Showing papers on "Fourier transform spectroscopy published in 2006"
TL;DR: FT-IR spectroscopy is used as an effective analytical tool in order to determine extra virgin olive oil adulteration with lower priced vegetable oils and to monitor the oxidation process of corn oil samples undergone during heating or/and exposure to ultraviolet radiation.
529 citations
TL;DR: This work proposes an automated compound identification algorithm (CIA) for the analysis of ultra-high-resolution mass spectra of natural organic matter acquired by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and finds that CIA works well for data sets with high mass accuracy and can accurately determine the elemental formulas for >95% of all compounds.
Abstract: The advent of ultra-high-resolution mass spectrometry has revolutionized the ability of aquatic biogeochemists to examine molecular-level components of complex mixtures of organic matter. The ability to accurately assess the chemical composition, elemental formulas, or both of detected compounds is critical to these studies. Here we build on previous work that uses functional group relationships between compounds to extend elemental formulas of low molecular weight compounds to those of higher molecular weight. We propose an automated compound identification algorithm (CIA) for the analysis of ultra-high-resolution mass spectra of natural organic matter acquired by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. This approach is benchmarked with synthetic data sets of compounds cited in the literature. The sensitivity of our results is examined for different sources of error, and CIA is applied to two previously published data sets. We find that CIA works well for data...
315 citations
TL;DR: In this paper, the phase evolution of the nonlinear polarization field during the initial evolution and the final detection period was analyzed using optical two-dimensional Fourier transform spectroscopy.
Abstract: We study many-body interactions between excitons in semiconductors by applying the powerful technique of optical two-dimensional Fourier transform spectroscopy. A two-dimensional spectrum correlates the phase (frequency) evolution of the nonlinear polarization field during the initial evolution and the final detection period. A single two-dimensional spectrum can identify couplings between resonances, separate quantum mechanical pathways, and distinguish among microscopic many-body interactions.
218 citations
TL;DR: High-speed complex full-range Fourier domain optical coherence tomography (FD-OCT) is demonstrated, which investigates a sweat duct in a finger pad in vivo and visualizes it with an acquisition time of 27 ms.
Abstract: High-speed complex full-range Fourier domain optical coherence tomography (FD-OCT) is demonstrated. In this FD-OCT, the phase modulation of a reference beam (M scan) and transversal scanning (B scan) are simultaneously performed. The Fourier transform method is applied along the direction of the B scan to reconstruct complex spectra, and the complex spectra comprise a full-range OCT image. Because of this simultaneous B-M-mode scan, the FD-OCT requires only a single A scan for each single transversal position to obtain a full-range FD-OCT image. A simple but slow version of the FD-OCT visualizes the cross section of a plastic plate. A modified fast version of this FD-OCT investigates a sweat duct in a finger pad in vivo and visualizes it with an acquisition time of 27 ms.
157 citations
TL;DR: This is the first unambiguous detection of fulvic acid molecules and sulfated components in atmospheric aerosol and the first detection even of nitrated analogues.
Abstract: The water-soluble organic fractions of aerosol samples collected in Riverside, CA, in summer 2005 were analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Elemental compositions of about 1000 molecular species were determined in the range m/z 220-420, and four series of organic compounds were identified, fulvic acids, and S-containing, N-containing, and S- and N-containing molecules. Low-resolution product ion spectra proved the presence of organosulfates, organonitrates, and mixed organosulfates and -nitrates that appear to be structurally closely related to each other and to the fulvic acids. This is the first unambiguous detection of fulvic acid molecules and sulfated components in atmospheric aerosol and the first detection even of nitrated analogues. These species provide new clues to the nature of particulate organic matter in atmospheric aerosol.
151 citations
TL;DR: Amino acid family crystals exhibit excellent nonlinear optical and electrooptical properties L-Alanine single crystal belongs to the amino acid group and has been grown by the slow evaporation solution growth technique at room temperature The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), UV-Vis, Raman spectroscopy, mass spectra analyses and density measurements.
