Gallone Samples Archive: a resource for Cultural Heritage studies

A vast collection of samples from artworks. A unique resource for future research in the field of conservation: investigating samples, implementing more advanced techniques

Dual wavelength excitation for the time-resolved photoluminescence imaging of painted ancient Egyptian objects

Background: The scientific imaging of works of art is crucial for the assessment of the presence and distribution of pigments and other materials on surfaces. It is known that some ancient pigments are luminescent: these include pink red-lakes and the blue and purple pigments Egyptian Blue (CaCuSi4O10), Han blue (BaCuSi4O10) and Han purple (BaCuSi2O6). Indeed, the unique near-infrared luminescence emission of Egyptian blue allows the imaging of its distribution on surfaces. Results: We focus on the imaging of the time-resolved photoluminescence of ancient Egyptian objects in the Burri Collection from the Civic Museum of Crema and of the Cremasco (Italy). Time-resolved photoluminescence images have been acquired using excitation at 355 nm for detecting the ns-emission of red lakes and binding media; by employing 532 nm excitation Egyptian blue is probed, and the spatial distribution of its long-lived microsecond emission is imaged. For the first time we provide data on the photoluminescence lifetime of Egyptian blue directly from objects. Moreover, we demonstrate that the use of a pulsed laser emitting at two different wavelengths increases the effectiveness of the lifetime imaging technique for mapping the presence of emissions from pigments on painted surfaces. Laser-induced luminescence spectra from different areas of the objects and traditional digital imaging, using led-based lamps, long pass filters and a commercial photographic camera, complement the results from photoluminescence lifetime imaging. We demonstrate the versatility of a new instrumental setup, capable of recording decay emission kinetics with lifetimes from nanosecond to microseconds. Conclusions: While the combined wavelength approach for the imaging of emissions from different materials has been demonstrated for the study of ancient Egyptian pigments (both organic and inorganic), the method could be extended to the analysis of modern pigments and paintings

Integrating multimodal Raman and photoluminescence microscopy with enhanced insights through multivariate analysis

This paper introduces a novel multimodal optical microscope, integrating Raman and laser-induced photoluminescence (PL) spectroscopy for the analysis of micro-samples relevant in Heritage Science. Micro-samples extracted from artworks, such as paintings, exhibit intricate material compositions characterized by high complexity and spatial heterogeneity, featuring multiple layers of paint that may be also affected by degradation phenomena. Employing a multimodal strategy becomes imperative for a comprehensive understanding of their material composition and condition. The effectiveness of the proposed setup derives from synergistically harnessing the distinct strengths of Raman and laser-induced PL spectroscopy. The capacity to identify various chemical species through the latter technique is enhanced by using multiple excitation wavelengths and two distinct excitation fluence regimes. The combination of the two complementary techniques allows the setup to effectively achieve comprehensive chemical mapping of sample through a raster scanning approach. To attain a competitive overall measurement time, we employ a short integration time for each measurement point. We further propose an analysis protocol rooted in a multivariate approach. Specifically, we employ non-negative matrix factorization as the spectral decomposition method. This enables the identification of spectral endmembers, effectively correlated with specific chemical compounds present in samples. To demonstrate its efficacy in Heritage Science, we present examples involving pigment powder dispersions and stratigraphic micro-samples from paintings. Through these examples, we show how the multimodal approach reinforces material identification and, more importantly, facilitates the extraction of complementary information. This is pivotal as the two optical techniques exhibit sensitivity to different materials. Looking ahead, our method holds potential applications in diverse research fields, including material science and biology

A photoluminescence study of the changes induced in the zinc white pigment by formation of zinc complexes

