Effective octadecylamine system for nanocrystal synthesis

Article abstract of DOI:10.1021/ic200485v

New chemical reactions and synthetic systems are of key importance for materials fabrication. In this work, we reported a facile and effective octadecylamine (ODA) synthetic system for various nanocrystals including metals, mixed metal oxides, metal/metal

Full text of DOI:10.1021/ic200485v

ARTICLE
pubs.acs.org/IC
Effective Octadecylamine System for Nanocrystal Synthesis
Dingsheng Wang and Yadong Li*
Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China
S Supporting Information
b
ABSTRACT: New chemical reactions and synthetic systems are of key importance for
materials fabrication. In this work, we reported a facile and effective octadecylamine
(
ODA) synthetic system for various nanocrystals including metals, mixed metal
oxides, metal/metal oxide heterostructured nanocrystals, intermetallics, and alloys.
We found that the products were mainly determined by metal ions used in our
synthetic system: noble metal ions led to the formation of metals; two kinds of non-
noble metal ions led to the formation of mixed metal oxides; silver ions and non-noble
metal ions led to the formation of metal/metal oxide heterostructured nanocrystals;
non-noble metal ions and noble metal (excluding Ag) ions led to the formation of
intermetallics and alloys. The difference was attributed to different ability to attract electrons from ODA solvent among these
metal ions. This effective system provides a general strategy for various nanocrystals which would find potential applications in
many significant fields.
3
9
’
INTRODUCTION
metal oxide nanocrystals. In our synthesis, inorganic salts (metal
nitrates) were used as precursors and ODA was adopted as single
solvent functioning simultaneously as surfactant and reducing
agent. The reaction was performed in air and finished within a
few minutes. Now, the question is why different metal ions lead
to the formation of different kinds of products in ODA solvent.
As we know, at the nanoscale, materials exhibit very interesting
size- and shape-dependent optical, electrical, magnetic, and
chemical properties that differ drastically from the bulky ones.
Therefore, synthesis of nanomaterials has been among the key
research topics in the field of nanoscience and nanotechnology
over the past decades.
nanorelated fields have achieved successful synthesis of nearly all
kinds of nanomaterials with controllable composition, structure,
size, and morphology.
industrial applications of nanomaterials, much effort is still
required in the exploration of new synthetic process for large-
scale synthesis of nanocrystals in a facile, efficient, and econo-
mical way.
In 1993, high-quality cadmium chalcogenide semiconductor
quantum dots were successfully synthesized by Murray, Norris,
and Bawendi for the first time. The method involved the
injection of a “cold” solution of precursor molecules (organo-
metallic CdMe and TOPSe) into a hot coordinating alkyl
solvent (TOPO). This hot-injection method represented a clear
break with previous wet-synthetic methods, which opened the
door to wide preparation of high-quality monodisperse nano-
crystals. In the following years, many research groups proposed
1
ꢀ5
4
0
6
ꢀ15
According to the investigation results of Alivisatos’ group,
Up to now, worldwide scientists in
ODA can offer electrons at an elevated temperature (eq 1). So,
the ODA solvent has some reducing power at high temperature,
and the ability to attract electrons of metal ions determines the
products. As we know, the order of the ability to attract electrons
of metal ions is Zn < Co < Ni < Ag < Pd < Pt
Au . Since Ni cannot attract electrons from ODA and thus
NiO is the product, it is easy to understand that all metal ions
whose abilities to attract electrons are weaker than that of Ni
cannot be reduced and corresponding metal oxides are the
products. Since Ag can attract electrons from ODA and is
reduced to Ag, we can deduce that all metal ions whose abilities to
1
6ꢀ29
However, given the demand in future
2
þ
2þ
2þ
þ
2þ
4þ
<
3
þ 41
2þ
2
þ
þ
30
þ
attract electrons are stronger than that of Ag can be reduced to
2
metals (eq 2). Furthermore, various nanomaterials can be
synthesized when two kinds of inorganic salts are used as
reactants together in this electron-rich system. If we introduce
two kinds of non-noble metal inorganic salts into this system,
mixed metal oxide nanocrystals (NiꢀCoꢀO, ZnꢀCoꢀO, Cuꢀ
31ꢀ38
numerous adaptations to this synthesis route.