Abstract: Amino acid family crystals exhibit excellent nonlinear optical and electrooptical properties L-Alanine single crystal belongs to the amino acid group and has been grown by the slow evaporation solution growth technique at room temperature The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, UV-Vis, Raman spectroscopy, mass spectra analyses and density measurements Its laser damage threshold was measured and its nonlinear optical response was tested by using a Q-switched Nd:YAG laser, and the value of laser damage threshold is greater than that of potassium dihydrogen phosphate (KDP)
126 citations
TL;DR: An interferometric biosensor comprised of two layers of porous Si, stacked one on top of the other, is described, and the FFT method allows discrimination of target analyte binding from matrix effects due to nonspecific changes in the analyte solution.
Abstract: An interferometric biosensor comprised of two layers of porous Si, stacked one on top of the other, is described. A fast Fourier transform (FFT) of the reflectivity spectrum reveals three peaks that correspond to the optical thickness of the top layer, the bottom layer, and both layers together. Binding of immunoglobulin G to a protein A capture probe adsorbed to the surface of the top layer induces changes in reflectivity at the top layer/solution interface. The FFT method allows discrimination of target analyte binding from matrix effects due to nonspecific changes in the analyte solution. The sensor response is shown to be insensitive to the addition of 4000-fold excess sucrose or 80-fold excess bovine serum albumin interferents.
125 citations
TL;DR: In this article, the authors explored the opportunity of enhancing the sensitivity of FTIR spectroscopy to detect trace amounts of materials using the FTIR imaging approach based on a focal plane array (FPA) detector.
Abstract: FTIR spectroscopy is one of the most powerful methods for material characterization. However, the sensitivity of this analytical tool is often very limited especially for materials with weak infrared absorption or when spectral bands of the targeted trace material overlap with the spectral bands of major components. Fortunately, for heterogeneous samples, there is an opportunity to improve the sensitivity of detection by using an imaging approach. This paper explores the opportunity of enhancing the sensitivity of FTIR spectroscopy to detect trace amounts of materials using the FTIR imaging approach based on a focal plane array (FPA) detector. Model sample tablets of ibuprofen in hydroxypropyl methylcellulose (HPMC) have been used to exemplify the detection limits of FTIR spectroscopy using: (a) a conventional mercury cadmium telluride (MCT) detector and (b) a FPA detector. The sensitivity level was compared and it has been found that for this particular set of samples, the lowest concentration of ibuprofen in HPMC that can be detected using attenuated total reflection (ATR) measuring mode with the single element MCT detector was 0.35 wt% while using the FPA detector, the presence of drug has been detected in a sample that contains as little as 0.075 wt% of drug. The application of using this enhanced sensitivity offered by the multi-channel detector to probe trace amounts of drug particles left on the surface of a finger after handling a small amount of the drug has also been demonstrated. These results have broad implications for forensic, biomedical and pharmaceutical research.
108 citations
TL;DR: In this article, a miniaturized Fourier transform spectrometer is implemented on a silicon optical bench platform, which combines the flexible definition capability of deep reactive ion etching with the good surface quality provided by anisotropic KOH wet etching.
Abstract: We present a miniaturized Fourier transform spectrometer implemented on a silicon optical bench platform. Both optical and opto-mechanical components of a Michelson interferometer, including a silicon beam splitter, micromirrors, MEMS actuators, and fiber U-grooves, are simultaneously fabricated by micromachining of the device layer of a silicon-on-insulator wafer. Our specialized bulk micromachining process combines the flexible definition capability of deep reactive ion etching with the good surface quality provided by anisotropic KOH wet etching. This integrated Fourier transform spectrometer has a measured spectral resolution of approximately 45 nm near 1500 nm wavelength.
101 citations
TL;DR: In this article, the spectra of DNA samples have been measured in liquid phase (gel) over the spectral range 10 − 25 cm−1 and compared with spectra obtained from solid films.
