Ion polished Cr/Sc attosecond multilayer mirrors for high water window reflectivity.

Recent advances in the development of attosecond soft X-ray sources ranging into the water window spectral range, between the 1s states of carbon and oxygen (284 eV-543 eV), are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of broadband Cr/Sc attosecond multilayer mirrors with nearly atomically smooth interfaces by an optimized ion beam deposition and assisted interface polishing process. This yields to our knowledge highest multilayer mirror reflectivity at 300 eV near normal incidence. The results are verified by transmission electron microscopy (TEM) and soft/hard X-ray reflectometry.

Narrow-band red-emitting Sr[LiAl3N4]:Eu²âº as a next-generation LED-phosphor material.

To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu(2+), Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at λ(max) ~ 650 nm with a full-width at half-maximum of ~1,180 cm(-1) (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (R(a)8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

TEM preparation methods and influence of radiation damage on the beam sensitive CaCO3 shell of Emiliania huxleyi.

The ultrastructure of biologically formed calcium carbonate crystals like the shell of Emiliania huxleyi depends on the environmental conditions such as pH value, temperature and salinity. Therefore, they can be used as indicator for climate changes. However, for this a detailed understanding of their crystal structure and chemical composition is required. High resolution methods like transmission electron microscopy can provide those information on the nanoscale, given that sufficiently thin samples can be prepared. In our study, we developed sample preparation techniques for cross-section and plan-view investigations and studied the sample stability under electron bombardment. In addition to the biological material (Emiliania huxleyi) we also prepared mineralogical samples (Iceland spar) for comparison. High resolution transmission electron microscopy imaging, electron diffraction and electron energy-loss spectroscopy studies revealed that all prepared samples are relatively stable under electron bombardment at an acceleration voltage of 300 kV when using a parallel illumination. Above an accumulated dose of ∼10(5) e/nm2 the material--independent whether its origin is biological or geological--transformed to poly-crystalline calcium oxide.

Increasing crystallinity for improved electrical conductivity of TiO2 blocking layers.

In this Research Article, we present our results on the optimization of the TiO2 blocking layer to improve the efficiency of organic and hybrid solar cells and make them more competitive with standard silicon devices. The major aim of the present work is to increase the electrical conductivity within the TiO2 blocking layer to guarantee for efficient charge carrier transport and separation. This is realized by optimizing the calcination processes toward an increase in particle/domain size to increase the unpercolated pathways for charge carriers and to get deeper insight into the morphology of the sol-gel produced films.

Infiltration of polymer hole-conductor into mesoporous titania structures for solid-state dye-sensitized solar cells.

The degree of filling of titania nanostructures with a solid hole-conducting material is important for the performance of solid-state dye-sensitized solar cells (ssDSSCs). Different ways to infiltrate the hole-conducting polymer poly(3-hexylthiophene) (P3HT) into titania structures, both granular structures as they are already applied commercially and tailored sponge nanostructures, are investigated. The solar cell performance is compared to the morphology determined with scanning electron microscopy (SEM) and time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The granular titania structure, commonly used for ssDSSCs, shows a large distribution of particle and pore sizes, with porosities in the range from 41 to 67%, including even dense parts without pores. In contrast, the tailored sponge nanostructure has well-defined pore sizes of 25 nm with an all-over porosity of 54%. Filling of the titania structures with P3HT by solution casting results in a mesoscopic P3HT overlayer and consequently a bad solar cell performance, even though a filling ratio of 67% is observed. For the infiltration by repeated spin coating, only 57% pore filling is achieved, whereas filling by soaking in the solvent with subsequent spin coating yields filling as high as 84% in the case of the tailored titania sponge structures. The granular titania structure is filled less completely than the well-defined porous structures. The solar cell performance is increased with an increasing filling ratio for these two ways of infiltration. Therefore, filling by soaking in the solvent with subsequent spin coating is proposed.

Synchronous emission from nanometric silver particles through plasmonic coupling on silver nanowires.

We investigated silver nanowires using correlative wide-field fluorescence and transmission electron microscopy. In the wide-field fluorescence images, synchronous emission from different distinct positions along the silver nanowires was observed. The sites of emission were separated spatially by up to several micrometers. Nanowires emitting in such cooperative manner were then also investigated with a combination of transmission electron microscopy based techniques, such as high-resolution, bright-field imaging, electron diffraction, high-angle annular dark-field imaging, and energy-dispersive X-ray spectroscopy. In particular, analyzing the chemical composition of the emissive areas using energy-dispersive X-ray spectroscopy led to the model that the active emissive centers are small silver clusters generated photochemically and that individual clusters are coupled via surface plasmons of the nanowire.

The FoxP subclass in Xenopus laevis development.

We have investigated the sequences and the expression patterns of different members of the Xenopus laevis FoxP gene subfamily during embryogenesis. Low stringency hybridisation of a tadpole cDNA library with an xlFoxP2 fragment led to the isolation of several splice variants of xlFoxP1, xlFoxP2 and xlFoxP4. These variants do not only differ by utilisation of different leader exons, but also by alternative usage of coding exons thereby leading to functional alterations. For xlFoxP1b, we show that insertion of an additional exon disrupts binding to the co-repressor C-terminal binding protein1. Temporal and spatial expression patterns of xlFoxP2 and xlFoxP4 were analysed by RT-PCR and by whole mount in situ hybridisation. xlFoxP2 transcripts are detected from mid-gastrula to late tadpole stages and are found to be localised to pronephros, branchial arches and distinct structures of the hind-, mid- and forebrain, including the ciliary marginal zone of the retina. xlFoxP4 RNA is already present in early cleavage stage embryos and accumulates from midblastula until the end of embryogenesis. Localised expression is found within the anterior neural fold, in the mid- and hindbrain, in the branchial arches as well as in the pancreas.