Binding Energy Shifts Research Articles

Optimizing Cu 3d Bands with Nanotubular SnO2 to Boost Their Catalytic Transfer Hydrogenation Activity.

Catalytic transfer hydrogenation (CTH) using Cu nanocatalysts offers significant advantages over direct high-pressure hydrogenation. However, the active hydrogen (H*) in this process exhibits poor adsorption and tends to release H2 readily due to the fully occupied 3d states of Cu. To address this issue, a tubular SnO2 support with electron-accepting ability was selected to host Cu nanoparticles, aiming to optimize the Cu 3d bands. The Cu/SnO2 nanohybrids were prepared through an electrospinning technique, followed by hydrothermal synthesis. As evidenced by X-ray photoelectron spectroscopy (XPS) binding energy shifts and density functional theory (DFT) simulations, some electrons from Cu transferred to SnO2 in the Cu/SnO2 nanohybrids due to their different work functions. Such electron transfer enables the Cu 3d orbitals to lose electrons and alters its valence configuration from 3d10 to 3d10-x, which enhances the adsorption of active H* atoms and thereby inhibits undesirable H2 release. The 15 wt % Cu/SnO2 exhibits improved catalytic hydrogenation of 4-nitrophenol with NaBH4, with an optimal normalized rate constant of 56.98 mg-1 min-1 and a turnover frequency of 4.82 min-1, surpassing most reported catalysts. The enhanced activity is attributed to the optimized electronic states, improved hydrogen adsorption, and the tubular structure of the support. This work might shed light on developing more non-noble metal nanocatalysts for CTH by tuning their d bands with appropriate oxide supports.

Epitaxial SiGeSn grown on Si by ion implantation

We have formed SixGe1−x−ySny compounds on Si substrates by ion implantation and annealing and investigated their concentration profiles, crystallization, and optical properties. Ge and Sn ions were implanted in the range (2.5–10) × 1016 Ge/cm2 at 65 keV, and (1.0–4.0) × 1016 Sn/cm2 at 100 keV, resulting in a peak implant dose at a depth of 50 nm for both species. Epitaxially regrown SixGe1−x−ySny layers (110 nm thick) were produced with Ge and Sn contents that allowed bandgap tuning in the (0.88–1.1) eV range. Shifts in photoelectron binding energies (Si 2p, Ge 3d, and Sn 3d) were consistent with ternary compound formation. Sn segregation was observed for annealing temperatures ≥600 °C. A significant increase in the optical absorption coefficient (×104 cm−1 for λ = (800–1700) nm) was observed for SiGe, SiSn, and SiGeSn alloys, with SiGeSn having coefficients several orders of magnitude higher than for Si. Contributions of segregated Sn to these properties were observed. Metastable SixGe1−x−ySny layers were achieved, which may point to a promising route to mitigate Sn incorporation challenges for near-infrared detectors.

Photovoltaic response promoted via intramolecular charge transfer in triphenylpyridine core with small acceptors: A DFT/TD-DFT study

Currently, A−π−A configured molecules (TTP1-TTP6) were designed from the reference compound (TPPR) by modifying the terminal acceptors for photovoltaic materials. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using the M06/6-311G(d,p) functional were employed to analyze the photonic and electronic properties of the newly designed derivatives. Various analyses; frontier molecular orbitals (FMOs), density of states (DOS), absorption spectra (λmax), transition density matrix (TDM), binding energy (Eb), hole-electron and open circuit voltage (Voc) were performed to explore the photovoltaic properties of triphenylpyridine based compounds. The structural modulation with acceptor moieties significantly tuned their HOMO and LUMO levels, resulting in reduced band gaps (2.833–3.037 eV). They also exhibited broader absorption spectra (λmax) ranging from 482.560 to 514.756 nm as compared to the reference compound (486.289 nm). Notably, TPP3 showed the good photovoltaic response as it displayed the least energy gap (2.833 eV) with lower binding energy (0.415 eV) and bathochromic shift (512.798 nm) in absorption spectra as compared to all other derivatives. Beside this, a comparative study with spiro-OMeTAD and P3HT standard hole transport materials illustrated that these materials can also be utilized as effective photovoltaic materials.