Abstract: Significant progress has been achieved during the last several years relating to experimental and theoretical aspects of terahertz (or submillimetre wave) Fourier transform spectroscopy of biological macromolecules. However, previous research in this spectral range has been focused on bio-materials in solid state since it was common opinion that high water absorption will obscure the spectral signatures of the bio-molecules in solutions. At the same time, the biological functions of DNA and proteins take place in water solutions. In this work, the spectra of DNA samples have been measured in liquid phase (gel) over the spectral range 10–25 cm−1 and compared with spectra obtained from solid films. The results demonstrate that there is very little interference between the spectral features of the material under test and the water background except for the band around 18.6 cm−1. Multiple resonances due to low frequency vibrational modes within biological macromolecules in solutions are unambiguously demonstrated. Higher level of sensitivity and higher sharpness of vibrational modes are observed in the liquid environment in comparison with the solid phase, with the width of spectral lines 0.3–0.5 cm−1. Gel sample spectra are found to be polarization-dependent. The ability of THz spectroscopy to characterize samples in liquid phase could be very important since it permits examination of DNA interactions in real (wet) samples. One demonstrated example of practical importance is the ability to discriminate between spectral patterns for native and denaturated DNA.
98 citations
TL;DR: This work used Fourier transform infrared spectroscopy to detect the surface species and the nature of surface chemical interactions and suggests that there is a direct correlation between the strength of surface-ligand interactions and interior crystallinity.
Abstract: Combined small-angle and high energy wide-angle x-ray scattering measurements of nanoparticle size and structure permit interior strain and disorder to be directly observed in the real-space pair distribution function (PDF). PDF analysis showed that samples of ZnS nanoparticle with similar mean diameters (3.2-3.6 nm) but synthesized and treated differently possess a dramatic range of interior disorder. We used Fourier transform infra-red spectroscopy to detect the surface species and the nature of surface chemical interactions. Our results suggest that there is a direct correlation between the strength of surface-ligand interactions and interior crystallinity.
TL;DR: In this paper, the first application of optical feedback cavity-enhanced absorption spectroscopy with a blue (411 nm) extended cavity diode laser (ECDL) for NO2 detection was reported.
Abstract: We report preliminary results on the first application of optical feedback cavity-enhanced absorption spectroscopy with a blue (411 nm) extended cavity diode laser (ECDL) for NO2 detection. While this technique was originally developed to operate with distributed feedback diode lasers in the near infrared, it is here extended to ECDLs and applied to the blue spectral region. With a simple and compact optical setup, we demonstrate from the baseline noise a minimum detectable NO2 concentration of 6×109 molecules/cm3 for a single laser scan (70 ms), which extrapolated under atmospheric conditions corresponds to 200 pptv. Signal averaging should allow further lowering of this limit. Observed absorption spectra display more structure than previous spectra obtained at lower resolution by Fourier-transform spectroscopy at the same wavelength.
TL;DR: Polarization sensitive Fourier domain optical coherence tomography (PS-FD-OCT) using fiber components with continuous polarization modulation is demonstrated in this paper, where the incident polarized light is modulated by electro-optic modulator (EO modulator) synchronized with lateral B-scanning.
Abstract: Polarization sensitive Fourier domain optical coherence tomography (PS-FD-OCT) using fiber components with continuous polarization modulation is demonstrated.
The incident polarized light is modulated by electro-optic modulator (EO modulator) synchronized with lateral B-scanning.
By the incident polarization modulation and the polarization sensitive spectrometer, the depth-resolved Jones matrix image of biological sample can be measured.
This method uses both polarization modulation method and Fourier transform method.
In this paper, the algorithm is described and the phase retardation image of chicken breast muscle is measured.
15 Aug 2006
TL;DR: In this paper, a brief introduction to the theory of vibrational spectroscopy is given in this chapter, and the factors governing the shapes and widths of lines in vapor-phase and condensed-phase spectra are discussed.
