JPH01208A - Method for producing gold particles - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing fine gold particles.

(Prior art and its problems) As a conventional method for producing fine gold particles, a method has been used in which a chloroauric acid solution or the like is reduced using a reducing acid such as hydrazine.

However, this method has the disadvantage that the reduced particles are attracted to each other and aggregate, resulting in only fine gold particles with a wide particle size distribution being obtained.

(Purpose of the invention) The inventor has created a potassium iodide solution (((
x) When potassium hydroxide solution is added to C [formula 21],
We focused on the fact that fine gold particles can be obtained [Equation (3)], but the particles obtained by this method have a particle size of several microns to several tens of microns, and it is difficult to obtain fine gold particles with a size of several microns or less. Ta.

K I + A u I 3 K A u I
a −−−−−−−−−−−−(11KAu 1
4 −→K”+ (Au Ig) −−(212(A
u! +) -+ 6KOH→2Au↓+1 for 5KI+
03+3HffiO+2 Do (3) The present invention has been made to solve the above-mentioned drawbacks, and it is an object of the present invention to provide a method for producing fine gold particles that are dispersed and have a narrow particle size distribution and whose particle size can be controlled. It is.

(Means for solving the problem) In order to obtain fine gold particles, an alkali metal hydroxide solution is added to an aqueous solution containing iodoaurate ions to precipitate gold. It is characterized by the addition of a surfactant.

The fine gold particles obtained by this method have a narrow particle size of several microns or less.

The pH of the aqueous solution containing iodoauric acid ions is preferably 13 or less; if it exceeds ptit3, the reaction of formula (3) will occur, making it impossible to obtain the desired gold particles.

In addition, the pH of this aqueous solution is 8 to 8 to account for the addition of alkali.
13th place is good.

When gold iodide is dissolved in an alkali metal iodide salt, the pH ranges from neutral to weakly acidic (pH 3 to 8). In order to adjust the pH, examples of acids include sulfuric acid, hydrochloric acid, nitric acid, hydroiodic acid, phosphoric acid, and acetic acid. As an alkali,
Examples include sodium hydroxide, potassium hydroxide, and aqueous ammonia.

In addition, in order to suppress extreme pH fluctuations before the reaction, combinations with salts, acids, and alkalis that have a pH buffering effect, such as disodium hydrogen phosphate - sodium dihydrogen phosphate, sodium hydrogen carbonate - sodium carbonate, etc. , sodium carbonate-sodium hydroxide, acetic acid-sodium acetate, etc. may be used to adjust the pH.

Examples of gold iodide salts for obtaining an aqueous solution containing iodoauric acid ions include potassium kola compound and sodium iodide compound, as well as Mg salt, Ca salt, NH salt, and the like. Alternatively, gold iodide may be dissolved in iodide salt (Kl, Na L Mg 1, etc.).

An aqueous solution containing iodoaurate ions in which gold iodide is dissolved in an alkali metal iodide salt, and the alkali metal iodide concentration is 0.
5-5M 71st place is good.

At high concentrations, crystals tend to form as it approaches the saturation concentration of alkali metal iodide, and after the reaction ends, iodine ions become excessive, and due to the salting-out effect, potassium iodate, which is generated as gold powder is precipitated, precipitates together with the gold powder. Examples include:

The reaction temperature is preferably 20~20 to make the particle size uniform.
It is better to keep the temperature constant at 70°C, and the particle size can be controlled by changing the temperature conditions.

The alkali hydroxide concentration is preferably about 0.1 to 6N.

This is because if it is less than 0.0N, a large amount of alkaline hydroxide solution is required for the reaction, and if it exceeds 6N, the gold fine particles tend to aggregate.

The pH at the end point of the reaction is 12.5 or higher at 20°C and 80°C.
In this case, it is sufficient if the pH is 12.0 or higher, but if the pH at the end point is low, the yield will be poor, so the pH is preferably 13 or higher.

In the examples, lithium iodide is used as the alkali metal, but sodium iodide, calcium iodide, magnesium iodide, ammonium iodide, etc. may also be used.

In the reaction solution in the present invention based on the above effects.

The reason why a cationic surfactant is added to the aqueous solution is to keep the gold particles precipitated in the aqueous solution in a monodisperse state without agglomeration, and to prevent crystal growth using the precipitated gold particles as nuclei. It is.

In the present invention, the cationic surfactants added to the reaction solution include C, H+, N(CH3)3Br, and CI
IIH! CIIHz-0+ such as IN(CH3)3CIt
N(C-H□zhX- type and C+zHzs(NCs
H4) CIIHz-t (NCsH) represented by C71 etc.
a) Type X (where n is 5 to 15, m is 1 to 3, and X-
(halogen ion), etc.

(Example 1) 3. Add 50- of a cationic surfactant ((+sHz+N(CHs)i"Br)-(5g/1) to 200 d of ON potassium hydroxide solution and warm to 30°C in advance. I'll keep it.

In a 1N beaker, take 500 m of an aqueous solution containing iodine-aurate ions containing 1.0 M potassium iodide alloy 0.1/11 and adjusted to pH 11.0, warm it to 30°C, and pre-heat it to 30°C. When added to a potassium hydroxide + surfactant solution, a dark yellow precipitate is obtained.

This was washed by decantation, and subjected to particle size distribution measurement and electron microscope observation, and the results shown in the figure and table were obtained.

(Example 2) When the reaction temperature was set to 50° C. in Example 1, the results shown in the figure and table were obtained.

(Example 3) In Example 1, the concentration of cationic surfactant was 20g.
/l, the results shown in the figure and table were obtained.

(Comparative Example) When Example 1 was carried out without adding a cationic surfactant, the results shown in the figure and table were obtained.

(Effects of the Invention) As can be seen from the above explanation, the method for producing fine gold particles according to the present invention can control the particle size and shape of fine gold particles with a narrow particle size distribution that could not be obtained by conventional methods. Since it can be manufactured using multiple steps, it can be said to be revolutionary compared to conventional manufacturing methods.

[Brief explanation of the drawing]

The figure shows the results of measuring the particle size distribution of each fine gold particle using a light transmission type particle size distribution measuring device, with the horizontal axis representing the particle diameter and the vertical axis representing the cumulative percentage. Applicant Tanaka Kikinzoku Kogyo Co., Ltd.

Claims (1)

[Claims] In the method of adding alkali hydroxide to an aqueous solution containing iodoaurate ions to decompose gold iodide to produce gold particles, monodispersed gold particles can be produced by adding a cationic surfactant to the reaction solution. A method for producing fine gold particles, characterized in that: