WO2024224517A1 - Method for producing single-crystal spherical sodium metal nanoparticles - Google Patents

Abstract

The present invention relates to a method for producing sodium metal nanoparticles that are single crystals, are spherical, and have an average particle diameter of 1-300 nm. Single-crystal spherical sodium metal nanoparticles yielded by the production method according to the present invention can generate fluorescence by excitation by ultraviolet light. The single-crystal spherical sodium metal nanoparticles can be used as a reducing agent for various organic substances due to the absence of the toxicity that is exhibited by compound semiconductors formed from cadmium, selenium, tellurium, and so forth. In addition, because they are spherical, the single-crystal spherical sodium metal nanoparticles can be used as a negative electrode for sodium batteries.

Description

Method for producing single-crystal spherical metallic sodium nanoparticles

The present invention relates to a method for producing single-crystal spherical metallic sodium nanoparticles.

Metallic sodium nanoparticles are nanoparticles made of metallic sodium atoms, and those with a particle diameter of less than 10 nm are also called metallic sodium quantum dots. Quantum dots are known to be made from metal elements such as CdSe, Cd, and Te, and exhibit fluorescence. However, as these quantum dots contain harmful elements, they must be collected after use, and so a search for alternative materials has been ongoing.

It is known that metallic sodium nanoparticles can be produced by a top-down method. For example, a method of producing metallic sodium nanoparticles by top-down is used in which sodium is dispersed in a solvent inert to metallic sodium in a stirring tank by high-speed stirring at a temperature equal to or higher than the melting point of sodium, thereby forming the sodium into fine particles. Patent Document 1 describes a method of producing metallic sodium dispersion by dispersing metallic sodium in transformer oil.

The method of stirring in a stirring tank has the problem that it is not possible to control and produce sodium to the desired particle size. As a method to improve this, Patent Document 2 describes a manufacturing method in which metallic sodium is stirred together with a dispersion medium in a stirring tank to produce a sodium dispersion in which sodium particles are dispersed in the dispersion medium, and the method produces metallic sodium particles based on a relationship between the average particle size of the sodium particles and the tip speed V of the stirring blade. However, it does not disclose a manufacturing method that can produce spherical metallic sodium single crystals of around 10 nm.

Patent Document 3 describes a method for producing a solvent dispersion of an alkali metal. However, it does not disclose that the sodium particles, which is an element of an alkali metal, are single crystal and spherical. In addition, the sodium to be dispersed is in a molten state, and a raw material obtained as sodium in advance is used, which is different from the single crystal spherical metallic sodium nanoparticles obtained by reducing a sodium raw material in a solution as in the present invention.

Patent document 4 discloses a method for using a colloidal suspension containing 2-60% alkali metal particles suspended in a neutral hydrophobic diluent to produce gaseous hydrogen, the metal particles being 0.1-1 μm in size, and the hydrophobic diluent being a material selected from vegetable oils and mineral oils. However, it is not disclosed that the alkali metal in Patent document 4 is produced by reduction in a solution, nor is it disclosed that the alkali metal is single crystalline and spherical.

Patent Document 5, which is owned by the same applicant as the present application, describes a method for producing semiconductor microparticles using a fluid treatment device equipped with relatively rotating treatment surfaces that can approach and separate. However, no specific examples of extremely reactive metallic sodium are described. Single-crystalline spherical metallic sodium nanoparticles cannot be obtained based on Patent Document 5.

Patent Document 6, owned by the present applicant, describes a method for producing metal microparticles using a fluid treatment device equipped with relatively rotating treatment surfaces that can approach and separate, and states that metallic sodium can be precipitated. It also describes that an ether-based organic solvent can be used for the treatment fluid, but makes no mention of the residual moisture and residual dissolved oxygen concentrations contained in the organic solvent. In addition, there is no mention of the oxidation-reduction potential required for precipitation, and there is no specific example of the potential hierarchy between a substance that reduces metallic sodium particles and metallic sodium, and no mention is made of the means by which it can be produced.

Non-Patent Document 1 describes the calculation results of metallic sodium plasmons that depend on the number of metallic sodium atoms. However, it does not describe a specific method for producing metallic sodium nanoparticles that can confirm the calculation results.

JP 10-110205 A Patent Publication 2004-300577 Patent Publication 2003-268417 Patent Publication 2011-526572 Patent 4458202 Patent 5950476

Physical Chemistry Chemical Physics, Vol. 22, 13285-13291 (2020)

The objective of the present invention is to provide a method for producing metallic sodium nanoparticles that can generate blue fluorescence when excited by ultraviolet light of an excitation wavelength, are virtually non-toxic, can be densely packed into electrode materials for secondary batteries that do not require recovery, and can be used as catalysts, reducing agents, etc.

As a result of intensive research aimed at solving the above-mentioned problems, the inventors have discovered that single-crystal spherical metallic sodium nanoparticles that are single crystal, spherical, and have an average particle size of 1 nm to 300 nm are single crystals that do not have grain boundaries that reduce luminous efficiency, and therefore can generate high fluorescence when excited by ultraviolet light, and can further be packed with electrode materials for secondary batteries at high density, thereby completing the present invention.
That is, the present invention is as follows.

[1] A method for producing single-crystal spherical metallic sodium nanoparticles, which are single crystals and spherical, comprising the steps of:
The method includes a step of mixing and reacting a raw material liquid containing sodium halide with a reducing liquid containing an anion of an aromatic compound,
The anion of the aromatic compound is prepared by mixing lithium, sodium or potassium with the aromatic compound.
[2] The method according to [1], wherein the circularity is defined as being 0.85 or more on average when calculated from the perimeter (Z) and area (S) of a projected image of the single crystal metallic sodium nanoparticles observed under a transmission electron microscope using the formula: 4πS/ ^Z2 .

[3] The method according to [1] or [2], wherein the average particle size of the monocrystalline spherical sodium metallic nanoparticles is 1 nm to 300 nm.
[4] The sodium halide is sodium iodide,
The method according to any one of [1] to [3], wherein the molar ratio of lithium, sodium or potassium to sodium iodide is 2:1 to 1:1.
[5] The method according to any one of [1] to [4], wherein the aromatic compound is at least one selected from the group consisting of 4,4'-di-tert-butylbiphenyl (DBB), biphenyl, naphthalene, and phenanthrene.

[6] When the aromatic compound is DBB or biphenyl, the aromatic compound exhibits a lower chemical shift than a neutral aromatic anion in the ¹ H-NMR spectrum of the reduced solution. The method according to any one of [1] to [5].
[7] When the aromatic compound is DBB or biphenyl, the reduction solution exhibits a chemical shift value of 2 ppm or more in the ⁷ Li-NMR spectrum. The production method according to any one of [1] to [6].
[8] The method according to any one of [1] to [7], wherein the solvent contained in the reduction solution is tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyltetrahydropyran, 1,2-dimethoxyethane, or a mixture thereof, having a residual water content of 10 ppm or less and a residual oxygen concentration of less than 0.1 ppm.

