JP2009197255A - Method for producing metal nanorod, metal nanorod produced thereby and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a metal nanorod, which provides nanoparticles containing metal nanorods that do not contain such impurities as to require a special separation and purification operation in a mixture after having been treated, without using an electrochemical reaction. <P>SOLUTION: The method for producing the metal nanorod includes producing nanoparticles containing metal nanorods having a uniform shape, by mechanically grinding a fine powder of a metal compound in the presence of a solvent. The metal nanorod is obtained by using the production method. An electroconductive composite polymer is formed by dispersing the metal nanorod in a polymer. An electronic product contains the electroconductive composite polymer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing metal nanorods, the metal nanorods obtained thereby, a conductive composite polymer, and an electronic product including the conductive composite polymer, and more specifically, a metal compound fine powder is mechanically treated in the presence of a solvent. The present invention relates to a method for producing a metal nanorod obtained by pulverization to obtain metal nanoparticles containing metal nanorods, a metal nanorod obtained thereby, a conductive composite polymer containing the metal nanorod, and an electronic product containing the conductive composite polymer.

  As one type of metal fine particles, metal nanorods, which are rod-shaped metal particles having a major axis and a minor axis and an aspect ratio larger than 1, have been proposed. Metal nanorods can be produced by depositing metal in the nanotube and then removing the metal from the tube. Elution from the anode using an electrolysis device, a current-carrying electrode such as a gold plate or platinum plate, or an ultrasonic irradiator. Electrochemical method for reducing metal ions to grow and growing rod-shaped metal fine particles by the action of surfactant under ultrasonic irradiation, adding a reducing agent to a metal salt solution to first create a fine metal species as a growth nucleus A chemical method in which a solution containing this metal species is added quantitatively to a growth solution in a separate container and grown into a rod shape, and metal nanorods are irradiated by irradiating metal ions in a surfactant-containing solution with ultraviolet rays for a long time. Optical methods of generating are known.

  However, these conventionally known methods for producing metal nanorods point out problems such as the need for a special apparatus or the reduction power of the reducing agent being too strong to control the growth of metal fine particles. ing. For this reason, the manufacturing method of the metal nanorod with sufficient reproducibility which can control the growth of a metal microparticle without requiring a special apparatus, and the metal microparticle containing composition obtained by it were proposed (patent documents 1-4).

JP 2005-68447 A JP 2005-317395 A JP 2006-118036 A JP 2006-169544 A

JP 2005-68447 A describes a method for producing metal nanorods by an electrochemical reaction in an aqueous solution containing dialkyldimethylammonium bromide as a surfactant.
However, the metal nanorods specifically described here are rod-shaped gold fine particles obtained using a gold plate as an anode.
JP-A-2005-317395 discloses a conductive composition containing metal nanowires or metal nanowires and metal nanorods, and a conductive coating film, a conductive paste, a wiring material, and an electrode formed from the composition. It is described that the material and the conductive film, and the metal nanowires and metal nanorods can be obtained by reduction of metal ions in an aqueous solution containing a surfactant.

In addition, in JP-A-2006-118036, production of rod-shaped metal fine particles for chemically reducing metal ions in an aqueous solution containing amines having a reducing ability and ammonium salts not having a reducing ability is disclosed. Method, rod-shaped metal fine particles having an aspect ratio of greater than 1 obtained by the production method, a composition containing the metal fine particles, and a coating composition, a coating film, a film, and a plate material formed by the composition A light-absorbing material, an electromagnetic shielding material, and the like.
Furthermore, Japanese Patent Laid-Open No. 2006-169544 discloses a nano-sized metal that performs reduction in two stages, using a reducing agent having a strong reducing power in the first reducing step, and using a reducing agent having a weak reducing power in the second reducing step. Method for producing metal fine particles for producing fine particles, rod-shaped metal fine particles having an aspect ratio larger than 1 obtained by the production method, a composition containing the metal fine particles, and a coating composition formed from the composition, A light absorbing material having a form of a coating film, a film and a plate material, an electromagnetic shielding material and the like are described.
According to these improved techniques, nano-sized rod-shaped metal fine particles can be obtained, which use electrochemical reaction or chemical reaction, and in the latter case, other than metal nanorods in the mixture after the reaction. Contains a reducing agent and / or an inorganic or organic impurity based on the reducing agent, and depending on the application, separation and purification are necessary.

