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International audience; Aluminium oxide (Al 2 O 3) films were deposited on silicon substrates using plasma-enhanced atomic layer de-position (PE-ALD) technique with tri-methyl-aluminium TMA (Al(CH 3) 3) and dioxygen (O 2) as precursors. PE-ALD experiments were performed in order to (i) investigate the interfacial properties between the silicon sub-strate and the alumina layer, and (ii) understand the impact of growth and crystallization phenomena on the Al 2 O 3 films properties (structural, optical, mechanical, dielectric and etch). The formation of oxide-based transition layers, either silicon oxide SiO 2 and/or aluminosilicate Al x Si y O, was evidenced for the TMA/O 2 PE-ALD process. Based on these results, it appears that no substrate-enhanced growth occurs at the early stages of the growth process, as assumed in previous reports. Thus, constant growth rate (0.08 nm per cycle) and re-fractive index (1.64 at a 450 nm wavelength) were obtained for the Al 2 O 3 layer deposited at 300 °C. Finally, thermal annealing experiments were performed on these films, evidencing the influences of atomic structural rearrangement and crystallization on the Al 2 O 3 film main characteristics: interface steepness, atomic structure, refractive index, residual stress, dielectric constant and etch rate.

Samples containing a majority of either single-wall carbon nanotubes (SWCNTs) or double-walled carbon nanotubes (DWCNTs) are prepared in the same catalytic chemical vapor deposition conditions but using slightly different catalytic materials, based on alumina impregnated with iron and molybdenum salts. There is a sharp SWCNTs-to-DWCNTs transition. By contrast to the usual findings, the selectivity is not correlated to the size of the iron-based catalyst nanoparticles, nor does the transition occur upon a decreasing carbon/catalyst ratio. The result is attributed to the increasing MoO3 concentration inducing modifications of the gas atmosphere, such as the formation of more reactive C2 species through C2H4 dissociation, which thus favors the nucleation and growth of a DWCNT. In the DWCNT sample, the average diameter of the SWCNTs is higher than the average outer diameter of the DWCNTs, which is uncommon, as many authors stress that SWCNTs show a lower diameter than DWCNTs. The study could provide guidelines for the synthesis of very small diameter DWCNTs.

International audience; A variety of iodine-based one-dimensional (1-D) nanocrystals were introduced into double-wall carbon nanotubes (DWCNTs) using the molten phase method, as an intermediate step for ultimately obtaining encapsulated metal nanowires. Based on high-resolution transmission electron microscopy (HRTEM) observations using different imaging modes (bright field, dark field, and scanningTEM)and associated analytical tools (electron energy loss spectroscopy), it is revealed that the reality of nanotube filling is much more complex than expected. For some iodides (typically NiI2 ), earlier decomposition during the filling step was observed, which could not be anticipated from the known data on the bulk material. Other filling materials (e.g., iodine) show a variety of atomic structuration inside and outside the CNTs, which is driven by the available space being filled. Most of the encapsulated structures were confirmed by modeling

Tailoring carbon nanomaterials for specificap-plicationsis of great importance in the quest to improve the properties of these materials and hence increase their functionality. Using a simple and easy to apply technique Zinc,Zinc oxide and Iodine were encapsulated and con-finedwithin double walled carbon nanotubes whose internal diameter ranges from 1.2to2.5 nm.The simultaneous confinement of Zinc and Iodine was shown to improve the sensitiv-ity by 100 times whileat the same time en-hancing the selectivity of DWNTs towards formaldehyde. By exploiting the p-doping effect of Iodine, CNTs networks were engineered to differentiate formaldehyde from ethanol and acetone, some of the common volatile organic compounds.The ability to tune the chemical selectivity and sensitivity of carbon nanotubes based sensors through inner encapsulation of a specific material thus appears as a new possible route compared to more conventional outer surface functionalization

