bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Representative Layer Theory to Near-Infrared Reflectance Spectra of Powdered Samples
Authors: Cairós Carlos , Coello Jordi , Maspoch Santiago
Published: October 2009

The diffuse reflectance near-infrared (NIR) spectrum of a powdered sample includes the contribution of specular and diffuse reflectance, which is a function of absorbance and scattering. The fraction of light scattered depends in a complex manner on the physical properties of the sample such as particle size, refraction index, etc. Several theories to study the dependence of NIR spectra on the particle size have been proposed. The best known is the Kubelka–Munk model, an approach based on continuous mathematics. Recently Dahm and Dahm put forward an alternative method, the representative layer theory (RLT), which uses discontinuous mathematics as a basis. This approach can be used to identify and disentangle the scattering and absorbance signals as well as their dependence on the particle size. The scattering and absorption coefficient of NaCl (a nonabsorbing material) and of potassium hydrogen phthalate, KHP (a strong absorber), have been estimated through the application of the representative layer theory, working on a particle size range from 63 to 450 μm. In both samples, the absorption coefficient of the sample (K) remains constant and practically independent of the particle size, while the scattering coefficient of the sample (S) decreases when the particle diameter increases, becoming stable around a diameter of 250 μm.
High Axial Resolution Raman Probe Made of a Single Hollow Optical Fiber
Authors: Katagiri Takashi , Yamamoto Yuko S. , Ozaki Yukihiro , Matsuura Yuji , Sato Hidetoshi
Published: October 2009

A ball lens mounted hollow optical fiber Raman probe (BHRP) consisting of a single hollow optical fiber (HOF) and a micro-ball lens was developed for performing a high axial resolution and high-sensitivity remote Raman analysis of biomedical tissues. The total diameter of the probe head is 640 μm. The BHRP is useful in the measurement of thin-layered tissues that are in contact with the probe's surface because the probe has a limited depth-of-field optical property. An optical calculation study suggested that it is possible to vary the probe's working distance by selecting different materials and diameters for the ball lens. Empirical studies revealed that this probe has a higher axial resolution and a higher sensitivity than an HOF Raman probe without the ball lens. The spectrum of a mouse stomach measured with the BHRP had better quality and considerably lower noise than that measured with a conventional Raman microscope. These results strongly suggest that the BHRP can be used effectively in biomedical applications.
Evaluation of Transmission and Reflection Modalities for Measuring Content Uniformity of Pharmaceutical Tablets with Near-Infrared Spectroscopy
Authors: Xiang Dong , LoBrutto Rosario , Cheney James , Wabuyele Busolo Wa , Berry Joseph , Lyon Robbe , Wu Huiquan , Khan Mansoor A. , Hussain Ajaz S.
Published: October 2009

This paper examines how one may assess spectral changes with instrument configuration (or composition), in combination with the spectral changes in the measurement that are caused by experimental effects, and subsequently select an appropriate measurement modality for tablet content uniformity determination with near-infrared (NIR) spectroscopy. Two NIR spectrometers furnished with three configurations in the sample measurement interface were evaluated. One spectrometer, Bruker MPA (multiple purpose analyzer), was equipped with two measurement modalities, diffuse transmission (DT) and diffuse reflection based on integrating sphere optics (DR/IS). The other spectrometer, Bruker StepOne, was equipped only with diffuse reflection mode based on a fiber-optic probe (DR/FO). The data were collected with each of the configurations for the tablets associated with two dosage strengths differing significantly in diameter and thickness. Spectral diagnosis was performed in terms of sensitivity and selectivity. The signal-to-noise ratio computed for the data collected with the DT and DR/IS spectrometers was approximately an order of magnitude greater than that computed for the DR/FO spectrometer. The net-analyte-signal-based selectivity analysis of NIR spectra associated with the sample tablet and the placebo tablet indicated that both transmission and reflection mode provided similar selectivity when the optimal spectral range was chosen. A partial least squares (PLS) calibration model was developed for each data set. The overall standard error of calibration for each DT and DR/IS measurement was approximately 0.3% in weight for each strength, significantly better than the value of 1.0% in weight produced by the DR/FO measurement. This result was consistent with the sensitivity analysis based on spectral noise characterization. The poor analytical performance of the DR/FO spectrometer was attributed to the small illumination spot size of the reflection probe and thus the sensitivity of the measurements to the tablet engraving. The PLS analysis and spectral diagnostics both showed that transmission and reflection modes based on the Bruker MPA provided similar measurement accuracy for each strength. However, the robustness study clearly revealed that the transmission mode would be more robust than the reflection mode when there is considerable variability in the chemical composition and physical properties of tablets.
Classification of Select Category A and B Bacteria by Fourier Transform Infrared Spectroscopy
Authors: Samuels Alan C. , Snyder A. Peter , Emge Darren K. , St. Amant Diane , Minter Jennifer , Campbell Mark , Tripathi Ashish
Published: October 2009

