Synthesis and characterizations of nanoribbons and monodispersed nanocrystals of CuBr

Article abstract of DOI:10.1016/j.materresbull.2004.10.016

Nanoribbons and monodispersed nanocrystals of CuBr have been prepared by a simple reaction between CuO suspension, NH₂OH·HCl and KBr in the presence of deionized gelatin at 10°C. The products were characterized by X-ray powder diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. The sizes of the monodispersed nanocrystals of CuBr were estimated by Debye-Scherrer formula according to XRD spectrum.

Full text of DOI:10.1016/j.materresbull.2004.10.016

Materials Research Bulletin 40 (2005) 265–270
www.elsevier.com/locate/matresbu
Synthesis and characterizations of nanoribbons
and monodispersed nanocrystals of CuBr
a,b
Ming Yang , Jun-Jie Zhu
a,*
a
Department of Chemistry, Key Lab of Analytical Chemistry for Life Science,
Nanjing University, Nanjing 210093, PR China
b
Department of Biotechnology and Chemical Engineering, Wuhan Polytechnic University,
Hankou, Wuhan 430023, PR China
Received 8 March 2004; received in revised form 21 September 2004; accepted 21 October 2004
Abstract
Nanoribbons and monodispersed nanocrystals of CuBr have been prepared by a simple reaction between CuO
suspension, NH OHꢀHCl and KBr in the presence of deionized gelatin at 10 8C. The products were characterized
2
by X-ray powder diffraction, transmission electron microscopy and UV–vis absorption spectroscopy. The sizes of
the monodispersed nanocrystals of CuBr were estimated by Debye-Scherrer formula according to XRD spectrum.
#
2004 Elsevier Ltd. All rights reserved.
Keywords: A. Nanostructures; B. Crystal growth; B. Sol–gel chemistry; C. X-ray diffraction
1
. Introduction
Nanoscales materials, such as monodispersed nanoparticles, nanowires, nanorods nanoribbobs and
nanotubes, have attracted extensive synthetic attention as a result of their novel size-dependent properties
+
1–6]. It is well known that CuBr is a good Cu ion conductor [7,8] through its three polymorphisms, the
[
g-phase with the zincblende structure below 385 8C, the b-phase with the wurtzite structure at
+
3
85 8C < T > 469 8C and the a-phase with the fcc structure in a disordered distribution of Cu ions
between 469 8C and the melting temperature 488 8C [9]. In the g-phase, the magnitude of electrical
conductivity depends strongly on a small deviation from the ideal stoichiometric composition and on a
*
Corresponding author. Tel.: +86 25 83594976; fax: +86 25 83317761.
E-mail address: jjzhu@nju.edu.cn (J.-J. Zhu).
0025-5408/$ – see front matter # 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.materresbull.2004.10.016

