We present trace-element and composition analysis of azurite pigments in six illuminated manuscript leaves, dating from the thirteenth to sixteenth century, using synchrotron-based, large-area x-ray ...fluorescence (SR-XRF) and diffraction (SR-XRD) mapping. SR-XRF mapping reveals several trace elements correlated with azurite, including arsenic, zirconium, antimony, barium, and bismuth, that appear in multiple manuscripts but were not always detected by point XRF. Within some manuscript leaves, variations in the concentration of trace elements associated with azurite coincide with distinct regions of the illuminations, suggesting systematic differences in azurite preparation or purification. Variations of the trace element concentrations in azurite are greater among different manuscript leaves than the variations within each individual leaf, suggesting the possibility that such impurities reflect distinct mineralogical/geologic sources. SR-XRD maps collected simultaneously with the SR-XRF maps confirm the identification of azurite regions and are consistent with impurities found in natural mineral sources of azurite. In general, our results suggest the feasibility of using azurite trace element analysis for provenance studies of illuminated manuscript fragments, and demonstrate the value of XRF mapping in non-destructive determination of trace element concentrations within a single pigment.
Polydimethylsiloxane (PDMS) has been widely used as a surface coating material, which has been reported to possess dynamic omniphobicity to a wide range of both polar and nonpolar solvents due to its ...high segmental flexibility and mobility. However, such high flexibility and mobility also enable penetration of small molecules into PDMS coatings, which alter the chemical and physical properties of the coating layers. To improve the anti-penetration properties of PDMS, a series of fluorinated alkyl segments are grafted to a diblock copolymer of polystyrene-block-poly(vinyl methyl siloxane) (PS-b-PVMS) using thiol–ene click reactions. This article reports the chemical characterization of these model fluorosilicone block copolymers and uses fluorescence measurements to investigate the dye penetration characteristics of polymer thin films. The introduction of longer fluorinated alkyl chains can gradually increase the anti-penetration properties as the time to reach the maximum fluorescence intensity (t peak) gradually increases from 11 s of PS-b-PVMS to more than 1000 s of PS-b-P(n-C6F13-VMS). The improvement of anti-penetration properties is attributed to stronger inter-/intrachain interactions, phase segregation of ordered fluorinated side chains, and enhanced hydrophobicity caused by the grafting of fluorinated alkyl chains.
Perylene diimide (PDI) derivatives are important components of organic circuits and photovoltaic systems, but the electron trapping mechanism(s) in higher-LUMO PDIs (−3 to −4 eV, where radical anions ...are expected to react with atmospheric water and oxygen) are not well characterized. Here, we examine the spatial distribution of traps in transistors made from PDIs with these higher LUMO levels and measure trap-clearing spectra in n-type organic materials using time- and wavelength-resolved frequency-modulated Kelvin probe force microscopy (FM-KPFM). We find that the rate of trap-clearing under visible light does not follow a LUMO-level trend, and we observe spectral evidence for different trapping mechanisms on bare versus HMDS-treated SiO2.
The Thannhauser Collection of the Solomon R. Guggenheim Museum, New York, represents an important survey of European avant-garde art production during the late 19th and early 20th centuries. Among ...the works included in this collection are three paintings by Vincent van Gogh, namely
Roadway with Underpass
(1887),
Landscape with Snow
(1888), and
Mountains at Saint-Rémy
(1889). These examples each exhibit some degree of surface alteration, including fading of specific pigments and, in one case, a non-original, discolored varnish, resulting in obscured color and spatial relationships, as well as being the subject of questions regarding authenticity in the case of the two earlier pictures. Initial examination involved documentation of the brushwork, paint quality, and distribution of colors under magnification. Infrared (IR) and ultraviolet (UV) photography, as well as X-radiography, provided additional information on the surface coatings, the structure of the works, and their supports. Subsequently, an in-depth scientific investigation of the ground and paint layers, with a special focus on fading colors and altered surfaces, was carried out non-invasively with point and macro-X-ray fluorescence (XRF) spectroscopy, visible reflection spectroscopy, and multi-channel visible spectrum four-light imaging, followed by the analysis of cross sections and dispersed pigment samples by means of optical microscopy, transmission Fourier-transform infrared (FTIR) and Raman spectroscopies, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), as well as high-performance liquid chromatography with photodiode array detection (HPLC-PDA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results indicated that both the brushwork and artist's palette of all three paintings are consistent with data previously reported for other Van Gogh works and with pigments described in the artist’s letters to his friends and his brother Theo. Most notably, evidence of biodeterioration and paint alteration phenomena was found on
Roadway with Underpass
, while specific pigments such as eosin red—historically sold as geranium lake—were detected in areas of
Landscape with Snow
and
Mountains at Saint-Rémy
that display severe fading. In addition to assisting the development of a suitable plan for the conservation of the 1887 painting, this study traces the progression of Van Gogh’s practice over three years critical to his artistic development, discusses the historical context in which each masterpiece was created, identifies the range of materials and techniques used, and addresses authenticity questions by providing a comparison with results of scientific analysis from other similar works.
The first commercially viable photographic image, the daguerreotype, captured images for a span of approximately 20 years (1839–1860). DeDterioration now disfigures many of these valuable images. One ...proposed restoration method is an electrochemical process. However, its safety and effectiveness are still under debate within the conservation community as the effects of this treatment, and its physical and chemical impact on the daguerreotype image, have not yet been analyzed in depth. This study used synchrotron-based micro-X-ray fluorescence to map the elemental distribution pre- and post-electrocleaning on 19th century daguerreotypes using both soft and hard incident X-rays. X-ray absorption spectroscopy was used to probe local chemistry before and after cleaning. Two different electro-treatment methods were compared: the original method proposed by Barger and a second put forward by Wei. When used correctly, both processes significantly reduced the S and Cl surface contamination without dulling the surface. However, both electrochemical methods used in this study resulted in a loss of Hg and Au from the surface. In all cases, the Hg distribution tracks with image particle density allowing the retrieval of full portraits from entirely corroded daguerreotypes, suggesting that Hg concentration may be a useful proxy for the original image.
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