Surface spectroscopic analysis

The infrared surface spectroscopic analysis was applied only to gas-solid surfaces imtil Bewick et al. succeeded ) to measure an in situ infiored spectra on electrode surfaces in electrochemical systems. They controlled the electrode potential and obtained the difference spectra between the measured and the reference potentials (EMIRS Electrochemically Modulated Infrared Reflectance Spectroscopy). This technique is employed in this theses also and discussed in detail in a later section. 

The situation is different for other carbon materials such as activated carbons. During activation of the precursor, partial oxidation of the carbon proceeds from the external surface of the carbon particle to the interior. Thus, the portion of the activated carbon particle close to the external surface is more severely activated than the interior and chemistry of the external and internal surface is most likely to be different. Before surface spectroscopy and gas adsorption data of OMCs are compared, the surface spectroscopic analysis of the carbon materials is reviewed very briefly. 

Darmstadt H, Roy C, Kaliaguine S, Ting JM, Alig RL, Surface spectroscopic analysis of vapour grown carbon fibres prepared under various conditions. Carbon, 36, 1183-1190, 1998. 

Volume 57A Spectroscopic Analysis of Heterogeneous Catalysts. Part A Methods of Surface Analysis edited by J.L.G. Fierro... 

Further structural information is available from physical methods of surface analysis such as scanning electron microscopy (SEM), X-ray photoelectron or Auger electron spectroscopy (XPS), or secondary-ion mass spectrometry (SIMS), and transmission or reflectance IR and UV/VIS spectroscopy. The application of both electroanalytical and surface spectroscopic methods has been thoroughly reviewed and appropriate methods are given in most of the references of this chapter. 

Surface spectroscopic techniques must be separated carefully into those which require dehydration for sample presentation and those which do not. Among the former are electron microscopy and microprobe analysis, X-ray photoelectron spectroscopy, and infrared spectroscopy. These methods have been applied fruitfully to show the existence of either inner-sphere surface complexes or surface precipitates on minerals found in soils and sediments (13b,30,31-37), but the applicability of the results to natural systems is not without some ambiguity because of the dessication pretreatment involved. If independent experimental evidence for inner-sphere complexation or surface precipitation exists, these methods provide a powerful means of corroboration. 

In order to investigate the active sites of these proteins, laccases I and III were subjected to ESR (electron spin resonance) spectroscopic analysis. The ESR spectra shown in Figure 5 indicate clear differences in peaks 2 and 6 which support the concept that the copper atoms in laccases I and III have different conformations in each molecule. Furthermore, immunological similarity between laccases I and III was also investigated. Antibody specific for laccase III was prepared from rabbit serum by conventional methods. When applied to Ouchterlony diffusion plates containing laccase I, no precipitation lines developed (Figure 6). This result showed that there were no conserved epitopes on the surfaces laccases I and III. 

X-Ray Photoelectron Spectroscopy (XPS). This technique is also known as electron spectroscopy for chemical analysis (ESCA), and as this name implies, it is a surface analytical technique. At present it is probably the most versatile and generally applicable surface spectroscopic technique. It is called XPS because of the type of beam used to study the interfacial region, that is, X-rays. These X-rays consist of monochromatic radiation—radiation of a given energy—emitted by a metal target bombarded by an electron beam of several kiloelectron volts of kinetic energy... 

This very short treatment of reversal techniques has the following basis. There are certainly treatments in the literature of chronopotentiometiy dealing with current reversal, or reversed-step voltammetry. However, their validity has to be diligently examined in each application. For example, is an assumption of a first-order reaction tacitly involved, when the actual solution may correspond to a fractional reaction order Another reason for the limited treatment has an eye on the future. There are those who see in the rapid development of in situ spectroscopic techniques (see, e.g., Section 6.3), together with advances in STM and AFM, the future of surface analysis in electrochemistry. If these surface spectroscopic techniques continue to grow in power, and give information on surface radicals in time ranges as short as milliseconds, transient techniques to catch intermediate radicals adsorbed on surfaces may become less needed. 

The quantities determined directly by the spectroscopic analysis as performed for hot stars are effective temperature Tef f surface gravity g and element abundances. Of course, this is not sufficient to place a star in the HR diagram. This is possible only with further knowledge of either luminosity, radius, mass or distance of the star. However, uncertainties in these quantities (which are usually much larger than the uncertainties in Te and g) directly translate into the HR diagram. On the other hand, theoretical evolutionary tracks can be easily expressed in terms of Teff and g without loss of precision. It is therefore good practice to discuss the results of spectroscopic analyses directly in a (log Te -log g) diagram as we shall do in this paper. 

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