Influence of OH- concentration on the illitization of kaolinite at high pressure

The products of hydrothermal reactions of kaolinite at 300°C and 1000 bars were studied in KOH solutions covering an OH- concentration, [OH-], of 1M to 3.5M. XRD patterns indicated a notable influence of the [OH-] on the reaction. At [OH]≥3M, the only stable phase was muscovite/illite. The content of muscovite/illite was calculated from the analysis of the diagnostic 060 reflections of kaolinite and muscovite/illite. The results showed a linear dependence of kaolinite and muscovite/illite contents with [OH-]. 27Al MAS NMR spectroscopy revealed the formation of small nuclei of K-F zeolite at high [OH-]. Finally, modelling of the 29Si MAS NMR spectra indicated that the Si/Al ratio of the muscovite/illite formed was very close to that of muscovite, at least in the mineral formed at low [OH-]. In good agreement with the XRD data, the quantification of the reaction products by 29Si MAS NMR indicated a linear decrease of the kaolinite content with increasing OH- concentration.Dirección General de Investigación Científica y Técnica CTQ2007-63297Junta de Andalucía P06-FQM-0217

Uniform, luminescent Eu:LuF3 nanoparticles

A simple procedure for the synthesis of orthorhombic, uniform, LuF3 particles with two different morphologies (rhombus- and cocoon-like) and nanometer and sub-micrometer size, respectively, is reported. The method consists in the aging, at 120 °C for 2 h, a solution containing [BMIM]BF4 ionic liquid (0.5 mL) and lutetium acetate (in the case of the rhombi) or lutetium nitrate (in the case of the cocoons) (0.02 M) in ethylene glycol (total volume 10 mL). This synthesis method was also adequate for the synthesis of Eu3+-doped LuF3 particles of both morphologies, whose luminescence properties were investigated in detail. The experimental observations reported herein suggest that these materials are suitable phosphors for optoelectronic as well as in vitro biotechnological applications.MEC MAT2012-34919Junta de Andalucía JA FQM 06090CSIC 201460E00

Morphological and structural behavior of TiO2 nanoparticles in the presence of WO3: crystallization of the oxide composite system

Composite TiO2–WO3 oxide materials were prepared by a single pot microemulsion method and studied during calcination treatments under dry air in order to analyze the influence of tungsten on the behavior of the dominant titania component. To this end, the surface and bulk morphological and structural evolution of the solid precursors was studied using X-ray diffraction and infrared spectroscopy. In the calcination process, differences in the dominant titania component behavior appeared as a function of the W/Ti atomic ratio of the precursor. First, the crystallization of the anatase phase is affected by tungsten through an effect on the primary particle size growth. Furthermore, such an effect also influences the anatase to rutile phase transformation. The study provides evidence that the W–Ti interaction develops differently for a low/high W/Ti atomic ratio below/above 0.25 affecting fundamentally the above-mentioned anatase primary particle size growth process and the subsequent formation of the rutile phase and showing that addition of tungsten provides a way to control morphology and phase behavior in anatase-based oxide complex materialsComisión Interminsterial de Ciencia y Tecnología CT2010- 14872/BQUJunta de Andalucía FQM6090Consejo Superior de Investigaciones Científicas 201460E00

Europium-doped NaGd(WO4)2 nanophosphors: synthesis, luminescence and their coating with fluorescein for pH sensing

Uniform Eu-doped NaGd(WO4)2 nanophosphors with a spherical shape have been synthesized for the first time by using a wet chemistry method based on a homogeneous precipitation process at low temperature (120 °C) in ethylene glycol/water mixtures. The obtained nanoparticles crystallized into the tetragonal structure and presented polycrystalline character. The europium content in such phosphors has been optimized through the analysis of the luminescence dynamics (lifetime measurements). By coating the Eu3+-doped wolframate based nanoparticles with fluorescein through a layer-by-layer (LbL) approach, a wide range (4¿10) ratiometric pH-sensitive sensor has been developed, which uses the pH insensitive emission of Eu3+ as a reference.Ministerio de Economía y Competitividad MAT2014-54852-RConsejo Superior de Investigaciones Científicas CSIC PIE 201460E005, PIE 201560E056European Union 26722

Rare earth based nanostructured materials: Synthesis, functionalization, properties and bioimaging and biosensing applications

Rare earth based nanostructures constitute a type of functional materials widely used and studied in the recent literature. The purpose of this review is to provide a general and comprehensive overview of the current state of the art, with special focus on the commonly employed synthesis methods and functionalization strategies of rare earth based nanoparticles and on their different bioimaging and biosensing applications. The luminescent (including downconversion, upconversion and permanent luminescence) and magnetic properties of rare earth based nanoparticles, as well as their ability to absorb X-rays, will also be explained and connected with their luminescent, magnetic resonance and X-ray computed tomography bioimaging applications, respectively. This review is not only restricted to nanoparticles, and recent advances reported for in other nanostructures containing rare earths, such as metal organic frameworks and lanthanide complexes conjugated with biological structures, will also be commented on.European Union 267226Ministerio de Economía y Competitividad MAT2014-54852-

