Micro-analytical evidence of origin and degradation of copper pigments found in Bohemian Gothic murals

Correct identification of pigments and all accompanying phases found in colour layers of historical paintings are relevant for searching their origin and pigment preparation pathways and for specification of their further degradation processes. We successfully applied the analytical route combining non-destructive in situ X-ray fluorescence analyses with subsequent laboratory investigation of micro-samples by optical microscopy, scanning electron microscopy/energy-dispersive spectroscopy and X-ray powder micro-diffraction (micro-XRD) to obtain efficiently all the data relevant for mineralogical interpretations of the copper pigments origin. Cu salts (carbonates, chlorides, sulphates, etc.) used as pigments exist in a range of polymorphs with similar or identical composition. The efficiency of the micro-XRD for direct identification of such crystal phases present in micro-samples of colour layers was demonstrated in the presented paper. A new, until now unpublished, type of copper pigment—cumengeite, Pb₂₁Cu₂₀Cl₄₂(OH)₄₀—used as a blue pigment on a sacral wall painting in the Czech Republic was found by means of micro-XRD. Furthermore, azurite, malachite, paratacamite, atacamite and posnjakite were identified in fragments of colour layers of selected Gothic wall paintings. We found Cu–Zn arsenates indicating the natural origin of azurite and malachite; artificial malachite was distinguishable according to its typical spherulitic crystals. The corrosion of blue azurite to green basic Cu chloride was clearly evidenced on some places exposed to the action of salts and moisture—in a good agreement with the results of laboratory experiments, which also show that oxalic acid accelerates the corrosion of Cu pigments.     

Analysis of layered AlxGa1 − xAs on gallium arsenide by electron microprobe and secondary-ion mass spectrometry

Two samples containing Al_xGa_{1 ? x}As layers (several micrometers thick) of different composition deposited on a gallium arsenide substrate were analyzed by two techniques. Electron microprobe analysis was used on a cross-section of the samples to measure layer thickness, to obtain qualitative information by means ov x-ray line scans, and to determine the composition of the layers accurately by energy-dispersive x-ray spectrometry. Depty profiles obtained by secondary-ion mass spectrometry were used to study depth resolution at large depth ranges. Results obtained by the two techniques are in excellent agreement and compare favourably with other published results concerning the same type of sample.     

Electric field induced permeability modulation in pure and mixed Langmuir-Blodgett multilayers of hemicyanine dyes and octadecanoic acid on nanoporous solid supports

Composite structures have been prepared, in which nanoporous (nuclear track-etched) membranes are coated with supported Langmuir-Blodgett (LB) barrier layers. Permeability in these structures is a strong function of membrane composition and applied dc and ac electric fields. Absolute permeabilities fall in the range 3×10⁻¹¹ cm² s⁻¹ ≤P≤3×10⁻⁹ cm² s⁻¹, depending on composition of the barrier layer, identity (charge state) of the probe, and presence of a supporting electrolyte. Zero-field permeabilities showed a definite dependence on composition, with membranes possessing barrier layers on both sides performing better than single-sided membranes, barrier layers with LB multilayers performing better than those with just the support layer, and LB layers composed of mixed stilbazolium amphiphiles and octadecanoic acid performing better than those composed purely of stilbazolium amphiphile. All types of barrier layers studied exhibit permeability changes in the presence of applied electric fields. The magnitude of the effect is a strong function of composition of the barrier layer and the presence of supporting electrolyte. The results support electroporation over iontophoresis as the dominant mechanism for field-mediated increases in permeability. Details of the field-induced permeability changes in phosphate buffer and deionized water suggest that at least two effects are important in determining the transport behavior in these structures: a field-induced structural change in the barrier layer which mediates the electroporation and a field-mediated alteration in transport through nanopores of the nuclear track-etched membrane.     