[9] The method according to any one of [1] to [8], wherein the single-crystal spherical single-crystal sodium metallic nanoparticles are made of cubic crystals.
[10] The method according to any one of [1] to [9], wherein the dispersion obtained by dispersing the single-crystal spherical sodium metallic nanoparticles in an organic solvent having an optical refractive index of 1.40 to 1.50 has an absorbance peak at 270 nm to 340 nm in an ultraviolet-visible absorption spectrum.
[11] The method according to any one of [1] to [10], wherein the single-crystal spherical sodium metallic nanoparticles have a fluorescence maximum in a wavelength range of 380 nm to 450 nm in a fluorescence spectrum.

[12] An apparatus comprising: a fluid pressure imparting mechanism which imparts pressure to the reducing solution; two processing members, a first processing member and a second processing member which can move relatively close to and away from the first processing member; and a rotation drive mechanism which rotates the first processing member and the second processing member relatively,
Two processing surfaces, a first processing surface and a second processing surface, are provided at positions facing each other in each of the processing parts, and each of the processing surfaces constitutes a part of a sealed flow path through which the reduction solution at the above pressure flows,
Between the two processing surfaces, a fluid to be processed, that is, the reduced liquid and the raw material liquid, containing single-crystal spherical sodium metallic nanoparticles as a reactant, is mixed and reacted with each other. Of the first and second processing members, the second processing member has a pressure-receiving surface, and a part of this pressure-receiving surface is constituted by the second processing surface, and this pressure-receiving surface receives a pressure applied to the reduced liquid by the fluid pressure imparting mechanism, and generates a force for moving the second processing surface in a direction away from the first processing surface, and the pressure-receiving surface is disposed between the first and second processing surfaces which can approach and separate and rotate relatively. a device for passing the reduced liquid, which is a fluid to be processed under a pressure, and the raw material liquid, so that the fluid to be processed forms a thin film fluid containing single-crystal spherical sodium metallic nanoparticles, and the device further comprises a separate inlet path independent of the flow path between the processing surfaces through which the reduced liquid under the pressure flows, the second processing surface is provided with one opening portion which leads to the separate inlet path, and the raw material liquid sent from the separate inlet path is introduced between both processing surfaces, thereby mixing the reduced liquid and the single-crystal spherical sodium metallic nanoparticles produced from the raw material liquid within the thin film fluid,
The method according to any one of [1] to [11], wherein the raw material liquid and the reduced liquid are mixed and reacted.

[13] The manufacturing method described in [12], in which the opening for introducing the sodium iodide raw material solution is located downstream of the point where the flow of the reducing solution passed between the two processing surfaces becomes laminar.

The single-crystal spherical sodium metal nanoparticles produced by the manufacturing method of the present invention are single crystals that do not have grain boundaries that reduce fluorescence efficiency, and therefore can fluoresce when excited by ultraviolet light. Furthermore, single-crystal spherical sodium metal nanoparticles do not have the toxicity of compound semiconductors formed from cadmium, selenium, tellurium, etc., and therefore can be used without the need to collect them after use. Furthermore, because single-crystal spherical sodium metal nanoparticles are spherical, they can be densely packed with electrode materials for secondary ion batteries, etc.

1 shows the ¹ H-NMR spectrum of DBB of a reduced solution of single crystal spherical metallic sodium nanoparticles. 1 shows the ¹ H-NMR spectrum of the DBB anion radical of a reduced solution of single-crystal spherical metallic sodium nanoparticles. 1 shows a ¹ H-NMR spectrum of the tert-butyl group of DBB in a reduced solution of single crystal spherical metallic sodium nanoparticles. 1 shows a ¹³ C-NMR spectrum of a reduced solution of single-crystal spherical metallic sodium nanoparticles in THF. 7 shows the ⁷ Li-NMR spectrum of lithium cations when THF is used as the solvent for the reduced solution of single crystal spherical metallic sodium nanoparticles. 1 shows the change over time in the ⁷ Li-NMR spectrum half-width of lithium cations after preparation of a reduced solution of single-crystal spherical sodium metallic nanoparticles using THF as the solvent. 7 shows the ⁷ Li-NMR spectrum of lithium cations when 4-methyltetrahydropyran (4MeTHP) is used as the solvent for the reduced solution of single-crystal spherical metallic sodium nanoparticles. ²³ Na-NMR spectrum of a sodium iodide THF solution of a raw material liquid of single crystal spherical sodium metallic nanoparticles is shown. 1 shows a TEM observation image of the single-crystal spherical metallic sodium nanoparticles produced in Example 1-1. A high-magnification TEM image of the single-crystal spherical metallic sodium nanoparticles produced in Example 1-1 is shown. Fig. 11(a) shows an XRD pattern of the single-crystal spherical sodium metallic nanoparticles prepared in Example 1-2, which were collected by centrifugation at low acceleration, and Fig. 11(b) shows an XRD pattern of the single-crystal spherical sodium metallic nanoparticles prepared in Example 1-2, which were collected by centrifugation at high acceleration. 1 shows the ultraviolet-visible absorption spectrum when the dispersion solvent for the single-crystal spherical sodium metallic nanoparticles prepared in Example 1-3 was hexane and tetrahydrofuran (THF). 1 shows the fluorescence spectrum when the single-crystal spherical metallic sodium nanoparticles prepared in Example 1-4 are dispersed in T benzene. 1 shows the fluorescence spectrum when the single-crystal spherical metallic sodium nanoparticles prepared in Example 1-4 are dispersed in THF.

Below, embodiments of the present invention are described. However, the present invention is not limited to the embodiments described below. As an example, application to a light-emitting material that generates fluorescence is described, but the uses of the single-crystal spherical metallic sodium nanoparticles produced by the manufacturing method of the present invention are not limited to these.

1. Single-crystal spherical sodium metal nanoparticles The single-crystal spherical sodium metal nanoparticles produced by the production method of the present invention are single crystals, spherical, and have an average particle size of 1 nm to 300 nm. If the average particle size is 300 nm or more, when the single-crystal spherical sodium metal nanoparticles are used as a secondary battery negative electrode material, it becomes difficult to pack them at a high density. The single-crystal spherical sodium metal nanoparticles preferably have an average circularity of 0.85 or more, more preferably 0.90 or more, and even more preferably 0.92 or more, calculated by the formula 4πS/ ^Z2 using the perimeter (Z) and area (S) of the projected image of the single-crystal spherical carbon nanoparticles observed by a transmission electron microscope. When fluorescence from the single-crystal spherical sodium metal nanoparticles is to be utilized, the average particle size of the single-crystal spherical sodium metal nanoparticles is preferably 1.2 nm to 20 nm, more preferably 1.5 nm to 15 nm, and even more preferably 2 nm to 10 nm.

