Method for producing microparticles, and colloidal solution

Abstract

Provided are a method for producing microparticles capable of improving the purity of microparticles, and a colloidal solution. A method for generating microparticles using a femtosecond pulse laser includes an irradiation step of irradiating a powder material 5 in a solvent 6 with a femtosecond pulse laser to generate microparticles containing a metal atom, in which the powder material 5 has a mid-diameter larger than that of the microparticle and contains the metal atom. For example, the powder material 5 includes a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the microparticle is an alloy containing the first metal atom and the second metal atom.

Description

Technical Field

[0001] The present invention relates to a method for producing microparticles and a colloidal solution.Background Art

[0002] Conventionally, as a method for generating microparticles using a laser, for example, a method for producing microparticles as disclosed in Patent Literature 1 has been proposed.

[0003] Patent Literature 1 discloses a method for generating metal nanoparticles by irradiating a basic solvent in which one or more metal ions are dissolved with a femtosecond pulse laser.Citation ListPatent Literature

[0004] Patent Literature 1: JP 2021-017622 ASummary of InventionTechnical Problem

[0005] Here, Patent Literature 1 discloses the method for generating metal nanoparticles by irradiating a basic solvent in which metal ions are dissolved with a femtosecond pulse laser to reduce the metal ions by radicals (for example, hydrogen radicals) generated by decomposing water molecules in the basic solvent. According to this generation method, in addition to the metal nanoparticles as the target substance, for example, chloride ions bonded to the metal ions may be oxidized during the reduction reaction of metal ions, and impurities other than the target substance may be generated. Therefore, the generated impurities may affect adhesion to the metal nanoparticles, and there is a concern that the quality of the metal nanoparticles is deteriorated.

[0006] Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for producing microparticles capable of suppressing deterioration in quality of microparticles, and a colloidal solution.Solution to Problem

[0007] A method for producing microparticles in a first aspect of the present invention is a method for producing microparticles using a femtosecond pulse laser, the method including an irradiation step of irradiating a powder material in a solvent with a femtosecond pulse laser to generate microparticles containing a metal atom, in which the powder material has a mid-diameter larger than that of the microparticle and contains a metal atom.

[0008] According to a method for producing microparticles in a second aspect of the present invention, in the first aspect of the present invention, the powder material includes a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the microparticle is an alloy containing the first metal atom and the second metal atom.

[0009] According to a method for producing microparticles in a third aspect of the present invention, in the second aspect of the present invention, a melting point of the second powder material is higher than a melting point of the first powder material.

[0010] According to a method for producing microparticles in a fourth aspect of the present invention, in the second or third aspect of the present invention, the microparticle is a solid solution in which the first metal atom and the second metal atom are combined.

[0011] According to a colloidal solution in a fifth aspect of the present invention, the colloidal solution includes the microparticles generated by the method for producing microparticles according to any one of the first to third aspects of the present invention; and a solvent in which the microparticles are dispersed.Advantageous Effects of Invention

[0012] According to the first to fourth aspects of the present invention, the method includes an irradiation step of irradiating a powder material in a solvent with a femtosecond pulse laser to generate microparticles containing a metal atom, and the powder material has a mid-diameter larger than that of the microparticle. Therefore, as compared with the method for producing microparticles using reduction of metal ions, generation of impurities that may affect the microparticles can be suppressed. This makes it possible to suppress deterioration in quality of the generated microparticles.

[0013] In particular, according to the second aspect of the present invention, the powder material includes a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the microparticle is an alloy containing the first metal atom and the second metal atom. Therefore, the ratio between the first powder material and the second powder material can be adjusted, and the composition ratio of metal atoms contained in the microparticle is easily controlled. This makes it possible to suppress variations in the composition ratio of metal atoms contained in the microparticle.

[0014] In particular, according to the third aspect of the present invention, the melting point of the second powder material is higher than the melting point of the first powder material. That is, microparticles having characteristics of the first powder material and a melting point higher than that of the first powder material are generated. Therefore, as compared with a case where microparticles are produced without using the second powder material, a temperature range in which the microparticles are stable can be expanded. This makes it possible to improve the stability of the generated microparticles.

