Chemistry Reference
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lanthanides, co-ligands such as 1,10-phenanthroline and 2,2
0
-bipyridine,
commonly used in the preparation of rare-earth complexes were employed
during the preparation of the precursors, and these ligands were found to
play an important role in nanoparticle synthesis, coordinating to the particle
surface a
er precursor decomposition. These precursors were thermolysed
in either TOP, OAm or an ODE solution of OAm and OA, producing a range of
materials with morphologies ranging from cubes to spherical particles,
depending upon the system used. Similarly, xanthates with similar co-
ligands or a potassium ethylxanthate were used, although nanoparticles
prepared by this route were found to be of a lower quality than those
prepared by dithiocarbamates. The optical characteristic of the nanoparticles
were dominated by the electronic structure of the rare-earth ion, not the
overall band structure of the solid-state material. Notably the nanoparticles
decomposed in polar solvents such as tetrahydrofuran, yielding a lumines-
cent trivalent europium complex. The particles, in general, displayed optical
properties similar to bulk materials.
107
In a similar synthesis, EuS was prepared from a slurry of
Eu(S
2
CNEt
2
)
3
:1,10-phenanthroline in OAm at 200
C, giving a material that
was easily isolated and redispersed in non-polar solvents. The resulting
nanoparticles were compared to EuS nanoparticles prepared by a furnace
route using the same precursor and found to be signi
d
n
1
y
4
n
g
|
4
cantly smaller (5.5 nm
compared to at least 50 nm, and up to 120 nm), and exhibited cluster glass-
like behaviour and quasi-ferrimagnetic behaviour upon surface oxidation.
108
Nanoparticulate EuS has also been prepared by the photolytic decompo-
sition of Na[Eu(S
2
CNEt
2
)
4
]
.
$
3.5H
2
O, by irradiating the ligand to metal charge
transfer band of the precursor in solution, with no capping agents. The
particles,
ca.
9 nm in diameter, exhibited weak luminescence although this
was the
rst time the emission spectrum of nanoparticulate EuS was reported
and was attributed to an f
-
d transition with a blue-shi
ed band edge of
1.9 eV.
109
Several groups have reported similar routes to EuS, exploring the magnetic
properties,
110,111
polymer encapsulation,
112
superlattice formation
113
and the
di
erent products obtained when the precursors were thermolysed in air,
observing that Eu
2
O
2
S was obtained instead.
114
Hasegawa
et al.
also reported
one of the few preparations of EuSe using a diselenophosphinate, and it was
found that the tetraphenylphosphine cation, a decomposition product of the
precursor, coordinated to the particle surface, a
ecting the particle
morphology and electronic properties.
115
The use of single-source precursors to binary compounds has been
extended; Castro
et al.
reported a notable synthesis, where all three elements
of a ternary system were provided by a single-source precursor.
116
The
compound, (PPh
3
)
2
CuIn(SEt)
4
, was dissolved in dioctylphthalate and heated
with hexanethiol, and decomposed above 200
C to give CuInS
2
between 2
and 4 nm in diameter. The reaction did not proceed when using TOPO,
carboxylic acid or long-chain amines as coordinating ligands, but TOPO can
be used to replace the thiol a
er the reaction has been completed and the
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