Fourier Transform Infrared Photoacoustic Spectroscopy Research Articles

Rapid estimation of sugar release from winter wheat straw during bioethanol production using FTIR-photoacoustic spectroscopy.

BackgroundComplexity and high cost are the main limitations for high-throughput screening methods for the estimation of the sugar release from plant materials during bioethanol production. In addition, it is important that we improve our understanding of the mechanisms by which different chemical components are affecting the degradability of plant material. In this study, Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was combined with advanced chemometrics to develop calibration models predicting the amount of sugars released after pretreatment and enzymatic hydrolysis of wheat straw during bioethanol production, and the spectra were analysed to identify components associated with recalcitrance.ResultsA total of 1122 wheat straw samples from nine different locations in Denmark and one location in the United Kingdom, spanning a large variation in genetic material and environmental conditions during growth, were analysed. The FTIR-PAS spectra of non-pretreated wheat straw were correlated with the measured sugar release, determined by a high-throughput pretreatment and enzymatic hydrolysis (HTPH) assay. A partial least square regression (PLSR) calibration model predicting the glucose and xylose release was developed. The interpretation of the regression coefficients revealed a positive correlation between the released glucose and xylose with easily hydrolysable compounds, such as amorphous cellulose and hemicellulose. Additionally, a negative correlation with crystalline cellulose and lignin, which inhibits cellulose and hemicellulose hydrolysis, was observed.ConclusionsFTIR-PAS was used as a reliable method for the rapid estimation of sugar release during bioethanol production. The spectra revealed that lignin inhibited the hydrolysis of polysaccharides into monomers, while the crystallinity of cellulose retarded its hydrolysis into glucose. Amorphous cellulose and xylans were found to contribute significantly to the released amounts of glucose and xylose, respectively.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0267-2) contains supplementary material, which is available to authorized users.

Preparation and characterization of flexible ferromagnetic nanocomposites for microwave applications

Abstract Magnetic Fe 3 O 4 nanoparticles (∼20 nm) were synthesized using the chemical co-precipitation method with a view of developing flexible and easily processable ferromagnetic materials with high mouldability to be used as microwave absorbers. The nanoparticles prepared were incorporated into natural rubber through latex stage processing. This novel processing method gives better dispersion of particles in the rubber matrix. The composites were characterized using XRD, SEM, vibrating sample magnetometer, dynamic mechanical analyzer, cavity perturbation, thermogravimetry (TGA), and Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). A notable improvement in the mechanical properties of composites was observed upon adding Fe 3 O 4 particles. Magnetic and microwave characteristics of the composites indicate the formation of a flexible ferromagnetic material with good microwave absorption characteristics.

FTIR–PAS: A powerful tool for characterising the chemical composition and predicting the labile C fraction of various organic waste products

Fourier transform infrared (FT-IR) spectroscopy has been used for several years as a fast, low-cost, reliable technique for characterising a large variety of materials. However, the strong influence of sample particle size and the inability to measure the absorption of very dark and opaque samples have made FTIR unsuitable for many waste materials. FTIR–photoacoustic spectroscopy (FTIR–PAS) can eliminate some of the shortcomings of traditional FTIR caused by scattering effects and reflection issues, and recent advances in PAS technology have made commercial instruments available. In this study, FTIR–PAS was used to characterise a wide range of organic waste products and predict their labile carbon fraction, which is normally determined from time-consuming assays. FTIR–PAS was found to be capable of predicting the labile fraction of carbon as efficiently as near infrared spectroscopy (NIR) and furthermore of identifying the compounds that are correlated with the predicted parameter, thus facilitating a more mechanistic interpretation.

Characterization of hydrophobic soils: a novel approach using mid-infrared photoacoustic spectroscopy.

Previous research has produced conclusive evidence to show that soil hydrophobicity is affected by soil organic matter (SOM) and soil water content (WC). Soil hydrophobicity that responds to WC is a unique form of hydrophobicity called reversible hydrophobicity. The mechanistic processes by which water and SOM interact continue to be a subject of investigation. This article presents a novel application of photoacoustic Fourier transform infrared spectroscopy (FT-IR) for the investigation of reversibly hydrophobic soils. Photoacoustic FT-IR data show that, in response to hydration, surface molecules on wetted soil particles interacted differently with mid-infrared radiation than surface molecules present on air-dried soil. This can be interpreted as an effect of the reorienting of amphiphilic molecules in response to hydration-driven entropic processes. These results suggest that the photoacoustic FT-IR method can be used to elucidate how SOM and water interact at the molecular scale to drive soil hydrophobicity.

