The Preparation of IV–VI Semiconductor Nanomaterials - Semiconductor Quantum Dots: Organometallic and Inorganic Synthesis - page 78

and heated, followed by injection of a chalcogen precursor solution into the
reagents. The rst organometallic synthesis of capped Pb chalcogenide QDs

was actually achieved by the thermolysis of single-source precursors. 21,22 In
these cases, lead dithio- and diselenocarbamates were thermolysed in
trioctylphosphine oxide (TOPO) at relatively low temperatures (<200 C),
giving lead sul



de and lead selenide particles of varying sizes and shapes.
The electronic spectra clearly showed absorption in the red/near infrared
region, although no excitonic peak or emission was observed. Similar work,
reported later, also described the synthesis of PbS using Pb(S 2 CNEt 2 ) 2 , with
nanoparticles exhibiting a wide range of morphologies. 23
The



d n 1 y 4 n g | 7

rst hot injection method using two precursors was reported by
Murray et al. , 24 who importantly showed the



 rst absorption spectra with

clear features (Figure 3.1), highlighting the rst excitonic transition which



.

Figure 3.1 Absorption spectra of PbSe QDs of various diameters: (a) 3.0 nm, (b) 3.5
nm, (c) 4.5 nm, (d) 5.0 nm, (e) 5.5 nm, (f) 7.0 nm, (g) 8.0 nm, (h) 9.0 nm.
Reprinted with permission from C. B. Murray, S. Sun, W. Gaschler, H.
Doyle, T. A. Betley and C. R. Kagan, IBM J. Res. Dev. , 2001, 45 , 47.
Copyright 2001 IBM.