Preparation of Pb0.98La0.02(Zr0.65Ti0.35)O3 films and their fine patterning

The photosensitive lanthanum-doped lead zirconate titanate (PLZT) gel films were prepared by chemical modification with acetylacetone (AcAcH), and their fourier transform infrared (FT-IR) spectra and ultraviolet visible (UV-Vis) spectra were measured. The results show that the chelate rings of AcAcH with Ti or Zr are formed in the PLZT gel films. With irradiation of UV light, the chelate rings are photolyzed, and lead to a change of the solubility of the PLZT gel films in methanol. Transmission electron microscope (TEM) observations show that the perovskite phase is crystallized in PLZT thin film after heat treatment at 700 °C, whose grain sizes are less than or equal to 60 nm. The PLZT thin films exhibited hysteresis loops and good fatigue properties.     

Identification of chemical substances by their near-infrared spectra

Salamin, P.A., Cornelis, Y. and Bartels, H., 1988. Identification of chemical substances by their near-infrared spectra. Chemometrics and Intelligent Laboratory Systems, 3: 329–333.Near-infrared spectra show a large variability due to physical parameters such as particle size. This makes the identification of chemical substances by spectral comparison difficult. This article reviews an earlier method of identification of chemical substances by near-infrared spectra based on the Mahalanobis distance and introduces a new method based on the multiplicative scatter correction. This new method can to a great extent eliminate the spectral variation due to physical parameters and allows a plain comparison of two complete spectra.     

Chemical imaging of latent fingerprint residues

In situ attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopic imaging has been used to obtain chemical images of fingerprints under controlled humidity and temperature. The distribution of lipid and amino acid components in the fingerprints from different donors left on the surface of the ZnSe crystal has been studied using an in situ FT-IR spectroscopic imaging approach under a controlled environment and studied as a function of time. Univariate and multivariate analyses were employed to analyze the spectroscopic dataset. Changes in the spectra of lipids with temperature and time have been detected. This information is needed to understand aging of the fingerprints. The ATR-FT-IR spectroscopic imaging offers a new and complementary means for studying the chemistry of fingerprints that are left pristine for further analysis. This study demonstrates the potential for visualizing the chemical changes of fingerprints for forensic applications by spectroscopic imaging.     

Revealing covariance structures in fourier transform infrared and Raman microspectroscopy spectra: a study on pork muscle fiber tissue subjected to different processing parameters

The aim of this study was to investigate the correlation patterns between Fourier transform infrared (FT-IR) and Raman microspectroscopic data obtained from pork muscle tissue, which helped to improve the interpretation and band assignment of the observed spectral features. The pork muscle tissue was subjected to different processing factors, including aging, salting, and heat treatment, in order to induce the necessary degree of variation of the spectra. For comparing the information gained from the two spectroscopic techniques with respect to the experimental design, multiblock principal component analysis (MPCA) was utilized for data analysis. The results showed that both FT-IR and Raman spectra were mostly affected by heat treatment, followed by the variation in salt content. Furthermore, it could be observed that IR amide I, II, and III band components appear to be effected to a different degree by brine-salting and heating. FT-IR bands assigned to specific protein secondary structures could be related to different Raman C-C stretching bands. The Raman C-C skeletal stretching bands at 1,031, 1,061, and 1,081 cm(-1) are related to the IR bands indicative of aggregated beta-structures, while the Raman bands at 901 cm(-1) and 934 cm(-1) showed a strong correlation with IR bands assigned to a alpha-helical structures. At the same time, the IR band at 1,610 cm(-1), which formerly was assigned to tyrosine in spectra originating from pork muscle, did not show a correlation to the strong tyrosine doublet at 827 and 852 cm(-1) found in Raman spectra, leading to the conclusion that the IR band at 1,610 cm(-1) found in pork muscle tissue is not originating from tyrosine.     

