Syringe pump abstract
Synthetic methods for producing uniform in diameter and highly
crystalline nanorods of metals, alloys, metal oxides, metal nitrides,
metal pnictides or metal chalcogenides by reaction of metal-surfactant
complexes injected at a constant injection rate using a syringe
pump into a surfactant solution in order to induce the one-dimensional
growth of the nanostructured materials, where the reaction includes
thermal decomposition, reduction, oxidation, sulfidation and phosphidation,
are disclosed. The steps of a typical synthetic method consist of
forming metal-surfactant complexes from the reaction of metal precursors
and surfactant, injecting said metal-surfactant complex into a solution
containing a surfactant and a reagent at high temperature using
a syringe pump at a constant injection rate, aging at high temperature,
and separating as well as precipitating by adding a poor solvent,
and finally retrieving the desired nanorods by centrifuging.
Syringe pump claims
What is claimed is:
1. A method of synthesizing uniform nanorods of metals, alloys,
metal oxides, metal nitrides, metal pnictides, and metal chalcogenides,
comprising the steps of; reacting a metal precursor and a surfactant
in a solvent to form a metal-surfactant complex solution; injecting
said metal-surfactant complex into a solution containing a surfactant
and a reagent at high temperature using a syringe pump at a constant
injection rate to form a reaction mixture; reacting said reaction
mixture to form said nanorods; separating and precipitating said
nanorods in the reacted mixture by adding a poor solvent; and retrieving
said nanorods by centrifuging.
2. The method of claim 1 wherein said metal precursor is selected
from a group of (a) organometallic compounds including typically
iron pentacarbonyl [Fe(CO).sub.5], ferrocene, cobalt tricarbonylnitrosyl
[Co(CO).sub.3(NO)], dicobalt octacarbonyl [CO.sub.2(CO).sub.8],
chromium hexacarbonyl [Cr(CO).sub.6], nickel tetracarbonyl [Ni(CO).sub.4]
and dimanganese decacarbonyl [Mn.sub.2(CO).sub.10], (b) metal acetylacetonate
compounds including typically iron acetylacetonate [Fe(acac).sub.3],
cobalt acetylacetonate [Co(acac).sub.3], barium acetylacetonate
[Ba(acac).sub.2], strontium acetylacetonate [Sr(acac).sub.2], platinum
acetylacetonate [Pt(acac).sub.2] and palladium acetylacetonate [Pd(acac).sub.2],
and (c) metal alkoxide compounds including typically titanium tetraisopropoxide
[Ti(.sup.iOC.sub.3H.sub.7).sub.4] and zirconium tetrabutoxide [Zr(OC.sub.4H.sub.9).sub.4].
3. The method of claim 1 wherein said metals used for the precursors
are selected from typically iron [Fe], cobalt [Co], nickel [Ni],
chromium [Cr], manganese [Mn], barium [Ba], strontium [Sr], titanium
[Ti], zirconium [Zr], platinum [Pt], palladium [Pd] and the groups
11 through X transition metals in particular.
4. The method of claim 1 wherein the ligands associated with said
precursors are typically carbonyl [CO], nitrosyl [NO], cyclopentadienyl
[C.sub.5H.sub.5], acetate, aromatic compounds and alkoxide family.
5. The method of claim 1 wherein said metal salts used as precursors
are typically iron(III) chloride [FeCl.sub.3], iron(II) chloride
[FeCl.sub.2], iron(II) sulfate [FeSO.sub.4], iron(III) nitrate [Fe(NO.sub.3).sub.3],
cobalt(III) chloride [COCl.sub.3], cobalt(II) chloride [COCl.sub.2],
cobalt(III) nitrate [Co(NO.sub.3).sub.3], nickel(II) sulfate [NiSO.sub.4],
nickel(II) chloride [NiCl.sub.2], nickel(II) nitrate [Ni(NO.sub.3).sub.2],
titanium tetrachloride [TiCl.sub.4], zirconium tetrachloride [ZrCl.sub.4],
hydrogen hexachloroplatinate(IV) [H.sub.2PtCl.sub.6], hydrogen hexachloropalladiate(IV)
[H.sub.2PdCl.sub.6], barium chloride [BaCl.sub.2], barium sulfate
[BaSO.sub.4], strontium chloride [SrCl.sub.2] and strontium sulfate
[SrSO.sub.4], whereby these metal salts consist of various metals
including typically iron [Fe], cobalt [Co], nickel [Ni], chromium
[Cr], manganese [Mn], barium [Ba], strontium [Sr], titanium [Ti],
zirconium [Zr], platinum [Pt], palladium [Pd], and anions including
typically chloride [Cl.sup.-], nitrate [NO.sub.3.sup.-], sulfate
[SO.sub.4.sup.2-], phosphate [PO.sub.4.sup.3-] and alkoxides.
