ABSTRACTAmong 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.

ABSTRACTSurface 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.

ABSTRACTUnderstanding 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.

ABSTRACTIn this paper, we investigate a twisted bilayer graphene on an h‐BN substrate. The graphene is grown using high‐quality chemical vapor deposition (CVD) and subsequently transferred onto the h‐BN substrate. Our focus is on the stacking transition within the bilayer system, based on fluctuations in both intralayer and interlayer processes. Our findings reveal that post‐annealing induces alterations in the electron–phonon interaction, corresponding to the spatially dependent stacking changes in the bilayer structure. This makes it possible to modify the electronic band structure of graphene and subsequently all its optoelectronic properties.

No abstract is available for this article.

Abstract Attempting to compute the excess Raman spectra, the authors found that the method of spectral normalization greatly influences not only the intensity but also the shape of the excess spectra. We here present a method for the computation of normalized excess Raman spectra that is regarded as thermodynamically consistent. In the presented method, the normalized excess Raman spectra are computed from molar Raman spectra, which cannot be measured directly. It is therefore described how they can be obtained from intensity‐normalized Raman spectra and a regression of mixture Raman spectra.

Abstract Brillouin light scattering (BLS) is the inelastic scattering of light from elementary excitations with periodic density modulation. The characteristics of non‐contact, high sensitivity, and high resolution in energy, wavevector, time, space, and phase make the BLS spectrometer widely used in investigating many intriguing physical phenomena, including the acoustic phonon confinement effects, Bose‐Einstein condensation (BEC), supercurrent, and soliton formation. Generally, the quick and correct assignment of the signals in the BLS spectra is a prerequisite for further investigations. Herein, we experimentally identify the high‐order spurious signals in the BLS spectra, which make the interpretation of the spectra difficult. The additional signals are demonstrated to originate from the laser and the temperature‐controlled laser filter used for laser filtering. Our results would contribute to the rapid assignment of the signals from the sample after excluding the spurious signals reported here. Moreover, the series of high‐order modes spaced by the free spectral range can serve as a weak broadband light source, which has great potential for investigating the optical responses of materials.

Abstract Drug resistance plays a vital role in both cancer treatment and prognosis. Especially, early insights into such drug‐induced resistance in acute myeloid leukemia (AML) can help to improve treatment plans, reduce costs, and bring overall positive outcomes for patients. Raman spectroscopy provides precise biomolecular information and can provide all these necessities effectively. In this study, we employed machine learning (ML) discrimination of Raman micro‐spectroscopic data of myelocytic leukemia cell line HL‐60 from its drug‐resistant counterpart HL‐60/MX2. Principal component analysis (PCA), linear discriminant analysis (LDA), and logistic regression (LR) methods were evaluated for their ability to identify and discriminate drug resistance in AML cells. Our study demonstrates the power of ML to classify drug‐induced resistance in AML cells utilizing subtle variations in biomolecular information contained in molecular spectroscopic data by obtaining 94.11% and 97.05% classification accuracies by LDA and LR models, respectively. We also showed that the ML methods are discernable. Our findings depict the importance of automation and its optimal usage in cancer study and diagnosis. The results of our study are expected to take ML‐assisted Raman spectroscopy one step closer to making it a generalized tool in medical diagnosis in the future.

No abstract is available for this article.

Abstract Raman spectra of (As1–xBix)2S3 glass samples with x ≤ 0.2 measured at the excitation with above‐bandgap (532 nm) laser light at a relatively low power density (Pexc = 4 kW/cm2) clearly confirm the amorphous character, thereby markedly extending the known compositional interval of existence of the (As1–xBix)2S3 glass previously known (x ≤ 0.06). Spectra measured at an increased Pexc (40 kW/cm2) reveal a photostructural transformation in the illuminated area of the glass leading to an additional contribution of Bi–S bonds as well as to an increasing number of cage‐type As4S4 units with homopolar As–As bonds. A number of new features in a broad range up to about 1,000 cm−1, which emerge in the Raman spectra of the (As1–xBix)2S3 glasses with high (x ≥ 0.14) Bi content and increase in intensity with the exposure time, are related to a photochemical transformation, namely, oxidation of arsenic and sulphur on the (As1–xBix)2S3 glass surface with formation of units containing arsenate AsO43− and sulphate SO42− ions. These processes are irreversible and occur only in the presence of a sufficient amount of bismuth.