Journal of Raman Spectroscopy最新文献

The combination of optical microscopy and spectroscopy is a powerful tool for accessing both spatial and chemical information from a diverse range of samples. Applications of spectroscopic imaging techniques in biological samples are often limited by high backgrounds and autofluorescence. Surface enhanced Raman scattering (SERS) provides highly specific signals that can be used as labels or to monitor chemical interactions in complex environments. Previous work establishing a spectrally resolved SERS imaging approach demonstrated the presence of high backgrounds when imaging biological samples, causing interference with clear detection and identification of SERS signals. To minimize this out of focus scattering, this work demonstrates the incorporation of selective plane illumination microscopy (SPIM) with wide-field SERS spectral imaging, an approach we term selective plane illumination surface enhanced Raman scattering (SPI-SERS) spectral imaging. The generated light sheet avoids exposure outside of the focal plane altogether, which simultaneously improves image contrast and signal-to-noise ratios (SNRs) in the observed spectra. These improvements enable molecular identification in both 3-dimensional (3D) matrices and biological cellular samples, advancements which hold promise for the ability of this methodology to achieve high-contrast SERS imaging in complex biological samples.

The cover image is based on the article Surface-Enhanced Raman Scattering Optical Fiber Sensors: Advances and Prospects by Tao Lei et al., https://doi.org/10.1002/jrs.70058.

The cover image features amphibole inclusions in an emerald from Zimbabwe (image width: 1 mm; photomicrograph by Ugo Hennebois, LFG) and it is based on the article Raman Spectroscopy of Amphibole Inclusions in Emeralds by Karampelas et al., https://doi.org/10.1002/jrs.6839.

This special issue of the Journal of Raman Spectroscopy (JRS) presents selected papers from the 16th International GeoRAMAN Conference, held in Rhodes, Greece, from 24 to 27 September 2024. The meeting brought together the global GeoRAMAN community to share the latest developments and applications of Raman spectroscopy across geoscience, planetary science, cultural heritage and emerging fields such as geoenergy and geoenvironmental research. The 23 contributions, published in this issue, present new knowledge in the field of applications of Raman spectroscopy to Earth and planetary materials and reflect the scientific diversity, methodological innovation and collaborative spirit that continue to define this vibrant community.

Raman spectroscopy is being developed for resource evaluation on planetary surfaces, especially on the Moon. Analogue studies were undertaken to collect data that would indicate the presence of water and help develop the technology to search for valuable trace elements. Analysis of a gabbro-anorthosite suite by Raman spectroscopy distinguished pyroxene, olivine and feldspar in samples whose mineralogy had been cross-checked by electron microscopy. Examination of the olivine by electron microscopy showed a complex distribution of hydrated alteration products referable as serpentine or iddingsite. The altered olivine is thus a proxy for water. Raman spectroscopy of similar olivine produced a map of alteration products, which is a first depiction of a map of hydration. A targeted set of trace elements was more abundant in the feldspar. Raman spectroscopy of feldspar in cross-cutting pegmatite veins detected a range of minerals containing trace elements, including anomalous amounts of the critical elements lithium and caesium. Measurement of Li and Cs in hot spring deposits which lie on the gabbro-anorthosite suite shows much higher enrichment in shale sediments, which Raman spectroscopy identified as muscovite. This conclusion is consistent with the concentration of some trace elements (including Li) in detrital minerals and other trace elements (including Cs) in fluid precipitates.

Garnets are minerals offering valuable insights into geological and planetary processes, in both terrestrial and extraterrestrial contexts. Their presence in metamorphic rocks, as well as in meteorites, makes them key indicators of the conditions under which they formed, such as pressure, temperature, and chemical environment. This information is valuable for understanding the history and evolution of planetary bodies, including Earth and Mars.

Developing automatic classification models for garnets using Raman spectroscopy has a potential application for planetary exploration, particularly for the Raman Laser Spectrometer (RLS) on the Rosalind Franklin rover of the upcoming ExoMars mission. In this work, we used a dataset combining spectra from ADAMM and RRUFF databases, ensuring a well-distributed representation of the two main garnet groups: pyralspites and ugrandites. The spectra from ADAMM were obtained using the RLS SIM, a laboratory version of RLS, while RRUFF data helped increase the number of samples in the dataset. After standardizing all data, we designed a two-step classification model: a top-level model to classify into the two main groups and two specific models to classify the garnet type within each group. We tested multiple machine learning algorithms, including support vector machine (SVM), k-nearest neighbors (KNN), artificial neural networks (ANN), decision tree, and naive Bayes. The top-level classification reached 100% accuracy in testing, while the final combined model achieved 80.42% accuracy. These results demonstrate that machine learning and Raman spectroscopy can effectively classify garnets, providing a valuable tool for planetary missions and mineralogical studies.

A new protocol for the laboratory preparation of archaeological samples, aimed at concentrating and analysing heavy minerals by optical microscope and Raman spectroscopy, is presented. The potential of heavy-mineral studies in geoarchaeology could be enhanced conspicuously by using a state-of-the-art protocol for sample preparation, analysing potteries, tempers and archaeological items, by high-resolution mineralogical analyses in medium silt and fine sand (15–250 μm). This method is repeatable by different operators, achievable in reasonable times, applicable also with a few grams of materials, and it is conceived to remove the abundant clayey and fine and very fine silt and liberate minerals from the ground mass. To test the proposed protocol, the mineralogical composition of 5 samples (common wares, red-painted ceramics and amphorae), collected in a Roman Villa sited in Fiumana, Forlì-Cesena, Italy, was investigated. The grain size analysed is representative (63%–75% in weight), and the amount of the ‘heavy fraction’ is very low (0.35%–0.72%), but sufficient to prepare a grain mount. Metamorphic versus magmatic minerals were quantified using a transmitted light, polarizing microscope, coupled with a Raman spectrometer and the presence of opaque and semi-opaque grains using an oblique light. This quantitative study allows us to differentiate samples that have been hand-crafted using different sediments as raw materials, discussing the source from the Alps and collected from the modern Po River depositional area; the sedimentary rocks of the Apennines; the volcanic source rocks from the Roman Province. This protocol is conceived to help improve the quality of heavy-mineral separation for applications in geoarchaeology.

The Pace di Siena is a unique en ronde bosse enamel, with few comparable pieces in Europe. The enamel, preserved and exhibited in the Arezzo Diocesan Museum (Italy), is surrounded by a frame decorated with thirty blue and pink gems whose identity has never been explored through analytical studies. The historical art literature has traditionally described these gems as tourmaline, aquamarine, beryl, and quartz, without delving into their provenance. Only a few hypotheses exist regarding the manufacture of the precious frame. Gemological analysis, in situ Raman spectroscopy, and energy-dispersive portable x-ray fluorescence (ED-pXRF) analysis have, for the first time, revealed the true nature of the gems, identifying them as fourteen natural blue corundum (sapphires) and sixteen natural pink spinels. The analysis of the inclusions also supports the hypothesis of heat treatment in the natural sapphires while suggesting a possible reuse for the natural untreated spinels, as indicated by the presence of distinctive holes. Additionally, semiquantitative geochemical data obtained by ED-pXRF after calibration through particle-induced x-ray emission (PIXE) analysis on a set of reference gemstones has provided valuable insights into the possible origins of the sapphires (which seems to have a metamorphic origin consistent with a possible Sri Lankan origin) and the pink spinels (which may have originated be come from Myanmar or Tajikistan). The study highlights the intersections between the materiality of the object, the concept of object biography, the provenance of their gems, and its chaîne opératoire.