Ute Kolb

Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ-43

A zeolite with microporous channels (6 to 7 angstrom diameter) and mesoporous channels (~2-nanometer diameter) was made. The formation of mesopores in microporous zeolites is generally performed by postsynthesis acid, basic, and steam treatments. The hierarchical pore systems thus formed allow better adsorption, diffusion, and reactivity of these materials. By combining organic and inorganic structure-directing agents and high-throughput methodologies, we were able to synthesize a zeolite with a hierarchical system of micropores and mesopores, with channel openings delimited by 28 tetrahedral atoms. Its complex crystalline structure was solved with the use of automated diffraction tomography.

Towards automated diffraction tomography. Part II—Cell parameter determination

Automated diffraction tomography (ADT) allows the collection of three-dimensional (3d) diffraction data sets from crystals down to a size of only few nanometres. Imaging is done in STEM mode, and diffraction data are collected with quasi-parallel beam nanoelectron diffraction (NED). Here, we present a set of developed processing steps necessary for automatic unit-cell parameter determination from the collected 3d diffraction data. Cell parameter determination is done via extraction of peak positions from a recorded data set (called the data reduction path) followed by subsequent cluster analysis of difference vectors. The procedure of lattice parameter determination is presented in detail for a beam-sensitive organic material. Independently, we demonstrate a potential (called the full integration path) based on 3d reconstruction of the reciprocal space visualising special structural features of materials such as partial disorder. Furthermore, we describe new features implemented into the acquisition part.

Direct access to metal or metal oxide nanocrystals integrated with one-dimensional nanoporous carbons for electrochemical energy storage.

Metal and metal oxide nanocrystals have sparked great interest due to their excellent catalytic, magnetic, and electronic properties. Particularly, the integration of metallic nanocrystals and one-dimensional (1D) electronically conducting carbons to form metal-carbon hybrids can lead to enhanced physical and chemical properties or even the creation of new properties with respect to single component materials. However, direct access to thermally stable and structurally ordered 1D metal-carbon hybrids remains a primary challenge. We report an in situ fabrication of Co(3)O(4) or Pt nanocrystals incorporated into 1D nanoporous carbons (NPCs) via an organometallic precursor-controlled thermolysis approach. The AB(2)-type (one diene and two dienophile) 3,4-bis(4-dodecynylphenyl)-substituted cyclopentadienone and its relevant cobalt or platinum complex are first impregnated into the nanochannels of AAO (anodic alumina oxide) membranes. The intermolecular Diels-Alder reaction of these precursor molecules affords the formation of cobalt or platinum functionalized polyphenylene skeletons. Subsequent thermolysis transforms the polyphenylene backbones into 1D nanoporous carbonaceous frameworks, while the metallic moieties are reduced into Co or Pt nanocrystals, respectively. After removal of the AAO template, 1D NPCs/Co(3)O(4) or NPCs/Pt are obtained, for which structural characterizations reveal that high-quality Co(3)O(4) or Pt nanocrystals are distributed homogeneously within carbon frameworks. These unique 1D metal-carbon hybrids exhibit a promising potential in electrochemical energy storage. NPCs/Co(3)O(4) is evaluated as an electrode material in a supercapacitor, for which Co(3)O(4) nanocrystals contribute an exceptionally high gravimetric capacitance value of 1066 F g(-1). NPCs/Pt is applied as an electrocatalyst showing excellent catalytic efficiency toward methanol oxidation in comparison to commercial E-TEK (Pt/C) catalyst.

The role of biosilica in the osteoprotegerin/RANKL ratio in human osteoblast-like cells

Earlier studies have demonstrated that biosilica, synthesized by the enzyme silicatein, induces hydroxyapatite formation in osteoblast-like SaOS-2 cells. Here we study the effect of biosilica on the expressions of osteoprotegerin [OPG] and the receptor activator for NF-kappaB ligand [RANKL] in the SaOS-2 cell model. We show that during growth of SaOS-2 cells on biosiliceous matrices hydroxyapatite formation is induced, while syntheses of cartilaginous proteoglycans and sulfated glycosaminoglycans are down-regulated. Furthermore, quantitative real-time RT-PCR analysis revealed a strong time-depended increase in expression of OPG in biosilica exposed SaOS-2 cells while the steady-state expression level of RANKL remained unchanged. These results have been corroborated on the protein level by ELISA assays. Therefore, we propose that biosilica stimulated OPG synthesis in osteoblast-like cells counteracts those pathways that control RANKL expression and function (e.g. maturation of pre-osteoclasts and activation of osteoclasts). Hence, the data obtained in the present study reveal the considerable biomedical potential of biosilica for treatment and prophylaxis of osteoporotic disorders.