Fourier transform infrared (FT-IR) spectroscopy historically is a powerful tool for the taxonomic classification of bacteria by genus, species, and strain when they are grown under carefully controlled conditions. Relatively few reports have investigated the determination and classification of pathogens such as the National Institute of Allergy and Infectious Diseases (NIAID) Category A Bacillus anthracis spores and cells (BA), Yersinia species, Francisella tularensis (FT), and Category B Brucella species from FT-IR spectra. We investigated the multivariate statistics classification ability of the FT-IR spectra of viable pathogenic and nonpathogenic NIAID Category A and B bacteria. The impact of different growth media, growth time and temperature, rolling circle filter of the data, and wavelength range were investigated for their microorganism differentiation capability. Viability of the bacteria was confirmed by agar plate growth after the FT-IR experimental procedures were performed. Principal component analysis (PCA) was reduced to maps of two PC vectors in order to distill the FT-IR spectral features into manageable, visual presentations. The PCA results of the strains of BA, FT, Brucella, and Yersinia spectra from conditions of varying growth media and culture time were readily separable in two-dimensional (2D) PC plots. FT spectra were separated from those of the three other genera. The BA pathogenic spore strains 1029, LA1, and Ames were clearly differentiated from the rest of the dataset. Yersinia rhodei, Y. enterocolitica, and Y. pestis species were distinctly separated from the remaining dataset and could also be classified by growth media. Different growth media produced distinct subsets in the FT, BA, and Yersinia spp. regions in the 2D PC plots. Various 2D PC plots provided differential degrees of separation with respect to the four viable bacterial genera including the BA sub-categories of pathogenic spores, vegetative cells, and nonpathogenic vegetative cells. This work provided evidence that FT-IR spectroscopy can indeed separate the four major pathogenic bacterial genera of NIAID Category A and B biological threat agents including details according to the growth conditions and statistical parameters.
A Method for Source Apportionment of Lead in Fine Particulate Matter Based on Individual Particle Analysis Using a Synchrotron X-ray Fluorescence Microprobe
Authors: Li Xiaolin , Zhang Guilin , Li Yan
Published: October 2009

A source apportionment method based on individual particle analysis carried out using a synchrotron X-ray fluorescence microprobe was developed for source apportionment of lead in fine particulate matter. Mass contributions of every emission source were obtained by intensity ratios of the characteristic X-ray spectrum of lead in individual airborne particles. The validity of the method was evaluated. The uncertainty of the source apportionment was estimated, which was within 10% in this work. The method was applied to the apportionment of lead in fine airborne particles of Shanghai, indicating that the method has a finer performance for source apportionment.
Spectroscopic Investigation of Polystyrene Surface Grafting on Natural Rubber
Authors: Prakanrat Supinya , Phinyocheep Pranee , Daniel Philippe
Published: October 2009

This paper investigates the structural characteristics of polystyrene (PS) grafted on a natural rubber (NR) surface using Raman scattering spectroscopy. The nitroxide-mediated radical polymerization (NMRP) technique was used to achieve the graft copolymerization of PS onto the surface of NR film using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a nitroxide mediator. The reversible reaction between propagating radical and TEMPO of the NMRP process leads to a controlled radical polymerization of styrene on the NR surface. The grafting degree of PS on the NR was first measured by gravimetric methods. It was found to depend linearly on the grafting time. The characteristic signals detected by Raman scattering and by attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy provide clear evidence of the PS being grafted onto the NR. The distribution of the grafted PS on the NR substrate was determined from the Raman mapping. It is seen that the grafting occurs homogeneously over the entire surface (∼40 mole % PS). The study using the Raman depth profiling technique on the original sample compared with the analysis carried out on the sample prepared by cross-sectioning led to important and comparable information regarding the uniform distribution of PS grafting inside the substrate.
Two-Dimensional Raman Correlation Spectroscopy Study of an Emulsion Copolymerization Reaction Process
Authors: Noda Isao , Allen William M. , Lindberg Seth E.
Published: October 2009

The emulsion copolymerization of styrene and 1,3-butadiene using an oligomeric nonionic surfactant as an emulsifier to make a styrene–butadiene rubber (SBR) copolymer latex was monitored by real-time in situ Raman spectroscopy. Time-resolved Raman spectra collected during the early stage of the polymerization reaction were subjected to a series of data analysis techniques, including two-dimensional (2D) correlation spectroscopy, multivariate self-modeling curve resolution (SMCR), and kernel analysis, to elucidate the fine details of the complex reaction process. Generalized 2D correlation analysis of time-resolved Raman spectra readily identified the characteristic Raman scattering bands for the monomers and copolymer. Cross-peaks appearing in 2D Raman correlation spectra showed that the decrease in the spectral intensity of Raman bands assignable to 1,3-butadiene occurs before the band intensity changes for styrene or SBR copolymer. The positions of asynchronous cross-peaks were used to identify a spectral region with the most distinct pattern of intensity variations, which in turn could be used as the starting point for the alternating least squares iteration of the SMCR analysis. SMCR analysis of the time-resolved Raman spectra generated a set of estimated pure component spectra and concentration profiles of styrene, 1,3-butadiene, and SBR copolymer without requiring independently measured calibration data. The estimated concentration profiles of monomers and copolymer indicated that the reaction of 1,3-butadiene started before the consumption of styrene and production of SBR copolymer. Kernel analysis of the estimated concentration profiles provided a succinct measure of the similarity and dissimilarity of the concentration changes of monomers and copolymer.
Surface Treatment Analyses of Car Bearings by Using Laser-Induced Breakdown Spectroscopy
Authors: Alvira F. C. , Orzi D. J. O. , Bilmes G. M.
Published: October 2009

