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1.
  • Taylor, M. J., et al. (författare)
  • Raman investigations of indium iodide complexes : evidence for the In2I7- ion
  • 2000
  • Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 31:6, s. 465-468
  • Tidskriftsartikel (refereegranskat)abstract
    • Raman spectra of some indium iodide complexes were studied, including alpha- and beta-InI3 and In2I4. InI3 with KI yields K+InI4-. With CsI the spectra reveal, in addition to Cs+InI4-, the complex anion In2I7- in the solid phase CsI:2InI(3), This structure consists of InI3 groups with a linking In-I-in bridge which appears to be linear. The vibrational spectra were calculated for the dimeric In2I6 molecule at the HF, B3LYP and MP2 levels, but the structure turned out to be unstable when such calculations were attempted for In2I7-.
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2.
  • Frost, Ray L., et al. (författare)
  • Raman spectroscopy at temperatures between 298 and 423 K and at 77 K of kaolinites intercalated with formamide
  • 1998
  • Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 29:12, s. 1065-1069
  • Tidskriftsartikel (refereegranskat)abstract
    • Raman spectra of kaolinite and of the formamide-intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5 cm-1 to lower wavenumbers and the bands assigned to the inner surface hydroxyls move to higher wavenumbers. Upon intercalation of the kaolinite with formamide, an additional Raman band attributed to the formation of a hydrogen-bonded complex between the inner surface hydroxyls and the carbonyl group of the formamide is observed at 3627 cm-1 at 298 K and at 3631 cm-1 at 77 K. Raman spectra of the deintercalation of the formamide-intercalated kaolinite are obtained by using the thermal stage to heat the intercalated kaolinite in situ. A decrease in intensity of the bands formed through intercalation and at the same time an increase in intensity of the inner surface hydroxyl bands are observed. A loss of intensity of the low-wavenumber region of the formamide-intercalated kaolinite is also observed.
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3.
  • Afzelius, Mikael, et al. (författare)
  • Precision of single-shot dual-broadband rotational CARS thermometry with single-mode and multi-mode Nd : YAG lasers
  • 2003
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 34:12, s. 940-945
  • Konferensbidrag (refereegranskat)abstract
    • The precision of single-shot coherent anti-Stokes Raman spectroscopy (CARS) thermometry is an important characteristic for the application of CARS in various combustion devices such as internal combustion engines. It is generally assumed that the precision of CARS is directly related to the spectral noise of the interacting laser fields, and previous studies have presented a theoretical model describing the behaviour of the noise as a function of various experimental parameters. In this work, the aim was to test the results predicted by the previously developed model for dual-broadband rotational CARS. We studied the precision of evaluated temperatures in pure nitrogen under different experimental conditions, namely the dependence of precision on the gas pressure and on the linewidth of the narrowband laser (the Nd: YAG laser). It was demonstrated that our experiments reproduce the main features of the model, and that a single-mode Nd: YAG laser leads to better precision than a multi-mode Nd: YAG laser for dual-broadband rotational CARS thermometry. Copyright (C) 2003 John Wiley Sons, Ltd.
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4.
  • Ali, Hassan, et al. (författare)
  • Insight into thermally induced solid-state polymorphic transformation of sulfathiazole using simultaneous in situ Raman spectroscopy and differential scanning calorimetry
  • 2009
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:8, s. 887-892
  • Tidskriftsartikel (refereegranskat)abstract
    • Pharmaceutical solids exposed to thermal stress during manufacturing processes undergo various phase transformations in bulk drug substances or excipients, resulting in altered dosage form performance. Due to its relatively rapid spectral acquisition rate, as well as the possibility of incorporation into in-line monitoring, Raman spectroscopy is ideally suited to monitoring the transformation between different solid-state forms. In this study, we demonstrate that the transition temperature for polymorphs can be estimated from the transformation profiles obtained from real-time, in situ, simultaneous Raman spectroscopic, and differential scanning calorimetric data. Using this method, we have estimated the transition temperature of the solid-state transformation of the enantiotropically related sulfathiazole polymorphs III and I. These results suggest that this method is a useful approach to determine transition temperatures in systems that are not amenable to accessing other methods
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5.
  • Ali, Hassan, et al. (författare)
  • Vibrational spectroscopic study of budesonide
  • 2007
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 38:7, s. 903-908
  • Tidskriftsartikel (refereegranskat)abstract
    • The Raman spectrum of budesonide is reported for the first time, and molecular assignments are proposed on the basis of ab initio BLYP DFT calculations with a 6-31 G* basis set and vibrational wavenumbers predicted on a quasi-harmonic approximation. Comparison with previously published infrared data has explained several spectral features, and the relative band intensities in the C=O and C=C stretching regions are interpreted. The results from this study provide data that can be used for the preparative process monitoring of budesonide, an important steroidal pharmaceutical in various dosage forms, and its interaction with excipients and other components
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6.
  • Bohlin, Alexis, et al. (författare)
  • Improvement of rotational CARS thermometry in fuel-rich hydrocarbon flames by inclusion of N-2-H-2 Raman line widths
  • 2009
  • Ingår i: Journal Of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 788-794
  • Konferensbidrag (refereegranskat)abstract
    • In rotational coherent anti-Stokes Raman spectroscopy (CARS) thermometry applied to air-fed flames, the temperature sensitivity mainly depends on the intensity distribution of the nitrogen spectral lines. Temperatures are estimated by numerical fitting of theoretical spectra to experimental ones, and one uncertainty in the calculation of theoretical CARS spectra for specific flame conditions is the accuracy in utilized line-broadening coefficients. In a previous article, self-broadened N-2-N-2 line widths were considered in the spectral calculations as well as those of N-2-CO, N-2-CO2, N-2-H2O, and N-2-O-2- In the present article, we also include N-2-H-2 line widths calculated from a newly developed model, and it is shown that the evaluated temperature from flame spectra increases with increasing mole fractions of hydrogen. For example, in a very rich flame at Phi = 2.5, the use of available line-width data for all major species gives a temperature raise of 72 K at a temperature of similar to 1700 K, in comparison with using self-broadened N-2-N-2 line widths only. Half of this temperature raise is related to the inclusion of N-2-H-2 line widths. This article emphasizes the importance of using adequate line-broadening models for rotational CARS thermometry in flames. Copyright (C) 2009 John Wiley & Sons, Ltd.
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7.
  • Bohlin, Alexis, et al. (författare)
  • On the sensitivity of rotational CARS N-2 thermometry to the Herman-Wallis factor
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 42:10, s. 1843-1847
  • Tidskriftsartikel (refereegranskat)abstract
    • Purely rotational spectral signals of coherent anti-Stokes Raman scattering (CARS) from nitrogen molecules are studied as a function of the vibration-rotation interaction that weakens the rigid rotor approximation under which the dominant terms of the Raman cross section are calculated. The effect of the vibration-rotation interaction is quantified by means of the Herman-Wallis (HW) factor, and different approaches to its determination are evaluated in terms of their relative contribution to the CARS intensity and thermometric measurements made in a fuel-rich hydrocarbon flame. Known HW factors are contrasted with more complete expressions of recent derivation, and it is found that relative line strength adjustments amount to about a few percent. Such differences result in temperature corrections of less than 1%. This value should be considered for the definition of the ideal thermometric accuracy of the technique but it is of minor importance in comparison with other sources of uncertainty (e. g. Raman line widths) that emerge from the complexity typical of reactive gas mixtures. Copyright (C) 2011 John Wiley & Sons, Ltd.
