pinecone/core-2020-05-10-deduplication huggingface dataset:
Raman spectroscopy of gallium- and zinc-based hydrotalcites

Insight into the unique structure of hydrotalcites (HTs) has been obtained using Raman spectroscopy.  Gallium-contg. HTs of formula Zn4 Ga2(CO3)(OH)12 · xH2O (2:1 ZnGa-HT), Zn6 Ga2(CO3)(OH)16 · xH2O (3:1 ZnGa-HT) and Zn8 Ga2(CO3)(OH)18 · xH2O (4:1 ZnGa-HT) have been successfully synthesized and characterised by X-ray diffraction (XRD) and Raman spectroscopy.  The d(003) spacing varies from 7.62 Å for the 2:1 ZnGa-HT to 7.64 Å for the 3:1 ZnGa-HT.  The 4:1 ZnGa-HT showed a decrease in the d(003) spacing, compared to the 2:1 and 3:1 compds.  Raman spectroscopy complemented with selected IR data has been used to characterize the synthesized gallium-contg. HTs.  Raman bands obsd. at around 1050, 1060 and 1067 cm-1 are attributed to the sym. stretching modes of the (CO32-) units.  Multiple ν3 (CO32-) antisym. stretching modes are found between 1350 and 1520 cm-1, confirming multiple carbonate species in the HT structure.  The splitting of this mode indicates that the carbonate anion is in a perturbed state.  Raman bands obsd. at 710 and 717 cm-1 and assigned to the ν4 (CO32-) modes support the concept of multiple carbonate species in the interlayer
High-pressure Raman spectroscopic and other structural studies of hydrotalcites containing intercalated dicarboxylic acid anions

The results of pressure-tuning Raman spectroscopic, X-ray powder diffraction and solid-state 13C-NMR studies of selected dicarboxylate anions intercalated in a Mg-Al layered double hydroxide (talcite) lattice are reported. The pressure dependences of the vibrational modes are linear for pressures up to 4.6 GPa indicating that no phase transitions occur. The interlayer spacings show that the oxalate, malonate and succinate dianions are oriented perpendicular to the layers, but the glutarate and adipate are tilted. The solid-state 13C-NMR spectra of these materials show full chemical shift anisotropy and, therefore, the anions are not mobile at room temperature
Raman spectroscopic study of the minerals diadochite and destinezite\ud
Fe3+2(PO4,SO4)2(OH)•6H2O – implications for soil science

The two minerals diadochite and destinezite of formula Fe2(PO4,SO4)2(OH)•6H2O have been characterised by Raman spectroscopy and complimented with infrared spectroscopy.  These two minerals are both found in soils and are identical except for their morphology. Diadochite is amorphous whereas destinezite is highly crystalline. The spectra of diadochite are broad and ill-defined, whereas the spectra of destinezite are intense and well defined. Bands are assigned to phosphate and sulphate stretching and bending modes. Two symmetric stretching modes for both the phosphate and sulphate symmetric stretching modes support the concept of non-equivalent phosphate and sulphate units in the mineral structure.  Multiple water bending and stretching modes imply that non-equivalent water molecules in the structure exist with different hydrogen bond strengths
A Raman spectroscopic study of bukovskýite Fe2(AsO4)(SO4)(OH)•7H2O-a mineral phase with a significant role in arsenic migration

The Raman spectrum of bukovskýite, Fe3+2(OH)(SO4)(AsO4)•7H2O has been studied and compared with the Raman spectrum of an amorphous gel containing specifically Fe, As and S elements and is understood as an intermediate product in the formation of bukovskýite. Observed bands are assigned to the stretching and bending vibrations of (SO4)2- and (AsO4)3- units, stretching and bending vibrations and librational modes of hydrogen bonded water molecules, stretching and bending vibrations of hydrogen bonded (OH)- ions and Fe3+-(O,OH) units. Approximate range of O-H...O hydrogen bond lengths is inferred from the Raman spectra. Raman spectra of crystalline bukovskýite and of the amorphous gel differ in that the bukovskýite spectrum is more complex, observed bands are sharp, the degenerate bands of (SO4)2- and (AsO4)3- are split and more intense. Lower wavenumbers of  H2O bending vibration in the spectrum of the amorphous gel may indicate the presence of weaker hydrogen bonds compared with those in bukovskýite
A Raman spectroscopic study of the different vanadate-groups in solid-state compounds, model case : mineral phases vésigniéite, BaCu3(VO4)2(OH)2, and volborthite, Cu3V2O7(OH)2•2H2O