Analytical investigations of tunnel magnetoresistance layers

The basic elements of tunnel magnetoresists are two magnetic layers separated by an insulating barrier layer. The uniformity of this only 1–2 nm thick barrier layer up to dot edges and the chemical composition of the layers are properties important for the efficiency of tunnel magnetoresistance devices. These key-properties have been investigated by analytical TEM methods like high resolution TEM imaging and energy-filtered imaging. With regard to the chemical composition the TEM results have been confirmed by XPS investigations. The subsequent oxidation of the barrier is one of the most critical steps of the deposition procedure of the layer stacks. An undersized oxygen dose leads to an incomplete oxidation of the barrier layer with uncontrollable tunnel behaviour. An overdose of oxygen leads to oxygen diffusion in the layers beneath the barrier and uncontrollable magnetic hardness of the lower magnetic electrode.     

Study of a XVIII century hand-painted Chinese wallpaper by multianalytical non-destructive techniques

In this work, hand-painted wallpaper belonging to a private Portuguese collection was analyzed in order to identify the pigments used. The analyzed artwork was an extraordinary XVIII century Chinese wallpaper that depicts exotic birds and flowers, which was painted with considerable accuracy and expertise. Thorough, in situ, X-ray fluorescence analyses were performed on nearly all the wallpaper. Since the elemental content of several colors was consistent for the four papered walls, strategic micro-samples were taken and analyzed by confocal Raman spectroscopy to further identify the pigments used. Pigments such as yellow ochre, lead white and barium white, vermilion, carmine, azurite and malachite were identified. Optical microscopy was used to analyze the fibers in the paper support, and fibers such as kozo, ramie and hemp or linen were identified.     

The degradation of poly(vinyl acetate) as a material for design objects: A multi-analytical study of the Cocoon lamps. Part 2

After the systematic study of poly(vinyl acetate) degradation presented in part 1, this work reports results from the analysis of polymeric materials from five Italian design lamps from the 1960s made of the material known as cocoon. Micro- and non-destructive molecular spectroscopic techniques have been applied directly on the object surfaces using an optical fibre probe and through examination of micro-samples: the combined use of Fourier-transform infrared spectroscopy (FTIR), pyrolysis gas-chromatography/mass-spectrometry (py-GC/MS) and Fluorescence spectroscopy allowed the assessment of the material composition and the chemical modifications of the polymers related to on-going deterioration processes. Fluorescence spectroscopy proved particularly sensitive for the detection of variations in composition among lamps and between areas on the same object, and was used to classify objects in different groups using principal component analysis of excitation emission spectra. Specific degradation products have been mapped using FTIR on micro-samples. Moreover, the interpretation of the emission spectra of the studied polymeric lamps suggests that fluorescence spectroscopy can be used for non-destructive monitoring of the degradation of historical polymeric objects.     

Microspectroscopic imaging of heterophase layers of metal-oxide sensors using a video camera

The methodological foundations of digital specular reflectance microspectroscopic imaging are reported. The digital optical images of a microscopic area of the metal surface with an inhomogeneous nanostructural layer can be processed using the algorithms of spectroscopic imaging ellipsometry modified to fit reflectometry. This makes it possible to monitor the thickness, topography, and chemical composition depth profiles of thin surface metal-oxide nanolayered structures, active layers of microsensors with an active substrate. The method has been used for nondestructive analysis of the thickness and chemical composition over the volume of the oxide layer on the surface of heat-treated steel X18H10T, a system with pronounced photo-electrochemical response.     

Analysis of apatite crystals and their fluid inclusions by synchrotron radiation X-ray flourescence microprobe

Chemical composition analysis of apatites and their fluid inclusions from Yu'erya granite was carried out by synchrotron radiation X-ray fluorescence (SRXRF) microprobe. The result shows that all these apatite crystals have a similar chemical signature, with Ca, P, Cl, Mn, Fe, K, S, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu, Sr, Y, Zr, U, Th, etc. The rare earth elements chondrite-normalized pattern indicates that these apatites are derived from S-type granite. It is shown by the SRXRF analysis that Zn, Cu and Cl are main components of fluid inclusions in apatites. It is the first time that SRXRF analysis is successfully applied in determination of composition of single fluid inclusions in apatite crystals. This technique was proved to be suitable for crystals with homogenously distributing components and thin covering layer would help to determine the composition of fluid inclusions.     

