KR101166365B1 - Fabrication method for continuous preparing metal nanoparticle and metal nanoparticle prepared thereby - Google Patents

Abstract

The present invention relates to a method for producing metal nanoparticles, comprising the steps of: (a) preparing a metal precursor solution in which a metal precursor is dissolved in alcohol; (b) continuously introducing the metal precursor solution into a reactor in supercritical conditions to produce metal nanoparticles; (c) cooling the solution obtained in step (b); And (d) separating and recovering the metal nanoparticles from the solution obtained in step (c). The present invention relates to a method for continuously preparing metal nanoparticles, and metal nanoparticles prepared thereby.

Metal nanoparticles, alcohol solvents, supercritical conditions, continuous process

Description

Continuous production method of metal nanoparticles and metal nanoparticles produced by the above method {FABRICATION METHOD FOR CONTINUOUS PREPARING METAL NANOPARTICLE AND METAL NANOPARTICLE PREPARED THEREBY}

The present invention relates to a method for producing metal nanoparticles having a uniform particle size, and to metal nanoparticles prepared by the above method, and more particularly, to metal nanoparticles characterized in that the solvent is used in a continuous process. It relates to a method for producing the particles.

Metal nanoparticles, due to their unique optical, magnetic, electrical and chemical properties, differ from bulk particles, they can be used for electronic components, catalysts, paints, sensors, antimicrobials, fungicides, capacitors, paints, inks, magnetic tapes, electromagnetic wave absorbers, Applications are expected in a variety of industries, such as medical materials, the importance of which is increasing rapidly in recent years.

In general, a method of manufacturing metal nanoparticles can be roughly divided into physical and chemical methods.

First, the physical manufacturing method is a gas evaporation-condensation method of heating the target metal in a vacuum or low pressure atmosphere to form a gas, then cooling and condensing it to produce metal nanoparticles, melting the metal and then dispersed in a gas using a spray There are an automated method for producing nanoparticles, a mechanical grinding method using ball milling, and the like. Among them, the gas evaporation-condensation method and the automating method have advantages of manufacturing uniformly sized metal nanoparticles with high purity, but the complexity of the device configuration, low yield and low production rate, high energy consumption, It is uneconomical due to high production price and is not suitable for mass production. On the other hand, the mechanical grinding method is suitable for industrial mass production, but it is difficult to produce high-purity particles due to the incorporation of impurities in the process, and it is difficult to produce uniform particles of nano size due to the limitation of mechanical precision. .

In the case of the chemical preparation method, a vapor phase reduction method for reducing steam of metal chlorides to hydrogen or carbon monoxide, a liquid phase reduction method for forming particles by reducing a metal precursor using a reducing agent in an organic solvent or an aqueous solution, and a metal electrode rod in a metal ion in a solution By applying a direct current or an alternating current through, an electrolysis method for producing metal nanoparticles by reducing ions in a solution. Among these, the gas phase reduction method requires a costly device such as a plasma or chemical vapor evaporation device. The liquid phase reduction method is relatively simple, but the hydrazine, formic acid, boron compounds (NaBH ₄ , LiBH ₄ , KBH ₄ ), etc. Because of the use of toxic reducing agents and organic solvents, the application of the prepared metal nanoparticles to cosmetics, medicines, biodoses, etc. requires a great deal of time and money in post-treatment processes, resulting in a large amount of organic waste. Therefore, there is a problem of being non-environmental. In addition, when the volume of the batch reactor is increased for mass production, there is a problem that the particle size distribution of the manufactured nanoparticles is very uneven because the temperature inside the reactor or the temperature inside the precursor becomes uneven. On the other hand, the electrolysis method has a problem in that the production time is long, the concentration is low, the productivity is very low, and the waste water treatment is expensive because of the use of strong acids such as sulfuric acid.

Therefore, there is an urgent need to develop a process that can continuously produce uniform metal nanoparticles at high speed and high yield using a simple apparatus without using expensive and toxic reducing agents or strong acids.

An object of the present invention is to avoid the use of expensive toxic reducing agents, organic solvents or strong acids in order to overcome the above-mentioned problems, and to form a continuous reactor using a supercritical fluid, high purity metal nanoparticles of uniform size at high speed It is to provide a high-purity metal nanoparticles having a uniform method of producing and uniform particle size.

