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Objectives We provide a brief introduction to the objectives, data, methods and results of the World Health Organization (WHO)/International Labor Organization (ILO) Joint Estimates of the Work-related Burden of Disease and Injury (WHO/ILO Joint Estimates), which estimated the burden attributable to 19 selected occupational risk factors. Methods The WHO/ILO Joint Estimates were produced within the global Comparative Risk Assessment framework, which attributes the burden of one specific health outcome (ie, disease/injury) to a specific occupational risk factor. For 39 established occupational risk factor-health outcome pairs, estimates are produced using population attributable fractions (PAF) from recent burden of disease estimates. For two additional pairs, PAF are calculated from new databases of exposure and risk ratios produced in WHO/ILO systematic reviews. Attributable disease burdens were estimated by applying the PAF to total disease burdens. Results Globally in 2016, it is estimated that 1.88 [95% uncertainty range (UR) 1.84-1.92] million deaths and 89.72 (95% UR 88.61-90.83) million disability-adjusted life years were attributable to the 19 selected occupational risk factors and their health outcomes. A disproportionately large work-related burden of disease is observed in the WHO African Region (for disability-adjusted life years), South-East Asia Region, and Western Pacific Region (for deaths), males and older age groups. Conclusions The WHO/ILO Joint Estimates can be used for global monitoring of exposure to occupational risk factors and work-related burden of disease and to identify, plan, cost, implement and evaluate policies, programs and actions to prevent exposure to occupational risk factors and their associated burden.

In the field of magnetoelectric coupling, especially via the spin-dependent metal-ligand d-p hybridization mechanism found in multiferroic Ba2MGe2O7 (M = Mn, Co), detailed knowledge of the microscopic structural parameters is essential, also for the theoretical modeling. In this article, we report a systematic structural study of Ba2MnGe2O7 single crystal under varying temperatures between 110 and 673 K using non-destructive in situ single crystal synchrotron radiation diffraction. The maximum entropy method (MEM) was applied to the X-ray diffraction data for the determination of the deformation in the electron density and the orbital hybridization between the 3d of Mn and 2p of O in the Mn-O bond. Within this entire temperature range, the structure was described in a single crystallographic space group P (4) over bar2(1)m and no structural phase transition has been detected. Interestingly, the forbidden reflections, which arise from multiple diffractions so-called "Renninger effect," were observed at all temperatures without any symmetry lowering. The changes in the structural parameters [bond-lengths, bond-angles, anisotropic displacement parameters, and electron density distributions (EDDs) of the atoms] with temperature are revealed, helping to understand some aspects comprising orbital hybridization in multiferroic Ba2MnGe2O7.

Highlights • We present the first WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. • Globally in 2016, 488 million people were exposed to long working hours (≥55 hours/week). • This exposure had 745,194 attributable deaths and 23.3 million DALYs from ischemic heart disease and stroke. • These are 4.9% of all deaths and 6.9% of all DALYs from these causes. • The Western Pacific, South-East Asia, men, and older people carried higher burdens., Background World Health Organization (WHO) and International Labour Organization (ILO) systematic reviews reported sufficient evidence for higher risks of ischemic heart disease and stroke amongst people working long hours (≥55 hours/week), compared with people working standard hours (35–40 hours/week). This article presents WHO/ILO Joint Estimates of global, regional, and national exposure to long working hours, for 194 countries, and the attributable burdens of ischemic heart disease and stroke, for 183 countries, by sex and age, for 2000, 2010, and 2016. Methods and Findings We calculated population-attributable fractions from estimates of the population exposed to long working hours and relative risks of exposure on the diseases from the systematic reviews. The exposed population was modelled using data from 2324 cross-sectional surveys and 1742 quarterly survey datasets. Attributable disease burdens were estimated by applying the population-attributable fractions to WHO’s Global Health Estimates of total disease burdens. Results In 2016, 488 million people (95% uncertainty range: 472–503 million), or 8.9% (8.6–9.1) of the global population, were exposed to working long hours (≥55 hours/week). An estimated 745,194 deaths (705,786–784,601) and 23.3 million disability-adjusted life years (22.2–24.4) from ischemic heart disease and stroke combined were attributable to this exposure. The population-attributable fractions for deaths were 3.7% (3.4–4.0) for ischemic heart disease and 6.9% for stroke (6.4–7.5); for disability-adjusted life years they were 5.3% (4.9–5.6) for ischemic heart disease and 9.3% (8.7–9.9) for stroke. Conclusions WHO and ILO estimate exposure to long working hours (≥55 hours/week) is common and causes large attributable burdens of ischemic heart disease and stroke. Protecting and promoting occupational and workers’ safety and health requires interventions to reduce hazardous long working hours.

