VUV Photoelectron Spectroscopy of Cysteine Aqueous Aerosols: A Microscopic View of Its Nucleophilicity at Varying pH Conditions

2015 ◽  
Vol 6 (5) ◽  
pp. 817-823 ◽  
Author(s):  
Chien-Cheng Su ◽  
Youqing Yu ◽  
Po-Chiao Chang ◽  
Yu-Wei Chen ◽  
I-Ying Chen ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ph Conditions ◽  
Aqueous Aerosols

scholarly journals Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 437 ◽  
Author(s):  
Peter Cook ◽  
YoungJae Kim ◽  
Ke Yuan ◽  
Maria C. Marcano ◽  
Udo Becker
Keyword(s):  
Photoelectron Spectroscopy ◽  
Redox Reactions ◽  
Redox Potentials ◽  
Free Energies ◽  
Cathodic Peak ◽  
Redox Transformation ◽  
Hydrogen Electrode ◽  
Midpoint Potential ◽  
Ph Conditions ◽  
Cv Measurements

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV.

scholarly journals A new insight into the restriction of Cr(VI) removal performance of activated carbon under neutral pH condition

2021 ◽  
Author(s):  
Yi Fang ◽  
Ke Yang ◽  
Yipeng Zhang ◽  
Changsheng Peng ◽  
Aurora Robledo-Cabrera ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Removal Efficiency ◽  
Photoelectron Spectroscopy ◽  
Toxic Heavy Metal ◽  
X Ray ◽  
Neutral Ph ◽  
Removal Capacity ◽  
Ph Conditions ◽  
Neutral Conditions ◽  
The Impact

Abstract Activated carbon has been widely used to remove hazardous Cr(VI), however, the impact of Cr2O3 precipitate on gradually declined removal ability as pH increased has received little attention. Herein, to investigate the effect of Cr2O3, SEM-EDX (scanning electron microscope-energy dispersive X-ray analysis) coupling elements mapping of chromium loaded powder activated carbon (PAC) revealed that a chromium layer was formed on the PAC exterior after being treated with Cr(VI) at pH 7. XPS (X-ray photoelectron spectroscopy) study confirmed that 69.93% and 39.91% Cr2O3 precipitated on the PAC surface at pH 7 and pH 3, respectively, corresponding to 17.77 mg/g and 20 mg/g removal capacity. Exhausted PAC had a removal efficiency of 92.43% after Cr2O3 being washed by H2SO4 solution, which was much higher than the removal efficiency of 51.27 % after NaOH washing. This further verified the intrinsically developed Cr2O3 precipitate on PAC under neutral conditions limited the durability of PAC as an adsorbent. Consecutive elution assessments confirmed that adsorption and reduction ability both declined as pH increased. Raman spectroscopy and C 1s spectra of materials demonstrated two distinct Cr(VI) removal mechanisms under pH 3 and pH 7. In conclusion, the exhausted AC after Cr(VI) adsorption can be rejuvenated after the surface coated Cr2O3 being washed by the acid solution which can expand the longevity of AC and recover Cr(III). HIGHLIGHT In this work, we scrutinized the mechanism of poor removal capacity of commercial activated carbon on toxic heavy metal Cr(VI) under neutral pH conditions. Differing from the most accepted view that electrostatic repulsion is the main consideration, our study suggested that the relatively more Cr2O3 precipitate on the surface of activated carbon under higher pH led to the low Cr(VI) sequestration capability.

Arsenopyrite: a spectroscopic investigation of altered surfaces

1989 ◽  
Vol 53 (370) ◽  
pp. 223-229 ◽  
Author(s):  
S. Richardson ◽  
D. J. Vaughan
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ammonium Hydroxide ◽  
Binding Energies ◽  
Spectroscopic Techniques ◽  
Xps Spectra ◽  
Natural Systems ◽  
Surface Alteration ◽  
Core Electrons ◽  
Ph Conditions ◽  
Iron Sulphates

