Method for producing fine particles, and method for evaluating fine particles

Abstract

To provide a fine particle production method and a fine particle evaluation method which are capable of clarifying the quality of fine particles.SOLUTION: A method for producing fine particles comprising a plurality of materials includes a particle formation step of forming fine particles using a plurality of precursors and an evaluation step of evaluating the presence state of the materials contained in the fine particles. The evaluation step has an observation step of observing the fine particles to acquire a particle image, a detection step of acquiring a detection result showing a relation between the detection strength of the materials contained in the particle image and a detection position and a comparison step of comparing a relation between the detection strength and the detection position for each of the materials based on the detection result.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing fine particles containing a plurality of materials and a method for evaluating the fine particles.

Background Art

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

[0003] Patent Document 1 discloses a method for generating nanoparticles in which an ultrashort pulse laser beam is generated at a pulse repetition rate greater than 100 kHz and used to generate a stable nanoparticle colloid without adding a further stabilizing chemical substance. Further, Patent Document 1 discloses a method for generating nanoparticles in which large particles are subdivided by irradiation with the laser beam to obtain a particle size distribution mainly composed of nanoparticles and having the same composition as the metal alloy of the target material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in fine particles (alloy fine particles) containing a plurality of materials, the solid solubility of the contained materials may vary depending on manufacturing conditions and the like. However, a method for quantitatively evaluating the solid solubility of the fine particles has not been established. In this regard, Patent Document 1 neither describes nor suggests the above method. Therefore, a method for clarifying the quality of fine particles containing a plurality of materials is desired.

[0006] Therefore, the present invention was devised in view of the above-mentioned problems, and its objective is to provide a method for producing fine particles that can clearly define the quality of fine particles, and a method for evaluating fine particles. [Means for solving the problem]

[0007] According to the method for producing fine particles in the first invention, a plurality of materials are included. This shows the alloy. A method for producing fine particles, comprising: a particle formation step of forming fine particles using a precursor containing a plurality of materials; and an evaluation step of evaluating the state of existence of the plurality of materials contained in the fine particles, wherein the evaluation step is Using a scanning transmission electron microscope or a high-angle scattering dark-field scanning transmission electron microscope An observation step of observing the aforementioned fine particles and obtaining a particle image, Using known X-ray elemental analysis methods, Detection intensity of multiple materials included in the aforementioned particle image Obtain the detection intensity The process includes a detection step of obtaining a detection result that shows the relationship with the detection position, and a comparison step of comparing the relationship between the detection intensity and the detection position for each of the multiple materials based on the detection result. Furthermore, the comparison step involves comparing the spatial frequencies of each material contained in the fine particles based on the detection results, and deriving the difference in content of each material. It is characterized by the following:

[0008] According to the method for producing fine particles in the second invention, in the first invention, the observation step is characterized by acquiring the particle image using a scanning transmission electron microscope.

[0009] According to the method for producing fine particles in the third invention, in the first or second invention, the detection step is the detection intensity The X-ray scattering intensity intensity obtained for each material, Relationship with the aforementioned detection position A two-dimensional graph showing the relationship on two axes. The method is characterized by obtaining the approximation result obtained by performing an approximation method as the detection result.

[0010] According to the method for producing fine particles in the fourth invention, in the third invention, the comparison step is characterized by comparing the detection position associated with the maximum value of the detection intensity in the approximation result for each of the multiple materials.

[0012] The 5According to the method for producing fine particles in the invention, in the first or second invention, the comparison step is a measurement step of measuring the content of each of the multiple materials using X-ray diffraction, and the measurement results in the measurement step Based on the content measured by, Comparison results in the aforementioned comparison step Contents included The method is characterized by including a precision verification step for evaluating the precision of the method.

