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

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

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.

Application of wavelet packet transform to compressing Raman spectra data

NASA Astrophysics Data System (ADS)

Chen, Chen; Peng, Fei; Cheng, Qinghua; Xu, Dahai

2008-12-01

Abstract The Wavelet transform has been established with the Fourier transform as a data-processing method in analytical fields. The main fields of application are related to de-noising, compression, variable reduction, and signal suppression. Raman spectroscopy (RS) is characterized by the frequency excursion that can show the information of molecule. Every substance has its own feature Raman spectroscopy, which can analyze the structure, components, concentrations and some other properties of samples easily. RS is a powerful analytical tool for detection and identification. There are many databases of RS. But the data of Raman spectrum needs large space to storing and long time to searching. In this paper, Wavelet packet is chosen to compress Raman spectra data of some benzene series. The obtained results show that the energy retained is as high as 99.9% after compression, while the percentage for number of zeros is 87.50%. It was concluded that the Wavelet packet has significance in compressing the RS data.

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.

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.

Infrared and Raman spectra of triacetoxyvinylsilane, aqueous sol-gel and xerogel

NASA Astrophysics Data System (ADS)

Li, Ying-Sing; Ba, Abdul; Mahmood, Maleeha S.

2009-04-01

Triacetoxyvinylsilane (TAVS) has been used as a precursor to prepare sol-gel under aqueous conditions. The sol-gel product has been applied for the surface treatment of aluminum. Infrared and Raman spectra have been collected for TAVS and for TAVS sol-gel, xerogel and sol-gel-coated aluminum. Vibrational analyses have been suggested for the recorded spectra based essentially on the group frequencies and the spectral variation with the change of the sol-gel product states and the vibrational assignments of similar molecules. From the recorded infrared and Raman spectra of the sol-gel and xerogel, it is found that the sol-gel produced in the process with TAVS is essentially the same as that prepared from vinyltriethoxysilane. Thermo-gravimetric analysis (TGA) of TAVS xerogel has been conducted, and an explanation has been given in coordination with the results obtained from IR spectroscopic study of the xerogels cured at different temperatures. The study has demonstrated the thermal effect on the condensation of the sol-gel process and on the vinyl decomposition of TAVS xerogel.

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.

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.

[Raman spectra of monkey cerebral cortex tissue].

PubMed

Zhu, Ji-chun; Guo, Jian-yu; Cai, Wei-ying; Wang, Zu-geng; Sun, Zhen-rong

2010-01-01

Monkey cerebral cortex, an important part in the brain to control action and thought activities, is mainly composed of grey matter and nerve cell. In the present paper, the in situ Raman spectra of the cerebral cortex of the birth, teenage and aged monkeys were achieved for the first time. The results show that the Raman spectra for the different age monkey cerebral cortex exhibit most obvious changes in the regions of 1000-1400 and 2800-3000 cm(-1). With monkey growing up, the relative intensities of the Raman bands at 1313 and 2885 cm(-1) mainly assigned to CH2 chain vibrational mode of lipid become stronger and stronger whereas the relative intensities of the Raman bands at 1338 and 2932 cm(-1) mainly assigned to CH3 chain vibrational mode of protein become weaker and weaker. In addition, the two new Raman bands at 1296 and 2850 cm(-1) are only observed in the aged monkey cerebral cortex, therefore, the two bands can be considered as a character or "marker" to differentiate the caducity degree with monkey growth In order to further explore the changes, the relative intensity ratios of the Raman band at 1313 cm(-1) to that at 1338 cm(-1) and the Raman band at 2885 cm(-1) to that at 2 932 cm(-1), I1313/I1338 and I2885/I2932, which are the lipid-to-protein ratios, are introduced to denote the degree of the lipid content. The results show that the relative intensity ratios increase significantly with monkey growth, namely, the lipid content in the cerebral cortex increases greatly with monkey growth. So, the authors can deduce that the overmuch lipid is an important cause to induce the caducity. Therefore, the results will be a powerful assistance and valuable parameter to study the order of life growth and diagnose diseases.

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.

[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.

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.

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.

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

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.

Strong surface enhanced Raman scattering from gold nanoarrays obtained by direct laser writing

NASA Astrophysics Data System (ADS)

Ivanov, V. G.; Todorov, N. D.; Petrov, L. S.; Ritacco, T.; Giocondo, M.; Vlakhov, E. S.

2016-10-01

We report for surface enhanced Raman scattering (SERS) from arrays of gold nanoparticles produced by 2-photons photo-reduction of the metallic precursor (HAuCl4) hosted in a Poly-Vinyl Alcohol (PVA) matrix, on glass substrates. Samples with the same pattern but featuring different nanoparticles size and density were obtained by varying the writing laser power and scanning speed. The Raman spectra were recorded from samples immersed in a solution of rhodamine-6G (R6G), as well as, after exposure of the samples in xylene. SERS enhancement factors of up to ∼104 were obtained for both analytes. The measurements show that the SERS enhancement is maximized on golden strips produced at higher writing laser power and lower scanning speed, where closer nanoparticles packing is obtained..

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.

First-principles Raman Spectra of Lead Titanate with Pressure

NASA Astrophysics Data System (ADS)

Schad, A.; Ganesh, P.; Cohen, R. E.; Ahart, M.

2010-03-01

PbTiO3 displays[1,2] a morphotropic phase boundary (MPB) under pressure at which electromechanical properties are maximal. Previously only complex solid-solutions were thought to exhibit such a boundary. To aid in the experimental study of the MPB region, we compute Raman scattering spectra of different phases of PbTiO3 with pressure using a DFT based first-principles approach and Density Functional Perturbation Theory (DFPT) [3]. The computed intensities and shifts with pressure agree very well with the experimental data measured on powder samples. Computations further allow comparison of Raman spectra and shifts in energetically competing phases raising the possibility of using calculations for experimental calibration of Raman spectra at any pressure. The results substantiate previous claims of a low-temperature monoclinic phase at the MPB at approximately 10 GPa in PbTiO3 as well as refute the possibility of an I4cm phase at higher pressures as suggested by other groups [4]. [1] Z. Wu and R. E. Cohen, Phys. Rev. Lett. 95, 037601 (2005), [2] M. Ahart et.al., Nature 451, 545 (2008), [3] P. Hermet et.al., J. Phys.:Condens. Matter 21, 215901 (2009) [4] P.E. Janolin et.al., Phys. Rev. Lett. 101, 237601 (2008).

[A new peak detection algorithm of Raman spectra].

PubMed

Jiang, Cheng-Zhi; Sun, Qiang; Liu, Ying; Liang, Jing-Qiu; An, Yan; Liu, Bing

2014-01-01

The authors proposed a new Raman peak recognition method named bi-scale correlation algorithm. The algorithm uses the combination of the correlation coefficient and the local signal-to-noise ratio under two scales to achieve Raman peak identification. We compared the performance of the proposed algorithm with that of the traditional continuous wavelet transform method through MATLAB, and then tested the algorithm with real Raman spectra. The results show that the average time for identifying a Raman spectrum is 0.51 s with the algorithm, while it is 0.71 s with the continuous wavelet transform. When the signal-to-noise ratio of Raman peak is greater than or equal to 6 (modern Raman spectrometers feature an excellent signal-to-noise ratio), the recognition accuracy with the algorithm is higher than 99%, while it is less than 84% with the continuous wavelet transform method. The mean and the standard deviations of the peak position identification error of the algorithm are both less than that of the continuous wavelet transform method. Simulation analysis and experimental verification prove that the new algorithm possesses the following advantages: no needs of human intervention, no needs of de-noising and background removal operation, higher recognition speed and higher recognition accuracy. The proposed algorithm is operable in Raman peak identification.

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

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.

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.

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.

FT-IR and FT-Raman spectra of cimetidine and its metallocomplexes

NASA Astrophysics Data System (ADS)

Barańska, M.; Proniewicz, L. M.

1999-11-01

We present vibrational spectra of three stable, well-reproducible, polymorphic forms of cimetidine ( cim), a drug which is a powerful histamine H 2-receptor antagonist used in the treatment of peptic ulcer and the Zollinger-Ellison syndrome. Assignments of Raman and IR bands are made using semiempirical methods: MNDO, AM1 and PM3. We also describe the synthesis of Me( cim) 2(ClO 4) 2, where Me=Cu(II), Cd(II), Co(II) and Ni(II), and present their vibrational data. We show that the obtained complexes are isostructural, however a metal ion that occupies a center of octahedral unit introduces some distortions that can be seen in the spectra. We also make tentative assignment of metal-ligand stretching modes observed in low frequency range.

Anharmonic effects in IR, Raman, and Raman optical activity spectra of alanine and proline zwitterions.

PubMed

Danecek, Petr; Kapitán, Josef; Baumruk, Vladimír; Bednárová, Lucie; Kopecký, Vladimír; Bour, Petr

2007-06-14

The difference spectroscopy of the Raman optical activity (ROA) provides extended information about molecular structure. However, interpretation of the spectra is based on complex and often inaccurate simulations. Previously, the authors attempted to make the calculations more robust by including the solvent and exploring the role of molecular flexibility for alanine and proline zwitterions. In the current study, they analyze the IR, Raman, and ROA spectra of these molecules with the emphasis on the force field modeling. Vibrational harmonic frequencies obtained with 25 ab initio methods are compared to experimental band positions. The role of anharmonic terms in the potential and intensity tensors is also systematically explored using the vibrational self-consistent field, vibrational configuration interaction (VCI), and degeneracy-corrected perturbation calculations. The harmonic approach appeared satisfactory for most of the lower-wavelength (200-1800 cm(-1)) vibrations. Modern generalized gradient approximation and hybrid density functionals, such as the common B3LYP method, provided a very good statistical agreement with the experiment. Although the inclusion of the anharmonic corrections still did not lead to complete agreement between the simulations and the experiment, occasional enhancements were achieved across the entire region of wave numbers. Not only the transitional frequencies of the C-H stretching modes were significantly improved but also Raman and ROA spectral profiles including N-H and C-H lower-frequency bending modes were more realistic after application of the VCI correction. A limited Boltzmann averaging for the lowest-frequency modes that could not be included directly in the anharmonic calculus provided a realistic inhomogeneous band broadening. The anharmonic parts of the intensity tensors (second dipole and polarizability derivatives) were found less important for the entire spectral profiles than the force field anharmonicities (third

Anharmonic effects in IR, Raman, and Raman optical activity spectra of alanine and proline zwitterions

NASA Astrophysics Data System (ADS)

Daněček, Petr; Kapitán, Josef; Baumruk, Vladimír; Bednárová, Lucie; Kopecký, Vladimír; Bouř, Petr

2007-06-01

The difference spectroscopy of the Raman optical activity (ROA) provides extended information about molecular structure. However, interpretation of the spectra is based on complex and often inaccurate simulations. Previously, the authors attempted to make the calculations more robust by including the solvent and exploring the role of molecular flexibility for alanine and proline zwitterions. In the current study, they analyze the IR, Raman, and ROA spectra of these molecules with the emphasis on the force field modeling. Vibrational harmonic frequencies obtained with 25 ab initio methods are compared to experimental band positions. The role of anharmonic terms in the potential and intensity tensors is also systematically explored using the vibrational self-consistent field, vibrational configuration interaction (VCI), and degeneracy-corrected perturbation calculations. The harmonic approach appeared satisfactory for most of the lower-wavelength (200-1800cm-1) vibrations. Modern generalized gradient approximation and hybrid density functionals, such as the common B3LYP method, provided a very good statistical agreement with the experiment. Although the inclusion of the anharmonic corrections still did not lead to complete agreement between the simulations and the experiment, occasional enhancements were achieved across the entire region of wave numbers. Not only the transitional frequencies of the C-H stretching modes were significantly improved but also Raman and ROA spectral profiles including N-H and C-H lower-frequency bending modes were more realistic after application of the VCI correction. A limited Boltzmann averaging for the lowest-frequency modes that could not be included directly in the anharmonic calculus provided a realistic inhomogeneous band broadening. The anharmonic parts of the intensity tensors (second dipole and polarizability derivatives) were found less important for the entire spectral profiles than the force field anharmonicities (third and

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.

Structural, optoelectronic, infrared and Raman spectra of orthorhombic SrSnO{sub 3} from DFT calculations

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

Moreira, E.; Henriques, J.M.; Azevedo, D.L.

2011-04-15

Orthorhombic SrSnO{sub 3} was investigated using density functional theory (DFT) considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The electronic band structure, density of states, complex dielectric function, optical absorption, and the infrared and Raman spectra were computed. Calculated lattice parameters are close to the experimental measurements, and an indirect band gap E(S{yields}{Gamma})=1.97eV (2.27 eV) was obtained within the GGA (LDA) level of calculation. Effective masses for holes and electrons were estimated, being very anisotropic in comparison with similar results for orthorhombic CaSnO{sub 3}. The complex dielectric function and the optical absorption of SrSnO{sub 3}more » were shown to be sensitive to the plane of polarization of the incident light. The infrared spectrum between 100 and 600 cm{sup -1} was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum of orthorhombic SrSnO{sub 3} was achieved. -- Graphical abstract: Orthorhombic SrSnO{sub 3}: a view of the unit cell (left) and plots showing the calculated and experimental Raman spectra (right). Display Omitted Research highlights: {yields} We have performed DFT calculations on orthorhombic SrSnO{sub 3} crystals, obtaining their structural, electronical and optical properties. {yields} An indirect band gap was obtained, and anisotropic effective masses were found for both electrons and holes. {yields} The complex dielectric function and the optical absorption of SrSnO{sub 3} were shown to be very sensitive to the plane of polarization of the incident light. {yields} The infrared spectrum between 100 and 600 cm{sup -1} was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum was achieved.« less

Investigation of various factors influencing Raman spectra interpretation with the use of likelihood ratio approach.

PubMed

Michalska, Aleksandra; Martyna, Agnieszka; Zadora, Grzegorz

2018-01-01

The main aim of this study was to verify whether selected analytical parameters may affect solving the comparison problem of Raman spectra with the use of the likelihood ratio (LR) approach. Firstly the LR methodologies developed for Raman spectra of blue automotive paints obtained with the use of 785nm laser source (results published by the authors previously) were implemented for good quality spectra recorded for these paints with the use of 514.5nm laser source. For LR models construction two types of variables were used i.e. areas under selected pigments bands and coefficients derived from discrete wavelet transform procedure (DWT). Few experiments were designed for 785nm and 514.5nm Raman spectra databases after constructing well performing LR models (low rates of false positive and false negative answers and acceptable results of empirical cross entropy approach). In order to verify whether objective magnification described by its numerical aperture affects spectra interpretation, three objective magnifications -20×(N.A.=0.4.), 50×(N.A.=0.75) and 100×(N.A.=0.85) within each of the applied laser sources (514.5nm and 785nm) were tested for a group of blue solid and metallic automotive paints having the same sets of pigments depending on the applied laser source. The findings obtained by two types of LR models indicate the importance of this parameter for solving the comparison problem of both solid and metallic automotive paints regardless of the laser source used for measuring Raman signal. Hence, the same objective magnification, preferably 50× (established based on the analysis of within- and between-samples variability and F-factor value), should be used when focusing the laser on samples during Raman measurements. Then the influence of parameters (laser power and time of irradiation) of one of the recommended fluorescence suppression techniques, namely photobleaching, was under investigation. Analysis performed on a group of solid automotive paint

Measurement and Simulation of Spontaneous Raman Scattering Spectra in High-Pressure, Fuel-Rich H2-Air Flames

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet

2003-01-01

Rotational vibrational spontaneous Raman spectra (SRS) of H2, N2, and H2O have been measured in H2-air flames at pressures up to 30 atm as a first stem towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. A newly developed high-pressure burner facility provides steady, reproducible flames with a high degree of flow precision. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in terms of spectral resolution, wavelength coverage, and signal-to-noise ratio for use in future reference standards. The fully resolved Stokes and anti-Stokes shifted SRS spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a non-intensified CCD spectrograph with a high-speed shutter. Reasonable temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometry and fuel-rich conditions. Theoretical Raman spectra of H2 were computed using a semi-classical harmonic-oscillator model with recent pressure broadening data and were compared with experimental results. The data and simulation indicated that high-J rotational lines of H2 might interfere with the N2 vibrational Q-branch lines, and this could lead to errors in N2-Raman thermometry based on the line-fitting method. From a comparison of N2 Q-branch spectra in lean H2 low-pressure (1.2 atm) and high-pressure (30 atm) flames, we found no significant line-narrowing or -broadening effects at the current spectrometer resolution of 0.04 nm.

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.

[Raman, FTIR spectra and normal mode analysis of acetanilide].

PubMed

Liang, Hui-Qin; Tao, Ya-Ping; Han, Li-Gang; Han, Yun-Xia; Mo, Yu-Jun

2012-10-01

The Raman and FTIR spectra of acetanilide (ACN) were measured experimentally in the regions of 3 500-50 and 3 500-600 cm(-1) respectively. The equilibrium geometry and vibration frequencies of ACN were calculated based on density functional theory (DFT) method (B3LYP/6-311G(d, p)). The results showed that the theoretical calculation of molecular structure parameters are in good agreement with previous report and better than the ones calculated based on 6-31G(d), and the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis, and based on this, a detailed and accurate vibration frequency assignment of ACN was obtained.

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.

High-pressure Raman spectra and DFT calculations of L-tyrosine hydrochloride crystal

NASA Astrophysics Data System (ADS)

dos Santos, C. A. A. S. S.; Carvalho, J. O.; da Silva Filho, J. G.; Rodrigues, J. L.; Lima, R. J. C.; Pinheiro, G. S.; Freire, P. T. C.; Façanha Filho, P. F.

2018-02-01

High-pressure Raman spectra of L-tyrosine hydrochloride crystal were obtained from 1.0 atm to 7.0 GPa in the 90-1800 cm-1 spectral region. At atmospheric pressure, the Raman spectrum was obtained in the 50-3200 cm-1 spectral range and the assignment of the normal modes based on density functional theory calculations was provided. We found good correspondence between the calculated and the observed intramolecular geometry parameters. This confirms the correct assignment of the normal modes, since it was crucial to understand the meaning of the changes observed in particular Raman active modes. Here we show that bands associated with internal modes undergo slight modifications during compression. However, an inversion of the relative intensity of bands around 125 cm-1 as well as a change of slope dω/dP from 1.0 to 1.5 GPa was understood as a conformational change involving a torsion of the L-tyrosine molecule. As a consequence, it is possible to conclude that the crystal remained in the same monoclinic structure in the 1 atm-7.0 GPa interval, although conformational change of the molecule was verified. A comparison of our results with other selected studies provided insights about the role of the amino acid side chain on the arrangement of hydrogen bonds. Finally, when the pressure was released back to 1 atm, the Raman spectrum was recovered and no hysteresis was observed.

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.

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.

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.

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.

Comparative study of human blood Raman spectra and biochemical analysis of patients with cancer

NASA Astrophysics Data System (ADS)

Shamina, Lyudmila A.; Bratchenko, Ivan A.; Artemyev, Dmitry N.; Myakinin, Oleg O.; Moryatov, Alexander A.; Orlov, Andrey E.; Kozlov, Sergey V.; Zakharov, Valery P.

2018-04-01

In this study we measured spectral features of blood by Raman spectroscopy. Correlation of the obtained spectral data and biochemical studies results is investigated. Analysis of specific spectra allows for identification of informative spectral bands proportional to components whose content is associated with body fluids homeostasis changes at various pathological conditions. Regression analysis of the obtained spectral data allows for discriminating the lung cancer from other tumors with a posteriori probability of 88.3%. The potentiality of applying surface-enhanced Raman spectroscopy with utilized experimental setup for further studies of the body fluids component composition was estimated. The greatest signal amplification was achieved for the gold substrate with a surface roughness of 1 μm. In general, the developed approach of body fluids analysis provides the basis of a useful and minimally invasive method of pathologies screening.

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)

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.

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.

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.

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

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.

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

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

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)

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.

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.

Signal-to-noise contribution of principal component loads in reconstructed near-infrared Raman tissue spectra.

PubMed

Grimbergen, M C M; van Swol, C F P; Kendall, C; Verdaasdonk, R M; Stone, N; Bosch, J L H R

2010-01-01

The overall quality of Raman spectra in the near-infrared region, where biological samples are often studied, has benefited from various improvements to optical instrumentation over the past decade. However, obtaining ample spectral quality for analysis is still challenging due to device requirements and short integration times required for (in vivo) clinical applications of Raman spectroscopy. Multivariate analytical methods, such as principal component analysis (PCA) and linear discriminant analysis (LDA), are routinely applied to Raman spectral datasets to develop classification models. Data compression is necessary prior to discriminant analysis to prevent or decrease the degree of over-fitting. The logical threshold for the selection of principal components (PCs) to be used in discriminant analysis is likely to be at a point before the PCs begin to introduce equivalent signal and noise and, hence, include no additional value. Assessment of the signal-to-noise ratio (SNR) at a certain peak or over a specific spectral region will depend on the sample measured. Therefore, the mean SNR over the whole spectral region (SNR(msr)) is determined in the original spectrum as well as for spectra reconstructed from an increasing number of principal components. This paper introduces a method of assessing the influence of signal and noise from individual PC loads and indicates a method of selection of PCs for LDA. To evaluate this method, two data sets with different SNRs were used. The sets were obtained with the same Raman system and the same measurement parameters on bladder tissue collected during white light cystoscopy (set A) and fluorescence-guided cystoscopy (set B). This method shows that the mean SNR over the spectral range in the original Raman spectra of these two data sets is related to the signal and noise contribution of principal component loads. The difference in mean SNR over the spectral range can also be appreciated since fewer principal components can

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.

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.

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.

[Experimental study of Raman spectra of magnesite at 297 K and at the pressure of 0.13-1 GPa].

PubMed

Wang, Yu; Zheng, Hai-fei

2005-09-01

The experimental study of Raman spectra of magnesite has been conducted at the pressure of 967 MPa and at the temperatureof 297 K using a cubic zirconia-anvil cell. The result shows that neither phase transition nor organic substances were observed during compression, and the Raman peak of magnesite shifted to higher frequency with increasing pressure. The relation between the pressure and the Raman peak position of magnesite (1094 cm(-1)) was obtained as follows: v (cm(-1)) = 0.007 44 x P(MPa) + 1 093.3. The value of dv/dP of magnesite is greater than the previous data obtained by Gillet, which was mostly taken under the mantle pressure. And at the ambient temperature, magnesite can be used as a pressure gauge, and the relation between the pressure and Raman shift of 1 094 cm(-1) peak position is given as following: P(MPa) = 125.8 x (deltavp) 1094 + 124.7 (1094 cm(-1) < vp < 1101 cm(-1)).

Anharmonic Effects on Vibrational Spectra Intensities: Infrared, Raman, Vibrational Circular Dichroism and Raman Optical Activity

PubMed Central

Bloino, Julien; Biczysko, Malgorzata; Barone, Vincenzo

2017-01-01

The aim of this paper is twofold. First, we want to report the extension of our virtual multifrequency spectrometer (VMS) to anharmonic intensities for Raman Optical Activity (ROA) with the full inclusion of first- and second-order resonances for both frequencies and intensities in the framework of the generalized second-order vibrational perturbation theory (GVPT2) for all kinds of vibrational spectroscopies. Then, from a more general point of view, we want to present and validate the performance of VMS for the parallel analysis of different vibrational spectra for medium-sized molecules (IR, Raman, VCD, ROA) including both mechanical and electric/magnetic anharmonicity. For the well-known methyloxirane benchmark, careful selection of density functional, basis set, and resonance tresholds permitted to reach qualitative and quantitative vis-à-vis comparison between experimental and computed band positions and shapes. Next, the whole series of halogenated azetidinones is analyzed, showing that it is now possible to interpret different spectra in terms of electronegativity, polarizability, and hindrance variation between closely related substituents, chiral spectroscopies being particular effective in this connection. PMID:26580121

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.

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.

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.

Electron-electron correlations in Raman spectra of VO2

NASA Astrophysics Data System (ADS)

Goncharuk, I. N.; Ilinskiy, A. V.; Kvashenkina, O. E.; Shadrin, E. B.

