Medium Infrared Research Articles

Comparative analysis of spectroscopic methods for rapid authentication of hazelnut cultivar and origin

Hazelnut market prices fluctuate significantly based on cultivar and provenance, making them susceptible to counterfeiting. To develop an accurate authentication method, we compared the performances of three spectroscopic methods: near infrared (NIR), handheld near infrared (hNIR), and medium infrared (MIR), on over 300 samples from various origins, cultivars, and harvest years. Spectroscopic fingerprints were used to develop and externally validate PLS-DA classification models. Both cultivar and origin models showed high accuracy in external validation. The hNIR model effectively distinguished cultivars but struggled with geographic distinctions due to lower sensitivity. NIR and MIR models showed over 93 % accuracy, with NIR slightly outperforming MIR for geographic origin. NIR proved to be a fast and suitable tool for hazelnut authentication. This study is the first to systematically compare spectroscopic tools for authenticating hazelnut cultivar and origin using the same dataset, offering valuable insights for future food authentication applications.

Photodetectors performance of nanostructured materials in antimony III-V InGaAsSb/AlGaAsSb interband cascade structures

The aim of the study is to increase the performance of solar conversion by integrating nanostructured materials within conventional solar cells by employing multi-energy stages (i.e., interband and intersubband) in cascade systems to overcome the absorption length barrier and achieve large photo-generated carrier values. Specifically, InGaAsSb/Al GaAsSb MQWs are investigated with narrow well widths (2-20 nm) and transition energies of the structures are calculated for varied well/barrier widths and depths using numerical modelling. The results show that both interband and intersubband transitions are valuable for improving photovoltaic and photodetection applications, but their mechanisms and applications are distinct, so understanding and controlling these transitions within semiconductor materials is essential for optimising the performance of devices in both areas of optoelectronics, including strain as an important parameter of integrity. The data suggests that a single electron requires multiple photons to be transported, with the formation of a type-I broken-gap alignment between AlGa AsSb (barrier) and InGaAsSb (well). A wide range of wavelengths, from visible to medium infrared (MIR), will greatly enhance solar spectrum absorption. The long-term goal is to combine the thermal properties of antimonies (GaSbInSb) with a low band gap and the optical properties of arsenide (GaAsAlAs) with a large band gap.

Fire Characterization by Using an Original RST-Based Approach for Fire Radiative Power (FRP) Computation

Fire radiative power (FRP) is a basic parameter for fire characterization since it represents the heat emission rate of fires. Moreover, its temporal integration (fire radiative energy, FRE) is used as a proxy for estimating biomass burning and emissions. From satellite, FRP is generally computed by comparing the Medium InfraRed (MIR) signal of the fire pixel with the background value on the event image. Such an approach is possibly affected by some issues due to fire extent, clouds and smoke over the event area. The enlargement of the background window is the commonly used gimmick to face these issues. However, it may include unrepresentative signals of the fire pixel because of very different land use/cover. In this paper, the alternative Background Radiance Estimator by a Multi-temporal Approach (BREMA), based on the Robust Satellite Technique (RST), is proposed to characterize background and compute FRP. The approach is presented using data from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) platform. Moreover, BREMA is here combined with the RST-FIRES (RST for FIRES detection) technique for fire pixel identification and the σ-SEVIRI retrieval algorithm for transmittance evaluation. Results compared to the operational SEVIRI-based FRP-PIXEL product, although highly correlated in terms of background radiance (r2 = 0.95) and FRP values (r2 = 0.96), demonstrated a major capability of BREMA to estimate background radiances regardless of cloudiness or smoke presence during the event and independently on fire extent. The possible impact of the proposed approach on the estimates of CO2 emissions was also evaluated for comparison with the Global Fire Emissions Database (GFED4s).

