The derivatives of the spectra are commonly used for quantification in Auger Electron Spectroscopy (AES) spectra, while the derivative of the KLL C Auger line has proven to be valuable in obtaining a measure of the relative proportions of sp2‐ and sp3‐hybridization using the D‐parameter in both AES and X‐ray Photoelectron Spectroscopy (XPS). Differentiation of X‐ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) spectra by numerical means is presented and illustrated for polymeric, such as PEEK and Nylon, as well as for graphitic materials including highly ordered pyrolytic graphite and graphene oxide. The most commonly available Savitzky–Golay method is explained mathematically and developed through the case of constructing a 5‐point quadratic polynomial convolution kernel suitable for differentiating spectra of adequate signal to noise. The concept of differentiation of spectra where signal to noise is less than adequate is also developed. Two alternative strategies to Savitzky–Golay differentiation are presented, which fit curves to data that allow derivatives to be obtained where Savitzky–Golay would otherwise fail. These alternative methods involve constructing a parametric curve that fits data over the entire energy interval of interest. Derivatives of spectra are then obtained by differentiating these parametric curves directly. A comparison of results for different materials for which specific sp2‐ vs sp3‐hybridized carbon proportions are of interest is used to emphasize the importance of characterizing methods used to differentiate spectra and understanding the characteristics of instrumentation used to measure spectra. The case for using Principal Component Analysis noise reduction with C KLL spectra is made for spectra collected from a heterogeneous graphene oxide sample.

The existence of asymmetry in X‐ray photoelectron spectroscopy (XPS) photoemission lines is widely accepted, but line shapes designed to accommodate asymmetry are generally lacking in theoretical justification. In this work, we present a new line shape for describing asymmetry in XPS signals that is based on two facts. First, the most widely known line shape for fitting asymmetric XPS signals that has a theoretical basis, referred to as the Doniach‐Sunjic (DS) line shape, suffers from a mathematical inconvenience, which is that for asymmetric shapes the area beneath the curve (above the x‐axis) is infinite. Second, it is common practice in XPS to remove the inelastically scattered background response of a peak in question with the Shirley algorithm. The new line shape described herein attempts to retain the theoretical virtues of the DS line shape, while allowing the use of a Shirley background, with the consequence that the resulting line shape has a finite area. To illustrate the use of this Doniach‐Sunjic‐Shirley (DSS) line shape, a set of spectra obtained from varying amounts of graphene oxide (GO) and reduced GO on a patterned, heterogeneous surface are fit and discussed.

Abstract Marine and terrestrial sediments stabilise organic carbon (OC) against microbial respiration, influencing the climate by slowing the release of CO2 into the atmosphere. Redox-active element-bearing minerals, such as the manganese oxide mineral birnessite (δMnO2) play an important role in OC stabilisation. However, the mechanism for birnessite-OC stabilisation is unclear, limiting further understanding of the role of birnessite in the carbon cycle. We hypothesise that bond formation is promoted on δMnO2 surfaces, ultimately producing a complex assembly of stabilised OC. We test our hypothesis by investigating δMnO2 samples spanning < 1 year to 2.5 billion years old, using X-ray photoelectron spectroscopy and thermogravimetric analysis to synergistically observe OC thermal decomposition. We propose that thermally stable OC is generated during δMnO2 reduction. We speculate that thermally stable OC is unsuitable for rapid microbial respiration and is therefore chronologically stable. We conclude that the OC stabilisation described here could be an important but hitherto unrecognised process that removes OC from the readily exchangeable OC pool, thereby helping to modulate the climate.

