X-ray Photoelectron Spectrometry XPS

Let us assume that the primary X-ray with energy hv creates a photoelectron at the core energy level (a). The Einstein equation gives the relation between exd- 

In Fig. 3, one observes the core level transitions of Cls and 01s as well as the Auger transition of oxygen, O yv Indeed, the photoemlsslon process is followed by a relaxation process either (b) or (c) as shown in Fig. 2. In the process (c) a third elec- 

Ek can exhibit dependence upon the oxidation state of the element. Narrow scans around an element of interest allow one to determine quantitatively the various binding states of this element. In particular for polymers, carbon and oxygen binding states can be Identified as Illustrated In Fig. 4 for the Cls transition of PM-MA. 

XPS peak intensities (areas) I are a means of quantification. The relation between I and the atomic concentration c of an element or chemical component at a depth z is 

Typical values of the escape depth A for polymers are between 5 and 10 nm indicating the shallow information depth of XPS [10]. Quantification is performed by application of the simple formula 

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Dynamic SIMS is used to measure elemental impurities in a wide variety of materials, but is almost new used to provide chemical bonding and molecular information because of the destructive nature of the technique. Molecular identihcation or measurement of the chemical bonds present in the sample is better performed using analytical techniques, such as X-Ray Photoelectron Spectrometry (XPS), Infrared (IR) Spectroscopy, or Static SIMS. 

Charge distributions and bonding in compounds of Cd and Hg in the solid and gaseous states can be studied by the well-established X-ray photoelectron spectrometry (XPS) and ultraviolet photoelectron spectrometry (UPS), respectively. With XPS, inner-shell electrons are removed which are indirectly influenced by the bonding, i.e., distribution of the valence electrons. UPS sees this electron distribution directly, since it measures the residual kinetic energies of electrons removed from the valence shells of the atoms, or, better, from the outer occupied orbitals of the molecules. The most detailed information accessible by UPS is obtained on gases, and it is thus applied here to volatile compounds, i.e., to the halides mainly of Hg and to organometallic compounds. 

X-Ray Photoelectron Spectrometry. X-ray photoelectron spectrometry (XPS) was applied to analyses of the surface composition of polymer-stabilized metal nanoparticles, which was mentioned in the previous section. This is true in the case of bimetallic nanoparticles as well. In addition, the XPS data can support the structural analyses proposed by EXAFS, which often have considerably wide errors. Quantitative XPS data analyses can be carried out by using an intensity factor of each element. Since the photoelectron emitted by x-ray irradiation is measured in XPS, elements located near the surface can preferentially be detected. The quantitative analysis data of PVP-stabilized bimetallic nanoparticles at a 1/1 (mol/mol) ratio are collected in Table 9.1.1. For example, the composition of Pd and Pt near the surface of PVP-stabilized Pd/Pt bimetallic nanoparticles is calculated to be Pd/Pt = 2.06/1 (mol/ mol) by XPS as shown in Table 9.1.1, while the metal composition charged for the preparation is 1/1. Thus, Pd is preferentially detected, suggesting the Pd-shell structure. This result supports the Pt-core/Pd-shell structure. The similar consideration results in the Au-core/Pd-shell and Au-core/Pt-shell structure for PVP-stabilized Au/Pd and Au/Pt bimetallic nanoparticles, respectively (53). 

Ion scattering spectrometry (ISS) Secondary ion mass spectrometry (SIMS) Auger electron spectrometry (AES) X-ray photoelectron spectrometry (XPS)... 

X-ray photoelectron spectrometry (XPS) is used to determine major and minor element compositions of metallic and ceramic surfaces. It can also be used to determine the oxidation states of ions on the surface of a sample. However, it has a limited depth penetration of 2-20 atomic layers and so the measurements taken will be greatly influenced by the method of sample preparation. The ability to characterize elements with atomic numbers less than 10, coupled with the ability to analyze samples smaller than 1.5 cm, make this technique particularly useful for the colorants and clarifying agents used in glasses and ceramics. For example, it has been used to... 

The surface comi>osition of the powder was determined by X-ray photoelectron spectrometry (XPS). In addition to the expected major constituents of the powder (silicon, nitrogen, and oxygen), carbon and fluorine are also present on the surface. Chlorine, iron, calcium and aluminum, although present in greater amounts than fluorine in the bulk sample, were not detected on the surface in measurable quantities. 

Surface analysis such as dynamic contact angle and surface tension are used to ensure proper wetting of epoxy and the substrate. Microscopic techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), are widely used to study morphology, fracture, and adhesion issues of cured epoxy systems. Chemical analysis techniques, such as micro-IR, X-ray photoelectron spectrometry (XPS), and secondary ion mass... 

The techniques mentioned so far provide no direct spatially resolved information on the chemical composition of materials. Various established analytical techniques, such as secondary-ion mass spectrometry (SIMS), X-ray photoelectron spectrometry (XPS), and infrared (IR) and Raman microspectrometry, can be used to carry out local compositional studies. In the case of SIMS and XPS, the sample needs to be held in high vacuum, while in IR and Raman microspectrometry, the resolution is limited by the relatively large wavelength... 

Study the influence of MNP morphology on their surface properties and catalytic performances. In parallel to these methods for the preparation of MNPs, heterogeneous catalysis has developed powerful tools to model and characterize the surface of the nanoparticles. Interestingly, these studies can be achieved during the catalytic process (Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (DRX), X-ray Photoelectron Spectrometry (XPS), Extended X-Ray Absorption Fine Structure (EXAFS), IR in operando) [26-34]. However, simple spectroscopic methods, such as UVA is, IR, or NMR both in solution and in solid state, which are adapted from molecular chemistry and homogeneous catalysis, offer interesting alternatives to precisely characterize the metallic surface of MNPs. 

In the work by Fadeeva et al. (2011) and Fadeeva (2014), X-ray photoelectron spectrometry (XPS) analysis was performed to compare the chemical composition of a base metal (titanium) and noble metal (platinum) before and after laser structuring (Table 1).These XPS measurements were performed approximately 2 months after the laser structuring had taken place. The untreated, as well as laser structured samples, were stored under normal ambient conditions. 

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