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acetate and a strongly binding ligand (thioglycerol) were added to a solution
of bis(2-ethylhexyl)sulfosuccinate in hexane. It is interesting to note that the
mixture of thioglycerol and Hg(CO
2
CH
3
)
2
resulted in the almost instanta-
neous precipitation of HgS, therefore the order of addition was speci
ed to
minimise this side reaction, with thioglycerol added last. Gradual addition of
a hexane solution of S(SiMe
3
)
2
resulted in the slow growth over several
minutes of the HgS particles, clearly observable by the colour change, until
the particles precipitated when they reached 5 nm in diameter. In this case,
the actual size of the nanoparticles produced did not rely on the size of the
micellar water pool, unlike other micelle-based routes to nanomaterials. To
further protect the particles, a layer of either zinc or cadmium was grown on
the surface by replacing the sulfur precursor with the relevant metal alkyl or
acetate at the required stage. A
d
n
1
y
4
n
g
|
1
er surface treatment, a surfactant was then
added to passivate the particle; thiophenol for cadmium-capped particles,
long-chain thiols for zinc-capped particles. The absorption and emission
characteristics are shown in Figure 1.3. Emission quantum yields of uncap-
ped particles were below 1%, whereas the metal-capped particles had
d
n
4
.
Figure 1.3
Absorption (solid line) and corresponding emission (dashed line) for HgS
nanoparticles. Reprinted with permission from K. A. Higginson, M.
Kuno, J. Bonevich, S. B. Qadri, M. Yousuf and H. Mattoussi,
J. Phys.
Chem. B
, 2002, 106, 9982. Copyright 2002 American Chemical Society.
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