WO2011114579A1 - Method for producing low-melting-point metal nanoparticles - Google Patents

Abstract

Provided is a method for producing low-melting-point metal nanoparticles, which can produce low-melting-point metal nanoparticles without using a high-vacuum container and which can produce alloy nanoparticles having a stable metal composition ratio. Specifically, provided is a method for producing low-melting-point metal nanoparticles, which involves: a step for obtaining a mixture by placing a solid or liquid low-melting-point metal, a non-water-based solvent, and pulverization balls having a diameter of 0.015mm to 5mm in a container; a step for stirring and heating the aforementioned mixture between the temperatures of -5°C to +20°C of the melting point of the aforementioned low-melting-point metal; a step for separating the aforementioned pulverization balls from the stirred mixture, and for obtaining a mixture of low-melting-point metal nanoparticles and the non-water-based solvent; and a step for performing solid-liquid separation on the mixture of the low-melting-point nanoparticles and the non-water-based solvent, and for obtaining low-melting-point nanoparticles.

Description

Method for producing low melting point metal nanoparticles

The present invention relates to a method for producing low melting point metal nanoparticles having a fine particle size.

In general, it is known that metal particles have a different particle size and ^exhibit characteristics different from those of bulk metals when the particle size becomes several tens of nanometers (10 ⁻⁹ m) or less. In particular, in the case of metal particles, it is known that the melting point is drastically lowered as compared with that in a bulk state. Therefore, in the case of metal particles having a particle size of submicron (over 0.1 μm), even if the metal particles are only melted at high temperature, the temperature is lower in the case of metal particles having a particle size of several tens of nanometers or less. It can be melted by heating. Utilizing this property, silver nanoparticles (silver particles having an average particle diameter of several tens of nanometers) that can be melted at a low temperature to form a metal wiring have been put into practical use.

A metal wiring can be formed by pasting the silver nanoparticle powder, creating a conductive paste, and applying and firing. In this case, in order to obtain a highly conductive metal wiring, firing is performed. It was necessary to set the temperature to about 120 ° C. or higher.

If a conductive paste that can be sintered at a low temperature of less than 100 ° C., preferably about 80 ° C. or less, can be produced by a simple method, its application can be expected to be significantly expanded. For example, an inexpensive antenna in which fine wiring is drawn on a PET (polyethylene terephthalate) substrate having a low glass transition temperature, an IC tag using paper as a material, and the like can be realized more easily. Furthermore, it is considered that it is possible to draw a metal wiring directly on a conductive polymer, and it is expected that applications of various electrode materials will be expanded.

In the conductive paste using silver nanoparticle powder, the melting point of silver as a bulk is high, so it is expected that it is difficult to further lower the sintering temperature necessary to obtain highly conductive metal wiring. The As a method for obtaining a conductive paste that can be sintered at a lower temperature, it is conceivable to mix a low melting point metal nanoparticle powder into the conductive paste. As a method for obtaining low melting point metal nanoparticles, Patent Document 1 discloses a method in which an indium gas is brought into contact with a low vapor pressure liquid.

JP 2009-240968 A

However, although the method of Patent Document 1 can obtain nanoparticles of indium, which is a low melting point metal, the environment in which indium is used as a gas and in contact with the low vapor pressure liquid is set to a high vacuum of 10 ⁻¹ Pa or less. Need expensive equipment. Further, since a high vacuum container is required, it is considered that it is not easy to scale up, and there is room for improvement in terms of manufacturing cost and productivity. In addition, when producing nanoparticles of an alloy containing two or more kinds of metal elements, it is difficult to obtain a metal gas having a stable metal element composition ratio when a solid or liquid metal is used as a gas. It was considered difficult to obtain alloy nanopowder having a stable composition ratio.

Accordingly, an object of the present invention is to provide a method for producing low melting point metal nanoparticles that can produce low melting point metal nanoparticles without the need for a high vacuum vessel and can obtain alloy nanopowder with a stable metal composition ratio. There is. In the present invention, a metal having a melting point of 25 ° C. or higher (solid at room temperature) and 300 ° C. or lower is referred to as a low melting point metal.