Interest in fast and easy detection of high-energy radiation (x-, γ-rays and neutrons) is closely related to numerous practical applications ranging from biomedicine and industry to homeland security issues. In this regard, crystals of hybrid halide perovskite have proven to be excellent detectors of x- and γ-rays, offering exceptionally high sensitivities in parallel to the ease of design and handling. Here, we demonstrate that by assembling a methylammonium lead tri-bromide perovskite single crystal (CH3NH3PbBr3 SC) with a Gadolinium (Gd) foil, one can very efficiently detect a flux of thermal neutrons. The neutrons absorbed by the Gd foil turn into γ-rays, which photo-generate charge carriers in the CH3NH3PbBr3 SC. The induced photo-carriers contribute to the electric current, which can easily be measured, providing information on the radiation intensity of thermal neutrons. The dependence on the beam size, bias voltage and the converting distance is investigated. To ensure stable and efficient charge extraction, the perovskite SCs were equipped with carbon electrodes. Furthermore, other types of conversion layers were also tested, including borated polyethylene sheets as well as Gd grains and Gd2O3 pellets directly engulfed into the SCs. Monte Carlo N-Particle (MCNP) radiation transport code calculations quantitatively confirmed the detection mechanism herein proposed.

Based on the reported ion migration under electric field in hybrid lead halide perovskites we have developed a bright, light emitting electrochemical cell with CH3NH3PbBr3 single crystals directly grown on vertically aligned carbon nanotube (VACNT) forests as contact electrodes. Under the applied electric field, charged ions in the crystal drift and accumulate in the vicinity of the electrodes, resulting in an in operando formed p-i-n heterojunction. The decreased interface energy barrier and the strong charge injection due to the CNT tip enhanced electric field, result in a bright green light emission up to 1800 cd/m2 at room temperature (average = 60 cd/m2). Beyond the light emission, this original device architecture points to the possibility of implementing vertically aligned CNTs as electrodes in operationally-stable perovskite-based optoelectronic devices., Comment: 29 pages, 5 figures

We demonstrate that single crystals of methylammonium lead bromide (MAPbBr3) could be grown directly on vertically aligned carbon nanotube (VACNT) forests. The fast-growing MAPbBr3 single crystals engulfed the protogenetic inclusions in the form of individual CNTs, thus resulting in a three-dimensionally enlarged photosensitive interface. Photodetector devices were obtained, detecting low light intensities (~20 nW) from UV range to 550 nm. Moreover, a photocurrent was recorded at zero external bias voltage which points to the plausible formation of a p-n junction resulting from interpenetration of MAPbBr3 single crystals into the VACNT forest. This reveals that vertically aligned CNTs can be used as electrodes in operationally stable perovskite-based optoelectronic devices and can serve as a versatile platform for future selective electrode development., Comment: 16 pages, 3 figures

International audience; The exotic properties of quantum spin liquids (QSLs) have continually been of interest since Anderson’s 1973 ground-breaking idea. Geometrical frustration, quantum fluctuations, and low dimensionality are the most often evoked material’s characteristics that favor the long-range fluctuating spin state without freezing into an ordered magnet or a spin glass at low temperatures. Among the few known QSL candidates, organic crystals have the advantage of having rich chemistry capable of finely tuning their microscopic parameters. Here, we demonstrate the emergence of a QSL state in [EDT-TTF-CONH2]2+[BABCO−] (EDT-BCO), where the EDT molecules with spin-1/2 on a triangular lattice form layers which are separated by a sublattice of BCO molecular rotors. By several magnetic measurements, we show that the subtle random potential of frozen BCO Brownian rotors suppresses magnetic order down to the lowest temperatures. Our study identifies the relevance of disorder in the stabilization of QSLs.

Detection and direct power conversion of high energy and high intensity ionizing radiation could be a key element in next generation nuclear reactor safety systems and space-born devices. For example, the Fukushima catastrophe in 2011 could have been largely prevented if 1\% of the reactor's remnant radiation ($\gamma$-rays of the nuclear fission) were directly converted within the reactor to electricity to power the water cooling circuit. It is reported here that the hybrid halide perovskite methylammonium lead triiodide could perfectly play the role of a converter. Single crystals were irradiated by a typical shut-down $\gamma$-spectrum of a nuclear reactor with 7.61E14 Bq activity exhibit a high-efficiency of $\gamma$-ray to free charge carrier conversion with radiation hardening. The power density of 0.3 mW/kg of methylammonium lead triiodide at 50 Sv/h means a four times higher efficiency than that for silicon-based cells. The material was stable to the limits of the experiment without changing its performance up to 100 Sv/h dose rate and 57 Sv H*(10) ambient total $\gamma$-dose. Moreover, the {\gamma}-shielding performance of methylammonium lead triiodide was found to be superior to both ordinary and barite concrete.