Hydrogel-based piezoresistive pH sensors: investigations using FT-IR attenuated total reflection spectroscopic imaging

The strong swelling ability of the pH-responsive poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) hydrogel makes the development of a new type of sensor possible, which combines piezoresistive-responsive elements as mechanoelectrical transducers and the phase transition behavior of hydrogels as a chemomechanical transducer. The sensor consists of a pH-responsive PAA/PVA hydrogel and a standard pressure sensor chip. However, a time-dependent sensor output voltage mirrors only the physical swelling process of the hydrogel but not the corresponding chemical reactions. Therefore, an investigation of the swelling behavior of this hydrogel is essential for the optimization of sensor design. In this work, Fourier transform infrared (FT-IR) spectroscopic imaging was used to study the swelling of the hydrogel under in situ conditions. In particular, laterally and time-resolved FT-IR images were obtained in the attenuated total reflection mode and the entire data set of more than 80,000 FT-IR spectra was evaluated by principal component analysis (PCA). The first and third principal components (PCs) indicate the swelling process. Molecular changes within the carboxyl groups were observed in the second and fourth PC and identified as key processes for the swelling behavior. It was found that time-dependent molecular changes are similar to the electrical sensor output signal. The results of the FT-IR spectroscopic images render an improved chemical sensor possible and demonstrate that in situ FT-IR imaging is a powerful method for the characterization of molecular processes within chemical-sensitive materials.     

Stopped flow apparatus for time-resolved Fourier transform infrared difference spectroscopy of biological macromolecules in 1H2O

Stopped flow spectroscopy is an established technique for acquiring kinetic data on dynamic processes in chemical and biochemical reactions, and Fourier transform infrared (FT-IR) techniques can provide particularly rich structural information on biological macromolecules. However, it is a considerable challenge to design an FT-IR stopped flow system with an optical path length low enough for work with aqueous (1H2O) solutions. The system presented here is designed for minimal sample volumes (approximately 5 microL) and allows simultaneous FT-IR rapid-scan and VIS measurements. The system employs a micro-structured diffusional mixer to achieve effective mixing on the millisecond time scale under moderate flow and pressure conditions, allowing measurements in a cell path length of less than 10 microns. This makes it possible to record spectra in 1H2O solutions over a wide spectral range. The system layout is also designed for a combination of kinetic and static measurements, in particular to obtain detailed information on the faster spectral changes occurring during the system dead time. A detailed characterization of the FT-IR stopped flow system is presented, including a demonstration of the alkaline conformational transition of cytochrome c as an example.     

Effective use of molecular recognition in gas sensing: results from acoustic wave and in situ FT-IR measurements.

To probe directly the analyte/film interactions that characterize molecular recognition in gas sensors, we recorded changes to the in situ surface vibrational spectra of specifically functionalized surface acoustic wave (SAW) devices concurrently with analyte exposure and SAW measurement of the extent of sorption. Fourier transform infrared external-reflectance spectra (FT-IR-ERS) were collected from operating 97-MHz SAW delay lines during exposure to a range of analytes as they interacted with thin-film coatings previously shown to be selective: cyclodextrins for chiral recognition, nickel camphorates for Lewis bases such as pyridine or organophosphonates, and phthalocyanines for aromatic compounds. In most cases where specific chemical interactions--metal coordination, "cage" compound inclusion, or pi-stacking--were expected, analyte dosing caused distinctive changes in the IR spectra, together with anomalously large SAW sensor responses. In contrast, control experiments involving the physisorption of the same analytes by conventional organic polymers did not cause similar changes in the IR spectra, and the SAW responses were smaller. For a given conventional polymer, the partition coefficients (or SAW sensor signals) roughly followed the analyte fraction of saturation vapor pressure. These SAW/FT-IR results support earlier conclusions derived from thickness-shear mode resonator data.     

Application of near-infrared and Fourier transform infrared spectroscopy in the characterization of ligand-induced conformation changes in folate binding protein purified from bovine milk: influence of buffer type and pH

Fourier transform infrared (FT-IR) and near-infrared (NIR) spectroscopy have been applied to detect structural alterations in folate binding protein (FBP) induced by ligation in different buffer types. The amide I region pointed to a beta-sheet to alpha-helix transition upon ligation in acetate and phosphate buffers, and the formation of intermolecular beta-sheet was indicated at pH 5.0, in agreement with a dimerization of FBP taking place at this pH. The ligand-induced changes in the 2100-2300 nm NIR region were significant for FBP in acetate and phosphate buffers of pH 5.0, and the variations were interpreted as secondary structure changes, based on previous assignments of secondary structures to the combination bands in the NIR region. In the case of acetate buffer, variations in the amide combination bands agreed with the amide I analysis, but for the other buffer types some discrepancies were found and explained by side-chain contributions to the NIR, which could reflect the tertiary and quaternary structure differences. NIR spectra of FBP at pH 7.4 and 5.0 revealed contradictory effects on the side chains, reflecting different polymerization events at the two pH values, whereas the amide I region indicated similar changes at the two pH values. Therefore, we suggest that FT-IR and NIR spectroscopy may complement each other, such that the two techniques in combination may give information on all three types of protein conformational changes. While the secondary structure changes are revealed by FT-IR, the tertiary and quaternary structure changes are reflected in the NIR spectra, although the general influence of the latter changes on the NIR spectra remains to be confirmed.     

