Directed Dehydration as Synthetic Tool for Generation of a New Na4 SnS4 Polymorph: Crystal Structure, Na+ Conductivity, and Influence of Sb-Substitution.

We present the convenient synthesis and characterization of the new ternary thiostannate Na4 SnS4 (space group I 4 1 / a c d ) by directed removal of crystal water molecules from Na4 SnS4 ⋅14 H2 O. The compound represents a new kinetically stable polymorph of Na4 SnS4 , which is transformed into the known, thermodynamically stable form (space group P 4 ‾ 2 1 c ) at elevated temperatures. Thermal co-decomposition of mixtures with Na3 SbS4 ⋅9 H2 O generates solid solution products Na4-x Sn1-x Sbx S4 (x=0.01, 0.10) isostructural to the new polymorph (x=0). Incorporation of Sb5+ affects the bonding and local structural situation noticeably evidenced by X-ray diffraction, 119 Sn and 23 Na NMR, and 119 Sn Mössbauer spectroscopy. Electrochemical impedance spectroscopy demonstrates an enormous improvement of the ionic conductivity with increasing Sb content for the solid solution (σ25°C =2×10-3 , 2×10-2 , and 0.1 mS cm-1 for x=0, 0.01, and 0.10), being several orders of magnitude higher than for the known Na4 SnS4 polymorph.

Synthesis and Characterization of a Rare Transition-Metal Oxothiostannate and Investigation of Its Photocatalytic Properties.

The new transition-metal oxothiostannate [Ni(cyclen)(H2O)2]4[Sn10S20O4]·âˆ¼13H2O (1) was prepared under hydrothermal conditions using Na4SnS4·14H2O as the precursor in the presence of [Ni(cyclen)(H2O)2](ClO4)2·H2O. Compound 1 comprises the [Sn10S20O4]8- anion constructed by the T3-type supertetrahedron [Sn10S20] and the [Sn10O4] anti-T2 cluster. Channels host the H2O molecules, and the sample can be reversibly dehydrated and rehydrated without significantly affecting the crystallinity of the material. 119Sn NMR spectroscopy of an aqueous solution of Na4SnS4·14H2O evidences that between 25 and 120 °C only [SnS4]4- and [Sn2S6]4- anions are present. In further experiments, hints were found that the formation of tin oxosulfide ions depends on the Ni2+-centered complexes. Compound 1 exhibits promising photocatalytic properties for the visible-light-driven hydrogen evolution reaction, with 18.7 mmol·g-1 H2 being evolved after 3 h.

Influence of the percutaneous myofasciotomy on gait of children with spastic cerebral palsy - A short term, retrospective controlled analysis.

BACKGROUND: One of the primary causes in children with cerebral palsy (CP) leading to gait disorders is an increased muscle tone which may secondary result in a shortening of the muscle fascia. Percutaneous myofasciotomy (pMF) is a minimal-invasive surgical intervention correcting the shortened muscle fascia and aims to extend the range of motion. RESEARCH QUESTION: What is the effect of pMF on gait in children with CP three months and one year post-OP? METHODS: Thirty-seven children (f: n = 17, m: n = 20; age: 9,1 ± 3,9 years) with spastic CP (GMFCS: I-III, bilateral (BSCP): n = 24, unilateral (USCP): n = 13) were retrospectively included. All children underwent a three dimensional gait analysis with the Plug-in-Gait-Model before (T0) and three months after pMF (T1). Twenty-eight children (bilateral: n = 19, unilateral: n = 9) underwent a one-year follow-up-measurement (T2). Differences in the Gait Profile Score (GPS), kinematic gait data, gait-related functions and mobility in daily living were statistically analyzed. Results were compared to a control group (CG) matched in age (9,5 ± 3,5 years), diagnosis (BSCP: n = 17; USCP: n = 8) and GMFCS-level (GMFCS I-III). This group was not treated with pMF but underwent two gait analyses in twelve months. RESULTS: The GPS improved significantly in BSCP-pMF (16,46 ± 3,71° to 13,37 ± 3,19°; p < .0001) and USCP-pMF (13,24 ± 3,27° to 10,16 ± 2,06°; p = .003) from T0 to T1 with no significant difference between T1 and T2 in both groups. In CG there was no difference in the GPS between the two analyses. SIGNIFICANCE: PMF may in some children with spastic CP improve gait function three months as well as for one-year post-OP. Medium and long-term effects, however, remain unknown and further studies are needed.

Time-dependent investigation of a mechanochemical synthesis of bismuth telluride-based materials and their structural and thermoelectric properties.

Here, we report on the time dependence of a synthesis procedure for generation of both n- and p-type bismuth telluride-based materials. To initiate the reaction, the starting materials were first mechanical pre-reacted. The Rietveld refinements of X-ray diffraction (XRD) data collected after different milling times demonstrate that Bi2Te3 was formed after only 10 min, and longer milling times do not alter the composition. To complete the phase formation, the powders were treated by field-assisted sintering and heat treatment afterwards. The effect of this fast procedure on the structural and thermoelectric properties was investigated. Samples were obtained with relative densities above 99%. A clear preferred orientation of the crystallites in the samples is evidenced by Rietveld refinements of XRD data. The thermoelectric characteristics demonstrate a good performance despite the short milling time. Further, it was demonstrated for this fast synthesis that the physical transport properties can be varied with well-known n- and p-type dopants like CHI3 or Pb. For these non-optimized materials, a ZT value of 0.7 (n-type) and 0.9 (p-type) between 400 and 450 K was achieved. The long-term stability is demonstrated by repeated measurements up to 523 K showing no significant alteration of the thermoelectric performance.