Chemistry Reference
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although the emission was signi
cantly broader than reports of ZnSe parti-
cles described in Chapter 1. Particles of ZnS prepared in a similar manner
using EtZnS
2
CNEt
2
as a precursor displayed similar optical characteristics
with similar shi
s in the band edge.
34
The particles appeared to have
a smaller size range of 3.0
4.5 nm and possessed a cubic crystalline core.
Dithio- and diselenocarbamates have been used to prepare materials other
than II
-
d
n
1
y
4
n
g
|
4
VI semiconductors. The simple copper dithiocarbamate Cu(S
2
CNEt
2
)
2
has been used to prepare Cu
1.8
S nanoparticles capped with TOPO.
35
During
the synthesis, TOPS was also added to facilitate formation of the sul
-
de, due
to the stability of the carbon
de resulted
in a material rich in copper metal impurities. The materials prepared
exhibited band edge of
ca.
2.35 eV (
ca.
530 nm) and displayed broad emission.
Similarly, Cu(S
2
CNEt
2
)
2
has been used to make Cu
2
S particles in the presence
of octylamine (OA) and dodecanethiol and used in the preparation of e
-
sulfur bond. Failure to add the sul
cient
photovoltaic cells.
36
Using a similar precursor, Revaprasadu
et al.
prepared nanoparticles of
Cu
2
S in solution using Cu(S
2
CNMe(
n
-hex))
2
,
ca.
4 nm in diameter with a blue
shi
of 2.09 eV.
37
The particles exhibited broad emission, with a maximum at
477 nm. The use of Cu(S
2
CNEt
2
)
2
was extended to make nanodiscs of Cu
2
Son
a silicon substrate, by thermolysing the precursor in TOP with the substrate
submerged in the reaction solvent.
38
By using a bismuth-covered substrate,
nanowires could be grown using the same technique, due to the formation of
bismuth catalyst particles resulting in solution
-
liquid
-
solid (SLS) growth as
described earlier.
The simple diselenocarbamate of copper, Cu(Se
2
CNEt
2
)
2
, has been used to
prepare CuSe nanoparticles capped with TOPO.
39
The particles,
ca.
16 nm in
diameter, exhibited an increase in the bandgap although the emission pro
.
le
was not described. The particles exhibited a di
raction pattern consistent
with a hexagonal crystalline core.
7.3 Single-Source Routes to Anisotropic Particles
The preparation of anisotropic particles has been extensively examined, and
a complicated relationship between monomer concentration, capping
agents, reaction temperature and particle morphology has been uncovered
(Chapter 1). The thermolysis of the simple cadmium diethyldithiocarbamate
in TOPO has shown to give spherical particles, but the use of the same
precursor in hexadecylamine (HDA) produced a range of anisotropic parti-
cles.
40
This varies from the usual method of producing anisotropic particles
as only one surfactant and one precursor/monomer is used. Growth at 300
C
resulted in wurtzite nanorods of CdS, 6 nm wide with an aspect ratio of
ca.
4.
Increasing precursor concentration resulted in the increase in width up to 25
nm, yet still maintained the aspect ratio of 4. By varying the temperature at
a
erent-shaped particles could be prepared, with
bipods, tripods and tetrapods forming at lower temperatures. Interestingly,
the formation of tetrapods is primarily at 120
C and dominates at least 80%
xed concentration di
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