Classifying rapeseed varieties using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS)

This study proposed a methodology for classification of rapeseed varieties using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). For this purpose, principal components analysis (PCA) was first used to reveal the separation of three varieties of rapeseeds, and then partial least squares-discriminant analysis (PLS-DA) and support vector machines (SVM) were employed for the classification task. The overall classification error rates (ERs) of prediction set were 7.5% and 0 for the models of PLS-DA and SVM, respectively. Furthermore, successive projections algorithm (SPA) was adopted to choose an appropriate variable subset as the inputs of PLS-DA and SVM. Both SPA-PLS-DA and SPA-SVM models gave improved predictive accuracy with significantly reduced model variables. The results of this study had showed the good performance of FTIR-PAS as a rapid, non-destructive and objective tool for classifying varieties of rapeseeds.

Polydomy in the antEctatomma opaciventre

Tropical ants commonly exhibit a hyper-dispersed pattern of spatial distribution of nests. In polydomous species, nests may be satellites, that is, secondary structures of the main nest, where the queen is found. In order to evaluate whether the ant Ectatomma opaciventre Roger (Formicidae: Ectatomminae) uses the strategy of building polydomous nests, the spatial distribution pattern of 33 nests in a 1,800 m2 degraded area located in Rio Claro, SP, Brazil, were investigated using the nearest neighbor method. To complement the results of this investigation, the cuticular chemical profile of eight colonies was analyzed using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). The nests of E. opaciventre presented a hyper-dispersed or regular distribution, which is the most common in ants. The analysis of the cuticular hydrocarbons apparently confirmed the hypothesis that this species is polydomous, since the chemical profiles of all studied colonies with nests at different sites were very similar to the chemical signature of the single found queen and were also different from those of colonies used as control.

Polydomy in the ant Ectatomma opaciventre.

Tropical ants commonly exhibit a hyper-dispersed pattern of spatial distribution of nests. In polydomous species, nests may be satellites, that is, secondary structures of the main nest, where the queen is found. In order to evaluate whether the ant Ectatomma opaciventre Roger (Formicidae: Ectatomminae) uses the strategy of building polydomous nests, the spatial distribution pattern of 33 nests in a 1,800 m 2 degraded area located in Rio Claro, SP, Brazil, were investigated using the nearest neighbor method. To complement the results of this investigation, the cuticular chemical profile of eight colonies was analyzed using Fourier transform infrared photoacoustic spectrosco-py (FTIR-PAS). The nests of E. opaciventre presented a hyper-dispersed or regular distribution, which is the most common in ants. The analysis of the cuticular hydrocarbons apparently con-firmed the hypothesis that this species is polydomous, since the chemical profiles of all studied colonies with nests at different sites were very similar to the chemical signature of the single found queen and were also different from those of colonies used as control.

Improving the bonding between henequen fibers and high density polyethylene using atmospheric pressure ethylene-plasma treatments

In order to improve the bonding between henequen fibers (Agave fourcroydes) and High Density Polyethylene (HDPE), they were treated in an ethylene-dielectric barrier discharge (DBD) plasma operating at atmospheric pressure. A 2 3 factorial experimental design was used to study the effects of the plasma operational parameters, namely, frequency, flow rate and exposure time, over the fiber tensile mechanical properties and its adhesion to HDPE. The fiber-matrix Inter- facial Shear Strength (IFSS) was evaluated by means of the single fiber pull-out test. The fiber surface chemical changes were assessed by photoacoustic Fourier transform infrared spectroscopy (PAS-FTIR) and the changes in surface morphol- ogy with scanning electron microscopy (SEM). The results indicate that individual operational parameters in the DBD plasma treatment have different effects on the tensile properties of the henequen fibers and on its bonding to HDPE. The SEM results show that the plasma treatment increased the roughness of the fiber surface. The FTIR result seems to indicate the presence of a hydrocarbon-like polymer film, bearing some vinyl groups deposited onto the fibers. These suggests that the improvement in the henequen-HDPE bonding could be the result of the enhancement of the mechanical interlocking, due the increment in roughness, and the possible reaction of the vinyl groups on the film deposited onto the fiber with the HDPE.

