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The influence of particle size on the intensity and reproducibility of Raman spectra of compacted samples
摘要： Given the growing interest in the application of Raman spectroscopy for quantitative purposes in solid pharmaceutical preparations, a revision of the effect of particle size on Raman spectra of compacted samples is presented. For this purpose, a set of tablets of potassium hydrogen phthalate (KHP) of different particle size were prepared. KHP was used because of its purity and stability, which allow to consider that samples will not be altered during measurements; but also because of its chemical structure (aromatic ring and carboxylic groups), that are present in many active pharmaceutical ingredients (API). The latter makes possible to consider KHP as a model pseudo-API. As KHP tablets only contain a pure compound, the mapping strategy that was considered for measuring our samples will not be affected by subsampling issues. The spectra variance can be attributed to the intrinsically reproducibility in recording the spectra (which mainly depends on the instrument set-up) and the site-to-site differences in elastic scattering properties. Two different instrumental optics have been studied: a macro-Raman system and a Raman microscope (500 μm and 50 μm laser spot size, respectively). The effect of the spectra preprocessing is also evaluated. The overall results demonstrate raw Raman intensity increases with particle size up to a value that depends on tablet width and that the applied spectral preprocessing (baseline correction and a unit vector normalization), reduces the differences in Raman intensities due to the particle size, but does not completely eliminate it for the lower particle sizes (< 20 μm). For tablets containing particles with predefined sizes, it corrects the mapping site-to-site differences in elastic scattering.
关键词： Raman spectroscopy,Peak intensity,Reproducibility of a raman spectrum,Particle size
更新于2025-11-14 15:16:37
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Soil Particles and Phenanthrene Interact in Defining the Metabolic Profile of Pseudomonas putida G7: A Vibrational Spectroscopy Approach
摘要： In soil, organic matter and mineral particles (soil particles; SPs) strongly influence the bio-available fraction of organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), and the metabolic activity of bacteria. However, the effect of SPs as well as comparative approaches to discriminate the metabolic responses to PAHs from those to simple carbon sources are seldom considered in mineralization experiments, limiting our knowledge concerning the dynamics of contaminants in soil. In this study, the metabolic profile of a model PAH-degrading bacterium, Pseudomonas putida G7, grown in the absence and presence of different SPs (i.e., sand, clays and humic acids), using either phenanthrene or glucose as the sole carbon and energy source, was characterized using vibrational spectroscopy (i.e., FT-Raman and FT-IR spectroscopy) and multivariate classification analysis (i.e., PLS-DA). The different type of SPs specifically altered the metabolic profile of P. putida, especially in combination with phenanthrene. In comparison to the cells grown in the absence of SPs, sand induced no remarkable change in the metabolic profile of the cells, whereas clays and humic acids affected it the most, as revealed by the higher discriminative accuracy (R2, RMSEP and sensitivity) of the PLS-DA for those conditions. With respect to the carbon-source (phenanthrene vs. glucose), no effect on the metabolic profile was evident in the absence of SPs or in the presence of sand. On the other hand, with clays and humic acids, more pronounced spectral clusters between cells grown on glucose or on phenanthrene were evident, suggesting that these SPs modify the way cells access and metabolize PAHs. The macromolecular changes regarded mainly protein secondary structures (a shift from α-helices to β-sheets), amino acid levels, nucleic acid conformation and cell wall carbohydrates. Our results provide new interesting evidences that SPs specifically interact with PAHs in defining bacteria metabolic profiles and further emphasize the importance of studying the interaction of bacteria with their surrounding matrix to deeply understand PAHs degradation in soils.