In order to achieve the above-mentioned object, the present inventors, as a result of intensive studies, put a solid or liquid low melting point metal, a non-aqueous solvent, and a grinding ball having a diameter of 0.015 mm to 5 mm in a container. Obtaining a mixture, heating the mixture within a temperature range from 5 ° C. to 20 ° C. higher than the melting point of the low melting point metal, stirring, and then separating the grinding balls from the mixture to By obtaining a mixture of a melting point metal nanoparticle and a non-aqueous solvent and subjecting the mixture of the low melting point metal nanoparticle and the non-aqueous solvent to solid-liquid separation, a low melting point metal nanoparticle having an average particle size of 3 nm or more and less than 50 nm is obtained. Knowing that particles can be obtained, the present invention has been completed.

According to the present invention based on such knowledge, a step of obtaining a mixture by placing a solid or liquid low melting point metal, a non-aqueous solvent, and a pulverizing ball having a diameter of 0.015 mm to 5 mm in a container; Is heated from the melting point of the low melting point metal to -5 ° C. to the melting point of the low melting point metal + 20 ° C., and the ball for pulverization is separated from the mixture after stirring to obtain a low melting point metal nanoparticle and a non-aqueous system. Provided is a method for producing a low-melting-point metal nanoparticle comprising a step of obtaining a solvent mixture and a step of obtaining a low-melting-point metal nanoparticle by solid-liquid separation of the low-melting-point metal nanoparticle and non-aqueous solvent mixture. .

In the method for producing low-melting-point metal nanoparticles, the low-melting-point metal may be one or more selected from the group of In, Ga, Bi, and Sn. The non-aqueous solvent may be an organic solvent having an aldehyde group or a hydroxy group. The non-aqueous solvent may be an organic solvent containing at least one of a primary amino group, a secondary amino group, or a tertiary amino group.

Further, the stirring step may be performed by rotating a stirring blade at a peripheral speed of 200 cm / second to 200000 cm / second. The solid-liquid separation may be performed by centrifugation. The mixture of the low-melting-point metal nanoparticles and the non-aqueous solvent may be subjected to solid-liquid separation, and then the low-melting-point metal nanoparticles may be washed with an organic solvent having a boiling point of 150 ° C. or lower. The volume of the metal may be 0.1 volume% to 20 volume% of the volume of the non-aqueous solvent.

According to the present invention, low melting point metal nanoparticles that can produce low melting point metal nanoparticles having an average particle size of less than 50 nm without the need for a high vacuum container, and can obtain alloy nanopowder with a stable metal composition ratio. It is in providing the manufacturing method of.

It is a figure which shows the measurement result in Example 1 of this invention. It is a figure which shows the observation result in Example 1 of this invention.

Hereinafter, embodiments of the present invention will be described. Note that this embodiment does not limit the present invention.

<Metal composition of low melting point metal nanoparticles>
As the metal composition of the low melting point metal nanoparticles in the present invention, it is possible to use a metal having a melting point in the range of 25 ° C. to 300 ° C. and an alloy of the metal. Specific examples of the metal element include In, Ga, Bi, Sn, and alloys composed of two or more of these metals. These metals or alloys have a low melting point, which is advantageous in applying the production method of the present invention that is stirred in a solvent. The metal or alloy may contain other metal elements as required, as long as the melting point is not outside the range of 25 ° C. to 300 ° C.

<Average particle size of low melting point metal nanoparticles>
The average particle size of the low melting point metal nanoparticles is preferably 3 nm or more and less than 50 nm. In the case of 50 nm or more, the sintering temperature may not be sufficiently lowered, and the low melting point metal nanoparticles of less than 3 nm have a high surface activity and may cause problems due to alteration such as oxidation. From the viewpoint of sufficiently lowering the sintering temperature, the average particle size of the low melting point metal nanoparticles is more preferably less than 30 nm, and even more preferably 20 nm or less.

According to the present invention, low-melting-point metal nanoparticles having an average particle size of less than 50 nm can be produced through the following steps (1) to (4).
(1) A step of placing a solid or liquid metal, a non-aqueous solvent, and a grinding ball having a diameter of 0.015 mm to 5 mm in a container to obtain a mixture.
(2) A step of heating the mixture from a temperature 5 ° C. lower than the melting point of the metal (melting point −5 ° C.) to a temperature 20 ° C. higher than the melting point of the metal (melting point + 20 ° C.) and stirring.
(3) A step of separating the balls for grinding from the mixture to obtain a mixture of low melting point metal nanoparticles and a non-aqueous solvent.
(4) A step of obtaining a low melting point metal nanoparticle by solid-liquid separation of the mixture of the low melting point metal nanoparticle and the non-aqueous solvent.
As needed, you may perform washing | cleaning, drying, etc. with respect to the obtained low melting metal nanoparticle.

