Showing papers on "Fourier transform infrared spectroscopy published in 2005"
TL;DR: In this paper, the effects of charge density on weak polyelectrolyte multilayer growth were investigated by assembling several strong poly electrolytes with either poly(allylamine hydrochloride) (PAH) or poly(acrylic acid) (PAA) to keep one polymer fully charged while varying the degree of ionization of the other.
Abstract: The effects of charge density on weak polyelectrolyte multilayer growth were investigated by assembling several strong polyelectrolytes with either poly(allylamine hydrochloride) (PAH) or poly(acrylic acid) (PAA) to keep one polymer fully charged while varying the degree of ionization of the other. The degree of ionization of the weak polyelectrolytes in solution and in a multilayer film was controlled by pH adjustment and quantified by Fourier transform infrared spectroscopy analyses. In all cases, the bilayer thickness exhibited a dramatic change from molecularly thin bilayers (case of two fully charged polymers) to much thicker bilayers when the degree of ionization of the weak polyelectrolyte decreased below 70−90% charged units. We also confirmed and quantified earlier observations that both the charge density and the effective pKa of a weak polyelectrolyte can change substantially from solution-state values when the polymer is incorporated into a multilayer film. In addition, it was found that the d...
734 citations
TL;DR: In this article, surface modification of coal-based activated carbon (F400) was performed using thermal and chemical methods using Fourier transform infra red (FTIR) spectroscopy, pH titration, zeta potential measurements and sodium uptake capacity results.
601 citations
TL;DR: In this article, a highly oxidized graphite oxide was synthesized from natural graphite powder by oxidation with KMnO4 in concentrated H2SO4 followed by hydrolysis, washing and centrifugation.
585 citations
TL;DR: An Fe-Ce bimetal adsorbent was investigated with X-ray powder diffraction, transmission electron micrograph, Fourier transform infrared spectra, andXPS methods for a better understanding of the effect of surface properties on arsenate (As(V), proving that the adsorption of As(V) by Fe- CeO8 is mainly realized through the mechanism of quantitative ligand exchange.
Abstract: An Fe−Ce bimetal adsorbent was investigated with X-ray powder diffraction (XRD), transmission electron micrograph (TEM), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS) methods for a better understanding of the effect of surface properties on arsenate (As(V)) adsorption. In the adsorption test, the bimetal oxide adsorbent showed a significantly higher As(V) adsorption capacity than the referenced Ce and Fe oxides (CeO2 and Fe3O4) prepared by the same procedure and some other arsenate adsorbents reported recently. XRD measurement of the adsorbent demonstrated that the phase of magnetite (Fe3O4) disappears gradually with the increasing dosage of Ce4+ ions until reaching a molar ratio of Ce4+ to Fe3+ and Fe2+ of 0.08:0.2:0.1 (Fe−Ce08 refers to the adsorbent prepared at this ratio), and the phase of CeO2 begins to appear following a further increase of the Ce dose. Combined with the results of TEM observation, it was assumed that a solid solution of Fe−Ce is formed follow...
482 citations
TL;DR: In this article, the spectral features of edible oils and fats were studied and the unsaturation bond (C C) in IR and Raman spectra was identified and used for discriminant analysis.
428 citations
TL;DR: The difference in hydrogen bonding between hardwood and softwood lignin and the observed differences in the glass transition temperature are discussed.
408 citations
TL;DR: Biocompatible ferrofluid containing dye-functionalized magnetite nanoparticles that can serve as fluorescent markers enable optical tracking of basic processes at the cellular level combined with magnetophoretic manipulation and should be of substantial value to researchers engaged in both fundamental and applied biomedical research.
Abstract: A method is presented for the preparation of a biocompatible ferrofluid containing dye-functionalized magnetite nanoparticles that can serve as fluorescent markers. This method entails the surface functionalization of magnetite nanoparticles using citric acid to produce a stable aqueous dispersion and the subsequent binding of fluorescent dyes to the surface of the particles. Several ferrofluid samples were prepared and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), BET surface area analysis, transmission electron microscopy (TEM), and SQUID magnetometry. In addition, confocal fluorescence microscopy was used to study the response of the fluorescent nanoparticles to an applied magnetic field and their uptake by cells in vitro. Results are presented on the distribution of particle sizes, the fluorescent and magnetic properties of the nanoparticles, and the nature of their surface bonds. Biocompatible ferrofluids ...
