Shape-Controlled Synthesis of Trimetallic Nanoclusters: Structure Elucidation and Properties Investigation

Article abstract of DOI:10.1002/chem.201603893

The shape-controlled synthesis of metal nanoclusters (NCs) with precise atomic arrangement is crucial for tailoring the properties. In this work, we successfully control the shape of alloy NCs by altering the dopants in the alloying processes. The shape of the spherical [Pt₁Ag₂₄(SPhMe₂)₁₈] NC is maintained when [Au^ISR] is used as dopant. By contrast, the shape of Pt₁Ag₂₄is changed to be rodlike by alloying with [Au^I(PPh₃)Br]. The structures of the trimetallic NCs were determined by X-ray crystallography and further confirmed by both DFT and far-IR measurements. The shape-preserved [Pt₁Au_6.4Ag_17.6(SPhMe₂)₁₈] NC is in a tristratified arrangement—[Pt(center)@Au/Ag(shell)@Ag(exterior)]—and is indeed the first X-ray crystal structure of thiolated trimetallic NCs. On the other hand, the resulting rodlike NC ([Pt₂Au₁₀Ag₁₃(PPh₃)₁₀Br₇]) exhibits a high quantum yield (QY=14.7 %), which is in striking contrast to the weakly luminescent Pt₁Ag₂₄(QY=0.1 %, about 150-fold enhancement). In addition, the thermal stabilities of both trimetallic products are remarkably improved. This study presents a controllable strategy for synthesis of alloy NCs with different shapes (by alloying heteroatom complexes coordinated by different ligands), and may stimulate future work for a deeper understanding of the morphology (shape)–property correlation in NCs.

Full text of DOI:10.1002/chem.201603893

DOI: 10.1002/chem.201603893
Communication
&
Nanochemistry |Hot Paper|
Shape-Controlled Synthesis of Trimetallic Nanoclusters: Structure
Elucidation and Properties Investigation
[
a]
[b]
[a]
[a]
[a]
[a]
[a]
Xi Kang, Lin Xiong, Shuxin Wang,* Haizhu Yu, Shan Jin, Yongbo Song, Tao Chen,
[c]
[c]
[b]
[a]
Liwei Zheng, Chensong Pan, Yong Pei,* and Manzhou Zhu*
portance for guiding the synthesis of NPs with specific func-
Abstract: The shape-controlled synthesis of metal nano-
clusters (NCs) with precise atomic arrangement is crucial
for tailoring the properties. In this work, we successfully
control the shape of alloy NCs by altering the dopants in
[4–6]
tionalities.
However, a general issue lies in the uncertainty
of the surface structure of NPs; this significantly limits
a deeper understanding of the structure–property correlations.
On this basis, noble-metal nanoclusters (NCs) with ultra-small
sizes (<2 nm in diameter of the metal core) have attracted
considerable research interest for their precise structures. In
addition, accurately characterized structures by X-ray crystal-
lography provide exciting opportunities to investigate the
mechanism of the structure-induced properties at the atomic
the alloying processes. The shape of the spherical
I
[
Pt Ag (SPhMe ) ] NC is maintained when [Au SR] is used
1
24
2 18
as dopant. By contrast, the shape of Pt Ag is changed to
1
24
I
be rodlike by alloying with [Au (PPh )Br]. The structures of
3
the trimetallic NCs were determined by X-ray crystallogra-
phy and further confirmed by both DFT and far-IR mea-
surements. The shape-preserved [Pt Au Ag (SPhMe ) ]
[7–13]
level.
1
6.4
17.6
2 18
So far, much effort has been devoted to synthesis of alloy
NC is in a tristratified arrangement—[Pt(center)@Au/Ag-
shell)@Ag(exterior)]—and is indeed the first X-ray crystal
[14–25]
NCs.
