bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatty Acid Profiling of Soybean Cotyledons by Near-Infrared Spectroscopy
Authors: Roberts C. A. , Ren C. , Beuselinck P. R. , Benedict H. R. , Bilyeu K.
Published: October 2009

Genetically improved soybean grain often contains altered fatty acid profiles. Such alterations can have deleterious effects on seed germination and seedling development, making it necessary to monitor fatty acid profiles in follow-up physiological studies. The objective of this research was to quantify the five fatty acids in soybean ( Glycine max) cotyledons using near-infrared (NIR) spectroscopy. Soybean cotyledon samples were dried, ground, and scanned with visible and NIR radiation from 400 to 2500 nm, and reflectance was recorded. Samples were also analyzed by gas chromatography (GC) for palmitic, stearic, oleic, linoleic, and linolenic acids and total oil; GC data, expressed as actual concentration and proportion of total oil, were regressed against spectral data to develop calibration equations. Equation statistics indicated that four of the five fatty acids could be predicted accurately by NIR spectroscopy; the fifth fatty acid could be determined by subtraction. Principal component analysis revealed that most of the spectral variation in this population was due to chlorophyll absorbance in the visible region. Therefore, the spectra were trimmed to include the NIR region only (1100–2500 nm), and a second set of equations was developed. Equations based exclusively on NIR spectra had equal or greater precision than equations based on visible and NIR spectra. Principal component analysis and partial least squares analysis revealed that even after trimming, at least 90% of the spectral variation was unrelated to fatty acid, though variation from fatty acid was identified in the second and third principal components. This research provides an NIR method for complete fatty acid profiling of soybean cotyledons. Equations were achieved with NIR spectra only, so spectrophotometers that analyze both the visible and NIR regions are not needed for this analysis. In addition, equations were possible with a 250 mg sample, which is one-tenth the normal sample size for this analysis.
Application of Fourier Transform Raman Spectroscopy for Prediction of Bitterness of Peptides
Authors: Kim Hyun-Ock , Li-Chan Eunice C. Y.
Published: October 2009

The potential application of Fourier transform (FT) Raman spectroscopy to predict the bitterness of peptides was investigated. FT-Raman spectra were measured for the amino acid Phe and 9 synthetic di-, tri-, and tetra peptides composed of Phe, Gly, and Pro. Partial least squares regression (PLS)-1 analysis was applied to correlate the FT-Raman spectra with bitterness intensity values ( Rcaf and log 1/ T) reported in the literature. Using full cross-validation, Model 1 based on the single spectral data set for the nine peptides yielded a high correlation coefficient for calibration ( R = 0.99), but a low correlation coefficient for prediction ( R = 0.56). Two models were constructed using the data sets including replicate spectra for the calibrations and were validated using full cross-validation. Using leave-one-sample-set-out calibrations, Model 2, which was developed with the data for the peptides as well as Phe, yielded a low correlation coefficient ( R = 0.533) for the prediction of the bitterness, while Model 3 developed with only the peptide data provided better correlation coefficients ( R = 0.807 and 0.724 for Rcaf and log 1/ T values, respectively). The correlation coefficients for prediction were 0.975 ( Rcaf values) and 0.874 (log 1/ T values) for Model 4, which was developed using subtracted spectral data (spectra of peptides with higher Rcaf values minus spectra of peptides with lower Rcaf values). Examination of the PLS regression coefficients at wavenumbers most highly correlated with bitterness revealed the importance of hydrophobicity and peptide length on bitterness. This study indicates the potential of FT-Raman spectroscopy as a useful tool for predicting bitterness of peptides and amino acids.
Drug Characterization in Low Dosage Pharmaceutical Tablets Using Raman Microscopic Mapping
Authors: Henson Mark J. , Zhang Lin
Published: October 2009

Raman micro-spectroscopic mapping is utilized to analyze pharmaceutical tablets containing a low concentration (0.5% w/w) of active pharmaceutical ingredient (API). The domain sizes and spatial distributions of the API and the major excipients are obtained. Domain size of the API is found to be dependent upon the particle size distribution of the ingoing API material, making the Raman maps good indicators of the source of API used in tablet manufacturing. Multivariate classification was performed to simultaneously check for the presence of two undesired API polymorphs within tablets. Raman mapping was demonstrated capable of detecting in the tablet matrix as little as 10% form conversion of the low-dosage (0.5% w/w) API, which is equivalent to detection of a 0.05% w/w polymorphic impurity. Overall, the information provided by Raman micro-spectroscopic mapping was found to have potential utility for manufacturing process optimization or predictive stability assessments.
Photooxidative Degradation and Conformational Changes in Syndiotactic Polypropylene/Clay Nanocomposites
Authors: Kandilioti Georgia , Elenis Athanasios , Macchiarola Katherine A. , Gregoriou Vasilis G.
Published: October 2009