Determination of surface coating composition is a problem of great importance for industry and production related to the quality control of products and processes. One of the most outstanding aspects of laser-induced breakdown spectroscopy (LIBS) is its unique ability to carry out real-time depth profile analysis. This allows, for instance, the identification of layered coatings composition. In this work we performed depth profile analysis using LIBS to determine the composition of layered surface treatments of car bearings. Laser ablation thresholds for each coating layer were determined by acoustic measurements. Transitions between the different coating layers were also identified by an acoustic method. We developed faster and simpler semi-quantitative procedures to determine the relative composition of alloy surface coatings of car bearings as well as the possibility to characterize in real time these treatments.
An Insight into Sequential Order in Two-Dimensional Correlation Spectroscopy
Authors: Jia Qi , Wang Nan-Nan , Yu Zhi-Wu
Published: October 2009

Determination of the sequential order of events is a very important feature of generalized two-dimensional correlation spectroscopy (2D-COS). Recently, queries have been put forward on the actual effectiveness of this method when changes are non-periodic, particularly in the presence of local sequential order. Consequently, it brings an urgent necessity to understand the true connotation of the sequential order parameter derived from 2D-COS analysis. This article presents an attempt to address these questions based on the analysis of simulated spectra by assuming the band intensity changes in a logarithmic, exponential, hyperbolic, or polynomial manner. It is concluded that for two events changing monotonically and without local sequential orders, one event occurring prior to the other as determined using 2D-COS means in most cases that the former has both a shorter half-time and a greater half-intensity. As a rule of thumb, intensity versus the perturbation factor should be plotted before performing the 2D-COS analysis to determine the sequential order of the involved events. In the presence of obvious local sequential order, 2D-COS analysis is unnecessary. Otherwise, sequential order can be determined quite reliably based on 2D-COS analysis.
Mid-Infrared Trace Gas Analysis with Single-Pass Fourier Transform Infrared Hollow Waveguide Gas Sensors
Authors: Kim Seong-Soo , Menegazzo Nicola , Young Christina , Chan James , Carter Chance , Mizaikoff Boris
Published: October 2009

A hollow core optical fiber gas sensor has been developed in combination with a Fourier transform infrared (FT-IR) spectrometer operating in the spectral range of 4000–500 cm−1, enabling continuous detection of small volume gas-phase analytes such as CH4, CO2, C2H5Cl, or their mixtures at trace levels. Ag/Ag-halide hollow core optical fibers simultaneously serve as an optical waveguide for broad-band mid-infrared radiation and as a miniaturized absorption gas cell. Specifically, carbon dioxide, methane, and ethyl chloride as well as binary mixtures in a carrier gas were analyzed during exponential dilution experiments. In the studies reported here, the integration of an optical gas sensor with FT-IR spectroscopy provides excellent detection limits for small gas volumes (∼1.5 mL) of individual analytes at a few tens of parts per billion (ppb, vol/vol) for carbon dioxide and a few hundreds of ppb (vol/vol) for methane. Furthermore, the broad-band nature of the radiation source and of the hollow core optical waveguide provides the capability of multi-constituent analysis in mixtures.
Dispersion of Light and Heavy Pollutants in Urban Scale Models: CO2 Laser Photoacoustic Studies
Authors: Zelinger Z. , Střižík M. , Kubát P. , Civiš S. , Grigorová E. , Janečková R. , Zavila O. , Nevrlý V. , Herecova L. , Bailleux S. , Horka V. , Ferus M. , Skřínský J. , Kozubková M. , Drabková S. , Jaňour Z.
Published: October 2009

The distribution of pollutants in two urban scale models (point emission source and street canyon with extensive transport) was investigated by means of CO2 laser photoacoustic spectroscopy in the region of the atmospheric window (9–10 μm). The experimental results of physical modeling are in a good agreement with the numerical calculations performed in the frame of computational fluid dynamic (CFD) modeling. Methanol, ethanol, and ozone (examples of light pollutants), as well as sulfur hexafluoride and 1,2 dichlorethane (examples of heavy pollutants), were selected on the basis of their high resolution spectra acquired by Fourier transform and laser diode spectroscopy.
Nanostructural Silver and Gold Substrates for Surface-Enhanced Raman Spectroscopy Measurements Prepared by Galvanic Displacement on Germanium Disks
Authors: Brejna Przemysław R. , Griffiths Peter R. , Yang Jyisy
Published: October 2009

A germanium disk on which silver nanoparticles have been deposited by galvanic displacement is shown to be an inexpensive substrate for surface-enhanced Raman spectroscopy (SERS). The preparation, which is based on spontaneous reduction of silver cations at the surface of a germanium disk, is quick and requires nothing more than a Petri dish. The SERS enhancement of silver and gold substrates prepared in this way was measured using benzenethiol and was compared to enhancement of Klarite®, a commercially available gold-coated nanoengineered SERS substrate. The enhancement provided by electrolessly deposited metals was found to be superior over Klarite® and the reproducibility was generally below 15%. Furthermore, unlike the case for nanoengineered substrates, germanium disks can be polished and reused.
A New Experimental Setup for in Situ Infrared Reflection Absorption Spectroscopy Studies of Atmospheric Corrosion on Metal Surfaces considering the Influence of Ultraviolet Light
Authors: Wiesinger R. , Kleber Ch. , Frank J. , Schreiner M.
Published: October 2009