Thus, there is no known method for producing metal nanorods that does not use an electrochemical reaction and does not require special separation and purification for removing impurities other than the solvent from the mixture after the reaction.
Therefore, an object of the present invention is to provide a novel method for producing metal nanorods that does not use electrochemical reaction and obtains nanoparticles containing metal nanorods that do not contain impurities that require special separation and purification in the treated mixture. Is to provide.
Another object of the present invention is to provide a metal nanorod obtained by the above production method, and a conductive composite polymer and an electronic product using the metal nanorod.

The present invention relates to a method for producing metal nanorods, in which fine particles of a metal compound are mechanically pulverized in the presence of a solvent to obtain nanoparticles containing metal nanorods having a uniform shape.
Moreover, this invention relates to the metal nanorod obtained by the said manufacturing method.
The present invention also relates to a conductive composite polymer obtained by dispersing the metal nanorods in a polymer.
Furthermore, this invention relates to the electronic product containing the said conductive composite polymer.

In the present invention, the above-mentioned nanoparticles mean a combination of metal nanoparticles or metal compound nanoparticles and metal nanoparticles.
In the present invention, nanoparticles and nanorods are 50% or more in any SEM photograph by observing a scanning electron microscope (SEM) photograph measured by the measurement method described in detail in the column of Examples described later. This refers to the case where the number of particles is less than 1500 nm or the minor axis of 50% or more of the rods is less than 1500 nm.

  According to the present invention, it is possible to obtain nanoparticles containing metal nanorods that do not contain impurities and that do not contain an electrochemical reaction and that do not contain impurities that require special separation and purification in the mixture after treatment.

A preferred embodiment of the present invention will be described below.
1) The said manufacturing method with which a grinding | pulverization is performed until the shape of a rod becomes fixed with the scanning electron microscope (SEM) photograph about the fine powder obtained by carrying out mechanical grinding | pulverization.
2) The said manufacturing method whose metal compound is a metal oxide.
3) The said manufacturing method further including the process of isolate | separating and acquiring a metal nanorod using the difference in the physical property of a metal nanorod and a metal nanoparticle.
4) The said conductive composite polymer whose polymer is resin or an elastomer.

The metal compound in the present invention is not particularly limited, and examples thereof include oxides and sulfides of metals such as silver, palladium, nickel, copper, and iron, preferably metal oxides, among which silver, palladium, or nickel Oxides, particularly silver oxide (Ag ₂ O).
The shape of the metal oxide is not particularly limited as long as it is a fine powder having a commercially available particle size. For example, the average particle size (median diameter) is about 5 to 200 μm, particularly about 10 to 100 μm. Some are preferred.

In the present invention, it is necessary to mechanically grind the fine powder of the metal compound in the presence of a solvent.
The role of the solvent in the present invention is not only the uniform dispersion of the fine powder in the process of forming the metal compound nanoparticles and metal nanoparticles, and the metal nanorods obtained by mechanically pulverizing the fine powder of the metal compound, It is considered that the formed metal nanoparticles and the metal nanorods are shielded from the air and the dispersion of the metal nanoparticles (including metal nanorods) after the mechanical pulverization is promoted.

The solvent is not particularly limited as long as it does not dissolve the metal compound, and examples thereof include ethanol, methanol, isopropanol, t-butanol, phenol, phenoltoluene, phenolxylene, acetone and the like.
The solvent can be used at a rate of about 10 to 1000 times, especially about 25 to 200 times the volume of the fine powder of the metal compound.

  Regarding the reaction in which metal nanoparticles are formed from the fine powder of the fine metal compound, it is unlikely that the reaction with a chemical substance (solvent) in the system because a reducing agent is not included in the system. It is presumed that shear heat due to mechanical grinding is involved. For example, it is known that when silver oxide is heated to a high temperature in the atmosphere, it releases oxygen and becomes silver.