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8.
  • Bohlin, Alexis, et al. (författare)
  • On the sensitivity of rotational O2 CARS thermometry to the Herman-Wallis factor
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:5, s. 599-603
  • Tidskriftsartikel (refereegranskat)abstract
    • Contributions of vibrationrotation interaction to line intensities of pure rotational coherent anti-Stokes Raman scattering (CARS) of oxygen are here considered in the perspective of what was remarked by us recently for nitrogen. The interaction is conventionally evaluated by means of the so-called HermanWallis (HW) factor, the need of which is conceptually clear but the theoretical expression is debatable, as shown in the literature of this field. In this work, the various solutions for the anisotropic HW factor of pure rotational Raman transitions are compared in light of the implications for the corresponding CARS spectral line intensities. The results show that neglecting the use of HW factors in rotational N2 and O2 CARS thermometry leads to systematic overestimation of temperatures; on the order of 1.5% in the temperature range 300-2100K in comparison with the use of the most plausible HW factors. The results also suggest that, in general, oxygen is more sensitive than nitrogen to the HW correction, and in particular, different S-branch HW expressions for oxygen are responsible for thermometric uncertainties between 0.5% and 1% at flame temperatures. Copyright (c) 2012 John Wiley & Sons, Ltd.
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9.
  • Bohlin, Alexis, et al. (författare)
  • Validation of a rotational coherent anti-Stokes Raman scattering model for N2O at temperatures from 295K to 796K
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:5, s. 604-610
  • Tidskriftsartikel (refereegranskat)abstract
    • Pure rotational coherent anti-Stokes Raman scattering (CARS) spectra of N2O was recorded in a series of temperature calibrated cell measurements in the region 295-796K. A theoretical rotational CARS code for N2O was implemented and temperature analysis was performed by fitting the modeled theoretical spectra to the experimental spectra. Excellent agreement between the experimental and modeled spectra was obtained and the thermometric accuracy for the measurements was evaluated to be better than 1%. Also, rotational N2 CARS spectra were recorded at the same measurement conditions and the temperature analysis performed on these spectra resulted in the same accuracy. The peak signal strength was found to be similar to 5 times stronger for N2O than for N2 at ambient temperature and pressure. The temperature precision was evaluated to a relative standard deviation of 2.0%-2.7% in the studied temperature range, about half of the values for N2, which is attributed to the larger number of spectral lines for N2O. Rotational N2O CARS thermometry show great potential, because of a high Raman cross-section and large number of populated rotational states at any temperature. Copyright (c) 2012 John Wiley & Sons, Ltd.
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10.
  • Brackmann, Christian, 1973, et al. (författare)
  • CARS microscopy of lipid stores in yeast: the impact of nutritional state and genetic background
  • 2009
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 748-756
  • Tidskriftsartikel (refereegranskat)abstract
    • We have developed a protocol for sub-micrometer resolved and chemically specific imaging of lipid storage in vivo employing coherent anti-Stokes Raman scattering (CARS) microscopy of one of the most important model organisms Saccharomyces cerevisiae - the yeast cell. By probing the carbon-hydrogen vibration using the nonlinear process of CARS, lipid droplets in the yeast cells clearly appear, as confirmed by comparative studies on relevant labeled organelles using two-photon fluorescence microscopy. From the images, unique quantitative data can be deduced with high three-dimensional resolution, such as the volume, shape, number, and intracellular location of the neutral lipid stores. We exemplify the strength and usability of the method for two cases: the impact on lipid storage of the nutritional condition (starvation and type of carbon source available) as well as of genetic modification of two fundamental metabolic regulation pathways involving carbohydrate and lipid storage (BCY1 and DGA1, LRO1, ARE1/2 deletions), respectively. While the impact of carbon source on the total cellular lipid volume was minimal, long-term starvation induces a significant accumulation of lipid droplets. We also confirm that the lipid-storage-deficient mutant is indeed unable to synthesize lipid droplets, and that the inability of the bcy1-mutant to store carbohydrates is compensated by a two-fold increase in stored neutral lipids. We note that there is a significant cell-to-cell variability in neutral lipid storage in general, i.e. that there is a correspondence to the noise found for gene expression also in lipidomics. Copyright (C) 2009 John Wiley & Sons, Ltd.
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11.
  • Brackmann, Christian, 1973, et al. (författare)
  • Visualization of β-carotene and starch granules in plant cells using CARS and SHG microscopy
  • 2010
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 42:4, s. 586-592
  • Tidskriftsartikel (refereegranskat)abstract
    • Information on the content and bioavailability of provitamin A carotenoids, such as beta-carotene, in plant foods is of great interest due to the widespread vitamin A deficiency in developing countries. While the amount of beta-carotene can readily be quantified with analytical techniques, there is limited information on beta-carotene morphology in native plant materials. Here, we introduce nonlinear microscopy for three-dimensional, label-free imaging of carotenoids in fresh and thermally treated plant tissues, providing quantitative information at single-aggregate level and detailed insight into their distribution. Carotenoids in orange-fleshed sweet potato (OFSP), carrot, and mango were visualized by coherent anti-Stokes Raman scattering (CARS) microscopy and, in the case of OFSP, related to the plant-matrix morphology by simultaneous second-harmonic generation (SHG) microscopy of starch granules. Sizes, shapes, densities, and location of different types of carotenoid bodies were quantified. While OFSP and carrot showed heterogeneous rod-shaped bodies with high carotenoid densities indicated by higher CARS signals, the carotenoid-filled lipid droplets in mango appeared as homogeneous low-density aggregates of rounded shape. In addition, beta-carotene densities and morphologies in OFSP were studied after thermal processing, showing that the bodies remain intact despite significant changes of the surrounding starch granules.
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12.
  • Buldyreva, J, et al. (författare)
  • Linewidth modelling of C2H2-N-2 mixtures tested by rotational CARS measurements
  • 2006
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 37:6, s. 647-654
  • Tidskriftsartikel (refereegranskat)abstract
    • The acetylene-nitrogen system is investigated in a combined theoretical and experimental effort in view of its thermometry applications. Accurate values of the rotational Raman linewidths of acetylene are of crucial importance for the computation of spectra from rotational coherent anti-Stokes Raman scattering (CARS) used for temperature and concentration evaluations. Since the direct measurements of these linewidths are not available, they are rigorously calculated by a semi-classical Robert-Bonamy formalism employing exact trajectories. The computed linewidths are used as input parameters in the theoretical spectra simulation, which is also improved by the inclusion of an interbranch interference with coherent Stokes Raman scattering (CSRS). These theoretical spectra are used to evaluate the temperature from experimental CARS spectra of acetylene-nitrogen mixtures recorded in the pressure range 0.1-0.6 MPa. The new linewidths (NLWs) and the CSRS interference inclusion result in a clear improvement of spectral fitting as well as in reasonable values of evaluated temperatures. Copyright (c) 2006 John Wiley & Sons, Ltd.
