Spectra and structure of organophosphorus compounds. LI. IR and Raman spectra, conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of n-propylphosphine

NASA Astrophysics Data System (ADS)

Durig, J. R.; Gounev, T. K.; Lee, M. S.; Little, T. S.

1994-10-01

The Raman (3100 to 50 cm -1) and IR (3100 to 50 cm -1) spectra of gaseous and solid n-propylphosphine, C 3H 7PH 2, and the corresponding P- d2 isotopomer have been recorded. Additionally, the Raman spectra of the liquids have been obtained with qualitative depolarization ratios. From these data, all five possible conformers have been identified in the fluid states and the trans-trans conformer is shown to be the most stable rotamer in both the gaseous and liquid states and it is the only conformer present in the solid. The first trans refers to the orientation of the lone pair to the ethylene group (rotation around the PC bond) whereas the second trans refers to the orientation of the methyl group relative to the PC bond (rotation around the -CH 2CH 2 bond). The next most stable conformer is the gauche-trans rotamer where the enthalpy difference has been determined from variable-temperature Raman studies to be 140 ± 5 cm -1 (400 ± 14 cal mol -1) for the vapor and 351 ± 20 cm -1 (1004 ± 57 cal mol -1) for the liquid. The other three conformers have nearly the same stabilities but significantly higher energies than the two more stable rotamers. From the far-IR data and relative conformer stabilities, some of the coefficients of the potential function governing conformer interconversion are estimated. A complete vibrational assignment is proposed for the trans-trans conformer and for the fundamentals for most of the heavy atom motions for the other conformers. The conformational stabilities, barriers to internal rotation, and fundamental vibrational frequencies which have been determined experimentally are compared to those obtained from ab initio calculations employing the RHF/3-21G* and/or RHF/6-31G* basis sets. Additionally, the conformational stabilities and structural parameters have been determined with the 6-31G* basis set with electron correlation at the MP2 level. These results are compared with the corresponding quantities for some similar molecules.

Vibrational spectra of cyclopentadienyl chlorides of titanium, zirconium and hafnium. internal rotation and thermodynamic functions

NASA Astrophysics Data System (ADS)

Balducci, G.; Bencivenni, L.; De Rosa, G.; Gigli, R.; Martine, B.; Cesaro, S. Nunziante

1980-05-01

The infrared and Raman spectra of some cyclopentadienyl compounds of the transition metals, namely Ti(C 5H 5)Cl 3 and M(C 5H 5) 2Cl 2 (M = Ti, Zr and Hf), are reported and discussed. The infrared spectra of the gaseous species isolated in argon matrices at 10 K provide structural information about the single molecules. Particular attention has been paid to the low-frequency region in order to achieve more reliable assignments for the internal-rotation modes. The structural data and the fundamental frequencies derived from the spectra are employed in a calculation of the thermodynamic functions for these compounds in the ideal gas state.

Computer program to simulate Raman scattering

NASA Technical Reports Server (NTRS)

Zilles, B.; Carter, R.

1977-01-01

A computer program is described for simulating the vibration-rotation and pure rotational spectrum of a combustion system consisting of various diatomic molecules and CO2 as a function of temperature and number density. Two kinds of spectra are generated: a pure rotational spectrum for any mixture of diatomic and linear triatomic molecules, and a vibrational spectrum for diatomic molecules. The program is designed to accept independent rotational and vibrational temperatures for each molecule, as well as number densities.

Proline zwitterion dynamics in solution, glass, and crystalline state.

PubMed

Kapitán, Josef; Baumruk, Vladimír; Kopecký, Vladimír; Pohl, Radek; Bour, Petr

2006-10-18

Raman and Raman optical activity spectra of L- and D-proline zwitterionic (PROZW) forms were recorded for H(2)O and D(2)O solutions in a wide frequency range and analyzed with respect to the motion of the proline ring and rotation of the carbonyl group. The solution spectra were additionally compared to Raman scattering of glass and crystalline powder proline. Solution and glass spectral band broadenings are similar and reveal information about the extent of internal molecular motion. Two distinct but equally populated flexible forms were found in the glass and the solution. The equal population is consistent with NMR data, temperature, and concentration dependencies. The molecular flexibility is reduced significantly in the crystal, however, where only one conformer is present. Consequently, the crystal bands are narrow and exhibit minor frequency shifts. The spectra were interpreted with the aid of density functional theory computations involving both continuum and explicit solvent. A two-dimensional potential energy surface pertaining to the five-member ring puckering coordinates was constructed and used for dynamical averaging of spectral properties. Comparison of the computed and experimental bandwidths suggests that the puckering is strongly correlated with the carbonyl rotation. An averaging over these two motions produces similar results. The interpretation of the Raman experiments with the aid of the simulation techniques also indicates that the environment modulates properties of the hydrophobic part of the molecule indirectly by interacting with the ionic group. Such behavior may be important for the reactivity and biological activity of proline-containing peptides and proteins.

Pressure Monitoring Using Hybrid fs/ps Rotational CARS

NASA Technical Reports Server (NTRS)

Kearney, Sean P.; Danehy, Paul M.

2015-01-01

We investigate the feasibility of gas-phase pressure measurements at kHz-rates using fs/ps rotational CARS. Femtosecond pump and Stokes pulses impulsively prepare a rotational Raman coherence, which is then probed by a high-energy 6-ps pulse introduced at a time delay from the Raman preparation. Rotational CARS spectra were recorded in N2 contained in a room-temperature gas cell for pressures from 0.1 to 3 atm and probe delays ranging from 10-330 ps. Using published self-broadened collisional linewidth data for N2, both the spectrally integrated coherence decay rate and the spectrally resolved decay were investigated as means for detecting pressure. Shot-averaged and single-laser-shot spectra were interrogated for pressure and the accuracy and precision as a function of probe delay and cell pressure are discussed. Single-shot measurement accuracies were within 0.1 to 6.5% when compared to a transducer values, while the precision was generally between 1% and 6% of measured pressure for probe delays of 200 ps or more, and better than 2% as the delay approached 300 ps. A byproduct of the pressure measurement is an independent but simultaneous measurement of the gas temperature.

Effects induced by gamma-irradiation and thermal treatment on the infrared spectra of ferrocene in its disordered state

NASA Astrophysics Data System (ADS)

Gaffar, M. A.; Abd-Elrahman, M. I.

2004-10-01

Lattice, rotation and intramolecular vibrations of ferrocene, Fe(C5H5)(2), crystallites of the C-2h(5) factor group in the disordered phase are calculated using the correlation theorem based on group theory. The correlation between the species of the C-1 site symmetry occupied by cyclopentadienyl molecules and those of the factor group C-2h, of the crystal are calculated. The number of lattice vibrations of the cyclopentadienyl molecules is found to be 12. with active modes in Raman and infrared (IR) spectra. The same number of rotations for the cyclopentadienyl molecules is expected to be allowed in both spectra. The active number of intramolecular vibrations for the cyclopentadienyl molecules having D-5 molecular symmetry is expected to be 80 vibrations in both the Raman and the IR spectra. The effect of gamma-irradiation with different doses and heat treatment at different temperatures on the IR spectra of ferrocene in the energy range 4000-200 cm(-1) is discussed. A number of bands continuously shifted their position, and a decrease in intensity with increasing gamma-dose is observed. New bands appeared in this spectral region for different annealing temperatures and different gamma-doses. These changes are discussed in terms of intermolecular interactions between molecules within the unit cell.

Hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering temperature and concentration measurements using two different picosecond-duration probes.

PubMed

Kearney, Sean P; Scoglietti, Daniel J; Kliewer, Christopher J

2013-05-20

A hybrid fs/ps pure-rotational CARS scheme is characterized in furnace-heated air at temperatures from 290 to 800 K. Impulsive femtosecond excitation is used to prepare a rotational Raman coherence that is probed with a ps-duration beam generated from an initially broadband fs pulse that is bandwidth limited using air-spaced Fabry-Perot etalons. CARS spectra are generated using 1.5- and 7.0-ps duration probe beams with corresponding coarse and narrow spectral widths. The spectra are fitted using a simple phenomenological model for both shot-averaged and single-shot measurements of temperature and oxygen mole fraction. Our single-shot temperature measurements exhibit high levels of precision and accuracy when the spectrally coarse 1.5-ps probe beam is used, demonstrating that high spectral resolution is not required for thermometry. An initial assessment of concentration measurements in air is also provided, with best results obtained using the higher resolution 7.0-ps probe. This systematic assessment of the hybrid CARS technique demonstrates its utility for practical application in low-temperature gas-phase systems.

Raman Spectroscopic Analysis of Cupriavidus metallidurans LMG 1195 (CH34) Cultured in Low-shear Microgravity Conditions

NASA Astrophysics Data System (ADS)

De Gelder, Joke; Vandenabeele, Peter; De Boever, Patrick; Mergeay, Max; Moens, Luc; De Vos, Paul

2009-07-01

In this study, the effect of low-shear microgravity on the metabolism of Cupriavidus metallidurans LMG 1195 was studied with Raman spectroscopy. Therefore, the strain was cultured for 24 or 48 h in a rotating wall vessel to simulate microgravity (SMG) and in a control setup. The differences in Raman spectra recorded from both setups after 24 h of culturing were small. The most prominent features in a difference spectrum, calculated between the mean spectra from the microgravity and the control setup separately, could be assigned to the presence of poly-β-hydroxybutyrate (PHB). SMG seems to yield a higher PHB production after 24 h of culturing. Additional processing of the spectra suggested that SMG induced also other changes in the carbon-metabolism. After 48 h, similar results were found for the carbon metabolism, while PHB concentrations were reduced in SMG compared to the control. However, these differences could also be caused by interfering effects that may occur in the bioreactors after a prolonged incubation time.

Microwave, infrared and Raman spectra, conformational stability and vibrational assignment of methoxyflurane

NASA Astrophysics Data System (ADS)

Li, Y. S.; Durig, J. R.

1982-05-01

The low resolution microwave spectrum of methoxyflurane, CHCl 2CF 2OCH 3, has been recorded from 26.5 to 39.0 GHz. From the spacing of the major transitions it is shown that the value of 2036 MHz for B + C is consistent with the trans-trans or gauche-trans conformers where the first term ( trans or gauche) refers to the internal rotation around the C-C bond. The infrared (40-3500 cm -1) and the Raman (20-3500 cm -1) spectra have been recorded for gaseous and solid methoxyflurane. Additionally, the Raman spectrum of the liquid has been obtained and qualitative depolarization ratios measured. From these data it is shown that the most stable form in the fluid phases at ambient temperature is the gauche-trans conformer but the trans-trans form is the most stable in the solid state. A complete vibrational analysis based on infrared band contours, depolarization values and group frequencies is proposed for this conformer. From the analysis of the low frequency vibrational data, values of some of the barriers to internal rotation are estimated. These results are compared to some similar quantities for some corresponding molecules.

PGOPHER: A program for simulating rotational, vibrational and electronic spectra

NASA Astrophysics Data System (ADS)

Western, Colin M.

2017-01-01

The PGOPHER program is a general purpose program for simulating and fitting molecular spectra, particularly the rotational structure. The current version can handle linear molecules, symmetric tops and asymmetric tops and many possible transitions, both allowed and forbidden, including multiphoton and Raman spectra in addition to the common electric dipole absorptions. Many different interactions can be included in the calculation, including those arising from electron and nuclear spin, and external electric and magnetic fields. Multiple states and interactions between them can also be accounted for, limited only by available memory. Fitting of experimental data can be to line positions (in many common formats), intensities or band contours and the parameters determined can be level populations as well as rotational constants. PGOPHER is provided with a powerful and flexible graphical user interface to simplify many of the tasks required in simulating, understanding and fitting molecular spectra, including Fortrat diagrams and energy level plots in addition to overlaying experimental and simulated spectra. The program is open source, and can be compiled with open source tools. This paper provides a formal description of the operation of version 9.1.

Processing Raman Spectra of High-Pressure Hydrogen Flames

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet; Kojima, Jun

2006-01-01

The Raman Code automates the analysis of laser-Raman-spectroscopy data for diagnosis of combustion at high pressure. On the basis of the theory of molecular spectroscopy, the software calculates the rovibrational and pure rotational Raman spectra of H2, O2, N2, and H2O in hydrogen/air flames at given temperatures and pressures. Given a set of Raman spectral data from measurements on a given flame and results from the aforementioned calculations, the software calculates the thermodynamic temperature and number densities of the aforementioned species. The software accounts for collisional spectral-line-broadening effects at pressures up to 60 bar (6 MPa). The line-broadening effects increase with pressure and thereby complicate the analysis. The software also corrects for spectral interference ("cross-talk") among the various chemical species. In the absence of such correction, the cross-talk is a significant source of error in temperatures and number densities. This is the first known comprehensive computer code that, when used in conjunction with a spectral calibration database, can process Raman-scattering spectral data from high-pressure hydrogen/air flames to obtain temperatures accurate to within 10 K and chemical-species number densities accurate to within 2 percent.

Mechanochemical induced structural changes in sucrose using the rotational diamond anvil cell

NASA Astrophysics Data System (ADS)

Ciezak-Jenkins, Jennifer A.; Jenkins, Timothy A.

2018-02-01

The response of sucrose to high-pressure and shear conditions has been studied in a rotational diamond anvil cell. Previous experiments conducted by Bridgman and Teller showed divergent behavior in regard to the existence of a rheological explosion under mechanochemical stimuli. Raman spectroscopy confirmed the existence of the isostructural Phase I to Phase II transition near 5 GPa. When subjected to high-pressure and shear, Raman spectra of Phase I showed evidence that while the sucrose molecule underwent significant molecular deformation, there was no evidence of a complete chemical reaction. In contrast, Phase II showed a near-total loss of the in-situ Raman signal in response to shear, suggesting the onset of amorphization or decomposition. The divergent behaviors of Phase I and Phase II are examined in light of the differences in the hydrogen bonding and plasticity of the material.

Study of A-site doping of SrBi4Ti4O15 Bi-layered compounds using micro-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Hao, H.; Liu, H. X.; Cao, M. H.; Min, X. M.; Ouyang, S. X.

2006-10-01

The temperature-dependent Raman spectra of Mg- and La-doped SrBi4Ti4O15 (SBT) were studied in the range 40 590 °C. A quantum chemistry calculation was employed to estimate these two substitution states. It was found that A-site doping in this study not only caused multiplicative substitution states, but also the Raman spectra changed with the substitution amount. In a La-doped perovskite-like layer, La would occupy the Bi site when x>0.10 and the 314 and 550 cm-1 modes related to the rotating and tilting of the TiO6 octahedron firstly became wide and then became sharp. With the increase of the substitution amount, both substitution states of Mg-doped SBT lead to the widening of 270 and 520 cm-1 peaks.

Raman Spectra of Nitrogen, Carbon Dioxide, and Hydrogen in a Methane Environment

NASA Astrophysics Data System (ADS)

Petrov, D. V.; Matrosov, I. I.; Sedinkin, D. O.; Zaripov, A. R.

2018-01-01

Changes in the Raman spectra of N2, H2, and CO2 are studied in the range of 200-3800 cm-1 depending on the concentration of surrounding CH4 molecules at a fixed medium pressure of 25 atm and temperature of 300 K. It has been found that changes in the spectral characteristics of purely rotational H2 lines in a CH4 medium are negligible, while the Q-branches of the v 1/2 v 2 Fermi dyad in CO2 become narrower and wavenumbers of its high-frequency component and v 1 band of N2 decrease. In addition, under these conditions, the ratio of intensities of the CO2 Fermi dyad Q-branch varies in proportion to the concentration of surrounding molecules of CH4. The obtained data will be used in diagnosing the composition of natural gas using Raman spectroscopy.

Defining Multiple Characteristic Raman Bands of α-Amino Acids as Biomarkers for Planetary Missions Using a Statistical Method

NASA Astrophysics Data System (ADS)

Rolfe, S. M.; Patel, M. R.; Gilmour, I.; Olsson-Francis, K.; Ringrose, T. J.

2016-06-01

Biomarker molecules, such as amino acids, are key to discovering whether life exists elsewhere in the Solar System. Raman spectroscopy, a technique capable of detecting biomarkers, will be on board future planetary missions including the ExoMars rover. Generally, the position of the strongest band in the spectra of amino acids is reported as the identifying band. However, for an unknown sample, it is desirable to define multiple characteristic bands for molecules to avoid any ambiguous identification. To date, there has been no definition of multiple characteristic bands for amino acids of interest to astrobiology. This study examined l-alanine, l-aspartic acid, l-cysteine, l-glutamine and glycine and defined several Raman bands per molecule for reference as characteristic identifiers. Per amino acid, 240 spectra were recorded and compared using established statistical tests including ANOVA. The number of characteristic bands defined were 10, 12, 12, 14 and 19 for l-alanine (strongest intensity band: 832 cm-1), l-aspartic acid (938 cm-1), l-cysteine (679 cm-1), l-glutamine (1090 cm-1) and glycine (875 cm-1), respectively. The intensity of bands differed by up to six times when several points on the crystal sample were rotated through 360 °; to reduce this effect when defining characteristic bands for other molecules, we find that spectra should be recorded at a statistically significant number of points per sample to remove the effect of sample rotation. It is crucial that sets of characteristic Raman bands are defined for biomarkers that are targets for future planetary missions to ensure a positive identification can be made.

Defining Multiple Characteristic Raman Bands of α-Amino Acids as Biomarkers for Planetary Missions Using a Statistical Method.

PubMed

Rolfe, S M; Patel, M R; Gilmour, I; Olsson-Francis, K; Ringrose, T J

2016-06-01

Biomarker molecules, such as amino acids, are key to discovering whether life exists elsewhere in the Solar System. Raman spectroscopy, a technique capable of detecting biomarkers, will be on board future planetary missions including the ExoMars rover. Generally, the position of the strongest band in the spectra of amino acids is reported as the identifying band. However, for an unknown sample, it is desirable to define multiple characteristic bands for molecules to avoid any ambiguous identification. To date, there has been no definition of multiple characteristic bands for amino acids of interest to astrobiology. This study examined L-alanine, L-aspartic acid, L-cysteine, L-glutamine and glycine and defined several Raman bands per molecule for reference as characteristic identifiers. Per amino acid, 240 spectra were recorded and compared using established statistical tests including ANOVA. The number of characteristic bands defined were 10, 12, 12, 14 and 19 for L-alanine (strongest intensity band: 832 cm(-1)), L-aspartic acid (938 cm(-1)), L-cysteine (679 cm(-1)), L-glutamine (1090 cm(-1)) and glycine (875 cm(-1)), respectively. The intensity of bands differed by up to six times when several points on the crystal sample were rotated through 360 °; to reduce this effect when defining characteristic bands for other molecules, we find that spectra should be recorded at a statistically significant number of points per sample to remove the effect of sample rotation. It is crucial that sets of characteristic Raman bands are defined for biomarkers that are targets for future planetary missions to ensure a positive identification can be made.

Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bohlin, Alexis; Kliewer, Christopher J.

2013-01-01

Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the highmore » efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15, 000 spatially correlated rotational CARS spectra in N 2 and air over a 2D field of 40 mm 2.« less

Minor Distortions with Major Consequences: Correcting Distortions in Imaging Spectrographs

PubMed Central

Esmonde-White, Francis W. L.; Esmonde-White, Karen A.; Morris, Michael D.

2010-01-01

Projective transformation is a mathematical correction (implemented in software) used in the remote imaging field to produce distortion-free images. We present the application of projective transformation to correct minor alignment and astigmatism distortions that are inherent in dispersive spectrographs. Patterned white-light images and neon emission spectra were used to produce registration points for the transformation. Raman transects collected on microscopy and fiber-optic systems were corrected using established methods and compared with the same transects corrected using the projective transformation. Even minor distortions have a significant effect on reproducibility and apparent fluorescence background complexity. Simulated Raman spectra were used to optimize the projective transformation algorithm. We demonstrate that the projective transformation reduced the apparent fluorescent background complexity and improved reproducibility of measured parameters of Raman spectra. Distortion correction using a projective transformation provides a major advantage in reducing the background fluorescence complexity even in instrumentation where slit-image distortions and camera rotation were minimized using manual or mechanical means. We expect these advantages should be readily applicable to other spectroscopic modalities using dispersive imaging spectrographs. PMID:21211158

Spin-symmetry conversion and internal rotation in high J molecular systems

NASA Astrophysics Data System (ADS)

Mitchell, Justin; Harter, William

2006-05-01

Dynamics and spectra of molecules with internal rotation or rovibrational coupling is approximately modeled by rigid or semi-rigid rotors with attached gyroscopes. Using Rotational Energy (RE)^1 surfaces, high resolution molecular spectra for high angular momentum show two distinct but related phenomena; spin-symmetry conversion and internal rotation. For both cases the high total angular momentum allows for transitions that would otherwise be forbidden. Molecular body-frame J-localization effects associated with tight energy level-clusters dominate the rovibronic spectra of high symmetry molecules, particularly spherical tops at J>10. ^2 The effects include large and widespread spin-symmetry mixing contrary to conventional wisdom^3 about weak nuclear moments. Such effects are discussed showing how RE surface plots may predict them even at low J. Classical dynamics of axially constrained rotors are approximated by intersecting rotational-energy-surfaces (RES) that have (J-S).B.(J-S) forms in the limit of constraints that do no work. Semi-classical eigensolutions are compared to those found by direct diagonalization. ^1 W.G Hater, in Handbook of Atomic, Molecular and Optical Physics, edited by G.W.F Drake (Springer, Germany 2006) ^2 W. G. Harter, Phys. Rev. A24,192-262(1981). ^3 G. Herzberg, Infrared and Raman Spectra (VanNostrand 1945) pp. 458,463.

Gas-phase Raman spectra and the potential energy function for the internal rotation of 1,3-butadiene and its isotopologues.

PubMed

Boopalachandran, Praveenkumar; Craig, Norman; Groner, Peter; Laane, Jaan

2011-08-18

The gas-phase Raman spectra of 1,3-butadiene and its 2,3-d(2), 1,1,4,4-d(4), and -d(6) isotopologues have been recorded with high sensitivity in the region below 350 cm(-1) in order to investigate the internal rotation (torsional) vibration. Based on more accurate structural information, the internal rotor constants F(n) were calculated as a function of rotation angle (ϕ). The data for all the isotopologues were then fit using a one-dimensional potential energy function of the form V = (1)/(2)∑V(n)(1 - cos ϕ). Initial V(n) values were based on those generated from theoretical calculations. The agreement between observed and calculated frequencies is very good, although bands not taken into account were present in the spectra. The energy difference between the trans and gauche forms was determined to be about 1030 cm(-1) (2.94 kcal/mol), and the barrier between the two equivalent gauche forms was determined to be about 180 cm(-1) (0.51 kcal/mol), which agrees well with high-level ab initio calculations. An alternative set of assignments also fits the data quite well for all of the isotopologues. For this model, the energy difference between the trans and gauche forms is about 1080 cm(-1) (3.09 kcal/mol), and the barrier between gauche forms is about 405 cm(-1) (1.16 kcal/mol). © 2011 American Chemical Society

Coherent anti-Stokes Raman spectroscopic modeling for combustion diagnostics

NASA Technical Reports Server (NTRS)

Hall, R. J.

1983-01-01

The status of modelling the coherent anti-Stokes Raman spectroscopy (CARS) spectra of molecules important in combustion, such as N2, H2O, and CO2, is reviewed. It is shown that accurate modelling generally requires highly precise knowledge of line positions and reasonable estimates of Raman linewidths, and the sources of these data are discussed. CARS technique and theory is reviewed, and the status of modelling the phenomenon of collisional narrowing at pressures well above atmospheric for N2, H2O, and CO2 is described. It is shown that good agreement with experiment can be achieved using either the Gordon rotational diffusion model or phenomenological models for inelastic energy transfer rates.

Line Interference Effects Using a Refined Robert-Bonamy Formalism: the Test Case of the Isotropic Raman Spectra of Autoperturbed N2

NASA Technical Reports Server (NTRS)

Boulet, Christian; Ma, Qiancheng; Thibault, Franck

2014-01-01

A symmetrized version of the recently developed refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] is proposed. This model takes into account line coupling effects and hence allows the calculation of the off-diagonal elements of the relaxation matrix, without neglecting the rotational structure of the perturbing molecule. The formalism is applied to the isotropic Raman spectra of autoperturbed N2 for which a benchmark quantum relaxation matrix has recently been proposed. The consequences of the classical path approximation are carefully analyzed. Methods correcting for effects of inelasticity are considered. While in the right direction, these corrections appear to be too crude to provide off diagonal elements which would yield, via the sum rule, diagonal elements in good agreement with the quantum results. In order to overcome this difficulty, a re-normalization procedure is applied, which ensures that the off-diagonal elements do lead to the exact quantum diagonal elements. The agreement between the (re-normalized) semi-classical and quantum relaxation matrices is excellent, at least for the Raman spectra of N2, opening the way to the analysis of more complex molecular systems.

Rotamer-Specific Photoisomerization of Difluorostilbenes from Transient Absorption and Transient Raman Spectroscopy.

PubMed

Quick, M; Dobryakov, A L; Ioffe, I N; Berndt, F; Mahrwald, R; Ernsting, N P; Kovalenko, S A

2018-01-25

Photoisomerization of 2,2'-, 3,3'-, and 4,4'-difluorostilbene (F2, F3, F4, respectively) in n-hexane, perfluoro-n-hexane, and acetonitrile is studied with broadband transient absorption (TA) and femtosecond stimulated Raman (FSR) spectroscopy and by DFT/TDDFT calculations. F2 and F3 possess three rotamers (rotational isomers) each, while F4 has one single conformation only. These differences are reflected in TA and FSR spectra. Thus F4 reveals a monoexponential decay of TA with τ 1 = 172 ps in n-hexane, as expected for a single species. For F2 and F3, the decays are biexponential in all solvents, corresponding to two distinctly discerned rotamers or rotamer fractions. Specifically, for F2 in n-hexane, τ 1 = 357 ps (83%) and τ 2 = 62 ps (17%), and for F3 in the same solvent, τ 1 = 222 ps (57%), and τ 2 = 81 ps (43%). The weights in brackets agree with theoretically estimated ground-state abundances of the rotamers. Furthermore, a global fit of the TA and FSR data allows us to extract the spectra of the pure rotamers. The Raman spectra of S 0 and S 1 are in qualitative agreement with calculations.

Raman spectral evidence of methyl rotation in liquid toluene.

PubMed

Kapitán, Josef; Hecht, Lutz; Bour, Petr

2008-02-21

In order to rationalize subtle details in the liquid phase toluene Raman backscattering spectra, an analysis was performed based on a quantum-mechanical Hamiltonian operator comprising rotation of the methyl group and the angular dependence of vibrational frequencies and polarizability derivatives. The separation of the methyl torsion from the other vibrational motions appears to be necessary in order to explain relative intensity ratios of several bands and an anomalous broadening of spectral intensity observed at 1440 cm(-1). These results suggest that the CH3 group in the liquid phase rotates almost freely, similarly as in the gaseous phase, and that the molecule consequently exhibits effectively C(2v) point group symmetry. A classical description and an adiabatic separation of the methyl rotation from other molecular motion previously used in peptide models is not applicable to toluene because of a strong coupling with other vibrational motions. Density functional computations, particularly the BPW91 functional, provide reasonable estimates of harmonic frequencies and spectral intensities, as well as qualitatively correct fourth-order anharmonic corrections to the vibrational potential.

Low-Resolution Raman-Spectroscopy Combustion Thermometry

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet; Kojima, Jun

2008-01-01

A method of optical thermometry, now undergoing development, involves low-resolution measurement of the spectrum of spontaneous Raman scattering (SRS) from N2 and O2 molecules. The method is especially suitable for measuring temperatures in high pressure combustion environments that contain N2, O2, or N2/O2 mixtures (including air). Methods based on SRS (in which scattered light is shifted in wavelength by amounts that depend on vibrational and rotational energy levels of laser-illuminated molecules) have been popular means of probing flames because they are almost the only methods that provide spatially and temporally resolved concentrations and temperatures of multiple molecular species in turbulent combustion. The present SRS-based method differs from prior SRS-based methods that have various drawbacks, a description of which would exceed the scope of this article. Two main differences between this and prior SRS-based methods are that it involves analysis in the frequency (equivalently, wavelength) domain, in contradistinction to analysis in the intensity domain in prior methods; and it involves low-resolution measurement of what amounts to predominantly the rotational Raman spectra of N2 and O2, in contradistinction to higher-resolution measurement of the vibrational Raman spectrum of N2 only in prior methods.

Low vibration high numerical aperture automated variable temperature Raman microscope

DOE PAGES

Tian, Y.; Reijnders, A. A.; Osterhoudt, G. B.; ...

2016-04-05

Raman micro-spectroscopy is well suited for studying a variety of properties and has been applied to wide- ranging areas. Combined with tuneable temperature, Raman spectra can offer even more insights into the properties of materials. However, previous designs of variable temperature Raman microscopes have made it extremely challenging to measure samples with low signal levels due to thermal and positional instability as well as low collection efficiencies. Thus, contemporary Raman microscope has found limited applicability to probing the subtle physics involved in phase transitions and hysteresis. This paper describes a new design of a closed-cycle, Raman microscope with full polarizationmore » rotation. High collection efficiency, thermal and mechanical stability are ensured by both deliberate optical, cryogenic, and mechanical design. Measurements on two samples, Bi 2Se 3 and V 2O 3, which are known as challenging due to low thermal conductivities, low signal levels and/or hysteretic effects, are measured with previously undemonstrated temperature resolution.« less

Low vibration high numerical aperture automated variable temperature Raman microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Y.; Reijnders, A. A.; Osterhoudt, G. B.

Raman micro-spectroscopy is well suited for studying a variety of properties and has been applied to wide- ranging areas. Combined with tuneable temperature, Raman spectra can offer even more insights into the properties of materials. However, previous designs of variable temperature Raman microscopes have made it extremely challenging to measure samples with low signal levels due to thermal and positional instability as well as low collection efficiencies. Thus, contemporary Raman microscope has found limited applicability to probing the subtle physics involved in phase transitions and hysteresis. This paper describes a new design of a closed-cycle, Raman microscope with full polarizationmore » rotation. High collection efficiency, thermal and mechanical stability are ensured by both deliberate optical, cryogenic, and mechanical design. Measurements on two samples, Bi 2Se 3 and V 2O 3, which are known as challenging due to low thermal conductivities, low signal levels and/or hysteretic effects, are measured with previously undemonstrated temperature resolution.« less

Spectral and far-field broadening due to stimulated rotational Raman scattering driven by the Nike krypton fluoride laser.

PubMed

Weaver, James; Lehmberg, Robert; Obenschain, Stephen; Kehne, David; Wolford, Matthew

2017-11-01

Stimulated rotational Raman scattering (SRRS) in the ultraviolet region (λ=248  nm) has been observed at the Nike laser over extended propagation paths in air during high power operation. Although this phenomenon is not significant for standard operating configurations at Nike, broadening of the laser spectrum and far-field focal profiles has been observed once the intensity-path length product exceeds a threshold of approximately 1  TW/cm. This paper presents experimental results and a new theoretical evaluation of these effects. The observations suggest that significantly broader spectra can be achieved with modest degradation of the final focal distribution. These results point to a possible path for enhanced laser-target coupling with the reduction of laser-plasma instabilities due to broad laser bandwidth produced by the SRRS.

Near infrared Raman spectra of Rhizoma dioscoreae

NASA Astrophysics Data System (ADS)

Lin, Wenshuo; Chen, Rong; Chen, Guannan; Feng, Sangyuan; Li, Yongzeng; Huang, Zufang; Li, Yongsen

2008-03-01

A novel and compact near-infrared (NIR) Raman system is developed using 785-nm diode laser, volume-phase technology holographic system, and NIR intensified charge-coupled device (CCD). Raman spectra and first derivative spectra of Rhizoma Dioscoreae are obtained. Raman spectra of Rhizoma Dioscoreae showed three strong characteristic peaks at 477.4cm -1, 863.9cm -1, and 936.0cm -1. The major ingredients are protein, amino acid, starch, polysaccharides and so on, matched with the known basic biochemical composition of Rhizoma Dioscoreae. In the first derivative spectra of Rhizoma Dioscoreae, distinguishing characteristic peaks appeared at 467.674cm -1, 484.603cm -1, 870.37cm -1, 943.368cm -1. Contrasted with Rhizoma Dioscoreae Raman spectra, in 600cm -1 to 800cm -1, 1000cm -1 to 1400cm -1 regions, changes in Rhizoma Dioscoreae Raman first derivative spectra are represented more clearly than Rhizoma Dioscoreae Raman spectra. So Rhizoma Dioscoreae raman first derivative spectra can be an accurate supplementary analysis method to Rhizoma Dioscoreae Raman spectra.

Rovibrational states of interstitial H2 in Si

NASA Astrophysics Data System (ADS)

Koch, S.; Lavrov, E. V.; Weber, J.

2011-06-01

Rovibrational Q(J) transitions of the interstitial H2 molecule in Si have been investigated by Raman scattering in the temperature range 90-388 K. In accordance with an earlier suggestion [M. Hiller, E. V. Lavrov, and J. Weber, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.74.235214 74, 235214 (2006)], it is shown that the Q(2) transition of para hydrogen couples to the TAX phonon of Si and appears in the Raman spectra at temperatures above 200 K. The results presented also indicate that the rotational J=3 state of ortho hydrogen is resonantly coupled to the OΓ phonon.

Spectral structure of laser light scattering revisited: bandwidths of nonresonant scattering lidars.

PubMed

She, C Y

2001-09-20

It is well known that scattering lidars, i.e., Mie, aerosol-wind, Rayleigh, high-spectral-resolution, molecular-wind, rotational Raman, and vibrational Raman lidars, are workhorses for probing atmospheric properties, including the backscatter ratio, aerosol extinction coefficient, temperature, pressure, density, and winds. The spectral structure of molecular scattering (strength and bandwidth) and its constituent spectra associated with Rayleigh and vibrational Raman scattering are reviewed. Revisiting the correct name by distinguishing Cabannes scattering from Rayleigh scattering, and sharpening the definition of each scattering component in the Rayleigh scattering spectrum, the review allows a systematic, logical, and useful comparison in strength and bandwidth between each scattering component and in receiver bandwidths (for both nighttime and daytime operation) between the various scattering lidars for atmospheric sensing.

The infrared spectrum of matrix isolated hydrogen and deuterium

NASA Technical Reports Server (NTRS)

Warren, J. A.; Smith, G. R.; Guillory, W. A.

1980-01-01

The induced infrared spectra of H2 and D2, trapped in matrices of Ar, Kr, N2, CO, have been investigated. It is found that in Ar and Kr, the pure rotation spectrum is always readily observable. Portions of the fundamental region, however, are induced by impurities, while the entire spectrum is impurity induced in N2 matrices. These results are discussed in light of a recent Raman study of this system, and in comparison with several single crystal studies. Effective rotational and vibrational constants for matrix isolated H2 are also given.

Optimization of advanced Wiener estimation methods for Raman reconstruction from narrow-band measurements in the presence of fluorescence background

PubMed Central

Chen, Shuo; Ong, Yi Hong; Lin, Xiaoqian; Liu, Quan

2015-01-01

Raman spectroscopy has shown great potential in biomedical applications. However, intrinsically weak Raman signals cause slow data acquisition especially in Raman imaging. This problem can be overcome by narrow-band Raman imaging followed by spectral reconstruction. Our previous study has shown that Raman spectra free of fluorescence background can be reconstructed from narrow-band Raman measurements using traditional Wiener estimation. However, fluorescence-free Raman spectra are only available from those sophisticated Raman setups capable of fluorescence suppression. The reconstruction of Raman spectra with fluorescence background from narrow-band measurements is much more challenging due to the significant variation in fluorescence background. In this study, two advanced Wiener estimation methods, i.e. modified Wiener estimation and sequential weighted Wiener estimation, were optimized to achieve this goal. Both spontaneous Raman spectra and surface enhanced Raman spectra were evaluated. Compared with traditional Wiener estimation, two advanced methods showed significant improvement in the reconstruction of spontaneous Raman spectra. However, traditional Wiener estimation can work as effectively as the advanced methods for SERS spectra but much faster. The wise selection of these methods would enable accurate Raman reconstruction in a simple Raman setup without the function of fluorescence suppression for fast Raman imaging. PMID:26203387

Quantum Dynamics of H2 Trapped within Organic Clathrate Cages

NASA Astrophysics Data System (ADS)

Strobel, Timothy A.; Ramirez-Cuesta, Anibal J.; Daemen, Luke L.; Bhadram, Venkata S.; Jenkins, Timothy A.; Brown, Craig M.; Cheng, Yongqiang

2018-03-01

The rotational and translational dynamics of molecular hydrogen trapped within β -hydroquinone clathrate (H2 @β -HQ)—a practical example of a quantum particle trapped within an anisotropic confining potential—were investigated using inelastic neutron scattering and Raman spectroscopy. High-resolution vibrational spectra, including those collected from the VISION spectrometer at Oak Ridge National Laboratory, indicate relatively strong attractive interaction between guest and host with a strikingly large splitting of rotational energy levels compared with similar guest-host systems. Unlike related molecular systems in which confined H2 exhibits nearly free rotation, the behavior of H2 @β -HQ is explained using a two-dimensional (2D) hindered rotor model with barrier height more than 2 times the rotational constant (-16.2 meV ).

Two-dimensional H2 in Si: Raman scattering and modeling study

NASA Astrophysics Data System (ADS)

Melnikov, V. V.; Hiller, M.; Lavrov, E. V.

2018-03-01

Molecular hydrogen trapped within {111}-oriented platelets in silicon is studied by means of Raman scattering and first principles theory. The rotational transition S0(0 ) (J =0 →J =2 ) of para-H2 (nuclear spin I =0 ) at 353 cm-1 is used as a probe. We find that for temperatures below 100 K the S0(0 ) Raman line starts to broaden asymmetrically, which is interpreted as the onset of a phase transition from a state with a short-range order ("gaseous" or "liquid" phase) to a two-dimensional molecular crystal lying in the {111} plane of silicon. The shape of the S0(0 ) line at helium temperatures strongly depends on the relative content of ortho- (nuclear spin I =1 ) and para-H2 revealing the details of the intermolecular interaction. A comprehensive theoretical analysis based on ab initio calculations, molecular dynamics simulations, and rotational spectra modeling reveals that the phase transition to the crystalline state of the two-dimensional hydrogen does occur at temperatures substantially higher compared to those of bulk H2.

Line interference effects using a refined Robert-Bonamy formalism: The test case of the isotropic Raman spectra of autoperturbed N{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boulet, Christian, E-mail: Christian.boulet@u-psud.fr; Ma, Qiancheng; Thibault, Franck

A symmetrized version of the recently developed refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] is proposed. This model takes into account line coupling effects and hence allows the calculation of the off-diagonal elements of the relaxation matrix, without neglecting the rotational structure of the perturbing molecule. The formalism is applied to the isotropic Raman spectra of autoperturbed N{sub 2} for which a benchmark quantum relaxation matrix has recently been proposed. The consequences of the classical path approximation are carefully analyzed. Methods correcting for effects of inelasticity are considered. While inmore » the right direction, these corrections appear to be too crude to provide off diagonal elements which would yield, via the sum rule, diagonal elements in good agreement with the quantum results. In order to overcome this difficulty, a re-normalization procedure is applied, which ensures that the off-diagonal elements do lead to the exact quantum diagonal elements. The agreement between the (re-normalized) semi-classical and quantum relaxation matrices is excellent, at least for the Raman spectra of N{sub 2}, opening the way to the analysis of more complex molecular systems.« less

Effective Young's modulus of bacterial and microfibrillated cellulose fibrils in fibrous networks.

PubMed

Tanpichai, Supachok; Quero, Franck; Nogi, Masaya; Yano, Hiroyuki; Young, Robert J; Lindström, Tom; Sampson, William W; Eichhorn, Stephen J

2012-05-14

The deformation micromechanics of bacterial cellulose (BC) and microfibrillated cellulose (MFC) networks have been investigated using Raman spectroscopy. The Raman spectra of both BC and MFC networks exhibit a band initially located at ≈ 1095 cm(-1). We have used the intensity of this band as a function of rotation angle of the specimens to study the cellulose fibril orientation in BC and MFC networks. We have also used the change in this peak's wavenumber position with applied tensile deformation to probe the stress-transfer behavior of these cellulosic materials. The intensity of this Raman band did not change significantly with rotation angle, indicating an in-plane 2D network of fibrils with uniform random orientation; conversely, a highly oriented flax fiber exhibited a marked change in intensity with rotation angle. Experimental data and theoretical analysis shows that the Raman band shift rate arising from deformation of networks under tension is dependent on the angles between the axis of fibrils, the strain axis, the incident laser polarization direction, and the back scattered polarization configurations. From this analysis, the effective moduli of single fibrils of BC and MFC in the networks were estimated to be in the ranges of 79-88 and 29-36 GPa, respectively. It is shown also that for the model to fit the data it is necessary to use a negative Poisson's ratio for MFC networks and BC networks. Discussion of this in-plane "auxetic" behavior is given.

Contract W911NF-12-C-0102 (Advanced Diamond Technologies, Inc.)

DTIC Science & Technology

2013-06-24

resistivity, residual stress and Raman spectra measurement is finished. Raman spectra shows basically regular nanocrystalline diamond signature as expected...diamond films including thickness, resistivity, residual stress and Raman spectra measurement is finished. Raman spectra shows basically regular...15743 WF600B05 3000 0.02 0.03 0.0018 4 Fig. 2 Raman spectra (λ=532 nm) of (a) all diamond with different doping level and (b) diamond only with

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craig, Norman C.; Leyden, Matthew C.; Moore, Michael C.

Assignments of the vibrational fundamentals of cis- and trans-1,3,5-hexatriene are reevaluated with new infrared and Raman spectra and with quantum chemical predictions of intensities and anharmonic frequencies. The rotational structure is analyzed in the high-resolution (0.0013-0.0018 cm -1) infrared spectra of three C-type bands of the trans isomer and two C-type bands of the cis isomer. The bands for the trans isomer are at 1010.96 cm-1 (v14), 900.908 cm-1 (v16), and 683.46 cm-1 (v17). Ground state (GS) rotational constants have been fitted to the combined ground state combination differences (GSCDs) for the three bands of the trans isomer. The bandsmore » for the cis isomer are at 907.70 cm-1 (v33) and 587.89 cm-1 (v35). GS rotational constants have been fitted to the combined GSCDs for the two bands of the cis isomer and compared with those obtained from microwave spectroscopy. Small inertial defects in the GSs confirm that both molecules are planar. Upper state rotational constants were fitted for all five bands.« less

Phase Transition in all-trans-β-Carotene Crystal: Temperature-Dependent Raman Spectra.

PubMed

da Silva, Kleber J R; Paschoal, Waldomiro; Belo, Ezequiel A; Moreira, Sanclayton G C

2015-09-24

In this study, we studied the stability of an all-trans-β-carotene single crystal using Raman spectroscopy with line excitation at 632.8 nm, in the temperature range 20–300 K. The Raman spectra exhibit clear modifications in the spectral range of the lattice and internal vibrational modes. The temperature dependence of the most intense vibrational modes ν1 (1511 cm(–1)) and ν2 (1156 cm(–1)) that are related to the C═C and C—C stretching vibrations of the polyene chain, respectively, shows an upward shift on the Raman modes. This behavior is similar to that stated in the theoretical work of Wei-Long Liu et al. We conclude that the all-trans-β-carotene crystal undergoes a temperature-induced phase transition at approximately 219 K. This transition is interpreted as a rotation experienced by β-ring groups at each end of the all-trans-β-carotene molecule around the dihedral angle. At low temperatures, the new molecular configuration affects the sliding plane of the space group C2h(5)(P2(1)/n), and the phase transition leads to an unchanged monoclinic structure; however, the original space group is possibly lowered to the space group C2. In the temperature range 200–220 K, the spectral ratio (S) of the integrated intensities of the spectral modes around the symmetric and asymmetric stretching wavenumbers of the methyl group (CH3) changes as a function of temperature in agreement with the phase transition. Furthermore, according to phase transition undergone by the all-trans-β-carotene, the thermal results obtained by differential scanning calorimetry show an exothermic process that occurs near the transition temperature assigned by the Raman spectra.

Theoretical and experimental vibrational spectroscopy study on rotational isomer of 4-phenylbutylamine

NASA Astrophysics Data System (ADS)

Ünal, A.; Okur, M.

2017-02-01

The possible four stable rotational isomers of 4-phenylbutylamine (4PBA) molecule were experimentally and theoretically studied by vibrational spectroscopy. The FT-IR (4000-400 cm-1) and Raman (3700-60 cm-1) spectra of 4PBA were recorded at room temperature in liquid phase. The complete vibrational wavenumbers and corresponding vibrational assignments of 4PBA molecule were discussed assisted with B3LYP/6-311++G(d,p) level of theory along with scaled quantum mechanics force field (SQM-FF) method. Results from experimental and theoretical data the most stable form of 4PBA molecule was obtained.

Investigation of Skin Cancers Using MicroRaman Spectroscopy

NASA Astrophysics Data System (ADS)

Short, M. A.; Chen, X. K.; Zeng, H.; Ajlan, A. A.; McLean, D. I.; Hui, H.

2004-03-01

We have measured the Raman spectra of skin cancers, including melanoma and basal cell carcinoma, using a confocal microRaman spectrograph. In an attempt to identify the origin of the observed Raman modes, we investigated the spectra obtained from different locations of the samples, compared the observed spectra with those measured from normal human skin and pig skin, and studied the polarization dependence of the spectra. In addition, we will discuss the effects of fluorescence in the measurement of Raman spectra of skin samples.

The 1980 summer research fellowship program

NASA Technical Reports Server (NTRS)

Darden, G. C. (Compiler)

1980-01-01

The problem of incorporating visual input into robot systems is described. The photochemistry of the stratosphere, particularly possible permutations of the ozone layer, is discussed. Photoelectrochemical properties of metal thio-hypodiphosphates are investigated. Extreme eigenvalues are computed by the Lancqos approach. The rotational Raman spectra of the molecular atmosphere is studied. A computer operated mathematical symbolic manipulation system is described. Preparation of polycrystalline semiconductor electrodes of tungsten and molybdenum dichalcogenides is received.

[Ultrastructure and Raman Spectral Characteristics of Two Kinds of Acute Myeloid Leukemia Cells].

PubMed

Liang, Hao-Yue; Cheng, Xue-Lian; Dong, Shu-Xu; Zhao, Shi-Xuan; Wang, Ying; Ru, Yong-Xin

2018-02-01

To investigate the Raman spectral characteristics of leukemia cells from 4 patients with acute promyelocytic leukemia (M 3 ) and 3 patients with acute monoblastic leukemia (M 5 ), establish a novel Raman label-free method to distinguish 2 kinds of acute myeloid leukemia cells so as to provide basis for clinical research. Leukemia cells were collected from bone marrow of above-mentioned patients. Raman spectra were acquired by Horiba Xplora Raman spectrometer and Raman spectra of 30-50 cells from each patient were recorded. The diagnostic model was established according to principle component analysis (PCA), discriminant function analysis (DFA) and cluster analysis, and the spectra of leukemia cells from 7 patients were analyzed and classified. Characteristics of Raman spectra were analyzed combining with ultrastructure of leukemia cells. There were significant differences between Raman spectra of 2 kinds of leukemia cells. Compared with acute monoblastic leukemia cells, the spectra of acute promyelocytic leukemia cells showed stronger peaks in 622, 643, 757, 852, 1003, 1033, 1117, 1157, 1173, 1208, 1340, 1551, 1581 cm -1 . The diagnostic models established by PCA-DFA and cluster analysis could successfully classify these Raman spectra of different samples with a high accuracy of 100% (233/233). The model was evaluated by "Leave-one-out" cross-validation and reached a high accuracy of 97% (226/233). The level of macromolecules of M 3 cells is higher than that of M 5 . The diagnostic models established by PCA-DFA can classify these Raman spectra of different cells with a high accuracy. Raman spectra shows consistent result with ultrastructure by TEM.

Classification of the degenerative grade of lesions of supraspinatus rotator cuff tendons by FT-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Palma Fogazza, Bianca; da Silva Carvalho, Carolina; Godoy Penteado, Sergio; Meneses, Cláudio S.; Abrahão Martin, Airton; da Silva Martinho, Herculano

2007-02-01

FT-Raman spectroscopy was employed to access the biochemical alterations occurring on the degenerative process of the rotator cuff supraspinatus tendons. The spectral characteristic variations in the 351 spectra of samples of 39 patients were identified with the help of Principal Components Analysis. The main variations occurred in the 840-911; 1022- 1218; 1257; 1270; 1300; 1452; 1663; and 1751 cm -1 regions corresponding to the vibrational bands of proline, hydroxiproline, lipids, nucleic acids, carbohydrates, collagen, and elastin. These alterations are compatible with the pathology alterations reported on the literature. Scattering plots of PC 4 vs PC 2 and PC 3 vs PC 2 contrasted with histopathological analysis has enabled the spectral classification of the data into normal and degenerated groups of tendons. By depicting empiric lines the estimated sensibility and specificity were 39,6 % and 97,8 %, respectively for PC 4 vs PC 2 and 36,0 % and 100 %, respectively for PC 3 vs PC 2. These results indicate that Raman spectroscopy can be used to probe the general tendon quality and could be applied as co adjuvant element in the usual arthroscopy surgery apparatus to guide the procedure and possibly infer about the probability of rerupture.

Rotational and vibrational Raman spectroscopy for thermochemistry measurements in supersonic flames

NASA Astrophysics Data System (ADS)

Bayeh, Alexander Christian

High speed chemically reacting flows are important in a variety of aerospace applications, namely ramjets, scramjets, afterburners, and rocket exhausts. To study flame extinction under similar high Mach number conditions, we need access to thermochemistry measurements in supersonic environments. In the current work a two-stage miniaturized combustor has been designed that can produce open supersonic methane-air flames amenable to laser diagnostics. The first stage is a vitiation burner, and was inspired by well-known principles of jet combustors. We explored the salient parameters of operation experimentally, and verified flame holding computationally using a well-stirred reactor model. The second stage of the burner generates an external supersonic flame, operating in premixed and partially premixed modes. The very high Mach numbers present in the supersonic flames should provide a useful test bed for the examination of flame suppression and extinction using laser diagnostics. We also present the development of new line imaging diagnostics for thermochemistry measurements in high speed flows. A novel combination of vibrational and rotational Raman scattering is used to measure major species densities (O 2, N2, CH4, H2O,CO2, CO, & H2) and temperature. Temperature is determined by the rotational Raman technique by comparing measured rotational spectra to simulated spectra based on the measured chemical composition. Pressure is calculated from density and temperature measurements through the ideal gas law. The independent assessment of density and temperature allows for measurements in environments where the pressure is not known a priori. In the present study we applied the diagnostics to laboratory scale supersonic air and vitiation jets, and examine the feasibility of such measurements in reacting supersonic flames. Results of full thermochemistry were obtained for the air and vitiation jets that reveal the expected structure of an under-expanded jet. Centerline traces of density, temperature, and pressure of the air jet agree well with computations, while measurements of chemical composition for the vitiation flow also agree well with predicted equilibrium values. Finally, we apply the new diagnostics to the exhaust of the developed burner, and show the first ever results for density, temperature, and pressure, as well as chemical composition in a supersonic flame.

Effect on the partial least-squares prediction of yarn properties combining raman and infrared measurements and applying wavelength selection.

PubMed

de Groot, P J; Swierenga, H; Postma, G J; Melssen, W J; Buydens, L M C

2003-06-01

The combination of Raman and infrared spectroscopy on the one hand and wavelength selection on the other hand is used to improve the partial least-squares (PLS) prediction of seven selected yarn properties. These properties are important for on-line quality control during production. From 71 yarn samples, the Raman and infrared spectra are measured and reference methods are used to determine the selected properties. Making separate PLS models for all yarn properties using the Raman and infrared spectra, prior to wavelength selection, reveals that Raman spectroscopy outperforms infrared spectroscopy. If wavelength selection is applied, the PLS prediction error decreases and the correlation coefficient increases for all properties. However, a substantial wavelength selection effect is present for the infrared spectra compared to the Raman spectra. For the infrared spectra, wavelength selection results in PLS prediction errors comparable with the prediction performance of the Raman spectra prior to wavelength selection. Concatenating the Raman and infrared spectra does not enhance the PLS prediction performance, not even after wavelength selection. It is concluded that an infrared spectrometer, combined with a wavelength selection procedure, can be used if no (suitable) Raman instrument is available.

Quantitative fiber-optic Raman spectroscopy for tissue Raman measurements

NASA Astrophysics Data System (ADS)

Duraipandian, Shiyamala; Bergholt, Mads; Zheng, Wei; Huang, Zhiwei

2014-03-01

Molecular profiling of tissue using near-infrared (NIR) Raman spectroscopy has shown great promise for in vivo detection and prognostication of cancer. The Raman spectra measured from the tissue generally contain fundamental information about the absolute biomolecular concentrations in tissue and its changes associated with disease transformation. However, producing analogues tissue Raman spectra present a great technical challenge. In this preliminary study, we propose a method to ensure the reproducible tissue Raman measurements and validated with the in vivo Raman spectra (n=150) of inner lip acquired using different laser powers (i.e., 30 and 60 mW). A rapid Raman spectroscopy system coupled with a ball-lens fiber-optic Raman probe was utilized for tissue Raman measurements. The investigational results showed that the variations between the spectra measured with different laser powers are almost negligible, facilitating the quantitative analysis of tissue Raman measurements in vivo.

Optimization design of the tuning method for FBG spectroscopy based on the numerical analysis of all-fiber Raman temperature lidar

NASA Astrophysics Data System (ADS)

Wang, Li; Wang, Jun; Bao, Dong; Yang, Rong; Yan, Qing; Gao, Fei; Hua, Dengxin

2018-01-01

All fiber Raman temperature lidar for space borne platform has been proposed for profiling of the temperature with high accuracy. Fiber Bragg grating (FBG) is proposed as the spectroscopic system of Raman lidar because of good wavelength selectivity, high spectral resolution and high out-of-band rejection rate. Two sets of FBGs at visible wavelength 532 nm as Raman spectroscopy system are designed for extracting the rotational Raman spectra of atmospheric molecules, which intensities depend on the atmospheric temperature. The optimization design of the tuning method of an all-fiber rotational Raman spectroscopy system is analyzed and tested for estimating the potential temperature inversion error caused by the instability of FBG. The cantilever structure with temperature control device is designed to realize the tuning and stabilization of the central wavelengths of FBGs. According to numerical calculation of FBG and finite element analysis of the cantilever structure, the center wavelength offset of FBG is 11.03 nm/°C with the temperature change in the spectroscopy system. By experimental observation, the center wavelength offset of surface-bonded FBG is 9.80 nm/°C with temperature changing when subjected to certain strain for the high quantum number channel, while 10.01 nm/°C for the low quantum number channel. The tunable wavelength range of FBG is from 528.707 nm to 529.014 nm for the high quantum number channel and from 530.226 nm to 530.547 nm for the low quantum number channel. The temperature control accuracy of the FBG spectroscopy system is up to 0.03 °C, the corresponding potential atmospheric temperature inversion error is 0.04 K based on the numerical analysis of all-fiber Raman temperature lidar. The fine tuning and stabilization of the FBG wavelength realize the elaborate spectroscope of Raman lidar system. The conclusion is of great significance for the application of FBG spectroscopy system for space-borne platform Raman lidar.

Single Molecule Raman Spectroscopy Under High Pressure

NASA Astrophysics Data System (ADS)

Fu, Yuanxi; Dlott, Dana

2014-06-01

Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.

Resonance Raman spectra of bacteriorhodopsin's primary photoproduct: evidence for a distorted 13-cis retinal chromophore.

PubMed Central

Braiman, M; Mathies, R

1982-01-01

We have obtained the resonance Raman spectrum of bacteriorhodopsin's primary photoproduct K with a novel low-temperature spinning sample technique. Purple membrane at 77 K is illuminated with spatially separated actinic (pump) and probe laser beams. The 514-nm pump beam produces a photostationary steady-state mixture of bacteriorhodopsin and K. This mixture is then rotated through the red (676 nm) probe beam, which selectively enhances the Raman scattering from K. The essential advantage of our successive pump-and-probe technique is that it prevents the fluorescence excited by the pump beam from masking the red probe Raman scattering. K exhibits strong Raman lines at 1516, 1294, 1194, 1012, 957, and 811 cm-1. The effects of C15 deuteration on K's fingerprint lines correlate well with those seen in 13-cis model compounds, indicating that K has a 13-cis chromophore. However, the presence of unusually strong "low-wavenumber" lines at 811 and 957 cm-1, attributable to hydrogen out-of-plane wags, indicates that the protein holds the chromophore in a distorted conformation after trans leads to cis isomerization. PMID:6281770

Coherent Raman Spectra of the nu(1) Mode of 10BF3 and 11BF3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirkpatrick, Robynne; Masiello, Tony; Weber, Alfons

2006-05-01

High resolution (0.001cm-1) coherent anti-Stokes Raman spectroscopy (CARS) was used to directly examine the v1 symmetric stretching mode of the planar symmetric D3h molecules 10BF3 and 11BF3. Simulations of the spectra were done using v1 rovibrational parameters deduced from published infrared hot-band and difference-band studies and the close similarity to the observed CARS spectra confirms the validity of the infrared constants. No significant perturbations by Fermi resonance or Coriolis interactions with nearby states are observed, in marked contrast to the case of sulfur trioxide, a similar D3h molecule recently studied. In the harmonic approximation, the 10BF3 and 11BF3 v1 Q-more » branches would be identical since the isotopic substitution is at the center of mass but, interestingly, the v1 stretching frequency for 11BF3 is found to be 0.198 cm-1 higher than for the lighter 10BF3 isotopomer. This counterintuitive result is reproduced almost exactly (0.200 cm -1) by ab initio calculations (B3LYP/cc-pVTZ) that included evaluation of cubic and quartic forced constants and xij anharmonicity constants. The ab initio computations also predict to within 1% the ?B, ?C changes in the rotational constants in going from the ground state to the v1=1 vibrational level. The results illustrate nicely the complementary interplay of modern infrared, Raman, and ab initio methods in obtaining and analyzing rovibrational spectra.« less

IR and Raman spectra of nitroanthracene isomers: substitional effects based on density functional theory study.

PubMed

Alparone, Andrea; Librando, Vito

2012-04-01

Structure, IR and Raman spectra of 1-, 2- and 9-nitroanthracene isomers (1-NA, 2-NA and 9-NA) were calculated and analyzed through density functional theory computations using the B3LYP functional with the 6-311+G** basis set. Steric and π-conjugative effects determine the characteristic ONCC dihedral angles, which vary from 0° (2-NA) to 28-29° (1-NA) and 59° (9-NA), influencing the relative order of stability along the series 9-NA<1-NA<2-NA. The spectral regions at wavenumber values>3000 cm(-1) and <1000 cm(-1) little depend on the substituent position. The Raman and IR intensity values of the characteristic symmetric nitro group stretching transition, appearing between 1310 and 1345 cm(-1), are rather sensitive to the position of the substituent, decreasing regularly on passing from the planar to the NO2-rotated isomers (9-NA<1-NA<2-NA). In the medium-energy spectral region (1000-1700 cm(-1)), the number and the relative position of the strongest Raman bands are of potential utility to discriminate the NA isomers. Structural and spectroscopic results suggest that the unknown mutagenic activity of 1-NA is expected to be between that of 9-NA and 2-NA. Copyright © 2011 Elsevier B.V. All rights reserved.

Rapid acquisition of mean Raman spectra of eukaryotic cells for a robust single cell classification.

PubMed

Schie, Iwan W; Kiselev, Roman; Krafft, Christoph; Popp, Jürgen

2016-11-14

Raman spectroscopy has previously been used to identify eukaryotic and prokaryotic cells. While prokaryotic cells are small in size and can be assessed by a single Raman spectrum, the larger size of eukaryotic cells and their complex organization requires the acquisition of multiple Raman spectra to properly characterize them. A Raman spectrum from a diffraction-limited spot at an arbitrary location within a cell results in spectral variations that affect classification approaches. To probe whole cells with Raman imaging at high spatial resolution is time consuming, because a large number of Raman spectra need to be collected, resulting in low cell throughput and impairing statistical analysis due to low cell numbers. Here we propose a method to overcome the effects of cellular heterogeneity by acquiring integrated Raman spectra covering a large portion of a cell. The acquired spectrum represents the mean macromolecular composition of a cell with an exposure time that is comparable to acquisition of a single Raman spectrum. Data sets were collected from T lymphocyte Jurkat cells, and pancreatic cell lines Capan1 and MiaPaca2. Cell classification by support vector machines was compared for single spectra, spectra of images and integrated Raman spectra of cells. The integrated approach provides better and more stable prediction for individual cells, and in the current implementation, the mean macromolecular information of a cell can be acquired faster than with the acquisition of individual spectra from a comparable region. It is expected that this approach will have a major impact on the implementation of Raman based cell classification.

Excitation wavelength selection for quantitative analysis of carotenoids in tomatoes using Raman spectroscopy.

PubMed

Hara, Risa; Ishigaki, Mika; Kitahama, Yasutaka; Ozaki, Yukihiro; Genkawa, Takuma

2018-08-30

The difference in Raman spectra for different excitation wavelengths (532 nm, 785 nm, and 1064 nm) was investigated to identify an appropriate wavelength for the quantitative analysis of carotenoids in tomatoes. For the 532 nm-excited Raman spectra, the intensity of the peak assigned to the carotenoid has no correlation with carotenoid concentration, and the peak shift reflects carotenoid composition changing from lycopene to β-carotene and lutein. Thus, 532 nm-excited Raman spectra are useful for the qualitative analysis of carotenoids. For the 785 nm- and 1064 nm-excited Raman spectra, the peak intensity of the carotenoid showed good correlation with carotenoid concentration; thus, regression models for carotenoid concentration were developed using these Raman spectra and partial least squares regression. A regression model designed using the 785 nm-excited Raman spectra showed a better result than the 532 nm- and 1064 nm-excited Raman spectra. Therefore, it can be concluded that 785 nm is the most suitable excitation wavelength for the quantitative analysis of carotenoid concentration in tomatoes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Conformational analysis of a trihydroxylated derivative of cinnamic acid—a combined Raman spectroscopy and Ab initio study

NASA Astrophysics Data System (ADS)

Fiuza, S. M.; Van Besien, E.; Milhazes, N.; Borges, F.; Marques, M. P. M.

2004-05-01

A conformational analysis of 3-(3,4,5-trihydroxyphenyl)-2-propenoic acid (3,4,5-trihydroxycinnamic acid, THPPE), a trihydroxylated cinnamic acid analogous to caffeic acid (a natural compound often present in diet), was carried out by Raman spectroscopy coupled to Ab initio MO calculations. Apart from the optimised geometrical parameters for the most stable conformers of this compound, and for one of its dimeric species, the corresponding harmonic vibrational frequencies, as well as potential-energy profiles for rotation around several bonds within the molecule, were obtained. Twenty one distinct conformers were found for THPPE, the lowest energy ones—THPPE 1 and THPPE 2—displaying a completely planar geometry. The conformational preferences of this system were thus found to be mainly ruled by the stabilising effect of π-electron delocalisation. At the light of these results, a complete assignment of the corresponding solid state Raman spectra was performed.

Lif and Raman Spectroscopy in Undergraduate Labs Using Green Diode-Pumped Solid-State Lasers

NASA Astrophysics Data System (ADS)

Gray, Jeffrey A.

2015-06-01

Electronic spectroscopy of molecular iodine vapor has long been studied in undergraduate physical chemistry teaching laboratories, but the effectiveness of emission work has typically been limited by availability of instrumentation. This talk shows how to make inexpensive green diode-pumped solid-state (DPSS) lasers easily tunable for efficient, selective excitation of I2. Miniature fiber-optic spectrometers then enable rotationally resolved fluorescence spectroscopy up to v" = 42 near 900 nm with acquisition times of less than one minute. DPSS lasers are also versatile excitation sources for vibrational Raman spectroscopy, which is another common exercise that has been limited by lack of proper instrumentation in the teaching laboratory. This talk shows how to construct a simple accessory for commercial fluorimeters to record vibrational Raman spectra and depolarization ratios for CCl4 and C2Cl4 as part of a lab exercise featuring molecular symmetry.

Linear Regression Links Transcriptomic Data and Cellular Raman Spectra.

PubMed

Kobayashi-Kirschvink, Koseki J; Nakaoka, Hidenori; Oda, Arisa; Kamei, Ken-Ichiro F; Nosho, Kazuki; Fukushima, Hiroko; Kanesaki, Yu; Yajima, Shunsuke; Masaki, Haruhiko; Ohta, Kunihiro; Wakamoto, Yuichi

2018-06-08

Raman microscopy is an imaging technique that has been applied to assess molecular compositions of living cells to characterize cell types and states. However, owing to the diverse molecular species in cells and challenges of assigning peaks to specific molecules, it has not been clear how to interpret cellular Raman spectra. Here, we provide firm evidence that cellular Raman spectra and transcriptomic profiles of Schizosaccharomyces pombe and Escherichia coli can be computationally connected and thus interpreted. We find that the dimensions of high-dimensional Raman spectra and transcriptomes measured by RNA sequencing can be reduced and connected linearly through a shared low-dimensional subspace. Accordingly, we were able to predict global gene expression profiles by applying the calculated transformation matrix to Raman spectra, and vice versa. Highly expressed non-coding RNAs contributed to the Raman-transcriptome linear correspondence more significantly than mRNAs in S. pombe. This demonstration of correspondence between cellular Raman spectra and transcriptomes is a promising step toward establishing spectroscopic live-cell omics studies. Copyright © 2018 Elsevier Inc. All rights reserved.

Collisional excitation of CO by H2O - An astrophysicist's guide to obtaining rate constants from coherent anti-Stokes Raman line shape data

NASA Technical Reports Server (NTRS)

Green, Sheldon

1993-01-01

Rate constants for excitation of CO by collisions with H2O are needed to understand recent observations of comet spectra. These collision rates are closely related to spectral line shape parameters, especially those for Raman Q-branch spectra. Because such spectra have become quite important for thermometry applications, much effort has been invested in understanding this process. Although it is not generally possible to extract state-to-state rate constants directly from the data as there are too many unknowns, if the matrix of state-to-state rates can be expressed in terms of a rate-law model which depends only on rotational quantum numbers plus a few parameters, the parameters can be determined from the data; this has been done with some success for many systems, especially those relevant to combustion processes. Although such an analysis has not yet been done for CO-H2O, this system is expected to behave similarly to N2-H2O which has been well studies; modifications of parameters for the latter system are suggested which should provide a reasonable description of rate constants for the former.

Detection of explosives on the surface of banknotes by Raman hyperspectral imaging and independent component analysis.

PubMed

Almeida, Mariana R; Correa, Deleon N; Zacca, Jorge J; Logrado, Lucio Paulo Lima; Poppi, Ronei J

2015-02-20

The aim of this study was to develop a methodology using Raman hyperspectral imaging and chemometric methods for identification of pre- and post-blast explosive residues on banknote surfaces. The explosives studied were of military, commercial and propellant uses. After the acquisition of the hyperspectral imaging, independent component analysis (ICA) was applied to extract the pure spectra and the distribution of the corresponding image constituents. The performance of the methodology was evaluated by the explained variance and the lack of fit of the models, by comparing the ICA recovered spectra with the reference spectra using correlation coefficients and by the presence of rotational ambiguity in the ICA solutions. The methodology was applied to forensic samples to solve an automated teller machine explosion case. Independent component analysis proved to be a suitable method of resolving curves, achieving equivalent performance with the multivariate curve resolution with alternating least squares (MCR-ALS) method. At low concentrations, MCR-ALS presents some limitations, as it did not provide the correct solution. The detection limit of the methodology presented in this study was 50 μg cm(-2). Copyright © 2014 Elsevier B.V. All rights reserved.

Fluorescence background removal method for biological Raman spectroscopy based on empirical mode decomposition.

PubMed

Leon-Bejarano, Maritza; Dorantes-Mendez, Guadalupe; Ramirez-Elias, Miguel; Mendez, Martin O; Alba, Alfonso; Rodriguez-Leyva, Ildefonso; Jimenez, M

2016-08-01

Raman spectroscopy of biological tissue presents fluorescence background, an undesirable effect that generates false Raman intensities. This paper proposes the application of the Empirical Mode Decomposition (EMD) method to baseline correction. EMD is a suitable approach since it is an adaptive signal processing method for nonlinear and non-stationary signal analysis that does not require parameters selection such as polynomial methods. EMD performance was assessed through synthetic Raman spectra with different signal to noise ratio (SNR). The correlation coefficient between synthetic Raman spectra and the recovered one after EMD denoising was higher than 0.92. Additionally, twenty Raman spectra from skin were used to evaluate EMD performance and the results were compared with Vancouver Raman algorithm (VRA). The comparison resulted in a mean square error (MSE) of 0.001554. High correlation coefficient using synthetic spectra and low MSE in the comparison between EMD and VRA suggest that EMD could be an effective method to remove fluorescence background in biological Raman spectra.

Approximate chemical analysis of volcanic glasses using Raman spectroscopy

PubMed Central

Morgavi, Daniele; Hess, Kai‐Uwe; Neuville, Daniel R.; Borovkov, Nikita; Perugini, Diego; Dingwell, Donald B.

