Journal of Raman Spectroscopy最新文献

Raman spectroscopy is a popular tool for characterizing complex biological materials and their geological remains. Ordination methods, such as principal component analysis (PCA), use spectral variance to create a compositional space, the ChemoSpace, grouping samples based on spectroscopic manifestations reflecting different biological properties or geological processes. PCA allows to reduce the dimensionality of complex spectroscopic data and facilitates the extraction of informative features into formats suitable for downstream statistical analyses, thus representing a first step in the development of diagnostic biosignatures from complex modern and fossil tissues. For such samples, however, there is presently no systematic and accessible survey of the impact of sample, instrument, and spectral processing on the occupation of the ChemoSpace. Here, the influence of sample count, unwanted signals and different signal-to-noise ratios, spectrometer decalibration, baseline subtraction, and spectral normalization on ChemoSpace grouping is investigated and exemplified using synthetic spectra. Increase in sample size improves the dissociation of groups in the ChemoSpace, and our sample yields a representative and mostly stable pattern in occupation with less than 10 samples per group. The impact of systemic interference of different amplitude and frequency, periodical or random features that can be introduced by instrument or sample, on compositional biological signatures is reduced by PCA and allows to extract biological information even when spectra of differing signal-to-noise ratios are compared. Routine offsets ($�\pm$1 cm⁻¹) in spectrometer calibration contribute in our sample to less than 0.1% of the total spectral variance captured in the ChemoSpace and do not obscure biological information. Standard adaptive baselining, together with normalization, increases spectral comparability and facilitates the extraction of informative features. The ChemoSpace approach to biosignatures represents a powerful tool for exploring, denoising, and integrating molecular information from modern and ancient organismal samples.

Systemic amyloidosis is a group of diseases in which misfolded proteins aggregate as fibrous amyloid proteins with a β-sheet structure and deposit in organs, resulting in organ failure. Most types of amyloidosis have a poor prognosis, and prompt diagnosis is essential for treatment. Systemic immunoglobulin light-chain (AL) amyloidosis is a type of amyloidosis that occurs when abnormal immunoglobulin light-chain proteins are deposited in various organs and tissues. The deposition of amyloid proteins in tissues has traditionally been confirmed using Congo red staining and polarised light microscopy, which show apple-green birefringence. In this study, we aimed to verify whether amyloid deposition in the heart, kidney, rectum, duodenum and skin can be detected using Raman microspectroscopy. Serial sections were prepared from formalin-fixed paraffin-embedded tissue biopsy samples obtained from patients with systemic amyloidosis. One of the serial sections was stained with Congo red to confirm the deposition of amyloid proteins using polarised light microscopy, whereas the other was left unstained for Raman microspectroscopy. A characteristic peak at Raman shift of 1665–1680 cm⁻¹, which may represent a β-sheet structure of amyloid proteins, was recorded in the area where the amyloid deposition had been confirmed by Congo red staining. Based on the peak at 1640–1680 cm⁻¹, a colour map was obtained to detect amyloid protein-positive regions. Thus, amyloid protein detection using Raman microspectroscopy may be useful for rapid diagnosis of amyloidosis.

Core (Co)/shell (Co-oxide) nanoparticles assembly exhibits interesting magnetic properties that depend on the inorganic shell characteristic (composition and crystalline structure). Assemblies of pure and partially oxidized cobalt (core/shell) nanoparticles, ~9 nm in diameter, were prepared and analyzed by techniques probing the matter at macroscale to nanoscale: UV–visible-near-infrared (NIR) transmission, FTIR, Raman microspectroscopy, and transmission electron microscopy. Attention is paid to compare nonoxidized and (partially) oxidized Co nanoparticles, coated with lauric acid as stabilizing agent (ligands). The approximately 1 nm disordered inorganic coating is perfectly detected by transmission electron microscopy, UV–visible–NIR, infrared, and Raman spectroscopy. The Raman spectrum is sensitive to laser wavelength and power due to the local heating induced by the laser, which modifies the interaction between the organic chains and the nanoparticle inorganic shell. For comparison, nanoparticle films were analyzed under heating from room temperature to 300°C. The “fusion” (dynamic disorder) of lauric (dodecanoic) chains is observed concomitantly with the merging of very low wavenumber Lambs' modes into a Rayleigh wing, which is consistent with an increase in the topological nanoparticle disorder. Hydroxylation or water adsorption is observed for Co film. The UV–visible–NIR and Raman spectra of the Co-oxide shell do not correspond to that of CoO (rock salt) nor to that of Co₃O₄ (spinel) but has some similarity to that of 2D delafossite (CoOOH) phase.

