bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman spectroscopy of II–VI semiconductor nanostructures: CdS quantum dots
Authors: Schreder B. , Dem C. , Schmitt M. , Materny A. , Kiefer W. , Winkler U. , Umbach E. 
Published: February 2003

AbstractInformation about confinement effects and dot–matrix interactions of CdS nanoparticles was obtained from resonance Raman spectroscopy. The quantum dots had diameters of 3 and 5 nm and were prepared with and without organic spacer groups. It was found that the spacer improves the quality of the nanocrystallites. No phonon confinement shift could be observed even for the small quantum dots. The linewidths of the overtone series point to a mechanism of vibrational relaxation which is dominated by the decay of the LO phonons into acoustic phonons. Copyright © 2003 John Wiley & Sons, Ltd.
Spectral investigations on 2‐methyl‐1,4‐naphthoquinone: solvent effects, host–guest interactions and SERS
Authors: Umadevi M. , Ramasubbu A. , Vanelle P. , Ramakrishnan V. 
Published: February 2003

AbstractOptical absorption and fluorescence emission spectroscopic techniques were employed to investigate the solvent effects on 2‐methyl‐1,4‐naphthoquinone (2‐mNQ) and the molecular recognition of 2‐mNQ in calix(8)arene. The orientation of 2‐mNQ on a silver surface was analysed by SERS. The optical absorption and fluorescence emission spectra of 2‐mNQ in different solvents reveal the n → π* transition and the observed features show that the singlet excited state is more stabilized in polar protic solvents by intermolecular hydrogen bonding and in polar aprotic solvents by dipole–dipole interaction. The evidence for the formation of inclusion complexes of calix(8)arene with 2‐mNQ in dichloromethane was obtained by optical absorption and fluorescence emission studies. From the observations, the existence of association of molecules is proposed and the association constant is evaluated. The orientation of 2‐mNQ on a silver surface was studied by SERS measurements, and was found to be ‘flat‐on.’ Copyright © 2003 John Wiley & Sons, Ltd.
Hyper‐spectral Raman imaging using a diffractive optical element
Authors: Thomson G. A. , Thorley F. C. , Batchelder D. N. 
Published: February 2003

AbstractA modification to a conventional imaging Raman microscope to allow the acquisition of quasi‐confocal spectra from multiple discrete Raman sampling volumes is reported. Preliminary performance was demonstrated by generating an extended area hyper‐spectral chemical map of a number of ground sulfur crystals deposited on an aluminium mirror. Images generated using this multiplexed sampling arrangement were found to contain a number of weak ghost images (cross‐talk), corresponding to inadequate separation of the focused laser spots at the sample. Copyright © 2003 John Wiley & Sons, Ltd.
Lattice dynamics and temperature dependence of the first‐order Raman spectra for α‐SiO2 crystals
Authors: Ichikawa Shinya , Suda Jun , Sato Tsutomu , Suzuki Yushi 
Published: February 2003

AbstractThe phonon dispersion curves for α‐SiO2 crystals were calculated on the basis of a rigid‐ion model. The first‐order Raman spectra of the A1 mode of the α‐SiO2 crystal were measured in the temperature range from 303.1 to 773.1 K. The temperature dependence of the linewidth was analyzed by using the phonon dispersion curves, and the results showed that it was caused approximately by the cubic anharmonic term in the crystal potential energy. The temperature dependence of the frequency shift of the A1 mode was analyzed by using the lattice dynamic perturbative treatment. We found that the quartic anharmonic term of the first‐order perturbation and also the cubic term of the second‐order perturbation contribute to the temperature dependence of the frequency shift of the A1 mode in the α‐SiO2 crystal. Copyright © 2003 John Wiley & Sons, Ltd.
High‐pressure Raman scattering study of the A1 mode of CuInS2
Authors: Pinnick D. A. , Lee S. A. 
Published: February 2003

AbstractRaman spectroscopy was used to measure the wavenumber of the A1 mode of CuInS2 as a function of hydrostatic pressure up to about 5 GPa. This mode was found to have a linear pressure dependence of 5.17 ± 0.12 cm−1 GPa−1. The Grüneisen parameter for this mode was determined as 1.33. Copyright © 2003 John Wiley & Sons, Ltd.
Raman spectroscopic study of the basic copper sulphates—implications for copper corrosion and ‘bronze disease’
Authors: Martens Wayde , Frost Ray L. , Kloprogge J. Theo , Williams Peter A. 
Published: February 2003