For example, our group recently developed a metal-
(
exchange strategy to prepare the atomically precise alloy NCs,
providing an efficient method to study the composition–prop-
structure of thiolated trimetallic NCs. On the other hand,
the resulting rodlike NC ([Pt Au Ag (PPh ) Br ]) exhibits
2
10
13
3 10
7
[26]
erty correlations. The atomically precise homometallic NCs
a high quantum yield (QY=14.7%), which is in striking
contrast to the weakly luminescent Pt Ag (QY=0.1%,
are used as templates, and are doped with the heteroatom
complexes to generate the target alloy NCs. Compared with
monometallic NCs, the alloy NCs may show significantly en-
1
24
about 150-fold enhancement). In addition, the thermal
stabilities of both trimetallic products are remarkably im-
proved. This study presents a controllable strategy for syn-
thesis of alloy NCs with different shapes (by alloying het-
eroatom complexes coordinated by different ligands), and
may stimulate future work for a deeper understanding of
the morphology (shape)–property correlation in NCs.
[14,17,18,19a]
[16a,17b,23a,27]
hanced optical,
catalytic,
and electrochemi-
[16b,20,28]
cal
properties. However, the previously reported alloy
NCs only show changes in composition compared with the
monometallic counterparts, and less effects on the properties
of the NCs. We are motivated to pursue both composition and
shape alterations; this would create new opportunities for tai-
loring the material properties. To achieve this goal, a major
question is how to control the shape of the alloy NCs at the
atomic level; this necessitates the development of new syn-
thetic methods for alloy NCs.
Mastery over the size, shape or composition of alloy nanoparti-
cles (NPs) enables control of their properties and enhancement
[
1–3]
of their usefulness for various applications.
Therefore, the
In the previously described metal-exchange method, the
shape of the templating NCs is maintained by alloying with
heteroatom complexes coordinated by the same ligands (ex-
insights into structure–property correlations are of great im-
[26]
clusively thiolates in previous work).
Therefore, it remains
[
a] X. Kang, Dr. S. Wang, Prof. H. Yu, S. Jin, Y. Song, T. Chen, Prof. M. Zhu
unknown whether the shape could be altered or not when the
templating NCs are doped by heteroatom complexes with dif-
ferent ligands (such as, the very different M–SR and M–PR3
complexes, M=Au/Ag/Pt). In addition, whether or not the al-
tered shape could induce the qualitative leap in properties de-
serves exploration. These studies will not only help us better
understand the ligand effect in alloying processes in a confined
environment (in the NC range), but also provide a reliable
method to synthesize alloy NCs in an unprecedented shape-
changing manner.
Department of Chemistry and
Center for Atomic Engineering of Advanced Materials
Anhui University, Hefei, Anhui, 230601 (P.R. China)
E-mail: ixing@ahu.edu.cn
zmz@ahu.edu.cn
[
b] L. Xiong, Prof. Y. Pei
Department of Chemistry
Key Laboratory of Environmentally Friendly Chemistry and
Applications of MOE, Xiangtan University, Xiangtan
Hunan, 411105 (P.R. China)
E-mail: ypnku78@gmail.com
[
c] L. Zheng, C. Pan
Bruker (Beijing) Scientific Technology Co., Ltd., Beijing, 100081 (P.R. China)
Herein, we report an effective way to change the shape of
NCs by alloying the same precursor—Pt Ag (protected by
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201603893.
1
24
-SPhMe )—with heteroatom complexes bearing different li-
2
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gands. Specifically, when alloying the Pt Ag
NC with
between the surface structures of Ag , Pt Ag , and
1
24
25
1
24
I
[
Au(PPh )Br] we successfully obtained a rod-shaped trimetallic
Pt Au Ag
(including the bond lengths, bond angles, as well
24Àx
3
1
x
I
M25 (M=Au/Ag/Pt) NC, whereas [Au SR] (SR=SPhMe , the
as the p–p interactions) are given in the Supporting Informa-
2
same thiolate ligand as in the precursor NC) generated a spheri-
cal trimetallic M25 without any changes in shape. The crystal
structures of these two trimetallic NCs are determined by X-ray
crystallography, and further characterized by high-resolution
ESI-TOF-MS, far IR (FIR) measurements, and DFT computations.
As to the spherical-shaped NC, the X-ray crystal structure indi-
tion (Figure S5 and Table S1).
