KR20150118737A - Methods of preparing metal nano particles - Google Patents

Abstract

In the method for producing metal nanoparticles, a metal precursor solution is prepared by dissolving a metal precursor in a solvent. The precursor complex is prepared by mixing the metal precursor solution with a metal salt powder. The precursor composite is heat treated. The metal nanoparticles can be easily prepared by using a dry-based reaction system.

Description

METHODS OF PREPARING METAL NANO PARTICLES [0002]

The present invention relates to a method for producing metal nanoparticles. More particularly, the present invention relates to a method for preparing metal nanoparticles through the reaction of metal salts.

Nanoparticles have new optical, electrical, and magnetic properties as the particle size is reduced to nanometer scale and have been developed and used in a variety of applications in the fields of information electronics, biotechnology, and environmental engineering. For example, copper nanoparticles have excellent thermal and electrical conductivity and can be manufactured at relatively low cost.

For example, the metal nanoparticles are manufactured in the form of a conductive paste or a nano ink, and can be used as various display devices such as a printed circuit board (PCB), an organic light emitting display (OLED) Can be applied to conductive structures of electronic devices. In this case, the metal nanoparticles can easily form the conductive structure through a printing process, and can replace the conventional complicated and expensive photolithography process.

However, in order to produce the metal nanoparticles, methods such as a liquid phase reduction method, a sol-gel method, a hydrothermal synthesis method, and a microemulsion method have been utilized. However, since these methods use a solution-based wet process, a large amount of solvent is required for mass production. Thus, there are problems such as an increase in manufacturing cost, environmental pollution caused by the solvent, and cost inconvenience of controlling solution-based reaction conditions.

For example, Patent Document 1 discloses a method for producing wet-based copper nanoparticles using copper oxide.

[Patent Document 1] Korean Published Patent Application No. 2009-0032839 (2009.04.01)

It is an object of the present invention to provide a method for producing metal nanoparticles having excellent processability.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, but may be variously expanded without departing from the spirit and scope of the present invention.

According to an exemplary embodiment of the present invention, a metal precursor solution is prepared by dissolving a metal precursor in a solvent. The precursor complex is prepared by mixing the metal precursor solution with a metal salt powder. The precursor composite is heat treated.

According to exemplary embodiments, the metal precursor may comprise a copper salt.

According to exemplary embodiments, the copper salt may include copper oxide, copper sulfate, copper oxides, copper halides, copper formates, copper acetates, copper acetylacetonates or copper carbonates. These may be used alone or in combination of two or more.

According to exemplary embodiments, the solvent may comprise an organic solvent such as xylene, hexane or toluene. These may be used alone or in combination of two or more.

According to exemplary embodiments, the metal precursor solution may further comprise a phase change material containing an amine based compound.

According to exemplary embodiments, the metal salt powder may comprise an alkali metal salt or an alkaline earth metal salt.

According to exemplary embodiments, the metal salt powder may include sodium sulfate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, sodium chloride, magnesium sulfate, potassium sulfate, potassium chloride or sodium ascorbate. These may be used alone or in combination of two or more.

According to exemplary embodiments, the precursor composite may be formed in the form of a powder or paste.

According to an exemplary embodiment, the precursor complex may be heat treated at a temperature of about 200 ^o C to about 300 ^o C.

According to exemplary embodiments, the precursor complex may be heat treated in a nitrogen atmosphere or an argon atmosphere.

According to exemplary embodiments, the heat treated precursor complex may be cleaned using hydrazine.

According to exemplary embodiments, after washing the heat treated precursor composite, the metal salt powder and the unreacted metal precursor may be removed using centrifugation.

