The ordered tin disulfide (SnS2) nanowire arrays were first fabricated by sulfurizing the Sn nanowires, which are embedded in the nanochannels of anodic aluminum oxide (AAO) template. SnS2nanowire arrays are highly ordered and highly dense. X-ray diffraction (XRD) and corresponding selected area electron diffraction (SAED) patterns demonstrate the SnS2nanowire is hexagonal polycrystalline. The study of UV/Visible/NIR absorption shows the SnS2nanowire is a wide-band semiconductor with three band gap energies (3.3, 4.4, and 5.8 eV)

CA Ross

CD Lokhande

Chih-Jung Chen

CR Wang

D Vollath

DL Greenaway

EC Greyson

G Burns

G Said

G Yi

H Chang

JB Shi

Jen-Bin Shi

K Matsumoto

MP Zach

NG Deshpande

Po-Feng Wu

QH Zhang

S Polarz

SK Panda

Ya-Ting Lin

YJ Ji

Yu-Cheng Chen

English

PubMed

Springer - Publisher Connector

NANO EXPRESS
Synthesis and Characterization of Tin Disulfide (SnS2) Nanowires
Ya-Ting Lin Æ Jen-Bin Shi Æ Yu-Cheng Chen Æ
Chih-Jung Chen Æ Po-Feng Wu
Received: 7 October 2008 / Accepted: 24 March 2009 / Published online: 5 April 2009
 to the authors 2009
Abstract The ordered tin disulfide (SnS2) nanowire
arrays were first fabricated by sulfurizing the Sn nanowires,
which are embedded in the nanochannels of anodic alu-
minum oxide (AAO) template. SnS2 nanowire arrays are
highly ordered and highly dense. X-ray diffraction (XRD)
and corresponding selected area electron diffraction
(SAED) patterns demonstrate the SnS2 nanowire is hex-
agonal polycrystalline. The study of UV/Visible/NIR
absorption shows the SnS2 nanowire is a wide-band
semiconductor with three band gap energies (3.3, 4.4, and
5.8 eV).
Keywords Nanomaterials  SnS2  Nanowire 
AAO  Template
Introduction
In recent years, one-dimensional (1-D) nanostructural
materials have been attractive due to their physical and
chemical properties. These nanostructures in particular
show results in electronics [1], magnetic [2], optics, etc.,
that have great potential applications in the next generation
of nanodevices [3]. Anodic aluminum oxide (AAO) tem-
plate-based assembling has been widely applied in recent
years to produce nanowires with extremely long length and
high aspect ratio, and it also provides a simple, rapid, and
cheap way for fabricating nanowires as aligned arrays [4].
Tin disulfide (SnS2) is an n-type semiconductor with
hexagonal cadmium iodide (Cdl2) structure. It is composed
of sheets of tin atoms sandwiched between two close-
packed sheets of sulfur atoms [5]. Single crystal and
polycrystalline films of SnS2 have shown optical band gaps
in the range of 2.12–2.44 eV [6]. As an important member
of the IV–VI group semiconductors, SnS2 is a possible
choice in solar cells and optoelectronic devices [7]. A
variety of methods have been developed into synthesized
SnS2 nanoparticles, films, and crystals. SnS2 nanoparticles
were synthesized through the microware plasma process
either by the reaction between chloride or carbonyl of tin
and H2S [8]. The films of SnS2 were prepared by chemical
deposition from an acidic medium solution containing
Sn4? ions [9]. Single crystals of SnS2 have been grown by
the vapor phase [10]. In addition, SnS2 nanocrystallites
with hexagon flake shape were synthesized by a hydro-
thermal reaction between SnCl4  5H2O and (NH2)2CS
[11]. SnS2 nanobelts were produced from SnCl2  2H2O
and Na2S by a thioglycollic acid (TGA) assisted hydro-
thermal method [12]. However, SnS2 nanowires are
fabricated within AAO template synthesis, using the elec-
trodeposition and sulfurizing methods that are not yet
reported.
For this purpose, we report a new synthesis method for
semiconductor SnS2 nanowires. Pure metal Sn is electro-
deposited in the nanochannels of the AAO template. Sn
nanowires are sulfurized in the S atmosphere to form SnS2
nanowires. According to past research, our first successful
fabrication attempt was sulfurizing the Sn nanowires that
were electrodeposited in the AAO template and studying
its properties.
Y.-T. Lin (&)  Y.-C. Chen  C.-J. Chen  P.-F. Wu
