JP2007031799A - Method for producing metal nanoparticle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing metal nanoparticles where supersonic waves are emitted to a continuously fed solution comprising a metallic compound and a reducing agent, thus metal nanoparticles are continuously synthesized. <P>SOLUTION: The production method for synthesizing metal nanoparticles using a solution composed of a metal salt by a liquid phase process is characterized in that a precursor is previously prepared, and is continuously transported to a reaction field, and is irradiated with supersonic waves in which irradiation energy at a supersonic irradiation cell in the reaction field is 10 to 1,000 W/ml, thus metal nanoparticles are synthesized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing metal nanoparticles, which is a method for producing metal nanoparticles by continuously synthesizing metal nanoparticles by irradiating ultrasonic waves onto a solution containing a continuously supplied metal compound and a reducing agent. It relates to a manufacturing method.

  Metal nanoparticles with particle diameters of several nanometers to several tens of nanometers are formed with new characteristics due to quantum size effects, nanoparticles with the original single domain structure and large specific surface area of nanoparticles, and with uniform particle diameters Because it has new functions such as self-assembled films that do not exist in conventional submicron fine particles, information / communications, life sciences, focusing on new electronic materials, optical materials, magnetic materials, catalysts, etc. using these metal nanoparticles It is attracting attention as a new material in the field of energy and environment.

For example, it has been reported that when magnetic particles are miniaturized to a single nanosize, properties significantly different from those of the bulk appear, and the magnetic anisotropy (U> 10 ⁶ J / cm ³ ) is strong. When a magnetic substance becomes a nanoparticle, it is expected to be applied to an electronic information device such as a 1 Tbit / cm ² class ultrahigh density magnetic recording medium, and many studies have been conducted.

In particular, FePt has a crystal form of L1 ₀ phase, to indicate a significantly larger magnetic anisotropy ^{(> 6 × 10 6 / Jm} -3), shows a ferromagnetic both single nano range, also because of the high corrosion resistance It is attracting attention as a future magnetic recording element material.

  In general, a method for producing metal nanoparticles is a chemical reaction in which a reducing agent is added and reduced in a reaction solution containing a metal ion, a metal complex, and a dispersing agent while maintaining a uniform temperature, concentration, and stirring speed. In addition, a batch method is used.

Conventionally, there has been proposed a method for producing nanoparticles of an alloy of Au and Pd or an alloy of Pd and Pt by irradiating a solution containing a metal ion or a metal complex with ultrasonic waves. (See Patent Document 1).
Patent Document 2 or 3 describes a continuous manufacturing method and a continuous manufacturing apparatus for semiconductor CdSe and the like as examples of nanoparticle synthesis by a continuous method.

JP 2001-152213 A International Publication No. 01/46499 Pamphlet JP 2002-052336 A

  The ultrasonic irradiation synthesis method according to the aforementioned Patent Document 1 is a batch method. In the examples, the ultrasonic irradiation frequency is 200 kHz, the output is 6 W / cm 2, and the reduction reaction time is 90 minutes with respect to 60 cc of the reaction solution. Although this method can produce alloy nanoparticles, since it is a batch production method, the resulting alloy nanoparticles have a wide particle size distribution and cannot be produced in large quantities.

  In the above-mentioned Patent Document 2 or 3, the method using ultrasonic waves and further application to the synthesis of magnetic metal nanoparticles are not examined.

  Therefore, the present invention is to provide an industrially advantageous continuous production method for synthesizing a large amount of metal nanoparticles having a particle diameter of several nanometers to several tens of nanometers.

  The technical problem can be achieved by the present invention as follows.

  That is, the present invention relates to a method for synthesizing metal nanoparticles using a solution comprising a metal salt by a liquid phase method, in which a precursor is prepared in advance, the precursor is continuously transported to an ultrasonic irradiation cell, and reduced. A metal nanoparticle production method comprising synthesizing metal nanoparticles by irradiating ultrasonic waves having an irradiation energy of 10 to 1000 W / ml in an ultrasonic irradiation cell in the presence of an agent (this invention) 1).

  The present invention also provides a precursor containing two or more metal salts in advance in a production method for synthesizing metal nanoparticles composed of two or more metals using a solution comprising two or more metal salts by a liquid phase method. The precursor is continuously transported to the ultrasonic irradiation cell, and in the presence of a reducing agent, the irradiation energy in the ultrasonic irradiation cell is irradiated with ultrasonic waves of 10 to 1000 W / ml, thereby forming metal nano-particles. It is a method for producing metal nanoparticles characterized by synthesizing particles (Invention 2).

  Further, the present invention is a production method for synthesizing metal nanoparticles composed of two or more metals using a solution composed of two or more compounds by a liquid phase method, and each of them does not react with the target nanoparticles alone. By preparing two kinds of precursors in advance, transporting each precursor continuously to the ultrasonic irradiation cell and mixing them, and irradiating ultrasonic waves with an irradiation energy of 10 to 1000 W / ml in the ultrasonic irradiation cell A metal nanoparticle production method characterized by synthesizing metal nanoparticles (Invention 3).

  Further, the present invention provides the method for producing metal nanoparticles according to any one of claims 1 to 3, wherein the gap of the ultrasonic irradiation cell is between 0.1 and 20 mm, and the amplitude of the ultrasonic oscillator head Is a method for producing metal nanoparticles characterized by being 1 to 50 μm (Invention 4).