International audience; The (Y,REE,U,Th)–(Nb,Ta,Ti) oxides, like euxenite, fergusonite, pyrochlore, zirconolite, are known to contain nanometric spherical cavities or bubbles, interpreted to contain radiogenic helium. In-situ analyses by Scanning Transmission Electron Microscopy (STEM) coupled with Electron Energy Loss Spectroscopy (EELS) inside nano-bubbles from an euxenite crystal, sampled in its host c. 920 Ma old pegmatite in Norway, deliver, for the first time, a positive identification of helium and an estimation of helium pressure in such bubbles. The chemically unaltered euxenite crystal proves amorphous and homogeneously speckled with bubbles ranging from 5 to 68 nm in diameter, around a log-normal distribution centered at 19 nm. The euxenite contains 9.87 wt% UO2 and 3.15 wt% ThO2. It accumulated a theoretical alpha-decay dose of (i.e. 170 He/nm3), at a dose rate of . This corresponds to production of 0.23 wt% He. The density of helium inside the bubbles, estimated from EELS data, ranges from 2 to 45 He/nm3, leading to a pressure of 8 to 500 MPa. The proportion of produced helium trapped in bubbles is about 10%. Helium bubbles clearly influence helium diffusion. They may contribute to the swelling of euxenite during amorphization and to the fracturing of the host rock. Our results suggest that dose, dose rate and structural state seem to be important parameters for the nucleation, growth and coalescence of helium bubbles but also demonstrate the crucial need of experimental studies to be able to develop a predictive model of the long term behavior of materials in response to helium irradiation. Furthermore, chemical alteration of euxenite, here materialized by fluid driven dissolution–precipitation towards silica bearing euxenite, removes the bubbles and mobilizes helium into the rock via cracks and grain boundaries. It is then suggested that helium-rich fluid released from such U–Th rich sources may percolate into surrounding rock units, inducing perturbation of the (U–Th)/He systematics of apatite and zircon in these units.

cited By 0; Conference of 11th IEEE Nanotechnology Materials and Devices Conference, NMDC 2016 ; Conference Date: 9 October 2016 Through 12 October 2016; Conference Code:125383; International audience; A variety of iodine-based 1D nanocrystals were introduced into double-wall carbon nanotubes using the molten phase method, as an intermediate step for ultimately obtaining encapsulated metal nanowires. Based on HRTEM observations using different imaging modes (bright field, dark field, STEM) and associated analytical tools (EELS), it is revealed that the reality of nanotube filling is much more complex than expected. For some halides (typically Nih), earlier decomposition during the filling step was observed, which could not be anticipated from the known data on the bulk material. Others (e.g., iodine) show a variety of atomic structuration inside and outside the CNTs which is driven by the available space being filled, and was ascertained by modelling. Overall, the whole study reveals a variety of filling efficiencies, the reason of which is discussed.

Inorganic ultraviolet filters such as titanium dioxide (TiO(2)), safe to use on healthy skin, are often applied on compromised and irradiated skin. The aim of this study was to evaluate in vitro the cutaneous penetration of TiO(2) nanoparticles (≥20 nm primary size), included in a sunscreen, in intact, damaged, irradiated, and damaged/irradiated pigskin. Cutaneous penetration and localization of TiO(2) after a 24-h sunscreen application were investigated quantitatively using inductively coupled plasma-mass spectrometry, and qualitatively using transmission electron microscopy (TEM). Elemental identity of the nanoparticles was evaluated by TEM-coupled Energy Dispersive X-ray analysis (TEM-EDX). In intact and damaged/irradiated skins, 102.35±4.20% and 102.84±5.67% of the titanium deposited, respectively, were found at the surface and stratum corneum (SC), whereas only 0.19±0.15% and 0.39±0.39% were found in the viable epidermis and dermis and no titanium was detected in the receptor fluid. TEM-EDX analysis confirmed the presence of titanium in the aggregates formed by TiO(2) at the SC surface, as already characterized in the sunscreen formulation. TiO(2) nanoparticles included in a sunscreen thus remain in the uppermost layers of the SC, whether in intact skin or in compromised and/or skin exposed to simulated solar radiation.

International audience; Infrared femtosecond laser induced damage has been studied in order to determine, with analytical protocols, the processes involved in laser ablation in this regime. Transmission Electron Microscopy (TEM) coupled with Focused Ion Beam (FIB) milled cross-sections of natural ablated monazite were used. Craters were formed using N = 1 and 3 shots, E0 = 0.1 and 0.8 mJ per pulse and τ = 60 fs. Observations revealed that laser settings induce little changes in the nature and size of damaged structures. The crater bottom forms a ∼0.5 μm layer composed of melted and recrystallized monazite grains, and spherical ∼10 nm voids. The underlying sample shows lattice distortions, progressively attenuated with depth, typical of mechanical shocks (thermoelastic relaxation and plasma recoil pressure). No chemical difference appears between these two domains, excluding preferential vaporization and thus laser induced chemical fractionation. Correlations with existing molecular dynamics (MD) simulations indicate that the deep distorted lattice probably undergoes spallation whereas the upper layer rather goes through homogeneous nucleation. Nevertheless, these processes are not pushed forward enough to induce matter removal in the present conditions. In consequence, photomechanical fragmentation and vaporization, requiring higher energy density states, would rather be the main ablation mechanisms. This hypothesis was supported by an additional study focused on the laser produced aerosols. Further links to LA-ICP-MS measurements can then be developed.

