JP2013049886A - Noble metal colloid particle and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity of noble metal colloid particles by eliminating a cleaning process for removing an excessive reducing agent or the like and provide the noble metal colloid particles having low sintering temperature and high colloidal coloring.SOLUTION: A method for manufacturing the noble metal colloid particles include: a first step in which noble metal salt 2 is converted to a protective colloid state and is extracted as the noble metal colloid particles 6 in a nonaqueous organic solvent phase by mixing and heating noble metal-containing solution including water 1, the noble metal salt 2, a nonaqueous organic solvent 3, and a reducing agent 4 working as protective colloids 10; a second step of separating the nonaqueous organic solvent phase from an aqueous phase; and a third step of obtaining the noble metal colloid particles 6 from the nonaqueous organic solvent phase.

Description

  The present invention relates to noble metal colloidal particles and a method for producing the same.

  In recent years, application of noble metal colloidal particles to low-temperature sinterable conductive pastes is expected.

  In particular, it is expected that nano-sized noble metal colloidal particles that are monodispersed and have a uniform shape will be used for nanocrystalline materials having a two-dimensional or three-dimensional structure.

  Conventionally, it is known that metal colloidal particles are precipitated by mixing a polar solvent in a dispersion using alkylamine as a dispersant for metal fine particles, and purified by a decantation method (for example, Patent Document 1).

JP 2002-121606 A

  However, even using the above technique, nano-sized noble metal colloidal particles having a monodispersed and uniform shape have not been provided with high productivity.

  That is, in Patent Document 1, metal fine particles using an alkylamine as a dispersant are generated by a thermal decomposition method using an acetylacetonate salt as a raw material, and a large noble metal colloid often precipitates. In some cases, noble metal colloidal particles having a uniform shape cannot be obtained.

  Further, since it takes time to separate the noble metal colloid and the polar solvent, the productivity may be deteriorated.

  In addition, since the alkylamine as the dispersant is attached with a straight chain hydrocarbon, it is difficult to donate electrons and does not act as a reducing agent, so that a separate reducing agent is required.

  An object of the present invention is to provide precious metal colloidal particles with high productivity that can be suitably used as materials such as high-performance pigments, nanocrystals, and low-temperature sinterable conductive pastes and that have a low sintering temperature and a high colloid color. And

  In view of the above problems, the method for producing noble metal colloidal particles of the present invention comprises heating a noble metal-containing liquid containing water, a noble metal salt, a water-insoluble organic solvent, and a reducing agent acting as a protective colloid while stirring. A first step of converting the reduced noble metal into a protective colloid and extracting it as a noble metal colloid particle into a water-insoluble organic solvent phase, a second step of separating the water-insoluble organic solvent phase and the water phase, and the water-insoluble And a third step of obtaining the noble metal colloid particles from the basic organic solvent phase.

  According to the method for producing noble metal colloidal particles of the present invention, the use of a reducing agent that acts as a protective colloid eliminates the need for a washing step for removing excess reducing agent and the like. Since there is no need to input, the productivity of noble metal colloidal particles can be improved.

  Furthermore, since the precious metal colloidal particles obtained by the production method of the present invention are monodispersed and easily form a uniform shape, the sintering temperature can be lowered and the colloid color can be enhanced.

  Thereby, it can use suitably as materials, such as a high performance pigment, a nanocrystal, and a low-temperature sintering conductive paste.

It is a graph of the ultraviolet-visible absorption spectrum of the noble metal colloid particle obtained by the Example and comparative example which concern on one Embodiment of this invention. It is a drawing substitute photograph by the electron microscope (500,000 times) of the silver colloid particle obtained with the manufacturing method which concerns on one Embodiment of this invention. It is a schematic diagram of the manufacturing process in the 1st process of the manufacturing method of the noble metal colloid particle which concerns on one Embodiment of this invention. It is a schematic diagram which shows the state in the liquid separation interface vicinity in the 1st process which concerns on one Embodiment of this invention, Comprising: (a) is before protection colloid formation, (b) is the state after protection colloid formation.

  Hereinafter, an embodiment of the present invention will be described in detail.

  In the present embodiment, a noble metal-containing liquid containing water, a noble metal salt, a water-insoluble organic solvent, and a reducing agent that acts as a protective colloid is heated with stirring, whereby the reduced noble metal is converted into a protective colloid to form a noble metal. A first step of extracting the water-insoluble organic solvent phase as colloidal particles, a second step of separating the water-insoluble organic solvent phase and the water phase from the noble metal-containing liquid obtained by the method for producing a noble metal colloid, A third step of obtaining noble metal colloidal particles from the basic organic solvent phase.

