होम Journal of Alloys and Compounds Large-scale synthesis of bismuth sulfide nanorods by microwave irradiation

Large-scale synthesis of bismuth sulfide nanorods by microwave irradiation

, , , , , , , , ,
यह पुस्तक आपको कितनी अच्छी लगी?
फ़ाइल की गुणवत्ता क्या है?
पुस्तक की गुणवत्ता का मूल्यांकन करने के लिए यह पुस्तक डाउनलोड करें
डाउनलोड की गई फ़ाइलों की गुणवत्ता क्या है?
खंड:
509
साल:
2011
भाषा:
english
DOI:
10.1016/j.jallcom.2010.10.160
फ़ाइल:
PDF, 2.46 MB
0 comments
 

To post a review, please sign in or sign up
आप पुस्तक समीक्षा लिख सकते हैं और अपना अनुभव साझा कर सकते हैं. पढ़ूी हुई पुस्तकों के बारे में आपकी राय जानने में अन्य पाठकों को दिलचस्पी होगी. भले ही आपको किताब पसंद हो या न हो, अगर आप इसके बारे में ईमानदारी से और विस्तार से बताएँगे, तो लोग अपने लिए नई रुचिकर पुस्तकें खोज पाएँगे.
1

Investigation of Sn–Zn electrodeposition from acidic bath on EQCM

साल:
2011
भाषा:
english
फ़ाइल:
PDF, 561 KB
2

Growth of AlN nanobelts, nanorings and branched nanostructures

साल:
2011
भाषा:
english
फ़ाइल:
PDF, 1019 KB
Journal of Alloys and Compounds 509 (2011) 2116–2126

Contents lists available at ScienceDirect

Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom

Large-scale synthesis of bismuth sulfide nanorods by microwave irradiation
Jiliang Wu a , Fan Qin a , Gang Cheng a , Hui Li a , Jiuhong Zhang a , Yaoping Xie a,b , Hai-Jian Yang b,∗ ,
Zhong Lu a , Xianglin Yu a , Rong Chen a,∗
a

Key Laboratory for Green Chemical Process of Ministry of Education and School of Chemical Engineering & Pharmacy, Wuhan Institute of Technology, Wuhan, 430073, PR China
Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission & Ministry of Education, College of Chemistry and Materials Science, South-Central University
for Nationalities, Wuhan, 430074, PR China
b

a r t i c l e

i n f o

Article history:
Received 20 August 2010
Received in revised form 22 October 2010
Accepted 27 October 2010
Available online 4 November 2010
Keywords:
Microwave irradiation
Bismuth sulfide
Nanorods
Growth mechanism

a b s t r a c t
Bismuth sulfide (Bi2 S3 ) has attracted considerable interest due to its potential applications in thermoelectric and electronic devices, optoelectronic devices, and biomedicine. In this study, large-scale
highly crystalline Bi2 S3 nanorods were successfully prepared from bismuth citrate and thiourea (Tu) by
microwave irradiation methods. The products were characterized by powder X-ray diffraction (XRD),
scanning electron microscopy (SEM), transmission electron microscopy (TEM, HRTEM) and selected area
electron diffraction (SAED). The influences of reaction time, surfactants, solvents, and precursors on the
formation of Bi2 S3 nanorods were discussed. The microwave irradiation method reduced reaction time
by at least 80% in the synthesis of Bi2 S3 nanorods compared with the refluxing method. Cetyltrimethylammonium bromide (CTAB) and ˇ-cyclodextrin (ˇ-CD) were found to be beneficial to the formation
of Bi2 S3 nanorods. N,N-dimethylformamide, ethylene glycol, and d; iethylene glycol were the favorable
solvents in the fabrication of these nanorods. It was found that different bismuth and sulfur precursors
influenced the sizes and morphologies of the Bi2 S3 nanorods. The proposed growth mechanism of Bi2 S3
nanorods was also discussed.
© 2010 Elsevier B.V. All rights reserved.

1. Introduction
As a good semiconducting main-group metal chalcogenide with
a direct energy band gap ranging from 1.2 to 1.7 eV, bismuth
sulfide (Bi2 S3 ) has many potential applications in the fabrication of optoelectronic and thermoelectric cooler devices, as well
as in photovoltaic and thermoelectric transport, photoconductivity, electrical photoresponse, and field-emission [1–5]. Bi2 S3
has also been proposed as a good electrode for liquid-junction
solar cells [6,7]. Recently, the Weissleder and co-workers reported
the use of polymer-coated Bi2 S3 nanoparticles as injectable computed tomography (CT) imaging agent with excellent stability
at high concentrations, high X-ray absorption and long circulation times in vivo [8]. It demonstrated a strong example of the
biological application of Bi2 S3 . Owing to its unique properties,
extensive investigation of Bi2 S3 nanomaterials has been carried
out with the development of nanotechnology. In recent years,
many methods have been developed to synthesize Bi2 S3 nanomaterials with different morphologies, such as nanotubes [9,10],
nanowires [11–13], nanoribbons [14,15], nanoflowers [4,13,16],

∗ Corresponding authors. Tel.: +86 13659815698; fax: +86 2787194465.
E-mail addresses: rchenhku@hotmail.com (R. Chen),
yanghaijian@vip.sina.com (H.-J. Yang).
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.10.160

microbelts [17], snowflake-like Bi2 S3 nanostructures [18–20] and
self-supported patterns of radially aligned one-dimensional (1D)
Bi2 S3 nanostructures [21].
Among 1D Bi2 S3 nanomaterials, Bi2 S3 nanorods are the most
extensively studied morphology. They have been fabricated
through various synthetic approaches, including ionic liquid [22],
solvothermal [14,23–25], hydrothermal [26–29], sonochemical
[30,31], microemulsion [32] and refluxing methods [33]. However,
these methods generally require rigorous experimental conditions
(under a stream of N2 ), long reaction time, or intricate instruments,
which makes production in large scale difficult. Therefore, a simple, rapid and environment-friendly approach for the large-scale
preparation of Bi2 S3 nanorods is highly desired.
As a rapid, simple and effective heating method, microwave irradiation, with direct microwave heating of the molecular precursors,
has been widely used in the synthesis of high-quality nanomaterials [34–48]. It can reduce the reaction time significantly and has
the advantage of uniform heating without heating temperature
gradient and lag effect [49–51]. Furthermore, microwave irradiation has a short thermal induction period with no convection
processes, easy controllability, and low cost. Therefore, it is very
useful in the fabrication of monodisperse nanomaterials. Currently,
there are few publications relevant to the microwave synthesis of
Bi2 S3 nanomaterials. Zhu and co-worker reported the microwaveassisted synthesis of Bi2 S3 nanorods by using an ionic liquid [22].

