Non‐destructive characterization of 17th century painted silk banner by the combined use of Raman and XRF portable systems

X‐ray fluorescence spectroscopy (XRF) and Raman spectroscopy analysis were performed to examine a 17th century painted silk banner in order to characterize the pigments and materials used. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the used compounds. The paint layer, ground layer under gilding, and gilding layer were investigated. For the studied object, vermilion (HgS), lead white (2PbCO₃ · Pb(OH)₂), red lead (Pb₃O₄), and aurichalcite ((Cu,Zn)₅(CO₃)₂(OH)₆) were found. The presence of silver and gold foils was confirmed. The techniques used in the analysis were portable, non‐destructive, and non‐invasive, which is very desirable when analyzing cultural heritage objects. The obtained results were used by the conservators to develop a showcase prototype for safe exhibition. Copyright © 2015 John Wiley & Sons, Ltd.     

Raman and surface enhanced Raman scattering of a black dyed silk

The Raman and surface enhanced Raman scattering (SERS) spectra of a black dyed silk sample (BDS) were registered. The spectral analysis was performed on the basis of Raman and SERS spectral data of isolated samples of Bombyx mori silk fibroin, its motif peptide component (GAGAGS) and the synthetic reactive black 5 dye (RB5). The macro FT‐Raman spectrum of the silk sample is consistent with a silk II‐Cp crystalline fraction of Bombyx mori silk fibroin; the SERS spectrum is highly consistent with conformational modifications of the fibroin due to the interactions with the Ag nanoparticles. The GAGAGS peptide sequence dominates the Raman spectrum of the silk. The SERS spectrum of the peptide suggests a random coil conformation imposed by the surface interaction; the serine residue in the new conformation is exposed to the surface. Quantum chemical calculations for a model of the GAGAGS–Ag surface predict a nearly extended conformation at the Ag surface. The Raman spectrum of the dye was analysed, and a complete band assignment was proposed; it was not possible to propose a preferential orientation or organization of the molecule on the metal surface. Quantum chemical calculations for a model of the dye interacting with a silver surface predict a rather coplanar orientation of the RB5 on the Ag metal surface. The Raman spectrum of the BDS sample is dominated by signals from the dye; the general spectral behaviour indicates that the dye mainly interacts with the silk through the sulphone (–SO₂–) and sulphonate (–SO₂–O–) groups. Besides the presence of dye signals, mainly ascribed to the sulphone and sulphonate bands, the SERS spectrum of the BDS sample also displays bands belonging to the amino acids alanine, glycine, serine and particularly tyrosine. Copyright © 2013 John Wiley & Sons, Ltd.     

Microanalysis of clay‐based pigments in painted artworks by the means of Raman spectroscopy

FT Raman spectroscopy and micro‐Raman spectroscopy with lasers of three different wavelengths (1064 nm, 785 nm and 532 nm) were used for analysis of reference samples of natural clay pigments including white clay minerals (kaolinite, illite, montmorillonite), green earths (glauconite and celadonite) and red earths (natural mixtures of white clay minerals with hematite). In addition, eight micro‐samples obtained from historical paintings containing clay pigments in ground and colour layers have been examined. Powder X‐ray diffraction and micro‐diffraction were used as supplementary methods. It was found that laser operating at 1064 nm provided the best quality Raman spectra for distinguishing different white clay minerals, but the spectra of green and red earths were affected by strong fluorescence caused by the presence of iron. Green earth minerals could be easily distinguished by 532 or 785 nm excitation lasers, even in small concentrations in the paint layers. On the other hand, when anatase (TiO₂) or iron oxides (such as hematite) were present as admixtures (both are quite common, particularly in red earths), the collection of characteristic spectra of clay minerals which form the main component of the layer was hindered or even prevented. Another complicating factor was the fluorescence produced by organic binders when analysing the micro‐samples of artworks. In those cases, it is always necessary to use powder X‐ray micro‐diffraction to avoid misleading interpretations of the pigment's composition. Copyright © 2013 John Wiley & Sons, Ltd.     

