Total Reflection Mode Research Articles

Rapid optimization of decapod crustacean digestion for efficient microplastic extraction (MPs)

The objective of this study was to develop and apply a rapid digestion protocol for extracting microplastics (MPs) from commercial crab samples using four different digestion methods. The methods employed included thermo alkaline digestion with potassium hydroxide (KOH), oxidative digestion with hydrogen peroxide (H2O2), enzymatic digestion with protease, and digestion using the surfactant dodecyl dimethyl betaine (DDB). Among these, protocols 2 and 4 (P2 and P4) achieved efficient digestion rates of 93% and 96%, respectively. These protocols were validated based on recovery percentage, repeatability, color assessment, and the chemical integrity of the MPs. The MPs extracted were analyzed using optical microscopy, revealing their presence in the forms of fibers, films, and fragments. Additionally, MPs were characterized by Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), with spectral quality indices (Q) ranging from 0.82 to 0.90.

In situ analysis of magnesium ([NH4]2Mg[CO3]2·4H2O), copper ([NH3]2Cu(CO3)), and zinc ((NH3)Zn(CO3)) ammonium carbonate thermal properties

AbstractThree metal ammonium (ammonia) carbonate double salts were mechanochemically synthesized including magnesium ammonium carbonate ([NH4]2Mg[CO3]2·4H2O, MAC), copper ammonium carbonate ([NH3]2Cu(CO3), CAC), and zinc ammonium carbonate ((NH3)Zn(CO3), ZAC), and their crystallinity and thermal stability were investigated using in situ X-ray diffraction. The crystal structures were investigated in the temperature interval from 25 to 355 °C. MAC exhibited relatively low thermal stability with its crystal structure rapidly losing crystalline water as well as ammonium ions already at 85 °C and transforming into an amorphous carbonate, as confirmed by in situ infrared spectroscopy. CAC and ZAC exhibited loss of the corresponding NH3 at much higher temperatures transforming into a mixture of the corresponding metal oxides according to the XRD with the outer layer of the carbonate, as suggested by infrared spectroscopy measurements. The thermogravimetric analysis has been carried out to investigate the thermal degradation behavior. Initial fast mass loss was observed in the parent [NH4]2CO3 already under 100 °C with complex mass loss patterns from basic carbonate precursors achieving stable mass at above 500 °C for magnesium carbonate. CAC and ZAC inherited intermediate responses to temperature when compared to the precursors exhibiting stable mass at ~ 300 °C. This can be associated with the distinct crystal structure of the compounds whereby CAC and ZAC exhibit strong bonds with metal ions, while in MAC crystalline water contributes to lower stability of the crystal as well as the loosely bound ammonium ion. Infrared spectra were obtained and interpreted at room temperature followed by their in situ thermal analysis up to 250 °C in attenuated total reflection mode. Changes in the complex room temperature spectra with increasing temperature were interpreted as loss of N–H bonds, as confirmed by the concurrent decrease in the 3350–3000 and 1248 cm−1 band region. It was found that ZAC was the most thermally stable compound among the three double salts. The thermal data obtained in this work have practical implications for nutrient recovery and their release in the environment.

Polarization-insensitive ultra-wideband tunable perfect absorber based on a vanadium dioxide metasurface

This paper provides a polarization-insensitive ultra-wideband tunable perfect absorber based on a patterned vanadium dioxide (VO2) metasurface. The absorption bandwidth reaches 18.5 THz, surpassing that of most previous studies, through integrating two distinct region patterns (A and B). The proposed absorber features a three-layer sandwiched structure and a simpler metasurface pattern, demonstrating the advantages of lower manufacturing cost and a simplified photolithography process. In addition, by optimizing geometric parameters and manipulating VO2 conductivity, the absorption spectrum reveals three specific perfect absorption peaks with the absorptance of 99.06%, 99.85%, and 99.85% at 10 THz, 14 THz, and 21.5 THz and shows polarization-insensitive performance due to the C4 rotational symmetry of the metasurface pattern. Furthermore, we illustrate that the intrinsic mechanism of the proposed perfect absorber arises from the lossy localized surface plasmon polarization (LSPP) excited by the incident wave, with the Fabry–Perot (FP) cavity enhancing LSPP absorption. The absorber reveals a good impedance matching with the free space, where the real and imaginary parts are close to 1 and 0, which also explains the perfect absorption from the perspective of the impedance matching theory. The device can transition between perfect absorption mode and total reflection mode, with relative absorptance also adjustable via manipulating the VO2 conductivity. Ultimately, the absorber displays an excellent angle tolerance maintaining absorptance above 90% in the range of 0°–50°. Consequently, the proposed polarization-insensitive ultra-wideband tunable perfect absorber can be applied in optical switching, object cloaking, and wireless communication.

