bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Spectra and Molecular Organization in Thin Solid Films of Bis(Neopentylimido) Perylene
Authors: Del Caño T. , Duff J. , Aroca R.
Published: October 2003

The synthesis, molecular spectra, and thin solid film properties of a perylene dye, bis(neopentylimido) perylene (BNPTCD),§ are reported. Absorption and emission molecular spectra are used to probe the structure of vacuum-evaporated thin films and Langmuir–Blodgett monolayers of BNPTCD. The experimental assignment of electronic, infrared, and Raman spectra are aided with calculated molecular structure and spectra using density functional theory (DFT) and Hartree–Fock (HF) computational methods at 6–31G level of theory. Characteristic vibrational modes and local symmetry of the planar perylene tetracarboxylic chromophore (PTCD) are used to extract molecular organization and film packing properties from spectral data collected using transmission and reflection-absorption (RAIRS) infrared spectroscopy. From the infrared spectra, using surface selection rules and polarization properties, it was extracted that the PTCD plane in BNPTCD is organized in the evaporated film with the plane head-on tilted over the substrate. After the molecular organization was identified, the effect of thermal annealing and solvent vapors on the film structure was examined. It is found that the PTCD plane turns to a flat-on orientation when the film is thermal annealed or solvent treated. The aggregation and molecular stacking in films was also inspected using the electronic absorption and fluorescence of monomers and aggregates.
Adsorption of Carboxylic Acids on Submicrocrystalline Aluminum Hydroxides in Aqueous Solution. Part I: Qualitative Study by Infrared and Raman Spectroscopy
Authors: Phambu Nsoki
Published: October 2003

Adsorption of acetic, oleic, benzoic, and salicylic acids on submicrocrystalline aluminum hydroxide samples is investigated in aqueous solutions. Experimental infrared and Raman spectroscopic data are analyzed to determine the reactivity of the monocoordinated hydroxyl groups located on the edge faces of bayerite or gibbsite crystals. Two key parameters were (1) the effect of concentration of aqueous solutions of the acids, and (2) the variation in specific surface areas of different samples of bayerite and gibbsite powders. Strong preferential adsorption to bayerite was observed over the whole pH range. No adsorption to gibbsite was detected. Data from the literature indicate that acetate, oleate, and benzoate form bidentate complexes on bayerite while salicylate forms a monodentate complex. The infrared spectra show that only monocoordinated hydroxyl groups are reactive, in the bayerite samples, and the band at 1020 cm−1 corresponds to the deformation mode of the monocoordinated hydroxyl groups whose stretching vibration was at 3465 cm−1. It is suggested that the specific surface areas given by the adsorption isotherms is a condition necessary for adsorption, but not sufficient in itself. Adsorption requires the presence of Al-OH2+1/2 species as well as the presence of steps or of a packaging sequence ABABABA rather than a packaging sequence ABBAABBA of the hydroxyl planes. The gibbsite impurity present in the bayerite sample reacted completely, while the lateral OH in the gibbsite sample did not, reflecting the lower reactivity in gibbsite relative to extended domains of bayerite.
Separation of the Raman Spectral Signatures of Bioapatite and Collagen in Compact Mouse Bone Bleached with Hydrogen Peroxide
Authors: Freeman John J. , Silva Matthew J.
Published: October 2003

We studied the effectiveness of hydrogen peroxide in removing visible laser-induced photoluminescence from the Raman spectra of compact bone of mice. In testing various bone sample preparations, we found that hydrogen peroxide bleaching was most effective when applied directly to fresh or fresh-frozen bone samples. The extent of the reduction in photoluminescence in the peroxide-bleached bone was such that the Raman spectrum could be readily recorded with 532-nm laser excitation. A comparison of bone samples before and after hydrogen peroxide bleaching shows that the Raman shifts of all the collagen and bioapatite bands are unaffected by the peroxide bleach. Moreover, the low spectral backgrounds of the peroxide-treated bone samples permit the Raman spectra of these two major components of bone to be fully separated. The Raman spectrum of collagen-rich periosteum was subtracted from the Raman spectrum of compact bone, which isolated the Raman spectral signature of the bioapatite fraction of the bone. This derived spectrum of bioapatite was then used, through spectral subtraction, to generate the spectral signature of the collagen component of the bone. All the major and minor Raman bands of collagen and bioapatite can be identified in these separate spectra.
Fluid Phase Equilibria of Ethanol and Carbon Dioxide Mixtures with Concentration Measurements by Raman Spectroscopy
Authors: Stratmann A. , Schweiger G.
Published: October 2003

Phase equilibria data for the system ethanol/carbon dioxide for T = 313.15 K and pressures up to p = 7.9 MPa are presented. The measurements were made by Raman spectroscopy without the extraction of probes from the autoclave. To the authors knowledge this is the first use of Raman spectroscopy for phase equilibria investigations at high pressure with supercritical carbon dioxide. The data show very good agreement with literature data.
Determination of Si/Al Ratios in Semicrystalline Aluminosilicates by FT-IR Spectroscopy
Authors: Jakobsson Sigurdur
Published: October 2003