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13.
  • Chaix-Pluchery, O., et al. (författare)
  • First-order Raman scattering in three-layered Mo-based ternaries: MoAlB, Mo2Ga2C and Mo2GaC
  • 2017
  • Ingår i: Journal of Raman Spectroscopy. - : WILEY. - 0377-0486 .- 1097-4555. ; 48:5, s. 631-638
  • Tidskriftsartikel (refereegranskat)abstract
    • Here, we report, for the first time, on the first-order Raman spectra of the layered Mo-based ternaries: MoAlB, Mo2Ga2C and Mo2GaC. Polycrystalline samples were fabricated, and well-defined Raman spectra were recorded. When the experimental peak positions were compared with those predicted from density functional theory, good agreement was obtained, indirectly validating both. Furthermore, all modes in the three compounds were symmetry assigned. Copyright (c) 2017 John Wiley amp; Sons, Ltd.
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14.
  • Dong, Bin, et al. (författare)
  • Experimental and theoretical evidence for the chemical mechanism in SERRS of rhodamine 6G adsorbed on colloidal silver excited at 1064 nm
  • 2010
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 41:7, s. 719-720
  • Tidskriftsartikel (refereegranskat)abstract
    • The evidence for the existence of a chemical mechanism in surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) adsorbed on colloidal silver excited at 1064 nm is reported on the basis of experimental and theoretical analyses. A weak absorption peak at around 1060 nm for R6G-functionalized silver nanoparticles was observed, which is not present in the individual spectra of R6G or silver nanoparticles. Theoretically, the charge difference density reveals that this weak absorption is a metal-to-molecule charge transfer excited state. Copyright (C) 2010 John Wiley & Sons, Ltd.
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15.
  • Dong, Bin, et al. (författare)
  • Is 4-nitrobenzenethiol converted to p,p '-dimercaptoazobenzene or 4-aminothiophenol by surface photochemistry reaction?
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 42:6, s. 1205-1206
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, the experimental and theoretical evidence for the conversion of 4-nitrobenzenethiol (4-NBT) to p,p'-dimercaptoazobenzene (DMAB) in Ag and Cu sols by surface photochemistry reaction is obtained with surface-enhanced Raman scattering (SERS) spectroscopy. The SERS spectrum of 4-NBT in Cu sol is identical to that of DMAB produced from 4-aminothiophenol in Ag sol as reported in recent literature, thereby providing direct spectral evidence. Copyright (C) 2011 John Wiley & Sons, Ltd.
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16.
  • Dyakov, Sergey, et al. (författare)
  • Influence of the buffer layer properties on the intensity of Raman scattering of graphene
  • 2013
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 44:6, s. 803-809
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a model of oscillating dipoles, we simulate the intensity of the G-band in the Raman signal from structures consisting of graphene, separated by an arbitrary buffer layer from a substrate. It is found that a structure with an optimized buffer layer refractive index and thickness exhibits a Raman signal which is nearly 50 times more intense than that from the same structure with a non-optimized buffer layer. The theoretical simulations are verified by Raman measurements on structures consisting of a layer of graphene on SiO2 and Al2O3 buffer layers. The optical contrast of the single graphene layer is calculated for an arbitrary buffer layer. It was found that both the Raman intensity and optical contrast can be maximized by varying the buffer layer thickness.
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17.
  • Ehn, Andreas, et al. (författare)
  • Temporal filtering with fast ICCD cameras in Raman studies
  • 2013
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 44:4, s. 622-629
  • Tidskriftsartikel (refereegranskat)abstract
    • A common problem when applying Raman scattering in applied research is spectral interference from laser-induced fluorescence. Extensive work has been invested in developing spectral and polarization filters as well as modulation schemes to refine spontaneous Raman signals. This current work, however, focuses on utilizing the temporal domain using a picosecond laser system and ICCD cameras with relatively short decay of the camera gate to prevent the fluorescence tail from being captured in Raman experiments. Further, the approach of using an ICCD camera to perform temporal filtering is compared to earlier proposed detection schemes using streak cameras or Kerr gates. The temporal-filtering scheme is evaluated in a spectroscopic investigation where a background subtraction algorithm is presented. The temporal-filtering scheme was also evaluated for Raman imaging of a levitated water droplet surrounded by fluorescing toluene vapor. Furthermore, the temporal-filter detection scheme was simulated in order to provide straight forward evaluation tools to estimate the potential of performing temporal filtering with a laser/camera system considering: laser-pulse duration, time jitter, camera-gate characteristics, gate delay times, fluorescence lifetimes, and relative signal strength between the Raman and fluorescence signal. The fluorescence signal was modeled with a closed two-level system, and the simulated results were compared to results from an investigation of the rising slope of toluene fluorescence. These evaluation tools and experimental investigations may serve as guidelines for planning and performing Raman measurements in situations where traditional filter-rejection schemes are insufficient.
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18.
  • Enman, Josefine, et al. (författare)
  • Raman analysis of synthetic eritadenine
  • 2008
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:10, s. 1464-1468
  • Tidskriftsartikel (refereegranskat)abstract
    • Eritadenine, 2(R),3(R)-dihydroxy-4-(9-adenyl)-butyric acid, is a cholesterol-reducing compound naturally occurring in the shitake mushroom (Lentinus edodes). To identify the unknown Raman spectrum of this compound, pure synthetic eritadenine was examined and the vibrational modes were assigned by following the synthesis pathway. This was accomplished by comparing the known spectra of the starting compounds adenine and D-ribose with the spectra of a synthesis intermediate, methyl 5-(6-Aminopurin-9H-9-yl)-2,3-O-isopropylidene-5-deoxy-β-D-ribofuranoside (MAIR) and eritadenine. In the Raman spectrum of eritadenine, a distinctive vibrational mode at 773 cm-1 was detected and ascribed to vibrations in the carbon chain, ν(C--C). A Raman line that arose at 1212 cm-1, both in the Raman spectrum of MAIR and eritadenine, was also assigned to ν(C--C). Additional Raman lines detected at 1526 and at 1583 cm-1 in the Raman spectrum of MAIR and eritadenine were assigned to ν(N--C) and a deformation of the purine ring structure. In these cases the vibrational modes are due to the linkage between adenine and the ribofuranoside moiety for MAIR, and between adenine and the carbon chain for eritadenine. This link is also the cause for the disappearance of adenine specific Raman lines in the spectrum of both MAIR and eritadenine. Several vibrations observed in the spectrum of D-ribose were not observed in the Raman spectrum of eritadenine due to the absence of the ribose ring structure. In the Raman spectrum of MAIR some of the D-ribose specific Raman lines disappeared due to the introduction of methyl and isopropylidene moieties to the ribose unit. With the approach presented in this study the so far unknown Raman spectrum of eritadenine could be successfully identified and is presented here for the first time.
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19.