The single-crystalline spherical sodium metallic nanoparticles preferably have an absorption maximum in the UV-Visible absorption spectrum below 400 nm.
The single-crystal spherical sodium metal nanoparticles are preferably those which produce a fluorescence maximum in the wavelength range of 400 nm to 600 nm in the fluorescence spectrum.

The fluorescence of metallic sodium nanoparticles occurs through the following mechanism.
(A) The fluorescent color is controlled by controlling the physical factor of changing the band gap of electronic energy according to the particle size of metallic sodium nanoparticles, a mechanism known as the quantum effect.
(B) The mechanism is that the surface state of metallic sodium nanoparticles is involved in fluorescence due to the presence of a slightly oxidized surface layer on the surface of the metallic sodium nanoparticles.
The monocrystalline spherical sodium metallic nanoparticles of the present invention preferably produce a fluorescence maximum in the wavelength range of 400 nm to 600 nm.

2. Manufacturing method of single-crystalline spherical metallic sodium nanoparticles The manufacturing method of the present invention is a manufacturing method of single-crystalline spherical metallic sodium nanoparticles that are single-crystalline, spherical, and have an average particle size of 1 nm to 300 nm, and includes a step of mixing and reacting a raw material liquid containing sodium halide with a reducing liquid containing an anion of an aromatic compound, the anion of the aromatic compound being prepared by mixing lithium, sodium or potassium with an aromatic compound. For example, the nanoparticles can be manufactured by mixing a liquid (liquid B) containing raw materials for single-crystalline spherical metallic sodium nanoparticles with a reducing liquid (liquid A) containing metallic lithium and an aromatic compound in a thin film fluid formed between two processing surfaces arranged opposite to each other, capable of approaching and separating, at least one of which rotates relative to the other.

(Single-crystal spherical metallic sodium nanoparticle raw material liquid (liquid B))
The raw material for the single-crystal spherical sodium metal nanoparticles is not particularly limited as long as it is a substance that can precipitate single-crystal spherical sodium metal nanoparticles by reduction. The raw material is preferably sodium halide, more preferably sodium iodide.

The solvent for the raw material solution of single-crystal spherical sodium metal nanoparticles is not particularly limited, so long as it is a substance that can reduce the raw material of single-crystal spherical sodium metal nanoparticles to precipitate single-crystal spherical sodium metal nanoparticles, and is inactive and does not affect the reduction reaction. Preferred examples of the solvent include ether, and more preferred examples include tetrahydrofuran (THF), 1,2-dimethoxyethane (DME), 2-methyltetrahydrofuran, 4-methyltetrahydropyran, or mixtures thereof. These solvents have a higher boiling point than diethyl ether, ensuring temperature stability, and have low reactivity with alkali metals, suppressing the generation of by-products due to decomposition of the solvent.

(Residual moisture/residual oxygen in solvent)
It is necessary to use a solvent in which the residual moisture content is 10 ppm or less and the residual oxygen content is less than 0.1 ppm in the present invention, because when single-crystal spherical metallic sodium nanoparticles are produced in a solvent by a reduction reaction, if the residual moisture content is more than 10 ppm, the metallic sodium particles will be completely oxidized even to the inside of the particles.

(Single-crystal spherical metallic sodium nanoparticle reduced solution (solution A))
The reducing agent contained in the reduced solution of single-crystal spherical sodium metal nanoparticles is not particularly limited as long as it can reduce the raw material of single-crystal spherical sodium metal nanoparticles contained in the raw material solution of single-crystal spherical sodium metal nanoparticles to precipitate as single-crystal spherical sodium metal nanoparticles. For example, the reducing agent can be a combination of metallic lithium and an aromatic compound.

It has been reported that the redox potential of metallic sodium in a THF solvent, which is an example of the production method of the present invention, is −3.04 V (based on the ferrocene/ferricinium ion (Fc/Fc ⁺ ) potential). This corresponds to −2.84 V based on an Ag/AgCl electrode.
Examples of aromatic compounds include those that can transfer one electron from metallic lithium to an aromatic compound to generate a lithium cation and an aromatic compound anion (radical anion). The aromatic compound anion to which one electron has been transferred has one electron in the lowest unoccupied molecular orbital (LUMO) of the aromatic compound. In order to reduce the aromatic compound to single-crystalline spherical metallic sodium nanoparticles, the potential of the aromatic compound anion must be lower than −2.84 V. A preferred aromatic compound is 4,4′-di-tert-butylbiphenyl (DBB) (−3.13 V).

In the manufacturing method of the present invention using an aromatic compound as a reducing agent, it is possible to utilize a disproportionation reaction caused by electron transfer between two molecules of an aromatic compound anion radical. This disproportionation reaction between two molecules is a reaction in which a naphthalene dianion, which is a divalent anion that has further transferred one electron to a naphthalene anion radical, and neutral naphthalene are generated. Since the oxidation-reduction potential of the naphthalene dianion is lower than that of the naphthalene anion radical (-2.53 V), it is possible to manufacture metallic sodium nanoparticles even if naphthalene is used. In addition to naphthalene, aromatic compounds that generate dianions having a lower potential than the anion radical through a disproportionation reaction include biphenyl anion radical (-2.68 V), biphenyl dianion (-3.18 V), phenanthrene anion radical (-2.49 V), and phenanthrene dianion (-3.13 V), and therefore metallic sodium nanoparticles can be manufactured using any of these aromatic compounds or mixtures thereof, and preferably DBB, biphenyl, etc.

The molar ratio of metallic lithium to the aromatic compound is, for example, 1:1 to 1:5, preferably 1:1 to 1:1.2, and more preferably 1:1 to 1:1.15.
The molar ratio of metallic lithium to the raw material of the single crystal spherical sodium metal nanoparticles is, for example, 10:1 to 1.2:1, preferably 7:1 to 1.5:1, and more preferably 5:1 to 3:1. It is preferable to use metallic lithium in excess of the raw material of the single crystal spherical sodium metal nanoparticles. By using an excess amount, single crystal spherical sodium metal nanoparticles can be prepared. When metallic lithium is used in an amount of 3/4 less than the raw material of the single crystal spherical sodium metal nanoparticles, the single crystal spherical sodium metal nanoparticles are not completely reduced, and halogen atoms derived from the raw material remain in the single crystal spherical sodium metal nanoparticles, becoming polycrystalline and no longer spherical. Examples of the solvent for the single crystal spherical sodium metal nanoparticle reduced solution include the above-mentioned solvents used in the single crystal spherical sodium metal nanoparticle raw material solution. The concentration of metallic lithium in the single crystal spherical sodium metal nanoparticle reduced solution is not particularly limited, but is determined according to the molar ratio of the above metallic lithium to the raw material of the single crystal spherical sodium metal nanoparticles.

