theoretical and experimental results for Co-OEP on Ni(100)

Metal octaethylporphyrins (M-OEP), M-N4C20H4(C2H5)8, adsorbed at a metallic substrate are promising candidates to provide spin dependent electric transport. Despite these systems having been studied extensively by experiment, details of the adsorbate geometry and surface binding are still unclear. We have carried out density functional theory calculations for cobalt octaethyl porphyrin (Co-OEP) adsorbate at clean and oxygen-covered Ni(100) surfaces as well as for the free Co-OEP molecule where equilibrium structures were obtained by corresponding energy optimizations. These geometries were then used in calculations of Co-OEP carbon and nitrogen 1s core excitations yielding theoretical excitation spectra to be compared with corresponding K-edge x-ray absorption fine structure (NEXAFS) measurements. The experimental NEXAFS spectra near the carbon K-edge of Co-OEP bulk material show large intensity close to the ionization threshold and a triple-peak structure at lower energies, which can be reproduced by the calculations on free Co-OEP. The experimental nitrogen K-edge spectra of adsorbed Co-OEP layers exhibit always a double-peak structure below ionization threshold, independent of the layer thickness. The peaks are shifted slightly and their separation varies with adsorbate-substrate distance. This can be explained by hybridization of N 2p with corresponding 3d contributions of the Ni substrate in the excited final state orbitals as a result of adsorbate-substrate binding via N–Ni bond formation

SchussenAktivplus: reduction of micropollutants and of potentially pathogenic bacteria for further water quality improvement of the river Schussen, a tributary of Lake Constance, Germany

The project focuses on the efficiency of combined technologies to reduce the release of micropollutants and bacteria into surface waters via sewage treatment plants of different size and via stormwater overflow basins of different types. As a model river in a highly populated catchment area, the river Schussen and, as a control, the river Argen, two tributaries of Lake Constance, Southern Germany, are under investigation in this project. The efficiency of the different cleaning technologies is monitored by a wide range of exposure and effect analyses including chemical and microbiological techniques as well as effect studies ranging from molecules to communities

Site-specific bonding of copper adatoms to pyridine end groups mediating the formation of two-dimensional coordination networks on metal surfaces

We study the formation of a coordination network consisting of the organic pyridine-based 2,4,6-tris(4-pyridine)-1,3,5-triazine (T4PT) species and Cu atoms on Cu(111) and Ag(111) metal surfaces. Using scanning tunneling microscopy, we find that the organic molecule T4PT forms stable two- dimensional porous networks on the surface of Cu(111) and, by codeposition of Cu atoms, also on the Ag(111) crystal, in which Cu atoms are twofold coordinated by T4PT molecules. X-ray absorption spectroscopy measurements of the metal-organic network Cu–T4PT on Ag(111) accompanied by density-functional theory calculations show that the nitrogen atoms of the pyridine end groups of the T4PT molecules are the active sites in coordinating the Cu adatoms. X-ray magnetic circular dichroism experiments reveal that the Cu atom in such a metal-organic motif is in a low-valent d10 state and has no magnetic moment

XPS Lineshape Analysis of Potassium Coadsorbed with Water on Ni(111)

The line profiles of XP spectra of H2O/K/Ni(111) were investigated for K submonolayer coverages. The K2p spectra exhibit a strong alteration of lineshape with increasing water coverage. Without coadsorbed water a significant asymmetry was found which decreased rapidly and independently of the potassium precoverage with increasing water exposure up to ΘH2O = 0.7. The asymmetry observed in the K2p spectra is assigned to a coupling of the potassium adatoms to the electronic structure of the nickel substrate. The coadsorption of water suppresses this mechanism via a loosening of the potassium-nickel coupling. Since the decrease of asymmetry is independent of the potassium coverage, it is concluded that this process is due to an adsorbate-substrate interaction between the water and the nickel substrate only. This contradicts models in which the coadsorption of water and potassium on metal substrates is manifested in hydration of the potassium adatoms