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

2117

Table 1
Experimental conditions for the preparation of Bi2 S3 nanomaterials.
Sample

Bismuth precursora

Sulfur precursorb

R1
R2
R3
R4
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23

Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(NO3 )3 ·5H2 O
BiCl3
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)
Bi(cit)

Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Tu
Na2 S
Na2 S2 O3
GSH
Tu
Tu

Bi/S ratio
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:5
1:5

Solventc

Surfactant

Surfactant amount (g)

Reaction time (min)

DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
EG
DEG
formamide
ethylenediamine
EG
EG
EG
DMF
EG
DMF
DMF
DMF
DMF
DMF
DMF
DMF

CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
PVP
ˇ-CD
PEG
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
None
None
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
None

0.128
0.128
0.128
0.128
0.128
0.128
0.128
0.128
0.1
0.2
0.1
0.128
0.128
0.128
0.128
0.128
0.128
0.128
0
0
0.128
0.128
0.128
0.128
0.128
0.128
0

30
60
90
120
5
10
15
20
20
20
20
20
20
20
20
3
7
13
20
20
20
20
20
20
20
20
20

Note: R1–R4 were prepared by refluxing method. All other samples were prepared by using microwave irradiation method.
a
The molarity of bismuth precursor was 0.5 mmol.
b
The molarity of sulfur precursor was 1.5 mmol.
c
The volume of solvent was 35 mL.

Rod-like and urchin-like morphologies were also obtained with
microwave heating [42,52–54]. However, the large-scale synthesis
of high crystalline Bi2 S3 nanorods has not been mentioned using
the microwave heating method.
In our previous work, we described a refluxing method for
synthesizing high crystalline and large-scale Bi2 S3 nanorods in a
two-hour timeframe [33]. Bismuth citrate, a linear polymer, assists
the fabrication of Bi2 S3 nanorods in this synthesis. In the current
study, we developed the microwave heating approach to synthesize
high crystalline Bi2 S3 nanorods at large scale. By changing various experiment parameters, such as the surfactant, reaction time,
solvent, reactant ratio, bismuth and sulfur precursor, different morphologies and sizes of Bi2 S3 nanostructures were obtained. The
results have helped us greatly to understand the growth mechanism of the Bi2 S3 nanorods under microwave irradiation.

subsequently conducted to collect the solid product. Finally, the product was dried
in a desiccator for a few days for further characterization (R1). Samples R2–R4 were
also prepared using the same method under identical condition except that the
reaction time is 60, 90, and 120 min, respectively (Table 1).
2.3. Synthesis of Bi2 S3 nanomaterials by microwave heating
In a typical experiment, 0.199 g (0.5 mmol) of Bi (cit), 0.114 g (1.5 mmol) of
Tu and 0.128 g (0.35 mmol) of CTAB were added to a round-bottom flask which
contained 35 mL of DMF. The mixture was stirred and sonicated until all the chemicals were well-dispersed. Then the mixed solution was heated up to 200 ◦ C by an
800 W microwave radiation for 5 min with continuous vigorous stirring. After cooling down to room temperature, the mixture was centrifuged, washed and collected
as described above (S1). Other samples of Bi2 S3 nanomaterials were also prepared
by microwave irradiation under identical conditions by changing the reaction time
(S2–S4), surfactants (S5–S7, S15 and S16), solvents (S8–S14), bismuth precursors
(S17 and S18), sulfur precursors (S19–S21) and the amounts of Tu (S22 and S23),
respectively. The detail procedure is same as described above and all the experiment
parameters are listed in Table 1.

2. Experimental procedures
2.4. Characterization
2.1. Materials
Bismuth citrate (Bi(cit)), polyethylene glycol (PEG, with average Mw of 10,000)
and polyvinylpyrrolidone (PVP, with average Mw of 10,000) were purchased
from Aldrich (USA). Cetyltrimethylammonium bromide (CTAB) was purchased
from Lancaster (UK). N,N-dimethylformamide (DMF) was purchased from Bodi
Chemical Reagents Co. (China). Sodium sulfite (Na2 S2 O3 ) was purchased from
Fuchen Chemical Reagents Co. (China). Formamide, ˇ-cyclodextrin (ˇ-CD), bismuth
nitrate pentahydrate (Bi(NO3 )3 ·5H2 O), bismuth chloride (BiCl3 ), ethylene glycol
(EG), thiourea (Tu), sulfur (S), sodium sulfide (Na2 S), diethylene glycol (DEG) and
ethylenediamine were obtained from Sinopharm Chemical Reagent Co. (China). All
the reagents were analytical grade and used directly without further purification.
2.2. Synthesis of Bi2 S3 nanomaterials by refluxing method
In a typical experiment, 0.199 g (0.5 mmol) of Bi (cit), 0.114 g (1.5 mmol) of Tu
and 0.128 g (0.35 mmol) of CTAB were added to a round-bottom flask which contained 35 mL of DMF. The mixture was stirred and sonicated until all the chemicals
were well-dispersed. Then the mixture was refluxed at 160 ◦ C for 30 min in an oil
bath with continuous vigorous stirring. After cooling down to room temperature,
the mixture was centrifuged and a solid product was collected. The product was
washed with deionized water and acetone twice, respectively. Centrifugation was

Bi2 S3 nanorods were characterized by powder X-ray diffraction (XRD), scanning
electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM) techniques including high-resolution TEM imaging (HRTEM)
and selected area electron diffraction pattern (SAED). XRD was carried out on Bruker
AXS D8 Discover (Cu K˛ = 1.5406 Å). The scanning rate is 1◦ min−1 in the 2 range
from 10◦ to 80◦ . TEM images and SAED patterns were recorded on a Philips Tecnai
20 electron microscope at an accelerating voltage of 200 kV. SEM images were taken
on a LEO 1530 SEM operated at 5 kV and a Hitachi S4800 SEM at 5 eV. TEM samples
were prepared by dispersing some of the solid products into ethanol and then sonicating for approximately 30 s. A few drops of the suspension were deposited on
copper grids, which were then put into the desiccators for drying.

3. Results
3.1. Characterizations of Bi2 S3 nanorods synthesized by
microwave method
Fig. 1a shows powder XRD spectra of the samples prepared from
Bi(cit) and Tu in DMF by different time of microwave heating in the

2118

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

Fig. 1. Powder XRD spectra (a) and SEM images (b–f) of the products prepared from Bi(cit) and Tu by microwave heating method under different reaction time (b: 5 min; c:
10 min; d: 15 min; e: 20 min; f: 30 min).

