Franziska Conrad

Oxide Nanomaterials: Synthetic Developments, Mechanistic Studies, and Technological Innovations

Oxide nanomaterials are indispensable for nanotechnological innovations, because they combine an infinite variety of structural motifs and properties with manifold morphological features. Given that new oxide materials are almost reported on a daily basis, considerable synthetic and technological work remains to be done to fully exploit this ever increasing family of compounds for innovative nano-applications. This calls for reliable and scalable preparative approaches to oxide nanomaterials and their development remains a challenge for many complex nanostructured oxides. Oxide nanomaterials with special physicochemical features and unusual morphologies are still difficult to access by classic synthetic pathways. The limitless options for creating nano-oxide building blocks open up new technological perspectives with the potential to revolutionize areas ranging from data processing to biocatalysis. Oxide nanotechnology of the 21st century thus needs a strong interplay of preparative creativity, analytical skills, and new ideas for synergistic implementations.

A Gadolinium-Bridged Polytungstoarsenate(III) Nanocluster: [Gd8As12W124O432(H2O)22]60−†

This work was supported by the Swiss National Science Foundation (SNSF Professorship PP002-114711/1) and the University of Zurich. We thank Dr. B. Spingler, Institute of Inorganic Chemistry, University of Zurich, for helpful crystallographic discussions, and S. Weyeneth, Physics Institute, University of Zurich, for assistance with the magnetic measurements. We are grateful to Prof. A. Stemmer and R. Enning, Micro and Nano Science Platform, ETH Zurich, for help with AFM measurements. We thank Dr. R. Wepf, Electron Microscopy ETH Zurich, EMEZ, for Cryo-SEM investigations. The support of the Center for Microscopy and Image Analysis, University of Zurich, is gratefully acknowledged, and we thank Y. Zhou, UZH, for help with SEM measurements.

Caesium-templated lanthanoid-containing polyoxotungstates

A family of novel lanthanoid-containing polytungstoarsenate(iii) polyanions with interesting structural features has been isolated: six lacunary {alpha-AsW(9)O(33)} building blocks comprising unusual pyramidal WO(5) units are templated by a caesium cation in a central cavity of the structure.

Microwave-hydrothermal synthesis and characterization of nanostructured copper substituted ZnM2O4 (M = Al, Ga) spinels as precursors for thermally stable Cu catalysts

Nanostructured Cu(x)Zn(1-x)Al(2)O(4) with a Cu:Zn ratio of ¼:¾ has been prepared by a microwave-assisted hydrothermal synthesis at 150 °C and used as a precursor for Cu/ZnO/Al(2)O(3)-based catalysts. The spinel nanoparticles exhibit an average size of approximately 5 nm and a high specific surface area (above 250 m(2) g(-1)). Cu nanoparticles of an average size of 3.3 nm can be formed by reduction of the spinel precursor in hydrogen and the accessible metallic Cu(0) surface area of the reduced catalyst was 8 m(2) g(-1). The catalytic performance of the material in CO(2) hydrogenation and methanol steam reforming was compared with conventionally prepared Cu/ZnO/Al(2)O(3) reference catalysts. The observed lower performance of the spinel-based samples is attributed to a lack of synergetic interaction of the Cu nanoparticles with ZnO due to the incorporation of Zn(2+) in the stable spinel lattice. Despite its lower performance, however, the nanostructured nature of the spinel catalyst was stable after thermal treatment up to 500 °C in contrast to other Cu-based catalysts. Furthermore, a large fraction of the re-oxidized copper migrates back into the spinel upon calcination of the reduced catalyst, thereby enabling a regeneration of sintered catalysts after prolonged usage at high temperatures. Similarly prepared samples with Ga instead of Al exhibit a more crystalline catalyst with a spinel particle size around 20 nm. The slightly decreased Cu(0) surface area of 3.2 m(2) g(-1) due to less copper incorporation is not a significant drawback for the methanol steam reforming.

New spinel oxide catalysts for visible-light-driven water oxidation

Nanoscale Co–Mn–Ga spinels are promoted by the “synergistic” interaction of Co and Mn, thus paving the way to tailored and flexible catalyst design concepts for visible-light-driven water oxidation.

2,2`-Bipyridin-1,2-dithiolat Gemischtligand-Komplexe. Synthese, Charakterisierung und EPR-Spektroskopie / 2,2`-Bipyridine-1,2-dithiolate Mixed Ligand Complexes. Synthesis, Characterisation and EPR Spectroscopy

A series of new 2,2` -bipyridine/1,2-dithiolate transition metal complexes has been synthesised and characterised. As 1,2-dithiolate ligands 1,2-dithiooxalate (dto) and 1,2-dithiosquarate (dtsq) were used. It follows from the IR spectra that the multidentate dithiolate ligands coordinate exclusively via their sulfur atoms forming an MN2S2 coordination sphere. The central metal ions (M) are Cu2+, Ni2+, Pd2+, Pt2+, and Zn2+. The complex [CuII(bpy)(dto)] could be studied by EPR spectroscopy and was measured as powder, diamagnetically diluted in the isostructural [NiII(bpy)(dto)] host structure. The spin density contribution calculated from the experimental parameters is compared with the electronic situation in the frontier orbitals, namely in the semi-occupied SOMO of the copper complex, derived from quantum chemical calculations on different levels (EHT and DFT). Graphical Abstract 2,2`-Bipyridin-1,2-dithiolat Gemischtligand-Komplexe. Synthese, Charakterisierung und EPR-Spektroskopie / 2,2`-Bipyridine-1,2-dithiolate Mixed Ligand Complexes. Synthesis, Characterisation and EPR Spectroscopy