(Low temperature preparation of reducing solution)
Alkali metals can be dissolved in ether-based organic solvents in the presence of aromatic compounds, but when the dissolution temperature is 30° C. or higher, the aromatic compound anions become unstable, and a chemical reaction occurs between the aromatic compound and the alkali metal atom, which impairs the effect of the reducing solution. For example, when naphthalene (molecular formula: C ₁₀ H ₈ ) is used as the aromatic compound and lithium (Li) is used as the alkali metal, a compound such as C ₁₀ H ₇ Li is generated, which tends to cause a change in the concentration of the naphthalene anion acting as a reducing agent, and this is also a problem when DBB is used as the aromatic compound. For this reason, in the manufacturing method according to the present invention, the temperature of the solution preparation in the stage of preparing the reduced solution of single-crystal spherical metallic sodium nanoparticles is maintained below 30° C., allowing the aromatic compound anions to exist stably, and suppressing the decomposition of the aromatic compound anions.

(Alkali metal cation and aromatic compound anion mediated by solvent molecules)
The aromatic compound anion generated by electron transfer of metallic lithium to an aromatic compound can be bonded to the metallic lithium cation generated by electron transfer via Coulomb force. The state in which the lithium cation and the aromatic compound anion are bonded via Coulomb force can be evaluated from the chemical shift value and spectrum width of the ⁷ Li-NMR spectrum. The state in which the lithium cation is bonded to the aromatic anion radical via Coulomb force is confirmed by the spectrum width being wider than the state in which only the lithium cation is dissolved in the solvent. The usable time of the reducing solution can be estimated from this spectrum width, so the state in which the reducing power of the reducing solution is maintained can be confirmed by ⁷ Li-NMR spectrum measurement before reduction of the single-crystalline spherical metallic sodium nanoparticles. As a result, by confirming that the reducing power is maintained in the same manner as when the solution was prepared before production, the spread of the particle size distribution of the resulting single-crystalline spherical metallic sodium nanoparticles can be reduced. As described above, when metallic lithium and DBB are dissolved in THF, it is possible to confirm whether the reducing power of the reducing solution is suitable for producing ^single -crystalline spherical metallic sodium nanoparticles by measuring the state in which the aromatic compound DBB changes from a neutral state to a DBB anion radical in the 7 Li-NMR spectrum and the chemical shift and spectral width reflecting the bonding due to Coulomb force of the lithium cation.

(Polymerization Inhibition of THF Solvent)
The necessity of preparing the reducing solution at a low temperature is as described above from the viewpoint of solvation. In addition, it is preferable to keep the storage temperature after preparation low. When the storage temperature of the reducing solution is high, if a cyclic ether such as THF is used as a solvent, a reduction polymerization reaction of the cyclic ether occurs due to the aromatic compound anion. When such a polymer is generated by polymerization of the cyclic ether, it will be mixed with the single crystal spherical metallic sodium nanoparticles generated by the reduction of the halocarbon, so it is preferable to suppress the polymerization reaction. Examples of polymerization reaction inhibitors for cyclic ethers such as THF include phenol-based polymerization inhibitors added to suppress the generation of peroxides of cyclic ethers such as THF, and preferably BHT (2,6-di-tert-butyl-4-methylphenol).

(Production method and equipment for single-crystal spherical metallic sodium nanoparticles)
The single-crystal spherical sodium metallic nanoparticles of the present invention can be produced, for example, by mixing a raw material liquid (liquid B) containing the raw materials for single-crystal spherical sodium metallic nanoparticles with a reducing liquid (liquid A) containing metallic lithium and an aromatic compound in a thin film fluid formed between two processing surfaces arranged opposite each other, which are capable of approaching and separating each other and at least one of which rotates relative to the other.
An example of the apparatus used in the production method of the present invention is a fluid treatment apparatus proposed by the applicant of the present application and described in JP 2009-112892 A. The apparatus has a stirring tank having an inner peripheral surface with a circular cross section and a stirring tool attached to the inner peripheral surface of the stirring tank with a small gap therebetween, and the stirring tank has at least two fluid inlets and at least one fluid outlet, and a first treated fluid containing one of the reactants among the treated fluids is introduced into the stirring tank from one of the fluid inlets, and a second treated fluid containing one of the reactants different from the reactant is introduced into the stirring tank from the other of the fluid inlets through a flow path different from that of the first treated fluid. At least one of the stirring tank and the stirring tool rotates at high speed relative to the other to make the treated fluid into a thin film state, and reactants contained in at least the first treated fluid and the second treated fluid react with each other in this thin film.

Preferably, the raw material liquid (liquid B) and the reduced liquid (liquid A) are mixed in the thin film fluid to produce single-crystal spherical sodium metal nanoparticles. Single-crystal spherical sodium metal nanoparticles are produced in the following steps: first, clusters, which are aggregates of metallic sodium atoms, are generated as nuclei of single-crystal spherical sodium metal nanoparticles, and then these cluster together to grow single-crystal spherical sodium metal nanoparticles. Even if the reaction starts when liquid B comes into contact with liquid A, which has a temperature of less than 10°C, the frequency of generation of nuclei for single-crystal spherical sodium metal nanoparticle growth is low, so the frequency of contact between clusters at the nuclei of single-crystal spherical sodium metal nanoparticles is also low. Therefore, the growth of single-crystal spherical sodium metal nanoparticles is less susceptible to changes in the raw material liquid concentration due to the growth of surrounding single-crystal spherical sodium metal nanoparticles, and the supply of raw materials necessary for the growth of single-crystal spherical sodium metal nanoparticles is uniform.

The temperature of the single crystal spherical sodium metal nanoparticle reduction solution (Solution A) introduced into the thin film fluid formed between two processing surfaces arranged opposite each other, which can approach and separate, and at least one of which rotates relative to the other, can be, for example, -30°C to 25°C, preferably -10°C to 25°C, and more preferably 0°C to 25°C.

The temperature of the raw material liquid (liquid B) of single crystal spherical metallic sodium nanoparticles introduced into the thin film fluid formed between two processing surfaces arranged opposite to each other, capable of approaching and separating, at least one of which rotates relative to the other, can be, for example, -10°C to 25°C, preferably 0°C to 25°C, and more preferably 10°C to 25°C. In Examples 1 to 3, production was performed with the temperature of liquid B at 23°C, and as a result, single crystal spherical metallic sodium nanoparticles that are single crystal, spherical, and fluorescent could be produced.

In the production of single-crystal spherical sodium metal nanoparticles, for example, lithium chloride is produced as a by-product. Because lithium chloride has high solubility in the reaction solvent, it can be easily separated from the single-crystal spherical sodium metal nanoparticles by centrifugation.

3. Uses of Single-Crystal Spherical Sodium Metallic Nanoparticles The single-crystal spherical sodium metallic nanoparticles of the present invention can be used, for example, as a luminescent material that generates fluorescence, a negative electrode for a secondary battery, a reducing agent for various organic substances, a catalyst, etc.

The present invention will be further explained below with reference to examples, but the present invention is not limited to these examples.