According to the exemplary embodiments of the present invention described above, a metal precursor solution can be prepared and then injected into a metal salt powder to form a powder or paste-like precursor complex. The metal nanoparticles can be easily produced by heat-treating the precursor complex. By using a dry synthesis process on a solid, non-solution-based powder or paste-based process, the process can be easily controlled and the storage and transport of raw materials can be improved. Furthermore, copper nanoparticles having uniform particle distribution can be produced using copper precursors, which are excellent in electrical and thermal conductivity and are synthesized at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart for explaining a method for producing metal nanoparticles according to exemplary embodiments. FIG.
FIGS. 2, 3 and 4 are transmission electron microscopy (TEM) images, scanning electron microscopy (SEM) images, and scanning electron microscopy (SEM) images of metal nanoparticles prepared according to Experimental Examples, respectively. Transmission Electron Microscopy (STEM) images.
5 is an image showing energy dispersive spectroscopy (EDS) analysis results of the metal nanoparticles prepared according to Experimental Example.

Hereinafter, a salt extraction and recovery method according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

 It is to be understood that the invention is not to be limited to the specific embodiments disclosed and that all changes which fall within the spirit and scope of the present invention are intended to be illustrative, , ≪ / RTI > equivalents, and alternatives.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart for explaining a method for producing metal nanoparticles according to exemplary embodiments. FIG.

Referring to FIG. 1, a metal precursor solution is prepared (step S10).

The metal precursor solution may be prepared by dissolving a metal precursor in a suitable solvent. The metal precursor may include, for example, metal inorganic salts such as metal oxides, metal sulfates, metal oxides, and metal halides. Alternatively, the metal precursor may include metal organic salts such as metal foramates, metal acetates, metal acetyl acetonates, and metal carbonates.

According to exemplary embodiments, a copper salt such as a copper inorganic salt and / or a copper organic salt may be used as the metal precursor. Examples of the copper inorganic salt include copper (I) oxide (Cu ₂ O), copper nitrate (Cu (NO ₃ ) ₂ ), copper sulfate (CuSO ₄ ) Or copper (I) chloride (CuCl). Examples of the copper organic salt include copper formate, copper acetate, copper acetylacetonate, copper carbonate and the like. These may be used alone or in combination of two or more.

The solvent used to prepare the metal precursor solution may include an organic solvent. According to exemplary embodiments, examples of the organic solvent include organic solvents such as xylene, hexane or toluene. These may be used alone or in combination of two or more.

These organic solvents are relatively volatile and can be easily evaporated or removed in subsequent processes.

In one embodiment, the metal precursor solution may further comprise a phase change material. The phase change material may promote dissolution of the metal precursor and the phase change material may form a substantially homogeneous phase of the metal precursor solution.

The phase change material may include, for example, an amine-based compound. The amine compound may include, for example, an alkyl substituent having 6 or more carbon atoms. In this case, for example, a non-covalent electron pair of the nitrogen atom contained in the amine compound interacts with the metal precursor, and the alkyl substituent of the amine compound can interact with the organic solvent. Thus, the interaction between the metal precursor and the organic solvent may be mediated by the amine compound.

According to exemplary embodiments, the phase change material is selected from the group consisting of hexylamine (CH ₃ (CH ₂ ) ₅ NH ₂ ), octylamine (CH ₃ (CH ₂ ) ₇ NH ₂ ), hexadecylamine _{: CH 3 (CH 2) 15} NH 2), octadecylamine _{(octadecylamine: CH 3 (CH 2} ) 17 NH 2) , or oleyl amine _{(oleylamine: CH 3 (CH 2} ) 7 CH = CH (CH 2) 7 CH ₂ NH ₂ ), and the like. These may be used alone or in combination of two or more.

The precursor complex may be prepared by mixing the metal precursor solution with a metal salt powder (step S20).

According to exemplary embodiments, the precursor complex may be prepared by injecting the precursor solution into the metal salt powder and then stirring the resulting mixture to form a substantially uniform phase.

