XANES

About: XANES is a research topic. Over the lifetime, 7737 publications have been published within this topic receiving 188032 citations.

Hollandite-type Al-doped VO1.52(OH)0.77 as a zinc ion insertion host material

Abstract: For the first time, we suggest VO1.52(OH)0.77 and Al-doped VO1.52(OH)0.77 as possible candidate electrode materials for aqueous zinc-ion batteries (ZIBs). Structural analysis data indicate successful doping of Al into the hollandite VO1.52(OH)0.77 tunnel structure, as confirmed by Rietveld refinement of the X-ray diffraction data (XRD) and X-ray absorption near edge structure (XANES) spectroscopy data. Al is preferred to replace V3+, such that the resulting average oxidation state of V increases with increasing Al content in V1−xAlxO1.52(OH)0.77. Electrochemical test results indicate significant improvement in capacity and retention in the Al-doped V1−xAlxO1.52(OH)0.77 due to the presence of strong Al–O bonds, which stabilizes the crystal structure. This is confirmed from the post-cycled data that show less variation in the lattice parameters. Combining the XRD and XANES data, we suggest that the present V1−xAlxO1.52(OH)0.77 is activated by the V4+/3+ redox reaction, accompanied by Zn2+ insertion into the tunnel structure upon reduction and Zn2+ extraction upon oxidation.

Selective Aerobic Oxidation of Crotyl Alcohol Using AuPd Core-Shell Nanoparticles

Abstract: Bimetallic nanoparticles containing Au and Pd were synthesized using poly(vinylpyrrolidone) (PVP) as the polymer stabilizer using both co-reduction and sequential reduction strategies. The nanoparticle structures and catalytic activities for the aerobic oxidation of crotyl alcohol to crotonaldehyde at room temperature in the absence of base were investigated. The chemical, structural, and electronic properties of these nanoparticles were investigated using Pd-K-edge and Au-LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and Pd-LIII and Au-LIII edge X-ray absorption near edge structure (XANES) spectroscopy. EXAFS analysis for the sequentially reduced bimetallic systems indicates the presence of significantly Pd-enriched surfaces and Au cores. XANES spectra of the Pd-LIII edges indicated that the sequentially reduced particles showed significant d-charge depletion compared to pure monometallic Pd and co-reduced AuPd nanoparticles. The sequentially reduced nanoparticles with Pd rich s...

Effect of annealing on the electronic structure of poly(3-hexylthiophene) thin film.

Abstract: The electronic structure and film structure of poly(3-hexylthiophene) (P3HT) have been studied by X-ray diffraction (XRD) measurements, ultraviolet-visible (UV-vis) absorption spectroscopy, near-edge X-ray absorption fine structure (NEXAFS) measurements, ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES). As reported in previous works, XRD results show that the crystallinity of the film with regioregular P3HT is significantly improved by annealing at 170 °C. The effects of annealing on the electronic structure strongly depend on the substrate and the degree of regioregularity of the P3HT polymer backbone. Even in the case of the regiorandom sample, annealing considerably changes the vacuum level energy, which is the result of changes in the conformation of the hexyl groups at the free surface of the film. The π- and π*-band onsets uniformly shift downward by the annealing resulting in an increased hole-injection barrier at the electrode interface. The effects of annealing on the electronic structure of regioregular samples are more complex and depend on multiple factors. It is necessary to take into account variations in the π- and π*-band widths and the polarization energy to determine the effects of annealing. The former is associated with the conformation of the backbones of the polymer chains, and the latter is associated with the packing density of the conjugated polymer planes. The combination of these variations determines the effects of annealing on the electronic structure of the regioregular film. This is a possible reason for the strong dependence of the effects of annealing on the surface roughness of the substrate, since substrate roughness has a considerable effect on the morphology and crystallinity of regioregular P3HT films.

The use of X‐ray absorption spectroscopy for monitoring the thickness of antiwear films from ZDDP

Abstract: X‐ray absorption near edge structure (XANES) spectroscopy at the P K‐edge was used to monitor ZDDP antiwear film thickness with rubbing time. Thermal immersion films of varying thickness were generated from the ZDDP and analysed using XANES spectroscopy and the particle induced X‐ray emission (PIXE) technique. P K‐edge XANES edge jumps and (1s → np) peak heights of the spectra were plotted against PIXE mass thickness values in order to establish calibration curves. Antiwear films were analysed using XANES spectroscopy, and average mass thicknesses were extrapolated from the calibration curves. A set of antiwear films formed in the presence of ZDDP and then further rubbed in base oil (no ZDDP) showed no significant decrease in film thickness. A set of antiwear films rubbed in the presence of ZDDP for various lengths of time showed an increase in film thickness, followed by thinning of the film. The decrease in film thickness is believed to be due to wear caused by the ZDDP solution decomposition products acting as an abrasive in the contact region.