Chemical modification such as intercalation or doping of novel materials is of great importance for exploratory material science and applications in various fields of physics and chemistry. Herein, the systematic intercalation of chemically exfoliated few-layer graphene with potassium is reported while monitoring the sample resistance using microwave conductivity. It is found that the conductivity of the samples increases by about an order of magnitude upon potassium exposure. The increased number of charge carriers deduced from the electron spin resonance (ESR) intensity also reflects this increment. The doped phases exhibit two asymmetric Dysonian lines in ESR, a usual sign of the presence of mobile charge carriers. The width of the broader component increases with the doping steps; however, the narrow components seem to have a constant line width.

The performance of organic–inorganic metal halide perovskites-based (MHPs) photovoltaic devices critically depends on the design and material properties of the interface between the light-harvesting MHP layer and the electron transport layer (ETL). Therefore, the detailed insight into the transfer mechanisms of photogenerated carriers at the ETL/MHP interface is of utmost importance. Owing to its high charge mobilities and well-matched band structure with MHPs, titanium dioxide (TiO2) has emerged as the most widely used ETL material in MHPs-based photovoltaic devices. Here, we report a contactless method to directly track the photo-carriers at the ETL/MHP interface using the technique of low-temperature electron paramagnetic resonance (EPR) in combination with in situ illuminations (Photo-EPR). Specifically, we focus on a model nanohybrid material consisting of TiO2-based nanowires (TiO2NWs) dispersed in the polycrystalline methylammonium lead triiodide (MAPbI3) matrix. Our approach is based on observation of the light-induced decrease in intensity of the EPR signal of paramagnetic Ti3+ ( S = 1 / 2 ) in non-stoichiometric TiO2NWs. We associate the diminishment of the EPR signal with the photo-excited electrons that cross the ETL/MHP interface and contribute to the conversion of Ti3+ states to EPR-silent Ti2+ states. Overall, we infer that the technique of low-temperature Photo-EPR is an effective strategy to study the transfer mechanisms of photogenerated carriers at the ETL/MHP interface in MAPbI3-based photovoltaic and photoelectronic systems.

Most digital information today is encoded in the magnetization of ferromagnetic domains. The demand for ever-increasing storage space fuels continuous research for energy-efficient manipulation of magnetism at smaller and smaller length scales. Writing a bit is usually achieved by rotating the magnetization of domains of the magnetic medium, which relies on effective magnetic fields. An alternative approach is to change the magnetic state directly by acting on the interaction between magnetic moments. Correlated oxides are ideal materials for this because the effects of a small external control parameter are amplified by the electronic correlations. Here, we present a radical method for reversible, light-induced tuning of ferromagnetism at room temperature using a halide perovskite/oxide perovskite heterostructure. We demonstrate that photoinduced charge carriers from the C H 3 N H 3 P b I 3 photovoltaic perovskite efficiently dope the thin L a 0.7 S r 0.3 M n O 3 film and decrease the magnetization of the ferromagnetic state, allowing rapid rewriting of the magnetic bit. This manipulation could be accomplished at room temperature; hence this opens avenues for magnetooptical memory devices.