Infrared spectra of synthetic, semicrystalline aluminosilicates in the region 500–1200 cm−1 show a dominant band due to Si–O stretching at 980–1030 cm−1 and two combined bands due to Si–O–Al bending at 600–700 cm−1. These bands can be used to determine quantitatively the Si/Al ratio of the aluminosilicates. A calibration curve has been obtained by integrating the intensities of the bands and relating them to Si/Al ratios of 10 aluminosilicate samples as measured with inductively coupled plasma (ICP) with Si/Al ratios ranging from 0.19 to 1.46.
Remote Pulsed Laser Raman Spectroscopy System for Mineral Analysis on Planetary Surfaces to 66 Meters
Authors: Sharma Shiv K. , Angel S. Michael , Ghosh Manash , Hubble Hugh W. , Lucey Paul G.
Published: October 2003

There is a need for an instrument that can be used for remote in situ identification of biogenic and a-biogenic minerals, various types of ices, and organic and inorganic materials on planetary surfaces. In this paper, we explore the use of remote pulsed laser Raman spectroscopy for mineral analysis at distances from 10 to 66 m on planetary surfaces. We have constructed a remote Raman system utilizing a small pulsed Nd:YAG laser and a 5-in. telescope coupled to a spectrograph with an optical fiber. The performance of our system is demonstrated by presenting spectra of benzene and marble (calcium carbonate) while varying the integration time (i.e., number of laser shots), as well as single laser shot spectra of marble while decreasing laser power. Finally, Raman spectra of representatives of several different mineral groups are presented, including hydrated substances, carbonates, silicates (e.g., olivine, pyroxene, feldspars, etc.), water, and ice.
Time-Resolved NIR/Vis Spectroscopy for Analysis of Solids: Pharmaceutical Tablets
Authors: Johansson Jonas , Folestad Staffan , Josefson Mats , Sparén Anders , Abrahamsson Christoffer , Andersson-Engels Stefan , Svanberg Sune
Published: October 2003

Time-resolved spectroscopy in the visible and near-infrared (NIR) regions was used in a feasibility study for analysis of solid pharmaceuticals. The objective of the experiments was to study the interaction of light with pharmaceutical solids and to investigate the usefulness of the method as an analytical tool for spectroscopic analysis. In these experiments, a pulsed Ti:sapphire laser and white light generation in water was utilized to form a pulsed light source in the visible/NIR region. The light was focused onto the surface of tablets, and the transmitted light was detected by a time-resolving streak camera. Two types of measurements were performed. First, a spectrometer was put in front of the streak camera for spectral resolution. Secondly, the signal originating from different locations of the sample was collected. Time-resolved and wavelength/spatially resolved data were generated and compared for a number of different samples. The most striking result from the experiments is that the typical optical path length through a 3.5-mm-thick tablet is about 20–25 cm. This indicates very strong multiple scattering in these samples. Monte Carlo simulations and comparison with experimental data support very high scattering coefficients on the order of 500 cm−1. Furthermore, the data evaluation shows that photons with a particular propagation time through the sample contain a higher chemical contrast than other propagation times or than steady-state information. In conclusion, time-resolved NIR spectroscopy yields more information about solid pharmaceutical samples than conventional steady-state spectroscopy.
Stopped-Flow FT-IR Spectroscopy of Aqueous Solutions Using Attenuated Total Reflectance
Authors: Dunn Brian C. , Marda Jonathan R. , Eyring Edward M.
Published: October 2003

An apparatus for the study of solution phase kinetics using FT-IR spectroscopy has been developed. The observation chamber consists of an integrated tangential mixer-flow cell and a ZnSe element permitting attenuated total reflectance (ATR) measurements. The short optical pathlength afforded by ATR allows mid-IR observation of chemical reactions in aqueous solution, including the spectral region near the water bending vibration (1640 cm−1). High hydraulic backpressures required to force solution rapidly through a thin layer flow cell are not necessary with the ATR flow cell because the optical pathlength and the flow cross-section have been decoupled, allowing for a relativity large flow chamber when compared with instruments incorporating a transmission flow cell. Overall system performance has been evaluated using the hydrolysis of methylchloroacetate as a test reaction. The feasibility of observing reactions with initial half-lives of approximately 250 ms is demonstrated. The system is very robust, with little risk of damaging the optics during routine maintenance.
FT-Raman Spectroscopic Study of the Structural Evolution in Binary UV-Curable Vinyltriethoxysilane/Tetraethoxysilane Mixtures from the Sol to the Xerogel State
Authors: Gigant K. , Posset U. , Schottner G.
Published: October 2003

Fourier transform Raman spectroscopy was used in order to study acid catalyzed hydrolysis and polycondensation processes from the sol via the gel until the xerogel state in binary mixtures of vinyltriethoxysilane (ViTEOS) and tetraethoxysilane (TEOS). Supplementary 29Si-, 13C-MAS-NMR, and FT-IR data were considered. Intermediate hydrolysates, oligomers, and polycondensates were detected independently of the sample's physical state. Vibrational assignments are given for pure ViTEOS and its partially hydrolyzed intermediates. The corresponding mono-, di-, and tri-hydroxylated species are found to exhibit characteristic νsym(CSiO3) vibrational modes in the 650–672 cm−1 region. Subsequent oligomerization results in a progressive shift of the νsym(CSiO3) bands towards lower wavenumbers. Condensation proceeds faster in ViTEOS–TEOS mixtures than in pure ViTEOS. Assignments for some early oligomeric species and some network connectivity are given. The Raman spectra suggest that the main building blocks of the evolving network are already present in the wet gels. Moreover, it is shown that residual ethoxy groups attached to the siloxane network are still present in xerogels, whereas no silanol groups are detected. The spectra demonstrate that the vinyl groups did not react under the applied conditions. This system has potential for the preparation of UV-curable abrasion-resistant coatings for plastic substrates.
Dynamic Fourier Transform Polarized Raman Spectroscopy of Polyethylene Fibers under a Modulated Strain
Authors: Griffiths P. R. , Chase D. B. , Ikeda R. M. , Catron J. W.
Published: October 2003

