μ-Raman Spectroscopy Research Articles

Multi-Technique Diagnostic Investigation in View of the Restoration of “The Glory of St. Barbara” Painting by Mattia Preti

The present paper illustrates the results of a diagnostic investigation performed on the oil on canvas painting “The Glory of St. Barbara” (1680–1688) by Mattia Preti. The painting is located inside the St. Barbara Church in Taverna (Catanzaro, Italy), the city that gave birth to the artist. In situ, non-invasive studies, by applying X-ray fluorescence (XRF) spectroscopy, along with laboratory micro-destructive analytical investigations, by employing electron probe microanalyses (EPMA) coupled with energy-dispersive spectrometry (EDS) and micro-Raman (µ-Raman) spectroscopy, were combined to retrieve the color palette and identify the painting technique and style of the famous master. As a result of this multi-scale characterization, an extraordinary pictorial technique was revealed, enriching knowledge about one of the oldest pictorial traditions outlined by Mattia Preti, and solving doubts still existing about many of his investigated artworks. Moreover, the achieved results represent useful and essential tools to address management issues of the artwork, by providing valuable information for planning and monitoring future restoration interventions of the canvas.

Nitrate Removal by Donnan Dialysis and Anion-Exchange Membrane Bioreactor Using Upcycled End-of-Life Reverse Osmosis Membranes.

This work explores the application of Reverse Osmosis (RO) upcycled membranes, as Anion Exchange Membranes (AEMs) in Donnan Dialysis (DD) and related processes, such as the Ion Exchange Membrane Bioreactor (IEMB), for the removal of nitrate from contaminated water, to meet drinking water standards. Such upcycled membranes might be manufactured at a lower price than commercial AEMs, while their utilization reinforces the commitment to a circular economy transition. In an effort to gain a better understanding of such AEMs, confocal µ-Raman spectroscopy was employed, to assess the distribution of the ion-exchange sites through the thickness of the prepared membranes, and 2D fluorescence spectroscopy, to evaluate alterations in the membranes caused by fouling and chemical cleaning The best performing membrane reached a 56% average nitrate removal within 24 h in the DD and IEMB systems, with the latter furthermore allowing for simultaneous elimination of the pollutant by biological denitrification, thus avoiding its discharge into the environment. Overall, this work validates the technical feasibility of using RO upcycled AEMs in DD and IEMB processes for nitrate removal. This membrane recycling concept might also find applications for the removal and/or recovery of other target negatively charged species.

Microplastics in the abyss: a first investigation into sediments at 2443-m depth (Toulon, France).

Plastic and microplastic pollutions are known to be widespread across the planet in all types of environments. However, relatively little about microplastic quantities in the deeper areas of the oceans is known, due to the difficulty to reach these environments. In this work, we present an investigation of microplastic (<5 mm) distribution performed in the bottom sediments of the abyssal plain off the coast and the canyon of Toulon (France). Four samples of deep-sea sediment were collected at the depth of 2443 m during the sea operations carried out by the French oceanographic cruises for the KM3NeT project. The chemical and physical characterisation of the sediment was carried out, and items were extracted from sediments by density separation and analysed by optical microscope and µRaman spectroscopy. Results show microplastics in the deep-sea sediments with a concentration of about 80 particles L-1, confirming the hypothesis of microplastics spread to abyssal sediments in the Mediterranean Sea.

Metal Antik conservation coatings on iron specimens

Abstract The surface treatment of historical iron artefacts involves application of right conservation coating to the material to prevent further corrosion deterioration. Among common conservation agent of iron belong tannate coating, which is considerably preferred with the desired black appearance of the surface. In this work the new potentional conservation agent Metal Antik was studied. The change of this possible surface treatment was evaluated over time. The comparison between long-term exposed samples (15 years), short-term exposed samples (1.5 year) and fresh cured samples was done by spectrocolorimetry measurement. This was also compared to standard samples prepared with tannate coating. Surface analysis for all types of samples was done by μ-Raman spectroscopy. Results proved that effect of time changes the surface of coatings. It was demonstrated by colour change of surface and by formation of areas with local corrosion. Another study of Metal Antik in order to improve corrosion resistance is open.