(Transmission Electron Microscope (TEM): Preparation of Samples for TEM Observation)
The single-crystal spherical metallic sodium nanoparticles obtained in the Examples and Comparative Examples were dispersed in THF at a concentration of about 0.001% in a container. The container containing the resulting dispersion was introduced into a glove box in an argon atmosphere, and the dispersion was dropped onto a carbon support film and dried to prepare a sample for TEM observation.

(TEM Observation)
A transmission electron microscope JEM-2100 (manufactured by JEOL Ltd.) was used for TEM observation of the single-crystal spherical sodium metallic nanoparticles. The above-mentioned TEM observation sample was used as the specimen. The observation conditions were an acceleration voltage of 200 kV and an observation magnification of 10,000 times or more. The particle size was calculated from the distance between the maximum outer circumferences of the single-crystal spherical sodium metallic nanoparticles observed by TEM, and the average value (average particle size) of the results of measuring the single-crystal spherical sodium metallic nanoparticle size for 50 particles was calculated.

(Confirmation of the generation of anions of aromatic compounds by NMR spectroscopy)
The case of naphthalene will be described as an example of an aromatic compound. Metallic lithium was added to a THF solution in which naphthalene was dissolved, generating naphthalene anions as a reducing species, and the generation was confirmed by ¹ H-NMR and ⁷ Li-NMR spectra. The measurement sample was prepared by filling an NMR sample tube with the reducing solution in a glove box in an argon atmosphere, mixing tetramethylsilane (TMS) as a chemical shift standard substance, sealing the tube, and then removing the tube from the glove box in an argon atmosphere. The sample was measured by a transmission method using a Fourier transform nuclear magnetic resonance apparatus (manufactured by JEOL Ltd.). The measurement conditions were 23°C to 25°C, and 128 integration times for ¹ H-NMR and 16 integration times for ⁷ Li-NMR.

(Fluorescence spectrum)
The fluorescence spectrum of the single crystal spherical metallic sodium nanoparticles was measured using a spectrofluorometer FT-6500 (manufactured by JASCO Corporation). The above-mentioned TEM observation sample was used as the sample. As the sample, the sample solution dispersed in THF was placed in a quartz cell (optical path length: 1 cm) in a glove box with an argon atmosphere, the top was sealed, and the cell was removed from the glove box and measured. The measurement conditions were an excitation bandwidth of 3 nm, a fluorescence bandwidth of 3 nm, a response of 0.1 seconds, a scanning speed of 100 nm/min, and a data acquisition interval of 0.5 nm.

(Ultraviolet-visible: UV-vis absorption spectrum measurement)
The UV-vis (ultraviolet-visible) absorption spectrum of the single crystal spherical metallic sodium nanoparticles was measured using an ultraviolet-visible-near infrared spectrophotometer (product name: V-770, manufactured by JASCO Corporation). The measurement range was 200 nm to 900 nm, the sampling rate was 0.2 nm, and the measurement speed was slow. A 10 mm thick quartz cell for liquids was used for the measurement.

(Circularity)
The circularity was calculated as an index for evaluating the sphericity of the single-crystal spherical sodium metal nanoparticles as follows. The circularity of the single-crystal spherical sodium metal nanoparticles was calculated by approximating the image obtained by TEM observation as an ellipse using TEM image software iTEM (manufactured by Olympus Soft Imaging Solutions GmbH). Next, the major axis (D), perimeter (Z) and area (S) of the ellipse, which is the projected image of the single-crystal spherical sodium metal nanoparticle, were obtained from the analysis results of the TEM image analysis software. 4πS/ ^Z2 was calculated using the values of the perimeter (Z) and area (S) to obtain the circularity. The closer the circularity value is to 1, the closer the particle is to a sphere, and when the particle shape is a perfect sphere, the circularity is a maximum of 1.
The average value of the major axis (D) of the ellipses was calculated as the average particle size. The measurement was performed for 50 independent single-crystal spherical sodium metallic nanoparticles.

(X-ray diffraction: XRD)
For the X-ray diffraction (XRD) measurement, an EMPYREAN powder X-ray diffraction measuring device (manufactured by Malvern Panalytical Division of Spectris Co., Ltd.) was used. The measurement conditions were: measurement range: 10 to 100 [°2θ], Cu anticathode, tube voltage: 45 kV, tube current: 40 mA, and scan speed: 0.013°/min.

Example 1
In Example 1, a THF solution of sodium iodide (single-crystalline spherical sodium metal nanoparticle raw material liquid) was reduced using a DBB-dissolved THF solution of metallic lithium (single-crystalline spherical sodium metal nanoparticle reduced liquid) to produce single-crystalline spherical sodium metal nanoparticles. Table 1 shows the recipes for Examples 1-1 to 1-4. Table 1 shows a case where the molar ratio of metallic lithium to sodium iodide is 1:1, but in the present invention, a molar ratio of metallic lithium to sodium iodide of up to 2:1 is applicable. In addition to metallic lithium, metallic sodium and metallic potassium can also be used in a similar molar ratio.

The solvent used in Example 1 was ultra-dehydrated tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with a residual moisture content of 10 ppm or less. In a glove box with an argon atmosphere, a single-crystal spherical metallic sodium nanoparticle reduction solution (Liquid A) and a single-crystal spherical metallic sodium nanoparticle raw material solution (Liquid B) were prepared. Specifically, the single-crystal spherical metallic sodium nanoparticle reduction solution (Liquid A) was prepared by dissolving metallic lithium to a concentration of 0.1 mol/L in a THF solution in which DBB was dissolved to a concentration of 0.1 mol/L at a preparation temperature of 20°C using a glass-coated magnetic stirrer. Similarly, sodium iodide, which is the raw material for the single-crystal spherical metallic sodium nanoparticles of Liquid B, was dissolved in THF and stirred for at least 60 minutes using a glass-coated magnetic stirrer. For substances indicated by chemical formulas or abbreviations in Table 1, DBB is 4,4'-di-tert-butylbiphenyl (manufactured by Tokyo Chemical Industry Co., Ltd.), NaI is sodium iodide (manufactured by Kanto Chemical Co., Ltd.), and Li is metallic lithium (manufactured by Kishida Chemical Co., Ltd.).

The generation of 4,4'-di-tert-butylbiphenyl (DBB) anion in solution A was confirmed by the ^1H -NMR spectrum shown in Figure 1. The neutral DBB molecule before electron transfer exhibits a chemical shift of 7.4 ppm to 7.6 ppm, but the peak disappears due to the generation of the DBB anion radical.

Since changes in the reducing power of Solution A result in a distribution of particle sizes of the produced single crystal spherical metallic sodium particles, it is necessary to confirm the reducing power. Figure 2 shows a ^1H -NMR spectrum due to the generation of DBB anion radicals that have accepted electrons produced by the dissolution of metallic lithium. The four peaks observed at 5.8 ppm to 7.4 ppm are due to the generation of DBB anion radicals, and the peak width increases as the DBB anion radicals solvate with lithium cations and THF molecules.

