JP2013129903A - Method for producing inorganic nanoparticle and inorganic nanoparticle dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing inorganic nanoparticles which maintains a stably dispersed state for a long period of time in a solvent without using a chemical reagent or the like.SOLUTION: The method for producing inorganic nanoparticles is provided, which uses a liquid-phase laser ablation apparatus including: a laser oscillator 10 for generating a laser beam L; a light condensing means 12 for condensing the laser beam; a treatment container 13 for holding a solvent 14; the solvent 14 held in the treatment container 13; and a powdery target 15 added into the solvent 14 and comprising at least one inorganic material selected from the group consisting of copper, noble metal, an oxide of them, and an alloy including at least one of them. While stirring the solvent 14, the target 15 in the solvent 14 is irradiated with the laser beam L by performing light condensing irradiation of the laser beam L on an interface I between a liquid phase and a gas phase from the gas phase side such that fluence on the interface I is 0.70 J/cmor more, thereby producing the inorganic nanoparticles in the solvent 14.

Description

  The present invention relates to a method for producing inorganic nanoparticles and an inorganic nanoparticle dispersion.

  Conventionally, nano-sized particles (nanoparticles) have been formed using various methods using chemical methods and physical methods. However, the conventional method for producing nanoparticles using a chemical method has a problem in that there are materials that are difficult to form nanoparticles. In addition, in the conventional method for producing nanoparticles using a physical method, there is a problem that the size of the obtained particles cannot be sufficiently reduced and impurities are easily mixed. Therefore, as a method for producing nanoparticles, a method employing so-called liquid phase laser ablation has attracted attention from the viewpoint of sufficiently suppressing the mixing of impurities.

  Such liquid phase laser ablation is said to be possible in principle to make all materials nano-sized as long as the material absorbs laser light. Nowadays, various methods for producing nanoparticles of inorganic materials by liquid phase laser ablation of inorganic materials have been proposed.

See, for example, T.P. 7840-7847 of Applied Surface Science (vol. 253) published in 2007. Okada, J .; Suehiro et al., “Synthesis of nano-structured materials by laser-ablation and their application to sensors” (Non-Patent Document 1), THE JOURNAL OF PHYSICAL CHEMISTRY (vol. 115) published in 2011, pages 5073-5083. The G. described. Cristoforetti et al., “Production of Palladium Nanoparticles by
Pulsed Laser Ablation in Water and Their Characterization (Non-Patent Document 2), Journal of Laser Micro / Nanoengineering (vol. 5) published in 2010, pages 192-196. Nishi, A. In Takeichi et al.'S paper “Fabrication of Palladium Nanoparticles by Laser Ablation in Liquid” (Non-patent Document 3), a liquid phase laser ablation is performed by irradiating a target made of palladium in a solvent with laser light. A method of forming the nanoparticles is described.

  Furthermore, Nishitetsuhei's manuscript “Preparation of Compound Nanoparticles by Laser Irradiation to Mixed Powder Targets” described in the Proceedings of the 71st Annual Meeting of the Japan Society of Applied Physics published on August 30, 2010 (Non-Patent Document 4) ) ", A target made of palladium powder is placed at the bottom of a processing vessel holding the solvent, and the target is irradiated with laser light through the bottom of the processing vessel in the solvent. A method of forming palladium nanoparticles is disclosed.

  However, in the conventional method for producing inorganic nanoparticles as described in Non-Patent Documents 1 to 4, inorganic material particles are formed in a solvent, and the inorganic nanoparticles are dispersed in the solvent. In some cases, it is possible to obtain a dispersion (colloid). However, the nanoparticles in the dispersion easily aggregate over time, and if a chemical reagent such as a surfactant is not used, it is inorganic. The dispersibility of the nanoparticle dispersion could not be maintained sufficiently stably for a long time.

T. Okada, J .; Suehiro, “Synthesis of nano-structured materials by laser-ablation and their application to sensors”, Applied Surface Science, 2007, vol. 253, 7840-7784 G. Cristoforetti et al., “Production of Palladium Nanoparticles by Pulsed Laser Ablation in Water and Their Characterization”, THE JOURNAL OF PHYSICAL CHEMISTRY, 2011, vol. 115, 5073-5083 T. Nishi, A. Takeichi et al., “Fabrication of Palladium Nanoparticles by Laser Ablation in Liquid”, Journal of Laser Micro / Nanoengineering, 2010, vol. 5, pages 192-196 Seihei Nishi, “Preparation of Compound Nanoparticles by Laser Irradiation to Mixed Powder Targets”, Proceedings of the 71st JSAP Academic Lecture Meeting, published on August 30, 2010

  The present invention has been made in view of the above-described problems of the prior art, and is an inorganic nanoparticle capable of maintaining a state of being stably dispersed in a solvent for a sufficiently long period of time without using a chemical reagent or the like. It aims at providing the manufacturing method of the inorganic nanoparticle which can manufacture particle | grains, and the inorganic nanoparticle dispersion liquid obtained using the method.

As a result of intensive studies to achieve the above object, the present inventors have found that the inorganic nanoparticle is dispersed in the dispersion when the method for producing inorganic nanoparticles as described in Non-Patent Documents 1 to 4 as described above is used. The reason why the nanoparticles could not be dispersed stably for a long period of time was examined. When inorganic materials were used as targets, they were adopted in the method for producing inorganic nanoparticles as described in Non-Patent Documents 1 to 4. Under the conditions of the liquid phase laser ablation, the nanoparticles of the inorganic material could not be sufficiently charged depending on the irradiation condition of the laser beam, and it was assumed that the particles would aggregate. And in view of such points, the present inventors have conducted further research, as a result, a laser oscillator for generating laser light, and a condensing means for condensing the laser light, Using a liquid phase laser ablation apparatus comprising a processing container for holding a solvent, a solvent held in the processing container, and a target made of a predetermined powdery inorganic material added to the solvent While stirring the solvent, focused irradiation with laser light from the gas phase side (from the gas phase side to the surface of the solvent so that the fluence at the interface between the liquid phase and the gas phase is 0.70 J / cm ² or more) Surprisingly, the target in the solvent is irradiated with the laser light, and surprisingly, the target is dispersed stably in the solvent for a long time without using a chemical reagent. The inventors have found that it is possible to produce inorganic nanoparticles capable of maintaining the state, and have completed the present invention.

That is, the method for producing inorganic nanoparticles of the present invention includes a laser oscillator for generating laser light, a condensing means for condensing the laser light, a processing container for holding a solvent, and the processing At least one selected from the group consisting of a solvent held in a container, and copper, a noble metal, an oxide thereof, and an alloy containing at least one of copper and a noble metal added to the solvent Using a liquid phase laser ablation apparatus comprising a powdery target made of an inorganic material of
While stirring the solvent, the solvent is condensed and irradiated from the gas phase side to the interface such that the fluence at the interface between the liquid phase and the gas phase is 0.70 J / cm ² or more. The target is irradiated with the laser light to form nanoparticles of the inorganic material in the solvent.

In the method for producing inorganic nanoparticles of the present invention, the fluence at the interface between the liquid phase and the gas phase of the laser light is 0.70 to 200 J / cm ² (more preferably 0.70 to 100 J / cm ² , Preferably it is 2.0-100 J / cm < ² >).

  In the method for producing inorganic nanoparticles of the present invention, the target is a powder made of an inorganic material formed by separately irradiating a laser beam in a liquid phase, and the solvent is stirred. More preferably, the target powder is dispersed in the solvent prior to the step.

The inorganic nanoparticle dispersion of the present invention is an inorganic nanoparticle dispersion in which inorganic nanoparticles are dispersed in a solvent,
UV-visible light absorption with respect to the initial inorganic nanoparticle dispersion within 2 hours after production and the inorganic nanoparticle dispersion which has been allowed to pass for more than one year after production under conditions of atmospheric pressure and temperature of 20 to 25 ° C. Each of the spectrum measurements is performed, and any two different points selected from the wavelength range in which the absorbance value of the absorption spectrum of the initial inorganic nanoparticle dispersion in the wavelength range of 200 to 800 nm is a positive value. The wavelengths are the first wavelength and the second wavelength, respectively, and the ratio of the absorbance of the light at the two wavelengths ([absorbance of the light of the first wavelength] / [absorbance of the light of the second wavelength]), respectively. When obtained, both the absorbance value of the light of the first wavelength and the absorbance of the light of the second wavelength of the inorganic nanoparticle dispersion liquid that has passed for more than one year after production are both positive values, and The strength ratio of the initial inorganic nanoparticle dispersion Change rate ([initial strength ratio] / [after 1 year or more] of the strength ratio (strength ratio after 1 year or more) of the inorganic nanoparticle dispersion that has been passed for more than 1 year after production Intensity ratio]) is in the range of 0.9 to 1.1,
It is characterized by. Here, the “first wavelength” is selected from the wavelength region in which the absorbance value of the absorption spectrum of the initial inorganic nanoparticle dispersion liquid in the 200 to 800 nm wavelength region is a positive value. The wavelength of the second wavelength is an arbitrary wavelength of the other selected from the wavelength region.

  The inorganic nanoparticle dispersion of the present invention has an average particle size of the inorganic nanoparticles of 0.5 to 20 nm and a standard deviation of the particle size of the inorganic nanoparticles of 3.0 nm or less. It is preferable. As described above, the inorganic nanoparticle dispersion of the present invention is preferably a sufficiently uniform nanoparticle in a solvent, and such a nanoparticle adopts the above-described method for producing the inorganic nanoparticle of the present invention. Thus, it can be suitably manufactured.

  The inorganic nanoparticle dispersion liquid of the present invention is preferably obtained using the method for producing inorganic nanoparticles of the present invention.

  According to the present invention, an inorganic nanoparticle production method capable of producing inorganic nanoparticles capable of maintaining a state of being stably dispersed in a solvent for a sufficiently long period of time without using a chemical reagent or the like. In addition, it is possible to provide an inorganic nanoparticle dispersion obtained by using the method.

It is a schematic diagram which shows one Embodiment of the liquid phase laser ablation apparatus which can be utilized suitably for the manufacturing method of the inorganic nanoparticle of this invention. 2 is a transmission electron microscope (TEM) photograph of palladium nanoparticles obtained in Example 1. FIG. 2 is a graph showing a UV-visible light absorption spectrum of a dispersion of palladium nanoparticles obtained in Example 1 (2 hours after production). It is a schematic diagram which shows the liquid phase laser ablation apparatus utilized in the comparative example 2. 3 is a transmission electron microscope (TEM) photograph of palladium nanoparticles obtained in Comparative Example 2. It is a graph which shows the UV-visible light absorption spectrum of the dispersion liquid (2 hours after manufacture) obtained by Comparative Examples 2-3. It is a schematic diagram which shows the liquid phase laser ablation apparatus utilized in the comparative example 4. 4 is a transmission electron microscope (TEM) photograph of palladium nanoparticles obtained in Comparative Example 4. It is a graph which shows the UV-visible light absorption spectrum measured immediately after manufacture (after 2 hour passage after manufacture) and after 1 year passage about the dispersion liquid of the gold nanoparticle obtained in Example 4. It is a graph which shows the UV-visible light absorption spectrum measured immediately after manufacture (after 2 hours progress after manufacture) and after 2 days progress regarding the dispersion liquid of the gold nanoparticle obtained in Comparative Example 5. It is a graph which shows the UV-visible light absorption spectrum measured about the dispersion liquid of the platinum nanoparticle obtained in Example 5 immediately after manufacture (after 2 hours progress after manufacture) and after 1 year progress. It is a graph which shows the UV-visible light absorption spectrum measured immediately after manufacture (after 2 hours progress after manufacture) and after 1 year progress regarding the dispersion liquid of the copper nanoparticle obtained in Example 6. FIG. It is a graph which shows the UV-visible light absorption spectrum measured immediately after manufacture (after 2 hours progress after manufacture) and after 1 year progress regarding the dispersion liquid of the copper oxide nanoparticle obtained in Example 7. FIG. It is a graph which shows the UV-visible light absorption spectrum measured immediately after manufacture (after 2 hours progress after manufacture) and after 1 year progress regarding the dispersion liquid of the alloy nanoparticle obtained in Example 8. FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[Production method of inorganic nanoparticles]
The method for producing inorganic nanoparticles of the present invention includes a laser oscillator for generating laser light, a condensing means for condensing the laser light, a processing container for holding a solvent, and the inside of the processing container And at least one inorganic selected from the group consisting of a copper, a noble metal, an oxide thereof, and an alloy containing at least one of copper and a noble metal added to the solvent. Using a liquid phase laser ablation device comprising a powdery target made of material,
While stirring the solvent, the solvent is condensed and irradiated from the gas phase side to the interface such that the fluence at the interface between the liquid phase and the gas phase is 0.70 J / cm ² or more. The target is irradiated with the laser light to form nanoparticles of the inorganic material in the solvent.

  First, a preferred embodiment of a liquid phase laser ablation apparatus that can be used in the method for producing inorganic nanoparticles of the present invention will be described. FIG. 1 shows a schematic diagram of an embodiment of a liquid phase laser ablation apparatus that can be suitably used in the method for producing inorganic nanoparticles of the present invention.