Abstract: A brief introduction to the theory of vibrational spectroscopy is given in this chapter. Molecular vibrations are first described in terms of the harmonic oscillator. The Morse potential energy diagram and the concept of anharmonicity are then introduced. The way in which Raman spectra are generated is described in the third section of the article. The factors governing band intensities in infrared and Raman spectra are discussed. In the next section, vibration–rotation spectra of gases are introduced. Then the factors governing the shapes and widths of lines in vapor–phase and condensed-phase spectra are discussed. In the section on quantitative considerations, Beer's law is described and parameters such as absorptivity, linear absorption coefficient and the optical constants, refractive index, and index of absorption are defined. Finally, a brief introduction to the polarization of radiation is given.
Keywords:
vibrational spectroscopy;
vibrational quantum number;
infrared spectroscopy;
Fourier transform spectroscopy;
FT-IR spectrometers;
Raman spectroscopy;
near-infrared spectroscopy;
Fourier transform Raman;
CCD Raman;
bandwidths;
anharmonicity;
anharmonicity constant;
vibration–rotation spectra;
rotational quantum number;
centrifugal distortion;
band shapes;
Doppler broadening;
collision broadening;
absorptivity;
linear absorption coefficient;
refractive index;
index of absorption;
polarization
TL;DR: Using two-dimensional Fourier transform spectral interferometry, chromatic and spherical aberrations that are present in multiphoton microscopy are measured and deduced in a single shot spatiotemporal effects in high-numerical-aperture objectives are measured.
Abstract: We demonstrate the use of a simple tool to simultaneously visualize and characterize chromatic and spherical aberrations that are present in multiphoton microscopy. Using two-dimensional Fourier transform spectral interferometry, we measured these aberrations, deducing in a single shot spatiotemporal effects in high-numerical-aperture objectives.
TL;DR: Differences in the Raman profile for each whey component reflect their intrinsic compositional differences and distinct spatial arrangement, which may be responsible for their diversified behaviors in solubility, rheological and functional properties.
TL;DR: In this paper, the rotational structure of a large number of bands involving vibrational levels was analyzed, and improved spectroscopic constants were determined by combining the microwave and infrared measurements from previous studies.
TL;DR: In this paper, the growth of a novel organometallic nonlinear optical (NLO) crystal of thiourea complex bis(thiaourea) cadmium formate (BTCF) in larger size is reported for the first time by the slow evaporation method.
Abstract: The growth of a novel organometallic nonlinear optical (NLO) crystal of thiourea complex bis(thiourea) cadmium formate (BTCF) in larger size is reported for the first time by the slow evaporation method. The grown crystal was subjected to single-crystal X-ray diffraction, morphology, optical transmission, Fourier transform infrared (FT-IR) spectroscopy, second harmonic generation (SHG) efficiency test and microhardness studies. The powder SHG efficiency of BTCF is comparable with KDP.
TL;DR: The thickness of the sample layer deposited on the irradiated metal foil and the number of laser shots fired on the backside of the foil were found to have a significant effect on the overall signal and the relative abundances of the ions formed in the experiment.
Abstract: Several experimental factors have been investigated that influence the efficiency of desorption and subsequent chemical ionization of nonvolatile, thermally labile molecules during laser-induced acoustic desorption/Fourier transform ion cyclotron resonance mass spectrometry (LIAD/FT-ICR) experiments. The experiments were performed by using two specially designed LIAD probes of different outer diameters (1/2 and 7/8 in.) and designs. Several improvements to the design of the “first generation” (1/2 in.) LIAD probe are presented. The larger diameter (7/8 in.) probe provides a larger surface area for desorption than the smaller diameter probe. Further, it was designed to desorb molecules on-axis with the magnetic field of the instrument. This is in contrast to the smaller probe for which desorption occurs 1.3 mm off-axis. This improved alignment, which provides better overlap between the desorbed molecules and trapped reagent ions, results in a substantial increase in the sensitivity of LIAD analyses. The th...
TL;DR: Isothermal self-sustained kinetic oscillations in CO oxidation over silica-supported Pt at near-atmospheric pressure were studied and indicate that during the high reactive periods the reaction mainly occurs on the oxide surface.