拉曼光谱法结合薄层层析分析红酵母色素

利用薄层层析色谱法分离红酵母色素,结果显示,红酵母细胞能合成至少三种色素,即β-胡萝卜素、红酵母红素、圆酵母红素;采集三种色素的拉曼光谱,光谱数据经过背景扣除、基线校正、三点平滑等方法预处理,统计不同色素的平均光谱,结果表明三种色素的CC拉曼位移不同,并且β-胡萝卜素的拉曼位移最多,红酵母红素和圆酵母红素的含量较多;定量分析色素特征峰高比值,各色素峰高比值差异不大,峰高比值能用作参数,为深入研究活体细胞内色素的相对含量提供参考。以上结果表明,拉曼光谱法结合薄层层析能够分析红酵母色素,可以提供红酵母色素的丰富信息,是研究色素的有效方法。     

Spectroscopic investigation of modern pigments on purportedly medieval miniatures by the ‘Spanish Forger’

Five miniatures by the so‐called ‘Spanish Forger’ were acquired by the Victoria and Albert Museum in 2008. Believed to be authentic medieval miniatures until the mid‐twentieth century, they are now considered to have been painted around the end of the nineteenth and the beginning of the twentieth century. To investigate this attribution and to gather detailed knowledge about the materials used by the artist, a comprehensive pigment analysis by Raman microscopy and X‐ray fluorescence was carried out. Although traditional materials such as vermilion, carbon black, red lead, lead white and indigo were identified, many others (chrome yellow, Scheele's green, emerald green and ultramarine blue) are modern and synthetic pigments, a result which provides a firm scientific basis for stating that the miniatures are forgeries. Copyright © 2009 John Wiley & Sons, Ltd.     

An integrated Raman and petrographic characterization of Italian mediaeval artifacts in pietra ollare (soapstone)

Ten fragments of pots made by pietra ollare (basic and ultrabasic metamorphic rocks belonging to greenschist facies) found in the archaeological site of Crocetta di Sant'Agata Bolognese (Bologna, Italy) have been studied to characterize them and to define their provenance. The fragments, dated between the 9^th and 10^th century AD, show traces of blackening from fire, indicating the use of these findings as pots by fire. The extensive use of a non‐destructive technique, Raman spectroscopy, in both laboratory and portable forms, for the provenance analysis of pietra ollare artifacts has been evaluated. Micro‐Raman spectroscopy was used for a detailed study of the main components, to identify the secondary minerals and to study the distribution of the mineral phases in the samples. The samples show schistose texture, are fine grained and consist mainly of talc and chlorite, and subordinate carbonates, oxides and serpentine. Olivine is rare. Based on the mineralogical composition, the material can be defined as chlorite and carbonate talc‐schist. Our samples of pietra ollare may be assigned to chlorite and magnesite‐bearing talc‐schists. The alpine areas of origin of this lithotype are Valtellina, Valchiavenna and Val Bregaglia. In particular, we can hypothesize that the origin of these findings is Valchiavenna, which had great commercial importance in the Middle Ages. Further measurements, obtained with a portable Raman spectrometer, directly on a quarry near Chiavenna, support our hypothesis. Copyright © 2013 John Wiley & Sons, Ltd.     

Nanomechanics of single silkworm and spider fibres: a Raman and micro‐mechanical in situ study of the conformation change with stress

The combination of micro‐Raman spectroscopy and an advanced universal fibre tester (UFT) made it possible to probe at the nanoscale (through monitoring the modification of chemical bonds) the change in conformation (α‐helix, β‐sheet, etc.), macromolecular fibroin chain orientation and coupling during the application of stress, quantitatively. Different single fibres of silkworms (Bombyx mori, Gonometa rufobrunea, Gonometa postica) and a spider (Nephila madagascariensis) were tested in a dry environment and compared with the behaviour of keratin fibre. As observed previously for single keratin fibres, a direct relationship is observed between nano‐ and micro‐mechanical tensile behaviour. The phase transition plateau, well defined for some pristine B. mori fibres, disappears in degummed fibres, which indicates a structural modification and increasing disorder with chemical treatments. Stress‐controlled micro‐Raman analysis shows that a few modes involving CH₂ and/or amide groups of β‐conformation chains undergo a wavenumber softening during the elastic behaviour (∼0–3%), although most of the modes are not affected. A different behaviour is observed for modes associated with ‘ordered’ and ‘disordered’ β‐sheets and helical chains. Larger softening is observed for lattice modes with increasing stress/strain, as expected. Structural changes and relationships with mechanical behaviour are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

An assessment study of tiles from Topkapı Palace Museum with energy‐dispersive X‐ray and Raman spectrometers