Changes in electronic structure within NiSx (0.60 < x < 1.53) compound series

In this article, changes in electronic properties of NiSx series of films with different sulfur content (x = S/Ni) are studied using X-ray (XPS) and ultra-violet (UPS) photoelectron spectroscopy techniques. NiSx (0.60 < x < 1.53) films are synthesized on native oxide of Si(111) substrates via reactive deposition of Ni and S in an ultra-high vacuum chamber by varying the sulfur pressures and substrate temperatures. The binding energy (BE) of Ni2p3/2 core level, the separation between the Ni2p3/2 main peaks and satellite peaks, and the Ni3d valence band binding energies are all found to vary nearly linearly with the sulfur content in NiSx series of compounds, suggesting a direct dependence of Ni electronic charge on the sulfur content. The shift of the Ni3d and S3p states (to higher and lower BE, respectively) with an increase in the S content provides experimental confirmation of the theoretical prediction previously reported (Wen et al., 2020) [1]. All NiSx films showed density of states (DOS) at the Fermi level, indicating their metallic nature. The Ni2p3/2 binding energy shift of NiSx films are much smaller than that of oxide-based compounds, confirming the significantly more covalent nature of the sulfides. NiSx film grown on Si (111) substrate showed nickel silicide interface formation. This study provides information on the growth and trends in the electronic properties of NiSx relevant for their applications in catalysis, energy storage, and electronic devices.

Copper-saturated chitosan beads (CuSCBs) for Enhanced phosphate removal

This study investigates the sequential use of non-cross-linked chitosan beads (CBs) for copper and phosphate adsorption, emphasizing copper site saturation and selective phosphate binding. Initially, CBs were loaded with copper until saturation was achieved, where all available sites were occupied by copper at an initial concentration of 100 mg/L. These copper-saturated chitosan beads (CuSCBs) were subsequently applied for phosphate adsorption, achieving a maximum adsorption capacity of 85.89 mg/g at pH 5. X-ray Photoelectron Spectroscopy (XPS) analysis revealed a shift in the Cu2O binding energy to lower values upon phosphate adsorption, indicating that phosphate ions interact primarily with the copper ions intercalated on the CBs rather than the chitosan matrix. Additionally, the nitrogen spectra showed no shift, confirming that the amine groups of chitosan do not participate in phosphate binding. The findings suggest a 1:1 interaction ratio between copper and phosphate ions, with each phosphate ion binding to one copper ion, creating a stable and selective adsorption site. The adsorption data fit the Langmuir isotherm and pseudo-second-order kinetic models, suggesting a homogeneous monolayer adsorption mechanism driven by chemisorption, where each copper site on the chitosan surface selectively binds one phosphate ion. Furthermore, the CuSCBs demonstrated minimal copper leaching and retained 90 % of their phosphate adsorption capacity over multiple adsorption–desorption cycles, highlighting their potential as effective and reusable adsorbents for water treatment applications targeting copper and phosphate removal.

Probing structural and electrochemical properties of a 2D CoMoO4@hBN nanocomposite as pseudocapacitive electrode for high-performance supercapacitors

The effectiveness of energy storage is largely determined by the electrode material's performance in critical areas. Enhancements in ion transport, cyclic stability, rate capability, and specific capacitance directly boost the supercapacitors' overall performance and broaden their application potential. This study aims to enhance these properties by incorporating hexagonal boron nitride (hBN) into cobalt molybdate (CoMoO4) material in a 1:1 stoichiometric ratio. The CoMoO₄@hBN nanocomposite was synthesized using a hydrothermal method followed by ball milling. The X-ray diffraction (XRD) analysis confirmed the formation of a single-phase CoMoO4@hBN composite, with a significant increase in crystallite size from 18.21 nm in pure CoMoO₄ to 25.6 nm, along with a slight shift in diffraction peaks, indicating enhanced crystallinity and structural defects due to the substitution of oxygen with boron atoms. Raman spectroscopy revealed that the composite retains the characteristic peaks of both CoMoO₄ and hBN, with stable sharp peaks at 936 cm−1 (Mo=O bond) and 1367 cm−1 (E2g peak of hBN) even after 20 depth measurements, confirming successful conjugation and consistent vibrational properties. The X-ray photoelectron spectroscopy (XPS) showed a slight shift in Co 2p and Mo 3d binding energies to higher values, suggesting improved electronic interactions between CoMoO4 and hBN, which could enhance the composite's conductivity. The electrochemical analysis demonstrated that incorporating h-BN significantly boosts the electrode's performance compared to pristine CoMoO4, with about 37 % increase in specific capacitance at 1 A g−1, reduced charge transfer resistance (0.11 Ω), and superior cyclic stability with 96 % capacitance retention after 5000 cycles. These findings indicate that hBN enhances both the electrical conductivity and structural integrity of CoMoO4, positioning the CoMoO4@hBN composite as a promising material for high-performance supercapacitors.

