JP2007314869A - Method of producing metal nanoparticle and metal nanoparticle produced thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing metal nanoparticles and the metal nanoparticles produced thereby. <P>SOLUTION: The method of producing metal nanoparticles comprises preparing a first solution including a dispersing stabilizer and a polar solvent; preparing a second solution including a metal precursor and a polar solvent; and adding the second solution into the first solution by dividing at least 2 times. The metal nanoparticles are produced thereby. According to the present invention, it is possible to produce isotropic metal nanoparticles with high efficiency using small amount of dispersion stabilizer through controlling reaction in the synthesis of the metal nanoparticles for a water system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing metal nanoparticles and metal nanoparticles produced thereby, and in particular, isotropic metal nanoparticles can be produced in high yield while the particle size is uniform. The present invention relates to a method for producing metal nanoparticles and metal nanoparticles produced thereby.

  Methods for producing metal nanoparticles include chemical synthesis methods, mechanical production methods, and electrical production methods, but mechanical production methods that use mechanical force to pulverize are more difficult due to contamination of impurities in the process. It is difficult to synthesize pure particles, and it is impossible to form nano-sized uniform particles. In addition, the electrical manufacturing method by electrolysis has the disadvantages that the manufacturing time is long, the concentration is low, and the efficiency is low. Chemical synthesis methods include a gas phase method and a liquid phase method (colloid method), but in the case of a gas phase method using plasma or gas evaporation, there is a disadvantage that expensive equipment is required. The liquid phase method that can synthesize uniform particles at high cost is mainly used.

  This method of producing metal nanoparticles by the liquid phase method is a method of producing metal nanoparticles in a hydrosol form using a reducing agent or a surfactant after dissociating a metal compound in an aqueous system. . However, a problem with the synthesis of such aqueous nanoparticles is that the number of dispersion stabilizers that can be used is limited. For example, monodisperse dispersion stabilizers such as citric acid cannot have dispersion stability unless the nanoparticles are several nanometers or smaller in size, and are effective only at low concentrations. Are known. In addition, when using polymer-based PVP or the like, nanoparticles having a size of several tens of nanometers can be stably dispersed in the aqueous phase, but such PVP is more than 10 times the silver precursor weight. It is known that isotropic (spherical) particles cannot be obtained without using. In addition, the low solubility of PVP increases the size of the reaction batch and reduces the amount of synthesis per reaction batch.

  In order to solve the above-mentioned problems, the object of the present invention is to obtain a yield while using a small amount of a dispersion stabilizer when synthesizing metal nanoparticles using a polar solvent such as a polyol. The present invention provides a method for producing metal nanoparticles, which is capable of producing highly isotropic metal nanoparticles with a uniform particle size.

Another object of the present invention is to provide metal nanoparticles produced by the above method.

  According to one aspect of the present invention, a step of preparing a first solution containing a dispersion stabilizer and a polar solvent, a step of preparing a second solution containing a metal precursor and a polar solvent, and the second solution at least Injecting into the first solution in two or more steps, a method for producing metal nanoparticles is provided.

  Moreover, in the said manufacturing method, it is preferable that the said dispersion stabilizer is one or more selected from the group which consists of polyvinylpyrrolidone (PVP), multiple acids, and these derivatives. Here, the multiple acid is selected from the group consisting of polyacrylic acid, polymaleic acid, polymethylmethacrylic acid, polyacrylic acid-co-methacrylic acid, polymaleic acid-co-acrylic acid, and polyacrylamide-co-acrylic acid. And the derivative is one or more selected from the group consisting of sodium salt, potassium salt and ammonium salt of the multiacid.

The metal precursor is AgNO ₃ , AgBF ₄ , AgPF ₆ , Ag ₂ O, CH ₃ COOAg, AgCF ₃ SO ₃ , AgClO ₄ , AgCl, Ag ₂ SO ₄ , CH ₃ COCH═COCH ₃ Ag, Cu ( One or more metal salts selected from the group consisting of NO ₃ ) ₂ , CuCl ₂ , CuSO ₄ , C ₅ H ₇ CuO ₂ , NiCl ₂ , Ni (NO ₃ ) ₂ , NiSO ₄ , and HAuCl ₄ .

