pinecone/core-2020-05-10-deduplication huggingface dataset:
Raman and infrared spectroscopic characterization of the arsenate-bearing mineral tangdanite– and in comparison with the discredited mineral clinotyrolite

The minerals clinotyrolite and fuxiaotuite are discredited in terms of the mineral tangdanite. The mixed anion mineral tangdanite Ca2Cu9(AsO4)4(SO4)0.5(OH)9 9H2O has been studied using a combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. These bands are assigned to water and hydroxyl stretching vibrations. Two intense Raman bands at 837 and approximately 734 cm−1 are assigned to the ν1 (AsO4)3− symmetric stretching and ν3 (AsO4)3− antisymmetric stretching modes. Infrared bands at 1023 cm−1 are assigned to the (SO4)2− ν1 symmetric stretching mode, and infrared bands at 1052, 1110 and 1132 cm−1 assigned to (SO4)2− ν3 antisymmetric stretching modes, confirming the presence of the sulphate anion in the tangdanite structure. Raman bands at 593 and 628 cm−1 are attributed to the (SO4)2− ν4 bending modes. Low-intensity Raman bands found at 457 and 472 cm−1 are assigned to the (AsO4)3− ν2 bending modes. A comparison is made with the previously obtained spectral data on the discredited mineral clinotyrolite
Raman spectroscopy of pyrite in marble from Chillagoe, Queensland

Samples of marble from Chillagoe, North Queensland have been analysed using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. Different types of marble were studied including soft white marble, hard white marble and a black marble. In this work, we try to ascertain why the black marble has this colour. Chemical analyses provide evidence for the presence of minerals other calcite in the marble, including the pyrite mineral. Some of these chemical analyses correspond to pyrite minerals in the black marble. The Raman spectra of these crystals were obtained and the Raman spectrum corresponds to that of pyrite from the RRUFF data base. The combination of SEM with EDS and Raman spectroscopy enables the characterisation of the mineral pyrite in Chillagoe black marble
Raman spectra and phase composition of MnGeO3 crystals

MnGeO3 single-crystal samples have been synthesized by optical zonal melting and spontaneous crystallization. X-ray crystal analysis showed the first sample to be a two-phase one with phase ratio as follows: 17% – monoclinic C2/c, and 83%– orthorhombic Pbca; the phase ratio of the second sample was unknown. Raman spectra have been produced for these samples. Lattice dynamics has been simulated and polarization dependencies of lines’ intensities have been analyzed to interpret experimental Raman spectra and to attribute lines to the spectra of monoclinic and orthorhombic phases
Quantitative, Comparable Coherent Anti-Stokes Raman Scattering (CARS)
  Spectroscopy: Correcting Errors in Phase Retrieval

Coherent anti-Stokes Raman scattering (CARS) microspectroscopy has
demonstrated significant potential for biological and materials imaging. To
date, however, the primary mechanism of disseminating CARS spectroscopic
information is through pseudocolor imagery, which explicitly neglects a vast
majority of the hyperspectral data. Furthermore, current paradigms in CARS
spectral processing do not lend themselves to quantitative sample-to-sample
comparability. The primary limitation stems from the need to accurately measure
the so-called nonresonant background (NRB) that is used to extract the
chemically-sensitive Raman information from the raw spectra. Measurement of the
NRB on a pixel-by-pixel basis is a nontrivial task; thus, reference NRB from
glass or water are typically utilized, resulting in error between the actual
and estimated amplitude and phase. In this manuscript, we present a new
methodology for extracting the Raman spectral features that significantly
suppresses these errors through phase detrending and scaling. Classic methods
of error-correction, such as baseline detrending, are demonstrated to be
inaccurate and to simply mask the underlying errors. The theoretical
justification is presented by re-developing the theory of phase retrieval via
the Kramers-Kronig relation, and we demonstrate that these results are also
applicable to maximum entropy method-based phase retrieval. This new
error-correction approach is experimentally applied to glycerol spectra and
tissue images, demonstrating marked consistency between spectra obtained using
different NRB estimates, and between spectra obtained on different instruments.
Additionally, in order to facilitate implementation of these approaches, we
have made many of the tools described herein available free for download.Comment: Body: 13 pages, 5 figures. Supplemental: 21 pages, 16 figure
Raman analysis of bilayer graphene film prepared on commercial Cu(0.5 at% Ni) foil

