Attenuated Total Reflection Research Articles

Direct Determination of the Relationship between the Intramolecular Oxygen-Hydrogen Bond Length and Its Stretching Vibrational Frequency of the Methanol Molecule in the Liquid State.

Time-of-flight (TOF) neutron diffraction measurements on pure liquid deuterated methanol and concentrated methanolic LiClO4 and LiTFSA solutions have been carried out to investigate the effect of intermolecular hydrogen bonds on the intramolecular O-D distance (rOD) of the methanol molecule in the liquid state. Intramolecular parameters for the methanol molecule are determined by the least-squares fitting analysis of the neutron total interference term observed in the high-Q region. Attenuated total reflection (ATR) IR spectra have been measured for methanolic solutions of natural abundance to determine the gravitational center frequency (νOH) of the stretching vibrational band of the methanol molecule. The relationship between rOD and νOH is approximated well by a linear function. The value dνOH/drOD = -17000 ± 3000 cm-1 Å-1 has been derived from the slope of the fitted function. It has been revealed that the O-D bond length of the methanol molecule is sensitively affected by the intermolecular hydrogen bonding interaction.

Antibody Titer Prediction from Serum Immunodiffusion Test of Patients with Paracoccidioidomycosis Using Infrared Spectroscopy and Chemometrics

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by fungi of the genus Paracoccidioides. Serological tests are auxiliary in the diagnosis of PCM. However, the lack of standardization is a central problem in serodiagnosis and antibody titration. The objective of this study was to propose a methodology based on Fourier transform infrared spectroscopy (FTIR) for predicting antibody titers in patients with PCM. A total of 118 serum samples from patients with PCM were included, for which antibody titration using double immunodiffusion (DID) was previously performed. Serum samples were analyzed by attenuated total reflection (ATR)-FTIR and a supervised analysis with partial least squares regression (PLS) was used to predict the antibody titers. The PLS model with two latent variables and with the use of one orthogonal signal correction (OSC) showed a determination coefficient (R2) higher than 0.9999 for both the calibration and prediction set. The model was able to predict the antibody titers from patients with PCM with a minimal error. Therefore, modeling with FTIR/ATR and multivariate calibration proved to be a fast and highly accurate method for antibody titration, replacing the need for antigen production and performance of traditional serological tests.

ATR FTIR spectroscopy of protein and surfactant adsorption to the oil-water interface

An oil-infused polyelectrolyte multilayer (PEM) immersed in aqueous solution is a valid mimic for an oil-water interface, that can be used to probe adsorption of surfactants (including co-/competitive adsorption) using attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR). A PEM has been formed on an ATR internal reflection element, dried and then re-solvated with oil, then exposed to a flowing solution of protein, and subsequently a solution of surfactant. The PEM had undergone prior characterization with atomic force microscopy (AFM). The experiment was replicated using profile analysis tensiometry (PAT). The PEM displays a high degree of solvation with oil; it retains most of this oil in the presence of flowing aqueous solution. FTIR spectra confirmed adsorption of a dairy protein (β-lactoglobulin) to the medium chain triglyceride (MCT)-water interface, and the response of the adsorbed protein layer to a common food formulation surfactant (Tween 60) in the aqueous phase above the interface. The protein is observed to adsorb strongly and irreversibly to the MCT oil-water interface, and the Tween 60 molecules are seen to co-adsorb rather than displace the protein. This observation is supported by measurements of sequential co-adsorption undertaken with PAT.