  Moreover, it is preferable that the polar solvent used for the first solution and the second solution is independently one or more selected from the group consisting of water, alcohol and polyol. Here, the alcohol is one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, hexanol and octanol, and the polyol is One selected from the group consisting of glycerol, glycol, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, tetraethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentadiol and 1,2-hexadiol More than one.

  In the manufacturing method, the polar solvent of the first solution is preferably included in an amount of 200 to 10,000 parts by weight with respect to 100 parts by weight of the dispersion stabilizer, and the polar solvent of the second solution is a metal precursor. It is preferably contained in 150 to 100,000 parts by weight with respect to 100 parts by weight. The first solution may further include one or more solid catalysts selected from the group consisting of Cu (II), Cu (I), Fe (III), and Fe (II). Here, the solid catalyst is preferably included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the metal precursor.

In addition, the second solution used in the present invention includes dimethylformamide (DMF), dimethyl sulfoxide (DMSO), NaBH ₄ , LiBH ₄ , tetrabutylammonium borohydride, N ₂ H ₄ and a mixture thereof. A reducing agent selected from the group consisting of: Here, the reducing agent is preferably included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the metal precursor.

  Moreover, in the said manufacturing method, it is preferable that the injection | pouring speed | rate of the said 2nd solution is inject | poured in the ratio of 0.001 thru | or 1 mol of metal precursors with respect to 1 mol of dispersion stabilizers per minute (min). Meanwhile, the step of injecting the second solution into the first solution is preferably performed at a temperature of 120 to 190 ° C.

  The manufacturing method may further include a step of washing the mixed solution of the first solution and the second solution with an organic solvent after the injection step, and a step of obtaining the metal nanoparticles by centrifugation. Can do.

  Moreover, according to another form of this invention, the metal nanoparticle manufactured by the said manufacturing method is provided. Here, the content of the dispersion stabilizer bound to the metal nanoparticles is 2 to 8% by weight.

  The method for producing metal nanoparticles according to the present invention and the metal nanoparticles produced thereby are used to produce isotropic metal nanoparticles in a high yield by reaction control even in the case of using a small amount of dispersion stabilizer in the synthesis of metal nanoparticles for aqueous systems. Particles can be synthesized.

  Hereinafter, a method for producing metal nanoparticles according to an embodiment of the present invention and metal nanoparticles produced thereby will be described in detail with reference to the accompanying drawings.

  In order to uniformly produce metal nanoparticles at a high concentration, selection of a metal precursor, a dispersion stabilizer, a solvent and an additional reducing agent is very important. The combination of such components and the reaction temperature and reaction time affect the nucleation and growth of the nanoparticles.

  According to the nucleation and growth model, the nuclei generated at the beginning of the reaction are unstable and can be dissolved again in the solvent if they do not have a threshold value or more. With the size of, the nucleus can grow stably. Such a threshold value is determined by the amount of precursor and dispersion stabilizer. According to this theory, particles having a high concentration of precursor and uniformly dispersed particles are formed in the initial stage. However, as the reaction proceeds, the concentration of the precursor is decreased and the particle size distribution is widened. (See Alivisatos et al, Nature 2005). Therefore, in order to produce uniform particles, the concentration of the precursor during the reaction and the ratio of the precursor to the dispersion stabilizer are important.

  In addition, studies on the synthesis of silver nanoparticles by Xia and others show that initial nucleation greatly affects the pattern of the final particles. Without the quasi-spherical morphology at the initial nucleation stage, the final spherical nanoparticles cannot be formed. At this time, it is suggested that the molar ratio of the proposed dispersion stabilizer polyvinyl pyrrolidone (PVP) to the silver precursor should be 10 times or more, and actually 15 times or more of PVP was used. In some cases, anisotropic particles were also shown (see Xia et al, Chem. Eur. J. 2005).