  Moreover, this invention is a manufacturing method of the metal nanoparticle in any one of Claims 1 thru | or 4, The temperature of each precursor liquid is controlled to the temperature range of room temperature to 300 degreeC, The metal nanoparticle characterized by the above-mentioned. This is a manufacturing method (Invention 5).

  Further, the present invention provides the method for producing metal nanoparticles according to claim 3, wherein the speed ratio of the transport pump of each precursor liquid is controlled to 0.1 to 9.9. (Invention 6).

  Since the method for producing metal nanoparticles according to the present invention can be produced efficiently and in large quantities, it is suitable as a method for producing metal nanoparticles.

  In the present invention, it is possible to produce metal nanoparticles having a uniform particle diameter by circulating a solution containing two or more kinds of metal ions, metal complexes, a reducing agent and a dispersing agent and irradiating with ultrasonic waves. Became.

  The configuration of the present invention will be described in more detail as follows.

  First, a method for producing metal nanoparticles according to the present invention will be described.

  In the present invention, a single metal selected from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, W, Pt and Au, or two or more alloys selected from the metal elements are manufactured. Can do.

As the starting material for the metal nanoparticles in the present invention, various salts of the target metal ion, metal alkoxides, organometallic complexes, metal compounds and the like may be used.
In particular,
In iron compounds, iron (III) chloride, iron (III) chloride hexahydrate, iron (II) chloride tetrahydrate, iron (II) sulfate, iron (II) sulfate heptahydrate, iron sulfate (III ) Ammonium, iron (II) bromide, iron (II) iodide, iron (III) sulfate nonahydrate, iron (II) sulfate hydrate, iron (II) nitrate, iron (III) nitrate, iron nitrate (III) 9 hydrate, iron (III) perchlorate, iron (III) pyrophosphate, iron (II) acetate, iron (III) acetate, iron (III) phosphate, iron (II) phosphate 8 water Japanese hydrate, iron (III) phosphate n hydrate, iron (II) citrate, iron (III) citrate hydrate, iron (III) ammonium citrate, iron (II) oxalate, iron oxalate ( II) Hydrate, iron (III) oxalate ammonium trihydrate, potassium hexacyanoferrate (III), hexacyanoiron II) Potassium acid trihydrate, sodium hexacyanoferrate (III) decahydrate, iron (II) fumarate, iron (II) lactate, iron (II) lactate trihydrate, iron (II) gluconate dihydrate, iron (II) ethoxide, acetylacetonate iron (II) acetylacetonate, iron (III), tris Gigi pivalic iron (III), carbonyl iron _{Fe (CO) 5, Fe 3} (CO) 12, Fe ₂ (CO) ₉ , ammonium iron sulfate (II) hexahydrate, sodium pentacyanonitrosyl iron (III) dihydrate, and the like can be used.
Among the cobalt compounds, cobalt chloride (II), cobalt chloride (II) hexahydrate, ammonium cobalt chloride (II) hexahydrate, cobalt sulfate (II) heptahydrate, cobalt carbonate, cobalt bromide (II) , Cobalt (II) bromide hexahydrate, cobalt (II) iodide, cobalt (II) carbonate, cobalt (III) sulfate nonahydrate, cobalt (II) sulfate heptahydrate, cobalt (II) sulfate Ammonium hexahydrate, cobalt nitrate (II), cobalt nitrate (II) hexahydrate, cobalt nitrate (III), cobalt nitrate (III) nonahydrate, cobalt nitrite sodium (III), cobalt perchlorate (II), cobalt (III) phosphate, cobalt (II) acetate, cobalt (III) acetate, cobalt (II) oxalate dihydrate, cobalt (III) citrate tetrahydrate , Ammonium cobalt oxalate (III) trihydrate, cobalt stearate, cobalt oleate, cobalt fumarate (II) cobalt gluconate (II) dihydrate, cobalt (II) ethoxide, cobalt acetylacetonate (II) , Cobalt acetylacetonate (III), cobalt acetylacetonate (II) dihydrate, cobalt trisdipivalate (III), ammonium cobalt (II) sulfate hexahydrate, cobalt thiocyanate (II, hexaamine cobalt (III) chloride Products, carbonyl cobalt, cobalt naphthenate, sodium hexanitrocobalt (III), and the like can be used.
