Characterization of adsorbed

Conventionally RAIRS has been used for both qualitative and quantitative characterization of adsorbed molecules or films on mirror-like (metallic) substrates [4.265]. In the last decade the applicability of RAIRS to the quantitative analysis of adsorbates on non-metallic surfaces (e.g. semiconductors, glasses [4.267], and water [4.273]) has also been proven. The classical three-phase model for a thin isotropic adsorbate layer on a metallic surface was developed by Greenler [4.265, 4.272]. Calculations for the model have been extended to include description of anisotropic layers on dielectric substrates [4.274-4.276]. 

IR Spectroscopic Characterization of Adsorbed Species and Processes on Surfaces... 

Polarization-dependent surface EXAFS measurements have provided some of the best-defined characterizations of adsorbate structures. 

The complexity and inhomogenicity of catalytic sites of metals and metal oxides make it difficult to interpret the mechanism of catalytic reactions on solid surfaces. Investigations that may lead to a better characterization of adsorbed species on catalytic sites could add much to our understanding of heterogeneous catalysis. 

J. B. Lhoest, M. S. Wagner, C. D. Tidwell and D. G. Castner, Characterization of adsorbed protein films by time of flight secondary ion mass spectrometry, Journal of Biomedical Materials Research, 57, 432 440 (2001). 

New directions have been recently advanced in the use of IR spectroscopy for the characterization of adsorbates, including the investigation of liquid-solid interfaces in situ during catalysis. Both ATR [91,92] and RAIRS [86,93] have been recently implemented for that purpose. RAIRS has also been used for the detection of intermediates on model surfaces in situ during catalytic reactions [94-96], The ability to detect monolayers in situ under catalytic environments on small-area samples promises to advance the fundamental understanding of surface catalytic reactions. 

Electron paramagnetic resonance has played a major role in the characterization of adsorbed oxygen species and the use of 17Oz has enabled a major advance to be made in the understanding of the nature of the various oxygen species and how they can be bonded to the surface. The use of IR spectroscopy as a technique has tended to be neglected because of the... 

Most of the adsorbents used in the adsorption process are also useful to catalysis, because they can act as solid catalysts or their supports. The basic function of catalyst supports, usually porous adsorbents, is to keep the catalytically active phase in a highly dispersed state. It is obvious that the methods of preparation and characterization of adsorbents and catalysts are very similar or identical. The physical structure of catalysts is investigated by means of both adsorption methods and various instrumental techniques derived for estimating their porosity and surface area. Factors such as surface area, distribution of pore volumes, pore sizes, stability, and mechanical properties of materials used are also very important in both processes—adsorption and catalysis. Activated carbons, silica, and alumina species as well as natural amorphous aluminosilicates and zeolites are widely used as either catalyst supports or heterogeneous catalysts. From the above, the following conclusions can be easily drawn (Dabrowski, 2001) ... 

R. J. Kokes, "Characterization of Adsorbed Intermediates on Zinc Oxide by Infrared Spectroscopy, Accounts of Chemical Research 6, 226 (1973). This article is rather mistitled and actually is concerned mostly with the mechanism of heterogeneous hydrogenation of alkenes,... 

The first chapter of this volume, by Sheppard and de la Cruz, addresses the application of vibrational spectroscopy for the characterization of adsorbed hydrocarbons. This chapter is a successor to the 1958 Advances in Catalysis chapter about infrared spectra of adsorbed species, authored by the pioneers Eischens and Pliskin. Vibrational spectroscopy continues to provide some of the most incisive techniques available for determination of adsorbate structures. The present chapter is concerned with introductory principles and spectra of adsorbed alkenes a sequel is scheduled to appear in a subsequent volume of Advances in Catalysis. 

The Application of High Resolution Electron Energy Loss Spectroscopy to the Characterization of Adsorbed Molecules on Rhodium Single Crystal Surfaces... 

