, but the pH was lowered to 3.0 after the reaction of Example 2. In this case, the solubility of the ZnO nanowires used as a template increases in the acidity of the solution (which corresponds to the lower pH), especially in the polar plane inside the nanowire than in the nonpolar nonplane plane. This rapid etching rate is shown.

3 is a graph showing the increase in acidity and the remaining ZnO content in the metal precursor solution over time.

Referring to FIG. 3, it can be seen that the pH of the ZnO nanowires of Example 1 was immersed in the metal precursor solution and the pH continuously decreased over time. In addition, referring to Figure 3, it can be seen that the amount of ZnO nanowires grown on the substrate also decreases with increasing acidity. Analyzing the results, the ZnO nanowires are dissolved in a solution with increasing acidity, and the dissolution causes the nanowire template to melt away, resulting in the removal of the nanowires in the center, thereby producing a metal tube. have. The present invention enables the manufacture of the metal tube of Example 2 and the removal of the mold of Example 3 to be carried out simultaneously in the same apparatus, in particular without using a separate device or process for removing the mold. As a result, unlike the prior art of removing molds in a separate process, the present invention is economical because the metal nanotube manufacturing and mold removal proceed in the same environment.

Experimental Example  One

Platinum Nanotube Test Results

SEM, TEM, and EDS analysis were performed to analyze the shape and composition of the platinum nanotubes prepared in Examples 1 to 3.

4 is an SEM image of platinum nanotubes, FIGS. 5A to 5B are TEM images, and FIG. 6 is an EDS analysis result.

Looking at the analysis results, it can be seen that the platinum nanotubes effectively formed inside the hollow according to the present invention (see FIG. 4).

In addition, from the SEM and TEM images, it could be confirmed that platinum nanotubes having a diameter of about 50 to 60 nm and a thickness of 10 nm were prepared according to the present invention, and the platinum nanoparticles were agglomerated and attached to the tube surface. This phenomenon is believed to be due to the addition of sodium citrate, the corresponding level of capping reagent, when a high concentration of platinum is added.

Referring to the EDS analysis of FIG. 6, it can be seen that most of the ZnO nanowires used as templates disappeared and platinum nanotubes were effectively manufactured.

Experimental Example  2

Palladium Nanotube Test Results

SEM, TEM analysis was performed on the palladium nanotubes prepared according to the present invention.

FIG. 7 is an SEM image of palladium nanotubes, and FIGS. 8A and 8B are TEM images.

Looking at the results of the analysis, it can be seen that the palladium nanotubes effectively formed inside the hollow palladium nanotubes were prepared according to the present invention, and from the SEM and TEM images, palladium nanotubes are different from the platinum nanotubes of Experimental Example 1 It can be seen that the thickness is 50 nm thicker form.

In order to analyze the composition ratio of the obtained palladium nanotubes, the cross-sectional composition component line file (9a) graph and the high angle annular dark-field (HAADF) -STEM-EDS mapping (9b) results of the nanotubes are shown in FIGS. 9A and 9B, respectively.

9A and 9B, it was confirmed that the ZnO nanowires used as the template disappeared and only the palladium component remained in the tube. In particular, referring to Figure 9a, while the ZnO content of the tube as a whole, palladium content is reduced only in the center of the tube, it can be seen that the palladium nanotubes are formed.

Claims (14)

In the metal nanotube manufacturing method,
Growing a nanowire template on the substrate;
Immersing the nanowire template grown on the substrate in a metal solution;
Reducing metal ions of the metal solution to precipitate metal on the nanowire template; And
And dissolving the nanowire template by a solution pH which decreases with the metal ion reduction.
The method of claim 1,
The nanowire template is characterized in that the metal oxide, metal nanotube manufacturing method.
The method of claim 1,
The nanowire template is characterized in that the solubility in the solution is increased as the pH of the immersed solution is reduced, metal nanotube manufacturing method.
The method of claim 3,
The nanowires are ZnO nanowires, characterized in that the metal nanotube manufacturing method.
The method of claim 1,
After the nanowire template growth step, characterized in that the amine-based compound is present on the surface of the nanowire, metal nanotube manufacturing method.
The method of claim 1,
The nanowire template is characterized in that the nanowires on the substrate is immersed in the metal precursor solution in a downward direction, metal nanotube manufacturing method.
delete In the metal nanotube manufacturing method,
Growing a ZnO nanowire template on a substrate by hydrothermal synthesis in a solution containing a zinc salt and an amine compound;
Immersing the mold in a metal solution;
Reducing the metal ions of the metal solution on the surface of the ZnO nanowire mold to precipitate;
Dissolving and removing the ZnO nanowire template by the pH of the solution which decreases with the reduction of the metal ions; And
And collecting the metal nanotubes deposited on the surface of the ZnO nanowire template.
The method of claim 8,
The ZnO nanowire template growth,
Immersing the substrate in an aqueous solution containing the zinc salt and the amine compound; And
Method for producing a metal nanotube, characterized in that it comprises the step of heating the solution.
The method of claim 8,
The grown ZnO nanowire surface, characterized in that the amine compound is bonded, metal nanotube manufacturing method.
The method of claim 10,
The amine-based compound is characterized in that acts as a reducing agent of the metal ions, metal nanotube manufacturing method.
The method of claim 8,
The ZnO nanowire template is characterized in that more dissolved in the metal precursor solution as the pH is lowered, metal nanotube manufacturing method.
The method of claim 8,
The step of depositing the metal and the step of removing the ZnO nanowire template, characterized in that carried out in the same vessel, metal nanotube manufacturing method.

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