AbstractThe basic copper sulphates are of interest because of their appearance in many environmental situations such as copper pipe corrosion, restoration of brass and bronze objects, leaching from waste mineral dumps and the restoration of frescoes. The Raman spectra of the basic copper sulphate minerals antlerite, brochantite, posnjakite and langite are reported using a diode laser operating at an excitation wavelength of 785 nm. In line with their crystal structures, each basic copper sulphate mineral has its own characteristic Raman spectrum, which allows their identification. Except for brochantite, multiple bands are observed for the SO stretching vibration. Similarly, multiple bands are observed for the antisymmetric SO and OSO bending regions. Hydroxyl deformation modes in the 730–790 cm−1 region are observed. The use of an He–Ne laser operating at an excitation wavelength of 633 nm allowed the hydroxyl stretching bands of the minerals to be obtained. Antlerite and brochantite are characterized by hydroxyl stretching bands at 3580 and 3488 cm−1. The minerals posnjakite and langite display Raman hydroxyl stretching vibrations at 3588 and 3564 cm−1. The Raman spectra of these two minerals show water OH stretching bands at 3405, 3372 and 3260 cm−1. Raman spectroscopy allows the ready identification of these minerals. Copyright © 2003 John Wiley & Sons, Ltd.
Study of ordered nano‐regions in Pb(Zn1/3Nb2/3)0.915Ti0.085O3 single crystal using Raman spectroscopy
Authors: Dobal P. S. , Katiyar R. S. , Tu C.‐S. 
Published: February 2003

AbstractA Raman spectroscopic study was performed on a Pb(Zn1/3Nb2/3)0.915Ti0.085O3 crystal to study the ordered nano‐regions. The variation of the Raman spectra with temperature in the range from −200 to 1000°C clearly exhibited a rhombohedral–tetragonal transition at about 75°C followed by a tetragonal–cubic transition at about 175°C. The polarization behavior of the 777 cm−1 octahedral mode suggested the existence of Fm3m nano‐ordered regions in Pm3m cubic symmetry. Thermal switching of nano‐region polarization was observed above 388°C as the thermal energy became greater than the activation energy of nano‐clusters and resulted in a decrease in the polarized intensity of the 777 cm−1 mode. However, both the 51 and 777 cm−1 modes were observed up to 1000°C. Copyright © 2003 John Wiley & Sons, Ltd.
Fourier transform Raman spectroscopic data on the fossil resin siegburgite
Authors: Winkler Waltraud , Musso Maurizio , Kirchner Elisabeth Ch. 
Published: February 2003

AbstractThe fossil resin siegburgite is known from two localities in Europe: Siegburg, near Bonn, and the ‘Goitsche,’ near Bitterfeld, both in Germany. Raman spectroscopic data on the material proved the polystyrene character of siegburgite and therefore supported the chemical investigations conducted previously. Cinnamic acid, which was identified as a major constituent in recent resins of Liquidambar ssp. (Hamamelidaceae), was included as a standard pointing towards the origin of siegburgite in the Hamamelidaceae. The rapid and non‐destructive method used permits a quick distinction of fossil resins, especially when different resin types occur together in the same deposit, as in Bitterfeld. Copyright © 2003 John Wiley & Sons, Ltd.
Combination of GC‐MS with local resolution for determining volatile components in si‐wu decoction
Authors: Gong Fan , Liang Yi‐Zeng , Chau Foo‐Tim 
Published: February 2003

AbstractIn this paper, the combination of gas chromatography‐mass spectrometry with chemometric local resolution techniques such as subwindow factor analysis (SFA) and orthogonal projection resolution (OPR) is investigated as a method of determining volatile components present in a traditional Chinese medicinal formulation known as si‐wu decoction and its two individual herbs Rhizoma chuanxiong and Radix angelicae sinensis. In order to validate the reliability of the results obtained, the volatile components of interest were further separated on open glass columns and then analyzed in the same way as above. With the help of SFA and OPR approaches, the purity of chromatographic peaks can first be identified. Then, the pure chromatogram and mass spectrum of each component involved in a target peak cluster can be easily resolved and subsequently subjected to similarity searches in the NIST MS database to qualitatively and quantitatively determine the volatile components. Our results showed that about 127, 80, and 97 chemical components could be separated and 81, 49, and 55 of them identified, representing 83.95%, 91.86%, and 85.11% of the total relative content of volatile components from Rhizoma chuanxiong, Radix angelicae sinensis, and si‐wu decoction, respectively. The results obtained in this work strongly indicate that the combination of GC‐MS with chemometric local resolution methods could greatly improve the chromatographic separation ability by means of mathematical approaches. Moreover, they indicated the reliability and practicability of this combined technique.
Comparison of micellar electrokinetic chromatography and microemulsion electrokinetic chromatography for separation of pharmacologically active xanthones from Securidaca inappendiculata
Authors: Bo Tao , Yang Xuedong , Li Ke An , Xu Lizhen , Liu Huwei 
Published: February 2003

AbstractMicellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC) have been investigated for the separation of nine xanthones from Securidaca inappendiculata, based on the systematic optimization of such parameters as pH, concentration of borate buffer, and sodium dodecyl sulfate (SDS) concentration. The study indicated that, in MEKC, although the addition of modifiers including organic solvents and cyclodextrins (CDs) could greatly affect the separation selectivity of xanthones, the baseline separation for nine xanthones could not be completed. As a special variant of electrokinetic chromatography (EKC), MEEKC successfully achieved the baseline separation of nine xanthones with satisfactory repeatability. Compared with MEKC, MEEKC showed better separation selectivity and higher separation efficiency.
Forensic analysis of hair surface components using off‐line supercritical fluid extraction and large volume injection
Authors: Goodpaster John V. , Bishop Jeremiah J. , Benner Bruce A. 
Published: February 2003

AbstractThe analysis of organic material on the surface of human hair may indicate various subject characteristics such as age, race, gender, or the use of hair products. In addition, comparisons of hair chemical composition may be used to assess the potential for a common origin between a known and unknown sample. However, evidentiary hair samples are often extremely small, necessitating highly sensitive extraction and analysis techniques. In this communication, off‐line supercritical fluid extraction (SFE) followed by gas chromatography/mass spectrometry (GC/MS) using large volume injection (LVI) is demonstrated as a potential method for extracting and analyzing hair surface components. The retention gap technique was used to achieve large volume injections, allowing up to 30 μL of the off‐line extracts to be analyzed. Subsequent chemical analysis by GC/MS identified various natural components on the hair surface such as saturated and unsaturated free fatty acids, squalene, and cholesterol. Overall, off‐line SFE was quite efficient, allowing the measurement of surface components of sample amounts ranging from 0.22 mg to 0.24 mg. In addition, derivatization of free fatty acids using a silylating agent increased both chromatographic resolution and sensitivity. Results from two hair samples are discussed to demonstrate the technique.
Synthesis and characteristics of composite chiral stationary phases based on cellulose derivatives
Authors: Chen Xiaoming , Zou Hanfa , Ni Jianyi , Feng Shun 
Published: February 2003

AbstractComposite chiral stationary phases (CSPs) were prepared on the basis of cellulose derivatives coated or bonded onto silica. “Molecular exterior” type CSPs were prepared by mixing together two different cellulose tris‐derivatives before or after being coated or bonded onto silica, and the “molecular interior” type was obtained by synthesizing non‐regioselectively heterosubstituted cellulose derivatives coated or bonded onto silica. For the sake of comparison, the individual phases were also prepared with corresponding cellulose derivatives by coating or bonding approaches, respectively. All of the prepared CSPs were characterized and their chiral recognition properties were evaluated by HPLC with several test racemates. The experimental results demonstrated that the “molecular exterior” CSPs generally exhibit chiral recognition capacities intermediate between those of the two individual phases. However, in the separation of some racemates higher enantioselectivity may be achieved on the “molecular interior” phases than on individual phases, thus broadening the application range of a single cellulose‐based CSP.
Separation of basic central nervous system drugs by capillary electrochromatography
Authors: Jiskra Jan , Claessens Henk A. , Cramers Carel A. 
Published: February 2003

AbstractThis article describes the sample preparation and separation of three strongly basic central nervous system (CNS) drugs by capillary electrochromatography. The separation was developed on Hypersil C8 MOS and Hypersil Phenyl stationary phases using acetonitrile (ACN) as organic modifier together with mobile phase additives, ammonia, ethylenediamine, or 1,3‐diaminopropane. A successful, fast separation after a simple derivatization procedure of the compound was achieved on the Hypersil Phenyl stationary phase using ethylenediamine as mobile phase additive. The general approach to method development for complex mixtures is discussed.
Analysis of chemical processes at single bovine adrenergic chromaffin cells with micellar electrokinetic capillary chromatography and electrochemical detection
Authors: Suljak Steven W. , Swanek Franklin D. , Gavin Peter F. , Ewing Andrew G. 
Published: February 2003