Monodis-
MnꢀO, etc.) will be obtained (eq 3), if we introduce AgNO and
3
perse metal, semiconductor, and metal oxide nanocrystals were
synthesized using various organometallic precursors (metal
acetylacetonates, metal cupferronates, metal alkoxides, metal
carbonyls, etc.) and mixed organic solvents (TOPO, HPA, oleic
acid, oleylamine, hexadecanediol, dodecanethiol, etc.) in an inert
atmosphere. However, complex operation, high cost, and low
production limited the industrial applications of nanocrystals.
Recently, we developed an improved hot-injection method for
the preparation of monodisperse Ag nanoparticles and transition
non-noble metal inorganic salts into this system, metal/metal
oxide heterostructured nanocrystals (AgꢀCoO, AgꢀNiO,
AgꢀFe O , etc.) will be obtained (eq 4), and if we introduce
2
3
noble metal (excluding Ag) inorganic salts and non-noble metal
inorganic salts into this system, intermetallic and alloyed
Received: March 9, 2011
Published: May 11, 2011
r 2011 American Chemical Society
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|Inorg. Chem. 2011, 50, 5196–5202

Inorganic Chemistry
ARTICLE
Figure 1. Synthesis of various nanocrystals in ODA solvent.
nanocrystals (CdPt , ZnPt , CoPd , CoRh, CuRh, NiRu, etc.)
3
3
2
will be obtained (eq 5). All the results are summarized in
Figure 1.
Δ
f
RNH2
s
RNH2 þ eꢀ
þ
ð1Þ
ð2Þ
Figure 2. TEM images of (a) Au, (b) Pd, (c) Pt, and (d) Ir nanocrystals.
ODA
xþ
xþ
M
s
f
M ðM ¼ Ag, Au, Pd, Pt, Ir, Rh, Ru, etc:Þ
mixture was magnetically stirred for 10 min at this temperature. After
reaction, products were collected at the bottom of the beaker.
Characterization of Products. Powder X-ray diffraction (XRD)
patterns of all the products obtained in this work were recorded with a
Bruker D8-advance X-ray powder diffractometer with monochroma-
tized Cu KR radiation (λ = 1.5406 Å). The size and morphology of all
the products synthesized in this work were determined by using Hitachi
model H-800 transmission electron microscope (TEM), JSM-6301F
scanning electron microscope (SEM), and JEOL-2010F high-resolution
transmission electron microscope (HRTEM). The specimen was pre-
pared as follows: a small amount of product was dispersed in cyclohex-
ane, and then one drop of the resulting suspension was transferred onto a
standard holey carbon-covered copper microgrid and dried at room
temperature in air.
ODA
þ Nyþ
M
s
f
M ꢀ N
ꢀ
O ðM, N ¼ Mn, Fe, Co, Ni, Cu, Zn, etc:Þ
ð3Þ
ODA
s M
f
xþ
þ Nyþ
M
ꢀ
NO ðM ¼ Ag; N ¼ Mn, Fe, Co, Ni, Cu, Zn, etc:Þ
ð4Þ
ODA
xþ
þ Nyþ
M
s
f
MN ðM ¼ Au, Pd, Pt, Ir, Rh, Ru, etc:;
N ¼ Mn, Fe, Co, Ni, Cu, Zn, etc:Þ ð5Þ
’
EXPERIMENTAL SECTION
’ RESULTS AND DISCUSSION
Synthesis of Noble Metal Nanocrystals. All the reagents used
Noble Metal Nanocrystals. We employ synthesis of Au
nanoparticles as an example to introduce the preparation of
noble metal nanocrystals in ODA system (eq 2). In our synthesis,
in this work, including various kinds of metal inorganic salts, ODA,
ethanol, and cyclohexane, were of analytical grade from the Beijing
Chemical Factory, China.
In a typical synthesis of Au nanocrystals, 10 mL of ODA was added
into a 50 mL beaker in air. The resulting solution was heated up to 160 °C,
4
and then 0.05 g of HAuCl was added. The mixture was magnetically
stirred for 10 min. After reaction, particles were collected at the bottom of
the beaker. The collected products were washed several times with ethanol
and then dispersed in nonpolar solvent such as cyclohexane.