Recent interest in potassium-doped p-terphenyl has been fueled by reports of superconductivity at Tc values surprisingly high for organic compounds. Despite these interesting properties, studies of the structure–function relationships within these materials have been scarce. Here, we isolate a phase-pure crystal of potassium-doped p-terphenyl: [K(222)]2[p-terphenyl3]. Emerging antiferromagnetism in the anisotropic structure is studied in depth by magnetometry and electron spin resonance. Combining these experimental results with density functional theory calculations, we describe the antiferromagnetic coupling in this system that occurs in all 3 crystallographic directions. The strongest coupling was found along the ends of the terphenyls, where the additional electron on neighboring p-terphenyls antiferromagnetically couple. This delocalized bonding interaction is reminiscent of the doubly degenerate resonance structure depiction of polyacetylene. These findings hint toward magnetic fluctuation-induced superconductivity in potassium-doped p-terphenyl, which has a close analogy with high Tc cuprate superconductors. The new approach described here is very versatile as shown by the preparation of two additional salts through systematic changing of the building blocks., C.N. thanks Sheldon and Dorothea Buckler for their generous support. Support for this research was provided by the Center for Precision Assembly of Superstratic and Superatomic Solids, an NSF MRSEC (award numbers DMR-1420634 and DMR-2011738), and the Air Force Office of Scientific Research (award number FA9550-18-1-0020). R.H.S. acknowledges support from the Columbia Nano Initiative Postdoctoral Fellowship. X.R. acknowledges support from the NSF CAREER award (NSF DMR-1751949). A.K.B. is supported by the Arnold O. Beckman Fellowship in Chemical Sciences. I.S. is supported by the National Science Foundation under award number CHE-1807654. Single-crystal X-ray diffraction was performed at the Shared Materials Characterization Laboratory at Columbia University, maintained using funding from Columbia University for which we are grateful. Work in Lausanne was supported by the Swiss National Science Foundation. Work in Spain was supported by MICIU (Spain) through Grants PGC2018-096955-B-C44 and PGC2018-093863-B-C22 and Generalitat de Catalunya (2017SGR1506 and 2017SGR1289). E.C. acknowledges support from the Spanish MINECO through the Severo Ochoa Centers of Excellence Program (SEV-2015-0496) and P.A. from the Maria de Maeztu Units of Excellence Program (MDM-2017-0767). S.C. was supported by FONDECYT (Chile) through project 11107163.

For a symmetry-consistent theoretical description of the ferroelectric phase of Ba2MnGe2O7 melilite compound, a precise knowledge of its crystal structure is a prerequisite. Here we report results of single-crystal neutron diffraction experiments on Ba2MnGe2O7 at room (300 K) and low (10 K) temperatures. The structural model based on the tetragonal space group P421m describes the Ba2MnGe2O7 symmetry both at room and low temperatures. We found reflections forbidden in the typical P421m melilite-type structure. A comparison of the experimental data collected by means of both thermal and cold neutrons with simulated multiple diffraction patterns allows us to unambiguously demonstrate that forbidden peaks originate from multiple diffraction (Renninger effect) rather than from real symmetry lowering. The precise structural parameters at 300 and 10 K are presented for the first time and compared with those of other magnetoelectric melilite-type germanates.

Simple, rapid, and inexpensive fabrication of self-cleaning glass surfaces based on wet chemical deposition of H2Ti3O7 (trititanate) and subsequent transformation of it into TiO2 (anatase) nanowires on pristine glass surfaces is reported. Despite the low, 55%, surface coverage, the nanowire roughened glass surface showed self-cleaning properties comparable to much thicker, over 100-nm-thick, TiO2 nanoparticle coated glasses. The superwettable surface showed 12° contact angle. Moreover, ultraviolet (UV) and natural light activated photocatalysis remained effective at enhancing the self-cleaning process in the case of the TiO2 nanowire coated glass. Time-resolved study of the water droplet spread in millisecond time scales revealed that capillary forces induced by the random nanowire network significantly enhance the water sheeting effect of these textured glass surfaces. Time-resolved experiments revealed that the spreading velocity of the droplets were enhanced by 19% for the TiO2 nanowire roughened surfa...

The surface of a material is not only a window into its bulk physical properties, but also hosts unique phenomena important for understanding the properties of a solid as a whole. Surface sensitive techniques, like ARPES (Angle-resolved photoemission spectroscopy), STM (Scanning tunneling microscopy), AFM (Atomic force microscopy), pump-probe optical measurements etc. require flat, clean surfaces. These can be obtained by cleaving, which is usually possible for layered materials. Such measurements have proven their worth by providing valuable information about cuprate superconductors, graphene, transition metal dichalcogenides, topological insulators and many other novel materials. Unfortunately, this was so far not the case for the cubic, organo-metallic photovoltaic perovskite which morsels during the cleavage. Here we show a method which results in flat, clean surfaces of CH3NH3PbBr3 which allows surface sensitive measurements, badly needed for the understanding and further engineering of this material family.

We have investigated the optical absorption of metallic and semiconducting carbon nanotubes/CH3NH3PbI3 micro- and nanowire composites. Upon visible light illumination semiconducting carbon nanotube based samples show a photo-induced doping, originating from the charge carriers created in the perovskite while this kind of change is absent in the composites containing metallic nanotubes, due to their strikingly different electronic structure. The response in the nanotubes shows, beside a fast diffusion of photo-generated charges, a slow component similar to that observed in pristine CH3NH3PbI3 attributed to structural rearrangement, and leading to slight, light induced changes of the optical gap of the perovskite. This charge transfer from the illuminated perovskite confirms that carbon nanotubes (especially semiconducting ones) can form efficient charge-transporting layers in the novel organometallic perovskite based optoelectronic devices.