  The liquid phase laser ablation apparatus shown in FIG. 1 includes a laser oscillator 10, a mirror 11, a condensing means 12, a processing container 13, a solvent 14 added to the processing container 13, a target 15, and a stirring device 16. Are provided. In FIG. 1, symbol G indicates the atmospheric gas in the processing container 13, symbol I indicates the interface between the liquid phase (phase of the solvent 14) and the gas phase (phase of the atmospheric gas G), and symbol L indicates the laser. Show light. In such a liquid phase laser ablation apparatus, when the powder target 15 is irradiated with laser light, the solvent 14 is stirred so that the target 15 is sufficiently dispersed in the solvent 14. Laser light L emitted from the laser oscillator 10 is reflected by the mirror 11 disposed on the optical path, and then passes through the condensing means 12 so that the liquid phase and gas phase interface I ( The surface of the solvent 145 is focused and irradiated, and the target 15 in the solvent 14 is irradiated with the laser light L.

  The laser oscillator 10 is not particularly limited as long as it can generate the laser light L, and a laser light generator that can irradiate pulsed laser light having a pulse width of 80 femtoseconds to 100 nanoseconds is suitably used. Can be used. Among such laser light generators, the pulse width is 80 femtoseconds to 100 nanoseconds, the wavelength is 19 nm to 10.6 μm (more preferably 248 nm to 10.6 μm), and per pulse. A laser light generator capable of irradiating pulsed laser light having an energy of 50 mJ to 5 J (more preferably 200 mJ to 2 J, still more preferably 400 to 800 mJ) is more preferable. Examples of such a laser oscillator 10 include a YAG laser device and an excimer laser device, among which a YAG laser device is more preferable. The mirror 11 is not particularly limited, and a known reflector or the like (for example, a mirror) can be used as appropriate.

The condensing means 12 is not particularly limited, and a known condensing lens can be used as appropriate. Among them, the fluence of the laser light L irradiated to the interface I is 0.70 J / cm ² or more (preferably 0. 7 to 200 J / cm ² , more preferably 0.7 to 100 J / cm ² , still more preferably ^{2 to} 100 J / cm ² , and particularly preferably 40 to 70 J / cm ² ). It can be suitably used.

  The processing container 13 is capable of allowing laser light to enter the container, and can hold the solvent 14 in the container 13. In the present embodiment, a container 13 having an opening at a portion where laser light is introduced is used, and the light collecting means 12 is disposed in the opening to seal the inside of the container, and the light is transmitted through the light collecting means 12. The laser beam is designed to be introduced into the container 13. Such a processing vessel 13 may be any vessel capable of holding the solvent 14 in the vessel 13 and capable of performing laser ablation processing by dispersing the target in the liquid phase. A known container (for example, a glass volumetric flask) that can be used for the above can be used as appropriate.

  The material or the like of the processing container 13 is not particularly limited, and the material or the like can be appropriately changed according to the target design. For example, a resin container or a metal container can be used as appropriate. it can. In addition, since impurities due to the material of the container 13 may be mixed during laser ablation, from the viewpoint of preventing this, a glass or resin made of glass depending on the conditions of the laser light L to be used, etc. A product made of acrylic resin (such as an acrylic resin) can be used as appropriate.

  Further, the shape and size of the processing container 13 are not particularly limited, and can be an arbitrary shape or the like in consideration of the type of the light collecting unit 12 to be used and the optical system. Moreover, in order to prevent such a processing container 13 from moving when performing laser ablation, the container 13 itself may be appropriately fixed.

  As the solvent 14, a known solvent that can be used in the liquid phase laser ablation method can be appropriately used. Such a solvent is not particularly limited, and water, an organic solvent, and an inorganic solvent can be appropriately used. Examples thereof include ethanol, isopropanol, xylene, kerosene, methanol, water, acetone, and liquid nitrogen.

  The target 15 is in a powder form and is made of at least one inorganic material selected from the group consisting of copper, noble metals, oxides thereof, and alloys containing at least one of copper and noble metals. It will be. Examples of such noble metals include platinum (Pt), rhodium (Rh), palladium (Pd), ruthenium (Ru), osmium (Os), iridium (Ir), gold (Au), and silver (Ag). From the viewpoint that finer and more uniform particles can be formed, platinum (Pt), palladium (Pd), gold (Au), and rhodium (Rh) are preferable, and platinum (Pt), palladium (Pd), Gold (Au) is more preferable, and palladium (Pd) is particularly preferable.

  Further, the oxides of copper and noble metal are not particularly limited, but from the viewpoint of ease of production, etc., oxides of copper (Cu), silver (Ag), and palladium (Pd) are more preferable, and copper (Cu) Further, an oxide of silver (Ag) is more preferable.

  Further, the alloy containing at least one of copper and noble metal is not particularly limited as long as it contains at least one metal of copper and noble metal. From the viewpoint of the stability of the particles, those containing at least one of the noble metals are preferred, and the noble metals in such alloys are more preferably Pd, Pt, Au, Rh, Ag, and Pt, Pd, Au Is particularly preferred. Furthermore, as said alloy, other metals other than at least 1 sort (s) of copper and a noble metal may be included. Examples of such other metals include iron, titanium, chromium, manganese, cobalt, nickel, aluminum, yttrium, vanadium, zirconium, niobium, molybdenum, and tantalum. Further, as other metals other than copper and noble metals, iron, chromium, nickel, manganese, and cobalt are preferable from the viewpoints of stability in a solvent (for example, water), application (applicability), and safety. Iron, chromium and nickel are more preferable.

  In the alloy, the content of the copper and noble metal (total amount of copper and noble metal in the alloy) is preferably 1% by mass or more, more preferably 3% by mass or more, and more preferably 5 to 90% by mass. Those are particularly preferred. When the content of at least one metal of the copper and the noble metal is less than the lower limit, the effect of adding the metal element tends to hardly appear in the properties of the nanoparticles. Here, “alloy” means a metal compound composed of two or more kinds of metal elements, and as such an alloy, various metal elements contained in the alloy are mixed at the atomic level. What is in the state which was made is more preferable. The state of such an alloy can be confirmed by determining whether or not a diffraction line attributed to a single compound is shown by XRD measurement.

  Examples of such an alloy include Pd—Fe alloy, Pd—Cr alloy, Pd—Ni alloy, Pt—Au alloy, Au—Ag alloy, Pt—Rh alloy, Pd—Mn. Alloy, Pd—Co alloy, Cu—Ag alloy, Cu—Au alloy, etc. can be used as appropriate. From the viewpoint of ease of production, cost, and applicability, Pd—Fe alloy, Pt— An alloy of Au, an alloy of Pd—Ni, an alloy of Cu—Au, and an alloy of Cu—Ag are preferable.

  Moreover, it does not restrict | limit especially as a manufacturing method of such an alloy, After obtaining the melt | dissolution mixture which melt | dissolved the raw material of 2 or more types of metal species containing at least 1 sort (s) of copper and a noble metal, the melt | dissolution mixture The method of manufacturing by solidifying may be used, or the method of manufacturing by a known chemical synthesis method may be used. A method for obtaining such a molten mixture is not particularly limited, and a known method capable of dissolving the raw materials of the two or more metal species can be appropriately employed. For example, an arc melting furnace is used. An arc melting method may be employed to produce the melt mixture. Further, in such a melting step, the various metals of the raw metal may be dissolved separately, or the various metals of the raw metal may be simultaneously dissolved and mixed in the same furnace. Further, the method for solidification is not particularly limited, and a known method can be appropriately used. As such an alloy, commercially available materials may be used as appropriate.

  Of these inorganic materials, Cu, Pd, Pt, Au, and oxides and alloys thereof are preferable from the viewpoint of stability and applicability, and Cu, Pd, Pt, Au, CuO, and at least Pd. The alloy containing is preferred. Further, such inorganic materials may be used alone or in combination of two or more.

  As such a powdery target (inorganic material), one having an average primary particle diameter of 0.02 to 200 μm is preferably used, and one having 0.02 to 170 μm is more preferable. In addition, when the inorganic material is palladium, it is particularly preferable to use a material having an average primary particle size of 0.5 to 4 μm, and it is more preferable to use a material having a mean primary particle size of 0.5 to 1.5 μm. When the average primary particle diameter of the particles of such powdery target (powdered inorganic material) is less than the lower limit, the ablation efficiency tends to decrease. On the other hand, when the upper limit is exceeded, the powder becomes heavier and dispersed. This tends to be difficult. In addition, the average primary particle diameter of such a powdery target (powdered inorganic material) is obtained by measuring and averaging the particle diameter of 100 or more primary particles with a scanning electron microscope (SEM). be able to. Moreover, as such a powdery inorganic material, a commercially available material (for example, trade name “Palladium / powder” manufactured by Niraco Co., Ltd.) may be appropriately used.

  The amount of the target (powdered inorganic material) 15 added is preferably 5 to 20 mg / mL, more preferably 12 to 20 mg / mL with respect to the solvent 14. When the amount of the target (powdered inorganic material) 15 added is less than the lower limit, the ablation efficiency tends to decrease. On the other hand, when the upper limit is exceeded, droplets and powder are scattered by stirring, and the lens It tends to adhere to the surface.

  The target 15 is a powder of the inorganic material formed by irradiating a laser beam in the liquid phase, and before performing the step of stirring the solvent 14 (of the inorganic material). It is preferred that the target powder be present in the processing vessel dispersed in the solvent at a stage prior to the step of forming the nanoparticles. That is, the target 15 is a powdery target (inorganic material) formed by performing laser ablation in the liquid phase separately from the liquid phase laser ablation method performed in the method for producing inorganic nanoparticles of the present invention. It is preferable to use the colloid formed during the treatment (a colloid composed of the solvent used in the production of the target 15 and the powder of the inorganic material formed and dispersed in the solvent) as it is. In this way, the target 15 may be separately “liquid phase laser ablation treatment” (hereinafter referred to as “pretreatment” so that the distinction from the liquid phase laser ablation method performed in the method for producing inorganic nanoparticles of the present invention is clear). The colloid obtained by the pretreatment is directly used as the target 15 and the solvent 14 in the processing container of the liquid phase laser ablation apparatus according to the present invention. In this case, since the method for producing inorganic nanoparticles of the present invention can be performed on the colloidal target 15, the vicinity of the interface is formed when forming the inorganic material nanoparticles. The ratio of the target existing in a dispersed state tends to be higher. Since it is possible to irradiate a more efficient laser light is, it is possible to more efficiently form the inorganic nanoparticles. From the viewpoint of using the colloid obtained by the pretreatment as it is in the method for producing inorganic nanoparticles of the present invention, the pretreatment (liquid phase laser ablation treatment) for producing the target (inorganic material powder) 15 is performed. As the solvent used in the above, it is preferable to use the same solvent as the solvent 14 according to the present invention. Moreover, the processing container at the time of performing such pretreatment can use the thing similar to the processing container 13 concerning the above-mentioned this invention suitably. And you may utilize the processing container and solvent which were used for pre-processing as the above-mentioned processing container 13 and the solvent 14 concerning this invention. The “colloid” formed by such pretreatment is not limited to long-term dispersion stability or the like as long as the powder of the inorganic material is dispersed in the solvent. . That is, when the known conditions of liquid phase laser ablation are adopted, the generated particles can be charged by appropriately changing the laser ablation conditions to maintain the dispersion state of the particles in the liquid phase to some extent. Although possible, as described above, the particles easily aggregate and precipitate over time. The period required for such agglomeration varies depending on the type of inorganic material, and may be several days or several hours. Therefore, if the powder of the inorganic material obtained by performing the pretreatment is used within the time in which the colloidal state is maintained, the target powder is dispersed in the solvent from the stage before stirring. The state (colloidal state) can be achieved. Further, the colloid obtained by performing the pretreatment referred to here preferably maintains the dispersed state of particles during dissolution without using a chemical reagent or the like.

  As a liquid phase laser ablation method employed in the pretreatment for producing such a target 15, a powder of an inorganic material can be produced and the powder is dispersed in a solvent (colloid) Any known liquid phase laser ablation method can be used as appropriate, and is not particularly limited. For example, Non-Patent Document 4 (No. 4 issued on Aug. 30, 2010) can be used. The method described in Setsuhei Nishi, “Preparation of Compound Nanoparticles by Laser Irradiation to Mixed Powder Targets” described in the 71th JSAP Scientific Lecture Collection, and Japanese Patent Application Laid-Open No. 2011-161379 The methods described in the above may be adopted as appropriate. Further, the liquid phase laser ablation apparatus used for such pretreatment is not particularly limited as long as it can perform a known liquid phase laser ablation process, and a known liquid phase laser ablation apparatus (for example, The apparatus described in Non-Patent Document 4 and Japanese Patent Application Laid-Open No. 2011-161379 may be used as they are. Thus, in the liquid phase laser ablation treatment (pretreatment) for producing the target (inorganic material powder) 15, the inorganic material powder can be produced and the powder can be dispersed in the liquid phase. A known liquid phase laser ablation apparatus and method may be appropriately used.

