The Preparation of II–VI Semiconductor Nanomaterials - Semiconductor Quantum Dots: Organometallic and Inorganic Synthesis - page 32

d n 1 y 4 n g | 1

d n 4 .

Figure 1.6 Nanocrystal heterostructures: (a) CdS nanorods; (b) CdS nanorods with
CdSe ends; (c) CdSe tetrapods; (d) CdSe tetrapods with CdTe arms; (e)
CdSe nanorods with CdTe tetrapods termination; (f) CdSe nanorods;
(g) CdSe tetrapods; (h) CdTe tetrapods on the ends of the arms of
CdSe tetrapods. Reprinted by permission from Macmillan Publishers
Ltd: Nature , D. J. Milliron, S. M. Hughes, Y. Cui, L. Manna, J. Li, L.-W.
Wang and A. P. Alivisatos, Nature , 2004, 430, 190. Copyright 2004.

tetrapods at the end of the arms (Figure 1.6). Similarly, CdTe tetrapods with
CdSe arms have been prepared using the standard chemistry, with on
average 10 arms per crystals being observed. These materials exhibited type II
behaviour and were successfully incorporated into photovoltaic devices. 201
This high degree of control over heterostructure morphology and composi-
tion may make molecular wiring a realistic proposal, and is especially
impressive as it was achieved by a single, simple reaction. The end-to-end
assembly of various structures can also be achieved using gold nanoparticles
grown on speci c parts of a nanoparticles as welding points. The gold

particles, destabilised by I 2 , coalesced forming larger particles and in the
process linked the particles, including rods and tetrapods, together. 202 The
potential for the use of anisotropic materials is high; CdTe tetrapods have
been suggested to be suitable components in electronic devices. 203

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1.6.3 Seed Growth of Anisotropic Particles
Straight and branched rods of CdSe have also been grown using gold/
bismuth particles as catalysts and seeds for growth in combination with CdO,
TOPO, octanoic acid and TOPSe in a ' geminate ' nucleation mechanism. 204