Enhancing Upconversion Luminescence Emission of Rare Earth Nanophosphors in Aqueous Solution with Thousands Fold Enhancement Factor by Low Refractive Index Resonant Waveguide Grating

Abstract

The enhancement of upconversion luminescence (UCL) of rare earth doped upconversion nanoparticles (UCNPs) in aqueous solution is particularly important and urgently required for a broad range of biomedical applications. Herein, an effective approach to achieve highly enhanced UCL from NaYF4:Yb3+,Tm3+ UCNPs in aqueous solution is presented. We demonstrate that UCL of these UCNPs can be enhanced more than 104-fold by using a mesoporous silica low refractive index resonant waveguide grating (low-n RWG) in contact with aqueous solution, which makes it well-suited for biomedical applications. The structure parameters of the low-n RWG are tuned via rigorous coupled-wave analysis simulation to ensure strong local excitation field to form atop the TiO2 surface of the low-n RWG, where UCNPs are deposited. As the low-n RWG is excited by a near-infrared laser at 976 nm to match its guided mode resonance (GMR) condition, UCL emitted from UCNPs is greatly enhanced thanks to the strong interaction between excitation local field and UCNPs. UCL emission of UCNPs can be further enhanced about two to four times when the UCL emission condition (wavelength and angle) matches with the GMR condition. Furthermore, we show that the presence of biotin molecules atop of the low-n RWG can be easily detected through UCL emission generated from streptavidin-functionalized UCNPs with the help of the streptavidin–biotin specific binding. The results indicate that the low-n RWG has high potential for UCL biosensing and bioimaging applications.

A Synergy Approach to Enhance Upconversion Luminescence Emission of Rare Earth Nanophosphors with Million-Fold Enhancement Factor

“…Although the local field enhancement provided by dielectric nanostructures is typically smaller than that of plasmonic nanostructures, dielectric nanostructures do not suffer parasitic energy losses manifested by fluorescence quench caused by the metal's electron gas through its many internal degrees of freedom (Joule losses). Through proper design of the structure, some dielectric nanostructures can enhance the UCL of UCNPs more than 100 times [28,[41][42][43][44][45][46][47]. A variety of dielectric nanostructures, such as photonic crystals [28,[41][42][43][44], and metasurfaces [45][46][47] have been employed to enhance the UCL of UCNPs.…”

“…Through proper design of the structure, some dielectric nanostructures can enhance the UCL of UCNPs more than 100 times [28,[41][42][43][44][45][46][47]. A variety of dielectric nanostructures, such as photonic crystals [28,[41][42][43][44], and metasurfaces [45][46][47] have been employed to enhance the UCL of UCNPs. Recently, we demonstrated that the UCL of UCNPs can be enhanced more than 1000-fold by depositing UCNPs atop a resonant waveguide grating (RWG) structure, also termed 1D photonic crystal substrate, thanks to its guided mode resonance (GMR) to promote the local field of the excitation light atop the RWG [41,42].…”

Gold nanorods conjugated upconversion nanoparticles nanocomposites for simultaneous bioimaging, local temperature sensing and photothermal therapy of OML-1 oral cancer cells

“…The monodisperse hexagonal-phase (β-phase)_ NaYF 4 :Yb 3+ ,Er 3+ nanocrystals were synthesized through a thermal decomposition process as our previous study [40]. The typical procedure is as follows: 0.78 mmol of YCl 3 , 0.2 mmol of YbCl 3 , 0.02 mmol of ErCl 3 were mixed with 6 mL of OA and 15 mL of ODE into a 100 mL three-necked flask.…”

“…The PAA-modified NaYF 4 :Yb 3+ ,Er 3+ UCNPs (UCNP-PAA) were prepared by using a modified ligand exchange strategy [40,41]. A typical procedure is as follows: the mixture containing 1 mL of PAA solution in ethanol (~1 wt%) and 0.5 mL of UCNP-OA dispersed in chloroform (~1 wt%) was stirred vigorously for at least 12 h at room temperature.…”

Hierarchical Self-Assembled Structures from Diblock Copolymer Mixtures by Competitive Hydrogen Bonding Strength

“…Diblock copolymers can display different self-assembly behaviors, including lamellar, gyroid, cylinder, and spherical nanostructures, which possess several potential applications in drug delivery, photonic crystals, and nanotechnology [ 1 , 2 , 3 , 4 ]. However, mediating the different molecular weights of each block segment to control the volume fraction by using living polymerization methods may be time-consuming and difficult and thus blending the homopolymer or another block copolymer through intermolecular hydrogen bonding interactions has received much interest recently [ 5 , 6 , 7 ].…”