For nickel compounds, nickel chloride, nickel chloride hexahydrate, nickel chloride tetrahydrate, nickel sulfate heptahydrate, nickel ammonium sulfate hexahydrate, nickel carbonate, nickel iodide, nickel bromide, nickel bromide Trihydrate, nickel iodide, nickel sulfate, nickel sulfate hexahydrate, nickel nitrate, nickel nitrate hexahydrate, nickel perchlorate hexahydrate, nickel phosphate, nickel acetate tetrahydrate, nickel acetate , Nickel cyanide potassium monohydrate, nickel oxalate dihydrate, nickel benzoate, nickel citrate hydrate, nickel oxalate trihydrate, nickel fumarate nickel gluconate dihydrate, acetylacetone Nickel oxide, nickel acetylacetonate dihydrate, nickel bisdidipivalate, nickel ammonium sulfate 6 water , Hexamine nickel chloride can be used hexane butyl nickel cyclohexane, hexane nickel to 2 Echirushikuro, nickel octoate, trifluoromethanesulfonic acid nickel, a hypophosphite nickel hexahydrate like.
Among copper compounds, copper chloride (I), copper chloride (II), copper chloride (II) dihydrate, ammonium chloride copper (II) dihydrate, potassium copper chloride (II), potassium copper chloride (II) Dihydrate, copper nitrate (II), copper nitrate (II) trihydrate, copper sulfate (II), copper sulfate (II) pentahydrate, copper acetate (II), copper acetate (II) 5 water Japanese, Copper (II) acetate monohydrate, Copper (I) bromide, Copper (II) bromide, Copper (II) iodide, Copper (I) cyanide, Copper (II) perchlorate, Base Copper (II) carbonate, copper (I) chloride, copper (II) chloride, copper (II) chloride dihydrate, copper pyrophosphate (II), cyclohexanebutyl copper (II), copper oxalate (II) 0.5 hydrate, copper (II) formate, copper (II) tartrate, copper (II) benzoate, copper (II) citrate 2.5 hydrate, copper resinate, copper gluconate (II) 4-ammonium copper (II) sulfate monohydrate, copper (II) 2-ethylhexanoate, copper (II) acetylacetonate, copper (II) oleate, copper (II) dipivaloylmethanate, tetra Copper (II) fluoroborate, copper (II) trifluoromethanesulfonate, copper (II) bishexafluoroacetylacetonate, copper (II) naphthenate, and the like can be used.
In the case of platinum compounds, chloroplatinic acid, chloroplatinic acid hexahydrate, potassium chloroplatinum (II) acid, potassium chloroplatinum (IV) acid, chloroplatinum (IV) acid hexahydrate, chloroplatinum (IV) acid 2 Sodium hexahydrate, sodium platinum (IV) chloride hexahydrate, platinum acetylacetonate, platinum hexafluoroacetylacetonate and the like can be used.
As the palladium compound, potassium palladium chloride, sodium palladium chloride, palladium ammonium chloride, palladium chloride, palladium nitrate, palladium sulfate dihydrate, palladium acetate, palladium acetylacetonate and the like can be used.
As the ruthenium compound, ruthenium chloride, ruthenium acetylacetonate, ruthenium tridipivalonate, or the like can be used.
As the rhodium compound, rhodium acetate, rhodium chloride trihydrate, rhodium nitrate, sodium rhodium chloride dihydrate and the like can be used.
Examples of the gold compound include chloroauric acid tetrahydrate, chloroauric acid trihydrate, sodium chloride gold dihydrate, ammonium chloroaurate, and potassium cyanide cyanide.
For silver compounds, silver sulfate, silver carbonate, silver nitrate, silver acetate, silver iodide, silver perchlorate, silver phosphate, silver benzoate, silver tetrafluoroborate, silver trifluoroacetate, silver hexafluoroacetylacetonate, etc. are used. be able to.

