Micro‐Raman spectroscopy on analcime and pollucite in comparison to X‐ray diffraction

Natural and synthetic samples of analcime and pollucite (both zeolites belonging to the analcime group) were studied by means of micro‐Raman spectrometry, X‐ray fluorescence analysis (XFA) and X‐ray diffraction (XRD). On knowing the chemical and structural characteristics of each solid‐solution member, the observed shift in the spectral position of the Raman active modes can be explained and used for phase determination. As shown, the distinction between members of the analcime–pollucite solid‐solution series using Raman spectroscopy is significantly more conclusive than the corresponding XRD findings. Also, information about the structurally bound water inside the zeolite structure can be gained using Raman spectroscopy as long as a suitable exciting wavelength is selected. Copyright © 2008 John Wiley & Sons, Ltd.     

Characterization of pottery from Republic of Macedonia. III. A study of comparative mineralogical detection efficiency using micro‐Raman mapping and X‐ray diffraction

Point‐to‐point micro‐Raman and X‐ray diffraction (XRD) techniques were employed for characterization of minerals present in the pottery body of 27 glazed Byzantine and Ottoman pottery shreds, excavated at two different archaeological sites in the Republic of Macedonia: in Skopje (Skopsko Kale) and in Prilep (Markovi Kuli and Sv. Atanas Church). The Raman spectra of 18 Byzantine samples (dating from 12th−14th century) and nine Ottoman samples (dating from 17th−19th century) revealed 26 different minerals. XRD measurements were further performed on the same powder samples to validate the mineralogical assessment obtained by point‐to‐point micro‐Raman spectroscopy. Although only 13 different mineral phases were obtained by the XRD, the results obtained from the Raman and XRD spectra for the most abundant minerals in the investigated pottery bodies match quite well. However, the identification of the less abundant minerals in the clay matrixes from the XRD data was very difficult, if at all possible. The results emphasize the specifics of the applied techniques and their limits. Additionally, wavelength dispersive X‐ray fluorescence spectroscopy was used for the elemental analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

A combined microRaman and microdiffraction set‐up at the European Synchrotron Radiation Facility ID13 beamline

This article describes the current status of the microRaman set‐up at the ID13 beamline of the European Synchrotron Radiation Facility. This offers an in situ on‐axis microprobe which has a common focal position to the X‐ray microbeam and can collect spectral data simultaneously. It can also be used in an offline sample characterization role, both before and after beamline experiments. To demonstrate the application of microRaman spectroscopy within a beamline environment, a number of examples are given.     

Indirect Raman identification of the proton insertion in the high‐temperature [Ba/Sr][Zr/Ti]O3‐modified perovskite protonic conductors

OH⁻ and H₃O⁺ species in hydrates and simple oxides are rather well characterised from their IR, Raman and inelastic neutron points of view. For the H⁺ (H₂O) species in solid state the variability is well established and assignment remains discussed. The question of the vibrational signature of isolated proton (e.g. the ionic proton, a proton sharing its interaction with more than two acceptors) and its dynamic nature (proton gas, polaron,…) is open. H⁺‐containing modified perovskites A(Ba,Sr,…) B(Zr,Ce,Ti,…) O₃ are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 °C). Comparison studies of the protonated and non‐protonated lanthanide/rare earth‐modified perovskites of type Ba(Sr)Zr(Ti)O₃ as well as Al‐modified BaTiO₃ show that a broad component centred at 2500 cm⁻¹ is observed after ‘proton insertion’. Its intensity is correlated to the protonic species content as well as to the conductivity of the materials. The mixed nature of this feature is discussed: fluorescence related to the dangling bonds, A, B, C bands or new phenomena related to the ionic protons and associated electronic defect. Copyright © 2008 John Wiley & Sons, Ltd.     

Identification and spectra–structure determination of soil minerals: Raman study supported by IR spectroscopy and X‐ray powder diffraction

Raman and IR spectroscopy were used for the characterization of several minerals in morphologically similar vertisol sequences from Kiževak (Serbia). It helped us to establish the surface layer transition going from calcic vertisols (containing gypsum and calcite) to calcimagnesic vertisols (containing aragonite, magnesium‐calcite and dolomite) derived from peridotite and serpentinite. The observed band positions are found to be solely characteristic for each carbonate mineral and are used to discuss the main structural features of carbonates and sulfates present in the studied soil. It was found that the dolomite, calcite and aragonite concretions are present in the deepest layer of the soil, whereas the gypsum is found in the topsoil. The identification was confirmed of the carbonates having calcite and aragonite structure, and the representative from the sulfate group (gypsum) was confirmed by X‐ray powder diffraction. Copyright © 2009 John Wiley & Sons, Ltd.     