关键词： phenanthrene,FTIR spectroscopy,soil particles,multivariate classification analysis,bacteria,metabolic profile,FT-Raman spectroscopy
更新于2025-11-14 15:16:37
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Near-infrared (NIR) surface-enhanced Raman spectroscopy (SERS) study of novel functional phenothiazines for potential use in dye sensitized solar cells (DSSC)
摘要： Near-infrared (NIR) surface-enhanced Raman spectroscopy (SERS) is used to investigate the interaction between six novel phenothiazine-merocyanine dyes containing the three different functional groups rhodanine, 1,3-indanedione and cyanoacylic acid with plasmonic nanomaterials, to decide if the incorporation of plasmonic nanoparticles could enhance the efficiency of a Gr?tzel-type solar cell. The studies were carried out in the solution state using spherical and rod-shaped gold nanostructures. With KCl induced agglomerated spherical gold nanoparticles, forming SERS hot spots, the results showed low detection limits between 0.1 mmol L?1 for rhodanine containing phenothiazine dyes, because of the formation of Au–S bonds and 3 mmol L?1 for cyanoacrylic acid containing dyes, which formed H-aggregates in the watery dispersion. Results with gold nanorods showed similar trends in the SERS measurements with lower limits of detection, because of a shielding effect from the strongly-bound surfactant. Additional fluorescence studies were carried out to determine if the incorporation of nanostructures leads to fluorescence quenching. Overall we conclude that the addition of gold nanoparticles to rhodanine and 1,3-indanedione containing phenothiazine merocyanine dyes could enhance their performance in Gr?tzel-type solar cells, because of their strong interactions with plasmonic nanoparticles.
关键词： surface-enhanced Raman spectroscopy,plasmonic nanoparticles,dye sensitized solar cells,phenothiazine-merocyanine dyes,Near-infrared
更新于2025-11-14 15:16:37
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Spectroscopic and theoretical studies of potassium sodium l-(+)-tartrate tetrahydrate and l-tartaric acid used as precursors for in situ laser-induced deposition of the catalytically active copper microstructures
摘要： In this work we study the influence of l-(+)-КNaC4H4O6 × 4H2O (KNaT) and l-H2C4H4O6 (H2T) on the complexation processes occurring during in situ laser-induced catalytic destruction of the organic components of the aqueous solutions with formation of the unsaturated hydrocarbons. For that purpose, ATR-FTIR, Raman, IR, and NIR spectroscopy as well as quantum chemical calculations were implemented. It was observed that hydration of T2? anion via carboxylate groups is stronger than that via hydroxyl groups. We also established the changes in the spectral characteristics of the absorption bands corresponding to vibrations of T2?, HT?, and H2T, at solid state-liquid and acid-salt transitions, depending on concentration of the solution components and the [OH?]/[H2T] ratio. Finally, it was shown that ethylene is a main product of the catalytic destruction of the copper tartrate complexes.
关键词： IR,Laser-induced copper deposition,DFT calculations,Tartaric acid,ATR-FTIR,Catalysis,NIR,Raman spectroscopy,Sodium potassium tartrate tetrahydrate
更新于2025-10-22 19:40:53
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Structural, electronic and optical properties of pulsed laser deposited Cu2SnS3 photo absorber thin films: A combined experimental and computational study
摘要： Pulsed laser deposited thin films of Cu2SnS3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm?1 at 1.5 eV which is comparable to other CuS based materials like CuInS2 and Cu2ZnSnS4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications.
关键词： Annealing,Raman spectroscopy,Thin films,Density functional theory,Pulsed laser deposition,Optical properties
更新于2025-10-22 19:40:53
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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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Transmission Low-Frequency Raman Spectroscopy for Quantification of Crystalline Polymorphs in Pharmaceutical Tablets
摘要： The purpose of this study was to quantify polymorphs of active pharmaceutical ingredients in pharmaceutical tablets using a novel transmission low-frequency Raman spectroscopy method. We developed a novel transmission geometry for low-frequency Raman spectroscopy and compared quantitative ability in transmission mode versus backscattering mode using chemometrics. We prepared two series of tablets: 1) containing different weight-based contents of carbamazepine form III and 2) including different ratios of carbamazepine polymorphs (forms I/ III). From the relationship between the contents of carbamazepine form III and partial least squares (PLS) predictions in the tablets, correlation coefficients in transmission mode (R2= 0.98) were found to be higher than in backscattering mode (R2= 0.97). The root mean square error of cross-validation (RMSECV) of the transmission mode was 3.9 compared to 4.9 for the backscattering mode. The tablets containing a mixture of carbamazepine (I/ III) polymorphs were measured by transmission low-frequency Raman spectroscopy, and it was found that the spectral shape changed according to the ratio of polymorphs: the relationship between the actual content and the prediction showed high correlation. These findings indicate that transmission low-frequency Raman spectroscopy possess the potential to complement existing analytical methods for the quantification of polymorphs.