  As a method that can be suitably used as such a pretreatment method, for example, a laser oscillator for generating laser light and a treatment for holding the solvent having a bottom through which the laser light can be transmitted. A container and a material for manufacturing a target (target manufacturing material) disposed on the bottom of the processing container, and the laser beam transmitted through the bottom of the processing container is applied to the target manufacturing material Using a liquid phase laser ablation apparatus (for example, an apparatus as shown in FIG. 7 described later) in which the processing container is disposed so as to be irradiated, the laser light is applied to the target manufacturing material. Liquid phase laser ablation treatment is performed by irradiating through the bottom of the container. Get (powdered inorganic materials) 15 to produce, may be a powder of the target to employ a method of dispersing in the liquid phase. Hereinafter, a method suitable as such a pretreatment method will be described.

  The target manufacturing material used for such pretreatment is not particularly limited as long as it is made of the inorganic material, and it is made of a bulk material even if it is made of particles of the inorganic material. However, it is preferable to use a particulate material from the viewpoint of efficiently obtaining a colloid (dispersion) state. In addition, as such a target manufacturing material, a material that satisfies the above-described target 15 conditions (a material that is already a powdered inorganic material, such as commercially available particles) may be used as it is. By subjecting the particles and the like to liquid phase laser ablation treatment as the pretreatment, the powder can be further refined and used as the target 15. Moreover, as the target 15 obtained by performing such a pretreatment as a refinement process, an average primary particle diameter of 0.02 to 2 μm is preferable, and a target of 0.05 to 1 μm is more preferable. When the average primary particle size is less than the lower limit, the ablation efficiency tends to decrease. On the other hand, when the upper limit is exceeded, the particles are not efficiently supplied to the interface during stirring, and the efficiency tends to decrease. Moreover, as a processing container used for such a pre-processing, what has a bottom part which can permeate | transmit a laser beam is preferable, and a round bottom flask, an eggplant type flask, a pear type flask etc. can be utilized suitably.

Further, the laser oscillator for oscillating the laser beam used for such pretreatment is not particularly limited, but it is preferable to use the same laser oscillator as that described above. In such pretreatment, the laser irradiation conditions are appropriately set so that the obtained target (inorganic material powder) 15 is in a colloidal state dispersed in the solvent (liquid phase) used in the pretreatment. It is preferable. That is, such laser irradiation conditions vary depending on the type of inorganic material, and cannot be generally stated. For example, for materials for manufacturing targets (particles of inorganic materials or bulk bodies, etc.) Thus, a condition of irradiating laser light oscillated from a laser oscillator in the liquid phase for 0.5 to 5 hours may be employed. In this case, the fluence of laser light applied to the surface of the target manufacturing material (inorganic material particles or bulk body) in the liquid phase is adjusted to 0.3 to 4 J / cm ^2. May be. If the fluence and the irradiation time are less than the lower limit, it tends to be difficult to form a colloid in which the powder of the inorganic material formed by the pretreatment is dispersed in the solvent. Since the damage threshold of the container is exceeded, the possibility of the container being broken tends to increase. Further, the amount of the target production material used for such pretreatment is not particularly limited, and suitable conditions vary depending on the type of the inorganic material, but the density in the solvent is 2 to 20 g / m ³ is preferred. When such a density is outside the above range, it tends to be difficult to obtain an inorganic material powder in a colloid (dispersed liquid) state dispersed in a solvent.

  The stirring device 16 is a device (so-called “magnetic stirrer”) such as a stirring bar (star rubber) 16A and a device 16B capable of rotating the stirring bar. As such a stirring device 16, the rotational speed of the stirring bar is 300 rpm or more (more preferably 600 rpm or more, so that the powdery target (powdered inorganic material) 15 can be more sufficiently dispersed. More preferably, a material that can be set to 1000 rpm) can be used. Such a stirring device 16 is not particularly limited, and a known one can be used as appropriate, and a commercially available one may be used.

Next, using the liquid phase laser ablation apparatus shown in FIG. 1 as an example, the fluence at the interface between the liquid phase and the gas phase is 0.70 J / cm ² or more while stirring the solvent. A method of irradiating the laser beam to the interface from the gas phase side to the interface to irradiate the target with the laser beam to form inorganic material nanoparticles in the solvent will be described. .

  In such a method, laser light is condensed and irradiated onto the interface I while stirring the solvent 14. Such a stirring method of the solvent 14 is not particularly limited as long as the target 15 can be sufficiently dispersed in the solvent 14 by stirring, and the rotational speed of the stirring bar 16A is set to 300 rpm. It is preferable to employ a method of stirring the solvent 14 by the above (more preferably 600 rpm to 2400 rpm, still more preferably 800 rpm to 1400 rpm). If the rotational speed is less than the lower limit, the target 15 cannot be sufficiently dispersed in the solvent 14, and it becomes difficult to uniformly perform laser ablation on the powder target 15, and uniform inorganic There is a tendency that nanoparticles of the material cannot be formed. On the other hand, when the upper limit is exceeded, droplets or powder tends to scatter and adhere to the lens or the like (powder or the like adheres to the lens). If the laser beam is irradiated in this state, the lens tends to be easily damaged).

When condensing and irradiating such laser light, the energy density (fluence) per pulse of the laser light L at the interface I is 0.70 J / cm ² or more using the condensing means 12. must preferably be 0.70~200J / cm ² as such fluence, more preferably, to 0.70~100J / cm ^2, be 2.0~100J / cm ² More preferably, it is especially preferable to set it as 40-70 J / cm < ² >. When the fluence of the laser beam L at the interface I between the liquid phase and the gas phase is less than the lower limit, the uniformity of the particle size of the obtained nanoparticles is not sufficient, and it is formed in a solvent. The nanoparticles easily aggregate over time, and it becomes impossible to obtain a dispersion in which the nanoparticles are sufficiently stably dispersed over a long period of time. Furthermore, when the fluence of the laser beam L is less than the lower limit, the amount of particles generated is reduced and the production efficiency is lowered. On the other hand, when the above upper limit is exceeded, it tends to cause the scattering of droplets and the mixing of impurities due to the ablation of the stirring bar.

  The condensing shape (irradiation surface shape) of the laser light L at the interface I is not particularly limited as long as the energy density (fluence) of the laser light L after condensing satisfies the above conditions, The diameter may be about 0.5 to 9 mm (more preferably, the diameter is about 0.5 to 5 mm).

  In addition, as the atmospheric gas G in the processing vessel 13 that forms a gas phase when irradiating the laser beam L in this way, air, nitrogen, argon, helium, oxygen, or the like can be used as appropriate. From the viewpoint of simplicity of the apparatus, it is preferable to use air or inert gas (nitrogen, argon, etc.).

  Further, the pressure condition of the gas phase when irradiating the laser beam L in this manner is preferably 1 to 2 atmospheres (atm), and more preferably 1 to 1.5 atmospheres (atm). If the pressure in the gas phase is less than the lower limit, the solvent tends to vaporize. On the other hand, if the pressure exceeds the upper limit, the plume generated on the gas phase side is deformed, and the particle size of the generated particles is reduced. Uniformity tends to decrease. Furthermore, the temperature condition for irradiating the laser beam L is not particularly limited, but is preferably about room temperature (25 ° C.).

  As described above, the liquid phase laser ablation apparatus as described above is used to focus and irradiate the laser light from the gas phase side to the interface I while stirring the solvent 14, thereby existing at the interface of the solvent 14 or in the vicinity thereof. By irradiating the target 15 with the laser beam L, the target 15 can be subjected to laser ablation processing in the liquid phase. That is, in such a method, first, the solvent 14 is stirred by the stirring device 16 to sufficiently disperse the particles of the target 15. Then, while the solvent 14 is stirred in this way (the particles of the target 15 are sufficiently dispersed), the laser light L is emitted from the laser oscillator 10, and the mirror (reflector) 11 disposed on the optical path. Reflect by. Next, the laser beam L reflected from the mirror 11 passes through the condensing means 12 and enters the processing container 13, and is condensed and applied to the interface I between the liquid phase and the gas phase. As a result, the target 15 existing on or near the surface of the solvent 14 is irradiated with the laser light L, and the liquid phase laser ablation process is performed at and near the interface between the liquid phase and the gas phase. Is formed. And the nanoparticle formed by such a laser ablation process is cooled by the solvent which exists around, and is easily stabilized.

In the present invention, the laser beam L is condensed at an interface I (surface of the solvent 14) between the liquid phase and the gas phase so that the energy density (fluence) is 0.70 J / cm ² or more. It is considered that the plume (a group of fine particles released from the target) generated by ablation is affected by both the solvent 14 forming the liquid phase and the atmospheric gas G forming the gas phase. In the process of producing nanoparticles, the ion species produced by the ablation of the solvent 14 and the atmospheric gas G adhere to the surface of the nanoparticles, so that sufficiently uniform nanoparticles of inorganic material can be obtained, The formed inorganic nanoparticles are charged and can be dispersed stably for a long period of time by electrostatic repulsion without using chemical reagents. The inventors speculate.

  And by such a method, an average particle diameter is 0.5-20 nm (more preferably 0.5-15 nm), and the standard deviation of the particle diameter of the said inorganic nanoparticle is 3.0 nm or less (more preferably). It is also possible to produce inorganic nanoparticles having a diameter of 2.0 nm or less, more preferably 1.5 or less. For example, when palladium is used as the inorganic material, the average particle size is 3 to 8 nm (more preferably 4 to 6 nm) and the standard deviation of the particle size is 3.0 nm or less (more preferably 2.0 nm or less, It is also possible to form nanoparticles with very high uniformity, such as 1.5 or less. When an alloy is used as the inorganic material, the average particle size is 0.5 to 20 nm (more preferably 1 to 10 nm) and the standard deviation of the particle size is 2.0 nm or less (more preferably 1.5 nm). It is also possible to form nanoparticles with very high uniformity, such as 1.0 or less. As described above, the method for producing inorganic nanoparticles of the present invention can also be used as a method capable of efficiently producing sufficiently uniform palladium nanoparticles in a solvent.

  In addition, the inorganic material nanoparticles thus obtained in the solvent are sufficiently stably dispersed in the solvent for a long period of time without using a chemical reagent or the like. And according to such a method, it becomes possible to manufacture efficiently the inorganic nanoparticle dispersion liquid of this invention mentioned later. In addition, the inorganic nanoparticle dispersion obtained in this manner tends to be able to maintain sufficient dispersibility even when concentrated using an evaporator or the like. Furthermore, the nanoparticles obtained by completely evaporating the solvent tend to be viscous.

  As described above, the preferred embodiment of the method for producing inorganic nanoparticles of the present invention has been described with reference to FIG. 1, but the method for producing inorganic nanoparticles of the present invention and the liquid phase laser ablation that can be used for the method. The apparatus is not limited to the above embodiment.

  For example, although the mirror 11 is used in the embodiment shown in FIG. 1 (the above embodiment), a liquid phase laser ablation apparatus according to the present invention includes a laser oscillator for generating laser light, and the laser light. Condensing means for condensing, a processing container for holding a solvent, a solvent held in the processing container, and a target made of the powdered inorganic material added to the solvent The mirror 11 may not be used. In this case, the laser oscillator 10 and the processing container 13 may be arranged so that the laser light L is directly incident on the processing container 13.

  In the above embodiment, a so-called magnetic stirrer is used as the stirring device 16. However, in the liquid phase laser ablation device according to the present invention, the means for stirring the solvent is limited to the stirring device 16 described above. First, any solvent can be used as long as the target can be sufficiently dispersed by stirring the solvent. For example, a stirring device that rotates a stirring blade with a motor or the like, or an ultrasonic wave is applied to the solvent. A stirrer or the like for stirring can be used as appropriate.

[Inorganic nanoparticle dispersion]
The inorganic nanoparticle dispersion of the present invention is an inorganic nanoparticle dispersion in which inorganic nanoparticles are dispersed in a solvent,
UV-visible light absorption with respect to the initial inorganic nanoparticle dispersion within 2 hours after production and the inorganic nanoparticle dispersion which has been allowed to pass for more than one year after production under conditions of atmospheric pressure and temperature of 20 to 25 ° C. Each of the spectrum measurements is performed, and any two different points selected from the wavelength range in which the absorbance value of the absorption spectrum of the initial inorganic nanoparticle dispersion in the wavelength range of 200 to 800 nm is a positive value. The wavelengths are the first wavelength and the second wavelength, respectively, and the ratio of the absorbance of the light at the two wavelengths ([absorbance of the light of the first wavelength] / [absorbance of the light of the second wavelength]), respectively. When obtained, both the absorbance value of the light of the first wavelength and the absorbance of the light of the second wavelength of the inorganic nanoparticle dispersion liquid that has passed for more than one year after production are both positive values, and The strength ratio of the initial inorganic nanoparticle dispersion Change rate ([initial strength ratio] / [after 1 year or more] of the strength ratio (strength ratio after 1 year or more) of the inorganic nanoparticle dispersion that has been passed for more than 1 year after production Intensity ratio]) is in the range of 0.9 to 1.1,
It is characterized by.

  Such a solvent is the same as the solvent described in the above-described method for producing inorganic nanoparticles of the present invention.

