Resolution X-ray Photoelectron Spectroscopy Spectra Research Articles

Effect of Fe on Bi2Te3: Structure, magnetic properties, and XPS valence band

The crystal structure and magnetic properties of Fe doped Bi2Te3 are presented. The samples were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetization measurements. Rietveld refinement results show a decrease in volume due to the decrease in c lattice parameter as iron is introduced. By XPS measurements, the Te 3d, Bi 4f, Bi 5d, Te 4d, and Fe 3d core levels were identified, and the XPS valence band (VB) was measured. The deconvolution process of high resolution XPS spectra in Fe 3d orbital shows that the Fe3+ ion is present in the samples. Theoretical calculations by DFT reveal that the Bi2Te3 compound is a semiconductor with a narrow energy band gap in agreement with experimental results. DOS analysis shows that the main contributions to the valence band are the Te 5p, Bi 6p, and Fe 3d states. XPS VB shows a decrease in the intensity at zero eV due to increased Fe 3d states and good correspondence with DOS calculated for Bi2Te3. Finally, magnetic susceptibility measurements on Bi2Te3 do not show a magnetic behavior; however, for the doped sample with x = 0.2, a weak ferromagnetic behavior (WFM) below 14 K is observed.

Synergistic effects of ionic and nonionic surfactants treatment on activated carbon electrodes for inverted capacitive deionization

Application of surfactants has attracted great interest in capacitive technologies owing to their potent interfacial activity. However, the reported surfactants utilization on Capacitive Deionization (CDI) technology is limited to ionic catalog. Herein, we reported a significant enhancement of capacitive behaviors by functionalizing inverted CDI (i-CDI) electrodes with dual surfactants, wherein nonionic surfactant induces synergistic effects with ionic surfactants. Brunauer-Emmett-Teller (BET) and Discrete Fourier Transform (DFT) isotherms analysis demonstrates that the surfactants loading reduce the pore volume and specific surface of activated carbon (AC) in accordance with the amount uptake. X-ray photoelectron spectroscopy (XPS) analysis shows the surfactant distribution within AC and its surface chemistry. The high resolution XPS spectra show the surfactants influence on binding energy and nitrogen is the most sensitive. The contact angle testing unveiled the fine wettability pertains on Tween 80. The surface charge evaluation in the context of Zeta potential measurement is presented. Through multiple electrochemical characterizations, dual surfactants treated electrodes display a superior capacitive behavior at a wide working voltage window. As such, the AC-T80-HDTMA/AC-T80-SDS system exhibits a higher salts removal capacity (7.5 mg g−1) with extended cyclic stability (38%) compare with AC-HDTMA/AC-SDS system (5.2 mg g−1) at 1.2 V. This work discloses profitable effects of ionic and nonionic surfactants synergy on i-CDI electrodes performance.

Bulk In2O3 crystals grown by chemical vapour transport: a combination of XPS and DFT studies

High purity In2O3 crystals were synthesized by the chemical vapour transport (CVT) as confirmed by X-ray Photoelectron Spectroscopy (XPS) using survey, core-levels and valence band scans of the samples. Further, high energy resolution XPS spectra revealed perfectly bonded In 3d configuration and excluded the presence of metallic In0, concurrently, the dual band observed for O 1s configuration was interpreted in term of the additional defectiveness in the oxygen sublattice. The valence band as measured by XPS is in agreement with the calculated one using DFT approach, and an insignificant shift of valence band toward Fermi level (about 0.05 eV) caused by the presence of the defects was established. Moreover, the energetics of the primarily defects were calculated and the trends were set in the perspective of XPS measurements. Altogether we make CVT In2O3 crystals ready to be used for the onward studies and technical applications.