<Raw metal>
As the raw metal of the low melting point metal nanoparticles, for example, an alloy composed of In, Ga, Bi, Sn, and two or more of these metals having the same metal composition as the low melting point metal nanoparticles to be obtained is used. can do.

<Non-aqueous solvent>
The non-aqueous solvent in the present invention preferably has a boiling point equal to or higher than the melting point of the raw metal (bulk). For example, when the raw material metal is In, the melting point of the non-aqueous solvent is preferably 156.6 ° C. or higher. For example, when the raw metal is Bi, the non-aqueous solvent has a melting point of 271.3 ° C. The above is preferable. A nonaqueous solvent having a boiling point higher by 10 ° C. or higher than the melting point of the raw material metal (bulk) is particularly suitable, and a solvent having a boiling point of 20 ° C. or higher is particularly suitable. As will be described later, in order to obtain low-melting point metal nanoparticles, those having a boiling point higher than the melting point of the low-melting point metal nanoparticles to be obtained as the non-aqueous solvent are preferable, but a pressure vessel is used as a vessel for stirring. By using it, it is possible to use even a non-aqueous solvent in which the atmospheric pressure is increased and the boiling point of atmospheric pressure is lower than the melting point of the raw metal (bulk). However, since the pressure resistance performance is required for the production apparatus, the boiling point is desirably higher by 10 ° C. or more than the melting point of the raw material metal (bulk) to be obtained. Furthermore, as the non-aqueous solvent, since the low melting point metal nanoparticles react with oxygen and easily form an oxide on the surface, a solvent having a reducing property is more preferable.

For example, an alcohol solvent having a boiling point in the range of 150 ° C. to 400 ° C. is an example of such a non-aqueous solvent. Specifically, the non-aqueous solvent includes a monohydric alcohol or a dihydric alcohol glycol. Examples of the monohydric alcohol include butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, decyl alcohol, nonyl alcohol, cyclopentanol, benzyl alcohol, and cinnamyl alcohol. Examples of glycol solvents include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, benzpinacol, hydro Benzoyl, cyclopentadiol, cyclohexanediol, cyclohexanediol, glycolic acid amide, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monoethyl ether, diethylene glycol dibutyl ether, acetic acid diethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, etc. big Intended polyethylene glycol, polyethylene glycol esters, polyethylene glycol ethers. In particular, glycols and diols are preferable because they have two hydroxyl groups and thus have polarity and contribute to the dispersibility of the powder. Examples of such a solvent include —CH2-CHOH, or —CHR—CHOH, —CR1R2-CHOH, ═CHCHOH, ═CRCHOH (R, R1, R2: side chain) in the molecule, and the solvent Has a boiling point of at least 100 ° C. or higher. Furthermore, an organic compound having an aldehyde group —CHO has the same effect. Examples include aliphatic aldehydes such as succindialdehyde, aliphatic unsaturated aldehydes such as crotonaldehyde, and aromatic aldehydes such as benzaldehyde, tolualdehyde, salicylaldehyde, and cinnamaldehyde. And naphthaldehyde, and the heterocyclic aldehyde includes furfural. Examples of amine-based reducing solvents include hexylamine, hebutinamine, octylamine, undecylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine, dibutylamine, diamylamine, cyclohexylamine, aniline, naphthylamine, and toluidine. is there.

<Crushing ball>
As the grinding balls used in the present invention, alumina balls, zirconia balls, mullite balls, glass balls, metal stainless steel balls or iron balls using ceramics as materials can be used, and the material is not particularly limited. However, zirconia and alumina are particularly suitable as the material for the ball for pulverization, which has the advantages of high durability and low mixing of impurities into the low melting point metal nanoparticles.

The grinding balls preferably have a particle size of 0.015 mm to 5 mm. If only pulverizing balls having a particle diameter of more than 5 mm are used, it becomes difficult to obtain low melting point metal nanoparticles having a desired fine particle diameter. If only pulverizing balls having a particle diameter of less than 0.015 mm are used, stirring is performed. Subsequent solid-liquid separation may take time. In order to easily obtain a low melting point metal nanoparticle having a smaller particle diameter, the particle diameter of the ball for pulverization is more preferably 0.05 to 3 mm, further preferably 0.1 to 1 mm, and 0.1 to 0.00. 5 mm is even more preferable. It is also possible to use a pulverizing ball in combination of a large particle size and a small particle size. In this case, the large ball size need not be particularly concerned with the particle size of 5 mm, and may be, for example, a particle size of 10 mm. It is necessary that at least 50% by mass of grinding balls having a particle diameter of 0.015 mm to 5 mm is contained.