2015-01-01

The effect of chemical composition on the Raman spectra of a series of natural calcalkaline silicate glasses has been quantified by performing electron microprobe analyses and obtaining Raman spectra on glassy filaments (~450 µm) derived from a magma mingling experiment. The results provide a robust compositionally‐dependent database for the Raman spectra of natural silicate glasses along the calcalkaline series. An empirical model based on both the acquired Raman spectra and an ideal mixing equation between calcalkaline basaltic and rhyolitic end‐members is constructed enabling the estimation of the chemical composition and degree of polymerization of silicate glasses using Raman spectra. The model is relatively insensitive to acquisition conditions and has been validated using the MPI‐DING geochemical standard glasses1 as well as further samples. The methods and model developed here offer several advantages compared with other analytical and spectroscopic methods such as infrared spectroscopy, X‐ray fluorescence spectroscopy, electron and ion microprobe analyses, inasmuch as Raman spectroscopy can be performed with a high spatial resolution (1 µm2) without the need for any sample preparation as a nondestructive technique. This study represents an advance in efforts to provide the first database of Raman spectra for natural silicate glasses and yields a new approach for the treatment of Raman spectra, which allows us to extract approximate information about the chemical composition of natural silicate glasses using Raman spectroscopy. We anticipate its application in handheld in situ terrestrial field studies of silicate glasses under extreme conditions (e.g. extraterrestrial and submarine environments). © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd PMID:27656038

Temperature measurements in metalized propellant combustion using hybrid fs/ps coherent anti-Stokes Raman scattering.

PubMed

Kearney, Sean P; Guildenbecher, Daniel R

2016-06-20

We apply ultrafast pure-rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning, aluminized ammonium-perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laser-based diagnostics, with intense background luminosity and scattering from hot metal particles as large as several hundred micrometers in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminum-particle-seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulate-enhanced laser-induced breakdown. Introduction of femtosecond/picosecond (fs/ps) laser pulses improves CARS detection by providing time-gated elimination of strong nonresonant background interference. Single-laser-shot fs/ps CARS spectra were acquired from the burning propellant plume, with picosecond probe-pulse delays of 0 and 16 ps from the femtosecond pump and Stokes pulses. At zero delay, nonresonant background overwhelms the Raman-resonant spectroscopic features. Time-delayed probing results in the acquisition of background-free spectra that were successfully fit for temperature and relative oxygen content. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements with the CARS measurement volume positioned within 3 mm or less of the burning propellant surface. The results show that ultrafast CARS is a potentially enabling technology for probing harsh, particle-laden flame environments.

Temperature measurements in metalized propellant combustion using hybrid fs/ps coherent anti-Stokes Raman scattering

DOE PAGES

Kearney, Sean P.; Guildenbecher, Daniel R.

2016-06-20

We apply ultrafast pure-rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning, aluminized ammonium-perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laser-based diagnostics, with intense background luminosity and scattering from hot metal particles as large as several hundred micrometers in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminum-particle-seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulate-enhanced laser-induced breakdown. Introduction of femtosecond/picosecond (fs/ps)more » laser pulses improves CARS detection by providing time-gated elimination of strong nonresonant background interference. Single-laser-shot fs/ps CARS spectra were acquired from the burning propellant plume, with picosecond probe-pulse delays of 0 and 16 ps from the femtosecond pump and Stokes pulses. At zero delay, nonresonant background overwhelms the Raman-resonant spectroscopic features. Time-delayed probing results in the acquisition of background-free spectra that were successfully fit for temperature and relative oxygen content. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements with the CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Lastly, the results show that ultrafast CARS is a potentially enabling technology for probing harsh, particle-laden flame environments.« less

Temperature measurements in metalized propellant combustion using hybrid fs/ps coherent anti-Stokes Raman scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kearney, Sean P.; Guildenbecher, Daniel R.

We apply ultrafast pure-rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning, aluminized ammonium-perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laser-based diagnostics, with intense background luminosity and scattering from hot metal particles as large as several hundred micrometers in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminum-particle-seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulate-enhanced laser-induced breakdown. Introduction of femtosecond/picosecond (fs/ps)more » laser pulses improves CARS detection by providing time-gated elimination of strong nonresonant background interference. Single-laser-shot fs/ps CARS spectra were acquired from the burning propellant plume, with picosecond probe-pulse delays of 0 and 16 ps from the femtosecond pump and Stokes pulses. At zero delay, nonresonant background overwhelms the Raman-resonant spectroscopic features. Time-delayed probing results in the acquisition of background-free spectra that were successfully fit for temperature and relative oxygen content. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements with the CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Lastly, the results show that ultrafast CARS is a potentially enabling technology for probing harsh, particle-laden flame environments.« less

Theoretical studies of surface enhanced hyper-Raman spectroscopy: The chemical enhancement mechanism

NASA Astrophysics Data System (ADS)

Valley, Nicholas; Jensen, Lasse; Autschbach, Jochen; Schatz, George C.

2010-08-01

Hyper-Raman spectra for pyridine and pyridine on the surface of a tetrahedral 20 silver atom cluster are calculated using static hyperpolarizability derivatives obtained from time dependent density functional theory. The stability of the results with respect to choice of exchange-correlation functional and basis set is verified by comparison with experiment and with Raman spectra calculated for the same systems using the same methods. Calculated Raman spectra were found to match well with experiment and previous theoretical calculations. The calculated normal and surface enhanced hyper-Raman spectra closely match experimental results. The chemical enhancement factors for hyper-Raman are generally larger than for Raman (102-104 versus 101-102). Integrated hyper-Raman chemical enhancement factors are presented for a set of substituted pyridines. A two-state model is developed to predict these chemical enhancement factors and this was found to work well for the majority of the molecules considered, providing a rationalization for the difference between hyper-Raman and Raman enhancement factors.

Combined experimental and theoretical study on the Raman and Raman optical activity signatures of pentamethylundecane diastereoisomers.

PubMed

Drooghaag, Xavier; Marchand-Brynaert, Jacqueline; Champagne, Benoît; Liégeois, Vincent

2010-09-16

The synthesis and the separation of the four stereoisomers of 2,4,6,8,10-pentamethylundecane (PMU) are described together with their characterization by Raman spectroscopy. In parallel, theoretical calculations of the Raman and vibrational Raman optical activity (VROA) spectra are reported and analyzed in relation with the recorded spectra. A very good agreement is found between the experimental and theoretical spectra. The Raman spectra are also shown to be less affected by the change of configuration than the VROA spectra. Nevertheless, by studying the overlap between the theoretical Raman spectra, we show clear relationships between the spectral fingerprints and the structures displaying a mixture of the TGTGTGTG conformation of the (4R,6s,8S)-PMU (isotactic compound) with the TTTTTTTT conformation of the (4R,6r,8S)-PMU (syndiotactic compound). Then, the fingerprints of the VROA spectra of the five conformers of the (4R,8R)-PMU have been related to the fingerprints of the regular (TG)(N) isotactic compound as a function of the torsion angles. Since the (TT)(N) syndiotactic compound has no VROA signatures, the VROA spectroscopy is very sensitive to the helical structures, as demonstrated here.

A combined remote Raman and LIBS instrument for characterizing minerals with 532 nm laser excitation.

PubMed

Sharma, Shiv K; Misra, Anupam K; Lucey, Paul G; Lentz, Rachel C F

2009-08-01

The authors have developed an integrated remote Raman and laser-induced breakdown spectroscopy (LIBS) system for measuring both the Raman and LIBS spectra of minerals with a single 532 nm laser line of 35 mJ/pulse and 20 Hz. The instrument has been used for analyzing both Raman and LIBS spectra of carbonates, sulfates, hydrous and anhydrous silicates, and iron oxide minerals in air. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10x beam expander to a 529-microm diameter spot on a mineral surface located at 9 m, it is possible to measure simultaneously both the remote Raman and LIBS spectra of calcite, gypsum and olivine by adjusting the laser power electronically. The spectra of calcite, gypsum, and olivine contain fingerprint Raman lines; however, it was not possible to measure the remote Raman spectra of magnetite and hematite at 9 m because of strong absorption of 532 nm laser radiation and low intensities of Raman lines from these minerals. The remote LIBS spectra of both magnetite and hematite contain common iron emission lines but show difference in the minor amount of Li present in these two minerals. Remote Raman and LIBS spectra of a number of carbonates, sulfates, feldspars and phyllosilicates at a distance of 9 m were measured with a 532-nm laser operating at 35 mJ/pulse and by changing photon flux density at the sample by varying the spot diameter from 10 mm for Raman to 530 microm for LIBS measurements. The complementary nature of these spectra is highlighted and discussed. The combined Raman and LIBS system can also be re-configured to perform micro-Raman and micro-LIBS analyses, which have applications in trace/residue analysis and analysis of very small samples in the nano-gram range.

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for gas-phase temperature measurements

NASA Astrophysics Data System (ADS)

Miller, Joseph Daniel

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is employed for quantitative gas-phase temperature measurements in combustion processes and heated flows. In this approach, ultrafast 100-fs laser pulses are used to induce vibrational and rotational transitions in N2 and O2, while a third spectrally narrowed picosecond pulse is used to probe the molecular response. Temporal suppression of the nonresonant contribution and elimination of collisional effects are achieved by delay of the probe pulse, while sufficient spectral resolution is maintained for frequency-domain detection and thermometry. A theoretical framework is developed to model experimental spectra by phenomenologically describing the temporal evolution of the vibrational and rotational wavepackets as a function of temperature and pressure. Interference-free, single-shot vibrational fs/ps CARS thermometry is demonstrated at 1-kHz from 1400-2400 K in a H2-air flame, with accuracy better than 3%. A time-asymmetric exponential pulse shape is introduced to optimize nonresonant suppression with a 103 reduction at a probe delay of 0.31 ps. Low-temperature single-shot thermometry (300-700 K) with better than 1.5% accuracy is demonstrated using a fully degenerate rotational fs/ps CARS scheme, and the influence of collision energy transfer on thermometry error is quantified at atmospheric pressure. Interference-free thermometry, without nonresonant contributions and collision-induced error, is demonstrated for the first time using rotational fs/ps CARS at room temperature and pressures from 1-15 atm. Finally, the temporal and spectral resolution of fs/ps CARS is exploited for transition-resolved time-domain measurements of N2 and O2 self-broadened S-branch Raman linewidths at pressures of 1-20 atm.

Quick detection of traditional Chinese medicine ‘Atractylodis Macrocephalae Rhizoma’ pieces by surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Huang, Hao; Shi, Hong; Feng, Shangyuan; Lin, Juqiang; Chen, Weiwei; Yu, Yun; Lin, Duo; Xu, Qian; Chen, Rong

2013-01-01

A surface-enhanced Raman spectroscopy (SERS) method was developed for the analysis of traditional Chinese medicine ‘Atractylodis Macrocephalae Rhizoma’ pieces (AMRP) for the first time with the aim to develop a quick method for traditional Chinese medicine detection. Both Raman spectra and SERS spectra were obtained from AMRP, and tentative assignments of the Raman bands in the measured spectra suggested that only a few weak Raman peaks could be observed in the regular Raman spectra, while primary Raman peaks at around 536, 555, 619, 648, 691, 733, 790, 958, 1004, 1031, 1112, 1244, 1324, 1395, 1469, 1574 and 1632 cm-1 could be observed in the SERS spectra, with the strongest signals at 619, 733, 958, 1324, 1395 and 1469 cm-1. This was due to a strong interaction between the silver colloids and the AMRP, which led to an extraordinary enhancement in the intensity of the Raman scattering in AMRP. This exploratory study suggests the SERS technique has great potential for providing a novel non-destructive method for effectively and accurately detecting traditional Chinese medicine without complicated separation and extraction.

Gem and mineral identification using GL Gem Raman and comparison with other portable instruments

NASA Astrophysics Data System (ADS)

Culka, Adam; Hyršl, Jaroslav; Jehlička, Jan

2016-11-01

Several mainly silicate minerals in their gemstone varieties have been analysed by the Gem Raman portable system by Gemlab R&T, Vancouver, Canada, in order to ascertain the general performance of this relatively non-expensive tool developed exactly for the purpose of gemstone identification. The Raman spectra of gemstones acquired by this system have been subsequently critically compared with the data obtained by several other portable or handheld Raman instruments. The Raman spectra acquired with the Gem Raman instrument were typically of lesser quality when compared with the spectra taken by other instruments. Characteristic features such as steep baseline probably due to the fluorescence of the minerals, Raman bands much broader and therefore less resolved closely located Raman bands, and generally greater shifts of the band positions from the reference values were encountered. Some gemstone groups such as rubies did not provide useful Raman spectra at all. Nevertheless, general identification of gemstones was possible for a selection of gemstones.

The temporal evolution process from fluorescence bleaching to clean Raman spectra of single solid particles optically trapped in air

NASA Astrophysics Data System (ADS)

Gong, Zhiyong; Pan, Yong-Le; Videen, Gorden; Wang, Chuji

2017-12-01

We observe the entire temporal evolution process of fluorescence and Raman spectra of single solid particles optically trapped in air. The spectra initially contain strong fluorescence with weak Raman peaks, then the fluorescence was bleached within seconds, and finally only the clean Raman peaks remain. We construct an optical trap using two counter-propagating hollow beams, which is able to stably trap both absorbing and non-absorbing particles in air, for observing such temporal processes. This technique offers a new method to study dynamic changes in the fluorescence and Raman spectra from a single optically trapped particle in air.

Absorption and resonance Raman spectra of Pb2, Pb3, and Pb4 in xenon matrices

NASA Technical Reports Server (NTRS)

Stranz, D. D.; Khanna, R. K.

1981-01-01

Matrix isolation techniques are used to investigate the spectra of lead molecules and, in particular, to obtain resonance Raman spectra of lead vapors isolated in solid xenon matrices. The presence of Pb2 is confirmed by the visible adsorption, and Raman spectra yield a vibrational frequency for the ground state of 108 per cm and a dissociation energy of 8200 per cm. A second resonance Raman progression indicates a Pb3 species of D3h symmetry. Finally, two additional Raman features at approximately 111 per cm spacing are evidence for a third species, tentatively identified as Pb4.

Surface-enhanced Raman scattering (SERS) spectra of sodium benzoate and 4-picoline in Ag colloids prepared by γ-irradiation

NASA Astrophysics Data System (ADS)

Choi, Seong-Ho; Park, Hyun Gyu

2005-04-01

PVP-protected silver colloids were prepared by γ-irradiation and chemical reduction method. Surface-enhanced Raman scattering (SERS) spectra of sodium benzoate and 4-picoline in Ag colloids prepared by γ-irradiation were recorded. The SERS spectra of sodium benzoate were successfully recorded in Ag colloids, whereas the Raman spectra did not appear without Ag colloids. The Raman spectra of 4-picoline were not detected without Ag colloids, while the SERS spectra of 4-picoline were increased by adding Ag colloids. The carboxylate group of sodium benzoate and N donor of 4-picoline were adsorbed on the surface of Ag nanoparticles.

Chemical composition of matrix-embedded ternary II-VI nanocrystals derived from first- and second-order Raman spectra

NASA Astrophysics Data System (ADS)

Azhniuk, Yu. M.; Hutych, Yu. I.; Lopushansky, V. V.; Prymak, M. V.; Gomonnai, A. V.; Zahn, D. R. T.

2016-12-01

A one- and multiphonon Raman scattering study is performed for an extensive set of CdS1-xSex, Cd1-yZnyS, Cd1-yZnySe, and CdSe1-xTex nanocrystals to investigate the applicability of first- and second-order Raman spectra for the determination of the matrix-embedded ternary nanocrystal composition. For one-mode ternary systems both the LO and 2LO phonon frequencies in the Raman spectra are shown to be a good measure of the nanocrystal composition. For two-mode systems, the approaches based on the difference of the LO phonon frequencies (first-order Raman spectra) or double LO overtone and combination tone frequencies (second-order Raman spectra) as well as on the LO phonon band intensity ratios are analysed. The weak electron-phonon coupling in the II-VI nanocrystals and the polaron constant values for the nanocrystal sublattices are discussed.

Coherent anti-Stokes Raman scattering and spontaneous Raman scattering diagnostics of nonequilibrium plasmas and flows

NASA Astrophysics Data System (ADS)

Lempert, Walter R.; Adamovich, Igor V.

2014-10-01

The paper provides an overview of the use of coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering for diagnostics of low-temperature nonequilibrium plasmas and nonequilibrium high-enthalpy flows. A brief review of the theoretical background of CARS, four-wave mixing and Raman scattering, as well as a discussion of experimental techniques and data reduction, are included. The experimental results reviewed include measurements of vibrational level populations, rotational/translational temperature, electric fields in a quasi-steady-state and transient molecular plasmas and afterglow, in nonequilibrium expansion flows, and behind strong shock waves. Insight into the kinetics of vibrational energy transfer, energy thermalization mechanisms and dynamics of the pulse discharge development, provided by these experiments, is discussed. Availability of short pulse duration, high peak power lasers, as well as broadband dye lasers, makes possible the use of these diagnostics at relatively low pressures, potentially with a sub-nanosecond time resolution, as well as obtaining single laser shot, high signal-to-noise spectra at higher pressures. Possibilities for the development of single-shot 2D CARS imaging and spectroscopy, using picosecond and femtosecond lasers, as well as novel phase matching and detection techniques, are discussed.

Detection of munitions grade g-series nerve agents using Raman excitation at 1064 nm

NASA Astrophysics Data System (ADS)

Roy, Eric; Wilcox, Phillip G.; Hoffland, Soren; Pardoe, Ian

2015-05-01

Raman spectroscopy is a powerful tool for obtaining molecular structure information of a sample. While Raman spectroscopy is a common laboratory based analytical tool, miniaturization of opto-electronic components has allowed handheld Raman analyzers to become commercially available. These handheld systems are utilized by Military and First Responder operators tasked with rapidly identifying potentially hazardous chemicals in the field. However, one limitation of many handheld Raman detection systems is strong interference caused by fluorescence of the sample or underlying surface which obscures the characteristic Raman signature of the target analyte. Munitions grade chemical warfare agents (CWAs) are produced and stored in large batches and typically have more impurities from the storage container, degradation, or unreacted precursors. In this work, Raman spectra of munitions grade CWAs were collected using a handheld Raman spectrometer with a 1064 nm excitation laser. While Raman scattering generated by a 1064 nm laser is inherently less efficient than excitation at shorter wavelengths, high quality spectra were easily obtained due to significantly reduced fluorescence of the munitions grade CWAs. The spectra of these less pure, but more operationally relevant, munitions grade CWAs were then compared to spectra of CASARM grade CWAs, as well as Raman spectra collected using the more common 785 nm excitation laser.

Discriminating model for diagnosis of basal cell carcinoma and melanoma in vitro based on the Raman spectra of selected biochemicals

NASA Astrophysics Data System (ADS)

Silveira, Landulfo; Silveira, Fabrício Luiz; Bodanese, Benito; Zângaro, Renato Amaro; Pacheco, Marcos Tadeu T.

2012-07-01

Raman spectroscopy has been employed to identify differences in the biochemical constitution of malignant [basal cell carcinoma (BCC) and melanoma (MEL)] cells compared to normal skin tissues, with the goal of skin cancer diagnosis. We collected Raman spectra from compounds such as proteins, lipids, and nucleic acids, which are expected to be represented in human skin spectra, and developed a linear least-squares fitting model to estimate the contributions of these compounds to the tissue spectra. We used a set of 145 spectra from biopsy fragments of normal (30 spectra), BCC (96 spectra), and MEL (19 spectra) skin tissues, collected using a near-infrared Raman spectrometer (830 nm, 50 to 200 mW, and 20 s exposure time) coupled to a Raman probe. We applied the best-fitting model to the spectra of biochemicals and tissues, hypothesizing that the relative spectral contribution of each compound to the tissue Raman spectrum changes according to the disease. We verified that actin, collagen, elastin, and triolein were the most important biochemicals representing the spectral features of skin tissues. A classification model applied to the relative contribution of collagen III, elastin, and melanin using Euclidean distance as a discriminator could differentiate normal from BCC and MEL.

Time Resolved Raman and Fluorescence Spectrometer for Planetary Mineralogy

NASA Astrophysics Data System (ADS)

Blacksberg, Jordana; Rossman, George

2010-05-01

Raman spectroscopy is a prime candidate for the next generation of planetary instruments, as it addresses the primary goal of mineralogical analysis which is structure and composition. It does not require sample preparation and provides unique mineral fingerprints, even for mixed phase samples. However, large fluorescence return from many mineral samples under visible light excitation can seriously compromise the quality of the spectra or even render Raman spectra unattainable. Fluorescence interference is likely to be a problem on Mars and is evident in Raman spectra of Martian Meteorites[1]. Our approach uses time resolution for elimination of fluorescence from Raman spectra, allowing for traditional visible laser excitation (532 nm). Since Raman occurs instantaneously with the laser pulse and fluorescence lifetimes vary from nsec to msec depending on the mineral, it is possible to separate them out in time. Complementary information can also be obtained simultaneously using the time resolved fluorescence data. The Simultaneous Spectral Temporal Adaptive Raman Spectrometer (SSTARS) is a planetary instrument under development at the Jet Propulsion Laboratory, capable of time-resolved in situ Raman and fluorescence spectroscopy. A streak camera and pulsed miniature microchip laser provide psec scale time resolution. Our ability to observe the complete time evolution of Raman and fluorescence in minerals provides a foundation for design of pulsed Raman and fluorescence spectrometers in diverse planetary environments. We will discuss the SSTARS instrument design and performance capability. We will also present time-resolved pulsed Raman spectra collected from a relevant set of minerals selected using available data on Mars mineralogy[2]. Of particular interest are minerals resulting from aqueous alteration on Mars. For comparison, we will present Raman spectra obtained using a commercial continuous wave (CW) green (514 nm) Raman system. In many cases using a CW laser the strong mineral fluorescence saturates the detector and Raman spectra are unattainable. This problem is overcome by using time resolved Raman where fluorescence is eliminated. [1]Frosch et al., Anal. Chem. 2007, 79, 1101-1108 [2]Bell, J.,ed, The Martian Surface: Composition, Mineralogy, and physical Properties, Cambridge University Press, 2008

Excited-state Raman spectroscopy with and without actinic excitation: S{sub 1} Raman spectra of trans-azobenzene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobryakov, A. L.; Quick, M.; Ioffe, I. N.

We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S{sub 1} and S{sub 0} spectra of trans-azobenzene in n-hexane. The S{sub 1} spectra were also measured conventionally, upon nπ* (S{sub 0} → S{sub 1}) actinic excitation. The results are discussed and compared to earlier reports.

Application of Raman spectroscopy technology to studying Sudan I

NASA Astrophysics Data System (ADS)

Li, Gang; Zhang, Guoping; Chen, Chen

2006-06-01

Being an industrial dye, the Sudan I may have a toxic effect after oral intake on the body, and has recently been shown to cause cancer in rats, mice and rabbits. Because China and some other countries have detected the Sudan I in samples of the hot chilli powder and the chilli products, it is necessary to study the characteristics of this dye. As one kind of molecule scattering spectroscopy, Raman spectroscopy is characterized by the frequency excursion caused by interactions of molecules and photons. The frequency excursion reflects the margin between certain two vibrational or rotational energy states, and shows the information of the molecule. Because Raman spectroscopy can provides quick, easy, reproducible, and non-destructive analysis, both qualitative and quantitative, with no sample preparation required, Raman spectroscopy has been a particularly promising technique for analyzing the characteristics and structures of molecules, especially organic ones. Now, it has a broad application in biological, chemical, environmental and industrial applications. This paper firstly introduces Sudan I dye and the Raman spectroscopy technology, and then describes its application to the Sudan I. Secondly, the fingerprint spectra of the Sudan I are respectively assigned and analyzed in detail. Finally, the conclusion that the Raman spectroscopy technology is a powerful tool to determine the Sudan I is drawn.

Preliminary observations on differences in the Raman spectra of cancerous and noncancerous cells and connective tissue of human skin

NASA Astrophysics Data System (ADS)

Short, Michael A.; Lui, Harvey; McLean, David I.; Zeng, Haishan; Alajlan, Abdulmajeed; Chen, Michael X.

2005-04-01

A less invasive method of reliably detecting skin cancers is required. Raman spectroscopy is just one of several spectroscopic methods that look promising, but are not yet sufficiently reliable. More information is needed on how and why the Raman spectra of cancerous skin tissue is different from its normal counterpart. We have used confocal micro-Raman spectroscopy with a spatial resolution of about a micron to obtain spectra of unstained thin sections of human skin. We found that there were clear differences in the Raman spectra between cancerous and non-cancerous tissue both in cells and in the connective tissue. The DNA contribution to the spectra was generally stronger in malignant cells than normal ones. In regions of the dermis far away from the tumor one obtains the usual collagen spectra of normal skin, but adjacent to the tumor the spectra no longer appeared to be those of native collagen.

Sensitivity of Raman spectroscopy to normal patient variability

NASA Astrophysics Data System (ADS)

Vargis, Elizabeth; Byrd, Teresa; Logan, Quinisha; Khabele, Dineo; Mahadevan-Jansen, Anita

2011-11-01

Many groups have used Raman spectroscopy for diagnosing cervical dysplasia; however, there have been few studies looking at the effect of normal physiological variations on Raman spectra. We assess four patient variables that may affect normal Raman spectra: Race/ethnicity, body mass index (BMI), parity, and socioeconomic status. Raman spectra were acquired from a diverse population of 75 patients undergoing routine screening for cervical dysplasia. Classification of Raman spectra from patients with a normal cervix is performed using sparse multinomial logistic regression (SMLR) to determine if any of these variables has a significant effect. Results suggest that BMI and parity have the greatest impact, whereas race/ethnicity and socioeconomic status have a limited effect. Incorporating BMI and obstetric history into classification algorithms may increase sensitivity and specificity rates of disease classification using Raman spectroscopy. Studies are underway to assess the effect of these variables on disease.

Spectroscopic diagnosis of laryngeal carcinoma using near-infrared Raman spectroscopy and random recursive partitioning ensemble techniques.

PubMed

Teh, Seng Khoon; Zheng, Wei; Lau, David P; Huang, Zhiwei

2009-06-01

In this work, we evaluated the diagnostic ability of near-infrared (NIR) Raman spectroscopy associated with the ensemble recursive partitioning algorithm based on random forests for identifying cancer from normal tissue in the larynx. A rapid-acquisition NIR Raman system was utilized for tissue Raman measurements at 785 nm excitation, and 50 human laryngeal tissue specimens (20 normal; 30 malignant tumors) were used for NIR Raman studies. The random forests method was introduced to develop effective diagnostic algorithms for classification of Raman spectra of different laryngeal tissues. High-quality Raman spectra in the range of 800-1800 cm(-1) can be acquired from laryngeal tissue within 5 seconds. Raman spectra differed significantly between normal and malignant laryngeal tissues. Classification results obtained from the random forests algorithm on tissue Raman spectra yielded a diagnostic sensitivity of 88.0% and specificity of 91.4% for laryngeal malignancy identification. The random forests technique also provided variables importance that facilitates correlation of significant Raman spectral features with cancer transformation. This study shows that NIR Raman spectroscopy in conjunction with random forests algorithm has a great potential for the rapid diagnosis and detection of malignant tumors in the larynx.

Multivariate Analysis of Mixed Lipid Aggregate Phase Transitions Monitored Using Raman Spectroscopy.

PubMed

Neal, Sharon L

2018-01-01

The phase behavior of aqueous 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC)/1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) mixtures between 8.0 ℃ and 41.0 ℃ were monitored using Raman spectroscopy. Temperature-dependent Raman matrices were assembled from series of spectra and subjected to multivariate analysis. The consensus of pseudo-rank estimation results is that seven to eight components account for the temperature-dependent changes observed in the spectra. The spectra and temperature response profiles of the mixture components were resolved by applying a variant of the non-negative matrix factorization (NMF) algorithm described by Lee and Seung (1999). The rotational ambiguity of the data matrix was reduced by augmenting the original temperature-dependent spectral matrix with its cumulative counterpart, i.e., the matrix formed by successive integration of the spectra across the temperature index (columns). Successive rounds of constrained NMF were used to isolate component spectra from a significant fluorescence background. Five major components exhibiting varying degrees of gel and liquid crystalline lipid character were resolved. Hydrogen-bonded water networks exhibiting varying degrees of organization are associated with the lipid components. Spectral parameters were computed to compare the chain conformation, packing, and hydration indicated by the resolved spectra. Based on spectral features and relative amounts of the components observed, four components reflect long chain lipid response. The fifth component could reflect the response of the short chain lipid, DHPC, but there were no definitive spectral features confirming this assignment. A minor component of uncertain assignment that exhibits a striking response to the DMPC pre-transition and chain melting transition also was recovered. While none of the spectra resolved exhibit features unequivocally attributable to a specific aggregate morphology or step in the gelation process, the results are consistent with the evolution of mixed phase bicelles (nanodisks) and small amounts of worm-like DMPC/DHPC aggregates, and perhaps DHPC micelles, at low temperature to suspensions of branched and entangled worm-like aggregates above the DMPC gel phase transition and perforated multi-lamellar aggregates at high temperature.

Raman Imaging of Plant Cell Walls in Sections of Cucumis sativus

PubMed Central

Zeise, Ingrid; Heiner, Zsuzsanna; Holz, Sabine; Joester, Maike; Büttner, Carmen

2018-01-01

Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus, using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues. PMID:29370089

Raman Imaging of Plant Cell Walls in Sections of Cucumis sativus.

PubMed

Zeise, Ingrid; Heiner, Zsuzsanna; Holz, Sabine; Joester, Maike; Büttner, Carmen; Kneipp, Janina

2018-01-25

Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus , using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues.

Diagnosing basal cell carcinoma in vivo by near-infrared Raman spectroscopy: a Principal Components Analysis discrimination algorithm

NASA Astrophysics Data System (ADS)

Silveira, Landulfo, Jr.; Silveira, Fabrício L.; Bodanese, Benito; Pacheco, Marcos Tadeu T.; Zângaro, Renato A.

2012-02-01

This work demonstrated the discrimination among basal cell carcinoma (BCC) and normal human skin in vivo using near-infrared Raman spectroscopy. Spectra were obtained in the suspected lesion prior resectional surgery. After tissue withdrawn, biopsy fragments were submitted to histopathology. Spectra were also obtained in the adjacent, clinically normal skin. Raman spectra were measured using a Raman spectrometer (830 nm) with a fiber Raman probe. By comparing the mean spectra of BCC with the normal skin, it has been found important differences in the 800-1000 cm-1 and 1250-1350 cm-1 (vibrations of C-C and amide III, respectively, from lipids and proteins). A discrimination algorithm based on Principal Components Analysis and Mahalanobis distance (PCA/MD) could discriminate the spectra of both tissues with high sensitivity and specificity.

Whispering gallery modes in photoluminescence and Raman spectra of a spherical microcavity with CdTe quantum dots: anti-Stokes emission and interference effects

PubMed Central

Gaponik, Nikolai; Gerlach, Matthias; Donegan, John F; Savateeva, Diana; Rogach, Andrey L

2006-01-01

We have studied the photoluminescence and Raman spectra of a system consisting of a polystyrene latex microsphere coated by CdTe colloidal quantum dots. The cavity-induced enhancement of the Raman scattering allows the observation of Raman spectra from only a monolayer of CdTe quantum dots. Periodic structure with very narrow peaks in the photoluminescence spectra of a single microsphere was detected both in the Stokes and anti-Stokes spectral regions, arising from the coupling between the emission of quantum dots and spherical cavity modes.

Use of Raman spectroscopy in the analysis of nickel allergy

NASA Astrophysics Data System (ADS)

Alda, Javier; Castillo-Martinez, Claudio; Valdes-Rodriguez, Rodrigo; Hernández-Blanco, Diana; Moncada, Benjamin; González, Francisco J.

2013-06-01

Raman spectra of the skin of subjects with nickel allergy are analyzed and compared to the spectra of healthy subjects to detect possible biochemical differences in the structure of the skin that could help diagnose metal allergies in a noninvasive manner. Results show differences between the two groups of Raman spectra. These spectral differences can be classified using principal component analysis. Based on these findings, a novel computational technique to make a fast evaluation and classification of the Raman spectra of the skin is presented and proposed as a noninvasive technique for the detection of nickel allergy.

Polarized Raman spectra in β-Ga2O3 single crystals

NASA Astrophysics Data System (ADS)

Onuma, T.; Fujioka, S.; Yamaguchi, T.; Itoh, Y.; Higashiwaki, M.; Sasaki, K.; Masui, T.; Honda, T.

2014-09-01

Polarized Raman spectra were measured from (010) Mg-doped, (100) Si-doped, and (001) unintentionally-doped β-Ga2O3 substrates prepared by either the floating zone growth or edge-defined film-fed growth methods. The Ag and Bg Raman active modes were perfectly separated in the spectra according to the polarization selection rules. To the best of our knowledge, this is the first experimental observation of a complete set of polarized Raman spectra of β-Ga2O3. The results are ensured by the high uniformity of crystalline orientation and surface flatness of the present substrates.

NIR Raman spectroscopy in medicine and biology: results and aspects

NASA Astrophysics Data System (ADS)

Schrader, B.; Dippel, B.; Erb, I.; Keller, S.; Löchte, T.; Schulz, H.; Tatsch, E.; Wessel, S.

1999-05-01

Analyses of biomaterial by 'classical' Raman spectroscopy with excitation in the visible range has not been possible since the fluorescence of many essential constituents of all animal and plant cells and tissues overlays the Raman spectra completely. Fluorescence, however, is virtually avoided, when Raman spectra are excited with the Nd : YAG laser line at 1064 nm. Within seven dissertations we explored different fields of potential applications to medical diagnostics. Identification and qualification of tissues and cells is possible. Tumors show small but significant differences to normal tissues; in order to develop a reliable tool for tumor diagnostics more research is necessary, especially a collection of reference spectra in a data bank is needed. Raman spectra of biomineralization structures in teeth and bones show pathological tissues as well as the development of new mineralized structures. NIR Raman spectra of flowers, leaves, and fruit show, without special preparation, their constituents: alkaloids, the essential oils, natural dyes, flavors, spices and drugs. They allow application to taxonomy, optimizing plant breeding and control of food.

Development of high-resolution n(2) coherent anti-stokes Raman scattering for measuring pressure, temperature, and density in high-speed gas flows.

PubMed

Woodmansee, M A; Lucht, R P; Dutton, J C

2000-11-20

Mean and instantaneous measurements of pressure, temperature, and density have been acquired in an optically accessible gas cell and in the flow field of an underexpanded sonic jet by use of the high-resolution N(2) coherent anti-Stokes Raman scattering (CARS) technique. This nonintrusive method resolves the pressure- and temperature-sensitive rotational transitions of the nu = 0 ? 1 N(2) Q-branch to within Domega = 0.10 cm(-1). To extract thermodynamic information from the experimental spectra, theoretical spectra, generated by a N(2) spectral modeling program, are fit to the experimental spectra in a least-squares manner. In the gas cell, the CARS-measured pressures compare favorably with transducer-measured pressures. The precision and accuracy of the single-shot CARS pressure measurements increase at subatmospheric conditions. Along the centerline of the underexpanded jet, the agreement between the mean CARS P/T/rho measurements and similar quantities extracted from a Reynolds-averaged Navier-Stokes computational fluid dynamic simulation is generally excellent. This CARS technique is able to capture the low-pressure and low-temperature conditions of the M = 3.4 flow entering the Mach disk, as well as the subsonic conditions immediately downstream of this normal shock.

[Raman spectroscopy fluorescence background correction and its application in clustering analysis of medicines].

PubMed

Chen, Shan; Li, Xiao-ning; Liang, Yi-zeng; Zhang, Zhi-min; Liu, Zhao-xia; Zhang, Qi-ming; Ding, Li-xia; Ye, Fei

2010-08-01

During Raman spectroscopy analysis, the organic molecules and contaminations will obscure or swamp Raman signals. The present study starts from Raman spectra of prednisone acetate tablets and glibenclamide tables, which are acquired from the BWTek i-Raman spectrometer. The background is corrected by R package baselineWavelet. Then principle component analysis and random forests are used to perform clustering analysis. Through analyzing the Raman spectra of two medicines, the accurate and validity of this background-correction algorithm is checked and the influences of fluorescence background on Raman spectra clustering analysis is discussed. Thus, it is concluded that it is important to correct fluorescence background for further analysis, and an effective background correction solution is provided for clustering or other analysis.

Temperature dependent Raman spectroscopy of melamine and structural analogs in milk powder

USDA-ARS?s Scientific Manuscript database

Hyperspectral Raman imaging has the potential for rapid screening of solid-phase samples for potential adulterants. We found that the Raman spectra of melamine analogs changed dramatically and uniquely as a function of elevated temperature. Raman spectra were acquired for urea, biuret, cyanuric acid...

Structure, phonon properties, and order-disorder transition in the metal formate framework of [NH4][Mg(HCOO)3].

PubMed

Mączka, Mirosław; Pietraszko, Adam; Macalik, Bogusław; Hermanowicz, Krzysztof

2014-01-21

We report the synthesis, crystal structure, thermal, dielectric, IR, and Raman studies of [NH4][Mg(HCOO)3] formate. Single-crystal X-ray diffraction shows that it crystallizes in the hexagonal space group P6322, with orientationally disordered NH4(+) ions located in the cages of the network. Upon cooling, [NH4][Mg(HCOO)3] undergoes a phase transition at around 255 K to the ferroelectric P63 structure. Raman and IR spectra show a strong increase in intensity of the N-H stretching bands as well as narrowing of the bands related to the NH4(+) ions upon cooling. These changes indicate that the phase transition is due to orientational ordering of the NH4(+) ions. Analysis of the Raman data show, however, that the rotational and translational motions of NH4(+) do not freeze completely at the phase transition but exhibit further slowing down below 255 K, and the motional freezing becomes nearly complete below 140 K.

Raman microscopy of freeze-dried mouse eyeball-slice in conjunction with the "in vivo cryotechnique".

PubMed

Terada, Nobuo; Ohno, Nobuhiko; Saitoh, Sei; Fujii, Yasuhisa; Ohguro, Hiroshi; Ohno, Shinichi

2007-07-01

The wavelength of Raman-scattered light depends on the molecular composition of the substance. This is the first attempt to acquire Raman spectra of a mouse eyeball removed from a living mouse, in which the eyeball was preserved using the "in vivo cryotechnique" followed by freeze-drying. Eyeballs were cryofixed using a rapid freezing cryotechnique, and then sliced in the cryostat machine. The slices were sandwiched between glass slides, freeze-dried, and analyzed with confocal Raman microscopy. Important areas including various eyeball tissue layers were selected using bright-field microscopy, and then the Raman spectra were obtained at 240 locations. Four typical patterns of Raman spectra were electronically mapped on the specimen images obtained by the bright-field microscopy. Tissue organization was confirmed by embedding the same eyeball slice used for Raman spectra into epoxy resin and the thick sections were prepared with the inverted capsule method. Each Raman spectral pattern represents a different histological layer in the eyeball which was mapped by comparing the images of toluidine blue staining and Raman mapping with different colors. In the choroid and pigment cell layer, the Raman spectrum had two peaks, corresponding to melanin. Some of the peaks of the Raman spectra obtained from the blood vessels in sclera and the photoreceptor layer were similar to those obtained from the purified hemoglobin and rhodopsin proteins, respectively. Our experimental protocol can distinguish different tissue components with Raman microscopy; therefore, this method can be very useful for examining the distribution of a biological structures and/or chemical components in rapidly frozen freeze-dried tissue.

The Raman and SERS spectra of indigo and indigo-Ag2 complex: DFT calculation and comparison with experiment.

PubMed

Ricci, Marilena; Lofrumento, Cristiana; Becucci, Maurizio; Castellucci, Emilio M

2018-01-05

Using time-dependent density functional theory in conjunction with B3LYP functional and LANL2DZ/6-31+g(d,p) basis sets, static and pre-resonance Raman spectra of the indigo-Ag 2 complex have been calculated. Structure optimization, excitation energies and pre-resonance Raman spectra of the indigo molecule have been obtained at the same level of theory. The available experimental Raman spectra at 1064, 785 and 514nm and the SERS spectra at 785 and 514nm have been well reproduced by the calculation. Experimental SERS spectra are confronted with the calculated pre-resonance Raman spectra obtained for the indigo-Ag 2 complex. The Raman activities calculated under the infinite lifetime approximation show a strong dependence upon the proximity to the energy and the oscillator strength of the excitation electronic transition. The comparison of the integrated EFs for indigo and indigo-Ag 2 calculated Raman spectra, gave some hints as to the enhancement mechanisms acting for the different excitation wavelengths. Whereas for excitation at a wavelength corresponding to 785nm, the enhancement mechanism for the Raman spectrum of the metal complex seems the chemical one, the strong increment (ten times) of the integrated EF of the Raman spectra of the complex in the case of 514nm excitation, suggests the onset of other enhancement mechanisms. Assuming that intra-cluster transitions with high oscillator strength can be thought of as to mimic surface plasmons excitations, we suggest the onset of the electromagnetic mechanisms (EM) as the origin of the Raman spectrum enhancement. Nevertheless, other enhancement effects cannot be ruled out, as a new molecular transition gains strength in the proximity of the excitation wavelength, as a consequence of the symmetry lowering of the molecule in the complex. A large variation across vibrational modes, by a factor of at least 10 4 , was found for the EFs. This large variation in the EFs can indicate that B-term Herzberg-Teller scattering, due to metal and/or charge transfer states, can feed intensity to the inactive (in the molecule) and/or non totally symmetric modes. Copyright © 2017 Elsevier B.V. All rights reserved.

The Raman and SERS spectra of indigo and indigo-Ag2 complex: DFT calculation and comparison with experiment

NASA Astrophysics Data System (ADS)

Ricci, Marilena; Lofrumento, Cristiana; Becucci, Maurizio; Castellucci, Emilio M.

2018-01-01

Using time-dependent density functional theory in conjunction with B3LYP functional and LANL2DZ/6-31+g(d,p) basis sets, static and pre-resonance Raman spectra of the indigo-Ag2 complex have been calculated. Structure optimization, excitation energies and pre-resonance Raman spectra of the indigo molecule have been obtained at the same level of theory. The available experimental Raman spectra at 1064, 785 and 514 nm and the SERS spectra at 785 and 514 nm have been well reproduced by the calculation. Experimental SERS spectra are confronted with the calculated pre-resonance Raman spectra obtained for the indigo-Ag2 complex. The Raman activities calculated under the infinite lifetime approximation show a strong dependence upon the proximity to the energy and the oscillator strength of the excitation electronic transition. The comparison of the integrated EFs for indigo and indigo-Ag2 calculated Raman spectra, gave some hints as to the enhancement mechanisms acting for the different excitation wavelengths. Whereas for excitation at a wavelength corresponding to 785 nm, the enhancement mechanism for the Raman spectrum of the metal complex seems the chemical one, the strong increment (ten times) of the integrated EF of the Raman spectra of the complex in the case of 514 nm excitation, suggests the onset of other enhancement mechanisms. Assuming that intra-cluster transitions with high oscillator strength can be thought of as to mimic surface plasmons excitations, we suggest the onset of the electromagnetic mechanisms (EM) as the origin of the Raman spectrum enhancement. Nevertheless, other enhancement effects cannot be ruled out, as a new molecular transition gains strength in the proximity of the excitation wavelength, as a consequence of the symmetry lowering of the molecule in the complex. A large variation across vibrational modes, by a factor of at least 104, was found for the EFs. This large variation in the EFs can indicate that B-term Herzberg-Teller scattering, due to metal and/or charge transfer states, can feed intensity to the inactive (in the molecule) and/or non totally symmetric modes.

Surface-Enhanced Raman and Surface-Enhanced Hyper-Raman Scattering of Thiol-Functionalized Carotene

PubMed Central

2016-01-01

A thiol-modified carotene, 7′-apo-7′-(4-mercaptomethylphenyl)-β-carotene, was used to obtain nonresonant surface-enhanced Raman scattering (SERS) spectra of carotene at an excitation wavelength of 1064 nm, which were compared with resonant SERS spectra at an excitation wavelength of 532 nm. These spectra and surface-enhanced hyper-Raman scattering (SEHRS) spectra of the functionalized carotene were compared with the spectra of nonmodified β-carotene. Using SERS, normal Raman, and SEHRS spectra, all obtained for the resonant case, the interaction of the carotene molecules with silver nanoparticles, as well as the influence of the resonance enhancement and the SERS enhancement on the spectra, were investigated. The interaction with the silver surface occurs for both functionalized and nonfunctionalized β-carotene, but only the stronger functionalization-induced interaction enables the acquisition of nonresonant SERS spectra of β-carotene at low concentrations. The resonant SEHRS and SERS spectra are very similar. Nevertheless, the SEHRS spectra contain additional bands of infrared-active modes of carotene. Increased contributions from bands that experience low resonance enhancement point to a strong interaction between silver nanoparticles and electronic levels of the molecules, thereby giving rise to a decrease in the resonance enhancement in SERS and SEHRS. PMID:28077983

Blood analysis by Raman spectroscopy.

PubMed

Enejder, Annika M K; Koo, Tae-Woong; Oh, Jeankun; Hunter, Martin; Sasic, Slobodan; Feld, Michael S; Horowitz, Gary L

2002-11-15

Concentrations of multiple analytes were simultaneously measured in whole blood with clinical accuracy, without sample processing, using near-infrared Raman spectroscopy. Spectra were acquired with an instrument employing nonimaging optics, designed using Monte Carlo simulations of the influence of light-scattering-absorbing blood cells on the excitation and emission of Raman light in turbid medium. Raman spectra were collected from whole blood drawn from 31 individuals. Quantitative predictions of glucose, urea, total protein, albumin, triglycerides, hematocrit, and hemoglobin were made by means of partial least-squares (PLS) analysis with clinically relevant precision (r(2) values >0.93). The similarity of the features of the PLS calibration spectra to those of the respective analyte spectra illustrates that the predictions are based on molecular information carried by the Raman light. This demonstrates the feasibility of using Raman spectroscopy for quantitative measurements of biomolecular contents in highly light-scattering and absorbing media.

Raman spectra of lignin model compounds

Treesearch

Umesh P. Agarwal; Richard S. Reiner; Ashok K. Pandey; Sally A. Ralph; Kolby C. Hirth; Rajai H. Atalla

2005-01-01

To fully exploit the value of Raman spectroscopy for analyzing lignins and lignin containing materials, a detailed understanding of lignins’ Raman spectra needs to be achieved. Although advances made thus far have led to significant growth in application of Raman techniques, further developments are needed to improve upon the existing knowledge. Considering that lignin...

Computer-generated predictions of the structure and of the IR and Raman spectra of VX. Final report, May-August 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hameka, H.F.; Jensen, J.O.

1993-05-01

This report presents the computed optimized geometry and vibrational IR and Raman frequencies of the V-agent VX. The computations are performed with the Gaussian 90 Program Package using 6-31G* basis sets. We assign the vibrational frequencies and correct each frequency by multiplying it with a previously derived 6-31G* correction factor. The result is a computer-generated prediction of the IR and Raman spectra of VX. This study was intended as a blind test of the utility of IR spectral prediction. Therefore, we intentionally did not look at experimental data on the IR and Raman spectra of VX.... IR Spectra, VX, Ramanmore » spectra, Computer predictions.« less

Cancer detection based on Raman spectra super-paramagnetic clustering

NASA Astrophysics Data System (ADS)

González-Solís, José Luis; Guizar-Ruiz, Juan Ignacio; Martínez-Espinosa, Juan Carlos; Martínez-Zerega, Brenda Esmeralda; Juárez-López, Héctor Alfonso; Vargas-Rodríguez, Héctor; Gallegos-Infante, Luis Armando; González-Silva, Ricardo Armando; Espinoza-Padilla, Pedro Basilio; Palomares-Anda, Pascual

2016-08-01

The clustering of Raman spectra of serum sample is analyzed using the super-paramagnetic clustering technique based in the Potts spin model. We investigated the clustering of biochemical networks by using Raman data that define edge lengths in the network, and where the interactions are functions of the Raman spectra's individual band intensities. For this study, we used two groups of 58 and 102 control Raman spectra and the intensities of 160, 150 and 42 Raman spectra of serum samples from breast and cervical cancer and leukemia patients, respectively. The spectra were collected from patients from different hospitals from Mexico. By using super-paramagnetic clustering technique, we identified the most natural and compact clusters allowing us to discriminate the control and cancer patients. A special interest was the leukemia case where its nearly hierarchical observed structure allowed the identification of the patients's leukemia type. The goal of this study is to apply a model of statistical physics, as the super-paramagnetic, to find these natural clusters that allow us to design a cancer detection method. To the best of our knowledge, this is the first report of preliminary results evaluating the usefulness of super-paramagnetic clustering in the discipline of spectroscopy where it is used for classification of spectra.

Analytic calculations of anharmonic infrared and Raman vibrational spectra

PubMed Central

Louant, Orian; Ruud, Kenneth

2016-01-01

Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives—that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree–Fock and Kohn–Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used. PMID:26784673

In-vitro micro-Raman study of tissue samples for detecting cervical and ovarian cancer with 785-nm laser excitation

NASA Astrophysics Data System (ADS)

Sharma, S. K.; Kamemoto, L. E.; Misra, A. K.; Goodman, M. T.; Luk, H. W.; Killeen, J. L.

2010-04-01

We present results of in vitro micro-Raman spectroscopy of normal and cancerous cervical and ovarian tissues excited with 785 nm near-infrared (NIR) laser. Micro- Raman spectra of squamous cervical cells of both cervix and ovarian tissues show significant differences in the spectra of normal and cancerous cells. In particular, several well-defined Raman peaks in the 775-975 cm-1 region are observed in the spectra of normal cervix squamous cells but are completely missing in the spectra of invasive cervical cancer cells. In the high-frequency 2800-3100 cm-1 region it is shown that the peak area under CH stretching band is much lower than the corresponding area in the spectra of normal cells. In the case of ovarian tissues, the micro-Raman spectra show noticeable spectral differences between normal cells and ovarian serous cancer cells. In particular, we observed the accumulation of β-carotene in ovarian serous cancer cells compared to normal ovarian cells from women with no ovarian cancer. The NIR micro-Raman spectroscopy offers a potential molecular technique for detecting cervical and ovarian cancer from the respective tissues.

Remote Raman Spectroscopy of Minerals at Elevated Temperature Relevant to Venus Exploration

NASA Technical Reports Server (NTRS)

Sharma, Shiv K.; Misra, Anupam K.; Singh, Upendra N.

2008-01-01

We have used a remote time-resolved telescopic Raman system equipped with 532 nm pulsed laser excitation and a gated intensified CCD (ICCD) detector for measuring Raman spectra of a number of minerals at high temperature to 970 K. Remote Raman measurements were made with samples at 9-meter in side a high-temperature furnace by gating the ICCD detector with 2 micro-sec gate to minimize interference from blackbody emission from mineral surfaces at high temperature as well as interference from ambient light. A comparison of Raman spectra of gypsum (CaSO4.2H2O), dolomite (CaMg(CO3)2), and olivine (Mg2Fe2-xSiO4), as a function of temperature shows that the Raman lines remains sharp and well defined even in the high-temperature spectra. In the case of gypsum, Raman spectral fingerprints of CaSO4.H2O at 518 K were observed due to dehydration of gypsum. In the case of dolomite, partial mineral dissociation was observed at 973 K at ambient pressure indicating that some of the dolomite might survive on Venus surface that is at approximately 750 K and 92 atmospheric pressure. Time-resolved Raman spectra of low clino-enstatite (MgSiO3) measured at 75 mm from the sample in side the high-temperature furnace also show that the Raman lines remains sharp and well defined in the high temperature spectra. These high-temperature remote Raman spectra of minerals show that time-resolved Raman spectroscopy can be used as a potential tool for exploring Venus surface mineralogy at shorter (75 mm) and long (9 m) distances from the samples both during daytime and nighttime. The remote Raman system could also be used for measuring profiles of molecular species in the dense Venus atmosphere during descent as well as on the surface.

Raman Spectra of High-κ Dielectric Layers Investigated with Micro-Raman Spectroscopy Comparison with Silicon Dioxide

PubMed Central

Borowicz, P.; Taube, A.; Rzodkiewicz, W.; Latek, M.; Gierałtowska, S.

2013-01-01

Three samples with dielectric layers from high-κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high-κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above), the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide. PMID:24072982

van der Waals Heterostructures with High Accuracy Rotational Alignment.

PubMed

Kim, Kyounghwan; Yankowitz, Matthew; Fallahazad, Babak; Kang, Sangwoo; Movva, Hema C P; Huang, Shengqiang; Larentis, Stefano; Corbet, Chris M; Taniguchi, Takashi; Watanabe, Kenji; Banerjee, Sanjay K; LeRoy, Brian J; Tutuc, Emanuel

2016-03-09

We describe the realization of van der Waals (vdW) heterostructures with accurate rotational alignment of individual layer crystal axes. We illustrate the approach by demonstrating a Bernal-stacked bilayer graphene formed using successive transfers of monolayer graphene flakes. The Raman spectra of this artificial bilayer graphene possess a wide 2D band, which is best fit by four Lorentzians, consistent with Bernal stacking. Scanning tunneling microscopy reveals no moiré pattern on the artificial bilayer graphene, and tunneling spectroscopy as a function of gate voltage reveals a constant density of states, also in agreement with Bernal stacking. In addition, electron transport probed in dual-gated samples reveals a band gap opening as a function of transverse electric field. To illustrate the applicability of this technique to realize vdW heterostructuctures in which the functionality is critically dependent on rotational alignment, we demonstrate resonant tunneling double bilayer graphene heterostructures separated by hexagonal boron-nitride dielectric.

Pure-rotational H2 thermometry by ultrabroadband coherent anti-Stokes Raman spectroscopy.

PubMed

Courtney, Trevor L; Bohlin, Alexis; Patterson, Brian D; Kliewer, Christopher J

2017-06-14

Coherent anti-Stokes Raman spectroscopy (CARS) is a sensitive technique for probing highly luminous flames in combustion applications to determine temperatures and species concentrations. CARS thermometry has been demonstrated for the vibrational Q-branch and pure-rotational S-branch of several small molecules. Practical advantages of pure-rotational CARS, such as multi-species detection, reduction of coherent line mixing and collisional narrowing even at high pressures, and the potential for more precise thermometry, have motivated experimental and theoretical advances in S-branch CARS of nitrogen (N 2 ), for example, which is a dominant species in air-fed combustion processes. Although hydrogen (H 2 ) is of interest given its prevalence as a reactant and product in many gas-phase reactions, laser bandwidth limitations have precluded the extension of CARS thermometry to the H 2 S-branch. We demonstrate H 2 thermometry using hybrid femtosecond/picosecond pure-rotational CARS, in which a broadband pump/Stokes pulse enables simultaneous excitation of the set of H 2 S-branch transitions populated at flame temperatures over the spectral region of 0-2200 cm -1 . We present a pure-rotational H 2 CARS spectral model for data fitting and compare extracted temperatures to those from simultaneously collected N 2 spectra in two systems of study: a heated flow and a diffusion flame on a Wolfhard-Parker slot burner. From 300 to 650 K in the heated flow, the H 2 and N 2 CARS extracted temperatures are, on average, within 2% of the set temperature. For flame measurements, the fitted H 2 and N 2 temperatures are, on average, within 5% of each other from 300 to 1600 K. Our results confirm the viability of pure-rotational H 2 CARS thermometry for probing combustion reactions.

Pure-rotational H2 thermometry by ultrabroadband coherent anti-Stokes Raman spectroscopy

NASA Astrophysics Data System (ADS)

Courtney, Trevor L.; Bohlin, Alexis; Patterson, Brian D.; Kliewer, Christopher J.

2017-06-01

Coherent anti-Stokes Raman spectroscopy (CARS) is a sensitive technique for probing highly luminous flames in combustion applications to determine temperatures and species concentrations. CARS thermometry has been demonstrated for the vibrational Q-branch and pure-rotational S-branch of several small molecules. Practical advantages of pure-rotational CARS, such as multi-species detection, reduction of coherent line mixing and collisional narrowing even at high pressures, and the potential for more precise thermometry, have motivated experimental and theoretical advances in S-branch CARS of nitrogen (N2), for example, which is a dominant species in air-fed combustion processes. Although hydrogen (H2) is of interest given its prevalence as a reactant and product in many gas-phase reactions, laser bandwidth limitations have precluded the extension of CARS thermometry to the H2 S-branch. We demonstrate H2 thermometry using hybrid femtosecond/picosecond pure-rotational CARS, in which a broadband pump/Stokes pulse enables simultaneous excitation of the set of H2 S-branch transitions populated at flame temperatures over the spectral region of 0-2200 cm-1. We present a pure-rotational H2 CARS spectral model for data fitting and compare extracted temperatures to those from simultaneously collected N2 spectra in two systems of study: a heated flow and a diffusion flame on a Wolfhard-Parker slot burner. From 300 to 650 K in the heated flow, the H2 and N2 CARS extracted temperatures are, on average, within 2% of the set temperature. For flame measurements, the fitted H2 and N2 temperatures are, on average, within 5% of each other from 300 to 1600 K. Our results confirm the viability of pure-rotational H2 CARS thermometry for probing combustion reactions.

A review of Raman spectroscopy advances with an emphasis on clinical translation challenges in oncology

NASA Astrophysics Data System (ADS)

Jermyn, Michael; Desroches, Joannie; Aubertin, Kelly; St-Arnaud, Karl; Madore, Wendy-Julie; De Montigny, Etienne; Guiot, Marie-Christine; Trudel, Dominique; Wilson, Brian C.; Petrecca, Kevin; Leblond, Frederic

2016-12-01

There is an urgent need for improved techniques for disease detection. Optical spectroscopy and imaging technologies have potential for non- or minimally-invasive use in a wide range of clinical applications. The focus here, in vivo Raman spectroscopy (RS), measures inelastic light scattering based on interaction with the vibrational and rotational modes of common molecular bonds in cells and tissue. The Raman ‘signature’ can be used to assess physiological status and can also be altered by disease. This information can supplement existing diagnostic (e.g. radiological imaging) techniques for disease screening and diagnosis, in interventional guidance for identifying disease margins, and in monitoring treatment responses. Using fiberoptic-based light delivery and collection, RS is most easily performed on accessible tissue surfaces, either on the skin, in hollow organs or intra-operatively. The strength of RS lies in the high biochemical information content of the spectra, that characteristically show an array of very narrow peaks associated with specific chemical bonds. This results in high sensitivity and specificity, for example to distinguish malignant or premalignant from normal tissues. A critical issue is that the Raman signal is often very weak, limiting clinical use to point-by-point measurements. However, non-linear techniques using pulsed-laser sources have been developed to enable in vivo Raman imaging. Changes in Raman spectra with disease are often subtle and spectrally distributed, requiring full spectral scanning, together with the use of tissue classification algorithms that must be trained on large numbers of independent measurements. Recent advances in instrumentation and spectral analysis have substantially improved the clinical feasibility of RS, so that it is now being investigated with increased success in a wide range of cancer types and locations, as well as for non-oncological conditions. This review covers recent advances and continuing challenges, with emphasis on clinical translation.

Conformational and Structural Studies of Isopropylamine from Temperature Dependent Raman Spectra of Xenon Solutions and {AB INITIO} Calculations

NASA Astrophysics Data System (ADS)

Klaassen, Joshua J.; Darkhalil, Ikhlas D.; Durig, James R.

2012-06-01

The Raman and infrared spectra (4000 to 50 cm-1) of the gas, liquid or solution, and solid have been recorded of isopropylamine, (CH3)2CHNH2. Variable temperature (-50 to -100oC) studies of the Raman spectra (3500 to 100 cm-1) dissolved in liquid xenon have been carried out. From these data, both the {trans} and {gauche} conformers have been identified and their relative stability obtained. The enthalpy difference has been determined from 20 band pairs at 6 temperatures to be 113 +/- 11 cm-1 (1.35 +/- 0.13 kJ mol-1) with the {trans} conformer the more stable form. The percentage of the {gauche} conformer is estimated to be 54 +/- 1 percent at ambient temperature. The conformational stabilities have been predicted from {ab initio} calculations utilizing several different basis sets up to aug-cc-pVTZ from both MP2(full) and density functional theory calculations by the B3LYP method. By utilizing previously reported microwave rotational constants along with {ab initio} MP2(full)/6-311+G(d,p) predicted structural values, adjusted r0 parameters have been obtained for the {trans} conformer. The determined heavy atom and NH2 distances in angstroms are C-C = 1.530(3), C-N = 1.465(3), N-H = 1.019(3) and angles in degrees NCC = 108.9(5), CCC = 111.0(5), HNC = 110.3(5). The structural parameters for the {gauche} conformer were estimated by using the same adjustment differences to the {gauche} form as those obtained for the corresponding {trans} parameters. Vibrational assignments have been provided for the observed bands for both conformers which are supported by MP2(full)/6-31G(d) {ab initio} calculations to predict harmonic force constants, wavenumbers, infrared intensities, Raman activities and depolarization ratios for both conformers. The results are discussed and compared to the corresponding properties of some related molecules.

Raman scattering spectra of superconducting Bi2Sr2CaCu2O8 single crystals

NASA Astrophysics Data System (ADS)

Kirillov, D.; Bozovic, I.; Geballe, T. H.; Kapitulnik, A.; Mitzi, D. B.

1988-12-01

Raman spectra of Bi2Sr2CaCu2O8 single crystals with superconducting phase-transition temperature of 90 K have been studied. The spectra contained phonon lines and electronic continuum. Phonon energies and polarization selection rules were measured. A gap in the electronic continuum spectrum was observed in a superconducting state. Noticeable similarity between Raman spectra of Bi2Sr2CaCu2O8 and YBa2Cu3O7 was found.

UV Raman spectroscopy of H2-air flames excited with a narrowband KrF laser

NASA Technical Reports Server (NTRS)

Shirley, John A.

1990-01-01

Raman spectra of H2 and H2O in flames excited by a narrowband KrF excimer laser are reported. Observations are made over a porous-plug, flat-flame burner reacting H2 in air, fuel-rich with nitrogen dilution to control the temperature, and with an H2 diffusion flame. Measurements made from UV Raman spectra show good agreement with measurements made by other means, both for gas temperature and relative major species concentrations. Laser-induced fluorescence interferences arising from OH and O2 are observed in emission near the Raman spectra. These interferences do not preclude Raman measurements, however.

Raman spectroscopic studies of hydrogen clathrate hydrates.

PubMed

Strobel, Timothy A; Sloan, E Dendy; Koh, Carolyn A

2009-01-07

Raman spectroscopic measurements of simple hydrogen and tetrahydrofuran+hydrogen sII clathrate hydrates have been performed. Both the roton and vibron bands illuminate interesting quantum dynamics of enclathrated H(2) molecules. The complex vibron region of the Raman spectrum has been interpreted by observing the change in population of these bands with temperature, measuring the absolute H(2) content as a function of pressure, and with D(2) isotopic substitution. Quadruple occupancy of the large sII clathrate cavity shows the highest H(2) vibrational frequency, followed by triple and double occupancies. Singly occupied small cavities display the lowest vibrational frequency. The vibrational frequencies of H(2) within all cavity environments are redshifted from the free gas phase value. At 76 K, the progression from ortho- to para-H(2) occurs over a relatively slow time period (days). The rotational degeneracy of H(2) molecules within the clathrate cavities is lifted, observed directly in splitting of the para-H(2) roton band. Raman spectra from H(2) and D(2) hydrates suggest that the occupancy patterns between the two hydrates are analogous, increasing confidence that D(2) is a suitable substitute for H(2). The measurements suggest that Raman is an effective and convenient method to determine the relative occupancy of hydrogen molecules in different clathrate cavities.

Rovibrational hybrid fs/ps CARS using a volume Bragg grating for N₂ thermometry.

PubMed

Scherman, M; Nafa, M; Schmid, T; Godard, A; Bresson, A; Attal-Tretout, B; Joubert, P

2016-02-01

Coherent anti-Stokes Raman scattering (CARS) spectra of N2 in the hybrid femtosecond/picosecond regime have been recorded with 0.7  cm(-1) resolution. The Q-branch rovibrational structure has been resolved, making it suitable for gas-phase simultaneous rotational and vibrational thermometry applications. Resolving this spectral structure requires synchronization of a narrowband picosecond probe pulse with a broadband femtosecond pair of pump and Stokes pulses. It is achieved using a single femtosecond ytterbium-laser source and a volume Bragg grating in a compact experimental arrangement.

Laser radar studies: A study of the feasibility of remote measurement of atmospheric density and turbidity by means of rotational Raman scattering of laser light

NASA Technical Reports Server (NTRS)

Reiss, N.; Schotland, R. M.

1973-01-01

A remote sensing technique is described which utilizes elastic scattering and rotational Raman scattering of laser light in the atmosphere to obtain soundings of turbidity, transmissivity and density. A scheme is devised whereby, through selective weighting of the rotational Raman lines, the effect of atmospheric temperature structure may be eliminated. The close spectral proximity of the elastic and Raman-scattered signals, combined with the fact that the Raman scattering is quite weak, produces special requirements for the spectroscopic and light-gathering components of a rotational Raman laser radar system. These requirements are investigated. A computation of typical signal-to-noise ratios is made. It is shown that daytime signal-to-noise ratios greater than 10 db are to be expected for observation heights of 5 km and below. For nighttime work, 10 db signal-to-noise ratios are achievable to altitudes as high as 15 km.

Dual-resolution Raman spectroscopy for measurements of temperature and twelve species in hydrocarbon–air flames

DOE Office of Scientific and Technical Information (OSTI.GOV)

Magnotti, Gaetano; Barlow, Robert S.

2016-07-12

This study introduces dual-resolution Raman spectroscopy as a novel diagnostics approach for measurements of temperature and species in flames where multiple hydrocarbons are present. Simultaneous measurement of multiple hydrocarbons is challenging because their vibrational Raman spectra in the C–H stretch region are closely overlapped and are not well known over the range of temperature encountered in flames. Overlap between the hydrocarbon spectra is mitigated by adding a second spectrometer, with a higher dispersion grating, to collect the Raman spectra in the C–H stretch region. A dual-resolution Raman spectroscopy instrument has been developed and optimized for measurements of major species (Nmore » 2, O 2, H 2O, CO 2, CO, H 2, DME) and major combustion intermediates (CH 4, CH 2O, C 2H 2, C 2H 4 and C 2H 6) in DME–air flames. The temperature dependences of the hydrocarbon Raman spectra over fixed spectral regions have been determined through a series of measurements in laminar Bunsen-burner flames, and have been used to extend a library of previously acquired Raman spectra up to flame temperature. The paper presents the first Raman measurements of up to twelve species in hydrocarbon flames, and the first quantitative Raman measurements of formaldehyde in flames. Lastly, the accuracy and precision of the instrument are determined from measurements in laminar flames and the applicability of the instrument to turbulent DME–air flames is discussed.« less

Remote-Raman spectroscopic study of minerals under supercritical CO2 relevant to Venus exploration.

PubMed

Sharma, Shiv K; Misra, Anupam K; Clegg, Samuel M; Barefield, James E; Wiens, Roger C; Acosta, Tayro E; Bates, David E

2011-10-01

The authors have utilized a recently developed compact Raman spectrometer equipped with an 85 mm focal length (f/1.8) Nikon camera lens and a custom mini-ICCD detector at the University of Hawaii for measuring remote Raman spectra of minerals under supercritical CO(2) (Venus chamber, ∼102 atm pressure and 423 K) excited with a pulsed 532 nm laser beam of 6 mJ/pulse and 10 Hz. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10× beam expander to a 1mm spot on minerals located at 2m inside a Venus chamber, it is possible to measure the remote Raman spectra of anhydrous sulfates, carbonates, and silicate minerals relevant to Venus exploration during daytime or nighttime with 10s integration time. The remote Raman spectra of gypsum, anhydrite, barite, dolomite and siderite contain fingerprint Raman lines along with the Fermi resonance doublet of CO(2). Raman spectra of gypsum revealed dehydration of the mineral with time under supercritical CO(2) at 423 K. Fingerprint Raman lines of olivine, diopside, wollastonite and α-quartz can easily be identified in the spectra of these respective minerals under supercritical CO(2). The results of the present study show that time-resolved remote Raman spectroscopy with a compact Raman spectrometer of moderate resolution equipped with a gated intensified CCD detector and low power laser source could be a potential tool for exploring Venus surface mineralogy both during daytime and nighttime from a lander. Copyright © 2011 Elsevier B.V. All rights reserved.

Vibrational fingerprinting of bacterial pathogens by surface enhanced Raman scattering (SERS)

NASA Astrophysics Data System (ADS)

Premasiri, W. Ranjith; Moir, D. T.; Ziegler, Lawrence D.