[0013] The 6 According to the method for evaluating fine particles in the invention, multiple materials are contained This shows the alloy. A method for evaluating fine particles, Using a scanning transmission electron microscope or a high-angle scattering dark-field scanning transmission electron microscope An observation process to observe fine particles and obtain particle images, Using known X-ray elemental analysis methods, Detection intensity of multiple materials included in the aforementioned particle image Obtain the detection intensity The system comprises a detection step of obtaining a detection result that shows the relationship with the detection position, and a comparison step of comparing the relationship between the detection intensity and the detection position for each of the multiple materials based on the detection result. The comparison step, based on the detection results, compares the spatial frequencies of each material contained in the fine particles and derives the difference in content of each material. It is characterized by the following: [Effects of the Invention]

[0014] First Invention ~ 6 According to the invention, the comparison step compares the relationship between the detection intensity and the detection position for each of several materials based on the detection results. Therefore, the degree of solid solubility of each material contained in the fine particles can be quantitatively evaluated. This makes it possible to clearly determine the quality of the fine particles.

[0015] In particular, according to the second invention, the observation step involves acquiring particle images using a scanning transmission electron microscope. Therefore, compared to other methods for acquiring particle images, the degree of solid solubility for each material can be obtained with high accuracy. This makes it possible to evaluate the degree of solid solubility with high accuracy.

[0016] In particular, according to the third invention, in the detection step, an approximation result obtained by performing an approximation method on the relationship between the detection intensity and the detection position is acquired as the detection result. Therefore, even when the shape of the fine particles differs from a perfect sphere by a sub-nanometer value in the profile signal of the particle image, a decrease in the comparison accuracy can be suppressed. As a result, it becomes possible to realize a stable evaluation of the solid solubility.

[0017] In particular, according to the fourth invention, in the comparison step, the detection positions associated with the maximum values of the detection intensity in the approximation result are compared for each of a plurality of materials. Therefore, the difference in the deviation of the solid solubility for each material contained in the fine particles can be easily evaluated. As a result, it becomes possible to easily evaluate the solid solubility.

[0019] In particular, according to the 5 invention, in the accuracy verification step, based on the measurement result in the measurement step, the accuracy of the comparison result in the comparison step is evaluated. That is, using the measurement result indicating the content ratio for each material contained in the entire fine particle, the accuracy of the comparison result obtained by comparing the existence states for each material contained in a part of the fine particle is evaluated. Therefore, it is possible to evaluate whether the comparison result is valid as a characteristic of the entire fine particle. As a result, it becomes possible to efficiently evaluate the solid solubility of the fine particle.

Brief Description of the Drawings

[0020] [Figure 1] FIG. 1 is a schematic perspective view showing an example of a manufacturing apparatus used in the method for manufacturing fine particles in the present embodiment. [Figure 2] FIG. 2 is a flowchart showing an example of the method for evaluating fine particles in the present embodiment. [Figure 3] FIG. 3 is a microscopic image showing an example of a particle image. [Figure 4] FIGS. 4(a) and 4(b) are schematic diagrams showing an example of the detection result based on the two-dimensional direction. [Figure 5]Figures 5(a) and 5(b) are schematic diagrams showing an example of detection results based on one dimension, and Figures 5(c) and 5(d) are schematic diagrams showing the relationship between detection results based on two dimensions and detection results based on one dimension. [Figure 6] Figures 6(a) and 6(b) are schematic diagrams showing an example of the approximation results. [Figure 7] Figures 7(a) and 7(b) are schematic diagrams showing an example of fine particles. [Figure 8] Figures 8(a) and 8(b) are schematic diagrams illustrating an example of the degree of deviation. [Figure 9] Figure 9 is a flowchart showing an example of a method for producing fine particles in this embodiment. [Modes for carrying out the invention]

[0021] Hereinafter, an example of a method for producing fine particles and a method for evaluating fine particles as embodiments of the present invention will be described with reference to the drawings.

[0022] (Embodiment: fine particles, colloidal solution) The fine particles in this embodiment can be used in electronic devices such as power generation elements, as well as in fields such as medicine and food. The fine particles may include metal fine particles or non-metallic fine particles. The fine particles can be used in energy fields such as power generation elements, and in electronic device fields such as conductive components. In addition to the above, the fine particles can be used in fields such as medicine as pharmaceuticals or cosmetics, materials as part of composite materials, and food. In particular, by performing any surface treatment (e.g., forming a coating) on ​​the surface of the fine particles, fine particles with additional functions can be produced, and their application to various uses is expected.