This study reports the Raman analysis of bilayer graphene films prepared on commercial dilute Cu(0.5 at% Ni) foils using atmospheric pressure chemical vapor deposition. A bilayer graphene film obtained on Cu foil is known to have small areas of bilayer (islands) with a significant fraction of non-Bernal stacking, while that obtained on Cu/Ni is known to grow over a large area with Bernal stacking. In the Raman optical microscope images, a wafer-scale monolayer and large-area bilayer graphene films were distinguished and confirmed with Raman spectra intensities ratios of 2D to G peaks. The large-area part of bilayer graphene film obtained was assisted by Ni surface segregation because Ni has higher methane decomposition rate and carbon solubility compared with Cu. The Raman data suggest a Bernal stacking order in the prepared bilayer graphene film. A four-point probe sheet resistance of graphene films confirmed a bilayer graphene film sheet resistance distinguished from that of monolayer graphene. A relatively higher Ni surface concentration in Cu(0.5 at% Ni) foil was confirmed with time-of-flight secondary ion mass spectrometry. The inhomogeneous distribution of Ni in a foil and the diverse crystallographic surface of a foil (confirmed with proton-induced X-ray emission and electron backscatter diffraction, respectively) could be a reason for incomplete wafer-scale bilayer graphene film. The Ni surface segregation in dilute Cu(0.5 at% Ni) foil has a potential to impact on atmospheric pressure chemical vapor deposition growth of large-area bilayer graphene film.The South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation (NRF) of South Africa (grant no. 97994). M.J. Madito acknowledges the financial support from University of Pretoria and NRF for his PhD studies.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-45552017-05-31Physic
Automatic classification system of Raman spectra applied to pigments analysis

Raman spectroscopy is one of the few non-destructive techniques capable of identifying pigments in art works. Raman spectra contain powerful information that can be used to identify unknown compounds and their chemical structures. However, the analysis of spectral data comes with some difficulties, and therefore the spectral interpretation is not straightforward. Sometimes, there are very little differences in the spectral data concerning to specific identification objectives, for instance, in polymorphic discrimination or in the discrimination of natural and synthetic forms of certain pigments. Moreover, this discrimination is often performed manually so that the process can be repetitive, subjective and particularly time-consuming. The result is an increasing motivation to automate the identification process involved in the classification of pigments in paint. In this paper, we propose a system to automatically classify the spectral data into specific and well-known classes, i.e. reference classes. The proposal is based on a combination of chemometric techniques, which provides a powerful way to achieve spectral separability so that it is possible to discriminate between very similar spectra in an automatic way. In this regard, a decision-making algorithm was specifically developed to select the corresponding reference class with no user input, which was successfully validated using simulated spectra. The implemented methodology was used to classify Raman spectra of pigments commonly present in artist's paints in experimental cases, providing reliable and consistent results. Therefore, the presented system can play a good auxiliary role in the analysts' endpoint classification.Peer ReviewedPostprint (author's final draft
Microcrystalline testing used in combination with Raman micro-spectroscopy for absolute identification of novel psychoactive substances

