This work presents an extreme biomimetics route for the creation of nanostructured biocomposites utilizing a chitinous template of poriferan origin. The specific thermal stability of the nanostructured chitinous template allowed for the formation under hydrothermal conditions of a novel germanium oxide− chitin composite with a defined nanoscale structure. Using a variety of analytical techniques (FTIR, Raman, energy dispersive X-ray (EDX), near-edge X-ray absorption fine structure (NEXAFS), and photoluminescence (PL) spectroscopy, EDS-mapping, selected area for the electron diffraction pattern (SAEDP), and transmission electron microscopy (TEM)), we showed that this bioorganic scaffold induces the growth of GeO 2 nanocrystals with a narrow (150-300 nm) size distribution and predominantly hexagonal phase, demonstrating the chitin template's control over the crystal morphology. The formed GeO 2 -chitin composite showed several specific physical properties, such as a striking enhancement in photoluminescence exceeding values previously reported in GeO 2 -based biomaterials. These data demonstrate the potential of extreme biomimetics for developing new-generation nanostructured materials.

In this article, the work on Ge nanocrystals embedded in dielectric films formed by phase separation from supersaturated solid solutions is reviewed. Different methods to synthesize supersaturated solid solutions are covered, e.g., magnetron sputtering, ion implantation, and chemical vapor deposition. The phase separation is activated by subsequent high temperature annealing. Important parameters that influence the formation and properties of the Ge nanocrystals are discussed. Various matrix materials like SiO2, Al2O3, HfO2, HfAlOx, Lu2O3, ZrO2, TaZrOx, and Si3N4 are reported in the literature. The influence of the matrix on the formation and properties of the Ge nanocrystals is addressed in this review. Ge nanocrystals are investigated for applications such as charge storage nodes in nonvolatile memory devices or as silicon technology compatible light emitters. A key to establish these applications seems to be embedding the Ge nanocrystals in still amorphous matrices. This could help to avoid grain boundaries that act as leakage paths for electrical charges (unfavorable for nonvolatile memories) and facilitate defects, which could act as recombination centers (unfavorable for light emitters). A further important point is the synthesis of size and position controlled Ge nanocrystals. Both aspects are reviewed for Ge nanocrystals embedded in the mentioned matrix materials.

New energy, transport, computer and telecommunication technologies require an increasing supply of rare earth elements (REEs). As a consequence, adequate and robust detection methods become essential for the exploration and discovery of new deposits, the improved characterization of existing deposits and the future recycling of today’s high-tech products. Within this paper, we investigate the potential of combining passive reflectance (imaging and point sampling) with laser stimulated luminescence (point sampling) spectroscopic measurements across the visible, near and shortwave infrared for REE detection in non-invasive near-field mineral exploration. We analyse natural REE-bearing mineral samples from main REE-deposits around the world and focus on challenges such as the discrimination of overlapping spectroscopic features and the influence of the mineral type on detectability, feature position and mineral matrix luminescence. We demonstrate that the cross-validation of results from both methods increases the robustness and sensitivity, provides the potential for semi-quantification and enables the time- and cost-efficient detection of economically important REE, including Ce, Pr, Nd, Sm, Eu, Dy, Er, Yb and potentially also Ho and Tm.

Room-temperature optical and spin polarization up to 35% is reported in InAs/GaAs quantum dots in zero magnetic field under optical spin injection using continuous-wave optical orientation spectroscopy. The observed strong spin polarization is suggested to be facilitated by a shortened trion lifetime, which constrains electron spin relaxation. Our finding provides experimental demonstration of the highly anticipated capability of semiconductor quantum dots as highly polarized spin/light sources and efficient spin detectors, with efficiency greater than 35% in the studied quantum dots.Original Publication:Jan Beyer, Irina A Buyanova, S. Suraprapapich, C. W. Tu and Weimin Chen, Strong room-temperature optical and spin polarization in InAs/GaAs quantum dot structures, 2011, Applied Physics Letters, (98), 20, 203110.http://dx.doi.org/10.1063/1.3592572Copyright: American Institute of Physicshttp://www.aip.org

Thin films of pure Ge and ZrO 2 , composite Ge-ZrO 2 layers and [Ge-ZrO 2 /ZrO 2 ] 40 multilayers were fabricated by confocal radio frequency magnetron sputtering. The structural and optical properties of these samples were studied by spectroscopic ellipsometry, Raman scattering and Fourier transform infrared spectroscopy in dependence of the chemical composition and the annealing treatment. It could be shown that rapid thermal annealing stimulates a phase separation process within the Ge-ZrO 2 composite films leading to a formation of Ge nanocrystals and tetragonal ZrO 2. The starting point of this process depends significantly on the Ge content: the higher the Ge content, the lower is the crystallization temperature. Compared to the monoclinic phase, the tetragonal ZrO 2 phase offers an enhanced permittivity.