[0023] The fine particles include, for example, multiple particles having a particle size of 1 nm to 100 nm. The fine particles may also include particles having a median diameter (central diameter: D50) of 1 nm to 10 nm, or particles having an average particle size of 1 nm to 10 nm. The median diameter or average particle size can be measured, for example, using a particle size distribution analyzer. As a particle size distribution analyzer, for example, a particle size distribution analyzer using dynamic light scattering (e.g., Malvern Panalytical's Zetasizer Ultra) may be used.

[0024] In this embodiment, the fine particles represent a group of alloy particles, each containing multiple materials. The materials contained in the fine particles may include any metal such as gold or platinum, or materials such as carbon.

[0025] The colloidal solution in this embodiment is used in the same fields as fine particles. A colloidal solution is a state in which two or more substances, for example, fine particles, are mixed. A colloidal solution contains, for example, a solvent in which fine particles are dispersed. Any liquid such as water or toluene can be used as the solvent.

[0026] (Manufacturing equipment 100) Next, an example of a manufacturing apparatus 100 used in the method for producing fine particles in this embodiment will be described. Figure 1 is a schematic perspective view showing an example of a manufacturing apparatus 100 in this embodiment.

[0027] The manufacturing apparatus 100 comprises, for example, a laser device 1, a lens 2, a container 3, and a solution 4, as shown in Figure 1. The manufacturing apparatus 100 may also be equipped with multiple containers 3 and solutions 4 for, for example, one laser device 1.

[0028] <Laser device 1> Laser device 1 is, for example, 10 -15A pulsed laser with a time width of approximately a few seconds is emitted. As the laser device 1, for example, a femtosecond pulsed laser such as the Astrella manufactured by COHERENT can be used, exhibiting the following characteristics. Oscillation wavelength: 800nm ​​± 20nm Pulse width: 100 fs Energy: 5-9 mJ Repetition frequency: 100Hz (Output 0.5-0.9W)

[0029] In addition to the above, a laser device 1 such as the Spitfire Pro from Spectra Physics can be used and can be arbitrarily selected depending on the application. Note that the laser emitted from laser device 1 has an energy of several mJ, and it is difficult to efficiently generate fine particles with an energy of several μJ, for example, that is used in laser processing.

[0030] <Lens 2> Lens 2 focuses the laser emitted from the laser device 1. By using lens 2, the light intensity can be increased for a specific area. In particular, by using lens 2, the laser can be focused into the interior of solution 4 rather than at the interface of the solution 4. A known lens such as a focusing lens can be used as lens 2. By irradiating solution 4 with the laser focused through lens 2, the efficiency of fine particle generation can be improved.

[0031] <Container 3> Container 3 holds the solution 4. A transparent material is used for container 3, for example, a fused silica cuvette. For container 3, a material is used that has a lower absorption rate at a wavelength around 800 nm compared to a lower absorption rate at a wavelength around 400 nm. In this case, when irradiating with a laser through container 3, the decrease in the efficiency of fine particle generation can be suppressed.

[0032] <Solution 4> Solution 4 represents a liquid mixture of a precursor for fine particles and a solvent. Fine particles are generated when a laser is irradiated onto Solution 4. The precursor contains two or more materials, for example, two or more metal salts. The solvent may include, for example, water or alcohol. "Material" refers to the material contained in the fine particles, for example, atoms such as metal atoms.

[0033] The concentration of the metal salt in solution 4 is, for example, 1.0 × 10⁻⁶. -5 mol·dm -3 The above 1.0 × 10 -1 mol·dm -3 The range is as follows, and can be arbitrarily set depending on the intended use of the generated microparticles.

[0034] Metal salts contain known compounds that include metal ions, and can contain any material depending on the application. A metal salt contains one or more materials. For example, if a metal salt contains two or more materials, fine particles containing each material can be produced. Known metal salts such as HAuCl4·3H2O and H2PtCl6·6H2O can be used as metal salts.

[0035] For example, a metal salt may contain multiple materials that exhibit a negative oxidation-reduction potential (e.g., base metals). In this case, two types of materials, such as FeCl3·6H2O and NiCl2·6H2O, can be used as the metal salt. Even when producing fine particles of an alloy that is easily oxidized, the oxidation of the fine particles can be suppressed by using alcohol as a solvent and utilizing the oxidation reaction of the alcohol. This makes it possible to produce fine particles of alloys that were previously difficult to produce. Therefore, it becomes possible to further expand the applications of fine particles.