Microstructural characteristics of aluminosilicate minerals in cement clinker prepared from coal gangue, carbide slag, and desulfurization gypsum

Utilizing solid waste to prepare cement clinker with low-calcium minerals is crucial for the low-carbon evolution of cementitious materials. In this study, a belite-ye’elimite-ternesite cement clinker was prepared using coal gangue, carbide slag, and desulfurization gypsum instead of non-renewable resources. The evolution law of the silica-alumina mineral phase in cement clinker under different calcining temperatures was tested and analysed. The results show that the predominant mineral phases in cement clinker consist of belite, ye’elimite, and ternesite at 1200 °C to 1250 °C. The composition of cement clinker transforms into belite and ye’elimite as the calcination temperature increases to 1300–1400 °C. At 1400 ℃, the content of belite in cement clinker reaches a remarkable 85 %. The results of XPS and NMR spectra showed that the chemical binding energy and chemical shift of Al in the cement clinker changed after calcination, representing the transformation of the aluminate in kaolinite, with [AlO6], to ye’elimite, with [AlO4]. The peak fitting results of 29Si NMR spectra semi-quantitatively describe the transition process of the silicate mineral phase from kaolinite to ternesite and then to belite. Morphologically, the increase in calcination temperature leads to a significant enlargement of the grain size of belite in cement clinker. This study can provide a basis for research on the phase regulation of cement clinker composed mainly of low-calcium minerals.

Unraveling the Origin of Elemental Chemical Shift and the Role of Atomic Hydrogen in a Surface Ullmann Coupling System.

The Ullmann coupling of aryl halides is a powerful method in the on-surface synthesis of functional materials. Understanding its basic aspects and influencing factors can aid in the use of this tool for the fabrication of intriguing structures. In this study, we unveil (1) the origin of the shift in the elemental binding energy (BE) and (2) the functions of atomic hydrogen (AH) in a typical Ullmann coupling system using combined spectroscopy and microscopy techniques. During debromination of the aryl halide precursor, the work function (WF) alteration is correlated with the surface Br amount. The WF change instead of C-Ag formation is proposed to play a dominant role in the shift of the molecular C 1s BE. AH dosing onto organometallic chains leads to chain decomposition and surface Br removal. In contrast, AH dosing onto covalent poly(para-phenylene) (PPP) chains results in superhydrogenation in addition to Br removal. The C 1s BE shift is attributed to both WF change and superhydrogenation effects. Thermal annealing restores the PPP chains by eliminating superhydrogenation, which causes the C 1s BE to shift to a high BE. This study provides deep insights into the mechanisms of Ullmann coupling on surfaces, highlighting the significant role of WF alterations and AH treatments in these processes.

XPS Binding Energy Shifts in 2D Ti3C2Tz MXene go largely Beyond Intuitive Explanations: Rationalization from DFT Simulations and Experiments.

MXenes are prototypes of surface tunable 2D materials with vast potential for properties tuning. Accurately characterizing their surface functionalization and its role in electronic structure is crucial, X-ray photoelectron spectroscopy (XPS) being among the go-to methods to do so. Despite extensive use, XPS analysis remains however intricate. Focusing on the benchmark MXene Ti3C2Tz, Density Functional Theory (DFT) calculations of core-level binding energy shifts (BE.s.) are combined with experiments in order to provide a quantitative interpretation of XPS spectra. This approach demonstrates that BE.s. are driven by the complex interplay between chemical, structural, and subtle electronic structure effects preventing analysis from intuitive arguments or comparison with reference materials. In particular, it is shown that O terminations induce the largest BE.s. at Ti 2p levels despite lower electronegativity than F. Additionally, F 1s levels show weak sensitivity to the F local environment, explaining the single contribution in the spectrum, whereas O 1s states are significantly affected by the local surface chemistry. Finally, clear indicators of surface group vacancies are given at Ti 2p and O 1s levels. These results demonstrate the combination of calculations with experiments as a method of the highest value for MXenes XPS spectra analysis, providing guidelines for otherwise complex interpretations.