According to exemplary embodiments, the metal salt powder may comprise an alkali metal salt or an alkaline earth metal salt. For example, sodium salt (NaSO ₄ ), sodium bicarbonate (NaHCO ₃ ), potassium carbonate Potassium bicarbonate (KHCO ₃ ), calcium bicarbonate (Ca (HCO ₃ ) ₂ ), sodium chloride (NaCl), magnesium sulfate (MgSO ₄ ), potassium sulfate K ₂ SO ₄ ), potassium chloride (KCl) or sodium ascorbate (C ₆ H ₇ NaO ₆ ). These may be used alone or in combination of two or more.

According to exemplary embodiments, the precursor composite may have a substantially uniformly mixed powder or dough shape. Therefore, the subsequent reaction or process for preparing metal nanoparticles can be performed on a dry basis rather than on a solution basis, so that storage and transfer of reaction intermediates, final reaction products and the like can be simplified and the processability can be improved.

The metal salt flushing may be provided as a support or a reaction medium for the synthesis of metal nanoparticles. In one embodiment, the metal salt powder particles may have a diameter of about 1 [mu] m to about 100 [mu] m. When the diameter of the metal salt powder particle is less than about 1 占 퐉, a substantially powder or dough-like precursor complex may not be easily obtained. When the diameter of the metal salt powder particle is more than about 100 mu m, the surface area of the metal salt powder may be reduced as a whole, and the function as the support or the reaction medium may be deteriorated.

The obtained precursor composite is heat-treated (Step S30). For example, after the precursor complex is put in an oven, it can be heat-treated at a predetermined temperature.

According to an exemplary embodiment, the heat treatment may be carried out at a temperature of about 200 ^o C to about 300 ^o C. If the heat treatment temperature is lower than about 200 ^° C, the reaction between the metal precursors may not be sufficiently performed, and metal nanoparticles of substantially a single structure may not be obtained. If the heat treatment temperature exceeds about 300 ^° C, the metal salt powder may be damaged to lose its function as a support or reaction medium, and the precursor complex may be partially lost.

According to exemplary embodiments, the heat treatment temperature may be performed in an inert atmosphere, for example, an argon gas or a nitrogen gas atmosphere. Thus, it is possible to prevent oxidation of a metal material, for example copper, during the heat treatment.

The heat-treated precursor complex may be washed and / or dried to produce metal nanoparticles (step S40).

According to exemplary embodiments, the precursor complex that has been heat treated can be cooled to room temperature and then dissolved in the cleaning solution. As the cleaning solution, a hydrazine (N ₂ H ₂ ) solution may be used. Since the hydrazine solution has strong reducibility, oxidation of copper, which may occur when the precursor complex is exposed to the air again, can be prevented. The metal salt powder component contained in the precursor complex can be dissolved by the washing solution.

In one embodiment, the wash solution containing the precursor complex can be filtered, for example, by centrifugation. In this case, an unreacted material among the metal precursors and a supernatant containing the metal salt powder separated from the generated metal nanoparticles may be generated, and the supernatant may be removed to perform the filtration process.

The cleaning and filtration process described above can be repeatedly performed a predetermined number of times.

Thereafter, the metal nanoparticles according to the exemplary embodiments can be obtained by injecting the obtained filtrate into a dispersion solvent and then drying.

For example, an alcohol-based solvent such as ethanol may be used as the dispersion solvent. The drying process may also be performed at a temperature of from about 70 ^° C to about 90 ^° C.

According to the exemplary embodiments of the present invention described above, metal nanoparticles can be prepared by mixing a metal precursor in powder or paste form to induce a reaction. Therefore, the production process is simplified, the reaction conditions such as the reaction temperature or the reaction pressure can be easily controlled, the storage and mobility of the reaction product can be improved, and thus it is advantageous for mass production. In addition, when a copper precursor is used, metal nanoparticles can be produced at low cost.

Hereinafter, a method of manufacturing metal nanoparticles according to exemplary embodiments will be described in detail with reference to specific experimental examples.

