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Raman/XRF/EDX microanalysis of 2nd-century stuccoes from Domus Valeriorum in Rome
摘要： 2nd-century stucco fragments from the roman Domus Valeriorum were analyzed by Raman spectroscopy (Raman), imaging X-ray fluorescence (XRF) and energy dispersive X-ray microanalysis (EDX) in order to identify the pigments and materials thereon. Cinnabar, malachite, hematite, goethite and Egyptian blue were detected by the synergistic use of these techniques whereas calcite, with some traces of gypsum, was detected as materials for the bas-relief figures and the pictorial background. This non-destructive characterization is the first carried out on the Domus Valeriorum finds. The multi-analytical approach highlighted the complementarity and versatility of these techniques, suitable for both laboratory and in-situ analysis, on macroscopic or microscopic fragments without preliminary manipulation.
关键词： Energy dispersive X-ray fluorescence,X-ray fluorescence imaging,Domus Valeriorum,Pigments,Raman spectroscopy
更新于2025-09-23 15:23:52
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studied with angle-resolved photoemission spectroscopy
摘要： We study the band structure of twinned and detwinned BaFe2As2 using angle-resolved photoemission spectroscopy. The combination of measurements in the ordered and normal states along four high-symmetry momentum directions (Γ/Z-X/Y) enables us to identify the complex reconstructed band structure in the ordered state in great detail. We clearly observe the nematic splitting of the dxz and dyz orbitals as well as folding due to magnetic order with a wave vector of (π, π, π). We are able to assign all observed bands. In particular we suggest an assignment of the electron bands different from previous reports. The high-quality spectra allow us to achieve a comprehensive understanding of the band structure of BaFe2As2.
关键词： band structure,BaFe2As2,angle-resolved photoemission spectroscopy,magnetic order,nematic splitting
更新于2025-09-23 15:23:52
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Flow cytometry and micro-Raman spectroscopy: Identification of hemocyte populations in the mussel Mytilus galloprovincialis (Bivalvia: Mytilidae) from Faro Lake and Tyrrhenian Sea (Sicily, Italy)
摘要： Immunological and structural characteristics of hemocyte populations in the mussel Mytilus galloprovincialis (Bivalvia: Mytilidae), going from two different Sicilian habitats (Faro Lake and Tyrrhenian sea), was investigated by means of two different techniques (flow cytometric and micro-Raman spectroscopy analyses). For this purpose, three hundred and sixty mussels Mytilus galloprovincialis were analyzed during November 2017. They were divided into two equal groups (triplicate sample) on the basis of the site of collection (n = 60 caught in Faro Lake - group A, and n = 60 caught in Tyrrhenian Sea - group B). Some several differences between the species of Faro Lake and Tyrrhenian Sea are observed and ascribed to the disruption of immune parameters induced by the variations of some qualitative water parameters (temperature, salinity, dissolved oxygen, pH, ammonium 10, free chlorine, total chlorine, total phosphate, orthofhosphate) recorded in the two habitats. This study is relevant for monitoring the conditions of the sea and Faro Lake, which is strongly influenced by the currents of the Tyrrhenian Sea. Faro lake is well known for the cultivation of mussels and this is part of a coastal habitat of particular interest, consisted of a peculiar biocenotic complex. Further, for the first time, significant different arrangement in the mussels cell structural organization was evidenced by simply following their highly reproducible Raman biomolecular signatures.
关键词： Hemocyte,Bivalve immunology,Deep-sea,Mussel Mytilus galloprovincialis,Flow cytometry,Raman spectroscopy
更新于2025-09-23 15:23:52
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UV luminescence characterisation of organics in Mars-analogue substrates
摘要： Detection of organic matter is one of the core objectives of future Mars exploration. The ability to probe rocks, soils, and other geological substrates for organic targets is a high priority for in situ investigation, sample caching, and sample return. UV luminescence—the emission of visible light following UV irradiation—is a tool that is beginning to be harnessed for planetary exploration. We conducted UV photoluminescence analyses of (i) Mars analogue sediments doped with polyaromatic hydrocarbons (PAHs; <15 ppm), (ii) carbonaceous CM chondrites and terrestrial kerogen (Type IV), and (iii) synthetic salt crystals doped with PAHs (2 ppm). We show that detection of PAHs is possible within synthetic and natural gypsum, and synthetic halite. These substrates show the most apparent spectral modifications, suggesting that the most transparent minerals are more conducive to UV photoluminescence detection of trapped organic matter. Iron oxide, ubiquitously present on Mars surface, hampers but does not completely quench the UV luminescence emission. Finally, the maturity of organic carbonaceous material influences the luminescence response, resulting in a reduced signal for UV excitation wavelengths down to 225 nm. This study demonstrates the utility of UV luminescence spectroscopy for the analysis of mixed organic-inorganic materials applicable to Mars exploration.
