Method for producing fine particle and colloidal solution

Abstract

To provide a method for producing fine particles which prevents a decline in quality, and to provide a colloidal solution.SOLUTION: A method for producing fine particles includes an irradiation step of irradiating a solution comprising a precursor containing a metal atom, a reaction promoter, and water with a femtosecond pulsed laser, thereby producing the fine particles. The reaction promoter comprises at least one of alcohol, sodium hydroxide, and potassium hydroxide. For example, a ratio of the alcohol to the water is 1 or less. For example, a concentration of the alcohol to the solution is 0.01 vol% or more and 30.00 vol% or less. For example, the precursor comprises platinum and a metal, the mixed heat with the platinum of which is 0 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing fine particles and a colloidal solution. [Background technology]

[0002] Conventionally, as a method for producing fine particles, for example, a method for producing fine particles as disclosed in Patent Document 1 has been proposed.

[0003] Patent Document 1 discloses a technology for a method for generating fine particles using a femtosecond pulse laser, which includes an irradiation step of irradiating a powder material in a solvent with a femtosecond pulse laser to generate fine particles containing metal atoms, the powder material having a larger median diameter than the fine particles and containing metal atoms. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7185969 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when generating fine particles using a femtosecond pulse laser, the laser is irradiated for a certain period of time on an irradiated object such as a powder material. At this time, the laser is irradiated not only on the irradiated object but also on the generated fine particles, which may change the crystal structure of the fine particles. For this reason, there is a concern that the quality of the generated fine particles may be reduced by long-term irradiation.

[0006] The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing fine particles and a colloidal solution which are capable of suppressing deterioration in quality. [Means for solving the problem]

[0007] The method for producing microparticles in the first invention includes an irradiation step of irradiating a solution of a mixture of a precursor containing a metal atom, a reaction accelerator, and water with a femtosecond pulse laser to generate microparticles, and the reaction accelerator contains at least one of alcohol, sodium hydroxide, and potassium hydroxide.

[0008] The method for producing fine particles according to the second invention is characterized in that, in the first invention, the reaction accelerator represents the alcohol.

[0009] The method for producing fine particles according to a third aspect of the present invention is characterized in that, in the second aspect of the present invention, the ratio of the alcohol to the water is 1 or less.

[0010] A fourth aspect of the present invention relates to a method for producing fine particles, and in the third aspect of the present invention, the concentration of the alcohol in the solution is 0.01 vol % or more and 30.00 vol % or less.

[0011] A fifth aspect of the present invention provides a method for producing fine particles according to the fourth aspect of the present invention, wherein the precursor contains platinum and a metal having a heat of mixing with platinum of 0 or less.

[0012] The method for producing fine particles according to a sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects of the present invention, the precursor contains a base metal.

[0013] The method for producing fine particles according to the seventh aspect of the present invention is characterized in that, in the first aspect of the present invention, the reaction accelerator is sodium hydroxide or potassium hydroxide.

[0014] The colloidal solution in an eighth aspect of the present invention comprises a solution containing fine particles, a reaction accelerator, and water, and is characterized in that the reaction accelerator contains at least one of alcohol, sodium hydroxide, and potassium hydroxide.

[0015] The colloidal solution in a ninth aspect of the present invention is the colloidal solution in the eighth aspect of the present invention, characterized in that the reaction accelerator represents the alcohol, and the solution contains an oxide of the alcohol. Effect of the Invention

[0016] According to the first to seventh inventions, the irradiation step generates microparticles by irradiating a solution in which a precursor containing metal atoms, a reaction accelerator, and water are mixed with a femtosecond pulse laser. Therefore, compared to the case where a solution in which only a precursor and water are mixed is used, microparticles can be generated more efficiently. This makes it possible to suppress changes in the crystal structure of the microparticles by shortening the laser irradiation time. Therefore, it becomes possible to suppress deterioration in the quality of the microparticles.

[0017] In particular, according to the second invention, the reaction accelerator represents an alcohol. In this case, in the irradiation step, the oxidizing species that inhibit the reduction reaction of the precursor reacts with the alcohol. Therefore, the inhibition of the reduction reaction of the precursor can be suppressed. In addition, the alcohol that reacts with the oxidizing species is changed into a reducing compound, so that the reduction reaction of the precursor can be promoted. That is, the above-mentioned irradiation step can generate fine particles more efficiently. As a result, by shortening the laser irradiation time, the change in the crystal structure of the fine particles can be further suppressed. Therefore, it is possible to further suppress the deterioration of the quality of the fine particles.

