Preparation, Compositing, Properties Of NaYF₄Up-conversion（UC） Luminescent Materials

Rare earth ion doped up-conversion （UC） luminescent nanomaterials have been widelyapplied in biolabeling, bioimaging, photodynamic therapy and drug delivery due to theirunique physical and chemical properties. The present dissertation established thepreparation method of rare earth ion doped NaYF4UC nanomaterials with strongluminescence, uniform size and controlled morphology, and studied the effect of reactionparameters on the formation mechanism of the nanomaterials. To expand the functionality,we synthesized various NaYF4based multifunctional nanocomposite materials with simpleexperimental method, and carried out a series of investigations into the structure,morphology, and properties. The details are as following:（1）The preparation methods were optimized. NaYF₄: Yb³⁺, Er³⁺UC luminescencenanoparticles were prepared with controlled size, morphology and structure. The effect ofvarious reaction parameters on formation mechanism of the nanoparticles was analyzed.The experimental results showed that the size, phase structure, and luminescence propertiesof the UC luminescent nanoparticles can be controlled by adjusting various parameters,such as reaction time, the ratio of reactants, and the molar ratio of the rare earth ion. In vivoimaging of mice from different positions was achieved using NaYF₄: Yb³⁺, Er³⁺UCluminescent nanoparticles with relatively high green emission.（2）To enhance the water-solubility and biocompatibility of the UC luminescentnanomaterials, NaYF₄: Yb³⁺, Er³⁺/SiO2core-shell nanocomposites were synthesized andtheir UC luminescence properties were analyzed. The results showed that the increase ofTEOS content, reaction time and concentration would lead to the self-nucleation of SiO2nanoparticles and cross-linking of nanoparticles. The surface/interface have an impact onUC luminescence properties of the nanocomposites.（3） In order to further optimize the luminescent properties of UC nanomaterials andexpand their application areas, NaYF4: Yb³⁺, Er³⁺/PVP and NaYF₄: Yb³⁺, Er³⁺/SiO2nanotubes with various diameters were synthesized via electrospinning and hightemperature calcination. The inner and outer diameters of the nanotubes can be controlledby changing the electrospinning voltage. PVP molecules might produce the passivation onthe surface defects of NaYF₄: Yb³⁺, Er³⁺nanoparticles and reduce the nonradiativerelaxation of Er³⁺ion. After high temperature calcination, the red emissions of thenanotubes were further enhanced, which will facilitate to improve the penetration depth inbiotissues and enhance the sensitivity of imaging. The luminescent nanotubes with desirableUC properties are expected to have potential applications in drug delivery and real-timeimaging. （4） To expand the functionality of the UC luminescent nanomaterials, thewater-soluble and surface-functionalized Fe₃O₄/NaYF4:Yb³⁺, Er³⁺nanocubes were prepared.The results of magnetization curves and photoluminescence spectra revealed that thenanocubes simultaneously possessed the superparamagnetic properties of Fe₃O₄and UCluminescent properties of NaYF4: Yb³⁺, Er³⁺. These unique properties make thesemagnetic-upconversion nanomaterials promising candidates for bioseparation, bioimaging,biodetection, and targeted drug delivery.