A highly stable nanocomposite of antioxidant activity was developed by immobilization of a superoxide dismutase-mimicking metal complex on copolymer-functionalized nanoclay. The layered double hydroxide (LDH) nanoclays were synthesized and surface modification was performed by adsorbing poly(vinylpyridine-b-methacrylic acid) (PVPMAA). The effect of the adsorption on the charging and aggregation properties was investigated and the copolymer dose was optimized to obtain stable LDH dispersions. The LDH-PVPMAA hybrid particles showed high resistance against salt-induced destabilization in aqueous dispersions. Copper(II)-histamine (Cu(Hsm)(2)) complexes were immobilized via the formation of dative bonds between the metal ions and the nitrogen atoms of the functional groups of the copolymer adsorbed on the particles. Changes in the coordination geometry of the complex upon immobilization led to higher superoxide radical anion scavenging activity than the one determined for the non-immobilized complex. Comparison of superoxide dismutase (SOD)-like activity of the obtained hybrid LDH-PVPMAA-Cu(Hsm)(2) with the nanoclay-immobilized SOD enzyme revealed that the developed composite maintained its activity over several days and was able to function at elevated temperature, while the immobilized native enzyme lost its activity under these experimental conditions. The developed nanocomposite is a promising antioxidant candidate in applications, where high electrolyte concentration and elevated temperature are applied. (C) 2019 Elsevier Inc. All rights reserved.

7 pags., 6 figs., The evolution of the magnetic anisotropy directions has been studied in a magnetite (FeO) thin film grown by infrared pulsed-laser deposition on SrTiO(100):Nb substrate. The magnetic easy axes at room temperature are found along the in-plane 〈100〉 film directions, which means a rotation of the easy axis by 45° with respect to the directions typically reported for bulk magnetite and films grown on single-crystal substrates. Moreover, when undergoing the Verwey transition temperature, T, the easy axis orientation evolves to the 〈110〉 film directions. This anomalous behavior has been demonstrated by measuring first the angular dependence of coercivity and remanence well above and below T by high-resolution vectorial magneto-optical Kerr effect (v-MOKE). Ferromagnetic resonance (FMR) measurements have additionally proven a well-defined fourfold magnetic anisotropy induced during growth with confirmed easy axis directions along 〈100〉 for T > T and 〈110〉 for T < T. These results provide a clear proof of the possibility of tuning magnetic anisotropy in FeO thin films by proper control on the growth parameters and substrate choice., This research was supported by the Regional Government of Madrid through NANOMAGCOST project (P2018/NMT-4321) and by the Spanish Ministry of Economy and Competitiveness (MINECO) through Project CTQ2016-75880-P. M. O. thanks CSIC for contract and E. R. thanks MINECO for the tenure of a Ramón y Cajal contract (No. RYC-2011-08069). The work in Lausanne was supported by the Sinergia grant “Mott physics beyond the Heisenberg model” of the Swiss NSF. The work in BUTE (Hungary) was supported by NKFIH Grant No. K119442 and 2017-1.2.1-NKP-2017-00001, and by the BME-Nanotechnology FIKP grant of EMMI (BME FIKP-NAT). IMDEA Nanoscience is supported by the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D, MINECO [grant number SEV-2016-0686]

A structural study of methyl­ammonium lead triiodide [CH3NH3PbI3 (MAPbI3)], at high pressures up to 20 GPa using noble gases Ne and Ar as pressure-transmitting media is reported. It is found that both noble gases are chemically active at high pressures. In particular, Ne stabilizes the high-pressure structure of NexMAPbI3 and prevents amorphization up to 20 GPa. In contrast, Ar acts as a stabilizer only up to 2.4 GPa and accelerates irreversible amorphization upon further compression., The photovoltaic perovskite, methyl­ammonium lead triiodide [CH3NH3PbI3 (MAPbI3)], is one of the most efficient materials for solar energy conversion. Various kinds of chemical and physical modifications have been applied to MAPbI3 towards better understanding of the relation between composition, structure, electronic properties and energy conversion efficiency of this material. Pressure is a particularly useful tool, as it can substantially reduce the interatomic spacing in this relatively soft material and cause significant modifications to the electronic structure. Application of high pressure induces changes in the crystal symmetry up to a threshold level above which it leads to amorphization. Here, a detailed structural study of MAPbI3 at high hydro­static pressures using Ne and Ar as pressure transmitting media is reported. Single-crystal X-ray diffraction experiments with synchrotron radiation at room temperature in the 0–20 GPa pressure range show that atoms of both gaseous media, Ne and Ar, are gradually incorporated into MAPbI3, thus leading to marked structural changes of the material. Specifically, Ne stabilizes the high-pressure phase of NexMAPbI3 and prevents amorphization up to 20 GPa. After releasing the pressure, the crystal has the composition of Ne0.97MAPbI3, which remains stable under ambient conditions. In contrast, above 2.4 GPa, Ar accelerates an irreversible amorphization. The distinct impacts of Ne and Ar are attributed to differences in their chemical reactivity under pressure inside the restricted space between the PbI6 octahedra.