The knowledge available regarding the influence of ultraviolet (UV) light on the atmospheric corrosion of materials is very rudimentary. Therefore, a new experimental setup consisting of a cell for studying in situ reactions occurring at the metal/atmosphere interface by simultaneously applying infrared reflection absorption spectroscopy (IRRAS) and quartz crystal microbalance (QCM) measurements was designed and built. The cell presented consists of an acrylic glass body with a UV-light-transparent window mounted in such a way that the sample can be irradiated and weathered under controlled atmospheric conditions under a grazing angle of incidence of the IR beam. This new setup was tested by using a specimen of polycrystalline silver, where the growth of Ag2CO3 and AgOH as basic silver carbonate on the surface could be observed. The weathering tests were carried out in synthetic air containing 90% relative humidity (RH) and 250 ppm CO2, with and without UV light. The results obtained from the IRRAS spectra could be perfectly correlated with the in situ QCM data.
Analysis of Crystals Leading to Joint Arthropathies by Raman Spectroscopy: Comparison with Compensated Polarized Imaging
Authors: Cheng Xingguo , Haggins Donard G. , York Russel H. , Yeni Yener N. , Akkus Ozan
Published: October 2009

The current study assessed the feasibility of the application of Raman spectroscopy toward the diagnosis of gout and pseudogout. First, the lowest concentrations of monosodium urate monohydrate (MSUM) and calcium pyrophosphate dihydrate (CPPD) crystals detectable by Raman spectroscopy were investigated by mixing known amounts of synthetic crystals with synovial fluid in the concentration range of 1 to 100 μg/mL. Second, a digestion protocol was developed for clinical samples to improve crystal extraction. The ensuing centrifugation of the digest congregated crystals at a well-defined point and allowed for point-and-shoot Raman analysis without having to conduct an extensive search for individual crystals. Finally, synovial fluid samples obtained from patients ( n = 35) were cross-analyzed by polarized light microscopy (PLM) and the Raman method to compare and contrast the diagnoses of the two methods. It was found that Raman spectroscopy can detect MSUM and CPPD crystals with good sensitivity and specificity at concentrations as low as 5 μg/mL and 2.5 μg/mL, respectively, using the current method. This detection limit of Raman analysis is lower than that reported for PLM. Raman and PLM diagnoses of clinical samples agreed in 32 out of 35 samples in the entire sample pool. However, the rate of disagreement between PLM-based and Raman-based diagnoses was noteworthy within the subset of diseased samples (3 out of 10), indicating that PLM has limitations and that the confirmation by a secondary method is essential for a reliable outcome. The proposed protocol of sample preparation and Raman analysis ascribes baseline feasibility to the diagnosis of gout and pseudogout by Raman spectroscopy, thus justifying further studies using a larger clinical sample set for obtaining sensitivity and specificity.
Abnormal Behavior in Stern—Volmer Luminescence Quenching Measurements via Apparent Lifetime Methods
Authors: Payne Sarah J. , Demas J. N. , DeGraff B. A.
Published: October 2009

Luminescence lifetimes are widely used as an analysis tool. Since decays in analytical systems are frequently complex decays rather than single exponentials, apparent lifetime methods based on the rapid lifetime determination (RLD) method or single frequency phase shift (SFPS) measurements are frequently used to reduce cost and simplify data analysis. It is demonstrated here that these methods can produce large errors under the right conditions. Both methods can give unexpected and uncharacteristic Stern-Volmer quenching plots (SVQPs) in two-component systems. Behaviors include bimodal quenching curves as well as “anti-quenching” curves. These phenomena are exacerbated by small fractions of long unquenched components.
Structural Differences of Proteins between Solution State and Solid State Probed by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy
Authors: Sachdeva Amita , Cai Shuowei
Published: October 2009

A Fourier transform infrared (FT-IR) spectroscopic method combined with an attenuated total reflection (ATR) sampling technique has been developed to analyze protein secondary structure in both solid and solution states. The method has been applied to analyze the protein structural differences between solution state and solid state. For α-helix dominant proteins, β-sheet structures increase significantly in the solid state, with significant decrease in α-helical structures. For β-sheet dominant proteins, β-sheet structures increase only moderately in the solid state. When proteins are re-dissolved in solution, their structures are re-natured to their native structures, as suggested by the fact that their structures in solution state are similar to those determined by X-ray crystallography or other spectroscopic methods in solution state. The ATR sampling technique avoids the high pressure and chemicals that are needed for the conventional potassium bromide (KBr) disc method for solid samples in FT-IR spectroscopy. Our approach from this study demonstrated that ATR sampling is more appropriate for analysis of protein structures in the solid state.
Analysis of Titanium Dioxide in Synthetic Fibers Using Raman Microspectroscopy
Authors: Vann Brandi C. , Angel S. Michael , Hendrix James E. , Bartick Edward G. , Morgan Stephen L.
Published: October 2009

The ability of Raman microspectroscopy to distinguish between rutile and anatase forms of the inorganic pigment titanium dioxide (TiO2) and to make quantitative measurements of titania loading in fibers is demonstrated. Issues that affect the validity of the Raman measurements include the spatial heterogeneity of TiO2 in the fiber, the polarization of the laser beam, and the polarizing properties of the fiber itself. The amount of titanium dioxide in single delustered polyamide fibers was quantitated at concentration levels ranging from 0 to 7.1% TiO2. Fiber polarization and orientation effects were shown to be minimized by scrambling the polarization of the laser.
Targeted Surface-Enhanced Raman Scattering Nanosensors for Whole-Cell pH Imagery
Authors: Nowak-Lovato K. L. , Rector K. D.
Published: October 2009

