Using adsorption kinetics to assemble vertically aligned nanorods at liquid interfaces for metamaterial applications.

Vertically aligned monolayers of metallic nanorods have a wide range of applications as metamaterials or in surface enhanced Raman spectroscopy. However the fabrication of such structures using current top-down methods or through assembly on solid substrates is either difficult to scale up or have limited possibilities for further modification after assembly. The aim of this paper is to use the adsorption kinetics of cylindrical nanorods at a liquid interface as a novel route for assembling vertically aligned nanorod arrays that overcomes these problems. Specifically, we model the adsorption kinetics of the particle using Langevin dynamics coupled to a finite element model, accurately capturing the deformation of the liquid meniscus and particle friction coefficients during adsorption. We find that the final orientation of the cylindrical nanorod is determined by their initial attack angle when they contact the liquid interface, and that the range of attack angles leading to the end-on state is maximised when nanorods approach the liquid interface from the bulk phase that is more energetically favorable. In the absence of an external field, only a fraction of adsorbing nanorods end up in the end-on state (≲40% even for nanorods approaching from the energetically favourable phase). However, by pre-aligning the metallic nanorods with experimentally achievable electric fields, this fraction can be effectively increased to 100%. Using nanophotonic calculations, we also demonstrate that the resultant vertically aligned structures can be used as epsilon-near-zero and hyperbolic metamaterials. Our kinetic assembly method is applicable to nanorods with a range of diameters, aspect ratios and materials and therefore represents a versatile, low-cost and powerful platform for fabricating vertically aligned nanorods for metamaterial applications.

Adsorption trajectories of nonspherical particles at liquid interfaces.

The adsorption of colloidal particles at liquid interfaces is of great importance scientifically and industrially, but the dynamics of the adsorption process is still poorly understood. In this paper we use a Langevin model to study the adsorption dynamics of ellipsoidal colloids at a liquid interface. Interfacial deformations are included by coupling our Langevin dynamics to a finite element model while transient contact line pinning due to nanoscale defects on the particle surface is encoded into our model by renormalizing particle friction coefficients and using dynamic contact angles relevant to the adsorption timescale. Our simple model reproduces the monotonic variation of particle orientation with time that is observed experimentally and is also able to quantitatively model the adsorption dynamics for some experimental ellipsoidal systems but not others. However, even for the latter case, our model accurately captures the adsorption trajectory (i.e., particle orientation versus height) of the particles. Our study clarifies the subtle interplay between capillary, viscous, and contact line forces in determining the wetting dynamics of micron-scale objects, allowing us to design more efficient assembly processes for complex particles at liquid interfaces.

Iodine solubility and speciation in glasses.

The study of iodine in glasses and melts is critical in many areas, from geosciences to materials science to waste management. Glasses in the ternary system Na2O-B2O3-SiO2 were studied with the goal of identifying a glass matrix able to dissolve large quantities of this element, and to identify the main parameters affecting the solubility of iodine. Two sets of experiments were carried out: the first one with the aim of determining the solubility limit of iodine, and the second one to identify the structural variations occurring within the glass network upon iodine incorporation, and to identify the parameters influencing the most both iodine solubility and speciation. We demonstrated that there is a strong dependence of iodine incorporation on bulk chemistry and glass physical properties. A solubility limit of ~5 mol% I has been assessed for B2O3-rich glasses and of ~1 mol% for SiO2-rich ones, and this composition dependence has been explained by considering the fragility parameter of the glass network. Structural variations in the iodine local environment and in the glass network were characterized by Raman, X-ray Absorption Spectroscopy, and 11B NMR. Spectroscopy data point out the coexistence of different I species within the glasses, with iodide being the predominant one, surrounded by Na+ ions.

Insights into possibilities for grouping and read-across for nanomaterials in EU chemicals legislation.

