Surface-sensitive analytical

Studies of the first atomic layer in the formation of a compound are essentially studies of UPD. As noted, there are a number of excellent reviews [83-85, 87, 88], To really learn about the structure of UPD layers, single crystals and surface sensitive analytical techniques are required. A recent review covers atomic level studies of UPD on important single crystal electrode interfaces, such as Au, Pt, Ag and Cu [88], but does not go deeply into most of the systems of interest for EC-ALE. In this section, UPD of the first atomic layers in the formation of a compound will be discussed, as will atomic level studies of the formation of the first monolayers of compounds, where information is available. 

STM has matured enormously since the development of the first microscope 20 years ago, an achievement for which Binning and Rohrer were awarded the Nobel Prize in physics in 1986 39,41. STM has emerged as a powerful technique for exploring surfaces at the atomic scale. This ability makes the STM unique in comparison to other surface-sensitive analytical techniques, and the progress of... 

The influence of the surface structure of electrodes on electrochemical processes has been a central topic of basic electrochemical research in recent years. Advances were mainly achieved due to the utilization of structurally defined electrodes, usually low-index single-crystal surfaces, and to the development of surface-sensitive analytical techniques for the in-situ characterization of electrodes [1, 2]. Most of the advances can be attributed to the application of the latter, the new techniques, to the former, namely the well-defined surfaces. This approach has proven very powerful and its... 

Summary. The development of in-situ scanning tunneling microscopy (STM) has opened new avenues of research in electrochemical surface science. By itself, this nanometer-scale structural tool cannot be regarded as a panacea for the many problems that confront researchers in the interfacial sciences. However, when employed in tandem with other surface-sensitive analytical methods, even exceedingly complex processes can be investigated. Two cases are presented here that showcase the power of in-situ STM coupled with combined electrochemical UHV techniques. 

In addition to the plasmon resonance displayed by AuNPs, gold films also exhibit a surface plasmon resonance (SPR) that fluctuates in response to surface-bound molecules. Using SPR, surface-sensitive analytical techniques have been designed based on the ability of SPR to detect changes in the dielectric constant induced by molecular adsorption onto the metal surface. SPR has been used for the detection of a variety of... 

TABLE 13.5 Depths of Penetration for Surface-Sensitive Analytical ... 

The specific nature of ionic hquids at the gas-hquid and sohd-liquid interface and the exact mechanisms of interaction have been studied extensively using various surface-sensitive analytical techniques. Experimental research data, supplemented by computational modehng [1, 8], and their findings are discussed in the foUowing sections. 

The final cation orientation may be influenced by the anion that is also present at the surface, depending on its type and size. These findings from SFG analytical work are generally in agreement with the results from other surface-sensitive analytical techniques that are presented in more detail in the following section. 

The surface nonstoichiometry has made it very difficult to use inherently surface-sensitive analytical techniques like tunneling measurements, thus one should be always reminded that the surface electronic properties may be different from those of the bulk. 

Surface Chemical Composition. The atomic composition of catalyst surfaces plays a decisive role for the catalyst properties. Electron and ion spectroscopies (48) are surface-sensitive analytical tools, which provide information on the atomic composition within the topmost atomic layers. The information depth, that is, the number of atomic layers contributing to the measured signal, depends on the method used. Concentration profiles can be obtained by sputter etching of the surface by ion bombardment. The application of these particle spectroscopies requires ultrahigh vacuum (UHV) conditions. 

The understanding of the interactions which take place between a material surface and the components of the biological system is an important requirement of biomaterial development. The uppermost atomic layers of a biomaterial, which present characteristic chemical structural parameters and physical properties, define the contact surface. An important contribution to biomaterial development is, therefore, made by surface-sensitive analytical methods [71] which allow the surface modifications to the biomaterial to be proved. 

X-ray photoelectron spectroscopy (XPS) is a more surface-sensitive analytical method which suppHes information not only about the type and amount of elements present but also about their oxidation state and chemical surroundings. Applying this method informational depths of approximately 10 nm can be achieved, which means about 50 atomic layers. In secondary ion mass spectroscopy (SIMS) primary ions interact with the polymer surface and the mass spectra of the formed secondary ions are obtained which give information about the chemical composition of the outermost atomic layers (approximately 1 nm in thickness). 

Surface analysis is the study of the chemistry, crystal structure, and morphology of surfaces, using a combination of various surface sensitive analytical methods. Surface sensitivity can mean different things for different applications however, a good working definition would be the uppermost 0.5 to 3 nanometers (nm) of a surface, or two to ten layers of atoms. Because surfaces are often modified with films in the tens to hundreds of nanometers range, the uppermost 100 nm can be considered the surface for some applications. Any surface thicker than 100 nm is typically considered bulk material. 

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an extremely surface-sensitive analytical technique that uses a beam of hquid metal ions to probe the top one to three molecular layers of a sample, causing the emission of ions from the sample to be detected in a time-of-flight mass spectrometer, which gives detailed information about the specific molecules and atoms at a surfiice. 

The strategy adopted in this chapter is to describe the type of information which can be obtained from a variety of analytical techniques. These techniques have been applied to a set of different industrial catalyst samples. The discussion will focus on only the qualitative results which were common for all samples. It is beyond the scope of this chapter to make a detailed analysis of the significant quantitive discrepancies found with different catalysts. It should be stressed that although such differences between the catalysts were large for bulk-sensitive properties, they were generally less pronounced in the properties of the outer (geometric) surfaces which are probed by surface-sensitive analytical methods, e.g., electron spectroscopy. 

Auger electron spectroscopy is a surface-sensitive analytical techiuque that utilizes the Auger electrons that are emitted from a surface when it is bombarded (excited) by... 

X-ray photoelectron spectroscopy (XPS) or, as it is sometimes called, electron spectroscopy for chemical analysis (ESCA), is a surface-sensitive analytical technique that analyzes the energy of the photoelectrons (50-2000eV) that are emitted when a surface is bombarded with X-rays in a vacuum. The energy of these electrons is characteristic of the atom being bombarded and thus allows identification of elements in a similar maimer to that used in AES. 

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