In Situ Analysis of the Effect of Tetraakylammonium Salts on the Selectivity and Efficiency of Acrylonitrile Electrohydrodimerization

Traditional chemical manufacturing processes are primarily powered by fossil-fuel combustion, and often require operation at elevated temperatures and pressures. Introducing electrosynthesis as an alternative to thermal processes at industrial scale can allow direct integration of renewable electricity with chemical manufacturing, accelerating the decarbonization of large-scale chemical processes. However, there are major challenges that must be addressed before implementing organic electrosynthesis on an industrial level, such as the low solubility of organic reactants in aqueous electrolytes and the existence of multiple reaction pathways that lead to undesired byproducts. In this presentation, we will discuss our work on electrolyte design strategies to enhance the performance of adiponitrile (ADN) electrosynthesis. ADN is a large volume precursor of hexamethylenediamine, which is a monomer used in Nylon 6,6 manufacturing. The most commonly used method for ADN production, the thermochemical hydrocyanation of 1,3-butadiene, is energy intensive and uses hydrogen cyanide, a highly toxic reactant. Alternatively, ADN can be produced electrochemically via the hydrodimerization of acrylonitrile (AN), which is the largest and most successful industrial organic electrochemical process. In this reaction, the addition of tetraalkylammonium (TAA) salts as supporting electrolytes in large concentrations has been widely accepted to enhance the solubility of organic reactants. It has been hypothesized that TAA ions boost the selectivity towards ADN by increasing the AN concentration in the electrical double layer (EDL). Recent studies by our group explored the effect of the molecular size and concentration of TAA ions on the selectivity and efficiency of ADN production. Resulting trends suggest that the reaction is strongly limited by mass transport of organic reactants to the EDL at high current densities. Despite these advances, the local effects of TAA ions on the concentration of reactants and intermediates in the EDL remain unclear. Inspired by prior demonstrations, we developed a spectroelectrochemical method for quantitatively assessing the concentration of species at the electrode/electrolyte interface. This method relies on an electrochemical flow cell integrated with an attenuated total reflection (ATR) Fourier-transform infrared (FTIR) spectrometer to quantify concentrations of reactive species in the near-electrode region. Our results demonstrate that the presence of TAA ions increases the local concentration of AN at the electrode, and that applied potential increases TAA ion concentration. These results provide insights into the effects of supporting ions and potential in organic electrosynthesis selectivity.Figure caption: Schematic view of the enhancement of acrylonitrile (AN) concentration in the electrical double layer (EDL) by the addition of Tetrabutylammonium (TBA) ions to the aqueous electrolyte. Figure 1

All natural mussel-inspired bioadhesives from soy proteins and plant derived polyphenols with marked water-resistance and favourable antibacterial profile for wound treatment applications

HypothesisImplementation of tissue adhesives from natural sources endowed with good mechanical properties and underwater resistance still represents a challenging research goal. Inspired by the extraordinary wet adhesion properties of mussel byssus proteins resulting from interaction of catechol and amino residues, hydrogels from soy protein isolate (SPI) and selected polyphenols i.e. caffeic acid (CA), chlorogenic acid (CGA) and gallic acid (GA) under mild aerial oxidative conditions were prepared. ExperimentsThe hydrogels were subjected to chemical assays, ATR FT-IR and EPR spectroscopy, rheological and morphological SEM analysis. Mechanical tests were carried out on hydrogels prepared by inclusion of agarose. Biological tests included evaluation of the antibacterial and wound healing activity, and hemocompatibility. FindingsThe decrease of free NH2 and SH groups of SPI, the EPR features, the good cohesive strength and excellent underwater resistance (15 days for SPI/GA) under conditions relevant to their use as surgical glues indicated an efficient interaction of the polyphenols with the protein in the hydrogels. The polyphenols greatly also improved the mechanical properties of the SPI/ agarose/polyphenols hydrogels. These latter proved biocompatible, hemocompatible, not harmful to skin, displayed durable adhesiveness and good water-vapour permeability. Excellent antibacterial properties and in some cases (SPI/CGA) a favourable wound healing activity on dermal fibroblasts was obtained.

Does dinocyst wall composition really reflect trophic affinity? New evidence from ATR micro-FTIR spectroscopy measurements.

