U.S. patent application number 14/254965 was filed with the patent office on 2014-08-14 for nanowire preparation methods, compositions, and articles.
This patent application is currently assigned to Carestream Health, Inc.. The applicant listed for this patent is Carestream Health, Inc.. Invention is credited to David R. Whitcomb.
Application Number | 20140227519 14/254965 |
Document ID | / |
Family ID | 46026948 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140227519 |
Kind Code |
A1 |
Whitcomb; David R. |
August 14, 2014 |
NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES
Abstract
Methods of preparing metal nanowire are disclosed that employ
quaternary phosphonium salts. Such processes can produce long and
thin nanowires. Compositions and articles comprising such nanowires
are useful in electronics applications.
Inventors: |
Whitcomb; David R.;
(Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Carestream Health, Inc. |
Rochester |
NY |
US |
|
|
Assignee: |
Carestream Health, Inc.
Rochester
NY
|
Family ID: |
46026948 |
Appl. No.: |
14/254965 |
Filed: |
April 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13449397 |
Apr 18, 2012 |
8741025 |
|
|
14254965 |
|
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Current U.S.
Class: |
428/401 ;
420/501; 75/343 |
Current CPC
Class: |
Y10T 428/298 20150115;
B82Y 30/00 20130101; B22F 2998/00 20130101; B22F 2998/00 20130101;
B22F 9/24 20130101; B82Y 40/00 20130101; B22F 2998/00 20130101;
H01B 1/02 20130101; C22C 5/06 20130101; B22F 2301/255 20130101;
B22F 1/0025 20130101; B22F 9/18 20130101; B22F 2303/01
20130101 |
Class at
Publication: |
428/401 ; 75/343;
420/501 |
International
Class: |
B22F 9/18 20060101
B22F009/18; H01B 1/02 20060101 H01B001/02; C22C 5/06 20060101
C22C005/06 |
Claims
1. A method comprising: providing at least one first compound
capable of forming at least one first halide ion, said first
compound comprising at least one quaternary phosphonium salt
represented by (I): ##STR00004## wherein R.sub.1, R.sub.2, R.sub.3,
and R.sub.4 each independently comprise an alkyl group, an aryl
group, an alkoxy group, or an aryloxy group, and X.sup.- comprises
a halide ion; and reducing at least one first reducible metal ion
to at least one first metal nanowire in the presence of at least
one of the at least one first compound or the at least one first
halide ion.
2. The method according to claim 1, wherein the at least one
quaternary phosphonium salt comprises tetraphenylphosphonium
chloride.
3. The method according to claim 1, wherein the at least one first
halide ion comprises at least one chloride ion or bromide ion.
4. The method according to claim 1, wherein the at least one first
reducible metal ion comprises at least one of an ion from
International Union of Pure and Applied Chemistry (IUPAC) Group
11.
5. The method according to claim 1, further comprising providing at
least one second compound comprising the at least one reducible
metal ion, wherein at least a first portion of the at least one
second compound is provided prior to providing at least a second
portion of the at least one first compound.
6. The method according to claim 1, further comprising providing at
least one second compound comprising the at least one reducible
metal ion, wherein at least a first portion of the at least one
second compound is provided after providing at least a second
portion of the at least one first compound.
7. The method according to claim 1, wherein the at least one first
reducible metal ion comprises at least one silver ion.
8. The at least one first metal nanowire produced according to the
method of claim 1.
9. The at least one first metal nanowire according to claim 8
comprising an average length greater than about 10 .mu.m and an
average diameter less than about 50 nm.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/449,397, filed Apr. 18, 2012, entitled NANOWIRE PREPARATION
METHODS, COMPOSITIONS, AND ARTICLES, which claimed the benefit of
U.S. Provisional Application No. 61/488,926, filed May 23, 2011,
entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES,
both of which are hereby incorporated by reference in their
entirety.
BACKGROUND
[0002] The general preparation of silver nanowires (10-200 aspect
ratio) is known. See, for example, Angew. Chem. Int. Ed., 2009, 48,
60, Y. Xia, Y. Xiong, B. Lim, S. E. Skrabalak, which is hereby
incorporated by reference in its entirety. Such preparations
typically employ Fe.sup.2+ or Cu.sup.2+ ions to "catalyze" the wire
formation over other morphologies. The controlled preparation of
silver nanowires having desired lengths and widths, however, is not
known. For example, the Fe.sup.2+ produces a wide variety of
lengths or thicknesses and the Cu.sup.2+ produces wires that are
too thick for many applications.
