Conventional XPS Research Articles

Dispersion Stability of Inorganic Powders Harnessed to Mosaic Surface Ligands via Multifit Hansen Solubility Parameters.

This study assessed the dispersion stability of industrial carbide/oxide powders that have mosaic surfaces comprised of multiple surface ligands. A large number (∼50) of probe liquids were used with an aim to effectively explain the data within the Hansen solubility parameter (HSP) framework. The proposed log-fit method, complemented by multi-HSP analysis featuring harmonic-mean-mixing HSPs, significantly improved the fit to experimental results for various mosaic-surface powders composed of complex surface ligands. X-ray photoelectron spectroscopy and thermal desorption spectroscopy analyses were employed synergistically to decipher the surface ligands of these mosaic-surface powders, which facilitated credible identification and quantification of the surface ligands. These results are in good agreement with the surface ligands and their coverage as determined by the multi-HSP analysis. Consequently, when it comes to characterizing powder surfaces, dispersion stability measurements paired with multi-HSP analysis are superior to conventional XPS and TDS analyses in terms of both topmost surface sensitivity and practicality.

Seismic and energy upgrading of existing buildings—full‐scale testing of retrofitted masonry‐infilled RC frames

AbstractTaking into consideration the seismic vulnerability and the poor energy performance of the European building stock, and the increasing socio‐economic and environmental need for integrating seismic upgrading with energy efficiency improvement, an experimental study involving the lateral load testing of full‐scale one‐story one‐bay masonry infilled RC frames and load‐bearing masonry walls was carried out in the framework of the SupERB research project aiming to investigate the efficiency of integrated seismic and energy upgrading systems. The integrated approach is based on the use of textile reinforced mortar (TRM) overlays combined either with traditional thermal insulation (extruded polystyrene, XPS) or with thermally efficient mortar incorporating phase change material (PCMs). The proposed integrated approach can be applied on the exterior face of the structure, so as to facilitate its application in real structures in the easiest possible way and with minimum disturbance to the inhabitants of the buildings. In this paper, only the structural performance of masonry‐infilled RC frames retrofitted with the proposed integrated approach is presented, while the energy benefits will be presented in a separate paper. Thus, in this paper, the structural performance of an integrated seismic and energy upgrading approach was assessed through five full‐scale one‐story one‐bay masonry infilled RC frames that were retrofitted with different schemes of TRM combined with thermal insulation materials subjected to in‐plane displacement‐controlled cyclic loading. The following parameters were investigated experimentally: the number of TRM overlays (one or two layers of TRM combined with thermal insulation), the use of thermally efficient PCM‐enhanced TRM layer in contrast to the use of conventional XPS insulation, and different retrofitting configurations (placement of the TRM in a sandwich form over and/or under the novel or the traditional insulation). From the results obtained in this study, it can be concluded that all energy and seismic upgrading systems examined have a positive impact on the response of the structural system to cyclic loading, with the ones with two layers of TRM having a better performance compared to the ones with one layer of TRM and all of them a better performance than the control specimen. The use of two layers of TRM cancels the drawback of infilled frames, which at very small drifts they reach their maximum capacity and after that they rapidly fall to the capacity of the bare frame, providing capacities above 80% of their peak capacity for drifts up to 2%. In all the tests the TRM whether it was combined with XPS or included PCMs contributed to a better distribution of the cracks in the infill and delayed premature brittle failures. The presence of the TRM had also the advantage that it remained intact throughout the tests preventing the fall of debris out of the plane of the infilled frame, both in the retrofitted and unretrofitted sides.

Near ambient pressure–x-ray photoelectron spectroscopy spectra of lithium hexafluorophosphate in ethylene/dimethyl carbonate

Near ambient pressure–x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 5000 Pa. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, Li 1s, P 2p, C 1s, N 1s, O 1s, and F1s NAP-XPS spectra of a Li-based electrolyte solution, which is a material that would be difficult to analyze by conventional XPS. The measurements were performed at 1000 Pa in ambient gas atmosphere to compensate for surface charging. Peak fits of the C 1s, O 1s, and F 1s narrow scans are presented.