Development of the NIST X-ray Photoelectron Spectroscopy (XPS) Database, Version 5

It has been over 20 years since the National Institute of Standards and Technology (NIST) launched the first web version of its X-ray Photoelectron Spectroscopy (XPS) database (Lee et al., 2002; Wagner, 1991) which has approximately 1000 active users every day. This database was recently redesigned to meet NIST security requirements and to include new features and enhancements. The new application is built upon a relational database using a cross-platform and open-source framework (Henning et al., 2002). In addition to a modern design interface, the new features include custom-built components for displaying formatted molecular formulas and spectral lines, for sorting spectral lines, and for graphical display of chemical shifts of binding energies, Auger-electron kinetic energies, and Auger parameters for elements in different compounds.

Interfacial Engineering over Pt-Calcium Ferrite/2D Carbon Nitride Nanosheet p-n Heterojunctions for Superior Photocatalytic Properties.

The present study discloses the fabrication of efficient p-n heterojunctions using n-type polymeric bulk carbon nitride (b-CN, E g = 2.7 eV) or exfoliated nanosheets of carbon nitride (NSCN, E g = 2.9 eV) with p-type spinel ferrite CaFe2O4 (CFO, E g = 1.9 eV) for photocatalytic hydrogen generation. A series of p-n combinations were fabricated and characterized by various techniques. The oxide-carbon nitride interactions, light absorption, band alignment at the interface, and water/H3O+ adsorption capability were elucidated over heterojunctions and correlated with the photocatalytic hydrogen yield. The main developments in the present study are as follows: (1) All heterojunctions were more active than pure phases. (2) The photocatalytic activity trend validated an increase in the lifetime of charge carriers from TRPL. Pt(1 wt %)-CFO(1 wt %)/NSCN (481.5 μmol/h/g under ultraviolet (UV)-visible-simulated light, 147.5 μmol/h/g under CFL illumination for 20 h, τavg = 10.33 ns) > Pt-NSCN > Pt-CFO/b-CN > CFO/NSCN > CFO/b-CN > NSCN > Pt/b-CN > mechanical mixture (MM) of 1 wt %CFO + NSCN-MM > 1 wt %CFO + b-CN-MM > CFO > b-CN (τavg = 4.5 ns). (3) Pt-CFO/NSCN was most active and exhibited 250 times enhanced photocatalytic activity as compared to parent bulk carbon nitride, 6.5 times more active than CFO/NSCN, and twice more active than Pt-NSCN. Thus, enhanced activity is attributed to the smooth channelizing of electrons across p-n junctions. (4) NSCN evidently offered improved characteristics as a support and photocatalyst over b-CN. The exfoliated NSCN occupied a superior few-layer morphology with 0.35 nm width as compared to parent b-CN. NSCN allowed 57% dispersion of 6 nm-sized CFO, while b-CN supported 14% dispersion of 7.8 nm-sized CFO particles, as revealed by small-angle X-ray scattering spectroscopy (SAXS). Sizes of 2-4 nm were observed for Pt nanoparticles in the 1 wt %Pt/1 wt % CFO/NSCN sample. A binding energy shift and an increase in the FWHM of X-ray photoelectron spectroscopy (XPS) core level peaks established charge transfer and enhanced band bending on p-n contact in Pt-CFO/NSCN. FsTAS revealed the decay of photogenerated electrons via trapping in shallow traps (τ1, τ2) and deep traps (τ3). Lifetimes τ1 (3.19 ps, 42%) and τ2 (187 ps, 31%) were higher in NSCN than those in b-CN (τ1 = 2.2 ps, 42%, τ2 = 30 ps, 31%), which verified that the recombination reaction rate was suppressed by 6 times in NSCN (k 2 = 0.53 × 1010 s-1) as compared to b-CN (k 2 = 3.33 × 1010 s-1). Deep traps lie below the H+/H2 reduction potential; thus, electrons in deep traps are not available for photocatalytic H2 generation. (5) The role of CFO in enhancing water adsorption capability was modeled by molecular dynamics. NSCN or b-CN both showed very poor interaction with water molecules; however, the CFO cluster adsorbed H3O+ ions very strongly through the electrostatic interaction between calcium and oxygen (of H3O+). Pt also showed a strong affinity for H2O but not for H3O+. Thus, both CFO and Pt facilitated NSCN to access water molecules, and CFO further sustained the adsorption of H3O+ molecules, crucial for the photocatalytic reduction of water molecules. (6) Band potentials of CFO and NSCN aligned suitably at the interface of CFO/NSCN, resulting in a type-II band structure. Valence band offset (VBO, ΔE VB) and conduction band offset (CBO, ΔE CB) were calculated at the interface, resulting in an effective band gap of 1.41 eV (2.9 - ΔE VB = 1.9 - ΔE CB), much lower than parent compounds. The interfacial band structure was efficient in driving photogenerated electrons from the CB of CFO to the CB of NSCN and holes from the VB of NSCN to the VB of CFO, thus successfully separating charge carriers, as supported by the increased lifetime of charge carriers and favorable photocatalytic H2 yield.