[0003] When iron or copper are used, they are typically provided as
the metal halide salts FeCl.sub.2 or CuCl.sub.2. See, for example,
B. Wiley et al., Nano Letters, 2004, 4, 1733-1739 and K. E. Korte
et al., J. Mats. Chem., 2008, 18, 437. Other metal halide salts
have been used in nanowire synthesis. See, for example, J. Jiu, K.
Murai, D. Kim, K. Kim, K. Suganuma, Mat. Chem. & Phys., 2009,
114, 333, which refers to NaCl, CoCl.sub.2, CuCl.sub.2, NiCl.sub.2
and ZnCl.sub.2, and S. Nandikonda, "Microwave Assisted Synthesis of
Silver Nanorods," M. S. Thesis, Auburn University, Auburn, Ala.,
USA, Aug. 9, 2010, which refers to NaCl, KCl, MgCl.sub.2,
CaCl.sub.2, MnCl.sub.2, CuCl.sub.2, and FeCl.sub.3, and Japanese
patent application publication 2009-155674, which discloses
SnCl.sub.4. U.S. patent application publication 2011/0174190
discloses nanowire preparation in the presence of
tetra-n-butylammonium chloride.
SUMMARY
[0004] At least a first embodiment provides methods comprising
providing at least one first compound capable of forming at least
one first halide ion, where the at least one first compound
comprises at least one quaternary phosphonium salt, and reducing at
least one first reducible metal ion to at least one first metal
nanowire in the presence of at least one of the at least one first
composition or the at least one first halide ion. In at least some
embodiments, the at least one first halide ion comprises at least
one chloride ion or bromide ion.
[0005] Some such embodiments further comprise providing at least
one second compound comprising the at least one reducible metal
ion, wherein at least a first portion of the at least one second
compound is provided prior to providing at least a second portion
of the at least one first compound. Other such embodiments further
comprise providing at least one second compound comprising the at
least one reducible metal ion, wherein at least a first portion of
the at least one second compound is provided after providing at
least a second portion of the at least one first compound. Still
other embodiments further comprise providing at least one second
compound comprising the at least one reducible metal ion, wherein
at least a first portion of the at least one second compound is
provided simultaneously with at least a second portion of the at
least one first compound.
[0006] In at least some embodiments, the at least one quaternary
phosphonium salt may be represented by (I):
##STR00001##
where: [0007] R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each
independently comprise an alkyl group, an aryl group, an alkoxy
group, or an aryloxy group, and [0008] X.sup.- comprises a halide
ion. The at least one quaternary phosphonium salt may, for example,
comprise at least one organic phosphonium halide, such as, for
example, tetraphenylphosphonium chloride. The halide ion may, for
example, be a chloride ion or a bromide ion.
[0009] In at least some embodiments, the at least one first metal
ion may, for example, comprise at least one ion from IUPAC Group 11
or at least one coinage metal ion, such as, for example, at least
one silver ion.
[0010] The at reducing may occur, in at least some cases, in the
presence of at least one second metal or metal ion having an atomic
number different from that of the at least one first metal ion. In
some cases, the reducing may occur in the presence of propylene
glycol. Some embodiments employ reducing at at least one
temperature between about 90.degree. C. and about 150.degree.
C.
[0011] Other embodiments provide the at least one first metal
product produced according to such methods. Such a first metal
product may, for example, comprise at least one metal nanowire.
Such metal nanowires may, in some cases, comprise at least one
silver nanowire. Some embodiments provide metal nanowires
comprising an average length greater than about 10 .mu.m and an
average diameter less than about 50 nm.
[0012] Still other embodiments provide articles comprising at least
one such first metal product produced according to such
methods.
[0013] These and other embodiments will be understood by the brief
description of figures, description, exemplary embodiments,
examples, and claims that follow.
BRIEF DESCRIPTION OF FIGURES
[0014] FIG. 1 shows a micrograph of the silver nanowire product of
Example 1.
[0015] FIG. 2 shows a micrograph of the silver nanowire product of
Example 2.
[0016] FIG. 3 shows a micrograph of the silver nanowire product of
Example 3.
[0017] FIG. 4 shows a micrograph of the silver nanowire product of
Example 4.
