Journal articles: 'Fluorescence and Raman spectroscopy'

1

Zhao, Jun, Mike M. Carrabba, and Fritz S. Allen. "Automated Fluorescence Rejection Using Shifted Excitation Raman Difference Spectroscopy." Applied Spectroscopy 56, no. 7 (July 2002): 834–45. http://dx.doi.org/10.1366/000370202760171491.

Full text

Abstract:

Sample fluorescence is detrimental to Raman spectroscopic analysis. Several algorithms are proposed to achieve automatic fluorescence rejection (AFR) based on shifted excitation Raman difference spectroscopy. The algorithms are mathematically linear and can be automated. The methods are based on a wavelength-tunable laser and the measurement and calibration of both the Raman and the excitation spectra. Applying the AFR methods to highly fluorescent samples significantly reduces the fluorescence background and reveals weak Raman features unidentifiable using traditional methods. Fixed pattern “noise” associated with the background can be completely removed. The merits of each algorithm are discussed and the best excitation frequency shift to perform the analysis is found to be comparable to the widths of major Raman peaks.

APA, Harvard, Vancouver, ISO, and other styles

2

Wong Kee Song, Louis-Michel, and Norman E. Marcon. "Fluorescence and Raman spectroscopy." Gastrointestinal Endoscopy Clinics of North America 13, no. 2 (April 2003): 279–96. http://dx.doi.org/10.1016/s1052-5157(03)00013-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Anastassiades, Constantinos P., Brian C. Wilson, and Louis-Michel Wong Kee Song. "Fluorescence and Raman Spectroscopy." Gastrointestinal Endoscopy Clinics of North America 19, no. 2 (April 2009): 221–31. http://dx.doi.org/10.1016/j.giec.2009.02.009.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Li, Boyu, and Peter J. Larkin. "Chemical Bleaching to Minimize Fluorescence Interference in Raman Spectroscopic Measurements for Sulfonated Polystyrene Solutions." Applied Spectroscopy 74, no. 7 (May 4, 2020): 741–50. http://dx.doi.org/10.1177/0003702820919823.

Full text

Abstract:

Auto-fluorescence is a significant challenge for Raman spectroscopic analyses. Since fluorescence is a much stronger phenomenon than Raman scattering, even trace fluorescent impurities can overwhelm the Raman signal. Strategies to minimize fluorescence interference in Raman measurements include either an instrumental-based approach or treatment of the sample itself to minimize fluorescence. Efforts focused on sample-based treatments to reduce fluorescence interferences have generally focused on sample purification and photobleaching methodologies. In this work, we present a sample treatment approach based upon chemical bleaching to remove fluorescence from Raman measurements of aqueous solutions of sulfonated polystyrene (SPS). Synthetic batches of SPS are characterized by a wide variation in fluorescence from minimum to a catastrophic level, which greatly limits the use of Raman spectroscopy. We systematically investigate the efficacy of various sample-based treatments of the SPS samples. An important acceptance criterion is that the procedure effectively and reliably removes fluorescence without damaging the SPS component. The chemical bleaching, which involves the addition of hydrogen peroxide and incubation at 60 ℃, is found to be highly effective. The parameters affecting the bleaching efficacy are studied, including temperature, hydrogen peroxide dosage, and bleaching time. Classification models are then developed based on the drastically diverse fluorescence background levels in Raman spectra of SPS to help optimize bleaching time for each specific sample. This work serves as an example of using chemical bleaching to remove fluorescence, which is inexpensive and readily available. It can facilitate a broader use of Raman spectroscopy as a quantitative qualitative control method in industrial settings.

APA, Harvard, Vancouver, ISO, and other styles

5

Porterfield, Donivan R., and Alan Campion. "Fluorescence-free scanning Raman spectroscopy." Journal of the American Chemical Society 110, no. 2 (January 1988): 408–10. http://dx.doi.org/10.1021/ja00210a016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Lindley, Matthew, Kotaro Hiramatsu, Hayate Nomoto, Fukashi Shibata, Tsuyoshi Takeshita, Shigeyuki Kawano, and Keisuke Goda. "Ultrafast Simultaneous Raman-Fluorescence Spectroscopy." Analytical Chemistry 91, no. 24 (November 27, 2019): 15563–69. http://dx.doi.org/10.1021/acs.analchem.9b03563.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Wahadoszamen, Md, Arifur Rahaman, Nabil Md Rakinul Hoque, Aminul I Talukder, Kazi Monowar Abedin, and A. F. M. Yusuf Haider. "Laser Raman Spectroscopy with Different Excitation Sources and Extension to Surface Enhanced Raman Spectroscopy." Journal of Spectroscopy 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/895317.

Full text

Abstract:

A dispersive Raman spectrometer was used with three different excitation sources (Argon-ion, He-Ne, and Diode lasers operating at 514.5 nm, 633 nm, and 782 nm, resp.). The system was employed to a variety of Raman active compounds. Many of the compounds exhibit very strong fluorescence while being excited with a laser emitting at UV-VIS region, hereby imposing severe limitation to the detection efficiency of the particular Raman system. The Raman system with variable excitation laser sources provided us with a desired flexibility toward the suppression of unwanted fluorescence signal. With this Raman system, we could detect and specify the different vibrational modes of various hazardous organic compounds and some typical dyes (both fluorescent and nonfluorescent). We then compared those results with the ones reported in literature and found the deviation within the range of ±2 cm−1, which indicates reasonable accuracy and usability of the Raman system. Then, the surface enhancement technique of Raman spectrum was employed to the present system. To this end, we used chemically prepared colloidal suspension of silver nanoparticles as substrate and Rhodamine 6G as probe. We could observe significant enhancement of Raman signal from Rhodamine 6G using the colloidal solution of silver nanoparticles the average magnitude of which is estimated to be 103.

APA, Harvard, Vancouver, ISO, and other styles

8

Goldrick, Stephen, David Lovett, Gary Montague, and Barry Lennox. "Influence of Incident Wavelength and Detector Material Selection on Fluorescence in the Application of Raman Spectroscopy to a Fungal Fermentation Process." Bioengineering 5, no. 4 (September 25, 2018): 79. http://dx.doi.org/10.3390/bioengineering5040079.