Analytical and real-time technology in pharmaceutical manufacturing process is an important need to ensure that manufactured drugs are safe and effective. Raman spectroscopy is an emerging technique that is able to perform quantitative analysis nondestructively due to the molecular structure of many drugs. Monitoring the content uniformity and quantification of active pharmaceutical ingredient (API) in the tablet preparation process, without the assistance of solvent, is one of the key concerns in the formulation design in order to provide stable, pure, and homogenous finished products. In this study, we investigated the possibility of using Raman data as an analytical method to quantify API, the intra- and inter-sample uniformity of content in the tableting process of Metformin hydrochloride tablets (C₄H₁₁N₅.HCl). Analysis of all standard samples for prediction of API uniformity represents an acceptable accuracy and precision with a relative standard deviation of 2.55%. Further investigation of tablets regarding to relative Raman intensity of some characteristic peaks demonstrates the amount of API content with an accuracy of ≥96%. These values have a good adaption with pharmacopeia monograph. Findings reveal that the Raman method can be routinely utilized for quantifying API, controlling the content uniformity and the stability of drugs in different stages of manufacturing.

The vibrational properties of orthorhombic MgCu₂O₃ compound have been investigated within the framework of the density functional perturbation theory (DFPT) as well as experimentally, to validate the computational results. MgCu₂O₃ was synthesized by solid-state reaction and characterized by synchrotron-based X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The DFT + U-based first principle calculations were performed to obtain the correct electronic ground state and the band structure of this compound. The same DFT + U methodology was employed along with DFPT calculations for obtaining vibrational properties: phonon density of states and phonon band structure. The atomic vibrations for each mode were also analyzed, and the Raman and the IR active modes are identified. Experimentally observed Raman and infrared (IR) spectra agree well with the computed ones.

The Raman and infrared (IR) wavenumbers were computed for the Aurivillius structure ABi₄Ti₄O₁₅ (ABT) (ACa, Sr, Ba) in an orthorhombic space group (A21am, No. 36, C₁₂^2v) using normal coordinate analysis. This study aimed to investigate the impact of A-site cations on vibrational phonons. The analysis of zone center phonons primarily involved numerous stretching and bending bonds, serving as force constants. These force constants were utilized to assign the calculated wavenumbers in the examined phase for the first time. The theoretical findings in this paper exhibited a favorable correlation with the wavenumbers reported in the literature. Comparisons of force constants, bond lengths, and wavenumbers were conducted to elucidate A-site cation disordering in these intricate compounds. The outcomes indicated that, in the studied complexes, the Sr atom exhibited an ideal radius for fitting into the structure. The mass of the A-site cations was identified as a factor contributing to tilts in the octahedra. An additional analysis was carried out to assess the impact of A-cations on both the affected equatorial and axial bonds, providing a clearer understanding of the structure. Outer octahedra displayed greater sensitivity to A-site cations compared with inner octahedra. A study of potential energy distribution was also conducted in this work to determine the significance of each force constant in all calculated wavenumbers. It was observed that higher wavenumbers were predominantly influenced by vibrations in oxygen atoms, while lower wavenumbers were mainly affected by A-site cations. Notably, overdamping was observed in the lowest frequency of the BBT compound.