As the reducing agent in the present invention, hydrazine, sodium borohydride, sodium diphosphite, lithium aluminum hydride, sodium sulfite, sodium phosphinate and the like can be used.
In the case of a single noble metal, hydrazine or sodium borohydride, which has a slow reducing action, can be preferably used.
In the case of a transition metal alone, in addition to the above reducing agent, those having a strong reducing action such as sodium diphosphite, lithium aluminum hydride, sodium sulfite and sodium phosphinate are preferably used.
In the case of an alloy, a noble metal and noble metal, and a noble metal and transition gold system use a reducing agent used in a noble metal system, and a transition metal and transition metal system use a reducing agent used in a transition metal system.

  On the other hand, in the polyol method, 1,2-alkanediols such as ethylene glycol, diethylene glycol, trimethylene glycol, propylene glycol, tetraethylene glycol, and 1,2-hexadecanediol are used, and these polyols are thermally decomposed under heating. When oxidized, it exhibits a reducing action.

  The amount of the reducing agent added to the metal is preferably equivalent to 10 times.

In the present invention, a dispersant may be used in combination as necessary. As the dispersant, one or more selected from amine, diamine, ethanolamine, alkoxyamine, diamine alcohol, diaminoalkoxy, cyclic amine, alkylthiol, carboxylic acid or polymer dispersant Two or more kinds can be used.
Specifically, for amine systems, propylamine, dipropylamine, butylamine, dibutylamine, tributylamine, isobutylamine, diisobutylamine, hexylamine, N-methylhexylamine, di-N-octylamine, tri-N-octyl Amine, 2-ethylhexylamine, di (2-ethylhexyl) amine, allylamine, diallylamine, 3-pentylamine, 2-octylamine, oleylamine and the like can be used.
In diamine, dimethylaminoethylamine, ethylaminoethylamine, diethylaminoethylamine, N, N-diisopropylaminoethylamine, tetramethylethylenediamine, 1,2, -diaminopropane, 1,3-diaminopropane, methylaminopropylamine, dimethylaminopropylamine , Dibutylaminopropylamine, tetramethyl-1,3-diaminopropane, 1,2-diaminobutane, 1,4-diaminobutane, laurylaminopropylamine, tetramethylhexamethylenediamine, N-aminoethylpiperidine, N-amino Ethyl-4-n-pipecoline, N-aminopropylpiperidine, N-aminopropyl-2-pipecoline and the like can be used.
In ethanolamine system, monoethanolamine, 2-aminopropanol, 3-aminopropanol, 3-dimethylaminopropanol, 4-aminobutanol, 4-methylaminobutanol, 2-amino-1,3-propanediol oxalate 2-hydroxymethylaminoethanol, 4-piperidinol, and the like can be used.
In the alkoxyamine system, 3-methoxypropylamine, 3ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 2-ethylhexyloxypropylamine, 3 -Decyloxypropylamine, 3-lauryloxypropylamine, 3-myristyloxypropylamine, etc. can be used.
In the diamine alcohol system, 2-hydroxyethylaminopropylamine, N, N′-dimethylaminoethoxyethanol or the like can be used.
In the diaminoalkoxy system, bis (3-aminopropyl) ether, dimethylaminoethoxypropylamine, 1,2-bis (3-aminopropoxy) ethane, α, ω-bis (3-aminopropyl) polyethylene glycol ether, α, ω-bis (3-aminopropyl) diethylene glycol ether or the like can be used.
In the cyclic amine system, N-aminopropylpiperidine, N-aminopropyl-4-pipecholine, N-aminopropylmorpholine, aminopropylpiperazine, 1,4-bisaminopropylpiperazine and the like can be used.
In the alkylthiol system, dodecyl mercaptan, stearyl mercaptan, or the like can be used.
In the carboxylic acid system, polycarboxylic acid, polycarboxylic acid ammonium salt, polycarboxylic acid sodium salt, oleic acid, lauric acid, stearic acid citric acid and the like can be used.
In the thiol system, dodecanethiol, mercaptocitric acid and the like can be used.
As the polymer dispersant, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyethylene oxide, polyvinyl pyrrolidone, polyethylene imine, polyacrylic acid polymer and the like can be used.
In addition, naphthalene sulfonic acid / formalin condensate sodium, polycarboxylic acid, polyoxyethylene lauryl ether sodium sulfate, triphenylphosphine and the like can be used.

  As for the addition amount of a dispersing agent, 0.1-10 are preferable at the molar ratio with respect to a metal salt.

  In the present invention, as the solvent, water, alcohol, dioxane, ethylene glycol, etc. as polar solvents, n-hexane, cyclohexane, octane, decane, dodecane, etc. as nonpolar solvents, toluene, xylene, etc. as aromatic solvents Dioctyl ether or the like as a high-boiling solvent.

  The transport speed of the precursor depends on the size of the reaction field (ultrasound irradiation cell), but a flow rate of 0.1 to 10 cc / sec is preferable.

  In addition, in the continuous production of alloy nanoparticles with a controlled alloy composition ratio, when two kinds of precursor liquids containing each metal ion constituting the alloy to be synthesized are mixed immediately before the ultrasonic irradiation cell (reaction field). Two kinds of precursor liquids containing each metal ion may be prepared, and the transport speed ratio of a transport pump for transporting the precursor liquid may be adjusted. Since the composition ratio of each metal of the alloy nanoparticles to be deposited differs from the composition of each metal ion in the precursor, the transport speed ratio of the transport pump can be appropriately controlled by detecting the composition ratio of the alloy to be deposited. It is possible to control the composition ratio of each metal of the alloy nanoparticles on the production process online.

  For the production of the alloy, it is preferable to control the speed ratio of the transport pump for each precursor liquid to 0.01 to 0.99.

  The reduction reaction is accelerated when the reaction solution is locally brought into a high temperature and high pressure state by ultrasonic irradiation, and the reaction is completed in a short time.

  In this invention, it adjusts so that irradiation energy may be 10-1000 W / ml with respect to an ultrasonic irradiation cell (reaction field). In the case of less than 10 W / ml, since the energy of the ultrasonic wave to be irradiated is small, the reduction reaction cannot be accelerated sufficiently. Irradiating energy exceeding 1000 W / ml is not industrial. Preferably, it is 100-600 W / ml.

  In the present invention, in order to complete the reaction by instantaneously causing the reduction reaction of the reaction liquid by ultrasonic irradiation to the flowing reaction liquid in the ultrasonic irradiation cell, irradiation at a low output is performed when the flow speed of the reaction liquid is slow. However, in order to complete the reduction reaction at a high flow rate for mass production, high-power ultrasonic irradiation energy is required.

  In this invention, what is necessary is just to select the frequency of the ultrasonic wave to irradiate between 20-100kHz. It is well known that cavitation is less likely to occur in a liquid when the frequency of the ultrasonic wave is high. When the ultrasonic frequency is several tens of kHz, the amplitude of the vibrator increases, and thus cavitation is maximized. In order to cause cavitation at several hundreds of kilohertz, it is necessary to increase the sound intensity. For this reason, the output of the ultrasonic oscillator also requires a larger output than the oscillation of several tens of kHz. It is difficult to manufacture the material, which is not preferable for practical use.

In the present invention, it is preferable to maintain the pressure of the flowing reaction solution from atmospheric pressure to 30 atm. In the pressurized state, collisions due to Brownian motion of the reaction molecules are mitigated, and collisions between the nuclei generated by the reduction reaction are reduced, so that uniform particles are likely to be produced, especially for the production of nanoparticles at high concentrations. High pressure atmosphere is effective.
If the pressure is within the above range, the amplitude due to the vibration of the ultrasonic oscillator chip can be obtained, so that the cavitation is sufficiently generated, the reduction reaction of the solution containing metal ions or metal complexes proceeds, and the metal nanoparticles having a uniform particle size Is synthesized. More preferably, it is preferable to maintain a pressurized state up to 10 atm.

