Synthesis and characterization of Bi nanorods and superconducting NiBi particles

Article abstract of DOI:10.1016/j.jallcom.2005.03.063

Bi nanorods and NiBi particles were prepared using a simple hydrothermal reduction method at moderate temperatures of 150 °C. Transmission electron microscopy (TEM) reveals pure Bi nanorods with diameters of about 50 nm and superconducting NiBi particles. The magnetic susceptibility (χ) of the superconducting NiBi was measured as a function of temperature at 10 Oe.

Full text of DOI:10.1016/j.jallcom.2005.03.063

Journal of Alloys and Compounds 400 (2005) 88–91
Synthesis and characterization of Bi nanorods and superconducting
NiBi particles
Sangmoon Parka,b, Kyongha Kangc, Weiqiang Hana, Thomas Vogta,b,∗
a
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
b
Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
c
Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
Received 8 March 2005; received in revised form 9 March 2005; accepted 16 March 2005
Available online 23 May 2005
Abstract
Bi nanorods and NiBi particles were prepared using a simple hydrothermal reduction method at moderate temperatures of 150 ◦C. Transmis-
sion electron microscopy (TEM) reveals pure Bi nanorods with diameters of about 50 nm and superconducting NiBi particles. The magnetic
susceptibility (χ) of the superconducting NiBi was measured as a function of temperature at 10 Oe.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Hydrothermal reduction; Nanorods; Superconductor
1. Introduction
and co-workers in a previous report using hydrazine hydrate
in basic solution followed by several washing steps to prevent
oxidation [20]. Bismuth nanowires have unusual transport
properties caused by their anisotropic Fermi surface, low car-
rier densities, small carrier effective masses, and long carrier
mean free paths [21,22]. Furthermore, a giant magnetoresis-
tance (GMR) effect was observed in Bi thin films (1–10 ␮m)
and single crystals (23 mm × 1.1 mm × 2.2 mm) [23,24]. The
Ni–Bi phase diagram contains only two intermetallic com-
pounds: NiBi and NiBi3 [25]. The crystal structure of NiBi3
is a CaLiSi2-type with orthorhombic symmetry (Pnma) and
the structure of NiBi is a complex superstructure based on
a pseudo-hexagonal unit cell (P63/mmc) [26,27]. NiBi was
shown to be superconducting (Tc ∼ 4.25 K) [28,29]. It was
also proposed to be ferromagnetic [30] with a Curie tem-
perature of 675 K. The single-crystal Bi nanorods and the
binary superconducting NiBi were synthesized using a sim-
ple hydrothermal reduction method at 150 ◦C and charac-
terized by transmission electron microscopy (TEM), X-ray
and electron diffraction, and energy dispersive X-ray spec-
troscopy (EDS). The magnetic susceptibility (χ) was mea-
sured as a function of temperature in a magnetic field of
10 Oe.
The study of nanoscale metals or alloys is an intensive
research area due to their potential applications in single-
electrondevices[1–3], catalysts[4], optical/electricaldevices
[5,6], and ultra-high-density magnetic recording [7]. Such
nanoscale metals and alloys can be made by reducing metal
salt solutions [8–10]. Hydrothermal synthesis routes lead to
1D nanostructures due to the dissolution–recrystallization
(solution–solid) process established for binary rare earth
oxides and metals [11,12]. In solution, hydrazine hydrate
(N2H4·H2O) can function as both a reducing agent and a
coordinating ligand [13,14]. The one-dimensional epitax-
ial growth is facilitated by this coordination to the metal
ions in solution [15,16]. Bi nanowires with diameters of
roughly 50 nm or smaller show semi-conducting behavior
while above 70 nm metallic behavior is observed. They can
also be synthesized by electro-chemical deposition using
templates [17–19]. Bismuth nanotubes were reported by Li
∗
Corresponding author. Tel.:+1 631 3443731; fax: +1 631 3442918.
E-mail address: tvogt@bnl.gov (T. Vogt).
0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2005.03.063