Raman spectroscopy has been used to study vanadates in the solid state. The molecular structure of the vanadate minerals vésigniéite [BaCu3(VO4)2(OH)2] and volborthite [Cu3V2O7(OH)2·2H2O] have been studied by Raman spectroscopy and infrared spectroscopy. The spectra are related to the structure of the two minerals. The Raman spectrum of vésigniéite is characterized by two intense bands at 821 and 856 cm−1 assigned to ν1 (VO4)3− symmetric stretching modes. A series of infrared bands at 755, 787 and 899 cm−1 are assigned to the ν3 (VO4)3− antisymmetric stretching vibrational mode. Raman bands at 307 and 332 cm−1 and at 466 and 511 cm−1 are assigned to the ν2 and ν4 (VO4)3− bending modes. The Raman spectrum of volborthite is characterized by the strong band at 888 cm−1, assigned to the ν1 (VO3) symmetric stretching vibrations. Raman bands at 858 and 749 cm−1 are assigned to the ν3 (VO3) antisymmetric stretching vibrations; those at 814 cm−1 to the ν3 (VOV) antisymmetric vibrations; that at 508 cm−1 to the ν1 (VOV) symmetric stretching vibration and those at 442 and 476 cm−1 and 347 and 308 cm−1 to the ν4 (VO3) and ν2 (VO3) bending vibrations, respectively. The spectra of vésigniéite and volborthite are similar, especially in the region of skeletal vibrations, even though their crystal structures differ
Synthesis and Raman spectroscopic investigation of a new self-assembly monolayer material 4-[N-phenyl-N-(3-methylphenyl)-amino]-benzoic acid for organic light-emitting devices

We have synthesized 4-[N-phenyl-N-(3-methylphenyl)-amino]-benzoic acid (4-[PBA]) and investigated its molecular vibrations by infrared and Raman spectroscopies as well as by calculations based on the density functional theory (DFT) approach. The Fourier transform (FT) Raman, dispersive Raman and FT-IR spectra of 4-[PBA] were recorded in the solid phase. We analyzed the optimized geometric structure and energies of 4-[PBA] in the ground state. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was studied using natural bond orbital analysis. The results show that change in electron density in the δ* and π* antibonding orbitals and E 2 energies confirm the occurrence of intramolecular charge transfer within the molecule. Theoretical calculations were performed at the DFT level using the Gaussian 09 program. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution. The good agreement between the experimental and theoretical spectra allowed positive assignment of the observed vibrational absorption bands. Finally, the calculation results were applied to simulate the Raman and IR spectra of the title compound, which show agreement with the observed spectra.TÜBİTAK (TBAG-108T718
Raman spectroscopic study of the magnesium carbonate mineral– hydromagnesite Mg5[(CO3)4(OH)2]•4H2O

Magnesium minerals are important for the understanding of the concept of geosequestration.  One method of studying the hydrated hydroxy magnesium carbonate minerals is through vibrational spectroscopy.  A combination of Raman and infrared spectroscopy has been used to study the mineral hydromagnesite. An intense band is observed at 1121 cm-1 attributed CO32- ν1 symmetric stretching mode.  A series of infrared bands at 1387, 1413, 1474 cm-1 are assigned to the CO32- ν3 antisymmetric stretching modes. The CO32- ν3 antisymmetric stretching vibrations are extremely weak in the Raman spectrum and are observed at 1404, 1451, 1490 and 1520 cm-1. A series of Raman bands at 708, 716, 728, 758 cm-1 are assigned to the CO32- ν2 in-plane bending mode.  The Raman spectrum in the OH stretching region is characterised by bands at 3416, 3516 and 3447 cm-1. In the infrared spectrum a broad band is found at 2940 cm-1 assigned to water stretching vibrations. Infrared bands at 3430, 3446, 3511, 2648 and 3685 cm-1 are attributed to MgOH stretching modes
Raman spectroscopy of decrespignyite (Y,REE)4Cu(CO3)4Cl(OH)5•2(H2O) and in relation with other halogenated carbonates including bastnasite, hydroxybastnasite, parisite and northupite

