EXPLOITING TRANSITION METAL AND LANTHANIDE IONS AS DOPANTS IN OXIDE AND FULORIDE NANOPARTICLES FOR NANOTHERMOMETRY AND BROAD BAND OPTICAL SENSITIZATION

Lanthanide activated nanoparticles are an important class of nanomaterials with unique properties and useful functionalities for a wide range of applications in na-nomedicine such as optical imaging, magnetic resonance imaging (MRI), nanother-mometry and theranostics. In this thesis some new lanthanide activated, fluoride or oxide nanoparticles for nanomedicine have been investigated. In particular, their synthesis, chemico-physical characterization and spectroscopic properties have been carried out. Two new nanothermometers have been developed through proper lanthanide doping and core@shell architecture, exploiting the peculiar energy level scheme of the lanthanide ions. The obtained nanomaterials show good thermal sen-sitivity, using both excitation and emission radiation in the near infrared biological windows, suggesting their possible use for in-vivo applications. One nanothermom-eter is based on the upconversion emission of Eu3+ ions sensitized by Yb3+ and Tm3+ ions as dopants in SrF2 nanoparticles. The other investigated nanothermometer is based on the excitation from thermally excited Stark levels of Nd3+ ions present as dopants in KY3F10 nanoparticles. Cr3+ and Yb3+ co-doped fluoride and oxide nanoparticles have been synthesized in order to sensitize the Yb3+ ions in a wide optical region, exploiting the Cr3+ absorp-tion and possible energy transfer to Yb3+ ions. Fluoride based NaSrAlF6:Cr3+, Yb3+ nanoparticles have been obtained and upon a excitation in the red region (around 650 nm) they show a strong Cr3+ emission in the NIR range (around 800 nm) but no Yb3+ ions emission was observed. On the other hand, for the ZnWO4:Cr3+, Yb3+ nanoparticles, that have been obtained and properly characterized, a strong Yb3+ emission around 980 nm is observed on exciting in the absorption range of Cr3+ (for this host around 750 nm), due to efficient Cr3+ → Yb3+ energy transfer. The spec-troscopic results show that the ZnWO4:Cr3+, Yb3+ nanoparticles are good candidates for upconversion emission with broad NIR excitation.