A pigment (CuS) identified by micro‐Raman spectroscopy on a Chinese funerary lacquer ware of West Han Dynasty

A blue pigment was identified by micro‐Raman spectroscopy, X‐ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM)/energy dispersive X‐ray (EDX) and X‐ray diffraction (XRD). The test sample, a funerary lacquer tray, belongs to West Han Dynasty (206 BC–AD 8) of China and was decorated with faint blue patterns. The result from Raman spectroscopy showed that the faint blue is covellite (CuS) due to the presence of a characteristic peak at 474.5 cm⁻¹, which further was confirmed by XRF, SEM–EDX and XRD. This research indicated that CuS had been used as a blue pigment to decorate lacquer wares from the West Han Dynasty in China. Copyright © 2009 John Wiley & Sons, Ltd.     

A study on red lead degradation in a medieval manuscript Lorvão Apocalypse (1189)

The mechanisms of red lead degradation were studied in a medieval Portuguese codex, Lorvão Apocalypse (1189), by Raman microscopy (µ‐Raman) and micro‐X‐ray diffraction (µ‐XRD). The range of pigments found for the illuminations is mainly limited to vermilion, orpiment and red lead. Micro‐Fourier transform infrared spectroscopy (µ‐FTIR) determined that the pigments were applied in a proteinaceous binding medium. In the red and orange colours, arsenic (As) was determined, by micro‐energy dispersive X‐ray fluorescence (µ‐EDXRF), to be ranging 1–4% (wt %). For those colours, lead white and calcium carbonate were found as fillers whereas orpiment was applied as a pure pigment. Raman microscopy identified, unequivocally, the degradation product of red lead as galena [lead (II) sulphide, PbS]. To determine the main factors affecting red lead degradation, a set of accelerating ageing experiments was designed to assess the influence of extenders and of the two other pigments, vermilion and orpiment. The experiments were followed by µ‐Raman, µ‐EDXRF and XRD. Raman microscopy results for the simulation of degradation of red lead, in the presence of orpiment, are in agreement to what was found in the Lorvão Apocalypse, galena being the main degradation product; also in common is a Raman band at ca. 810 cm⁻¹, which was attributed to a lead arsenate compound. It was concluded that in Lorvão Apocalypse, the degradation of red lead was a result of its reaction with orpiment. Copyright © 2009 John Wiley & Sons, Ltd.     

New insights into the colour origin of archaeological Egyptian blue and green by XAFS at the Cu K‐edge

New results on the local chemical environment of Cu²⁺ in archaeological Egyptian blue and green and also modern Egyptian green were obtained by x‐ray absorption fine structure (XAFS) analysis. The information is essential for the understanding of the colouring mechanisms in both pigments. In a previous study, a clear physico‐chemical characterisation of Egyptian blue and green was achieved using a complementary analytical approach with ancient and modern synthesized pigments. Electron microscopy (SEM–EDX and TEM), x‐ray diffraction and micro‐Raman and UV–visible spectroscopy were used to gain information about the conditions of the ancient Egyptian fabrication processes and permitted the clear distinction of both pigments. However, the exact colouring mechanisms could not be elucidated by these methods. Different Cu‐bearing amorphous and crystalline phases were found in both pigments. These phases should be at the origin of the blue and turquoise colours. Using XAFS data at the Cu K‐edge, new insights into the origin of the colouring mechanisms of both pigments could be obtained from the precision of the Cu speciation. In Egyptian blue, Cu²⁺ is mainly allocated in a square‐planar site in a crystalline cuprorivaite phase, whereas in Egyptian green, Cu²⁺ is basically situated in a distorted octahedral site in an amorphous phase. Copyright © 2006 John Wiley & Sons, Ltd.     

Characterization of colorants and opacifiers in roman glass mosaic tesserae through spectroscopic and spectrometric techniques

Several glass mosaic tesserae were recovered during the archeological excavation of the thermal baths at the ‘Villa dei Quintili’ in Rome and dated to the second century ad . This work reports the results of an archeometrical investigation performed, through a multi‐technique approach, on 19 colored opaque tesserae. The aims of the study were (1) the characterization of coloring and opacifying agents used for the production of the glass tesserae and (2) the definition of the technological processes involved. Colorimetric measurements allowed us to classify the tesserae in color groups, while the glassy matrix and the dispersed crystallites were characterized in detail through micro‐Raman spectroscopy, field emission scanning electron microscopy with energy dispersive X‐ray spectroscopy, laser ablation‐inductively coupled plasma‐mass spectrometry, and X‐ray powder diffraction analyses. Most of the glass shows the typical soda‐lime‐silicate composition (except for the orange and red tesserae). Raman results and elemental analysis prove the use of Sn–Pb antimonates to create yellow glass and of Ca‐antimonates for the white tesserae. A mixture of Sn–Pb antimonates and copper ions was used to obtain the emerald green color, while Ca‐antimonates were employed in both copper‐colored and cobalt‐colored blue glass to obtain different shades (blue‐green, dark, and light blue). X‐ray powder diffraction analyses reveal the presence of metallic copper (Cu⁰) and Cu₂O particles (cuprite) in red and orange tesserae, respectively. These results confirm the high technological level reached by the glassmakers of the Imperial Age. Copyright © 2014 John Wiley & Sons, Ltd.     