[0015] In particular, according to the fourth aspect of the present invention, the microparticle is a solid solution in which the first metal atom and the second metal atom are combined. Therefore, a partial state change or chemical change of the microparticle is less likely to occur as compared with a microparticle that is not a solid solution. This makes it possible to further improve the stability of the generated microparticles.

[0016] In particular, according to the fifth aspect of the present invention, the colloidal solution includes a solvent in which the microparticles are dispersed. Therefore, aggregation of the microparticles is easily suppressed as compared with a case where the microparticles are stored without using a solvent. This makes it possible to provide microparticles with maintained quality.Brief Description of Drawings

[0017] Fig. 1 is a schematic perspective view showing an example of a manufacturing device used in a method for producing microparticles in the present embodiment.Description of Embodiments

[0018] Hereinafter, an example of a method for producing microparticles, a microparticle, and a colloidal solution as embodiments of the present invention will be described with reference to the drawings.(Embodiments: Microparticle, colloidal solution)

[0019] The microparticle in the present embodiment is used in electronic devices such as power generation elements, and also used, for example, in the fields of medicine, food, and the like. The microparticles include a metal microparticle, and may include a microparticle containing a metal atom and a non-metal atom. The microparticle can be used, for example, in the energy field such as a power generation element and in the electronic device field such as a conductive component. In addition to the above, the microparticle can be used, for example, in the medical field as a pharmaceutical product or a cosmetic product, the material field as a part of a composite material, the field of food, and the like. In particular, by performing an arbitrary surface treatment (for example, formation of coating) on the surface of the microparticle, a microparticle having an additional function can be generated, and development to various applications is expected.

[0020] 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, for example, particles having a median diameter (mid-diameter: D50) of 1 nm or more and 10 nm or less, and may include, for example, particles having an average particle diameter of 1 nm or more and 10 nm or less. The median diameter or the average particle diameter can be measured by using, for example, a particle size distribution measuring device. As the particle size distribution measuring device, for example, a particle size distribution measuring device using a dynamic light scattering method (for example, Zetasizer Ultra manufactured by Malvern Panalytical Ltd.) may be used.

[0021] The microparticles indicate a group of particles generated from a single metal, and also indicate, for example, a group of particles generated from a plurality of kinds of metal particles. The microparticles may indicate a group of particles generated by, for example, an alloy.

[0022] The colloidal solution in the present embodiment is used in the same fields as the microparticle. The colloidal solution indicates, for example, a state in which two or more kinds of substances including microparticles are mixed. The colloidal solution includes, for example, a solvent 6 in which microparticles are dispersed.

[0023] The colloidal solution includes the solvent 6 in which microparticles are dispersed. In this case, aggregation of the microparticles is easily suppressed as compared with a case where the microparticles are stored without using the solvent 6. This makes it possible to provide microparticles with maintained quality.

[0024] For example, the microparticle contains a known metal atom such as nickel, platinum, gold, or titanium. The microparticle may include, for example, any of a pure metal, an alloy containing no non-metal, and a metal oxide as long as it contains a metal atom. In the case of producing a colloidal solution in which microparticles of a pure metal or an alloy containing no non-metal are dispersed, it is possible to reduce a factor of promoting oxidation of the microparticles by using an alcohol as the solvent 6. This makes it possible to provide microparticles with better quality.

[0025] The microparticle has, for example, a perovskite structure. The microparticle may include, for example, at least one of barium titanate (BaTiO 3 ), strontium titanate (SrTiO 3 ), calcium titanate (CaTiO 3 ), lead titanate (PbTiO 3 ), tin titanate (SnTiO 3 ), cadmium titanate (CdTiO 3 ), and strontium zirconate (SrZrO 3 ).

