X-ray Photoelectron Spectroscopy Investigation Research Articles

In-situ near-ambient-pressure photoelectron spectroscopy investigations of high-work-function MoO3 on 4H-SiC(0001)

How to realize effective Ohmic contact to SiC represents one of the major challenges for high-power and high-frequency SiC electronics. Forming a high-work-function interfacial layer between metal electrode and semiconductor has been considered as a promising approach to realize effective Ohmic contact with wide bandgap semiconductors. In this work, a high-work-function (∼7.2 eV) interfacial molybdenum trioxide (MoO3) layer was grown on 4H-SiC(0001) using conventional vacuum thermal deposition process. We have also systematically investigated the evolution of surface properties of MoO3/4H-SiC(0001) via annealing under high vacuum and various gas environments (H2 and O2). The combination of in-situ near-ambient-pressure x-ray photoelectron spectroscopy (NAP-XPS) and ultra-high vacuum (UHV) ultraviolet photoelectron spectroscopy (UPS) investigations of the MoO3/4H-SiC(0001) reveal that the surface MoO3 tends to be reduced into Mo5+ and Mo4+ during annealing under UHV and 0.5 mbar H2. Most importantly, the surface work function of MoO3/4H-SiC(0001) was found to decrease accordingly together with the defect states originated from the transition from Mo+6 to Mo5+ and Mo4+. In contrast, the oxygen sites as well as its high work function are retained even after 400 °C annealing under 0.5 mbar O2, which indicates that the MoO3/4H-SiC(0001) interface is more thermally stable under oxygen treatment.

Surface characterization of covalently functionalized carbon-based nanomaterials using comprehensive XP and NEXAFS spectroscopies

Reliable and straightforward characterization and analysis of carbon-based nanomaterials on the atomic level is essential to exploring their potential for application. Here we use a combination of highly surface sensitive x-ray photoelectron (XP) spectroscopy and near edge x-ray absorption fine structure spectroscopy (NEXAFS) to study and quantify the covalent functionalization of nanographene and single-walled carbon nanotubes with nitrene [2 + 1]-cycloaddition. With this comprehensive analytical approach, we demonstrate that the π-conjugated system of functionalized carbon-based nanomaterials is preserved according to NEXAFS analysis, which is challenging to prove with XP spectroscopy investigation alone. Using this combination of analytical approaches, we show significant similarities after functionalization for various carbon-based nanomaterials. Both analytical methods are strongly suited to study possible post-modification reactions of functionalized carbon-based nanomaterials.

Unraveling the passive film formation and degradation mechanism of NiTi shape memory alloy: An experimental investigation

TiO 2 passive film plays an important role in defining biocompatibility of NiTi shape memory alloy. The corrosion behaviour of Ni 50.8 Ti 49.2 was investigated in 0.9 wt.% aqueous NaCl solution. Grazing incident X-ray diffraction (GIXRD) reveals the formation of a compressive passive film having 2.12% d-spacing variation, noticeably in B19’ structure. The surface topography (undulation) and passive film thickness was recorded in a unique way using atomic force microscopy (AFM). Raman spectrometer and X-ray photoelectron spectroscopy (XPS) investigation confirm the formation of TiO 2 -dominated passive film. Film rupture and breakdown initiation sites were precisely captured by field emission scanning electron microscope (FESEM).

The Effects of Carbon Dots from Hordei Fructus Germinatus Carbonisatus on Glycometabolism and α-Glycosidase Activity

Hordei Fructus Germinatus Carbonisatus (HFC), the carbonized malt known as Maiya-tan in China, has been used as an effective natural treatment to improve digestion for a long time. In this research, we separated and distinguished CDs (carbon dots) from HFC, which were prepared using traditional methods. The HFC CDs had a lattice spacing of 0.26 nm and an average size of 4.3 nm, according to morphology investigations, which revealed that they were nearly spherical. The significant elements in the HFC CDs were C, O, and N. These HFC CDs produced several emissive traps between π − π* states because they had functional groups including C–OH, –NH, C=O, and C–H on their surface, according to X-ray photoelectron spectroscopy investigation. Our results indicated that HFC CDs could effectively reduce postprandial blood glucose and inhibit α-glycosidase in vitro, which suggested that HFC CDs may affect aspects of carbohydrate metabolism. This work indicates that HFC CDs may have the potential to play a crucial clinical role in regulating blood sugar.