2005-05-01

The surface enhanced Raman scattering (SERS) spectra of vegetative whole-cell bacteria were obtained using in-situ grown gold nanoparticle cluster-covered silicon dioxide substrates excited at 785 nm. SERS spectra of Gram-negative bacteria; E. coli and S. typhimurium, and Gram-positive bacteria; B. subtilis, B. cereus, B. thuringeinsis and B. anthracis Sterne, have been observed. Raman enhancement factors of ~104-105 per cell are found for both Gram positive and Gram negative bacteria on this novel SERS substrate. The bacterial SERS spectra are species specific and exhibit greater species differentiation and reduced spectral congestion than their corresponding non-SERS (bulk) Raman spectra. Fluorescence observed in the 785 nm excited bulk Raman emission of Bacillus species is not apparent in the corresponding SERS spectra. The surface enhancement effect allows the observation of Raman spectra at the single cell level excited by low incident laser powers (< 3 mW) and short data acquisition times (~20 sec.). Comparison with previous SERS studies suggests that these SERS vibrational signatures are sensitively dependent on the specific morphology and nature of the SERS active substrate. Exposure to biological environments, such as human blood serum, has an observable effect on the bacterial SERS spectra. However, reproducible, species specific SERS vibrational fingerprints are still obtained. The potential of SERS for detection and identification of bacteria with species specificity on these gold nanoparticle coated substrates is demonstrated by these results.

Osteoarthritis screening using Raman spectroscopy of dried human synovial fluid drops

NASA Astrophysics Data System (ADS)

Esmonde-White, Karen A.; Mandair, Gurjit S.; Esmonde-White, Francis W. L.; Raaii, Farhang; Roessler, Blake J.; Morris, Michael D.

2009-02-01

We describe the use of Raman spectroscopy to investigate synovial fluid drops deposited onto fused silica microscope slides. This spectral information can be used to identify chemical changes in synovial fluid associated with osteoarthritis (OA) damage to knee joints. The chemical composition of synovial fluid is predominately proteins (enzymes, cytokines, or collagen fragments), glycosaminoglycans, and a mixture of minor components such as inorganic phosphate crystals. During osteoarthritis, the chemical, viscoelastic and biological properties of synovial fluid are altered. A pilot study was conducted to determine if Raman spectra of synovial fluid correlated with radiological scoring of knee joint damage. After informed consent, synovial fluid was drawn and x-rays were collected from the knee joints of 40 patients. Raman spectra and microscope images were obtained from the dried synovial fluid drops using a Raman microprobe and indicate a coarse separation of synovial fluid components. Individual protein signatures could not be identified; Raman spectra were useful as a general marker of overall protein content and secondary structure. Band intensity ratios used to describe protein and glycosaminoglycan structure were used in synovial fluid spectra. Band intensity ratios of Raman spectra indicate that there is less ordered protein secondary structure in synovial fluid from the damage group. Combination of drop deposition with Raman spectroscopy is a powerful approach to examining synovial fluid for the purposes of assessing osteoarthritis damage.

Condensing Raman spectrum for single-cell phenotype analysis.

PubMed

Sun, Shiwei; Wang, Xuetao; Gao, Xin; Ren, Lihui; Su, Xiaoquan; Bu, Dongbo; Ning, Kang

2015-01-01

In recent years, high throughput and non-invasive Raman spectrometry technique has matured as an effective approach to identification of individual cells by species, even in complex, mixed populations. Raman profiling is an appealing optical microscopic method to achieve this. To fully utilize Raman proling for single-cell analysis, an extensive understanding of Raman spectra is necessary to answer questions such as which filtering methodologies are effective for pre-processing of Raman spectra, what strains can be distinguished by Raman spectra, and what features serve best as Raman-based biomarkers for single-cells, etc. In this work, we have proposed an approach called rDisc to discretize the original Raman spectrum into only a few (usually less than 20) representative peaks (Raman shifts). The approach has advantages in removing noises, and condensing the original spectrum. In particular, effective signal processing procedures were designed to eliminate noise, utilising wavelet transform denoising, baseline correction, and signal normalization. In the discretizing process, representative peaks were selected to signicantly decrease the Raman data size. More importantly, the selected peaks are chosen as suitable to serve as key biological markers to differentiate species and other cellular features. Additionally, the classication performance of discretized spectra was found to be comparable to full spectrum having more than 1000 Raman shifts. Overall, the discretized spectrum needs about 5storage space of a full spectrum and the processing speed is considerably faster. This makes rDisc clearly superior to other methods for single-cell classication.

Time-Resolved Remote-Raman Spectroscopic study of Minerals at High Temperature and under Supercritical CO2 Relevant to Venus Exploration

NASA Astrophysics Data System (ADS)

Sharma, S. K.; Misra, A. K.; Clegg, S. M.; Barefield, J. E.; Wiens, R. C.; Acosta, T.

2009-12-01

We have used a remote time-resolved (TR) telescopic Raman system equipped with 532 nm pulsed laser excitation and a gated intensified CCD (ICCD) detector for measuring Raman spectra of a number of minerals under two sets of conditions. The first set of experiments involved probing samples as a function of temperature ranging from 300 to 973 K at 1 atm. These experiments involve a 5x beam expander to focus the 532 nm (30 mJ/pulse 20 Hz) laser beams onto the sample at 9 m from the remote Raman system. The second set of experiments involved placing the samples in a high pressure vessel with a sapphire window containing supercritical CO2 at pressures up to 93 atm and 423 K. At high temperatures and ambient pressure, the remote Raman measurements were made with samples at 9 meter distance inside a high temperature furnace by gating the ICCD detector with 2 micro-s gate to minimize interference from blackbody emission from mineral surfaces at high temperature as well as interference from ambient light. A comparison of Raman spectra of gypsum (CaSO4.2H2O), dolomite (CaMg(CO3)2), and olivine (Mg2Fe2-xSiO4), as a function of temperature shows that the Raman lines remains sharp and well defined even in the high temperature spectra. In the pressure vessel, Cr3+ fluorescence from sapphire window interfere with the Raman spectra of hydrous minerals in the high-frequency region (2500-4500 cm-1). With time-resolved Raman measurements the interference of the fluorescence in the Raman spectra on minerals was minimized by gating ICCD to <100 ns. The Fermi resonance doublet of CO2 molecules consisting of Raman lines at 1285 (2ν2) and 1388 (ν1) cm-1 does not interfere with the major Raman fingerprints of silicates, carbonate, sulfates minerals. With suitable time delay of the ICCD detector, the Raman bands from supercritical CO2 atmosphere can be minimized providing pure Raman spectra of the mineral targets. We will present remote Raman data on silicates (olivine, pyroxene, quartz, feldspars and talc), dolomite, gypsum, hydrous iron sulfate and barite under supercritical CO2 environment. With TR remote Raman system using 532 nm (15 mJ/pulse, 20Hz) laser excitation, a large varieties of minerals could be easily identified from their respective Raman fingerprints typically in 1s. Minerals with low Raman cross section (e.g., feldspars, pyroxene, olivine, talc, etc) can be detected and quantified from their respective Raman spectra in 10 to 30 s. These results show that time-resolve remote Raman system is capable of making spectral measurements at several hundred to thousand target points on Venus surface within limited (a few hours) expected lifetime of a lander because of extreme temperature and pressure conditions.

Principal component analysis and analysis of variance on the effects of Entellan New on the Raman spectra of fibers.

PubMed

Yu, Marcia M L; Sandercock, P Mark L

2012-01-01

During the forensic examination of textile fibers, fibers are usually mounted on glass slides for visual inspection and identification under the microscope. One method that has the capability to accurately identify single textile fibers without subsequent demounting is Raman microspectroscopy. The effect of the mountant Entellan New on the Raman spectra of fibers was investigated to determine if it is suitable for fiber analysis. Raman spectra of synthetic fibers mounted in three different ways were collected and subjected to multivariate analysis. Principal component analysis score plots revealed that while spectra from different fiber classes formed distinct groups, fibers of the same class formed a single group regardless of the mounting method. The spectra of bare fibers and those mounted in Entellan New were found to be statistically indistinguishable by analysis of variance calculations. These results demonstrate that fibers mounted in Entellan New may be identified directly by Raman microspectroscopy without further sample preparation. © 2011 American Academy of Forensic Sciences.

An Investigation on Micro-Raman Spectra and Wavelet Data Analysis for Pemphigus Vulgaris Follow-up Monitoring.

PubMed

Camerlingo, Carlo; Zenone, Flora; Perna, Giuseppe; Capozzi, Vito; Cirillo, Nicola; Gaeta, Giovanni Maria; Lepore, Maria

2008-06-01

A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra of blood serum samples from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. Spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome problems related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. This numerical data treatment can automatically extract quantitative information from the Raman spectra and makes more reliable the data comparison. Even if an exhaustive investigation has not been done in this work, the feasibility of the follow-up monitoring of pemphigus vulgaris pathology has been clearly proved with useful implications for the clinical applications.

An Investigation on Micro-Raman Spectra and Wavelet Data Analysis for Pemphigus Vulgaris Follow-up Monitoring

PubMed Central

Camerlingo, Carlo; Zenone, Flora; Perna, Giuseppe; Capozzi, Vito; Cirillo, Nicola; Gaeta, Giovanni Maria; Lepore, Maria

2008-01-01

A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra of blood serum samples from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. Spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome problems related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. This numerical data treatment can automatically extract quantitative information from the Raman spectra and makes more reliable the data comparison. Even if an exhaustive investigation has not been done in this work, the feasibility of the follow-up monitoring of pemphigus vulgaris pathology has been clearly proved with useful implications for the clinical applications. PMID:27879899

Modulated FT- Raman Fiber-Optic Spectroscopy: A technique for Remotely Monitoring High-Temperature Reactions in Real-Time

NASA Technical Reports Server (NTRS)

Cooper, John B.; Wise, Kent L.; Jensen, Brian J.

1997-01-01

A modification to a commercial FT-Raman spectrometer is presented for the elimination of thermal backgrounds in FT-Raman spectra. The modification involves the use of a mechanical chopper to modulate the CW laser, remote collection of the signal via fiber optics, and connection of a dual-phase digital signal processor lock-in amplifier between the detector and the spectrometer's collection electronics to demodulate and filter the optical signals. The resulting modulated FT-Raman fiber-optic spectrometer is capable of completely eliminating thermal backgrounds at temperatures exceeding 370 C. In addition, the signal/noise of generated Raman spectra is greater than for spectra collected with the conventional FT-Raman under identical conditions and incident laser power. This is true for both room-temperature and hot samples. The method allows collection of data using preexisting spectrometer software. The total cost of the modification (excluding fiber optics) is approximately $3000 and requires less than 2 h to implement. This is the first report of Fr-Raman spectra collected at temperatures in excess of 300 C in the absence of thermal backgrounds.

Faraday effect on stimulated Raman scattering in the linear region

NASA Astrophysics Data System (ADS)

Liu, Z. J.; Li, B.; Xiang, J.; Cao, L. H.; Zheng, C. Y.; Hao, L.

2018-04-01

The paper presents the effect of Faraday rotation on stimulated Raman scattering (SRS). When light propagates along the magnetic field upon plasma, Faraday rotation occurs. The rotation angle can be expressed as {{d}}θ /{{d}}{s}=2.93× {10}-4B\\tfrac{{n}e/{n}c}{\\sqrt{1-{n}e/{n}c}} {cm}}-1 approximately, where θ is the rotation angle and s is distance, n e is the electron density, n c is the critical density and B is magnetic field in unit of Gauss. Both the incident light and Raman light have Faraday effects. The angle between the polarization directions of incident light and Raman light changes with position. The driven force of electron plasma wave also reduces, and then SRS scattering level is reduced. Faraday rotation effect can increase the laser intensity threshold of Raman scattering, even if the magnetic field strength is small. The circularly polarized light incident case is also compared with that of the linearly polarized light incident. The Raman scattering level of linearly polarized light is much smaller than that of circularly polarized light in the magnetized plasma. The difference between linearly and circularly polarized lights is also discussed.

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, and trimethylgermyl derivatives of 3,3-dimethylcyclopropene II. 3,3-Dimethyl-1,2-bis(trimethylsilyl)cyclopropene

NASA Astrophysics Data System (ADS)

Panchenko, Yu. N.; De Maré, G. R.; Abramenkov, A. V.; Baird, M. S.; Tverezovsky, V. V.; Nizovtsev, A. V.; Bolesov, I. G.

2003-07-01

The IR and Raman spectra of 3,3-dimethyl-1,2-bis(trimethylsilyl)cyclopropene (I) (synthesised using standard procedures) were measured in the liquid phase. Total geometry optimisation was performed at the HF/6-31G* level. The HF/6-31G*//HF/6-31G* quantum mechanical force field (QMFF) was calculated and used to determine the theoretical fundamental vibrational frequencies, their predicted IR intensities, Raman activities, and Raman depolarisation ratios. Using Pulay's scaling method and the theoretical molecular geometry, the QMFF of I was scaled by a set of scaling factors used previously for 3,3-dimethyl-1,2-bis(tert-butyl)cyclopropene (17 scale factors for a 105-dimensional problem). The scaled QMFF obtained was used to solve the vibrational problem. The quantum mechanical values of the Raman activities were converted to differential Raman cross sections. The figures for the experimental and theoretical Raman and IR spectra are presented. Assignments of the experimental vibrational spectra of I are given. They take into account the calculated potential energy distribution and the correlation between the estimations of the experimental IR and Raman intensities and Raman depolarisation ratios and the corresponding theoretical values (including Raman cross sections) calculated using the unscaled QMFF.

Raman spectroscopic analysis of Mexican natural artists' materials

NASA Astrophysics Data System (ADS)

Vandenabeele, Peter; Ortega-Avilès, Mayahuel; Castilleros, Dolores Tenorio; Moens, Luc

2007-12-01

This work represents the Raman spectra of 15 natural artists' materials that were obtained from local market in Mexico. Some of these products are not endemic to the region, but are often used in local conservation practice. Other materials are of local origin and have been used for centuries by local craftsmen. The Raman spectra that are reported here are: Chia oil, linseed oil, Campeche wax, beeswax, white copal, dammar, colophony, mastic, pixoy, chapopote, chucum, aje gum, gutta gum, peach gum and gum Arabic. The sample of pixoy was mixed with TiO 2, although it was not clear whether this was done intentionally or not. The Raman spectrum of chapopote, the local name for bitumen, contained features of carbonaceous and terpenoid matter. The Raman spectra of chapopote and chucum suffered severely from fluorescence, resulting in noisy Raman spectra. Aje gum and gutta gum are not gums, since they are resinous (terpenoid) in nature. Aje is a rare animal resin originating from Coccus axin.

Raman spectra of thiolated arsenicals with biological importance.

PubMed

Yang, Mingwei; Sun, Yuzhen; Zhang, Xiaobin; McCord, Bruce; McGoron, Anthony J; Mebel, Alexander; Cai, Yong

2018-03-01

Surface enhanced Raman scattering (SERS) has great potential as an alternative tool for arsenic speciation in biological matrices. SERS measurements have advantages over other techniques due to its ability to maintain the integrity of arsenic species and its minimal requirements for sample preparation. Up to now, very few Raman spectra of arsenic compounds have been reported. This is particularly true for thiolated arsenicals, which have recently been found to be widely present in humans. The lack of data for Raman spectra in arsenic speciation hampers the development of new tools using SERS. Herein, we report the results of a study combining the analysis of experimental Raman spectra with that obtained from density functional calculations for some important arsenic metabolites. The results were obtained with a hybrid functional B3LYP approach using different basis sets to calculate Raman spectra of the selected arsenicals. By comparing experimental and calculated spectra of dimethylarsinic acid (DMA V ), the basis set 6-311++G** was found to provide computational efficiency and precision in vibrational frequency prediction. The Raman frequencies for the rest of organoarsenicals were studied using this basis set, including monomethylarsonous acid (MMA III ), dimethylarsinous acid (DMA III ), dimethylmonothioarinic acid (DMMTA V ), dimethyldithioarsinic acid (DMDTA V ), S-(Dimethylarsenic) cysteine (DMA III (Cys)) and dimethylarsinous glutathione (DMA III GS). The results were compared with fingerprint Raman frequencies from As─O, As─C, and As─S obtained under different chemical environments. These fingerprint vibrational frequencies should prove useful in future measurements of different species of arsenic using SERS. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of nanostructured biocompatible materials for chemical and biological sensors

NASA Astrophysics Data System (ADS)

Curley, Michael; Chilvery, Ashwith K.; Kukhatreva, Tatiana; Sharma, Anup; Corda, John; Farley, Carlton

2012-10-01

This research is focused on the fabrication of thin films followed by Surface Enhanced Raman Spectroscopy (SERS) testing of these films for various applications. One technique involves the mixture of nanoparticles with twophoton material to be used as an indicator dye. Another method involved embedding silver nanoparticles in a ceramic nano-membrane. The substrates were characterized by both Atom Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). We applied the nanostructured substrate to measure the SERS spectra of 10-6 Mol/L Rhodomine 6G(Rh6G), e-coli bacteria and RDX explosive. Our results showed that silver coated ceramic membranes can serve as appropriate substrates to enhance Raman signals. In addition, we demonstrated that the in-house-made colloidal silver can work for enhancement of the Raman spectra for bacteria. We measured the Raman spectra of Rh6G molecules on a substrate absorbed by a nanofluid of silver. We observed several strong Raman bands - 613cm-1,768 cm-1,1308cm-1 1356 cm-1,1510cm-1, which correspond to Rh6G vibrational modes υ53,υ65,υ115,υ117,υ146 respectively, using a ceramic membrane coated by silver. The Raman spectra of Rh6G absorbed by silver nanofluid showed strong enhancement of Raman bands 1175cm-1 and 1529cm-1, 1590 cm-1. Those correspond to vibrational frequency modes - υ103,υ151,152. We also measured the Raman spectra of e-coli bacteria, both absorbed by silver nanofluid, and on nanostructured substrate. In addition, the Fourier Transfer Infrared Spectra (FTIR) of the bacteria was measured.

Near-field Raman spectroscopy

NASA Astrophysics Data System (ADS)

Ayars, Eric James

2000-10-01

The purpose of this research is to investigate differences observed between Raman spectra when seen through a Near-field Scanning Optical Microscope (NSOM) and spectra of the same materials in conventional Raman or micro-Raman configurations. One source of differences in the observed spectra is a strong z polarized component in the near-field radiation; observations of the magnitude of this effect are compared with theoretical predictions for the field intensity near an NSOM tip. Large electric field gradients near the sharp NSOM probe may be another source of differences. This Gradient-Field Raman (GFR) effect was observed, and there is good evidence that it plays a significant role in Surface-Enhanced Raman Spectroscopy (SERS). The NSOM data seen, however, are not sufficient to prove conclusively that the spectral variations seen are due to the field gradients.

[Micro-Raman and fluorescence spectra of several agrochemicals].

PubMed

Xiao, Yi-lin; Zhang, Peng-xiang; Qian, Xiao-fan

2004-05-01

Raman and fluorescence spectra from several agrochemicals were measured, which are sold for the use in vegetables, fruits and grains. Characteristic vibration Raman peaks from some of the agrochemicals were recorded, hence the spectra can be used for their identification. Other marketed agrochemicals demonstrated strong fluorescence under 514.5 nm excitation. It was found that the fluorescence spectra of the agrochemicals are very different. According to these results one can detect the trace amount of agrochemicals left on the surface of fruits, vegetables and grains in situ and conveniently.

[In Vivo Study of Chitin in Fungal Hyphae Based on Confocal Raman Microscopy].

PubMed

Li, Xiao-li; Luo, Liu-bin; Zhou, Bin-xiong; Hu, Xiao-qian; Sun, Chan-jun; He, Yong

2016-01-01

Chitin is an important structural polysaccharide of fungal cell wall. In this paper, aerial hyphae of Colletotrichum camelliae Massee was first studied by confocal Raman microscopy in vivo. Firstly, the optimal experimental parameters of hyphae for collecting the Raman spectra were determined, and the typical Raman spectra of hyphae, chitin standard and background were acquired. By comparing analysis, characteristic peaks of chitin were found in hyphae. Then, a region of interesting on hyphae was selected for Raman scanning. Through principal component analysis, the Raman signal of hyphae and background in the scanning area can be separated clearly. Combined with loading weight plot, two main characteristic peaks of hyphae were obtained, 1 622 cm(-1) was belong to chitin and 1 368 cm(-1) was assigned to pectic polysaccharide. Finally, two and three dimension chemical images of fungal hyphae were realized based on Raman fingerprint spectra of chitin in a nondestructive way.

Differentiating Pseudomonas sp. strain ADP cells in suspensions and biofilms using Raman spectroscopy and scanning electron microscopy.

PubMed

Henry, Victoria A; Jessop, Julie L P; Peeples, Tonya L

2017-02-01

High quality spectra of Pseudomonas sp. strain ADP in the planktonic and biofilm state were obtained using Raman microspectroscopy. These spectra enabled the identification of key differences between free and biofilm cells in the fingerprint region of Raman spectra in the nucleic acid, carbohydrate, and protein regions. Scanning electron microscopy (SEM) enabled detailed visualization of ADP biofilm with confirmation of associated extracellular matrix structure. Following extraction and Raman analysis of extracellular polymeric substances, Raman spectral differences between free and biofilm cells were largely attributed to the contribution of extracellular matrix components produced in mature biofilms. Raman spectroscopy complemented with SEM proves to be useful in distinguishing physiological properties among cells of the same species. Graphical Abstract Raman spectroscopy complemented with SEM proves to be useful in distinguishing physiological properties among cells of the same species.

Analysis of Individual Cells and Endospores by Micro-Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Esposito, Anthony; Huser, Thomas; Talley, Chad; Hollars, Christopher; Balhorn, Rod; Lane, Stephen

2003-03-01

We have collected Raman spectra of individual sperm cells by confocal micro-Raman spectroscopy. The high spatial resolution of this technique allows for compositional analysis of different sections of the sperm cells. The relative intensities of protein and DNA Raman transitions allow one to define a protein-DNA ratio. We have also collected the Raman spectra of individual bacterial endospores from four species in the genus Bacillus. The spectra were generally dominated by scattering from calcium dipicolinate, although scattering assignable to protein bands was also observed. A small fraction of the spores did not exhibit Raman scattering from CaDPA, possibly due to incomplete sporulation. These examples demonstrate the applicability of micro-Raman spectroscopy as a non-invasive method for addressing variability in the composition of cells.* *This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract number W-7405-Eng-48.

Dental caries detection by optical spectroscopy: a polarized Raman approach with fibre-optic coupling

NASA Astrophysics Data System (ADS)

Ko, A. C.-T.; Choo-Smith, L.-P.; Werner, J.; Hewko, M.; Sowa, M. G.; Dong, C.; Cleghorn, B.

2006-09-01

Incipient dental caries lesions appear as white spots on the tooth surface; however, accurate detection of early approximal lesions is difficult due to limited sensitivity of dental radiography and other traditional diagnostic tools. A new fibre-optic coupled spectroscopic method based on polarized Raman spectroscopy (P-RS) with near-IR laser excitation is introduced which provides contrast for detecting and characterizing incipient caries. Changes in polarized Raman spectra are observed in PO 4 3- vibrations arising from hydroxyapatite of mineralized tooth tissue. Demineralization-induced morphological/orientational alteration of enamel crystallites is believed to be responsible for the reduction of Raman polarization anisotropy observed in the polarized Raman spectra of caries lesions. Supporting evidence obtained by polarized Raman spectral imaging is presented. A specially designed fibre-optic coupled setup for simultaneous measurement of parallel- and cross-polarized tooth Raman spectra is demonstrated in this study.

Infrared and Raman spectra of N-acetyl- L-amino acid methylamides with aromatic side groups

NASA Astrophysics Data System (ADS)

Matsuura, Hiroatsu; Hasegawa, Kodo; Miyazawa, Tatsuo

Infrared and Raman spectra of N-acetyl- L-phenylalanine methylamide, N-acetyl- L-tyrosine methylamide and N-acetyl- L-tryptophan methylamide, as model compounds of aromatic amino acid residues in proteins, were measured in the solid state and in methanol solutions. Vibrational assignments of the spectra were made by utilizing the deuteration effect and by comparison with the spectra of related compounds which include toluene, p-cresol and 3-methylindole. The amide I, III and IV bands were strong in Raman scattering, but other characteristic amide bands were ill-defined. In the Raman spectra of methanol solutions, only the bands due to the aromatic side group vibrations were markedly observed, but those due to the peptide backbone vibrations were very weak, suggesting the coexistence of various molecular conformations in solution.

Rotational isomers of N-(β-phenylpropionyl)alanine ethyl dithioester: a Raman spectroscopic and MO study

NASA Astrophysics Data System (ADS)

Fausto, R.; Teixeira-Dias, J. J. C.; Tonge, P. J.; Carey, P. R.

1994-07-01

Raman spectra of N-(β-phenylpropionyl)alanine ethyl dithioester (C 6H 5CH 2CH 2C(O)NHCH(CH 3)C(S)SC 2H 5) in CCl 4 and CH 3CN solutions were measured as a function of temperature and the enthalpy differences (Δ H) between rotational isomers differing by internal rotation around the NHCH(CH 3) and CH(CH 3)C(S) bonds (forms A, B and C 5) were evaluated from relative band intensities. The spectroscopic results are consistent with a greater thermodynamical stability of the B-type conformer, where the N and S (thiol) atoms are in close contact. In addition, a comparison of the measured Δ H(A-B) for the present molecules with previously reported values for a series of similar glycine-based ethyl dithioesters shows that the presence of the extra CH 3 group at the α-carbon atom leads to a stabilization of the B-type conformer relative to the A-type form in the alanine-based dithioester. Semiempirical AM1 molecular orbital calculations were also performed on the title molecule and on its glycine analogue, N(β-phenylpropionyl)glycine ethyl dithioester. In general terms, the results of these calculations agree with the experimental findings, thus providing good theoretical support for the experimental data.

In-situ detection of drugs-of-abuse on clothing using confocal Raman microscopy.

PubMed

Ali, Esam M A; Edwards, Howell G M; Hargreaves, Michael D; Scowen, Ian J

2008-05-12

This study describes the application of confocal Raman microscopy to the detection and identification of drugs-of-abuse in situ on undyed natural synthetic fibres, and coloured textile specimens. Raman spectra were obtained from drug particles trapped between the fibres of the specimens. Pure samples of cocaine hydrochloride and N-methyl-3,4-methylenedioxy-amphetamine HCl (MDMA-HCl) were used in this study. Raman spectra were collected from drug particles of an average size in the range 5-15 microm. Despite the presence of spectral bands arising from the natural and synthetic polymer and dyed textiles, the drugs could be identified by their characteristic Raman bands. If necessary, interfering bands could be successfully removed by spectral subtraction. Furthermore, Raman spectra were recorded from drug particles trapped between the fibres of highly fluorescent specimens. Interference from the fibres, including background fluorescence, was overcome by careful focusing of the confocal beam and the resulting spectra allow ready differentiation from interference from the fibres substrate bands. Spectra of several drugs-of-abuse on dyed and undyed clothing substrates were readily obtained within 3 min with little or no sample preparation and with no alteration of the evidential material.

Analytic calculations of hyper-Raman spectra from density functional theory hyperpolarizability gradients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ringholm, Magnus; Ruud, Kenneth; Bast, Radovan

We present the first analytic calculations of the geometrical gradients of the first hyperpolarizability tensors at the density-functional theory (DFT) level. We use the analytically calculated hyperpolarizability gradients to explore the importance of electron correlation effects, as described by DFT, on hyper-Raman spectra. In particular, we calculate the hyper-Raman spectra of the all-trans and 11-cis isomers of retinal at the Hartree-Fock (HF) and density-functional levels of theory, also allowing us to explore the sensitivity of the hyper-Raman spectra on the geometrical characteristics of these structurally related molecules. We show that the HF results, using B3LYP-calculated vibrational frequencies and force fields,more » reproduce the experimental data for all-trans-retinal well, and that electron correlation effects are of minor importance for the hyper-Raman intensities.« less

Analysis of disulphide bonds found in human hair by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Pina-Ruiz, A. L.; Cordova-Fraga, T.; Plascencia-Castro, A. S.; Hernandez-Rayas, A.; Ruvalcaba, J. M.

2017-04-01

Raman spectroscopy offers information-rich spectra, making it a technique easy to use in areas such as biology, chemistry, and in the field. Human hair spectra has been recorded obtaining interesting information about its composition. Correlating information obtained from these spectra to bone health and determining if Raman spectroscopy could be used as a diagnostic tool of bone health is proposed. Spectra from healthy women were compared to the spectra of women who have suffered a bone fracture, all which were aged 39-60. This technique has potential to become a regular diagnostic tool and further investigation to improve and validate this method are needed.

Efficient "on-the-fly" calculation of Raman spectra from ab-initio molecular dynamics: Application to hydrophobic/hydrophilic solutes in bulk water.

PubMed

Partovi-Azar, Pouya; Kühne, Thomas D

2015-11-05

We present a novel computational method to accurately calculate Raman spectra from first principles. Together with an extension of the second-generation Car-Parrinello method of Kühne et al. (Phys. Rev. Lett. 2007, 98, 066401) to propagate maximally localized Wannier functions together with the nuclei, a speed-up of one order of magnitude can be observed. This scheme thus allows to routinely calculate finite-temperature Raman spectra "on-the-fly" by means of ab-initio molecular dynamics simulations. To demonstrate the predictive power of this approach we investigate the effect of hydrophobic and hydrophilic solutes in water solution on the infrared and Raman spectra. © 2015 Wiley Periodicals, Inc.

Structural and interfacial defects in c-axis oriented LiNbO3 thin films grown by pulsed laser deposition on Si using Al : ZnO conducting layer

NASA Astrophysics Data System (ADS)

Shandilya, Swati; Tomar, Monika; Sreenivas, K.; Gupta, Vinay

2009-05-01

Highly c-axis oriented LiNbO3 films are deposited using pulsed laser deposition on a silicon substrate using a transparent conducting Al doped ZnO layer. X-ray diffraction and Raman spectroscopic analysis show the fabrication of single phase and oriented LiNbO3 films under the optimized deposition condition. An extra peak at 905 cm-1 was observed in the Raman spectra of LiNbO3 film deposited at higher substrate temperature and higher oxygen pressure, and attributed to the presence of niobium antisite defects in the lattice. Dielectric constant and ac conductivity of oriented LiNbO3 films deposited under the static and rotating substrate modes have been studied. Films deposited under the rotating substrate mode exhibit dielectric properties close to the LiNbO3 single crystal. The cause of deviation in the dielectric properties of the film deposited under the static substrate mode, in comparison with the bulk, are discussed in the light of the possible formation of an interdiffusion layer at the interface of the LiNbO3 film and the Al : ZnO layer.

Raman microspectroscopy of optically trapped micro- and nanoobjects

NASA Astrophysics Data System (ADS)

Jonáš, Alexandr; Ježek, Jan; Šerý, Mojmír; Zemánek, Pavel

2008-12-01

We describe and characterize an experimental system for Raman microspectroscopy of micro- and nanoobjects optically trapped in aqueous suspensions with the use of a single-beam gradient optical trap (Raman tweezers). This system features two separate lasers providing light for the optical trapping and excitation of the Raman scattering spectra from the trapped specimen, respectively. Using independent laser beams for trapping and spectroscopy enables optimizing the parameters of both beams for their respective purposes. Moreover, it is possible to modulate the position of the trapped object relative to the Raman beam focus for maximizing the detected Raman signal and obtaining spatially resolved images of the trapped specimen. Using this experimental system, we have obtained Raman scattering spectra of individual optically confined micron and sub-micron sized polystyrene beads and baker's yeast cells. Sufficiently high signal-to-noise ratio of the spectra could be achieved using a few tens of milliwatts of the Raman beam power and detector integration times on the order of seconds.

Analysis of root surface properties by fluorescence/Raman intensity ratio.

PubMed

Nakamura, Shino; Ando, Masahiro; Hamaguchi, Hiro-O; Yamamoto, Matsuo

2017-11-01

The aim of this study is to evaluate the existence of residual calculus on root surfaces by determining the fluorescence/Raman intensity ratio. Thirty-two extracted human teeth, partially covered with calculus on the root surface, were evaluated by using a portable Raman spectrophotometer, and a 785-nm, 100-mW laser was applied for fluorescence/Raman excitation. The collected spectra were normalized to the hydroxyapatite Raman band intensity at 960 cm -1 . Raman spectra were recorded from the same point after changing the focal distance of the laser and the target radiating angle. In seven teeth, the condition of calculus, cementum, and dentin were evaluated. In 25 teeth, we determined the fluorescence/Raman intensity ratio following three strokes of debridement. Raman spectra collected from the dentin, cementum, and calculus were different. After normalization, spectra values were constant. The fluorescence/Raman intensity ratio of calculus region showed significant differences compared to the cementum and dentin (p < 0.05). The fluorescence/Raman intensity ratio decreased with calculus debridement. For this analysis, the delta value was defined as the difference between the values before and after three strokes, with the final 2 delta values close to zero, indicating a gradual asymptotic curve and the change in intensity ratio approximating that of individual constants. Fluorescence/Raman intensity ratio was effectively used to cancel the angle- and distance-dependent fluctuations of fluorescence collection efficiency during measurement. Changes in the fluorescence/Raman intensity ratio near zero suggested that cementum or dentin was exposed, and calculus removed.

Detection of molecular changes induced by antibiotics in Escherichia coli using vibrational spectroscopy

NASA Astrophysics Data System (ADS)

Xuan Nguyen, N. T.; Sarter, Samira; Hai Nguyen, N.; Daniel, Philippe

2017-08-01

This study aimed to test Raman (400-1800 cm- 1) and Infra-red (1900-500 cm- 1) spectroscopies followed by statistical analysis (principal component analysis) to detect molecular changes induced by antibiotics (ampicillin, cefotaxime - cell wall synthesis inhibitors, tetracycline - protein synthesis inhibitor, ciprofloxacin - DNA synthesis inhibitor) against Escherichia coli TOP10. In case of ampicillin and cefotaxime, a decrease in protein bands in both Raman (1240, 1660 cm- 1), and IR spectra (1230, 1530, 1630 cm- 1), and an increase in carbohydrate bands (1150, 1020 cm- 1) in IR spectra were observed. Tetracycline addition caused an increase in nucleic acid bands (775, 1478, 1578 cm- 1), a sharp decrease in phenylalanine (995 cm- 1) in Raman spectra and the amide I and amide II bands (1630, 1530 cm- 1) in IR spectra, an increase in DNA in both Raman (1083 cm- 1) and IR spectra (1080 cm- 1). Regarding ciprofloxacin, an increase in nucleic acids (775, 1478, 1578 cm- 1) in Raman spectra and in protein bands (1230, 1520, 1630 cm- 1), in DNA (1080 cm- 1) in IR spectra were detected. Clear discrimination of antibiotic-treated samples compared to the control was recorded, showing that Raman and IR spectroscopies, coupled to principal component analysis for data, could be used to detect molecular modifications in bacteria exposed to different classes of antibiotics. These findings contribute to the understanding of the mechanisms of action of antibiotics in bacteria.

Assessment of Cell Line Models of Primary Human Cells by Raman Spectral Phenotyping

PubMed Central

Swain, Robin J.; Kemp, Sarah J.; Goldstraw, Peter; Tetley, Teresa D.; Stevens, Molly M.

2010-01-01

Abstract Researchers have previously questioned the suitability of cell lines as models for primary cells. In this study, we used Raman microspectroscopy to characterize live A549 cells from a unique molecular biochemical perspective to shed light on their suitability as a model for primary human pulmonary alveolar type II (ATII) cells. We also investigated a recently developed transduced type I (TT1) cell line as a model for alveolar type I (ATI) cells. Single-cell Raman spectra provide unique biomolecular fingerprints that can be used to characterize cellular phenotypes. A multivariate statistical analysis of Raman spectra indicated that the spectra of A549 and TT1 cells are characterized by significantly lower phospholipid content compared to ATII and ATI spectra because their cytoplasm contains fewer surfactant lamellar bodies. Furthermore, we found that A549 spectra are statistically more similar to ATI spectra than to ATII spectra. The spectral variation permitted phenotypic classification of cells based on Raman spectral signatures with >99% accuracy. These results suggest that A549 cells are not a good model for ATII cells, but TT1 cells do provide a reasonable model for ATI cells. The findings have far-reaching implications for the assessment of cell lines as suitable primary cellular models in live cultures. PMID:20409492

Classification model based on Raman spectra of selected morphological and biochemical tissue constituents for identification of atherosclerosis in human coronary arteries.

PubMed

Peres, Marines Bertolo; Silveira, Landulfo; Zângaro, Renato Amaro; Pacheco, Marcos Tadeu Tavares; Pasqualucci, Carlos Augusto

2011-09-01

This study presents the results of Raman spectroscopy applied to the classification of arterial tissue based on a simplified model using basal morphological and biochemical information extracted from the Raman spectra of arteries. The Raman spectrograph uses an 830-nm diode laser, imaging spectrograph, and a CCD camera. A total of 111 Raman spectra from arterial fragments were used to develop the model, and those spectra were compared to the spectra of collagen, fat cells, smooth muscle cells, calcification, and cholesterol in a linear fit model. Non-atherosclerotic (NA), fatty and fibrous-fatty atherosclerotic plaques (A) and calcified (C) arteries exhibited different spectral signatures related to different morphological structures presented in each tissue type. Discriminant analysis based on Mahalanobis distance was employed to classify the tissue type with respect to the relative intensity of each compound. This model was subsequently tested prospectively in a set of 55 spectra. The simplified diagnostic model showed that cholesterol, collagen, and adipocytes were the tissue constituents that gave the best classification capability and that those changes were correlated to histopathology. The simplified model, using spectra obtained from a few tissue morphological and biochemical constituents, showed feasibility by using a small amount of variables, easily extracted from gross samples.

Real-time Raman spectroscopy of optically trapped living cells and organelles

NASA Astrophysics Data System (ADS)

Xie, Changan; Goodman, Charles; Dinno, Mumtaz A.; Li, Yong-Qing

2004-12-01

We report on real-time Raman spectroscopic studies of optically trapped living cells and organelles using an inverted confocal laser-tweezers-Raman-spectroscopy (LTRS) system. The LTRS system was used to hold a single living cell in a physiological solution or to hold a functional organelle within a living cell and consequently measured its Raman spectra. We have measured the changes in Raman spectra of a trapped yeast cell as the function of the temperature of the bathing solution and studied the irreversible cell degeneration during the heat denaturation. In addition, we measured the in-vitro Raman spectra of the nuclei within living pine cells and B. sporeformer, Strep. salivarius, and E. coli bacteria suspended in solution and showed the possibility of using LTRS system as a sensor for rapid identification of microbes in a fluid.

Identification of Foreign Particles in Human Tissues using Raman Microscopy.

PubMed

Campion, Alan; Smith, Kenneth J; Fedulov, Alexey V; Gregory, David; Fan, Yuwei; Godleski, John J

2018-06-12

The precise identification of foreign particles in tissue for patient care and research has been studied using polarized light microscopy, electron microscopy with X-ray analysis, and electron diffraction. The goal of this study was to unambiguously identify particles in tissues using a combina-tion of polarized light microscopy and Raman microscopy, which provides chemical composition and microstructural characterization of complex materials with submicron spatial resolution. We designed a model system of stained and unstained cells that contained birefringent talc particles, and systematically investigated the influence of slide and coverslip materials, laser wavelengths, and mounting media on the Raman spectra ob-tained. Hematoxylin and eosin stained slides did not produce useful results because of fluorescence interference from the stains. Unstained cell samples prepared with standard slides and coverslips produce high quality Raman spectra when excited at 532 nm; the spectra are uniquely as-signed to talc. We also obtain high quality Raman spectra specific for talc in unstained tissue samples (pleural tissue following talc pleurodesis and ovarian tissue following long-term perineal talc exposure). Raman microscopy is sufficiently sensitive and compositionally selective to identify particles as small as one micron in diameter. Among commonly used coverslip mounting media, Cytoseal 60 is recommended; Permount was unacceptable due to intense background interference. Raman spectra have been catalogued for thousands of substances, which suggests that this approach is likely to be successful in identifying other particles of interest in tissues, potentially making Raman microscopy a powerful new tool in pathology.

In-line near-infrared (NIR) and Raman spectroscopy coupled with principal component analysis (PCA) for in situ evaluation of the transesterification reaction.

PubMed

Fontalvo-Gómez, Miriam; Colucci, José A; Velez, Natasha; Romañach, Rodolfo J

2013-10-01

Biodiesel was synthesized from different commercially available oils while in-line Raman and near-infrared (NIR) spectra were obtained simultaneously, and the spectral changes that occurred during the reaction were evaluated with principal component analysis (PCA). Raman and NIR spectra were acquired every 30 s with fiber optic probes inserted into the reaction vessel. The reaction was performed at 60-70 °C using magnetic stirring. The time of reaction was 90 min, and during this time, 180 Raman and NIR spectra were collected. NIR spectra were collected using a transflectance probe and an optical path length of 1 mm at 8 cm(-1) spectral resolution and averaging 32 scans; for Raman spectra a 3 s exposure time and three accumulations were adequate for the analysis. Raman spectroscopy showed the ester conversion as evidenced by the displacement of the C=O band from 1747 to 1744 cm(-1) and the decrease in the intensity of the 1000-1050 cm(-1) band and the 1405 cm(-1) band as methanol was consumed in the reaction. NIR spectra also showed the decrease in methanol concentration with the band in the 4750-5000 cm(-1) region; this signal is present in the spectra of the transesterification reaction but not in the neat oils. The variations in the intensity of the methanol band were a main factor in the in-line monitoring of the transesterification reaction using Raman and NIR spectroscopy. The score plot of the first principal component showed the progress of the reaction. The final product was analyzed using (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy and using mid-infrared spectroscopy, confirming the conversion of the oils to biodiesel.

Evaluation of Raman spectra of human brain tumor tissue using the learning vector quantization neural network

NASA Astrophysics Data System (ADS)

Liu, Tuo; Chen, Changshui; Shi, Xingzhe; Liu, Chengyong

2016-05-01

The Raman spectra of tissue of 20 brain tumor patients was recorded using a confocal microlaser Raman spectroscope with 785 nm excitation in vitro. A total of 133 spectra were investigated. Spectra peaks from normal white matter tissue and tumor tissue were analyzed. Algorithms, such as principal component analysis, linear discriminant analysis, and the support vector machine, are commonly used to analyze spectral data. However, in this study, we employed the learning vector quantization (LVQ) neural network, which is typically used for pattern recognition. By applying the proposed method, a normal diagnosis accuracy of 85.7% and a glioma diagnosis accuracy of 89.5% were achieved. The LVQ neural network is a recent approach to excavating Raman spectra information. Moreover, it is fast and convenient, does not require the spectra peak counterpart, and achieves a relatively high accuracy. It can be used in brain tumor prognostics and in helping to optimize the cutting margins of gliomas.

Study of dynamical process of heat denaturation in optically trapped single microorganisms by near-infrared Raman spectroscopy

NASA Astrophysics Data System (ADS)

Xie, Changan; Li, Yong-qing; Tang, Wei; Newton, Ronald J.

2003-11-01

The development of laser traps has made it possible to investigate single cells and record real-time Raman spectra during a heat-denaturation process when the temperature of the surrounding medium is increased. Large changes in the phenylalanine band (1004 cm-1) of near-infrared spectra between living and heat-treated cells were observed in yeast and Escerichia coli and Enterobacter aerogenes bacteria. This change appears to reflect the change in environment of phenylalanine as proteins within the cells unfold as a result of increasing temperatures. As a comparison, we measured Raman spectra of native and heat-denatured solutions of bovine serum albumin proteins, and a similar change in the phenylalanine band of spectra was observed. In addition, we measured Raman spectra of native and heat-treated solutions of pure phenylalanine molecules; no observable difference in vibrational spectra was observed. These findings may make it possible to study conformational changes in proteins within single cells.

Nitric oxide concentration measurements in atmospheric pressure flames using electronic-resonance-enhanced coherent anti-Stokes Raman scattering

NASA Astrophysics Data System (ADS)

Chai, N.; Kulatilaka, W. D.; Naik, S. V.; Laurendeau, N. M.; Lucht, R. P.; Kuehner, J. P.; Roy, S.; Katta, V. R.; Gord, J. R.

2007-06-01

We report the application of electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) for measurements of nitric oxide concentration ([NO]) in three different atmospheric pressure flames. Visible pump (532 nm) and Stokes (591 nm) beams are used to probe the Q-branch of the Raman transition. A significant resonance enhancement is obtained by tuning an ultraviolet probe beam (236 nm) into resonance with specific rotational transitions in the (v’=0, v”=1) vibrational band of the A2Σ+-X2Π electronic system of NO. ERE-CARS spectra are recorded at various heights within a hydrogen-air flame producing relatively low concentrations of NO over a Hencken burner. Good agreement is obtained between NO ERE-CARS measurements and the results of flame computations using UNICORN, a two-dimensional flame code. Excellent agreement between measured and calculated NO spectra is also obtained when using a modified version of the Sandia CARSFT code for heavily sooting acetylene-air flames (φ=0.8 to φ=1.6) on the same Hencken burner. Finally, NO concentration profiles are measured using ERE-CARS in a laminar, counter-flow, non-premixed hydrogen-air flame. Spectral scans are recorded by probing the Q1 (9.5), Q1 (13.5) and Q1 (17.5) Raman transitions. The measured shape of the [NO] profile is in good agreement with that predicted using the OPPDIF code, even without correcting for collisional effects. These comparisons between [NO] measurements and predictions establish the utility of ERE-CARS for detection of NO in flames with large temperature and concentration gradients as well as in sooting environments.

Raman microspectroscopy of nucleus and cytoplasm for human colon cancer diagnosis.

PubMed

Liu, Wenjing; Wang, Hongbo; Du, Jingjing; Jing, Chuanyong

2017-11-15

Subcellular Raman analysis is a promising clinic tool for cancer diagnosis, but constrained by the difficulty of deciphering subcellular spectra in actual human tissues. We report a label-free subcellular Raman analysis for use in cancer diagnosis that integrates subcellular signature spectra by subtracting cytoplasm from nucleus spectra (Nuc.-Cyt.) with a partial least squares-discriminant analysis (PLS-DA) model. Raman mapping with the classical least-squares (CLS) model allowed direct visualization of the distribution of the cytoplasm and nucleus. The PLS-DA model was employed to evaluate the diagnostic performance of five types of spectral datasets, including non-selective, nucleus, cytoplasm, ratio of nucleus to cytoplasm (Nuc./Cyt.), and nucleus minus cytoplasm (Nuc.-Cyt.), resulting in diagnostic sensitivity of 88.3%, 84.0%, 98.4%, 84.5%, and 98.9%, respectively. Discriminating between normal and cancerous cells of actual human tissues through subcellular Raman markers is feasible, especially when using the nucleus-cytoplasm difference spectra. The subcellular Raman approach had good stability, and had excellent diagnostic performance for rectal as well as colon tissues. The insights gained from this study shed new light on the general applicability of subcellular Raman analysis in clinical trials. Copyright © 2017 Elsevier B.V. All rights reserved.

Raman Spectroscopy of DNA Packaging in Individual Human Sperm Cells distinguishes Normal from Abnormal Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huser, T; Orme, C; Hollars, C

Healthy human males produce sperm cells of which about 25-40% have abnormal head shapes. Increases in the percentage of sperm exhibiting aberrant sperm head morphologies have been correlated with male infertility, and biochemical studies of pooled sperm have suggested that sperm with abnormal shape may contain DNA that has not been properly repackaged by protamine during spermatid development. We have used micro-Raman spectroscopy to obtain Raman spectra from individual human sperm cells and examined how differences in the Raman spectra of sperm chromatin correlate with cell shape. We show that Raman spectra of individual sperm cells contain vibrational marker modesmore » that can be used to assess the efficiency of DNA-packaging for each cell. Raman spectra obtained from sperm cells with normal shape provide evidence that DNA in these sperm is very efficiently packaged. We find, however, that the relative protein content per cell and DNA packaging efficiencies are distributed over a relatively wide range for sperm cells with both normal and abnormal shape. These findings indicate that single cell Raman spectroscopy should be a valuable tool in assessing the quality of sperm cells for in-vitro fertilization.« less

Investigation on tip enhanced Raman spectra of graphene

NASA Astrophysics Data System (ADS)

Li, Xinjuan; Liu, Yanqi; Zeng, Zhuo; Wang, Peijie; Fang, Yan; Zhang, Lisheng

2018-02-01

Tip-enhanced Raman scattering (TERS) is a promising analytical approach for some two-dimensional materials and offers the possibility to correlate imaging and chemical data. Tip-enhanced Raman spectra of graphene are discussed in some details, including substrate, gap between tip-apex and sample surface as well as Ag-nanowire. The TERS spectra give special emphasis to the possibility of TERS tip to induce a large number of defects only while got the tip attached to sample surface. Then the dependence of the TERS spectra of graphene and gap between the probe tip and sample surface was studied, and distribution features of electromagnetic (EM) field around tip were also simulated by finite-difference time-domain (FDTD). The Raman signal enhancement of graphene was further discussed with respect to experimental data. Furthermore, the Ag-nanowire as a nano-antenna could significantly enhance the weak Raman signal of D-band of monolayer graphene is shown, and the TERS spectra of graphene with regard to different regions of Ag-nanowires (endpoints, body) were obtained toward investigating into the distribution of electromagnetic field.

Rapid in situ detection of street samples of drugs of abuse on textile substrates using microRaman spectroscopy.

PubMed

Ali, Esam M A; Edwards, Howell G M; Scowen, Ian J

2011-10-01

Trace amounts of street samples of cocaine hydrochloride and N-methyl-3,4-methylenedioxy-amphetamine (MDMA) on natural and synthetic textiles were successfully detected in situ using confocal Raman microscopy. The presence of some excipient bands in the spectra of the drugs did not prevent the unambiguous identification of the drugs. Raman spectra of the drugs were readily obtained without significant interference from the fibre substrates. Interfering bands arising from the fibre natural or synthetic polymer structure and/or dye molecules did not overlap with the characteristic Raman bands of the drugs. If needed, interfering bands could be successfully removed by spectral subtraction. Also, Raman spectra could be acquired from drug particles trapped between the fibres of highly fluorescent textile specimens. The total acquisition time of the spectra of the drug particles was 90 s accomplished non-destructively and without detachment from their substrates. Sample preparation was not required and spectra of the drugs could be obtained non-invasively preserving the integrity of the evidential material for further analysis. Copyright © 2010 Elsevier B.V. All rights reserved.

Rapid in situ detection of street samples of drugs of abuse on textile substrates using microRaman spectroscopy

NASA Astrophysics Data System (ADS)

Ali, Esam M. A.; Edwards, Howell G. M.; Scowen, Ian J.

2011-10-01

Trace amounts of street samples of cocaine hydrochloride and N-methyl-3,4-methylenedioxy-amphetamine (MDMA) on natural and synthetic textiles were successfully detected in situ using confocal Raman microscopy. The presence of some excipient bands in the spectra of the drugs did not prevent the unambiguous identification of the drugs. Raman spectra of the drugs were readily obtained without significant interference from the fibre substrates. Interfering bands arising from the fibre natural or synthetic polymer structure and/or dye molecules did not overlap with the characteristic Raman bands of the drugs. If needed, interfering bands could be successfully removed by spectral subtraction. Also, Raman spectra could be acquired from drug particles trapped between the fibres of highly fluorescent textile specimens. The total acquisition time of the spectra of the drug particles was 90 s accomplished non-destructively and without detachment from their substrates. Sample preparation was not required and spectra of the drugs could be obtained non-invasively preserving the integrity of the evidential material for further analysis.

Raman spectra of amino acids and their aqueous solutions

NASA Astrophysics Data System (ADS)

Zhu, Guangyong; Zhu, Xian; Fan, Qi; Wan, Xueliang

2011-03-01

Amino acids are the basic "building blocks" that combine to form proteins and play an important physiological role in all life-forms. Amino acids can be used as models for the examination of the importance of intermolecular bonding in life processes. Raman spectra serve to obtain information regarding molecular conformation, giving valuable insights into the topology of more complex molecules (peptides and proteins). In this paper, amino acids and their aqueous solution have been studied by Raman spectroscopy. Comparisons of certain values for these frequencies in amino acids and their aqueous solutions are given. Spectra of solids when compared to those of the solute in solution are invariably much more complex and almost always sharper. We present a collection of Raman spectra of 18 kinds of amino acids ( L-alanine, L-arginine, L-aspartic acid, cystine, L-glutamic acid, L-glycine, L-histidine, L-isoluecine, L-leucine, L-lysine, L-phenylalanine, L-methionone, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine) and their aqueous solutions that can serve as references for the interpretation of Raman spectra of proteins and biological materials.

Optical Characterization of Lead Monoxide Films Grown by Laser-Assisted Deposition

NASA Astrophysics Data System (ADS)

Baleva, M.; Tuncheva, V.

1994-05-01

The Raman spectra of PbO films, grown by laser-assisted deposition (LAD) at different substrate temperatures are investigated. The spectra of the films, deposited on amorphous, single crystal quartz and polycrystal PbTe substrates, are compared with the Raman spectra of tetragonal and orthorhombic powder samples. The phonon frequencies determined in our experiment with powder samples coincide fairly well with those obtained by Adams and Stevens, J. Chem. Soc., Dalton Trans., 1096 (1977). Thus the Raman spectra of the powder samples presented in this paper can be considered as unambiguous characteristics of the two different PbO crystal phases. It was concluded that the Raman scattering may serve as a tool for identification of PbO films and their crystal modifications. On the basis of this investigation it was concluded that the film structure changes from orthorhombic to tetragonal with increased substrate temperature, and that the nature of the substrate influences the crystal structure of the films. On the basis of the Raman spectra of the β-PbO films with prevailing (001) orientation of crystallization, an assignment of the modes is proposed.

Gas Phase Raman Spectra of Butadiene and BUTADIENE-d_{6} and the Internal Rotation Potential Energy Function

NASA Astrophysics Data System (ADS)

Boopalachandran, Praveenkumar; Laane, Jaan; Craig, Norman C.

2009-06-01

The Raman spectrum of butadiene has been previously reported by Carreira and by Engeln and co-workers. Both studies reported a series of bands corresponding to double quantum jumps of ν_{13}, the internal rotation vibration, of the trans rotamer. Both studies also reported weaker bands assigned to the higher energy conformer. Carriera assigned these to the cis form while Engeln assigned them to the gauche form. Recent high level calculations by Feller and Craig also assign the higher energy form as gauche. In the present study we report the gas phase Raman spectrum of butadiene and its d_{6} isotopomer at both 25^°C and 260^°C. Several new spectral features in the 330 to 210 cm^{-1} region were observed and the effect of heating on the band intensities was studied. In addition, combination bands were observed in the 630 to 690 cm^{-1} (ν_{12} + ν_{13}) and 1130 to 1180 cm^{-1} (ν_{10} + ν_{13}) regions. A periodic potential energy function with V_{1}, V_{2}, V_{3}, V_{4}, and V_{6} terms was utilized to fit the data. This function was compared to the results from previous work and to the theoretical calculation. L. Carreira, J. Phys. Chem. 62, 3851 (1975). R. Engeln, D. Consalvo, and J. Reuss, J. Chem. Phys. 160, 427 (1992). D. Feller and N. C. Craig, J. Phys. Chem. 113, 1601 (2009).

FT-Raman and FT-IR spectra of some heterobimetallic complexes with phenylcyclopentadienyl ligands

NASA Astrophysics Data System (ADS)

Nie, Chong-Shi; Guo, Jianhua; Qian, Changtao; Tan, Ying

1996-11-01

The FT-Raman and selected IR spectra of 14 heterobimetallic complexes of (CO) 3CrC 6H 5-C 5H 4M(CO) n(NO) mX (M = transition metal, X = other ligands) are reported. FT-Raman exhibits distinct strong characteristic bands of coordinated C 6H 5-C 5H 4 ligand ring deformation near 1540, 1490 and 1280 cm -1 and the coordinated phenyl ring deformation mode near 1000 cm -1, which are negligible in IR spectra. It is also easy to find the M-CO stretching and M-C-O bending as well as phenyl-M stretching bands in the FT-Raman spectra. The v(CO) IR absorptions in THF solution were reasonably assigned according to the local symmetry of the complexes.

Raman spectroscopic study of plasma-treated salmon DNA

NASA Astrophysics Data System (ADS)

Joon Lee, Geon; Kwon, Young-Wan; Hee Kim, Yong; Ha Choi, Eun

2013-01-01

In this research, we studied the effect of plasma treatment on the optical/structural properties of the deoxyribonucleic acid (DNA) extracted from salmon sperm. DNA-cetyltrimethylammonium (CTMA) films were obtained by complexation of DNA with CTMA. Circular dichroism (CD) and Raman spectra indicated that DNA retained its double helical structure in the solid film. The Raman spectra exhibited several vibration modes corresponding to the nuclear bases and the deoxyribose-phosphate backbones of the DNA, as well as the alkylchains of CTMA. Dielectric-barrier-discharge (DBD) plasma treatment induced structural modification and damage to the DNA, as observed by changes in the ultraviolet-visible absorption, CD, and Raman spectra. The optical emission spectra of the DBD plasma confirmed that DNA modification was induced by plasma ions such as reactive oxygen species and reactive nitrogen species.

Comparative studies by IR, Raman, and surface-enhanced Raman spectroscopy of azodicarbonamide, biurea and semicarbazide hydrochloride

NASA Astrophysics Data System (ADS)

Xie, Yunfei; Li, Pei; Zhang, Jin; Wang, Heya; Qian, He; Yao, Weirong

2013-10-01

Azodicarbonamide is widely applied in the food industry as a new flour gluten fortifier in China, Canada, the United States, and some other countries, whose metabolites of biurea and semicarbazide hydrochloride are reaction products during baking. In this study, IR, Raman and surface-enhanced Raman scattering (SERS) spectra of azodicarbonamide, biurea, and semicarbazide hydrochloride have been studied, and vibrational bands have been assigned on the basis of density functional theory (DFT) calculations. The calculated Raman spectra were in good agreement with experimental Raman spectra. The SERS method coupled with active gold substrates has also been applied for detection of the three chemicals with pure water as solvent, with the limit of detection of this method being as low as 10 μg/mL (less than 45 μg/mL). These results showed that azodicarbonamide and its metabolites could be detected by the vibrational spectra technique, which might be applied as a powerful tool for the rapid detection on these species derived from agents added to flour.

Effect of hormonal variation on in vivo high wavenumber Raman spectra improves cervical precancer detection

NASA Astrophysics Data System (ADS)

Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J. H.; Ilancheran, A.; Huang, Zhiwei

2012-03-01

Raman spectroscopy is a unique analytical probe for molecular vibration and is capable of providing specific spectroscopic fingerprints of molecular compositions and structures of biological tissues. The aim of this study is to improve the classification accuracy of cervical precancer by characterizing the variations in the normal high wavenumber (HW - 2800-3700cm-1) Raman spectra arising from the menopausal status of the cervix. A rapidacquisition near-infrared (NIR) Raman spectroscopic system was used for in vivo tissue Raman measurements at 785 nm excitation. Individual HW Raman spectrum was measured with a 5s exposure time from both normal and precancer tissue sites of 15 patients recruited. The acquired Raman spectra were stratified based on the menopausal status of the cervix before the data analysis. Significant differences were noticed in Raman intensities of prominent band at 2924 cm-1 (CH3 stretching of proteins) and the broad water Raman band (in the 3100-3700 cm-1 range) with a peak at 3390 cm-1 in normal and dysplasia cervical tissue sites. Multivariate diagnostic decision algorithm based on principal component analysis (PCA) and linear discriminant analysis (LDA) was utilized to successfully differentiate the normal and precancer cervical tissue sites. By considering the variations in the Raman spectra of normal cervix due to the hormonal or menopausal status of women, the diagnostic accuracy was improved from 71 to 91%. By incorporating these variations prior to tissue classification, we can significantly improve the accuracy of cervical precancer detection using HW Raman spectroscopy.

Rotational coherent anti-stokes Raman spectroscopy measurements in a rotating cavity with axial throughflow of cooling air: oxygen concentration measurements.

PubMed

Black, J D; Long, C A

1992-07-20

In a rotating cavity rig, which models cooling air flow in the spaces between disks of a gas turbine compressor, the buildup of oxygen concentration after the cooling gas was changed from nitrogen to air was monitored using rotational coherent anti-Stokes Raman spectroscopy (CARS). From this information an estimate of the fraction of the throughflow entering the rotating cavity was obtained. This demonstrates that rotational CARS can be applied as a nonintrusive concentration-measurement technique in a rotating engineering test rig.

Surface-Enhanced Hyper-Raman Spectra of Adenine, Guanine, Cytosine, Thymine, and Uracil

PubMed Central

2016-01-01

Using picosecond excitation at 1064 nm, surface-enhanced hyper-Raman scattering (SEHRS) spectra of the nucleobases adenine, guanine, cytosine, thymine, and uracil with two different types of silver nanoparticles were obtained. Comparing the SEHRS spectra with SERS data from the identical samples excited at 532 nm and with known infrared spectra, the major bands in the spectra are assigned. Due to the different selection rules for the one- and two-photon excited Raman scattering, we observe strong variation in relative signal strengths of many molecular vibrations obtained in SEHRS and SERS spectra. The two-photon excited spectra of the nucleobases are found to be very sensitive with respect to molecule–nanoparticle interactions. Using both the SEHRS and SERS data, a comprehensive vibrational characterization of the interaction of nucleobases with silver nanostructures can be achieved. PMID:28077982

Discrimination of selected species of pathogenic bacteria using near-infrared Raman spectroscopy and principal components analysis

NASA Astrophysics Data System (ADS)

de Siqueira e Oliveira, Fernanda S.; Giana, Hector E.; Silveira, Landulfo, Jr.

2012-03-01

It has been proposed a method based on Raman spectroscopy for identification of different microorganisms involved in bacterial urinary tract infections. Spectra were collected from different bacterial colonies (Gram negative: E. coli, K. pneumoniae, P. mirabilis, P. aeruginosa, E. cloacae and Gram positive: S. aureus and Enterococcus sp.), grown in culture medium (Agar), using a Raman spectrometer with a fiber Raman probe (830 nm). Colonies were scraped from Agar surface placed in an aluminum foil for Raman measurements. After pre-processing, spectra were submitted to a Principal Component Analysis and Mahalanobis distance (PCA/MD) discrimination algorithm. It has been found that the mean Raman spectra of different bacterial species show similar bands, being the S. aureus well characterized by strong bands related to carotenoids. PCA/MD could discriminate Gram positive bacteria with sensitivity and specificity of 100% and Gram negative bacteria with good sensitivity and high specificity.

Application of NIR Raman spectroscopy for detecting and characterizing early dental caries

NASA Astrophysics Data System (ADS)

Ko, A. C.; Choo-Smith, L.-P.; Zhu, R.; Hewko, M.; Dong, C.; Cleghorn, B.; Sowa, M. G.

2006-02-01

Early dental caries detection facilitates implementation of non-surgical methods for arresting caries progression and promoting tooth remineralization. We present a method based on Raman spectroscopy with near-IR laser excitation to provide biochemical contrast for detecting and characterizing incipient carious lesions found in extracted human teeth. Changes in Raman spectra are observed in PO 4 3- vibrations arising from hydroxyapatite of mineralized tooth tissue. Examination of various intensities of the PO 4 3- ν2, ν3, ν4 vibrations showed consistent increased intensities in spectra of carious lesions compared to sound enamel. The spectral changes are attributed to demineralization-induced alterations of enamel crystallite morphology and/or orientation. This hypothesis is supported by reduced Raman polarization anisotropy derived from polarized Raman spectra of carious lesions. Polarized Raman spectral imaging of carious lesions found on whole (i.e. un-sectioned) tooth samples will also be presented.

Raman spectra and optical trapping of highly refractive and nontransparent particles

NASA Astrophysics Data System (ADS)

Xie, Changan; Li, Yong-qing

2002-08-01

We measured the Raman spectra of single optically trapped highly refractive and nontransparent microscopic particles suspended in a liquid using an inverted confocal laser-tweezers-Raman-spectroscopy system. A low-power diode-laser beam of TEM00 mode was used both for optical trapping and Raman excitation of refractive, absorptive, and reflective metal particles. To form a stable trap for a nontransparent particle, the beam focus was located near the top of the particle and the particle was pushed against a glass plate by the axial repulsive force. Raman spectra from single micron-sized crystals with high index of refraction including silicon, germanium, and KNbO3, and from absorptive particles of black and color paints were recorded. Surface-enhanced Raman scattering of R6G and phenylalanine molecules absorbed on the surface of a trapped cluster of silver particles was also demonstrated.

A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine ( Pinus sylvestris) wood . Part I: Lipophilic compounds

NASA Astrophysics Data System (ADS)

Nuopponen, M.; Willför, S.; Jääskeläinen, A.-S.; Sundberg, A.; Vuorinen, T.

2004-11-01

The wood resin in Scots pine ( Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm -1. Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at ˜1650 cm -1 due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.

A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine (Pinus sylvestris) wood. Part I: lipophilic compounds.

PubMed

Nuopponen, M; Willför, S; Jääskeläinen, A-S; Sundberg, A; Vuorinen, T

2004-11-01

The wood resin in Scots pine (Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm(-1). Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at approximately 1650 cm(-1) due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.

The detection of drugs of abuse in fingerprints using Raman spectroscopy I: latent fingerprints

NASA Astrophysics Data System (ADS)

Day, Joanna S.; Edwards, Howell G. M.; Dobrowski, Steven A.; Voice, Alison M.

2004-02-01

This paper describes the application of Raman spectroscopy to the detection of exogenous substances in latent fingerprints. The scenario considered was that of an individual handling a substance and subsequently depositing a contaminated fingerprint. Five drugs of abuse (codeine phosphate, cocaine hydrochloride, amphetamine sulphate, barbital and nitrazepam) and five non-controlled substances of similar appearance, which may be used in the adulteration of drugs of abuse (caffeine, aspirin, paracetamol, starch and talc), were studied in both sweat-rich and sebum-rich latent fingerprints. The substances studied could be clearly distinguished using their Raman spectra and were all successfully detected in latent fingerprints. Photobleaching was necessary to reduce the fluorescence background in the spectra of some substances. Raman spectra obtained from the substances in sweat-rich latent fingerprints were of a similar quality to spectra that obtained from the substances under normal sampling conditions. Interfering Raman bands arising from latent fingerprint material were present in the spectra obtained from the substances in sebum-rich fingerprints. These bands did not prevent identification of the substances and could be successfully removed by spectral subtraction. The most difficult aspect of the detection of these substances in latent fingerprints was visually locating the substance in the fingerprint in order to obtain a Raman spectrum.

An infrared and Raman spectroscopic study of natural zinc phosphates.

PubMed

Frost, Ray L

2004-06-01

Zinc phosphates are important in the study of the phosphatisation of metals. Raman spectroscopy in combination with infrared spectroscopy has been used to characterise the zinc phosphate minerals. The minerals may be characterised by the patterns of the hydroxyl stretching vibrations in both the Raman and infrared spectra. Spencerite is characterised by a sharp Raman band at 3516 cm(-1) and tarbuttite by a single band at 3446 cm(-1). The patterns of the Raman spectra of the hydroxyl stretching region of hopeite and parahopeite are different in line with their differing crystal structures. The Raman spectrum of the PO4 stretching region shows better band separated peaks than the infrared spectra which consist of a complex set of overlapping bands. The position of the PO4 symmetric stretching mode can be used to identify the zinc phosphate mineral. It is apparent that Raman spectroscopy lends itself to the fundamental study of the evolution of zinc phosphate films.

Raman background photobleaching as a possible method of cancer diagnostics

NASA Astrophysics Data System (ADS)

Brandt, Nikolai N.; Brandt, Nikolai B.; Chikishev, Andrey Y.; Gangardt, Mihail G.; Karyakina, Nina F.

2001-06-01

Kinetics of photobleaching of background in Raman spectra of aqueous solutions of plant toxins ricin and ricin agglutinin, ricin binding subunit, and normal and malignant human blood serum were measured. For the excitation of the spectra cw and pulsed laser radiation were used. The spectra of Raman background change upon laser irradiation. Background intensity is lower for the samples with small molecular weight. The cyclization of amino acid residues in the toxin molecules as well as in human blood serum can be a reason of the Raman background. The model of the background photobleaching is proposed. The differences in photobleaching kinetics in the cases of cw and pulsed laser radiation are discussed. It is shown that Raman background photobleaching can be very informative for cancer diagnostics.

Interplay of valley selection and helicity exchange of light in Raman scattering for graphene and MoS2

NASA Astrophysics Data System (ADS)

Tatsumi, Yuki; Saito, Riichiro

2018-03-01

Raman spectra of graphene and MoS2 are calculated for incident and scattered circularly polarized light. In the case of graphene, the well known G -band Raman spectra have a not well known property that the helicity of the incident circularly polarized light changes to another helicity in the scattered light. Using the electron-photon and electron-phonon matrix elements by first-principles calculation, we calculate resonant Raman spectra of graphene and MoS2 for circularly polarized light which are compared with recent experiments. The Raman intensity for circularly polarized light is relevant to optical valley polarization in the case of MoS2. We also discuss how the helicity-selection rule can be modified by applying stress to graphene.

Kerr-gated picosecond Raman spectroscopy and Raman photon migration of equine bone tissue with 400-nm excitation

NASA Astrophysics Data System (ADS)

Morris, Michael D.; Goodship, Allen E.; Draper, Edward R. C.; Matousek, Pavel; Towrie, Michael; Parker, Anthony W.

