Synthesis,characterization and thermoluminescence studies of (ZnS)1‐x(MnTe)x nanophosphors

The present paper reports the thermoluminescence (TL) of (ZnS)_1‐x(MnTe)_x nanophosphors that were prepared by a wet chemical synthesis method. The structure investigated by X‐ray diffraction patterns confirms the formation of a sphalerite phase whose space group was found to be F 3m. From XRD, TEM and SEM analyses the average sizes of the particles were found to be 12 nm, 11 nm and 15 nm, respectively. Initially the TL intensity increased with increasing values of x because the number of luminescence centres increased; however, for higher values of x the TL intensity decreased because of the concentration quenching. Thus the TL, mechanoluminescence and photoluminescence intensities are optimum for a particular value of x, that is for x = 0.05. Thermoluminescence of the (ZnS)_1‐x (MnTe)_x nanophosphor has not been reported previously. There were two peaks seen in the thermoluminescence glow curves in which the first peak lay at 105–100 °C and the second peak lay at 183.5–178.5 °C. The activation energies for the first and second peaks were found to be 0.45 eV and 0.75 eV, respectively.     

Unassisted Water Splitting Using a GaSbxP(1−x) Photoanode

Here, unbiased water splitting with 2% solar‐to‐hydrogen efficiency under AM 1.5 G illumination using new materials based on GaSb_0.03P_0.97 alloy is reported. Freestanding GaSb_xP_1?x is grown using halide vapor phase epitaxy. The native conductivity type of the alloy is modified by silicon doping, resulting in an open‐circuit potential (OCP) of 750 mV, photocurrents of 7 mA cm^?2 at 10 sun illumination, and corrosion resistance in an aqueous acidic environment. Alloying GaP with Sb at 3 at% improves the absorption of high‐energy photons above 2.68 eV compared to pure GaP material. Electrochemical Impedance Spectroscopy and illuminated OCP measurements show that the conduction band of GaSb_xP_1?x is at ?0.55 V versus RHE irrespective of the Sb concentration, while photocurrent spectroscopy indicates that only radiation with photon energies greater than 2.68 eV generate mobile and extractable charges, thus suggesting that the higher‐laying conduction bands in the Γ 1 valley of the alloys are responsible for exciton generation.     

New Na‐Ion Solid Electrolytes Na4−xSn1−xSbxS4 (0.02 ≤ x ≤ 0.33) for All‐Solid‐State Na‐Ion Batteries

Sulfide Na‐ion solid electrolytes (SEs) are key to enable room‐temperature operable all‐solid‐state Na‐ion batteries that are attractive for large‐scale energy storage applications. To date, few sulfide Na‐ion SEs have been developed and most of the SEs developed contain P and suffer from poor chemical stability. Herein, discovery of a new structural class of tetragonal Na_4?xSn_1?xSb_xS₄ (0.02 ≤ x ≤ 0.33) with space group I4₁/acd is described. The evolution of a new phase, distinctly different from Na₄SnS₄ or Na₃SbS₄, allows fast ionic conduction in 3D pathways (0.2–0.5 mS cm^?1 at 30 °C). Moreover, their excellent air stability and reversible dissolution in water and precipitation are highlighted. Specifically, TiS₂/Na–Sn all‐solid‐state Na‐ion batteries using Na_3.75Sn_0.75Sb_0.25S₄ demonstrates high capacity (201 mA h (g of TiS₂)^?1) with excellent reversibility.     

Nanoscale Probing of Voltage Activated Oxygen Reduction/Evolution Reactions in Nanopatterned (LaxSr1‐x)CoO3‐δ Cathodes

Bias‐dependent mechanisms of reversible and irreversible electrochemical processes on a (La_0.5Sr_0.5)₂CoO_4±δ modified (La_xSr_1‐x)CoO₃‐ surface are studied using dynamic electrochemical strain microscopy (D‐ESM). The reversible oxygen reduction/evolution process is activated at voltages as low as 3–4 V and the degree of transformation increases linearly with applied bias. The irreversible processes associated with static surface deformation become apparent above 10–12 V. Post‐mortem focused‐ion milling combined with atomic resolution scanning transmission electron microscopy and electron energy loss spectroscopy is used to establish the mechanisms of irreversible transformations and attribute it to amorphization of the top layer of material. These studies both establish the framework for probing irreversible electrochemical processes in solids and illustrate rich spectrum of electrochemical transformations underpinning electrocatalytic activity in cobaltites.     

Mesoporous MoO3–x Material as an Efficient Electrocatalyst for Hydrogen Evolution Reactions

A unique approach for the synthesis of nonstoichiometric, mesoporous molybdenum oxide (MoO_3–x) with nanosized crystalline walls by using a soft template (PEO‐b‐PS) synthesis method is introduced. The as‐synthesized mesoporous MoO_3–x is very active and stable (durability > 12 h) for the electrochemical hydrogen evolution reaction (HER) under both acidic and alkaline conditions. The intrinsic MoO₃ serves as an HER electrocatalyst without the assistance of carbon materials, noble metals, or MoS₂ materials. The results from transmission electron microscopy and N₂ sorption techniques show that the as‐synthesized mesoporous MoO_3–x has large accessible pores (20–40 nm), which are able to facilitate mass transport and charge transfer during HER. In terms of X‐ray diffraction, X‐ray photoelectron spectroscopy, temperature‐programmed oxidation, and diffusive reflectance UV–vis spectroscopy, the mesoporous MoO_3–x exhibits mixed oxidation states (Mo⁵⁺, Mo⁶⁺) and an oxygen‐deficient structure. The as‐synthesized MoO_3–x only requires a low overpotential (≈0.14 V) to achieve a 10 mA cm^?2 current density in 0.1 m KOH and the Tafel slope is as low as 56 mV dec^?1. Density functional theory calculations demonstrate a change of electronic structure and the possible reaction pathway of HER. Oxygen vacancies and mesoporosity serve as key factors for excellent performance.     

