Two dimensional dipolar coupling in monolayers of silver and gold nanoparticles on a dielectric substrate

The dimensionality of assembled nanoparticles plays an important role in their optical and magnetic properties, via dipolar effects and the interaction with their environment. In this work we develop a methodology for distinguishing between two (2D) and three (3D) dimensional collective interactions on the surface plasmon resonance of assembled metal nanoparticles. Towards that goal, we elaborate different sets of Au and Ag nanoparticles as suspensions, random 3D arrangements and well organized 2D arrays. Then we model their scattering cross-section using effective field methods in dimension n, including interparticle as well as particle-substrate dipolar interactions. For this modelling, two effective field medium approaches are employed, taking into account the filling factors of the assemblies. Our results are important for realizing photonic amplifier devices

Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H2O)] with Ln = Eu3+, Gd3+, Tb3+ , Dy3+ , Ho3+ and Yb3+ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO3)(3)center dot xH(2)O with the 1,3-bis(carboxymethyl)imidazolium [HE] ligand and oxalic acid (H(2)ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb1-xEux(L)(ox)(H2O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb3+ and Eu3+ . The best sensitivities were obtained using the ratio between the emission intensities of Eu3+ (D-5(0) -> F-7(2) transition) and of the ligand as the thermometric parameter. [Tb0.97Eu0.03 (L)(ox)(H2O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%.K-1 at 340 K

Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers

Modern humans have populated Europe for more than 45,000 years1,2. Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period3. Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe4, but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants

Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers

Modern humans have populated Europe for more than 45,000 years(1,2). Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period(3). Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe(4), but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants.Molecular Technology and Informatics for Personalised Medicine and Healt

Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers

Modern humans have populated Europe for more than 45,000 years. Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period. Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe, but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants.Archaeological Heritage Managemen

Investigation of KBiFe2O5 as a Photovoltaic Absorber

International audienceKBiFe 2 O 5 (KBFO) was grown by pulsed laser deposition (PLD) on SrTiO 3 (001) (STO), 1 at% Nb-SrTiO 3 (001) (Nb-STO) and MgAl 2 O 4 (001) (MAO). In the case of MAO substrate, epitaxial growth is obtained. As its bandgap is relatively low (1.6 eV in the bulk), KBFO is a promising candidate for oxide photovoltaics. In this work we examine the growth of KBFO by PLD by looking at its structure and composition and we investigate the optical properties of the films obtained. A photovoltaic architecture based on KBFO films is proposed and a solar cell behaviour based on KBFO absorber is obtained

Salts and Solvents Effect on the Crystal Structure of Imidazolium Dicarboxylate Salt Based Coordination Networks

The solvothermal synthesis of novel metal–organic networks from the 1,3-bis(carboxymethyl)-imidazolium chloride ([H2L][Cl]) and cobalt or nickel salts (acetate or nitrate) in different solvents (water or ethanol and water/ethanol or water/ethylene glycol mixture) has been explored leading to four isotypic compounds of general formula [M(L)(H2O)4][Cl]·Solv with M = Ni or Co and Solv = H2O for 1 and 2, respectively, and M = Ni or Co and Solv = (EG)0.5 for 3 and 4, respectively, and two other isostructural compounds, namely, [Ni(L)(ox)0.5(μ2-H2O)0.5] (5) and [Co(L)(ox)0.5(μ2-H2O)0.5] (6) where the in situ formation of oxalate (ox) was observed. The structural characterizations evidence a significant influence of the solvent as well as of the metal salt on the structure and crystallinity of the final compounds, the former leading to observation of different magnetic behaviors. A one-dimensional antiferromagnetic behavior is thus observed in compounds 5 and 6 containing oxalate ligand while compounds 1–4 exhibited typical behavior of quasi-isolated magnetic species

Influence of the Carbo-Chromization Process on the Microstructural, Hardness, and Corrosion Properties of 316L Sintered Stainless Steel

