U.S. patent application number 11/520731 was filed with the patent office on 2007-03-15 for metal nanoparticles and method for manufacturing thereof.
This patent application is currently assigned to SAMSUNG ELECTRO-MACHANICS CO. LTD.. Invention is credited to Hye-Jin Cho, Sung-Nam Cho, Sung-II Oh.
Application Number | 20070056402 11/520731 |
Document ID | / |
Family ID | 37853731 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070056402 |
Kind Code |
A1 |
Cho; Sung-Nam ; et
al. |
March 15, 2007 |
Metal nanoparticles and method for manufacturing thereof
Abstract
The present invention provides a method of producing metal
nanoparticles, having a high yield rate and uniform size achieved
by employing a heterologous reducing agent that considerably
reduces unreactant, and using ethylene glycol that allows effective
separation of desired metal nanoparticles. In addition, the present
invention provides metal nanoparticles having high dispersion
stability achieved by capping with polyvinyl pyrrolidone(PVP) and
conductive ink including these metal nanoparticles. One aspect of
the invention may provide a method of producing nanoparticles
comprising, (a) mixing ethylene glycol, capping molecules and a
reducing agent, (b) mixing a metal precursor with alcohol-based
compound and reacting it with the mixture of (a), and (c) finishing
the reaction by adding acetone and ethylene glycol to the reaction
solution (b).
Inventors: |
Cho; Sung-Nam; (Suwon-si,
KR) ; Oh; Sung-II; (Seoul, KR) ; Cho;
Hye-Jin; (Suwon-si, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRO-MACHANICS CO.
LTD.
Suwon-si
KR
|
Family ID: |
37853731 |
Appl. No.: |
11/520731 |
Filed: |
September 14, 2006 |
Current U.S.
Class: |
75/362 ;
75/371 |
Current CPC
Class: |
B82Y 30/00 20130101;
C09D 11/30 20130101; B22F 9/24 20130101; B22F 1/0018 20130101; B22F
1/0014 20130101 |
Class at
Publication: |
075/362 ;
075/371 |
International
Class: |
B22F 9/24 20060101
B22F009/24 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2005 |
KR |
10-2005-0085708 |
Claims
1. A method of producing metal nanoparticles, said method
comprising: (a) mixing ethylene glycol, capping molecules and a
reducing agent; (b) reacting a mixture of a metal precursor and an
alcohol-based compound with the mixture in the step (a); and (c)
adding acetone and ethylene glycol to the reacting solution in the
step (b).
2. The method of claim 1, wherein the mixture in the step (a) is
heated to a temperature of 100-140.degree. C. before the step
(b).
3. The method of claim 1, wherein the ethylene glycol in the step
(a) is mixed in 100 to 200 parts by weight with respect to 10 parts
by weight of the metal precursor.
4. The method of claim 1, wherein in the step of (b), the mixture
of the metal precursor and the alcohol-based compound and the
mixture in the step (a) are added together within a short period of
time to react.
5. The method of claim 1, wherein recovering metal nanoparticles by
centrifuging the solution after the step of (c) is further
included.
6. The method of claim 1, wherein the capping molecule is polyvinyl
pyrrolidone.
7. The method of claim 6, wherein the polyvinyl pyrrolidone is
mixed in 30-70 parts by weight with respect to 10 parts by weight
of the metal precursor.
8. The method of claim 1, wherein the reducing agent includes one
or more compounds selected from the group consisting of glucose,
ascorbic acid, tannic acid, dimethylformamide, tetrabutyl ammonium
borohydride, NaBH.sub.4, LiBH.sub.4 and N.sub.2H.sub.4.
9. The method of claim 8, wherein the reducing agent is
glucose.
10. The method of claim 1, wherein the reducing agent is mixed in a
mole ratio of 0.2 to 0.5 with respect to the metal precursor.
11. The method of claim 1, wherein the metal precursor includes one
or more metals selected from the group consisting of gold, silver,
copper, nickel, zinc, platinum, palladium, rhodium, ruthenium,
iridium, osmium, tungsten, tantalum, titanium, aluminum, cobalt,
iron and a mixture thereof.