Degradation characteristics of epoxy resin of GFRP rod in the decay-like fracture of composite insulator

The decay-like fracture is an emerging mode of abnormal mechanical failure of composite insulators the study of which is still in its infancy. The degradation of epoxy resin of glass fiber reinforced polymer (GFRP) rod caused by discharge and current distinguish the decay-like fracture from both normal mechanical fracture and brittle fracture. In the present work, the detailed degradation of epoxy resin of GFRP rod in the decay-like fracture of composite insulator were examined using scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results show that the generation, expansion and release of pyrolysis gas is responsible for the formation of the bubbles and holes in the epoxy resin and the initial formation of holes in the silicone rubber housing during the degradation process. The erosion and pyrolyzation of epoxy resin results in mass loss of epoxy resin leading to degradation of the GFRP rod. High resolution XPS spectra of C1s and N 1s in GFRP rod reflects that oxidization process, exposure of glass fiber, and the introduction of nitrogen-containing compounds occurs during the degradation process. Microscopic photographs to explain the degradation of the epoxy resin and the initial formation of puncture holes in the silicone rubber housing are proposed based on the experimental results.

Compositional ratio effect on the surface characteristics of CuZn thin films

CuZn thin films were fabricated by RF co-sputtering method on p-type Si(100) wafer with various RF powers applied on metallic Cu and Zn targets. This paper aimed to determine the morphological, chemical, and electrical properties of the deposited CuZn thin films by utilizing a surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), UV photoelectron spectroscopy (UPS), and a 4-point probe. The thickness of the thin films was fixed at 200 ± 8 nm and the roughness of the thin films containing Cu was smaller than pure Zn thin films. XRD studies confirmed that the preferred phase changed, and this tendency is dependent on the ratio of Cu to Zn. AES spectra indicate that the obtained thin films consisted of Cu and Zn. The high resolution XPS spectra indicate that as the content of Cu increased, the intensities of Zn2+ decreased. The work function of CuZn thin films increased from 4.87 to 5.36 eV. The conductivity of CuZn alloy thin films was higher than pure metallic thin films.

Reference binding energies of transition metal carbides by core-level x-ray photoelectron spectroscopy free from Ar+ etching artefacts

We report x-ray photoelectron spectroscopy (XPS) core level binding energies (BE’s) for the widely-applicable groups IVb-VIb transition metal carbides (TMCs) TiC, VC, CrC, ZrC, NbC, MoC, HfC, TaC, and WC. Thin film samples are grown in the same deposition system, by dc magnetron co-sputtering from graphite and respective elemental metal targets in Ar atmosphere. To remove surface contaminations resulting from exposure to air during sample transfer from the growth chamber into the XPS system, layers are either (i) Ar+ ion-etched or (ii) UHV-annealed in situ prior to XPS analyses. High resolution XPS spectra reveal that even gentle etching affects the shape of core level signals, as well as BE values, which are systematically offset by 0.2–0.5 eV towards lower BE. These destructive effects of Ar+ ion etch become more pronounced with increasing the metal atom mass due to an increasing carbon-to-metal sputter yield ratio. Systematic analysis reveals that for each row in the periodic table (3d, 4d, and 5d) C 1s BE increases from left to right indicative of a decreased charge transfer from TM to C atoms, hence bond weakening. Moreover, C 1s BE decreases linearly with increasing carbide/metal melting point ratio. Spectra reported here, acquired from a consistent set of samples in the same instrument, should serve as a reference for true deconvolution of complex XPS cases, including multinary carbides, nitrides, and carbonitrides.

Surface modification of model hydrogel contact lenses with hyaluronic acid via thiol-ene "click" chemistry for enhancing surface characteristics.

Discontinuation of contact lens wear as a result of ocular dryness and discomfort is extremely common; as many as 26% of contact lens wearers discontinue use within the first year. While patients are generally satisfied with conventional hydrogel lenses, improving on-eye comfort continues to remain a goal. Surface modification with a biomimetic, ocular friendly hydrophilic layer of a wetting agent is hypothesized to improve the interfacial interactions of the contact lens with the ocular surface. In this work, the synthesis and characterization of poly(2-hydroxyethyl methacrylate) surfaces grafted with a hydrophilic layer of hyaluronic acid are described. The immobilization reaction involved the covalent attachment of thiolated hyaluronic acid (20 kDa) on acrylated poly(2-hydroxyethyl methacrylate) via nucleophile-initiated Michael addition thiol-ene "click" chemistry. The surface chemistry of the modified surfaces was analyzed by Fourier transform infrared spectroscopy-attenuated total reflectance and X-ray photoelectron spectroscopy. The appearance of N (1s) and S (2p) peaks on the low resolution X-ray photoelectron spectroscopy spectra confirmed successful immobilization of hyaluronic acid. Grafting hyaluronic acid to the poly(2-hydroxyethyl methacrylate) surfaces decreased the contact angle, the dehydration rate, and the amount of nonspecific sorption of lysozyme and albumin in comparison to pristine hydrogel materials, suggesting the development of more wettable surfaces with improved water-retentive and antifouling properties, while maintaining optical transparency (>92%). In vitro testing also showed excellent viability of human corneal epithelial cells with the hyaluronic acid-grafted poly(2-hydroxyethyl methacrylate) surfaces. Hence, surface modification with hyaluronic acid via thiol-ene "click" chemistry could be useful in improving contact lens surface properties, potentially alleviating symptoms of contact lens related dryness and discomfort during wear.