2013-01-01

It has been shown that, in single crystals and films of a strongly correlated material, namely, vanadium dioxide, upon a thermally stimulated phase transition from the low-temperature monoclinic phase to the high-temperature tetragonal phase, the narrow-line Raman spectrum of the insulating (monoclinic) phase transforms into the broad-band Raman spectrum, which contains two peaks at 500 and 5000 cm-1 with widths of 400 and 3500 cm-1, respectively. It has been found that, as the temperature of the monoclinic phase approaches the structural phase transition temperature (340 K), the line profile of soft-mode phonons at a frequency of 149 cm-1 with A g symmetry and the line profile of phonons at a frequency of 201 cm-1 with A g symmetry acquire an asymmetric shape with a Fano antiresonance that is characteristic of the interaction of a single phonon vibration with a continuum of strongly correlated electrons. It has been demonstrated that the thermal transformation of peaks in the Raman spectra of the VO2 metallic phase is in quantitative agreement with the theory of Raman scattering in strongly correlated materials.

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

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...

Resonant Raman scattering background in XRF spectra of binary samples

NASA Astrophysics Data System (ADS)

Sánchez, Héctor Jorge; Leani, Juan José

2015-02-01

In x-ray fluorescence analysis, spectra present singular characteristics produced by the different scattering processes. When atoms are irradiated with incident energy lower and close to an absorption edge, scattering peaks appear due to an inelastic process known as resonant Raman scattering. In this work we present theoretical calculations of the resonant Raman scattering contributions to the background of x-ray fluorescence spectra of binary samples of current technological or biological interest. On one hand, a binary alloy of Fe with traces of Mn (Mn: 0.01%, Fe: 99.99%) was studied because of its importance in the stainless steels industries. On the second hand a pure sample of Ti with V traces (Ti: 99%, V: 1%) was analyzed due to the current relevance in medical applications. In order to perform the calculations the Shiraiwa and Fujino's model was used to calculate characteristic intensities and scattering interactions. This model makes certain assumptions and approximations to achieve the calculations, especially in the case of the geometrical conditions and the incident and take-off beams. For the binary sample studied in this work and the considered experimental conditions, the calculations show that the resonant Raman scattering background is significant under the fluorescent peak, affects the symmetry of the peaks and, depending on the concentrations, overcomes the enhancements contributions (secondary fluorescence).

FT-Raman, FT-IR spectra and total energy distribution of 3-pentyl-2,6-diphenylpiperidin-4-one: DFT method.

PubMed

Subashchandrabose, S; Saleem, H; Erdogdu, Y; Rajarajan, G; Thanikachalam, V

2011-11-01

FT-Raman and FT-IR spectra were recorded for 3-pentyl-2,6-diphenylpiperidin-4-one (PDPO) sample in solid state. The equilibrium geometries, harmonic vibrational frequencies, infrared and the Raman scattering intensities were computed using DFT/6-31G(d,p) level. Results obtained at this level of theory were used for a detailed interpretation of the infrared and Raman spectra, based on the total energy distribution (TED) of the normal modes. Molecular parameters such as bond lengths, bond angles and dihedral angles were calculated and compared with X-ray diffraction data. This comparison was good agreement. The intra-molecular charge transfer was calculated by means of natural bond orbital analysis (NBO). Hyperconjugative interaction energy was more during the π-π* transition. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. Atomic charges of the carbon, nitrogen and oxygen were calculated using same level of calculation. Copyright © 2011 Elsevier B.V. All rights reserved.

FT-IR, FT-Raman spectra and DFT calculations of melaminium perchlorate monohydrate.

PubMed

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 (1)H and (13)C NMR spectra. No detectable signal was observed during powder test for second harmonic generation. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

Near infrared Raman spectra of human brain lipids

NASA Astrophysics Data System (ADS)

Krafft, Christoph; Neudert, Lars; Simat, Thomas; Salzer, Reiner

2005-05-01

Human brain tissue, in particular white matter, contains high lipid content. These brain lipids can be divided into three principal classes: neutral lipids including the steroid cholesterol, phospholipids and sphingolipids. Major lipids in normal human brain tissue are phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidic acid, sphingomyelin, galactocerebrosides, gangliosides, sulfatides and cholesterol. Minor lipids are cholesterolester and triacylglycerides. During transformation from normal brain tissue to tumors, composition and concentration of lipids change in a specific way. Therefore, analysis of lipids might be used as a diagnostic parameter to distinguish normal tissue from tumors and to determine the tumor type and tumor grade. Raman spectroscopy has been suggested as an analytical tool to detect these changes even under intra-operative conditions. We recorded Raman spectra of the 12 major and minor brain lipids with 785 nm excitation in order to identify their spectral fingerprints for qualitative and quantitative analyses.

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.

Raman spectra boron doped amorphous carbon thin film deposited by bias assisted-CVD

NASA Astrophysics Data System (ADS)

Ishak, A.; Fadzilah, A. N.; Dayana, K.; Saurdi, I.; Malek, M. F.; Nurbaya, Z.; Shafura, A. K.; Rusop, M.

2018-05-01

Boron doped amorphous carbon thin film carbon was deposited at 200°C-350°C by bias assisted-CVD using palm oil as a precursor material. The structural boron doped amorphous carbon films were discussed by Raman analysis through the evolution of D and G bands. The spectral evolution observed showed the increase of upward shift of D and G peaks as substrate deposition temperatures increased. These structural changes were further correlated with optical gap and the results obtained are discussed and compared. The estimated optical band gap is found to be 1.9 to 2.05 eV and conductivity is to be in the range of 10-5 Scm-1 to 10-4 Scm-1. The decrease of optical band gap is associated to conductivity increased which change the characteristic parameters of Raman spectra including the position of G peak, full width at half maximum of G peak, and ID/IG.

Raman spectra of crystalline secondary amides

NASA Astrophysics Data System (ADS)

Kolesov, Boris A.

2017-05-01

We present a Raman-spectroscopic study of secondary amides (acetanilide, methacetin, phenacetine, orthorhombic and monoclinic polymorphs of paracetamol) as well as simple amides formanilide and benzanilide. The study was carried out on single crystals and in the temperature range of 5-300 K. The series of compounds with the same molecular fragment - acetamide group - can serve as a model system to study the interrelation between this group and the properties of the intermolecular "peptide-type" NH ⋯ Odbnd C hydrogen bonds. For all of the "acetamide family" of the compounds, similar changes in the Raman spectra were observed upon cooling of the samples: emergence of new Amide I(-) and Amide I(+) bands, which are red and blue shifted, respectively, from the conventional Amide-I band by around of 5-10 cm- 1. Corresponding changes in the same temperature range were observed for the Nsbnd H out-of-plane bending (Amide V) and Nsbnd H stretching vibrations of the Nsbnd H ⋯ Odbnd C hydrogen bond. All of the spectral changes observed upon cooling of the samples can be presumed to result from a delocalization of the Amide-I and Nsbnd H modes and appearance of dynamical (Davydov's) splitting at low temperature.

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.

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

Raman Spectra of Glasses

DTIC Science & Technology

1986-11-30

Howard University , Department of Chemistry, Washington, DC Distribution Unlimited Per.. .Dr. Donald Polk, ONR/Code 1131M .IL. OFFICE OF NAVAL...the specific facilities to perform this extremely high temperature Raman work at Howard university . Of course, we do have very extensive facilities at... Howard University for CW laser-Raman spectroscopy of melts to about 1600 or 1800 OC. We have four complete laser-Raman instruments; Lhree holographic

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.

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.

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.

Preliminary investigation on the relationship of Raman spectra of sheep meat with shear force and cooking loss.

PubMed

Schmidt, Heinar; Scheier, Rico; Hopkins, David L

2013-01-01

A prototype handheld Raman system was used as a rapid non-invasive optical device to measure raw sheep meat to estimate cooked meat tenderness and cooking loss. Raman measurements were conducted on m. longissimus thoracis et lumborum samples from two sheep flocks from two different origins which had been aged for five days at 3-4°C before deep freezing and further analysis. The Raman data of 140 samples were correlated with shear force and cooking loss data using PLS regression. Both sample origins could be discriminated and separate correlation models yielded better correlations than the joint correlation model. For shear force, R(2)=0.79 and R(2)=0.86 were obtained for the two sites. Results for cooking loss were comparable: separate models yielded R(2)=0.79 and R(2)=0.83 for the two sites. The results show the potential usefulness of Raman spectra which can be recorded during meat processing for the prediction of quality traits such as tenderness and cooking loss. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

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.

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.

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

[Application of surface-enhanced Raman spectra to the analysis of Chinese Ephedra soup medicines].

PubMed

Zhang, J; Wang, Y

1998-06-01

A new method was developed to analyse the spectra of ephedrine in Chinese ephedra soup medicines, using surface-enhanced technique to combine thin layer chromatographic (TLC) technique with surface-enhanced Raman spectroscopy (SERS). The study indicates that the main vibrant characteristic spec tral band of the ephedrine molecules can be obtained by TLC in the samples of about 8 microg, and expounds char acteristics of the sample molecules and the silica gel. Therefore, it is clarified that the main chemical composi tion of Chinese medicines can be carried as finger-print type appraisal by combining TLC and SERS.

Resonant Raman and FTIR spectra of carbon doped GaN

NASA Astrophysics Data System (ADS)

Ito, S.; Kobayashi, H.; Araki, K.; Suzuki, K.; Sawaki, N.; Yamashita, K.; Honda, Y.; Amano, H.

2015-03-01

Intentionally carbon (C) doped (0 0 0 1)GaN was grown using C2H2 on a sapphire substrate by metalorganic vapor phase epitaxy. Optical spectra of the heavily doped samples were investigated at room temperature. In Raman spectra excited by the 325 nm line of a He-Cd laser, multiple LO phonon scattering signals up to 7th order were observed, and the A1(LO) phonon energy was determined to be 737.5 cm-1 (91.45 meV). In infrared reflectance spectra, on the other hand, a local vibration mode was found at 777.5 cm-1, which is attributed to a Ga-C bond in the GaN matrix suggesting that the C sits on an N site (CN). In spite of the strong suggestion of CN, the samples did not show p-type conduction. Possible origin of the carrier compensation is discussed in relation to the enhancement of defect related yellow luminescence in the photoluminescence spectra.

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 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.

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.

Dispersive Fourier transformation for megahertz detection of coherent stokes and anti-stokes Raman spectra

NASA Astrophysics Data System (ADS)

Bohlin, Alexis; Patterson, Brian D.; Kliewer, Christopher J.

2017-11-01

In many fields of study, from coherent Raman microscopy on living cells to time-resolved coherent Raman spectroscopy of gas-phase turbulence and combustion reaction dynamics, the need for the capability to time-resolve fast dynamical and nonrepetitive processes has led to the continued development of high-speed coherent Raman methods and new high-repetition rate laser sources, such as pulse-burst laser systems. However, much less emphasis has been placed on our ability to detect shot to shot coherent Raman spectra at equivalently high scan rates, across the kilohertz to megahertz regime. This is beyond the capability of modern scientific charge coupled device (CCD) cameras, for instance, as would be employed with a Czerny-Turner type spectrograph. As an alternative detection strategy with megahertz spectral detection rate, we demonstrate dispersive Fourier transformation detection of pulsed (∼90 ps) coherent Raman signals in the time-domain. Instead of reading the frequency domain signal out using a spectrometer and CCD, the signal is transformed into a time-domain waveform through dispersive Fourier transformation in a long single-mode fiber and read-out with a fast sampling photodiode and oscilloscope. Molecular O- and S-branch rotational sideband spectra from both N2 and H2 were acquired employing this scheme, and the waveform is fitted to show highly quantitative agreement with a molecular model. The total detection time for the rotational spectrum was 20 ns, indicating an upper limit to the detection frequency of ∼50 MHz, significantly faster than any other reported spectrally-resolved coherent anti-Stokes Raman detection strategy to date.

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.

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.

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.

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.

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.

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.

The effect of nonlocal dielectric response on the surface-enhanced Raman and fluorescence spectra of molecular systems

NASA Astrophysics Data System (ADS)

Wei, Yong; Pei, Huan; Li, Li; Zhu, Yanying

2018-06-01

We present a theoretical study on the influence of the nonlocal dielectric response on surface-enhanced resonant Raman scattering (SERRS) and fluorescence (SEF) spectra of a model molecule confined in the center of a Ag nanoparticle (NP) dimer. In the simulations, the nonlocal dielectric response caused by the electron–hole pair generation in Ag NPs was computed with the d-parameter theory, and the scattering spectra of a model molecule representing the commonly used fluorescent dye rhodamine 6G (R6G) were obtained by density-matrix calculations. The influence of the separation between Ag NP dimers on the damping rate and scattering spectra with and without the nonlocal response were systematically analyzed. The results show that the nonlocal dielectric response is very sensitive to the gap distance of the NP dimers, and it undergoes much faster decay with the increase of the separation than the radiative and energy transfer rates. The Raman and fluorescence peaks as simulated with the nonlocal dielectric response are relative weaker than that without the nonlocal effect for smaller NP separations because the extra decay rates of the nonlocal effect could reduce both the population of the excited state and the interband coherence between the ground and excited states. Our result also indicates that the nonlocal effect is more prominent on the SEF process than the SERRS process.

The effect of nonlocal dielectric response on the surface-enhanced Raman and fluorescence spectra of molecular systems.

PubMed

Wei, Yong; Pei, Huan; Li, Li; Zhu, Yanying

2018-05-04

We present a theoretical study on the influence of the nonlocal dielectric response on surface-enhanced resonant Raman scattering (SERRS) and fluorescence (SEF) spectra of a model molecule confined in the center of a Ag nanoparticle (NP) dimer. In the simulations, the nonlocal dielectric response caused by the electron-hole pair generation in Ag NPs was computed with the d-parameter theory, and the scattering spectra of a model molecule representing the commonly used fluorescent dye rhodamine 6G (R6G) were obtained by density-matrix calculations. The influence of the separation between Ag NP dimers on the damping rate and scattering spectra with and without the nonlocal response were systematically analyzed. The results show that the nonlocal dielectric response is very sensitive to the gap distance of the NP dimers, and it undergoes much faster decay with the increase of the separation than the radiative and energy transfer rates. The Raman and fluorescence peaks as simulated with the nonlocal dielectric response are relative weaker than that without the nonlocal effect for smaller NP separations because the extra decay rates of the nonlocal effect could reduce both the population of the excited state and the interband coherence between the ground and excited states. Our result also indicates that the nonlocal effect is more prominent on the SEF process than the SERRS process.

Surface-enhanced Raman spectra of hemoglobin for esophageal cancer diagnosis

NASA Astrophysics Data System (ADS)

Zhou, Xue; Diao, Zhenqi; Fan, Chunzhen; Guo, Huiqiang; Xiong, Yang; Tang, Weiyue

2014-03-01

Surface-enhanced Raman scattering (SERS) spectra of hemoglobin from 30 esophageal cancer patients and 30 healthy persons have been detected and analyzed. The results indicate that, there are more iron ions in low spin state and less in high for the hemoglobin of esophageal cancer patients than normal persons, which is consistent with the fact that it is easier to hemolyze for the blood of cancer patients. By using principal component analysis (PCA) and discriminate analysis, we can get a three-dimensional scatter plot of PC scores from the SERS spectra of healthy persons and cancer patients, from which the two groups can be discriminated. The total accuracy of this method is 90%, while the diagnostic specificity is 93.3% and sensitivity is 86.7%. Thus SERS spectra of hemoglobin analysis combined with PCA may be a new technique for the early diagnose of esophageal cancer.

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.

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.

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.

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.

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

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(2

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

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.

Resonance Raman and surface-enhanced resonance Raman spectra of LH2 antenna complex from Rhodobacter sphaeroides and Ectothiorhodospira sp. excited in the Qx and Qy transitions.

PubMed

Chumanov, G; Picorel, R; Ortiz de Zarate, I; Cotton, T M; Seibert, M

2000-05-01

Well-resolved vibrational spectra of LH2 complex isolated from two photosynthetic bacteria, Rhodobacter sphaeroides and Ectothiorhodospira sp., were obtained using surface-enhanced resonance Raman scattering (SERRS) exciting into the Qx and the Qy transitions of bacteriochlorophyll a. High-quality SERRS spectra in the Qy region were accessible because the strong fluorescence background was quenched near the roughened Ag surface. A comparison of the spectra obtained with 590 nm and 752 nm excitation in the mid- and low-frequency regions revealed spectral differences between the two LH2 complexes as well as between the LH2 complexes and isolated bacteriochlorophyll a. Because peripheral modes of pigments contribute mainly to the low-frequency spectral region, frequencies and intensities of many vibrational bands in this region are affected by interactions with the protein. The results demonstrate that the microenvironment surrounding the pigments within the two LH2 complexes is somewhat different, despite the fact that the complexes exhibit similar electronic absorption spectra. These differences are most probably due to specific pigment-pigment and pigment-protein interactions within the LH2 complexes, and the approach might be useful for addressing subtle static and dynamic structural variances between pigment-protein complexes from different sources or in complexes altered chemically or genetically.

Comparison of several chemometric methods of libraries and classifiers for the analysis of expired drugs based on Raman spectra.

PubMed

Gao, Qun; Liu, Yan; Li, Hao; Chen, Hui; Chai, Yifeng; Lu, Feng

2014-06-01

Some expired drugs are difficult to detect by conventional means. If they are repackaged and sold back into market, they will constitute a new public health challenge. For the detection of repackaged expired drugs within specification, paracetamol tablet from a manufacturer was used as a model drug in this study for comparison of Raman spectra-based library verification and classification methods. Raman spectra of different batches of paracetamol tablets were collected and a library including standard spectra of unexpired batches of tablets was established. The Raman spectrum of each sample was identified by cosine and correlation with the standard spectrum. The average HQI of the suspicious samples and the standard spectrum were calculated. The optimum threshold values were 0.997 and 0.998 respectively as a result of ROC and four evaluations, for which the accuracy was up to 97%. Three supervised classifiers, PLS-DA, SVM and k-NN, were chosen to establish two-class classification models and compared subsequently. They were used to establish a classification of expired batches and an unexpired batch, and predict the suspect samples. The average accuracy was 90.12%, 96.80% and 89.37% respectively. Different pre-processing techniques were tried to find that first derivative was optimal for methods of libraries and max-min normalization was optimal for that of classifiers. The results obtained from these studies indicated both libraries and classifier methods could detect the expired drugs effectively, and they should be used complementarily in the fast-screening. Copyright © 2014 Elsevier B.V. All rights reserved.

Interpretation of IR and Raman spectra of dopamine neurotransmitter and effect of hydrogen bond in HCl

NASA Astrophysics Data System (ADS)

Yadav, T.; Mukherjee, V.

2018-05-01

The potential energy scanning with respect to the different dihedral angles were performed to search possible numbers of dopamine (neutral) conformers and further, fifteen conformers of dopamine were identified on the basis of energy minima. Vibrational frequencies were calculated for all the conformers of dopamine. Density functional theory was employed to carry out all the computations. The exchange correlation functional B3LYP and the basis set 6-31++G(d,p) were included in DFT calculation. The FTIR and FT-Raman spectra of dopamine hydrochloride were also recorded in the spectral region 400-4000 cm-1 and 50-4000 cm-1 respectively. The normal coordinate analysis was also performed to scale DFT calculated force constants and to calculate potential energy distributions. The detailed vibrational spectral analysis and the assignments of the bands, done on the best-fit basis comparison of the experimentally obtained and theoretically calculated IR and Raman spectra, match quite well indicating DFT calculations as very accurate source of normal mode assignments. The interaction of the most stable conformer of dopamine with HCl was also studied to know the effect of hydrogen bond on its geometry and dynamics. The stability of the dopamine in isolated and protonated forms arising from hyperconjugative interactions was also analyzed by natural bond orbital analysis.

Predicting Raman Spectra of Aqueous Silica and Alumina Species in Solution From First Principles

NASA Astrophysics Data System (ADS)

Hunt, J. D.; Schauble, E. A.; Manning, C. E.

2006-12-01

Dissolved silica and alumina play an important role in lithospheric fluid chemistry. Silica concentrations in aqueous fluids vary over the range of crustal temperatures and pressures enough to allow for significant mass transport of silica via fluid-rock interaction. The polymerization of silica, and the possible incorporation of alumina into the polymer structure, could afford crystal-like or melt-like sites to otherwise insoluble elements such as titanium, leading to enhanced mobility. Raman spectroscopy in a hydrothermal diamond anvil cell (HDAC) has been used to study silica polymerization at elevated pressure and temperature [Ref. 1, 2], but Raman spectra of expected solutes are not fully understood. We calculated Raman spectra of H4SiO4 monomers, H6Si2O7 dimers, and H6SiAlO_7^- dimers, from first principles using hybrid density functional theory (B3LYP). These spectra take into account the variation in bridging angle (Si-O-Si and Si-O-Al angles) that the dimers will have at a given temperature by calculating a potential energy surface of the dimer as the bridging angle varies, and using a Boltzmann distribution at that temperature to determine relative populations at each geometry. Solution effects can be incorporated by using a polarizable continuum model (PCM), and a potential energy surface has been constructed for the silica dimer using a PCM. The bridging angle variation explains the broadness of the 630 cm^-^1 silica dimer peak observed in HDAC experiments [Ref. 1, 2] at high temperatures. The silica-alumina dimer bridging angle is shown to be stiffer than the silica dimer bridging angle, which results in a much narrower main peak. The synthetic spectrum obtained for the silica-alumina dimer suggests that there may be a higher ratio of complexed alumina to free alumina in solution at highly basic pH than previously estimated [Ref. 3]. References: 1. Zotov, N. and H. Keppler, Chemical Geology, 2002. 184: p. 71-82. 2. Zotov, N. and H. Keppler, American

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.

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.

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.

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.

RER SPECTRA OBTAINED WITH A MULTICRYSTAL SPECTROMETER

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

Austin, W.E.; Champion, W.R.

1959-11-01

Relative gamma spectra were obtained twenty feet from the Hadiation Effects Reactor. The measurements were made using a multicry-stal spectrometer. This design incorporates pair and anticompton spectrometers in combination. Two reactor configurations were used; with shield tanks empty- and water filled. The spectra were obtained before the fuel elements were run at high power. Consequently very little of the fission product spectrum is tntermined. (J.R.D.)

Theoretical study of NMR, infrared and Raman spectra on triple-decker phthalocyanines

NASA Astrophysics Data System (ADS)

Suzuki, Atsushi; Oku, Takeo

2016-02-01

Electronic structures and magnetic properties of multi-decker phthalocyanines were studied by theoretical calculation. Electronic structures, excited processes at multi-states, isotropic chemical shifts of 13C, 14N and 1H-nuclear magnetic resonance (NMR), principle V-tensor in electronic field gradient (EFG) tensor and asymmetry parameters (η), vibration mode in infrared (IR) and Raman spectra of triple-decker phthalocyanines were calculated by density functional theory (DFT) and time-dependent DFT using B3LYP as basis function. Electron density distribution was delocalized on the phthalocyanine rings with electron static potential. Considerable separation of chemical shifts in 13C, 14N and 1H-NMR was originated from nuclear spin interaction between nitrogen and carbon atoms, nuclear quadrupole interaction based on EFG and η of central metal under crystal field. Calculated optical absorption at multi-excited process was derived from overlapping π-orbital on the phthalocyanine rings. The vibration modes in IR and Raman spectra were based on in-plane deformation and stretching vibrations of metal-ligand coordination bond on the deformed structure.

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

Combined use of infrared and Raman spectra in the characterization of orthoclase under various hydrostatic pressures.

PubMed

Liu, Rui; Wang, Zhi-Hua; Xu, Qiang; Yu, Na; Cao, Miao-Cong

2014-02-01

Colorless and pink orthoclase from Balikun granite body, East Zhunger in Xinjiang, served as the samples for the research on hydrostatic pressure experiment. The in-situ hydrostatic pressure test for orthoclases was conducted at the room temperature and pressures from 100 to 600 MPa using cubic zirconia anvil cell, with quartz as pressure gauge. The water located in the orthoclases for the conditions of different hydrostatic pressures was characterized through the methods of Fourier transform infrared (FTIR) and Raman spectra. The results showed that there was a linear correlation between the shifting of Raman bands and hydrostatic pressure applied to the feldspar. All of vibration peaks of M-O structural groups in orthoclases, the bending vibration peaks of Si(Al(IV))-O-Si bond and tetrahedron groups of [SiO4] in Raman spectra shifted toward the higher frequency regularly, the drift distance is 2, 2.19 and less than 2 cm(-1) respectively. The spectra of FTIR suggested that there was more water in colorless orthoclases than the pink one under certain conditions of hydrostatic pressure. The intensity and integral area centered at 3420 cm(-1) in FTIR spectra increased with the rising of hydrostatic pressure. The integral area for colorless and pink feldspar in FTIR spectra rose from 120, 1383 cm(-1) under normal pressure to 1570, 2001 cm(-1) at 600 MPa respectively. The experimental results might indicate that the water in the earth crust could enter the orthoclases in certain condition of the aqueous confining pressure.