In article number 2001882, Pavao Andričević, László Forró, and co‐workers introduce the ‘oriented crystal‒crystal intergrowth’ method, yielding solution‐grown MAPbBr(3) crystals with volume and mass of over 1000 cm(3) and 3 kg. Its increased size, equipped with carbon electrodes, is utilized for sensitive gamma ray detection of a (60)Co source at the dose rate up to 2.3 Gy h(−1) at ambient conditions. [Image: see text]

We report Electron Spin Resonance (ESR) measurements on stage-I potassium intercalated graphite (KC$_8$). Angular dependent measurements show that the spin-lattice relaxation time is longer when the magnetic field is perpendicular to the graphene layer as compared to when the magnetic field is in the plane. This anisotropy is analyzed in the framework of the Elliott-Yafet theory of spin-relaxation in metals. The analysis considers an anisotropic spin-orbit Hamiltonian and the first order perturbative treatment of Elliott is reproduced for this model Hamiltonian. The result provides an experimental input for the first-principles theories of spin-orbit interaction in layered carbon and thus to a better understanding of spin-relaxation phenomena in graphene and in other layered materials as well.

Hybrid halide perovskite photovoltaic materials show a remarkable light conversion efficiency in various optoelectronic devices. In the fabrication of these solar cells, light emitting diodes, laser and photodetector prototypes the thickness of the perovskite is an important parameter since the light is absorbed within a thin layer of a few hundred nanometers. Nevertheless, making perovskite coatings with various solution-based and evaporation methods showing highly reproducible thickness and area coverage is still an issue. Therefore, rapid and reliable quality-control of the film morphology is needed. This report shows a simple, rapid, and calibration-free method for reading the thickness directly from the color map of nanowire perovskite films seen in standard optical microscope with visible light. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In the antiferromagnetic ground state, belowTN≃ 5.7 K, Ca2CoSi2O7exhibits strong magnetoelectric coupling. For a symmetry-consistent theoretical description of this multiferroic phase, precise knowledge of its crystal structure is a prerequisite. Here we report the results of single-crystal neutron diffraction on Ca2CoSi2O7at temperatures between 10 and 250 K. The low-temperature structure at 10 K was refined assuming twinning in the orthorhombic space groupP21212 with a 3 × 3 × 1 supercell [a= 23.52 (1),b= 23.52 (1),c= 5.030 (3) Å] compared with the high-temperature normal state [tetragonal space group P\overline {4}2_{1}m,a=b≃ 7.86,c≃ 5.03 Å]. The precise structural parameters of Ca2CoSi2O7at 10 K are presented and compared with the literature X-ray diffraction results at 130 and 170 K (low-temperature commensurate phase), as well as at ∼ 500 K (high-temperature normal phase).

For a symmetry-consistent theoretical description of the ferroelectric phase of Ba

We report a systematic study of the mechanical response of methylammonium lead triiodide CH3NH3PbI3 nanowires by employing bending measurements using atomic force microscope on suspended wires over photo-lithographically patterned channels. Force-deflection curves measured at room temperature give a Young's modulus between 2 and 14 GPa. This broad range of values is attributed to the variations in the microcrystalline texture of halide perovskite nanowires. The mechanical response of a highly crystalline nanowire is linear with force and has a brittle character. The braking modulus of 48 ± 20 MPa corresponds to 100 μm of radius of curvature of the nanowires, rendering them much better structures for flexible devices than spin coated films. The measured moduli decrease rapidly if the NW is exposed to water vapor. Published version

