Aqueous-Phase Synthesis of Size-Tunable Copper Nanocubes for Efficient Aryl Alkyne Hydroboration

Article abstract of DOI:10.1002/asia.201700856

Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC) surfactant, copper acetate, and sodium ascorbate reductant heated at 100 °C for 40 min. Copper nanowires with a

Full text of DOI:10.1002/asia.201700856

CHEMISTRY
AN ASIAN JOURNAL
www.chemasianj.org
Accepted Article
Title: Aqueous Phase Synthesis of Size-Tunable Copper Nanocubes
for Efficient Aryl Alkyne Hydroboration
Authors: Subashchandrabose Thoka, Mahesh Madasu, Chi-Fu Hsia,
Shu-Ya Liu, and Michael Hsuan-Yi Huang
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Asian J. 10.1002/asia.201700856
Link to VoR: http://dx.doi.org/10.1002/asia.201700856
A Journal of
A sister journal of Angewandte Chemie
and Chemistry – A European Journal

10.1002/asia.201700856
Chemistry - An Asian Journal
Aqueous Phase Synthesis of Size-Tunable Copper Nanocubes for Efficient Aryl
Alkyne Hydroboration
Subashchandrabose Thoka, Mahesh Madasu, Chi-Fu Hsia, Shu-Ya Liu, and Michael
H. Huang*[a]
[a] S. Thoka, M. Madasu, C.-F. Hsia, S.-Y. Liu, Prof. M. H. Huang
Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan)
E-mail: hyhuang@mx.nthu.edu.tw
Supporting Information for this article is given via a link at the end of the document.
Abstract: Copper nanocubes with average sizes of 82, 95, and 108 nm have been
synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC)
surfactant, copper acetate, and sodium ascorbate reductant heated at 100 ºC for 40 min.
Copper nanowires with an average length of 25 m can also be prepared this way by
simply increasing the volume of sodium ascorbate introduced. Small shifts in the
plasmonic absorption band positions with tunable particle sizes have been observed.
The copper nanocubes were employed to catalyze hydroboration of phenylacetylene
and various substituted aryl alkynes with 100% (E)-product selectivity and 82‒95%
product yields. The copper nanocubes are cheap to make and should catalyze a broad
1
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
scope of organic coupling reactions.
Introduction
Compared to the more successful development in the aqueous phase synthesis of
polyhedral Au, Ag, and Pd nanocrystals,[1‒8] copper nanocubes and octahedra have
mainly been synthesized in hydrophobic organic media at very high temperatures.[9‒12]
Cu nanocubes have also been made in anhydrous ethylene glycol in the presence of
poly(vinylpyrrolidone).[13] There are few literature reports describing the growth of
Cu nanocubes and octahedra in an aqueous solution.[14‒16] Depending on the amount
of hexadecylamine (HDA) added, Cu nanowires and nanocubes were obtained by
heating an aqueous solution of CuCl2, HDA, and glucose at 100 ºC for 6 h.[14] Au‒Cu
core‒shell cubes and octahedra can be easily made by heating an aqueous mixture of
HDA, copper acetate solution, ascorbic acid, and octahedral Au nanocrystals at 100 ºC
for 1.5 h.[15] However, it remains unexplored to prepare pure polyhedral Cu
nanoparticles such as cubes with tunable sizes in an aqueous solution without
introducing HDA as a coordinating and pH-tuning reagent. Copper nanocrystals are
cheap and attractive materials with great promise to catalyze a diverse spectrum of
organic transformations.[17] For example, Cu nanoparticles immobilized on charcoal
support have been shown to catalyze multicomponent azide‒alkyne cycloaddition
2
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
reaction.[18,19] Recently copper nanocubes have been used to catalyze the synthesis of
diverse triazoles via click chemistry.[20] Cu nanoparticles were also employed to
catalyze a cross-coupling reaction between alkyl halides and various Grignard
reagents.[21] After surveying all organic reactions catalyzed by Cu-based nanoparticles,
it is interesting to learn that hydroboration of aryl alkynes has not been reported
before for Cu nanocrystals.[17] Only studies on micro copper powder and
CuO/MgO-catalyzed hydroboration and Cu nanoparticle-catalyzed borylation of alkyl
bromides with bis(pinacolato)diboron (B2pin2) are available.[22‒24] However, use of
specially designed Cu or Rh complexes to catalyze terminal alkyne hydroboration is
an active field of research in the organic chemistry community because of the great
utility of the resulting products.[25‒29]
In this study, we have developed an aqueous solution approach for the synthesis
of copper nanocubes with tunable sizes using simply copper acetate as the copper
source, CTAC as the surfactant, and sodium ascorbate as the reducing agent. The
reaction mixture was heated at 100 ºC for just 40 min to obtain Cu nanocubes.