Operando FTIR Characterization of Interphases from Organosulfur Electrolytes in High Voltage Lithium-Ion Batteries

The widespread adoption of renewable energy storage technologies like electric vehicles and grid storage largely relies on the improvements of the energy density of the batteries inside those devices. Lithium-ion batteries (LIBs) are typically used for these applications due to their high energy density,[1] but the operating voltage of LIBs is limited by the electrochemical stability windows of the electrolyte. Resistive interphase layers form as a result of the breakdown of electrolyte molecules and limit LIB cycling stability. However, there is significant difficulty in the study and characterization of both the components and structure of the electrode-electrolyte interphases formed via electrolyte degradation.[2] Traditional characterization techniques provide information on what the interphase layers look like after cell disassembly, but sample preparations are difficult and destructive.[3] Therefore, it is crucial to develop in operando techniques to better understand the relationship between the interphase layers and battery performance.In this work, we develop a custom surface-enhanced infrared absorption spectroscopy in the attenuated total reflectance mode (ATR-SEIRAS) setup for in operando studies of the solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) in organosulfur electrolyte systems. Organosulfur molecules are potential components for high voltage LIBs due to their excellent performance.[4] We apply our custom ATR-SEIRAS setup to study ethyl methyl sulfone (EMS) containing electrolytes and propose possible reduction routes with the help of ex situ and postmortem characterization techniques. We study both SEI and CEI formed and correlate favorable interphase components with contributing molecules to identify important functional groups for novel molecular design. The work provides an opportunity to elevate our understanding of currently elusive electrochemical phenomena like the structure-reactivity relationships of SEI and CEI, and why certain sulfone systems outperform other formulations. Furthermore, it will provide molecular design principle for electrolyte systems in high performing and high voltage LIBs.References S. Chu, Y. Cui, and N. Liu, Nat. Mater., 16, 16–22 (2017).H. Wan, J. Xu, and C. Wang, Nat. Rev. Chem., 8, 30–44 (2024).A. Dopilka, Y. Gu, J. M. Larson, V. Zorba, and R. Kostecki, ACS Appl. Mater. Interfaces, 15, 6755–6767 (2023).M. A. Dato et al., Adv. Energy Mater., 2303794 (2024).

Animal family discrimination from hair using ATR-FTIR and machine learning methods for applications in illegal wildlife trafficking.

Wildlife forensics plays a pivotal role in the combating illegal trafficking, supporting biodiversity conservation, and aiding in the identification of animals in wildlife. Animal hair, often found in trafficking crimes, serves as vital biological evidence that can provide significant information for animal identification. This study proposes a novel method integrating machine learning classifiers with Fourier transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode to enhance the effectiveness of animal identification in wildlife forensic casework. Additionally, compound microscopy has also been utilized as a preliminary tool to perform morphological analysis of hair samples from four animal families, including Bovidae, Cervidae, Elephantidae, and Felidae. Further, chemical profiling through spectral data revealed significant overlapping peaks between family Bovidae and Cervidae. The classification experiment provides the random forest (RF) classifier as the most effective for family discrimination model. This research offers valuable insights for wildlife forensics by improving the identification accuracy of unknown hair samples, thus enhancing the overall effectiveness in forensic investigations.

Alkaline-Metal Cations Affect Pt Deactivation for the Electrooxidation of Small Organic Molecules by Affecting the Formation of Inactive Pt Oxide.