The response of materials under stress is a critical aspect of the in-use performance of fibers and films. Dynamic infrared measurements have been shown to be very informative and have provided information about both chain reorientation and conformational state change during deformation. However, the use of infrared transmission techniques necessarily confines the measurements to thin films. Polymeric fibers present a real challenge to this approach. Raman scattering is extremely well suited for fibers. There is no real constraint on sample size, shape, or thickness. Dynamic measurements on fibers under deformation have been extended using a Raman probe. Step-scan FT-Raman spectroscopy has allowed the decoupling of the sample strain frequencies from the Fourier frequencies, and the sensitivity is sufficient to observe the small changes associated with an elastic tensile deformation. For polyethylene fibers, the dynamic spectra exhibit both stress-induced frequency shifts and intensity changes due to chain reorientation. Vibrational modes that are coupled to chain backbone motions are found to exhibit the strongest stress-induced frequency shifts, while decoupled motions, such as C–H stretching modes, exhibit the effects of chain reorientation.
Remote Detection Using Surface-Enhanced Resonance Raman Scattering
Authors: McCabe Ailie , Smith W. Ewen , Thomson Grant , Batchelder David , Lacey Richard , Ashcroft Geoffrey , Foulger Brian F.
Published: October 2003

Surface-enhanced resonance Raman scattering (SERRS) provides intense Raman signals that are shown here to be stable in a target and to be detectable at least 10 meters from the spectrometer. The results indicate that SERRS labeling of objects and their detection at a distance with a low-power laser is feasible. Rhodamine and a dye specifically designed to give good surface adhesion, [4(5′-azobenzotriazyl)-3,5-dimethoxyphenylamine] (ABT DMOPA), were adsorbed onto silver particles and the particles dispersed in poly(vinyl acetate) (PVA) and varnish. SERRS from rhodamine was not detected from colloid dispersed either in PVA or varnish, presumably due to displacement of the dye from the silver surface. ABT DMOPA gave good SERRS. Maps of the SERRS intensity of films indicated variability of 10–20% if ultrasound was applied to improve dispersion during mixing. Scattering performance was evaluated using a system with the sample held up to one meter from the probe head. The intensity of the scattering from samples kept in the dark showed little change over a period of up to one year. However, when the samples were left in direct sunlight, the scattering intensity dropped significantly over the same period but could still be determined after eight months. An optical system was designed and constructed to detect scattering at longer distances. It consisted of a probe head based on a telephoto or CCTV lens that was fiber-optically coupled to the spectrometer. Effective detection of SERRS was obtained 10 m from the spectrometer using 3.6 mW of power and a 20 s accumulation time.
Automated Fluorescence Rejection Using Shifted Excitation Raman Difference Spectroscopy
Authors: Zhao Jun , Carrabba Mike M. , Allen Fritz S.
Published: October 2003

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.
Characteristics of Gasoline Fluorescence Using 404-nm Semi-Conductor Laser Diode Excitation
Authors: Yeo T. L. , Ozanyan K. B. , Hindle F. , Poolton N. R. J. , McCann H.
Published: October 2003

The recent availability of reliable and relatively low-cost GaN based semi-conductor laser diode sources emitting at 404 nm has opened many new areas for fluorescence based measurements. This article characterizes the fluorescence behavior of commercial liquid-phase gasoline samples using such excitation sources. Comparison is drawn with the emission when excited using broad-band sources at shorter wavelengths (340 nm). Here, 404 nm is shown to selectively excite the larger C xH y polycyclic aromatic hydrocarbons (PAH) commonly found as minor constituents of gasoline, mainly for ( x, y) ≥ (14, 10). Both Stokes and anti-Stokes shifted emission was observed in all the gasoline tested and in some PAH samples. The fluorescence is usually superimposed on Raman scattered laser light, arising from vibrations within the basic benzene structures. The fluorescence features of the gasoline samples tested were found to be broadly similar, but, because of its distinctive spectroscopic features, the fluorescence arising from benzo(a)pyrene was found to be one of the main variants. More generally, principal component analysis of the spectra was able to highlight differences between both the sample provenance and the fuel variety.
Laser-Induced Breakdown Spectroscopy for the On-Line Multielement Analysis of Highly Radioactive Glass Melt Simulants. Part II: Analyses of Molten Glass Samples
Authors: Yun Jong-Il , Klenze Reinhardt , Kim Jae-Il
Published: October 2003

