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growth was essential for high-quality particles, although crystals were
obtained a
er 2 days. Size-selective precipitation allowed particles between 2
and 5 nm to be isolated with a size distribution of
20%, capped with both
TOPO and the second capping agent, such as dodecylamine (DDA), the
presence of which improved the solubility of the particles. The particles
exhibited bandgaps of 1.7
2.4 eV (
ca.
730 nm and
ca.
520 nm) as shown in
Figure 2.1. It was also reported that when exposed to air, both surface indium
and phosphorus sites oxidised to a depth of more than one monolayer. This
is important, as the particles did not exhibit any photoluminescence prior to
surface oxidation, attributed to the surface oxide blocking trapping sites. The
emission spectra consisted of both band edge emission, and weaker deep
-
d
n
1
y
4
n
g
|
3
.
Figure 2.1
Absorption edges of a range of InP QDs. Reprinted with permission from
A. A. Guzelian, J. E. B. Katari, A. V. Kadavanich, U. Banin, K. Hamad, E.
Juban, R. H. Wolters, C. C. Arnold and J. R. Heath,
J. Phys. Chem.
, 1996,
100, 7212. Copyright 1996 American Chemical Society.
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