Influence of sintering on the structural and electronic properties of TiO2 nanoporous layers prepared via a non-sol–gel approach

In this work, a nonaqueous method is used to fabricate thin TiO₂ layers. In contrast to the common aqueous sol–gel approach, our method yields layers of anatase nanocrystallites already at low temperature. Raman spectroscopy, electron microscopy and charge extraction by linearly increasing voltage are employed to study the effect of sintering temperature on the structural and electronic properties of the nanocrystalline TiO₂ layer. Raising the sintering temperature from 120 to 600?°C is found to alter the chemical composition, the layer’s porosity and its surface but not the crystal phase. The room temperature mobility increases from 2?×?10^?6 to 3?×?10^?5?cm²/Vs when the sinter temperature is increased from 400 to 600?°C, which is explained by a better interparticle connectivity. Solar cells comprising such nanoporous TiO₂ layers and a soluble derivative of cyclohexylamino-poly(p-phenylene vinylene) were fabricated and studied with regard to their structural and photovoltaic properties. We found only weak polymer infiltration into the oxide layer for sintering temperatures up to 550?°C, while the polymer penetrated deeply into titania layers that were sintered at 600?°C. Best photovoltaic performance was reached with a nanoporous TiO₂ film sintered at 550?°C, which yielded a power conversion efficiency of 0.5?%. Noticeably, samples with the TiO₂ layer dried at 120?°C displayed short-circuit currents and open circuit voltages only about 15–20?% lower than for the most efficient devices, meaning that our nonaqueous route yields titania layers with reasonable transport properties even at low sintering temperatures.     

Identification of the finishing technique of an early eighteenth century musical instrument using FTIR spectromicroscopy

The study of varnishes from musical instruments presents the difficulty of analysing very thin layers of heterogeneous materials on samples most of which are generally brittle and difficult to prepare. Such study is crucial to the understanding of historical musical instrument varnishing practices since written sources before 1800 are very rare and not precise. Fourier-transform infrared (FTIR) spectroscopy and imaging methods were applied to identify the major chemical components within the build-up of the varnish layers on a cello made by one of the most prominent French violin-makers of the eighteenth century (Jacques Boquay, ca. 1680–1730). Two types of FTIR imaging methods were used: scanning with a synchrotron-based microscope and full-field imaging using a 2D imager with a conventional source. An interpretation of the results obtained from these studies on the Boquay cello is that the maker first applied a proteinaceous layer, probably gelatine-based animal glue. He later applied a second layer based on a mixture of a drying oil and diterpenic resin from Pinaceae sp. From an historical perspective, the results complement previous studies by describing a second technique used for musical instrument finishes at the beginning of the eighteenth century in Europe.     

Preparation and characterisation of chromium and sodium tantalate layers by anodic spark deposition

A plasma-electrochemical synthesis was used to prepare chromium and sodium tantalate layers. These layers were deposited on a tantalum anode surface as ceramic compounds from aqueous electrolytes. The typical pore structure morphology of the tantalate layer was characterised by SEM as well as fractures which provide evidence of an intimate contact between layers and substrate. An XRD-study showed that the layers are composed of a mixture of Ta₂O₅ and either NaTaO₃ or CrTaO₄ depending on the electrolyte composition. Quantitative characterisation by EPM indicated higher chromium and tantalum concentrations on the electrolyte/layer interface than at the layer/tantalum interface. The chemical state of tantalum was investigated by means of XPS.     