6. The method of claim 1 wherein said nanorods of alloys and multi-metallic
oxides are formed using mixtures of two or more metal precursors
selected from the list in claim 2 instead of using a metal precursor.
7. The methods of claim 1 wherein said surfactant is selected
from (a) cationic surfactants including typically alkyltrimethylammonium
halides such as cetyltrimethylammonium bromide, (b) neutral surfactants
including typically oleic acid, trioctylphosphine oxide (TOPO),
triphenylphosphine (TPP), and trioctylphosphine (TOP), alkyl amines,
RNH.sub.2 where R is alkyl groups with 3-18 carbons, such as oleylamine,
octylamine, and hexadecylamine, and trialkylamine and alkyl thiols,
and (c) anionic surfactants including typically sodium alkyl sulfates
and sodium alkyl phosphates, and mixtures of two or more surfactants
listed above.
8. The methods of claim 1 wherein said solvent is selected from
typically (a) ethers such as octyl ether, butyl ether, hexyl ether
and decyl ether, (b) heterocyclic compounds such as pyridine and
tetrahydrofurane (THF), (c) aromatic compounds such as toluene,
xylene, mesitylene, benzene, (d) dimethyl sulfoxide (DMSO) and dimethylformamide
(DMF), (e) alcohols such as octyl alcohol and decanol, (f) hydrocarbons
such as heptane, octane, decane, dodecane, tetradecane and hexadecane,
and also (g) water.
9. The method of claim 1 wherein said metal-surfactant complex
is formed at a temperature between 20.degree. C. and 200.degree.
C.
10. The method of claim 1 wherein the molar ratio of said metal
precursor to said surfactant is in the range between 1:0.1 and 1:100.
11. The method of claim 1 wherein for synthesizing nanorods of
metal chalcogenides said reagent is selected typically from elemental
sulfur (S.sub.8), selenium (Se), tellurium (Te), trioctylphosphine
selenide (TOPSe), trioctylphosphine sulfide (TOPS) and trioctylphosphine
telluride (TOPTe).
12. The method of claim 1 wherein for synthesizing nanorods of
metal oxides said oxidant is selected typically from oxygen (O.sub.2),
hydrogen peroxide (H.sub.2O.sub.2), and amine N-oxide such as pyridine
N-oxide and trimethylamine N-oxide.
13. The method of claim 1 wherein for synthesizing metal nanorods
said reductant is selected typically from sodium borohydride (NaBH.sub.4),
lithium aluminum hydride (LiAlH.sub.4), lithium triethylborohydride
(super-hydride, LiB(C.sub.2H.sub.5).sub.3H), tetramethylammonium
borohydride ((CH.sub.3).sub.4NBH.sub.4) and hydrogen gas.
14. The method of claim 1 wherein said metal-surfactant complexes
are injected into a solution at a temperature between 0.degree.
C. and 400.degree. C.
15. The method of claim 1 wherein said metal-surfactant complexe
is injected into a solution using a syringe pump at an injection
rate between 1 mL/hr and 100 mL/hr.
16. The method of claim 1 wherein said reaction process of said
reaction mixture is carried out at a temperature between 0.degree.
C. and 400.degree. C.
17. The method of claim 1 wherein said reaction process of the
reaction mixture is carried out for a time period between 1 minute
and 72 hours.
Syringe pump description
TECHNICAL FIELD
[0001] The present invention relates to a method of synthesizing
uniform nanorods of metals, alloys, metal oxides, metal nitrides,
metal pnictides, or metal chalcogenides by reaction of metal-surfactant
complexes injected using a syringe pump, where the reaction includes
thermal decomposition, reduction, oxidation, sulfidation and phosphidation,
BACKGROUND ART
[0002] One-dimensional (1-D) nanostructured materials including
nanorods, nanowires and nanotubes have been receiving a great deal
of attention recently primarily due to their unique properties of
low dimensionality and possibly quantum confinement effect [Xia,
Y. et al., "One-dimensional Nanostructures: Synthesis, Characterization
and Applications", Adv. Mater. 2003 15 353]. These 1-D nanostructured
materials found their way to be used for wide applications in interconnections
and functional blocks for fabricating electronic, magnetic and optical
devices in nanoscale. In the past several years, a variety of chemical
methods have been used in demonstrating methods of synthesizing
many types of nanorods. These synthetic methods are typically anisotropic
growth with the intrinsic anisotropic crystal structure in a solid
material, anisotropic growth using tubular templates, and anisotropic
growth kinetically controlled by super-saturation or by using an
appropriate capping surfactant. The synthesis of nanostructured
magnetic materials is a very important area of research because
of their potentially practical applications in the areas of magnetic
storage devices at the density level of multi-terabit/in.sup.2 and
also of the use of magnetic carriers for drug targeting, particularly,
for cancer treatment purposes.