Attenuated total reflection (ATR) microscope Fourier transform infrared (micro-FTIR) spectroscopy was used to investigate the dinosporin composition in the walls of modern, organic-walled dinoflagellate resting cysts (dinocysts). Variable cyst wall compositions were observed, which led to the erection of four spectrochemical groups, some with striking similarities to other resistant biomacromolecules such as sporopollenin and algaenan. Furthermore, possible proxies derivable from the spectrochemical composition of modern and fossil dinocysts were discussed. The color of the dinocyst walls was reflected in the spectral data. When comparing that color with a standard and the results of a series of bleaching experiments with oxidative agents, eumelanin was assigned as a likely pigment contributing to the observed color. Following this assignment, the role of eumelanin as an ultraviolet sunscreen in colored dinocysts was hypothesized, and its implications on the autofluorescence and morphological preservation of dinocysts were further discussed. Unlike what had previously been assumed, it was shown that micro-FTIR data from dinocysts cannot be used to unambiguously infer trophic affinities of their associated cells. Finally, using methods with high spatial resolutions (synchrotron transmission micro-FTIR and optical photothermal infrared spectroscopy), it was shown that dinocyst wall layers are chemically homogenous at the probed scales. This study fills a large knowledge gap in our understanding of the chemical nature of dinocyst walls and has nuanced certain assumptions and interpretations made in the past.

Identification of macronutrients by FT-IR analysis and physicochemical characterization of snacks elaborated from quinoa (Chenopodium quinoa Willd) and sacha inchi (Plukenetia volubilis)

Background: Currently, the consumption of high-protein foods that replace animal sources is increasing, a trend that promotes the design of new food systems. Spectroscopy methods with physicochemical tests allow for rapid and reliable identification of macronutrients and bioactive compounds. Methods: Snacks were made using hyperproteic quinoa flour (HPQF) and sacha inchi flour (SIF) through an extrusion process and subsequent compression molding. Spectra infrared (IR) analysis was used to identify macronutrients such as starch, proteins, lipids, and fiber. Specific frequencies were selected that provided the greatest discrimination of the sample. Physicochemical measurements were performed using extractable (EPC) and hydrolyzable (HPC) phenolic compound analyses, carotenoid content, and antioxidant capacity through ABTS• + (2,2-azinobis- 3-ethylbenzothiazoline-6-sulphonic acid), DPPH (2,2-diphenyl-1-picrylhydrazyl), and FRAP (ferric reducing antioxidant power) methods. Color and texture parameters of the snacks were also measured. Results: The identification of macronutrients using Fourier transform infrared spectroscopy – attenuated total reflectance (FTIR–ATR) was as follows: lipids showed two characteristic peaks at 2870 and 2960 cm−1; protein showed three peaks at 1540, 1630, and 1660 cm −1; starch showed two peaks at 1170 and 1155 cm −1. Regarding the content of free polyphenols, hydrolyzable polyphenols and carotenoids, the mixtures added with the highest inclusion of quinoa, i.e. 50%, showed the highest values of 3.05 mg GAE/g, 14.16 mg GAE/g and 14.06 µg-β carotene/g of dry base sample, respectively. The snacks showed significant differences (p<0.05) in the antioxidant properties determined by the ABTS and FRAP methods, with the highest values in the samples with 50% HPQF. The inclusion of HPQF was associated with a higher browning index, and snacks with a higher quinoa content exhibited greater hardness and crispness. Conclusions: Snacks were obtained with protein percentages between 26–33%, containing bioactive compounds, gluten-free, and without the addition of oil during their production.

