Cooperative and non-cooperative sensitization upconversion in lanthanide-doped LiYbF₄ nanoparticles

Abstract

. By means of temperature-dependent steady-state and transient UC spectroscopy, we unraveled the dominant mechanisms of phonon-assisted cooperative energy transfer (T > 100 K) and sequential dimer ground-state absorption/excited-state absorption (T < 100 K) for the CSU process in LiYbF 4 :Tb 3+ UCNPs.

Near-infrared-triggered photon upconversion tuning in all-inorganic cesium lead halide perovskite quantum dots

“…We synthesized LiYbF 4 :Tm 3+ @LiYF 4 core/shell NPs through a high-temperature co-precipitation method (Supplementary Note 1 ) and selected them as the energy donors in view of their intense upconversion emission at 362 nm that can potentially excite the whole series of CsPbX 3 PeQDs 43 . The as-synthesized NPs were rhombohedral and highly crystallized with a mean size of (26.7 ± 1.2) × (33.3 ± 1.8) nm and a shell thickness of 5.5 ± 0.6 nm (Supplementary Fig.…”

Long‐Term Colloidal and Chemical Stability in Aqueous Media of NaYF4‐Type Upconversion Nanoparticles Modified by Ligand‐Exchange

“…But this comes with several challenges like chemical and colloidal stability in aqueous media or the controlled functionalization by a defined number of receptor molecules . Most upconversion nanoparticles described in literature are consisting of a NaYF 4 host lattice as this materials has a preferable low phonon‐energy (≈300 cm −1 ) compared to other host materials like fluorides (LiYbF 4, ≈460 cm −1 ), oxides (Y 2 O 3 , ≈591 cm −1 ), or vanadates (YVO 3 , ≈890 cm −1 ). Therefore, it is not surprising that this host material together with Yb 3+ and Er 3+ has been used to design the most efficient upconversion nanoparticles .…”

Controllable Synthesis of Upconversion Nanophosphors toward Scale‐Up Productions

“…Later in stage three, the α‐phase begins to transform into the β‐phase, followed by ripening and finally particle growth in stage four. [ 59 ] More recently, the high‐temperature co‐precipitation method has been used in the synthesis of a wider range of UCNPs: including NaYF 4 , [ 60 ] NaLuF 4 , [ 61 ] LiYF 4 , [ 62 ] KLu 2 F 7 , [ 63 ] NaGdF 4 , [ 64 ] NaYbF 4 , [ 65 ] LiYbF 4 , [ 66 ] and KSc 2 F 7 . [ 67 ] With proper optimization of the conditions, uniform 4 nm NaREF 4 UCNPs with enhanced upconversion luminescence could be achieved.…”

“…Even though the relationship between optical performance and morphology of UCNPs have had been well understood, [ 23–26 ] relevant developments on commercializing such nanomaterials are hampered due to scaling‐up production process, where bottlenecks normally exist in the reproducibility, repeatability as well as the yield from these methods. By recapping these reported synthesis methods, for example, thermal decomposition, [ 35–40 ] co‐precipitation, [ 60–66 ] hydrothermal, [ 73–78 ] and ion exchange, [ 98–101 ] a common characteristics is discovered that these processes require large amounts of solvents, which easily lead to nonuniform precursor concentrations and temperature distributions. This characteristic represents an essential challenge in managing thermodynamic equilibrium for a smooth and uniform synthesis in lab, [ 27,28 ] and the scale‐up process where the breaking of local thermodynamic equilibrium is likely to occur to yield the uncontrollable changes on the phases and other features for the particle, especially the luminescent performance.…”