The potential of metallic copper as an intrinsically antibacterial material is gaining increasing attention in the face of growing antibiotics resistance of bacteria. However, the mechanism of the so-called "contact killing" of bacteria by copper surfaces is poorly understood and requires further investigation. In particular, the influences of bacteria-metal interaction, media composition, and copper surface chemistry on contact killing are not fully understood. In this study, copper oxide formation on copper during standard antimicrobial testing was measured in situ by spectroscopic ellipsometry. In parallel, contact killing under these conditions was assessed with bacteria in phosphate buffered saline (PBS) or Tris-Cl. For comparison, defined Cu2O and CuO layers were thermally generated and characterized by grazing incidence X-ray diffraction. The antibacterial properties of these copper oxides were tested under the conditions used above. Finally, copper ion release was recorded for both buffer systems by inductively coupled plasma atomic absorption spectroscopy, and exposed copper samples were analyzed for topographical surface alterations. It was found that there was a fairly even growth of CuO under wet plating conditions, reaching 4-10 nm in 300 min, but no measurable Cu2O was formed during this time. CuO was found to significantly inhibit contact killing, compared to pure copper. In contrast, thermally generated Cu2O was essentially as effective in contact killing as pure copper. Copper ion release from the different surfaces roughly correlated with their antibacterial efficacy and was highest for pure copper, followed by Cu2O and CuO. Tris-Cl induced a 10-50-fold faster copper ion release compared to PBS. Since the Cu2O that primarily forms on copper under ambient conditions is as active in contact killing as pure copper, antimicrobial objects will retain their antimicrobial properties even after oxide formation.

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The linear sequence KLAL (KLALKLALKALKAALKLA-NH(2)) and its corresponding d,l-isomers k(9)a(10)-KLAL (KLALKLALkaLKAALKLA-NH(2)) and l(11)k(12)-KLAL (KLALKLALKAlkAALKLA-NH(2)) are model compounds for potentially amphipathic alpha-helical peptides which are able to bind to membranes and to increase the membrane permeability in a structure- and target-dependent manner (Dathe and Wieprecht, 1999) We first studied the secondary structure of KLAL and its analogs bound to the air/water using infrared reflection absorption spectroscopy. For the peptide films the shape and position of the amide I and amide II bands indicate that the KLAL adopts at large areas per molecule an alpha-helical secondary structure, whereas at higher surface pressures or smaller areas it converts into a beta-sheet structure. This transition could be observed in the compression isotherm as well as during the adsorption at the air/water interface from the subphase as a function of time. The secondary structures are essentially orientated parallel to the air/water interface. The analogs with d-amino acids in two different positions of the sequence, k(9)a(10)-KLAL and l(11)k(12)-KLAL, form only beta-sheet structures at all surface pressures. The observed results are interpreted using a comparison of hydrophobic moments calculated for alpha-helices and beta-sheets. The differences between the hydrophobic moments calculated using the consensus scale are not large. Using the optimal matching hydrophobicity scale or the whole-residue hydrophobicity scale the beta-sheet even has the larger hydrophobic moment.

During the oxygen evolution reaction, manganese rapidly dissolves, however, it has a disordered oxide layer with a steady state thickness.

The oxide layer spontaneously formed on zinc and an ''electrochemically reduced'' oxide has been characterised by a combination of X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE). The onset of the main electronic absorption, which is directly related to the bandgap, is extracted from the SE measurements. The SE results are compared with simulations on the basis of zinc and bulk zinc oxide optical constant data. Measurements in the ultraviolet and visible (UV-vis) spectral range show the presence of an absorption at B1.8 eV (680 nm) which is unaccounted for from the bulk data, and is likely to originate from intragap energy levels, implicating the presence of surface defects in the layers. Analysis of the Zn LMM Auger peaks in XPS data show the presence of Zn different from bulk zinc and bulk ZnO, attributed to excess Zn in the oxide films. Mid-infrared (IR) ellipsometry shows two peaks around 0.12 and 0.15 eV (1000 and 1200 cm À1 ), which strengthen the assumption of the presence of a locally distorted structure in the oxide layers. Electrochemically reduced samples show a much thinner oxide layer and higher Zn-doping concentration films than samples purely dipped in NaOH solution. Using a self-contained multiple sample SE analysis, estimates of the refractive index and absorption coefficient (i.e., the optical constants) of the oxide films are presented from 1.5-4.4 eV (280 to 810 nm).

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Titanium dioxide nanowire (NW) arrays are incorporated in many devices for energy conversion, energy storage, and catalysis. A common approach to fabricate these NWs is based on hydrothermal synthesis strategies. A drawback of this low-temperature method is that the NWs have a high density of defects, such as stacking faults, dislocations, and oxygen vacancies. These defects compromise the performance of devices. Here, we report a postgrowth thermal annealing procedure to remove these lattice defects and propose a mechanism to explain the underlying changes in the structure of the NWs. A detailed transmission electron microscopy study including in situ observation at elevated temperatures reveals a two-stage process. Additional spectroscopic analyses and X-ray diffraction experiments clarify the underlying mechanisms. In an early, low-temperature stage, the as-grown mesocrystalline NW converts to a single crystal by the dehydration of surface-bound OH groups. At temperatures above 500 °C, condensation of oxygen vacancies takes place, which leads to the fabrication of NWs with internal voids. These voids are faceted and covered with Ti-rich amorphous TiO.

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