JP2006299354A - Method for producing metal nanoparticulate by high energy electron beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method where hyperfine metal nanoparticulates with a uniform particle diameter of about 10 nm can be produced at high reproducibility in a short time. <P>SOLUTION: An Au ion-containing sodium tetraaurate (III) aqueous solution is prepared, so as to be an original liquid, further, using a surfactant (produced utilizing 4 m mol of a polyethylene glycol monosterate solution as an original liquid) and ultrapure water, so as to be a raw material solution, and electron beam energy of 10 MeV is emitted, thus metal nanoparticulates with a uniform particle diameter are produced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to the production of nanoparticles having a uniform particle size using a high energy electron beam.

  It is known that when the size of a material is reduced and nanometer-sized ultrafine particles are formed, properties that are completely different from the bulk state are manifested due to the quantum size effect in terms of its electronic state, lattice vibration, magnetism, light, specific heat, etc. .

  By utilizing the excellent properties of nano-order ultrafine particles, it is possible to improve the properties of various materials and apply them to functional materials such as various devices and catalysts. It is being advanced.

  In the production of fine metal particles, examples of conventional techniques include physical methods such as gas evaporation, sputtering, metal evaporation synthesis, and fluid oil vacuum evaporation. Also in the chemical method, as a method using the gas phase, a metal chloride reduction / oxidation / nitridation method, a hydrogen reduction method, a solvent evaporation method, and the like are exemplified. On the other hand, in a chemical method, for example, alcohol reduction is the mainstream as a production method using a liquid phase. These methods are all methods for obtaining nano-particles as aggregates, that is, as ultrafine powders, and are not suitable for research on properties and applications as ultrafine particles alone.

In addition, the method using the electron microscope beam has an electron beam intensity on the order of 10 ²⁰ e / cm ² · sec, and the actual beam diameter is extremely narrow with a diameter of 1 μm or less. It is considered small. Since an electron microscope is used, the process is performed in a high vacuum, and only a solid sample with little degassing can be used as a raw material. In the conventional method of irradiating an electron beam in a high vacuum atmosphere using an electron microscope, the amount of nano-particles produced is small, and future industrial applicability is difficult.

  It is an object to easily produce metal nanoparticles having a uniform particle diameter in a short time. In addition, we aim to create a manufacturing method suitable for future industrial applicability.

  In the present invention, in order to achieve the above-mentioned target, the ultrasonic and radiation methods have many controllable parameters and are easy to obtain reproducibility. Among them, electron beam irradiation can generate fine particles in a very short time. it can. Furthermore, the electron beam can be uniform with less diameter dispersion per unit time compared to gamma rays.

  The nanoparticle production method using an electron beam from an accelerator can perform a reduction reaction in a wide region with a beam diameter of 1 cm or more, and can be said to be excellent in production efficiency. Further, since the beam is once taken out into the air and again applied to the raw material, there is no restriction on the raw material. It may be solid, liquid or gas.

  Furthermore, the beam current (the number of irradiated electrons for one second), the total amount of irradiated electrons, and the like can be easily changed, and it is easy to obtain the optimum conditions for producing nano-particles. Since it is irradiated in the air, it has the feature that the temperature of the raw material can be easily controlled (it can be irradiated at a constant temperature if it is cooled with cold water controlled in temperature).

  On the other hand, irradiation with an electron microscope has the disadvantage that the temperature is difficult to control because the sample is placed in a vacuum, so that it is difficult to control the optimum conditions for fine particles (for example, increasing the amount of beam increases the temperature). There is.

  The present inventors considered liquid irradiation.

  As raw materials, transition metals (including noble metals) such as titanium (photocatalyst), silver (fine connection), gold (DNA sensor), iron, nickel, cobalt (magnetic fine particles), etc. may be used for industrial use. it can.

  It is important that the same fine particles (the same particle size and the same structure) are reproducible and can be mass-produced in a short time. Fine particle generation using a high-energy electron beam from an accelerator sufficiently satisfies these conditions.

  As described above, according to the electron beam irradiation of the present invention, the particle shape is almost spherical, the particle size of the fine particles is in the range of about 27 nm or less, and the average particle size is 12 nm. Since the particles are aligned, metal nanoparticles having a uniform particle size can be generated.