The activity of Pt for the electro-oxidation of several organic molecules changes with the cation of the electrolyte. It has been proposed that the underlying reason behind that effect is the so-called noncovalent interactions between the hydrated cations and adsorbed OH (OHad). However, there is a lack of spectroscopic evidence for this phenomenon, resulting in an incomplete understanding at the microscopic level of these electrochemical processes. Herein, we explore the electro-oxidation of glycerol (EOG) on platinum (Pt) in LiOH, NaOH and KOH using in situ surface-enhanced infrared absorption spectroscopy in the attenuated total reflectance mode (ATR-SEIRAS) and in situ X-ray absorption spectroscopy (XAS). Our results show that the electrolyte cation influences the rate and potential at which adsorbed CO (COad), a catalytic poison, is formed and oxidized. We attribute this to the cation-dependent stability of oxygenated species on the metallic Pt surface and the different intensities of the electric field at the electrode/electrolyte interface. We also demonstrate that the formation of an inactive Pt oxide layer is indirectly also cation-dependent: the formation of this layer is triggered by the cation-dependent oxidative removal of reaction intermediates (for instance, CO). This phenomenon explains the well-known cation-induced differences in the voltammetric profiles, of not just glycerol, but generally of alcohols and polyols.

Effects of Laboratory Ageing on the Chemical Composition and High-Temperature Performance of Warm Mix Asphalt Binders

Warm asphalt mixtures can suffer from decreased short-term high-temperature performance; therefore, introducing additional modifiers can mitigate this risk. This study investigates the effects of a liquid organosilane warm mix additive (WMAd) and grade-bumping polyethylene-based additive added simultaneously to asphalt binders on their chemical composition and its relationship with performance characteristics. Previous studies found relationships between the formation of certain chemical species during bitumen ageing and the increase in their viscosity, stiffness and other performance characteristics—the present work intended to verify these relationships when the two mentioned additives are used. Two asphalt binders were investigated—a paving-grade 50/70 binder and a 45/80-55 polymer-modified bitumen. The chemical analysis was performed using Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance mode and focused on the quantification of carbonyl, sulfoxide, polybutadiene and polystyrene structures in the asphalt binders subjected to laboratory short- and long-term ageing. Additionally, the relationships between asphalt binder performance and selected FTIR indices were evaluated using a dynamic shear rheometer. It was found that the investigated additives significantly affected the apparent contents of all evaluated chemical structures in the asphalt binders; however, these changes were not reflected in their performance evaluation.

Preliminary characterization of microplastics in beef hamburgers

The diffusion of microplastics in meat products is an emerging topic, as their impact on animal and human health is still largely unknown. The present study aimed to preliminarily determine the number and the quality of microplastics diffusion in beef hamburgers (n = 10) through Fourier-transformed infrared micro-spectroscopy in attenuated total reflectance mode analysis. Microplastics were detected in all analyzed samples. The abundance of microplastics ranged from 200.00 to 30,300.00 MP/kg. Microplastics observed in the analyzed samples were mainly characterized by irregular shapes (95.99%), grey color (70.16%), and dimensions comprised between 51 and 100 μm (57.46%). Eighteen different polymers were detected, with polycarbonate (30,300.00 MP/kg), polyethylene (1580.00 MP/kg) and polypropylene (750.00 MP/kg) being the most abundant classes. Results demonstrate an extensive diffusion of microplastics in the analyzed samples, which may be originated from various sources, including animal body, industrial processing, and packaging. Findings from this study will aid in pinpointing the source of microplastics contamination, enabling the creation of targeted guidelines to mitigate microplastics spread in processed meat food.

Photonic crystal-connected bidirectional micro-ring resonator array for duplex mode and wavelength channel (de)multiplexing

The progress of on-chip optical communication relies on integrated multi-dimensional mode (de)multiplexers to enhance communication capacity and establish comprehensive networks. However, existing multi-dimensional (de)multiplexers, involving modes and wavelengths, face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles. These constraints restrict their potential for full-duplex functionality and highly integrated communication. We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array (PBMRA) and apply it to duplex mode-wavelength multiplexing communication. The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference, improving on-chip integration in single-level mode conversion. As a proof of concept, we fabricated a nine-channel bidirectional multi-dimensional (de)multiplexer, featuring three wavelengths and three TE modes, compactly housed within a footprint of 80 μm×80 μm, which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s, achieving a bit error rate lower than 10−4. Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel, this (de)multiplexer also enables a doubling of communication capacity using two physical transmission channels.