The synthesis of nanoparticles of copper metal via a soft chemistry route is presented in this paper. The method is based on the thermal decomposition under nitrogen or hydrogen of oxalic precursors with a well-controlled morphology and particle size. The precipitation of the copper oxalates in a water-alcohol medium allows the submicron size of the precursor grains to be controlled and, consequently, the nanometric size of the metallic copper particles to be determined, as required, between 3.5 and 40 nm. The majority of the final particles are made of pure copper metal although some present a superficial layer of cuprous oxide (Cu2O).

International audience; Effects of infrared femtosecond laser ablation (800 nm, 60 fs, 5 Hz, 85 mJ/pulse, objective  15) of a well-characterized monazite on its micro-and nano-structure were investigated. Craters were produced by single and multiple pulses (N ¼ 10, 20, 50, 150 and 300) to follow the evolution of laser-induced damage in monazite using Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM) coupled with Focused Ion Beam (FIB) sample preparation, in order to characterize this damage. Voids are observed within craters from the first pulse and cracks appear already after 10 pulses, at the sample surface; radial cracks are well-defined for 50 pulses, and become conchoidal after 150 pulses, indicating high-strain fields in the vicinity of craters. After the first pulse, the monazite lattice is highly strained to depths greater than $1 mm with a spotty ring diffraction pattern demonstrating that the damaged monazite is a mosaic crystal. Under this area monazite is moderately strained over 6 mm in depth. Crack formation within the crystal is observed from the first pulse. Cracks formed at the surface and propagated over 2 mm into the crystal. Their number increased notably after 10 pulses, with some cracks propagating 8 mm into the crystal. Increasing lattice defects (mosaic crystal, twins) and fracture intensities demonstrate that a cumulative effect exists. Part of the energy carried by the laser is stored within the crystal and used in the formation of defects. This study highlights the intense damages that are created during a femtosecond laser ablation in monazite. Mechanical effects dominate thermal ones, limited to a thin layer (200 nm-1 pulse) of resolidified monazite, and are induced by high-pressure shock wave from plasma expansion.

Ordered anodic aluminium oxide (AAO) films were first prepared by anodising in a phosphoric acid electrolyte and then studied extensively and characterised by field emission gun-scanning electron microscopy (FEG-SEM), X-ray diffraction, Raman and infrared spectroscopy at a macroscopic scale. These analyses showed that the as-prepared AAO film is in fact amorphous, partially hydrated and that its initial global chemical composition can be described, in agreement with previous works, as: Al2O3, 0.186AlPO4 · 0.005H2O. Additional analyses (thermogravimetric analysis, differential thermal analysis and FEG-SEM) showed geometrical changes of the film structure at different scales, explained by various steps of dehydration and allotropic transformations of the resulting crystallised alumina. However, because their structure remains unchanged up to 900 °C, the phosphoric templates appear to be particularly suitable for applications or processes at medium or high temperatures, such as the preparation of carbon nanotubes or oxide rods. Copyright © 2010 John Wiley & Sons, Ltd.

Carbon nanotubes (CNT) were synthesized from a H2–CH4 mixture with W/Co–MgO catalyst by a catalytic chemical vapour deposition (CCVD) method. Different W/Co ratios were investigated. From transmission electron microscopy observations, we observed that both the number of walls and the diameter of CNT increased with the proportion of tungsten. A promoter effect was observed as long as the proportion of tungsten was kept low and CNT with a number of walls ranging from 2 to 5 were obtained. With a higher proportion of tungsten, multi-walled carbon nanotubes (MWNT) up to 10 walls were synthesised, together with additional undesirable carbon nanofibres.

