Analysis of green copper pigments in illuminated manuscripts by micro-Raman spectroscopy

In the majority of the literature describing green coloured materials used on ancient painting layers (15th or 16th century), two copper greens are mainly cited: malachite [CuCOr3 x Cu(OH)2] and verdigris [Cu(CH3COO)2 x [Cu(OH)2]3 x 2H2O]. It is shown, by micro-Raman spectroscopy, that the artists were actually employing more than these two copper greens, in particular various copper sulfates, among which the most common pigment found is posnjakite [CuSO4 x 3Cu(OH)2 x H2O]. In contrast to the PIXE (particle induced X-ray emission) technique, Raman spectroscopy is a technique of choice, able to distinguish not only a copper sulfate from a carbonate or acetate but also the different sulfates themselves; in this respect, we found that the high wavenumber region (2800-4000 cm(-1)), characteristic of H2O vibrations, is of particular interest. It is also shown that numerous green areas were created with mixtures of a copper sulfate mixed with other pigments, for instance to enhance the colour depth. Finally, in some cases, no green pigment is actually employed but the colour is obtained by intimately mixing yellow and blue pigments. All these results led to a new look at the pigments which were in use on the palettes of the ancient artists.     

Discrimination of natural gas-related bacteria by means of micro-Raman spectroscopy

Methane-oxidizing bacteria (MOB) are a unique group of gram-negative bacteria that are proved to be biological indicator for gas prospecting since they utilize methane as a sole source of carbon and energy. Herein the feasibility of a novel and efficient gas prospecting method using Raman spectroscopy is studied. Confocal Raman spectroscopy is utilized to establish a Raman database of 11 species of methanotrophs and other closely related bacteria with similar morphology that generally coexist in the upper soil of natural gas. After strict and consistent spectral preprocessing, Raman spectra from the whole cell area are analyzed using the combination of principal component analysis (PCA) and Mahalanobis distance (MD) that allow unambiguous classification of the different cell types with an accuracy of 95.91%. The discrimination model based on multivariate analysis is further evaluated by classifying Raman spectra from independently cultivated bacteria, and achieves an overall accuracy of 94.04% on species level. Our approach using Raman spectroscopy in combination with statistical analysis of various gas reservoirs related bacteria provides rapid distinction that can potentially play a vital role in gas exploration.     

ATR and transmission analysis of pigments by means of far infrared spectroscopy

In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared (MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation. The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated on a real case study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Earth pigments in painting: characterisation and differentiation by means of FTIR spectroscopy and SEM-EDS microanalysis

Analytical characterisation of natural earths (ochres, siennas, umbers and green earths) has been carried out using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled to an energy dispersive X-Ray spectrometer (EDS). The study of these pigments, which are found in works of art, is very important since it can shed light on their source or the pictorial technique used. FTIR spectroscopy is suitable for the identification and differentiation of ochres and siennas. According to the matrix of the sample, FTIR allows the classification of ochres into ochres containing kaolinite and ochres containing sulphate. One of the goals of this research has been to establish a relationship between the matrix and the source of the samples tested. SEM-EDS is probably a better technique than FTIR for characterising umbers and green earths since they do not exhibit significant differences when FTIR studies are performed.     

Organic content evaluation of corrosion patinas in outdoor bronze monuments

Summary As opposed to inorganic composition, the characterization of organic content in patinas of bronze monuments has been neglected. Analytical pyrolysis coupled with gaschromatographyάss-spectrometry (Py/GC-MS) has been shown to be a valid and rapid technique to identify organic materials in corrosion patina of bronze monuments. In this paper six renaissance Italian outdoor bronze monuments were analyzed in order to determine organic composition of the patina. Results show the presence of both environmental organic compounds and chemicals coming from protective treatment.     

