Lifetime nanomanometry – high-pressure luminescence of up-converting lanthanide nanocrystals – SrF₂:Yb³⁺,Er³⁺

Abstract

Anti-Stokes luminescence of up-converting nanocrystals SrF:Yb,Er can be used as a high pressure optical sensor alternative to the ruby fluorescence-scale. In nanocrystalline SrF:Yb,Er, high pressure reversibly shortens the emission lifetimes nearly linearly up to 5.29 GPa at least. Its advantage is the use of NIR (≈980 nm) radiation, highly penetrable for many materials. The shortening of up-conversion lifetimes has been attributed mainly to the changes in energy transfer rates, caused by decreased interatomic distances and increased overlap integrals between 4f electrons and the valence shells of ligand ions. The origin of high-pressure effects on the luminescence intensity, band ratio and their spectral position has been explained by the increased interactions and distortions of the crystal-field symmetry around the emitting ions in the compressed structure.

Design of Layer‐Structured KAlF4:Yb/Er for Pressure‐Enhanced Upconversion Luminescence

“…In addition, after an ultrahigh‐pressure compression and release circle, the upconversion luminescence spectra were measured again for the second circle under pressure of R0.00→5.03 GPa where the luminescence intensity still exhibits an enhancement, indicating that the coordination environment of the luminescent ions within the crystallographic structure of the host lattice is retained even an ultrahigh pressure of up to 22.98 GPa is applied. However, the emission intensity was only improved to about 50% of that measured in the first compression cycle at 6.01 GPa (Figure b), which is probably due to the crystal defects formed during compression and release process, which leads to the weakened luminescence intensity …”

“…Compared to the above endeavors, hydrostatic pressure could offer unique merits to regulate and explore the luminescent properties, especially of upconversion luminescent materials, which is growing as a prevalent topic . The tunable hydrostatic pressure can be utilized not only to probe the crystal structure and coordination bonding information of luminescent materials, but also to influence the electronic state and/or crystal field symmetry of luminescent ions .…”

“…In addition, pressure‐induced upconversion emission changes have wide applications in health monitoring, bioimaging, intelligent signature, optical sensors, nanomanometry, nanothermometry, as well as real‐time monitoring of the working status of constructions via special coatings . However, majority of such studies focused on downshifting luminescence and very limited examples targeted at upconversion emission whereas unfortunately, the unwanted decreased luminescence intensities are usually obtained under pressure . The reason might be due to the increased probability of nonradiative relaxation resulted from the over shortened distance between luminescent ions, or the destroyed coordination environment of luminescent ions under high pressure …”

Physical Manipulation of Lanthanide‐Activated Photoluminescence

“…This result may be important for low-pressure sensing. Runowski et al [120] reported a lifetime nanomanometry based on SrF 2 :Yb/Er upconverting nanocrystals, utilizing the reversible and nearly linear shortening of the emission lifetimes at increased high pressures.…”

Luminescence properties and energy transfer of K3LuF6:Tb3+,Eu3+ multicolor phosphors with a cryolite structure

“…Fluoride compounds are potential hosts for luminescent materials due to their suitable chemical stability and excellent luminous properties, and as such, have received a lot of attentions over the past few decades. [1][2][3][4] Cryolite is an important kind of uoride compound, the chemical formula of which can be expressed as M 3 NF 6 , where M represents monovalent cations such as alkali metal ions (Li + , Na + , K + , Rb + ) and NH 4 + , and the sites of N can be occupied by trivalent cations, that is Al 3+ , Y 3+ , Sc 3+ , Ga 3+ , etc. 5,6 In addition, the N sites can also be occupied by rare earth ions by isomorphic replacement in the cryolite lattice, such as K 3 GaF 6 , 7 K 3 InF 6 , 8 and K 3 LuF 6 .…”