Unilateral NMR, 13C CPMAS NMR spectroscopy and micro-analytical techniques for studying the materials and state of conservation of an ancient Egyptian wooden sarcophagus

A multi-technique approach was employed to study a decorated Egyptian wooden sarcophagus (XXV–XXVI dynasty, Third Intermediate Period), belonging to the Museo del Vicino Oriente of the Sapienza University of Rome. Portable non-invasive unilateral NMR was applied to evaluate the conservation state of the sarcophagus. Moreover, using unilateral NMR, a non-invasive analytical protocol was established to detect the presence of organic substances on the surface and/or embedded in the wooden matrix. This protocol allowed for an educated sampling campaign aimed at further investigating the state of degradation of the wood and the presence of organic substances by ¹³C cross polarization magic angle spinning (CPMAS) NMR spectroscopy. The composition of the painted layer was analysed by optical microscopy (OM), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), Raman and surface enhanced (resonance) Raman spectroscopy (SERS/SERRS), infrared and GC–MS techniques, evidencing original components such as clay minerals, Egyptian green, indigo, natural gums, and also highlighting restoration pigments and alteration compounds. The identification of the wood, of great value for the reconstruction of the history of the artwork, was achieved by means of optical microscopy.     

Detection of magnesium compounds in dietary supplements and medicinal products by DSC,Infrared and Raman techniques

The aim of this study was to learn to what extent the selected instrumental techniques, differential scanning calorimetry (DSC), as well as Fourier-transform infrared (FTIR) and Raman spectroscopies, can be used to detect both organic or inorganic magnesium compounds in the dietary supplements and medicinal products. Besides magnesium compounds as the active pharmaceutical ingredients (APIs), the preparations contain also other organic and inorganic APIs and several excipients. The study will be extended over the analysis of the products manufactured by various firms but containing the same API at different levels. In this way, it will be possible to assess the impact of excipients on the DSC scans and the FTIR and Raman spectra of a dominant constituent present in a studied preparation. The study on thirty commercially available dietary supplements and medicinal products has shown that in the majority of cases the DSC, FTIR and Raman techniques could be used for the detection of APIs in these commercial products. This was possible with the aid of the endothermic DSC peaks and the so-called matching factors of the FTIR and Raman spectra to those of substances used as standards. Both the complex composition and low levels of API in the studied preparations have been identified as the factors which have a strong impact on the usefulness of the three techniques for the detection of APIs in the dietary and medicinal products.     

Characterization of Green Paints in Ming and Qianlong Dynasties’ Lin’xi Pavilion by Complimentary Techniques

During conservation of the painted ceiling decoration of Lin’xi Pavilion in the Forbidden City, two distinct paint campaigns were isolated as a unique case study into architectural paint materials during both the Ming and Qing dynasties. Paint samples and cross sections from both paint generations were analyzed with SEM-EDX, time of flight-secondary ion mass spectrometry (ToF-SIMS), XRD, FTIR, and Raman spectroscopies. Similar organic and inorganic materials characteristic of these time periods were identified. The pigments of interest found in both paint generations were botallackite and atacamite polymorphs. This suggests a shift from natural mineral sources to synthetic copper-based pigments for these larger architectural projects.     

XPS analysis of petroleum well tubing adherence

Undesired material adhered to the internal surface of the tubing wall of some petroleum wells is critical for crude oil production. Field samples of steel with petroleum solid adherence were characterized by means of x‐ray photoelectron spectroscopy, x‐ray diffraction and atomic absorption spectroscopy. The deposit naturally adhered on the steel surface is structurally formed by a thin, black and hard corrosion product layer (inner layer) ～15 µm thick under a thick, black and brittle organic deposit layer (outer layer) ～0.01 m thick composed mainly of hydrocarbons. This outer layer contains small amounts of barium sulphate (BaSO₄) co‐precipitated with organic compounds, which may contribute to the deposit's lack of cohesion. On the contrary, the inner layer of the deposit is firmly adhered to the steel substrate and contains clay minerals and iron compounds embedded in the hydrocarbon layer. Copyright © 2003 John Wiley & Sons, Ltd.     