HAuCl was dissolved in a warm solvent of ODA. After 10 min of
4
magnetic stirring, nearly monodisperse Au nanoparticles could
be obtained. Figure S1 (Supporting Information) shows the
XRD pattern of as-synthesized Au nanocrystals. The peaks at
3
(
2
8.2°, 44.4°, 64.6°, and 77.6° 2θ correspond to the (111), (200),
220), and (311) reflections of Au, respectively (JCPDS 65-
870). Slight peak broadening of the XRD peaks was primarily
Synthesis of Mixed Metal Oxide Nanocrystals. In a typical
synthesis of NiꢀCoꢀO nanocrystals, 10 mL of ODA was added into a
due to the small particle size. TEM image of the products is
depicted in Figure 2a. We can see that as-obtained Au nanopar-
ticles have an average diameter of 10 nm. The synthetic process
for other noble metal nanocrystals was similar to that for Au
nanoparticles. Figure 2b shows the TEM image of as-synthesized
Pd nanocrystals which display worm-like morphology with an
average diameter of 5 nm and a length of 20ꢀ50 nm. Pt nano-
crystals obtained in the ODA system show spherical morphology
5
0 mL beaker in air. The resulting solution was heated up to 200 °C, and
3 2 3 2
then 1 mmol of Ni(NO ) and 1 mmol of Co(NO ) were added. The
mixture was magnetically stirred for 10 min. After reaction, products
were collected at the bottom of the beaker.
Synthesis of Metal/Metal Oxide Heterostructured Nano-
crystals. In a typical synthesis of Ag/CoO nanocrystals, 10 mL of ODA
was added into a 50 mL beaker in air. The resulting solution was heated
(
Figure 2c). These Pt spheres have an average size of 50 nm and
3 3 2
up to 200 °C, and then 1 mmol of AgNO and 1 mmol of Co(NO )
consist of smaller particles. Figure 2d shows the TEM image of as-
synthesized Ir nanoflowers with an average size of 20 nm. Ru and
Rh nanocrystals could also be prepared in this synthetic system
were added. The mixture was magnetically stirred for 10 min. After
reaction, products were collected at the bottom of the beaker.
Synthesis of Intermetallic and Alloyed Nanocrystals. In a
typical synthesis of CoPd nanocrystals, 10 mL of ODA was added into a
when RuCl
We note that the order of the ability to attract electrons of
3 3
and RhCl were used as the reactants, respectively.
2
5
0 mL beaker in air. The resulting solution was heated up to 160 °C.
Then, 0.2 mmol of PdCl and 0.1 mmol of Co(NO were added. After
the reactants were dissolved, the system was heated up to 280 °C. The
2
þ
4þ
3þ
3þ
)
2
metal ions is Pd < Pt < Au , indicating that Au has a
2
3
2þ
greater tendency to attract electrons from ODA solvent than Pd
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Figure 3. (a) TEM image and (b) EDS spectrum of NiꢀCoꢀO nanocrystals. (c) The line elemental EDS data across one single sphere.
4
þ
3þ
and Pt . So, under the same condition, Au should be more
2
þ
4þ
easily reduced than Pd and Pt , which has been confirmed
by the preceding experimental results. In the ODA system, Au
nanocrystals can be obtained at temperature as low as 160 °C,
while the reaction temperatures for Pd and Pt are 220 and
2
00 °C, respectively.
Mixed Metal Oxide Nanocrystals. When two kinds of non-
noble metal inorganic salts were used as the reactants simulta-
neously, mixed metal oxide nanocrystals could be prepared in the
ODA system (eq 3). For example, after 1:1 molar ratio of
Ni(NO ) and Co(NO ) were dissolved in a warm solvent of
3
2
3 2
ODA, 10 min of magnetic stirring at 200 °C led to the formation
of NiꢀCoꢀO nanocrystals. The typical TEM image of NiꢀCoꢀO
nanocrystals is depicted in Figure 3a. We can see that nearly
monodisperse NiꢀCoꢀO spheres with an average diameter of
5
0 nm could be obtained via this facile strategy. From the
HRTEM image of a single sphere (Figure 3a, inset), it is obvious
that these spheres are composed of smaller nanoparticles. The
SAED pattern (Figure 3a, inset) also confirms that the sphere is
polycrystalline. An EDS experiment was performed on an as-
synthesized sample. From the spectrum shown in Figure 3b, we
can see that Ni and Co peaks can be observed together, and the
composition confirmed by EDS is nearly Ni0.53Co0.47O. The line
elemental EDS data (Figure 3c) across one single sphere show a
rather homogeneous distribution of both Ni and Co in each sphere.
