A facile sulfur vapor assisted reaction method to grow boron nitride nanorings at relative low temperature

Article abstract of DOI:10.1021/jp053500t

Boron nitride (BN) nanorings were synthesized using a sulfur vapor assisted solid-state method at 600?°C. The rings had typical diameters of 100-300 nm, and the shells were 5-20 nm thick and about 50 nm wide. On the basis of the characterization of X-ray powder diffraction pattern (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transformation infrared spectroscopy (FTIR) measurement, the as-prepared product was pure-phase hexagonal BN. High-resolution transmission electron microscopy (HRTEM) images proved that the nanorings were formed through the coiling of the (002) planes of hexagonal BN. A possible growth process for BN nanorings is suggested. ? 2005 American Chemical Society.

Full text of DOI:10.1021/jp053500t

19188
J. Phys. Chem. B 2005, 109, 19188-19190
A Facile Sulfur Vapor Assisted Reaction Method To Grow Boron Nitride Nanorings at
Relative Low Temperature
Xiaopeng Hao,* Yongzhong Wu, Jie Zhan, Jiaxiang Yang, Xiangang Xu, and Minhua Jiang
State Key Lab of Crystal Materials, Shandong UniVersity, Jinan 250100, People’s Republic of China
ReceiVed: June 28, 2005; In Final Form: August 15, 2005
Boron nitride (BN) nanorings were synthesized using a sulfur vapor assisted solid-state method at 600 °C.
The rings had typical diameters of 100-300 nm, and the shells were 5-20 nm thick and about 50 nm wide.
On the basis of the characterization of X-ray powder diffraction pattern (XRD), X-ray photoelectron
spectroscopy (XPS), and Fourier transformation infrared spectroscopy (FTIR) measurement, the as-prepared
product was pure-phase hexagonal BN. High-resolution transmission electron microscopy (HRTEM) images
proved that the nanorings were formed through the coiling of the (002) planes of hexagonal BN. A possible
growth process for BN nanorings is suggested.
Introduction
charged with Ar to 1 atm, the tube was heated to 600 °C and
kept for 1 h. After the growth, the sample was cooled to room
temperature. The product was filtered with CS2 and water to
remove the byproducts, separately. Finally, the BN was obtained.
1
Since the discovery of carbon nanotubes, one-dimensional
materials have become the focus of intensive recent studies
because of their wide potential applications in electronics, optics,
2
,3
The X-ray powder diffraction (XRD) pattern was recorded
on a Rigaku D max-γA X-ray diffractometer with Ni filtered
Cu KR radiation. The X-ray photoelectron spectroscopy (XPS)
was performed on an ESCALAB 2200-XL X-ray photoelectron
spectrometer. Fourier transformation infrared spectroscopy
and mechanics. There has been a great deal of interest in the
4
,5
6,7
preparation and characterization of nanotubes, nanowires,
nanorods,8,9 nanocables,
10,11
12,13
14,15
nanofibers,
and nanobelt
in
recent years.
Boron nitride (BN) is one of the most interesting non-oxide
materials with a potentially bright future in advanced materials
(FTIR) measurement was carried out using a Nicolet FTIR760
infrared spectrometer. About 3-5% (in weight) samples were
mixed with KBr and ground thoroughly, and then they were
pressed into a thin pellet for characterization. Field emission
scanning electron microscopy (FESEM) was taken on a
JSEM6700F (JEOL) field emission scanning electron micro-
scope. High-resolution transmission electron microscopy
1
6
design and exists in several forms. Hexagonal BN (hBN) and
cubic BN (cBN) are the two main forms. hBN, having hexagonal
2
structure similar to that of graphite, consists of sp -bonded
layers. The lattice constants of hBN (a ) 2.504 Å, c ) 6.656
17
Å) are very close to those of graphite (a ) 2.470 Å, c ) 6.790
1
8
Å). These form the basis of growing a one-dimensional
nanostructure. Furthermore, the desirable mechanical, electronic,
thermal, and chemical properties of hBN make it an important
material in some specific application fields of nanoscience and
nanotechnology. Until now, various methods have been used
for the preparation of BN one-dimensional materials, by arc
discharge,19 by chemical vapor deposition (CVD), by template-
(HRTEM) images were taken with a Philips Tecnai 20U-Twin
high-resolution transmission electron microscope. The accelerat-
ing voltage was 200 kV.
Results and Discussion
20
Composition of the Sample. Figure 1shows the typical XRD
patterns of BN nanorings. All of the diffraction peaks could be
indexed as hBN with lattice constants of a ) 2.495 Å and c )
2
1
22
based synthesis, by co-pyrolysis method to grow BN
23
nanotubes, by B4N2O3 precursors to grow BN nanocages, and
by synergic nitrogen source to grow BN vessel and hollow
sphere nanostructures.24 However, there are few reports on the
synthesis of BN nanorings. Nanorings are an important category
of fullerene-like structures, to which particular attention should
be addressed. Also, they may have novel physical and chemical
properties within these particular one-dimensional materials. In
this paper, we report some novel BN nanorings synthesized
through a sulfur vapor assisted solid-state reaction method at
the temperature of 600 °C.
6
)
.702 Å, consistent with the reported values of the literature a
2.504 Å, c ) 6.656 Å. The prominence of the (002) peak
1
7
indicates the presence of well-stacked layered structures in hBN.
No impurities such as B2O3 were detected by the XRD.
The composition of the as-prepared hBN could also be
derived from the XPS spectra (Figure 2). Figure 2 is a typical
survey spectrum of the hBN nanorings, which indicates the
presence of B and N elements. The appearance of C and O is
due to the adsorption of CO2 and O2 onto the surface of the
sample. The binding energy of B1s with 190.2 eV and that of
N1s with 398.0 eV are consistent with the reference value.25
Quantification of the peaks gives the atomic ratio of B to N of
1.05:1, from which we can conclude that the sample is BN.
Figure 3 shows the typical FTIR spectra of the hBN nanorings,
in which two strong characteristic peaks positioned at 1384 and
Experimental Section
First, 0.31 g of H3BO3 (A.R.), 0.17 g of Li3N (C.P.), and
0.16 g of S (C.P.) were pressed together into a pellet. The pellet
was placed into a quartz tube. After being under vacuum and
-
1
-1
*
Corresponding author. E-mail: hxp@icm.sdu.edu.cn.
815 cm are observed. The broad peak at 1384 cm is a
1
0.1021/jp053500t CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/23/2005