In this paper the ability to develop a gold-core, silver-shell surface-enhanced Raman scattering (SERS) nanosensor that has both a targeting component as well as a sensing component is demonstrated. The nanosensor is capable of targeting through the FcεRI receptor-mediated endocytic pathway due to the adsorption of 2,4-ε-dinitrophenol-L-lysine (DNP) ligand on the nanoparticle surface. The nanosensor is also sensitive to pH changes in the endocytic vesicle within the pH range of 4.5–7.5 by 4-mercaptopyridine (4-MPy) adsorbed to the particle surface. The targeting and sensing moieties do not significantly interfere with each other's function. The sensing component of the nanosensor is calibrated with in vivo measurements of rat basophil leukemia (RBL-2H3) cells in standard buffer solutions using the ionophore nigericin, which serves to equilibrate the external [H+] concentration with that of the cell compartments. The targeting of the nanosensor is verified with a β-hexosaminidase assay. It is also demonstrated that the targeted nanosensor is capable of making accurate cellular pH measurements in RBL-2H3 cells, out to ninety minutes after targeted nanosensor addition. Whole-cell, time-lapse, hyperspectral image cubes demonstrating endocytic vesicular pH changes during FcεRI receptor mediated endocytosis are demonstrated.
Emission Enhancement of Laser-Induced Breakdown Spectroscopy by Localized Surface Plasmon Resonance for Analyzing Plant Nutrients
Authors: Ohta Takayuki , Ito Masafumi , Kotani Takashi , Hattori Takeaki
Published: October 2009

We demonstrate the monitoring of plant nutrients in leaves of Citrus unshiu and Rhododendron obtusum using low-energy (<1 mJ) laser-induced breakdown spectroscopy. The raw plant leaf was successfully ablated without desiccation before laser irradiation, by applying metallic colloidal particles to the leaf surface. The emission intensity with the metallic particles was larger than that without the particles. This result indicates an improvement of the sensitivity and the detection limit of laser-induced breakdown spectroscopy. The emission enhancement was caused by localized surface plasmon resonance and was dependent on the size and material of metallic particles.
A Reference-Wavelength-Based Method for Improved Analysis of Near-Infrared Spectroscopy
Authors: Chen Yun , Chen Wenliang , Shi Zhenzhi , Yang Yue , Xu Kexin
Published: October 2009

Near-infrared (NIR) spectroscopy has been widely used in many industrial applications. It also has tremendous potential for trace element detection and noninvasive human physiological measurements. In NIR spectroscopy, however, the measurement precision is often dependent on temperature, measurement position, and sample status. In order to improve measurement precision, a method using spectral information at a reference wavelength is developed in this paper. Based on the displacement effect between solvent and solute molecules in a solution, the signal at the reference wavelength is used as an internal reference to correct the spectrum of the sample under test. As an example, the spectra of glucose aqueous solutions under different temperatures are measured, and our method for eliminating the temperature disturbance is evaluated. The experimental results obtained show that the relative error of glucose concentration prediction is 330% per degree before the spectrum correction. After the correction, the relative error is reduced to 5.12%, and the error is no longer dependent on temperature. As the displacement effect can be found commonly in various solutions, the method described in this work may be used to improve the accuracy of spectral analysis of many other solutions.
Spectroscopic System for Direct Lanthanide Photoluminescence Spectroscopy with Nanomolar Detection Limits
Authors: Andolina Christopher M. , Holthoff William G. , Page Phillip M. , Mathews Ryan A. , Morrow Janet R. , Bright Frank V.
Published: October 2009

A new spectroscopic system for direct photoluminescence of lanthanide ions (Ln(III)) through electronic transitions within the 4fn manifold is described. The system is based on an injection seeded frequency tripled (λ = 355 nm) Nd:YAG pump laser coupled with a master oscillator power oscillator (MOPO). The MOPO delivers an average pulse energy of ⪝60 mJ/pulse, is continuously tunable from 425 to 690 nm (Signal) and 735 to 1800 nm (Idler) with a linewidth of <0.2 cm−1, and has a pulse duration of 10–12 ns. Aqueous solutions containing two polyaminocarboxylate complexes, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), and Ln3+ aqua ion for several lanthanides including Eu(III), Tb(III), Dy(III), and Sm(III)) are used as steady-state and time-resolved photoluminescence standards. The versatility of the instrument is demonstrated by excitation scans over a broad visible range for aqueous solutions of complexes of Eu(III), Dy(III), Sm(III), and Tb(III). The Eu(III) excitation band (7Fo→5Do) is recorded over a range of complex concentrations that are 1000–fold less than reported previously, including Eu(EDTA) (1.00 nM), Eu(DTPA) (1.00 nM), and Eu(III) aqua ion (50.0 nM). Emission spectra are recorded in the visible range for Ln(III) complexes at pH 6.5 and 1.00 mM. Excited-state lifetimes for the standards were constant as a function of concentration from 10.0 nM to 1.00 mM for Eu(EDTA) and Eu(DTPA) and from 100 nM to 1.00 mM for Eu(III) aqua ion. Photoluminescence lifetimes in H2O and D2O are recorded and used to calculate the number of bound water molecules for all complexes.
Ultraviolet—Visible Spectral Analysis for the Reaction of Hydrogen Peroxide with a Titanium(IV)-Porphyrin Reagent
Authors: Takamura Kiyoko , Matsumoto Takatoshi
Published: October 2009

