Search Results (230)

This article presents a comprehensive analysis of the polychrome paintings on the Flower Peking Opera Theatre in Bozhou, Anhui Province, China. A multi-technique approach was employed, including polarized light microscopy (PLM), X-ray fluorescence (XRF), micro-Raman spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS), and Herzberg staining to determine the composition and methodologies involved in the formation of the pigment layer, the white primer, and the ground layer. The analysis identified cinnabar (red), both artificial ultramarine and Prussian blue (blue), a mixture of barite and gypsum (white), a mixture of chromite and Prussian blue (green), and carbon black (black) in the pigment layer. The ground layer was found to consist of clay and plant fibers (cotton and hemp), while the white prime layer was primarily composed of barite and gypsum. This research provides insights for future conservation and restoration efforts. Full article

Neodymium-doped bioactive wollastonite–tricalcium phosphate (W-TCP:Nd) coatings were fabricated by combining dip-coating and laser floating zone (LFZ) techniques to investigate the dependence of optical emission on polarization. Structural and spectroscopic analyses were performed on both longitudinal and transversal sections of the coating to assess the effects of directional solidification on luminescence and vibrational behavior. Micro-Raman spectroscopy revealed that the coating exhibited sharp, well-defined peaks compared to the W-TCP:Nd glass, confirming its glass-ceramic nature. New Raman modes appeared in the longitudinal section, accompanied by red and blue shifts in some bands relative to the transversal section, suggesting the presence of anisotropic stress and orientation-dependent crystal growth. Optical emission measurements showed that while the ⁴F_3/2→⁴I_11/2 transition near 1060 nm was nearly polarization independent, the ⁴F_3/2→⁴I_9/2 transition around 870–900 nm exhibited strong polarization dependence with notable Stark splitting. The relative intensity and spectral position of the Stark components varied systematically with the rotation of the emission polarization. These findings demonstrate that directional solidification induces polarization-dependent optical behavior, indicating potential applications for polarization-sensitive optical tracking and sensing in bioactive implant coatings. Full article

Portuguese ceramic tile (azulejo) production has evolved significantly since its beginnings in the 16th century. While historic tiles reflect well-established traditional techniques and styles, modern and contemporary works began to explore new aesthetic and material possibilities, introducing textures, surface effects, and experimental approaches that challenge conventional conservation methods. This study examines a contemporary Portuguese tile panel dated from 1987, featuring decorative effect glazes with crater and crazing textures, which were characterized and reproduced. Analytical techniques, including optical microscopy, micro-X-ray fluorescence spectrometry, and Raman spectroscopy in microscopic mode, were employed to characterize material composition and formation mechanisms. Results showed that the crater-effect glazes were achieved with a silica-rich glaze recipe with MnO₂ and ZrO₂. The crazing effect developed in regions where unmelted crystalline silica induced internal stresses within a lead-silicate glaze, contributing to localized degradation. Experimental reproductions of the glazes, guided by analytical data, were conducted to better understand their formation and inform conservation strategies. The results provide essential insights for the technical assessment, documentation, and preservation of contemporary ceramic artworks featuring decorative effect glazes and contribute to the broader field of cultural heritage conservation. Full article

Understanding the molecular mechanisms of protein–nanoparticle interactions is crucial for enabling the development of new applications in biomedicine and nanotechnology. Ubiquitin, an important and structurally small functional protein, plays a central role in numerous cellular processes. Therefore, in the current study, we focused on the few-layer graphene (FLG)–Ubiquitin complexes formed by exfoliating FLG structures using only water. Optical spectroscopic techniques (Raman, FT-IR, UV-Vis and circular dichroism) were employed to investigate these complexes on the molecular level. Overall, both CD and FT-IR data reveal that the formation of the FLG–Ubiquitin complexes occurred without inducing disordered structures in the protein. Based on the existence of a blue shift (hypsochromic shift) in the UV-Vis data, the presence of a single tyrosine and two phenylalanine residues in ubiquitin enables the detection of FLG-induced micro-environmental changes, particularly influencing the protein’s β-sheet and α-helix structures. The CD spectral results and CDPro quantitative estimations are in line with ATR FT-IR results, confirming the absence of disordered structure formation while altering the protein’s chirality. UV-Vis and CD spectroscopy results revealed concentration-dependent trends consistent with FLG–protein interactions that preserve the overall protein structure. This study has potential applications in both academic research and practical usage, particularly in biomedicine and nanotechnology specifically for FLG. Full article