In this study, we use zeolite Y as a support for the synthesis of Sn and Ga doped zeolites aimed at the isomerization of glucose to fructose. Though these materials are inactive in water, they are active in methanol and we could ascertain a reaction pathway involving a hydride shift for the interconversion of glucose to fructose and mannose, and a Brønsted acid pathway with the formation of a methyl fructoside intermediate and its hydrolysis to fructose if water was added afterwards. By using characterizations comprising: chemisorption, XPS, XRD, HAADF-STEM and EXAFS; it was possible to demonstrate that a straightforward impregnation protocol for the preparation of our catalysts, led to Sn/Y mainly consisting of small SnO2 clusters on the external surface of the zeolite, whereas Ga/Y consisting of highly dispersed Ga species mostly inside the zeolite pores; and a catalytic activity that appears to be dominated by Brønsted acid sites.

Argon Gas Cluster-Ion Beam sources have become widely-used on x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) instruments in recent years, but there is little reference data on sputter yields in the literature as yet. Total sputter yield reference data is needed in order to plan, and later calibrate the depth scale, of XPS or SIMS depth profiles. We previously published a semi-empirical Threshold equation for estimating cluster total sputter yield from the energy-per-atom of the cluster and the effective monatomic sputter threshold of the material. This has already been shown to agree extremely well with sputter yield measurements on a range of organic and inorganic materials for clusters of around a thousand atoms. Here we use the molecular dynamics (MD) approach to explore a wider range of energy and cluster size than is easy to do experimentally to high precision. We have performed MD simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) parallel MD code on high-performance computer (HPC) systems at Cincinnati and Newcastle. We performed 1,150 simulations of individual collisions with a silicon (100) surface as an archetypal inorganic substrate, for cluster sizes between 30 and 3,000 argon atoms and energies in the range 5 to 40eV per atom. This corresponds to the most important regime for experimental cluster depth-profiling in SIMS and XPS. Our MD results show a dependence on cluster size as well as energy-per-atom. Using the exponent previously suggested by Paruch et al, we modified the Threshold model equation published previously to take this into account. The modified Threshold equation fits all our MD results extremely well, building on its success in fitting experimental sputter yield measurements.

Earlier investigations have suggested that an extensive deep biosphere with a significant fungal component is present within the sub-oceanic crust. To investigate this further, the organic material in the lithic sections of a sub-oceanic volcaniclastic tuff obtained from the eastern lobe of the Ontong Java Plateau (OJP tuff) were characterised using X-ray photoelectron spectroscopy and thermal hydrolysis and methylation coupled to gas chromatography/mass spectrometry. In the investigation here, the chemical and molecular composition of plant and fungal structural biopolymer standards were characterised using the same techniques and then compared to the organic material from the OJP tuff. This was conducted on untreated material and after hydrous pyrolysis, a process that simulated the physical and thermal decomposition of organic material that occurs during late diagenesis. The characteristics of the organic material in the OJP tuff matched the products of hydrous-pyrolysed chitin. This result suggested that OJP tuff contained organic material that could have been derived from fossilised chitin, implying that the OJP tuff potentially contained the remnants of a microbial community with a fungal component.

The procedures for detecting fossils on Mars can be derived from the methods that are already used in terrestrial paleobiology (Cady et al., 2003). Here fossils preserving regions are visually located, then inspected for morphological features that might imply fossilised biology (Cady and Noffke, 2009; Westall et al., 2015). Morphological evidence of microfossils on its own is not a completely reliable biosignature (García Ruiz et al., 2002). However, evidence of biological activity may be implanted within the molecular and isotopic composition of organic compounds, which can serve as biosignatures (Summons et al., 2008). Thus, combining both morphological with organo-geochemical evidence could strengthen any argument that a given geological feature could be associated with biological activity. The results from the simultaneous morphological and geochemical analysis of geobiological structures on Earth could provide evidence that any comparable structures that may be observed on Mars, are potentially connected to biological activity, and therefore, may be suitable for collection for return to the Earth, for further analysis. As a proof of concept, the distribution of the organic material that is associated with distinctive microtubules in the glassy volcaniclastic shards within tuff, that have been suggested to be putative ichnofossils (Banergee and Muehlenbachs, 2003), these were analysed by us using X-ray photoelectron spectroscopy, nanoSIMS and the Ionoptika J105 time of flight secondary ion mass spectrometer, with an argon gas cluster ion beam. This indicated that nitrogenous organic material occurred in regions of the sample that were rich in microtubule textures and in the surrounding microfractures (Sano et al., 2016). These results demonstrated that the J105 ToF-SIMS combined with XPS and GC/MS analysis is able to match geomorphological features with their organic and inorganic composition at the µm scale, which may be a useful approach for the identification of fossilised life on Mars. References: Banerjee et al., (2003). Geochemistry, Geophysics, Geosystems, 4(4). Cady et al., (2003). Astrobiology, 3(2), pp.351-368. Cady et al., (2009). GSA Today, 19(11). García Ruiz et al., (2002). Astrobiology, 2(3), pp.353-369. Summons et al., (2008) Astrobiology, 90, 1151–1154. Westall, F., et al., (2015). Astrobiology, 15(11), pp.998-1029. Sano, N et al., (2016). J. of Vac Sci & Tech A: 34(4), p.041405

