Metal oxides surface properties

Effect of Metal Oxide Surface Properties on Photoinduced Redox Reactions... 

Rohrer, G. S. 2001. The anisotropy of metal oxide surface properties. In Chemical Physics of Solid Surfaces Vol 9 Oxide Surfaces, ed. D. R Woodruff, pp. 485-513. Amsterdam, the Netherlands Elsevier. 

Boehm, P. (1971) Acidic and basic properties of hydroxylated metal oxide surfaces. Disc. Para-day Soc. 52 264-275... 

When immersed in aqueous solutions, the surfaces of metal oxides are expected to be hydroxylated (see Section 3.1). However, metal oxides may also react with aqueous solutions leading to dissolution, which can effectively be thought of as mass transfer from the solid to aqueous phase. The rate and extent of dissolution reactions depend on a number of factors, including solution pH, acid-base properties of oxo groups on the metal oxide surface, types of ligands present in solution, metal... 

Thus, the possibility of adsorption is of primary importance. Adsorption may originate either from chelating properties of the organic substrate toward surface metal species or, because of the low hydrophobicity of the metal oxide surface, from the expulsion of the organic molecules from the solution for entropy reasons. Because there is depletion of substrate at the catalyst surface when degradation takes place, migration from the solution is assisted by a concentration difference in the two environments. 

Furthermore, titanium oxide thin films have been found to exhibit a unique and useful function (i.e., a superhydrophilic property). Usually, the contact angle of a water droplet on a surface is 50 -70° therefore, metal oxide surfaces become cloudy when water is dropped on them or if there is moisture in the atmosphere. However, under UV light irradiation of the titanium oxide surfaces, this contact angle of water droplets becomes smaller, even reaching zero (superhydrophil-icity), its extent depending on the UV irradiation time and irradiation intensity. Thus, under UV light irradiation, titanium oxide thin-film surfaces never become... 

The technological and commercial interest in metal oxide surfaces and interfaces has also continued to grow. For decades, oxide surfaces have played a key role in corrosion protection, catalysis, sensors, fuel cells, ceramics, etc. Over the last few years, totally new devices and technologies that rely on the properties of oxide surfaces and interfaces have emerged. Non-volatile ferroelectric field-... 

Several of the chapters in this book are concerned with the electronic and geometric properties of clean metal oxide surfaces i.e., the oxide-vacuum interface. Theoretical and experimental determination of clean surface properties is crucial to understanding the physics of metal oxides. This physics can be rather complicated, due to the ionic nature of the system and the strong effect of electron correlation. Some of this work is at the cutting edge of current solid-state physics. 

Many other chapters are concerned with how metal oxide surfaces react chemically with atoms and molecules. Chaps. 6-9 deal with oxide films grown epitaxially on bulk metals or other oxides. The interfacial properties of oxides are where much of their technological, commercial and environmental utility lies, and these fields will be expanding tremendously over the next few years. 

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