[0036] Note that "oxidation-reduction potential" refers to a known value, such as that listed in the Analytical Chemistry Data Book (Maruzen Publishing). Furthermore, "base metals" refer to metals whose oxidation-reduction potential of metal ions is classified as negative, and include lithium, potassium, calcium, sodium, magnesium, aluminum, zinc, iron, nickel, tin, and lead.

[0037] For example, a metal salt may contain two or more materials exhibiting the same crystal structure. In this case, since the crystal structure tends to be the same throughout the entire resulting alloy of fine particles, the stabilization of the fine particles can be improved. This makes it possible to enhance the stability of the fine particles.

[0038] For example, the crystal structures of iron, sodium, and potassium exhibit a body-centered cubic lattice. Therefore, by including a material containing at least two of these metal salts (iron, sodium, and potassium), the entire resulting alloy microparticles will exhibit the same crystal structure. Similarly, for example, the crystal structures of nickel, aluminum, and calcium exhibit a face-centered cubic lattice. Therefore, by including a material containing at least two of these metal salts (nickel, aluminum, and calcium), the entire resulting alloy microparticles will exhibit the same crystal structure.

[0039] The precursor may include, for example, solid particles. The solid particles include, for example, multiple particles having a finite particle diameter of 500 μm or less. The solid particles have a central diameter larger than the central diameter of the resulting fine particles. For example, the solid particles have a central diameter of about 50 nm to 100 μm.

[0040] The material of the solid particles, similar to the material of the metal salt described above, refers to the material contained in the fine particles, and for example, refers to atoms such as metal atoms. The precursor includes, for example, two or more types of solid particles, each containing a different material.

[0041] Since the solid particles directly reflect the material of the resulting microparticles, they can be arbitrarily set according to the type of microparticles to be generated. For example, if gold is used as the solid particle, the resulting microparticles will contain gold. In this case, unlike the metal salts mentioned above, the solid particles do not contain materials that are not included in the microparticles, such as chlorine. Therefore, the generation of unwanted materials that would otherwise be lost during the generation of microparticles can be suppressed.

[0042] The solvent may include, for example, known alcohols having a hydroxyl group. The solvent may also include monohydric alcohols such as ethanol, methanol, and 1-propanol. The solvent may also include compounds having, for example, an aldehyde group and at least one of a carboxyl group.

[0043] For example, the solvent may contain only alcohol. In this case, the factors that promote oxidation of the generated fine particles in solution 4 can be reduced. This makes it possible to suppress the deterioration of the quality of the fine particles.

[0044] (Embodiment: Evaluation Method) Next, an example of a method for evaluating fine particles in this embodiment will be described. Figure 2 is a flowchart of an example of a method for evaluating fine particles in this embodiment. The method for evaluating fine particles comprises an observation step S121, a detection step S122, and a comparison step S123.

[0045] <Observation process S121> Observation step S121 involves observing the fine particles and acquiring a particle image of the fine particles, as shown in Figure 3, for example. In observation step S121, a particle image can be acquired by observing the fine particles using, for example, a scanning transmission electron microscope (STEM). In this case, the degree of solid solubility for each material can be observed with higher precision compared to other methods of acquiring particle images. In addition to the above, a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) may also be used in observation step S121. The following describes the case using a STEM, particularly a HAADF-STEM.

[0046] For example, when observing fine particles stored in solution 4 using a STEM or similar device, the solution 4 containing the fine particles is dropped onto a microgrid with a carbon support film to fix the fine particles. This allows for the acquisition of particle images using the scanning transmission electron microscope or similar device described above.

[0047] <Detection process S122> The detection step S122 acquires detection results that show the relationship between the detection intensity of multiple materials contained in the particle image and their detection positions. In the detection step S122, the detection results can be acquired using known elemental analysis methods, such as energy dispersive X-ray spectroscopy (EDS).

