JP2684413B2 - Method for preparing ultrafine gold particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for preparing ultrafine particles of gold such as a catalyst, various pastes and colloidal solutions.

(Prior art and its problems) Conventionally, as fine particles of gold, only fine particles having a size of 200 Å or more can be prepared as stable fine particles.

As the main method, gelatin or the like is added to an acidic solution of gold as a protective colloid, and gold is reduced with a reducing agent such as hydrogen or hydrazine, or gold is extracted into an organic solvent, and then the organic solvent is divided into fine particles. For example, there is a method in which the particles are dispersed in an inert gas stream, decomposed by heating, and reduced to gold to form fine particles.

However, even if the concentration of the gold solution, the amount of protective colloid, and the type and amount of other polymeric surfactants and the like were changed, stable particles could be prepared with a particle size of about 200Å.

(Object of the invention) The present invention has been made to solve the above-mentioned drawbacks, and provides a method for preparing ultrafine gold particles having a particle size of 30 to 200Å and a stable particle size. The purpose is to do.

(Means for Solving Problems) The present invention involves reacting a gold-containing solution with a solution containing a reducing agent to prepare ultrafine particles of gold, and then adding water-soluble chitin to the gold-containing solution and then performing reduction. A method for preparing ultrafine gold particles, which comprises reacting by adding a solution containing an agent,
A solution containing a reducing agent containing a structure in which water-soluble chitin is deacetylated from chitin is a formaldehyde solution containing alkali hydroxide.

 Hereinafter, details of the present invention will be described.

The gold-containing solution of the present invention may be the most common aqueous solution of chloroauric acid, and the gold concentration is preferably 0.01 to 0.5 g /.

The reason described above is that the prepared gold ultrafine particles do not aggregate and the amount to be prepared is in an economical range.

Water-soluble chitin contains a structure in which deacetylated chitin (about 850 N-acetyl-D-glucosamine chains) is included, and gold ultrafine particles have the effect of stabilizing water-soluble polymer compounds. Considered to have.

The amount of the water-soluble chitin added is such that the concentration in the solution to be reacted is 0.2 to 3 g /, so that the particle size of gold is 30 to
The particle size can be adjusted to 200Å, and the relationship between the particle size and water-soluble chitin decreases as the concentration of water-soluble chitin increases, and the particle size distribution range is ± 20% of the average particle size.
More than 85% can be obtained.

The solution containing the reducing agent is an aqueous solution of about 3% formaldehyde to which sodium hydroxide or potassium hydroxide is added as an alkali hydroxide, and the alkali hydroxide is added to make the reaction condition easy to reduce gold with formaldehyde. .

Further, the amount of formaldehyde added as a reducing agent is preferably 70 times equivalent to that of gold. If added in excess, it is not economical and the particle size distribution of gold ultrafine particles becomes wide. Problems such as occur.

 The liquid temperature of each of the solutions to be reacted may be room temperature.

Hereinafter, examples of the present invention will be described, but the examples do not limit the present invention.

(Example 1) A chloroauric acid solution (Au 0.05 g /) was placed in a 50 ml colorimetric tube, and 1 ml of water-soluble chitin (dissolved 0.5 g in water to 50 ml) was added and stirred sufficiently. After that, 1 ml of formaldehyde solution (5 ml of 1N-KOH + 20 ml of water + 2.5 ml of 35% formaldehyde) was added and stirred to react,
The solution turned red-purple and gold fine particles were formed.

When the fine particles were enlarged and observed, the average particle size was
At 200Å, 85% was in the range of ± 20% and was stable for 30 days without agglomeration.

Example 2 When the same procedure as in Example 1 was carried out except that the amount of water-soluble chitin added was changed to 3 stages of 2 ml, 5 ml and 15 ml, the results shown in Table 1 below were obtained.

(Comparative Example) The same results as shown in Table 2 below were obtained by the same method as in Example 1 except that the amount of water-soluble chitin added was changed to three stages of 0.1 ml, 0.2 ml and 0.5 ml. It was

(Effect of the invention) As is clear from the above results, the present invention can prepare a particle size of ultrafine gold particles of 30 to 200 Å which cannot be obtained by the conventional method, and the reaction conditions and the like are extremely simple. It is expected that ultrafine gold particles will be widely used as catalysts, pastes, raw materials for thin film forming materials, and the like, which utilize the characteristics of gold.

Claims (3)

(57) [Claims] 1. When gold ultrafine particles are prepared by reacting a gold-containing solution with a solution containing a reducing agent, water-soluble chitin is added to the gold-containing solution, and then a solution containing a reducing agent is added and reacted. A method for preparing ultrafine gold particles, comprising: 2. The method for preparing ultrafine gold particles according to claim 1, wherein the water-soluble chitin contains a structure in which chitin is deacetylated. 3. The solution containing a reducing agent is a formaldehyde solution containing an alkali hydroxide.
Method for preparing ultrafine gold particles.