Abstract: We report on a wearable fingertip sensor for on-the-spot identification of cocaine and its cutting agents in street samples. Traditionally, on-site screening is performed by means of colour tests which are difficult to interpret and lack selectivity. By presenting the distinct voltammetric response of cocaine, cutting agents, binary mixtures of cocaine and street samples in solution and powder street samples, we were able to elucidate the electrochemical fingerprint of all these compounds. The new electrochemical concept holds considerable promise as an on-site screening method.

Abstract: In the present work, a novel graphene (GN) and gelatin (GTN) composite was prepared and used as an immobilization matrix for hemoglobin (Hb). Compared with Hb immobilized on a bare, GN or GTN modified glassy carbon electrode (GCE), a stable and pair of well-defined quasi redox couple was observed at an Hb modified GN/GTN composite GCE at a formal potential of −0.306 V versus Ag|AgCl. The direct electrochemical behavior of Hb was greatly enhanced by the presence of both GTN and GN. A heterogeneous electron transfer rate constant (Ks) was calculated as 3.82 s−1 for Hb immobilized at GN/GTN modified GCE, which indicates the fast direct electron transfer of Hb toward the electrode surface. The biosensor shows a stable and wide linear response for H2O2 in the linear response range from 0.1 μM to 786.6 μM with an analytical sensitivity and limit of detection of 0.48 μAμM−1 cm−2 and 0.04 μM, respectively. The fabricated biosensor holds its high selectivity in the presence of potentially active interfering species and metal ions. The biosensor shows its satisfactory practical ability in the commercial contact lens solution and human serum samples.

Abstract: Macro X-ray fluorescence scanning (MA-XRF) is gradually becoming an established technique for the non-invasive analytical investigation of painted surfaces. This paper discusses some of the benefits and limitations of employing MA-XRF for the study of manuscript illuminations. Art historical research on this type of artefacts that is based on scientific measurements is often limited by the fact that usually no sampling can take place. Hence there is a need for non-invasive analytical tools that make it possible to conduct systematic investigations. As a representative example of this type of objects, a 15th century Italian manuscript fragment from the collection of the Fitzwilliam Museum in Cambridge (UK) is investigated. The aims of the study were to gain insight into the materials and techniques employed by Renaissance illuminators and to help answer specific questions regarding the fragment's authorship and geographic origin. The complementarity and advantages of MA-XRF mapping versus site-specific analyses are discussed. For this purpose, MA-XRF data are evaluated and compared with the results of other analytical techniques. The interpretation of the elemental maps is discussed along with the challenges faced during the analysis. (C) 2015 Elsevier B.V. All rights reserved.

Abstract: There is a long tradition in evaluating industrial atmospheres by measuring the corrosion rate of exposed metal coupons. The heritage community also uses this method, but the interpretation of the corrosion rate often lacks clarity due to the low corrosivity in indoor museum environments. This investigation explores the possibilities and drawbacks of different silver corrosion rate assessments. The corrosion rate is determined by three approaches: (1) chemical characterization of metal coupons using analytical techniques such as electrochemical measurements, SEM-EDX, XRD, and µ-Raman spectroscopy, (2) continuous corrosion monitoring methods based on electrical resistivity loss of a corroding nm-sized metal wire and weight gain of a corroding silver coated quartz crystal, and (3) characterization of the visual degradation of the metal coupons. This study confirms that subtle differences in corrosivity between locations inside a museum can be determined on condition that the same corrosion rate assessment is used. However, the impact of the coupon orientation with respect to the prevailing direction of air circulation can be substantially larger than the impact of the coupon location.