S. Park et al. / Journal of Alloys and Compounds 400 (2005) 88–91
89
2. Experimental
respectively. The JCPDF #70–1849 and 85–1329 data were
used for indexing Ni (cubic) and Bi (hexagonal). No ox-
ide impurities such as Bi2O3 or NiO were detected in the
XRD patterns as shown in figures (a) and (b). The Bragg
reflections of NiBi were indexed by using the basis cell
(P63/mmc) determined by Liden et al. [27] in Fig. 1(c). The
lattice constants for the NiBi product were determined to
Bi(NO3)3·5H2O (Alfa, 99.999%) and Ni(NH4)2
(SO4)2·6H2O (Alfa) were used for preparing Bi, Ni and
NiBi. 10 mL of distilled water was added to a Teflon-lined
Parr reactorTM with a capacity of 23 mL. Appropriate
stoichiometric mixtures of 0.005 mol% Bi(NO3)3·5H2O and
Ni(NH4)2(SO4)2·6H2O were dissolved into the water under
rapid stirring for 15 min, and finally 3 mL of N2H4·H2O
(Alfa 99+) was slowly added to the solution. The solution
was sealed in the autoclave and maintained at 150 ◦C
for 18 h. When the reaction was finished, the black-solid
products were washed with distilled water and ethanol using
a centrifuge, and then stored in ethanol to prevent oxidation.
Phase identification was done using a MiniFlexTM
(Rigaku) diffractometer (Cu K␣ radiation). A SQUID mag-
netometer (Quantum Design) was used to determine the mag-
neticsusceptibility(χ)asafunctionoftemperature. Fortrans-
mission electron microscopy (TEM) studies the samples were
in ethanol when dispersed onto holey-carbon coated cop-
per grids. A JEOL 4000EX high resolution TEM was used
to investigate the microstructure of the samples. A JEOL
3000FEG TEM equipped with an electron energy loss spec-
trometer (EELS) was used to investigate the crystalline struc-
ture in more detail. The advantage of using EELS in a high-
resolution electron microscope (HRTEM) is that a single
nanoscale particle can be examined and its composition and
stoichiometry determined.
˚
be a = 4.078(8), c = 5.324(7) A compared to Lidin’s values
˚
of a = 4.1 and c = 5.3 A, which are based on a single crys-
tal study. The lattice constants for the other superstructure
(orthorhombic, Pmcm (Pmma)) peaks indexed from the ob-
tained XRD pattern were also determined to be a = 8.152(4),
˚
b = 14.110(6), and c = 5.328(2) A compared to Lidin’s values
˚
of a = 8.1527, b = 14.1209, and c = 5.3243 A (Uncertainties
were not provided in Ref. [27]). As seen in Fig. 1(c), small
quantities of un-reacted Bi and Ni nanoparticles are present
in the NiBi product. The Ni impurities result in the observa-
tion of ferromagnetism in the NiBi sample. Additional reflec-
tions (*) shown in Fig. 1(c) in the XRD pattern of NiBi could
possibly be associated with a highly textured NiBi3 phase
[26]. However, the severe overlap of the diffraction peaks
and no observation of NiBi3 particles in numerous electron
diffraction studies provides only equivocal evidence of this
phase.
The microstructures of Bi nanoparticles and nanorods are
shown in Fig. 2. The TEM bright-field plan-view image in
Fig. 2(a) shows Bi nanorods with diameters of about 50 nm
and nanoparticles with diameters of about 10 to 200 nm. This
wide size distribution is most likely a consequence of the
aggregation of nanoparticles, which occurs during the hy-
drothermal reduction. The inset in Fig. 2(a) is a selected area
diffraction pattern (SAD) for a Bi nanorod. The marked cir-
cle was selected for the SAD pattern (A). The sets of spots
with six-fold symmetry show that the rod is a single crystal
of Bi. The basal plane of the hexagonal structure of Bi is
oriented along the length of the nanorod. This was found in
all other Bi nanorods investigated. A Bi nanorod observed
using the JEOL 3000FEG TEM equipped with EELS and
EDS is presented in Fig. 2(b) and (c). The end and the mid-
dle of the Bi nanorod shown in Fig. 2(b) and (c), marked
as B and C, are shown. The high-resolution lattice fringe
image in these and other images, not presented here, sup-
port the fact that the nanorod is a Bi single crystal, which
has no internal grain boundaries. Electron diffraction and
EDS showed that no bismuth oxides were present in our
samples.
3. Results
The Ni, Bi, and NiBi nanoparticles were all black after
the hydrothermal reduction process. The X-ray diffraction
(XRD) patterns of Bi, Ni, and NiBi are shown in Fig. 1(a)–(c),
Fig. 3(a) is a typical low-magnification TEM image of
NiBi, which shows the presence of aggregates of polycrys-
talline particles. Fig. 3(b) shows a HRTEM image of a big
single crystalline particle of NiBi, which has attached many
small Ni nanoparticles. EDS measurements show that this
particle is composed of only Ni and Bi and the atomic ra-
tio is close to 1. Fig. 3(c) is a Fast Fourier transform (FFT)
diffraction pattern taken from the single domain area 1 shown
in Fig. 3(b), which can be indexed as hexagonal BiNi [27].
The incident direction of the electron beam is along ꢀ0,−1,1ꢁ.
Fig. 1. XRD patterns of (a) Bi, (b) Ni, and (c) NiBi products (Tickmarks
for I–III indicate reflections of the NiBi hexagonal sublattice (P63/mmc),
the NiBi orthorhombic superstructure (Pmcm(Pmma)), and NiBi3 (Pnma),
respectively).