Electrochemical Characteristics of a Biomedical Ti70Zr20Nb7.5Ta2.5 Refractory High Entropy Alloy in an Artificial Saliva Solution

High entropy alloys are a new type of multi-component material with improved mechanical properties that could be useful in medical implants. The corrosion behavior of a biomedical Ti70Zr20Nb7.5Ta2.5 alloy was examined and matched with that of commercial Ti and the traditional biomaterial Ti6Al4V in artificial saliva. Moreover, the impact of different pH and concentrations of fluoride ions on the corrosion behavior of Ti70Zr20Nb7.5Ta2.5 was also investigated. The Ecorr decreases in the following order: Ti70Zr20Nb7.5Ta2.5 > Ti6Al4V > Ti. The steady-state potential of the OCP indicates that the corrosion resistance decreases in the same order: Ti70Zr20Nb7.5Ta2.5 > Ti6Al4V > Ti. The Ti70Zr20Nb7.5Ta2.5 immersed in saliva at low pH (pH 2.0) and a high fluoride ion concentration (2000 ppm) suffers from cracking and exhibits the lowest resistance to corrosion compared to the sample immersed in the saliva without and with low concentrations of fluoride ions (0–1000 ppm) and at high pH values (5.0 and 7.0). These data reveal that if the fluoride ion concentrations are enhanced or the pH falls, the alloy corrosion resistance reduces. The EIS data show that the passive layer is made up of a duplex outer and inner oxide layer and that the alloy's resistance to corrosion in fluoride-containing solutions has been significantly reduced. Additionally, the data demonstrate that a Ti70Zr20Nb7.5Ta2.5 alloy's corrosion resistance rises with increasing immersion time with and without fluoride ions. According to the X-ray photoelectron spectroscopy investigation, the protective passive oxides include TiO2, ZrO2, Nb2O5, and Ta2O5. The alloy Ti70Zr20Nb7.5Ta2.5 can be considered as a promising material suitable for usage as a biomaterial among all the materials tested in this work.

XPS Investigation on Improving Hydrogen Sorption Kinetics of the KSiH3 System by Using Zr-Based Catalysts.

The superior hydrogen storage properties makes the KSiH3 system a potential hydrogen storage material for practical applications. A theoretical capacity of 4.3 wt% bring this material to the front line of all the available hydrogen storage materials; however, the activation barrier of the reaction restricts the system to absorb and desorb hydrogen reversibly at elevated temperatures even if the thermodynamics suggest its room temperature operation. Several catalysts have already been tested to enhance its kinetic properties. In this work, the efforts were made to reduce the activation energy by using Zr-based catalysts to the KSi/KSiH3 system. The value of activation energy was found to be lowest (i.e., 87 kJ mol-1) for the ZrH2-added KSiH3 system. The mechanism of this improvement was investigated by using X-ray photoelectron spectroscopy (XPS).

(Invited) The Behavior of High-Capacity Anodes at Low Temperature for Li-Ion Batteries

Lithium metal and alloy anodes offer the promise of improved capacity for Li-based batteries, and they could overcome low-temperature diffusion limitations associated with graphite. However, the electrochemical behavior of these materials at low temperatures has been seldom investigated, and most liquid electrolytes exhibit extremely low Coulombic efficiency (CE) for cycling of these high-capacity electrode materials at low temperatures. Here, we demonstrate an ether-based electrolyte system with carbonate additives that substantially improves the CE of lithium metal cycling down to -60 °C. Lithium metal deposited at low temperatures in this and other electrolytes shows a clear reduction in grain size with decreasing temperature, which is correlated with lower CE. Cryo-TEM and X-ray photoelectron spectroscopy investigation of the solid-electrolyte interphase (SEI) shows that this tailored electrolyte allows for greater inorganic content in the SEI at low temperatures, which enables a compact and conducting passivation layer. We further extend these studies to sodium metal anodes, which show improved CE at low temperatures compared to lithium. Finally, we investigate alloy anode materials and show that they can exhibit stable electrochemical cycling down to -40 °C, indicating the promise of these high-capacity materials for low-temperature batteries.

