α-Titanium phosphate intercalated with propylamine: An alternative pathway for efficient europium(III) uptake into layered tetravalent metal phosphates

Abstractα-Ti(HPO4)2·H2O (α-TiP) and its propylamine intercalation product, Ti(HPO4)2·2C3H7NH2·H2O (α-TiPPr), have been synthesized and characterized. Later, their sorption capacity for europium(III) was investigated, and this purpose was accomplished by treating α-TiP and α-TiPPr with europium(III) nitrate solutions at different concentrations until the equilibrium is reached. All samples were characterized, among others, by powder X-ray diffraction (PXRD), scanning and transmission electron microscopies (SEM, TEM, STEM-EDX, SAED), thermogravimetric analysis (TGA), and photoluminescence (PL) measurements. The results show that the Eu3+ uptake is limited to surface when α-TiP is used as sorbent. Nevertheless, the Eu-retention is considerably enhanced with α-TiPPr as a consequence of an ion-exchange process into the interlayer space of the layered titanium phosphate (involving propylammonium cations, C3H7NH3+, and hexahydrate europium(III) species, [Eu(H2O)6]3+), and the crystal structure of a hypothetical final product, α-[Eu(H2O)6]2/3Ti(PO4)2·[(H2O)6]1/3, has been proposed by using DFT calculations

Organoindium precursor purification by new sorbents based on titanium and zirconium phosphates

High purity requirements for organometallic precursors have recently become critical in the field of III–V semiconductor films obtained by chemical vapour deposition techniques. Traditional purification routes employing physical methods need to be replaced by ones which are more rapid and effective. Such a route is described in this paper. This involves the elimination of any traces of impurity by applying several combinations of sorbents. In this way, complete elimination of lithium impurities introduced during precursor synthesis has been achieved by the use of titanium or zirconium phosphate sorbents (usually used as acidic ion exchangers in aqueous media). The method also preserves the stability of the organoindium precursor which is normally extremely sensitive to moisture. A possible explanation for these observations is given

Chemical and physical characterization of iron-intercalated vermiculite compounds

Herein we report on synthetic iron-intercalated vermiculites prepared from a Mg-vermiculite mineral from Santa Olalla, Huelva, Spain, by means of an ion exchange process from aqueous solutions of FeCl2 and FeCl3. Thermogravimetric, X-ray diffraction, magnetic susceptibility and Mössbauer spectral studies have been used to characterize the synthetic iron-intercalated vermiculites. The results suggest that the intercalation process employed induces modifications in both the interlayer spacing and in the octahedral sheet; the disordered structure of the Mg-vermiculite mineral is not altered. The presence of solvated Fe(H2O) n 2+ ions has been shown by the Mössbauer spectroscopy. No magnetic order has been observed between 2 and 300 K neither in the Mg-vermiculite mineral nor in the two synthetic iron-intercalated vermiculites.Peer Reviewe

K2Ta4O11 (“kalitantite”): a wide band gap semiconductor synthesized in molybdate flux medium

The successful application of molybdate flux for the crystal growth of complex tantalum oxide, verbi causa kalitantite, was shown at a submillimetre scale. The structure was determined via X-ray single crystal refinements (space group Rc, a = 627.32(2) pm, c = 3685.75(13) pm, V = 1256.11(7) pm3 × 10−6, Z = 6) to be an α-U3O8-type layered compound presenting the general formula Mx(Nb,Ta)3n+1O8n+3 (where n = 1 in the case of M being Na, Ca or Ag and n = 2 when M is La–Eu, Y or Bi), thus corroborating earlier studies. Experimental evaluations and complementary ab initio calculations revealed the semiconductor nature of K2Ta4O11. The former were used to explain the vibrational spectrum in the mid-infrared range of wavenumbers.SGG is grateful for financial support from ERDF and the Spanish MINECO (MAT2010-15094).Peer reviewe

High-yielding green hydrothermal synthesis of ruthenium nanoparticles and their characterization