Non-destructive in situ determination of pigments in 15th century wall paintings by Raman microscopy

Raman microscopy has been applied to the study of 15th century wall paintings in a chapel of St. Orso Priory palace (Aosta, Italy) in view of their restoration. The use of a transportable instrument has made it possible to work non-destructively in situ without sampling. The main inorganic pigments used by the unknown artist, namely mercury sulphide, azurite, white lead, red and yellow ochre, carbon black and lead tin yellow type I have been identified, and the presence of organic substances and of some decay products (calcium sulphate and oxalate) has been observed.     

Catalogue of 45 reference Raman spectra of minerals concerning research in art history or archaeology,especially on corroded metals and coloured glass

Small catalogues of reference Raman spectra of interest for analysing geomaterials or biomaterials of relevance to art history or archaeology are gradually being published by different research groups. However, except for some older catalogues, they are all concerned primarily with pigments, whether inorganic or organic. Here we present for the first time a catalogue of Raman spectra of minerals that may be found in corroded metal artworks or artefacts. At the same time we include some inorganic pigments that may be found in or on stained glass. Most of the minerals analysed came from the Gallery of Mineralogy at the Muséum National d'Histoire Naturelle and most were verified by X-ray diffraction in order to augment the confidence in the mineral identity (which is not the case with many other catalogues). A number of problems encountered with mineral terminology are discussed. Comments are made on the spectra where appropriate.     

Characterisation of organic residues in pottery vessels of the Roman age from Antinoe (Egypt)

In the framework of a study on the Egyptian ceramic vessels belonging to the archaeological collection of the Istituto Papirologico Vitelli (Florence), the characterisation of organic residues from three findings of the 5th–7th centuries A.D. has been performed. The materials were identified by two analytical procedures based on Fourier transformed infrared spectroscopy (FTIR) and on gas chromatography coupled with mass spectrometry (GC–MS), respectively. The first procedure is suitable for detecting the functional groups of organic substances and thus for distinguishing them; the second permits the simultaneous analysis of several natural substances such as vegetable resins and oils, bitumen, tar and pitch, and waxes.The presence of monocarboxylic acids, α,ω-dicarboxylic acids, long-chain dihydroxylated acids, and terpenic species, highlights that although the organic residues showed a high heterogeneity in composition, they mainly consisted of materials of vegetable origin. In particular, the presence of oxidation products of characteristic unsaturated fatty acids suggests the occurrence of oil produced from plant seeds of the Cruciferae family, some of which are reported to have been used in ancient Egypt to produce oil. Moreover, the presence of characteristic diterpenic biomarkers in two of the three pieces of pottery enables us to assess the use of both pine resin and pine pitch.     

HUMIC MACROMOLECULES IN NATURAL WATERS

Abstract

Humic substances are the major organic constituents of soils and sediments. They also occur in small concentrations in natural surface waters and groundwaters. They form through the breakdown of plant and animal tissues by chemical and biological processes that tend to produce complex chemical structures that are more stable than the original material from which they were derived. One of the more important characteristics of humic substances is their ability to form water-soluble and water-insoluble complexes with metal ions and hydrous oxides and to interact with clay minerals and various organic compounds such as alkanes, fatty acids, and toxic organic substances such as pesticides.     

Nanocomposites of NLO chromophore‐modified layered silicates and polypropylene

Intercalation of guest species into layered inorganic solids is a method of producing ordered inorganic–organic assemblies with unique microstructures controlled by host–guest and guest–guest interactions. Smectite clay minerals, such as montmorillonite, having appropriate functional molecules in between the silicate layers are supposed to exhibit a wide range of novel characteristics. Nanocomposite material based on maleic anhydride‐grafted polypropylene and dye‐modified layered silicate was developed. Characteristics of organo‐modified montmorillonite particles and polymer/clay hybrids have been investigated through FTIR, SAXS, DSC, UV measurements, and transmission electron microscopy. The results of the intercalation process, structural characterization, and thermal properties will be discussed in comparison with the intercalation and nanocomposite preparation results. The intercalation was successfully conducted by the ion‐exchange method. It was shown that intercalated dibenzilidene acetone type chromophores exist in the clay galleries in an aggregated form, probably as J‐aggregates. This feature strongly effects on optical and nonlinear optical properties of nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2493–2502, 2005     