Bismuth‐Catalyzed Growth of SnS2 Nanotubes and Their Stability

Along with carbon nanotubes, non-carbon nanostructureshave attracted much attention over the past few years. Owingto their unusual geometry and promising physical properties,the study of inorganic fullerene nanostructures has becomeone of the key topics in nanoscale research since the firstreport on WS

The structure of charoite, (K,Sr,Ba,Mn)(15-16)(Ca,Na)(32) (Si(70)(O,OH)(180)) (OH,F)(4.0)center dot nH(2)O, solved by conventional and automated electron diffraction

Abstract Charoite, ideally (K,Sr,Ba,Mn)15-16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4.0·nH2O, a rare mineral from the Murun massif in Yakutiya, Russia, was studied using high-resolution transmission electron microscopy, selected-area electron diffraction, X-ray spectroscopy, precession electron diffraction and the newly developed technique of automated electron-diffraction tomography. The structure of charoite (a = 31.96(6) Å, b = 19.64(4) Å, c = 7.09(1) Å, β = 90.0(1)º, V = 4450(24) Å3, space group P21/m) was solved ab initio by direct methods from 2878 unique observed reflections and refined to R1/wR2 = 0.17/0.21. The structure can be visualized as being composed of three different dreier silicate chains: a double dreier chain, [Si6O17]10-; a tubular loop-branched dreier triple chain, [Si12O30]12-; and a tubular hybrid dreier quadruple chain, [Si17O43]18-. The silicate chains occur between ribbons of edge-sharing Ca and Na-octahedra. The chains of tetrahedra and the ribbons of octahedra extend parallel to the z axis. K+, Ba2+, Sr2+, Mn2+ and H2O molecules lie inside tubes and channels of the structure. On the basis of microprobe analyses and occupancy refinement of the cation sites, the crystal chemical formula of this charoite can be written as (Z = 1): (K13.88Sr1.0Ba0.32Mn0.36)∑15.56(Ca25.64Na6.36)∑32[(Si6O11(O,OH)6)2(Si12O18(O,OH)12)2(Si17O25(O,OH)18)2](OH,F)4.0·3.18H2O.

Controlled synthesis of linear and branched Au@ZnO hybrid nanocrystals and their photocatalytic properties

Colloidal Au@ZnO hybrid nanocrystals with linear and branched shape were synthesized. The number of ZnO domains on the Au seeds can be controlled by the solvent mixture. Imidazole-functionalized Au@ZnO hybrid nanocrystals were soluble in water and exhibited a greatly enhanced photocatalytic activity compared to ZnO nanocrystals. The pristine heterodimeric NPs were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis spectroscopy.

Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa

This work describes the preparation of ternary nanoparticles based on the Heusler compound Co2FeGa. Nanoparticles with sizes of about 20?nm were synthesized by reducing a methanol impregnated mixture of CoCl2 ? 6H2O, Fe(NO3)3 ? 9H2O and Ga(NO3)3 ? xH2O after loading on fumed silica. The dried samples were heated under pure H2 gas at 900??C. The obtained nanoparticles?embedded in silica?were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and M??bauer spectroscopy. All methods clearly revealed the Heusler-type L21 structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addition to the occurrence of the L21 structure. The magnetic moment of the particles is about 5?B at low temperature in good agreement with the value of bulk material. This suggests that the half-metallic properties are conserved even in particles on the 10?nm scale.

