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We report on structure-property relationships in Pr-doped CeO2 and ZrO2 using X-ray diffraction (XRD), Raman, UV to Vis Diffuse Reflectance (DR-UV/Vis), X-ray Photoelectron (XPS), and luminescence (PL) spectroscopies. Both 3+ and 4+ valence states of Pr are evidenced, irrespective of the host and calcination temperature, T (T = 500 and 1000 °C) with consequences on absorption, surface, vibrational and luminescence properties. Only zirconia represents a suitable host for Pr(3+) luminescence. The distinct trivalent Pr centers and their excitation mechanism are identified in relation to the tetragonal and monoclinic phases of ZrO2. A near-infrared to visible up-conversion (UPC) emission of Pr(3+) is observed upon excitation at 959 nm which occurs, most probably, via a two-photon excited state process. By using a multi-wavelength, time-gated excitation, the UPC process is established as phase selective, i.e. only Pr(3+) located in the monoclinic sites of the mixed phase, monoclinic and tetragonal ZrO2 (T = 1000 °C) contribute to the UPC emission. We believe that, besides the local symmetry, a key role in phase selective UPC is played by the presence of Pr(3+) low-lying 4f 5d levels. To the best of our knowledge, this is the first report of phase selective up-conversion emission in a lanthanide doped multi-phase host.

Nanotechnology is revolutionizing the development of different branches of science. The investigation of nanomaterials in the battle against cancer is not an exception. The main goal of this contribution is to bring an overview about the types of organic and inorganic nanomaterials that are under investigation for its applications in different aspects of cancer therapy: detection, diagnosis, contrast agents, controlled drug delivery, and hyperthermia. This review also includes fundamental aspects such as basic properties and synthesis of nanoparticles, with an emphasis on the use of selfassembed systems such as micelles, microemulsions, nanoemulsions, and liposomes.

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