Nanoscale chemical surface characterization of four different types of dental pulp-capping materials

ObjectivesThe surface of any dental pulp-capping material has important implications for its clinical success because it is in direct contact with dental tissue, which influences its cytotoxicity. The aim was to determine the chemical composition of the first atomic layers of four pulp-protection agents because these atoms can initiate the pulp healing process. MethodsBiodentine (Septodont), ProRoot MTA (Dentsply), Dycal (Caulk) and TheraCal (Bisco) were prepared (n=5) according to manufacturer recommendations. The chemical surface composition was analyzed using X-ray photoelectron spectroscopy (XPS), and the bulk composition was analyzed by Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX). Both survey and high resolution XPS spectra of the elements detected were obtained, with element-dependent probe depths of 4–5nm; the binding energy scale was normalized to the C1s adventitious carbon peak at 285eV. ResultsThere was a significant difference between bulk and surface compositions for all the pulp-capping materials. The calcium surface concentrations at 0nm and 70nm were Dycal 7.9% and 15.1%; ProRoot MTA 14.1% and 17%; TheraCal 0% and 3.6%; and Biodentine 17.6% and 33.7%, respectively. Trace amounts of the following elements (<1%) were also found: Ti, S and Zr in Biodentine; Bi in ProRoot MTA and TheraCal; Na, P, Zn and N in Dycal. ConclusionsThe XPS results showed that Ca in the surface layer could vary from 0 to 18%, depending on the material. Aliphatic carbons, from the polymerization reactions, especially in Dycal and TheraCal, were found to mask the other components. Clinical significanceThis study compares, for the first time, the chemical composition of the first atomic layers of four pulp-capping materials. This information is relevant because the interaction between pulpar cells and the material's outermost atomic layer is an important factor for leading the pulpal response.

Combined DFT and XPS investigation of iodine anions adsorption on the sulfur terminated (001) chalcopyrite surface

The adsorption of iodine anions (iodide and iodate) on the sulfur terminated (001) chalcopyrite surface has been systematically investigated combining first-principles calculations based on density functional theory (DFT) with X-ray photoelectron spectroscopy (XPS) measurements. Based on the total energy calculations and geometric optimization, the thermodynamically preferred site was copper atom for iodide adsorption and iron atom for iodate adsorption, respectively. In the case of Cu site mode, the iodate underwent a dissociative adsorption, where one IO bond of iodate ion was broken and the dissociative oxygen atom adsorbed on the adjacent sulphur site. Projected density of states (PDOS) analysis further clarified the interaction mechanism between active sites of chalcopyrite surface and adsorbates. In addition, full-range XPS spectra qualitatively revealed the presence of iodine on chalcopyrite surface. High resolution XPS spectra of the I 3d peaks after adsorption verified the chemical environment of iodine. The binding energies of 618.8eV and 623.5eV for I 3d5/2 peaks unveiled that the adsorption of iodide and iodate ions on copper-iron sulfide minerals was the result of formation of low solubility metal iodides precipitate. Also two I 3d peaks with low intensity around 618eV and 630eV might be related to the inorganic reduction of iodate to iodide by reducing S2− ion of chalcopyrite.

Characterization of endotoxins on orthopaedic fixation screws, using physicochemical surface analyses.