  • Erjavec, Nika, et al. (författare)
  • Raman spectroscopy as a tool for detecting mitochondrial fitness
  • 2016
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 47:8, s. 933-939
  • Tidskriftsartikel (refereegranskat)abstract
    • Raman spectroscopy allows the molecular chemical analysis of whole living cells by comparing them to known Raman signatures of specific vibrational bonds. In this work we used Raman spectroscopy to differentiate between wild type yeast cells and mutants characterized by increased or reduced mitochondrial fragmentation. To associate mitochondrial fragmentation with biochemical markers, we performed Linear Discriminant Analysis (LDA) of whole cell Raman spectra (~50–100 cells/spectrum). We show that the long-lived, less fragmented mutants fall into a significantly distant cluster from the wild type and short-lived, more fragmented mutants. Clustering depends on respiratory growth and coincides with that of membrane phospholipids and some respiratory chain components. Spectral clustering is supported by enzymatic activity measurements of OXPHOS Complexes. In addition, we find that NAD(P)H autofluorescence also correlates with mitochondrial fragmentation, representing another likely aging biomarker, besides phospholipids and OXPHOS components. In summary, we demonstrate that Raman spectroscopy has the potential to become a powerful tool for differentiating healthy from unhealthy aged tissues, as well as for the prognostic evaluation of mitochondrial function and fitness.
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20.
  • Ghignone, Stefano, et al. (författare)
  • The Raman spectrum of florencite-(REE) [REEAl3(PO4)2(OH)6] : An integrated experimental and computational approach
  • 2024
  • Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 55:3, s. 394-405
  • Tidskriftsartikel (refereegranskat)abstract
    • Florencite is a hydrous light rare-earth elements (LREE) aluminium phosphate [REEAl3(PO4)2(OH)6], that amongst the REE-rich minerals is quite common. The main end-members are Ce-, La- and Nd-rich terms that were found in several genetic environments. Despite the large occurrence worldwide, to the authors' knowledge, florencite has attracted very few studies, particularly concerning the characterization of its Raman spectrum. We present a detailed study of the Raman spectrum of florencite, combining experimental measurements and theoretical calculations. Experimental Raman spectra (in the 100–1300 cm−1 spectral range) are measured on four florencite samples characterized by different chemical composition, that is, different REE abundance. The results highlight a remarkable coincidence between different Raman spectra measured on each sample, despite the significantly different chemical compositions in terms of their REE content. The same similarities were also observed in the computed spectra at the ab initio level; moreover, the calculations allowed the attributions of the different Raman signals to specific vibrational modes. 
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21.
  • Gomes, Adriano, et al. (författare)
  • A micro-Raman spectroscopic study of Cr(OH)3 and Cr2O3 nanoparticles obtained by the hydrothermal method
  • 2017
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 48:10, s. 1256-1263
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2017 John Wiley & Sons, Ltd. Cr 2 O 3 nanoparticles, widely used in the industry, can be obtained by calcination of the nanoparticles synthesized via the hydrothermal method. The chemical nature and the morphology of as-prepared and calcined nanoparticles are investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Our results indicate that the as-prepared nanoparticles mainly consist of amorphous and hydrated Cr(OH) 3 , with only minor amounts of Cr 2 O 3 . By contrast, and as already known before, calcined nanoparticles consist of Cr 2 O 3 . We also demonstrate the effect of inappropriately chosen experimental conditions, because the use of laser intensities above 0.7 mW during the Raman experiments causes a local heating and thus induces the transformation of Cr(OH) 3 into Cr 2 O 3 . The correlation between the laser power and a local heating is further corroborated by thermogravimetric analyses, which show that upon increased temperature, Cr(OH) 3 first dehydrates and then partially condensates to the intermediate CrO(OH) form, to finally attain the crystalline form of Cr 2 O 3 at about 409°C.
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22.
  • Grondin, J., et al. (författare)
  • Revisited vibrational assignments of imidazolium-based ionic liquids
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 42:4, s. 733-743
  • Tidskriftsartikel (refereegranskat)abstract
    • Imidazolium-based ionic liquids (ILs) involving anions of variable coordinating strength have been investigated using infrared (IR) and Raman spectroscopies, density functional theory (DFT) calculations and selective deuteration of the imidazolium CH groups. Particular emphasis has been placed on the vibrational assignments of the anion and cation internal vibrations, a prerequisite before any interpretation of spectral changes due to ion-ion interactions in these unconventional liquids. The vibrations of highly symmetric and weakly coordinating anions, such as PF(6)(-), have unperturbed wavenumbers, but unexpected IR or Raman activity for some modes, showing that the anion is subjected to an anisotropic electric field. The stretching as well as the in-plane and out-of-plane bending modes of the imidazolium CH groups are anharmonic. They give broad bands that reflect a large distribution of interactions with the surrounding anions. All the bending modes are mixed with ring vibrations and the stretching modes are complicated by Fermi resonance interactions with overtones and combination of in-plane ring modes. However, the stretching vibration of the quasi-diatomic C((2))-D bond appears to be a good spectroscopic probe of the increasing cation-anion interactions when the coordinating strength of the anion increases. The broad absorption observed in the far IR with weakly coordinating anions remains practically unchanged when the acidic C((2))-H imidazolium bond is methylated and even when the imidazolium cation is substituted by tetra-alkyl ammonium or pyrrolidinium cations. It is concluded that this absorption is a general feature of any IL, coming from the relative translational and librational motions of the ions without needing to invoke C((2))-H anion hydrogen bonds.
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23.
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24.
  • Holmlid, Leif, 1942 (författare)
  • Vibrational transitions in Rydberg matter clusters from stimulated Raman and Rabi-flopping phase delay in the infrared
  • 2008
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:10, s. 1364-1374
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, rotational spectra of giant Rydberg matter (RM) clusters were studied in the radio frequency range (Mol. Phys. 105 (2007) 933-939), giving high-precision bond distances in the nanometer range. However, the theoretical and experimental problem of vibrational motion or, rather, coupled electronic-vibrational motion in the RM clusters is still unsolved; but it is expected that broad phonon bands will exist. Spectroscopic signatures from space make it likely that RM is a common form of matter in the Universe, and phonon bands in this spectroscopic range have not been taken into account so far. Spectroscopic results are now reported on transitions in the range 0.01-20 cm-1, using primarily infrared (IR) lasers to probe the RM in a tunable open cavity with a Fabry-Perot interferometer to aid in the identification of the shifts. Stimulated Raman scattering from electronic transitions and Rabi-flopping from electronic states in the clusters are observed. The broad stimulated Raman peaks are assigned to one and two consecutive vibrational (electronic-vibrational) transitions. Theoretical values predicted for vibrations (phonon maxima) and electronic processes are in reasonable agreement with the experimental results. Improved calculations are needed to verify the assignments of the vibrational phonon distributions.
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25.
  • Holomb, Roman, et al. (författare)
  • Ionic liquid structure: the conformational isomerism in 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4])
  • 2008
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:7, s. 793-805
  • Tidskriftsartikel (refereegranskat)abstract
    • As a probe of local structure, the vibrational properties of the 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] ionic liquid were studied by infrared (IR), Raman spectroscopy, and ab initio calculations. The coexistence of at least four [bmim]+ conformers (GG, GA, TA, and AA) at room temperature was established through unique spectral responses. The Raman modes characteristic of the two most stable [bmim] + conformers, GA and AA, according to the ab initio calculations, increase in intensity with decreasing temperature. To assess the total spectral behavior of the ionic liquid both the contributions of different [bmim] + conformers and the [bmim]+- [BF4]- interactions to the vibrational spectra are discussed.