A diamond-like carbon (DLC) or a compound such as B, C, or N, which is a material to which a low melting point metal hardly adheres, can be formed on the surface of the grinding ball.

<Volume ratio of the mixture>
The volume ratio of the mixture is preferably 0.05% by volume to 20% by volume, and more preferably 0.1% by volume to 10% by volume with respect to the volume of the non-aqueous solvent used. The grinding balls are preferably 20% by volume to 600% by volume with respect to the volume of the non-aqueous solvent used. When the metal raw material is less than 0.1% by volume, the productivity is low, and when it exceeds 20% by volume, the particle size of the obtained low melting point metal nanoparticles may not be sufficiently small. When the pulverizing ball is less than 20% by volume, the resulting low melting point metal nanoparticles may not have a sufficiently small particle size. When the pulverizing ball exceeds 600% by volume, the surface of the pulverizing ball contains a large amount of raw material metal. It may become attached. When the mixture is allowed to stand in a container, the volume ratio of the grinding ball to the non-aqueous solvent is set so that the height of the top surface of the grinding ball and the top surface of the non-aqueous solvent are substantially the same. The adjustment is more preferable because low melting point metal nanoparticles can be easily obtained.

<Heating and stirring process>
By heating and stirring the mixture of the metal raw material, the non-aqueous solvent, and the ball for grinding, low melting point metal nanoparticles having an average particle size of 3 nm or more and less than 50 nm can be generated.

The atmosphere for heating and stirring is preferably an inert gas or a reducing gas. When the atmosphere is air, a thick oxide film may be formed on the surface of the generated low melting point metal nanoparticles, and it is preferable that the oxygen concentration in the atmosphere is low. Examples of the inert gas include nitrogen and argon, and examples of the reducing gas include hydrogen or a mixed gas of hydrogen and an inert gas.

When heating and stirring, the heating temperature of the mixture may be higher than the melting point of the metal raw material (bulk) to be used, but it may be heated to a temperature 5 ° C. lower than the melting point to 20 ° C. higher than the melting point. preferable. More preferably, the temperature may be the same temperature as the melting point to 15 ° C. higher than the melting point. More preferably, the temperature may be 5 ° C. higher than the melting point to 10 ° C. higher than the melting point. By heating and stirring at a temperature in the vicinity of the melting point of the raw material metal (bulk) to be used, the yield of the low melting point metal nanoparticles (low melting point metal nanoparticle yield / metal raw material input amount) becomes suitable. The heating temperature is set to a temperature lower than the boiling point of the non-aqueous solvent to be used (in the case of heating and stirring under pressure, the boiling point under pressure).

Stirring can be performed by rotating a stirring blade, and may be performed using a pulverizer that can use pulverizing balls such as a mill. The pulverization conditions such as the number of revolutions may be appropriately selected according to the content of the mixture and the average particle diameter of the low melting point metal nanoparticles to be obtained, and can be obtained by increasing the number of revolutions of the stirring blade and the like. The average particle diameter of the melting point metal nanoparticles can be reduced. For example, when a stirring blade is used, the rotation speed can be set in the range of 100 to 100,000 rpm, and the peripheral speed of the stirring blade can be set in the range of 100 to 5000 cm / sec.

<Separation of balls for grinding>
After the heating and stirring, the mixture is cooled to a temperature lower by 10 ° C. or more than the melting point of the raw material metal (bulk) in the state of stirring. Thereafter, the mixture is separated from the mixture by a known means such as passing a pulverizing ball through a mesh to obtain a mixture of low melting point metal nanoparticles and a non-aqueous solvent.