Raman spectra of zircon have recently been used as a pressure scale for studies of geological fluids at high temperatures and high pressures using diamond anvil cells (DACs). The zircon scale is advantageous in high chemical stability and the large pressure response of the B_1g mode. Despite its excellent applicability, the calibration of the scale has been carried out only in a narrow pressure–temperature range, especially under limited high-temperature and high-pressure conditions. In this study, the pressure and temperature dependence of the Raman modes of synthetic zircon was investigated up to 9.5 GPa and from room temperature to 776 K using an externally heated diamond anvil cell. Ruby and gold were used as the reference pressure scales. The Raman shift of the B_1g mode for the antisymmetric stretching of the SiO₄ structure in zircon showed a linear pressure dependence of 5.48(4) cm⁻¹/GPa up to 8 GPa at room temperature, in agreement with the previous studies. Measurements under high-pressure and high-temperature conditions confirmed that the pressure dependence up to 9.5 GPa along the isotherms from 373 to 675 K was consistent with the room-temperature value; the wavenumbers can be well deduced from the sum of the individual effects of pressure and temperature, obtained at ambient temperature and pressure, respectively. A comparison of the zircon scale with the c-BN Raman spectroscopic scale confirmed that the pressures determined with these scales were in reasonable agreement. The present results provide a confident use of the zircon Raman spectroscopic scale in a wider pressure–temperature range than previous studies for the internally consistent pressure determination.

We report the results of polarization-dependent Raman spectroscopy of phonon states in single-crystalline quasi-one-dimensional NbTe₄ and TaTe₄ van der Waals materials. The measurements were conducted in the wide temperature range from 80 to 560 K. Our results show that although both materials have identical crystal structures and symmetries, there is a drastic difference in the intensity of their Raman spectra. While TaTe₄ exhibits well-defined peaks through the examined wavenumber and temperature ranges, NbTe₄ reveals extremely weak Raman signatures. The measured spectral positions of the phonon peaks agree with the phonon band structure calculated using the density-functional theory. We offer possible reasons for the intensity differences between the two van der Waals materials. Our results provide insights into the phonon properties of NbTe₄ and TaTe₄ van der Waals materials and indicate the potential of Raman spectroscopy for studying charge-density-wave quantum condensate phases.

The cover image is based on the Special Issue – Research Article Raman identification of pigments and opacifiers: Interest and limitation of multivariate analysis by comparison with solid state spectroscopical approach—I. Lead-tin and Naples Yellow by Jacques Burlot et al., https://doi.org/10.1002/jrs.6600.

Semiconductors have attracted great attention for surface-enhanced Raman scattering (SERS) applications due to their rich variety, adjustable band structure, good chemical stability, and biocompatibility. However, their intrinsic weak SERS activity limited the further development of semiconductor substrates. Here, the α-Fe₂O₃ films with high {$�1�\overline{1}�0$} and {$�110$} facet exposure ratios were fabricated through an electrodeposition method with the existence of NH₄Cl and CH₃COONa. The α-Fe₂O₃{$�1�\overline{1}�0$} and α-Fe₂O₃{$�110$} films show excellent SERS properties with enhancement factor of 4.155×10³ and 5.481×10³, as well as the relatively low limit of detection down to 2 × 10⁻⁷ M for 4-nitrobenzenethiol. Meanwhile, the lower relative standard deviation values (<10%) confirm the well uniformity of as-prepared substrates. Ultraviolet photoelectron spectroscopy analysis reveals that the α-Fe₂O₃{$�110$} possesses the lower work function, which could guarantee the efficient interfacial charge transfer between substrates and probe molecules. Moreover, first principles calculations further indicates that the charge transfer efficiency on {$�110$} facet can be effectively improved, and thus significantly enhance the SERS activity of α-Fe₂O₃. The current study provides a strategy for the fabrication and application of semiconductor-based SERS substrates.