The optimization of BiVO₄-based structures significantly contributes to the development of a global system towards clean, renewable, and sustainable energies. Enhanced photocatalytic performance has been reported for numerous doped BiVO₄ materials. Bi³⁺-based compounds can be easily doped with rare earth (RE³⁺) ions due to their equal valence and similar ionic radius. This means that RE³⁺ ions could be regarded as active co-catalysts and dopants to enhance the photocatalytic activity of BiVO₄. In this study, a simple microwave-assisted approach was used for preparing nanostructured Bi_1−xEu_xVO₄ (x = 0, 0.03, 0.06, 0.09, and 0.12) samples. Microwave heating at 170 °C yields a bright yellow powder after 10 min of radiation. The materials are characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible–near-infrared diffuse reflectance spectroscopy (UV-Vis-NIR DRS), photoluminescence spectroscopy (PL), and micro-Raman techniques. The effects of the different Eu³⁺ ion concentrations incorporated into the BiVO₄ matrix on the formation of the monoclinic scheelite (ms-) or tetragonal zircon-type (tz-) BiVO₄ structure, on the photoluminescent intensity, on the decay dynamics of europium emission, and on photocatalytic efficiency in the degradation of Rhodamine B (RhB) were studied in detail. Additionally, microwave chemistry proved to be beneficial in the synthesis of the tz-BiVO₄ nanostructure and Eu³⁺ ion doping, leading to an enhanced luminescent and photocatalytic performance. Full article

Two folding screens by futurist artist Giacomo Balla (1871–1958) in the collection of the Kröller-Müller Museum (the Netherlands) were investigated: Paravento con linea di velocità (1916–1917) and Paravento (1916/1917–1958). The screens are painted on both sides, the first on four canvases, stretched onto two wooden strainers and framed with painted wooden strips, and the second on wooden panels set into four painted stiles. In the past, damages on Paravento con linea di velocità were restored by conservators, while Paravento was probably first reworked by the artist himself and later restored by conservators. Yellowed varnish and discolored retouches on both screens led to a wish for treatment. The aim of this research was to gain insight into the painting techniques, layer buildup, pigments, binders, and varnishes of the two artworks. This information supported the decision making for treatment, and it broadens the knowledge on the materials used by Balla. Up to now, only a few published studies deal with the technical examination of paintings by this artist. Both folding screens were subjected to technical photography (UV, IR photography, and X-ray) and were examined with portable point X-ray fluorescence (pXRF) and Raman spectroscopy. Moreover, samples were taken. Cross-sections were studied with optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), attenuated total reflection Fourier-transform infrared (ATR-FTIR) imaging, and micro-Raman spectroscopy. Loose samples were examined with SEM-EDX, FTIR and micro-Raman spectroscopy, and pyrolysis gas chromatography mass spectrometry (Py-GC/MS). For Paravento con linea di velocità, all pigments and fillers of the painted canvases are compatible with the dating of the screen (1916–1917), but they differ from those on the frame. Here, rutile, in combination with various pigments, among which are blue copper phthalocyanine (PB15) and other synthetic organic pigments, was found. This indicates that the frame has been painted later, likely after the Second World War. The composition of the binders differs as well. Drying oil and pine resin have been used on the canvases, explaining the smooth and glossy appearance and solvent-sensitivity of the paint. On the frame, oil with some alkyd resin was identified. The provenance of the screen before 1972 is not clear, nor when the frame was made and painted and by whom. The results for Paravento indicate that the palettes of the two sides—painted in different styles—are comparable. Mainly inorganic pigments were found, except for the dark red areas, where toluidine red (PR3) is present. pXRF showed high amounts of zinc; cross-sections revealed that zinc white is present in the lower layers. These pigments are compatible with the dating of the screen (1916–1917). In many of the upper paint layers though, except for some green, dark red, and black areas, rutile has been identified. This indicates that these layers were applied later, likely after the Second World War. Since this folding screen was used by the artist and his family until his death in 1958, it seems likely that Balla himself reworked the screen. Full article

