Light-induced inhibition of photoluminescence emission of core/shell semiconductor nanorods and its application for optical data storage

In this work, we demonstrate that the photoluminescence emission of CdSe/CdS spherical core/rod like shell nanorods can be completely inhibited by using low-energy femtosecond laser pulses at 720 nm. A combined analysis of optical confocal microscopy images and transmission electron microscope micrographs reveals the presence of different power regimes in the nanocrystals photodegradation process. The photoluminescence inhibition of the nanorods is found to start at a power range in which no apparent structural damage occurs to the nanorods after irradiation. This suggests the presence of a photochemical transformation of the nanocrystals that is of potential interest for application in optical data storage. This is because in recording systems based on photochemical processes the photoexcited volume can be effectively confined within the diffraction-limited laser focus. We indeed demonstrate that the recorded mark can be scaled down to a few nanorods, or even to a single nanorod, without crosstalk between adjacent nanostructures separated by the optical resolution of the instrument used. Finally, the intensities required for inhibiting the emission of nanorods and for avoiding any peripheral thermal damage of the hosting polymer matrix are determined (200-360 GW/cm²), and the mechanism underlying the photochemical process is discussed.