3 shows the ^1H -NMR spectrum of the tert-butyl group, which is a substituent of DBB. The peak at 1.34 ppm disappears due to the generation of DBB anion radical, but after 65 hours, it was confirmed that a peak reappears at 1.4 ppm. This reappearance is due to a decrease in the Coulomb force between the DBB anion radical and the lithium cation, and it is therefore considered that the reducing power is maintained for up to 24 hours.

The DBB anion radical can form an ion pair bound by Coulomb force with a lithium cation. Three states are known when an aromatic compound anion and a metal cation form an ion pair. (1) An ion pair in which the DBB anion radical and the lithium cation are directly bound by Coulomb force without a solvent [DBB ^·- Li ⁺ ], (2) An ion pair in which a solvent is interposed between the DBB anion radical and the lithium cation [DBB ^·- /THF/Li ⁺ ], and (3) An ion pair in which the DBB anion radical and the lithium cation are solvated and bound by Coulomb force [THF/DBB ^·- /THF/THF/Li ⁺ /THF] are possible. The Coulomb force between the ion pairs is strongest in (1), followed by weaker Coulomb forces in (2) and (3). Since the state of these ion pairs is reflected in the NMR spectrum, it is possible to evaluate the reducing power by also measuring the NMR of the solvent that may be present between the DBB anion radical and the lithium cation.

FIG. 4 shows the spectrum of the carbon atom at the (2,5) position of CH ₂ bonded to oxygen in the THF of the reduced solution measured by ¹³ C-NMR. Since this carbon atom is bonded to oxygen, it is sensitive to the solvation state of THF by the oxygen atom, and the solvation state of THF with lithium cations and DBB anion radicals can be confirmed by the chemical shift shown by this carbon atom. As time passes after metallic lithium is added, the peak of THF shifts lower, and after 65 hours, it coincides with the same chemical shift and spectral line width as the DBB dissolved THF solution not containing lithium cations. This result is considered to indicate that the solvation state of DBB neutral molecules with no lithium cations by THF and the solvation state of DBB anion radicals with lithium cations by THF are in a similar state, so it is judged that the reducing solution has almost no reducing power after 65 hours. This result corresponds to the behavior shown in FIG. 3, in which the peak of the tert-butyl group of the DBB anion radical in 1H-NMR reappeared after 65 hours.

The electrons generated by the dissolution of metallic lithium are transferred to the DBB and become lithium cations, and the generation of these cations can be confirmed by the change in the chemical shift and the spectral line width at about 3.8 ppm in the ⁷ Li-NMR spectrum. Even 24 hours after the addition of metallic lithium, the spectral line width is broadened, which reflects the state in which the lithium cations and DBB anions directly interact with each other through Coulomb force.

The interaction between lithium cations and DBB anion radicals broadens the spectral line width in the cases (1) and (2) explained above, which indicates that the reducing power of the reducing solution is maintained because the two states of direct Coulomb force interaction and interaction via the solvent contribute to the broadening of the spectral line width.

FIG. 5 shows the lithium cation spectrum of the ⁷ Li-NMR spectrum of a 0.1 mol/L concentration DBB ^{-THF solution containing metallic lithium when THF is used as the solvent for the reducing solution. FIG. 6 shows the time change in the line width of this NMR spectrum. After 65 hours of preparation, the spectrum width is close to that of DBB-} THF in which no lithium cation is present, and it can be determined that the reducing power of the reducing solution has decreased. As described above, the reducing power of the reducing solution for producing single-crystalline spherical metallic sodium nanoparticles can be evaluated from the ¹ H-NMR spectrum, the ¹³ C-NMR spectrum, and the ⁷ Li-NMR spectrum, and it is necessary to use the reducing solution within 24 hours after adding metallic lithium. The state of an ion pair in which a lithium cation and a DBB anion radical are directly bound by Coulomb force, and the state of an ion pair in which a THF molecule is interposed and bound by Coulomb force are thought to be reflected in the peak on the high chemical shift side obtained by spectral waveform separation. The chemical shifts of the two peaks obtained by waveform separation of the spectrum after 24 hours and the spectral widths shown in parentheses were 3.823 ppm (96.8 Hz) and 4.528 ppm (406.8 Hz).

7 shows the spectrum of lithium cations in the ⁷ Li-NMR spectrum when 4-methyltetrahydropyran (4MeTHP) was used as the solvent for the reduction solution. As in the case of using THF as the solvent for the reduction solution, the spectrum width after preparation is broadened, and it is confirmed that an ion pair between lithium cations and DBB anion radicals is formed in the presence of 4MeTHP. In addition, in the spectrum after centrifugation of the reaction solution after the reduction reaction with a THF solution of sodium iodide, the spectrum width is narrowed, indicating that the DBB anion radical has changed into a neutral DBB molecule and has an interaction with the lithium cation.

8 shows the results of measuring the ^23Na -NMR spectrum of a THF solution containing 0.1 mol/L sodium iodide as the sodium source for the single-crystal spherical metallic sodium nanoparticles. The chemical shift peak at 7.7 ppm shows the result of calibrating the chemical shift with the peak obtained from the measurement of a 3 mol/L solution of sodium chloride dissolved in heavy water as the chemical shift standard. Although the figure shows a state in which NaI is dissolved in THF and the sodium ions are solvated with THF, strictly speaking, the figure shows a mixed solvation state of THF and water molecules due to the 10 ppm moisture remaining in the THF solvent. It has been confirmed that the chemical shift due to the residual moisture in the THF solvent becomes lower as the moisture concentration increases. The chemical shift at a residual moisture content of 50 ppm is estimated to be 7.5 ppm, and residual moisture above this level causes oxidation of the single-crystalline spherical metallic sodium nanoparticles obtained by the production method of the present invention, resulting in significant deviation of the particle shape from sphericity due to oxidation, so it is preferable that the chemical shift of ²³ Na measured by ²³ Na-NMR is 8.0 ppm or more and less than 7.5 ppm. The solvation state can also be confirmed from the spectral width of ²³ Na-NMR, and the line width when sodium ions are solvated with heavy water is 8.5 Hz, and when solvated with THF and 10 ppm residual moisture, it is 21.3 Hz, confirming the increase in line width due to THF solvation.

