Published online by Cambridge University Press: 02 March 2011
Small size CdS QDs were synthesized by (i) the single source precursormethodology and by (ii) the microwave synthetic route. The consequences ofCdS QD direct exposure to air for a period of 7 days were investigated byfollowing the evolution of the photoluminescence (PL) and absortion spectra.For QDs obtained by (i), the excitonic emission band (3.0 ‑ 3.1 eV)decreases in intensity, relatively to the low energy one (2.2 ‑ 2.5 eV)tentatively associated to midgap surface states. This suggests arising ofnew recombination path(s) associated to degradations during aging, possiblyan oxidative formation of a CdO surface layer. On the other hand, nosignificant change is observed in the absorption spectra. For QDs obtainedby (ii), no degradation is revealed by the PL spectra which remainunchanged. On the other hand, the absorption spectra are dominated by anunexplained broad band around 3.6 eV which tends to hide the fundamentalexcitonic transition one and increases in intensity with aging.