λ³/1000 plasmonic nanocavities for biosensing fabricated by soft UV nanoimprint lithography

Arrays of plasmonic nanocavities with very low volumes, down to λ(3)/1000, have been fabricated by soft UV nanoimprint lithography. Nearly perfect omnidirectional absorption (3-70°) is demonstrated for the fundamental mode of the cavity (λ ? 1.15 μm). The second-order mode exhibits a sharper resonance with strong angular dependence and total optical absorption when the critical coupling condition is fulfilled (45-50°, λ ? 750 nm). It leads to high refractive index sensitivity (405 nm/RIU) and figure of merit (～21) and offers new perspectives for efficient biosensing experiments in ultralow volumes.     

Structure-dependent coherent acoustic vibrations of hollow gold nanospheres

Hollow gold nanospheres (HGNs) were excited with ultrashort laser pulses, and the coherent vibrational response was examined using femtosecond time-resolved transient absorption. The results indicated that HGNs support an isotropic mode, resulting in periodic modulation of the surface plasmon differential absorption. Two different categories of coherent acoustic vibrations, which depend on particle dimensions, were observed for HGNs. Further, the vibration launching mechanism was dependent upon the dimensions of the HGN. Coherent vibrations in HGNs characterized by small outer radii (<10 nm) and low cavity-radius-to-outer-shell radius aspect ratios (<0.5) were excited by a direct mechanism, whereas the vibrations observed for the larger particles (>25 nm OR) with higher aspect ratios (>0.5) resulted from an indirect mechanism. These findings may be significant for developing a predictive understanding of nanostructure optical and mechanical properties.     

Synthesis of YAG:Ce/TiO2 nanocomposite films

Our work is devoted to the development of YAG:Ce³⁺ phosphor nanoparticle-based converter layer for white LEDs. To avoid losses due to scattering effects, the strategy is to control separately the down-conversion and the extraction of light instead of using micron-sized luminescent particles acting simultaneously as both converter and scatterer. YAG:Ce nanoparticles were synthesized by a glycothermal method in autoclave at low temperature (300 °C). Y₃Al₅O₁₂ garnet phase with a crystallite size of 25 nm was obtained, as verified by X-ray diffraction and electron microscopy. The quantum yield of nanoparticles is 55%. The colloidal nanoparticles are finally incorporated into a sol-gel matrix of TiO₂. The small difference in refractive index between particles and matrix and the nanosize of the particles contribute to the transparency of the converter films. The surface of these layers can be periodically patterned by soft nano-imprint lithography. The diffraction due to the obtained photonic crystal at the surface may offer the opportunity to compensate the absence of scattering to extract the converted light.     

Contamination of bottled waters with antimony leaching from polyethylene terephthalate (PET) increases upon storage

Antimony concentrations were determined in 132 brands of bottled water from 28 countries. Two of the brands were at or above the maximum allowable Sb concentration for drinking water in Japan (2 microg/L). Elevated concentrations of Sb in bottled waters are due mainly to the Sb2O3 used as the catalyst in the manufacture of polyethylene terephthalate (PET(E)). The leaching of Sb from PET(E) bottles shows variable reactivity. In 14 brands of bottled water from Canada, Sb concentrations increased on average 19% during 6 months storage at room temperature, but 48 brands of water from 11 European countries increased on average 90% under identical conditions. A mineral water from France in PET(E), purchased in Germany, yielded 725 ng/L when first tested, but 1510 ng/L when it was stored for 6 months at room temperature; the same brand of water, purchased in Hong Kong, yielded 1990 ng/L Sb. Pristine groundwater containing 1.7+/-0.4 ng/L Sb (n = 6) yielded 26.6+/-2.3 ng/L Sb (n = 3) after storage in PET(E) bottles from Canada for 6 months versus 281+/-38 ng/L Sb (n = 3) in PET(E) bottles from Germany. Tap water bottled commercially in PET(E) in December 2005 contained 450+/-56 ng/L Sb (n = 3) versus 70.3+/-0.3 ng/L Sb (n = 3) when sampled from a household faucet in the same village (Bammental, Germany), and 25.7+/-1.5 ng/L Sb (n = 3) from a local artesian flow.     

Experimental evidence for mobility/immobility of metals in peat

The biogeochemical cycles of most toxic metals have been significantly altered by anthropogenic activities. Anaerobic, rain-fed organic soils are believed to record historical changes in atmospheric pollution. Suspected postdepositional mobility of trace elements, however, hinders the usefulness of peat bogs as pollution archives. To lower this uncertainty, we quantified the mobility of six trace metals in peat during an 18-month field manipulation. A replicated, reciprocal peat transplant experiment was conducted between a heavily polluted and a relatively unpolluted peatland, located 200 km apart in the Czech Republic (Central Europe). Both peatlands were Sphagnum-derived, lawn-dominated, and had water table close to the surface. A strikingly different behavior was observed for two groups of elements. Elements of group I, Fe and Mn, adjusted their abundances and vertical patterns to the host site, showing an extremely high degree of mobility. In contrast, elements of group II, Pb, Cu, Zn, and Ti, preserved their original vertical patterns at the host site, showing a high degree of immobility. Our experimental results suggest that not just lead, but also copper and zinc concentration profiles in peat are a reliable archive of temporal pollution changes within a wide pH range (2.5-5.8).     

Carnobacterium maltaromaticum: Identification,isolation tools,ecology and technological aspects in dairy products

Carnobacterium species constitute a genus of Lactic Acid Bacteria (LAB) present in different ecological niches. The aim of this article is to summarize the knowledge about Carnobacterium maltaromaticum species at different microbiological levels such as taxonomy, isolation and identification, ecology, technological aspects and safety in dairy products. Works published during the last decade concerning C. maltaromaticum have shown that this non-starter LAB (NSLAB) could present major interests in dairy product technology. Four reasons can be mentioned: i) it can grow in milk during the ripening period with no competition with starter LAB, ii) this species synthesizes different flavouring compounds e.g., 3-methylbutanal, iii) it can inhibit the growth of foodborne pathogens as Listeria monocytogenes due to its ability to produce bacteriocins, iv) it has never been reported to be involved in human diseases as no cases of human infection have been directly linked to the consumption of dairy products containing this species.