Synthesis and Reactions of Substituted 3-amino-2-furyl(aryl)-thieno[2,3-b]pyridines

New substituted thieno[2,3-b]pyridines which contain 4-nitropehnyl and 5-nitro-, carboxy-, methoxycarbonyl-2-furyl groups in the 2 position have been obtained

Simultaneous measurement of the mission quantum yield and local temperature: The illustrative example of SrF2:Yb3+/Er3+ Single Crystale

The emission quantum yield is one of the key figures of merit to evaluate the photoluminescence performance of luminescent materials. The emission quantum yield of upconverting materials is still not widely reported due to technical difficulties and intricate dependence on the excitation power density that is mirrored in a temperature increase. This work describes the simultaneous determination of the emission quantum yield (for both downshifting and upconverting processes) and of the temperature by using the output of a commercial integrating sphere. The temperature is calculated by primary luminescence thermometry through the Boltzmann equation, analyzing the intensity ratio between the 2H11/2, 4S3/2→4I15/2 transitions. The procedure is illustrated using of SrF2: Yb3+/Er3+ single crystals with distinct Yb3+ compositions and the effect of the Yb3+ content on the emission quantum yield and the temperature increase of the sample.publishe

An up-conversion luminophore with high quantum yield and brightness based on BaF<inf>2</inf>:Yb³⁺,Er³⁺single crystals

Up-conversion (UC) of near-infrared radiation to visible light has received much attention because of its use in the conversion of solar radiation, luminescence thermometry, biosensing, and anti-counterfeiting applications. However, the main issue hindering the successful utilization of UC is the relatively low quantum efficiency of the process. In order to design new UC systems with high quantum yield (ϕUC) values, we synthesized two series of co-doped BaF2single crystals with nominal concentrations of Yb3+(2-15 mol%)/Er3+(2 mol%) as well as Yb3+(3 mol%)/Er3+(2-15 mol%). The highestϕUCvalue of 10.0% was demonstrated for the BaF2:Er3+(2 mol%) and Yb3+(3 mol%) sample under 490 W cm−2of 976 nm excitation. To study the natural limit of UC efficiency, quantum yield values upon direct excitation (ϕDS) of the4S3/2(ϕDS≤ 4%) and4F9/2(ϕDS≤ 26%) levels were measured. Comparison of experimental values of quantum yields to the ones obtained using Judd-Ofelt theory reveals strong quenching of the4S3/2state for all investigated compositions. In addition, we observed an unusually strong contribution of the Er3+:4I9/2excited state to both UC and down-shifting luminescent processes. This contribution becomes possible due to the very low maximum phonon energy of BaF2crystals (240 cm−1)