[0003] There have been several reports on the synthesis of discrete
1-D magnetic nanorods.
[0004] Park, S. L. et al. reported on the synthesis of iron nanorods
by using the process of oriented attachment of monodisperse spherical
nanoparticles [Park, S. J. et al., "Synthesis and Magnetic
Studies of Uniform Iron Nanorods and Nanospheres", J. Am. Chem.
Soc. 2000 122 8581]. Puntes, V. F. et al. reported on the synthesis
of cobalt nanodisks by means of thermal decomposition of the cobalt
carbonyl precursors [Puntes, V. F. et al., "Colloidal Nanocrystal
Shape and Size Control: The Case of Cobalt", Science 2001
291 2115]. Dumestre, F., et al. reported on the synthesis of cobalt
nanorods [Dumestre, F. et al., "Shape Control of Thermodynamically
Stable Cobalt Nanorods through Organometallic Chemistry," Angew,
Chem. Int. Ed. 2002 41 4286], and Cordente, N. et al. reported
on the synthesis of nickel nanorods by means of high-temperature
reduction of organometallic complexes [Cordente, N. et al., "Synthesis
and Magnetic Properties of Nickel Nanorods", Nano Lett., 2001
1 565.].
[0005] However, most of the synthesis methods aforementioned deal
with nanorods with diameter larger than 20 nm, and also the methods
of synthesizing nanorods with diameter ranging from 2 nm to 20 nm.
Furthermore, the case where the diameter of the nanorods is uniform
and, in particular, the diameter-controlled synthesis method of
nanorods with diameter less than 20 nm have not been reported. This
is primarily due to the complexity of the necessary synthesis procedures
and also due to very low reproducibility of the nanorods of uniform
in size.
[0006] Hyeon, T. et al. [Hyeon, T., "Chemical Synthesis of
Magnetic Nanoparticles", Chem. Comm., 2003 927; and also Hyeon,
T. et al., "Synthesis of Highly Crystalline and Monodisperse
Maghemite Nanocrystallites without a Size-Selection Process,"
J. Am. Chem. Soc. 2001 123 12798] and Joo, J. et al. [Joo, J.
et al., "Multi-gram Scale Synthesis and Characterization of
Monodisperse Tetragonal Zirconia Nanocrystals," J. Am. Chem.
Soc. 2003 125 6553.] have previously reported on the methods of
synthesizing monodisperse nanocrystals of metals, oxides and sulfides,
where a method of thermal decomposition of metal-surfactant complex
is employed.
[0007] The present invention is a new and novel method of synthesizing
desired nanorods, which method is an outgrowth of the work carried
out previously by Hyeon, T., et al. aforementioned. The main objective
of the present invention is to disclose methods of synthesizing
nanorods of metals, alloys, metal oxides, metal nitrides, metal
pnictides, or metal chalcogenides having excellent characteristics
of uniformity in diameter and crystallinity as previously described
elsewhere by reacting continuously injected metal-surfactant complexes
using a syringe pump.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0008] FIG. 1 is a flowchart showing a synthetic procedure of nanorods
according to the present invention.
[0009] FIG. 1-A-1 is an exemplary TEM (Transmission Electron Microscope)
image of iron phosphide (Fe.sub.2P) nanorods of size 5 nm (diameter).times.88
nm (length) synthesized according to Embodiment 1-A.
[0010] FIG. 1-A-2 is an exemplary HRTEM (High Resolution Transmission
Electron Microscope) image of iron phosphide (Fe.sub.2P) nanorods
of size 5 nm (diameter).times.88 nm (length) synthesized according
to Embodiment 1-A.
[0011] FIG. 1-A-3 is an exemplary X-ray diffraction (XRD) pattern
of iron phosphide (Fe.sub.2P) nanorods of size 5 nm (diameter).times.88
nm (length) synthesized according to Embodiment 1-A.
[0012] FIG. 1-B is an exemplary TEM image of iron phosphide (Fe.sub.2P)
nanorods of size 6 nm (diameter).times.107 nm (length) synthesized
according to Embodiment 1-B.
[0013] FIG. 1-C is an exemplary TEM image of iron phosphide (Fe.sub.2P)
nanorods of size 6 nm (diameter).times.290 nm (length) synthesized
according to Embodiment 1-C.
[0014] FIG. 1-D is an exemplary TEM image of iron phosphide (Fe.sub.2P)
nanorods of size 9 nm (diameter).times.50 nm (length) synthesized
according to Embodiment 1-D.
[0015] FIG. 1-E is an exemplary TEM image of iron phosphide (Fe.sub.2P)
nanorods of size 18 nm (diameter).times.75 nm (length) synthesized
according to Embodiment 1-E.