These objects include (a) preparing a metal precursor solution in which the metal precursor is dissolved in alcohol; (b) continuously introducing the metal precursor solution into a reactor in supercritical conditions to produce metal nanoparticles; (c) cooling the solution obtained in step (b); And (d) separating and recovering the metal nanoparticles from the solution obtained in the step (c); and the method for producing the metal nanoparticles, which is prepared by the above method, has a diameter of 1 nm to 500 nm, and Cu , Ni, Ag, Au, Ru, Rh, Pd and Pt can be achieved by a metal nanoparticle comprising a metal selected from at least one member.

According to the present invention, by using a supercritical fluid as a solvent and a reducing agent, it is economical and environmentally friendly because it does not use expensive and toxic reducing agents and strong acids, and it is possible to obtain a product having uniform physical properties because of the continuous production method. Because of the relatively simple configuration of the device, the device cost and operation cost are low, mass production is easy, and since the metal nanoparticles are manufactured at a high speed, they are economical and can produce various kinds of metal nanoparticles.

Method for producing a metal nanoparticle of the present invention comprises the steps of (a) preparing a metal precursor solution in which a metal precursor is dissolved in alcohol; (b) continuously introducing the metal precursor solution into a reactor in supercritical conditions to produce metal nanoparticles; (c) cooling the solution obtained in step (b); And (d) separating and recovering the metal nanoparticles from the solution obtained in step (c). In addition, after step (d), (e) may further comprise the step of washing and drying the metal nanoparticles.

The alcohol may be one or more selected from the group consisting of methanol, ethanol, propanol, butanol and pentanol. Although the present invention is not limited thereto, alcohols having 1 to 5 carbon atoms are particularly preferred. This is because the solubility of the particle precursor can be remarkably reduced in the case of alcohol having 6 or more carbon atoms exceeding the above range.

The metal precursor may be a compound of at least one metal selected from the group consisting of Cu, Ni, Ag, Au, Ru, Rh, Pd and Pt or a salt of the metal.

Examples of such metal precursors include Cu (NO ₃ ) ₂ , CuSO ₄ , Ni (NO ₃ ) ₂ , NiSO ₄ , AgNO ₃ , Ag ₂ SO ₄ , Ru (NO ₃ ) ₃ , Ru ₂ (SO ₄ ) ₃ , Rh (NO ₃ ) ₃ , H ₃ RhCl ₆ , RhPO ₄ , Rh ₂ (SO ₄ ) ₃ , Pd (NO ₃ ) ₂ , Pd (NH ₃ ) ₄ Cl ₂ , Pd (NH ₃ ) ₂ Cl ₂ , H ₂ PdCl ₆ , Pt (NO ₃ ) ₂ , H ₂ PtCl ₆ , K ₂ PtCl ₄ , Pt (NH ₃ ) ₂ (NO ₂ ) ₂ , Pt (NH ₃ ) ₆ Cl ₄ , Pt (NH ₃ ) ₄ Cl ₄ , It may be any one selected from the group consisting of HAuCl ₄ and Na ₃ Au (SO ₃ ) ₂ . However, the present invention is not limited thereto and may be used as the metal precursor of the present invention as long as it can be dissolved in alcohol.

The concentration of the solution prepared by dissolving the metal precursor in an alcohol solvent may be 0.001 mol / l to 1 mol / l, and preferably 0.01 mol / l to 0.5 mol / l. Although the present invention is not limited thereto, when the concentration of the metal precursor is less than 0.001 mol / l outside the above range, the concentration may be too lean to deteriorate the economic efficiency, and the concentration of the metal precursor may be 1 mol / l. If it exceeds, the concentration is too high because the size of the nanoparticles produced is too large, or the uniformity may deteriorate and the quality may be degraded.

On the other hand, the supercritical conditions of step (b) is the reaction temperature is 200 ℃ to 600 ℃, the reaction pressure may be 20 bar to 500 bar, preferably the reaction temperature is 250 ℃ to 400 ℃, the reaction pressure is 50 bar to It can be 500 bar. If the reaction temperature is less than 200 ℃ or the reaction pressure is less than 20bar there is a problem that the size of the metal nanoparticles to be produced, the particle size distribution is widened and the crystallinity is reduced, the reaction temperature exceeds 600 ℃, or the reaction pressure is 500bar This is because there is a problem in that economic efficiency is lowered because it must maintain a high temperature and high pressure.

