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Interaction of water and methanol was found to be different with anatase (101) and rutile (110). XPS results indicate a unique shift in the O 1s core level.

Studies the adsorption of the sulphur compound H[sub 2]S on clean and gold 'promoted' oxides of chromium. Chemisorbed layer produced by the decomposition of H[sub2]S on polycrystalline chromium; Rate of dissociation; Correlation between the size of the band gap in the oxide and its reactivity toward H[sub 2]S.

We present a short overview of surface studies on the main low-index surfaces of anatase, the technologically most interesting crystallographic form of titanium dioxide. Results are compared to the extensively investigated surfaces of TiO2 rutile. The anatase (1 0 1) surface is stable in a (1×1) configuration. It exhibits twofold coordinated (bridging) oxygen atoms and fivefold coordinated Ti atoms with a density comparable to the one found on rutile (1 1 0). Step edges are terminated by fourfold coordinated Ti sites. In contrast to rutile (1 1 0), anatase (1 0 1) does not show a strong tendency for losing twofold coordinated oxygen atoms upon annealing in ultrahigh vacuum. The apparent lack of point defects is also reflected in the adsorption/desorption behavior of water and methanol. The anatase (1 0 0) surface has the second-lowest surface energy and tends to from a (1×2) reconstruction. A model with (1 0 1)-oriented microfacets agrees with the observed features in atomically-resolved STM images. The (0 0 1) surface forms a (1×4) reconstruction that is well explained by an ‘ad-molecule’ model predicted from density functional theory calculations. A (1×3) reconstruction was observed for the anatase (1 0 3) surface. [Copyright &y& Elsevier]

Titanium oxides are used in a wide variety of technological applications where surface properties play a role. TiO[SUB2] surfaces, especially the (110) face of rutile, have become prototypical model systems in the surface science of metal oxides. Reduced TiO[SUB2] single crystals are easy to work with experimentally, and their surfaces have been characterized with virtually all surface-science techniques. Recently, TiO[SUB2] has also been used to refine computational ab initio approaches and to calculate properties of adsorption systems. Scanning tunneling microscopy (STM) studies have shown that the surface structure of TiO[SUB2](110) is more complex than originally anticipated. The reduction state of the sample, i.e. the number and type of bulk defects, as well as the surface treatment (annealing in vacuum vs. annealing in oxygen), can give rise to different structures, such as two different (1 x 2) reconstructions, a 'rosette' overlayer, and crystallographic shear planes. Single point defects can be identified with STM and influence the surface chemistry in a variety of ways; the adsorption of water is discussed as one example. The growth of a large number of different metal overlayers has been studied on TiO[SUB2](110). Some of these studies have been instrumental in furthering the understanding of the 'strong metal support interaction' between group-VIII metals and TiO[SUB2], as well as low-temperature oxidation reactions on TiO[SUB2]-supported nanoscopic gold clusters. The growth morphology, interfacial oxidation/reduction reaction, thermal stability, and geometric structure of ultra-thin metal overlayers follow general trends where the most critical parameter is the reactivity of the overlayer metal towards oxygen. It has been shown recently that the technologically more relevant TiO[SUB2] anatase phase can also be made accessible to surface investigations. [ABSTRACT FROM AUTHOR]

Corpuscular and biochemical components of blood create the viscoelastic nature of blood flow, which varies because of changes in flow velocity. The flow properties of blood are of special interest in arteriosclerotic diseases for vasoregulatory mechanisms are often disturbed in these states. The authors compared the rheologic properties of blood in patients with arteriosclerotic lesions (coronary heart disease: n=56; cerebrovascular disease: n=37; peripheral arterial occlusive disease: n=29 and healthy controls: n=42). With a new oscillating capillary rheometer imitating the physiologic pulsations of blood flow in an unbranched artery, the viscosity (η') and elasticity (η") of whole blood and plasma were measured (diameter of the capillary: 0.9928 mm; pulse rate: 2/s; shear rate: γ-0.03-200/s; temperature: 37°C). In arteriosclerotic patients a statistically significant elevation of the viscoelasticity of whole blood and plasma was found. In addition, plasma fibrinogen levels were augmented in the patients' groups. Clotting parameters (Quick, partial thromboplastin time, platelet count) and total serum protein levels were in the normal range in all patients investigated. In conclusion the question arises whether the increase of blood viscoelasticity is an additional risk face tor for patients with arteriosclerotic disease or if it is just a consequence of the underlying disease. The authors' observations concerning blood viscoelasticity support the clinical importance of improving blood rheology by appropriate therapeutic measures. [ABSTRACT FROM AUTHOR]

We have used oxygen-plasma-assisted molecular-beam epitaxy (OPA-MBE) to grow Co[sub x]Ti[sub 1-x]O[sub 2] anatase on SrTiO[sub 3](001) for x=∼0.01–0.10, and have measured the structural, compositional, and magnetic properties of the resulting films. Whether epitaxial or polycrystalline, these Co[sub x]Ti[sub 1-x]O[sub 2] films are ferromagnetic semiconductors at and above room temperature. However, the magnetic and structural properties depend critically on the Co distribution, which varies widely with growth conditions. Co is substitutional in the anatase lattice and in the +2 formal oxidation state in ferromagnetic Co[sub x]Ti[sub 1-x]O[sub 2]. The magnetic properties of OPA-MBE grown material are significantly better than those of analogous pulsed laser deposition-grown material. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The adsorption of chlorine, dosed from an electrochemical cell, on the (1 1 0)-surface of a bulk-reduced TiO2 crystal was studied with scanning tunneling microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy (UPS). At room temperature chlorine adsorbs on the fivefold coordinated Ti atoms and on the vacancies in the bridging oxygen rows. Chlorine exposure at 200 and 300 °C leads to adsorption at the position of bridging oxygen atoms. In addition, ∼15 A˚ wide protrusions are formed that contain several chlorine atoms. No long-range ordering was found in the adsorbed layer. UPS shows that adsorption of Cl on the hot surface leads to an increase in the Ti 3d-related defect state. This indicates a replacement of bridging oxygen atoms by chlorine. Interestingly, the rate of the site exchange depends on the bulk reduction state of the TiO2 crystal. After dosing Cl at 200 °C, negligible adsorption was found on a slightly reduced, light blue crystal. The data are compared and contrasted with similar experimental results on the S/TiO2(1 1 0) system. [Copyright &y& Elsevier]

The observation of photocatalytic water splitting on the surface of anatase TiO2 crystals has stimulated many investigations of the underlying processes. Nevertheless, a molecular-level understanding of the reaction is not available. This requires knowledge of the crystal facets present, the atomistic structure of the surfaces, and thus the reaction sites involved. In this paper we establish the atomistic structure of two surfaces, vicinal to the low-energy (101) surface. We compute the relative stability and electronic properties of the (514) and (516) surfaces and compare these to the low-index (101), (001), and (100) surfaces. The (516) surface is remarkably stable, and is predicted to contribute significantly to the surface area of a crystallite in equilibrium. We simulate constant current scanning tunneling microscopy images and, by comparing with those measured, we conclude that a surface previously observed in a miscut single crystal is the (516) surface described here. The computed stability of this surface indicates that it will be present in TiO2 nanostructures and the relative positions of its band edges suggests that it will play a significant role in the water-TiO2 reactions in solar water splitting. [ABSTRACT FROM AUTHOR]