Search

Abstract The assessment of cucurbituril (CBn) for selective removal of actinides from nuclear waste streams requires comprehensive understanding of binding parameters and coordination of these complexes. The present work is the first experimental report on complexation of actinide ion with Cucurbit[5]uril (CB5) in solution. The thermodynamic parameters (ΔG, ΔH and ΔS) for complexation of CB5 with U(VI) in formic acid water medium were determined using microcalorimetry and UV‐Vis spectroscopy. The enthalpy and entropy of complexation revealed the partial binding of U(VI) to CB5 portal. The partial binding was confirmed by spectroscopic techniques viz. extended X absorption fine structure spectroscopy (EXAFS), 1H and 13C NMR. The EXAFS χ (r) versus r spectra for U-CB5 complex has been fitted from 1.4 to 3.5 Å with two oxygen shells and a carbon shell. The presence of three carbon atom in secondary shell shows the involvement of only three carbonyl oxygens directly bonding to U(VI) which is in contrast to that calculated from gas phase DFT calculation of unhydrated system. The combined effect of hydration and formic acid encapsulation led to the enhanced stability of partially bound U(VI) to CB5. In the present work the binding of formic acid has also been studied by fluorescence spectroscopy. ESI-MS data shows the unusual stabilization of U(VI) by CB5 in gas phase. Graphical Abstract Unlabelled Image Highlights • First report on systematic structural and thermodynamic investigation of CB5 complexation with U(VI) in solutions. • Enthalpy and entropy of complexation revealed the partial binding of U(VI) to CB5 portal. • The partial binding was confirmed by spectroscopic techniques EXAFS, 1H and 13C NMR. • Computational studies to support the experimental observation has been performed. • Importance in understanding basic actinide chemistry and helps in designing ligands with improved affinity and selectivity. [ABSTRACT FROM AUTHOR]

Abstract We report the structural and optical properties of ternary α-(Ga x Cr (1- x)) 2 O 3 with 0 ≤ x ≤ 0.45 which is synthesized by solid state reaction method. Single phase with space group R-3c is obtained for the gallium composition range of 0 ≤ x ≤ 0.45 and further increase in Ga concentration results in appearance of secondary C 2/ m phase corresponds to Ga 2 O 3. Variations in the in-plane ’ a’ and out of plane ’ c’ lattice parameters shows a clear daviation from the Vegard's law with the bowing parameters of −0.0510 Å and 0.0305 Å respectively. Extended X-ray absorption fine structure (EXAFS) spectroscopy shows larger values of Ga-O bond lengths, which elucidate the deviation in lattice parameters from the Vegard's law and immisibility of Ga in Cr 2 O 3 lattice. Diffuse reflectance spectroscopy (DRS) confirms a blue shift of 0.5 eV in the band gap of α-(Ga x Cr (1- x)) 2 O 3. It has also observed that Cr 3d level shifted towards the O 2p level in the valence band which has been reconfirmed by photo electron spectroscopy. The observed shift indicates enhancement of mixing between these levels which can leads to further delocalization of hole states in the valence band responsible for p-type conduction in the α-Cr 2 O 3. These results suggest that ternary α-(Ga x Cr (1- x)) 2 O 3 (0 ≤ x ≤ 0.45) can be useful in the field of UV transperant electronics and photodetectors. Highlights • Synthesis of α-(Ga x Cr (1- x)) 2 O 3 (0 ≤ x ≤ 0.45) by solid sate reaction method. • Deviation of lattice parameters from the Vegard's law and immiscibility of Ga is discussed. • Tunability of ∼0.5 eV in the bandgap of α-Cr 2 O 3 as a function of Ga composition. • Enhancement in the mixing of Cr d and O 2p states in the valance band. [ABSTRACT FROM AUTHOR]

The structure of WO 3 -TeO 2 glasses containing 15, 20 and 25 mol% WO 3 are studied by neutron diffraction (ND), high energy X-ray diffraction (XRD) and X-ray Absorption Near Edge spectroscopy (XANES). The short-range structural properties of glasses i.e. Te O and W O speciation, coordination number distributions, bond-lengths, and the O Te O, O W O and O O O bond angle distributions in the glass network are determined by the Reverse Monte Carlo (RMC) simulations of the ND and XRD data. RMC technique successfully determined all partial pair correlation functions and the coordination number distributions revealed that glass network consists predominantly of TeO 4 and WO 4 units with small amounts of triangular, penta and hexa co-ordinated units. The average W O and Te O bond lengths are in the ranges: 1.69–1.75 ± 0.01 Å and 1.99–2.00 ± 0.01 Å respectively. Both W O and Te O correlation peaks are asymmetrical, that indicate a distribution of their bond lengths in the respective structural units. The O-Te-O bond angle distribution has a peak at 107 ± 2°. Similarly the O-W-O bond angle distribution has a peak at 108 ± 5°. On increasing the WO 3 concentration from 15 to 25 mol%, the average Te O coordination number decreases from 3.80 to 3.61 ± 0.02 due to the structural transformation: TeO 4  → TeO 3 , similarly the W O coordination also decreases and is in the range: 3.79–3.67 ± 0.02. XANES studies found that the oxidation state of Te and W ions in the glasses are 4 + and 6 + respectively. [ABSTRACT FROM AUTHOR]

