U.S. patent application number 11/498837 was filed with the patent office on 2009-09-10 for method for producing silver nanoparticles and conductive ink.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Hye-Jin Cho, Jae-Woo Joung, Byung-Ho Jun, Kwi-Jong Lee.
Application Number | 20090223410 11/498837 |
Document ID | / |
Family ID | 37849227 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090223410 |
Kind Code |
A1 |
Jun; Byung-Ho ; et
al. |
September 10, 2009 |
METHOD FOR PRODUCING SILVER NANOPARTICLES AND CONDUCTIVE INK
Abstract
A method of producing metal nanoparticles in a high yield rate
and uniform shape and size, which is thus suitable for mass
production. In addition, metal nanoparticles are provided that have
superior dispersion stability when re-dispersed in various organic
solvents, which thus suitable for use as a conductive ink having
high conductivity. The method of producing nanoparticles includes
mixing a metal precursor with a copper compound to a hydrocarbon
based solvent, mixing an amine-based compound to the mixed solution
of the metal precursor with copper compound and hydrocarbon based
solvent, and mixing a compound including one or more atoms having
at least one lone pair, selected from a group consisting of
nitrogen, oxygen, sulfur and phosphorous to the mixed solution of
the amine-based compound, metal precursor with a copper compound
and hydrocarbon based solvent.
Inventors: |
Jun; Byung-Ho; (Seoul,
KR) ; Lee; Kwi-Jong; (Seoul, KR) ; Cho;
Hye-Jin; (Suwon-si, KR) ; Joung; Jae-Woo;
(Suwon-si, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700, 1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
37849227 |
Appl. No.: |
11/498837 |
Filed: |
August 4, 2006 |
Current U.S.
Class: |
106/31.92 ;
428/402; 75/370; 977/777; 977/896 |
Current CPC
Class: |
B22F 9/24 20130101; C09D
11/52 20130101; C08K 3/08 20130101; C09D 11/38 20130101; H01B 1/22
20130101; Y10S 977/896 20130101; Y10T 428/2982 20150115; C09D 7/67
20180101; B22F 2998/00 20130101; C09D 7/62 20180101; B22F 2998/00
20130101; B22F 1/0018 20130101 |
Class at
Publication: |
106/31.92 ;
75/370; 428/402; 977/896; 977/777 |
International
Class: |
C09D 11/00 20060101
C09D011/00; B22F 9/20 20060101 B22F009/20; B32B 15/02 20060101
B32B015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2005 |
KR |
10-2005-0072478 |
Claims
1. A method of producing metal nanoparticles, said method
comprising: mixing a metal precursor with a copper compound as a
reducing agent to a hydrocarbon-based solvent, said metal precursor
containing a metal having a higher standard oxidation/reduction
potential than that of copper; mixing an amine-based compound to
the mixed solution of the metal precursor with a copper compound
and hydrocarbon-based solvent; and mixing a compound including one
or more atoms having at least one lone pair, selected from a group
consisting of nitrogen, oxygen, sulfur and phosphorous, to the
mixed solution of the amine-based compound, metal precursor with
copper compound and hydrocarbon-based solvent.
2. The method of claim 1, wherein the metal precursor of includes a
compound including one or more metals selected from a group
consisting of silver, gold, platinum, palladium and a mixture
thereof.
3. The method of claim 2, wherein the metal precursor is one or
more compounds selected from a group consisting of nitrate,
carbonate, chloride, phosphate, borate, oxide, sulfonate, sulfate
stearate, myristate, and acetate.
4. The method of claim 3, wherein the metal precursor is a compound
including one or more compounds selected from a group consisting of
AgNO3, AgBF4, AgPF6, Ag2O, CH3COOAg, AgCF3SO3 and AgClO4.
5. The method of claim 1, wherein the metal precursor is mixed in a
mole concentration of 0.05 to 5.