Theoretical study of Urbach tail behavior in Hg1−xCdxTe in the 0.21 ≤ x ≤ 0.6 medium and far infrared optical ranges

We present a theoretical study of the optical absorption coefficient Urbach tail broadening parameter Γ behavior in the Hg1−xCdxTe alloy semiconductor in the 0.21 ≤ x ≤ 0.6 alloy composition interval. This x interval corresponds to the very attractive 0.10 ≤ EG ≤ 0.75 eV medium infrared (MIR) and far infrared (FIR) optical ranges. We compare two absorption coefficient nonparabolic models based on Kane 4-band formalism, one including the Burstein–Moss shift called the NPBM-model and the other one without and called the NP-model. By comparing the results of both models with existing experimental and theoretical data, we show the strong nonparabolic behavior of the absorption coefficient in Hg1−xCdxTe in agreement with previous studies. The best fitting is obtained with the NPBM-model, where Γ is used as an adjustable parameter varying with x, temperature (T), and photon energy (ħω) in the E ≤ EG sub-bandgap energy range. With decreasing x, Γ is found to increase first slightly with x in the 0.443 ≤ x ≤ 0.6 MIR range and then strongly and nonlinearly in the 0.21 ≤ x < 0.443 FIR range. These unusual Γ(x, ħω) dependences suggest a strong influence of nonparabolicity and band state mixing effects, which become strongly enhanced in the FIR range between strongly interacting and almost overlapping bands as x tends to 0.16 of the critical value, making Hg1−xCdxTe experience a semiconductor–semimetal transition.

Room-temperature deposition of ZnS antireflection coatings for MIR-LWIR applications

Integration of unconventional materials on established CMOS platforms requires to fulfill tight thermal budget constraints. However, low temperature processing may result in poor mechanical properties of the deposited films, which can exhibit stress-induced degradation of the optical properties or even delamination. This work focuses on a CMOS-compatible low-temperature deposition process for ZnS films on silicon and its use for the realization of an antireflection coating (ARC) operating in the medium infrared (MIR)–longwave infrared (LWIR) range. A thin interlayer of Al2O3 is employed to achieve good adhesion of a ZnS film deposited on Si by e-beam evaporation at room temperature. Numerical simulations are carried out to optimize the performance of single- and double-side ARC structures, quantifying the impact of the Al2O3 interlayer and of the fabrication tolerances on the optical transmission. Experimental results on an 8” silicon wafer demonstrate a peak transmittance of 66% for single-side ARC and 89% for a double-side ARC at a wavelength of 10 µm, resulting in an average transmission of 76.2% for black body radiation at 36 °C in the 6–20 μm wavelength range.

Characterization of the medium infrared spectra of polyphenols of red and white wines by integrating FT IR and UV–Vis spectral data

Infrared spectroscopy is widely applied in the wine sector. The medium infrared (MIR) spectral region between 1800 and 900 cm-1 is very informative for polyphenols. Aim of this work was to perform an in-depth analysis of this spectral region of polyphenolic wine extracts. To this goal evolution of the polyphenolic fractions of white (Vermentino) and red (Cannonau) typical Sardinian wines was studied during wine-making. Wine polyphenolic extracts, obtained by solid phase extraction, were analyzed by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) and UV–Vis spectroscopy. Spectral data from the two techniques were integrated and results depicted as Heat Map of the correlation coefficient values allowing a more accurate characterization of the MIR fingerprint region. For Cannonau, correlations between absorptions in the 420–650 and 380 nm visible spectral ranges allowed assignment of MIR peaks to anthocyanins (1016 and 1198 cm-1) and flavonols (1159 and 1277 cm-1), respectively. In Vermentino we identified MIR bands due to non-flavonols and others arising from flavonols (1376 and 1407 cm-1), present in this white wine where vinification allows short time contact with grape skins. During time, intensities of MIR bands at lower frequencies assigned to the sugar moiety of glycosylated phenols decreased in both wines.

Determination of nitrogen and acrylic / styrene components in nitrocellulose systems by UATR and NIRA infrared techniques

Nitrocellulose (NC) is a polymer of great interest in the aerospace and paint/coating fields. However, there are gaps regarding quantitative analysis. Fast and accurate methodologies for the quality control of raw materials are limited. In this context, the determination of the nitrogen content in NC and the contents of different acrylic/styrene components in formulations with NC were assessed. The applicability of non-conventional Fourier transform infrared spectroscopy (FT-IR) techniques, using the universal attenuated total reflection (UATR) mode, in the medium infrared (MIR) region and of the transflectance in the near infrared region (NIRA) were evaluated. For nitrogen determination, FT-MIR/UATR analysis proved to be the most accurate methodology. For the analysis of acrylic/styrene components in NC, it was possible to determine, with good precision, the contents of most samples by FT-MIR/UATR and FT-NIRA.