Two new psychoactive substances, namely 4-methylmethcathinone (mephedrone) and 5,6-methylenedioxy-2-aminoindane (MDAI) were analysed with a novel combination of microcrystalline tests followed by Raman micro-spectroscopy to facilitate their absolute identification. The discrimination power of the proposed combination was successfully demonstrated through the analysis of the positional isomers 2- and 3-methylmethcathinone. The addition of mercury dichloride as a microcrystalline test reagent produced specific microcrystals of each tested analyte. The robustness of the method was evaluated in the presence of common cutting agents (caffeine and benzocaine) as well as on street samples. The crystal lattice structures of mephedrone, 2-methylmethcathinone and MDAI mercury dichloride microcrystals were determined by single crystal X-ray diffraction. This confirmed the presence of both drug and reagent together in the lattice and accounts for the distinct habit of the observed microcrystals. Raman spectra of the formed microcrystals differed from those obtained from their standard salt form by loss and/or gain of some vibrational modes. Particularly important was the appearance of the mercury chloride link to each tested drug molecule which showed as strong bands at low wavenumbers. Its presence was corroborated by its detection in the crystal lattice. It was therefore concluded that microcrystalline testing followed by Raman micro-spectroscopy satisfies the technique combination requirement for psychoactive substances recommended by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) and provides a rapid and cheap analysis route. The proposed technique combination also aids the development of new microcrystalline tests as it allows for confirmation of the uniqueness of the developed microcrystals almost in-situ rather than growing single crystals for often long periods of time needed for single crystal X-ray diffraction analysis. Copyright © 2016 John Wiley & Sons, Ltd
Quantification of the degree of mixing of cellulose nanocrystals in thermoplastics using Raman spectroscopy

A combination of Raman imaging with image analysis has been used to quantify the degree of mixing of cellulose nanocrystals (CNCs) in melt compounded high density polyethylene (HDPE). Raman spectroscopy is shown to provide an accurate “fingerprint” of the composition of the crosssectional area of the end section of a formed composite. This information is then converted to a chemical image allowing spatial quantification of the mixing of CNCs in the HDPE. A degree of mixing between CNCs and HDPE is reported, with a strong tendency for the former to agglomerate with little dispersion. Freeze-dried CNCs show better mixing with HDPE and a lower tendency to agglomerate than spray-dried CNCs. This approach shows the potential to use Raman spectroscopy to quantify the degree of mixing of CNCs in a thermoplastic matrix.The authors would like to thank the EU FP7 funding programme for supporting the work under
grant agreement no 604168 (www.newspec.eu).This publication reflects the views only of the
author and the European Commission cannot be held responsible for any use which may be made
of the information contained therein
Identification of intracellular squalene in living algae, Aurantiochytrium mangrovei with hyper-spectral coherent anti-Stokes Raman microscopy using a sub-nanosecond supercontinuum laser source

We applied hyper-spectral coherent anti-Stokes Raman scattering imaging to intracellular lipid identification in living microalgae, Aurantiochytrium mangrovei 18W-13a. Two different lipids, squalene and triacylglycerol, were found inside living cells with clear vibrational contrast. Based on the endogenous lipid band as a result of the cis C[DOUBLE BOND]C stretch vibrational mode, squalene and triacylglycerol were clearly distinguished in different intracellular areas. In particular, squalene was detected solely in vacuoles as lipid particles, which was also supported by electron microscopy
Mirrored stainless steel substrate provides improved signal for Raman spectroscopy of tissue and cells.