I
Unlike the case of [Au SR], in which the doped trimetallic
I
NCs possess the same spherical shape, the use of [Au (PPh )Br]
3
in the alloying process leads to a shape-changed trimetallic
NC. As shown in Figure 1, the initial spherical core-shell struc-
ture of Pt Ag is altered to a biicosahedral configuration in
1
24
2À
cates that the average formula is [Pt Au Ag (SR) ]
Pt Au Ag . The thiolates of the precursor are completely
2 10 13
1
6.4
17.6
18
(
Pt Au Ag for short). To the best of our knowledge, this is
peeled away and none is left in the final product, and thus the
1
x
24Àx
the first report of an X-ray crystal structure of thiolated trime-
tallic NCs. In addition, the rod-shaped NC is identified to be
final biicosahedral core is co-protected by PPh and Br ligands.
3
In addition, the partial occupancy analysis indicates that each
position of Pt Au Ag is essentially occupied by a single com-
[
Pt Au Ag (PPh ) Br ] (Pt Au Ag for short). Interestingly, the
2 10 13 3 10 7 2 10 13
2
10
13
luminescent quantum yield (QY) of Pt Au Ag is drastically in-
position. In conclusion, the shape is altered from spherical to
2
10
13
I
creased from 0.1 to 14.7% (about 150 times that of the Pt Ag
rodlike when doped with [Au (PPh )Br]. Similar structures of
1
24
3
precursor NC), presumably owing to the changes in chemical
composition (surface) as well as the transformation in mor-
phology (shape). Furthermore, the thermal stability of both
Pt Au Ag has been reported by Teo and co-workers, as well
2
10
13
as Steggerda and co-workers; these differ only by the halogen
[25]
atom (i.e., Cl instead of Br).
Pt Au Ag and Pt Au Ag NCs is remarkably improved com-
24Àx
Nonetheless, given the difficulty in distinguishing Au from Pt
in X-ray crystallographic analysis, both the FIR measurements
and DFT computations further clarify the accurate site of the Pt
atom (see below).
2
10
13
1
x
pared with the Pt Ag precursor.
1
24
Briefly, the syntheses of either Pt Au Ag
or Pt Au Ag in-
2 10 13
1
x
24Àx
volve two steps: the first step is the synthesis of the precursor
(
Pt Ag ), and the second step is the alloying of Pt Ag with
High-resolution ESI-TOF-MS was employed to characterize
the chemical composition of the trimetallic NCs and confirmed
the trimetallic compositions of the NCs (Figure S6 in the Sup-
1
I
24
1
24
I
[AuSR] or [Au(PPh )Br] (see the Supporting Information for de-
3
tails). An illustrative scheme of the synthetic method and the
related X-ray crystal structures of the trimetallic NCs are given
in Figure 1 (and Figures S1–S4 for more details).
porting Information). The mass spectrum of Pt Au Ag sug-
24Àx
1
x
2À
gests that the product is a mixture of [Pt Au Ag (SR) ]
1
x
24Àx
18
with x=4–9, and the percentages of these components are
.3, 12.5, 33.0, 34.8, 14.9, and 2.5%, respectively. As a result,
2
the average number of gold atoms is 6.5 (see Table S2 in the
Supporting Information for the calculation details). Herein, the
calculated component from ESI is consistent with the X-ray
2À
À
crystal structure [Pt Au Ag (SR) ] (counter ion: [PPh ] ). By
1
6.4
17.6
18
4
contrast, the Pt Au Ag NC is charge neutral, and it is difficult
2
10
13
to observe the molecular ion peak, thus, the ESI mass spec-
trum of Pt Au Ag was not obtained. To ensure the composi-
2
10
13
tion of these trimetallic NCs, the atom ratio was examined by
both inductively coupled plasma (ICP) MS, X-ray photoelectron
spectroscopy (XPS), and elemental analysis (EA) measurements
(
see Figures S8 and S9 and Tables S3 and S4, in the Supporting
Figure 1. Illustrative scheme of the transformations from Pt
1
Ag24 to
Information, for the detailed results), and the ratio of elements
agrees well with that from the X-ray crystallographic analysis.