Inter/Micro 2022 — International Microscopy Conference

McCrone Research Institute in Chicago was pleased to hold the Inter/Micro international microscopy conference again on Sept. 20 – 23, 2022, after a two-year hiatus due to the Covid-19 pandemic. This 72nd annual gathering of professional and amateur microscopists featured research talks on the first two days, covering advancements in instrumentation, new techniques, and practical applications in various fields of microscopy and microanalysis. Speakers focused on light microscopy, SEM, TEM, EDS, microspectrophotometry, electron backscatter diffraction, ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry, μ-Raman and FTIR spectroscopy, microchemistry, forensic trace evidence, and materials analysis.

New Biocalcifying Marine Bacterial Strains Isolated from Calcareous Deposits and Immediate Surroundings.

Marine bacterial biomineralisation by CaCO3 precipitation provides natural limestone structures, like beachrocks and stromatolites. Calcareous deposits can also be abiotically formed in seawater at the surface of steel grids under cathodic polarisation. In this work, we showed that this mineral-rich alkaline environment harbours bacteria belonging to different genera able to induce CaCO3 precipitation. We previously isolated 14 biocalcifying marine bacteria from electrochemically formed calcareous deposits and their immediate environment. By microscopy and µ-Raman spectroscopy, these bacterial strains were shown to produce calcite-type CaCO3. Identification by 16S rDNA sequencing provided between 98.5 and 100% identity with genera Pseudoalteromonas, Pseudidiomarina, Epibacterium, Virgibacillus, Planococcus, and Bhargavaea. All 14 strains produced carbonic anhydrase, and six were urease positive. Both proteins are major enzymes involved in the biocalcification process. However, this does not preclude that one or more other metabolisms could also be involved in the process. In the presence of urea, Virgibacillus halodenitrificans CD6 exhibited the most efficient precipitation of CaCO3. However, the urease pathway has the disadvantage of producing ammonia, a toxic molecule. We showed herein that different marine bacteria could induce CaCO3 precipitation without urea. These bacteria could then be used for eco-friendly applications, e.g., the formation of bio-cements to strengthen dikes and delay coastal erosion.

Microplastic accumulation in commercial fish from the Adriatic Sea

We assessed the presence and concentration of microplastics in fishes from the Northern Adriatic Sea on sale for human consumption. Microplastics were extracted from the digestive tract of 180 specimens, belonging to 6 different species (2 pelagic, and 4 demersal). Microplastics were identified through Nile red staining, and selected particles were analyzed by μ-Raman spectroscopy. The 47.8% of examined fish were found to contain microplastics (233 fragments). The mean concentration of microplastics in the 6 species ranged between 4.11 ± 2.85 items/individual in Adriatic soles, and 1.75 ± 0.71 items/individual in pilchards. Microplastics ranged in size between 0.054 mm and 0.765 mm. Polyethylene and polypropylene were the polymer types identified through μ-Raman spectroscopy. Despite our estimates are underestimations, these results are of particular concern, as the fish analyzed are consumed without being eviscerated, and the microplastics they contain are transferred directly to humans.

A Multi-Analytical Approach for Studying the Effect of New LED Lighting Systems on Modern Paints: Chemical Stability Investigations.

This study aims to investigate the chemical stability of some modern paint samples exposed to a new Light Emitting Diode (LED)-lighting system and a halogen lamp by using micro-attenuated total reflectance of Fourier transform infrared spectroscopy (µ-ATR-FTIR), µ-Raman, pyrolysis—gas chromatography/mass spectrometry (Py-GC/MS), and thermally assisted hydrolysis and methylation of GC/MS (THM-GC/MS). Those investigations were performed before and after the exposure of the samples to lightings for 1250, 2400, 3300, and 5000 h. The results obtained with µ-Raman spectroscopy show the high stability of the selected inorganic pigments after the exposure to the lighting systems; while similar to the UV/Vis/NIR results reported in a previous study, µ-ATR-FTIR and THM-GC/MS results evidence greater chemical changes occurring principally on the linseed oil binder-based mock-ups among the acrylic and alkyd-based samples. Moreover, principal component analyses (PCA) and hierarchical cluster analyses (HCA) of THM-GC/MS results highlight that those changes were mostly dependent on the exposure time and on the type of pigment, while being independent of the lighting system used. Finally, semi-quantitative µ-ATR-FTIR results show slight pigment enrichment at the paint surface due to the auto and photo-oxidative degradation of the linseed oil binder.