In the present invention, nanoparticles (including metal nanoparticles) including metal nanorods with a uniform shape can be formed by mechanically pulverizing the fine powder of the metal compound in the presence of a solvent.
The mechanical pulverization is performed by adding mechanical energy to the fine powder. Various mechanical pulverizers (mills) can be used as the means. These mechanical pulverizers finely pulverize fine powders using impact force, pressure, shear force, rotational friction force, etc., and are suitable for implementation depending on the type of metal compound and the size of the fine powder. It is possible to select a crusher. Examples of the mechanical pulverizer (mill) include a ball mill, a ball mill, an attrition mill, a nutation mill, a tower mill, a planetary mill, a vibration mill, a jet mill, a rod mill, a roller mill, a crusher mill, and the like. it can.

When the mechanical pulverization is performed using a ball mill, a pulverizing medium such as a steel ball, a ceramic pulverized ball, particularly a zirconia (ZrO ₂ ) ball, zirconia is used as a pot material, and mechanical energy is used. During the collision between the pulverized sphere, the metal compound fine powder and the pulverized sphere, the energy applied to the metal compound fine powder, and further to the nanoparticles is sufficient to form metal nanoparticles and further shaped metal nanorods. It is preferable to continue the mechanical grinding as it is. The reactivity (metallization) of the metal compound fine powder is due to the increase in the reaction area accompanying the decrease in the particle size of the fine powder involved and the number of collisions between the pulverized sphere and the metal compound fine powder and the pulverized sphere. It is thought that metallization is improved.

  Hereinafter, regarding the present invention, changes in the fine powder until a metal nanorod having a uniform shape is formed by mechanical grinding of a fine powder of silver oxide, which is an example of a metal compound in ethanol according to one embodiment of the present invention, with a ball mill. FIG. 1 shows an SEM photograph showing the surface element / composition analysis by Auger electron spectroscopy described in detail in the column of Examples below and FIG. 2 which is an X-ray diffraction diagram of fine powder before and after grinding. It demonstrates using FIG. 3 which shows a result.

From FIG. 1, nanorods having a well-shaped nanorod formed after mechanical pulverization of a metal oxide fine powder before pulverization in a solvent for a sufficient period of time (4 to 7 days) are obtained. Indicates that it has changed. However, FIG. 1 shows that even with mechanical pulverization in a solvent, mechanical pulverization for one day was insufficient, and nanorods with a well-formed shape were not formed.
From FIG. 2, it can be seen that the fine powder before pulverization is silver oxide (Ag ₂ O), and the nanoparticles including the nanorods after pulverization are mainly silver (Ag).
From FIG. 3, it can be seen that the nanorods are silver, not silver oxide.
Accordingly, from FIGS. 1 to 3, the major axis is several μm or less by mechanical grinding until a nanorod having a uniform shape in a solvent (ethanol) is formed in a silver oxide fine powder having a large particle diameter before grinding, It is understood that nanoparticles including metal (silver) nanorods having an aspect ratio larger than 1 can be obtained.

  In the mechanical pulverization using the ball mill, the mechanical pulverization conditions, for example, the volume ratio between the total volume of the metal compound fine powder to be filled in the pot and the pot volume, the total volume of the metal compound fine powder to be filled in the pot and the total of the balls Regarding the volume ratio with respect to the volume, the pulverization temperature, and the pulverization time, conditions under which metal nanorods having a well-formed shape are formed can be appropriately selected. Preferably, the volume ratio of the total volume of the metal compound fine powder to be filled to the pot volume is preferably about 1: 500 to 10: 100, particularly preferably about 1: 200 to 5: 100. The total volume of the fine powder: The total volume of the balls is preferably about 5: 100 to 50: 100, more preferably about 7.5: 100 to 25: 100, and the grinding temperature is preferably about 0 to 50 ° C., particularly about room temperature. The SEM photograph of the pulverized fine powder obtained by pulverization includes a pulverization time until the rod shape becomes constant, for example, about 3 to 14 days, particularly about 4 to 10 days. The SEM photograph of the pulverized fine powder can be measured by performing mechanical pulverization continuously and sampling at regular intervals.