Significantly increasing the amount of sodium ascorbate added led to formation of Cu
nanowires. The Cu nanocubes were used to catalyze a hydroboration reaction between
phenylacetylene and B2pin2 with exclusive (E)-product selectivity and a high yield of
95% in 2 h. Use of other substituted aryl alkynes also gave excellent product yields.
3
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
The resulting products are building blocks for subsequent coupling reactions, showing
the great utility of this Cu nanocrystal-catalyzed reaction.
Results and Discussion
To grow Cu nanocubes, an aqueous solution containing CTAC surfactant, copper
acetate, and sodium ascorbate was well mixed and heated at 100 ºC for 40 min. Figure
S1 in the Supporting Information gives the reaction scheme and the exact reagent
amounts used to make Cu nanocubes with tunable sizes and Cu nanowires. While
many studies on spherical and ill-defined Cu nanoparticles are known, literature
reports on the formation of cubic Cu nanocrystals in aqueous solutions are scarce.[15,16]
By increasing the volume of 0.1 M copper acetate solution from 50 to 75 and 85 L,
and adding 100, 150 and 150 L of 0.5 M sodium ascorbate, Cu nanocubes with
respective average edge lengths of 82, 95 and 108 nm were synthesized. Figure 1
shows scanning electron microscopy (SEM) images of the three Cu nanocube samples
prepared. The Cu nanocubes are highly uniform in size and shape. Particle sizes can
be gradually increased by adding more copper source and reducing agent. Figure S2
provides their size distribution histograms and standard deviations. There are about
20% of right bipyramids formed in all the samples with similar edge lengths as the
cubes. This is understandable because they also expose {100} crystal faces as the
4
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
cubes do. Preparation of Au and Ag nanocubes also yields right bipyramids as a
byproduct.[2,30] Attempts to make monodisperse Cu nanocubes smaller than 70 nm by
reducing the amount of copper acetate used were unsuccessful; a mixture of smaller
cubes, right bipyramids and rods were produced. However, we found Cu nanocubes
with an average edge length of 60 nm can be obtained by heating the reaction mixture
for just 20 min, although more right bipyramids are present as judged from its UV‒vis
absorption spectrum (see Figure S3). Possibly due to a relatively low standard
reduction potential of copper at 0.34 V, the reaction mixture needs to be heated to
produce copper. Figure S4 shows a photograph of the reaction mixture as a function
of time in the growth of Cu nanocubes. The solution is initially lightly blue from
copper acetate, but becomes colorless after heating at 100 ºC for 5 min, showing Cu(II)
ions are first reduced to Cu(I) ions by ascorbate, and there is minimum formation of
white CuCl precipitate. The solution remains transparent after 10 min of reaction. At
15 min, the solution shows a light brown appearance. The solution color turns light
reddish brown after 20 min and dark reddish brown within 40 min of reaction. The
clear solution becomes opaque after 25 min of reaction. These observations show Cu
nanocube formation is quite slow, so Cu nanoparticles would not form without
sufficient heating.