Cu-In metallic hybrid is a promising non-noble catalyst for selective electrochemical CO2 reduction (eCO2R) to CO, but the lack of direct assembly with a gas diffusion electrode (GDE) limits the further development of eCO2R to CO with both high Faradaic efficiency (FE) and high current density. In this study, an in situ electrochemical spontaneous precipitation (ESP) method was applied for the first time to prepare GDE-combined Cu-In electrocatalysts. The optimum Cu-In catalyst consists of a nanoscale "core-shell" structure of polycrystalline CuxO covered by the amorphous In(OH)3 interface. Higher than 90% FE of CO production has been achieved. With the synergy of a GDE flow cell and 1 M KOH catholyte, a current density of ∼200 mA cm-2 was reached at -1.17 V (reversible hydrogen electrode), which enabled a CO yield efficiency record of 3.05 mg min-1(CO2/15 mL min-1 with a 2 cm2 electrode). The ratios between CO and H2 produced can be effectively modulated via fine-tuning ESP conditions demonstrating possibility of generating CO or syngas with tuneable ratios. The present study provides a simple approach for constructing novel catalytic interfaces with dual active centers for eCO2R and other emerging electrochemical catalysis research.

Rhodium nanoparticles or rhodium organometallic complexes are mainly used in catalysis for reduction or hydroformylation reactions. In this work instead, we explored the capabilities of Rh nanoparticles as an oxidation catalyst, applied to the oxidation of benzyl alcohol to benzaldehyde under very mild conditions (100 degrees C, and atmospheric pressure) as a model reaction. Here we report the preparation of novel Rh/C catalysts by using an impregnation protocol, with particular emphasis on the pre-treatment of the carbon supports by using HNO3 and HCl, as well as the characterization of these materials by using an array of methods involving TEM, XPS and XRPD. Our preparation method led to a wide Rh particle size distribution ranging from 20 to 100 nm, and we estimate an upper limit diameter of Rh nanoparticles for their activity towards benzyl alcohol oxidation to be ca. 30 nm. Furthermore, a HNO3 pre-treatment of the activated carbon support was able to induce a smaller and narrower particle size distribution of Rh nanoparticles, whereas a HCl pre-treatment had no effect or sintered the Rh nanoparticles. We rationalise these results by HNO3 as an acid able to create new nucleation sites for Rh on the carbon surface, with the final effect of smaller nanoparticles, whereas for HCl the effect of sintering was most likely due to site blocking of the nucleation sites over the carbon surface. The roles of acid centres on the carbon surfaces for the oxidation reaction was also investigated, and the larger their amounts the larger the amounts of by-products. However, by treatment with HNO3 we were able to convert neutral or basic carbons into supports capable to enhance the catalytic activity of Rh, and yet minimised detrimental effects on the selectivity of the oxidation to benzaldehyde.