The paper presents the application of laser-induced breakdown spectroscopy (LIBS) for the on-line multielement analyses of glass melts in a vitrification process of high level liquid waste (HLLW). The third harmonic pulse of an Nd:YAG laser is used for the generation of plasma on the molten glass surface and the plasma emission is monitored by an echelle spectrometer with an intensified charge-coupled device (ICCD), which simultaneously covers the wavelength range from 200 to 780 nm. Twelve different reference HLLW glass melts with a complex composition of about 27 chemical elements are simulated on a laboratory scale, varying the HLLW component concentration. By real-time analyses of the reference glasses at 1200 °C, the analytical method is calibrated. A multivariate regression approach with partial least squares (PLS) is used for the data evaluation. The LIBS method thus calibrated is then applied for the multielement analysis of molten glass samples from the prototype vitrification plant under operation in our institute. The results underline that the LIBS method can be applied to a vitrification process for the on-line multielement analysis of highly radioactive glass melts.
Standardless Analysis of Hg with the Cold Vapor Method: Evaluation of the Best Use of Modern Instrumentation
Authors: Vecchiati Giorgio , Fagioli Francesco , Torsi Giancarlo , Locatelli Clinio , Mazzotta Dionisio , Pagnoni Antonella
Published: October 2003

The so-called cold vapor method is extensively used in atomic absorption spectroscopy for the quantitation of Hg and hydride forming elements. In the case of Hg it is possible to take advantage of the standardless method of analysis (which gives a quantitative result from a single measurement) if a stannous salt is used as a reducing agent. This type of analysis, which has the advantages of high sensitivity, low analysis time, and easy checking of the perfect working conditions of all the components of the apparatus, can be made with very slightly altered commercial instruments if flowmeters of good accuracy and precision are used. The mode of operation of modern commercial instruments can be either discontinuous, with a chromatographic-like injector, or continuous. A survey of the instruction manuals shows that virtually all manufacturers prefer the discontinuous mode. Our experimental results demonstrate that only with the continuous mode, if sufficient sample volume is available, is it possible to use the standardless method of analysis.
New Hybrid Algorithm for Transferring Multivariate Quantitative Calibrations of Intra-Vendor Near-Infrared Spectrometers
Authors: Wehlburg Christine M. , Haaland David M. , Melgaard David K.
Published: October 2003

A new prediction-augmented classical least-squares/partial least-squares (PACLS/PLS) hybrid algorithm is ideally suited for use in transferring multivariate calibrations between spectrometers. Spectral variations such as instrument response differences can be explicitly incorporated into the algorithm through the use of subset sample spectra collected on both spectrometers. Two current calibration transfer methods, subset recalibration and piecewise direct standardization (PDS), also utilize subset sample spectra to facilitate transfer of calibration. The three methods were applied to the transfer of quantitative multivariate calibration models for near-infrared (NIR) data of organic samples containing chlorobenzene, heptane, and toluene between a primary and three secondary spectrometers that were all the same model, called intra-vendor transfer of calibration. The hybrid PACLS/PLS method outperformed subset recalibration and provided predictions equivalent to PDS with additive background correction on the two secondary spectrometers whose instrument drift appeared to be dominated by simple linear baseline variations. One of the secondary spectrometers had complex instrument drift that was captured by repeatedly measuring the spectrum of a single repeat sample. In calculating a transfer function to correct prediction spectra, PDS assumes no instrumental drift on the secondary spectrometer. Therefore, PDS was unable to directly accommodate both the subset samples and the use of a single repeat sample to transfer and maintain a calibration on that secondary instrument. In order to implement the transfer of calibration with PDS in the presence of complex instrument drift, recalibrated PLS models that included the repeat spectra from the secondary spectrometer were used to predict the spectra transformed by PDS. The importance of correcting for drift on the secondary spectrometer during calibration transfer was illustrated by the improvements in prediction for all three methods vs. using only the instrument response differences derived from the subset sample spectra. When the effects of instrument drift were complex on the secondary spectrometer, the PACLS/PLS hybrid algorithm outperformed both PDS and subset recalibration. Through the explicit incorporation of spectral variations, due to instrument response differences and drift on the secondary spectrometer, the PACLS/PLS algorithm was successful at intra-vendor transfer of calibrations between NIR spectrometers.
Identification of Overlapped Near-Infrared Bands of Glucose Anomers Using Two-Dimensional Near-Infrared and Middle-Infrared Correlation Spectroscopy
Authors: Awichi Aminiel , Tee Eric M. , Srikanthan Giri , Zhao Wei
Published: October 2003

Near-infrared (NIR) spectroscopy is a useful tool in determining glucose in biological matrices. Because α-anomers and β-anomers of glucose are in equilibrium in the solution, the observed NIR bands may come from the overlapping of vibrational modes of the anomers. We have conducted NIR and mid-infrared (MIR) absorption spectra measurements to determine the nature of the observed NIR features by using two-dimensional (2D) NIR and MIR correlation spectroscopy. The 2D NIR correlation spectra and 2D synchronous NIR and MIR correlation heterospectra are constructed based on the spectral changes of individual anomers upon mutarotation. We have identified a new NIR feature at 4350 cm−1 for the α-anomers and two new NIR features at 4200 and 4250 for the β-anomers. The 4350-cm−1 band of the α-anomers could be assigned to the combination band of C–H stretch at 2945 cm−1 and a mixed mode of C–H bending and O–H bending at 1415 cm−1. The 4200/4250-cm−1 bands of the β-anomers might be tentatively assigned to the combination band of C–H stretching at 2870 cm−1 and a mixed mode of C–H bending and O–H bending at 1315/1370 cm−1. This finding provides the spectral information needed for implementation of a highly selective coherent two-dimensional vibrational spectroscopic method, the DOVE-Raman four wave mixing for selective identification of glucose anomers from aqueous solutions.
Flow-through Picoliter Dispenser: A New Approach for Solvent Elimination in FT-IR Spectroscopy
Authors: Haberkorn Michael , Frank Johannes , Harasek Michael , Nilsson Johan , Laurell Thomas , Lendl Bernhard
Published: October 2003