2
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M. Yang, J.-J. Zhu / Materials Research Bulletin 40 (2005) 265–270
small amount of impurity element included unavoidably in preparing specimens, while in the b-phase
and a-phase the conductivity shows the intrinsic value almost independent of the way of the sample
preparation. The copper(I) bromide is a candidate material for realization of electrochemical micro-
+
sensors, because the Cu ion conductivity permits in principle a fast adaptation to chemical potential
variations in the environment and, furthermore, a non-negligible electron hole conductivity makes
integration into microelectronic circuitry possible [10–12]. CuBr has been prepared by several different
methods, such as laser deposition technique [13], vacuum evaporation [14], electrodeposition [15], sol–
gel process [16] and liquid phase reaction [17]. In this paper, we report a method to synthesize CuBr
nanoribbobs and monodispersed nanocrystals by a very simple reaction between Cu(CH COO) , NaOH,
3
2
NH OHꢀHCl and KBr in the presence of deionized gelatin agents at 10 8C. The nanoribbobs and
2
monodispersed nanocrystals of CuBr were characterized by X-ray diffraction (XRD), transmission
electron microscopy (TEM) and UV–vis absorption spectroscopy. The sizes of the monodispersed
nanocrystals of CuBr were estimated by Debye-Scherrer formula according to XRD spectrum.
2
. Experimental procedure
2
.1. Materials
All the reagents used in the experiment were of the analytical purity. Cu(CH COO) , NaOH,
3
2
NH OHꢀHCl, KBr, HCl, C H OH and deionized gelatin were purchased from Shanghai Chemical
2
2 5
Reagent Factory (China). Distilled water was used throughout.
2
.2. Instruments
Powder XRD patterns were recorded on a Shimadzu X-ray diffractometer XD-3A (Cu Ka radiation,
l = 0.15418 nm). TEM was performed using a JEOL-JEM 200CX instrument. The samples used for
TEM observations were prepared by dispersing some products in ethanol followed by ultrasonic
vibration for 10 min using a ultrasonic washing machine (50 W, 20 KHZ), then placing a drop of
the dispersion onto a copper grid coated with a layer of amorphous carbon. A shimadzu UV-3100
photospectrometer was used to record the UV–vis absorption spectra of the as-prepared nanoribbobs and
monodispersed nanocrystals.
2
.3. Standard procedure for the preparation of CuBr
Synthesis of CuO suspension. CuO powder was prepared by adding 100 ml of 1.0 mol L NaOH to
ꢁ
1
ꢁ1
the same volume of 0.5 mol L Cu(CH COO) , aging the precipitated Cu(OH) gel at 80 8C for 2 days
in a laboratory oven, thoroughly washing with doubly distilled water and freeze drying. 0.5 mol L CuO
suspension was prepared in which 4% deionized gelatin was contained.
3
2
2
ꢁ1
ꢁ1
Preparation of CuBr nanoribborns. The same volume of the 0.5 mol L CuO suspension stabilized,
ꢁ
1
ꢁ1
0
1
.3 mol L NH OHꢀHCl and 0.5 mol L KBr were added rapidly with stirring for 8 h under agitation at
2
0 8C. The pH values were adjusted to 4–6 with HCl in the course of the reaction. The products obtained
were washed thoroughly with absolute ethanol in an inert glove box (O < 2 ppm) and vacuum dried at
room temperature overnight.
2

M. Yang, J.-J. Zhu / Materials Research Bulletin 40 (2005) 265–270
267
ꢁ
1
Synthesis of monodispersed CuBr nanocrystals. The same volume of the 0.5 mol L CuO suspension
ꢁ
1
stabilized and 0.3 mol L NH OHꢀHCl were added rapidly with stirring for 10 h under agitation at
2
1
intermediate product was separated using centrifuge machine. The same volume of the 0.5 mol L CuCl
0 8C. The pH values were adjusted to 4–6 with HCl in the course of the reaction. The CuCl as
1
ꢁ
ꢁ
1
suspension and 0.5 mol L KBr were added rapidly with stirring for 10 min under agitation at 10 8C.
After reaction, the nanoparticles of CuBr were rapidly separated from the solutions by centrifugation at
10,000 rpm for 8 min. The CuBr nanocrystals obtained were washed thoroughly with absolute ethanol in
an inert glove box (O < 2 ppm) and vacuum dried at room temperature overnight.
2
3
. Results and discussion
3
.1. XRD study
XRD patterns of the as-prepared CuBr were given in Fig. 1. Every XRD spectrum contains five peaks
that are clearly distinguishable as shown in Fig. 1a and b. All of them can be perfectly indexed to
crystalline g-CuBr, not only in peak position, but also in their relative intensity. The peak positions are in
good agreement with those for CuBr powder obtained from the International Center of Diffraction Data
card (ICDD, formerly JCPDS, 06–0292). The size of the monodispersed nanocrystals of CuBr was
calculated to be about 10 nm according to half-width of the diffraction peaks using Debye-Scherer
equation.
3
.2. TEM measurements
The morphology of the as prepared CuBr was studied by TEM. Fig. 2a shows the as prepared
CuBr with nanoribborns by direct reaction. In indirect reaction, the CuCl as intermediate products
exhibited fabric of flakes as shown in Fig. 2b. The monodispersed nanocrystals of CuBr with dia-
meters range from 6 to 15 nm can clearly observe in Fig. 2c. This result is in good agreement with XRD
result.
Fig. 1. Powder X-ray diffraction pattern of (a) the nanoribbons of CuBr and (b) monodispersed nanocrystals of CuBr.

