Abstract: Luminescent copper indium sulfide (CIS) nanocrystals are a potential solution to the toxicity issues associated with Cd- and Pb-based nanocrystals. However, the development of high-quality CIS nanocrystals has been complicated by insufficient knowledge of the electronic structure and of the factors that lead to luminescence quenching. Here we investigate the exciton decay pathways in CIS nanocrystals using time resolved photoluminescence and transient absorption spectroscopy. Core-only CIS nanocrystals with low quantum yield are compared to core/shell nanocrystals (CIS/ZnS and CIS/CdS) with higher quantum yield. Our measurements support the model of photoluminescence by radiative recombination of a conduction band electron with a localized hole. Moreover, we find that photoluminescence quenching in low-quantum-yield nanocrystals involves initially uncoupled decay pathways for the electron and hole. The electron decay pathway determines whether the exciton recombines radiatively or nonradiatively. The development of high-quality CIS nanocrystals should therefore focus on the elimination of electron traps.

Abstract: Motivated by two-band superconductivity in, e.g., borides and pnictides, starting from the two-band Ginzburg-Landau energy functional, we discuss how the presence of two order parameters and the coupling between them influence a superconducting ring in the fluctuative regime. Our method is an extension of the von OppenRiedel formalism for rings; it is exact, but requires numerical implementation. We also study approximations for which analytic expressions can be obtained, and check their ranges of validity. We provide estimates for the temperature ranges where fluctuations are important, calculate the persistent current in MgB2 rings as a function of temperature and enclosed flux, and point out its additional dependence on the cross-section area of the wire from which the ring is made. We find temperature regions in which fluctuations enhance the persistent currents and regions where they inhibit the persistent current. The presence of two order parameters that can fluctuate independently always leads to larger averages of the order parameters at Tc, but yields larger persistent current only for appropriate parameters. In cases of very different material parameters for the two coupled condensates, the persistent current is inhibited.

Abstract: Multishell carbon nanotubules are studied by means of diffraction contrast dark field images. This results in an electron microscopy method for the determination of the sign of the chiral angles in carbon nanotubes. The method is justified by a reasoning either in direct space or in diffraction space. We also investigate a carbon nanotubule exhibiting a bend and we confront the observations with the heptagon-pentagon pair model.

Abstract: End-group-functionalized hyperbranched polymers were synthesized to act as a carbon nanotube (CNT) surfactant in aqueous solutions. Variation of the percentage of triphenylmethyl (trityl) functionalization and of the molar mass of the hyperbranched polyglycerol (PG) core resulted in the highest measured surfactant efficiency for a 5000 g/mol PG with 5.6% of the available hydroxyl end-groups replaced by trityl functions, as shown by UV-vis measurements. Semiempirical model calculations suggest an even higher efficiency for PG5000 with 2.5% functionalization and maximal molecule specific efficiency in general at low degrees of functionalization. Addition of trityl groups increases the surfactant-nanotube interactions in comparison to unfunctionalized PG because of pi-pi stacking interactions. However, at higher functionalization degrees mutual interactions between trityl groups come into play, decreasing the surfactant efficiency, while lack of water solubility becomes an issue at very high functionalization degrees. Low molar mass surfactants are less efficient compared to higher molar mass species most likely because the higher bulkiness of the latter allows for a better CNT separation and stabilization. The most efficient surfactant studied allowed dispersing 2.85 mg of CNT in 20 mL with as little as 1 mg of surfactant. These dispersions, remaining stable for at least 2 months, were mainly composed of individual CNTs as revealed by electron microscopy.

Abstract: We present an efficient method for the quantification of crystalline versus amorphous phase content in mesoporous materials, making use of electron energy loss spectroscopy. The method is based on fitting a superposition of core-loss edges using the maximum likelihood method with measured reference spectra. We apply the method to mesoporous TiO2 samples. We show that the absolute amount of the crystalline phase can be determined with an accuracy below 5%. This method takes also the amorphous phase into account, where standard X-ray diffraction is only quantitative for crystalline phases and not for amorphous phase. (c) 2006 Elsevier B.V.. All rights reserved.

Abstract: The use of synchrotron radiation techniques to study cultural heritage and archaeological materials has undergone a steep increase over the past 10-15 years. The range of materials studied is very broad and encompasses painting materials, stone, glass, ceramics, metals, cellulosic and wooden materials, and a cluster of organic-based materials, in phase with the diversity observed at archaeological sites, museums, historical buildings, etc. Main areas of investigation are: (1) the study of the alteration and corrosion processes, for which the unique non-destructive speciation capabilities of X-ray absorption have proved very beneficial, (2) the understanding of the technologies and identification of the raw materials used to produce archaeological artefacts and art objects and, to a lesser extent, (3) the investigation of current or novel stabilisation, conservation and restoration practices. In terms of the synchrotron methods used, the main focus so far has been on X-ray techniques, primarily X-ray fluorescence, absorption and diffraction, and Fourier-transform infrared spectroscopy. We review here the use of these techniques from recent works published in the field demonstrating the breadth of applications and future potential offered by third generation synchrotron techniques. New developments in imaging and advanced spectroscopy, included in the UV/visible and IR ranges, could even broaden the variety of materials studied, in particular by fostering more studies on organic and complex organic-inorganic mixtures, while new support activities at synchrotron facilities might facilitate transfer of knowledge between synchrotron specialists and users from archaeology and cultural heritage sciences.