2004-07-01

We show that Raman spectroscopy with visible lasers, even in the deep blue is possible with time-gated Raman spectroscopy. A 4 picosec time gate allows efficient fluorescence rejection, up to 1000X, and provides almost background-free Raman spectra with low incident laser power. The technology enables spectroscopy with better than 10X higher scattering efficiency than is possible with the NIR (785 nm and 830 nm) lasers that are conventionally used. Raman photon migration is shown to allow depth penetration. We show for the first time that Kerr-gated Raman spectra of bone tissue with blue laser excitation enables both fluorescence rejection and depth penetration.

Surface Enhanced Raman Spectroscopy (SERS) and multivariate analysis as a screening tool for detecting Sudan I dye in culinary spices

NASA Astrophysics Data System (ADS)

Di Anibal, Carolina V.; Marsal, Lluís F.; Callao, M. Pilar; Ruisánchez, Itziar

2012-02-01

Raman spectroscopy combined with multivariate analysis was evaluated as a tool for detecting Sudan I dye in culinary spices. Three Raman modalities were studied: normal Raman, FT-Raman and SERS. The results show that SERS is the most appropriate modality capable of providing a proper Raman signal when a complex matrix is analyzed. To get rid of the spectral noise and background, Savitzky-Golay smoothing with polynomial baseline correction and wavelet transform were applied. Finally, to check whether unadulterated samples can be differentiated from samples adulterated with Sudan I dye, an exploratory analysis such as principal component analysis (PCA) was applied to raw data and data processed with the two mentioned strategies. The results obtained by PCA show that Raman spectra need to be properly treated if useful information is to be obtained and both spectra treatments are appropriate for processing the Raman signal. The proposed methodology shows that SERS combined with appropriate spectra treatment can be used as a practical screening tool to distinguish samples suspicious to be adulterated with Sudan I dye.

Background photobleaching in raman spectra of aqueous solutions of plant toxins

NASA Astrophysics Data System (ADS)

Brandt, Nikolai N.; Chikishev, Andrey Y.; Tonevitsky, Alexander G.

2002-05-01

Kinetics of background photobleaching in Raman spectra of aqueous solutions of ricin, ricin agglutinin and ricin binding subunit were measured. It was found that the spectrum of Raman background changes upon laser irradiation. Background intensity is lower for the samples with lower molecular weight. Photobleaching is characterized by oscillations in the multi exponentially decaying intensity.

Characterization of Materials by Raman Scattering

NASA Astrophysics Data System (ADS)

Kozielski, M.

2007-03-01

The paper reports on the use of phonon spectra obtained with the Raman spectroscopy for characterization of different materials. The Raman scattering spectra obtained for zinc selenide crystals, mixed crystals zinc selenide admixtured with magnesium or beryllium, oxide crystals including strontium lanthanum gallate, molecular crystals of triammonium hydrogen diseleniate and a homologous series of polyoxyethylene glycols are analysed.

Development and characterization of a handheld hyperspectral Raman imaging probe system for molecular characterization of tissue on mesoscopic scales.

PubMed

St-Arnaud, Karl; Aubertin, Kelly; Strupler, Mathias; Madore, Wendy-Julie; Grosset, Andrée-Anne; Petrecca, Kevin; Trudel, Dominique; Leblond, Frédéric

2018-01-01

Raman spectroscopy is a promising cancer detection technique for surgical guidance applications. It can provide quantitative information relating to global tissue properties associated with structural, metabolic, immunological, and genetic biochemical phenomena in terms of molecular species including amino acids, lipids, proteins, and nucleic acid (DNA). To date in vivo Raman spectroscopy systems mostly included probes and biopsy needles typically limited to single-point tissue interrogation over a scale between 100 and 500 microns. The development of wider field handheld systems could improve tumor localization for a range of open surgery applications including brain, ovarian, and skin cancers. Here we present a novel Raman spectroscopy implementation using a coherent imaging bundle of fibers to create a probe capable of reconstructing molecular images over mesoscopic fields of view. Detection is performed using linear scanning with a rotation mirror and an imaging spectrometer. Different slits widths were tested at the entrance of the spectrometer to optimize spatial and spectral resolution while preserving sufficient signal-to-noise ratios to detect the principal Raman tissue features. The nonbiological samples, calcite and polytetrafluoroethylene (PTFE), were used to characterize the performance of the system. The new wide-field probe was tested on ex vivo samples of calf brain and swine tissue. Raman spectral content of both tissue types were validated with data from the literature and compared with data acquired with a single-point Raman spectroscopy probe. The single-point probe was used as the gold standard against which the new instrument was benchmarked as it has already been thoroughly validated for biological tissue characterization. We have developed and characterized a practical noncontact handheld Raman imager providing tissue information at a spatial resolution of 115 microns over a field of view >14 mm 2 and a spectral resolution of 6 cm -1 over the whole fingerprint region. Typical integration time to acquire an entire Raman image over swine tissue was set to approximately 100 s. Spectra acquired with both probes (single-point and wide-field) showed good agreement, with a Pearson correlation factor >0.85 over different tissue categories. Protein and lipid content of imaged tissue were manifested into the measured spectra which correlated well with previous findings in the literature. An example of quantitative molecular map is presented for swine tissue and calf brain based on the ratio of protein-to-lipid content showing clear delineations between white and gray matter as well as between adipose and muscle tissue. We presented the development of a Raman imaging probe with a field of view of a few millimeters and a spatial resolution consistent with standard surgical imaging methods using an imaging bundle. Spectra acquired with the newly developed system on swine tissue and calf brain correlated well with an establish single-point probe and observed spectral features agreed with previous finding in the literature. The imaging probe has demonstrated its ability to reconstruct molecular images of soft tissues. The approach presented here has a lot of potential for the development of surgical Raman imaging probe to guide the surgeon during cancer surgery. © 2017 American Association of Physicists in Medicine.

Dynamics of an [Fe4S4(SPh)4]2- cluster explored via IR, Raman, and nuclear resonance vibrational spectroscopy (NRVS)-analysis using 36S substitution, DFT calculations, and empirical force fields.

PubMed

Xiao, Yuming; Koutmos, Markos; Case, David A; Coucouvanis, Dimitri; Wang, Hongxin; Cramer, Stephen P

2006-05-14

We have used four vibrational spectroscopies--FT-IR, FT-Raman, resonance Raman, and 57Fe nuclear resonance vibrational spectroscopy (NRVS)--to study the normal modes of the Fe-S cluster in [(n-Bu)4N]2[Fe4S4(SPh)4]. This [Fe4S4(SR)4]2- complex serves as a model for the clusters in 4Fe ferredoxins and high-potential iron proteins (HiPIPs). The IR spectra exhibited differences above and below the 243 K phase transition. Significant shifts with 36S substitution into the bridging S positions were also observed. The NRVS results were in good agreement with the low temperature data from the conventional spectroscopies. The NRVS spectra were interpreted by normal mode analysis using optimized Urey-Bradley force fields (UBFF) as well as from DFT theory. For the UBFF calculations, the parameters were refined by comparing calculated and observed NRVS frequencies and intensities. The frequency shifts after 36S substitution were used as an additional constraint. A D 2d symmetry Fe4S4S'4 model could explain most of the observed frequencies, but a better match to the observed intensities was obtained when the ligand aromatic rings were included for a D 2d Fe4S4(SPh)4 model. The best results were obtained using the low temperature structure without symmetry constraints. In addition to stretching and bending vibrations, low frequency modes between approximately 50 and 100 cm(-1) were observed. These modes, which have not been seen before, are interpreted as twisting motions with opposing sides of the cube rotating in opposite directions. In contrast with a recent paper on a related Fe4S4 cluster, we find no need to assign a large fraction of the low frequency NRVS intensity to 'rotational lattice modes'. We also reassign the 430 cm(-1) band as primarily an elongation of the thiophenolate ring, with approximately 10% terminal Fe-S stretch character. This study illustrates the benefits of combining NRVS with conventional Raman and IR analysis for characterization of Fe-S centers. DFT theory is shown to provide remarkable agreement with the experimental NRVS data. These results provide a reference point for the analysis of more complex Fe-S clusters in proteins.

Transmission Raman Measurements Using a Spatial Heterodyne Raman Spectrometer (SHRS).

PubMed

Strange, K Alicia; Paul, Kelly C; Angel, S Michael

2017-02-01

A spatial heterodyne Raman spectrometer (SHRS) was used to measure transmission Raman spectra of highly scattering compounds. Transmission Raman spectral intensities of ibuprofen were only 2.4 times lower in intensity than backscatter Raman spectra. The throughput was about eight times higher than an f/1.8 dispersive spectrometer, and the width of the area viewed was found to be seven to nine times higher, using 50.8 mm and 250 mm focal length collection lenses. However, the signal-to-noise (S/N) ratio was two times lower for the SHRS than the f/1.8 dispersive spectrometer, apparently due to high levels of stray light.

[Study of alkaline lignin from Arundo donax linn based on FT Raman spectroscopy].

PubMed

You, Ting-ting; Ma, Jian-feng; Guo, Si-qin; Xu, Feng

2014-08-01

Arundo donax linn, as a perennial energy crop, has promising application prospect. In the present study, Fourier transform Raman (FT Raman) spectroscopy was applied to determine the structural information of materials, milled wood lignin (MWL), and alkaline lignins (AL, under different treated time) from A. donax stem nondestructively. The results indicated that, extractable compounds in A. donax had negative contribution to the Raman spectra without rising new Raman peaks. FT Raman spectrum of MWL indicated that MWL from A. donax was HGS type lignins. Compared with the spectra of MWL from wood materials, the peak at 1173 cm(-1) was much higher in intensity for the MWL from A. donax stem, which may be assigned to hydroxycinnamic acid by analyzing the standard. With respect to FT Raman spectra of ALs, the relatively highest intensity of 1173 cm(-1) was found in alkaline lignin (AL2), which was treated for 40 min by alkaline. Moreover, the peak of coniferaldehyde/sinapaldehyde (1630 cm(-1)) was lowest in intensity while the band attributed to coniferyl alcohol/sinapyl alcohol (1660 cm(-1)) was almost disappeared in AL2. It could be inferred that AL2 demonstrated a highest content of phenolic acid, which may improve its potential application, such as for antioxidant activity. Furthermore, the results obtained by FT Raman spectra were verified by two dimensional heteronuclear singlequantum coherence nuclear magnetic resonance analyses. Above all, FT Raman spectroscopy provided alternative safe, rapid, accurate, and nondestructive technology for lignin structure determination.

Raman active components of skin cancer.

PubMed

Feng, Xu; Moy, Austin J; Nguyen, Hieu T M; Zhang, Jason; Fox, Matthew C; Sebastian, Katherine R; Reichenberg, Jason S; Markey, Mia K; Tunnell, James W

2017-06-01

Raman spectroscopy (RS) has shown great potential in noninvasive cancer screening. Statistically based algorithms, such as principal component analysis, are commonly employed to provide tissue classification; however, they are difficult to relate to the chemical and morphological basis of the spectroscopic features and underlying disease. As a result, we propose the first Raman biophysical model applied to in vivo skin cancer screening data. We expand upon previous models by utilizing in situ skin constituents as the building blocks, and validate the model using previous clinical screening data collected from a Raman optical fiber probe. We built an 830nm confocal Raman microscope integrated with a confocal laser-scanning microscope. Raman imaging was performed on skin sections spanning various disease states, and multivariate curve resolution (MCR) analysis was used to resolve the Raman spectra of individual in situ skin constituents. The basis spectra of the most relevant skin constituents were combined linearly to fit in vivo human skin spectra. Our results suggest collagen, elastin, keratin, cell nucleus, triolein, ceramide, melanin and water are the most important model components. We make available for download (see supplemental information) a database of Raman spectra for these eight components for others to use as a reference. Our model reveals the biochemical and structural makeup of normal, nonmelanoma and melanoma skin cancers, and precancers and paves the way for future development of this approach to noninvasive skin cancer diagnosis.

Raman active components of skin cancer

PubMed Central

Feng, Xu; Moy, Austin J; Nguyen, Hieu T. M.; Zhang, Jason; Fox, Matthew C.; Sebastian, Katherine R.; Reichenberg, Jason S.; Markey, Mia K.; Tunnell, James W.

2017-01-01

Raman spectroscopy (RS) has shown great potential in noninvasive cancer screening. Statistically based algorithms, such as principal component analysis, are commonly employed to provide tissue classification; however, they are difficult to relate to the chemical and morphological basis of the spectroscopic features and underlying disease. As a result, we propose the first Raman biophysical model applied to in vivo skin cancer screening data. We expand upon previous models by utilizing in situ skin constituents as the building blocks, and validate the model using previous clinical screening data collected from a Raman optical fiber probe. We built an 830nm confocal Raman microscope integrated with a confocal laser-scanning microscope. Raman imaging was performed on skin sections spanning various disease states, and multivariate curve resolution (MCR) analysis was used to resolve the Raman spectra of individual in situ skin constituents. The basis spectra of the most relevant skin constituents were combined linearly to fit in vivo human skin spectra. Our results suggest collagen, elastin, keratin, cell nucleus, triolein, ceramide, melanin and water are the most important model components. We make available for download (see supplemental information) a database of Raman spectra for these eight components for others to use as a reference. Our model reveals the biochemical and structural makeup of normal, nonmelanoma and melanoma skin cancers, and precancers and paves the way for future development of this approach to noninvasive skin cancer diagnosis. PMID:28663910

Application of Raman spectroscopy, surface-enhanced Raman scattering (SERS), and density functional theory for the identification of phenethylamines.

PubMed

Taplin, Francis; O'Donnell, Deanna; Kubic, Thomas; Leona, Marco; Lombardi, John

2013-10-01

We evaluated the normal Raman (NR) and the surface-enhanced Raman scattering (SERS) of three sympathomimetic amines: phenethylamine, ephedrine, and 3,4-methylenedioxymethamphetamine (MDMA). In addition, quantum mechanical calculations-geometry optimization and calculations of the harmonic vibrational frequencies-were performed using the density functional theory (DFT) approach. Vibrational assignments were made by comparing the experimental and calculated spectra. The study found that both NR and SERS provided excellent spectra for the drugs tested. Certain conditions, such as response to various laser wavelengths and background fluorescence of the analyte, could be easily managed using SERS techniques. The DFT-calculated spectra could be correlated with the experimental spectra without the aid of a scaling factor. We also present a set of discriminant bands, useful for distinguishing the three compounds, despite their structural similarities.

Raman spectroscopy of different types of Mexican copal resins

NASA Astrophysics Data System (ADS)

Vandenabeele, Peter; Grimaldi, Dulce Maria; Edwards, Howell G. M.; Moens, Luc

2003-08-01

Dispersive Raman spectra of six copal resins, that were purchased in local markets in Mexico, are presented. The spectra were interpreted and compared with each other. For all these spectra, the relative intensity of the Raman band at approximately 1645 cm -1, attributed to the exomethylene ν(CC) stretching vibration, was rather low, especially as fresh samples are involved. In one resin, viz. Incienso, CaCO 3 was detected. Probably this inorganic pigment was added as a whitener. In the spectrum of Lágrima a starch fraction was present. Raman spectra of a sample from an Aztec figurine were recorded. It was shown that its composition was inhomogeneous at the micrometer level. Here, too, CaCO 3 was observed. It was not possible to identify the resin applied in the antique figurine due to material degradation by age and environmental exposure.

Medium-range structural properties of vitreous germania obtained through first-principles analysis of vibrational spectra.

PubMed

Giacomazzi, Luigi; Umari, P; Pasquarello, Alfredo

2005-08-12

We analyze the principal vibrational spectra of vitreous GeO(2) and derive therefrom structural properties referring to length scales beyond the basic tetrahedral unit. We generate a model structure that yields a neutron structure factor in accord with experiment. The inelastic-neutron, the infrared, and the Raman spectra, calculated within a density-functional approach, also agree with respective experimental spectra. The accord for the Raman spectrum supports a Ge-O-Ge angle distribution centered at 135 degrees. The Raman feature X(2) is found to result from vibrations in three-membered rings, and therefore constitutes a distinctive characteristic of the medium-range structure.

Discrimination of Medicine Radix Astragali from Different Geographic Origins Using Multiple Spectroscopies Combined with Data Fusion Methods

NASA Astrophysics Data System (ADS)

Wang, Hai-Yan; Song, Chao; Sha, Min; Liu, Jun; Li, Li-Ping; Zhang, Zheng-Yong

2018-05-01

Raman spectra and ultraviolet-visible absorption spectra of four different geographic origins of Radix Astragali were collected. These data were analyzed using kernel principal component analysis combined with sparse representation classification. The results showed that the recognition rate reached 70.44% using Raman spectra for data input and 90.34% using ultraviolet-visible absorption spectra for data input. A new fusion method based on Raman combined with ultraviolet-visible data was investigated and the recognition rate was increased to 96.43%. The experimental results suggested that the proposed data fusion method effectively improved the utilization rate of the original data.

Time-resolved remote Raman study of minerals under supercritical CO2 and high temperatures relevant to Venus exploration.

PubMed

Sharma, Shiv K; Misra, Anupam K; Clegg, Samuel M; Barefield, James E; Wiens, Roger C; Acosta, Tayro

2010-07-13

We report time-resolved (TR) remote Raman spectra of minerals under supercritical CO(2) (approx. 95 atm pressure and 423 K) and under atmospheric pressure and high temperature up to 1003 K at distances of 1.5 and 9 m, respectively. The TR Raman spectra of hydrous and anhydrous sulphates, carbonate and silicate minerals (e.g. talc, olivine, pyroxenes and feldspars) under supercritical CO(2) (approx. 95 atm pressure and 423 K) clearly show the well-defined Raman fingerprints of each mineral along with the Fermi resonance doublet of CO(2). Besides the CO(2) doublet and the effect of the viewing window, the main differences in the Raman spectra under Venus conditions are the phase transitions, the dehydration and decarbonation of various minerals, along with a slight shift in the peak positions and an increase in line-widths. The dehydration of melanterite (FeSO(4).7H(2)O) at 423 K under approximately 95 atm CO(2) is detected by the presence of the Raman fingerprints of rozenite (FeSO(4).4H(2)O) in the spectrum. Similarly, the high-temperature Raman spectra under ambient pressure of gypsum (CaSO(4).2H(2)O) and talc (Mg(3)Si(4)O(10)(OH)(2)) indicate that gypsum dehydrates at 518 K, but talc remains stable up to 1003 K. Partial dissociation of dolomite (CaMg(CO(3))(2)) is observed at 973 K. The TR remote Raman spectra of olivine, alpha-spodumene (LiAlSi(2)O(6)) and clino-enstatite (MgSiO(3)) pyroxenes and of albite (NaAlSi(3)O(8)) and microcline (KAlSi(3)O(8)) feldspars at high temperatures also show that the Raman lines remain sharp and well defined in the high-temperature spectra. The results of this study show that TR remote Raman spectroscopy could be a potential tool for exploring the surface mineralogy of Venus during both daytime and nighttime at short and long distances.

Feasibility of Raman spectroscopy as PAT tool in active coating.

PubMed

Müller, Joshua; Knop, Klaus; Thies, Jochen; Uerpmann, Carsten; Kleinebudde, Peter

2010-02-01

Active coating is a specific application of film coating where the active ingredient is comprised in the coating layer. This implementation is a challenging operation regarding the achievement of desired amount of coating and coating uniformity. To guarantee the quality of such dosage forms it is desirable to develop a tool that is able to monitor the coating operation and detect the end of the process. Coating experiments were performed at which the model drug diprophylline is coated in a pan coater on placebo tablets and tablets containing the active ingredient itself. During the active coating Raman spectra were recorded in-line. The spectral measurements were correlated with the average weight gain and the amount of coated active ingredient at each time point. The developed chemometric model was tested by monitoring further coated batches. Furthermore, the effects of pan rotation speed and working distance on the acquired Raman signal and, hence, resulting effect of the chemometric model were examined. Besides coating on placebo cores it was possible to determine the amount of active ingredient in the film when coated onto cores containing the same active ingredient. In addition, the method is even applicable when varying the process parameters and measurement conditions within a restricted range. Raman spectroscopy is an appropriate process analytical technology too.

Raman scattering or fluorescence emission? Raman spectroscopy study on lime-based building and conservation materials.

PubMed

Kaszowska, Zofia; Malek, Kamilla; Staniszewska-Slezak, Emilia; Niedzielska, Karina

2016-12-05

This work presents an in-depth study on Raman spectra excited with 1064 and 532nm lasers of lime binders employed in the past as building materials and revealed today as valuable conservation materials. We focus our interest on the bands of strong intensity, which are present in the spectra of all binders acquired with laser excitation at 1064nm, but absent in the corresponding spectra acquired with laser excitation at 532nm. We suggest, that the first group of spectra represents fluorescence phenomena of unknown origin and the second true Raman scattering. In our studies, we also include two other phases of lime cycle, i.e. calcium carbonate (a few samples of calcite of various origins) and calcium oxide (quicklime) to assess how structural and chemical transformations of lime phases affect the NIR-Raman spectral profile. Furthermore, we analyse a set of carbonated limewashes and lime binders derived from old plasters to give an insight into their spectral characteristics after excitation with the 1064nm laser line. NIR-Raman micro-mapping results are also presented to reveal the spatial distribution of building materials and fluorescent species in the cross-section of plaster samples taken from a 15th century chapel. Our study shows that the Raman analysis can help identify lime-based building and conservation materials, however, a caution is advised in the interpretation of the spectra acquired using 1064nm excitation. Copyright © 2016. Published by Elsevier B.V.

Fraction of boroxol rings in vitreous boron oxide from a first-principles analysis of Raman and NMR spectra.

PubMed

Umari, P; Pasquarello, Alfredo

2005-09-23

We determine the fraction f of B atoms belonging to boroxol rings in vitreous boron oxide through a first-principles analysis. After generating a model structure of vitreous B2O3 by first-principles molecular dynamics, we address a large set of properties, including the neutron structure factor, the neutron density of vibrational states, the infrared spectra, the Raman spectra, and the 11B NMR spectra, and find overall good agreement with corresponding experimental data. From the analysis of Raman and 11B NMR spectra, we yield consistently for both probes a fraction f of approximately 0.75. This result indicates that the structure of vitreous boron oxide is largely dominated by boroxol rings.

Combining Raman and laser induced breakdown spectroscopy by double pulse lasing.

PubMed

Lednev, Vasily N; Pershin, Sergey M; Sdvizhenskii, Pavel A; Grishin, Mikhail Ya; Fedorov, Alexander N; Bukin, Vladimir V; Oshurko, Vadim B; Shchegolikhin, Alexander N

2018-01-01

A new approach combining Raman spectrometry and laser induced breakdown spectrometry (LIBS) within a single laser event was suggested. A pulsed solid state Nd:YAG laser running in double pulse mode (two frequency-doubled sequential nanosecond laser pulses with dozens microseconds delay) was used to combine two spectrometry methods within a single instrument (Raman/LIBS spectrometer). First, a low-energy laser pulse (power density far below ablation threshold) was used for Raman measurements while a second powerful laser pulse created the plasma suitable for LIBS analysis. A short time delay between two successive pulses allows measuring LIBS and Raman spectra at different moments but within a single laser flash-lamp pumping. Principal advantages of the developed instrument include high quality Raman/LIBS spectra acquisition (due to optimal gating for Raman/LIBS independently) and absence of target thermal alteration during Raman measurements. A series of high quality Raman and LIBS spectra were acquired for inorganic salts (gypsum, anhydrite) as well as for pharmaceutical samples (acetylsalicylic acid). To the best of our knowledge, the quantitative analysis feasibility by combined Raman/LIBS instrument was demonstrated for the first time by calibration curves construction for acetylsalicylic acid (Raman) and copper (LIBS) in gypsum matrix. Combining ablation pulses and Raman measurements (LIBS/Raman measurements) within a single instrument makes it an efficient tool for identification of samples hidden by non-transparent covering or performing depth profiling analysis including remote sensing. Graphical abstract Combining Raman and laser induced breakdown spectroscopy by double pulse lasing.

Micro-Raman spectroscopy study of ALVAC virus infected chicken embryo cells

NASA Astrophysics Data System (ADS)

Misra, Anupam K.; Kamemoto, Lori E.; Hu, Ningjie; Dykes, Ava C.; Yu, Qigui; Zinin, Pavel V.; Sharma, Shiv K.

2011-05-01

Micro- Raman spectroscopic investigation of ALVAC virus and of normal chicken embryo fibroblast cells and the cells infected with ALVAC virus labeled with green fluorescence protein (GFP) were performed with a 785 nm laser. Good quality Micro-Raman spectra of the Alvac II virus were obtained. These spectra show that the ALVAC II virus contains buried tyrosine residues and the coat protein of the virus has α-helical structure. A comparison of Raman spectra of normal and virus infected chicken embryo fibroblast cells revealed that the virus infected cells show additional bands at 535, 928, and 1091 cm-1, respectively, corresponding to δ(C-O-C) glycosidic ring, protein α-helix, and DNA (O-P-O) modes. In addition, the tyrosine resonance double (833 and 855 cm-1) shows reversal in the intensity of the higher-frequency band as compared to the normal cells that can be used to identify the infected cells. In the C-H stretching region, the infected cells show bands with higher intensity as compared to that of the corresponding bands in the normal cells. We also found that the presence of GFP does not affect the Raman spectra of samples when using a 785 nm micro-Raman system because the green fluorescence wavelength of GFP is well below the Stokes-Raman shifted spectral region.

A comparison of the far-infrared and low-frequency Raman spectra of glass-forming liquids

NASA Astrophysics Data System (ADS)

Perova, T. S.; Vij, J. K.; Christensen, D. H.; Nielsen, O. F.

1999-04-01

Far-infrared and low-frequency Raman spectra in the wavenumber range from 15 to 500 cm -1 were recorded for glycerol, triacetin (glycerol triacetate) and o-terphenyl at temperatures from 253 to 355 K. The far-infrared spectra of glycerol appear complex compared with the spectra of triacetin owing to the presence of hydrogen bonding in glycerol. The experimental results obtained for o-terphenyl are in good agreement with normal mode analyses carried out for crystalline o-terphenyl (A. Criado, F.J. Bermejo, A. de Andres, Mol. Phys. 82 (1994) 787). The far-infrared results are compared with the low-frequency Raman spectra of these three glass-forming liquids. The difference in temperature dependences found from these spectra is explained on the basis of different temperature contributions of the relaxational and vibrational processes to the low-frequency vibrational spectra.

Comparison of experimental and calculated chiroptical spectra for chiral molecular structure determination.

PubMed

Polavarapu, Prasad L; Covington, Cody L

2014-09-01

For three different chiroptical spectroscopic methods, namely, vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and Raman optical activity (ROA), the measures of similarity of the experimental spectra to the corresponding spectra predicted using quantum chemical theories are summarized. In determining the absolute configuration and/or predominant conformations of chiral molecules, these similarity measures provide numerical estimates of agreement between experimental observations and theoretical predictions. Selected applications illustrating the similarity measures for absorption, circular dichroism, and corresponding dissymmetry factor (DF) spectra, in the case of VCD and ECD, and for Raman, ROA, and circular intensity differential (CID) spectra in the case of ROA, are presented. The analysis of similarity in DF or CID spectra is considered to be much more discerning and accurate than that in absorption (or Raman) and circular dichroism (or ROA) spectra, undertaken individually. © 2014 Wiley Periodicals, Inc.

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

NASA Astrophysics Data System (ADS)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

Radiative transfer equation accounting for rotational Raman scattering and its solution by the discrete-ordinates method

NASA Astrophysics Data System (ADS)

Rozanov, Vladimir V.; Vountas, Marco

2014-01-01

Rotational Raman scattering of solar light in Earth's atmosphere leads to the filling-in of Fraunhofer and telluric lines observed in the reflected spectrum. The phenomenological derivation of the inelastic radiative transfer equation including rotational Raman scattering is presented. The different forms of the approximate radiative transfer equation with first-order rotational Raman scattering terms are obtained employing the Cabannes, Rayleigh, and Cabannes-Rayleigh scattering models. The solution of these equations is considered in the framework of the discrete-ordinates method using rigorous and approximate approaches to derive particular integrals. An alternative forward-adjoint technique is suggested as well. A detailed description of the model including the exact spectral matching and a binning scheme that significantly speeds up the calculations is given. The considered solution techniques are implemented in the radiative transfer software package SCIATRAN and a specified benchmark setup is presented to enable readers to compare with own results transparently.

Micro-Raman spectroscopy of tissue samples for oral pathology follow-up monitoring

NASA Astrophysics Data System (ADS)

Delfino, I.; Camerlingo, C.; Zenone, F.; Perna, G.; Capozzi, V.; Cirillo, N.; Gaeta, G. M.; Lepore, M.

2010-04-01

An "in vitro" study of Raman spectra from oral human tissues is reported in order to the develop a diagnostic method suitable for "in vivo" oral pathology follow-up. The investigated pathology is Pemphigus Vulgaris (PV) for which new techniques for guiding and monitoring therapy would be particularly useful. Raman spectra were obtained in the wavenumber regions from 1000 to 1800 cm-1 and 2700 to 3200 cm-1 from tissues from patients at different stages of pathology (active PV, under therapy and in PV remission stage) as confirmed by histopathological and immunofluorescence analysis. Differences in the spectra depending on tissue illness stage arise in 1150-1250 cm-1 (amide III) and 1420-1450 cm-1 (CH3 deformation) regions and around 1650 cm-1 (amide I) and 2930 cm-1 (CH3 symmetric stretch). A wavelet deconvolution procedure was applied to the spectra for better discriminating among the three different stages of illness and a linear regression analysis was used to fully exploit the content of information of Raman spectra.

Spectral reconstruction for shifted-excitation Raman difference spectroscopy (SERDS).

PubMed

Guo, Shuxia; Chernavskaia, Olga; Popp, Jürgen; Bocklitz, Thomas

2018-08-15

Fluorescence emission is one of the major obstacles to apply Raman spectroscopy in biological investigations. It is usually several orders more intense than Raman scattering and hampers further analysis. In cases where the fluorescence emission is too intense to be efficiently removed via routine mathematical baseline correction algorithms, an alternative approach is needed. One alternative approach is shifted-excitation Raman difference spectroscopy (SERDS), where two Raman spectra are recorded with two slightly different excitation wavelengths. Ideally, the fluorescence emission at the two excitations does not change while the Raman spectrum shifts according to the excitation wavelength. Hence the fluorescence is removed in the difference of the two recorded Raman spectra. For better interpretability a spectral reconstruction procedure is necessary to recover the fluorescence-free Raman spectrum. This is challenging due to the intensity variations between the two recorded Raman spectra caused by unavoidable experimental changes as well as the presence of noise. Existent approaches suffer from drawbacks like spectral resolution loss, fluorescence residual, and artefacts. In this contribution, we proposed a reconstruction method based on non-negative least squares (NNLS), where the intensity variations between the two measurements are utilized in the reconstruction model. The method achieved fluorescence-free reconstruction on three real-world SERDS datasets without significant information loss. Thereafter, we quantified the performance of the reconstruction based on artificial datasets from four aspects: reconstructed spectral resolution, precision of reconstruction, signal-to-noise-ratio (SNR), and fluorescence residual. The artificial datasets were constructed with varied Raman to fluorescence intensity ratio (RFIR), SNR, full-width at half-maximum (FWHM), excitation wavelength shift, and fluorescence variation between the two spectra. It was demonstrated that the NNLS approach provides a faithful reconstruction without significantly changing the spectral resolution. Meanwhile, the reconstruction is almost robust to fluorescence variations between the two spectra. Last but not the least the SNR was improved after reconstruction for extremely noisy SERDS datasets. Copyright © 2018 Elsevier B.V. All rights reserved.

Spectra and structure of small ring molecules. XLV. Microwave, infrared, and Raman spectra, conformational stability, dipole moment and vibrational assignment of cyclobutylcarboxaldehyde

NASA Astrophysics Data System (ADS)

Durig, J. R.; Badawi, H. M.

1990-12-01

The microwave spectrum of cyclobutylcarboxaldehyde, c-C 4H 7CHO, has been recorded from 12.4 to 39.0 GHz. Two sets of a-type R-branch transitions were observed and assigned, on the basis of the rigid rotor model, to the equatorial-trans and the equatorial-gauche conformers. The rotational constants for the ground state for the equatorial-trans conformer are: A=9653.70 ± 0.47, B=2224.15 ± 0.01 and C=1986.68 ± 0.01 MHz. The lines for the first excited state of the asymmetric torsion for the equatorial-trans conformer have also been identified and assigned and, from relative intensity measurements, the frequency of the asymmetric torsion of this conformer is estimated to be 71 ± 10 cm -1. For the equatorial-gauche conformer in addition to the R-branch assignments, Q-branch assignments have been made for b- and c-type transitions for the ground state. The rotational constants for this conformer are: A=8108.08 ± 0.05, B=2554.89 ± 0.01, and C=2215.78 ± 0.01 MHz. From the Stark effect the dipole moment components for both conformers were determined. For the equatorial-trans conformer the dipole moment components were determined to be: &|μ a&| = 1.65 ± 0.01 D, &|μ b&|=0.00 (by symmetry), &|μ c&|=1.23 ± 0.01 &|μ t&|=2.06 ± 0.01 D. For the equatorial-gauge conformer the dipole moment components were determined to be: &|μ a&|=2.03 ± &|μ b&|=1.52 ± 0.04, &|μ c&|=0.83 ± 0.06 and &|μ t&|=2.66 ± 0.02 D. The infrared (3500-30 cm -1 and Raman have been recorded for the gaseous and solid states of cyclobutylcarboxaldehyde. Additionally, the Raman spectrum of the liquid phase has been recorded and qualitative depolarization values have been obtained. From variable temperature measurements of the microwave and Raman spectra, for the gaseous and liquid phases, respectively, the equatorial-gauche conformer was found to be thermodynamically preferred for the gas phase; however, it is the equatorial-trans rotamer which is most stable in the liquid. Furthermore, the only conformation present in the annealed solid is the equatorial-trans rotamer. From these data a complete vibrational assignment is proposed. The observed splitting of many of the fundamentals in the solid state indicates that there are at least two molecules per primitive cell. These results are compared to similar quantities in some related molecules.

Temperature-dependent μ-Raman investigation of struvite crystals.

PubMed

Prywer, Jolanta; Kasprowicz, D; Runka, T

2016-04-05

The effect of temperature on the vibrational properties of struvite crystals grown from silica gels was systematically studied by μ-Raman spectroscopy. The time-dependent Raman spectra recorded in the process of long time annealing of struvite crystal at 353 K do not indicate structural changes in the struvite crystal with the time of annealing. The temperature-dependent Raman spectra recorded in the range 298-423 K reveal a phase transition in struvite at about 368 K. Above this characteristic temperature, some of bands assigned to vibrations of the PO4 and NH4 tetrahedra and water molecules observed in the Raman spectra in low temperatures (orthorhombic phase) change their spectral parameters or disappear, which indicates a transition to a higher symmetry structure of struvite in the range of high temperatures. Copyright © 2016 Elsevier B.V. All rights reserved.

Resonant Raman spectra of diindenoperylene thin films

NASA Astrophysics Data System (ADS)

Scholz, R.; Gisslén, L.; Schuster, B.-E.; Casu, M. B.; Chassé, T.; Heinemeyer, U.; Schreiber, F.

2011-01-01

Resonant and preresonant Raman spectra obtained on diindenoperylene (DIP) thin films are interpreted with calculations of the deformation of a relaxed excited molecule with density functional theory (DFT). The comparison of excited state geometries based on time-dependent DFT or on a constrained DFT scheme with observed absorption spectra of dissolved DIP reveals that the deformation pattern deduced from constrained DFT is more reliable. Most observed Raman peaks can be assigned to calculated A_g-symmetric breathing modes of DIP or their combinations. As the position of one of the laser lines used falls into a highly structured absorption band, we have carefully analyzed the Raman excitation profile arising from the frequency dependence of the dielectric tensor. This procedure gives Raman cross sections in good agreement with the observed relative intensities, both in the fully resonant and in the preresonant case.

Application of Raman spectroscopy and surface-enhanced Raman scattering to the analysis of synthetic dyes found in ballpoint pen inks.

PubMed

Geiman, Irina; Leona, Marco; Lombardi, John R

2009-07-01

The applicability of Raman spectroscopy and surface-enhanced Raman scattering (SERS) to the analysis of synthetic dyes commonly found in ballpoint inks was investigated in a comparative study. Spectra of 10 dyes were obtained using a dispersive system (633 nm, 785 nm lasers) and a Fourier transform system (1064 nm laser) under different analytical conditions (e.g., powdered pigments, solutions, thin layer chromatography [TLC] spots). While high fluorescence background and poor spectral quality often characterized the normal Raman spectra of the dyes studied, SERS was found to be generally helpful. Additionally, dye standards and a single ballpoint ink were developed on a TLC plate following a typical ink analysis procedure. SERS spectra were successfully collected directly from the TLC plate, thus demonstrating a possible forensic application for the technique.

Resonant Raman spectra of diindenoperylene thin films.

PubMed

Scholz, R; Gisslén, L; Schuster, B-E; Casu, M B; Chassé, T; Heinemeyer, U; Schreiber, F

2011-01-07

Resonant and preresonant Raman spectra obtained on diindenoperylene (DIP) thin films are interpreted with calculations of the deformation of a relaxed excited molecule with density functional theory (DFT). The comparison of excited state geometries based on time-dependent DFT or on a constrained DFT scheme with observed absorption spectra of dissolved DIP reveals that the deformation pattern deduced from constrained DFT is more reliable. Most observed Raman peaks can be assigned to calculated A(g)-symmetric breathing modes of DIP or their combinations. As the position of one of the laser lines used falls into a highly structured absorption band, we have carefully analyzed the Raman excitation profile arising from the frequency dependence of the dielectric tensor. This procedure gives Raman cross sections in good agreement with the observed relative intensities, both in the fully resonant and in the preresonant case.

Raman Spectra and Cross Sections of Ammonia, Chlorine, Hydrogen Sulfide, Phosgene, and Sulfur Dioxide Toxic Gases in the Fingerprint Region 400-1400 cm-1

DTIC Science & Technology

2016-02-11

AIP ADVANCES 6, 025310 (2016) Raman spectra and cross sections of ammonia , chlorine, hydrogen sulfide, phosgene, and sulfur dioxide toxic gases in...Received 10 December 2015; accepted 3 February 2016; published online 11 February 2016) Raman spectra of ammonia (NH3), chlorine (Cl2), hydrogen...and cross sections of ammonia (NH3), chlorine (Cl2), hydrogen sulfide (H2S), phosgene (CCl2O), and sulfur dioxide (SO2) toxic gases in the fingerprint

Raman band intensities of tellurite glasses.

PubMed

Plotnichenko, V G; Sokolov, V O; Koltashev, V V; Dianov, E M; Grishin, I A; Churbanov, M F

2005-05-15

Raman spectra of TeO2-based glasses doped with WO3, ZnO, GeO2, TiO2, MoO3, and Sb2O3 are measured. The intensity of bands in the Raman spectra of MoO3-TeO2 and MoO3-WO3-TeO2 glasses is shown to be 80-95 times higher than that for silica glass. It is shown that these glasses can be considered as one of the most promising materials for Raman fiber amplifiers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kearney, Sean Patrick

A hybrid fs/ps pure-rotational coherent anti-Stokes Raman scattering (CARS) scheme is systematically evaluated over a wide range of flame conditions in the product gases of two canonical flat-flame burners. Near-transform-limited, broadband femtosecond pump and Stokes pulses impulsively prepare a rotational Raman coherence, which is later probed using a high-energy, frequency-narrow picosecond beam generated by the second-harmonic bandwidth compression scheme that has recently been demonstrated for rotational CARS generation in H 2/air flat flames. The measured spectra are free of collision effects and nonresonant background and can be obtained on a single-shot basis at 1 kHz. The technique is evaluated formore » temperature/oxygen measurements in near-adiabatic H 2/air flames stabilized on the Hencken burner for equivalence ratios of φ = 0.20–1.20. Thermometry is demonstrated in hydrocarbon/air products for φ = 0.75–3.14 in premixed C 2H 4/air flat flames on the McKenna burner. Reliable spectral fitting is demonstrated for both shot-averaged and single-laser-shot data using a simple phenomenological model. Measurement accuracy is benchmarked by comparison to adiabatic-equilibrium calculations for the H 2/air flames, and by comparison with nanosecond CARS measurements for the C 2H 4/air flames. Quantitative accuracy comparable to nanosecond rotational CARS measurements is observed, while the observed precision in both the temperature and oxygen data is extraordinarily high, exceeding nanosecond CARS, and on par with the best published thermometric precision by femtosecond vibrational CARS in flames, and rotational femtosecond CARS at low temperature. Threshold levels of signal-to-noise ratio to achieve 1–2% precision in temperature and O 2/N 2 ratio are identified. Our results show that pure-rotational fs/ps CARS is a robust and quantitative tool when applied across a wide range of flame conditions spanning lean H 2/air combustion to fuel-rich sooting hydrocarbon flames.« less

Simultaneous observation of rotational coherent Stokes Raman scattering and coherent anti-Stokes Raman scattering in air and nitrogen

NASA Technical Reports Server (NTRS)

Snow, J. B.; Chang, R. K.; Zheng, J. B.; Leipertz, A.

1983-01-01

Rotational coherent Stokes Raman scattering (CSRS) and coherent anti-Stokes Raman scattering (CARS) in air and in nitrogen were observed simultaneously by using broadband generation and detection. In the broadband technique used, the entire CARS and CSRS spectrum was generated in a single laser pulse; the CSRS and CARS signals were dispersed by a spectrograph and detected simultaneously by an optical multichannel analyzer. A three-dimensional phase-matching geometry was used to achieve spatial resolution of the CSRS and CARS beams from the input beams. Under resonant conditions, similar experiments may provide a means of investigating the possible interaction between the CSRS and CARS processes in driving the rotational levels.

UV irradiation-induced Raman spectra changes in lead silicate glasses

NASA Astrophysics Data System (ADS)

Jia, Hongzhi; Chen, Guanghui; Wang, Wencheng

2006-12-01

The Raman spectra for a series of lead silicate glasses with different PbO content before and after irradiation with different energy density by the frequency-quadrupled output of a Q-switched YAG laser (266 nm, 10 Hz repetition rate) were measured. The intensity of Pb-O band near 140 cm -1 in the Raman spectra decreases after UV irradiation and no new band appears in the Raman spectra. Exposed to the UV beam with high energy density (150 mJ/cm 2), although the total dose is smaller than the dose with low energy density (50 mJ/cm 2), the intensity of the 140 cm -1 band drops heavilier than exposed to the UV beam with low energy density. This shows that the UV irradiation can cause the broken of Pb-O bond in lead silicate glasses and the broken of Pb-O bond is related to the energy density of UV beam.

A novel method for detection of phosphorylation in single cells by surface enhanced Raman scattering (SERS) using composite organic-inorganic nanoparticles (COINs).

PubMed

Shachaf, Catherine M; Elchuri, Sailaja V; Koh, Ai Leen; Zhu, Jing; Nguyen, Lienchi N; Mitchell, Dennis J; Zhang, Jingwu; Swartz, Kenneth B; Sun, Lei; Chan, Selena; Sinclair, Robert; Nolan, Garry P

2009-01-01

Detection of single cell epitopes has been a mainstay of immunophenotyping for over three decades, primarily using fluorescence techniques for quantitation. Fluorescence has broad overlapping spectra, limiting multiplexing abilities. To expand upon current detection systems, we developed a novel method for multi-color immuno-detection in single cells using "Composite Organic-Inorganic Nanoparticles" (COINs) Raman nanoparticles. COINs are Surface-Enhanced Raman Scattering (SERS) nanoparticles, with unique Raman spectra. To measure Raman spectra in single cells, we constructed an automated, compact, low noise and sensitive Raman microscopy device (Integrated Raman BioAnalyzer). Using this technology, we detected proteins expressed on the surface in single cells that distinguish T-cells among human blood cells. Finally, we measured intracellular phosphorylation of Stat1 (Y701) and Stat6 (Y641), with results comparable to flow cytometry. Thus, we have demonstrated the practicality of applying COIN nanoparticles for measuring intracellular phosphorylation, offering new possibilities to expand on the current fluorescent technology used for immunoassays in single cells.

A Novel Method for Detection of Phosphorylation in Single Cells by Surface Enhanced Raman Scattering (SERS) using Composite Organic-Inorganic Nanoparticles (COINs)

PubMed Central

Shachaf, Catherine M.; Elchuri, Sailaja V.; Koh, Ai Leen; Zhu, Jing; Nguyen, Lienchi N.; Mitchell, Dennis J.; Zhang, Jingwu; Swartz, Kenneth B.; Sun, Lei; Chan, Selena; Sinclair, Robert; Nolan, Garry P.

2009-01-01

Background Detection of single cell epitopes has been a mainstay of immunophenotyping for over three decades, primarily using fluorescence techniques for quantitation. Fluorescence has broad overlapping spectra, limiting multiplexing abilities. Methodology/Principal Findings To expand upon current detection systems, we developed a novel method for multi-color immuno-detection in single cells using “Composite Organic-Inorganic Nanoparticles” (COINs) Raman nanoparticles. COINs are Surface-Enhanced Raman Scattering (SERS) nanoparticles, with unique Raman spectra. To measure Raman spectra in single cells, we constructed an automated, compact, low noise and sensitive Raman microscopy device (Integrated Raman BioAnalyzer). Using this technology, we detected proteins expressed on the surface in single cells that distinguish T-cells among human blood cells. Finally, we measured intracellular phosphorylation of Stat1 (Y701) and Stat6 (Y641), with results comparable to flow cytometry. Conclusions/Significance Thus, we have demonstrated the practicality of applying COIN nanoparticles for measuring intracellular phosphorylation, offering new possibilities to expand on the current fluorescent technology used for immunoassays in single cells. PMID:19367337

Detection of nasopharyngeal cancer using confocal Raman spectroscopy and genetic algorithm technique

NASA Astrophysics Data System (ADS)

Li, Shao-Xin; Chen, Qiu-Yan; Zhang, Yan-Jiao; Liu, Zhi-Ming; Xiong, Hong-Lian; Guo, Zhou-Yi; Mai, Hai-Qiang; Liu, Song-Hao

2012-12-01

Raman spectroscopy (RS) and a genetic algorithm (GA) were applied to distinguish nasopharyngeal cancer (NPC) from normal nasopharyngeal tissue. A total of 225 Raman spectra are acquired from 120 tissue sites of 63 nasopharyngeal patients, 56 Raman spectra from normal tissue and 169 Raman spectra from NPC tissue. The GA integrated with linear discriminant analysis (LDA) is developed to differentiate NPC and normal tissue according to spectral variables in the selected regions of 792-805, 867-880, 996-1009, 1086-1099, 1288-1304, 1663-1670, and 1742-1752 cm-1 related to proteins, nucleic acids and lipids of tissue. The GA-LDA algorithms with the leave-one-out cross-validation method provide a sensitivity of 69.2% and specificity of 100%. The results are better than that of principal component analysis which is applied to the same Raman dataset of nasopharyngeal tissue with a sensitivity of 63.3% and specificity of 94.6%. This demonstrates that Raman spectroscopy associated with GA-LDA diagnostic algorithm has enormous potential to detect and diagnose nasopharyngeal cancer.

Raman scattering of Cisplatin near silver nanoparticles

NASA Astrophysics Data System (ADS)

Mirsaleh-Kohan, Nasrin; Duplanty, Michael; Torres, Marjorie; Moazzezi, Mojtaba; Rostovtsev, Yuri V.

2018-03-01

The Raman scattering of Cisplatin (the first generation of anticancer drugs) has been studied. In the presence of silver nanoparticles, strong modifications of Raman spectra have been observed. The Raman frequencies have been shifted and the line profiles are broadened. We develop a theoretical model to explain the observed features of the Raman scattering. The model takes into account self-consistently the interaction of molecules with surface plasmonic waves excited in the silver nanoparticles, and it provides a qualitative agreement with the observed Raman spectra. We have demonstrated that the using silver nanoparticles can increase sensitivity of the technique, and potentially it has a broader range of applications to both spectroscopy and microscopy.

Discrimination of selected species of pathogenic bacteria using near-infrared Raman spectroscopy and principal components analysis

NASA Astrophysics Data System (ADS)

de Siqueira e Oliveira, Fernanda SantAna; Giana, Hector Enrique; Silveira, Landulfo

2012-10-01

A method, based on Raman spectroscopy, for identification of different microorganisms involved in bacterial urinary tract infections has been proposed. Spectra were collected from different bacterial colonies (Gram-negative: Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Enterobacter cloacae, and Gram-positive: Staphylococcus aureus and Enterococcus spp.), grown on culture medium (agar), using a Raman spectrometer with a fiber Raman probe (830 nm). Colonies were scraped from the agar surface and placed on an aluminum foil for Raman measurements. After preprocessing, spectra were submitted to a principal component analysis and Mahalanobis distance (PCA/MD) discrimination algorithm. We found that the mean Raman spectra of different bacterial species show similar bands, and S. aureus was well characterized by strong bands related to carotenoids. PCA/MD could discriminate Gram-positive bacteria with sensitivity and specificity of 100% and Gram-negative bacteria with sensitivity ranging from 58 to 88% and specificity ranging from 87% to 99%.

Amide I vibrational mode suppression in surface (SERS) and tip (TERS) enhanced Raman spectra of protein specimens

PubMed Central

Kurouski, Dmitry; Postiglione, Thomas; Deckert-Gaudig, Tanja; Deckert, Volker; Lednev, Igor K.

2013-01-01

Surface- and tip-enhanced Raman spectroscopy (SERS and TERS) are modern spectroscopic techniques, which are becoming widely used and show a great potential for the structural characterisation of biological systems. Strong enhancement of the Raman signal through localised surface plasmon resonance enables chemical detection at the single-molecule scale. Enhanced Raman spectra collected from biological specimens, such as peptides, proteins or microorganisms, were often observed to lack the amide I band, which is commonly used as a marker for the interpretation of secondary protein structure. The cause of this phenomenon was unclear for many decades. In this work, we investigated this phenomenon for native insulin and insulin fibrils using both TERS and SERS and compared these spectra to the spectra of well-defined homo peptides. The results indicate that the appearance of the amide I Raman band does not correlate with the protein aggregation state, but is instead determined by the size of the amino acid side chain. For short model peptides, the absence of the amide I band in TERS and SERS spectra correlates with the presence of a bulky side chain. Homo-glycine and -alanine, which are peptides with small side chain groups (H and CH3, respectively), exhibited an intense amide I band in almost 100% of the acquired spectra. Peptides with bulky side chains, such as tyrosine and tryptophan, exhibited the amide I band in 70% and 31% of the acquired spectra, respectively. PMID:23330149

Complementary analysis of tissue homogenates composition obtained by Vis and NIR laser excitations and Raman spectroscopy.

PubMed

Staniszewska-Slezak, Emilia; Malek, Kamilla; Baranska, Malgorzata

2015-08-05

Raman spectroscopy and four excitation lines in the visible (Vis: 488, 532, 633 nm) and near infrared (NIR: 785 nm) were used for biochemical analysis of rat tissue homogenates, i.e. myocardium, brain, liver, lung, intestine, and kidney. The Vis Raman spectra are very similar for some organs (brain/intestines and kidney/liver) and dominated by heme signals when tissues of lung and myocardium were investigated (especially with 532 nm excitation). On the other hand, the NIR Raman spectra are specific for each tissue and more informative than the corresponding ones collected with the Vis excitations. The spectra analyzed without any special pre-processing clearly illustrate different chemical composition of each tissue and give information about main components e.g. lipids or proteins, but also about the content of some specific compounds such as amino acid residues, nucleotides and nucleobases. However, in order to obtain the whole spectral information about tissues complex composition the spectra of Vis and NIR excitations should be collected and analyzed together. A good agreement of data gathered from Raman spectra of the homogenates and those obtained previously from Raman imaging of the tissue cross-sections indicates that the presented here approach can be a method of choice for an investigation of biochemical variation in animal tissues. Moreover, the Raman spectral profile of tissue homogenates is specific enough to be used for an investigation of potential pathological changes the organism undergoes, in particular when supported by the complementary FTIR spectroscopy. Copyright © 2015 Elsevier B.V. All rights reserved.

The Use of Raman Tweezers and Chemometric Analysis to Discriminate the Urological Cell Lines, PC-3, LNCaP, BPH and MGH-U1

NASA Astrophysics Data System (ADS)

Harvey, T. J.; Hughes, C.; Ward, A. D.; Gazi, E.; Faria, E. Correia; Clarke, N. W.; Brown, M.; Snook, R.; Gardner, P.

2008-11-01

Here we report on investigations into using Raman optical tweezers to analyse both live and chemically fixed prostate and bladder cells. Spectra were subjected to chemometric analysis to discriminate and classify the cell types based on their spectra. Subsequent results revealed the potential of Raman tweezers as a potential clinical diagnostic tool.

Raman spectra of single cells with autofluorescence suppression by modulated wavelength excitation

NASA Astrophysics Data System (ADS)

Krafft, Christoph; Dochow, Sebastian; Bergner, Norbert; Clement, Joachim H.; Praveen, Bavishna B.; Mazilu, Michael; Marchington, Rob; Dholakia, Kishan; Popp, Jürgen

2012-01-01

Raman spectroscopy is a non-invasive technique offering great potential in the biomedical field for label-free discrimination between normal and tumor cells based on their biochemical composition. First, this contribution describes Raman spectra of lymphocytes after drying, in laser tweezers, and trapped in a microfluidic environment. Second, spectral differences between lymphocytes and acute myeloid leukemia cells (OCI-AML3) are compared for these three experimental conditions. Significant similarities of difference spectra are consistent with the biological relevance of the spectral features. Third, modulated wavelength Raman spectroscopy has been applied to this model system to demonstrate background suppression. Here, the laser excitation wavelength of 785 nm was modulated with a frequency of 40 mHz by 0.6 nm. 40 spectra were accumulated with an exposure time of 5 seconds each. These data were subjected to principal component analysis to calculate modulated Raman signatures. The loading of the principal component shows characteristics of first derivatives with derivative like band shapes. The derivative of this loading corresponds to a pseudo-second derivative spectrum and enables to determine band positions.

Raman and Brillouin scattering studies of bulk 2H-WSe2

NASA Astrophysics Data System (ADS)

Akintola, K.; Andrews, G. T.; Curnoe, S. H.; Koehler, M. R.; Keppens, V.

2015-10-01

Raman and Brillouin spectroscopy were used to probe optic and acoustic phonons in bulk 2H-WSe2. Raman spectra collected under different polarization conditions allowed assignment of spectral peaks to various first- and second-order processes. In contrast to some previous studies, a Raman peak at  ˜259 cm-1was found not to be due to the A1g mode but to a second-order process involving phonons at either the M or K point of the Brillouin zone. Resonance effects due to excitons were also observed in the Raman spectra. Brillouin spectra of 2H-WSe2 contain a single peak doublet arising from a Rayleigh surface mode propagating with a velocity of 1340+/- 20 m s-1. This value is comparable to that estimated from Density Functional Theory calculations and also to those for the transition metal diselenides 2H-TaSe2 and 2H-NbSe2. Unlike these two materials, however, peaks arising from scattering via the elasto-optic mechanism were not observed in Brillouin spectra of WSe2 despite its lower opacity.

Wavelet data analysis of micro-Raman spectra for follow-up monitoring in oral pathologies

NASA Astrophysics Data System (ADS)

Camerlingo, C.; Zenone, F.; Perna, G.; Capozzi, V.; Cirillo, N.; Gaeta, G. M.; Lepore, M.

2008-02-01

A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra from human biological samples. In particular, measurements have been performed on some samples of oral tissue and blood serum from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. The disease is characterized histologically by intradermal blisters and immunopathologically by the finding of tissue bound and circulating immunoglobulin G (IgG) antibody directed against the cell surface of keratinocytes. More than 150 spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. The results indicate that appropriate data processing can contribute to enlarge the medical applications of micro-Raman spectroscopy.

Raman Spectroscopy for Analysis of Thorium Compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Yin-Fong; Johnson, Timothy J.; Olsen, Khris B.

2016-05-12

The thorium fuel cycle is an alternative to the uranium fuel cycle in that when 232Th is irradiated with neutrons it is converted to 233U, another fissile isotope. There are several chemical forms of thorium which are used in the Th fuel cycle. Recently, Raman spectroscopy has become a very portable and facile analytical technique useful for many applications, including e.g. determining the chemical composition of different materials such as for thorium compounds. The technique continues to improve with the development of ever-more sensitive instrumentation and better software. Using a laboratory Fourier-transform (FT)-Raman spectrometer with a 785 nm wavelength laser,more » we were able to obtain Raman spectra from a series of thorium-bearing compounds of unknown origin. These spectra were compared to the spectra of in-stock-laboratory thorium compounds including ThO2, ThF4, Th(CO3)2 and Th(C2O4)2. The unknown spectra showed very good agreement to the known standards, demonstrating the applicability of Raman spectroscopy for detection and identification of these nuclear materials.« less

Raman spectroscopy in biomedicine – non-invasive in vitro analysis of cells and extracellular matrix components in tissues

PubMed Central

Brauchle, Eva; Schenke-Layland, Katja

2013-01-01

Raman spectroscopy is an established laser-based technology for the quality assurance of pharmaceutical products. Over the past few years, Raman spectroscopy has become a powerful diagnostic tool in the life sciences. Raman spectra allow assessment of the overall molecular constitution of biological samples, based on specific signals from proteins, nucleic acids, lipids, carbohydrates, and inorganic crystals. Measurements are non-invasive and do not require sample processing, making Raman spectroscopy a reliable and robust method with numerous applications in biomedicine. Moreover, Raman spectroscopy allows the highly sensitive discrimination of bacteria. Rama spectra retain information on continuous metabolic processes and kinetics such as lipid storage and recombinant protein production. Raman spectra are specific for each cell type and provide additional information on cell viability, differentiation status, and tumorigenicity. In tissues, Raman spectroscopy can detect major extracellular matrix components and their secondary structures. Furthermore, the non-invasive characterization of healthy and pathological tissues as well as quality control and process monitoring of in vitro-engineered matrix is possible. This review provides comprehensive insight to the current progress in expanding the applicability of Raman spectroscopy for the characterization of living cells and tissues, and serves as a good reference point for those starting in the field. PMID:23161832

REMOTE RAMAN SPECTROSCOPY OF VARIOUS MIXED AND COMPOSITE MINERAL PHASES AT 7.2 m DISTANCE

NASA Technical Reports Server (NTRS)

Sharma, S. K.; Misra, A. K.; Ismail, Syed; Singh, U. N.

2006-01-01

Remote Raman [e.g.,1-5] and micro-Raman spectroscopy [e.g., 6-10] are being evaluated on geological samples for their potential applications on Mars rover or lander. The Raman lines of minerals are sharp and distinct. The Raman finger-prints of minerals do not shift appreciably but remain distinct even in sub-micron grains and, therefore, can be used for mineral identification in fine-grained rocks [e.g., 4,7]. In this work we have evaluated the capability of a directly coupled remote Raman system (co-axial configuration) for distinguishing the mineralogy of multiple crystals in the exciting laser beam. We have measured the Raman spectra of minerals in the near vicinity of each other and excited with a laser beam (e.g. -quartz (Qz) and K-feldspar (Feld) plates, each 5 mm thick). The spectra of composite transparent mineral plates of 5 mm thickness of -quartz and gypsum over calcite crystal were measured with the composite samples perpendicular to the exciting laser beam. The measurements of remote Raman spectra of various bulk minerals, and mixed and composite minerals with our portable UH remote Raman system were carried out at the Langley Research Center in a fully illuminated laboratory.

Principles and applications of Raman spectroscopy in pharmaceutical drug discovery and development.

PubMed

Gala, Urvi; Chauhan, Harsh

2015-02-01

In recent years, Raman spectroscopy has become increasingly important as an analytical technique in various scientific areas of research and development. This is partly due to the technological advancements in Raman instrumentation and partly due to detailed fingerprinting that can be derived from Raman spectra. Its versatility of applications, rapidness of collection and easy analysis have made Raman spectroscopy an attractive analytical tool. The following review describes Raman spectroscopy and its application within the pharmaceutical industry. The authors explain the theory of Raman scattering and its variations in Raman spectroscopy. The authors also highlight how Raman spectra are interpreted, providing examples. Raman spectroscopy has a number of potential applications within drug discovery and development. It can be used to estimate the molecular activity of drugs and to establish a drug's physicochemical properties such as its partition coefficient. It can also be used in compatibility studies during the drug formulation process. Raman spectroscopy's immense potential should be further investigated in future.

Raman spectroscopic study on the excystation process in a single unicellular organism amoeba (Acanthamoeba polyphaga)

NASA Astrophysics Data System (ADS)

Lin, Yu-Chung; Perevedentseva, Elena; Cheng, Chia-Liang

2015-05-01

An in vivo Raman spectroscopic study of amoeba (Acanthamoeba polyphaga) is presented. The changes of the spectra during the amoeba cyst activation and excystation are analyzed. The spectra show the changes of the relative intensities of bands corresponding to protein, lipid, and carotenoid components during cyst activation. The presence of carotenoids in the amoeba is observed via characteristic Raman bands. These signals in the Raman spectra are intense in cysts but decrease in intensity with cyst activation and exhibit a correlation with the life cycle of amoeba. This work demonstrates the feasibility of using Raman spectroscopy for the detection of single amoeba microorganisms in vivo and for the analysis of the amoeba life activity. The information obtained may have implications for the estimation of epidemiological situations and for the diagnostics and prognosis of the development of amoebic inflammations.

Raman spectroscopic study on the excystation process in a single unicellular organism amoeba (Acanthamoeba polyphaga).

PubMed

Lin, Yu-Chung; Perevedentseva, Elena; Cheng, Chia-Liang

2015-05-01

An in vivo Raman spectroscopic study of amoeba (Acanthamoeba polyphaga) is presented. The changes of the spectra during the amoeba cyst activation and excystation are analyzed. The spectra show the changes of the relative intensities of bands corresponding to protein, lipid, and carotenoid components during cyst activation. The presence of carotenoids in the amoeba is observed via characteristic Raman bands. These signals in the Raman spectra are intense in cysts but decrease in intensity with cyst activation and exhibit a correlation with the life cycle of amoeba. This work demonstrates the feasibility of using Raman spectroscopy for the detection of single amoeba microorganisms in vivo and for the analysis of the amoeba life activity. The information obtained may have implications for the estimation of epidemiological situations and for the diagnostics and prognosis of the development of amoebic inflammations.

Comparative study of mobile Raman instrumentation for art analysis.

PubMed

Vandenabeele, P; Castro, K; Hargreaves, M; Moens, L; Madariaga, J M; Edwards, H G M

2007-04-04

In archaeometry, one of the main concerns is to extract information from an art object, without damaging it. Raman spectroscopy is being applied in this research field with recent developments in mobile instrumentation facilitating more routine analysis. This research paper evaluates the performances of five mobile Raman instruments (Renishaw RA100, Renishaw Portable Raman Analyser RX210, Ocean Optics RSL-1, Delta Nu Inspector Raman, Mobile Art Analyser--MArtA) in three different laboratories. A set of samples were collected, in order to obtain information on the spectral performances of the instruments including: spectral resolution, calibration, laser cut-off, the ability to record spectra of organic and inorganic pigments through varnish layers and on the possibilities to identify biomaterials. Spectra were recorded from predefined regions on a canvas painting to simulate the investigation of artworks and the capabilities to record spectra from hardly accessible areas was evaluated.

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Georgiadis, Nicholas J.; Locke, Randy J.

2018-01-01

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48 cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Georgiadis, Nicholas J.; Locke, Randy J.

2018-01-01

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

Evaluation of linear discriminant analysis for automated Raman histological mapping of esophageal high-grade dysplasia

NASA Astrophysics Data System (ADS)

Hutchings, Joanne; Kendall, Catherine; Shepherd, Neil; Barr, Hugh; Stone, Nicholas

2010-11-01

Rapid Raman mapping has the potential to be used for automated histopathology diagnosis, providing an adjunct technique to histology diagnosis. The aim of this work is to evaluate the feasibility of automated and objective pathology classification of Raman maps using linear discriminant analysis. Raman maps of esophageal tissue sections are acquired. Principal component (PC)-fed linear discriminant analysis (LDA) is carried out using subsets of the Raman map data (6483 spectra). An overall (validated) training classification model performance of 97.7% (sensitivity 95.0 to 100% and specificity 98.6 to 100%) is obtained. The remainder of the map spectra (131,672 spectra) are projected onto the classification model resulting in Raman images, demonstrating good correlation with contiguous hematoxylin and eosin (HE) sections. Initial results suggest that LDA has the potential to automate pathology diagnosis of esophageal Raman images, but since the classification of test spectra is forced into existing training groups, further work is required to optimize the training model. A small pixel size is advantageous for developing the training datasets using mapping data, despite lengthy mapping times, due to additional morphological information gained, and could facilitate differentiation of further tissue groups, such as the basal cells/lamina propria, in the future, but larger pixels sizes (and faster mapping) may be more feasible for clinical application.

Matrix Effects in Quantitative Assessment of Pharmaceutical Tablets Using Transmission Raman and Near-Infrared (NIR) Spectroscopy.

PubMed

Sparén, Anders; Hartman, Madeleine; Fransson, Magnus; Johansson, Jonas; Svensson, Olof

2015-05-01

Raman spectroscopy can be an alternative to near-infrared spectroscopy (NIR) for nondestructive quantitative analysis of solid pharmaceutical formulations. Compared with NIR spectra, Raman spectra have much better selectivity, but subsampling was always an issue for quantitative assessment. Raman spectroscopy in transmission mode has reduced this issue, since a large volume of the sample is measured in transmission mode. The sample matrix, such as particle size of the drug substance in a tablet, may affect the Raman signal. In this work, matrix effects in transmission NIR and Raman spectroscopy were systematically investigated for a solid pharmaceutical formulation. Tablets were manufactured according to an experimental design, varying the factors particle size of the drug substance (DS), particle size of the filler, compression force, and content of drug substance. All factors were varied at two levels plus a center point, except the drug substance content, which was varied at five levels. Six tablets from each experimental point were measured with transmission NIR and Raman spectroscopy, and their concentration of DS was determined for a third of those tablets. Principal component analysis of NIR and Raman spectra showed that the drug substance content and particle size, the particle size of the filler, and the compression force affected both NIR and Raman spectra. For quantitative assessment, orthogonal partial least squares regression was applied. All factors varied in the experimental design influenced the prediction of the DS content to some extent, both for NIR and Raman spectroscopy, the particle size of the filler having the largest effect. When all matrix variations were included in the multivariate calibrations, however, good predictions of all types of tablets were obtained, both for NIR and Raman spectroscopy. The prediction error using transmission Raman spectroscopy was about 30% lower than that obtained with transmission NIR spectroscopy.

Spectral analysis of the structure of ultradispersed diamonds

NASA Astrophysics Data System (ADS)

Uglov, V. V.; Shimanski, V. I.; Rusalsky, D. P.; Samtsov, M. P.

2008-07-01

The structure of ultradispersed diamonds (UDD) is studied by spectral methods. The presence of diamond crystal phase in the UDD is found based on x-ray analysis and Raman spectra. The Raman spectra also show sp2-and sp3-hybridized carbon. Analysis of IR absorption spectra suggests that the composition of functional groups present in the particles changes during the treatment.

The use of UV, FT-IR and Raman spectra for the identification of the newest penem analogs: solutions based on mathematic procedure and the density functional theory.

PubMed

Cielecka-Piontek, J; Lewandowska, K; Barszcz, B; Paczkowska, M

2013-02-15

The application of ultraviolet, FT-IR and Raman spectra was proposed for identification studies of the newest penem analogs (doripenem, biapenem and faropenem). An identification of the newest penem analogs based on their separation from related substances was achieved after the application of first derivative of direct spectra in ultraviolet which permitted elimination of overlapping effects. A combination of experimental and theoretical studies was performed for analyzing the structure and vibrational spectra (FT-IR and Raman spectra) of doripenem, biapenem and faropenem. The calculations were conducted using the density functional theory with the B3LYP hybrid functional and 6-31G(d,p) basis set. The confirmation of the applicability of the DFT methodology for interpretation of vibrational IR and Raman spectra of the newest penem analogs contributed to determination of changes of vibrations in the area of the most labile bonds. By employing the theoretical approach it was possible to eliminate necessity of using reference standards which - considering the instability of penem analogs - require that correction coefficients are factored in. Copyright © 2012 Elsevier B.V. All rights reserved.

Assessing the age of animal bones and ivories by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Sharikova, Anna; Peerzada, Lubna; Khmaladze, Alexander

2018-02-01

A fast, convenient way to determine the age of bones and ivories is important both in forensics and for classifying art objects in collections of art experts, restorers, art galleries and museums. Knowing the age of elephant tusks is also essential because there are many date-specific regulations of ivory trade. Radiocarbon dating is the standard method used to determine the age of organic materials, but it is expensive, time consuming, and damages the sample in the process. Raman spectroscopy is sensitive to rotational and vibrational molecular transitions, and also intermolecular vibrations. Therefore, it can provide information about sample make up, such as proteins and minerals, as well as detect spectral signatures associated with structural changes in molecules. Since Raman spectroscopy identifies the molecular bonds present in a sample, it is often used to determine its chemical composition. Bones and ivories contain two primary components: collagen and bioapatite. As the protein collagen deteriorates with time, its Raman signal decreases. The ratio of collagen-to-bioapatite peaks, therefore, is smaller in the older samples compared to the younger ones, providing a basis for sample dating. We employed Raman spectroscopy to non-destructively determine the age of several elephant tusk fragments. We have also used it to identify ivory imitations made of vegetable and plastic materials. Such materials have entirely different chemical composition, and their spectra are easily distinguished from those of bone and ivory. Peak fitting was employed to determine collagen and bioapatite components.

