Chemistry Reference
In-Depth Information
quantum yields in the 5
6% region. The cadmium-capped particles were
stable for months, while the zinc-capped particles displayed evidence of
etching over a period of days, as determined by a blue shi
-
in the absorption
spectrum.
This route was amended by replacing the surfactant solution with TOP and
polyoxyethylene 4-lauryl ether.
135
This resulted in clusters up to 3 nm in
diameter, capped with TOP (which may have oxidised to TOPO), the poly-
ether surfactant and thiogycerol. The use of Se(SiMe
3
)
2
instead of the anal-
ogous sul
d
n
1
y
4
n
g
|
1
de resulted in HgSe nanoparticles being formed, while a mixture
of the two chalcogen precursors resulted in an alloy of HgSe
1
x
S
x
. Emission
from the alloy showed evidence of surface trapping states. An unusually
stable cluster of HgSe was observed with a band edge at 2.08 eV; even with the
addition of further precursor, further particle growth was not observed,
resulting in an increased concentration of clusters in solution. An in-depth
analysis on the electronic structure of the cluster was reported, with
ve
d
n
4
.
excited states being identi
ed. Investigations into the high-temperature
stability of
rming the crystal
core of both materials remains stable up to 600 K, despite an expansion of the
lattice.
136
The
b
-HgS and HgSe have also been reported, con
rst organometallic-type route to passivated HgTe utilised the ther-
molysis of mercury halides and TOPTe in TOPO and amines at low temper-
atures (
ca.
100
C) resulting in nanoparticles of crystalline HgTe, 3
6nmin
diameter with a near infrared band edge, although the growth was found to
be extremely rapid and the use of temperatures normally associated with
nanoparticle synthesis resulted in bulk material.
137
This route has been used
to prepare materials incorporated in e
-
ective photodetectors that span the
atmospheric mid-wavelength infrared transparency window.
138
The synthesis
was then improved by reducing the reaction temperature signi
cantly, and
injecting TOPTe while the reaction
er
the initial heating required for the formation of the Hg precursor.
139
The
particles of HgTe,
ca.
3.5 nm in diameter, exhibited an excitonic peak in the
absorption spectrum at
ca.
1150 nm, with near band emission observed at
ca.
1200 nm with quantum yields of 55
ask was being cooled with dry ice a
-
60%. The sample, upon ageing in
toluene solution for 2 weeks, shi
ed further into the red but still maintained
a quantum yield of 26%. A similar reaction was found to proceed at room
temperature, using mercury oleate and an ODE solution of TOPTe as
precursors, and dodecanethiol as a capping agent, giving HgTe particles
ca.
2.3 nm in diameter with emission at
ca.
830 nm and quantum yields of 20
-
30%.
140
This route was used to prepare HgTe suitable for incorporation into
photodetectors.
141
Keuleyan developed the route in more depth, using HgCl
2
,
TOPTe and a long-chain amine at a range of temperatures to yield a range of
triangular HgTe particles that emitted up at to 5
m.
142
The method was
again extended to the preparation of HgTe particles that were successfully
used in the preparation of a mid-infrared photodetector.
143,144
The room-temperature synthesis was utilised in the preparation of HgSe
QDs, which were prepared by injecting TOPSe into an ethanol solution of
m
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