JP2014152374A - Method for manufacturing composite nanoparticle and apparatus for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a composite nanoparticle by varying the combination of materials to be combined with each other and to provide an apparatus for manufacturing the composite nanoparticle.SOLUTION: The composite nanoparticle produced by combining a first material with a second material in which the first material is a metal and the second material is a metal different from the first material or a carbon material is manufactured by the manufacturing method comprising a step of generating a discharge plasma between a plurality of electrodes 10 disposed in an aqueous solution S containing a metal salt. In the manufacturing method, the metal salt is a salt of the first material and the electrodes are formed of the second material. A variety fo the composite nanoparticle can be manufactured by varying the combination of the first material and the second material.

Description

  The present invention relates to a method and apparatus for producing composite nanoparticles.

  Metal nanoparticles are widely used for substrate wiring materials, catalysts, electrode materials, medical test reagents, and the like. Recently, the amount of use has increased, and various manufacturing methods have been studied for the purpose of reducing the cost and energy consumption in addition to the stability of quality. In addition, for the purpose of expressing new functions and reducing the amount of metal used, the development from single metal nanoparticles to composite nanoparticles is also underway.

  As a method for producing metal nanoparticles, there are a gas phase method, a liquid phase method, a crushing method and the like, but the liquid phase method is advantageous for producing a large amount of metal nanoparticles of uniform size in a short time. Among the liquid phase methods, a process using plasma in liquid as a reaction field has an advantage that it can be produced without adding a protective agent for stably dispersing the produced metal nanoparticles. Impurities are hardly mixed in the metal nanoparticles produced by this method, and the metal is efficiently exposed on the surface of the metal nanoparticles, and the activity can be improved when used in the catalytic reaction.

  For example, a high-frequency high voltage is continuously applied between a pair of submerged electrodes placed in a metal salt solution such as chloroauric acid to generate submerged plasma, and the generated ions and radicals reduce the metal ions in the solution. And the method of manufacturing a metal nanoparticle is proposed (refer patent document 1). Also proposed is a method for producing nanoparticles in which zinc in the center and zinc oxide in the outer layer are generated by generating a plasma in liquid by supplying microwaves to an in-liquid electrode placed in ethanol. (See Patent Document 2). The metal nanoparticles produced by the method of Patent Literature 1 are gold nanoparticles, silver nanoparticles, and platinum nanoparticles, and the metal nanoparticles produced by the method of Patent Literature 2 are zinc-zinc oxide nanoparticles. All were nanoparticles having a single metal species.

  As a method for producing composite nanoparticles using in-liquid plasma, in a liquid organic compound, between a cathode made of a metal electrode such as silicon or titanium or a carbon electrode and an anode made of a metal electrode such as silicon or titanium. A method of producing a carbon-metal composite by performing pulsed plasma discharge has been proposed (see Patent Document 3). However, the composite nanoparticles produced by the method of Patent Document 3 were composite nanoparticles having a structure covered with a carbon material with the metal constituting the metal electrode as a nucleus.

JP 2008-13810 A JP 2012-36468 A JP 2012-211049 A

  As described above, in the conventional method for producing nanoparticles using in-liquid plasma, the produced nanoparticles are limited to single metal nanoparticles or nanoparticles having a structure in which a metal is covered with a carbon material. Therefore, there has been no manufacturing method that can freely combine the composite materials for the development of new functions.

  Then, this invention aims at providing the manufacturing method and manufacturing apparatus of the composite nanoparticle which diversify the combination of the composite material.

  The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems. As a result, when discharge plasma is generated between electrodes arranged in an aqueous solution containing a metal salt, the metal constituting the metal salt and the electrode The present inventors have found that composite nanoparticles containing a material constituting the material can be produced as a constituent, and have completed the present invention. That is, the present invention is as follows.

(1) A composite nanostructure comprising a composite of a first material and a second material, wherein the first material is a metal, and the second material is a metal or carbon material different from the first material. A method for producing particles, comprising a step of generating a discharge plasma between a plurality of electrodes arranged in an aqueous solution containing a metal salt, wherein the metal salt is a salt of the first material, and the electrode is A manufacturing method comprising the second material.
(2) Composite nanoparticles produced by the production method according to (1).
(3) The composite nanoparticle according to (2), which has a zeta potential having an absolute value of 30 mV or more.
(4) A composite nanostructure comprising a composite of a first material and a second material, wherein the first material is a metal, and the second material is a metal or carbon material different from the first material. A particle manufacturing apparatus, wherein a cell in which an aqueous solution containing a metal salt that is a salt of the first material is stored, and a plurality of electrodes made of the second material disposed in the aqueous solution, An application unit that applies a high-frequency high voltage so that discharge plasma is generated between the electrodes.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and manufacturing apparatus of composite nanoparticle which diversify the combination of the composite material can be provided.

