2018, Eleazer, B.J., Smith, M.D., Popov, A.A., Peryshkov, D.V.

In this work, we introduce a novel approach for the selective assembly of heterometallic complexes by unprecedented coordination of coinage metal cations to strained single ruthenium-boron bonds on a surface of icosahedral boron clusters. M(i) cations (M = Cu, Ag, and Au) insert into B-Ru bonds of the (BB)-carboryne complex of ruthenium with the formation of four-membered B-M-Ru-B metalacycles. Results of theoretical calculations suggest that bonding within these metalacycles can be best described as unusual three-center-two-electron B-M⋯Ru interactions that are isolobal to B-H⋯Ru borane coordination for M = Cu and Ag, or the pairs of two-center-two electron B-Au and Au-Ru interactions for M = Au. These transformations comprise the first synthetic route to exohedral coinage metal boryl complexes of icosahedral closo-{C2B10} clusters, which feature short Cu-B (2.029(2) Å) and Ag-B (2.182(3) Å) bonds and the shortest Au-B bond (2.027(2) Å) reported to date. The reported heterometallic complexes contain Cu(i) and Au(i) centers in uncharacteristic square-planar coordination environments. These findings pave the way to rational construction of a broader class of multimetallic architectures featuring M-B bonds.

2014, Asenova, I., Manova, D., Mändl, S.

In this paper we investigate the possibility of incorporating nitrogen into amorphous, photocatalytic TiO2 thin films, prepared at room temperature, during the growth process. The aim is to reduce the bandgap of the UV active thin films. Physical vapor deposition experiments employing a titanium vacuum arc with gas backfill ranging from pure oxygen to pure nitrogen, are carried out. The resulting films are characterized for chemical composition, phase composition, optical properties and hydrophilicity in order to determine a correlation between gas composition and thin film properties. The experimental results point that a visible change in the band structure of the deposited layers is achieved.

2016, Siles, P.F., Hahn, T., Salvan, G., Knupfer, M., Zhu, F., Zahn, D.R.T., Schmidt, O.G.

Organic materials such as phthalocyanine-based systems present a great potential for organic device applications due to the possibility of integrating films of different organic materials to create organic heterostructures which combine the electrical capabilities of each material. This opens the possibility to precisely engineer and tune new electrical properties. In particular, similar transition metal phthalocyanines demonstrate hybridization and charge transfer properties which could lead to interesting physical phenomena. Although, when considering device dimensions, a better understanding and control of the tuning of the transport properties still remain in the focus of research. Here, by employing conductive atomic force microscopy techniques, we provide an insight about the nanoscale electrical properties and transport mechanisms of MnPc and fluorinated phthalocyanines such as F16CuPc and F16CoPc. We report a transition from typical diode-like transport mechanisms for pure MnPc thin films to space-charge-limited current transport regime (SCLC) for Pc-based heterostructures. The controlled addition of fluorinated phthalocyanine also provides highly uniform and symmetric-polarized transport characteristics with conductance enhancements up to two orders of magnitude depending on the polarization. We present a method to spatially map the mobility of the MnPc/F16CuPc structures with a nanoscale resolution and provide theoretical calculations to support our experimental findings. This well-controlled nanoscale tuning of the electrical properties for metal transition phthalocyanine junctions stands as key step for future phthalocyanine-based electronic devices, where the low dimension charge transfer, mediated by transition metal atoms could be intrinsically linked to a transfer of magnetic moment or spin.

2018, Stolle, H.L.K.S., Garwe, F., Müller, R., Krech, T., Oberleiter, B., Rainer, T., Fritzsche, W., Stolle, A.

In this work we present a simple, fast and cost-efficient synthesis of a metal nanoparticle catalyst on a glass support for plasmon driven heterogeneous photocatalysis. It is based on efficient mixing of metal salts as particle precursors with porous glass as the supporting material in a mixer ball mill, and the subsequent realization of a complete catalyst system by laser sintering the obtained powder on a glass plate as the support. By this, we could obtain catalyst systems with a high particle proportion and an even spatial particle distribution in a rapid process, which could be applied to various kinds of metal salt resulting in plasmon active metal nanoparticles. Furthermore, the catalyst production process presented here is easily scalable to any size of area that is to be coated. Finally, we demonstrate the catalytic performance of our catalysts by a model reaction of ethanol degradation in a self-designed lab-scale reactor.

2014, Auguste, J.-L., Humbert, G., Leparmentier, S., Kudinova, M., Martin, P.-O., Delaizir, G., Schuster, K., Litzkendorf, D.

The objective of this paper is to demonstrate the interest of a consolidation process associated with the powder-in-tube technique in order to fabricate a long length of specialty optical fibers. This so-called Modified Powder-in-Tube (MPIT) process is very flexible and paves the way to multimaterial optical fiber fabrications with different core and cladding glassy materials. Another feature of this technique lies in the sintering of the preform under reducing or oxidizing atmosphere. The fabrication of such optical fibers implies different constraints that we have to deal with, namely chemical species diffusion or mechanical stress due to the mismatches between thermal expansion coefficients and working temperatures of the fiber materials. This paper focuses on preliminary results obtained with a lanthano-aluminosilicate glass used as the core material for the fabrication of all-glass fibers or specialty Photonic Crystal Fibers (PCFs). To complete the panel of original microstructures now available by the MPIT technique, we also present several optical fibers in which metallic particles or microwires are included into a silica-based matrix.

