Construction and optimization of biofunctional upconversion nanoplatforms

This thesis deals with several key issues related to the functionalization of lanthanide ions doped upconversion nanoparticles (UCNPs), and focuses on the construction of biofunctional upconversion nanoplatforms and obtaining a fundamental understanding of energy transfer (ET) mechanisms needed to come to a rational optimization of upconversion nanotheranostic platforms. Antibody functionalized NaYF₄: Yb³⁺, Er³⁺ UCNPs allow for the visualization of the tumor targeting process in vivo with chick embryo chorioallantoic membrane (CAM) model. Magnetic targeted UCL bioimaging is realized with multimagnetic-beads-embedded Fe₃O₄/NaYF₄: Yb³⁺, Er³⁺ bifunctional nanocomposites. A theoretical model of UCNPs-based ET mechanism is proposed and validated with a typical biofunctional upconversion nanoplatform composed of NaYF₄: Yb³⁺, Er³⁺/NaYF₄ UCNPs and energy-acceptor photosensitizing molecule Rose Bengal (RB). It is found that a proper shell improves both the static (radiative) and dynamic (nonradiative) ET. Finally, the shell thickness dependence of broad band near-infrared (NIR) dye sensitized UCL is investigated with both Yb³⁺, Er³⁺-codoped NaYF₄ and undoped NaErF₄ as energy acceptors.