A new interface for FT-IR analysis of liquid samples on the basis of solvent elimination is presented. The approach is based on a piezoactuated flow-through microdispenser, a device built of two microstructured silicon wafers designed for micro-liquid handling. It could be verified during preliminary studies using a sequential injection (SI) system for automated liquid handling that the flow-through microdispenser as a possible interface for flow system–FT-IR analysis has the capability of meeting the demands of hyphenated miniaturized liquid handling systems (e.g., μ-HPLC, microhigh performance liquid chromatography), as it successfully provides highly stable, reliable and reproducible operating conditions for liquid handling in the picoliter range. Moreover, an increase in sensitivity for FT-IR measurements could be achieved, lowering the mass detection limit of sugars (such as the investigated sucrose) to 53 picograms. As is demonstrated on the example of an HPLC separation of a mixture of glucose and fructose, interfacing LC systems to FT-IR using a piezoactuated flow-through microdispenser is a feasible and promising approach.
Vibrational Spectroscopic Study of Iodine-Doped Poly(Isothianaphthene)
Authors: Chen Wei-Te , Bowmaker Graham A. , Seakins John M. , Cooney Ralph P.
Published: October 2003

Far-infrared, mid-infrared, and Raman spectroscopy were used to characterize iodine-doped poly(isothianaphthene) (PITN) films and powders. The far-infrared and mid-infrared results show changes from absorption mode to reflective mode as the doping level increases, consistent with the iodine-doped PITN becoming more metallic and more conductive at higher doping levels. The far-IR and Raman (514.5-nm laser excitation) results show that I3− is dominant in iodine-doped PITN. The Raman spectral changes observed using 1064-nm excitation are different from those measured using 514.5-nm excitation. The spectra recorded with 514.5-nm excitation show features due to the undoped parts of the polymer, and these indicate that the effective conjugated chain length decreases with increased doping. The Raman spectra obtained by using 1064-nm excitation show features due to polaron and bipolaron states in the doped polymer.
Optimal Absorbance for Transmission or Reflection Spectra Measured under Conditions of Constant Detector Noise in the Presence of Stray Radiation
Authors: Isaksson Tomas , Griffiths Peter R.
Published: October 2003

The signal-to-noise ratio ( S/N) for absorption spectrometers can be expressed as absorbance/absorbance noise ( Am/ SAm), where Am is the measured absorbance and Smm is the standard deviation in Am, or as concentration/concentration noise ( c/sc) calculated from Beer's law. For measurements made under ideal conditions, Am/ SAm. However, when stray radiation, or an analogous phenomenon, such as detector nonlinearity in FT-IR measurements or surface reflection in diffuse reflection spectrometry, contributes to the spectrum, C/ Sc ≠ Am/ SAm. It is known that the optimum value of Am/ SAm in the absence of stray light is found at an absorbance of 0.4816 when noise from the reference spectrum is taken into account and 0.4343 when noise from the reference spectrum is excluded from the calculations. In the present paper we discuss the effect of stray light on the absorbance and concentration S/N. The maximum value of c/sc is found at lower absorbance than is the case if stray light is absent. While this effect is negligibly small for the typical levels of stray light found with most contemporary monochromators, it can be significant when, for example, the response of a detector used in Fourier transform spectrometry is nonlinear or when the front-surface reflection in diffuse reflection measurements is large. For effective stray light levels of 10%, the maximum value of c/sc is found at an absorbance that is 22% lower than when no source of stray light is present.
Broadband Spectroelectrochemical Attenuated Total Reflectance Instrument for Molecular Adlayer Studies
Authors: Doherty Walter J. , Donley Carrie L. , Armstrong Neal R. , Saavedra S. Scott
Published: October 2003

The study of thin film molecular architectures is an increasingly important endeavor with respect to the development and characterization of materials ranging from liquid crystalline displays to receptor-based biosensors. Here we describe an apparatus capable of simultaneously acquiring broadband spectroscopic and electrochemical information on molecularly thin films deposited on a transparent electrode surface through a multiple internal reflection geometry. To demonstrate the capabilities of this system, the spectroelectrochemical behavior of a single, neutral copper phthalocyanine bilayer was evaluated.
New Technique for Determining the Optical Constants of Liquids
Authors: Keefe C. Dale , Pearson Jason K.
Published: October 2003