Raman spectroscopy complimented with infrared spectroscopy has been used to study the rare earth based mineral decrespignyite (Y,REE)4Cu(CO3)4Cl(OH)5•2(H2O) and compared with the Raman spectra of a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The Raman spectrum of decrespignyite displays three bands are at 1056, 1070 and 1088 cm-1 attributed to the CO32- symmetric stretching vibration.  The observation of three symmetric stretching vibrations is very unusual. The position of CO32- symmetric stretching vibration varies with mineral composition. Raman bands of decrespignyite show bands at 1391, 1414, 1489 and 1547 cm-1.  Raman spectra of bastnasite, parisite and northupite show a single band at 1433, 1420 and 1554  cm-1 assigned to the ν3 (CO3)2- antisymmetric stretching mode.  The observation of additional Raman bands for the ν3 modes for some halogenated carbonates is significant in that it shows distortion of the carbonate anion in the mineral structure.  Four Raman bands are observed at 791, 815, 837 and 849 cm-1and assigned to the (CO3)2- ν2 bending modes.  Raman bands are observed for decrespignyite at 694, 718 and 746 cm-1 and are assigned to the (CO3)2- ν4 bending modes. Raman bands are observed for the carbonate ν4 in phase bending modes at 722 cm-1 for bastnasite, 736 and 684 cm-1 for parisite, 714 cm-1 for northupite.  Multiple bands are observed in the OH stretching region for decrespignyite, bastnasite and parisite indicating the presence of water and OH units in the mineral structure
Interference spectroscopy with coherent anti-Stokes Raman scattering of
  noisy broadband pulses

We propose a new technique for comparing two Raman active samples. The method
employs optical interference of the signals generated via coherent anti-Stokes
Raman scattering (CARS) of broadband laser pulses with noisy spectra. It does
not require spectrally resolved detection, and no prior knowledge about either
the Raman spectrum of the samples, or the spectrum of the incident light is
needed. We study the proposed method theoretically, and demonstrate it in a
proof-of-principle experiment on Toluene and ortho-Xylene samples.Comment: 15 pages, 6 figure
Raman spectroscopy of synthetic CaHPO4•2H2O– and in comparison with the cave mineral brushite

The mineral brushite has been synthesised by mixing calcium ions and hydrogen phosphate anions to mimic the reactions in a Cave. The vibrational spectra of the synthesised brushite were compared with that of the natural Cave mineral. Bands attributable to the PO43- and HPO42- anions are observed.  Brushite, both synthetic and natural, is characterised by an intense sharp band at 985 cm-1 with a shoulder at 1000 cm-1.  Characteristic bending modes are observed in the 300 to 600 cm-1 region.  The spectra of the synthesised brushite matches very well the spectrum of brushite from the Moorba Cave, Western Australia
Raman classification of the glass beads excavated on Mapungubwe Hill and K2, two archaeological sites in South Africa

About 200 coloured glass beads (red, yellow, green, blue, white, black, pink, plum) excavated on Mapungubwe hill and at K2, archaeological sites in the Limpopo valley South Africa, were studied with Raman scattering. This is also the most southern site in Africa where evidence for glass reworking has been found. The glass matrix of the beads was classified according to its Raman signature into three main subgroups and corroded glass could also be identified. At least seven different chromophores or pigments (lazurite, lead tin yellow type II, Ca/Pb arsenate, chromate, calcium antimonate, Fe–S ‘amber’ and a spinel) were identified. Many of the pigments were manufactured after the 13th century, confirming the presence of modern beads in the archaeological record. This calls for further research to find a way to reconcile the carbon dating of the hill, which currently gives the last occupation date on the hill as 1290 AD with the physical evidence of the modern beads excavated on the hill. The results are discussed in terms of the glass production origin of the beads (Europe, Mediterranean area, India, China).http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-4555hb2013ai201
Analysis of the composition of the passive film on iron under pitting conditions in 0.05M NaOH/NaCl using Raman microscopy in situ with anodic polarisation and MCR-ALS