[0018] According to the second invention, a solution of a precursor, alcohol, and water is used in the irradiation step. Therefore, the oxidation of the microparticles can be suppressed by the reducing species generated by the oxidation reaction of the alcohol. This makes it possible to suppress the structural change of the microparticles due to oxidation. Therefore, it is possible to suppress the deterioration of the quality of the microparticles from the above viewpoint as well.

[0019] In particular, according to the third aspect of the present invention, the ratio of alcohol to water is equal to or less than 1. In this case, the efficiency of generating fine particles is improved and the variation in particle size of the fine particles can be reduced, compared to when the ratio of alcohol to water is greater than 1.

[0020] In particular, according to the fourth aspect of the present invention, the concentration of alcohol in the solution is 0.01 vol% or more and 30.00 vol% or less. In this case, the variation in particle size of the fine particles can be further reduced. This makes it possible to improve the quality of the fine particles.

[0021] In particular, according to the fifth aspect of the present invention, the precursor contains platinum and a metal whose heat of mixing with platinum is 0 or less. Therefore, when generating fine particles by the irradiation step, the degree of solid solubility of the fine particles can be increased. Therefore, it is possible to generate fine particles that can exhibit the characteristics of each metal contained therein.

[0022] In particular, according to the sixth aspect of the present invention, the precursor contains a base metal. Therefore, the oxidation reaction of the fine particles containing the base metal can be suppressed by the oxidation reaction of the alcohol mixed in the solution. This makes it possible to generate fine particles in which the formation of oxides is suppressed, and it becomes possible to expand the uses of the fine particles.

[0023] According to the eighth aspect of the present invention, the solution contains fine particles, a reaction accelerator, and water. Therefore, compared to the case where only water is used as the solution, it is possible to maintain a state in which oxidation of the fine particles is suppressed. This makes it possible to suppress the structural change of the fine particles due to oxidation. Therefore, it is possible to suppress the deterioration of the quality of the fine particles.

[0024] According to the ninth aspect of the present invention, the reaction accelerator represents an alcohol, and the solution contains an oxidized product of the alcohol. Therefore, the reducing species generated by the oxidation reaction of the alcohol can easily maintain a state in which the oxidation of the fine particles is suppressed. This can further suppress the structural change of the fine particles due to oxidation. Therefore, it is possible to further suppress the deterioration of the quality of the fine particles. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing an example of a fine particle in this embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a production apparatus used in the method for producing fine particles in this embodiment. [Diagram 3] FIG. 3 is a flowchart showing an example of the method for producing fine particles in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an example of a method for producing fine particles and a colloidal solution according to an embodiment of the present invention will be described with reference to the drawings.

[0027] (Embodiment: Microparticles) The microparticles in this embodiment are used in electronic devices such as power generation elements, as well as in fields such as medicine and food. The microparticles can be used in the energy field, such as power generation elements, and in the electronic device field, such as conductive parts. In addition to the above, the microparticles can be used in the medical field, such as medicines or cosmetics, in the materials field as part of composite materials, and in the food field. In particular, by performing any surface treatment (for example, forming a coating) on ​​the surface of the microparticles, it is possible to generate microparticles with additional functions, and it is expected that they will be used in a variety of applications.

[0028] The microparticles include a plurality of particles having a particle diameter of, for example, 1 nm or more and 100 nm or less. The microparticles may include particles having a median diameter (median diameter: D50) of, for example, 1 nm or more and 50 nm or less, and may also include particles having an average particle diameter of, for example, 1 nm or more and 50 nm or less. The median diameter or average particle diameter can be measured, for example, by using a particle size distribution measuring instrument. As the particle size distribution measuring instrument, for example, a known particle size distribution measuring instrument using a dynamic light scattering method (for example, Zetasizer Ultra manufactured by Malvern Panalytical, etc.) is used.

[0029] The fine particles may contain one material or may contain two or more materials (a first material A1 and a second material A2 in FIG. 1) as shown in FIG. 1. The fine particles may represent one type of particle group or may represent multiple types of particle groups each containing a different material.

[0030] (Embodiment: Colloidal solution) The colloidal solution in this embodiment is used in the same field as, for example, fine particles. The colloidal solution includes fine particles and a solvent in which the fine particles are dispersed. That is, the colloidal solution indicates a state in which two or more kinds of substances including, for example, fine particles are mixed.