The reaction time of step (b) may be 5 seconds to 10 minutes, preferably 10 seconds to 5 minutes. If the reaction time is less than 5 seconds, the crystallinity and purity is reduced, if the reaction time exceeds 10 minutes there is a problem that the size of the nanoparticles is excessively large and the particle size uniformity is large.

On the other hand, the cooling of step (c) may utilize a general cooling device such as a heat exchanger, it is preferable to use water of 50 ℃ or less.

In addition, the separation of step (d) may be by filtration or centrifugation. The pore size of the filter may be selected according to the size of the desired metal nanoparticles to obtain even distribution of the metal nanoparticles. It is also possible to obtain metal nanoparticles from solution using a centrifuge.

The diameter of the metal nanoparticles obtained in step (d) may be 1 nm to 500 nm, preferably 3 nm to 250 nm, more preferably 5 nm to 100 nm. This may vary with the type of metal and may vary with other process variables.

The washing in step (e) may use water or an organic solvent selected from the group consisting of methanol, ethanol, propanol, acetone and tetrahydrofuran, and the drying may be vacuum drying, oven drying or freeze drying.

In addition, the present invention includes a metal formed by the above-described method for producing metal nanoparticles having a diameter of 1 nm to 500 nm and at least one metal selected from the group consisting of Cu, Ni, Ag, Au, Ru, Rh, Pd, and Pt. The present invention relates to metal nanoparticles. The diameter of the metal nanoparticles may be 1 nm to 500 nm, preferably 3 nm to 250 nm, more preferably 5 nm to 100 nm. If the diameter of the metal nanoparticles exceeds 500 nm, magnetic, optical, chemical and catalytic This is because the properties of metal-sized particles of nano size, such as properties, are greatly reduced and dispersibility is reduced. In addition, when the diameter of the particle is less than 1nm, not only the prepared particles are difficult to handle, but also the dispersibility may decrease due to the increase of cohesion between particles.

1 is a schematic diagram showing a supercritical fluid testing apparatus used for the continuous production of metal nanoparticles of the present invention. The apparatus includes a high pressure reactor (10), a high pressure pump (70, 71), a heater (30, 31), a preheater (20), a filter (50), a rear pressure regulator (60), a metal precursor solution storage container (80), and And an alcohol storage container 81.

Referring to Figure 1 describes a method for producing a metal nanoparticle of the present invention. First, the metal precursor is dissolved in an alcohol solvent and then introduced into the metal precursor solution storage container 80. Alcohol in the alcohol storage container 81 is transferred to the high pressure reactor 10 using the high pressure pump 71. At this time, the temperature of the alcohol introduced into the high pressure reactor is controlled by using the preheater 20, the temperature of the high pressure reactor is controlled by using the heater 30, the pressure of the high pressure reactor using the rear pressure regulator 60 Control to keep the alcohol introduced into the high pressure reactor in a supercritical fluid state. Metal nanoparticles are prepared by continuously transferring a metal precursor solution into a high pressure reactor at a predetermined temperature and pressure to react with the supercritical fluid alcohol. The temperature of the solution containing the metal nanoparticles thus prepared is lowered by the cooler 40, and then the filter 50 is used to separate and recover the metal nanoparticles from the solution.

Example

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. However, this is only an example for detailed description, and the present invention is not limited thereto. In addition, in order to analyze the shape of the metal nanoparticles prepared by the manufacturing method of the present invention in order to compare the properties of the metal nanoparticles obtained through Examples and Comparative Examples Hitachi (Scanning electron microscopy, SEM) Rigaku's X-ray Diffractor Meter (XRD) was used to analyze the components of the metal nanoparticles.