The Graduate Institute of Electrical and Communications
Engineering, Feng Chia University, 100, Wen-Hwa Rd, Seatwen,
Taichung 40724, Taiwan
e-mail: p9431597@fcu.edu.tw
J.-B. Shi
Department of Electronic Engineering, Feng Chia University,
Taichung 40724, Taiwan
123
Nanoscale Res Lett (2009) 4:694–698
DOI 10.1007/s11671-009-9299-5
Experimental Details
Preparation of AAO Template
The AAO template used in our experiment was prepared by
a two-step anodization process as described previously
[13]. Briefly, high purity aluminum sheet (99.9995%) was
first anodized at constant voltage in the sulfuric acid
solution for 3 h. After anodization, the anodized Al sheet
was put into an acid to completely remove the porous layer.
Then, the AAO template can be fabricated by repeating the
anodization process under the same conditions of the first
step anodization. The AAO template was obtained by
etching away the underlying aluminum substrates with a
mercuric chloride solution. The transparent AAO template
was immersed in a phosphoric acid solution to widen the
nanochannels. After this process, the diameter of the
nanochannel was about 40 nm.
Preparation of SnS2 Nanowires
In order to prepare Sn nanowires, a platinum (Pt) film was
deposited by vacuum evaporation onto one surface of the
AAO template to provide a conductive contact. The Sn
nanowires were electrodeposited in the pore of the nano-
channels of AAO template under constant voltage, using an
electrolyte containing SnSO4 and distilled water. After
washing with distilled water and air drying, the AAO
template with Sn nanowires was put into a glass tube with
the pure S powder together. The glass tube was evacuated
by using a pump, and it was placed into the furnace. The
samples were then heated from room temperature (heating
rate: 5 C/min) to 500 C and kept at this temperature for
10 h to completely sulfurize the Sn nanowires. It is
expected that S atoms would react with the metal Sn to
form SnS2. After the reaction was terminated, the furnace
was naturally cooled down to room temperature and SnS2
nanowires were completely formed after sulfurization.
Characterization of SnS2 Nanowires
The morphology and microstructure of the as-prepared
SnS2 nanowire arrays were characterized by field emission
scanning electron microscopy/energy dispersive spec-
trometer (FE-SEM/EDS, HITACHI S-4800). The iden-
tification of the crystallization and phase structure were
analyzed by X-ray diffraction (XRD, SHIMADZU XRD-
6000) utilizing Cu Ka radiation. More details about the
microstructure of the SnS2 nanowires were investigated by
the high-resolution transmission electron microscopy/cor-
responding selected area electron diffraction (HR-TEM/
SAED, JEOL JEM-2010). For HR-TEM and SAED anal-
ysis, the SnS2 nanowires were dispersed in ethanol and
vibrated for few minutes. Then, a few drops of the resulting
suspension were dripped onto a copper grid. For optical
analysis, the AAO template was dissolved by NaOH
solution at room temperature and was washed with distilled
water to expose freely nanowires of SnS2. After the SnS2
nanowires are absolutely dispersed in distilled water using
a supersonic disperser, the absorption spectra of the SnS2
nanowires were measured on an UV/Visible/NIR spectro-
photometer (HITACHI U-3501).
Results and Discussion
Morphology of AAO Template and SnS2 Nanowires
The morphology of the as-synthesized product was exam-
ined by FE-SEM. Typical FE-SEM morphology (Fig. 1a)
shows the pores on the AAO template had a uniform size
and were arranged in a honeycomb hexagonal structure.
Figure 1b shows the pure Sn nanowire arrays in the pore of
nanochannels of AAO template. It shows the length of Sn
nanowires is about 5 lm. Figure 1c shows the SnS2
nanowires embedded in an AAO template. It reveals the
aspect ratio (length/diameter) of SnS2 nanowires around
125. When the sulfurization temperature was fixed at
500 C, the formation of SnS2 nanowires was confirmed by
sulfurization up to 10 h. From the high-magnification FE-
SEM micrograph (Fig. 1d), SnS2 nanowires with the
