Journal of Raman Spectroscopy最新文献

Desoutter, A, Slimani, A, Al-Obaidi, R, et al. Cross striation in human permanent and deciduous enamel measured with confocal Raman microscopy. J Raman Spectrosc. 2019; 50: 548–556. https://doi.org/10.1002/jrs.5555

Rand Al-Obaidi was listed as third author in the article and below is the additional affiliation of the author.

College of Dentistry, Mustansiriyah University, Iraq

Silicate minerals have a rich structural variety consisting of silicon oxide clusters or networks of any dimensionality interdispersed with different types of elements, which is reflected in marked changes in the Raman spectra. Understanding how the changes in the Raman spectra are correlated with the atomic structure would be highly desirable for fast material identification and analysis. Extracting such trends from experimental spectra can be difficult owing to the uncertainties in the structural details of the samples and in ensuring consistency between measurements from different sources. Simulated spectra, however, avoid these problems, making them a good candidate for systematic studies. Here, we study the correlation between the structure and Raman spectral features of 179 silicates derived from a database of Raman spectra simulated using first-principles calculations. We investigate the spectral similarities with a specific emphasis on materials containing isolated 0D clusters in nesosilicate (SiO₄), sorosilicate (Si₂O₇), and cyclosilicate (Si₃O₉ and Si₄O₁₂) configurations. While trends identified in the previous reports can be confirmed, we find that the variations within each group of similar structural motifs tend to be larger than the changes across groups, and therefore, developing a reliable automated classification algorithm is likely to be challenging.

The study of gems in jewellery of the Roman period from known archaeological contexts may provide valuable information for the trading routes of gems in antiquity, the techniques of their manufacture and decoration, the popularity of certain gems or their relation to a specific type of jewellery. Moreover, by the correct identification of these gems, the museum will better inform its public. In the present work, 19 green-coloured gems, which were integral parts of 14 Roman jewellery pieces, dated between the first and fourth century CE, from the collections of the Archaeological Museum of Thessaloniki in Greece, were studied. Most samples were found during rescue excavations in western and eastern Roman cemeteries of Thessaloniki, while one was found in Edessa, a city in northern Greece. All samples were investigated by using strictly non-destructive techniques, for example, optical microscope as well as Raman and Vis-NIR mobile instruments. For the chemical characterisation of the samples, micro-EDXRF was used. Seventeen samples were identified as natural emeralds with characteristics similar to emeralds that originate from Egypt. Among the studied samples, a natural chrome chalcedony and an artificial glass were also identified. The geographic origin of the artificial glass is unknown and that of chrome chalcedony is under discussion with Turkey being the most possible source.

Raman spectroscopy is very sensitive to the U-O bonding strength changes under high pressure, and it could reveal important information about the bonding and stoichiometry of the U-O systems. The pressure and temperature (P–T) phase diagram of U₃O₈ was investigated by Raman spectroscopy via four independent P–T experimental paths. The phase boundaries between different phases have been determined by the changes in Raman spectra. A new phase (α′-U₃O₈) was observed below 233 K at 0.6 GPa or 198 K at zero pressure accompanied by the discontinuities in Raman wavenumber and the new shoulder peak near the B₂⁽⁶⁾ Raman modes. Upon compressing at low temperature (123 K), the high-pressure irreversible phase transition from orthorhombic to cubic structure (α′-δ) was observed at around 11.3 GPa, evidenced by the merging of B₂⁽⁶⁾ and B′₂⁽⁶⁾ Raman modes.

The variation of structural and electric properties is investigated via different characterization methods for NaNbO₃ ceramics modified with Ta⁵⁺ ions. At room temperature, substitution of Ta⁵⁺ ions can effectively induce the phase coexistence and transition between orthorhombic antiferroelectric P and orthorhombic ferroelectric Q phase in NaNb_1-xTa_xO₃ ceramics. Thus, the ferroelectric and piezoelectric properties could be regulated with the maximum value of d₃₃ (~37.3) at x = 0.05. Besides, with increasing temperature, multiple phase transitions are demonstrated through dielectric, XRD, and in situ Raman results. Moreover, the temperature of various phase transitions gradually shifts toward lower temperature with increasing Ta⁵⁺ ions. Correspondingly, the modulation mechanism is also discussed based on the evolution of Raman vibration. This work is instructive for regulatable applications of NaNbO₃-based materials.

Echinococcosis chiefly includes cystic and alveolar echinococcosis, which is a parasitic disease. It is very important to find a quick and non-staining method to determine whether a tissue sample has echinococcosis lesions; it is not only conducive to the diagnosis of echinococcosis but also conducive to the judgment after surgery. In the study, tissue surface-enhanced Raman spectroscopy (SERS) in combination with deep learning was used to classify cystic and alveolar echinococcosis and healthy controls. Silver nanoparticles served as SERS-enhanced substrates, and a large amount of tissue SERS spectra was collected. There were 24 cases of cystic echinococcosis tissue, 14 cases of alveolar echinococcosis tissue, and 21 cases of healthy control tissues, and the numbers of SERS spectra collected were 594, 410, and 990, respectively, for a total of 1994 spectra. The convolutional neural network (CNN) was used to categorize SERS spectra into three types. Four other common machine learning classification algorithms were compared with the CNN model to highlight the classification effect of the CNN model. The results show that the model with the best effect is the CNN model, whose accuracy reaches 95%. Therefore, SERS combined with the CNN model has great potential for distinguishing the tissues of cystic and alveolar echinococcosis.

The nature of the nonequilibrium states of materials upon rapid compression/decompression processes in the intermediate regime, between static and shock compression, is an emerging field of high pressure research. Rapid compression experiments were performed to examine the structural response of silicon (Si) up to 11 GPa and over compression rates ranging from 0.011 to 0.325 GPa/s, using a piezo-driven dynamic diamond anvil cell (dDAC) coupled with time-resolved Raman spectroscopy. The observed structural stability and the remarkable consistency in the pressure-dependent Raman shift of the diamond cubic Si (Si-I) showed its high potential as a Raman pressure scale for compression rate below 0.325 GPa/s. The validity of the derived Si scale was verified by in situ continuously monitoring pressure of two rapid compressed samples, that is, gypsum and ZnO. Results indicated that pressures determined using Si were in good agreement with those estimated from the ruby scale. Success in pressure calibration with Si, during time-resolved Raman spectroscopy measurements of material under rapid compression using a dDAC, will greatly simplify the required hardware system in home-laboratory and may also help in reaching a higher signal-to-noise in Raman measurement on a short time scale.

In this study, the resonance Raman spectra of hydrothermally produced 2H-MoS₂ nanoflakes excited by a 633-nm laser were examined. Spectral observations include both fundamental MoS₂ modes and additional Raman lines, which arise from alterations in the energy states of the semiconductor owing to the incidence of laser radiation. Phonon softening and alterations in the phonon lifetime were computed for different laser powers. The Fano resonance, which causes asymmetry in the Raman spectral lines, was analyzed at different laser powers. The Fano line-shape function is used to fit the asymmetry in the in-plane vibrational mode whereas multi-peak fitting using the Fano-Lorentzian function is used to fit the out-of-the-plane fundamental mode, which is coupled with “b” mode. A direct study of the electron–phonon interaction was carried out with the “b” mode. The shift in laser wavenumber was then investigated using the 2LA(M) modes observed in the resonance Raman spectra. These findings provide new optoelectronic device designers with an understanding of the intricate electron–phonon interactions in transition metal dichalcogenides.

We prepared two types of trench-test metal-oxide semiconductor field-effect transistor (MOSFET) structures on m- and a-faces in 4H silicon carbide (4H-SiC) and investigated the anisotropic stress distribution of small trenches with a depth of 1 μm using a scanning near-field optical Raman microscope (SNOM) that we developed. The stress distributions of σ₁₁ (a-axis) under the bottom of the trench for m-face were approximately 100 MPa larger than those for a-face, and the stress distributions of σ₃₃ (c-axis) under the bottom of the trench for m-face were almost the same as those for a-face. The experimental result agrees well with that calculated by the finite element method (FEM). These results indicate that the anisotropic stress distributions of σ₁₁ components around the apex of the trenches of 4H-SiC trench-test MOSFET occur in m- and a-faces. Thus, it is possible that the differences in mobilities for m- and a-faces might be caused by the anisotropic stresses.

This paper addresses the challenge posed by the size of certain objects that do not conform to the constraints of microscope-coupled Raman spectrometers, making sample collection impossible due to their inherent value or nature. Specifically, materials like hydroxyapatite-based substances used in artistic and ornamental carvings, such as bone or ivory, fall within this problematic category. The focus of this study is the enhancement of analytical capabilities in the context of large objects using a Raman microscope system. The study details the innovation involving a remote probe integrated with fiber optics, elaborating on the design and performance aspects, and emphasizing the appropriateness of chosen components in the analysis of ivory artifacts belonging to private collectors. In order to assess the robustness of our discriminative approaches, an archaeological bone and the exposed dentine in a human tooth were also evaluated and compared. Results showed that using an 805-nm longpass dichroic mirror successfully directed the near-infrared laser onto the samples and significantly suppressed the Rayleigh scattering contribution to the spectrum. Regarding the preprocessing methods to spectra evaluation essayed, the most promising approach was the use of principal component analysis for dimension reduction followed by k-means cluster analysis. By leveraging the complementary strengths of PCA and k-means clustering, the robustness and interpretability of clustering analyses are enhanced.