[0048] In the detection step S122, the detection result may be obtained for, for example, one particle captured in the particle image (for example, the particle within the dashed frame in Figure 3), or for multiple particles. In the detection step S122, the detection result may be obtained after, for example, the particle image, or for example, simultaneously with the particle image. That is, the timing of the observation step S121 and the detection step S122 can be arbitrarily set according to the equipment used in each step.

[0049] The detection step S122 acquires a detection image showing the detection intensity at each detection position in a two-dimensional direction for the particle image, for example. In this case, the detection result is obtained that shows the relationship between the detection intensity (white circles, black circles) of each material A1 and A2 and the detection position (position X, position Y), as shown in Figures 4(a) and 4(b).

[0050] In addition to the above, the detection step S122 acquires detection results that show the detection intensity at each detection position in the one-dimensional direction for the particle image, for example. In this case, the detection results acquire detection results that show the relationship between the detection intensity of each material A1 and A2 and the detection position (position X), as shown in Figures 5(a) and 5(b). The detection results based on the one-dimensional direction correspond to the detection intensity along the AA line in the two-dimensional detection results shown in Figures 5(c) and 5(d). Note that the detection position in the detection results based on the one-dimensional direction may be in the direction along the AA line (position X) as described above, or in the direction intersecting the AA line (for example, position Y), and is arbitrary.

[0051] For example, in the detection step S122, the detection result may be obtained by performing an approximation method on the relationship between the detection intensity and the detection position. In this case, as shown in Figures 6(a) and 6(b), for example, the detection result will show the approximation result of performing an even function approximation on the detection intensity at each detection position in the one-dimensional direction. This makes it possible to suppress the decrease in comparison accuracy described later, even when the particle image contains noise, etc. The function used as the approximation method may be an even function or a known function whose position can be uniquely determined. The function used as the approximation method may be, for example, a Gaussian function or a function like the one in equation (1) below. Y=SQRT(r 2 -X 2 ) (1)

[0052] For example, in the detection step S122, the detection result may be obtained as the result of smoothing, which is the result of averaging the relationship between the detection intensity and the detection position. This makes it possible to suppress the decrease in comparison accuracy described later, even when the particle image contains noise, etc. The range of the detection position when performing averaging can be set arbitrarily according to the application.

[0053] <Comparison process S123> In comparison step S123, the relationship between detection intensity and detection location is compared for each of the multiple materials based on the detection results. In comparison step S123, the degree of solid solubility of each material contained in the fine particles can be quantitatively evaluated based on the comparison results for each of the multiple materials.

[0054] The comparison step S123 compares, for example, the characteristics of the detection intensity distribution in the detection results for multiple materials. Then, the comparison step S123 obtains the degree of deviation of the characteristics of the detection intensity distribution for each material as the comparison result. In this case, for example, a comparison result with a small degree of deviation indicates good solid solubility, and a comparison result with a large degree of deviation indicates poor solid solubility.

[0055] Furthermore, "solid solubility" indicates the degree to which multiple materials contained in a fine particle are uniformly present within the particle. By using "solid solubility," for example, as shown in Figures 7(a) and 7(b), it is possible to show the difference between fine particle PA containing material A1 and material A2 and fine particle PB containing material B1 and material B2.

[0056] For example, fine particles PB have areas where material B2 is densely concentrated (e.g., within the dashed frame in Figure 7(b)). In contrast, fine particles PA have a more uniform distribution of material A2 compared to fine particles PB. In this case, the degree of separation between materials A1 and A2 in fine particles PA tends to be smaller than the degree of separation between materials B1 and B2 in fine particles PB. Therefore, in the comparison step S123, the solid solubility of fine particles PA can be evaluated as better than that of fine particles PB.

[0057] Furthermore, the degree of solid solubility may indicate not only the relative degree described above, but also, for example, a degree based on a predetermined threshold. In addition, the degree of solid solubility may be expressed not only as the two values ​​of "good" and "bad" described above, but also as a numerical value such as a percentage or a multi-level scale. As a specific value, for example, if expressed as a percentage normalized by particle size, 5% or less may be considered "good".