Examination of cellulose textile fibres in historical objects by micro-Raman spectroscopy

The investigation and characterisation of historical objects can be an exacting piece of work because of the small quantity of material that can be investigated and the degradation of the material and its value, which sometimes demands only non-destructive methods. In this study, as one such method, Raman spectroscopy was used to investigate the cellulose fibres of painting canvases and linings. Historical samples of fabrics were taken from different paintings and their linings from different locations in Slovenia. Raman spectra were recorded on the fibres of these historical samples. Additionally, a database of the Raman spectra of modern cellulose fibres was created and compared with the literature data. Differences in the Raman spectra of different cellulose fibres were observed, and on this basis fibres of different types were discriminated. The recorded Raman spectra of historical samples were compared with the database spectra of modern cellulose fibres. Strong luminescence effects because of the changes caused by ageing, degradation products and surface contamination caused difficulties in interpreting the Raman spectra of historical fibres. The luminescence effects were partly overcome by prolonged exposition times and previous "signal quenching" with the laser. The Raman spectra of historical cotton showed no luminescence effects, and only slight differences to the reference spectra of modern cotton fibres appeared, whereas the Raman spectra of historical flax fibres were overwhelmed with luminescence and showed changes in spectra through degradation. The research showed that by using Raman spectroscopy the identification and differentiation of different cellulose fibres and materials that accompany cellulose in the fibres are possible and that degraded and aged material can be differentiated.     

利用显微拉曼光谱结合化学计量学检验包装物中的毒品

利用显微拉曼光谱对包装物中的常见毒品进行了检验,分别分析了同种包装物中的五种常见毒品,以及同种毒品在物证袋、塑料袋、半透明文件夹、玻璃片、牛皮纸袋等五种不同的包装物中的拉曼光谱.并测量了硅片上的毒品样品粉末作为对照.实验结果表明,通过将激光光斑聚焦于包装物中的毒品,可以通过其特征峰对毒品的种类进行识别,但是需要排除28...     

Study of thermally treated dickite by infrared and micro-Raman spectroscopy using curve-fitting technique

The products of dickite heated in air at 1000 to 1300°C were studied using curve-fitting of transmission and photoacoustic infrared and micro-Raman spectra. The spectra were compared with those of mullite, Al-spinel, corundum, cristobalite, amorphous silica and meta-dickite. Bands that characterize crystalline phases appeared at 1100°C and became stronger with increasing temperature. Mullite, Al-spinel, corundum and amorphous silica were identified by their characteristic bands. The characteristic IR bands of cristobalite overlap those of mullite and amorphous silica, and its presence was therefore established from intensity ratios of the appropriate bands. The research clearly demonstrated the advantage of using curve-fitting for the identification of high temperature phases in the study of the thermal treatment of kaolin-like minerals by infrared and Raman spectroscopy. This technique seems to be a useful method for materials analysis in the ceramic industry.This revised version was published online in November 2005 with corrections to the Cover Date.     

Characterisation of red mud by UV-vis-NIR spectroscopy

The characterisation of red mud has been studied by diffuse reflectance spectroscopy in the UV-vis-NIR region (DRS). For the first time the ferric ion responsible for the bands has been identified from electronic spectroscopy. It contains valuable amounts of oxidised iron (Fe(3+)) and aluminium hydroxide. The NIR peak at around 11,630 cm(-1) (860 nm) with a split of two components and a pair of sharp bands near 500 nm (20000 cm(-1)) in the visible spectrum are attributed to Fe(3+) ion in distorted sixfold coordinations. The observation of identical spectral patterns (both electronic and vibrational spectra) of red mud before and after seawater neutralisation (SWN) confirmed that there is no effect of seawater neutralisation on structural cation substitutions such as Al(3+), Fe(3+), Fe(2+), Ti(3+), etc.     

Laser-induced fluorescence and FT-Raman spectroscopy for characterizing patinas on stone substrates

This article reports on a compositional investigation of stone patinas: thin colored layers applied for protective and/or aesthetic purposes on architectural or sculptural substrates of cultural heritage. The analysis and classification of patinas provide important information of historic and artistic interest, as their composition reflects local practices, the availabilities of different materials, and the development of technological knowledge during specific historical periods. Model patinas fabricated according to traditional procedures and applied onto limestone, and a historic patina sample from the main façade of the San Blas Monastery in Lerma (a village in the province of Burgos, Spain), were analyzed by laser-induced fluorescence and Fourier transform Raman spectroscopy. The results obtained demonstrate the ability of these two analytical techniques to identify the key components of each formulation and those of the reaction products which result from the chemical and mineralogical transformations that occur during aging, as well as to provide information that can aid the classification of different types of patinas.

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Figure Cross section of model patina (left) and FT-Raman spectrum of historic patina from the façade of San Blas Monastery, Lerma, Burgos, Spain (right).

