Study On The Luminescent Properties Of Rare Earth Doped Fluoride Nanocrystals By Synergistic Enhancement Of Surface Plasma And Photonic Band Gap

Rare-earth-doped upconversion (UC) nanoparticles can convert low-energy infrared to higher energy visible photons, which have attracted increasing attention due to their potential application in biological labeling, therapeutics, imaging and solar cell. Unfortunately, the application of rare earth doped UC nanoparticles has been constrained by their low emission efficiencies, which is largely attributed to the very small near-infrared or infrared absorption section of rare earth ions. At present, major investigations on the UC nanoparticles are developed various methods including the host selection, surface coating, and broadband dye sensitization to improve their UC emission efficiency. Here, we used the surface plasmons resonance and photonic crystals effects to enhance the UC emission. The emission mechanism were also investigated.The opal photonic crystals were used to enhance UC emission of YF3:Yb3+, Er3+ nanoparticles. The red or green upconversion emission of YF3:Yb3+, Er3+ nanoparticles can be selectively enhanced when the red or green upconversion emission wavelength overlapped with the photonic band gaps of opals, which is attributed to Bragg reflection of photonic band. gap. When the 980 nm excitation light wavelength was in the region of the photonic bandgap, red and green UC emissions of YF3 nanoparticles were enhanced due to the enhancement of excitation field.The porous Ag films with diffierent surface plasmonic absorption were fabricated, and the surface plasmonic absorption from Ag films with narrow and ultra-broad are located at 430nm and from 350 to 1400 nm, respectively. The influence of the porous Ag films on UC emission were investigated. About 10 and 60-fold UC emission enhancement of NaYF4:Yb3+, Er3+ nanoparticles were obtained on the Ag films with narrow and ultra-broad surface plasmonic absorption, respectively. The larger UC emission enhancement at the surface of porous Ag film surface with the ultra-broad plasmonic absorption, which is attributed to strong coupling between the ultra-broad surface plasmonic absorption and the 980 nm near infrared excitation light and UC emission.The UC emission of Er3+/Yb3+ doped NaYF4 nanoparticles deposited on inverse opal photonic crystals with different bandgap and coupling with the nobel metal nanoparticles were investigated. The seclective enhancement of UC emission of Er3+/Yb3+ doped NaYF4 nanoparticles on the inverse opal photonic crystals were obtained. When the nobel metal nanoparticles embedded into the interior of inverse opal, which coupling of the surface plasmons resonance and photonic crystal effect lead a larger UC emission enhancement of NaYF4 nanoparticles.