Microstructure, Spectroscopic Studies and Nanomechanical Properties of Human Cortical Bone with Osteogenesis Imperfecta

ABSTRACTBone is a natural protein (collagen)-mineral (hydroxyapatite) nanocomposite with hierarchically organized structure. Our previous work has demonstrated orientational differences in stoichiometry of hydroxyapatite resulting from orientationally dependent collagen-mineral interactions in bone. The nature of these interactions has been investigated both through molecular dynamics simulations as well as nanomechanical and infrared spectroscopic experiments. In this study, we report experimental studies on human cortical bone with osteogenesis imperfecta (OI), a disease characterized by fragility of bones and other tissues rich in type I collagen. About 90% of OI cases result from causative variant in one of the two structural genes (COL1A1 or COL1A2) for type I procollagens. OI provides an interesting platform for investigating how alterations of collagen at the molecular level cause changes in structure and mechanics of bone. Fourier transform spectroscopy, electron microscopy (SEM), and nanomechanical experiments describe the structural and molecular differences in bone ultrastructure due to presence of diseases. Photoacoustic-Fourier transform infrared spectroscopy (PA-FTIR) experiments have been conducted to investigate the orientational differences in molecular structure of OI bone, which is also compared with that of healthy human cortical bone. Further, in situ SEM static nanomechanical testing is conducted in the transverse and longitudinal directions in the OI bone. Microstructural defects and abnormities of OI bone were ascertained using scanning electron microscopies. These results provide an insight into molecular basis of deformation and mechanical behavior of healthy human bone and OI bone.

A 1915–2011 microscale record of soil organic matter under wheat cultivation using FTIR-PAS depth-profiling

Soil organic matter (SOM) is a keystone soil property that influences soil biological, chemical, and physical properties important for soil health. Due to the high fraction of carbon within SOM, soil organic C is an important and readily manageable component of the global carbon cycle. Agroecosystem management practices strongly influence SOM content and structural chemistry. However, there are few sites where long-term effects, e.g., more than 100 years, of agroecosystem management on SOM can be studied. We hypothesized that long-term wheat production and changes in residue management would alter SOM structural chemistry through time and space. Here, soil samples from years 1915, 1938, 1962, 1988, and 2011 were acquired from the continuous wheat with inorganic fertilizer application plot (plot 2) established in the year 1888 at Sanborn Field, Columbia, Missouri, USA. Control soil samples were collected in the year 2011 from a nearby native prairie. SOM structure was analyzed as a function of distance from the particle surface, at the micrometer scale, by Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). Our results show that SOM profiles are very heterogeneous, but three different layers were identifiable in spectra collected using FTIR-PAS depth-profiling as follows: (1) a surface layer, ranging 0–20 μm, that exhibits enrichment of C–O bonds, (2) a middle layer, ranging 20–40 μm, displaying an abundance of aromatic C = C bonds, and (3) an inner layer, ranging 40–100 μm, containing more heterocyclic N moieties. Our findings show that transformation of SOM was accelerated during the first 50 years of wheat cropping and fertilization, especially in the surface layer. However, further changes in SOM structure were remarkably retarded between 1962 and 2011 due to a change in cropping practice that retained crop residue on the plot.

Crude extract ofFusarium oxysporuminduces apoptosis and structural alterations in the skin of healthy rats

We evaluate the biological and physicochemical effects of a Fusarium oxysporum crude extract (CE) on the skin of healthy rats. The CE is topically applied and subsequently the skin is collected after 3, 6, 12, and 24 h. The samples are analyzed by Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) and histomorphometric analysis. Terminal dUTP nick end labeling (TUNEL assay) is performed to detect both the cells in apoptosis and proliferation. There is a thickening of the epidermis after 6, 12, and 24 h and dermis after 12 and 24 h of CE application. A reduction of the dermis thickness is observed at 3 and 6 h. The treated skin shows higher labeling intensity by TUNEL at 3 h, while a higher intensity by proliferating cell nuclear antigen occurs at 3 and 12 h. FTIR-PAS data support the histology observations showing an increase in the absorption peaks in the dermis after the application of the CE. F. oxysporum CE permeated through the epidermis and the dermis, reaching the subcutaneous tissue, inducing cell apoptosis, and causing physicochemical changes in the organic molecules located in the dermis. This is the first known study associating histopathological and physical chemistry changes on healthy skin after the application of F. oxysporum CE.