X‐ray photon correlation spectroscopy in systems without long‐range order: existence of an intermediate‐field regime

Successful X‐ray photon correlation spectroscopy studies often require that signals be optimized while minimizing power density in the sample to decrease radiation damage and, at free‐electron laser sources, thermal impact. This suggests exploration of scattering outside the Fraunhofer far‐field diffraction limit d²/λR, where d is the incident beam size, λ is the photon wavelength and R is the sample‐to‐detector distance. Here it is shown that, in an intermediate regime d²/λ > Rdξ/λ, where ξ is the structural correlation length in the material, the ensemble averages of the scattered intensity and of the structure factor are equal. Similarly, in the regime d²/λ > Rdξ(τ)/λ, where ξ(τ) is a time‐dependent dynamics length scale of interest, the ensemble‐averaged correlation functions g₁(τ) and g₂(τ) of the scattered electric field are also equal to their values in the far‐field limit. This broadens the parameter space for X‐ray photon correlation spectroscopy experiments, but detectors with smaller pixel size and variable focusing are required to more fully exploit the potential for such studies.     

Structural variation in a synchrotron‐induced contamination layer (a‐C:H) deposited on a toroidal Au mirror surface

A carbon layer deposited on an optical component is the result of complex interactions between the optical surface, adsorbed hydrocarbons, photons and secondary electrons (photoelectrons generated on the surface of optical elements). In the present study a synchrotron‐induced contamination layer on a 340 mm × 60 mm Au‐coated toroidal mirror has been characterized. The contamination layer showed a strong variation in structural properties from the centre of the mirror to the edge region (along the long dimension of the mirror) due to the Gaussian distribution of the incident photon beam intensity/power on the mirror surface. Raman scattering measurements were carried out at 12 equidistant (25 mm) locations along the length of the mirror. The surface contamination layer that formed on the Au surface was observed to be hydrogenated amorphous carbon film in nature. The effects of the synchrotron beam intensity/power distribution on the structural properties of the contamination layer are discussed. The I(D)/I(G) ratio, cluster size and disordering were found to increase whereas the sp²:sp³ ratio, G peak position and H content decreased with photon dose. The structural parameters of the contamination layer in the central region were estimated (thickness ? 400 Å, roughness ? 60 Å, density ? 72% of bulk graphitic carbon density) by soft X‐ray reflectivity measurements. The amorphous nature of the layer in the central region was observed by grazing‐incidence X‐ray diffraction.     

Spectroscopic and structural investigations of α‐, β‐, and γ‐AlH3 phases

With its reputation as a high‐energy density fuel, aluminum hydride (AlH₃) has received renewed attention as a material that is particularly suitable, not only for hydrogen storage but also for rocket propulsion. While the various phases of AlH₃ have been investigated theoretically, there is a shortage of experimental studies corroborating the theoretical findings. In response to this, we present here an investigation of these compounds based primarily on two research areas in which there is the greatest scarcity of information in the literature, namely Raman and infrared (IR) absorption analysis. To the authors' knowledge, this is the first report of experimental far‐IR absorption results on these compounds. Two different samples prepared by broadly similar ethereal reactions of AlCl₃ with LiAlH₄ were analyzed. Both Raman and IR absorption measurements indicate that one sample is purely γ‐AlH₃ and that the other is a mixture of α‐, β‐, and γ‐AlH₃ phases. X‐ray diffraction confirms the spectroscopic findings, most notably for the β‐AlH₃ phase, for which optical spectroscopic data are reported here for the first time. Copyright © 2010 John Wiley & Sons, Ltd.     

A large‐solid‐angle X‐ray Raman scattering spectrometer at ID20 of the European Synchrotron Radiation Facility

An end‐station for X‐ray Raman scattering spectroscopy at beamline ID20 of the European Synchrotron Radiation Facility is described. This end‐station is dedicated to the study of shallow core electronic excitations using non‐resonant inelastic X‐ray scattering. The spectrometer has 72 spherically bent analyzer crystals arranged in six modular groups of 12 analyzer crystals each for a combined maximum flexibility and large solid angle of detection. Each of the six analyzer modules houses one pixelated area detector allowing for X‐ray Raman scattering based imaging and efficient separation of the desired signal from the sample and spurious scattering from the often used complicated sample environments. This new end‐station provides an unprecedented instrument for X‐ray Raman scattering, which is a spectroscopic tool of great interest for the study of low‐energy X‐ray absorption spectra in materials under in situ conditions, such as in operando batteries and fuel cells, in situ catalytic reactions, and extreme pressure and temperature conditions.     

