Geochemistry of the cretaceous-tertiary boundary (Fish clay) at Stevns Klint (Denmark): Ir, Ni and Zn in kerogen

Geochemical analyses of trace metals (Ir, Ni and Zn) in the kerogen of the black marl of the Cretaceous-Tertiary boundary succession (Fish Clay) at Stevns Klint (Hojerup Church) were undertaken. The data for this kerogen were in accordance with a previous hypothesis(1) that this (insoluble) geoorganic polymer was derived from humic substances (mainly humic acids) of a nearshore soil. Substantial proportions of Ir, Ni and Zn within the kerogen structure were probably contained in these substances arriving at the sedimentary site. It is proposed that these humics were probably transported by acid surface waters (induced by the KT asteroid impact) into the shallow marine basin of Stevns Klint. It is also suggested that local leaching/weathering of the asteroidal impact fallout oil the land near these waters played an important role in providing Ir, Ni and Zn for these substances. Apparently, Ir, Ni and Zn of the kerogen were created by the chondritic component of the impact ejecta fallout

Synthesis, structure and luminescence of Er3+-doped Y3Ga5O12 nano-garnets

A novel Y3(1-x)Er3xGa5O12 nanocrystalline garnet has been synthesized by a sol-gel technique and a complete structural, morphological, vibrational, and optical characterization has been carried out in order to correlate the local structure of the Er3+ ions with their optical properties. The synthesized nanocrystals are found in a single-phase garnet structure with an average grain size of around 60 nm. The good crystalline quality of the garnet structure is confirmed by FTIR and Raman measurements, since the phonon modes of the nano-garnet are similar to those found in the single crystal garnet. Under blue laser excitation, intense green and red visible and 1.5 mu m infrared luminescences are observed, whose relative intensities are very sensitive to the Er3+ concentration. The dynamics of these emissions under pulsed laser excitations are analyzed in the framework of different energy transfer interactions. Intense visible upconverted luminescence can be clearly observed by the naked eye for all synthesized Er3+-doped Y3Ga5O12 nano-garnets under a cw 790 nm laser excitation. The power dependency and the dynamics of the upconverted luminescence confirm the existence of different two-photon upconversion processes for the green and red emissions that strongly depend on the Er3+ concentration, showing the potential of these nano-garnets as excellent candidates for developing new optical devices.This work has been partially supported by Ministerio de Ciencia e Innovacion of Spain (MICCIN) under The National Program of Materials (MAT2010-21270-C04-02; -03; -04), The Consolider-Ingenio 2010 Program (MALTA CSD2007-0045), and The National Infrastructure Program, by Ministerio de Economia y Competitividad of Spain (MINECO) within The Indo-Spanish Joint Programme of Cooperation in Science and Technology (PRI-PIBIN-2011-1153/DST-INT-Spain-P-38-11), and by the EU-FEDER funds (UCAN08-4E-008). S.F. Leon-Luis and V. Monteseguro wish to thank MICINN for the FPI grants (BES-2008-003353 and BES-2011-044596). Dr V. Venkatramu is grateful to DAE-BRNS, Government of India for the award of DAE Research Award for Young Scientists (no. 2010/20/34/5/BRNS/2223).Venkatramu, V.; León-Luis, SF.; Rodriguez-Mendoza, UR.; Monteseguro, V.; Manjón, FJ.; Lozano-Gorrín, AD.; Valiente, R.... (2012). Synthesis, structure and luminescence of Er3+-doped Y3Ga5O12 nano-garnets. Journal of Materials Chemistry. 22:13788-13799. doi:10.1039/c2jm31386cS13788137992

Characterization of rare-earth doped Lu2O3 nanopowders prepared with polymer complex solution synthesis

We explored a synthesis route based on the polymer complex solution method for the production of the rare-earth doped Lu2O3 crystalline nanopowders. In this type of synthesis polyethylene glycol is used both as fuel for the combustion reaction, and as nucleation agent for the crystallization process. Synthesized materials were characterized with X-ray diffraction technique, scanning and transmission electron microscopy, EDX technique and photoluminescence spectroscopy with steady state and time domain measurements. X-ray diffraction and electron diffraction analysis showed that presented synthesis procedure yields pure-phase, well crystallized Lu2O3 nanopowders with the particles dimensions in the 30-50 nm range, as observed from TEM images. Luminescence properties of Sm3+ and Tb3+ doped Lu2O3 exhibited characteristic red and pseudo-white emissions from these rare-earth ions, with an average emission lifetime of 0.8 and 0.6 ms, respectively. (C) 2010 Elsevier B.V. All rights reserved

Speciations of Trace Metals in the Accumulation Bogovina on the Crni Timok River

Samples of various ecochemical types of soil were collected in the region of the future accumulation of Lake Bogovina (Serbia). They were analyzed for ten elements using AAS, GFAAS and ICP. Investigation of the nature of association of heavy metals and identification of their substrates was provided by sequential extraction in five steps by successive extraction of soil samples with different mediums. Besides the acid soluble residual phase, most microelements were extracted in the easily and moderate reducible phases. Correlation between manganese and iron from the second and third phase with trace metals from non-residual phases was provided in order to determine their bioavailability. Besides principal component and cluster analysis, the enrichment factors were provided in order to check the impact of anthropogenic factors on trace elements. Most samples contained trace elements mainly from crustal origin with the exception of cadmium