[0026] The microparticles are generated using, for example, a first powder material and a second powder material. The first powder material contains a first metal atom, and the second powder material contains a second metal atom. The microparticle is, for example, an alloy containing a first metal atom and a second metal atom. The microparticle contains, for example, a second powder material having a melting point higher than a melting point of the first powder material. That is, microparticles having characteristics of the first powder material and having a melting point higher than that of the first powder material are generated. In this case, as compared with a case where microparticles are produced without using the second powder material, a temperature range in which the microparticles are stable can be expanded. This makes it possible to improve the stability of the microparticles. The microparticle may be an alloy containing two different kinds of metal atoms or an alloy containing three or more different kinds of metal atoms.

[0027] The microparticle is, for example, a solid solution in which a first metal atom and a second metal atom are combined. In this case, a partial state change or chemical change of the microparticle is less likely to occur as compared with a microparticle that is not a solid solution, and the entire microparticles are likely to be stably present. This makes it possible to further improve the stability of the generated microparticles. Examples of the combination of metal atoms contained in the microparticle of the solid solution include a combination of nickel and platinum, a combination of nickel and ruthenium, a combination of nickel and rhodium, a combination of nickel and palladium, a combination of nickel and iridium, and the like. The microparticle of the solid solution may contain three or more kinds of metal atoms. As an example of a combination of metal atoms contained in the microparticle of the solid solution, for example, a combination of metal atoms with a mixing enthalpy of 0 or less may be selected.

[0028] The microparticle is, for example, a eutectic in which a first metal atom and a second metal atom are combined. In this case, the stability of the microparticle can be improved as compared with that of a microparticle that is not eutectic.

[0029] The microparticle includes, for example, two or more kinds of materials exhibiting the same crystal structure. In this case, the crystal structure shows the same tendency throughout the microparticles of the alloy. This makes it possible to improve the stability of the generated microparticles.(Manufacturing device 100)

[0030] Next, an example of a manufacturing device 100 used in the method for producing microparticles in the present embodiment will be described. Fig. 1 is a schematic perspective view showing an example of the manufacturing device 100 in the present embodiment.

[0031] For example, as shown in Fig. 1, the manufacturing device 100 includes a laser device 1, a lens 2, a container 3, and a solution 4. The manufacturing device 100 may include, for example, a plurality of containers 3 and solutions 4 for one laser device 1.<Laser device 1>

[0032] The laser device 1 emits a pulse laser with a time width of, for example, about 10 -15< seconds. As the laser device 1, for example, a femtosecond pulse laser such as Astrella manufactured by COHERENT, which exhibits the following characteristics, can be used. Oscillation wavelength: 800 nm ± 20 nm Pulse width: 100 fs Energy: 5 to 9 mJ Repetition frequency: 100 Hz (output 0.5 to 0.9 W)

[0033] In addition to the above, for example, Spitfire Pro manufactured by Spectra-Physics, Inc. or the like is used as the laser device 1, and the device can be arbitrarily selected according to the application. Note that the laser emitted from the laser device 1 has energy of about several mJ, and for example, it is difficult to efficiently generate microparticles with energy of about several µJ used for laser processing or the like.<Lens 2>

[0034] The lens 2 focuses the laser emitted from the laser device 1. By using the lens 2, the light intensity can be increased for a specific region. In particular, by using the lens 2, the laser can be focused inside the solution 4 rather than the interface of the solution 4. As the lens 2, a known lens such as a condenser lens is used. By irradiating the solution 4 with the laser focused through the lens 2, the generation efficiency of microparticles can be improved.

[0035] The lens 2 may adjust a position where the laser is focused inside the solution 4, for example, by adjusting the shape of the lens 2, the distance from the solution 4, and the like. The lens 2 may use, for example, a variable focus lens to adjust the position where the laser is focused inside the solution 4 while the position of the lens 2 is fixed.<Container 3>

[0036] The container 3 contains the solution 4. As the container 3, a transparent material is used, and for example, a quartz cuvette is used. As the container 3, for example, a material having a lower absorption rate of a wavelength in the vicinity of 800 nm than an absorption rate of a wavelength in the vicinity of 400 nm is used. In this case, when laser irradiation is performed through the container 3, a decrease in generation efficiency of microparticles can be suppressed.<Solution 4>

[0037] The solution 4 contains the powder material 5 and the solvent 6. The solvent 6 suspends the powder material 5. The microparticles in the present embodiment are generated by irradiating the powder material 5 suspended in the solvent 6 with a laser emitted from the laser device 1.<Powder material 5>

[0038] The powder material 5 has a mid-diameter larger than, for example, that of the microparticle. The powder material 5 includes a plurality of particles having a finite particle diameter of, for example, 500 µm or less. The powder material 5 includes particles having a mid-diameter of, for example, 50 nm or more and 100 um or less.