PublishedJournal ArticleThis is the final version of the article. Available from Wiley via the DOI in this record.Raman spectroscopy (RS) is a powerful technique that permits the non-destructive chemical analysis of cells and tissues without the need for expensive and complex sample preparation. To date, samples have been routinely mounted onto calcium fluoride (CaF2) as this material possesses the desired mechanical and optical properties for analysis, but CaF2 is both expensive and brittle and this prevents the technique from being routinely adopted. Furthermore, Raman scattering is a weak phenomenon and CaF2 provides no means of increasing signal. For RS to be widely adopted, particularly in the clinical field, it is crucial that spectroscopists identify an alternative, low-cost substrate capable of providing high spectral signal to noise ratios with good spatial resolution. Results show that these desired properties are attainable when using mirrored stainless steel as a Raman substrate. When compared with CaF2, data show that stainless steel has a low background signal and provides an average signal increase of 1.43 times during tissue analysis and 1.64 times when analyzing cells. This result is attributed to a double-pass of the laser beam through the sample where the photons from the source laser and the forward scattered Raman signal are backreflected and retroreflected from the mirrored steel surface and focused towards collection optics. The spatial resolution on stainless steel is at least comparable to that on CaF2 and it is not compromised by the reflection of the laser. Steel is a fraction of the cost of CaF2 and the reflection and focusing of photons improve signal to noise ratios permitting more rapid mapping. The low cost of steel coupled with its Raman signal increasing properties and robust durability indicates that steel is an ideal substrate for biological and clinical RS as it possesses key advantages over routinely used CaF2. © 2016 The Authors. Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd.Innovate UK – ‘SMART: Stratified Medicine through Advanced Raman Technologies’
UCL/UCLH Biomedical Research Centre (BRC
Quantitative interpretation of time-resolved coherent anti-Stokes Raman
  spectroscopy with all Gaussian pulses

Coherent Raman scattering spectroscopy is studied purposely, with the
Gaussian ultrashort pulses as a hands-on elucidatory extraction tool of the
clean coherent Raman resonant spectra from the overall measured data
contaminated with the non-resonant four wave mixing background. The integral
formulae for both the coherent anti-Stokes and Stokes Raman scattering are
given in the semiclassical picture, and the closed-form solutions in terms of a
complex error function are obtained. An analytic form of maximum enhancement of
pure coherent Raman spectra at threshold time delay depending on bandwidth of
probe pulse is also obtained. The observed experimental data for pyridine in
liquid-phase are quantitatively elucidated and the inferred time-resolved
coherent Raman resonant results are reconstructed with a new insight.Comment: 4 pages, 2 figure
Iterative morphological and mollifier-based baseline correction for Raman spectra

In vivo Raman spectroscopy with low signal-to-noise ratio and strong, irregularly shaped fluorescence background imposes a challenge for automatic baseline correction methods. In this work, an approach that enables fast and efficient batch baseline correction has been developed, which is based on a morphological operation in combination with a mollifier algorithm. As this algorithm relies only on three parameters, which are determined by the given experimental conditions, it can be used for automatic and objective processing of many Raman spectra. The applicability of the baseline correction is demonstrated on resonance Raman spectra of beta-carotene mixed with fluorescent red ink as model system, on carotenoids in human skin, and on an excitation–emission map of the green alga Haematococcus pluvialis. In the future, the algorithm opens the potential for wide application in Raman spectra analysis in biological contexts. In particular, it greatly facilitates data processing in cases where special photochemical sample preparation or complex experimental baseline removal was required before. Similarly, processing data of experiments using resonant excitation techniques yielding strong fluorescence background is possible.
This is the peer reviewed version of the following article: Koch, M.; Suhr, C.; Roth, B.; Meinhardt-Wollweber, M.: Iterative morphological and mollifier-based baseline correction for Raman spectra. In: Journal of Raman Spectroscopy 48 (2016), Nr. 2, S. 336-342, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/jrs.5010/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.BMBF/MeDiOO/03V0826BMBF/03V082
Raman spectroscopy and imaging of Bernal-stacked bilayer graphene synthesized on copper foil by chemical vapour deposition : growth dependence on temperature

