JP2982055B2 - Method for producing fine metal particles of gold, silver or copper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine particles of gold, silver or copper on a solid substrate.

[0002]

2. Description of the Related Art Fine particles of gold, silver or copper have been applied to oxidation catalysts for organic compounds and reduction catalysts for NO. Further, by dispersing these metal fine particles in a glass matrix, application as a nonlinear optical material is expected. The key in these applications is how to reduce the size of the individual gold, silver or copper metal particles. In the catalytic reaction, since the chemical reaction takes place on the surface of the catalyst, when using gold, silver or copper metal fine particles as a catalyst, the surface area of the gold, silver or copper metal fine particles is as large as possible, It is necessary to uniformly disperse silver or copper metal fine particles. Also,
When applying metal particles of gold, silver or copper to a nonlinear optical material, the nonlinear optical effect is manifested by the quantum size effect caused by the extremely small particle size of these metals, so the gold, silver or copper metal It is necessary to minimize the size of the fine particles.

[0003] Conventionally, gold,
As a method for producing silver or copper metal fine particles, there is a vacuum deposition method of these metals. This is a method in which the above-described metal is heated and vaporized in a container evacuated to vacuum, and this is deposited on the substrate surface. However, among these metals conventionally used as catalysts, for example, fine gold particles mainly use an organic complex of gold as a raw material and use SiO ₂ , Al ₂ O
It has been obtained by mixing or co-precipitating with various carriers such as ₃ , and then heat-treating. In addition, the method for producing glass in which fine gold particles used as a nonlinear optical material are dispersed is almost the same, and an organic gold complex is often used as a raw material. As described above, one of the reasons that the gold fine particles obtained by a method such as vacuum deposition were not used as a catalyst or as a nonlinear optical material is that gold fine particles deposited on many solid surfaces are particles each other. This is because the size of the particles increases or the film is formed due to coalescence and growth. In such a state of gold, it has been difficult to obtain the desired catalytic function and nonlinear optical effect. Such a phenomenon that the particles coalesce and grow together was also observed for silver and copper metals. Therefore, in order to expect a catalytic function and a nonlinear optical effect for fine particles of a metal such as gold, silver or copper obtained by an evaporation method, it is necessary to suppress the progress of coalescence of the particles.

[0004]

When the present inventors obtain fine particles of gold, silver or copper metal by a vapor deposition method, the present inventors suppress the progress of coalescence of the vapor-deposited metal particles,
As a result of various studies on a method for producing these metal fine particles, the present invention has been completed, and an object of the present invention is to provide a method for producing gold, silver or copper metal fine particles uniformly dispersed on a solid substrate. provide.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is to produce gold, silver or copper metal fine particles on a substrate surface by vapor deposition, wherein iodine is present. A method for producing metal fine particles of the above, in which iodine is previously adsorbed on a substrate as a means for causing iodine to exist, or a method in which iodine is supplied simultaneously with supply of gold, silver, or copper metal to the substrate surface. preferable.

[0006]

That is, in the present invention, highly oriented pyrolytic graphite (HOPG) and SiO ₂ glass are used as a substrate, and gold, silver or copper metal is vacuum-deposited under the condition where iodine is present, thereby forming a substrate surface. In addition, it is possible to obtain fine particles of these metals, to suppress coalescence of the evaporated fine particles of gold, silver or copper, and to prevent them from growing into a film. Although this phenomenon has not been sufficiently elucidated yet, it can be predicted that similar fine particles can be produced for metals other than gold, silver or copper. However, when the coexisting element is other than iodine, the reactivity with the metal to be deposited must be sufficiently considered.

Hereinafter, the present invention will be described in detail. As the substrate in the present invention, it is preferable to use a substrate made of highly oriented pyrolytic graphite (HOPG) and SiO ₂ glass. In particular, (0) of highly oriented pyrolytic graphite
Since the iodine physically adsorbs on the (001) plane (base plane),
Therefore, the coalescence of the gold, silver, or copper metal fine particles deposited on the substrate can be more effectively suppressed, and the deposited gold, silver, or copper metal fine particles can be moved in the three-dimensional direction, that is, in the height direction. grow up.

