Pulsed Laser ablation (PLA) from a Si target in an inert He ambient has been used to produce Si/SiOx nanostructured thin films on Si substrates. After the film exposition to atmospheric air, they exhibited photoluminescence (PL) signals with peak energy between 1.58 and 2.15 eV. It was found that both natural and thermal oxidation of the films can cause dramatic changes in PL properties giving rise to the appearance or considerable enhancement of fixed Pt peaks around 1.6-1.65 and 2.2-2.25 eV, Quite different time-dependent PL degradation behavior under continuous laser irradiation gives an evidence for different mechanisms responsible for the PL peaks, Possible origins of Pt are discussed.