  The first step proceeds in the steps shown in FIG. 3, and the water-insoluble organic solvent 3 is a protective agent / reducing agent 4 (hereinafter, also simply referred to as the reducing agent 4). ) And the mixture is heated in the range of 70 to 150 ° C. with stirring. Alternatively, even if the water-insoluble organic solvent 3 is added to the precious metal salt 2 dissolved in water 1 and the reducing agent 4 is added dropwise to a place where heating is performed in a range of 70 to 150 ° C. with stirring. Good.

  If the heating temperature is 70 to 150 ° C., the noble metal ion 2 can be sufficiently reduced by the protective agent / reducing agent 4 and the noble metal ion 2 can be protected by the protective agent / reducing agent 4.

  At this time, the reducing agent 4 exists in the vicinity of the interface 7 between the water phase and the water-insoluble organic solvent phase.

  The concentration of the noble metal-containing liquid 5 is not particularly limited as long as the noble metal salt 2 is completely dissolved (saturated) in the water 1.

  The amount of the water-insoluble organic solvent 3 is not particularly limited as long as it is sufficient to extract the noble metal colloid particles 6 as a protective colloid.

  The first step protects the reduced noble metal by heating the noble metal-containing liquid 5 containing water, the noble metal salt 2, the water-insoluble organic solvent 3, and the reducing agent 4 acting as a protective colloid while stirring. Colloidalized and extracted as noble metal colloidal particles 6 into a water-insoluble organic solvent phase.

  That is, in the first step, as shown in FIG. 4, in the vicinity of the interface 7 between the aqueous phase and the water-insoluble organic solvent phase, the noble metal colloid 6 converts the noble metal ion 2 in the aqueous phase to the amine group (hydrophobic of the reducing agent 4. While being reduced by the group 4 b), it is surrounded by the hydrophilic groups 4 a of the plurality of reducing agents 4 to form a protective colloid and is taken into the water-insoluble organic solvent 3 as the protective colloid 10.

  This is because the water-insoluble organic solvent phase exhibits a unique color with each precious metal colloidal particle 6 as the heating time e.g. gold colloidal particles are reddish purple, silver colloidal particles are yellow, platinum colloidal particles If present, it is observed as a brown color.

  The second step is obtained by a method for producing a noble metal colloid, and separates a water-insoluble organic solvent phase and an aqueous phase from the noble metal-containing liquid 5.

  That is, in the second step, the water-insoluble organic solvent phase is separated from the noble metal-containing liquid 5, and the separated water-insoluble organic solvent 3 is further washed with unreacted silver ions and nitrate ions with distilled water. Later, only the water-insoluble organic solvent phase may be separated again.

  A solvent extraction method is used as a separation method, and a separatory funnel is used as a separation device, and a countercurrent extraction device and a centrifugal device may be used at a mass production level.

In the third step, noble metal colloidal particles 6 are obtained from the water-insoluble organic solvent phase 3.
That is, in the third step, the water-insoluble organic solvent phase is concentrated to a required concentration by vacuum concentration or heating concentration using an evaporator or the like to obtain the noble metal colloid particles 6 having a desired concentration.

  By extracting the noble metal colloidal particles 6 from the water-insoluble organic solvent 3, physical properties such as the boiling point of the solvent are eliminated.

  Further, in the present embodiment, the reducing agent is at least one selected from an amine having an N hydroxyalkyl group and an amine having a polyoxyethylene group.

  For example, N hydroxyethylamine, N hydroxypropylamine, etc. are mentioned. Moreover, for example, polyoxyethylenepropylamine, polyoxyethylenebutylamine, polyoxyethylenedecylamine, polyoxyethylene stearylamine and the like can be mentioned.

  When the heating temperature is 70 ° C. to 150 ° C., the reduction reaction becomes sufficient while reducing the decomposition of the reducing agent 4 during heating and stirring, and the necessary noble metal colloidal particles 6 are obtained.

  The relationship between the addition amount (A) of the reducing agent 4 in this embodiment and the addition amount (B) of the noble metal in the noble metal salt 2 may be in the range of (B) / (A) = 0.05 to 1.0. If the noble metal concentration is too thin, productivity can be reduced, and the noble metal concentration is too high to be protected by the protective agent / reducing agent 4 and can be prevented from precipitating. Is preferable.