Syndiotactic polypropylene nanocomposites based on layered silicates in various proportions were subjected to prolonged (246 h) ultraviolet (UV)-c irradiation. Fourier transform infrared (FT-IR) spectroscopy was used in order to investigate the molecular alterations of the polymeric matrix during the UV exposure relative to the concentration of nanoclay. It was found that a significant increase of the helical conformation upon the irradiation took place as a result of scissions of the polymeric chains. In addition, a simultaneous increase in the crystallinity was verified by X-ray diffraction (XRD) measurements. Furthermore, a variety of photooxidation products were detected, among them carboxylic acids, ketones, γ-lactones, and esters. We report in this paper the impact of the clay on the degradation mechanism of syndiotactic polypropylene mostly by the production of additional free radicals. Therefore, the relative intensities of the produced photooxidative species are affected drastically as a function of the concentration of the layered silicate present. Finally, an interaction of the carbonyl groups formed in the polymer upon irradiation with the polar groups of the layered silicates was confirmed both from infrared and UV-visible spectroscopic studies.
Spectroscopic Assessment of Australian Cotton Waxes
Authors: Church Jeffrey S. , Woodhead Andrea L.
Published: October 2009

An investigation into the spectroscopic analysis of cotton waxes on Australian cottons was undertaken. The chemical composition of cotton wax is complex and contains a number of lipid classes. Infrared transmission spectroscopy coupled with principal component analysis was found to be capable of discriminating between solvent-extracted cotton waxes with differences in their alkyl functionality. Based on high-performance thin-layer chromatography (HPTLC) results, these differences were associated with an increase in levels of the alkane wax component. On the basis of these results, a photo-acoustic spectroscopic method was developed that could be used to distinguish raw cottons on the basis of these differences. This method was utilized to screen cottons from the Cotton Seed Distributors 2001 seed trial. A preliminary assessment of the scouring and dyeing properties of the various cottons, identified using the photo-acoustic method, was carried out. The results tended to confirm that cottons with increased alkyl functionality, most likely associated with alkane wax, were more difficult to remove and residual wax on the fiber acted as a barrier to dyestuff penetration, thus lowering color yield.
Sample Presentation Considerations in Laser-Induced Breakdown Spectroscopy in Aqueous Solution
Authors: Fang Xiao , Ahmad S. Rafi
Published: October 2009

Various sample presentation configurations for elemental analysis in aqueous media by laser-induced breakdown spectroscopy (LIBS) have been tested and analyzed. Direct and quantitative comparison between the two different sample presentation methods, plasma excitation within water bulk and on the surface in a water jet, has been carried out using the same LIBS system under the same experimental conditions. Temporal characteristics of light emitted from the plasma induced in both the water bulk and the jet surface containing calcium (Ca) were recorded and presented. Spectral data recorded under optimum detection gating conditions showed that the signal-to-noise ratio (S/N) for excitation in the water jet configuration is approximately 10 times higher than that in the bulk excitation, the actual values of enhancement being dependent on the element type. The typical spectra of aqueous samples containing sodium (Na), calcium (Ca), zinc (Zn), cadmium (Cd), and mercury (Hg) were detected and the signal-to-noise ratios were evaluated and compared for the sample presentation configurations under considerations. The results suggest that for better sensitivity of detection, a simple water jet sample presentation configuration could be designed and implemented for cost-effective commercial use of this technique for elemental analysis in a water environment.
Ellipsometric Advances for Local Surface Plasmon Resonance to Determine Chitosan Adsorption on Layer-By-Layer Gold Nanoparticles
Authors: Su Yen Hsun , Teoh Lay Gaik , Lai Wei Hao , Chang Shih-Hui , Yang Hui-Chia , Hon Min Hsiung
Published: October 2009

The ellipsometric measurement of local surface plasmon resonance (LSPR) caused by the adsorption of chitosan on layer-by-layer gold nanoparticles (Au NPs) was investigated. Six nanometer (6 nm) Au NPs were prepared and layer-by-layer Au NPs were fabricated to shift the LSPR to 520, 540, and 560 nm, respectively, due to the Mie theory. The thicknesses and the fractions of the layer-by-layer Au NPs were measured accurately using a combination of the Fresnel equation and the Maxwell–Garnett equations for ellipsometry. Furthermore, the position of the LSPR was shifted by chitosan. Using trajectory to record the trace of polarized light for ellipsometry resulting from LSPR, it was found that LSPR is predominantly induced when the LSPR position is close to the wavelength of the ellipsometric measurement. The trajectory circle of LSPR is very large for an increase of chitosan adsorption on Au NPs when the LSPR position is close to the detected wavelength. The linear approximation aspect quantifying the trajectory corresponds with the change of LSPR for the adsorption of chitosan, except for cases with low incidence and Brewster angles. The aspects and technologies of ellipsometry will benefit from the findings in this study, with potential applications in the fields of determination of molecular adsorption.
Chi-Squared-Based Filters for High-Fidelity Signal-to-Noise Ratio Enhancement of Spectra
Authors: Schulze H. Georg , Foist Rod B. , Ivanov Andre , Turner Robin F. B.
Published: October 2009

When reconstructing a measured spectrum to enhance its signal-to-noise ratio (SNR), the objective is to minimize the variance between the smooth reconstructed spectrum and the original measured spectrum, hence to attain an acceptably small χ2 value. The χ2 value thus measures the fidelity of the reconstruction to the original. Smoothness can be conceived as attenuated variation between adjacent points in a spectrum. Thus, a conceptual change in the application of the χ2 function to the difference between adjacent points of the reconstructed spectrum permits its use, in principle, as both a measure of smoothness and a measure of fidelity. We show here that implementations of this concept produce results superior to Savitzky–Golay filters.
Identification of Explosives with Two-Dimensional Ultraviolet Resonance Raman Spectroscopy
Authors: Comanescu Gelu , Manka Charles K. , Grun Jacob , Nikitin Sergei , Zabetakis Daniel
Published: October 2009