This paper presents a comprehensive review of European Union (EU) legislation addressing the safety of chemical substances, and possibilities within each piece of legislation for applying grouping and read-across approaches for the assessment of nanomaterials (NMs). Hence, this review considers both the overarching regulation of chemical substances under REACH (Regulation (EC) No 1907/2006 on registration, evaluation, authorization, and restriction of chemicals) and CLP (Regulation (EC) No 1272/2008 on classification, labeling and packaging of substances and mixtures) and the sector-specific pieces of legislation for cosmetic, plant protection and biocidal products, and legislation addressing food, novel food, and food contact materials. The relevant supporting documents (e.g. guidance documents) regarding each piece of legislation were identified and reviewed, considering the relevant technical and scientific literature. Prospective regulatory needs for implementing grouping in the assessment of NMs were identified, and the question whether each particular piece of legislation permits the use of grouping and read-across to address information gaps was answered.

Boundary effects in finite size plasmonic crystals: focusing and routing of plasmonic beams for optical communications.

Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components.

Shaping plasmon beams via the controlled illumination of finite-size plasmonic crystals.

Plasmonic crystals provide many passive and active optical functionalities, including enhanced sensing, optical nonlinearities, light extraction from LEDs and coupling to and from subwavelength waveguides. Here we study, both experimentally and numerically, the coherent control of SPP beam excitation in finite size plasmonic crystals under focussed illumination. The correct combination of the illuminating spot size, its position relative to the plasmonic crystal, wavelength and polarisation enables the efficient shaping and directionality of SPP beam launching. We show that under strongly focussed illumination, the illuminated part of the crystal acts as an antenna, launching surface plasmon waves which are subsequently filtered by the surrounding periodic lattice. Changing the illumination conditions provides rich opportunities to engineer the SPP emission pattern. This offers an alternative technique to actively modulate and control plasmonic signals, either via micro- and nano-electromechanical switches or with electro- and all-optical beam steering which have direct implications for the development of new integrated nanophotonic devices, such as plasmonic couplers and switches and on-chip signal demultiplexing. This approach can be generalised to all kinds of surface waves, either for the coupling and discrimination of light in planar dielectric waveguides or the generation and control of non-diffractive SPP beams.

Biosynthesis of luminescent quantum dots in an earthworm.

The synthesis of designer solid-state materials by living organisms is an emerging field in bio-nanotechnology. Key examples include the use of engineered viruses as templates for cobalt oxide (Co(3)O(4)) particles, superparamagnetic cobalt-platinum alloy nanowires and gold-cobalt oxide nanowires for photovoltaic and battery-related applications. Here, we show that the earthworm's metal detoxification pathway can be exploited to produce luminescent, water-soluble semiconductor cadmium telluride (CdTe) quantum dots that emit in the green region of the visible spectrum when excited in the ultraviolet region. Standard wild-type Lumbricus rubellus earthworms were exposed to soil spiked with CdCl(2) and Na(2)TeO(3) salts for 11 days. Luminescent quantum dots were isolated from chloragogenous tissues surrounding the gut of the worm, and were successfully used in live-cell imaging. The addition of polyethylene glycol on the surface of the quantum dots allowed for non-targeted, fluid-phase uptake by macrophage cells.

Broadband and broadangle SPP antennas based on plasmonic crystals with linear chirp.

Plasmonic technology relies on the coupling of light to surface electromagnetic modes on smooth or structured metal surfaces. While some applications utilise the resonant nature of surface polaritons, others require broadband characteristics. We demonstrate unidirectional and broadband plasmonic antennas with large acceptance angles based on chirped plasmonic gratings. Near-field optical measurements have been used to visualise the excitation of surface plasmon polaritons by such aperiodic structures. These weakly aperiodic plasmonic crystals allow the formation of a trapped rainbow-type effect in a two-dimensional geometry as surface polaritons of different frequencies are coherently excited in different locations over the plasmonic structure. Both the crystal's finite size and the finite lifetime of plasmonic states are crucial for the generation of broadband surface plasmon polaritons. This approach presents new opportunities for building unidirectional, broadband and broad-angle plasmonic couplers for sensing purposes, information processing, photovoltaic applications and shaping and manipulating ultrashort optical pulses.

