The Synthesis of Core/Shell Quantum Dots - Semiconductor Quantum Dots: Organometallic and Inorganic Synthesis - page 132

CdSe has also been used as the shelling material on magnetic particles
such as NiPt, 74 CoPt, 75 Co 76 and FePt 77 using standard precursors. In the case
of CoPt/CdSe, quantum yields of emission from the shell was found to be
3

5%, the relatively low value attributed to the core species. Shell thickness
increased with growth time, and hence the shell emission also red-shi

-

ed
across the entire visible spectrum. Similarly, for Co/CdSe, a maximum
quantum yield of 3% was reported, whereas for FePt/CdSe, the quantum
emission was found to be up to 9% at ca. 500 nm. Other semiconducting
species, such as PbS and PbSe, have also been deposited on FePt, although in
some cases the structure was better described as FePt inside a cubic PbS
particle (Figure 5.4). 78 These methods, however, used materials with a large
lattice mismatch and the resulting shells varied in quality. In an interesting
example to counter this, semiconductor shells were grown on metal core
using a non-epitaxial mechanism. 79,80



d n 1 y 4 n g | 3

In a typical synthesis, a strong acid

silver layer was rst deposited on a gold core, followed by a chalcogen (E)

giving an amorphous AgE shell, which was then cation-exchanged using TBP,
giving the semiconductor shell. The shells were of a high quality, and various
structures and materials could be grown, such as Au/CdS/CdSe.
In an unusual example of core/shell particles, plasmonic



uorescent QDs
have been prepared where a precise space was engineered between the core
and the shell



— important in this case as plasmonic materials such as gold

.

Figure 5.4 Electron microscope images of FePt/PbS core/shell particles. Reprinted
with permission from J.-S. Lee, M. I. Bodnarchuk, E. V. Shevchenko and
D. V. Talapin, J. Am. Chem. Soc. , 2010, 132, 6382. Copyright 2010
American Chemical Society.