The gold vapor deposition means does not differ from the conventional vapor deposition conditions even by the presence of iodine. For example, a raw material such as a gold wire or a metal plate is used, and the pressure is reduced under about 2 × 10 ^-4 Torr or under a vacuum. Heating and vapor deposition are performed. It is important to control the deposition rate as a condition for the deposition. Usually, the deposition is performed at a deposition rate in the range of about 0.1 to 1 Å / s, and the deposition is performed on the substrate surface. The temperature on the substrate surface is usually room temperature. The deposition of silver or copper metal other than gold is the same as the conventional deposition method. At the time of vapor deposition, as a method for causing iodine to be present, the iodine may be adsorbed on the substrate surface in advance, or supplied to the vapor deposition device simultaneously with gold. As iodine to be used, it is preferable to use commercially available iodine (I ₂ ) or the like. The size of the obtained gold fine particles is about 10 to 30 which is almost the same as that of the gold colloid.
nm, which are independent on the substrate surface. The same applies to other metals.

[0009]

Examples and Comparative Examples Hereinafter, the present invention will be described specifically with reference to examples. Example 1 A HOPG substrate whose surface has been cleaned in advance is placed in a glass container, and after evacuation, iodine vapor is introduced into the container at room temperature to expose the substrate to iodine vapor. Thereafter, this is taken out and placed in a vacuum steam device. After evacuating the vacuum vapor apparatus, gold is deposited. The temperature of the substrate at this time was room temperature. The amount of gold to be deposited was measured by a film thickness meter. FE- of fine gold particles on HOPG obtained by this method
An SEM photograph is shown in FIG. For comparison, an FE-SEM photograph of a sample vacuum-deposited without supplying iodine is also shown in FIG. The average film thickness of each sample was 1
This is the result when 00 ° is set. Gold produced by a normal vapor deposition method is in the form of a film, whereas when iodine is supplied, individual particles are present independently. The particle size of the obtained gold particles was distributed from several nm to several tens nm.

Example 2 A HOPG substrate whose surface has been previously cleaned is placed in a vacuum evaporation apparatus, and the apparatus is evacuated. Thereafter, iodine vapor is directly blown onto the substrate from a nozzle arranged near the substrate by a gas introduction device provided in the device. The introduction of the iodine vapor starts prior to the vapor deposition. After iodine is introduced, gold deposition is started. Iodine is supplied continuously during the deposition of gold. Immediately after the deposition, the supply of iodine is stopped. The substrate temperature at this time was room temperature. Also, by depositing gold particles on a SiO ₂ substrate by the same method using SiO ₂ as a substrate. FIG. 3 shows an FE-SEM photograph of the fine gold particles on the HOPG substrate produced by these methods. FIG. 3 shows the FE-SE of the fine gold particles on the SiO ₂ substrate.
An M photograph is shown in FIG. The average film thickness of this sample is about 60 ° in both cases, based on the deposition rate and the deposition time.
The average particle size of the obtained gold fine particles was nm size as in the case of Example 1. Further, comparing FIGS. 3 and 4 with FIG. 1, it was found that the particle size and distribution of the gold fine particles obtained by the method of the present embodiment were more uniform than in the case of the first embodiment.

[0011]

As described above, when depositing a metal of gold, silver or copper, the presence of iodine makes it possible to produce fine particles of these metals on a substrate.
Thus, it can be expected that gold, silver or copper metal fine particles obtained by a vapor deposition method are used as a catalyst or a nonlinear optical material.

[Brief description of the drawings]

FIG. 1 is an FE-SEM photograph of fine gold particles on a HOPG substrate obtained by the method of Example 1.

FIG. 2 FE of a sample vacuum-deposited without supplying iodine
-SEM photograph

FIG. 3 is an FE-SEM photograph of fine gold particles on a HOPG substrate manufactured by the method of Example 2.

FIG. 4 is an FE-SEM photograph of fine gold particles on a SiO ₂ substrate produced by the method of Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G02F 1/35 505 G02F 1/35 505 (56) References JP-A-7-97226 (JP, A) JP-A-4-73722 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) C23C 14/00-14/58 B01J 23 / 48,23 / 72,27 / 06 G02F 1/35

Claims (3)

(57) [Claims] 1. A method for producing fine metal particles of gold, silver or copper, wherein iodine is present when producing fine metal particles of gold, silver or copper on a substrate surface by vapor deposition. 2. The method for producing fine metal particles of gold, silver or copper according to claim 1, wherein iodine is adsorbed on the substrate in advance. 3. The method for producing fine metal particles of gold, silver or copper according to claim 1, wherein iodine is supplied simultaneously with the supply of gold, silver or copper metal to the substrate surface.