presence of CTAB (S1–S4). All the diffraction peaks in the spectra
of the four samples could be indexed to the orthorhombic phase of
Bi2 S3 (JCPDS 17-0320). No other impurities could be detected in the
XRD spectra. These observations indicated that well-crystallized
Bi2 S3 can be obtained easily under this synthetic condition, even
when the microwave heating time is only 5 min.
The morphology evolution of prepared Bi2 S3 samples (S1–S4)
that were obtained at different reaction time were investigated
by SEM imaging, as shown in Fig. 1b–f. After only 5 min of
microwave heating, rod-like Bi2 S3 nanostructures were observed
(S1, Fig. 1b). More and more Bi2 S3 nanorods showed up as reaction time increased. It was observed that a large quantity (nearly
100%) of Bi2 S3 nanorods were obtained when the reaction time was
prolonged to 15 min, as shown in Fig. 1d. SEM images (Fig. 1e) displayed the uniform Bi2 S3 nanorods with a high yield after 20 min
of microwave heating. Obviously, the morphologies of the products
were slightly different with the increase of reaction time. However,
there was no Bi2 S3 nanorod obtained until 90 min of refluxing had
been carried out (see Supplementary Materials Fig. S1). The SEM
images (Fig. S1) revealed that a large quantity of uniform Bi2 S3
nanorods were obtained after 2 h of refluxing (R4), which is consistent with our reported data [33].
The structures of the Bi2 S3 nanorods prepared by microwave
heating (S1–S4) were further characterized by TEM images and
SAED pattern. Similar to the SEM images, Bi2 S3 nanorods can be
detected in the sample after 5 min microwave heating. The aspect

ratio, which is the average ratio of the length to the diameter of
nanorods, was about 6, 7, 9 and 11, respectively (see Supplementary
Materials Fig. S2). The diameter of these nanorods varied from 20
to 90 nm and the length was less than 1 ␮m when the reaction time
was less than 20 min. The Bi2 S3 nanorods had equal diameter (about
50 nm) after 20 min microwave heating and the length reached
several micrometers. However, other morphologies of Bi2 S3 were
also observed in the whole sample (see Supplementary Materials
Fig. S2). For example, Bi2 S3 nanoparticles of less than 50 nm were
obtained, which had a tendency to assemble into nanorods. Fig. 2
shows the TEM, HRTEM images and SAED pattern of the Bi2 S3
nanorods prepared by 20 min of microwave heating (S4). The lowmagnification TEM image (Fig. 2a) clearly revealed well-defined
rod morphology. The length of the nanorods varies from 500 nm
to more than 1 ␮m. The diameter of the Bi2 S3 nanorods is in the
range of 30–80 nm, with an average diameter of about 50 nm. The
SAED pattern of Bi2 S3 nanorods in Fig. 2b revealed several diffraction rings, which is the sum of the diffraction pattern of different
individual nanorods, indicating of good crystallinity. A corresponding SAED pattern (inset of Fig. 2c) of one single nanorod was further
examined and its unique pattern of diffraction spots could readily
be indexed to (0 0 2) and (2 0 0) in [0 1 0] zone axis, which confirms
that the nanorods examined are single crystalline and might have
[0 0 1] growth direction. The preferred growth direction and the
nature of the single crystallinity of the Bi2 S3 nanorod could be verified by the HRTEM image. Fig. 2d shows a well-resolved interplanar

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

2119

Fig. 2. Typical TEM images (a and c), SAED pattern (b) and HRTEM image (d) of Bi2 S3 nanorods prepared by 20 min of microwave heating in DMF (S4). Inset of (c) is the SAED
pattern of a selected single nanorod.

d-spacing of 1.110 and 0.398 nm, corresponding to the (1 0 0) and
(0 0 1) lattice planes, respectively. The elemental compositions of
the nanorods were also analyzed by EDX spectrum. It confirms that
the nanorods are composed of bismuth and sulfur with an average
atomic ratio of about 2:3 (see Supplementary Materials Fig. S3). The
copper and carbon signals are from the carbon-coated copper grid.
An interesting result was that sheet-like Bi2 S3 nanostructures
were fabricated after 30 min of microwave heating (Fig. 1f). By
increasing the reaction time, these nanorods assembled to nanorod
arrays gradually, then aggregated to form the sheet-like structures.
This indicates that 20 min is the optimum microwave heating time
for the large scale fabrication of Bi2 S3 nanorods.
3.2. Effect of surfactants
To investigate the effect of the surfactant on the formation
of the nanorods, different surfactants were used in the synthesis
of Bi2 S3 nanorods under identical experiment conditions. Fig. 3a
shows the XRD pattern of the products prepared from bismuth
citrate and thiourea with 20 min microwave heating in DMF in
the presence of PVP (S5), ˇ-CD (S6), and PEG (S7). All the diffraction peaks can be indexed to the orthorhombic phase of Bi2 S3
(JCPDS 17-0320), indicating the production of Bi2 S3 . Fig. 3b–d
shows the SEM images of Bi2 S3 nanostructures prepared from bismuth citrate and Tu in DMF in the presence of different surfactants,
revealing differences in morphologies. When PVP was introduced
into DMF (S5), only sheet-like Bi2 S3 nanostructure were obtained,
which can be observed in the whole sample (Fig. 3b). As shown in
Fig. 3d, there are no rod-like nanomaterials observed in the presence of PEG (S7); only microflowers, which consisted of flakes, were
obtained. However, in the presence of 5 mmol/L ˇ-CD, large quanti-

ties of Bi2 S3 nanorods were obtained (Fig. 3c). These nanorods were
well segregated with an average diameter of about 40 nm. Nevertheless, no Bi2 S3 nanorod was obtained when the concentration
of ˇ-CD decreased to 2.5 mmol/L or increased to 10 mmol/L (see
Supplementary Materials Fig. S4).
3.3. Effect of the solvents
To understand the function of solvents in the synthesis of Bi2 S3
nanorods, Bi2 S3 nanomaterials were prepared by microwave heating in the presence of CTAB in EG (S8), DEG (S9), formamide (S10),
and ethylenediamine (S11) under identical experiment condition,
using Bi(cit) and Tu as precursors.
Fig. 4a displays the typical XRD patterns of Bi2 S3 nanomaterials prepared in different solvents (S8–S11). The powder XRD
spectra of the samples S8, S9 and S10 could be perfectly indexed
to orthorhombic Bi2 S3 (JCPDS 84-0279), (JCPDS 65-2431) and
(JCPDS 06-0333), respectively. It indicated the production of crystalline pure Bi2 S3 in the EG, DEG, and formamide. However, when
ethylenediamine was used as a solvent, the powder XRD pattern
was devoid of relatively sharp features, which indicated a rather
isotropic nanocrystalline component of pure Bi2 S3 [55].
The morphologies of the samples of S8–S11 were depicted
by SEM images. As shown in Fig. 4b and e, a large quantity of
Bi2 S3 nanorods were obtained when EG and DEG were used as
solvents (S8 and S9). However, no rod-like nanomaterials were
obtained in formamide and ethylenediamine. Bi2 S3 nanoparticles
and nanoplates were obtained in formamide and ethylenediamine,
respectively (Fig. 4c and d). The above results showed that the solvents EG and DEG benefit the formation of Bi2 S3 nanorods, similar
to DMF.

2120

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

Fig. 3. Powder XRD spectra (a) and SEM images (b–d) of Bi2 S3 nanomaterials prepared by microwave heating in DMF in the presence of PVP (b), ˇ-CD (c) and PEG (d),
respectively.