AbstractMicellar electrokinetic capillary chromatography with electrochemical detection (MEKC‐EC) has been applied to the investigation of single cell systems. Separations of bovine adrenergic chromaffin cells reveal average contents of 33 ± 14 fmol of norepinephrine and 24 ± 11 fmol of epinephrine. The resolution benefits of MEKC‐EC have been more fully realized in the analysis of a complex mixture resulting when adrenal cells are incubated with the dopamine precursor, L‐dihydroxyphenylalanine (L‐DOPA). Dopamine has been unambiguously identified in these cells, supporting the hypothesis that transport of dopamine into vesicles is a slow, rate‐limiting process. In addition, MEKC‐EC has been used to monitor the release of catecholamines from single adrenal cells when stimulated by nicotine. Low‐fmol quantities of norepinephrine and epinephrine have been detected in the extracellular environment following stimulation.
Marfey's reagent: Past, present, and future uses of 1‐fluoro‐2,4‐dinitrophenyl‐5‐L‐alanine amide
Authors: B'Hymer Clayton , Montes‐Bayon Maria , Caruso Joseph A. 
Published: February 2003

AbstractThis article describes some of the uses of Marfey's reagent, 1‐fluoro‐2,4‐dinitrophenyl‐5‐L‐alanine amide (FDAA), a pre‐column derivatizing reagent for the separation of enantiomeric isomers of amino acids and amine compounds. An introduction to the basic implementation of this reagent and its historical development are presented. Actual uses in amino acid, short peptide, and pharmaceutical compounds are included, as well as the advantages and disadvantages over other pre‐column derivatization techniques and direct chromatographic separations. Applications of current interest, including its use as an orthogonal analysis and in enantiomeric purity analysis of selenoamino acids using element specific detection, are also discussed.
Determination of phthalic monoesters in aqueous and urine samples by solid‐phase microextraction–diazomethane on‐fibre derivatization–gas chromatography–mass spectrometry
Authors: Alzaga Roberto , Peña Araceli , Bayona Josep María 
Published: February 2003

AbstractA solvent‐free analytical methodology for the determination of phthalic monoesters (MPs) with diazomethane on‐fibre derivatization using solid‐phase microextraction–gas chromatography–mass spectrometry (SPME–DOFD–GC–MS) was developed. Among the different SPME fibres evaluated, the polydimethylsiloxane/divinylbenzene (PDMS/DVB) proved to be the most suitable for the determination of four MPs. The diazomethane on‐fibre derivatization (DOFD) procedure was improved, avoiding diethyl ether as solvent. Equilibrium conditions were reached (15 min) and K′MP values were calculated. Under optimum MP extraction conditions (e. g. direct immersion, 4 mL of sample, 25°C extraction temperature, stirring at 1 100 rpm, 20 min extraction time, 10 min derivatization reaction, and pH = 1.5), trace level concentrations of MPs (0.3–8.6 ng/mL) were detected, allowing the simultaneous determination of phthalic diesters (DPs). The overall SPME–GC–MS precision was improved by using four deuterated internal standards. The developed analytical methodology was applied to different environmental water matrices and human urine samples at MP concentrations ranging from 0.1–538 ng/mL. The developed analytical procedure is robust (50 analyses with the same fibre), rapid (40 min), and of low cost, improving the conventional analysis methods in terms of analysis time, background levels, and cost.
Evaluation of corrosion resistance of two engineering alloys in molten salts by electrochemical techniques
Authors: Martínez‐Villafañe A. , Almeraya‐Calderón F. , Gaona‐Tiburcio C. , Chacón‐Nava J. , González‐Rodríguez G. 
Published: February 2003