Micro‐EDXRF investigation of Chalcolithic gold ornaments from Portuguese Estremadura

Chalcolithic gold artefacts assigned to the Bell Beaker Culture in Portuguese Estremadura were analysed by micro‐energy dispersive X‐ray fluorescence spectrometry. These high‐status jewels comprise beads of tubular, spiral and double‐conical type, a spiral ring and a wire fragment. The collection is mainly composed of gold with 8.7–16.3 wt% Ag and <0.04 wt% Cu. Additionally, there is a typologically uncommon double‐conical bead showing a lower Ag content (6.7 wt%). The relative intensity of the Ag‐Kα and Ag‐Lα X‐rays from artefacts established the existence of a surface layer depleted in silver, while the reasonable effective penetration depth of the Ag‐Kα (about 25–30 μm) provided suitable results for such high fineness gold alloys. A uniform Au–Ag composition at the joint indicates that the double‐conical bead was made by joining two sheets without solder. Overall, the collection shows a composition that is similar to known Chalcolithic gold in Portuguese Estremadura but different from coeval gold in Southwestern Iberian Peninsula. The distinct compositional pattern of Chalcolithic gold in Portuguese Estremadura seems to be inconsistent with the natural variability of silver content in alluvial deposits of gold in Iberian Peninsula, thus suggesting a continuous use of particular sources and limited exchange of nuggets and jewels with the neighbouring region. Copyright © 2017 John Wiley & Sons, Ltd.     

On‐site Raman and XRF analysis of Japanese/Chinese bronze/brass patina – the search for specific Raman signatures

The assignment of Asian bronzes and brasses is difficult because the copies of ancient pieces have been made a long time ago in different countries. A selection of 30 Japanese and/or Chinese bronzes/brasses are studied on‐site in the storage and exhibition rooms of the Cernuschi Museum, in Paris, using portable Raman and X‐ray fluorescence spectrometers. Attempts are made to identify specific Raman signatures of the patina to detect similarity in a nondestructive procedure. X‐ray fluorescence measurements allow an identification of two brass artefacts and different types of bronze, including lead‐rich and mixed lead–tin–zinc‐rich compositions. The following phases are identified: CuO, Cu₂O, Cu₂S, tin oxides, ZnO, Cu₃(OH)₄SO₄, Cu₄(OH)₆SO₄, 3PbOPbSO₄ H₂O, PbSO₄/PbO, Pb(AsO₄)₃Cl, HgO/HgS. Relics of the mould, retained as concretions at the artefact surface are also identified: TiO₂, SiO₂, and different soda(−lime) glasses. Patina with very similar colour and habit may have different Raman signatures. This study offers tools to classify the artefacts in a noninvasive way. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Micro‐Raman spectroscopic study of cord‐marked pottery decorated with red coatings from Taiwan,ca 2600–1700 B.C.

Micro‐Raman spectroscopy is applied for the first time to identify mineralogical characteristics of ceramic bodies and red coatings on decorative cord‐marked pottery (ca 2600–1700 B.C.) from an archeological site in northern Taiwan. X‐ray diffraction and scanning electron microscopy‐energy dispersive X‐ray spectrometry were used as complementary techniques. The combined results of mineralogical and elemental composition suggest that the pottery items were produced from illitic clays and fired to a temperature less than 800 °C under oxidizing conditions. The slight discrepancy in composition between the red coatings and ceramic bodies possibly indicates a somewhat different source of raw materials and/or clay refining processes used by ancient potters. Additionally, feldspar, hornblende, and pyroxenes detected in the samples are closely related to the main compositions of nearby volcanic rocks, implying that the raw materials could have come from a local source. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman investigation of polymorphism in 1,1,4,4‐tetraphenyl‐butadiene

We present a Raman investigation of polymorphism in 1,1,4,4‐tetraphenyl‐butadiene (TPB), a well‐known blue luminescent molecule, which retains its emissive properties in the solid state. The use of low‐wavenumber (10–150 cm⁻¹) Raman microscopy, very sensitive to the crystal packing, allows us to single and pick up four different polymorphs. X‐ray analysis shows that the TPB molecules assume different conformations in the various polymorphs, a fact revealed also by the Raman spectra in the region of intra‐molecular vibrations. Lattice dynamics calculations yield a preliminary assignment of the low‐wavenumber Raman spectra and provide information of the relative stability of the phases. Copyright © 2013 John Wiley & Sons, Ltd.     