Valorization of citrus waste for circular economy: A case study on bergamot pomace as sorbent for Cd2+ removal and source of added value compounds

The potential of bergamot pomace for the development of materials able to efficiently remove cadmium(II) from water and for the recovery of bioactive compounds has been explored. To this purpose, raw bergamot waste resulting after industrial essential oil and juice extraction was mechanically ground, desiccated, pretreated with various chemicals (e.g. NaOH, HNO3, H2O2, H2O, 2-propanol) and dried up to constant weight thus affording solid samples that were characterized by ATR FT-IR spectroscopy. The solutions recovered after the pomace pretreatments were investigated by means of HPLC in combination with PDA and MS detectors to assess the residual content of bioactive components, e.g., phenolic and oxygenated heterocyclic compounds (OHCs). Potentiometric studies were performed on suspensions at t = 25 °C, I = 0.10 mol dm−3 in NaNO3(aq) to investigate pomace acid-base properties and binding ability towards Cd2+ ions. Sorption efficiency was investigated by means of kinetic and isotherm batch experiments and resulted to be 92 ± 7 mg g−1. Once loaded, sorbent reusability was tested by performing metal stripping cycles using various desorbents (HCl, HNO3, L-GLDA, S,S-EDDS, EDTA) with an efficiency of ∼ 60% after one cycle. The equilibrium Cd2+ concentration in solution was determined by differential pulse voltammetry and ICP-OES.

Eco-Friendly Degradation of Natural Rubber Powder Waste Using Some Microorganisms with Focus on Antioxidant and Antibacterial Activities of Biodegraded Rubber

Natural rubber (NR) powder wastes contribute to the pollution of the environment and pose a risk to human health. Therefore, Escherichia coli AY1 and Aspergillus oryzae were used to degrade NR in the present investigation. The biodegradation was further confirmed using E. coli AY1 and A. oryzae’s ability to create biofilm, which grew on the surface of the NR. Additionally, the biodegraded NR was examined by scanning electron microscopy (SEM), attenuated total reflection–Fourier transform infrared (ATR–FTIR) spectroscopy, and gas chromatography–mass spectrometry (GC–MS). The highest weight loss (69%) of NR was detected (p < 0.05) after 210 d of incubation with the mixed microbial culture (E. coli AY1 + A. oryzae). In the SEM, the surface of the control treatment appeared uniform and normal, whereas the surface of the microbial treatment displayed an irregular shape, with apparent particle deformation and surface erosion. After biodegradation by E. coli AY1 and A. oryzae, the particle size range of the untreated NR dropped from (5.367–9.623 µm) to (2.55–6.549 µm). After treating NR with E. coli AY1 and A. oryzae, new bands appeared in the ATR–FTIR technique; others shifted down in the range of 3910–450 cm−1, suggesting the existence of active groups belonging to alcohol, secondary amine, aromatic amine, conjugated anhydride, aldehyde, alkene, and halo compounds. On the other hand, the GC–MS profile reports a significant decline (p < 0.05) in the amount of hydrocarbons while simultaneously reporting a significant increase (p < 0.05) in the proportion of oxygenated, sulfurous, and nitrogenous compounds. These active groups are attributed to the antioxidant and antibacterial properties of biodegraded NR by a mixture of E. coli AY1 and A. oryzae, which rose 9-fold (p < 0.05) compared to untreated NR. Through the use of this research, we will be able to transform NR waste into a valuable product that possesses both antioxidant and antibacterial properties.

Synthesis and characterization of polyvalent high-performance synthetic base oil for drilling operations in recalcitrant and unconventional oil and gas reservoirs

