Small size CdS QDs were synthesized by (i) the single source precursor
methodology and by (ii) the microwave synthetic route. The consequences of
CdS QD direct exposure to air for a period of 7 days were investigated by
following 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 of
new recombination path(s) associated to degradations during aging, possibly
an oxidative formation of a CdO surface layer. On the other hand, no
significant change is observed in the absorption spectra. For QDs obtained
by (ii), no degradation is revealed by the PL spectra which remain
unchanged. On the other hand, the absorption spectra are dominated by an
unexplained broad band around 3.6 eV which tends to hide the fundamental
excitonic transition one and increases in intensity with aging.