12. The method of claim 1, wherein the metal precursor is one or
more compound selected from the group consisting of AgNO.sub.3,
AgBF.sub.4, AgPF.sub.6, Ag.sub.2O, CH.sub.3COOAg,
AgCF.sub.3SO.sub.3, AgClO.sub.4, AgCl, and
CH.sub.3COCH.dbd.COCH.sub.3Ag.
13. The method of claim 1, wherein the alcohol-based compound is
one or more compounds selected from the group consisting of
methanol, ethanol, ethylene glycol and diethylene glycol.
14. The method of claim 1, wherein the alcohol-based compound is
mixed in 30-50 parts by weight with respect to 10 parts by weight
of the metal precursor.
15. The method of claim 1, wherein the ethylene glycol in the step
(c) is added in 2-10 parts by weight with respect to 1 part by
weight of the capping molecule.
16. The method of claim 1, wherein the reaction time of the step
(b) ranges from 30 minutes to 4 hours.
17. Metal nanoparticles produced by a method of claim 1.
18. The metal nanoparticles of claim 17, wherein the metal
nanoparticles are capped with polyvinyl pyrrolidone.
19. The metal nanoparticles of claim 18, wherein the particles of
the polyvinyl pyrrolidone are 5-10 weight %.
20. Conductive ink including metal nanoparticles according to claim
17.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2005-0085708 filed on Sep. 14, 2005, with the
Korea Intellectual Property Office, the contents of which are
incorporated here by reference in their entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a method of producing metal
nanoparticles, in particular, to a method of producing metal
nanoparticles with the solution method.
[0004] 2. Description of the Related Art
[0005] Major ways to produce metal nanoparticles are the chemical
synthesis method, the mechanical production method and the
electrical production method. However, in case of the mechanical
production method which uses mechanical power for comminuting, it
is hard to produce highly pure particles because of intrusion of
impurities during the process and impossible to form uniform-sized
metal nanoparticles. Further, the electrical production method by
electrolysis has shortcomings in that it requires a long period for
production time and provides a low yield rate caused by low
concentration. The chemical synthesis method includes the
vapor-phase method and the solution (colloid) method, where the
vapor-phase method which uses plasma or gas evaporation has
shortcomings in that it requires highly expensive equipments, so
the solution method which is possible to generate uniform particles
with low cost is generally used.
[0006] A method of producing metal nanoparticles by the solution
method up to now comprises dissociating metal compound and then
producing metal nanoparticles in the form of hydrosol using a
reducing agent or a surfactant. However, the production of metal
nanoparticles by this existing solution method provides a very low
yield rate, as it is limited by the concentration of the metal
compound solution. That is, it is possible to form metal
nanoparticles of uniform size only when the concentration of the
metal compound is less than mM. Thus, there is a limit also on the
yield of metal nanoparticles, and to obtain metal nanoparticles of
uniform size in quantities of several grams, 1000 liters or more of
functional group are needed. This represents a limitation to
efficient mass production. In addition, the un-reactant remaining
after completion of the reaction reduces the yield rate, and a vast
amount of loss which occurs during the separation step of formed
metal nanoparticles results in further reduction of the yield rate.
Furthermore, when the generated metal nanoparticles are
re-dispersed in order to use them in various areas, the dispersion
stability is important, but the existing method provides a very low
dispersion rate of 0.1 weight %.
[0007] Approaches to solve such existing problems and to produce a
high yield rate of metal nanoparticles with uniform size are in
progress.
SUMMARY
[0008] The present invention provides a method of producing metal
nanoparticles, having a high yield rate and uniform size achieved
by employing a heterologous reducing agent that considerably
reduces un-reactant, and using ethylene glycol that allows
effective separation of desired metal- nanoparticles. In addition,
the present invention provides metal nanoparticles having high
dispersion stability achieved by capping with polyvinyl
pyrrolidone(PVP) and conductive ink including these metal
nanoparticles.
[0009] Additional aspects and advantages of the present invention
will be set forth in part in the description which follows and, in
part, will be obvious from the description, or may be learned by
practice of the invention.
[0010] One aspect of the invention may provide a method of
producing nanoparticles comprising, (a) mixing ethylene glycol,
capping molecules and a reducing agent, (b) reacting a mixture of a
metal precursor and an alcohol-based compound with the mixture of
(a), and (c) adding acetone and ethylene glycol to the reaction
solution of (b).