Since both Ni and Co cannot be reduced by ODA sol-
vent, it is easy to understand the formation of mixed metal oxides
when Ni and Co salts react in the ODA system. Similarly, we can
also synthesize other mixed metal oxide nanocrystals. Figure S2
Figure 4. (a) TEM image, (b) EDS spectrum, and (c) HAADF-STEM
image of Ag/CoO nanocrystals. (d) The line elemental EDS data across
one single particle.
2
þ
2þ
generated by the copper grid, further confirming the composi-
tion of as-obtained samples. TEM image (Figure 4a) and high-
angle annular dark-field scanning transmission electron mi-
croscopy (HAADF-STEM) image (Figure 4c) display Ag/
CoO nanocrystals showing spindlelike morphology. The line
elemental EDS data (Figure 4d) across a single particle further
confirm that the tip is Ag and the tail is CoO.
(
Supporting Information) shows the TEM images of as-obtained
ZnꢀCoꢀO, CuꢀCoꢀO, CuꢀMnꢀO, and NiꢀMnꢀO nano-
crystals. Additionally, we can even synthesize trimetallic mixed
oxide nanocrystals (e.g., Co Ni Mn O) by using three kinds of
x
y
z
As we know, noble metal supported catalysts are the most
important catalysts in industrial applications. The traditional
preparation method for noble metal supported catalysts usually
contains two steps. The first step is to synthesize noble metal
nanoparticles and metal oxide nanocrystals (used as the supports),
respectively. The next step is to load noble metal nanoparticles
onto the supports. Synthesis of metal/metal oxide nanocryst-
als in the ODA system provides a one-step method for prepa-
ration of noble metal supported catalysts which will find
applications in catalysis.
transition metal inorganic salts as precursors. These mixed metal
oxide nanocrystals are believed to be applicable in Li ion battery
as electrode materials or in catalysis as the supports.
Metal/Metal Oxide Nanocrystals. If AgNO and non-noble
3
metal inorganic salts (e.g., Co(NO ) , Ni(NO ) , Fe(NO ) ,
3
2
3 2
3 3
etc.) were used as the reactants together, we could synthesize
metal/metal oxide heterostructured nanocrystals (AgꢀCoO,
AgꢀNiO, AgꢀFe O , etc.) in the ODA system (eq 4). Here,
2
3
we take AgꢀCoO as an example to describe the results. The XRD
pattern in Figure S3 (Supporting Information) shows the resulting
products composed of Ag and CoO mixture. From the EDS
spectrum shown in Figure 4b, we can see that only Ag, Co, and
O peaks are observed together with the Cu peak which was
þ
Intermetallic and Alloyed Nanocrystals. Because Ag can
be reduced while non-noble metal ions cannot be reduced by
ODA solvent, it is also easy to understand the formation of Ag/
þ
metal oxide nanocrystals when Ag and non-noble metal ions
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Inorganic Chemistry
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Figure 5. (a) SEM image of CoPd
2
nanocrystals; (b and d) HAADF-STEM images of CoPd
2
nanocrystals. (c) The elemental profiles for Co and Pd
obtained by recording EDS signal intensities along the line shown in part b; (e) the elemental profiles for Co and Pd obtained by recording EDS signal
intensities along the line shown in part d.
Figure 6. TEM images of (a) CoRh, (b) CuRh, (c) NiRh, and (d) NiRu
nanocrystals.