Hyperspectral imaging with scanning near-field optical microscopy: applications in plasmonics.

We present the realisation of near-field spectroscopic measurements with fibre-tip-based scanning near-field microscopy. It allows the simultaneous acquisition of near-field images in a broad spectral range (400 nm to 1000 nm), thus recovering local spectroscopic information. This technique is essential in order to understand the resonant interaction of light with nanostructured material as the far-field and near-field spectral response can differ significantly, e.g., in the case of plasmonic nanostructures. Several example applications of hyperspectral near-field imaging are given for visualisation of Bloch modes in plasmonic crystals and plasmon-assisted transmission through a slit.

Ignition and explosion risks of nanopowders.

Characterization methods with regard to nanopowder flammability and explosivity are presented and illustrated for few nanopowders. Analytical models are developed in order to explain the dependency of the combustion times on the particle diameter. Experimental evidence shows that there exists, for carbonaceous and metallic materials, mainly two combustion regimes that are either kinetically controlled, for small size particles, or diffusion controlled, for large size particles. From the experimentally measured combustion data of those materials, the dependencies of the ignition temperature and the minimal explosive concentration (MEC) with regard to the particle size have been analyzed. We found that the two combustion regimes yield two different tendencies with respect to the particle size. Overall, it is found that as the particle size decreases, minimum ignition temperature (MIT) and minimum ignition energy (MIE) decrease, indicating higher potential inflammation and explosion risks for the use of nanopowders. By contrast, the minimal explosion concentration (MEC) did not show strong variations as the particle size decreases. Rather, a theoretical plateau is observed, which was experimentally confirmed. We also observed that carbon nanopowders exhibit a low propensity to explode while metallic nanopowders can be very reactive, thus delineating high potentials for explosion risks in manufacturing facilities.

Near-field investigation of porous silicon photoluminescence modification after oxidation in water.

We report on local photo-induced oxidation of porous silicon in water at room temperature. Starting from a nonluminescent sample, the oxidation process induces luminescence which was found to first increase and then decrease as a function of the oxidation time. A clear blue shift is also observed. This effect is believed to be owing to size modification of silicon nanocrystallites and thus is explained in terms of quantum confinement. Optical near-field images and spectrum are used to monitor the photoluminescence modifications after oxidation. As the photoluminescence can be widely tuned in wavelength and intensity, this method offers a way to pattern the emission properties of the sample.

Detection in near-field domain of biomolecules adsorbed on a single metallic nanoparticle.

In this paper, we study the performances of nanosensors based on Localized Surface Plasmon Resonance in the context of biological sensing. We demonstrate the sensitivity and the selectivity of our designed nanosensors by studying the influence of the concentration of Streptavidin on the shift of Localized Surface Plasmon Resonance wavelength. In addition, to study the detection of biomolecules on a single Au nanoparticle, we used a Scanning Near-field Optical Microscope. These results represent new steps for applications in biological research and medical diagnostics.

[Occupational asthma to metabisulfites . Three cases]. / Asthme professionnel aux métabisulfites. Trois observations.

Sulfites are compounds which are mainly used in the agricultural, food and pharmaceutical industry as preservatives. The possibility of manifestations of acute hypersensitivity appearing after the ingestion or inhalation of sulfites has already been described several times, over the past twenty years. Amongst these manifestations and indeed the one that is most often present is bronchospasm, which can sometimes be severe. A few cases of occupational intolerance through contact eczema to sulfites have also been published. The idea of occupational asthma to metabisulphates is, on the other hand, extremely recent; its legal recognition only dates back to 1989. The authors present three new cases of occupational asthma to metabisulphites stressing the value of a specific provocation test and the different hypotheses for the pathogenesis of the disorder are reviewed. Preventative measures are always preferable to avoid the development of severe occupational asthma. In all cases, notification of occupational asthma is necessary.