[0058] For example, as shown in Figures 4(a) and 4(b), if detection results are obtained based on two-dimensional directions, the comparison step S123 may compare the detection intensity of each material A1 and A2 for each detection position. In this case, the comparison result will show the degree of deviation obtained by comparing, for example, the characteristics of the distribution of detection intensity in each material A1 and A2. By obtaining a comparison result showing the degree of deviation, the degree of solid solubility can be quantitatively evaluated. The degree of deviation can be obtained using known processing techniques such as matching processing.

[0059] For example, the comparison step S123 may include in the comparison results the results obtained by deriving the content of each material based on the detection results based on two dimensions. Alternatively, the comparison step S123 may consider the results obtained by counting the frequency of detection intensities included in the detection range in the detection results for each material as the content of each material.

[0060] For example, the comparison step S123 compares the detection positions associated with the maximum detection intensity in the approximate results for each of several materials. The comparison step S123 identifies the detection positions (A1t, A2t, B1t, B2t) associated with the maximum detection intensity, as shown in Figures 8(a) and 8(b), for example. Subsequently, the comparison step S123 compares the detection positions for each material contained in the fine particles (fine particles PA or fine particles PB) (materials A1 and A2 for fine particles PA, and materials B1 and B2 for fine particles PB). As a result of this comparison, the degree of deviation Ad is obtained in the case of fine particles PA, and the degree of deviation Bd is obtained in the case of fine particles PB.

[0061] The deviation degrees Ad and Bd obtained as a result of the above comparison correspond to the states of existence of materials A1, A2, B1, and B2, for example, shown in Figures 7(a) and 7(b). Therefore, the deviation degree Ad is smaller than the deviation degree Bd, and the solid solubility of fine particles PA can be evaluated as being better than that of fine particles PB.

[0062] Although the above explanation described the case where approximate results were obtained as the detection result, the same processing and evaluation of the degree of solid solubility can be performed even when smoothing results are obtained as the detection result.

[0063] In addition to the above, for example, the comparison step S123 may compare the spatial frequencies based on the detection results for each of the multiple materials. In this case, the difference in the content of each material contained in the fine particles can be derived from the difference in spatial frequencies. For example, if there are components with low spatial frequencies, the probability of the material being present at each detection position can be considered high, and therefore the content can be judged to be high. Conversely, as the presence of components with high spatial frequencies increases, the probability of the material being present at each detection position decreases, and therefore the content can be judged to be low. For this reason, by combining the degree of deviation described above with the comparison of spatial frequency components, it becomes possible to evaluate the degree of solid solubility considering the content.

[0064] Furthermore, the degree of solid solubility of the fine particles is defined as the difference between the processed signal obtained by applying even-function approximation to the profile signal from STEM observation and the center of each material, as described above.

[0065] The comparison step S123 may include, for example, a measurement step and an accuracy verification step. The measurement step may be performed, for example, before the observation step S121 or before the detection step S122, and is optional. The accuracy verification step is performed after obtaining the comparison results described above.

[0066] The measurement process involves measuring the content of each of several materials using X-ray diffraction. X-ray diffraction can be performed using a known X-ray diffraction apparatus.

[0067] The accuracy verification step evaluates the accuracy of the comparison results in the comparison step S123 based on the measurement results in the measurement step. For example, the content derived in the comparison step S123 is compared with the content measured using the X-ray diffraction method. Here, the content derived in the comparison step S123 is derived from specific particles and therefore does not take into account the variation between individual particles. In contrast, the content measured using the X-ray diffraction method is a measurement result targeting multiple particles and can therefore be considered as the content of all fine particles. For this reason, the accuracy of the content derived in the comparison step S123 can be evaluated using the content measured in the measurement step as a reference.

[0068] This completes the method for evaluating fine particles in this embodiment. When performing at least one of the above steps, electronic equipment including a arithmetic processing unit such as a CPU (Central Processing Unit) and a memory device such as RAM (Random Access Memory) may be used, and the arithmetic processing in each step can be performed using known processing techniques using electronic equipment.

[0069] (Embodiment: Method for producing fine particles) Next, an example of a method for manufacturing fine particles in this embodiment will be described. Figure 9 is a flowchart of an example of a method for manufacturing fine particles in this embodiment. The method for manufacturing fine particles includes, for example, a particle formation step S110 and an evaluation step S120, as shown in Figure 9. The evaluation step S120 includes the observation step S121, the detection step S122, and the comparison step S123 described above.