[0039] The powder material 5 is directly reflected in the composition of microparticles to be generated, and thus can be arbitrarily set according to the type of microparticles to be generated. For example, when gold is used as the powder material 5, the microparticles generated include gold. In this case, for example, as compared with a method for producing microparticles by reducing a gold(III) chloride hydrate, generation of impurities that may adhere to the microparticles can be suppressed. This makes it possible to suppress deterioration in quality of the generated microparticles.

[0040] The powder material 5 includes, for example, one or more kinds of materials. For example, when the powder material 5 includes two or more kinds of materials, microparticles of an alloy containing each material can be generated. The powder material 5 contains a known metal atom such as nickel, platinum, gold, or titanium. The powder material 5 may include, for example, any of a pure metal, an alloy containing no non-metal, and a metal oxide as long as it contains a metal atom.

[0041] The powder material 5 includes, for example, a first powder material and a second powder material. The first powder material contains a first metal atom. The second powder material contains a second metal atom different from the first metal atom. The first powder material has, for example, a composition different from that of the second powder material. In this case, the ratio between the first powder material and the second powder material can be adjusted, and the composition ratio of metal atoms contained in the microparticle is easily controlled. This makes it possible to suppress variations in the composition ratio of metal atoms contained in the microparticle. For example, when the powder material 5 in which the molar ratio of nickel to platinum is 8: 2 is used, microparticles having a composition close to nickel: platinum = 8: 2 are easily generated.

[0042] The second powder material has, for example, a melting point higher than a melting point of the first powder material. That is, microparticles having characteristics of the first powder material and a melting point higher than that of the first powder material are generated. In this case, as compared with a case where microparticles are produced without using the second powder material, a temperature range in which the microparticles are stable can be expanded. This makes it possible to improve the stability of the generated microparticles.

[0043] The powder material 5 may include, for example, two or more kinds of materials exhibiting the same crystal structure. In this case, the crystal structure shows the same tendency throughout the microparticles of the generated alloy. This makes it possible to improve the stability of the microparticles.

[0044] For example, the crystal structures of iron, sodium, and potassium exhibit a body-centered cubic lattice. Therefore, when the powder material 5 includes a material including at least two or more of iron, sodium, and potassium, the crystal structure shows the same tendency throughout the microparticles of the generated alloy. In addition, for example, the crystal structures of nickel, aluminum, and calcium exhibit a face-centered cubic lattice. Therefore, when the powder material 5 includes a material including at least two or more of nickel, aluminum, and calcium, the crystal structure shows the same tendency throughout the microparticles of the generated alloy.(Embodiment: Method for producing microparticles)

[0045] Next, an example of a method for producing microparticles in the present embodiment will be described.

[0046] The method for producing microparticles includes, for example, an irradiation step. The method for producing microparticles may include at least one of an adjustment step and a stirring step.<Irradiation step>

[0047] In the irradiation step, a femtosecond pulse laser is focused, and the powder material 5 suspended in the solvent 6 is irradiated with the femtosecond pulse laser. In the irradiation step, for example, the femtosecond pulse laser is emitted from the laser device 1 to irradiate the powder material 5 suspended in the solvent 6. At this time, since the pulse width of the femtosecond pulse laser is shorter than the time during which the heat of the laser is transferred to the inside of the powder material 5, the femtosecond pulse laser does not thermally diffuse to other than the irradiation target. In this case, the energy of the laser is less likely to be consumed in a reaction other than generation of microparticles. This makes it possible to improve the generation efficiency of microparticles.