Next, the prepared reduced solution of single crystal spherical sodium metallic nanoparticles (Solution A) and the raw solution of single crystal spherical sodium metallic nanoparticles (Solution B) were mixed using a fluid treatment device described in Patent Document 6 by the applicant of the present application. Here, the fluid treatment device described in Patent Document 6 is the device described in Figure 1 (A) of the same publication, in which the opening d2 of the second introduction part is a concentric ring shape surrounding the central opening of the processing surface 2, which is a disk formed in a ring shape. Specifically, the reduced solution of A or the raw solution of B was introduced between the processing surfaces 1 and 2 from the first introduction part d1, and while the processing part 10 was operated at a rotation speed of 500 rpm to 5000 rpm, the raw solution of B or the other liquid of the reduced solution of single-crystal spherical metallic sodium nanoparticles, which is different from the liquid sent as A, was introduced between the processing surfaces 1 and 2 from the second introduction part d2, and the raw solution of single-crystal spherical metallic sodium nanoparticles and the reduced solution of single-crystal spherical metallic sodium nanoparticles were mixed in the thin film fluid, and single-crystal spherical metallic sodium nanoparticles were precipitated between the processing surfaces 1 and 2. The discharged solution containing single-crystal spherical metallic sodium nanoparticles was discharged from between the processing surfaces 1 and 2 of the fluid processing device. The discharged single-crystal spherical metallic sodium nanoparticle dispersion was recovered in a beaker via a vessel. In order to block the liquid sent and the recovered liquid from the atmosphere, the connecting pipe and the recovery vessel were sealed pipes, and argon gas was flowed in this pipe for one hour to prevent the influence of the atmosphere.

Table 2 shows the operating conditions of the fluid treatment device of Example 1. The introduction temperature (liquid delivery temperature) and introduction pressure (liquid delivery pressure) of liquid A and liquid B shown in Table 2 were measured using a thermometer and a pressure gauge installed in the sealed introduction path (first introduction part d1 and second introduction part d2) leading between the processing surfaces 1 and 2. The introduction temperature of liquid A shown in Table 2 is the actual temperature of liquid A under the introduction pressure in the first introduction part d1, and the introduction temperature of liquid B is the actual temperature of liquid B under the introduction pressure in the second introduction part d2.

A wet cake sample was prepared from the dispersion of single-crystal spherical sodium metal nanoparticles discharged from the fluid processing device and collected in a beaker. The preparation was carried out according to a conventional method, where the discharged dispersion of single-crystal spherical sodium metal nanoparticles was collected, and the single-crystal spherical carbon nanoparticles were precipitated from this collected liquid by centrifugation (30,190G for 2 hours) to separate the supernatant. After that, ultrasonic cleaning with THF and precipitation were repeated, and the wet cake state was collected in an airtight container and stored in an argon atmosphere glove box.

Figure 9 shows a TEM image of the single-crystal spherical sodium metal nanoparticles of Example 1-1. It was confirmed that spherical sodium metal nanoparticles of less than 20 nm were produced. Similar results were confirmed for the single-crystal spherical sodium metal nanoparticles of Examples 1-2 to 1-4.

Figure 10 shows a high-magnification TEM image of the single-crystal spherical metallic sodium nanoparticles of Example 1-1. Similar results were confirmed for the single-crystal spherical metallic sodium nanoparticles of Examples 1-2 to 1-4. As the lattice fringes were observed in one direction, it was confirmed that the nanoparticles were single crystals. The average lattice spacing measured from the seven interference fringes of the electron beam was 337 pm. This value is close to the lattice spacing of the 101 plane of metallic sodium, which is 353 pm.

Figure 11(a) shows an XRD pattern obtained by immersing the precipitate obtained by centrifuging the single crystal spherical metallic sodium nanoparticles of Example 1-2 at 500G for 30 minutes in mineral oil and measuring it by the reflection method. The crystallite diameter obtained by the Scherrer method from the half-width of the peak at a diffraction angle of 28.5° was 15.8 nm. The XRD pattern shows an XRD pattern obtained by sandwiching metallic sodium recovered as a precipitate between Mylar films in an argon glove box and measuring it by the transmission method. Figure 11(b) shows the result of XRD measurement of the single crystal spherical metallic sodium nanoparticles of Example 1-2 in a state where the precipitate particles were aggregated on a metal foil by a high acceleration of 30,000G. The crystallite diameter calculated by the Scherrer method from the half-width of the peak at a diffraction angle of 29.4° in the XRD pattern was 456 nm.

It is known that the absorbance of metal nanoparticles varies depending on the refractive index of the solvent used in the absorbance measurement. In the case of metallic silver, it is known that the absorbance peak wavelength shifts to the longer wavelength side as the refractive index of the solvent increases.
12 shows the ultraviolet-visible absorption spectra measured when the single-crystal spherical sodium metallic nanoparticles obtained in Example 1-3 were dispersed in hexane and THF, respectively. When the dispersion solvent was hexane, a maximum absorbance was observed at 260 nm, and when the dispersion solvent was THF, a maximum absorbance was observed at 315 nm. The refractive index of hexane was 1.375, and the refractive index of THF was 1.408, and the results showed that the maximum wavelength of metal plasmon absorbance shifted to the longer wavelength side as the refractive index of the dispersion solvent increased. All of these are thought to be absorption due to plasmon excitation of the single-crystal spherical sodium metallic particles.

Non-Patent Document 1 explains the relationship between the number of metallic sodium atoms and the absorption of surface plasmons. According to this, when the number of metallic sodium atoms is 300, the imaginary component of the dielectric constant that gives optical absorption is 4.6 eV (electron volts), which is said to be the maximum absorption by surface plasmons in clusters that are aggregates of metallic sodium atoms. When this energy value is converted to a wavelength, it becomes 269.5 nm, which corresponds to the result in the above case of hexane, where the maximum absorbance was confirmed at 260 nm. It is described that clusters with sodium atoms of 150 to 200 atoms or more are approximately 2 nm or more, which corresponds to the size of the single-crystal spherical metallic sodium nanoparticles produced in this invention, which are about 5 nm.

Figures 13 and 14 show the fluorescence spectra of the single crystal spherical sodium metallic nanoparticles of Examples 1-4. The fluorescence spectra are normalized with the maximum intensity of the fluorescence spectrum obtained for each excitation wavelength set to 1.0, and are the results of changing the excitation wavelength from 320 nm to 580 nm in increments of 20 nm. From these results, it was confirmed that the fluorescence of the single crystal spherical sodium metallic nanoparticles of Examples 1-3 shows a maximum peak at 380 nm to 450 nm depending on the excitation wavelength. The results of Example 1 are shown in Table 3.

Comparative Example 1
The recipe of Comparative Example 1 was the same as that of Example 1 shown in Table 1, but the disk rotation speed was reduced to 600 rpm and 500 rpm to produce single-crystal spherical nanoparticles as shown in Table 4. Table 5 shows the results of the obtained single-crystal spherical metallic sodium nanoparticles. By reducing the disk rotation speed to less than 700 rpm, no change was observed in the crystal structure, but the average circularity was less than 0.9.

Example 2
Example 2 shows the results of single crystal spherical sodium metal nanoparticles produced when the reduced solution of single crystal spherical sodium metal nanoparticles was set at 5° C. and 10° C. and the disk rotation speed was set at 5000 rpm and 3500 rpm. The compositions of the reduced solution of single crystal spherical sodium metal nanoparticles and the raw solution of single crystal spherical sodium metal nanoparticles were the same as in Example 1, and they were produced under the conditions shown in Table 1. Table 6 shows the production conditions for Example 2, and the results of the obtained single crystal spherical sodium metal nanoparticles are as shown in Table 7. In the single crystal spherical sodium metal nanoparticles produced in Example 2, the lower the temperature of the reduced solution of single crystal spherical sodium metal nanoparticles (Liquid A), the smaller the average particle size became.