396 citations
TL;DR: A detailed interpretations of the infrared and Raman spectra of 5-bromo-2-nitropyridine is reported on the basis of the calculated potential energy distribution (PED).
378 citations
TL;DR: This work demonstrates real-time recording of chemical vapor fluc-tuations from 22m away with a fast Fourier-transform infrared (FTIR) spectrometer that uses a laser-like infrared probing beam generated from two 10-fs Ti:sapphire lasers.
Abstract: We demonstrate real-time recording of chemical vapor fluctuations from 22m away with a fast Fourier-transform infrared (FTIR) spectrometer that uses a laser-like infrared probing beam generated from two 10-fs Ti:sapphire lasers. The FTIR’s broad 9–12μm spectrum in the “molecular fingerprint” region is dispersed by fast heterodyne self-scanning, enabling spectra at 2cm-1 resolution to be recorded in 70μs snapshots. We achieve continuous acquisition at a rate of 950 IR spectra per second by actively manipulating the repetition rate of one laser. Potential applications include video-rate chemical imaging and transient spectroscopy of e.g. gas plumes, flames and plasmas, and generally non-repetitive phenomena such as those found in protein folding dynamics and pulsed magnetic fields research.
369 citations
TL;DR: Solution chemistry effects on ciprofloxacin sorption to hydrous oxides of Al (HAO) and Fe (HFO) were investigated using macroscopic and spectroscopic analyses to increase the understanding of the environmental reactivity of fluoroquinolones, an important class of antimicrobial compounds.
Abstract: Solution chemistry (pH, ionic strength (I), and sorbate-to-sorbent ratio) effects on ciprofloxacin sorption to hydrous oxides of Al (HAO) and Fe (HFO) were investigated using macroscopic and spectroscopic analyses. Sorption to both HAO and HFO showed a strong pH-dependent behavior, following the fraction of zwitterionic species over the entire pH range studied. Increase in I from 0.01 to 0.5 M had an insignificant effect on the extent of ciprofloxacin sorption, and isotherms were well-described by the Langmuir model. HFO possessed a higher sorption capacity (0.066 mmol kg(-1)) than HAO (0.041 mmol kg(-1)). Ligand-promoted dissolution of hydrous oxides, more pronounced for HAO, was observed in the presence of ciprofloxacin, but at a fairly high initial concentration (0.5 mM). Attenuated total reflectance Fourier transform infrared spectroscopy analysis indicated that different types of ciprofloxacin surface complexes are formed with HAO and HFO; while a monodentate mononuclear complex (with -COO-) appears likely between ciprofloxacin and HAO, keto O and one O from COO- seem to be involved in the formation of a six-membered ring with Fe on the HFO surface. The study results are expected to increase our understanding of the environmental reactivity of fluoroquinolones, an important class of antimicrobial compounds.
348 citations
TL;DR: In this paper, the annealing effect on the structural perfection of Fe-doped LiNbO3 single crystals has been studied by high-resolution X-ray diffractometry (HRXRD), XRT and Fourier transform infrared (FT-IR) spectroscopy.
Abstract: The annealing effect on the structural perfection of Fe-doped LiNbO3 single crystals has been studied by high-resolution X-ray diffractometry (HRXRD), X-ray topography (XRT) and Fourier transform infrared (FT–IR) spectroscopy. The single crystals, prepared by mixing Li2CO3 and Nb2O5 powders in the molar ratio 48.6:51.4 with 0.05 mol% of iron at 1415 (1) K, were grown by the Czochralski (CZ) method along the [001] direction in air and poled during crystal growth by the application of a DC field. Two low-angle (tilt angle ∼1 arc minute) structural grain boundaries were observed in as-grown specimens. FT–IR spectra revealed that these crystals contain OH− and CO32− ionic defects. Grain boundaries and CO32− ionic defects were successfully removed, while the concentration of OH− ions was considerably reduced by post-growth thermal annealing at elevated temperatures.
TL;DR: The impact and promise of this spectroscopic imaging methodology are illustrated and fundamental principles of the technique are presented in the context of FTIR spectroscopy and new applications are reviewed ranging from the physical chemistry of macromolecular systems to the detection of human disease.