Although the composition and ratio of different metal
Pt Au Au10Ag13 NCs. Color legend: dark green sphere, Pt;
1
x
Ag24Àx and Pt
2
orange sphere, Au; cerulean sphere, Ag; violet sphere, Au/Ag; red sphere, S;
purple sphere, P; pink sphere, Br. For clarity, the carbon and hydrogen
atoms are not shown.
atoms in Pt Au Ag
and Pt Au Ag NCs have been success-
2 10 13
1
x
24Àx
fully identified by ESI, ICP, XPS, and EA measurements, the ac-
curate site of the Pt atom(s) remains to be ascertained. As X-
ray crystallographic analysis can hardly distinguish Au from Pt
(due to the close atomic numbers), we sought to examine the
As the X-ray crystallography only gave an average electron-
density map of the Pt Au Ag alloy NCs, consisting of differ-
24Àx
1
x
ent numbers of Au atoms, we carried out further partial occu-
accurate location of the Pt atom in the core of Pt Au Ag
1 x 24Àx
pancy analysis to ascertain the average number of Au dopants
(i.e., the center or the icosahedral shell. Note: the occupancy
analyses reveal that no Pt/Au atoms are located on the exter-
nal staple motifs). Similarly, the possibility that the Pt atoms
are placed at the center or at the neck sites in Pt Au Ag was
(
x=6.4) in the total structure. Thus, the average molecular for-
mula of the thiolated Pt Au Ag is [Pt @Au Ag @(-SR-Ag-
1
x
24Àx
1
6.4
5.6
SR-Ag-SR-) ] with a tristratified arrangement. The heteroatoms
6
2
10
13
(
Au atoms) are controllably doped in the icosahedral shell of
also examined. Considering that one primary distinction be-
tween these different positions is the absence/presence of the
PtÀS (PtÀP) bond, we performed FIR measurements to address
Pt Ag , with the spherical shape of Pt Ag maintained
1
24
1
24
(
Figure 1). More information and discussion on the comparison
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this issue (Figures S10–S12 in the Supporting Information). We
first measured the FIR spectra of the reference samples, M–
contrary, according to a recent study of Bakr and co-workers,
the central Ag atom of Ag25 would be replaced by a Au atom
I
[14a]
SPhMe (M=Au, Ag, or Pt, see Figure S10a–c in the Supporting
when alloying with [Au (PPh )Br].
Regarding the formation
2
3
Information) and Br–M–PPh3 (M=Au or Pt, see Figure S12a
and b in the Supporting Information), for the MÀS and MÀP
mechanism, Bakr et al. suggest that the Au atom first replaces
one Ag atom on the icosahedral surface of the Ag25 NC, and
then immediately diffuses into the center due to the thermo-
dynamic stability of the resultant configuration. In this context,
bond vibration energies. For Pt Au Ag , the FIR spectrum
1
x
24Àx
À1
clearly shows the bands centered at 343 cm (i.e., an AuÀS
bond according to the FIR spectrum of Au–SPhMe ) and
the structural arrangements of the Pt Au Ag
and
Pt Au Ag NCs imply that the Pt atom in Pt Ag is stable
2
1
x
24Àx
À1
3
81 cm (i.e., AgÀS), whereas no band can be identified
2
10
13
1
24
À1
around 323 cm
(i.e., PtÀS). The results indicate that
enough to hold the central position (compared to the Ag
Pt Au Ag
consists of both AuÀS and AgÀS bonds, but no
atom in Ag ). Note that the stability of the central Pt atom is
1
x
24Àx
25
PtÀS bonds. Hence, the absence of PtÀS bonds implies that
the only plausible location for the Pt atom is the central posi-
tion. On the other hand, the presence of AuÀP bonds
also supported by both DFT calculations and experiments on
[22a,23a]
Pt Ag and Pt Au NCs.
The difference in alloying pro-
1
24
1
24
cess of the Ag25 and Pt Ag NCs is most likely controlled by
1
24
À1
À1
(
436 cm ) and absence of PtÀP bonds (394 cm ) in
the intrinsic electronic structure and the thermodynamic stabil-
ity of the NCs. Applying this rule would provide a promising
strategy to engineer the heteroatoms into the designated posi-
tion.