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26.
  • Hot, Dina, et al. (författare)
  • Investigation of laser-induced grating spectroscopy of O2 for accurate temperature measurements towards applications in harsh environments
  • 2021
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 52:9, s. 1569-1581
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an in-depth investigation of laser-induced grating spectroscopy (LIGS) for temperature measurements in practical applications using a narrow-band dye laser with 760 nm wavelength and a pulse duration of 8 ns as the source for the pump beams creating the laser-induced grating. The pump laser wavelength was set to be either resonant with the (Formula presented.) transition from the (Formula presented.) band of O2 for generation of thermal LIGS or nonresonant for generation of purely electrostrictive LIGS. Signals were generated in ambient air as well as in high-pressure or high-temperature dry air mixtures. Pump laser irradiances up to 11 GW/cm2 were used, which resulted in strong electrostrictive contribution to the overall LIGS signals at atmospheric pressure, with a low thermal contribution due to the weak absorption by the singlet O2 (Formula presented.). The advantage and disadvantage of thermal or electrostrictive LIGS for temperature measurements are discussed, as well as potential applications in high-pressure environments. Furthermore, the precision of the temperature measurement is discussed by comparing different analysis methods.
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27.
  • Kiefer, J., et al. (författare)
  • OH-thermometry using laser polarization spectroscopy and laser-induced fluorescence spectroscopy in the OH A-X (1,0) band
  • 2009
  • Ingår i: Journal Of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 828-835
  • Konferensbidrag (refereegranskat)abstract
    • Laser-induced fluorescence (LIF) and polarization spectroscopy (PS) is used for OH-thermometry utilizing the off-diagonal A-X (1,0) band. Both techniques are used simultaneously in order to allow a comparison of the results. For deriving temperature information from the spectra, three methods are employed: (1) a contour fit method comparing experimental and calculated spectra, (2) spectral fitting of a single highly resolved spectral line and (3) a two-line intensity ratio approach. In general, both spectroscopic techniques gave similar results. The high-resolution approach (2) did not deliver reasonable results in our experiments. The most accurate but also most time consuming method was the contour fit (1). For future two-dimensional temperature measurements, the 2-line-method (3) was identified to be the method of choice. The present study contains, to the best of our knowledge, the first polarization spectroscopic study in the A-X (1,0) band of OH. Copyright (C) 2009 John Wiley & Sons, Ltd.
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28.
  • Kocsis, L., et al. (författare)
  • Vibrational spectroscopic study of the hydrated platinum(II), palladium(II) and cis-diammineplatinum(II) ions in acidic aqueous solutions
  • 2009
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:5, s. 481-490
  • Tidskriftsartikel (refereegranskat)abstract
    • Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, were performed for the 1 hydrated platinum(II) and palladium(II) ions and cis-diammineplatinum(II) complex in acidic aqueous solutions. Simplified Density Functional Theory (DFT) calculations were made for the equatorial plane of the platinum complexes. Careful subtraction of solvent spectra allowed a number of 'internal' modes of coordinated H2O and NH3 to be determined as weak residual bands. The [Pt(OH2)(6)](2+) and [cis-Pt(NH3)(2)(OH2)(4)](2+) complexes were found to be six-coordinated with four ligands strongly bound in an equatorial plane. The assignments of the vibrational modes in the equatorial plane could be performed on the basis of the experimental observations and by comparison with metal-ligand vibrations of square-planar complexes, aided by normal coordinate calculations. For the weakly coordinated axial aqua ligands, the low wavenumber range and the polarizibility properties allowed the assignments of the bands at about 365 and 325 cm(-1) to the stretching modes of one short and one longer Pt - O* bound to axial aqua ligands, respectively. A similar picture with even less strongly bound axial water molecules emerges from Raman spectroscopy data for the hydrated palladium(II) ion, [Pd(OH2)(6)](2+). The results are consistent with a description of the [Pt(OH2)(6)](2+) and [Pd(OH2)(6)](2+) aqua ions in C-4v symmetry, and with the [cis-Pt(NH3)(2)(OH2)(4)](2+) complex in the Cs point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements.
  •  
29.
  • Käll, Mikael, 1963, et al. (författare)
  • Field enhancement and molecular response in surface-enhanced Raman scattering and fluorescence spectroscopy
  • 2005
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 36, s. 510-514
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a theoretical analysis of surface-enhanced Raman scattering and fluorescence emission from chromophoric molecules located at electromagnetic 'hot spots' in nanoparticle aggregates. The model combines classical electrodynamic enhancement effects with molecular quantum dynamics and allows us to quantify various molecular cross-sections and spectral properties. For a model molecule that simulates rhodamine 6G, we find that an electromagnetic Raman enhancement of the order of loll results in an effective Raman cross-section of the order of 10(-14) cm(2), in agreement with single-molecule Raman measurements.
  •  
30.
  • Lane, Nina J, et al. (författare)
  • First-order Raman scattering of the MAX phases Ta4AlC3, Nb4AlC3, Ti4AlN3, and Ta2AlC
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : John Wiley and Sons. - 0377-0486 .- 1097-4555. ; 43:7, s. 954-958
  • Tidskriftsartikel (refereegranskat)abstract
    • Herein, we report on the Raman spectra of the following ternary hexagonal carbides and nitrides (MAX phases): Ta4AlC3, Ta2AlC and Ti4AlN3. We also present the Raman-active modes of a- and beta-Ta4AlC3, Nb4AlC3 and Ti4AlN3, also referred to as the 413 MAX phases as predicted from first principles calculations using density functional theory. We compare the obtained experimental and calculated results with previous studies on Ta2AlC and Ti4AlN3. The vibrational behavior associated with the Raman-active modes for the 413 phases has been identified for the first time. In general, the agreement is good between theory and experiment. The experimental and calculated results indicate that the modes at low wavenumbers - dominated by the Al atoms - are a weak function of chemistry and the differences in energy can be traced to variations in the reduced mass. The modes at higher wavenumbers are dominated by the C and N atoms and show a strong dependence on the unit cell chemistry, with the TaC bond being stiffer than the NbC bond, which is in turn stiffer than TiN.
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31.
  •  
32.
  • Larsson, Mina, et al. (författare)
  • Analysis of glutathione and immunoglobulin G inside chromatographic beads using surface-enhanced Raman scattering spectroscopy
  • 2005
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 36, s. 394-399
  • Tidskriftsartikel (refereegranskat)abstract
    • Gold-containing chromatographic beads were used to record spectra of the tripeptide glutathione and the protein immunoglobulin G (IgG) by surface-enhanced Raman scattering (SERS) spectroscopy. SERS spectra were recorded from glutathione in solution at three different pH values, 2, 6 and 10. It was found that the SERS spectra are strongly dependent on pH, which indicates that the adsorption mode of glutathione changes with the pH value of the solution. Assignment of some of the observed bands and a suggestion for adsorption modes at the different pH were made. A SERS spectrum of human IgG in ethanolamine was also recorded. No complete assignment of the bands in this spectrum was performed, but the results indicate adsorption to the gold nanoparticles by aromatic amino acids and cystine residues.