  In the present embodiment, the noble metal contained in the noble metal salt is at least one selected from the group consisting of gold, silver, ruthenium, rhodium, palladium and platinum.

  The noble metal salt 2 is not particularly limited as long as it contains the above-mentioned noble metal and is water-soluble, and examples thereof include chloroauric acid, sodium chloroaurate, silver nitrate, silver chloride, chloroplatinic acid, and potassium chloroplatinate. preferable.

  Furthermore, in this embodiment, the water-insoluble organic solvent is at least one selected from the group consisting of aromatic hydrocarbon solvents, ethylene glycol solvents, diethylene glycol solvents, ether solvents, and ester solvents.

  The water-insoluble organic solvent 3 is not particularly limited as long as it is sufficiently separated from the water 1, but a non-polar solvent is preferable.

  Furthermore, the noble metal colloidal particles obtained by the production method of the present embodiment have an average particle size of 50 nm or less.

  In order to control the average particle size to 50 nm or less, the aforementioned (B) / (A) may be set to 1.0 or less.

  Thereby, since the reducing agent 4 which can fully protect the noble metal in the noble metal salt 2 can be secured, it can be reduced that the average particle diameter becomes larger than 50 nm and some noble metal colloids start to precipitate.

  If the average particle size is 50 nm or less, for example, the particle size is 1 to 2 orders of magnitude smaller than that of commonly used silver powder and the particle surface area is increased, so that the reactivity can be improved and surface plasmon resonance absorption is achieved. This is preferable in that it is easy to obtain colloid coloration.

  Here, the average particle size can be measured by a technique such as a transmission electron microscope (500,000 times by TEM) as shown in FIG. 2, and the average particle size distribution is within ± 15% in standard deviation. It is desirable that

  The noble metal colloid particles 6 as described above can be used as, for example, a conductive paste in a conductor printing method such as inkjet, and can also be used for a coloring material or a conductive adhesive material using the noble metal colloid particles 6. it can.

  In the production method of the present invention, 10 to 100 ml of an aqueous solution of 0.1 to 1N noble metal salt 2, 5 to 25 ml of water-insoluble organic solvent 3, and a reducing agent having a protective action (here, N hydroxyalkyl group) It is appropriate that the amount of the amine having an amine or amine having a polyoxyethylene group is 0.2 to 5 g.

  Hereinafter, the result of verifying the productivity based on the embodiment of the manufacturing method of the present invention will be described.

(Sample preparation)
For sample numbers 1 to 5, silver chloride was used as the noble metal salt 2, toluene, ethylene glycol, diethylene glycol, ether, ethyl acetate, and N-hydroxyethylamine as the reducing agent 4 were used as the water-insoluble organic solvent 3.

  For sample numbers 6 to 10, silver chloride, ruthenium chloride, rhodium chloride, palladium chloride, platinum chloride, toluene as the water-insoluble organic solvent 3 and N-hydroxyethylamine as the reducing agent 4 were used as the noble metal salt 2.

  As sample number 11, silver chloride was used as the noble metal salt 2, toluene was used as the water-insoluble organic solvent 3, and polyoxyethyleneamine was used as the reducing agent 4.

  For these samples 1 to 11, weigh 50 mL of 0.1N aqueous solution of each noble metal salt 2 in a beaker, 25 mL of each water-insoluble organic solvent 3 in another beaker, and 1.0 g of each reducing agent 4. After mixing, both beakers were mixed and heated at 110 ° C. with stirring. Subsequently, the water-insoluble organic solvent phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours to obtain each noble metal colloidal particle.

  Sample Nos. 12 to 15 are examples in which the temperature range of the reduction reaction was changed. Silver chloride was used as the noble metal salt 2, toluene was used as the water-insoluble organic solvent 3, and N-hydroxyethylamine was used as the reducing agent 4. In a beaker, 50 mL of 0.1N silver chloride aqueous solution was weighed, and 25 mL of toluene and 1.0 g of N-hydroxyethylamine were mixed in another beaker. A toluene mixed solution was added to a beaker containing a silver chloride aqueous solution, and the mixture was stirred at each temperature condition for 30 minutes. Next, the toluene phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours to obtain silver colloidal particles. In Samples 12 and 15, although the yield of silver colloidal particles was low, the usable amount could be obtained.