Full text

Abstract:

Raman spectroscopy is a novel tool used in the on-line monitoring and control of bioprocesses, offering both quantitative and qualitative determination of key process variables through spectroscopic analysis. However, the wide-spread application of Raman spectroscopy analysers to industrial fermentation processes has been hindered by problems related to the high background fluorescence signal associated with the analysis of biological samples. To address this issue, we investigated the influence of fluorescence on the spectra collected from two Raman spectroscopic devices with different wavelengths and detectors in the analysis of the critical process parameters (CPPs) and critical quality attributes (CQAs) of a fungal fermentation process. The spectra collected using a Raman analyser with the shorter wavelength (903 nm) and a charged coupled device detector (CCD) was corrupted by high fluorescence and was therefore unusable in the prediction of these CPPs and CQAs. In contrast, the spectra collected using a Raman analyser with the longer wavelength (993 nm) and an indium gallium arsenide (InGaAs) detector was only moderately affected by fluorescence and enabled the generation of accurate estimates of the fermentation’s critical variables. This novel work is the first direct comparison of two different Raman spectroscopy probes on the same process highlighting the significant detrimental effect caused by high fluorescence on spectra recorded throughout fermentation runs. Furthermore, this paper demonstrates the importance of correctly selecting both the incident wavelength and detector material type of the Raman spectroscopy devices to ensure corrupting fluorescence is minimised during bioprocess monitoring applications.

APA, Harvard, Vancouver, ISO, and other styles

9

Chiuri, Andrea, and Federico Angelini. "Fast Gating for Raman Spectroscopy." Sensors 21, no. 8 (April 7, 2021): 2579. http://dx.doi.org/10.3390/s21082579.

Full text

Abstract:

Fast gating in Raman spectroscopy is used to reject the fluorescence contribution from the sample and/or the substrate. Several techniques have been set up in the last few decades aiming either to enhance the Raman signal (CARS, SERS or Resonant Raman scattering) or to cancel out the fluorescence contribution (SERDS), and a number of reviews have already been published on these sub-topics. However, for many reasons it is sometimes necessary to reject fluorescence in traditional Raman spectroscopy, and in the last few decades a variety of papers dealt with this issue, which is still challenging due to the time scales at stake (down to picoseconds). Fast gating (<1 ns) in the time domain allows one to cut off part of the fluorescence signal and retrieve the best Raman signal, depending on the fluorescence lifetime of the sample and laser pulse duration. In particular, three different techniques have been developed to accomplish this task: optical Kerr cells, intensified Charge Coupling Devices and systems based on Single Photon Avalanche Photodiodes. The utility of time domain fast gating will be discussed, and In this work, the utility of time domain fast gating is discussed, as well as the performances of the mentioned techniques as reported in literature.

APA, Harvard, Vancouver, ISO, and other styles

10

Sato, Hidetoshi, Satoshi Wada, and Hideo Tashiro. "Fluorescence Backgroundless Ti: Sapphire Laser Using Acousto-Optical Tunable Filter for Raman Spectroscopic Measurements." Applied Spectroscopy 56, no. 10 (October 2002): 1303–7. http://dx.doi.org/10.1366/000370202760355019.

Full text

Abstract:

The background noise inherent to tunable lasers, which emit broad band spontaneous fluorescence from the laser-active medium, is detrimental for sensitive Raman measurement. Using the diffraction effect in an acousto-optic device, we have developed a fluorescence backgroundless Ti: sapphire laser suited for near-infrared Raman spectroscopy. A Raman excitation profile consisting of series of Raman spectra of deoxygenated hemoglobin aqueous solutions was measured by changing excitation wavelengths, revealing the high potential of this laser as a spectroscopic light source.

APA, Harvard, Vancouver, ISO, and other styles

11

Manninen, S. "Resonant raman scattering and fluorescence spectroscopy." Radiation Physics and Chemistry 50, no. 1 (July 1997): 77–89. http://dx.doi.org/10.1016/s0969-806x(97)00025-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Mogilevsky, Gregory, Laura Borland, Mark Brickhouse, and Augustus W. Fountain III. "Raman Spectroscopy for Homeland Security Applications." International Journal of Spectroscopy 2012 (June 6, 2012): 1–12. http://dx.doi.org/10.1155/2012/808079.

Full text

Abstract:

Raman spectroscopy is an analytical technique with vast applications in the homeland security and defense arenas. The Raman effect is defined by the inelastic interaction of the incident laser with the analyte molecule’s vibrational modes, which can be exploited to detect and identify chemicals in various environments and for the detection of hazards in the field, at checkpoints, or in a forensic laboratory with no contact with the substance. A major source of error that overwhelms the Raman signal is fluorescence caused by the background and the sample matrix. Novel methods are being developed to enhance the Raman signal’s sensitivity and to reduce the effects of fluorescence by altering how the hazard material interacts with its environment and the incident laser. Basic Raman techniques applicable to homeland security applications include conventional (off-resonance) Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), resonance Raman spectroscopy, and spatially or temporally offset Raman spectroscopy (SORS and TORS). Additional emerging Raman techniques, including remote Raman detection, Raman imaging, and Heterodyne imaging, are being developed to further enhance the Raman signal, mitigate fluorescence effects, and monitor hazards at a distance for use in homeland security and defense applications.

APA, Harvard, Vancouver, ISO, and other styles

13

Madonini, Francesca, and Federica Villa. "Single Photon Avalanche Diode Arrays for Time-Resolved Raman Spectroscopy." Sensors 21, no. 13 (June 23, 2021): 4287. http://dx.doi.org/10.3390/s21134287.

Full text

Abstract:

The detection of peaks shifts in Raman spectroscopy enables a fingerprint reconstruction to discriminate among molecules with neither labelling nor sample preparation. Time-resolved Raman spectroscopy is an effective technique to reject the strong fluorescence background that profits from the time scale difference in the two responses: Raman photons are scattered almost instantaneously while fluorescence shows a nanoseconds time constant decay. The combination of short laser pulses with time-gated detectors enables the collection of only those photons synchronous with the pulse, thus rejecting fluorescent ones. This review addresses time-gating issues from the sensor standpoint and identifies single photon avalanche diode (SPAD) arrays as the most suitable single-photon detectors to be rapidly and precisely time-gated without bulky, complex, or expensive setups. At first, we discuss the requirements for ideal Raman SPAD arrays, particularly focusing on the design guidelines for optimized on-chip processing electronics. Then we present some existing SPAD-based architectures, featuring specific operation modes which can be usefully exploited for Raman spectroscopy. Finally, we highlight key aspects for future ultrafast Raman platforms and highly integrated sensors capable of undistorted identification of Raman peaks across many pixels.