关键词： UV luminescence,Spectroscopy,Analogue,Organic,Mars
更新于2025-09-23 15:23:52
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A Study of Two Dimensional Tomography Reconstruction of Temperature and Gas Concentration in a Combustion Field Using TDLAS
摘要： Based on tunable diode laser absorption spectroscopy (TDLAS), two-dimensional (2D) distribution reconstructions of gas concentration and temperature are realized using an algebraic reconstruction technique (ART). The influence of the beam distribution and grid size on combustion field reconstruction is investigated to attain optimal reconstruction results with a limited number of beams. Under limited optical-path numbers, it shows that a better spatial resolution is attainable only when the laser beam paths are vertical and parallel to the symmetry axis of the combustion field. Furthermore, experiments with 16 beam paths using one and two flat flame combustion fields are carried out in different fuel-air equivalence ratios under room temperature. The results are in agreement with the simulation results, and the time resolution is less than 1 s.
关键词： tomographic imaging,diode lasers,temperature,spectroscopy,combustion diagnostics,absorption
更新于2025-09-23 15:23:52
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Infrared Spectroscopy of Triatomics for Space Observation || Clathrate Nano-Cages
摘要： Determining the presence and evolution of molecular species and their physicochemical environment in astrophysical media makes high-resolution infrared spectroscopy a powerful investigative tool that would provide a great deal of information on how these molecules behave in their environments. In this chapter, we describe the theoretical models developed to analyze the absorption spectra of a triatomic molecule trapped in a clathrate nano-cage at very low temperatures. The Lakhlifi–Dahoo extended inclusion model allows the determination of the trapping site (cage structure type), position and movements of the molecule in its site. Frequency shifts due to the solid environment can be interpreted using an atom–atom potential model to describe the interaction between the clathrate matrix and the trapped molecule. Moreover, this inclusion model makes it possible to determine the IR spectra and the couplings with the atoms or molecules forming the nano-cage.
关键词： clathrate,nano-cage,inclusion model,infrared spectroscopy,astrophysical media,triatomic molecule
更新于2025-09-23 15:23:52
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Nuclear Spin Singlet States in Photoactive Molecules: From Fluorescence/NMR Bimodality to a Bimolecular Spin Singlet State Switch
摘要： Nuclear spin singlet states are silent states in nuclear magnetic resonance (NMR). However, they can be probed indirectly and offer great potential for the development of contrast agents for magnetic resonance imaging (MRI). Here, we are introducing two novel concepts: Firstly, we investigate the bimodal NMR/fluorescence properties of 13C2-tetraphenylethylene. It possesses a long-lived singlet state in organic solvents, which shortens upon the addition of water. This simultaneously increases the fluorescence emission in a substantial enhancement of fluorescence. Secondly, we introduce a bimolecular singlet state switch based on 3-2H-coumarin containing an isolated proton. Upon UV-light exposure, a dimer forms leading to a coupling between two previously isolated protons. A nuclear spin singlet state can now be populated. Excitation with a wavelength of 254 nm results in partly cleavage of the molecule back into its monomer.
关键词： Photoswitches,NMR spectroscopy,Aggregation induced emission,Fluorescence,Nuclear spin singlet state
更新于2025-09-23 15:23:52
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Variable-Temperature Resonance Raman Studies to Probe Interchain Ordering for Semiconducting Conjugated Polymers with Different Chain Curvature
摘要： The morphology and crystallinity of the polymers used to fabricate bulk heterojuction (BHJ) solar cells significantly influences the efficiency of the cells. We have used variable-temperature (VT) spectroscopy techniques, namely VT emission and VT resonance Raman spectroscopy (VT-RRS), to examine how the backbone linearity of a conducting polymer affects its electronic response to temperature and variations in solution behavior. We have studied two types of donor–acceptor polymers used in BHJ cells with differing backbone structures; they are poly-{5,6-bis(tetradecyloxy)-4-(thiophen-2-yl)benzo[c]-1,2,5-thiadiazole} (PTBT) which has a curved and poly-{5,6-bis(tetradecyloxy)-4-(thieno[3,2-b]-thiophen-2-yl)benzo[c]-1,2,5-thiadiazole} (PTTBT) which has a linear chain structure. Time-dependent density functional theory (TD-DFT) calculations and resonance Raman spectra (RRS) of PTTBT revealed the presence of three electronic transitions, with character that varies between p to p*, mixed p to p*/charge transfer and pure charge transfer in nature. Emission spectra of PTTBT showed spectral changes at 650 and 710 nm with varied temperature ((cid:2)10 to 60 8C). Variable-temperature RRS was measured in resonance with the lowest and highest energy electronic transitions. The changes were interpreted using two-dimensional correlation spectroscopy (2DCOS) analysis. PTTBT showed gradual shifts to lower wavenumbers of modes at around 1425, 1450 and 1500 cm(cid:2)1. For PTBT larger and more rapid spectral changes are observed at 1440 and 1460 cm(cid:2)1 consistent with greater variation in the electronic nature upon heating. Further study into the influence of polymer linearity on crystallinity and long range order was carried out using low-frequency Raman (LFR) to examine drop cast films under a variety of different conditions. LFR spectra showed that PTTBT has a band at 73 cm(cid:2)1. This is observed under a variety of film-forming conditions. PTBT does not show distinct low frequency modes, consistent with its low crystallinity.