AbstractSurfaces of a natural sample of arsenopyrite (FeAsS) were oxidized by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The oxidants used were air during heating to relatively low temperatures (150°C), steam, ammonium hydroxide, hydrogen peroxide, and sulphuric acid. Electrochemical oxidation in water was also undertaken. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and spectral reflectance measurements, were used to characterize the surface compositions. New data are proposed for the binding energies of core electrons in arsenopyrite based on the fitted XPS spectra: 706.9 eV for the Fe 2p3/2 level, 161.2 eV for the S 2p level, and 40.7eV for the As 3d level. Spectroscopic analyses of the surfaces following oxidation indicated a range of iron oxides and hydroxides (Fe1−xO, Fe3O4, Fe2O3, FeOOH and Fe(OH)3), arsenic oxides (As2O3 and As2O5), sulphur and iron sulphates (FeSO4, Fe2(SO4)3). The relative proportions of the different phases present in the surface layer are related to the strength of the oxidant employed and, where relevant, the Eh/pH conditions prevalent during oxidation. The conclusions regarding the nature of the oxidation of arsenopyrite are discussed in relation to arsenopyrite extraction by flotation and leaching, and the breakdown of arsenopyrite in natural systems.

scholarly journals Chemical Dissolution of Pt(111) during Potential Cycling under Negative pH Conditions Studied by Operando X-ray Photoelectron Spectroscopy

2019 ◽  
Vol 123 (41) ◽  
pp. 25128-25134 ◽  
Author(s):  
Harri Ali-Löytty ◽  
Markku Hannula ◽  
Mika Valden ◽  
André Eilert ◽  
Hirohito Ogasawara ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Dissolution ◽  
Potential Cycling ◽  
X Ray ◽  
Ph Conditions

Preferential Sputtering of Ni3Al Single Crystals Studied Using Atom-Probe Field-Ion Microscopy and XPS

1981 ◽  
Vol 39 ◽  
pp. 16-17
Author(s):  
M.P. Thomas ◽  
A.R. Waugh ◽  
M.J. Southon ◽  
Brian Ralph
Keyword(s):  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Depth Profiling ◽  
Analytical Techniques ◽  
Atom Probe ◽  
Probe Field ◽  
Preferential Sputtering ◽  
Argon Ion Bombardment ◽  
Argon Ion

It is well known that ion-induced sputtering from numerous multicomponent targets results in marked changes in surface composition (1). Preferential removal of one component results in surface enrichment in the less easily removed species. In this investigation, a time-of-flight atom-probe field-ion microscope A.P. together with X-ray photoelectron spectroscopy XPS have been used to monitor alterations in surface composition of Ni3Al single crystals under argon ion bombardment. The A.P. has been chosen for this investigation because of its ability using field evaporation to depth profile through a sputtered surface without the need for further ion sputtering. Incident ion energy and ion dose have been selected to reflect conditions widely used in surface analytical techniques for cleaning and depth-profiling of samples, typically 3keV and 1018 - 1020 ion m-2.

Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans

1990 ◽  
Vol 48 (2) ◽  
pp. 388-389
Author(s):  
A. M. Bradshaw
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Reactivity ◽  
Target Material ◽  
Orbital Energy ◽  
Light Sources ◽  
Analytical Technique ◽  
Hartree Fock ◽  
Spatially Resolved ◽  
Koopmans Theorem ◽  
Surface Analytical Technique

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).

Two dimensional Sr silicate grown on Si(001) studied using X-ray Photoelectron Spectroscopy

2006 ◽  
Vol 132 ◽  
pp. 87-90
Author(s):  
M. El Kazzi ◽  
G. Delhaye ◽  
S. Gaillard ◽  
E. Bergignat ◽  
G. Hollinger
Keyword(s):  
Photoelectron Spectroscopy ◽  
Two Dimensional ◽  
X Ray

BONDS IN AMORPHOUS Nb1-xSixSTUDIED BY X-RAY EMISSION AND X-RAY PHOTOELECTRON SPECTROSCOPY

1987 ◽  
Vol 48 (C9) ◽  
pp. C9-1025-C9-1028 ◽  
Author(s):  
W. ZAHOROWSKI ◽  
A. SIMUNEK ◽  
G. WIECH ◽  
K. SÖLDNER ◽  
R. KNAUF ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
X Ray
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