Identification of glass and ceramics by X-ray fluorescence analysis with a pyroelectric X-ray generator.

Applications of X-ray fluorescence (XRF) analysis with a pyroelectric X-ray generator are presented. Glass and ceramics were analyzed with this novel X-ray generator to examine its capability for analyzing nonmetallic inorganic material. Although the power of X-ray output was a few orders of magnitude lower than conventional X-ray tubes, many elements such as Si, K, Ca, Ti, Cr, Fe, Zn, Sr, Ba, and Pb were detected in glass and ceramic samples. Light elements such as Na, Mg, and Al were not detected because of the low fluorescence yield and the absorption of fluorescent X-rays in air. The elements detected or the relative peak intensities of the elements were different from each other, and the samples analyzed were identified by the XRF spectrum, notwithstanding the low power of the X-ray output. This novel device showed the sufficient capability for preliminary screening before strict identification of analytes. The pyroelectric X-ray generator can also be used to analyze large samples that cannot be put into ordinary XRF spectrometers because the device has no dimensional limitation of analytes.     

Identification of steel by X-ray fluorescence analysis with a pyroelectric X-ray generator

An application of X-ray fluorescence analysis with a pyroelectric X-ray generator is presented. Steel standard samples were identified by X-ray fluorescence analysis with this novel X-ray generator to check its capability for performing qualitative and quantitative analysis as an X-ray source for X-ray fluorescence spectrometers. Cr, Ni, V, Co, and W were detected in steel standard samples. V and Cr can be detected even when the content is below 1%. Although it is difficult to detect minor elements because of the low power of the excitation X-rays, it is possible to identify the analyzed samples on the basis of major elements at the percentage level. The pyroelectric X-ray generator is very suitable for portable X-ray fluorescence spectrometers.     

Electrochemical noise of a Li-ion battery: measurement and spectral analysis

Journal of Solid State Electrochemistry - Electrochemical noise of a Li-ion battery was measured during discharge at a constant value resistor. Power spectral density spectra calculations were...     

Automated analysis of SEM X-ray spectral images: a powerful new microanalysis tool.

Spectral imaging in the scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer has the potential to be a powerful tool for chemical phase identification, but the large data sets have, in the past, proved too large to efficiently analyze. In the present work, we describe the application of a new automated, unbiased, multivariate statistical analysis technique to very large X-ray spectral image data sets. The method, based in part on principal components analysis, returns physically accurate (all positive) component spectra and images in a few minutes on a standard personal computer. The efficacy of the technique for microanalysis is illustrated by the analysis of complex multi-phase materials, particulates, a diffusion couple, and a single-pixel-detection problem.     

Spatially resolved X-ray fluorescence analysis with a pyroelectric X-ray emitter.

A portable instrument for two-dimensional X-ray fluorescence imaging was assembled with an X-ray source using a pyroelectric crystal, which was driven by a 9-V dry battery, a Si-PIN detector, a slit, and pulse motors. Line scanning for a mug and a knife-edge-scan of an iron sheet were carried out using this spectrometer. The sensitivity of the spectrometer was sufficient for elemental analysis of a mug using a 1 mm(2) slit, and several elements, such as Co, Ni, Zn, Pb and Zr, were detected. The estimated spatial resolution using a 0.8-mm pinhole was 3.5 mm.     

X-ray absorption spectral studies on the anion-selectivity of a ruthenium(II) polypyridine complex-impregnated polymer ultrathin film.

The anion-selectivity of the surface of a polymer ultrathin film incorporating an amphiphilic ruthenium(II) polypyridine complex with diperchlorate was examined using X-ray absorption spectroscopy with the total electron-yield method. The adsorbed species on the film surface were found to depend on the chemical composition in water where the film was prepared. By combining the X-ray absorption spectra with a molecular-orbital calculation, the molar ratio (MClO4/MRu) between the ClO4- ions and the Ru head group on the film surface could be semi-quantitatively analyzed; it was 0.88 for a film prepared on fresh water, and 1.4 for one prepared on old water.     

