Cubic versus hexagonal – phase, size and morphology effects on the photoluminescence quantum yield of NaGdF₄:Er³⁺/Yb³⁺ upconverting nanoparticles

Abstract

Upconverting nanoparticles (UCNPs) are well-known for their capacity to convert near-infrared light into UV/visible light, benefitting various applications where light triggering is required. At the nanoscale, loss of luminescence intensity...

Dopant ion concentration-dependent upconversion luminescence of cubic SrF2:Yb3+,Er3+ nanocrystals prepared by a fluorolytic sol–gel method

“…Also, previously reported cubic UC-host matrices such as α-NaYF 4 , CaF 2 , SrF 2 , and α-NaYbF 4 exhibit a strong red emission. 19,23,35,[50][51][52] Moreover, the evolution of the 855 nm and 806 nm bands upon increasing χ Yb differ from the behaviour commonly observed for hexagonal β-NaYF 4 UCNC. High amounts of Yb 3+ are known to elevate surface quenching, i.e., the migration of the excitation energy to quenching sites at the surface via multiple Yb 3+ -ions.…”

“…Also, previously reported cubic UC-host matrices such as α-NaYF 4 , CaF 2 , SrF 2 , and α-NaYbF 4 exhibit a strong red emission. 19,23,35,50–52…”

The universal defect cluster architecture of fluorite-type nanostructured crystals

“…39 Both the cubic and hexagonal NaRF 4 phases give different up-conversion efficiencies. [40][41][42] The hexagonal NaRF 4 phase was first obtained. 43,44 We defined it belonging to the structural type of mineral gagarinite (NaCaYF 6 ) 45 (named after the first cosmonaut Yuri Gagarin).…”

Dye-sensitized lanthanide containing nanoparticles for luminescence based applications

“…This highlights the complexity of the NP preparation and complex encapsulation steps for preparing luminescent NPs with size uniformity in the nm range. Yuan Wang and colleagues designed poly(methylmethacrylate-comethacrylic acid) NPs embedding circa 3500 [Eu(16) 3 (54)] complexes per NP, for application as cell imaging probe. 146 52 nm water-dispersible nanospheres were obtained by co-precipitation, exhibiting two-photon-sensitized luminescence properties: Eu ion emits red light through two-photon excitation of 54 at 832 nm via a singlet energy-transfer pathway predominantly.…”

“…For example, Krämer et al reported that the NaYF 4 :Yb 3+ /Er 3+ UC efficiency of green emission is approximately 10 times stronger in hexagonal phase compared to cubic phase, 53 when Quintanilla et al revealed that the photoluminescence quantum yield of α-phase NaGdF 4 Er 3+ ,Yb 3+ surpasses that of β-NaGdF 4 for sizes below 20 nm, which can be related to distortion of the crystal lattice when the UC NPs become smaller. 54 Consequently, with typical bare NPs, it is essential to carefully select the host material with appropriate parameters of interest for achieving optimal Ln luminescence in a given application.…”