  Further, it is conceivable that the particle size can be controlled by changing various irradiation parameters (energy, irradiation amount, dose rate, etc.).

(Example)
First, a sodium tetragold (III) aqueous solution containing 10 mmol of Au ions was prepared as a raw material, and used as a stock solution.

  Based on this, a surfactant (polyethylene glycol monostearate (PEG-MS); prepared as a stock solution of 4 mmole) and ultrapure water purified at the Institute of Advanced Science, Osaka Prefecture University Then, a sample solution containing 0.5 mmol of Au ions and 0.4 mmol of a surfactant was prepared.

  Next, bubbling for 10 minutes was performed using Ar gas. This is to remove active gas atoms present as impurities in the solution and obtain data with good reproducibility.

The prepared sample was poured into a polystyrene mole (4-sided transparent type; 10 × 10 × 45 mm ³ ; can also be used for absorbance measurement) in 4 ml aliquots, coated with aluminum foil, and used as a sample for irradiation.

  As irradiation conditions, an electron beam LINAC (linear accelerator (4-16 MeV high-energy electron beam irradiation is possible with an energy beam of 10 MeV and an average beam current of 50 μA is standard in the source building of Osaka Prefecture University Advanced Science Laboratory) The beam diameter is about 10mm, and it is equipped with an electron beam scanner (runout width 30cm) and a conveyor device, which can irradiate relatively large samples uniformly, thereby irradiating 10kGy per minute. )) Is used to generate nanoparticles by a reduction reaction field by electron beam irradiation with a certain number of repetitions.

  Since the electron irradiation energy of LINAC is very strong, there was a possibility that the sample solution might bump. Therefore, there has been a need to always cool the sample container during irradiation. For this reason, the sample container was sandwiched between two water-cooled cooling boards and fixed to perform electron irradiation. This cooling plate is made of copper, has a circular hole through which an electron beam passes, and a water-cooled pipe passes inside. The irradiation conditions are shown in the table below.

  The energy of 10 MeV of the electron beam passes through a sufficient distance in the aqueous solution and produces efficient nanoparticles. In addition, the irradiation time is only 1 minute, and since gamma rays require 100 minutes, dramatically high efficiency can be achieved.

  When the produced fine particles are seen, they are dispersed almost uniformly throughout. The shape of the particles is almost spherical, and on average there are particles with a size of 12 nm on average, so it can be said that the particles as a whole are collected.

  The present invention can reproducibly produce the same nanoparticle each time (same diameter, same structure, etc.), and can be mass-produced in a short time.

  The production of nanoparticles using a high-energy electron beam from an accelerator sufficiently satisfies these conditions.

  With such metal nanoparticles, application development can be greatly expected. The nano fine particles can be used for catalysts, fine wiring, paints and pigments.

(A) It is a figure which shows typically the preparation condition of the nanoparticle of Au particle | grains of this invention. (B) It is a figure which shows typically the state which Au particle | grains of this invention are irradiated with an electron beam, become Au nanoparticle, and are scattered. It is a part of electron micrograph after irradiating an electron beam to Au particle | grains in the Example of this invention. It is a figure which shows the measurement result of the particle diameter of Au nanoparticle produced in the Example of this invention.

Explanation of symbols

1 Raw Material Particle 2 Electron Beam 3 Metal Nanoparticle 4 Surfactant

Claims (5)

  A method for producing metal nanoparticles comprising irradiating a mixed solution containing a salt of a transition metal (including noble metal), a surfactant and ultrapure water with an electron beam to obtain metal nanoparticles.   The method for producing metal nanoparticles according to claim 1, wherein the transition metal (including noble metal) is gold, silver, titanium, iron, nickel, or cobalt.   The method for producing metal nanoparticles according to claim 2, wherein the gold salt is sodium tetragold (III) acid containing Au ions.   The method for producing metal nanoparticles according to any one of claims 1 to 3, wherein the electron beam is a high energy electron beam.   The method for producing metal nanoparticles according to any one of claims 1 to 4, wherein the irradiation time of the electron beam is 0.06 to 60 seconds.