Investigating the mechanism of SiO2/4H-SiC interface traps passivation by boron incorporation through FT-IR analysis of near-interface SiO2

This study investigates the effect of boron-incorporation (B-incorp) on SiO2 properties near the SiO2/4H-SiC interface by Fourier transforms infrared spectroscopy with attenuated total reflection mode. We focus on the range of Si–O–Si asymmetric stretching vibrations, whereas B-incorp samples exhibited a different peak shift trend compared to the thermal oxidized samples. The observed peak shift, corroborated by the calculated spectral simulation, suggests a reduction in oxygen deficiency near the interface for B-incorp samples. This suggests a potential link between B-incorp and the passivation of traps near the interface, possibly through its influence on SiO2 stoichiometry.

Plastics and plastic-bound toxic metals in municipal solid waste compost from Sri Lanka.

This study examined plastics and toxic metals in municipal solid waste compost from various regions in Sri Lanka. Plastics were extracted using density separation, digested using wet peroxidation, and identified using Fourier Transform Infra-Red Spectroscopy in Attenuated Total Reflection mode. Compost and plastics were acid-digested to quantify total Cd, Cu, Co, Cr, Pb, and Zn concentrations and analyzed for the bioavailable fraction using 0.01M CaCl2. Notably, plastics were highly abundant in most compost samples. The main plastic types detected were polyethylene, polypropylene, and cellophane. However, the average Cd, Cu, Co, Cr, Pb, and Zn levels were 0.727, 60.78, 3.670, 25.44, 18.95, and 130.7mg/kg, respectively, which are well below the recommended levels. Zn was the most bioavailable (2.476mg/kg), and Cd was the least bioavailable (0.053mg/kg) metal associated with compost. The Contamination factor data show that there is considerable enhancement of Cd and Cu, however, Cr, Cu, Co, and Pb are at low contamination levels. Mean geo accumulation index values were 1.39, 1.07, - 1.06, - 0.84, - 0.32, and 0.08 for Cd, Cu, Co, Cr, Pb, and Zn. Therefore, the contamination level of compost samples with Cd and Cu ranges from uncontaminated to contaminated levels, whereas Co, Cr, Pb, and Zn are at uncontaminated levels. Despite no direct metal-plastic correlation, plastics in compost could harm plants, animals, and humans due to ingestion. Hence, reducing plastic and metal contamination in compost is crucial.

Exploring novel circulating biomarkers for liver cancer through extracellular vesicle characterization with infrared spectroscopy and plasmonics

BackgroundHepatocellular carcinoma (HCC) is the most common form of liver cancer, with cirrhosis being a major risk factor. Traditional blood markers like alpha-fetoprotein (AFP) demonstrate limited efficacy in distinguishing between HCC and cirrhosis, underscoring the need for more effective diagnostic methodologies. In this context, extracellular vesicles (EVs) have emerged as promising candidates; however, their practical diagnostic application is restricted by the current lack of label-free methods to accurately profile their molecular content. To address this gap, our study explores the potential of mid-infrared (mid-IR) spectroscopy, both alone and in combination with plasmonic nanostructures, to detect and characterize circulating EVs. ResultsEVs were extracted from HCC and cirrhotic patients. Mid-IR spectroscopy in the Attenuated Total Reflection (ATR) mode was utilized to identify potential signatures for patient classification, highlighting significant changes in the Amide I-II region (1475-1700 cm−1). This signature demonstrated diagnostic performance comparable to AFP and surpassed it when the two markers were combined. Further investigations utilized a plasmonic metasurface suitable for ultrasensitive spectroscopy within this spectral range. This device consists of two sets of parallel rod-shaped gold nanoantennas (NAs); the longer NAs produced an intense near-field amplification in the Amide I-II bands, while the shorter NAs were utilized to provide a sharp reflectivity edge at 1800–2200 cm−1 for EV mass-sensing. A clinically relevant subpopulation of EVs was targeted by conjugating NAs with an antibody specific to Epithelial Cell Adhesion Molecule (EpCAM). This methodology enabled the detection of variations in the quantity of EpCAM-presenting EVs and revealed changes in the Amide I-II lineshape. SignificanceThe presented results can positively impact the development of novel laboratory methods for the label-free characterization of EVs, based on the combination between mid-IR spectroscopy and plasmonics. Additionally, data obtained by using HCC and cirrhotic subjects as a model system, suggest that this approach could be adapted for monitoring these conditions.