Pt Au Ag indicate that the two Pt atoms are exclusively lo-
2
10
13
cated at the central positions of two icosahedrons. In other
words, the central position for the Pt atom in the precursor
nanocluster is retained, rather than displaced by Au dopant
atoms, regardless if the shape changes or not.
Based on the well-defined structures of these NCs, we pro-
I
pose a plausible mechanisms of alloying Pt Ag with [AuSR]
1
24
3
1
I
I
The P NMR spectra of both Pt Au Ag and the precursor
or [Au (PPh )Br] complexes (Figure 3). In Figure 3a, the [Au SR]
2
10
13
3
3
(
[PPh AuBr]) were measured. As shown in Figure S13 in the
complexes diffuse to the surface of the icosahedral Pt Ag
1
12
31
Supporting Information, the narrow P NMR signals of the NCs
indicate high purity of the final product.
core, and then replace the Ag atoms. These processes are simi-
lar to those reported in previous studies on alloying Au with
2
5
I
To further confirm the position of the Pt atoms in the trime-
tallic NCs, DFT calculations were performed. Three possible Pt
positions were considered, that is, the center of the icosahe-
dron (M1), the shell of the icosahedron (M2), and a staple
motif (M3). For each scenario, the ten lowest-energy isomer
structures were used as parent structures. To illustrate the fa-
vorable position of the Pt atom, the position of the Au or Ag
atom is mutually exchanged for a Pt atom. According to the
relative electronic energies of the different isomer structures
[Ag SR]. The alloying processes occur and eventually stabilize
in the thermodynamically favorable state with a tristratified ar-
rangement, that is, [Pt(center)@Au/Ag(shell)@Ag(exterior)]. Re-
garding Pt Au Ag (Figure 3b), the Ag atoms on the icosahe-
2
10
13
dral Pt Ag core are exchanged by the Au atoms of the
1
12
I
[Au(PPh )Br] complexes (the thiolates binding to these Ag
3
atoms are simultaneously peeled away), and the PPh ligands
3
keep in connection with Au atoms in this process. Meanwhile,
À
the Br ions link to the Ag atoms neighboring the Au atoms,
(
Figure 2), the Pt atom favors the central position. Moving the
and the AgÀS bond dissociates simultaneously (because of the
stronger AgÀBr). As a consequence, the icosahedral Pt Ag
Pt atom to the shell of icosahedral core or to the staple motif
significantly increases the electronic energy. This energy ten-
dency agrees with the FIR spectral analysis and confirms the
1
12
core is peeled away from the surrounding six [Ag (SR) ] motifs
2
3
and the Pt@Au–Ag NCs, co-protected by PPh and Br ligands,
3
central position of the Pt atom in Pt Au Ag .
24Àx
are generated. Finally, two icosahedral Pt@Au–Ag NCs, couple
together by sharing the Ag atom in vertex and five Br atoms,
are formed. The Pt atom maintain the central position in the
final biicosahedral structure and the neck sites are completely
occupied by Au atoms to form a symmetric structure.
1
x
Structurally, the central Pt atom in the M13 core of the two
synthesized trimetallic alloy NCs was unexceptionally retained
compared to the positions in the Pt Ag precursor. On the
1
24
To investigate the correlation between the composition/
shape and the optical properties, the absorption spectra on
the energy scale and photoluminescence (PL) of all samples
were analyzed. The energy-scale UV/Vis spectra of the homosil-
ver, Ag , bi-metallic, Pt Ag , and trimetallic, Pt Au Ag , as
25
1
24
1
x
24Àx
well as the Pt Au Ag NCs are shown in Figure 4a. The optical
2
10
13
energy gap of Ag25 occurs at 1.57 eV and significantly blue-
shifts to 1.72 and 1.93 eV in Pt Ag and Pt Au Ag , respec-
1
24
2
10
13
tively. On the other hand, a slight blueshift by 0.05 eV (1.62–
.57 eV) is determined from the spectrum of Pt Au Ag . The
1
1
x
24Àx
results indicate an increase of energy gap in Pt Au Ag ,
1
x
24Àx
Pt Ag , or Pt Au Ag NCs. Meanwhile, the three NCs with the
1
24
2
10
13
Figure 2. Left: M1 is the central atom in the icosahedral core. M2 is the shell
atoms of icosahedral core. M3 is the metal atoms in the motif. Right: The rel-
ative energies of isomers with Pt atoms located at different positions in
same framework (i.e., Pt Au Ag , Pt Ag , and Ag ) vary in
1
x
24Àx
1
24
25
color from greenish yellow to green and orange, indicating
Pt
1 x
Au Ag24Àx (x=5–8).