The effect of different reaction time on the formation of Bi2 S3
nanorods in EG was also investigated. Fig. 5 showed the SEM images
of as-prepared Bi2 S3 nanorods prepared under different microwave
heating time in EG (S12–S14). It revealed predominantly rod-like
Bi2 S3 nanostructures after 3 min of microwave heating. The mor-

phologies and size of the products do not show obvious differences
after 13 min of microwave heating.
Sample S8 was further characterized by TEM images and SAED
pattern. Fig. 6a depicts the typical TEM image of Bi2 S3 nanorods. The
length of the nanorods varies from 200 to 800 nm, with an average

Fig. 4. Powder XRD spectra (a) and SEM images of Bi2 S3 nanomaterials prepared by microwave heating in different solvents (b: EG; c: formamide; d: ethylenediamine; e
and f: DEG).

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

2121

Fig. 5. SEM images of Bi2 S3 nanorods prepared under different microwave heating time in EG (a: 3 min; b: 7 min; c: 13 min; d: 20 min).

length of about 500 nm, which is shorter than that of the nanorods
fabricated in DMF. The diameters of the Bi2 S3 nanorods are in the
range of 20–70 nm, with an average diameter of about 35 nm. Fig. 6c
shows the TEM images and SAED pattern of a single nanorod. The
clear diffraction spots could readily be indexed to (0 0 2) and (2̄ 2 0)
in [1 1 0] zone axis, which confirms that the nanorods examined
are single-crystalline and might have a [0 0 1] growth direction. The

HRTEM image (Fig. 6d) reveals clear lattice fringes with d-spacing
of 0.389 nm and 0.795 nm, which is very close to the interplanar
spacing of (0 0 1) and (1̄ 1 0), respectively.
The EDX spectra were performed for the quantitative analyses
of Bi2 S3 . As shown in Fig. S5 (see Supplementary Materials), the
typical EDX spectrum of Bi2 S3 (S11) revealed the average atom ratio
of bismuth and sulfur was approximate to 2:3, indicating of good

Fig. 6. Typical TEM images (a and c), SAED pattern (b) and HRTEM image (d) of Bi2 S3 nanorods prepared by 20 min of microwave heating in EG (S8). Inset of (c) is the SAED
pattern of a selected single nanorod.

2122

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

Fig. 7. TEM and SEM images of Bi2 S3 nanorods prepared from Bi(cit) and Tu in the absence of CTAB in DMF (S15, a) and in EG (S16, b).

sample stoichiometry. The copper and carbon signals are from the
carbon-coated copper grid.
The SEM and TEM images also indicated that the dispersity of
Bi2 S3 nanorods prepared in EG is little worse than that of nanorods
prepared in DMF. To further investigate the effect of solvent on
the dispersity of products, Bi2 S3 nanorods were prepared under
identical condition in the absence of CTAB in DMF and EG (S15 and
S16, respectively). As depicted in Fig. 7a, the products prepared in
DMF (S14) have a short and wide rod-like morphology and grew
to wide nanorods with a small ratio of length to diameter in the
absence of CTAB in DMF, compared with the products prepared in
the presence of CTAB (S4). However, there is no obvious difference
between products prepared in the absence and presence of CTAB
in EG (Fig. 7b).
To further understand the function of solvents in the formation of Bi2 S3 nanorods, the pH value of the different solvents were
measured, and qualitative analysis experiments of solubility of
CTAB in different solvents were carried out. In DMF, EG, DEG, formamide, or ethylenediamine medium, the pH value is about 5, 7,
7, 9, and 12, respectively (see Supplementary Materials Fig. S6).
The results of CTAB solubility showed that yellow precipitate was
only observed in DMF solution, when AgNO3 was added to DMF,
EG, formamide and ethylenediamine solution of containing the
same amount of CTAB, respectively (see Supplementary Materials
Fig. S7).

Different sulfur precursors were also introduced into the
synthesis of Bi2 S3 nanorods. Na2 S2 O3 , Na2 S and glutathione (-lGlu-l-Cys-Gly, GSH) were used to replace Tu as the sulfur precursor
(S19–S21). As shown in SEM images, petal-like morphologies of
Bi2 S3 nanomaterials were observed, using Na2 S2 O3 as a sulfur
source (Fig. 9a). Bulk materials were obtained when Na2 S was used
as a sulfur precursor (Fig. 9b). The SEM image (Fig. 9c) demonstrated
the formation of the flower-like Bi2 S3 nanostructures which was
built up of many interlaced nanoflakes in the presence of GSH. No
Bi2 S3 nanorod was obtained when Na2 S2 O3 , Na2 S and GSH were
used as sulfur precursor, respectively.
The effect of Tu amount on the morphologies of Bi2 S3 nanorods
was also investigated. Fig. 10 shows the TEM images of Bi2 S3
nanorods prepared by increasing the Bi(cit):Tu molar ratio to 1:5

3.4. Effect of precursors
In literatures, different bismuth precursors were used in
the synthesis of Bi2 S3 nanorods. For example, Chen and coworkers reported a one-step method for synthesizing high-quality
single-crystalline Bi2 S3 nanorods by thermal decomposition of
Bi[S2 P(OC8 H17 )2 ]3 in the presence of oleylamine [25]. Han et al.
demonstrated a hydrothermal synthesis of crystalline Bi2 S3
nanorods from Bi alkyldithiocarbonatio (xanthate) precursors [56].
Recently, BiOCl was also used as a bismuth precursor to synthesize
Bi2 S3 nanomaterials with various morphologies, including wires,
rods, and flowers [57,58]. In most cases, bismuth nitrate was used
as the reactant. The releasing Bi3+ ions can coordinate with Tu
to create an environment which benefits the formation of Bi2 S3
nanorods. In this study, Bi(NO3 )3 and BiCl3 was also introduced into
DMF solution (S17 and S18), instead of bismuth citrate. As a result,
three-dimensional nanoflowers of corn-like nanorods fabricated by
using Bi(NO3 )3 as precursor (Fig. 8a). When BiCl3 was used instead
of bismuth citrate, large-scale Bi2 S3 nanorods were also observed,
as shown in Fig. 8b (S18). The dispersity is little worse than that of
the sample prepared by bismuth citrate.

Fig. 8. SEM images of Bi2 S3 nanomaterials prepared by using Bi(NO3 )3 (a) and BiCl3
(b) as bismuth precursors.