Caltrop particles synthesized by photochemical reaction induced by X‐ray radiolysis

X‐ray radiolysis of a Cu(CH₃COO)₂ solution was observed to produce caltrop‐shaped particles of cupric oxide (CuO, Cu₂O), which were characterized using high‐resolution scanning electron microscopy and micro‐Raman spectrometry. X‐ray irradiation from a synchrotron source drove the room‐temperature synthesis of submicrometer‐ and micrometer‐scale cupric oxide caltrop particles from an aqueous Cu(CH₃COO)₂ solution spiked with ethanol. The size of the caltrop particles depended on the ratio of ethanol in the stock solution and the surface of the substrate. The results indicated that there were several synthetic routes to obtain caltrop particles, each associated with electron donation. The technique of X‐ray irradiation enables the rapid synthesis of caltrop cupric oxide particles compared with conventional synthetic methods.     

A simple calibration procedure of polycapillary based portable micro‐XRF spectrometers for reliable quantitative analysis of cultural heritage materials

Portable micro‐X‐ray fluorescence (micro‐XRF) spectrometers mostly utilize a polycapillary X‐ray lens along the excitation channel to collect, propagate and focus down to few tens of micrometers the X‐ray tube radiation. However, the polycapillary X‐ray lens increases the complexity of the quantification of micro‐XRF data because its transmission efficiency is strongly dependent on the lens specifications and the propagated X‐ray energy. This feature results to a significant and not easily predicted modification of the energy distribution of the primary X‐ray tube spectrum. In the present work, we propose a simple calibration procedure of the X‐ray lens transmission efficiency based on the fundamental parameters approach in XRF analysis. This analytical methodology is best suited for compact commercial and portable micro‐XRF spectrometers. The developed calibration procedure is validated through the quantitative analysis of a broad range of samples with archeological relevance such as glasses, historical copper alloys, silver and gold alloys offering an overall accuracy of less than 10%–15%. Copyright © 2015 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.     

SERS study of Ag nanoparticles electrodeposited on patterned TiO2 nanotube films

In this work, Ag nanoparticles (NPs) were deposited on patterned TiO₂ nanotube films through pulse‐current (PC) electrodeposition, and as a result patterned Ag NPs films were achieved. Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X‐ray diffraction (XRD) were used, respectively, to study the morphology, uniformity, and phase structure of the patterned Ag NP films. The size and density of the as‐deposited Ag NPs could be controlled by changing the deposition charge density, and it was found that the patterned Ag NP films produced under a charge density of 2.0 C cm⁻² gave intense UV–vis and Raman peaks. Two‐dimensional surface‐enhanced Raman scattering (SERS) mapping of rhodamine 6G (R6G) on the patterned Ag NP films demonstrated a high‐throughput, localized molecular adsorption and micropatterned SERS effect. Copyright © 2010 John Wiley & Sons, Ltd.     

Identification of pigments from the Shrine of Kaiping Diaolou by micro‐Raman spectroscopy

Shrines (or altars) are constructed in China for worshiping ancestors, Bodhisattva, and God of Wealth. In this work, pigments from the shrine of Kaiping Diaolou tower were analyzed by micro‐Raman spectroscopy, in conjunction with other analytical methods including scanning electron microscopy (SEM) with energy dispersive X‐ray spectroscopy (EDX) and X‐ray fluorescence (XRF). Paintings of the shrine were composed of 2–3 pigment layers and the total thickness was determined as about 200–300 µm by optical microscopy and SEM, indicating the fine painting skills applied in the construction of the shrine. The green pigments on the surface layer of the green fragment were identified as a mixture of lead phthalocyanine (PbPc) and cornwallite (Cu₅(AsO₄)₂(OH)₄) by XRF and micro‐Raman spectroscopy with two different excitation wavelengths (488 and 785 nm). Underneath the green layer, red and yellow ochre were found. The pigments on the surface layer of red and blue fragments were identified as hematite (Fe₂O₃) and lazurite or synthetic ultramarine [(Na₈(Al₆Si₆O₂₄)S₃)], respectively. Finally, the pigments under the two surface layers were identified by EDX and micro‐Raman spectroscopy as chromium oxide (Cr₂O₃), gypsum (CaSO₄·2H₂O) and calcite (CaCO₃). Copyright © 2011 John Wiley & Sons, Ltd.     