Automated Diffraction Tomography for the Structure Elucidation of Twinned, Sub‐micrometer Crystals of a Highly Porous, Catalytically Active Bismuth Metal–Organic Framework

The number of metal–organic framework (MOF) compounds has increased almost exponentially over the last decade as a consequence of their fascinating structures and potential applications. They are composed of inorganic building units, such as metal ions or clusters, which are connected through organic linker molecules to form a porous three-dimensional network. Most of the MOFs are based on rigid polycarboxylate linker molecules, but a large variety of metal ions, mainly transition-metal ions, have also been incorporated. The chemical and thermal stability of metal carboxylate based MOFs is crucial for potential applications and depends on the metal ions incorporated. In general, metal ions in higher oxidation states lead to more stable structures. While the use of divalent metal ions often results in the formation of single crystals, whose structures can be routinely determined by single-crystal X-ray diffraction, triand tetravalent metal carboxylates are mostly obtained as microcrystalline powders and the determination of their structures poses immense challenges. 4c,5] Direct methods have been successfully employed, but complicated structures with large unit cells necessitate the use of nonstandard approaches. Thus, computational assisted structure determination, namely, the AASBU approach (assembling of secondary building units), the ligand-replacement strategy, and DFT calculations have been applied. Recently automated diffraction tomography (ADT) has been introduced as a new method for collecting three-dimensional electron diffraction data from single nanosized crystals, thus allowing singlecrystal analysis even for porous and organic sub-microcrystalline samples. A trivalent metal that exhibits interesting catalytic properties is bismuth. It is nontoxic, noncarcinogenic, and for a rare metal relatively inexpensive, and thus bismuth compounds are used as green catalysts. Despite these characteristics, the number of bismuth-based MOFs is rather limited and only a few compounds with limited porosity have been described. This is in contrast to the many known bismuth-oxo clusters, which could possibly be used for the construction of new MOFs. Here, we present the synthesis of the first highly crystalline, porous, and catalytically active bismuth-based MOF Bi(BTB) (BTB = 1,3,5-benzenetrisbenzoate), whose structure was elucidated by a combination of electron diffraction, Rietveld refinement, and DFT calculations. Bi(BTB), denoted as CAU-7 (CAU = ChristianAlbrechts-Universit t) was synthesized by using conventional as well as microwave (MW) assisted heating. The reaction of Bi(NO3)3·5 H2O with H3BTB in methanol at 120 8C led to phase-pure CAU-7 (for a detailed synthesis procedure see the Supporting Information). The reaction time can be reduced from 12 h to 20 min by using MW-assisted instead of conventional heating, but this leads to the formation of 10–20 mm large agglomerates of strongly intergrown elongated crystals of about 100 nm (see Figures S2–S4 in the Supporting Information). The addition of DMF in the conventional synthesis results in the formation of larger rodlike crystals ranging from 200 to 300 nm in length. Transmission electron microscopy confirmed that isolated CAU-7 crystals have a typical rodlike shape with different length/diameter ratios (see Figure S5 in the Supporting Information). Such isolated rods were used to collect electron diffraction data by automated diffraction tomography (ATD). Single-crystal ADT electron diffraction datasets were collected using a cryo holder cooled to 120 K and mild illumination conditions. To prevent beam damage and improve the signal intensity, the diffraction data were acquired in the precession mode. The three-dimensional diffraction space reconstruction leads to lattice parameters a = 32 , b = 28 , c = 4 , a = b = g = 908, and extinction group Pb-a. The reconstructed reciprocal space is shown in Figure 1. [*] M. Feyand, T. Reimer, Prof. Dr. N. Stock Institut f r Anorganische Chemie Christian Albrechts Universit t zu Kiel Max-Eyth Strasse 2, 24118 Kiel (Germany) E-mail: stock@ac.uni-kiel.de

Structural Characterization of Organics Using Manual and Automated Electron Diffraction

In the last decade the importance of transmission electron microscopic studies has become increasingly important with respect to the characterization of organic materials, ranging from small organic molecules to polymers and biological macromolecules. This review will focus on the use of transmission electron microscope to perform electron crystallography experiments, detailing the approaches in acquiring electron crystallographic data. The traditional selected area approach and the recently developed method of automated diffraction tomography (ADT) will be discussed with special attention paid to the handling of electron beam sensitive organic materials.