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

2123

in the presence and absence of CTAB (S22 and S23, respectively).
It revealed that the morphologies of as-prepared Bi2 S3 nanorods
showed obviously difference in the presence of different concentration of Tu (see Figs. 7a, and 10a, 2a and 10b). As depicted in Fig. 10,
when the initial molar ratio of Bi(cit):Tu was increased to 1:5 (S23)
in the absence of CTAB, the product still contained a large quantity
of nanorods. The average aspect ratio is larger than that of those prepared by using Bi(cit):Tu molar ratio of 1:3 in the absence of CTAB
(S15, see Fig. 7a). It was also found that the average aspect ratio
increased with the increasing concentration of Tu in the presence
of CTAB (S4 and S22, see Figs. 2a and 10b).
4. Discussion
4.1. General discussion

Fig. 9. SEM images (a–c) of Bi2 S3 nanomaterials prepared from different sulfur
precursors by microwave heating (a: Na2 S2 O3 ; b: Na2 S; c: GSH).

Microwave irradiation, in which energy is delivered to the reactants through molecular interactions with the electromagnetic
field, provides rapid and uniform heating of reagents, solvents,
intermediates, and products. This rapid heating mode accelerates
the reaction and nucleation in the synthesis of nanomaterials, leading to the formation of uniform, well-crystalline nanomaterials
[51]. Hence, in the synthesis of Bi2 S3 nanorods, microwave irradiation can significantly reduce reaction time by about 80%, compared
to the refluxing method under identical conditions.
Formation of Bi2 S3 nanostructures in the presence and absence
of capping agent (CTAB, PVP, PEG, ˇ-CD, etc.) has enabled us not
only to understand the effect of the capping agents, but also to
further determine of the growth mechanism of Bi2 S3 nanorods.
It is known that Bi2 S3 is a highly anisotropic semiconductor with
a layered structure parallel to the growth direction, with linked
Bi2 S3 units forming infinite sheets which in turn are connected via
considerably weaker van der Waals interactions [59]. It consists
of infinite ribbon-like (Bi4 S6 ) polymers, linked together by intermolecular attraction between bismuth and sulfur atoms, which are
parallel to the c-axis. Therefore, the preferential growth into elongated crystals is determined by the anisotropic Bi–S atom chain or
layer structure of the orthorhombic Bi2 S3 [60]. It is reported that the
formation of Bi2 S3 nanorods may have originated from the cleavage
of large particles from the van der Waals planes and/or from preferential directional growth of the particles [61,62]. Growth kinetics
of nanorods in the presence of capping agents is determined by
several complex factors.
When CTAB was used as a surfactant, micellar solutions formed
by CTAB are essential to synthesize the Bi2 S3 nanorods. It could
form double layers to control anisotropic growth, leading to the
idea that the CTAB-passivated Bi2 S3 nanorods can disperse for long

Fig. 10. TEM images of Bi2 S3 nanorods prepared in the absence (a) and presence (b) of CTAB when the molar ratio of Bi(cit):Tu is 1:5.

2124

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

periods of time without forming aggregates. This indicates that the
CTAB bilayers can give good stability of the colloidal dispersion to
the Bi2 S3 nanorods. It was also proposed that CTAB capped onto the
newly-formed nanorods and hence prevented the nanorods from
aggregation by steric stabilization [33]. The removal of the CTAB
layers tended to induce aggregation of the Bi2 S3 nanorods.
Previous studies revealed that surfactant CTAB could act not
only as a stabilizer to prevent aggregation of the crystals, but also
as a shape controller to assist the formation of anisotropic metal
nanostructures [63]. CTAB is a cationic surfactant consisting of a
hydrocarbon chain (CTA+ ) and a bromide ion (Br− ). The CTA+ ion
can adsorb onto the Bi2 S3 surface through electrostatic effect, and
acts as a capping agent to control the growth rate of the adsorbed
crystal faces and to prevent those nanorods from aggregation by
steric stabilization [64]. The details are shown as follows:
CTAB → CTA+ + Br−
S2− + 2CTA+ → (CTA+ )2 S2−
3(CTA+ )2 S2− + 2Bi3+ → Bi2 S3 + 6CTA+
Hence, the released CTA+ ions may have absorbed S2− to form
(CTA+ )2 S2− , which prevented the production of excessive free S2−
ions and their quick reaction with Bi3+ ions, resulting in the slow
production of Bi2 S3 . Once (CTA+ )2 S2− reacted with Bi3+ to form
Bi2 S3 , CTA+ also played an important role in stabilizing nanorods
and reducing the surface relaxation in the formation of nanorods,
resulting in well-dispersed Bi2 S3 nanorods. CTA+ ions can enhance
the bonding strength of the adsorbed surfactant layer, which can
also change the growth rate of the rods and increase surfactant
capability.
PVP has a polyvinyl skeleton with polar groups, which induced
an anisotropic growth of the nuclei [65]. There could also be
potential crystal face inhibitors in the system, which benefits the
formation of oriented nucleation, leading to the construction of
anisotropic growth of the nanostructures. PVP can be adsorbed onto
Bi2 S3 nanoplates by coordinating with both nitrogen and oxygen
atoms in the polar pyrrolidone groups [66]. However, the electrostatic interactions of PVP with the Bi2 S3 surface are complicated
in the formation of Bi2 S3 nanorods. PVP can selectively cap the
side facet of Bi2 S3 nanocrystal, and thus result in different orientation attachment, which deviates from Ostwald ripening. The
PVP absorption on Bi2 S3 plane surface, which is not the growthdirection plane, suggested that there is a repulsive effect on the
growth along the growth direction. A typical example is the shape
control of gold and silver nanoparticles using the surfactant PVP as a
capping agent, which can selectively interact with gold planes (e.g.,
1 1 1, 1 0 0 and 1 1 0), and thus results in different metal nanostructures including nanorods, nanowires, nanoplates, and nanocubes
[67–69].
PEG is a non-ionic polymer containing hydrophilic –O– and
hydrophobic –CH2 –CH2 – groups. PEG macromolecules bond with
the solid surface mainly via the –OH group of nanomaterials, which
may interact with PEG through hydrogen bonding. It was assumed
that PEG would act as a nucleus for aggregation. Once Bi2 S3 seeds
were formed, PEG capped on the surface of Bi2 S3 nuclei, which
induced the aggregation of Bi2 S3 nanocrystals. This may be because,
in contrast to densely packed CTAB layers, PEG is amphiphilic
molecules that form spontaneous molecular assemblies which in
turn could act as barriers and affect the reshaping of Bi2 S3 nanostructures [70].
The exact role of ˇ-CD in the formation of Bi2 S3 nanorods is still
unclear, but intriguing. The morphology is strongly dependent on
the concentration of ˇ-CD in the formation of Bi2 S3 nanomaterials.
It was proposed that the viscosity of the reaction system increased

with the increase of ˇ-CD concentration, leading to the aggregation
of Bi2 S3 nanorods. However, very low concentrations can also be
adverse to the dispersity of the product. This finding is in good
agreement with the reported literature [71].
On the basis of the observations, it was found that different solvents have a strong influence on the Bi2 S3 morphologies, which
might be due to the decomposition of Tu in the solvents. The decomposition reaction could be represented by the following equations
[72,73]:


