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Chemical state
About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.
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TL;DR: The role of the Zn promoter and the preparation route in the catalytic properties of Cu-Zn/γ-Al 2 O 3 catalysts towards NO reduction with CO were investigated in this paper.
29 citations
TL;DR: The surface potential of an insulating specimen will generally change during an X-ray photoelectron spectroscopy (XPS) measurement due to surface charging, and it is then difficult to determine binding energies with the accuracy needed for elemental identification or chemical state determination as discussed by the authors.
Abstract: X-ray photoelectron spectroscopy (XPS) is widely used for characterization of surfaces of materials. Elements in the sample (with the exception of hydrogen and helium) are identified from comparisons of the binding energies of their core levels, determined from measured photoelectron spectra, with tabulated values of these binding energies for the various elements. Information on the chemical state of the detected elements can frequently be obtained from small variations (typically between 0.1 eV and 10 eV) of the core-level binding energies from the corresponding values for the pure elements. Reliable determination of chemical shifts often requires that the binding-energy scale of the XPS instrument be calibrated with an uncertainty that could be as small as 0.1 eV. The surface potential of an insulating specimen will generally change during an XPS measurement due to surface charging, and it is then difficult to determine binding energies with the accuracy needed for elemental identification or chemical-state determination. There are two steps in dealing with this problem. First, experimental steps can be taken to minimize the amount of surface charging (charge-control methods). Second, corrections for the effects of surface charging can be made after acquisition of the XPS data (charge-correction methods). Although the buildup ofmore » surface charge can complicate analysis in some circumstances, it can be creatively used as a tool to gain information about a specimen.« less
29 citations
TL;DR: A solid state synthetic approach for the fabrication of Fe3O4@M core-shell nanostructures in nearly quantitative yields that involves a simple physical grinding of a metal precursor over Fe3 O4 core, followed by calcination.
Abstract: Solvent-less synthesis of nanostructures is highly significant due to its economical, eco-friendly and industrially viable nature. Here we report a solid state synthetic approach for the fabrication of Fe3O4@M (where M = Au, Ag and Au-Ag alloy) core-shell nanostructures in nearly quantitative yields that involves a simple physical grinding of a metal precursor over Fe3O4 core, followed by calcination. The process involves smooth coating of low melting hybrid organic-inorganic precursor over the Fe3O4 core, which in turn facilitates a continuous shell layer post thermolysis. The obtained core-shell nanostructures are characterized using, XRD, XPS, ED-XRF, FE-SEM and HR-TEM for their phase, chemical state, elemental composition, surface morphology, and shell thickness, respectively. Homogeneous and continuous coating of the metal shell layer over a large area of the sample is ascertained by SAXS and STEM analyses. The synthesized catalysts have been studied for their applicability towards a model catalytic hydrogen generation from NH3BH3 and NaBH4 as hydrogen sources. The catalytic efficacy of the Fe3O4@Ag and Ag rich alloy shell materials are found to be superior to the corresponding Au counterparts. The saturation magnetization studies reveal the potential of the core-shell nanostructured catalysts to be magnetically recoverable and recyclable.
29 citations
TL;DR: In this article, an empirical approach was adopted in order to establish correlation between structural features, nitrogen content and photocatalytic properties of these thin N TiO2 films, and the impact of surface N O groups such as N O Ti O (or O N Ti O) and bulk substitutional nitrogen groups is discussed.
Abstract: Nitrogen-doped titania (N TiO2) thin films were synthesized using atmospheric-pressure chemical vapor deposition (APCVD) using ammonia, tert-butylamine or benzylamine as the nitrogen source. The influence of these precursors on the structural, morphological and optical absorption properties of the films was studied using X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and UV/Vis spectroscopy. The chemical state and location of the nitrogen species in the films was investigated using X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of films with similar structural properties was evaluated during degradation of stearic acid under UVA and visible light illumination. A previous study established a potential photosensitization mechanism involving surface N groups with binding energy of ∼400 eV, which would result in extrinsic enhanced UV activity of the N TiO2 films. Here, an empirical approach was adopted in order to establish correlation between structural features, nitrogen content and photocatalytic properties of these films. Within the thickness range considered, the photocatalytic activities of the undoped TiO2 films were consistent with their diffraction features (peak intensities and sharpness). Nevertheless, the activities of the N TiO2 films did not follow the same trend but it was consistent with their nitrogen content. Further evidence is provided on the participation of nitrogen species on the enhanced UV activity of N TiO2 films and the impact of surface N O groups such as N O Ti O (or O N Ti O) and bulk substitutional nitrogen groups is discussed. Discussion is also provided on the apparent visible light activity of the N TiO2 films.
29 citations
TL;DR: In this article, the relationship between surface chemical reaction and the formation of hydrophilic polar groups was investigated with a view of the compositional change on the polymer surface and the kinetic energy of ions.
Abstract: Argon ions of a kiloelectronvolt energy were irradiated on saturated simple‐chain polymers, such as polyethylene , poly(vinylidene fluoride) , and poly(tetrafluoroethylene) in an oxygen environment. Irradiating ions have induced chemical changes in polymeric chains, which includes substitution reactions for environment gas species resulting in the formation of radicals, carbonization, and bond scission but, exceeding the optimum ion dose, a carbonized phase was formed on the polymer surface. The relationship between the surface chemical reaction and the formation of hydrophilic polar groups was investigated with a view of the compositional change on the polymer surface and the kinetic energy of ions. From experimental results, identification of newly formed bonds and chemical changes depending on the depositing energy of the incident ions is represented. © 1999 The Electrochemical Society. All rights reserved.
29 citations