Raman bands in Ag nanoparticles obtained in extract of Opuntia ficus-indica plant

NASA Astrophysics Data System (ADS)

Bocarando-Chacon, J.-G.; Cortez-Valadez, M.; Vargas-Vazquez, D.; Rodríguez Melgarejo, F.; Flores-Acosta, M.; Mani-Gonzalez, P. G.; Leon-Sarabia, E.; Navarro-Badilla, A.; Ramírez-Bon, R.

2014-05-01

Silver nanoparticles have been obtained in an extract of Opuntia ficus-indica plant. The size and distribution of nanoparticles were quantified by atomic force microscopy (AFM). The diameter was estimated to be about 15 nm. In addition, energy dispersive X-ray spectroscopy (EDX) peaks of silver were observed in these samples. Three Raman bands have been experimentally detected at 83, 110 and 160 cm-1. The bands at 83 and 110 cm-1 are assigned to the silver-silver Raman modes (skeletal modes) and the Raman mode located at 160 cm-1 has been assigned to breathing modes. Vibrational assignments of Raman modes have been carried out based on the Density Functional Theory (DFT) quantum mechanical calculation. Structural and vibrational properties for small Agn clusters with 2≤n≤9 were determined. Calculated Raman modes for small metal clusters have an approximation trend of Raman bands. These Raman bands were obtained experimentally for silver nanoparticles (AgNP).

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.

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.

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

FT-IR, FT-Raman, UV spectra and DFT calculations on monomeric and dimeric structure of 2-amino-5-bromobenzoic acid.

PubMed

Karabacak, Mehmet; Cinar, Mehmet

2012-02-01

In this work, the molecular conformation, vibrational and electronic transition analysis of 2-amino-5-bromobenzoic acid (2A5BrBA) were presented for the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-311++G(d,p) basis set. FT-IR and FT-Raman spectra were recorded in the regions of 400-4000 cm(-1) and 50-4000 cm(-1), respectively. There are four conformers, C1, C2, C3 and C4 for this molecule. The geometrical parameters, energies and wavenumbers have been obtained for all four conformers. The computational results diagnose the most stable conformer of 2A5BrBA as the C1 form. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Raman activities calculated by DFT method have been converted to the corresponding Raman intensities using Raman scattering theory. The UV spectra of investigated compound were recorded in the region of 200-400 nm for ethanol and water solutions. The electronic properties were evaluated with help of time-dependent DFT (TD-DFT) theoretically and results were compared with experimental observations. The thermodynamic properties of the studied compound at different temperatures were calculated, revealing the correlations between standard heat capacity, standard entropy, standard enthalpy changes and temperatures. The observed and the calculated geometric parameters, vibrational wavenumbers and electronic transitions were compared with observed data and found to be in good agreement. 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.

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.

Principal component analysis of Raman spectra for TiO2 nanoparticle characterization

NASA Astrophysics Data System (ADS)

Ilie, Alina Georgiana; Scarisoareanu, Monica; Morjan, Ion; Dutu, Elena; Badiceanu, Maria; Mihailescu, Ion

2017-09-01

The Raman spectra of anatase/rutile mixed phases of Sn doped TiO2 nanoparticles and undoped TiO2 nanoparticles, synthesised by laser pyrolysis, with nanocrystallite dimensions varying from 8 to 28 nm, was simultaneously processed with a self-written software that applies Principal Component Analysis (PCA) on the measured spectrum to verify the possibility of objective auto-characterization of nanoparticles from their vibrational modes. The photo-excited process of Raman scattering is very sensible to the material characteristics, especially in the case of nanomaterials, where more properties become relevant for the vibrational behaviour. We used PCA, a statistical procedure that performs eigenvalue decomposition of descriptive data covariance, to automatically analyse the sample's measured Raman spectrum, and to interfere the correlation between nanoparticle dimensions, tin and carbon concentration, and their Principal Component values (PCs). This type of application can allow an approximation of the crystallite size, or tin concentration, only by measuring the Raman spectrum of the sample. The study of loadings of the principal components provides information of the way the vibrational modes are affected by the nanoparticle features and the spectral area relevant for the classification.

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.

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.

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.

[Raman spectra of complexes of rare earth nitrate with histidine].

PubMed

Gao, S; Ji, M; Liu, J; Hou, Y; Chen, S

1999-12-01

Raman spectra of solid complexes RE(His)(NO3)3 x H2O (RE = La-Nd, Sm-Lu, Y; His = L-alpha-histidine ) have been investigated. The results indicate that RE3+ coordinates with one O atome of carboxyl group in the complex, while amino group and imidazole ring do not take part in coordination and NO3 is double coordination. The vibration peaks of carboxyl group delta(v)COO-(as-s) were plotted against the atomic number of the lanthanoids, which obeys Oddo-Harkins law.

Density functional IR, Raman, and VCD spectra of halogen substituted β-lactams

NASA Astrophysics Data System (ADS)

Rode, Joanna E.; Dobrowolski, Jan Cz.

2003-06-01

Halogenoazetidinones are important as synthetic intermediates for preparation of halogen β-lactam (2-azetidinone) antibiotics and as building blocks for carbohydrates and amino acids. In this paper, we consider the influence of the halogen atom, substituted at the C4 position of the 2-azetidinone ring, on the geometry, IR, Raman, and vibrational circular dichroism spectra. The vibrational spectra were calculated for the chiral 4-( R)-X-2-azetidinone (X=F, Cl or Br) molecules at the B3PW91/aug-cc-pVTZ level. It was shown that the geometry of the molecules studied do not change much upon the change of the halogen atom. In case of the vibrational spectra, the position but even more the intensities depend strongly on the kind of halogen substituent.

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 imaging of lipid bilayer membrane by surface enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Mori, Motoaki; Abe, Shunsuke; Kondo, Takahiro; Saito, Yuika

2018-04-01

We investigated two-dimensional lipid bilayers by spectroscopic imaging with surface enhanced Raman spectroscopy (SERS). A DSPC lipid bilayer incubated on a glass substrate was coated with a thin layer of silver. Due to the strong electromagnetic enhancement of the silver film and the affinity to lipid molecules, the Raman spectrum of a single bilayer was obtained in a 1 s exposure time with 0.1 mW of incident laser power. In the C-H vibrational region of the spectra, which is sensitive to bilayer configurations, a randomly stacked area was dominated by the CH3 asymmetric-stretch mode, whereas flat areas including double bilayers showed typical SERS spectra. The spectral features of the randomly stacked area are explained by the existence of many free lipid molecules, which is supported by DFT calculations of paired DSPC molecules. Our method can be applied to reveal the local crystallinity of single lipid bilayers, which is difficult to assess by conventional Raman imaging.

Reversible formation of ammonium persulfate/sulfuric acid graphite intercalation compounds and their peculiar Raman spectra.

PubMed

Dimiev, Ayrat M; Bachilo, Sergei M; Saito, Riichiro; Tour, James M

2012-09-25

Graphite intercalation compounds (GICs) can be considered stacks of individual doped graphene layers. Here we demonstrate a reversible formation of sulfuric acid-based GICs using ammonium persulfate as the chemical oxidizing agent. No covalent chemical oxidation leading to the formation of graphite oxide occurs, which inevitably happens when other compounds such as potassium permanganate are used to charge carbon layers. The resulting acid/persulfate-induced stage-1 and stage-2 GICs are characterized by suppression of the 2D band in the Raman spectra and by unusually strong enhancement of the G band. The G band is selectively enhanced at different doping levels with different excitations. These observations are in line with recent reports for chemically doped and gate-modulated graphene and support newly proposed theories of Raman processes. At the same time GICs have some advantageous differences over graphene, which are demonstrated in this report. Our experimental observations, along with earlier reported data, suggest that at high doping levels the G band cannot be used as the reference peak for normalizing Raman spectra, which is a commonly used practice today. A Fermi energy shift of 1.20-1.25 eV and ∼1.0 eV was estimated for the stage-1 and stage-2 GICs, respectively, from the Raman and optical spectroscopy data.

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.

Raman spectra of gases. XVI - Torsional transitions in ethanol and ethanethiol

NASA Technical Reports Server (NTRS)

Durig, J. R.; Bucy, W. E.; Wurrey, C. J.; Carreira, L. A.

1975-01-01

The Raman spectra of gaseous ethanol and ethanethiol have been investigated. Thiol torsional fundamentals for the gauche conformer of EtSH and EtSD have been observed and the asymmetric potential function for this vibration has been calculated. Methyl torsional transitions and overtones have also been observed for both of these molecules. Barriers to internal rotation for the methyl top are calculated to be 3.77 and 3.84 kcal/mol for the EtSH and EtSD compounds, respectively. Hydroxyl torsional fundamentals were observed at 207 and 170 per cm in the EtOH and EtOD spectra, respectively. Overtones of the methyl torsion in both molecules yield a barrier to internal rotation of 3.62 kcal/mol for the gauche conformer.

Independent component analysis-based algorithm for automatic identification of Raman spectra applied to artistic pigments and pigment mixtures.

PubMed

González-Vidal, Juan José; Pérez-Pueyo, Rosanna; Soneira, María José; Ruiz-Moreno, Sergio

2015-03-01

A new method has been developed to automatically identify Raman spectra, whether they correspond to single- or multicomponent spectra. The method requires no user input or judgment. There are thus no parameters to be tweaked. Furthermore, it provides a reliability factor on the resulting identification, with the aim of becoming a useful support tool for the analyst in the decision-making process. The method relies on the multivariate techniques of principal component analysis (PCA) and independent component analysis (ICA), and on some metrics. It has been developed for the application of automated spectral analysis, where the analyzed spectrum is provided by a spectrometer that has no previous knowledge of the analyzed sample, meaning that the number of components in the sample is unknown. We describe the details of this method and demonstrate its efficiency by identifying both simulated spectra and real spectra. The method has been applied to artistic pigment identification. The reliable and consistent results that were obtained make the methodology a helpful tool suitable for the identification of pigments in artwork or in paint in general.

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.

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

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.

Raman spectra of pigmented skin conditions

NASA Astrophysics Data System (ADS)

Bitar, Renata; Moreno, Marcelo; Oliveira, Andréa; Cartaxo, Sidney; Martinho, Herculano; Espírito Santo, Ana Maria do; Santos, Ivan Dunshee; Ferreira, Lydia Massako; Martin, Airton

2007-02-01

Melanoma is the most aggressive skin cancer and is invariably fatal if left untreated. Melanoma removal at early stages is almost always curative and therefore early detection is essential. Removal of every pigmented lesion is unacceptable for the patient, especially in the case of multiple skin lesions or lesions localized in cosmetically important parts of the body such as the face because of risk of scarring. The development of a technique to detect these changes in a noninvasive way is therefore crucial for melanoma detection. In this study, we have used FT-Raman Spectroscopy to investigate through PCA analysis the alterations in the molecular structure of 90 skin spectra, being 30 Pigmented Nevi, 30 Primary Melanoma, and 30 Metastasis, for 6 patients. For projection of data, the scores (Principal Components) PC1 to PC3 were calculated. PC1 versus PC3 for the 800 to 1800 cm -1 spectral region. PC1 versus PC2 for the 1200 to 1400 cm -1 spectral region. In both analysis, we could differentiate the three different types of tissues.

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

A combined experimental and theoretical studies on FT-IR, FT-Raman and UV-vis spectra of 2-chloro-3-quinolinecarboxaldehyde

NASA Astrophysics Data System (ADS)

Prasad, M. V. S.; Udaya Sri, N.; Veeraiah, V.

2015-09-01

In the present study, the FT-IR and FT-Raman spectra of 2-chloro-3-quinolinecarboxaldehyde (2Cl3QC) have been recorded in the region 4000-400 and 3500-50 cm-1, respectively. The fundamental modes of vibrational frequencies of 2Cl3QC are assigned. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization have been analyzed using natural bond orbitals (NBO) analysis. The results show that charge in electron density (ED) in the π∗ antibonding orbitals and E(2) energies confirms the occurrence of ICT (intra-molecular charge transfer) within the molecule. UV-visible spectrum of the title molecule has also been calculated using TD-DFT/CAM-B3LYP/6-31G(d,p) method. The calculated energy and oscillator strength almost exactly reproduces reported experimental data.

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.

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.

Analysis of human hair by Raman microspectroscopy

NASA Astrophysics Data System (ADS)

Plascencia-Castro, A. S.; Cordova-Fraga, T.; Piña-Ruiz, A. L.; Hernández-Rayas, A.; Bernal, J. J.

2017-04-01

Raman microspectroscopy is an optical compound identification technique, which is widely used nowadays for different field applications. A crucial part of this technique is the focus given to the sample in the microscope because it depends on which part of the sample it will analyze. In this work, the effects of irradiating a natural hair samples, obtained from women aged 18 to 55, with a monochromatic light of the Raman spectrometer in two different focus is presented. Two different spectra were obtained with a peak in common. Depending on the information wanted, how the sample is focused plays a crucial role, either way the spectra is information-rich and may be used for biomedical applications.

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.

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.

Raman spectra from very concentrated aqueous NaOH and from wet and dry, solid, and anhydrous molten, LiOH, NaOH, and KOH.

PubMed

Walrafen, George E; Douglas, Rudolph T W

2006-03-21

High-temperature, high-pressure Raman spectra were obtained from aqueous NaOH solutions up to 2NaOHH2O, with X(NaOH)=0.667 at 480 K. The spectra corresponding to the highest compositions, X(NaOH)> or =0.5, are dominated by H3O2-. An IR xi-function dispersion curve for aqueous NaOH, at 473 K and 1 kbar, calculated from the data of Franck and Charuel indicates that the OH- ion forms H3O2- by preferential H bonding with nonhydrogen-bonded OH groups. Raman spectra from wet to anhydrous, solid LiOH, NaOH, and KOH yield sharp, symmetric OH- stretching peaks at 3664, 3633, and 3596 cm(-1), respectively, plus water-related, i.e., H3O2-, peaks near LiOH, 3562 cm(-1), NaOH, 3596 cm(-1), and, KOH, 3500 cm(-1). Absence of H3O2- peaks from the solid assures that the corresponding melt is anhydrous. Raman spectra from the anhydrous melts yield OH- stretching peak frequencies: LiOH, 3614+/-4 cm(-1), 873 K; NaOH, 3610+/-2 cm(-1), 975 K; and, KOH, 3607+/-2 cm(-1), 773 K, but low-frequency asymmetry due to ion-pair interactions is present which is centered near 3550 cm(-1). The ion-pair-related asymmetry corresponds to the sole IR maximum near 3550 cm(-1) from anhydrous molten NaOH, at 623 K. Bose-Einstein correction of published low-frequency Raman data from molten LiOH revealed an acoustic phonon, near 205 cm(-1), related to restricted translation of OH- versus Li+, and an optical phonon, at 625 cm(-1) and tau approximately 0.05 ps, due to protonic precession and/or pendular motion. Strong H bonding between water and the O atom of OH- forms H3O2-, but the proton of OH- does not bond with H significantly. Large Raman bandwidths (aqueous solutions) are explained in terms of inhomogeneous broadening due to proton transfer in a double well. Vibrational assignments are presented for H3O2-.

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

Raman backscatter measurement research on water vapor systems

NASA Technical Reports Server (NTRS)

Workman, G. L.

1975-01-01

Raman backscatter techniques proved to be a useful remote sensing tool, whose full potential has not been realized. The types of information available from laser probes in atmospheric studies are reviewed. Detection levels for known Raman cross sections are calculated using the laser radar equation. Laboratory experiments performed for H2O, N2, SO2, O2 and HCL indicate that accurate wavelength cross sections need to be obtained, as well as more emphasis on obtaining accurate Raman cross sections of molecular species at wavelengths in the ultraviolet spectra.

Raman spectroscopy and Raman imaging for early detection of cancer

NASA Astrophysics Data System (ADS)

Joshi, Narahari V.; Ortega, Angel; Estrela, Jose Maria

2004-06-01

Raman spectroscopy is a powerful technique as it provides fundamental information about vibrational modes of a system. Eigenvalues of these modes are very sensitive to the strength of the chemical bonds and perturbations caused by the environment, particularly charge distribution and alterations in the dipole strength of the system. All these parameters are profoundly modified during the tumor formation process nad hence Raman technique could be a unique and also a direct approach for evaluating tumor genesis at early stages. for this pupose the present investigation was carried out. We used cultured wild type and c-ras transformed NIH 3T3 fibroblast. The samples were treated with methyl alcohol solution ina conventional manner and then Raman spectra nad images were obtained by a specially developed confocal Raman microscope. The present results reveal differences between both cell types in the spectral details as well as in the morphology. Raman images are able to detect the exact site where cancer-related changes have taken place. These results clearly indicate the superiority of the present technique over conventional methods such as images obtained by X-rays or Nuclear Magnetic Resonance (NMR). Moreover, unlike other approaches, Raman images detect alterations at the submicron level rather than in the centimeter or millimeter range. Being an optical method it can be applied in vivo as a non-invasive technique potentially useful to early detection of cancer (particularly easy accessible cancers such as those of the skin and the digestive tract). The obtained resulsts suggest the great potential of Raman imaging in premature clinical diagnostic approaches.

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

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.

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.

A two-dimensionally coincident second difference cosmic ray spike removal method for the fully automated processing of Raman spectra.

PubMed

Schulze, H Georg; Turner, Robin F B

2014-01-01

Charge-coupled device detectors are vulnerable to cosmic rays that can contaminate Raman spectra with positive going spikes. Because spikes can adversely affect spectral processing and data analyses, they must be removed. Although both hardware-based and software-based spike removal methods exist, they typically require parameter and threshold specification dependent on well-considered user input. Here, we present a fully automated spike removal algorithm that proceeds without requiring user input. It is minimally dependent on sample attributes, and those that are required (e.g., standard deviation of spectral noise) can be determined with other fully automated procedures. At the core of the method is the identification and location of spikes with coincident second derivatives along both the spectral and spatiotemporal dimensions of two-dimensional datasets. The method can be applied to spectra that are relatively inhomogeneous because it provides fairly effective and selective targeting of spikes resulting in minimal distortion of spectra. Relatively effective spike removal obtained with full automation could provide substantial benefits to users where large numbers of spectra must be processed.

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.

Pressure-tuning micro-Raman spectra of artists' pigments: α- and β-copper phthalocyanine polymorphs.

PubMed

Beaulieu-Houle, Guillaume; Gilson, Denis F R; Butler, Ian S

2014-01-03

The two polymorphs of copper phthalocyanine, α- and β-CuPc, have been examined by micro-Raman spectroscopy at pressures approaching 5.0 GPa. The metastable α-polymorph does not exhibit any structural changes, while the more thermodynamically stable β-polymorph does exhibit a reversible phase transition at 2.0 GPa. The pressure dependences (dν/dP) for a selected number of vibrational modes are reported. Two regions of the Raman spectra, 800-900 cm(-1) and 1100-1200 cm(-1), are sensitive to pressure such that they can be used as indicators of the polymorphic form. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

A combined experimental and theoretical studies on FT-IR, FT-Raman and UV-vis spectra of 2-chloro-3-quinolinecarboxaldehyde.

PubMed

Prasad, M V S; Udaya Sri, N; Veeraiah, V

2015-09-05

In the present study, the FT-IR and FT-Raman spectra of 2-chloro-3-quinolinecarboxaldehyde (2Cl3QC) have been recorded in the region 4000-400 and 3500-50 cm(-1), respectively. The fundamental modes of vibrational frequencies of 2Cl3QC are assigned. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization have been analyzed using natural bond orbitals (NBO) analysis. The results show that charge in electron density (ED) in the π(∗) antibonding orbitals and E((2)) energies confirms the occurrence of ICT (intra-molecular charge transfer) within the molecule. UV-visible spectrum of the title molecule has also been calculated using TD-DFT/CAM-B3LYP/6-31G(d,p) method. The calculated energy and oscillator strength almost exactly reproduces reported experimental data. Copyright © 2015 Elsevier B.V. All rights reserved.

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...

Determination of human coronary artery composition by Raman spectroscopy.

PubMed

Brennan, J F; Römer, T J; Lees, R S; Tercyak, A M; Kramer, J R; Feld, M S

1997-07-01

We present a method for in situ chemical analysis of human coronary artery using near-infrared Raman spectroscopy. It is rapid and accurate and does not require tissue removal; small volumes, approximately 1 mm3, can be sampled. This methodology is likely to be useful as a tool for intravascular diagnosis of artery disease. Human coronary artery segments were obtained from nine explanted recipient hearts within 1 hour of heart transplantation. Minces from one or more segments were obtained through grinding in a mortar and pestle containing liquid nitrogen. Artery segments and minces were excited with 830 nm near-infrared light, and Raman spectra were collected with a specially designed spectrometer. A model was developed to analyze the spectra and quantify the amounts of cholesterol, cholesterol esters, triglycerides and phospholipids, and calcium salts present. The model provided excellent fits to spectra from the artery segments, indicating its applicability to intact tissue. In addition, the minces were assayed chemically for lipid and calcium salt content, and the results were compared. The relative weights obtained using the Raman technique agreed with those of the standard assays within a few percentage points. The chemical composition of coronary artery can be quantified accurately with Raman spectroscopy. This opens the possibility of using histochemical analysis to predict acute events such as plaque rupture, to follow the progression of disease, and to select appropriate therapeutic interventions.

[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.

Diversity in C-Xanes Spectra Obtained from Carbonaceous Solid Inclusions from Monahans Halite

NASA Technical Reports Server (NTRS)

Kebukawa, Y.; Zolensky, M. E.; Fries, M.; Kilcoyne, A. L. D.; Rahman, Z.; Cody, G. D.

2014-01-01

Monahans meteorite (H5) contains fluid inclusion- bearing halite (NaCl) crystals [1]. Microthermometry and Raman spectroscopy showed that the fluid in the inclusions is an aqueous brine and they were trapped near 25degC [1]. Their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism [2]. Abundant solid inclusions are also present in the halites. The solid inclusions include abundant and widely variable organics [2]. Analyses by Raman microprobe, SEM/EDX, synchrotron X-ray diffraction and TEM reveal that these grains include macromolecular carbon similar in structure to CV3 chondrite matrix carbon, aliphatic carbon compounds, olivine (Fo99-59), high- and low-Ca pyroxene, feldspars, magnetite, sulfides, lepidocrocite, carbonates, diamond, apatite and possibly the zeolite phillipsite [3]. Here we report organic analyses of these carbonaceous residues in Monahans halite using C-, N-, and O- X-ray absorption near edge structure (XANES). Samples and Methods: Approximately 100 nm-thick sections were extracted with a focused ion beam (FIB) at JSC from solid inclusions from Monahans halite. The sections were analyzed using the scanning transmission X-ray microscope (STXM) on beamline 5.3.2.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory for XANES spectroscopy. Results and Discussion: C-XANES spectra of the solid inclusions show micrometer-scale heterogeneity, indicating that the macromolecular carbon in the inclusions have complex chemical variations. C-XANES features include 284.7 eV assigned to aromatic C=C, 288.4-288.8 eV assigned to carboxyl, and 290.6 eV assigned to carbonate. The carbonyl features obtained by CXANES might have been caused by the FIB used in sample preparation. No specific N-XANES features are observed. The CXANES spectra obtained from several areas in the FIB sections include type 1&2 chondritic IOM like, type 3 chondritic IOM like, and none of the above

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.

Analysis of torsional spectra of molecules with two internal C/3v/ rotors. III - Far-infrared and gas phase Raman spectra of dimethylamine-d0, -d3, and -d6

NASA Technical Reports Server (NTRS)

Durig, J. R.; Griffin, M. G.; Groner, P.

1977-01-01

The Raman spectra of gaseous dimethylamine-d0, -d3, and -d6 have been recorded between 0 and 4000/cm. The far-infrared spectra have been recorded between 300 and 100/cm. Considerable torsional data are reported and used to characterize the torsional potential function based on a semi-rigid model. The average effective V3 for the dimethylamines was found to be 1052 plus or minus 12/cm. The cos-cos coupling term was approximately 15% of the effective V3, whereas the sine-sine coupling term was of an order of magnitude smaller for (CH3)2NH and (CD3)2NH. However, for the mixed isotope the sine-sine term was found to be negligible and the cos-cos about one-half the value obtained for the other two isotopes.