Electronic structure studies of Kondo lattice compounds CeRhSn[formula omitted] and CeRuSn[formula omitted]: Comparative study

We report on X-ray photoelectron spectroscopy and ab initio electronic structure investigations of CeRuSn3 and CeRhSn3 and their La counterparts. A combined experimental study and band structure calculations indicate a stable configuration of Ce3+ in the both Ce-based compounds. We also documented that the transition metal Rh or Ru with different number of 4d electrons plays a decisive role in controlling the hybridization strength V between the 4f and conduction electron states, which in turn governs the magnetic ground state properties of these compounds. For CeRuSn3V is ∼1.2 times larger than V of CeRhSn3, which is a reason of stronger Kondo interaction in Ru sample, expressed by larger Kondo temperature TK. On the basis of Schrieffer–Wolff transformation, ab initio calculations, and XPS data, we estimated on-site Jfc coupling constants, which are dependent on Wyckoff position of Ce, and allowed to determine Kondo temperatures, as well as explain nature of the magnetic ground states. The interband hybridization forms a pseudogap in the density of states of CeRuSn3, CeRhSn3 and their La-bearing counterparts at the Fermi level, which could be a reason of Mott variable-range hoping behavior.

Erosion Resistant Hydrophobic Coatings for Passive Ice Protection of Aircraft

Novel polymeric coatings, namely slippery polyurethane (SPU) coatings, with high surface hydrophobicity and superior erosion resistance against high speed solid particles and water droplets were successfully developed to protect the leading edge of fast moving aerodynamic structures, such as aircraft wings and rotor blades, against ice accretion. The coatings comprise newly synthesized surface-modifying polymers (SMPs) bearing fluorinated and polydimethylsiloxane branches at a loading level of 1–5 wt.%, based on the total resin solid, which showed good compatibility with the erosion-resistant polyurethane matrix (PU-R) and rendered effective surface hydrophobicity and slipperiness to the coatings, as evidenced by the high water contact angles of 100–115°. The coatings can be easily be sprayed or solution cast and cured at ambient temperature to provide highly durable thin coating films. X-ray photoelectron spectroscopy (XPS) investigation showed concentration of fluorine on the surface. The presence of 1–5 wt.% of SMPs in the polyurethane matrix slightly reduced the tensile modulus but had no significant impact on the tensile strength. All coating films exhibited good thermal stability with no material softening or degradation after heating at 121 °C for 24 h. DSC heating scans revealed no thermal transitions in the temperature range of −80 °C to 200 °C. Ice adhesion strength (IAS) tests using a static push rig in a cold room of −14 °C showed IAS as low as 220 kPa for the SPU coatings, which is much lower than that of PU-R (i.e., about 620 kPa). Sand erosion tests using 50 μm angular alumina particles at an impinging speed of 150 m/s and an impinging angle of 30° revealed very low erosion rates of ca. 100 μg/g sand for the coatings. Water droplet erosion tests at 175 m/s using 463 μm droplets with 42,000 impingements every minute showed no significant coating removal after 20 min of testing. The combination of the high surface hydrophobicity, low ice adhesion strength and superior erosion resistance makes the SPU coatings attractive for ice protection of aircraft structures, where the coatings’ erosion durability is of paramount importance.