It is known that oil paintings containing zinc white are subject to rapid degradation. This is caused by the interaction between the active groups of binder and the metal ions of the pigment, which gives rise to the formation of new zinc complexes (metal soaps). Ongoing studies on zinc white paints have been limited to the chemical mechanisms that lead to the formation of zinc complexes. On the contrary, little is known of the photo-physical changes induced in the zinc oxide crystal structure following this interaction. Time-resolved photoluminescence spectroscopy has been applied to follow modifications in the luminescent zinc white pigment when mixed with binder. Significant changes in trap state photoluminescence emissions have been detected: the enhancement of a blue emission combined with a change of the decay kinetic of the well-known green emission. Complementary data from molecular analysis of paints using Fourier transform infrared spectroscopy confirms the formation of zinc carboxylates and corroborates the mechanism for zinc complexes formation. We support the hypothesis that zinc ions migrate into binder creating novel vacancies, affecting the photoluminescence intensity and lifetime properties of zinc oxide. Here, we further demonstrate the advantages of a time-resolved photoluminescence approach for studying defects in semiconductor pigments

Time-resolved photoluminescence microscopy for the analysis of semiconductor-based paint layers

In conservation, science semiconductors occur as the constituent matter of the so-called semiconductor pigments, produced following the Industrial Revolution and extensively used by modern painters. With recent research highlighting the occurrence of various degradation phenomena in semiconductor paints, it is clear that their detection by conventional optical fluorescence imaging and microscopy is limited by the complexity of historical painting materials. Here, we illustrate and prove the capabilities of time-resolved photoluminescence (TRPL) microscopy, equipped with both spectral and lifetime sensitivity at timescales ranging from nanoseconds to hundreds of microseconds, for the analysis of cross-sections of paint layers made of luminescent semiconductor pigments. The method is sensitive to heterogeneities within micro-samples and provides valuable information for the interpretation of the nature of the emissions in samples. A case study is presented on micro samples from a painting by Henri Matisse and serves to demonstrate how TRPL can be used to identify the semiconductor pigments zinc white and cadmium yellow, and to inform future investigations of the degradation of a cadmium yellow paint

Time-resolved photoluminescence spectroscopy and imaging: New approaches to the analysis of cultural heritage and its degradation

Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested

Imaging and micro-invasive analyses of black stains on the passepartout of Codex Atlanticus Folio 843 by Leonardo da Vinci

: This paper accounts for the diagnostic campaign aimed at understanding the phenomenon of black stains appeared on the passepartout close to the margins of Folio 843 of Leonardo da Vinci's Codex Atlanticus. Previous studies excluded microbiological deterioration processes. The study is based on a multi-analytical approach, including non-invasive imaging measurements of the folio, micro-imaging and synchrotron spectroscopy investigations of passepartout fragments at different magnifications and spectral ranges. Photoluminescence hyperspectral and lifetime imaging highlighted that black stains are not composed of fluorescent materials. μATR-FTIR imaging of fragments from the passepartout revealed the presence of a mixture of starch and PVAc glues localized only in the stained areas close to the margin of the folio. FE-SEM observations showed that the dark stains are localized inside cavities formed among cellulose fibers, where an accumulation of inorganic roundish particles (∅100-200 nm in diameter size), composed of Hg and S, was detected. Finally, by employing synchrotron μXRF, μXANES and HR-XRD analyses it was possible to identify these particles as metacinnabar (β-HgS). Further research is needed to assess the chemical process leading to the metacinnabar formation in the controlled conservation condition of Leonardo's Codex

Adolescência, uso de drogas e prática infracional: reflexões a partir de estudos brasileiros

A questão do uso de drogas entre adolescentes em conflito com a lei aparece com frequência nos estudos nacionais e internacionais e desperta preocupações sobre a associação entre estas duas variáveis e suas consequências às condições de saúde dessa população. Através de  revisão integrativa buscou-se analisar o estado da arte da produção científica brasileira sobre a temática. Foram selecionados 30 artigos, analisados pelas categorias: Metodologia, Distribuição anual, Áreas de Conhecimento, Objetivos, Resultados, Políticas Públicas. Resultados: a questão é amplamente discutida na literatura nacional, sendo a análise da variável “uso de drogas”, em alguns artigos, determinante na associação com o conflito com a lei e, em outros, um entre múltiplos fatores que se combinam na construção do fenômeno. Poucos estudos abordaram a prática profissional e as políticas públicas relacionadas à temática. Conclui-se que o fenômeno é complexo e necessita de abordagens ampliadas, bem como suporte das políticas públicas a ele relacionadas