关键词： resonance Raman spectroscopy,low-frequency Raman,long range order,variable temperature,conducting polymers
更新于2025-09-23 15:23:52
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Total polyphenol quantitation using integrated NIR and MIR spectroscopy: A case study of Chinese dates ( <i>Ziziphus jujuba</i> )
摘要： Polyphenols are the foremost measure of phytochemicals in Chinese dates due to their many potential health benefits such as averting cancers, reducing the risk of coronary artery disease, diuretic activity, myocardial stimulant, coronary dilator and muscle relaxant. To quantitate the polyphenols in Chinese dates using a data fusion approach with near‐infrared (NIR) and mid‐infrared (MIR) spectroscopy. A total of 80 Chinese dates samples were used for data acquisition from both NIR and MIR spectroscopy. The efficient spectral intervals were extracted by the synergy interval partial least square (Si‐PLS) algorithm as input variables for NIR‐MIR fusion model. A genetic algorithm (GA) was used to construct the model based on NIR‐MIR fusion. The performance of the developed models was evaluated using correlation coefficients of calibration (R2) and prediction (r2), root mean square error of prediction (RMSEP), bias and residual prediction deviation (RPD). The data fusion model based on the GA was superior compared to NIR and MIR build model. The optimal GA‐fusion model yielded R2 = 0.9621, r2 = 0.9451, RPD = 2.44, calibration set bias = 0.004 and prediction set bias = 0.061, computing only 15 variables. These findings reveal that integration of NIR and MIR is possible for the prediction of total polyphenol content in Chinese dates.
关键词： spectroscopy techniques,polyphenols,genetic algorithms,principal component analysis,spectral interval selection
更新于2025-09-23 15:23:52
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Photolysis of PCl <sub/>3</sub> /POCl <sub/>3</sub> with Oxygen Dopant Using 193?nm ArF Excimer at Low Temperatures: Oxygen Insertion through ‘Phosphadioxirane’ Pathway
摘要： Photolysis was performed on PCl3 and POCl3 in the presence of oxygen dopant in Ar matrix at low temperatures using 193 nm ArF excimer laser. The photo irradiation initially facilitated the formation of ozone in situ in the low temperature matrix. For PCl3 + O2 photolysis with 193 nm ArF excimer, initially POCl3 was produced and subsequent oxygen atom insertion on POCl3 generated PO2Cl3. Furthermore, secondary reaction channel opens up in PCl3 + O2 photolysis to form a variety of photoproducts such as POCl, PIIIO2Cl, PVO2Cl and PO3Cl. The insertion of oxygen atom on POCl through phosphadioxirane intermediate generated PIIIO2Cl and the direct oxygen atom addition resulted in PVO2Cl. A successive oxygen insertion on PVO2Cl triggered the PO3Cl generation. The identification of all the photoproducts was confirmed through 18O2 isotopic experiments and quantum chemical computations performed using density functional theory (DFT). Computations carried out at B3LYP level of theory with 6–311 + + G(d,p) basis set were used to correlate the structure of photo products obtained experimentally. Interestingly, photo irradiation of POCl3 with oxygen dopant in Ar matrix @193 nm ArF excimer resulted in the generation of PO2Cl3, PO3Cl3 and PO4Cl3 photo products by a sequential insertion of oxygen atoms through phosphadioxirane intermediate. A compelling evidence for the passage of the reaction through phosphadioxirane intermediate is established through 18O2 isotopic substitution experiments.
关键词： DFT computations,matrix isolation,infrared spectroscopy,photolysis,phosphadioxirane intermediate
更新于2025-09-23 15:23:52