Broadband near-infrared downconversion luminescence in Eu2+–Yb3+ codoped Ca9Y(PO4)7

Near‐Infrared Quantum Cutting via Downconversion Energy Transfers in Ho3+/Yb3+ Codoped Tellurite Glass Ceramics

“…All the decay curves demonstrate double‐exponential feature, and the decay times can be determined using a curve fitting technique based on the following formula: where I is phosphorescence intensity, A , B 1 , and B 2 are constants, t is time, τ 1 and τ 2 are decay constants deciding the rates for rapid and the slow exponentially decay components, respectively. The average decay times τ avg can be calculated by the following equation: also, from the luminescence decay curves an estimate of energy‐transfer efficiency (ETE, η tr, x %Yb ) and the total quantum efficiency (QE, η x %Yb ) can be obtained using the following equations: where I denotes the decay intensity and x % stands for the Yb 3+ concentration. η Ho and η Yb represent the QE of Ho 3+ and Yb 3+ , and both of them are set to one where the nonradiative relaxation is ignored .…”

Ligand-Sensitized Lanthanide Nanocrystals: Merging Solid-State Photophysics and Molecular Solution Chemistry

“…Our current understanding of the periodic table’s f block marks the result of decades of research pursued by scientists of various stripes: from chemists to materials scientists, physicists, and biologists. As a consequence, the modern scientific catalog of understood phenomena arising either directly or indirectly from lanthanide chemistry and electronic structure is expansive, ranging from multiphoton up- and downconversion processes − to ligand–lanthanide chelation thermodynamics in solution − to lanthanide binding and efflux mechanisms in biological systems. − In particular, it has become both widely accepted and abundantly clear that the diversity in the f-orbital electronic structures of the lanthanide elements makes them prime candidates for various possible applications in optoelectronic devices, deep-tissue imaging, and luminescence sensing. ,− ,,, Interest in these applications provides much of the motivation driving both applied and fundamental research in lanthanide photochemistry.…”

“…With respect to their possible photonic applications, the bulk of the photochemical literature of lanthanides has involved work on either molecular complexes, nanocrystalline forms of lanthanides, or glasses where emissive lanthanides occur as either doped or primary constituents. − ,,,− In the case of molecular complexes, lanthanide luminescence is typically interrogated through the photosensitization of lanthanide excited states using organic ligands, as schematically depicted in Figure (panel a). ,, The employment of this “antenna” effect has the benefit of yielding lanthanide excited states with far greater efficiency than is generally possible through direct, intraband pumping of f levels, a partial result of the generally high molar absorptivities of organic/aromatic ligands (∼10 3 –10 5 M –1 cm –1 ). This process stands in stark contrast to the relatively dismal absorption coefficients observed for the direct excitation of most lanthanide transitions (∼1–10 M –1 cm –1 ), a consequence of the symmetry-forbidden and, in some cases, spin-forbidden nature of intraconfigurational f transitions present in these elements.…”

“…The direction of research on solid-state glasses and nanocolloidal lanthanide systems has largely been governed by a desire to understand and utilize the photophysical traits of these elements. Studies of the luminescence behavior in nanoparticulate systems have been especially progressive, with much of the work being geared toward the development of multiphoton conversion for applications in solar energy utilization. ,, In essence, the lanthanide ions, with their mostly forbidden electronic transitions, possess long-lived and ladder-like excited-state manifolds, of which electrons can climb through successive absorptions of one, two, or more low-energy photons. Radiative relaxation all the way to the ground state follows this excitation process, emitting a single photon of energy roughly equal to the sum of energies of the exciting photons in the case of upconversion or several photons of lower energy in the case of downconversion (Figure , panel d).…”

The influence of charge compensation defects on the spectroscopic properties of europium doped Ca9Y(PO4)7

“…7 One of the promising materials in phosphates family is Ca 9 Y(PO 4 ) 7 , which has two different cations (Ca 2+ and Y 3+ ) that are available for lanthanides substitution. [8][9][10][11] This material doped with Eu 2+ and Eu 3+ ions simultaneously consists of two components that are essential to achieve the emission of white light. Ca 9 Y(PO 4 ) 7 belongs to the whitlockite family and can be described by the general formula: Ca 9 R(PO 4 ) 7 , where R ¼ Ln, Pr, Eu, Tb, Dy, Ho, Er, Y, Bi, Al, Lu.…”