Reaction Method To Grow Boron Nitride Nanorings
J. Phys. Chem. B, Vol. 109, No. 41, 2005 19189
Figure 1. XRD pattern of the synthesized hBN nanorings.
Figure 4. (a) SEM image of the as-synthesized hBN nanorings. The
inset is the high magnification SEM image of a free-standing BN
nanoring, showing uniform and perfect geometrical shape. The ring
diameter is 100-300 nm, the thickness of the ring is 5-20 nm, and
the width of the ring shell is about 50 nm. (b) TEM image of a separate
nanoring. (c and d) HRTEM image corresponding to the separate
nanoring.
Morphologies and Structures. FESEM, TEM, and HRTEM
images of the as-synthesized hBN are shown in Figure 4. Figure
4
a shows the FESEM images of hBN and exhibits its ring-like
morphology. The as-synthesized hBN is composed of many
nanorings. Also, two types of rings have been found in the
sample. One type is that the ring has nearly circular shape. The
rings have typical diameters of 100-300 nm, and the shells
are 5-20 nm thick and about 50 nm wide. The inset SEM
images recorded at high magnification clearly show the perfect
circular shape of the complete rings. The other type is that the
ring is not entirely closed.
Figure 2. XPS spectra of hBN nanorings.
Figure 4b shows the TEM image of a separate hBN nanoring.
The ring diameter is about 300 nm, and the thickness is 15 nm.
Figure 4c and d shows the lattice images of the parts marked
with c and d in Figure 4b. The interplaner spacing of 0.33 nm
corresponds to the distance between the (002) planes of hBN.
This indicates that nanoring is formed through the coiling of
the (002) planes of hBN.
From the above analysis about the nanorings, we suggest a
possible growth mechanism of BN nanoring as follows.
(1) The formation of hBN belts: hBN can be synthesized
through the reaction between H3BO3 and Li3N without sulfur
added at the same reaction conditions as the above. The reaction
could be described by the following equation:
2
H BO + 2Li N ) 2BN + 3Li O + 3H O
3 3 3 2 2
Figure 3. FTIR spectra of the obtained hBN nanorings.
Although we can obtain hBN through this equation, the
morphology of the products is very different from that of
nanoring. In these reaction conditions, most of the particles of
the product are belt or sheet structures (as shown in Figure 5).
(2) Growth mechanism of hBN nanoring: In many ways
analogous to carbon, boron nitride forms both hard, diamond-
like sp -bonded phases and softer, graphite-like sp -bonded
phases. hBN is a layered structure that is similar to graphite
with the exception that hexagonal rings of the basal planes in
stretching of the B-N bond within the basal plane of the sp2-
bonded hexagonal BN, while the absorption band of the sharp,
-
1
weak peak at 815 cm could be attributed to the bending of
16
the B-N-B bond between the basal planes. The peak around
-
1
3
428 cm can be attributed to the water molecules absorbed
3
2
on the surface of BN nanorings. On the basis of the above
characterization of XRD patterns, XPS, and FTIR spectra, the
as-prepared product is pure-phase hBN.

19190 J. Phys. Chem. B, Vol. 109, No. 41, 2005
Hao et al.
will expand in the sealed system (Figure 6b). The expanding
vapor can provide a momentary driving force for rolling of the
hBN layers (Figure 6A and B). Furthermore, after the vapor
escaped from the pellet, some holes are left in the pressed pellet
(Figure 6c). The hBN belts can encircle along this hole and
form a ring structure (Figure 6C).
Conclusions
In summary, hBN nanorings of 100-300 nm in diameter,
-20 nm in thickness, and 50 nm in width were synthesized
5
by a sulfur vapor assisted solid-state method at 600 °C. The
nanoring was formed through the coiling of the (002) planes of
hexagonal BN. Sulfur plays an important role in the formation
of hBN nanoring. The sulfur vapor can provide a momentary
driving force for rolling of the hBN layers when sulfur sublime.
Furthermore, the hBN belts can encircle along the holes that
were left after the sulfur vapor escaped and form a ring structure.
Acknowledgment. This work was supported by the NSFC
Contract Nos. 50302005, 90206042), the grant for state key
program of China (2004CB619002), and the Fund for the
Excellent Young Scientists of Shandong Province (03BS075).
Figure 5. TEM image of the hBN nanobelts through the reaction
between H BO and Li N.
(
3
3
3
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