that the doped heteroatoms significantly affect the electronic
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structure of the NCs, and thus strongly perturb the optical
properties.
With respect to the PL intensity of these NCs, the QY of
Pt Ag is about 20 times that of Ag . Nonetheless, the PL in-
1
24
25
tensity of Pt Ag (QY=0.1%) is still too weak to be observed
1
24
by the naked eye. Meanwhile, the PL intensity of the doped
Pt Au Ag was totally quenched and no PL was detected
1
x
24Àx
even by highly sensitive instruments. Considering that the al-
teration of shape is more likely to lead to a qualitative leap in
properties, the PL measurement of shape-altered Pt Au Ag
13
2
10
was performed. Interestingly, Pt Au Ag exhibits a strong
2
10
13
emission centered at 648 nm with a QY of 14.7% (Figure 4b).
In other words, the QY increases from 0.1 to 14.7% (150 times)
and the fluorescence is strong enough to be perceived by the
naked eye (Figure 4a, inset). With a view to the difference be-
tween Pt Au Ag and its precursor, we speculated that the in-
2
10
13
crease in QY of emission originated not only from the changes
in the chemical composition, but also from the transformation
in shape. The PL excitation spectrum of Pt Au Ag is almost
2
10
13
Figure 3. Proposed exchange mechanisms of alloying Pt
1
Ag24 with:
identical to the absorption spectrum (Figure S14 in the Sup-
porting Information). From the PL spectra in Figure 4b, the
emission peaks of Ag , Pt Ag , and Pt Au Ag are deter-
I
I
a) [Au SR] or b) [Au(PPh
3
)Br] complexes; i/ii) is the site for Au/Ag replace-
ment; iii) is the site of AgÀBr bonding.
25
1
24
2
10
13
mined to be 1.53, 1.70 and 1.91 eV, respectively; these are con-
sistent with the energy gaps derived from the spectra on the
energy scale. The almost identical energies imply that the fluo-
rescence possibly corresponds to the gap transition.
To further explore the properties of the trimetallic NCs, we
investigated the thermodynamic stability of the shape-altered
and conserved trimetallic NCs (relative to Pt Ag ). It should be
1
24
noted that Ag25 is far less stable than Pt Ag at room tempera-
1
24
ture (Figure S15 in the Supporting Information). The stability of
all three alloy NCs was tested at 508C (dissolved in CHCl , ex-
3
posed to air). The optical absorption spectra of the
Pt Au Ag
and Pt Au Ag NCs remained unchanged after
2 10 13
1
x
24Àx
1
2 h, whereas that of Pt Ag significantly decreased in intensi-
1 24
ty after 2 h, and completely disappeared in approximately 6 h
Figure S16 in the Supporting Information). In addition, the PL
intensity of the Pt Au Ag NCs did not decreased at all (Fig-
(
2
10
13
ure S17 in the Supporting Information). Therefore, the stability
of Pt Ag is drastically enhanced when doped with Au com-
1
24
plexes, regardless if the shape is altered or conserved.
In summary, syntheses of alloy NCs of different shapes have
been achieved by modulating the dopants. The spherical
2
À
[
Pt Ag (SR) ] NC could be controllably converted to spheri-
1 24 18
cal or rodlike trimetallic NCs by a metal-exchange method. Our
results illustrate that alloying Pt Ag with Au complexes coor-
1
24
dinated by the same ligands maintains the spherical structure.