International audience; Magnetic and semi-conducting nano-composite films have been prepared under bias polarization, by radio-frequency sputtering of a pure zinc ferrite target. These composite thin films are made of cubic Zn1 − yFeyO monoxide islands inside a spinel ferrite matrix. The relative proportion of each phase depends on the substrate polarization (i.e. bias power). When no bias is applied the films solely display the diffraction pattern of a spinel phase even if some islands inside the film can be observed by electron microscopy. When the bias power is increased, the spinel phase disappears progressively as enhanced formation of islands takes place in such a manner that the cubic Zn1 − yFeyO monoxide is solely revealed by X-ray diffraction for a bias power higher than 5 W. From bibliographical data and calculated phase diagrams, it can be inferred that these phases would require very low oxygen partial pressure, high temperature and mechanical pressure, to be obtained simultaneously by a conventional ceramic process. This underlines the strong potential of radio-frequency sputtering of oxide targets to prepare original oxides or composite materials.

Natural and well-crystallized hematite was suspended in water and treated at room-temperature (RT) with sodium borohydride in acid medium. The product of the reaction is a highly magnetic black powder, which is stable at RT. The NaBH4 treatment converts about half of the hematite to an amorphous Fe–B alloy and to a small fraction of sub-micron sized, amorphous metallic-Fe nodules. Heating at 400 °C of this composite has resulted in the crystallization and/or oxidation of more than half of the amorphous Fe–B phase to α-Fe and Fe3O4 and B2O3, respectively. Further, the already present superficial, amorphous metallic Fe is converted to α-Fe and the original, plate like morphology of the hematite has changed to a mix of nodular and acicular particles. After treatment at 800 °C, the metallic Fe and the amorphous Fe–B have completely vanished, and the resulting product consists of hematite and FeBO3 embedded in a matrix of α-Fe2O3.

An approach to the synthesis and the organization of magnetic bimetallic NiFe nanoparticles of controlled size and composition was developed using thermolysis of the cyano-bridged Ni2+/[Fe(CN)6]3− coordination polymer nanoparticles anchored within a hybrid mesostructured silica either under argon or under hydrogen atmospheres. The obtained NiFe nanoparticles were studied by high resolution transmission electronic microscopy (HRTEM), nitrogen sorption (BET), X-ray diffraction (XRD) and magnetic measurements, which reveal the presence of uniform bimetallic NiFe nanoparticles inside the silica pores. The size of these nanoparticles is controlled by the pore size of the silica used and by the size of the cyano-bridged coordination polymer nanoparticles. The magnetic measurements show a superparamagnetic behaviour of the nanoparticles with a decrease of the blocking temperature as the size of the nanoparticles decreases.

Well-crystallized hematite was suspended in water and treated at room-temperature (RT) with sodium borohydride. The product of the reaction is a highly magnetic black powder, which is stable at RT. The NaBH4 treatment converts about half of the hematite to an amorphous Fe-B alloy and to a small fraction of sub-micron sized, amorphous metallic-Fe nodules. Heating at 400°C of this composite has resulted in the crystallization and/or oxidation of more than half of the amorphous Fe-B phase to α-Fe and Fe3O4 and B2O3, respectively. After treatment at 800°C, the metallic Fe and the amorphous Fe-B have completely vanished, and the resulting product consists of hematite and FeBO3 embedded in the matrix of α-Fe2O3.

The strengths of porous phosphate glass-ceramic specimens, with relative densities ranging between 0.25 and 0.50, were measured by four-point bending at room temperature. An analysis of the data, using Weibull statistics, indicated that such a treatment, usually performed on dense ceramics, can also be used on porous materials. In the sets studied, the nature of critical flaws was determined, which led to the proposal of a mechanism of fracture initiation in such porous materials.

A novel method for synthesis of aluminium hematites, based upon the homogeneous precipitation of Fe and Al oxinates in various proportions, is presented. The precursor precipitates are heated in air at 700 °C. X-ray diffraction, thermal analyses, BET, FTIR, optical reflection analysis, TEM and Mossbauer spectroscopy at room temperature and 80 K of the resulting products indicate that single-phase hematites are formed with structural Al substitution of up to 10 at%. Interestingly, the particle size (>100 nm) is not substantially reduced by the Al content. Although it remains difficult to obtain a homogeneously distributed Al substitution in the final hematite, this processing line offers a unique opportunity to separate the effects of grain size and Al substitution on the Morin transition temperature (T M) of Al hematite. From the comparison between the present hematites and a series of Al-substituted hematites with lepidocrocite as precursor, it could be shown that the effect on T M, associated with a change of a factor 10 in grain size, is about 1/3 of the effect caused by a change of 10 in the degree of substitution. Finally, it is suggested that proper thermal treatments under different conditions of the same precursors are likely to produce spinel phases.