6. The method of claim 1, wherein the copper compound is one or
more compounds selected from a group consisting of Copper(II)
acetate, Copper (II) acetoacetate, Copper(II) carbonate, Copper(II)
cyclohexane butyrate, Copper(II) nitrate, Copper(II) stearate,
Copper(II) perchlorate, Copper(II) ethylenediamine, Copper(II)
trifluoroacetylacetonate.
7. The method of claim 6, wherein the copper compound is mixed in a
mole ratio of 0.01 to 1 with respect to the metal precursor.
8. The method of claim 1, wherein the hydrocarbon-based solvent is
one or more solvents selected from a hydrophobic solvent groups of
hexane, toluene, xylene, chlorobenzoic acid, 1-hexadecene,
1-tetradecene and 1-octadecene.
9. The method of claim 1, wherein the amine-based compound has a
composition of RNH2, where R is a saturated or unsaturated
aliphatic hydrocarbon of C3-C19.
10. The method of claim 1, wherein the compound, including one or
more atoms having at least one lone pair, is alkanoic acid or an
amine-based compound
11. The method of claim 1, further comprising heating the mixed
solution of the compound, the mixed solution of the amine-based
compound, metal precursor with copper compound and
hydrocarbon-based solvent to 50-200.degree. C.
12. Metal nanoparticles, produced according to the method of claim
1.
13. The metal nanoparticles of claim 12, wherein the size of the
metal nanoparticles is 1 to 20 nm.
14. A conductive ink including metal nanoparticles produced
according to claim 12.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2005-0072478 filed on Aug. 8, 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
vapor-phase method and the solution (colloid) method. Since the
vapor-phase method which uses plasma or gas evaporation requires
highly expensive equipments, the solution method which is easy for
the production is generally used.
[0006] A method of producing metal nanoparticles by the solution
method up to now is to dissociate a metal compound in a hydrophilic
solvent and then apply a reducing agent or a surfactant to produce
metal nanoparticles in the form of hydrosol. Another method is the
phase transfer method, which produces metal nanoparticles by
transferring a compound from a hydrophilic solvent to a hydrophobic
solvent to produce metal nanoparticles which are dispersed in the
hydrophobic solvent. However, the production of metal nanoparticles
by this existing 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 or equal
to 0.05M. 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. Moreover, the phase transfer method necessarily
requires a phase transfer, which is a cause of increased production
costs.
[0007] Approaches to solve such existing problems and to produce
high yield rate of metal nanoparticles with uniform size are in
progress.
SUMMARY
[0008] The present invention provides a method of producing metal
nanoparticles, not requiring high reaction temperature by using a
copper compound as a reducing agent and having a high yield rate
and uniform size achieved by a simple process. In addition, the
present invention provides metal nanoparticles of several or
several tens of nanometer size and a high conductive ink including
the metal nanoparticles thus obtained.
[0009] One aspect of the invention may provide a method of
producing nanoparticles comprising, (a) mixing a metal precursor
with a copper compound in a hydrocarbon based solvent, (b) mixing
an amine-based compound in the mixed solution of (a), and (c)
mixing a compound including one or more atoms having at least one
lone pair which is selected from a group consisting of nitrogen,
oxygen, sulfur and phosphorous in the mixed solution of (b).
[0010] Here, the metal precursor may include a compound including
one or more metals selected from a group consisting of silver,
gold, platinum, palladium and a mixture thereof. In a preferred
embodiment, the metal precursor may be one or more compounds
selected from a group consisting of nitrate, carbonate, chloride,
phosphate, borate, oxide, sulfonate, sulfate stearate, myristate,
and acetate, and preferably, one or more compounds selected from a
group consisting of AgNO.sub.3, AgBF.sub.4, AgPF.sub.6, Ag.sub.2O,
CH.sub.3COOAg, AgCF.sub.3SO.sub.3 and AgClO.sub.4. And the metal
precursor may be mixed in a mole ratio of 0.05 to 5.