XPS investigation of 5N purity Al thin foils for MEMS devices

Thin Al foils are promising materials for applications in devices of microelectromechanical systems (MEMS). In this work, three foils of high purity (5N) Al with different thickness (10, 50, and 125 μm) were analyzed by means of X‐ray photoelectron spectroscopy (XPS), before and after annealing (720 K for 30 min). XPS surface analysis and depth profiling of chemical composition were performed to investigate the distribution of Al oxide. Electron energy loss spectroscopy (EELS) measurements were also carried out in order to identify the plasmon losses and chemical state of Al. The loss peaks in the 5N‐Al thin foils were compared with those of an Al foil of commercial purity (99.95 wt%). The thickness of the oxide layer on the sample surface of all the samples is not constant and oxide is thicker in the samples of high purity than in those of commercial quality. Moreover, the thinnest foils of 5N‐Al (10 μm) exhibit the thinnest oxide layer. These findings have been discussed by considering the size effect, that is, mechanical properties of thin foils are improving as the thickness decreases. The complex morphology of the metal‐oxide interface may contribute to enhance the mechanical performances of Al foils with a thickness below ~50 μm, because the free dislocations pile up against the interface which represents an obstacle for their motion hindering plastic deformation. Obtained results suggest that Al foils to be used in MEMS devices should be of high purity and annealed to get a surface completely covered by the oxide layer.

Resistive switching, endurance and retention properties of ZnO/HfO2 bilayer heterostructure memory device

This work reports the fabrication of resistive memory device with a bilayer ZnO/HfO2 structure. Highly stable and uniform bipolar resistance switching (RS) characteristics were attained when HfO2 interfacial layer is introduced in ZnO device. The bilayer device attains good resistive switching with increased resistance ON-OFF ratio of the order of ∼102, better dc endurance of > 102 cycles and retention of >104 s at room temperature. X-ray Photoelectron Spectroscopy (XPS) investigation is also done and it is confirmed that oxygen vacancies in ZnO thin film are responsible for improved resistance switching. The current-voltage (I–V) relationship reveals that switching behavior of these devices is mainly dominated by Space-Charge-Limited-Current mechanism (SCLC) regulated due to localized oxygen vacancies. Effect of temperature on the electrical conductivity has also been investigated to analyze the behavior of Low Resistance States (LRS) and High Resistance States (HRS). The findings imply that the bilayer ZnO/HfO2 device structure is a promising one for upcoming non-volatile memory applications.

Tuning of magnetic properties in Cr-doped lithium ferrite

Cationic substitutions in lithium ferrite spinel (LiFe 5 O 8 ) leading to modifications in magnetic properties have a significant role in their technological applications. In this context, LiFe 5− x Cr x O 8 , compounds with 0 ≤ x ≤ 3 were synthesized and studied using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), M o ¨ ssbauer spectroscopy and magnetization measurements. Oxidation states of Fe and Cr are found to be 3 + from XPS investigations and further confirmed from the M o ¨ ssbauer analysis. Cr replaces Fe from both tetrahedral and octahedral sites. Magnetization and magnetic ordering temperature decrease with increasing Cr concentration. This is consequent to reduced strength of dominant Fe - O - Fe interactions due to replacement of Fe with Cr cation possessing relatively smaller magnetic moment. The positive value of Curie-Weiss constant implies that the system has dominant ferromagnetic interactions. The much important negative magnetization and spin compensation phenomena are observed only in specific range of doping concentration (x = 2.5–3). Spin compensation in LiFe 2.5 Cr 2.5 O 8 occurs at 315 K, close to room temperature. • The effect of Cr doping on oxidation state of cations and their distribution at tetrahedral and octahedral sites is reported. • The influence of Cr doping on the magnetic properties of LiFe 5 O 8 is reported. • Spin compensation behavior is observed in LiFe 2.5 CR 2.5 O 8 and LiFe 2 CR 3 O 8 compounds.

The Os substitution into Fe sites in LuFeO3 multiferroic and its effects on the electrical and dielectric features

Solid-state technique was utilized to obtain the LuFeO 3 (LFO) and LuFe 1−x Os x O 3 (LFOO) compounds having x = 0.05 and 0.10. The orthorhombic structure and the presence of secondary phases in the studied samples have been unveiled by X-ray diffractometer (XRD) investigations. The scanning electron microscope (SEM) examinations have unveiled that not only the particle sizes enlarge with Os substitution but also particle agglomeration takes place. The X-ray photoelectron spectroscopy (XPS) investigations have exposed the oxidations of Fe as 2 + and 3 + for the LFO sample, 3 + for 5 mol% Os substituted specimen and mix of 2 + and 3 + for 10 mol% Os doped sample. In addition, it was shown that Os has 4 + oxidation state in the doped samples. Dielectrical and electrical conductivity studies of the obtained ceramics conducted between − 100 °C (173 K) up to 100 °C (373 K) with 20 °C temperature pace have shown that the undoped sample has much higher values than the Os doped samples. Such differences have been ascribed to the absence of Fe 2+ ions and lattice distortions in the Os doped samples. In addition, it was realized that different conduction models need to be adapted to comprehend the conduction mechanism in the examined specimens. • LuFeO 3 (LFO) and Os doped LFO were synthesized by solid-state reaction. • Os substitution lowers the ratio of Fe 2+ ions in LFO structure. • LFO and Os doped LFO have multiple relaxations. • Dielectric constant and electrical conductivity were deteriorated after Os substitution. • Conduction mechanism can be comprehended by multiple models depending upon frequency and temperature.