[0016] FIG. 1-F is an exemplary TEM image of iron phosphide (Fe.sub.2P)
nanorods of size 5 nm (diameter).times.160 nm (length) synthesized
according to Embodiment 1-F.
[0017] FIG. 2-A is an exemplary TEM image of cobalt phosphide (CO.sub.2P)
nanorods of size 5 nm (diameter).times.15 nm (length) synthesized
according to Embodiment 2.
[0018] FIG. 2-B is an exemplary HRTEM image of cobalt phosphide
(CO.sub.2P) nanorods of size 5 nm (diameter).times.15 nm (length)
synthesized according to Embodiment 2.
[0019] FIG. 2-C is an exemplary X-ray diffraction (XRD) pattern
of cobalt phosphide (CO.sub.2P) nanorods of size 5 nm (diameter).times.15
nm (length) synthesized according to Embodiment 2.
[0020] FIG. 3-A is an exemplary TEM image of manganese phosphide
(MnP) nanorods of size of 5 nm (diameter).times.16 nm (length) synthesized
according to Embodiment 3.
[0021] FIG. 3-B is an exemplary X-ray diffraction (XRD) pattern
of manganese phosphide (MnP) nanorods of size of 5 nm (diameter).times.16
nm (length) synthesized according to Embodiment 3.
[0022] FIG. 4-A is an exemplary TEM image of zinc oxide (ZnO) nanorods
of size 8 nm (diameter).times.140 nm (length) synthesized according
to Embodiment 4.
[0023] FIG. 4-B is an exemplary HRTEM image of zinc oxide (ZnO)
nanorods of size 8 nm (diameter).times.140 nm (length) synthesized
according to Embodiment 4.
[0024] FIG. 4-C is an exemplary X-ray diffraction (XRD) pattern
of zinc oxide (ZnO) nanorods of size of 8 nm (diameter).times.140
nm (length) synthesized according to Embodiment 4.
DISCLOSURE OF THE INVENTION
[0025] The primary object of the present invention is, therefore,
to disclose novel synthesis methods of producing discrete and uniform-in-diameter
nanorods of metals, alloys, metal oxides, metal nitrides, metal
pnictides, or metal chalcogenides by reacting continuously injected
metal-surfactant complexes using a syringe pump, whereby the resulting
1-D nanorods possess the desirable property of uniformity in diameter
and the characteristics in consistency both useful for practical
applications.
[0026] The present invention discloses the procedures for producing
nanorod materials, wherein a syringe pump is employed for continuously
injecting metal-surfactant complexes into a hot surfactant solution
in order to induce the one-dimensional growth of the desired nanorods.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0027] The present invention discloses new and novel methods of
synthesizing nanorods of metals, alloys, metal oxides, metal nitrides,
metal pnictides, or metal chalcogenides by continuously injecting
metal-surfactant complexes into a hot surfactant solution in order
to induce the one-dimensional growth of the nanostructured materials,
whereby a syringe pump is employed for continuous feeding of metal-surfactant
complexes by injection. More specifically, the present invention
discloses a method of synthesizing discrete nanorods by reacting
metal-surfactant complexes while the metal-surfactant complexes
are being continuously injected into a surfactant solution using
a syringe pump.
[0028] Another aspect of the present invention is to disclose synthetic
methods of synthesizing nanorods highly uniform in diameter through
the reaction of metal-surfactant complexes injected using a syringe
pump. Such high level of uniformity in size in diameter of the nanorods
is attributed to form superlattices by self-assembly, thereby the
nanorods synthesized according to the present invention have a property
of forming superlattices, and such nanorods can be used as a high
density magnetic data storage medium at the density level of as
high as in the range of terabits/in.sup.2.
[0029] Another object of the present invention is to disclose synthetic
methods of controlling the diameter as well as the level of size-uniformity
in diameter of the nanorods produced by using a syringe pump for
delivering the metal-surfactant complexes at a controlled injection
rate.
[0030] Another object of the present invention is to disclose synthetic
methods of synthesizing nanorods possessing the characteristics,
whereby the nanorods maintain a uniform size in diameter and also
they do not aggregate even when the nanorods are recovered in a
powder form, and also the nanorods can be dispersed many times in
various solvents without being aggregated. Such physical properties
of non-aggregation and maintaining uniform particle size when the
nanorods are recovered according to the present invention, widen
the possibility of application areas and the usability of the nanorods
suggesting the possibility of potentially recycling as well as reusing.
[0031] Yet, another object of the present invention is to disclose
synthetic methods of controlling the diameter of the uniformly-formed
nanorods by using different stabilizing surfactants.
[0032] The methods of synthesizing nanorods disclosed here according
to the present invention are described below in reference to FIG.
1.