I
On the contrary, alloying with [Au(PPh )Br] alters the shape to
3
a rodlike one, owing to the different ligands. The crystal struc-
tures of the products were determined by X-ray crystallogra-
phy and confirmed by ESI, XPS, ICP, and FIR measurements,
as well as DFT calculations. The shape-maintained
[
Pt Au Ag (SPhMe ) ](PPh ) NCs exhibit a tristratified ar-
1 x 24Àx 2 18 4 2
rangement—[Pt(center)@Au/Ag(shell)@Ag(exterior)]—that rep-
Figure 4. The optical properties of the trimetallic NCs; a) energy scale optical
absorption spectra of the different NCs, b) PL of the Ag25, Pt Ag24,
1
resents the first X-ray crystal structure of thiolated trimetallic
NCs. The PL QY of the rodlike [Pt Au Ag (PPh ) Br ] cluster is
Pt
1
Au
x
Ag24Àx, and Pt
2
Au10Ag13 NCs. Insets: a) digital photo of each NC in
2
10
13
3 10
7
CH
2
Cl
2
under visible and UV light; b) the peak shift in normalized PL spectra.
drastically increased from 0.1% for Pt Ag to 14.7% (about
1 24
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Communication
150-fold). Besides, heteroatom alloying leads to a significant in-
three times and collected by centrifugation (9 mg, 1.5 mmol, yield
8
3.3%).
crease in the stability. This study provides new insights into
the morphology (shape)–property correlation and also shed
light on how to understand and engineer shape-controlled
multimetallic NCs with enhanced properties.
Synthesis of [Pt Au Ag (PPh ) Br ]
2
10
13
3 10
7
For the NC synthesis, [Pt Ag (SPhMe ) ](PPh ) (10 mg, 1.8 mmol)
was dissolved in CH Cl (20 mL), and Au (PPh )Br (powder; 10 mg,
1
24
2 18
4 2
I
2
2
3
1
8.6 mmol, ca. 10 equiv) was added to the solution. The reaction
Experimental Section
was allowed to proceed for 60 min at room temperature. The color
of solvent transformed from bright green to orange. The reaction
mixture was transferred to a centrifuge tube and centrifuged at
about 9000 rpm. The organic layer was separated from the precipi-
[29]
Synthesis of [Pt Ag (SPhMe ) ](PPh )
4 2
1
24
2 18
For the NC synthesis, AgNO (30 mg, 0.18 mmol) was dissolved in
3
CH OH (5 mL) and CH COOC H (15 mL), and H PtCl ·6H O (4 mg,
tate and evaporated to dryness. The [Pt Au10Ag13(PPh )10Br ] NC
2 3 7
3
3
2
5
2
6
2
0
.0075 mmol) dissolved in CH OH (5 mL) was added. The solution
was obtained. The dried NC was washed with methanol at least
3
was vigorously stirred (about 1200 rpm) through magnetic stirring
three times and collected by centrifugation (11 mg, 1.6 mmol, yield
for 15 min. HSPhMe2 (100 mL) was added. After another 15 min,
88.9% based on the Pt Ag24 NC).
1
À1
a NaBH aqueous solution (1 mL, 20 mgmL ) was added quickly
4
to the above mixture under vigorous stirring. The reaction was al-
Crystallization of [Pt Au Ag (SPhMe ) ](PPh ) and
1
5.3
18.7
2 18
4 2
lowed to proceed for 24 h under N atmosphere. After which, the
2
[
Pt Au Ag (PPh ) Br ]
2
10
13
3 10
7
solvents of organic-phase mixture were rota-evaporated under
vacuum, and then CH OH (20 mL) was used to extract the product,
which also contained the redundant HSPhMe2 and byproducts.
3
Single
crystals
of
[Pt Au Ag (SPhMe ) ](PPh )
4 2
and
1
5.3
18.7
2 18
Pt Au Ag (PPh ) Br nanoclusters were grown for 2–3 days at 48C
2
10
13
3 10
7
Subsequently, a CH OH solution (5 mL), containing excess PPh Br,
3
4
in CH Cl /hexane mixture solutions. Dark crystals were collected
2 2
was added into the above CH OH solution and the resulting solu-
3
and the structures were determined by X-ray diffraction.
tion mixture was centrifuged to obtain the solid. Methanol (ca.