The effect of photoinitiator type and filler load on physicochemical and mechanical properties of experimental light-cured resin cements through lithium disilicate ceramics of different shades and thicknesses

ObjectiveThis study investigated the influence of photoinitiator types on degree of conversion (DC), rate of polymerization (RP), flexural strength (FS), flexural modulus (FM), and light transmittance (LT) of filled and unfilled light-curable resin cements through different thicknesses and shades of lithium disilicate ceramics. MethodsLithium disilicate ceramic discs (IPS Emax Press, background [0.0], 0.5, 1.0, 2.0, 3.0, and 4.0 mm, shades A1 and BL3) were prepared. Experimental resin-based cements [TEGDMA/BisGMA (50/50 mass%)] were prepared using either camphorquinone (CQ)/amine (0.44/1.85 mol%) or TPO (0.44 mol%)], and a micro and nanofiller loads of nil (unfilled); 40/10 mass%; and 50/10 mass%). Resin cements (0.2 mm thick) were placed on the lower surface of the ceramic specimens and light-activated for 30 s from the upper surface using a Bluephase Style curing light (exitance at tip: 1236 mW/cm2 ± 1.20). LT and distribution of irradiance through the ceramics were measured using a UV–vis spectrometer and a beam profile camera, respectively (n = 3). The DC and RP were measured in real-time using mid infrared spectroscopy in attenuated total reflectance (ATR) mode (n = 3). FS and FM were measured using a universal testing machine (n = 5). Statistical analyses were performed on LT, DC, RP, FS, and FM data using a general linear model, and supplementary ANOVA and post hoc Tukey multiple comparison test were also performed (α = .05). ResultsThicknesses, shades, photoinitiator type, and fillers load significantly influenced the optical and mechanical characteristics of the resin-based materials (p < 0.05). The BL3 shade ceramic provided higher values of DC, RP, FS, FM, and LT compared with the A1 shade (p < 0.05). Increasing ceramic thickness decreased the properties of the resin-based materials (p < 0.05). Generally, TPO improved mechanical properties of the resin cement compared with CQ (p < 0.05). SignificanceThe luting process of indirect restorations may be improved by using high molar absorptivity, more reactive, and more efficient photoinitiators such as TPO, as opposed to conventional CQ. The use of such initiator may allow the placement of thicker and more opaque indirect restorations.

Precise refractive index measurement of fused silica optics

Abstract We have developed an experimental platform that non-destructively and precisely measures the Refractive Index (RI) and dispersion of ultra-polished fused silica optics. Using Total Internal Reflection Digital Holographic Microscopy (TIRDHM), we exploit the phase change of reflected light in Total Internal Reflection (TIR) mode. This phase change depends on the incident angle at the TIR interface and the refractive indices of the involved media. We have optimized a combination of higher TIR phase sensitivity, considerable penetration depth, and minimized phase measurement inaccuracies through simulations to design our experiment. Key features include a custom-made precision Right-Angle Prism (RAP) of Astrositall material, a seamless interface with fused silica optics on TIR interface through optical contact, and single-shot measurement. We have demonstrated the accuracy of measuring fused silica optics through proof of concept and experimental results. Our measurements on two different samples show accuracy better than ±3 × 10−4 compared to those obtained using a commercially available critical angle Refractometer (Metricon). Importantly, the setup offers the advantage of spatially mapping the refractive index, unlike point measurements by available Refractometers.

Antimicrobial Composites Based on Methacrylic Acid-Methyl Methacrylate Electrospun Fibers Stabilized with Copper(II).