Bayesian maximum entropy (two-dimensional) lifetime distribution reconstruction from time-resolved spectroscopic data

Time-resolved spectroscopy is often used to monitor the relaxation processes (or reactions) of physical, chemical, and biochemical systems after some fast physical or chemical perturbation. Time-resolved spectra contain information about the relaxation kinetics, in the form of macroscopic time constants of decay and their decay associated spectra. In the present paper we show how the Bayesian maximum entropy inversion of the Laplace transform (MaxEnt-iLT) can provide a lifetime distribution without sign-restrictions (or two-dimensional (2D)-lifetime distribution), representing the most probable inference given the data. From the reconstructed (2D) lifetime distribution it is possible to obtain the number of exponentials decays, macroscopic rate constants, and exponential amplitudes (or their decay associated spectra) present in the data. More importantly, the obtained (2D) lifetime distribution is obtained free from pre-conditioned ideas about the number of exponential decays present in the data. In contrast to the standard regularized maximum entropy method, the Bayesian MaxEnt approach automatically estimates the regularization parameter, providing an unsupervised and more objective analysis. We also show that the regularization parameter can be automatically determined by the L-curve and generalized cross-validation methods, providing (2D) lifetime reconstructions relatively close to the Bayesian best inference. Finally, we propose the use of MaxEnt-iLT for a more objective discrimination between data-supported and data-unsupported quantitative kinetic models, which takes both the data and the analysis limitations into account. All these aspects are illustrated with realistic time-resolved Fourier transform infrared (FT-IR) synthetic spectra of the bacteriorhodopsin photocycle.     

Absorption Anomalies in Ratio and Subtraction FT-IR Spectroscopy

Subtraction and ratioing of strong absorption bands in Fourier transform infrared (FT-IR) spectroscopy produces anomalous absorption errors. One source of error is the instability in the wavenumber scale of the FT-IR spectra. The possible causes of this error are explored. The thermal expansion and contraction of the cavity of the HeNe reference laser from a typical commercial instrument was found to produce changes in the laser wavenumber of ±0.034 cm(-)(1). Changes of this size are shown to introduce errors into the wavenumber scales of FT-IR spectra which are sufficient to produce the observed anomalies. The dependence of the error on instrumental and spectroscopic parameters is explored. Solutions to the problem are proposed.     

Corroded surface roughness of copper analyzed by Fourier transform infrared mapping microscopy and optical profilometric study

This study shows the effects of roughness on infrared spectra shapes of thin corrosion products on metallic substrates. The calculated spectra show that the baseline is mainly affected by increasing roughness and that such effects do not shift the position of the absorption bands. The model obtained has been used to extract data of artificial patina on a copper surface. Surface defects of copper substrates can be distinguished on the whole surface, from the morphological and chemical points of view, using optical profilometry and infrared microspectroscopy. An homogeneous layer of cuprite covers the surface except in the linear defects. Fourier transform infrared (FT-IR) analysis indicates that a mixture of atacamite and clinoatacamite is mainly located in these scratches. The width of these particular areas is in good agreement with profilometric observations.     

Heat treatment and aging effect on the structural and optical properties of plasma polymerized 2,6-diethylaniline thin films

The monomer, 2,6-diethylaniline has been used to deposit plasma polymerized 2,6-diethylaniline (PPDEA) thin films at room temperature on to glass substrates by a capacitively coupled parallel plate glow discharge reactor. A comparative analysis on the changes of morphological, structural and optical properties of as-deposited, heat treated and aged PPDEA thin films is ascertained. Scanning electron microscopy shows uniform and pinhole free surface of PPDEA thin films and no significant difference in the surface morphology is observed due to heat treatment. Electron dispersive X-ray and Fourier transform infrared spectroscopic investigations indicate some structural rearrangement in PPDEA thin films due to heat treatment. Differential thermal analysis, thermogravimetric analysis and differential thermogravimetric analysis suggest that the PPDEA is thermally stable up to about 580 K. The study on the optical absorption spectra of as-deposited, heat treated and aged PPDEA thin films of different thicknesses lead to the determination of the allowed direct and indirect transition energies ranging from 3.63 to 2.73 and 2.38 to 1.26 eV respectively. Urbach energy, steepness parameter and extinction coefficient are also assessed. It is observed that the optical parameters of as-deposited PPDEA thin films change due to heat treatment and do not change appreciably due to aging.     