AbstractThe electrochemical behaviour of two steels typically used in power boilers has been studied in the temperature range from 540°C to 680°C. Two environments were used: a) a synthetic salt mixture of 80% V2O5 − 20% Na2SO4 and b) oil ash collected from a high temperature reheater. Corrosion rates obtained from electrochemical potentiodynamic polarisation curves (Tafel extrapolation) were compared for both steels exposed in each environment. The results showed that increases in temperature resulted in higher corrosion rates, being this effect most notorious above about 620°C. In the synthetic salt, and at temperatures up to about 580°C, both steels showed similar behaviour. With further increases in temperature, the T22 steel was less resistant and, at the highest temperature used here, its corrosion rate was almost seven times higher than that measured for the 347H steel. The results obtained with the natural oil ash for the T22 steel showed a dramatic increase in corrosion rate as temperature goes up over the range used. For the 347H steel, and up to about 580°C, the corrosion rates were similar to those obtained with the synthetic salt. Above 580°C, the corrosion rate measured increased slightly with temperature, being at 680°C about 2.5 times higher than that found by using the synthetic salt. Therefore, an important difference in corrosion rates has been found depending upon the corrosive salt used. This is an important result because imply that, at least for materials used in fossil power plants, more realistic data can be obtained by using natural ashes in the experimental work.
Interactions between polysulphides and stainless steel materials
Authors: Rämö J. , Sillanpää M. , Hyökyvirta O. 
Published: February 2003

AbstractAbility of polysulphide to enhance the potential of digester materials (S30400, S31603, S32205, S32304) was studied in the impregnation stage of the pulping process. Polysulphides were generated by adding elemental sulphur to alkaline sulphide solutions. Polysulphide levels 0.3–0.48, 1.25–2, 5–8 and 12.5–20 g/l enhanced the potentials of the steels by 70, 90, 170 and 190 mV, respectively. The polysulphide concentrations were calculated values, because concentrations of polysulphides are very difficult to measure in kraft liquors. No weight changes were observed, but slight accumulation of sulphur onto surfaces, particularly onto S31603 was seen in X‐ray fluorescence analysis. Otherwise, differences in behaviour among the steel materials were minimal.
Praxisnaher Nachweis zur Wirksamkeit von VCI‐Korrosionsschutzmitteln an flächigen Proben –Prüfverfahren nach BFSV –
Authors: Eschke K. R. , Petzoldt J. , Tiedemann S. 
Published: February 2003

AbstractIm Bereich des temporären Korrosionsschutzes metallischer Halbfabrikate hat sich die VCI‐Methode (VCI‐Volatile Corrosion Inhibitor) erfolgreich am Markt etabliert. Die Wirksamkeit der VCI's wurde bisher durch Laborprüfungen (Liefernormen) nachgewiesen, die nur in geringem Maße die Praxisbelastungen wiederspiegelten.Die Reproduzierbarkeit der Ergebnisse war bisher ebenfalls eingeschränkt. Im Institut für BFSV an der Hochschule für Angewandte Wissenschaften Hamburg (Hamburg University of Applied Sciences) wurde im Rahmen des AIF‐Projektes 12115 (gefördert vom BMWI) ein Prüfverfahren mit einer hohen Korrelation zu den Metalloberflächen in der Praxis und einer guten Reproduzierbarkeit der Prüfergebnisse entwickelt und nachgewiesen.Zusätzlich wurden Vorgehensweisen zur Ermittlung von realen klimatischen Belastungsprofilen und für ein objektives Beurteilungsverfahren zur Korrosionsgradbestimmung aufgezeigt.
Corrosion behaviour of magnesium sacrificial anodes in tap water
Authors: Andrei M. , di Gabriele F. , Bonora P. L. , Scantlebury D. 
Published: February 2003

AbstractThe effects of applied current, testing time and microstructure on the electrochemical properties of magnesium‐based sacrificial anodes in potable water were evaluated. Galvanostatic tests, potentiodynamic polarisation and scanning electron microscopy (SEM) analyses were used to determine anode efficiency, corrosion rate and microstructures of the Mg‐anodes under study. The contribution of processes as mechanical material loss and hydrogen evolution on the current wastage was investigated. The effect of the different microstructures like those obtained by heat treatments to reduce the intermetallic phase was also tested.
A 13C NMR Study of the Products and Mechanism of the Thermal Oxidative Degradation of Poly(ethylene oxide)
Authors: Mkhatresh Omar A. , Heatley Frank 
Published: February 2003

AbstractThe products and mechanism of the thermal oxidative degradation of poly(ethylene oxide) at 150 °C have been analysed using 13C NMR spectroscopy. The analysis was assisted by the use of distortionless enhancement by polarisation transfer spectra, longitudinal relaxation time measurements, long‐range 13C1H coupling and chemical shift simulation software. The major result of degradation was chain scission resulting in two formate ester chain ends. Minor products were in‐chain esters, peroxy groups, oxymethylene links and hydroxy and methoxy chain ends.
Initial steps for the mechanism of chain scission.magnified imageInitial steps for the mechanism of chain scission.