The traditional techniques of transmission and attenuated total reflectance (ATR) spectroscopy for determining the optical constants of liquids are not practical or reliable for very strong absorption bands. Specular reflectance can be used in these cases, but for volatile liquids it is impossible to separate the reflectance spectrum of the liquid from the absorption spectrum of the vapor above the liquid. Methods using special cells have been described in the literature to prevent the liquid from evaporating. In this paper, a similar technique that makes use of traditional transmission cells is presented. It is shown that this new technique generates k(ν˜) spectra for strong absorption bands that are accurate to approximately 2%.
Measurement of Wavelength-Dependent Complex Refractive Index of Transparent and Absorbing Liquids by a Multifunction Reflectometer
Authors: Räty Jukka , Peiponen Kai-Erik , Jääskeläinen Anssi , Mäkinen Martti O. A.
Published: October 2003

We have modified a recently developed reflectometer so that surface plasmon resonance (SPR) sensing is now possible. Thus, the complex refractive index of liquids can be obtained at a desired wavelength (the existing setup allows the use of the visible-NIR spectral range) using both the SPR and conventional measurement modes of the reflectometer. The multifunction operation of the present apparatus offers possibilities for off- and on-line industrial inspection of liquids.
Generalized Implementation of Rapid-Scan Fourier Transform Infrared Spectroscopic Imaging
Authors: Huffman Scott W. , Bhargava Rohit , Levin Ira W.
Published: October 2003

We describe a novel, generalized data acquisition sequence to allow rapid-scan Fourier transform infrared (FT-IR) spectroscopic imaging using focal plane array (FPA) detectors. This technique derives its applicability from the reproducible performance of modern FT-IR instrumentation and the availability of FPAs with simultaneous, full array acquisition, or snapshot electronics. Instead of sampling the entire interferogram in one mirror sweep over a predetermined retardation, as in traditional continuous-scanning techniques, the modulated light from the interferometer is recorded over several mirror sweeps. The FPA detector is synchronized for data acquisition after a specified delay with respect to the initiation of the mirror motion to provide a highly under-sampled interferogram. By incorporating appropriate delays in subsequent interferometer mirror scans, the entire interferogram is sampled and reconstructed. The signal-to-noise ratios (SNR) of the resulting interferograms are analyzed and are compared with step-scan spectroscopic imaging data.
Optimization of the Emission Characteristics of Laser-Produced Steel Plasmas in the Vacuum Ultraviolet: Significant Improvements in Carbon Detection Limits
Authors: Khater Mohamed A. , Costello John T. , Kennedy Eugene T.
Published: October 2003

A detailed optimization study for laser-produced steel plasmas using time-integrated, spatially resolved emission spectroscopy in the vacuum ultraviolet (VUV) (40–160 nm) is presented. The influences of the laser focusing lens type, laser power density, laser wavelength, laser pulse energy, ambient atmospheres, and pressure, as well as spatial distribution of emitting species, on the emission characteristics of the steel plasmas are investigated. The aim of the work is to improve the detection power of the technique for the quantitative determination of carbon in solid steel alloys. In most of the work, Q-switched Nd:YAG (1064 nm, 820 mJ max. energy) laser pulses were used to create the steel plasmas. For the laser harmonics investigations, a second Q-switched Nd:YAG laser system that generated radiation at the second, third, and fourth harmonics as well as at the fundamental was employed. Air, argon, and helium were used as the surrounding atmospheres, and the pressure was varied from 0.005 mbar to 5.0 mbar depending on the gas composition. A 1 m normal incidence vacuum spectrometer, equipped with a 1200 grooves/mm concave reflective grating, was used to disperse the VUV radiation. The radiation was detected by a back-illuminated, anti-reflection coated, charge-coupled device (CCD) array detector. In general, the emission characteristics of the VUV spectral lines studied are similar to those previously investigated in the UV-visible spectral range. An unprecedented limit of detection for carbon in steels of 1.2 ± 0.2 μg/g was measured in this work.
Laser-Induced Breakdown Spectroscopy for the Analysis of Cobalt—Chromium Orthopaedic Wear Debris Particles
Authors: Mokhbat E. A. , Hahn D. W.
Published: October 2003

Laser-induced breakdown spectroscopy (LIBS) is investigated for the quantitative analysis of individual cobalt–chromium wear particles generated in vivo from human artificial knee joints. As implemented, the LIBS technique provided a measurement of the absolute chromium and cobalt masses for individual wear particles, which enabled calculation of chromium-to-cobalt mass ratios and the equivalent spherical diameter on a particle-to-particle basis. Using a multiple analyte emission line spectral filtering process, absolute cobalt and chromium mass measurements were made as low as 40 and 20 fg, respectively, corresponding to a particle diameter of approximately 200 nm. The size of the wear debris ranged from approximately 200 to 800 nm, with a mean diameter of 385 nm. In addition, the wear particles exhibited a depletion of cobalt with respect to the bulk composition of the cobalt–chromium alloy. The cobalt depletion exhibited a strong correlation with size, with the larger particles characterized by a more significant depletion of cobalt. All synovial fluid samples were inactivated with 10% bleach to reduce risks of infection by bloodborne pathogens. Control wear debris was generated from manual abrasion of pristine cobalt–chromium alloy specimens and analyzed with the LIBS technique to address the potential effects of bleach addition. No statistical differences were recorded between the particle suspensions treated and untreated with bleach. Overall, the LIBS method was successfully implemented for the quantitative analysis of cobalt–chromium wear particles.
Direct Measurement of Charge Current by Employing a Mesh Electrode in the Laser Plasma Induced by a Nd:YAG Laser (I)
Authors: Pardede Marincan , Kurniawan Hendrik , Lie Tjung Jie , Tjia May On , Kagawa Kiichiro
Published: October 2003