The Minnesang riddle: A multi-analytical approach to an undated colour woodcut

In this work, a multi-colour woodcut on paper, representing a Minnesanger (love poet) who declares his love to a young lady, was studied from both historical and archaeometric points of view. In the absence of historical or documentary information, non-invasive imaging, EDXRF, and µ-Raman spectroscopies were employed, in order to date this artefact. The woodcut Minnesang is known in a single and so-far undescribed copy and shows the influence of German Renaissance colour woodcuts as well as Arras 15th century tapestries. Nevertheless, according to our investigations, it does not date back to that period. In fact, the presence of Prussian blue and chrome yellow and, most of all, the finding of two organic pigments, namely PR53:1 and PR81, suggest to date the artwork at the beginning of the 20th century, in the context of a neo-Gothic Arts and Crafts revival.

Tuning Inactive Phases in Si-Ti-B Ternary Alloy Anodes to Achieve Stable Cycling for High-Energy-Density Lithium-Ion Batteries.

Cycle stability improvement of a high-capacity Si anode is a challenge for its wide application in high-energy-density lithium-ion batteries. Active amorphous/nanosized Si embedded in an inactive matrix is a strategy to improve the cycle stability of Si anodes. Ternary Si100-x-yTixBy (5 ≤ y ≤ x ≤ 20) alloys are designed and prepared by ball milling using elemental Si, Ti, and B as starting materials. The formation sequence of inactive phases during mechanical alloying is predicted by an effective heat-of-formation model and verified by microstructural characterization. The local-fine distribution of free amorphous and nanocrystalline Si in the Si100-x-yTixBy is analyzed by confocal μ-Raman spectroscopy. When used as lithium-ion anodes, the capacity and voltage affected by Si and inactive compounds in the Si100-x-yTixBy are concerned to assess their high energy density. Furthermore, the impact of free active Si, the inactive phase, and amorphous Si on the cyclability of Si100-x-yTixBy is studied. The results show that the Si100-x-yTixBy material is a potential anode for high-energy-density Li-ion batteries and could be used to guide the design of multi-component Si-alloy anodes.

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared.

Group IV nanocrystals (NCs), in particular from the Si–Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO2 were obtained by magnetron sputtering deposition followed by rapid thermal annealing at 600 °C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, μ-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3–7 nm diameter) in a matrix of nanocrystallized HfO2. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO2 layers. Nanocrystallized HfO2 with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO2 and SiGe NCs–HfO2 layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600–2000 nm at low temperatures. The high-quality SiGe NC/HfO2 matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO2 matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.

Can the presence of additives result in false positive errors for microplastics in infant feeding bottles?

ABSTRACT In recent years, it has been shown that food contact materials can be a potential source of microplastics (MP). Recently, it was reported that more than 16 million polypropylene (PP) particles L−1 may be released from infant feeding bottles (IFBs) made of PP. In the present study seven different IFBs were investigated by the same method used in the aforementioned publication. In our tests, however, only one IFB showed a level of MP above the limit of detection. More importantly, the MP detected were not of the same material as the bottle and are more likely the result of contamination. In addition, there was a notable difference in released MP particles when the water simulant was filtered for µ-Raman spectroscopy at hot temperature (70°C) instead of filtering it after cooling down to room temperature. Thermal desorption gas chromatography mass spectrometry showed that these differences may be the result of migration and precipitation of additives such as fatty acid esters, often used as release agents in bottle production. These observations, that migrating additives could result in false positive errors for MP, indicate the need for critical consideration when polymers have been subjected to heat.