Integrated X-ray photoelectron spectroscopy and DFT investigations of DNA adsorption on nanostructured SiOx surface

The adsorption of DNA on SiOx and nanostructured-SiOx substrates has been investigated here in order to understand their binding behaviour. The XPS results indicate that DNA binding on nanostructured-SiOx introduces chemical states like Si⋯O⋯N and Si⋯N. On the other hand, on SiOx surface only Si⋯O⋯N state is observed. Formation of Si⋯O⋯N and Si⋯N states emphasize the dominant participation of nitrogenous DNA bases during the adsorption as well as transport of charge carriers. We complement the experimental findings with first principles DFT investigations on the linkage of DNA base, adenine, with SiOx and nanostructured-SiOx, respectively. DFT results show that linkage appears to occur via electrostatic interaction and charge transfer from the substrate to the nitrogen bases of DNA. The molecular electrostatic potential maps, highest occupied molecular orbitals and lowest unoccupied molecular orbitals support the experimental findings. These results will be important for biosensing applications.

Synergistic Incorporating RuO2 and NiFeOOH Layers onto Ni3 S2 Nanoflakes with Modulated Electron Structure for Efficient Water Splitting.

Synergistic electronic modulations is an effective strategy to develop efficient and stable electrocatalysts for the electrochemical hydrogen production via water splitting. Herein, tremella-like Ni3 S2 @RuO2 and Ni3 S2 @NiFeOOH heterostructures catalysts are constructed on Ni foams (NF) by coupling RuO2 and NiFeOOH on Ni3 S2 nanoflake arrays. The resulting Ni3 S2 @RuO2 /NF electrode exhibits top-level hydrogen evolution reaction electrocatalysis with an extremely low overpotential of 12 mV at 10 mA cm-2 and a Tafel slope of 30.7 mV dec-1 , as well as the as-obtained Ni3 S2 @NiFeOOH/NF electrode with tunable binding energy for OH* intermediates shows remarkable oxygen evolution reaction electrocatalysis with an overpotential of 227 mV at 10 mA cm-2 . The electrolyzer employing Ni3 S2 @RuO2 /NF electrode for cathodic H2 production and Ni3 S2 @NiFeOOH/NF for anodic O2 production merely needs a low voltage of 1.47 V to drive 10 mA cm-2 with excellent durability. The combined theoretical calculation and X-ray photoelectron spectroscopy investigation reveal that heterogeneous configuration can induce electron transfer from Ni3 S2 to RuO2 through NiRu/SRu bonds, and thus tailor the d-band center and optimize the activated H2 O/H* Gibbs free energies for enhanced hydrogen evolution reaction on Ni3 S2 @RuO2 . This study may shed new light on the construction of heterostructures as highest-performing electrocatalysts and offer unique insight into the theory mechanism.