XPS study of the nitridation of hafnia on silicon

We report a comprehensive quantitative ARXPS study of 20-cycle ALD-grown HfO2 films on Si (001) substrates with and without remote plasma nitridation. The films comprised a 0.6 nm HfO2 layer atop a 1 nm hafnium-rich silicate interlayer. A detailed analysis of the Hf 4f, Si 2p, O 1s, C 1s, and N 1s core level spectra is presented for samples with and without nitridation. The fitting of the Hf 4f spectra reveals four contributing components associated with silicate, hafnia, and their respective nitrided species. The Hf 4f, O 1s, and C 1s spectra exhibit a negative binding energy shift of about 0.2 eV upon nitridation induced by a Si2+-N dipole formed at the interface. Quantitative ARXPS analysis, employing the MultiLayer Model, enabled the determination of the thicknesses, and composition together with their associated uncertainties. The analysis showed that the composition of the nitrided hafnia is HfO1.66N0.33. There is a higher degree of nitridation in the silicate interlayer compared to the overlying hafnia layer. The degree of nitridation is found to increase with plasma power; N2+ is identified as the primary plasma species responsible for the nitridation of hafnia.

Tuning the amount of Sn0 around Ru to promote hydrodeoxygenation of furfural

2-methylfuran (2-MF) is a high-performance gasoline additive due to its high-octane value and good explosion resistance. In this study, cerium tin oxide solid solutions were prepared by a co-precipitation method. The selectivity of 2-MF and the conversion of furfural significantly improved after doping CeO2 with SnO2. 95 % yield of 2-MF was obtained on 5 %Ru/Ce0.975Sn0.025O2, compared to only 40 % yield on 5 %Ru/CeO2. The reaction rate of furfural over 5 %Ru/Ce0.975Sn0.025O2 was 4.9 times higher than that with 5 %Ru/CeO2. Characterizations show an increased concentration of SnO2 around Ru, and the ratio of Ruδ+/Ru reaches a maximum on 5 %Ru/Ce0.975Sn0.025O2. The binding energy shift of Ru0, Sn0, O, and Ce3+ indicates that the introduction of Sn plays an important role in regulating the interface between Ru and CeO2. The increase of Ruδ+/Ru ratio benefits the hydrodeoxygenation of furfural and contributes to the high yield of 2-MF. This study provides a highly active catalyst for the hydrodeoxygenation of furfural.

Deconvoluting XPS Spectra of La-Containing Perovskites from First-Principles.