Spectral discrimination of serum from liver cancer and liver cirrhosis using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Yang, Tianyue; Li, Xiaozhou; Yu, Ting; Sun, Ruomin; Li, Siqi

2011-07-01

In this paper, Raman spectra of human serum were measured using Raman spectroscopy, then the spectra was analyzed by multivariate statistical methods of principal component analysis (PCA). Then linear discriminant analysis (LDA) was utilized to differentiate the loading score of different diseases as the diagnosing algorithm. Artificial neural network (ANN) was used for cross-validation. The diagnosis sensitivity and specificity by PCA-LDA are 88% and 79%, while that of the PCA-ANN are 89% and 95%. It can be seen that modern analyzing method is a useful tool for the analysis of serum spectra for diagnosing diseases.

Spectra and structure of silicon containing compounds. XXXII. Raman and infrared spectra, conformational stability, vibrational assignment and ab initio calculations of n-propylsilane-d0 and Si-d3.

PubMed

Durig, James R; Pan, Chunhua; Guirgis, Gamil A

2003-03-15

The infrared (3100-40 cm(-1)) and Raman (3100-20 cm(-1)) spectra of gaseous and solid n-propylsilane, CH(3)CH(2)CH(2)SiH(3) and the Si-d(3) isotopomer, CH(3)CH(2)CH(2)SiD(3), have been recorded. Additionally, the Raman spectra of the liquids have been recorded and qualitative depolarization values obtained. Both the anti and gauche conformers have been identified in the fluid phases but only the anti conformer remains in the solid. Variable temperature (-105 to -150 degrees C) studies of the infrared spectra of n-propylsilane dissolved in liquid krypton have been recorded and the enthalpy difference has been determined to be 220+/-22 cm(-1) (2.63+/-0.26 kJ mol(-1)) with the anti conformer the more stable form. A similar value of 234+/-23 cm(-1) (2.80+/-0.28 kJ mol(-1)) was obtained for deltaH for the Si-d(3) isotopomer. At ambient temperature it is estimated that there is 30+/-2% of the gauche conformer present. The potential function governing the conformation interchange has been estimated from the far infrared spectral data, the enthalpy difference, and the dihedral angle of the gauche conformer, which is compared to the one predicted from ab initio MP2/6-31G(d) calculations. The barriers to conformational interchange are: 942, 970 and 716 cm(-1) for the anti to gauche, gauche to gauche, and gauche to anti conformers, respectively. Relatively complete vibrational assignments are proposed for both the n-propylsilane-d(0) and Si-d(3) molecules based on the relative infrared and Raman spectral intensities, infrared band contours, depolarization ratios, and normal coordinate calculations. The geometrical parameters, harmonic force constants, vibrational frequencies, infrared intensities, Raman activities and depolarization ratios, and energy differences have been obtained for the anti and gauche conformers from ab initio MP2/6-31G(d) calculations. Structural parameters and energy differences have also been obtained utilizing the larger 6-311 + G(d,p) and 6-311 + G(2d,2p) basis sets. From the isolated Si-H stretching frequency from the Si-d(2) isotopomer the r(0) distances of 1.484 and 1.485 A have been determined for the SiH(s) and SiH(a) bonds, respectively, for the anti conformer, and 1.486 A for the SiH bond for the gauche conformer. Utilizing previously reported microwave rotational constants for the anti conformer and the determined SiH distances along with ab initio predicted parameters 'adjusted r(0)' parameters have been obtained for the anti conformer. The results are discussed and compared to those obtained for some similar molecules. Copyright 2002 Elsevier Science B.V.

Spectra and structure of silicon containing compounds. XXXII. Raman and infrared spectra, conformational stability, vibrational assignment and ab initio calculations of n-propylsilane-d 0 and Si-d 3

NASA Astrophysics Data System (ADS)

Durig, James R.; Pan, Chunhua; Guirgis, Gamil A.

2003-03-01

The infrared (3100-40 cm -1) and Raman (3100-20 cm -1) spectra of gaseous and solid n-propylsilane, CH 3CH 2CH 2SiH 3 and the Si-d 3 isotopomer, CH 3CH 2CH 2SiD 3, have been recorded. Additionally, the Raman spectra of the liquids have been recorded and qualitative depolarization values obtained. Both the anti and gauche conformers have been identified in the fluid phases but only the anti conformer remains in the solid. Variable temperature (-105 to -150 °C) studies of the infrared spectra of n-propylsilane dissolved in liquid krypton have been recorded and the enthalpy difference has been determined to be 220±22 cm -1 (2.63±0.26 kJ mol -1) with the anti conformer the more stable form. A similar value of 234±23 cm -1 (2.80±0.28 kJ mol -1) was obtained for Δ H for the Si-d 3 isotopomer. At ambient temperature it is estimated that there is 30±2% of the gauche conformer present. The potential function governing the conformation interchange has been estimated from the far infrared spectral data, the enthalpy difference, and the dihedral angle of the gauche conformer, which is compared to the one predicted from ab initio MP2/6-31G(d) calculations. The barriers to conformational interchange are: 942, 970 and 716 cm -1 for the anti to gauche, gauche to gauche, and gauche to anti conformers, respectively. Relatively complete vibrational assignments are proposed for both the n-propylsilane-d 0 and Si-d 3 molecules based on the relative infrared and Raman spectral intensities, infrared band contours, depolarization ratios, and normal coordinate calculations. The geometrical parameters, harmonic force constants, vibrational frequencies, infrared intensities, Raman activities and depolarization ratios, and energy differences have been obtained for the anti and gauche conformers from ab initio MP2/6-31G(d) calculations. Structural parameters and energy differences have also been obtained utilizing the larger 6-311+G(d,p) and 6-311+G(2d,2p) basis sets. From the isolated SiH stretching frequency from the Si-d 2 isotopomer the r0 distances of 1.484 and 1.485 Å have been determined for the SiH s and SiH a bonds, respectively, for the anti conformer, and 1.486 Å for the SiH bond for the gauche conformer. Utilizing previously reported microwave rotational constants for the anti conformer and the determined SiH distances along with ab initio predicted parameters 'adjusted r0' parameters have been obtained for the anti conformer. The results are discussed and compared to those obtained for some similar molecules.

Raman bandshape analysis of the symmetric bending vibration in liquid chloroform

NASA Astrophysics Data System (ADS)

Yuan, P.; Schwartz, M.

In order to determine whether accurate rotational diffusion coefficients in liquids may be determined from the bandshapes of isotopically broadened vibrational peaks, we have investigated the isotropic and anisotropic Raman spectra of the ν 3( A1), CCl 3 symmetric bending, vibration in CHCl 3 as a function of temperature in the liquid phase. The spectral lineshapes were fitted by a model containing four Lorentzian/Gaussian summation bands with relative peak intensities equal to the relative abundances of the four isotopic combinations and frequency displacements constrained to values measured in the matrix infrared spectrum. The calculated room temperature perpendicular diffusion coefficient, D⊥ (25°C) = 8.310 10 s -1, was within the range of values reported from Raman measurements on the ν 1, symmetric carbon-hydrogen stretching, vibration, but was somewhat lower than published results from NMR relaxation time measurements, T1( 2D), on CDCl 3, and from dielectric relaxation. The activation energy, Ea( D⊥), determined from the ν 3 bandshape measurements was 30% higher than the average value from the NMR and dielectric studies. The deviation is believed to result from the sensitivity of this quantity to the fractional Lorentzian character of the fitting functions.

Investigation of biochemical property changes in activation-induced CD 8 + T cell apoptosis using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Young Ju; Ahn, Hyung Joon; Lee, Gi-Ja; Jung, Gyeong Bok; Lee, Gihyun; Kim, Dohyun; Shin, Jae-Ho; Jin, Kyung-Hyun; Park, Hun-Kuk

2015-07-01

The study was to investigate the changes in biochemical properties of activated mature CD8+ T cells related to apoptosis at a molecular level. We confirmed the activation and apoptosis of CD8+ T cells by fluorescence-activated cell sorting and atomic force microscopy and then performed Raman spectral measurements on activated mature CD8+ T cells and cellular deoxyribose nucleic acid (DNA). In the activated mature CD8+ T cells, there were increases in protein spectra at 1002 and 1234 cm-1. In particular, to assess the apoptosis-related DNA spectral signatures, we investigated the spectra of the cellular DNA isolated from resting and activated mature CD8+ T cells. Raman spectra at 765 to 786 cm-1 and 1053 to 1087 cm-1 were decreased in activated mature DNA. In addition, we analyzed Raman spectrum using the multivariate statistical method including principal component analysis. Raman spectra of activated mature DNA are especially well-discriminated from those of resting DNA. Our findings regarding the biochemical and structural changes associated with apoptosis in activated mature T cells and cellular DNA according to Raman spectroscopy provide important insights into allospecific immune responses generated after organ transplantation, and may be useful for therapeutic manipulation of the immune response.

A portable Raman acoustic levitation spectroscopic system for the identification and environmental monitoring of algal cells.

PubMed

Wood, Bayden R; Heraud, Philip; Stojkovic, Slobodanka; Morrison, Danielle; Beardall, John; McNaughton, Don

2005-08-01

We report the coupling of a portable Raman spectrometer to an acoustic levitation device to enable environmental monitoring and the potential taxonomic identification of microalgae. Spectra of living cells were recorded at 785 nm using a fiber-optic probe coupled to a portable Raman spectrometer. The spectra exhibit an excellent signal-to-noise ratio and clearly show bands from chlorophyll a and beta-carotene. Spectra of levitated photobleached microalgae clearly show a reduction in chlorophyll a concentration relative to beta-carotene after 10 min of exposure to a quartz halogen lamp. Spectra recorded from levitated nitrogen-limited cells also show a significant reduction in bands associated with chlorophyll a, as compared to nitrogen-replete cells. To investigate the diagnostic capability of the technique, four species of microalgae were analyzed. Good quality spectra of all four species were obtained showing varying ratios of beta-carotene to chlorophyll. The combination of an acoustic levitation device and a portable Raman spectrometer shows potential as a taxonomic and environmental monitoring tool with direct application to field studies in remote environments.

Application of Raman Spectroscopy for Nondestructive Evaluation of Composite Materials

NASA Technical Reports Server (NTRS)

Washer, Glenn A.; Brooks, Thomas M. B.; Saulsberry, Regor

2007-01-01

This paper will present an overview of efforts to investigate the application of Raman spectroscopy for the characterization of Kevlar materials. Raman spectroscopy is a laser technique that is sensitive to molecular interactions in materials such as Kevlar, graphite and carbon used in composite materials. The overall goal of this research reported here is to evaluate Raman spectroscopy as a potential nondestructive evaluation (NDE) tool for the detection of stress rupture in Kevlar composite over-wrapped pressure vessels (COPVs). Characterization of the Raman spectra of Kevlar yarn and strands will be presented and compared with analytical models provided in the literature. Results of testing to investigate the effects of creep and high-temperature aging on the Raman spectra will be presented.

Identification of individual biofilm-forming bacterial cells using Raman tweezers

NASA Astrophysics Data System (ADS)

Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

2015-05-01

A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral "Raman fingerprints" obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

Identification of individual biofilm-forming bacterial cells using Raman tweezers.

PubMed

Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

2015-05-01

A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral “Raman fingerprints” obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

Simulation of IR and Raman spectra of p-hydroxyanisole and p-nitroanisole based on scaled DFT force fields and their vibrational assignments.

PubMed

Krishnakumar, V; Prabavathi, N

2009-09-15

This work deals with the vibrational spectroscopy of p-hydroxyanisole (PHA) and p-nitroanisole (PNA) by means of quantum chemical calculations. The mid and far FT-IR and FT-Raman spectra were recorded in the condensed state. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-31G* method and basis set combination and were scaled using various scale factors which yield a good agreement between observed and calculated frequencies. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results of the calculations were applied to simulate infrared and Raman spectra of the title compounds, which showed excellent agreement with the observed spectra.

Spectral monitoring of toluene and ethanol in gasoline blends using Fourier-Transform Raman spectroscopy

NASA Astrophysics Data System (ADS)

Ortega Clavero, Valentin; Weber, Andreas; Schröder, Werner; Curticapean, Dan; Meyrueis, Patrick; Javahiraly, Nicolas

2013-04-01

The combination of fossil-derived fuels with ethanol and methanol has acquired relevance and attention in several countries in recent years. This trend is strongly affected by market prices, constant geopolitical events, new sustainability policies, new laws and regulations, etc. Besides bio-fuels these materials also include different additives as anti-shock agents and as octane enhancer. Some of the chemical compounds in these additives may have harmful properties for both environment and public health (besides the inherent properties, like volatility). We present detailed Raman spectral information from toluene (C7H8) and ethanol (C2H6O) contained in samples of ElO gasoline-ethanol blends. The spectral information has been extracted by using a robust, high resolution Fourier-Transform Raman spectrometer (FT-Raman) prototype. This spectral information has been also compared with Raman spectra from pure additives and with standard Raman lines in order to validate its accuracy in frequency. The spectral information is presented in the range of 0 cm-1 to 3500 cm-1 with a resolution of 1.66cm-1. This allows resolving tight adjacent Raman lines like the ones observed around 1003cm-1 and 1030cm-1 (characteristic lines of toluene). The Raman spectra obtained show a reduced frequency deviation when compared to standard Raman spectra from different calibration materials. The FT-Raman spectrometer prototype used for the analysis consist basically of a Michelson interferometer and a self-designed photon counter cooled down on a Peltier element arrangement. The light coupling is achieved with conventional62.5/125μm multi-mode fibers. This FT-Raman setup is able to extract high resolution and frequency precise Raman spectra from the additives in the fuels analyzed. The proposed prototype has no additional complex hardware components or costly software modules. The mechanical and thermal disturbances affecting the FT-Raman system are mathematically compensated by accurately extracting the optical path information of the Michelson interferometer. This is accomplished by generating an additional interference pattern with a λ = 632.8 nm Helium-Neon laser (HeNe laser). It enables the FT-Raman system to perform reliable and clean spectral measurements from the materials under observation.

Inelastic scattering in planetary atmospheres. I - The Ring effect, without aerosols

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Young, A. T.; Humphreys, T. J.

1981-01-01

The contribution of inelastic molecular scattering (Rayleigh-Brillouin and rotational Raman scattering) to the filling-in of Fraunhofer lines in the light of the blue sky is studied. Aerosol fluorescence is shown to be negligible, and aerosol scattering is ignored. The angular and polarization dependences of the filling-in detail for single scattering are discussed. An approximate treatment of multiple scattering, using a backward Monte Carlo technique, makes it possible to investigate the effects of the ground albedo. As the molecular scatterings alone produce more line-filling than is observed, it seems likely that aerosols dilute the effect by contributing unaltered sunlight to the observed spectra.

In-line solid state prediction during pharmaceutical hot-melt extrusion in a 12 mm twin screw extruder using Raman spectroscopy.

PubMed

Saerens, Lien; Ghanam, Dima; Raemdonck, Cedric; Francois, Kjell; Manz, Jürgen; Krüger, Rainer; Krüger, Susan; Vervaet, Chris; Remon, Jean Paul; De Beer, Thomas

2014-08-01

The aim of this research was to use Raman spectroscopy for the in-line monitoring of the solid state of materials during pharmaceutical hot-melt extrusion in the die head of a 12 mm (development scale) twin-screw extruder during formulation development. A full factorial (mixed) design was generated to determine the influence of variations in concentration of Celecoxib (CEL) in Eudragit® E PO, three different screw configurations and varying barrel temperature profiles on the solid state, 'melt temperature' and die pressure of continuously produced extrudates in real-time. Off-line XRD and DSC analysis were used to evaluate the suitability of Raman spectroscopy for solid state predictions. First, principal component analysis (PCA) was performed on all in-line collected Raman spectra from the experimental design. The resulting PC 1 versus PC 2 scores plot showed clustering according to solid state of the extrudates, and two classes, one class where crystalline CEL is still present and a second class where no crystalline CEL was detected, were found. Then, a soft independent modelling of class analogy (SIMCA) model was developed, by modelling these two classes separately by disjoint PCA models. These two separate PCA models were then used for the classification of new produced extrudates and allowed distinction between glassy solid solutions of CEL and crystalline dispersions of CEL. All extrudates were classified similarly by Raman spectroscopy, XRD and DSC measurements, with exception of the extrudates with a 30% CEL concentration extruded at 130 °C. The Raman spectra of these experiments showed bands which were sharper than the amorphous spectra, but broader than the crystalline spectra, indicating the presence of CEL that has dissolved into the matrix and CEL in its crystalline state. XRD and DSC measurements did not detect this. Modifications in the screw configuration did not affect the solid state and did not have an effect on the solid state prediction of new produced extrudates. Secondly, the influence of variations in die pressure on the Raman spectra was examined. The applied drug concentration, processing temperature and feeder performance influence the die pressure, which is reflected in the Raman spectra as a change in spectral intensity. When applying PCA on the raw spectra from the experimental design, the first principal component describes the influence of die pressure on the spectra, which was seen as a decrease in Raman intensity of the whole spectrum when the pressure in the sample increased. Clustering according to processing temperature was found, although the temperature in the die remained constant, indicating that a difference in viscosity, resulting in a changed die pressure, was detected. When the feeder was stopped, the score values of the first principal component almost simultaneously decreased, and only stabilized once the die pressure became stable. Since Raman spectra collected in the extrusion die are influenced by changes in die pressure, disturbances upstream of the extrusion process can be observed and identified in the Raman measurements. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of a multiplexing fingerprint and high wavenumber Raman spectroscopy technique for real-time in vivo tissue Raman measurements at endoscopy

NASA Astrophysics Data System (ADS)

Bergholt, Mads Sylvest; Zheng, Wei; Huang, Zhiwei

2013-03-01

We report on the development of a novel multiplexing Raman spectroscopy technique using a single laser light together with a volume phase holographic (VPH) grating that simultaneously acquires both fingerprint (FP) and high wavenumber (HW) tissue Raman spectra at endoscopy. We utilize a customized VPH dual-transmission grating, which disperses the incident Raman scattered light vertically onto two separate segments (i.e., -150 to 1950 cm-1 1750 to 3600 cm-1) of a charge-coupled device camera. We demonstrate that the multiplexing Raman technique can acquire high quality in vivo tissue Raman spectra ranging from 800 to 3600 cm-1 within 1.0 s with a spectral resolution of 3 to 6 cm-1 during clinical endoscopy. The rapid multiplexing Raman spectroscopy technique covering both FP and HW ranges developed in this work has potential for improving in vivo tissue diagnosis and characterization at endoscopy.

Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

PubMed

Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

2016-01-01

In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the pharmaceutical setting, process analytical technology (PAT), and the life sciences.

Simultaneous Spectral Temporal Adaptive Raman Spectrometer - SSTARS

NASA Technical Reports Server (NTRS)

Blacksberg, Jordana

2010-01-01

Raman spectroscopy is a prime candidate for the next generation of planetary instruments, as it addresses the primary goal of mineralogical analysis, which is structure and composition. However, large fluorescence return from many mineral samples under visible light excitation can render Raman spectra unattainable. Using the described approach, Raman and fluorescence, which occur on different time scales, can be simultaneously obtained from mineral samples using a compact instrument in a planetary environment. This new approach is taken based on the use of time-resolved spectroscopy for removing the fluorescence background from Raman spectra in the laboratory. In the SSTARS instrument, a visible excitation source (a green, pulsed laser) is used to generate Raman and fluorescence signals in a mineral sample. A spectral notch filter eliminates the directly reflected beam. A grating then disperses the signal spectrally, and a streak camera provides temporal resolution. The output of the streak camera is imaged on the CCD (charge-coupled device), and the data are read out electronically. By adjusting the sweep speed of the streak camera, anywhere from picoseconds to milliseconds, it is possible to resolve Raman spectra from numerous fluorescence spectra in the same sample. The key features of SSTARS include a compact streak tube capable of picosecond time resolution for collection of simultaneous spectral and temporal information, adaptive streak tube electronics that can rapidly change from one sweep rate to another over ranges of picoseconds to milliseconds, enabling collection of both Raman and fluorescence signatures versus time and wavelength, and Synchroscan integration that allows for a compact, low-power laser without compromising ultimate sensitivity.

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, and trimethylgermyl derivatives of 3,3-dimethylcyclopropene IV. 3,3-Dimethyl-1,2-bis(trimethylgermyl)cyclopropene

NASA Astrophysics Data System (ADS)

Panchenko, Yu. N.; De Maré, G. R.; Abramenkov, A. V.; Baird, M. S.; Tverezovsky, V. V.; Nizovtsev, A. V.; Bolesov, I. G.

2003-06-01

The infrared (IR) and Raman spectra of 3,3-dimethyl-1,2-bis(trimethylgermyl)cyclopropene (I) were measured in the liquid phase. Total geometry optimisation was performed at the HF/6-31G* level. The HF/6-31G*//HF6-31G* quantum mechanical force field (QMFF) was calculated and used to determine the theoretical fundamental vibrational frequencies, their predicted IR intensities, Raman activities, and Raman depolarisation ratios. Using Pulay's scaling method and the theoretical molecular geometry, the QMFF of I was scaled by a set of scaling factors comprised of elements transferred from the sets used to correct the QMFF's of 3,3-dimethylbutene-1, and 1-methyl-, 1,2-dimethyl-, and 3,3-dimethylcyclopropene (17 scale factors for a 105-dimensional problem). This set of scale factors was used previously to correct the QMFF of 3,3-dimethyl-1,2-bis(tert-butyl)cyclopropene and 3,3-dimethyl-1,2-bis(trimethylsilyl)cyclopropene. The scaled QMFF obtained was used to solve the vibrational problem. Differential Raman cross-sections were calculated using the quantum mechanical values of the Raman activities. The appropriate theoretical spectrograms for the Raman and IR spectra of I were constructed. Assignments of the experimental vibrational spectra of I are given. They take into account the calculated potential energy distributions and the correlation between the estimations of the experimental IR and Raman intensities and Raman depolarisation ratios and the corresponding theoretical values calculated using the unscaled QMFF.

Measurement of diabetic sugar concentration in human blood using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Firdous, S.; Nawaz, M.; Ahmed, M.; Anwar, S.; Rehman, A.; Rashid, R.; Mahmood, A.

2012-06-01

This study demonstrates the use of Raman spectroscopy for the direct measurement of diabetic sugar in human blood using 532 nm laser system. Raman spectra were collected from whole blood drawn from 21 individuals. We have elicited a reliable glucose signature in diabetic patients, and measured glucose levels in blood serum of normal, healthy diabetic and diabetic patients with other malignancies like cancer and hepatitis. Quantitative predictions of glucose spectra illustrate the predictions based on molecular information carried by the Raman light in highly light-scattering and absorbing media. Raman spectrum peaks for diabetic blood serum are observed at 1168, 1531, 1463, 1021 cm-1 with intensity level 17000 to 18500 pixels attributed to carbohydrates, proteins, lipids, collagen, and skeletal C-C stretch of lipids acyl chains. Raman spectra for normal, diabetic patients having cancer and hepatitis were also recorded. This in vitro glucose monitoring methodology will lead in vivo noninvasive on-line monitoring having painless and at the same time the data will be displayed on-line and in real time. The measured Raman peaks provides detailed bio-chemical fingerprint of the sample and could confer diagnostic benefit in a clinical setting.

Electrochemistry of Metal Surfaces

DTIC Science & Technology

1990-06-30

i) 3-pyridine carboxylic acid ( nicotinic acid, NA) binds to Pt surfaces through both the nitrogen atom and an oxygen atom of the carboxylate group...formed from aqueous electrolytes at Pt(1l1) electrode surfaces have been compared with the IR and Raman spectra of the unadsorbed compounds in order...vibrational absorptivities between EELS spectra of adsorbed species and IR and Raman spectra of the corresponding unadsorbed compounds (146). Of

Near-infrared Raman spectroscopy to detect anti-Toxoplasma gondii antibody in blood sera of domestic cats: quantitative analysis based on partial least-squares multivariate statistics

NASA Astrophysics Data System (ADS)

Duarte, Janaína; Pacheco, Marcos T. T.; Villaverde, Antonio Balbin; Machado, Rosangela Z.; Zângaro, Renato A.; Silveira, Landulfo

2010-07-01

Toxoplasmosis is an important zoonosis in public health because domestic cats are the main agents responsible for the transmission of this disease in Brazil. We investigate a method for diagnosing toxoplasmosis based on Raman spectroscopy. Dispersive near-infrared Raman spectra are used to quantify anti-Toxoplasma gondii (IgG) antibodies in blood sera from domestic cats. An 830-nm laser is used for sample excitation, and a dispersive spectrometer is used to detect the Raman scattering. A serological test is performed in all serum samples by the enzyme-linked immunosorbent assay (ELISA) for validation. Raman spectra are taken from 59 blood serum samples and a quantification model is implemented based on partial least squares (PLS) to quantify the sample's serology by Raman spectra compared to the results provided by the ELISA test. Based on the serological values provided by the Raman/PLS model, diagnostic parameters such as sensitivity, specificity, accuracy, positive prediction values, and negative prediction values are calculated to discriminate negative from positive samples, obtaining 100, 80, 90, 83.3, and 100%, respectively. Raman spectroscopy, associated with the PLS, is promising as a serological assay for toxoplasmosis, enabling fast and sensitive diagnosis.

RAMAN spectroscopy imaging improves the diagnosis of papillary thyroid carcinoma

NASA Astrophysics Data System (ADS)

Rau, Julietta V.; Graziani, Valerio; Fosca, Marco; Taffon, Chiara; Rocchia, Massimiliano; Crucitti, Pierfilippo; Pozzilli, Paolo; Onetti Muda, Andrea; Caricato, Marco; Crescenzi, Anna

2016-10-01

Recent investigations strongly suggest that Raman spectroscopy (RS) can be used as a clinical tool in cancer diagnosis to improve diagnostic accuracy. In this study, we evaluated the efficiency of Raman imaging microscopy to discriminate between healthy and neoplastic thyroid tissue, by analyzing main variants of Papillary Thyroid Carcinoma (PTC), the most common type of thyroid cancer. We performed Raman imaging of large tissue areas (from 100 × 100 μm2 up to 1 × 1 mm2), collecting 38 maps containing about 9000 Raman spectra. Multivariate statistical methods, including Linear Discriminant Analysis (LDA), were applied to translate Raman spectra differences between healthy and PTC tissues into diagnostically useful information for a reliable tissue classification. Our study is the first demonstration of specific biochemical features of the PTC profile, characterized by significant presence of carotenoids with respect to the healthy tissue. Moreover, this is the first evidence of Raman spectra differentiation between classical and follicular variant of PTC, discriminated by LDA with high efficiency. The combined histological and Raman microscopy analyses allow clear-cut integration of morphological and biochemical observations, with dramatic improvement of efficiency and reliability in the differential diagnosis of neoplastic thyroid nodules, paving the way to integrative findings for tumorigenesis and novel therapeutic strategies.

Use of Raman microscopy and multivariate data analysis to observe the biomimetic growth of carbonated hydroxyapatite on bioactive glass.

PubMed

Seah, Regina K H; Garland, Marc; Loo, Joachim S C; Widjaja, Effendi

2009-02-15

In the present contribution, the biomimetic growth of carbonated hydroxyapatite (HA) on bioactive glass were investigated by Raman microscopy. Bioactive glass samples were immersed in simulated body fluid (SBF) buffered solution at pH 7.40 up to 17 days at 37 degrees C. Raman microscopy mapping was performed on the bioglass samples immersed in SBF solution for different periods of time. The collected data was then analyzed using the band-target entropy minimization technique to extract the observable pure component Raman spectral information. In this study, the pure component Raman spectra of the precursor amorphous calcium phosphate, transient octacalcium phosphate, and matured HA were all recovered. In addition, pure component Raman spectra of calcite, silica glass, and some organic impurities were also recovered. The resolved pure component spectra were fit to the normalized measured Raman data to provide the spatial distribution of these species on the sample surfaces. The current results show that Raman microscopy and multivariate data analysis provide a sensitive and accurate tool to characterize the surface morphology, as well as to give more specific information on the chemical species present and the phase transformation of phosphate species during the formation of HA on bioactive glass.

Instant detection and identification of concealed explosive-related compounds: Induced Stokes Raman versus infrared.

PubMed

Elbasuney, Sherif; El-Sherif, Ashraf F

2017-01-01

The instant detection of explosives and explosive-related compounds has become an urgent priority in recent years for homeland security and counter-terrorism applications. Modern techniques should offer enhancement in selectivity, sensitivity, and standoff distances. Miniaturisation, portability, and field-ruggedisation are crucial requirements. This study reports on instant and standoff identification of concealed explosive-related compounds using customized Raman technique. Stokes Raman spectra of common explosive-related compounds were generated and spectrally resolved to create characteristic finger print spectra. The scattered Raman emissions over the band 400:2000cm -1 were compared to infrared absorption using FTIR. It has been demonstrated that the two vibrational spectroscopic techniques were opposite and completing each other. Molecular vibrations with strong absorption in infrared (those involve strong change in dipole moments) induced weak signals in Raman and vice versa. The tailored Raman offered instant detection, high sensitivity, and standoff detection capabilities. Raman demonstrated characteristic fingerprint spectra with stable baseline and sharp intense peaks. Complete correlations of absorption/scattered signals to certain molecular vibrations were conducted to generate an entire spectroscopic profile of explosive-related compounds. This manuscript shades the light on Raman as one of the prevailing technologies for instantaneous detection of explosive-related compounds. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Vibrational Spectroscopy of Ionic Liquids.

PubMed

Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C

2017-05-24

Vibrational spectroscopy has continued use as a powerful tool to characterize ionic liquids since the literature on room temperature molten salts experienced the rapid increase in number of publications in the 1990's. In the past years, infrared (IR) and Raman spectroscopies have provided insights on ionic interactions and the resulting liquid structure in ionic liquids. A large body of information is now available concerning vibrational spectra of ionic liquids made of many different combinations of anions and cations, but reviews on this literature are scarce. This review is an attempt at filling this gap. Some basic care needed while recording IR or Raman spectra of ionic liquids is explained. We have reviewed the conceptual basis of theoretical frameworks which have been used to interpret vibrational spectra of ionic liquids, helping the reader to distinguish the scope of application of different methods of calculation. Vibrational frequencies observed in IR and Raman spectra of ionic liquids based on different anions and cations are discussed and eventual disagreements between different sources are critically reviewed. The aim is that the reader can use this information while assigning vibrational spectra of an ionic liquid containing another particular combination of anions and cations. Different applications of IR and Raman spectroscopies are given for both pure ionic liquids and solutions. Further issues addressed in this review are the intermolecular vibrations that are more directly probed by the low-frequency range of IR and Raman spectra and the applications of vibrational spectroscopy in studying phase transitions of ionic liquids.

An intraoperative diagnosis of parotid gland tumors using Raman spectroscopy and support vector machine

NASA Astrophysics Data System (ADS)

Yan, Bing; Wen, Zhining; Li, Yi; Li, Longjiang; Xue, Lili

2014-11-01

The preoperative and intraoperative diagnosis of parotid gland tumors is difficult, but is important for their surgical management. In order to explore an intraoperative diagnostic method, Raman spectroscopy is applied to detect the normal parotid gland and tumors, including pleomorphic adenoma, Warthin’s tumor and mucoepidermoid carcinoma. In the 600-1800 cm-1 region of the Raman shift, there are numerous spectral differences between the parotid gland and tumors. Compared with Raman spectra of the normal parotid gland, the Raman spectra of parotid tumors show an increase of the peaks assigned to nucleic acids and proteins, but a decrease of the peaks related to lipids. Spectral differences also exist between the spectra of parotid tumors. Based on these differences, a remarkable classification and diagnosis of the parotid gland and tumors are carried out by support vector machine (SVM), with high accuracy (96.7~100%), sensitivity (93.3~100%) and specificity (96.7~100%). Raman spectroscopy combined with SVM has a great potential to aid the intraoperative diagnosis of parotid tumors and could provide an accurate and rapid diagnostic approach.

Spectroscopic and vibrational analysis of the methoxypsoralen system: A comparative experimental and theoretical study

NASA Astrophysics Data System (ADS)

Liu, Y.; Yuan, H.; Vo-Dinh, T.

2013-03-01

Raman spectra measurements and density functional theory (DFT) calculations were performed to investigate three psoralens: 5-amino-8-methoxypsoralen (5-A-8-MOP), 5-methoxypsoralen (5-MOP) and 8-methoxypsoralen (8-MOP) with the aim of differentiating these similar bioactive molecules. The Raman spectra were recorded in the region 300-3500 cm-1. All three psoralens were found to have similar Raman spectrum in the region 1500-1650 cm-1. 5-A-8-MOP can be easily differentiated from 5-MOP or 8-MOP based on the Raman spectrum. The Raman spectrum differences at 651 and 795 cm-1 can be used to identify 5-MOP from 8-MOP. The theoretically computed vibrational frequencies and relative peak intensities were compared with experimental data. DFT calculations using the B3LYP method and 6-311++G(d,p) basis set were found to yield results that are very comparable to experimental Raman spectra. Detailed vibrational assignments were performed with DFT calculations and the potential energy distribution (PED) obtained from the Vibrational Energy Distribution Analysis (VEDA) program.

Raman Studies on Pre- and Post-Processed CVD Graphene Films Grown under Various Nitrogen Carrier Gas Flows

NASA Astrophysics Data System (ADS)

Beh, K. P.; Yam, F. K.; Abdalrheem, Raed; Ng, Y. Z.; Suhaimi, F. H. A.; Lim, H. S.; Mat Jafri, M. Z.

2018-04-01

In this work, graphene films were grown on copper substrates using chemical vapour deposition method under various N2 carrier flow rate. The samples were characterized using Raman spectroscopy. Three sets of Raman measurements have been performed: graphene/Cu (as-grown samples), pre-annealed graphene/glass, and post-annealed graphene/glass. It was found that the Raman spectra of graphene/Cu samples possessed a hump-shaped baseline, additionally higher signal-to-noise ratio (SNR) that leads to attenuation graphene-related bands. Significant improvement of SNR and flat baseline were observed for graphene films transferred on glass substrate. Further analysis on the remaining sets of Raman spectra highlighted minute traces of polymethyl methacrylate (PMMA) could yield misleading results. Hence, the set of Raman spectra on annealed graphene/glass samples would be suitable in further elucidating the effects of N2 carrier flow towards graphene growth. From there, higher N2 flow implied dilution of methanol/H2 mixture, limiting interactions between reactants and substrate. This leads to smaller crystallite size and lesser graphene layers.

OPTIMIZATION OF RAMAN SPECTROSCOPY FOR SPECIATION OF ORGANICS IN WATER

EPA Science Inventory

We describe herein a method for determining constants for simultaneously occurring, site-specific "microequilibria" (as with tautomers) for organics in water. The method is based in part on modeling temperature-variant Raman spectra according to the van't Hoff equation. Spectra a...

Raman effect in icosahedral boron-rich solids

PubMed Central

Werheit, Helmut; Filipov, Volodymyr; Kuhlmann, Udo; Schwarz, Ulrich; Armbrüster, Marc; Leithe-Jasper, Andreas; Tanaka, Takaho; Higashi, Iwami; Lundström, Torsten; Gurin, Vladimir N; Korsukova, Maria M

2010-01-01

We present Raman spectra of numerous icosahedral boron-rich solids having the structure of α-rhombohedral, β-rhombohedral, α-tetragonal, β-tetragonal, YB66, orthorhombic or amorphous boron. The spectra were newly measured and, in some cases, compared with reported data and discussed. We emphasize the importance of a high signal-to-noise ratio in the Raman spectra for detecting weak effects evoked by the modification of compounds, accommodation of interstitial atoms and other structural defects. Vibrations of the icosahedra, occurring in all the spectra, are interpreted using the description of modes in α-rhombohedral boron by Beckel et al. The Raman spectrum of boron carbide is largely clarified. Relative intra- and inter-icosahedral bonding forces are estimated for the different structural groups and for vanadium-doped β-rhombohedral boron. The validity of Badger's rule is demonstrated for the force constants of inter-icosahedral B–B bonds, whereas the agreement is less satisfactory for the intra-icosahedral B–B bonds. PMID:27877328

An Automated Baseline Correction Method Based on Iterative Morphological Operations.

PubMed

Chen, Yunliang; Dai, Liankui

2018-05-01

Raman spectra usually suffer from baseline drift caused by fluorescence or other reasons. Therefore, baseline correction is a necessary and crucial step that must be performed before subsequent processing and analysis of Raman spectra. An automated baseline correction method based on iterative morphological operations is proposed in this work. The method can adaptively determine the structuring element first and then gradually remove the spectral peaks during iteration to get an estimated baseline. Experiments on simulated data and real-world Raman data show that the proposed method is accurate, fast, and flexible for handling different kinds of baselines in various practical situations. The comparison of the proposed method with some state-of-the-art baseline correction methods demonstrates its advantages over the existing methods in terms of accuracy, adaptability, and flexibility. Although only Raman spectra are investigated in this paper, the proposed method is hopefully to be used for the baseline correction of other analytical instrumental signals, such as IR spectra and chromatograms.

Raman and Infrared Spectroscopy of Yttrium Aluminum Borate Glasses and Glass-ceramics

NASA Technical Reports Server (NTRS)

Bradley, J.; Brooks, M.; Crenshaw, T.; Morris, A.; Chattopadhyay, K.; Morgan, S.

1998-01-01

Raman spectra of glasses and glass-ceramics in the Y2O3-Al2O3-B2O3 system are reported. Glasses with B2O3 contents ranging from 40 to 60 mole percent were prepared by melting 20 g of the appropriate oxide or carbonate powders in alumina crucibles at 1400 C for 45 minutes. Subsequent heat treatments of the glasses at temperatures ranging from 600 to 800 C were performed in order to induce nucleation and crystallization. It was found that Na2CO3 added to the melt served as a nucleating agent and resulted in uniform bulk crystallization. The Raman spectra of the glasses are interpreted primarily in terms of vibrations of boron - oxygen structural groups. Comparison of the Raman spectra of the glass-ceramic samples with spectra of aluminate and borate crystalline materials reveal that these glasses crystallize primarily as yttrium aluminum borate, YAl3(BO3)4.

Lattice dynamics of A Sb2O6 (A =Cu , Co) with trirutile structure

NASA Astrophysics Data System (ADS)

Maimone, D. T.; Christian, A. B.; Neumeier, J. J.; Granado, E.

2018-03-01

Raman spectroscopy experiments on single crystals of CuSb2O6 and CoSb2O6 quasi-one-dimensional antiferromagnets with trirutile crystal structure were performed, with a focus on the first material. The observed Raman-active phonon modes and previously reported infrared-active modes were identified with the aid of ab initio lattice dynamics calculations. The structural transition between monoclinic β -CuSb2O6 and tetragonal α -CuSb2O6 phases at Ts=400 K is manifested in our spectra by a "repulsion" of two accidentally quasidegenerate symmetric modes below Ts, caused by a phonon mixing effect that is only operative in the monoclinic β -CuSb2O6 phase due to symmetry restrictions. Also, two specific phonons, associated with CuO6 octahedra rotation and with a Jahn-Teller elongation mode, soften and broaden appreciably as T →Ts . A crossover from a displacive to an order-disorder transition at Ts is inferred.

Fast label-free detection of Legionella spp. in biofilms by applying immunomagnetic beads and Raman spectroscopy.

PubMed

Kusić, Dragana; Rösch, Petra; Popp, Jürgen

2016-03-01

Legionellae colonize biofilms, can form a biofilm by itself and multiply intracellularly within the protozoa commonly found in water distribution systems. Approximately half of the known species are pathogenic and have been connected to severe multisystem Legionnaires' disease. The detection methods for Legionella spp. in water samples are still based on cultivation, which is time consuming due to the slow growth of this bacterium. Here, we developed a cultivation-independent, label-free and fast detection method for legionellae in a biofilm matrix based on the Raman spectroscopic analysis of isolated single cells via immunomagnetic separation (IMS). A database comprising the Raman spectra of single bacterial cells captured and separated from the biofilms formed by each species was used to build the identification method based on a support vector machine (SVM) discriminative classifier. The complete method allows the detection of Legionella spp. in 100 min. Cross-reactivity of Legionella spp. specific immunomagnetic beads to the other studied genera was tested, where only small cell amounts of Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli compared to the initial number of cells were isolated by the immunobeads. Nevertheless, the Raman spectra collected from isolated non-targeted bacteria were well-discriminated from the Raman spectra collected from isolated Legionella cells, whereby the Raman spectra of the independent dataset of Legionella strains were assigned with an accuracy of 98.6%. In addition, Raman spectroscopy was also used to differentiate between isolated Legionella species. Copyright © 2016 Elsevier GmbH. All rights reserved.

Raman and surface enhanced Raman spectroscopy of amino acids and peptide

NASA Astrophysics Data System (ADS)

Yuan, Xiaojuan; Gu, Huaimin; Wu, Jiwei; Kang, Jian; Dong, Xiao

2009-08-01

Surface enhanced Raman scattering (SERS) is potentially tool in the characterization of biomolecules such as amino acids, complicated peptides and proteins, and even tissues or living cells. Amino acids and short peptides contain different functional groups. Therefore, they are suitable for the investigations of the competitive-interactions of these functional groups with colloidal silver surfaces. In this paper, Normal Raman and SERS of amino acids Leucine and Isoleucine and short peptide Leu-Leu were measured on the silver colloidal substrate. Raman shifts that stem from different vibrational mode in the molecular inner structure, and the variations of SERS of the samples were analyzed in this study. The results show that different connection of one methyl to the main chains of the isomer amino acids resulted in different vibration modes in the Normal Raman spectra of Leucine and Isoleucine. In the SERS spectra of the isomer amino acids, all frequency shifts are expressed more differently than those in Normal Raman spectra of solid state. Orientation of this isomer amino acids, as well as specific-competitive interactions of their functional groups with the colloidal silver surface, were speculated by detailed spectral analysis of the obtained SERS spectra. In addition, the dipeptide Leu-Leu, as the corresponding homodipeptide of Leucine, was also measured adsorbed on the colloidal silver surface. The SERS spectrum of Leu-Leu is different from its corresponding amino acid Leucine but both of them are adsorbed on the silver surface through the carboxylate moiety.

Hybrid fs/ps rotational CARS temperature and oxygen measurements in the product gases of canonical flat flames

DOE PAGES

Kearney, Sean Patrick

2014-12-31

A hybrid fs/ps pure-rotational coherent anti-Stokes Raman scattering (CARS) scheme is systematically evaluated over a wide range of flame conditions in the product gases of two canonical flat-flame burners. Near-transform-limited, broadband femtosecond pump and Stokes pulses impulsively prepare a rotational Raman coherence, which is later probed using a high-energy, frequency-narrow picosecond beam generated by the second-harmonic bandwidth compression scheme that has recently been demonstrated for rotational CARS generation in H 2/air flat flames. The measured spectra are free of collision effects and nonresonant background and can be obtained on a single-shot basis at 1 kHz. The technique is evaluated formore » temperature/oxygen measurements in near-adiabatic H 2/air flames stabilized on the Hencken burner for equivalence ratios of φ = 0.20–1.20. Thermometry is demonstrated in hydrocarbon/air products for φ = 0.75–3.14 in premixed C 2H 4/air flat flames on the McKenna burner. Reliable spectral fitting is demonstrated for both shot-averaged and single-laser-shot data using a simple phenomenological model. Measurement accuracy is benchmarked by comparison to adiabatic-equilibrium calculations for the H 2/air flames, and by comparison with nanosecond CARS measurements for the C 2H 4/air flames. Quantitative accuracy comparable to nanosecond rotational CARS measurements is observed, while the observed precision in both the temperature and oxygen data is extraordinarily high, exceeding nanosecond CARS, and on par with the best published thermometric precision by femtosecond vibrational CARS in flames, and rotational femtosecond CARS at low temperature. Threshold levels of signal-to-noise ratio to achieve 1–2% precision in temperature and O 2/N 2 ratio are identified. Our results show that pure-rotational fs/ps CARS is a robust and quantitative tool when applied across a wide range of flame conditions spanning lean H 2/air combustion to fuel-rich sooting hydrocarbon flames.« less

The pH dependent Raman spectroscopic study of caffeine

NASA Astrophysics Data System (ADS)

Kang, Jian; Gu, Huaimin; Zhong, Liang; Hu, Yongjun; Liu, Fang

2011-02-01

First of all the surface enhanced Raman spectroscopy (SERS) and normal Raman spectra of caffeine aqueous solution were obtained at different pH values. In order to obtain the detailed vibrational assignments of the Raman spectroscopy, the geometry of caffeine molecule was optimized by density functional theory (DFT) calculation. By comparing the SERS of caffeine with its normal spectra at different pH values; it is concluded that pH value can dramatically affect the SERS of caffeine, but barely affect the normal Raman spectrum of caffeine aqueous solution. It can essentially affect the reorientation of caffeine molecule to the Ag colloid surface, but cannot impact the vibration of functional groups and chemical bonds in caffeine molecule.

Resonance Raman scattering of β-carotene solution excited by visible laser beams into second singlet state.

PubMed

Lu, Luyao; Shi, Lingyan; Secor, Jeff; Alfano, Robert

2018-02-01

This study aimed to use self-absorption correction to determine the Raman enhancement of β-carotene. The Raman spectra of β-carotene solutions were measured using 488nm, 514nm, 532nm and 633nm laser beams, which exhibited significant resonance Raman (RR) enhancement when the laser energy approaches the electronic transition energy from S 0 to S 2 state. The Raman intensity and the actual resonance Raman gain without self-absorption from S 2 state by β-carotene were also obtained to evaluate the effect of self-absorption on RR scattering. Moreover, we observed the Raman intensity strength followed the absorption spectra. Our study found that, although 488nm and 514nm pumps seemed better for stronger RR enhancement, 532nm would be the optimum Raman pump laser with moderate RR enhancement due to reduced fluorescence and self-absorption. The 532nm excitation will be helpful for applying resonance Raman spectroscopy to investigate biological molecules in tissues. Copyright © 2017 Elsevier B.V. All rights reserved.

The research of Raman spectra measurement system based on tiled-grating monochromator

NASA Astrophysics Data System (ADS)

Liu, Li-na; Zhang, Yin-chao; Chen, Si-ying; Chen, He; Guo, Pan; Wang, Yuan

2013-09-01

A set of Raman spectrum measurement system, essentially a Raman spectrometer, has been independently designed and accomplished by our research group. This system adopts tiled-grating structure, namely two 50mm × 50mm holographic gratings are tiled to form a big spectral grating. It not only improves the resolution but also reduces the cost. This article outlines the Raman spectroscopy system's composition structure and performance parameters. Then corresponding resolutions of the instrument under different criterions are deduced through experiments and data fitting. The result shows that the system's minimum resolution is up to 0.02nm, equivalent to 0.5cm-1 wavenumber under Rayleigh criterion; and it will be up to 0.007nm, equivalent to 0.19cm-1 wavenumber under Sparrow criterion. Then Raman spectra of CCl4 and alcohol have been obtained by the spectrometer, which agreed with the standard spectrum respectively very well. Finally, we measured the spectra of the alcohol solutions with different concentrations and extracted the intensity of characteristic peaks from smoothed spectra. Linear fitting between intensity of characteristic peaks and alcohol solution concentrations has been made. And the linear correlation coefficient is 0.96.

Characterization and calibration of a combined laser Raman, fluorescence and coherent Raman spectrometer

NASA Astrophysics Data System (ADS)

Lawhead, Carlos; Cooper, Nathan; Anderson, Josiah; Shiver, Tegan; Ujj, Laszlo

2014-03-01

Electronic and vibrational spectroscopy is extremely important tools used in material characterization; therefore a table-top laser spectrometer system was built in the spectroscopy lab at the UWF physics department. The system is based upon an injection seeded nanosecond Nd:YAG Laser. The second and the third harmonics of the fundamental 1064 nm radiation are used to generate Raman and fluorescence spectra measured with MS260i imaging spectrograph occupied with a CCD detector and cooled to -85 °C, in order to minimize the dark background noise. The wavelength calibration was performed with the emission spectra of standard gas-discharge lamps. Spectral sensitivity calibration is needed before any spectra are recorded, because of the table-top nature of the instrument. A variety of intensity standards were investigated to find standards suitable for our table top setup that do not change the geometry of the system. High quality measurement of Raman standards where analyzed to test spectral corrections. Background fluorescence removal methods were used to improve Raman signal intensity reading on highly fluorescent molecules. This instrument will be used to measure vibrational and electronic spectra of biological molecules.

Safranin-O dye in the ground state. A study by density functional theory, Raman, SERS and infrared spectroscopy

NASA Astrophysics Data System (ADS)

Lofrumento, C.; Arci, F.; Carlesi, S.; Ricci, M.; Castellucci, E.; Becucci, M.

2015-02-01

The analysis of ground state structural and vibrational properties of Safranin-O is presented. The experimental results, obtained by FTIR, Raman and SERS spectroscopy, are discussed in comparison to the results of DFT calculations carried out at the B3LYP/6-311 + G(d,p) level of theory. The calculated spectra reproduce quite satisfactorily the experimental data. The calculated Safranin-O equilibrium structure and the assignment of the vibrational spectra are reported as well. From the changes between Raman and SERS spectra a model is presented for the interaction of Safranin-O with silver nanoparticles.

Characterization of DNA isolated from normal and cancerous ovarian tissues by ultraviolet resonance Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zhao, Xiaojie; Vinson, Michael A.; Malins, Donald C.; Spiro, Thomas G.

2000-05-01

We report significant differences in UV resonance Raman (UVRR) spectra of DNA samples from normal and cancerous tissues. The four bases of DNA, adenosine, thymine, guanosine and cytidine, can be enhanced in UVRR spectra, and their intensities are very sensitive to base stacking and DNA H-bonding. 14 DNA samples from patients at different stages of ovarian cancer, 5 from normal, 2 from primary, 3 from metastasis primary and 4 from distant metastasis tumor tissues, were characterized by 257, 238, 229, 220 and 210 nm-excited UVRR spectra. Raman spectral difference between normal and tumor DNA could be readily detected.

Molecular near-field antenna effect in resonance hyper-Raman scattering: Intermolecular vibronic intensity borrowing of solvent from solute through dipole-dipole and dipole-quadrupole interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimada, Rintaro; Hamaguchi, Hiro-o, E-mail: hhama@nctu.edu.tw

2014-05-28

We quantitatively interpret the recently discovered intriguing phenomenon related to resonance Hyper-Raman (HR) scattering. In resonance HR spectra of all-trans-β-carotene (β-carotene) in solution, vibrations of proximate solvent molecules are observed concomitantly with the solute β-carotene HR bands. It has been shown that these solvent bands are subject to marked intensity enhancements by more than 5 orders of magnitude under the presence of β-carotene. We have called this phenomenon the molecular-near field effect. Resonance HR spectra of β-carotene in benzene, deuterated benzene, cyclohexane, and deuterated cyclohexane have been measured precisely for a quantitative analysis of this effect. The assignments of themore » observed peaks are made by referring to the infrared, Raman, and HR spectra of neat solvents. It has been revealed that infrared active and some Raman active vibrations are active in the HR molecular near-field effect. The observed spectra in the form of difference spectra (between benzene/deuterated benzene and cyclohexane/deuterated cyclohexane) are quantitatively analyzed on the basis of the extended vibronic theory of resonance HR scattering. The theory incorporates the coupling of excited electronic states of β-carotene with the vibrations of a proximate solvent molecule through solute–solvent dipole–dipole and dipole–quadrupole interactions. It is shown that the infrared active modes arise from the dipole–dipole interaction, whereas Raman active modes from the dipole–quadrupole interaction. It is also shown that vibrations that give strongly polarized Raman bands are weak in the HR molecular near-field effect. The observed solvent HR spectra are simulated with the help of quantum chemical calculations for various orientations and distances of a solvent molecule with respect to the solute. The observed spectra are best simulated with random orientations of the solvent molecule at an intermolecular distance of 10 Å.« less

MicroRaman Spectroscopy and Raman Imaging of Basal Cell Carcinoma

NASA Astrophysics Data System (ADS)

Short, M. A.; Zeng, H.; Lui, H.

2005-03-01

We have measured the Raman spectra of normal and cancerous skin tissues using a confocal microRaman spectrograph with a sub-micron spatial resolution. We found that the Raman spectrum of a cell nucleolus is different from the spectra measured outside the nucleolus and considerably different from those measured outside the nucleus. In addition, we found significant spectroscopic differences between normal and cancer-bearing sites in the dermis region. In order to utilize these differences for non-invasive skin cancer diagnosis, we have developed a Raman imaging system that clearly demonstrates the structure, location and distribution of cells in unstained skin biopsy samples. Our method is expected to be useful for the detection and characterization of skin cancer based on the known distinct cellular differences between normal and malignant skin.

Quantitative determination of the human breast milk macronutrients by near-infrared Raman spectroscopy

NASA Astrophysics Data System (ADS)

Motta, Edlene d. C. M.; Zângaro, Renato A.; Silveira, Landulfo, Jr.

2012-03-01

This work proposes the evaluation of the macronutrient constitution of human breast milk based on the spectral information provided by near-infrared Raman spectroscopy. Human breast milk (5 mL) from a subject was collected during the first two weeks of breastfeeding and stocked in -20°C freezer. Raman spectra were measured using a Raman spectrometer (830 nm excitation) coupled to a fiber based Raman probe. Spectra of human milk were dominated by bands of proteins, lipids and carbohydrates in the 600-1800 cm-1 spectral region. Raman spectroscopy revealed differences in the biochemical constitution of human milk depending on the time of breastfeeding startup. This technique could be employed to develop a classification routine for the milk in Human Milk Banking (HMB) depending on the nutritional facts.

Resonance Raman study of a two-chromophore system. The 2:1 complex of hexamethylbenzene with tetracyanoethylene

NASA Astrophysics Data System (ADS)

Mark Britt, B.; McHale, Jeanne L.

1997-05-01

Raman excitation profiles are presented for the 2:1 electron donor-acceptor (EDA) complex of hexamethylbenzene (HMB) and tetracyanoethylene (TCNE) in cyclohexane. Though the absorption and Raman spectra of the 1:1 and 2:1 complexes are similar, distinct differences are found in the Raman excitation profiles (REPs) of vibrational modes common to both systems. REPs of the 2:1 complex show intensity cancellation that is taken as evidence for interference of two charge-transfer excited states. The implications of the observed spectra concerning excited state electron delocalization are considered.

How to make Raman-inactive helium visible in Raman spectra of tritium-helium gas mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schloesser, M.; Pakari, O.; Rupp, S.

2015-03-15

Raman spectroscopy, a powerful method for the quantitative compositional analysis of molecular gases, e.g. mixtures of hydrogen isotopologues, is not able to detect monoatomic species like helium. This deficit can be overcome by using radioluminescence emission from helium atoms induced by β-electrons from tritium decay. We present theoretical considerations and combined Raman/radioluminescence spectra. Furthermore, we discuss the linearity of the method together with validation measurements for determining the pressure dependence. Finally, we conclude how this technique can be used for samples of helium with traces of tritium, and vice versa. (authors)

Infrared spectra of molecules and materials of astrophysical interest

NASA Technical Reports Server (NTRS)

Durig, J. R.

1978-01-01

The Raman spectra of gaseous, liquid and solid, and infrared spectra of gaseous and solid isopropylamine-d sub 0 and -d sub 2 was investigated between 4000 and 50 cm superscript -1. Differences between the spectrum of the solid phase and that of the fluid phases were interpreted in terms of an equilibrium between low energy s-trans and high energy gauche conformers, and a complete vibrational assignment was proposed for the s-trans conformer. The far infrared spectra of the gaseous compounds contained bands due to the asymmetric amino and coupled methyl torsions; the assignment of these bands was aided by observation of a number of two quantum transitions for each vibrational mode. The asymmetric potential functions were calculated, which resulted in values for the enthalpy differences between conformers in the gaseous phase of 446 and 523 callmole for the sub 0 -d and -d sub 2 compounds, respectively. The methyl torsional potential function of isopropylamine-d sub 0 was calculated which led to a value for the barrier height to internal rotation of the methyl rotors of 4.23 + or - 0.06 kcal/mole. Values for the ideal gas thermodynamic functions were calculated over a range of temperatures.

Solution and solid trinitrotoluene (TNT) photochemistry: persistence of TNT-like ultraviolet (UV) resonance Raman bands.

PubMed

Gares, Katie L; Bykov, Sergei V; Godugu, Bhaskar; Asher, Sanford A

2014-01-01

We examined the 229 nm deep-ultraviolet resonance Raman (DUVRR) spectra of solution and solid-state trinitrotoluene (TNT) and its solution and solid-state photochemistry. Although TNT photodegrades with a solution quantum yield of ϕ ∼ 0.015, the initial photoproducts show DUVRR spectra extraordinarily similar to pure TNT, due to the similar photoproduct enhancement of the -NO2 stretching vibrations. This results in TNT-like DUVRR spectra even after complete TNT photolysis. These ultraviolet resonance Raman spectral bands enable DUVRR of trace as well as DUVRR standoff TNT detection. We determined the structure of various initial TNT photoproducts by using liquid chromatography-mass spectrometry and tandem mass spectrometry. Similar TNT DUVRR spectra and photoproducts are observed in the solution and solid states.

FTIR, FT-Raman spectra and ab initio, DFT vibrational analysis of 2,4-dinitrophenylhydrazine.

PubMed

Sundaraganesan, N; Ayyappan, S; Umamaheswari, H; Joshua, B Dominic

2007-01-01

The FTIR and FT-Raman spectra of 2,4-dinitrophenylhydrazine (2,4-DNPH) has been recorded in the region 4000-400 and 3500-50cm-1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of 2,4-DNPH were obtained by the ab initio and density functional theory (DFT) levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) and 6-311G(d,p) basis sets. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.

FTIR, FT-Raman spectra and ab initio, DFT vibrational analysis of 2,4-dinitrophenylhydrazine

NASA Astrophysics Data System (ADS)

Sundaraganesan, N.; Ayyappan, S.; Umamaheswari, H.; Dominic Joshua, B.

2007-01-01

The FTIR and FT-Raman spectra of 2,4-dinitrophenylhydrazine (2,4-DNPH) has been recorded in the region 4000-400 and 3500-50 cm -1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of 2,4-DNPH were obtained by the ab initio and density functional theory (DFT) levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) and 6-311G(d,p) basis sets. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.

Polarization-Dependent Raman Spectroscopy of Epitaxial TiO 2 (B) Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jokisaari, Jacob R.; Bayerl, Dylan; Zhang, Kui

2015-12-08

The bronze polymorph of titanium dioxide, known as TiO 2(B), has promising photochemical and electronic properties for potential applications in Li-ion batteries, photocatalysis, chemical sensing, and solar cells. In contrast to previous studies performed with powder samples, which often suffer from impurities and lattice water, here we report Raman spectra from highly crystalline TiO 2(B) films epitaxially grown on Si substrates with a thin SrTiO 3 buffer layer. The reduced background from the Si substrate significantly benefits acquisition of polarization-dependent Raman spectra collected from the high-quality thin films, which are compared to nanopowder results reported in the literature. The experimentalmore » spectra were compared with density functional theory calculations to analyze the atomic displacements associated with each Raman-active vibrational mode. These results provide a standard reference for further investigation of the crystallinity, structure, composition, and properties of TiO 2(B) materials with Raman spectroscopy.« less

Characterization of titanyl phthalocyanine (TiOPc) thin films by microscopic and spectroscopic method

NASA Astrophysics Data System (ADS)

Skonieczny, R.; Makowiecki, J.; Bursa, B.; Krzykowski, A.; Szybowicz, M.

2018-02-01

The titanyl phthalocyanine (TiOPc) thin film deposited on glass, silicon and gold substrate have been studied using Raman spectroscopy, atomic force microscopy (AFM), absorption and profilometry measurements. The TiOPc thin layers have been deposited at room temperature by the quasi-molecular beam evaporation technique. The Raman spectra have been recorded using micro Raman system equipped with a confocal microscope. Using surface Raman mapping techni que with polarized Raman spectra the polymorphic forms of the TiOPc thin films distribution have been obtained. The AFM height and phase image were examined in order to find surface features and morphology of the thin films. Additionally to compare experimental results, structure optimization and vibrational spectra calculation of single TiOPc molecule were performed using DFT calculations. The received results showed that the parameters like polymorphic form, grain size, roughness of the surface in TiOPc thin films can well characterize the obtained organic thin films structures in terms of their use in optoelectronics and photovoltaics devices.

Automatic and objective oral cancer diagnosis by Raman spectroscopic detection of keratin with multivariate curve resolution analysis

NASA Astrophysics Data System (ADS)

Chen, Po-Hsiung; Shimada, Rintaro; Yabumoto, Sohshi; Okajima, Hajime; Ando, Masahiro; Chang, Chiou-Tzu; Lee, Li-Tzu; Wong, Yong-Kie; Chiou, Arthur; Hamaguchi, Hiro-O.

2016-01-01

We have developed an automatic and objective method for detecting human oral squamous cell carcinoma (OSCC) tissues with Raman microspectroscopy. We measure 196 independent Raman spectra from 196 different points of one oral tissue sample and globally analyze these spectra using a Multivariate Curve Resolution (MCR) analysis. Discrimination of OSCC tissues is automatically and objectively made by spectral matching comparison of the MCR decomposed Raman spectra and the standard Raman spectrum of keratin, a well-established molecular marker of OSCC. We use a total of 24 tissue samples, 10 OSCC and 10 normal tissues from the same 10 patients, 3 OSCC and 1 normal tissues from different patients. Following the newly developed protocol presented here, we have been able to detect OSCC tissues with 77 to 92% sensitivity (depending on how to define positivity) and 100% specificity. The present approach lends itself to a reliable clinical diagnosis of OSCC substantiated by the “molecular fingerprint” of keratin.

Raman spectroscopy of normal oral buccal mucosa tissues: study on intact and incised biopsies

NASA Astrophysics Data System (ADS)

Deshmukh, Atul; Singh, S. P.; Chaturvedi, Pankaj; Krishna, C. Murali

2011-12-01

Oral squamous cell carcinoma is one of among the top 10 malignancies. Optical spectroscopy, including Raman, is being actively pursued as alternative/adjunct for cancer diagnosis. Earlier studies have demonstrated the feasibility of classifying normal, premalignant, and malignant oral ex vivo tissues. Spectral features showed predominance of lipids and proteins in normal and cancer conditions, respectively, which were attributed to membrane lipids and surface proteins. In view of recent developments in deep tissue Raman spectroscopy, we have recorded Raman spectra from superior and inferior surfaces of 10 normal oral tissues on intact, as well as incised, biopsies after separation of epithelium from connective tissue. Spectral variations and similarities among different groups were explored by unsupervised (principal component analysis) and supervised (linear discriminant analysis, factorial discriminant analysis) methodologies. Clusters of spectra from superior and inferior surfaces of intact tissues show a high overlap; whereas spectra from separated epithelium and connective tissue sections yielded clear clusters, though they also overlap on clusters of intact tissues. Spectra of all four groups of normal tissues gave exclusive clusters when tested against malignant spectra. Thus, this study demonstrates that spectra recorded from the superior surface of an intact tissue may have contributions from deeper layers but has no bearing from the classification of a malignant tissues point of view.

Effect of particle size and laser power on the Raman spectra of CuAlO2 delafossite nanoparticles

NASA Astrophysics Data System (ADS)

Yassin, O. A.; Alamri, S. N.; Joraid, A. A.

2013-06-01

A transparent conductive oxide CuAlO2 delafossite is studied using x-ray powder diffraction (XRD) and micro-Raman spectroscopy measurements as a function of the particle size and laser power from 2 to 20 mW. The XRD results indicate that the lattice parameters and the cell volume expand as the particle size reduces. Large red shifts (˜60 cm-1) and line broadening (˜50 cm-1) are observed as the particle size becomes of the order of 13 nm. These huge values can only be justified if collective effects on the Raman spectra created by the lattice expansion, confinement of phonons and enhanced phonon-phonon interactions are included in the interpretations of the Raman spectra of the CuAlO2 nanoparticles.

The detection of drugs of abuse in fingerprints using Raman spectroscopy II: cyanoacrylate-fumed fingerprints

NASA Astrophysics Data System (ADS)

Day, Joanna S.; Edwards, Howell G. M.; Dobrowski, Steven A.; Voice, Alison M.

2004-07-01

This paper describes the application of Raman spectroscopy to the detection of exogenous substances in cyanoacrylate-fumed fingerprints. The scenario considered was that of an individual handling a substance and subsequently depositing a contaminated fingerprint. These fingerprints were enhanced by cyanoacrylate fuming, a process in which a layer of white cyanoacrylate polymer is deposited on the fingerprint material, enabling visual detection. Five drugs of abuse (codeine phosphate, cocaine hydrochloride, amphetamine sulphate, barbital and nitrazepam) and five non-controlled substances of similar appearance, which may be used in the adulteration of drugs of abuse (caffeine, aspirin, paracetamol, starch and talc), were used. The substances studied could be clearly distinguished using their Raman spectra and were all successfully detected in cyanoacrylate-fumed fingerprints. Photobleaching was necessary to reduce the fluorescence background in the spectra of some substances. Raman spectra obtained from the substances in cyanoacrylate-fumed fingerprints were of a similar quality to spectra obtained from the substances under normal sampling conditions, however, interfering Raman bands arising from the cyanoacrylate polymer were present in the spectra. In most cases the only interfering band was the CN stretching mode of the polymer, and there were no cases where the interfering bands prevented identification of the substances. If necessary, the interfering bands could be successfully removed by spectral subtraction. The most difficult aspect of the detection of these substances in cyanoacrylate-fumed fingerprints was visually locating the substance in the fingerprint beneath the polymer layer in order to obtain a Raman spectrum.

Characterizing variability in in vivo Raman spectra of different anatomical locations in the upper gastrointestinal tract toward cancer detection

NASA Astrophysics Data System (ADS)

Bergholt, Mads Sylvest; Zheng, Wei; Lin, Kan; Ho, Khek Yu; Teh, Ming; Yeoh, Khay Guan; So, Jimmy Bok Yan; Huang, Zhiwei

2011-03-01

Raman spectroscopy is an optical vibrational technology capable of probing biomolecular changes of tissue associated with cancer transformation. This study aimed to characterize in vivo Raman spectroscopic properties of tissues belonging to different anatomical regions in the upper gastrointestinal (GI) tract and explore the implications for early detection of neoplastic lesions during clinical gastroscopy. A novel fiber-optic Raman endoscopy technique was utilized for real-time in vivo tissue Raman measurements of normal esophageal (distal, middle, and proximal), gastric (antrum, body, and cardia) as well as cancerous esophagous and gastric tissues from 107 patients who underwent endoscopic examinations. The non-negativity-constrained least squares minimization coupled with a reference database of Raman active biochemicals (i.e., actin, histones, collagen, DNA, and triolein) was employed for semiquantitative biomolecular modeling of tissue constituents in the upper GI. A total of 1189 in vivo Raman spectra were acquired from different locations in the upper GI. The Raman spectra among the distal, middle, and proximal sites of the esophagus showed no significant interanatomical variability. The interanatomical variability of Raman spectra among normal gastric tissue (antrum, body, and cardia) was subtle compared to cancerous tissue transformation, whereas biomolecular modeling revealed significant differences between the two organs, particularly in the gastroesophageal junction associated with proteins, DNA, and lipids. Cancerous tissues can be identified across interanatomical regions with accuracies of 89.3% [sensitivity of 92.6% (162/175) specificity of 88.6% (665/751)], and of 94.7% [sensitivity of 90.9% (30/33) specificity of 93.9% (216/230)] in the gastric and esophagus, respectively, using partial least squares-discriminant analysis together with the leave-one tissue site-out, cross validation. This work demonstrates that Raman endoscopy technique has promising clinical potential for real-time, in vivo diagnosis and detection of malignancies in the upper GI at the molecular level.

Pre-resonance Raman spectra of some simple gases. [sulfur oxides, hydrogen sulfide, and nitrogen oxides

NASA Technical Reports Server (NTRS)

Low, P. W.

1974-01-01

The pre-resonance Raman spectra of SO2, N2O, and H2S were investigated using the 4880 A, 4727 A, and 4579 A lines of the argon ion laser. Although these molecules have electronic absorption bands in the near ultraviolet, none exhibit any pre-resonance enhancement within our experimental error of + or - 10%. Possible explanations taking into account the current theories for resonance Raman are discussed.

FT-Raman spectra of cellulose and lignocellulose materials : “self-absorption” phenomenon and its implications for quantitative work

Treesearch

Umesh Agarwal; Nancy Kawai

2003-01-01

The phenomenon of “self-absorption” was found to exist in the FT-Raman spectra of cellulose and thermomechanical pulp (TMP), but not in the spectrum of milled wood lignin. For cellulose and TMP, the effect was responsible for reducing the intensity of the Raman bands in the C-H stretch region. Several factors including sampling position, sample thickness, and moisture...

Applications of Fourier transform Raman and infrared spectroscopy in forensic sciences

NASA Astrophysics Data System (ADS)

Kuptsov, Albert N.