A special technique has been developed for the detection of the charge current in conjunction with emission measurement during laser plasma generation. The current detection was performed by placing a partially transmitting metal mesh electrode at a distance of 7 mm from the sample surface with the sample serving as the counter electrode. The electric field between the mesh and sample surface was set up and varied by applying a dc high voltage (0–400 V) between them. The laser plasma was generated by a Nd:YAG laser (64 mJ, 8 ns) tightly focused on a Cu sample through the mesh electrode in surrounding gas of various low pressures. Three Cu emission lines associated with different excited energy levels were detected, namely the Cu(I) 510.5 nm (3.8 eV), Cu(I) 521.8 nm (6.2 eV), and Cu(I) 427.5 nm (7.8 eV) spectral lines. The correlation between the time profile of plasma emission and that of the charge current was examined to elucidate the roles of electron recombination and electron collision processes in the excitation of Cu atoms in the plasma. The charge current time profiles obtained at various gas pressures were invariably found to exhibit spiky signal followed by a slowly decaying component, a lack of consistent correlation with the emission profile of the Cu(I) 521.8 and 510.5 nm lines, showing characteristics of the shock wave model. The result of this study has thus failed to turn up evidence for the significant roles of electron recombination and electron collision comparable to the role of the shock wave mechanism in the plasma emission process.
Determination of Memory-Prone Elements Using Direct Injection High Efficiency Nebulizer Inductively Coupled Plasma Mass Spectrometry
Authors: O'Brien Su-Ann E. , McLean John A. , Acon Billy W. , Eshelman Barbara J. , Bauer William F. , Montaser Akbar
Published: October 2003

A direct injection high efficiency nebulizer (DIHEN) and a large-bore DIHEN (LB-DIHEN) are investigated for the determination of difficult-to-analyze and memory-prone elements (mercury, iodine, and boron). The determination of such elements is problematic using conventional sample introduction systems incorporating spray chambers and/or desolvation devices owing to their large surface area and hence long wash-out characteristics. With the DIHEN or LB-DIHEN, the spray chamber is eliminated and the dead volume is reduced to <10 μL, thus reducing memory effects. In comparison with the crossflow-spray chamber combination, wash-in and wash-out times are reduced to less than 10 s when a DIHEN or LB-DIHEN is used for mercury, iodine, and boron at a concentration of 100 ng/mL. The accuracy of the DIHEN-ICPMS (inductively coupled plasma mass spectrometry) technique is evaluated in the analysis of the National Institute of Standards and Technology standard reference material (NIST SRM) 2670 (Toxic Metals in Freeze-Dried Urine) and NIST SRM 8414 (Bovine Muscle Powder). Further, the effectiveness of the DIHEN-ICPMS technique is examined in the determination of mercury and iodine in an alternative remedy medicine (seahorse genital tonic pills) and boron in rodent liver samples as part of a pharmacokinetic screening study for boron neutron capture therapy.
Study of Dose—Envelope Reactions in Metal Halide Discharge Lamps Using Raman Microscopy
Authors: Forrest Robert J. , Devonshire Robin , Varanasi Chakrapani V. , Brumleve Timothy R.
Published: October 2003

Raman microscopy has been used to investigate the reactions between the chemical dosants in scandium metal halide discharge lamps and their silica lamp envelopes; such lamps are typically dosed with Hg, NaI, ScI3, and sometimes, additionally, excess Sc metal. Raman measurements were made both on operated lamps and dosed silica ampoules that had been furnace heat-treated. The ampoules mimic closely the dose–envelope interactions of lamps in a convenient manner while avoiding the obscuring and complicating effects in whole-lamp studies resulting from the reactions and mobility of electrode materials. In situ Raman analyses of deposits in the envelopes and ampoules, supported by an extensive database of the Raman spectra of lamp materials, and ex situ X-ray diffraction (XRD) analyses of refractory deposits to confirm independently the Raman assignments, have demonstrated that: (1) Sc metal reacts with envelope silica to produce Sc2O3 and elemental Si; (2) Sc metal in the presence of ScI3 reacts with the envelope silica to produce Sc2Si2O7; and (3) Sc metal reacts with envelope silica in the presence of NaI alone to produce Sc2O3 and not Sc2Si2O7. The results confirm and extend previous studies and demonstrate the value of Raman microscopy as a nondestructive investigative tool for lamp chemistry.
Raman Spectroscopy of Redox Activity in Cathodically Electrodeposited Nickel Hexacyanoferrate Thin Films
Authors: Steen William A. , Jeerage Kavita M. , Schwartz Daniel T.
Published: October 2003