<Solid-liquid separation>
Solid-liquid separation of the mixture of the low-melting-point metal nanoparticles obtained in the above step and the non-aqueous solvent is performed. Solid-liquid separation can be performed by centrifugation. In addition, when the used non-aqueous solvent does not have a trouble as a dispersion medium of a low melting-point metal nanoparticle, it does not necessarily need to perform solid-liquid separation. In the solid obtained by the solid-liquid separation, agglomerates of low melting point metal nanoparticles may be present. In this case, aggregation can be dispersed by dispersing the solid in a solvent and irradiating with ultrasonic waves. The ultrasonic irradiation can be performed for 1 minute or longer using an ultrasonic cleaning apparatus. The treatment can be performed for 1 minute to 1 hour. In addition, by dispersing the solid in a solvent and centrifuging under a condition of about 500 rpm to 1500 rpm, agglomerated low melting point metal nanoparticles can be separated.

<Washing and drying>
The solid-liquid separated metal nanoparticles can be washed with a solvent. A suitable example of the solvent is an organic solvent of alcohol having a low boiling point such as methanol or ethanol. After washing, the powder is dried by a method that does not perform high-temperature heating such as vacuum drying, whereby low-melting-point metal nanoparticle powders with little residual non-aqueous solvent used can be obtained.

As Examples 1 to 6, low melting point metal nanoparticles were produced by the method for producing low melting point metal nanoparticles according to the present invention, and the produced low melting point metal nanoparticles were measured and observed. Further, as Comparative Examples 1 and 2, the requirement of the present invention is that the mixture is heated and stirred at the melting point of the low melting point metal, which is the material of the mixture, from −5 ° C. to the melting point of the low melting point metal + 20 ° C. Attempts were made to produce low-melting-point metal nanoparticles in a state that was changed outside the scope of the present invention.

[Example 1]
10 g of 6N indium was weighed, and this indium was put into a 500 mL separable flask. As a result of measuring the melting point of indium with a differential scanning calorimeter (DSC) (Thermoplus DSC8230, manufactured by Rigaku Corporation), the melting point was 157 ° C. Next, 1 kg of 0.3 mmφ zirconia balls was charged into the separable flask, and 300 mL of tetraethylene glycol was further charged to obtain a mixture. Thereafter, the upper lid of the separable flask was sealed and sealed, and nitrogen gas was allowed to flow at 100 mL / min to perform gas replacement for 10 minutes. Next, the mixture was heated to 161 ° C. (heating temperature) in a state where stirring was performed by rotating a stirring blade made of stainless steel having a rotational diameter of 6 cm, which had been installed in the separable flask, by rotating 700 rpm. The temperature of the mixture was measured with a thermocouple installed in a separable flask. After maintaining the mixture at the heating temperature for 5 hours, the mixture was cooled at a cooling rate of 5 ° C./min while maintaining the stirring state. When the mixture became 40 ° C. or lower, the rotation of the stirring blade was stopped. The mixture was then passed through a mesh of 250 mesh nylon fabric to separate 0.3 mmΦ zirconia balls from the mixture. On the filtered side, a solvent (tetraethylene glycol) in which the low melting point metal nanoparticles were dispersed was recovered.

In order to wash away tetraethylene glycol, the solvent in which the low-melting-point metal nanoparticles are dispersed is centrifuged at 3500 rpm for 3 hours to perform solid-liquid separation, and the supernatant liquid is removed to recover the solid content. did. Thereafter, cleaning was performed in the following manner. The collected solid content is stirred and mixed with 500 mL of ethanol for 1 hour, redispersed, centrifuged at 3500 rpm for 3 hours and solid-liquid separation, and the operation of removing the supernatant liquid is repeated 3 times. A solid content containing a small amount of was obtained.

After the solid content containing a small amount of ethanol was dried, X-ray diffraction measurement was performed using an X-ray diffractometer (RINT-1200, manufactured by Rigaku Corporation). The measurement results are shown in FIG. The detected peak position was coincident with In, and did not coincide with In ₂ O ₃ . From this, it was confirmed that the obtained particle powder was In particle powder.

A solid content of 0.1 g containing a small amount of ethanol was collected and added to 50 mL of ethanol, and then treated and dispersed for 10 minutes using an ultrasonic cleaning device. FIG. 2 shows the result of drying this dispersion and observing it with a TEM (transmission electron microscope, 400,000 magnifications). It was found that nanoparticles of around 8 nm were generated.

The average particle diameter of the low melting point metal nanoparticles was determined from the TEM image obtained above. In the present invention, employing the average particle diameter D _TEM of an average particle diameter of the low melting point metal nanoparticles obtained by TEM (transmission electron microscope). In the present invention, among the particles observed by a TEM at a magnification of 400,000, 50 independent particle diameters (major axis diameters) that do not overlap are measured to calculate an average particle diameter. The average particle size results are shown in Table 1.