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33.
  • Larsson, Mina, et al. (författare)
  • Surface-enhanced Raman scattering from analytes adsorbed on gold nanoparticles inside polymer beads
  • 2004
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 35, s. 826-834
  • Tidskriftsartikel (refereegranskat)abstract
    • Porous polymer beads with a large inner area were used as a stabilizing matrix for SERS-active gold particles. A commercially available ion exchanger (SOURCETM) was used together with HAuCl4. Absorbance measurements and an x-ray diffraction study confirmed that nanocrystalline gold was obtained in the polymer beads. Transmission electron microscope measurements were performed and showed that larger nanoparticles, 20-100 nm, were obtained on the surface, whereas in the interior smaller particles, approximately 2-10 nm, could be found. Three analytes, mercaptoethanesulfonate, mercaptopropionic acid and thiocyanate, were adsorbed on the gold particles inside the polymer beads. From all analytes enhanced Raman spectra could be obtained. The distribution of analytes adsorbed on gold nanoparticles was investigated by confocal Raman spectroscopy. SERS spectra from the analytes could be observed throughout the polymer bead, indicating a fairly uniform distribution of analytes adsorbed on gold nanoparticles.
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34.
  • Le, Kim Cuong, et al. (författare)
  • Polarization effects in Raman spectroscopy of light-absorbing carbon
  • 2021
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 52:6, s. 1115-1122
  • Tidskriftsartikel (refereegranskat)abstract
    • Raman spectroscopy is widely used for characterization of carbon-based mate- rials including light-absorbing carbonaceous (LAC) matter. However, informa- tion on polarization properties of these materials are generally lacking, and often the polarization characteristics of experiments are not presented in the literature thereby giving uncertainty to presented data. In this work, the polari- zation properties of various LACs are studied using Raman spectroscopy. The Raman spectra have been compared while varying the relative polarization, particularly the relative direction of the electric field between the incident light and the detected scattered light. Specifically, the intensity ratio between the D1 and G peaks (ID1/IG) was analyzed in parallel and perpendicular polarization configurations for samples taken from a sooting flame, in the exhaust of a soot generator and carbon blacks. In this work, the parallel and perpendicular polarization configurations mean that the polarization of the detected scattered light is parallel and orthogonal, respectively, to the linearly polarized incident light. It was found that the (ID1/IG) ratio decreased in the more ordered carbo- naceous structures when changing the polarization configuration from parallel to perpendicular. Additionally, based on the depolarization ratios (Dp < 0.75), the prominent Raman peaks of LAC were found to originate from totally sym- metric vibrations. For the G peak, the depolarization ratio was measured to be in the range 0.46–0.56 for all LAC materials.
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35.
  • Lejon, Christian, et al. (författare)
  • Influence of quantum confinement, hydrostatic pressure and critical Zr dopant concentration on the Raman vibrational properties of Zr doped anatase TiO2 nanoparticles
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - : John Wiley & Sons. - 0377-0486 .- 1097-4555. ; 42:11, s. 2026-2035
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a comprehensive analysis of the Ramanspectra of pure and zirconium-doped anatase TiO2 nanoparticles. To accountfor the wavenumber shifts of the Eg(ν6)mode as a function of particle size (L) and dopant concentration (x), a modification of the standard phonon confinement model (PCM) is introduced, which takes into account the contribution of surface stress by means of the Laplace–Young equation. Together with X-ray diffraction (XRD) and transmission electronmicroscopy data, our analysis shows that the surface stress contribution to the observed blue shift of the Ramanwavenumber is of the same magnitude as the spatial phonon confinement effect. Annealing experiments show that Zr-doped nanoparticles exhibit retarded grain growth and delayed anatase-to-rutile phase transition by up to 200 K compared to pure anatase TiO2. XRD shows that Zr doping leads to a unit cell expansion of the anatase structure. Applying themodified PCM to the x-dependent variations of the Eg(ν6) Raman mode, the mode-Gr ¨ uneisen parameter is found to increase abruptly at x > 0.07 with a concomitant mode softening. This coincides with the x range over which the Zr cations are reported to be displaced from their position in the tetrahedral lattice, and where Zr precipitation occurs upon annealing. The results have implications for the interpretation of Raman spectra of ionic metal oxide nanoparticles and how these are modified upon cation doping
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36.
  • Lin, Ke, et al. (författare)
  • Reorientation dynamics in liquid alcohols from Raman spectroscopy
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 43, s. 82-88
  • Tidskriftsartikel (refereegranskat)abstract
    • Polarized Raman spectroscopy has been employed to study the reorientational, or more specifically the translational relaxation dynamics, of alcohol molecules in pure liquids and aqueous solutions. It is found from the spectral width measurements that alcohol molecules in pure liquids have typically translational relaxation times on the order of picoseconds, following the order methanol < ethanol < i-propanol < n-propanol. Temperature-dependent measurements show that hydrogen-bonding (HB) and hydrophobic interactions control the translational motion. The hydrophobic interaction reduces the relaxation time more apparently in view of the –CH3 group than the skeleton motion. For alcohol–water mixtures, the increaseofwater concentration generally slows down the relaxation process in a non-monotonic behavior. However, the trend stops at a certain point and the motion of alcohol molecules becomes faster when the alcohol concentration further drops. Different mechanisms have been proposed to interpret these observations, which might be helpful to gain deeper insight into the HB networks of alcohols with water. Our study strongly illustrates that Raman spectroscopy can be applied to the study of fast translational motion of molecules in HB systems.
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37.
  • Liu, Dedi, et al. (författare)
  • In situ Raman and photoluminescence study on pressure-induced phase transition in C60 nanotubes
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 43:6, s. 737-740
  • Tidskriftsartikel (refereegranskat)abstract
    • Single crystalline C60 nanotubes having face-centered-cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C60 nanotubes. A phase transition, probably because of the orientational ordering of C60 molecules, from face-centered-cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570cm-1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied.
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38.
  • Lorén, Anders, 1974, et al. (författare)
  • Feasibility of quantitative determination of doxorubicin with surface-enhanced Raman spectroscopy
  • 2001
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 32:11, s. 971-974
  • Tidskriftsartikel (refereegranskat)abstract
    • Surface-enhanced Raman spectroscopy (SERS) was performed using excitation at 488 nm in a blood plasma-doxorubicin-silver colloid system. With a blood plasma content of 1%, a partial least-squares calibration of the doxorubicin was made in the 10-750 nM range. Predictions for a test set generated a root mean square error of prediction of 70 nM. The use of SERS and chemometrics in complex systems made it possible to use the highly informative Raman signals even at low concentrations without the need for sample pretreatment such as extraction. Copyright © 2001 John Wiley & Sons, Ltd.
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39.