  In addition, the inorganic nanoparticle dispersion of the present invention passed (stored) for more than one year after production under the conditions of the initial inorganic nanoparticle dispersion within 2 hours after production and atmospheric pressure and a temperature of 20 to 25 ° C. UV-visible light absorption spectrum measurement is performed on the inorganic nanoparticle dispersion liquid (preferably within one month after one year has passed), and the initial inorganic nanoparticle dispersion in the wavelength region of 200 to 800 nm is performed. Two different wavelengths selected from the wavelength region in which the absorbance value of the absorption spectrum of the liquid is a positive value are defined as the first wavelength and the second wavelength, respectively. When the ratio of absorbance ([absorbance of light of the first wavelength] / [absorbance of light of the second wavelength]) was determined, the absorbance of the light of the first wavelength and the second wavelength of each dispersion liquid. The light absorbance values of all are positive, and The change in the strength ratio (initial strength ratio) of the inorganic nanoparticle dispersion at the initial stage and the strength ratio (strength ratio after one year or more) of the inorganic nanoparticle dispersion that has been passed for more than one year after production. The rate ([initial strength ratio] / [strength ratio after 1 year or more]) is in the range of 0.9 to 1.1. When the value of such a change rate is outside the above range, the dispersibility of the nanoparticles in the dispersion is low, and the inorganic nanoparticles aggregate to cause precipitation and the like. Dispersibility cannot be maintained over a period of time. Thus, in the inorganic nanoparticle dispersion liquid of the present invention, the absorbance value of the absorption spectrum of the initial inorganic nanoparticle dispersion liquid in the wavelength region of 200 to 800 nm of the UV-visible light absorption spectrum is a positive value. The ratio at which the absorbances of light at two different wavelengths selected from the wavelength region to be changed with time is used as an index of dispersibility. In addition, the value of the rate of change is more preferably in the range of 0.9 to 1.0 because the dispersion satisfies higher dispersion stability.

  As a UV-visible light absorption spectrum measuring method for the inorganic nanoparticle dispersion for obtaining such a change rate of the intensity ratio, the following method is adopted. That is, when measuring the UV-visible light absorption spectrum, first, a measurement sample is formed by adjusting the concentration of the inorganic nanoparticle dispersion liquid (initial and after one year or more) used for the measurement to 0.1 mg / mL. Subsequently, a temperature condition of 25 ° C. is applied to the measurement sample by using a UV-visible light absorption spectrum measurement device (for example, trade name “UV-Visible Near-Infrared Spectrophotometer (UV-3600)” manufactured by Shimadzu Corporation). Below, the method of measuring the absorption spectrum is adopted. Then, from the absorption spectrum thus determined, in the initial inorganic nanoparticle dispersion, the absorbances of light at two different wavelengths in the wavelength region where the absorbance value of the absorption spectrum is a positive value are respectively obtained. Then, the intensity ratio is obtained. Note that the use of the intensity ratio at any two points as an index of dispersibility in this way makes it possible to infer the dispersion stability of the particles based on the absorbance of light at any two different wavelengths. It is because it becomes. Further, two different wavelengths (first and second wavelengths) selected from wavelength ranges in which the intensity of the absorption spectrum of the initial inorganic nanoparticle dispersion liquid in the wavelength range of 200 to 800 nm is a positive value. The dispersibility is inferred based on the absorbance at the position of the second wavelength). However, when the intensity of the absorption spectrum of the initial inorganic nanoparticle dispersion becomes 0, or becomes negative due to noise, error, etc. Since the region is considered to be a wavelength region where absorption by particles of the inorganic material is not confirmed in the first place, it is difficult to use as an index for inferring dispersibility stability. The wavelength is selected from a wavelength region in which the intensity of the absorption spectrum of the initial inorganic nanoparticle dispersion is a positive value. In addition, in such a measurement, when the absorbance value becomes zero after one year or when it becomes a negative value due to noise or error, the particles are aggregated and the dispersibility is very low. Or particles are aggregated, settled and not dispersed. For this reason, in the present invention, it is a condition that the absorbance values of the light of the two arbitrary wavelengths of each dispersion liquid are positive values. Thus, a dispersion liquid in which the absorbance value of light of any wavelength becomes 0 or negative after one year has low dispersibility and satisfies the conditions of the inorganic nanoparticle dispersion liquid of the present invention. It will not be.

  In addition, as such two arbitrary wavelengths, when a peak of plasmon absorption is confirmed in the absorption spectrum of the initial inorganic nanoparticle dispersion, the wavelength region in the vicinity of the peak (preferably the peak maximum) It is preferable to select at least one point (more preferably two points) from a wavelength range within ± 20 nm from the wavelength of the value, and when the peak of plasmon absorption is confirmed, the wavelength at the peak maximum and minimum It is preferable to select the wavelengths as the two arbitrary points.

  For example, when the metal species of the inorganic material in the dispersion is palladium and the particle diameter is about 1 to 5 nm, the peak of plasmon absorption is confirmed at a position with a wavelength of about 200 nm to 400 nm. It is preferable to select a wavelength of 265 nm and a wavelength of 383 nm as two different wavelengths. When the inorganic material is palladium, the ratio of the absorbance of light having a wavelength of 265 nm and the absorbance of light having a wavelength of 383 nm is adopted as the value of the intensity ratio. This is because the dispersion stability of the particles can be estimated more efficiently by the absorbance. Thus, when the metal species of the inorganic material is palladium, the palladium nanoparticle dispersion liquid in the initial stage within 2 hours after production and atmospheric pressure, at a temperature of 20 to 25 ° C., 1 year or more after production. UV-visible light absorption spectrum measurement was performed on the elapsed (stored) palladium nanoparticle dispersion liquid (preferably within 1 month after 1 year), respectively, and the absorbance of light at a wavelength of 265 nm and the wavelength of 383 nm When the ratio of the light intensity to the light absorbance ([absorbance of light at 265 nm] / [absorbance of light at 383 nm]) is obtained, the absorbance of light at a wavelength of 265 nm and the light at a wavelength of 383 nm of each dispersion liquid are obtained. The absorbance values are all positive values, and the initial strength ratio (initial strength ratio) of the palladium nanoparticle dispersion and the palladium that has passed for more than one year after production. The rate of change ([initial strength ratio] / [strength ratio after one year or more]) of the strength ratio (strength ratio after one year or more) of the particle dispersion is in the range of 0.9 to 1.1. It is preferable that. When the value of the rate of change is a value outside the above range, the dispersibility of the nanoparticles in the dispersion is low, and the palladium nanoparticles aggregate to cause precipitation or the like, Dispersibility cannot be maintained over a long period of time. Thus, in the inorganic nanoparticle dispersion liquid of the present invention in which the inorganic material is palladium, the intensity ratio between the absorbance of light having a wavelength of 265 nm and the absorbance of light having a wavelength of 383 nm in the UV-visible light absorption spectrum ([265 nm The ratio of change in light absorbance] / [absorbance of light at 383 nm] over time is preferably used as an index of dispersibility, and the value of such change rate indicates that the dispersion has a higher dispersion stability. The range of 0.9 to 1.0 is more preferable because it satisfies the requirement. In such a measurement, when the inorganic material is palladium, the value of the absorbance of light at a wavelength of 265 nm or the light of a wavelength of 383 nm of the dispersion at the initial stage and after the lapse of one year has been zero. If the value is negative due to noise or error, it can be said that the particles are agglomerated and the dispersibility is very low, or the particles are agglomerated, settled and not dispersed. The preferable condition is that each of the dispersions has a positive value for the absorbance of light having a wavelength of 265 nm and the absorbance of light having a wavelength of 383 nm. Thus, when the inorganic material is palladium, a dispersion in which the absorbance value of light having a wavelength of either 265 nm or 383 nm is 0 or a negative value has low dispersibility, and It does not satisfy the suitable conditions for the inorganic nanoparticle dispersion. As mentioned above, regarding the case where the metal species of the inorganic material in the dispersion is palladium, the wavelength suitable as the wavelength of any two points has been described, but in the following, the case where the inorganic material in the dispersion is another metal species Is also briefly described. For example, when the metal species of the inorganic material is gold (Au), the peak of plasmon absorption is confirmed at a position with a wavelength of about 500 nm to 600 nm. Therefore, the wavelength of 550 nm and 600 nm as the two different wavelengths. It is preferable to select the wavelength. Furthermore, when the metal species of the inorganic material is copper (Cu), the plasmon absorption peak is confirmed at a position with a wavelength of about 300 nm to 400 nm and a position with a wavelength of about 550 nm to 700 nm. It is preferable to select a wavelength of 350 nm and a wavelength of 700 nm as the wavelength. Furthermore, as such suitable two different wavelengths (first and second wavelengths), for example, when the inorganic material is platinum (Pt), 350 nm and 700 nm are used, and the inorganic material is rhodium (Rh). It is preferable to select 400 nm and 600 nm in the case, 300 nm and 600 nm in the case of osmium (Os), and 400 nm and 700 nm in the case of iridium (Ir), respectively. In addition, plasmon absorption may not be confirmed depending on the type of inorganic material (for example, copper oxide). However, in the case of a dispersion liquid in which such plasmon absorption is not confirmed, the wavelengths of 450 nm and 500 nm may be arbitrarily selected. It is preferable to select as two wavelengths (first wavelength and second wavelength) having different points. In the case of a dispersion in which plasmon absorption is not confirmed, if a positive absorbance is not confirmed at either or both of the positions of 450 nm and 500 nm with respect to the initial dispersion, the positive value What is necessary is just to change the wavelength from which an absorbance is not confirmed to another wavelength from which the positive absorbance is confirmed.

  Moreover, it is preferable that the inorganic nanoparticle (dispersoid) in the inorganic nanoparticle dispersion liquid of the present invention has an average particle diameter of 0.5 to 20 nm. When such an average particle diameter is less than the lower limit, the particle surface is difficult to be charged and the stability of the colloid is lowered. On the other hand, when the average particle diameter exceeds the upper limit, the influence of sedimentation due to gravity becomes larger than the stabilization of the colloid due to charging, and the colloid becomes unstable. Further, from the same viewpoint as the reason for the upper limit value and the lower limit value described above, the upper limit value of the average particle diameter of the inorganic nanoparticles is more preferably 15 nm (more preferably 10 nm). The lower limit value of the average particle diameter is more preferably 0.5 nm. For the same reason, particularly when the inorganic material is palladium, the average particle diameter is preferably 3 to 8 nm, and the upper limit of the average particle diameter is 6 nm (more preferably 5 nm). More preferably, the lower limit is more preferably 4 nm. Moreover, when an inorganic material is Au, it is preferable that an average particle diameter is 5-15 nm, and it is more preferable that the upper limit of the average particle diameter is 13 nm. When the inorganic material is an alloy, the average particle diameter is preferably 0.5 to 20 nm, the upper limit value of the average particle diameter is more preferably 5 nm, and the lower limit value is More preferably, it is 0.5 nm. Regarding other metal species of the inorganic material, for example, when the inorganic material is copper (Cu) or an oxide thereof, the average particle diameter is preferably 0.5 to 10 nm, and the inorganic material is platinum (Pt ), The average particle size is preferably 5 to 15 nm.

  Furthermore, the inorganic nanoparticles preferably have a particle diameter standard deviation of 3.0 nm or less. When such a standard deviation exceeds the upper limit, the uniformity of the particles is lowered, which causes a decrease in colloidal stability and nanoparticle characteristics. From the same viewpoint, the standard deviation of the particle size of the inorganic nanoparticles is more preferably 2.0 nm or less (more preferably 1.5 or less, particularly preferably 0.5 to 1.0 nm). In particular, when the inorganic material forming the inorganic nanoparticles is an alloy, by adopting the above-described method for producing inorganic nanoparticles of the present invention, the standard deviation is 1.0 nm or less. For example, when the inorganic material forming the inorganic nanoparticles is an alloy, the standard deviation is preferably 1.0 nm or less.

  In addition, the average particle diameter of such nanoparticles and the standard deviation of the particle diameter are obtained by measuring the particle diameter of arbitrary 100 or more primary particles with a transmission electron microscope (TEM), and measuring the particle diameter. Calculate based on Furthermore, the particle diameter here refers to the maximum diameter of a circumscribed circle when the particles are not spherical.

  Moreover, as the inorganic nanoparticle dispersion liquid of the present invention, the first wavelength and the second wavelength light absorbance (initial absorbance) of the initial inorganic nanoparticle dispersion liquid, and more than one year after the production Each of the first wavelength and the second wavelength is based on the absorbance values (absorbances after one year or more) of the first wavelength and second wavelength of the passed inorganic nanoparticle dispersion. The rate of change in absorbance at the position of the wavelength (formula: [initial absorbance]-[absorbance after lapse of one year or more] / [absolute value of the value obtained by calculating the initial absorbance]) is measured (for example, When the first wavelength is 350 nm and the second wavelength is 700 nm, the change rate of the absorbance of the light at the first wavelength (350 nm) and the absorbance of the light at the second wavelength (700 nm) When measuring the rate of change) It is preferable to satisfy the condition that the rate of change at at least one wavelength is 0.20 or less (more preferably 0.15 or less, more preferably 0.10 or less, particularly preferably 0.09 or less). More preferably, the wavelength satisfies the above conditions. Inorganic nanoparticle dispersions with such a rate of change exceeding the upper limit at both the first and second wavelengths are considered to have a large change in the intensity of the absorption spectrum and a large change in dispersibility. It is considered that the dispersion stability over a long period is not always sufficient. As described above, the inorganic nanoparticle dispersion of the present invention preferably satisfies the above conditions from the viewpoint of sufficiently high dispersion stability over a long period of time.

