Physical techniques

Some physical techniques have also been used to characterize metallic nanoparticles prepared by surface redox reactions, for example  

Extended X-ray absorption fine structure (EXAFS) measurements for Pd-Pt systems prepared either by direct redox or refilling method indicated the presence of platinum in the vicinity of palladium for both preparations [13]. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalysis was carried out on Pd or Pt modified by Cu, Ag and Au [35], Pd-Sn [38], Pd-Cu [36], Rh-Ge [41], Pt-Ru-Sn and Pt-Ru-Mo (Fig. 9.5) [76], Pd-Sn-Au and Pt-Sn-Au [46] to collect more information on metallic particles in terms of particle size and composition. The catalysts prepared by redox reactions showed that the parent metal is always associated to the additive, but can be found isolated for supports which are able to adsorb the modifier. 

Mossbauer spectroscopy showed that on silica supported catalysts, only Pd-Sn solid solutions or alloys are present, whereas, on alumina supported catalysts, tin is present at 

All these techniques are valuable in assessing the degree of alloying. By combining some of these techniques, it was possible to go further in the determination of the location of the deposit (M2) on parent metal particles (Mi). Effectively, in the course of redox reactions, the deposit exhibited a selectivity depending on the relative redox potential of Mi /Mi and M2 /M2. Then, when the difference in potential is low such for the Pt-Au, Pd-Pt or Cu-Ru couples, the additive was preferentially deposited on low coordination sites (comers, edges, etc.) [6, 7, 10, 13], but when the difference in potential is high, for e omple with Cu-Pt, Cu-Au, all Cu sites were involved in the redox reaction [7]. 

The catalytic properties are strongly influenced by the activation mode of the catalysts. Then, the influence of different gas treatments at the end of the additive deposition by redox reactions was examined. These treatments may lead to a sintering or a segregation of the metals. 

---

In the first chapter, devoted to thiazole itself, specific emphasis has been given to the structure and mechanistic aspects of the reactivity of the molecule most of the theoretical methods and physical techniques available to date have been applied in the study of thiazole and its derivatives, and the results are discussed in detail The chapter devoted to methods of synthesis is especially detailed and traces the way for the preparation of any monocyclic thiazole derivative. Three chapters concern the non-tautomeric functional derivatives, and two are devoted to amino-, hydroxy- and mercaptothiazoles these chapters constitute the core of the book. All discussion of chemical properties is complemented by tables in which all the known derivatives are inventoried and characterized by their usual physical properties. This information should be of particular value to organic chemists in identifying natural or Synthetic thiazoles. Two brief chapters concern mesoionic thiazoles and selenazoles. Finally, an important chapter is devoted to cyanine dyes derived from thiazolium salts, completing some classical reviews on the subject and discussing recent developments in the studies of the reaction mechanisms involved in their synthesis. 

Nuclear magnetic resonance (NMR) spectroscopy is another physical technique which is especially useful for microstructure studies. Because of the sensitivity of this technique to an atom s environment in a molecule, NMR is useful for a variety of microstructural investigations We shall consider the application to copolymers now and to questions of stereoregularity in Sec. 7.11... 

The physical techniques used in IC analysis all employ some type of primary analytical beam to irradiate a substrate and interact with the substrate s physical or chemical properties, producing a secondary effect that is measured and interpreted. The three most commonly used analytical beams are electron, ion, and photon x-ray beams. Each combination of primary irradiation and secondary effect defines a specific analytical technique. The IC substrate properties that are most frequendy analyzed include size, elemental and compositional identification, topology, morphology, lateral and depth resolution of surface features or implantation profiles, and film thickness and conformance. A summary of commonly used analytical techniques for VLSI technology can be found in Table 3. 

Among the modem procedures utilized to estabUsh the chemical stmcture of a molecule, nuclear magnetic resonance (nmr) is the most widely used technique. Mass spectrometry is distinguished by its abiUty to determine molecular formulas on minute amounts, but provides no information on stereochemistry. The third most important technique is x-ray diffraction crystallography, used to estabUsh the relative and absolute configuration of any molecule that forms suitable crystals. Other physical techniques, although useful, provide less information on stmctural problems. 

R. Barer, in A. W. PoUister, ed.. Physical Techniques in Biological Research Ilia, Academic Press, New York, 1966, Chapt. 1. 

The conducted researches of complexing processes of noble metals on a sulfur-containing CMSG surface formed the basis for development of sorption-photometric, sorption-luminescent, soi ption-atomic-absoi ption, sorption-atomic-emission and sorption-nuclear-physic techniques of the analysis of noble metals in rocks, technological objects and environmental objects. Techniques of separation and detenuination of noble metals in various oxidation levels have been proposed in some cases. 

---