scholarly journals Influence of Interfacial Oxidation on Friction in Structural Superlubricity

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
Alper Özoğul ◽  
Benedykt R. Jany ◽  
Franciszek Krok ◽  
Enrico Gnecco ◽  
Mehmet Z. Baykara
Keyword(s):  
Shear Stress ◽  
Photoelectron Spectroscopy ◽  
Chemical Interaction ◽  
Pyrolytic Graphite ◽  
Graphite Substrate ◽  
Ambient Conditions ◽  
Interfacial Chemistry ◽  
Friction Forces ◽  
X Ray ◽  
Contact Size

AbstractWe present the results of friction experiments performed by manipulation of oxidized platinum nanoislands on highly oriented pyrolytic graphite (HOPG) substrates through atomic force microscopy (AFM). The oxidation of the platinum nanoislands, performed via mild plasma exposure, is confirmed through X-ray photoelectron spectroscopy (XPS) and high-resolution energy-dispersive X-ray spectroscopy (EDX), the latter of which reveals partial oxidation on the sliding surfaces of the nanoislands. Oxidized platinum nanoislands are found to exhibit higher friction than non-oxidized islands, with a ~ 70% increase in mean shear stress over the investigated contact size regime. An increase in chemical interaction forces between the oxidized platinum and the graphite substrate is proposed to explain the increase in friction forces. Our results reveal that alteration of interfacial chemistry through oxidation leads to a noticeable modulation of friction forces, but not a total breakdown of the superlubric state (as evidenced by the signature observation of decreasing shear stress with increasing contact size), providing further feasibility for the design of superlubric mechanical systems to be operated under ambient conditions. Graphic Abstract

scholarly journals Re-Oxidation of ZnO Clusters Grown on HOPG

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 401
Author(s):  
Carlos Morales ◽  
Adolfo del Campo ◽  
Javier Méndez ◽  
Pilar Prieto ◽  
Leonardo Soriano
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Interaction ◽  
Pyrolytic Graphite ◽  
Ex Situ ◽  
X Ray ◽  
Oxidation Processes ◽  
Two Factors ◽  
Operating Limits ◽  
Zno Clusters

This article studies the chemical interaction between ZnO and highly oriented pyrolytic graphite for as grown and thermally treated samples. In-situ X-ray photoelectron spectroscopy and ex-situ Raman spectroscopy confirm that graphite is affected by these processes, becoming oxidized and defective only in the presence of ZnO clusters that become recrystallized upon thermal re-oxidation processes performed at 400 °C. By comparing these results with other identical experiments performed with ZnO clusters grown on graphene and even with CoO clusters grown on graphite, the present results show how the interaction of the ZnO clusters with graphitic substrates depend on two factors—firstly, the mode of growth and corresponding morphology, and secondly, the reactivity of the graphitic substrates, either graphene or graphite. The results presented here will help us understand the fundamental interactions in ZnO/graphitic heterostructures and to define their operating limits.

scholarly journals Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 202
Author(s):  
Miranda Martinez ◽  
Anil R. Chourasia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Chemical Interaction ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Increasing Trend ◽  
Substrate Temperatures ◽  
Beam Technique

The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO2 upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

Insights into the Li-Metal/Organic Carbonate Interfacial Chemistry by Combined First-Principles Theory and X-ray Photoelectron Spectroscopy

2018 ◽  
Vol 123 (1) ◽  
pp. 347-355 ◽  
Author(s):  
Mahsa Ebadi ◽  
Antoine Nasser ◽  
Marco Carboni ◽  
Reza Younesi ◽  
Cleber F. N. Marchiori ◽  
...  
Keyword(s):  
First Principles ◽  
Photoelectron Spectroscopy ◽  
Interfacial Chemistry ◽  
X Ray ◽  
Metal Organic ◽  
Organic Carbonate

High Resolution X-Ray Photoelectron Spectroscopy Study of the Interaction of Copper Ion with Chitosan Thin Film

2015 ◽  
Vol 1087 ◽  
pp. 241-245 ◽  
Author(s):  
Wing Fen Yap ◽  
W. Mahmood Mat Yunus ◽  
Zainal Abdib Talib ◽  
Yusof Nor Azah
Keyword(s):  
Thin Film ◽  
High Resolution ◽  
Photoelectron Spectroscopy ◽  
Chemical Interaction ◽  
Crosslinking Agent ◽  
Copper Ion ◽  
Aqueous Acetic Acid ◽  
X Ray ◽  
Glass Cover Slip ◽  
Crosslinked Chitosan

In this study, high-resolution X-ray photoelectron spectroscopy (XPS) has been used to study the chemical interaction between copper ion and chitosan thin film. The chitosan solution was synthesized by homogeneous reaction of medium molecular weight chitosan in aqueous acetic acid with glutaraldehyde as crosslinking agent. Then the solution was deposited on glass cover slip by spin coater to form a thin film. The functional group and chemical binding of crosslinked chitosan thin film has been confirmed by XPS. XPS revealed that copper ion adsorbed to the crosslinked chitosan thin film and the functional groups involved in the adsorption mechanisms of copper ion on the thin film were determined.