[0033] Specifically, according to the present invention and referring
to FIG. 1 the desired nanorods are synthesized by the following
five steps; Step A 101: A metal-surfactant complex solution is formed
by reacting a metal precursor and a surfactant in a solvent. Step
B 102: Said metal-surfactant complex solution is injected into a
solution containing a surfactant and a reagent in a solvent at a
controlled injection rate using a syringe pump to produce a reaction
mixture. Step C 103: Nanorods are formed by a process of reaction
of said reaction mixture obtained in Step B 102 where the reaction
includes thermal decomposition, reduction, oxidation, sulfidation
and phosphidation. Step D 104: The desired nanorods are separated
and precipitated in the reacted mixture resulted in Step C 103 by
adding a poor solvent. Step E 105: The desired nanorods are retrieved
from the resulting solution in Step D 104 by centrifuging, thereby
the process of synthesizing the desired nanorods is completed.
[0034] To be more specific, according to the present invention,
referring to FIG. 1 Step A 101 the metal precursors usable for
synthesizing the desired nanorods are various organometallic compounds
including iron pentacarbonyl [Fe(CO).sub.5], ferrocene, cobalt tricarbonylnitrosyl
[Co(CO).sub.3(NO)], dicobalt octacarbonyl [CO.sub.2(CO).sub.8],
chromium hexacarbonyl [Cr(CO).sub.6], nickel tetracarbonyl [Ni(CO).sub.4]
and dimanganese decacarbonyl [Mn.sub.2(CO).sub.10]; metal acetylacetonate
compounds including iron acetylacetonate [Fe(acac).sub.3], cobalt
acetylacetonate [Co(acac).sub.3], barium acetylacetonate [Ba(acac).sub.2],
strontium acetylacetonate [Sr(acac).sub.2], platinum acetylacetonate
[Pt(acac).sub.2] and palladium acetylacetonate [Pd(acac).sub.2];
and metal alkoxide compounds including titanium tetraisopropoxide
[Ti(.sup.iOC.sub.3H.sub.7).sub.4] and zirconium tetrabutoxide [Zr(OC.sub.4H.sub.9).sub.4].
[0035] According to the present invention, the metals usable as
precursors according to the present invention include iron [Fe],
cobalt [Co], nickel [Ni], chromium [Cr], manganese [Mn], barium
[Ba], strontium [Sr], titanium [Ti], zirconium [Zr], platinum [Pt],
palladium [Pd] and the group II through group X transition metals,
in particular.
[0036] The ligands associated with the precursors include carbonyl
[CO], nitrosyl [NO], cyclopentadienyl [C.sub.5H.sub.5], acetate,
aromatic compounds and alkoxide family.
[0037] According to the present invention, the metal salts usable
as precursors are typically iron(III) chloride [FeCl.sub.3], iron(II)
chloride [FeCl.sub.2], iron(II) sulfate [FeSO.sub.4], iron(III)
nitrate [Fe(NO.sub.3).sub.3], cobalt(III) chloride [COCl.sub.3],
cobalt(II) chloride [COCl.sub.2], cobalt(III) nitrate [Co(NO.sub.3).sub.3],
nickel(II) sulfate [NiSO.sub.4], nickel(II) chloride [NiCl.sub.2],
nickel(II) nitrate [Ni(NO.sub.3).sub.2], titanium tetrachloride
[TiCl.sub.4], zirconium tetrachloride [ZrCl.sub.4], hydrogen hexachloroplatinate(IV)
[H.sub.2PtCl.sub.6], hydrogen hexachloropalladiate(IV) [H.sub.2PdCl.sub.6],
barium chloride [BaCl.sub.2], barium sulfate [BaSO.sub.4], strontium
chloride [SrCl.sub.2] and strontium sulfate [SrSO.sub.4], wherein
these metal salts consist of various metals including iron [Fe],
cobalt [Co], nickel [Ni], chromium [Cr], manganese [Mn], barium
[Ba], strontium [Sr], titanium [Ti], zirconium [Zr], platinum [Pt],
palladium [Pd] and anions including typically chloride [Cl], nitrate
[NO.sub.3], sulfate [SO.sub.4.sup.2-], phosphate [PO.sub.4.sup.3-]
and alkoxides.
[0038] According to the present invention, in order to synthesize
the nanorods of alloys and multi-metallic oxides, mixtures of two
or more metal precursors listed above can be used as precursors.
[0039] According to the present invention, referring to FIG. 1
Step A 101 and Step B 102 the following surfactants can be used
for stabilizing the nanorods, where said surfactants include (1)
cationic surfactants including typically alkyltrimethylammonium
halides such as cetyltrimethylammonium bromide, (2) neutral surfactants
including typically oleic acid, trioctylphosphine oxide (TOPO),
triphenylphosphine (TPP), trioctylphosphine (TOP) and alkyl amines,
RNH.sub.2 where R is alkyl groups with 3-18 carbons, such as oleylamine,
octylamine, hexadecylamine, trialkylamine and alkyl thiols, and
also (3) anionic surfactants including typically sodium alkyl sulfates
and sodium alkyl phosphates. According to the present invention,
mixtures of two or more surfactants can also be used.