The intercalation of cations into electrodeposited nickel hexacyanoferrate (NiHCF) depends on the stoichiometry and oxidation state of the material. To better understand this material's performance as a cation separation matrix, the oxidation state needs to be measured independently from the stoichiometry, regardless of the particular intercalated cation. Reported is the use of Raman spectroscopy to quantify the absolute oxidation state of NiHCF thin films. Raman spectroscopy probes NiHCF's cyanide bonds, which are sensitive to the oxidation state of the matrix. The oxidation state is controlled via potentiostatic experiments in electrolytes containing Na+, K+, and Cs+ (NO3− is the common anion). Principal component analysis (PCA) on the Raman spectra shows that more than 90% of the spectral variance is captured by one principal component, with a score value shown to be directly related to the oxidation state of the film. A universal, predictive regression model was developed using these score values as the dependent variables and Raman spectra as the independent variables. The results were confirmed with electrochemistry and energy dispersive X-ray spectroscopy.
Human Tooth Enamel: A Raman Polarized Approach
Authors: Leroy G. , Penel G. , Leroy N. , Brès E.
Published: October 2003

Despite numerous studies of human biominerals, some problems still remain concerning the relationship between their composition and their structure. For a better understanding of this problem, full spectra of the internal vibrations of human tooth enamel crystallites were obtained through polarized Raman microspectrometry and these are published for the first time. The micro-Raman technique is nondestructive and enables micrometric-scale examination of all the samples with a minimum of artifacts. The spectra show some variation from the predicted bands and many similarities with fluorapatite spectra. The mineral part of enamel is initiated in an organic environment and contains carbonate ions. Despite the carbonation, the crystal structure is preserved. Based on these results, a new description of the structure of apatite crystal is proposed. A box of Ca2+ ions surrounds and isolates the PO43– ions from one another, decreasing the influence of substitutions.
Effect of Hydrogen Peroxide Bleaching on Bone Mineral/Matrix Ratio
Authors: Chen T.-C. , Shea D. A. , Morris M. D.
Published: October 2003

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.
Determination of the Complex Refractive Index of Materials via Infrared Measurements
Authors: Varsamis Christos-Platon E.
Published: October 2003

In this work, methods are presented for obtaining the real, n, and imaginary, k, parts of the complex refractive index of materials considered as semi-infinite and finite from infrared reflectance, R( ν), and/or transmittance, T( ν), spectra. In semi-infinite samples, with negligible T( ν), only R( ν) is measured, and n and k can derive from the Kramers–Kronig (K–K) transformation or the modeling of the dielectric function of the material. In finite samples, the interference fringes due to multiple internal reflections can significantly alter the measured spectra. It was demonstrated that whenever the period of the fringes is on the order of a few cm−1, n and k can be equivalently obtained by the extended K–K analysis for T( ν) spectra, the modeling of the dielectric function, and the inversion of low-resolution R( ν) and T( ν) spectra, as well as the acquisition of a single high-resolution R( ν) or T( ν) spectrum. Otherwise, n and k can be calculated by modeling the dielectric function of the material once the optical effects are carefully removed. These methods were applied in infrared measurements of crystalline Si wafer and of glassy 0.20AgI·0.80[Ag2O·2B2O3].
Raman Spectroscopic Analysis of Paper Coatings
Authors: He Pei , Bitla Shivashanker , Bousfield Doug , Tripp Carl P.
Published: October 2003

An overview of the use of Raman spectroscopy for compositional mapping of paper coatings is presented. Raman spectroscopy is able to give the spatial distribution of pigments and binders in coated papers containing kaolin, anatase, and styrene butadiene (SB). Moreover, there are subtle differences in the Raman spectra of two forms of calcite, ground (GCC) and precipitated calcium carbonate (PCC), and these differences can be used to monitor the spatial distribution of coatings containing mixtures of PCC and GCC. Surface compositional mapping is relatively straightforward and is demonstrated with measurements of SB/CaCO3 ratios in mottled regions in printed coatings and the measurement of the same pigment/binder ratio in both thin and thick coated regions. For depth profiling, microtome methods are preferred, whereas the data obtained using confocal-based methods do not work.
Raman Images of Stress and Structural Variations in Laser-Annealed Polysilicon
Authors: Gardiner Derek J. , Parr Andrea A.
Published: October 2003

Stress and structural variations in laser-annealed polysilicon have been investigated using Raman microscopy. Stress images derived from Raman shift and bandwidth data at sub-micrometer resolution have been generated for samples with and without phosphorous implantation as a function of anneal laser fluence. Large variations in stress leading to cracking and delamination were observed for the P-implanted samples, which were essentially absent in the unimplanted samples.
Raman Microspectroscopy of Normal Erythrocytes and Plasmodium Berghei -Infected Erythrocytes
Authors: Ong C. W. , Shen Z. X. , Ang K. K. H. , Kara U. A. K. , Tang S. H.
Published: October 2003

Raman spectroscopy was applied to study β-haematin, normal erythrocytes, parasite-infected erythrocytes, and lysed samples of the parasite-infected erythrocytes. Differences were observed between spectra excited by the Ar+ laser and those excited by the HeNe laser. The significant difference lies in the fact that with the HeNe laser excitation at 632.8 nm, band absorption is a result of the charge transfer, while laser excitation in Qv-absorption bands of the active site of the haem1 occurs for the Ar+ laser. Similarity in the spectra of β-haematin and parasite-infected erythrocyte was observed with the HeNe laser. The differences between the normal erythrocyte and the parasite-infected erythrocyte may still be distinguished by the band at 754 cm−1 for the parasite-infected erythrocyte. In addition, with the HeNe laser, the band at 1080 cm−1 may also be used as a reference to whether the erythrocyte has been infected.