Synthetic ester fluid is one of the most widely recommended drilling fluids for unconventional and recalcitrant reservoirs owing to its numerous technical advantages, high sustainability, non-toxic and inherently biodegradable. However, there are serious concerns about its thermal and hydrolytic stability at high temperatures and pressures (HTHP) as well as its viscosity and flow characteristics in low temperature climates such as deep-water wells. Hence, its inability to maintain stable borehole and flat rheology characteristics may invariably threaten its application under these aforementioned scenarios.In this study, a high-performance ternary mixture of synthetic ethyl esters of plants oil (SEEP mixture) fluid was synthesized by a non-catalyzed supercritical ethanol transesterification process using coconut, castor seed and linseed oil as starting materials. The nature, chemistry and fluid particle interactions of the individual components that make up the synthetic ester fluid were critically studied. The process equipment consists of a continuous flow reactor equipped with a PID controlled furnace as heat source to the reactor and a high- pressure transducer. The conversion efficiency was monitored by an Agilent 5500a FTIR machine with attenuated total reflectance (ATR) system while a GC-EIMSD system was used for fatty acid ester compositional analysis. The oil was extracted by a Soxhlet apparatus mechanism. The extracted Plant oil and the synthetic esters were characterized under standard recommended laboratory procedures by API, ASTM and the European Union (EN) standard protocols. Also, fluid's toxicity and biodegradability tests were conducted according to OECD recommended practices. The results were compared with existing synthetic hydrocarbon fluids (SHFs) for HTHP and deep-water wells.The conversion efficiency of the non-catalyzed transesterification process was 96.50%. The amount of oil yield from the plant oil after Soxhlet extraction is commendable. Hence, synthetic ester fluid raw materials are readily available in large quantities and in a sustainable manner. The GC-MS analysis shows that the coconut oil contains 92% saturated fatty acid. Whereas, the castor seed oil contains 98.31% unsaturated fatty acid with 89.75% of mono-unsaturated ricin-oleic acid (D-12-hydroxyoctadec-cis-9-enoic acid). The linseed oil has high content of linolenic acid with 89.60% unsaturated fatty acid. The designed fluid has excellent lubricity characteristics, extremely low cloud and pour point temperatures, higher oxidative stability, low peroxide value, lower copper strip corrosion value and lower kinematic viscosity and density variations with temperatures which signals flat rheology when used to form a synthetic based mud. Also, its flash point and auto-ignition temperatures are high and thus forestall possible fire hazard in high temperature zones. Finally, the fluid is non-toxic and inherently biodegradable.

Removal of fipronil by advanced oxidative processes using sulfite activated by cobalt immobilized on silica

Sulfite auto-oxidation catalyzed by cobalt complexed with ammonia deposited on silica (CoNSi) was used to generate sulfate radicals. The material was characterized by ATR–FTIR, suggesting that the silica structure did not change, and SEM–EDS, indicating an uniform dispersion of cobalt across the material surface according with XRD results. BET analysis provided information on a mesoporous material (type IV isotherm) with regular morphology (H1 hysteresis). The DSC analysis showed that CoNSi is thermally stable under the studied conditions. Quantitative analysis of Fipronil (FIP) was performed by HPLC-DAD, where the applied method was selective and linear. The Box–Behnken experimental design (BBD) method was used to define the best condition for removing the analyte in water. It was found that in 60 min, 76% removal of 1.8 mg L−1 of FIP was reached by adding 0.30 g of the material and 0.30 g of the sulfite in a solution under stirring, aeration, pH 8.0, and room temperature and protected from radiation. However, analysis of cobalt leaching into the solution by FAAS showed a small amount of the metal (0.44 mg L−1) informing that the synthesis of the material must be improved.

Surface modification of polyethylene using argon and argon/methane DBD atmospheric pressure plasma jet

This article investigates the surface modification of polyethylene (PE) using an atmospheric pressure plasma jet of the DBD type (APPJ) maintained with pure argon (Ar) and with a premixed gas containing 90% argon and 10% of CH4. First and for both plasma jets, the jet length and the optical emissions coming from the plasma species were studied in terms of flow rate and applied voltage. Comparing to Ar, it has been shown that when the premixed gas is used, the jet length gets smaller, the transition point from laminar to turbulent regime was shifted to a low flow rate, and the emission of CH, H2 and C2 appeared, while O and N2 emission coming from ambient air was quenching. The PE surface treatment in both laminar and turbulent regime has been evaluated using water contact angle (WCA) measurement and attenuated total reflection (ATR). The obtained results showed that the hydrophilicity of PE has been improved in both plasma jets due to oxygen group (C=O) incorporation, but Ar plasma jet was observed to induce surface degradation compared to Ar/CH4 plasma due to the higher excited species.