[0011] Here, the copper compound may be one or more compounds
selected from a group consisting of Copper(II) acetate, Copper (II)
acetoacetate, Copper(II) carbonate, Copper(II) cyclohexane
butyrate, Copper(II) nitrate, Copper(II) stearate, Copper(II)
perchlorate, Copper(II) ethylenediamine, and Copper(II)
trifluoroacetylacetonate. In a preferred embodiment, the copper
compound may be mixed in a mole ratio of 0.01 to 1 with respect to
the metal precursor.
[0012] Here, the hydrocarbon-based solvent may be one or more
solvents selected from a hydrophobic solvent group consisting of
hexane, toluene, xylene, chlorobenzoic acid, 1-hexadecene,
1-tetradecene and 1-octadecene.
[0013] Further, the amine-based compound may have a composition of
RNH.sub.2, where R may be a saturated or unsaturated aliphatic
hydrocarbon of C.sub.3-C.sub.19.
[0014] Here, the compound of step (c), including one or more atoms
having at least one lone pair may be an alkanoic acid or
amine-based compound, and a procedure of heating the mixed solution
of (c) to 50-200.degree. C. may further be added.
[0015] In addition, according to another aspect of the invention
may provide metal nanoparticles produced by the method of producing
metal nanoparticles described above. Here, metal nanoparticles with
a size of 1-20 nm may be obtained.
[0016] Still another aspect of the invention may provide conductive
ink including the metal nanoparticles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and/or other aspects and advantages of the present
invention will become apparent and more readily appreciated from
the following description of the embodiments, taken in conjunction
with the accompanying drawings of which:
[0018] FIG. 1 is a TEM image of the metal nanoparticles produced
according to a preferred embodiment of the invention.
[0019] FIG. 2 is a graph representing the result of TGA analysis
for the metal nanoparticles produced according to a preferred
embodiment of the invention; and
[0020] FIG. 3 is a TEM image of the metal nanoparticles produced
according to another preferred embodiment of the invention.
DETAILED DESCRIPTION
[0021] Hereinafter, though a method of producing metal
nanoparticles according to the present invention will be described
in detail, the reactions occur in the procedure of the present
invention will be explained first.
[0022] The copper compound used in the invention acts as a weak
reducing agent, so that it allows an oxidation/reduction reaction
between another metal ion and a copper ion. In this reaction, the
copper ion functions as a reducing agent that make desired metal
nanoparticles possible to form seeds which is responsible for the
seed growth, and the seeds thus formed allow metal nanoparticles to
grow into uniform size.
[0023] As this case, the oxidation/reduction reaction between the
copper compound and the metal precursors relates to the standard
oxidation/reduction potential of each metal ion. For example, in
the case of a silver ion and a copper ion, they have the following
oxidation/reduction potential.
Ag.sup.++e.sup.-.fwdarw.Ag E.sup.o=+0.8V
Cu.sup.2++e.sup.-.fwdarw.Cu.sup.+ E.sup.o=+0.15 V
[0024] According to a reaction formula as follows, the copper ion
is oxidized to become copper 2.sup.+ ion, the silver ion is reduced
to become Ag particle.
Ag.sup.++Cu.sup.+.fwdarw.Ag+Cu.sup.2+ E.sub.total=+0.65 V
[0025] As a result of the reaction, the total oxidation/reduction
potential is a positive value, so that a forward reaction may occur
to enable the formation of Ag having zero of oxidation number.
According to this, the silver particle grows, so that desired size
of silver nanoparticles can be obtained. Gold, platinum, palladium
ion also have the same oxidation/reduction potential as follows.
Since the value is higher than the standard oxidation/reduction
potential of copper, the oxidation/reduction reaction naturally
occurs when these metals react with the copper ion.