This study presents fibers based on methacrylic acid-methyl methacrylate (Eudragit L100) as Cu(II) adsorbents, resulting in antimicrobial complexes. Eudragit L100, an anionic copolymer synthesized by radical polymerization, was electrospun in dimethylformamide (DMF) and ethanol (EtOH). The electrospinning process was optimized through a 22-factorial design, with independent variables (copolymer concentration and EtOH/DMF volume ratio) and three repetitions at the central point. The smallest average fiber diameter (259 ± 53 nm) was obtained at 14% w/v Eudragit L100 and 80/20 EtOH/DMF volume ratio. The fibers were characterized using scanning electron microscopy (SEM), infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), and differential scanning calorimetry (DSC). The pseudo-second-order mechanism explained the kinetic adsorption toward Cu(II). The fibers exhibited a maximum adsorption capacity (qe) of 43.70 mg/g. The DSC analysis confirmed the Cu(II) absorption, indicating complexation between metallic ions and copolymer networks. The complexed fibers showed a lower degree of swelling than the non-complexed fibers. The complexed fibers exhibited bacteriostatic activity against Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria. This study successfully optimized the electrospinning process to produce thin fibers based on Eudragit L100 for potential applications as adsorbents for Cu(II) ions in aqueous media and for controlling bacterial growth.

Plastics in biogenic matrices intended for reuse in agriculture and the potential contribution to soil accumulation

The spread of biogenic matrices for agricultural purposes can lead to plastic input into soils, raising a question on possible consequences for the environment. Nonetheless, the current knowledge concerning the presence of plastics in biogenic matrices is very poor. Therefore, the objective of the present study was a quali-quantitative characterization of plastics in different matrices reused in agriculture as manures, digestate, compost and sewage sludges. Plastics were quantified and characterized using a Fourier Transform Infrared Spectroscopy coupled with an optical microscope (μFT-IR) in Attenuated Total Reflectance mode. Our study showed the presence of plastics in all the investigated samples, albeit with differences in the content among the matrices. We measured a lower presence in animal matrices (0.06–0.08 plastics/g wet weight w.w.), while 3.14–5.07 plastics/g w.w. were measured in sewage sludges. Fibres were the prevalent shape and plastic debris were mostly in the micrometric size. The most abundant polymers were polyester (PEST), polypropylene (PP) and polyethylene (PE). The worst case was observed in the compost sample, where 986 plastics/g w.w. were detected. The majority of these plastics were compostable and biodegradable, with only 8% consisting of fragments of PEST and PE. Our results highlighted the need to thoroughly evaluate the contribution of reused matrices in agriculture to the plastic accumulation in the soil system.

Characterization of microplastics in skim-milk powders

The diffusion of microplastics in the food supply chain is prompting public concern as their impact on human health is still largely unknown. The aim of this study was to qualitatively and quantitatively characterize microplastics in skim-milk powder samples (n = 16) from different European countries (n = 8) through Fourier-transform infrared microspectroscopy in attenuated total reflectance mode analysis. The present study highlights that the use of hot alkaline digestion has enabled the efficacious identification of microplastics in skim-milk powders used for cheesemaking across European countries. The adopted protocol allowed detection of 29 different types of polymeric matrices for a total of 536 plastic particles. The most abundant microplastics were polypropylene, polyethylene, polystyrene, and polyethylene terephthalate. Microplastics were found in skim-milk powders in 3 different shapes (fiber, sphere, and irregular fragments) and 6 different colors (black, blue, brown, fuchsia, green, and gray). Results demonstrate the presence of microplastics in all skim-milk powder samples, suggesting a general contamination. Results of the present study will help to evaluate the impact of microplastics intake on human health.

