Nanoscale
PAPER
Cite this: DOI: 10.1039/c5nr02131f
Received 2nd April 2015,
Accepted 15th May 2015
DOI: 10.1039/c5nr02131f
www.rsc.o rg/nanoscale
Plasma-assisted synthesis and pressure-induced
structural transition of single-crystalline SnSe
nanosheets†
Jian Zhang,
a
Hongyang Zhu,
a
Xiaoxin Wu,
a
Hang Cui,
c
Dongmei Li,
a
Junru Jiang,
a
Chunxiao Gao,
a
Qiushi Wang*
b
and Qiliang Cui*
a
Two-dimensional tin selenide (SnSe) nanosheets were synthesized using a plasma-assisted direct current
arc discharge method. The structural characterization indicates that the nanosheets are single-crystalline
with an average thickness of ∼25 nm and a lateral dimension of ∼500 nm. The high pressure behaviors of
the as-synthesized SnSe nanosheets were investigated by in situ high-pressure synchrotron angle-dis-
persive X-ray diffraction and Raman scattering up to ∼30 GPa in diamond anvil cells at room temperature.
A second-order isostructural continuous phase transition (Pnma → Cmcm) was observed at ∼7GPa,
which is considerably lower than the transition pressure of bulk SnSe. The reduction of transition pressure
is induced by the volumetric expansion with softening of the Poisson ratio and shear modulus. Moreover,
the measured zero-pressure bulk modulus of the SnSe nanosheets coincides with bulk SnSe. This abnor-
mal phenomenon is attributed to the unique intrinsic geometry in the nanosheets. The high-pressure
bulk modulus is considerably higher than the theoretical value. The pressure-induced morphology
change should be responsible for the improved bulk modulus.
Introduction
The past decades have witnessed great progress in the pro-
duction of ultrathin nanomaterials.
1–5
Since the first introduc-
tion of strictly two-dimensional (2D) atomic crystal graphene,
6
2D nanomaterials have become a highly promising new class
of materials and have sparked a diversity of applications in the
next generation of electronic and optoelectronic devices due to
their unique dimension-dependent optical,
7–9
electrical,
10,11
magnetic
12,13
and superconducting properties.
14,15
As a typical
2D layered material, tin selenide (SnSe) nanocrystals have been
exploited in a diverse range of fields such as solar energy con-
version,
16,17
holographic recording,
18
near-infrared opto-
electronic devices
19
and rechargeable Li ion batteries.
20
In
addition, other advantages, such as earth-abundance, less toxi-
city and chemical stability, have also made the controlled syn-
thesis and property study of SnSe a focus of interest.
Current synthetic strategies for SnSe nanostructures primar-
ily focus on the so-called wet-chemical synthetic processes
such as solvothermal, chemical bath deposition and electrode-
position. Various nanostructures, such as 0D nanocrystals,
21,22
1D nanowires
17,23
and 2D nanosheets,
24,25
have been prepared
through these methods. However, the precursor, intermediate
and solvent residues adsorbed at the surface of the products
are difficult to remove and substantially modify the intrinsic
properties. Moreover, “solvent-free” synthesis approaches (e.g.
chemical or physical vapor depositions (CVD/PVD))
26–28
have
also been explored for the growth of SnSe. These methods are
easy to operate, less toxic, assemble fewer defects and avoid
residual impurities. However, the synthesis process normally
needs complex procedures, essential substrates and long reac-
tion times, which reduce the synthetic efficiency. Thus, the
controlled synthesis of pure-phase and free-standing SnSe
nanostructures in a convenient way is still a great challenge.
One aim of this study is to explore a rapid, low-cost and high-
yield method for the synthesis of SnSe nanosheets (NSs).
In general, the properties of nanomaterials largely depend
on their crystal phase, surface area, morphology and architec-
ture. Therefore, the structural stability of sheet-shape nano-
materials is one of the crucial factors for their application. It is
well known that high pressure provides a powerful method for
investigating the physicochemical properties and structural
phase transitions of materials. Most previous studies on SnSe
mainly focused on the synthesis method and property analysis.
Only a few studies on the high-pressure behavior of SnSe have
been reported. In 1984, Chattopadhyay et al. reported that
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c5nr02131f
a
State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012,
Jilin, China. E-mail: cql@jlu.edu.cn
b
College of New Energy, Bohai University, JinZhou 121013, Liaoning, China.
E-mail: wang_jiu_jiu@foxmail.com
c
College of Physics, Jilin University, Changchun 130012, Jilin, China
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