[0011] Here, it may be possible to raise a temperature of the mixed
solution of (a) up to 100-140.degree. C. before the step of (b),
the ethylene glycol in the step (a) may be mixed in 100 to 200
parts by weight with respect to 10 parts by weight of the metal
precursor.
[0012] Also here, in the step (b), the mixed solution of the metal
precursor and the alcohol-based compound may react with the mixture
of (a) by adding together within a short period of time, and a step
of recovering metal nanoparticles by centrifuging the reaction
solution after the step (c) may further be included.
[0013] Here, the capping molecule may be preferably polyvinyl
pyrrolidone and according to a preferred embodiment, the polyvinyl
pyrrolidone may be mixed in 30-70 parts by weight with respect to
10 parts by weight of the metal precursor.
[0014] Here, the reducing agent may include one or more compounds
selected from the group consisting of glucose, ascorbic acid,
tannic acid, dimethylformamide, tetrabuthylammonium borohydride,
NaBH.sub.4, LiBH.sub.4 and N.sub.2H.sub.4. According to a preferred
embodiment, the reducing agent is preferably glucose and mixed in a
mole ratio of 0.2 to 0.5 with respect to the metal precursor.
[0015] Here, the metal precursor may include one or more metals
selected from the group consisting of gold, silver, copper, nickel,
zinc, platinum, palladium, rhodium, ruthenium, iridium, osmium,
tungsten, tantalum, titanium, aluminum, cobalt, iron and a mixture
thereof. In a preferred embodiment, the metal precursor is one or
more compounds selected from the group consisting of AgNO.sub.3,
AgBF.sub.4, AgPF.sub.6, Ag.sub.2O, CH.sub.3COOAg,
AgCF.sub.3SO.sub.3, AgClO.sub.4, AgCl, and
CH.sub.3COCH.dbd.COCH.sub.3Ag.
[0016] Here, the alcohol-based compound may be one or more
compounds selected from the group consisting of methanol, ethanol,
ethylene glycol and diethylene glycol. In a preferred embodiment,
the alcohol-based compound may be mixed in 30-50 parts by weight
with respect to 10 parts by weight of the metal precursor.
[0017] Here, the ethylene glycol in the step (c) may be added in
2-10 parts by weight with respect to 1 part by weight of the
capping molecule, and preferably, a reaction time in the step (b)
ranges from 30 minutes to 4 hours.
[0018] Another aspect of the invention may provide metal
nanoparticles produced by the method for producing metal
nanoparticles set forth above.
[0019] Here, the metal nanoparticles may be metal nanoparticles
capped with the polyvinyl pyrrolidone, and according to a preferred
embodiment, the particles of polyvinyl pyrrolidone are 5-10 weight
%.
[0020] Another aspect of the invention may provide conductive ink
including metal nanoparticles set forth above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is data representing the result of TGA analysis for
the metal nanoparticles produced according to an embodiment of the
invention;
[0022] FIGS. 2 and 3 are FE-SEM images of the metal nanoparticles
produced according to preferred embodiments of the invention;
[0023] FIG. 4 is a graph that represents the result of UW-VIS
spectroscopy(UV spectrum) of the metal nanoparticles produced
according to a preferred embodiment of the invention; and
[0024] FIG. 5 is a graph that represents the result of particle
size analysis of the metal nanoparticles produced according to a
preferred embodiment of the invention.
DETAILED DESCRIPTION
[0025] Hereinafter, the method of producing metal nanoparticles and
metal nanoparticles thus produced according to the present
invention will be described in detail.
[0026] To produce metal nanoparticles of the present invention, the
invention include a step of mixing ethylene glycol, capping
molecules, and a reducing agent.
[0027] In the invention, ethylene glycol along with the reducing
agent reduces the metal precursor to prevent formation of
un-reactants and allow production of metal nanoparticles in a high
yield rate. Ethylene glycol may be also used as a solvent that
dissolves the metal precursor. Also, ethylene glycol is added with
excess amount of acetone so that removes un-reacted PVP and
terminates the reaction. So far, though ethylene glycol has been
used to act as both a solvent and a reducing agent, it performs
poor in the reducing capacity, to result in a low yield rate. But
in the invention, ethylene glycol plays various roles mentioned
above and is used as an important compound for producing metal
nanoparticles at a high concentration and a high yield rate.