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.

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.

Surface enhanced Raman scattering (SERS) spectra of trinitrotoluene in silver colloids prepared by microwave heating method.

PubMed

Zhang, Chunling; Wang, Kaijun; Han, Dejun; Pang, Qing

2014-03-25

Surface enhanced Raman spectroscopy (SERS) has been demonstrated for the detection of trace levels of explosives due to its high sensitivity, speed of detection and fingerprint feature. 2,4,6-Trinitrotoluene (TNT), a leading example of nitroaromatic explosives, is causing wide concern. In this study, SERS spectra of TNT solution in silver colloids have been successfully measured and a comparison was drawn with the normal Raman spectra of bulk TNT. The silver colloids were prepared by the microwave heating method and characterized by UV-Vis spectra and the scanning electron microscopy (SEM). NaCl and pH value have a great impact on SERS intensity of TNT, the corresponding experimental research results and theoretical interpretations were further illustrated to a certain extent. Moreover, the detection limit of TNT in aqueous solution was achieved as low as 10(-10) mol L(-1) and some preliminary experiments of detecting TNT vapor (about 10 μg/L) using SERS have been carried out. Our results demonstrated the potential of SERS for probing TNT with high sensitivity, and suggest SERS as a powerful method for detection of TNT and similar species at trace levels. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

Wavelet data processing of micro-Raman spectra of biological samples

NASA Astrophysics Data System (ADS)

Camerlingo, C.; Zenone, F.; Gaeta, G. M.; Riccio, R.; Lepore, M.

2006-02-01

A wavelet multi-component decomposition algorithm is proposed for processing data from micro-Raman spectroscopy (μ-RS) of biological tissue. The μ-RS has been recently recognized as a promising tool for the biopsy test and in vivo diagnosis of degenerative human tissue pathologies, due to the high chemical and structural information contents of this spectroscopic technique. However, measurements of biological tissues are usually hampered by typically low-level signals and by the presence of noise and background components caused by light diffusion or fluorescence processes. In order to overcome these problems, a numerical method based on discrete wavelet transform is used for the analysis of data from μ-RS measurements performed in vitro on animal (pig and chicken) tissue samples and, in a preliminary form, on human skin and oral tissue biopsy from normal subjects. Visible light μ-RS was performed using a He-Ne laser and a monochromator with a liquid nitrogen cooled charge coupled device equipped with a grating of 1800 grooves mm-1. The validity of the proposed data procedure has been tested on the well-characterized Raman spectra of reference acetylsalicylic acid samples.

Influence of annealing temperature on Raman and photoluminescence spectra of electron beam evaporated TiO₂ thin films.

PubMed

Vishwas, M; Narasimha Rao, K; Chakradhar, R P S

2012-12-01

Titanium dioxide (TiO(2)) thin films were deposited on fused quartz substrates by electron beam evaporation method at room temperature. The films were annealed at different temperatures in ambient air. The surface morphology/roughness at different annealing temperatures were analyzed by atomic force microscopy (AFM). The crystallinity of the film has improved with the increase of annealing temperature. The effect of annealing temperature on optical, photoluminescence and Raman spectra of TiO(2) films were investigated. The refractive index of TiO(2) films were studied by envelope method and reflectance spectra and it is observed that the refractive index of the films was high. The photoluminescence intensity corresponding to green emission was enhanced with increase of annealing temperature. The peaks in Raman spectra depicts that the TiO(2) film is of anatase phase after annealing at 300°C and higher. The films show high refractive index, good optical quality and photoluminescence characteristics suggest that possible usage in opto-electronic and optical coating applications. Copyright © 2012 Elsevier B.V. All rights reserved.

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.

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.

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.

Discriminant analysis of Raman spectra for body fluid identification for forensic purposes.

PubMed

Sikirzhytski, Vitali; Virkler, Kelly; Lednev, Igor K

2010-01-01

Detection and identification of blood, semen and saliva stains, the most common body fluids encountered at a crime scene, are very important aspects of forensic science today. This study targets the development of a nondestructive, confirmatory method for body fluid identification based on Raman spectroscopy coupled with advanced statistical analysis. Dry traces of blood, semen and saliva obtained from multiple donors were probed using a confocal Raman microscope with a 785-nm excitation wavelength under controlled laboratory conditions. Results demonstrated the capability of Raman spectroscopy to identify an unknown substance to be semen, blood or saliva with high confidence.

Discriminant Analysis of Raman Spectra for Body Fluid Identification for Forensic Purposes

PubMed Central

Sikirzhytski, Vitali; Virkler, Kelly; Lednev, Igor K.

2010-01-01

Detection and identification of blood, semen and saliva stains, the most common body fluids encountered at a crime scene, are very important aspects of forensic science today. This study targets the development of a nondestructive, confirmatory method for body fluid identification based on Raman spectroscopy coupled with advanced statistical analysis. Dry traces of blood, semen and saliva obtained from multiple donors were probed using a confocal Raman microscope with a 785-nm excitation wavelength under controlled laboratory conditions. Results demonstrated the capability of Raman spectroscopy to identify an unknown substance to be semen, blood or saliva with high confidence. PMID:22319277

Structural characterization of tellurite glasses doped with transition metal oxides using Raman spectra and ab initio calculations.

PubMed

Mohamed, Tarek A; Shaltout, I; Al Yahyaei, K M

2006-05-01

Systems of iron tellurite glasses were prepared by melt quenching with compositions of [85%TeO2+5%Fe2O3+10%TMO], where transition metal oxides (TMO) are TiO2, V2O5, MnO, CoO, NiO and CuO. Furthermore, the main structural units of these samples have been characterized by means of Raman spectra (150-1200 cm(-1)) as well as wavenumber predictions by means of Gaussian 98 ab initio calculations for the proposed site symmetries of TeO4(4-) triagonal bipyramid (C2v) and Te2O7(6-) bridged tetrahedra (Cs and C1). Aided by normal coordinate analysis, calculated vibrational frequencies, Raman scattering activities, force constants in internal coordinates and potential energy distributions (PEDs), revised vibrational assignments for the fundamental modes have been proposed. The main structural features are correlated to the dominant units of triagonal bipyramid (tbp) or bridged tetrahedral (TeO3+1 binds to TeO3 through TeOTe bridge; corner sharing). Moreover, the Raman spectra of the investigated tellurites reflect a structural change from tbp (coordination number is four) to triagonal pyramidal (coordination number is three).

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.

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.

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.

Using Separable Nonnegative Matrix Factorization Techniques for the Analysis of Time-Resolved Raman Spectra

NASA Astrophysics Data System (ADS)

Luce, R.; Hildebrandt, P.; Kuhlmann, U.; Liesen, J.

2016-09-01

The key challenge of time-resolved Raman spectroscopy is the identification of the constituent species and the analysis of the kinetics of the underlying reaction network. In this work we present an integral approach that allows for determining both the component spectra and the rate constants simultaneously from a series of vibrational spectra. It is based on an algorithm for non-negative matrix factorization which is applied to the experimental data set following a few pre-processing steps. As a prerequisite for physically unambiguous solutions, each component spectrum must include one vibrational band that does not significantly interfere with vibrational bands of other species. The approach is applied to synthetic "experimental" spectra derived from model systems comprising a set of species with component spectra differing with respect to their degree of spectral interferences and signal-to-noise ratios. In each case, the species involved are connected via monomolecular reaction pathways. The potential and limitations of the approach for recovering the respective rate constants and component spectra are discussed.

Using Separable Nonnegative Matrix Factorization Techniques for the Analysis of Time-Resolved Raman Spectra.

PubMed

Luce, Robert; Hildebrandt, Peter; Kuhlmann, Uwe; Liesen, Jörg

2016-09-01

The key challenge of time-resolved Raman spectroscopy is the identification of the constituent species and the analysis of the kinetics of the underlying reaction network. In this work we present an integral approach that allows for determining both the component spectra and the rate constants simultaneously from a series of vibrational spectra. It is based on an algorithm for nonnegative matrix factorization that is applied to the experimental data set following a few pre-processing steps. As a prerequisite for physically unambiguous solutions, each component spectrum must include one vibrational band that does not significantly interfere with the vibrational bands of other species. The approach is applied to synthetic "experimental" spectra derived from model systems comprising a set of species with component spectra differing with respect to their degree of spectral interferences and signal-to-noise ratios. In each case, the species involved are connected via monomolecular reaction pathways. The potential and limitations of the approach for recovering the respective rate constants and component spectra are discussed. © The Author(s) 2016.

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.

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.

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

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 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.

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.

FT-IR and Raman spectra, DFT and SQMFF calculations for geometrical interpretation and vibrational analysis of 3-nitro-p-toluic acid

NASA Astrophysics Data System (ADS)

Nataraj, A.; Balachandran, V.; Karthick, T.

2012-08-01

The Fourier transform infrared (FT-IR) and FT-Raman of 3-nitro-p-toluic acid (NTA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The optimized geometric bond lengths and bond angles obtained by computation show good agreement with experimental data of the relative compound. The computed dimer parameters also show good agreement with experimental data. The first hyperpolarizability (β0) of this noval molecular system and related properties (β, α0, and Δα) of NTA are calculated using B3LYP/6-311++G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbital and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The calculated HOMO and LUMO energies also show that charge transfer occurs within the molecule. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra.

Theoretical Study of Infrared and Raman Spectra of Hydrated Magnesium Sulfate Salts

NASA Technical Reports Server (NTRS)

Chaban, Galina M.; Huo, Winifred M.; Lee, Timothy J.; Kwak, Dochan (Technical Monitor)

2002-01-01

Harmonic and anharmonic vibrational frequencies, as well as infrared and Raman intensities, are calculated for MgSO4.nH20 (n=1-3). Electronic structure theory at the second order Moller-Plesset perturbation theory (MP2) level with a triple-zeta + polarization (TZP) basis set is used to determine the geometry, properties, and vibrational spectra of pure and hydrated MgSO4 salts. The direct vibrational self-consistent field (VSCF) method and its correlation corrected (CC-VSCF) extension are used to determine anharmonic corrections to vibrational frequencies and intensities for the pure MgSO4 and its complex with one water molecule. Very significant differences are found between vibrational of water molecules in complexes with MgSO4 and pure water. Some of the O-H stretching frequencies are shifted to the red very significantly (by up to 1500-2000/cm) upon complexation with magnesium sulfate. They should be observed between 1700 and 3000/cm in a region very different from the corresponding O-H stretch frequency region of pure water (3700-3800/cm). In addition, the SO2 stretching vibrations are found at lower frequency regions than the water vibrations. They can serve as unique identifiers for the presence of sulfate salts. The predicted infrared and Raman spectra should be of valuable help in the design of future missions and analysis of observed data from the ice surface of Jupiter's moon Europa that possibly contains hydrated MgSO4 salts.

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.

The spectroscopic (FTIR, FT-Raman and UV-Vis spectra), DFT and normal coordinate computations of m-nitromethylbenzoate

NASA Astrophysics Data System (ADS)

Gnanasambandan, T.; Gunasekaran, S.; Seshadri, S.

2013-08-01

A combined experimental and theoretical study on molecular structure, vibrational spectra, NBO and UV-spectral analysis of m-nitromethylbenzoate (MNMB) has been reported in the present work. The FT-IR solid phase (4000-400 cm-1) and FT-Raman spectra (3500-100 cm-1) of MNMB was recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of MNMB in the ground-state have been calculated by using the density functional method B3LYP with 6-31G (d,p) and 6-31+G(d,p) basis sets. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). Stability of the molecule arising from hyperconjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ∗ antibonding orbitals and E(2) energies confirms the occurrence of ICT (Intra-molecular Charge Transfer) within the molecule. The UV spectrum was measured in ethyl acetate solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) result complements the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra.

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.

Geometry and Raman spectra of P.R. 255 and its furo-furanone analogue

NASA Astrophysics Data System (ADS)

Luňák, Stanislav, Jr.; Frumarová, Božena; Vyňuchal, Jan; Hrdina, Radim

2009-05-01

Fourier transform Raman spectra of two π-isoelectronic compounds 3,6-diphenyl-2,5-dihydro-pyrrolo-[3,4-c]pyrrole-1,4-dione (BPPB, C.I. Pigment Red 255) and 3,6-diphenyl-2,5-dihydro-furo-[3,4-c]furanone (BFFB) with the same 1,4-diphenyl-buta-1,3-diene (DPB) backbone were first time measured in polycrystalline phase. The ground state geometry and vibrational frequencies together with Raman intensities were computed by density functional theory (DFT: B3LYP/6-311G++(d,p)). All intensive observed Raman frequencies were identified as totally symmetric. The difference of carbon-carbon bond lengths of BPPB and BFFB compared to DPB, relating very well with the shifts of C dbnd C and C-C stretching modes frequencies, was explained by aromatization of central butadiene unit bounded in diketo-pyrrolo-pyrrole and furo-furanone heterocycles. A strong coupling of modes was observed for BFFB enhancing selectively the intensity of one peak 1593 cm -1 in C dbnd C stretching region and one peak 1372 cm -1 in C-C stretching region. C dbnd O stretching and N-H bending modes of BPPB are significantly affected by intermolecular hydrogen bonding.

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

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.

Influence of polarity of solvents on IR absorption and Raman spectra of ascorbic acid

NASA Astrophysics Data System (ADS)

Kutsenko, S. A.; Danyaeva, Y. S.; Maximova, S. V.

2018-04-01

The results of numerical calculations of IR absorption and Raman spectra of ascorbic acid in polar and nonpolar solutions are presented. The dependence of the change in the total energy and the dipole moment of the molecule on the characteristics of the solvents was investigated using the two solvation models. Spectral bands and the corresponding structural groups of the molecule are found, the characteristics of which are most vulnerable to solvents.

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.

Structure, IR and Raman spectra of phosphotrihydrazide studied by DFT

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

2016-09-01

The FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2]3 have been performed. This compound is a zero generation dendrimer G0 with terminal amine groups. Structural optimization and normal mode analysis were obtained for G0 by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614 cm- 1 in the experimental IR spectrum and by bands at 3327, 3241 cm- 1 in the Raman spectrum of G0. The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular Nsbnd H ⋯ S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimer.

In-line monitoring of a pharmaceutical blending process using FT-Raman spectroscopy.

PubMed

Vergote, G J; De Beer, T R M; Vervaet, C; Remon, J P; Baeyens, W R G; Diericx, N; Verpoort, F

2004-03-01

FT-Raman spectroscopy (in combination with a fibre optic probe) was evaluated as an in-line tool to monitor a blending process of diltiazem hydrochloride pellets and paraffinic wax beads. The mean square of differences (MSD) between two consecutive spectra was used to identify the time required to obtain a homogeneous mixture. A traditional end-sampling thief probe was used to collect samples, followed by HPLC analysis to verify the Raman data. Large variations were seen in the FT-Raman spectra logged during the initial minutes of the blending process using a binary mixture (ratio: 50/50, w/w) of diltiazem pellets and paraffinic wax beads (particle size: 800-1200 microm). The MSD-profiles showed that a homogeneous mixture was obtained after about 15 min blending. HPLC analysis confirmed these observations. The Raman data showed that the mixing kinetics depended on the particle size of the material and on the mixing speed. The results of this study proved that FT-Raman spectroscopy can be successfully implemented as an in-line monitoring tool for blending processes.

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.

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.

Noninvasive deep Raman detection with 2D correlation analysis

NASA Astrophysics Data System (ADS)

Kim, Hyung Min; Park, Hyo Sun; Cho, Youngho; Jin, Seung Min; Lee, Kang Taek; Jung, Young Mee; Suh, Yung Doug

2014-07-01

The detection of poisonous chemicals enclosed in daily necessaries is prerequisite essential for homeland security with the increasing threat of terrorism. For the detection of toxic chemicals, we combined a sensitive deep Raman spectroscopic method with 2D correlation analysis. We obtained the Raman spectra from concealed chemicals employing spatially offset Raman spectroscopy in which incident line-shaped light experiences multiple scatterings before being delivered to inner component and yielding deep Raman signal. Furthermore, we restored the pure Raman spectrum of each component using 2D correlation spectroscopic analysis with chemical inspection. Using this method, we could elucidate subsurface component under thick powder and packed contents in a bottle.

Molecules-in-molecules fragment-based method for the calculation of chiroptical spectra of large molecules: Vibrational circular dichroism and Raman optical activity spectra of alanine polypeptides.

PubMed

Jose, K V Jovan; Raghavachari, Krishnan

2016-12-01

The molecules-in-molecules (MIM) fragment-based method has recently been adapted to evaluate the chiroptical (vibrational circular dichroism [VCD] and Raman optical activity [ROA]) spectra of large molecules such as peptides. In the MIM-VCD and MIM-ROA methods, the relevant higher energy derivatives of the parent molecule are assembled from the corresponding derivatives of smaller fragment subsystems. In addition, the missing long-range interfragment interactions are accounted at a computationally less expensive level of theory (MIM2). In this work we employed the MIM-VCD and MIM-ROA fragment-based methods to explore the evolution of the chiroptical spectroscopic characteristics of 3 10 -helix, α-helix, β-hairpin, γ-turn, and β-extended conformers of gas phase polyalanine (chain length n = 6-14). The different conformers of polyalanine show distinctive features in the MIM chiroptical spectra and the associated spectral intensities increase with evolution of system size. For a better understanding the site-specific effects on the vibrational spectra, isotopic substitutions were also performed employing the MIM method. An increasing redshift with the number of isotopically labeled 13 C=O functional groups in the peptide molecule was seen. For larger polypeptides, we implemented the two-step-MIM model to circumvent the high computational expense associated with the evaluation of chiroptical spectra at a high level of theory using large basis sets. The chiroptical spectra of α-(alanine) 20 polypeptide obtained using the two-step-MIM model, including continuum solvation effects, show good agreement with the full calculations and experiment. This benchmark study suggests that the MIM-fragment approach can assist in predicting and interpreting chiroptical spectra of large polypeptides. © 2016 Wiley Periodicals, Inc.

Cross section of resonant Raman scattering of light by polyenes

NASA Astrophysics Data System (ADS)

Verdyugin, V. V.; Burshteyn, K. Ya.; Shorygin, P. P.

1987-03-01

An experimental study is presented of the resonant Raman spectra of beta carotene. Absolute differential cross sections are obtained for the most intensive Raman spectral lines with excitation at the absorption maximum. A theoretical analysis is presented of the variation in absolute differential cross section as a function of a number of conjunct double bonds in the polyenes.

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.

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.

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.

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.

[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.

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.

Pressure effect on the Raman and photoluminescence spectra of Eu3+-doped Na2Ti6O13 nanorods

NASA Astrophysics Data System (ADS)

Zeng, Q. G.; Yang, G. T.; Chen, F.; Luo, J. Y.; Zhang, Z. M.; Leung, C. W.; Ding, Z. J.; Sheng, Y. Q.

2013-12-01

Eu3+-doped Na2Ti6O13 (Na2Ti6O13:Eu) nanorods with diameters of 30 nm and lengths 400 nm were synthesized by hydrothermal and heat treatment methods. Raman spectra at ambient conditions indicated a pure monoclinic phase (space group C2/m) of the nanorods. The relations between structural and optical properties of Na2Ti6O13:Eu nanorods under high pressures were obtained by photoluminescence and Raman spectra. Two structural transition points at 1.39 and 15.48 GPa were observed when the samples were pressurized. The first transition point was attributed to the crystalline structural distortion. The later transition point was the result of pressure-induced amorphization, and the high-density amorphous (HDA) phase formed after 15.48 GPa was structurally related to the monoclinic baddeleyite structured TiO2 (P21/c). However, the site symmetry of the local environment around the Eu3+ ions in Na2Ti6O13 increased with the rising pressure. These above results indicate the occurrence of short-range order for the local asymmetry around the Eu3+ ions and long-range disorder for the crystalline structure of Na2Ti6O13:Eu nanorods by applying pressure. After releasing the pressure from 22.74 GPa, the HDA phase is transformed to low-density amorphous form, which is attributed to be structurally related to the α-PbO2-type TiO2.

Matrix isolation infrared and Raman spectra of binary and mixed group II B fluorides

NASA Astrophysics Data System (ADS)

Givan, A.; Loewenschuss, A.

1980-03-01

Infrared and Raman spectra of all MF2 and MFX molecules (M=Zn, Cd, Hg; X=Cl, Br) and the infrared spectrum of the fluoroidide HgFI isolated in solid krypton at 20 °K are reported. The MFX species were formed in a vapor mixture of the appropriate MF2 and MX2 dihalides, vaporized, at different temperatures, from separate compartments of a double-oven crucible. The spectra are the first experimental evidence for the existence of the molecular fluorohalides. All three fundamentals of the MF2 molecules and the two stretching mode frequencies of the MFX molecules are assigned. Harmonic force constants are evaluated and isotope effects are used to discuss their geometry. Thermodynamic functions are tabulated for the binary difluorides.

Study on Properties of Energy Spectra of the Molecular Crystals

NASA Astrophysics Data System (ADS)

Pang, Xiao-Feng; Chen, Xiang-Rong

The energy-spectra of nonlinear vibration of molecular crystals such as acetanilide have been calculated by using discrete nonlinear Schrödinger equation appropriate to the systems, containing various interactions. The energy levels including higher excited states are basically consistent with experimental values obtained by infrared absorption and Raman scattering in acetanilide. We further give the features of distribution of the energy-spectra for the acetanilide. Using the energy spectra we also explained well experimental results obtained by Careri et al..

Resonance Raman spectra of the copper-sulfur chromophores in Achromobacter cycloclastes nitrite reductase.

PubMed

Dooley, D M; Moog, R S; Liu, M Y; Payne, W J; LeGall, J

1988-10-15

Resonance Raman spectroscopy at ambient temperature and 77 K has been used to probe the structures of the copper sites in Achromobacter cycloclastes nitrite reductase. This enzyme contains three copper ions per protein molecule and has two principal electronic absorption bands with lambda max values of 458 and 585 nm. Comparisons between the resonance Raman spectra of nitrite reductase and blue copper proteins establish that both the 458 and 585 nm bands are associated with Cu(II)-S(Cys) chromophores. A histidine ligand probably is also present. Different sets of vibrational frequencies are observed with 457.9 nm (ambient) or 476.1 nm (77 K) excitation as compared with 590 nm (ambient) or 593 nm (77 K) excitation. Excitation profiles indicate that the 458 and 585 nm absorption bands are associated with separate [Cu(II)-S(Cys)N(His)] sites or with inequivalent and uncoupled cysteine ligands in the same site. The former possibility is considered to be more likely.

Structural properties and FTIR-Raman spectra of the anti-hypertensive clonidine hydrochloride agent and their dimeric species

NASA Astrophysics Data System (ADS)

Romano, Elida; Davies, Lilian; Brandán, Silvia Antonia

2017-04-01

The structural and vibrational properties of the α-adrenergic agonist clonidine hydrochloride agent and their anionic and dimeric species were studied combining the experimental FT-IR and Raman spectra in solid phase with ab-initio calculations based on the density functional theory (DFT). All the calculations were performed by using the hybrid B3LYP with the 6-31G* and 6-311++G** basis sets. The structural properties for those species were studied employing the Natural Bond Orbital (NBO), Atoms in Molecules theory (AIM) and frontier orbitals calculations. The complete assignments of the FTIR and Raman spectra were performed combining the DFT calculations with the Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology. Very good concordances between the theoretical and experimental spectra were found. In addition, the force constants for those three species were computed and compared with the values reported for similar antihypertensive agents. The ionic nature of the H→Cl bond and the high value of the LP(1)N4 → LP*(1)H18 charge transfer could explain the high reactivity of clonidine hydrochloride in relation to other antihypertensive agent and the strong shifthing of the band assigned to the Nsbnd H stretching mode linked to the Hsbnd Cl bond toward lower wavenumbers.

Experimental and theoretical IR and Raman spectra of picolinic, nicotinic and isonicotinic acids

NASA Astrophysics Data System (ADS)

Koczoń, P.; Dobrowolski, J. Cz.; Lewandowski, W.; Mazurek, A. P.

2003-07-01

The experimental and theoretical (B3PW91/6-311++G**) vibrational (IR and Raman) spectra of picolinic, nicotinic and isonicotinic acids (pyridine-2-, -3-, and -4-carboxylic acid, respectively) were studied. Three stable calculated structures were found for picolinic acid: the structure with intramolecular hydrogen COOH⋯N bond, and the two without hydrogen bond. For the nicotinic acid two stable theoretical structures differ in orientation of the COOH group with respect to the nitrogen atom, whereas for the isonicotinic acid only one form was stable. The theoretical vibrational spectra of the three acids were interpreted by means of potential energy distributions (PEDs) using VEDA 3 program. Next, selected experimental bands were assigned based on the scaled theoretical wavenumbers. Finally, the wavenumbers and intensities for the three isomeric acids were compared and discussed in terms of location of the carboxylic group.