[0031] The solvent contains, for example, water and a reaction promoter, and the reaction promoter contains at least one of alcohol, sodium hydroxide, and potassium hydroxide.

[0032] For example, the reaction accelerator is alcohol. That is, the reaction accelerator contains only alcohol, and the solvent contains water, alcohol, and an oxidized product of alcohol. In this case, the reducing species generated by the oxidation reaction of the alcohol can maintain a state in which the oxidation of the fine particles is suppressed. This can suppress the structural change of the fine particles due to oxidation. Therefore, it is possible to suppress the deterioration of the quality of the fine particles.

[0033] In addition to the above, for example, the microparticles with suppressed oxidation can be subjected to any surface treatment, which makes it possible to expand the range of uses for the microparticles.

[0034] The colloidal solution is stored, for example, in any container, for example, in a container that suppresses the intrusion of oxygen, such as in an inert gas-filled environment. In this case, oxidation of the microparticles over time can be suppressed. This makes it possible to maintain the quality of the microparticles.

[0035] Alcohol includes monohydric alcohols such as ethanol, methanol, 1-propanol, etc. For example, when the solvent contains ethanol, the oxidation product of the alcohol includes at least one of acetaldehyde produced by oxidation of ethanol and acetic acid produced by oxidation of acetaldehyde.

[0036] For example, when a primary alcohol is used as the alcohol, a compound having an aldehyde group may be used as the alcohol oxide. In this case, the reduction property of the aldehyde group can be utilized to maintain a state in which the oxidation of the fine particles is suppressed. This makes it possible to maintain the quality of the fine particles.

[0037] For example, when a secondary alcohol is used as the alcohol, the oxide of the alcohol may be a compound having a ketone group. In this case, unlike the oxide of a primary alcohol, since it does not have a carboxylic acid, it can also be used for fine particles that dissolve in acid.

[0038] For example, the fine particles contain one or more kinds of base metal materials. In this case, the fine particles, which have the characteristic of being easily oxidized, can be kept in contact with the solvent in the colloidal solution, and the oxidation of the fine particles can be suppressed. This makes it possible to suppress the deterioration of the quality of the fine particles.

[0039] (Manufacturing equipment 100) Next, an example of a manufacturing apparatus 100 used in the method for manufacturing fine particles in this embodiment will be described. Fig. 2 is a schematic diagram showing an example of the manufacturing apparatus 100 in this embodiment.

[0040] 2, the manufacturing apparatus 100 includes a laser device 1, a lens 2, a container 3, and a solution 4. The manufacturing apparatus 100 may include a plurality of containers 3 and solutions 4 for one laser device 1, for example.

[0041] <Laser device 1> The laser device 1 is, for example, -15The laser device 1 emits a pulsed laser having a time width of about 1000 s. As the laser device 1, for example, a femtosecond pulsed laser such as Astrella manufactured by COHERENT Corporation, which has the following characteristics, can be used. Wavelength: 800nm±20nm Pulse width: 100fs Energy: 5-7mJ Repetition frequency: 10-1000Hz (output 0.05-7W)

[0042] In addition to the above, for example, Solstice Ace manufactured by Spectra Physics, etc. can be used as the laser device 1, and can be selected as desired depending on the application. Note that the laser emitted from the laser device 1 has an energy of about several mJ, and it is difficult to efficiently generate fine particles with an energy of about several μJ used in laser processing, for example.

[0043] <Lens 2> The lens 2 focuses the laser emitted from the laser device 1. By using the lens 2, it is possible to increase the light intensity in a specific area. In particular, by using the lens 2, it is possible to focus the laser inside the solution 4 rather than on the interface of the solution 4. As the lens 2, a known lens such as a focusing lens is used. By irradiating the solution 4 with the laser focused via the lens 2, it is possible to improve the efficiency of generating fine particles.

[0044] <Container 3> The container 3 contains the solution 4. A transparent material, such as a fused quartz cuvette, is used for the container 3. For example, a material having a lower absorptivity at wavelengths around 800 nm compared to absorptivity at wavelengths around 400 nm is used for the container 3. In this case, when a laser is irradiated through the container 3, a decrease in the efficiency of generating fine particles can be suppressed.

[0045] The container 3 may include, for example, a lid for covering the opening. In this case, the evaporation of the alcohol can be suppressed. This makes it possible to suppress changes over time when producing the microparticles.