A limited number of studies concerning Ottoman ceramic technology have been performed using the scanning electron microscopy‐energy dispersive X‐ray spectrometry and micro‐Raman spectroscopy techniques. The discovery of the ceramics, which were described as ‘Iznik’, at excavation sites outside of the city of Iznik, caused disagreements over the exact origin of Iznik products. In this study, bodies, glazes, and pigments of 46 tile/ceramic shards of unknown origin, which were supplied from the vaults of Topkapı Palace Museum, and two reference tile fragments, known as Kütahya products, supplied from the demolished Surp Krikor Lusavoriç church and, additionally, two Iznik reference tiles were examined using the scanning electron microscopy‐energy dispersive X‐ray spectrometry and micro‐Raman spectroscopy techniques. Results of both techniques were evaluated together for the first time to determine the power of nondestructive Raman spectroscopy technique in differentiation of Ottoman tiles. In this work, bodies of the Kütahya tiles were found to be different than Iznik and Tekfur stone‐paste bodies, which are rich in clay rather than quartz. Two different lead‐alkali glaze compositions were found for Kütahya tiles; one was rich in PbO (over 35%) and the other one was rich in alkali (PbO less than 25%). Barite inclusions were detected in the bodies and in the glazes of some Ottoman tiles, which could be the fingerprint for the Kütahya products. It was found that the under glaze red decoration is essentially a mixture of hematite and quartz in different proportions. Shades of red decoration mainly depend on the amount of hematite in the mixture. Sixteenth century tomato red decoration contains more quartz compared with 17th century dark red decoration. This study showed that a similar technology was also applied at Kütahya in the 16th century. A linear correlation was found between the position of the Raman intense stretching peak Q₃ and lead oxide content of lead‐alkali glazes, which could allow for the differentiation of Ottoman tiles based on the nondestructive Raman analysis. This study provides an important additional reference data and discussion for the Ottoman tiles. Copyright © 2011 John Wiley & Sons, Ltd.     

SERS investigation of interfacial water at a silver electrode in acetonitrile solutions

Surface-enhanced Raman scattering from a silver electrode in solution of 0.1 M LiClO₄ in acetonitrile has been analyzed as a function of applied potential. Three ν(O-H) bands associated with the interfacial water and two ν(O-H) bands associated with the OH⁻ ion species were observed depending on the electrode potential. The band at 3487 cm⁻¹ is favored at relatively positive potentials and assigned to H₂O molecules interacting with the electrode surface via the oxygen atoms. Another band at 3586 cm⁻¹ appears in a wider potential region and is assigned to the H₂O molecules with one or both of the hydrogen atoms facing the electrode surface. Additionally, evidence for the possible surface ion pair, Li⁺OH⁻, which is closely associated with H₂O molecules and the quasi-crystalline form of LiOH are also presented in this paper.     

Polymorphism incidence in commercial tablets of mebendazole: a vibrational spectroscopy investigation

Mebendazole is a broad spectrum anthelminthic drug, which is widely used in large scale deworming programmes. This active pharmaceutical ingredient exhibits three crystal forms, namely, polymorphs A, B, and C. Therapeutic trials suggested that the most stable form, polymorph A, is inactive. However, the dissolution test normally used as a quality control tool is not able to discriminate among the polymorphs of mebendazole. In this work, the ability of the vibrational spectroscopic techniques (mid and nearinfrared absorption and Raman scattering) for the identification of the crystal form of this compound is evaluated. On the basis of these observations, this methodology is applied to determine the polymorphs of MBZ used in the formulation of the commercial tablets available in the Brazilian and German markets. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman analysis assessed by Fourier‐Transformed infrared and X‐ray fluorescence spectroscopies: a multi‐analytical approach of ancient chromolithographs from the 19th century

A set of chromolithographs from the 19th century were analysed to identify the fillers and pigments used for their elaboration. Because of the delicacy of the chromolithographs, the research involved the use of Raman, Fourier‐transform infrared and energy dispersive X‐ray fluorescence spectroscopies for a complete characterization of the works on paper without removing any microsamples. Despite the high fluorescence of the samples when analyzed by Raman spectroscopy, in this paper, we demonstrated that ink spectra can be successfully enhanced by subtracting the spectra of the supporting background paper. The results of the study showed that, apparently, the lithographer used a limited range of common inorganic pigments from the 19th century (carbon black, chrome yellow, Prussian blue, red ochre, red lead and vermilion) together with organic pigments (indigo blue, gamboge and a red organic pigment). The study also found that despite the fact that during the 19th and early 20th century the use of mixtures of several pigments was a common practice, unusual admixtures were used for the preparation of some colours of the studied chromolithographs. Copyright © 2011 John Wiley & Sons, Ltd.     

