Properties of the metal surface

There is a double charge layer at the surface of a metal which has its origin in the unsymmetric distribution of the electronic charge (6). On quantum-mechanical grounds, the electronic charge distribution spreads beyond the limits normally imposed by the presence of adjacent cells in the interior of the metal in order to lower the kinetic energy of the electrons. The consequence is seen in Fig. 7. In Fig. 7a the charge distribution about the sur- 

Charge distribution at a metal surface (a) as for atoms in bulk metal, (b) actual distribution, and (c) charge density (b minus a). 

The difference in electrostatic potential which exists between the inside and the outside of the metal is termed the surface potential. The related properties—the work function and the contact potential difference—respectively measure free energy changes when electrons are moved from one conductor to a vacuum and from one conductor to another. The thermodynamic basis of these properties has been reviewed by Herring and Nichols (6), and Chalmers (7) has considered the theory of contact potentials. 

The state of a gaseous or solid phase containing electrons may be described thermodynamically by the electrochemical potential of the electrons. Thus, in an isolated body of volume V containing n electrons, the electrochemical potential jS is defined as 

SO that it depends only upon the temperature and the internal conditions 

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The surface properties of metals are such that the surface tends to relax inwards bu systems described by two-body interactions tend to relax outwards. 

The surface properties of metals and of semiconductors reflect in certain respects the differences of the bulk characteristics accordingly, the conventional approaches to studying these two classes of surfaces have been quite different. It is believed, however, that metal and semiconductor surfaces have many common characteristics and that an effective interchange of theory and technology between these two fields of study should advance the understanding of surface behavior. 

Before discussing the surface properties of metal oxides, it is instructive to consider some of the important bulk electronic and geometric properties that characterize them and determine their behavior. 

Low temperature IR spectroscopy of CO as a test molecule provides means to display the difference of surface properties of Ti-containing adsorbents. Two kinds of TS-1 zeolite samples, which have identical structure and slightly different amount of residual alkali cations, characterized by this method, show great dissimilarity in the amount of acidic OH groups, Lewis acid sites of different strength, or of the reduced Ti atoms. Thus, the method could really be used as a rapid test for the surface properties of metal containing zeolites. 

It should be emphasized that the surface properties of metal sulfides are very sensitive to the redox conditions. 

Parkyns ND (1969) The surface properties of metal oxides. Part II. An infrared study of the adsorption of carbon dioxide on y-alumina. J Chem Soc A4 10-417... 

The surface properties of metal oxides can be studied by a variety of methods. Different characterization methods can be used to give different information about the surface properties. No one method can be used to give a complete understanding of a surface, but integration of results gained from different techniques can lead to an understanding of the structure, reactivity, strengths, and amount of acidic and basic sites on the surface of metal oxides. 

Conducting polymers have been used to modify the surface properties of metallic electrodes, in particular microelectrodes [49]. TTie prosthetic functional groups covalently attached to the polymer chains can be used as molecular sensors or molecular transducers that can reversibly transfer electrochemical information between the medium and the electrodes. These systems are useful for solution sensing in both amperometric and resistometric modes. Enzymes (for example, glucose oxidase) can be incorporated directly into the polymeric layer during polymerization and subsequently used as biosensors. 

Synthesis Tools to Produce Metal Nanoparticles 44 Organometallic complexes as the source of metal atoms 46 Ligands as stabilizers of metal nanoparticles 46 Tools for the Characterization of Metal Nanoparticles 47 Quantif cation of hydrides at metal nanoparticle surface 48 Coordination of CO to probe the surface properties of metal nanoparticles 48 Catalysis to probe the surface state of metal nanoparticles 50... 

Coordination of CO to probe the surface properties of metal nanoparticles... 

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