Figure 8. (a) XRD patterns of as-synthesized FeꢀPt nanomaterials and
TEM images of FeꢀPt nanocrystals: (b) 1#, (c) 2#, (d) 3#.
react in the ODA system. However, when other noble metal ions
and non-noble metal ions react in ODA solvent, the products are
not noble metal/metal oxide nanocrystals; instead, intermetallics
and alloys form (eq 5). For example, after 2:1 molar ratio of
PdCl and Co(NO ) were dissolved in a warm solvent of ODA,
2
3 2
1
0 min of magnetic stirring at 280 °C led to the formation of
CoPd nanocrystals. Figure S4 (Supporting Information) shows
2
the XRD pattern of as-synthesized intermetallic CoPd nano-
2
crystals. The characteristic peaks match exactly with the standard
JCPDS card 50-1437 of CoPd . The typical SEM image of
2
intermetallic CoPd nanocrystals is depicted in Figure 5a. We
2
can see that nearly monodisperse CoPd spheres with an average
2
diameter of 100 nm could be obtained via this facile strategy. EDS
experiment was performed on this sample. From the spectrum
shown in Figure S5 (Supporting Information), we can see that
only Co and Pd peaks are observed together with the Cu peak
which was generated by the copper grid. From the HAADF-STEM
Figure 7. TEM images of (a) AgAu, (b) AgPt, (c) AuPt, and (d) AuPdPt
nanocrystals.
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Figure 9. (a) XRD patterns of as-synthesized NiꢀPt nanomaterials and TEM images of NiꢀPt nanocrystals: (b) 1#; (c) 2#; (d) 3#; (e) 4#; (f) 5#.
with a similar chemical process. Figure 6 shows the TEM image of
as-prepared CoRh, CuRh, NiRh, and NiRu nanocrystals.
Since noble and non-noble metal ions can be coreduced by
ODA solvent, it should be much easier to synthesize interme-
tallics and alloys of two noble metals in the ODA system. The
experimental results confirmed this viewpoint. Figure S6
(
Supporting Information) shows the XRD pattern of as-synthe-
sized AgAu nanocrystals. The characteristic peaks match exactly
with the standard JCPDS card 65-8424 of intermetallic AgAu.
The typical TEM image of intermetallic AgAu nanocrystals is
depicted in Figure 7a. We can see that nearly monodisperse AgAu
nanoparticles with an average diameter of 10 nm could be
obtained via this facile strategy. Similarly, AgPt, AuPt, and even
trimetallic AuPdPt alloys can also be easily synthesized in this
system. XRD measurements (Supporting Information, Figure
S7ꢀ9) confirm the formation of these alloys, and TEM images
(
Figure 7bꢀd) show that as-obtained alloys are nearly mono-
disperse nanoparticles.
3
Figure 10. TEM images of ZnPt nanocrystals with controllable
morphology.
On the other hand, the composition, size, and morphology of
intermetallic and alloyed nanocrystals could be well controlled by
adjusting the reaction parameters in the ODA system. With
FeꢀPt as an example, the composition was mainly controlled by
the molar ratio of Fe and Pt precursors. When the molar ratio was
1:1, intermetallic FePt could be synthesized. XRD measurements
were used to identify the internal crystalline structures of the
products. It can be seen form Figure 8a (1#) that cubic FePt
(JCPDS 65-9122) was obtained. When the molar ratio was 1:3,
image (Figure 5b), it is clear that CoPd spheres are composed
2
of smaller nanoparticles. The line elemental EDS data
(
Figure 5c) across one single sphere show a rather homo-
geneous distribution of both Co and Pd in each sphere. The
line-scanning profile across one single particle (Figure 5e)
further confirms the homogeneous distribution of Co and Pd.
The formation of CoPd in ODA solvent is a novel and inge-
intermetallic FePt
3
could be synthesized. XRD measurement
2
2
þ
2þ
nious chemical process. Why can Co and Pd be coreduced
since Co cannot attract electrons from ODA solvent? Accord-
ing to the very recent work in our group, Au and transition
metal ions (Co , Ni ) can be coreduced in ODA solvent; that
(Figure 8a, 2#) confirmed that cubic FePt
3
(JCPDS 29-0716)
2
þ
was obtained. When the molar ratio was 1:7, FeꢀPt alloy could
be obtained (Figure 8a, 3#). EDS experiment was performed on
FeꢀPt alloy. From the spectrum shown in Figure S10 (Supporting
Information), we can see that only Fe and Pt peaks are obser-
ved together with the Cu peak which was generated by the
copper grid. The composition of FeꢀPt alloy confirmed by
EDS is nearly Fe0 Pt (SupportingInformation, Table S1). The
39c
3þ
2
þ
2þ
is, Au first reduced by ODA can transfer electrons from ODA to
2
þ
2þ
Co or Ni and induce their reduction. Similarly, Pd first
2
þ
reduced by ODA can also induce the reduction of Co in the
ODA system. After Pd and Co are reduced, the kinetic parameters
.12
0.88
lead to the formation of intermetallic CoPd . Then, various
intermetallic and alloyed nanocrystals can be easily synthesized
size and morphology of FeꢀPt nanomaterials with different
2
compositions were examined by TEM images. As seen in
5
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Inorganic Chemistry
ARTICLE
3
Figure 11. TEM images of CdPt nanocrystals with controllable size.