[0028] Here, the capping molecules refer to molecules that allow
metal particles to grow stably in a solvent and form nano-sized
particles by encapsulating the metal particles. Any known compounds
may be used as such capping molecules, and compounds having oxygen,
nitrogen, and sulfur atoms may be typically used. More
specifically, compounds having thiol group(--SH), amine
group(--NH2), carboxyl group(--COOH) may be used as capping
molecules, and according to an embodiment of the invention,
PVP(Polyvinyl pyrrolidone) is preferable. This is because the PVP
strongly adheres to metal nanoparticles to enhance the dispersion
stability of metal nanoparticles thus obtained, and allows the
metal nanoparticles to have a high dispersion rate when they are
re-dispersed.
[0029] If the metal precursor is reduced only with ethylene glycol,
the yield rate of metal nanoparticles becomes declined since an
excess amount of un-reactant is generated. Thus a reducing agent
may be added to increase the yield rate of metal nanoparticles in
the invention. Example of this reducing agent, but not limited to
these, may include borate hydroxides such as NaBH.sub.4,
LiBH.sub.4, and tetrabutylammonium borohydride(TBAB), hydrazines
such as N.sub.2H.sub.4, glucose, acids such as ascorbic acid,
tannic acid etc., and dimethylformamide(DMF) etc. In a preferred
embodiment of the invention, glucose is used since it is low in
price, environment-friendly, and easily dissolved in water or an
alcohol-based compound. Glucose is used as a reducing agent because
when a hydroxyl group of glucose is oxidized, it may release
electrons during its conversion to the corresponding aldehyde.
[0030] In this step, ethylene glycol is added to dissolve PVP while
functioning as a reducing agent, where ethylene glycol is
preferably added in 100-200 parts by weight with respect to 10
parts by weight of the metal precursor since this is the most
optimal amount for reducing the metal precursor with the reducing
agent. Here, since the addition of more than 200 parts by weight of
ethylene glycol does not result in a increased yield of
nanoparticles, the addition of more ethylene glycol than the
desired amount is not economical.
[0031] Also, it is preferable that the capping molecules be added
in 30-70 parts by weight with respect to 10 parts by weight of the
metal nanoparticles. If the capping molecule is added less than 30
parts by weight, metal nanoparticles thus formed become larger than
nano size and lack of uniformity and further deteriorates the
dispersion stability since it is impossible to obtain fully capped
metal nanoparticles. On the other hand, if the capping molecules is
added more than 70 parts by weight, the yield rate does not
increase as much as of that extent, which just results in an
increase of unit cost. Here, when PVP is used as a capping
molecule, it is preferable that the PVP be mixed in 30-50 parts by
weight with respect to 10 parts by weight of the metal
precursor.
[0032] Preferably, the reducing agent is added in a mole ratio of
0.2-0.5 with respect to 1 mole of the metal precursor. Because the
addition within this ratio allows the formation of uniform metal
nanoparticles and reduces un-reactant to increase the yield rate.
When the reducing agent is added more than 0.5 mole ratio, it
results in precipitation of metal particles and unequal growth of
particles. When glucose is used as a reducing agent, it is
preferable that it be mixed in 1-4 parts by weight with respect to
10 parts by weight of the metal precursor.
[0033] After thoroughly dissolving PVP and the reducing agent in
ethylene glycol, the mixed solution is heated up to 100-140.degree.
C. If a mixture of the metal precursor and ethylene glycol is added
at this temperature, uniform metal nanoparticles may be obtained
with desired size. If the heating-up is performed after adding the
mixture of the metal precursor and ethylene glycol to the mixed
solution of ethylene glycol, PVP and the reducing agent, it causes
unequal formation of metal nanoparticles and undesirable large size
of particles.
[0034] Any metal precursor, that is known and used for the
production of metal nanoparticles, may be used without limitation
in the present invention, preferably that is suitable for the
alcohol reduction method. But not limited to these, preferable
example of the metal precursor may include one or more metals
selected from the group consisting of gold, silver, copper, nickel,
zinc, platinum, palladium, rhodium, ruthenium, iridium, osmium,
tungsten, tantalum, titanium, aluminum, cobalt, iron and a mixture
thereof.