The objective of this study was to determine if surface analysis techniques could be used to detect endotoxin on stainless steel malleolus screws. New malleolus screws were compared to ones that had been coated in purified lipopolysaccharide (LPS) or Artificial Test Soil (ATS) containing lipopolysaccharide. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and time-of flight secondary ion mass spectrometry (TOF-SIMS) were used to assess the fixation screws surface. Organic material was visualized on the LPS and ATS-LPS inoculated screws but not on the new unsoiled screws. This was further supported by the peaks observed at masses between 40 and 100 D in TOF-SIMS spectra of the LPS and ATS-LPS inoculated screws. After deconvolution of N1s high resolution XPS spectra, the LPS inoculated screws showed amide groups whereas the ATS-LPS inoculated screws showed predominantly nitroso groups (C-NO). Our data demonstrate that surface analysis can be used to detect organic residuals present on fixation screws. The XPS data confirmed that LPS reacted predominantly with positively charged surface metallic ions (Fe and Cr), whereas proteins reacted with the surface oxide layer of fixation screws, forming C-NO groups. The application of these surface analysis techniques will be helpful in determining if the reprocessing of such items results in an accumulation of organic material that might lead to aseptic loosening, when implanted. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:240-247, 2017.

Analysis of Surface Deposit Formed on the Binder-Free Si Nanoparticle Electrode in Room-Temperature Ionic Liquid Containing Lithium Bis(trifluoromethanesulfonyl)Amide

1. Introduction Si is expected to be a promising alternative negative electrode material for lithium secondary batteries. Despite that, it suffers from poor cyclability due to the cracks caused by the large volume change during a charge-discharge reaction. On the other hand, room-temperature ionic liquids (RTILs) have attracted much attentions as an electrolyte for lithium-ion secondary batteries due to their non-flammability and negligible volatility. However, the electrochemical behavior of the Si electrode in many types of RTILs is not enough in spite of many researchers' vigorous efforts. As one reason, the SEI film on the Si electrode in RTILs may be less effective than that on the graphite electrode in the conventional electrolyte. To solve the problem, the analysis of the surface deposit formed on the Si electrode during a charge-discharge reaction is desired. To analyze it in more detail, we focus on an electrophoretic deposition (EPD) method because the binder-free (BF) electrode not containing conductive additives and a binder can be prepared. In this study, we prepared the BF nano-Si film electrode by using the EPD method and then investigated the electrochemical behavior in the RTILs. By employing the BF nano-Si film electrode not containing carbon, the surface deposit on the Si electrode was analyzed. 2. Experimental An EPD bath was prepared as follows: a concentration of nano-Si (average particle size: 50 nm) in acetone bath of 1.0 g L-1. Nano-Si was deposited on a Cu foil as a current collector substrate. The electrolyte was prepared by dissolving lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) in N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethanesulfonyl)amide (DEME-TFSA). The R2032 coin type cell, which consisted of the BF nano-Si film electrode (W.E.), a pressed lithium metal foil (C.E.), a 1 mol dm−3 solution of LiTFSA/DEME-TFSA (electrolyte), and celgard#2500 (separator), was used for the electrochemical measurements such as cyclic voltammetry (CV) and the charge-discharge cycle tests. For comparison, a 1 mol dm−3 solution of LiPF6/EC + DEC (50:50 vol. %) was used as a conventional electrolyte. The surface analysis of the BF nano-Si film electrode was carried out by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). 3. Results and Discussion The CVs of the BF nano-Si film electrodes in the above RTILs (DEME type) and above organic solvent electrolyte (organic solvent type) were measured. The reduction wave at the 1st cycle was observed in the cell voltage from 0.25 V to 5 mV regardless of the electrolyte type. Similarly, the oxidation wave at the 1st cycle was observed in the potential range from 0.20 V to 0.85 V in both electrolyte types. The reduction and oxidation currents would be due to the insertion and extraction reactions of Li+ ion into and from Si. Figure 1 shows the initial charge-discharge curves of the BF nano-Si film electrodes (ca. 0.23 mg cm-2) (a) in the DEME type and (b) in the organic solvent type at 25 oC. The 1st discharge capacity and the 1st charge-discharge efficiency of the BF nano-Si film electrode in the DEME type are 1507 mAh g-1 and 67.5%, respectively. In contrast, the 1st discharge capacity and the 1st charge-discharge efficiency in the organic solvent type are 1968 mAh g-1 and 73.2%, respectively. After the 2 cycle, the charge-discharge efficiency of the BF nano-Si film electrode increased and achieved to 98% regardless of the electrolyte type. These results suggest that the SEI film would be mostly formed on the BF nano-Si film electrode during the 1st charge. About the DEME type, the surface of the BF nano-Si film electrode was analyzed by the EDX mappings after charging down to 5 mV and after discharging up to 2.0 V, respectively. The EDX mapping results showed that C, O, F, and S were detected on the surface of the BF nano-Si film electrode. The surface deposit was uniformly formed on the nano-Si particle. The high resolution XPS spectra of F 1s region were measured. The peaks were assigned to the fluorine of a Li-F bond derived from LiF, suggesting that the layer of LiF was present on the surface. It was clarified that the LiF-based compound as the surface deposit was formed on the BF nano-Si film electrode. Based on these results, it was found that the compound containing LiF, C, O, and S as a surface deposit was formed on the BF nano-Si film electrode due to the cathodic decomposition of a DEME+ cation as well as a TFSA- anion as a side reaction after the 1st charging. Figure 1