[0070] <Particle formation step S110> In the particle formation step S110, fine particles are formed using a precursor. Known techniques can be used as the method for forming these fine particles.

[0071] In the particle formation step S110, fine particles are formed, for example, by a method using a femtosecond pulsed laser. In this case, the degree of solid solubility of the formed fine particles can be easily set according to the application. Furthermore, femtosecond pulsed lasers can suppress the thermal energy acting on the fine particles compared to other lasers. Therefore, variations in the degree of solid solubility of the formed fine particles can be suppressed, and the accuracy of the degree of solid solubility of the fine particles in the evaluation step S120 can be improved.

[0072] The following describes the case where a femtosecond pulsed laser is used in the particle formation process S110.

[0073] The particle formation step S110 involves forming a solution 4, for example, by mixing a precursor and a solvent, in a container 3. For example, in the particle formation step S110, the solvent may be added in stages after the precursor is placed in the container 3. In this case, the concentration of the precursor can be easily adjusted.

[0074] Subsequently, in the particle formation step S110, a femtosecond pulsed laser is focused and irradiated onto solution 4. In the particle formation step S110, for example, when a femtosecond pulsed laser emitted from laser device 1 is irradiated onto solution 4, solvent molecules in solution 4 are decomposed and radicals are generated. Then, free electrons from the generated radicals reduce metal ions contained in the precursor, and fine particles are generated. In this way, fine particles based on the precursor are generated by irradiating solution 4 with a laser.

[0075] In the particle formation 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 the solvent can be suppressed compared to when the laser is irradiated from the interface between the solution 4 and the atmosphere. This makes it possible to improve safety when manufacturing fine particles.

[0076] <Evaluation Process S120> The evaluation step S120 evaluates the state of presence of multiple materials contained in the fine particles. The evaluation step S120 includes, for example, the observation step S121, detection step S122, and comparison step S123 described above, and is performed in the order of observation step S121, detection step S122, and comparison step S123. In the evaluation step S120, for example, the fine particles formed in the particle formation step S110 are separated from the solvent and observation step S121 is performed.

[0077] In the evaluation step S120, for example, the results of comparing the comparison results obtained in the comparison step S123 with a predetermined quality condition such as a threshold value are used to determine whether the formed particles are good or defective. In addition to the threshold value, any index according to the product specifications can be used as a quality condition.

[0078] This generates the fine particles and colloidal solution in this embodiment.

[0079] According to this embodiment, the comparison step S123 compares the relationship between the detection intensity and the detection position for each of several materials based on the detection results. This makes it possible to quantitatively evaluate the degree of solid solubility of each material contained in the fine particles. This makes it possible to clearly determine the quality of the fine particles.

[0080] Furthermore, according to this embodiment, the observation step S121 acquires particle images using a scanning transmission electron microscope. Therefore, compared to other methods for acquiring particle images, the degree of solid solubility for each material can be acquired with high accuracy. This makes it possible to evaluate the degree of solid solubility with high accuracy.

[0081] Furthermore, according to this embodiment, the detection step S122 obtains an approximate result as the detection result by performing an approximation method on the relationship between the detection intensity and the detection position. Therefore, even when the shape of the fine particles differs from a perfect sphere to a sub-nanometer value in the profile signal of the particle image, a decrease in comparison accuracy can be suppressed. This makes it possible to achieve stable evaluation of the degree of solid solubility.

[0082] Furthermore, according to this embodiment, the comparison step S123 compares the detection position associated with the maximum detection intensity in the approximate results for each of the multiple materials. Therefore, it is possible to easily evaluate the differences in the bias of the degree of solid solubility for each material contained in the fine particles. This makes it possible to easily evaluate the degree of solid solubility.

[0083] Furthermore, according to this embodiment, the comparison step S123 compares the spatial frequencies based on the detection results for each of the multiple materials. Therefore, the differences in the content of each material contained in the fine particles can be easily evaluated. This makes it possible to evaluate the degree of solid solubility while taking the content into account.