A Ti-TPyP reagent, i.e., an acidic aqueous solution of oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) complex, TiO(tpyp), was developed as a highly sensitive and selective spectrophotometric reagent for the determination of traces of hydrogen peroxide. The reagent exhibited a single absorption peak at 432 nm, and the addition of hydrogen peroxide to the reagent gave rise to a new peak at 450 nm, with height being proportional to the added hydrogen peroxide concentration. Recently we succeeded in clarifying the reaction specificity of the TiO(tpyp) complex to hydrogen peroxide from the viewpoint of the reaction mechanisms and molecular orbitals based on ab initio calculations. In the present study, we performed ultraviolet–visible (UV-Vis) spectral simulations for individual species in the proposed reaction mechanisms based on the theoretical calculations carried out using the Zerner's intermediate neglect of differential overlap (ZINDO) method, since the assignment of the observed absorption peaks to the respective reaction species is important to confirm the reliability of the analysis of hydrogen peroxide using the Ti-TPyP reagent. The absorption peaks at 432 nm and 450 nm were assigned to a H2O-adduct structure of the protonated TiO(tpyp) complex and the important structure corresponding to the monoperoxo TiO(tpyp) complex, respectively, under acidic conditions. Particularly, it should be noted that the addition of water molecules to the protonated TiO(tpyp) complex affects the maximum absorption wavelength appreciably. Taking the addition of water molecules to the complex into consideration, the reaction mechanism proposed previously was revised in this study. The results should contribute to providing a new way to evaluate analytical reagents.
High-Resolution J-Scaling Nuclear Magnetic Resonance Spectra in Inhomogeneous Fields via Intermolecular Multiple-Quantum Coherences
Authors: Lin Yanqin , Chen Zhong , Cai Shuhui , Zhong Jianhui
Published: October 2009

High-resolution nuclear magnetic resonance (NMR) spectroscopy with information on chemical shifts and J-coupling constants is a sensitive tool for studying physical, chemical, and biological properties of materials at the molecular level. In this paper, a pulse sequence is developed for acquiring high-resolution NMR spectra of liquid samples with J-scaling in inhomogeneous fields via two-dimensional intermolecular multiple-quantum coherence acquisitions. In the resulting one-dimensional projection spectra, apparent J-coupling constants were obtained with a scaling factor theoretically varying from zero (completely decoupled) to infinity relative to the original J-coupling constants while retaining information on chemical shifts, relative peak areas, and multiplet patterns. This allows either an accurate measurement of small J-coupling constants of weakly coupled spin systems or less crowded spectra for spin systems with J-splitting. Experimental observations and simulation results agree with theoretical analysis.
Probing Water and Biomolecules at the Air—Water Interface with a Broad Bandwidth Vibrational Sum Frequency Generation Spectrometer from 3800 to 900 cm−1
Authors: Ma Gang , Liu Jian , Fu Li , Yan Elsa C. Y.
Published: October 2009

We have built a broad bandwidth vibrational sum frequency generation (VSFG) spectrometer that can provide high-quality spectra over the range of 3800 to 900 cm−1. The spectrometer contains a commercial Ti:sapphire based 6 W regenerative amplifier as the master light source, a home-built pulse shaper to produce a narrow bandwidth 800 nm beam, a commercial optical parametric amplifier to generate a broad bandwidth femtosecond infrared (IR) pulse, and a detection system with a monochromator and a charge-coupled device (CCD). We applied this spectrometer to obtain VSFG spectra of a lipid monolayer at the air–water interface in the O–H stretching region (3800–3000 cm−1), the C–H stretching region (3100–2700 cm−1), the C–D stretching region (2300–2000 cm−1), the C=O stretching region (1800–1700 cm−1), and the PO2− symmetric stretching region (1200–1000 cm−1). We also obtained the VSFG spectrum of neat water in the O–H stretching region (3800–3000 cm−1) and the VSFG spectrum of a protein, α-synuclein, in the amide I region (1700–1600 cm−1) at the air–water interface. The spectrometer can provide a VSFG spectrum in the O–H stretching region (3800–3000 cm−1) without scanning the IR frequency. This feature will be useful in probing water dynamics at interfaces because the free OH and H-bonded OH can be investigated simultaneously. We have also provided instrumental details and discussed further improvements that should be beneficial to other researchers interested in setting up VSFG instrumentation.
Sensitivity of Micro-Raman Spectrum to Crystallite Size of Electrospray-Deposited and Post-Annealed Films of Iron-Oxide Nanoparticle Suspensions
Authors: Lopez Luis B. Modesto , Pasteris Jill D. , Biswas Pratim
Published: October 2009