[0046] The lid may be made of, for example, the same material as the container 3, or may be made of a material having alcohol resistance. The lid may be in the form of a plate or may have, for example, a shape having a rim for fitting into the opening.

[0047] <Solution 4> The solution 4 is a liquid obtained by mixing a precursor containing metal atoms, a reaction accelerator, and water. By irradiating the solution 4 with a laser, fine particles containing the metal atoms contained in the precursor are generated. The reaction accelerator is, for example, alcohol.

[0048] Here, when a liquid containing only a precursor and water is used as the solution 4, the solution 4 is irradiated with a femtosecond pulse laser, and the water contained in the solution reacts to generate reduced species such as hydrated electrons and hydrogen radicals (H·), as well as oxidized species such as hydroxide radicals (OH·) and hydrogen peroxide (H2O2). The inventors have found that while the reduced species contribute to the generation of fine particles, the oxidized species inhibit the reduction reaction of metal ions and complex ions that directly affect the generation of fine particles, and the time required to generate fine particles may be delayed. In addition, the inventors have found that when a liquid containing only a precursor and alcohol is used as the solution 4, the time required to generate fine particles is significantly delayed, as shown in the examples described below. One possible reason for this is that the time required to generate fine particles may be delayed because reduced species based on the decomposition reaction of water cannot be generated.

[0049] In contrast, in this embodiment, a solution 4 containing a mixture of a precursor, alcohol, and water is used. At this time, the oxidizing species that inhibit the reduction reaction of the precursor reacts with the alcohol. Therefore, the inhibition of the reduction reaction of metal ions, complex ions, etc. contained in the precursor can be suppressed. In addition to the above, the alcohol that reacts with the oxidizing species changes to a reducing compound, so that the reduction reaction of the precursor can be promoted. That is, by using the above-mentioned solution 4, it is possible to efficiently generate fine particles. As a result, the structural change of the fine particles can be suppressed by optimizing the laser irradiation time. Therefore, it is possible to suppress the deterioration of the quality of the fine particles.

[0050] As the alcohol, a secondary alcohol such as 2-propanol (IPA: isopropyl alcohol) is used. Compared to the case where a primary alcohol is used, a secondary alcohol is more likely to maintain a stable state of radicals due to hyperconjugation. In addition, a secondary alcohol is more likely to react with oxidizing species than a case where a tertiary alcohol is used. For these reasons, the use of a secondary alcohol as the alcohol makes it possible to further promote the reduction reaction of the precursor.

[0051] In addition, polyhydric alcohols such as glycerin and sorbitol may be used as the alcohol. In this case, the number of reaction sites with the oxidizing species can be increased compared to the case where a monohydric alcohol is used. Therefore, by using a polyhydric alcohol as the alcohol, it is possible to further promote the reduction reaction of the precursor.

[0052] For example, the ratio of alcohol to water contained in the solution 4 is equal to or less than 1. In this case, the efficiency of generating fine particles is improved and the variation in particle size of the fine particles can be reduced, compared to when the ratio of alcohol to water is greater than 1.

[0053] For example, the concentration of alcohol in the solution 4 is 0.01 vol% or more and 30.00 vol% or less. Here, if the concentration of alcohol in the solution 4 is less than 0.01 vol%, the laser irradiation time for generating the microparticles is little different from the case where the solution 4 does not contain alcohol, and it may be difficult to effectively shorten the irradiation time. Also, if the concentration of alcohol in the solution 4 is higher than 30.00 vol%, there is a risk that the variation in particle diameter of the generated microparticles will increase. For these reasons, by setting the concentration of alcohol in the solution 4 to 0.01 vol% or more and 30.00 vol% or less, it is possible to shorten the laser irradiation time and further reduce the variation in particle diameter of the microparticles. This makes it possible to improve the quality of the microparticles.

[0054] In the above, the reaction accelerator contains only alcohol, but may contain, for example, at least one of sodium hydroxide and potassium hydroxide in addition to alcohol. Also, the reaction accelerator may contain, for example, at least one of sodium hydroxide and potassium hydroxide instead of alcohol. In these cases, it is possible to suppress the deterioration of the quality of the microparticles in the same manner as above.