The aim of this work is to study the influence of two surface modification methods, surface grinding to change the surface roughness (from 240 to 4000 grit) and oxidation (furnace at 703 K for 5 h in air), on antibacterial activity against E. coli. K12 of a Cu-based bulk metallic glass composite (BMGC). Variations of roughness obtained through grinding in both as-cast and oxidized samples had a minimal effect on antimicrobial activity. Oxidation in resulted in a multilayered structure with an outer CuO layer, followed by Cu2O layer and other phases at greater depths according to microscopy and energy dispersive X-ray results. This oxidation increased antimicrobial performance despite the CuO layer is poorer in copper than the Cu55Zr40Al5 at. % bulk metallic glass composite substrate. This improvement could be attributed to microstructural differences between the layer and the substrate. The fine needle-shape structure of the crystalline oxide layer may account for the improvement since interphase boundaries could constitute easy diffusion paths for Cu ion release while the shape could trigger mechanosensitive channels that can favour and thus promote the migration of copper ions into the cell. Microscopy of the deposited bacteria revealed limited changes of the outer layer of the cells, with slight changes in morphology for the oxidized samples and this is attributed to the higher copper ion released. Minimum Inhibitory Concentration tests revealed that cell degradation takes place at copper concentrations of 222.4 mg/mL, much higher than measurements of copper ion diffusion in the as-cast samples, suggesting that lysis is not the first step in copper ion toxicity. These studies indicate that Cu55Zr40Al5 bulk metallic glass composite shows promise as an antimicrobial material with tuned performance through surface oxidation.

What follows is a method applicable generically to the analysis of low levels of organic matter that is embedded in either loose fine-grained or solid geological material. Initially, the range of organic compounds that could be detected in a geological sample using conventional pyrolysis chromatography/mass spectrometry was compared to the range that was detected using thermally assisted hydrolysis and methylation-gas chromatography/mass spectrometry (THM-GC/MS). This method was used to validate the synthetic components fitted to X-ray photoelectron spectroscopy (XPS) carbon spectra of the sample. Reciprocally, XPS analysis was able to identify the constituent carbon-carbon, carbon-oxygen and carbon-nitrogen bonds of the functional groups in the compounds identified by THM-GC/MS. The two independently derived outputs from the THM-GC/MS and the XPS techniques mutually validated the identification of organic compounds in our geological samples. We describe in detail the improvements to: •The preparation of geological samples for analysis by XPS.•Measurements of organic material in geological samples using GC/MS.•The use of THM-GC/MS and XPS data used together to characterise low levels of organic material in geological samples.

We explore a number of different electrochemical, wet chemical, and gas phase approaches to study intercalation and oxidation at the buried graphene-Ge interface. While the previous literature focused on the passivation of the Ge surface by chemical vapor deposited graphene, we show that particularly via electrochemical intercalation in a 0.25 N solution of anhydrous sodium acetate in glacial acetic acid, this passivation can be overcome to grow GeO2 under graphene. Angle resolved photoemission spectroscopy, Raman spectroscopy, He ion microscopy, and time-of-flight secondary ion mass spectrometry show that the monolayer graphene remains undamaged and its intrinsic strain is released by the interface oxidation. Graphene acts as a protection layer for the as-grown Ge oxide, and we discuss how these insights can be utilized for new processing approaches.