[0040] The solvents used in the present invention are required
to have high enough boiling temperature in order to produce the
desired nanorods because the metal-surfactant precursors must be
decomposed. According to the present invention, referring to FIG.
1 Step A 101 and Step B 102 the usable solvents include typically
(1) ethers such as octyl ether, butyl ether, hexyl ether and decyl
ether, (2) heterocyclic compounds such as pyridine and tetrahydrofurane
(THF), and also (3) aromatic compounds such as toluene, xylene,
mesitylene, benzene, dimethyl sulfoxide (DMSO) and dimethylformamide
(DMF), and (4) alcohols such as octyl alcohol and decanol, and (5)
hydrocarbons such as heptane, octane, decane, dodecane, tetradecane,
hexadecane, and also (6) water.
[0041] According to the present invention, referring to FIG. 1
Step A 101 during the process of synthesizing nanorods, a metal-surfactant
complex is formed at the temperature between 20.degree. C. and 200.degree.
C.
[0042] According to the present invention, the molar ratio of said
metal precursor to said surfactant is maintained between 1:0.1 and
1:1000.
[0043] According to the present invention, referring to FIG. 1
Step B 102 the following chalcogenide reagents are used for synthesizing
nanorods of metal chalcogenides including elemental sulfur (S.sub.8),
selenium (Se), tellurium (Te), trioctylphosphine selenide (TOPSe),
trioctylphosphine sulfide (TOPS) and trioctylphosphine telluride
(TOPTe).
[0044] According to the present invention, referring to FIG. 1
Step B 102 in order to synthesize oxide nanorods, the oxidants
including typically oxygen (O.sub.2), hydrogen peroxide (H.sub.2O.sub.2),
amine N-oxide such as pyridine N-oxide and trimethylamine N-oxide
are used. And also in order to synthesize metal nanorods, according
to the present invention, the reductants including typically sodium
borohydride (NaBH.sub.4), lithium aluminum hydride (LiAlH.sub.4),
lithium triethylborohydride (super-hydride, LiB(C.sub.2H.sub.5).sub.3H),
tetraalkylammonium borohydride (R.sub.4NBH.sub.4) and hydrogen gas
are used.
[0045] According to the present invention, referring to FIG. 1
Step B 102 said metal-surfactant complexes are injected into a
surfactant solution at a temperature between 0.degree. C. and 400.degree.
C.
[0046] According to the present invention, referring to FIG. 1
Step B 102 said metal-surfactant complexes are injected into a
solution using a syringe pump at an injection rate between 1 mL/hr
and 100 mL/hr.
[0047] According to the present invention, referring to FIG. 1
Step C 103 said reaction process is carried out at a temperature
between 0.degree. C. and 400.degree. C.
[0048] According to the present invention, referring to FIG. 1
Step C 103 said reaction process of the reaction mixture is carried
out for a time duration between 1 minute and 72 hours.
[0049] According to the present invention, referring to FIG. 1
Step D 104 said nanorods are separated and precipitated by adding
a poor solvent, where the poor solvent is a solvent that does not
disperse said nanorods effectively, but induces precipitation of
said nanorods readily.
[0050] According to the present invention, the desired nanorods
are retrieved by centrifuging.
BEST MODES FOR CARRYING OUT THE PRESENT INVENTION
[0051] According to the present invention, the nanorods synthesized
by using the method disclosed in the present invention exhibit a
narrow size-distribution in diameter and high crystallinity. The
embodiments and the corresponding results of the best modes for
carrying out the present invention are presented in detail in the
following.
Embodiment 1-A
Synthesis of Uniform Iron Phosphide (Fe.sub.2P) Nanorods: 1-A
[0052] The first exemplary embodiment is to synthesize iron phosphide
(Fe.sub.2P) nanorods uniform in diameter according to the present
invention disclosed here. A volume of 10 mL of Fe-TOP complex solution
prepared by mixing 0.2 mL of iron pentacarbonyl (Fe(CO).sub.5) or
1.52 mmol and 10 mL of trioctylphosphine (TOP) is injected into
a mixture containing 10 mL of octylether and 2 mL of oleylamine
at 300.degree. C. using a syringe pump at the injection rate of
10 mL/hr. A TEM (Transmission Electron Microscope) image of the
resulting nanorods of iron phosphide (Fe.sub.2P) is shown in FIG.