Early and rapid detection of potato's fungal infection by Fourier transform infrared microscopy

Fungi are considered serious pathogens to many plants and can cause severe economic damage. Early detection of these pathogens is very important and might be critical for their control. The available methods for detection of fungi are time consuming and not always very specific. Fourier transform infrared (FT-IR) microscopy has proved to be a reliable and sensitive method for detection of molecular changes in cells. Fungi pathogens display typical infrared spectra that differ from the spectra of substrate material such as potato. In the present study we used FT-IR microscopy for early and rapid detection of the potato fungal pathogen Colletotrichum coccodes on the surface of potato tubers. Infected potatoes with this fungal pathogen and uninfected potatoes were examined and correctly classified as infected or not infected by FT-IR microscopy at very early stages of infection when no morphological signs of infection could be seen. Unique spectral biomarkers were found in naturally infected potatoes compared to disease-free control potatoes.     

New opportunities in micro- and macro-attenuated total reflection infrared spectroscopic imaging: spatial resolution and sampling versatility

New opportunities exist to obtain chemical images using attenuated total reflection infrared (ATR-IR) spectroscopy. This paper shows the feasibility of obtaining FT-IR images with a spatial resolution of at least 3-4 microm using a Ge ATR objective coupled with an infrared microscope. The improved spatial resolution compared to FT-IR images obtained by the transmission method is due to the high refractive index of the ATR crystal, which gives a high numerical aperture and hence, a higher spatial resolution. FT-IR imaging with a conventional diamond ATR accessory has been investigated. This is the first time that FT-IR imaging is reported using such a versatile accessory based on a diamond ATR crystal. These results showed that a spatial resolution up to 13 microm can be achieved without the use of infrared microscope objectives. One advantage of the diamond element is that it allows pressure to be applied and hence, good contact to be obtained over the whole field of view.     

Fourier transform infrared spectroscopic imaging of anisotropic poly(vinylidene fluoride) films with polarized radiation

The technique of Fourier transform infrared (FT-IR) spectroscopic imaging with focal plane array detectors has proved to be a powerful technique for rapid chemical visualization of samples with a lateral resolution up to about 10 mum. However, the potential of FT-IR imaging for the characterization of anisotropic materials can be significantly enhanced by using polarized radiation. This issue will be addressed in the present communication, which reports for the first time imaging investigations based on the FT-IR polarization spectra of poly(vinylidene fluoride) films that have been uniaxially elongated below and above the threshold temperature of the II(alpha) --> I(beta) phase transition.     

Attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy of oxidized polymer-modified bitumens

Oxidative age hardening of bitumen results in increasing fatigue susceptibility of bituminous mixtures, thus reducing the service life of asphalt pavements. Polymer additives to bitumen have been shown to improve its viscoelastic properties and, in some cases, reduce the level of bitumen hardening. Fourier transform infrared (FT-IR) spectroscopy enables evaluation of oxidation levels in bitumen by measuring the concentration of oxygen-containing chemical functionalities. This paper summarizes the results of the investigation of oxidative age hardening of polymer-modified bitumens (PMB) caused by accelerated aging in laboratory conditions. The PMB samples are prepared with different concentrations of styrene-butadiene-based co-polymers. Next, the PMB samples are aged using standard procedures that employ air blowing at 163 °C for 85 min followed by conditioning the samples at 100 °C and 2.1 MPa pressure for 20 to 48 hours. The resultant changes in their chemical composition are evaluated by portable attenuated total reflection (ATR) spectrometer. Measurements of ketone, sulfoxide, and hydroxyl content in PMB samples indicated similar oxidation pathways to those of non-modified bitumens. In addition, no evidence of polymer degradation due to accelerated aging of PMB was found in this study.     