2000-02-01

First in the world literature comprehensive digital complementary vibrational spectra collection of polymer materials and search system was developed. Non-destructive combined analysis using complementary FT-Raman and FTIR spectra followed by cross-parallel searching on digital spectral libraries, was applied in different fields of forensic sciences. Some unique possibilities of Raman spectroscopy has been shown in the fields of examination of questioned documents, paper, paints, polymer materials, gemstones and other physical evidences.

Low-Cost Elimination of Plasma Lines in Raman Spectra.

ERIC Educational Resources Information Center

Behlow, Herbert W., Jr.; Petersen, John D.

1985-01-01

Describes a low-cost ($120) device which eliminates plasma lines in Raman spectra. The device consists of two prisms and two mirrors which are held in a symmetrical relationship to one another so that a particular position will allow only one wavelength to pass through on a given axis. (JN)

Artificial neural network and classical least-squares methods for neurotransmitter mixture analysis.

PubMed

Schulze, H G; Greek, L S; Gorzalka, B B; Bree, A V; Blades, M W; Turner, R F

1995-02-01

Identification of individual components in biological mixtures can be a difficult problem regardless of the analytical method employed. In this work, Raman spectroscopy was chosen as a prototype analytical method due to its inherent versatility and applicability to aqueous media, making it useful for the study of biological samples. Artificial neural networks (ANNs) and the classical least-squares (CLS) method were used to identify and quantify the Raman spectra of the small-molecule neurotransmitters and mixtures of such molecules. The transfer functions used by a network, as well as the architecture of a network, played an important role in the ability of the network to identify the Raman spectra of individual neurotransmitters and the Raman spectra of neurotransmitter mixtures. Specifically, networks using sigmoid and hyperbolic tangent transfer functions generalized better from the mixtures in the training data set to those in the testing data sets than networks using sine functions. Networks with connections that permit the local processing of inputs generally performed better than other networks on all the testing data sets. and better than the CLS method of curve fitting, on novel spectra of some neurotransmitters. The CLS method was found to perform well on noisy, shifted, and difference spectra.

Single-Shot Rotational Raman Thermometry for Turbulent Flames Using a Low-Resolution Bandwidth Technique

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet

2007-01-01

An alternative optical thermometry technique that utilizes the low-resolution (order 10(exp 1)/cm) pure-rotational spontaneous Raman scattering of air is developed to aid single-shot multiscalar measurements in turbulent combustion studies. Temperature measurements are realized by correlating the measured envelope bandwidth of the pure-rotational manifold of the N2/O2 spectrum with a theoretical prediction of a species-weighted bandwidth. By coupling this thermometry technique with conventional vibrational Raman scattering for species determination, we demonstrate quantitative spatially resolved, single-shot measurements of the temperature and fuel/oxidizer concentrations in a high-pressure turbulent Cf4-air flame. Our technique provides not only an effective means of validating other temperature measurement methods, but also serves as a secondary thermometry technique in cases where the anti-Stokes vibrational N2 Raman signals are too low for a conventional vibrational temperature analysis.

The Influence of Trace Gases Absorption on Differential Ring Cross Sections

NASA Astrophysics Data System (ADS)

Han, Dong; Zhao, Keyi

2017-04-01

The Ring effect refers to the filling in of Fraunhofer lines, which is known as solar absorption lines, caused almost entirely by rotational Raman scattering. The rotational Raman scattering by N2 and O2 in the atmosphere is the main factor that leads to Ring effect. The Ring effect is one significant limitation to the accuracy of the retrieval of trace gas constituents in atmosphere, while using satellite data with Differential Optical Absorption Spectroscopy technique. In this study, firstly the solar spectrum is convolved with rotational Raman cross sections of atmosphere, which is calculated with rotational Raman cross sections of N2 and O2, divided by the original solar spectrum, with a cubic polynomial subtracted off, to create differential Ring spectrum Ring1. Secondly, the Ring effect for pure Raman scattering of the Fraunhofer spectrum plus the contribution from interference by terrestrial absorption which always comes from a kind of trace gas (e.g., O3) are derived. To allow for more generality, the optically thin term as well as the next term in the expansion for the Beer-Lambert law are calculated.Ring1, Ring2, and Ring3are the Fraunhofer only, 1st terrestrial correction, and 2nd terrestrial correction for DOAS fitting.

Evaluation of Shifted Excitation Raman Difference Spectroscopy and Comparison to Computational Background Correction Methods Applied to Biochemical Raman Spectra.

PubMed

Cordero, Eliana; Korinth, Florian; Stiebing, Clara; Krafft, Christoph; Schie, Iwan W; Popp, Jürgen

2017-07-27

Raman spectroscopy provides label-free biochemical information from tissue samples without complicated sample preparation. The clinical capability of Raman spectroscopy has been demonstrated in a wide range of in vitro and in vivo applications. However, a challenge for in vivo applications is the simultaneous excitation of auto-fluorescence in the majority of tissues of interest, such as liver, bladder, brain, and others. Raman bands are then superimposed on a fluorescence background, which can be several orders of magnitude larger than the Raman signal. To eliminate the disturbing fluorescence background, several approaches are available. Among instrumentational methods shifted excitation Raman difference spectroscopy (SERDS) has been widely applied and studied. Similarly, computational techniques, for instance extended multiplicative scatter correction (EMSC), have also been employed to remove undesired background contributions. Here, we present a theoretical and experimental evaluation and comparison of fluorescence background removal approaches for Raman spectra based on SERDS and EMSC.

Development of a multiplexing fingerprint and high wavenumber Raman spectroscopy technique for real-time in vivo tissue Raman measurements at endoscopy.

PubMed

Bergholt, Mads Sylvest; Zheng, Wei; Huang, Zhiwei

2013-03-01

We report on the development of a novel multiplexing Raman spectroscopy technique using a single laser light together with a volume phase holographic (VPH) grating that simultaneously acquires both fingerprint (FP) and high wavenumber (HW) tissue Raman spectra at endoscopy. We utilize a customized VPH dual-transmission grating, which disperses the incident Raman scattered light vertically onto two separate segments (i.e., -150 to 1950  cm⁻¹; 1750 to 3600  cm⁻¹) of a charge-coupled device camera. We demonstrate that the multiplexing Raman technique can acquire high quality in vivo tissue Raman spectra ranging from 800 to 3600  cm⁻¹ within 1.0 s with a spectral resolution of 3 to 6  cm⁻¹ during clinical endoscopy. The rapid multiplexing Raman spectroscopy technique covering both FP and HW ranges developed in this work has potential for improving in vivo tissue diagnosis and characterization at endoscopy.

Evaluation of Shifted Excitation Raman Difference Spectroscopy and Comparison to Computational Background Correction Methods Applied to Biochemical Raman Spectra

PubMed Central

Cordero, Eliana; Korinth, Florian; Stiebing, Clara; Krafft, Christoph; Schie, Iwan W.; Popp, Jürgen

2017-01-01

Raman spectroscopy provides label-free biochemical information from tissue samples without complicated sample preparation. The clinical capability of Raman spectroscopy has been demonstrated in a wide range of in vitro and in vivo applications. However, a challenge for in vivo applications is the simultaneous excitation of auto-fluorescence in the majority of tissues of interest, such as liver, bladder, brain, and others. Raman bands are then superimposed on a fluorescence background, which can be several orders of magnitude larger than the Raman signal. To eliminate the disturbing fluorescence background, several approaches are available. Among instrumentational methods shifted excitation Raman difference spectroscopy (SERDS) has been widely applied and studied. Similarly, computational techniques, for instance extended multiplicative scatter correction (EMSC), have also been employed to remove undesired background contributions. Here, we present a theoretical and experimental evaluation and comparison of fluorescence background removal approaches for Raman spectra based on SERDS and EMSC. PMID:28749450

Comparison of time-gated surface-enhanced Raman spectroscopy (TG-SERS) and classical SERS based monitoring of Escherichia coli cultivation samples.

PubMed

Kögler, Martin; Paul, Andrea; Anane, Emmanuel; Birkholz, Mario; Bunker, Alex; Viitala, Tapani; Maiwald, Michael; Junne, Stefan; Neubauer, Peter

2018-06-08

The application of Raman spectroscopy as a monitoring technique for bioprocesses is severely limited by a large background signal originating from fluorescing compounds in the culture media. Here we compare time-gated Raman (TG-Raman)-, continuous wave NIR-process Raman (NIR-Raman) and continuous wave micro-Raman (micro-Raman) approaches in combination with surface enhanced Raman spectroscopy (SERS) for their potential to overcome this limit. For that purpose, we monitored metabolite concentrations of Escherichia coli bioreactor cultivations in cell-free supernatant samples. We investigated concentration transients of glucose, acetate, AMP and cAMP at alternating substrate availability, from deficiency to excess. Raman and SERS signals were compared to off-line metabolite analysis of carbohydrates, carboxylic acids and nucleotides. Results demonstrate that SERS, in almost all cases, led to a higher number of identifiable signals and better resolved spectra. Spectra derived from the TG-Raman were comparable to those of micro-Raman resulting in well-discernable Raman peaks, which allowed for the identification of a higher number of compounds. In contrast, NIR-Raman provided a superior performance for the quantitative evaluation of analytes, both with and without SERS nanoparticles when using multivariate data analysis. This article is protected by copyright. All rights reserved. © 2018 American Institute of Chemical Engineers.

Raman spectra of adsorbed layers on space shuttle and AOTV thermal protection system surface

NASA Technical Reports Server (NTRS)

Willey, Ronald J.

1987-01-01

Surfaces of interest to space vehicle heat shield design were struck by a 2 W argon ion laser line while subjected to supersonic arc jet flow conditions. Emission spectra were taken at 90 deg to the angle of laser incidence on the test object. Results showed possible weak Raman shifts which could not be directly tied to any particular parameter such as surface temperature or gas composition. The investigation must be considered exploratory in terms of findings. Many undesirable effects were found and corrected as the project progressed. For instance, initial spectra settings led to ghosts which were eliminated by closing the intermediate of filter slit of the Spex from 8 to 3 mm. Further, under certain conditions, plasma lines from the laser were observed. Several materials were also investigated at room temperature for Raman shifts. Results showed Raman shifts for RCC and TEOS coated materials. The HRSI materials showed only weak Raman shifts, however, substantial efforts were made in studying these materials. Baseline materials showed the technique to be sound. The original goal was to find a Raman shift for the High-temperature Reusable Surface Insulation (HRSI) Reaction Cured borosilicate Glass (RCG) coated material and tie the amplitude of this peak to Arc jet conditions. Weak Raman shifts may be present, however, time limitations prevented confirmation.

Vibrational spectra (FT-IR, Raman and MI-IR) of α- and β-alanine

NASA Astrophysics Data System (ADS)

Rosado, Mário Túlio S.; Duarte, Maria Leonor R. S.; Fausto, Rui

1997-06-01

The vibrational spectra of α- and β-alaine molecules in both their zwitterionic and neutral forms are studied by FT-IR, Raman and MI-IR spectroscopy. Together with results from theoretical SCF-MO ab initio calculations, the spectroscopic data obtained under the various experimental conditions used in this study (crystalline phase; low temperature matrix isolated molecules) enable to undertake a detailed assignment of the vibrational spectra of the studied compounds.

Effect of guest-host interaction on Raman spectrum of a CO2 clathrate hydrate single crystal

NASA Astrophysics Data System (ADS)

Ikeda, Tomoko; Mae, Shinji; Uchida, Tsutomu

1998-01-01

The polarized Raman spectra of an artificial CO2 clathrate hydrate single crystal have been measured in order to examine the crystal-orientation dependence of the Raman spectra. Since the crystal had crystallographic facets, the orientation of the crystal was determined by using the Miller indices of the facets. When the angle θ between the polarization plane of the incident laser beam and the direction of one of the <110> axes of the single crystal varied, it was observed that the intensities of the peaks, which were caused by the Fermi resonance of the symmetric stretching mode and the overtone of the bending mode of CO2, and the O-H symmetric stretching vibration mode, varied with θ. Since the tetrakaidecahedron cage in the CO2 clathrate hydrate is distorted along the <100> axis, the variations of the scattering intensities of the CO2 have been calculated by using a simple model that assumes that the CO2 rotates on the {100} plane in the tetrakaidecahedron cage. The results obtained from the experiments are consistent with the calculations made by using this model. It has been concluded that the anisotropy of the peak intensities of the CO2 show the influence of the cage geometry on the motion of the guest molecule. The anisotropy of the O-H symmetric stretching vibration mode was interpreted with a five-body structure model. As the calculation with the model was consistent with the result obtained from the experiment, it was found that the anisotropy of the peak intensity of the O-H symmetric stretching vibration mode was related to the arrangement of the water molecules. We consider that the result indicates the influence of the motion of the guest molecule on the surrounding hydrogen-bonded network.

Raman Spectroscopy Differentiates Each Tissue From the Skin to the Spinal Cord: A Novel Method for Epidural Needle Placement?

PubMed Central

Anderson, T. Anthony; Kang, Jeon Woong; Gubin, Tatyana; Dasari, Ramachandra R.; So, Peter T. C.

2016-01-01

BACKGROUND Neuraxial anesthesia and epidural steroid injection techniques require precise anatomical targeting to ensure successful and safe analgesia. Previous studies suggest that only some of the tissues encountered during these procedures can be identified by spectroscopic methods, and no previous study has investigated the use of Raman, diffuse reflectance, and fluorescence spectroscopies. The authors hypothesized that real-time needle-tip spectroscopy may aid epidural needle placement and tested the ability of spectroscopy to distinguish each of the tissues in the path of neuraxial needles. METHODS For comparison of detection methods, the spectra of individual, dissected ex vivo paravertebral and neuraxial porcine tissues were collected using Raman spectroscopy (RS), diffuse reflectance spectroscopy (DRS), and fluorescence spectroscopy (FS). Real-time spectral guidance was tested using a 2 mm inner diameter fiber optic probe-in-needle device. Raman spectra were collected during the needle’s passage through intact paravertebral and neuraxial porcine tissue and analyzed afterward. The RS tissue signatures were verified as mapping to individual tissue layers using histochemical staining and widefield microscopy. RESULTS Raman spectroscopy revealed a unique spectrum for all ex vivo paravertebral and neuraxial tissue layers; DRS and FS spectra were not distinct for all tissues. Moreover, when accounting for the expected order of tissues, real-time Raman spectra recorded during needle insertion also permitted identification of each paravertebral and neuraxial porcine tissue. CONCLUSIONS This study demonstrates Raman spectroscopy can distinguish the tissues encountered during epidural needle insertion. This technology may prove useful during needle placement by providing evidence of its anatomical localization. PMID:27466032

Raman Scattering at Plasmonic Junctions Shorted by Conductive Molecular Bridges

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Khoury, Patrick Z.; Hu, Dehong; Apkarian, V. Ara

2013-04-10

Intensity spikes in Raman scattering, accompanied by switching between line spectra and band spectra, can be assigned to shorting the junction plasmon through molecular conductive bridges. This is demonstrated through Raman trajectories recorded at a plasmonic junction formed by a gold AFM tip in contact with a silver surface coated either with biphenyl-4,4’-dithiol or biphenyl-4-thiol. The fluctuations are absent in the monothiol. In effect, the making and breaking of chemical bonds is tracked.

A study of amber and copal samples using FT-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Brody, Rachel H.; Edwards, Howell G. M.; Pollard, A. Mark

2001-05-01

FT-Raman spectra were collected from fossil resins originating from a variety of geographical locations. The spectral profiles of most of the fossil resins could be related to modern resins containing diterpenoid components with predominantly labdane skeletons. The spectra collected from the fossil resin sample from Borneo differed from other fossil resins and was found to contain triterpenoid components. The differences in the spectral profile of fossil resins containing diterpenoid components are shown to relate to differences in level of maturation rather than geographical origin. FT-Raman spectra of fossil resins cannot be used to distinguish source although the degree of maturation can be used as an indicator to narrow the range of possible geographical origins.

Safranin-O dye in the ground state. A study by density functional theory, Raman, SERS and infrared spectroscopy.

PubMed

Lofrumento, C; Arci, F; Carlesi, S; Ricci, M; Castellucci, E; Becucci, M

2015-02-25

The analysis of ground state structural and vibrational properties of Safranin-O is presented. The experimental results, obtained by FTIR, Raman and SERS spectroscopy, are discussed in comparison to the results of DFT calculations carried out at the B3LYP/6-311+G(d,p) level of theory. The calculated spectra reproduce quite satisfactorily the experimental data. The calculated Safranin-O equilibrium structure and the assignment of the vibrational spectra are reported as well. From the changes between Raman and SERS spectra a model is presented for the interaction of Safranin-O with silver nanoparticles. Copyright © 2014 Elsevier B.V. All rights reserved.

Raman study of the Hg0.7Cr0.3Sr2CuO4+δ superconductors

NASA Astrophysics Data System (ADS)

Lee, S.-Y.; Chang, B.-Y.; Yang, I.-S.; Gwak, J.-H.; Kim, S.-J.; Choi, J.-H.; Lee, S.-I.; Yakhmi, J. V.; Mandal, J. B.; Bandyopadhyay, B.; Ghosh, B.

1997-08-01

The local environment of the apical oxygens (OA) in the Sr-substituted mercury-based superconductor Hg0.7Cr0.3Sr2CuO4+δ is investigated using Raman spectroscopy. Raman spectra from the Sr-substituted Hg-1201 samples show broad OA A1g double peaks at 553 and 583 cm-l, which are 10 - 20 cm-1 lower than the pristine Hg-1201. The existence of, and lower shift of, the double peaks in the Raman spectra of the Sr-substituted Hg-1201 superconductors indicate changes in the environment of OA in the Sr-substituted mercury-based superconductors.

Raman fingerprints for unambiguous identification of organotin compounds.

PubMed

Pankin, Dmitrii; Kolesnikov, Ilya; Vasileva, Anna; Pilip, Anna; Zigel, Vladislav; Manshina, Alina

2018-06-13

Raman spectra of the different ecotoxicants such as perfluorooctane sulfonate acid, organotin compounds of different families tributyl-, and triphenyl-, as well as chemically close compounds belonging to the same family - such as mono-, di-, and tributyl organotin compounds were analyzed. The comprehensive Raman spectra analysis allowed suggesting the identification scheme for clear recognition of the toxins family and the following intra-group specification. Possibility of unambiguous toxins detection and identification was demonstrated also for complex mixtures of various toxins on a base of control of characteristic peak groups, which can be considered as Raman fingerprints of the listed environmentally hazardous substances. Copyright © 2018. Published by Elsevier B.V.

Characteristics of Raman spectra for graphene oxide from ab initio simulations.

PubMed

Wang, Lu; Zhao, Jijun; Sun, Yi-Yang; Zhang, Shengbai B

2011-11-14

The Raman spectra of several locally stable structures of the graphene oxide (GO) have been simulated by ab initio calculations. Compared to graphite, the G band of GO is broadened and blueshifted due to the emergence of a series of new Raman peaks. The Raman intensities and positions of the D and G bands depend sensitively on the local atomic configurations. In addition to the normal epoxy and hydroxyl groups, other oxidation groups such as epoxy pairs are also studied. Epoxy pairs induce large blueshift of G band with respect to that of the graphite. © 2011 American Institute of Physics

Raman Spectroscopy of the Interferon-Induced 2’,5’-Oligoadenylates

DTIC Science & Technology

1987-06-25

generation of the Raman spectrum of triethyl ammonium ion ••••••••••••••••••••••••••••••• 41 12. structures of purine, adenine, purine riboside , adenosine...ribose 5 1-phosphate, AMP, and ATP........ 48 13. Raman spectra of adenine and purine •••••••.••••••••• 49 14. Raman spectra of purine riboside and... nicotinamide adenine dinucleotide; TFAB, triethyl anunonium bicarbonate; TFA, triethyl amm::mium. ion; CD circular _dichroism; NMR, nuclear magnetic

Confocal Raman imaging for cancer cell classification

NASA Astrophysics Data System (ADS)

Mathieu, Evelien; Van Dorpe, Pol; Stakenborg, Tim; Liu, Chengxun; Lagae, Liesbet

2014-05-01

We propose confocal Raman imaging as a label-free single cell characterization method that can be used as an alternative for conventional cell identification techniques that typically require labels, long incubation times and complex sample preparation. In this study it is investigated whether cancer and blood cells can be distinguished based on their Raman spectra. 2D Raman scans are recorded of 114 single cells, i.e. 60 breast (MCF-7), 5 cervix (HeLa) and 39 prostate (LNCaP) cancer cells and 10 monocytes (from healthy donors). For each cell an average spectrum is calculated and principal component analysis is performed on all average cell spectra. The main features of these principal components indicate that the information for cell identification based on Raman spectra mainly comes from the fatty acid composition in the cell. Based on the second and third principal component, blood cells could be distinguished from cancer cells; and prostate cancer cells could be distinguished from breast and cervix cancer cells. However, it was not possible to distinguish breast and cervix cancer cells. The results obtained in this study, demonstrate the potential of confocal Raman imaging for cell type classification and identification purposes.

Effect of Red Light-Emitting Diodes Irradiation on Hemoglobin for Potential Hypertension Treatment Based on Confocal Micro-Raman Spectroscopy.

PubMed

Qiu, Xuejun; Huang, Hanchuan; Huang, Zhitong; Zhuang, Zhengfei; Guo, Zhouyi; Liu, Songhao

2017-01-01

Red light-emitting diodes (LED) were used to irradiate the isolated hypertension hemoglobin (Hb) and Raman spectra difference was recorded using confocal micro-Raman spectroscopy. Differences were observed between the controlled and irradiated Hb by comparing the spectra records. The Raman spectrum at the 1399 cm -1 band decreased following prolonged LED irradiation. The intensity of the 1639 cm -1 band decreased dramatically in the first five minutes and then gradually increased in a time-dependent manner. This observation indicated that LED irradiation increased the ability of oxygen binding in Hb. The appearance of the heme aggregation band at 1399 cm -1 , in addition to the oxygen marker band at 1639 cm -1 , indicated that, in our study, 30 min of irradiation with 15.0 mW was suitable for inhibiting heme aggregation and enhancing the oxygen-carrying capacity of Hb. Principal component analysis showed a one-to-one relationship between irradiated Hb at different time points and the corresponding Raman spectra. Our approach could be used to analyze the hemoglobin from patients with confocal micro-Raman spectroscopy and is helpful for developing new nondrug hypertension therapy.

A spectroscopic and computational study of Al(III) complexes in sodium cryolite melts: ionic composition in a wide range of cryolite ratios.

PubMed

Nazmutdinov, Renat R; Zinkicheva, Tamara T; Vassiliev, Sergey Yu; Glukhov, Dmitri V; Tsirlina, Galina A; Probst, Michael

2010-04-01

The structure of sodium cryolite melts was studied using Raman spectroscopy and quantum chemical calculations performed at the density functional theory level. The existence of bridged forms in the melts was argued first from the analysis of experimental Raman spectra. In the quantum chemical modelling emphasis was put on the construction of potential energy surfaces describing the formation/dissociation of certain complex species. Effects of the ionic environment were found to play a crucial role in the energetics of model processes. The structure of the simplest possible polymeric forms involving two Al centres linked through F atoms ("dimers") was thoroughly investigated. The calculated equilibrium constants and model Raman spectra yield additional evidence in favour of the dimers. This agrees with a self-consistent analysis of a series of Raman spectra for a wide range of the melt composition. Copyright 2010. Published by Elsevier B.V.

Theoretical study of the Raman active CDW gap mode in manganites.

PubMed

Rout, G C; Panda, Saswati; Behera, S N

2010-09-22

We report here the microscopic theory of the Raman spectra of the colossal magnetoresistive (CMR) manganite systems. The system is described by a model Hamiltonian consisting of the double exchange interaction in addition to the charge ordering interaction in the e(g) band and spin-spin interaction among the t(2g) core electrons. Further the phonon coupling to the conduction electron density is incorporated in the model for phonons in the harmonic approximation. The spectral density function for the Raman spectra is calculated from the imaginary part of the phonon Green's function. The calculated spectra display the Raman active bare phonon peak along with the charge ordering peak. The magnetic field and temperature dependence of the charge ordering peak agrees with the 480 cm(-1) JT mode observed in the experiments. The evolution of this mode is investigated in the report.

DFT, FT-IR, FT-Raman and vibrational studies of 3-methoxyphenyl boronic acid

NASA Astrophysics Data System (ADS)

Patil, N. R.; Hiremath, Sudhir M.; Hiremath, C. S.

2018-05-01

The aim of this work is to study the possible stable, geometrical molecular structure, experimental and theoretical FT-IR and FT-Raman spectroscopic methods of 3-Methoxyphenyl boronic acid (3MPBA). FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm-1 and 40000-50 cm-1 respectively. The optimized geometric structure and vibrational wavenumbers of the title compound were searched by B3LYP hybrid density functional theory method with 6-311++G (d, p) basis set. The Selectedexperimentalbandswereassignedandcharacterizedonthebasisofthescaledtheoreticalwavenumbersby their potential energy distribution (PED) of the vibrational modes obtained from VEDA 4 program. Finally, the predicted calculation results were applied to simulated FT-IR and FT-Raman spectra of the title compound, which show agreement with the observed spectra. Whereas, it is observed that, the theoretical frequencies are more than the experimental one for O-H stretching vibration modes of the title molecule.

Comparing two tetraalkylammonium ionic liquids. II. Phase transitions.

PubMed

Lima, Thamires A; Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C; Ferreira, Fabio F; Costa, Fanny N; Giles, Carlos

2016-06-14

Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.

Optical phonon behavior of columbite MgNb2O6 single crystals

NASA Astrophysics Data System (ADS)

Xu, Dapeng; Liu, Wenqiang; Zhou, Qiang; Cui, Tian; Yuan, Hongming; Wang, Wenquan; Liu, Ying; Shi, Zhan; Li, Liang

2014-08-01

To explore potential applications, MgNb2O6 single crystal grown previously by optical floating zone method was used as a prototype for optical phonon behavior investigation. Polarized Raman spectra obtained in adequate parallel and crossed polarization were presented. All the obtained Raman modes were identified for the MgNb2O6, in good agreement with previous theory analysis. The selection rules of Raman for the columbite group were validated. Additionally, in-site temperature-dependent Raman spectra of MgNb2O6 were also investigated in the range from 83 to 803 K. The strong four Ag phonon modes all exhibits red shift with the temperature increasing. But thermal expansion of spectra is sectional linear with inflection points at about 373 K. And the absolute value of dω/dT at high temperature is higher than the one at lower temperature.

Time-resolved resonance Raman spectroscopy of intermediates of bacteriorhodopsin: The bK(590) intermediate.

PubMed

Terner, J; Hsieh, C L; Burns, A R; El-Sayed, M A

1979-07-01

We have combined microbeam and flow techniques with computer subtraction methods to obtain the resonance Raman spectrum of the short lived batho-intermediate (bK(590)) of bacteriorhodopsin. Comparison of the spectra obtained in (1)H(2)O and (2)H(2)O, as well as the fact that the bK(590) intermediate shows large optical red shifts, suggests that the Schiff base linkage of this intermediate is protonated. The fingerprint region of the spectrum of bK(590), sensitive to the isomeric configuration of the retinal chromophore, does not resemble the corresponding region of the parent bR(570) form. The resonance Raman spectrum of bK(590) as well as the spectra of all of the other main intermediates in the photoreaction cycle of bacteriorhodopsin are discussed and compared with resonance Raman spectra of published model compounds.

Identification and discrimination of polycyclic aromatic hydrocarbons using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Cloutis, Edward; Szymanski, Paul; Applin, Daniel; Goltz, Douglas

2016-08-01

Polycyclic aromatic hydrocarbons (PAHs) are widely present throughout the Solar System and beyond. They have been implicated as a contributor to unidentified infrared emission bands in the interstellar medium, comprise a substantial portion of the insoluble organic matter in carbonaceous chondrites, are expected stable components of organic matter on Mars, and are present in a wide range of terrestrial hydrocarbons and as components of biomolecules. However, PAH structures can be very complicated, making their identification challenging. Raman spectroscopy is known to be especially sensitive to the highly polarizable C-C and C=C bonds found in PAHs, and therefore, can be a powerful tool for PAH structural and compositional elucidation. This study examined Raman spectra of 48 different PAHs to determine the degree to which Raman spectroscopy could be used to uniquely identify different species, factors that control the positions of major Raman peaks, the degree to which induced fluorescence affects the intensity of Raman peaks, its usefulness for PAH discrimination, and the effects of varying excitation wavelength on some PAH Raman spectra. It was found that the arrangement and composition of phenyl (benzene) rings, and the type and position of functional groups can greatly affect fluorescence, positions and intensities of Raman peaks associated with the PAH backbone, and the introduction of new Raman peaks. Among the functional groups found on many of the PAHs that were analyzed, only a few Raman peaks corresponding to the molecular vibrations of these groups could be clearly distinguished. Comparison of the PAH Raman spectra that were acquired with both 532 and 785 nm excitation found that the longer wavelength resulted in reduced fluorescence, consistent with previous studies.

Raman scattering-based multiconformational analysis for probing the structural differences between acetylcholine and acetylthiocholine.

PubMed

Hernández, Belén; Houzé, Pascal; Pflüger, Fernando; Kruglik, Sergei G; Ghomi, Mahmoud

2017-05-10

Acetylcholine is the first discovered neurotransmitter that has received a great attention regarding its capability of binding to several cellular targets. The chemical composition of acetylcholine, including a positively charged trimethylammonium and a carbonyl group, as well as its conformational flexibility was pointed out as the key factors in the stabilization of its interactions. Here, the possibilities offered by a Raman scattering-based multiconformatioal analysis to access the most stable conformers of acetylcholine, is discussed. To control the validity of this protocol, acetylcholine and one of its closely structured analogues, acetylthiocholine, were simultaneously analyzed. Solution Raman spectra revealed distinct and well resolved strong markers for each molecule. Density functional theory calculations were consistent with the fact that the energy order of the low energy conformers is considerably affected by the acyloxy oxygen→sulfur atom substitution. Raman spectra were calculated on the basis of the thermal average of the spectra arising from the low energy conformers. It has been evidenced that the carbonyl and trimethylammonium groups are the most favorable hydration sites in aqueous environment. Taking into account the large gap between the carbonyl bond-stretch and aliphatic bending bands, Raman spectra also allowed separation of the HOH bending vibrations arising from the bound and bulk water molecules. Copyright © 2017 Elsevier B.V. All rights reserved.

Raman spectroscopy of coloured resins used in antiquity: dragon's blood and related substances.

PubMed

Edward, H G; de Oliveira, L F; Quye, A

2001-12-01

Dragon's blood is a deep red resin which has been used for centuries by many cultures and much prized for it's rarity, depth of colour and alchemical associations. The original source of dragon's blood resin is believed to be Dracaena cinnabari from Socotra in Africa, but since mediaeval times there have been several alternatives from different geographical locations from the Canary Islands to the East Indies. Here, the Raman spectra of dragon's blood resins from Dracaena draco Liliacae trees growing in several different locations bordering the Mediterranean and Middle East are compared with the resins from alternative botanical sources such as Daemonorops draco, Dracaena cinnabari and Eucalyptus terminalis, which all generically come under the description of dragon's blood. Key vibrational spectroscopic marker bands are identified in the Raman spectra of the resins, which are suggested for adoption as a protocol for the identification of the botanical and possible geographical sources of modern dragon's blood resins. The Raman spectra of materials, which are falsely attributed to dragon's blood resin are also shown for comparison and identification purposes. Changes in the Raman spectra of genuine dragon's blood resin specimens arising from simple processing treatment during the preparation of the resins for sale are also identified, which suggests a possible attribution characteristic for unknown samples.

Raman spectroscopy of coloured resins used in antiquity: dragon's blood and related substances

NASA Astrophysics Data System (ADS)

Edward, Howell G. M.; de Oliveira, Luiz Fernando C.; Quye, Anita

2001-12-01

Dragon's blood is a deep red resin which has been used for centuries by many cultures and much prized for it's rarity, depth of colour and alchemical associations. The original source of dragon's blood resin is believed to be Dracaena cinnabari from Socotra in Africa, but since mediaeval times there have been several alternatives from different geographical locations from the Canary Islands to the East Indies. Here, the Raman spectra of dragon's blood resins from Dracaena draco Liliacae trees growing in several different locations bordering the Mediterranean and Middle East are compared with the resins from alternative botanical sources such as Daemonorops draco, Dracaena cinnabari and Eucalyptus terminalis, which all generically come under the description of dragon's blood. Key vibrational spectroscopic marker bands are identified in the Raman spectra of the resins, which are suggested for adoption as a protocol for the identification of the botanical and possible geographical sources of modern dragon's blood resins. The Raman spectra of materials, which are falsely attributed to dragon's blood resin are also shown for comparison and identification purposes. Changes in the Raman spectra of genuine dragon's blood resin specimens arising from simple processing treatment during the preparation of the resins for sale are also identified, which suggests a possible attribution characteristic for unknown samples.

UV-vis and Raman spectroelectrochemical investigation of the redox behavior of poly(5-cyanoindole) in acidic aqueous solutions.

PubMed

Talbi, H; Billaud, D; Louarn, G; Pron, A

2000-03-01

Spectroelectrochemical properties of conducting poly(5-cyanoindole) films deposited on indium tin oxide (ITO) and platinum electrodes are investigated using UV-vis and resonant Raman spectroscopies. The transitions from undoped to semi-conducting state of P5CN require the partial oxidation of the polymer to create radical-cations by insertion of charge-neutralizing anions into the polymer. In order to obtain detailed structural information from the vibrational spectra, it is necessary to know the vibrational modes of oxidation-sensitive bands. Vibrational assignments were made on the basis of the results obtained on polyindole and P5CN in acetonitrile solution. The drastic changes in optical absorption and Raman spectra observed at various stage of oxidation were explained by the conversions between at least three different structures. On the basis of the Raman spectra, we have identified the vibrational modes associated with neutral and polaronic segments. The perturbation associated with the coexistence of these polaronic segments has been described as a quinoid structure growing on the expense of the benzoid one. The results obtained indicate that the molecular properties of the conducting polymers at various stages of an oxidation are better revealed by in-situ Raman spectra than by ex-situ studies.

UV Raman imaging--a promising tool for astrobiology: comparative Raman studies with different excitation wavelengths on SNC Martian meteorites.

PubMed

Frosch, Torsten; Tarcea, Nicolae; Schmitt, Michael; Thiele, Hans; Langenhorst, Falko; Popp, Jürgen

2007-02-01

The great capabilities of UV Raman imaging have been demonstrated on the three Martian meteorites: Sayh al Uhaymir, Dar al Gani, and Zagami. Raman spectra without disturbing fluorescence and with high signal-to-noise-ratios and full of spectral features were derived. This result is of utmost importance for the development of powerful instruments for space missions. By point scanning the surfaces of the meteorite samples, it was possible for the first time to construct UV-Raman images out of the array of Raman spectra. Deep-UV Raman images are to the best of our knowledge presented for the first time. The images were used for a discussion of the chemical-mineralogical composition and texture of the meteorite surfaces. Comparative Raman studies applying visible and NIR Raman excitation wavelengths demonstrate a much better performance for UV Raman excitation. This comparative study of different Raman excitation wavelengths at the same sample spots was done by constructing a versatile, robust sample holder with a fixed micro-raster. The overall advantages of UV resonance Raman spectroscopy in terms of sensitivity and selectivity are demonstrated and discussed. Finally the application of this new technique for a UV Raman instrument for envisaged astrobiological focused space missions is suggested.

Vibrational spectroscopy and DFT calculations of flavonoid derriobtusone A

NASA Astrophysics Data System (ADS)

Marques, A. N. L.; Mendes Filho, J.; Freire, P. T. C.; Santos, H. S.; Albuquerque, M. R. J. R.; Bandeira, P. N.; Leite, R. V.; Braz-Filho, R.; Gusmão, G. O. M.; Nogueira, C. E. S.; Teixeira, A. M. R.

2017-02-01

Flavonoids are secondary metabolites of plants which perform various functions. One subclass of flavonoid is auronol that can present immunostimulating activity. In this work Fourier-Transform Infrared with Attenuated Total Reflectance (FTIR-ATR) and Fourier-Transform Raman (FT-Raman) spectra of an auronol, derriobtusone A (C18H12O4), were obtained at room temperature. Theoretical calculations using Density Functional Theory (DFT) were performed in order to assign the normal modes and to interpret the spectra of the derriobtusone A molecule. The FTIR-ATR and FT-Raman spectra of the crystal, were recorded at room temperature in the regions 600 cm-1 to 4000 cm-1 and 40 cm-1 to 4000 cm-1, respectively. The normal modes of vibrations were obtained using Density Functional Theory with B3LYP functional and 6-31G+ (d,p) basis set. The calculated frequencies are in good agreement with those obtained experimentally. Detailed assignments of the normal modes present in both the Fourier-Transform infrared and the Fourier-Transform Raman spectra of the crystal are given.

Infrared optical constants, dielectric constants, molar polarizabilities, transition moments, dipole moment derivatives and Raman spectrum of liquid cyclohexane

NASA Astrophysics Data System (ADS)

Keefe, C. Dale; Pickup, Janet E.

2009-06-01

Previous studies have been done in this laboratory focusing on the optical properties of several liquid aromatic and aliphatic hydrocarbons in the infrared. The current study reports the infrared and absorption Raman spectra of liquid cyclohexane. Infrared spectra were recorded at 25 °C over a wavenumber range of 7400-490 cm -1. Infrared measurements were taken using transmission cells with pathlengths ranging from 3 to 5000 μm. Raman spectra were recorded between 3700 and 100 cm -1 at 25 °C using a 180° reflection geometry. Ab initio calculations of the vibrational wavenumbers at the B3LYP/6311G level of theory were performed and used to help assign the observed IR and Raman spectra. Extensive assignments of the fundamentals and binary combinations observed in the infrared imaginary molar polarizability spectrum are reported. The imaginary molar polarizability spectrum was curve fitted to separate the intensity from the various transitions and used to determine the transition moments and magnitudes of the derivatives of the dipole moment with respect to the normal coordinates for the fundamentals.

Surface-enhanced Raman spectroscopy of urine by an ingenious near-infrared Raman spectrometer

NASA Astrophysics Data System (ADS)

Feng, Shangyuan; Chen, Weiwei; Li, Yongzeng; Chen, Guannan; Huang, Zufang; Liao, Xiaohua; Xie, Zhiming; Chen, Rong

2007-11-01

This paper demonstrates the potential of an elaborately devised near-infrared Raman system in analysis of urine. The broad band in the long-wavelength region of the electronic absorption spectra of the sol with added adsorbent at certain concentrations has been explained in terms of the aggregation of the colloidal silver particles. We have reported the surface-enhanced Raman (SERS) spectra of urine, and studied the silver solution enhanced effects on the urine Raman scattering. The Raman bands of human's urine was assigned to certain molecule vibrations. We have found that different donators have dissimilar SERS of urine in different physiological condition. Comparatively few studies have explored the ability of Raman spectroscopy for the analysis of urine acid. In the present report, we investigated the ability of surface enhanced Raman spectroscopy to measure uric acid in the human urine. The results suggested that the present Raman system holds considerable promise for practical use. Practical applications such as the quantitative medical examination of urine metabolites may also be feasible in the near future.

Comparison of infrared and Raman wave numbers of neat molecular liquids: Which is the correct infrared wave number to use?

NASA Astrophysics Data System (ADS)

Bertie, John E.; Michaelian, Kirk H.

1998-10-01

This paper is concerned with the peak wave number of very strong absorption bands in infrared spectra of molecular liquids. It is well known that the peak wave number can differ depending on how the spectrum is measured. It can be different, for example, in a transmission spectrum and in an attenuated total reflection spectrum. This difference can be removed by transforming both spectra to the real, n, and imaginary, k, refractive index spectra, because both spectra yield the same k spectrum. However, the n and k spectra can be transformed to spectra of any other intensity quantity, and the peak wave numbers of strong bands may differ by up to 6 cm-1 in the spectra of the different quantities. The question which then arises is "which infrared peak wave number is the correct one to use in the comparison of infrared wave numbers of molecular liquids with wave numbers in other spectra?" For example, infrared wave numbers in the gas and liquid phase are compared to observe differences between the two phases. Of equal importance, the wave numbers of peaks in infrared and Raman spectra of liquids are compared to determine whether the infrared-active and Raman-active vibrations coincide, and thus are likely to be the same, or are distinct. This question is explored in this paper by presenting the experimental facts for different intensity quantities. The intensity quantities described are macroscopic properties of the liquid, specifically the absorbance, attenuated total reflectance, imaginary refractive index, k, imaginary dielectric constant, ɛ″, and molar absorption coefficient, Em, and one microscopic property of a molecule in the liquid, specifically the imaginary molar polarizability, αm″, which is calculated under the approximation of the Lorentz local field. The main experimental observations are presented for the strongest band in the infrared spectrum of each of the liquids methanol, chlorobenzene, dichloromethane, and acetone. Particular care was paid to wave number calibration of both infrared and Raman spectra. Theoretical arguments indicate that the peak wave number in the αm″ spectrum is the correct one to use, because it is the only one that reflects the properties of molecules in their local environment in the liquid free from predictable long-range resonant dielectric effects. However, it is found that the comparison with Raman wave numbers is confused when the anisotropic local intermolecular forces and configuration in the liquid are significant. In these cases, the well known noncoincidence of the isotropic and anisotropic Raman scattering is observed, and the same factors lead to noncoincidence of the infrared and Raman bands.

Ring distributions in alkali- and alkaline-earth aluminosilicate framework glasses- a raman spectroscopic study

USGS Publications Warehouse

Sharma, S.K.; Philpotts, J.A.; Matson, D.W.

1985-01-01

Raman spectra of crystalline polymorphs of a number of tectosilicate minerals having various sizes of smallest rings of TO4 tetrahedra (T = Si, Al) have been investigated to identify the bands that are sensitive indicators of the smallest rings in the network. The information obtained from the Raman spectra of tectosilicate minerals (e.g., SiO2 polymorphs, NaAlSi3O8 (Ab), NaAlSiO4 (Ne), KAlSi3O8 (Or), and KAlSi2O6 (Lc)) is used to interpret the Raman spectra of the isochemical glasses. It is shown that the frequency of the dominant ??s (TOT) band in the spectra of both crystals and glasses is related to the dominant size of TO4 rings in the structure. In agreement with previous X-ray RDF work, it is found that in the glasses of Ab and Jd (NaAlSi2O6) compositions, six-membered rings of TO4 tetrahedra predominate. The Raman spectrum of Or glass, however, indicates that clusters of intermixed four- and six-membered rings of TO4 tetrahedra, similar to those existing in crystalline leucite, are also present in the glass. Raman evidence indicates that four-membered rings of TO4 tetrahedra predominate in the glass of An composition. Similarly, the higher frequency of the ??s (TOT) band in the spectrum of Ne glass as compared with the frequency the ??s (TOT) band in the spectra of crystalline cargenieite and nephelite indicates either an admixture of the four- and six-membered rings or the puckering of six-membered rings in the glass structure. ?? 1985.

New topics in coherent anti-stokes raman scattering gas-phase diagnostics : femtosecond rotational CARS and electric-field measurements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lempert, Walter R.; Barnat, Edward V.; Kearney, Sean Patrick

2010-07-01

We discuss two recent diagnostic-development efforts in our laboratory: femtosecond pure-rotational Coherent anti-Stokes Raman scattering (CARS) for thermometry and species detection in nitrogen and air, and nanosecond vibrational CARS measurements of electric fields in air. Transient pure-rotational fs-CARS data show the evolution of the rotational Raman polarization in nitrogen and air over the first 20 ps after impulsive pump/Stokes excitation. The Raman-resonant signal strength at long time delays is large, and we additionally observe large time separation between the fs-CARS signatures of nitrogen and oxygen, so that the pure-rotational approach to fs-CARS has promise for simultaneous species and temperature measurementsmore » with suppressed nonresonant background. Nanosecond vibrational CARS of nitrogen for electric-field measurements is also demonstrated. In the presence of an electric field, a dipole is induced in the otherwise nonpolar nitrogen molecule, which can be probed with the introduction of strong collinear pump and Stokes fields, resulting in CARS signal radiation in the infrared. The electric-field diagnostic is demonstrated in air, where the strength of the coherent infrared emission and sensitivity our field measurements is quantified, and the scaling of the infrared signal with field strength is verified.« less

IR, Raman and Vibrational Optical Activity Spectra of Methyl Glycidate in Chloroform and Water: The Clusters-in-a-Liquid Solvation Model.

PubMed

Xu, Yunjie; Perera, Angelo Shehan; Cheramy, Joseph; Merten, Christian; Thomas, Javix

2018-05-16

Solvent effects, in particular those involving water as the solvent, are of significant interest to chemistry and physics communities. IR, vibrational circular dichroism (VCD), Raman, and Raman optical activity (ROA) spectra of methyl glycidate in two very different solvents, namely CCl4 and water, have been measured experimentally and simulated theoretically. While the observed spectra in CCl4 could be well modelled using the polarizable continuum model for the solvent, the situation is much different in water. The experimental VCD spectrum of methyl glycidate in water reveals strong induced VCD signatures in the water bending region, indicating the presence of the relatively long-lived methyl glycidate-watern complexes. We applied the clusters-in-a-liquid approach to identify the dominant methyl glycidate-water1,2 complexes which are the long-lived species responsible for all the spectra observed in water. We examined the influences of solvent dielectric environment and the hydrogen-bonding interactions on the conformational distribution of methyl glycidate. The geometry optimizations, frequency calculations, IR, VCD, Raman and ROA intensity calculations were performed at the B3LYP/6-311++G(2d,p) and aug-cc-pVTZ levels of theory with D3BJ dispersion correction. It is particularly satisfying to note that the clusters-in-a-liquid approach has captured all main experimental features in IR, VCD, Raman and ROA spectra of methyl glycidate in water. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effective suppression of stray light in rotational coherent anti-stokes Raman spectroscopy using an angle-tuned short-wave-pass filter.

PubMed

Bohlin, Alexis; Bengtsson, Per-Erik

2010-08-01

Stray light interference is a common problem in spontaneous rotational Raman spectroscopy and rotational coherent anti-Stokes Raman spectropscopy (CARS). The reason is that the detected spectrum appears in the spectral vicinity of the probe beam wavelength, and stray light at this wavelength from optics and surfaces is hard to suppress. In this Note, efficient suppression of stray light is demonstrated for rotational CARS measurements using a commercially available short-wave-pass filter. By angle-tuning this filter with a specified cut-off wavelength at 561 nm, the cut-off wavelength could be tuned to a desired spectral position so that more than 80% transmission is achieved as close as 15 cm(-1) (approximately 0.4 nm) from the probe beam wavelength of 532.0 nm, while the intensity at this wavelength is suppressed by two orders of magnitude.

Communication: hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering thermometry using a narrowband time-asymmetric probe pulse.

PubMed

Stauffer, Hans U; Miller, Joseph D; Roy, Sukesh; Gord, James R; Meyer, Terrence R

2012-03-21

A narrowband, time-asymmetric probe pulse is introduced into the hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering (fs/ps RCARS) technique to provide accurate and precise single-shot, high-repetition-rate gas-phase thermometric measurements. This narrowband pulse-generated by inserting a Fabry-Pérot étalon into the probe-pulse beam path-enables frequency-domain detection of pure-rotational transitions. The unique time-asymmetric nature of this pulse, in turn, allows for detection of resonant Raman-active rotational transitions free of signal contamination by nonresonant four-wave-mixing processes while still allowing detection at short probe-pulse delays, where collisional dephasing processes are negligible. We demonstrate that this approach provides excellent single-shot thermometric accuracy (<1% error) and precision (~2.5%) in gas-phase environments. © 2012 American Institute of Physics

Spatially offset Raman spectroscopy based on a line-scan hyperspectral Raman system

USDA-ARS?s Scientific Manuscript database

Spatially offset Raman spectroscopy (SORS) is a technique that can obtain subsurface layered information by collecting Raman spectra from a series of surface positions laterally offset from the excitation laser. The current methods of SORS measurement are typically either slow due to mechanical move...

Raman spectroscopy for diagnosis of glioblastoma multiforme

NASA Astrophysics Data System (ADS)

Clary, Candace Elise

Glioblastoma multiforme (GBM), the most common and most fatal malignant brain tumor, is highly infiltrative and incurable. Although improved prognosis has been demonstrated by surgically resecting the bulk tumor, a lack of clear borders at the tumor margins complicates the selection decision during surgery. This dissertation investigates the potential of Raman spectroscopy for distinguishing between normal and malignant brain tissue and sets the groundwork for a surgical diagnostic guide for resection of gross malignant gliomas. These studies revealed that Raman spectroscopy was capable of discriminating between normal scid mouse brain tissue and human xenograft tumors induced in those mice. The spectra of normal and malignant tissue were normalized by dividing by the respective magnitudes of the peaks near 1440 cm -1. Spectral differences include the shape of the broad peaks near 1440 cm-1 and 1660 cm-1 and the relative magnitudes of the peaks at 1264 cm-1, 1287 cm-1, 1297 cm-1, 1556 cm -1, 1586 cm-1, 1614 cm-1, and 1683 cm-1. From these studies emerged questions regarding how to objectively normalize and compare spectra for future automation. Some differences in the Raman spectra were shown to be inherent in the disease states of the cells themselves via differences in the Raman spectra of normal human astrocytes in culture and cultured cells derived from GBM tumors. The spectra of astrocytes and glioma cells were normalized by dividing by the respective magnitudes of the peaks near 1450 cm-1. The differences between the Raman spectra of normal and transformed cells include the ratio of the 1450 cm-1/1650 cm-1 peaks and the relative magnitudes of the peaks at 1181 cm-1, 1191 cm-1, 1225 cm-1, 1263 cm -1, 1300 cm-1, 1336 cm-1, 1477 cm-1, 1494 cm-1, and 1695 cm -1. Previous Raman spectroscopic studies of biological cells have shown that the magnitude of the Raman signal decreases over time, indicating sample damage. Cells exposed to laser excitation at similar power densities were evaluated in terms of mitochondrial oxidative/reductive activity as well as protein, RNA, and DNA syntheses. Although cell death was not significant, the cells' abilities to synthesize DNA, RNA, and protein were profoundly affected by the laser irradiation.

On Sagnac frequency splitting in a solid-state ring Raman laser.

PubMed

Liang, Wei; Savchenkov, Anatoliy; Ilchenko, Vladimir; Griffith, Robert; De Cuir, Edwin; Kim, Steven; Matsko, Andrey; Maleki, Lute

2017-11-15

We report on an accurate measurement of the frequency splitting of an optical rotating ring microcavity made out of calcium fluoride. By measuring the frequencies of the clockwise and counter-clockwise coherent Raman emissions confined in the cavity modes, we show that the frequency splitting is inversely proportional to the refractive index of the cavity host material. The measurement has an accuracy of 1% and unambiguously confirms the classical theoretical prediction based on special theory of relativity. This Letter also demonstrates the usefulness of the ring Raman microlaser for rotation measurements.

Classification of normal and malignant human gastric mucosa tissue with confocal Raman microspectroscopy and wavelet analysis

NASA Astrophysics Data System (ADS)

Hu, Yaogai; Shen, Aiguo; Jiang, Tao; Ai, Yong; Hu, Jiming

2008-02-01

Thirty-two samples from the human gastric mucosa tissue, including 13 normal and 19 malignant tissue samples were measured by confocal Raman microspectroscopy. The low signal-to-background ratio spectra from human gastric mucosa tissues were obtained by this technique without any sample preparation. Raman spectral interferences include a broad featureless sloping background due to fluorescence and noise. They mask most Raman spectral feature and lead to problems with precision and quantitation of the original spectral information. A preprocessed algorithm based on wavelet analysis was used to reduce noise and eliminate background/baseline of Raman spectra. Comparing preprocessed spectra of malignant gastric mucosa tissues with those of counterpart normal ones, there were obvious spectral changes, including intensity increase at ˜1156 cm -1 and intensity decrease at ˜1587 cm -1. The quantitative criterion based upon the intensity ratio of the ˜1156 and ˜1587 cm -1 was extracted for classification of the normal and malignant gastric mucosa tissue samples. This could result in a new diagnostic method, which would assist the early diagnosis of gastric cancer.

Absorption and resonance Raman characteristics of β-carotene in water-ethanol mixtures, emulsion and hydrogel

NASA Astrophysics Data System (ADS)

Meinhardt-Wollweber, Merve; Suhr, Christian; Kniggendorf, Ann-Kathrin; Roth, Bernhard

2018-05-01

Absorption or resonance Raman scattering are often used to identify and even quantify carotenoids in situ. We studied the absorption spectra, the Raman spectra and their resonance behavior of β-carotene in different molecular environments set up as mixtures from lipid (emulsion) and non-polar (ethanol) solvents and a polar component (water) with regard to their application as references for in situ measurement. We show how both absorption profiles and resonance spectra of β-carotene strongly depend on the molecular environment. Most notably, our data suggests that the characteristic bathochromic absorption peak of J-aggregates does not contribute to carotenoid resonance conditions, and show how the Raman shift of the C=C stretching mode is dependent on both, the molecular environment and the excitation wavelength. Overall, the spectroscopic data collected here is highly relevant for the interpretation of in situ spectroscopic data in terms of carotenoid identification and quantification by resonance Raman spectroscopy as well as the preparation of reference samples. In particular, our data promotes careful consideration of appropriate molecular environment for reference samples.

[Analysis of pigments from Rhodotorula glutinis by Raman spectroscopy and thin layer chromatography].

PubMed

Yuan, Yu-feng; Tao, Zhan-hua; Wang, Xue; Li, Yong-qing; Liu, Jun-xian

2012-03-01

The pigments from Rhodotorula glutinis were separated by using thin layer chromatography, and the result showed that Rhodotorula glutinis cells could synthesize at least three kinds of pigments, which were beta-carotene, torulene, and torularhodin. The Raman spectra based on the three pigments were acquired, and original spectra were preprocessed by background elimination, baseline correction, and three-point-smoothing, then the averaged spectra from different pigments were investigated, and the result indicated that Raman shift which represents C-C bond was different, and the wave number of beta-carotene demonstrated the largest deviation, finally torulene and torularhodin in Rhodotorula glutinis had more content than beta-carotene. Quantitative analysis of Raman peak height ratio revealed that peak height ratio of pigments showed little difference, which could be used as parameters for further research on living cells, providing reference content of pigments. The above results suggest that Raman spectroscopy combined with thin layer chromatography can be applied to analyze pigments from Rhodotorula glutinis, provides abundant information about pigments, and serves as an effective method to study pigments.

Detecting changes during pregnancy with Raman spectroscopy

NASA Astrophysics Data System (ADS)

Vargis, Elizabeth; Robertson, Kesha; Al-Hendy, Ayman; Reese, Jeff; Mahadevan-Jansen, Anita

2010-02-01

Preterm labor is the second leading cause of neonatal mortality and leads to a myriad of complications like delayed development and cerebral palsy. Currently, there is no way to accurately predict preterm labor, making its prevention and treatment virtually impossible. While there are some at-risk patients, over half of all preterm births do not fall into any high-risk category. This study seeks to predict and prevent preterm labor by using Raman spectroscopy to detect changes in the cervix during pregnancy. Since Raman spectroscopy has been used to detect cancers in vivo in organs like the cervix and skin, it follows that spectra will change over the course of pregnancy. Previous studies have shown that fluorescence decreased during pregnancy and increased during post-partum exams to pre-pregnancy levels. We believe significant changes will occur in the Raman spectra obtained during the course of pregnancy. In this study, Raman spectra from the cervix of pregnant mice and women will be acquired. Specific changes that occur due to cervical softening or changes in hormonal levels will be observed to understand the likelihood that a female mouse or a woman will enter labor.

Raman study of transition-metal oxides with perovskite-like structure

NASA Astrophysics Data System (ADS)

Kolev, Nikolay Iliev

Perovskite-like oxides exhibit a rich variety of properties of fundamental scientific interest and potential application value. The motivation for this work is to contribute to our knowledge of perovskite-like systems and strongly correlated systems in general. The polarized Raman spectra of single crystal and thin film CaCu3Ti4O12, single crystal and thin film CaRuO3, microcrystals of La0.5Ca 0.5MnO3, and ceramic and thin film CaMnO3 have been investigated. In close comparison to results from lattice dynamics calculations most of the Raman lines in the CaCu3Ti4O12, CaRuO3, La0.5Ca0.5MnO3 and CaMnO 3 spectra, have been assigned to definite phonon modes. The validity of the model for twin orientation in the Pnma structure for CaRuO3 and La0.5Ca0.5MnO3 is confirmed. The analysis of the CaMnO3 spectra contributed to the development of a model, based on four basic distortions of the (distorted) perovskite structure. The temperature behavior of the CaCu3Ti4O 12 spectra shows that there is no evidence for structural phase transition in the temperature range 20--600 K, so such a transition cannot be responsible for the sharp drop in the dielectric constant below 100 K. The Raman spectra indirectly support the mechanism of formation of barrier layer capacitances in CaCu3Ti4O12.The observation of additional Raman mode of nominal Ag symmetry is discussed in terms of coexistence of domains of different atomic arrangement, or alternatively of non-stoichiometry (Cu deficiency). In the case of the thin film, the tetragonal distortions could be responsible for the greater separation of the additional Ag line. No anomalies in the temperature behavior of the Raman lines of CaRuO3 is observed, which is an indirect evidence for its lack of long-range magnetic ordering at low temperatures (depending on whether this ordering would be observable by Raman spectroscopy through spin-phonon coupling). In La0.5Ca0.5MnO 3 the appearance of several Raman lines below TN is analyzed in terms of ordering and freezing of the Jahn-Teller distortions in a superstructure. Polarized Raman spectra confirmed their usefulness in studying thin films and their properties.

Time-resolved infrared and resonance Raman studies of benzil. Vibrational analysis and structures of the excited states

NASA Astrophysics Data System (ADS)

Mizuno, Misao; Iwata, Koichi; Takahashi, Hiroaki

2003-12-01

Structures of the S 1 and T 1 states of benzil are examined based on the experimental results from nanosecond time-resolved infrared spectroscopy and picosecond time-resolved Raman spectroscopy. Nanosecond time-resolved infrared spectra of the T 1 state of benzil as well as its three isotopically substituted analogues were measured in carbon tetrachloride. The observed infrared bands of T 1 benzil were assigned based on the frequency shifts on isotopic ( 18O, and deuteration) substitutions. The infrared band at 1312 cm -1 is assigned to the CO anti-symmetric stretch vibration. An infrared band that has large contribution from the central C-C stretch is not observed. Picosecond time-resolved resonance Raman spectra of the S 1 state of benzil were also measured. It has been reported that after the photoexcitation, the benzil molecule shows an ultrafast conformational change in the S 1 state. The observed resonance Raman bands are attributable to the vibrations of the relaxed form of the S 1 state. By comparing the Raman and infrared spectra of the S 0, S 1, and T 1 states of benzil, the structures of benzil in the excited states are discussed. Upon going from the S 0 state to the S 1 or T 1 state, the bond order of the CO bond decreases while that of the central C-C bond increases. Although several ground-state bands appear in both the infrared and Raman spectra, there is no band observed simultaneously in the infrared and Raman spectra of the T 1 state, except for bands attributable to the phenyl ring vibrations. We conclude that T 1 benzil has the inversion center that arises from the trans-planar structure. The spectral pattern of the resonance Raman scattering of the relaxed S 1 state is very similar to that of the T 1 state. This implies that the molecular structure of the relaxed S 1 state is similar to that of the T 1 state. The structure of the relaxed form of the S 1 state is also considered to be trans-planar.

Single Pulse Remote Raman Detection of Minerals and Organics Under Illuminated Condition from 10 Meters Distance

NASA Technical Reports Server (NTRS)

Misra, A. K.; Sharma, S. K.; Lucey, P. G.

2005-01-01

A directly coupled portable remote Raman instrument developed by the University of Hawaii has been shown here to identify several minerals, chemicals and organics from a distance of 10 m using a single laser pulse in a well illuminated background. Raman spectra, obtained during a very short period of time, of common minerals e.g., dolomite, calcite, marble, barite, gypsum, quarts, rutile, fluorapatite etc. clearly show Raman features which could be used as fingerprints for mineral identification. Raman features of organics such as benzene, cyclohexane, 2-propanol, naphthalene, etc. and other chemicals containing various functional groups like oxides, silicates, sulphates, nitrates, phosphates and carbonates were also easily detected. Ability to measure Raman spectra with a single laser pulse would be promising for future space missions where power consumption is critical and a rapid survey of the minerals with moderate to high Raman cross section might be desirable for selecting rocks that would provide high scientific return or for acquiring rocks for sample return to the Earth.

In vivo Raman spectroscopy for oral cancers diagnosis

NASA Astrophysics Data System (ADS)

Singh, S. P.; Deshmukh, Atul; Chaturvedi, Pankaj; Krishna, C. Murali

2012-01-01

Oral squamous cell carcinoma is sixth among the major malignancies worldwide. Tobacco habits are known as major causative factor in tumor carcinogenesis in oral cancer. Optical spectroscopy methods, including Raman, are being actively pursued as alternative/adjunct for cancer diagnosis. Earlier studies have demonstrated the feasibility of classifying normal, premalignant and malignant oral ex-vivo tissues. In the present study we have recorded in vivo spectra from contralateral normal and diseased sites of 50 subjects with pathologically confirmed lesions of buccal mucosa using fiber-optic-probe-coupled HE-785 Raman spectrometer. Spectra were recorded on similar points as per teeth positions with an average acquisition time of 8 seconds. A total of 215 and 225 spectra from normal and tumor sites, respectively, were recorded. Finger print region (1200-1800 cm-1) was utilized for classification using LDA. Standard-model was developed using 125 normal and 139 tumor spectra from 27 subjects. Two separate clusters with an efficiency of ~95% were obtained. Cross-validation with leave-one-out yielded ~90% efficiency. Remaining 90 normal and 86 tumor spectra were used as test data and predication efficiency of model was evaluated. Findings of the study indicate that Raman spectroscopic methods in combination with appropriate multivariate tool can be used for objective, noninvasive and rapid diagnosis.

Theoretical studies on absorption, emission, and resonance Raman spectra of Coumarin 343 isomers

NASA Astrophysics Data System (ADS)

Wu, Wenpeng; Cao, Zexing; Zhao, Yi

2012-03-01

The vibrationally resolved spectral method and quantum chemical calculations are employed to reveal the structural and spectral properties of Coumarin 343 (C343), an ideal candidate for organic dye photosensitizers, in vacuum and solution. The results manifest that the ground-state energies are dominantly determined by different placements of hydrogen atom in carboxylic group of C343 conformations. Compared to those in vacuum, the electronic absorption spectra in methanol solvent show a hyperchromic property together with the redshift and blueshift for the neutral C343 isomers and their deprotonated anions, respectively. From the absorption, emission, and resonance Raman spectra, it is found that the maximal absorption and emission come from low-frequency modes whereas the high-frequency modes have high Raman activities. The detailed spectra are further analyzed for the identification of the conformers and understanding the potential charge transfer mechanism in their photovoltaic applications.

Extracting Optical Fiber Background from Surface-Enhanced Raman Spectroscopy Spectra Based on Bi-Objective Optimization Modeling.

PubMed

Huang, Jie; Shi, Tielin; Tang, Zirong; Zhu, Wei; Liao, Guanglan; Li, Xiaoping; Gong, Bo; Zhou, Tengyuan

2017-08-01

We propose a bi-objective optimization model for extracting optical fiber background from the measured surface-enhanced Raman spectroscopy (SERS) spectrum of the target sample in the application of fiber optic SERS. The model is built using curve fitting to resolve the SERS spectrum into several individual bands, and simultaneously matching some resolved bands with the measured background spectrum. The Pearson correlation coefficient is selected as the similarity index and its maximum value is pursued during the spectral matching process. An algorithm is proposed, programmed, and demonstrated successfully in extracting optical fiber background or fluorescence background from the measured SERS spectra of rhodamine 6G (R6G) and crystal violet (CV). The proposed model not only can be applied to remove optical fiber background or fluorescence background for SERS spectra, but also can be transferred to conventional Raman spectra recorded using fiber optic instrumentation.

Real-time in vivo diagnosis of laryngeal carcinoma with rapid fiber-optic Raman spectroscopy

PubMed Central

Lin, Kan; Zheng, Wei; Lim, Chwee Ming; Huang, Zhiwei

2016-01-01

We assess the clinical utility of a unique simultaneous fingerprint (FP) (i.e., 800-1800 cm−1) and high-wavenumber (HW) (i.e., 2800-3600 cm−1) fiber-optic Raman spectroscopy for in vivo diagnosis of laryngeal cancer at endoscopy. A total of 2124 high-quality in vivo FP/HW Raman spectra (normal = 1321; cancer = 581) were acquired from 101 tissue sites (normal = 71; cancer = 30) of 60 patients (normal = 44; cancer = 16) undergoing routine endoscopic examination. FP/HW Raman spectra differ significantly between normal and cancerous laryngeal tissue that could be attributed to changes of proteins, lipids, nucleic acids, and the bound water content in the larynx. Partial least squares-discriminant analysis and leave-one tissue site-out, cross-validation were employed on the in vivo FP/HW tissue Raman spectra acquired, yielding a diagnostic accuracy of 91.1% (sensitivity: 93.3% (28/30); specificity: 90.1% (64/71)) for laryngeal cancer identification, which is superior to using either FP (accuracy: 86.1%; sensitivity: 86.7% (26/30); specificity: 85.9% (61/71)) or HW (accuracy: 84.2%; sensitivity: 76.7% (23/30); specificity: 87.3% (62/71)) Raman technique alone. Further receiver operating characteristic analysis reconfirms the best performance of the simultaneous FP/HW Raman technique for laryngeal cancer diagnosis. We demonstrate for the first time that the simultaneous FP/HW Raman spectroscopy technique can be used for improving real-time in vivo diagnosis of laryngeal carcinoma during endoscopic examination. PMID:27699131

Raman Optical Activity Spectra from Density Functional Perturbation Theory and Density-Functional-Theory-Based Molecular Dynamics.

PubMed

Luber, Sandra

2017-03-14

We describe the calculation of Raman optical activity (ROA) tensors from density functional perturbation theory, which has been implemented into the CP2K software package. Using the mixed Gaussian and plane waves method, ROA spectra are evaluated in the double-harmonic approximation. Moreover, an approach for the calculation of ROA spectra by means of density functional theory-based molecular dynamics is derived and used to obtain an ROA spectrum via time correlation functions, which paves the way for the calculation of ROA spectra taking into account anharmonicities and dynamic effects at ambient conditions.

Fitting the low-frequency Raman spectra to boson peak models: glycerol, triacetin and polystyrene

NASA Astrophysics Data System (ADS)

Kirillov, S. A.; Perova, T. S.; Faurskov Nielsen, O.; Praestgaard, E.; Rasmussen, U.; Kolomiyets, T. M.; Voyiatzis, G. A.; Anastasiadis, S. H.

1999-04-01

A computational approach was elaborated to explicitly account for the Rayleigh line wing, the Boson peak and vibrational contributions to the low-frequency Raman spectra of amorphous solids and viscous liquids. It was shown that the low-frequency Raman spectra of glycerol and polystyrene consist of the Rayleigh contribution of Lorentzian form and the Boson peak which profile follows the predictions of the theory by Martin and Brenig in the version by Malinovsky and Sokolov. In the case of triacetin, the Boson peaks decay faster in their high-frequency side than the above theory predicts. Their form can be successfully modeled with a newly introduced empirical function intermediate between the Martin-Brenig and Malinovsky-Sokolov predictions.

Raman spectroscopy of glasses in the As-Te system

NASA Astrophysics Data System (ADS)

Tverjanovich, A.; Rodionov, K.; Bychkov, E.

2012-06-01

For the first time, the Raman spectra of AsxTe1-x glasses, 0.2≤x≤0.6, have been measured over the entire glass-forming range. The spectra exhibit three broad spectral features attributed to vibrations of structural units having Te-Te, As-Te and As-As bonds. The observed chemical disorder in the glasses is discussed on the basis of partial bond fractions derived from the integrated intensity of the Raman modes. The underlying structural model suggests a dissociation of AsTe- or As2Te3-related units in the glass melt. The spectra of glasses quenched from different temperatures, as well as those of the annealed vitreous alloys, are consistent with predictions of the model.

Comparison between infrared and Raman spectroscopic analysis of maturing rabbit cortical bone.

PubMed

Turunen, Mikael J; Saarakkala, Simo; Rieppo, Lassi; Helminen, Heikki J; Jurvelin, Jukka S; Isaksson, Hanna

2011-06-01

The molecular composition of the organic and inorganic matrices of bone undergoes alterations during maturation. The aim of this study was to compare Fourier transform infrared (FT-IR) and near-infrared (NIR) Raman microspectroscopy techniques for characterization of the composition of growing and developing bone from young to skeletally mature rabbits. Moreover, the specificity and differences of the techniques for determining bone composition were clarified. The humeri of female New Zealand White rabbits, with age range from young to skeletally mature animals (four age groups, n = 7 per group), were studied. Spectral peak areas, intensities, and ratios related to organic and inorganic matrices of bone were analyzed and compared between the age groups and between FT-IR and Raman microspectroscopic techniques. Specifically, the degree of mineralization, type-B carbonate substitution, crystallinity of hydroxyapatite (HA), mineral content, and collagen maturity were examined. Significant changes during maturation were observed in various compositional parameters with one or both techniques. Overall, the compositional parameters calculated from the Raman spectra correlated with analogous parameters calculated from the IR spectra. Collagen cross-linking (XLR), as determined through peak fitting and directly from the IR spectra, were highly correlated. The mineral/matrix ratio in the Raman spectra was evaluated with multiple different peaks representing the organic matrix. The results showed high correlation with each other. After comparison with the bone mineral density (BMD) values from micro-computed tomography (micro-CT) imaging measurements and crystal size from XRD measurements, it is suggested that Raman microspectroscopy is more sensitive than FT-IR microspectroscopy for the inorganic matrix of the bone. In the literature, similar spectroscopic parameters obtained with FT-IR and NIR Raman microspectroscopic techniques are often compared. According to the present results, however, caution is required when performing this kind of comparison.