Evaluation of laboratory powder X-ray micro-diffraction for applications in the fields of cultural heritage and forensic science

The uniqueness and limited amounts of forensic samples and samples from objects of cultural heritage together with the complexity of their composition requires the application of a wide range of micro-analytical methods, which are non-destructive to the samples, because these must be preserved for potential late revision. Laboratory powder X-ray micro-diffraction (micro-XRD) is a very effective non-destructive technique for direct phase analysis of samples smaller than 1 mm containing crystal constituents. It compliments optical and electron microscopy with elemental micro-analysis, especially in cases of complicated mixtures containing phases with similar chemical composition. However, modification of X-ray diffraction to the micro-scale together with its application for very heterogeneous real samples leads to deviations from the standard procedure. Knowledge of both the limits and the phenomena which can arise during the analysis is crucial for the meaningful and proper application of the method. We evaluated basic limits of micro-XRD equipped with a mono-capillary with an exit diameter of 0.1 mm, for example the size of irradiated area, appropriate grain size, and detection limits allowing identification of given phases. We tested the reliability and accuracy of quantitative phase analysis based on micro-XRD data in comparison with conventional XRD (reflection and transmission), carrying out experiments with two-phase model mixtures simulating historic colour layers. Furthermore, we demonstrate the wide use of micro-XRD for investigation of various types of micro-samples (contact traces, powder traps, colour layers) and we show how to enhance data quality by proper choice of experiment geometry and conditions.     

Differences in the hippocampal frequency of creatine inclusions between the acute and latent phases of pilocarpine model defined using synchrotron radiation-based FTIR microspectroscopy

Temporal lobe epilepsy (TLE) is the most common type of epilepsy in adults. Of the animal models developed to investigate the pathogenesis of TLE, the one with pilocarpine-induced seizures is most often used. After pilocarpine administration in animals, three distinct periods—acute, latent, and chronic—can be distinguished according to their behavior. The present paper is the continuation of our previous study which has shown an increased occurrence of creatine inclusions in rat hippocampal formations from the acute phase of pilocarpine-induced status epilepticus (SE) and positive correlation between their quantity and the total time of seizure activity within the observation period. In this paper, we tried to verify if anomalies in hippocampal creatine accumulation were the temporary or permanent effect of pilocarpine-evoked seizures. To realize this purpose, male Wistar rats in the latent phase (3 days after pilocarpine administration) were examined. The results obtained for the period when stabilization of animal behavior and EEG occurs were afterwards compared with ones obtained for the acute phase of pilocarpine-induced SE and for naive controls. To investigate the frequency of creatine inclusions within the hippocampal formation as well as in its selected areas (sectors 1–3 of Ammon’s horn (CA1–CA3), dentate gyrus (DG), and hilus of DG) and cellular layers (pyramidal, molecular, multiform, and granular cell layers), synchrotron radiation-based Fourier-transform infrared microspectroscopy was used. The applied technique, being a combination of light microscopy and infrared spectroscopy, allowed us to localize microscopic details in the analyzed samples and provided information concerning their chemical composition. Moreover, the use of a synchrotron source of IR radiation allowed us to carry out the research at the diffraction-limited spatial resolution which, because of the typical size of creatine inclusions (from a few to dozens of micrometers), was necessary for our study. The comparison of epileptic animals in the latent phase with controls showed statistically significant increase in the number of creatine inclusions for most of the analyzed hippocampal regions, all examined cellular layers, as well as the whole hippocampal formation. Moreover, for the hilus of the DG and CA3 area, the number of creatine deposits was higher in the latent than in the acute phase after pilocarpine injection. In light of the obtained results, an anomaly in the hippocampal accumulation of creatine is the long-term effect of pilocarpine-evoked seizures, and the intensity of this phenomenon may increase with time passing from the primary injury.