(H2 N)2 C S −→S2− + N CNH2 + 2H+
This illustrates that releasing of H+ ions accompanies the generation of S2− ions in the decomposition of Tu. The pH value of the
reaction medium affects the balance of this reaction. The different pH values of DMF, EG, DEG, formamide, and ethylenediamine
solution resulted in the different decomposition of Tu. High pH
value can accelerate the decomposition of Tu, leading to the quick
production of a large amount of S2− ions. This accelerates the
aggregation of Bi2 S3 nuclei, which results in the formation of bulk
materials.
On the other hand, it has been mentioned above that CTA+
ions can control the formation speed and the dispersity during
the growth of Bi2 S3 nanorods. However, it was shown that there
are obvious differences in morphology and dispersity among different solvents. We proposed here that the different solubility of
CTAB in different solvent had a strong influence on the morphology
and dispersity. Qualitative analysis experiments showed different
solubility of CTAB in different solvents, indicating that only free
Br− ions from CTAB was presented in DMF solution. There were
no free Br− ions in EG, ethylenediamine, or formamide solution
of CTAB, indicating of poor solubility of CTAB in these solvents. In
DMF, the release of CTA+ ions led to formation of well-separated
Bi2 S3 nanorods. That is why there was no rod-like Bi2 S3 obtained
in ethylenediamine or formamide.
Interestingly, Bi2 S3 nanorods were obtained in EG, even with the
poor CTAB solubility or without CTAB, indicating that the solvent
EG plays a very important role in the formation of Bi2 S3 nanorods.
Once the Bi2 S3 nuclei formed, EG can effectively cap and stabilize
the surface of the Bi2 S3 nuclei via hydroxyl groups of the solvent
molecules, which was beneficial for the preparation of stable and
uniform Bi2 S3 nanorods. Due to the effects of the hydrogen bonding
between hydroxyl groups, EG molecules could exist in long chains
and act as a soft template, leading to the growth of Bi2 S3 nuclei into
nanorods, similar to the function of DEG [27]. That is why there are
no significant changes in morphology after 3, 7, 13, and 20 min of
microwave heating in EG, as well as no difference in the presence
and absence of CTAB.
Our previous study indicated that the bismuth precursor was
very important to the formation of Bi2 S3 nanorods. It was also
confirmed by the observations in this study. In the microwave synthesis, Bi(NO3 )3 dissociates into Bi3+ and NO3 − ions immediately
under the ambient conditions of DMF. Then the nucleation occurs
when Tu decomposes to S2− ions at an outburst speed, leading to
the quick formation of a large quantity of Bi2 S3 nuclei which works
against the fabrication of individual Bi2 S3 nanorods. However, there
are few free Bi3+ ions when bismuth citrate is dispersed in DMF,
resulting in little opportunity of reacting with Tu directly. Hence,
large quantities of Bi3+ ions are conductive to formation of Bi2 S3
nanorods in microwave synthesis. Similarly, few free Bi3+ ions were
generated from BiCl3 due to the hydrolysis of BiCl3 to BiOCl in the
initial reaction stage in DMF, which has a pH value of 4. Based on
the findings, the bismuth precursors can be divided into two groups.
One is a bismuth compound with poor solubility in the solutions,
such as Bi(cit) and BiOCl, which can only slowly release the Bi3+ ions
during the microwave heating process. The other is a bismuth com-

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

2125

Scheme 1. Supposed formation process of the Bi2 S3 nanorods.

pound, such as Bi(NO3 )3 , which can rapidly release the Bi3+ ions in
the reaction system.
It was found that Bi2 S3 nanorods were fabricated only by using
Tu as sulfur precursor, indicating that slow release of S2− would
benefit the formation of Bi2 S3 nanorods. It is well known that only
Na2 S can directly give S2− ions in the solvent, leading to the quick
formation of Bi2 S3 nuclei. Similar to Na2 S, S2 O3 2− ions come from
Na2 S2 O3 could react with H+ ion in the reaction solution, which also


induced the releasing of S2− ions (2H+ + S2 O3 2− −→S2− + 2H+ +
SO3 2− ) [30]. The quick production of S2− ions in these two precursors is not beneficial for the formation of Bi2 S3 nanorods. When
GSH was used as a precursor, the lone electron pair of the S atom
of GSH strongly interacted with the Bi2 S3 nuclei surface. The long
hydrophilic carboxyl and amidogen tails formed a steric barrier and
prevented the production of many excessive S2− ions in the reaction system, resulting in a relatively slow reaction rate between S2−
ions and Bi(cit). However, no Bi2 S3 nanorod was obtained in the
presence of GSH. It was proposed that the steric hindrance effect of
GSH prevented the fabrication of rod-like nanostructures. At the
same time, the formation and in situ decomposition of Bi–GSH
complex resulted in the fabrication of flower-like Bi2 S3 nanostructures. In the literature, it was also reported that l-cysteine was used
as a sulfur precursor and self-sacrificed templates to produce the
interesting CuS nanostructures [74].
Small organic molecules which can slowly release S2− by hydrolysis are especially useful in the controlled synthesis of Bi2 S3
nanomaterials because of their special chemical properties and
self-assembling functions [75]. It was reported that the S2− ions
generate slowly due to the cleavage of C S bond of Tu [76]. During this reaction, the Tu gradually decomposes to release S2− ions
slowly as the temperature increases, preventing the production of
too many free S2− ions. At the same time, due to the excessive
amount of Tu in the system, the lone electron pair of the S atom
can strongly interact with and selectively adhere to the Bi2 S3 nuclei
surface. This can stabilize some special crystalline facets and these
crystalline facets are electronegative, as indicated in the following
equations:


(H2 N)2 C S−→S2− + N CNH2 + 2H+

2Bi3+ + 3S2− → Bi2 S3
Furthermore, almost no free Bi3+ ions are available in DMF owing
to the unique coordination by citrate anions. These reasons resulted
in the relatively slow reaction rate of formation Bi2 S3 nuclei, leading
to the aggregation of Tu on the existing Bi2 S3 nuclei and resulting
in the increase of their dimensions.