X-ray diffraction (XRD) pattern of Cu cubes having an average edge length of
5
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
95 nm is shown in Figure S5. The Cu (200) peak has an exceptionally strong intensity
relative to that of the (111) peak, supporting the formation of Cu cubes and right
bipyramids exposing {100} surfaces. Figure 2 presents UV‒vis absorption spectra of
the three Cu nanocube samples. The 82, 95, and 108 nm Cu cubes show a surface
plasmon resonance (SPR) absorption band at 606, 611, and 617 nm, respectively. This
minor but progressively red-shifted SPR band position as particle size increases is
expected; Au‒Cu core‒shell nanocubes also display a smaller SPR band shift with
increasing particle size.[15] Cu nanocubes with an average edge length of ~76 nm
show a plasmonic band at 588 nm when dispersed in toluene.[10] For the 95 nm Cu
cube sample, there is a broad absorption band centered at ~830 nm. This feature is
likely attributed to absorption by the right bipyramids.[2] Such feature is not
observable in other samples possibly due to a smoother absorption tail from a broader
size distribution of right bipyramids, or the relative insensitivity of light absorption of
Cu nanocrystals to size variation. Figure 3 offers transmission electron microscopy
(TEM) characterization on a single Cu nanocube. Selected-area electron diffraction
(SAED) pattern shows the expected spot pattern matching with the viewing
orientation of the cube. Cu (200) lattice fringes run parallel to the edge of the cube,
confirming the cube is bound by the {100} faces. Energy-dispersive X-ray
spectroscopy (EDS) line scan over the cube gives essentially Cu signals. Oxygen
6
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
signals are very weak and discontinuous and are considered as background noise. It is
interesting to note that CuO (111) or (200) lattice planes with a d-spacing of 2.35 Å
have been formed over the cube surface. Oxide formation has been known to appear
on Cu nanocrystal surfaces.[15,31] We also used X-ray photoelectron spectroscopy
(XPS) characterization to analyze Cu cube surfaces (Figure 4). The Cu 2p3/2 and 2p1/2
peaks are located at 932.6 and 952.4 eV, respectively. These peak positions are
consistent with those recorded for Au‒Cu nanocrystals.[15] The Cu 2p3/2 peak of CuO
should appear at 933.6 eV with very strong satellite peaks.[32,33] Figure 4 shows there
are essentially no satellite peaks. Judging from the XPS results, one can conclude that
only a tiny amount of CuO has been formed, and the particle surfaces should be
mostly metallic copper.
By keeping the volume of 0.1 M copper acetate solution at 75 L, but raising the
volume of 0.5 M sodium ascorbate solution significantly to 500 L, the resulting
product has surprisingly become Cu nanowires. Figure 5 shows SEM and TEM
images of the synthesized Cu nanowires. Figure S6 provides a large-area SEM image
of the Cu nanowires with an average length of 25 m. Some small cubic particles are
also produced. Average diameter of the wires is ~75 nm. XRD pattern confirms the
formation of metallic copper nanowires. This is a simple method to grow Cu
nanowires in aqueous solution using easily removable CTAC surfactant for possible
7
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
conductive substrate fabrication.[34,35] UV‒vis absorption spectrum of the Cu
nanowires show a SPR band at 584 nm, which should correspond to the transverse
mode of SPR bands. Detailed TEM analysis on individual nanowires is provided in
Figure S7. The examined Cu nanowire grows along the <110> direction with Cu (200)
planes running parallel to the side face of the wire and Cu (220) planes perpendicular
to the long axis of the wire. On the basis of high-resolution TEM (HR-TEM) image
and SAED pattern examination, as well as the appearance of the Cu nanowires with a
line running along the wire axis (Figure S7e), the wires should have a penta-twinned
structure with {100} side faces.[35‒38] Since Cu nanocubes and nanowires can both be
synthesized by mainly tuning the amount of sodium ascorbate added, it suggests that
adjusting the metal precursor reduction rate is very important to tuning the resulting
nanostructure morphology. In fact, it takes just 15 min for the solution color to turn
light reddish brown in the synthesis of Cu nanowires. Again CuO can form on some
regions of the wire, as seen from HR-TEM image and the weak CuO (002) ring in the
SAED pattern. Surface composition of the Cu nanowires was also investigated using
XPS spectroscopy (Figure S8). The Cu 2p peak positions are the same as the Cu
nanocubes, and no satellite peaks from CuO are present, confirming that there is only
a tiny amount of CuO formed on the Cu nanowires.
The 95 nm Cu nanocubes were employed as the catalyst for aryl alkyne
8
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
hydroboration reaction because of its best sample quality. Initially, we performed the
reaction using phenylacetylene, B2pin2 and various bases (i.e., triethylamine, NaOMe
and PPh3) at room temperature and 50 ºC (Table S1). PPh3 gave the best product yield
at 50 ºC and was chosen as the base for further examination. For a catalytic reaction,
0.2 mmol of aryl alkyne, 0.25 mmol of bis(pinacolato)diboron (B2pin2), and 0.1 mmol
of PPh3 as base were added to a glass vial. Then 3 mg of copper nanocubes as catalyst
and 2 mL of ethanol solution as solvent were introduced. The reaction glass vial was
kept in an oil bath at 50 oC for 2 h under constant stirring. After 2 h, the solution was
cooled down to room temperature and centrifuged at 6000 rpm for 5 min to separate
Cu particles from the product. Ethanol solvent from the product mixture was removed
by using a rotary evaporator. Crude 1H-NMR spectra were used for product yield and
selectivity analysis. The exact yields were calculated by adding 0.2 mmol of
mesitylene as an internal standard to the product mixture and then performed the
1H-NMR analysis.