[0048] In the irradiation step, for example, the solvent 6 may also be irradiated in the process of focusing the femtosecond pulse laser and irradiating the powder material 5. At this time, radicals are generated in the solvent 6, but the method for producing microparticles in the present embodiment does not require a process of chemically reacting the radicals with the powder material 5. In this case, the amount of microparticles generated is less likely to be affected by the reaction rate between the radicals and the powder material 5 or the amount of radicals generated.

[0049] In the irradiation step, for example, the powder material 5 having a mid-diameter larger than that of the microparticle is irradiated with the femtosecond pulse laser. Therefore, as compared with the method for producing microparticles using reduction of metal ions, generation of impurities that are generated due to the reduction reaction of metal ions and may affect the microparticles can be suppressed. This makes it possible to generate microparticles whose quality is hardly deteriorated.

[0050] In the irradiation step, for example, the powder material 5 including the first powder material containing the first metal atom and the second powder material containing the first metal atom may be irradiated with the femtosecond pulse laser. At this time, microparticles of an alloy containing the first metal atom and the second metal atom are generated. In this case, the ratio between the first powder material and the second powder material can be adjusted, and the composition ratio of metal atoms contained in the microparticle is easily controlled. This makes it possible to generate microparticles in which variations in the composition ratio of metal atoms contained are suppressed.

[0051] In the irradiation step, for example, the powder material 5 including the first powder material and the second powder material having a melting point higher than that of the first powder material may be irradiated with the femtosecond pulse laser. That is, microparticles having characteristics of the first powder material and a melting point higher than that of the first powder material are generated. In this case, as compared with a case where microparticles are produced without using the second powder material, a temperature range in which the microparticles are stable can be expanded. This makes it possible to produce highly stable microparticles.

[0052] In the irradiation step, for example, the powder material 5 containing the first metal atom and the second metal atom may be irradiated with the femtosecond pulse laser to generate microparticles of a solid solution in which the first metal atom and the second metal atom are combined. In this case, a partial state change or chemical change of the microparticle is less likely to occur as compared with a microparticle that is not a solid solution. This makes it possible to produce highly stable microparticles.

[0053] In the irradiation step, for example, the powder material 5 containing the first metal atom and the second metal atom may be irradiated with the femtosecond pulse laser to generate eutectic microparticles in which the first metal atom and the second metal atom are combined. In this case, it is possible to produce microparticles with higher stability than microparticles that are not eutectic.<Adjustment step>

[0054] In the present embodiment, the powder material 5 contains a metal atom. At this time, depending on the wavelength of the laser with which the powder material 5 is irradiated, it is assumed that the laser is absorbed by the surface of the metal atom contained in the powder material 5 before reaching the focal point, and the laser with which the powder material 5 is irradiated is not efficiently consumed for generation of microparticles. That is, by adjusting the wavelength of the laser to be irradiated, the generation efficiency of microparticles can be improved.

[0055] In the adjustment step, for example, the oscillation wavelength of the laser emitted from the laser device 1 is adjusted to a wavelength that avoids the wavelength range absorbed by the metal atoms contained in the powder material 5. In this case, the energy of the laser is less likely to be absorbed by the metal atoms contained in the powder material 5, and is more likely to be efficiently consumed for generation of microparticles. This makes it possible to improve the generation efficiency of microparticles.

[0056] In the adjustment step, for example, the oscillation wavelength of the laser emitted from the laser device 1 may be adjusted using the wavelength conversion function of the laser device 1. The adjustment step may be performed during the irradiation step, may be performed at least either before or after the irradiation step, or may be performed a plurality of times.<Stirring step>

[0057] In the present embodiment, the powder material 5 is irradiated with the laser. At this time, it is necessary to focus the laser on the powder material 5, but it is assumed that the powder material 5 settles in the solvent 6 with the lapse of time, and the laser is hardly irradiated. That is, by stirring the solvent 6 so that the powder material 5 passes through the focal point of the laser, the generation efficiency of microparticles can be improved.