[0055] <Precursor> The precursor includes, for example, a metal salt. In this case, for example, the precursor may include a plurality of metal salts each having a different metal. In this case, the concentration of each metal salt mixed in the solution 4 can be easily controlled, so that the content of each metal contained in the generated alloy microparticles can be easily controlled.

[0056] The concentration of the metal salts mixed in the solution 4 is, for example, 1.0×10 -5 mоl·dm -3 Above 1.0×10 -1 mоl·dm -3 or less, and can be set arbitrarily depending on the application of the fine particles to be produced.

[0057] The metal salt contains a known compound containing a metal ion, and any material can be contained depending on the application. For example, known metal salts such as H2PtCl6·6H2O, FeCl3·6H2O, and NiCl2·6H2O can be used.

[0058] For example, the redox potential of the metal ion contained in the metal salt may be negative. In this case, for example, a material containing a base metal is used as the metal salt. Here, when a metal salt containing a metal ion with a negative redox potential is used, there is a concern that oxidation may occur as the fine particles are generated. In contrast, according to this embodiment, the oxidation reaction of the fine particles can be suppressed by the action of a reducing substance generated by the oxidation reaction of the alcohol contained in the solution 4. This makes it possible to generate fine particles that have been difficult to generate in the past. Therefore, it is possible to further expand the uses of the fine particles.

[0059] The "oxidation-reduction potential" refers to a known value described in, for example, "Analytical Chemistry Data Book (Maruzen Publishing)" etc. Furthermore, the "base metal" refers to metals whose metal ion oxidation-reduction potentials are classified as negative values, and refers to lithium, potassium, calcium, sodium, magnesium, aluminum, zinc, iron, nickel, tin, and lead.

[0060] In addition to the above, for example, the precursor may include solid particles. In this case, for example, the precursor may include a plurality of solid particles each having a different metal. The solid particles have a median diameter (or average particle diameter) larger than the median diameter (or average particle diameter) of the generated fine particles. The solid particles have a median diameter (or average particle diameter) of, for example, 50 nm or more and about 200 μm.

[0061] Unlike the metal salts described above, the solid particles do not contain materials that are not contained in the fine particles, such as chlorine, etc. Therefore, it is possible to suppress the generation of unnecessary materials that are generated along with the generation of the fine particles.

[0062] For example, the precursor contains platinum and one or more metals that have a heat of mixing with platinum of 0 or less. Here, it is difficult to maintain a mixed state of two or more materials that have a heat of mixing greater than 0. For this reason, the structure of the microparticles containing two or more materials that have a heat of mixing greater than 0 is likely to exhibit a core-shell structure with a low degree of solid solubility.

[0063] In contrast, the material contained in the microparticles in this embodiment includes platinum and a metal whose heat of mixing with platinum is 0 or less. Therefore, the structure of the microparticles is easy to maintain a structure with a high degree of solid solubility in which materials are mixed together, and the possibility of containing a phase separation structure in which materials are unevenly present within the microparticles or a core-shell structure in which only a specific material is present on the surface can be suppressed. This makes it possible to provide microparticles that can exhibit the characteristics of each metal contained therein. Note that the "degree of solid solubility" indicates the degree to which multiple materials contained in the microparticles are uniformly present within the microparticles. In other words, when the degree of solid solubility is low, it indicates a state in which a specific material is unevenly present within the microparticles or a state of a core-shell structure.

[0064] Examples of metals having a heat of mixing with platinum of 0 or less include tungsten, osmium, iridium, ruthenium, hafnium, rhodium, chromium, zirconium, titanium, palladium, iron, cobalt, nickel, copper, silver, etc. The metal having a heat of mixing with platinum of 0 or less can be selected in accordance with the description in known documents such as "Classification of Bulk Metallic Glasses by Atomic Size Difference, Heat of Mixing and Period of Constituent Elements and Its Application to Characterization of the Main Alloying Element" A. Takeuchi and A. Inoue, Mater. Trans., 46 (2005) 2817.

[0065] The crystal structure of the metal is, for example, a face-centered cubic lattice structure. That is, the metal has the same crystal structure as platinum. In this case, when generating fine particles by laser irradiation, the amount of grain boundaries generated can be reduced compared to when a metal having a crystal structure different from platinum is contained.

[0066] In particular, by using a metal that exhibits a face-centered cubic lattice structure among metals that have a heat of mixing with platinum of 0 or less, it is possible to suppress the endothermic reaction as well as the decrease in thermal conductivity caused by the crystal grain boundaries. Therefore, even if thermal energy acts on the fine particles, it is possible to suppress the deterioration of the degree of solid solubility caused by the thermal energy. Therefore, the effect of heat on the fine particles can be further reduced.