In this invention, in order to separate and obtain fine powder from a solvent mixture containing finely pulverized mechanical powder, if necessary, using a solvent mixture containing nanoparticles containing metal nanorods shaped by the above production method Nanoparticles having a solid content can be obtained by a method known per se, for example, a method such as coagulation, filtration, centrifugation, and drying under reduced pressure, or a combination of two or more thereof. A membrane filter or the like is preferably used for the filtration.
The nanoparticles containing the metal nanorods obtained in this manner are used as they are or the difference in physical properties such as the difference in specific gravity between the metal nanorods and the nanoparticles, the difference in particle diameter and the major axis length of the rods (for example, the metal is silver In this case, the specific gravity of silver is about 10.5 and the specific gravity of silver oxide is about 7.2.) The metal nanorods can be obtained by a method of separating and obtaining the metal nanorods using the above method.

  As described above, the metal nanorods in the present invention may include metal nanoparticles. When the metal compound is a metal oxide, depending on the use of the metal nanorod, for example, when obtaining a conductive composite, it is necessary to separate the metal oxide nanoparticle in the nanoparticle from the metal nanoparticle including the metal nanorod. It can be used as it is as nanoparticles.

The conductive composite polymer of the present invention can be obtained by dispersing metal nanorods in a polymer using the metal nanorods alone or colloids containing the metal nanorods. The metal nanorods may include metal nanoparticles.
Depending on the purpose, the conductive composite polymer may contain pigments, leveling agents, antifoaming agents, metal oxides, and other various additives.

  The colloid containing the metal nanorods includes a solvent mixture of nanoparticles containing metal nanorods obtained by mechanically pulverizing metal compound fine powder in the presence of a solvent or a solvent mixture of nanoparticles containing metal nanorods. It may be a colloid composed of a partially evaporated mixture, or a colloid in which metal nanorods separated and obtained from a solvent mixture of nanoparticles containing metal nanorods are dispersed in the same or different solvent.

There is no restriction | limiting in particular as said another kind of solvent, For example, normal hexane, a cyclohexane, toluene, methyl isobutyl ketone, methyl ethyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran, ethylbenzene etc. can be mentioned.
The metal nanorods in the colloid preferably contain 3% by mass or more and 70% by mass or less of the nanoparticle component including metal nanoparticles and optionally a small amount of metal compound nanoparticles.

  Examples of the polymer include acrylic resin, epoxy resin, polyamide, polyimide, polycarbonate resin, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polylactic acid, polyethylene, polypropylene, copolymer with at least one of isoprene and acrylonitrile, polyurethane, and the like. Mention may be made of elastomers such as resins, polyisoprene, polybutadiene, copolymers of styrene and butadiene.

  The polymer and the metal nanorod may be mixed with the polymer and the metal nanorod which have been polymerized alone or with a colloid containing the metal nanorod, or the solvent solution containing the precursor or monomer of the polymer and the metal nanorod alone. Alternatively, the polymerization may be completed after mixing with the colloid containing the metal nanorods. In the latter case, additives known to those skilled in the art, heat, or light irradiation can be applied to accelerate the polymerization reaction such as a catalyst or a reaction accelerator to complete the polymerization.

Although the ratio of the said polymer and metal nanorod changes with uses, for example, in electroconductive use, it is preferable that metal nanorods are 500-1900 mass parts with respect to 100 mass parts of polymers.
The conductive composite polymer can be used in various forms such as a coating composition, a coating film, a film, and a plate material.
The electronic product of the present invention can be obtained by using the conductive composite polymer as various members such as a coating film, an electromagnetic shielding material, a wiring material, an electrode material, a recording material, and a recording element.

Examples of the present invention will be described below.
In each of the following examples, the shape of the fine powder before and after the mechanical pulverization was measured with a scanning electron microscope (SEM) to obtain SEM photographs. Also, the composition of fine powder before and after mechanical pulverization is determined by X-ray diffraction, and the surface elements and composition of nanorods contained in nanoparticles after mechanical pulverization in a solvent are determined by high energy ion beam excitation Auger electron spectroscopy (hereinafter referred to as Auger electron spectroscopy). Spectroscopic method).
Auger electron spectroscopy was performed after the sample was fixed on a double-sided tape, and the analysis was performed after etching by sputtering about 30 nm in terms of SiO ₂ in order to remove carbon and oxygen adsorbed on the outermost surface.