The results also indicated that Tu, which attached on Bi2 S3 seeds,
can act as another kind of capping agent to control the growth rate
and morphology of Bi2 S3 nanorods under microwave irradiation.
We proposed that the larger quantity of Tu adsorbed on Bi2 S3 seeds
by electrostatic effect of the lone electron pair of the S atom is beneficial for the formation of “growing seeds” and the aspect ratio
control. As a result, the growth of such an anisotropic structure
requires a relatively high chemical potential environment, i.e., high
monomer concentration in the solution. This may also explain why
the aspect ratio increased with the increase of reaction time under
microwave heating (S1–S4). Tu can thus also act as a shape controller in the formation of Bi2 S3 nanorods. Therefore, it was seen
that Tu plays an important role in the formation of Bi2 S3 nanorods
and high concentrations of Tu favor the growth of Bi2 S3 nanorods.
4.2. Formation mechanism of the Bi2 S3 nanorods
Based on the observations of the products under different experimental conditions, a proposed formation mechanism of the Bi2 S3
nanorods under different condition was summarized in Scheme 1.
As illustrated in this scheme, Bi2 S3 nuclei were formed quickly
under microwave heating, and with the help of Tu at the first stage,
were subsequently preferential in the growth of Bi2 S3 nanorods. At
this stage, excessive Tu stabilized the Bi2 S3 nuclei and promoted the
growth of Bi2 S3 nanorods though the adherence to the Bi2 S3 nuclei
surface. In the presence of CTAB, CTA+ ions were generated in DMF,
which were capped on the surface of Bi2 S3 nanorods and led to
the formation of long Bi2 S3 nanorods with good dispersity with the
increase of reaction time. At the same time, DEG also acted as a soft
template in the formation of Bi2 S3 nanorods. The poor solubility
of CTAB and the high pH value of formamide and ethylenediamine
resulted in the aggregation of Bi2 S3 nanomaterials. However, the
poor solubility of CTAB in EG did not affect the formation of Bi2 S3
nanorods. Instead of CTAB, EG also played the role of capping agent,
leading to the fabrication of Bi2 S3 nanorods.
5. Conclusions
In this study, microwave irradiation, where energy is delivered
to the reactants through molecular interactions with electromagnetic field, was found to be a convenient, efficient, and
environmentally friendly route for the formation of Bi2 S3 nanorods,
as well as a new method of quick synthesis of other bismuth
nanomaterials. A possible growth mechanism of Bi2 S3 nanorods
was also proposed in this study. Large-scale, well-separated Bi2 S3
nanorods were successfully prepared from bismuth citrate and Tu
by a microwave heating method. Microwave irradiation was found
to reduce the reaction time by at least 80% compared with refluxing

2126

J. Wu et al. / Journal of Alloys and Compounds 509 (2011) 2116–2126

under identical reaction conditions. CTAB and ˇ-CD were found to
facilitate the formation of Bi2 S3 nanorods. DMF, EG and DEG are
friendly solvents in the synthesis of Bi2 S3 nanorods. The amount of
Tu has a strong influence on the formation of Bi2 S3 nanorods. It was
also found that the dimensions of Bi2 S3 are highly dependent on the
bismuth and sulfur species. During the synthesis, the reaction time,
surfactant, and solvent played important roles on the morphologies and dispersities of Bi2 S3 nanomaterials. This new approach is
believed to offer a more attractive, convenient, quick method for
large-scale synthesis of Bi2 S3 nanorods, and provide some useful
clues for designing 1D nanostructural materials.
Acknowledgements
This work was supported by National Natural Science Foundation of China (Grant 20801043), Program for New Century
Excellent Talents in University (NCET-09-0136) and Wuhan Chenguang Scheme (Grant 200850731376) established under Wuhan
Science and Technology Bureau. We thank Mr. Frankie Y.F. Chan
for his kind help with TEM characterizations.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jallcom.2010.10.160.
References
[1] S.-C. Liufu, H.-Y. Chen, Q. Yao, C.-F. Wang, Appl. Phys. Lett. 90 (2007),
112106.1–112106.3.
[2] G. Konstantatos, L. Levina, J. Tang, E.H. Sargent, Nano Lett. 8 (2008) 4002–4006.
[3] S.K. Batabyal, C. Basu, A.R. Das, G.S. Sanyal, J. Nanosci. Nanotechnol. 7 (2007)
565–569.
[4] X. Yu, C. Cao, Cryst. Growth Des. 8 (2008) 3951–3955.
[5] J.D. Desai, C.D. Lokhande, Mater. Chem. Phys. 41 (1995) 98–103.
[6] G. Hodes, J. Manassen, D. Cahen, Nature 261 (1976) 403–404.
[7] B. Miller, A. Heller, Nature 262 (1976) 680–681.
[8] O. Rabin, J. Manuel Perez, J. Grimm, G. Wojtkiewicz, R. Weissleder, Nat. Mater.
5 (2006) 118–122.
[9] C. Ye, G. Meng, Z. Jiang, Y. Wang, G. Wang, L. Zhang, J. Am. Chem. Soc. 124 (2002)
15180–15181.
[10] J.R. Ota, S.K. Srivastava, Nanotechnology 16 (2005) 2415–2419.
[11] Y.W. Koh, C.S. Lai, A.Y. Du, E.R.T. Tiekink, K.P. Loh, Chem. Mater. 15 (2003)
4544–4554.
[12] H. Bao, C.M. Li, X. Cui, Y. Gan, Q. Song, J. Guo, Small 4 (2008) 1125–1129.
[13] J.H. Kim, H. Park, C.-H. Hsu, J. Xu, J. Phys. Chem. C 114 (2010) 9634–9639.
[14] Z. Liu, S. Peng, Q. Xie, Z. Hu, Y. Yang, S. Zhang, Y. Qian, Adv. Mater. 15 (2003)
936–940.
[15] Z. Liu, J. Liang, S. Li, S. Peng, Y. Qian, Chem. Eur. J. 10 (2004) 634–640.
[16] A. Phuruangrat, T. Thongtem, S. Thongtem, Mater. Lett. 63 (2009) 1496–1498.
[17] Y. Zhao, X. Zhu, Y. Huang, S. Wang, J. Yang, Y. Xie, J. Phys. Chem. C 111 (2007)
12145–12148.
[18] Q. Lu, F. Gao, S. Komarneni, J. Am. Chem. Soc. 126 (2004) 54–55.
[19] F. Gao, Q. Lu, X. Meng, S. Komarneni, J. Mater. Sci. 43 (2008) 2377–2386.
[20] J. Wu, F. Qin, F.Y.F. Chan, G. Cheng, H. Li, Z. Lu, R. Chen, Mater. Lett. 64 (2010)
287–290.
[21] C. An, S. Wang, Y. Liu, Mater. Lett. 61 (2007) 2284–2287.
[22] Y. Jiang, Y.-J. Zhu, J. Phys. Chem. B 109 (2005) 4361–4364.
[23] J. Lu, Q. Han, X. Yang, L. Lu, X. Wang, Mater. Lett. 61 (2007) 3425–3428.
[24] F. Wei, J. Zhang, L. Wang, Z.-K. Zhang, Cryst. Growth Des. 6 (2006) 1942–
1944.
[25] W. Lou, M. Chen, X. Wang, W. Liu, Chem. Mater. 19 (2007) 872–878.