Au.sup.2++2e.sup.-.fwdarw.Au E.sup.o=+1.42 V
Pt.sup.2++2e.sup.-.fwdarw.Pt E.sup.o=+1.2V
Pd.sup.2++2e.sup.-.fwdarw.Pd E.sup.o=+0.83 V
[0026] Beside these cases, any precursor including a metal that has
higher standard oxidation/reduction potential than that of the
copper may be used without limitation, preferably, that are
dissociated well in a hydrophobic solvent.
[0027] Examples of the copper compound that can be used in the
present invention may include, but not limited to these, Copper(II)
acetate, Copper (II) acetoacetate, Copper(II) carbonate, Copper(II)
cyclohexane butyrate, Copper(II) nitrate, Copper(II) stearate,
Copper(II) perchlorate, Copper(II) ethylenediamine, and Copper(II)
trifluoroacetylacetonate. Besides, any copper compound having
Cu.sup.2+ which has strong reduction power may be used without
limitation.
[0028] Here, the copper compound is preferably mixed with a metal
precursor in a mole ratio of 0.01 to 1. This mole ratio makes metal
nanoparticles possible to grow into a uniform size. When the copper
compound is mixed less than the mole ratio of 0.01, desired growth
of metal nanoparticles does not occur well, so that the copper
compound may not play its full role as a reducing agent. On the
other hand, when the copper compound is mixed more than a mole
ratio of 1, a rapid reaction may occur and thus undesirably cause
non-uniform growth. More preferably, the copper compound is mixed
in the mole ratio of 0.1 with respect to the metal precursor, which
allows uniform and fast formation of metal nanoparticles.
[0029] Here, examples of the metal precursor may include inorganic
acid salts, such as nitrate, carbonate, chloride, phosphate,
borate, oxide, sulfonate, sulfate, etc. and organic acid salts,
such as stearate, myristate, and acetate, which include at least
one metal selected from a group consisting of silver, gold,
platinum, palladium and a mixture thereof. 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
compound solutions such as of AgNO.sub.3, AgBF.sub.4, AgPF.sub.6,
Ag.sub.2O, CH.sub.3COOAg, AgCF.sub.3SO.sub.3 and AgClO.sub.4.
[0030] Although such metal precursors are generally known to
dissociate well in a hydrophilic solvent, the present invention
provides a method by which a metal compound is dissociated in a
hydrophobic solvent. An amine-based compound was selected for the
hydrophobic solvent. Therefore, when a hydrocarbon-based compound
is added as a reflux solvent in a later stage, the solubility
between the metal ion solution dissociated by an amine
based-compound and the hydrocarbon-based compound increases. Thus,
the metal nanoparticles may consequently be retrieved with a high
yield rate.
[0031] These metal precursors may be added in a molarity of 0.05 to
5, this molarity is preferable that the metal nanoparticles be
formed uniformly. It is apparent that the existing solution method
provides a low yield rate, because metal nanoparticles can be
formed at a low concentration of below 0.05 mole ratio. However,
the present invention ensures a high yield rate, enabling metal
nanoparticles to be formed at a high concentration. The molarity of
the metal precursor relates to a yield rate of metal nanoparticles
produced, if the concentration can be maintained highly and stably,
the higher the concentration, the higher the yield of metal
nanoparticles obtained. Here, the concentration of nanoparticles
may be below 0.05 mole ratio, but it is not different from the
existing solution method and just not preferable in light of the
aim of this invention, which is obtaining a high yield rate of
metal nanoparticles. On the other hand, it is not preferable that
metal nanoparticles be added in more than 5 mole ratio, as the
uniform growth of metal nanoparticles may be disturbed. Such a
metal precursor and a copper compound are mixed with a
hydrocarbon-based solvent, where the hydrocarbon-based solvent is
used as a reflux solvent to control reflux temperature. A variety
of organic solvents may be selected as a reflux solvent. In the
present invention, because a hydrophobic amine-based compound is
used as a dissociating solvent, it is preferable that a hydrophobic
organic solvent be also used as a reflux solvent. Representative
hydrophobic solvent includes hydrocarbon-based compounds. Hence,
the type of hydrocarbon-based compound is determined according to a
desired condition of reflux.