  As described above, in order to synthesize metal nanoparticles having a uniform spherical particle size, a large amount of dispersion stabilizer is used, resulting in an increase in the reaction batch size. The synthesis yield per reaction batch will be reduced. Therefore, in this embodiment, isotropic metal nanoparticles having a uniform particle size are produced with high efficiency by controlling the reaction in the mixing process of the dispersion stabilizer and the metal precursor.

  The method for producing metal nanoparticles according to the present embodiment includes a step of preparing a first solution containing a dispersion stabilizer and a polar solvent, a step of preparing a second solution containing a metal precursor and a polar solvent, and the first step. Injecting the two solutions into the first solution at least twice.

  As shown in FIG. 1, when a second solution containing a metal precursor is injected at a time into a first solution containing a dispersion stabilizer, a complex with metal ions is formed as the reaction proceeds. The amount of dispersion stabilizer to be reduced will decrease and the amount of independent dispersion stabilizer will increase. If the remaining amount after stabilizing the nanoparticles is excluded, the dispersion stabilizer put in the initial stage of the reaction is discarded.

  However, if the second solution containing the metal precursor is injected in two portions as in this embodiment, the actual equivalent ratio of the dispersion stabilizer to the metal precursor is doubled as shown in FIG. This is advantageous for the formation of isotropic particles. If the second solution is injected in several times, the actual equivalent ratio of the dispersion stabilizer to the metal precursor is close to infinity, as shown in FIG. Therefore, according to this embodiment, even if the addition amount of the dispersion stabilizer decreases, the real equivalent ratio of the metal precursor can be maintained at 10 times or more, and isotropic metal nanoparticles are obtained with high efficiency. be able to.

  According to a preferred embodiment, the dispersion stabilizer is preferably one or more selected from the group consisting of polyvinyl pyrrolidone (PVP), polyacid and derivatives thereof. Here, the polyacid is a polymer containing a carboxy group or a derivative thereof in the main chain or side chain, and it is preferable to use a polymer having a polymerization degree of 10 to 100,000. Specific examples of such multiple acids include polyacrylic acid, polymaleic acid, polymethylmethacrylic acid, polyacrylic acid-co-methacrylic acid, polymaleic acid-co-acrylic acid), and polyacrylamide-co-acrylic acid. However, it is not limited to this.

In addition, the multiple acid derivative refers to a compound in which the hydrogen atom of the carboxy group is substituted with a different atom or molecule, for example, the sodium salt, potassium salt or ammonium salt of the multiple acid. In the present embodiment, the metal that can form the metal nanoparticles is not particularly limited, but metals such as gold, silver, copper, nickel, and palladium can be used. As a metal precursor that provides a metal ion that can be reduced to form such metal nanoparticles, salts containing these metals can be used. For example, AgNO ₃ , AgBF ₄ , AgPF ₆ , Ag ₂ O, CH ₃ COOAg, AgCF ₃ SO ₃ , AgClO ₄ , AgCl, Ag ₂ SO ₄ , CH ₃ COCH═COCH ₃ Ag, Cu (NO ₃ ) ₂ , Cu ₂ , one or more metal salts selected from the group consisting of CuSO ₄ , C ₅ H ₇ CuO ₂ , NiCl ₂ , Ni (NO ₃ ) ₂ , NiSO ₄ , and HAuCl ₄ can be used. It is not limited to.

  The polar solvent used in the first solution and the second solution is not particularly limited as long as it is a polar solvent usually used in the art. This polar solvent also serves as a reducing agent that induces reduction of metal ions to form metal particles. For example, water, alcohol, polyol or a mixed solvent thereof can be used. Here, examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, hexanol, and octanol, but are not limited thereto. is not.

  The polyol is a low-molecular-weight water-soluble polymer containing a large number of hydroxyl groups and diols, and includes glycerol, glycol, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, tetraethylene glycol, propylene glycol, Examples thereof include, but are not limited to, polyethylene glycol, polypropylene glycol, 1,2-pentadiol, and 1,2-hexadiol.