[A metastatic neuroendocrine tumor with exceptional outcome!]. / Une tumeur neuroendocrine métastatique d'évolution exceptionnelle!

INTRODUCTION: Neuroendocrine tumors are rare, with poor prognosis when not or poorly differentiated. EXEGESIS: The authors report the case of a patient who presented with a metastatic poorly differentiated neuroendocrine tumor that was resistant to chemotherapy. The different sites of the carcinoma were lung, pancreas, kidney and lymph nodes. The patient received no treatment and complete spontaneous remission appeared after 21 months. This remission has been lasting for five years. CONCLUSION: It is the first case of spontaneous remission of a metastatic poorly differentiated neuroendocrine tumor. The evolution and classical sites of neuroendocrine tumors are reviewed. Renal metastasis is also unusual. This report illustrates the fact that neuroendocrine tumors are heterogeneous.

[Smoking in professional soccer players in France]. / Tabac et football professionnel en France.

An enquiry was conducted to determine the smoking habits of coaches and professional soccer players in the first and second division of the French championship in 1993 and 1994. The rate of response was 31% for coaches (36 responded) and 54% for players (257 responded). Among the coaches, 19% were smokers, 14% were ex-smokers and 67% were non-smokers; for players, the rates were 36%, 3% and 71% respectively. The percentage of smokers was higher in second division players (31%) than in first division players (20%). Forty percent smoked less than 6 cigarettes a day. Fifty-eight percent of the coaches and 39% of the players thought that smoking and sports were compatible. This study shows that even the highest level sports are not spared from the effect of smoking. Other reports of similar smoking habits have been reported in other sports in France. The image of athletes who smoke given by the media is in contradiction with the national French policy forbidding tobacco advertising in stadiums.

[Acute pneumopathy caused by exposure to zinc oxide]. / Pneumopathie aiguë au cours d'une exposition à l'oxyde de zinc.

The authors report the case of an acute lung reaction due to an accidental exposition to zinc oxide. This episode showed features of metal fume fever. The bronchoalveolar lavage showed an increased cellularity (1,300 cells/mm3) with 28% neutrophils and 25% eosinophils. The characteristics of pulmonary disease associated with fever associated to exposure to zinc, as well as its pathogenic mechanism are discussed.

[Asthma and air pollution. A study of admissions to the Hospital of Saint-Nazaire]. / Asthme et pollution atmosphérique. Une étude des admissions à l'Hôpital de Saint-Nazaire.

To test the possible influence of atmospheric pollution on the frequency of asthmatic exacerbations we have looked to see whether there is a link between the number of daily admissions for asthma in hospitals in Saint-Nazaire and data from pollution sensors in the network of the Association for the Measurement of Atmospheric Pollution in the Loire estuary. The pollutions studied were sulphur dioxide, oxide of nitrogen (NOx) and non sedimenting dust (black smoke). The meteorological data (speed and direction of the wind and temperature) were also recorded. The study was carried out for 18 months in a retrospective fashion. During this period 372 hospital admissions were recorded in 229 subjects. The number of daily admissions correlated in a significant fashion with the level of black smoke (r = 0.149, p less than 0.001) and this result was particularly due to subjects who were less than 15 years old. In this group the frequency of hospital admission was doubled on those days when the level of smoke was at its most elevated. There was a weak link between the peaks of SO2 (r = 0.116, p less than 0.05). An analysis of the place of residence in those hospitals and the dominant direction of the wind did not enable us to confirm the role of the principal sources of industrial pollution, which were all situated to the east of Saint-Nazaire.

[Takayasu's disease localized exclusively in the pulmonary artery]. / Maladie de Takayasu à localisation artérielle pulmonaire exclusive.

A 35 year-old woman exhibited a stenotic lesion of the right pulmonary artery with a severe inflammatory syndrome. A diagnosis of Takayasu arteritis was made, although no aortographic abnormality was present. Involvement of pulmonary arteries during the course of Takayasu arteritis is frequent, but a localisation of the disease to the pulmonary arterial tree alone is a very rare condition.