The composition of the surface film formed on pure iron was investigated in a solution of 0.05M NaOH and 0.05M NaCl.
Raman spectra of the film were recorded in situ during anodic polarisation over the passive region after addition of the NaCl
to the electrolyte, under conditions of preresonance enhancement using excitation at 636.4 nm. Multivariate curve resolution
with alternating least squares analysis was applied to the spectra to measure the relative amounts of different iron oxide and
oxyhydroxides in the film at different potentials. The water content was also determined in this way from Raman spectra
recorded using excitation at 514.5 nm. It was found that the composition of the film and the amount of incorporated water
were influenced by the applied anodic potential. The results show that stable pitting can occur when the composition changes
from the primary constituents b-FeOOH and Green Complex (a hydrated, amorphous magnetite) with smaller amounts of
g-Fe2O3 and g-FeOOH, to d-FeOOH and Green Complex, simultaneously with a reduction in water content. These changes
result in conditions that favour the rate of localised breakdown of the film by Cl  ions over the rate of repassivation by water
in the passive film.The National Research Foundation under Grant number 2053306, The University of the Witwatersrand and the DST/NRF Centre of Excellence in Strong Materials.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-4555hb2016Chemistr
Effect of grain size distribution on Raman analyses and the consequences for in situ planetary missions

International audienceRaman spectroscopy can be used for analysing both mineral and organic phases, thus allowing characterisation of the microbial-scale geological context as well as the search for possible traces of life. This method is therefore very useful for in situ planetary exploration missions. Compared with the myriad of sample preparation techniques available in terrestrial laboratories, the possibilities for sample preparation during in situ missions on other planetary bodies are extremely limited and are generally restricted to abrasion of rock surfaces or crushing of the target samples. Whereas certain techniques need samples to be prepared in powder form, such as X-ray diffraction, this kind of preparation is not particularly suitable for optical microscopy and/or Raman spectroscopy. In this contribution, we examine the effects of powdering rock and mineral samples on optical observations and Raman analyses. We used a commercial Raman spectrometer, as well as a Raman laser spectrometer that simulates the instrument being developed for the future ExoMars 2018 mission. The commercial Raman spectrometer documents significant modifications to the spectra of the powdered samples, including broadening of the peaks and shifts in their position, as well as the appearance of new peaks. These effects are caused by localised heating of the sample under the laser beam and amplification of nominal surface effects due to the increase in surface area in finer grain sizes. However, most changes observed in the Raman spectra using the Raman laser spectrometer system are negligible because the relatively large (50 µm diameter) laser spot size produces lower irradiance. Furthermore, minor phases were more easily detectable in the powdered samples. Most importantly, however, this sample preparation method results in the loss of the textural features and context, making identification of potential fossilized microbial remains more problematic
Effect of Al content on the structure of Al-substituted goethite : a micro-Raman spectroscopic study

The characterization of X-ray diffraction, X-ray fluorescence, and field emission scanning electron microscope were used to confirm the successful preparation of Al-substituted goethite with different Al content. The micro-Raman spectroscopy was utilized to investigate the effect of Al content on the goethite lattice. The results show that all the feature bands of goethite shifted to high wavenumbers after the occurrence of Al substitution for Fe in the structure of goethite. The shift of wavenumber shows a good linear relationship as a function of increasing Al content especially for the band at 299 cm−1 (R2 = 0.9992). The in situ Raman spectroscopy of thermally treated goethite indicated that the Al substitution not only hinders the transformation of goethite, but also retarded the crystallization of thermally formed hematite. All the results indicated that Raman spectrum displayed an excellent performance in characterizing Al-substituted goethite, which implied the promising application in other substituted metal oxides or hydroxides
An acoustically enhanced gold film Raman sensor on a lithium niobate substrate

The surface enhanced Raman scattering effect has shown immense potential for detecting trace amounts of explosive vapor molecules. To date, efforts to produce a commercially available, reliable SERS sensor have been impeded by an inability to separate the electromagnetic enhancement produced by the metallic nanostructure from other signal enhancing effects. Here, we show a new Raman sensor that uses surface acoustic waves (SAWs) to produce controllable surface structures on gold films deposited on LiNbO3 substrates that modulate the Raman signal of a target compound (thiophenol) adsorbed on the films. We\ud
demonstrate that this sensor can dynamically control the Raman signal simply by changing the SAW’s amplitude, allowing the Raman signal enhancement factor to be directly measured with no variation in the concentration of the target compound. The physically adsorbed molecules can be removed from the sensor without physical cleaning or damage, making it possible to reuse it for real-time Raman detection
Estimating the concentrations of pigments and binders in lead-based paints using FT-Raman spectroscopy and principal component analysis