     

Annealing behavior of ultrahigh molecular weight polyethylene investigated by confocal micro-Raman spectroscopy combined with two-dimensional correlation spectroscopy

Annealing was performed for ultrahigh molecular weight polyethylene (UHMWPE), including an isothermal process at 110.0°C and cooling process from 110.0 to 30.0°C. The processes were in situ investigated by confocal micro-Raman spectroscopy combined with two-dimensional correlation spectroscopy. Two phase transitions were directly observed in the annealing processes, i.e., from the amorphous phase to the intermediate phase and from the intermediate phase to the crystalline phase. The phase transitions derive from molecular chain segments sliding between different phases of UHMWPE and occur in different orders during the isothermal and cooling processes.     

Characterisation of glycidylmethacrylate/methacrylonitrile copolymers by NMR spectroscopy

Glycidylmethacrylate/methacrylonitrile (G/M) copolymers of different compositions were prepared and a copolymer composition was obtained from quantitative ¹³C NMR spectroscopy. Reactivity ratios for comonomers were calculated using the Kelen–Tudos (KT) and non linear error in variable (EVM) methods. The reactivity ratios obtained from KT and EVM are r_G=1.14±0.1, r_M=0.76±0.06 and r_G=1.12, r_M=0.75, respectively. Complete spectral assignment of ¹³C- and ¹H-NMR spectra were done with the help of Distortionless Enhancement by Polarization Transfer (DEPT) and 2D ¹³C–¹H heteronuclear single quantum coherence (HSQC).     

Analysis of corrosion and oxidation on metals by spectroscopic means

Summary This paper addresses three aspects of the surface analytical experiment which are felt to be particularly crucial in characterizing corrosion mechanisms: chemical speciation, microscopic analysis and improved control of experimental conditions. X-ray Photoelectron Spectroscopy (XPS or ESCA) has been particularly effective in differentiating chemical species. The major chemical use of XPS is limited however to the outer surface of the film. Depth profiling by ion bombardment frequently degrades the chemical information available in the film interior and at the metal-oxide interface, and this is often where corrosion mechanisms are established. Mechanical methods of film penetration are thus encouraged to use XPS to its maximum capability. Microscopic analysis of corrosion surfaces using Scanning Auger Microscopy (SAM) or Secondary Ion Mass Spectrometry can reveal effects such as grain boundary segregation and oxide nucleation. Another important aspect of corrosion film analysis is the preparation of the metal surface itself. The oxidized surface can be strongly influenced by preparation artefacts such as cold work or impurities. Three different studies are used to illustrate these aspects: (i) the analysis of a molybdenum inhibitor layer on a steel surface; (ii) the study of corrosion product release from 304-stainless steel; and (iii) the effects of H⁺ ion bombardment to anneal mechanical work on Ni-Cr alloy surfaces, prior to oxidation.

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Untersuchung der Korrosion und Oxidation an Metallen mit Hilfe spektroskopischer Methoden

Zusammenfassung Diese Arbeit betont drei Gesichtspunkte oberflächenanalytischer Untersuchung, die für die Charakterisierung von Korrosionsmechanismen als besonders wesentlich erachtet werden: die chemische Bindung, die mikroskopische Analyse und die verbesserte Steuerung experimenteller Bedingungen. Die Röntgen-Photoelektronenspektroskopie (XPS oder ESCA) ist für die Unterscheidung chemischer Spezies besonders erfolgreich gewesen. Die Anwendung von XPS beschränkt sich jedoch im wesentlichen auf die äußere Oberfläche einer Schicht. Die Aufnahme von Tiefenprofilen mit Hilfe von Ionenbeschuß vermindert häufig die chemische Information, die vom Schichtinnern und vom Metall-Oxid-Interface erhältlich wäre; und hier spielen sich oft die Korrosionsvorgänge ab. Mechanische Methoden des Dünnschichtabtrags sind somit aufgefordert, XPS bis an die Leistungsgrenze zu bringen. Mikroskopische Untersuchungen von Korrosionsschichten mittels Raster-Auger-Mikroskopie (SAM) oder Sekundärionen-Massenspektrometrie können Effekte wie die Korngrenzensegregation und die Oxidbildung aufdecken. Ein weiterer bedeutender Gesichtspunkt der Analyse von Korrosionsschichten ist die Behandlung der Metalloberflächen selbst. Die oxidierte Oberfläche kann durch Behandlungsfehler wie z.B. Kaltbearbeitung oder Verunreinigung stark beeinflußt werden. An Hand von drei verschiedenen Beispielen werden diese Aspekte illustriert: (i) die Analyse einer Molybdän-Schutzschicht auf Stahl; (ii) die Untersuchung von Korrosionsprodukten auf 304-Edelstahl; und (iii) die Effekte des H⁺-Ionenbeschusses zum Ausheilen mechanischer Schäden auf der Oberfläche von Ni-CrLegierungen, vor der Oxidation.