The preferential adsorption of NH3 gas molecules on multiwalled carbon nanotubes (MWCNTs) was studied using in situ Raman spectroscopy. It was observed that the full widths at half maximum of the G band and the intensity ratio I2D/IG of the MWCNTs decreased significantly during NH3 gas adsorption at elevated temperatures. These observations were explained in terms of suppressed second-order-defect associated Raman vibrations resulting in a lower disorder Raman band due to ammonia adsorption on the defect sites. Another corresponding effect was a temporary increase in electron doping levels due to ammonia adsorption. This behaviour was accompanied by a drop of ca. 2% in the resistance of the MWCNTs corresponding to the occupancy of most of the defect sites. We suggest preferential adsorption of ammonia gas molecules on the thermally activated defect sites of MWCNTs as an appropriate gas sensing mechanism. This knowledge can be used to design and tune the selectivity of ammonia gas sensors

International audience; We compared the effect of different oxidizing agents on purification, functionalization andopening of double-walled carbon nanotubes. The oxidative treatments were realized innitric acid solutions at different concentrations (3 M or 15 M), in a mixture of two oxoacids(conc. HNO3/conc. H2SO4) or in sulphuric acid solutions of KMnO4 or K2Cr2O7. Most of thesetreatments were very efficient for purification (removal of residual catalytic metal nanoparticlesand/or of disorganized carbon) but also caused secondary reactions such as shorteningof the nanotubes, creation of functionalized amorphous carbon deposits and covalentfunctionalization of the outer wall. Secondary treatments were undertaken in order toremove functionalized carbon deposit by washing with sodium hydroxide solutions or byheat treatment in air. A partial filling in solution was obtained with uranyl nitrate, in orderto evidence the opening of carbon nanotubes. Effects of purification and filling treatmentswere characterized both qualitatively by TEM and HRTEM, AFM and Raman spectroscopy,and quantitatively by elemental chemical analysis and chemical titrations.

A study of the characteristics of the Morin transition in aluminous hematites, alpha-(Fe1-xAlx)(2)O-3, produced from thermally transformed lepidocrocites, is reported. Six compositions with Al contents between 0.2 and 10 at% have been considered. It is argued that these samples present the advantage that they contain smaller amounts of hydroxyl and water as compared to hematites obtained by other preparation methods. The samples were characterised by a variety of conventional techniques, including thermal analyses, X-ray diffraction, FTIR, TEM/EDX, BET surface-area measurements and diffuse reflectance spectroscopy. All results indicate that the Al is structurally incorporated in the hematite lattices. Transmission Mossbauer spectra were recorded at various temperatures between 80 K and room temperature in order to precisely determine the Morin-transition region and the spin structure in both the low-temperature antiferromagnetic and weakly ferromagnetic states. It was found that the Morin-transition temperatures are markedly higher as compared to similar hematites made from aluminous goethites and that a transition phenomenon persists to an Al substitution of up to at least 10 at%. This different behaviour is ascribed to lower concentrations of structural hydroxyl groups in these lepidocrocite-based hematites.

International audience; Carbon nanotubes (CNTs) tend to readily agglomerate and settle down in water, while the adsorption of compounds present in natural aquatic media could enhance their dispersion and stabilization in the water column. We designed a new exposure protocol to compare the biological responses of Xenopus laevis larvae exposed in semi-static conditions to size-reduced agglomerates of multi-walled carbon nanotubes (MWCNTs) in suspension in the water column and/or to larger agglomerates. Suspensions were prepared using a combination of a non-covalent functionalization with a non-toxic polymer (either carboxymethylcellulose, CMC, or gum arabic, GA) and mechanical dispersion methods (mainly ultrasonication). The ingestion of agglomerates which have settled down was incriminated in the disruption of the intestinal transit and the assimilation of nutrients, leading to acute and chronic toxicities at the highest tested concentrations. Rise in mortality, decrease in the growth rate and induction of genotoxicity from low concentrations (1 mg/L in the presence of CMC) were evidenced in presence of suspended MWCNTs in the water column. The biological responses seemed to be modulated when GA, a potential antioxidant, was used. We hypothesized that MWCNTs should interfere mainly at the surface of the gills, acting as a potential respiratory toxicant and generally inducing indirect effects.