CCDC 1510048 ([Pt Au Ag (SPhMe ) ](PPh ) ) and 1510047
1
5.3
18.7
2 18
4 2
1
5 mL) was added to wash the synthesized NC. The precipitate ob-
(
[Pt Au Ag (PPh ) Br ]) contain the supplementary crystallograph-
2 10 13 3 10 7
tained was then dissolved into CH Cl2 that produced a bright
2
ic data for this paper. These data are provided free of charge by
The Cambridge Crystallographic Data Centre.
green [Pt Ag (SPhMe ) ](PPh ) NC.
1
24
2 18
4 2
Synthesis of the [Au/Ag/Pt–SR] complexes (SR=SPhMe2)
Acknowledgements
For the synthesis of the Au/Ag/Pt-SR complexes, HAuCl /AgNO /
4
3
H PtCl (1 mmol) was dissolved inCH CN (5 mL), and HSPhMe2
2
6
3
We acknowledge financial support by NSFC (21372006,
U1532141, 21631001), the Ministry of Education, the Education
Department of Anhui Province, 211 Project of Anhui University.
Y.P. is supported by NSFC (21373176, 21422305), Hunan Provin-
cial Natural Science Foundation of China (12JJ1003), and Scien-
tific Research Fund of Hunan Provincial Education Department
(
300 mg, 2.2 mmol) was dissolved in CH CN (5 mL) and added
3
dropwise to the solution under vigorous stirring (about 1200 rpm).
The reaction was allowed to proceed for 24 h. The resulting solu-
tion mixture was then washed several times with CH OH. Then the
3
final product was rota-evaporated under vacuum and used directly
(
[AuSR] 0.93 mmol, yield 93%; [AgSR] 0.95 mmol, yield 95%; [PtSR]
0
.65 mmol, yield 65%. Based on the metal salt).
(
13A100).
I
Synthesis of [Au (PPh )Br]
3
Keywords: crystallography
·
photoluminescence
·
shape
I
control · surface chemistry · trimetallic nanoclusters
For the synthesis of the [Au(PPh )Br] complexes, HAuBr (517 mg,
3
4
1
4
mmol) was dissolved in CH OH (5 mL), and PPh3 (1048 mg,
3
mmol) in CH OH( 5 mL) was added dropwise to the solution
3
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2
final product (PPh AuBr) was rota-evaporated under vacuum and
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[
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[
proceed for 60 min at room temperature. The color of solvent
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about 9000 rpm. The organic layer was separated from the precipi-
[
[
5
2
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Chem. Eur. J. 2016, 22, 1 – 7
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ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: August 27, 2016
[
Published online on && &&, 0000
&
&
Chem. Eur. J. 2016, 22, 1 – 7
www.chemeurj.org
6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Communication
COMMUNICATION
Shape-controlled synthesis of alloy
metal nanoclusters (NCs) is achieved
with atomic precision for the first time.
The spherical [Pt Ag (SR) ] was doped
&
Nanochemistry
X. Kang, L. Xiong, S. Wang,* H. Yu, S. Jin,
Y. Song, T. Chen, L. Zheng, C. Pan, Y. Pei,*
M. Zhu*
1
24
18
I
I
with [AuSR] or [Au (PPh )Br], resulting in
3
spherical or rodlike trimetallic products,
respectively. The spherical
&& – &&
[
Pt Au Ag (SPhMe ) ] NC represents
Shape-Controlled Synthesis of
Trimetallic Nanoclusters: Structure
Elucidation and Properties
Investigation
1
6.4
17.6
2 18
the first X-ray crystal structure of a thio-
lated trimetallic NCs. The rodlike trime-
tallic [Pt Au Ag (PPh ) Br ] exhibits
2
10
13
3 10
7
strong emission with a quantum yield
of 14.7%.
Chem. Eur. J. 2016, 22, 1 – 7
www.chemeurj.org
7
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