Previous studies have shown that the use of a 20 keV water cluster beam as a primary beam for the analysis of organic and bio-organic systems resulted in a 10-100 times increase in positive molecular ion yield for a range of typical analytes compared to C-60 and argon cluster beams. This resulted in increased sensitivity to important lipid molecules in the bioimaging of rat brain. Building on these studies, the present work compares 40 and 70 keV water cluster beams with cluster beams composed of pure argon, argon and 10%CO2, and pure CO2. First, as previously, we show that for E/nucleon about 0.3 eV/nucleon water and nonwater containing cluster beams generate very similar ion yields, but below this value, the water beams yields of BOTH negative and positive "molecular" ions increase, in many cases reaching a maximum in the <0.2 region, with yield increases of similar to 10-100. Ion fragment yields in general decrease quite dramatically in this region. Second, for water cluster beams at a constant E/nucleon, "molecular" ion yield increases with beam energy and hence cluster size due to increased sputter yield (ionization probability is constant). Third, as a consequence of the increased ion yield and the improved focusability using high-energy cluster beams, imaging in the 1 mu m spatial resolution region is demonstrated on HeLa cells and rat brain tissue, monitoring molecules that were previously difficult to detect with other primary beams. Finally, the suggestion that the secondary ion emission zone has quasi-aqueous character seems to be sustained.

Solution-casted poly(lactic acid) (PLA) membranes reinforced by halloysite nanotubes (HNTs) were uniaxially stretched to rupture using a novel micromechanical tester to evaluate their mechanical properties in dry and wet environments. X-ray photoelectron spectroscopy indicated that the PLA was not chemically modified when HNTs were blended into the matrix. In all cases, statistical analysis revealed that the yield strength, fracture strength, and fracture toughness differed significantly among the different treatments. In particular, the yield strength of dry PLA/HNT was significantly higher than dry PLA membranes; the yield strength of dry PLA/HNT membrane was higher than wet PLA membranes. The fracture strength of dry PLA/HNT was significantly higher than dry PLA membranes, wet PLA membranes, and wet PLA/HNT membranes. The fracture toughness of the membrane differed significantly among the different treatments. In particular, the fracture toughness of dry PLA/HNT was significantly higher than wet PLA membranes. On the other hand, these findings revealed that wet PLA/HNT and PLA exhibit similar yield strength, fracture strength, and fracture toughness. It was concluded that there would be no advantage (no enhancement in the yield strength, fracture strength, or fracture toughness) in reinforcing PLA with HNT if these PLA-based membranes were deployed in applications that subject the membrane to hydration, in a wet environment.

This study highlights the importance of CO2 supply method and impact of electrolyte alkalinity in aqueous electrochemical CO2 reduction using CuxO catalyst. Two different CO2 supply methods using a two-chamber (2C) cell with CO2 purging into catholyte and a CO2 gas diffusion electrode (GDE) cell were compared. Faradaic efficiency (FE) of carbonaceous products in GDE cell was more than 3-folds higher than the 2C cell due to improved CO2 mass transfer. From the investigation of alkaline catholyte in GDE cell, the higher catholyte alkalinity led to higher current density and higher FE of carbonaceous products with a better selectivity of C2 (ethanol and ethylene). The reason lies in the OH groups around catalyst surface which improve the reaction kinetics and moreover stabilize the catalyst surface oxygen during the reduction process. With the potential of −1.17 V (RHE) in 2.0 M KOH, C2 FE of 40% and current density of −234 mA cm−2 were achieved. The production rate of ethylene and ethanol was respectively 0.105 mg min−1 and 0.035 mg min−1 on 2 cm2 electrode with CO2 flow rate 15 ml min−1, which are promising for further development and scale-up.

Structures in geological samples are often interpreted as fossilised life; however, such interpretations are equivocal, as abiotic processes can be invoked to explain their presence. Thus, additional lines of chemical evidence are invaluable in confirming or refuting such morphological evidence. Glass shards in tuff from the Ontong Java Plateau (OJP) contain microtubular structures that are in close proximity to functionalised nitrogen substituted aromatic compounds that may be indicative of the chemical remnants of biological activity. The organic composition of the OJP tuff containing microtubular alteration structures was compared with tuff without such features. In addition, organic matter associated with horizons with compacted remnants of woody material buried in the OJP tuff and overlying pelagic calcareous foraminifer sediment were also characterised, to ascertain the provenance of the organic matter found in the OJP tuff. As a further control, the organic material in submarine and terrestrial basalts from other locations were also characterised providing further evidence to support the view that the organic matter in the OJP tuff is authigenic. Carbon-nitrogen chemistry was detected across all OJP tuff samples irrespective of the presence or absence of microtubular features, but was not detected in either the wood material, the overlying pelagic sediments or in the basalts from other locations. The results indicate no direct link between the OJP nitrogenous organic compounds and the presence or absence of microtubular features.