2
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M. Yang, J.-J. Zhu / Materials Research Bulletin 40 (2005) 265–270
Fig. 2. TEM micrograph of (a) nanoribbons of CuBr; (b) the CuCl as intermediate products and (c) monodispersed nanocrystals
of CuBr.
3
.3. Proposed reaction path
Based on the investigation on the formation of CuBr, the possible mechanism may be summarized as
below:
CuðCH COOÞ þ 2NaOH ! CuðOHÞ þ 2NaCH COO
3
2
2
3
CuðOHÞ ! CuO þ H O
2
2
The directed reaction as below:
4
CuO þ 2NH OH ꢀ HCl þ 2HCl þ 4KBr ! 4CuBr þ N O þ 5H O þ 4KCl
2
2
2

M. Yang, J.-J. Zhu / Materials Research Bulletin 40 (2005) 265–270
269
Fig. 3. The UV–vis absorption spectrum of (a) the nanoribbons of CuBr and (b) monodispersed nanocrystals of CuBr dispersed
in ethanol solution.
The indirected reaction as below:
4
CuO þ 2NH OH ꢀ HCl þ 2HCl ! 4CuCl þ N O þ 5H O
2
2
2
CuCl þ KBr ! CuBr þ KCl
In the experiment, we employed hydroxylamine hydrochloride as the reducing agent. The gelatin on
the surfaces of CuO particles may form an adsorption layer to control the diffusion of NH OH, Br ions
2
and Cl ions. The reaction may occur mainly in a balanced region of the reagent flux and counter flux of
the released mental ions, more or less away from the surface of each solid precursor particle. As a result,
the obtained CuBr particles possess the nanoribborns structure and the CuCl as exhibited fabric of flakes.
The gelation works as an inhibitor of both the direct reaction of NH OH with CuO and coagulation of the
2
ꢁ
produced CuBr and CuCl particles. The reaction of CuCl with Br may rapidly occur in each region of
the surface of CuCl flakes. A lot of CuBr nanoparticles was produced with stirring for 10 min under
agitation at low temperature. After reaction, the nanoparticles were rapidly separated from the solutions
by centrifugation. The monodispersed nanocrystals of CuBr were produced.
3
.4. Optical properties
The as-prepared CuBr werewell dispersed in ethanol to form a transparent solution (the concentration is
.1200 mg/ml) by ultrasonic vibration for 10 min. UV–vis absorption spectrums of the CuBr nanoribbons
0
shows two absorption peaks at 394 and 412 nm in Fig. 3a. As shown in Fig. 3b, the Peaks of the
monodispersed nanocrystals of CuBr at 390 and 410 nm are in good agreement with the reported value for
the CuBr nanoparticles with diameters ranging from 2 to 28 nm (exhibited peaks at 391 and 410 nm) [18].
4
. Conclusion
The nanoribbons of CuBr have been successfully prepared by a sol–gel/emulsion technique at 10 8C.
The monodispersed nanocrystals of CuBr have been successfully prepared by a reaction of the CuCl

2
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M. Yang, J.-J. Zhu / Materials Research Bulletin 40 (2005) 265–270
flakes with KBr at 10 8C. The possible mechanism was summarized. It is expected that the method can be
extended to prepare other nanoribbons and monodispersed nanomaterials.
Acknowledgement
This work was supported by the National Nature Science Foundation of China (20325516), the Nature
Science Foundation of Hubei Province (2004ABA095) and Pastdoctoral Science Foundation of China
(2003033480).
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