It is a conceptual diagram of the manufacturing apparatus of the composite nanoparticle which concerns on one Embodiment of this invention. 4 is a diagram showing a TEM observation image of the Pd—Pt composite nanoparticle dispersion liquid produced in Test Example 1. FIG. 4 is a diagram showing a particle size distribution of Pd—Pt composite nanoparticles produced in Test Example 1. FIG. 6 is a diagram showing an example of an EDX spectrum of Pd—Pt composite nanoparticles produced in Test Example 1. FIG. 4 is a diagram showing a TEM observation image of a Pd—Pt composite nanoparticle dispersion produced in Test Example 2. FIG. 6 is a diagram showing a particle size distribution of Pd—Pt composite nanoparticles produced in Test Example 2. FIG. 6 is a diagram showing a TEM observation image of a gold nanoparticle dispersion liquid produced in Test Example 3. FIG. 6 is a view showing a TEM observation image of a gold nanoparticle dispersion liquid produced in Test Example 4. FIG. 6 is a view showing a TEM observation image of a gold nanoparticle dispersion liquid produced in Test Example 5. FIG. It is a figure which shows the relationship between the zeta potential of the gold nanoparticle manufactured in Test Example 6, and the space | interval of the front-end | tip of a cathode at the time of manufacture, and the front-end | tip of an anode.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. .

The composite nanoparticle production apparatus of the present invention is a composite of a first material and a second material, wherein the first material is a metal and the second material is different from the first material. An apparatus for producing composite nanoparticles that are a metal or a carbon material, wherein a cell in which an aqueous solution containing a metal salt that is a salt of the first material is stored, and the second arranged in the aqueous solution A plurality of electrodes made of a material, and an application unit that applies a high-frequency high voltage so that discharge plasma is generated between the electrodes are provided.
Hereinafter, an embodiment of the composite nanoparticle production apparatus of the present invention will be described with reference to FIG.

  FIG. 1 is a conceptual diagram of an apparatus for producing composite nanoparticles according to an embodiment of the present invention. The manufacturing apparatus includes a cell 30 storing a metal salt aqueous solution S and electrodes 10 and 11 arranged in the metal salt aqueous solution S. The manufacturing apparatus further includes insulating tubes 20 and 21 that hold the electrodes 10 and 11, an optical window 40, and a fixing plate 70. The optical window 40 includes a packing 50, a fixing rod 60, and a fastening plate. It is fixed to the cell 30 using the tool 80. The electrodes 10 and 11 are connected to a pulse power supply 90. At this time, one electrode 10 is connected to the transformer 100 built in the pulse power supply 90, and the other electrode 11 is connected to the earth 110 built in the pulse power supply 90.

  The cell 30 stores the metal salt aqueous solution S. The material is not particularly limited as long as the metal salt aqueous solution S can be stored.

  The metal salt aqueous solution S stored in the cell 30 is an aqueous solution containing a metal salt that is a salt of the first material. The first material is a metal, and platinum, gold, palladium, tungsten, tin, silver, copper, or the like is used.

  Although the kind of metal salt contained in the metal salt aqueous solution S is not specifically limited, chloride salt, nitrate, sulfate, acetate, etc. can be mentioned.

  The concentration of the metal salt aqueous solution S is generally about several mM although it depends on the purpose.

  The electrodes 10 and 11 are made of the second material. The second material is a metal or a carbon material. Examples of the metal used for the second material include pure metals such as platinum, gold, palladium, tungsten, tin, silver, and copper, and alloys thereof. Examples of the carbon material used for the second material include carbon materials such as graphite and glassy carbon, and composite carbon materials obtained by doping the carbon material with other elements such as boron and nitrogen. When the second material is a metal, a metal different from the first material is selected.

  In the present invention, a plurality of electrodes 10 and 11 are arranged in the metal salt aqueous solution S stored in the cell 30 in order to generate discharge plasma in the liquid. One type of the second material may be used for each electrode, or the second material may be different for each electrode.