We demonstrate that single crystals of methylammonium lead bromide (MAPbBr3) could be grown directly on vertically aligned carbon nanotube (VACNT) forests.[1] The fast-growing MAPbBr3 single crystals engulfed the protogenetic inclusions in the form of individual CNTs, thus resulting in a three- dimensionally enlarged photosensitive interface. Photodetector devices were obtained, detecting low light intensities (~20 nW) from UV range to 550 nm. Moreover, a photocurrent was recorded at zero external bias voltage which points to the plausible formation of a p-n junction resulting from interpenetration of MAPbBr3 single crystals into the VACNT forest. Moreover, bright green electroluminescence of the MAPbBr3 single crystals, using symmetrical VACNT electrodes, was observed at room temperature for both polarities.[2] The electroluminescence spectra and light intensity was recorded from room temperature to cryogenic temperatures (20 K). The underlying mechanism behind the light emission is the well documented ion migration. In fact charged ions or vacancies inside the perovskite, drift under an external electric field accumulating at the cathode and anode, forming a p-i-n heterojunction structure. These characteristics have a strong similarity with the operational mechanism of polymer light- emitting electrochemical cells (LECs), especially the device structure and the involvement of mobile ions for efficient electroluminescence. This reveals that vertically aligned CNTs can be used as electrodes in operationally stable perovskite- based optoelectronic devices and can serve as a versatile platform for future selective electrode development.

We report on photocurrent generation by X-ray irradiation in methylammonium lead iodide CH3NH3PbI3 single crystals. We observed 75% of charge collection efficiency in millimeter sized samples. This efficiency is partially due to the high photon absorption coefficient and X-ray beam stopping power of our lead containing material. The material shows a less than 20% decrease in its performance up to 40 Sv of total X-ray dose, which represents a very good stability. Moreover, our Monte Carlo N-Particle Transport calculations indicate that energetic particle radiation can also be harvested by CH3NH3PbI3. These properties are compared to CH3NH3SnI3 and PbI2. The possible application of these advantageous properties could be in simultaneous radiation protection and direct electricity production in environments with highly energetic background radiation.

We study the vibrational, magnetic and transport properties of Few Layer Graphene (FLG) using Raman and electron spin resonance spectroscopy and microwave conductivity measurements. FLG samples were produced using wet chemical exfoliation with different post-processing, namely ultrasound treatment, shear mixing, and magnetic stirring. Raman spectroscopy shows a low intensity D mode which attests a high sample quality. The G mode is present at 1580 cm(-1) as expected for graphene. The 2D mode consists of 2 components with varying intensities among the different samples. This is assigned to the presence of single and few layer graphene in the samples. Electron Spin Resonance (ESR) spectroscopy shows a main line in all types of materials with a width of about 1 mT and a g-factor in the range of 2.005-2.010. Paramagnetic defect centers with a uniaxial g-factor anisotropy are identified, which shows that these are related to the local sp2 bonds of the material. All kinds of investigated FLGs have a temperature dependent resistance which is compatible with a small gap semiconductor. The difference in resistance is related to the different grain size of the samples. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Single crystals of WS2 were prepared by chemical vapor transport method using sulfur as a transport agent. Measurements of electrical resistivity, Seebeck coefficient and thermal conductivity as a function of temperature, along the in-plane and the out-of-plane directions reveal distinct trends. In our interpretation these differences are mainly due to the different nature of the chemical bonding in the two directions and to the presence of impurity intercalates in between the planes. (C) 2015 Elsevier Ltd. All rights reserved.

We have investigated the optical absorption of metallic and semiconducting carbon nanotubes/CH

We report magnetic and thermodynamic properties of a 4d1 (Mo5+) magnetic insulator MoOPO4 single crystal, which realizes a J1−J2 Heisenberg spin-1/2 model on a stacked square lattice. The specific-heat measurements show a magnetic transition at 16 K which is also confirmed by magnetic susceptibility, ESR, and neutron diffraction measurements. Magnetic entropy deduced from the specific heat corresponds to a two-level degree of freedom per Mo5+ ion, and the effective moment from the susceptibility corresponds to the spin-only value. Using ab initio quantum chemistry calculations, we demonstrate that the Mo5+ ion hosts a purely spin-1/2 magnetic moment, indicating negligible effects of spin-orbit interaction. The quenched orbital moments originate from the large displacement of Mo ions inside the MoO6 octahedra along the apical direction. The ground state is shown by neutron diffraction to support a collinear Neel-type magnetic order, and a spin-flop transition is observed around an applied magnetic field of 3.5 T. The magnetic phase diagram is reproduced by a mean-field calculation assuming a small easy-axis anisotropy in the exchange interactions. Our results suggest 4d molybdates as an alternative playground to search for model quantum magnets.

