Efficient green-emitting Tb3+-doped di-ureasil coating phosphors for near-UV excited light-emitting diodes

Light-emitting diodes (LEDs) are replacing conventional lighting sources, like incandescent and fluorescent lamps, due to their higher efficiency, lower energy consumption and environmental friendliness characteristics. Additional applications envisaging “engineered light” able to control the human circadian rhythm are now in place with emphases on green-emitting LEDs. In this work, transparent and flexible coatings based on organic–inorganic di-ureasil hybrids doped in-situ with a terbium (Tb3+) complex involving salicylic acid as ligands were synthesized. The materials are transparent, essentially amorphous and thermal stable up to 180 °C. Under near-UV excitation, bright green emission with high quantum yield (0.565 ± 0.057) and enhanced photostability are observed. Green-emitting prototypes were fabricated using a commercial near-UV-emitting LED (NUV-LED) combined with the Tb3+-doped di-ureasil coating showing narrow-band green emission with yellowish-green color coordinates (Commission Internationale de l'Éclairage, CIE 1931) of (0.329, 0.606) and high luminous efficacy (21.5 lm/W). This efficacy is the largest one reported for analogous prototypes formed by an NUV-LED coated with a green-emitting phosphor prepared under mild synthetic conditions (<100 °C), demonstrating that in-situ formation of carboxylate lanthanide-based complexes is an energy saving process with potential for solid-state lighting and backlight for flexible displays.publishe

Field-induced slow magnetic relaxation and luminescence thermometry in a mononuclear ytterbium complex

The mononuclear complex [Yb(H3L1,1,4)]·2MeOH (1·2MeOH), with a new heptadentate N4O3 ligand, was isolated and structurally characterised. The opto-magnetic properties of 1·2MeOH were investigated, showing that this complex is a bifunctional compound. Accordingly, 1·2MeOH reveals two coexisting functionalities: field-induced single molecule magnet behaviour, and Yb3+-centred NIR fluorescence dependent on temperature (25–300 K). The magnetic relaxation in this pentagonal bipyramidal complex does not seem to be of the Orbach type, and this is supported by the discrepancy between the anisotropic energy barrier found by fitting the magnetic data to an Orbach model and by spectroscopic studies. Ab initio calculations further validate the magnetic relaxation mechanisms and spectroscopic results.Spanish Ministerio de Innovación, Ciencia y Universidades (PGC2018 102052-B-C21)S

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results