Abstract: The painting Saul and David, considered to date from c. 1652 and previously attributed to Rembrandt van Rijn and/or his studio, is a complex work of art that has been recently subjected to intensive investigation and conservation treatment. The goal of the research was to give insight into the painting's physical construction and condition in preparation for conservation treatment. It was also anticipated that analysis would shed light on authenticity questions and Rembrandt's role in the creation of the painting. The painting depicts the Old Testament figures of King Saul and David. At left is Saul, seated, holding a spear and wiping a tear from his eye with a curtain. David kneels before him at the right playing his harp. In the past, the large sections with the life-size figures were cut apart and later reassembled. A third piece of canvas was added to replace a missing piece of canvas above the head of David. As part of the investigation into the authenticity of the curtain area, a number of paint micro samples were examined with LM and SEM-EDX. Given that the earth, smalt and lake pigments used in the painting could not be imaged with traditional imaging techniques, the entire painting was also examined with state of the art non-destructive imaging techniques. Special attention was devoted to the presence of cobalt-containing materials, specifically the blue glass pigment smalt considered characteristic for the late Rembrandt. A combination of quantitative electron microprobe analysis and macroscopic X-ray fluorescence scanning revealed that three types of cobalt-containing materials are present in the painting. The first type is a cobalt drier that was found in the overpaint used to cover up the canvas inset and the joins that were added in the 19th century. The other two Co-containing materials are part of the original paint used by Rembrandt and comprise two varieties of smalt, a K-rich glass pigment that derives its gray-blue color by doping with Co-ions. Smalt paint with a higher Ni content (NiO:CoO ratio of around 1:4) was used to depict the blue stripes in Saul's colorful turban, while smalt with a lower Ni content was employed (NiO:CoO ratio of around 1:5) for the broad expanses of Saul's garments. The presence of two types of smalt not only supports the recent re-attribution of the painting to Rembrandt, but also that the picture was painted in two phases. Saul's dark red garment is painted in a rough, “loose” manner and the now discolored smalt-rich layer was found to have been partially removed during a past restoration treatment/s. In contrast, the blue-green smalt in the turban is much better preserved and provides a colorful accent. While the use of different types of smalt in a Rembrandt painting has been previously identified using quantitative EDX analysis of paint cross-sections, to the best of our knowledge this is the first time such a distinction has been observed in a 17th-century painting using non-destructive imaging techniques. In addition to the XRF-based non-invasive elemental mapping, hyperspectral imaging in the visual to near-infrared (VNIR) region was also carried out. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: Caravaggio's early production as a portrait painter is still the subject of research and a fount of enigmas. Despite the numerous citations in documents, only rarely have these been linked unequivocally to paintings known to date. This is also the case with the `portrait of Farinaccio criminalist painted on a head-size canvas believed to be by Michelangelo from Caravaggio', that was listed in the 1638 inventory of the Marquis Giustiniani and with `the speaker wearing a robe, painted by Caravaggio' on a head-size canvas, owned in 1652 by Caterina Campani, Onorio Longhi's wife. The present multidisciplinary research examines the rediscovery of the portrait of Prospero Farinacci by Caravaggio. The painting, undisclosed until now, hides an underlying female portrait. The authors investigate both compositions from a technical, iconographical and critical point of view, supporting Caravaggio's attribution. The technical researches allow cross-validation in the brushwork and materials of the picture, compared to Caravaggio's early painting technique and style. The portrait of Maffeo Barberini, recently re-ascribed to Caravaggio, shows a significant similarity, while the underlying woman of the retrieved painting closely resembles the gipsy of the Louvre Fortune Teller. In addition, a newly introduced and advanced imaging technique (MaXRF) has detected on the male portrait the feature of the lawyer's robe, which supports the identification with Prospero Farinacci. The intriguing topic of physiognomic accuracy versus stylizing tendency in Caravaggio's portraiture is considered with the aid of Giulio Mancini's observations. Besides, the possible interpretation of the underlying figure as a religious subject sheds a light on the obscure activity of the young Caravaggio in Lorenzo Carli's workshop, recently brought to scholars' attention by new documents and hypotheses.

Abstract: Understanding the reactivity of (semiconductor) pigments provides vital information on how to improve conservation strategies for works of art in order to avoid rapid degradation of the pigments. This study focuses on the photoactivity of minium (Pb3O4), a semiconductor pigment, that gives rise to strong discoloration phenomena upon exposure to various environmental conditions. To demonstrate its photoactivity, an electrochemical setup with minium-modified graphite electrode (C|Pb3O4) was used. It is confirmed that minium is a p-type semiconductor which is photoactive during illumination and becomes inactive in the dark. Raman measurements confirm the formation of the degradation products. The photoactivity of a semiconductor pigment is partly defined by the presence of lead oxide (PbO) impurities; these introduce new states in the original band gap. It will be experi-mentally evidenced that the presence of PbO particles in minium leads to an upward shift of the valence band that reduces the band gap. Thus, upon photoexcitation, the electron/hole separation is more easily initialized. The PbO/Pb3O4 composite electrodes demonstrate a higher reductive photocurrent compared to the photocurrent registered at pure PbO or Pb3O4 modified electrodes. Upon exposure to light with energy close to and above the band gap, electrons are excited from the valence band to the conduction band to initialize the reduction of Pb(IV) to Pb(II), resulting in the initial formation of PbO. However in the presence of bicarbonate ions, a significantly higher photoreduction current is recorded since the PbO reacts further to form hydrocerussite. Therefore the presence of bicarbonates in the environment stimulates the photodecomposition process of minium and plays an important role in the degradation process.