Hydrogen bonding,mechanical properties,and surface morphology of clay/waterborne polyurethane nanocomposites

A novel clay/waterborne polyurethane (WPU) nanocomposite was synthesized from polyurethane and saponite organoclay. The clay was organically modified with various swelling agents, the effect of which has been investigated. Hydrogen bonding between organic and inorganic materials was characterized with Fourier transform infrared (FTIR) spectroscopy. The results implied that hydrogen bonding increased when organoclay was added. Mechanical and wear property studies revealed that introducing clay into waterborne polyurethane will enhance the Young's modulus (from 56 to 126 MPa), the maximum stress (from 3.9 to 7.6 MPa), and the elongation at break (from 27.7 to 58.7%) of the nanocomposite by a factor of two, whereas the wear loss will be only one third of the neat waterborne polyurethane. Atomic force microscopy (AFM) was used to analyze the surface morphology of the nanocomposite. An AFM microphotograph showed that the surface of the clay/waterborne polyurethane nanocomposite was smoother when clay was added in waterborne polyurethane. The average roughness (R_a) decreased from 1.00 to 0.12. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1–12, 2005     

Characterization of Ultra Fine Solids（BS） in Athabasca Bitumen

The ultra fine (＜200 nm) inorganic solids (BS) were separated from bitumen which was washed by toluene and centrifugated at 2000 rpm. The result of PAS FTIR and image of TEM showed that the structure of BS particles was smiliar to that of kaolinite clay. On the surface of BS, both toluene insoluble organic matter and structural OH group are detected at the same time.The surface characteristics imparted a bi-wettable nature to the BS. As a result, the BS is able to stabilize fine water emulsion in the bitumen phase. The organic matter associated with BS is a possible factor of the fouling on catalyst and equipment.     

Application of dsc to study crystallization kinetics of polypropylene containing fillers

The present work is concerned with the comparison of nucleating efficiency of various organic and inorganic fillers of isotactic polypropylene: talc, chalk, wood flour, nano clay particles, carbon black, chitosan in the form of powder of the same content equal to 5 mass%. The kinetics of isothermal crystallization of isotactic polypropylene in the composite systems was evaluated by using DSC. Avrami equation was applied to the results. Calculated K and n parameters depend on filler applied. The σσ_e surface free energies were also found. The best nucleating agent found here was talc and carbon black. The organic filler as a chitosan powder forms amorphous inclusions in the composites on which IPP molecules cannot be adsorbed. Their presence disturbs a macromolecular diffusion and delays crystallization process of IPP. This revised version was published online in July 2006 with corrections to the Cover Date.     

Unveiling the chromatic palette used for mural paintings in a recently discovered Ptolemaic‐era tomb (Sohag,Upper Egypt): A multitechnique surface investigation

In 2019, an exceptional Ptolemaic‐era tomb was discovered in Al‐Diabat archaeological site, Sohag, Upper Egypt. Numerous fallen painted fragments in the floor of tomb were collected and studied. The microstructural and chemical makeup of samples was discerned by virtue of a field‐emission scanning electron microscopy (FE‐SEM) with an energy‐dispersive x‐ray (EDX) spectrometry. Further, the molecular‐vibrational property was acknowledged by Fourier‐transform infrared (FT‐IR) and micro‐Raman (μ‐Raman) spectrometers. Also, the crystalline structure of stone and plaster samples was defined by x‐ray diffraction (XRD) analysis. The results have demonstrated that the murals were implemented on a thick mud plaster followed by a thin preparation layer, which, unusually, was made of calcite. Gypsum was also detected in variable quantity throughout the render samples. Colouring substances of Egyptian blue, green earth, red ochre, yellow ochre and carbon black were recognized in the studied murals. Besides, maghemite (γFe₂O₃) was disclosed in the red pigment sample. Unexpectedly, gold was detected in the yellow paint areas, possibly associated with a religious tradition. As well, the recognition of an organic binder (probably egg yolk) nominates the application of tempera technique. Noteworthy, this research contributes in presenting significant findings on painting materials used in unusual rock‐cut tomb from the Ptolemaic era.     