Behavior of Passive Film on New Ti-Zr-Ta-Ag Alloy Surface in Simulated Biofluid

We elaborated a new Ti-20Zr-5Ta-2Ag alloy with innovative composition and properties to fulfil the necessities of corrosion resistance, biocompatibility and antibacterial protection; this alloy was complete and complex characterized: its microstructure by scanning electron microscopy (SEM); its native passive film by X-ray photoelectron spectroscopy (XPS); the surface wettability by contact angle measurements; the electrochemical behaviour in simulated human biofluid (Ringer solution of different pH values) by cyclic and linear polarization, electrochemical impedance spectroscopy (EIS) and monitoring of the open circuit potentials for 1000 exposure hours; the quantity of ions released in time by inductively coupled plasma-mass spectroscopy (ICP-MS). The new alloy has bi-phase, α + β, acicular microstructure, homogeneous and fine; also, lamellas of α and β phases, separated by distances of few microns can be observed (SEM images). Both survey and high resolution XPS spectra showed that the native passive film on Ti-20Zr-5Ta-2Ag alloy surface consists from the protective TiO2, ZrO2, Ta2O5 oxides, Ti and Ta suboxides and metallic Ag, which compact, reinforce and thicken the alloy passive film in comparison with that of Ti. The new alloy native passive film has a thickness of about 12 nm that is well above of that for Ti (1.3 – 3.7 nm). The contact angle for the new Ti-20Zr-5Ta-2Ag alloy has value of 64.54 0; it is a surface with high hydrophilic properties; its surface energy is 29.4 mJ/m2, representing a good value that promotes the interactions with biological fluids, cells and tissue and leads to a better biocompatibility. The corrosion and passivation potentials of the new alloy have more electropositive values than those of Ti, as result of the beneficial effect of Zr and Ta elements (which take part to the formation of the new alloy passive film, as XPS data showed) and of Ag that has a higher mixed potential. The passive current densities for Ti-20Zr-5Ta-2Ag alloy have lower values (of about 6 times) than those of Ti; corrosion current densities and rates are about 25-28 times lower and the polarisation resistances are about 21-28 times higher than those of Ti; this behaviour is due to the more protective passive layer existing on the new alloy surface. Nyquist spectra displayed capacitive loops associated with passive film like an insulator. Bode impedance spectra presented higher impedance values for the new alloy suggesting a more protective passive film than that on Ti surface. The new Ti-20Zr-5Ta-2Ag alloy exhibited higher phase angles than those for Ti, fact that demonstrates a nobler behaviour, a more capacitive film, a more resistant layer as result of its more compact, thicker, more complex composition. The impedance results were modelled with an electric equivalent circuit with two time constants corresponding to those two phase angles; the high phase angle represents a very capacitive, very resistant, barrier layer; the lower phase angle reflects the defective, less resistant, porous layer. The electrical parameters evinced slightly more unfavourable values for Ti, indicating that the passive film on its surface has lower insulating properties than the passive film on Ti-20Zr-5Ta-2Ag alloy surface; this fact is normal because the passive film on the new alloy surface is more compact, thicker, and, in addition, contains very protective ZrO2, Ta2O5 oxides, Ta suboxide and metallic Ag (as results from XPS data). The new Ti-20Zr-5Ta-2Ag alloy releases into Ringer solution low quantities of metallic ions, order of parts per million (ppm) beginning after 120 immersion hours; the quantity of the released ions increased over time. Silver ions were released in very low amount that enhanced in time, assuring long term antibacterial activity of the new alloy (ICP-MS data). The values of the open circuit potentials for the new Ti-20Zr-5Ta-2Ag alloy have more electropositive values than those of Ti, due to the alloy thicker, more compact (XPS results), more resistant (electrochemical and corrosion parameters) passive film. After about 500 immersion hours, all open circuit potential values tended to constant levels and maintained very constantly till 1000 hours, proving the alloy good stability. Open circuit potential differences had very low values situated under limits of 500 mV ÷ 600 mV necessary to form galvanic cells. Therefore, both Ti and new Ti-20Zr-5Ta-2Ag alloy are not susceptible to galvanic corrosion. The coupling of Ti with noble metals (Pt, Au, Ag) conducts to a higher mixed potential, because the noble metals are catalyst for the reducing both of the oxygen and water reactions. Thus, a quantity of 2% Ag is capable to increase the corrosion potentials of the new alloy.