Temperature‐dependent Raman scattering studies of polycrystalline BiFeO3 bulk ceramics

This work reports the temperature‐dependent Raman scattering study of mutiferroic BiFeO₃ (BFO) bulk ceramics in a wide temperature range of 93–843 K. The polycrystalline samples are sintered at four different temperatures and characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), vibrating sample magnetometry, differential scanning calorimetry (DSC), and optical microscopy. The microstructure shows remarkable changes in terms of grain size and domain pattern as the sintering temperature increases. The DSC curves show prominent exothermic peaks at 645 K, the antiferromagnetic–paramagnetic phase transition temperature. The Raman spectra of all the four specimens reveal strong anomalies in the vicinity of the Neel temperature, which can be attributed to the multiferroic nature of BFO. The Raman scattering studies also reveal considerable spectral changes at a temperature range of 140–200 K in all the specimens, which can be inferred to a further spin–reorientation transition exhibited in BFO at a cryogenic temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Thickness and composition of gold and silver alloys determined by combining EDXRF‐analysis and transmission measurements

Energy‐dispersive X‐ray fluorescence (EDXRF)‐analysis is a technique which in the case of metals analyzes thin surface layers. For example, when gold and silver alloys are analyzed, it typically interests a depth of microns up to a maximum of tens of microns. Therefore, it can give wrong results or be affected by a large indetermination when the sample composition is altered because of surface processes, as often happens when silver alloys are oxidated, and sometimes in the case of gold alloys rich on copper or silver. A complementary technique was therefore developed, of bulk analysis, which uses the same equipment employed for EDXRF‐analysis; the X‐ray beam from the X‐ray tube is monochromatized by means of a tin secondary target, which K lines bracket the silver‐K discontinuity. The sample to be analyzed is positioned between the secondary target and the detector. This technique is able to determine (by measuring the attenuation of tin‐K rays) thickness and/or composition of gold and silver alloys having a thickness of less than about 120 µm for gold and about 0.7 mm for silver. The method was tested with Au–Ag–Cu alloys of known composition and thickness and then applied to gold and silver artifacts from the tomb of the Lady of Cao, which belongs to the Moche pre‐hispanic culture from the North of Peru, and dates about 300 A.D. Copyright © 2014 John Wiley & Sons, Ltd.     

EDXRF analysis of metal artefacts from the grave goods of the Royal Tomb 14 of Sipán,Peru

Several metallic sheets (about 1 mm thick) from the grave goods of the Royal Tomb 14 (Sipán, Peru) were characterised by energy dispersive X‐ray fluorescence analysis, using both a portable instrument and a capillary collimated spectrometer to investigate details, and micro‐Raman spectroscopy. The samples, belonging to the clothing of the warrior priest, resulted composed of thin copper sheets or tumbaga (natural alloy of copper, silver and gold). They were unearthed covered with typical green patina, formed during their long burial and characterised mainly by copper minerals, such as malachite, atacamite and magnetite identified with micro‐Raman spectroscopy. Due to deterioration of the original alloy, the artefacts analyzed in this work were rather fragile and could not resist hard polishing aimed at cleaning off corrosion products. So a non‐destructive qualitative EDXRF analysis was performed to identify the elemental composition of the metal alloy and a quantitative estimation was made applying the fundamental parameter method. The presence of superficial patina layer and the non‐homogeneous composition was also taken into account during calculation. The data obtained, compared to published results from several artefacts found in the nearby tombs, have been treated with a hierarchical statistic analysis. Copyright © 2011 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.     

Analysis of the Hoard of Beçin using X‐ray‐based techniques

Four hundred and sixteen silver coins stemming from the Ottoman Empire (16th and 17th centuries) were analyzed to confirm the fineness of the coinage as well as to study the provenance of the alloy used for the coins. As most of the coins showed the typical green patina on their surfaces due to corrosion processes that have led to the depletion of copper in the near surface domains of the silver coins in comparison to their core composition, small samples had to be taken, embedded in synthetic resin, and cross sectioned to investigate the true‐heart metal composition. μ‐synchrotron micro X‐ray fluorescence analysis and μ‐proton‐induced X‐ray emission were applied to determine the silver contents as well as the minor and trace elements. The type of the alloy was investigated as well as if coins minted in different locations demonstrated homogeneous traits concerning the predominant impurities (Au and Bi), which could suggest a common ore. Finally, energy‐dispersive microanalysis in a scanning electron microscope was applied to study the homogeneity/heterogeneity of the coins and the presence of surface enrichments and to explain differences between the μ‐synchrotron micro X‐ray fluorescence analysis and μ‐proton‐induced X‐ray emission measurements concerning the main component. In general, the silver content of the analyzed specimen varies between 90 and 95%. These outcomes have not supported the historical interpretations, which predict that during the period studied, a debasement of approximately 44% of the silver content of the coins should have occurred. Copyright © 2012 John Wiley & Sons, Ltd.