Experiments were conducted using enterohemorrhagic Escherichia coli O157:H7 cells to investigate the influence of extracellular macromolecules on cell surface properties and adhesion behavior to quartz sand. Partial removal of the extracellular macromolecules on cells by a proteolytic enzyme (proteinase K) was confirmed using Fourier transform infrared spectroscopy analyses. The proteinase K treated cells exhibited more negative electrophoretic mobility (EPM) at an ionic strength (IS) e 1 mM, a slightly lower isoelectric point, and were less hydrophobic as compared to the untreated cells. Potentiometric titration results indicated that the total site concentration (i.e., the total amount of exposed functional groups per cell) on the treated cells was approximately 22% smaller than the untreated cells, while the dissociation constants were almost identical. Analysis of the EPM data using soft particle theory showed that the removal of extracellular macromolecules resulted in polymeric layers outside the cell surface that were less electrophoretically soft. The more negative mobility for the treated cells was likely due to the combined effects of a change in the distribution of functional groups and an increase in the charges per unit volume after enzyme treatment and not just removal of extracellular macromolecules. The proteolytic digestion of extracellular macromolecules led to a significant difference in the cell adhesion to quartz sand. The adhesion behavior for treated cells was consistent with DLVO theory and increased with IS due to less negativity in the EPM. In contrast, the adhesion behavior of untreated cells was much more complex and exhibited a maximum at IS ) 1 mM. The treated cells exhibited less adhesion than the untreated cells when the IS e 1 mM due to their more negative EPM. However, when the IS g 10 mM, a sudden decrease in the removal efficiency was observed only for the untreated cells even through EPM values were similar for both treated and untreated cells. This result suggested that an additional non-DLVO type interaction, electrosteric repulsion, occurred at higher IS (g10 mM in this study) for the untreated cells due to the presence of extracellular macromolecules that hindered cell adhesion to the quartz surface. This finding provides important insight into the role of macromolecule-induced E. coli O157:H7 interactions in aquatic environments.

The initial stages of the uptake of molecular oxygen on V(100) single-crystal surfaces were characterized by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and ion scattering spectroscopy (ISS). As in previous reports on this system, a small amount of oxygen contamination was always detected on the surface, but that could be minimized by avoiding severe annealing after sputtering of the surface and appears to not affect the chemistry of the surface in any significant way, at least in terms of methanol conversion. Oxygen adsorption is dissociative even at liquid nitrogen temperatures. At low temperatures, saturation is reached at a coverage of approximately 1.0 ML, but above 170 K further uptake can occur, leading to the formation of a thin V 2 O 3 + VO 2 mixed oxide film. Thick oxide films, with thicknesses of the order of nanometers, could only be generated above 320 K and by using high oxygen doses. In general, the temperature at which the adsorption is carried out proved to play an important role in determining the surface stoichiometry and film thickness of the resulting surface oxides. Diffusion of oxygen into the bulk starts at approximately 500 K and displays an estimated activation energy of 132 kJ/mol.

Ethene, propene, allyl chloride, and carbon monoxide were used to probe the effects of adding an average of one chlorine atom for every eight Ag atoms of a Ag(111) surface. On the basis of reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD), this coverage is sufficient to alter the electronic structure of more than 95% of the surface Ag atoms. For CO, C2H4, and C3H6, TPD peak temperatures increase, indicating increased adsorbate-substrate bond strength, and vibrational bands are both red-and blue-shifted compared to the case for adsorption on clean Ag(111). Modes reflecting interactions of π adsorbate orbitals with the substrate are particularly sensitive to the presence of Cl. These changes are attributed to altered electronic structure of Ag atoms, i.e., partially empty d-band character, induced by the presence of electron-withdrawing Cl. C3H5Cl is different in that C-Cl bond dissociation to form Cl and C3H5 (allyl) accompanies adsorption on both clean and Cl-covered Ag(111). The influence of adsorbed Cl on the thermal chemistry of C3H5 is evident in TPD, and the adsorption structure taken by adsorbed C3H5 is evident in RAIRS.

A simple methodology was successfully demonstrated for the nanoscale patterning of silicon wafers. Thin films are grown by atomic layer deposition (ALD) and patterned by using selective surface chemistry: First, all the nucleation sites on the original oxide surface are silylated in order to render them unreactive; then, a pattern is developed by selective removal of the silylation agent using a mask and a combination of ultraviolet radiation and ozonolysis. Subsequent ALD is carried out selectively on the areas where the silylation moieties have been removed. This simple procedure affords patterning of oxide surfaces with monolayer control and a lateral resolution on the order of a few tens of nanometers or better. Other selective ALD processes have shown only limited discrimination during deposition, but our method shows absolute inhibition of film growth on the silylated areas while films as thick as 10 nm are grown on the re-exposed sectors. Our example involved the deposition of hafnium oxide films on the native silicon oxide film that forms on Si(100) wafers, but we believe that the approach is general and easily extendable to other ALD processes.