Comparative Example 2
The formulation of Comparative Example 2 was the same as that of Example 1 shown in Table 1, but as shown in Table 8, the disk rotation speed was reduced to 700 rpm, and single crystal spherical sodium metallic nanoparticles were produced at temperatures of the single crystal spherical sodium metallic nanoparticle reduction solution of Solution A of 5° C. and 10° C. Table 9 shows the results of the single crystal spherical sodium metallic nanoparticles produced. The average circularity of the single crystal spherical sodium metallic nanoparticles produced by reducing the disk rotation speed to 700 rpm and setting the temperature of Solution A at 10° C. or less was less than 0.9.

In Example 3, the formulations of solutions A and B were the same as those in Table 1, and single-crystal spherical sodium metal nanoparticles were produced by varying the flow rate ratio of single-crystal spherical sodium metal nanoparticle raw material solution B to single-crystal spherical sodium metal nanoparticle reduction solution A. Table 10 shows the production conditions for single-crystal spherical sodium metal nanoparticles. Table 11 shows the results for the single-crystal spherical sodium metal nanoparticles obtained.

In Examples 1 to 3 of the present invention, the aromatic compound in the reduced solution of single-crystal spherical sodium metal nanoparticles was DBB, but the results were shown for a case in which DBB was used. However, single-crystal spherical sodium metal nanoparticles could also be produced when biphenyl, naphthalene, or phenanthrene was used instead of DBB.

The single-crystal spherical sodium metal nanoparticles produced by the manufacturing method of the present invention can have their absorbance peak changed by changing the refractive index of the dispersion solvent, and can emit fluorescence by forming nanoparticles of about 10 nm in size. Single-crystal spherical sodium metal nanoparticles are not toxic to living organisms, unlike compound semiconductors formed from cadmium, selenium, tellurium, etc., and therefore do not require collection after use and are environmentally safe. Furthermore, because single-crystal spherical sodium metal nanoparticles are spherical, they can be densely packed with electrode materials for solar cells and secondary ion batteries, and can be used as the negative electrode of lithium ion batteries and electrode materials for solar cells. They can also be widely used as catalysts, reducing agents, etc.

Claims (13)

A method for producing single-crystal spherical metallic sodium nanoparticles, which are single crystals and spherical, comprising the steps of:
The method includes a step of mixing and reacting a raw material liquid containing sodium halide with a reducing liquid containing an anion of an aromatic compound,
The anion of the aromatic compound is prepared by mixing lithium, sodium or potassium with the aromatic compound. 2. The method according to claim ¹ , wherein the circularity is defined as a circularity calculated from the perimeter (Z) and area (S) of a projected image of the single crystal metallic sodium nanoparticles observed under a transmission electron microscope using the formula 4πS/Z2, and the average circularity is 0.85 or more. The method of claim 1 or 2, wherein the mean particle size of the single-crystal spherical single-crystal metallic sodium nanoparticles is 1 nm to 300 nm. the sodium halide is sodium iodide;
The method according to any one of claims 1 to 3, wherein the molar ratio of lithium, sodium or potassium to sodium iodide is from 2:1 to 1:1. The method according to any one of claims 1 to 4, wherein the aromatic compound is at least one selected from the group consisting of 4,4'-di-tert-butylbiphenyl (DBB), biphenyl, naphthalene, and phenanthrene. The method according to any one of claims 1 to 5, wherein when the aromatic compound is DBB or biphenyl, it exhibits a lower chemical shift than a neutral aromatic anion in the ¹ H-NMR spectrum of the reduced solution. The method according to any one of claims 1 to 6, wherein when the aromatic compound is DBB or biphenyl, the reduced solution exhibits a chemical shift value of 2 ppm or more in a ⁷ Li-NMR spectrum. The method according to any one of claims 1 to 7, wherein the solvent contained in the reduction solution is tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyltetrahydropyran, 1,2-dimethoxyethane, or a mixture thereof, with a residual moisture content of 10 ppm or less and a residual oxygen concentration of less than 0.1 ppm. The method of any one of claims 1 to 8, wherein the single-crystal spherical single-crystal metallic sodium nanoparticles are made of cubic crystals. The manufacturing method according to any one of claims 1 to 9, wherein the dispersion obtained by dispersing the single-crystal spherical metallic sodium nanoparticles in an organic solvent having an optical refractive index of 1.40 to 1.50 has an absorbance peak at 270 nm to 340 nm in the ultraviolet-visible absorption spectrum. The method of any one of claims 1 to 10, wherein the single-crystal spherical metallic sodium nanoparticles have a fluorescence maximum in the wavelength range of 380 nm to 450 nm in the fluorescence spectrum. an apparatus comprising: a fluid pressure imparting mechanism which imparts pressure to the reducing solution; two processing members, a first processing member and a second processing member which can move relatively close to and away from the first processing member; and a rotation drive mechanism which rotates the first processing member and the second processing member relatively,
Two processing surfaces, a first processing surface and a second processing surface, are provided at positions facing each other in each of the processing parts, and each of the processing surfaces constitutes a part of a sealed flow path through which the reduction solution at the above pressure flows,
Between the two processing surfaces, a fluid to be processed, that is, the reduced liquid and the raw material liquid, containing single-crystal spherical sodium metallic nanoparticles as a reactant, is mixed and reacted with each other. Of the first and second processing members, the second processing member has a pressure-receiving surface, and a part of this pressure-receiving surface is constituted by the second processing surface, and this pressure-receiving surface receives a pressure applied to the reduced liquid by the fluid pressure imparting mechanism, and generates a force for moving the second processing surface in a direction away from the first processing surface, and the pressure-receiving surface is disposed between the first and second processing surfaces which can approach and separate and rotate relatively. a device for passing the reduced liquid, which is a fluid to be processed under a pressure, and the raw material liquid, so that the fluid to be processed forms a thin film fluid containing single-crystal spherical sodium metallic nanoparticles, and the device further comprises a separate inlet path independent of the flow path between the processing surfaces through which the reduced liquid under the pressure flows, the second processing surface is provided with one opening portion which leads to the separate inlet path, and the raw material liquid sent from the separate inlet path is introduced between both processing surfaces, thereby mixing the reduced liquid and the single-crystal spherical sodium metallic nanoparticles produced from the raw material liquid within the thin film fluid,
The method according to any one of claims 1 to 11, wherein the raw material liquid and the reduced liquid are mixed and reacted. The manufacturing method according to claim 12, wherein the opening for introducing the sodium iodide raw material solution is located downstream of the point where the flow of the reducing solution passed between the two processing surfaces becomes laminar.