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High-power density applications using up-conversion (UC) systems rely mostly on the Yb, Tm lanthanide couple. Herein, we investigate the extent to which Gd high energy levels can enhance the four-order UC process in NaGdF4:Yb, Er under pulsed excitation, making the Yb, Er UC system suitable for high power density applications. Unlike cw excitation, pulsed laser excitation enables higher equivalent power densities with reduced local heating effects. We found that Gd upholds the saturation level by one order of magnitude in NaGdF4:Yb, Er@NaYF4 compared to NaYF4:Yb, Er@NaYF4 nanoparticles, i.e., from 5 × 106 to 5 × 107 W cm−2. Such an effect is determined by efficient two-step Er–Gd energy transfer, in which the Gd levels, populated by four-order Yb–Er processes, act further as the long(est)-lived reservoir level for Er UC emissions. Notably, above 108 W cm−2, NaGdF4:Yb, Er@NaYF4 shows similar performance to NaGdF4:Yb, Tm@NaYF4 in terms of UC photon order, which is considered a direct indicator of spatial resolution in high power density applications. Our results showcase the promise of the Yb, (Gd) Er UC system for high power density applications, thus stimulating research for expanding the presently limited range of applicable UC systems. [ABSTRACT FROM AUTHOR]

The properties of the adsorption and steady-state photoluminescence (PL) properties of the terbium-doped CdS and ZnS nanocrystals (NCs) are discussed. The terbium PL in ZnS NCs is stronger and presents a slower dynamics.

Three 1D coordination polymers with benzoate bridges have been assembled in the presence of 18-crown-6-ether (18C6): 1∞[Tb(PhCOO)3(H2O)(EtOH)]·0.5(18C6) 1, 1∞[Eu(PhCOO)3(H2O)2]·0.5(18C6) 2, 1∞[Nd(PhCOO)3(H2O)2]·0.5(18C6) 3. Compounds 2 and 3 are isomorphous. The crown ether molecules co-crystallize with the resulting 1D coordination polymers and play an important role in the supramolecular architecture of the crystals. A molecular alloy was prepared in a similar way to compound 1 using TbCl3·6H2O and EuCl3·6H2O in a molar ratio of 95 : 5. The EuIII ions have statistically substituted the TbIII ions in the host lattice The luminescence thermometry performance of the Tb0.95Eu0.05 system was investigated using pulsed excitation into TbIII absorption at 352 nm. The maximum Sr value is 1.88% K−1 at 80 K which is slightly reduced at 1.60% K−1 at 313 K. Time-gated emission spectroscopy, employed here for the first time, allows us to reduce the spectral overlap of Tb and Eu emissions in the 610 to 625 nm range by 100% at 80 K, from 18 to 9%. Compound 1 as well as the molecular alloy, Tb0.95Eu0.05, show X-ray induced luminescence. [ABSTRACT FROM AUTHOR]

Doping SnO2 with trivalent lanthanide (Ln) metals aiming at optical applications faces several challenges. The elastic and electrostatic misfit between bulkier Ln activators and Sn host cation induces strain in the lattice as well as defects as a result of charge-compensation. These effects can be partially healed by thermal annealing. However, dopant segregation which occurs above a certain temperature drives quenching of Ln emission. In this work, we explore Li co-doping as a vehicle to improve the luminescence of lanthanide (Eu, Sm, Er, Dy and, Tb) doped SnO2 nanoparticles. In case of substitutional Ln dopants (Eu, Sm and Er), Li enhances significantly the Ln luminescence up to 40–46 times. The luminescence enhancement induced by Li co-doping is explained by an interplay of removal of nearby oxygen vacancies (Eu, Sm), improved Ln doping homogeneity (Er) and, improved crystallinity (Eu, Sm, Er). The improved crystallinity caused by Li co-doping accounts for less than 30% of the total enhancement. In the case of surface Ln dopants (Dy and Tb), Li co-doping does not alter the Ln emission, either in shape or intensity. Only a few Dy dopants succeed to substitute for Sn in the rutile lattice as shown by single-photon counting investigations. Collectively, our results show that the extent of luminescence enhancement induced by Li co-doping depend strongly on the Ln type. In SnO2, the common mechanisms that explain the Li induced enhancement of Ln luminescence in various hosts, either contribute partially (improved crystallization) or do not contribute at all (local structure distortion). [ABSTRACT FROM AUTHOR]

The local structure amorphous ZrO2 doped with europium (Eu3+) and its evolution during crystallization was investigated by using spectrally and temporally resolved luminescence of europium. A small contribution of a crystalline, tetragonal-like local phase emission to the overall broad/amorphous emission could be observed in the amorphous state before calcination. Also, a non- negligible amount of amorphous type emission was still detectable with the crystalline europium-doped ZrO2 obtained on calcination at 500 and 1000 °C being assigned to a disordered, monoclinic-like local phase. [ABSTRACT FROM AUTHOR]

Terbium-exchanged ultrastable Y (USY) zeolites were investigated by using time-resolved photoluminescence spectroscopy techniques and methods. To determine the distribution of terbium species in USY zeolites together with their photoluminescence properties, several analysis methods for the time-resolved luminescence spectra were used such as the area normalization of time-resolved photoluminescence spectra, singular value decomposition, global nonlinear least squares, and the maximum entropy. Except for a questionable long lifetime, small contribution of a terbium species with lifetime of 1.9–2.1 ms, all the experimental and analysis results converged to a two terbium species distribution with lifetimes varying between 410–440 and 1000–1100 μs. The effects of the silylation of terbium-exchanged USY zeolites with phenyl-, vinyl-, and hexadecyltrimethoxysilanes on the lanthanide’s photoluminescence properties were also described. [ABSTRACT FROM AUTHOR]