关键词： Transmission,Carbamazepine,Pharmaceutical Tablets,Quantification,Low-Frequency Raman Spectroscopy,THz-Raman,Crystalline Polymorph
更新于2025-09-23 15:23:52
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Symmetries of modes in Ni <sub/>3</sub> V <sub/>2</sub> O <sub/>8</sub> : Polarized Raman spectroscopy and ab initio phonon calculations
摘要： Knowledge of symmetries of vibrational modes is essential for understanding structural transitions and spin‐phonon coupling in multiferroics where phonons play a vital role. Using polarized Raman spectroscopy, we have identified and assigned symmetries of 30 out of the 36 expected zone‐centred phonon mode Raman active modes in Ni3V2O8. The wavenumbers are calculated using ab initio calculations. The gerade mode wavenumbers are compared with our polarized Raman data whereas ungerade mode wavenumbers are compared with the reported infrared measurements and a good agreement was observed between the experimentally measured wavenumbers and the calculated wavenumbers. The displacements of different types of vibrations calculated and visualized using ab initio phonon calculation are presented. These assignments will be useful for visualization of Raman modes that may be sensitive to different magnetic states and to explore spin–lattice coupling across magnetic transitions.
关键词： displacements of phonon modes,gerade and ungerade modes,polarized Raman spectroscopy,symmetries of Raman active modes,ab initio calculations
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Investigation of the Phase Composition and Morphology of Silicon Structures by Using the Raman Spectroscopy to Determine the Parameter of Crystallinity
摘要： This work aims to investigate the dependence of the phase composition of thin films of microcrystalline silicon deposition on process parameters. The films of microcrystalline silicon were obtained by plasma-chemical deposition method (PECVD). Phase composition and correlation between degree of crystallinity and structure of the obtained layers were analyzed by Raman Spectroscopy. The results show that the control of several technical parameters, e.g. pressure, discharge power and monosilane flow, allows to reach the crystallinity parameter in the range 50-70 %. Based on the conducted experiments, the recommendations for the control of the crystallinity parameter, which are planned to be implemented when working with silicon-based porous structures, were proposed.
关键词： Morphology,Semiconductors,Silicon,Por-silicon,Phase composition,Raman spectroscopy,Raman Crystallinity
更新于2025-09-23 15:23:52
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Low-damage nitrogen incorporation in graphene films by nitrogen plasma treatment: Effect of airborne contaminants
摘要： Graphene films grown on copper by chemical vapor deposition were exposed to the late afterglow of a reduced-pressure N2 plasma sustained by microwave electromagnetic fields. X-ray photoelectron and Raman spectroscopies reveal extremely high incorporation of plasma-generated N atoms into the graphene film (N/C = 29%) while maintaining an unprecedentedly low-damage generation (D:G = 0.35-0.45) compared to the literature (0.5 to 2.5). The incorporation dynamics between graphene on copper and graphene on copper oxide are also compared and discussed. After transfer on SiO2/Si substrate, the N/C content decrease to only 6%. This reveals that a large part of the N atoms are weakly bonded to the graphene surface. Most of the nitrogen incorporation seems linked to the functionalization of weakly bonded hydrocarbons initially adsorbed from air exposure or carbon-nitrogen structures arising from plasma-surface interactions.
关键词： X-Ray photoelectron spectroscopy,Raman spectroscopy,graphene,downstream plasma treatment,N-incorporation
更新于2025-09-23 15:23:52