Agro Residues of Dendranthema x grandiflorum as Raw Material for a Potential Larvicidal Product

Residues of the chrysanthemum agroindustry from different cultivars of Dendranthema x grandiflorum are sold in the Vitoria (Espirito Santo State, Brazil) marketplaces. Because of the large of varieties of this hybrid species, this study aimed to confirm the chemical similarity of the residual material collected in one year at the commercial places in neighborhoods of the city (Vitoria) for using it as an homogenous raw material to prepare larvicidal products. Dichloromethane and methanol extracts were produced from 27 samples. Medium infrared (MIR) spectra were obtained in triplicate for the 54 extracts. MIR data were analyzed by principal components analysis (PCA), which divided the samples into two groups (GA1 and GA2) for dichloromethane extracts and into four groups (GB1, GB2, GB3 and GB4) for methanol extracts. The methanol extracts, we could see clear separation among the groups based on their classes of substances. The dichloromethane ones, it was possible to identify separation between GA1 and GA2 by classes of triterpene esters and diacylglycerols based on their mass peak intensities. Mixtures obtained from dichloromethane extracts (FA) and methanol extracts (FB) were assayed on Aedes aegypti larvae at the concentration 15 ppm. FB mixtures no larval mortality was observed, but FA mixtures were 100% active, possibly by the presence of fatty acids, triterpenes, steroids and alkamides in the samples of this group. These results show that residues of different varieties of the hybrid Dendranthema x grandiflorum generate chemically similar extracts, particularly for the lipophilic ones (FA), which can be used as a homogeneous raw material to obtain biologically active products, notably larvicides products.

Emissivity of agricultural soil attributes in southeastern Brazil via terrestrial and satellite sensors

Soil texture and organic carbon (OC) content influence the spectral response. These attributes are relevant for the preservation and proper management of land use in the pursuit of a sustainable agriculture. Laboratory and satellite sensors have been applied as a powerful tool for studying so is, but their analysis using these sensors has mainly focused on the visible (Vis), near infrared (NIR) and shortwave infrared (SWIR) regions of the electromagnetic spectrum, with few studies in the Medium Infrared (MIR). The aim of this study was to identify the spectral pattern of soils with different granulometry (sand and clay) and OC content using laboratory and satellite sensors in the MIR region, specifically in the Thermal Infrared (TIR) range (ASTER, Landsat satellites). The study performed qualitative and quantitative analyses of clay, OC and sand fractions (fine and coarse). The study area is located in the region of Piracicaba, São Paulo, Brazil, where collected 150 soil samples (0–20 cm depth). Soil texture was determined by the pipette method and OC via dry combustion. Reflectance and emissivity (Ɛ) spectral data were obtained with the Fourier Transform Infrared (FT-IR) Alpha sensor (Bruker Optics Corporation). An image “ASTER_05” from July 15, 2017 was acquired with values of Ɛ. Samples were separated by textural classes and the spectral behavior in the TIR region was described. The data obtained by the laboratory sensor were resampled to the satellite sensor bands. The behavior between spectra of both sensors was similar and had significant correlation with the studied attributes, mainly sand. For the partial least squares regression (PLSR) models, six strategies were used (MIR, MIR_ASTER, ASTER, TIR, TIR Correlation Index (TIR_CID), and MIR Correlation Index (MIR_CID)), which consisted in the use of all sensors bands, or by the selection of bands that presented the most significant correlations with each one of the attributes. Models presented a good performance in the prediction of all attributes using the whole MIR. In the TIR region, the models for total sand content and for fine and coarse fractions were good. Models created with ASTER sensor data were not as promising as those with laboratory ones. The use of specific bands was useful in estimating some attributes in the MIR and TIR, improving the predictive performance and validation of models. Therefore, the discrimination of soil attributes with satellite sensors can be improved with the identification of specific bands, as observed in the results with laboratory sensors.