Microplastic (MP) analysis via microspectroscopy typically examines only 1–10% of filter substrates due to time constraints, requiring reliable extrapolation methods for quantitative environmental monitoring. Current subsampling strategies suffer from heterogeneous particle dispersion, leading to 50–80% error in MP quantification. Additionally, MP researchers require enhanced environmental MP mass datasets, necessitating reliable conversion algorithms from two-dimensional morphological data to mass estimates. This study introduces an area-based extrapolation technique for organic rich samples that compares the MP-to-generic particle area ratio within a rectangular field of view against total particle area on the entire filter membrane, combined with a simplified fragment morphology-to-mass conversion model (SFMM). First, two Sphagnum moss samples were analyzed using Raman microspectroscopy and critical angle darkfield illumination microscopy. The results demonstrated stable MP concentrations (17% RSD [n = 8]) despite heterogeneous generic particle distribution (31% RSD [n = 8]), with mean particle-area coverage of 2.4% per subsample. Then, twenty EasyMP^TM fragment reference materials (10 µm to 1500 µm), of known composite mass, were used to calibrate two different volume (V) expressions, one based on analyzed particle area (A) and minimum Feret diameter (F_Min, i.e., width), yielding V = 0.34 × F_Min × A. A second more approximate expression based on only the maximum Feret diameter (F_Max, i.e., length) yielded V = 0.097 × (F_Max)³. These methods enable MP quantification and mass estimation from limited spectroscopic analysis. Full article

Two-dimensional cell cultures are crucial research tools, and they have been widely used, although they are not completely representative of biological processes in vivo due to the lack of tissue architecture and complexity. Recent advances in organoid technology have addressed these limitations and are revolutionizing the tools available for in vitro culture. Although there are no unified protocols for generating organoids, they can be obtained with various techniques, leading to cell aggregation by promoting cell adhesion. This work aims to generate and characterise organoid models of dental pulp from dental pulp stem cells (DPSCs), a type of mesenchymal stem/stromal cells known for their high regenerative potential and ease of accessibility, to establish a model for translational studies. The organoids were subjected to osteogenic differentiation conditions. Cell viability was evaluated using a CCK-8 assay, while osteogenic morphology and mineralization were confirmed by Alizarin red analysis, Raman microspectroscopy, and by immunofluorescence for the lineage markers expression. The Alizarin red analysis indicated a higher presence of calcium phosphate deposits in the differentiated organoids than in the control group (CTR). These results were confirmed by spectral profiles obtained using Raman microspectroscopy, which were attributable to a hydroxyapatite-based biomaterial. Immunofluorescence analysis also revealed increased expression of odonto/osteogenic markers (RUNX and OSX), alongside reduced expression of stemness markers. In conclusion, the organoids appeared to have successfully differentiated into an osteogenic lineage, forming a mineralized matrix containing hydroxyapatite and showing increased expression of relevant lineage markers. Full article

This study presents a Raman-spectroscopy-based quantitative analysis technique for measuring strain in Kevlar single fibers embedded in concrete. By irradiating the fibers with a laser, the researchers established a linear relationship between Raman scattering intensity and the fibers’ cross-sectional area, linking spectral parameters (e.g., peak position, half-width, intensity, and area) to mechanical strain. Experiments on DuPont Kevlar 49 fibers involved axial tensile loading using a micro-loading device, with Raman spectra (785 nm laser) captured at each displacement step. The results showed that the G’ peak position (1610 cm⁻¹) shifted linearly with strain, while the peak area provided the most reliable correlation. Scanning electron microscopy (SEM) validation confirmed the method’s accuracy for early-stage strain measurements (maximum deviation: 7.31%), although excessive loading caused surface damage and signal distortion. The study demonstrates the feasibility of Raman spectroscopy for micro-scale strain analysis in fiber-reinforced concrete, despite sensitivity to experimental conditions (e.g., laser intensity, optical alignment). Full article