Spectroscopic study of phase transitions in dolomite mineral

The process and the formation of new minerals upon heating carbonate rocks containing clay minerals together with dolomite are determined by thermal analysis, X‐ray diffraction (XRD), infrared and Raman spectroscopy. The dolomite–calcite–calcium oxide phase transition sequences were followed up to 947 °C in a naturally occurring dolomite sample. The spectral variations of the internal modes of the carbonate trigonal (ν₁, ν₂, ν₃ and ν₄) were used to probe the structural phase transitions. A new Raman mode emerged at 1090 cm⁻¹ in the ν₁ mode region, and infrared modes emerged at 713, 874, and 1420 cm⁻¹ in the ν₄, ν₂ and ν₃ regions at 750 °C, indicating the onset of the dolomite phase. The calcium oxide phase, (which on reaction with atmospheric water forms portlandite) with an onset temperature of around 950 °C, was also characterized by the appearance of the infrared mode around 450 cm⁻¹. The minerals, which were formed upon heating the dolomite, were calcite, calcium oxide and diopside. Copyright © 2007 John Wiley & Sons, Ltd.     

Coherent X‐ray scattering beamline at port 9C of Pohang Light Source II

The coherent X‐ray scattering beamline at the 9C port of the upgraded Pohang Light Source (PLS‐II) at Pohang Accelerator Laboratory in Korea is introduced. This beamline provides X‐rays of 5–20 keV, and targets coherent X‐ray experiments such as coherent diffraction imaging and X‐ray photon correlation spectroscopy. The main parameters of the beamline are summarized, and some preliminary experimental results are described.     

The use of chromium minerals in the 4th–3rd century BC China? A preliminary study of a bronze Pan unearthed from Jiuliandun Graves,Hubei Province,central southern China

A bronze Pan (water vessel), dating back to the 4th–3rd century BC, was excavated at Jiuliandun in Hubei Province, central southern China, in 2002. The Pan attracts wide attention among the Chinese archaeologists and conservators for its uniqueness in style and color, which turns out to be due to a black‐brown film of about 1 mm thickness. In the present work, a combined use of X‐ray fluorescence (XRF), micro‐Raman, and X‐ray diffraction (XRD) was employed to determine both chemical and physical compositions of the Pan's film. The results are summarized as follows: (1) The film, as XRF analysis indicates, has high concentrations of chromium (Cr) and iron (Fe); (2) Both Raman and XRD analyses suggest that the element Cr probably exists in the film mainly in the form of chromium oxide (Cr₂O₃). Raman analysis also implies the presence of PbCrO₄·PbO in the film; (3) XRD analysis suggests that the element Fe exists in the film in the form of magnetite (Fe₃O₄). Based on these analytical results and Chinese historical records, we propose that, as early as in the 3rd century BC, people in central southern China might have discovered and intentionally used chromium minerals for bronze surface treatment (such as coating). The source of chromium minerals used in this period was likely Cr‐spinel minerals from meteorites. More work remains to be done to test the possibility of using Cr‐spinel minerals for bronze production and decoration. Other issues, such as the possibility of forming a chromium‐rich film during the underground burial, also need to be solved. Copyright © 2011 John Wiley & Sons, Ltd.     

An attempt at kidney stone analysis with the application of synchrotron radiation

X‐ray absorption near‐edge spectroscopy (XANES) is a spectroscopic technique using synchrotron light to determine the valence state of excited atoms as well as the electronegativity of their neighbouring atoms. XANES spectra can provide information about the chemical bond in the second coordination shell of the excited atom. In this study, XANES spectra of unknown compounds from human kidney stones were recorded around the K‐edges of sulfur, phosphorus and calcium. The XANES results agree well with the diffractogram data of the same stones obtained through an X‐ray powder diffraction (XRPD) technique. By comparing the measurement techniques presented here, it is shown that XANES requires a smaller amount of each sample than XRPD for analysis.     

Structural,thermal and optical study of nanocrystalline silicon produced by ball milling

The ball milling process was used to obtain nanocrystalline cubic silicon. Between 5 and 10 h of milling, amorphous silicon was also formed. The differential scanning calorimetry (DSC) spectrum of a powder milled for 10 h showed that the amorphous–crystalline phase transition occurs at about 450 °C. According to Raman spectroscopy and X‐ray diffraction results, volume fractions of the crystalline, interfacial and amorphous phases were about 30, 39 and 31%, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Microfocus X‐ray scattering and micro‐Raman spectroscopy: Transcrystallinity in isotactic polypropylene

Microfocus X‐ray scattering and micro Raman spectroscopy have been applied to study the β‐transcrystalline morphology in isotactic polypropylene. The transformation from the α‐ to the β‐form through the so‐called bifurcation of growth mechanism has been investigated with high spatial resolution. We found that the mixed α–β region does not present spatial correlation along the shearing direction, implying that there is no cooperative crystallization from the different β‐nucleation centres. In addition, a strong change in the lamellar orientation of the α‐form thin layer that induces the growth of the β‐crystallites has been observed for the first time. Finally, changes in the relative intensities of some selected Raman bands allowed the observation of the α–β transformation process at the molecular level.