XPS surface chemical characterization of atmospheric particles of different sizes

Surface chemical composition of particles has a key role in determining the reactivity and optical properties of atmospheric aerosol. This composition depend on the particles sources and formation processes and it influences human health and climate. In this work, the X-ray photoelectron spectroscopy (XPS) has been used for the systematic surface characterization of atmospheric particles of different sizes, collected using a 10-stage MOUDI-II rotating cascade impactor in an urban background site. The high resolution XPS spectra allowed to distinguish different organic functional groups (C–C/CC, –C–O, –CO/-C(O)N, –C(O)O, C¯O3=) and to speciate the detectable hetero-elements, sulphur (S¯O42−, sulphone and sulphide compounds), nitrogen (N¯H4+, N¯O3−, N¯O2− and organic-nitrogen compounds), sodium (Na+) and chlorine (Cl−) species. Significant differences in particles belonging to accumulation (small particles) and coarse (large particles) modes were observed being due to the formation processes and sources from which particles originated. The oxygen concentrations is inversely correlated with carbon concentrations, however, the content of oxidized organic carbon is not correlated with oxygen content confirming that the oxygen increment observed in large particles can likely be attributed to the contribution of inorganic species (crustal origin). The speciation of nitrogen showed ammonium only in the accumulation mode and nitrate only in coarse mode excluding the presence of ammonium nitrate of secondary origin in the area studied. A correlation of Na and Cl was attributed to the marine contribution with an excess of Cl on the surface correlated with the depletion of Cl observed in the bulk of particles.

Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen.

Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 × 10(4) ions μm(-2) and that their average height is centered at 4.5 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (HAADF-STEM) further confirm that the soft-landed PtRu nanoparticles are uniform in size. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in atomic concentrations of ∼9% and ∼33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt 4f and Ru 3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He(+) and O(+) ions. The activity of electrodes containing 7 × 10(4) ions μm(-2) of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was evaluated by employing the same experimental parameters to prepare nanoparticles on glassy carbon electrodes on three occasions separated by several days. Surfaces with almost identical electrochemical behavior were observed with CV, demonstrating the highly reproducible preparation of bare nanoparticles using physical synthesis in the gas-phase combined with soft landing of mass-selected ions.