diameter of about 40 nm can be clearly observed. The
chemical composition of the SnS2 nanowires was investi-
gated by EDS. Figure 1e reveals EDS spectra of SnS2
nanowires arrays, indicating only aluminum, oxygen, tin,
and sulfur were present, and that there was no contami-
nation by other elements. Quantitative analysis reveals the
atomic ratio of Sn to S with 33.92:66.08 is close to 1:2,
indicating the SnS2 nanowires are well-crystallized, and
they are in good agreement with the XRD results. In order
to investigate the morphology of the SnS2 nanowires, the
AAO template was completely removed in NaOH for
15 min to expose them, followed by thoroughly rinsing
with distilled water. Figure 1f reveals the SnS2 nanowires
with diameter of about 40 nm detached from the AAO
template. The individual SnS2 nanowires were almost the
same diameter of the AAO template. The geometrical
characteristics of the SnS2 nanowires could be controlled
by choosing the proper type of AAO template.
Crystal Structures of SnS2 Nanowires
Figure 2 shows the X-ray diffraction (XRD) spectra of the
as-prepared SnS2 nanowires without AAO template, which
makes the crystal structure of the SnS2 nanowires conve-
nient for characterization. It can be seen that there are no
Nanoscale Res Lett (2009) 4:694–698 695
123
peaks of Sn and S after the metal Sn nanowires are sulf-
urated at 500 C for 10 h. Furthermore, the Sn peaks
totally disappear after sulfuration and the SnS2 peaks
appear. The indicated formation of SnS2 in hexagonal
crystal phase has a preferred orientation (011), which is in
good agreement with the reported values (JCPDS Card
no.83-1705). Metal oxides such as SnO2 nanowires have
been prepared by oxidation of metal Sn nanowires, and it is
generally accepted that the chemical properties of oxygen
and sulfur are similar to each other. Hence, the technique
used here for formation of SnS2 is understandable. The
formation mechanism of SnS2 nanowires with the reaction
equation can be expressed as follows:
Sn4þ þ 2S ! SnS2 ð1Þ
in which the S atoms would react with metal Sn atoms at
high temperatures to form SnS2 nanowires. Since the
reaction rates of S and Sn atoms are mainly dominated by
time and temperature, long periods and high temperatures
of the sulfurization process were needed to prepare the fine
crystalline SnS2 nanowires. When the sulfurization time
was fixed for 10 h, the formation of SnS2 nanowires were
confirmed by sulfurization at a temperature of 500 C.
Detailed information on the microstructure of as-pre-
pared SnS2 nanowires was obtained by HR-TEM. Low-
magnification HR-TEM image (Fig. 3a) illustrates the
numerous SnS2 nanowires. Figure 3b reveals the HR-TEM
image of an individual SnS2 nanowire. The diameter of the
nanowire is about 40 nm. Nevertheless, the grain size of
the SnS2 nanowire cannot be clearly observed. In Fig. 3c,
the corresponding SAED pattern of an individual nanowire
exhibits a polycrystalline. Moreover, the concentric dif-
fraction rings could be indexed outward as (011), (001),
(012), and (110) lattice planes of hexagonal SnS2. The HR-
TEM image (Fig. 3d) shows a single nanowire with the
lattice spacing of about 0.2777 nm, which corresponds to
(011) plane of SnS2.
Optical Properties of SnS2 Nanowires
Figure 4 shows the UV/Visible/NIR absorbance spectra of
the as-grown sample recorded in the spectral range 200–
900 nm for SnS2 nanowires. Our absorption spectra results
of SnS2 nanowires have a very strong absorption peak at
Fig. 1 FE-SEM micrographs of a top view of the AAO template, b
cross-section view of Sn nanowires arrays in the pore of the
nanochannels of AAO template, c cross-section view of SnS2
nanowires were embedded in an AAO template, d the magnified
FE-SEM micrograph of (c), e EDS spectra of the SnS2 nanowires, and
f the AAO template was absolutely dissolved by NaOH solution
Fig. 2 X-ray diffraction patterns of SnS2 nanowires without AAO
template
696 Nanoscale Res Lett (2009) 4:694–698
123
260 nm, no other peaks can be observed. We infer the