On‐site analysis of Limoges enamels from sixteenth to nineteenth centuries: an attempt to differentiate between genuine artefacts and copies

A selection of 15 painted enamels, most of which belong to Limoges productions, from 1500 to 1900 A.D. , has been studied on‐site in the storage rooms of musée des Arts décoratifs in Paris. The Raman signatures of the transparent and/or opacified glass matrix are discussed and compared with those which were previously recorded on glazed pottery, enamelled and stained glasses as well as Chinese cloisonné enamels. Analysed enamels mostly belong to soda‐lime‐based glass. Three types of compositions such as soda‐lime (fifteenth to sixteenth century), soda‐rich (fifteenth, sixteenth/nineteenth centuries) and lead‐potash‐lime (sixteenth and nineteenth centuries) are identified on the basis of the Raman signature of the glaze according to the wavenumber maxima of the Si O stretching and bending multiplets. The pigment signatures are similar to those recorded on ceramic glazes and glass enamels, which proves the similarity of the technologies. Cassiterite as an opacifier and hematite red and Naples yellow pigment variations give characteristic Raman signatures. The presence of lead arsenate as a pigment opacifier in nineteenth‐century samples is confirmed. Attempts are made to establish tools for the differentiation between genuine artefacts and nineteenth‐century restoration or fakes. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman Spectroscopy Analysis of a Playing Card from the 18th Century

We present the characterization, by means of three complementary experimental techniques (optical microscopy [OM], scanning electron microscopy equipped with energy dispersive X-Ray spectroscopy [SEM-EDX], and micro-Raman spectroscopy [µRaman]), of a card belonging to a deck of the Spanish pattern made in Perú at the time of Virreinato de Perú (18th century). The objective is to obtain detailed information on the pictorial palette used for the decoration of the cards, where two basic colors, red and green, are seen. Small samples from both colored regions were analyzed.     

Identification of Raman spectra through a case‐based reasoning system: application to artistic pigments

This paper presents a methodology conceived as a support system to identify unknown materials by means of the automatic recognition of their Raman spectra. Initially, the design and implementation of the system were framed in an artistic context where the Raman spectra analyzed belong to artistic pigments. The analysis of the pigmentation used in an artwork constitutes one of the most important contributions in its global study. This paper proposes a methodology to systematically identify Raman spectra, following the way analysts usually work in their laboratory but avoiding their assessment and subjectivity. It is a three‐phase methodology that automates the spectral comparison, which is based on one of the most powerful paradigms inmachine learning: the case‐based reasoning (CBR) systems. A CBR system is able to solve a problem by using specific knowledge of previous experiences (well‐known spectral library of patterns) and finding the most similar past cases (patterns), reusing and adapting them to the new problem situation (unknown spectrum). The system results in a global signal processing methodology that includes different phases such as reducing the Raman spectral expression by means of the principal component analysis, the definition of similarity measures to objectively quantify the spectral similarity and providing a final value obtained by a fuzzy logic system that will help the analyst to take a decision. The major benefit of a Raman spectral identification system lies in offering a decision‐support tool to those who are not experts or under difficult situations with respect to Raman spectroscopy. Copyright © 2011 John Wiley & Sons, Ltd.     

Feasibility of arsenic and antimony NMR spectroscopy in solids: An investigation of some group 15 compounds

The feasibility of obtaining ⁷⁵As and ^121/123Sb NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, ^121/123Sb NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide “salts” are reflected in the measured ⁷⁵As and ¹²¹Sb nuclear quadrupole coupling constants, C_Q(⁷⁵As)=7.8 MHz and C_Q(¹²¹Sb)=159 MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of ⁷⁵As and ¹²¹Sb NMR spectra (at 154 and 215 MHz, respectively, i.e., at B₀=21.14 T) with linewidths in excess of 1 MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG).     

Raman spectroscopy of fibroblast cells from a Huntington's disease patient

ABSTRACT

We present a Raman spectroscopy case study of living fibroblast (skin) cells from a patient who developed Huntington’s disease, with fibroblasts from a healthy volunteer as a control. Spectra were processed to remove cosmic rays, had a spectrum of the quartz substrate subtracted, and were flattened to remove cellular autofluorescence. We achieved an accuracy of 95% in discriminating individual cells, and assign spectral differences to (i) the reduction of cholesterol, (ii) the reduction of lipids, and (iii) an increase in beta-sheet proteins for fibroblasts with Huntington’s disease. All these biochemical changes have been previously measured by other methods. Averages over all the cells in this study yield a difference which is extremely statistically significant [p?相似文献   

High pressure behavior of nano-crystalline CeO2 up to 35 GPa: a Raman investigation

The present paper reports the results of in situ Raman studies carried out on nano-crystalline CeO₂ up to a pressure of 35 GPa at room temperature. The material was characterized at ambient conditions using X-ray diffraction and Raman spectroscopy and was found to have a cubic structure. We observed the Raman peak at ambient at 465 cm^?1, which is characteristic of the cubic structure of the material. The sample was pressurized using a diamond anvil cell using ruby fluorescence as the pressure monitor, and the phase evolution was tracked by Raman spectroscopy. With an increase in the applied pressure, the cubic band was seen to steadily shift to higher wavenumbers. However, we observed the appearance of a number of new peaks around a pressure of about 34.7 GPa. CeO₂ was found to undergo a phase transition to an orthorhombic α -PbCl₂-type structure at this pressure. With the release of the applied pressure, the observed peaks steadily shift to lower wavenumbers. On decompression, the high pressure phase existed down to a total release of pressure.     