[0032] Preferred examples of hydrocarbon-based compounds include
hexane, toluene, xylene, 1-tetradecene, 1-hexadecene, 1-octadecene,
and chlorobenzoic acid. Here, toluene, xylene, 1-hexadecene,
chlorobenzoic acid, or 1-octadecene, etc. are more preferable for a
reflux solvent. That is because it is possible to use a variety of
hydrocarbon-based compounds having a low boiling point, which are
economical as they does not require a mixed solution to be refluxed
in a high temperature and easy to purchase. According to a
preferred embodiment, the reflux temperature is in the range from
50 to 110.degree. C. Therefore, hexane, toluene, xylene,
dichlorobenzene is more preferably used.
[0033] It is preferable that the hydrocarbon-based compound be
added to the dissociated metal ion solution so that the
concentration of the metal precursor becomes from 0.001 to 10 mole
ratio, because preferable reflux condition may be achieved within
this range of mole ratio that are suitable for obtaining metal
nanoparticles. Preferably, the higher concentration of the metal
precursor, the smaller size of the functional group, to be
preferable in terms of economy as mass production is made possible.
Such concentration of the metal precursor is ultimately related to
the yield rate of the metal nanoparticles, and in the existing
solution method, the metal nanoparticles are formed only at a low
concentration of 0.01 mole ratio or less, which results in a low
yield rate. Using the present invention, however, the metal
nanoparticles may be formed at a high concentration to ensure a
high yield rate.
[0034] In addition, the amine-based compound used in the invention
may have a composition of RNH.sub.2, where R may be a saturated or
unsaturated aliphatic hydrocarbon of C3-C19, more preferably
C4-C18. It is preferable that this amine-based compound be also in
a liquid state to dissociate the metal precursor.
[0035] Examples of such amine-based compounds, not limited to
these, may include propylamine(C.sub.3H.sub.7NH.sub.2),
butylamine(C.sub.4H.sub.9NH.sub.2),
octylamine(C.sub.8H.sub.17NH.sub.2),
decylamine(C.sub.10H.sub.21NH.sub.2),
dodecylamine(C.sub.12H.sub.25NH.sub.2),
hexadecylamine(C.sub.16H.sub.33NH.sub.2), and
oleylamine(C.sub.18H.sub.35NH.sub.2), preferably butylamine and
propylamine, and more preferably butyl amine, because butylamine
and propylamine have a stronger ability of dissociating a metal
precursor, moreover, butylamine has a stronger ability of
dissociating silver salts than does propylamine. Although
octylamine and oleylamine are also in a liquid state, the ability
to dissociate silver salts is inferior compared to butylamine and
propylamine. Among these amine-based compounds,
decylamine(C.sub.10H.sub.21NH.sub.2),
dodecylamine(C.sub.12H.sub.25NH.sub.2), and
hexadecylamine(C.sub.16H.sub.33NH.sub.2) are in a solid state, and
may be used by heating or dissolving in an organic solvent.
[0036] According to a preferred embodiment, the amine-based
compound may be mixed with the metal precursor in a mole ratio of
0.05 or more. Considering the reaction conditions and yield rate,
etc., it is preferable that the amine-based compounds such as
propylamine and butylamine be mixed in a mole ratio of 1 or more.
Thus the amine-based compound may be mixed in a mole ratio of 1 to
100 with respect to the metal precursor, where it is preferable
that the amine-based compound be mixed as little as possible in
terms of economy, within a range where the metal precursor can be
dissociated.
[0037] In the solution method, capping molecules are required to
produce metal nanoparticles, where compounds having one or more
atoms selected from oxygen, nitrogen, sulfur and phosphorus may be
used as such capping molecules. More specifically, compounds having
thiol group (--SH), amine group (--NH2), carboxyl group (--COOH),
and --P group may be used, and in a preferred embodiment of the
present invention, compounds having alkanoate molecule (--COOR) or
amine group are used as the capping molecules.