Abstract: The recent development of Fourier transform infrared (FTIR) spectroscopic imaging has enhanced our capability to examine, on a microscopic scale, the spatial distribution of vibrational spectroscopic signatures of materials spanning the physical and biomedical disciplines. Recent activity in this emerging area has concentrated on instrumentation development, theoretical analyses to provide guidelines for imaging practice, novel data processing algorithms, and the introduction of the technique to new fields. To illustrate the impact and promise of this spectroscopic imaging methodology, we present fundamental principles of the technique in the context of FTIR spectroscopy and review new applications in various venues ranging from the physical chemistry of macromolecular systems to the detection of human disease.
TL;DR: Study of the early steps of reaction of 2-microm sized particles of Bioglass, in solutions buffered with TRIS at different pH, by means of ICP-ES and FTIR spectroscopy showed that the process of silica formation is not separable from cation leaching from the glass, as well as the formation of the calcium phosphate rich layer.
TL;DR: In this paper, a liquid phase redox process was designed to prepare monodispersed Co3O4 nanocrystals with particle sizes of 2 nm (spherical), 2.5 nm (cubelike), and 4.7 nm (closest to ours).
Abstract: A liquid-phase redox process has been designed to prepare monodispersed Co3O4 nanocrystals with particle sizes of 2 nm (spherical), 2.5 nm (cubelike), and 4.7 nm (cubelike). The nanocrystals were characterized by transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric techniques. The nucleation and growth, which were tracked by UV−visible spectroscopy, can be separated by adjusting the solubility of sodium nitrate, and the smallest possible Co3O4 nanocubes, 2.5 nm on a side, were obtained. A solubility-controlled mechanism for the redox reaction is discussed which is critical in avoiding secondary nucleation and interparticle ripening growth of Co3O4 nanocrystals.
TL;DR: The relationship between gluten structure and mechanical properties is discussed in terms of a model in which conversion of beta-turn to beta-sheet structure is a response to extension and a means by which elastic energy is stored in the system.
15 Jul 2005
TL;DR: The available methods to monitor lipid oxidation in foods can be classified into five groups based on what they measure: the absorption of oxygen, the loss of initial substrates, the formation of free radicals, and formation of primary and secondary oxidation products.
Abstract: Numerous analytical methods are routinely used for measuring lipid oxidation in foods. However, there is no uniform and standard method for detecting all oxidative changes in all food systems. Therefore, it is necessary to select a proper and adequate method for a particular application. The available methods to monitor lipid oxidation in foods can be classified into five groups based on what they measure: the absorption of oxygen, the loss of initial substrates, the formation of free radicals, and the formation of primary and secondary oxidation products. A number of physical and chemical tests, including instrumental analyses, have been employed in laboratories and the industry for measurement of various lipid oxidation parameters. These include the weight-gain and headspace oxygen uptake method for oxygen absorption: chromatographic analysis for changes in reactants; iodometric titration, ferric ion complexes, and Fourier transform infrared (FTIR) method for peroxide value; spectrometry for conjugated dienes and trienes, 2-thio-barbituric acid (TBA) value, p-anisidine value (p-AnV), and carbonyl value; Rancimat and Oxidative Stability Instrument method for oil stability index; and electron spin resonance (ESR) spectrometric assay for free-radical type and concentration. Other techniques based on different principles, such as differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR), have also been used for measuring lipid oxidation. In addition, sensory tests provide subjective or objective evaluation of oxidative deterioration, depending on certain details.
Keywords:
lipid oxidation;
dietary lipids;
food quality;
differential scanning calorimetry;
nuclear magnetic resonance;
electron spin resonance;
sensory analysis;
Fourier transform infrared method
TL;DR: Detailed analysis of the IR spectrum utilizing quantum chemical (Hartree-Fock) calculations indicates that intermolecular association through O...Li...O interactions is very important in this compound.
Abstract: Lithium ethylene dicarbonate ((CH2OCO2Li)2) was chemically synthesized and its Fourier transform infrared (FTIR) spectrum was obtained and compared with that of surface films formed on Ni after cyclic voltammetry (CV) in 1.2 M lithium hexafluorophosphate (LiPF6)/ethylene carbonate (EC):ethyl methyl carbonate (EMC) (3:7, w/w) electrolyte and on metallic lithium cleaved in-situ in the same electrolyte. By comparison of IR experimental spectra with that of the synthesized compound, we established that the title compound is the predominant surface species in both instances. Detailed analysis of the IR spectrum utilizing quantum chemical (Hartree-Fock) calculations indicates that intermolecular association through O...Li...O interactions is very important in this compound. It is likely that the title compound in the passivation layer has a highly associated structure, but the exact intermolecular conformation could not be established on the basis of analysis of the IR spectrum.