• Cu benzimidazole complexes 1–6 studied by XANES fingerprinting, EXAFS fitting and XANES simulations. • XANES indicated Cu2+ nature in all complexes with square pyramidal geometry for 1–5. • EXAFS further showed presence of two independent Cu formula units in 1 and 2. • XANES and EXAFS showed that Cu has tetrahedrally distorted square planar structure in 6. • p-DOS and d-DOS were correlated to splitting of white line and intensity of pre-edge peak. X-ray absorption fine structure (XAFS) at the Cu K-edge in copper complexes, viz., [Cu(BzImH) 4 X 2 ], where BzImH= benzimidazole and X= ClO 4 (1), NO 3 (2), ½ SO 4 (3), Br (4), Cl (5) and their 'inner complex' [Cu(BzImH) 2 ] (6) have been investigated using synchrotron radiation. The crystal structures of 4, 5 and 6 are not available. From EXAFS analysis, the structures of 4 and 5 have been estimated to be distorted square pyramidal and that of 6 to be tetrahedrally distorted square planar. Though, the crystal structure of the complexes 1 and 2 have been studied earlier using X-ray crystallography and found to be distorted square pyramidal, these complexes have been included in the study because each of these complexes has two independent formula units having two Cu sites in a molecule. In 2 the axial bond lengths are not similar at Cu1 and Cu2 sites. The electronic nature of Cu metal center in the complexes has been studied using XANES. The XANES spectra have been simulated and p-DOS and d-DOS calculated simultaneously for the Cu center in the complexes. The splitting of Cu K-edge into two edges K 1 and K 2 has been correlated with the p-DOS and the occurrence of pre-edge has been correlated with d-DOS. [Display omitted] [ABSTRACT FROM AUTHOR]

Layered oxide material LiNi x Mn y Co z O 2 is emerging out as promising cathode for new generation of Li-ion batteries, especially as power sources for electric vehicles and plug-in hybrid vehicles. In this work, structural and electronic changes occurring in LiNi x Mn y Co z O 2 (LNMC) cathode materials during charge/discharge cycle of the battery is studied over a wide composition range using in-situ X-ray diffraction (XRD) and in-situ X-ray absorption spectroscopy (XAS) techniques. While in-situ XRD measurements decipher the overall structural changes during the charging/discharging cycles, in-situ element specific XAS measurements reveal site specific information on electronic and local structural changes. It has been found that for the LNMC samples the major charge compensation at the metal site during charging or Li ion de-intercalation is achieved by oxidation of Ni2+ ions without significant change in the oxidation state of Co or Mn ions. It is also found that local structure around Ni undergoes reversible change during charging and discharging cycles whereas local structure around Co or Mn sites show no significant change. Moreover, it has been found that local structural changes at Ni sites in the samples with higher Ni concentrations are much less compared to that in the samples with lower Ni concentrations during charging/discharging cycles, the result being corroborated by ab-initio theoretical simulations also. This is a new finding and would have significant implications in determining the optimum composition of LNMC electrodes of Li ion batteries for commercial applications. • LiNi x Mn y Co z O 2 electrodes have been prepared with four compositions with low to high Ni. • Li ion batteries have been prepared using LNMC as cathode material and Li foil as anode. • Operando XAS measurements show major charge compensation happens at Ni sites only. • Operando XAS and XRD show structural changes in samples with higher Ni are much less. • The results have been corroborated by DFT simulations. [ABSTRACT FROM AUTHOR]

The solid-solution formation mechanism and defect dynamics in U 1- x Ce x O 2±δ solid solutions have been investigated by means of X-ray diffraction (XRD) analysis, Raman spectroscopy, and X-ray absorption near-edge structure (XANES) spectroscopy. Diffraction studies have revealed the formation of single-phase solid solutions with a fluorite-type structure at x ≤ 0.2 and a single-phase fluorite-type structure with broadened diffraction peaks, attributed to inhomogeneity in the O/M ratio, at 0.3 ≤ x ≤ 0.8 under reducing conditions. Oxidizing conditions result in the formation of single-phase solid solutions with fluorite-type structure at x ≥ 0.4. Upon the formation of Ce3+ in solid solutions at x ≤ 0.2 under reducing conditions, charge neutrality is achieved through oxygen vacancy creation and formation of higher oxidation states of uranium through a charge compensation mechanism. Lattice parameter–composition relationships for fluorite-type phases synthesized under oxidizing conditions show a decrease in lattice parameters as compared to their stoichiometric counterparts due to the oxidation of U4+ to U5+/U6+. XANES studies provide direct experimental evidence of the presence of Ce3+ in solid solutions, despite synthesis under oxidizing conditions. [Display omitted] • Detailed phase relations reported in U 1−x Ce x O 2±δ system under reducing and oxidizing conditions. • Presence of multivalent cations in F-type solid solutions at x ≤ 0.2 (reduced samples) suggested by lattice parameter trend. • Retention of F-type structure at x ≥ 0.4 in oxidizing conditions despite presence of combination of oxidation states. • Defect dynamics and solid solution formation mechanism elucidated by conjunction of XRD, Raman spectroscopy and XANES. • Presence of Ce3+confirmed by XANES in air-synthesized U 1-x Ce x O 2+δ. [ABSTRACT FROM AUTHOR]

In this report, a sol–gel method has been developed using tantalum ethoxide to produce homogenous thin films of amorphous Ta 2 O 5 for application in optical coating for high power laser as well as photodetection in the UV range. Morphology, stoichiometry, optical properties, short range atomic structure and valence band have been investigated at various annealing temperature up to 500 °C. A large valence band onset of 3.5 ± 0.20 eV has been measured for the film annealed at 500 °C, ensuring hole blockage through the film and electron selective transport. Extended X-ray absorption fine structure (EXAFS) study has revealed the Ta–O bond distance to be 1.85 Å for as-deposited film, which increased with annealing and approached the crystallographic value. The sol-gel prepared Ta 2 O 5 film has been used as antireflection (AR) coating on silicon and fused silica (FS) substrates. 99.4% transmission with a LIDT of 20 J/cm2 @6 ns at 1064 nm is obtained for Ta 2 O 5 /SiO 2 AR coatings on FS. Using these sol-gel films, Ta 2 O 5 /Si vertical heterojunction photodetectors have been fabricated, which exhibited a responsivity of 560 mA/W, external quantum efficiency of 213%, and specific detectivity ∼1 × 1012 Jones at −1 V bias voltage and 325 nm illumination wavelength. • Sol-gel Ta 2 O 5 films are demonstrated for AR coating and UV photodetection. • Ta 2 O 5 /Si show valence band offset as large as 3.2 ± 0.20 eV facilitating hole blockage. • Short range atomic structure of sol-gel Ta 2 O 5 is determined through EXAFS. • High LIDT AR coatings on Si and fused silica are obtained using Ta 2 O 5 thin films. • Responsivity∼0.6A/W and detectivity∼1012 Jones are obtained at 325 nm. [ABSTRACT FROM AUTHOR]