Tin nitride thin films fabricated by reactive radio frequency magnetron sputtering at various nitrogen gas ratios

Sn nitride thin films are remarkable materials that can be implemented in applications such as microelectronic devices and recording media. This paper presents the analysis of the various Sn nitride thin films' structural, electrical, and chemical properties using a surface profiler, X-ray diffraction, a 4-point probe, X-ray photoelectron spectroscopy (XPS), and distilled water and ethylene glycol contact angle measurements. The Sn nitride thin films were prepared via radio frequency magnetron sputtering. The thickness of Sn nitride thin films decreased in the regions where N2 gas ratios ranged from 20% to 100%. The surface resistance decreased from 6.34×104 to 56.2Ω/sq with gradual increasing of N2 gas ratios from 20% to 100%. Change in crystallinity of the films was observed as N2 gas was progressively introduced, from metallic Sn to the amorphous Sn nitride phase. The high resolution XPS spectra indicates that the intensity of Sn2+ increased, while those of Sn4+ and Sn0 decreased with increasing N2 gas ratios, confirming the bond formation of Sn and N. The total surface free energy (SFE) varied by changing the N2 gas ratio. When the N2 gas ratio in the sputter gas was low (less than 20%), the dominant contributing factor to the total SFE switched from polar to dispersive SFE. In samples where the N2 gas ratio was over 20%, the major contribution to the total SFE was dispersive SFE.

Analysis of Electrochemical Behavior of Natural Graphite Electrode in N, N-Diethyl-N-Methyl-N-(2-methoxyethyl) Ammonium Bis (trifluoromethylsulfonyl) Amide Containing Lithium Ion

1. Introduction Recently, room-temperature ionic liquids (RTILs) have attracted much attentions as an electrolyte for lithium-ion secondary batteries due to their non-flammability and negligible volatility. However, the electrochemical behavior of the natural graphite electrode in many types of RTILs is not clear in spite of many researchers' vigorous efforts. This would be due to the electrochemical organic cation intercalation into the graphite layers before the formation of an effective solid electrolyte interface (SEI) layer on the graphite particles during the 1st charging. In this study, we have analyzed the electrochemical behavior of the natural graphite electrode in the N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) amide (DEME-TFSA) containing lithium ion. 2. Experimental The electrolyte was prepared by dissolving lithium bis (trifluoromethylsulfonyl) amide (LiTFSA) in DEME-TFSA. The R2032 coin type cell which consisted of the natural graphite electrode (NG-3, average size 3 mm) using the poly (vinylidene fluoride) binder as s working electrode, a pressed lithium metal foil as a counter electrode, and 1 mol dm-3LiTFSA/DEME-TFSA as the electrolyte was used for the electrochemical measurements such as cyclic voltammetry (CV) and the charge-discharge cycle tests. The surface analysis of the NG-3 electrodes was carried out by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). 3. Results and Discussion An irreversible reduction peak at the 1st cycle was observed in the CV. It might be due to the reduction of the RTIL. The charge-discharge cycle tests showed that the discharge capacity and the charge-discharge efficiency of the NG-3 electrode at the 1st cycle were 318.1 mAh g-1 and 75.6%, respectively. The surface of the NG-3 electrode was analyzed by the EDX mappings after charging down to 5 mV and after discharging up to 2.0 V, respectively. The EDX mapping results showed that C, O, F, and S were detected on the surface of the NG-3 electrode. The reduction products were uniformity formed on the graphite particle. Figure 1 shows the high resolution XPS spectra of F 1s region for the NG-3 electrode in the 1 mol dm-3 LiTFSA/DEME-TFSA electrolyte before soaking, after charging down to 5 mV, and after discharging up to 2.0 V, respectively. The peak at around 688 eV was assigned to a C-F bond derived from PVdF. The peak intensity at around 688 eV was decreased after charging down to 5 mV and discharging up to 2.0 V, indicating that the surface of the NG-3 particles was covered. In contrast, the peak intensity at around 685 eV was increased after charging down to 5 mV and discharging up to 2.0 V. The peaks were assigned to the fluorine of a Li-F bond derived from LiF. The results suggest that a layer of LiF was present on the surface. The small peaks were identified for -CF3 derived from a TSFA-anion at 689eV, indicating that they would be due to the residue of the RTIL. Based on these results, it was found that the LiF-based compound as a reductive product was formed on the natural graphite electrode due to the cathodic decomposition of a TFSA-anion as a side reaction after the 1st charging. Acknowledgement This work was partially supported by Grant-in-Aid for Scientific Research (C) from the Japanese Ministry of Education, Science, Sports and Culture.