Synthesis of POSS–polyurethane hybrids using octakis(m‐isoprenyl‐α,α′‐dimethylbenzylisocyanato dimethylsiloxy) octasilsesquioxane (Q8M8TMI) as a crosslinking agent

ABSTRACTA series of polyurethane hybrid networks have been synthesized using octakis(m‐isoprenyl‐α,α′‐dimethylbenzylisocyanato dimethylsiloxy) octasilsesquioxane (Q8M8TMI) as a crosslinking agent. The formation of the urethane linkages within the polyurethane hybrids was confirmed by photoacoustic FTIR spectroscopy. The TGA and DSC studies demonstrated that the incorporation of the POSS crosslinking agents altered the thermal properties of the polyurethanes, and that this was dependent on the length of the polyethylene glycol chain. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5038–5045

Hydrogen Peroxide Diffusion Dynamics in Dental Tissues

The aim of this study was to investigate the diffusion dynamics of 25% hydrogen peroxide (H2O2) through enamel-dentin layers and to correlate it with dentin’s structural alterations. Micro-Raman Spectroscopy (MRS) and Fourier Transform Infrared Photoacoustic Spectroscopy (FTIR-PAS) were used to measure the spectra of specimens before and during the bleaching procedure. H2O2 was applied to the outer surface of human enamel specimens for 60 minutes. MRS measurements were performed on the inner surface of enamel or on the subsurface dentin. In addition, H2O2 diffusion dynamics from outer enamel to dentin, passing through the dentin-enamel junction (DEJ) was obtained with Raman transverse scans. FTIR-PAS spectra were collected on the outer dentin. MRS findings revealed that H2O2 (O-O stretching µ-Raman band) crossed enamel, had a more marked concentration at DEJ, and accumulated in dentin. FTIR-PAS analysis showed that H2O2 modified dentin’s organic compounds, observed by the decrease in amides I, II, and III absorption band intensities. In conclusion, H2O2 penetration was demonstrated to be not merely a physical passage through enamel interprismatic spaces into the dentinal tubules. H2O2 diffusion dynamics presented a concentration gradient determined by the chemical affinity of the H2O2 with each specific dental tissue.

Morphology, Structure, Thermal Stability, XR-Diffraction, and Infrared Study of Hexadecyltrimethylammonium Bromide–Modified Smectite

We characterized the interlayer structure and morphology of modified natural clays. Organoclay-based materials are increasingly used for multiple applications. We modified a purified Na-bentonite using cation exchange with hexadecyltrimethyl ammonium bromide (HDTMA) and characterized it using; UV spectroscopy, X-ray diffraction, photoacoustic FTIR spectroscopy (PA-FTIR), thermogravimetric analysis (TGA) techniques, laser scattering distribution (LSD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The adsorption of HDTMA on interlayer sites of Na-smectite fraction is nearly total until an adsorption equivalent to 1.85 times the cation exchange capacity (CEC) of the clay. The formation of the HDTMA-smectite changes the properties of the clay from hydrophilic to hydrophobic. The XRD patterns show an increase in the basal spacings. TGA characterization and analysis were shown to be useful to estimate the amount of surfactant within the organoclay. LSD analyses have shown a decrease of the effective particle diameter with increasing sonication times. AFM images showed that these Na-smectite surfaces appeared foliated with irregular aggregate structures at high HDTMA loading. The present study shows that not only the basal spacing but the morphology and the particle size of the organoclay strongly depend on the packing density of surfactant within the smectite interlayer space.

Pollen Identification by Fourier Transform Infrared Photoacoustic Spectroscopy

Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS) has been applied to the problem of identifying pollen samples. One hundred measurements were made on a set of pollen samples comprising five families and ten species. Chemometric analysis of the resulting spectra showed evidence of clustering. Construction of a spectral library allowed pollens in the set to be correctly identified as the first match on the basis of photoacoustic spectra at the species (99%) or family (100%) level.

