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Chemistry Letters Vol.37, No.3 (2008)
Benzene-thermal Route to InP and InAs Nanocrystals Using Triphenylphosphine and
Triphenylarsine as Pnicogen Sources
Junli Wang and Qing Yangꢀ
Hefei National Laboratory for Physical Sciences at Microscale & Department of Chemistry,
University of Science and Technology of China, Hefei 230026, P. R. China
(Received November 26, 2007; CL-071309; E-mail: qyoung@ustc.edu.cn)
Nanocrystalline InP and InAs were solvothermally synthe-
Meanwhile, InAs nanocrystals are also obtained via the ben-
zene-thermal route by replacing PPh3 with AsPh3. We believe
that it will be a novel and wide way to prepare III–V semicon-
ductor materials in nanoscale by gaining V elements from novel
organic compounds such as PPh3 and AsPh3.
sized by the reaction of newly reduced indium with tri-
phenylphosphine (PPh3) and triphenylarsine (AsPh3) in benzene.
The products were characterized by XRD, TEM, and EDX.
PPh3 and AsPh3 with high safety as excellent P and As
sources will provide a novelly alternative synthetic route to
III–V semiconductor compouds.
.
Typically, 0.150 g (0.5 mmol) of analytically pure InCl3
4H2O, 0.086 g (1.5 mmol) of KBH4, and 1.000 g (4 mmol) of
PPh3 were added into 2–5 mL of benzene in a quartz container
with a 20-mL volume, and the container was sealed in a auto-
clave, kept at 350–380 ꢁC for 8–12 h, finally cooled to the room
temperature on standing. The products obtained were washed
with benzene, absolute alcohol, and distilled water, respectively.
For detailed investigations, the products were divided into two
parts: one part was washed with 1 M HCl and the other not,
and then dried in vacuum at 60 ꢁC for 4 h.
Recently, group III–V semiconductor nanocrystals have
gained considerable attention because of their properties superi-
or to those of Si and group II–VI compounds in many ways as
well as their potential applications in electronics, optoelectron-
ics, nanodevices, and sensors.1–4 However, the preparation of
group III–V nanocrystals is largely restricted owing to numerous
difficulties mainly relavant to their greater degree of covalent
bonding and less-available precursors of pnicogens in compari-
son to those of II–VI materials. Up to now, many efforts have
been paid for the fabrication of III–V nanostructures and some
strategies have been developed, for instance, metal–organic
chemical vapor deposition (MOCVD),5 metal–organic vapor-
phase epitaxy (MOVPE),6,7 laser-assisted catalytic growth
(LCG),8 and nanocrystal-seeded growth,9,10 along with solu-
tion-based methods.11–14
It is noticeable that a key focus of most of the above studies
is how to gain group V elements (N, P, As, and Sb) properly
from the reaction precursors, such as NH3, EH3, (Na/K)3E,
ECl3 (E = P and As), Li3N, As2O3, P4 (yellow), As powder,
and organic compounds with elemental pnicogens. It is a smart
pathway to gain V elements from organic compounds to prepare
III–V semiconductor nanocrystals.5,6,10–12 Metal–organic com-
pounds, however, are usually of high toxicity and unstable in
air, which arouses many difficulties in the synthesis, for exam-
ple, the absolutely nonaqueous and nonoxygen system. Triphen-
ylphosphine (PPh3) with little toxicity and high safety is one of
widely used compounds in chemistry, and it can be used as an
available precursor of the novel P source for the preparation of
III–P semiconductor nanocrystals. On the basis of the idea, re-
cently, we have successfully prepared InP and GaP nanocrystals
by commercial metal In and Ga reacting directly with PPh3.15
Here, we developed the above idea, and prepared InP nano-
The XRD pattern reveals the production of InP from PPh3.
As shown in Figure 1a for the sample obtained after 1 M HCl
treatment, the pattern can be well indexed to zinc-blend (ZB)
˚
phase InP with a lattice parameter a ¼ 5:861 A (JCPDS File
No. 73-1983), which suggests that pure InP can be obtained in
the present route. There are not any other impurities detected
in the product. It is noted that metallic indium is mixed with
the InP product before the sample was treated with 1 M HCl
solution, which is confirmed by the XRD pattern shown in
Figure 1b. The result indicates the presence of newly reduced in-
dium in the synthesis. The synthetic route of InP is successfully
employed to synthesize zinc-blend InAs nanocrystals by substi-
tuting AsPh3 for PPh3, though the product contains small amount
of elemental As (Figure 1c). Elemental As may be produced by
pyrogenesis from AsPh3. According to the conversion of indium,
the yield of InP is about 70%, and that of InAs is 85%.
TEM image of the InP sample is shown in Figure 2a, and the
sample appears in irregular particles. Figure 2b demonstrates a
magnified TEM image for an individual InP nanocrystal, and
the corresponding ED pattern (inset of Figure 2b) confirms that
.
crystals by the reduction of InCl3 4H2O with PPh3 in the pres-
ence of KBH4 in benzene solution at 350–380 ꢁC. The developed
method involved newborn metallic indium acting actively with
PPh3 to form nanocrystalline InP, and the whole reaction can
be expressed as follows:
2InCl 4H O þ 6KBH þ 2PPh
3ꢂ
2
4
3
Figure 1. XRD patterns of the products: a) pure InP, after 1 M
HCl treatment; b) InP with In before washing with 1 M HCl; c)
Crystalline InAs with elemental As after washing with 1 M HCl.
ð1Þ
! 2InP þ 6KCl þ 6BH3 þ 3H2 þ 8H2O þ 3Ph{Ph:
Copyright Ó 2008 The Chemical Society of Japan
Wang, Junli