International audience; Well-aligned, open-ended carbon nanotubes (CNTs), free of catalyst and other carbon products, were synthesized inside the pores of an anodic aluminium oxide (AO) template without using any metallic catalyst. The CNTs and the CNT/AO composites were characterizedby scanning and transmission electron microscopy, thermogravimetric analysis, Ramanspectroscopy and X-ray diffraction. Particular care was devoted to the reactor design, synthesis conditions, the catalytic role of the templating alumina surface and the preservation of the alumina structure. The transport properties (sorption, diffusion and permeability) to water vapor were evaluated for both the alumina template and the CNT/AO composite membrane. The measured effective electrical volume conductivity of the CNT/AO composite was found ranging from a few up to 10 kS/m, in line with the recent literature. The estimated averaged values of the CNTs-wall conductivity was around 50 kS/m.

Inorganic ultraviolet filters such as titanium dioxide (TiO(2)), safe to use on healthy skin, are often applied on compromised and irradiated skin. The aim of this study was to evaluate in vitro the cutaneous penetration of TiO(2) nanoparticles (≥20 nm primary size), included in a sunscreen, in intact, damaged, irradiated, and damaged/irradiated pigskin. Cutaneous penetration and localization of TiO(2) after a 24-h sunscreen application were investigated quantitatively using inductively coupled plasma-mass spectrometry, and qualitatively using transmission electron microscopy (TEM). Elemental identity of the nanoparticles was evaluated by TEM-coupled Energy Dispersive X-ray analysis (TEM-EDX). In intact and damaged/irradiated skins, 102.35±4.20% and 102.84±5.67% of the titanium deposited, respectively, were found at the surface and stratum corneum (SC), whereas only 0.19±0.15% and 0.39±0.39% were found in the viable epidermis and dermis and no titanium was detected in the receptor fluid. TEM-EDX analysis confirmed the presence of titanium in the aggregates formed by TiO(2) at the SC surface, as already characterized in the sunscreen formulation. TiO(2) nanoparticles included in a sunscreen thus remain in the uppermost layers of the SC, whether in intact skin or in compromised and/or skin exposed to simulated solar radiation.

International audience; A process route for the fabrication of solvent-redispersible, surfactant-free Cu2ZnSnS4 (CZTS) nanoparticles has been designed with the objective to have the benefit of a simple sulfide source which advantageously acts as (i) a complexing agent inhibiting crystallite growth, (ii) a surface additive providing redispersion in low ionic strength polar solvents and (iii) a transient ligand easily replaced by an carbon-free surface additive. This multifunctional use of the sulfide source has been achieved through a fine tuning of ((Cu2+)(a)(Zn2+)(b)(Sn4+)(c)(Tu)(d)(OH-)(e))(t+), Tu = thiourea) oligomers, leading after temperature polycondensation and S2- exchange to highly concentrated (c > 100 g l(-1)), stable, ethanolic CZTS dispersions. The good electronic properties and low-defect concentration of the sintered, crack-free CZTSe films resulting from these building blocks was shown by photoluminescence investigation, making these building blocks interesting for low-cost, high-performance CZTSe solar cells.

The analytical study of infra red femtosecond laser induced particles has been performed using Transmission Electron Microscopy (TEM) and Low Pressure Impaction (ELPI). Various natural and synthetic matrices have been tested: monazite (phosphate), zircon (silicate), NIST610 (glass), spinel (oxide), quartz (silicate structure), silicon (semiconductor) and Nordic gold (metallic alloy). Three types of particles are systematically observed: very rare large round spherical particles (d(p) approximate to 1 mm) whose composition is close to the initial sample, spherical particles of smaller size (d(p)

International audience; After exposure to ionic silver or nanosilver-containing plasma coating, the same visual aspect of scanning transmission electron microscopy (STEM) images was observed for the model yeast Saccharomyces cerevisiae. The main common feature was the presence of electron-dense nodules all over the cell. However, high resolution TEM (HRTEM), STEM, energy dispersive x-ray microanalysis spectroscopy (EDS) and electron microdiffraction revealed some striking differences. Regarding ionic silver exposure, the formation of electron-dense nodules was related to the Ag+ reactivity towards sulfur-containing compounds to form clusters with Ag2S-like structures, together with the production of a few silver nanocrystals, mainly at the cell wall periphery. For nanosilver-based treatment, some sulfur-containing silver clusters preferentially located at the cell wall periphery were detected, together with nodules composed of silver, sulfur and phosphorus all over the cell. In both silver-based treatments, nitrogen and silver signals overlapped, confirming the affinity of silver entities for proteinaceous compounds. Moreover, in the case of nanosilver, interactions of silver with phosphorus-containing subcellular structures were indicated.

