Structural and optical studies of strong red emitting NaxScF3+x:Yb3+,Er3+ upconversion nanoparticles

Tuning the Red-to-Green-Upconversion Luminescence Intensity Ratio of Na3ScF6: 20% Yb3+, 2% Er3+ Particles by Changes in Size

“…Lanthanide-doped nanomaterials enable the conversion from near-infrared light to visible light due to the anti-Stokes effect when two or more low-energy photons are sequentially absorbed and higher-energy photons are emitted [ 1 , 2 , 3 , 4 ]. These nanomaterials have the advantages of long luminescence lifetimes, narrow emission bands, high penetration abilities and chemical stability, making them suitable for potential applications in bioimaging, infrared photothermal therapy, fluorescent biomarkers, anti-counterfeiting, photocatalysis, photodetectors, optoelectronic devices, sensors and other fields [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

“…Sc, as a special rare earth element different from other lanthanide elements, has a unique electronic configuration and a smaller ionic radius (0.83 Å) such that it can more easily produce red-upconversion luminescence, and so people began to turn to Sc 3+ as a matrix in materials research. Therefore, in recent years there has been an increasing amount of research on NaScF 4 nanocrystals co-doped with Yb 3+ and Er 3+ , which can readily produce red-upconversion luminescence [ 2 , 5 , 25 , 26 , 27 , 28 , 29 , 30 ]. Min Pang et al directly synthesized water-soluble hexagonal NaScF 4 : Yb 3+ /Er 3+ nanocrystals with strong red-upconversion luminescence by a hydrothermal method; afterwards, an active shell layer containing Yb 3+ was wrapped around the NaScF 4 : Yb 3+ , Er 3+ core nanocrystals, which further increased the intensity of the upconversion luminescence by a factor of 6.8 [ 6 ].…”