The Rule Of Upconversion Fluorescence Of Nanocrystal And The Realization Of Comochrome Nir Upconversion

Rare-earth doped luminescent upconverting nanocrystal has great potential applications in many areas, such as solar cells, display devices, laser anti-counterfeiting material and biomedicine. Particularly, much attention is paid as its prominent advantage in fluorescent probes and imaging of biomedical field. However, due to the low up-convert luminescent efficiency and weak monochromaticity, it still has a big obstacle for the practical application of rare-earth doped luminescent upconverting nanocrystal. Therefore, it has a practical significance to study how to improve the up-convert luminescent efficiency and luminous monochrome. In this thesis, the issues of influence of external environment to optical properties of up-convert nanocrystals and high efficient implementation of monochromatic near-infrared light have been discussed.The law of external environment influence on the optical properties on nanocrystals has been researched. Through the establishment of core-shell model the influence of shell thickness on light-emitting shell has been studied. A series of NaYF4/NaYF4:Yb20%,Er20%/NaYF4core-shell structure has been prepared using thermal method; eight different sizes of nanocrystals have been obtained by changing homogeneous shell thickness; morphology and structure of the core-shell nanocrystals have been characterized by XRD and TEM, and it has been confirmed that uniform sized, good dispersion of hexagonal crystal phase nanocrystals have been synthesized; the up-converting luminescence spectrum of nanocrystal of different shell thickness have been measured, and it has been discovered that, luminescent intensity enhanced by a exponentially increasing regularity with the increase of shell thickness; through fluorescence and excitation light power relations and the steady-state rate equation theory, the relationship between Er3+doped up-converted emission and rare earth ions properties has been explained; the measurement results has been proved to be accurate by the analysis of time-resolved spectrum; this work has discovered that upconverting efficiency could be improved300times more by core-shell structure; and it has been studied that the external environment influence could be effectively shielded when shell thickness is3nm.A efficient near-infrared light was carried out. By increasing Tm3+doped, It will cause enhanced fluorescence quenching and the monochrome. So this article substrate NaYbF4toNaYF4by adjust the concentration of Tm3+.A series NaYb1-xF4:Tmx/NaYF4were prepared and the uniform size hexagonal nanocrystalline was proved. By measure the nanocrystalline’s fluorescence spectroscopy and monochrome definition, monochrome accordance with the law of a exponential growth and the intensity accordance with the law of a exponential weaken.