The first two-dimensional (2D) resonance Raman spectra of TNT, RDX, HMX, and PETN are measured with an instrument that sequentially and rapidly switches between laser wavelengths, illuminating these explosives with forty wavelengths between 210 nm and 280 nm. Two-dimensional spectra reflect variations in resonance Raman scatter with illumination wavelength, adding information not available from single or few one-dimensional spectra, thereby increasing the number of variables available for use in identification, which is especially useful in environments with contaminants and interferents. We have recently shown that 2D resonance Raman spectra can identify bacteria. Thus, a single device that identifies the presence of explosives, bacteria, and other chemicals in complex backgrounds may be feasible.
Determination of Humic Acids Content in Composts by Means of Near- and Mid-Infrared Spectroscopy and Partial Least Squares Regression Models
Authors: Meissl Katharina , Smidt Ena , Schwanninger Manfred , Tintner Johannes
Published: October 2009

Humic acids are part of the stable organic matter fraction in soils and composts. Due to their favorable properties for soils and plants, and their role in carbon sequestration, they are considered a quality criterion of composts. Time-consuming chemical extraction of humic acids and the inherent source of errors require alternative approaches for humic acids quantification. Different measurement techniques in the mid-infrared (MIR: KBr pellet technique) and near-infrared (NIR: fiber probe as well as an integrating sphere with a sample rotator) regions were applied. Partial least squares regression (PLSR) models based on infrared spectra were developed to determine humic acids contents in composts. As the wavenumber regions used (NIR: 6105–5380 cm−1 and 4360–4220 cm−1, MIR: 1745–1685 cm−1 and 1610–1567 cm−1) represent different molecular vibrations, the importance of the methylene-group-derived vibrations for the NIR models is discussed. The correlation coefficients obtained for the KBr pellet technique, the NIR fiber probe technique, and the NIR integrating sphere ( r = 0.94, 0.93, and 0.94) and the root mean square errors of cross-validation (RMSECV = 2.2% organic dry matter (ODM), 2.5% ODM, and 2.2% ODM) make the models appropriate for application in composting practice.
Near-Infrared Spectroscopic Monitoring of the Water Adsorption/Desorption Process in Modern and Archaeological Wood
Authors: Inagaki Tetsuya , Yonenobu Hitoshi , Tsuchikawa Satoru
Published: October 2009

We investigated the adsorption/desorption mechanism of water and the variation of water adsorption for modern and archaeological wood using near-infrared spectroscopy. A mixture model of water was used to decompose the near-infrared difference spectra into three components (free water molecules (S0), those with one OH group engaged in hydrogen bonding (S1), and those with two OH groups engaged in hydrogen bonding (S2)) based on a principal component analysis. The variations of each water component with relative humidity could be explained by proposing a model that describes water absorption in three stages. It was concluded that the aging phenomenon in wood is due to the decrease of adsorption sites on hemicellulose and amorphous cellulose.
Following Multi-Component Reactions in Liquid Medium Using Spectral Band-Fitting Techniques
Authors: Costa L. , Brissos V. , Lemos F. , Ribeiro F. RAMÔA , Cabral J. M. S.
Published: October 2009

The kinetics of the hydrolysis reaction of p-nitrophenyl butyrate catalyzed by a single-site mutant of Fusarium solani pisi cutinase, supported on zeolite NaY by adsorption, was followed using ultraviolet–visible (UV/Vis) in situ diode array spectrophotometry. Spectral band-fitting techniques allowed the use of in situ diode array spectrophotometry to obtain quantitative data on the concentrations of the various species present in an aqueous reaction medium even in the presence of the solid catalyst particles, which interfere with the absorption measurements. This technique overcame the problems arising from the variable light scattering produced by these highly dispersible catalyst particles. Kinetic modeling of the reaction system was used to compute estimates of the reaction rate constants involved.
Sampling and Quantitative Analysis of Clean B. Subtilis Spores at Sub-Monolayer Coverage by Reflectance Fourier Transform Infrared Microscopy Using Gold-Coated Filter Substrates
Authors: Brooke Heather , Perkins David L. , Setlow Barbara , Setlow Peter , Bronk Burt V. , Myrick Michael L.
Published: October 2009