Conventional and biological treatment for the removal of microplastics from drinking water

This study examines the removal of microplastics and other anthropogenic particles (>10 μm) from surface water by a full-scale conventional drinking water treatment plant. The treatment process is composed of coagulation with aluminum hydroxide, flocculation, anthracite-sand filtration, and chlorination. Samples were also collected from pilot-scale biological filters consisting of anthracite-sand or granular activated carbon (GAC) media operated with or without pre-ozonation and at a range of different empty-bed contact times (EBCTs). Particles in 10 L water samples collected in duplicate using a fully enclosed sampling apparatus were separated using sieves with 500 μm, 300 μm, 125 μm, and 45 μm openings followed by filtration through 10 μm polycarbonate filters. Particles were counted using stereomicroscopy and characterized using μ-Raman spectroscopy. Full-scale conventional treatment removed 52 % of anthropogenic particles when comparing raw (42 ± 18 particles/L) and finished water (20 ± 8 particles/L). Coagulation, flocculation, and sedimentation accounted for the highest removal (70 %) of any individual unit process. Overall removal was reduced to 52 %, the difference being attributed to airborne particle deposition that occurred while water was detained in a clearwell (exposed to atmosphere via ventilation) that was used to achieve the required contact time for disinfection. The majority of the particles (>80 %) were identified as fibers 10–45 μm; microplastics were predominantly composed of polyester while the non-plastic anthropogenic particles were primarily cellulose. None of the pilot filter configurations examined resulted in significantly fewer microplastics when compared to full-scale conventional filtration. This study illustrates that the removal efficiency of conventional treatment may be limited when considering microfibers <45 μm in size.

Identification of microplastics in conventional drinking water treatment plants in Tehran, Iran.

The online version contains supplementary material available at 10.1007/s40201-021-00737-3.

Microplastic contamination of sandy beaches of national parks, protected and recreational areas in southern parts of the Baltic Sea

The distribution of small (0.5–2 mm, S-MPs) and large (2–5 mm, L-MPs) microplastics and mesoplastic particles in 51 samples of surface beach sands at 7 locations along the southern shore of the Baltic Sea was investigated. MPs particles (3267 in total) were found at all the sites and in all the beach zones. The bulk mean MPs (0.5–5 mm) contamination is 68 ± 117 (median 33) items/kg DW (n = 51). The results were confirmed by μ-Raman spectroscopy analysis. National park areas did not differ substantially from other beaches. Expanded polystyrene fragments accounted for about 38% of the total collected particles. Fibres were the predominant type of MPs (55%). The highest contamination was found within the current wrack line (60.1 ± 36.6 items/kg DW of S-MPs). A consistent picture for S-MPs was observed at the beach face, where the mean values in different locations varied between 21.0 and 58.1 items/kg DW, with a bulk mean of 30.4 ± 13.7 items/kg DW.

Cultural and technology elucidation of the Tupi-Guarani tradition through analysis of potsherds from Travessão do Rio Vermelho site (Santa Catarina - Brazil) by spectroscopy, SEM-EDS and chemometrics

Ceramic fragments can provide an insight into the ancient culture and practices of groups of humans and their way of life (technology, cultural identity, social organization, habitation and economy). Scientific analysis can be used to obtain information on the ceramic production process, as well as the specificities of the material employed. In this research, all samples of archaeological potsherd from the Tupi-Guarani tradition were analyzed in order to identify and to characterize the structures, morphologies and the elemental composition by using by scanning electron microscopy (SEM-EDS) and multivariate statistical methods (PCA and HCA). FTIR spectroscopy revealed the presence of an organic residue in three samples along with carbonates, clay minerals, quartz and hematite. In addition, the presence of the stretching attributed to water molecules in crystalline systems was observed. Also, the presence of TiO2 in the anatase polymorphic form was detected using μ-Raman spectroscopy. These results indicate a firing temperature of between 800 and 1000°C. In relation to the morphology, all samples revealed amorphous structures presenting isolated and heterogenic particles of different forms and sizes, and the EDS spectrum confirmed the elements present in the molecular structures elucidated by vibrational spectroscopy. The multivariate analysis has confirmed the correlation between the elemental compositions of ceramics collected from two different sites: a mountain region and a coastal area in Santa Catarina State, Brazil.