TL;DR: In this paper, a diamond-like carbon (DLC) film was fabricated by plasma immersion ion implantation and deposition (PIII and D) and the structure, physicochemical characteristics, electrical properties, as well as surface biomedical compatibility, were evaluated using different characterization techniques.
TL;DR: In this paper, the infrared spectra of phthalocyanine and (Mg+2, Mn+2 and Pb+2) were investigated using FTIR in the range from (4000-400 cm−1), as halide discs.
TL;DR: In this paper, the stereoselective annealing conditions for polylactides to crystallize as α homocrystals (Tm = 180 °C) and/or higher melting temperature η stereocomplex crystals are reported.
Abstract: The stereoselective annealing conditions for polylactides to crystallize as α homocrystals (Tm = 180 °C) and/or higher melting temperature (Tm = 230 °C) η stereocomplex crystals are reported in this paper. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies provide evidence of the isothermal annealing conditions in which equimolar mixtures of optically pure poly(l-lactide) and poly(d-lactide) take exclusively the form α, exclusively the form η, or coexist as both α and η crystal polymorphs. Fourier transformed infrared (FTIR) spectroscopy studies reveal a shift to lower wavenumbers in the CO stretching band of polylactides in the stereocomplex with regard to that in the homocrystal. This band shift is accompanied by similar displacements in the C−H spectral bands. These results are interpreted in terms of H-bonding forces causing specific CH3···OC and CαH···OC interactions between both stereoisomers of polylactide. Molecular models support that the suggested hydrogen-bonding arrang...
TL;DR: In this article, the structural and spectral information of polyvinyl alcohol (ZnO) hybrid nanofibers were characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, resonant Raman, and photoluminescence (PL).
Abstract: Polyvinyl alcohol∕ZnO (PVA∕ZnO) hybrid nanofibers were prepared by the electrospinning technique. The structural and spectral information of the nanofibers was characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, resonant Raman, and photoluminescence (PL). The results indicate that ZnO were successfully embedded in the one-dimensional hybrid fibers via chemical interactions between ZnO and PVA. PL results show the PVA∕ZnO nanofibers have an intense white-light emission, which originates from the simultaneous emission of three bands covering from the UV to visible range. A possible PL mechanism was proposed accordingly.
TL;DR: The spectroscopic results, the contact-angle results, and the swelling analysis altogether prove the retention of the hydrophilic pendant groups in the iCVD process.
Abstract: Initiated chemical vapor deposition (iCVD) is able to synthesize linear and cross-linked poly(2-hydroxyethyl methacrylate) (PHEMA) thin films, in one step, from vapors of 2-hydroxyethyl methacrylate (HEMA), ethylene glycol diacrylate (EGDA), and tert-butyl peroxide (TBPO) without using any solvents. This all-dry technique also allows control of the cross-link density by adjusting the partial pressure of the cross-linking agent EGDA in the vapor phase. Films with specific cross-link densities and hence thermal, wetting, and swelling properties can be created in one single vacuum processing step. Through selective thermal decomposition of the initiator TBPO, films with well-defined chemical structures and full functionality retention can be deposited, which is evident in the Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. These spectroscopic methods also facilitate determination of EGDA incorporation in the cross-linked films based on the fact that HEMA contains a hydr...
TL;DR: Co3O4 nanoplatelets exhibit a superparamagnetic behavior, and they might be a promising material to study the magnetic tunneling effect as anisotropic nanostructures as well as a simple, low-cost, and large-scale route to produce beta-cobalt hydroxide nanopatelets.
Abstract: Cobalt hydroxide nanoplatelets with a uniform hexagonal shape were prepared in high yield (∼95%) by a facile hydrothermal route in the presence of poly(vinylpyrrolidone). This method provides a simple, low-cost, and large-scale route to produce β-cobalt hydroxide nanoplatelets with an average diameter of 280 nm and a thickness of ca. 26 nm which show a predominant well-crystalline hexagonal brucite-like phase. Their thermal decomposition produced anisotropic nanoplatelets of cobalt oxides (CoO and Co3O4) under designed temperatures. The products were characterized by transmission electronic microscopy, selected-area electron diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetric, and thermogravimetric analysis. The magnetic properties of the products were investigated by a superconducting quantum interference device magnetometer. Co3O4 nanoplatelets exhibit a superparamagnetic behavior, and they might be a promising material to study the magnetic tunneling effect as aniso...