scholarly journals Vis-Responsive Copper-Modified Titania for Decomposition of Organic Compounds and Microorganisms

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1194
Author(s):  
Maya Endo-Kimura ◽  
Bariş Karabiyik ◽  
Kunlei Wang ◽  
Zhishun Wei ◽  
Bunsho Ohtani ◽  
...  
Keyword(s):  
Visible Light ◽  
Photoelectron Spectroscopy ◽  
Water Oxidation ◽  
Diffuse Reflectance Spectroscopy ◽  
Antimicrobial Properties ◽  
Localized Surface Plasmon ◽  
Intrinsic Activity ◽  
Ambient Conditions ◽  
Copper Species ◽  
X Ray

Seven commercial titania (titanium(IV) oxide; TiO2) powders with different structural properties and crystalline compositions (anatase/rutile) were modified with copper by two variants of a photodeposition method, i.e., methanol dehydrogenation and water oxidation. The samples were characterized by diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Although zero-valent copper was deposited on the surface of titania, oxidized forms of copper, post-formed in ambient conditions, were also detected in dried samples. All samples could absorb visible light (vis), due to localized surface plasmon resonance (LSPR) of zero-valent copper and by other copper species, including Cu2O, CuO and CuxO (x:1-2). The photocatalytic activities of samples were investigated under both ultraviolet (UV) and visible light irradiation (>450 nm) for oxidative decomposition of acetic acid. It was found that titania modification with copper significantly enhanced the photocatalytic activity, especially for anatase samples. The prolonged irradiation (from 1 to 5 h) during samples’ preparation resulted in aggregation of copper deposits, thus being detrimental for vis activity. It is proposed that oxidized forms of copper are more active under vis irradiation than plasmonic one. Antimicrobial properties against bacteria (Escherichia coli) and fungi (Aspergillus niger) under vis irradiation and in the dark confirmed that Cu/TiO2 exhibits a high antibacterial effect, mainly due to the intrinsic activity of copper species.

scholarly journals A modified ionic liquid clay to remove heavy metals from water: investigating its catalytic activity

2019 ◽  
Vol 17 (4) ◽  
pp. 2043-2058
Author(s):  
S. Kakaei ◽  
E. S. Khameneh ◽  
M. H. Hosseini ◽  
M. M. Moharreri
Keyword(s):  
Heavy Metal ◽  
Catalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Metal Ion ◽  
Kinetic Studies ◽  
Heavy Metal Ion ◽  
Ambient Conditions ◽  
X Ray ◽  
Metal Ion Adsorption ◽  
Map Analysis

Abstract The new clay modified with triazole and triazolium ligands was prepared in this research. These materials were applied as abundant and eco-friendly adsorbents for removal of heavy metal ions such as Pb(II), Co(II) and Zn(II) ions. The adsorption efficiency of these materials was calculated by relevant equations such as Langmuir and Freundlich as well as kinetic studies with pseudo-first-order and pseudo-second-order models. These adsorbents proved to be very active on heavy metal ion adsorption. The characterization of these new materials was carried out by various techniques such as X-ray diffraction, thermogravimetric analysis, scanning electron microscope (SEM), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy as well as SEM-map analysis. Eventually, the catalytic activity of the adsorbents which treated with heavy metal ion solutions was studied in the reduction of nitroarenes to its corresponding amines. The prepared adsorbent–catalyst materials indicated efficient catalytic activity in the reduction of nitroarenes to amines in ambient conditions. Graphic abstract

Metal Overlayers on Self-Organized Molecular Assemblies: X-ray Photoelectron Spectroscopy of CR/CM and NI/CM on 12-Nercaptododecanenitrile

1993 ◽  
Vol 304 ◽  
Author(s):  
D. R. Jung ◽  
A. W. Czanderna
Keyword(s):  
Binding Energy ◽  
Photoelectron Spectroscopy ◽  
Chemical Interaction ◽  
Molecular Assemblies ◽  
X Ray ◽  
Self Organized ◽  
Deposited Metal ◽  
Show Evidence ◽  
Metal Overlayers ◽  
End Group

AbstractOverlayers of Cr and Ni deposited at 22 °C and at -100 °C onto self-organized molecular assemblies of HS(CH2 )11 CN on Au have been studied by X-ray photoelectron spectroscopy (XPS). For the lowest overlayer coverages, the C ls and N is core levels show evidence for a chemical interaction between the deposited metal and the CN end-group. At 22 °C and for coverages of 0.6 nm or more, Cr/CN shows a C ls low binding energy, carbide-like shoulder. The degree of metal penetration is assessed based on the attenuation of the C ls and Au 4f intensities, and on the positions of the Cr and Ni 2p levels. In general, the least penetration and the largest binding energy shifts of the C, N, and the Cr or Ni core levels are observed for Cr/CN, while and Ni/CN shows smaller shifts and greater penetration.

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