Multicolor Luminescence Regulation And Enhancement Of Rare Earth Doped Multilayer Structure Yttrium Oxide

Rare earth doped materials have the advantages of narrow emission peak and long fluorescence life.So their research and application in lighting and display,fluorescence encryption anti-counterfeiting,biological imaging,3D imaging,fluorescence detection and optical temperature sensing fields have attracted researchers.However,the single structure rare earth luminescence materials face with the plight of low luminescence efficiency and difficulties in luminesence color regulation.These problems directly limit its development in optics.Therefore,the realization of fluorine yttrium oxide nanocrystal multicolor luminescence has been firstly explored in this dissertation.Then the yttrium fluoride-fluorine yttrium oxide-yttrium oxide nanocrystal system has been realized by adjusting the calcination temperature.On the basis of yttrium oxide as the matrix,the energy transfer between layer and layer of the structure as well as between different ions of the multilayer structure have been utilized.Combined with local surface plasmon resonance induced by noble metal modification,the multicolor luminescence of rare earth doped yttrium oxide has been controlled and the luminescence intensity has been improved.In this dissertation,the main research content includes the following several parts:The controllable up-conversion luminescence of Y_xO_yF_znanocrystals whose matrix phase is affected by calcination temperature has been investigated.The luminescence color of Y₇O₆F₉and YOF nanocrystals can be controlled under the doping of double activator and single activator respectively through adjusting the excitation conditions and sample temperature.According to the influence of sample temperature on the up-conversion white emission of Eu/Yb co-doped YOF nanocrystals,the color thermal stability of the white emission has been studied.And its potential application in the field of white-light illumination has been illustrated.The change of element content of matrix compounds has been realized by adjusting calcination temperature.The up-conversion luminescence and temperature sensing characteristics of yttrium fluoride-fluorine yttrium oxide-yttrium oxide nanocrystals have been studied in the same doping system.Compared with yttrium fluoride and fluorine yttrium oxide,yttrium oxide nanocrystals have higher physical stability and optical temperature sensitivity.A multilayer yttrium oxide composite nanomaterial capable of dual mode luminescence has been designed and synthesized.The luminescence characteristics of composite nanomaterials have been studied under dual beam co-excitation by matching the excitation light photon energy with the energy gap of different rare earth ions.The luminescence color of the composite nanomaterials excited by different wavelengths of laser can be dynamically regulated by doping different luminescence ions in the multilayer structure.The specific energy transfer mechanism between different layers has been analyzed combined with the relationship between layer and layer in the structure and energy level characteristic analysis of ions in each layer.And the change of luminescence color under different excitation has been explained.By adjusting the excitation power density of 980 nm laser,the power dependence of the luminescence color has been discussed and the resolution of luminescence color can be improved.The multilayer structure composite nanomaterial is expected to be applied in the field of fluorescence encryption and anti-counterfeiting.The luminescence enhancement of yttrium oxide multilayer thin films has been realized by the energy migration-mediated up-conversion process in the structure.Based on the strong absorption efficiency of near-infrared light by Yb³⁺ion sensitizer,the effect of sensitized layer doped with Yb³⁺ions on the multilayer thin film overall luminescence intensity has been studied.The energy transfer mechanism between ions in different layers has been analyzed based on the relationship between ion doping concentration in sensitized layer and luminescence enhancement effect.The energy transfer process and surface modification caused by sensitized layer have been discussed.In addition,the enhancement effect of multiple calcination on luminescence intensity has been studied.Combining the two enhancement methods,the thin film modified with sensitized layer was calcined for several times to significantly improve the luminescence intensity.Rare earth layers with other luminescence mechanisms have been introduced,so that the luminescence color can be regulated.Based on the local surface plasmon resonance effect of Ag nanolayer,the luminescence enhancement in the visible light range of multilayer thin film has been investigated combined with metal/spacer molecule/photoluminescent material structure.The luminescence enhancement effect of multilayer thin films can be improved by adjusting the spin-coating number of Ag nanolayer and Si O₂spacer in the multilayer structure.At the same time,the mechanism of enhanced luminescence has been analyzed according to the change of fluorescence lifetime.The effect of the coupling between Ag nanolayer and luminescence layer on the radiative transition rate and fluorescence quantum yield have been discussed.The up-conversion luminescence intensity of the multilayer thin film modified by precious metal can be further improved by combining the multilayer structure with sensitized layer.