One‐Step Synthesis of a [20]Silafullerane with an Endohedral Chloride Ion

Silicon analogues of the most prominent carbon nanostructures, namely, hollow spheroidals such as C₆₀ and the fullerene family, have been unknown to date. Herein we show that discrete Si₂₀ dodecahedra, stabilized by an endohedral guest and valence saturation, are accessible in preparative yields through a chloride‐induced disproportionation reaction of hexachlorodisilane in the presence of tri(n‐butyl)amine. X‐ray crystallography revealed that each silicon dodecahedron contains an endohedral chloride ion that imparts a net negative charge. Eight chloro substituents and twelve trichlorosilyl groups are attached to the surface of each cluster in a strictly regioregular arrangement, a thermodynamically preferred substitution pattern according to quantum‐chemical assessment. Our results demonstrate that the wet‐chemical self‐assembly of a complex, monodisperse Si nanostructure is possible under mild conditions starting from simple Si₂ building blocks.     

Characterization of different substrates for Raman spectroscopic imaging of eukaryotic cells

For Raman spectroscopic analyses of the cells and other biological samples, the choice of the right substrate material is very important to avoid loss of information in characteristic spectral features because of competing background signals. In the current study, Raman spectroscopy is used to characterize several potential Raman substrates. Raman vibrational bands of the substrate material are discussed. The surface topography is analyzed by atomic force microscopy, and the root mean square surface roughness values are reported. Biocompatibility of the substrates is tested with Hep G2 cells evaluating cellular morphology as well as live/dead staining. Calcium fluoride, silicon, fused silica, borofloat glass, and silicon nitride membranes support cell growth and adherence. Silicon, borofloat glass, and fused silica give rise to Raman signals in the region of interest. Calcium fluoride substrate (UV grade) is suitable for Raman spectroscopic investigation of living cells. Nickel foil is suitable substrate for Raman spectroscopic investigation but cellular adherence and viability depend on the quality of the foil. Silicon nitride membranes coated with nickel chrome is a suitable Raman substrate in closed microfluidic systems. Copyright © 2016 John Wiley & Sons, Ltd.     

Reactions of Polyarsenides with Acetylene: Synthesis and Characterization of [Cs([18]crown‐6)]2As7C14H11·6NH3 and As2C6H6

The reaction of Cs₃As₇ with diphenylacetylene in the presence of 18 crown‐6 in liquid ammonia results in the formation of the new compound [Cs( 18 crown‐6)]₂As₇C₁₄H₁₁ · 6NH₃, which crystallizes in black monoclinic crystals. It contains the first monosubstituated heptaarsenide anion with a hydrocarbon‐only substituent and theoretical calculations show a significant influence of the organic substituent on the electronic structure within the cage. The (Z)‐1, 2‐diphenylethenyl‐heptaarsenide di‐anion can be seen as the first step towards the formation of 1, 2,3‐triarsolides. Further experiments regarding the reaction of Rb₃As₁₁ and Cs₃As₁₁ with acetylene gas in liquid ammonia reveal the formation of the diarsabarrelene As₂C₆H₆, which crystallizes as colorless orthorhombic crystals. Calculations based on the structural data obtained by X‐ray crystallography show the electronically inert character of the arsenic lone pair.     

Capillary isoelectric focusing immunoassay as a new nanoscale approach for the detection of oligoclonal bands

The detection of oligoclonal bands (OCBs) in cerebrospinal fluid is an indicator of intrathecal synthesis of immunoglobulins which is a neurochemical sign of chronic inflammatory brain diseases. Intrathecally synthesized IgGs are typically observed in patients with multiple sclerosis. The current standard protocol for the detection of OCBs is IEF on agarose or polyacrylamide gels followed by immunoblotting or silver staining. These methods are time consuming, show substantial interlaboratory variation and cannot be used in a high throughput‐approach. We have developed a new nanoscale method for the detection of OCBs based on automated capillary IEF followed by immunological detection. Evidence for intrathecal IgG synthesis was found in all tested patients (n = 27) with multiple sclerosis, even in two subjects who did not have oligoclonal bands according to standard methods. The test specificity was at 97.5% (n = 19). Our findings indicate that the novel OCB‐CIEF‐immunoassay is suitable for the rapid and highly sensitive detection of OCBs in clinical samples. Furthermore, the method allows for a higher sample throughput than the current standard methods.     