Abstract: Orpiment and realgar, both arsenic sulfide pigments respectively used for their vivid yellow and red-orange hues, are two of many artists' pigments that appear not to be stable upon light exposure, quickly degrading to arsenic trioxide and arsenate. This often results in whitening or transparency in the painted surfaces. While conventional techniques such as microscopic Raman (mu-RS) and microscopic Fourier transform infrared (mu-FTIR) spectroscopies can allow a quick and relatively easy identification of the orpiment, realgar, artificial arsenic sulfide glass and, to some extent, arsenic oxide, the identification and visualization of distributions of the degradation products – and especially arsenate compounds – in the paint micro-samples is generally more challenging. This challenge is due to the rather unfavorable limit of detection and low spectral resolution of such conventional spectroscopic techniques. This restricts the conclusions that can be drawn regarding the conservation state of valuable works of art. In this paper, we present how synchrotron radiation (SR) based techniques can overcome this challenge while working on painting cross-sections taken from a 17th-century painting by the Flemish artist Daniel Seghers (oil on canvas, Statens Museum for Kunst, Denmark) and an 18th-century French Chinoiserie (private collection, France). SR micro-X-ray fluorescence (m-XRF) mapping analysis performed on a visually degraded orpiment-containing paint stratigraphy reveals that arsenic is distributed throughout the entire cross-section, while X-ray absorption near edge structure (mu-XANES) demonstrated that the arsenic is present in both arsenite (As-III) and arsenate (As-V) forms. The latter compound(s), despite being barely identifiable by means of FTIR, were not only located at the surface of large and partially altered grains of arsenic sulfide but also spread throughout the entire paint stratigraphy. Their presence and distribution are attributed either to the complete degradation of smaller arsenic sulfide grains or to migration of the arsenates within the paint layer away from their original location of formation. The combination of mu-XRF and mu-XANES was very useful for the characterization of the advanced degradation state of the arsenic-containing pigments in paint systems; this type of information could not be obtained by means of conventional spectroscopic methods of microanalysis.

Abstract: The present work reports on the application and the evaluation of a multitude of crosslinking approaches including high-energy irradiation, redox-initiating systems and conventional carbodiimide-coupling chemistry for frozen and/or freeze-dried porous gelatin scaffolds. The latter is particularly relevant for a plethora of biomedical applications such as tissue engineering supports, wound dressings, adhesive and absorbent pads for surgery, etc. Moreover, the results obtained for gelatin can be considered a proof-of-concept to be extrapolated to other polymer systems containing double bonds and/or amines and carboxylic acids to also realize scaffold crosslinking in dry or frozen state. The results showed that high-energy irradiation at -5 A degrees C enabled sufficient segmental mobility to induce chemical crosslinking after performing a cryogenic treatment of methacrylamide-modified gelatin scaffolds. Alternatively, although several redox-initiating systems were unable to chemically crosslink functionalized gelatin, the combination of ammonium persulphate and TEMED resulted in the formation of scaffolds with a reasonable gel fraction. Interestingly, carbodiimide-coupling was found suitable to crosslink freeze-dried gelatin matrices.

Abstract: Serpentine and amphibole asbestos occur naturally in certain geologic settings worldwide, most commonly in association with ultramafic rocks, along associated faults. Ultramafic rocks have been used in Pin County, Southern Brazil for decades for the purpose of road paving in rural and urban areas, but without the awareness of their adverse environmental and health impact. The aim of this study was the chemical characterization of aerosols re-suspended in two rural roads of Pin, paved with ultramafic rocks and to estimate the pulmonary deposition of asbestos aerosols. Bulk aerosol samples were analyzed by means of X-ray fluorescence spectrometry and X-ray diffraction analysis, in order to characterize elemental composition and crystallinity. Single-particle compositions of aerosols were analyzed by computer-controlled electron-probe microanalysis, indicating the presence of a few percentages of serpentine and amphibole. Given the chemical composition and size distribution of aerosol particles, the deposition efficiency of chrysotile, a sub-group of serpentine, in two principal segments of the human respiratory system was estimated using a lung deposition model. As an important finding, almost half of the inhaled particles were calculated to be deposited in the respiratory system. Asbestos depositions were significant (similar to 25 %) in the lower airways, even though the selected breathing conditions (rest situation, nose breathing) implied the lowest rate of respiratory deposition. Considering the fraction of inhalable suspended chrysotile near local roads, and the long-term exposure of humans to these aerosols, chrysotile may represent a hazard, regarding more frequent development of lung cancer in the population of the exposed region.