[26] Y. Yu, C.H. Jin, R.H. Wang, Q. Chen, L.M. Peng, J. Phys. Chem. B 109 (2005)
18772–18776.
[27] H. Zhang, L. Wang, Mater. Lett. 61 (2007) 1667–1670.
[28] J. Wang, Y. Li, Mater. Chem. Phys. 87 (2004) 420–423.
[29] M. Salavati-Niasari, D. Ghanbari, F. Davar, J. Alloys Compd. 488 (2009) 442–447.
[30] H. Wang, J.-J. Zhu, J.-M. Zhu, H.-Y. Chen, J. Phys. Chem. B 106 (2002) 3848–3854.
[31] J.M. Zhu, K. Yang, J.J. Zhu, G.B. Ma, X.H. Zhu, S.H. Zhou, Z.G. Liu, Opt. Mater. 23
(2003) 89–92.
[32] X. Yu, C. Cao, H. Zhu, Solid State Commun. 134 (2005) 239–243.
[33] R. Chen, M.H. So, C.-M. Che, H. Sun, J. Mater. Chem. 15 (2005) 4540–4545.
[34] J. Zhu, O. Palchik, S. Chen, A. Gedanken, J. Phys. Chem. B 104 (2000) 7344–7347.
[35] X. Hu, J.C. Yu, Chem. Mater. 20 (2008) 6743–6749.
[36] J.A. Gerbec, D. Magana, A. Washington, G.F. Strouse, J. Am. Chem. Soc. 127 (2005)
15791–15800.
[37] X. Hu, J.C. Yu, J. Gong, J. Phys. Chem. C 111 (2007) 11180–11185.
[38] S. Komarneni, R. Roy, Q.H. Li, Mater. Res. Bull. 27 (1992) 1393–1405.
[39] S. Komarneni, R. Pidugu, Q.H. Li, R. Roy, J. Mater. Res. 10 (1995) 1687–1692.
[40] S. Komarneni, M.Z. Hussein, C. Liu, E. Breval, P.B. Malla, Eur. J. Solid State Inorg.
Chem. 32 (1995) 837–849.
[41] S. Beg, A. Al-Alas, N.A.S. Al-Areqi, J. Alloys Compd. 493 (2010) 299–304.
[42] T. Thongtem, C. Pilapong, J. Kavinchan, A. Phuruangrat, S. Thongtem, J. Alloys
Compd. 500 (2010) 195–199.
[43] J. Wu, H. Yang, H. Li, Z. Lu, X. Yu, R. Chen, J. Alloys Compd. 498 (2010) L8–L11.
[44] Q. Yao, Y. Zhu, L. Chen, Z. Sun, X. Chen, J. Alloys Compd. 481 (2009) 91–95.
[45] F.Y. Jiang, C.M. Wang, Y. Fu, R.C. Liu, J. Alloys Compd. 503 (2010) L31–L33.
[46] G. Wei, W. Qin, D. Zhang, G. Wang, R. Kim, K. Zheng, L. Wang, J. Alloys Compd.
481 (2009) 417–421.
[47] C.-H. Lu, B. Bhattacharjee, S.-Y. Chen, J. Alloys Compd. 475 (2009) 116–121.
[48] J. Bi, L. Wu, Z. Li, Z. Ding, X. Wang, X. Fu, J. Alloys Compd. 480 (2009) 684–688.
[49] S. Komarneni, Curr. Sci. India 85 (2003) 1730–1734.
[50] S.A. Galema, Chem. Soc. Rev. 26 (1997) 233–238.
[51] M. Tsuji, M. Hashimoto, Y. Nishizawa, M. Kubokawa, T. Tsuji, Chem. Eur. J. 11
(2005) 440–452.
[52] Y. Jiang, Y.-J. Zhu, Z.-L. Xu, Mater. Lett. 60 (2006) 2294–2298.
[53] X.-H. Liao, H. Wang, J.-J. Zhu, H.-Y. Chen, Mater. Res. Bull. 36 (2001) 2339–2346.
[54] T. Thongtema, A. Phuruangratb, S. Wannapopb, S. Thongtem, Mater. Lett. 64
(2010) 122–124.
[55] L. Cademartiri, R. Malakooti, G. Paul, A. O’Brien, Migliori S. Petrov, Nazir P.
Kherani, G.A. Ozin, Angew. Chem. Int. Ed. 47 (2008) 3814–3817.
[56] Q. Han, J. Chen, X. Yang, L. Lu, X. Wang, J. Phys. Chem. C 111 (2007) 14072–14077.
[57] Z. Quan, J. Yang, P. Yang, Z. Wang, C. Li, J. Lin, Cryst. Growth Des. 8 (2008)
200–207.
[58] J. Jiang, S.-H. Yu, W.-T. Yao, H. Ge, G.-Z. Zhang, Chem. Mater. 17 (2005)
6094–6100.
[59] J. Black, E.M. Conwell, L. Seigle, C.W. Spencer, J. Phys. Chem. Solids 2 (1957)
240–251.
[60] D. Tseng, E. Ruckenstein, Mater. Lett. 8 (1989) 69–71.
[61] H. Mizoguchi, H. Hosono, N. Ueda, H. Kawazoe, J. Appl. Phys. 78 (1995)
1376–1378.
[62] S.-H. Yu, L. Shu, J. Yang, Z.-H. Han, Y.-T. Qian, Y.-H. Zhang, J. Mater. Res. 14 (1999)
4157.
[63] Y. Huang, W. Wang, H. Liang, H. Xu, Cryst. Growth Des. 9 (2009) 858–862.
[64] Y. Xie, X. Zheng, X. Jiang, J. Lu, L. Zhu, Inorg. Chem. 41 (2002) 387–392.
[65] Z. Zhang, B. Zhao, L. Hu, J. Solid State Chem. 121 (1996) 105–110.
[66] H. Xue, Z. Li, H. Dong, L. Wu, X. Wang, X. Fu, Cryst. Growth Des. 8 (2008)
4469–4475.
[67] Y. Sun, Y. Xia, Science 298 (2002) 2176–2179.
[68] I. Washio, Y. Xiong, Y. Yin, Y. Xia, Adv. Mater. 18 (2006) 1745–1749.
[69] C.E. Hoppe, M. Lazzari, I. Pardinas-Blanco, M.A. Lopez-Quintela, Langmuir 22
(2006) 7027–7034.
[70] Y. Horiguchi, K. Honda, Y. Kato, N. Nakashima, Y. Niidome, Langmuir 24 (2008)
12026–12031.
[71] S.K. Batabyal, C. Basu, G.S. Sanyal, A.R. Das, Mater. Lett. 58 (2003) 169–171.
[72] J. Madarász, P. Bombicz, M. Okuya, S. Kaneko, G. Pokol, J. Anal. Appl. Pyrol. 72
(2004) 209–214.
[73] J. Madarász, P. Bombicz, M. Okuya, S. Kaneko, G. Pokol, Solid State Ionics 172
(2004) 577–581.
[74] B. Li, Y. Xie, Y. Xue, J. Phys. Chem. C 111 (2007) 12181–12187.
[75] P. Bombicz, I. Mutikainen, M. Krunks, T. Leskelä, J. Madarász, L. Niinistö, Inorg.
Chim. Acta 357 (2004) 513–525.
[76] L. Dong, Y. Chu, Y. Liu, L. Li, J. Colloid Interface Sci. 317 (2008) 485–492.