Abstract: Isothermal self-sustained kinetic oscillations in CO oxidation over silica-supported Pt at near-atmospheric pressure were studied by combined in situ Fourier transform infrared spectroscopy and mass spectrometry. The use of a specially designed reactor and careful choice of the physical properties of the catalyst and reaction conditions made it possible to eliminate diffusion limitations, to determine the maximum CO oxidation rate per Pt site in the purely kinetic regime and to clarify the mechanism of the oscillations. Specifically, our results indicate that during the high reactive periods the reaction mainly occurs on the oxide surface.
TL;DR: Fourier transform infrared spectroscopy (FTIR) was applied to the characterization of red inks used to print one-penny stamps in Britain during the period 1841-1880.
TL;DR: In this paper, the accuracy of near-infrared spectroscopy when quantifying polymorphic binary mixtures of ranitidine hydrochloride was investigated, however, not to the level of accuracy displayed by Raman spectroscopic techniques.
15 Sep 2006
TL;DR: In this article, Fourier transform infrared (FTIR) spectroscopy is used to measure the absorption of vibrating molecules and yields information about molecular structures and structural interactions, but the usefulness of the method is limited by difficulties in extracting the structural information contained in the IR absorption bands.
Abstract: Infrared (IR) spectroscopy is one of the two forms of vibrational spectroscopy, the other being Raman spectroscopy. IR spectroscopy measures absorptions of vibrating molecules and yields information about molecular structures and structural interactions. The development of computerized Fourier transform infrared (FTIR) techniques has opened up new dimensions in biological IR spectroscopy owing to the increase in achievable signal-to-noise ratios, wavenumber accuracy, and data aquisition rates, and the ability to perform measurements with strongly absorbing samples. High-quality FTIR spectra can be obtained with relative ease and rapidly with very small amounts of sample in a variety of environments. Measurements of proteins in aqueous solution are almost routine now, and can be performed under equilibrium and nonequilibrium conditions. There are many IR absorption bands characteristic of peptide groups and amino acid side-chain groups from which information on protein structures can be obtained. The information provided by FTIR spectroscopy may be a global one or highly specific for a single vibrating chemical group. In some cases, the usefulness of the method is limited by difficulties in extracting the structural information contained in the IR absorption bands.
TL;DR: In this article, experimental oscillator strengths for 88 Ti I tran sitions covering the wavelength range 465 to 3 892 nm, 67 of which had no previous experimental values, were reported.
Abstract: We report experimental oscillator strengths for 88 Ti I tran sitions covering the wavelength range 465 to 3 892 nm, 67 of which had no previous experimental values. Radiative lifetimes for thirteen energy levels, including the low energy levels 3d 2 ( 3 F) 4s4p ( 3 P) z 5 D ◦ , have been measured using time resolved laser induced fluorescenc e. Intensity calibrated Ti I spectra have been measured using Fourier transform spectroscopy to determine branching fractions for the decay channels of these levels. The branching fractions are combined with the radiative lifetimes to yield absolute transition probabilities and o scillator strengths. Our measurements include 50 transitions in the previously unobserved infrar ed region λ > 1.0 � m, a region of particular interest to the analysis of cool stars and brown d warfs.
TL;DR: A heat-induced unfolding step previous to protein hydrolysis was identified and the infrared spectra of the intermediate species showed a more disordered structure than native albumin, the decrease in alpha-helix conformation being especially noticeable.
Abstract: The hydrolysis of bovine serum albumin with protease K at 60 °C has been studied by means of infrared spectroscopy. Two-dimensional correlation spectroscopy (2DCoS) has been used to study spectral changes in the reaction. The use of the multivariate curve resolution-alternating least-squares method applied to infrared measurements allowed the recovery of pure infrared spectra and concentration profiles of the different species involved in the reaction. Special attention was paid to the careful inspection of residuals again using 2DCoS. In this way, a heat-induced unfolding step previous to protein hydrolysis was identified. The infrared spectra of the intermediate species showed a more disordered structure than native albumin, the decrease in α-helix conformation being especially noticeable. The formation of β-sheet aggregates due to heating was detected too.