APA, Harvard, Vancouver, ISO, and other styles

14

Marshall, Sarah, and John B. Cooper. "Quantitative Raman Spectroscopy when the Signal-to-Noise is Below the Limit of Quantitation due to Fluorescence Interference: Advantages of a Moving Window Sequentially Shifted Excitation Approach." Applied Spectroscopy 70, no. 9 (September 2016): 1489–501. http://dx.doi.org/10.1177/0003702816662621.

Full text

Abstract:

Raman spectroscopy is a useful analytical tool. However, its application is often limited because shot noise from fluorescence obscures the Raman signal. In such cases, quantitative analysis is not possible when the signal-to-noise ratio (SNR) drops below two. A method is described for performing quantitative Raman spectroscopy that not only removes fluorescence backgrounds, but also results in a significant improvement in the SNR. The Raman data is extracted using a moving window sequentially shifted excitation algorithm. To demonstrate the capabilities of the method, a binary mixture of two analytes at varying concentrations is quantified in the presence of a highly fluorescent dye. Linear calibration plots were constructed and validated for the binary model using individual Raman peaks with SNR ranging from 0.073–12.6; r2 values are greater than 0.96 in all cases, with all but the weakest peaks yielding values greater than 0.997. The presented method demonstrates a universal and autonomous approach for the quantitative analysis of highly fluorescent samples via Raman spectroscopy. The lower limit on the SNR ratio for quantitative Raman analysis with the described method is 0.1. In order to assess the effectiveness of the presented method, the entire set of experiments was also processed using the more common shifted excitation Raman difference spectroscopy (SERDS) approach. The advantages of the proposed method over SERDS are demonstrated for both the detection limit and the SNR of the processed spectra.

APA, Harvard, Vancouver, ISO, and other styles

15

Yin, Nai-Hao, Anthony W. Parker, Pavel Matousek, and Helen L. Birch. "Detection of Age-Related Changes in Tendon Molecular Composition by Raman Spectroscopy—Potential for Rapid, Non-Invasive Assessment of Susceptibility to Injury." International Journal of Molecular Sciences 21, no. 6 (March 20, 2020): 2150. http://dx.doi.org/10.3390/ijms21062150.

Full text

Abstract:

The lack of clinical detection tools at the molecular level hinders our progression in preventing age-related tendon pathologies. Raman spectroscopy can rapidly and non-invasively detect tissue molecular compositions and has great potential for in vivo applications. In biological tissues, a highly fluorescent background masks the Raman spectral features and is usually removed during data processing, but including this background could help age differentiation since fluorescence level in tendons increases with age. Therefore, we conducted a stepwise analysis of fluorescence and Raman combined spectra for better understanding of the chemical differences between young and old tendons. Spectra were collected from random locations of vacuum-dried young and old equine tendon samples (superficial digital flexor tendon (SDFT) and deep digital flexor tendon (DDFT), total n = 15) under identical instrumental settings. The fluorescence-Raman spectra showed an increase in old tendons as expected. Normalising the fluorescence-Raman spectra further indicated a potential change in intra-tendinous fluorophores as tendon ages. After fluorescence removal, the pure Raman spectra demonstrated between-group differences in CH2 bending (1450 cm−1) and various ring-structure and carbohydrate-associated bands (1000–1100 cm−1), possibly relating to a decline in cellular numbers and an accumulation of advanced glycation end products in old tendons. These results demonstrated that Raman spectroscopy can successfully detect age-related tendon molecular differences.

APA, Harvard, Vancouver, ISO, and other styles

16

Bergin, F. J., and H. F. Shurvell. "Applications of Fourier Transform Raman Spectroscopy in an Industrial Laboratory." Applied Spectroscopy 43, no. 3 (March 1989): 516–22. http://dx.doi.org/10.1366/0003702894202913.

Full text

Abstract:

In the past, the usefulness of laser Raman spectroscopy as an analytical technique in industrial laboratories has been greatly reduced by problems of laser-induced fluorescence. One method of circumventing this problem is to use near-infrared excitation coupled with a modified FT-IR spectrometer. In this paper, we report the results of some initial exploratory experiments which indicate that significant fluorescence rejection can be achieved. This fluorescence rejection opens up new areas of application for Raman spectroscopy. The advantages and limitations of FT-Raman spectroscopy are discussed. In addition, some initial experiments are outlined on Fourier transform Raman microscopy using a conventional microscope.

APA, Harvard, Vancouver, ISO, and other styles

17

De Luca, Anna Chiara, Michael Mazilu, Andrew Riches, C. Simon Herrington, and Kishan Dholakia. "Online Fluorescence Suppression in Modulated Raman Spectroscopy." Analytical Chemistry 82, no. 2 (January 15, 2010): 738–45. http://dx.doi.org/10.1021/ac9026737.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Xiong, Hanqing, Lixue Shi, Lu Wei, Yihui Shen, Rong Long, Zhilun Zhao, and Wei Min. "Stimulated Raman excited fluorescence spectroscopy and imaging." Nature Photonics 13, no. 6 (April 1, 2019): 412–17. http://dx.doi.org/10.1038/s41566-019-0396-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Kudryavtsev, O. S., A. A. Khomich, V. S. Sedov, E. A. Ekimov, and I. I. Vlasov. "Fluorescence and Raman Spectroscopy of Doped Nanodiamonds." Journal of Applied Spectroscopy 85, no. 2 (May 2018): 295–99. http://dx.doi.org/10.1007/s10812-018-0647-z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

He, Wencai, Bolan Li, and Shan Yang. "High-Frequency Raman Analysis in Biological Tissues Using Dual-Wavelength Excitation Raman Spectroscopy." Applied Spectroscopy 74, no. 2 (November 7, 2019): 241–44. http://dx.doi.org/10.1177/0003702819881762.

Full text

Abstract:

A dual-wavelength excitation Raman probe with laser inputs at 866 nm or 1064 nm is customized and integrated into a compact Raman spectrometer that is based on an InGaAs detector. Under 1064 nm illumination, the spectrometer detects fingerprint Raman signals below 2000 cm–1. While under 866 nm illumination, the spectral range is extended to cover high-frequency region (2400–4000 cm–1) that includes major C–H and O–H Raman vibrations. We demonstrate that the dual excitation InGaAs Raman is beneficial in detecting high-frequency Raman signals, especially water contents in high-fluorescent biological samples such as human dental tissues, grape skin, and plum skin due to the suppressed fluorescence interference.

APA, Harvard, Vancouver, ISO, and other styles

21

Chen, T. C., D. A. Shea, and M. D. Morris. "Effect of Hydrogen Peroxide Bleaching on Bone Mineral/Matrix Ratio." Applied Spectroscopy 56, no. 8 (August 2002): 1035–37. http://dx.doi.org/10.1366/000370202760249774.

Full text

Abstract:

It is shown that bone fluorescence reduction by bleaching in 30% hydrogen peroxide causes a change in the mineral/matrix ratio as measured by Raman spectroscopy. However, there are no observable spectral shifts in the mineral Raman spectrum or in the matrix Raman spectrum. Possible sources of the change in ratio are discussed. Peroxide bleaching is not recommended for fluorescence reduction in quantitative Raman spectroscopy.

APA, Harvard, Vancouver, ISO, and other styles

22

Shugar, Aaron, Krista Lough, and Jiuan Jiuan Chen. "Characterization of a Surface Tarnish Found on Daguerreotypes Revealed under Shortwave Ultraviolet Radiation." MRS Proceedings 1656 (July 18, 2014): 319–33. http://dx.doi.org/10.1557/opl.2014.706.

Full text

Abstract:

ABSTRACTA characteristic fluorescent tarnish can be observed on some daguerreotypes under shortwave ultraviolet radiation. The fluorescence can be seen in several distinct patterns: edge tarnish, rings, and continuous films. Dispersive Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were applied to characterize and identify the fluorescent compound. Raman spectroscopy identified the characteristic peak for copper cyanide, CuCN, at 2172 cm-1. Elemental k-ratio maps of the SEM analysis indicated an increase in copper, sodium, carbon and nitrogen in the area of fluorescence. XRD confirmed the identification of a copper cyanide compound. Shortwave ultraviolet radiation can be used in a monitoring program of daguerreotypes to further characterize the fluorescent tarnish and its effect on the deterioration of daguerreotypes.

APA, Harvard, Vancouver, ISO, and other styles

23

García-Bucio, Ma A., E. Casanova-González, and J. L. Ruvalcaba-Sil. "Raman Spectroscopy for the Study of XVI-XVII Centuries Colonial Paintings." MRS Proceedings 1618 (2014): 141–51. http://dx.doi.org/10.1557/opl.2014.463.

Full text

Abstract:

ABSTRACTOutstanding information about the material composition and pictorial techniques of the New Spain Colonial painting can be obtained via a full characterization using a set of analytical techniques. Given the cultural importance of this painting, a non-invasive approach is preferred. Moreover, the preparation and use of reference materials using original recipes is necessary for a correct interpretation of the spectroscopic data from historical objects. Here, we present the results obtained via an in-situ Raman spectroscopic analysis of a set of pictorial reference materials, created according to XVI and XVII centuries’ recipes. Several difficulties were encountered, such as the low Raman detection signal, an intrinsic fluorescence of the material, and in some cases even laser-induced degradation. For this reason, the usual molecular Raman analysis was extended to Surface Enhanced Raman Spectroscopy (SERS), which enhances the Raman signal and quenches the fluorescence. It was then applied to the analysis of two wood paintings from the ex-convent San Francisco Tepeyanco, in Tlaxcala.

APA, Harvard, Vancouver, ISO, and other styles

24

Conti, Claudia, Alessandra Botteon, Chiara Colombo, Marco Realini, and Pavel Matousek. "Fluorescence suppression using micro-scale spatially offset Raman spectroscopy." Analyst 141, no. 18 (2016): 5374–81. http://dx.doi.org/10.1039/c6an00852f.

Full text

Abstract:

We present a new concept of fluorescence suppression in Raman microscopy based on micro-spatially offset Raman spectroscopy which is applicable to thin stratified turbid (diffusely scattering) matrices permitting the retrieval of the Raman signals of sublayers below intensely fluorescing turbid over-layers.

APA, Harvard, Vancouver, ISO, and other styles

25

Lu, Zhang, Jiao, and Guan. "Large-Scale Fabrication of Nanostructure on Bio-Metallic Substrate for Surface Enhanced Raman and Fluorescence Scattering." Nanomaterials 9, no. 7 (June 26, 2019): 916. http://dx.doi.org/10.3390/nano9070916.

Full text

Abstract:

The integration of surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) has attracted increasing interest and is highly probable to improve the sensitivity and reproducibility of spectroscopic investigations in biomedical fields. In this work, dual-mode SERS and SEF hierarchical structures have been developed on a single bio-metallic substrate. The hierarchical structure was composed of micro-grooves, nano-particles, and nano-ripples. The crystal violet was selected as reporter molecule and both the intensity of Raman and fluorescence signals were enhanced because of the dual-mode SERS−SEF phenomena with enhancement factors (EFs) of 7.85 × 105 and 14.32, respectively. The Raman and fluorescence signals also exhibited good uniformity with the relative standard deviation value of 2.46% and 5.15%, respectively. Moreover, the substrate exhibited high sensitivity with the limits of detection (LOD) as low as 1 × 10−11 mol/L using Raman spectroscopy and 1 × 10−10 mol/L by fluorescence spectroscopy. The combined effect of surface plasmon resonance and “hot spots” induced by the hierarchical laser induced periodical surface structures (LIPSS) was mainly contributed to the enhancement of Raman and fluorescence signal. We propose that the integration of SERS and SEF in a single bio-metallic substrate is promising to improve the sensitivity and reproducibility of detection in biomedical investigations.

APA, Harvard, Vancouver, ISO, and other styles

26

Romanishkin, I. D., L. R. Bikmukhametova, T. A. Savelieva, S. A. Goryaynov, A. V. Kosyrkova, V. A. Okhlopkov, D. A. Golbin, I. Yu Poletaeva, A. A. Potapov, and V. B. Loschenov. "Spontaneous Raman spectroscopy for intracranial tumors diagnostics ex vivo." Biomedical Photonics 9, no. 3 (October 19, 2020): 4–12. http://dx.doi.org/10.24931/2413-9432-2020-9-3-4-12.