A study was conducted to determine the concentration dependency of the mid-infrared (MIR) absorbance of bacterial spores. A range of concentrations of Bacillus subtilis endospores filtered across gold-coated filter membranes were analyzed by Fourier transform infrared (FT-IR) reflectance microscopy. Calibration curves were derived from the peak absorbances associated with Amide A, Amide I, and Amide II vibrational frequencies by automatic baseline fitting to remove most of the scattering contribution. Linear relationships ( R2 ≥ 0.99) were observed between the concentrations of spores and the baseline-corrected peak absorbance for each frequency studied. Detection limits for our sampled area of 100 × 100 μm2 were determined to be 79, 39, and 184 spores (or 7.92 × 105, 3.92 × 105, and 1.84 × 106 spores/cm2) for the Amide A, Amide I, and Amide II peaks, respectively. Absorbance increased linearly above the scattering baseline with particle surface concentration up to 0.9 monolayer (ML) coverage, with the monolayer density calculated to be approximately 1.17 × 108 spores/cm2. Scattering as a function of surface concentration, as estimated from extinction values at wavelengths exhibiting low absorbance, becomes nonlinear at a much lower surface concentration. The apparent scattering cross-section per spore decreased monotonically as concentrations increased toward 1.2 ML, while the absolute scattering decreased between 0.9 ML and 1.2 ML coverage. Calculations suggest that transverse spatial coherence effects are the origin of this nonlinearity, while the onset of nonlinearity in the baseline-corrected absorption is probably due to multiple scattering effects, which appear at a high surface concentration. Absorption cross-sections at peaks of the three bands were measured to be (2.15 ± 0.05) × 10−9, (1.48 ± 0.03) × 10−9, and (0.805 ± 0.023) × 10−9 cm2, respectively. These values are smaller by a factor of 2–4 than expected from the literature. The origin of the reduced cross-section is hypothesized to be an electric field effect related to the surface selection rule.
Raman Mapping of Low-Content Active-Ingredient Pharmaceutical Formulations. Part II: Statistically Optimized Sampling for Detection of Less Than 1% of an Active Pharmaceutical Ingredient
Authors: Šašić Slobodan , Whitlock Mark
Published: October 2009

Several tablets are prepared with two forms of an active pharmaceutical ingredient (API) of which one (less than 1% w/w) is considered undesirable. The presence of this component is tested for by Raman microscopy in a series of mapping experiments. These experiments are conducted with a statistically based sampling routine in which the number of spectra to collect across the whole surface of a tablet is set so as to theoretically ensure spectral detection of the low-concentration form. Such experiments are then repeated a number of times to achieve ∼95% confidence that the strictly limited number of sampling points suffice to detect the low-concentration form and that Raman microscopy is technically a reliable method for analytical analysis of this type.
Raman and Infrared Fingerprint Spectroscopy of Peroxide-Based Explosives
Authors: Oxley Jimmie , Smith James , Brady Joseph , Dubnikova Faina , Kosloff Ronnie , Zeiri Leila , Zeiri Yehuda
Published: October 2009

A comparative study of the vibrational spectroscopy of peroxide-based explosives is presented. Triacetone triperoxide (TATP) and hexamethylenetriperoxide-diamine (HMTD), now commonly used by terrorists, are examined as well as other peroxide-ring structures: DADP (diacetone diperoxide); TPTP [3,3,6,6,9,9-Hexaethyl-1,2,4,5,7,8-hexaoxo-nonane (tripentanone triperoxide)]; DCypDp {6,7,13,14-Tetraoxadispiro [4.2.4.2]tetradecane (dicyclopentanone diperoxide)}; TCypDp {6,7,15,16,22,23-Hexaoxatrispiro[4.2.4.2.4.2] henicosane (tricyclopentanone triperoxide)}; DCyhDp {7,8,15,16-tetraoxadispiro [5.2.5.2] hexadecane (dicyclohexanone diperoxide)}; and TCyhTp {7,8,14,15,21,22-hexaoxatrispiro [5.2.5.2.5.2] tetracosane (tricyclohexanone triperoxide)}. Both Raman and infrared (IR) spectra were measured and compared to theoretical calculations. The calculated spectra were obtained by calculation of the harmonic frequencies of the studied compounds, at the density functional theory (DFT) B3LYP/cc-pVDZ level of theory, and by the use of scaling factors. It is found that the vibrational features related to the peroxide bonds are strongly mixed. As a result, the spectrum is congested and highly sensitive to minor changes in the molecule.
Excimer Laser Photofragmentation/Fragment Detection for Analysis of the Oxygenated Hydrocarbon Ethyl-3-Ethyoxypropionate: Implications for Atmospheric Monitoring
Authors: Dalyander P. S. , Hahn D. W.
Published: October 2009

In the present study, the use of ArF excimer laser photofragmentation/fragment detection (PF/FD) is considered for the characterization of gaseous ethyl-3-ethyoxypropionate (EEP), a representative solvent within the class of oxygenated volatile organic compounds (VOCs). PF/FD measurements of EEP resulted in identification of the resulting photofragments as C2 and CH, allowing photofragmentation pathways to be proposed for the parent molecule for the first time. In addition, PF/PD measurements of EEP recorded in the presence of sodium-based aerosol particles resulted in a reduced signal from the EEP, indicating adsorption onto the particulates, thereby demonstrating proof-of-concept that PF/FD can be used to study heterogeneous chemical reactions relevant to atmospheric chemistry. Finally, both time-integrated and time-resolved measurements of the EEP photofragmentation signal in varying concentrations of oxygen revealed that oxygen effectively acts as a dynamic quencher of the EEP signal. In consideration of oxygen quenching, care must be taken in calibrating/analyzing data in selected applications of PF/FD for VOC characterization (such as combustion emission monitoring) in order to account for the potential variability of oxygen concentration.
A Confocal Raman Microscopy Study of the Distribution of a Carotene-Containing Yeast in a Living Pseudomonas Aeruginosa Biofilm
Authors: Sandt Christophe , Smith-Palmer Truis , Pink Judith , Pink David
Published: October 2009