Indium phosphide (InP) surfaces develop a pronounced nanostructured texture upon irradiation by energetic ion beams. We have observed the mechanism of nanostructure evolution of InP under irradiation by an Ar gas cluster ion beam (GCIB) using helium ion microscopy (HIM). Initially, metallic indium nanoparticles form on the surface after removal of the top-most oxide layer. These nanoparticles form a mask which shadows the underlying InP. As the ion dose is increased, the masking effect results in substantial nanostructured topography in the form of pillars or nanocones, oriented along the axis of the incident GCIB. The surface sensitivity and high resolution of the HIM facilitates the direct observation of the metallic indium cap at the top of the pillars.

The organic matter within rocks contains chemical and isotopic evidence of its provenance, including information on past and extant life. Such information could further the understanding of life on the early Earth and yield evidence of the existence of past life on Mars. However, the collection of geological samples and subsequent transfer to analytical facilities possibly via long-term storage provides ample opportunity for organic contamination from a variety of sources prior to analysis. Erroneous assignment of organic contamination as authentic indigenous organic material is a significant issue in any geological specimen, but is exacerbated in rocks containing trace levels. This investigation evaluated two decontamination methods for geological samples, namely, the recently developed gas cluster ion beam etching, which supersedes monoatomic sputter etching, and ultra violet/ozone cleaning. Decontamination evaluation involved removal of intentionally applied organic contamination applied to basalt which initially possessed only trace levels of indigenous organic material. Pyrolysis-gas chromatography/mass spectrometry, and X-ray photoelectron spectroscopy were used to measure contaminant removal. Both techniques are suitable for removing organic contamination during the preparation of geological samples.

Chemical shifts observed in high‐resolution X‐ray photoelectron spectroscopy (XPS) spectra are normally used to determine the chemical state of the elements of interest. Often, these shifts are small, or an element is present in several oxidation states in the same sample, so that interpretation of the spectra is difficult without good reference data on binding energies of the likely constituents. In many cases, reference spectra taken from pure reference samples of the chemical components can aid the peak fitting procedure. However, reference materials are not always available, so that it becomes necessary to estimate the binding energies of likely components through quantum chemical calculations. In principle, such calculations have become much easier than in the past, due to the availability of powerful personal computers and excellent software. In practice, though, care needs to be taken in the approximations, assumptions, and settings used in applying such software to calculate binding energies.In this work, we present a general summary of the methods for the calculation of the core electron binding energies and compare the use of 2 of these methods using the popular “GAUSSIAN” software package. Furthermore, a series of results for molecules, containing elements of the second and the third row of the periodic table, are presented and compared with experimental results, in order to establish the quality and fitness‐for‐purpose of the quantum chemical‐based predictions.

Metal nanoparticles prepared by exsolution at the surface of perovskite oxides have been recently shown to enable new dimensions in catalysis and energy conversion and storage technologies owing to their socketed, well-anchored structure. Here we show that contrary to general belief, exsolved particles do not necessarily re-dissolve back into the underlying perovskite upon oxidation. Instead, they may remain pinned to their initial locations, allowing one to subject them to further chemical transformations to alter their composition, structure and functionality dramatically, while preserving their initial spatial arrangement. We refer to this concept as chemistry at a point and illustrate it by tracking individual nanoparticles throughout various chemical transformations. We demonstrate its remarkable practical utility by preparing a nanostructured earth abundant metal catalyst which rivals platinum on a weight basis over hundreds of hours of operation. Our concept enables the design of compositionally diverse confined oxide particles with superior stability and catalytic reactivity.