Perovskite-based oxides are used in electrochemical CO2 and H2O reduction in electrochemical cells due to their compositional versatility, redox properties, and stability. However, limited knowledge exists on the mechanisms driving these processes. Toward this understanding, herein we probe the core level binding energy shifts of water-derived adspecies (H, O, OH, H2O) as well as the adsorption of CO2 on LaCoO3 and LaNiO3 and correlate the simulated peaks with experimental temperature-programmed X-ray photoelectron spectroscopy (TPXPS) results. We find that the strong adsorption of such chemical species can affect the antiferromagnetic ordering of LaNiO3. The adsorption of such adspecies is further quantified through Bader and differential charge analyses. We find that the higher O 1s core level binding energy peak for both LaCoO3 and LaNiO3 corresponds to adsorption of water-related species and CO2, while the lower energy peak is due to lattice oxygen. We further correlate these density functional theory-based core level O 1s binding energies with the TPXPS measurements to quantify the decrease of the O 1s contribution due to desorption of adsorbates and the apparent increase of the lattice oxygen (both bulk and surface) with temperature. Finally, we quantify the influence of adsorbates on the La 4d, Co 2p, and the Ni 3p core level binding energy shifts. This work demonstrates how theoretically generated XPS data can be utilized to predict species-specific binding energy shifts to assist in deconvolution of the experimental results.

The effects of oxygen flow ratio on the properties of Ag x O thin films grown by radio frequency magnetron sputtering.

The Ag x O thin film with various oxygen flow ratios (R[O2]%) deposited by radio frequency magnetron sputtering (RFM-SPT) has been studied. While adjusting R[O2]% from 0% to 30%, the Ag x O thin film transitioned from metal to semiconductor and/or insulator with different transparent appearances on the surface observed using X-ray diffraction (XRD) and transmittance measurement. At high oxygen flow ratios, the Ag x O film is multi-phased as a mixture of Ag(II)O and Ag2 (III)O3. In addition, the work function (ϕ) of those samples changes from 4.7 eV to 5.6 eV as measured by photoelectron yield spectroscopy (PYS). The compositional and chemical state changes that occur at the Ag x O surface during the increments of R[O2]% are evaluated by the relative peak intensities and binding energy shifts in X-ray photoelectron spectroscopy (XPS). With the incorporation of more electrons in chemical bonding, the oxygen-induced band forms. And combining all the results from transmittance (band gap confirmation), PYS (work function confirmation), and XPS (valence band position confirmation), the estimated band diagrams are given for the oxidation state of Ag x O with various oxygen flow ratios.

Charge transfer effects in (HfNbTiVZr)C—Shown by ab initio calculations and X‐ray photoelectron spectroscopy

AbstractConsidering charge transfer effects and the variability of the bonding between elements with different electronegativity opens up a deeper understanding of the electronic structure and as a result many of the properties in high entropy‐related materials. This study investigates the importance of the diverse bonding and chemical environments when discussing multicomponent carbide materials. A combination of ab initio calculations and X‐ray photoelectron spectroscopy (XPS) was used to investigate the electronic structure of multicomponent thin films based on the (HfNbTiVZr)C system. The charge transfer was quantified theoretically using relaxed and nonrelaxed multicomponent as well as binary carbide reference structures, employing a fixed sphere model. High‐resolution XPS spectra from (HfNbTiVZr)C magnetron‐sputtered thin films displayed core‐level binding energy shifts and broadening effects as a result of the complex chemical environment. Charge transfer effects and a changed electronic structure in the multicomponent material, compared with the reference binary carbides, are observed both experimentally and in the density functional theory (DFT) simulations. The observed effects loosely follow electronegativity considerations, leading to a deviation from an ideal solid solution structure assuming nondistinguishable chemically equivalent environments.

Influence of tartaric acid on the electron transfer between oxyanions and lepidocrocite

Iron oxide minerals control the environmental behavior of trace elements. However, the potential effects of electron transfer directions by iron oxides between organic acids and trace elements remain unclear. This study investigates the redox capacity of tartaric acid (TA) with chromate (Cr(Ⅵ)) or arsenate (As(V)) on lepidocrocite (Lep) from the perspective of electron transfer. The results demonstrated the configurations of TA (bidentate binuclear (BB)), As(V) (BB), and Cr(Ⅵ) (BB and protonated monodentate binuclear (HMB)) on Lep. Frontier molecular orbital calculations and X-ray photoelectron spectroscopy (XPS) binding energy shifts further indicated different electron transfer directions between TA and the oxyanions on Lep. The iron of Lep might act as electron acceptors when TA is adsorbed, whereas the iron and oxygen of Lep act as electron donors when As(V) is adsorbed. The iron of Lep might accept electrons from its oxygen and subsequently transfer these electrons to Cr(Ⅵ). Macroscopic validation experiments showed the reduction of Cr(VI), whereas no reduction of As(V). The XPS analysis showed a peak shift, with the possible formation of As–Fe–TA ternary complexes and electron transfer on Lep. These findings indicate that mineral interfacial electron transfer considerably influences the transport and transformation of oxyanions.