Near ambient pressure–x-ray photoelectron spectroscopy spectra of lithium bis(trifluoromethane-sulfonyl) imide in propylene carbonate

Near ambient pressure–x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 5000 Pa. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, Li 1s, S 2p, C 1s, N 1s, O 1s, and F 1s NAP-XPS spectra of a Li-based electrolyte solution, which is a material that would be difficult to analyze by conventional XPS. The measurements were performed at 200 Pa in ambient gas atmosphere to compensate for surface charging. Peak fits of the C 1s, O 1s, and F 1s narrow scans are presented.

Sorption of Polar Sorbents into GO Powders and Membranes.

The comparative study of sorption of polar substances acetonitrile and water into powders and membranes (>10 μm thick) of modified Hummers (HGO) and Brodie (BGO) graphite oxides was performed using isopiestic method (IM) and differential scanning calorimetry (DSC). Additional sorption data were obtained for pyridine and 1-octanol. Sorption measurements were accompanied by conventional XRD and XPS control. Electron paramagnetic resonance (EPR) was additionally used to characterize ordering of the membranes. The impact on sorption of synthetic procedure (Brodie or Hummers), method of making membranes, chemical nature of the sorbent, and method of sorption was systematically examined. It was demonstrated that variations in synthetic procedures within both Hummers and Brodie methods did not lead to changes in the sorption properties of the corresponding powders. Sorption of acetonitrile and pyridine was reduced by approximately half when switching from powders to membranes at ambient temperature. DSC measurements at a lower temperature gave equal sorption of acetonitrile into HGO powder and membranes. Water has demonstrated unique sorption properties. Equal sorption of water was measured for HGO membranes and powders at T = 298 K and at T = 273 K. It was demonstrated that lowering the orientational alignment of the membranes led to the increase of sorption. In practice this could allow one to tune sorption/swelling and transport properties of the GO membranes directly by adjusting their internal ordering without the use of any composite materials.

Chemical state analysis of reactively sputtered zinc vanadium nitride: The Auger parameter as a tool in materials design

Photoelectron spectroscopy is an important tool for the development of new materials. However, especially for nitride semiconductors, the formation of surface oxides, surface band bending as well as the lack of a suitable charge reference often prevent a robust analysis. Here, we perform a comprehensive chemical state analysis of the Zn-V-N phase space using the Auger parameter concept, which is less sensitive to such uncertainties. Phase-pure Zn2VN3, VN, and Zn3N2 samples are analyzed in a dual-source lab-based HAXPES system, after transfer in inert-gas atmosphere. XPS and HAXPES measurements are performed using Al kα and Cr kα, respectively. In addition, high-throughput chemical state analysis is performed on combinatorial Zn1-xVxN thin film libraries using conventional XPS. The evolution of the Zn Auger parameter in Zn1-xVxN is consistent with previous mapping of the structural and functional properties. Strikingly, the study reveals a narrower stability range of wurtzite Zn1-xVxN than our previous high-throughput XRD screening, highlighting the sensitivity of the measurement approach. The procedures applied here are transferable to many other material systems and could be particularly useful for the high-throughput development of materials with low crystallinity where insights from XRD screenings are limited.

A general overview and comparative interpretation on element‐specific X‐ray spectroscopy techniques:XPS,XAS,andXRS

AbstractX‐ray photoelectron spectroscopy (XPS), X‐ray absorption spectroscopy (XAS) and X‐ray Raman scattering (XRS) spectroscopy are the element‐specific tools providing local electronic and chemical structure insights. XPS is widely used for qualitative/quantitative surface analysis of solids and replaced by synchrotron‐based ambient pressure‐XPS and hard‐XPS to benefit from the advantages of near‐ambient pressures and hard X‐rays to study complex sample environments. XAS is a well‐established soft and hard X‐ray probe to examine the coordination, spin and oxidation states in solids, liquids and gases with high resolutions and short data acquisition time. XRS, using the hard X‐rays of ~10 keV, is preferred to conventional XAS and XPS in the study of soft X‐ray absorption edges such as C, O, Li K‐edges bulk‐sensitively in vacuum‐free medium for energy storage systems during working operations, inner Earth elements under realistic conditions, probing chemical and biological reactions in the liquid phase, C speciation in archeological and paleontological samples and direct tomography. In this study, first the basics of XPS, XAS, and XRS techniques with their advantages and limitations are introduced to provide a general overview. In the Results and Discussion, the particular emphasis is given to the comparison of XPS, XAS, and XRS with the interpretation of the spectroscopic signatures for organic carbonate‐based electrolytes. The computed C 1 s binding energy shifts for ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) are presented to discuss the XPS peak assignments and the performed C K‐edge XRS measurements of 1 M LiPF6in DMC and EC are given for a detailed discussion of the XRS spectra. C 1 s XPS, C K‐edge XAS, and XRS of PC from the literature are discussed to interpret the spectra of each technique comparatively.

Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy

The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.

Near ambient pressure XPS investigation of hydrous palladium oxide under water and oxygen gas environments

Pd takes various chemical forms according to the types of catalysts and even its pristine chemical state is often subject to change in operation. To understand the mechanism how Pd-based catalysts activate reactions, it is important to have a capability to identify the surface chemical state of Pd-based catalysts in contact with reactants. In this study, we conducted in situ near ambient pressure-x-ray photoelectron spectroscopy (NAP-XPS) in gas conditions with water and oxygen for hydrous Pd oxide, which is also known as palladium hydroxide (Pd(OH)2) and it is the key component of the Pearlman’s catalyst widely used for organic reactions. We found that hydrous Pd oxide showed different spectral features to that of anhydrous Pd oxide under gaseous water environments. We believe that this NAP-XPS study provides new information for a better identification of hydrous Pd oxide under reaction conditions, which is not available from conventional XPS in ultrahigh vacuum.

Cuttlefish bone (cuttlebone), by near-ambient pressure XPS

Near ambient pressure-x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, Ca 2p, C 1s, O 1s, and N 1s NAP-XPS spectra of two biological samples (cuttlefish bones in their native state and implanted with nitrogen ions), which are materials that would be difficult to analyze by conventional XPS. The measurements were performed at 100 Pa in ambient air to compensate for surface charging. Peak fits of the Ca 2p, C 1s, and N 1s narrow scans are presented.

Sensitivity of Corrosion Behavior for Fe-Based Amorphous Coating to Temperature and Chloride Concentration

The effects of solution concentration and temperature on the electrochemical behavior of the Fe-based amorphous (AMCs) coatings in NaCl solution were studied by using conventional electrochemical measurement and XPS analysis. Results indicated that as solution concentration and temperature increased, the current density for the Fe-based AMCs increased and the pitting potential decreased. This reduced corrosion resistance was derived from the decreased passivation index and polarization resistance, which contributed to the decrease of the induction time (tm) for the initiation of corrosion pit. The passive films formed on Fe-based AMCs exhibit two types’ semiconductors higher and lower the flat band potential. The decrease of protectiveness of the passive film was mainly correlated with the reduction of Cr2O3 content, the increase of carrier density and the decrease of the work function (WF).

Surface and interface analysis of iron sulfides in aqueous media using X-ray photoelectron spectroscopy of fast-frozen dispersions

Iron sulfides are important minerals and materials, whose surface properties are largely determined by the interface with aqueous phases. Here, natural pyrrhotite (Fe9S10) and pyrite (FeS2) were ground, reacted in water and acidic non-oxidative and oxidative ferric chloride and sulfate solutions, then centrifuged, fast-frozen and examined with X-ray photoelectron spectroscopy at –160 °C (cryo-XPS) in comparison with the samples thawed in vacuum, dried in vacuum or air and measured at room temperature (RT). The interfacial layers were composed mainly of ferric (hydr)oxides and aqueous iron salts as the reaction products rather than reactants; RT-XPS found the products modified due to dehydration, further reactions and redistribution over the surface. The cryo-XPS revealed plentiful surface Fe-S centers with various spin and oxidation states at pyrrhotite and pyrite, particularly in water, missed in conventional XPS. The surfaces of pyrrhotite and, much less, pyrite are enriched with polysulfide anions -S-Sn-S-, which partially volatilize at RT both under non-oxidative and oxidative conditions; the number n can be larger than 6 at pyrrhotite. It was concluded, nevertheless, that elemental sulfur insignificantly contributes to the spectra under the conditions employed. Pros and cons of the technique in the case study of iron sulfides are discussed.

Clinoptilolite, a type of zeolite, by near ambient pressure-XPS

Near ambient pressure-x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this paper, we show the NAP-XPS survey; O 1s, Ca 2p, C 1s, K 2p, Al 2s, Al 2p, Si 2p, and Si 2s narrow scans; and the extended valence band spectrum of clinoptilolite, a natural zeolite that would be difficult to analyze by conventional XPS. A small N 1s signal from N2(g) is also observed in the survey spectrum. Signals in the narrow scans are fit to Gaussian–Lorentzian sum and Gaussian–Lorentzian product functions.