Improved multiple-pass Raman spectrometer

NASA Astrophysics Data System (ADS)

Kc, Utsav; Silver, Joel A.; Hovde, David C.; Varghese, Philip L.

2011-08-01

An improved Raman gain spectrometer for flame measurements of gas temperature and species concentrations is described. This instrument uses a multiple-pass optical cell to enhance the incident light intensity in the measurement volume. The Raman signal is 83 times larger than from a single pass, and the Raman signal-to-noise ratio (SNR) in room-temperature air of 153 is an improvement over that from a single-pass cell by a factor of 9.3 when the cell is operated with 100 passes and the signal is integrated over 20 laser shots. The SNR improvement with the multipass cell is even higher for flame measurements at atmospheric pressure, because detector readout noise is more significant for single-pass measurements when the gas density is lower. Raman scattering is collected and dispersed in a spectrograph with a transmission grating and recorded with a fast gated CCD array detector to help eliminate flame interferences. The instrument is used to record spontaneous Raman spectra from N2, CO2, O2, and CO in a methane--air flame. Curve fits of the recorded Raman spectra to detailed simulations of nitrogen spectra are used to determine the flame temperature from the shapes of the spectral signatures and from the ratio of the total intensities of the Stokes and anti-Stokes signals. The temperatures measured are in good agreement with radiation-corrected thermocouple measurements for a range of equivalence ratios.

How Does the Shape of the Stellar Spectrum Affect the Raman Scattering Features in the Albedo of Exoplanets?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oklopčić, Antonija; Hirata, Christopher M.; Heng, Kevin, E-mail: oklopcic@astro.caltech.edu

The diagnostic potential of the spectral signatures of Raman scattering, imprinted in planetary albedo spectra at short optical wavelengths, has been demonstrated in research on planets in the solar system, and has recently been proposed as a probe of exoplanet atmospheres, complementary to albedo studies at longer wavelengths. Spectral features caused by Raman scattering offer insight into the properties of planetary atmospheres, such as the atmospheric depth, composition, and temperature, as well as the possibility of detecting and spectroscopically identifying spectrally inactive species, such as H{sub 2} and N{sub 2}, in the visible wavelength range. Raman albedo features, however, dependmore » on both the properties of the atmosphere and the shape of the incident stellar spectrum. Identical planetary atmospheres can produce very different albedo spectra depending on the spectral properties of the host star. Here we present a set of geometric albedo spectra calculated for atmospheres with H{sub 2}/He, N{sub 2}, and CO{sub 2} composition, irradiated by different stellar types ranging from late A to late K stars. Prominent albedo features caused by Raman scattering appear at different wavelengths for different types of host stars. We investigate how absorption due to the alkali elements sodium and potassium may affect the intensity of Raman features, and we discuss the preferred strategies for detecting Raman features in future observations.« less

[Surface-enhanced raman spectra studies on roughened Zn electrode in alkaline solutions].

PubMed

Shen, Xiao-ying; Liu, Guo-kun; Gu, Ren-ao; Tian, Zhong-qun

2005-09-01

Electrochemical oxidation-reduction method was employed to roughen Zn electrode for obtaining SERS, and potential dependent surface enhanced Raman spectra (SERS) of roughened Zn electrode in KOH solution of different concentration wereobserved. The spectra of Zn electrode in various solutions had obvious differences which indicated the concentration of OH- had a great effect on the dissolution and passivation of zinc. Based on our experimental results, the authors attempt to analyse the behavior of zinc in alkaline and give the mechanism of its passivation.

Plasmon Mapping in Metallic Nanostructures and its Application to Single Molecule Surface Enhanced Raman Scattering: Imaging Electromagnetic Hot-Spots and Analyte Location

DOE Office of Scientific and Technical Information (OSTI.GOV)

Camden, Jon P.

2013-07-12

A major component of this proposal is to elucidate the connection between optical and electron excitation of plasmon modes in metallic nanostructures. These accomplishments are reported: developed a routine protocol for obtaining spatially resolved, low energy EELS spectra, and resonance Rayleigh scattering spectra from the same nanostructures; correlated optical scattering spectra and plasmon maps obtained using STEM/EELS; and imaged electromagnetic hot spots responsible for single-molecule surface-enhanced Raman scattering (SMSERS).

Characterization and Discrimination of Gram-Positive Bacteria Using Raman Spectroscopy with the Aid of Principal Component Analysis.

PubMed

Colniță, Alia; Dina, Nicoleta Elena; Leopold, Nicolae; Vodnar, Dan Cristian; Bogdan, Diana; Porav, Sebastian Alin; David, Leontin

2017-09-01

Raman scattering and its particular effect, surface-enhanced Raman scattering (SERS), are whole-organism fingerprinting spectroscopic techniques that gain more and more popularity in bacterial detection. In this work, two relevant Gram-positive bacteria species, Lactobacillus casei ( L. casei ) and Listeria monocytogenes ( L. monocytogenes ) were characterized based on their Raman and SERS spectral fingerprints. The SERS spectra were used to identify the biochemical structures of the bacterial cell wall. Two synthesis methods of the SERS-active nanomaterials were used and the recorded spectra were analyzed. L. casei and L. monocytogenes were successfully discriminated by applying Principal Component Analysis (PCA) to their specific spectral data.

Characterization and Discrimination of Gram-Positive Bacteria Using Raman Spectroscopy with the Aid of Principal Component Analysis

PubMed Central

Leopold, Nicolae; Vodnar, Dan Cristian; Bogdan, Diana; Porav, Sebastian Alin; David, Leontin

2017-01-01

Raman scattering and its particular effect, surface-enhanced Raman scattering (SERS), are whole-organism fingerprinting spectroscopic techniques that gain more and more popularity in bacterial detection. In this work, two relevant Gram-positive bacteria species, Lactobacillus casei (L. casei) and Listeria monocytogenes (L. monocytogenes) were characterized based on their Raman and SERS spectral fingerprints. The SERS spectra were used to identify the biochemical structures of the bacterial cell wall. Two synthesis methods of the SERS-active nanomaterials were used and the recorded spectra were analyzed. L. casei and L. monocytogenes were successfully discriminated by applying Principal Component Analysis (PCA) to their specific spectral data. PMID:28862655

The structural and Raman spectral studies on Ni0.5Cu0.5Fe2O4 ferrite

NASA Astrophysics Data System (ADS)

Somani, M.; Saleem, M.

2018-05-01

Spinel ferrite Ni0.5Cu0.5Fe2O4 has been successfully prepared via solid state reaction. The crystal structure studies using XRD technique revealed cubic structure of the sample. The XRD spectra was further refined via Retvield Refinement and all the parameters regarding structure were obtained which confirmed cubic structure. The assigned space group was found to be Fd-3m. Particle size was calculated to be 56 nm. The Raman Spectra revealed five active Raman modes which confirmed spinel structure.

[Study on the TLC-SERS of sulfamethoxazole].

PubMed

Zhang, Jin-Zhi; Wang, Yuan; Chen, Xiang-Ming

2006-08-01

The spectra of sulfamethoxazole, the efficient ingredient of sulfanilamide-like medicine, were investigated by combining the TLC and FT-Raman spectroscopy using the surface enhanced Raman spectroscopy technique. The result indicatesthat the main vibrant characteristic spectral band can be obtained by TLC in a samples of just about 1 microg. The difference between the compound sulfamethoxazole and the corresponding spectra picture is analyzed. The analysis shows that the method of combining TLC and FT-Raman spectroscopy by the SERS is practical and advantageous in the highly sensitive measurement of the chemical ingredient in medicine.

IR absorption and surface-enhanced Raman spectra of the isoquinoline alkaloid berberine

NASA Astrophysics Data System (ADS)

Strekal', N. D.; Motevich, I. G.; Nowicky, J. W.; Maskevich, S. A.

2007-01-01

We present the IR absorption and surface-enhanced Raman scattering (SERS) spectra of the isoquinoline alkaloid berberine adsorbed on a silver hydrosol and on the surface of a silver electrode for different potentials. Based on quantum chemical calculations, for the first time we have assigned the vibrations in the berberine molecule according to vibrational mode. The effect of the potential of the silver electrode on the geometry of sorption of the molecule on the surface is considered, assuming a short-range mechanism for enhancement of Raman scattering.

Raman linewidth measurements using time-resolved hybrid picosecond/nanosecond rotational CARS.

PubMed

Nordström, Emil; Hosseinnia, Ali; Brackmann, Christian; Bood, Joakim; Bengtsson, Per-Erik

2015-12-15

We report an innovative approach for time-domain measurements of S-branch Raman linewidths using hybrid picosecond/nanosecond pure-rotational coherent anti-Stokes Raman spectroscopy (RCARS). The Raman coherences are created by two picosecond excitation pulses and are probed using a narrow-band nanosecond pulse at 532 nm. The generated RCARS signal contains the entire coherence decay in a single pulse. By extracting the decay times of the individual transitions, the J-dependent Raman linewidths can be calculated. Self-broadened S-branch linewidths for nitrogen and oxygen at 293 K and ambient pressure are in good agreement with previous time-domain measurements. Experimental considerations of the approach are discussed along with its merits and limitations. The approach can be extended to a wide range of pressures and temperatures and has potential for simultaneous single-shot thermometry and linewidth determination.

Non-destructive NIR-FT-Raman spectroscopy of plant and animal tissues, of food and works of art.

PubMed

Schrader, B; Schulz, H; Andreev, G N; Klump, H H; Sawatzki, J

2000-10-02

Just after the discovery of Raman spectroscopy in 1928, it became evident that fluorescence with a quantum yield of several orders of magnitude higher than that of the Raman effect was a great and apparently unbeatable competitor. Raman spectroscopy could therefore, in spite of many exciting advantages during the last 60 years, not be applied as an analytical routine method: for nearly every sample, fluorescing impurities had to be removed by distillation or crystallisation. Purification, however, is not possible for cells and tissues, since the removal of the fluorescing enzymes and coenzymes would destroy the cells. There is fortunately one alternative solution. When excited with the radiation of the Nd:YAG laser at 1064 nm Raman spectra are practically free of fluorescence. Raman spectra can now be recorded with minimal sample preparation. In order to facilitate non-destructive Raman spectroscopy of any sample, cells and tissues, food, textiles and works of art, a new entrance optics for Raman spectrometers is used. Typical results from several fields are demonstrated.

Pressure broadening of the electric dipole and Raman lines of CO2 by argon: Stringent test of the classical impact theory at different temperatures on a benchmark system

NASA Astrophysics Data System (ADS)

Ivanov, Sergey V.; Buzykin, Oleg G.

2016-12-01

A classical approach is applied to calculate pressure broadening coefficients of CO2 vibration-rotational spectral lines perturbed by Ar. Three types of spectra are examined: electric dipole (infrared) absorption; isotropic and anisotropic Raman Q branches. Simple and explicit formulae of the classical impact theory are used along with exact 3D Hamilton equations for CO2-Ar molecular motion. The calculations utilize vibrationally independent most accurate ab initio potential energy surface (PES) of Hutson et al. expanded in Legendre polynomial series up to lmax = 24. New improved algorithm of classical rotational frequency selection is applied. The dependences of CO2 half-widths on rotational quantum number J up to J=100 are computed for the temperatures between 77 and 765 K and compared with available experimental data as well as with the results of fully quantum dynamical calculations performed on the same PES. To make the picture complete, the predictions of two independent variants of the semi-classical Robert-Bonamy formalism for dipole absorption lines are included. This method. however, has demonstrated poor accuracy almost for all temperatures. On the contrary, classical broadening coefficients are in excellent agreement both with measurements and with quantum results at all temperatures. The classical impact theory in its present variant is capable to produce quickly and accurately the pressure broadening coefficients of spectral lines of linear molecules for any J value (including high Js) using full-dimensional ab initio - based PES in the cases where other computational methods are either extremely time consuming (like the quantum close coupling method) or give erroneous results (like semi-classical methods).

Raman spectroscopic analysis of cytotoxic effect of cisplatin-treated leukemic cells

NASA Astrophysics Data System (ADS)

Lin, Juqiang; Li, Yongzeng; Feng, Shangyuan; Chen, Rong; Chen, Guannan; Chen, Qisong; Pan, Jianji; Lin, Shaojun; Yu, Yun

2009-08-01

An antitumor drug cisplatin was employed to treat the leukemic cells and induce apoptosis of the cancer cells. Confocal Raman micro-spectroscopy has been applied to investigate the effectiveness of the treatment using near-infrared laser (785nm) excitation, scanning range from 500 to 2000 cm-1. The Raman spectra of leukemic cell treated with cisplatin for 4, 6, 8, 12 and 14 h were measured separately. The major difference of the apoptotic cells from the cancer cells are the reduction in intensities of vibration bands generated by cellular lipids, proteins and nucleic acids. In particular, large intensity reduction in nucleic vibrations at 782, 1092, 1320, 1340, and 1578 cm-1 was observed upon apoptosis of the leukemic cells. Up to 45% reduction in the magnitude of the 782 cm-1 peak in Raman spectra of the apoptotic cells was observed, which suggests the breakdown of phosphodiester bonds and DNA bases. We showed that the principal components analysis (PCA), a multivariate statistical tool, can be used to distinguish single apoptotic cells and leukemic cells based on their Raman spectra. Our results indicate that the Raman spectroscopy with PCA is a novel, nondestructive mean for studying the cisplatin -treated leukemic cells, which could also provide useful data for clinical dosage optimization for cisplatin.

Bladder cancer diagnosis during cystoscopy using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Grimbergen, M. C. M.; van Swol, C. F. P.; Draga, R. O. P.; van Diest, P.; Verdaasdonk, R. M.; Stone, N.; Bosch, J. H. L. R.

2009-02-01

Raman spectroscopy is an optical technique that can be used to obtain specific molecular information of biological tissues. It has been used successfully to differentiate normal and pre-malignant tissue in many organs. The goal of this study is to determine the possibility to distinguish normal tissue from bladder cancer using this system. The endoscopic Raman system consists of a 6 Fr endoscopic probe connected to a 785nm diode laser and a spectral recording system. A total of 107 tissue samples were obtained from 54 patients with known bladder cancer during transurethral tumor resection. Immediately after surgical removal the samples were placed under the Raman probe and spectra were collected and stored for further analysis. The collected spectra were analyzed using multivariate statistical methods. In total 2949 Raman spectra were recorded ex vivo from cold cup biopsy samples with 2 seconds integration time. A multivariate algorithm allowed differentiation of normal and malignant tissue with a sensitivity and specificity of 78,5% and 78,9% respectively. The results show the possibility of discerning normal from malignant bladder tissue by means of Raman spectroscopy using a small fiber based system. Despite the low number of samples the results indicate that it might be possible to use this technique to grade identified bladder wall lesions during endoscopy.

Graphitic carbon nanospheres: A Raman spectroscopic investigation of thermal conductivity and morphological evolution by pulsed laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, Radhe; Sahoo, Satyaprakash, E-mail: satya504@gmail.com, E-mail: rkatiyar@hpcf.upr.edu; Chitturi, Venkateswara Rao

2015-12-07

Graphitic carbon nanospheres (GCNSs) were prepared by a unique acidic treatment of multi-walled nanotubes. Spherical morphology with a narrow size distribution was confirmed by transmission electron microscopy studies. The room temperature Raman spectra showed a clear signature of D- and G-peaks at around 1350 and 1591 cm{sup −1}, respectively. Temperature dependent Raman scattering measurements were performed to understand the phonon dynamics and first order temperature coefficients related to the D- and G-peaks. The temperature dependent Raman spectra in a range of 83–473 K were analysed, where the D-peak was observed to show a red-shift with increasing temperature. The relative intensity ratio ofmore » D- to G-peaks also showed a significant rise with increasing temperature. Such a temperature dependent behaviour can be attributed to lengthening of the C-C bond due to thermal expansion in material. The estimated value of the thermal conductivity of GCNSs ∼0.97 W m{sup −1} K{sup −1} was calculated using Raman spectroscopy. In addition, the effect of pulsed laser treatment on the GCNSs was demonstrated by analyzing the Raman spectra of post irradiated samples.« less

Analysis of the in vivo confocal Raman spectral variability in human skin

NASA Astrophysics Data System (ADS)

Mogilevych, Borys; dos Santos, Laurita; Rangel, Joao L.; Grancianinov, Karen J. S.; Sousa, Mariane P.; Martin, Airton A.

2015-06-01

Biochemical composition of the skin changes in each layer and, therefore, the skin spectral profile vary with the depth. In this work, in vivo Confocal Raman spectroscopy studies were performed at different skin regions and depth profile (from the surface down to 10 μm) of the stratum corneum, to verify the variability and reproducibility of the intra- and interindividual Raman data. The Raman spectra were collected from seven healthy female study participants using a confocal Raman system from Rivers Diagnostic, with 785 nm excitation line and a CCD detector. Measurements were performed in the volar forearm region, at three different points at different depth, with the step of 2 μm. For each depth point, three spectra were acquired. Data analysis included the descriptive statistics (mean, standard deviation and residual) and Pearson's correlation coefficient calculation. Our results show that inter-individual variability is higher than intraindividual variability, and variability inside the SC is higher than on the skin surface. In all these cases we obtained r values, higher than 0.94, which correspond to high correlation between Raman spectra. It reinforces the possibility of the data reproducibility and direct comparison of in vivo results obtained with different study participants of the same age group and phototype.

Recognizing different tissues in human fetal femur cartilage by label-free Raman microspectroscopy

NASA Astrophysics Data System (ADS)

Kunstar, Aliz; Leijten, Jeroen; van Leuveren, Stefan; Hilderink, Janneke; Otto, Cees; van Blitterswijk, Clemens A.; Karperien, Marcel; van Apeldoorn, Aart A.

2012-11-01

Traditionally, the composition of bone and cartilage is determined by standard histological methods. We used Raman microscopy, which provides a molecular "fingerprint" of the investigated sample, to detect differences between the zones in human fetal femur cartilage without the need for additional staining or labeling. Raman area scans were made from the (pre)articular cartilage, resting, proliferative, and hypertrophic zones of growth plate and endochondral bone within human fetal femora. Multivariate data analysis was performed on Raman spectral datasets to construct cluster images with corresponding cluster averages. Cluster analysis resulted in detection of individual chondrocyte spectra that could be separated from cartilage extracellular matrix (ECM) spectra and was verified by comparing cluster images with intensity-based Raman images for the deoxyribonucleic acid/ribonucleic acid (DNA/RNA) band. Specific dendrograms were created using Ward's clustering method, and principal component analysis (PCA) was performed with the separated and averaged Raman spectra of cells and ECM of all measured zones. Overall (dis)similarities between measured zones were effectively visualized on the dendrograms and main spectral differences were revealed by PCA allowing for label-free detection of individual cartilaginous zones and for label-free evaluation of proper cartilaginous matrix formation for future tissue engineering and clinical purposes.

Measurement of the human esophageal cancer in an early stage with Raman spectroscopy

NASA Astrophysics Data System (ADS)

Maeda, Yasuhiro; Ishigaki, Mika; Taketani, Akinori; Andriana, Bibin B.; Ishihara, Ryu; Sato, Hidetoshi

2014-02-01

The esophageal cancer has a tendency to transfer to another part of the body and the surgical operation itself sometimes gives high risk in vital function because many delicate organs exist near the esophagus. So the esophageal cancer is a disease with a high mortality. So, in order to lead a higher survival rate five years after the cancer's treatment, the investigation of the diagnosis methods or techniques of the cancer in an early stage and support the therapy are required. In this study, we performed the ex vivo experiments to obtain the Raman spectra from normal and early-stage tumor (stage-0) human esophageal sample by using Raman spectroscopy. The Raman spectra are collected by the homemade Raman spectrometer with the wavelength of 785 nm and Raman probe with 600-um-diameter. The principal component analysis (PCA) is performed after collection of spectra to recognize which materials changed in normal part and cancerous pert. After that, the linear discriminant analysis (LDA) is performed to predict the tissue type. The result of PCA indicates that the tumor tissue is associated with a decrease in tryptophan concentration. Furthermore, we can predict the tissue type with 80% accuracy by LDA which model is made by tryptophan bands.

Raman/LIBS Data Fusion via Two-Way Variational Autoencoders

NASA Astrophysics Data System (ADS)

Parente, M.; Gemp, I.

2018-04-01

We propose an original solution to extracting mineral abundances from Raman spectra by combining Raman data with LIBS using a novel deep learning model based on variational autoencoders and data fusion, which outperforms the current state of the art.

Interference-free gas-phase thermometry at elevated pressure using hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering.

PubMed

Miller, Joseph D; Dedic, Chloe E; Roy, Sukesh; Gord, James R; Meyer, Terrence R

2012-02-27

Rotational-level-dependent dephasing rates and nonresonant background can lead to significant uncertainties in coherent anti-Stokes Raman scattering (CARS) thermometry under high-pressure, low-temperature conditions if the gas composition is unknown. Hybrid femtosecond/picosecond rotational CARS is employed to minimize or eliminate the influence of collisions and nonresonant background for accurate, frequency-domain thermometry at elevated pressure. The ability to ignore these interferences and achieve thermometric errors of <5% is demonstrated for N2 and O2 at pressures up to 15 atm. Beyond 15 atm, the effects of collisions cannot be ignored but can be minimized using a short probe delay (~6.5 ps) after Raman excitation, thereby improving thermometric accuracy with a time- and frequency-resolved theoretical model.

Detection and identification of Huo-Xue-Hua-Yu decoction (HXHYD) using surface-enhanced Raman scattering (SERS) spectroscopy and multivariate analysis

NASA Astrophysics Data System (ADS)

Chen, Weiwei; Lin, Jia; Chen, Rong; Feng, Shangyuan; Yu, Yun; Lin, Duo; Huang, Meizhen; Shi, Hong; Huang, Hao

2015-04-01

We have evaluated the capabilities of surface-enhanced Raman scattering (SERS) technology for analyzing two Huo-Xue-Hua-Yu decoctions (HXHYDs) prepared according to different prescriptions. The aim of this study was to evaluate the relevance of SERS technology applied to decoction of traditional Chinese medicines (TCM). HXHYD I was prepared according to the original prescription; the same preparation method was used for the HXHYD II, except for the crudeweight ratio described in the original prescription. There was no Raman signal in conventional Raman spectra of HXHYDs. Silver nanoparticles were directly mixed with HXHYDs to enhance the Raman scattering of biochemical constituents, and high quality SERS spectra were obtained. Significant differences in SERS spectra between HXHYD I and II can be observed, which showed special changes in the percentage of biochemical constituents in different decoctions. Principal components analysis (PCA) combined with linear discriminant analysis (LDA) were employed to generate diagnostic algorithms for classification of SERS spectra of two HXHYDs, and showed that a diagnostic accuracy of 100% can be achieved. This work demonstrated that the SERS technique has potential for spectral characteristic detection for decoction of TCM with high sensitivity, and that this technique, combined with PCA-LDA, can be used for quality control of the extracted decoction of TCM and production management of Chinese herbal preparations.

In-situ high-temperature Raman spectroscopic studies of aluminosilicate liquids

NASA Astrophysics Data System (ADS)

Daniel, Isabelle; Gillet, Philippe; Poe, Brent T.; McMillan, Paul F.

1995-03-01

We have measured in-situ Raman spectra of aluminosilicate glasses and liquids with albite (NaAlSi3 O8) and anorthite (CaAl2Si2O8) compositions at high temperatures, through their glass transition range up to 1700 and 2000 K, respectively. For these experiments, we have used a wire-loop heating device coupled with micro-Raman spectroscopy, in order to achieve effective spatial filtering of the extraneous thermal radiation. A major concern in this work is the development of methodology for reliably extracting the first and second order contributions to the Raman scattering spectra of aluminosilicate glasses and liquids from the high temperature experimental data, and analyzing these in terms of vibrational (anharmonic) and configurational changes. The changes in the first order Raman spectra with temperature are subtle. The principal low frequency band remains nearly constant with increasing temperature, indicating little change in the T-O-T angle, and that the angle bending vibration is quite harmonic. This is in contrast to vitreous SiO2, studied previously. Above Tg, intensity changes in the 560 590 cm-1 regions of both sets of spectra indicate configurational changes in the supercooled liquids, associated with formation of additional Al-O-Al linkages, or 3-membered (Al, Si)-containing rings. Additional intensity at 800 cm-1 reflects also some rearrangement of the Si-O-Al network.

Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

DOE PAGES

Burris, Paul C.; Laage, Damien; Thompson, Ward H.

2016-05-20

Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this Paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D 2O is considered. An empirical mapping approach ismore » used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. Lastly, the simulated spectra indicate that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.« less

Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores.

PubMed

Burris, Paul C; Laage, Damien; Thompson, Ward H

2016-05-21

Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. The simulated spectra indicates that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.

Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burris, Paul C.; Thompson, Ward H., E-mail: wthompson@ku.edu; Laage, Damien, E-mail: damien.laage@ens.fr

2016-05-21

Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D{sub 2}O is considered. An empirical mapping approach ismore » used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. The simulated spectra indicates that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.« less

Blueberry juices: a rapid multi-analysis of quality indicators by means of dispersive Raman spectroscopy excited at 1064 nm

NASA Astrophysics Data System (ADS)

Ciaccheri, L.; Yuan, T.; Zhang, S.; Mencaglia, A. A.; Trono, C.; Yuan, L.; Mignani, A. G.

2017-04-01

Blueberry juices produced in China and in Italy were analyzed by means of Raman spectroscopy. The reference data of important nutraceutical indicators such as degrees Brix and carbohydrates were available. Some juices were produced from fresh organic fruits, while others were industrial grade, differing in qualities and prices. Raman spectra obtained with excitation at 1064 nm were acquired using a dispersive fiber-optic spectrometer. Degrees Brix were measured by means of a commercial refractometer, while carbohydrate contents were available from the producers. Multivariate processing was used for predicting Brix and carbohydrates from Raman spectra and from the reference data. Determination coefficients equal to 0.88 and 0.84, respectively, were obtained. This experiment further confirms the excellent potentials of Raman spectroscopy for both non-destructive and rapid assessments of food quality.

Spontaneous confocal Raman microscopy--a tool to study the uptake of nanoparticles and carbon nanotubes into cells

NASA Astrophysics Data System (ADS)

Romero, Gabriela; Rojas, Elena; Estrela-Lopis, Irina; Donath, Edwin; Moya, Sergio Enrique

2011-06-01

Confocal Raman microscopy as a label-free technique was applied to study the uptake and internalization of poly(lactide- co-glycolide) (PLGA) nanoparticles (NPs) and carbon nanotubes (CNTs) into hepatocarcinoma human HepG2 cells. Spontaneous confocal Raman spectra was recorded from the cells exposed to oxidized CNTs and to PLGA NPs. The Raman spectra showed bands arising from the cellular environment: lipids, proteins, nucleic acids, as well as bands characteristic for either PLGA NPs or CNTs. The simultaneous generation of Raman bands from the cell and nanomaterials from the same spot proves internalization, and also indicates the cellular region, where the nanomaterial is located. For PLGA NPs, it was found that they preferentially co-localized with lipid bodies, while the oxidized CNTs are located in the cytoplasm.

Carbon Isotopic Compositions in Carbon Dioxide Measured By Micro-Laser Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Li, J.-J.; Li, R.-X.; Dong, H.; Wang, Zh.-H.; Zhao, B.-S.; Wang, N.; Cheng, J.-H.

2017-05-01

We have prepared a series of 12CO2/13CO2 binary mixtures as standard samples at room temperature. Using microlaser Raman spectroscopy, it was found that the relationship between the 12CO2 mole fractions and the peak area ratios of 12CO2/13CO2 in the Raman spectra of CO2 binary mixtures showed a polynomial correlation. The establishment of the experimental working curve paves the way for estimating the mole fractions of each individual fluid inclusion and determining 13C/12C and δ13C u sing micro-Raman spectroscopy. The Raman spectra of 12CO2 and 13CO2 showed a characteristic peak at 1348 cm-1 with an argon laser at 785 nm, which is perhaps due to the formation of dimers.

Conformational stability, structural parameters and vibrational assignment from variable temperature infrared spectra of krypton solutions and ab initio calculations of ethylisothiocyanate.

PubMed

Durig, James R; Zheng, Chao

2007-11-01

Variable temperature (-105 to -150 degrees C) studies of the infrared spectra (3500-400 cm(-1)) of ethylisothiocyanate, CH(3)CH(2)NCS, dissolved in liquid krypton have been recorded. Additionally the infrared spectra of the gas and solid have been re-investigated. These spectroscopic data indicate a single conformer in all physical states with a large number of molecules in the gas phase at ambient temperature in excited states of the CN torsional mode which has a very low barrier to conformational interchange. To aid in the analyses of the vibrational and rotational spectra, ab initio calculations have been carried out by the perturbation method to the second order (MP2) with valence and core electron correlation using a variety of basis sets up to 6-311+G(2df,2pd). With the smaller basis sets up to 6-311+G(d,p) and cc-PVDZ, the cis conformer is indicated as a transition state with all larger basis sets the cis conformer is the only stable form. The predicted energy difference from these calculations between the cis form and the higher energy trans conformer is about 125 cm(-1) which represents essentially the barrier to internal rotation of the NCS group (rotation around NC axis). Density functional theory calculation by the B3LYP method with the same basis sets predicts this barrier to be about 25 cm(-1). By utilizing the previously reported microwave rotational constants with the structural parameters predicted by the ab initio MP2(full)/6-311+G(d,p) calculations, adjusted r(0) structural parameters have been obtained for the cis form. The determined heavy atom parameters are: r(NC)=1.196(5), r(CS)=1.579(5), r(CN)=1.439(5), r(CC)=1.519(5)A for the distances and angles of angleCCN=112.1(5), angleCNC=146.2(5), angleNCS=174.0(5) degrees . The centrifugal distortion constants, dipole moments, conformational stability, vibrational frequencies, infrared intensities and Raman activities have been predicted from ab initio calculations and compared to experimental quantities when available. These results are compared to the corresponding quantities of some similar molecules.

Composites Strengthened with Graphene Platelets and Formed in Semisolid State Based on α and α/β MgLiAl Alloys

NASA Astrophysics Data System (ADS)

Dutkiewicz, Jan; Rogal, Łukasz; Fima, Przemyslaw; Ozga, Piotr

2018-04-01

MgLiAl base composites strengthened with graphene platelets were prepared by semisolid processing of ball-milled alloy chips with 2% of graphene platelets. Composites strengthened with graphene platelets show higher hardness and yield stress than the cast alloys, i.e., 160 MPa as compared to 90 MPa for as-cast alloy MgLi9Al1.5. Mechanical properties for MgLiAl-based composites were similar or higher than for composites based on conventional AZ91 or WE43 alloys. The strengthening however was not only due to the presence of graphene, but also phases resulting from the reaction between carbon and lithium, i.e., Li2C2 carbide. Graphene platelets were located at globules boundaries resulting from semisolid processing for all investigated composites. Graphene platelets were in agglomerates forming continuous layers at grain boundaries in the composite based on the alloy MgLi4.5Al1.5. The shape of agglomerates was more complex and wavy in the composite based on MgLi9Al1.5 alloy most probably due to lithium-graphene reaction. Electron diffraction from the two-phase region α + β in MgLi9Al1.5 indicated that [001]α and [110]β directions are rotated about 4° from the ideal relationship [001] hex || [110] bcc phases. It showed higher lattice rotation than in earlier studies what is most probably caused by lattice slip and rotation during semisolid pressing causing substantial deformation particularly within the β phase. Raman spectroscopy studies confirmed the presence of graphene platelets within agglomerates and in addition the presence mainly of Li2C2 carbides in composites based on MgLi4.5Al1.5 and Mg9Li1.5Al alloys. From the character of Raman spectra refinement of graphene platelets was found in comparison with their initial size. The graphene areas without carbides contain graphene nanoplatelets with lateral dimension close to initial graphene sample. Electron diffraction allowed to confirm the presence of Li2C2 carbide at the surface of agglomerates found from Raman spectroscopy results.

Composites Strengthened with Graphene Platelets and Formed in Semisolid State Based on α and α/β MgLiAl Alloys

NASA Astrophysics Data System (ADS)

Dutkiewicz, Jan; Rogal, Łukasz; Fima, Przemyslaw; Ozga, Piotr

2018-05-01

MgLiAl base composites strengthened with graphene platelets were prepared by semisolid processing of ball-milled alloy chips with 2% of graphene platelets. Composites strengthened with graphene platelets show higher hardness and yield stress than the cast alloys, i.e., 160 MPa as compared to 90 MPa for as-cast alloy MgLi9Al1.5. Mechanical properties for MgLiAl-based composites were similar or higher than for composites based on conventional AZ91 or WE43 alloys. The strengthening however was not only due to the presence of graphene, but also phases resulting from the reaction between carbon and lithium, i.e., Li2C2 carbide. Graphene platelets were located at globules boundaries resulting from semisolid processing for all investigated composites. Graphene platelets were in agglomerates forming continuous layers at grain boundaries in the composite based on the alloy MgLi4.5Al1.5. The shape of agglomerates was more complex and wavy in the composite based on MgLi9Al1.5 alloy most probably due to lithium-graphene reaction. Electron diffraction from the two-phase region α + β in MgLi9Al1.5 indicated that [001]α and [110]β directions are rotated about 4° from the ideal relationship [001] hex || [110] bcc phases. It showed higher lattice rotation than in earlier studies what is most probably caused by lattice slip and rotation during semisolid pressing causing substantial deformation particularly within the β phase. Raman spectroscopy studies confirmed the presence of graphene platelets within agglomerates and in addition the presence mainly of Li2C2 carbides in composites based on MgLi4.5Al1.5 and Mg9Li1.5Al alloys. From the character of Raman spectra refinement of graphene platelets was found in comparison with their initial size. The graphene areas without carbides contain graphene nanoplatelets with lateral dimension close to initial graphene sample. Electron diffraction allowed to confirm the presence of Li2C2 carbide at the surface of agglomerates found from Raman spectroscopy results.

Vertically Oriented Graphene Electrochemical Double Layer Capacitor with Very Fast Dynamic Response

DTIC Science & Technology

2013-01-01

cauliflower type of morphology (see Figure A-2c). Figure A-3. (a) The intensity of D to G peak ratio in Raman spectra and the thickness (height) of...in a random, cauliflower type of morphology (see Figure A-2c). Figure A-2. (a) The intensity of D to G peak ratio in Raman spectra and the

Vibrational analysis, NBO analysis, NMR, UV-VIS, hyperpolarizability analysis of Trimethadione by density functional theory

NASA Astrophysics Data System (ADS)

Vijayachamundeeswari, S. P.; Yagna Narayana, B.; Jone Pradeepa, S.; Sundaraganesan, N.

2015-11-01

Trimethadione (TMD) is an anticonvulsant drug widely used against absences seizures. We have characterised the TMD by various spectra including UV-VIS, IR, Raman, GC-MS and NMR. In this work, we made use of Density Functional Theory (DFT) B3LYP method with 6-31G (d, p) basis set, to calculate the molecular structure of TMD, and predicted its infrared, Raman and ultraviolet spectra for the first time. FT-IR and FT-Raman spectra were recorded in the region 4000-400 cm-1 and 3500-50 cm-1, respectively. The vibrational frequencies were calculated and scaled values were compared with the experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes. The optimized geometry parameters were calculated. NMR chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. The predicted first hyperpolarizibility also shows that the molecule might have convincingly good nonlinear optical (NLO) activities. The calculated HOMO-LUMO energy gap discloses that charge transfer occurs within the molecule.

Solid-state cocrystal formation between acyclovir and fumaric acid: Terahertz and Raman vibrational spectroscopic studies.

PubMed

Cai, Qiang; Xue, Jiadan; Wang, Qiqi; Du, Yong

2017-11-05

The vibrational spectra of solid-state acyclovir, fumaric acid and their cocrystal have been investigated by using terahertz time-domain spectroscopy (THz-TDS) and Raman spectroscopy at room temperature. In experimental THz spectra, the cocrystal has absorption peaks in 0.65, 0.94 and 1.10THz respectively, while the raw materials are absolutely different in this region. Raman spectra also show similar results about differences between the cocrystal and raw materials. Density functional theory (DFT) was performed to simulate vibrational modes of different theoretical forms between acyclovir and fumaric acid. The calculation of theoretical THz spectra shows that O8C7N1H27 and the carboxyl group COOH establish a dimer theoretical cocrystal form by the hydrogen bonding effect, which makes contributions to the formation of absorption peaks in 0.70, 1.01 and 1.34THz, and agrees well with experimental observations. The theoretical Raman result also indicates that this dimer form matches with experimental results. The characteristic bands of the cocrystal between acyclovir and fumaric acid are also assigned based on the simulation results from the DFT calculation. Copyright © 2017 Elsevier B.V. All rights reserved.

Solid-state cocrystal formation between acyclovir and fumaric acid: Terahertz and Raman vibrational spectroscopic studies

NASA Astrophysics Data System (ADS)

Cai, Qiang; Xue, Jiadan; Wang, Qiqi; Du, Yong

2017-11-01

The vibrational spectra of solid-state acyclovir, fumaric acid and their cocrystal have been investigated by using terahertz time-domain spectroscopy (THz-TDS) and Raman spectroscopy at room temperature. In experimental THz spectra, the cocrystal has absorption peaks in 0.65, 0.94 and 1.10 THz respectively, while the raw materials are absolutely different in this region. Raman spectra also show similar results about differences between the cocrystal and raw materials. Density functional theory (DFT) was performed to simulate vibrational modes of different theoretical forms between acyclovir and fumaric acid. The calculation of theoretical THz spectra shows that O8dbnd C7sbnd N1sbnd H27 and the carboxyl group sbnd COOH establish a dimer theoretical cocrystal form by the hydrogen bonding effect, which makes contributions to the formation of absorption peaks in 0.70, 1.01 and 1.34 THz, and agrees well with experimental observations. The theoretical Raman result also indicates that this dimer form matches with experimental results. The characteristic bands of the cocrystal between acyclovir and fumaric acid are also assigned based on the simulation results from the DFT calculation.

Characterization and noninvasive diagnosis of bladder cancer with serum surface enhanced Raman spectroscopy and genetic algorithms

NASA Astrophysics Data System (ADS)

Li, Shaoxin; Li, Linfang; Zeng, Qiuyao; Zhang, Yanjiao; Guo, Zhouyi; Liu, Zhiming; Jin, Mei; Su, Chengkang; Lin, Lin; Xu, Junfa; Liu, Songhao

2015-05-01

This study aims to characterize and classify serum surface-enhanced Raman spectroscopy (SERS) spectra between bladder cancer patients and normal volunteers by genetic algorithms (GAs) combined with linear discriminate analysis (LDA). Two group serum SERS spectra excited with nanoparticles are collected from healthy volunteers (n = 36) and bladder cancer patients (n = 55). Six diagnostic Raman bands in the regions of 481-486, 682-687, 1018-1034, 1313-1323, 1450-1459 and 1582-1587 cm-1 related to proteins, nucleic acids and lipids are picked out with the GAs and LDA. By the diagnostic models built with the identified six Raman bands, the improved diagnostic sensitivity of 90.9% and specificity of 100% were acquired for classifying bladder cancer patients from normal serum SERS spectra. The results are superior to the sensitivity of 74.6% and specificity of 97.2% obtained with principal component analysis by the same serum SERS spectra dataset. Receiver operating characteristic (ROC) curves further confirmed the efficiency of diagnostic algorithm based on GA-LDA technique. This exploratory work demonstrates that the serum SERS associated with GA-LDA technique has enormous potential to characterize and non-invasively detect bladder cancer through peripheral blood.

Improvements in Alzheimer's disease diagnosis using principle components analysis (PCA) in combination with Raman spectroscopy

NASA Astrophysics Data System (ADS)

Archer, John K. J.; Sudworth, Caroline D.; Williams, Rachel; How, Thien; Stone, Nicholas; Mann, David; Black, Richard A.

2007-07-01

The significant achievements of medical science over the last century are evident in the increasing age of the global population, however this now brings new problems, the most prominent being the growth in the number of people suffering from dementia. Over half the people with dementia in the UK are sufferers of Alzheimer's disease, a condition in which intraneuronal neurofibrillary tangles and extraneuronal senile tangles take over neurons prompting their death. A definitive diagnosis is still only currently available post-mortem, whilst current symptom based processes of elimination are far from perfect, especially when the only treatments available are symptom inhibiting drugs. Principal component analysis (PCA) of the Raman spectra taken from brain tissue has proved to be a potential tool in the diagnosis. However, this work now has to be refined in order to progress to tissue less associated with the symptoms of Alzheimer's disease. The first step of this has already been taken in progressing from frontal tissue to occipital tissue point spectra taken at random positions from bulk tissue. Now we present initial work into acquiring Raman spectral maps from across a tissue area, in pursuit of identifying unique plaque and tangle spectra. These spectra are presented alongside synthetic β-Amyloid spectra, in a study of the role that the peptide plays in the biomarker spectra, and how this information can aid the PCA of bulk tissue, and point towards a Raman spectroscopic test on less sensitive tissue, such as blood.

Comparing two tetraalkylammonium ionic liquids. II. Phase transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.

Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N{sub 1114}][NTf{sub 2}], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N{sub 1444}][NTf{sub 2}], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N{sub 1444}][NTf{sub 2}] experiences glass transition at low temperature, whereas [N{sub 1114}][NTf{sub 2}] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picturemore » of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.« less

SERS and DFT study of p-hydroxybenzoic acid adsorbed on colloidal silver particles.

PubMed

Chen, Y; Chen, S J; Li, S; Wei, J J

2015-10-16

In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.

Photophoretic trapping of absorbing particles in air and measurement of their single-particle Raman spectra.

PubMed

Pan, Yong-Le; Hill, Steven C; Coleman, Mark

2012-02-27

A new method is demonstrated for optically trapping micron-sized absorbing particles in air and obtaining their single-particle Raman spectra. A 488-nm Gaussian beam from an Argon ion laser is transformed by conical lenses (axicons) and other optics into two counter-propagating hollow beams, which are then focused tightly to form hollow conical beams near the trapping region. The combination of the two coaxial conical beams, with focal points shifted relative to each other along the axis of the beams, generates a low-light-intensity biconical region totally enclosed by the high-intensity light at the surface of the bicone, which is a type of bottle beam. Particles within this region are trapped by the photophoretic forces that push particles toward the low-intensity center of this region. Raman spectra from individual trapped particles made from carbon nanotubes are measured. This trapping technique could lead to the development of an on-line real-time single-particle Raman spectrometer for characterization of absorbing aerosol particles.

Raman fingerprints of amyloid structures.

PubMed

Flynn, Jessica D; Lee, Jennifer C

2018-06-21

Structural differences in pathological and functional amyloid fibrils have been investigated by Raman microspectroscopy. Second-derivative analyses of amide-I and amide-III bands distinguish parallel in-register β-sheets from a β-solenoid. Further, spatially resolved Raman spectra reveal molecular heterogeneity in amyloid structures.

Tumor cell differentiation by label-free microscopy

NASA Astrophysics Data System (ADS)

Schneckenburger, Herbert; Weber, Petra; Wagner, Michael

2013-05-01

Autofluorescence and Raman measurements of U251-MG glioblastoma cells prior and subsequent to activation of tumor suppressor genes are compared. While phase contrast images and fluorescence intensity patterns of the tumor (control) cells and the less malignant cells are similar, differences can be deduced from fluorescence spectra and nanosecond decay times. In particular, upon excitation around 375nm, the fluorescence ratio of the protein bound and the free coenzyme NADH depends on the state of malignancy and reflects different cytoplasmic (including lysosomal) and mitochondrial contributions. Slight differences are also observed in the Raman spectra of these cell lines, mainly originating from small granules (lysosomes) surrounding the cell nucleus. While larger numbers of fluorescence and Raman spectra are evaluated by multivariate statistical methods, additional information is obtained from spectral images and fluorescence lifetime images (FLIM).

Structural and vibrational spectroscopy investigation of the 5-[(diphenyl) amino] isophthalic acid molecule

NASA Astrophysics Data System (ADS)

Kurt, M.; Şaş, E. Babur; Can, M.; Okur, S.; Icli, S.; Demic, S.

2014-10-01

The molecular structure and vibrations of 5-(diphenyl) amino] isophthalic acid (DPIFA) were investigated by different spectroscopic techniques (such as infrared and Raman). FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. HOMO-LUMO analyses were performed. The theoretical calculations for the molecular structure and spectroscopic studies were performed with DFT (B3LYP) and 6-311G(d,p) basis set calculations using the Gaussian 09 program. After optimizing the geometry of the molecule, vibration wavenumbers and fundamental vibrations wavenumbers were assigned on the basis of the potential energy distribution (PED) of the vibrational modes calculated with VEDA 4 program. The results of theoretical calculations for the spectra of the title compound were compared with the observed spectra.

Resonant Raman spectra of grades of human brain glioma tumors reveal the content of tryptophan by the 1588 cm-1 mode

NASA Astrophysics Data System (ADS)

Zhou, Yan; Liu, Cheng-hui; Zhou, Lixin; Zhu, Ke; Liu, Yulong; Zhang, Lin; Boydston-White, Susie; Cheng, Gangge; Pu, Yang; Bidyut, Das; Alfano, Robert R.

2015-03-01

RR spectra of brain normal tissue, gliomas in low grade I and II, and malignant glioma tumors in grade III and IV were measured using a confocal micro Raman spectrometer. This report focus on the relative contents of tryptophan (W) in various grades of brain glioma tumors by the intrinsic molecular resonance Raman (RR) spectroscopy method using the 1588cm-1 of tryptophan mode by 532 nm excitation. The RR spectra of key fingerprints of tryptophan, with a main vibrational mode at 1588cm-1 (W8b), were observed. It was found that tryptophan contribution was accumulated in grade I to IV gliomas and the mode of 1588cm-1 in grade III and IV malignant gliomas were enhanced by resonance.

Study on the noncoincidence effect phenomenon using matrix isolated Raman spectra and the proposed structural organization model of acetone in condense phase

NASA Astrophysics Data System (ADS)

Xu, Wenwen; Wu, Fengqi; Zhao, Yanying; Zhou, Ran; Wang, Huigang; Zheng, Xuming; Ni, Bukuo

2017-03-01

The isotropic and anisotropic Raman spectra of acetone and deuterated acetone isolated in an argon matrix have been recorded for the understanding of noncoincidence effect (NCE) phenomenon. According to the matrix isolated Raman spectra and DFT calculations, we proposed aggregated model for the explanations of the acetone C=O vibration NCE phenomenon and its concentration effect. The experimental data were in consistence with the DFT calculations performed at the B3LYP-D3/6-311 G (d,p) levels based on the proposed model. The experimental identification of the monomer, dimer and trimer are reported here, and the dynamic of the transformation from monomer to aggregated structure can be easily controlled by tuning annealing temperature.

Fourier transform Raman spectroscopy of synthetic and biological calcium phosphates.

PubMed

Sauer, G R; Zunic, W B; Durig, J R; Wuthier, R E

1994-05-01

Fourier-transform (FT) Raman spectroscopy was used to characterize the organic and mineral components of biological and synthetic calcium phosphate minerals. Raman spectroscopy provides information on biological minerals that is complimentary to more widely used infrared methodologies as some infrared-inactive vibrational modes are Raman-active. The application of FT-Raman technology has, for the first time, enabled the problems of high sample fluorescence and low signal-to-noise that are inherent in calcified tissues to be overcome. Raman spectra of calcium phosphates are dominated by a very strong band near 960 cm-1 that arises from the symmetric stretching mode (v1) of the phosphate group. Other Raman-active phosphate vibrational bands are seen at approximately 1075 (v3), 590 (v4), and 435 cm-1 (v2). Minerals containing acidic phosphate groups show additional vibrational modes. The different calcium phosphate mineral phases can be distinguished from one another by the relative positions and shapes of these bands in the Raman spectra. FT-Raman spectra of nascent, nonmineralized matrix vesicles (MV) show a distinct absence of the phosphate v1 band even though these structures are rich in calcium and phosphate. Similar results were seen with milk casein and synthetic Ca-phosphatidyl-serine-PO4 complexes. Hence, the phosphate and/or acidic phosphate ions in these noncrystalline biological calcium phosphates is in a molecular environment that differs from that in synthetic amorphous calcium phosphate. In MV, the first distinct mineral phase to form contained acidic phosphate bands similar to those seen in octacalcium phosphate. The mineral phase present in fully mineralized MV was much more apatitic, resembling that found in bones and teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

Condition Assessment of Kevlar Composite Materials Using Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Washer, Glenn; Brooks, Thomas; Saulsberry, Regor

2007-01-01

This viewgraph presentation includes the following main concepts. Goal: To evaluate Raman spectroscopy as a potential NDE tool for the detection of stress rupture in Kevlar. Objective: Test a series of strand samples that have been aged under various conditions and evaluate differences and trends in the Raman response. Hypothesis: Reduction in strength associated with stress rupture may manifest from changes in the polymer at a molecular level. If so, than these changes may effect the vibrational characteristics of the material, and consequently the Raman spectra produced from the material. Problem Statement: Kevlar composite over-wrapped pressure vessels (COPVs) on the space shuttles are greater than 25 years old. Stress rupture phenomena is not well understood for COPVs. Other COPVs are planned for hydrogen-fueled vehicles using Carbon composite material. Raman spectroscopy is being explored as an non-destructive evaluation (NDE) technique to predict the onset of stress rupture in Kevlar composite materials. Test aged Kevlar strands to discover trends in the Raman response. Strength reduction in Kevlar polymer will manifest itself on the Raman spectra. Conclusions: Raman spectroscopy has shown relative changes in the intensity and FWHM of the 1613 cm(exp -1) peak. Reduction in relative intensity for creep, fleet leader, and SIM specimens compared to the virgin strands. Increase in FWHM has been observed for the creep and fleet leader specimens compared to the virgin strands. Changes in the Raman spectra may result from redistributing loads within the material due to the disruption of hydrogen bonding between crystallites or defects in the crystallites from aging the Kevlar strands. Peak shifting has not been observed to date. Analysis is ongoing. Stress measurements may provide a tool in the short term.

Conservation law of angular momentum in helicity-dependent Raman and Rayleigh scattering

NASA Astrophysics Data System (ADS)

Tatsumi, Yuki; Kaneko, Tomoaki; Saito, Riichiro

2018-05-01

In first-order Raman scattering, helicity of circularly polarized incident light is either conserved or changed depending on the Raman modes. When the helicity of incident light changes in the scattered light, the angular momentum of a photon is transferred to the material. Here, we present the conservation law of pseudoangular momentum in the helicity-dependent Raman scattering for a N -fold (N =1 -4 ,6 ) rotational symmetry of a crystal. Furthermore, the conservation law of electron-phonon interaction is discussed by considering the vibration direction of a phonon that has the same or lower symmetry than the symmetry of the crystal, which is essential to allow the helicity change in Raman scattering in a highly symmetric material, such as graphene. We also discuss the conservation law of pseudoangular momentum in Rayleigh scattering and show that the helicity change is allowed only in the crystal with one- or twofold rotational symmetry.

NIS, IR and Raman spectra with quantum mechanical calculations for analyzing the force field of hypericin model compounds

NASA Astrophysics Data System (ADS)

Ulicny, Jozef; Leulliot, Nicolas; Grajcar, Lydie; Baron, Marie-Hélène; Jobic, Hervé; Ghomi, Mahmoud

1999-06-01

Geometry optimization as well as harmonic force field calculations at HF and DFT levels of theory have been performed in order to elucidate the ground state properties of anthrone and emodin, two polycyclic conjugated molecules considered as hypericin model compounds. NIS, IR and FT-Raman spectra of these compounds have been recorded to validate the calculated results (geometry and vibrational modes). Calculated NIS spectra using the lowest energy conformers are in agreement with experiment. In addition, the intramolecular H-bonds in emodin predicted by the calculations can be evidenced using IR spectra as a function of temperature.

NIS, IR and Raman spectra with quantum mechanical calculations for analyzing the force field of hypericin model compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulicny, Jozef; Department of Biophysics, Safarik University, Jesenna 5, 04154 Kosice; Leulliot, Nicolas

1999-06-15

Geometry optimization as well as harmonic force field calculations at HF and DFT levels of theory have been performed in order to elucidate the ground state properties of anthrone and emodin, two polycyclic conjugated molecules considered as hypericin model compounds. NIS, IR and FT-Raman spectra of these compounds have been recorded to validate the calculated results (geometry and vibrational modes). Calculated NIS spectra using the lowest energy conformers are in agreement with experiment. In addition, the intramolecular H-bonds in emodin predicted by the calculations can be evidenced using IR spectra as a function of temperature.

The molecular, electronic structures and vibrational spectra of metal-free, N,N'-dideuterio and magnesium tetra-2,3-pyridino-porphyrazines: Density functional calculations.

PubMed

Liu, Zhongqiang; Zhang, Xianxi; Zhang, Yuexing; Li, Renjie; Jiang, Jianzhuang

2006-10-01

A theoretical investigation of the fully optimized geometries and electronic structures of the metal-free (TPdPzH(2)), N,N'-dideuterio (TPdPzD(2)), and magnesium (TPdPzMg) tetra-2,3-pyridino-porphyrazine has been conducted based on density functional theory. The optimized geometries at density functional theory level for these compounds are reported here for the first time. A comparison between the different molecules for the geometry, molecular orbital, and atomic charge is made. The substituent effect of the N atoms on the molecular structures of these compounds is discussed. The IR and Raman spectra for these three compounds have also been calculated at density functional B3LYP level using the 6-31G(d) basis set. Detailed assignments of the NH, NM, and pyridine ring vibrational bands in the IR and Raman spectra have been made based on assistance of animated pictures. The simulated IR spectra of TPdPzH(2) are compared with the experimental absorption spectra, and very good consistency has been found. The isotope effect on the IR and Raman spectra is also discussed.

Challenges Analyzing Gypsum on Mars by Raman Spectroscopy.

PubMed

Marshall, Craig P; Olcott Marshall, Alison

2015-09-01

Raman spectroscopy can provide chemical information about organic and inorganic substances quickly and nondestructively with little to no sample preparation, thus making it an ideal instrument for Mars rover missions. The ESA ExoMars planetary mission scheduled for launch in 2018 will contain a miniaturized Raman spectrometer (RLS) as part of the Pasteur payload operating with a continuous wave (CW) laser emitting at 532 nm. In addition, NASA is independently developing two miniaturized Raman spectrometers for the upcoming Mars 2020 rover mission, one of which is a remote (stand-off) Raman spectrometer that uses a pulse-gated 532 nm excitation system (SuperCam). The other is an in situ Raman spectrometer that employs a CW excitation laser emitting at 248.6 nm (SHERLOC). Recently, it has been shown with analyses by Curiosity that Gale Crater contains significantly elevated concentrations of transition metals such as Cr and Mn. Significantly, these transition metals are known to undergo fluorescence emission in the visible portion of the electromagnetic spectrum. Consequently, samples containing these metals could be problematic for the successful acquisition of fluorescence-free Raman spectra when using a CW 532 nm excitation source. Here, we investigate one analog environment, with a similar mineralogy and sedimentology to that observed in martian environments, as well as elevated Cr contents, to ascertain the best excitation wavelength to successfully collect fluorescence-free spectra from Mars-like samples. Our results clearly show that CW near-infrared laser excitation emitting at 785 nm is better suited to the collection of fluorescence-free Raman spectra than would be a CW laser emitting at 532 nm.

Raman Spectroscopy for Mineral Identification and Quantification for in situ Planetary Surface Analysis: A Point Count Method

NASA Technical Reports Server (NTRS)

Haskin, Larry A.; Wang, Alian; Rockow, Kaylynn M.; Jolliff, Bradley L.; Korotev, Randy L.; Viskupic, Karen M.

1997-01-01

Quantification of mineral proportions in rocks and soils by Raman spectroscopy on a planetary surface is best done by taking many narrow-beam spectra from different locations on the rock or soil, with each spectrum yielding peaks from only one or two minerals. The proportion of each mineral in the rock or soil can then be determined from the fraction of the spectra that contain its peaks, in analogy with the standard petrographic technique of point counting. The method can also be used for nondestructive laboratory characterization of rock samples. Although Raman peaks for different minerals seldom overlap each other, it is impractical to obtain proportions of constituent minerals by Raman spectroscopy through analysis of peak intensities in a spectrum obtained by broad-beam sensing of a representative area of the target material. That is because the Raman signal strength produced by a mineral in a rock or soil is not related in a simple way through the Raman scattering cross section of that mineral to its proportion in the rock, and the signal-to-noise ratio of a Raman spectrum is poor when a sample is stimulated by a low-power laser beam of broad diameter. Results obtained by the Raman point-count method are demonstrated for a lunar thin section (14161,7062) and a rock fragment (15273,7039). Major minerals (plagioclase and pyroxene), minor minerals (cristobalite and K-feldspar), and accessory minerals (whitlockite, apatite, and baddeleyite) were easily identified. Identification of the rock types, KREEP basalt or melt rock, from the 100-location spectra was straightforward.

Biophotonics of skin: method for correction of deep Raman spectra distorted by elastic scattering

NASA Astrophysics Data System (ADS)

Roig, Blandine; Koenig, Anne; Perraut, François; Piot, Olivier; Gobinet, Cyril; Manfait, Michel; Dinten, Jean-Marc

2015-03-01

Confocal Raman microspectroscopy allows in-depth molecular and conformational characterization of biological tissues non-invasively. Unfortunately, spectral distortions occur due to elastic scattering. Our objective is to correct the attenuation of in-depth Raman peaks intensity by considering this phenomenon, enabling thus quantitative diagnosis. In this purpose, we developed PDMS phantoms mimicking skin optical properties used as tools for instrument calibration and data processing method validation. An optical system based on a fibers bundle has been previously developed for in vivo skin characterization with Diffuse Reflectance Spectroscopy (DRS). Used on our phantoms, this technique allows checking their optical properties: the targeted ones were retrieved. Raman microspectroscopy was performed using a commercial confocal microscope. Depth profiles were constructed from integrated intensity of some specific PDMS Raman vibrations. Acquired on monolayer phantoms, they display a decline which is increasing with the scattering coefficient. Furthermore, when acquiring Raman spectra on multilayered phantoms, the signal attenuation through each single layer is directly dependent on its own scattering property. Therefore, determining the optical properties of any biological sample, obtained with DRS for example, is crucial to correct properly Raman depth profiles. A model, inspired from S.L. Jacques's expression for Confocal Reflectance Microscopy and modified at some points, is proposed and tested to fit the depth profiles obtained on the phantoms as function of the reduced scattering coefficient. Consequently, once the optical properties of a biological sample are known, the intensity of deep Raman spectra distorted by elastic scattering can be corrected with our reliable model, permitting thus to consider quantitative studies for purposes of characterization or diagnosis.

Normal Raman and surface enhanced Raman spectroscopic experiments with thin layer chromatography spots of essential amino acids using different laser excitation sources.

PubMed

István, Krisztina; Keresztury, Gábor; Szép, Andrea

2003-06-01

A comparative study of the feasibility and efficiency of Raman spectroscopic detection of thin layer chromatography (TLC) spots of some weak Raman scatterers (essential amino acids, namely, glycine and L-forms of alanine, serine, valine, proline, hydroxyproline, and phenylalanine) was carried out using four different visible and near-infrared (NIR) laser radiations with wavelengths of 532, 633, 785, and 1064 nm. Three types of commercial TLC plates were tested and the possibility of inducing surface enhanced Raman scattering (SERS) by means of Ag-sol was also investigated. The spectra obtained from spotted analytes adsorbed on TLC plates were of very different quality strongly depending on the excitation wavelength, the wetness of the samples, and the compounds examined. The best results were obtained with the simple silica TLC plate, and it has been established that the longest wavelength (lowest energy) NIR excitation of a Nd:YAG laser is definitely more suitable for generating normal Raman scattering of analyte spots than any of the visible radiations. Concerning SERS with application of Ag-sol to the TLC spots, 1-3 orders of magnitude enhancement was observed with wet samples, the greatest with the 532 nm radiation and gradually smaller with the longer wavelength excitations. It is shown, however, that due to severe adsorption-induced spectral distortions and increased sensitivity to microscopic inhomogeneity of the sample, none of the SERS spectra obtained with the dispersive Raman microscope operating in the visible region were superior to the best NIR normal FT-Raman spectra, as far as sample identification is concerned.

Normal Raman and surface enhanced Raman spectroscopic experiments with thin layer chromatography spots of essential amino acids using different laser excitation sources

NASA Astrophysics Data System (ADS)

István, Krisztina; Keresztury, Gábor; Szép, Andrea

2003-06-01

A comparative study of the feasibility and efficiency of Raman spectroscopic detection of thin layer chromatography (TLC) spots of some weak Raman scatterers (essential amino acids, namely, glycine and L-forms of alanine, serine, valine, proline, hydroxyproline, and phenylalanine) was carried out using four different visible and near-infrared (NIR) laser radiations with wavelengths of 532, 633, 785, and 1064 nm. Three types of commercial TLC plates were tested and the possibility of inducing surface enhanced Raman scattering (SERS) by means of Ag-sol was also investigated. The spectra obtained from spotted analytes adsorbed on TLC plates were of very different quality strongly depending on the excitation wavelength, the wetness of the samples, and the compounds examined. The best results were obtained with the simple silica TLC plate, and it has been established that the longest wavelength (lowest energy) NIR excitation of a Nd:YAG laser is definitely more suitable for generating normal Raman scattering of analyte spots than any of the visible radiations. Concerning SERS with application of Ag-sol to the TLC spots, 1-3 orders of magnitude enhancement was observed with wet samples, the greatest with the 532 nm radiation and gradually smaller with the longer wavelength excitations. It is shown, however, that due to severe adsorption-induced spectral distortions and increased sensitivity to microscopic inhomogeneity of the sample, none of the SERS spectra obtained with the dispersive Raman microscope operating in the visible region were superior to the best NIR normal FT-Raman spectra, as far as sample identification is concerned.

Surface plasmon mediated Raman scattering in metal nanoparticles

NASA Astrophysics Data System (ADS)

Bachelier, G.; Mlayah, A.

2004-05-01

The Raman scattering due to confined acoustic vibrations in metal particles is studied theoretically. Various coupling mechanisms between the surface plasmon polaritons and the confined vibrations are investigated. Their relative contribution to the light scattering is discussed. We found that two mechanisms play an important role: (i) modulation of the interband dielectric susceptibility via deformation potential due to pure radial vibrations and (ii) modulation of the surface polarization charges by quadripolar vibrations. The dependence of the Raman spectra on the nanoparticles size and size distribution and on the excitation energy is studied in connection with the nature of the excited plasmon-polariton states. We found a good agreement between calculated line shapes and relatives intensities of the Raman bands and the experimental spectra reported in the literature.

Sensing of p53 and EGFR Biomarkers Using High Efficiency SERS Substrates

PubMed Central

Owens, Peter; Phillipson, Nigel; Perumal, Jayakumar; O’Connor, Gerard M.; Olivo, Malini

2015-01-01

In this paper we describe a method for the determination of protein concentration using Surface Enhanced Raman Resonance Scattering (SERRS) immunoassays. We use two different Raman active linkers, 4-aminothiophenol and 6-mercaptopurine, to bind to a high sensitivity SERS substrate and investigate the influence of varying concentrations of p53 and EGFR on the Raman spectra. Perturbations in the spectra are due to the influence of protein–antibody binding on Raman linker molecules and are attributed to small changes in localised mechanical stress, which are enhanced by SERRS. These influences are greatest for peaks due to the C-S functional group and the Full Width Half Maximum (FWHM) was found to be inversely proportional to protein concentration. PMID:26516922

The Development of a Fiber Optic Raman Temperature Measurement System for Rocket Flows

NASA Technical Reports Server (NTRS)

Degroot, Wim A.

1992-01-01

A fiberoptic Raman diagnostic system for H2/O2 rocket flows is currently under development. This system is designed for measurement of temperature and major species concentration in the combustion chamber and part of the nozzle of a 100 Newton thrust rocket currently undergoing testing. This paper describes a measurement system based on the spontaneous Raman scattering phenomenon. An analysis of the principles behind the technique is given. Software is developed to measure temperature and major species concentrations by comparing theoretical Raman scattering spectra with experimentally obtained spectra. Equipment selection and experimental approach are summarized. This experimental program is part of a program, which is in progress, to evaluate Navier-Stokes based analyses for this class of rocket.

Raman Scattering by Crystals of Rare-Earth Hexaborides with Different Isotopes of Boron

NASA Astrophysics Data System (ADS)

Markov, Yu. F.; Gurin, V. N.; Ponkratov, K. V.

2018-04-01

Monocrystals of lanthanum hexaboride LaB6 containing both natural boron and its isotopes 10B and 11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.

Hollow fiber-optic Raman probes for small experimental animals

NASA Astrophysics Data System (ADS)

Katagiri, Takashi; Hattori, Yusuke; Suzuki, Toshiaki; Matsuura, Yuji; Sato, Hidetoshi

2007-02-01

Two types of hollow fiber-optic probes are developed to measure the in vivo Raman spectra of small animals. One is the minimized probe which is end-sealed with the micro-ball lens. The measured spectra reflect the information of the sample's sub-surface. This probe is used for the measurement of the esophagus and the stomach via an endoscope. The other probe is a confocal Raman probe which consists of a single fiber and a lens system. It is integrated into the handheld microscope. A simple and small multimodal probe is realized because the hollow optical fiber requires no optical filters. The performance of each probe is examined and the effectiveness of these probes for in vivo Raman spectroscopy is shown by animal tests.

Raman spectra of ruthenium and tantalum trimers in argon matrices

NASA Astrophysics Data System (ADS)

Fang, Li; Shen, Xiaole; Chen, Xiaoyu; Lombardi, John R.

2000-12-01

The resonance Raman spectra of ruthenium trimers (Ru 3) in argon matrices have been obtained. Three resonance Raman transitions were observed between 570 and 590 nm. Two of them (303.4 and 603.7 cm -1) are assigned to the totally symmetric vibrational progression, giving k e=1.86 mdyne/ Å. The line at 581.5 cm-1 is assigned as the origin of a low-lying electronic state. We also report on the observation of a resonance Raman spectrum of tantalum trimers (Ta 3). Observed lines include 251.2 and 501.9 cm-1 which we assign to the fundamental and the first overtone of the symmetric stretch in Ta 3. This gives k e=2.25 mdyne/ Å.

On the use of spectra from portable Raman and ATR-IR instruments in synthesis route attribution of a chemical warfare agent by multivariate modeling.

PubMed

Wiktelius, Daniel; Ahlinder, Linnea; Larsson, Andreas; Höjer Holmgren, Karin; Norlin, Rikard; Andersson, Per Ola

2018-08-15

Collecting data under field conditions for forensic investigations of chemical warfare agents calls for the use of portable instruments. In this study, a set of aged, crude preparations of sulfur mustard were characterized spectroscopically without any sample preparation using handheld Raman and portable IR instruments. The spectral data was used to construct Random Forest multivariate models for the attribution of test set samples to the synthetic method used for their production. Colored and fluorescent samples were included in the study, which made Raman spectroscopy challenging although fluorescence was diminished by using an excitation wavelength of 1064 nm. The predictive power of models constructed with IR or Raman data alone, as well as with combined data was investigated. Both techniques gave useful data for attribution. Model performance was enhanced when Raman and IR spectra were combined, allowing correct classification of 19/23 (83%) of test set spectra. The results demonstrate that data obtained with spectroscopy instruments amenable for field deployment can be useful in forensic studies of chemical warfare agents. Copyright © 2018 Elsevier B.V. All rights reserved.