RNA Cleavage Catalyzed by Amphoteric Bis(acyl)guanidinium Derivatives

Described herein are two series (twelve compounds each) of very closely related guanidinium‐based receptors and their ability to catalyze hydrolytic cleavage of a unique RNA substrate – oligo‐dT flanked t rans‐ A ctivation R esponsive region of the HIV‐1 mRNA, TAR RNA. The significant difference in activities of otherwise very similar compounds is discussed, and direct and indirect evidences supporting our interpretation are presented. The results indicate that improvements in catalytic efficiency could be achieved with little modification of the structure of a relatively weak catalyst, and that a crucial feature could be a finely calibrated interplay between anion‐binding and proton‐donating abilities.     

Chemical mimicry: hierarchical 1D TiO2@ZrO2 core-shell structures reminiscent of sponge spicules by the synergistic effect of silicatein-α and silintaphin-1

In nature, mineralization of hard tissues occurs due to the synergistic effect of components present in the organic matrix of these tissues, with templating and catalytic effects. In Suberites domuncula, a well-studied example of the class of demosponges, silica formation is mediated and templated by an axial proteinaceous filament with silicatein-α, one of the main components. But so far, the effect of other organic constituents from the proteinaceous filament on the catalytic effect of silicatein-α has not been studied in detail. Here we describe the synthesis of core-shell TiO(2)@SiO(2) and TiO(2)@ZrO(2) nanofibers via grafting of silicatein-α onto a TiO(2) nanowire backbone followed by a coassembly of silintaphin-1 through its specifically interacting domains. We show for the first time a linker-free, one-step funtionalization of metal oxides with silicatein-α using glutamate tag. In the presence of silintaphin-1 silicatein-α facilitates the formation of a dense layer of SiO(2) or ZrO(2) on the TiO(2)@protein backbone template. The immobilization of silicatein-α onto TiO(2) probes was characterized by atomic force microscopy (AFM), optical light microscopy, and high-resolution transmission electron microscopy (HRTEM). The coassembly of silicatein-α and silintaphin-1 may contribute to biomimetic approaches that pursue a controlled formation of patterned biosilica-based biomaterials.     

Solution synthesis of nanoparticular binary transition metal antimonides

The preparation of nanoengineered materials with controlled nanostructures, for example, with an anisotropic phase segregated structure or a regular periodicity rather than with a broad range of interparticle distances, has remained a synthetic challenge for intermetallics. Artificially structured materials, including multilayers, amorphous alloys, quasicrystals, metastable crystalline alloys, or granular metals, are mostly prepared using physical gas phase procedures. We report a novel, powerful solution-mediated approach for the formation of nanoparticular binary antimonides based on presynthesized antimony nanoparticles. The transition metal antimonides M-Sb (M = Co, Ni, Cu(2), Zn) were obtained with sizes ranging from 20 and 60 nm. Through careful control of the reaction conditions, single-phase nanoparticular antimonides were synthesized. The nanophases were investigated by powder X-ray diffraction and (high resolution) electron microscopy. The approach is based on activated metal nanoparticles as precursors for the synthesis of the intermetallic compounds. X-ray powder diffraction studies of reaction intermediates allowed monitoring of the reaction kinetics. The small particle size of the reactants ensures short diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis.     

Wet chemical synthesis and a combined X-ray and Mössbauer study of the formation of FeSb2 nanoparticles

Understanding how solids form is a challenging task, and few strategies allow for elucidation of reaction pathways that are useful for designing the synthesis of solids. Here, we report a powerful solution-mediated approach for formation of nanocrystals of the thermoelectrically promising FeSb(2) that uses activated metal nanoparticles as precursors. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. A time- and temperature-dependent study of formation of nanoparticular FeSb(2) by X-ray powder diffraction and iron-57 M?ssbauer spectroscopy showed the incipient formation of the binary phase in the temperature range of 200-250 °C.