We report on the changes on the microstructural, hardness, and corrosion properties induced by carbo-chromization of 316L stainless steel prepared by Spark Plasma Sintering technique. The thermo-chemical treatments have been performed using pack cementation. The carburizing and chromization were carried out between 1153 K (880 A degrees C)/4 h to 1253 K (980 A degrees C)/12 h and 1223 K (950 A degrees C)/6 h to 1273 K (1000 A degrees C)/12 h in a solid powder mixture of charcoal/BaCO3 and ferrochromium/alumina/NH4Cl, respectively. The obtained layers were investigated using X-ray and electron diffraction, optical and scanning electron microscopies, Vickers micro-hardness, and potentiodynamic measurements. The thickness of the carbo-chromized layer ranges between 300 and 500 mu m. Besides the host gamma-phase, the layers are mainly constituted of carbides (Fe7C3, Cr23C6, Cr7C3, and Fe3C) and traces of alpha'-martensite. The average hardness values decrease smoothly from 650 HV at the sample surface down to 200 HV at the center of the sample. The potentiodynamic tests revealed that the carbo-chromized samples have smaller corrosion resistance with respect to the untreated material. For strong chromization regimes, the corrosion rate is increased by a factor of four with respect to that of the untreated material, while the micro-hardness of the layer is three times larger. Such materials are suited to be used in environments where good corrosion resistance and wear properties are required

Layered Simple Hydroxides Functionalized by Fluorene-Phosphonic Acids: Synthesis, Interface Theoretical Insights, and Magnetoelectric Effect

International audienceCopper- and cobalt-based layered simple hydroxides (LSH) are successfully functionalized by a series of fluorene mono- and diphosphonic acids, using anionic exchange reactions and a preintercalation strategy. The lateral functionalization of the fluorene moieties has only little impact on the overall structure of the obtained layered hybrid materials but it influences the organization of the molecules within the interlamellar spacing. For bulky fluorene (9,9-dioctyl derivative), luminescence is preserved when inserted into copper and cobalt hydroxydes, whereas it is completely quenched for the other fluorenes. Detailed characterization of the internal structure and chemical bonding properties for copper- and cobalt-based hybrids is performed via ancillary experimental techniques. For the copper-based LSH class, for which more elusive findings are found, first-principles molecular dynamics simulations unravel the fundamental stabilizing role of the H-bonding network promoted within the local environments of the fluorene mono- and diphosphonic acids. The cobalt series of compounds constitute a new class of hybrid magnets, with ordering temperatures ranging from 11.8 to 17.8 K and show a clear magnetoelectric effect. This effect appears above a threshold magnetic field, which is null below the magnetic ordering temperature, and it persists in the paramagnetic regime till about 110 K

Structural, optical, spectroscopic and electrical properties of Mo-doped ZnO thin films grown by radio frequency magnetron sputtering

Undoped and Mo-doped ZnO (2% Mo) films about 1 mu m thick were deposited by radio-frequency magnetron sputtering on Si(100) and glass substrates at 30 and 300 degrees C. X-ray diffraction patterns show that all films exhibit the hexagonal wurtzite crystal structure with a preferred orientation of the crystallites along the [002] direction. Plane view and cross-section transmission electron microscopy observations showed that the films present a columnar growth. Rutherford backscattering spectrometry indicates that Mo is homogeneously distributed inside the films. Scanning electron microscopy and atomic force microscopy show that Mo doping leads to a reduction of the grain size and surface roughness. According to X-ray photoelectron spectroscopy measurements, the valence of the Mo ions in the ZnO matrix is +5 and +6. Optical measurements in the UV-Visible range show a transmittance increasing from about 60 to 80% when increasing the wavelength from 400 to 800 nm. A sharp absorption onset is observed at about 375 nm corresponding to the fundamental absorption edge of ZnO at 3.26 eV. This gap value remains unchanged upon Mo doping. The Hall effect measurements carried out at room temperature show that both undoped and Mo-doped ZnO films present an n-type conduction. The 2% Mo doping increases the carrier concentration and decreases the resistivity measured in pure ZnO by about three orders of magnitude. A comparison with 2% Al-doped ZnO films grown in the same conditions underlines the important role of the preparation conditions on the transport properties of ZnO based transparent conductive oxides. (C) 2014 Elsevier B.V. All rights reserved