Preparation and characterisation of chromium and sodium tantalate layers by anodic spark deposition

A plasma-electrochemical synthesis was used to prepare chromium and sodium tantalate layers. These layers were deposited on a tantalum anode surface as ceramic compounds from aqueous electrolytes. The typical pore structure morphology of the tantalate layer was characterised by SEM as well as fractures which provide evidence of an intimate contact between layers and substrate. An XRD-study showed that the layers are composed of a mixture of Ta₂O₅ and either NaTaO₃ or CrTaO₄ depending on the electrolyte composition. Quantitative characterisation by EPM indicated higher chromium and tantalum concentrations on the electrolyte/layer interface than at the layer/tantalum interface. The chemical state of tantalum was investigated by means of XPS. Received: 15 July 1997 / Revised: 5 March 1998 / Accepted: 9 March 1998     

Membrane fouling from ammonia recovery analyzed by ATR-FTIR imaging

The composition of the fouling layer formed during ammonia stripping via membrane distillation from model pig manure and the change in fouling composition as a result of three cleaning procedures was examined using ATR-FTIR imaging and k-means clustering. The use of ATR-FTIR imaging is advantageous as it is a label free technique that provides information on the chemical composition of the fouling as well as a high spatial resolution. The model manure was designed to resemble average Danish pig manure containing representative concentrations of inorganic and organic compounds and particle size distribution similar to the liquid fraction from mechanically separated manure. The fouling layer deposited on polypropylene, PP, and polytetrafluoroethylene, PTFE, membranes were investigated in combination with three cleaning procedures applying deionized water, 1 M NaOH solution followed by a 1 M citric acid solution or Novadan cleaning agents. The spectral data revealed that the fouling layer deposited on both PP and PTFE membranes before cleaning mainly consisted of carbohydrates, protein and lipids. Carboxylates and free fatty acids originating from reactions between NaOH and straw and proteins and lipids, respectively, and lignin were identified in some of the samples. The combination of PTFE membrane and Novadan cleaning agent resulted in the cleanest membranes, as only residual lipids were identified on these samples.     

Chemical microcharacterization of ultrathin iodide conversion layers and adsorbed thiocyanate surface layers on silver halide microcrystals with time-of-flight SIMS.

The technique of imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) and dual beam depth profiling has been used to study the composition of the surface of tabular silver halide microcrystals. Analysis of individual microcrystals with a size well below 1 microm from a given emulsion is possible. The method is successfully applied for the characterization of silver halide microcrystals with subpercent global iodide concentrations confined in surface layers with a thickness below 5 nm. The developed TOF-SIMS analytical procedure is explicitly demonstrated for the molecular imaging of adsorbed thiocyanate layers (SCN) at crystal surfaces of individual crystals and for the differentiation of iodide conversion layers synthesized with KI and with AgI micrates (nanocrystals with a size between 10 and 50 nm). It can be concluded that TOF-SIMS as a microanalytical, surface-sensitive technique has some unique properties over other analytical techniques for the study of complex structured surface layers of silver halide microcrystals. This offers valuable information to support the synthesis of future photographic emulsions.     

Electrochemical properties of interface formed by interlaced layers of DNA- and lysozyme-coated single-walled carbon nanotubes

Multifunctional coatings were produced by the layer by layer assembly of single-walled carbon nanotubes (SWNT) dispersed in DNA and lysozyme (LSZ) on an insulating glass substrate. The electrochemical properties of these mechanically robust biocoatings were characterized for the first time using scanning electrochemical microscopy (SECM) and impedance spectroscopy (IS). SECM surface analysis demonstrated an increase in tip current with a corresponding increase in the number of oppositely polarized interlaced layers, indicating that subsequent layers were not electrically insulated from each other and a direct correlation exists between SECM feedback response and the number of layers. The rate of charge transport was also dependent on the chemical composition/polarity of the outermost surface layer. Coatings terminating in SWNT-DNA resulted in more positive feedback than those terminating in SWNT-LSZ. IS analysis demonstrated that the SWNT-DNA had a low charge transfer resistance in comparison with SWNT-LSZ, which is consistent with the results obtained by SECM. These results enable enhanced fundamental understanding and prediction of the electrical properties of SWNT-biopolymer layers with controlled interlaced polarities and orientation. Furthermore, these finding highlight the potential for SWNT-biopolymers in electronic and sensing applications.     