Using hydrothermal techniques, a novel synthetic approach to prepare ruthenium nanoparticles has been developed. At 180 degrees C and under autogenous pressure, starting from an aqueous solution of ruthenium trichloride, the method yielded nanoparticles whose form and size both depended on the reducing agent: sodium citrate (hexagonal shaped nanocrystals, 1-20 nm), ascorbic acid (spherical nanoparticles, 3-5 nm) and succinic acid (spherical nanoparticles, 1-120 nm). Depending on the reaction variables, the nature and concentration of partially reduced species determines the characteristics of the final products. HRTEM image analysis along with the simulation techniques were stabilized preferential growth of nanoparticles on specific directions. Ruthenium samples have been investigated by Temperature-Programmed Reduction (TPR) showing that the reduction temperature of nanoparticles is correlated to their nanocrystalline size.Peer Reviewe

Polyanionic identity of Ca2Zn2(V3O10)(VO4) photocatalyst manifested by X-ray powder diffraction and periodic boundary density functional theory calculations

The structure of photocatalytic and photoluminescent binary vanadate of the general formula “CaZnV2O7” has been investigated using X-ray powder diffraction. The compound is built up of isolated [V3O10], and [VO4] being this complex trivanadate–vanadate, in opposition to previous suggestions on isostructurality “CaMV2O7”, M – Mg or Co (Murashova et al., 1991, 36, 617–621). The present model has been confirmed by theoretical calculations. Thermal analysis and scanning electron microscopy have been performed, and the electronic structure analysis has been found to be in agreement with the experimental observations.Financial support from the Spanish Ministerio de Economía y Competitividad (MAT2013-40950-R), the Gobierno del Principado de Asturias (GRUPIN14-060) and the FEDER funding is acknowledged by AAB, SK and SGG. AAB and IVO acknowledge the JSPDS ICDD Grant-in-Aid program (12-02).Peer Reviewe

Series of 2D heterometallic coordination polymers based on ruthenium(III) oxalate building units: synthesis, structure, and catalytic and magnetic properties

A series of 2D ruthenium-based coordination polymers with hcb-hexagonal topology, {[K(18-crown-6)]3[M(II)3(H2O)4{Ru(ox)3}3]}n (M(II) = Mn (1), Fe (2), Co (3), Cu (4), Zn (5)), has been synthesized through self-assembly reaction. All compounds are isostructural frameworks that crystallize in the monoclinic space group C2/c. The crystal packing consists of a 2D honeycomb-like anionic mixed-metal framework intercalated by [K(18-crown-6)](+) cationic template. Dehydration processes take place in the range 40-200 °C exhibiting two phase transitions. However, the spontaneous rehydration occurs at room temperature. Both hydrated and dehydrated compounds were tested as Lewis acids heterogeneous catalysts in the acetalyzation of benzaldehyde achieving high yields with the possibility to be recovered and reused. All the investigated materials do not show any long-range magnetic ordering down to 2 K. However, the Fe-based compound 2 presents a magnetic irreversibility in the ZFC-FC magnetization data below 5 K, which suggest a spin-glass-like behavior, characterized also by short-range ferromagnetic correlations. The coercive field increases as the temperature is lowered below 5 K, reaching a value of 1 kOe at 2 K. Alternating current measurements obtained at different frequencies confirm the freezing process that shows weak frequency dependence, being characteristic of a system exhibiting competing magnetic interactions.The authors thank FEDER and Spanish MINECO for financial support under projects MAT2010-15094, MAT2008-06542-C04-03, MAT2011-27573-C04-02, and FC-08-IB08-036. A.D. also thanks the Spanish Ministerio de Educación, Cultura y Deporte for the predoctoral FPU grant (AP2008-03942).Peer reviewe

On the crystal structure and thermal decomposition of ammonium-iron(iii) bis(hydrogenphosphate)

NH4Fe(HPO4)2 and its deuterated form have been synthesized as monophasic polycrystalline materials. Their crystal structures, including hydrogen positions, were determined by Rietveld refinement and Fourier synthesis using constant-wavelength neutron powder diffraction data. In addition, the thermal decomposition of NH4Fe(HPO4)2 was found to give mixtures of Fe4(P2O7)3 and Fe(PO3)3via NH4FeP2O7 formation, the crystal structure of which has also been refined from X-ray powder diffraction data.This work has been carried out with the financial support of FEDER-MEC (MAT2006-01997, MAT2008-06542-C04-03, and Factoría Española de Cristalización-Consolider Ingenio 2010).Peer reviewe