Raman spectroscopic studies of chemical speciation in calcium chloride melts

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

Windisch, Charles F.; Lavender, Curt A.

2005-02-01

Raman spectroscopy was applied to CaCl2 melts at 900 degrees C under both non-electrolyzed and electrolyzed conditions. The later used titania cathodes supplied by TIMET, Inc. and graphite anodes. Use of pulse-gating to collect the Raman spectra successfully eliminated any interference from black-body radiation and other stray light. The spectrum of molten CaCl2 exhibited no distinct, resolvable bands that could be correlated with a calcium chloride complex similar to MgCl42- in MgCl2 melts. Rather, the low frequency region of the spectrum was dominated by a broad “tail” arising from collective oscillations of both charge and mass in the molten saltmore » “network.” Additions of both CaO and Ca at concentrations of a percent or two resulted in no new features in the spectra. Addition of CO2, both chemically and via electrolysis at concentrations dictated by stability and solubility at 900 degrees C and 1 bar pressure, also produced no new bands that could be correlated with either dissolved CO2 or the carbonate ion. These results indicated that Raman spectroscopy, at least under the conditions evaluated in the research, was not well suited for following the reactions and coordination chemistry of calcium ions, nor species such as dissolved metallic Ca and CO2 that are suspected to impact current efficiency in titanium electrolysis cells using molten CaCl2. Raman spectra of TIMET titania electrodes were successfully obtained as a function of temperature up to 900 degrees C, both in air and in-situ in CaCl2 melts. However, spectra of these electrodes could only be obtained when the material was in the unreduced state. When reduced, either with hydrogen or within an electrolysis cell, the resulting electrodes exhibited no measurable Raman bands under the conditions used in this work.« less

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.

Carbon Nanotubes' Effect on Mitochondrial Oxygen Flux Dynamics: Polarography Experimental Study and Machine Learning Models using Star Graph Trace Invariants of Raman Spectra.

PubMed

González-Durruthy, Michael; Monserrat, Jose M; Rasulev, Bakhtiyor; Casañola-Martín, Gerardo M; Barreiro Sorrivas, José María; Paraíso-Medina, Sergio; Maojo, Víctor; González-Díaz, Humberto; Pazos, Alejandro; Munteanu, Cristian R

2017-11-11

This study presents the impact of carbon nanotubes (CNTs) on mitochondrial oxygen mass flux ( J m ) under three experimental conditions. New experimental results and a new methodology are reported for the first time and they are based on CNT Raman spectra star graph transform (spectral moments) and perturbation theory. The experimental measures of J m showed that no tested CNT family can inhibit the oxygen consumption profiles of mitochondria. The best model for the prediction of J m for other CNTs was provided by random forest using eight features, obtaining test R-squared ( R ²) of 0.863 and test root-mean-square error (RMSE) of 0.0461. The results demonstrate the capability of encoding CNT information into spectral moments of the Raman star graphs (SG) transform with a potential applicability as predictive tools in nanotechnology and material risk assessments.

Monitoring of aqueous humor metabolites using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Wicksted, James P.; Erckens, Roel J.; Motamedi, Massoud; March, Wayne F.

1994-05-01

Laser Raman scattering has been used to monitor glucose and lactate metabolites within aqueous humor specimens obtained from nine human eyes during cataract surgery. Nine postmortem rabbit eyes were also investigated. Raman measurements were obtained using a single grating Raman spectrometer with a liquid nitrogen cooled CCD. A 514.5 nm line from an argon laser was used to illuminate capillaries containing several microliters of aqueous humor. A water background was subtracted from each of the aqueous humor Raman spectra. This experimental system was calibrated so that each metabolite in water could be measured down to 0.1 weight percent. Raman peaks indicative of the stretching vibrations of methylene and methyl groups associated with glucose and lactate, respectively, were observed in the human specimens. A second stretching mode characteristic of lactate between the carbon atom and either the carboxylic acid group or carboxylate ion group was also observed providing a distinguishing feature between the glucose and lactate Raman peaks. Similar structure was observed from the rabbit specimens, but these samples have recently been found to have been contaminated during euthanasia.

Appearance of radial breathing modes in Raman spectra of multi-walled carbon nanotubes upon laser illumination

NASA Astrophysics Data System (ADS)

Rai, Padmnabh; Mohapatra, Dipti R.; Hazra, K. S.; Misra, D. S.; Ghatak, Jay; Satyam, P. V.

2008-03-01

The Raman spectra of the multi-walled carbon nanotubes are studied with the laser power of 5-20 mW. We observe the Raman bands at ˜1352, 1581, 1607, and 2700 cm -1 with 5 mW laser power. As the laser power is increased to 10, 15 and 20 mW, the radial breathing modes (RBMs) of the single wall carbon nanotubes (SWNTs) appear in the range 200-610 cm -1. The diameter corresponding to the highest RBM is ˜0.37 nm, the lowest reported so far. The RBMs are attributed to the local synthesis of the SWNTs at the top surface of the samples at higher laser power.

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.

The characterization of photographic materials as substrates for surface enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Vaughan, J.; Hortin, N.; Christie, S.; Kvasnik, F.; Scully, P. J.

2005-06-01

In this study, five types of photographic materials were obtained from commercial sources and characterized for use as substrates for surface enhanced Raman spectroscopy. The substrates are photographic emulsions coated on glass or paper support. The emulsions were developed to maximize the amount of metallic silver aggregated into clusters. The test analyte, Cresyl Violet, was deposited directly onto the substrate surface. The permeable nature of the supporting gelatin matrix enables the interaction between the target analyte and the solid silver clusters. The surface enhanced Raman spectra of a 2.75 × 10-7 M concentration of Cresyl Violet in ethanol were obtained using these photographic substrates. The Raman and resonant Raman enhancement of Cresyl Violet varies from substrate to substrate, as does the ratio of Raman to resonant Raman peak heights.

Raman spectroscopic studies on bacteria

NASA Astrophysics Data System (ADS)

Maquelin, Kees; Choo-Smith, Lin-P'ing; Endtz, Hubert P.; Bruining, Hajo A.; Puppels, Gerwin J.

2000-11-01

Routine clinical microbiological identification of pathogenic micro-organisms is largely based on nutritional and biochemical tests. Laboratory results can be presented to a clinician after 2 - 3 days for most clinically relevant micro- organisms. Most of this time is required to obtain pure cultures and enough biomass for the tests to be performed. In the case of severely ill patients, this unavoidable time delay associated with such identification procedures can be fatal. A novel identification method based on confocal Raman microspectroscopy will be presented. With this method it is possible to obtain Raman spectra directly from microbial microcolonies on the solid culture medium, which have developed after only 6 hours of culturing for most commonly encountered organisms. Not only does this technique enable rapid (same day) identifications, but also preserves the sample allowing it to be double-checked with traditional tests. This, combined with the speed and minimal sample handling indicate that confocal Raman microspectroscopy has much potential as a powerful new tool in clinical diagnostic microbiology.

Experimental and theoretical studies on IR, Raman, and UV-Vis spectra of quinoline-7-carboxaldehyde.

PubMed

Kumru, M; Küçük, V; Kocademir, M; Alfanda, H M; Altun, A; Sarı, L

2015-01-05

Spectroscopic properties of quinoline-7-carboxaldehyde (Q7C) have been studied in detail both experimentally and theoretically. The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)), dispersive-Raman (3500-50 cm(-1)), and UV-Vis (200-400 nm) spectra of Q7C were recorded at room temperature (25 °C). Geometry parameters, potential energy surface about CCH(O) bond, harmonic vibrational frequencies, IR and Raman intensities, UV-Vis spectrum, and thermodynamic characteristics (at 298.15K) of Q7C were computed at Hartree-Fock (HF) and density functional B3LYP levels employing the 6-311++G(d,p) basis set. Frontier molecular orbitals, molecular electrostatic potential, and Mulliken charge analyses of Q7C have also been performed. Q7C has two stable conformers that are energetically very close to each other with slight preference to the conformer that has oxygen atom of the aldehyde away from the nitrogen atom of the quinoline. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of multivariate analysis methods for extracting the paraffin component from the paraffin-embedded cancer tissue spectra for Raman imaging

NASA Astrophysics Data System (ADS)

Meksiarun, Phiranuphon; Ishigaki, Mika; Huck-Pezzei, Verena A. C.; Huck, Christian W.; Wongravee, Kanet; Sato, Hidetoshi; Ozaki, Yukihiro

2017-03-01

This study aimed to extract the paraffin component from paraffin-embedded oral cancer tissue spectra using three multivariate analysis (MVA) methods; Independent Component Analysis (ICA), Partial Least Squares (PLS) and Independent Component - Partial Least Square (IC-PLS). The estimated paraffin components were used for removing the contribution of paraffin from the tissue spectra. These three methods were compared in terms of the efficiency of paraffin removal and the ability to retain the tissue information. It was found that ICA, PLS and IC-PLS could remove the paraffin component from the spectra at almost the same level while Principal Component Analysis (PCA) was incapable. In terms of retaining cancer tissue spectral integrity, effects of PLS and IC-PLS on the non-paraffin region were significantly less than that of ICA where cancer tissue spectral areas were deteriorated. The paraffin-removed spectra were used for constructing Raman images of oral cancer tissue and compared with Hematoxylin and Eosin (H&E) stained tissues for verification. This study has demonstrated the capability of Raman spectroscopy together with multivariate analysis methods as a diagnostic tool for the paraffin-embedded tissue section.

Raman Spectroscopy with High Power Diode Lasers

NASA Astrophysics Data System (ADS)

Claps, Ricardo

1998-10-01

Our group has demonstrated in the past that it is possible to record, with a high power Diode Laser, Raman spectra of low pressure gases. An external cavity was used to lock the laser into single mode operation. Also, the use of atomic filters permitted the observation of rotational Raman lines only 1 cm-1 apart from the excitation frequency ( J.Sabbaghzadeh, M.Fink, et-all; Applied Physics ) B 60 (1995), p.261-265.. We present now an improved version of the experiment, with beamshaping optics that help to correct the highly astigmatic output of the Diode Laser; this allowed us to put 300 mW of cw power through a multi-pass cell in the sample chamber, `increasing the signal by a factor of ~ 15. We present examples of rotational and vibrational spectra from CO_2, N_2, and air. The results show that we are able to obtain spectra with a S/N ratio of 0.011 per Torr, per √s, which means that we can detect 1 Torr of these gases in a few hours of exposure, at a maximum resolution of 0.85 cm-1 over a range of 200 cm-1. The laser stability in power, frequency and bandwidth, ensures the feasibility of long exposure experiments. We plan to apply the Raman technique to study flow properties of gases under different dynamic conditions; as a result, we expect to use our instrument for the study of the vibrational Raman spectra of alkali-halide dimers in vapour phase at low pressures.

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.

Discrimination of Aspergillus lentulus from Aspergillus fumigatus by Raman spectroscopy and MALDI-TOF MS.

PubMed

Verwer, P E B; van Leeuwen, W B; Girard, V; Monnin, V; van Belkum, A; Staab, J F; Verbrugh, H A; Bakker-Woudenberg, I A J M; van de Sande, W W J

2014-02-01

In 2005, a new sibling species of Aspergillus fumigatus was discovered: Aspergillus lentulus. Both species can cause invasive fungal disease in immune-compromised patients. The species are morphologically very similar. Current techniques for identification are PCR-based or morphology-based. These techniques are labour-intense and not sufficiently discriminatory. Since A. lentulus is less susceptible to several antifungal agents, it is important to correctly identify the causative infectious agent in order to optimize antifungal therapy. In this study we determined whether Raman spectroscopy and/or MALDI-TOF MS were able to differentiate between A. lentulus and A. fumigatus. For 16 isolates of A. lentulus and 16 isolates of A. fumigatus, Raman spectra and peptide profiles were obtained using the Spectracell and MALDI-TOF MS (VITEK MS RUO, bioMérieux) respectively. In order to obtain reliable Raman spectra for A. fumigatus and A. lentulus, the culture medium needed to be adjusted to obtain colourless conidia. Only Raman spectra obtained from colourless conidia were reproducible and correctly identified 25 out of 32 (78 %) of the Aspergillus strains. For VITEK MS RUO, no medium adjustments were necessary. Pigmented conidia resulted in reproducible peptide profiles as well in this case. VITEK MS RUO correctly identified 100 % of the Aspergillus isolates, within a timeframe of approximately 54 h including culture. Of the two techniques studied here, VITEK MS RUO was superior to Raman spectroscopy in the discrimination of A. lentulus from A. fumigatus. VITEK MS RUO seems to be a successful technique in the daily identification of Aspergillus spp. within a limited timeframe.

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.

Rapid and accurate peripheral nerve detection using multipoint Raman imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kumamoto, Yasuaki; Minamikawa, Takeo; Kawamura, Akinori; Matsumura, Junichi; Tsuda, Yuichiro; Ukon, Juichiro; Harada, Yoshinori; Tanaka, Hideo; Takamatsu, Tetsuro

2017-02-01

Nerve-sparing surgery is essential to avoid functional deficits of the limbs and organs. Raman scattering, a label-free, minimally invasive, and accurate modality, is one of the best candidate technologies to detect nerves for nerve-sparing surgery. However, Raman scattering imaging is too time-consuming to be employed in surgery. Here we present a rapid and accurate nerve visualization method using a multipoint Raman imaging technique that has enabled simultaneous spectra measurement from different locations (n=32) of a sample. Five sec is sufficient for measuring n=32 spectra with good S/N from a given tissue. Principal component regression discriminant analysis discriminated spectra obtained from peripheral nerves (n=863 from n=161 myelinated nerves) and connective tissue (n=828 from n=121 tendons) with sensitivity and specificity of 88.3% and 94.8%, respectively. To compensate the spatial information of a multipoint-Raman-derived tissue discrimination image that is too sparse to visualize nerve arrangement, we used morphological information obtained from a bright-field image. When merged with the sparse tissue discrimination image, a morphological image of a sample shows what portion of Raman measurement points in arbitrary structure is determined as nerve. Setting a nerve detection criterion on the portion of "nerve" points in the structure as 40% or more, myelinated nerves (n=161) and tendons (n=121) were discriminated with sensitivity and specificity of 97.5%. The presented technique utilizing a sparse multipoint Raman image and a bright-field image has enabled rapid, safe, and accurate detection of peripheral nerves.

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.

Laser Raman spectra of mono-, oligo- and polysaccharides in solution

NASA Astrophysics Data System (ADS)

Barrett, T. W.

We examined the Raman spectra of thirteen sugars—seven monosaccharides, two disaccharides, one trisaccharide and three polysaccharides—in the wavelength range 200—1700 cm -1 and (i) varied the phosphate buffered solution from pH 6.0 to 8.5 at constant ionic strength of 0.1 and (ii) varied HCl solutions from pH 0.8 to 5.0. As is to be expected with molecules containing COH groupings, all the molecular spectra are distinct. Of the thirteen sugars examined, only D-fructose 1,6-diphosphate (FDP) demonstrated spectral changes for the pH range 6.0—8.5 in phosphate buffer; but all exhibited band intensity enhancement in HCl at the lower pHs, but not band wavenumber changes. The results indicate that: (i) changes in the pH of the major intracellular buffer, phosphate, toward acidity, are able to hydrolyze the 1-phosphate group of FDP and the relative concentration of fructose 1-phosphate to fructose 6-phosphate is indicated by the intensity ratio of the 982 and 1080 cm -1 bands; (ii) it appears that all phosphate groups of FDP are hydrolyzed at pH 0.8 in HCl; and (iii) although conditions of extreme acidity are able to hydrolyze other sugars examined, there is no major degradation.

Spectroscopic characterization of biological agents using FTIR, normal Raman and surface-enhanced Raman spectroscopies

NASA Astrophysics Data System (ADS)

Luna-Pineda, Tatiana; Soto-Feliciano, Kristina; De La Cruz-Montoya, Edwin; Pacheco Londoño, Leonardo C.; Ríos-Velázquez, Carlos; Hernández-Rivera, Samuel P.

2007-04-01

FTIR, Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) requires a minimum of sample allows fast identification of microorganisms. The use of this technique for characterizing the spectroscopic signatures of these agents and their stimulants has recently gained considerable attention due to the fact that these techniques can be easily adapted for standoff detection from considerable distances. The techniques also show high sensitivity and selectivity and offer near real time detection duty cycles. This research focuses in laying the grounds for the spectroscopic differentiation of Staphylococcus spp., Pseudomonas spp., Bacillus spp., Salmonella spp., Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, and E. coli, together with identification of their subspecies. In order to achieve the proponed objective, protocols to handle, cultivate and analyze the strains have been developed. Spectroscopic similarities and marked differences have been found for Spontaneous or Normal Raman spectra and for SERS using silver nanoparticles have been found. The use of principal component analysis (PCA), discriminate factor analysis (DFA) and a cluster analysis were used to evaluate the efficacy of identifying potential threat bacterial from their spectra collected on single bacteria. The DFA from the bacteria Raman spectra show a little discrimination between the diverse bacterial species however the results obtained from the SERS demonstrate to be high discrimination technique. The spectroscopic study will be extended to examine the spores produced by selected strains since these are more prone to be used as Biological Warfare Agents due to their increased mobility and possibility of airborne transport. Micro infrared spectroscopy as well as fiber coupled FTIR will also be used as possible sensors of target compounds.

Design and build a compact Raman sensor for identification of chemical composition

NASA Astrophysics Data System (ADS)

Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Sandford, Stephen P.; Elsayed-Ali, Hani

2008-04-01

A compact remote Raman sensor system was developed at NASA Langley Research Center. This sensor is an improvement over the previously reported system, which consisted of a 532 nm pulsed laser, a 4-inch telescope, a spectrograph, and an intensified CCD camera. One of the attractive features of the previous system was its portability, thereby making it suitable for applications such as planetary surface explorations, homeland security and defense applications where a compact portable instrument is important. The new system was made more compact by replacing bulky components with smaller and lighter components. The new compact system uses a smaller spectrograph measuring 9 x 4 x 4 in. and a smaller intensified CCD camera measuring 5 in. long and 2 in. in diameter. The previous system was used to obtain the Raman spectra of several materials that are important to defense and security applications. Furthermore, the new compact Raman sensor system is used to obtain the Raman spectra of a diverse set of materials to demonstrate the sensor system's potential use in the identification of unknown materials.

Design and Build a Compact Raman Sensor for Identification of Chemical Composition

NASA Technical Reports Server (NTRS)

Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Sandford, Stephen P.; Elsayed-Ali, Hani

2008-01-01

A compact remote Raman sensor system was developed at NASA Langley Research Center. This sensor is an improvement over the previously reported system, which consisted of a 532 nm pulsed laser, a 4-inch telescope, a spectrograph, and an intensified charge-coupled devices (CCD) camera. One of the attractive features of the previous system was its portability, thereby making it suitable for applications such as planetary surface explorations, homeland security and defense applications where a compact portable instrument is important. The new system was made more compact by replacing bulky components with smaller and lighter components. The new compact system uses a smaller spectrograph measuring 9 x 4 x 4 in. and a smaller intensified CCD camera measuring 5 in. long and 2 in. in diameter. The previous system was used to obtain the Raman spectra of several materials that are important to defense and security applications. Furthermore, the new compact Raman sensor system is used to obtain the Raman spectra of a diverse set of materials to demonstrate the sensor system's potential use in the identification of unknown materials.

In Situ Raman Analysis of CO₂-Assisted Drying of Fruit-Slices.

PubMed

Braeuer, Andreas Siegfried; Schuster, Julian Jonathan; Gebrekidan, Medhanie Tesfay; Bahr, Leo; Michelino, Filippo; Zambon, Alessandro; Spilimbergo, Sara

2017-05-15

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO₂) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO₂ into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve.

Vibrational investigation on FT-IR and FT-Raman spectra, IR intensity, Raman activity, peak resemblance, ideal estimation, standard deviation of computed frequencies analyses and electronic structure on 3-methyl-1,2-butadiene using HF and DFT (LSDA/B3LYP/B3PW91) calculations.

PubMed

Ramalingam, S; Jayaprakash, A; Mohan, S; Karabacak, M

2011-11-01

FT-IR and FT-Raman (4000-100 cm(-1)) spectral measurements of 3-methyl-1,2-butadiene (3M12B) have been attempted in the present work. Ab-initio HF and DFT (LSDA/B3LYP/B3PW91) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, IR intensities and Raman activities. Complete vibrational assignments on the observed spectra are made with vibrational frequencies obtained by HF and DFT (LSDA/B3LYP/B3PW91) at 6-31G(d,p) and 6-311G(d,p) basis sets. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The potential energy distribution (PED) corresponding to each of the observed frequencies are calculated which confirms the reliability and precision of the assignment and analysis of the vibrational fundamentals modes. The oscillation of vibrational frequencies of butadiene due to the couple of methyl group is also discussed. A study on the electronic properties such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures reveal the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H). Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Interpretation of FTIR spectra of polymers and Raman spectra of car paints by means of likelihood ratio approach supported by wavelet transform for reducing data dimensionality.

PubMed

Martyna, Agnieszka; Michalska, Aleksandra; Zadora, Grzegorz

2015-05-01

The problem of interpretation of common provenance of the samples within the infrared spectra database of polypropylene samples from car body parts and plastic containers as well as Raman spectra databases of blue solid and metallic automotive paints was under investigation. The research involved statistical tools such as likelihood ratio (LR) approach for expressing the evidential value of observed similarities and differences in the recorded spectra. Since the LR models can be easily proposed for databases described by a few variables, research focused on the problem of spectra dimensionality reduction characterised by more than a thousand variables. The objective of the studies was to combine the chemometric tools easily dealing with multidimensionality with an LR approach. The final variables used for LR models' construction were derived from the discrete wavelet transform (DWT) as a data dimensionality reduction technique supported by methods for variance analysis and corresponded with chemical information, i.e. typical absorption bands for polypropylene and peaks associated with pigments present in the car paints. Univariate and multivariate LR models were proposed, aiming at obtaining more information about the chemical structure of the samples. Their performance was controlled by estimating the levels of false positive and false negative answers and using the empirical cross entropy approach. The results for most of the LR models were satisfactory and enabled solving the stated comparison problems. The results prove that the variables generated from DWT preserve signal characteristic, being a sparse representation of the original signal by keeping its shape and relevant chemical information.

Discrimination of serum Raman spectroscopy between normal and colorectal cancer

NASA Astrophysics Data System (ADS)

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

2011-07-01

Raman spectroscopy of tissues has been widely studied for the diagnosis of various cancers, but biofluids were seldom used as the analyte because of the low concentration. Herein, serum of 30 normal people, 46 colon cancer, and 44 rectum cancer patients were measured Raman spectra and analyzed. The information of Raman peaks (intensity and width) and that of the fluorescence background (baseline function coefficients) were selected as parameters for statistical analysis. Principal component regression (PCR) and partial least square regression (PLSR) were used on the selected parameters separately to see the performance of the parameters. PCR performed better than PLSR in our spectral data. Then linear discriminant analysis (LDA) was used on the principal components (PCs) of the two regression method on the selected parameters, and a diagnostic accuracy of 88% and 83% were obtained. The conclusion is that the selected features can maintain the information of original spectra well and Raman spectroscopy of serum has the potential for the diagnosis of colorectal cancer.

Blood proteins analysis by Raman spectroscopy method

NASA Astrophysics Data System (ADS)

Artemyev, D. N.; Bratchenko, I. A.; Khristoforova, Yu. A.; Lykina, A. A.; Myakinin, O. O.; Kuzmina, T. P.; Davydkin, I. L.; Zakharov, V. P.

2016-04-01

This work is devoted to study the possibility of plasma proteins (albumin, globulins) concentration measurement using Raman spectroscopy setup. The blood plasma and whole blood were studied in this research. The obtained Raman spectra showed significant variation of intensities of certain spectral bands 940, 1005, 1330, 1450 and 1650 cm-1 for different protein fractions. Partial least squares regression analysis was used for determination of correlation coefficients. We have shown that the proposed method represents the structure and biochemical composition of major blood proteins.

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.

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.

Resonance Raman spectroscopy of octopus rhodopsin and its photoproducts

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

Pande, C.; Pande, A.; Yue, K.T.