In this paper we discuss how neutron scattering spectroscopy can be applied to the study of the structure and dynamics of adsorbed molecules. Since reviews of elastic and inelastic neutron scattering from adsorbed films have recently appeared (1.-3), our purpose here is not to present a comprehensive survey of every adsorbed system investigated by neutron scattering. Rather, we shall be concerned primarily with two questions which are basic to the characterization of adsorbed species on catalysts and which have been central to the discussion of this symposium. These are the extent to which the neutron scattering technique can be used to determine 1) the orientation and position of an adsorbed molecule and 2) the strength and location of the forces bonding a molecule to a surface. 

There has recently been much activity in developing molecular spectroscopic probes of electrochemical interfaces, as for other types of heterogeneous systems. The ultimate objectives of these efforts include not only the characterization of adsorbate molecular structure interactions under equilibrium conditions, but also the extraction of mechanistic and kinetic information from spectral detection of reactive adsorbates. 

Rising pollution levels and the need for sustainable energy have necessitated new ways of using certain materials to combat these problems. Focusing on this emerging discipline, Physical Chemistry of Materials describes the methods of syntheses and characterization of adsorbents, ion exchangers, ionic conductors, catalysts, and permeable materials. It tackles key issues in materials science and physical chemistry. 

The author of this book has been permanently active during his career in the held of materials science, studying diffusion, adsorption, ion exchange, cationic conduction, catalysis and permeation in metals, zeolites, silica, and perovskites. From his experience, the author considers that during the last years, a new held in materials science, that he calls the physical chemistry of materials, which emphasizes the study of materials for chemical, sustainable energy, and pollution abatement applications, has been developed. With regard to this development, the aim of this book is to teach the methods of syntheses and characterization of adsorbents, ion exchangers, cationic conductors, catalysts, and permeable porous and dense materials and their properties and applications. 

J. C. T. Eijkel, Potentiometric detection and characterization of adsorbed protein using stimulus-response measurement techniques, thesis. University of Twente. Enschede, The Netherlands, ISBN 90-9008615-3, 1995. 

J. Kfiz, E. Adamcovd, J. H. Knox, and J. Hora, Characterization of adsorbents by high-performance liquid chromatography using aromatic hydrocarbons porous graphite and its comparison with silica gel, alumina, octadecylsilica and phenyl-silica, /. Chromatogr. A 663 (1994), 151-161. 

Abstract Paradoxes, problems and ideologies in the study of supercritical adsorption were discussed. A macroscopic interpretation of supercritical adsorption was presented basing on a general model that derived at fiom the Gibbs definition and a straightforward method of determining absolute adsorption. The model does not include any assumption, but relies on experimental data and keeps the formal continuity of adsorption theory. It was shown to apply for wide ranges of temperature and pressure, and bore an impact to the characterization of adsorbents. 

In designing an adsorption column, the characterization of adsorbents should be done prior to experiments. In particular, one should know not only the specific area but also the pore size distribution of the adsorbent in order to confirm that it would be proper for a given purpose. Nitrogen adsorption and desorption isotherms, BET surface areas, and BJH (Barrett, Joyner and Halenda) pore size distributions of the synthesized sorbents... 

Laniewski K., Boren H., Grimvall A., Jonsson S., and von Sydow L. (1995) Chemical characterization of adsorbable organic halogens (AOX) in precipitation. In Naturally Produced Organohalogens (eds. A. Grimvall and E. W. B. de Leer). Kluwer, Dordrecht, The Netherlands, pp. 113-130. 

The third stage came with the realization that even small amounts of bound moisture could have a dramatic impact on properties and processes of pharmaceutical interest. In the evolution of this scientific pursuit, it is now evident that the state of moisture is as important as the amount present. Although sophisticated thermodynamic characterization of adsorbates has been the subject of research since the pioneering work of Gibbs, this stage has been enhanced by the ability to examine behavior at the molecular level by using powerful new analytical tools. 

Joppien, G.R., Characterization of adsorbed polymers at the charged silica-aqueous electrolyte interface, 7. Phys. Chem., 82, 2210, 1978. 

Weesner, EJ. and Bleam, W.E, X-ray absorption and EPR spectroscopic characterization of adsorbed copper(ll) complexes at the boehmite (AIOOH) surface, J. Colloid Interf.Sci., 196, 79, 1997. 

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