  • Luo, Zhixun, et al. (författare)
  • Potential-induced Raman behavior of individual (R)-di-2-naphthylprolinol molecules on a Ag-modified Ag electrode
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 42:5, s. 951-957
  • Tidskriftsartikel (refereegranskat)abstract
    • The applicability of surface-enhanced Raman spectroscopy is demonstrated to probe the adsorption behavior of individual molecules on a Ag electrode. High-quality SERS spectra of (R)-di-2-naphthylprolinol (DNP) were obtained from ultradilute solutions (10(-12) M) on the Ag-nanoparticle-modified Ag electrode, which is attributed to the high electromagnetic (EM) effect of the SERS-active system as well as to the strong adsorption and interaction of DNP molecules with Ag. The stable SERS spectra present remarkable potential dependence, which gives evidence for the behavior of individual DNP molecules on the Ag surface. Based on statistical analysis for the probability of DNP molecules located in 'hot spots', we propose an SERS mechanism for individual molecules in the electrode system, in combination with the hot-spot model and orientation of the probemolecules.
  •  
40.
  • Malyshev, Dmitry, et al. (författare)
  • Reference Raman Spectrum and Mapping of Cryptosporidium parvum Oocysts
  • 2022
  • Ingår i: Journal of Raman Spectroscopy. - : John Wiley & Sons. - 0377-0486 .- 1097-4555. ; 53:7, s. 1293-1301
  • Tidskriftsartikel (refereegranskat)abstract
    • Cryptosporidium parvum is a protozoan parasite and among the most infectious diarrhea-causing pathogens, leading to severe health problems for malnourished children and immunocompromised individuals. Outbreaks are common even in developed countries, originating from water or food contamination and resulting in suffering and large costs for society. Therefore, robust, fast and highly specific detection strategies of Cryptosporidium are needed. Label-free detection techniques such as Raman spectroscopy have been suggested, however high-resolution reported spectra in the literature are limited. In this work, we report reference Raman spectra at 3 cm-1 resolution for viable and inactivated Cryptosporidium oocysts of the species C. parvum, gathered at a single oocyst level using a laser tweezers Raman spectroscopy system. We furthermore provide tentative Raman peak assignments for the Cryptosporidium oocysts, along with Raman mapping of the oocysts’ heterogeneous internal structure. Finally, we compare the C. parvum Raman spectrum with other common enterotoxigenic pathogens: Escherichia coli, Vibrio cholerae, Bacillus cereus and Clostridium difficile. Our results show a significant difference between C. parvum Raman spectra and the other pathogens.
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41.
  • Martinelli, Anna, 1978, et al. (författare)
  • Conformational evolution of TFSI− in protic and aprotic ionic liquids
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555.
  • Tidskriftsartikel (refereegranskat)abstract
    • We here report on the conformational evolution of the bis(trifluoromethanesulfonyl)imide anion (TFSI−) in protic and aprotic TFSI−-based ionic liquids as a function of temperature. The investigation is performed by Raman spectroscopy in the spectral ranges 240-380 cm−1 and 715-765 cm−1, where the interference from bands due to the cations is negligible. The contribution from each TFSI− conformation, i.e. the cisoid (C1) and the transoid (C2), is quantified in order to estimate the enthalpy of conformational change, ΔH, which is found to be in the range 3.4–7.3 kJ/mol in the liquid state. Conformational information is for the first time determined from the 740 cm−1 band, which previously mainly has been used as an indicator of ion-ion interactions. The similarity in ΔH values obtained from the two spectral ranges demonstrates the validity of using also the 740 cm−1 band for the quantification of the TFSI conformational evolution.
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42.
  • Milenov, Teodor, et al. (författare)
  • Raman fingerprint of the graphene buffer layer grown on the Si-terminated face of 4H-SiC(0001): Experiment and theory
  • 2023
  • Ingår i: Journal of Raman Spectroscopy. - : WILEY. - 0377-0486 .- 1097-4555.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we present the results of measurements of the Raman spectrum of the root 3x root 3R30 degrees reconstruction of graphene grown on 4H-SiC(0001), the so-called buffer layer. The extracted Raman spectrum of the buffer layer shows bands, different from those of graphene, which can be attributed to the interaction of the buffer layer with the SiC substrate. In particular, in the high-wavenumber region, at least three bands are observed in the wavenumber regions 1,350-1,420, 1,470-1,490 and 1,520-1,570 cm-1. The assignment of the buffer layer bands is supported here by tight-binding simulations of the one-phonon density of states for structures with a sufficiently large number of Si-C bilayers for reaching convergence. The converged phonon density of states is found to be in semi-quantitative agreement with the latter two bands, and therefore, the tight-binding predictions of the lattice dynamics of the structure can be used for their assignment to buffer layer vibrations. Namely, the Raman band at about 1,550 cm-1 can be assigned to modified in-plane optical phonon branches of graphene, while the Raman band at about 1,490 cm-1 can be assigned to modified folded parts of these branches inside the Brillouin zone of the buffer layer and can be considered as a Raman fingerprint of the buffer layer. We present the results of measurements of the Raman spectrum of the root 3x root 3R30 degrees reconstruction of graphene grown on 4H-SiC(0001), the so-called buffer layer (BL) in the wavenumber region 1,200-1,650 cm-1. The assignment of the BL bands is supported by tight-binding simulations of the one-phonon density of states (DOS) for structures with a sufficiently large number of Si-C bilayers for reaching convergence. The converged phonon DOS is found to be in semi-quantitative agreement with the experimental Raman spectra.image
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43.
  • Mink, Janos, et al. (författare)
  • Vibrational properties of -KSiH3 and -RbSiH3 : a combined Raman and inelastic neutron scattering study
  • 2017
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 48:2, s. 284-291
  • Tidskriftsartikel (refereegranskat)abstract
    • The hydrogen storage materials ASiH(3) (A=K and Rb) represent complex metal hydrides built from metal cations and pyramidal SiH3- ions. At room temperature, SiH3- moieties are randomly oriented because of dynamical disorder (-modifications). At temperatures below 200K, ASiH(3) exist as ordered low-temperature () modifications. The vibrational properties of -ASiH(3) were characterized by a combination of Raman spectroscopy and inelastic neutron scattering. Internal modes of SiH3- are observed in the spectral range 1800-1900cm(-1) (stretching modes) and 890-1000cm(-1) (bending modes). External modes are observed below 500cm(-1). Specifically, SiH3- librations are between 300-450cm(-1) and 270-400cm(-1) for A=K and Rb, respectively, SiH3- translations are between 95 and 160cm(-1), K+ translations are in the range 60-100cm(-1) and Rb+ translations in the range 50-70cm(-1). The red-shift of libration modes for A=Rb is associated with a 15-30% reduction of the libration force constants of SiH3- ions in -RbSiH3. This correlates with a lower temperature for the - order-disorder phase transition (278 vs 298K). Libration modes become significantly anharmonic with increasing temperature but are maintained up to at least 200K. The vibrational properties of ASiH(3) compare well to those of alkali metal borohydrides ABH(4) (A=Na-Cs).
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44.