  Sample Nos. 16 to 19 are examples in which the ratio (B) / (A) of the reducing agent (A) to the noble metal (B) was changed, silver chloride as the noble metal salt 2, toluene as the water-insoluble organic solvent 3, N-hydroxyethylamine was used as the reducing agent 4. Weigh 50 mL of silver chloride aqueous solution of each concentration in a beaker, mix 25 mL of toluene and each predetermined amount of N-hydroxyethylamine in another beaker, and reduce the reducing agent (A) and noble metal (B) listed in Table 1 below. Ratio (B) / (A). A toluene mixed solution was added to a beaker containing a silver chloride aqueous solution, and the mixture was stirred at 110 ° C. for 30 minutes. Next, the toluene phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours to obtain silver colloidal particles. In Sample 16, although the yield was not sufficient, it could be used. In Sample 19, although some silver colloidal particles precipitated as silver and the yield was not sufficient, it could be used.

  Sample No. 20 was an example in which no reducing agent was used, and silver chloride was used as the noble metal salt 2 and toluene was used as the water-insoluble organic solvent 3. 50 mL of 0.1N silver chloride aqueous solution was measured in a beaker, and another beaker containing 25 mL of toluene was prepared. Toluene was added to a beaker containing silver chloride aqueous solution and stirred at 110 ° C. for 30 minutes. Subsequently, the toluene phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours, but formation of silver colloid particles could not be confirmed.

  Sample No. 21 is a comparative example using a water-soluble organic solvent without using a water-insoluble organic solvent, silver chloride as the noble metal salt 2, n-propanol as the water-soluble organic solvent, and N-hydroxyethylamine as the reducing agent 4. Was used. In a beaker, 50 mL of a 0.1N silver chloride aqueous solution was weighed, and 25 mL of n-propanol and 1.0 g of N-hydroxyethylamine were mixed in another beaker. An n-propanol solution was added to a beaker containing an aqueous silver chloride solution, and the mixture was stirred at 110 ° C. for 30 minutes. In Material No. 21, since colloidal silver particles were present in the aqueous phase, the colloidal silver particles were obtained by washing with distilled water several times and concentrating by heating at 80 ° C. for 15 hours in a dryer.

(Evaluation method and results)
Table 1 shows the results of evaluating the production capacity per unit time and the color developability with respect to each sample in which the conditions of the water-insoluble organic solvent 3, the noble metal salt 2, and the reducing agent 4 were changed.

  The mark ◎ indicates that the productivity or color developability is excellent, the mark ◯ indicates that the productivity and color developability are at or above conventional levels, and the sign X indicates that the productivity and color developability are inferior to those of the conventional products.

  For sample numbers 1 to 19 as examples, noble metal colloidal particles 6 having better productivity and color developability than sample numbers 20 and 21 could be produced.

  For sample No. 12, although the heating temperature was low, the reduction did not proceed, but only the color development was good. Sample No. 15 had a high heating temperature, so that the protective colloid was not sufficient, but only the color development was good.

  For sample No. 16, the noble metal concentration was low and the productivity was not sufficient, but only the color development was good. Sample No. 19 had a high noble metal concentration and insufficient protective colloid formation, but only the color development was good.

For sample No. 20 which is a comparative example, the desired silver colloid could not be obtained because the reducing agent 4 was not used.
Sample No. 21, which is a comparative example, can confirm the formation of silver colloidal particles, but is a mixed solution of water and n-propanol. Therefore, it takes time to wash the silver colloidal particle dispersion and is concentrated by heating. Therefore, it took a long time, which was not preferable as a simple method for producing the noble metal colloidal particles 6. In particular, since it contains water, when it was applied to a substrate, the coating became uneven and the color development was poor.

  Next, the results of measuring the color developability of the colloidal particles by the surface plasmon absorption spectrum for each of the following samples will be described with reference to FIG.

(Sample preparation)
As Example 1, 50 mL of 0.1N silver nitrate aqueous solution was measured in a beaker, and 25 mL of toluene and 1.0 g of N-hydroxyethylamine were mixed in another beaker.

  The toluene mixture was added to a beaker containing an aqueous silver nitrate solution and stirred at 90 ° C. for 30 minutes, and the color of the toluene phase was blackish yellow. Next, the toluene phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours to obtain silver colloidal particles.

