Iron Catalysis in Organic Synthesis

X-ray photoelectron spectroscopy: Towards reliable binding energy referencing

Superoxide dismutase mimetic properties exhibited by vacancy engineered ceria nanoparticles

A correlation between the particle size and the lattice parameter has been established in nanocerium oxide particles (3–30nm). The variation in the lattice parameter is attributed to the lattice strain induced by the introduction of Ce3+ due to the formation of oxygen vacancies. Lattice strain was observed to decrease with an increase in the particle size. Ce3+ ions concentration increased from 17% to 44% with the reduction in the particle size.

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Size dependency variation in lattice parameter and valency states in nanocrystalline cerium oxide

A facile approach to synthesize novel oxygen-doped g-C3N4 with superior visible-light photoreactivity

An ESCA study of the termination of the passivation of elemental metals

It has become common practice to employ, as a binding energy reference for x‐ray photoelectron spectroscopy studies on nonconductive materials, the C(1s) spectra of the ubiquitous (adventitious) carbon that seems to exhibit an instantaneous presence on all air exposed materials. Despite this commonality, surface scientists, including many practitioners, have expressed substantial concerns about the validity of this approach. A detailed discussion of the method is presented including consideration of the types of materials and the electronic energy states involved, e.g., Fermi edges, vacuum levels, etc., and the couplings that must exist for the referencing method to be correctly applied. A number of other surface environments for which the carbon referencing method may be fallacious are also presented. This leads to a consideration of the electron spectroscopy for chemical analysis results for different types of adventitious species and how the presence of some of these may confuse the use of the method. In this regard, we will also discuss the use of other methods to establish binding energy scales, such as Fermi edge coupling and select doping (e.g., the Au dot approach).

Nature of the use of adventitious carbon as a binding energy standard

Important progressive alterations in chemical bonding are often realized through correlations with shifts in the x‐ray photoelectron spectroscopy (XPS) binding energies of key elements. For example, there are useful general XPS shifting schemes for such systems as oxides, nitrides, halides, and even various functional groups in organics. Very general patterns, based upon location in the periodic table, exist for many of these materials even when the structure is not strongly considered. Unfortunately, apparently because of the lack of direct XPS detection of hydrogen, there seems to be no general statements in the literature for describing hydrogen‐containing compounds, despite the fact that synergistic shifts obviously exist in the XPS spectra of elements attached to hydrogen (e.g., for M–O–H vs M–O–M units, where M is a typical metal). While not attempting a complete review paper, in the present work we use XPS shifting patterns to evolve a series of interrelated covalency/ionicity arguments to help exp...

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The nature of hydrogen in x-ray photoelectron spectroscopy: General patterns from hydroxides to hydrogen bonding

X‐ray photoelectron spectroscopy (XPS) has often played the major role in the chemical characterization of select surface species, but the extension of that role to larger classes of compounds has generally been limited by such problems as cleanliness, charging, and relaxation shifts. In this article we suggest that adequate command of these difficulties has now permitted the collective chemical description of quite diverse surfaces. In this regard the progressive bonding differences of representative, simple group A oxides (e.g., BaO and SiO2 ) are analyzed employing various features in the XPS core level and valence band results. Regular progressions in covalency/ionicity are demonstrated. Extensions of these studies to complex (AzMsOt) oxides (e.g., Na2Al2O4 ) are also described in which progressive alterations of the XPS spectra suggest that during this complex formation the A–O bond is generally made more ionic, whereas the M–O bond becomes more covalent. These results also indicate that for many of ...

Tery L. Barr

Papers

An ESCA study of the termination of the passivation of elemental metals

Nature of the use of adventitious carbon as a binding energy standard

The nature of hydrogen in x-ray photoelectron spectroscopy: General patterns from hydroxides to hydrogen bonding

Recent advances in x‐ray photoelectron spectroscopy studies of oxides

The nature of the relative bonding chemistry in zeolites : an XPS study