Preparation, structural and spectroscopical properties of silver terbium diphosphate AgTbP2O7

Abstract Silver terbium diphosphate AgTbP2O7 was prepared by solid state reaction at T=500° and characterized by combining SEM-EDS morphological investigation and semi-quantitative chemical analysis via Scanning Electron Microscopy (SEM) equipped with energy dispersive X-Ray spectroscopy (EDS), structure solution via Rietveld refinement of powder X-ray diffraction (PXRD) data, and Fourier transform infrared (FTIR) spectroscopy. The synthesized compound is monoclinic, P21/n space group, with cell parameters: a=11.9108(3) Å, b=6.90265(16) Å, c=6.62030(15) Å, β=90.3702(5)° and V=544.28(2) Å3. The crystal structure consists of a network of zig-zag chains of TbO8 polyhedra extending along the b axis, bridged by P2O7 diphosphate groups and by chains of AgO7 polyhedra running along the c crystallographic direction. MIR (medium infrared) spectrum shows bands typical of P–O modes of diphosphate compounds. Observed band multiplicity is in agreement with the symmetry reduction with respect to orthorhombic rare earth diphosphates with similar stoichiometries reported in the literature.

Evaluation of Techniques for Determination of Hydroxyl Value in Materials for Different Industrial Applications

When some materials need to be characterized, the hydroxyl number (IOH) determination is especially useful, mainly for those applied in the aerospace field. Usually, this characterization is performed by wet chemistry, using methodologies involving several steps, such as derivatization. This is a time-consuming and costly step. On the other hand, when the analysis is performed by Fourier transform infrared (FT-IR) spectroscopy, the most used region is the medium infrared (MIR) and transmission techniques are usually employed. However, FT-IR methodology developed error is usually not discussed. FT-IR methodology was developed in near infrared (NIR) and MIR regions, including non-conventional techniques, such as universal attenuated total reflection (UATR) and transflectance (near infrared reflection accessory [NIRA]), and transmission, to determine IOH in surfactants, used in aerospace catalysts/cosmetic products, and polyesters, applied in paints. According to the samples’ characteristics, surfactants were analyzed by transmission/solution and, as received, by NIRA. Polyesters were analyzed by UATR and NIRA, as received. The IOH values for all samples were also measured by wet chemistry and/or potentiometry (supplier’s data) and used as reference. Good linear correlations were observed between 0.939 and 0.976, being considered with good precision, and between 88% (NIRA) and 98% (MIR) of the results were explained by developed methodologies.

Quantification by FT-IR (UATR/NIRA) of NBR/SBR blends

Abstract Rubber blends are important materials in automotive industry, as well as in other sectors. However, there are implications when suitable use of a polymer in an artifact is not made. In the automotive area, for example, the use of an elastomer without the fuel resistance requirement would result in component degradation, potential fuel leakage, and danger of fire. The use of polymer blends may be the solution to this problem. Fourier transform infrared spectroscopy (FT-IR) can be used for the knowledge of the polymer content of these blends. Then, FT-IR quantitative methodologies for determining acrylonitrile-butadiene copolymer (NBR) copolymer and butadiene-styrene copolymer (SBR) contents were developed by the transflectance accessory, NIRA, and the transmission mode, being the sample analyzed by transmission and universal attenuated total reflection (UATR) in the medium infrared (MIR). UATR and NIRA methodologies showed better accuracy. However, the MIR analysis showed a detection limit between 10-20% of NBR.