Interlayer expansion and mechanisms of anion sorption of Na-montmorillonite modified by cetylpyridinium chloride: a Monte Carlo study

To study the change of interlayer structure of a Wyoming-type Na-montmorillonite as a result of the replacement of interlayer Na+ ions by cetylpyridinium (CP+) ions, a series of NPT Monte Carlo simulations of the clay mineral with different contents of CP+, Na+, Cl- ions and water in its interlayer space is carried out. In agreement with conclusions from experimental studies, the simulations show that the CP+ ions form monomolecular, bimolecular, and pseudotrimolecular layers with increasing interlayer contents. Calculated potential energies reveal that clay-organic interactions are stronger than organic-organic interactions in CP+-modified montmorillonite, which is in conformity with observations of earlier thermogravimetric experiments. The simulation results indicate that the pseudotrimolecular arrangement of CP+ ions is a prerequisite for the experimentally observed interlayer sorption of inorganic anions. Furthermore, in the interlayer space with a pseudotrimolecular layer, chloride ions favor the formation of pairs with inorganic rather than organic cations. On the basis of these findings and available experimental data, we propose that the interlayer sorption of inorganic anions from the pore space of an organically modified montmorillonite may occur not only in pairs with organic cations, as suggested earlier, but also in pairs with inorganic cations, which represents a so-far unconsidered and maybe more important mechanism of anion sorption on clay minerals.     

Critical evaluation of a handheld Raman spectrometer with near infrared (785nm) excitation for field identification of minerals

Handheld Raman spectrometers (Ahura First Defender XL, Inspector Raman DeltaNu) permit the recording of acceptable and good quality spectra of a large majority of minerals outdoors and on outcrops. Raman spectra of minerals in the current study were obtained using instruments equipped with 785 nm diode lasers. Repetitive measurements carried out under an identical instrumental setup confirmed the reliability of the tested Raman spectrometers. Raman bands are found at correct wavenumber positions within ±3 cm(-1) compared to reference values in the literature. Taking into account several limitations such as the spatial resolution and problems with metallic and black and green minerals handheld Raman spectrometers equipped with 785 nm diode lasers can be applied successfully for the detection of minerals from the majority of classes of the mineralogical system. For the detection of biomarkers and biomolecules using Raman spectroscopy, e.g. for exobiological applications, the near infrared excitation can be considered as a preferred excitation. Areas of potential applications of the actual instruments include all kind of common geoscience work outdoors. Modified Raman systems can be proposed for studies of superficial or subsurface targets for Mars or Lunar investigations.     

聚电解质中电活性物质氧化还原反应机理的现场显微红外光谱电化学研究

用现场显微红外光谱电化学方法研究了几种电活性物质,包括无机盐、有机物、无机聚合物微粒在聚电解质中的氧化还原反应及其机理。     

Gold Gilding and Pigment Identification on a Post-Byzantine Icon from Kastoria,Northern Greece

The investigation of gilded gold, black and red pigments from the Byzantine icon of Panagia from the church of Agioi Anargyroi Gymnasiou in Kastoria, northern Greece is the aim of this study. Small fragments, having a gold leaf finish, were detached from the icon and were analyzed by Environmental Scanning Electron Microscopy coupled to Energy Dispersive System (ESEM-EDS) and Raman microscopy. The chemical (EDS) composition of the gilding material revealed a high gold content alloy (Au 81.34 wt%) with trace amounts of silver (Ag 1.66 wt%), copper (Cu 0.62 wt%) and iron (Fe 0.58 wt%). The Raman spectrum of the gold leaf showed characteristic bands at 236, 369, and 468 cm^?1. The red pigment on the surface comprises of Hg, S, and minor amounts of Pb and is attributed to the minerals cinnabar (HgS) and minium (Pb₃O₄). The black pigment has high carbon content, attributed to organic material (black carbon). The micro-Raman spectroscopy provided a more detailed determination of the composition of the red and black pigments. In particular, the vivid red color was attributed to cinnabar (bands at 253 and 342 cm^?1). Particles of black carbon (bands at 1345 and 1577 cm^?1) and oxalates (band at 861 cm^?1) were determined on the black pigments. Dark regions on the pigmented surface were assigned to a mixture of cinnabar [bands at 253 and 342 cm^?1] and minium [bands at 120, 142, 288, and 545 cm^?1]. The latter lead oxides might have been used either as a dryer or a burnish agent for the gold leaf. The micro-structural and chemical analysis of several distinct strata of the icon, as observed under ESEM, revealed a red-colored stratum beneath the gold leaf, with an iron aluminosilicate composition. This is the so-called bole (red clay) commonly used as sub-strata for gilding art objects. Multiple layers of white ground material, composed of gesso (gypsum) underlie the bole strata. Moreover, one thin organic binder (animal glue) was is observed within the gesso ground of the icon.     