It is reported that 3 nm gold nanoparticles deposited on ZnO tetrapods show high activity for the selective oxidation of carbon monoxide in hydrogen rich streams; the catalytic activity of this system is at least twice as high as the values hither to observed on any conventional support for this reaction.

We prepared anodic aluminium oxide (AAO) templates with “honeycomb” geometry, i.e. hexagonally ordered circular pores. The structures were extensively studied and characterized by EPMA coupled with FEG-SEM and FEG-TEM coupled with EDX at meso and nanoscopic scales, in other words, at the scale of a single basic cell making up the highly ordered porous anodic film. The analyses allowed the identification of the chemical compounds present and the evaluation of their levels in the different parts of each cell. Of note was the absence of phosphates inside the “skeleton” and their high content in the “internal part”. Various models of porous anodic film growth are discussed on the basis of the results, contributing to a better understanding of AAO template preparation and self-nanostructuring phenomena.

Aqueous dispersions of functionalized carbon nanotubes (CNTs) are now widely used for biomedical applications. Their stability in different in vitro or in vivo environments, however, depends on a wide range of parameters, such as pH and salt concentrations of the surrounding medium, and length, aspect ratio, surface charge, and functionalization of the applied CNTs. Although many of these aspects have been investigated separately, no study is available in the literature to date, which examines these parameters simultaneously. Therefore, we have chosen five types of carbon nanotubes, varying in their dimensions and surface properties, for a multidimensional analysis of dispersion stability in salt solutions of differing pH and concentrations. Furthermore, we examine the dispersion stability of oxidized CNTs in biological fluids, such as cellular growth media and human plasma, and their toxicity toward cancer cells. To enhance dispersibility and biocompatibility, the influence of different functionalization schemes is studied. The results of our investigations indicate that both CNT dimensions and surface functionalization have a significant influence on their dispersion and in vitro behavior. In particular, factors such as a short aspect ratio, presence of oxidation debris and serum proteins, low salt concentration, and an appropriate pH are shown to improve the dispersion stability. Furthermore, covalent surface functionalization with amine-terminated polyethylene glycol (PEG) is demonstrated to stabilize CNT dispersions in various media and to reduce deleterious effects on cultured cells. These findings provide crucial data for the development of biofunctionalization protocols, for example, for future cancer theranostics, and optimizing the stability of functionalized CNTs in varied biological environments.

A previous paper described the low-temperature synthesis of mesoporous nanocrystalline anatase thin layers obtained by mesophase templating (Chem. Mater. 2003, 15, 2463). This work deals with the structural characterization of these anatase thin layers and with the extension of the synthesis method to films with a different mesostructure. Thus, two triblock copolymers are used as structuring agents and the effect of the volume fraction of surfactant in the dried layers is also considered. The determination of the mesostructures is mainly based on 2D X-ray diffraction experiments, completed with observations by transmission electron microscopy and atomic force microscopy. Nitrogen adsorption−desorption measurements are performed to investigate the porous texture of the thin layers.

Davet, Julien, Benoit Clavel, Lucien Datas, Laurence Mani-Ponset, Daniel Maurel, Serge Herbuté, Michel Viso, William Hinds, Joellen Jarvi, and Jacqueline Gabrion.Choroidal readaptation to gravity in rats after spaceflight and head-down tilt. J. Appl. Physiol.84(1): 19–29, 1998.—To determine when choroidal structures were restored after readaptation to Earth gravity or orthostatic position, fine structure and protein distribution were studied in rat choroid plexus dissected either 6 h [Space Life Sciences-2 (SLS-2) experiments] or 2 days [National Institutes of Health-Rodent 1 (NIH-R1) experiments] after a spaceflight, or 6 h after head-down tilt (HDT) experiments. Apical alterations were noted in choroidal cells from SLS-2 and HDT animals, confirming that weightlessness impaired choroidal structures and functions. However, the presence of small apical microvilli and kinocilia and the absence of vesicle accumulations showed that the apical organization began to be restored rapidly after landing. Very enlarged apical microvilli appeared after 2 days on Earth, suggesting increased choroidal activity. However, as distributions of ezrin and carbonic anhydrase II remained altered in both flight and suspended animals after readaptation to Earth gravity, it was concluded that choroidal structures and functions were not completely restored, even after 2 days in Earth’s gravity.