Table 1a summarizes the reaction conditions used. At 50 ºC, the reaction was
completed in just 2 h, giving 100% of (E)-products for all the aryl acetylenes tested.
Hydroboration conversion of phenylacetylene was 95%. The product yields after 0.5
and 1 h of reaction are 37 and 90%, respectively (Table S1 and Figures S9‒11). The
time needed to complete aryl alkyne hydroboration reaction using Cu nanocubes is
9
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
much shorter than that required for micro Cu powder (24 h at room temperature).[22]
We have examined the Cu nanocubes after the catalytic reaction. The particle
morphology appears intact, and XRD pattern of the nanocubes give only Cu peaks
(Figure S12). XPS spectra of the nanocubes after the hydroboration reaction show
essentially no shifts in the Cu 2p peak positions (932.8 eV for Cu 2p3/2 peak and 952.5
eV for 2p1/2 peak as seen in Figure S13). There is no evidence of formation of CuO
after the catalytic reaction. The nanocubes were recycled to perform the same reaction
again. After collecting the particles and dispersing them in 2 mL of ethanol, the same
amounts of phenylacetylene, B2pin2, and PPh3 were added. After 2 h of reaction, a
product yield of 88% was obtained, showing the particles can be used for additional
cycles of reaction (Figure S14). To further prove the heterogeneous nature of this
catalytic reaction, 3 mg of Cu nanocubes were first heated in 2 mL of ethanol for 2 h
at 50 ºC, and the ethanol solution after particle removal was subsequently used for
phenylacetylene hydroboration using the same amounts of reagents. No product was
formed as judged from 1H-NMR spectra, showing no copper atom leaching occurred
and the hydroboration reaction proceeded via heterogeneous catalysis. The Cu surface
should enable product regioselectivity. Table 1b shows the substrate scope of this
catalytic reaction using various substituted aryl alkynes (-H, -OCH3, -Cl, -CF3 and –F).
The product yields are generally quite good ranging from 82 to 95%, showing the
10
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
great value of Cu nanocubes to make diverse vinylboronates. 1H-NMR spectra of the
crude products are available in Figures S15 to S18.
Conclusions
We have developed an aqueous solution method to synthesize copper nanocubes with
tunable average sizes of 82 to 108 nm using simple CTAC surfactant, copper acetate
as the copper source, and sodium ascorbate as the reductant. Heating the reaction at
100 ºC for just 40 min or less gives the nanocubes. Copper nanowires can also be
prepared by primarily increasing the amount of sodium ascorbate introduced. The
copper nanocubes can efficiently catalyze various aryl alkyne hydroboration giving
100% (E)-product selectivity and up to 95% product yield in just 2 h at 50 ºC. The
copper nanocubes are cheap to make and should find broad organocatalysis
applications.
Experimental Section
Chemicals
Cupric acetate monohydrate (Cu(CH3COO)2·H 2O,98%, J.T. Baker), L(+)-sodium
ascorbate (SA, 98%, Sigma) and cetyltrimethylammonium chloride (CTAC, 95 %,
TCI) were used as received without further purification. Ultrapure distilled and
11
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
deionized water (18.3 MΩ) was used.
Synthesis of Cu Nanocubes and Nanowires
To make copper nanocubes, 0.048 g of CTAC, 9.765‒9.850 mL of deionized water,
and 50‒85 L of 0.1 M copper acetate solution were mixed thoroughly in a sample
vial. Then 100‒150 L of 0.5 M SA solution was introduced and mixed well. The vial
was placed in an oven and heated at 100 ºC for 40 min. After cooling the vial to room
temperature, the solution was centrifuged at 6500 rpm for 5 min. The precipitate was
centrifuged one more time with 5 mL of deionized water at 6500 rpm for 5 min.
Finally copper nanocubes were dispersed in deionized water. The particles were
stored in deionized water for subsequent characterization. For Cu nanowire growth,
75 L of 0.1 M copper acetate solution and 500 L of 0.5 M SA solution were used.
Instrumentation
SEM images of the nanocrystals were obtained using a JEOL JSM-7000F electron
microscope. XRD patterns were recorded on a Shimadzu XRD-6000 diffractometer
with CuKradiation. TEM characterization was performed on a JEOL JEM-3000F
microscope with an operating voltage of 300 kV. Elemental line scanning images
were acquired by EDS using a JEOL JEM-2100 microscope equipped with a STEM
12
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
unit and an Inca Energy 250 detector from Oxford Instrument. UV−vis absorption
spectra were taken using a JASCO V-670 spectrophotometer. XPS spectra were
collected using an ULVAC-PHI Quantera SXM spectrometer. A Varian Mercury 400
MHz NMR was used to collect 1H-NMR spectra.
