The cover image is based on the article Experimental Determination of the Temperature-Dependent Broadening Effect of Water Vapour on the S-Branch Raman Linewidths of Nitrogen by Jonas Immanuel Hölzer et al., https://doi.org/10.1002/jrs.6742.
The cover image is based on the article Experimental Determination of the Temperature-Dependent Broadening Effect of Water Vapour on the S-Branch Raman Linewidths of Nitrogen by Jonas Immanuel Hölzer et al., https://doi.org/10.1002/jrs.6742.
Among the materials constituting our cultural heritage, parchment has a significant role as the substrate of many archival documents. The assessment of its state of preservation has an important benefit to conservation and delineates the adequate preventive measures that would lead to better-controlled storage and exhibition conditions in museums and libraries worldwide. In the framework of this project, artificial aging of 48 new goat parchment samples was performed to induce deterioration similar to naturally aged parchment exposed to atmospheric pollutants. Five factors have been examined: relative humidity; NO2; SO2; exposure time, and the order of sequential exposure to NO2 and SO2. Temperature was kept constant at 25°C, while the effect of the above-mentioned factors was examined at two levels (low and high). Statistics was involved in advance in the experimental design. Raman spectroscopy along with attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy were used to investigate the condition of collagen in parchment. The entire set of environmental factors along with detected changes in the spectra were investigated through a chemometrics scheme involving analysis of variance (ANOVA). According to the results, the onset of collagen's secondary structure decomposition was observed. Statistical elaboration of data reveals that the two analytical methods (Raman and ATR-FTIR) function in a complementary manner related to the molecular changes and the chemical reactions that happen. In conclusion, both methods can increase their impact on the investigation of parchment degradation if they are combined with other analytical methods and chemometric applications.
The analytical findings concerning the red pigments used on various decorative features originating from a Macedonian, as well as the purple dye from the deceased's attire, are presented. The cist tomb, discovered in 1987 at the area of Lakkoma Chalcidice (Macedonia, Greece), dated to the 4th century bc and featured a wooden funeral couch with intricate ornaments, such as clay “eyes,” colored plaster, and clay gorgoneions. Vermilion and red ochre served as the main pigments of these decorative features. The pigments were applied in various combinations to produce a range of red hues, from deep to bright red. Furthermore, the precious vermilion was also used in every element of the couch. The stucco on the decoration was gypsum, whereas the preparation layers over clay and stucco elements consisted of calcite and lead white, respectively. The cloth covering the deceased was dyed with the most expensive organic dye of antiquity, the Tyrian (shellfish) purple. In this research, the preliminary identification of the chromophoric minerals in the colors of the samples was carried out with the examination of their optical characteristics in thin sections using polarizing light microscope (PLM) and with portable XRF. Physicochemical techniques, Raman and HPLC, were also used to definitively identify the pigments. Portable Raman spectrometer was used for the in situ analysis of the inorganic colorants of the decorative materials, whereas laboratory Raman spectrometer served for the identification of inorganic and organic colorants of the grain samples and the dye. High-pressure liquid chromatography with diode array detector (HPLC-DAD) was applied for the identification of the coloring components of the purple organic dye from the deceased's clothes. The samples examined (0.5- to 1.5-mm diameter) were collected during the initial cleaning of the surface.
This study aimed to characterize ammonium nitrate lattice vibrations in an ammonium nitrate and fuel oil mixture (ANFO) following authentic explosive events using confocal Raman microscopy and single-crystal X-ray diffraction (XRD). Two simulated IEDs were constructed and detonated, consisting of several different substrate materials, using ANFO as the main charge. Crystalline material was observed to be growing on several of the postblast substrates. Microscopical examination revealed the crystalline material to have isotropic and anisotropic characteristics. Following recrystallization from water, the material was identified as ammonium nitrate. Single-crystal X-ray diffraction enabled the identification of the unit cells and molecular structures of the crystals formed after the blast. The values corresponded to the known Phase IV structure of recrystallized ammonium nitrate; however, there were minor yet statistically significant variations in the distances in the unit cell dimensions and O–N–O angles. Ex situ analysis of isotropic crystalline fragment using confocal Raman microscopy determined that lattice vibrations within the material were different than the ANFO intact reference, with the blue shifting of several bands, the emergence of new bands, and the loss of other characteristic bands. It was determined that the isotropic crystalline material observed in the postblast residue consisted of stressed state Phase IV AN. This suggests that a thermal change of AN can be observed in the microscopical characteristics and Raman spectrum of the crystals, demonstrating the importance of low frequency Raman spectroscopy (10–250 cm−1), which allows the identification of distinct spectral features of crystalline salts.
