The arrangement of water molecules at charged aqueous interfaces is an important question in biology, electrochemistry, and geochemistry. Theoretical studies suggest that the molecules become arranged in several layers adjacent to a solid interface. Using atomic force microscopy we have measured the water dielectric-permittivity profile perpendicular to mica surfaces. The measured variable permittivity profile starting at $\epsilon \approx 4$ at the interface and increasing to $\epsilon =80\mathrm{}$ about 10 nm from the surface suggests a reorientation of water molecule dipoles in the presence of the mica interfacial charge.

The time‐dependent hydrogen evolution reaction (HER) on Ni electrodes shows a large increase in electrode over‐potential with time. This is ascribed to hydride formation at active Ni cathode surfaces. Hydride formation was detected by x‐ray diffraction, morphological changes at the electrode surfaces, and resulting changes in secondary electron emissivities. Nickel electrodes annealed for 2 h in an argon atmosphere at 1000°C after HER did not show x‐ray lines assigned to hydride. On the other hand, hard nickel electrodes (180 HV5/30) show high overvoltages as well as hydride x‐ray diffraction lines after HER. By taking the variation of the nickel electronic density of state following hydrogen sorption into account, we are able to satisfactorily explain the increase in nickel overpotential after a few hours of HER.

Lipopeptides produced by Bacillus subtilis are known for their high antifungal activity. The aim of this paper is to show that at high concentration they can damage the surface ultra-structure of bacterial cells. A lipopeptide extract containing iturin and surfactin (5 mg mL⁻¹) was prepared after isolation from B. subtilis (strain OG) by solid phase extraction. Analysis by atomic force microscope (AFM) showed that upon evaporation, lipopeptides form large aggregates (0.1–0.2 μm²) on the substrates silicon and mica. When the same solution is incubated with fungi and bacteria and the system is allowed to evaporate, dramatic changes are observed on the cells. AFM micrographs show disintegration of the hyphae of Phomopsis phaseoli and the cell walls of Xanthomonas campestris and X. axonopodis. Collapses to fungal and bacterial cells may be a result of formation of pores triggered by micelles and lamellar structures, which are formed above the critical micelar concentration of lipopeptides. As observed for P. phaseoli, the process involves binding, solubilization, and formation of novel structures in which cell wall components are solubilized within lipopeptide vesicles. This is the first report presenting evidences that vesicles of uncharged and negatively charged lipopeptides can alter the morphology of gram-negative bacteria.