Preparation Of Polymer/Upconversion Nanocrystals Composite Materials And Their Properties

Upconversion materials have attracted considerable interests recently owing to their unique optical properties. And polymer materials, especially polymer spheres as new advanced functional materials are becoming one focused research field, principally because of their excellent mechanical property and machinability. In this study, we combined the advantages of upconversion materials and polymer spheres together to explore further application. Three kinds of nanocomposite materials were fabricated to expand the application area of upconversion materials by combining with polymer spheres. All the research contents and results are shown as follows:(1) The first chapter presents a feasible and efficacious procedure to synthesize polystyrene/upconversion nanocrystals (PS/UCNCs) nanocomposite spheres with raspberry-like structure via an in situ dispersion polymerization technique. During\this process, polyacrylic acid (PAA) as stabilizer plays the key role in adsorbing UCNCs, including NaYF4:Yb3+-Er3+, NaYF4:Yb3+-Tm3+and NaYF4:Yb3+-Ho3+onto the PS surfaces. TEM and SEM images confirmed the raspberry-like morphology of the obtained nanocomposite spheres. The effect of synthetic conditions, for instances, PAA amount, type and concentration of UCNCs on the structure and fluorescence of PS/UCNCs nanocomposite spheres were studied in detail.(2) Three-dimensional periodic P(St-BA-AA)/SiO2/NaYF4colloidal crystal films have been fabricated via the film-formation of polymer colloid with silica nanoparticles and up-conversion rear-earth nanocrystals at room temperature. The as-obtained colloidal crystal films not only are robust and large-scale, but also present brilliant and tunable structural colors derived from the stop-band of three-dimensional structure, and fluorescence from up-conversion rear-earth nanocrystals. These films may provide new opportunities in anti-counterfeiting techniques, optical element and functional coatings.(3) In the third chapter, Ln3+ions doped Y2O3inverse opals were fabricated using template replication process combined with the sol-gel technique. During the filling process, ethanol was chosen to be solvent due to its low surface tension, and citric acid was used as chelator to preserve hydroxylation of nitrate. We demonstrate that by adjusting the macroporous diameter of the photonic crystals, the photonic band structure of the materials can be controlled in a way that modifies the UC photoluminescence of Ln3+doped Y2O3nanocrystals.