Optimized Design And Application Of Rare-earth Upconversion Nanoparticles Materials

As a novel kind of optical materials, rare-earth upconverison nanoparticles materials (UCNPs) were developed based on the organic dyes and Quantum dots (QDs) in recent years. Due to their ability to convert two or more low-energy pump photons at the NIR region to a higher-energy out put emission at the ultra violet (UV), visible, and shorter wavelengths of NIR, UCNPs have been applied in many areas including bio-sensing, in vivo imaging, drug delivery, photodynamic therapy and photoactivation. This thesis is mainly focusing on the design and optimizes the optical properties of UCNPs by adjusting Yb3+ doping and utilizing organic dyes, and applies in related fields; aim to overcome the drawback such as low efficiecy and limitation in excitation wavelength of UCNPs. The main research results are as follows:(1) A facile method was reported for amplifying the red-emission of NaYF4:Yb,Er@CaF2 by inherently adjusting the core Yb ratio, and found the doping of 80% Yb3+ in the core exhibited best red-emission, this optimal UCNP shows a high absolute upconversion quantum yield of 3.2% in red-emission. When conjugated to aminolevulinic acid, a clinically used photodynamic therapy (PDT) prodrug, significant PDT effect in tumor was demonstrated in a deep-tissue (>1.2 cm) setting in vivo at a biocompatible laser power density (0.5 W/cm2,980 nm). Furthermore, we show that our UCNP-PDT system with 980 nm NIR irradiation out performs clinically used red light irradiation in adeep tumor setting in vivo.(2) We have developed a means to systematically engineer excitation wavelengths of UCNPs via a set of near-infrared (NIR) absorbing organic dye molecules, We found that the NIR dyes act as a series of "antennae" to capture NIR photons at distinguishable excitation bands. Further, we demonstrated that the excitation band of a UCNP can be broadened by "mixing and matching" a pair of dyes. Finally, we extended this concept into aorthogonal imaging application.(3) We examined the upconversion emission by using IR-806 to sensitize a series of thickness core/shell hexagonal phased ?-NaYF4:20%Yb,2%Er@?-NaYF4 UCNPs, and found that the energy transfer from the IR-dye to these UCNPs was blocked due to the increased shell thickness of P-NaYF4. Then, an approach to achieve significantly enhanced upconversion luminescence in core-shell UCNPs with broadened absorption range via the doping of ytterbium ions in the UCNP shell to bridge energy transfer from the dye to the UCNP core, The absolute quantum yield of IR-806 sensitized core/active shell UCNPs (p-NaYF4:20%Yb,2%Er@?-NaYF4:10%Yb) at 800 nm was determined to be ?6% at 2 W/cm2, about 33 times larger than the highest value reported to date for existing 800 nm excitable UCNPs. Finally, amphiphilic triblock copolymer, Pluronic F127 coatings permit the transfer of hydrophobic UCNPs into water, resulting in water-soluble nanoparticles with well-preserved optical property in aqueous solution.