  As Example 2, 50 mL of 0.1N silver nitrate aqueous solution was measured in a beaker, and 25 mL of toluene and 1.0 g of polyoxyethyleneamine were mixed in another beaker.

  A toluene mixed solution was added to a beaker containing a silver nitrate aqueous solution, and the mixture was stirred at 90 ° C. for 30 minutes, so that the color of the toluene phase was dark yellow. Next, the toluene phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours to obtain silver colloidal particles.

  As Example 3, 25 mL of 0.1N chloroauric acid aqueous solution was measured in a beaker, and 25 mL of toluene and 1.5 g of N-hydroxyethylamine were mixed in another beaker.

  A toluene mixed solution was added to a beaker containing an aqueous chloroauric acid solution, and the mixture was stirred at 90 ° C. for 30 minutes, so that the toluene phase had a deep reddish purple color. Next, the toluene phase was taken out, washed with distilled water, and then heated and concentrated in a dryer at 80 ° C. for 1 to 2 hours to obtain colloidal gold particles.

  Moreover, the above-mentioned sample number 21 was used as a comparative example.

(Evaluation method and results)
About the production | generation of the noble metal colloid particle 6, the presence of surface plasmon absorption peculiar to each noble metal species was confirmed by measuring an ultraviolet-visible absorption spectrum using a spectrophotometer manufactured by JASCO Corporation.

  In this color development by surface plasmon absorption, free electrons in the metal are swayed by the photoelectric field, charges appear on the particle surface, and nonlinear polarization occurs.

  Color development by noble metal colloidal particles 6 such as gold colloid is color development by surface plasmon absorption resulting from electron plasma vibration, high saturation and light transmittance, excellent durability, etc. It is found in so-called nanoparticles of about several tens of nm.

  For example, as shown in FIG. 2 which shows an image of the silver colloid particles of Example 1 observed at 500,000 times with a transmission electron microscope, particles smaller than 30 nm can be confirmed, and silver colloid particles can be produced. It is supported.

  In FIG. 1, the ultraviolet-visible absorption spectrum of Example 1, 2, 3 and a comparative example is shown.

  In Example 1, Example 2, and Comparative Example, a peak due to surface plasmon absorption of silver colloid particles is observed at λ = 399.5 nm, 412.5 nm, and 410.5 nm, respectively. It is confirmed that colloidal particles are formed.

  In the above, the peak positions due to surface plasmon absorption are almost the same in Example 1, Example 2, and Comparative Example, but Comparative Example 3 had a poor appearance when a large amount of water and impurities remained.

  In Example 3, since a peak due to surface plasmon absorption of the gold colloid particles is observed at λ = 544.5 nm, it is confirmed that gold colloid particles having a size of several to several tens of nm are generated.

1: Water 2: Noble metal salt (noble metal ion)
3: water-insoluble organic solvent 4: (protective agent) reducing agent 4a: hydrophilic group 4b: hydrophobic group 5: noble metal-containing liquid 6: noble metal colloidal particle 7: interface 10: protective colloid

Claims (5)

By heating a precious metal-containing liquid containing water, a precious metal salt, a water-insoluble organic solvent, and a reducing agent that acts as a protective colloid while stirring, the reduced precious metal is converted into a protective colloid to form a water-insoluble precious metal colloid particle. A first step of extraction into a hydrophilic organic solvent phase;
A second step of separating the water-insoluble organic solvent phase and the aqueous phase;
And a third step of obtaining the noble metal colloid particles from the water-insoluble organic solvent phase.   2. The method for producing noble metal colloidal particles according to claim 1, wherein the reducing agent is at least one selected from an amine having an N hydroxyalkyl group and an amine having a polyoxyethylene group.   The method for producing noble metal colloidal particles according to claim 1 or 2, wherein the noble metal contained in the noble metal salt is at least one selected from the group consisting of gold, silver, ruthenium, rhodium, palladium and platinum.   4. The water-insoluble organic solvent is at least one selected from the group consisting of an aromatic hydrocarbon solvent, an ethylene glycol solvent, a diethylene glycol solvent, an ether solvent, and an ester solvent. A method for producing colloidal noble metal particles according to claim 1. Noble metal colloidal particles obtained by the method for producing noble metal colloidal particles according to any one of claims 1 to 4,
Noble metal colloidal particles having an average particle diameter of 50 nm or less.

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