Remote argon plasma (RP) and ozone in the presence of ultraviolet light (UV–O3) were used to render polystyrene (PS) surfaces hydrophilic in a controlled manner for eventual application in cell-surface interaction studies. X-ray photoelectron spectroscopy (XPS) was used to characterize both methods of modification. The degree of modification on PS was measured by an increase in surface oxygen and concomitant change in C 1s binding energies as a function of time. Both remote plasma and UV–O3 are shown to be partially surface destructive, producing polymer fragments which are easily washed away to leave stable modified surfaces of oxidized polymer comprising of distributions of C–O, C=O and O—C=O type groups. Of the two methods, UV–O3 is shown to be more versatile and conducive to preparing PS surfaces with controllably varying degrees of modification. UV–O3 modified polystyrene is shown to be stable in air for at least eight months. Contact angle methods were used in correlation with XPS in characterizing UV–O3 modified surfaces. It is shown that changes in surface tension and total surface oxygen content were related, however, not directly connected.

Passivation of Ti6Al4V and cpTi implants using methods based on the ASTM-F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM-F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X-ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill-annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill-annealed, Ti6Al4V and cpTi into serum-containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill-annealed cpTi. These results, derived from two mill-annealed Ti-based metals, would indicate that re-examination of ASTM-F86-based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices.

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Water chemisorbs molecularly on Ni(llO) at 180 K producing a c(2x2) overlayer, at 0.5 ML (ML= monolayer -1.15x 10 15 molecules cm -2 ). This water is undetectable by ir methods which indicates the absence of clustering (and, hence, no intermolecular H bonding) in the first 0.5 ML. Population of a second "icelike" layer, which is nearly saturated after an additional 0.5 ML, makes the first 0.5 ML ir active and produces strong H-bonding interactions. The plane of the chemisorbed water, which is originally parallel to the surface, is reoriented towards the surface normal on filling of the second layer.PACS numbers: 82.65.My, 33.20.EaThe interaction of water with solid surfaces has become of increasing interest in recent years. x This is due both to practical considerations related to electrochemistry and corrosion and to the rich chemistry and physics that arise from the complex interactions between adsorbed water molecules and the substrate and/or each other. The presence of hydrogen bonding (H bonding), which can be of comparable magnitude to the moleculesurface bond strength, leads to a range of phenomena such as clustering at low coverages, low-order desorption kinetics, and control of the double-layer properties in electrochemical systems, etc. x In this Letter, we show that it is possible to produce ordered chemisorbed overlayers of water on Ni(llO) in which clustering is not present, and to detect the molecular reorientation in the first layer of chemisorbed water caused by the adsorption of a specific coverage of water into the "second" layer. This second layer still shows residual interactions with the Ni(llO) surface and is distinguishable from bulk ice. We show that the H-O-H plane of the water molecules in the first chemisorbed layer must lie close to parallel to the plane of the surface. After adsorption into the second layer to form a bilayer, the H-O-H plane must lie much closer to the surface normal.The apparatus have been described in detail elsewhere. 2 "" 4 Briefly, the measurements were carried out in a standard ultrahigh vacuum chamber (base pressure -Ixl0~1 0 torr) to which water can be admitted through a differentially pumped, shuttered capillary array and by admission to the background. The chamber is equipped with an automated multimass quadrupole mass spectrometer and Kelvin probe to measure changes in work function A (sensitivity -1 mV, t c~~0 .1 s), and is interfaced to a Fourier-transform ir spectrometer for Fourier-transform ir-reflection-absorption spectroscopy (FTIR-RAS). 4 The ir radiation is incident at about 82° from the surface normal and a mercury cadmium telluride (MCT) detector is used. The lowest detectable absorbance has proven to be ~(2-3)xl0~5 absorbance units (a.u.) for a single reflection. A signal-to-noise ratio of > 100:1 can be obtained on adsorbed CO on Ni (110) in 90 s. The crystal was cleaned by a combination of Ar + -ion sputtering and annealing. The cleanliness was judged by Auger electron spectroscopy, by nuclear reaction analysis (NRA) in another chamber 2...

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