Trace Molecular Detection via Surface-Enhanced Raman Scattering and Surface-Enhanced Resonance Raman Scattering at a Distance of 15 Meters

Scaffidi, Jonathan; Gregas, Molly K.; Lauly, Benoit; Carter, J. Chance; Angel, S. M.; Vo‐Dinh, Tuan

doi:10.1366/000370210791211763

Cited by 24 publications

(16 citation statements)

References 29 publications

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“…It should be noted that researchers use various technical solutions to provide the required levels of the Raman signals. Among them are the application of multipass and intracavity systems of excitation of Raman scattering, hollow‐core fibers, and surface enhancement . However, the most efficient and easiest approach used to increase the Raman signals is the compression of the gas being analyzed .…”

Section: Introductionmentioning

confidence: 99%

Pressure dependence of the Raman signal intensity in high‐pressure gases

Petrov

Matrosov

2016

J Raman Spectroscopy

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At present gas analysis based on Raman, spectroscopy is actively developed. In most cases, to achieve the required Raman signal intensity, compression of the gas medium is used. However, in comparison with normal conditions, the character of motion of molecules and their electric properties change in high‐pressure gas media, thereby violating a linear dependence of the Raman signal intensity on the concentration of molecules and the gas pressure. In the present work, a theoretical model is presented that describes the Raman signal intensity as a function of the pressure of the gas medium considering the compressibility factor, the internal field factor, and the instrumental factor. To verify the model, changes in the Raman signal intensities of vibrational bands of nitrogen and oxygen in the pressure range 1–80 atm and carbon dioxide in the pressure range 1–60 atm are investigated. Under these conditions, we observe a deviation of ~3% from a linear dependence for nitrogen, ~7% for oxygen and ~80% for carbon dioxide, which is in good agreement with the theoretical model. Raman shifts, half‐widths of Q‐branches of vibrational bands ν1 (and 2ν2 for carbon dioxide) of these molecules and also ratio of integral intensities I(2ν2)/I(ν1) for carbon dioxide under these conditions are investigated. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Pressure dependence of the Raman signal intensity in high‐pressure gases

Petrov

Matrosov

2016

J Raman Spectroscopy

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“…Standoff Raman detection offers a wide area of applications and recently, several research groups across the world have been actively developing standoff Raman systems. 1,–18 Because of the recent rise in worldwide terrorist activities, standoff detection of hazardous chemicals (such as those used in homemade explosives, flammable solids and liquids, and toxic chemicals) is of significant interest. Standoff Raman spectroscopy can detect several hazardous chemicals from a safe distance without need for making contact with the sample.…”

Section: Introductionmentioning

confidence: 99%

Single-Pulse Standoff Raman Detection of Chemicals from 120 m Distance during Daytime

et al. 2012

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The capability to analyze and detect the composition of distant samples (minerals, organics, and chemicals) in real time is of interest for various fields including detecting explosives, geological surveying, and pollution mapping. For the past 10 years, the University of Hawaii has been developing standoff Raman systems suitable for measuring Raman spectra of various chemicals in daytime or nighttime. In this article we present standoff Raman spectra of various minerals and chemicals obtained from a distance of 120 m using single laser pulse excitation during daytime. The standoff Raman system utilizes an 8-inch Meade telescope as collection optics and a frequency-doubled 532 nm Nd : YAG laser with pulse energy of 100 mJ/pulse and pulse width of 10 ns. A gated intensified charge-coupled device (ICCD) detector is used to measure time-resolved Raman spectra in daytime with detection time of 100 ns. A gate delay of 800 ns (equivalent to target placed at 120 m distance) was used to minimize interference from the atmospheric gases along the laser beam path and near-field scattering. Reproducible, good quality single-shot Raman spectra of various inorganic and organic chemicals and minerals such as ammonium nitrate, potassium perchlorate, sulfur, gypsum, calcite, benzene, nitrobenzene, etc., were obtained through sealed glass vials during daytime. The data indicate that various chemicals could easily be identified from their Raman fingerprint spectra from a far standoff distance in real time using single-shot laser excitation.

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“…With the introduction of the Volume Bragg Grating (VBG), portable lasers now deliver a stable, monochromatic excitation signal without mode hopping [8,82]. Also, sensitive thermoelectrically cooled charge-coupled device (CCD) detectors collect scattered Raman signals, even in ambient conditions [10,83]. Further achievements in laser and detector technologies allow for excellent matching and distinguishing of chemicals using portable instruments.…”

Section: Applications Of Raman Spectroscopies For Homeland Security Amentioning

confidence: 99%

“…Several studies demonstrated limited ability for SERS in proximal mode. One group predeposited a SERS substrate with an analyte and then placed the prefabricated sample at a proximal distance for detection [83]. In another demonstration of portable SERS, a lowpower, battery-operated Inspector Raman spectrometer was used to identify Bacillus anthracis spores predeposited on a metal film-over-nanospheres (M-FON) SERS substrate [12].…”

Section: Remote Raman Spectroscopymentioning

confidence: 99%

Raman Spectroscopy for Homeland Security Applications

Mogilevsky

Borland

Brickhouse

et al. 2012

International Journal of Spectroscopy

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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.

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Trace Molecular Detection via Surface-Enhanced Raman Scattering and Surface-Enhanced Resonance Raman Scattering at a Distance of 15 Meters

Cited by 24 publications

References 29 publications

Pressure dependence of the Raman signal intensity in high‐pressure gases

Pressure dependence of the Raman signal intensity in high‐pressure gases

Single-Pulse Standoff Raman Detection of Chemicals from 120 m Distance during Daytime

Raman Spectroscopy for Homeland Security Applications

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