Example 1

Methanol was introduced into a 1000 ml glass container, and copper nitrate (Cu (NO ₃ ) ₂ ) was introduced as a metal precursor to prepare a copper nitrate solution having a concentration of 0.05 mol / L. The metal precursor solution was pumped at a rate of 6 ml / min using a high pressure pump and pressurized to 300 bar. Methanol was introduced into two other 1000 ml glass vessels, each pumped at a rate of 6 ml / min using a high pressure pump, pressurized to 300 bar and transferred to the preheater. The pressurized copper nitrate solution and methanol were mixed in a mixer maintained at 400 ° C., and then transferred to a high pressure reactor maintained at 400 ° C. for 40 seconds. The solution containing the produced copper nanoparticles was cooled using a cooler, and then the copper nanoparticles were separated and recovered using a filter. The remaining copper nitrate was separated from the recovered copper nanoparticles using a centrifugal separator. Centrifuges removed most of the copper nitrate, but were further washed with methanol because of the small amount of copper remaining. The washed copper nanoparticles were dried in a vacuum oven at 60 ° C. for one day to remove methanol.

Figure 2 (a) shows the XRD results of the copper nanoparticles prepared in Example 1, Figure 3 (a) shows the SEM image of the copper nanoparticles prepared in Example 1.

Comparative Example 1

In order to compare the metal nanoparticles prepared according to the present invention and metal nanoparticles prepared using non-alcohol supercritical water, a copper precursor and copper nitrate were dissolved in water instead of methanol, and a supercritical solvent introduced through a preheater was used instead of methanol. Using water Except, nanoparticles were prepared in the same manner as in Example 1.

The prepared copper nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in FIGS. 2 (b) and 3 (b).

Comparative Example 2

In order to compare the metal nanoparticles prepared by the continuous process of the present invention and the metal nanoparticles prepared by the batch reaction process rather than the continuous process, 0.05 mol of copper nitrate (Cu (NO ₃ ) ₂ ) as methanol was used as a copper precursor. After dissolving at a concentration of / l, 4 ml of the solution was introduced into a high temperature, high pressure batch reactor made of 10 ml of stainless steel (SUS 316). The reactor was introduced into a salt bath maintained at 400 ° C. to a pressure of 300 bar and then reacted for 5 minutes while maintaining this condition. The resulting solution of copper nanoparticles was cooled with 10 ° C. water and filtered through a filter to separate and recover the copper nanoparticles. The recovered metal nanoparticles were washed and dried in the same manner as in Example 1 and analyzed in the same manner as in Example 1, and the results are shown in FIGS. 2 (c) and 3 (c).

As compared with Example 1 and Comparative Examples 1 and 2, as shown in Figure 2, the copper nanoparticles prepared using the methanol solvent of Example 1 is a copper-specific crystal in the diffraction angle range of 10 to 90 degrees The same peak as the peak was shown (Fig. 2 (a)). On the other hand, in the case of the copper nanoparticles prepared using supercritical water instead of the supercritical methanol of Comparative Example 1, it was confirmed that the same peak as the crystal peak inherent to copper oxide (CuO) appeared in the diffraction angle of 10 to 90 degrees (FIG. 2 ( b)). Therefore, copper oxide was prepared when supercritical water was used, whereas pure copper particles were prepared when supercritical methanol was used. In addition, the particles prepared by using the batch process instead of the continuous process in 2 showed the same peak as the crystal peak inherent to copper (Fig. 3 (c)).

In addition, as shown in FIG. 3, the copper nanoparticles prepared using the methanol solvent of Example 1 were generally spherical, and their diameters were 50 nm to 150 nm (FIG. 3 (a)), whereas in Comparative Example 1 Copper oxide particles prepared using supercritical water instead of critical methanol have various shapes, and the size is 1000 nm to 3000 nm (FIG. 3 (b)).

On the other hand, in Comparative Example 2, the copper nanoparticles manufactured by using the batch process instead of the continuous process were found to have a large size of about 300 to 800 nm and to cause aggregation between the particles (FIG. 3 (c)). Therefore, it can be seen that when the continuous process is used, copper nanoparticles having a small size and no aggregation between particles can be produced.

Example 2

Copper nanoparticles were prepared in the same manner as in Example 1, except that the metal precursor was dissolved in ethanol instead of methanol. The prepared copper nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1.

Example 3

Copper nanoparticles were prepared in the same manner as in Example 1, except that the metal precursor was dissolved in propanol instead of methanol. The prepared copper nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1.

Example 4

Using copper nitrate (Cu (NO _{3) 2)} instead of silver nitrate (Ag (NO _{3) 2)} as the metal precursor in the same manner as in Example 1 was prepared nanoparticles. The prepared nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in FIGS. 4 (a), 5 (a) and Table 1.