Radio-frequency magnetron sputtering technique was employed to deposit transition metal doped TiO 2 thin film electrodes on polished stainless steel substrates. Rutile phase TiO 2 films have been deposited with 6% and 10% Fe, Mn and Co doping and separate coin cell type Lithium Ion Batteries (LIB's) have been prepared with these samples as anodes. LIB's with the doped thin film samples have marked very high charge storage capacities at high current rates, which are in some cases better than that obtained with pristine TiO 2 electrode. Further, among the three dopants the performance of the Fe doped samples are the best over a large no. of cycles. During the cycling test, 10% Fe doped TiO 2 electrode has marked very high specific capacity of 0.524 mAh cm−2μm−1 after 1000 cycles at low current rate of 0.13 mA cm−2 and of 0.264 mAh cm−2μm−1 after 500 cycles even at high current rate of 1.3 mA cm−2. Increase in the current rate by 10 folds has not affected the specific capacity much, manifesting excellent response of the battery at high current rate. In the present study we have applied Fe, Co and Mn doping to TiO 2 electrodes prepared under identical conditions and have compared their performances as anodes of thin film LIB's in detail and thus the results would be very useful in technological realization of these anodes in practical LIB systems. • Rutile phase TiO 2 films prepared on SS substrates by rf magnetron sputtering. • TiO 2 films have been deposited with 6% and 10% Fe, Mn and Co doping. • Coin cell type Li ion batteries have been prepared using these thin TiO 2 films as electrodes. • LIB's with doped TiO 2 films show very high charge storage capacities at high current rates. • Among the three dopants 10% Fe doped TiO 2 electrode marked highest specific capacity. [ABSTRACT FROM AUTHOR]

The comparable ionic-radius cation substitution provides a route to investigate the origin of the physical properties of ceramics on the local structure and electronic charge state background. In analogy to our previous work [19] of La 2 CuMnO 6 (LCM) prepared via solid-state route, here we are reporting the effect of Zn substitution at the Cu site of LCM. The detailed structural analysis confirmed the Jahn-Teller (JT) distortion in LCM and Zn2+ substituted LCM (i.e., LCZM) ceramics. Raman analysis further confirmed the JT distortion in these oxides. O K-edge and Mn K-edge XANES spectra confirmed the mixed hybridization states for Mn. A frequency-dependent relaxor state was observed in the dielectric study of LCM and LCZM. The dielectric responses of these systems are prominently driven by electron-phonon coupling. Their magnetic studies showed positive-Curie temperature (T C) and non-zero coercivity, indicating the ceramics' canted-antiferromagnetic nature. • Structural, vibrational, spectroscopy, dielectric, and magnetic studies of novel ceramic La 2 Cu 0.5 Zn 0.5 MnO 6 was carried out. • An investigation of disordering parameters revealed steric, orbital, and Jahn-Teller distortion in La 2 Cu 1-x Zn x MnO 6 ceramics. • O K-edge, Mn K-edge analysis was carried out using SXAS and XNES spectroscopy. • Below room temperature, frequency-dependent relaxor characteristic was observed and studied by C-W law. • DC-magnetic behavior of the samples exhibited canted-antiferromagnetic nature. [ABSTRACT FROM AUTHOR]

In this study, the solid solubility of uranium in Nd 2 Zr 2 O 7 pyrochlore and the ensuing phase evolution have been explored for nuclear waste immobilization and inert matrix fuel applications. To investigate the phase evolution upon U-substitution at the B-site of Nd 2 Zr 2 O 7 pyrochlore, Nd 2 Zr 2-x U x O 7 (0 ≤ x ≤ 2) samples have been synthesized by a solid-state route under reducing and oxidizing conditions and thoroughly characterized by X-ray diffraction and Raman spectroscopy. XRD studies reveal that uranium forms a solid solution throughout the composition range adopting the pyrochlore structure at x ≤ 0.8 and the fluorite-type structure at x ≥ 1.2 under reducing conditions at 1873 K. The pyrochlore-type phase-field shrinks (x ≤ 0.4) with the concomitant extension of the fluorite-type phase-field (0.8 ≤ x ≤ 2) upon oxidation of these reduced samples in air at 1473 K. The samples synthesized under oxidizing conditions (air) at 1873 K exhibit transformation of the pyrochlore-type phase to a fluorite-type phase through a biphasic phase-field. The pyrochlore-type ordering diminishes for the oxidized samples compared to that of the reduced counterpart, which could be attributed to the oxidation of U4+ to smaller-sized U5+/U6+ and the concomitant incorporation of additional oxygen anions in the lattice for charge balance. Raman spectroscopy has been used to shed light on the local structures. Chemical analysis indicates an O/U ratio of 2.00(3) and 2.66(3) for the reduced and oxidized samples, respectively. [ABSTRACT FROM AUTHOR]