  The reaction temperature of the present invention varies depending on the reaction scheme to be synthesized. Therefore, in this invention, it is preferable to control the temperature of the reaction liquid to distribute | circulate and the temperature of the reaction cell chamber which irradiates an ultrasonic wave between room temperature and 300 degreeC.

In the present invention, when producing alloy particles composed of two or more kinds of metal elements, it is preferable to consider the reactivity of each metal element.
For example, if the metal elements are easily alloyed, a mixed solution composed of two or more metal elements is prepared in advance and transported to an ultrasonic irradiation cell (reaction field). In the presence of a reducing agent, Metal nanoparticles can be obtained from two or more metal elements by irradiation with ultrasonic waves.
On the other hand, in the case of a combination of metal elements that are difficult to be alloyed, two types of precursors that do not react with the target nanoparticles alone are prepared in advance, and each precursor is transported continuously for mixing and reaction. When synthesizing, a high energy ultrasonic wave is irradiated immediately after mixing, and a reduction reaction of the metal ion or metal complex in the reaction solution is induced by receiving the high energy of the shock wave generated by cavitation generation. It is possible to synthesize.

  Alloy-based FePt nanoparticles as magnetic nanoparticles are synthesized by various methods, and a polyol reduction method using an Fe complex and a Pt complex is well known. In the polyol reduction method, a metal complex or the like is dissolved in a solution containing a polyol such as ethylene glycol and heated to oxidize when the polyol is decomposed, so that it functions as a reducing agent and the presence of a dispersant. Below, metal ions are reduced to metal to obtain metal nanoparticles.

As the polyol, ethylene glycol, tetraethylene glycol, 1,2 hexadodecanediol, or the like is used.
Fe (ACAC) ₃ is used as the Fe complex, and Pt (ACAC) ₂ is used as the Pt complex.
These complexes dissolve at a temperature of 120 ° C. or higher in the polyol, and in a polyol solution system in which an Fe complex and a Pt complex coexist, when Pt is 140 ° C. or higher, Pt preferentially undergoes nucleation due to a reduction reaction over Fe, It is believed that the reduction reaction of Fe occurs after the reaction of Pt, and thereafter an alloy composition is formed.
Therefore, in the present invention, the respective precursors of Fe and Pt are prepared, and each of them is flowed while being maintained at a temperature of 120 to 140 ° C., mixed immediately before the ultrasonic reaction cell, and the polyol solution in the reaction cell. It is possible to synthesize FePt nanoparticles instantaneously by inducing a reduction reaction by raising the boiling point of the solution to an ultrasonic wave and irradiating ultrasonic waves.

  In the production of the FePt nanoparticles by the polyol reduction reaction, PVP has been conventionally used in the reaction using ethylene glycol (boiling point 198 ° C.) as a dispersant, but in the FePt polyol synthesis method of the present invention, two or more types are used. By using ethoxyamine, it was possible to perform a reduction reaction in a high concentration system of 100 mM or more, and it was possible to synthesize uniform FePt nanoparticles with a uniform particle diameter.

  With respect to the reaction temperature, in the polyol reduction method, the reduction reaction is performed at the boiling temperature of a solvent such as polyol, and the reduction reaction occurs at 198 ° C. with ethylene glycol and 298 ° C. with diol. To 300 ° C.

The metal nanoparticles obtained by the method for producing metal nanoparticles according to the present invention have an average particle diameter of about 1 to 100 nm.
The particle size distribution is 10% to 30% in σ value.

  Next, the manufacturing apparatus used for the manufacturing method of the metal nanoparticle which concerns on this invention is described.

The manufacturing apparatus according to the present invention includes the following units as shown in FIG.
That is, a two-component preparation tank (1 in FIG. 1), a two-component transport unit (2 in FIG. 1), a two-component mixer (3 in FIG. 1), a reaction cell (ultrasonic irradiation cell: 4 in FIG. 1) , A residence zone (5 in FIG. 1), a cooling unit (6 in FIG. 1), and a synthetic slurry solution storage tank (7 in FIG. 1).
By controlling the temperature and pressure of the entire reaction system from the precursor preparation tank to the transport unit and the ultrasonic irradiation cell (reaction field), the reduction reaction accelerated by ultrasonic irradiation causes the metal nanoparticles to It becomes possible to control particle properties such as particle size, particle size distribution and crystallinity.

  Further, the reaction system may be purged with an inert gas such as nitrogen gas or argon gas.

  The continuous ultrasonic synthesizer used (Fig. 1) incorporates an ultrasonic irradiation cell in the reaction line, and when the reaction solution passes through the ultrasonic irradiation cell, it receives direct ultrasonic irradiation and is generated simultaneously with the reduction reaction. The dispersion of the nanoparticles is performed.

  It is also possible to provide a multistage ultrasonic irradiation cell in the reaction line.

Further, in the present invention, the flat plate at the tip of the ultrasonic oscillator and the flat plate so that the ultrasonic wave irradiated in the reaction cell portion that receives the ultrasonic irradiation is uniformly irradiated to the entire flowing reaction liquid. A cell structure having a slit plate structure with a uniform gap between the flat plate and the flat plate is effective. When the reaction liquid flows between the flat plates, a reduction reaction occurs due to ultrasonic irradiation, and the flat plate gap of the reaction cell is preferably between 0.5 and 20 mm. When the gap between the flat plates is less than 0.5 mm, it is difficult to distribute the reaction solution. When it exceeds 20 mm, it becomes difficult to maintain a uniform reaction field. More preferably, it is between 1.0 and 10 mm.
The amplitude of the ultrasonic oscillator head is preferably 1 to 50 μm.