Energy-dispersive X-ray fluorescence spectrometer for analysis of conventional and micro-samples: Preliminary assessment

The energy-dispersive X-ray fluorescence spectrometer for analysis of conventional and micro-samples using pinhole collimators of various sizes is developed. The measurements can be performed in the air or, in order to decrease the absorption of long-wavelength radiation of low-Z elements, in helium atmosphere. The sample is excited by the air-cooled Rh target X-ray tube of ca. 100 μm nominal focal spot size and maximum power 75 W. The X-ray spectra of the samples are collected by thermoelectrically cooled Si-PIN detector. The tungsten pinhole collimators of the size holes from 50 to 2000 μm are placed between primary filter and analyzed sample to reduce size of analyzed area. The sample can be moved using the X–Y stage. The position of the sample is monitored by CCD camera and two laser pointers. The beam spot sizes for various collimators are evaluated by the thin-wire and knife-edge methods. Beside the beam spot sizes, the loss of radiation intensity and the changes of spectral distribution of the incident radiation caused by applying various collimators are also investigated. The sample-surface-down geometry in the designed spectrometer allows for a simple analysis of various samples: solutions, loose powders, solid samples of conventional size and micro-samples.     

Temperature responsive surface layers of modified celluloses

The temperature-dependent properties of pre-adsorbed layers of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) were investigated on silica and hydrophobized silica surfaces. Three different techniques, quartz crystal microbalance with dissipation monitoring, ellipsometry, and atomic force microscopy imaging, were used, providing complementary and concise information on the structure, mass and viscoelastic properties of the polymer layer. Adsorption was conducted at 25 °C, followed by a rinsing step. The properties of such pre-adsorbed layers were determined as a function of temperature in the range 25 °C to 50 °C. It was found that the layers became more compact with increasing temperature and that this effect was reversible, when decreasing the temperature. The compaction was more prominent for MC, as shown in the AFM images and in the thickness data derived from the QCM analysis. This is consistent with the fact that the phase transition temperature is lower, in the vicinity of 50 °C, for MC than for HPMC. The water content of the adsorbed layers was found to be high, even at the highest temperature, 50 °C, explored in this investigation.     

Investigation of the multilayered structure and microfibril angle of different types of bamboo cell walls at the micro/nano level using a LC-PolScope imaging system

Bamboo has excellent mechanical properties compared to wood and other plant materials, due to its multilayered structure and polytropic microfibril angle (MFA). The micro/nano scale structure and MFA of fibers, parenchyma cells, and vessels from 4-year-old Moso bamboo (Phyllostachys Heterocycla Var. Pubescens) were investigated by a novel LC-PolScope imaging system and transmission electron microscopy. At the nanoscale, the numbers of layers and accurate MFA for each layer especially thin layers could be obtained quickly using this novel LC-PolScope imaging system. Based on the differences of structure and shape, fibers and parenchyma cells in the vascular bundle were divided into FI, II, III and PI, II cells, respectively. The former class of FI, II, III included 2, 6–8, and 6–8 secondary cell wall layers in turn. The latter class exhibited 9 secondary cell wall layers, with a maximum of 16 layers. To our knowledge, this is the first report of accurate MFA measurement based on the differences of structure and shape for every layer of single fibers, parenchyma cells and vessels in the vascular bundle. For all three cell types, the results also showed that the MFA of sub-layers in secondary walls followed the same changing law: alternating smaller and then bigger MFA. This structural form may be the consequence of natural selection and optimization indicating the long-term mechanical adaptation of bamboo.