Engineering Upconversion Luminescence Of Lanthanide-Doped Micro/Nano-Crystalline Spheres Via Purcell Effect Of Ag Hemi-shell

The lanthanide-doped upconversion luminescent material is capable of emitting shorter wavelengths of visible light and even ultraviolet light under the excitation of longer wavelength near-infrared light,making it has great application prospects in bioimaging,solar cells,short-wavelength lasers.However,up to now,lanthanide doped upconversion luminescent materials have not been widely used due to their low luminous efficiency.Enhancing luminescence intensity and regulating luminescent color are two major challenges faced by upconversion illuminating applications.According to the existing literature reports,the plasmon can not only enhance the luminescence through local field enhancement,but also realize the regulation of illuminating color through the Purcell effect.Based on the FDTD numerical calculation and considering the feasibility of preparing the structure from the laboratory,the effect of the plasmonic mode of the silver half-shell cavity on the upconversion luminescence of the up-converted core-shell particles wrapped in the cavity is systematically studied.Theoretical studies have shown that the cavity mode using plasmon can control the color of upconversion luminescence.The lower the original efficiency of the upconversion material,the better the regulation effect;and the enhancement of upconversion luminescence can be realized at the same time when the original efficiency is low.Finally,we tried to prepare the plasmon structure composite submicron particles of the structure.This thesis will explore the theoretical simulation of the luminescence properties of submicron particles wrapped in silver half-shell and the experimental preparation of the structure.(1)Assuming that the intrinsic efficiency is 5%,when the plasmon modes are matched with the green and red emission bands,respectively,the enhancements obtained by the position-weighted average of the 21 random electric dipoles in the kernel are obtained.9.3 times and 10.3 times,the corresponding green/red light intensity ratios are optimized to 3.3 and 0.87,respectively,which realizes selective enhancement of the light-emitting strip,that is,it is possible to achieve enhanced single-band up-conversion luminescence.When considering the excitation process,the up-conversion luminescence is enhanced only when the cavity mode matches the red light,and the red and green lights are enhanced by 76%and 47%,respectively.However,intensity enhancement and color regulation will weaken as the intrinsic efficiency increases.(2)The NaLuF4:Gd,Yb,Er@SiO2 core-shell submicrocrystals of SiO2 shells were synthesized by solvothermal method and coated with Stober method.The core shell particles were dispersed and uniformly dispersed on the glass sheets by colloidal self-assembly.Then,a silver film of 30 nm was vacuum-deposited.Finally,an isolated plasmonic cavity structure was obtained by peeling the silver-coated cap particles on the glass piece with a pre-cured PDMS film.The results of electron microscopy indicated that we successfully prepared the desired structure.