NaYF4:Pr ³⁺ nanocrystals displaying photon cascade emission

The quantum-cutting process is observed in nanocrystalline fluoride (NaYF(4)) doped with Pr(3+). The thermal decomposition synthesis method was used to synthesize the NaYF(4) nanocrystals with an average size of 42 nm. The morphological high resolution transmission electron microscopy (HRTEM), structural X-ray diffraction (XRD) and spectroscopy, with the use of synchrotron radiation, have been employed to characterize the material. The different excitation energies created different luminescence response of the NaYF(4):Pr(3+) nanocrystals. The quantum-cutting phenomenon has been observed under the direct excitation of the 4f5d bands of praseodymium. After excitation of the NaYF(4) matrix this process is quenched and part of the energy is released through the self-trapped excitons emission. The origin of the different types of emission transitions has been analyzed in detail.