  There is no restriction | limiting in particular in the shape of the electrodes 10 and 11, and electrodes, such as prismatic shape and a column shape, can be used. For example, in the case of a cylindrical shape, the electrodes 10 and 11 preferably have a diameter of several hundred μm to several mm.

  By providing at least two electrodes 10 and 11 in the cell 30, a pair of an anode and a cathode is formed, and discharge plasma can be generated between these electrodes. The electrode 10 and the electrode 11 are preferably disposed so that the tips thereof are opposed to each other in terms of control of the distance between the electrodes, but are not limited to this arrangement. The distance between the tip of the electrode 10 and the tip of the electrode 11 is preferably 100 μm to 1 mm, and more preferably 300 μm to 700 μm.

Electrodes 10 and 11 are held by insulating tubes 20 and 21, respectively. The material of the insulating tubes 20 and 21 is not particularly limited as long as it is a material that is not sputtered when a high-frequency high voltage is applied between the electrode 10 and the electrode 11 to generate discharge plasma, and examples thereof include alumina.
The tips of the electrodes 10 and 11 have portions that are not covered with the insulating tubes 20 and 21 so that discharge plasma is easily generated.

  The cell 30 includes an optical window 40. By analyzing the light emitted through the optical window by microspectroscopy, it is possible to analyze the components in the discharge plasma reaction field. The optical window 40 is tightly fixed to the cell 30 using a packing 50, a fixing bar 60, and a fastener 80 that fixes the fixing bar 60 from above the fixing plate 70. The fixing plate 70 only needs to be able to fix the fixing rod 60, and does not completely cover the upper part of the cell and seal the cell. Quartz etc. are used for the material of the optical window 40.

  The electrodes 10 and 11 are connected to a pulse power supply 90. At this time, one electrode 10 is connected to the transformer 100 built in the pulse power supply 90, and the other electrode 11 is connected to the earth 110 built in the pulse power supply 90. When a high frequency high voltage is applied between the electrode 10 and the electrode 11 connected in this way, discharge plasma is generated. The transformer 100 may be integrated with a pulse power source or may be used as a divided device.

Next, the manufacturing method of the composite nanoparticle of this invention is demonstrated.
In the method for producing composite nanoparticles of the present invention, the first material and the second material are combined, the first material is a metal, and the second material is different from the first material. A method for producing a composite nanoparticle which is a metal or carbon material, comprising a step of generating discharge plasma between a plurality of electrodes arranged in an aqueous solution containing a metal salt, wherein the metal salt is the first material The electrode is made of the second material.

  In FIG. 1, in order to generate discharge plasma between the electrode 10 and the electrode 11, a pulse power supply 90 with a built-in transformer 100 is used, and the electrode 10 connected to the transformer 100 and the electrode 11 connected to the earth 110 are connected. A high frequency high voltage is applied between them.

When generating discharge plasma, the voltage applied between the electrode 10 and the electrode 11 is preferably 0.5 to 4 kV, and more preferably about 1 kV.
The waveform of the voltage applied when generating the discharge plasma may be a sine wave or a non-sine wave. When a rectangular wave is applied as a non-sinusoidal wave, the pulse width is preferably within several microseconds, more preferably 1 to 2 microseconds.
The frequency when generating the discharge plasma is preferably 15 to 30 kHz, and more preferably 20 to 25 kHz.
The current for generating the discharge plasma is preferably about 1A.
The discharge time when generating the discharge plasma is preferably within a few minutes.
The pulse voltage may be either bipolar or unipolar input.

  When a discharge plasma is generated between the electrode 10 and the electrode 11 disposed in the metal salt aqueous solution S, metal ions derived from the metal salt contained in the metal salt aqueous solution S are generated when the discharge plasma is generated. It is reduced by electrons and hydrogen radicals and converted into the metal atoms of the first material, and becomes a component constituting the composite nanoparticles. Further, the second material constituting the electrode is sputtered and deposited, and becomes a component constituting the composite nanoparticles. For this reason, the composite nanoparticle which uses the said 1st material and said 2nd material as a structural component can be manufactured.