Enhanced orange persistence in Sr3Al2O5Cl2:Eu2+, Dy3+ phosphor by Mg2+ substitution in Sr2+lattice site

The initial intensity and afterglow duration of existing long-wavelength persistent phosphors are insufficient for practical applications. Herein, the afterglow of orange-emitting Sr 3 Al 2 O 5 Cl 2 :Eu 2+ , Dy 3+ phosphors are enhanced by co-doping with Mg 2+ using the conventional solid-state reaction. Rietveld refinement for the prepared phosphor revealed that all Eu 2+ cations were placed on the Sr 2+ sites, whereas Dy 3+ occupancy in the lattice was improved by incorporating Mg 2+ . All phosphor samples with different Mg 2+ concentrations emit 609-nm-centred orange luminescence caused by the 5d→4f transition of Eu 2+ . The photoluminescence was significantly enhanced with the increase in the Mg 2+ doping due to the increased amount of divalent Eu 2+ in the samples, as confirmed by the X-ray photoelectron spectroscopy investigation. Incorporating Mg 2+ also enhanced the afterglow performance by creating suitable electron traps in the phosphor. The afterglow profiles were simulated by a double exponential decay model, and the results revealed that significant improvement in the afterglow lifetime was achieved for the 0.3 Mg 2+ -doped phosphors. Also, Mg 2+ introduction resulted in a deeper trap level (∼0.72 eV) and an increased trap concentration. Consequently, the Mg 2+ -doped exhibits brighter initial photoluminescence and longer afterglow. • Sr 3−x Mg x O 5 Cl 2 :Eu 2+ , Dy 3+ phosphor exhibits orange emission at 609 nm. • The photoluminescence is improved due to the increased Eu 2+ content after Mg 2+ doping. • Enhanced afterglow is observed after the incorporation of Mg 2+ cations. • The improved afterglow is caused by the increased trap concentration and modified trap depth.

Morphology controlled synthesis of Fe and Mn co-doped In2O3 nanocubes and their Dopant-Atom effects on electronic structure and magnetic properties

Fe and Mn co-doped In2O3 single-phase cubic crystal structure nanocubes of uniform size and control over dopant concentration (In1.96Fe0.02Mn0.02O3, In1.94Fe0.02Mn0.04O3, In1.92Fe0.02Mn0.06O3 and In1.90Fe0.02Mn0.08O3) and microstructure were prepared using the hydrothermal-annealing technique. On a wider vision, we systematically investigated the influence of Fe and Mn co-doping in In2O3 through complementary experimental techniques and density functional theoretical (DFT) calculations to reveal the physical mechanisms involved in the origin of observed ferromagnetism. DFT calculations demonstrated that the substitution of surface indium atom by iron (FeIn) leads to impurity states on the top of In2O3 valence band maximum (VBM). Conversely, incorporation of interstitial (Mni) impurities in the host matrix without oxygen vacancies (VO) slightly shifts the top of the valence band and incorporation of interstitial Mn-impurity in the In2O3 (111) surface with oxygen vacancy does not provide noticeable changes in the electronic structure of the defective surface. High-resolution transmission electron microscopy measurements showed the formation of regular nanocubes in shape with 36.9–37.6 nm in average edge length. X-ray photoelectron spectroscopy investigations revealed that valence state of Fe mostly as Fe2+ and Fe3+ and Mn2+ for Mn atom in the In1.96Fe0.02Mn0.02O3, In1.94Fe0.02Mn0.04O3, In1.92Fe0.02Mn0.06O3 and In1.90Fe0.02Mn0.08O3. Magnetic studies exhibited room temperature ferromagnetism (RTFM) in the investigated samples with the high coercivity and saturation magnetization of 145.48 Oe and 0.023 emu/g, respectively for the In1.94Fe0.02Mn0.04O3. The origin of observed RTFM was described based on the bound magnetic polaron (BMP) model mechanism. DFT investigations demonstrated the clusters of impurities (FeIn-nMni) robust magnetic interactions within the cluster and between the clusters. Interestingly, only FeIn-nMni clusters contribute ferromagnetism observed in the investigated co-doped systems. Therefore, increasing the concentration of defects leads to the improvement of ferromagnetism. The comprehensive experimental and DFT investigations present new evidence to the observed ferromagnetism and electronic structure of Fe,Mn co-doped In2O3 nanocubes.