90
S. Park et al. / Journal of Alloys and Compounds 400 (2005) 88–91
Fig. 2. TEM bright-field images of a Bi sample. The inset in (a) is a SAD from the area A marked; (b) and (c) are high-resolution TEM images from the areas
B and C marked in (a), respectively.
Fig. 3. (a) A typical low-magnification TEM image of the NiBi product, (b) a high-resolution TEM image of the NiBi (area 1) and Ni (area 2) products, (c) and
(d) fast Fourier transform (FFT) diffraction patterns of hexagonal NiBi and cubic Ni, (e) and (f) a high-resolution TEM image and a FFT diffraction pattern of
orthorhombic NiBi products.
Fig. 3(d) is a FFT diffraction pattern taken from the area 2
shown in Fig. 3(b). The incidence direction of the electron
beam is also along ꢀ0,−1,1ꢁ. Besides the principal reflections
from the hexagonal lattice of NiBi, we also find orthorhombic
superlattice reflections. Fig. 3(e) shows a HRTEM image of
a big single crystalline particle of NiBi. Fig. 3(f) is another
FFT diffraction pattern taken from a single domain shown in
Fig. 3(e), which can also be indexed as NiBi [27].
at 4.25 K when in zero-field and field cooled in an external
magnetic field H of 10 Oe.
4. Conclusions
Bi nanorods and binary NiBi particles were synthe-
sized using a simple hydrothermal reduction method at low
temperatures (150 ◦C). Transmission electron microscopy
(TEM), electron diffraction, and energy dispersive X-ray
spectroscopy (EDS) experiments identify the pure single
The magnetic susceptibility (χ) of NiBi as a function of
temperature shows the typical behavior of a superconduct-
ing transition. The superconducting transition was observed