The distribution of a carotene-containing yeast (CCY) in a biofilm formed by a small colony variant (SCV) of Pseudomonas aeruginosa PA01 was followed by confocal Raman microspectroscopy (CRM). SCV PA01 and CCY cells were distinguished by their spectral signatures, and the distribution of the overall biomass was monitored by the C–H bending or stretching signal. The distributions of total biomass, PA01, and CCY cells were compared at various times and positions within the biofilm. The distribution of the CCY was very heterogeneous. It was found in the water channels as well as in regions within biofilm colonies. Many of the yeast cells observed within the biofilm colonies under conditions of low or stopped flow were removed when medium was flowing, suggesting that the yeast was not held in the matrix as tightly as were the bacteria.
A Practical Method to Fabricate Gold Substrates for Surface-Enhanced Raman Spectroscopy
Authors: Tantra Ratna , Brown Richard J. C. , Milton Martin J. T. , Gohil Dipak
Published: October 2009

We describe a practical method of fabricating surface-enhanced Raman spectroscopy (SERS) substrates based on dip-coating poly-l-lysine derivatized microscope slides in a gold colloidal suspension. The use of only commercially available starting materials in this preparation is particularly advantageous, aimed at both reducing time and the inconsistency associated with surface modification of substrates. The success of colloid deposition has been demonstrated by scanning electron microscopy (SEM) and the corresponding SERS response (giving performance comparable to the corresponding traditional colloidal SERS substrates). Reproducibility was evaluated by conducting replicate measurements across six different locations on the substrate and assessing the extent of the variability (standard deviation values of spectral parameters: peak width and height), in response to either Rhodamine 6G or Isoniazid. Of particular interest is the observation of how some peaks in a given spectrum are more susceptible to data variability than others. For example, in a Rhodamine 6G SERS spectrum, spectral parameters of the peak at 775 cm−1 were shown to have a relative standard deviation (RSD) % of <10%, while the peak at 1573 cm−1 has a RSD of ≥10%. This observation is best explained by taking into account spectral variations that arise from the effect of a chemisorption process and the local nature of chemical enhancement mechanisms, which affects the enhancement of some spectral peaks but not others (analogous to resonant Raman phenomenon).
Accurate Concentration Measurements Using Surface-Enhanced Raman and Deuterium Exchanged Dye Pairs
Authors: Deb Shirshendu K. , Davis Brandon , Ben-Amotz Dor , Davisson V. JO
Published: October 2009

Quantitative applications of surface-enhanced resonance Raman scattering (SERRS) are often limited by the reproducibility of SERRS intensities, given the difficulty of controlling analyte–substrate interactions and the associated local field enhancement. As demonstrated here, SERRS from dye molecules even within the same structural class that compete with similar substrates display distinct spectral intensities that are not proportional to analyte concentrations, which limits their use as internal standardization probes and/or for multiplex analysis. Recently, we demonstrated that isotopic variants of rhodamine 6G (R6G), namely R6G-d0 and R6G-d4, can be used for internal standards in SERRS experiments with a linear optical response from picomolar to micromolar concentrations (of total analytes). Here we extend these results by describing a straightforward method for obtaining isotopomeric pairs of other Raman active dyes by hydrogen–deuterium exchange conditions for substitution at electron rich aromatic heterocycles. Most of the known SERRS active probes can be converted into the corresponding isotopomeric molecule by this exchange method, which significantly expands the scope of the isotopic edited internal standard (IEIS) approach. The relative quantification using IEIS enables accurate, reproducible (residual standard deviation ±2.2%) concentration measurements over a range of 200 pM to 2 μM. These studies enable easy access to a variety of isotopically substituted Raman active dyes and establish the generality of the methodology for quantitative SERRS measurements. For the first time, three rhodamine 6G isotopomers have been created and show distinct Raman spectra, demonstrating the principle of the approach for application as a multiplex technique in biomolecular detection/quantification.
Crystallinity of Bamboo-Based Carbon Filaments for Incandescent Lamps Examined by Raman Spectroscopy as a Nondestructive Means of Analysis
Authors: Ohkawa Hideki , Yuge Yoji , Kamata Hiroshi , Matsuda Ryotaro , Ito Yasuo , Miura Akira , Tonotani Junichi
Published: October 2009

The crystallinities of bamboo-based carbon filaments have been examined by Raman spectroscopy as a nondestructive means of analysis of the historical lamp (ca. 1890s) manufactured by Ichisuke Fujioka of Japan, and the results have been compared with results from the study of Edison's lamp (ca. 1889) and replica lamps produced in 1979. The crystallinities for the three carbon filaments have been evaluated in terms of the intensity ratio ID/ IG, where ID is the intensity at 1350 cm−1 for the D band originating from the defect of graphite and IG is the intensity at 1585 cm−1 for the G band due to the stretching vibration of graphite layers. The ratios obtained are 0.3–0.4, 0.28–0.3, and 0.25–0.28 for the Fujioka, Edison, and replica lamps, respectively. The Raman spectrum of the bamboo-based carbon filament produced by thermal pyrolysis at 1273 K in a nitrogen atmosphere is significantly different from those of filaments inside the incandescent lamps. The raw bamboo filament was analyzed by ultraviolet (UV) Raman spectroscopy using an excitation wavelength of 325 nm from a HeCd laser to avoid the strong interference due to photoluminescence. An intense peak at 1585 cm−1 was recognized, which was ascribed to the C=C bond vibration for the lignin component in the bamboo. The upper shift of the D band for the carbon filament pyrolyzed at 1273 K was confirmed by varying the excitation wavelength at 514.5 nm to 325 nm, and this behavior was interpreted on the basis of the double resonance Raman scattering mechanism.
Impulse-Induced Compression Rheo-Optics Study of Polymers Using Attenuated Total Reflection Based Step-Scan Fourier Transform Infrared Time-Resolved Spectroscopy
Authors: Nishikawa Yuji , Nakano Tatsuhiko , Noda Isao
Published: October 2009