2016, Sun, Xiaolei, Hao, Guang-Ping, Lu, Xueyi, Xi, Lixia, Liu, Bo, Si, Wenping, Ma, Chuansheng, Liu, Qiming, Zhang, Qiang, Kaskel, Stefan, Schmidt, Oliver G.

We propose an effective strategy to engineer a unique kind of porous carbon cuboid with tightly anchored cobalt/cobalt oxide nanoparticles (PCC–CoOx) that exhibit outstanding electrochemical performance for many key aspects of lithium-ion battery electrodes. The host carbon cuboid features an ultra-polar surface reflected by its high hydrophilicity and rich surface defects due to high heteroatom doping (N-/O-doping both higher than 10 atom%) as well as hierarchical pore systems. We loaded the porous carbon cuboid with cobalt/cobalt oxide nanoparticles through an impregnation process followed by calcination treatment. The resulting PCC–CoOx anode exhibits superior rate capability (195 mA h g−1 at 20 A g−1) and excellent cycling stability (580 mA h g−1 after 2000 cycles at 1 A g−1 with only 0.0067% capacity loss per cycle). Impressively, even after an ultra-long cycle life exceeding 10 000 cycles at 5 A g−1, the battery can recover to 1050 mA h g−1 at 0.1 A g−1, perhaps the best performance demonstrated so far for lithium storage in cobalt oxide-based electrodes. This study provides a new perspective to engineer long-life, high-power metal oxide-based electrodes for lithium-ion batteries through controlling the surface chemistry of carbon host materials.

2020, Włodarczyk-Biegun, M.K., Paez, J.I., Villiou, M., Feng, J., Del Campo, A.

In this paper we explore the printability of reversible networks formed by catechol functionalized PEG solutions and metal cations (Al3+, Fe3+ or V3+). The printability and shape fidelity were dependent on the ink composition (metal ion type, pH, PEG molecular weight) and printing parameters (extrusion pressure and printing speed). The relaxation time, recovery rate and viscosity of the inks were analyzed in rheology studies and correlated with thermodynamic and ligand exchange kinetic constants of the dynamic bonds and the printing performance (i.e. shape fidelity of the printed structures). The relevance of the relaxation time and ligand exchange kinetics for printability was demonstrated. Cells seeded on the materials crosslinked with Al3+, Fe3+ ions were viable and revealed well-spread morphologies during 7 day culture, indicating the potential of the formulations to be used as inks for cell encapsulation. The proposed dynamic ink design offers significant flexibility for 3D bioprinting, and enables straightforward adjustment of the printable formulation to meet application-specific needs.

2013, Pauly, S., Löber, L., Petters, R., Stoica, M., Scudino, S., Kühn, U., Eckert, J.

Metallic glasses and their descendants, the so-called bulk metallic glasses (BMGs), can be regarded as frozen liquids with a high resistance to crystallization. The lack of a conventional structure turns them into a material exhibiting near-theoretical strength, low Young's modulus and large elasticity. These unique mechanical properties can be only obtained when the metallic melts are rapidly cooled to bypass the nucleation and growth of crystals. Most of the commonly known and used processing routes, such as casting, melt spinning or gas atomization, have intrinsic limitations regarding the complexity and dimensions of the geometries. Here, it is shown that selective laser melting (SLM), which is usually used to process conventional metallic alloys and polymers, can be applied to implement complex geometries and components from an Fe-base metallic glass. This approach is in principle viable for a large variety of metallic alloys and paves the way for the novel synthesis of materials and the development of parts with advanced functional and structural properties without limitations in size and intricacy.

2016, Deng, Qingming, Heine, Thomas, Irle, Stephan, Popov, Alexey A.

The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i.e. leading to Sc-EMFs) with more realistic cage-size distribution than simulations of the Sc/C system. The main Sc encapsulation mechanism involves nucleation of several hexagons and pentagons with Sc atoms already at the early stages of carbon vapor condensation. In such proto-cages, both Sc–C σ-bonds and coordination bonds between Sc atoms and the π-system of the carbon network are present. Sc atoms are thus rather labile and can move along the carbon network, but the overall bonding is sufficiently strong to prevent dissociation even at temperatures around 2000 kelvin. Further growth of the fullerene cage results in the encapsulation of one or two Sc atoms within the fullerene. In agreement with experimental studies, an extension of the simulations to Fe and Ti as the metal component showed that Fe-EMFs are not formed at all, whereas Ti is prone to form Ti-EMFs with small cage sizes, including Ti@C28-Td and Ti@C30-C2v(3).

2014, Dawkins, E.C.M., Plane, J.M.C., Chipperfield, M.P., Feng, W., Gumbel, J., Hedin, J., Höffner, J., Friedman, J.S.

Metal species, produced by meteoric ablation, act as useful tracers of upper atmosphere dynamics and chemistry. Of these meteoric metals, K is an enigma: at extratropical latitudes, limited available lidar data show that the K layer displays a semiannual seasonal variability, rather than the annual pattern seen in other metals such as Na and Fe. Here we present the first near-global K retrieval, where K atom number density profiles are derived from dayglow measurements made by the Optical Spectrograph and Infrared Imager System spectrometer on board the Odin satellite. This robust retrieval produces density profiles with typical layer peak errors of ±15% and a 2km vertical grid resolution. We demonstrate that these retrieved profiles compare well with available lidar data and show for the first time that the unusual semiannual behavior is near-global in extent. This new data set has wider applications for improving understanding of the K chemistry and of related upper atmosphere processes. Key Points First quantitative retrieval of the terrestrial K layer from space The unusual semiannual behavior of K is near global in extent.