Elimination of Photon Quenching by a Transition Layer to Fabricate a Quenching-Shield Sandwich Structure for 800 nm Excited Upconversion Luminescence of Nd~(3+)Sensitized Nanoparticles

摘要

Recently, near-infrared (NIR)-to-visible upconversion nano-particles (UCNPs) have been becoming a new class of pow-erful tools in biological and medical applications, such as cellular labeling, in vivo imaging, fluorescence resonance energy transfer (FRET)-based biosensors, drug delivery, and photody-namic therapy, due to their unique upconversion (UC) lumi-nescent properties that enable the conversion of low-energy photons (NIR photons) into high-energy photons (visible to ultraviolet photons) via multiphoton processes. However, one major limitation of conventional UCNPs is their low conversion efficiency especially under low-intensity laser excitation, mainly due to the extremely weak absorption of the sensitizer Yb~(3+) ion in the NIR wavelength range. Moreover, owing to the very narrow NIR absorption spectral window of UCNPs, the 980 nm laser is the most commonly used NIR excitation source to gen-erate UC emission.