[0018] FIG. 5 shows a micrograph of the silver nanowire product of
Example 5.
DESCRIPTION
[0019] All publications, patents, and patent documents referred to
in this document are incorporated by reference herein in the
entirety, as though individually incorporated by reference.
[0020] U.S. application Ser. No. 13/449,397, filed Apr. 18, 2012,
entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES,
is hereby incorporated by reference in its entirety.
[0021] U.S. Provisional Application No. 61/488,926, filed May 23,
2011, entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND
ARTICLES, is hereby incorporated by reference in its entirety.
Reducible Metal Ions and Metal Products
[0022] Some embodiments provide methods comprising reducing at
least one reducible metal ion to at least one metal. A reducible
metal ion is a cation that is capable of being reduced to a metal
under some set of reaction conditions. In such methods, the at
least one first reducible metal ion may, for example, comprise at
least one coinage metal ion. A coinage metal ion is an ion of one
of the coinage metals, which include copper, silver, and gold. Or
such a reducible metal ion may, for example, comprise at least one
ion of an IUPAC Group 11 element. An exemplary reducible metal ion
is a silver cation. Such reducible metal ions may, in some cases,
be provided as salts. For example, silver cations might, for
example, be provided as silver nitrate.
[0023] In such embodiments, the at least one metal is that metal to
which the at least one reducible metal ion is capable of being
reduced. For example, silver would be the metal to which a silver
cation would be capable of being reduced.
Nanostructures, Nanostructures, and Nanowires
[0024] In some embodiments, the metal product formed by such
methods is a nanostructure, such as, for example, a one-dimensional
nanostructure. Nanostructures are structures having at least one
"nanoscale" dimension less than 300 nm, and at least one other
dimension being much larger than the nanoscale dimension, such as,
for example, at least about 10 or at least about 100 or at least
about 200 or at least about 1000 times larger. Examples of such
nanostructures are nanorods, nanowires, nanotubes, nanopyramids,
nanoprisms, nanoplates, and the like. "One-dimensional"
nanostructures have one dimension that is much larger than the
other two dimensions, such as, for example, at least about 10 or at
least about 100 or at least about 200 or at least about 1000 times
larger.
[0025] Such one-dimensional nanostructures may, in some cases,
comprise nanowires. Nanowires are one-dimensional nanostructures in
which the two short dimensions (the thickness dimensions) are less
than 300 nm, preferably less than 100 nm, while the third dimension
(the length dimension) is greater than 1 micron, preferably greater
than 10 microns, and the aspect ratio (ratio of the length
dimension to the larger of the two thickness dimensions) is greater
than five. Nanowires are being employed as conductors in electronic
devices or as elements in optical devices, among other possible
uses. Silver nanowires are preferred in some such applications.
[0026] Such methods may be used to prepare nanostructures other
than nanowires, such as, for example, nanocubes, nanorods,
nanopyramids, nanotubes, and the like. Nanowires and other
nanostructure products may be incorporated into articles, such as,
for example, electronic displays, touch screens, portable
telephones, cellular telephones, computer displays, laptop
computers, tablet computers, point-of-purchase kiosks, music
players, televisions, electronic games, electronic book readers,
transparent electrodes, solar cells, light emitting diodes, other
electronic devices, medical imaging devices, medical imaging media,
and the like.
Preparation Methods
[0027] A common method of preparing nanostructures, such as, for
example, nanowires, is the "polyol" process. Such a process is
described in, for example, Angew. Chem. Int. Ed. 2009, 48, 60, Y.
Xia, Y. Xiong, B. Lim, S. E. Skrabalak, which is hereby
incorporated by reference in its entirety. Such processes typically
reduce a metal cation, such as, for example, a silver cation, to
the desired metal nanostructure product, such as, for example, a
silver nanowire. Such a reduction may be carried out in a reaction
mixture that may, for example, comprise one or more polyols, such
as, for example, ethylene glycol (EG), propylene glycol (PG),
butanediol, glycerol, sugars, carbohydrates, and the like; one or
more protecting agents, such as, for example,
polyvinylpyrrolidinone (also known as polyvinylpyrrolidone or PVP),
other polar polymers or copolymers, surfactants, acids, and the
like; and one or more metal ions. These and other components may be
used in such reaction mixtures, as is known in the art. The
reduction may, for example, be carried out at one or more
temperatures from about 90.degree. C. to about 190.degree. C.
