JP2004043572A - Platinum nanoparticle-polymethacrylate composite and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite in which platinum nanoparticles having a desired shape and particle diameter are stably dispersed in a polymer, and a simple manufacturing method therefor. <P>SOLUTION: The composite is a platinum nanoparticle-polymethacrylate composite in which platinum nanoparticles having various shapes or diameters are dispersed in a solid polymethacrylate. The platinum nanoparticles are preferably deformed ones in the form of a chestnut bur or having irregularities. Further, the composite can be obtained by irradiating a polymethacrylate containing a platinum complex with light in a hydrogen atmosphere, and then heating the irradiated polymethacrylate (ester) at a temperature of ≥120°C in a hydrogen atmosphere to reduce it. By adjusting at least one of the light irradiation time and the heating time for reduction, the shape and particle diameter of the platinum nanoparticles to be obtained can be varied. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a composite material in which noble metal nanoparticles having a desired shape and particle size are dispersed in a solid polymer, and a method for producing the same.
[0002]
[Prior art]
In general, noble metal nanoparticles obtained by converting a noble metal into ultrafine particles exhibit new optical effects and catalytic activities that bulk noble metal particles do not have, and furthermore, depending on the size and shape of the particles. It is known to exhibit different properties. Therefore, a composite material in which noble metal nanoparticles having various shapes and particle sizes are dispersed in a polymer is a useful material that can be applied to an optical material, a catalyst, and the like.
[0003]
Conventionally, a composite material in which noble metal nanoparticles are dispersed in a polymer is obtained by introducing a noble metal complex as a raw material into a polymer solution and then thermally decomposing the material. In the case of platinum, such a pyrolysis method is used. However, there is a problem that only spherical platinum nanoparticles having a diameter of 2 to 3 nm are generated, and irregular shaped particles or particles having other particle sizes cannot be obtained.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above situation in the related art. That is, an object of the present invention is to provide a composite in which platinum nanoparticles having a desired shape and particle size are stably dispersed in a polymer, and a simple production method thereof.
[0005]
[Means for Solving the Problems]
The platinum nanoparticle-polymethacrylate composite of the present invention is characterized in that platinum nanoparticles having various shapes or particle diameters are dispersed in a solid polymethacrylate. The platinum nanoparticles are preferably chestnut burs or irregular platinum nanoparticles having irregularities.
[0006]
Further, the method for producing a platinum nanoparticle-polymethacrylate composite of the present invention comprises: irradiating a polymethacrylate containing a platinum complex with light in a hydrogen atmosphere; And reducing by heating. In the production method, it is preferable to change the shape and the particle size of the obtained platinum nanoparticles by adjusting at least one of the light irradiation time and the heat reduction time.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In the composite of the present invention, as a matrix polymer, polymethacrylates, particularly, polymethyl methacrylate (PMMA), in which the thermal decomposition of the platinum complex is almost completely suppressed, are used. In this method, light irradiation in the presence of hydrogen and hydrogen reduction under heating are used in combination to prepare platinum nanoparticles of
[0008]
In the method for producing a composite of the present invention, examples of PMMA containing a platinum complex used as a starting material include those obtained by the following existing methods.
(1) A platinum complex soluble in an organic substance is dissolved in a methyl methacrylate monomer, and then polymerized and solidified (see JP-A-1-113464).
(2) After dissolving a platinum complex and PMMA soluble in an organic substance in an organic solvent, the solvent is removed and dried (Japanese Journal of Applied Physics, Vol. 33, pp. L331-333 (1994)) reference)
(3) Using a sublimable platinum complex, the vapor of the platinum complex generated at a high temperature is brought into contact with PMMA and dissolved in PMMA (see Japanese Patent No. 3062748).
[0009]
In the method for producing the composite of the present invention, the platinum complex-containing PMMA prepared by the above-described method is irradiated with light in a hydrogen atmosphere, and then heated and reduced in a hydrogen atmosphere to produce platinum nanoparticles in the PMMA. I do.
At that time, at least one of light irradiation time and heat reduction time in a hydrogen atmosphere, that is, by appropriately adjusting the time of light irradiation, the time of heating and reducing, or both, to have a desired shape and particle size It can be converted to platinum nanoparticles. As for the shape of the particles, a form in which many sharp needle-like objects protrude from the center of the particle, that is, a shape having a chestnut burd, a spherical body, a spherical body having irregularities on the surface, etc. can get. Further, the particle size can be in the range of 1 to 1000 nm, preferably 3 to 200 nm.
[0010]
When the light irradiation time is short, relatively large, chestnut bur-shaped platinum particles are generated, and by continuing heating in a hydrogen atmosphere, the platinum particles can be converted into relatively large spherical platinum particles. On the other hand, when the light irradiation time is prolonged, smaller platinum particles having irregularities are obtained, which can be converted into spherical platinum particles by continuing heating in a hydrogen atmosphere. Further, when the light irradiation time is longer, only extremely fine spherical platinum nanoparticles are generated. The hue of the obtained composite changes depending on the shape.