absorption peak at 260 nm in ultraviolet region is due to
the phase of the tin disulfide (SnS2). SnS was not observed
because it has a strong absorption onset around 980 nm of
direct band gap and a weaker absorption edge near
1100 nm of the indirect band gap [14]. This result proves
our sulfured nanowires are SnS2 phase, and it is in accor-
dance with our XRD results. To determine the band gap
energy (Eg) of the SnS2 nanowires, the dependence of
absorption coefficient (a) on the photon energy equation is
given as follows [15]:
ahm ¼ A hm Eg
 m ð2Þ
where hv is the photon energy, Eg the band gap energy, and
A is the constant having separate values for different
transitions. The values of m for allowed direct, allowed
indirect, forbidden direct, and forbidden indirect transition
are 1/2, 2, 3/2, and 3, respectively. This equation gives
band gap (Eg) when straight portion of (ahm)
1/m versus hm
plots are extrapolated to the point a = 0. However, m =
3/2, 2, and 3, the band gap energies were found to be a
negative number which is not reasonable in physics.
Relationship fitting to the absorption spectra of SnS2 as
m = 1/2, which means these nanowires are allowed direct
transition. As m = 1/2, the (ahm)2 versus hm plot is shown
in the inset in Fig. 4, exhibiting a linear relationship at 3.9–
4.75, 5.4–6.1, and 6.2–6.35 eV, respectively. The band gap
Fig. 3 a The low-magnification
HR-TEM image of SnS2
nanowires, b the high-
magnification HR-TEM image
of an individual SnS2 nanowire,
c SAED pattern of an individual
SnS2 nanowire, and d HR-TEM
image of a single SnS2 nanowire
with lattice fringes
Fig. 4 UV/Visible/NIR absorption spectra with SnS2 nanowires and
(ahm)2 versus hm plot (inset)
Nanoscale Res Lett (2009) 4:694–698 697
123
energies of 40 nm SnS2 nanowires are estimated to be 3.3,
4.4, and 5.8 eV by the extrapolation of relation. According
to the most recent study about the optical characteristics of
the SnS2 films, absorbance spectra were recorded in the
spectral range 350–800 nm. Deshpande et al. [16] recently
reported the band gap energy of the allowed direct transi-
tions at 2.2 eV in the SnS2 films with average grain sizes
of: 180–220 nm. The band gap energies of SnS2 nanowires
were higher than that of SnS2 films. Panda et al. [17]
observed the direct optical transition and the band gap
energy was 3.5 eV with crystalline nanoparticles of 15 nm
annealed at 150 C for 1 h. In this study, the band gap
energy of the allowed direct transitions at 3.3 eV of SnS2
nanowires with 40 nm diameter is agreeable to those
obtained of Panda et al. Our band gap energy (3.3 eV) of
SnS2 nanowires is reasonable when compared with the
band gap energy (2.2-3.5 eV) of SnS2 films. Wang et al.
[18] reported the absorption spectra were recorded in the
spectral range under 350 nm. They observed the emission
or excitation bands of SnS2 nanocrystallites, which are
associated with the transition between those sub-bands.
Those bands of SnS2 nanocrystallites may be associated
with the presence of defect either interface or interior. Our
band gap energies (4.4 and 5.8 eV) of SnS2 nanowires are
probably a result of sub-band in the electronic structure.
Chang et al. reported SnS2 nanotubes could be a one-
dimensional sensor material for NH3 detection, indicating
that SnS2 nanowires may be suitable for NH3 sensor
applications [19]. This can be explained by the calculated
binding energies for a NH3 molecule on the SnS2, which
are very close to those obtained previously in calculations
of NH3 adsorption onto a carbon nanotube [20]. In the
future, we will study the energy jump of physical phe-
nomenon, development and applications in gas sensor and
solar cell.
Conclusions
SnS2 nanowires arrays have been successfully fabricated
within template synthesis by using the electrodeposition
and sulfurizing methods. The results show SnS2 nanowires
have high wire packing densities with uniform wire
diameters and lengths of about 40 nm and 3–5 lm,
respectively. In XRD results, after sulfuring the Sn nano-