Quaternary Phosphonium Salts
[0028] Applicant has discovered that quaternary phosphonium salts
may be used to provide halide ions that catalyze (or co-catalyze,
with one or more metal or metal ion catalysts) the formation of
one-dimensional silver nanowires. Halide ions may thereby be
produced in a controlled fashion in contrast to simply adding the
halide ion to the reaction mixture in a fixed cation-to-anion
ratio.
[0029] In at least some embodiments, the at least one quaternary
phosphonium salt may be represented by (I):
##STR00002##
where: [0030] R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each
independently comprise an alkyl group, an aryl group, an alkoxy
group, or an aryloxy group, and [0031] X.sup.- comprises a halide
ion, such as, for example, chloride, bromide, or iodide.
[0032] "Alkyl" refers to, for example, straight chain and branched
chain alkyl groups having, for example, from about 1 to about 20
carbon atoms, or from about 1 to about 15 carbon atoms, or from
about 1 to about 5 carbon atoms. Exemplary alkyl groups include
methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, n-pentyl,
ethylhexyl, dodecyl, isopentyl, and the like.
[0033] "Aryl" refers to, for example, an aromatic carbocyclic group
of from about 6 to 20 carbon atoms having a single ring (e.g.,
phenyl) or multiple condensed rings (e.g., naphthyl or anthryl)
that may or may not all themselves be condensed, provided that the
point of attachment of the group is at an aromatic carbon atom.
Exemplary aryl groups include phenyl, naphthyl, and the like.
[0034] "Alkoxy" refers to, for example, the group "RO--", with "R"
being an alkyl group. It also refers to a group comprising a
sequence of two or more alkyl groups separated from each other by
oxygen atoms, provided that the point of attachment of the alkoxy
group is at a terminal oxygen atom, such as, for example,
"R.sub.a--O--R.sub.b--O--". Exemplary alkoxyl groups include
methoxy, ethoxy, n-propyloxy, iso-propyloxy, n-butyloxy,
t-butyloxy, n-pentyloxy, 1-ethylhex-1-yloxy, dodecyloxy,
isopentyloxy, methoxymethyoxy, methoxyethoxy, ethoxyethyoxy, and
the like.
[0035] "Aryloxy" refers to, for example, the group "RO--", with "R"
being an aryl group. It also refers to a group comprising a
sequence of two or more aryl groups separated from each other by
oxygen atoms, provided that the point of attachment of the aryloxy
group is at a terminal oxygen atom, such as, for example,
"R.sub.a--O--R.sub.b--O--". Exemplary aryloxy groups include
phenoxy, naphthoxy, and the like.
[0036] The at least one quaternary phosphonium salt may, in some
cases, comprise at least one organic phosphonium halide, such as,
for example, tetraphenylphosphonium chloride.
[0037] Mixtures of such quaternary phosphonium salts may be used.
Mixtures of such salts with other compounds capable of providing
halides may also be used. Mixtures capable of providing more than
one type of halide, such as both chloride and bromide, may also be
used.
[0038] The metal or metal ion catalysts, if used, may be provided
as metal halides, as metal cations with non-halide anions, or in
any other suitable form. For example, such catalysts may be
provided as alkali metal salts, alkaline earth metal salts,
metalloid salts, organometallic compounds, transition metal
complexes, and the like.
[0039] These methods are also believed to be applicable to
reducible metal cations other than silver cations, including, for
example, reducible cations of other IUPAC Group 11 elements,
reducible cations of other coinage metals, and the like. The
methods may also be used to prepare products other than nanowires,
such as, for example, nanocubes, nanorods, nanopyramids, nanotubes,
and the like. Such products may be incorporated into articles, such
as, for example, transparent electrodes, solar cells, light
emitting diodes, other electronic devices, medical imaging devices,
medical imaging media, and the like.
EXEMPLARY EMBODIMENTS
[0040] U.S. Provisional Application No. 61/488,926, filed May 23,
2011, entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND
ARTICLES, which is hereby incorporated by reference in its
entirety, disclosed the following 12 non-limiting exemplary
embodiments:
A. A method comprising:
[0041] providing a composition capable of forming at least one
first halide ion, said composition comprising at least one
quaternary phosphonium salt; and
[0042] reducing at least one first metal ion to at least one first
metal in the presence of the composition.