For example, when palladium is used for the electrodes 10 and 11 and a chloroplatinic acid aqueous solution is used for the metal salt aqueous solution S, composite nanoparticles containing palladium and platinum as constituent components can be produced.
As described above, according to the production method of the present invention, the combination of materials constituting the composite nanoparticles can be diversified by variously selecting the first material and the second material.

  The concentration of the metal salt aqueous solution S is generally about several mM, but when the concentration is increased, a larger amount of the first material can be deposited on the composite nanoparticles to be produced.

  In addition to the metal salt, another electrolyte may be added to the metal salt aqueous solution S. For example, when NaOH is added, discharge plasma can be generated stably. The concentration of the electrolyte is preferably about several mM.

  When the discharge plasma is generated between the electrode 10 and the electrode 11 arranged in the metal salt aqueous solution S, the particle diameter of the composite nanoparticles to be produced can be reduced by shortening the distance between the electrodes. For example, when the distance between the tip of the electrode 10 and the tip of the electrode 11 is 300 μm to 700 μm, it is easy to produce composite nanoparticles having an average particle diameter of several nm to several tens of nm.

  Moreover, when the area of the opposing surface of the electrode 10 and the electrode 11 is small, for example, if the electrodes 10 and 11 are cylindrical, if the diameter is small, the particle diameter of the composite nanoparticles to be manufactured tends to be small.

  Next, the composite nanoparticles produced by the method for producing composite nanoparticles of the present invention will be described. The composite nanoparticle includes the first material and the second material as constituent components.

  When generating discharge plasma between the electrode 10 and the electrode 11 arranged in the metal salt aqueous solution S, the second material constituting the electrodes 10 and 11 is sputtered and deposited to form nanoparticles, The rate at which metal ions derived from the metal salt contained in the metal salt aqueous solution S are reduced by electrons or hydrogen radicals generated by plasma and deposited as metal atoms of the first material is the former one. Therefore, it is considered that composite nanoparticles having the second material as a main constituent and the first material as a sub constituent are likely to be generated.

  Then, it is considered that composite nanoparticles having a core-shell structure in which the main component is a core and a sub-component is a shell, and a structure in which the sub-components are arranged in a patch shape on the particle surface of the main component are manufactured. . By making the composite nanoparticles into these structures and selecting a metal element having catalytic activity as a sub-component, in a fine particle type catalyst such as nanoparticles, a metal having catalytic activity while maintaining sufficient catalytic activity The amount of element used can be reduced.

  The composite nanoparticles tend to have a zeta potential exceeding an absolute value of 30 mV or 35 mV. In particular, the shorter the distance between the tip of the electrode 10 and the tip of the electrode 11, the greater the absolute value of the zeta potential. When the zeta potential has a large absolute value, the repulsive force between the nanoparticles increases and the dispersion stability of the nanoparticles increases. In general, in the production of nanoparticles, a protective agent such as polyvinyl pyrrolidone, polyethylene glycol, polysulfonic acid or the like is added to increase dispersion stability. The composite nanoparticles produced by the method of the present invention have an absolute value of zeta potential. Therefore, aggregation and precipitation do not occur even without adding a protective agent, and dispersion stability is high.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example etc., this invention is not limited to this Example etc. at all.

[Test Example 1]
Prepare a mixed solution of 1 ml of an aqueous solution of chloroplatinic acid (H ₂ PtCl ₆ ) adjusted to 50 mM and 0.15 ml of 1M sodium hydroxide (NaOH) aqueous solution, and add pure water so that the total volume becomes 50 ml. The female was up. The concentration of sodium hydroxide at this time is 3 mM. This solution was placed in a cell, and a pair of electrodes was placed in the solution. The electrode was a palladium (Pd) electrode having a diameter of 1 mm and a length of 100 mm, and the distance between the tip of the cathode and the tip of the anode was 300 μm. A pulse voltage having an applied voltage of about 1 kV, a pulse width of 2 μs, and a frequency of 25 kHz was applied between the electrodes, and a plasma was generated by discharging in an aqueous solution. After discharging for 3 minutes, the solution was recovered from the cell to obtain a brown dispersion. When this solution was observed with a transmission electron microscope (TEM), particles having a uniform particle diameter were observed as shown in FIG. The particle size distribution is shown in FIG. The average particle size at this time was 2.6 ± 1.7 nm. The pH of the solution at this time was 10.9, and the zeta potential at this pH was −43.8 ± 4.1 mV. Next, fine particles were identified, and energy dispersive X-ray analysis (EDX) was performed with an acceleration voltage of 200 kV, a beam diameter of about 1 nm, and an energy resolution of 137 eV. As a result, an EDX spectrum was obtained as shown in FIG. A signal of Pd element and a signal of Pt element were observed, and it was found to be a composite nanoparticle.