Example 1
Using the ball mill shown in FIG. 4, the ball mill pot material: zirconia (ZrO ₂ ), 300 mL pot volume, ball material: zirconia (ZrO ₂ ), 200 balls with a diameter of 5 mm, balls 50 with a diameter of 0.2 mm Individual, number of rotations: about 92 rpm, temperature: room temperature, silver oxide fine powder (Ag ₂ O, average particle diameter: around 60 μm: average particle diameter measured using a particle size distribution meter) 15 g (about 2 mL), solvent: ethanol 100 mL The silver oxide ball mill was continuously pulverized under the following ball mill pulverization conditions.
A SEM photograph of the fine powder after 7 days of pulverization is shown in FIG. Further, FIG. 2 shows an X-ray diffraction pattern of the fine powder after pulverization for 7 days together with an X-ray diffraction pattern of the fine silver oxide powder before pulverization. The vertical axis in FIG. u (Arbitrary Sec) is shown.

Further, the surface elements and composition of the nanorods in the fine powder after pulverization for 7 days were measured by Auger electron spectroscopy. The results are shown in FIG. In addition, the vertical axis | shaft of FIG. 3 shows CS (Count / Sec).
The result of FIG. 3 was a result that atomic composition was C76.0%, Ag20.1%, O2.2%, Si1.7% by atomic ratio.
With respect to this result, the results of consideration on the cause of the detection of C, O, and Si are as follows.
Since the sample has a rod shape with a minor axis diameter of 1 μm or less, the surface of the double-sided adhesive carbon tape is excited when the electron beam incident from the surface spreads inside, and the Auger generated from the carbon tape surface. It is thought that the electrons were detected together. On the surface of this double-sided adhesive carbon tape, there is organic silicon transferred from the release paper in addition to carbon, and it is considered that O and Si were detected.
That is, the amount of detected O was only suitable for Si, and it was determined that the component of the nanorod was only Ag, that is, the nanorod was not silver oxide but silver.

  Accordingly, from FIGS. 1 to 3, silver nanorods having a major axis of about 3 to 5 μm and a minor axis of several hundred nm are obtained by ball mill mechanical grinding for 7 days through ethanol of silver oxide fine powder before grinding. Mainly silver nanoparticles were formed.

Comparative Example 1
The same procedure as in Example 1 was performed except that the pulverization was performed for only one day as the mechanical pulverization condition.
An SEM photograph of the fine powder obtained is shown in FIG. 1 together with the results of Example 1.
As shown in FIG. 1, formation of metal nanorods could not be confirmed by ball mill mechanical grinding in ethanol for one day.

FIG. 1 shows changes in fine powder until a metal nanorod having a uniform shape is formed by mechanical grinding of a fine powder of silver oxide, which is an example of a metal compound in ethanol according to one embodiment of the present invention, with a ball mill. An SEM photograph is shown. In FIG. 1, the upper figure is a photograph at a magnification of 3500 times, and the lower figure is a photograph at a magnification of 10000 times. FIG. 2 shows X-ray diffraction patterns of the fine powder before and after mechanical grinding. FIG. 3 shows the surface element / composition analysis results of the nanorods obtained in the examples by Auger electron spectroscopy. FIG. 4 is a photograph showing the ball mill for machine grinding used in the examples.

Claims (8)

  A method for producing metal nanorods, in which fine particles of a metal compound are mechanically pulverized in the presence of a solvent to obtain nanoparticles containing metal nanorods having a uniform shape.   The manufacturing method according to claim 1, wherein the pulverization is performed until the shape of the rod becomes constant in a scanning electron microscope (SEM) photograph of fine powder obtained by mechanical pulverization.   The production method according to claim 1, wherein the metal compound is a metal oxide.   Furthermore, the manufacturing method of Claim 1 including the process of isolate | separating and acquiring a metal nanorod using the difference in the physical property of a metal nanorod and a nanoparticle.   The metal nanorod obtained by the manufacturing method of any one of Claims 1-4.   A conductive composite polymer obtained by dispersing the metal nanorods according to claim 5 in a polymer.   The conductive composite polymer according to claim 5, wherein the polymer is a resin or an elastomer.   An electronic product comprising the conductive composite polymer according to claim 7.