Moreover, as an inorganic nanoparticle dispersion liquid of this invention, the following formula | equation:
[Second rate of change in intensity ratio] = ([Initial intensity ratio] − [Intensity ratio after 1 year]) / [Initial intensity ratio]
When the second change rate of the intensity ratio is obtained as the absolute value of the calculated value, the second change rate of the intensity ratio is preferably 0.20 or less, and preferably 0.10 or less. preferable. When the second rate of change of the intensity ratio exceeds the upper limit, dispersion stability over a long period tends not to be sufficient.

  Moreover, such an inorganic nanoparticle dispersion of the present invention can be easily formed by utilizing the method for producing inorganic nanoparticles of the present invention. Therefore, the inorganic nanoparticle dispersion liquid of the present invention is preferably obtained using the above-described method for producing inorganic nanoparticles of the present invention. The inorganic nanoparticle dispersion liquid of the present invention in which nanoparticles of an inorganic material are dispersed in a solvent is formed by forming the inorganic material nanoparticles in a solvent by the above-described inorganic nanoparticle production method of the present invention. It is possible to obtain.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
Palladium (Pd) nanoparticles were produced using a liquid phase laser ablation apparatus having the same configuration as the liquid phase laser ablation apparatus shown in FIG. In addition, a Nd: YAG laser device is used as the laser oscillator 10, a commercially available reflecting mirror (manufactured by CVI) is used as the mirror 11, and a synthetic quartz lens having a focal length of 100 mm (product of Sigma Kogyo Co., Ltd.) is used as the condensing means 12. (Namely “spherical plano-convex lens”), a glass volumetric flask (capacity 250 mL) is used as the processing vessel 13, and pure water (200 mL, light water, D ₂ O concentration: 0% by mass) as the solvent 14 is ion-exchanged water. ) As a target 15, palladium powder (3 g, trade name “Palladium powder” manufactured by Nilaco Corporation, 300 mesh, average particle size 1 μm), and magnetic stirrer (trade name “Magne” manufactured by AS ONE Co., Ltd.) as the stirring device 16. “Tick stirrer” (using a rod-like stirrer 16A having a length of 30 mm) was used. Moreover, air was used as the atmospheric gas G forming the gas phase in the processing container 13.

First, after introducing the solvent 14 into the processing vessel 13, the palladium powder was added. Thereafter, using a magnetic stirrer, the stirrer 16A was rotated at a rotational speed of 1200 rpm to stir the solvent 14, and the target 15 (palladium powder) was forcibly dispersed in the solvent 14. And while maintaining the rotational speed of the stirrer 16A at 1200 rpm, the laser oscillator 10 emits a laser beam L having a wavelength of 532 nm, which is a second harmonic of the Nd: YAG laser, under irradiation conditions of 10 Hz and 700 mJ / pulse. The laser beam oscillates, is reflected by the mirror 11 and is incident on the condensing unit 12, and the condensing unit 12 causes the fluence of the laser beam L on the surface of the solvent 14 (interface I between the liquid phase and the gas phase) to be 90 J / cm. ² was condensed (condensed shape: circular shape with a diameter of 1 mm), and the laser beam L was condensed and irradiated onto the interface I between the liquid phase and the gas phase for 60 minutes. By condensing and irradiating the laser beam L so that the focal point is at the interface I in this way, the laser beam L enters the solvent from the interface between the liquid phase and the gas phase, and the surface of the solvent 14 or the vicinity thereof. The laser beam L was applied to the existing target 15 powder, and liquid phase laser ablation was performed on the target 15 powder. Thus, palladium nanoparticles were formed in the solvent 14, and a dispersion liquid (yellow colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of the palladium nanoparticles thus obtained (the weight of particles produced per hour) was 25 mg / h.

[Evaluation of characteristics of nanoparticles and dispersion obtained in Example 1]
(Transmission electron microscope (TEM) measurement)
Part of the dispersion (30 mL) obtained in Example 1 was transferred to a glass dish, and the solvent 13 (pure water) was evaporated by heating with a dryer to collect particles. The particles collected in this manner were measured with a transmission electron microscope (TEM) to measure the particle diameter. Of the results obtained by such measurement, a transmission electron microscope (TEM) photograph is shown in FIG. Moreover, as a result of such measurement, the average particle diameter of the obtained palladium nanoparticles was 5 nm, and the standard deviation of the particle diameter was 1.5 nm. From these results, it was confirmed that nanoparticles with sufficiently high uniformity were formed.

(Measurement of UV-visible light absorption spectrum A)
Using a dispersion immediately after production in Example 1 (two hours after production), a measurement sample was formed so that the concentration of palladium nanoparticles in the dispersion was adjusted to 0.1 mg / mL. Thereafter, using the measurement sample, a UV-visible light absorption spectrum measurement apparatus (trade name “Ultraviolet-Visible Near-Infrared Spectrophotometer (UV-3600)” manufactured by Shimadzu Corporation) was used at a temperature of 25 ° C. The UV-visible light absorption spectrum was measured. The graph of the absorption spectrum obtained by such measurement is shown in FIG. In addition, as an index for measuring dispersion stability, 265 nm was selected as the first wavelength and 383 nm was selected as the second wavelength, and the intensity ratio and the like were obtained. As apparent from the results shown in FIG. 3, absorbance peaks are observed at wavelengths of 265 nm and 383 nm (observed that the absorbance has a positive value), and the dispersibility of the dispersion is sufficiently high. I found it expensive. Further, when the intensity ratio of the absorbance of light having a wavelength of 265 nm to the absorbance of light having a wavelength of 383 nm ([absorbance of light of 265 nm] / [absorbance of light of 383 nm]) was determined, the intensity of the dispersion immediately after production was obtained. The ratio (initial strength ratio) was found to be 2.84.

(Measurement B of UV-visible light absorption spectrum B)
The same method as employed in “Measurement A of UV-Visible Light Absorption Spectrum”, except that the dispersion after one year has passed under atmospheric pressure and a temperature of 20 to 25 ° C. after the production in Example 1 was used. The UV-visible light absorption spectrum of the dispersion after 1 year was measured using the above method. From the graph of the absorption spectrum obtained by such measurement, it is confirmed that the absorbance has a positive value at the positions of wavelengths: 265 nm and 383 nm, and the absorbance of the light of 265 nm and the light of the wavelength of 383 nm are confirmed. As a result, the intensity ratio of the dispersion after one year (intensity ratio after one year) is 2. As a result, the intensity ratio (absorbance of light at 265 nm) / [absorbance of light at 383 nm] is obtained. It turned out to be 70.

From the results of the measurement A and B of the UV-visible light absorption spectrum, the rate of change of the intensity ratio after one year from the initial intensity ratio is expressed by the formula:
[Change rate of intensity ratio] = [Initial intensity ratio] / [Intensity ratio after 1 year]
As a result of calculation, it was found that the value of the change rate of the intensity ratio (the first change rate of the intensity ratio) was 1.05. From these results, it can be seen that in the dispersion obtained in Example 1, the dispersibility of the nanoparticles in the dispersion hardly changed, and the nanoparticles obtained by the liquid phase laser ablation as described above. Was found to be capable of maintaining dispersibility over a long period of time. That is, it was confirmed that the nanoparticles obtained in Example 1 have sufficiently high dispersion stability in the dispersion.

Moreover, from the results of the measurement A and B of the UV-visible light absorption spectrum, the change rate of the absorbance of light at 265 nm and the change rate of the absorbance of light at a wavelength of 383 nm are respectively expressed by the formulas:
[Change rate of absorbance at specific wavelength] = [initial absorbance at specific wavelength] − [absorbance after lapse of one year or more at specific wavelength] / [initial absorbance at specific wavelength]
When the absolute value of the calculated value was calculated, the rate of change in absorbance of light at 265 nm was 0.01, and the rate of change in absorbance of light at a wavelength of 383 nm was 0.01. As used herein, “initial absorbance” refers to the absorbance of the dispersion immediately after production (two hours after production), and “absorbance after one year has passed” refers to the absorbance after one year has elapsed. Refers to the absorbance of the dispersion. Further, the second change rate of the intensity ratio is expressed by the following formula:
[Second rate of change in intensity ratio] = ([Initial intensity ratio] − [Intensity ratio after 1 year]) / [Initial intensity ratio]
When the absolute value of the calculated value was obtained, the second change rate of the intensity ratio was 0.10. From these results, it was confirmed that the nanoparticles obtained in Example 1 have sufficiently high dispersion stability in the dispersion.

(Example 2)
The Nd: YAG laser device is used as the laser oscillator 10, and the laser beam L having a wavelength of 355 nm, which is the third harmonic of the Nd: YAG laser, is oscillated from the laser oscillator 10 under the irradiation condition of 10 Hz and 500 mJ / pulse, Example 1 except that light was condensed (condensed shape: circular shape with a diameter of 1 mm) so that the fluence of the laser beam L on the surface of the solvent (interface I between the liquid phase and the gas phase) was 60 J / cm ^2. In the same manner as above, palladium nanoparticles were formed in the solvent 14, and a dispersion liquid (yellow colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of the palladium nanoparticles thus obtained was 18 mg / h.

  When the characteristics of the nanoparticles and the dispersion obtained in Example 2 were evaluated by adopting the same method as the method for evaluating the characteristics of the nanoparticles and the dispersion obtained in Example 1, the obtained palladium nanoparticle was obtained. The average particle diameter of the particles was 6.5 nm, and the standard deviation of the particle diameter was 2.0 nm. In addition, by measuring the absorption spectrum, the absorbance was positive at the wavelengths of 265 nm and 383 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. It was confirmed to have. Further, the intensity ratio ([265 nm light absorbance] / [383 nm light absorbance]) of the dispersion immediately after production obtained from such an absorption spectrum is 2.80, one year after production. It was found that the intensity ratio of the dispersion was 2.85, and the value of the rate of change of the intensity ratio (the first rate of change of the intensity ratio) was 0.98. Further, when the change rate of the absorbance of the light of 265 nm and the change of the absorbance of the light of the wavelength of 383 nm were obtained, the change rate of the absorbance of the light of the wavelength of 265 nm was 0.01, and the change of the absorbance of the light of the wavelength of 383 nm was changed. The rate was 0.02. Furthermore, the second change rate of the intensity ratio was 0.15. From these results, in Example 2, it was confirmed that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion was hardly changed. The obtained nanoparticles were confirmed to have sufficiently high dispersion stability in the dispersion.

(Example 3)
The Nd: YAG laser device is used as the laser oscillator 10, and laser light L having a wavelength of 532 nm, which is a second harmonic of the Nd: YAG laser, is oscillated from the laser oscillator 10 under the irradiation condition of 10 Hz and 400 mJ / pulse, and the light collecting means 12 Except for condensing (condensing shape: circular shape with a diameter of 8 mm) so that the fluence of the laser beam L on the surface of the solvent (interface I between the liquid phase and the gas phase) is 0.80 J / cm ^2. In the same manner as in Example 1, palladium nanoparticles were formed in the solvent 14, and a dispersion liquid (yellow colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of the palladium nanoparticles thus obtained was 10 mg / h.

  The characteristics of the nanoparticles and dispersion obtained in Example 3 were evaluated by adopting the same method as the method for evaluating the characteristics of the nanoparticles and dispersion obtained in Example 1. The average particle size of the particles was 8.0 nm, and the standard deviation of the particle size was 2.0 nm. In addition, by measuring the absorption spectrum, the absorbance was positive at the wavelengths of 265 nm and 383 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. It was confirmed to have. Further, the intensity ratio ([absorbance of light at 265 nm] / [absorbance of light at 383 nm]) of the dispersion immediately after the production obtained from such an absorption spectrum is 1.90, which is 1 year after the production. It was found that the intensity ratio of the dispersion was 1.90, and the value of the rate of change of the intensity ratio was 1.00. Furthermore, when the change rate of the absorbance of light having a wavelength of 265 nm and the change of absorbance of light having a wavelength of 383 nm were respectively determined, the change rate of the absorbance of light having a wavelength of 265 nm was 0.01, and the absorbance of light having a wavelength of 383 nm The change rate of was 0.01. Furthermore, the second change rate of the intensity ratio was 0.10. From these results, in Example 3, it was confirmed that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion was not changed. It was confirmed that the obtained nanoparticles had sufficiently high dispersion stability in the dispersion.

(Comparative Example 1)
In the same manner as in Example 2, except that the condensing unit 12 is not used, the laser beam L is not collected, and the target 15 in the solvent 14 is irradiated with the laser beam L as it is. Particles were formed. Note that the fluence of the laser beam L at the interface I was 0.63 J / cm ² . When palladium nanoparticles were formed in this way, the nanoparticles aggregated and precipitated, and a dispersion was not obtained. Thus, under the condition that the fluence of the laser beam L at the interface I is 0.63 J / cm ² , even when the laser beam is irradiated with stirring, the dispersion stability sufficient for the formed palladium nanoparticles It was confirmed that it cannot be granted. Moreover, when the characteristic of the nanoparticle obtained in Comparative Example 1 was evaluated by adopting the same method as the method for evaluating the characteristic of the nanoparticle obtained in Example 1, the average particle of the obtained palladium nanoparticle was obtained. The diameter was 50 nm, and the standard deviation of the particle diameter was 30 nm. From these results, it was found that when the interface I was not focused and irradiated with laser light, nanoparticles having a sufficiently small and uniform particle size could not be formed. Further, the yield of palladium nanoparticles thus obtained (the weight of particles produced per hour) was 0.1 mg / h, and the yield was not sufficient.