Experimental Example

0.225 g of copper formate tetrahydrate ((HCO ₂ ) ₂ Cu 4 H ₂ O) as a metal precursor was dissolved in 0.5 mL of hexylamine and 0.5 mL of xylene to prepare a metal precursor solution.

The precursor solution was mixed with 20 g of sodium sulfate (NaSO ₄ ) as a metal salt powder and stirred to prepare a powder-form precursor complex. The precursor complex was charged into the reactor, slowly heated to 270 ^° C for 30 minutes under a nitrogen atmosphere, and further heat-treated at the same temperature for 1 hour. The heat-treated precursor complex was taken out of the reactor, cooled to room temperature, and then dissolved in 0.1 M hydrazine and washed. The resulting solution was centrifuged to remove unreacted metal precursors and supernatant containing sodium sulfate. The above washing and centrifugation were repeated five times, followed by dispersion in ethanol and drying in an 80 ^° C oven to obtain metal nanoparticles.

FIGS. 2, 3 and 4 are transmission electron microscopy (TEM) images, scanning electron microscopy (SEM) images, and scanning electron microscopy (SEM) images of metal nanoparticles prepared according to Experimental Examples Transmission Electron Microscopy (STEM) images. Meanwhile, FIG. 5 is an image showing energy dispersive spectroscopy (EDS) analysis results of the metal nanoparticles prepared according to Experimental Example.

Referring to FIGS. 2, 3 and 4, it can be confirmed that metal nanoparticles having a uniform particle size distribution with an average particle size of about 100 nm are obtained by the above experimental example. Referring to FIG. 5, it can be confirmed that copper nanoparticles having a dominant copper content were obtained by the above experimental example.

According to the method of manufacturing metal nanoparticles according to exemplary embodiments of the present invention, metal nanoparticles can be produced through a dry-based reaction system in the form of powder or paste using metal salt powder. Therefore, the ease of reaction control and manufacturing process is improved, and metal nanoparticles can be mass-produced.

For example, copper nanoparticles having a uniform size distribution and excellent electrical characteristics and being manufactured at a low cost can be obtained through the above-described method for producing metal nanoparticles.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but variations and modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. It can be understood that it is possible.

Claims (12)

Dissolving the metal precursor in a solvent to prepare a metal precursor solution;
Mixing the metal precursor solution with a metal salt powder to prepare a precursor composite; And
And heat treating the precursor composite. The method of claim 1, wherein the metal precursor comprises a copper salt. 3. The method of claim 2 wherein the copper salt comprises at least one selected from the group consisting of copper oxide, copper sulfate, copper oxides, copper halides, copper formates, copper acetates, copper acetylacetonates and copper carbonates. A method for producing metal nanoparticles. The method of claim 1, wherein the solvent comprises at least one organic solvent selected from the group consisting of xylene, hexane, and toluene. 5. The method of claim 4, wherein the metal precursor solution further comprises a phase change material containing an amine compound. The method according to claim 1, wherein the metal salt powder comprises an alkali metal salt or an alkaline earth metal salt. The method of claim 6, wherein the metal salt powder comprises at least one selected from the group consisting of sodium sulfate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, sodium chloride, magnesium sulfate, potassium sulfate, potassium chloride and sodium ascorbate Wherein the metal nanoparticles have an average particle size of from 1 to 10 nm. The method of claim 1, wherein the precursor composite is formed in powder or paste form. The method of claim 1 wherein the production of the metal nano-particles is carried out at a temperature range of heat treating the precursor composite is 200 ^o C to 300 ^o C. The method of claim 1, wherein the heat treatment of the precursor complex is performed in a nitrogen atmosphere or an argon atmosphere. The method of claim 1, further comprising washing the heat-treated precursor composite with hydrazine. 12. The method of claim 11, further comprising removing the metal salt powder and the unreacted metal precursor by centrifugation after washing the heat-treated precursor composite.

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