An impulse-induced attenuated total reflection (ATR) based dynamic compression step-scan time-resolved Fourier transform rheo-optical system has been developed. This system was used to observe different viscoelastic properties of poly(ethylene terephthalate) (PET), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx), and carbon-black-filled polyester-polyamide blend. In the case of PET, almost no viscoelastic response extending beyond 15 ms was observed in the dynamic absorbance difference time domain spectrum. In contrast, PHBHx showed apparently different viscoelastic responses in the dynamic absorbance difference spectrum, especially in the C=O stretching band region. A long relaxation tail of the 1723 cm−1 band lasting about 2.7 milliseconds was clearly seen. The tail corresponds to the structural or morphological reorganization of a less ordered crystalline form (Type II) under compressive perturbation. The carbon-black-filled polyester–polyamide blend film also shows different viscoelastic response tails. In this case, the amide C=O stretching vibration band does not show distinct viscoelastic responses, suggesting that the polyamide component does not contribute much to the viscoelastic properties. The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, copolymers, and semicrystalline polymers.
Chemical Probing of Single Cancer Cells with Gold Nanoaggregates by Surface-Enhanced Raman Scattering
Authors: Tang Hong-Wu , Yang Xuebin B. , Kirkham Jennifer , Smith D. Alastair
Published: October 2009

By using near-infrared surface-enhanced Raman scattering (SERS) with 60 nm gold nanoparticles (Au-NPs) to probe the chemical composition inside single human osteosarcoma cells we have shown that the SERS intensity may increase by a factor of 3–6 times in different parts of the cells depending on the density of gold nanoaggregates within the probed volume after the cell is dehydrated. The cellular points of low-density gold nanoaggregates exhibit more significant increase of SERS signal levels, the cellular macrochemicals such as nucleic acids show conformational changes, and new components can be probed after the cell is completely dried. A comparative study between viable and apoptotic cells indicates that most of the Au-NPs that enter the living cell reside in the cytoplasm and around the nucleus, whereas glyoxal-induced apoptotic cells show relatively uniform distribution of Au-NPs and, interestingly, the presence of DNA fragments is detected throughout the cell, including the cell surface.
Ultraviolet Raman Spectra and Cross-Sections of the G-series Nerve Agents
Authors: Christesen Steven D. , Jones Jay Pendell , Lochner Joseph M. , Hyre Aaron M.
Published: October 2009

Ultraviolet (UV) Raman spectroscopy is being applied to the detection of chemical agent contamination of natural and man-made surfaces. In support of these efforts, we have measured the UV Raman signatures of the G-series nerve agents GA (tabun), GB (sarin), GD (soman), GF (cyclosarin), and the agent simulant diisopropyl methylphosphonate (DIMP) at 248 nm and 262 nm, as well as taking their UV Raman and UV absorption cross-sections. Of these chemicals, only GA exhibits any significant pre-resonance enhancement. We also show that reduction of the excitation wavelength from 262 nm to 248 nm effectively shifts the Raman spectrum away from a substantial sample fluorescence background, implying a significant improvement in detection capability.
Dynamic Infrared Study of Polyphenylene Sulfide Using Planar Array Infrared Spectroscopy
Authors: Pesapane Andrea , Snively Christopher M. , Ikeda Richard M. , Chase D. Bruce , Rabolt John F.
Published: October 2009

Planar array infrared (PA-IR) spectroscopy was used to study polyphenylene sulfide (PPS) at room temperature during the application of a sinusoidal elastic deformation. All of the intensity in the dynamic spectra was contained within the in-phase spectrum, which was expected since the measurements were carried out at room temperature, far below the glass transition temperature. The contributions of chain orientation, sample thinning, and stress-induced band shifts were separated in the dynamic spectra. It was found that the effects of chain orientation and sample thinning canceled each other out. Stress-induced band shifts far below the spectral resolution, on the order of 0.01 cm−1, were quantified and used to calculate the stress optical coefficients and mode Gruneisen parameters for PPS.
Evaluation of Femtosecond Laser-Induced Breakdown Spectroscopy for Analysis of Animal Tissues
Authors: Santos Dário , Samad Ricardo Elgul , Trevizan Lílian Cristina , de Freitas Anderson Zanardi , Vieira Nilson Dias , Krug Francisco José
Published: October 2009

The aim of this work was to evaluate the performance of femtosecond laser-induced breakdown spectroscopy (fs-LIBS) for the determination of elements in animal tissues. Sample pellets were prepared from certified reference materials, such as liver, kidney, muscle, hepatopancreas, and oyster, after cryogenic grinding assisted homogenization. Individual samples were placed in a two-axis computer-controlled translation stage that moved in the plane orthogonal to a beam originating from a Ti:Sapphire chirped-pulse amplification (CPA) laser system operating at 800 nm and producing a train of 840 μJ and 40 fs pulses at 90 Hz. The plasma emission was coupled into the optical fiber of a high-resolution intensified charge-coupled device (ICCD)–echelle spectrometer. Time-resolved characteristics of the laser-produced plasmas showed that the best results were obtained with delay times between 80 and 120 ns. Data obtained indicate both that it is a matrix-independent sampling process and that fs-LIBS can be used for the determination of Ca, Cu, Fe, K, Mg, Na, and P, but efforts must be made to obtain more appropriate detection limits for Al, Sr, and Zn.
Classification of Organic and Biological Materials with Deep Ultraviolet Excitation
Authors: Bhartia Rohit , Hug Willam F. , Salas Everett C. , Reid Ray D. , Sijapati Kripa K. , Tsapin Alexandre , Abbey William , Nealson Kenneth H. , Lane Arthur L. , Conrad Pamela G.
Published: October 2009