Surface enhanced Raman spectroscopic investigation of orchil dyed wool from Roccella tinctoria and Lasallia pustulata

In this work Raman spectroscopic techniques have been utilized to characterize the vibrational spectral features of orchil dyed wool samples. Specifically, it is noted by surface enhanced Raman spectroscopy that wool dyed purple with two historically used orchil species (Roccella tinctoria and Lasallia pustulata) show spectral differences possibly owing to their specific dye‐precursor constituents. The additional natural dyestuff woad (Isatis tinctoria L.) overdyeing the R. tinctoria orchil dyed wool is a further challenge when distinguishing the mixed dye components given by the co‐adsorption of the dyestuffs as permitted by the selection rules of surface enhanced Raman spectroscopy. Furthermore, the effects of dilution of the L. pustulata species in its spectral detection have been assessed along with the evaluation of subsequent lichen extract boiling before dyeing which resulted in the detection of a degraded form of the orchil dye. Proof of concept included the surface enhanced Raman spectroscopy (SERS) investigation of a purple dyed tapestry (XVI century) which permitted an aged orchil dye to be determined. This contribution utilizes SERS as a fast, reproducible and specific method for both orchil dye detection and alteration induced by degradation. Copyright © 2014 John Wiley & Sons, Ltd.     

An investigation into the relaxation of the conformers of butan-2-ol in a supersonic expansion

The behavior of the chiral secondary alcohol butan-2-ol in both helium and argon-based supersonic expansions has been investigated by a combination of high-resolution microwave spectroscopy and ab initio molecular structure calculations. The study extends and complements a previous investigation that concentrated solely on an argon-based expansion. The spectrum of the helium-based expansion has been shown to contain at least six conformers of butan-2-ol, indicating a marked difference from the spectrum of the argon-based system, which has been shown to consist of contributions from only three. This indicates a difference in the relative abilities of the two gases to produce efficient conformer relaxation. By consideration of the calculated barriers to inter-conversion between the various conformers, we are able to show that this behavior is qualitatively consistent with previous observations of similar systems and a few remarks regarding the likely cause of this behavior are also made.Finally, we have been able to identify and characterize the four ¹³C isotopomers of the lowest energy butan-2-ol conformer and to perform a Kraitchmann-type analysis to confirm the conformation of the carbon chain in this species.     

X-ray photoelectron spectroscopy and Raman microscopy of a ferroan platinum crystal from the Kondyor Massif,Russian Far East

X-ray Photoelectron Spectroscopy was used to study a ferroan platinum crystal from the Kondyor Massif, Russian Far East. Prior to the X-ray Photoelectron Spectroscopic analyses, the nature of the crystal was confirmed by X-ray diffraction. The survey scan showed mainly the presence of Pt and Fe, with smaller amounts of O and Si. The high resolutions spectra of the Pt 4f and Fe 2p showed 18.3 atom% Fe in the crystal, which puts the composition on the lower boundary for ferroan platinum and confirms earlier analyses using other methods such as Scanning Electron Microscopy-Energy Dispersive X-ray analysis/microprobe. The binding energy of the Pt 4f5/2 was 74.0?eV and Pt 4f7/2 70.5?eV, while the Fe 2p3/2 for metallic Fe was observed at 707.2?eV. The Fe 2p3/2 for metallic Fe was significantly sharper than that of Fe 2p3/2 at 710.7?eV associated with surface material. The Raman spectrum was dominated by the Pt–Pt stretching mode at 253?cm^?1. Changed orientation resulted in the observation of two bands at 127 and 139?cm^?1, interpreted as being due to stretching modes of two Pt–Pt bonds with the third bond to Fe and Pt fixed. The presence of Ca-Fe-Al-Mg-Si-O on the surface was probably associated with the presence of a clinopyroxene. These minerals can be expected since the crystal came originally from a clinopyroxenite-dunite matrix. The spectra showed a variety of interferences, e.g. Al 2p with Pt 4f, Mg 2p with Fe 3p, and Ca 2p1/2 with Mg Auger, making exact determinations of the ratios of these elements difficult.