Local Electromagnetic Field Modulation And Applications Of Rare-earth Doped Upconversion Nano-phosphors

The upconversion nanophause of their great application potentials.However,for various applications,there exists a bottleneck problem to be solved,which is the low efficiency/strength for upconversion nanoparticles?UCNPs?.Various methods have been explored to solve this problem.osphors have great application potentials and have attracted extensive interests bec Among them,local electromagnetic field manipulation is a promising way.In this paper,we explored the efficient local field enhanced upconversion luminescent materials in detail.For the first time,we proposed to use the photonic crystal effect to enhance the upconversion luminescence and proposed a combination of surface plasmonic effect and photonic crystal effect to enhance the upconversion luminescence,and obtained three orders of magnitude of luminescence enhancement.These new types of high-performance nano-luminescent materials were designed for biological imaging and flexible display and other aspects of the application of exploration.The main results are as follows:[1] NaYF₄:Yb³⁺,Tm³⁺ and NaYF₄:Yb³⁺,Er³⁺ UCNCs/PMMA OPCs highly-ordered composites were fabricated for the first time and observed considerable improvement of UCL owing to the effective coupling of UCNPs with PMMA OPCs.And more,the PMMA OPCs were explored to assisted fluorescence cell imaging based on NaYF₄:Yb³⁺,Er³⁺ UCNPs,which successfully enhanced the brightness and definition of cell images.[2] In order to overcome the relatively small scattering/absorption ratios of pure Au or Ag nanostructures,Au-Ag alloy nanocages with tunable SPR were synthesized by galvanic replacement reaction and were further fabricated into plasmonic architecture with a broadened SPR absorption on the glass substrate.This plasmonic structure showed strong scattering/absorption ratio and was further explored to enhance the UCL of NaYF₄:Yb³⁺,Er³⁺ UCNPs.After optimisation,repeatable UCL enhancement of NaYF₄:Yb³⁺,Er³⁺ NPs up to 15 fold was acquired.[3] In order to control the "hot spot" on the surface of Au NRs,Au NRs were directionally assembled into a vertically aligned monolayer supercrystals over large areas.The FDTD simulation indicated that the electromagnetic field strength |E|2 can be improved about 113 folds at the hot spots of monolayer supercrystals.After optimization,on the surface of the vertically aligned monolayer supercrystals,the overall upconversion luminescence intensity of NaYF₄:Yb³⁺,Er³⁺ under 980-nm excitation was improved more than 35 folds.[4] For the first time,a combination of noble metal surface plasmonic effect and photonic crystal effect was proposed to modulate the upconversion luminescence.Au NRs were successfully implanted into the periodic surface apertures of the 3-D PMMA OPCs,in which the local electric field was dramatically amplified due to the effective combination of PC and SPR effects.This distinctive SPPC structure was explored to enhance the UCL of NaYF₄:Yb³⁺,Er³⁺ UCNPs by further assembling the UCNPs on the surface of the Au NRs/OPCs composites.After optimizing the size of NaYF₄:Yb³⁺,Er³⁺ UCNPs and the dimensions of Au NRs and the PSB of PMMA OPCs,the enhancement up to 1200 folds was achieved for the overall UCL intensity of Er³⁺.Furthermore,using FDTD simulations,at the hot spots of Au NRs/OPCs hybrids,the strength of incident light at 980 nm could be enhanced more than 770 folds.This SPPC structure could be easily integrated with nanoprinting technique,transplanted onto a flexible substrate or a paper,and explored to multicolor UCL display.