This study examines the pigments and materials used in Girolamo Romanino’s Musicians fresco (1537–1538), located in the Duomo Vecchio in Brescia, with the aim of identifying and analyzing the artist’s colour palette. Ten samples of the pictorial layer and mortar were collected from two frescoes and characterized using microscopic and spectroscopic techniques. Confocal laser scanning microscopy (CLSM) was used to define the best positions where single-point, spectroscopic techniques could be applied. Raman spectroscopy and micro-Fourier transform Infrared spectroscopy (micro-FTIR) were used to detect pigments and organic binders, respectively. X-ray powder diffraction (XRPD) provided additional insights into the mineral composition of the pigmenting layers, in combination with environmental scanning electron microscopy equipped with energy-dispersive spectroscopy (ESEM-EDS). The analysis revealed the use of traditional fresco pigments, including calcite, carbon black, ochres, and copper-based pigments. Smalt, manganese earths, and gold were also identified, reflecting Romanino’s approach to colour and material selection. Additionally, the detection of modern pigments such as titanium white and baryte points to restoration interventions, shedding light on the fresco’s conservation history. This research provides one of the most comprehensive analyses of pigments in Romanino’s works, contributing to a deeper understanding of his artistic practices and contemporary fresco techniques. Full article

The Chengyang City (城阳城) site in Xinyang, Henan Province, China, was a significant northern military stronghold of the Chu state during the Warring States period (475/403–221 BCE). The lacquered armor unearthed from Tomb M18 provides critical material evidence for studying ancient military technology and lacquer craftsmanship. In this study, a comprehensive analytical approach combining ultra-depth optical microscopy, Fourier-transform infrared spectroscopy (FTIR), confocal micro-Raman spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) were employed to systematically characterize the structural and compositional features of the armor samples. The results indicate that the armor was constructed with a leather substrate and lacked any lacquer ash layer, while the surface exhibited multiple layers of mixed laccol and urushiol-based lacquer coatings. Cinnabar (HgS) was identified as the primary red pigment, and no carbon black or iron-based blackening agents were detected in the dark lacquer layers. Notably, the presence of laccol suggests that such lacquer resources may have also been produced in mainland China, offering new perspectives on the prevailing view that associates laccol exclusively with “Vietnamese lacquer.” This study elucidates the technological characteristics of mid-Warring States period lacquered armor, provides scientific insights into ancient lacquering techniques, and contributes valuable data for the conservation and restoration of similar cultural heritage artifacts. Full article

In this study, a correlative approach using Raman spectroscopy and scanning electron microscopy (SEM) is introduced to meet the challenges of identifying impurities, especially carbon-related compounds in metal injection-molded (MIM) Mg-0.6Ca specimens designed for biomedical applications. This study addresses, for the first time, the issue of carbon residuals in the binder-based powder metallurgy (PM) processing of Mg-0.6Ca materials. A deeper understanding of the material microstructure is important to assess the microstructure homogeneity at submicron levels as this later affects material degradation and biocompatibility behavior. Both spectroscopic and microscopic techniques used in this study respond to the concerns of secondary phase distributions and their possible stoichiometry. Our micro-Raman measurements performed over a large area reveal Raman modes at ~1370 cm⁻¹ and ~1560 cm⁻¹, which are ascribed to the elemental carbon, and at ~1865 cm⁻¹, related to C≡C stretching modes. Our study found that these carbonaceous residuals/contaminations in the material microstructure originated from the polymeric binder components used in the MIM fabrication route, which then react with the base material components, including impurities, at elevated thermal debinding and sintering temperatures. Additionally, using evidence from the literature on thermal carbon cracking, the presence of both free carbon and calcium carbide phases is inferred in the sintered Mg-0.6Ca material in addition to the Mg₂Ca, oxide, and silicate phases. This first-of-its-kind correlative characterization approach for PM-processed Mg biomaterials is fast, non-destructive, and provides deeper knowledge on the formed residual carbonaceous phases. This is crucial in Mg alloy development strategies to ensure reproducible in vitro degradation and cell adhesion characteristics for the next generation of biocompatible magnesium materials. Full article