This paper demonstrates the sensitivity of the Raman spectra of electrospray-deposited iron-oxide nanoparticle films to their grain size. The grain size in the films was controlled using the temperature of annealing. The position and width of the bands at ∼ 225, 612, 660, and 1317 Δcm−1 were investigated for their sensitivity to both grain size and laser-induced heating, using 532 nm excitation. The parameter most sensitive to grain size was found to be the difference between the band position of the 660 Δcm−1 LO and 225 Δcm−1 TO bands (X660 - X225). The distance between the two bands narrowed with increasing annealing temperature of the films, suggesting that, as grain size increases, these two bands become closer. The 660 Δcm−1 band position was very stable regardless of variation in laser power and, thus, laser-induced heating effects. The films were prepared by electrospray deposition of a commercial maghemite (γ-Fe2O3) nanoparticle suspension onto a silicon wafer followed by post-annealing in a temperature range of 600–1000 °C for 15 min in an air atmosphere.
Multi-Contrast Light Profile Microscopy for the Depth-Resolved Imaging of the Properties of Multi-Ply Thin Films
Authors: Power J. F.
Published: October 2009

Light profile microscopy (LPM) is a direct method for the spectral depth imaging of thin film cross-sections on the micrometer scale. LPM uses a perpendicular viewing configuration that directly images a source beam propagated through a thin film. Images are formed in dark field contrast, which is highly sensitive to subtle interfacial structures that are invisible to reference methods. The independent focusing of illumination and imaging systems allows multiple registered optical sources to be hosted on a single platform. These features make LPM a powerful multi-contrast (MC) imaging technique, demonstrated in this work with six modes of imaging in a single instrument, based on (1) broad-band elastic scatter; (2) laser excited wideband luminescence; (3) coherent elastic scatter; (4) Raman scatter (three channels with RGB illumination); (5) wavelength resolved luminescence; and (6) spectral broadband scatter, resolved in immediate succession. MC-LPM integrates Raman images with a wider optical and morphological picture of the sample than prior art microprobes. Currently, MC-LPM resolves images at an effective spectral resolution better than 9 cm−1, at a spatial resolution approaching 1 üm, with optics that operate in air at half the maximum numerical aperture of the prior art microprobes.
Spectroscopic Study of an Expanded Argon Microwave (2.45 GHz) Plasma at Atmospheric Pressure in a Helium Environment
Authors: García M. C. , Varo M. , Martínez P.
Published: October 2009

In the present work, an argon microwave (2.45 GHz) plasma flame created at the end of a surface-wave-sustained discharge column in a helium environment has been experimentally studied. This is a plasma with new possibilities because under some experimental conditions it expands, being less contracted than the plasma flame created in open air. The new expanded discharge could offer additional advantages for applications in which larger extensions of plasma were required. The expansion phenomenon of this plasma flame was studied under different experimental conditions. In every case, the characteristic parameters of this expanded plasma such as electron density, electron and gas temperatures, or density population of excited atomic levels were measured by using optical emission spectroscopic techniques. From these results, the main advantages of this plasma source were pointed out.
Comparison of Vibrational Circular Dichroism Instruments: Development of a New Dispersive VCD
Authors: Lakhani Ahmed , Malon Petr , Keiderling Timothy A.
Published: October 2009

A dispersive vibrational circular dichroism (VCD) instrument has been designed and optimized for the measurement of mid-infrared (MIR) bands such as the amide I and amide II vibrational modes of peptides and proteins. The major design considerations were to construct a compact VCD instrument for biological molecules, to increase signal-to-noise (S/N) ratio, to simultaneously collect and digitize the sample transmission and polarization modulation signals, and to digitally ratio them to yield a VCD spectrum. These were realized by assembling new components using design factors adapted from previous VCD instruments. A collection of spectra for peptides and proteins having different dominant secondary structures (alpha-helix, beta-sheet, and random coil) measured for identical samples under the same conditions showed that the new instrument had substantially improved S/N as compared with our previous dispersive VCD instrument These instruments both provide protein VCD for the amide I that are comparable to or somewhat better than those measurable with commercial Fourier transform (FT) VCD instruments if just the amide I band in the spectra is obtained at modest resolution (8 cm−1) with the same total data collection time on each type of instrument.
Spectroscopic Ellipsometry of Mucin Layers on an Amphiphilic Diblock Copolymer Surface
Authors: Nikonenko Nataliya A. , Bushnak Braheem A. , Keddie Joseph L.
Published: October 2009

Both visible and infrared (IR) spectroscopic ellipsometry have been employed to study the structure of thin layers of bovine submaxillary mucin (BSM) adsorbed on poly(acrylic acid-block-methyl methacrylate) (PAA- b-PMMA) copolymer and poly(methyl methacrylate) (PMMA) surfaces at three pH values (3, 7, and 10). The adsorbed mucin layer on the copolymer surface had the greatest thickness (17 nm) when adsorbed from a mucin solution at a pH of 3. For the first time, IR ellipsometry was used to identify adhesive interactions and conformational changes in mucin/polymer double layers. After applying the regularized method of deconvolution in the analysis, the formation of hydrogen bonds between the carboxyl groups of the BSM and PAA- b-PMMA copolymer in double layers has been found. The IR ellipsometry data, in agreement with the visible ellipsometry analysis, indicate the pH dependence of adhesion of mucin to the copolymer surface. There is an increase in the amount of hydrogen-bonded carboxyl groups in mucin deposited at a pH of 3. There is no evidence that the amide groups of the mucin participate in this bonding. At the lower pH, the IR ellipsometry spectra after deconvolution reveal an increase in the proportion of β-sheets in the BSM upon adsorption on the copolymer surface, indicating a more unfolded, aggregated structure. The IR ellipsometry data also indicated some changes in the conformational states of the side groups in the copolymer induced by entanglements and bonding interactions with the mucin macromolecules. Deconvolution provides an unprecedented level of information from the IR ellipsometry spectra and yields important insights.
Sapphire Fiber Evanescent Wave Absorption in Turbid Media
Authors: Zhang Jian , Xiong Feibing , Djeu Nicholas
Published: October 2009

