Plasmonic enhancement of Eu:Y2O3 luminescence by Al percolated layer.

The coupling between Eu(3+) rare earth emitters and Al has been investigated in multilayer structures, which consist of an Eu:Y2O3 phosphor film deposited between percolated and continuous Al films. Passive buffer Y2O3 layers were deposited between phosphor and Al films with different thicknesses to analyze the role of the Eu-Al distance on the nanostructuration and emission of the Eu:Y2O3 film. By using Eu(3+) emitters as local structural probes completed by transmission electron microscopy analyses, we show that the deposition on Al promotes the growth of the cubic crystallites. A fluorescence analysis allows us to evaluate the presence of a perturbed structural shell around the cubic core of the crystallites. Moreover, the enhancement observed at short distances is attributed to the localized plasmon resonance of the percolated upper Al film.

Growth process of nanosized aluminum thin films by pulsed laser deposition for fluorescence enhancement.

Pulsed laser deposition was used to deposit aluminum thin films of various thicknesses (tAl) ranging from 5 to 40 nm and to investigate their growth process when they are deposited onto SiO2 and Y2O3. Atomic force microscopy and x-ray reflectivity measurements show that the structure of the Al films are related to the wettability properties of the underlaying layer. Onto SiO2, ultra-smooth layers of aluminum are obtained, due to a perfect wetting of SiO2 by Al. In contrast when deposited onto Y2O3, percolated Al layers are observed with apparent pore size decreasing from 200 to 82 nm as t(Al) is increased from 5 to 40 nm, respectively. This particular morphology is related to partial dewetting of Al on Y2O3. These two different growth mechanisms of aluminum depend therefore on the surface properties of SiO2 and Y2O3. The plasmon resonance of such Al nanostructures in the UV region was then analyzed by studying the coupling between Eu(3+) rare earth emitters and Al.

Femtosecond laser volume ablation rate and threshold measurements by differential weighing.

Precise weight measurements of stainless steel, PZT and PMMA samples were performed after groove machining with femtosecond laser pulses (150 fs, 800 nm, 5 kHz) to determine volume ablation rates and ablation threshold with good accuracy. Weighing clearly enables faster determination of such phenomenological parameters without any methodological issue compared to other methods. Comparisons of the three types of materials reveal similar monotonous trends depending on peak fluences from 0.2 to 15 J/cm². The metallic target exhibits both the lowest volume ablation rate under the highest irradiation conditions with almost 400 µm³/pulse and the lowest ablation threshold with 0.13 J/cm². Ceramic PZT reaches 3.10³ µm³/pulse with a threshold fluence of 0.26 J/cm² while polymer PMMA attains 104 µm³/pulse for a 0.76 J/cm² threshold. Pros and cons of this method are also deduced from complementary results obtained on microscopic and confocal characterizations.

Quantum cutting in CaYAlO4: Pr3+, Yb3+.

The deposition of a thin layer of a quantum-cutter material on top of silicon-based solar cells seems to be a promising solution to reduce the thermalization losses. This mechanism has been reported in materials codoped with Pr3+-Yb3+, where Pr3+ can sensitize two Yb3+ ions for one absorbed blue photon. In the present Letter, we analyze precisely energy transfers between Pr3+ and Yb3+ in CaYAlO4, and we measure a quantum-cutting rate of 145%. We show that a very efficient back transfer from Yb3+ toward the (1)G4 level of Pr3+ ion leads to a strong reduction of the quantum yield.

Molecular hydrogen in minerals as a clue to interpret ∂D variations in the mantle.

Trace amounts of water dissolved in minerals affect density, viscosity and melting behaviour of the Earth's mantle and play an important role in global tectonics, magmatism and volatile cycle. Water concentrations and the ratios of hydrogen isotopes in the mantle give insight into these processes, as well as into the origin of terrestrial water. Here we show the presence of molecular H2 in minerals (omphacites) from eclogites from the Kaapvaal and Siberian cratons. These omphacites contain both high amounts of H2 (70 to 460 wt. ppm) and OH. Furthermore, their ∂D values increase with dehydration, suggesting a positive H isotope fractionation factor between minerals and H2-bearing fluid, contrary to what is expected in case of isotopic exchange between minerals and H2O-fluids. The possibility of incorporation of large quantities of H as H2 in nominally anhydrous minerals implies that the storage capacity of H in the mantle may have been underestimated, and sheds new light on H isotope variations in mantle magmas and minerals.

[Toward a better knowledge of the pesticides used by municipality in rural society: example of Limousin Region (France)]. / Vers une meilleure connaissance de l'utilisation par les communes des produits phytosanitaires en zones rurale: exemple de la Région Limousin (France).

A survey concerning pesticide uses by municipalities located in countryside areas, was carried out through inquiries submitted to 39 different municipalities representative of the Limousin area (France) except for Limoges city. The rate of answers was 72 % (28 municipalities). Extensive breeding of bovines and sheep represents the majority of agricultural practices in this area. The objective of this investigation to highlight the operational pesticides uses among different municipalities. The main results showed the use of a large number of different commercial products (61, representing 46 active molecules) as well as the intensive use of herbicides such as Glyphosate. Compared to the usual regional agricultural uses in Limousin, the part of Dichlobenil, Diuron, Isoxaben and Diflufénicanil used by the municipalities could be strong. The municipalities usually try to comply with the safety requirements regarding pesticide uses but the need for preventive actions such as the training of municipality workers as well as informations regarding alternative weeding techniques is required. Moreover, due to the relatively low permeability of the treated surfaces, the discharge of pesticides by water run-off can be significant and thus can contribute significantly to the pollution of the natural aquatic environments or the water resources for water supply.