Abstract: One of the most striking but unexplained phenomena in the natural degradation of glass is the transformation of an almost colorless, transparent and homogeneous glass into a colored, opaque and heterogeneous degradation layer. In many cases, the degradation layer consists of numerous lamellae with a thickness between 0.1 and 10 pm. However, both internal structure and formation proess of laminated degradation layers remain unclear. In this paper, a model is proposed where we assume that transformed (degraded) glass consists of a random packing of nano-sized silica particles while the lamellae are the result of different packing densities. The model is able to connect the texture of numerous lamellae observed by several types of microscopic techniques with the structure at molecular level determined by means of chemical analysis. In addition, the model is able to explain numerous properties such as the parameters responsible for the contrast between lamellae. This contrast can be caused by differences in color, density, elemental composition, or surface roughness. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: Despite its widespread application in the fields of ophthalmology, orthopedics and dentistry and the stringent need for polymer packagings that induce in vivo tissue integration, the full potential of poly(methyl methacrylate) (PMMA) and its derivatives as medical device packaging material has not been explored yet. We therefore elaborated on the development of a universal coating for methacrylate-based materials which ideally should reveal cell-interactivity irrespective of the polymer substrate bulk properties. Within this perspective, the present work reports on the UV-induced synthesis of PMMA and its more flexible poly(ethyleneglycol) (PEG)-based derivative (PMMAPEG) and its subsequent surface decoration using polydopamine (PDA) as well as PDA combined with gelatin B (Gel B). Successful application of both layers was confirmed by multiple surface characterization techniques. The cell interactivity of the materials was studied by performing live-dead assays and immunostainings of the cytoskeletal components of fibroblasts. It can be concluded that only the combination of PDA and Gel B yields materials posessing similar cell interactivities, irrespective of the physicochemical properties of the underlying substrate. The proposed coating outperforms both the PDA functionalized and the pristine polymer surfaces. A universal cell-interactive coating for methacrylate-based medical device packaging materials has thus been realized.

Abstract: The cytoglobins of the Antarctic fish Chaenocephalus aceratus and Dissostichus mawsoni have many features in common with human cytoglobin. These cytoglobins are heme proteins in which the ferric and ferrous forms have a characteristic hexacoordination of the heme iron, i.e. axial ligation of two endogenous histidine residues, as confirmed by electron paramagnetic resonance, resonance Raman and optical absorption spectroscopy. The combined spectroscopic analysis revealed only small variations in the heme-pocket structure, in line with the small variations observed for the redox potential. Nevertheless, some striking differences were also discovered. Resonance Raman spectroscopy showed that the stabilization of an exogenous heme ligand, such as CO, occurs differently in human cytoglobin in comparison with Antarctic fish cytoglobins. Furthermore, while it has been extensively reported that human cytoglobin is essentially monomeric and can form an intramolecular disulfide bridge that can influence the ligand binding kinetics, 3D modeling of the Antarctic fish cytoglobins indicates that the cysteine residues are too far apart to form such an intramolecular bridge. Moreover, gel filtration and mass spectrometry reveal the occurrence of non-covalent multimers (up to pentamers) in the Antarctic fish cytoglobins that are formed at low concentrations. Stabilization of these oligomers by disulfide-bridge formation is possible, but not essential. If intermolecular disulfide bridges are formed, they influence the heme-pocket structure, as is shown by EPR measurements.

Abstract: This work reports the first systematic chemical characterization of Portuguese 18th century glassware. 28 selected glass fragments, recovered from an archaeological excavation carried out in the site where King D. João V of Portugal established an important glass manufacture, Real Fábrica de Vidros de Coina (Coina Royal Glass Factory), were studied. This factory operated from 1719 until 1747, the year in which the factory was transferred to Marinha Grande. The fragments were analysed by micro-energy dispersive X-ray fluorescence (micro-EDXRF), using a portable spectrometer ArtTAX, and scanning electron microscopy (SEM-EDX). The analytical data showed that a large variety of glass types was manufactured in that factory, namely soda-lime glass, mixed-alkali glass, high lime-low alkali glass, potash glass and lead glass. In general, the composition of the glass varies according to the function of the objects. It was demonstrated that micro-EDXRF can be an important tool to characterize museum glass objects when only in situ non-invasive analytical methods are allowed.

Abstract: A new electrocatalytic conversion of alcohols to ketones and aldehydes was developed based on an electrochemical study of Shvos complex. The oxidation of secondary alcohols was efficiently performed under mild conditions using a catalytic amount of Shvos catalyst, in combination with a sub-stoichiometric amount of 2,6-dimethoxy-1,4- benzoquinone in N,N-dimethylformamide at 80 8C. The hydroquinone thus formed is continuously reoxidized with the aid of an electrochemical device. Excellent yields for different ketones, aromatic as well as aliphatic and a,b-unsaturated ketones, are obtained. In addition, chemoselectivity towards oxidation of the secondary alcohol is achieved when converting vicinal diols such as 1,2-octanediol and 1,2-decanediol.