The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ( 27 Al, 13 C, 1 H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T 1 -measurements, 27 Al-MQMAS, 27 Al-1 H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related 27 Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated 27 Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out.

In this contribution the preparation and structural characterization of nanoscale fluorine doped tin-oxide (SnO2:F, FTO) is described. By using a microwave assisted polyol approach, nanoparticles with different doping levels are prepared, which show narrow size distribution as measured by X-ray diffraction, electron microscopy and dynamic light scattering. They were converted into electrically conductive optically transparent films at 500 °C by a specific thermal treatment (500 °C in air followed by 250 °C in forming gas), exhibiting a specific resistivity of (1.9 × 10−1 Ω cm). Solid-state MAS NMR and 119Sn Mössbauer spectroscopy were used to study how F atoms are incorporated into the SnO2:F nanoparticles. Distance constraints were determined by 119Sn{19F} REDOR, fluorine-doping homogeneity by homonuclear dipolar recoupling experiments (SR66 2). Cross-polarization was used to investigate the immediate environment of the dopant. The experiments were supplemented by first-principles quantum-chemical calculations for possible defect site models. The combined data strongly indicate that F doping is not directly related to an increase in charge-carrier concentration, even though F atoms do occupy O vacancy sites in SnO2:F. For this study we have implemented background compensated NMR 2D pulse-sequences which reliably suppress the fluorine background originating from the NMR probe. Moreover we show that cluster calculations on the basis of the extended embedded ion method (EEIM) can be used to study the structure of diluted defects in crystalline host structures and predict NMR properties.

Zinc phosphate nanoparticles are prepared via a polyol-mediated synthesis. The nanomaterial turns out to be nonagglomerated and very uniform in size and shape, in particular 20 nm in diameter. X-ray powder diffraction analysis and high-resolution transmission electron microscopy indicate as-prepared nanoparticles to be noncrystalline. To investigate the chemical composition (stoichiometry, material homogeneity, amount of ortho-/metaphosphate, water content, type of surface-allocated adsorbents, differentiation of surface/inner core), X-ray diffraction, NMR-spectroscopy, energy-dispersive X-ray analysis, infrared spectroscopy, and thermal analysis are performed. To validate the local structure and composition, we performed 1 H, 13 C, and 31 P magic angle spinning nuclear magnetic resonance spectroscopy and multidimensional homo-and heteronuclear multiple-pulse solid-state NMR experiments. Moreover, 31 P{ 1 H} rotational echo double-resonance experiments for various spin topologies are analyzed analytically and numerically, in order to differentiate between homogeneous nanoparticles and core-shell nanoparticles. The analysis gives a length scale to homogeneity and for bulk materials allows us to differentiate between mono-and dihydrogen phosphates, and phosphate hydrates.

The novel MOF hcp UiO-66 is synthesized using the ionic liquid ([PBuMEE]2[BDC]) as a linker precursor.

Microporous organically pillared layered silicates (MOPS) are a class of microporous hybrid materials that, by varying pillar density, allows for optimization of guest recognition without the need to explore different framework topologies. MOPS are found to be capable of discriminating two very similar gases, carbon dioxide and acetylene, by selective gate-opening solely through quenching pillar dynamics. Contrary to conventional gate-opening in metal organic frameworks, the additional adsorption capacity is realized without macroscopic volume changes, thus avoiding mechanical stress on the framework. Of the two gases studied, only CO can accomplish freezing of pillar dynamics. Moreover, the shape of the slit-type micropores in MOPS can easily be fine-tuned by reducing the charge density of the silicate layers. This concomitantly reduces the Coulomb attraction of cationic interlayer space and anionic host layers. Surprisingly, we found that reducing the charge density then alters the gate-opening mechanism to a conventional structural gate-opening involving an increase in volume.

Ultrasonically induced shock waves stimulate intensive interparticle collisions in suspensions and create large local temperature gradients in AlNi particles. These trigger phase transformations at the surface rather than in the particle interior. We show that ultrasonic processing is an effective approach for developing the desired compositional gradients in nm-thick interfacial regions of metal alloys and formation of effective catalysts toward the hydrogen evolution reaction

The covalent linkages formed during functionalization of MCM-41 mesoporous molecular sieves with five chloroalkylsilanes ((EtO)3Si(CH2Cl), (MeO)3Si(CH2CH2CH2Cl), Cl3Si(CH2CH2CH3), Cl2Si(CH3)(CH2Cl) and Cl2Si(CH3)2) have been investigated using high-resolution solid-state NMR spectroscopy and DFT calculations. Structural information was obtained from 1H-13C and 1H-29Si heteronuclear (HETCOR) NMR spectra, in which high resolution in the 1H dimension was obtained by using fast MAS. The 1H-13C HETCOR results provided the assignments of 1H and 13C resonances associated with the surface functional groups. Sensitivity-enhanced 1H-29Si HETCOR spectra, acquired using Carr-Purcell-Meiboom-Gill refocusing during data acquisition, revealed the identity of 29Si sites (Qn, Tn, and Dn) and the location of functional groups relative to these sites. Optimal geometries of local environments representing the Qn, Tn and Dn resonances were calculated using molecular mechanics and ab initio methods. Subsequently, DFT calculations of 29Si, 13C, and 1H chemical shifts were performed using Gaussian 03 at the B3LYP/6-311++G(2d,2p) level. The theoretical calculations are in excellent accord with the experimental chemical shifts. This work illustrates that state-of-the-art spectroscopic and theoretical tools can be used jointly to refine the complex structures of inorganic-organic hybrid materials.

A double zwitterionic Schiff base was synthesized using the amino acid L-histidine and o-vanillin (2-hydroxy-3methoxy benzaldehyde). Both the phenol and carboxyl groups are deprotonated, and the imine nitrogen atom and histidineimidazole ring are protonated to give the double zwitterion with an intramolecular (imine)N-H þ 3 3 3 -O(phenol) hydrogen bond (ketoamine form). Such a ketoamine form in a double zwitterion is assumed in the catalytic cycle of enzymatic transformations of amino acids with the cofactor (vitamin B6) pyridoxal-5 0 -phosphate (PLP). A high-resolution, lowtemperature, single-crystal X-ray diffraction data set on N-o-vanillylidene-L-histidine (also named 3-methoxysalicylidene-Lhistidine or N-(2-oxy-3-methoxy-benzylidene)-L-histidine, OVHIS) is used in the analysis of molecular electrostatic properties and intermolecular interactions. All oxygen atoms in the molecule (four in total) are mutually almost coplanar and located (externally) on the same side of molecule. These four O atoms carry significant negative charge and form a large area of strong negative electrostatic potential (appropriate for bonding to a metal atom). The protonated and, thus, positively charged imidazole ring is situated on the opposite side of the molecule from the area of the O atoms. Consequently, the OVHIS molecule is highly polarized and has a very high molecular dipole moment of 42.4 D in the solid state (calculated from experimental X-ray data). Two strong intermolecular charge-assisted N-H þ 3 3 3 -O hydrogen bonds (with H 3 3 3 O distances of 1.61 A ˚) together with other D-H 3 3 3 O interactions (D = N, C) contribute to a large molecular dipole enhancement which occurs upon crystallization. The topologies of the bonding within the molecule as well as its hydrogen bonds have been investigated according to Bader's quantum theory of atoms in molecules (QTAIM). 1 H solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) was used to confirm the zwitterionic structure in the solid state.