Iron(III) fumarate materials are well suited for biomedical applications as they feature biocompatible building blocks, porosity, chemical functionalizability, and magnetic resonance imaging (MRI) activity. The synthesis of these materials however is difficult to control and it has been challenging to produce monodisperse particle sizes and morphologies that are required in medical use. Here, we report the optimization of iron(III) fumarate nano and microparticles synthesis by surfactant-free methods, including room temperature, solvothermal, microwave, and microfluidic conditions. Four variants of iron(III) fumarate with distinct morphologies were isolated and are characterized in detail. Structural characterization shows that all iron(III) fumarate variants exhibit the metal-organic framework (MOF) structure of MIL-88A. Nanoparticles with a diameter of 50 nm were produced, which contain crystalline areas not exceeding 5 nm. Solvent-dependent swelling of the crystalline particles was monitored using in-situ X-ray diffraction. Cytotoxicity experiments showed that all iron(III) fumarate variants feature adequate bio-tolerability and no distinct interference with cellular metabolism at low concentrations. Magnetic resonance relaxivity studies using clinical MRI equipment, on the other hand, proved that the MRI contrast characteristics depend on particle size and morphology. All in all, this study demonstrates the possibility of tuning the morphological appearance of iron(III) fumarate particles and illustrates the importance of optimizing synthesis conditions for the development of new biomedical materials.

Professor Ulrich Mu È ller zum 60. Geburtstag gewidmet.Inhaltsu È bersicht. Cs 3 Sb 7 und Cs 4 Sb 2 wurden aus den Elementen dargestellt und ihre Kristallstrukturen auf der Basis von Ro È ntgeneinkristalldaten ermittelt. Cs 3 Sb 7 kristallisiert monoklin in der Raumgruppe P2 1 /c (a = 1605.7(1) pm, b = 1571.1(1) pm, c = 2793.9(2) pm, b = 96.300(2)°, Z = 16) und entha È lt Anionen Sb 7 3± . In der Kristallstruktur von Cs 4 Sb 2 (orthorhombisch, Raumgruppe Pnma, a = 1598.5(3) pm, b = 631.9(2) pm, c = 1099.5(2) pm, Z = 4) liegen Hanteln Sb 2 4± vor.Abstract. Cs 3 Sb 7 and Cs 4 Sb 2 were synthesized from the elements and their crystal structures were determined on the basis of single crystal x-ray data. Cs 3 Sb 7 crystallizes in the monoclinic system with space group P2 1 /c (a = 1605.7(1) pm, b = 1571.1(1) pm, c = 2793.9(2) pm, b = 96.300(2)°, Z = 16) and contains anions Sb 7 3± . In the structure of Cs 4 Sb 2 (ortho-rhombic, space group Pnma, a = 1598.5(3) pm, b = 631.9(2) pm, c = 1099.5(2) pm, Z = 4) dumbbells Sb 2 4± are present.

The coefficient of thermal expansion and elastic stiffnesses of spinel structure MgGa2O4 were determined from 103 K to 1673 K using dilatometry and resonant ultrasound spectroscopy. The state of cation order was investigated on specimens quenched from temperatures up to 1473 K via single-crystal X-ray diffraction. Even at room-temperature, the material is stiffer than what was expected from DFT simulations at 0 K, however, the stiffness falls within the predicted range based on the stiffness of the constituent oxides of MgGa2O4. The anisotropy of its longitudinal elastic stiffness is low, whereas there is a high anisotropy of the shear resistance compared to other cubic materials. At about 820 K–860 K, the temperature dependences of both thermal expansion and elastic properties change rapidly. Cation reordering also starts in this temperature range; the state of order is static at lower temperatures. Thus, MgGa2O4 undergoes a glass-like transition when heated above 820 K–860 K, where the state of cation order starts relaxing towards equilibrium in laboratory timescales. Landau-theory for nonconvergent cation ordering can describe the observed cation order at elevated temperatures well.

No abstract

The elastic properties of rare-earth scandates were only reported at room temperature based on simulations and experimental measurements with poor agreement thus far. Using resonant ultrasound spectroscopy and inductive gauge dilatometry, we determined the elastic stiffnesses, their temperature dependence, and thermal expansion coefficients of SmScO3, TbScO3, and DyScO3 between 103 K and 1673 K. Our set of elastic stiffnesses shows high internal consistency, e.g., the relations c11>c33>c22, c66>c44>c55, and c13≥c12>c23 hold for all crystal species at room temperature. The structures become overall stiffer with decreasing RE-radius and increased charge density. The behavior of c44 at low temperatures indicates in all REScO3 a structural instability that might lead to an orthorhombic→monoclinic transition involving shear of the (100)-plane upon increasing pressure. The transition seems to be promoted by a decreasing RE-radius. Anomalies in two mixed resistances of TbScO3 below room temperature are indicative of at least one more structural instability that may also cause a phase transition where the structure is sheared. So far, only magnetic phase transitions at about 3 K have been observed in REScO3 in literature. The thermoelastic properties in [100] and [001] directions of all materials become increasingly isotropic at high temperatures, suggesting decreased structural tilt. (100) or (010) crystal cuts should be chosen for applications of a REScO3 as a substrate material, when mostly isotropic thermal expansion or longitudinal stiffness in-plane is desired, respectively.