[0058] In the stirring step, the solvent 6 in which the powder material 5 is suspended is stirred. In the stirring step, the solvent 6 may be stirred while the irradiation step is performed. In this case, it is easy to uniformly irradiate the powder material 5 with the laser. This makes it possible to improve the generation efficiency of microparticles. In the stirring step, the solvent 6 may be stirred using a known agitator such as a stirrer. The stirring step may be performed at least either before or after the irradiation step.

[0059] For example, the stirring step makes it easy to maintain a state in which the powder material 5 in the solvent 6 is dispersed. That is, the powder material 5 in the solvent 6 is prevented from settling with the lapse of time. Therefore, the powder material 5 can be easily irradiated with the laser. As a result, the generation efficiency of microparticles can be improved.

[0060] For example, the stirring step makes it easy to maintain a state in which the first powder material containing the first metal atom and the second powder material containing the second metal atom in the solvent 6 are uniformly dispersed. Therefore, for the microparticle of the solid solution containing the first metal atom and the second metal atom, the composition ratio of each metal contained in the microparticle tends to be uniform. This makes it possible to produce microparticles with higher uniformity.

[0061] As a result, the microparticles and the colloidal solution in the present embodiment are generated.

[0062] According to the present embodiment, the method includes an irradiation step of irradiating the powder material 5 in the solvent 6 with the femtosecond pulse laser to generate microparticles containing a metal atom, and the powder material 5 has a mid-diameter larger than that of the microparticle. Therefore, as compared with the method for producing microparticles including reduction of metal ions, generation of impurities that may affect the microparticles can be suppressed. This makes it possible to suppress deterioration in quality of the generated microparticles.

[0063] Also, according to the present embodiment, the powder material 5 includes, for example, a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the microparticle is an alloy containing the first metal atom and the second metal atom. Therefore, the ratio between the first powder material and the second powder material can be adjusted, and the composition ratio of metal atoms contained in the microparticle is easily controlled. This makes it possible to suppress variations in the composition ratio of metal atoms contained in the microparticle.

[0064] In addition, according to the present embodiment, the melting point of the second powder material is higher than the melting point of the first powder material. That is, microparticles having characteristics of the first powder material and a melting point higher than that of the first powder material are generated. Therefore, as compared with a case where microparticles are produced without using the second powder material, a temperature range in which the microparticles are stable can be expanded. This makes it possible to improve the stability of the generated microparticles.

[0065] Further, according to the present embodiment, the microparticle is a solid solution in which the first metal atom and the second metal atom are combined. Therefore, a partial state change or chemical change of the microparticle is less likely to occur as compared with a microparticle that is not a solid solution. This makes it possible to further improve the stability of the generated microparticles.

[0066] In particular, according to the present embodiment, the colloidal solution includes the solvent 6 in which the microparticles are dispersed. Therefore, aggregation of the microparticles is easily suppressed as compared with a case where the microparticles are stored without using the solvent 6. This makes it possible to provide microparticles with maintained quality.

[0067] Although some embodiments of the present invention have been described, these embodiments have been 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 changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.Reference Signs List

[0068] 1Laser device 2Lens 3Container 3aOpening 4Solution 5Powder material 6Solvent 100Manufacturing device

Claims

1. A method for producing microparticles using a femtosecond pulse laser, the method comprising: an irradiation step of irradiating a powder material in a solvent with a femtosecond pulse laser to generate microparticles containing a metal atom, wherein the powder material has a mid-diameter larger than a mid-diameter of the microparticle and contains a metal atom.

2. The method for producing microparticles according to claim 1, wherein the powder material includes a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the microparticle is an alloy containing the first metal atom and the second metal atom.

3. The method for producing microparticles according to claim 2, wherein a melting point of the second powder material is higher than a melting point of the first powder material.

4. The method for producing microparticles according to claim 2 or 3, wherein the microparticle is a solid solution in which the first metal atom and the second metal atom are combined.

5. A colloidal solution comprising: the microparticles generated by the method for producing microparticles according to any one of claims 1 to 3; and a solvent in which the microparticles are dispersed.

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