[0084] Furthermore, according to this embodiment, the accuracy verification step evaluates the accuracy of the comparison results in the comparison step S123 based on the measurement results in the measurement step. That is, the accuracy of the comparison results, which compare the state of existence of each material contained in a part of the fine particles, is evaluated using the measurement results that show the content rate of each material contained in the entire fine particles. Therefore, it is possible to evaluate whether or not the comparison results are valid as characteristics of the entire fine particles. This makes it possible to efficiently evaluate the degree of solid solubility of the fine particles.

[0085] The microparticles produced by the microparticle manufacturing method described above, and the microparticles evaluated by the microparticle evaluation method, can be expected to have the following applications, for example. For instance, in research on artificial photosynthesis, several materials have been proposed for the microparticles used, including gold, platinum, and gold-silver alloys. Applying the microparticles described above to these examples could provide variables for optimizing the characteristics of artificial photosynthesis. Similarly, they can also be applied to electronic components such as multilayer ceramic capacitors and electrodes. Currently, materials being researched for microparticles include metals such as gold, silver, copper, tin, and nickel, as well as barium titanate (BaTiO3) and strontium titanate (SrTiO3). In particular, a concern is the large variation in solid solubility of the microparticle materials used in research. Therefore, a method for quantitatively evaluating the quality of microparticles may be required during the mass production consideration stage toward commercialization. In this regard, the microparticle manufacturing method and microparticle evaluation method described above can be used to clearly define the quality of the microparticles.

[0086] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0087] 1: Laser device 2: Lens 3: Container 4: Solution 100: Manufacturing equipment S110: Particle formation process S120: Evaluation process S121: Observation process S122: Detection process S123: Comparison process

Claims

1. A method for producing fine particles exhibiting an alloy containing multiple materials, A particle formation process in which fine particles are formed using a precursor containing multiple materials, An evaluation step for evaluating the state of existence of multiple materials contained in the fine particles, Equipped with, The aforementioned evaluation process is, An observation step of observing the fine particles using a scanning transmission electron microscope or a high-angle scattering dark-field scanning transmission electron microscope and acquiring a particle image, A detection step involves obtaining the detection intensity of multiple materials contained in the particle image using a known elemental analysis method utilizing X-rays, and obtaining a detection result that shows the relationship between the detection intensity and the detection position. Based on the detection results, a comparison step is performed to compare the relationship between the detection intensity and the detection position for each of the multiple materials. Includes, The comparison step involves comparing the spatial frequencies of each material contained in the fine particles based on the detection results, and deriving the difference in content of each material. A method for producing fine particles characterized by the following.

2. The observation step involves acquiring the particle image using a scanning transmission electron microscope. A method for producing fine particles according to claim 1, characterized by the above.

3. The detection step involves obtaining an approximate result as the detection result by applying an approximation method to a two-dimensional graph that shows the relationship between the X-ray scattering intensity intensity for each material, obtained as the detection intensity, and the detection position on two axes. A method for producing fine particles according to claim 1 or 2, characterized by the above.

4. The comparison step involves comparing the detection position associated with the maximum value of the detection intensity in the approximate result for each of the multiple materials. A method for producing fine particles according to claim 3, characterized by the above.

5. The aforementioned comparison step is, A measurement step of measuring the content of each of the multiple materials using X-ray diffraction, A precision verification step that evaluates the accuracy of the content percentage included in the comparison results in the comparison step, based on the content percentage measured in the measurement results in the measurement step, including A method for producing fine particles according to claim 1 or 2, characterized by the above.

6. A method for evaluating fine particles representing an alloy containing multiple materials, An observation step in which fine particles are observed using a scanning transmission electron microscope or a high-angle scattering dark-field scanning transmission electron microscope and particle images are obtained, A detection step involves obtaining the detection intensity of multiple materials contained in the particle image using a known elemental analysis method utilizing X-rays, and obtaining a detection result that shows the relationship between the detection intensity and the detection position. Based on the detection results, a comparison step is performed to compare the relationship between the detection intensity and the detection position for each of the multiple materials. Equipped with, The comparison step involves comparing the spatial frequencies of each material contained in the fine particles based on the detection results, and deriving the difference in content of each material. A method for evaluating fine particles characterized by [specific characteristics].

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