Understanding the composition of the paints used on works of art is crucial in attributing them to the artist or workshop that created them, as well as to devising strategies for their preservation and restoration. Much current research is focussed on the development of non-invasive spectroscopic methods, enabling in situ paint analysis without the need for sampling. However, whilst a lot of work has been carried out on looking at the composition of artists' materials qualitatively, little has been performed to analyse them quantitatively. In this work, we investigate the use of Fourier transform Raman spectroscopy, in isolation and in conjunction with complementary fibre optic reflectance spectroscopy, to look at the spectral changes that occur with varying the paint/binder ratio in model historic lead-based paints. When used in conjunction with multivariate analysis, we demonstrate that it can be possible to obtain a semi-quantitative estimation of the composition of a paint film from its Fourier transform Raman spectrum, given a set of suitable reference spectra recorded from paints produced within the workable mixture range. This represents a tentative first step towards a semi-automated and quantitative method for analysing cultural heritage objects, which may help boost our understanding of their history, and enable conservators to make more informed decisions so as to ensure their preservation
Confocal Raman spectroscopy to monitor intracellular penetration of TiO2 nanoparticles

Confocal Raman microscopy, a noninvasive, label-free, and high-spatial resolution imaging technique, in combination with K-mean cluster analysis and a correlation coefficient map, was employed to trace titanium dioxide (TiO2) nanoparticles in living MCF-7 and TERT cells. The penetration of TiO2 nanoparticles into cells revealed a gradual time-dependent diffusion of nanoparticles over the entire cell. Cell apoptosis was monitored by tracing cytochrome c diffusion into the cytoplasm. A comparison with the mitochondrial clustering indicated that cytochrome c was inside the mitochondria for TiO2 concentration of 2 mu gml(-1). This result demonstrates that the presence of TiO2 particles within a cell does not induce apoptosis. We demonstrated that confocal Raman microscopy allow to follow penetration of TiO2 particles in cell and to monitor the apoptotic status of the penetrated cells. Copyright (c) 2014 John Wiley & Sons, Ltd
A Fourier transform Raman spectrometer with visible laser excitation

We present the development and performance of a Fourier transformation (FT)
based Raman spectrometer working with visible laser (532 nm) excitation. It is
generally thought that FT-Raman spectrometers are not viable in the visible
range where shot-noise limits the detector performance and therein they are
outperformed by grating based, dispersive ones. We show that contrary to this
common belief, the recent advances of high-performance interference filters
makes the FT-Raman design a valid alternative to dispersive Raman spectrometers
for samples which do not luminesce. We critically compare the performance of
our spectrometer to two dispersive ones: a home-built single channel and a
state-of-the-art CCD based instruments. We demonstrate a similar or even better
sensitivity than the CCD based dispersive spectrometer particularly when the
laser power density is considered. The instrument possesses all the known
advantages of the FT principle of spectral accuracy, high throughput, and
economic design. We also discuss the general considerations which helps the
community reassess the utility of the different Raman spectrometer designs
Eye-safe UV stand-off Raman spectroscopy for the ranged detection of explosives in the field

Increasing worldwide terrorist attacks involving explosives presents a growing need for a rapid and ranged explosive detection method that can safely be deployed in the field. Stand-off Raman spectroscopy shows great promise; however, the radiant exposures of lasers required for adequate signal generation are often much greater than what is safe for the eye or the skin, restricting use of the technique to un-populated areas. Here, by determining the safe exposure levels for lasers typically used in Raman spectroscopy, optimal parameter values are identified, which produce the largest possible detection range using power densities that do not exceed the eye-safe limit. It is shown that safe ultraviolet pulse energies can be more than three orders of magnitude greater than equivalent safe visible pulse energies. Coupling this to the 16-fold increase in Raman signal obtained in the ultraviolet at 266 nm over that at 532 nm results in a 131 times larger detection range for the eye-safe 266-nm system over an equivalent eye-safe 532-nm laser system. For the Raman system described here, this translates to a maximum range of 42 m for detecting Teflon with a 266-nm laser emitting a 100-mm diameter beam of 23.5-mJ nanosecond pulses