1-A-1 and exhibits that the resulting iron phosphide (Fe.sub.2P)
nanorods have the size of 5 nm (diameter).times.88 nm (length) and
are uniform in diameter. A HRTEM (High Resolution Transmission Electron
Microscope) image shown in FIG. 1-A-2 indicates that the resulting
nanorods are highly crystalline, and also that the direction of
the growth is along the <002> direction. A corresponding X-ray
diffraction (XRD) graph shown in FIG. 1-A-3 reveals that the resulting
nanorods have a hexagonal iron phosphide (Fe.sub.2P) crystal structure
with the space group P{overscore (6)}2m.
Embodiment 1-B
Synthesis of Uniform Iron Phosphide (Fe.sub.2P) Nanorods: 1-B
[0053] Under the same reaction conditions employed in Embodiment
1-A with the exception of the reduced injection rate of the syringe
pump at 5 mL/hr, iron phosphide (Fe2P) nanorods are synthesized.
An exemplary TEM image of the resultant nanorods shown in FIG. 1-B
reveals that the average size is 6 nm (diameter).times.107 nm (length)
and the diameters are exceptionally uniform.
Embodiment 1-C
Synthesis of Uniform Iron Phosphide (Fe.sub.2P) Nanorods: 1-C
[0054] Under the same reaction conditions employed in Embodiment
1-A with the exception of the reduced injection rate of the syringe
pump at mL/hr, iron phosphide (Fe2P) nanorods are synthesized. An
exemplary TEM image of the resultant nanorods shown in FIG. 1-C
reveals that the average size is 6 nm (diameter).times.290 nm (length)
and the sizes in diameter are exceptionally uniform.
Embodiment 1-D
Synthesis of Uniform Iron Phosphide (Fe.sub.2P) Nanorods: 1-D
[0055] Under the same reaction conditions employed in Embodiment
1-A with the exception of using 2 mL of dioctylamine instead of
2 mL of oleylamine, iron phosphide (Fe.sub.2P) nanorods are synthesized.
An exemplary TEM image of the resultant nanorods shown in FIG. 1-D
reveals that the average size is 9 nm (diameter).times.50 nm (length)
and the diameters are exceptionally uniform.
Embodiment 1-E
Synthesis of Uniform Iron Phosphide (Fe.sub.2P) Nanorods: 1-E
[0056] Under the same reaction conditions employed in Embodiment
1-A with the exception of using 2 mL of octadecylamine instead of
2 mL of oleylamine, iron phosphide (Fe.sub.2P) nanorods are synthesized.
An exemplary TEM image of the resultant nanorods shown in FIG. 1-E
reveals that the average size is 18 nm (diameter).times.75 nm (length)
and the diameters are exceptionally uniform.
Embodiment 1-F
Synthesis of Uniform Iron Phosphide (Fe.sub.2P) Nanorods: 1-F
[0057] Under the same reaction conditions employed in Embodiment
1-A with the exception of using 2 mL of hexadecylamine instead of
2 mL of oleylamine, iron phosphide (Fe.sub.2P) nanorods are synthesized.
An exemplary TEM image of the resultant nanorods shown in FIG. 1-F
reveals that the average size is 5 nm (diameter).times.160 nm (length)
and the sizes in diameter are exceptionally uniform.
Embodiment 2
Synthesis of Uniform Cobalt Phosphide (CO.sub.2P) Nanorods
[0058] As an exemplary embodiment of synthesizing cobalt phosphide
(CO.sub.2P) nanorods uniform in diameter according to the present
invention disclosed here, a stock solution is prepared by reacting
0.27 g of Co(acac).sub.2 and 10 mL of TOP at 70.degree. C. The color
of the stock solution changed from pink to violet after complete
dissolution of the precursor, indicating that the Co-TOP complex
is formed. The stock solution is continuously delivered to the round-bottomed
flask containing a mixture of 10 mL of octyl ether and 1.47 g of
hexadecylamine at 300.degree. C. through a rubber septum via a syringe
pump. The continuous delivery of the stock solution produced a deep
black solution in few minutes. The temperature of the resulting
solution is maintained at 300.degree. C. for one hour. The resulting
cobalt phosphide (CO.sub.2P) nanorods are separated and precipitated
by adding 50 mL of ethanol, and retrieved by centrifugation. The
collected powdery substance is dispersible in many organic solvents.
A TEM image of the resulting cobalt phosphide (CO.sub.2P) nanorods,
synthesized by means of the methods disclosed here according to
the present invention, is shown in FIG. 2-A. The TEM image reveals
that cobalt phosphide (CO.sub.2P) nanorods have an average size
of 5 nm (diameter).times.15 nm (length). A high resolution TEM (HRTEM)
image of the cobalt phosphide (CO.sub.2P) nanorods shown in FIG.
2-B indicates that the nanorods are highly crystalline and that
the direction of the growth is in the direction of <002>.
