National Institute Of Materials Physics - Romania

Herein, we investigate the emission properties of Er - BiOCl in the range of similar to 500 to 1700 nm under down - (488 and 973 nm) and NIR (telecom - wavelength at similar to 1500 nm) up - conversion excitation as well high energy X-ray excitation. The dependencies of red (similar to 670 nm) and NIR (similar to 800 nm) to green emission (similar to 543 nm) ratio with Er concentration, excitation mode and delay after laser pulse as well as the up - conversion excitation spectra and decays are analyzed in terms of competitive ground state absorption/excited state absorption and energy transfer up - conversion mechanisms. The CIE chromaticity diagram show single excitation (similar to 1500 nm), delay induced emission color change from yellowish green (delay of 0.001 ms) to reddish orange (delay of 1 ms). The X-ray induced emission of Er - BiOCl presents an atypical red to green emission ratio that exceeds that measured under optical down - conversion excitation by a factor of 13. The potential of Er - BiOCl for optical/X-ray imaging applications is discussed. (C)2015 Optical Society of America

EuFeO3 perovskite was considered as a case study of the cooperative effects of the rare earth and transition metal elements in the total catalytic oxidation of aromatic hydrocarbons. For this purpose, a EuFeO3 perovskite was prepared using the citrate route. Extensive characterization was performed via ex situ and in situ methods. EXAFS revealed that oxygen vacancies are formed in the nearest neighborhood of Fe and next-nearest neighborhood of Eu. Combining Eu-151 and Fe-57 Mossbauer experiments also suggested local oxygen defects in the proximity of the Eu cations during the reaction, as well as cooperative electron delocalization effects between Eu and Fe. XPS has shown the +3 oxidation state of both Eu and Fe cations and the relatively strong ionicity of the Fe-O chemical bonds, as suggested by the weakened 2p(3/2) satellite in the Fe2p spectrum. A systematic change of this satellite with the A cation in AFeO(3) perovskites was also discussed. The thermal treatment of the catalyst at 623 K, in air or toluene, was accompanied by a partial reduction of Fe and a partial oxidation of Eu, respectively. The interaction between the two elements appeared to be influenced mainly by the temperature and only slightly by the sample environment during further treatments. Catalytic oxidation of toluene on this perovskite led only to the production of carbon dioxide and water with no side-product formation from partial oxidation reactions. All the characterization and catalytic results preferably agree with a Volkenstein mechanism. (C) 2014 Elsevier Inc. All rights reserved.