  In the method for producing metal nanoparticles according to this embodiment, the polar solvent in the step of preparing the first solution is preferably included in an amount of 200 to 10,000 parts by weight with respect to 100 parts by weight of the dispersion stabilizer. If the content is less than 200 parts by weight, it is not preferable because the dispersion stabilizer cannot be completely dissolved, and if it exceeds 10,000 parts by weight, the volume of the reactor increases and the productivity decreases, which is not preferable. .

  The polar solvent in the step of preparing the second solution is preferably included in an amount of 150 to 100,000 parts by weight with respect to 100 parts by weight of the metal precursor. If the content is less than 150 parts by weight, it is not preferable because the metal precursor cannot be completely dissolved, and if it exceeds 100,000 parts by weight, the volume of the reactor increases and the productivity decreases, which is not preferable. . Such first and second solutions can further include additives such as catalysts or reducing agents to control nucleation and reaction rate.

  The first solution used in the method for producing metal nanoparticles according to the present embodiment is one or more selected from the group consisting of Cu (II), Cu (I), Fe (III), and Fe (II). A solid catalyst may be further included. In this case, the solid catalyst is preferably included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the metal precursor.

In addition, the second solution used in the method for producing metal nanoparticles according to the present embodiment is dimethylformamide (DMF), dimethyl sulfoxide (DMSO), NaBH ₄ , LiBH ₄ , tetrabutylammonium borohydride, N A reducing agent selected from the group consisting of ₂ H ₄ and a mixture thereof may be further included. In this case, the reducing agent is preferably included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the metal precursor. .

  Thus, when the first solution and the second solution are prepared, the second solution is injected into the first solution at least twice. Any method of injecting the second solution can be used as long as it is a commonly used injection method. Preferably, the second solution is continuously introduced via the metal precursor feeder while stirring the first solution. throw into. At this time, it is preferable that the second solution is injected at a rate of 0.001 to 1 mole of metal precursor per 1 minute of dispersion stabilizer per minute (min). This is because injection at such a rate is effective for nucleation and isotropic nanoparticle formation.

  The step of injecting the second solution into the first solution is preferably performed at a temperature of 120 to 190 ° C. The reducing action will not occur unless the boiling point of the polar solvent is raised to the above temperature range. When the temperature of the mixed solution of the first solution and the second solution is increased while stirring, it is preferable to increase the temperature to the above temperature range at a constant rate. This is because the metal particles grow to a uniform size. This is because it is advantageous for control. When the reducing agent is added, the reaction can be performed at a lower temperature than when the reducing agent is not added.

  In this way, when the first solution and the second solution are mixed to start forming metal particles, the mixed solution turns red, and when the metal particles grow to nano size, it turns dark green. The size of the grown metal particles can be seen through the change of the metal peak in the UV-Vis spectrum. The reaction may be interrupted by observing the color change according to the desired size.

The time required for the reaction for forming the nanoparticles as described above may vary depending on the mixing ratio of the constituent elements, the temperature conditions, and the presence or absence of a reducing agent, and may take, for example, about 1 to 60 minutes. If it exceeds 60 minutes, the size of the particles may increase and become a problem.

  Thus, after manufacturing a metal nanoparticle, the metal nanoparticle formed in the liquid mixture by the usual method will be obtained. For example, in the method for producing metal nanoparticles according to the present embodiment, after the injection step, the mixed solution of the first solution and the second solution is washed with an organic solvent, and the metal nanoparticles are centrifuged. Obtaining. Can be further included. The metal nanoparticles thus obtained can further undergo a drying step. As an organic solvent that can be used at the time of washing, methanol, ethanol, MDF, or a mixture thereof can be used.