We report on the effect of temperature on the growth of bilayer graphene on a copper foil under atmospheric pressure chemical vapour deposition (AP-CVD). Before characterization of the AP-CVD bilayer graphene, a high-quality graphene flake was obtained from the Kish bulk graphite by micro-mechanical exfoliation and characterized by using Raman spectroscopy and imaging. The Raman data of the exfoliated, high-quality graphene flake show monolayer and bilayer graphenes and were compared with the Raman data of AP-CVD graphene. Raman spectroscopy of AP-CVD graphene shows bilayer films that exhibit predominantly Bernal stacking with an I-2D/I-G ratio of similar to 1. At low growth temperature (similar to 780 degrees C), Raman disorder-related peak intensity in the AP-CVD graphene is high and decreases with an increase in growth temperature to the lowest disorder intensity at similar to 973 degrees C. The selected area electron diffraction and atomic force microscopy average step height analysis showed the thickness of the bilayer graphene. The AP-CVD graphene is uniform at low growth temperatures (similar to 780 degrees C) with a high disorder and becomes non-uniform at high growth temperatures (similar to 867-973 degrees C) with a very low disorder as bilayer graphene evolves to form islands with an average lateral size of <10m. Competition between carbon adatoms supply through dehydrogenation of the CHx species, mobility and desorption rate of the carbon-adatom species for nucleation of the bilayer graphene as a function of temperature is elucidated. This study provides further insight into the growth mechanisms of bilayer graphene by AP-CVD on Cu.The South African Research Chairs Initiative of the South Africa Department of Science and Technology and the National Research Foundation (NRF) (grant no. 97994). MF thanks the University of Pretoria and the NRF for financial support during his PhD studies.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-45552018-05-30hj2017Physic
A method for the automated Raman spectra acquisition.

Raman spectroscopy is a very powerful analytical technique with an increasing acceptance in the scientific community. For theoptimization of the Raman acquisition, two main parameters, the integration time and the number of accumulations, need tobe adjusted to the sample under analysis, as the sample, or even different spots on the same sample, can provide very differentRaman responses one from another. In this paper, we present a suite of algorithms to automate the acquisition parameteradjustment to the sample under analysis, addressing issues such as spectral saturation, fluorescence, cosmic ray detection andremoval, and adjustment of the acquisition parameters to optimize the acquired spectral data. This suite has been developedin the framework of the Raman Laser Spectrometer (RLS) instrument development for the Exomars mission but can be appliedto any Raman spectrometer. This will allow the spectrometer to adapt to the characteristics of the sample that is being analyzed,optimizing the total operative time, while improving the usability and overall efficiency of the system. Copyright © 2017 JohnWiley & Sons, Ltd.MINECO ESP2014-56138-C3-1-
Enhanced Raman and photoluminescence response in monolayer MoS$_2$ due
  to laser healing of defects

Bound quasiparticles, negatively charged trions and neutral excitons, are
associated with the direct optical transitions at the K-points of the Brillouin
zone for monolayer MoS$_2$. The change in the carrier concentration,
surrounding dielectric constant and defect concentration can modulate the
photoluminescence and Raman spectra. Here we show that exposing the monolayer
MoS$_2$ in air to a modest laser intensity for a brief period of time enhances
simultaneously the photoluminescence (PL) intensity associated with both trions
and excitons, together with $\sim$ 3 to 5 times increase of the Raman intensity
of first and second order modes. The simultaneous increase of PL from trions
and excitons cannot be understood based only on known-scenario of depletion of
electron concentration in MoS$_2$ by adsorption of O$_2$ and H$_2$O molecules.
This is explained by laser induced healing of defect states resulting in
reduction of non-radiative Auger processes. This laser healing is corroborated
by an observed increase of intensity of both the first order and second order
2LA(M) Raman modes by a factor of $\sim$ 3 to 5. The A$_{1g}$ mode hardens by
$\sim$ 1.4 cm$^{-1}$ whereas the E$^1_{2g}$ mode softens by $\sim$ 1 cm$^{-1}$.
The second order 2LA(M) Raman mode at $\sim$ 440 cm$^{-1}$ shows an increase in
wavenumber by $\sim$ 8 cm$^{-1}$ with laser exposure. These changes are a
combined effect of change in electron concentrations and oxygen-induced lattice
displacements.Comment: 15 pages, 5 figures, Journal of Raman Spectroscopy, 201