Luminescence properties of lanthanide-containing layered double hydroxides

A series of layered double hydroxides with the hydrotalcite structure containing Mg2+ and Al3+ cations in the brucite-like layers and carbonate in the interlayer have been prepared, with different lanthanide cations (4% loading) in the brucite-like layers. The solids have been characterized by element chemical analysis, powder X-ray diffraction, thermal analysis, particle size distribution, FT-IR and UV-Vis spectroscopies and surface texture by adsorption-desorption of nitrogen at - 196 degrees C. The color and luminescent properties have been also studied. The results confirmed the hydrotalcite-type structure, without any sort of contaminating phases. The solids have been calcined at 1000 degrees C forming homogeneously dispersed mixed oxides, where the rock-salt structure of MgO and the MgAl2O4 spinet have been identified by powder X-ray diffraction, without any differentiated phase containing lanthanide ions. The samples (original and calcined) containing Tb3+ exhibited green fluorescence, detected under irradiation of 254 and 365 nm. The emission spectra showed a series of narrow lines ascribed to the Tb3+5D4 -> F-7(6-2) transitions. The decay curves monitored at 543 nm indicated the presence of a single local Tb3+ environment in the parent and calcined samples. For the calcined samples, the photoluminescence evidence supports the insertion of Tb3+ in MgAl2O4 rather than in MgO. (C) 2016 Elsevier Inc. All rights reserved

Adsorción de plaguicidas organofosforados por óxido grafítico

A study on the distribution of the mineral nutrients in the different parts of rose bush was carried out with the aim of chossing whichever of these might be most suitable as diagnostic tissue, the cultivar used being "Gabriela". Although for some nutrients (such as N, K) the leaf position on the stem does not seem to have a great effect on its foliar concentrations, in other cases (Ca, Mn, Cu) these concentrations vary widely according to the situation of the leaf. In general, the greatest concentration variations are noted in the youngest leaves, the maximum stability being shown by the first two leaves of 5 leaflets. This stabiliry of the mineral nutrient concentrations in these first two leaves of 5 leaflets makes suitable as samples for diagnostic purposes.Peer reviewe