Polymerization Process and Morphology of Polyurethane/Vinyl Ester Resin Interpenetrating Polymer Networks

A series of polyurethane （PU）/vinyl ester resin （VER） simultaneous IPNs （interpenetrating polymer networks） with different component ratios and comonomers types introduced to VER were synthesized and the polymerization processes were traced by Fourier transform infrared spectroscopy （FTIR） to study the kinetics of IPNs and hydrogen bonding action within multi-component. Furthermore, the relationship of polymerization process with morphology was investigated in detail for the first time by the morphological information given by chemical action between two networks besides physical entanglement, atomic force microscope （AFM） observation and dynamic mechanical analysis （DMA）. The results indicated that the degree of hydrogen bonding （Xb,UT,%）, calculated from functional group conversional rate and fine structures gained from FT-IR spectra of two networks, were affected by PU/VER weight ratios and comonomer types of VER. The relationship of formation kinetics and morphology showed that the change of Xb,UT （%） values exhibited excellent consistency with that of phase sizes observed by AFM and detected by DMA.     

Large-scale synthesis of a novel tri(8-hydroxyquioline) aluminum nanostructure

A novel tri(8-hydroxyquioline) aluminum (AlQ3) nanostructure was prepared on large scale at low cost by low-temperature physical vapor deposition (PVD). The morphologies, the chemical bondings, and photoluminescence of the AlQ3 nanostructure were investigated by environmental scanning electronic microscopy (ESEM), Fourier transform infrared spectrum (FT-IR), and photoluminescence (PL) spectra, respectively. The AlQ3 nanostructure was composed of micro-sphere with nanowire-cluster growing on the surface. The diameter of micro-sphere and nanowire were about 5 microm and 80 nm, respectively. FT-IR results indicated that the AlQ3 molecule had a strong thermal stability under research conditions. The growth mechanism of the novel nanostructure was discussed. The novel organic nanostructure would be believed to attractive building field-emission devices and other optical devices.     

Stress-induced plasma volume change determined using plasma FT-IR spectra

Our purpose was to determine the plasma-volume (PV) change induced by a physical stress independent of the metabolic events that may interfere with physiological fluid shifts in to and out of the intravascular space. Our methods included using 178 exercise tests of varying duration and intensity for determination of PV change during exercise. Plasma Fourier transform infrared (FT-IR) spectra were used to compare hematocrit change to the total spectral area (4000-500 cm(-1)) and the protein and albumin concentration changes induced by exercise. Our results showed that exercise induced a raise in protein (+10.4 +/- 3.1%) and albumin (+9.8 +/- 3.3%) concentrations that significantly correlated with PV change (14.1 +/- 5.2% of plasma volume; P = 0.05 with protein and albumin concentration changes). However, evolution of the total spectral area obtained from rest-plasma (524 +/- 21 a.u.) and exercise-plasma (611 +/- 26 a.u.; +14.1 +/- 4.8%) FT-IR spectra showed a higher correlation level with PV change (r = 0.98; P = 0.005; S(x/y) = 1.26 a.u.). It is our conclusion that although exercise-induced changes in protein and albumin concentrations were found to correlate with PV change, the use of the total spectral area of the plasma FT-IR spectra allowed a more precise measurement of PV change.     

Phase structure and vibrational spectra of rare-earth-oxide ceramics of Dy<Subscript>2(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>Tm<Subscript>2<Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3</Subscript>

Rare-earth-sesquioxide ceramics have been found to possess potential applications in solid-state lasers due to their excellent physical and chemical properties as well as low cost. In this paper, composite powders with the composition of Dy_2(1−x)Tm_2x O₃ were prepared by ball milling method and corresponding ceramics were obtained using the pressureless sintering technique. Phase structure and vibrational spectra were investigated using X-ray diffraction, Raman spectrometer, and FT-IR spectrometer. It is shown that the mixture of Dy₂O₃ and Tm₂O₃ converts to an ordered solid solution of body-centered cubic structure after heat treatment at 1,100 °C for 4 h. It is also found that the cell constants of ceramics decrease linearly with the increase of Tm₂O₃ content. Raman spectra analysis demonstrates that bond length plays a major role in determining the frequencies of Raman bands at high-frequency range and that peak positions exhibit a blue shift with the increase of Tm₂O₃ content due to decreasing cell constant. Similar phenomenon is also observed in infrared spectra, which shows linearly increasing infrared band frequency with decreasing cell volume. The ball milling method used for preparing composite powders and vibrational spectra analysis in this work provide some important references for the study of laser ceramics containing Dy₂O₃ and Tm₂O₃.