Coffee bean, by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., up to 2500 Pa, or higher in some cases. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we present NAP-XPS C 1s and O 1s narrow scans and a survey spectrum of a coffee bean, a material that would be difficult or even impossible to analyze by conventional XPS. Coffee beans are ground to produce coffee powder, which is the source of one of the world’s most common beverages, coffee. The survey spectrum shows small amounts of sulfur and calcium.

Coca-Cola, by near-ambient pressure XPS

Near ambient pressure-x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at ca. 2500 Pa, or higher in some cases. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show an NAP-XPS survey spectrum, and also O 1s and C 1s narrow scans, of a commercial soft drink, Coca-Cola. Clearly this is a material that could not be analyzed at moderate pressures by conventional XPS. The C 1s narrow scan is fit to five synthetic components. The O 1s narrow scan shows strong contributions from both liquid and gas phase water. A small N 1s signal in the survey spectrum is attributed to background nitrogen. The shape of the uniqueness plot corresponding to the C 1s fit suggests that the fit parameters are statistically significant.

Ambient air, by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at 2500 Pa or higher. With NAP-XPS, XPS can analyze moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. Because of the relatively high working pressure of NAP-XPS, the components of ambient air may be present in the analytical chamber during data acquisition. In this submission, we show survey, O 1s, N 1s, valence band, oxygen Auger (KLL), and nitrogen Auger (KLL) NAP-XPS spectra from ambient air, a material that could not be analyzed at moderate pressures by conventional XPS.

Oxygen gas, O2(g), by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., greater than 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, O 1s, valence band, and O KLL Auger NAP-XPS spectra of oxygen gas, O2, a material that would be difficult to analyze by conventional XPS. A small N 1s signal from N2(g) is also observed in the survey spectrum. The O 1s narrow scan is fit to Gaussian-Lorentzian sum functions. The Lorentzian character of this synthetic line shape was varied to obtain the best fit. Since it is likely that O2(g) will be present in other NAP-XPS analyses, these data should serve as a useful reference for other researchers.

Carbon dioxide gas, CO2(g), by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, O 1s, C 1s, valence band, O KLL Auger, and C KLL Auger NAP-XPS spectra of gaseous carbon dioxide, CO2, a material that would be difficult to analyze by conventional XPS. A small N 1s signal from N2(g) is also observed in the survey spectrum. The C 1s and O 1s signals in the narrow scans are fit to Gaussian–Lorentzian sum and asymmetric Lorentzian (LA) functions. Better fits are obtained with the LA synthetic line shape. Since it is likely that CO2(g) will be present in other NAP-XPS analyses, these data should serve as a useful reference for other researchers.

Clamshell, by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show NAP-XPS survey, Ca (3p, 2p, 2s), O 1s, C 1s, and N 1s narrow, and valence band spectra from a clamshell, a material of biological origin that would be challenging to analyze by conventional XPS approaches. Like most shells of biological origin, clamshells are primarily composed of calcium carbonate.

Notable Reactivity of Acetonitrile Towards Li2O2/LiO2 Probed by NAP XPS During Li–O2 Battery Discharge

One of the key factors responsible for the poor cycleability of Li–O2 batteries is a formation of byproducts from irreversible reactions between electrolyte and discharge product Li2O2 and/or intermediate LiO2. Among many solvents that are used as electrolyte component for Li–O2 batteries, acetonitrile (MeCN) is believed to be relatively stable towards oxidation. Using near ambient pressure X-ray photoemission spectroscopy (NAP XPS), we characterized the reactivity of MeCN in the Li–O2 battery. For this purpose, we designed the model electrochemical cell assembled with solid electrolyte. We discharged it first in O2 and then exposed to MeCN vapor. Further, the discharge was carried out in O2 + MeCN mixture. We have demonstrated that being in contact with Li–O2 discharge products, MeCN oxidizes. This yields species that are weakly bonded to the surface and can be easily desorbed. That’s why they cannot be detected by the conventional XPS. Our results suggest that the respective chemical process most probably does not give rise to electrode passivation but can decrease considerably the Coulombic efficiency of the battery.