Interaction of Corroding Iron with Eight Bentonites in the Alternative Buffer Materials Field Experiment (ABM2)

Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and cementation. The chemical interactions were investigated by analysing the Fe/clay interfaces of eight bentonite blocks which had been exposed to temperatures up to 130 °C for five years in the ABM2 borehole at the Äspö Hard Rock Laboratory managed by the Swedish Nuclear Fuel and Waste Management Co (SKB). Eleven interface samples were characterised by high spatial resolution methods, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and μ-Raman spectroscopy as well as by “bulk” methods X-ray diffraction, X-ray fluorescence and 57Fe Mössbauer spectrometry. Corrosion induced an iron front of 5–20 mm into the bentonite, except for the high-Fe bentonite where no Fe increase was detected. This Fe front consisted mainly of ferric (oxyhydr)oxides in addition to the structural Fe in the smectite fraction which had been partially reduced by the interaction process. Fe(II) was also found to extend further into the clay, but its nature could not be identified. The consistent behaviour is explained by the redox evolution, which shifts from oxidising to reducing conditions during the experiment. No indication of smectite alteration was found.

A study of colourant uses in illuminated Islamic manuscripts from the Qājār period (1789–1925 C.E), early modern Iran

The study was undertaken to explore the widespread use of colourants, raw materials and technology of colour production to illuminate Qur’ān manuscripts in the Qājār period, Iran (1789–1925 C.E.). SEM-EDX and µ-Raman spectroscopy were employed as non-invasive/non-destructive complementary techniques. The SEM-BSE images contribute to distinguishing between organic/inorganic origin of colourants and the EDX to identify gilding composition as well as providing a short-list of potential colourants to be confirmed by µ-Raman spectroscopy as a compound-specific technique. The results show the most identified colourants are mineral-based pigment; these include carbon black, ultramarine, Prussian blue, vermillion, and red lead. Brass, pure gold, and a gold-silver alloy were detected as metallic ink/paint as gilding. We hypothesise the red diacritic in S01 have organic nature with an anthraquinone derivative structure, but we were unable to specifically identify it. We also hypothesise the yellow constituents in S02 might contain saffron and lead-containing compound(s) as a thickening agent and/or chemical drier. Our findings were in agreement with information available in Persian and English bibliographical sources on Iranian painting and illuminated manuscripts of the Qājār period. Further analysis by SR-µFTIR, FORS, SERS and HPLC is required to confirm our assumption and to complete colourant identification.

Formation of Iron Sulfides on Carbon Steel in a Specific Cement Grout Designed for Radioactive Waste Repository and Associated Corrosion Mechanisms.

Carbon steel coupons were buried in a specific low-pH cement grout designed for radioactive waste disposal and left 6 months in anoxic conditions at 80 °C. The corrosion product layers were analyzed by µ-Raman spectroscopy, XRD, and SEM. They proved to be mainly composed of iron sulfides, with magnetite as a minor phase, mixed with components of the grout. Average corrosion rates were estimated by weight loss measurements between 3 and 6 µm yr−1. Corrosion profiles revealed local degradations with a depth up to 10 µm. It is assumed that the heterogeneity of the corrosion product layer, mainly composed of conductive compounds (FeS, Fe3S4, and Fe3O4), promotes the persistence of corrosion cells that may lead to locally aggravated degradations of the metal. New cement grouts, characterized by a slightly higher pH and a lower sulfide concentration, should then be designed for the considered application.

Facile surface treatment of precursors before rapid melt growth of GaSb on silicon

The efficient monolithic III-V integration on silicon (Si) substrates can leverage the excellent optoelectronic properties of III-V semiconductors and the Si microfabrication technology for electronic, optoelectronics, integrated photonics devices. However, the origin of the interfacial and material defects during III-V monolithic integration on Si poses the challenge to achieve efficient optical emitters, detectors. In this study, we investigated different surface treatment schemes before rapid melt growth (RMG) of GaSb on Si substrate to attain defect control. The deposition of an Sb layer (10 nm) on GaSb precursors surfaces resulted in achieving better structural and optical properties of GaSb post RMG. We achieved a reduction of 2.48 atomic % of unintentional incorporation of Si into the GaSb via Sb treatment compared to that of untreated GaSb analysed using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Improved surface morphology with reduced root mean square roughness of 3.7 nm is obtained with Sb layer treatment compared to 5.6 nm for untreated GaSb precursor measured by atomic force microscopy. We obtained improved optical properties and low defect density with an in-situ Sb treatment scheme on GaSb precursor surface by µ-Photoluminescence and µ-Raman spectroscopy analysis.