We show that native fluorescence can be used to differentiate classes or groups of organic molecules and biological materials when excitation occurs at specific excitation wavelengths in the deep ultraviolet (UV) region. Native fluorescence excitation–emission maps (EEMs) of pure organic materials, microbiological samples, and environmental background materials were compared using excitation wavelengths between 200–400 nm with emission wavelengths from 270 to 500 nm. These samples included polycyclic aromatic hydrocarbons (PAHs), nitrogen- and sulfur-bearing organic heterocycles, bacterial spores, and bacterial vegetative whole cells (both Gram positive and Gram negative). Each sample was categorized into ten distinct groups based on fluorescence properties. Emission spectra at each of 40 excitation wavelengths were analyzed using principal component analysis (PCA). Optimum excitation wavelengths for differentiating groups were determined using two metrics. We show that deep UV excitation at 235 (±2) nm optimally separates all organic and biological groups within our dataset with >90% confidence. For the specific case of separation of bacterial spores from all other samples in the database, excitation at wavelengths less than 250 nm provides maximum separation with >6σ confidence.
Alternative Statistical Methods for Spectral Data Processing: Applications to Laser-Induced Breakdown Spectroscopy of Gaseous and Aerosol Systems
Authors: Álvarez-Trujillo L. A. , Ferrero A. , Laserna J. J. , Hahn D. W.
Published: October 2009

A new spectral data processing scheme based on the standard deviation of collected spectra is compared with the traditional ensemble-averaging of laser-induced breakdown spectroscopy (LIBS)-based spectral data for homogenous (i.e., pure gas phase) systems and with a LIBS-based traditional conditional spectral analysis scheme for non-homogenous (e.g., aerosol system) analyte systems under discrete particle loadings. The range of conditions enables quantitative assessment of the analytical approaches under carefully controlled experimental conditions. In the homogeneous system with gaseous carbon dioxide producing the carbon atomic emission signal, the standard deviation method provided a suitable metric that is directly proportional to the analyte signal and compares favorably with a traditional ensemble averaging scheme. In contrast, the applicability of the standard deviation method for analysis of non-homogenous analyte systems (e.g., aerosol systems) must be carefully considered. It was shown both experimentally and via Monte Carlo simulations that the standard deviation approach can produce an analyte response that is monotonic with analyte concentration up to a point at which the analyte signal starts to transition from a non-homogeneous system to a homogeneous systems (i.e., around a 50% sampling point for aerosol particles). In addition, the standard deviation spectrum is capable of revealing spectral locations of non-homogeneously dispersed analyte species without a priori knowledge.
Study of the Infrared Spectral Features of an Epoxy Curing Mechanism
Authors: Li Liang , Wu Qili , Li Shanjun , Wu Peiyi
Published: October 2009

In this work, the isothermal curing process of diglycidyl ether of bisphenol A(DGEBA) cured with 4,4′-diaminodiphenylmethane (DDM) was monitored in situ by mid-infrared (MIR) and near-infrared (NIR) spectroscopy. With the help of generalized two-dimensional (2D) correlation analysis, the results obtained showed that, during curing, the change of amine and epoxy groups was simultaneous, taking place prior to the change of hydroxyl groups, followed by the change of CH2/CH groups, resulting from the ring-opening reaction of epoxy groups. In addition, 2D MIR×NIR hetero-spectral correlation analysis and second-derivative analysis were also employed, by means of which direct evidence of the curing mechanism could be obtained and obscure NIR band assignments in the overlapped CH combination region could be made.
Spectroscopic Properties of Some Derivatives of Polycyclic Aromatic Hydrocarbons
Authors: Catalfo Alfio , Serrentino Maria Elisabetta , Librando Vito , Perrini Giancarlo , De Guidi Guido
Published: October 2009

The aim of this paper is to provide a general picture of the spectral characteristics of some polycyclic aromatic hydrocarbon (PAH) derivatives. A great deal of data concerning PAHs has been reported in the literature, but there is lack of comprehensiveness about important parameters in the same experimental conditions for their nitro (NO2) and amino (NH2) derivatives such as absorption and emission characteristics. Thus, important parameters such as the molar extinction coefficient, absorption maxima, fluorescence maxima, and fluorescence quantum yield are reported here. The efficiencies of the reduction of NO2-PAHs to their corresponding amino compounds were also verified by means of high-performance liquid chromatography (HPLC). This class of derivatives represents one of the most toxic groups of carcinogenic substances and therefore the data reported here should be useful for toxicological research.
Characterization of Thermophilic Bacteria Using Surface-Enhanced Raman Scattering
Authors: Çulha Mustafa , Adigüzel Ahmet , Yazici M. MÜGE , Kahraman Mehmet , Slahin Fikrettin , Güllüce Medine
Published: October 2009