Prosthetic implant-associated inflammation and failure can be caused by bacterial infections and mechanical wear of the prosthesis. Currently, there is no diagnostic modality that allows simultaneous identification of both causes of implant failure. Here, we present a proof-of-principle study to assess whether Raman spectroscopy can be applied to diagnose implant failure. Synovial fluids from 10 patients with a clinical suspicion of implant-related complications were previously collected and cultured to determine the presence of bacteria. The presence of microparticles in these synovial fluids was assessed by Raman spectroscopy and verified by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). For control, the possibility to detect in vitro-cultured Staphylococcus aureus by Raman spectroscopy was investigated. Raman spectroscopy revealed that all 10 synovial fluid samples contained microparticles: eight contained microplastics (polyethylene, polypropylene, and polystyrene), and nine contained titanium dioxide nanoparticles (anatase and rutile) as verified by SEM-EDX. There was no clear difference in the microparticle content of synovial fluids with or without bacteria. Raman signals relating to individual bacteria and clusters of bacteria were detectable in in vitro cultures of S. aureus, but it was not possible to demonstrate the presence of bacteria in synovial fluids by Raman spectroscopy. Raman spectroscopy is a potential tool for characterizing microparticles in synovial fluids from patients with implant-related complications. This is of clinical relevance as these microparticles can cause joint inflammation. The identification of bacteria by Raman spectroscopy is feasible, but further research is needed before clinical implementation.
Surface enhanced Raman scattering (SERS) is a widely used vibrational spectroscopic technique employing metallic nanostructures to enhance an inherent Raman signal. This study aimed to develop a method for the characterization of SERS substrates in a single analysis by inductively coupled plasma mass spectrometry (ICP-MS) equipped with the single particle module (spICP-MS). For this development, the well-known Lee-Meisel protocol was selected as starting point to synthesize gold nanoparticles (AuNps) and silver nanoparticles (AgNps). A spICP-MS method was successfully developed and gave the mean size, size distribution, and concentration of nanoparticles in only one single analysis. Reference techniques were used to confirm these results namely dynamic light scattering, transmission electron microscopy, and UV–Visible spectroscopy. Thanks to the ICP-MS characterization, it was observed that AgNps synthesized by chemical reduction presented more variability than the AuNps. The dissolved elements concentration in the suspension was investigated. It appeared that reaction yields were close to 100% for the six syntheses. This analysis may be repeated over time to evaluate the suspension stability and monitor any potential degradation of Nps. To conclude, ICP-MS is a powerful technique to characterize SERS substrates and could be an interesting alternative to other characterization techniques.
High-quality Raman spectra of the two silicon nitride polymorphs - and -Si3N4 as well as of Si2N2O are presented here. This work significantly extends the previously available data on the Raman spectra of all three phases. For -Si3N4, a total of 34 Raman bands were confirmed, and for Si2N2O, a total of 19 Raman bands were observed for the first time. In the case of -Si3N4, all 11 known Raman modes were confirmed. For further accuracy and comparison, the spectra of the three phases were also calculated with different density functional theory functionals. Good agreement between the experimental data and the calculated vibrational modes is shown. Between the different DFT functionals, the rSCAN functional had the best agreement with the experimental data, clearly outperforming the PBEsol functional.
This paper investigates the applicability of time-gated Raman spectroscopy (TRS) for online mineralogy identification, focusing on a Li-bearing spodumene ore. The study provides an overview of existing online mineralogy tools and points out some limitations of elemental analysis techniques. Dense media separation concentrate and tailing samples used originated from a deposit in Quebec, Canada. Various techniques, including ICP-AES, XRD, laser diffraction, and specific gravity determination, were used for detailed sample characterization. Samples and their mixtures at known ratios were prepared as powder and slurries, before being analyzed using TRS, followed by spectrum quantitative analysis. Results show a linear correlation between spodumene percentage by weight and the main Raman peak height or area, in both dry and slurry form, with a higher determination coefficient in slurry form. TRS also provided indications as to the gangue minerals present in the samples. This study shows the potential for TRS as a tool for online mineralogical assessment of spodumene ores, and further work should target the determination of detection limits and quantification of both valuable and gangue minerals.
Understanding the effects of particle size is necessary for quantifying minerals in mixtures using Raman spectroscopy. Raman signal intensity is evaluated using six common silicate minerals (two olivines, two pyroxenes, and two feldspars) at 10 particle size ranges. For olivines and feldspars, the highest peak intensities are observed in samples with 38–63 and 63–106 μm particle sizes. There is no such consistent trend for the pyroxene samples, although the overall low signal strength complicates those measurements. Raman spectra of samples with varying particle sizes appear to be influenced by two competing effects: scattering from particle boundaries and effective sampling volume.
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