Detailed investigation of ${\mathrm{Ca}}_{2}{\mathrm{CoSi}}_{2}{\mathrm{O}}_{7}$ was performed in its low-temperature magnetoelectric state combining neutron diffraction with magnetization measurements on single crystals. The crystal and magnetic structures well below the antiferromagnetic transition temperature of ${T}_{\text{N}}\ensuremath{\approx}5.7$ K were determined using neutron diffraction. Neutron diffraction data imply no structural phase transition from 10 K down to 2.5 K and are well described within the orthorhombic space group $P{2}_{1}{2}_{1}2$ with a $3\ifmmode\times\else\texttimes\fi{}3\ifmmode\times\else\texttimes\fi{}1$ supercell compared with the high-temperature unmodulated state (tetragonal space group $P\overline{4}{2}_{1}m$). We found that in zero magnetic field the magnetic space group is $P{2}_{1}{2}_{1}^{\ensuremath{'}}{2}^{\ensuremath{'}}$ with antiferromagnetic order along the [100] or [010] axes for two types of ${90}^{\ensuremath{\circ}}$ twin domains, while neighboring spins along the [001] axis are ordered ferromagnetically. A noncollinear spin arrangement due to small canting within the $ab$ plane is allowed by symmetry and leads to the existence of the tiny spontaneous magnetization below ${T}_{\text{N}}$. The ordered moment with a magnitude of about 2.8 ${\ensuremath{\mu}}_{\text{B}}/{\mathrm{Co}}^{2+}$ at 2.5 K lies in the $ab$ plane. Distinct differences between the magnetic structure of ${\mathrm{Ca}}_{2}{\mathrm{CoSi}}_{2}{\mathrm{O}}_{7}$ as compared to those of ${\mathrm{Ba}}_{2}{\mathrm{CoGe}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Sr}}_{2}{\mathrm{CoSi}}_{2}{\mathrm{O}}_{7}$ are discussed.

Here we report another surprising feature of the methylammonium metal halide material family, the phototunability of the diode response of a heterojunction made of CH

We report on the mechanical properties of CH3NH3PbI3 photovoltaic perovskite measured by nanoindentation. The Young's modulus (E) of the pristine sample is 20.0 ± 1.5 GPa, while the hardness (H) is 1.0 ± 0.1 GPa. Upon extended exposure to water vapor, both quantities decrease dramatically and the sample changes color from silver-black to yellow. Calculations based on density functional theory support this trend in the mechanical response. Chemical treatment of the degraded crystal in methylammonium iodide solution recovers the color of the pristine sample and the values of E and H within 50%.

The electron spin lifetime in an assembly of chemically synthesized graphene sheets was found to be extremely sensitive to oxygen. Introducing small concentrations of physisorbed O-2 onto the graphene surface reduced the exceptionally long 140 ns electron spin lifetime by an order of magnitude. This effect was completely reversible: Removing the O-2 by using a dynamic vacuum restored the spin lifetime. The presence of covalently bound oxygen also decreased the electron spin lifetime in graphene, although to a far lesser extent compared to physisorbed O-2. The conduction electrons in graphene were found to play a significant role by counter-balancing the spin depolarization caused by oxygen molecules. Our results highlight the importance of chemical environment control and device packing in practical graphene-based spintronic applications.

Graphene is theoretically expected to be a highly suitable material for spintronic and quantum computation applications. Current experimental reports assign surprisingly low spin lifetimes to graphene and related carbon structures. Recently, we showed a solvothermal synthesis method that can be employed to produce a high-purity sample, which approximates very well the assembly of graphene sheets. Using the contactless spectroscopic technique of electron spin resonance (ESR), we were able to identify in this graphene material the ESR of both conduction electrons and localized spins [Nafradi et al., Carbon 74, 346-351 (2014)]. Here, we show the temperature dependent evolution of the ESR of these two spin species. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Alkali intercalated graphite compounds represent a compelling modification of carbon with significant application potential and various fundamentally important phases. We report on the intercalation of graphite with alkali atoms (Li and K) using liquid ammonia solution as mediating agent. Alkali atoms dissolve well in liquid ammonia which simplifies and speeds up the intercalation process, and it also avoids the high temperature formation of alkali carbides. Optical microscopy, Raman, and electron spin resonance spectroscopy attest that the prepared samples are highly and homogeneously intercalated to a level approaching Stage-I intercalation compounds. The method and the synthesis route may serve as a starting point for the various forms of alkali atom intercalated carbon compounds (including carbon nanotubes and graphene), which could be exploited in energy storage and further chemical modifications.