(Comparative Example 2)
Liquid phase laser ablation was performed using the liquid phase laser ablation apparatus shown in FIG. The liquid phase laser ablation apparatus shown in FIG. 4 basically includes a laser oscillator 10, a condensing lens 12 disposed on the optical path of the laser light L, and a sealed processing container 13 having a quartz window W; And a solvent 14 and a bulk target 15 held in the processing vessel 13.

In such a liquid phase laser ablation apparatus, an Nd: YAG laser apparatus is used as the laser oscillator 10 and a synthetic quartz lens having a focal length of 100 mm is used as the condenser lens 12. In addition, the condensing lens 12 was arrange | positioned so that it might closely_contact | adhere to the window W of the processing container 13 so that the condensing size on the surface of the target 15 might be 1.2 mm in diameter. Further, as the processing container 13, the surface on which the quartz window W is installed and the surface on which the target 15 is held are circular, and the cylindrical container having a length of 100 mm (the circular surface in the container). The inner diameter was 80 mm). Further, the processing container 13 is made of acrylic resin, and the window W is made of quartz having a diameter of 40 mm and a thickness of 8 mm. Further, pure water (light water, D ₂ O concentration: 0% by mass) was used as the solvent 14, and the inside of the container 13 was filled with the solvent 14. Further, as the target 15, a disk made of palladium having a diameter of 40.0 mm and a thickness of 1.0 mm (bulk target, trade name “Palladium disk” manufactured by Nilaco Co., Ltd.) is used. It is connected to the omitted motor and can be rotated by the motor.

In the step of performing liquid phase laser ablation, using this apparatus, laser light L having a wavelength 532 nm, which is twice as high as that of the Nd: YAG laser, is oscillated from the laser oscillator 10 under the conditions of 400 mJ / pulse and 10 Hz. The optical lens 12 focused the light so that the fluence on the surface of the target 15 was 5.66 J / cm ² (condensed shape: diameter 3 mm), and the target 15 was irradiated with the laser light L in the solvent 14. . Moreover, the irradiation time of such laser light L was 60 minutes. When irradiating the laser beam L, the laser beam L is appropriately rotated by the motor (not shown) so that the laser beam L is repeatedly irradiated to the same position on the surface of the target 15 and no hole is opened. Light L was irradiated. In this way, the bulk target 15 is irradiated with the laser beam L to perform laser ablation, thereby forming palladium nanoparticles, and a dispersion liquid in which the nanoparticles are dispersed in the solvent 14 (brown color) Colloid). The yield of the palladium nanoparticles thus obtained was 0.7 mg / h.

  The characteristics of the nanoparticles and the dispersion obtained in Comparative Example 2 were evaluated by adopting the same method as the method for evaluating the characteristics of the nanoparticles and the dispersion obtained in Example 1. As a result, it was confirmed that the average particle diameter of the palladium nanoparticles obtained in Comparative Example 2 was 30 nm, and the standard deviation of the particle diameter was 20 nm. In addition, the transmission electron microscope (TEM) photograph of the particle | grains obtained by the comparative example 2 obtained by such a measurement is shown in FIG. As is clear from the results shown in FIG. 5 and the standard deviation values, the comparative example 2 has a large variation in the particle diameter of the nanoparticles, and it is impossible to produce sufficiently uniform particles. I understood that. Moreover, in the comparative example 2, the average particle diameter of the formed nanoparticle became 30 nm, and the particle | grains obtained compared with Examples 1-2 were large.

  For the dispersion obtained in Comparative Example 2, the intensity ratio ([265 nm light absorbance] / [383 nm light absorbance]) of the dispersion immediately after production obtained from the absorption spectrum was 1.5. It was. However, the absorbance of the 265 nm light and the light of 383 nm light of the dispersion after one year from the production were both zero. Therefore, regarding the dispersion obtained in Comparative Example 2, the value of the rate of change in the intensity ratio (the first rate of change in the intensity ratio) cannot be measured (because the denominator is 0 in the calculation formula). I understood. From these results, it was found that in the dispersion obtained in Comparative Example 2, the dispersion stability of the nanoparticles was not sufficient. In addition, it was confirmed that the dispersion after one year had aggregated and precipitated particles and the color was colorless and transparent, and the dispersibility was also lowered visually.

(Comparative Example 3)
A dispersion in which palladium nanoparticles were formed in the solvent 14 and the nanoparticles were dispersed in the solvent 14 except that the solvent 14 was changed to heavy water having a D ₂ O concentration of 100% by mass. (Brown colloid) was obtained. The yield of the palladium nanoparticles thus obtained was 1.0 mg / h.

  The characteristics of the nanoparticles and the dispersion obtained in Comparative Example 3 were evaluated by adopting the same method as the method for evaluating the characteristics of the nanoparticles and the dispersion obtained in Example 1. As a result, it was confirmed that the average particle diameter of the palladium nanoparticles obtained in Comparative Example 3 was 15 nm, and the standard deviation of the particle diameter was 8 nm. From these results, it was found that in Comparative Example 3, the standard deviation of the nanoparticles was low, and particles with sufficiently high uniformity could not be produced. Moreover, in the comparative example 3, the average particle diameter of the formed nanoparticle was 15 nm, and the particle | grains obtained compared with Examples 1-2 were large.

  For the dispersion obtained in Comparative Example 3, the intensity ratio ([absorbance of light at 265 nm] / [absorbance of light at 383 nm]) of the dispersion immediately after production obtained from the absorption spectrum was 1.3. It was. However, the absorbance of the 265 nm light and the light of 383 nm light of the dispersion after one year from the production were both zero. Therefore, for the dispersion obtained in Comparative Example 3, the value of the rate of change in the intensity ratio (the first rate of change in the intensity ratio) cannot be measured (because the denominator is 0 in the calculation formula). I understood. From these results, it was found that in the dispersion obtained in Comparative Example 3, the dispersion stability of the nanoparticles was not sufficient. In addition, it was confirmed that the dispersion after one year had aggregated and precipitated particles and the color was colorless and transparent, and the dispersibility was also lowered visually.

  Moreover, the graph of the UV-visible light absorption spectrum of the dispersion immediately after manufacture obtained in Comparative Example 2 and the UV-visible light absorption spectrum of the dispersion immediately after manufacture obtained in Comparative Example 3 are shown in FIG. From the results shown in FIG. 6, it can be seen that the concentration of nanoparticles is increased by using heavy water as compared to the case of using light water. It was found that the uniformity of the particle diameter of the particles is low, and it is impossible to produce highly dispersible palladium nanoparticles by the liquid phase laser ablation method employed in Comparative Examples 2-3.

(Comparative Example 4)
Liquid phase laser ablation was performed using the liquid phase laser ablation apparatus shown in FIG. Note that the liquid phase laser ablation apparatus shown in FIG. 7 basically has a laser oscillator 10, a mirror 11 disposed on the optical path of the laser beam L, a processing vessel 13, a solvent 14, and the bottom of the processing vessel 13. And a powdery target 15 precipitated in B.

In such a liquid phase laser ablation apparatus, an Nd: YAG laser apparatus is used as the laser oscillator 10, a glass pear-shaped flask (capacity 100 mL) is used as the processing container 13, and pure water (100 mL: D) is used as the solvent 14. ₂ O concentration was 0 mass%), and palladium powder (3 g, trade name “Palladium powder” manufactured by Nilaco Corporation, 300 mesh, average particle diameter 1 μm) was used as the target 15.

And in the process of performing liquid phase laser ablation, after filling the processing container 13 (pear-shaped flask: capacity 100mL) with the solvent 14 using this apparatus, the powdery target 15 is added, and the target 15 is changed. It was precipitated at the bottom B of the processing vessel 13. Next, a laser beam L having a wavelength of 532 nm, which is a second harmonic of the Nd: YAG laser, is oscillated from the laser oscillator 10 under irradiation conditions of 10 Hz and 400 mJ / pulse, and is transmitted through the bottom B of the processing vessel 13 without being condensed. As a result, the laser beam L was applied to the target 15 precipitated at the bottom of the processing vessel 13 (irradiation light shape: circular shape with a diameter of 10 mm, fluence: 0.51 J / cm ² ). In this manner, the powdery target 15 deposited on the bottom B of the processing vessel 13 is irradiated with the laser beam L for 60 minutes to perform liquid phase laser ablation, and palladium nanoparticles in the solvent 14 And a dispersion liquid (brown colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of the palladium nanoparticles thus obtained was 20 mg / h.

  The characteristics of the nanoparticles and the dispersion obtained in Comparative Example 4 were evaluated by employing the same method as the method for evaluating the characteristics of the nanoparticles and the dispersion obtained in Example 1. As a result, it was confirmed that the average particle diameter of the palladium nanoparticles obtained in Comparative Example 4 was 20 nm, and the standard deviation of the particle diameter was 10 nm. In addition, the transmission electron microscope (TEM) photograph of the particle | grains obtained by the comparative example 4 obtained by such a measurement is shown in FIG. As is clear from the results shown in FIG. 8, the standard deviation value, and the like, in Comparative Example 4, there is a large variation in the particle diameter of the nanoparticles, and it is impossible to produce sufficiently uniform particles. I understood that.

  For the dispersion obtained in Comparative Example 4, the intensity ratio ([265 nm light absorbance] / [383 nm light absorbance]) of the dispersion immediately after production obtained from the absorption spectrum was 1.7. It was. However, the absorbance of the 265 nm light and the light of 383 nm light of the dispersion after one year from the production were both zero. Therefore, for the dispersion obtained in Comparative Example 4, the value of the change rate of the intensity ratio (the first change rate of the intensity ratio) cannot be measured (because the denominator is 0 in the calculation formula). I understood. From these results, it was found that in the dispersion obtained in Comparative Example 4, the dispersion stability of the nanoparticles was not sufficient. In addition, it was confirmed that the dispersion after one year had aggregated and precipitated particles and the color was colorless and transparent, and the dispersibility was also lowered visually.

As is clear from the results of the experiments performed in Examples 1 to 3 and Comparative Examples 1 to 4, the laser is used so that the fluence is 0.70 J / cm ² or more at the interface I between the liquid phase and the gas phase. According to the manufacturing method (Examples 1 to 3) of the inorganic nanoparticles of the present invention that collects and irradiates the light L, palladium nanoparticles formed by liquid phase laser ablation have sufficiently high particle size uniformity. It was confirmed that the dispersion stability in the dispersion was sufficiently high. Further, in comparison with Comparative Examples 1 to 4, according to the method for producing inorganic nanoparticles of the present invention (Examples 1 to 3), palladium nanoparticles having a sufficiently small particle diameter can be obtained in a sufficiently high yield. I also found that it can be manufactured. That is, it was confirmed that according to the method for producing inorganic nanoparticles of the present invention (Examples 1 to 3), uniform palladium nanoparticles having a sufficiently small particle size can be produced sufficiently efficiently.

Example 4
Gold (Au) nanoparticles were produced using a liquid phase laser ablation apparatus having the same configuration as the liquid phase laser ablation apparatus shown in FIG. In addition, a Nd: YAG laser apparatus is used as the laser oscillator 10, a commercially available reflecting mirror (manufactured by CVI) is used as the mirror 11, and a synthetic quartz lens having a focal length of 200 mm (product of Sigma Kogyo Co., Ltd.) is used as the condensing means 12. (Namely “spherical plano-convex lens”), a glass volumetric flask (capacity 100 mL) is used as the processing container 13, and pure water (80 mL, light water, D ₂ O concentration: 0% by mass) as the solvent 14 is ion-exchanged water. ), Gold powder (3 g, trade name “Au pure gold powder” manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle size 150 μm) as target 15, and magnetic stirrer (product made by AS ONE Co., Ltd.) as stirring device 16. The name “Magnetic Stirrer” (using a rod-like stirrer 16A of 30 mm in length) was used. Moreover, air was used as the atmospheric gas G forming the gas phase in the processing container 13. The distance between the lens, the liquid phase, and the gas phase interface before stirring was about 200 mm.

First, after introducing the solvent 14 into the processing vessel 13, the gold powder was added. Thereafter, using a magnetic stirrer, the stirrer 16 </ b> A was rotated at a rotational speed of 1200 rpm to stir the solvent 14, and the target 15 (gold powder) was forcibly dispersed in the solvent 14. Then, while continuing the stirring while maintaining the rotation speed of the stirrer 16A at 1200 rpm, a laser beam L having a wavelength of 532 nm, which is a second harmonic of the Nd: YAG laser, is emitted from the laser oscillator 10 at an irradiation condition of 10 Hz and 800 mJ / pulse. The laser beam oscillates, is reflected by the mirror 11 and is incident on the condensing unit 12, and the condensing unit 12 causes the fluence of the laser light L on the surface of the solvent 14 (interface I between the liquid phase and the gas phase) to be 100 J / cm. ² was condensed (condensed shape: circular shape with a diameter of 1 mm), and the laser beam L was condensed and irradiated onto the interface I between the liquid phase and the gas phase for 60 minutes. By condensing and irradiating the laser beam L so that the focal point is at the interface I in this way, the laser beam L enters the solvent from the interface between the liquid phase and the gas phase, and the surface of the solvent 14 or the vicinity thereof. The laser beam L was applied to the existing target 15 powder, and liquid phase laser ablation was performed on the target 15 powder. In this way, gold nanoparticles were formed in the solvent 14, and a dispersion liquid (red colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of gold nanoparticles thus obtained (weight of particles produced per hour) was 22 mg / h.