     

Localized quantification of anhydrous calcium carbonate polymorphs using micro-Raman spectroscopy

Micro-Raman spectroscopy is a powerful technique for qualitative and quantitative analysis of different mineral mixtures. In this paper, micro-Raman spectroscopy was used for quantification in local regions (180 × 180 μm area) of ternary mixtures of the synthetic calcium carbonate (CaCO₃) polymorphs (vaterite, aragonite, calcite) as well as CaCO₃ formed during the carbonation of nanolime suspension. The obtained results of localized quantification were in agreement with the detected concentrations obtained from bulk quantitative phase analysis of X-ray powder diffraction patterns. The detection limits were found to be below 0.5 wt.% for each CaCO₃ polymorphs. Through the use of 2D mapping, localized quantification of CaCO₃ polymorphs can be achieved. This information could be potentially useful for conservation of valuable Cultural Heritage objects, as it might influence the consolidation treatment chosen.     

Preliminary identification of Beta-carotene in the vitreous asteroid bodies by micro-Raman spectroscopy and HPLC analysis.

beta-carotene was first identified from the vitreous asteroid bodies (ABs) excised from one patient with asteroid hyalosis (AH) by confocal Raman microspectroscopy and was also verified by high performance liquid chromatography (HPLC). Two patients had been diagnosed with AH and intervened by surgical vitrectomy due to blurred vision. The morphology and components of both AB specimens were observed by optical microscopy and determined by using confocal Raman microspectroscopy and HPLC analysis, respectively. Surprisingly, two unique peaks at 1528 and 1157 cm(-1) were found in the Raman spectrum for the AB specimen of patient 1 alone, which were in close agreement with that of the Raman peaks at 1525 and 1158 cm(-1) for beta-carotene and/or lutein. However, HPLC analytical data clearly indicated that the retention time for the extracted sample from the AB specimen of patient 1 was observed at 13.685 min and just identical to that of beta-carotene (13.759 min) rather than lutein (2.978 min). In addition, the lack of any peak in the HPLC profile for the AB specimen of patient 2 also confirmed the absence of Raman peaks at 1525 and 1158 cm(-1). Thus this preliminary study strongly suggests that beta-carotene as a unique component of ABs was specifically detected from the AB specimen of one AH patient by using confocal Raman microspectroscopy and HPLC analysis.     

Characterisation of adsorbed layers on sulphide minerals by photoelectron spectroscopy

The systems galena/2-mercaptobenzothiazole (MBT) and pyrite/MBT have been studied using synchrotron radiation excited photoelectron spectroscopy (SRXPS). The chemisorption of MBT and the multilayer formation of 2,2′-dithiobis(benzothiazole) (BBTD) are evidenced by additional structures, observed beside the substrate signals, in the S2p-spectra of cleaved mineral surfaces after adsorption of MBT. The amount of the complex remains constant at concentrations as high as 10^–5 mol/L whereas the amount of BBTD increases. From the dependence of the adsorbate intensities on the excitation energy the conclusion can be drawn that an overlayer of BBTD on a chemisorbed layer of MBT is formed. The very weak adsorption of MBT on pyrite in alkaline solutions may explain the selective flotation of galena from pyrite in alkaline media.     

Characterisation of nanocrystalline magnesium oxide by X-ray absorption spectroscopy.

There are numerous methods of preparing nanocrystalline materials. Magnesium oxide is an ideal model system on which to probe the relation of the preparative route and the microstructure. Using X-ray absorption spectroscopy (XAS) we show that the sol-gel route can be used to prepare highly crystalline material provided there is careful control of the calcination conditions. In the present work this is achieved by calcining at high temperatures (at least 800 degrees C). However, this results in grain growth that can be prevented by the addition of a pinning agent, SiO(2), during the preparation of the sol. The pinned samples maintain a particle size of 11 nm even after calcining at 1000 degrees C. Ball-milling is a common method of preparing nanocrystalline oxides, however the present work shows that this produces a significant fraction of amorphous material, the fraction increasing with decreasing grain size (e.g. approximately 30 % for a grain size of 23 nm).