Flotation of quartz using imidazole ionic liquid collectors with different counterions

Four kinds of ionic liquids (ILs) with different counterions were used as collectors to perform flotation tests for pure quartz and quartz-hematite mixed ore. Pure quartz flotation showed that all ILs had excellent collection performance, exceeding 95% of the quartz was floated below the concentration of 8*10−5mol*L−1. All ILs showed much better collecting capacity than DDA. Mixed ore tests without inhibitor showed the best effect using imidazole ILs with chlorine ligands as collector, 61.9% grade iron ore was obtained from the 51% TFe quartz-hematite mixed ore, and the recovery rate was 94.54%. The flotation using starch inhibitor showed that imidazole-based ILs containing hexafluorophosphate ligands achieve the highest beneficiation efficiency. It obtains 64.86% iron concentrate and 86.07% recovery rate. In the tests with inhibitor, all four ILs performed better flotation effects than DDA. X-ray photoelectron spectroscopy (XPS) investigation was conducted of quartz that was treated by ILs and DDA, and adsorption analysis was performed based on N(1S) position, N/Si ratio and C(1S) peaks. Fourier transform infrared spectroscopy (FTIR) study was also conducted, and the adsorption of ILs and DDA was further analyzed by the appearance of new peaks and the shift of peaks in IR spectrum, Zeta potential study intuitively showed the adsorption difference between the four imidazole ILs and DDA. The flotation results were discussed together with XPS, IR and Zeta potential study. In conclusion the higher charge density on the overall semi-micelle of ILs caused greater collecting capacity than that of DDA, and weaker charge of single adsorption site caused greater selectively. And, it is believed that the counterions of ILs affect the floatation effect by affecting the formation process of the semi-micelle.

Band Structure Studies of the R5Rh6Sn18 (R = Sc, Y, Lu) Quasiskutteridite Superconductors.

We report on X-ray photoelectron spectroscopy and ab initio electronic structure investigations of the skutterudite-related RhSn superconductors, where R = Sc, Y, and Lu. These compounds crystallise with a tetragonal structure (space group I) and are characterised by a deficiency of R atoms in their formula unit (RhSn, ). Recently, we documented that the vacancies and atomic local defects (often induced by doping) are a reason for the enhancement in the superconducting transition temperature of these materials, as well as metallic () or semimetallic () behaviours in their normal state. Our band structure calculations show the pseudogap at a binding energy of −0.3 eV for the stoichiometric compounds, which can be easily moved towards the Fermi level by vacancies . As a result, dychotomic nature in electric transport of RhSn (metallic or semimetallic resistivity) depends on , which has not been interpreted before. We have shown that the densities of states are very similar for various RhSn compounds, and they practically do not depend on the metal R, while they are determined by the Rh d-and Sn s- and p-electron states. The band structure calculations for ScRhSn have not been reported yet. We also found that the electronic specific heat coefficients for the stoichiometric samples were always larger with respect to the of the respective samples with vacancies at the R sites, which correlates with the results of ab initio calculations.

Molybdenum co-catalytic promotion for Fe3+/peroxydisulfate process: performance, mechanism, and immobilization

In this work, we proposed that molybdenum (Mo) powder as the cocatalyst could promote the sulfamethoxazole (SMX) decomposition in the Fe3+/peroxydisulfate (PDS) Fenton-like process. Efficient SMX elimination (96.7%) was reached after 20 min under the circumstances of 0.20 g·L−1 Mo, 0.50 g·L−1 PDS, 0.07 g·L−1 Fe3+, and beginning pH 5.4. Sulfate radicals were verified as the main active species according to the quenching experiment and electron spin resonance spectroscopy analysis. The Mo cocatalyst improved the Fe3+ reduction and PDS activation. According to the investigation of X-ray photoelectron spectroscopy for the valence state change of Mo before and after the reaction, the mechanism of Fe3+/Fe2+ circulation being initiated through the Mo4+ and Mo0 was presented. There was no obvious change of surface structure between the original and used Mo, as certified through X-ray diffraction and scanning electron microscope analyses. The mass spectrometry was used to determine the SMX degradation byproducts, and their toxicities were evaluated by the computational toxicology. Importantly, even after five cycles, the Mo still displayed excellent recyclability, and above 93% SMX was degraded in the fifth recycle. In the end, the immobilization of Mo was attempted by fixing Mo on the cyanoacrylate and agar, which also both showed the good co-catalytic effect. This research affords a promising inorganic co-catalytic Fenton-like system for water treatment.