  In Example 1 except that instead of selecting 265 nm as the first wavelength, which is an index for measuring dispersion stability, 550 nm was selected and 600 nm was selected as the second wavelength instead of 383 nm. The characteristics of the nanoparticles and the dispersion obtained in Example 4 were evaluated by adopting the same method as the method for evaluating the characteristics of the obtained nanoparticles and the dispersion. The graph of the absorption spectrum of the dispersion immediately after manufacture obtained by such measurement and the dispersion after 1 year is shown in FIG. The reason for changing the wavelengths selected as the first and second wavelengths in this manner is that the plasmon having a peak at 520 nm in the absorption spectrum of gold nanoparticles, as is apparent from the graph shown in FIG. Since the absorption was confirmed, by measuring the change rate of the intensity ratio and the change rate of the absorbance by adopting the wavelength of 550 nm and the wavelength of 600 nm, which are two arbitrary wavelengths in the vicinity, the dispersion stability can be measured. This is because more accurate information can be obtained. As a result, it was found that the average particle diameter of the obtained gold nanoparticles was 10 nm, and the standard deviation of the particle diameter was 1.5 nm. Further, as is apparent from the results shown in FIG. 9, the absorbance at wavelengths of 550 nm and 600 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. Was confirmed to have a positive value. Furthermore, the value of the change rate ([absorbance of light at 550 nm] / [absorbance of light at 600 nm]) of the dispersion obtained from the absorption spectrum shown in FIG. It was found to be 0.9996. Further, as is apparent from the results shown in FIG. 9, when the change rate of the absorbance of light at 550 nm and the absorbance of light at 600 nm was determined, the change rate of the absorbance of light at a wavelength of 550 nm was 0.0018. The change rate of the absorbance of light having a wavelength of 600 nm was 0.0014. Further, it is obtained on the basis of the data of the absorbance of light at 550 nm and the absorbance of light at a wavelength of 600 nm of the dispersion immediately after production (after 2 hours from production) and the dispersion after 1 year from the production shown in FIG. From the obtained initial intensity ratio and the value of the intensity ratio after one year, the second change rate of the intensity ratio was determined to be 0.00045. From these results, in Example 4, it was confirmed that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion changed substantially even after 1 year. From this, it was confirmed that the obtained nanoparticles had sufficiently high dispersion stability in the dispersion.

(Comparative Example 5)
Liquid phase laser ablation was performed using the liquid phase laser ablation apparatus shown in FIG. In such a liquid phase laser ablation apparatus, an Nd: YAG laser apparatus is used as the laser oscillator 10, a glass pear-shaped flask (capacity 100 mL) is used as the processing container 13, and pure water (100 mL: D) is used as the solvent 14. ₂ O concentration was 0 mass%), and gold powder (0.5 g, trade name “Au pure gold powder” manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle diameter 150 μm) was used as the target 15.

And in the process of performing liquid phase laser ablation, after filling the processing container 13 (pear-shaped flask: capacity 100 mL) with the solvent 14 using this apparatus, the powdery target 15 (gold powder) is added. Then, the target 15 was deposited on the bottom B of the processing container 13. Next, laser light L having a wavelength of 532 nm, which is the second harmonic of the Nd: YAG laser, is oscillated from the laser oscillator 10 under irradiation conditions of 10 Hz and 600 mJ / pulse, and is transmitted through the bottom B of the processing vessel 13 without being condensed. As a result, the laser beam L was applied to the target 15 precipitated on the bottom of the processing vessel 13 (irradiation light shape: circular shape with a diameter of 10 mm, fluence: 0.76 J / cm ² ). In this manner, the powdery target 15 deposited on the bottom B of the processing vessel 13 is irradiated with the laser light L for 60 minutes to perform liquid phase laser ablation, and gold nanoparticles in the solvent 14 And a dispersion liquid (pink colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of the gold nanoparticles thus obtained was 20 mg / h.

  The properties of the gold nanoparticles and the dispersion obtained in Comparative Example 5 were evaluated by adopting the same method as the method for evaluating the properties of the gold nanoparticles and the dispersion obtained in Example 4. As a result of such measurement, it was confirmed that the average particle diameter of the gold nanoparticles obtained in Comparative Example 5 was 10 nm, and the standard deviation of the particle diameter was 5 nm. As is clear from the value of such standard deviation and the like, it was found that in Comparative Example 5, the particle size of the gold nanoparticles was greatly varied, and it was impossible to produce sufficiently uniform particles. . In addition, in the dispersion obtained in Comparative Example 5, agglomeration precipitation was also confirmed visually after 1 hour, and the absorbance of light at 550 nm and the absorbance of light at 600 nm after 1 year from the production were Both were found to be 0. Therefore, regarding the dispersion obtained in Comparative Example 5, it was found that the value of the rate of change in the intensity ratio was not measurable (because the denominator was 0 in the calculation formula). Therefore, the change in the intensity ratio of the dispersion ([absorbance of light at 550 nm] / [absorbance of light at 600 nm]) using the dispersion after 2 days after production instead of the dispersion after 1 year after production. The rate was determined. In addition, the graph of the absorption spectrum of the dispersion liquid just after manufacture and the dispersion liquid after two-day progress is shown in FIG. As is clear from the results shown in FIG. 10, the change rate of the intensity ratio (first change rate of the intensity ratio) in the dispersion immediately after the production and the dispersion after the lapse of 2 days from the production is 0.9871. Compared with Example 4, it was found that the degree of change was already large after only 2 days. Further, based on the results shown in FIG. 10, the rate of change in the absorbance of light having a wavelength of 550 nm and the absorbance of light having a wavelength of 600 nm in the dispersion immediately after production and in the dispersion after two days has elapsed ([specific wavelength (550 Or change rate of absorbance at 600 nm) = [initial absorbance at a specific wavelength] − [absorbance after 2 days at a specific wavelength] / [initial absorbance at a specific wavelength]), the absorbance of light having a wavelength of 550 nm. Was 0.175, and the absorbance change rate of light having a wavelength of 600 nm was 0.185. Furthermore, based on the absorption spectrum data of the dispersion immediately after production shown in FIG. 10 and the dispersion after 2 days, the second change rate of the intensity ratio was 0.013. From these results, it can be seen that the dispersion obtained in Comparative Example 5 has a lower dispersion stability of the nanoparticles after only 2 days than the dispersion obtained in Example 4. It was. In addition, it was confirmed that the dispersion after one year had aggregated and precipitated particles and the color was colorless and transparent, and the dispersibility was also lowered visually.

(Example 5)
Implemented except that platinum (Pt) powder (3 g, trade name “Pt platinum powder”, average particle diameter 75 μm) manufactured by Kojundo Chemical Laboratory Co., Ltd. was used in place of gold powder (3 g) as target 15 In the same manner as in Example 4, production of platinum nanoparticles (production of a dispersion) was performed. The obtained dispersion became a black colloid. The yield of platinum nanoparticles thus obtained (the weight of particles produced per hour) was 25 mg / h.

  In Example 1, except that 350 nm was selected instead of 265 nm as the first wavelength, which was an index for measuring dispersion stability, and 700 nm was selected instead of 383 nm as the second wavelength. The properties of the platinum nanoparticles and the dispersion obtained in Example 5 were evaluated by adopting the same method as the method for evaluating the properties of the obtained nanoparticles and the dispersion. The graph of the absorption spectrum of the dispersion immediately after manufacture obtained by such measurement and the dispersion after one year is shown in FIG. As a result of such measurement, it was found that the average particle diameter of the obtained platinum nanoparticles was 8 nm, and the standard deviation of the particle diameter was 1.0 nm. Further, as is apparent from the results shown in FIG. 11, the absorbance at wavelengths of 350 nm and 700 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. Was confirmed to have a positive value. Furthermore, the value of the rate of change ([absorbance of light at 350 nm] / [absorbance of light at 700 nm]) of the dispersion obtained from the absorption spectrum shown in FIG. It was found to be 0.975. Further, as apparent from the results shown in FIG. 11, when the change rate of the absorbance at 350 nm and 700 nm is obtained, the change rate of the absorbance at 350 nm is 0.0076. The rate of change in absorbance of light having a wavelength of 700 nm was 0.017. Further, based on the data on the absorbance of light having a wavelength of 350 nm and the absorbance of light having a wavelength of 700 nm of the dispersion immediately after production (two hours after production) and the dispersion after one year from production shown in FIG. The second change rate of the strength ratio was determined from the initial strength ratio and the strength ratio after one year, and the second change rate of the strength ratio was 0.025. From these results, in Example 5, it was confirmed that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion changed substantially even after 1 year. From this, it was confirmed that the obtained nanoparticles had sufficiently high dispersion stability in the dispersion.

(Example 6)
After the target 15 made of copper powder is manufactured as follows, the target 15 made of copper powder is used and a liquid phase laser ablation apparatus having the same configuration as the liquid phase laser ablation apparatus shown in FIG. 1 is used. Thus, copper (Cu) nanoparticles were produced.

<Manufacturing process of target 15 (copper powder)>
Using a liquid phase laser ablation apparatus shown in FIG. 7, liquid phase laser ablation treatment (pretreatment) in which laser light was irradiated in a liquid phase was performed on commercially available copper particles to produce a copper powder. In such a liquid phase laser ablation apparatus, an Nd: YAG laser apparatus is used as the laser oscillator 10, a glass pear-shaped flask (capacity 100 mL) is used as the processing container 13, and pure water (100 mL: D) is used as the solvent 14. ₂ O concentration was 0 mass%), and copper particles (0.5 g, trade name “Copper / powder” manufactured by Niraco Co., Ltd., average particle diameter of 100 μm) were used instead of the target 15 shown in FIG. And in the process of performing liquid phase laser ablation, after filling the processing container 13 (pear-shaped flask: capacity 100mL) with the solvent 14 using such an apparatus, the copper particles are added to treat the copper particles. It was precipitated at the bottom B of the container 13. Next, laser light L having a wavelength of 532 nm, which is the second harmonic of the Nd: YAG laser, is oscillated from the laser oscillator 10 under irradiation conditions of 10 Hz and 600 mJ / pulse, and is transmitted through the bottom B of the processing vessel 13 without being condensed. As a result, the laser beam L was applied to the copper particles precipitated on the bottom of the processing vessel 13 (irradiation light shape: circular shape with a diameter of 10 mm, fluence: 0.76 J / cm ² ). In this way, copper powder precipitated in the bottom B of the processing vessel 13 is irradiated with laser light L for 60 minutes to perform liquid phase laser ablation, thereby forming copper powder in the solvent 14. Thus, a dispersion (green colloid) of copper powder (average particle size: 0.05 μm) in which the copper powder was dispersed in the solvent 14 was obtained.

<Process for producing copper (Cu) nanoparticles>
Next, copper (Cu) nanoparticles were produced using a liquid phase laser ablation apparatus having the same configuration as the liquid phase laser ablation apparatus shown in FIG. In addition, a Nd: YAG laser apparatus is used as the laser oscillator 10, a commercially available reflecting mirror (manufactured by CVI) is used as the mirror 11, and a synthetic quartz lens having a focal length of 200 mm (product of Sigma Kogyo Co., Ltd.) is used as the condensing means 12. Obtained by carrying out the manufacturing process of the target 15 (copper powder) as the solvent 14 and the target 15 using a glass volumetric flask (capacity 100 mL) as the processing container 13. A dispersion of copper powder (the dispersoid copper powder is the target 15 and pure water (100 mL: D ₂ O concentration is 0% by mass) as the dispersion medium is the solvent 14) is used as it is, and stirred. A magnetic stirrer (trade name “Magnetic Stirrer” manufactured by AS ONE, using a bar-shaped stirrer 16A having a length of 30 mm) is used as the device 16. . In the present embodiment, the dispersion of the copper powder obtained by carrying out the manufacturing process of the target 15 (copper powder) is immediately introduced into the processing vessel 13 after the production. Thus, the target 15 is present in a dispersed state from the stage before the solvent 14 is stirred. Moreover, air was used as the atmospheric gas G forming the gas phase in the processing container 13. The distance between the lens, the liquid phase, and the gas phase interface before stirring was about 200 mm.