[Example 2]
The production and measurement of low melting point metal nanoparticles were attempted in the same manner as in Example 1 except that the heating temperature was changed from 161 ° C to 156 ° C and 166 ° C. Table 1 shows the average particle size of the obtained low melting point metal nanoparticles. The results of X-ray diffraction were the same as in Example 1 at 156 ° C. and 166 ° C.

[Comparative Example 1]
The production of low melting point metal nanoparticles was attempted in the same manner as in Example 1 except that the heating temperature was changed from 161 ° C. to 150 ° C. and 180 ° C. When large particles of In particles were formed and the mixture was passed through a mesh of 250 mesh nylon fabric, it could hardly pass through and low melting point metal nanoparticles were not obtained.

[Example 3]
The production and measurement of low-melting-point metal nanoparticles were attempted in the same manner as in Example 1 except that the raw material metal used was changed from 6N indium to 6N gallium and the heating temperature was changed from 161 ° C to 35 ° C. Table 2 shows the average particle diameter of the obtained low melting point metal nanoparticles. As a result of X-ray diffraction, a peak corresponding to the Ga peak position was confirmed.

[Example 4]
Except for changing the heating temperature from 35 ° C. to 29 ° C. and 40 ° C., production and measurement of low-melting-point metal nanoparticles were attempted in the same manner as in Example 3. Table 2 shows the average particle diameter of the obtained low melting point metal nanoparticles.

[Comparative Example 2]
The production of low melting point metal nanoparticles was attempted in the same manner as in Example 3 except that the heating temperature was changed from 35 ° C. to 24 ° C. and 50 ° C. When Ga particles having large particle sizes were formed and the mixture was passed through a mesh of 250 mesh nylon fabric, it was hardly possible to pass through the mixture, and low melting point metal nanoparticles were not obtained.

[Example 5]
The production and measurement of low-melting-point metal nanoparticles were attempted in the same manner as in Example 1 except that the raw material metal used was changed from 6N indium to bismuth and the heating temperature was changed from 161 ° C to 276 ° C. Table 3 shows the average particle size of the obtained low-melting-point metal nanoparticles. As a result of X-ray diffraction, a peak corresponding to the Bi peak position was confirmed.

[Example 6]
The production and measurement of low-melting-point metal nanoparticles were attempted in the same manner as in Example 5 except that the heating temperature was changed from 276 ° C. to 271 ° C. and 281 ° C. Table 3 shows the average particle size of the obtained low-melting-point metal nanoparticles.

The present invention can be applied to a method for producing low melting point metal nanoparticles having a fine particle size.

Claims (8)

1. Placing a solid or liquid low melting point metal, a non-aqueous solvent, and grinding balls having a diameter of 0.015 mm to 5 mm in a container to obtain a mixture;
   Heating the mixture from the melting point of the low melting point metal to -5 ° C. to the melting point of the low melting point metal + 20 ° C. and stirring;
   Separating the balls for grinding from the mixture after stirring to obtain a mixture of low melting point metal nanoparticles and a non-aqueous solvent;
   A method for producing a low-melting-point metal nanoparticle comprising a step of solid-liquid separation of a mixture of the low-melting-point metal nanoparticle and a non-aqueous solvent to obtain a low-melting-point metal nanoparticle.
2. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein the low-melting-point metal is at least one selected from the group of In, Ga, Bi, and Sn.
3. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein the non-aqueous solvent is an organic solvent having an aldehyde group or a hydroxy group.
4. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein the non-aqueous solvent is an organic solvent containing at least one of a primary amino group, a secondary amino group, or a tertiary amino group.
5. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein the stirring step is performed by rotating a stirring blade at a peripheral speed of 200 cm / sec to 200000 cm / sec.
6. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein the solid-liquid separation is performed by centrifugation.
7. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein after the mixture of the low-melting-point metal nanoparticles and the non-aqueous solvent is solid-liquid separated, the low-melting-point metal nanoparticles are washed with an organic solvent having a boiling point of 150 ° C or lower. .
8. The method for producing low-melting-point metal nanoparticles according to claim 1, wherein the volume of the low-melting-point metal is 0.1 vol% to 20 vol% of the volume of the non-aqueous solvent.

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