Journal of Raman Spectroscopy最新文献

A dedicated analysis method is presented to extract the Raman spectrum of an interphase layer thinner than the laser spot size. We focused on spatial correlations between the contrast of optical micrographs and Raman hyperspectral data to predict the constituents of the mixed spectra measured near the interphase. By employing a mapping step size of 0.1 μm, the Raman spectrum of approximately 0.3-μm-thick carbon interphase in a SiC fiber-reinforced SiC matrix composite was extracted from data acquired with a theoretical spot size of about 0.7 μm. Notably, conventional chemometrics procedures were unable to isolate the interphase signal, instead producing a spectrum representing a mixture of interphase and matrix. This study used another composite with approximately 0.9-μm-thick interphase to validate the analysis method, enabling direct measurement of the interphase spectrum. The proposed Raman analysis method has advantages in specimen volume and turnaround time compared to traditional characterization methods, such as transmission electron microscopy. This study also evaluates the applicability of the analysis method to different composite materials and identifies key requirements of the measurements, including the ratio of interphase thickness to spot size and the homogeneity of the surrounding matrix.

Layered perovskites AA′BO₄ are promising electrolyte materials for electrochemical devices as sources of renewable and distributed energy. Creation of new materials with target properties requires knowledge of their local structure. In this paper, the influence of the nature and concentration of dopants (Ca²⁺ and Sr²⁺) during isovalent doping in the layered perovskite BaLaInO₄ has been investigated for the first time. Doping was found to change the crystal symmetry from orthorhombic (space group Pbca) for the matrix BaLaInO₄ composition to tetragonal (space group I4/mmm) for the doped Ba_1 − xCa_xLaInO₄ and Ba_1 − xSr_xLaInO₄ compositions. Doping results in the redistribution of bond lengths and changes the tilt angle of In-containing polyhedra. These alterations in the crystal lattice increase the oxygen-ionic conductivity values up to 1–1.5 orders of magnitude.

Femtosecond chirped-probe-pulse (CPP) CARS technology has become a powerful tool for measuring complex high-temperature combustion temperatures due to its interference-free characteristics, high accuracy, and excellent time resolution. The experiment uses a specific energy-matching method to effectively separate the signal light from the background light and thus improve the accuracy of the measurement. The optimization was confirmed in the inner and outer flames of the butane Bunsen burner, with the best accuracy of 3.2% and 1.7% at 1385 and 1411 K, respectively. The two-dimensional temperature distribution at the outlet of the heat gun was experimentally measured using the aforementioned energy-matching method. The results show that the average accuracy can be below 2% at temperatures exceeding 700 K and that the temperature distribution corresponds to the nozzle structure at the air outlet. The experimental results demonstrate the successful acquisition of spatially resolved 2D temperature distributions under challenging high-temperature turbulent combustion conditions using femtosecond CPP CARS, providing valuable reference data for turbulent combustion studies.

Fluid and melt inclusions serve as invaluable micro-scale archives of geochemical processes, preserving snapshots of mineral-forming fluids and melts across a broad range of pressures and temperatures in natural environments. Their analysis provides critical insights into crystallization histories, metasomatic events, and volatile cycling in geological systems. However, the automated identification of minerals within these inclusions has long been hindered by spectral complexities arising from phase coexistence, host-mineral interference, and orientation-dependent Raman signatures. This study introduces the web-based tool Advanced spectRa Deconvolution Instrument (ArDI) (https://ardi.fmm.ru), which integrates fast search algorithms (Faiss), convolutional neural networks, and recursive spectral decomposition to analyze complex Raman spectra. Using pegmatitic quartz as a case study, we demonstrate that the method allows effective identification of minerals within fluid inclusions, e.g., sassolite and ramanite-(Rb), even when their spectra are integrated with host and other minerals. The developed approach unlocks new possibilities for nondestructive analysis of mineral assemblages in microscopic objects.

In this theoretical study, focusing on the single resonant Raman G mode, new details of Raman radiation from monolayer graphene are presented. The propagation direction of the emitted photon is discussed, explicitly considering the momenta of the incident photon, the scattered photon, and the phonon. It is demonstrated that graphene should be regarded as a quasi-two-dimensional system in light scattering phenomena, and the electron confined motion along the z-direction, perpendicular to the atomic monolayer plane, must be taken into account. It is established that the out-of-plane nature of the emitted photon arises from the uncertainty of the electron momentum along the z-direction. It is theoretically shown that at Raman G scattering, the wavenumber of the emitted iLO or iTO phonon is limited to a certain range, with boundaries determined by the crystal sizes and the wavenumber of the incident photon. Two-sided limitation of the Raman-active optical phonon wavenumber, in turn, restricts the propagation direction of the emitted photon. The developed approach is general and can also be applied to the analysis of other Raman lines of graphene.

Surface-enhanced Raman spectroscopy (SERS) is a rapid and sensitive method for ultra-trace analyte detection. The current work demonstrates the application of an array of Au-nanotriangles as a sensitive, efficient, and customized SERS substrate, manufactured via electron beam lithography on a silicon wafer. The Raman spectra of rhodamine 6G (R6G) at micromolar concentration have been accurately and efficiently detected to evaluate the SERS response of the proposed substrate. The suggested substrate also enables ultra-trace detection of the parasiticide leuco-malachite green (LMG) at nanomolar concentrations. It demonstrates exceptional repeatability and reproducibility of the SERS signal under examination, confirming the substantial resilience of the constructed substrate. The identification of the hazardous parasiticide LMG will assist healthcare professionals, since it is associated with several deleterious consequences in humans, including DNA damage, chromosomal mutations, and the potential development of tumors in vital organs such as the liver, thyroid, and bladder.

Surface-enhanced Raman spectroscopy (SERS) is a rapid and sensitive method for ultra-trace analyte detection. The current work demonstrates the application of an array of Au-nanotriangles as a sensitive, efficient, and customized SERS substrate, manufactured via electron beam lithography on a silicon wafer. The Raman spectra of rhodamine 6G (R6G) at micromolar concentration have been accurately and efficiently detected to evaluate the SERS response of the proposed substrate. The suggested substrate also enables ultra-trace detection of the parasiticide leuco-malachite green (LMG) at nanomolar concentrations. It demonstrates exceptional repeatability and reproducibility of the SERS signal under examination, confirming the substantial resilience of the constructed substrate. The identification of the hazardous parasiticide LMG will assist healthcare professionals, since it is associated with several deleterious consequences in humans, including DNA damage, chromosomal mutations, and the potential development of tumors in vital organs such as the liver, thyroid, and bladder.