We report the investigation of local structure, electronic and optical properties of different polymorphs of (YO 1.5) x (HfO 2) 1- x (x = 0, 0.05, 0.10, 0.15, and 0.20) epitaxial thin films on YSZ(100) substrate prepared by pulsed laser deposition technique. The X-ray diffraction results confirm that the deposited films are epitaxial and crystal structure changes from monoclinic to orthorhombic to cubic/tetragonal as Y concentration increases in HfO 2 thin films. Spectroscopic identification of phase transformation in these thin films was investigated using Fourier transform infrared and X-ray absorption spectroscopy (XAS). Effect of crystal structure on Hf-O & Hf-Hf bond distances and disorder were investigated by extended X-ray absorption fine structure. O K-edge XAS spectra show profound changes in e g and t 2g peaks for different HfO 2 polymorphs. X-ray photoelectron spectroscopic studies confirm that different chemical environments are present in different polymorphs of HfO 2 thin film. The photoluminescence measurements validate the wide band spectral emission in wavelength region of 400–550 nm for all polymorphs and photoluminescence areal intensity shows strong dependence on phase and local structure disorder. This work will be helpful in understanding the basic material properties and spectroscopic identification of different HfO 2 phases of high application relevance in semiconductor industry. [Display omitted] • The spectroscopic investigation of phase transformation in Y doped HfO2 epitaxial thin films by FTIR and XAS technique. • The crystal structure changes from monoclinic to orthorhombic to cubic as Y concentration increases in HfO 2 thin films. • The surface composition of thin films was calculated using XPS technique. • The photoluminescence areal intensity shows strong dependence on phase and local structure disorder. [ABSTRACT FROM AUTHOR]

In this study, effect of Nd doping, as a dopant material on the structural, optical and electronic properties of lanthanum monazite structure has been studied. Pure and Nd:LaPO 4 powders with varying Nd concentrations were prepared via conventional high-temperature solid-state reaction method. Compositional information obtained using Energy dispersive X-ray spectroscopy showed that within the detection limit, no impurities were present in the samples. Oxidation states of the elements were confirmed from X-ray photoelectron spectroscopy (La and Nd) and X-ray absorption near edge structure studies (La). X-ray diffraction showed the formation of monoclinic crystal structure without any phase impurity. Fourier transform infra-red spectroscopic measurements confirmed the substitution of Nd in LaPO 4 matrix. We also report the first ever local structure analysis using Extended X-ray absorption fine structure which showed that the Nd atoms have successfully substituted La atoms in LaPO 4 matrix. The bandgaps were obtained from Diffuse reflectance UV-Visible spectroscopy. [Display omitted] • Nd doping effect on structural, optical, electronic property of LaPO 4 was studied. • XRD showed pure monoclinic crystal structure without any phase impurity. • First ever report on local structure by EXAFS showed La substitution by Nd atoms. • Oxidation states of elements were confirmed from XPS and XANES. • FTIR revealed presence of PO 4 tetrahedra without any other chemical impurity. [ABSTRACT FROM AUTHOR]

TiO 2 is a potential candidate for thin film electrode in Li ion batteries since it is abundant, cheap, has high theoretical specific capacity and can be produced in thin film form of desired crystallographic phase relatively easily by various physical vapor deposition techniques. Rutile phase TiO 2 thin films have been prepared by radio frequency magnetron sputtering technique on stainless steel substrates at 450 °C substrate temperature, followed by post deposition annealing in air at 600 °C. These samples have been used as anode in Li ion batteries which are subjected to discharge/charge cycles. The electrodes have been extracted by de-crimping the batteries at various stages during the 1st discharge and 1st charge cycles and structural characterizations of these samples have been carried out by Grazing Incidence X-ray diffraction measurements with a laboratory X-ray source and Extended X-ray absorption fine structure measurements using synchrotron radiation. A clear signature of rutile to anatase phase transition has been observed in the samples during 1st discharge or Li ion insertion process, which is subsequently retained during the 1st charging cycle also. This is also verified by Raman spectroscopy measurements on few samples and is further corroborated by the constant voltage plateau observed in the galvanostatic cycle (potential versus capacitance plot) of the Li ion battery also during the 1st discharge cycle. • TiO 2 films prepared on SS substrates by rf magnetron sputtering at 450 °C substrate temperature. • Films are found to preferentially acquire rutile phase by post deposition annealing in air at 600 °C. • Coin cell type Li ion batteries have been prepared using these thin TiO 2 films as electrodes. • Galvanostatic C-V measurement shows a constant voltage plateau during 1st discharge cycle. • GIXRD and EXAFS measurements show transition from rutile to anatase phase during 1st discharge cycle. [ABSTRACT FROM AUTHOR]

• The long term stability of various kinds of W/B 4 C multilayers is studied. • Treated samples undergo structural degradation at faster rate. • Structural degradation clearly depends on the initial B 4 C layer thickness. • A B 4 C cap layer prevents multilayers consisting of thinner B 4 C layer from oxidation. The long term stability of as-deposited, annealed, and synchrotron radiation exposed W/B 4 C multilayer structures was investigated. The multilayer structures were studied using hard X-ray reflectivity, grazing incidence X-ray diffraction (GIXRD), extended X-ray absorption fine structure (EXAFS), and atomic force microscopy (AFM). The structural degradation in annealed and synchrotron radiation exposed samples occurs at faster rate as compared to untreated samples. The structural degradation rate clearly depends on the thickness of B 4 C layer in multilayer structures. GIXRD measurements confirm the formation of tungsten carbide and boride phases. From EXAFS measurements at the W L 3 -edge, we find that the increase in the diffusion of oxygen is responsible for the observed structural degradation at faster rate in annealed samples consisting of thinner B 4 C layer. AFM images reveal that the surface modifications occur at slower rate in untreated samples as compared to annealed samples. Moreover, B 4 C proves to be an efficient cap layer to protect the as-deposited and annealed multilayer structures from oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of reduced graphene oxide assisted two-dimensional graphitic ZnO. • Polarisation dependent x-ray absorption spectroscopy to identify 2D phase. • Electronic structure using ligand field theory. • Density Functional Theory simulated relaxed 2D ZnO structure as initial model for EXAFS analysis. Reduced graphene oxide (rGO) assisted two-dimensional (2D) graphitic ZnO (gZnO) have been prepared and characterized by Raman, FTIR, Cross-sectional high resolution transmission electron microscopy (HRTEM) and X-ray absorption spectroscopy (XAS) techniques comprising of X-ray near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Raman spectroscopy and FTIR measurements suggest formation of ZnO and the same has been corroborated by XANES measurements. HRTEM and polarization dependent XANES measurements with two different sample orientations confirm the formation of gZnO/rGO sandwiched layers. Density Functional Theory simulated relaxed initial structure of bilayers of gZnO sandwiched between successive rGO layers fits the EXAFS data reasonably well, supported by formation energy calculations which indicate better stability for samples having bilayers to a few layers of gZnO between rGO layers than with monolayer. These relaxed structures also help to understand the electronic structure contributing in XANES spectrum, with the help of ligand field theory. [ABSTRACT FROM AUTHOR]