An X-ray diffraction (XRD) graph of the resultant cobalt phosphide
(CO.sub.2P) nanorods shown in FIG. 2-C reveals that the resulting
nanorods have a hexagonal cobalt phosphide (CO.sub.2P) crystal structure.
Embodiment 3
Synthesis of Uniform Manganese Phosphide (MnP) Nanorods
[0059] As an exemplary embodiment of synthesizing manganese phosphide
(MnP) nanorods uniform in diameter according to the present invention,
a stock solution is prepared by mixing 0.148 g of Mn.sub.2(CO).sub.10
or 0.38 mmol and 5 mL of trioctylphosphine (TOP) at 70.degree. C.
This stock solution is continuously injected into the 5 g of trioctylphosphine
oxide (TOPO) solution while being vigorously stirred at 330.degree.
C. using a syringe pump at the injection rate of 10 mL/hr. The temperature
of the resulting solution is maintained at 330.degree. C. for one
hour, and thereafter cooled down to 60.degree. C. By adding 50 mL
of anhydrous ethanol (or acetone) to the resulting solution, the
nanorods in the state of flocculation are formed. By centrifugation,
the flocculates are separated and retrieved from the supernatant.
These flocculates are washed two times with 50 mL of ethanol to
remove excess TOP and TOPO. The resultant precipitate is dried under
vacuum, and a substance in a powder form is obtained. The resulting
powdery manganese phosphide nanorods (MnP) are found to be readily
dispersible in organic solvents such as hexane, toluene or chloroform.
A TEM image of the resulting manganese phosphide (MnP) nanorods,
synthesized by means of the methods disclosed here according to
the present invention, is as shown in FIG. 3-A, exhibiting that
the resulting manganese phosphide (MnP) nanorods have an average
size of 5 nm (diameter).times.16 nm (length). An X-ray diffraction
(XRD) graph shown in FIG. 3-B reveals that the resulting manganese
phosphide (MnP) nanorods have a hexagonal manganese phosphide (MnP)
structure.
Embodiment 4
Synthesis of Uniform Zinc Oxide (ZnO) Nanorods
[0060] As an exemplary embodiment of synthesizing zinc oxide (ZnO)
nanorods uniform in diameter according to the present invention
disclosed here, 5 g of trioctylphosphine oxide (TOPO) is heated
to 330.degree. C. as the first preparation step. A stock solution
is prepared by mixing 0.5 g of Zn(OAc).sub.2.2H.sub.20 or 2.27 mmol
and 2 mL of anhydrous ethanol in the presence of 10 mL of trioctylphosphine
(TOP) pre-heated to 80.degree. C. under a nitrogen atmosphere. By
using a syringe pump, this stock solution is injected at the rate
of 10 mL/hr into the TOPO solution already pre-heated to 330.degree.
C. After the injection, the temperature of the resulting reaction
mixture is maintained at 330.degree. C. for one hour. After the
reaction, the resulting mixture is cooled to 50.degree. C. and then
poured into methanol, producing a white precipitate. The resulting
precipitate is isolated by centrifugation and washed twice with
methanol, resulting in a white powdery substance or zinc oxide (ZnO)
nanorods which are easily re-dispersed in toluene or cyclohexane.
A TEM image of the resulting zinc oxide (ZnO) nanorods, synthesized
by means of the methods presented here according to the present
invention, is as shown in FIG. 4-A. The TEM image indicates that
the synthesized zinc oxide (ZnO) nanorods have a size of 8 nm (diameter).times.140
nm (length). A HRTEM image shown in FIG. 4-B reveals that the resulting
zinc oxide (ZnO) nanorods are highly crystalline and that the direction
of the growth is along the <002> direction. An X-ray diffraction
(XRD) graph of the resultant zinc oxide (ZnO) nanorods is shown
in FIG. 4-C, indicating that the nanorods have a hexagonal zinc
oxide (ZnO) structure.
[0061] The procedures and results presented here are merely illustrative
examples of carrying out the implementation of the underlying ideas
and procedures of the present invention, and the exemplary embodiments
given above are neither intended for exhaustively illustrating the
basic ideas and procedures nor limiting the scope of the present
invention. Furthermore, those who are familiar with the art related
to the present invention should be able to easily derive variations
and modifications of the underlying ideas and procedures of the
present invention disclosed here.
INDUSTRIAL APPLICABILITY
[0062] Uniform and highly crystalline nanorods synthesized according
to the present invention display very unique, excellent and consistent
electrical, magnetic as well as optical properties. In particular,
the optical property due to excellent uniformity in diameter demonstrated
by the nanorods produced by the synthetic method disclosed by the
present invention is very attractive for such applications as display
devices and biological labeling. Excellent uniformity in diameter
of the magnetic nanorods synthesized according to the present invention
is also attractive particularly for the applications in the area
of the ultra-high density magnetic storage media. |