The Use of Single-Source Precursors in Nanoparticle Synthesis - Semiconductor Quantum Dots: Organometallic and Inorganic Synthesis - page 227

d n 1 y 4 n g | 4

Figure 7.1 (a) Suggested ethane elimination for symmetrical

diethyldiselenocarbamates. (b) Suggested decomposition mechanism
for the asymmetric [Cd(SeCNMe( n -hex)) 2 ] 2 showing the eliminated
selenium containing heterocycle; suggested decomposition mecha-
nism for the asymmetric [Cd(Se 2 CNMe(CH 2 CH 2 Ph)) 2 ] 2 . Reprinted
with permission from N. L. Pickett and P. O

.

Brien, Chem. Record ,
2001, 1, 467. Copyright 2001 John Wiley & Sons, Inc. and The Japan
Chemical Journal Forum.

'

Other investigations into the decomposition mechanisms of zinc dithio-
carbamates in the presence of long-chain amines, using nuclear magnetic
resonance (NMR) and MS, highlighted that nucleophilic attack of the amine
on the electron-de  cient thiocarbonyl carbon atom induced precursor

decomposition. 21
A further precursor, [Cd(Se 2 CNMe( n -hex)) 2 ] 2 , was designed with reference
to the mechanistic data and prepared as described above. 22 The complex was
found to be inde nitely stable when stored in air at room temperature, yet

decomposed cleanly at 200 C in TOPO to give CdSe particles 3



5nmin
diameter with a hexagonal crystalline core. Absorption spectra showed the
blue-shi

-

ed absorption edge with clear excitonic features and band edge
emission with,



in some cases, slight evidence of trap emission. The

synthesis of CdS and ZnE (E S, Se) nanoparticles in TOPO using the

analogous asymmetrical dithio/selenocarbamate was also successful, giving
similar-sized particles. 23 With reference to the decomposition studies, other
precursors such as [Cd(Se 2 CNMe(CH 2 CH 2 Ph)) 2 ] 2 were designed with

¼