TL;DR: In this article, a flame-retardant nano-concentrates were added to flame-resistant nano-coating to improve its char layer structure and fire-resistant properties.
TL;DR: FTIR spectroscopy, temperature-programmed desorption (TPD), and pressure-composition (P-C) isotherms suggest that 75% of the H(2) is physisorbed and can be reversibly released upon pressure reduction.
Abstract: TiO(2) nanotubes can reproducibly store up to approximately 2 wt % H(2) at room temperature and 6 MPa. However, only about 75% of this stored hydrogen can be released when the hydrogen pressure is lowered to ambient conditions, suggesting that both physisorption and chemisorption are responsible for the hydrogen uptake. FTIR spectroscopy, temperature-programmed desorption (TPD), and pressure-composition (P-C) isotherms suggest that 75% of the H(2) is physisorbed and can be reversibly released upon pressure reduction. Approximately 13% is weakly chemisorbed and can be released at 70 degrees C as H(2), and approximately 12% is bonded to oxide ions and released only at temperatures above 120 degrees C as H(2)O.
TL;DR: In this article, the structural changes of E. coli cell membranes during TiO2 photocatalysis were investigated using attenuated total reflection Fourier transform infrared spectroscopy and atomic force microscopy (AFM).
Abstract: Escherichia coli (E. coli) photokilling due to the TiO2 under light irradiation in a batch reactor was studied by using of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM). The ATR-FTIR spectral features and AFM images were analyzed in relation to E. coli viability data. ATR-FTIR is shown to be a suitable technique to follow the structural changes of the E. coli cell membranes during TiO2 photocatalysis. Formation of the peroxidation products due to the photocatalysis of E. coli cell is reported by this technique. Time dependent ATR-FTIR experiments provides the evidence for the changes in the E. coli cell wall membranes as the precursor events leading to bacterial lysis. Under the same experimental conditions used by ATR-FTIR spectroscopy, AFM microscopy was carried out to provide direct evidence for the E. coli lysis taking place under light irradiation after about 1 h in the presence of TiO2. By transmission electron microscopy (TEM), the aggregated TiO2 Degussa P-25 in aqueous solution is shown to interact with the bacteria surface and partly to remain in the aqueous solution at the concentration of 1 mg/ml.
TL;DR: In this article, two types of monofunctional benzoxazines with imide functionalities have been synthesized for improved thermal properties, which achieve char yields above 55% and exhibit glass transition temperatures above 250 °C.
TL;DR: In this paper, a chitosan membrane having 84% degree of deacetylation was crosslinked with toluene-2,4-diisocyanate and tested for the dehydration of isopropanol by the pervaporation method.
TL;DR: In this paper, the polyimide/barium titanate (BaTiO3) composites were successfully synthesized through a colloidal process, in which the preparing suspension of fine BaTiO 3 particles in poly(amic acid) solution, the film casting of the suspension, and the imidization with heat treatment are involved in sequence.
Abstract: The polyimide/barium titanate (BaTiO3) composites were successfully synthesized through a colloidal process. In this process, the preparing suspension of fine BaTiO3 particles in poly(amic acid) solution, the film casting of the suspension, and the imidization with heat treatment are involved in sequence. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), thermal-gravimetric analyses (TGA) and electrometer were used to characterize the structure and properties of the obtained composites. It was found that the BaTiO3 particles in the size of 100 nm were dispersed homogeneously in the polyimide matrix without aggregation. Thermal stability of the composites could be improved with the incorporation of BaTiO3. The dielectric constant (e) and the dielectric loss (tan δ) of these composites increased with the increase of the volume fraction of BaTiO3 particles. e, tan δ was 35 and 0.0082, respectively at 10 kHz as the composite contains 50 vol% BaTiO3. Also, the dielectric properties of the composites displayed good stability within a wide range of temperature or frequency.
TL;DR: In this paper, the effect of freezing, formalin fixation, wax embedding and de-waxing on the Raman and IR spectra of placenta sections was investigated.