| dc.description.abstract | Lanthanide-doped nanocrystals (NCs) are suitable as luminescent labels for nanosystems due to their characteristic luminescence properties. In this work, LaPO4 and Y2O3 NCs of various sizes and compositions are synthesized. By doping the mentioned crystal lattices with other lanthanide ions (Ln3+), for instance Eu3+, Tb3+ or Ce3+, sharp emission lines are obtained. Furthermore, the traceability and robustness of the systems are studied by analysing their photoluminescence properties in temperature ranges from 25ºC to 600ºC.
More concretely, LaPO4 NCs doped with Eu3+ or Ce3+/Tb3+ show an increase in non-radiative decay at high temperatures, especially for samples with higher concentrations of Ln3+ ions at the surface. The small size around 4 nm makes the NCs generally unstable under high temperatures, where defects in the crystal lattice irreversibly reduce the luminescence efficiency.
On the other hand, Y2O3 NCs doped with Eu3+ ions show highly stable luminescence. The emission lines from the excited 5D0 and 5D1 energy levels exhibit a thermal equilibrium from 150ºC to 600ºC, following a Boltzmann distribution. This system arises as a suitable option for model systems and for further characterization under single-particle spectroscopy. Moreover, Y2O3 NCs doped with Tb3+ ions show strong thermal quenching of the emission for the temperature range studied. The process happens probably due to thermally activated photoionization or quenching by electron transfer. However, this process needs to be studied further for a coherent explanation.
To sum up, lanthanide-doped NCs show specific luminescence properties depending on the crystal lattice and dopant ion of study, where different radiative and non-radiative decay pathways can take place, changing the luminescent features of each material. | |
