Enrico Mugnaioli

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.

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.

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.

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.

Structure analysis of titanate nanorods by automated electron diffraction tomography.

A hitherto unknown phase of sodium titanate, NaTi(3)O(6)(OH)·2H(2)O, was identified as the intermediate species in the synthesis of TiO(2) nanorods. This new phase, prepared as nanorods, was investigated by electron diffraction, X-ray powder diffraction, thermogravimetric analysis and high-resolution transmission electron microscopy. The structure was determined ab initio using electron diffraction data collected by the recently developed automated diffraction tomography technique. NaTi(3)O(6)(OH)·2H(2)O crystallizes in the monoclinic space group C2/m. Corrugated layers of corner- and edge-sharing distorted TiO(6) octahedra are intercalated with Na(+) and water of crystallization. The nanorods are typically affected by pervasive defects, such as mutual layer shifts, that produce diffraction streaks along c*. In addition, edge dislocations were observed in HRTEM images.

A MULTI-TECHNIQUE CHARACTERIZATION OF CRONSTEDTITE SYNTHESIZED BY IRON–CLAY INTERACTION IN A STEP-BY-STEP COOLING PROCEDURE

The cooling of steel containers in radioactive-waste storage was simulated in a step-by-step experiment from 90 to 40ºC. Among newly formed clay minerals observed in run products, cronstedtite was identified by a number of analytical techniques (powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy). Cronstedtite has not previously been recognized to be so abundant and so well crystallized in an iron—clay interaction experiment. The supersaturation of experimental solutions with respect to cronstedtite was due to the availability of Fe and Si in solution, as a result of the dissolution of iron metal powder, quartz, and minor amounts of other silicates. Cronstedtite crystals are characterized by various morphologies: pyramidal (truncated or not) with a triangular base and conical with a rounded or hexagonal cross-section. The pyramidal crystals occur more frequently and their polytypes (2M1, 1M, 3T) were identified by selected area electron diffraction patterns and by automated diffraction tomography. Cronstedtite is stable within the 90-60ºC temperature range. At temperatures of ⩽ 50ºC, the cronstedite crystals showed evidence of alteration.

Accurate and precise lattice parameters by selected-area electron diffraction in the transmission electron microscope

Abstract Lattice parameters for gold nanocrystals, quartz, and vesuvianite have been determined by electron diffraction in routine transmission electron microscopy (TEM) work, with precision and accuracy near to 0.1%, after correction for elliptical distortion. The distortion, measured in three different microscopes, is constant for each microscope and may be easily eliminated. Variable camera constants have been avoided by positioning the oriented specimen on the eucentric plane and using parallel illumination. The current flowing in the first intermediate lens was kept fixed, assuring constant conditions of the TEM projecting system, with no further diffraction focus applied. Application of this method to micas from metamorphic rocks produced deviations between measured and expected values up to 0.8%. Although easy species distinction is still possible, minor crystal chemical differences within the sample may be lost. Likely causes of these deviations are the possible heterogeneous samples, as well as beam damage leading to cation loss with subsequent variation in basal spacings.