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Wurtzite ZnS and ZnO porous nanostructures have been obtained by annealing ZnS(en)0.5 nanosheets in air at different times and temperatures. The evolution of the morphological and structural transformation has been investigated at the nanoscale by transmission and scanning electron microscopy (TEM and SEM) analysis. At the annealing temperature of 400 °C, the ZnS(en)0.5 hybrid decomposes by a topotactic transformation, giving ZnS nanosheets. By increasing the annealing time, the gradual transformation ZnS->ZnO is observed to take place at the nanoscale. The transformation completes with the formation of highly porous ZnO crystals when the annealing temperature is increased to 600 °C. Remarkably, all the structural and morphological transformation steps during the annealing preserve the nanosheet crystalline character. These processes have been related to the materials photocatalytic activity in methylene blue degradation under UV-visible irradiation. The ZnS(en)0.5 precursor is the weakest photocatalyst, whereas porous ZnO is the strongest. Samples treated at 400 °C show degradation efficiencies that are intermediate between ZnS(en)0.5 and ZnO platelets and decrease with increasing annealing time due to the formation of ZnS/ZnO heterojunctions.

The reactions of stoichiometric Y 2 O 3 , CuO, and different barium salts (BaCO 3 , Ba(NO 3 ) 2 , BaO 2 , BaCuO 2 ) for forming various compounds in the yttrium-barium-copper-oxygen system (i.e., YBa 2 Cu 3 O 7-δ , BaCuO 2 , Y 2 BaCuO 5 , and Y 2 Cu 2 O 5 ) were systematically investigated by thermal analysis and X-ray diffractometry. In a few cases, the relevant activation energies were calculated. The reaction pathway and kinetics were significantly dependent on the physicochemical and thermal stability of the barium precursors, as well as on the crystalline size of the reagent. Binary BaO-CuO phases formed at low temperature (650°-700°C) when in the presence of easy-to-decompose barium precursors, and then slowly transformed to ternary compounds; in contrast, when barium ions were released at temperatures of >900°C, ternary phases formed directly from the components.

LaMn1−y3+Mny4+O3±d and La0.67R0.33Mn1−y3+Mny4+O3±d (R = Ca, Sr, Ba) phases were synthesized at 350°C by using very reactive, amorphous precursors obtained from the stoichiometric citrate solutions. The chemical process was optimized with respect to the solution concentration, pH, and additives. The precursor reactions were investigated as a function of the cation stoichiometry and the additive by simultaneous thermal and thermogravimetric analysis and X-ray diffraction. The reaction pathway was found to be independent of the cation stoichiometry, but related to the acid or base additive. The annealing temperature was systematically increased in the 350–1200°C interval and the La0.67Sr0.33MnO3±d properties (i.e., crystal sizes, Mn average valence, Curie temperature, magnetization, magnetic susceptibility) were measured and found to vary consistently as a function of it.

We demonstrate that highly porous ZnO nanobelts can be prepared by thermally decomposing ZnS(en)(0.5) hybrid nanobelts (NBs) synthesized through a solvothermal route using Zn layers deposited on alumina substrates as both the Zn substrate and source. Hybrid decomposition by thermal annealing at 400 °C gives porous ZnS NBs that are transformed by further annealing at 600 °C into wurtzite single crystal ZnO nanobelts with an axial direction of [0001]. The evolution of the morphological and structural transformation ZnS(en)(0.5)→ ZnS → ZnO is investigated at the nanoscale by transmission and scanning electron microscopy analyses. Control of the ZnO NB distributions by patterning the Zn metallization on alumina is achieved as a consequence of the parent hybrid NB patterned growth. The presence of NBs on alumina in a ∼100 μm wide region between Zn stripes allows us to fabricate two contact devices where contact pads are electrically connected through a porous ZnO NB entanglement. Such devices are suitable for employment in photodetectors as well as in gas and humidity sensors.

We have refined the structures for YBa2Cu2.94Nio.O6Oy (2% Ni) and YBa2Cu2.8ONio.20Oy (6.67% Ni) at y ∼ 6.95 and y ∼ 6.5 contents. Oxygen was reduced by two independent methods: quenching from 690 °C and oxygen gettering at 450 OC, Cu-O bond lengths were calculated based on Rietveld structure refinements for the various samples; they indicate the likely occupancy of Ni in the plane (Cu2) site of the 123 superconductor.

Well-oriented thin films of methyl-ammonium trihalogenostannates $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}\mathrm{Sn}{X}_{3}$ compounds $(X=\mathrm{Cl},\mathrm{Br})$ are grown by the single source thermal ablation technique. Optical absorption and structural analysis of $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}\mathrm{Sn}{X}_{3}$ thin films are combined with ab initio calculations in order to clarify their electronic properties and the role of the organic cation. The structural calculations reproduce well the measured lattice parameters, and optical measurements reveal a direct gap absorption onset for both compounds, in agreement with the calculated band structures. It turns out from projected density of states analysis that the valence and conduction bands take negligible contribution from the methylammonium. It is inferred that the band gap mainly depends on the ionicity and size of the inorganic cage $\mathrm{Sn}{X}_{3}$.

We have measured the ab-plane resistivity of La$_{2-x}$Sr$_x$CuO$_4$ single crystals with small Sr content (x=0.052 $\div$ 0.075) between 4.2 and 300 K by using the AC Van der Pauw technique. As recently suggested by Ichikawa et al., the deviation from the linearity of the $\rho_{\mathrm{ab}}(T)$ curve starting at a temperature T$_{\mathrm{ch}}$ can be interpreted as due to a progressive slowing down of the fluctuations of pre-formed charge stripes. An electronic transition of the stripes to a more ordered phase could instead be responsible for some very sharp anomalies present in the $\rho_{\mathrm{ab}}(T)$ of superconducting samples just above $T_{\mathrm{c}}$., Comment: M2S-HTSC-VI Conference paper (2 pages, 2 figures), using Elsevier style espcrc2.sty