[0067] Among metals whose heat of mixing with platinum is 0 or less, metals exhibiting a face-centered cubic lattice structure include iridium, rhodium, titanium, palladium, nickel, copper, silver, etc. The selection of metals exhibiting a face-centered cubic lattice structure can be made in accordance with the descriptions in known documents such as "Kittel Solid State Physics Introduction Vol. 1 (Maruzen Publishing)".

[0068] (Embodiment: Method for producing fine particles) Next, an example of a method for producing fine particles in this embodiment will be described. Fig. 3 is a flow chart showing an example of a method for producing fine particles in this embodiment. The method for producing fine particles includes an irradiation step S110 as shown in Fig. 3, and may include a coating step S120.

[0069] <Irradiation process S110> In the irradiation step S110, a femtosecond pulse laser is irradiated to a solution 4, which is a mixture of a precursor containing metal atoms, a reaction accelerator, and water, to generate fine particles. The precursor contains one or more types of metal atoms, and the type and number of metal atoms can be set arbitrarily depending on the application.

[0070] In the irradiation step S110, microparticles are generated by irradiating a femtosecond pulse laser to the precursor suspended in the solution 4. In the irradiation step S110, for example, the femtosecond pulse laser may be irradiated to the solution 4 flowing in a fixed direction, or the femtosecond pulse laser may be irradiated to the solution 4 in which the precursor is stirred using a stirrer or the like.

[0071] The femtosecond pulse laser used in the irradiation step S110 can suppress the variation in particle size of the generated microparticles compared to the case where a laser having another pulse width is used. Also, the femtosecond pulse laser can suppress the thermal energy acting on the microparticles compared to the other lasers. Therefore, the variation in the degree of solid solubility of each material contained in the generated microparticles can be suppressed.

[0072] For example, when alcohol is used as a reaction accelerator, in the irradiation step S110, for example, a compound having an aldehyde group or a ketone group is generated by oxidation of the alcohol. That is, the oxidation reaction of the generated fine particles can be suppressed by the oxidation reaction of the alcohol. Therefore, for example, the formation of an oxide film on the surface of the fine particles can be suppressed.

[0073] In the irradiation step S110, the solution 4 may be irradiated with a laser, for example, through the container 3. In this case, the possibility of ignition caused by alcohol or the like can be suppressed compared to the case where the laser is irradiated from the interface between the solution 4 and the atmosphere. This makes it possible to improve safety when producing microparticles.

[0074] In the irradiation step S110, the solution 4 may be irradiated with a laser, for example, in a state where a lid is provided to cover the opening of the container 3. In this case, it is possible to suppress volatilization of the solution 4. This makes it possible to suppress changes over time when producing the microparticles.

[0075] <Film formation process S120> For example, in the film forming step S120, a film is formed on the surface of the fine particles. A known method such as a phase transfer method can be used as the method for forming the film. Note that the formation of an oxide film is suppressed on the surface of the fine particles generated in the irradiation step S110. Therefore, the material contained in the fine particles is easily exposed on the surface, and the choice of materials to be used as the film can be expanded.

[0076] As a result, the fine particles and colloidal solution of this embodiment are produced.

[0077] According to this embodiment, in the irradiation step S110, a solution in which a precursor containing metal atoms, a reaction accelerator, and water are mixed is irradiated with a femtosecond pulse laser to generate fine particles. Therefore, fine particles can be generated more efficiently than when a solution in which only a precursor and water are mixed is used. This makes it possible to suppress changes in the crystal structure of the fine particles by shortening the laser irradiation time. Therefore, it is possible to suppress deterioration in the quality of the fine particles.

[0078] According to the present embodiment, the irradiation step S110 generates microparticles by irradiating a solution of a mixture of a precursor containing metal atoms, alcohol, and water with a femtosecond pulse laser. At this time, an oxidizing species that inhibits the reduction reaction of the precursor reacts with the alcohol. Therefore, the inhibition of the reduction reaction of the precursor can be suppressed. In addition, the alcohol that reacts with the oxidizing species is changed into a reducing compound, so that the reduction reaction of the precursor can be promoted. That is, the above-mentioned irradiation step S110 can generate microparticles more efficiently. This can further suppress the change in the crystal structure of the microparticles by shortening the laser irradiation time. Therefore, it is possible to further suppress the deterioration of the quality of the microparticles.