1987-08-11

The authors report here the resonance Raman spectra of octopus rhodopsin and its photoproducts, bathorhodopsin and acid metarhodopsin. These studies were undertaken in order to make comparisons with the well-studied bovine pigments, so as to understand the similarities and the differences in pigment structure and photochemical processes between vertebrates and invertebrates. The flow method was used to obtain the Raman spectrum of rhodopsin at 13 /sup 0/C. The bathorhodopsin spectrum was obtained by computer subtraction of the spectra containing different photostationary mixtures of rhodopsin, isorhodopsin, hypsorhodopsin, and bathorhodopsin, obtained at 12 K using the pump-probe technique and from measurements atmore » 80 K. Like their bovine counterparts, the Schiff base vibrational mode appears at approx. 1660 cm/sup -1/ in octopus rhodopsin and the photoproducts, bathorhodopsin and acid metarhodopsin, suggesting a proteonated Schiff base linkage between the chromophore and the protein. Differences between the Raman spectra of octopus rhodopsin and bathorhodopsin indicate that the formation of bathorhodopsin is associated with chromophore isomerization. This inference is substantiated by the chromophore chemical extraction data which show that, like the bovine system, octopus rhodopsin is an 11-cis pigment, while the photoproducts contain an all-trans pigment, in agreement with the previous work. The octopus rhodopsin and bathorhodopsin spectra show marked differences from their bovine counterparts in other respects, however. The differences are most dramatic in the structure-sensitive fingerprint and the HOOP regions. Thus, it appears that although the two species differ in the specific nature of the chromophore-protein interactions, the general process of visual transduction is the same.« less

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.

Raman microprobe analysis of single ramie fiber during mercerization

Treesearch

Akira Isogai; Umesh P. Agarwal; Rajai H. Atalla

2003-01-01

The Raman microprobe technique was applied to structural analysis of single ramie fibers during mercerization. Polarized laser beam was irradiated on a ramie fiber in 0-30 % NaOD/D2O with the electric vector at 0 or 90° to the fiber axis, and Raman spectra thus obtained were studied in relation to the concentration of NaOD in D2O. Conversion of -OH to -OD in ramie...

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.

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.

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.

Structural properties, vibrational spectra and surface-enhanced Raman scattering of 2,4,6-trichloro- and tribromoanilines: A comparative study

NASA Astrophysics Data System (ADS)

Haruna, Kabiru; Saleh, Tawfik A.; Al Thagfi, Jameel; Al-Saadi, Abdulaziz A.

2016-10-01

A comparative electronic and spectroscopic analysis of 2,4,6-trichloroaniline (TCA) and 2,4,6-tribromoaniline (TBA) was carried out by theoretical and experimental techniques. The NH2 inversion barrier in TCA and TBA molecules was predicted to be three times less than that in aniline and 2,4,6-trifluoroaniline. The size of the halogen substituents in the ortho positions is shown by density functional theory to play an important role in determining the electronic and structural properties of the amino group in the investigated haloaniline derivatives. A thorough interpretation of the infrared and Raman spectra has been performed on the basis of the observed and calculated infrared and Raman spectra as well as calculated potential energy distribution values. In addition, the SERS spectra for both trihaloanilines were successfully collected up to a concentration of 10-6 M using aged hydroxylamine-reduced silver colloid as an active substrate for TCA and TBA. SERS intensities of several peaks were found to linearly change with concentration allowing quantitative analyses of TCA and TBA. A relatively stronger interaction in the case of TBA-silver colloids is predicted compared to the TCA analogue.

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.

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.

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.

SERS spectrum of gallic acid obtained from a modified silver colloid

NASA Astrophysics Data System (ADS)

Garrido, C.; Diaz-Fleming, G.; Campos-Vallette, M. M.

2016-06-01

Two different crystals of the gallic acid were microscopically separated from a p.a. commercial product. The Raman spectra analysis allowed distinguishing monomeric and dimeric structures. The vibrational wave numbers were computed using DFT quantum chemical calculations. The data obtained from wave number calculations are used to assign vibrational bands obtained in the Raman spectrum. The dimer, characterized as ellagic acid, involves the carboxyl and hydroxyl moieties. The Raman spectrum in water solution of each species is dominated by the monomeric form. A low negatively charged Ag colloid allowed obtain to the best of our knowledge, the first surface enhanced Raman scattering (SERS) spectrum of the gallic acid. The possible electrophilic attacking sites of the title molecule are identified using MEP surface plot study and the orientation of the analyte on the metal surface is proposed tilted to the surface.

Rare-earth metal halogenide encapsulation-induced modifications in Raman spectra of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Kharlamova, M. V.

2015-01-01

In the present work, a detailed Raman spectroscopy investigation on the single-walled carbon nanotubes (SWCNTs) filled with praseodymium chloride, terbium chloride and thulium chloride was performed. The salts were incorporated inside the SWCNTs by a capillary filling method using melts, and the high-resolution transmission electron microscopy data proved the high filling degree of the nanotube channels. A thorough analysis of the radial breathing mode and G-band of the Raman spectra of the pristine and filled SWCNTs showed that the encapsulated salts cause acceptor doping of the host nanotubes, and the doping efficiency depends on the compound. The incorporated thulium chloride has the strongest doping effect on the SWCNTs, whereas praseodymium chloride has the weakest effect. It was found that the encapsulated salts modify more significantly the electronic structure of metallic nanotubes than semiconducting SWCNTs.

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.

Atomic substitution in selected high-temperature superconductors: Elucidating the nature of Raman spectra excitations

NASA Astrophysics Data System (ADS)

Hewitt, Kevin Cecil

2000-10-01

In this thesis, the effects of atomic substitution on the vibrational and electronic excitations found in the Raman spectra of selected high-temperature superconductors (HTS) are studied. In particular, atomic and isotopic substitution methods have been used to determine the character of features observed in the Raman spectra of Bi2Sr2Ca n-1CunO2 n+4+delta (n = 1 - Bi2201, n = 2 - Bi2212) and YBa2Cu3O7-delta (Y123). In Bi2201, Pb substitution for Bi (and Sr) has led to the reduction and eventual removal of the structural modulation, characteristic of all members of the Bi-family of HTS. The high quality single crystals and our sensitive triple spectrometer enabled identification of a pair of low frequency modes. The modes are determined to arise from shear and compressional rigid-layer vibrations. The normal state of underdoped cuprates is characterized by a pseudogap of unknown origin. In crystals of underdoped Bi2212 a spectral peak found at 590 cm-1, previously attributed to the pairing of quasiparticles (above Tc) and hence to the formation of a normal state pseudogap, has been found to soften by 3.8% with oxygen isotope exchange. In addition, the feature is absent in fully oxygenated and yttrium underdoped crystals. In this study, the first of its kind on underdoped and isotope substituted Bi2212, the feature has been assigned to stretching vibrations of oxygen in the a-b plane. Bi2212 crystals with varying hole concentrations (0.07 < p < 0.23) were studied to investigate the effects of doping on the symmetry and magnitude of the superconducting gap. Electronic Raman scattering experiments that sample the diagonal (B 2g) and principal axes (B1 g) of the BZ have led us to conclude that the superconducting gap possesses dx2-y2 symmetry, in the underdoped and overdoped regimes. It is found that the magnitude of the superconducting gap (Delta(k)) is sensitive to changes in p. Studies of the pair-breaking peak found in the B1g spectra allow us to conclude that the

The minimizing of fluorescence background in Raman optical activity and Raman spectra of human blood plasma.

PubMed

Tatarkovič, Michal; Synytsya, Alla; Šťovíčková, Lucie; Bunganič, Bohuš; Miškovičová, Michaela; Petruželka, Luboš; Setnička, Vladimír

2015-02-01

Raman optical activity (ROA) is inherently sensitive to the secondary structure of biomolecules, which makes it a method of interest for finding new approaches to clinical applications based on blood plasma analysis, for instance the diagnostics of several protein-misfolding diseases. Unfortunately, real blood plasma exhibits strong background fluorescence when excited at 532 nm; hence, measuring the ROA spectra appears to be impossible. Therefore, we established a suitable method using a combination of kinetic quenchers, filtering, photobleaching, and a mathematical correction of residual fluorescence. Our method reduced the background fluorescence approximately by 90%, which allowed speedup for each measurement by an average of 50%. In addition, the signal-to-noise ratio was significantly increased, while the baseline distortion remained low. We assume that our method is suitable for the investigation of human blood plasma by ROA and may lead to the development of a new tool for clinical diagnostics.

Far-Infrared and Raman Spectra and The Ring-Twisting Potential Energy Function of 1,3-Cyclohexadiene

NASA Astrophysics Data System (ADS)

Autrey, Daniel; Choo, Jaebum; Laane, Jaan

2001-10-01

The nu19 (A2) ring-twisting vibration of 1,3-cyclohexadiene has been analyzed from the vapor-phase Raman and infrared spectra. The Raman spectrum shows nine ring-twisting transitions in the 116 - 199 cm-1 region. The far-infrared spectrum confirms five of these transitions, despite the fact that the vibration is infrared forbidden in the C2v (planar) approximation. Other Raman and infrared combination bands verify the assignments and provide information on the vibrational coupling. A coordinate dependent kinetic energy expansion for the ring-twisting motion was calculated, and this was used to determine the ring-twisting potential function, which has a barrier to planarity of 1132 cm-1 and energy minima corresponding to twisting angles of 9.1º and 30.1º. Ab initio calculations were also carried out using Moller-Plesset perturbation theory (MP2) with a large number of different basis sets. The various ab initio calculations gave barriers to planarity in the 1197 - 1593 cm-1 range and calculated vibrational frequencies in excellent agreement with the experimental values.

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.

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.

Raman spectrum of natural and synthetic stishovite

USGS Publications Warehouse

Hemley, R.J.; Mao, Ho-kwang; Chao, E.C.T.

1986-01-01

Raman spectra of natural and synthetic samples of stishovite have been measured with a micro-optical spectrometer system. These spectra have a pattern that is characteristic of rutile-structured oxides. The spectrum of synthetic stishovite is characterized by well-resolved bands at 231, 589, 753, and 967 cm-1, which are assigned as the B1g, Eg, A1g, and B2g fundamentals, respectively, of the first-order Raman spectrum of the ideal, ordered structure. Natural stishovite obtained from Meteor Crater, Arizona has a first-order Raman spectrum that is fully consistent with that of the synthetic material. The observed spectrum of the natural sample, however, is weaker and has bands in addition to those identified as fundamentals in the spectrum of the synthetic material. A broad band at ???475 cm-1 may be indicative of glass or contaminants derived from the extraction procedure. Alternatively, this band may arise from multiphonon scattering that is enhanced by poor crystallinity or structural disorder in the natural shocked sample. ?? 1986 Springer-Verlag.

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

Raman spectra of bilayer graphene covered with Poly(methyl methacrylate) thin film

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

Xia Minggang; Center on Experimental Physics, School of Science, Xi'an Jiaotong University, 710049; Su Zhidan

The Raman spectra of bilayer graphene covered with poly(methyl methacrylate) (PMMA) were investigated. Both the G and 2D peaks of PMMA-coated graphene were stiff and broad compared with those of uncovered graphene. This could be attributed to the residual strain induced by high-temperature baking during fabrication of the nanodevice. Furthermore, the two 2D peaks stiffened and broadened with increasing laser power, which is just the reverse to uncovered graphene. The stiffness is likely caused by graphene compression induced by the circular bubble of the thin PMMA film generated by laser irradiation. Our findings may contribute to the application of PMMAmore » in the strain engineering of graphene nanodevices.« less

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

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.

Clustering/anticlustering effects on the GeSi Raman spectra at moderate (Ge,Si) contents: Percolation scheme vs. ab initio calculations

NASA Astrophysics Data System (ADS)

Torres, V. J. B.; Hajj Hussein, R.; Pagès, O.; Rayson, M. J.

2017-02-01

We test a presumed ability behind the phenomenological percolation scheme used for the basic description of the multi-mode Raman spectra of mixed crystals at one dimension along the linear chain approximation, to determine, via the Raman intensities, the nature of the atom substitution, as to whether this is random or due to local clustering/anticlustering. For doing so, we focus on the model percolation-type GeySi1-y system characterized by six oscillators { 1 × ( G e - G e ) , 3 × ( G e - S i ) , 2 × ( S i - S i ) } and place the study around the critical compositions y ˜ (0.16, 0.71, and 0.84) corresponding to nearly matching of intensities between the like Raman modes from a given multiplet ( G e - S i triplet or S i - S i doublet). The interplay between the GeySi1-y Raman intensities predicted by the percolation scheme depending on a suitable order parameter κ of local clustering/anticlustering is found to be consistent with ab initio calculations of the GeySi1-y Raman spectra done with the Ab Initio Modeling PROgram code using large (64-, 216-, and 512-atoms) disordered cubic supercells matching the required ( y , κ ) values. The actual "percolation vs. ab initio" comparative insight at moderate/dilute-(Ge,Si) limits, with an emphasis on the κ -induced intra-bond transfer of oscillator strength, extends a pioneering one earlier achieved at an intermediate composition ( y ˜ 0.50) by using small (32-atom) supercells [O. Pagès et al., J. Appl. Phys. 114, 033513 (2013)], mainly concerned with the inter-bond transfer of oscillator strength, providing altogether a complete picture.

Partitioning Ocean Wave Spectra Obtained from Radar Observations

NASA Astrophysics Data System (ADS)

Delaye, Lauriane; Vergely, Jean-Luc; Hauser, Daniele; Guitton, Gilles; Mouche, Alexis; Tison, Celine

2016-08-01

2D wave spectra of ocean waves can be partitioned into several wave components to better characterize the scene. We present here two methods of component detection: one based on watershed algorithm and the other based on a Bayesian approach. We tested both methods on a set of simulated SWIM data, the Ku-band real aperture radar embarked on the CFOSAT (China- France Oceanography Satellite) mission which launch is planned mid-2018. We present the results and the limits of both approaches and show that Bayesian method can also be applied to other kind of wave spectra observations as those obtained with the radar KuROS, an airborne radar wave spectrometer.

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.

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.

Multifocus confocal Raman microspectroscopy for fast multimode vibrational imaging of living cells.

PubMed

Okuno, Masanari; Hamaguchi, Hiro-o

2010-12-15

We have developed a multifocus confocal Raman microspectroscopic system for the fast multimode vibrational imaging of living cells. It consists of an inverted microscope equipped with a microlens array, a pinhole array, a fiber bundle, and a multichannel Raman spectrometer. Forty-eight Raman spectra from 48 foci under the microscope are simultaneously obtained by using multifocus excitation and image-compression techniques. The multifocus confocal configuration suppresses the background generated from the cover glass and the cell culturing medium so that high-contrast images are obtainable with a short accumulation time. The system enables us to obtain multimode (10 different vibrational modes) vibrational images of living cells in tens of seconds with only 1 mW laser power at one focal point. This image acquisition time is more than 10 times faster than that in conventional single-focus Raman microspectroscopy.

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.

Resonance Raman spectra of an O2-binding H-NOX domain reveal heme relaxation upon mutation.

PubMed

Tran, Rosalie; Boon, Elizabeth M; Marletta, Michael A; Mathies, Richard A

2009-09-15

Resonance Raman spectra were measured for the wild type Heme-Nitric oxide/OXygen binding domain from Thermoanaerobacter tengcongensis (Tt H-NOX WT) and three other Tt H-NOX proteins containing mutations at key conserved residues to determine the heme conformation in solution. The most dramatic changes in heme conformation occurred in the O2-bound forms, and the single Tt H-NOX P115A mutation was sufficient to generate a significant relaxation of the chromophore. Clear evidence of heme relaxation in the Tt H-NOX I5L, P115A, and I5L/P115A mutants in solution is demonstrated by the observation of reduced resonance Raman intensities for several out-of-plane low frequency modes (e.g., gamma11, gamma12, gamma13, and gamma15) in the 400-750 cm(-1) region known to be sensitive to ruffling and saddling deformations, as well as increased vibrational frequencies for the core heme skeletal stretching modes, nu3, nu2, and nu10. In addition, all three mutants exhibited some degree of heme conformational heterogeneity based on several broad skeletal markers (e.g., nu10) in the high frequency region. These results are comparable to those observed by Olea et al. for Tt H-NOX P115A in crystal form, where four different heme structures were determined from a single unit cell. On the basis of the resonance Raman spectra, it is clear that the actual heme conformation for Tt H-NOX P115A in solution is considerably more relaxed than that of the WT protein, with increased flexibility within the protein pocket, allowing for rapid sampling of alternate conformations.

The use of a handheld Raman system for virus detection

NASA Astrophysics Data System (ADS)

Song, Chunyuan; Driskell, Jeremy D.; Tripp, Ralph A.; Cui, Yiping; Zhao, Yiping

2012-06-01

The combination of surface enhanced Raman spectroscopy (SERS) with a handheld Raman system would lead to a powerful portable device for defense and security applications. The Thermo Scientific FirstDefender RM instrument is a 785-nm handheld Raman spectrometer intended for rapid field identification of unknown solid and liquid samples. Its sensitivity and effectiveness for SERS-based detection was initially confirmed by evaluating detection of 1,2-di(4- pyridyl)ethylene as a reporter molecule on a silver nanorod (AgNR) substrate, and the results are comparable to those from a confocal Bruker Raman system. As avian influenza A viruses (AIV) are recognized as an important emerging threat to public health, this portable handheld Raman spectrometer is used, for the first time, to detect and identify avian influenza A viruses using a multi-well AgNR SERS chip. The SERS spectra obtained had rich peaks which demonstrated that the instrument can be effectively used for SERS-based influenza virus detection. According to the SERS spectra, these different influenza viruses were distinguished from the negative control via the principal component analysis and by partial least squares-discriminate analysis. Together, these results show that the combination effective SERS substrates when combined with a portable Raman spectrometer provides a powerful field device for chemical and biological sensing.

A novel method for single bacteria identification by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Schultz, Emmanuelle; Simon, Anne-Catherine; Strola, Samy Andrea; Perenon, Rémi; Espagnon, Isabelle; Allier, Cédric; Claustre, Patricia; Jary, Dorothée.; Dinten, Jean-Marc

2014-03-01

In this paper we present results on single bacteria rapid identification obtained with a low-cost and compact Raman spectrometer. At present, we demonstrate that a 1 minute procedure, including the localization of single bacterium, is sufficient to acquire comprehensive Raman spectrum in the range of 600 to 3300 cm-1. Localization and detection of single bacteria is performed by means of lensfree imaging over a large field of view of 24 mm2. An excitation source of 532 nm and 30 mW illuminates single bacteria to collect Raman signal into a Tornado Spectral Systems prototype spectrometer (HTVS technology). The acquisition time to record a single bacterium spectrum is as low as 10 s owing to the high light throughput of this spectrometer. The spectra processing features different steps for cosmic spikes removal, background subtraction, and gain normalization to correct the residual inducted fluorescence and substrate fluctuations. This allows obtaining a fine chemical fingerprint analysis. We have recorded a total of 1200 spectra over 7 bacterial species (E. coli, Bacillus species, S. epidermis, M. luteus, S. marcescens). The analysis of this database results in a high classification score of almost 90 %. Hence we can conclude that our setup enables automatic recognition of bacteria species among 7 different species. The speed and the sensitivity (<30 minutes for localization and spectra collection of 30 single bacteria) of our Raman spectrometer pave the way for high-throughput and non-destructive real-time bacteria identification assays. This compact and low-cost technology can benefit biomedical, clinical diagnostic and environmental applications.

Influence of protein size on surface-enhanced Raman scattering (SERS) spectra in binary protein mixtures.

PubMed

Avci, Ertug; Culha, Mustafa

2014-01-01

The size-dependent interactions of eight blood proteins with silver nanoparticles (AgNPs) in their binary mixtures were investigated using surface-enhanced Raman scattering (SERS). Principal component analysis (PCA) was performed on the SERS spectra of each binary mixture, and the differentiation ability of the mixtures was tested. It was found that the effect of relative concentration change on the SERS spectra of the binary mixtures of small proteins could be detected using PCA. However, this change was not observed with the binary mixtures of large proteins. This study demonstrated that the relative interactions of the smaller proteins with an average size of 50 nm AgNPs smaller than the large proteins could be monitored, and this information can be used for the detection of proteins in protein mixtures.

Rapid identification of staphylococci by Raman spectroscopy.

PubMed

Rebrošová, Katarína; Šiler, Martin; Samek, Ota; Růžička, Filip; Bernatová, Silvie; Holá, Veronika; Ježek, Jan; Zemánek, Pavel; Sokolová, Jana; Petráš, Petr

2017-11-01

Clinical treatment of the infections caused by various staphylococcal species differ depending on the actual cause of infection. Therefore, it is necessary to develop a fast and reliable method for identification of staphylococci. Raman spectroscopy is an optical method used in multiple scientific fields. Recent studies showed that the method has a potential for use in microbiological research, too. Our work here shows a possibility to identify staphylococci by Raman spectroscopy. We present a method that enables almost 100% successful identification of 16 of the clinically most important staphylococcal species directly from bacterial colonies grown on a Mueller-Hinton agar plate. We obtained characteristic Raman spectra of 277 staphylococcal strains belonging to 16 species from a 24-hour culture of each strain grown on the Mueller-Hinton agar plate using the Raman instrument. The results show that it is possible to distinguish among the tested species using Raman spectroscopy and therefore it has a great potential for use in routine clinical diagnostics.

Raman spectroscopy of the organic and mineral structure of bone grafts

NASA Astrophysics Data System (ADS)

Timchenko, E. V.; Timchenko, P. E.; Volova, L. T.; Ponomareva, Yu V.; Taskina, L. A.

2014-07-01

We report the results of experimental Raman spectroscopy of donor bone samples (rat, rabbit and human) with varying degrees of mineralisation. Raman spectra are obtained for the Raman bands of 950 - 962 cm-1 (PO4)3-, 1065 - 1070 cm-1 (CO3)2- and 1665 cm-1 (amide I). In demineralised bone, a sharp (98%) decrease in the intensities of 950 - 962 and 1065 - 1070 cm-1 bands is observed, which is accompanied by the emergence of the 1079 - 1090 cm-1 band corresponding to the hydrated amorphous state CO3-3.

Understanding the application of Raman spectroscopy to the detection of traces of life.

PubMed

Marshall, Craig P; Edwards, Howell G M; Jehlicka, Jan

2010-03-01

Investigating carbonaceous microstructures and material in Earth's oldest sedimentary rocks is an essential part of tracing the origins of life on our planet; furthermore, it is important for developing techniques to search for traces of life on other planets, for example, Mars. NASA and ESA are considering the adoption of miniaturized Raman spectrometers for inclusion in suites of analytical instrumentation to be placed on robotic landers on Mars in the near future to search for fossil or extant biomolecules. Recently, Raman spectroscopy has been used to infer a biological origin of putative carbonaceous microfossils in Early Archean rocks. However, it has been demonstrated that the spectral signature obtained from kerogen (of known biological origin) is similar to spectra obtained from many poorly ordered carbonaceous materials that arise through abiotic processes. Yet there is still confusion in the literature as to whether the Raman spectroscopy of carbonaceous materials can indeed delineate a signature of ancient life. Despite the similar nature in spectra, rigorous structural interrogation between the thermal alteration products of biological and nonbiological organic materials has not been undertaken. Therefore, we propose a new way forward by investigating the second derivative, deconvolution, and chemometrics of the carbon first-order spectra to build a database of structural parameters that may yield distinguishable characteristics between biogenic and abiogenic carbonaceous material. To place Raman spectroscopy as a technique to delineate a biological origin for samples in context, we will discuss what is currently accepted as a spectral signature for life; review Raman spectroscopy of carbonaceous material; and provide a historical overview of Raman spectroscopy applied to Archean carbonaceous materials, interpretations of the origin of the ancient carbonaceous material, and a future way forward for Raman spectroscopy.

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.

Determination of nutritional parameters of yoghurts by FT Raman spectroscopy

NASA Astrophysics Data System (ADS)

Czaja, Tomasz; Baranowska, Maria; Mazurek, Sylwester; Szostak, Roman

2018-05-01

FT-Raman quantitative analysis of nutritional parameters of yoghurts was performed with the help of partial least squares models. The relative standard errors of prediction for fat, lactose and protein determination in the quantified commercial samples equalled to 3.9, 3.2 and 3.6%, respectively. Models based on attenuated total reflectance spectra of the liquid yoghurt samples and of dried yoghurt films collected with the single reflection diamond accessory showed relative standard errors of prediction values of 1.6-5.0% and 2.7-5.2%, respectively, for the analysed components. Despite a relatively low signal-to-noise ratio in the obtained spectra, Raman spectroscopy, combined with chemometrics, constitutes a fast and powerful tool for macronutrients quantification in yoghurts. Errors received for attenuated total reflectance method were found to be relatively higher than those for Raman spectroscopy due to inhomogeneity of the analysed samples.

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.

In Situ Raman Analysis of CO2—Assisted Drying of Fruit-Slices

PubMed Central

Braeuer, Andreas Siegfried; Schuster, Julian Jonathan; Gebrekidan, Medhanie Tesfay; Bahr, Leo; Michelino, Filippo; Zambon, Alessandro; Spilimbergo, Sara

2017-01-01

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO2) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO2 into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve. PMID:28505120

[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.

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.

First-principles calculations of phonons and Raman and infrared spectra in Cd-IV-N2 compounds

NASA Astrophysics Data System (ADS)

Lyu, Sai; Lambrecht, Walter R. L.

2018-05-01

A first-principles study of the phonons at the zone center in Cd-IV-N2 compounds is presented with IV = Si, Ge, Sn. The calculations are performed for the most likely Pbn21 crystal structure, after showing that it is indeed lower in total energy compared to the closely related Pmc21 structure. The normal mode frequencies are calculated using density functional perturbation theory and symmetry labeled. The longitudinal optical-transverse optical splittings are determined using the Born effective charges which are also reported. These are used to simulate polarized Raman spectra for different scattering configurations as well as the infrared absorption and reflection spectra. The mode frequencies are found to decrease from Si to Ge to Sn as group-IV cation. The spectra show a wide variety of number of prominent peaks and relative intensities in spite of the great similarities of these three materials. Phonon densities of states and their analysis in atom by atom contributions are also reported.

A fast, automated, polynomial-based cosmic ray spike-removal method for the high-throughput processing of Raman spectra.

PubMed

Schulze, H Georg; Turner, Robin F B

2013-04-01

Raman spectra often contain undesirable, randomly positioned, intense, narrow-bandwidth, positive, unidirectional spectral features generated when cosmic rays strike charge-coupled device cameras. These must be removed prior to analysis, but doing so manually is not feasible for large data sets. We developed a quick, simple, effective, semi-automated procedure to remove cosmic ray spikes from spectral data sets that contain large numbers of relatively homogenous spectra. Although some inhomogeneous spectral data sets can be accommodated--it requires replacing excessively modified spectra with the originals and removing their spikes with a median filter instead--caution is advised when processing such data sets. In addition, the technique is suitable for interpolating missing spectra or replacing aberrant spectra with good spectral estimates. The method is applied to baseline-flattened spectra and relies on fitting a third-order (or higher) polynomial through all the spectra at every wavenumber. Pixel intensities in excess of a threshold of 3× the noise standard deviation above the fit are reduced to the threshold level. Because only two parameters (with readily specified default values) might require further adjustment, the method is easily implemented for semi-automated processing of large spectral sets.

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.

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.

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.

Raman spectra and phase transitions in Rb{sub 2}KInF{sub 6} elpasolite

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

Krylov, A. S.; Krylova, S. N., E-mail: slanky@iph.krasn.ru; Vtyurin, A. N.

2011-01-15

The Raman spectra of Rb{sub 2}KInF{sub 6} elpasolite crystal have been studied in a wide temperature range, including two phase transitions: from the cubic phase to the tetragonal phase and then to the monoclinic phase. Several anomalies of internal modes of InF{sub 6} octahedra and low-frequency lattice vibrations, which are related to the structural changes at the transition points, have been found and quantitatively analyzed. The results of a quantitative analysis of the temperature dependences of the parameters of spectral lines are in good agreement with the thermodynamic data on the phase transitions.

Raman spectroscopy on ice cores from Greenland and Antarctica

NASA Astrophysics Data System (ADS)

Weikusat, C.; Kipfstuhl, S.

2012-04-01

Ice cores are invaluable archives for the reconstruction of the climatic history of the earth. Besides the analysis of various climatic processes from isotopes and chemical signatures they offer the unique possibility of directly extracting the past atmosphere from gaseous inclusions in the ice. Many aspects of the formation and alterations of these inclusions, e.g. the entrapment of air at the firn-ice-transition, the formation of crystalline gas hydrates (clathrates) from the bubbles or the structural relaxation during storage of the cores, need to be better understood to enable reliable interpretations of the obtained data. Modern micro Raman spectroscopy is an excellent tool to obtain high-quality data for all of these aspects. It has been productively used for phase identification of solid inclusions [1], investigation of air clathrates [2] and high-resolution measurements of N2/O2 mixing ratios inside individual air bubbles [3,4]. Detailed examples of the various uses of Raman spectroscopy will be presented along with practical information about the techniques required to obtain high-quality spectra. Retrieval and interpretation of quantitative data from the spectra will be explained. Future possibilities for advanced uses of Raman spectroscopy for ice core research will be discussed. [1] T. Sakurai et al., 2009, Direct observation of salts as micro-inclusions in the Greenland GRIP ice core. Journal of Glaciology, 55, 777-783. [2] F. Pauer et al., 1995, Raman spectroscopic study of nitrogen/oxygen ratio in natural ice clathrates in the GRIP ice core. Geophysical Research Letters, 22, 969-971. [3] T. Ikeda-Fukazawa et al., 2001, Variation in N2/O2 ratio of occluded air in Dome Fuji antarctic ice. Journal of Geophysical Research, 106, 17799-17810. [4] C. Weikusat et al., Raman spectroscopy of gaseous inclusions in EDML ice core: First results - microbubbles. Journal of Glaciology, accepted.

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.

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.

Properties of Energy Spectra of Molecular Crystals Investigated by Nonlinear Theory

NASA Astrophysics Data System (ADS)

Pang, Xiao-Feng; Zhang, Huai-Wu

We calculate the quantum energy spectra of molecular crystals, such as acetanilide, by using discrete nonlinear Schrodinger equation, containing various interactions, appropriate to the systems. The energy spectra consist of many energy bands, in each energy band there are a lot of energy levels including some higher excited states. The result of energy spectrum is basically consistent with experimental values obtained by infrared absorption and Raman scattering in acetanilide and can also explain some experimental results obtained by Careri et al. Finally, we further discuss the influences of variously characteristic parameters on the energy spectra of the systems.

FT-Raman, FT-IR spectroscopic and DFT studies of hexaphenoxycyclotriphosphazene

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukov, A. E.; Padie, C.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

2016-07-01

The FTIR and FT Raman measurements of zero Gc0‧ -H and first Gc1‧ -H generations of phosphorus dendrimer built from cyclotriphosphazene core with phenoxy and deuterophenoxy terminal groups have been performed. In order to evaluate how much the frequencies, shift when changing the electronics of the system the FTIR and FT Raman spectra of phosphorus‒containing dendron with five terminal oxybenzaldehyde and one ester function Gci‧ have been also studied. Structural optimization and normal mode analysis were obtained for Gc0‧ -H and Gc0‧ -D by the density functional theory (DFT). It is discovered that dendrimer molecule exists in a stable conformation with six phenoxy terminal groups spaced above and below the flat cyclotriphosphazene core. Optimized geometric bond length and angles obtained by DFT show good agreement with a previously-published X-ray study. The phenoxy terminal groups are characterized by the well-defined line at 993 cm-1 in the experimental Raman spectrum of Gc0‧ -H and by line at 960 cm-1 in the Raman spectrum of Gc0‧ -D. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimers. The frequencies and relative intensity of the bands at 1589, 1487 cm-1 in the IR spectra show marked difference in dependence of the substituents on the aromatic ring.

Native alunogen: A Raman spectroscopic study of a well-described specimen

NASA Astrophysics Data System (ADS)

Košek, Filip; Culka, Adam; Žáček, Vladimír; Laufek, František; Škoda, Radek; Jehlička, Jan

2018-04-01

Alunogen (Al2(SO4)3 · 17H2O) is a common secondary mineral in the terrestrial environment (acid mine drainage, volcanic or coal-fire fumaroles), and is also formed through the acidic weathering of aluminosilicates. Moreover, alunogen has been suggested as a part of the Al-bearing deposits on Mars. The identification of alunogen in secondary sulfate mixtures by Raman spectroscopy strictly depends on good knowledge of alunogen spectral features and band positions. However, comprehensive Raman data of alunogen of natural origin are lacking. This study reports on Raman spectra obtained from two natural specimens originating from a burning coal dump at the Schoeller mine, Kladno, Czech Republic, along with the additional characterizations by infrared spectroscopy, X-ray diffraction, and electron microprobe. For comparison purposes, a Raman spectrum of a synthetic analogue was also obtained. The studied specimens have (Al1.99Fe3+0.01)2 (SO4)3·17H2O as their calculated empirical formula, and the structural parameters correspond to the previously reported data for alunogen. Both natural specimens and the synthetic analogue showed uniform Raman spectra with no extensive band splitting in the sulfate vibrational regions. The most intensive Raman band associated with the symmetric stretching vibration of the SO4 tetrahedra (ν1) is located at 992 cm-1. A multicomponent band was observable in the characteristic region for OH-related vibrations. A small variation in the spectral intensity of the hydroxyl bands suggests that the studied specimens could possibly be slightly dehydrated.

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.

IR-Raman-VCD study of R-(+)-Pulegone: Influence of the solvent

NASA Astrophysics Data System (ADS)

Aviles-Moreno, Juan Ramón; Ureña Horno, Elena; Partal Ureña, Francisco; López González, Juan Jesús

2011-08-01

R-(+)-Pulegone is a natural monoterpene obtained from the essential oils of a variety of plants. It is used in flavouring agents, perfumery and aromatherapy. In this work, a study of the molecular structure and the infrared and Raman spectra of this chemical is presented. Theoretical calculations reveal the existence of two conformers depending on the position of the methyl group (axial and equatorial), being the equatorial conformer the most stable. A complete and reliable assignment of the IR and Raman spectra of the title compound is made, and the results are used to carry out a detailed interpretation of the VCD spectrum of this compound in the 4000-900 cm -1 region. Finally, the influence of the solvent in the VCD bands (intensity and sign) has been tested comparing the neat liquid spectrum with the VCD spectra recorded with four solvents.

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.

Raman Spectroscopy: A New Proposal for the Detection of Leukemia Using Blood Samples

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.; Sánchez-Gómez, R.

2008-08-01

The use of Raman spectroscopy to analyze blood biochemistry and hence distinguish between normal and abnormal blood was investigated. The blood samples were obtained from 6 patients who were clinically diagnosed with leukemia and 6 healthy volunteer. The imprint was put under the microscope and several points were chosen for Raman measurement. All spectra were collected at confocal Raman micro-spectroscopy (Renishaw) with 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) is 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. In addition, currently the degree of damage to the bone marrow is estimated through biopsies and therefore it is a very procedure painful. The preliminary results suggest that Raman spectroscopy could be a new technique to study the bone marrow using just blood samples.

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.

Performance Assessment of a Plate Beam Splitter for Deep-Ultraviolet Raman Measurements with a Spatial Heterodyne Raman Spectrometer.

PubMed

Lamsal, Nirmal; Angel, S Michael

2017-06-01

In earlier works, we demonstrated a high-resolution spatial heterodyne Raman spectrometer (SHRS) for deep-ultraviolet (UV) Raman measurements, and showed its ability to measure UV light-sensitive compounds using a large laser spot size. We recently modified the SHRS by replacing the cube beam splitter (BS) with a custom plate beam splitter with higher light transmission, an optimized reflectance/transmission ratio, higher surface flatness, and better refractive index homogeneity than the cube beam splitter. Ultraviolet Raman measurements were performed using a SHRS modified to use the plate beam splitter and a matching compensator plate and compared to the previously described cube beam splitter setup. Raman spectra obtained using the modified SHRS exhibit much higher signals and signal-to-noise (S/N) ratio and show fewer spectral artifacts. In this paper, we discuss the plate beam splitter SHRS design features, the advantages over previous designs, and discuss some general SHRS issues such as spectral bandwidth, S/N ratio characteristics, and optical efficiency.

Surface-enhanced Raman scattering of rat tissues.

PubMed

Aydin, Omer; Kahraman, Mehmet; Kiliç, Ertuğul; Culha, Mustafa

2009-06-01

Surface-enhanced Raman scattering (SERS) is proven to be a powerful tool for investigation of biological structures. In this study, tissues obtained from different rat organs are examined using SERS. The tissue samples are crushed with a pestle after sudden freezing in liquid nitrogen and mixed with a concentrated colloidal silver nanoparticle suspension. The reproducibility of SERS spectra acquired from several tissue samples from different organs is demonstrated. The collected spectra are comparatively evaluated based on the physiological function of the organ from which the tissue is obtained. The spectra from the tissues show significant differences and indicate that they can be used for tissue characterization and differentiation. The identification of the origins of the bands on the spectra is also attempted. This study suggests that SERS can be used to monitor the changes at the molecular level during metabolic changes in an organ or tissue as a result of a disease or another cause.

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.

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.

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.

Quantitative Analysis of Spectral Interference of Spontaneous Raman Scattering in High-Pressure Fuel-Rich H2-Air Combustion

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet

2004-01-01

We present a theoretical study of the spectral interferences in the spontaneous Raman scattering spectra of major combustion products in 30-atm fuel-rich hydrogen-air flames. An effective methodology is introduced to choose an appropriate line-shape model for simulating Raman spectra in high-pressure combustion environments. The Voigt profile with the additive approximation assumption was found to provide a reasonable model of the spectral line shape for the present analysis. The rotational/vibrational Raman spectra of H2, N2, and H2O were calculated using an anharmonic-oscillator model using the latest collisional broadening coefficients. The calculated spectra were validated with data obtained in a 10-atm fuel-rich H2-air flame and showed excellent agreement. Our quantitative spectral analysis for equivalence ratios ranging from 1.5 to 5.0 revealed substantial amounts of spectral cross-talk between the rotational H2 lines and the N2 O-/Q-branch; and between the vibrational H2O(0,3) line and the vibrational H2O spectrum. We also address the temperature dependence of the spectral cross-talk and extend our analysis to include a cross-talk compensation technique that removes the nterference arising from the H2 Raman spectra onto the N2, or H2O spectra.

Structural, electronic and vibrational properties of LaF3 according to density functional theory and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Oreshonkov, A. S.; Roginskii, E. M.; Krylov, A. S.; Ershov, A. A.; Voronov, V. N.

2018-06-01

Crystal structure of LaF3 single crystal is refined in tysonite-type trigonal unit cell P c1 using density functional theory calculations and Raman spectroscopy. It is shown that trigonal structure with P c1 space group is more energy-efficient than hexagonal structure with space group P63 cm. Simulated Raman spectra obtained using LDA approximation is in much better agreement with experimental data than that obtained with PBE and PBEsol functionals of GGA. The calculated frequency value of silent mode B 2 in case of hexagonal structure P63 cm was found to be imaginary (unstable mode), thus the energy surface obtains negative curvature with respect to the corresponding normal coordinates of the mode which leads to instability of the hexagonal structure in harmonic approximation. The A 1g line at 214 cm‑1 in Raman spectra of LaF3 related to the translation of F2 ions along c axis can be connected with F2 ionic conductivity.

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.

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

Raman spectroscopic study of reaction dynamics

NASA Astrophysics Data System (ADS)

MacPhail, R. A.

1990-12-01

The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

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.

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.

Rotating samples in FT-RAMAN spectrometers

NASA Astrophysics Data System (ADS)

De Paepe, A. T. G.; Dyke, J. M.; Hendra, P. J.; Langkilde, F. W.

1997-11-01

It is customary to rotate samples in Raman spectroscopy to avoid absorption or sample heating. In FT-Raman experiments the rotation is always shown (typically 30-60 rpm) because higher speeds are thought to generate noise in the spectra. In this article we show that more rapid rotation is possible. A tablet containing maleic acid and one made up of sub-millimetre silica particles with metoprolol succinate as active ingredient were rotated at different speeds, up to 6760 rpm. The FT-Raman spectra were recorded and studied. We conclude that it is perfectly acceptable to rotate samples up to 1500 rpm.

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

Detection of mast cell secretion by using surface enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Li, Juan; Li, Ren; Zheng, Liqin; Wang, Yuhua; Xie, Shusen; Lin, Juqiang

2016-10-01

Acupuncture can cause a remarkable increase in degranulation of the mast cells, which has attracted the interest of researchers since the 1980s. Surface-enhanced Raman scattering (SERS) could obtain biochemical information with high sensitivity and specificity. In this study, SERS was used to detect the degree of degranulation of mast cells according to different incubate time. Mast cells was incubated with culture medium for 0 h, 12 h and 24 h, then centrifuge the culture medium, decant the supernatant, and discard the mast cell. SERS was performed to obtain the biochemical fingerprinting signatures of the centrifuged medium. The spectra data are then analyzed by spectral peaks attribution and the principal component analysis (PCA). The measured Raman spectra of the two groups were separated well by PCA. It indicated that mast cells had secreted some substances into cultured medium though degranulation did not happen.

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.

FTIR and FT-Raman spectra and DFT vibrational analysis of phosphorus-containing dendrons

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukova, I. I.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

2008-12-01

FTIR and FT-Raman spectra of four generations of phosphorus-containing dendrons with terminal aldehyde or P sbnd Cl groups have been recorded and analyzed. Their spectral patterns are determined by the ratio T/ R ( T, the number of terminal groups; R, the number of repeated units). Bands assigned to the core, repeated units and terminal groups were separated by the difference spectroscopy method. The optimized geometry, frequencies and intensity of IR bands of G1v generation dendron with terminal aldehyde groups were obtained by the density functional theory (DFT). It was found that the internal skeleton of molecules exists in a single stable conformation with planar sbnd O- C6H4- CHdbnd N- N( CH3)- P( dbnd S)< fragments, but terminal groups may adopt the t, g, g- and t,- g, g-rotational isomers. The t,- g, g-conformer is 0.74 kcal/mol less stable compared to the t, g, g-conformer. The bond length and bond angles obtained by DFT show the best agreement with experimental data. Relying on DFT calculations a complete assignment of vibrations is proposed for different parts of the studied dendrons. The calculated frequencies and intensity of IR bands of the t, g, g- and t,- g, g-conformers of G1v are found to be in reasonable agreement with the experimental results. The most reactive site in dendron is the core function and vinyl group is preferred for nucleophilic attack. In dendrimer the most reactive are the terminal groups.

Raman and FTIR spectroscopy of methane in olivine

NASA Astrophysics Data System (ADS)

Smith, A.; Oze, C.; Rossman, G. R.; Celestian, A. J.

2017-12-01

Olivine has been proposed to be a direct source of methane (CH4) in serpentinization systems and experiments. Here, Raman and Fourier Transform Infrared (FTIR) spectroscopy were used to verify the presence and abundance of CH4 in olivine samples from nine localities, including the San Carlos olivine. Raman analyses did not identify any methane in the olivine samples. As olivine is orthorhombic, three polarized FTIR spectra were obtained for the olivine samples. No methane was detected in any of the olivine samples using FTIR. Overall, olivine investigated in this study does not appear to be a primary source of methane.

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.

Raman microscopy of lithium-manganese-rich transition metal oxide cathodes

DOE PAGES

Ruther, Rose E.; Callender, Andrew F.; Zhou, Hui; ...

2014-11-15

Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi 2MnO 3·(1-x)LiMO 2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this paper, Raman microscopymore » is used to investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. Finally, the results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets.« less

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.

Optimization of surface enhanced Raman scattering (SERS) assay for the transition from benchtop to handheld Raman systems

NASA Astrophysics Data System (ADS)

Schechinger, Monika; Marks, Haley; Locke, Andrea; Choudhury, Mahua; Coté, Gerard

2017-02-01

Human biomarkers are indicative of the body's relative state prior to the onset of disease, and sometimes before symptoms present. While blood biomarker detection has achieved considerable success in laboratory settings, its clinical application is lagging and commercial point-of-care devices are rare. A physician's ability to detect biomarkers such as microRNA-17, a potential epigenetic indicator of preeclampsia in pregnant woman, could enable early diagnosis and preventive intervention as early as the 1st trimester. One detection approach employing DNA-functionalized nanoparticles to detect microRNA-17, in conjunction with surface-enhanced Raman spectroscopy (SERS), has shown promise but is hindered, in part, by the use of large and expensive benchtop Raman microscopes. However, recent strides have been made in developing portable Raman systems for field applications. Characteristics of the SERS assay responsible for strengthening the assay's plasmonic response were explored, whilst comparing the results from both benchtop and portable Raman systems. The Raman spectra and intensity of three different types of photoactive molecules were compared as potential Raman reporter molecules: chromophores, fluorophores, and highly polarizable small molecules. Furthermore, the plasmonic characteristics governing the formation of SERS colloidal nanoparticle assemblies in response to DNA/miRNA hybridization were investigated. There were significant variations in the SERS enhancement in response to microRNA-17 using our assay depending on the excitation lasers at wavelengths of 532 nm and 785 nm, depending on which of the three different Raman systems were used (benchtop, portable, and handheld), and depending on which of the three different Raman reporters (chromophore, fluorophore, or Raman active molecule) were used. Analysis of data obtained did indicate that signal enhancement was better for the chromophore (MGITC) and Raman active molecule (DTNB) than it was for the

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

Renal mass biopsy using Raman spectroscopy identifies malignant and benign renal tumors: potential for pre-operative diagnosis.

PubMed

Liu, Yufei; Du, Zhebin; Zhang, Jin; Jiang, Haowen

2017-05-30

The accuracy of renal mass biopsy to diagnose malignancy can be affected by multiple factors. Here, we investigated the feasibility of Raman spectroscopy to distinguish malignant and benign renal tumors using biopsy specimens. Samples were collected from 63 patients who received radical or partial nephrectomy, mass suspicious of cancer and distal parenchyma were obtained from resected kidney using an 18-gauge biopsy needle. Four Raman spectra were obtained for each sample, and Discriminant Analysis was applied for data analysis. A total of 383 Raman spectra were eventually gathered and each type of tumor had its characteristic spectrum. Raman could separate tumoral and normal tissues with an accuracy of 82.53%, and distinguish malignant and benign tumors with a sensitivity of 91.79% and specificity of 71.15%. It could classify low-grade and high-grade tumors with an accuracy of 86.98%. Besides, clear cell renal carcinoma was differentiated with oncocytoma and angiomyolipoma with accuracy of 100% and 89.25%, respectively. And histological subtypes of cell carcinoma were distinguished with an accuracy of 93.48%. When compared with final pathology and biopsy, Raman spectroscopy was able to correctly identify 7 of 11 "missed" biopsy diagnoses. These results suggested that Raman may serve as a promising non-invasive approach in the future for pre-operative diagnosis.

Resonance Raman spectroscopic and density functional theory study of p-nitroacetophenone (PNAP)

NASA Astrophysics Data System (ADS)

Pei, Kemei; Ma, Yufang; Zheng, Xuming; Li, Haiyang

2007-03-01

Resonance Raman spectra of p-nitroacetophenone(PNAP) have been obtained in resonance with the charge-transfer (CT) band using 252.7, 266 and 273.9 nm in methanol solvent. The spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the C dbnd O stretching ν8(1691 cm -1) and the benzene ring stretch ν10(1593 cm -1). A preliminary resonance Raman intensity analysis was done and the results for PNAP were compared with nitrobenzene and aceptophenone. Our results indicate that -NO 2 is more photoactive than -COCH 3. The isomerization process of PNAP takes place somewhere after the wave packet leaves the Franck-Condon region.

Feasibility of Raman spectroscopy in vitro after 5-ALA-based fluorescence diagnosis in the bladder

NASA Astrophysics Data System (ADS)

Grimbergen, M. C. M.; van Swol, C. F. P.; van Moorselaar, R. J. A.; Mahadevan-Jansen, A.,; Stone, N.