XPS investigation of atomic environment changes on surface of B2O3–Bi2O3 glasses

Melt derived glasses of (1-x)B2O3∙xBi2O3 system with 0.1≤×≤0.875 were investigated by X-ray photoelectron spectroscopy (XPS) in order to evidence the structural changes that occur at the surface of bismuth borate glasses as Bi/B ratio increases from 1:9 to 7:1. The high resolution XPS spectra of O 1s, Bi 4f and B 1s photoelectrons emphasizes consistent changes in the vicinity of oxygen, and small changes around bismuth and boron atoms by increasing of Bi2O3 content. The deconvolution of O 1s spectra was used to investigate the Bi/B ratio effect on the number of bridging and non-bridging oxygens and the results obtained were discussed considering four components occurring from oxygen atoms implied in BOB, BOBi, BiOBi and BO/BiO bonds. From the deconvolution of Bi 4f high resolution spectra, four components related to Bi0 and bismuth atoms connected in bonds of BiOBi, BOBi and BiO types were identified. It was concluded that boron and bismuth play a network former role in the entire compositional range.

Selective depression of pyrite with chitosan in Pb–Fe sulfide flotation

Chitosan was used in the flotation of pyrite–galena mixtures. The results indicated that chitosan preferentially adsorbed on pyrite and galena was floated from the pyrite–galena mixtures. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) analyses were performed to study the interaction mechanism of chitosan on the pyrite and galena minerals at pH 4 and 6. ToF-SIMS showed that chitosan adsorbed heavily on pyrite but barely on galena when a mixture of pyrite and galena was treated by chitosan. The high resolution XPS spectra indicated that both the amine and the hydroxyl groups from chitosan reacted with pyrite surface, whereas no significant binding energy shifts were observed on galena. Combined with the authors’ previous studies of chitosan in other sulfide flotation systems, it was observed that chitosan could depress pyrite, galena, sphalerite and chalcopyrite to different extent when the minerals were floated alone. However, in the flotation of mineral mixtures, chitosan selectively adsorbed on one mineral which depressed its flotation, allowing the other mineral to be floated from the mixture. The competitive adsorption was attributed to the differences in the electron affinity value of the lattice metal ions. Chitosan strongly binds with metal ions with a high electron affinity.

Effects of Vanadium Content on Structure and Chemical State of TiVN Films Prepared by Reactive DC Magnetron Co-Sputtering

TiVN films were deposited on Si(100) wafers without external heating and biasing by reactive dc magnetron co-sputtering. Titanium and vanadium metals were used as sputtering targets. Ar and N2 gases were used as sputtering gas and reactive gas, respectively. The flow rates of Ar and N2 were 8 and 4 sccm, respectively. The Ti sputtering current (ITi) was kept constant at 0.6 Aand V sputtering current (IV) was varied from 0.4 to1.0 A. The deposition time for all the deposited films was 30 min. The effects of V sputtering current on the structure, surface and cross-sectional morphologies, and chemical composition and chemical state of the films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS), respectively. It was found that all the prepared film formed (Ti,V)N solid solution. The lattice parameter was found to decrease while crystallite size, RMS roughness and film thickness increased with increasing V sputtering current. High resolution XPS spectra of the Ti 2p, V 2p and N 1s revealed that the fraction of Ti-N and V-N bonds increased as the V sputtering current increased. However, the V-N bond was observed only at a high V sputtering current.

Adsorption of chitosan on chalcopyrite and galena from aqueous suspensions

Chitosan was recently found to be a potential replacement for toxic inorganic depressants commonly used in the flotation separation of Cu–Pb sulfide minerals. The current work focused on the interaction mechanisms and investigated the reasons for the preferential adsorption of chitosan on copper sulfide (chalcopyrite) over lead sulfide (galena). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) were employed in the study. ATR-FTIR spectra of chitosan showed that the absorption peaks due to amino groups shifted upon adsorption on chalcopyrite. High resolution XPS spectra detected binding energy shifts of N 1s and O 1s electrons on chitosan-treated chalcopyrite. ToF-SIMS ion mass spectra revealed CuNH3 as the dominant stable species as a result of chalcopyrite–chitosan interactions. It was therefore concluded that the adsorption of chitosan on chalcopyrite was due to a strong chemical interaction between the surface copper atoms and the protonated amine as well as the hydroxyl groups on chitosan. Such a strong chemical interaction was not observed on galena.