[0079] Moreover, according to this embodiment, in the irradiation step S110, a solution 4 containing a mixture of a precursor, alcohol, and water is used. Therefore, the oxidation reaction of the alcohol can be used to maintain a state in which the oxidation of the particles is suppressed. This can suppress the structural change of the particles due to oxidation. Therefore, it is possible to suppress the deterioration of the quality of the particles from the above viewpoint as well.

[0080] According to the present embodiment, the irradiation step S110 generates microparticles by irradiating the solution 4 containing the precursors with a femtosecond pulse laser. Therefore, when generating microparticles, the influence of heat can be reduced compared to the case of using other lasers. This makes it possible to suppress the variation in the degree of solid solubility of each metal contained in the microparticles.

[0081] Moreover, according to the present embodiment, the ratio of alcohol to water is equal to or less than 1. In this case, the efficiency of generating fine particles is improved and the variation in particle size of the fine particles can be reduced, compared to when the ratio of alcohol to water is greater than 1.

[0082] According to the present embodiment, the concentration of alcohol in the solution 4 is 0.01 vol% or more and 30.00 vol% or less. In this case, the variation in particle size of the fine particles can be further reduced. This makes it possible to improve the quality of the fine particles.

[0083] According to the present embodiment, the precursor contains platinum and a metal having a heat of mixing with platinum of 0 or less. Therefore, when generating fine particles by the irradiation step S110, the degree of solid solubility of the fine particles can be increased. Therefore, it is possible to generate fine particles that can exhibit the characteristics of each metal contained therein.

[0084] Moreover, according to the present embodiment, the precursor contains a base metal. Therefore, the oxidation reaction of the fine particles containing the base metal can be suppressed by the oxidation reaction of the alcohol mixed in the solution 4. This makes it possible to generate fine particles in which the formation of oxides is suppressed, and it becomes possible to expand the applications of the fine particles.

[0085] Furthermore, according to this embodiment, for example, in the irradiation step S110, the solution 4 is irradiated with a femtosecond pulse laser through the container 3. In this case, the possibility of ignition caused by alcohol or the like can be suppressed compared to the case where the femtosecond pulse laser is irradiated from the interface between the solution 4 and the atmosphere. This makes it possible to improve safety when producing microparticles.

[0086] Furthermore, according to this embodiment, for example, the container 3 includes a lid that covers the opening of the container 3. This can suppress the volatilization of the solution 4. In this case, it is possible to suppress the change over time when producing the microparticles. EXAMPLES

[0087] Next, an example of the method for producing fine particles according to this embodiment will be described.

[0088] In this embodiment, the above-mentioned irradiation step S110 was performed on solutions with different conditions, and the time until a certain amount of fine particles was generated was compared. In addition, the tendency of variation in particle diameter of the generated fine particles was compared. The femtosecond pulse laser used was Solstice Ace manufactured by Spectra Physics, and the irradiation conditions common to each condition were used. In addition, FLAME manufactured by Ocean Photonics was used to measure the time until fine particles were generated and the tendency of variation in particle diameter of the fine particles.

[0089] [Table 1]

[0090] In this example, microparticles were generated by irradiating a femtosecond pulse laser to a solution in which the type and concentration [vol%] of the solvent shown in Comparative Examples 1-2 and Examples 1-15 was mixed with chloroauric acid trihydrate as a precursor, as shown in Table 1. The type and amount of the precursor were the same for each condition, and the total amount of the solution was also constant.

[0091] The "generation time of fine particles" was measured using an ultraviolet-visible light absorption spectrum. The absorption peak value in the light absorption spectrum was plotted against the laser irradiation time, and the time when the maximum value was shown was determined as the end of the generation of fine particles. The generation time of fine particles under each condition was determined as a relative value, with the generation time of fine particles in Comparative Example 1 taken as 1.

[0092] "Peak wavelength [nm]" was measured using an ultraviolet-visible light absorption spectrum. As the value of the absorption peak wavelength in the absorption spectrum increases, the variation in particle size of the fine particles tends to increase. Therefore, the degree of variation in particle size under each condition was evaluated based on the relative value where the peak wavelength in Comparative Example 1 is x.