[0038] Here, when the alkanoate molecules are used as the capping
molecules, they can be mixed readily with a hydrophobic solvent,
and bond with metal nanoparticles by a certain strength to form
metal nanoparticles that are stable. Also, when the metal
nanoparticles having alkanoate molecules are used as conductive
ink, the capping molecules may be removed easily by firing, to form
wiring that is superior in electrical conductivity. In addition,
compounds having amine group is convenient in producing metal
nanoparticles, because they can be readily mixed with hydrophobic
solvent and easily separated. In the present invention, alkanoic
acid is used as the compound having alkanoate molecules. Alkanoic
acid has a composition of RCOOH, where R is a saturated or
unsaturated aliphatic hydrocarbon of C.sub.3-C.sub.20. That is, R
may be an alkyl group, an alkenyl group or alkylene group of
C.sub.3-C.sub.20. More specific examples of these alkanoic acids
may include lauric acid(C.sub.11H.sub.22COOH), oleic
acid(C.sub.17H.sub.33COOH), decanoic acid(C.sub.9H.sub.19COOH),
palmitic acid(C.sub.15H.sub.31COOH), etc. Among these, lauric acid
and oleic acid are used in terms of yield rate and conductivity
according to a preferred embodiment of the present invention.
[0039] Moreover, any compound having amine group of
C.sub.4-C.sub.40 can be used as capping molecules. This compound is
not limited to primary amines, but secondary and third amines may
be used too, and an aliphatic hydrocarbon or an aromatic
hydrocarbon may bind to it. Specific examples of such amine
compounds may include previously described amine-based compounds
that are used for a dissociating solution. Alkanoic acid or an
amine-based compound may be mixed more than 0.05 mole ratio with
respect to the metal precursor for capping metal nanoparticles.
[0040] In the invention, since the available boiling point is
50.degree. C. or more, additional reducing agent is not required to
raise the reflux temperature and yield rate, and the copper
compound conduct such a role to ensure a high yield rate. To
facilitate the oxidation/reduction reaction, the method of the
invention may further include a step that provides reflux
conditions. The reflux temperature is decided according to the
boiling point of a selected hydrocarbon compound. Such reflux is
performed at a temperature ranges from 50 to 200.degree. C., for 10
minutes to 10 hours. Preferably, metal nanoparticles may be
obtained at 60 to 110.degree. C. for 30 minutes to 4 hours.
[0041] The metal nanoparticles thus produced may be retrieved by
depositing in a polar solvent without size grading procedure and
then by centrifuging. Since the metal nanoparticles thus formed
have uniform size so that a size grading procedure is not required.
Here, the available polar solvent may include acetone, ethanol,
methanol or a mixture thereof.
[0042] The metal nanoparticles thus retrieved have a uniform size
of 1 to 20 nm, and preferably, uniformly sized metal nanoparticles
of 4 to 7 nm were obtained. FIG. 1 shows a TEM image of metal
nanoparticles produced according to a preferred embodiment of the
invention. Referring to FIG. 1, the result of analysis of silver
nanoparticles retrieved by the production method of the invention
shows that silver nanoparticles having uniform size of 4 nm has
been formed. According to this image, it is seen that also the
stability of retrieved silver nanoparticles is quite good.
[0043] The metal nanoparticles are produced in a high-viscousity
hydrophobic hydrocarbon-based compound, so that the yield rate of
metal nanoparticles may be increased to 60-90%. Compared to the
fact that the existing method reaches only 10% yield rate, more
than 6 times of yield rate may be expected in the present
invention, which is also suitable for mass production.