International audience; A series of Ru(II) complexes with monosilylated-dipyridine ligand have been synthesized and fully characterized and were then covalently attached to silica nanoparticles. Two types of hybrids were obtained depending on the experimental procedure. In the first approach, metal complexes were incorporated inside the silica nanoparticles leaving a free hydroxylated silica surface for further functionalization. These silica based nanohybrids are similar to the well known nanoparticles encapsulating [Ru(bpy)3]2+ complexes preventing the release of the dye when used in aqueous or organic solutions. Size and luminescence properties vary throughout the series of metal complexes. The second approach leads to ruthenium(II) complexes covalently attached to the silica nanoparticle surface via hydrolysis and condensation of the ethoxysilyl group with silanol sites of Ludox type silica nanoparticles. This leads to the grafting of a monolayer for complexes with the monoethoxysilyl dipyridine ligand. In contrast, the complexes with triethoxysilyl ligands can lead to small amounts of oligomers, but their quantity is limited by the sterical constraints imposed by the molecular structure. The size of the hybrids depends on the starting particles. 29Si and 13C solid state NMR are used to characterize silica surface properties whereas TEM and SEM confirm nanosize and morphology of the hybrids. The complexes and the nanohybrids are luminescent, with variations for ruthenium(II) complexes that are covalently incorporated or grafted on the silica surface.

Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects.

This article presents the first example of ultra-small (3-4 nm) magneto-luminescent cyano-bridged coordination polymer nanoparticles Ln0.33(3+)Gdx3+/[Mo(CN)8]3- (Ln=Eu (x=0.34), Tb (x=0.35)) enwrapped by a natural biocompatible polymer chitosan. The aqueous colloidal solutions of these nanoparticles present a luminescence characteristic of the corresponding lanthanides (5D0→7F0-4 (Eu3+) or the 5D4→7F6-2 (Tb3+)) under UV excitation and a green luminescence of the chitosan shell under excitation in the visible region. Magnetic Resonance Imaging (MRI) efficiency, i.e. the nuclear relaxivity, measurements performed for Ln0.33(3+)Gdx3+/[Mo(CN)8]3- nanoparticles show r1p and r2p relaxivities slightly higher than or comparable to the ones of the commercial paramagnetic compounds Gd-DTPA® or Omniscan® indicating that our samples may potentially be considered as a positive contrast agent for MRI. The in vitro studies performed on these nanoparticles show that they maybe internalized into human cancer and normal cells and well detected by fluorescence at the single cell level. They present high stability even at low pH and lack of cytotoxicity both in human cancer and normal cells.

Highly ordered hydrothermally stable SBA-15 mesoporous silica containing phosphonic acid groups are synthesised for the first time by using amphiphilic block copolymers as the structure-directing agents.

Selenium-filled double-walled carbon nanotubes (Se@DWNT) have been studied by high resolution transmission electron microscopy (HRTEM) and micro-Raman spectroscopy in the temperature interval from 80to600K employing 785nm excitation wavelength. The temperature dependences of the dominant bands (G-band and G′-band) are analyzed in terms of the model developed by Klemens [Phys. Rev. 148, 845 (1966)], Hart et al. [Phys. Rev. B 1, 638 (1970)], Cowley [J. Phys. (France) 26, 659 (1965)] and extended by Balkanski et al. [Phys. Rev. B 26, 1928 (1983)] for anharmonic decay of optical phonons. The findings were compared to analogous study for empty double-walled carbon nanotubes (DWNTs). The DWNT interatomic force constant modification as a result of the presence of the Se atoms inside the tubes is revealed through larger anharmonicity constants describing the temperature dependences of the G′-band and the inner tube tangential modes (G-band).

Si3N4 nanopores functionalized with 4–4’ bipyridyl, 3.2–6.5 nm in diameter and 30–50 nm in length, are shown to interact with single, negatively charged, coated gold nanoparticles from 2.4 to 8.9 nm diameter. It is possible to detect the interactions through alterations in the ionic current, whether or not the electric-field driven nanoparticle threads through the pore.