• The eg-t2g sub band splitting in O K edge for NixCd1-xO thin films is explained. • Crystal field and band anti-crossing interaction are considered for explanation. • Extended X-ray absorption fine structure simulation for Ni K edge is performed. • Ni-O and Ni-Ni bond lengths and Debye Waller factors are calculated. In the present work, full composition range of Ni x Cd 1-x O thin films, from Cadmium oxide to Nickel oxide are prepared with sol-gel chemical synthesis route on corning glass substrates. The Fourier transform infrared spectra provide a direct indication of compositional dependence for different vibrational modes with increasing Ni doping. The microscopy images reflect the reduced crystallinity and closely packed morphology with increasing Ni doping which endorses the changes reflected in electronic structure. The O K edge, soft X-ray absorption spectra (XAS) for thin films indicate a clear evidence of e g and t 2g sub band splitting and has been explained via crystal field splitting and three level band anti-crossing (BAC) interaction phenomena. At higher doping fraction, the inhomogeneous electric field of neighboring ions surrounding the unfilled Ni 3 d level results in rupturing of L − S coupling and further crystal field splitting. The BAC interaction brings about partially unoccupied localized Ni 3 d and empty d acceptor levels above conduction band minima (CBM). As saturated Fermi level goes below CBM with increasing Ni doping, transitions to antibonding orbital [e g (π *) and t 2g (σ *)] with finite energy difference, is reflected as separated e g -t 2g peaks in XAS spectra. On the other hand, extended X-ray absorption fine structure for Ni K edge fitting provides a complete information for nearest (Ni-O) and next nearest (Ni-Ni) neighbor bond length. [ABSTRACT FROM AUTHOR]

• Undoped and Co-doped Nd based cuprate francisite were synthesized. • XRD and EXAFS studies confirmed a substitutional replacement of Cu with Co. • Magnetism has been significantly changed upon Co doping. To understand the physical mechanism of intralayer ferromagnetic (FM) and interlayer antiferromagnetic (AFM) interactions in quasi-two-dimensional model of a real three-dimensional system, rare earth (RE)-Nd based cuprate francisite, Cu 3 Nd(SeO 3) 2 O 2 Cl (NdCufr) was doped with Co and studied using structural (X-ray diffraction technique), magnetic (temperature and field dependent magnetization and specific heat measurements) and local structural (X-ray absorption technique) techniques supported by first principle theoretical calculation. The structure of the samples is orthorhombic and doped specimens indicate more or less substitutional incorporation of Co at Cu site. The magnetic properties highlighted with two transitions, viz. AFM to paramagnetic (PM) transition around 30 K and a spin reorientation transition (SRT) below 10 K. Two phenomena viz. magnetic hysteresis below SRT and magnetic field induced metamagnetic transition (MMT) were observed. Co doping significantly enhanced these two phenomena in addition to change the transition temperatures. The concomitant change and enhancement of magnetic properties by Co doping has been interpreted using splitting scheme of Cu-d and Nd-f states. The local structure study corroborates the overall findings and detects the cause of unexpected trend of magnetism with increasing Co doping. [ABSTRACT FROM AUTHOR]

We have developed an Ultra-High Vacuum (UHV) compatible Pulsed Laser Deposition (PLD) set-up at Angle Resolved Photo Electron Spectroscopy (ARPES) beamline (BL-3) at Indus-1 synchrotron radiation source, Raja Ramanna Centre for Advanced Technology, Indore, India. The set-up is successfully tested and integrated at beamline for in-situ photoelectron spectroscopic (PES) studies of thin films. In present PLD set-up, quick in-situ transfer of deposited thin films to analysis chamber enables the surface sensitive PES measurements on atomically cleaned surfaces without the requirement of any sputtering. This set-up has the capability of thin film depositions using six number of one-inch targets with precise control of various deposition parameters at a base pressure of ∼ 1x10−9 mbar. To explore the capability of the system, a set of thin films of HfO 2 , 5 % Ga 2 O 3 doped ZnO (GZO) and GZO/HfO 2 are deposited and the band offset of GZO/HfO 2 heterostructure is investigated by in-situ PES measurements using synchrotron radiation. The film surface is found to be contamination free, which demonstrates the capability of the set-up for in-situ PES studies. The Hf 4 f and Zn 3 d core level peaks along with valence band maxima positions are used to determine the valence band offset. The valence band offset is found to be 0.31 ± 0.08 eV, which is the first result reported on this heterostructure system. [ABSTRACT FROM AUTHOR]

The modified sodium borosilicate glass was synthesized by incorporating CaO, TiO 2 and Al 2 O 3 to the primary glass forming constituents (SiO 2 , B 2 O 3 and Na 2 O) and on melting the mixture at 1373–1473K/3h by melt quench method. Uranium loaded analogues were synthesized by adding varying amounts of UO 3 (2,4,6 and 8 mol %) to the borosilicate glass forming reagents then on melting at 1373–1473K. The U-loaded matrices were characterized by XRD to ensure the formation of glass matrices. Solubility of uranium in sodium borosilicate glass has been investigated. Further, the glasses were characterized by X-ray photoelectron spectroscopy (XPS) to unravel the oxidation states of uranium in the modified glass composition. X-ray absorption spectroscopy (EXAFS) revealed the chemical environment of uranium in the glass matrix indicating the coordination number of U in glass. Image 1 • Modified borosilicate glass 47SiO 2 -24B 2 O 3 -17Na 2 O-9.5CaO-1.0Al 2 O 3 -1.5 TiO 2 was prepared. • 2–8 mol% of UO 3 in the form of U 3 O 8 was loaded to the modified borosilicate glass. • Above 6 mol% of UO 3 loading, Na 2 U 2 O 7 separated out from the glass unravelled by XRD studies. • XPS studies show the presence of U in two different oxidation states (U6+ and U4+). • EXAFS studies reveal a decrease in coordination of uranium in glass matrix on increasing uranium loading. [ABSTRACT FROM AUTHOR]

• Fe-doped TiO 2 amorphous thin films deposited using rf magnetron sputtering. • Band-gap energy reduction with Fe doping due to oxygen vacancy. • Maximum Fe substitution is up to 2 at. % doping. The present study deals with the local structure of amorphous TiO 2 and Fe-doped TiO 2 thin films deposited on Si substrate using magnetron sputtering. The absence of long range order is confirmed by grazing incidence x-ray diffraction and the short range order is studied using x-ray absorption near edge structure (XANES) measurements at Ti, Fe and O K-edges and Fe and Ti L 3 -edge. The XANES provides understanding about the electronic transition induced from the short range ordering and dependence of electronic hybridization of the central Ti- p orbitals with the Ti- d orbitals. The XANES measurements also show that maximum Fe doping concentration allowed to replace Ti is 2 at.% and after that separate phase starts appearing, which is consistent with simulation by ab-initio multiple scattering theory based code FEFF9. Ellipsometry measurements show gradual decrease in band-gap energy upto 2 at.% Fe doping from pristine TiO 2 , however a drastic decrease in band-gap energy is observed at 4 at.% or higher doping concentration due to formation of other phases. [ABSTRACT FROM AUTHOR]

We report the synthesis of iron mononitride (FeN) thin films having zinc blende (ZB) type structure, deposited using a direct current magnetron sputtering process on amorphous quartz substrates. The effect of substrate temperature (T s) on the structure of FeN thin films was systematically investigated by varying the T s from 300 to 500 K(in close intervals of 25K). The long-range as well as the local structure of samples was studied using x-ray diffraction (XRD), x-ray absorption near edge spectroscopy (XANES) at N K-edge, Fe L and K-edge and extended x-ray absorption fine structure (EXAFS) at Fe K-edge. The lattice parameter (LP) obtained from XRD and the presence of an intense pre-edge feature in Fe K-edge XANES confirms the ZB-structure of FeN samples. It was found in this work that the stoichiometric FeN with a LP close to its theoretical value can only be obtained in a narrow temperature regime due to minimization of stresses generated during the growth near the thermodynamic equilibrium conditions. These findings were further validated by EXAFS results yielding Fe–N and Fe–Fe bond distances, in conformity with the theoretically predicted values for FeN in ZB type structure. • Stoichiometric phase in FeN can be achieved in a narrow temperature range, only. • Lattice parameter of FeN at 4.28 Å, is closest to its theoretical value at 4.24 Å. • Minimization of stress generated during film growth led to stoichiometric FeN. • Through Fe & N K-edge XANES, ZB-type structure of FeN was confirmed. • First ever usage of EXAFS in FeN, yield bond distances as predicted for ZB-type FeN. [ABSTRACT FROM AUTHOR]

Distortion in mononuclear Schiff base nickel (II) complexes having pyridine and related N-containing heterocyclic derivatives has been studied using X-ray absorption spectroscopy. Extended X-ray absorption fine structure (EXAFS) analysis has been used to confirm the octahedral nature of Ni center and obtain a simple cluster of atoms around this metal ion. Ab-initio X-ray absorption near edge structure (XANES) simulations have been performed using FEFF9 for almost similar coordination around nickel metal in these complexes. The study supports variation in the order of distorted octahedral nature of Ni complexes with O and N atoms around the metal ions, with respect to changing nature of ligand. Theoretical XANES spectra generated for clusters of atoms around the metal ion have been correlated to corresponding p-DOS and s-DOS of the metal. • Distorted octahedral Ni complexes have been studied using EXAFS as well as XANES. • Simulated XANES spectra show different features depending on metal p- and s-DOS. • s-DOS contribution to rising part of edge has been found to vary among complexes. • Constant p-DOS over 0–10 eV give rise to weak and split while line in complex 1. [ABSTRACT FROM AUTHOR]

• Modified deposition precipitation (DP) method for synthesizing highly mono dispersed Pd nanoparticles of size 1-2 nm on SBA-15. • Onset of CO oxidation activity close to room temperature (50 deg C) for the reduced Pd-SBA-15 catalyst. • Evidences from ex-situ XPS and in-situ IR for easily decomposable high valent PdO 2 species being responsible for low temperature CO oxidation activity. A comprehensive size dependent CO oxidation activity has been demonstrated for Pd-SBA-15 catalysts with Pd NPs of varying sizes such as 1-2, 4-6 and 7-10 nm. Pd-SBA-15 catalyst with smallest sized NPs (Pd-S-N) has been synthesized by modified deposition precipitation method recently developed in our lab. Pd-S-N catalyst (reduced at 400 °C) demonstrated CO oxidation activity with lower light off temperature (50 °C), clearly one of the best reported for a Pd-silica system. A detailed XPS and in-situ DRIFTS analyses further supported by XAS and DFT calculations reveal the presence of easily decomposable highvalent Pd-oxide on co-ordinatively unsaturated Pd sites (Pd cus). Weak binding of CO on Pd cus sites in small Pd NPs leaving sites for oxygen activation is attributed to the low temperature activity of Pd-S-N for CO oxidation. [ABSTRACT FROM AUTHOR]

An electrochemical cell with Kapton X-ray windows has been in-house developed and related facilities have been set-up for in-situ X-ray Absorption Spectroscopy (XAS) measurements on electrode materials of Li-ion batteries at the Energy Scanning EXAFS beamlines (BL-09) at Indus-2 Synchrotron Source at Indore, India. The set-up has been tested by carrying out in-situ XAS measurements at Mn K-edge on a Li-ion battery with LiMn 2 O 4 as cathode material during charging and discharging when Li ions are de-intercalated and intercalated respectively. The in-situ XAS measurements, (which comprise of both XANES and EXAFS measurements) reveal electronic and structural changes at the Mn sites of the cathode material during the charging/discharging processes which are not fully reversible. Such in-situ studies are very important since cyclic instability of batteries during the charging/discharging processes depend on the variation in the local structure around the active atoms of the electrode materials and thus the above facility would open up a new avenue to the users of Indus-2 synchrotron facility at India in elucidating such phenomena in new generation batteries with novel electrode materials. [ABSTRACT FROM AUTHOR]

Topological insulator thin films of Bi 2 Se 3 have been deposited on SrTiO 3 (111) substrate by dc magnetron sputtering and annealed in Se environment. X-ray Diffraction (XRD) measurement shows (00 l) (l = 3n, where n is an integer) type of reflections over 2θ range of 10–80° without any other peaks indicating that the films are of single crystalline quality along the [001] growth direction confirming that highly c-axis-preferred orientated Bi 2 Se 3 thin films can be obtained by relatively simpler and easily scalable dc magnetron sputtering technique. The results are also confirmed by Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDXS), Photo-electron Spectroscopy (PES) and X-ray absorption spectroscopy (XAS) measurements. • Bi 2 Se 3 films have been prepared on SrTiO 3 substrates by dc magnetron sputtering. • Films prepared at higher substrate temperature followed by annealing under Se ambient. • As-deposited and annealed films were characterized by XRD, XAS and PES. • Annealed samples show perfect stiochiometry and better c-axis orientation. • Annealed samples show enhanced presence of states near Fermi edge. [ABSTRACT FROM AUTHOR]

The systematic X-ray absorption near edge structure (XANES) investigation at Au L 3 -edge was made on Au in metallic form and its compounds in various definite oxidation states, viz., Au(OH) 3 , AuCl, AuCl 3 , HAuCl 4 , AuI and AuBr 3. The spectra have been recorded with linearly polarized photon beam from 2.5 GeV INDUS-2 Synchrotron source. All XANES spectra were deconvoluted to configure the energy positions of bound and continuum state transitions. With respect to the reference metallic Au, the absorption edge of the Au-compounds shifts towards higher energies with increasing valency of the absorbing atom. The origin of different shifts is found to be dependent on the charge transfer mechanism between Au and ligands in the measured spectra at Au L 3 -edge. The shifts in the absorption energies have also correlated to an increase in the ligand field strength. The absorption edge energy and area of the white-line peaks for the Au-compounds with Au in +3 oxidation state increase systematically in the spectrochemical series as AuBr< AuCl< HAuCl 4 < Au(OH) 3 , which indicates hybridization of d -orbitals and increasing tendency of ligand atom to attract electrons. Theoretical simulations are in line with this trend and the Au-series demonstrates that energy shifts in XANES spectra of Au(III) compounds can be understood in terms of crystal field theory. • The systematic XANES investigation at Au L 3 edge for various definite oxidation states and ligand field strength. • The shifts found to be dependent on charge transfer mechanism between Au and ligands in the measured spectra at Au L 3 edge. • The absorption edge energy for Au compounds in +3 oxidation state increases systematically in the spectrochemical series. • The areas of the pre-edge peaks for Au in +3 oxidation state increases systematically in the spectroschemical series. • The systematic increase indicates hybridization of d orbitals and increasing tendency of ligand atom to attract electrons. [ABSTRACT FROM AUTHOR]

• Ga doped ZnO films grown by reactive cosputtering of GaAs and Zn in Ar-O 2 mixture. • Resistivity increases from 10−3 Ω-cm to 0.2 Ω-cm as O 2 in mixture changed from 5 to 6%.% • X-ray absorption studies reveal the nature of Ga incorporation in the films. • Ga is substitutionally incorporated in low resistivity Ga doped ZnO films. • Compensating Ga Zn +O i complexes are formed in high resistivity Ga doped ZnO films. Ga-doped ZnO (GZO) films were grown by reactive co-sputtering of a Zn-GaAs target (3% area coverage of Zn by GaAs) at 375 °C with different partial pressures of oxygen. The resistivity of GZO films increases drastically from ≲10−3 Ω-cm to ~ 0.2 Ω-cm as the O 2 in the sputtering atmosphere is changed from 5 % to 6 %. The films grown at 5% or lower O 2 have the Ga/Zn ratio of ~ 0.1 and display low resistivity with carrier concentration ~ 1021 cm−3, while the films grown at 6% or higher O 2 have lower Ga/Zn ratio of ~ 0.01 and display high resistivity with carrier concentration ~ 1019 cm−3. Extended X-ray absorption fine structure (EXAFS) measurements at Zn and Ga K-edges reveal substitutional incorporation of Ga in low resistivity films. X ray photoelectron spectroscopy (XPS) studies reveal a substantial decrease in oxygen vacancies together with increase in oxygen interstitials, in high resistivity GZO films. EXAFS measurements of the high resistivity films show a substantial increase in Ga-O and Ga-Zn bond distances and Ga-O coordination, indicating incorporation of oxygen interstitials in the vicinity of Ga. The comparison of measured and simulated X–ray absorption near edge spectra at O K-edge, together with XPS and EXAFS results, provides adequate experimental evidence of the presence of acceptor type (Ga Zn +O i) defect complex, which cause carrier compensation in high resistivity films. [ABSTRACT FROM AUTHOR]