Synthesis and characterization of Y(1‐x)Eu(x)(TTA)3(Phen) organic luminescent thin films

Yttrium is stoichiometrically doped into europium by mole percentage, during the synthesis of Y_(1‐x)Eu_(x)(TTA)₃(Phen), using solution techniques (where x = 0.2, 0.4, 0.5, 0.6 and 0.8, TTA = thenoyltrifluoroacetone and Phen = 1,10‐phenanthroline).These complexes were characterized using different techniques such as X‐ray diffraction, thermogravimetric/differential thermal analysis, optical absorption and emission spectra. Thin films of the doped Eu–Y complexes were prepared on a glass substrate under a high vacuum of 10^‐6 Torr. The photoluminescence spectra of these thin films were recorded by exciting the sample at a wavelength of 360 nm. The emission peak for all the synthesized complexes centered at 611 nm; maximum emission intensity was obtained from Y_0.6Eu_0.4 (TTA)₃(Phen). The results proved that these doped complexes are more economical than pure Eu(TTA)₃(Phen) and are best suited as red emissive material for energy‐efficient and eco‐friendly organic light‐emitting diodes and displays. Copyright © 2013 John Wiley & Sons, Ltd.     

The deubiquitinase Usp27x stabilizes the BH3‐only protein Bim and enhances apoptosis

Bim is a pro‐apoptotic Bcl‐2 family member of the BH3‐only protein subgroup. Expression levels of Bim determine apoptosis susceptibility in non‐malignant and in tumour cells. Bim protein expression is downregulated by proteasomal degradation following ERK‐dependent phosphorylation and ubiquitination. Here, we report the identification of a deubiquitinase, Usp27x, that binds Bim upon its ERK‐dependent phosphorylation and can upregulate its expression levels. Overexpression of Usp27x reduces ERK‐dependent Bim ubiquitination, stabilizes phosphorylated Bim, and induces apoptosis in PMA‐stimulated cells, as well as in tumour cells with a constitutively active Raf/ERK pathway. Loss of endogenous Usp27x enhances the Bim‐degrading activity of oncogenic Raf. Overexpression of Usp27x induces low levels of apoptosis in melanoma and non‐small cell lung cancer (NSCLC) cells and substantially enhances apoptosis induced in these cells by the inhibition of ERK signalling. Finally, deletion of Usp27x reduces apoptosis in NSCLC cells treated with an EGFR inhibitor. Thus, Usp27x can trigger via its proteolytic activity the deubiquitination of Bim and enhance its levels, counteracting the anti‐apoptotic effects of ERK activity, and therefore acts as a tumour suppressor.     

Upslope movements and large scale expansions: the taxonomy and biogeography of the Coenonympha arcania –C. d arwiniana –C. gardetta butterfly species complex

Sibling species groups are suitable models for the understanding of inter‐ and intraspecific processes in taxonomy and biogeography. We analysed 262 individuals from the Alps of the Coenonympha arcania/gardetta species complex by allozyme electrophoresis. These taxa showed high variance amongst populations (F_ST: 0.391) and strong intertaxon genetic differentiation (F_CT: 0.376). Although morphologically similar, Coenonympha gardetta and Coenonympha arcania clearly differ in their genetic characteristics; the morphologically intermediate taxa Coenonympha darwiniana darwiniana and Coenonympha darwiniana macromma are genetically well distinguished from each other and the two other taxa. Coenonympha arcania and C. d. macromma most probably share a common ancestor and evolved by cladogenesis, whereas the taxonomic situation of C. d. darwiniana is still unresolved: This taxon might be the result of hybridization between C. arcania and C. gardetta or it might have a common ancestor together with C. gardetta. We suggest species rank for all four taxa. The distribution of genetic diversity of these populations and the differentiation amongst populations suggest rather different biogeographical scenarios: C. arcania most probably is of Mediterranean origin with postglacial range expansion northwards; C. gardetta survived the last ice age in peripheral refugia of the Alps and has spread all over this high mountain system in the postglacial; C. darwiniana and C. macromma survived the Würm in geographic proximity to their actual distribution areas and only have performed moderate uphill translocations during postglacial warming. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 890–904.     

Synthesis of 8‐Substituted 2′‐Deoxyisoguanosines via Unprotected 8‐Brominated 2‐Amino‐2′‐deoxyadenosine

A variety of applications of 8‐alkynylated nucleosides has prompted the synthesis of new purine analogues. Bromination of unprotected 2‐amino‐2′‐deoxyadenosine with Br₂/AcOH/AcONa gives 2‐amino‐8‐bromo‐2′‐deoxyadenosine (87%). The brominated derivative is converted to 8‐alkynylated 2‐amino‐2′‐deoxyadenosines by palladium‐catalyzed Sonogashira cross‐coupling reaction via microwave assistance (81 – 95%). The resulting compounds are further transformed to 8‐alkynylated 2′‐deoxyisoguanosines (52 – 70%). The physical properties of new compounds are investigated.