Figure 8bꢀd, all the three samples display polygonal shape
and their sizes increase as Pt content increases.
The experimental results for NiꢀPt nanomaterials are similar
to those for FeꢀPt nanomaterials. XRD measurements were
used to identify the internal crystalline structures of various
NiꢀPt nanomaterials obtained with different molar ratios of Pt
and Ni precursors. It can be seen from Figure 9a that, as more Ni
is added, all the peaks are shifted slightly to larger 2θ values,
indicative of decreased d-spacing and contraction of the lattice
constant, due to the incorporation of increasing amounts of the
smaller Ni atoms into the Pt fcc lattice. No Pt or Ni peaks appear,
indicating that NiꢀPt intermetallic nanostructures or alloys
formed. Figure 9bꢀf shows the TEM images of series of NiꢀPt
nanomaterials with different compositions. All the samples dis-
play nearly monodisperse size and platelike shape. Other alloys
with series of compositions could also be prepared via similar
procedures. For example, we could prepare CoꢀPt nanomater-
ials with controlled compositions by using different molar ratios
of Co and Pt precursors (Supporting Information, Figure S11).
The morphology of nanocrystals was mainly controlled by
experimental conditions including reaction temperature and
Figure 12. TEM images of CuPd nanocrystals with controllable size.
(Supporting Information) shows the XRD pattern of as-synthe-
reaction time. We employ ZnPt as an example to show shape-
sized intermetallic CdPt (JCPDS 65-8871) nanocrystals. The
3
3
controlled synthesis of intermetallic and alloyed nanocrystals.
Figure S12 (Supporting Information) shows the XRD patterns of
typical TEM image of intermetallic CdPt nanocrystals is de-
3
picted in Figure 11a. We can see that nearly monodisperse CdPt3
nanoparticles with an average diameter of 10 nm could be
obtained via this facile strategy. Increasing the concentration of
as-synthesized ZnPt products under different conditions. For all
3
the patterns, the peaks at 40.1°, 46.6°, and 68.1° 2θ correspond
to the (111), (200), and (220) reflections of ZnPt , respectively
reactants would lead to the formation of CdPt nanocrystals with
3
3
(JCPDS 65-3257), indicating the successful synthesis of ZnPt3
smaller size. When 0.02 mmol of Cd(Ac) and 0.06 mmol of
2
intermetallic compound. However, TEM results (Figure 10)
H PtCl reacted at 260 °C for 10 min, CdPt nanoparticles with
2
6
3
show that the morphology of intermetallic ZnPt nanocrystals
an average diameter of 5 nm (Figure 11b) were prepared.
3
obtained under different conditions are different from each other.
Furthermore, CdPt nanoparticles with an average diameter of
3
When 1:3 molar ratio of Zn(NO ) and H PtCl reacted at
3 nm (Figure 11c) could be synthesized when 0.03 mmol of
3
2
2
6
2
40 °C for 10 min, ZnPt nanocubes were obtained (Figure 10a).
Cd(Ac) and 0.09 mmol of H PtCl reacted at 260 °C for 10 min.
3
2
2
6
We can see that they are likely to evolve to flowers. When the
reaction was performed first at 240 °C for 5 min and then at 260 °C
for another 5 min, ZnPt nanocubes could completely evolve to
The reaction temperature and time are also key parameters in
determining the size of intermetallic and alloyed nanocrystals.
CuPd was employed as an example to show size-controlled
synthesis of intermetallic and alloyed nanocrystals via adjusting
the reaction temperature and time. After 1:1 mol ratio of PdCl2
and Cu(NO ) were dissolved in a warm solvent of ODA, 10 min
3
nanoflowers (Figure 10b). Figure 10c shows TEM image of ZnPt3
nanospheres when the starting materials reacted at 260 °C for 10
min. It can be seen that these spheres consist of smaller particles.