B. The method according to embodiment A, wherein the at least one
quaternary phosphonium salt is represented by (I):
##STR00003##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each independently
comprise an alkyl group, an aryl group, an alkoxy group, or an
aryloxy group, and X.sup.- comprises a halide ion. C. The method
according to embodiment A, wherein the at least one quaternary
phosphonium salt comprises at least one organic phosphonium halide.
D. The method according to embodiment A, wherein the at least one
quaternary phosphonium salt comprises tetraphenylphosphonium
chloride. E. The method according to embodiment A, wherein the at
least one first halide ion comprises at least one chloride ion or
bromide ion. F. The method according to embodiment A, wherein the
at least one first metal ion comprises at least one element from
IUPAC Group 11. G. The method according to embodiment A, wherein
the at least one first metal ion comprises at least one coinage
metal ion. H. The method according to embodiment A, wherein the at
least one first metal ion comprises at least one silver ion. J. The
method according to embodiment A, wherein the reducing occurs in
the presence of at least one second metal or metal ion having an
atomic number different from that of the at least one first metal
ion. K. The at least one first metal product produced according to
the method of embodiment A. L. The at least one first metal product
according to embodiment K, said at least one product comprising at
least one nanowire. M. An article comprising the at least one first
metal product according to embodiment K.
EXAMPLES
Example 1
[0043] A 500 mL reaction flask containing 280 mL ethylene glycol
(EG) was stripped of at least some dissolved gases (hereafter,
"degassed") by bubbling nitrogen into the solution overnight using
a TEFLON.RTM. fluoropolymer tube. To the EG was then added 13 mg of
tetraphenylphosphonium chloride and 3.3 g of a 3 mM solution of
iron (II) acetylacetone in EG. The fluoropolymer tube was then
retracted to provide nitrogen blanketing of the headspace of the
reaction flask at a 0.5 L/min purge rate. Solutions of 0.77 M
polyvinylpyrrolidinone (PVP) in EG and 0.25 M AgNO.sub.3 in EG were
degassed with N.sub.2, then 20 mL syringes of each were prepared.
The reaction mixture was heated to 145.degree. C. under N.sub.2,
then the AgNO.sub.3 and PVP solutions were added at a constant rate
over 25 minutes via a 12 gauge a TEFLON.RTM. fluoropolymer syringe
needle. The reaction was held at 145.degree. C. for 90 minutes, and
then allowed to cool to ambient temperature.
[0044] An optical microscope picture of the unpurified silver
nanowire product is shown in FIG. 1. Average length and diameter
was determined by measuring a sample of at least 100 nanowires. The
average nanowire diameter was found to be 135.+-.100 nm and the
average length was found to be 20.4.+-.2.02 .mu.m.
Example 2
[0045] A 500 mL reaction flask containing 300 mL propylene glycol
(1,2-propanediol, PG), 1.9 mg polyvinylpyrrolidinone (PVP, 55,000
molecular weight), and 61.5 mg tetraphenylphosphonium chloride was
degassed overnight with N.sub.2 using a TEFLON.RTM. fluoropolymer
tube. The fluoropolymer tube was then retracted to provide nitrogen
blanketing of the headspace of the reaction flask at a 0.5 L/min
purge rate. A solution of 0.50 M AgNO.sub.3 in PG was degassed with
N.sub.2, then a 20 mL syringe of the solution was prepared. The
reaction mixture was heated to 125.degree. C. under N.sub.2, then
the AgNO.sub.3 solution was added at a constant rate over 25
minutes via a 12 gauge TEFLON.RTM. fluoropolymer syringe needle.
The reaction mixture was held at 125.degree. C. for 60 minutes, and
then allowed to cool to ambient temperature.
[0046] An optical microscope picture of the unpurified silver
nanowire product is shown in FIG. 2. Average length and diameter
was determined by measuring a sample of at least 100 nanowires. The
average nanowire diameter was found to be 46.4.+-.13.4 nm and the
average length was found to be 9.9.+-.4.6 .mu.m.