Acknowledgments
We thank the Ministry of Science and Technology of Taiwan for the support of this
work (MOST 104-2119-M-007-013-MY3 and 105-2633-M-007-003).
Conflict of interest
The authors declare no conflict of interest.
Keywords: copper · heterogeneous catalysis · hydroboration · nanocubes · nanowires
References
[1] P.-J. Chung, L.-M. Lyu, M. H. Huang, Chem. Eur. J. 2011, 17, 9746‒9752.
[2] Z.-W. Lin, Y.-C. Tsao, M.-Y. Yang, M. H. Huang, Chem. Eur. J. 2016, 22,
2326‒2332.
[3] C. Chiang, M. H. Huang, Small 2015, 11, 6018‒6025.
13
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
[4] S. Zhou, J. Li, K. D. Gilroy, J. Tao, C. Zhu, X. Yang, X. Sun, Y. Xia, ACS Nano
2016, 10, 9861‒9870.
[5] J. Zhang, C. Feng, Y. Deng, L. Liu, Y. Wu, B. Shen, C. Zhong, W. Hu, Chem.
Mater. 2014, 26, 1213‒1218.
[6] S.-Y. Liu, Y.-T. Shen, C.-Y. Chiu, S. Rej, P.-H. Lin, Y.-C. Tsao, M. H. Huang,
Langmuir 2015, 31, 6538‒6545.
[7] H.-X. Zhang, H. Wang, Y.-S. Re, W.-B. Cai, Chem. Commun. 2012, 48,
8362‒8364.
[8] W. Niu, L. Zhang, G. Xu, ACS Nano 2010, 4, 1987‒1996.
[9] S.-C. Lu, M.-C. Hsiao, M. Yorulmaz, L.-Y. Wang, P.-Y.; Yang, S. Link, W.-S.
Chang, H.-Y. Tuan, Chem. Mater. 2015, 17, 8185‒8188.
[10] H.-J. Yang, S.-Y. He, H.-L. Chen, H.-Y. Tuan, Chem. Mater. 2014, 26,
1785‒1793.
[11] H. Guo, Y. Chen, H. Ping, J. Jin, D.-L. Peng, Nanoscale 2013, 5, 2394‒2402.
[12] H. Guo, Y. Chen, M. B. Cortie, X. Liu, Q. Xie, X. Wang, D.-L. Peng, J. Phys.
Chem. C 2014, 118, 9801‒9808.
[13] Y. Wang, P. Chen, M. Liu, Nanotechnology 2006, 17, 6000‒6006.
[14] M. Jin, G. He, H. Zhang, J. Zeng, Z. Xie, Y. Xia, Angew. Chem. Int. Ed. 2011,
50, 10560‒10564.
14
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
[15] C.-F. Hsia, M. Madasu, M. H. Huang, Chem. Mater. 2016, 28, 3073‒3079.
[16] X. Ren, D. Chen, F. Tang, J. Phys. Chem. B 2005, 109, 15803‒15807.
[17] M. B. Gawande, A. Goswami, F.-X. Felpin, T. Asefa, X. Huang, R. Silva, X.
Zou, R. Zboril, R. S. Varma, Chem. Rev. 2016, 116, 3722‒3811.
[18] F. Alonso, Y. Moglie, G. Radivoy, M. Yus, J. Org. Chem. 2011, 76, 8394‒8405.
[19] F. Alonso, Y. Moglie, G. Radivoy, M. Yus, Org. Biomol. Chem. 2011, 9,
6385‒6395.
[20] M. Madasu, C.-F. Hsia, M. H. Huang, Nanoscale 2017, 9, 6970‒6974.
[21] J. H. Kim, Y. K. Chung, Chem. Commun. 2013, 49, 11101‒11103.
[22] J. Zhao, Z. Niu, H. Fu, Y. Li, Chem. Commun. 2014, 50, 2058‒2060.
[23] A. Grirrane, A. Corma, H. Garcia, Chem. Eur. J. 2011, 17, 2467‒2478.
[24] J. H. Kim, Y. K. Chung, RSC Adv. 2014, 4, 39755‒39758.