[0035] Specific example may include inorganic acid salts such as
nitrates, carbonates, chlorides, phosphates, borates, oxides,
sulfonates, and sulfates, etc., and organic acid salts, such as
stearates, myristates, and acetates, etc. The use of nitrates may
be more preferable, as they are economical and widely used. More
specific examples of the metal precursor may include silver
precursors such as AgNO.sub.3, AgBF.sub.4, AgPF.sub.6, Ag.sub.2O,
CH.sub.3COOAg, AgCF.sub.3SO.sub.3, AgClO.sub.4, AgCl, and
CH.sub.3COCH.dbd.COCH.sub.3Ag, copper salts such as of
Cu(NO.sub.3), CuCl.sub.2, and CuSO.sub.4, and nickel salts such as
of NiCl.sub.2, Ni(NO.sub.3).sub.2, and NiSO.sub.4, etc.
[0036] After such a metal precursor is thoroughly dissolved in an
alcohol-based compound, it is mixed with the mixed solution of
ethylene glycol, capping molecules and the reducing agent because
addition of the metal precursor in solid phase may result in an
unequal reaction. Here, the solution of the metal precursor is
preferably added once within a short time to the mixed solution set
forth above. That is because when the metal precursor is added
several times, the size of metal nanoparticles varies with addition
time, which results in formation of metal nanoparticles having an
uninformed particle distribution.
[0037] Here, the alcohol-based compound refers to a compound having
alcohol group(--OH), but not limited to these, of which example may
include methanol, ethanol, ethylene glycol, and diethylene glycol.
These alcohol-based solvents may readily be mixed with PVP or
ethylene glycol that is used as a reducing agent. These
alcohol-based compounds may be preferably mixed in 30-50 parts by
weight with respect to 10 parts by weight of the metal precursor,
which is enough amount to dissolve the metal precursor.
[0038] The reaction set forth above is preferably performed for 30
minutes to 4 hours. An excess reaction over 4 hours is not
preferable because it causes precipitation of the metal particles
on the wall of a reaction chamber.
[0039] The compounds react with each other, the cores of particles
are formed and then the cores grow to form metal nanoparticles.
When the reaction is completed to form metal nanoparticles with
desired size, ethylene glycol is added again and subsequently
excess amount of acetone is added. They separate out metal
nanoparticles from by-products and unreactants of the reaction by
using difference of solubility.
[0040] According to a preferred embodiment, the acetone is
preferably used in 200-300 parts by weight with respect to 100
parts by weight of total weight of the solution in the previous
step. Besides acetone, methanol, ethanol, or a mixed solution
thereof may be used. In addition, the additionally annexed ethylene
glycol is preferably added in more than 2 parts by weight with
respect to 1 part by weight of the capping molecule, more
preferably 2-10 parts by weight. When ethylene glycol and acetone
are added within the range, the metal nanoparticles capped with PVP
may be selectively separated from the unreactants and the
by-products by using difference of solubility. In a highly
effective production of the metal nanoparticles, the metal
nanoparticles are not readily separated from the by-products when
using acetone alone in the end stage of the reaction, the
additional annexing of ethylene glycol is required. Thus, to obtain
the metal nanoparticles having high concentration and high
efficiency like the present invention, ethylene glycol should be
added in the end stage of the reaction.
[0041] When the metal nanoparticles obtained by this production
method are dispersed in ethanol in a concentration of more than 50
weight % and centrifuged at 5000 rpm for 10 minutes, the dispersion
stability is more than 98%. When the metal nanoparticles are
obtained by the existing method and then centrifuged, the
dispersion stability becomes very low of 0.1 weight %.
[0042] FIG. 1 is data representing the result of TGA analysis
(Thermo Gravimetric Analysis) for the metal nanoparticles produced
according to an embodiment of the invention. Referring to FIG. 1,
when metal nanoparticles are fully dried and analyzed with TGA, the
result confirms that 7 weight % of PVP attach to 93 weight % of
silver particles. FIGS. 2 and 3 are FE-SEM images of the metal
nanoparticles produced according to preferred embodiments of the
invention. FIG. 4 is a graph that represents the result of UV-VIS
spectroscopy(UV spectrum) of the metal nanoparticles produced
according to preferred embodiments of the invention. FIG. 5 is a
graph that represents the result of particle size analysis of the
metal nanoparticles produced according to preferred embodiments of
the invention. This particle size analysis shows that average 10-30
nm of the metal nanoparticles may be obtained and the particle
distribution rate are even.