  In addition, it is preferable to irradiate 0.1-50 kW of ultrasonic energy with respect to an ultrasonic irradiation cell (reaction cell).

  The flow rate of the reaction solution in the ultrasonic irradiation cell is preferably 1 ml / second to 20 ml / second. A long-time reaction is not preferable because the particle size distribution becomes wide.

  The metal nanoparticles obtained by ultrasonic irradiation are preferably provided with a residence zone in a reaction system that requires an aging process.

  The amount of synthesis by the batch method is about several grams per hour when a 1 l class reaction vessel is used, but the particle size distribution is wide. According to the production method of the present invention, it is possible to produce 100 g or more of metal nanoparticles having a uniform particle size per unit time per one nanoparticle production process.

<Action>
Conventional methods for producing metal nanoparticles include a method in which a metal ion or metal complex is chemically reduced by a reducing agent in the presence of a dispersant, or a reduction reaction by physically applying high energy such as ultrasonic waves. In order to synthesize metal nanoparticles having a uniform particle diameter, a batch method with a small scale of several tens to several liters is used. For mass production of metal nanoparticles, the scale-up method for reaction conditions synthesized on a small scale is a batch method where the concentration of metal ions, metal complexes or additives reacting in the reaction vessel is uneven or temperature or Due to the nonuniformity of the stirring speed, nonuniformity occurs in the nucleation and growth that are instantaneously caused by the reduction reaction, and the synthesized nanoparticles are sized from several nanometers to several tens of nanometers in size distribution However, it was difficult to produce nanoparticles having a uniform particle size.

As a result of various studies, the present invention has obtained the following knowledge. That is, the synthesis of metal nanoparticles is changed from a batch method to a distribution method, and at that time, by setting the ultrasonic energy irradiated per reaction solution to be distributed to 10 to 1000 W / ml, metal nanoparticles having a small particle size can be obtained. It became possible to manufacture in large quantities.
Moreover, the metal ion and the metal complex are applied to the ultrasonic cell having a specific structure under the condition that the ultrasonic energy to be irradiated is 0.1 to 50 kW, the amplitude of the ultrasonic oscillator is 1 to 50 μm, and the pressure is 1.5 to 30 atm. The metal nanoparticle which has a sharp particle size distribution was able to be obtained by distribute | circulating the solution which contains it with the flow rate of 0.1-10 cm / sec.

  A typical embodiment of the present invention is as follows.

  The particle diameter of the metal nanoparticles was confirmed with a JEOL JEM-2010 electron microscope manufactured by JEOL.

  The composition analysis of the metal nanoparticles was performed with an SPS-4000 ICP analyzer manufactured by Seiko Denshi.

Comparative Example 1: Example of synthesis of FePt by high-concentration batch method Fe (ACAC) ₃ (manufactured by Soekawa Riken Co., Ltd.) as a precursor for FePt nanoparticle synthesis in a glass four-necked 1000 ml flask equipped with a reflux device And Pt (ACAC) ₂ (manufactured by Soekawa Rikagaku Co., Ltd.) 19.67 g with EtGL (special grade reagent manufactured by Kanto Chemical Co., Ltd.) 1000 mL are added and dissolved to make each concentration 50 mM, and as a dispersant, two types of ethoxyamine each. 35 ml of N, N-dimethylaminoethoxyethoxyethanol (Kao Corporation) and 26 ml of N, N-dimethylaminoethoxyethoxyethanol (Kao Corporation) were added. The reaction solution is stirred and heated while flowing Ar gas. When the reaction solution reaches around 160 ° C, the reaction solution turns blackish brown and then gradually turns black, and the temperature reaches 198 ° C, the boiling point of ethylene glycol. The reaction was then continued for 2 hours at that temperature. In order to purify and collect the precipitated FePt nanoparticles, the reaction solution is distilled, and the ethylene glycol solution is distilled and concentrated. Then, ethyl alcohol with ethoxyamine added as a dispersant is redispersed and centrifuged. The separated FePt nanoparticles were redispersed in alcohol again, and this operation was repeated. The size of the purified and recovered FePt nanoparticles was 12 g of FePt nanoparticles having a wide particle size distribution ranging from several nanometers to several tens of nanometers, and contained aggregates. An electron micrograph of the obtained FePt nanoparticles is shown in FIG.

Comparative Example 2 Synthesis of FePt at Low Concentration As a precursor for synthesizing FePt nanoparticles in a glass four-necked 1000 mL flask equipped with a reflux apparatus, 0.883 g Fe (ACAC) _{3 and} 0.983 g Pt (ACAC) ₂ together with 1000 mL EtGL In addition, each was dissolved to a concentration of 2.5 mM, and 14 g of polyvinyl pyrrolidone (molecular weight 10,000) manufactured by Sigma-Aldrich was added as a dispersant.
When the reaction solution is stirred and heated while circulating Ar gas, and the reaction solution reaches around 160 ° C., the reaction solution becomes blackish brown and then gradually changes to black, and when the temperature reaches 198 ° C., the boiling point of ethylene glycol. The reaction was continued for 2 hours at that temperature. The precipitated FePt nanoparticles were purified and recovered according to the operation procedure of Comparative Example 2. The size of the purified and recovered FePt nanoparticles was several nm, and 0.6 g of FePt nanoparticles with a sharp distribution was obtained.
Although the particle size distribution of the obtained FePt nanoparticles is uniform, the synthesis amount is 1 g / hour or less. An electron micrograph of the obtained FePt nanoparticles is shown in FIG.