TL;DR: In this article, the effects of hydrogen and nitrogen on the spectra of a number of elements (Fe, Ti, V, Ni, Zn etc) have been investigated and it has been shown that asymmetric charge transfer involving hydrogen ions (H-ACT) is a very important selective excitation mechanism for spectral lines with a total excitation energy close to 13.6 eV.
TL;DR: In this paper, a fast isotopic transient kinetic analysis (ITKA) was performed in which both the gaseous and adsorbed species inside the catalytic reactor were monitored simultaneously with rapid-scan transmission Fourier transform infrared (FTIR), and its gaseus effluent can be monitored by mass spectroscopy during rapid switching of reagent gas streams.
Abstract: A novel apparatus for gas phase heterogeneous catalysis kinetics is described. The apparatus enables fast isotopic transient kinetic analysis (ITKA) to be performed in which both the gaseous and adsorbed species inside the catalytic reactor are monitored simultaneously with rapid-scan transmission Fourier transform infrared (FTIR), and its gaseous effluent can be monitored by mass spectroscopy during rapid switching of reagent gas streams. This enables a more powerful version of the well-known steady-state isotopic transient kinetic analysis (SSITKA) technique in which the vibrational spectra of the gas phase and adsorbed species are also probed: FTIR-SSITKA. Unique reactor characteristics include tungsten construction, liquid nitrogen cooling or heating (∼200–770K), pressures of 1.0–2.5atm, fast reactor disassembly and reassembly, and catalyst loading in a common volume. The FTIR data acquisition rate of this apparatus (3Hz) is tenfold faster than previously reported instruments. A 95% signal decay time ...
TL;DR: In this paper, the organic portion of an acylamine derivation grafted by 3-aminopropyl trimethoxysilane and covalently linked together via sulfonamide linkages was prepared for the first time.
Abstract: A new kind of sol–gel derived organic–inorganic hybrid material was prepared for the first time.In this case the organic portion of an acylamine derivation grafted by 3-aminopropyl trimethoxysilane and covalently linked together via sulfonamide linkages. Fourier transform infrared (FTIR), in ultraviolet absorption (UV) spectra and 1H nuclear magnetic resonance (NMR) spectra were used to confirm these modifications and the X-ray diffraction (XRD) spectra were used to determine the framework. The material’s phosphorescent spectra and luminescence spectra were recorded. An efficient intramolecular energy transfer process between acylamine and lanthanide ions took place within these molecular-based hybrids. Strong green and red emissions were achieved for Tb3+ and Sm3+ ions, respectively.
TL;DR: It was shown that the use of derived spectra did not provide more efficiency and required additional preprocessing such as smoothing to obtain results similar to those obtained from non-derived ones, and results obtained with derivatives were less sensitive to scaling, a useful feature when scaling is problematic.
Abstract: Fourier transform infrared (FT-IR) spectroscopy has become a powerful tool for biodiagnostics and cell line classification. Typical experimental perturbations included in spectra are baseline shift and scale variation between spectra. They have to be removed by data preprocessings to allow further data analysis and classification. In this work, we addressed baseline shift corrections and normalizations in attenuated total reflection (ATR) FT-IR spectra. We compared the efficiency of several preprocessing methods with series of spectra containing typical perturbations (baseline shift, scaling factor, and noise) and a priori known definite spectral difference. Several baseline-correction and normalization possibilities were evaluated. Our results were generally sensitive, selective, and robust with respect to baseline and scaling. Full-range scaling generated more false-positive results. Use of first- and second-derivative spectra was tested. Results obtained on model spectra were confirmed with series of spectra from sensitive and multidrug-resistant leukemia K562 cells. We showed that the use of derived spectra did not provide more efficiency and required additional preprocessing such as smoothing to obtain results similar to those obtained from non-derived ones. On the other hand, results obtained with derivatives were less sensitive to scaling, a useful feature when scaling is problematic.
TL;DR: In this article, a global analysis based on an effective Hamiltonian including the five interacting states was performed on the absorption spectrum of 16 O 3 and the energy values of the three dark vibrational states provided by the fit were found in good agreement with theoretical predictions.