Twelve sherds of blue-and-white Chinese porcelains recovered from archaeological excavations in the Santana Convent (Ming and Qing Dynasties) in Lisbon were studied using several non-invasive spectroscopies, namely micro-Raman, X-ray Fluorescence (XRF), Ground State Diffuse Reflectance (GSDR), and stereomicroscopy. The use of the X-ray diffraction technique (XRD) allowed us to complete the mineralogical characterization of the ceramic bodies and glazes of the porcelains. The sample selection ranges from the 16th to the 18th centuries. The micro-Raman spectra clearly showed two types of glazes, alkaline glaze and calcium-based glaze. The GSDR absorption spectra of the blue glazes point to the use of different cobalt pigments, but a strong dependence on the glaze type does not seem to exist. The kilns where the porcelains were produced also play an important role. Both the GSDR absorption and the micro-Raman spectroscopies allow us to differentiate the Iranian blue pigment from the Chinese pigment. A direct and simple correlation between the use of Iranian blue pigment, mixtures of Iranian and Chinese pigments, or simply Chinese pigments and the stylistic dating of each sample was established. Furthermore, several important spectroscopic characterizations could be achieved in this study. Full article

Graphene, a two-dimensional carbon material, possesses exceptional properties such as high electron mobility, exceptional strength that surpasses that of steel, chemical resistance, environmental friendliness, and a large specific surface area. In this study, we used the modified Hummer process to produce graphene oxide, which was applied to an aluminum alloy substrate as a corrosion-resistant coating. The aluminum alloy used in our study is AA2024, which is widely applied in industry and aircraft. The coating layer was characterized by micro-Raman spectroscopy and atomic force microscopy (AFM) before and after the reduction process. Micro-Raman spectroscopy provided information on the degree of reduction and the presence of functional groups in the coating layer. AFM images enabled the study of surface morphology and topography. After the reduction process, achieved by annealing in an argon atmosphere at 140 °C, micro-Raman spectroscopy and AFM were again used to assess structural and morphological changes. The reduction resulted in the formation of reduced graphene oxide (RGO), which exhibited improved conductivity and stability. The combination of micro-Raman spectroscopy and AFM characterization techniques provided detailed information on the properties and effectiveness of the coating layer. This research contributes to developing anti-corrosion methods using advanced materials and surface engineering techniques. Full article

Due to their excellent mechanical properties and good biocompatibility, titanium (Ti) and its alloys are widely used as biomaterials. However, when implanted in the body, metallic materials may cause serious complications such as wear and infection, leading to patient discomfort and, in some cases, the need for revision surgery. Micro-arc oxidation (MAO) is a surface modification technique that offers a promising strategy to overcome these challenges. This study investigated the impact of the microstructure of Ti-25 Ta-xNb alloys (x = 10, 20, and 30 wt%) and the variation in applied voltage during the MAO process on the characteristics of the TiO₂ oxide coatings formed. The alloys were treated by MAO at 200, 250, and 300 V using a bioactive electrolyte containing Ca, P, Mg, and Ag. EDS, SEM, XRD, Raman spectroscopy, and adhesion tests performed characterization. Results indicated that Nb addition stabilized the β phase and anticipated the potentiostatic regime. Increasing the voltage supplied to the system provides greater energy, prolonging the galvanostatic regime and promoting the formation of larger and more uniform pores. The oxide coating thickness ranged from approximately 3 to 10 μm, with a tendency to decrease at higher voltages. The coatings exhibited low c, with anatase and rutile phases predominating, the applied voltage and Nb concentration influencing their relative proportions. Even in small amounts, all electrolyte elements (P, Mg, and Ag) were successfully incorporated into the coatings under all conditions. Raman and XRD analyses confirmed a decrease in anatase and an increase in rutile phases with increasing voltage and Nb content. Mechanical testing revealed good adhesion of the coatings in all samples, with the best results obtained at 200 V. The findings demonstrate that the developed coatings exhibit promising characteristics for future surface engineering strategies aimed at improving the performance of metallic biomaterials. Full article