When the reaction was performed at higher temperature (280 °C)
3
2
of magnetic stirring at 240 °C led to the formation of CuPd
nanocrystals. XRD measurement (Supporting Information, Fig-
ure S14) confirmed the successful synthesis of CuPd intermetallic
compound (JCPDS 48-1551). The typical TEM image depicted in
Figure 12a shows that nearly monodisperse CuPd nanoparticles
with an average diameter of 10 nm were prepared. If the reaction
time was prolonged to 15 min, we could obtain intermetallic
CuPd nanoparticles with larger size (∼14 nm, Figure 12b).
for 10 min, intermetallic ZnPt nanocrystals with worm-like
3
morphology could be synthesized (Figure 10d).
The size of intermetallic and alloyed nanocrystals could be
controlled by the concentration of reactants. For example, after
0
.01 mmol of Cd(Ac) and 0.03 mmol of H PtCl were dissolved
2 2 6
in a warm solvent of ODA, 10 min of magnetic stirring at
2
60 °C led to the formation of CdPt nanocrystals. Figure S13
3
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When the starting materials reacted at 220 °C for 10 min,
(14) Duan, X. F.; Huang, Y.; Cui, Y.; Wang, J. F.; Lieber, C. M.
Nature 2001, 409, 66.
CuPd nanoparticles with an average diameter of 16 nm
(
15) Peng, X. G.; Manna, L.; Yang, W. D.; Wickham, J.; Scher, E.;
Kadavanich, A.; Alivisatos, A. P. Nature 2000, 404, 59.
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(
Figure 12c) could be synthesized. Figure 12d shows the
TEM image of CuPd nanoparticles with an average diameter of
0 nm obtained when the reaction was performed at 220 °C
for 15 min.
(
2
2
(
’
SUMMARY
(
In conclusion, an effective ODA synthetic system for the
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preparation of various nanocrystals including metals, mixed
metal oxides, metal/metal oxide heterostructured nanocrystals,
intermetallics, and alloys has been successfully developed in the
present study. Nontoxic and inexpensive metal inorganic salts
were employed as reagents. The composition, size, and morphol-
ogy of nanocrystals can be easily controlled by adjusting the
experimental parameters including the molar ratio of two pre-
cursors, the concentration of reactants, the reaction temperature,
and time. This facile and general strategy offers the possibility of
low-cost and large-scale production of various nanocrystals
which can find potential applications in important fields such
as environmental and industrial catalysis.
(
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’
ASSOCIATED CONTENT
S
Supporting Information. Detailed analytical data, XRD
b
(
(
24) Wang, L. L.; Johnson, D. D. J. Am. Chem. Soc. 2009, 131, 14023.
25) (a) Huang, X. Q.; Zheng, N. F. J. Am. Chem. Soc. 2009,
patterns, and TEM images. This material is available free of
charge via the Internet at http://pubs.acs.org.
131, 4602. (b) Wu, B. H.; Zhang, H.; Chen, C.; Lin, S. C.; Zheng,
N. F. Nano Res. 2009, 2, 12. (c) Huang, X. Q.; Tang, S. H.; Zhang, H. H.;
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’
AUTHOR INFORMATION
(
(
26) Gu, X. H.; Xu, L. Q.; Tian, F.; Ding, Y. Nano Res. 2009, 2, 386.
27) (a) Maksimuk, S.; Yang, S.; Peng, Z.; Yang, H. J. Am. Chem. Soc.
Corresponding Author
*E-mail: ydli@tsinghua.edu.cn.
2
(
007, 129, 8684. (b) Peng, Z. M.; Yang, H. Nano Res. 2009, 2, 406.
c) Wu, J. B.; Zhang, J. L.; Peng, Z. M.; Yang, S. C.; Wagner, F. T.;
Yang, H. J. Am. Chem. Soc. 2010, 132, 4984.
28) Lee, Y. W.; Kim, M.; Kim, Z. H.; Han, S. W. J. Am. Chem. Soc.
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ACKNOWLEDGMENT
(
This work was supported by the State Key Project of Fundamental
2009, 131, 17036.
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Research for Nanoscience and Nanotechnology (2011CB932401,
011CBA00500), NSFC (20921001, 21051001), and China Post-
doctoral Science Foundation (20100470335).
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