Characterizing the formation of organic layers on the surface of inorganic/aqueous aerosols by Raman spectroscopy

We demonstrate that nonlinear Raman spectroscopy coupled with aerosol optical tweezers can be used to probe the evolving phase partitioning in mixed organic/inorganic/aqueous aerosol droplets that adopt a core-shell structure in which the aqueous phase is coated in an organic layer. Specifically, we demonstrate that the characteristic fingerprint of wavelengths at which stimulated Raman scattering is observed can be used to assess the phase behavior of multiphase decane/aqueous sodium chloride droplets. Decane is observed to form a layer on the surface of the core aqueous droplet, and from the spectroscopic signature the aqueous core size can be determined with nanometer accuracy and the thickness of the decane layer with an accuracy of +/-8 nm. Further, the presence of the organic layer is observed to reduce the rate at which water evaporates from the core of the droplet with an increasing rate of evaporation observed with diminishing layer thickness.     

Modeling of copper(II) and lead(II) adsorption on kaolinite-based clay minerals individually and in the presence of humic acid

The aim of this study is to explain how clay minerals adsorb heavy metals individually and in the presence of humic acid, and to model heavy metal adsorption specifically based on surface-metal binary and surface-metal-ligand ternary complexation. The adsorption of Cu(II) and Pb(II) on kaolinite-based clay minerals has been modeled by the aid of the FITEQL3.2 computer program using single- and double-site binding models of the Langmuir approach. Potentiometric titrations and adsorption capacity experiments were carried out in solutions containing different concentrations of the inert electrolyte NaClO4; however, the modeling of binary and ternary surface complexation was deliberately done at high ionic strength (0.1 M electrolyte) for eliminating adsorption onto the permanent negatively charged sites of kaolinite. A "two-site, two pKa" model was adapted, and as for the two surface sites responsible for adsorption, it may be arbitrarily assigned that [triple bond]S1OH sites represent silanol and organic functional groups such as carboxyl having pKa values close to that of silanol, and [triple bond]S2OH sites represent aluminol and organic functional groups such as phenolics whose pKa values are close to that of aluminol, as all the studied clays contained organic carbon. Copper(II) showed a higher adsorption capacity and higher binding constants, while lead(II), being a softer cation (in respect to HSAB theory) preferred the softer basic sites with aluminol-phenol functional groups. Heavy metal cations are assumed to bind to the clay surface as the sole (unhydrolyzed) M(II) ion and form monodentate surface complexes. Cu(II) and Pb(II) adsorption in the presence of humic acid was modeled using a double-site binding model by the aid of FITEQL3.2, and then the whole system including binary surface-metal and surface-ligand and ternary surface-metal-ligand complexes was resolved with respect to species distributions and relevant stability constants. Electrostatic effects were accounted for using a diffuse layer model (DLM) requiring minimum number of adjustable parameters. Metal adsorption onto clay at low pH increased in the presence of humic acid, and the metal adsorption vs pH curves of metal-kaolinite-humic acid suspensions were much steeper (and distinctly S shaped) compared to the wider pH-gradient curves observed in binary clay-metal systems. The clay mineral in the presence of humic acid probably behaved more like a chelating ion-exchanger sorbent for heavy metals rather than being a simple inorganic ion exchanger.