Example 1 Production of FePt Particles Fe (ACAC) ₃ and Pt (ACAC) ₂ were dissolved in EtGL as precursors for synthesizing FePt nanoparticles, respectively, to a concentration of 50 mM, and two types of ethoxyamine, N as a dispersant, respectively. , N-dimethylaminoethoxyethoxyethoxyethanol and N, N-dimethylaminoethoxyethoxyethoxyethanol were added to each, heated to 120 ° C or higher, filled in a 20 L precursor preparation tank under N2 atmosphere and kept at 120 ° C, Nanoparticles were synthesized by introduction into an ultrasonic reaction cell heated to 200 ° C. from a 140 ° C. piping line with a transport pump. The ultrasonic output is 1.2 kW × 2 stages, the frequency is 20 kHz, and the pressure in the reaction system is a maximum of 10 atm. All these reactions proceeded in an inert gas.
The gap of the ultrasonic irradiation cell was 2 mm, and the amplitude of the ultrasonic oscillator head was 50 μm. The irradiation energy at this time was 600 W / ml. The flow rate for transporting the Pt raw material was 8.3 ml / second, and the ratio of the flow rate of the Fe raw material to the Pt raw material was Fe / Pt of 1.15 / 1.

  The feature of the two-component mixed ultrasonic continuous synthesis test equipment used (Fig. 1) is that a multistage ultrasonic irradiation cell is installed in the reaction line, and when the reaction liquid passes, it receives direct ultrasonic irradiation to reduce the reaction. At the same time, the generated nanoparticles are dispersed.

  The TEM observation result of the FePt nanoparticles synthesized by the ultrasonic continuous synthesis test apparatus is shown in FIG. As a result, it was clarified that the present invention can be applied to mass synthesis of FePt single nanoparticles, which is an alloy having an average particle size of 4 nm and a good particle size distribution. The FePt synthesis rate at this time corresponds to 100 g / hr.

  As a result of examining the composition of Fe and Pt of the precursor and the composition of each element of Fe and Pt of the synthesized FePt nanoparticles from ICP analysis, the relationship shown in FIG. 5 is obtained, and the reduction reaction of Fe is lower than that of Pt. Is shown.

The FePt nanoparticles were annealed at 600 ° C. in a reducing atmosphere to cause crystal transformation from FePt (fcc) to FePt (L1 ₀ ) to obtain a ferromagnetic material, and a magnetization hysteresis curve was obtained by SQUID (24 KOe). As an example, the hysteresis curve obtained for Fe _0.6 Pt _0.4 at room temperature is shown in FIG.
Furthermore, the graph which shows the relationship between the composition ratio of Fe and Pt in the synthesized FePt and the coercive force is shown in FIG. X on the horizontal axis represents the composition ratio of Fe represented by Fe _x Pt _(100−x) . As shown in FIG. 7, it was confirmed that the alloy composition of Fe and Pt with Fe _0.55 Pt _0.45 shows a maximum value (Hc> 10,000 Oe).

Example 2 Production of Pd Particles Two solutions of an aqueous solution precursor containing 50 mM Pd chloride and 200 mM PVP and an aqueous solution containing 100 mM hydrazine were prepared as precursors in a continuous ultrasonic synthesizer, and the flow rate was 250 ml / min. Each precursor was made to flow, and ultrasonic irradiation was performed in the ultrasonic irradiation cell. The flowed pressure is 3 atm. The apparatus was the same as that used in Example 1, and the gap of the ultrasonic irradiation cell and the amplitude of the ultrasonic oscillator head were the same as in Example 1. The irradiation energy at this time was 600 W / ml. The flow rate of the reaction solution was 8 ml / second.
FIG. 8 shows an SEM photograph of Pd nanoparticles when irradiated with ultrasonic waves.
The average particle size is 7 nm, indicating a sharp particle size distribution.

Comparative Example 3 Production of Pd Particles Pd particles were produced in the same manner as in Example 2 except that the ultrasonic irradiation was not activated. An SEM photograph of the synthesized Pd nanoparticles is shown in FIG.
In addition to the formation of Pd single nanoparticles, coarse particles of 70 nm or more were formed, and it was observed that the particle size distribution was extremely large without an ultrasonic irradiation process.
From these results, it was confirmed that the continuous synthesis method incorporating ultrasonic irradiation according to the present invention can generate Pd particles having a uniform particle diameter.
The synthesis rate of Pd nanoparticles under the test conditions was 60 g / hr.