  The metal nanoparticles produced by the production method as described above can be uniformly grown without being kneaded with each other because the metal particles are uniformly dispersed by the dispersion stabilizer, and isotropic nanoparticles can be obtained. it can. According to the method for producing metal nanoparticles according to the present embodiment, the content of the dispersion stabilizer bound to the metal nanoparticles is 2 to 8% by weight.

  Below, the Example of the manufacturing method of the metal nanoparticle which concerns on this embodiment is described. However, the following examples do not limit the present embodiment.

After mixing 100 parts by weight of polyvinylpyrrolidone (PVP) and 300 parts by weight of ethylene glycol with stirring, the mixture was heated to 170 ° C. After mixing 100 parts by weight of silver nitrate (AgNO ₃ ) and 250 parts by weight of ethylene glycol, the fluid regulator was adjusted so that the injection rate was per minute and the molar ratio of silver ions to the total amount of polyvinylpyrrolidone was 0.4. And then allowed to react for 20 minutes. When the solution changed to dark green, silver nanoparticles were obtained by washing with an acetone / methanol mixed solution and centrifuging.

  In Example 1 above, silver nanoparticles were obtained by performing the same process except that the reaction temperature was 150 ° C. and the injection rate was 0.2 molar ratio per minute for 30 minutes.

After 100 parts by weight of polyvinyl pyrrolidone (PVP) and 400 parts by weight of ethylene glycol were mixed with stirring, the temperature was raised to 150 ° C. After mixing 100 parts by weight of silver nitrate (AgNO ₃ ) and 300 parts by weight of ethylene glycol, the fluid regulator was adjusted so that the injection rate was per minute and the molar ratio of silver ions to the total amount of polyvinylpyrrolidone was 0.07. And then allowed to react for 60 minutes. When the solution changed to dark green, silver nanoparticles were obtained by washing with acetone / methanol mixture and centrifuging.

After mixing 100 parts by weight of polyvinylpyrrolidone (PVP), 6 parts by weight of Cu (II) and 400 parts by weight of ethylene glycol, the mixture was heated to 160 ° C. After mixing 100 parts by weight of silver nitrate (AgNO ₃ ), 100 parts by weight of DMF and 100 parts by weight of ethylene glycol, the fluid was adjusted so that the injection rate was per minute and the molar ratio of silver ions to the total amount of polyvinylpyrrolidone was 0.2. The vessel was adjusted to inject and allowed to react for 60 minutes. When the solution changed to dark green, silver nanoparticles were obtained by washing with acetone / methanol mixture and centrifuging.

  In Example 4 above, silver nanoparticles were obtained by performing the same process except that the Cu (II) catalyst was not used, the reaction temperature was 150 ° C., the injection rate was 0.2 mol per minute, and the reaction was performed for 15 minutes. Got.

  SEM photographs of the silver nanoparticles prepared in Examples 1 to 5 are shown in FIGS. 4 to 8, respectively. Referring to FIGS. 4 to 8, isotropic silver nanoparticles having an average of about 20 to 60 nm can be produced by the method for producing metal nanoparticles according to this embodiment. Moreover, when a metal catalyst and a reducing agent are added as in Example 4, the formation of nuclei is accelerated, and uniform nanoparticles of about 10 nm can be produced. On the other hand, when the molar ratio of PVP to silver ions is high as in Example 5, it can be seen that the yield is excellent despite the short reaction time.

  The manufacturing method of the metal nanoparticles according to the present embodiment is not limited to the above-described examples, and many modifications are possible by those having ordinary knowledge in the field within the concept of the present invention.

It is a virtual graph which shows the density | concentration change at the time of inject | pouring a metal precursor solution (2nd solution) at once into the solution (1st solution) of a dispersion stabilizer. It is a virtual graph which shows the density | concentration change at the time of inject | pouring a metal precursor solution (2nd solution) in two steps to the solution (1st solution) of a dispersion stabilizer. It is a virtual graph which shows the density | concentration change at the time of inject | pouring a metal precursor solution (2nd solution) in several times to the solution (1st solution) of a dispersion stabilizer. It is a SEM photograph of the metal nanoparticle obtained from Example 1 of this invention. It is a SEM photograph of the metal nanoparticle obtained from Example 2 of the present invention. It is a SEM photograph of the metal nanoparticle obtained from Example 3 of the present invention. It is a SEM photograph of the metal nanoparticle obtained from Example 4 of the present invention. It is a SEM photograph of the metal nanoparticle obtained from Example 5 of this invention.