[Test Example 2]
Plasma was generated in the same manner as in Test Example 1 except that the concentration of the H ₂ PtCl ₆ aqueous solution was changed from 1 mM to 2 mM. When the solution was collected and subjected to TEM observation, particles having a uniform particle diameter were observed as shown in FIG. The particle size distribution is shown in FIG. The average particle size at this time was 3.2 ± 1.8 nm. The pH of the solution at this time was 9.6, and the zeta potential at this pH was −36.2 ± 4.4 mV. When EDX was performed on these fine particles, the signal of the Pt element was strong and the content of Pt constituting the metal salt was high.

[Test Example 3]
In the same manner as in Test Example 1, 50 ml of a 3 mM aqueous solution of NaOH was placed in a cell, and a gold (Au) electrode having a diameter of 1 mm and a length of 100 mm was used as a pair of electrodes. The distance between the tip of the cathode and the tip of the anode was set to 300 μm, a pulse voltage having an applied voltage of about 1 kV, a pulse width of 2 μs, and a frequency of 25 kHz was applied between the electrodes, and discharge was performed in an aqueous solution to generate plasma. After discharging for 3 minutes, the solution was recovered from the cell to obtain a dispersion of red gold nanoparticles. No precipitation occurred when this dispersion was allowed to stand for 2 weeks. The TEM observation of this solution is shown in FIG. The average particle size was 4.16 ± 0.79 nm. The pH of the solution at this time was 13.1, and the zeta potential at this pH was −60.8 ± 1.3 mV.

[Test Example 4]
A discharge plasma was generated between the electrodes in the same manner as in Test Example 3, except that the distance between the tip of the cathode and the tip of the anode was 500 μm. The results of collecting the solution and performing TEM observation are shown in FIG. The generated gold nanoparticles had an average particle size of 9.69 ± 4.53 nm. The pH of the solution at this time was 12.4, and the zeta potential at this pH was −52.7 ± 1.4 mV.

[Test Example 5]
A discharge plasma was generated between the electrodes in the same manner as in Test Example 3, except that the distance between the tip of the cathode and the tip of the anode was 700 μm. The results of collecting the solution and performing TEM observation are shown in FIG. The average particle diameter of the produced gold nanoparticles was 12.6 ± 8.15 nm. The pH of the solution at this time was 12.7, and the zeta potential at this pH was −44.3 ± 1.1 mV.

[Test Example 6]
A solution containing gold nanoparticles was collected in the same manner as in Test Example 3, except that the distance between the tip of the cathode and the tip of the anode was changed. When the zeta potential of the recovered solution was measured, as shown in FIG. 10, the zeta potential exceeding 40 mV in absolute value was observed with the interval between 100 to 900 μm. The absolute value of the zeta potential was larger as the above interval was shorter.

DESCRIPTION OF SYMBOLS 10 Electrode 11 Electrode 20 Insulation tube 21 Insulation tube 30 Cell 40 Optical window 50 Packing 60 Fixing rod 70 Fixing plate 80 Fastener 90 Pulse power supply 100 Transformer 110 Ground S Metal salt aqueous solution

Claims (4)

Production of composite nanoparticles comprising a composite of a first material and a second material, wherein the first material is a metal and the second material is a metal or carbon material different from the first material. A method,
Generating a discharge plasma between a plurality of electrodes disposed in an aqueous solution containing a metal salt,
The metal salt is a salt of the first material;
The manufacturing method, wherein the electrode is made of the second material.   The composite nanoparticle manufactured with the manufacturing method of Claim 1.   The composite nanoparticle according to claim 2, which has a zeta potential of 30 mV or more in absolute value. Production of composite nanoparticles comprising a composite of a first material and a second material, wherein the first material is a metal and the second material is a metal or carbon material different from the first material. A device,
A cell in which an aqueous solution containing a metal salt that is a salt of the first material is stored;
A plurality of electrodes made of the second material, disposed in the aqueous solution;
An application unit for applying a high-frequency high voltage so that discharge plasma is generated between the electrodes;
A manufacturing apparatus comprising: