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1.
Sharma SK Misra AK Sharma B 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(10):2404-2412
We report our initial efforts to use a small portable Raman system for stand-off detection and identification of various types of organic chemicals including benzene, toluene, ethyl benzene and xylenes (BTEX). Both fiber-optic (FO) coupled and a directly coupled f/2.2 spectrograph with the telescope have been developed and tested. A frequency-doubled Nd:YAG pulsed laser (20 Hz, 532 nm, 35 mJ/pulse) is used as the excitation source. The operational range of the FO coupled Raman system was tested to 66 m, and the directly coupled system was tested to a distance of 120 m. We have also measured remote Raman spectra of compressed methane gas and methane gas hydrate. The usefulness of the remote Raman system for identifying unknown compounds is demonstrated by measuring stand-off spectra of two plastic explosives, e.g. tri-amino tri-nitrobenzene (TATB) and beta-HMX at 10 m stand-off distance. The remote Raman system will be useful for terrestrial applications such as monitoring environmental pollution, in identifying unknown materials in public places in 10s or less, and for detecting hydrocarbon plumes and gas hydrates on planetary surfaces such as Mars. 相似文献
2.
Vibrational spectroscopy standoff detection of explosives 总被引:1,自引:0,他引:1
Leonardo C. Pacheco-Londoño William Ortiz-Rivera Oliva M. Primera-Pedrozo Samuel P. Hernández-Rivera 《Analytical and bioanalytical chemistry》2009,395(2):323-335
Standoff infrared and Raman spectroscopy (SIRS and SRS) detection systems were designed from commercial instrumentation and
successfully tested in remote detection of high explosives (HE). The SIRS system was configured by coupling a Fourier-transform
infrared interferometer to a gold mirror and detector. The SRS instrument was built by fiber coupling a spectrograph to a
reflective telescope. HE samples were detected on stainless steel surfaces as thin films (2–30 μg/cm2) for SIRS experiments and as particles (3–85 mg) for SRS measurements. Nitroaromatic HEs: TNT, DNT, RDX, C4, and Semtex-H
and TATP cyclic peroxide homemade explosive were used as targets. For the SIRS experiments, samples were placed at increasing
distances and an infrared beam was reflected from the stainless steel surfaces coated with the target chemicals at an angle
of ∼180° from surface normal. Stainless steel plates containing TNT and RDX were first characterized for coverage distribution
and surface concentration by reflection–absorption infrared spectroscopy. Targets were then placed at the standoff distance
and SIRS spectra were collected in active reflectance mode. Limits of detection (LOD) were determined for all distances measured
for the target HE. LOD values of 18 and 20 μg/cm2 were obtained for TNT and RDX, respectively, for the SIR longest standoff distance measured. For SRS experiments, as low
as 3 mg of TNT and RDX were detected at 7 m source–target distance employing 488 and 514.5 nm excitation wavelengths. The
first detection and quantification study of the important formulation C4 is reported. Detection limits as function of laser
powers and acquisition times and at a standoff distance of 7 m were obtained. 相似文献
3.
Moore DS McGrane SD Greenfield MT Scharff RJ Chalmers RE 《Analytical and bioanalytical chemistry》2012,402(1):423-428
We are utilizing recent advances in ultrafast laser technology and recent discoveries in optimal shaping of laser pulses to
significantly enhance the stand-off detection of explosives via control of molecular processes at the quantum level. Optimal
dynamic detection of explosives is a method whereby the selectivity and sensitivity of any of a number of nonlinear spectroscopic
methods are enhanced using optimal shaping of ultrafast laser pulses. We have recently investigated the Gerchberg–Saxton algorithm
as a method to very quickly estimate the optimal spectral phase for a given analyte from its spontaneous Raman spectrum and
the ultrafast laser pulse spectrum. Results for obtaining selective coherent anti-Stokes Raman spectra (CARS) for an analyte
in a mixture, while suppressing the CARS signals from the other mixture components, are compared for the Gerchberg–Saxton
method versus previously obtained results from closed-loop machine-learning optimization using evolutionary strategies. 相似文献
4.
Carter JC Scaffidi J Burnett S Vasser B Sharma SK Angel SM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(10):2288-2298
Small, transportable Raman systems are being developed for stand-off Raman measurements at intermediate ranges (e.g. <20 m) for planetary measurements. Four variations of stand-off Raman systems are described that use a small telescope for light collection that is either fiber-optic or lens-coupled to a detection system. The performance of an acousto-optic tunable filter for wavelength selection and spectral imaging is tested by comparing signal-to-noise ratio and throughput to similar measurements using a conventional spectrograph, and by measuring a variety of organic and inorganic mineral samples at distances up to 15 m. We also determine optimal ICCD gate widths for acquiring remote Raman spectra under high ambient light conditions. 相似文献
5.
Sharma SK Lucey PG Ghosh M Hubble HW Horton KA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(10):2391-2407
We have designed and developed two breadboard versions of stand-off Raman spectroscopic systems for landers based on a 5-in. Maksutov-Cassegrain telescope and a small (4-in. diameter) Newtonian telescope receiver. These systems are capable of measuring the Raman spectra of minerals located at a distance of 4.5-66 m from the telescope. Both continuous wave (CW) Ar-ion and frequency doubled Nd:YAG (532 nm) pulsed (20 Hz) lasers are used as excitation sources for measuring remote Raman spectra of rocks and minerals. We have also made complementary measurements on the same rock samples with a micro-Raman system in 180 and 135 degrees geometry for evaluating the system performance and for estimating effect of grain size and laser-induced heating on the spectra of minerals using alpha-quartz as a model mineral. A field portable remote pulsed Raman spectroscopic system based on the 5-in. telescope and an f/2.2 spectrograph has been developed and tested. We have also demonstrated a prototype of a combined Raman and laser-induced breakdown spectroscopy (LIBS) system, capable of providing major element composition and mineralogical information on both biogenic and inorganic minerals at a distance of 10 m from the receiver. 相似文献
6.
A new, simple, and efficient approach for on-column surface-enhanced Raman scattering (SERS) detection in capillary electrophoresis
(CE) is reported. A ∼50-μm SERS substrate spot was prepared by laser-induced growth of silver particles in the 100-μm inner
diameter CE capillary window or in a flow cell consisting of a 250-μm inner diameter fused silica capillary connector. For
this purpose, the Raman laser was focused by a 20× objective into the detection window filled with a 0.5 mM silver nitrate
and 10 mM citrate buffer solution. During the CE runs, the silver substrate spot was formed in a few seconds after the analyte
injection, hence the analytes adsorbed sequentially to the silver surface when the detection window was reached, followed
by desorption from the silver surface and continuing the electrophoretic migration to the capillary end. Thus, beyond migration
time, valuable molecular specific information was delivered by the SERS spectra. Accurate separations and high-intensity SERS
spectra are shown by CE-SERS time-dependent 3D electropherograms for the analytes rhodamine 6G, 4-(2-pyridylazo)resorcinol
(PAR), PAR complex with Cu(II) and methylene blue at 0.25–25 ppm concentrations, by using 1.4–3.6 mW HeNe laser power and
an acquisition time of 5 s for each spectrum. Before and after each analyte passes the detection window, clean background
spectra were recorded and no memory effects perturbed the SERS detection. The silver substrate is characterized by a fast
preparation rate, good reproducibility, a preparation success rate of over 95% and no mentionable influence on the electrophoretic
migration time, the CE-SERS and CE-UV electropherograms being in good agreement. The successful coupling of CE and on-column
SERS detection opens new perspectives for monitoring CE separations. 相似文献
7.
We investigate effects of Co dopant concentration on the structure and low temperature Raman scattering properties in SrTi1−x
Co
x
O3 (x = 0.00, 0.10, 0.20, 0.30) nanoparticles prepared by sol–gel method. The dopant induced changes are studied by XRD, and Raman
scattering measurements. The results show an average particle size of about 20 nm depending on the Co content and the lattice
parameters decrease as increasing the Co content. In the Raman spectra, a broad structure in the region 100–500 cm−1 is almost absent and the peaks in the region 600–800 cm−1 show different weights with respect to SrTiO3, relating to structural changes. The anomalous change in the area ratio of Raman peaks as function of temperature suggests
a phase transition in our samples in the range of 110–130 K. These results indicate that the Co ion has replaced the site
of Ti in unit cell. This novel route also demonstrates the advantage of synthesizing the compound with low annealing temperature. 相似文献
8.
We investigate effects of Fe dopant concentration on the structure, as well as low temperature Raman scattering and electrical
transport properties in SrTi1−x
Fe
x
O3 (x = 0.00, 0.10, 0.20, 0.30, 0.40) nanoparticles prepared by sol-gel method. The results show an average particle size of powder
is about 30 nm, and the lattice parameters decrease as increasing the Fe content. In the Raman spectra, a broad structure
in the region 200–500 cm−1 is almost absent and the peaks in the region 600–800 cm−1 show different weights with respect to SrTiO3, relating to structural changes with increasing dopant concentration in conjunction with increasing grain boundary contribution
to the impedance. The abrupt change in Raman peak position as function of temperature suggests a phase transition in our samples
in the range of 110–150 K. These results indicate that the Fe ion has replaced the site of Ti in unit cell. These results
also demonstrate the feasibility of synthesizing the compound with low annealing temperature. 相似文献
9.
Magdalena Staszewska Monika Dzieciuch Joanna Lewandowska Mariusz Kepczynski Szczepan Zapotoczny Marcin Oszajca Anna Łatkiewicz Maria Nowakowska 《Journal of Sol-Gel Science and Technology》2011,59(2):276-282
In this article, we report on the formation of well-defined highly emissive silica-covered porphyrin microstructures in base-catalyzed
sol–gel processes. The microstructures were obtained by self-assembly of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (mTHPP)
at room temperature. Tetraethoxysilane (TEOS) was used as a silica precursor. The hybrid mTHPP- silica particles were characterized
by means of reflectance UV–Vis and microscopy techniques including atomic force microscopy, scanning electron microscopy (SEM)
and confocal fluorescence microscopy (CM). The SEM and TEM observations revealed that depending on the porphyrin concentration
used in the synthesis, the shape of the hybrid mTHPP-silica particles has changed from ribbon-like (c
mTHPP = 2.09 mM) to rhombus-like structures (c
mTHPP = 4.35 mM). The ribbons were straight-edged, uniform in width (1.2–1.8 μm) and height (350–400 nm), and variable in length
(40–100 μm). The rhombs were 1–3.7 μm in height, 7–25 μm in length, and 3.5–15 μm in width, and the ratio of length to width
was uniform and equal to ca. 1.8–2. UV–Vis absorption spectra indicated that the J-aggregates and H-aggregates formed in the
systems with lower and higher porphyrin content, respectively. Formation of different type of porphyrin aggregates in both
systems resulted in different emission spectra, as it was shown with CM. 相似文献
10.
Iqbal T. Shadi William Cheung Royston Goodacre 《Analytical and bioanalytical chemistry》2009,394(7):1833-1838
Surface-enhanced resonance Raman scattering (SERRS) spectra of aqueous solutions of the triphenylmethane dye methyl green
have been obtained for the first time by use of citrate-reduced silver colloids and a laser excitation wavelength of 632.8 nm.
Given the highly fluorescent nature of the analyte, which precluded collection of normal Raman spectra of the dye in solution
and powdered state, it was highly encouraging that SERRS spectra showed no fluorescence due to quenching by the silver sol.
The pH conditions for SERRS were optimised over the pH range 0.5–10 and the biggest enhancement for SERRS of this charged
dye was found to be at pH 2.02, thus this condition was used for quantitative analysis. SERRS was found to be highly sensitive
and enabled quantitative determination of methyl green over the range 10−9 to 10−7 mol dm−3. Good fits to correlation coefficients were obtained over this range using the areas under the vibrational bands at 1615
and 737 cm−1. Finally, a limit of detection of 83 ppb was calculated, demonstrating the sensitivity of the technique. 相似文献
11.
Tim De Meyer Davy Sinnaeve Bjorn Van Gasse Ernst-R Rietzschel Marc L. De Buyzere Michel R. Langlois Sofie Bekaert José C. Martins Wim Van Criekinge 《Analytical and bioanalytical chemistry》2010,398(4):1781-1790
Proton nuclear magnetic resonance (1H-NMR)-based metabolomics enables the high-resolution and high-throughput assessment of a broad spectrum of metabolites in
biofluids. Despite the straightforward character of the experimental methodology, the analysis of spectral profiles is rather
complex, particularly due to the requirement of numerous data preprocessing steps. Here, we evaluate how several of the most
common preprocessing procedures affect the subsequent univariate analyses of blood serum spectra, with a particular focus
on how the standard methods perform compared to more advanced examples. Carr–Purcell–Meiboom–Gill 1D 1H spectra were obtained for 240 serum samples from healthy subjects of the Asklepios study. We studied the impact of different
preprocessing steps—integral (standard method) and probabilistic quotient normalization; no, equidistant (standard), and adaptive-intelligent
binning; mean (standard) and maximum bin intensity data summation—on the resonance intensities of three different types of
metabolites: triglycerides, glucose, and creatinine. The effects were evaluated by correlating the differently preprocessed
NMR data with the independently measured metabolite concentrations. The analyses revealed that the standard methods performed
inferiorly and that a combination of probabilistic quotient normalization after adaptive-intelligent binning and maximum intensity
variable definition yielded the best overall results (triglycerides, R = 0.98; glucose, R = 0.76; creatinine, R = 0.70). Therefore, at least in the case of serum metabolomics, these or equivalent methods should be preferred above the
standard preprocessing methods, particularly for univariate analyses. Additional optimization of the normalization procedure
might further improve the analyses. 相似文献
12.
13.
S. V. Ingale P. U. Sastry A. K. Patra R. Tewari P. B. Wagh Satish C. Gupta 《Journal of Sol-Gel Science and Technology》2010,54(2):238-242
Silica xerogels incorporated with trinitrotoluene (TNT) and pentaerythritoltetranitrate (PETN) were synthesized using sol–gel
method. Tetramethoxysilane was used as precursor for silica. TNT and PETN content in the resulted explosive/silica xerogel
was varied ranging from 50 to 90%. Infra red spectra showed that explosives were retained in the silica xerogel matrix. Transmission
electron microscopy (TEM) reveal that explosives particles were uniformly distributed in xerogel matrix and the size of the
PETN and TNT particles are in the range 15–18 nm. Small angle x-ray scattering showed that the sizes of the pores in the silica
matrix are in the range 25–13 nm. The particles of TNT and PETN occupy the pores in the matrix resulting in gradual reduction
of pore-size affecting the surface characteristics of the pore-matrix interface. Understanding of the structure of aggregates
of small particles thus produced could be useful to explain the properties shown by the fine explosives. Our study suggests
that particle size of explosives in the nanometer range can be achieved using the sol–gel method. 相似文献
14.
Confocal Raman microscopy is shown to detect picogram quantities of explosives in-situ on undyed natural and synthetic fibres, and coloured textile specimens leaving potentially evidential materials unaltered. Raman spectra were obtained from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), and ammonium nitrate particles trapped between the fibres of the specimens. Despite the presence of spectral bands arising from the natural and synthetic polymers and dyed textiles, the explosive substances could be identified by their characteristic Raman bands. Furthermore, Raman spectra were obtained from explosives particles trapped between highly fluorescent clothing fibres. Raman spectra were collected from explosives particles with maximum dimensions in the range 5-10 μm. Spectra of the explosives on dyed and undyed clothing substrates were readily obtained in-situ within 90 s and without sample preparation. 相似文献
15.
De Gelder J Scheldeman P Leus K Heyndrickx M Vandenabeele P Moens L De Vos P 《Analytical and bioanalytical chemistry》2007,389(7-8):2143-2151
Endospores and endospore-forming bacteria were studied by Raman spectroscopy. Raman spectra were recorded from Bacillus licheniformis LMG 7634 at different steps during growth and spore formation, and from spore suspensions obtained from diverse Bacillus and Paenibacillus strains cultured in different conditions (growth media, temperature, peroxide treatment). Raman bands of calcium dipicolinate
and amino acids such as phenylalanine and tyrosine are more intense in the spectra of sporulating bacteria compared with those
of bacteria from earlier phases of growth. Raman spectroscopy can thus be used to detect sporulation of cells by a characteristic
band at 1,018 cm–1 from calcium dipicolinate. The increase in amino acids could possibly be explained by the formation of small acid-soluble
proteins that saturate the endospore DNA. Large variations in Raman spectra of endospore suspensions of different strains
or different culturing conditions were observed. Next to calcium dipicolinate, tyrosine and phenylalanine, band differences
at 527 and 638 cm–1 were observed in the spectra of some of the B. sporothermodurans spore suspensions. These bands were assigned to the incorporation of cysteine residues in spore coat proteins. In conclusion,
Raman spectroscopy is a fast technique to provide useful information about several spore components.
Figure A difference spectrum between Raman spectra of B. licheniformis LMG 7634 cultured for 6 days and 1 day, together with the
reference Raman spectrum of calcium dipicolinate 相似文献
16.
Kelly JG Ahmadzai AA Hermansen P Pitt MA Saidan Z Martin-Hirsch PL Martin FL 《Analytical and bioanalytical chemistry》2011,401(3):957-967
Fine needle aspirates (FNAs) of suspicious breast lesions are often used to aid the diagnosis of female breast cancer. Biospectroscopy
tools facilitate the acquisition of a biochemical cell fingerprint representative of chemical bonds present in a biological
sample. The mid-infrared (IR; 4,000–400 cm−1) is absorbed by the chemical bonds present, allowing one to derive an absorbance spectrum. Complementary to IR spectroscopy,
Raman spectroscopy measures the scattering by chemical bonds following excitation by a laser to generate an intensity spectrum.
Our objective was to apply these methods to determine whether a biospectroscopy approach could objectively segregate different
categories of FNAs. FNAs of breast tissue were collected (n = 48) in a preservative solution and graded into categories by a cytologist as C1 (non-diagnostic), C2 (benign), C3 (suspicious,
probably benign) or C5 (malignant) [or C4 (suspicious, probably malignant); no samples falling within this category were identified
during the collection period of the study]. Following washing, the cellular material was transferred onto BaF2 (IR-transparent) slides for interrogation by Raman or Fourier-transform IR (FTIR) microspectroscopy. In some cases where
sufficient material was obtained, this was transferred to low-E (IR-reflective) glass slides for attenuated total reflection–FTIR
spectroscopy. The spectral datasets produced from these techniques required multivariate analysis for data handling. Principal
component analysis followed by linear discriminant analysis was performed independently on each of the spectral datasets for
only C2, C3 and C5. The resulting scores plots revealed a marked overlap of C2 with C3 and C5, although the latter pair were
both significantly segregated (P < 0.001) in the Raman spectra. Good separation was observed between C3 and C5 in all three spectral datasets. Analysis performed
on the average spectra showed the presence of three distinct cytological groups. Our findings suggest that biospectroscopy
tools coupled with multivariate analysis may support the current FNA tests whilst increasing the sensitivity and associated
reliability for improved diagnostics. 相似文献
17.
J. Svorec M. Valko J. Moncol M. Mazúr M. Melník J. Telser 《Transition Metal Chemistry》2009,34(2):129-134
An EPR method involving measurement of half-field transitions was applied to determine the intermolecular Cu–Cu distances
in copper(II)-carboxylate complexes with biologically important ligands. The experimental powder EPR spectra are composed
of allowed (ΔM
S
= ±1) transitions centered at ~3,200 Gauss and of weak intensity, nominally forbidden, half-field (ΔM
S
= ±2) peaks observable at ~1,600 Gauss. Values of the average interspin distance for each complex were determined from the
ratios of integrated allowed and forbidden peak areas using each of several methods. The calculated interspin distances were
correlated with the copper–copper distances experimentally obtained by X-ray crystallography. The distances determined from
the EPR spectra agree well with the X-ray determined values when the crystallographic value for one member of a series is
used to calibrate the series. Less satisfactory agreement is found when methods based on Cu-spin-label systems are used. 相似文献
18.
Mohammed A. Abounassif Mohammed M. Hefnawy Gamal A. E. Mostafa 《Monatshefte für Chemie / Chemical Monthly》2012,73(Z1):365-371
Abstract
A stereoselective HPLC method has been developed for the simultaneous determination of oxprenolol enantiomers in urine and pharmaceutical products. Enantiomeric resolution of oxprenolol was achieved on cellulose tris(3,5-dichlorophenylcarbamate) immobilized onto a 5 μm spherical porous silica chiral stationary phase (CSP) known as Chiralpak IC with UV detection at 273 nm. The mobile phase consisted of n-hexane:isopropanol:triethylamine 70:30:0.1 (v/v/v) at a flow rate of 1.0 cm3/min. The method was validated for its linearity, accuracy, precision, and robustness. The calibration curves were linear over the range of 0.5–75 μg/cm3, with a detection limit of 0.1 μg/cm3 for each enantiomer. An average recovery of 99.0% and a mean relative standard deviation of 2.6% at 40.0 μg/cm3 for S-(−)- and R-(+)-enantiomers were obtained. The overall recoveries of oxprenolol enantiomers from pharmaceutical formulations were in the range 97.5–99.0%, with RSDs ranging from 0.6 to 0.8%. The mean extraction efficiency of oxprenolol from urine was in the range of 86.0–93.0% at 0.5–5 μg/cm3 for each enantiomer. The assay method proved to be suitable as a chiral quality control for oxprenolol formulations using HPLC and for therapeutic drug monitoring. 相似文献19.
L. S. Khaikin O. E. Grikina B. V. Lokshin K. P. Dyugaev A. M. Astakhov 《Russian Chemical Bulletin》2008,57(3):499-505
The IR (4000–50 cm−1) and Raman (3500–170 cm−1) spectra of solid 1,1,3,3-tetramethyl-2-nitroguanidine (TMNG) were obtained. The spectra were interpreted using the scaling
of the TMNG quantum-chemical force field in the B3LYP/6-311G(d,p) approximation. Transferable scale factors necessary for
the interpretation of spectra of more complex related compounds were determined. The scaled harmonic force field is supposed
to be used in the analysis of the available gas-phase electron diffraction data for TMNG.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 495–498, March, 2008. 相似文献
20.
Dartnell LR Page K Jorge-Villar SE Wright G Munshi T Scowen IJ Ward JM Edwards HG 《Analytical and bioanalytical chemistry》2012,403(1):131-144
Raman spectroscopy has proven to be a very effective approach for the detection of microorganisms colonising hostile environments
on Earth. The ExoMars rover, due for launch in 2018, will carry a Raman laser spectrometer to analyse samples of the martian
subsurface collected by the probe’s 2-m drill in a search for similar biosignatures. The martian surface is unprotected from
the flux of cosmic rays, an ionising radiation field that will degrade organic molecules and so diminish and distort the detectable
Raman signature of potential martian microbial life. This study employs Raman spectroscopy to analyse samples of two model
organisms, the cyanobacterium Synechocystis sp. PCC 6803 and the extremely radiation resistant polyextremophile Deinococcus radiodurans, that have been exposed to increasing doses of ionising radiation. The three most prominent peaks in the Raman spectra are
from cellular carotenoids: deinoxanthin in D. radiodurans and β-carotene in Synechocystis. The degradative effect of ionising radiation is clearly seen, with significant diminishment of carotenoid spectral peak
heights after 15 kGy and complete erasure of Raman biosignatures by 150 kGy of ionising radiation. The Raman signal of carotenoid
in D. radiodurans diminishes more rapidly than that of Synechocystis, believed to be due to deinoxanthin acting as a superior scavenger of radiolytically produced reactive oxygen species, and
so being destroyed more quickly than the less efficient antioxidant β-carotene. This study highlights the necessity for further
experimental work on the manner and rate of degradation of Raman biosignatures by ionising radiation, as this is of prime
importance for the successful detection of microbial life in the martian near subsurface. 相似文献