Small copper nanoclusters: X-ray absorption analysis

X-ray absorption near edge structure (XANES) spectra at the cooper L_2,3-edge of small cooper nanoclusters has been studied. Theoretical interpretation of XANES spectra measured for small copper nanoclusters have been performed. Theoretical analysis is based on a self-consistent full multiple scattering theory of X-ray absorption as well as on non-muffin-tin finite difference method (FDM). This approach allows choosing the best model for local geometry of small cooper nanoclusters.     

Using intrinsic X-ray absorption spectral differences to identify and map peptides and proteins

The intrinsic variation in the near-edge X-ray absorption fine structure (NEXAFS) spectra of peptides and proteins provide an opportunity to identify and map them in various biological environments, without additional labeling. In principle, with sufficiently accurate spectra, peptides (<50 amino acids) or proteins with unusual sequences (e.g., cysteine- or methionine-rich) should be differentiable from other proteins, since the NEXAFS spectrum of each amino acid is distinct. To evaluate the potential for this approach, we have developed X-SpecSim, a tool for quantitatively predicting the C, N, and O 1s NEXAFS spectra of peptides and proteins from their sequences. Here we present the methodology for predicting such spectra, along with tests of its precision using comparisons to the spectra of various proteins and peptides. The C 1s, N 1s, and O 1s spectra of two novel antimicrobial peptides, Indolicidin (ILPWKWPWWPWRR-NH2) and Sub6 (RWWKIWVIRWWR-NH2), as well as human serum albumin and fibrinogen are reported and interpreted. The ability to identify, differentiate, and quantitatively map an antimicrobial peptide against a background of protein is demonstrated by a scanning transmission X-ray microscopy study of a mixture of albumin and sub6.     

Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the negative electrode material Li0.5Ni0.25TiOPO4 in a Li-ion battery

We have studied the first lithiation/delithiation cycle of the Li-ion battery electrode material Li(x)Ni(0.25)TiOPO(4) applying X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). A set of ten identical Li(x)Ni(0.25)TiOPO(4) battery electrodes have been cycled and left in different states of charge in the range of x = 0.5 … 2.5, before disassembly in an Ar filled glove box. We find that Ni-, Ti-, and O-ions are affected simultaneously, rather than sequentially, upon lithiation of the material. In particular, Ni is reduced from Ni(2+) to Ni(0) but only partially re-oxidized to Ni(1+), again, by delithiation. Overall, there is considerable "crosstalk" between the different atomic species and non-linearity in the response of the electronic structure during the lithiation/delithiation process. Fortuitously, the background variation in Ni L-XAS shows to contain valuable information about solid-electrolyte interface (SEI) creation, showing that the SEI is a function of the degree of lithiation.     

Quantitative analysis of X-ray absorption spectra using a 2D map representation

A promising possibility for the quantitative analysis of X-ray absorption near edge structure (XANES) spectra of nanosized electrode materials is demonstrated. We used a 2D map representation technique, which utilizes the values of the first derivatives of the absorbance with respect to the inserted Li(+) content plotted over the two-dimensional space defined by the inserted Li(+) content (mole) versus photon energy (eV) as a single map. The technique was applied to XANES spectra of the Li(y)CoO system in the first Li(+) insertion reaction for determining the structural and electronic variations associated with the change in Li(+) content. The obtained show that the intensities of two peaks at 7725 and 7711 eV increased with the Li(+) content and the difference of intensity change of these two peaks carried out for successive couples of spectra yielded the largest changes at 1.05 and 1.98 mol of Li content. This approach for quantitative analysis of XANES without using conventional simulation techniques enable us to interpret X-ray absorption spectroscopy (XAS) as a quantitative analytical technique with greater confidence.     

X-ray absorption and X-ray photoelectron spectroscopy of a rhodium colloid

Transition metal colloids are potential precursors of heterogeneous catalysts with application to selective chemical reactions. Sample preparation techniques are described. Experimental details are given of the characterization of these often air-sensitive particles by X-ray photoelectron and X-ray absorption spectroscopy. First results obtained with both techniques for a Rh-colloid show that the metal is mainly present in the zerovalent chemical state. But the spectra indicate further chemical states of Rh which can be assigned to the outermost metal atoms of the colloid interacting with organic ligands or to the educt Rh-halides.     

X-ray absorption and X-ray photoelectron spectroscopy of a rhodium colloid

Transition metal colloids are potential precursors of heterogeneous catalysts with application to selective chemical reactions. Sample preparation techniques are described. Experimental details are given of the characterization of these often air-sensitive particles by X-ray photoelectron and X-ray absorption spectroscopy. First results obtained with both techniques for a Rh-colloid show that the metal is mainly present in the zerovalent chemical state. But the spectra indicate further chemical states of Rh which can be assigned to the outermost metal atoms of the colloid interacting with organic ligands or to the educt Rh-halides.     

Experimental study of a d.c. oxygen glow discharge by V.U.V. absorption spectroscopy

Vacuum ultraviolet absorption spectroscopy has been used to measure the concentration of oxygen molecules O₂(³), metastable singlet O₂(¹) molecules, atoms, and ozone in a d.c. glow discharge. The axial electric field, the electronic density, and the gas temperature are also determined. This set of measurements is presented for the positive column of a glow discharge created in a 1.6-cm-diameter Pyrex tube, for a pressure between 0.2 and 5 Torr and a d.c. current up to 80 mA.     

X-ray crystallographic analysis of 9-cis-rhodopsin, a model analogue visual pigment

Recent progress in high-resolution structural study of rhodopsin has been enabled by a novel selective extraction procedure with rod photoreceptor cells. In this study, we applied the method for rapid and efficient preparation of a purified analogue pigment using bovine rod outer segment membranes with 9-cis-retinal. After complete bleaching of the membranes and subsequent regeneration with the exogenous retinal, 9-cis-rhodopsin is selectively extracted from the membranes using combination of zinc and heptylthioglucoside. The solubilized sample, even with a small amount of contaminating retinal oximes, is shown to be pure enough for three-dimensional crystallization. The X-ray diffraction from 9-cis-rhodopsin crystals was examined and the electron density map at 2.9 angstroms resolution in the chromophore region can be fitted well with the model of 9-cis-retinal Schiff base.     

An X-ray fluorescence spectrometer with a pyroelectric X-ray generator and a secondary target for the determination of Cr in steel

An X-ray fluorescence (XRF) setup with a pyroelectric X-ray generator and a secondary target for the determination of Cr in steel is presented. The pyroelectric X-ray generator, which can be driven by a dry battery, is a low power X-ray source and emits X-rays over a large solid angle. X-rays emitted by this generator can be effectively put to use by a disk-shaped secondary target. An appropriate arrangement of (i) X-ray generator, (ii) sample support, (iii) secondary target, and (iv) detector enables secondary X-rays to irradiate the sample from a short distance. The secondary X-rays are emitted from a wide-area secondary target. The present arrangement also enables the sample to be placed near the detector. The short distance from the sample to both the secondary target and the detector enhances signal intensity. An absolute amount of 1.3 μg Cr can be detected by the present setup. A minimum detection limit of 0.09 wt.% Cr in steel by 1000-s measurement has been achieved.     

Order parameters from U.V. spectra with incompletely polarized absorption bands

A new method is developed for the determination of Saupe's order parameters S* and D* from I.R. or U.V. spectra and the temperature dependence of their degree of anisotropy R. This method can be applied to molecules with one uniformly polarized band and another band of mixed polarization if all bands concerned are polarized in the same plane. For that a relation D* = f(S*) between the order parameters as a function of temperature is necessary, which can be obtained from the lines of constant entropy in the order triangle. These isentropics are calculated from the orientational distribution function of the ordered system. The resulting function D* = f(S*) is equal to that of the mean field theory given by Luckhurst et al., but can be derived here in a very easy way. The method is applied to diaminoanthraquinones with a point symmetry C_2v.