2006-02-01

Photodynamic diagnosis (PDD) has become popular in bladder cancer detection. Several studies have however shown an increased false positive biopsies rate under PDD guidance compared to conventional cystoscopy. Raman spectroscopy is an optical technique that utilizes molecular specific, inelastic scattering of light photons to interrogate biological tissues, which can successfully differentiate epithelial neoplasia from normal tissue and inflammations in vitro. This investigation was performed to show the feasibility of NIR Raman spectroscopy in vitro on biopsies obtained under guidance of 5-ALA induced PPIX fluorescence imaging. Raman spectra of a PPIX solution was measured to obtain a characteristic signature for the photosensitzer without contributions from tissue constituents. Biopsies were obtained from patients with known bladder cancer instilled with 50ml, 5mg 5-ALA two hours prior to trans-urethral resection of tumor (TURT). Additional biopsies were obtained at a fluorescent and non-fluorescent area, snap-frozen in liquid nitrogen and stored at -80 °C. Each biopsy was thawed before measurements (10sec integration time) with a confocal Raman system (Renishaw Gloucestershire, UK). The 830 nm excitation (300mW) source is focused on the tissue by a 20X ultra-long-working-distance objective. Differences in fluorescence background between the two groups were removed by means of a special developed fluorescence subtraction algorithm. Raman spectra from ALA biopsies showed different fluorescence background which can be effectively removed by a fluorescence subtraction algorithm. This investigation shows that the interaction of the ALA induced PPIX with Raman spectroscopy in bladder samples. Combination of these techniques in-vivo may lead to a viable method of optical biopsies in bladder cancer detection.

The biochemical origins of the surface-enhanced Raman spectra of bacteria: a metabolomics profiling by SERS.

PubMed

Premasiri, W Ranjith; Lee, Jean C; Sauer-Budge, Alexis; Théberge, Roger; Costello, Catherine E; Ziegler, Lawrence D

2016-07-01

The dominant molecular species contributing to the surface-enhanced Raman spectroscopy (SERS) spectra of bacteria excited at 785 nm are the metabolites of purine degradation: adenine, hypoxanthine, xanthine, guanine, uric acid, and adenosine monophosphate. These molecules result from the starvation response of the bacterial cells in pure water washes following enrichment from nutrient-rich environments. Vibrational shifts due to isotopic labeling, bacterial SERS spectral fitting, SERS and mass spectrometry analysis of bacterial supernatant, SERS spectra of defined bacterial mutants, and the enzymatic substrate dependence of SERS spectra are used to identify these molecular components. The absence or presence of different degradation/salvage enzymes in the known purine metabolism pathways of these organisms plays a central role in determining the bacterial specificity of these purine-base SERS signatures. These results provide the biochemical basis for the development of SERS as a rapid bacterial diagnostic and illustrate how SERS can be applied more generally for metabolic profiling as a probe of cellular activity. Graphical Abstract Bacterial typing by metabolites released under stress.

Absolute tracer dye concentration using airborne laser-induced water Raman backscatter

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1981-01-01

The use of simultaneous airborne-laser-induced dye fluorescence and water Raman backscatter to measure the absolute concentration of an ocean-dispersed tracer dye is discussed. Theoretical considerations of the calculation of dye concentration by the numerical comparison of airborne laser-induced fluorescence spectra with laboratory spectra for known dye concentrations using the 3400/cm OH-stretch water Raman scatter as a calibration signal are presented which show that minimum errors are obtained and no data concerning water mass transmission properties are required when the laser wavelength is chosen to yield a Raman signal near the dye emission band. Results of field experiments conducted with an airborne conical scan lidar over a site in New York Bight into which rhodamine dye had been injected in a study of oil spill dispersion are then indicated which resulted in a contour map of dye concentrations, with a minimum detectable dye concentration of approximately 2 ppb by weight.

Unified analysis of optical absorption spectra of carotenoids based on a stochastic model.

PubMed

Uragami, Chiasa; Saito, Keisuke; Yoshizawa, Masayuki; Molnár, Péter; Hashimoto, Hideki

2018-05-03

The chemical structures of the carotenoid molecules are very simple and one might think that the electronic feature of it is easily predicted. However, it still has so much unknown information except the correlation between the electronic energy state and the length of effective conjugation chain of carotenoids. To investigate the electronic feature of the carotenoids, the most essential method is measuring the optical absorption spectra, but simulating it from the resonance Raman spectra is also the effective way. From this reason, we studied the optical absorption spectra as well as resonance Raman spectra of 15 different kinds of cyclic carotenoid molecules, recorded in tetrahydrofuran (THF) solutions at room temperature. The whole band shapes of the absorption spectra of all these carotenoid molecules were successfully simulated based on a stochastic model using Brownian oscillators. The parameters obtained from the simulation made it possible to discuss the intermolecular interaction between carotenoids and solvent THF molecules quantitatively. Copyright © 2018. Published by Elsevier Inc.

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.

Stratospheric HBr mixing ratio obtained from far infrared emission spectra

NASA Technical Reports Server (NTRS)

Park, J. H.; Carli, B.; Barbis, A.

1989-01-01

Emission features of HBr isotopes have been identified in high-resolution FIR emission spectra obtained with a balloon-borne Fourier-transform spectrometer in the spring of 1979 at 32 deg N latitude. When six single-scan spectra at a zenith angle of 93.2 deg were averaged, two features of HBr isotopes at 50.054 and 50.069/cm were obtained with a signal-to-noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 x 10 to the -11th, which is assumed to be constant above 28 km, with an uncertainty of 35 percent. This stratospheric amount of HBr is about the same as the current level of tropospheric organic bromine compounds, 25 pptv. Thus HBr could be the major stratospheric bromine species.

Raman spectroscopy for monitoring of organic and mineral structure of bone grafts

NASA Astrophysics Data System (ADS)

Timchenko, Elena V.; Timchenko, Pavel E.; Volova, Larisa T.; Ponomareva, Julia V.; Taskina, Larisa A.; Pershutkina, Svetlana V.

2014-09-01

The results of experimental studies of donor bone samples (rat, rabbit and human) with varying degrees of mineralisation by Raman spectroscopy were presented. Raman spectra were obtained for the Raman bands 950-962 (РО4)3-, 1065-1070 (СО3)2- and 1665 cm-1 (Amide I). In demineralized bone a sharp decline (to 98 %) in the range of 950-962 cm-1 (РО4)3- and 1065 - 1070 cm-1 was observed. This decrease was accompanied by the emergence of the 1079-1090 cm-1 band corresponding to the hydrated state СО3 2-.

The stability and Raman spectra of ikaite, CaCO3·6H2O, at high pressure and temperature

USGS Publications Warehouse

Shahar, Anat; Bassett, William A.; Mao, Ho-kwang; Chou, I-Ming; Mao, Wendy

2005-01-01

Raman analyses of single crystals of ikaite, CaCO3·6H2O, synthesized in a diamond-anvil cell at ambient temperature yield spectra from 0.14 to 4.08 GPa; the most intense peaks are at 228 and 1081 cm−1 corresponding to Eg(external) and A1g (internal) modes of vibrations in CO2− 3 ions, respectively. These are in good agreement with Raman spectra previously published for ikaite in powder form at ambient temperature and pressure. Visual observations of a sample consisting initially of a mixture of calcite + water in a hydrothermal diamond-anvil cell yielded a P-T phase diagram up to 2 GPa and 120 °C; the boundary for the reaction ikaite ↔ aragonite + water has a positive slope and is curved convexly toward the aragonite + water field similar to typical melt curves. This curvature can be explained in terms of the Clapeyron equation for a boundary between a solid phase and a more compressible liquid phase or largely liquid phase assemblage.

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.

Mid-infrared emission and Raman spectra analysis of Er(3+)-doped oxyfluorotellurite glasses.

PubMed

Chen, Fangze; Xu, Shaoqiong; Wei, Tao; Wang, Fengchao; Cai, Muzhi; Tian, Ying; Xu, Shiqing

2015-04-10

This paper reports on the spectroscopic and structural properties in Er(3+)-doped oxyfluorotellurite glasses. The compositional variation accounts for the evolutions of Raman spectra, Judd-Ofelt parameters, radiative properties, and fluorescent emission. It is found that, when maximum phonon energy changes slightly, phonon density plays a crucial role in quenching the 2.7 μm emission generated by the Er(3+):(4)I11/2→(4)I13/2 transition. The comparative low phonon density contributes strong 2.7 μm emission intensity. The high branching ratio (18.63%) and large emission cross section (0.95×10(-20)  cm(2)) demonstrate that oxyfluorotellurite glass contained with 50 mol.% TeO2 has potential application in the mid-infrared region laser.

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

Excitonic resonance effects and Davydov splitting in circularly polarized Raman spectra of few-layer WSe2

NASA Astrophysics Data System (ADS)

Kim, Sanghun; Kim, Kangwon; Lee, Jae-Ung; Cheong, Hyeonsik

2017-12-01

Few-layer tungsten diselenide (WSe2) is investigated using circularly polarized Raman spectroscopy with up to eight excitation energies. The main E2\\text{g}1 and A 1g modes near 250 cm-1 appear as a single peak in the Raman spectrum taken without consideration of polarization but are resolved by using circularly polarized Raman scattering. The resonance behaviors of the E2\\text{g}1 and A 1g modes are examined. Firstly, both the E2\\text{g}1 and A 1g modes are enhanced near resonances with the exciton states. The A 1g mode exhibits Davydov splitting for trilayers or thicker near some of the exciton resonances. The low-frequency Raman spectra show shear and breathing modes involving rigid vibrations of the layers and also exhibit strong dependence on the excitation energy. An unidentified peak at ~19 cm-1 that does not depend on the number of layers appears near resonance with the B exciton state at 1.96 eV (632.8 nm). The strengths of the intra- and inter-layer interactions are estimated by comparing the mode frequencies and Davydov splitting with the linear chain model, and the contribution of the next-nearest-neighbor interaction to the inter-layer interaction turns out to be about 34% of the nearest-neighbor interaction. Fano resonance is observed for 1.58 eV excitation, and its origin is found to be the interplay between two-phonon scattering and indirect band transition.

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.

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.

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.

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...

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.

Using a portable Raman spectrometer to detect carotenoids of halophilic prokaryotes in synthetic inclusions in NaCl, KCl, and sulfates.

PubMed

Jehlička, Jan; Culka, Adam; Mana, Lilly; Oren, Aharon

2018-05-03

Cell suspensions of the haloarchaea Halorubrum sodomense and Halobacterium salinarum and the extremely halophilic bacterium Salinibacter ruber (Bacteroidetes) in saturated solutions of chlorides and sulfates (NaCl, KCl, MgSO 4 ·7H 2 O, K 2 SO 4 , and (NH 4 )Al(SO 4 ) 2 ·12H 2 O) were left to evaporate to produce micrometric inclusions in laboratory-grown crystals. Raman spectra of these pinkish inclusions were obtained using a handheld Raman spectrometer with green excitation (532 nm). This portable instrument does not include any microscopic tool. Acceptable Raman spectra of carotenoids were obtained in the range of 200-4000 cm -1 . This detection achievement was related to the mode of illumination and collection of scattered light as well as due to resonance Raman enhancement of carotenoid signals under green excitation. The position of diagnostic Raman carotenoid bands corresponds well to those specific carotenoids produced by a given halophile. To our best knowledge, this is the first study of carotenoids included in the laboratory in crystalline chlorides and sulfates, using a miniature portable Raman spectrometer. Graphical abstract ᅟ.

Concentration of small ring structures in vitreous silica from a first-principles analysis of the Raman spectrum.

PubMed

Umari, P; Gonze, Xavier; Pasquarello, Alfredo

2003-01-17

Using a first-principles approach, we calculate Raman spectra for a model structure of vitreous silica. We develop a perturbational method for calculating the dielectric tensor in an ultrasoft pseudopotential scheme and obtain Raman coupling tensors by finite differences with respect to atomic displacements. For frequencies below 1000 cm(-1), the parallel-polarized Raman spectrum of vitreous silica is dominated by oxygen bending motions, showing a strong sensitivity to the intermediate range structure. By modeling the Raman coupling, we derive estimates for the concentrations of three- and four-membered rings from the experimental intensities of the Raman defect lines.

Automatic Preocessing of Impact Ionization Mass Spectra Obtained by Cassini CDA

NASA Astrophysics Data System (ADS)

Villeneuve, M.

2015-12-01

Since Cassini's arrival at Saturn in 2004, the Comic Dust Analyzer (CDA) has recorded nearly 200,000 mass spectra of dust particles. A majority of this data has been collected in Saturn's diffuse E ring where sodium salts embedded in water ice particles indicate that many particles are in fact frozen droplets from Enceladus' subsurface ocean that have been expelled from cracks in the icy crust. So far only a small fraction of the obtained spectra have been processed because the steps in processing the spectra require human manipulation. We developed an automatic processing pipeline for CDA mass spectra which will consistently analyze this data. The preprocessing steps are to de-noise the spectra, determine and remove the baseline, calculate the correct stretch parameter, and finally to identify elements and compounds in the spectra. With the E ring constantly evolving due to embedded active moons, this data will provide valuable information about the source of the E ring, the subsurface of Saturn's ice moon Enceladus, as well as about the dynamics of the ring itself.

Resonance and Variable Temperature Raman Studies of Chloroperoxidase and Methemoglobin.

NASA Astrophysics Data System (ADS)

Remba, Ronald David

1980-12-01

Raman spectra of the heme proteins chloroperoxidase and methemoglobin, chemically and temperature modified, are obtained for laser excitation near the Soret absorption band. Numerous biochemical and physical results are obtained. The following observations for chloroperoxidase have been made. The scattered intensity for resonance (406.7 nm) excitation is at least twenty times that for near resonance (457.9 nm) excitation. In resonance only totally symmetric modes are enhanced. The positions of marker band I ((TURN) 1370 cm(' -1)) for both the native and reduced enzymes are lower than expected for high-spin heme proteins indicating a strongly electron donating axial ligand. From shifts in spin-sensitive Raman peaks as the temperature is lowered, a high-spin to low-spin transition of the heme iron is inferred. Raman spectra of chloroperoxidase liganded with small ions indicate that there is a second anion binding site near the heme. Photo-dissociation of CO from reduced chloroperoxidase is observed. The position of marker band I in the CO complex indicates that electron density is transferred from the heme onto the CO. The resonance Raman spectra of chloroperoxidase and cytochrome P-450 are nearly identical and are very different from those of horseradish peroxidase and cytochrome c. These results, particularly for the reduced enzymes, indicate that the heme sites in chloroperoxidase and P -450 are essentially the same. Raman spectra of a number of methemoglobins complexed with various small ions are obtained as a function of temperature in the region of spin-sensitive marker band (II) ((TURN) 1500 cm('-1)) for laser excitation near the Soret absorption band. For certain ligands, H(,2)O, N(,3)('-), OCN('-), OH('-) and SCN('-), the iron spin state changes from high spin to low spin with decreasing temperature. The relative spin concentrations are monitored by measuring the Raman intensity ratio, I(,h)/I(,1), of the high-spin and low -spin versions of marker band (II

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.

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.

Surface-enhanced hyper-Raman spectroscopy with a picosecond laser: gold and copper colloids

NASA Astrophysics Data System (ADS)

Lipscomb, Leigh Ann; Nie, Shuming; Feng, Sibo; Yu, Nai-Teng

1990-07-01

We have obtained surface-enhanced hyper-Raman scattering (SEHRS) spectra of crystal violet, rhodamine 6G and Ru(trpy) (BPE) 32+ adsorbed on gold and copper colloidal surfaces (where trpy=2,2',2″-terpyridine, BPE=trans-bis(4-pyridyl)ethylene). Our results demonstrate that the SEHRS effect is not intrinsically restricted to a Ag substrate and that surface enhancements at the emitted hyper-Raman photon frequencies are not required for observing SEHRS signals.

Shell morphology and Raman spectra of epitaxial Ge-SixGe1-x and Si-SixGe1-x core-shell nanowires

NASA Astrophysics Data System (ADS)

Wen, Feng; Dillen, David C.; Kim, Kyounghwan; Tutuc, Emanuel

2017-06-01

We investigate the shell morphology and Raman spectra of epitaxial Ge-SixGe1-x and Si-SixGe1-x core-shell nanowire heterostructures grown using a combination of a vapor-liquid-solid (VLS) growth mechanism for the core, followed by in-situ epitaxial shell growth using ultra-high vacuum chemical vapor deposition. Cross-sectional transmission electron microscopy reveals that the VLS growth yields cylindrical Ge, and Si nanowire cores grown along the ⟨111⟩, and ⟨110⟩ or ⟨112⟩ directions, respectively. A hexagonal cross-sectional morphology is observed for Ge-SixGe1-x core-shell nanowires terminated by six {112} facets. Two distinct morphologies are observed for Si-SixGe1-x core-shell nanowires that are either terminated by four {111} and two {100} planes associated with the ⟨110⟩ growth direction or four {113} and two {111} planes associated with the ⟨112⟩ growth direction. We show that the Raman spectra of Si- SixGe1-x are correlated with the shell morphology thanks to epitaxial growth-induced strain, with the core Si-Si mode showing a larger red shift in ⟨112⟩ core-shell nanowires compared to their ⟨110⟩ counterparts. We compare the Si-Si Raman mode value with calculations based on a continuum elasticity model coupled with the lattice dynamic theory.

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

Detection of advanced glycation end products (AGEs) on human skin by in vivo confocal Raman spectroscopy

NASA Astrophysics Data System (ADS)

Martin, A. A.; Pereira, L.; Ali, S. M.; Pizzol, C. D.; Tellez, C. A.; Favero, P. P.; Santos, L.; da Silva, V. V.; Praes, C. E. O.

2016-03-01

The aging process involves the reduction in the production of the major components of skin tissue. During intrinsic aging and photoaging processes, in dermis of human skin, fibroblasts become senescent and have decreased activity, which produce low levels of collagen. Moreover, there is accumulation of advanced glycation end products (AGEs). AGEs have incidence in the progression of age-related diseases, principally in diabetes mellitus and in Alzheimer's diseases. AGEs causes intracellular damage and/or apoptosis leading to an increase of the free radicals, generating a crosslink with skin proteins and oxidative stress. The aim of this study is to detect AGEs markers on human skin by in vivo Confocal Raman spectroscopy. Spectra were obtained by using a Rivers Diagnostic System, 785 nm laser excitation and a CCD detector from the skin surface down to 120 μm depth. We analyzed the confocal Raman spectra of the skin dermis of 30 women volunteers divided into 3 groups: 10 volunteers with diabetes mellitus type II, 65-80 years old (DEW); 10 young healthy women, 20-33 years old (HYW); and 10 elderly healthy women, 65-80 years old (HEW). Pentosidine and glucosepane were the principally identified AGEs in the hydroxyproline and proline Raman spectral region (1000-800 cm-1), in the 1.260-1.320 cm-1 region assignable to alpha-helical amide III modes, and in the Amide I region. Pentosidine and glucosepane calculated vibrational spectra were performed through Density Functional Theory using the B3LYP functional with 3-21G basis set. Difference between the Raman spectra of diabetic elderly women and healthy young women, and between healthy elderly women and healthy young women were also obtained with the purpose of identifying AGEs Raman bands markers. AGEs peaks and collagen changes have been identified and used to quantify the glycation process in human skin.

Increasing the speed of tumour diagnosis during surgery with selective scanning Raman microscopy

NASA Astrophysics Data System (ADS)

Kong, Kenny; Rowlands, Christopher J.; Varma, Sandeep; Perkins, William; Leach, Iain H.; Koloydenko, Alexey A.; Pitiot, Alain; Williams, Hywel C.; Notingher, Ioan

2014-09-01

One of the main challenges in cancer surgery is ensuring that all tumour cells are removed during surgery, while sparing as much healthy tissue as possible. Histopathology, the gold-standard technique for cancer diagnosis, is often impractical for intra-operative use because of the time-consuming tissue preparation procedures (sectioning and staining). Raman micro-spectroscopy is a powerful technique that can discriminate between tumours and healthy tissues with high accuracy, based entirely on intrinsic chemical differences. However, raster-scanning Raman micro-spectroscopy is a slow imaging technique that typically requires data acquisition times as long as several days for typical tissue samples obtained during surgery (1 × 1 cm2) - in particular when high signal-to-noise ratio spectra are required to ensure accurate diagnosis. In this paper we present two techniques based on selective sampling Raman micro-spectroscopy that can overcome these limitations. In selective sampling, information regarding the spatial features of the tissue, either measured by an alternative optical technique or estimated in real-time from the Raman spectra, can be used to drastically reduce the number of Raman spectra required for diagnosis. These sampling strategies allowed diagnosis of basal cell carcinoma in skin tissue samples excised during Mohs micrographic surgery faster than frozen section histopathology, and two orders of magnitude faster than previous techniques based on raster-scanning Raman microscopy. Further development of these techniques may help during cancer surgery by providing a fast and objective way for surgeons to ensure the complete removal of tumour cells while sparing as much healthy tissue as possible.

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.

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.

Volume properties and spectroscopy: A terahertz Raman investigation of hen egg white lysozyme

NASA Astrophysics Data System (ADS)

Sassi, Paola; Perticaroli, Stefania; Comez, Lucia; Giugliarelli, Alessandra; Paolantoni, Marco; Fioretto, Daniele; Morresi, Assunta

2013-12-01

The low frequency depolarized Raman spectra of 100 mg/ml aqueous solutions of hen egg white lysozyme (HEWL) have been collected in the 25-85 °C range. Short and long exposures to high temperatures have been used to modulate the competition between the thermally induced reversible and irreversible denaturation processes. A peculiar temperature evolution of spectra is evidenced under prolonged exposure of the protein solution at temperatures higher than 65 °C. This result is connected to the self-assembling of polypeptide chains and testifies the sensitivity of the technique to the properties of both protein molecule and its surrounding. Solvent free spectra have been obtained after subtraction of elastic and solvent components and assigned to a genuine vibrational contribution of hydrated HEWL. A straight similarity is observed between the solvent-free THz Raman feature and the vibrational density of states as obtained by molecular dynamics simulations; according to this, we verify the relation between this spectroscopic observable and the effective protein volume, and distinguish the properties of this latter respect to those of the hydration shell in the pre-melting region.

Methodology of mycobacteria tuberculosis bacteria detection by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zyubin, A.; Lavrova, A.; Manicheva, O.; Dogonadze, M.; Tsibulnikova, A.; Samusev, I.

2018-01-01

We have developed a methodology for the study of deactivated strains of Mycobacterium tuberculosis. Strains of the Beijing species obtained from pulmonary patient secrete (XDR strain) and reference strain (H37Rv) were investigated by Raman spectrometry with He-Ne (632,8 nm) laser excitation source. As a result of the research, the optimal experimental parameters have been obtained to get spectra of mycolic acids, which are part of the cell wall of mycobacteria.

Investigation of the Brill transition in nylon 6,6 by Raman, THz-Raman, and two-dimensional correlation spectroscopy.

PubMed

Bertoldo Menezes, D; Reyer, A; Musso, M

2018-02-05

The Brill transition is a phase transition process in polyamides related with structural changes between the hydrogen bonds of the lateral functional groups (CO) and (NH). In this study, we have used the potential of Raman spectroscopy for exploring this phase transition in polyamide 6,6 (nylon 6,6), due to the sensitivity of this spectroscopic technique to small intermolecular changes affecting vibrational properties of relevant functional groups. During a step by step heating and cooling process of the sample we collected Raman spectra allowing us from two-dimensional Raman correlation spectroscopy to identify which spectral regions suffered the largest influence during the Brill transition, and from Terahertz Stokes and anti-Stokes Raman spectroscopy to obtain complementary information, e.g. on the temperature of the sample. This allowed us to grasp signatures of the Brill transition from peak parameters of vibrational modes associated with (CC) skeletal stretches and (CNH) bending, and to verify the Brill transition temperature at around 160°C, as well as the reversibility of this phase transition. Copyright © 2017 Elsevier B.V. All rights reserved.

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

Resonance Raman spectroscopy in malaria research.

PubMed

Wood, Bayden R; McNaughton, Don

2006-10-01

In recent years, the field of Raman spectroscopy has witnessed a surge in technological development, with the incorporation of ultrasensitive, charge-coupled devices, improved laser sources and precision Rayleigh-filter systems. This has led to the development of sensitive confocal micro-Raman spectrometers and imaging spectrometers that are capable of obtaining high spatial-resolution spectra and images of subcellular components within single living cells. This review reports on the application of resonance micro-Raman spectroscopy to the study of malaria pigment (hemozoin), a by-product of hemoglobin catabolization by the malaria parasite, which is an important target site for antimalarial drugs. The review aims to briefly describe recent studies on the application of this technology, elucidate molecular and electronic properties of the malaria pigment and its synthetic analog beta-hematin, provide insight into the mechanism of hemozoin formation within the food vacuole of the parasite, and comment on developing strategies for using this technology in drug-screening protocols.

A rapid detection method of Escherichia coli by surface enhanced Raman scattering