S. Park et al. / Journal of Alloys and Compounds 400 (2005) 88–91
91
crystal Bi nanorods with diameter around 50 nm. NiBi par-
ticles show superconductivity with a transition-temperature
(Tc) of 4.25 K.
[11] A.-W. Xu, Y.-P. Fang, L.-P. You, H.-Q. Liu, J. Am. Chem. Soc. 125
(2003) 1494.
[12] J. Wnag, L.J. Gau, Mater. Chem. 13 (2003) 2551.
[13] Y. Jin, K. Tang, C. An, L.J. Huang, Cryst. Growth 253 (2003) 429.
[14] Z. Gui, R. Fan, W. Mo, X. Chen, L. Yang, S. Zhang, Y. Hu, Z.
Wang, W. Fan, Chem. Mater. 14 (2002) 5053.
Acknowledgement
[15] Y. Li, H. Liao, Y. Ding, Y. Fan, Y. Zhang, Y. Qian, Inorg. Chem.
38 (1999) 1382.
[16] Y. Li, Y. Ding, Adv. Mater. 11 (1999) 1382.
[17] T. Yian, G. Meng, S.K. Biswas, P.M. Ajayan, S. Sun, L. Zhang,
Appl. Phys. Lett. 85 (2004) 967.
This work was supported by an LDRD from Brookhaven
National Laboratory.
[18] M.E.T. Molares, N. Chtanko, T.W. Cornelius, D. Dobrev, I. En-
culescu, R.H. Blick, R. Neumann, Nanotechnology 15 (2004) 201.
[19] T.E. Huber, A. Nikolaeva, D. Gitsu, L. Konopko, C.A. Foss Jr., M.J.
Graf, Appl. Phys. Lett. 84 (2004) 1326.
References
[1] R.P. Andres, T. Bein, M. Dorogi, S. Feng, J.I. Henderson, C.P. Ku-
biakk, W. Mahoney, R.G. Osifchin, R. Reifenberger, Science 272
(1996) 1323.
[2] D. Davidovic´, M. Tinkham, Appl. Phys. Lett. 73 (1998) 3959.
[3] M.H. Devoret, D. Esteve, C. Urbina, Nature 360 (1992) 547.
[4] J.S. Bradley, in: G. Schmid (Ed.), Cluster and Colloids, VCH, New
York, 1994 (Chapter 6).
[5] C.B. Murray, C.R. Kagan, M.G. Bawendi, Science 270 (1995) 1335.
[6] R.J. Skomski, Phys.: Condens. Matter 15 (2003) R841.
[7] S. Sun, C.B. Murray, D. Weller, L. Folks, A. Moser, Science 287
(2000) 1989.
[8] V.F. Punters, K.M. Krishnan, A.P. Alivisatos, Science 291 (2001)
2115.
[20] Y. Li, J. Wang, Z. Deng, Y. Wu, X. Sun, D. Yu, P. Yang, J. Am.
Chem. Soc. 123 (2001) 9904.
[21] K. Liu, C.L. Chien, P.C. Searson, Phys. Rev. B 58 (1998) 14681.
[22] Y.-M. Lin, X. Sun, M.S. Dresselhaus, Phys. Rev. B 62 (2000) 4610.
[23] F.Y. Yang, K. Liu, C.L. Chien, P.C. Searson, Phys. Rev. Lett. 82
(1999) 3328.
[24] J.H. Mangez, J.-P. Issi, J. Heremans, Phys. Rev. B 14 (1976) 4381.
[25] H. Baker, ASM Handbook, Alloy Phase Diagram, vol. 3, ASM In-
ternational, Materials Park, OH, 1992.
[26] M.S. Lee, C. Chen, C.R. Kao, Chem. Mater. 11 (1999) 292.
[27] S. Lidin, V. Petricek, L. Stenberg, S. Furuseth, H. Fjellvag, A.-K.
Larsson, Solid State Sci. 2 (2000) 353.
[28] B.T. Matthias, Phys. Rev. 92 (1953) 874.
[9] D. Wang, D. Yu, Y. Peng, Z. Meng, S. Zhang, Y. Qian, Nanotech-
nology 14 (2003) 748.
[29] Y. Fujimori, S.-I. Kan, B. Shinozaki, T. Kawaguti, J. Phys. Soc. Jpn.
69 (2000) 3017.
[10] H.L. Niu, Q.W. Chen, Y.S. Lin, Y.S. Jia, H.F. Zhu, M. Ning, Nan-
otechnology 15 (2004) 1054.
[30] H. Yoshida, T. Shima, T. Takahashi, T. Knaeko, T. Suzuki, M.H.
Kimura, K. Asami, A. Inoue, J Magn. Magn. Mater. 239 (2002) 5.