In-situ Mössbauer Spectroscopy with MIMOS II at Rio Tinto, Spain

The Rio Tinto, located in southwest Spain, exhibits a nearly constant, acidic pHvalue along its course. Due to the formation of sulfate minerals, Rio Tinto is considered a potential analogue site for sulfate-rich regions on Mars, in particular at the landing site of the Mars Exploration Rover Opportunity, where the ferric sulfate mineral jarosite was identified with Opportunity's Mössbauer spectrometer. Primary and secondary mineralogy was investigated in situ with portable Raman and Mössbauer spectrometers at four different Rio Tinto sampling sites. The two techniques analyse different sample portions due to their specific field of view and sampling depth and provide complementary mineralogical information

High-throughput synthesis of CeO₂ nanoparticles for transparent nanocomposites repelling Pseudomonas aeruginosa biofilms

Preventing bacteria from adhering to material surfaces is an important technical problem and a major cause of infection. One of nature’s defense strategies against bacterial colonization is based on the biohalogenation of signal substances that interfere with bacterial communication. Biohalogenation is catalyzed by haloperoxidases, a class of metal-dependent enzymes whose activity can be mimicked by ceria nanoparticles. Transparent CeO(2)/polycarbonate surfaces that prevent adhesion, proliferation, and spread of Pseudomonas aeruginosa PA14 were manufactured. Large amounts of monodisperse CeO(2) nanoparticles were synthesized in segmented flow using a high-throughput microfluidic benchtop system using water/benzyl alcohol mixtures and oleylamine as capping agent. This reduced the reaction time for nanoceria by more than one order of magnitude compared to conventional batch methods. Ceria nanoparticles prepared by segmented flow showed high catalytic activity in halogenation reactions, which makes them highly efficient functional mimics of haloperoxidase enzymes. Haloperoxidases are used in nature by macroalgae to prevent formation of biofilms via halogenation of signaling compounds that interfere with bacterial cell–cell communication (“quorum sensing”). CeO(2)/polycarbonate nanocomposites were prepared by dip-coating plasma-treated polycarbonate panels in CeO(2) dispersions. These showed a reduction in bacterial biofilm formation of up to 85% using P. aeruginosa PA14 as model organism. Besides biofilm formation, also the production of the virulence factor pyocyanin in is under control of the entire quorum sensing systems P. aeruginosa. CeO(2)/PC showed a decrease of up to 55% in pyocyanin production, whereas no effect on bacterial growth in liquid culture was observed. This indicates that CeO(2) nanoparticles affect quorum sensing and inhibit biofilm formation in a non-biocidal manner

Extraordinary Performance of Carbon-Coated Anatase TiO2 as Sodium-Ion Anode

The synthesis of in situ polymer-functionalized anatase TiO2 particles using an anchoring block copolymer with hydroxamate as coordinating species is reported, which yields nanoparticles (≈11 nm) in multigram scale. Thermal annealing converts the polymer brushes into a uniform and homogeneous carbon coating as proven by high resolution transmission electron microscopy and Raman spectroscopy. The strong impact of particle size as well as carbon coating on the electrochemical performance of anatase TiO2 is demonstrated. Downsizing the particles leads to higher reversible uptake/release of sodium cations per formula unit TiO2 (e.g., 0.72 eq. Na+ (11 nm) vs only 0.56 eq. Na+ (40 nm)) while the carbon coating improves rate performance. The combination of small particle size and homogeneous carbon coating allows for the excellent electrochemical performance of anatase TiO2 at high (134 mAh g−1 at 10 C (3.35 A g−1)) and low (≈227 mAh g−1 at 0.1 C) current rates, high cycling stability (full capacity retention between 2nd and 300th cycle at 1 C) and improved coulombic efficiency (≈99.8%)

Opening a new vista in solid-state science: Tuning electronic properties by gate-induced doping

Superconductivity at temperatures as high as T-C = 117 K is found in single-crystal field effect transistor devices based on C-60 co-crystals (C-60.2CHX(3), X = Cl, Br) on gate-induced doping. The method, recent breakthroughs, and its fundamental character towards tuning the valence electron concentration of solids in general are highlighted in this article

Ta

Bulk Ta4FeTe4 is a highly anisotropic metallic compound consisting of single molecular wires. In the crystalline bulk phase, sub-nanometer wires self-assemble to form a hexagonal packing of rods resulting in a fibrous crystal morphology. In this work we report the synthesis and crystal growth of single crystalline Ta4FeTe4 nanowire bundles with a length of several millimeters and an aspect ratio exceeding  > 105. The nanowire bundle diameter could further be decreased by intercalation-exfoliation. Our results show that depending on the unbundling method nanowires of different length and diameter are accessible. A complete unbundling to single molecular wires of 7.9 Å is feasible with this methodology. As the Ta4FeTe4 nanowires are held together only by van der Waals interactions the properties of single molecular wires may be expected similar to those of the metallic bulk material