Chemistry Reference
In-Depth Information
Cu
1.0
In
1.0
Tl
1.0
S
3.5
were
ca.
16 nm in diameter with relatively narrow size
distributions. The absorption spectra of Cu
1.0
Ga
x
In
2
x
S
3.5
was also shown to
red-shi
with increasing indium content in agreement with Vegard
'
s law,
from a band edge at
ca.
450 nm to
ca.
900 nm.
The use of simple dithiocarbamates has been used to make ZnS
AgInS
2
solid-solution nanoparticles. Thermolysis of (AgIn)
x
Zn
2(1
x
)
(S
2
CNEt
2
)
4
in
OAm resulted in particles
ca.
4 nm in diameter, which exhibited an XRD
pattern consistent with a solid solution. By varying the precursor composi-
tion, the emission could be tuned across the entire visible region of the
spectrum.
122
There are other single-source routes to related ternary semi-
conducting systems such as AgInSe
2
.
123
Thermolysis of [(PPh
3
)
2
AgIn(SeC{O}
Ph
4
)] in a mixture of OAm and dodecanethiol caused the formation of
a hitherto unknown orthorhombic phase of AgInSe
2
rods,
ca.
14.5
-
d
n
1
y
4
n
g
|
4
50 nm in
size, isostructural with AgInS
2
. The use of both surfactants was essential, as
removal of the amine resulted in formation of the bulk phase, while removal
of the thiol resulted in the formation of impure, irregular-shaped particles.
Similarly, [(Ph
3
P)
2
AgIn(SCOPh)
4
] has been used as a single-source precursor
to AgInS
2
, when thermolysed in OA and dodecanethiol at between 125
220
C.
124,125
Thermolysis of a related precursor [(PPh
3
)
3
Ag
2
(SeC{O}Ph)
2
]in
a mixture of TOP and HDA at temperatures between 95 and 180
C gave Ag
2
Se
nanoparticles of varying morphology depending on reaction temperature
and nuclei concentration. It was suggested that at lower temperatures the
phosphine stabilised the precursor and inhibited the decomposition
process, slowing the nucleation process and controlling the morphology
observed. The amine was responsible for the activation of the precursor,
providing a
b
-elimination pathway, giving the pure Ag
2
Se phase and sepa-
rating the nucleation and growth steps.
126
Similarly, thermolysis of Ag(S-
COPh) in TOP at 160
C resulted in the formation of both silver
nanoparticles, 80 nm in diameter, and Ag
2
S nanoparticles,
ca.
25 nm in
diameter. The formation of silver particles was reportedly due to the
absence of alkylamine activators.
127,128
The bismuth analogue of the
precursor, Bi(SCOPh), has been thermolysed in TOPO and dodecanethiol at
150
C for 1 hour, yielding rods
ca.
300 nm
-
.
21 nm, although longer rods
which agglomerated could be obtained by replacing TOPO with OAm.
129
Although group-VI-containing QDs are the most common, others such as
group III
V materials (
e.g.
InP, InAs) are also important and in many way,
these systems may well bene
-
t more from a single-source approach than the
II
-
VI materials. Phosphide and arsenide precursors are usually toxic and
di
de, selenide and telluride
nanoparticles is much simpler and can use the elements themselves in
solution as precursors.
Cadmium phosphide, Cd
3
P
2
, is a narrow-bandgap semiconductor (0.55 eV,
ca.
2250 nm) with a large excitonic diameter of 36 nm, providing the potential
to tune the emission across a wide spectral range. The diorganophosphide
[MeCdP
t
Bu
2
]
3
, prepared by the direct reaction of Me
2
Cd and HP
t
Bu
2
in
a range of solvents, was thermolysed in either TOPO or 4-ethylpyridine to give
cult to handle, but the preparation of sul
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