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Chemistry Letters Vol.33, No.8 (2004)
CTAB-controlled Synthesis of One-dimensional Selenium Nanostructures
Juan Zhang, Sheng-Yi Zhang, and Hong-Yuan Chenꢀ
The Laboratory of Life Analytical Chemistry, Institute of Analytical Chemistry, Department of Chemistry,
Nanjing University, Nanjing, 210093, P. R. China
(Received April 14, 2004; CL-040408)
Selenium nanowires, nanorods, and nanotubes have been
successfully synthesized in aqueous solution by using cetyltri-
methyl ammonium bromide (CTAB) as the soft template. The
synthesis is performed by controlling CTAB concentration and
temperature.
b
a
One-dimensional (1-D) selenium (Se) nanostructures have
high photoconductivity1 and would provide new opportunities
in fabricating nanoscale optoelectronic devices.2 On the other
hand, the 1-D Se nanostructures may be used as templates for
the construction of other 1-D nanostructures which are techno-
logically important materials.3,4 Thus, the synthesis of 1-D Se
nanostructures has aroused considerable interest. Especially,
some chemical methods, because of their low cost and potential
application for large-scale production, have been actively ex-
plored to process Se into 1-D nanostructures.5–7
CTAB is a cationic surfactant that could favor the formation
of 1-D nanostructures.8 Recently, SnS, ZnO, and Ag 1-D nano-
structures have been prepared with CTAB.9–11 In this paper,
CTAB was firstly used as the soft template for the synthesis of
1-D Se nanostructures. By controlling CTAB concentration
and reaction temperature, Se nanowires, nanorods, and nano-
tubes were prepared. Especially, there is no report about the
study of Se nanotubes that were firstly obtained.
Figure 1. SEM images of the Se nanowires obtained: (a) at
80 ꢁC for 3 h; (b) at 80 ꢁC under ultrasound for 1 h.
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Typically, our experiments were carried out as follows.
First, the 2.0 mL of 1 M selenious acid was mixed with
20.0 mL of 0.06 M CTAB aqueous solution. (Alcohol or NaBr
was also added into reaction solution for the study of mecha-
nism). Then 4.0 mL of 1 M ascorbic acid solution was added into
selenious acid/CTAB mixture at 80 ꢁC (and under ultrasound).
After the reaction solution was aged for 3 h, the products were
separated from the reaction solution by centrifugation, washed
by alcohol and deionized water, and then characterized by trans-
mission electron microscopy (TEM), scanning electron micros-
copy (SEM) and X-ray diffraction (XRD).
Figure 1a shows the SEM images of the products as-pre-
pared. From the images, it can be seen that uniform Se nanowires
with the diameter from 80 to 100 nm (the length up to 200 mm)
were obtained. The crystallization and the purity of Se nanowires
were studied by XRD that was performed using a Japan Rigaku
D/max-RA X-ray diffractometer with graphite monochromat-
ized Cu Kꢀ1 radiation (ꢁ ¼ 0:15406 nm). A scanning rate of
10ꢁ/min was applied to the XRD patterns in the 2ꢂ range of
15–70ꢁ. As shown in Figure 2, all the diffraction peaks could
be indexed as the trigonal of Se. The lattice constants were cal-
culated as a ¼ 0:436 nm, c ¼ 0:496 nm which correspond well
to those of the trigonal phase (a ¼ 0:434 nm, c ¼ 0:495 nm) re-
ported in literature.12 The XRD pattern indicates that the nano-
wires was a single phase of well-crystallized trigonal Se.
When the ultrasonic irradiation was used at 80 ꢁC, Se nano-
Figure 2. XRD patterns of Se nanowires.
wires in bundle were obtained with high yields (as shown in
Figure 1b). This result can be explained as follows.6,13 First, ul-
trasonic irradiation can dramatically increase reactivity, induce
the transformation of amorphous Se to trigonal Se, and improve
the yield of products. Second, ultrasonic irradiation may effec-
tively remove the surface coating and cause the agglomeration
of Se nanowires. Both the effects resulted in the formation of
bundle Se nanowires.
The boost of temperature could speed up the progress of re-
action and favor the formation of Se nanowires. When the tem-
perature was increased from 80 to 100 ꢁC, Se nanowires as
shown in Figure 1a were obtained within 20 min. At room tem-
perature, it would take several months to get the same products.
It had been shown that CTAB concentration played the ma-
jor role in determining Se product morphology. With the in-
crease of CTAB concentration, the shapes of Se products
changed from spherical nanoparticles to linearly aligned spheri-
cal nanoparticles, nanowires and nanorods. Moreover, the diam-
eter of nanorods increased with the boost of CTAB concentra-
tion. When CTAB concentration increased up to 0.6 M, some
Se nanotubes with thick nanorods were obtained (as shown in
Figure 3).
The mechanism about the influence of CTAB concentration
on Se product morphology could be speculated as follows. Be-
Copyright ꢀ 2004 The Chemical Society of Japan