Claims (18)

Providing a first solution comprising a dispersion stabilizer and a polar solvent;
Providing a second solution comprising a metal precursor and a polar solvent;
A step of dividing the second solution into at least two times and injecting the second solution into the first solution.   The method for producing metal nanoparticles according to claim 1, wherein the dispersion stabilizer is one or more selected from the group consisting of polyvinylpyrrolidone (PVP), multiple acids, and derivatives thereof.   The polyacid is selected from the group consisting of polyacrylic acid, polymaleic acid, polymethylmethacrylic acid, polyacrylic acid-co-methacrylic acid, polymaleic acid-co-acrylic acid, and polyacrylamide-co-acrylic acid. 3. The method for producing metal nanoparticles according to claim 2, wherein the number of the derivatives is one or more selected from the group consisting of a sodium salt, a potassium salt, and an ammonium salt of the multiple acid. The metal precursor is AgNO ₃ , AgBF ₄ , AgPF ₆ , Ag ₂ O, CH ₃ COOAg, AgCF ₃ SO ₃ , AgClO ₄ , AgCl, Ag ₂ SO ₄ , CH ₃ COCH═COCH ₃ Ag, Cu (NO _{3 2} ) ₂ , CuCl ₂ , CuSO ₄ , C ₅ H ₇ CuO ₂ , NiCl ₂ , Ni (NO ₃ ) ₂ , NiSO ₄ , and HAuCl ₄ . A method for producing metal nanoparticles.   The method for producing metal nanoparticles according to claim 1, wherein the polar solvent used in the first solution and the second solution is independently one or more selected from the group consisting of water, alcohol and polyol.   6. The metal nano of claim 5, wherein the alcohol is one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, hexanol and octanol. Particle production method.   The polyol is selected from the group consisting of glycerol, glycol, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, tetraethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentadiol and 1,2-hexadiol. The method for producing metal nanoparticles according to claim 5, wherein one or more selected.   The method for producing metal nanoparticles according to claim 1, wherein the polar solvent of the first solution is included in an amount of 200 to 10,000 parts by weight with respect to 100 parts by weight of the dispersion stabilizer.   The method of claim 1, wherein the polar solvent of the second solution is included in an amount of 150 to 100,000 parts by weight with respect to 100 parts by weight of the metal precursor.   The metal nanoparticles according to claim 1, wherein the first solution further includes one or more solid catalysts selected from the group consisting of Cu (II), Cu (I), Fe (III), and Fe (II). Manufacturing method.   The method of claim 10, wherein the solid catalyst is included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the metal precursor. The second solution is a reduction selected from the group consisting of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), NaBH ₄ , LiBH ₄ , tetrabutylammonium borohydride, N ₂ H ₄ and mixtures thereof. The method for producing metal nanoparticles according to claim 1, further comprising an agent.   The method of claim 12, wherein the reducing agent is included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the metal precursor.   2. The method for producing metal nanoparticles according to claim 1, wherein the second solution is injected at a rate of 0.001 to 1 mole of metal precursor per 1 minute of dispersion stabilizer per minute (min).   The method of claim 1, wherein the injecting step is performed at a temperature of 120 to 190 ° C.   2. The metal nanoparticles according to claim 1, further comprising: after the injection step, washing the mixed solution of the first solution and the second solution with an organic solvent; and centrifuging the metal nanoparticles. Manufacturing method.   The metal nanoparticle manufactured by the method in any one of Claims 1 thru | or 16.   The metal nanoparticles according to claim 17, wherein the content of the dispersion stabilizer bound to the metal nanoparticles is 2 to 8% by weight.