Analysis of Resistant Starches in Rat Cecal Contents Using Fourier Transform Infrared Photoacoustic Spectroscopy

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) qualitatively and quantitatively measured resistant starch (RS) in rat cecal contents. Fisher 344 rats were fed diets of 55% (w/w, dry basis) starch for 8 weeks. Cecal contents were collected from sacrificed rats. A corn starch control was compared against three RS diets. The RS diets were high-amylose corn starch (HA7), HA7 chemically modified with octenyl succinic anhydride, and stearic-acid-complexed HA7 starch. To calibrate the FTIR-PAS analysis, samples from each diet were analyzed using an enzymatic assay. A partial least-squares cross-validation plot generated from the enzymatic assay and FTIR-PAS spectral results for starch fit the ideal curve with a R(2) of 0.997. A principal component analysis plot of components 1 and 2 showed that spectra from diets clustered significantly from each other. This study clearly showed that FTIR-PAS can accurately quantify starch content and identify the form of starch in complex matrices.

Social Parasitism and Dynamics of Cuticular Hydrocarbons in Paper Wasps of the GenusMischocyttarus

Facultative social parasitism has been recorded in several taxa of social insects. Most recently, this phenomenon has been recorded in colonies of the neotropical social wasp Mischocyttarus cerberus (parasitized by Mischocyttarus consimilis). This is the first case of interspecific parasitism described for the genus Mischocyttarus. How social parasites are able to remain in the host colony has been one of the central subjects of studies on this theme. Chemical signals are used by social insects to recognize their nestmates, which suggests that female parasites use a chemical strategy to hide their identity and become accepted as a member in host colonies. This study investigated the dynamics of cuticular hydrocarbons (CHs) of workers of M. consimilis and M. cerberus in both control and host colonies. Fourier Transform Infrared-Photoacoustic Spectroscopy (FTIR-PAS) was used to read the CHs; this technique is somewhat unusual but is quite reliable for this type of study. A stepwise canonical discrimination analysis detected significant differences between the mid-infrared spectra of the two species. This analysis provided a dispersion diagram of the results in order to differentiate the species, in which the first axis explained 61% of the results. These results demonstrated a clear difference in the CHs profile between non-conspecific workers from the control colonies. However, non-conspecific workers from the host colonies underwent a significant modification of CHs in comparison to the workers from the control colonies, and this modification was similar in all the host colonies non-conspecific workers. These data suggest that females of parasitic-specie modify the chemical profile of the host-specie females, and also alter their own profiles in order to be recognized as “nestmates” and to achieve success in parasitism.

Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone

Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ν2 carbonate bands. The ν3 phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747cm−1 possibly resulting from CO stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

Differentiation of Neotropical Fish Species with Statistical Analysis of Fourier Transform Infrared Photoacoustic Spectroscopy Data

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was applied to nineteen fish species in Brazil's Upper Paraná River basin to identify differences in the structural composition of their scales. To differentiate the species, a canonical discriminant analysis was used to indicate the most important absorption peaks in the mid-infrared region. Significant differences were found in the chemical composition of scales among the studied fish species, with Wilk's lambda = 5.2 × 10(-6), F((13,18,394)) = 37.57, and P < 0.001, indicating that O-CH(2) wag at 1396 cm(-1) can be used as a biomarker of this species group. The species could be categorized into four groups according to phylogenetic similarity, suggesting that the O-CH(2) 1396 cm(-1) absorbance is related to the biological traits of each species. This procedure can also be used to complement evolutionary studies.

An in situ FTIR step-scan photoacoustic investigation of kerogen and minerals in oil shale

Step-scan photoacoustic infrared spectroscopy experiments were performed on Green River oil shale samples obtained from the Piceance Basin located in Colorado, USA. We have investigated the molecular nature of light and dark colored areas of the oil shale core using FTIR photoacoustic step-scan spectroscopy. This technique provided us with the means to analyze the oil shale in its original in situ form with the kerogen–mineral interactions intact. All vibrational bands characteristic of kerogen were found in the dark and light colored oil shale samples confirming that kerogen is present throughout the depth of the core. Depth profiling experiments indicated that there are changes between layers in the oil shale molecular structure at a length scale of micron. Comparisons of spectra from the light and dark colored oil shale core samples suggest that the light colored regions have high kerogen content, with spectra similar to that from isolated kerogen, whereas, the dark colored areas contain more mineral components which include clay minerals, dolomite, calcite, and pyrite. The mineral components of the oil shale are important in understanding how the kerogen is “trapped” in the oil shale. Comparing in situ kerogen spectra with spectra from isolated kerogen indicate significant band shifts suggesting important nonbonded molecular interactions between the kerogen and minerals.