Abstract: Lanthanum carbonate is a new phosphate binder that is poorly absorbed from the gastrointestinal tract and eliminated largely by the liver. After oral treatment, we and others had noticed 23 fold higher lanthanum levels in the livers of rats with chronic renal failure compared to rats with normal renal function. Here we studied the kinetics and tissue distribution, absorption, and subcellular localization of lanthanum in the liver using transmission electron microscopy, electron energy loss spectrometry, and X-ray fluoresence. We found that in the liver lanthanum was located in lysosomes and in the biliary canal but not in any other cellular organelles. This suggests that lanthanum is transported and eliminated by the liver via a transcellular, endosomal-lysosomal-biliary canicular transport route. Feeding rats with chronic renal failure orally with lanthanum resulted in a doubling of the liver levels compared to rats with normal renal function, but the serum levels were similar in both animal groups. These levels plateaued after 6 weeks at a concentration below 3 g/g in both groups. When lanthanum was administered intravenously, thereby bypassing the gastrointestinal tract-portal vein pathway, no difference in liver levels was found between rats with and without renal failure. This suggests that there is an increased gastrointestinal permeability or absorption of oral lanthanum in uremia. Lanthanum levels in the brain and heart fluctuated near its detection limit with long-term treatment (20 weeks) having no effect on organ weight, liver enzyme activities, or liver histology. We suggest that the kinetics of lanthanum in the liver are consistent with a transcellular transport pathway, with higher levels in the liver of uremic rats due to higher intestinal absorption.

Abstract: SmFe8.75 Si-0.25 C/alpha-Fe nanocomposites have been successfully synthesized using high energy milling, followed by annealing at 750 degrees C. The crystal structure of these compounds was characterized by the Rietveld method using powder X-ray diffraction data. By increasing the concentration of Sm, we observed a decrease in the amount of alpha-Fe phase. The morphology of the samples was determined by scanning and transmission electron microscopy. The average grain size is about 20 nm. The magnetic properties were investigated at room temperature and at 10 K. A ferromagnetic behavior was observed in all samples at both temperatures. An increase of the soft magnetic phase alpha-Fe induced an increase in the magnetization and a decrease in coercivity. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: Single crystals of Ln5Ru2O12 (Ln=Pr, Nd, SmTb) were grown out of either NaOH or KOH fluxes in sealed silver tubes. The crystals of all the phases were observed to be twinned as confirmed by TEM studies. The series crystallize in the C2/m monoclinic system with lattice parameters, a=12.4049(4)12.7621(6) Å, b=5.8414(2)5.9488(3) Å, c=7.3489(2)7.6424(4) Å, β=107.425(3)107.432(2)° and Z=2. The crystal structure is isotypic with the defect/disorder model of Ln5Re2O12 (Ln = Y, Gd) and consists of one dimensional edge shared RuO6 octahedral chains separated by a two dimensional LnOx polyhedral framework. Magnetic measurements indicate paramagnetic and antiferromagnetic behavior for Ln=Nd, SmGd and Ln=Tb, respectively.

Abstract: The addition of potassium thiocyanate (KSCN) to the FAPbBr3 structure and subsequent post-treatment of nanocrystals (NCs) lead to high quantum confinement, resulting in a photoluminescent quantum yield (PLQY) approaching unity and microsecond decay times. This synergistic approach demonstrated exceptional stability under humid conditions, retaining 70% of the PLQY for over a month, while the untreated NCs degrade within 24 h. Additionally, the devices incorporating the post-treated NCs displayed 1.5% external quantum efficiency (EQE), a 5-fold improvement over untreated devices. These results provide promising opportunities for the use of perovskites in moisture-stable optoelectronics.

Abstract: Binary ZrCu nanocomposite amorphous films are synthetized by pulsed laser deposition (PLD) under vac-uum (2 x 10-3 Pa) and 10 Pa He pressure, leading to fully amorphous compact and nanogranular mor-phologies, respectively. Then, post-thermal annealing treatments are carried out to explore thermal stability and crystallization phenomena together with the evolution of mechanical properties. Compact films exhibit larger thermal stability with partial crystallization phenomena starting at 420 degrees C, still to be completed at 550 degrees C, while nanogranular films exhibit early-stage crystallization at 300 degrees C and com-pleted at 485 degrees C. The microstructural differences are related to a distinct evolution of mechanical