The influence of particulates on sapphire fiber evanescent wave absorption by water has been studied. Suspensions containing microsized graphite flakes and glassy carbon powder were used. Conventional free-space transmittance measurements of these samples showed strong absorption and scattering, which severely screened the absorption by water. However, the absorption on the water band determined from the evanescent wave interaction was unaffected by the presence of the graphite flakes. These results indicate that fiber-optic evanescent wave chemical sensors may be suitable for process control applications involving turbid reactor streams.
Self-Weighted Correlation Coefficients and Their Application to Measure Spectral Similarity
Authors: Griffiths Peter R. , Shao Limin
Published: October 2009

A technique for spectral searching with noisy data is described that improves the performance over contemporary approaches. Instead of simply calculating the correlation coefficient between the spectrum of an unknown and a series of reference spectra, greater weight is given to the more intense features in the reference spectra. The weight array, w, is given by |r|/{1 + d}, where the vector r represents the reference spectrum and the difference vector, d, contains the difference between the sample and reference data points, equal to |s — kr|, where k is a scaling factor that eliminates the effect of signal strength. By this approach, a large weight is only given to those points that have relatively high absorbance and are close to their counterparts in the reference spectrum. This technique was shown to give significantly improved performance when applied to noisy spectra of trace atmospheric components obtained by target factor analysis.
Investigation of Hydrogenation of Toluene to Methylcyclohexane in a Trickle Bed Reactor by Low-Field Nuclear Magnetic Resonance Spectroscopy
Authors: Guthausen Gisela , von Garnier Agnes , Reimert Rainer
Published: October 2009

Low-field nuclear magnetic resonance (NMR) spectroscopy is applied to study the hydrogenation of toluene in a lab-scale reactor. A conventional benchtop NMR system was modified to achieve chemical shift resolution. After an off-line validity check of the approach, the reaction product is analyzed on-line during the process, applying chemometric data processing. The conversion of toluene to methylcyclohexane is compared with off-line gas chromatographic analysis. Both classic analytical and chemometric data processing was applied. As the results, which are obtained within a few tens of seconds, are equivalent within the experimental accuracy of both methods, low-field NMR spectroscopy was shown to provide an analytical tool for reaction characterization and immediate feedback.
Patterned Silver Nanorod Array Substrates for Surface-Enhanced Raman Scattering
Authors: Marotta Nicole E. , Barber Jabulani R. , Dluhy Peter R. , Bottomley Lawrence A.
Published: October 2009

A novel method for batch fabrication of substrates for surface-enhanced Raman scattering (SERS) has been developed. A modified platen that fits in a commercial electron beam evaporator enables the simultaneous deposition of Ag nanorod arrays onto six microscope slides by glancing angle deposition. Following removal of substrates from the evaporator, patterned wells are formed by contact printing of a polymer onto the surface. Well dimensions are defined by penetration of the polymer into the nanorod array and subsequent photochemical curing. Inherent advantages of this method include: (1) simultaneous production of several nanorod array substrates with high structural uniformity, (2) physical isolation of nanorod arrays from one another to minimize cross contamination during sample loading, (3) dimensional compatibility of the patterned array with existing SERS microscope, (4) large SERS enhancement afforded by the nanorod array format, (5) small fluid volumes, and (6) ease of use for manual delivery of fluids to each element in the patterned array. In this article, the well-to-well, slide-to-slide, and batch-to-batch variability in physical characteristics and SERS response of substrates prepared via this method is critically examined.
Determination of Phase Transition Temperatures by the Analysis of Baseline Variations in Transmittance Infrared Spectroscopy
Authors: Zimmermann Boris , Baranović Goran
Published: October 2009

A simple method for obtaining phase transition temperatures is proposed. It is based on absolute variations of a baseline in a temperature-dependent mid-infrared transmittance spectral data set recorded for a sample KBr pellet. The method is rapid, inexpensive, and completely free of any personal bias. The method efficiency was corroborated by measuring the phase transitions of mesomorphic ( trans-4-heptyl cyclohexanecarboxylic acid) and polymorphic compounds (polycyclic aromatic hydrocarbons and phenylacetylenes). In addition, the exothermic decomposition of phenylacetylenes was also monitored, thereby opening the possibility for simple and rapid monitoring of chemical reactions in solid and liquid phase. A great prospect of the method as an economical way of establishing critical temperature regions for analytical and quality control purposes is foreseen.
The Infrared Absorption Spectra of the n-2 Trans, 4 Trans Dienaldehydes, C5 through C12
Authors: Bailey Glen F. , Nonaka M.
Published: October 2009

The infrared absorption spectra of the normal 2, 4-dienaldehydes, from pentadienal through dodecadienal, were measured in the liquid state over the spectral range from 400 to 4000 cm−1. The compounds were prepared by conventional methods and purified by gas-liquid chromatographic procedures immediately before spectrophotometry. Two strong bands near 1685 and 1643 cm−1, four strong bands in the 980-1180 cm−1 region, and a doublet in the aldehyde C-H stretching region are characteristic of the n-2 tram, 4 tram dienal structure.