  • Mozhzhukhina, Nataliia, et al. (författare)
  • Short-range ordering in the Li-rich disordered rock salt cathode material Li2VO2F revealed by Raman spectroscopy
  • 2020
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 51:10, s. 2095-2101
  • Tidskriftsartikel (refereegranskat)abstract
    • Li‐rich disordered rock salt (DRS) materials are new promising high‐capacity cathode candidates for Li‐ion batteries. DRS structures were initially assumed to have a completely random cation and anion distribution, but recent reports suggest that some of these structures can exhibit local atomic arrangements, or short‐range ordering (SRO). Here, we prove the existence of SRO in the Li‐rich DRS material Li2VO2F by employing Raman spectroscopy supported by density functional theory (DFT) calculations. Our results suggest that this combination of Raman spectroscopy with computational tools is useful for SRO estimation in this new class of Li‐rich DRS cathode materials.
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45.
  • Nordström, Emil, et al. (författare)
  • Fourier-based approach to overcome anomalies in high-resolution spectra of vibrational CARS measurements of gases
  • 2014
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 45:7, s. 489-494
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we report on an unconventional experimental procedure useful for thermometric measurements on the basis of high-resolution vibrational coherent anti-Stokes Raman scattering (CARS) generated using conventional lasers. The high spectral dispersion of 0.02 cm(-1)/pixel is achieved by means of some specific spectral arrangements (single-mode pump laser and diffraction grating providing spectra at the sixth order) and is further strengthened by the use of a relay lens system mounted before the charge-coupled device camera. Surprisingly, at the high spectral dispersion of our measurements, a significant and persistent thermometric inaccuracy is observed. The effect arises from an inevitable spectral modulation of defined frequency hidden in the main CARS signal of the gas under study, and to secure a good thermometric evaluation, we describe a Fourier approach that is experimentally demonstrated for the typical nitrogen CARS spectrum measured at room temperature. Copyright (C) 2014 John Wiley & Sons, Ltd.
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46.
  • Nordström, Emil, et al. (författare)
  • Pure rotational Coherent anti-Stokes Raman spectroscopy of water vapor and its relevance for combustion diagnostics
  • 2013
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 44:10, s. 1322-1325
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we report for the first time the rotational coherent anti-Stokes Raman spectroscopy (CARS) spectrum of water vapor, recorded through experiments at 400K and 670K for Raman shifts up to 600cm(-1). Using the standard dual-broadband pure rotational CARS approach, the resonant structure was overwhelmed by a strong non-resonant background. By employing a polarization technique, this background could be suppressed and the resonant structure discerned. The spectral line structure matched spectra from spontaneous rotational Raman scattering found in the literature. The CARS signal intensity at the highest peak from water vapor at 400K was more than five orders of magnitude weaker than for N-2 because of a low Raman cross section and a larger number of transitions. Due to the weak resonant signal, water vapor is an unsuitable candidate for CARS thermometry and relative concentration measurements in combustion. Still, rotational CARS spectra from product gases in combustion will be affected by the presence of water, which is briefly discussed. Copyright (c) 2013 John Wiley & Sons, Ltd.
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47.
  • Ostrovskii, Denis, 1967, et al. (författare)
  • Weak polymer-electrolyte interaction revealed by Fermi resonance perturbed Raman bands.
  • 2003
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 34:1, s. 40-49
  • Tidskriftsartikel (refereegranskat)abstract
    • A detailed analysis of isotropic and anisotropic Raman spectra of carbonyl stretching vibrations of ethylene carbonate in different systems was conducted. The variation of Fermi resonance perturbed spectral profiles was used to investigate changes in local molecular surroundings in polymer gel-electrolyte systems as a function of their composition. In poly(methyl methacrylate)-based gels it is found that the matrix interacts very weakly with the solvent molecules, ethylene and propylene carbonates, mostly playing a role of a hydrogen bond-breaking agent. In gel systems containing lithium salt, however, a new type of coordination appears. Along with the solvent-solvent and solvent-cation couplings characteristic of liquid electrolytes, the spectra of gels demonstrate the presence of mixed states in which cations, solvent molecules and polymer segments take part. The importance of the mixed states for ionic conduction is discussed. Copyright © 2002 John Wiley & Sons, Ltd.
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48.
  • Sahlberg, Anna-Lena, et al. (författare)
  • Non-intrusive in situ detection of methyl chloride in hot gas flows using infrared degenerate four-wave mixing
  • 2015
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 46:8, s. 695-701
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate the potential of infrared degenerate four-wave mixing (IR-DFWM) as a tool for non-intrusive in situ spatially resolved detection of CH3Cl in reactive hot gas flows especially feasible for applications to biomass combustion and gasification. IR-DFWM spectra of CH3Cl, by probing ro-vibrational transitions belonging to the fundamental stretching modes v(1) and v(4), have been successfully recorded in gas flows diluted with nitrogen at atmospheric pressure and elevated temperatures up to 820K. In order to identify the spectral lines of CH3Cl, the recorded IR-DFWM spectra are compared with simulations using molecular parameters extracted from the HITRAN database. The potential interference from water vapor is discussed from measurements of H2O spectrum at 820K combined with simulations of H2O IR-DFWM spectrum based on the HITEMP database, and it was found that the (Q)Q(6) line of the v(1) band is relatively free from water interference at elevated temperatures. At atmospheric pressure, the detection limits for temperatures at 296, 550 and 820K were estimated to be 2.1, 3.1 and 6.2 (x10(15) molecules/cm(3)), respectively, by scanning the (Q)Q(6) line of the v(1) band. These results show the potential of interference free detection of CH3Cl with IR-DFWM in harsh environments like combustion. Copyright (c) 2015 John Wiley & Sons, Ltd.
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49.
  • Sajan, D., et al. (författare)
  • Dimerisation and vibrational spectroscopic properties of (RS)-phenylsuccinic acid
  • 2006
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 37:11, s. 1307-1318
  • Tidskriftsartikel (refereegranskat)abstract
    • Single crystals of (RS)-phenylsuccinic acid (RSPSA) were grown by the slow evaporation technique and vibrational spectral analysis was carried out using near-IR Fourier transform Raman and Fourier transform IR spectroscopy. The density functional theoretical (DFT) computations were also performed at the B3LYP/6-31G(d) level to derive the equilibrium geometry, vibrational wavenumbers, intensities and atomic charges. Vibrational spectral investigation confirmed the formation of cyclic dimers in the crystal, with the carboxyl groups of each acid molecule being hydrogen bonded to those of the adjacent molecules. Each molecule is connected to two other molecules, forming infinite chains. The wavenumber difference observed between the carbonyl modes in the IR and Raman spectra might be attributed to the intramolecular association based on C=O center dot center dot center dot H type hydrogen bonding in the molecule. In a hydrogen-bonded carbonyl, resonance can occur, which places a partial negative charge on the oxygen atom accepting the hydrogen bond and a positive charge on the atom donating the hydrogen. The resulting partial 'transfer of allegiance' of the proton enhances resonance and lowers the carbonyl stretching wavenumber. The O-H stretching vibrational wavenumber is red-shifted owing to the formation of strong O-H center dot center dot center dot O hydrogen bonds by hyperconjugation between carbonyl oxygen lone electron pairs and O-H sigma* antibonding orbitals. Vibrational analysis was used to investigate the C-H center dot center dot center dot O interaction and electronic effects, induction of the methylene group by an adjacent electronegative atom and the resulting increase of stretching mode wavenumbers and decrease of infrared intensities.
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50.
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