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Chemistry Letters Vol.32, No.5 (2003)
Synthesis of Novel Selenium Tubular Structure
Yuan-tao Chen, Qiao-yu Sun, and Hu-lin Liꢀ
College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
(Received December 10, 2002; CL-021047)
Tubular selenium has been synthesized successfully by re-
30 min. The white turbid mixture quickly became brick red,
then slowly turned into gray black. All the steps above were
performed under magnetic stirring. Finally, the resultant sample
was centrifuged, washed with distilled water and absolute alco-
hol, and then dried in air before further characterization.
The crystal structure and composition of the obtained sam-
ple were analyzed by X-ray diffraction (XRD) on a Japan Riga-
ku D/MAX-2400 X-ray diffractometer wiꢂthꢃC1 u Ka radiation
of 20ꢂ to 80ꢂ. Figure 1 shows a typical XRD pattern for as-ob-
tained sample. All the diffraction peaks, within experimental er-
ror, have a one-to-one correspondence to those of the bulk tri-
gonal selenium (JCPDS card no. 06-362). The morphology
and size were characterized by a JSM-5600LV scanning elec-
tron microscope. Figures 2A and B displayed hollow tubes with
inner and external diameter of ca. 0.8 mm and 2 mm, and length
of 10 mm. Some irregular spherical agglomerates were also ob-
served. The yield of the tubular selenium was ca. 30%.
ducing selenious acid with ascorbic acid in the presence of pri-
mary amines (CnH2nþ1NH2 with 10 ꢁ n ꢁ 16) at room tem-
perature.
The discovery of carbon nanotubes in 19911 has greatly ini-
tiated intense experimental and theoretical interest in such tub-
ular structures. Tubular materials are envisaged for potential ap-
plications in the synthesis of designed catalysts, photonic band
gap materials, chemical separations media and as selective ad-
sorbents.2;3 However, most considerable efforts have been
placed on the materials commonly having sheetlike (layered)
structural features, such as carbon-based substances,4 sulfide,5
and nitride.6 It is still a challenging field for chemists or mate-
rialists to prepare tubular crystals from materials without sheet-
like building blocks.
ꢀ
(l ¼ 1:54178 A), at a scanning rate of 0.02 s in the 2ꢀ range
Selenium is well-known for photoelectrical and semicon-
ducting properties. It is used as rectifiers, solar cells, photo-
graphic exposure meters, and xerograph. Selenium also has a
high reactivity towards a wealth of chemicals that can be poten-
tially exploited to convert selenium into other functional mate-
rials. For example, Ag2Se could be prepared by reacting single
crystalline selenium with AgNO3 aqueous solution.7 Recently,
Abdelouas and his co-workers synthesized selenium nanowires
by the use of protein cytochrome c3 to reduce selenate.8 Iris et
al. reported the work on preparing nanostructured mesoporous
selenium films by electrodeposition.9 Gao’s research group
synthesized hollow sphere selenium nanoparticles by in-situ
template interface reaction.10 Xie et al. synthesized selenium
tubular single crystals by solvothermal route.11 Of very late,
Gates et al. prepared trigonal selenium nanowires by aging
amorphous selenium in the dark.12 This synthetic process in-
volved one-dimensional anisotropic growth on seeds of trigonal
selenium that were generated in the same reaction solution
through homogeneous nucleation, selenium atoms being pro-
vided continuously through the slow dissolution of amorphous
colloidal selenium particles. It was of great interest to develop
a solution phase route to prepare trigonal selenium tubular
structures. We have indeed found it feasible to obtain tubular
selenium by a simple solution-phase route.
In this communication, selenious acid was used as selenium
precursor and ascorbic acid as reductant. The use of ascorbic
acid in the synthesis originates from the previous study. First,
the reaction between selenious acid and ascorbic acid was mild.
Second, no by-product was introduced into the system, which
may influence the interaction between selenium atom and long
chain primary amine. A typical procedure is as follows. 0.360 g
of ascorbic acid was introduced into 30 mL aqueous solution
containing 0.128 g of selenious acid and 1.0 g of primary amine
(CnH2nþ1NH2 with 10 ꢁ n ꢁ 16) at temperature 10 ꢂC, then the
mixture was heated to 80 ꢂC and kept at this temperature for
20
40
60
80
2ꢀ/degree
Figure 1. XRD pattern for selenium
sample prepared at 80 ꢂC.
Though the exact growth mechanism is still under investi-
gation, our experiment results indicated that the one dimen-
sional characteristics of the helical chains in the trigonal phase
and the chain length of primary amine both played important
roles in the formation of tubular structure. There have been
some evidences through extensive and careful observations.
For example, the coexistence of some unclosed structure in a
single tubular selenium, as shown in Figure 2C, indicated that
the growth of tubular selenium can not be determined by the
rolling mechanism as the formation of WS2 nanotubes.13 Sec-
ondly, the unclosed tube in Figure 2D, in a way, also is helical.
It seems feasible that this microscopic helicity could be re-
flected in the macroscopic helicity.
It is rational to believe primary amines will readily chelate
selenium atom, since selenium is soluble in ethylenediamine.
To understand the role of amine in the tubular formation, we de-
signed a series of related experiments to test it. In order to
weaken or eliminate the interaction between amine and sele-
nium, 1 mL of 6 M hydrochloric acid was introduced into the re-
action system. The resultant selenium displayed pure spherical
Copyright ꢀ 2003 The Chemical Society of Japan
Chen, Yuan-Tao