wire at 500 C for 10 h, the sulfured nanowires have SnS2
phase and a preferred orientation (011). The analysis of the
HR-TEM/SAED reveals the SnS2 nanowire is polycrys-
talline. The SnS2 nanowires show three band gap energies
(3.3, 4.4, and 5.8 eV) and exhibit a linear relationship
at 3.9–4.75, 5.4–6.1, and 6.2–6.35 eV, respectively as
m = 1/2. The absorption spectra of nanowires contain
three spectral intervals with the shapes typical for direct
allowed interband transitions with the effective bandgaps.
Acknowledgments The research was supported by the National
Science Council of R.OC. under grant No. NSC-96-2122-M-035-
003-MY2.
References
1. G. Yi, W. Schwarzacher, Appl. Phys. Lett. 74, 1746 (1999). doi:
10.1063/1.123675
2. C.A. Ross, M. Hwang, M. Shima, H.I. Smith, M. Farhoud, T.A.
Savas et al., J. Magn. Magn. Mater. 249, 200 (2002). doi:
10.1016/S0304-8853(02)00531-0
3. M.P. Zach, K.H. Ng, R.M. Penner, Science 290, 2120 (2000). doi:
10.1126/science.290.5499.2120
4. Q.H. Zhang, Z.J. Chang, M.F. Zhu, X.M. Mo, D.J. Chen,
Nanotechnology 18, 115611 (2007). doi:10.1088/0957-4484/18/
11/115611
5. D.L. Greenaway, R. Nitsche, J. Phys. Chem. Solids 26, 1445
(1965). doi:10.1016/0022-3697(65)90043-0
6. G. Said, P.A. Lee, Phys. Status Solidi, A Appl. Res. 15, 99
(1973). doi:10.1002/pssa.2210150111
7. S. Polarz, B. Smarsly, C. Goltner, M. Antonietti, Adv. Mater. 12,
1499 (2000). doi:10.1002/1521-4095(200010)12:20\1503::AID-
ADMA1503[3.0.CO;2-X
8. D. Vollath, D.V. Szab’o, Acta Mater 48, 953 (2000). doi:
10.1016/S1359-6454(99)00395-X
9. K. Matsumoto, S. Kaneko, Thin Solid Films 121, 227 (1984). doi:
10.1016/0040-6090(84)90304-3
10. C.D. Lokhande, J. Phys. D Appl. Phys. (Berl) 23, 1703 (1990)
11. C.R. Wang, K.B. Tang, Q. Yang, Y.T. Qian, C.Y. Xu, Chem.
Lett. 12, 1294 (2001). doi:10.1246/cl.2001.1294
12. Y.J. Ji, H. Zhang, X.Y. Ma, J. Xu, D.E. Yang, J. Phys. Condens.
Matter 15, 661 (2003). doi:10.1088/0953-8984/15/44/L02
13. J.B. Shi, Y.C. Chen, C.W. Lee, Y.T. Lin, C. Wu, C.J. Chen,
Mater. Lett. 62, 15 (2008). doi:10.1016/j.matlet.2007.04.060
14. E.C. Greyson, J.E. Barton, T.W. Odom, Small 2, 368 (2006). doi:
10.1002/smll.200500460
15. G. Burns, Solid State Physics (Academic Press, Orlando, 1985)
16. N.G. Deshpande, A.A. Sagade, Y.G. Gudage, C.D. Lokhande, R.
Sharma, J. Alloys Compd. 436, 421 (2007). doi:10.1016/
j.jallcom.2006.12.108
17. S.K. Panda, A. Antonakos, E. Liarokapis, S. Bhattacharya, S.
Chaudhuri, Mater. Res. Bull. 42, 576 (2007). doi:10.1016/
j.materresbull.2006.06.028
18. C.R. Wang, K.B. Tang, Q. Yang, Y.T. Qian, Chem. Phys. Lett.
357, 371 (2002). doi:10.1016/S0009-2614(02)00495-5
19. H. Chang, E. In, K.J. Kong, J.O. Lee, Y. Choi, B.H. Ryu, J. Phys.
Chem. B 109, 30 (2005). doi:10.1021/jp044983o
20. H. Chang, J.D. Lee, S.M. Lee, Y.H. Lee, Appl. Phys. Lett. 79,
3863 (2001). doi:10.1063/1.1424069
698 Nanoscale Res Lett (2009) 4:694–698
123


Synthesis and Characterization of Tin Disulfide (SnS) Nanowires

Synthesis and Characterization of Tin Disulfide (SnS2) Nanowires

Crossref

Abstract The ordered tin disulfide (SnS2) nanowire arrays were first fabricated by sulfurizing the Sn nanowires, which are embedded in the nanochannels of anodic aluminum oxide (AAO) template. SnS2nanowire arrays are highly ordered and highly dense. X-ray diffraction (XRD) and corresponding selected area electron diffraction (SAED) patterns demonstrate the SnS2nanowire is hexagonal polycrystalline. The study of UV/Visible/NIR absorption shows the SnS2nanowire is a wide-band semiconductor with three band gap energies (3.3, 4.4, and 5.8 eV).</p

Shi Jen-Bin

Lin Ya-Ting

Chen Yu-Cheng

Chen Chih-Jung

Wu Po-Feng

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Nanoscale Research Letters

Synthesis and Characterization of Tin Disulfide (SnS<sub>2</sub>) Nanowires

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Status Solidi,

Thin Solid Films 121,

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Synthesis and Characterization of Tin Disulfide (SnS2) Nanowires

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