[0011]
The platinum complex can be used as long as it is soluble in PMMA, and a complex composed of Pt (II) or Pt (IV) and an organic ligand is used. Among them, acetyl of Pt (II) is particularly preferred. Preferably, an acetonate complex is used.
As a light source for light irradiation, a mercury lamp, sunlight, incandescent lamp, fluorescent lamp, or the like is used, but a fluorescent lamp is sufficient because only visible light is required.
The heating temperature in hydrogen only needs to be equal to or higher than the glass transition point of the polymer to be used. In the case of PMMA, the glass transition temperature is equal to or higher than 105 ° C., and preferably in the range of 120 to 200 ° C. The heating time in hydrogen varies depending on the temperature, but is usually in the range of 1 to 50 hours. It is preferable that the change in color is tracked by a visible spectrum and heating is continued until the temperature becomes constant.
[0012]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Example 1
After dissolving 0.2 mmol of bis (acetylacetonato) platinum (II) (Pt-AA) and 5 mg of 2,2′-azobis (isobutyronitrile) in 10 g of methyl methacrylate and degassing under reduced pressure, The inside was replaced with nitrogen and heated at 70 ° C. for about 20 minutes.
The resulting viscous solution was transferred into a mold in which a 0.5 mm thick Teflon (registered trademark) spacer was sandwiched between two 40 mm × 60 mm glass plates, and further kept at 45 ° C. for 20 hours to carry out polymerization. Completed.
The resulting polymethyl methacrylate (Pt-AA / PMMA) plate containing Pt-AA having a thickness of 0.5 mm was divided into 10 mm x 18 mm, and each of the plates was made of Pyrex (registered trademark) glass in which the inside was replaced with hydrogen. Stored in test tubes.
[0013]
The divided Pt-AA / PMMA plate was irradiated with two 10W-fluorescent lamps at a distance of 45 mm from the surface for 30 minutes in a hydrogen atmosphere, and then heated at 150 ° C. for 3 hours in a hydrogen atmosphere. A composite plate was obtained. During this time, the Pt-AA / PMMA plate turned dark blue.
When this was observed with an electron microscope (TEM), it was a complex in which 40 to 100 nm chestnut bur-shaped platinum particles were uniformly dispersed in PMMA. FIG. 1 shows a TEM photograph of the composite. The length of the black line shown in the figure is 40 nm.
[0014]
Example 2
When the dark dark blue PMMA plate obtained in Example 1 was further heated at 180 ° C. for 32 hours in a hydrogen atmosphere, a brown plate was obtained. According to TEM, this was a composite in which substantially spherical platinum particles having an average particle diameter of 35.4 nm were dispersed in PMMA. FIG. 2 shows a TEM photograph of this composite.
[0015]
Example 3
After irradiating the Pt-AA / PMMA plate with a fluorescent lamp for 2 hours under the same conditions as in Example 1, the plate was heated at 150 ° C. for 1.5 hours in a hydrogen atmosphere. During this time, Pt-AA / PMMA turned dark brown. According to TEM, this was a composite in which platinum particles having irregularities of 15 to 20 nm were uniformly dispersed in PMMA. FIG. 3 shows a TEM photograph of the composite.
[0016]
Example 4
The dark brown PMMA plate obtained in Example 3 was further heated in a hydrogen atmosphere at 180 ° C. for 2 hours to obtain a brown plate. According to TEM, this was a composite in which substantially spherical platinum particles having an average particle size of 15.2 nm were dispersed in PMMA. FIG. 4 shows a TEM photograph of the composite.
[0017]
Example 5
After irradiating the Pt-AA / PMMA plate with a fluorescent lamp for 20 hours under the same conditions as in Example 1, the plate was heated at 150 ° C. for 1 hour in a hydrogen atmosphere. During this time, Pt-AA / PMMA turned brown. According to TEM, this was a composite in which spherical platinum particles having an average particle diameter of 3.3 nm were uniformly dispersed in PMMA. The platinum particles did not change even when heated at 180 ° C. in a hydrogen atmosphere. FIG. 5 shows a TEM photograph of this composite.
[0018]
【The invention's effect】
According to the present invention, it is possible to easily provide a composite in which platinum nanoparticles having a desired shape and particle size are dispersed in a transparent polymer, and thus the obtained composite is useful as an optical material, a catalyst, and the like. It is.
[Brief description of the drawings]
FIG. 1 is an electron micrograph showing an example of the structure of a composite according to the present invention.
FIG. 2 is an electron micrograph showing another example of the structure of the composite according to the present invention.
FIG. 3 is an electron micrograph showing another example of the structure of the composite according to the present invention.
FIG. 4 is an electron micrograph showing another example of the structure of the composite according to the present invention.
FIG. 5 is an electron micrograph showing another example of the structure of the composite according to the present invention.

Claims (4)

A platinum nanoparticle-polymethacrylate composite, wherein platinum nanoparticles having various shapes or particle diameters are dispersed in a solid polymethacrylate. The platinum nanoparticle-polymethacrylate composite according to claim 1, wherein the platinum nanoparticle is a chestnut bur-shaped or irregular platinum nanoparticle having irregularities. After irradiating the polymethacrylate containing a platinum complex with light in a hydrogen atmosphere, the platinum nanoparticle-polymethacrylate composite is characterized in that it is heated and reduced at a temperature of 120 ° C. or more in a hydrogen atmosphere. Production method. The platinum nanoparticle-polymethacrylate composite according to claim 3, wherein the shape and the particle size of the obtained platinum nanoparticle are converted by adjusting at least one of a light irradiation time and a heat reduction time. How to make the body.

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