Full text

Abstract:

Neurosurgery of intracranial tumors, especially of glial origin, is a non-trivial task due to their infiltrative growth. In recent years, optical methods of intraoperative navigation have been actively used in neurosurgery. However, one of the most widely used approaches based on the selective accumulation of fluorescent contrast medium (5-ALA-induced protoporphyrin IX) by the tumor cannot be applied to a significant number of tumors due to its low accumulation. On the contrary, Raman spectroscopy, which allows analyzing the molecular composition of tissues while preserving all the advantages of the method of fluorescence spectroscopy, does not require the use of an exogenous dye and may become a method of choice when composing a system for intraoperative navigation or optical biopsy. This work presents the first results of using the principal component method to classify Raman spectra of human glioblastoma with intermediate processing of spectra to minimize possible errors from the fluorescence of both endogenous fluorophores and photosensitizers used in fluorescence navigation. As a result, differences were found in the principal component space, corresponding to tissue samples with microcystic components, extensive areas of necrosis, and foci of fresh hemorrhages. It is shown that this approach can serve as the basis for constructing a system for automatic intraoperative tissue classification based on the analysis of Raman spectra.

APA, Harvard, Vancouver, ISO, and other styles

27

Higuchi, Sciichiro, Er Jie Yu, and Shigeyuki Tanaka. "The Influence of Solvents on the Fluorescence Background in Raman Spectroscopy." Applied Spectroscopy 41, no. 3 (March 1987): 413–16. http://dx.doi.org/10.1366/0003702874448977.

Full text

Abstract:

For the purpose of reducing the fluorescence background induced by the laser irradiation in the measurements of Raman spectra, the influence of solvents on the background intensities for three polycyclic aromatic compounds was examined, where the experiments were conducted with typical solvents. It was demonstrated that the behaviors of the fluorescence background against the laser irradiation time were quite different according to the solvents, and that the behaviors could be classified roughly into the three categories. It was proved that when suitable solvents were used, the background intensities could be reduced sufficiently, even for the fluorescent samples such as those treated here; thus, the clear observation of Raman spectra is obtained. As an example of the solvent influence on the Raman spectra, the results of measurements for three separate cases were shown for 1-nitropyrene. The three cases are as follows: first, the Raman bands are masked almost completely by the strong background (solvent: 1,1,2,2-tetrachloroethane); second, though the spectrum can be obtained, its S/N ratio is low because of the relatively large background (solvent: acetonitrile); third, a clear spectrum with excellent S/N ratio can be obtained because the background intensity is low enough (solvent: carbon tetrachloride).

APA, Harvard, Vancouver, ISO, and other styles

28

Mann, Charles K., and Thomas J. Vickers. "Raman Measurements in the Presence of Fluorescence." Applied Spectroscopy 41, no. 3 (March 1987): 427–30. http://dx.doi.org/10.1366/0003702874449075.

Full text

Abstract:

A method for eliminating the direct effects of fluorescence on Raman spectra is described. It is based upon the differences in widths of Raman and fluorescence peaks and is intended for applications of Raman measurements in chemical analysis. It involves only calculations that are carried out after the measurement has been made and does not require any instrumental enhancement beyond that normally used for Raman measurements. The extent of improvement that can be expected is shown, and the conditions under which its limits are reached are indicated. A technique involving an empirical correction is described which allows extension of these limits in certain cases.

APA, Harvard, Vancouver, ISO, and other styles

29

Wentrup-Byrne, E., L. Rintoul, J. L. Smith, and P. M. Fredericks. "Comparison of Vibrational Spectroscopic Techniques for the Characterization of Human Gallstones." Applied Spectroscopy 49, no. 7 (July 1995): 1028–36. http://dx.doi.org/10.1366/0003702953964813.

Full text

Abstract:

A suite of human gallstones was investigated by vibrational spectroscopic techniques with a view to developing an effective characterization procedure. Using infrared microscopy, microspectroscopic mapping, infrared photoacoustic spectroscopy (PAS), and FT-Raman spectroscopy, we have examined both the chemical composition and the microstructure of the different categories of human gallstones. We show how infrared microscopy can be used to determine the chemical identity of particular microstructural features of a stone. Infrared mapping produces functional group maps of the surface of a gallstone and shows the actual distribution of the different chemical components. Good fluorescence-free FT-Raman spectra were obtained from all categories of stones except black stones, which gave a fluorescence background with no observable Raman spectrum. Of the vibrational techniques studied, PAS proved the most suited to the spectroscopic categorization of gallstones because data for the whole stone can be obtained with minimal sample preparation. The advantages and disadvantages of each technique are discussed.

APA, Harvard, Vancouver, ISO, and other styles

30

Hoffmann, Günter Georg, Hans-Ulrich Menzebach, Bernhard Oelichmann, and Bernhard Schrader. "Combined Raman and Fluorescence Spectroscopy with the Same Compact CCD-Based Instrument." Applied Spectroscopy 46, no. 4 (April 1992): 568–70. http://dx.doi.org/10.1366/0003702924124925.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Tahara, Tahei, and Hiro-O. Hamaguchi. "Picosecond Raman Spectroscopy Using a Streak Camera." Applied Spectroscopy 47, no. 4 (April 1993): 391–98. http://dx.doi.org/10.1366/0003702934335001.

Full text

Abstract:

A Raman measuring system using a streak camera has been constructed. This system consists of a picosecond pulsed laser, an astigmatism-corrected spectrograph, and a streak camera. It enables two-dimensional multichannel detection (time and frequency) of Raman scattering with time resolution as high as 10 ps (without deconvolution). The system was first applied to fluorescence background rejection. Raman spectra of benzene containing a trace amount of Rhodamine 640 were measured. The improvement factor of the Raman-to-fluorescence intensity ratio was estimated as 281, compared with the time-integrated cw measurement. Second, the system was used for picosecond time-resolved Raman spectroscopy. Nanosecond probing laser pulses were used with picosecond pumping. Raman scattering at each delay time was time-resolved and detected by the streak camera. Time-resolved Raman spectra of benzophenone at delay times ranging from −1.25 ns to 1.5 ns were obtained from one single measurement. These results indicate that, if properly designed and properly combined with a suitable optical setup, a streak camera has very high potential for Raman spectroscopy.

APA, Harvard, Vancouver, ISO, and other styles

32

Hammannavar, Preeti B., and Blaise Lobo. "Spectroscopic Studies on Films of Lead Nitrate Doped Polyvinyl Alcohol – Polyvinyl Pyrrolidone Blend." Material Science Research India 15, no. 1 (January 31, 2018): 55–67. http://dx.doi.org/10.13005/msri/150107.

Full text

Abstract:

Films of polyvinyl alcohol (PVA) – polyvinyl pyrrolidone (PVP) blend doped with lead nitrate (Pb(NO3)2) were prepared by solution casting method, with doping level (DL) of Pb(NO3)2 in PVA – PVP polymeric blend varying from 2.7 up to 50.5 wt%. The prepared films were characterized using UV-Visible spectroscopy, fluorescence (or photo- luminescence) spectroscopy, FTIR and Raman spectroscopy. Parameters like optical band gaps due to indirect allowed transition (IAT) and direct allowed transition (DAT), as well as the activation energy (Ea) for optical transitions are extracted from the UV- Visible (or optical) spectra of these films. Objective of the FTIR, Raman and Fluorescence spectroscopic study is to understand the molecular chemical changes in PVA and PVP caused by the dopant (Pb(NO3)2). There is an enhancement of fluorescence intensity at DLs of 2.7 wt%, and at DL 7.6 wt%, the fluorescence intensity decreases (quenching). PVP acts as a capping agent for the dopant species, and is considered to be responsible for changes in fluorescence intensity. Signature of nitrate ion (NO3-) vibration is observed at wavenumber 1037 cm-1 in Raman spectra, and in the FTIR spectra, the NO3- vibration is seen at the wavenumber equal to 1380 cm-1.

APA, Harvard, Vancouver, ISO, and other styles

33

Christensen, Kenneth A., Nancy L. Bradley, Michael D. Morris, and Robert V. Morrison. "Raman Imaging Using a Tunable Dual-Stage Liquid Crystal Fabry-Perot Interferometer." Applied Spectroscopy 49, no. 8 (August 1995): 1120–25. http://dx.doi.org/10.1366/0003702953965155.

Full text

Abstract:

A 11 12 cm−1 bandpass electronically tunable liquid crystal dual-stage Fabry-Perot filter (DFPF) has been developed for use in Raman and fluorescence microscopic imaging. The imaging performance of the filter was demonstrated in the fluorescence and Raman modes. In the fluorescence mode, the filter was shown to give sharpened images using the nearest-neighbors deblurring algorithm. In the Raman imaging mode, background subtraction was shown to be useful for removal of the fluorescence from Raman images. With the use of a 100 × /1.25 objective, no significant decrease in the spatial resolution of the microscope was observed when the DFPF was inserted in the optical system.

APA, Harvard, Vancouver, ISO, and other styles

34

Lähdetie, Anni, Paula Nousiainen, Jussi Sipilä, Tarja Tamminen, and Anna-Stiina Jääskeläinen. "Laser-induced fluorescence (LIF) of lignin and lignin model compounds in Raman spectroscopy." Holzforschung 67, no. 5 (July 1, 2013): 531–38. http://dx.doi.org/10.1515/hf-2012-0177.

Full text

Abstract:

Abstract Raman spectroscopy is a technique that provides structural information on lignin and other components of wood and pulp in situ. However, especially lignin-containing samples may produce laser-induced fluorescence (LIF) that overlaps with Raman bands. In the worst case, this background signal can overwhelm the weaker Raman signal completely. In this study, the LIF of lignin was investigated with the excitation wavelength 532 nm applied in Raman spectroscopy to clarify the correlations between lignin structure and LIF intensity. Raman spectroscopic analyses with lignin model compounds illustrated that the 5-5′ structures induce LIF. It was also shown that the intensity of LIF was significantly less intense when the 5-5′ model compound was structurally rigid (as in dibenzodioxocin) compared with the flexible simple counterpart. The comparison between the free phenolic model compounds with the methylated analogue showed that the presence of the free phenolic structure was not a prerequisite for LIF. It was thus concluded that the conformation of the molecule is the key factor with respect to fluorescence. The role of conformational aspects was further investigated by comparing wood with chemical pulps and isolated lignins.

APA, Harvard, Vancouver, ISO, and other styles

35

Barnett, Steven M., François Dicaire, and Ashraf A. Ismail. "Application of FT-Raman spectroscopy to the study of selected organometallic complexes and proteins." Canadian Journal of Chemistry 68, no. 7 (July 1, 1990): 1196–200. http://dx.doi.org/10.1139/v90-185.

Full text

Abstract:

The study of colored organometallic complexes by dispersive Raman spectroscopy has been limited due to fluorescence or photodecomposition caused by the visible laser used as the excitation source. As a solution to this problem, FT-Raman spectroscopy with a near-infrared laser source has been useful in lowering fluorescence or photolysis in these samples. To investigate the utility of this technique, we have obtained and assigned the FT-Raman spectra of a series of arene chromium tricarbonyl complexes and of cyclopentadienyl manganese tricarbonyl. Some bands previously unobserved by dispersive Raman spectroscopy were seen, including a band assigned to a 13CO satellite in the spectrum of methylbenzoate chromium tricarbonyl. In addition, FT-Raman data for bovine serum albumin (BSA) and Protein-A are presented. Keywords: FT-Raman spectroscopy, metal carbonyl, proteins, organometallics, near infrared.

APA, Harvard, Vancouver, ISO, and other styles

36

Iwata, K., H. Hamaguchi, and M. Tasumi. "Sensitivity Calibration of Multichannel Raman Spectrometers Using the Least-Squares-Fitted Fluorescence Spectrum of Quinine." Applied Spectroscopy 42, no. 1 (January 1988): 12–14. http://dx.doi.org/10.1366/0003702884428608.

Full text

Abstract:

A method of sensitivity calibration of multichannel Raman spectrometers is described which employs the fluorescence spectrum of quinine as an intensity standard. The reported absolute fluorescence spectrum of quinine was least-squares fitted with a polynomial so that it gave an interpolation of the spectrum in the “Raman scale.” The obtained least-squares-fitted fluorescence spectrum was cross-checked with the rotational Raman spectrum of D2. The fluorescence intensities calculated for every 100 cm−1 from the two Ar+ laser lines are tabulated for convenience.

APA, Harvard, Vancouver, ISO, and other styles

37

Zalaffi, Maria Sole, Ines Agostinelli, Najmeh Karimian, and Paolo Ugo. "Ag-Nanostars for the Sensitive SERS Detection of Dyes in Artistic Cross-Sections—Madonna della Misericordia of the National Gallery of Parma: A Case Study." Heritage 3, no. 4 (November 12, 2020): 1344–59. http://dx.doi.org/10.3390/heritage3040074.

Full text

Abstract:

In historical paintings, the detection of low amounts of pigments and dyes by Raman spectroscopy can sometimes be challenging, in particular for fluorescent dyes. This issue can be overcome by using SERS (surface-enhanced Raman spectroscopy) which takes advantage of the properties of nanostructured metal surfaces to quench fluorescence and enhance Raman signals. In this work, silver nanostars (AgNSs) are applied for the first time to real art samples, in particular to painting cross-sections, exploiting their effective SERS properties for pigment identification. The case study is the Madonna della Misericordia of the National Gallery of Parma (Italy). Cross-sections were analyzed at first by optical microscopy, SEM-EDS, and micro-Raman spectroscopy. Unfortunately, in some cross-sections, the application of conventional Raman spectroscopy was hindered by an intense background fluorescence. Therefore, AgNSs were deposited and used as SERS-active agent. The experimentation was successful, allowing us to identify a modern dye, namely copper phthalocyanine. This result, together with the detection of other modern pigments (titanium white) and expert visual examination, allowed to reconstruct the painting history, postdating its realization from the 15th century (according to the Gallery inventory) to 19th century with a heavy role of recent (middle 20th century) restoration interventions.

APA, Harvard, Vancouver, ISO, and other styles

38

Anderson, T. Anthony, Jeon Woong Kang, Tatyana Gubin, Ramachandra R. Dasari, and Peter T. C. So. "Raman Spectroscopy Differentiates Each Tissue from the Skin to the Spinal Cord." Anesthesiology 125, no. 4 (October 1, 2016): 793–804. http://dx.doi.org/10.1097/aln.0000000000001249.

Full text

Abstract:

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

APA, Harvard, Vancouver, ISO, and other styles

39

Zhang, Chunling, Liying Zhang, Ru Yang, Kun Liang, and Dejun Han. "Time-Correlated Raman and Fluorescence Spectroscopy Based on a Silicon Photomultiplier and Time-Correlated Single Photon Counting Technique." Applied Spectroscopy 67, no. 2 (February 2013): 136–40. http://dx.doi.org/10.1366/12-06736.

Full text

Abstract:

We report a time-correlated Raman spectroscopy technique based on a silicon photomultiplier (SiPM) and a time-correlated single photon counting (TCSPC) technique to exploit the natural temporal separation between Raman and fluorescence phenomena to alleviate the high fluorescence background with conventional Raman detection. The TCSPC technique employed can greatly reduce the effect of high dark count rate (DCR) and crosstalk of SiPM that seriously hinder its application in low light level detection. The operating principle and performance of the 400 ps time resolution system are discussed along with the improvement of the peak-to-background ratio (PBR) for bulk trinitrotoluene (TNT) Raman spectrum relative to a commercial Raman spectrometer with charge coupled device (CCD). The fluorescence lifetime for solid TNT and Surface Enhanced Raman Scattering (SERS) spectrum for 10−6 mol/L trace TNT have also been obtained by this system, showing excellent versatility and convenience in spectroscopy measurement.

APA, Harvard, Vancouver, ISO, and other styles

40

Kadıoğlu, Yusuf Kağan, Zafer Üstündağ, and Zafer Yazıcıgil. "Spectroscopic Application of Realgar Using X-ray Fluorescence and Raman Spectroscopy." Spectroscopy Letters 42, no. 3 (March 24, 2009): 121–28. http://dx.doi.org/10.1080/00387010902728825.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Xiong, Hanqing, Naixin Qian, Yupeng Miao, Zhilun Zhao, and Wei Min. "Stimulated Raman Excited Fluorescence Spectroscopy of Visible Dyes." Journal of Physical Chemistry Letters 10, no. 13 (June 11, 2019): 3563–70. http://dx.doi.org/10.1021/acs.jpclett.9b01289.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Wei, Dong, Shuo Chen, and Quan Liu. "Review of Fluorescence Suppression Techniques in Raman Spectroscopy." Applied Spectroscopy Reviews 50, no. 5 (January 20, 2015): 387–406. http://dx.doi.org/10.1080/05704928.2014.999936.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Huang, Ya-Ping, Sheng-Chao Huang, Xiang-Jie Wang, Nataraju Bodappa, Chao-Yu Li, Hao Yin, Hai-Sheng Su, et al. "Shell-Isolated Tip-Enhanced Raman and Fluorescence Spectroscopy." Angewandte Chemie 130, no. 25 (April 26, 2018): 7645–49. http://dx.doi.org/10.1002/ange.201802892.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Huang, Ya-Ping, Sheng-Chao Huang, Xiang-Jie Wang, Nataraju Bodappa, Chao-Yu Li, Hao Yin, Hai-Sheng Su, et al. "Shell-Isolated Tip-Enhanced Raman and Fluorescence Spectroscopy." Angewandte Chemie International Edition 57, no. 25 (April 26, 2018): 7523–27. http://dx.doi.org/10.1002/anie.201802892.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

McCain, Scott T., Rebecca M. Willett, and David J. Brady. "Multi-excitation Raman spectroscopy technique for fluorescence rejection." Optics Express 16, no. 15 (July 9, 2008): 10975. http://dx.doi.org/10.1364/oe.16.010975.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Carvalho, Fabíola Bastos de, Artur Felipe Santos Barbosa, Fátima Antonia Aparecida Zanin, Aldo Brugnera Júnior, Landulfo Silveira Júnior, and Antonio Luiz Barbosa Pinheiro. "Use of laser fluorescence in dental caries diagnosis: a fluorescence x biomolecular vibrational spectroscopic comparative study." Brazilian Dental Journal 24, no. 1 (2013): 59–63. http://dx.doi.org/10.1590/0103-6440201302123.

Full text

Abstract:

The aim of this work was to verify the existence of correlation between Raman spectroscopy readings of phosphate apatite (∼960 cm−1), fluoridated apatite (∼575 cm−1) and organic matrix (∼1450 cm−1) levels and Diagnodent® readings at different stages of dental caries in extracted human teeth. The mean peak value of fluorescence in the carious area was recorded and teeth were divided in enamel caries, dentin caries and sound dental structure. After fluorescence readings, Raman spectroscopy was carried out on the same sites. The results showed significant difference (ANOVA, p<0.05) between the fluorescence readings for enamel (16.4 ± 2.3) and dentin (57.6 ± 23.7) on carious teeth. Raman peaks of enamel and dentin revealed that ∼575 and ∼960 cm−1 peaks were more intense in enamel caries. There was significant negative correlation (p<0.05) between the ∼575 and ∼960 cm−1 peaks and dentin caries. It may be concluded that the higher the fluorescence detected by Diagnodent the lower the peaks of phosphate apatite and fluoridated apatite. As the early diagnosis of caries is directly related to the identification of changes in the inorganic tooth components, Raman spectroscopy was more sensitive to variations of these components than Diagnodent.

APA, Harvard, Vancouver, ISO, and other styles

47

Aminzadeh, A. "Excitation Frequency Dependence and Fluorescence in the Raman Spectra of Al2O3." Applied Spectroscopy 51, no. 6 (June 1997): 817–19. http://dx.doi.org/10.1366/0003702971941331.

Full text

Abstract:

Raman spectra of aluminum oxide, Al2O3, have been a subject of interest over the last two decades. The origin of the fluorescence background in the Raman spectra of Al2O3 is still a subject of discussion. It has been believed to be due to hydrocarbon, iron ion impurities, or hydroxy groups on the surface of Al2O3. In this paper, Raman spectra of Al2O3 are reported that were acquired with different excitation frequencies as well as different spectrometers and different temperatures. It is shown that, whereas at an excitation frequency of 1064 nm a strong fluorescence background is observed, a sample of Al2O3 heated at 1250 °C when excited with a 632.8-nm frequency exhibits strong and remarkable fluorescence ne structure. It is concluded that the origin of the fluorescence background in the Raman spectra of Al2O3 is iron, and Fe impurity, and the intensity of this fluorescence depends upon the structure of Al2O3 and the excitation frequency used.

APA, Harvard, Vancouver, ISO, and other styles

48

Shaik, Tanveer Ahmed, Alba Alfonso-Garcia, Martin Richter, Florian Korinth, Christoph Krafft, Laura Marcu, and Jürgen Popp. "FLIm and Raman Spectroscopy for Investigating Biochemical Changes of Bovine Pericardium upon Genipin Cross-Linking." Molecules 25, no. 17 (August 25, 2020): 3857. http://dx.doi.org/10.3390/molecules25173857.

Full text

Abstract:

Biomaterials used in tissue engineering and regenerative medicine applications benefit from longitudinal monitoring in a non-destructive manner. Label-free imaging based on fluorescence lifetime imaging (FLIm) and Raman spectroscopy were used to monitor the degree of genipin (GE) cross-linking of antigen-removed bovine pericardium (ARBP) at three incubation time points (0.5, 1.0, and 2.5 h). Fluorescence lifetime decreased and the emission spectrum redshifted compared to that of uncross-linked ARBP. The Raman signature of GE-ARBP was resonance-enhanced due to the GE cross-linker that generated new Raman bands at 1165, 1326, 1350, 1380, 1402, 1470, 1506, 1535, 1574, 1630, 1728, and 1741 cm−1. These were validated through density functional theory calculations as cross-linker-specific bands. A multivariate multiple regression model was developed to enhance the biochemical specificity of FLIm parameters fluorescence intensity ratio (R2 = 0.92) and lifetime (R2 = 0.94)) with Raman spectral results. FLIm and Raman spectroscopy detected biochemical changes occurring in the collagenous tissue during the cross-linking process that were characterized by the formation of a blue pigment which affected the tissue fluorescence and scattering properties. In conclusion, FLIm parameters and Raman spectroscopy were used to monitor the degree of cross-linking non-destructively.

APA, Harvard, Vancouver, ISO, and other styles

49

Asselin, Kelly J., and Bruce Chase. "FT-Raman Spectroscopy at 1.339 Micrometers." Applied Spectroscopy 48, no. 6 (June 1994): 699–701. http://dx.doi.org/10.1366/000370294774369009.

Full text

Abstract:

The usual laser employed for Fourier transform Raman spectroscopy is a Nd:YAG unit lasing at 1.064 μm. In this work, use of the 1.339-μm lasing emission from Nd:YAG has been demonstrated. The sensitivity of this instrument is comparable to that of conventional FT-Raman instruments, and excellent anti-Stokes spectra can be easily obtained. Operation further into the near-infrared offers additional possibilities for fluorescence minimization. Results are shown for copper phthalocyanine.

APA, Harvard, Vancouver, ISO, and other styles

50

Berg, B. L., J. Ronholm, D. M. Applin, P. Mann, M. Izawa, E. A. Cloutis, and L. G. Whyte. "Spectral features of biogenic calcium carbonates and implications for astrobiology." International Journal of Astrobiology 13, no. 4 (September 10, 2014): 353–65. http://dx.doi.org/10.1017/s1473550414000366.

Full text

Abstract:

AbstractThe ability to discriminate biogenic from abiogenic calcium carbonate (CaCO3) would be useful in the search for extant or extinct life, since CaCO3can be produced by both biotic and abiotic processes on Earth. Bioprecipitated CaCO3material was produced during the growth of heterotrophic microbial isolates on medium enriched with calcium acetate or calcium citrate. These biologically produced CaCO3, along with natural and synthetic non-biologically produced CaCO3samples, were analysed by reflectance spectroscopy (0.35–2.5 μm), Raman spectroscopy (532 and 785 nm), and laser-induced fluorescence spectroscopy (365 and 405 nm excitation). Optimal instruments for the discrimination of biogenic from abiogenic CaCO3were determined to be reflectance spectroscopy, and laser-induced fluorescence spectroscopy. Multiple absorption features in the visible light region occurred in reflectance spectra for most biogenic CaCO3samples, which are likely due to organic pigments. Multiple fluorescence peaks occurred in emission spectra (405 nm excitation) of biogenic CaCO3samples, which also are best attributed to the presence of organic compounds; however, further analyses must be performed in order to better determine the cause of these features to establish criteria for confirming the origin of a given CaCO3sample. Raman spectroscopy was not useful for discrimination since any potential Raman peaks in spectra of biogenic carbonates collected by both the 532 and 785 nm lasers were overwhelmed by fluorescence. However, this also suggests that biogenic carbonates may be identified by the presence of this organic-associated fluorescence. No reliable spectroscopic differences in terms of parameters such as positions or widths of carbonate-associated absorption bands were found between the biogenic and abiogenic carbonate samples. These results indicate that the presence or absence of organic matter intimately associated with carbonate minerals is the only potentially useful spectral discriminator for the techniques that were examined, and that multiple spectroscopic techniques are capable of detecting the presence of associated organic materials. However, the presence or absence of intimately associated organic matter is not, in itself, an indicator of biogenicity.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Fluorescence and Raman spectroscopy'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles