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

Synthesis, structures and luminescence properties of metal-organic frameworks based on lithium-lanthanide and terephthalate

Metal-organic frameworks assembled from Ln(III), Li(I) and rigid dicarboxylate ligand, formulated as [LiLn(BDC)2(H2O)·2(H2O)] (MS1-6,7a) and [LiTb(BDC)2] (MS7b) (Ln = Tb, Dy, Ho, Er, Yb, Y0.96Eu0.04, Y0.93Tb0.07, and H2BDC = terephthalic acid), were obtained under hydrothermal conditions. The isostructural MS1-6 crystallize in monoclinic P21/c space group. While, in the case of Tb3+ a mixture of at least two phases was obtained, the former one (MS7a) and a new monoclinic C2/c phase (MS7b). All compounds have been studied by single-crystal and powder X-ray diffraction, thermal analyses (TGA), vibrational spectroscopy (FTIR), and scanning electron microscopy (SEM-EDX). The structures of MS1-6 and MS7a are built up of inorganic-organic hybrid chains. These chains constructed from unusual four-membered rings, are formed by edge- and vertex-shared {LnO8} and {LiO4} polyhedra through oxygen atoms O3 (vertex) and O6-O7 (edge). Each chain is cross-linked to six neighboring chains through six terephthalate bridges. While, the structure of MS7b is constructed from double inorganic chains, and each chain is, in turn, related symmetrically to the adjacent one through the c glide plane. These chains are formed by infinitely alternating {LiO4} and {TbO8} polyhedra through (O2-O3) edges to create Tb–O–Li connectivity along the c-axis. Both MS1-6,7a and MS7b structures possess a 3D framework with 1D trigonal channels running along the a and c axes, containing water molecules and anhydrous, respectively. Topological studies revealed that MS1-6 and MS7a have a new 2-nodal 3,10-c net, while MS7b generates a 3D net with unusual β-Sn topology. The photoluminescence properties Eu- and Tb-doped compounds (MS5-6) are also investigated, exhibiting strong red and green light emissions, respectively, which are attributed to the efficient energy transfer process from the BDC ligand to Eu3+ and Tb3+.Financial support from Spanish Ministerio de Economía y Competitividad (MINECO-13-MAT2013-40950-R, and FPI grant BES-2011-046948 to MSM.A.) and Gobierno del Principado de Asturias (GRUPIN14-060), and El Fondo Europeo de Desarrollo Regional (FEDER) are acknowledged.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Structural and Proton Conductivity Studies of Fibrous π-Ti2O(PO4)2·2H2O: Application in Chitosan- Based Composite Membranes

Although the fibrous polymorphic modification of titanium phosphate, π-Ti2O(PO4)2·2H2O (π-TiP) is known for decades, its crystal structure has remained unsolved. Herewith we report the crystal structure of π-TiP at a room temperature, determined from the synchrotron radiation powder X-ray diffraction, and corroborated by 31P solid state NMR and the accurate density functional theory calculations. In contrast to the previously reported ρ-TiP polymorph, the as-synthesized hydrated phase crystallizes in the monoclinic system (P21/c, a = 5.1121(2) Å, b = 14.4921(9) Å, c = 12.0450(11), β = 115.31(1)°, Z=4) and is composed of corner-sharing titanium octahedra and phosphate units arranged in a pattern distinct of ρ-TiP polymorph. The unit cell was confirmed by SAED, while the formation of planar packing imperfections and stacking faults along the [101] was revealed by HRTEM analysis. In situ dehydration study of π-TiP, monitored by high-temperature powder X-ray diffraction, led to a new anhydrous monoclinic [P21/c, a = 5.1187(13) Å, b = 11.0600(21) Å, c = 14.4556(26), β = 107.65(2)°, Z=4) phase that crystallizes at 500°C. The latter resembles the packing fashion of the parental π-TiP, albeit titanium atoms are present both in distorted tetrahedral and octahedral coordination environments. Anhydrous π-TiP was found to partially rehydrate at room temperature adopting reversibly the structure of the initial phase. The studies carried out under different conditions of leaching and impregnation with H3PO4 showed that π-TiP exhibits an extrinsic proton conductivity (1.3·10−3 S·cm−1 at 90 °C and 95% RH) due to the presence of protonated phosphate species bounded on the particles surface, as revealed by 31P MAS-NMR spectroscopy data. The composite membranes of Chitosan (CS) matrices filled with H3PO4-impregnated π-TiP solid show an increment of proton conductivity up to 4.5·10–3 S·cm–1, at 80 °C and 95% RH, 1.8-fold higher than those of bare CS membranesMAT2016-77648-R and PID2019-110249RB-I00), Junta deAndalucía (FQM-113) M. Bazaga-García thanks Junta de Andalucía for her Postdoc PAIDI grant and R. M. P. Colodrero thanks UMA Research Plan for her financial support

Consequences of Nitrogen Doping and Oxygen Enrichment on Titanium Local Order and Photocatalytic Performance of TiO2 Anatase

This work was financially supported by Spanish MINECO (MAT2013-40950-R, MAT2016-78155-C2-1-R, and CTQ2014-52956-C3-1-R), Gobierno del Principado de Asturias (GRUPIN14-060 and GRUPIN14-078), FEDER and South Ural State University thanks for the support the Ministry of Education and Science of the Russian Federation (grant No 16.2674.2014/K

Entangled core/shell magnetic structure driven by surface magnetic symmetry-breaking in Cr2O3 nanoparticles

Bulk Cr2O3 is an antiferromagnetic (AFM) oxide that exhibits the magnetoelectric effect at room temperature, with neither spontaneous magnetization nor net electric polarization. These physical properties stem from a subtle competition between exchange and crystal field interactions. In this article, we exploit the symmetry breaking at the surface of Cr2O3 nanoparticles for unbalancing this delicate physical equilibrium. The emerging weak ferromagnetic signal we observe persists up to near room temperature (≈ 270 K) at which the antiferromagnetic order disappears. In addition, an exchange-bias effect, that rapidly decreases on heating from low temperature up to 30 K, is resistant to thermal disorder above 200 K. Our findings point to the possible formation of an entangled core/shell magnetic structure, where pinned uncompensated spins at the shell are randomly distributed in a low-temperature spin-glass ordering, with low net magnetic moment and an ordering temperature governed by the AFM Néel temperature.Work at University of Oviedo was financially supported by research projects MCIU-19-RTI2018-094683-B-C52 (MCIU/AEI/FEDER, UE) and AYUD/2021/51822 (FICyT, Principality of Asturias). Thanks are due to Elettra-Sincrotrone Trieste (Italy) and to Institut Laue-Langevin (France) for allocating beam time. We are grateful to the Scientific-Technical Services of the University Oviedo for providing assistance in transmission microscopy image acquisition and processing. Work at USF supported partially through US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award # DE-FG02-07ER46438. H. S. acknowledges support from the Bizkaia Talent Program, Basque Country (Spain). X. M. acknowledges support from the Grant Agency of the Czech Republic Grant no. 14-37427.Peer reviewe

A review on the synthesis and current and prospective applications of zirconium and titanium phosphates

Metal phosphates represent an important group of materials with established industrial applications that are still attracting special scientific interest, owing to their outstanding physical and chemical properties. In this review, we account on the different synthetic routes and applications of zirconium and titanium phosphates, with a special focus on their application in the medicinal field. While zirconium phosphate has been extensively studied and explored with several reported industrial and medicinal applications, especially for drug delivery applications, titanium phosphates have not yet attracted the deserved attention regarding their established applications. However, titanium phosphates have been the focus of several structural studies with their different polymorphic forms, varied chemical structures, and morphologies. These variations introduce titanium phosphates as a strong candidate for technological and, particularly, biomedical applications.This review project was funded by MINECO, grant numbers MAT2016-78155-C2-1-R and MCI-415 21-PID2020-113558RB-C41; and by the Government of the Principality of Asturias, grant number 416 GRUPIN-IDI/2018/170

A Review on the Synthesis and Current and Prospective Applications of Zirconium and Titanium Phosphates

Metal phosphates represent an important group of materials with established industrial applications that are still attracting special scientific interest, owing to their outstanding physical and chemical properties. In this review, we account on the different synthetic routes and applications of zirconium and titanium phosphates, with a special focus on their application in the medicinal field. While zirconium phosphate has been extensively studied and explored with several reported industrial and medicinal applications, especially for drug delivery applications, titanium phosphates have not yet attracted the deserved attention regarding their established applications. However, titanium phosphates have been the focus of several structural studies with their different polymorphic forms, varied chemical structures, and morphologies. These variations introduce titanium phosphates as a strong candidate for technological and, particularly, biomedical applications