Synthesis and functionalization of biocompatible Tb:CePO4 nanophosphors with spindle-like shape

Monoclinic Tb:CePO4 nanophosphors with a spindle-like morphology and tailored size (in the nanometer and micrometer range) have been prepared through a very simple procedure, which consists of aging, at low temperature (120 C), ethylene glycol solutions containing only cerium and terbium acetylacetonates and phosphoric acid, not requiring the addition of surfactants or capping agents. The influence of the heating mode (conventional convection oven or microwave oven) and the Tb doping level on the luminescent, structural and morphological features of the precipitated nanoparticles have also been analyzed. This study showed that microwave-assisted heating resulted in an important beneficial effect on the luminescent properties of these nanophosphors. Finally, a procedure for the functionalization of the Tb:CePO4 nanoparticles with asparticdextran is also reported. The functionalized nanospindles presented negligible toxicity for Verocells, which along with theirs excellent luminescent properties, make them suitable for biomedical applications.Junta de Andalucía FQM6090España CICYT MAT2011-2359

Autoaprendizaje experimental de contenidos científico-técnicos avanzados a partir de material didáctico elemental

Se describe la programación de actividades de autoaprendizaje experimental sobre contenidos cientí- fico-técnicos avanzados, a partir de un material didáctico elemental. Dichas actividades se han referido a la asignatura Química del Estado Sólido, correspondiente a la titulación Ingeniería de Materiales, de segundo ciclo, la cual se imparte por primera vez en la Universidad de Sevilla durante el curso 2005-06. La programación se ha aplicado por sus autores, miembros del Grupo de Investigación FQM 212 del PAI, de carácter multidisciplinar, en un contexto caracterizado por la diversidad de los estudios realizados previamente por los alumnos. Ello ha permitido llevar a cabo su evaluación y presentar los resultados obtenidos.The programmed activities for the experimental selflearnig of advanced scientific and technological contents are proposed. These activities fit into the subject Solid State Chemistry of the Materials Engineering (University of Seville) which has started the academic year 2005-06. The proposed activities have already been tested by the authors, which belong to the Andaluzian Research Group FQM 212, in a multidisciplinary group of students. This experimental trial has allowed the evaluation of the results

Structural and kinetic study of phase transitions in LaYSi 2O 7

Phase transitions in LaYSi 2O 7 have been investigated as a function of temperature using XRD, NMR and TEM. Previously described empirical crystal structure guidelines based on average cation radius in rare-earth RE 2Si 2O 7-type disilicates predict a stable tetragonal A-LaYSi 2O 7 polymorph at temperatures below 1500°C. This study demonstrates that A-LaYSi 2O 7 is not thermodynamically stable at these temperatures and suggests that guidelines based on average cation size do not accurately describe the equilibrium behaviour of this silicate system. The A to G-type polymorph transition is extremely sluggish; complete transformation requires ~250h at 1200°C, and more than 3 weeks of calcination at 1100°C. This observation is important when this type of material is used as environmental barrier coating (EBC) of advanced ceramics. Analysis of XRD and TEM data reveal complete substitution of Y and La on the rare-earth cation sites in both LaYSi 2O 7 polymorphs, but indicate preferential site occupancies in the G-type polymorph.Dirección General de Investigación Científica y Técnica (DGICYT) CTQ2010-14874/BQUJunta de Andalucía FQM-609

Structural elucidation of Β-(Y,Sc) 2Si 2O 7: Combined use of 89Y MAS NMR and powder diffraction

Although the structures of pure Sc2Si2O7 and Β-Y 2Si 2O 7 have been described in the literature using the C2/m space group, 29Si magic angle spinning (MAS) NMR measurements of the intermediate members of the Sc 2Si 2O 7-Β- Y 2Si 2O 7 system indicate a lowering of the symmetry to the C2 space group. Indeed, these compositions exhibit a unique Si crystallographic site and an Si-O-Si angle lower than 180°, incompatible with the C2/m space group. C2 is the only possible alternative. Space group Cm can be discarded with regard to its two different Si sites per unit cell. Moreover, 89Y MAS NMR data have revealed the existence of two different Y sites in the structure of the intermediate members of the Sc 2Si 2O 7-Β-Y 2Si 2O 7 system, confirming the lowering of the symmetry to the C2 space group. The viability of the C2 model has therefore been tested and confirmed by refinement of synchrotron and neutron powder diffraction data for the different members of the system. The structural evolutions across the Sc 2Si 2O 7-Β-Y 2Si 2O 7 system are discussed.US Department of Energy DE-AC02-06CH11357European Union MRTN-CT-2006-035957Dirección General de Investigación Científica y Técnica (DGICYT) CTQ2010-14874/BQUJunta de Andalucía FQM 0609