Comparative Example 3

Using copper nitrate (Cu (NO _{3) 2)} instead of silver nitrate (Ag (NO _{3) 2)} as the metal precursor same manner as in Comparative Example 2, that is, the batch type reaction process is not a continuous process to prepare a nanoparticle . The prepared nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in FIGS. 4 (b), 5 (b) and Table 1.

As shown in FIG. 4, silver nanoparticles prepared in Example 4 and Comparative Example 3 showed peaks identical to silver-specific crystal peaks in a diffraction angle of 10 to 90 degrees. That is, it can be confirmed that the silver nitrate was formed of silver nanoparticles at an effective level.

On the other hand, silver nanoparticles prepared using the continuous process in Example 4 is generally spherical, very uniform in size, and its diameter is about 40-60 nm (Fig. 5 (a)), whereas in Comparative Example 3 The silver nanoparticles prepared by the batch reaction process rather than the continuous process have a very large size of 300-700 nm and a very wide particle size distribution. Therefore, it can be seen that when the continuous process according to the present invention is used instead of the batch reaction process, silver nanoparticles having a small size and a uniform distribution can be produced.

division Manufactured Nanoparticles menstruum Particle diameter (nm) Particle shape Example 1 Copper (Cu) Supercritical methanol 50 to 150 rectangle Example 2 Copper (Cu) Supercritical ethanol 50-200 rectangle Example 3 Copper (Cu) Supercritical propanol 50-200 rectangle Example 4 Silver (Ag) Supercritical methanol 40-60 rectangle Comparative Example 1 Copper Oxide (CuO) Supercritical water 1,000-3,000 Several models Comparative Example 2 Copper (Cu) Supercritical methanol 300-800 rectangle Comparative Example 3 Silver (Ag) Supercritical methanol 300-700 rectangle

1 is a schematic representation of a supercritical fluid testing apparatus used for the continuous production of metal nanoparticles of the present invention.

2 is an XRD analysis result of the particles prepared in (a) Example 1, (b) Comparative Example 1 and (c) Comparative Example 2.

Figure 3 is an SEM image of the particles prepared in (a) Example 1, (b) Comparative Example 1 and (c) Comparative Example 2.

Figure 4 is a XRD analysis of the silver nanoparticles prepared in (a) Example 4 and (b) Comparative Example 3.

5 is a SEM image of the silver nanoparticles prepared in (a) Example 4 and (b) Comparative Example 3.

* Description of symbols for the main devices in the drawings

10: high pressure reactor 20: preheater

30, 31: heater 40: cooler

50 filter 60 rear pressure regulator

70, 71: high pressure pump 80: particle precursor storage container

81: Alcohol Storage Container

Claims (14)

(a) preparing a metal precursor solution in which a silver precursor is dissolved in methanol; (b) continuously introducing the metal precursor solution into a supercritical condition reactor to produce silver nanoparticles; (c) cooling the solution obtained in step (b); And (d) separating and recovering the silver nanoparticles from the solution obtained in step (c); Continuous manufacturing method of silver nanoparticles whose diameter includes 40 nm-60 nm. The process of claim 1, wherein after step (d), (e) washing and drying the silver nanoparticles. delete delete The method of claim 1 or 2, wherein the silver precursor is one or more selected from the group consisting of AgNO ₃ and Ag ₂ SO ₄ . The method of claim 1 or 2, wherein the silver precursor concentration of the metal precursor solution is 0.001 mol / l to 1 mol / l. 3. The method of claim 1, wherein the supercritical conditions of step (b) have a reaction temperature of 200 ° C. to 600 ° C. and a reaction pressure of 20 bar to 500 bar. 3. The method of claim 1, wherein the supercritical conditions of step (b) have a reaction temperature of 250 ° C. to 400 ° C. and a reaction pressure of 50 bar to 500 bar. 4. The method of claim 1 or 2, wherein the reaction time of step (b) is from 5 seconds to 10 minutes. The method of claim 1 or 2, wherein in step (d), the silver nanoparticles are separated by filtration or centrifugation. delete delete The method of claim 2, wherein the washing in step (e) uses water or an organic solvent selected from the group consisting of methanol, ethanol, propanol, acetone and tetrahydrofuran, wherein the drying is vacuum drying, oven drying. Or freeze-drying. delete

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