[0044] The metal nanoparticles thus obtained may be used for
desired utility such as an antibiotic, a deodorant, a disinfectant,
conductive adhesive, conductive ink, or an electromagnetic shield
for a display device. When the metal nanoparticles are used as
conductive ink, the metal nanoparticles may be dispersed in a
hydrophobic hydrocarbon-based solvent. This is because the
solubility of the metal nanoparticles is high in hydrocarbon-based
solvents, because they were produced in a hydrophobic solvent.
[0045] Specific examples of the method of producing metal
nanoparticles and conductive ink will be described here in
detail.
Example 1
[0046] 170 g of AgNO.sub.3 and 20 g of copper (II) acetoacetate
(Cu(acac).sub.2) compound were mixed to 300 g of toluene solvent
and then 100 g of butylamine was further added and stirred. 50 g of
palmitic acid was added to this mixed solution. The reaction
mixture was heated to 110.degree. C. and then sustained by stirring
for 2 hours and cooled to room temperature (28.degree. C.). Ag
nanoparticles thus formed were added to methanol and centrifuged to
precipitate and the precipitates, Ag nanoparticles, were separated
out. As shown in FIG. 1, 90 g of metal nanoparticles that have
uniform size distribution of 4 nm were obtained. As illustrated in
FIG. 2, the result of TGA analysis shows that Ag content by
percentage is 85 wt %. When Ag nanoparticles thus retrieved were
re-dispersed in an organic solvent, high dispersion stability was
observed, re-dispersion yield rate was also high.
Example 2
[0047] 170 g of AgNO.sub.3 and 20 g of copper (II) acetoacetate
(Cu(acac).sub.2) compound were mixed to 300 g of toluene solvent
and then 100 g of butylamine was further added and stirred. 50 g of
oleylamine was added to this mixed solution, and these mixed
compounds were heated to 110.degree. C. and then sustained by
stirring for 1 hour and cooled to room temperature (28.degree. C.).
Ag nanoparticles thus formed were added to methanol and centrifuged
to precipitate and the precipitates, Ag nanoparticles, were
separated out. As shown in FIG. 3, 90 g of metal nanoparticles that
have uniform size distribution of 5 nm were obtained.
Comparison Example
[0048] 170 g of AgNO.sub.3 was mixed to 300 g of toluene solvent
and then 100 g of butylamine was further added. 50 g of palmitic
acid was added to this mixed solution, and these mixed compounds
were heated to 110.degree. C. and then sustained by stirring for 2
hours and cooled to room temperature (28.degree. C.). Ag
nanoparticles thus formed were added to methanol and centrifuged to
precipitate and the precipitates, Ag nanoparticles, were separated
out. 10 g of metal nanoparticles were obtained. Ag nanoparticles
having ununiform distribution and size of 4 to 12 nm were
obtained.
[0049] Production of Conductive Ink
[0050] 10 g of silver nanoparticles having 4 to 5 nm in size,
produced by Examples 1 and 2, was added to an aqueous solution of
diethyleneglycol butylether acetate and ethanol, and then dispersed
with an ultra-sonicator to produce conductive ink of 20 cps. The
conductive ink thus produced was printed on a circuit board to form
conductive wiring by inkjet techniques.
[0051] Although the embodiment of the present invention mainly
provides the production of silver nanoparticles, beside a silver
compound, metal precursor containing a metal chosen from gold,
platinum, palladium or a mixture thereof is also applicable. That
is, metal nanoparticles may be produced by the same method of
examples described above.
[0052] It is also apparent that the present invention is not
limited to the examples set forth above and more changes may be
made by those skilled in the art without departing from the
principles and spirit of the present invention.
[0053] As described above, the method of producing metal
nanoparticles according to the present invention provides a high
yield rate of nanoparticles having uniform shape and size, which is
suitable for mass production. In addition, the metal nanoparticles
produced according to the present invention have superior
dispersion stability when re-dispersed in various organic solvents,
so that a variety of uses are available, which includes a
conductive ink having high conductivity.
* * * * *