[25] G. Gunanathan, M. Hölscher, F. Pan, W. Leitner, J. Am. Chem. Soc. 2012, 134,
14349‒14352.
[26] J. Cid, J. J. Carbó, E. Fernández, Chem. Eur. J. 2012, 18, 1512‒1521.
[27] C.-C. Tai, M.-S. Yu, Y.-L. Chen, W.-H. Chuang, T.-H. Lin, G. P. A. Yap, T.-G.
Ong, Chem. Commun. 2014, 50, 4344‒4346.
[28] Y. D. Bidal, F. Lazreg, C. S. J. Cazin, ACS Catal. 2014, 4, 1564‒1569.
[29] T. Fujihara, K. Semba, J. Terao, Y. Tsuji, Catal. Sci. Technol. 2014, 4,
15
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
1699‒1709.
[30] H.-L. Wu, C.-H. Kuo, M.-H. Huang, Langmuir 2010, 26, 12307‒12313.
[31] M. Jin, H. Zhang, J. Wang, X. Zhong, N. Lu, Z. Li, Z. Xie, M. J. Kim, Y. Xia,
ACS Nano 2012, 6, 2566‒2573.
[32] R. Ji, W. Sun, Y. Chu, RSC Adv. 2014, 4, 6055‒6059.
[33] S.-C. Wu, C.-S. Tan, M. H. Huang, M. H. Adv. Funct. Mater. 2017, 27,
1604635.
[34] H.-C. Chu, Y.-C. Chang, Y. Lin, S.-H. Chang, W.-C. Chang, G.-A. Li, H.-Y.
Tuan, ACS Appl. Mater. Interfaces 2016, 8, 13009‒13017.
[35] S. Ye, A. R. Rathmell, I. E. Stewart, Y. -C. Ha, A. R. Wilson, Z. Chen, B. J.
Wiley, Chem. Commun. 2014, 50, 2562‒2564.
[36] C. J. Johnson, E. Dujardin, S. A. Davis, C. J. Murphy, S. Mann, J. Mater. Chem.
2002, 12, 1765‒1770.
[37] H.-J. Yang, S.-Y. He, H.-Y. Tuan, Langmuir 2014, 30, 602‒610.
[38] M. Luo, M. Zhou, R. R. da Silva, J. Tao, L. Figueroa-Cosme, K. D. Gilroy, H.-C.
Peng, Z. He, Y. Xia, ChemNanoMat 2017, 3, 190‒195.
16
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
Figure 1. SEM images of a1, a2) 82 nm, b1, b2) 95 nm, and c1, c2) 108 nm Cu
nanocubes.
Figure 2. UV‒vis spectra of the synthesized Cu nanocubes with tunable sizes.
17
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
220
a
b
200
20 nm
Zone axis [100]
d
c
CuO (111)/(200)
2.35 Å
2 nm
Figure 3. a, b) TEM image of a 95 nm Cu nanocube and the corresponding SAED
pattern. c) HR-TEM image of the red box region in panel a. d) EDS line scan on a Cu
nanocube. The red and blue signals refer to copper and oxygen, respectively.
18
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
Figure 4. a) Full XPS spectrum of 95 nm Cu nanocubes. The oxygen peak should
come from surface oxide or molecular oxygen. The carbon peak should originate from
the residual reagents. b) XPS spectrum showing the Cu 2p peak region.
19
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
a
b
d
100 nm
1 µm
c
Figure 5. a) SEM and b) TEM images of the synthesized Cu nanowires. c) XRD
pattern of the Cu nanowires. d) UV‒vis spectrum of the Cu nanowires.
20
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
Table 1. a) General reaction scheme and conditions: alkyne (0.2 mmol), B2pin2 (0.25
mmol), PPh3 (0.1 mmol) and Cu nanocube catalyst (3 mg). b) Hydroboration yields
using different alkynes. These yields were calculated with respect to an internal
standard.
21
This article is protected by copyright. All rights reserved.

10.1002/asia.201700856
Chemistry - An Asian Journal
X = -H, -OCH3, -Cl,
-CF3, -F
Selectivity : 100 %
Yield range : 82-95 %
TOC Graphic
Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized
by simply heating an aqueous mixture of cetyltrimethylammonium chloride, copper
acetate, and sodium ascorbate. Copper nanowires can also be prepared this way. These
nanocubes can catalyze terminal aryl alkyne hydroboration reaction with 100%
product selectivity.
22
This article is protected by copyright. All rights reserved.