[0093] From Table 1, the generation time of fine particles in Examples 1 to 15 all showed values ​​greater than the generation time of fine particles in Comparative Example 1. Moreover, the generation time of fine particles in Comparative Example 2 showed a tendency to be significantly slower than that in Comparative Example 1, and therefore was not measurable. For these reasons, it was confirmed that when water and IPA or glycerin were used as a solvent, the generation time of fine particles was shorter than when only water was included and when no water was included.

[0094] Moreover, the peak wavelengths in Examples 1 to 15 were smaller than those in Comparative Example 2. Therefore, it was confirmed that when the ratio of water in the solution is low, the value of the peak wavelength increases and the variation in particle size of the microparticles increases. Since IPA used as a solvent in Examples 1 to 8 and glycerin used as a solvent in Examples 9 to 15 can both be classified as alcohol, it can be assumed that similar results can be obtained even when alcohol other than IPA and glycerin is used. In other words, it was confirmed that it is possible to improve the generation efficiency of microparticles and reduce the variation in particle size of microparticles by setting the ratio of alcohol to water contained in the solution to 1 or less.

[0095] Moreover, the peak wavelengths in Examples 1 to 7 and Examples 9 to 14 all showed values ​​of x+3 or less compared to the peak wavelength (x [nm]) in Comparative Example 1. In contrast, the peak wavelengths in Examples 8 and 15 showed x+4 and x+11, respectively.

[0096] Here, when the above-mentioned peak wavelengths show a difference of 4 nm or more, it can be determined that there is a difference in the variation in particle diameter of the corresponding fine particles. That is, since the peak wavelengths in Examples 8 and 15 are different from the peak wavelength in Comparative Example 1 by 4 nm or more, it can be determined that the variation in particle diameter of the fine particles in Examples 8 and 15 is larger than that in Comparative Example 1. For this reason, it was confirmed that the variation in particle diameter of the fine particles can be reduced by setting the IPA concentration range in Examples 1 to 7 and the glycerin concentration range in Examples 9 to 14.

[0097] In particular, the generation time of the fine particles in Example 1 is 1.2, which is shorter than the generation time of the fine particles in Examples 2 to 7 and Examples 9 to 14. Therefore, it was confirmed that by setting the concentration range of IPA in Examples 2 to 7 and the concentration range of glycerin in Examples 9 to 14 (both of which are 0.01 vol% or more and 30.00 vol% or less), fine particles with small variation in particle size can be generated in a shortened generation time. As described above, since IPA used as a solvent in Examples 2 to 7 and glycerin used as a solvent in Examples 9 to 15 can both be classified as alcohols, it can be assumed that similar results will be obtained even when alcohols other than IPA and glycerin are used.

[0098] In this example, it was confirmed that the fine particles can be efficiently generated by irradiating a solution of a precursor, alcohol, and water with a femtosecond pulse laser to generate the fine particles. In other words, it was confirmed that the structure of the fine particles can be prevented from changing by shortening the laser irradiation time, and the deterioration of the quality of the fine particles can be prevented.

[0099] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0100] 1: Laser device 2: Lens 3: Container 4: Solution 100: Manufacturing equipment S110: Irradiation process S120: Film formation process

Claims

1. The method includes an irradiation step of irradiating a solution of a mixture of a precursor containing metal atoms, a reaction accelerator, and water with a femtosecond pulse laser to generate fine particles; The reaction accelerator contains at least one of alcohol, sodium hydroxide, and potassium hydroxide. A method for producing fine particles, comprising the steps of:

2. The reaction accelerator represents the alcohol. The method for producing fine particles according to claim 1,

3. The ratio of the alcohol to the water is 1 or less. The method for producing fine particles according to claim 2,

4. The concentration of the alcohol in the solution is 0.01 vol % or more and 30.00 vol % or less. The method for producing fine particles according to claim 3,

5. The precursor contains platinum and a metal having a heat of mixing with the platinum of 0 or less. The method for producing fine particles according to claim 4,

6. The precursor contains a base metal. The method for producing fine particles according to any one of claims 1 to 5,

7. The reaction accelerator is the sodium hydroxide or the potassium hydroxide. The method for producing fine particles according to claim 1,

8. The particles, A reaction accelerator; Water, a solution comprising The reaction accelerator contains at least one of alcohol, sodium hydroxide, and potassium hydroxide. A colloidal solution characterized by:

9. the reaction accelerator represents the alcohol, The solution contains an oxide of the alcohol. The colloidal solution according to claim 8, characterized in that

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