Agro-ecological variability effects on an index-based insurance design for extreme events

Index-based insurance (IBI) is a risk transfer tool that is widely used in low-incomes countries, especially catered to smallholder farmers. A good correlation between the selected index (in this case Normalized Difference Vegetation Index -NDVI-) and the crop losses of the insured area is a key requirement for well-performing system. Usually, IBI application area is defined by political boundaries, despite that variation in soil, topography, and climate is more important. In this work, agro-ecological variability effects will be studied in the IBI context. The case study was the rice crop failure in Babahoyo canton (Ecuador), using NDVI as the crop damage indicator.In a previous study, zones of similar soil, topographic and climatic characteristics (AHZs) were defined using principal component analysis in Babahoyo canton. Two largest AHZs were found in this canton. They were f7 and f15, which account for 91% of the total rice crop area in Babahoyo. We sampled reflectance values of red, blue, near infra-red (NIR) and medium infra-red (MIR) bands over bare soil (1st of January) by observation points, within f7 and f15. The reflectance band values were used to study whether the difference between the two AHZs could be appreciated through remote sensing. Then, we did the same but for NDVI average of the rice crop cycle, i.e., 15th of January to 15th of May (NDVI_ave). It was done for confirming that the AHZs (f7 and f15) have an influence over rice crop development. The used product was MODIS imagery (2001–2017).We stratified the sampling through the AHZs, applying 30% density for ensuring the accuracy of the selected pixels. Statistically significant differences between the f7 and f15 zones were found in all the analysed reflectance bands and in NDVI_ave. This found supported the differences that the agro-ecological map pointed out in its database. At the same time, the NDVI_ave distribution for each AHZ presented a statistically significant difference of the accumulated probability below the threshold (0.4), which is confirmed as a reliable threshold for rice crop failure. This stratified sampling could improve the representativeness and accuracy of crop state assessments and reduce the basis risk.

Accelerated Ageing Effects on Curcubitea Pepo Seed Oil

Accelerated ageing of curcubitea pepo seed oil was followed by simulation of UV (light) and ambiant oxygen actions held separately then simultaneously in order to know the effects of these parameters on this oil resistance to deterioraton. Nine withdrawals had undergone analyses by titrimetry supported by spectroscopic analyses notably MIR (Medium Infrared), DSC (Differential Scanning Calorimetry) and also a gas chromatography for the composition in FA. This study has showed that pumpkin seed oil displays a weak resistance to UV which results among other in decrease of unsaponifiable compounds. Its oxidization takes place very quickly in the presence of ambiant oxygen. However the accumulated action of the two factors weakens to the highest degree pumpkin seed oil and these results in polymerization. It has also enabled us to show the link between the formation of recticulations in the oil matrix and variations at the level of the molecular structure of pumpkin seed oil.

Study of organo-hybrid layered double hydroxides by medium and near infrared spectroscopy

An Mg/Al layered double hydroxide (LDH) containing carbonate ion in its interlayer region was examined by medium infrared (MIR) and near infrared reflectance spectroscopy (NIRS). The MIR and NIR spectroscopy techniques was also used to study two organo-hybrid LDHs containing interlayer dodecylbenzenesulphonate (DBS) and dodecylsulphate (DS) ions, respectively. The NIR spectra for the latter solids were found to exhibit the overtone and combination bands for the hydroxyl groups in addition to those typical bands of the organic host functions.

Scanning beam medium infra-red interferometry for plasma density measurements

In magnetically confined fusion experiments interferometry is commonly used to measure plasma electron density. This because interferometry is a very reliable technique, not affected by calibration problem. The main drawbacks of interferometers are the integral characteristic of the measurement and the fringe loosing problem. Scanning beam interferometry can always overcome the former problem and in some cases the second as well. The advantages of the scanning beam technique can better exploited in two colours vibration compensated medium infra-red (MIR) interferometers. Indeed the short wavelength of the probing beams provide small beam sizes allowing plasma density measurement along many non-overlapping paths, furthermore the vibration compensation system relaxes the requirement of massive interferometer structures embracing the fusion device, actually allowing to install back-reflecting mirror directly attached to the experimental machine.As an example of application of this technique the two-color medium-infra-red-compensated scanning beam interferometer installed on the Frascati Tokamak Upgrade (FTU) experiment is presented. We present also a preliminary design of a scanning interferometer for the new proposed Fusion Advanced Studies Torus (FAST) experiment. The interferometer uses retroreflectors installed inside the vessel to back reflect the scanning beams; this will allow realizing scanning beams measuring from the plasma edge. This feature in principle can solve the fundamental problem of interferometers: the fringe loosing problem.