Example 3 Production of CoPd Particles As a precursor for synthesizing CoPd nanoparticles, 51.4 g of cobalt (II) acetylacetonate: Co (ACAC) ₂ was dissolved in 10 l of ethylene glycol, and N, N′-dimethylamino was used as a dispersant. 20 ml of ethoxyethanol was added, and NaOH was added to adjust the pH to 10-11. On the other hand, 17.7 g of palladium (II) chloride PdCl ₂ was dissolved in ₂₀ l of ethylene glycol, and N, N′- Add 20 ml of dimethylaminoethoxyethanol, add NaOH to a pH of 10-11, and keep each at 120 ° C., keep in a precursor preparation tank purged with N ₂ gas, mix each two liquids and ultrasonic After reacting by irradiation, it was cooled and collected in a storage tank. The apparatus was the same as that used in Example 1, and the gap of the ultrasonic irradiation cell and the amplitude of the ultrasonic oscillator head were the same as in Example 1. The irradiation energy at this time was 600 W / ml. The flow rate for transporting the raw materials was 8.3 ml / sec.
The synthesized CoPd gave uniform particles with an average particle size of 4 nm.

Example 4 Production of PtRu Particles 39.3 g of platinum (II) acetylacetonate: Pt (ACAC) ₂ was dissolved in 10 l of ethylene glycol as a precursor for synthesizing PtRu nanoparticles, and N, N′-dimethylamino was used as a dispersant. A solution in which 20 ml of ethoxyethanol was added and pH was adjusted to 10 to 11 by adding NaOH, and 39.8 g of ruthenium acetylacetonate (III): Ru (ACAC) ₃ was dissolved in 20 l of ethylene glycol as a dispersant. 20 ml of N, N′-dimethylaminoethoxyethanol was added, NaOH was added to adjust the pH to 10 to 11, and each was kept at 120 ° C., kept in a precursor preparation tank purged with N ₂ gas, After being mixed and reacted by irradiating with ultrasonic waves, it was cooled and collected in a storage tank.
The apparatus was the same as that used in Example 1, and the gap of the ultrasonic irradiation cell and the amplitude of the ultrasonic oscillator head were the same as in Example 1. The irradiation energy at this time was 600 W / ml. The flow rate for transporting the raw materials was 8.3 ml / sec.
The synthesized PtRu gave uniform particles with an average particle size of 4 nm.

  As described above, the present invention is a metal nanoparticle having a uniform particle diameter by circulating a solution containing one or more kinds of metal ions, metal complexes, a reducing agent and a dispersing agent and irradiating ultrasonic waves. Can be manufactured.

It is a figure of the experimental apparatus used by this invention. 2 is an electron micrograph of FePt metal particles obtained in Comparative Example 1. (Magnification 500,000 times) 4 is an electron micrograph of FePt metal particles obtained in Comparative Example 2. (Magnification 500,000 times) 2 is an electron micrograph of FePt metal particles obtained in Example 1. FIG. (Magnification 500,000 times) It is a graph which shows the flow rate of a precursor, and the composition ratio of Fe and Pt in synthetic FePt. The speed ratio is Pt precursor speed / (Pt precursor speed + Fe precursor speed). Magnetization hysteresis curve of synthesized Fe _0.6 Pt _0.4 by SQUID (2.4T) at room temperature It is a graph which shows the relationship between the composition ratio of Fe and Pt in the synthesized FePt, and the coercive force. x is the composition ratio of Fe represented by Fe _x Pt _(100-x) The SEM photograph of the Pd nanoparticle continuously synthesize | combined in Example 2 (with ultrasonic irradiation). The SEM photograph of the Pd nanoparticle continuously synthesized by the comparative example 3 (no ultrasonic irradiation).

Explanation of symbols

1 Precursor preparation tank 2 Transport pump 3 Mixer 4 Ultrasonic irradiation cell 5 Residence zone 6 Cooling line 7 Storage tank

Claims (6)

In the production method of synthesizing metal nanoparticles using a solution comprising a metal salt by a liquid phase method, a precursor is prepared in advance, the precursor is continuously transported to an ultrasonic irradiation cell, and in the presence of a reducing agent, A method for producing metal nanoparticles, comprising synthesizing metal nanoparticles by irradiating ultrasonic waves having an irradiation energy of 10 to 1000 W / ml in an ultrasonic irradiation cell. In a production method for synthesizing metal nanoparticles comprising two or more metals using a solution comprising two or more metal salts by a liquid phase method, a precursor containing two or more metal salts is prepared in advance, and the precursor Is continuously transported to an ultrasonic irradiation cell, and in the presence of a reducing agent, the irradiation energy in the ultrasonic irradiation cell is irradiated with ultrasonic waves of 10 to 1000 W / ml to synthesize metal nanoparticles. A method for producing metal nanoparticles. In a production method for synthesizing metal nanoparticles composed of two or more metals using a solution composed of two or more compounds by a liquid phase method, two kinds of precursors that do not react with the target nanoparticles alone are previously prepared. Prepare and synthesize each metal precursor by continuously transporting and mixing each precursor to an ultrasonic irradiation cell and irradiating ultrasonic waves with an irradiation energy of 10 to 1000 W / ml in the ultrasonic irradiation cell. The manufacturing method of the metal nanoparticle characterized by the above-mentioned. The method for producing metal nanoparticles according to any one of claims 1 to 3, wherein the gap of the ultrasonic irradiation cell is between 0.1 and 20 mm, and the amplitude of the ultrasonic oscillator head is between 1 and 50 µm. The manufacturing method of the metal nanoparticle characterized by the above-mentioned. The method for producing metal nanoparticles according to any one of claims 1 to 4, wherein the temperature of each precursor liquid is controlled in a temperature range from room temperature to 300 ° C. The method for producing metal nanoparticles according to claim 3, wherein the speed ratio of the transport pump for each precursor liquid is controlled to 0.1 to 9.9.