Goldindec: A Novel Algorithm for Raman Spectrum Baseline Correction

PubMed Central

Liu, Juntao; Sun, Jianyang; Huang, Xiuzhen; Li, Guojun; Liu, Binqiang

2016-01-01

Raman spectra have been widely used in biology, physics, and chemistry and have become an essential tool for the studies of macromolecules. Nevertheless, the raw Raman signal is often obscured by a broad background curve (or baseline) due to the intrinsic fluorescence of the organic molecules, which leads to unpredictable negative effects in quantitative analysis of Raman spectra. Therefore, it is essential to correct this baseline before analyzing raw Raman spectra. Polynomial fitting has proven to be the most convenient and simplest method and has high accuracy. In polynomial fitting, the cost function used and its parameters are crucial. This article proposes a novel iterative algorithm named Goldindec, freely available for noncommercial use as noted in text, with a new cost function that not only conquers the influence of great peaks but also solves the problem of low correction accuracy when there is a high peak number. Goldindec automatically generates parameters from the raw data rather than by empirical choice, as in previous methods. Comparisons with other algorithms on the benchmark data show that Goldindec has a higher accuracy and computational efficiency, and is hardly affected by great peaks, peak number, and wavenumber. PMID:26037638

Raman spectroscopic investigation of spinal cord injury in a rat model

NASA Astrophysics Data System (ADS)

Saxena, Tarun; Deng, Bin; Stelzner, Dennis; Hasenwinkel, Julie; Chaiken, Joseph

2011-02-01

Raman spectroscopy was used to study temporal molecular changes associated with spinal cord injury (SCI) in a rat model. Raman spectra of saline-perfused, injured, and healthy rat spinal cords were obtained and compared. Two injury models, a lateral hemisection and a moderate contusion were investigated. The net fluorescence and the Raman spectra showed clear differences between the injured and healthy spinal cords. Based on extensive histological and biochemical characterization of SCI available in the literature, these differences were hypothesized to be due to cell death, demyelination, and changes in the extracellular matrix composition, such as increased expression of proteoglycans and hyaluronic acid, at the site of injury where the glial scar forms. Further, analysis of difference spectra indicated the presence of carbonyl containing compounds, hypothesized to be products of lipid peroxidation and acid catalyzed hydrolysis of glycosaminoglycan moieties. These results compared well with in vitro experiments conducted on chondroitin sulfate sugars. Since the glial scar is thought to be a potent biochemical barrier to nerve regeneration, this observation suggests the possibility of using near infrared Raman spectroscopy to study injury progression and explore potential treatments ex vivo, and ultimately monitor potential remedial treatments within the spinal cord in vivo.

Process spectroscopy in microemulsions—Raman spectroscopy for online monitoring of a homogeneous hydroformylation process

NASA Astrophysics Data System (ADS)

Paul, Andrea; Meyer, Klas; Ruiken, Jan-Paul; Illner, Markus; Müller, David-Nicolas; Esche, Erik; Wozny, Günther; Westad, Frank; Maiwald, Michael

2017-03-01

A major industrial reaction based on homogeneous catalysis is hydroformylation for the production of aldehydes from alkenes and syngas. Hydroformylation in microemulsions, which is currently under investigation at Technische Universität Berlin on a mini-plant scale, was identified as a cost efficient approach which also enhances product selectivity. Herein, we present the application of online Raman spectroscopy on the reaction of 1-dodecene to 1-tridecanal within a microemulsion. To achieve a good representation of the operation range in the mini-plant with regard to concentrations of the reactants a design of experiments was used. Based on initial Raman spectra partial least squares regression (PLSR) models were calibrated for the prediction of 1-dodecene and 1-tridecanal. Limits of predictions arise from nonlinear correlations between Raman intensity and mass fractions of compounds in the microemulsion system. Furthermore, the prediction power of PLSR models becomes limited due to unexpected by-product formation. Application of the lab-scale derived calibration spectra and PLSR models on online spectra from a mini-plant operation yielded promising estimations of 1-tridecanal and acceptable predictions of 1-dodecene mass fractions suggesting Raman spectroscopy as a suitable technique for process analytics in microemulsions.

Using Raman spectroscopy to study the onset of labor: a pilot study

NASA Astrophysics Data System (ADS)

Vargis, Elizabeth; Webb, C. Nathan; Paria, B. C.; Bennett, Kelly; Reese, Jeff; Al-Hendy, Ayman; Mahadevan-Jansen, Anita

2011-03-01

Preterm birth is the second leading cause of neonatal mortality and leads to a myriad of complications like delayed development and cerebral palsy. Currently, there is no way to accurately predict preterm labor, making its prevention and treatment virtually impossible. While there are some at-risk patients, over half of all preterm births do not fall into any high-risk category. This study seeks to predict and prevent preterm labor by using Raman spectroscopy to detect changes in the cervix during pregnancy indicative of labor. Since Raman spectroscopy has been used to detect cancers in vivo in organs like the cervix and skin, it follows that spectra will change over the course of pregnancy. Previous studies have shown that fluorescence decreased during pregnancy and increased during post-partum exams to pre-pregnancy levels. We believe significant changes will occur in the Raman spectra obtained during the course of pregnancy. In this study, Raman spectra from the cervix of pregnant mice and women will be acquired. Specific changes that occur due to cervical softening or changes in hormonal levels will be observed to understand the likelihood that a female mouse or a woman will enter labor.

FT-IR, FT-Raman spectra and DFT calculations of melaminium perchlorate monohydrate

NASA Astrophysics Data System (ADS)

Kanagathara, N.; Marchewka, M. K.; Drozd, M.; Renganathan, N. G.; Gunasekaran, S.; Anbalagan, G.

2013-08-01

Melaminium perchlorate monohydrate (MPM), an organic material has been synthesized by slow solvent evaporation method at room temperature. Powder X-ray diffraction analysis confirms that MPM crystal belongs to triclinic system with space group P-1. FTIR and FT Raman spectra are recorded at room temperature. Functional group assignment has been made for the melaminium cations and perchlorate anions. Vibrational spectra have also been discussed on the basis of quantum chemical density functional theory (DFT) calculations using Firefly (PC GAMESS) version 7.1 G. Vibrational frequencies are calculated and scaled values are compared with experimental values. The assignment of the bands has been made on the basis of the calculated PED. The Mulliken charges, HOMO-LUMO orbital energies are analyzed directly from Firefly program log files and graphically illustrated. HOMO-LUMO energy gap and other related molecular properties are also calculated. The theoretically constructed FT-IR and FT-Raman spectra of MPM coincide with the experimental one. The chemical structure of the compound has been established by 1H and 13C NMR spectra. No detectable signal was observed during powder test for second harmonic generation.

Coherent anti-Stokes Raman scattering enhancement of thymine adsorbed on graphene oxide

PubMed Central

2014-01-01

Coherent anti-Stokes Raman scattering (CARS) of carbon nanostructures, namely, highly oriented pyrolytic graphite, graphene nanoplatelets, graphene oxide, and multiwall carbon nanotubes as well CARS spectra of thymine (Thy) molecules adsorbed on graphene oxide were studied. The spectra of the samples were compared with spontaneous Raman scattering (RS) spectra. The CARS spectra of Thy adsorbed on graphene oxide are characterized by shifts of the main bands in comparison with RS. The CARS spectra of the initial nanocarbons are definitely different: for all investigated materials, there is a redistribution of D- and G-mode intensities, significant shift of their frequencies (more than 20 cm-1), and appearance of new modes about 1,400 and 1,500 cm-1. The D band in CARS spectra is less changed than the G band; there is an absence of 2D-mode at 2,600 cm-1 for graphene and appearance of intensive modes of the second order between 2,400 and 3,000 cm-1. Multiphonon processes in graphene under many photon excitations seem to be responsible for the features of the CARS spectra. We found an enhancement of the CARS signal from thymine adsorbed on graphene oxide with maximum enhancement factor about 105. The probable mechanism of CARS enhancement is discussed. PMID:24948887

High pressure studies on group VI metal hexacarbonyl molecular solids

NASA Astrophysics Data System (ADS)

Garimella, Subrahmanyam Venkata

Group VI metal hexacarbonyls, M(CO)6 (M = Cr, Mo and W), are of extreme importance as catalysts in industry and also of fundamental interest due to the established charge transfer mechanism between the carbon monoxide and the metal. They condense to molecular solids at ambient conditions retaining the octahedral (Oh) symmetry of gas phase and have been extensively investigated by previous workers to understand their fundamental chemical bonding and possible industrial applications. However little is known about their behavior at high pressures which is the focus of this dissertation. Metal hexacarbonyls were subjected to high pressures in Diamond-Anvil cells to understand the pressure effect on chemical bonding using Raman scattering in situ. The high-pressure results on each of the three metal hexacarbonyls are presented and are followed by a critical analysis of the entire family. The Raman study was conducted at pressures up to 45 GPa and X-ray up to 58 GPa. This is followed by a discussion on infra red spectra in conjunction with Raman and X-ray analysis to provide a rationale for polymerization. Finally the probable synthesis of extremely reactive species under high-pressures and as identified via Raman is discussed. The high-pressure Raman scattering, up to 30 GPa, demonstrated the absence of pi-backbonding. The disappearance of parental Raman spectra for (M = Cr, Mo and W) at 29.6, 23.3 and 22.2 GPa respectively was attributed to the total collapse of the Oh symmetry. This collapse under high-pressure lead to metal-mediated polymeric phase characterized by Raman active delta(OCO) feature, originating from intermolecular vibrational coupling in the parent sample. Further increase in pressures up to 45 GPa, did not affect this feature. The pressure quenched Raman spectra, revealed various chemical groups non-characteristic of the parent sample and adsorption of CO in addition to the characteristic delta(OCO) feature. The thus recorded Raman, complemented with the far and mid-infrared pressure quenched spectra, reveal the formation of novel metal-mediated polymers. The X-ray diffraction on W(CO)6 up to 58 GPa revealed the generation of amorphous polymeric pattern which was retained back to ambient conditions.

Understanding of local structure-function relationships of zeolites used in industry through polarized raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivera, O.; Lascola, R.; Fessler, K.

The overall objective of this project is to optics procurement and instrumental setup completed in Robert Lascola’s laboratory. An Ondax THz-Raman probe was installed in order to obtain Raman terahertz spectra of commercially available Zeolites.

Detection of Leukemia with Blood Samples Using Raman Spectroscopy and Multivariate Analysis

NASA Astrophysics Data System (ADS)

Martínez-Espinosa, J. C.; González-Solís, J. L.; Frausto-Reyes, C.; Miranda-Beltrán, M. L.; Soria-Fregoso, C.; Medina-Valtierra, J.

2009-06-01

The use of Raman spectroscopy to analyze blood biochemistry and hence distinguish between normal and abnormal blood was investigated. Blood samples were obtained from 6 patients who were clinically diagnosed with leukemia and 6 healthy volunteers. The imprint was put under the microscope and several points were chosen for Raman measurement. All the spectra were collected by a confocal Raman micro-spectroscopy (Renishaw) with a NIR 830 nm laser. It is shown that the serum samples from patients with leukemia and from the control group can be discriminated when the multivariate statistical methods of principal component analysis (PCA) and linear discriminated analysis (LDA) are applied to their Raman spectra. The ratios of some band intensities were analyzed and some band ratios were significant and corresponded to proteins, phospholipids, and polysaccharides. The preliminary results suggest that Raman Spectroscopy could be a new technique to study the degree of damage to the bone marrow using just blood samples instead of biopsies, treatment very painful for patients.

Joint analyses by laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy at stand-off distances.

PubMed

Wiens, Roger C; Sharma, Shiv K; Thompson, Justin; Misra, Anupam; Lucey, Paul G

2005-08-01

Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) of solid samples have both been shown to be feasible with sample-to-instrument distances of many meters. The two techniques are very useful together, as the combination of elemental compositions from LIBS and molecular vibrational information from Raman spectroscopy strongly complement each other. Remote LIBS and Raman spectroscopy spectra were taken together on a number of mineral samples including sulfates, carbonates and silicates at a distance of 8.3 m. The complementary nature of these spectra is highlighted and discussed. A factor of approximately 20 difference in intensity was observed between the brightest Raman line of calcite, at optimal laser power, and the brighter Ca I LIBS emission line measured with 55 mJ/pulse laser power. LIBS and Raman spectroscopy have several obstacles to devising a single instrument capable of both techniques. These include the differing spectral ranges and required detection sensitivity. The current state of technology in these areas is discussed.

UV Raman detection of 2,4-DNT in contact with sand particles

NASA Astrophysics Data System (ADS)

Blanco, Alejandro; Pacheco-Londoño, Leonardo C.; Peña-Quevedo, Alvaro J.; Hernández-Rivera, Samuel P.

2006-05-01

Deep Ultra Violet Raman Spectroscopy (DUV-RS) is an emerging tool for vibrational spectroscopy analysis and can be used in Point Detection mode to detect explosive components of landmines and Improvised Explosive Devices (IED). Interactions of explosives with different substrates can be measured by using quantitative vibrational signal shift information of scattered Raman light associated with these interactions. In this research, grounds were laid for detection of explosives using UV-Raman Spectroscopy equipped with 244 nm laser excitation line from a 488 nm frequency doubled Coherent FreD laser. In other experiments, samples of 2,4-DNT were allowed to interact with Ottawa Sand and were studied using DUV-RS. Characteristic vibrational signals of energetic compounds were analyzed in the ranges: 400-1200 cm -1, 1200-1800 cm -1, and 2800-3500 cm -1. In addition these Raman spectra were compared with dispersive spectra that were acquired using Raman Microscopy equipped with 514.5 nm (VIS) 785 nm (NIR) and 1064 nm (NIR) excitation lasers.

Characterization of Storage-Induced Red Blood Cell Hemolysis Using Raman Spectroscopy.

PubMed

Gautam, Rekha; Oh, Joo-Yeun; Marques, Marisa B; Dluhy, Richard A; Patel, Rakesh P

2018-06-11

The therapeutic efficacy and safety of stored red blood cells (RBCs) relies on minimal in-bag hemolysis. The accuracy of current methods of measuring hemolysis can suffer as a result of specimen collection and processing artefacts. To test whether Raman spectroscopy could be used to assess hemolysis. RBCs were stored for as long as 42 days. Raman spectra of RBCs were measured before and after washing, and hemolysis was measured in supernatant by visible spectroscopy. Raman spectra indicated increased concentrations of oxyhemoglobin (oxyHb) and methemoglobin (metHb), and decreased membrane fluidity with storage age. Changes in oxyHb and metHb were associated with the intraerythrocytic and extracellular fractions, respectively. Hemolysis increased in a storage age-dependent manner. Changes in Raman bands reflective of oxyHb, metHb, and RBC membranes correlated with hemolysis; the most statistically significant change was an increased intensity of metHb and decreased membrane fluidity. These data suggest that Raman spectroscopy may offer a new label-free modality to assess RBC hemolysis during cold storage.

Application of micro-Raman spectroscopy for fight against terrorism and smuggling

NASA Astrophysics Data System (ADS)

Almaviva, Salvatore; Botti, Sabina; Palucci, Antonio; Puiu, Adriana; Schnürer, Frank; Schweikert, Wenka; Romolo, Francesco Saverio

2014-04-01

We report the results of Raman measurements on some common military explosives and explosives precursors deposited on clothing fabrics, both synthetic and natural, in concentration comparable to those obtained from a single fingerprint or mixed with similar harmless substances to detect illegal compounds for smuggling activities. Raman spectra were obtained using an integrated portable Raman system equipped with an optical microscope and a 785-nm laser in an analysis of <1 min. The spectral features of each illicit substance have been identified and distinguished from those belonging to the substrate fabric or from the interfering compound. Our results show that the application of Raman spectroscopy (RS) with a microscope-based portable apparatus can provide interpretable Raman spectra for a fast, in-situ analysis, directly from explosive particles of some μ, despite the contribution of the substrate, leaving the sample completely unaltered for further, more specific, and propedeutic laboratory analysis. We also show how the RS is suitable for detecting illegal compounds mixed with harmless substances for smuggling purposes or for counterfeiting activities.

Laser spectroscopy and dynamics of crystal lattices of chirally pure and racemic phases of amino acids

NASA Astrophysics Data System (ADS)

Belyanchikov, M. A.; Gorelik, V. S.; Gorshunov, B. P.; Pyatyshev, A. Yu.

2017-03-01

Strong sharp lines due to the librational modes characterized by a pseudoscalar symmetry type have been found in the low-frequency Raman spectra of the lattices of glycine and tyrosine amino acids. The intensities of these lines exceed those for Raman scattering in the region of intramolecular vibrations. The spectra of chirally pure and racemic phases of amino acids differ significantly. The results obtained can be used to observe stimulated Raman scattering from the librational modes of crystalline amino acids and monitor the chiral purity of bioactive preparations containing amino acids.

Two-Dimensional Raman Correlation Analysis of Diseased Esophagus in a Rat

NASA Astrophysics Data System (ADS)

Takanezawa, Sota; Morita, Shin-ichi; Maruyama, Atsushi; Murakami, Takurou N.; Kawashima, Norimichi; Endo, Hiroyuki; Iijima, Katsunori; Asakura, Tohru; Shimosegawa, Tooru; Sato, Hidetoshi

2010-07-01

Generalized two-dimensional (2D) Raman correlation analysis effectively distinguished a benign tumor from normal tissue. Line profiling Raman spectra of a rat esophagus, including a benign tumor, were measured and the generalized 2D synchronous and asynchronous spectra were calculated. In the autocorrelation area of the amide I band of proteins in the asynchronous map, a cross-like pattern was observed. A simulation study indicated that the pattern was caused by a sharp band component in the amide I band region. We considered that the benign tumor corresponded to the sharp component.

Detection of liver cancer and abnormal liver tissue by Raman spectroscopy and fluorescence

NASA Astrophysics Data System (ADS)

Li, Xiaozhou; Ding, Jianhua; Zhang, Xiujun; Lin, Junxiu; Wang, Deli

2005-01-01

In this paper, laser induced human serum Raman spectra of liver cancer are measured. The spectra differences in serum from normal people and liver disease patients are analyzed. For the typical spectrum of normal serum, there are three sharp Raman peaks and relative intensity of Raman peaks excited by 514.5nm is higher than that excited by 488.0nm. For the Raman spectrum of liver cancer serum there are no peaks or very weak Raman peaks at the same positions. Results from more than two hundred case measurements show that clinical diagnostic accuracy is 92.86%. And then, the liver fibrosis and liver cirrhosis are studied applying the technology of LIF. To liver cirrhosis, the shape of Raman peak is similar to normal and fluorescence spectrum is similar to that of liver cancer from statistic data. The experiment indicates that there is notable fluorescence difference between the abnormal and normal liver tissue and have blue shift in fluorescence peak. Except for human serum, we use rats serum for researching either. Compared with results of path al examination, we analyze the spectra of normal cases, hepatic fibrosis and hepatocirrhosis respectively in an attempt to find some difference between them. Red shift of fluorescence peak is observed with disease evolution using 514.5nm excitation of an Ar-ion laser. However, no distinct changes happen with 488.0nm excitation. These results have important reference values to explore the method of laser spectrum diagnosis.

Quantitative Interpretation of Polarization SFG Vibrational Spectra of Air/Methanol Interface

NASA Astrophysics Data System (ADS)

Wu, Hui; Zhang, Wen-kai; Gan, Wei; Cui, Zhi-feng; Wang, Hong-fei

2006-06-01

Even though in IR and Raman spectra of liquid methanol there is always an apparent feature for the asymmetric stretching mode of the CH3 group around 2970 cm-1, this feature has not been observed in the Sum Frequency Generation Vibrational Spectroscopy (SFG-VS) in any polarizations from the air/methanol interface. Here we present a treatment based on a corrected bond additivity model to quantitatively interpret the SFG-VS of the air/methanol interface from the IR and Raman spectra of liquid methanol.

Raman spectra of solid benzene under high pressure

NASA Technical Reports Server (NTRS)

Thiery, M.-M.; Kobashi, K.; Spain, I. L.

1985-01-01

Raman spectra of solid benzene have been measured at room temperature up to about 140 kbar, using the diamond anvil cell. Effort has been focused upon the lattice vibration spectra at pressures above that of phase II. It is found that a change in slopes occurs in the frequency-pressure curves at about 40 kbar. Furthermore, a new band appears above 90 kbar. These features probably correspond respectively to the II-III phase transition, which has been reported previously, and a III-IV phase transition, reported here for the first time.

Analysis of normal and diseased liver tissue using auto-fluorescence and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Li, Xiaozhou; Jia, Chunde; Lin, Junxiu; Kang, Youping

2003-12-01

In this paper, laser induced human serum Raman spectra of liver cancer are measured. The spectra differences in serum from normal people and liver cancer patients are analyzed. For the typical spectrum of normal serum, there are three sharp Raman peaks and relative intensity of Raman peaks excited by 514.5 nm is higher than that excited by 488.0 nm. However, for the Raman spectrum of liver cancer serum there are no peaks or very weak Raman peaks at the same positions. Results from more than two hundred case measurements show that clinical diagnostic accuracy is 92.86%. And then, the liver fibrosis and liver cirrhosis are studied applying the technology of LIF. To liver cirrhosis, the shape of Raman peak is similar to normal and fluorescence spectrum is similar to that of liver cancer from statistic data. The experiment indicates that there is notable fluorescence difference between the abnormal and normal liver tissue and have blue shift in fluorescence peak. These results have important reference values to explore the method of laser spectrum diagnosis.

Raman spectral properties of squamous cell carcinoma of oral tissues and cells

NASA Astrophysics Data System (ADS)

Su, L.; Sun, Y. F.; Chen, Y.; Chen, P.; Shen, A. G.; Wang, X. H.; Jia, J.; Zhao, Y. F.; Zhou, X. D.; Hu, J. M.

2012-01-01

Early diagnosis is the key of the improved survival rates of oral cancer. Raman spectroscopy is sensitive to the early changes of molecular composition and structure that occur in benign lesion during carcinogenesis. In this study, in situ Raman analysis provided distinct spectra that can be used to discriminate between normal and malignant tissues, as well as normal and cancer cells. The biochemical variations between different groups were analyzed by the characteristic bands by comparing the normalized mean spectra. Spectral profiles of normal, malignant conditions show pronounced differences between one another, and multiple Raman markers associated with DNA and protein vibrational modes have been identified that exhibit excellent discrimination power for cancer sample identification. Statistical analyses of the Raman data and classification using principal component analysis (PCA) are shown to be effective for the Raman spectral diagnosis of oral mucosal diseases. The results indicate that the biomolecular differences between normal and malignant conditions are more obviously at the cellular level. This technique could provide a research foundation for the Raman spectral diagnosis of oral mucosal diseases.

Raman Spectroscopy Study of Prostatic Adenocarcinoma Bulk Tissues

NASA Astrophysics Data System (ADS)

Devpura, S.; Dai, H.; Thakur, J. S.; Naik, R.; Cao, A.; Pandya, A.; Auner, G. W.; Sarkar, F.; Sakr, W.; Naik, V.

2009-03-01

Prostate cancer is one of the most common types of cancer among men. The mortality rate for this disease can be dramatically reduced if it can be diagnosed in its early stages. Raman spectroscopy is one of the optical techniques which can provide fingerprints of a disease in terms of its molecular composition which changes due to the onset of disease. The aim of this project is to investigate the differences in the Raman spectra to identify benign epithelium (BE), prostatic intraepithelial neoplasia (PIN) and adenocarcinoma of various Gleason grades in archived bulk tissues embedded in paraffin wax. For each tissue, two adjacent tissue sections were cut and dewaxed, where one of the sections was stained using haematoxylin and eosin for histological examination and the other unstained adjacent section was used for Raman spectroscopic studies. We have collected Raman spectra from 10 prostatic adenocarcinoma dewaxed tissue sections using Raman microscope (785 nm excitation laser). The data were analyzed using statistical methods of principal component analysis and discriminant function analysis to classify the tissue regions. The results indicate that Raman Spectroscopy can differentiate between BE, PIN and Cancer regions.

Composition and Structure of Microalgae Indicated in Raman and Hyperspectral Spectra and Scanning Electron Microscopy: from Cyanobacteria to Isolates from Coal-bed Methane Water Ponds

NASA Astrophysics Data System (ADS)

Zhou, X.; Zhou, Z.; Apple, M. E.; Spangler, L.

2017-12-01

Microalgae can be used for many potential applications for human's benefits. These potential applications included biofuel production from microalgae, biofiltering to cleaning water, chemical extraction as nutrients, etc. However, exploration for such applications is still in the early stages. For instance, many species and strains of microalgae have been investigated for their lipid content and growing conditions for efficient productions of lipids, but no specific species have yet been chosen as a fuel source for commercial production because of the huge biodiversity and subsequently a wide range of species that can potentially be exploited for biodiesel production, the great variability between species in their fuel precursor producing capabilities. Numerous coal-bed methane water ponds were established in the world as a consequence of coal-bed methane production from deep coal seams. Microalgae were isolated from such ponds and potentially these ponds can be used as venues for algal production. In this study, we characterized chemical composition and structure of the Cyanobacteria Anabaena cylindrica (UTEX # 1611) and isolates from coal-bed methane ponds Nannochloropsis gaditana and PW95 using Laser Raman Spectroscopy (LRS), hyperspectral spectra, and Scanning Electron Microscope (SEM). The objective is to seek bio-indicators for potential applications of these microalgae species. For instance, indicator of rich content lips shows the great potential for biofuel production. Fig.1 shows an example of the Raman spectra of the three species in desiccated form. The spectral peaks were isolated and the corresponding composition was identified. The insert at the right hand of the Raman spectrum of each species is the micrograph of the cell morphology under a microscope. The Raman spectra of cells in aquatic solutions were also obtained and compared with the desiccated form. The hyperspectral reflectances of the three species show quite different characteristics and the main absorption bands and scattering bands were located and their association with composition and structure were analyzed and discussed. SEM micrographs will be collected and the composition and structure derived from the SEM micrographs will be discussed and compared with those derived from the Raman spectra and hyperspectral spectra.

Antarctic analogues for Mars exploration: a Raman spectroscopic study of biogeological signatures

NASA Astrophysics Data System (ADS)

Edwards, Howell G. M.; Moody, Caroline A.; Jorge Villar, Susana E.; Dickensheets, David L.; Wynn-Williams, David D.

2004-03-01

There is now much interest in the construction of portable Raman systems for the analysis of cyanobacterial and lichen communities in the field; to this extent, Raman spectra obtained with laboratory-based systems operating at different wavelengths have been evaluated for potential fieldwork applications of miniaturized units. Selected test specimens of the cyanobacterial Nostoc commune, epilithic lichens Acarospora chlorophana, and Caloplaca saxicola and the endolithic Chroococcidiopsis from Antarctic sites have been examined in the present preliminary studies. Although some organisms gave useable Raman spectra with short-wavelength lasers, 1064 nm was the only excitation that was consistently excellent for all organisms. We conclude that a miniaturized Raman spectrometer, operating at layer wavelength excitation, is the optimal instrument for in situ studies of pigmented communities at the limits of life on Earth. This has practical potential for the quest for biomolecules residual from any former surface or subsurface life on Mars.

Combined autofluorescence and Raman spectroscopy method for skin tumor detection in visible and near infrared regions

NASA Astrophysics Data System (ADS)

Zakharov, V. P.; Bratchenko, I. A.; Artemyev, D. N.; Myakinin, O. O.; Khristoforova, Y. A.; Kozlov, S. V.; Moryatov, A. A.

2015-07-01

The combined application of Raman and autofluorescence spectroscopy in visible and near infrared regions for the analysis of malignant neoplasms of human skin was demonstrated. Ex vivo experiments were performed for 130 skin tissue samples: 28 malignant melanomas, 19 basal cell carcinomas, 15 benign tumors, 9 nevi and 59 normal tissues. Proposed method of Raman spectra analysis allows for malignant melanoma differentiating from other skin tissues with accuracy of 84% (sensitivity of 97%, specificity of 72%). Autofluorescence analysis in near infrared and visible regions helped us to increase the diagnostic accuracy by 5-10%. Registration of autofluorescence in near infrared region is realized in one optical unit with Raman spectroscopy. Thus, the proposed method of combined skin tissues study makes possible simultaneous large skin area study with autofluorescence spectra analysis and precise neoplasm type determination with Raman spectroscopy.

Resonance Raman and UV-visible spectroscopy of black dyes on textiles.

PubMed

Abbott, Laurence C; Batchelor, Stephen N; Smith, John R Lindsay; Moore, John N

2010-10-10

Resonance Raman and UV-visible diffuse reflectance spectra were recorded from samples of cotton, viscose, polyester, nylon, and acrylic textile swatches dyed black with one of seven single dyes, a mixture of two dyes, or one of seven mixtures of three dyes. The samples generally gave characteristic Raman spectra of the dyes, demonstrating that the technique is applicable for the forensic analysis of dyed black textiles. Survey studies of the widely used dye Reactive Black 5 show that essentially the same Raman spectrum is obtained on bulk sampling from the dye in solution, on viscose, on cotton at different uptakes, and on microscope sampling from the dye in cotton threads and single fibres. The effects of laser irradiation on the Raman bands and emission backgrounds from textile samples with and without dye are also reported. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Chromophore Structure of Photochromic Fluorescent Protein Dronpa: Acid-Base Equilibrium of Two Cis Configurations.

PubMed

Higashino, Asuka; Mizuno, Misao; Mizutani, Yasuhisa

2016-04-07

Dronpa is a novel photochromic fluorescent protein that exhibits fast response to light. The present article is the first report of the resonance and preresonance Raman spectra of Dronpa. We used the intensity and frequency of Raman bands to determine the structure of the Dronpa chromophore in two thermally stable photochromic states. The acid-base equilibrium in one photochromic state was observed by spectroscopic pH titration. The Raman spectra revealed that the chromophore in this state shows a protonation/deprotonation transition with a pKa of 5.2 ± 0.3 and maintains the cis configuration. The observed resonance Raman bands showed that the other photochromic state of the chromophore is in a trans configuration. The results demonstrate that Raman bands selectively enhanced for the chromophore yield valuable information on the molecular structure of the chromophore in photochromic fluorescent proteins after careful elimination of the fluorescence background.

Angular dependence of Raman scattering selection rules for long-wavelength optical phonons in short-period GaAs/AlAs superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volodin, V. A., E-mail: volodin@isp.nsc.ru; Sachkov, V. A.; Sinyukov, M. P.

2016-07-15

The angular dependence of Raman scattering selection rules for optical phonons in short-period (001) GaAs/AlAs superlattices is calculated and experimentally studied. Experiments are performed using a micro-Raman setup, in the scattering geometry with the wavevectors of the incident and scattered light lying in the plane of superlattices (so-called in-plane geometry). Phonon frequencies are calculated using the Born model taking the Coulomb interaction into account in the rigid-ion approximation. Raman scattering spectra are calculated in the framework of the deformation potential and electro-optical mechanisms. Calculations show an angular dependence of the selection rules for optical phonons with different directions of themore » wavevectors. Drastic differences in the selection rules are found for experimental and calculated spectra. Presumably, these differences are due to the Fröhlich mechanism in Raman scattering for short-period superlattices.« less

Classification of narcotics in solid mixtures using principal component analysis and Raman spectroscopy.

PubMed

Ryder, Alan G

2002-03-01

Eighty-five solid samples consisting of illegal narcotics diluted with several different materials were analyzed by near-infrared (785 nm excitation) Raman spectroscopy. Principal Component Analysis (PCA) was employed to classify the samples according to narcotic type. The best sample discrimination was obtained by using the first derivative of the Raman spectra. Furthermore, restricting the spectral variables for PCA to 2 or 3% of the original spectral data according to the most intense peaks in the Raman spectrum of the pure narcotic resulted in a rapid discrimination method for classifying samples according to narcotic type. This method allows for the easy discrimination between cocaine, heroin, and MDMA mixtures even when the Raman spectra are complex or very similar. This approach of restricting the spectral variables also decreases the computational time by a factor of 30 (compared to the complete spectrum), making the methodology attractive for rapid automatic classification and identification of suspect materials.

Vibrational dynamics of rutile-type GeO2 from micro-Raman spectroscopy experiments and first-principles calculations

NASA Astrophysics Data System (ADS)

Sanson, A.; Pokrovski, G. S.; Giarola, M.; Mariotto, G.

2015-01-01

The vibrational dynamics of germanium dioxide in the rutile structure has been investigated by using polarized micro-Raman scattering spectroscopy coupled with first-principles calculations. Raman spectra were carried out in backscattering geometry at room temperature from micro-crystalline samples either unoriented or oriented by means of a micromanipulator, which enabled successful detection and identification of all the Raman active modes expected on the basis of the group theory. In particular, the Eg mode, incorrectly assigned or not detected in the literature, has been definitively observed by us and unambiguously identified at 525 \\text{cm}-1 under excitation by certain laser lines, thus revealing an unusual resonance phenomenon. First-principles calculations within the framework of the density functional theory allow quantifying both wave number and intensity of the Raman vibrational spectra. The excellent agreement between calculated and experimental data corroborates the reliability of our findings.

Raman spectroscopy and imaging: applications in human breast cancer diagnosis.

PubMed

Brozek-Pluska, Beata; Musial, Jacek; Kordek, Radzislaw; Bailo, Elena; Dieing, Thomas; Abramczyk, Halina

2012-08-21

The applications of spectroscopic methods in cancer detection open new possibilities in early stage diagnostics. Raman spectroscopy and Raman imaging represent novel and rapidly developing tools in cancer diagnosis. In the study described in this paper Raman spectroscopy has been employed to examine noncancerous and cancerous human breast tissues of the same patient. The most significant differences between noncancerous and cancerous tissues were found in regions characteristic for the vibrations of carotenoids, lipids and proteins. Particular attention was paid to the role played by unsaturated fatty acids in the differentiation between the noncancerous and the cancerous tissues. Comparison of Raman spectra of the noncancerous and the cancerous tissues with the spectra of oleic, linoleic, α-linolenic, γ-linolenic, docosahexaenoic and eicosapentaenoic acids has been presented. The role of sample preparation in the determination of cancer markers is also discussed in this study.

Open-Source Programming for Automated Generation of Graphene Raman Spectral Maps

NASA Astrophysics Data System (ADS)

Vendola, P.; Blades, M.; Pierre, W.; Jedlicka, S.; Rotkin, S. V.

Raman microscopy is a useful tool for studying the structural characteristics of graphene deposited onto substrates. However, extracting useful information from the Raman spectra requires data processing and 2D map generation. An existing home-built confocal Raman microscope was optimized for graphene samples and programmed to automatically generate Raman spectral maps across a specified area. In particular, an open source data collection scheme was generated to allow the efficient collection and analysis of the Raman spectral data for future use. NSF ECCS-1509786.

Fourier-Transform Raman Spectroscopy Of Biological Assemblies

NASA Astrophysics Data System (ADS)

Levin, Ira W.; Lewis, E. Neil

1989-12-01

Although the successful coupling of Raman scattered near-infrared radiation to a Michelson interferometer has recently created an outburst of intense interest in Fourier-transform (FT) Raman spectrometry," extended applications of the technique to macromolecular assemblies of biochemical and biophysical relevance have not progressed as rapidly as studies directed primarily at more conventional chemical characterizations. Since biological materials sampled with visible laser excitation sources typically emit a dominant fluorescence signal originating either from the intrinsic fluorescence of the molecular scatterer or from unrelenting contaminants, the use of near-infrared Nd:YAG laser excitation offers a convenient approach for avoiding this frequently overwhelming effect. In addition, the FT-Raman instrumentation provides a means of eliminating the deleterious resonance and decomposition effects often observed with the more accessible green and blue laser emissions. However, in choosing the incident near-infrared wavelength at, for example, 1064nm, the Raman scattered intensity decreases by factors of eighteen to forty from the Raman emissions induced by the shorter, visible excitations. Depending upon the experiment, this disadvantage is offset by the throughput and multiplex advantages afforded by the interferometric design. Thus, for most chemical systems, near-infrared FT-Raman spectroscopy, clearly provides a means for obtaining vibrational Raman spectra from samples intractable to the use of visible laser sources. In particular, for neat liquids, dilute solutions or polycrystalline materials, the ability to achieve high quality, reproducible spectra is, with moderate experience and perhaps relatively high laser powers, as straightforward as the conventional methods used to obtain Raman spectra with visible excitation and dispersive monochromators. In using near-infrared FT techniques to determine the Raman spectra of biological samples, one encounters new sets of experimental problems that may entail an initial, relatively steep learning curve. These difficulties originate particularly from the fragility of the weakly scattering aggregate paired with the dilute nature of the biochemical or cellular dispersion. Often, the Raman scattered intensity from these samples can be increased by carefully peileting the biological suspension using ultracentrifugation techniques. Since the overtone region of water, the usual medium for biological samples, absorbs radiation from both the Rayleigh signal at the exciting wavelength of the Nd:YAG laser and the longer wavelength Raman scattering from the sample, reproducible temperature measurements and temperature control become significant concerns. In these cases one appeals to internal temperature calibrations, use of deuterium oxide (D20) as a solvent (since absorptions of the laser exciting wavelength and Raman scattered photons are minimized), manipulation of incident laser spot size and the use of fiber optic bundles to carry the exciting and scattered radiation. In the present discussion we briefly cite some of the experimental approaches we have developed and experiences we have encountered in adapting near-infrared FT-Raman spectroscopy to the more challenging biophysical and biochemical systems amenable to vibrational analysis. We emphasize here the determination of the spectra of membrane assemblies and membrane related materials; in particular, we elucidate the interaction of several polyene antibiotics, including amphotericin A, amphotericin B and nystatin, with a model membrane system composed of dipalmitoylphosphatidylcholine bilayers.

Handheld confocal Raman microspectrometer for in-vivo skin cancer measurement

NASA Astrophysics Data System (ADS)

Lieber, Chad A.; Ellis, Darrel L.; Billheimer, D. D.; Mahadevan-Jansen, Anita

2004-07-01

Several studies have demonstrated Raman spectroscopy to be capable of tissue diagnosis with accuracy rivaling that of histopathologic analysis. This technique obtains biochemical-specific information noninvasively, and can eliminate the pain, time, and cost associated with biopsy and pathological analysis. Furthermore, when used in a confocal arrangement, Raman spectra can be obtained from localized regions of the tissue. Skin cancers are an ideal candidate for this emerging technology, due to their obvious accessibility and presentation at specific depths. However, most commercially available confocal Raman microspectrometers are large, rigid systems ill-suited for clinical application. We developed a bench-top confocal Raman microspectrometer using a portable external-cavity diode laser excitation source. This system was used to study several skin lesions in vitro. Results show the depth-resolved Raman spectra can diagnose in vitro skin lesions with 96% sensitivity, 88% specificity, and 86% pathological classification accuracy. Based on the success of this study, a portable Raman system with a handheld confocal microscope was developed for clinical application. Preliminary in vivo data show several distinct spectral differences between skin pathologies. Diagnostic algorithms are planned for this continuing study to assess the capability of Raman spectroscopy for clinical skin cancer diagnosis.

Silver Nanoscale Hexagonal Column Chips for Detecting Cell-free DNA and Circulating Nucleosomes in Cancer Patients.

PubMed

Ito, Hiroaki; Hasegawa, Katsuyuki; Hasegawa, Yuuki; Nishimaki, Tadashi; Hosomichi, Kazuyoshi; Kimura, Satoshi; Ohba, Motoi; Yao, Hiroshi; Onimaru, Manabu; Inoue, Ituro; Inoue, Haruhiro

2015-05-21

Blood tests, which are commonly used for cancer screening, generally have low sensitivity. Here, we developed a novel rapid and simple method to generate silver nanoscale hexagonal columns (NHCs) for use in surface-enhanced Raman scattering (SERS). We reported that the intensity of SERS spectra of clinical serum samples obtained from gastrointestinal cancer patients is was significantly higher than that of SERS spectra of clinical serum samples obtained from non-cancer patients. We estimated the combined constituents on silver NHCs by using a field emission-type scanning electron microscope, Raman microscopes, and a 3D laser scanning confocal microscope. We obtained the Raman scattering spectra of samples of physically fractured cells and clinical serum. No spectra were obtained for chemically lysed cultured cells and DNA, RNA, and protein extracted from cultured cells. We believe that our method, which uses SERS with silver NHCs to detect circulating nucleosomes bound by methylated cell-free DNA, may be successfully implemented in blood tests for cancer screening.

FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular conformational analysis of 2,5-di-tert-butyl-hydroquinone

NASA Astrophysics Data System (ADS)

Subramanian, N.; Sundaraganesan, N.; Dereli, Ö.; Türkkan, E.

2011-12-01

The purpose of finding conformer among six different possible conformers of 2,5-di-tert-butyl-hydroquinone (DTBHQ), its equilibrium geometry and harmonic wavenumbers were calculated by the B3LYP/6-31G(d,p) method. The infrared and Raman spectra of DTBHQ were recorded in the region 400-4000 cm -1 and 50-3500 cm -1, respectively. In addition, the IR spectra in CCl 4 at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers were compared with the IR and Raman experimental data. Computational calculations at B3LYP level with two different basis sets 6-31G(d,p) and 6-311++G(d,p) are also employed in the study of the possible conformer of DTBHQ. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA 4 program. The general agreement between the observed and calculated frequencies was established.

Molecular structure, natural bond analysis, vibrational and electronic spectra, surface enhanced Raman scattering and Mulliken atomic charges of the normal modes of [Mn(DDTC)2] complex.

PubMed

Téllez S, Claudio A; Costa, Anilton C; Mondragón, M A; Ferreira, Glaucio B; Versiane, O; Rangel, J L; Lima, G Müller; Martin, A A

2016-12-05

Theoretical and experimental bands have been assigned for the Fourier Transform Infrared and Raman spectra of the bis(diethyldithiocarbamate)Mn(II) complex, [Mn(DDTC)2]. The calculations have been based on the DFT/B3LYP method, second derivative spectra and band deconvolution analysis. The UV-vis experimental spectra were measured in acetonitrile solution, and the calculated electronic spectrum was obtained using the TD/B3LYP method with 6-311G(d, p) basis set for all atoms. Charge transfer bands and those d-d spin forbidden were assigned in the UV-vis spectrum. The natural bond orbital analysis was carried out using the DFT/B3LYP method and the Mn(II) hybridization leading to the planar geometry of the framework was discussed. Surface enhanced Raman scattering (SERS) was also performed. Mulliken charges of the normal modes were obtained and related to the SERS enhanced bands. Copyright © 2016 Elsevier B.V. All rights reserved.

Resonance Raman spectra of organic molecules absorbed on inorganic semiconducting surfaces: Contribution from both localized intramolecular excitation and intermolecular charge transfer excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, ChuanXiang; Zhao, Yi, E-mail: yizhao@xmu.edu.cn, E-mail: liangwz@xmu.edu.cn; Liang, WanZhen, E-mail: yizhao@xmu.edu.cn, E-mail: liangwz@xmu.edu.cn

2015-10-21

The time-dependent correlation function approach for the calculations of absorption and resonance Raman spectra (RRS) of organic molecules absorbed on semiconductor surfaces [Y. Zhao and W. Z. Liang, J. Chem. Phys. 135, 044108 (2011)] is extended to include the contribution of the intermolecular charge transfer (CT) excitation from the absorbers to the semiconducting nanoparticles. The results demonstrate that the bidirectionally interfacial CT significantly modifies the spectral line shapes. Although the intermolecular CT excitation makes the absorption spectra red shift slightly, it essentially changes the relative intensities of mode-specific RRS and causes the oscillation behavior of surface enhanced Raman spectra withmore » respect to interfacial electronic couplings. Furthermore, the constructive and destructive interferences of RRS from the localized molecular excitation and CT excitation are observed with respect to the electronic coupling and the bottom position of conductor band. The interferences are determined by both excitation pathways and bidirectionally interfacial CT.« less

Gain measurements in stimulated rotational Raman scattering in para hydrogen

NASA Astrophysics Data System (ADS)

Corat, E. J.; Airoldi, V. J. T.; Scolari, S. L.; Ghizoni, C. C.

1986-06-01

The dependence on CO2-laser pump energy of the output Stokes radiation obtained through stimulated rotational Raman scattering in parahydrogen is studied experimentally. The effective plane-wave gain for this process was determined as a function of the scattered wavelength by using a theoretical expression for the scattered pulse energy. Experimental values for the gain follow an inverse-wavelength law and are in close agreement with theory.

Dynamic surface-enhanced Raman spectroscopy and Chemometric methods for fast detection and intelligent identification of methamphetamine and 3, 4-Methylenedioxy methamphetamine in human urine

NASA Astrophysics Data System (ADS)

Weng, Shizhuang; Dong, Ronglu; Zhu, Zede; Zhang, Dongyan; Zhao, Jinling; Huang, Linsheng; Liang, Dong

2018-01-01

Conventional Surface-Enhanced Raman Spectroscopy (SERS) for fast detection of drugs in urine on the portable Raman spectrometer remains challenges because of low sensitivity and unreliable Raman signal, and spectra process with manual intervention. Here, we develop a novel detection method of drugs in urine using chemometric methods and dynamic SERS (D-SERS) with mPEG-SH coated gold nanorods (GNRs). D-SERS combined with the uniform GNRs can obtain giant enhancement, and the signal is also of high reproducibility. On the basis of the above advantages, we obtained the spectra of urine, urine with methamphetamine (MAMP), urine with 3, 4-Methylenedioxy Methamphetamine (MDMA) using D-SERS. Simultaneously, some chemometric methods were introduced for the intelligent and automatic analysis of spectra. Firstly, the spectra at the critical state were selected through using K-means. Then, the spectra were proposed by random forest (RF) with feature selection and principal component analysis (PCA) to develop the recognition model. And the identification accuracy of model were 100%, 98.7% and 96.7%, respectively. To validate the effect in practical issue further, the drug abusers'urine samples with 0.4, 3, 30 ppm MAMP were detected using D-SERS and identified by the classification model. The high recognition accuracy of > 92.0% can meet the demand of practical application. Additionally, the parameter optimization of RF classification model was simple. Compared with the general laboratory method, the detection process of urine's spectra using D-SERS only need 2 mins and 2 μL samples volume, and the identification of spectra based on chemometric methods can be finish in seconds. It is verified that the proposed approach can provide the accurate, convenient and rapid detection of drugs in urine.

A Comparison of the Raman Spectra and Crystal Chemistry of Norbergite and Clinohumite at High Pressure

NASA Astrophysics Data System (ADS)

Pease, A. M.; Gramsch, S. A.

2017-12-01

Humite group minerals n(Mg.Fe)2SiO4 - (Mg,Fe)(OH)2 have been suggested as possible candidates for water storage and transport in the mantle, and clinohumite in particular has been proposed as the source of ilmenite lamellae in Alpine ultrahigh pressure metamorphic terranes via its decomposition at high pressure and temperature. In this study, a comparison is made between the Raman spectra of norbergite (n = 1) and clinohumite (n = 4) up to 15 GPa to correlate the structural and vibrational properties of these two members of the group. All observed vibrational modes in the Raman spectra of both minerals increase in frequency with pressure, although the change in frequencies with pressure is much steeper in norbergite than for clinohumite. In norbergite, antisymmetric stretching modes of the SiO4 tetrahedra merge, but no such merging of modes occurs in clinohumite. In addition, the intensity of the antisymmetric stretching mode for clinohumite decreases dramatically in pressure compared to the intensity of the symmetric stretching mode. In the spectra of norbergite, these two modes retain their relative intensities with increasing pressure. The most striking difference between the spectra of norbergite and clinohumite is in the deformation modes of the brucite layer, which within the clinohumite structure retain their intensities with increasing pressure, while these modes are not observed in the spectra of norbergite. The nature of the Raman spectra and their evolution with pressure are correlated with the structural properties of the two minerals in terms of the interactions between olivine and brucite layers and the crystal chemistry of the humite group minerals.

Human brain cancer studied by resonance Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zhou, Yan; Liu, Cheng-Hui; Sun, Yi; Pu, Yang; Boydston-White, Susie; Liu, Yulong; Alfano, Robert R.

2012-11-01

The resonance Raman (RR) spectra of six types of human brain tissues are examined using a confocal micro-Raman system with 532-nm excitation in vitro. Forty-three RR spectra from seven subjects are investigated. The spectral peaks from malignant meningioma, stage III (cancer), benign meningioma (benign), normal meningeal tissues (normal), glioblastoma multiforme grade IV (cancer), acoustic neuroma (benign), and pituitary adenoma (benign) are analyzed. Using a 532-nm excitation, the resonance-enhanced peak at 1548 cm-1 (amide II) is observed in all of the tissue specimens, but is not observed in the spectra collected using the nonresonance Raman system. An increase in the intensity ratio of 1587 to 1605 cm-1 is observed in the RR spectra collected from meningeal cancer tissue as compared with the spectra collected from the benign and normal meningeal tissue. The peak around 1732 cm-1 attributed to fatty acids (lipids) are diminished in the spectra collected from the meningeal cancer tumors as compared with the spectra from normal and benign tissues. The characteristic band of spectral peaks observed between 2800 and 3100 cm-1 are attributed to the vibrations of methyl (-CH3) and methylene (-CH2-) groups. The ratio of the intensities of the spectral peaks of 2935 to 2880 cm-1 from the meningeal cancer tissues is found to be lower in comparison with that of the spectral peaks from normal, and benign tissues, which may be used as a distinct marker for distinguishing cancerous tissues from normal meningeal tissues. The statistical methods of principal component analysis and the support vector machine are used to analyze the RR spectral data collected from meningeal tissues, yielding a diagnostic sensitivity of 90.9% and specificity of 100% when two principal components are used.

Detection of Lipitor counterfeits: a comparison of NIR and Raman spectroscopy in combination with chemometrics.

PubMed

de Peinder, P; Vredenbregt, M J; Visser, T; de Kaste, D

2008-08-05

Research has been carried on the feasibility of near infrared (NIR) and Raman spectroscopy as rapid screening methods to discriminate between genuine and counterfeits of the cholesterol-lowering medicine Lipitor. Classification, based on partial least squares discriminant analysis (PLS-DA) models, appears to be successful for both spectroscopic techniques, irrespective of whether atorvastatine or lovastatine has been used as the active pharmaceutical ingredient (API). The discriminative power of the NIR model, in particular, largely relies on the spectral differences of the tablet matrix. This is due to the relative large sample volume that is probed with NIR and the strong spectroscopic activity of the excipients. PLS-DA models based on NIR or Raman spectra can also be applied to distinguish between atorvastatine and lovastatine as the API used in the counterfeits tested in this study. A disadvantage of Raman microscopy for this type of analysis is that it is primarily a surface technique. As a consequence spectra of the coating and the tablet core might differ. Besides, spectra may change with the position of the laser in case the sample is inhomogeneous. However, the robustness of the PLS-DA models turned out to be sufficiently large to allow a reliable discrimination. Principal component analysis (PCA) of the spectra revealed that the conditions, at which tablets have been stored, affect the NIR data. This effect is attributed to the adsorption of water from the atmosphere after unpacking from the blister. It implies that storage conditions should be taken into account when the NIR technique is used for discriminating purposes. However, in this study both models based on NIR spectra and Raman data enabled reliable discrimination between genuine and counterfeited Lipitor tablets, regardless of their storage conditions.

Novel approach of signal normalization for depth profile of cultural heritage materials

NASA Astrophysics Data System (ADS)

Syvilay, D.; Detalle, V.; Wilkie-Chancellier, N.; Texier, A.; Martinez, L.; Serfaty, S.

2017-01-01

The investigation of cultural heritage materials is always complex and specific because unique. Materials are most often heterogeneous and organized in several layers such as mural paintings or corrosion products. The characterization of a complete artwork's stratigraphy is actually one of the questions of science conservation. Indeed, the knowledge of these layers allows completing the history of the work of art and a better understanding of alteration processes in order to set up an appropriate conservation action. The LIBS technique has been employed to study the stratigraphy of an artwork thanks to the ablation laser. However, as we know, atomic information could be insufficient to characterize two materials composed by the same based elements. Therefore, an additional molecular analysis, like Raman spectroscopy; is sometimes necessary for a better identification of the material in particular for organic coatings in cultural heritage. We suggest in this study to use Standard Normal Variate (SNV) as a common normalization for different kinds of spectra (LIBS and Raman spectroscopy) combined with a 3D colour representation for stratigraphic identification of the different layers composing the complex material from artwork. So in this investigation, the SNV method will be applied on LIBS and Raman spectra but also on baseline Raman spectra often considering as nuisance. The aim of this study is to demonstrate the versatility of SNV applied on varied spectra like LIBS, Raman spectra as well as the luminescence background. This original work considers the SNV with a 3D colour representation as a probable new perspective for an easy recognition of a structure layered with a direct overview of the depth profile of the artwork.

Comparison of macro and micro Raman measurement for reliable quantitative analysis of pharmaceutical polymorphs.

PubMed

Paiva, Eduardo M; da Silva, Vitor H; Poppi, Ronei J; Pereira, Claudete F; Rohwedder, Jarbas J R

2018-05-12

This work reports on the use of micro- and macro-Raman measurements for quantification of mebendazole (MBZ) polymorphs A, B, and C in mixtures. Three Raman spectrophotometers were studied with a laser spot size of 3, 80 and 100 μm and spectral resolutions of 3.9, 9 and 4 cm -1 , respectively. The samples studied were ternary mixtures varying the MBZ polymorphs A and C from 0 to 100% and polymorph B from 0 to 30%. Partial Least Squares (PLS) regression models were developed using the pre-processing spectra (2nd derivative) of the ternary mixtures. The best performance was obtained when the macro-Raman configuration was applied, obtaining RMSEP values of 1.68%, 1.24% and 2.03% w/w for polymorphs A, B, and C, respectively. In general, micro-Raman presented worst results for MBZ polymorphs prediction because the spectra obtained with this configuration does not represent the bulk proportion of mixtures, which have different particle morphologies and sizes. In addition, the influence of these particle features on micro-Raman measurements was also studied. Finally, the results demonstrated that reliable analytical quantifying of MBZ polymorphs can be reached using a laser with wider area illuminated, thus enabling acquisition of more reproductive and representative spectra of the mixtures. Copyright © 2018 Elsevier B.V. All rights reserved.

In vivo diagnosis of cervical precancer using Raman spectroscopy and genetic algorithm techniques.

PubMed

Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J H; Ilancheran, A; Huang, Zhiwei

2011-10-21

This study aimed to evaluate the clinical utility of applying near-infrared (NIR) Raman spectroscopy and genetic algorithm-partial least squares-discriminant analysis (GA-PLS-DA) to identify biomolecular changes of cervical tissues associated with dysplastic transformation during colposcopic examination. A total of 105 in vivo Raman spectra were measured from 57 cervical sites (35 normal and 22 precancer sites) of 29 patients recruited, in which 65 spectra were from normal sites, while 40 spectra were from cervical precancerous lesions (i.e., 7 low-grade CIN and 33 high-grade CIN). The GA feature selection technique incorporated with PLS was utilized to study the significant biochemical Raman bands for differentiation between normal and precancer cervical tissues. The GA-PLS-DA algorithm with double cross-validation (dCV) identified seven diagnostically significant Raman bands in the ranges of 925-935, 979-999, 1080-1090, 1240-1260, 1320-1340, 1400-1420, and 1625-1645 cm(-1) related to proteins, nucleic acids and lipids in tissue, and yielded a diagnostic accuracy of 82.9% (sensitivity of 72.5% (29/40) and specificity of 89.2% (58/65)) for precancer detection. The results of this exploratory study suggest that Raman spectroscopy in conjunction with GA-PLS-DA and dCV methods has the potential to provide clinically significant discrimination between normal and precancer cervical tissues at the molecular level.

Structure, spectra and antioxidant action of ascorbic acid studied by density functional theory, Raman spectroscopic and nuclear magnetic resonance techniques.

PubMed

Singh, Gurpreet; Mohanty, B P; Saini, G S S

2016-02-15

Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet-visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet-visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide. Copyright © 2015 Elsevier B.V. All rights reserved.

A multimode vibronic treatment of absorption, resonance Raman, and hyper-Rayleigh scattering of excitonically coupled molecular dimers

NASA Astrophysics Data System (ADS)

Myers Kelley, Anne

2003-08-01

The linear absorption spectra, resonance Raman excitation profiles and depolarization dispersion curves, and hyper-Rayleigh scattering profiles are calculated for excitonically coupled homodimers of a model electron donor-acceptor "push-pull" conjugated chromophore as a function of dimer geometry. The vibronic eigenstates of the dimer are calculated by diagonalizing the matrix of transition dipole couplings among the vibronic transitions of the constituent monomers. The absorption spectra show the usual red- or blueshifted transitions for J-type or H-type dimers, respectively. When the electronic coupling is large compared with the vibronic width of the monomer spectrum, the dimer absorption spectra exhibit simple Franck-Condon progressions having reduced vibronic intensities compared with the monomer, and the resonance Raman excitation profiles are shifted but otherwise only weakly perturbed. When the coupling is comparable to the vibronic width, the H-dimer absorption spectra exhibit irregular vibronic frequency spacings and intensity patterns and the effects on the Raman excitation profiles are larger. There is strong dispersion in the Raman depolarization ratios for dimer geometries in which both transitions carry oscillator strength. The first hyperpolarizabilities are somewhat enhanced in J-dimers and considerably reduced in H-dimers. These effects on the molecular β will amplify the effects of dimerization on the ground-state dipole moment in electro-optic materials formed from chromophore-doped polymers that must be electric field poled to obtain the net alignment needed for a macroscopic χ(2).

A structural and vibrational study on the first condensed borosulfate K5[B(SO4)4] by using the FTIR-Raman spectra and DFT calculations

NASA Astrophysics Data System (ADS)

Höppe, Henning Alfred; Kazmierczak, Karolina; Romano, Elida; Brandán, Silvia Antonia

2013-04-01

The first borosulfate, K5[B(SO4)4] (recently synthesized by Henning A. Höppe, Karolina Kazmierczak, Michael Daub, Katharina Förg, Franziska Fuchs, Harald Hillebrecht, 2012) was characterized by infrared and Raman spectroscopies. Density functional theory (DFT) calculations were used to study the structure and vibrational properties of the compound. Employing the B3P86 and B3LYP levels of theory, the molecular structures of the compound were theoretically determined in gas phase and the harmonic vibrational frequencies were evaluated at the same levels. The calculated harmonic vibrational frequencies for the borosulfate compound are consistent with the experimental IR and Raman spectra. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by sulfate groups of this compound as ligands with C3v and C2v symmetries. A complete assignment of all the observed bands in the IR and Raman spectra for K5[B(SO4)4] was performed. Here, the infrared and Raman spectra of K5[B(SO4)4] were interpreted, discussed and completely assigned. The nature of the Ksbnd O, Ksbnd S, Bsbnd O, and Ssbnd O bonds and the topological properties of the compound were investigated and analyzed by means of Natural Bond Order (NBO) and Bader's Atoms in Molecules theory (AIM), respectively.

Improved Savitzky-Golay-method-based fluorescence subtraction algorithm for rapid recovery of Raman spectra.

PubMed

Chen, Kun; Zhang, Hongyuan; Wei, Haoyun; Li, Yan

2014-08-20

In this paper, we propose an improved subtraction algorithm for rapid recovery of Raman spectra that can substantially reduce the computation time. This algorithm is based on an improved Savitzky-Golay (SG) iterative smoothing method, which involves two key novel approaches: (a) the use of the Gauss-Seidel method and (b) the introduction of a relaxation factor into the iterative procedure. By applying a novel successive relaxation (SG-SR) iterative method to the relaxation factor, additional improvement in the convergence speed over the standard Savitzky-Golay procedure is realized. The proposed improved algorithm (the RIA-SG-SR algorithm), which uses SG-SR-based iteration instead of Savitzky-Golay iteration, has been optimized and validated with a mathematically simulated Raman spectrum, as well as experimentally measured Raman spectra from non-biological and biological samples. The method results in a significant reduction in computing cost while yielding consistent rejection of fluorescence and noise for spectra with low signal-to-fluorescence ratios and varied baselines. In the simulation, RIA-SG-SR achieved 1 order of magnitude improvement in iteration number and 2 orders of magnitude improvement in computation time compared with the range-independent background-subtraction algorithm (RIA). Furthermore the computation time of the experimentally measured raw Raman spectrum processing from skin tissue decreased from 6.72 to 0.094 s. In general, the processing of the SG-SR method can be conducted within dozens of milliseconds, which can provide a real-time procedure in practical situations.

In vivo Raman spectroscopy of cervix cancers

NASA Astrophysics Data System (ADS)

Rubina, S.; Sathe, Priyanka; Dora, Tapas Kumar; Chopra, Supriya; Maheshwari, Amita; Krishna, C. Murali

2014-03-01

Cervix-cancer is the third most common female cancer worldwide. It is the leading cancer among Indian females with more than million new diagnosed cases and 50% mortality, annually. The high mortality rates can be attributed to late diagnosis. Efficacy of Raman spectroscopy in classification of normal and pathological conditions in cervix cancers on diverse populations has already been demonstrated. Our earlier ex vivo studies have shown the feasibility of classifying normal and cancer cervix tissues as well as responders/non-responders to Concurrent chemoradiotherapy (CCRT). The present study was carried out to explore feasibility of in vivo Raman spectroscopic methods in classifying normal and cancerous conditions in Indian population. A total of 182 normal and 132 tumor in vivo Raman spectra, from 63 subjects, were recorded using a fiberoptic probe coupled HE-785 spectrometer, under clinical supervision. Spectra were acquired for 5 s and averaged over 3 times at 80 mW laser power. Spectra of normal conditions suggest strong collagenous features and abundance of non-collagenous proteins and DNA in case of tumors. Preprocessed spectra were subjected to Principal Component-Linear Discrimination Analysis (PCLDA) followed by leave-one-out-cross-validation. Classification efficiency of ~96.7% and 100% for normal and cancerous conditions respectively, were observed. Findings of the study corroborates earlier studies and suggest applicability of Raman spectroscopic methods in combination with appropriate multivariate tool for objective, noninvasive and rapid diagnosis of cervical cancers in Indian population. In view of encouraging results, extensive validation studies will be undertaken to confirm the findings.

Detection of carbon-fluorine bonds in organofluorine compounds by Raman spectroscopy using a copper-vapor laser

NASA Astrophysics Data System (ADS)

Sharts, Clay M.; Gorelik, Vladimir S.; Agoltsov, A. M.; Zlobina, Ludmila I.; Sharts, Olga N.

1999-02-01

The Raman spectra of fluoro-organic compounds show specific emission bands for carbon-fluorine bonds in the range 500- 800 wave numbers (cm-1)). With very limited exceptions, biological materials do not contain carbon- fluorine bonds. Fluoro-organic compounds introduced into biological samples can be detected by a Raman emission signal. Normal mode C-F bond bands are observed: (1) at 710- 785 cm -1 for trifluoromethyl groups; (2) at 530-610 cm -1 for aromatic organofluorine bonds; (3) a range centered at 690 cm -1 for difluoromethylene groups. Specific examples of normal mode C-F bond emissions for organofluorine compounds containing trifluoromethyl groups are: 1-bromoperfluorooctane, 726 cm -1; perfluorodecanoic acid, 730 cm -1; triperfluoropropylamine, 750 cm -1; 1,3,5-tris- (trifluoromethyl)-benzene, 730 cm -1; Fluoxetine (Prozac) commercial powdered pill at 782 cm -1. Compounds containing aromatic C-F bonds are: hexafluorobenzene, 569 cm MIN1; pentafluoropyridine, 589 cm -1. Difluoromethylene groups: perfluorodecalin, 692 cm-1; perfluorocyclohexane, 691 cm -1. Raman spectra were observed with a standard single monochromator. The 510.8 nm light source was a copper-vapor laser operated at 3-10 watts with 10-12 nanosecond pulses at 10 kHz repetition rate. Detection was made with a time-gated photomultiplier tube. Resonance Raman spectra were also observed at 255.4 nm, using a frequency doubling crystal. Observed spectra were free of fluorescence with very sharp strong C-F lines.

Comparative matrix isolation infrared spectroscopy study of 1,3- and 1,4-diene monoterpenes (α-phellandrene and γ-terpinene).

PubMed

Marzec, K M; Reva, I; Fausto, R; Proniewicz, L M

2011-05-05

In the present work, γ-terpinene (a 1,4-diene derivative) and α-phellandrene (1,3-diene derivative) were isolated in cryogenic argon matrices and their structures, vibrational spectra, and photochemistries were characterized with the aid of FTIR spectroscopy and quantum chemical calculations performed at the DFT/B3LYP/6-311++G(d,p) level of approximation. The molecules bear one conformationally relevant internal rotation axis, corresponding to the rotation of the isopropyl group. The calculations provide evidence of three minima on the potential energy surfaces of the studied molecules, where the isopropyl group assumes the trans, gauche+, and gauche- conformations (T, G+, G-). The signatures of all these conformers were identified in the experimental matrix infrared spectra, with the T forms dominating, in agreement with the theoretical predicted abundances in gas phase at room temperature. In situ UV (λ > 200 nm) irradiation of matrix-isolated α-phellandrene led to its isomerization into an open-ring species. The photoproduct was found to exhibit the ZE configuration of its backbone, which to be formed from the reactant molecule does not require extensive structural rearrangements of both the reagent and matrix. γ-Terpinene was photostable when subjected to irradiation under the same experimental conditions. In addition, the liquid compounds at room temperature were also investigated by FTIR-ATR and FT-Raman spectroscopies.

Hydrostatic pressure and temperature effect on the Raman spectra of the molecular crystal 2-amine-1,3,4-thiadiazole

NASA Astrophysics Data System (ADS)

de Toledo, T. A.; da Costa, R. C.; Bento, R. R. F.; Pizani, P. S.

2018-03-01

The structural, thermal and vibrational properties of the molecular crystal 2-amine-1,3,4-thiadiazole (ATD) were investigated combining X-ray diffraction, infrared spectroscopy, Raman scattering (in solid and in solution) and thermal analysis as experimental techniques and first principle calculations based on density functional theory using PZ, BLYP in condensed-phase and B3LYP/cc-pVTZ in isolated molecule methods. The structural stability and phonon anharmonicity were also studied using Raman spectroscopy at different temperatures and hydrostatic pressures. A reasonable agreement was obtained between calculated and experimental results. The main difference between experimental and computed structural and vibrational spectra occurred in the intermolecular bond distance Nsbnd H⋯N and stretching modes of NH2. The vibrational spectra were interpreted and assigned based on group theory and functional group analysis assisted by theoretical results, which led to a more comprehensive knowledge about external and internal modes at different thermodynamic conditions. As temperature increases, it was observed the line-width increases and red-shifts, indicating a phonon anharmonicity without a temperature-induced phase transition in the range 10-413 K. However, ATD crystal undergoes a phase transition in the temperature range 413-475 K, as indicated by thermal analysis curve and Raman spectra. Furthermore, increasing pressure from ambient to 3.1 GPa, it was observed the splitting of the external Raman bands centered at 122 cm-1 (at 0.2 GPa), 112 cm-1 (1.1 GPa), 93 cm-1 (2.4 GPa) in two components as well as the appearance of new band near 50 cm-1 at 1.1 GPa, indicating a possible phase-transition. The blue-shift of the Raman bands was associated to anharmonicity of the interatomic potential caused by unit cell contraction.

Investigation of stratigraphic mapping in paintings using micro-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Karagiannis, Georgios Th.; Apostolidis, Georgios K.

2016-04-01

In this work, microRaman spectroscopy is used to investigate the stratigraphic mapping in paintings. The objective of mapping imaging is to segment the dataset, here spectra, into clusters each of which consisting spectra that have similar characteristics; hence, similar chemical composition. The spatial distribution of such clusters can be illustrated in pseudocolor images, in which each pixel of image is colored according to its cluster membership. Such mapping images convey information about the spatial distribution of the chemical substances in an object. Moreover, the laser light source that is used has excitation in 1064 nm, i.e., near infrared (NIR), allowing the penetration of the radiation in deeper layers. Thus, the mapping images that are produced by clustering the acquired spectra (specifying specific bands of Raman shifts) can provide stratigraphic information in the mapping images, i.e., images that convey information of the distribution of substances from deeper, as well. To cluster the spectra, unsupervised machine learning algorithms are applied, e.g., hierarchical clustering. Furthermore, the optical microscopy camera (×50), where the Raman probe (B and WTek iRaman EX) is plugged in, is attached to a computerized numerical control (CNC) system which is driven by a software that is specially developed for Raman mapping. This software except for the conventional CNC operation allows the user to parameterize the spectrometer and check each and every measurement to ensure proper acquisition. This facility is important in painting investigation because some materials are vulnerable to such specific parameterization that other materials demand. The technique is tested on a portable experimental overpainted icon of a known stratigraphy. Specifically, the under icon, i.e., the wavy hair of "Saint James", can be separated from upper icon, i.e., the halo of Mother of God in the "Descent of the Cross".

Structural study, NCA, FT-IR, FT-Raman spectral investigations, NBO analysis, thermodynamic functions of N-acetyl-l-phenylalanine.

PubMed

Raja, B; Balachandran, V; Revathi, B

2015-03-05

The FT-IR and FT-Raman spectra of N-acetyl-l-phenylalanine were recorded and analyzed. Natural bond orbital analysis has been carried out for various intramolecular interactions that are responsible for the stabilization of the molecule. HOMO-LUMO energy gap has been computed with the help of density functional theory. The statistical thermodynamic functions (heat capacity, entropy, vibrational partition function and Gibbs energy) were obtained for the range of temperature 100-1000K. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the experimental and theoretical spectra values provides important information about the ability of the computational method to describe the vibrational modes. Copyright © 2014 Elsevier B.V. All rights reserved.

Raman and infrared spectra and theoretical calculations of dipicolinic acid, dinicotinic acid, and their dianions

NASA Astrophysics Data System (ADS)

McCann, Kathleen; Laane, Jaan

2008-11-01

The Raman and infrared spectra of dipicolinic acid (DPA) and dinicotinic acid (DNic) and their salts (CaDPA, Na 2DPA, and CaDNic) have been recorded and the spectra have been assigned. Ab initio and DFT calculations were carried out to predict the structures and vibrational spectra and were compared to the experimental results. Because of extensive intermolecular hydrogen bonding in the crystals of these molecules, the calculated structures and spectra for the individual molecules agree only moderately well with the experimental values. Theoretical calculations were also carried out for DPA dimers and DPA·2H 2O to better understand the intermolecular interactions. The spectra do show that DPA and its calcium salt, which are present in anthrax spores, can be distinguished from the very similar DNic and CaDNic.