Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Phase-oriented surface segregation in an aluminium casting alloy

There have been many reports of the surface segregation of minor elements, especially Mg, into surface layers and oxide films on the surface of Al alloys. LM6 casting alloy (Al-12%Si) represents a challenging system to examine such segregation as the alloy features a particularly inhomogeneous phase structure. The very low but mobile Mg content (approximately 0.001 wt.%), and the surface segregation of modifiers such as Na, mean the surface composition responds in a complex manner to thermal treatment conditions. X-ray photoelectron spectroscopy (XPS) has been used to determine the distribution of these elements within the oxide film. Further investigation by dynamic secondary ion mass spectrometry (DSIMS) confirmed a strong alignment of segregated Na and Mg into distinct phases of the structure.     

Photocatalytic properties of Ta-doped TiO2

Ionics - This work reports the effect of tantalum (0.1–1 at.% Ta) on the photocatalytic performance of TiO2 annealed at 1373 and 1673 K in air. It was shown that addition of...     

Niobium diffusion in niobium-doped titanium dioxide

The present work studied the self-diffusion coefficient of ⁹³Nb in Nb-doped TiO₂ single crystal (4.3 at.% Nb) at high oxygen activity [p(O₂) = 21 kPa] over the temperature range 1,073 to 1,573 K. The diffusion-induced ⁹³Nb concentration profile was determined by using secondary ion mass spectrometry (SIMS). The subsequently determined self-diffusion coefficient of ⁹³Nb exhibits the following temperature dependence:. This study builds upon a similar study performed previously for ⁹³Nb tracer diffusion in undoped TiO₂, and identifies the effect of compositional change on self-diffusion behaviour. The obtained activation energy has been considered in terms of migration and formation enthalpies of titanium vacancies. The present work is dedicated to Professor John Bockris on the occasion of his 85th birthday. His contribution to the progress of modern electrochemistry is well-known to several generations of students and researchers who have been using his textbooks. His specific contribution to the theory of photoelectrochemical water splitting is known to all working in this fascinating area.     

Toward sustainable energy: photocatalysis of Cr-doped TiO<Subscript>2</Subscript>: 2. effect of defect disorder

The present chain of five papers considers the concept of solar-to-chemical energy conversion using TiO₂-based semiconductors. The series reports the effect of chromium on the key performance-related properties of polycrystalline TiO₂ (rutile), including electronic structure, photocatalytic activity, intrinsic defect disorder, electrochemical coupling and surface versus bulk properties. In this work, we show that the effect of chromium on photocatalytic performance of TiO₂ depends on its elemental content and the related defect disorder that is determined by oxygen activity in the oxide lattice. At high oxygen activity, chromium leads to enhanced photocatalytic performance only for dilute solid solutions (up to 0.04–0.043 at.% Cr). Higher chromium content results in a decrease of photocatalytic activity below that for pure TiO₂, despite the observed substantial decrease of the band gap. The photocatalytic performance of Cr-doped TiO₂ annealed in reducing conditions is low within the entire studied range of compositions. The obtained results led to derivation of a theoretical model representing the mechanism of the light-induced reactivity of TiO₂ with water and the related charge transfer. The photocatalytic performance is considered in terms of a competitive effect of several key performance-related properties. The performance is predominantly influenced by the concentration of titanium vacancies acting as reactive surface sites related to anodic charge transfer.

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