Bio‐blends of virgin and post‐industrial poly(methyl methacrylate) waste/pristine chitosan: Structure, thermal, and physical properties

AbstractPolymer blends based on plastic waste and natural biodegradable polymers is an interesting strategy in view of environmental and technical concerns. This article investigates the structure, thermal and physical properties of virgin and post‐industrial polymethyl methacrylate (PMMA) waste/pristine chitosan (Cs) bio‐blends. Waste PMMA was generated by an extrusion process for the manufacturing of sheets. The results of gel permeation chromatography analysis (GPC) show a slight decrease (about 8%) in the average molecular weight of PMMA after extrusion. Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR‐ATR) spectra do not reveal changes in the chemical structure of post‐industrial PMMA/Cs blends compared to virgin PMMA/Cs samples, indicating that chain scission reactions are the dominant degradation mechanism of PMMA during processing. Dynamic mechanical analysis (DMA) results reveal a single glass transition temperature () for the blends, implying miscibility of the components. Post‐industrial PMMA/Cs samples exhibit slightly lower values of compared to virgin PMMA/Cs blends. The post‐industrial PMMA waste slightly reduces nano‐mechanical properties and thermal stability of the blends relative to those from virgin PMMA. In contrast, it increases the water uptake of the bio‐blends compared with virgin PMMA.Highlights Chain scission is the dominant degradation mechanism of PMMA during extrusion. Miscibility between the homopolymers within the blends. PMMA waste slightly reduced the nano‐mechanical properties of the bio‐blends. Post‐industrial PMMA waste increased the water uptake of the bio‐blends. Possibility of using post‐industrial PMMA waste by blending with chitosan.

Optical Anisotropy of Polyethylene Terephthalate Films Characterized by Spectral Means.

Polyethylene terephthalate (PET) films are the subject of intensive research because of great interest in using them in applications, especially in medicine. From an optical point of view, PET films with a low degree of stretching can be considered uniaxial materials, for which the determination of the linear birefringence and its dispersion is very important. Two methods were applied here for the estimation of these parameters: the ellipsometric method and the channeled spectra method. The ellipsometric method uses monochromatic radiation; therefore, the linear birefringence of the PET films is determined for a given value of the radiation wavelength. The channeled spectra method allows for the estimation of the linear birefringence and its dispersion for a large range of wavelengths in the visible spectrum. A decrease in both parameters with the increase in the wavelength was recorded. To evidence the microstructure of PET films and the conformational changes induced by elongation and to evaluate the degree of orientation, a polarized infrared spectral study in attenuated total reflection (ATR-FTIR) mode was performed. The dichroic ratio (between the absorbance measured with linearly polarized radiation parallel and orthogonal relative to the stretching direction, respectively) and the ATR absorbance ratio for the machine direction (MD) and transversal direction (TD) configurations both for the stretched and unstretched PET samples were measured.

Classification of South American Camelid and goat fiber samples based on fourier transform infrared spectroscopy and machine learning

Some animal fibers are considerably cheaper than others. Hence the existence of counterfeit products, which are detrimental to legitimate producers and consumers alike. Fourier-Transform Infrared (FTIR) spectroscopy can extract a characteristic waveform from fibers that can be later used for classification. However, visually inspecting such waveforms is imprecise. Previous research has complemented FTIR with other mathematical or physical methods to improve accuracy. In parallel, Artificial Intelligence (AI) is an emerging field that could be helpful in this domain. The objective of this work is therefore to develop and validate two machine learning models, namely, Deep Neural Networks (DNN) and Support Vector Machine (SVM) to classify spectra of fibers by species. The spectra are acquired using an FTIR spectrometer in Attenuated Total Reflectance (ATR) mode (FTIR-ATR). Camelid (alpaca: n = 51, llama: n = 50, vicuña: n = 50) and goat (mohair: n = 35 and cashmere: n = 20) samples were evaluated, from which 1236 FTIR-ATR spectra were obtained. Some visual differences were observed between the spectra of the different species. Accuracies up to 96.75% and 95.12% were obtained when evaluating the DNN and SVM models. Furthermore, an accuracy of 97.8% was obtained when evaluating the FTIR-ATR spectra of South American Camelids (SAC) fibers with DNN, and 97.2% when evaluating them with SVM. A 100% accuracy was obtained when evaluating the FTIR-ATR spectra of vicuña fibers with both models. No significant differences were found (p-value = 0.368) by comparing the number of hits against the total number of alpaca, llama, vicuña, mohair and cashmere fibers using DNN. As per the results, it seems that DNN is more accurate than SVM. In conclusion, FTIR-ATR spectrometry techniques combined with machine learning models are a reliable alternative for the identification of SAC and goats through the spectrum of their fibers.