Surface Characteristics of Nanocrystalline Apatites: Effect of Mg Surface Enrichment on Morphology, Surface Hydration Species, and Cationic Environments

The incorporation of foreign ions, such as Mg2+, exhibiting a biological activity for bone regeneration is presently considered as a promising route for increasing the bioactivity of bone-engineering scaffolds. In this work, the morphology, structure, and surface hydration of biomimetic nanocrystalline apatites were investigated before and after surface exchange with such Mg2+ ions, by combining chemical alterations (ion exchange, H2O-D2O exchanges) and physical examinations (Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM)). HRTEM data suggested that the Mg2+/Ca2+ exchange process did not affect the morphology and surface topology of the apatite nanocrystals significantly, while a new phase, likely a hydrated calcium and/or magnesium phosphate, was formed in small amount for high Mg concentrations. Near-infrared (NIR) and medium-infrared (MIR) spectroscopies indicated that the samples enriched with Mg2+ were found to retain more water at their surface than the Mg-free sample, both at the level of H2O coordinated to cations and adsorbed in the form of multilayers. Additionally, the H-bonding network in defective subsurface layers was also noticeably modified, indicating that the Mg2+/Ca2+ exchange involved was not limited to the surface. This work is intended to widen the present knowledge on Mg-enriched calcium phosphate-based bioactive materials intended for bone repair applications.

Vibrational analysis of glycine radical: a comparative ab initio static and dynamic study

We present quantum mechanical (QM) vibrational computations beyond the harmonic approximation for an organic molecule that exhibits both torsional and NH(2) out of plane type modes: the glycine radical. The effective second order perturbative, variational and variation-perturbation treatments-defined as static approaches-as well as vibrational analysis from ab initio molecular dynamics trajectories at 300 K and 600 K were performed using the B3LYP/6-31+G(d,p) description of the electronic structure. Theses schemes are compared in terms of prediction of fundamental transitions, simulation of the corresponding medium infrared (MIR) spectrum and extraction of substantial information for the understanding of chemical problems. The validity of the analyses is checked for a similar molecule, formamide, for which experimental data are available.

The P21/m- C2/m phase transition in synthetic amphiboles in the system Li2ONa2OMgOSiO2H2O: a high-T FTIR study

The P 2 1 / m ↔ C 2/ m phase-transition has been studied by high- T FTIR analysis on a series of synthetic amphiboles in the Li 2 O–Na 2 O–MgO–SiO 2 –H 2 O (LNMSH) system. Spectra were collected in the T range 25–450 °C on KBr disks. All examined amphiboles have P 2 1 / m symmetry at room T . Their OH-stretching FTIR spectrum consists of two main bands at ~3740 and 3715 cm −1 . At the transition temperature ( T c ), these bands merge into one single absorption centred at ~3720 cm −1 , and no further change is observed beyond this T . Significant modifications consisting in peak shifting and band broadening are also observed in the MIR (medium infrared) 1300–640 cm −1 region. T c values for the different compositions were estimated based on various methods; the most reliable procedure is considered to be the fit of Landau 2-4-6 potentials using band shifts observed in the MIR region. The T c values obtained for all samples are consistent with previous results obtained on two members of the series examined here by single-crystal or synchrotron powder H T -XRD (high- T X-ray diffraction). They correlate linearly with the aggregate cation radius at M (4) [ T c (°C) = 803–533 〈 r M (4) 〉; R 2 = 0.97]. This work thus provides a measure of the role played by the size of the M (4) polyhedron in determining the T c in simple chemical systems where the B-site occupancy (and geometry) is the only variable. The slope of the equation is far less steep in the LNMSH system than in cummingtonite; crystal-chemical reasons for this behaviour are discussed, and the local order between A and monovalent B cations is suggested to be the major constraint. In more complex systems, inspection of the available data shows that other factors such as the aggregate size of the strip of octahedra must be taken into account.