Surface-enhanced Raman scattering (SERS) can provide molecular-level information about the molecules and molecular structures in the vicinity of nanostructured noble metal surfaces such as gold and silver. The three thermophilic bacteria Bacillus licheniformis, Geobacillus stearothermophilus, and Geobacillus pallidus, a Gram-negative bacterium E. coli, and a Gram-positive bacterium B. megaterium are comparatively characterized using SERS. The SERS spectra of thermophilic bacteria are similar, while they show significant differences compared to E. coli and B. megaterium. The findings indicate that a higher number of thiol residues and possible S–S bridges are present in the cell wall structure of thermophilic bacteria, providing their stability at elevated temperatures. Incubating the thermophilic bacteria with colloidal silver suspension at longer times improved the bacteria–silver nanoparticle interaction kinetics, while increased temperature does not have a pronounced effect on spectral features. A tentative assignment of the SERS bands was attempted for thermophilic bacteria. The results indicate that SERS can be a useful tool to study bacterial cell wall molecular differences.
Spectroscopic Study on the Enhanced Excitation of an Electron Cyclotron Resonance Nitrogen Plasma by Pulsed Laser Ablation of an Aluminum Target
Authors: Tang J. Y. , Zhang W. , Sun J. , Xu N. , Ge C. , Wu J. D.
Published: October 2009

The influence of pulsed laser ablation of an aluminum target on the nitrogen plasma produced by electron cyclotron resonance (ECR) microwave discharge has been studied by optical emission spectroscopy (OES) with time and space resolution. The continuous wave (CW) feature of the optical emissions from the ECR nitrogen plasma turns to vary with time and space due to pulsed laser ablation and the expansion of the ablation-induced aluminum plume in the nitrogen plasma. The optical emissions from the nitrogen plasma increase significantly and the emission intensity of nitrogen molecular ions is observed to be more than 20 times higher with the target being ablated in comparison to the case without target ablation. The comparison of the optical emissions from the nitrogen plasma with those from the aluminum plume indicates that the excitation enhancement of the nitrogen plasma occurs in the region where the aluminum plume is expanding, revealing that the expansion of the aluminum plume leads to the excitation enhancement of the nitrogen plasma. Relevant mechanisms responsible for the excitation enhancement of the nitrogen plasma through hybrid processes of ECR microwave discharge and pulsed laser ablation are also discussed.
Two-Dimensional Imaging of Water Vapor by Near-Infrared Laser Absorption Spectroscopy
Authors: Morita Shigeaki , Hattori Eiji , Kitagawa Kuniyuki
Published: October 2009

Both a flow of water vapor generated from a humidification device and stable water vapor at constant moisture were successfully visualized by near-infrared (NIR) laser absorption spectroscopy. Two different types of optical arrangement for two-dimensional (2D) imaging, i.e., one-wave-length reflection and two-wavelength transmission, were tested. A flow of water vapor within a wide view range was clearly visualized by the former, while low content of stable water vapor was quantitatively detected by the latter. It was demonstrated that a detection limit of 0.8 g·m−3 was achieved by means of the 2D-NIR imaging system developed in the present study.
New Technique for the Direct Analysis of Food Powders Confined in a Small Hole Using Transversely Excited Atmospheric CO2 Laser-Induced Gas Plasma
Authors: Khumaeni Ali , Ramli Muliadi , Deguchi Yoji , Lee Yong Inn , Idris Nasrullah , Kurniawan Koo Hendrik , Lie Tjung Jie , Kagawa Kiichiro
Published: October 2009

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO2 lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO2 laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.
Sensing of Water Dissolved in Solvents Using a 5.629 μm Multimode Quantum Cascade Laser
Authors: Ouvrard A. , O'Dwyer K. , MacCraith B. D.
Published: October 2009

We report herein the detection of liquid water dissolved in a variety of solvents using a thermoelectrically cooled, pulsed, Fabry–Perot quantum cascade laser, operating at 5.629 μm at room temperature. The prototype sensor system consisted of the laser, a series of off-axis parabolic mirrors, and two mercury cadmium telluride detectors. When applied to the detection of water in tetrahydrofurane, a limit of detection of 0.85 parts per million was achieved. It is envisaged that such a sensor would be well suited to process control applications within the pharmaceuticals industry.
Possibilities for Using Raman Spectroscopy to Determine the Amount of Analyte Directly from a Solid-Phase Extraction Cartridge in Water-Based Applications
Authors: Niemelä Pentti
Published: October 2009

Raman spectroscopy is occasionally used as a detection technique in liquid chromatography. This paper shows that the amount of analyte can also be determined directly from a solid-phase extraction cartridge, which eliminates the need for solvents in the analysis. Transmission geometry was used in Raman probing of the sorbent bed and interferences from the tube material were reduced by using quartz glass instead of the commonly used plastic. Bonded-phase silica C18 was a test sorbent, and ethylbenzene, as a test analyte, was extracted from its water solutions. A detection limit of 3 μg/mL was obtained in the Raman calibration by using a univariate method with a CH band of the sorbent ligand as an internal standard. This is only an order of magnitude higher than what was estimated for liquid chromatography with the same Raman instrument as its detector. In addition, an optimal sorbent for each analyte can be chosen more freely if there is no need to bother about further elution of the analyte.