Journal of Raman Spectroscopy最新文献

In 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.

Sauce glazed wares of Yaozhou kilns are famous for their high gloss and distinctive glaze color palette varying from yellowish-brown to reddish-brown. In this work, sauce glazes were successfully replicated using the traditional technology of Yaozhou kilns. Micro-Raman spectroscopy, combined with optical microscopy, scanning electron microscopy, x-ray fluorescence, and reflective spectroscopy, was systematically applied to analyze the chemical composition, nature and distribution of crystals, and the coloration of the glazes. The results show that the yellowish-brown glaze is mainly original from dendritic ε-Fe₂O₃ crystals, whereas the reddish-brown color is mainly derived from dendritic hematite crystals. Such dendritic structure could account for slightly color variations of the glaze surface observed in different angles, which also reported in Japanese Bizen ceramics. The principal component analysis (PCA) was further applied to study the Raman spectra of these iron oxides. The PCA results effectively indicates the structural disorders of these crystals introduced by ion substitutions. These substitutions could not only stabilize the crystals but also darken the crystals color. Besides, high Mg in the raw materials was found to benefit the growth of magnesioferrite crystals. The relative low level of Fe₂O₃, high level of SiO₂, and CaO may relate to the formation of ε-Fe₂O₃ crystals.

Phospholipid bilayers, which are a major component of cellular membranes and some drug delivery vehicles, can be in different states of order depending on the conformations of the hydrocarbon tails and their mutual arrangement. The important task of experimental characterization of phospholipid order is often addressed using Raman spectra of the C–H stretching bands. Such characterization uses some empirical relationships for apparent maxima in the spectra, although the origin of the sensitivity of the C–H band to phospholipid order and its model description remain unclear. Surely, a correct description of the sensitivity of the C–H band to phospholipid order is critical for its proper application. Here, we provide a description of the ordering sensitivity of the C–H stretching band using a polarized Raman experiment with hydrated aligned multibilayers of a saturated phospholipid. By this way, Raman contributions from symmetric and antisymmetric vibrations of CH₂ were obtained in a model-free manner. Experiments in a wide temperature range and the use of isotopic isolation helped us to consider separately the effects of conformational and lateral order of chains. The conformational sensitivity of the spectrum of antisymmetric vibrations was confirmed by DFT modeling. The outcomes of the study allowed us to provide recommendations for the use of the Raman spectrum of the C–H stretching band to characterize the conformational and lateral order of phospholipid-containing materials.

The multidisciplinary, noninvasive analysis of baroque amber artworks is part of a research project that deals with the most valuable objects from the Museum of Gdansk (Poland). The two most interesting objects will be presented here: a Baroque Gdansk wardrobe-shaped amber cabinet (made by Johann Georg Zernebach, Gdansk, 1724) and a crucifix (Gdansk, 17th century). Macro- (UV, IR, and X-radiography) and micro- (XRF and Raman spectroscopy) analytical methods were applied to reveal traces of old conservation treatments and uncover the techniques of the 17th and 18th century amber masters. UV photography shows the differences between the amber plates that are not so easily detected under visible light, while XRF spectrometry detects elements atypical for amber objects, suggesting previous conservation treatments. Confocal Raman measurements, especially Raman depth profiling, were performed for the amber artworks and allowed to detect areas of previous conservation treatments. Single-point scans were collected from the surface (0 μm) to a depth of −200 μm, with a step of 50 μm. The results allowed us to identify three different types of zones: where the amber was preserved without any protective layer, places where the amber was covered with a thin layer of a protective substance, and places where amber elements were compensated for loss using a binding agent and filler. The presented project allowed the development of a comprehensive methodology for the analysis of amber objects, especially to optimize the capabilities of confocal Raman microscopy. The combination of macro- and microanalytical techniques made it possible to obtain a broad overview of such complex artworks while optimizing the time and effort spent on the investigations.

The study explores drawing materials from the 17th century to the present using noninvasive techniques like Raman spectroscopy in selected cases supplemented by x-ray fluorescence (XRF) spectroscopy. This publication is an effort to expand knowledge across diverse periods and materials. A collection of six drawings spanning from 1700 to 1899 from the National Museum in Krakow and a 20th-century birch bark artifact were analyzed. Noninvasive techniques facilitated the systematic analysis of drawing materials, providing insights into diverse substances over centuries. Identified materials include hematite, calcite, graphite, bister, sepia, iron gall ink, and crystal violet dye. Understanding the chemical composition aids conservation and is a reference for future art history and preservation studies.

The present work introduces a new approach to quantitative determine the reagent concentrations (thiourea and urea) using in situ Raman spectroscopy in the reaction mixture exemplified by the reactions of formation of allantoin and 4,5-dihydroxyimidazolidine-2-thione. The approach comprises the use of a commercially available immersion probe (MarqMetrix Process Elite BallProbe with sapphire lens) as a standard for the immersion probe band at 790 cm⁻¹ of optical glass. This leads to a linear dependence of the ratio of the intensity of non-overlapping analyte bands at 1003 cm⁻¹ of -C-N- vibrations in urea to the one of the 790 cm⁻¹ immersion probe band on the concentration of urea in the test solution. The definable method parameters such as precision (repeatability and reproducibility), linearity, limit of detection (LoD), limit of quantitation (LoQ), and accuracy were determined. The quantitative Raman spectroscopy method is linear, precise within the range of determined concentrations from 0.75 to 2.00 M and can be used to calculate the kinetics of allantoin formation. Using thiourea as an example, it is shown that despite the partial overlap of the analyte band at 730 cm⁻¹ of the -C=S vibrations of thiourea with the immersion probe band at 790 cm⁻¹, the method to determine thiourea in the reaction of 4,5-dihydroxyimidazolidine-2-thione preparation is also linear and precise in the range of determined concentrations from 0.10 to 1.57 M.