     

The materials science X‐ray beamline BL8 at the DELTA storage ring

The hard X‐ray beamline BL8 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA is described. This beamline is dedicated to X‐ray studies in the spectral range from ～1 keV to ～25 keV photon energy. The monochromator as well as the other optical components of the beamline are optimized accordingly. The endstation comprises a six‐axis diffractometer that is capable of carrying heavy loads related to non‐ambient sample environments such as, for example, ultrahigh‐vacuum systems, high‐pressure cells or liquid‐helium cryostats. X‐ray absorption spectra from several reference compounds illustrate the performance. Besides transmission measurements, fluorescence detection for dilute sample systems as well as surface‐sensitive reflection‐mode experiments have been performed. The results show that high‐quality EXAFS data can be obtained in the quick‐scanning EXAFS mode within a few seconds of acquisition time, enabling time‐resolved in situ experiments using standard beamline equipment that is permanently available. The performance of the new beamline, especially in terms of the photon flux and energy resolution, is competitive with other insertion‐device beamlines worldwide, and several sophisticated experiments including surface‐sensitive EXAFS experiments are feasible.     

The multi‐purpose hard X‐ray beamline BL10 at the DELTA storage ring

The layout and the characteristics of the hard X‐ray beamline BL10 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA are described. This beamline is equipped with a Si(111) channel‐cut monochromator and is dedicated to X‐ray studies in the spectral range from ～4 keV to ～16 keV photon energy. There are two different endstations available. While X‐ray absorption studies in different detection modes (transmission, fluorescence, reflectivity) can be performed on a designated table, a six‐axis kappa diffractometer is installed for X‐ray scattering and reflectivity experiments. Different detector set‐ups are integrated into the beamline control software, i.e. gas‐filled ionization chambers, different photodiodes, as well as a Pilatus 2D‐detector are permanently available. The performance of the beamline is illustrated by high‐quality X‐ray absorption spectra from several reference compounds. First applications include temperature‐dependent EXAFS experiments from liquid‐nitrogen temperature in a bath cryostat up to ～660 K by using a dedicated furnace. Besides transmission measurements, fluorescence detection for dilute sample systems as well as surface‐sensitive reflection‐mode experiments are presented.     

An X‐ray Raman spectrometer for EXAFS studies on minerals: bent Laue spectrometer with 20 keV X‐rays

An X‐ray Raman spectrometer for studies of local structures in minerals is discussed. Contrary to widely adopted back‐scattering spectrometers using ≤10 keV X‐rays, a spectrometer utilizing ～20 keV X‐rays and a bent Laue analyzer is proposed. The 20 keV photons penetrate mineral samples much more deeply than 10 keV photons, so that high intensity is obtained owing to an enhancement of the scattering volume. Furthermore, a bent Laue analyzer provides a wide band‐pass and a high reflectivity, leading to a much enhanced integrated intensity. A prototype spectrometer has been constructed and performance tests carried out. The oxygen K‐edge in SiO₂ glass and crystal (α‐quartz) has been measured with energy resolutions of 4 eV (EXAFS mode) and 1.3 eV (XANES mode). Unlike methods previously adopted, it is proposed to determine the pre‐edge curve based on a theoretical Compton profile and a Monte Carlo multiple‐scattering simulation before extracting EXAFS features. It is shown that the obtained EXAFS features are reproduced fairly well by a cluster model with a minimal set of fitting parameters. The spectrometer and the data processing proposed here are readily applicable to high‐pressure studies.     

Microbiological identification by surface-enhanced Raman spectroscopy

New methods for pathogens identification are of growing interest in clinical and food sectors. The challenge remains to develop rapid methods that are more simple, reliable, and specific. Surface-enhanced Raman spectroscopy (SERS) appears to be a promising tool to compete with current untargeted identification methods. This article presents the intensive research devoted to the use of SERS for bacterial identification, from the first to the very recent published results. Compared to normal Raman spectroscopy, the introduction of nanoparticles for SERS acquisition introduces a new degree of complexity. Bacterial Raman fingerprints, which are already subject to high spectral variability for a given strain, become then very dependent on numerous experimental parameters. To overcome these limitations, several approaches have been proposed to prepare the sample, from the microbiological culture conditions to the analysis of the spectrum including the coupling of nanoparticles on the bacterial membrane. Main strategies proposed over the last 20 years are examined here and discussed in the perspective of a protocol transfer towards industry.