Amplified spontaneous emission in β-In2S3–Ag based SQD-MNP superstructures with switching photoluminescence and enhanced photocatalytic activity

Optically modified MNPs coupled with SQDs (super structures) demonstrating tunable emission and enhanced photocatalytic activity are synthesized through homogeneous nucleation of indium chloride, thioacetamide and silver nitrate. Ag nanospheres (1–15 nm) are embedded in the matrix of β-In2S3 quantum dots. Modification of the absorption profile and shift in excitonic binding energy from 3.60 eV to 3.25 eV occurs due to plasmon mediated indirect columbic interaction between the SQDs. Raman spectrum of β-In2S3 (1:1)-Ag Nanohybrids (NHs) shows asymmetric line-shape broadening due to the fano-interaction (electron-phonon interaction) of the triply degenerate F2g mode of SQDs with a continuum of plasmon excitations. The emission spectra of the quantum dots, with significant peak shifting and enhanced intensity, indicates stronger coupling between the SQDs and MNPs. In the proximity of Ag NPs, the defect emission due to IIn (∼708 nm) is completely quenched, and an enhanced blue emission occurs at ∼ 496 nm. Further with increase in pump beam energy, there is a gradual peak maxima shift, spectral distortion, narrowing of emission profile and enhancement in emission intensity, which is attributed to amplified spontaneous emission assisted amplification in the gain media (SQDs). Measurement of photocatalytic efficiency for irradiation of 60 min (400 nm–700 nm) with β-In2S3 (1:1) QDs-Ag NHs as photocatalyst, prompted 100 % degradation while pure β-In2S3 (1:1) QDs as photocatalyst material could attain 98.6 % degradation only after 280 min of irradiation.

Surface chemistry of ion beam modified native titania/Ti interfaces examined using X-ray photoelectron spectroscopy

It is often assumed in X-ray Photoelectron Spectroscopy that binding energy shifts are synonymous with changes in the chemical state of an atom and the chemical state can be described in terms of oxidation state and stoichiometry of the elements in a material that correlates with photoemission peaks. However, when an atom is bonded into a crystal lattice, the shapes and binding energy of photoemission may not match the expected stoichiometry when measured by XPS, even though shifts in binding energy suggest new oxidation states. In this work, a set of experiments is presented, in which Ar+ and He+ ions of different energies modify the native oxide on a titanium foil which yields XPS spectra that are not easily open to analysis by conventional peak models. In the course of analyzing these complex photoemission data by linear algebraic methods, the prospect emerged that XPS is suggesting that sputtering a native oxide may be providing insight into structural perturbation in addition to the stoichiometry-type changes to the native oxide.

NC Loaded PtM Alloy from M-NC with Ultralow Pt Loading for Oxygen Reduction Reaction

Developing low Pt or non-precious metal catalysts for oxygen reduction reaction (ORR) has becoming necessary in recent years. Herein, PtM alloy anchored on nitrogen-doped carbon (PtM/NC, M=Fe, Co) catalyst with ultralow Pt loading (∼1 wt%) is prepared from the simple two-process pyrolysis, namely from C to M-NC then to PtM/NC. The as-prepared PtM/NC (M=Fe, Co) shows an excellent ORR catalytic performance with the peak potential and half-wave potential of 0.901 and 0.870 V for PtFe/NC, 0.868 and 0.845 V for Pt3Co/NC. The ORR on PtM/NC (M=Fe, Co) is a mainly direct 4-electron reaction pathway (3.75–3.90) in alkaline solution. Moreover, they possess good methanol tolerance and stability. Synergistic effect of Pt and M together with N species result in the excellent ORR catalytic activity of PtM/NC (M=Fe, Co). The negative shift of Pt binding energy caused by both lattice contraction and electron orbital coupling from M is beneficial for reducing the d-band center of Pt, weakening the oxygen binding energy and enhancing the ORR intrinsic activity of Pt. The strong interactions between NC and PtM alloy are beneficial for anchoring PtM nanoparticles, promoting the stability of catalyst. This work provides a new strategy for preparing ultralow Pt loading catalysts.