First, using a magnetic stirrer, the stirrer 16 </ b> A was rotated at a rotational speed of 1200 rpm to stir the solvent 14, and the target 15 (copper powder) was further dispersed in the solvent 14. Then, while continuing the stirring while maintaining the rotation speed of the stirrer 16A at 1200 rpm, a laser beam L having a wavelength of 532 nm, which is a second harmonic of the Nd: YAG laser, is emitted from the laser oscillator 10 at an irradiation condition of 10 Hz and 800 mJ / pulse. The laser beam oscillates, is reflected by the mirror 11 and is incident on the condensing unit 12, and the condensing unit 12 causes the fluence of the laser light L on the surface of the solvent 14 (interface I between the liquid phase and the gas phase) to be 100 J / cm. ² was condensed (condensed shape: circular shape with a diameter of 1 mm), and the laser beam L was condensed and irradiated onto the interface I between the liquid phase and the gas phase for 60 minutes. By condensing and irradiating the laser beam L so that the focal point is at the interface I in this way, the laser beam L enters the solvent from the interface between the liquid phase and the gas phase, and the surface of the solvent 14 or the vicinity thereof. The laser beam L was applied to the existing target 15 powder, and liquid phase laser ablation was performed on the target 15 powder. Thus, copper nanoparticles were formed in the solvent 14, and a dispersion liquid (green colloid) in which the nanoparticles were dispersed in the solvent 14 was obtained. The yield of the copper nanoparticles thus obtained (the weight of the particles produced per hour) was 20 mg / h.

  Thereafter, Example 1 was used except that 350 nm was selected instead of 265 nm as the first wavelength, which was an index for measuring dispersion stability, and 700 nm was selected instead of 383 nm as the second wavelength. The characteristics of the copper nanoparticles and dispersion obtained in Example 6 were evaluated by adopting the same method as the method for evaluating the characteristics of the obtained nanoparticles and dispersion. The graph of the absorption spectrum of the dispersion immediately after manufacture obtained by such measurement and the dispersion after one year is shown in FIG. As a result of such measurement, it was found that the average particle diameter of the obtained copper nanoparticles was 5 nm, and the standard deviation of the particle diameter was 0.5 nm. Further, as is clear from the results shown in FIG. 12, the absorbance at wavelengths of 350 nm and 700 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. Was confirmed to have a positive value. Furthermore, the value of the change rate (the first change rate of the intensity ratio) of the intensity ratio ([absorbance of 350 nm light] / [absorbance of 700 nm light]) of the dispersion obtained from the absorption spectrum shown in FIG. It was found to be 0.996. Further, as is apparent from the results shown in FIG. 12, the change rate of the absorbance of 350 nm light and the light of 700 nm wavelength was determined, and the change rate of 350 nm light absorbance was 0.013. The change rate of the absorbance of light having a wavelength of 700 nm was 0.048. Moreover, it calculates | requires based on the data of the light absorbency of the light of 350 nm and the light of the wavelength of 700 nm of the dispersion liquid (2 hours after manufacture) shown in FIG. From the obtained initial intensity ratio and the value of the intensity ratio after one year, the second change rate of the intensity ratio was found to be 0.0037. From these results, in Example 6, it was confirmed that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion changed substantially even after 1 year. From this, it was confirmed that the obtained nanoparticles had sufficiently high dispersion stability in the dispersion.

(Example 7)
Instead of producing the target 15 made of copper powder, a copper oxide powder was produced as follows, and instead of the copper powder dispersion, a copper oxide powder dispersion obtained as follows was used. Except that the solvent 14 and the target 15 were used, copper oxide nanoparticles (dispersion liquid) were produced in the same manner as in Example 6. The resulting dispersion of copper oxide nanoparticles became a brown colloid. The yield of the copper oxide nanoparticles thus obtained (weight of particles produced per hour) was 25 mg / h.

<Manufacturing process of target 15 (copper oxide powder)>
First, the process similar to the manufacturing process of the target 15 (copper powder) employ | adopted in Example 6 was implemented, and the dispersion liquid (green colloid) of copper powder was obtained. The dispersion was allowed to stand for 4 hours at room temperature (25 ° C.) and atmospheric pressure. By leaving in this way, the copper powder in the dispersion was oxidized. Note that the color of the dispersion changed to brown by such oxidation. Thus, a dispersion (brown colloid) of copper oxide (CuO) powder (average particle size: 0.05 μm) was obtained.

  Then, regarding the copper oxide nanoparticles and dispersion obtained in Example 7, instead of selecting 265 nm as the first wavelength, which is an index for measuring dispersion stability, 450 nm is selected and the second wavelength is selected. The characteristics were evaluated by adopting the same method as that for evaluating the properties of the nanoparticles and the dispersion obtained in Example 1 except that 500 nm was selected instead of 383 nm. FIG. 13 shows graphs of absorption spectra of the dispersion immediately after production and the dispersion after one year obtained by such measurement. As a result of such measurement, it was found that the average particle diameter of the obtained copper oxide nanoparticles was 3 nm, and the standard deviation of the particle diameter was 1 nm. Further, as is apparent from the results shown in FIG. 13, the absorbance at wavelengths of 450 nm and 500 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. Was confirmed to have a positive value. Furthermore, the value of the change rate ([absorbance of light at 450 nm] / [absorbance of light at 500 nm]) of the dispersion obtained from the absorption spectrum shown in FIG. It was found to be 1.006. Further, as apparent from the results shown in FIG. 13, when the change rate of the absorbance of light at 450 nm and the absorbance of light of 500 nm wavelength was obtained, the change rate of the absorbance of light of 450 nm wavelength was 0.017. The change rate of the absorbance of light having a wavelength of 500 nm was 0.011. Moreover, it calculates | requires based on the light absorbency of 450 nm light and the light absorbency of the wavelength of 500 nm of the dispersion liquid immediately after manufacture shown in FIG. 13 (those 2 hours after manufacture) and the dispersion liquid after 1 year from manufacture. From the obtained initial intensity ratio and the intensity ratio value after one year, the second change rate of the intensity ratio was determined to be 0.0056. From these results, in Example 7, it was confirmed that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion changed substantially even after 1 year. From this, it was confirmed that the obtained nanoparticles had sufficiently high dispersion stability in the dispersion.

(Example 8)
Instead of producing the target 15 made of copper powder, the target 15 made of Pd—Fe alloy powder was produced as follows, and instead of the copper powder dispersion, Pd— Except that the dispersion liquid of the Fe alloy powder was used as the solvent 14 and the target 15, the production of the alloy nanoparticles (production of the dispersion liquid) was performed in the same manner as in Example 6. The obtained dispersion became a yellow colloid. The nanoparticle yield (weight of particles produced per hour) of the alloy thus obtained was 20 mg / h.

<Manufacturing process of target 15 (Pd—Fe alloy powder)>
First, Pd—Fe alloy pellets having a palladium (Pd) content of 90 mass% and an iron (Fe) content of 10 mass% were produced by a chemical synthesis method. Next, the pellet was shaved with a drill to produce a powder (shaving residue having an average particle diameter of 100 μm). Next, the scrap was thoroughly washed to obtain a Pd—Fe alloy powder. Next, a process similar to the process for manufacturing the target 15 (copper powder) employed in Example 6 was performed except that the Pd—Fe alloy powder was used instead of the copper particles, and Pd— A dispersion (yellow colloid) of Pd—Fe powder (average particle size: 1 μm) of the alloy in which the Fe alloy powder was dispersed in the solvent 14 was obtained.

  For the Pd—Fe nanoparticles and dispersion obtained in Example 8, instead of selecting 265 nm as the first wavelength, which is an index for measuring dispersion stability, 450 nm is selected as the second wavelength. Except for selecting 500 nm instead of 383 nm, the characteristics were evaluated by adopting the same method as that for evaluating the characteristics of the nanoparticles and dispersion obtained in Example 1. FIG. 14 shows graphs of absorption spectra of the dispersion immediately after production and the dispersion after one year obtained by such measurement. As a result of such measurement, it was found that the average particle diameter of the nanoparticles of the obtained alloy was 1 nm, and the standard deviation of the particle diameter was 0.5 nm. Further, as is apparent from the results shown in FIG. 14, the absorbance at wavelengths of 450 nm and 500 nm in both the dispersion immediately after production (two hours after production) and the dispersion after one year from production. Was confirmed to have a positive value. Furthermore, the value of the rate of change ([absorbance of light at 450 nm] / [absorbance of light at 500 nm]) of the dispersion obtained from the absorption spectrum shown in FIG. It was found to be 1.0902. Further, as apparent from the results shown in FIG. 14, when the change rate of the absorbance of 450 nm light and the light of 500 nm wavelength was obtained, the change rate of the absorbance of 450 nm light was 0.089. The change rate of the absorbance of light having a wavelength of 500 nm was 0.187. Further, based on the data of the absorbance of light having a wavelength of 450 nm and the absorbance of light having a wavelength of 500 nm of the dispersion immediately after production (two hours after production) and the dispersion after one year from production shown in FIG. The second change rate of the intensity ratio was found to be 0.083 from the initial intensity ratio and the intensity ratio after one year. From these results, it was confirmed in Example 8 that nanoparticles with sufficiently high uniformity were formed, and the dispersibility of the nanoparticles in the dispersion changed substantially even after one year. From this, it was confirmed that the obtained nanoparticles had sufficiently high dispersion stability in the dispersion.

  From the above results, according to the method for producing inorganic nanoparticles of the present invention, it is possible to efficiently produce nanoparticles of inorganic materials such as copper, noble metals, oxides thereof, and alloys thereof. It can be seen that the nanoparticles can be made into particles capable of maintaining a state of being stably dispersed in the solvent for a sufficiently long period of time without using a chemical reagent or the like. confirmed. Moreover, according to the manufacturing method of the inorganic nanoparticle of this invention, it turned out that inorganic nanoparticle with sufficiently high uniformity can be manufactured efficiently.

  As described above, according to the present invention, it is possible to produce inorganic nanoparticles capable of maintaining a state of being stably dispersed in a solvent for a sufficiently long period of time without using a chemical reagent or the like. It becomes possible to provide the manufacturing method of an inorganic nanoparticle, and the inorganic nanoparticle dispersion liquid obtained using the method.

  Therefore, the inorganic nanoparticles obtained by the production method of the present invention are useful as materials such as various catalysts. For example, when the inorganic nanoparticles are palladium nanoparticles, such particles produce a hydrogen sensor or a catalyst. It is useful as a material for doing so.

  DESCRIPTION OF SYMBOLS 10 ... Laser oscillator, 11 ... Mirror, 12 ... Condensing means, 13 ... Processing container, 14 ... Solvent, 15 ... Target, 16 ... Stirrer, 16A ... Stirrer, 16B ... Device which can rotate a stirrer G: Atmospheric gas, I: Interface between liquid phase and gas phase, L: Laser light, W: Window, B: Bottom of processing vessel.

Claims (6)

A laser oscillator for generating laser light, a condensing means for condensing the laser light, a processing container for holding a solvent, a solvent held in the processing container, and the solvent And a liquid target comprising at least one inorganic material selected from the group consisting of copper, noble metals, oxides thereof, and alloys containing at least one of copper and noble metals. Using phase laser ablation equipment,
While stirring the solvent, the solvent is condensed and irradiated from the gas phase side to the interface such that the fluence at the interface between the liquid phase and the gas phase is 0.70 J / cm ² or more. A method for producing inorganic nanoparticles, wherein the target is irradiated with the laser beam to form nanoparticles of the inorganic material in the solvent. ^{2. The} method for producing inorganic nanoparticles according to claim 1, wherein a fluence at an interface between a liquid phase and a gas phase of the laser light is 0.70 to 200 J / cm ² .   The target is a powder made of an inorganic material that is separately formed by irradiating a laser beam in a liquid phase, and before the step of stirring the solvent, the target powder is placed in the solvent. The method for producing inorganic nanoparticles according to claim 1 or 2, wherein the inorganic nanoparticles are dispersed. An inorganic nanoparticle dispersion in which inorganic nanoparticles are dispersed in a solvent,
UV-visible light absorption with respect to the initial inorganic nanoparticle dispersion within 2 hours after production and the inorganic nanoparticle dispersion which has been allowed to pass for more than one year after production under conditions of atmospheric pressure and temperature of 20 to 25 ° C. Each of the spectrum measurements is performed, and any two different points selected from the wavelength range in which the absorbance value of the absorption spectrum of the initial inorganic nanoparticle dispersion in the wavelength range of 200 to 800 nm is a positive value. The wavelengths are the first wavelength and the second wavelength, respectively, and the ratio of the absorbance of the light at the two wavelengths ([absorbance of the light of the first wavelength] / [absorbance of the light of the second wavelength]), respectively. When obtained, both the absorbance value of the light of the first wavelength and the absorbance of the light of the second wavelength of the inorganic nanoparticle dispersion liquid that has passed for more than one year after production are both positive values, and The strength ratio of the initial inorganic nanoparticle dispersion Change rate ([initial strength ratio] / [after 1 year or more] of the strength ratio (strength ratio after 1 year or more) of the inorganic nanoparticle dispersion that has been passed for more than 1 year after production Intensity ratio]) is in the range of 0.9 to 1.1,
An inorganic nanoparticle dispersion characterized by. The inorganic nanoparticle dispersion according to claim 4, wherein the average particle diameter of the inorganic nanoparticles is 0.5 to 20 nm, and the standard deviation of the particle diameter of the inorganic nanoparticles is 3.0 nm or less. liquid.   The inorganic nanoparticle dispersion liquid according to claim 4 or 5, wherein the inorganic nanoparticle dispersion liquid is obtained using the method for producing inorganic nanoparticles according to any one of claims 1 to 3.