Interface roughness and interface diffusion are two very crucial parameters in determining the performances of thin film multilayer devices for applications in X-ray optics, neutron optics, giant magneto resistance devices etc. Preparation of these thin film multilayers with sharp interfaces is a technological challenge and researchers are using different methods to reduce the interface imperfections. It has been observed that by mixing nitrogen with argon in sputtering ambience during deposition of Ni layers, neutron reflectivity of Ni/Ti neutron supermirrors can be improved significantly.To elucidate the physical mechanism behind this observation, two sets of Ni/Ti periodic multilayers have been prepared using an indigenously built in-line magnetron sputtering system, in one set pure Ar has been used in sputtering ambience and in the other set a mixed ambience of Ar + N 2 has been used for deposition of Ni layers. Both the sets of multilayers have been thoroughly characterized by specular and diffused Grazing Incidence X-ray Reflectivity, Nuclear Resonance Reaction, X-ray diffraction and Grazing Incidence Extended X-ray Absorption Fine Structure measurements using synchrotron radiation. All the above complementary measurements unambiguously establish that the reason for improved performance of the supermirror deposited with Ar + N 2 ambience is the reduction of interface diffusion at Ti-on-Ni interfaces. • Ni/Ti multilayers and supermirrors deposited by magnetron sputtering technique. • Two sets deposited: (i) using pure Ar ambience and (ii) using Ar + N 2 ambience for Ni deposition. • Samples characterized by XRD, specular and diffused GIXR and Grazing Incidence EXAFS. • All measurements suggest less inter-diffusion at Ti-on-Ni interfaces due to use of N 2. • The effect is manifested in higher neutron reflectivity of supermirrors deposited under mixed ambience. [ABSTRACT FROM AUTHOR]

• Comprehensive IR and VUV photoabsorption studies of n-dodecane. • DFT calculations of ground state geometry and vibrational frequencies. • TDDFT calculation of vertical excited state energies & potential energy curves. • Assignment/interpretation of observed IR & VUV spectra backed by calculations. • First report of VUV absorption spectrum & TDDFT calculations of n-dodecane. We report here a comprehensive spectroscopic study of the absorption spectrum of the n-dodecane molecule using synchrotron radiation based photoabsorption and FTIR spectroscopy. Quantum chemical calculations using the DFT and TDDFT methodologies are used to predict relevant ground and excited state properties and correlate them with the experimental results. In the IR spectrum, assignment of the prominent CH stretching bands in the 2800–3000 cm−1 region are consolidated while a few new vibrational assignments are made in the 700–1500 cm−1 region. The electronic absorption spectrum of n-dodecane lies entirely in the vacuum ultraviolet (VUV) region and consists of a broad continuous absorption band starting from ∼7.5 eV, with no discernible structure. TDDFT calculations of vertical excited states predict that most of the excited states are Rydberg in nature. Potential energy curves of the first few excited states with respect to various bond lengths and bond angles are studied in order to gain additional insights into the nature of the excited states. The broad nature of the absorption is attributed partly to the effect of several conformers as well as hot bands from low frequency modes in the ground state and partly due to overlap of several Rydberg series converging to the first few ionization potentials (IPs). Energy separation between the first and second IP is theoretically predicted to be ∼0.65 eV, while successive separation between the second, third, fourth and fifth IPs is ∼0.03 eV. To the best of our knowledge this is the first report of the VUV absorption spectrum of n-dodecane in the region from 6 to 10 eV, as also the first report of theoretical calculations of its electronically excited states. [ABSTRACT FROM AUTHOR]

Brownmillerite KBiFe 2 O 5 (KBFO) absorbs large part of the solar spectrum due to its smaller bandgap. This optical response has immense potential in photocatalytic applications. In this work, KBFO was successfully synthesized using citrate combustion method. X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) as well as Mössbauer spectroscopic studies, identify the valence state of Iron (Fe) as Fe3+. The strong magneto-dielectric coupling in KBFO was demonstrated by integrating both magnetization (M) and dielectric constant (ε) characteristics as a function of temperature. Magnetic and dielectric transitions were observed in close proximity in temperature range ∼780 K–760 K respectively. To the best of our knowledge, the photoelectrochemical properties of as developed KBFO were analyzed for the first time revealing a significant photoresponse with an average photocurrent density of 0.1 μA cm−2. The photocatalytic properties of KBFO were investigated by degrading organic effluent methylene blue (MB) under direct sunlight followed by a comparison with the photodegradation performance of perovskite BiFeO 3 (BFO). KBFO showed enhanced photocatalytic performance as compared to BFO due to its enhanced structural and optical properties. Image 1 • Multifunctional brownmillerite KBiFe 2 O 5 developed using citrate combustion method. • Strong magneto-dielectric coupling in KBiFe 2 O 5. • Photoelectrochemical properties of KBiFe 2 O 5 analyzed for first time and average current density found to be ∼0.1 μA/cm2 • Enhanced photodegradation efficiency of KBiFe 2 O 5 (E g = 1.67eV), over regular perovskite BiFeO 3 (Eg = 2.1 eV). [ABSTRACT FROM AUTHOR]