[0043] The method for producing metal nanoparticles were generally
set forth above, hereinafter, explanations will be given in greater
detail with reference to specific examples.
[0044] While the embodiments of the invention have been described
to methods of producing silver nanoparticles, it is apparent that
the methods may be applied equally to metal compounds including
metals mentioned above besides silver salt.
EXAMPLE 1
[0045] PVP 30 g and glucose 6.5 g were thoroughly dissolved in
ethylene glycol 200 g and the mixture was poured to a flask. The
temperature was raised up to 120.degree. C. Silver nitrate 20 g was
thoroughly dissolved in 60 g of ethylene glycol and the mixture was
then promptly added into the reaction flask and agitated for 35
minutes. 200 g of ethylene glycol was added to the reaction
product, 1200 ml of acetone was added and silver nanoparticles were
selectively separated through centrifugation. When the silver
nanoparticles were completely dried, 10.3 g of powder was obtained.
As shown in FIG. 1, the examination of particle distribution
through FE-SEM confirmed that uniform nanoparticles of 16 nm were
generated.
EXAMPLE 2
[0046] PVP 30 g and glucose 1 g were thoroughly dissolved in
ethylene glycol 200 g and the mixture was poured to the reaction
flask. The temperature was raised up to 120.degree. C. Silver
nitrate 10 g was thoroughly dissolved in 50 g of ethylene glycol
and the mixture was then promptly put into a flask and agitated for
30 minutes. After cooling to room temperature, 200 g of ethylene
glycol was added to the reaction product, 1500 ml of acetone was
added and silver nanoparticles were selectively separated through
centrifugation. When the silver nanoparticles were completely
dried, 5 g of powder was obtained. As shown in FIG. 2, the
examination of particle distribution through FE-SEM confirmed that
uniform nanoparticles of 25 nm were generated.
COMPARISON EXAMPLE 1
[0047] After PVP 100 g was thoroughly dissolved in ethylene glycol
200 g and the mixture solution was placed into a flask, the
temperature was raised up to 120.degree. C. while the mixture
solution was agitated. Silver nitrate 20 g was thoroughly dissolved
in 60 g of ethylene glycol and the mixture was then promptly put
into the reaction flask and reacted for 35 minutes. After the
reaction was completed, the reaction was completely stopped by
adding 150 g of ethylene glycol to the flask, and silver
nanoparticles were selectively separated and perfectly dried.
Finally 12 g. of silver nanoparticles were obtained. The result of
the examination of particle distribution was average 15 nm size of
the particles.
[0048] The metal nanoparticles obtained from the examples had more
than 50% of yield rate, while the yield rate of the metal
nanoparticles from the comparison example was lower than this.
[0049] In addition, when the metal nanoparticles obtained from the
examples were dispersed at a high concentration of more than 50% in
ethanol and centrifuged at 5000 rpm for 10 minutes, they retained
more than 98% of dispersion stability. On the other hand, when the
metal nanoparticles obtained from the comparison example was
centrifuged like above, only 0.1 weight % remained.
[Production of Conductive Ink]
[0050] 100 g of 10-30 nm silver nanoparticles produced by example 1
or 2 was added to an aqueous solution of ethanol and diethylene
glycol butyl ether acetate, and dispersed with an ultra sonicator
to produce 20 cps of conductive ink. The conductive ink thus
produced may be printed on a circuit board via inkjet techniques to
form conductive wiring.
[0051] Although a few embodiments of the present invention have
been shown and described, it will be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the present invention,
the scope of which is defined in the appended claims and their
equivalents.
[0052] As described above, the method of production of metal
nanoparticles according to the present invention significantly can
reduce the unreactant to produce uniform metal nanoparticles with a
high yield rate. In addition, the method of production of metal
nanoparticles according to the present invention can separate
desired metal nanoparticles efficiently with ethylene glycol.
Again, the metal nanoparticles of the invention have high
dispersion stability as they are capped with polyvinyl
pyrrolidone(PVP). The invention also provides conductive ink
including these metal nanoparticles.
* * * * *