Example 3
[0047] A 500 mL reaction flask containing 270 mL propylene glycol
(1,2-propanediol, PG), 4.5 mg polyvinylpyrrolidinone (PVP, 55,000
molecular weight), and 78.3 mg tetraphenylphosphonium chloride was
degassed overnight with N.sub.2 using a TEFLON.RTM. fluoropolymer
tube. The fluoropolymer tube was then retracted to provide nitrogen
blanketing of the headspace of the reaction flask at a 0.5 L/min
purge rate. A solution of 1.0 M AgNO.sub.3 in PG was degassed with
N.sub.2, then a 24 mL syringe of the solution was prepared. The
reaction mixture was heated to 100.degree. C. under N.sub.2, then
the AgNO.sub.3 solution was added at a constant rate over 120
minutes via a 12 gauge TEFLON.RTM. fluoropolymer syringe needle.
The reaction mixture was then allowed to cool to ambient
temperature.
[0048] An optical microscope picture of the unpurified silver
nanowire product is shown in FIG. 3. Average length and diameter
was determined by measuring a sample of at least 100 nanowires. The
average nanowire diameter was found to be 53.0.+-.6.8 nm and the
average length was found to be 10.2.+-.46.4 .mu.m.
Example 4
[0049] A 500 mL reaction flask containing 280 mL propylene glycol
(1,2-propanediol, PG) and 1.9 g polyvinylpyrrolidinone (PVP, 55,000
molecular weight), was degassed overnight with N.sub.2 using a
TEFLON.RTM. fluoropolymer tube. The fluoropolymer tube was then
retracted to provide nitrogen blanketing of the headspace of the
reaction flask at a 0.5 L/min purge rate. Solutions of 0.50 M
AgNO.sub.3 in PG and 19.3 mM tetraphenylphosphonium chloride in PG
were degassed with N.sub.2. A 20 mL syringe of the AgNO.sub.3
solution and a 9 mL syringe of the tetraphenylphosphonium chloride
solution were prepared. The reaction mixture was heated to
110.degree. C. under N.sub.2, then the AgNO.sub.3 and
tetraphenylphosphonium chloride solutions were each added at a
constant rate of 0.8 mL/min via 12 gauge TEFLON.RTM. fluoropolymer
syringe needles. The reaction mixture was held for 1 hour after
completion of the tetraphenylphosphonium chloride, cooled to
100.degree. C., held for an additional 4 hours, then allowed to
cool to ambient temperature.
[0050] An optical microscope picture of the unpurified silver
nanowire product is shown in FIG. 4. Average length and diameter
was determined by measuring a sample of at least 100 nanowires. The
average nanowire diameter was found to be 44.5.+-.5.5 nm and the
average length was found to be 24.0.+-.11.5 .mu.m.
Example 5
[0051] A 500 mL reaction flask containing 280 mL propylene glycol
(1,2-propanediol, PG) and 4.5 g polyvinylpyrrolidinone (PVP, 55,000
molecular weight), was degassed overnight with N.sub.2 using a
TEFLON.RTM. fluoropolymer tube. The fluoropolymer tube was then
retracted to provide nitrogen blanketing of the headspace of the
reaction flask at a 0.5 L/min purge rate. Solutions of 1.0 M
AgNO.sub.3 in PG and 19.3 mM tetraphenylphosphonium chloride in PG
were degassed with N.sub.2. A 24 mL syringe of the AgNO.sub.3
solution and a 24 mL syringe of the tetraphenylphosphonium chloride
solution were prepared. The reaction mixture was heated to
110.degree. C. under N.sub.2, then the AgNO.sub.3 solution was
added at a constant rate of 0.2 mL/min via 12 gauge TEFLON.RTM.
fluoropolymer syringe needles. 10 min after initiating the
AgNO.sub.3 solution addition, the tetraphenylphosphonium chloride
solution was added via a separate syringe pump at a constant rate
of 0.8 mL/min. The reaction mixture was held for 2 hrs after
completion of the silver nitrate solution, then allowed to cool to
ambient temperature.
[0052] An optical microscope picture of the unpurified silver
nanowire product is shown in FIG. 5. Average length and diameter
was determined by measuring a sample of at least 100 nanowires. The
average nanowire diameter was found to be 44.2.+-.8.9 nm and the
average length was found to be 13.9.+-.9.7 .mu.m.
[0053] The invention has been described in detail with particular
reference to a presently preferred embodiment, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention. The presently disclosed
embodiments are therefore considered in all respects to be
illustrative and not restrictive. The scope of the invention is
indicated by the appended embodiments, and all changes that come
within the meaning and range of equivalents thereof are intended to
be embraced therein.
* * * * *