The catalytic reaction of cytochrome c oxidase probed by in situ gas titrations and FTIR difference spectroscopy

Cytochrome c oxidase (CcO) is a transmembrane heme‑copper metalloenzyme that catalyzes the reduction of O2 to H2O at the reducing end of the respiratory electron transport chain. To understand this reaction, we followed the conversion of CcO from Rhodobacter sphaeroides between several active-ready and carbon monoxide-inhibited states via attenuated total reflection Fourier-transform infrared (ATR FTIR) difference spectroscopy. Utilizing a novel gas titration setup, we prepared the mixed-valence, CO-inhibited R2CO state as well as the fully-reduced R4 and R4CO states and induced the “active ready” oxidized state OH. These experiments are performed in the dark yielding FTIR difference spectra exclusively triggered by exposure to O2, the natural substrate of CcO. Our data demonstrate that the presence of CO at heme a3 does not impair the catalytic oxidation of CcO when the cycle starts from the fully-reduced states. Interestingly, when starting from the R2CO state, the release of the CO ligand upon purging with inert gas yield a product that is indistinguishable from photolysis-induced states. The observed changes at heme a3 in the catalytic binuclear center (BNC) result from the loss of CO and are unrelated to electronic excitation upon illumination. Based on our experiments, we re-evaluate the assignment of marker bands that appear in time-resolved photolysis and perfusion-induced experiments on CcO.

Chernozem Land Use Differentiation by Temperature-Dependent IR Spectra

Granulometric aggregate fractions (20 µm–2 mm) of chernozem soils with different agriculture-use histories (native steppe, permanent bare fallow, arable land, and shelterbelt) were investigated in mid-IR and far IR regions (4000–100 cm−1) by heating in the air from 25 to 215 °C, using ATR FTIR and linear discriminant analysis to differentiate the land-use samples without chemical perturbation. The temperature dependences of the band maxima significantly differed for bands of silicate matrix and bands with the contribution of soil organic matter and were more stable to experimental conditions compared to the absolute positions. The thermal behavior of the integral intensities of the IR bands at 790–750 cm−1 and 440–420 cm−1 that was different compared to pure quartz, may be attributed to –C–H bending of alkanes and (poly)aromatic structures and skeletal bending, and could be used to distinguish intact soils from agriculturally used samples. The different temperature behaviors of the bands for fractions of soils with different land use are shown, with the maximum difference in fractions below 20–50 µm and medium fractions (50–200 µm). Changes in the band-maximum frequencies and the integral intensities of the bands were reversible for a heating–cooling cycle. The linear discriminant analysis of the spectra obtained for granulometric fractions of chernozem soils made it possible to separate the samples of native steppe, arable land, bare fallow, and shelterbelt with a high probability based on the type of vegetation and agrogenic load, mainly on the basis of the spectral ranges associated with biogenic forms of quartz and phytoliths.

Potential biomarkers for southern African hunter-gatherer arrow poisons applied to ethno-historical and archaeological samples

The detection of complex poison recipes applied to ancient hunting weapons has the potential to provide important insights into traditional pharmacological knowledge systems. Yet, recipes comprising many ingredients can be challenging to decipher, especially in older samples that have undergone biodegradation. We present the results of our attempt to analyze samples of poison collected from nineteenth and twentieth century arrowheads from southern Africa, and from a 1000-year-old archaeological bone point. The arrow poison residues and reference samples were analyzed by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) and Gas Chromatography Mass Spectrometry (GC–MS). The ATR FTIR analysis is primarily able to separate between different arrow poison binder recipes. The extractives identified by GC–MS analysis consist of a multitude of components from both binders and active substances, confirming and adding to the results from the ATR FTIR analyses. We discuss the results in terms of potential biomarkers for arrow poisons in organic residue analyses of archaeological artefacts; that residues of toxic cardiotonic glycosides can be detected on curated and excavated arrow tips of between about 1000 and 100 years old, serves as proof of concept for working with older materials in the future.

Early stages of X-ray induced molecular unit modifications in poly(lactic acid)

Exposure of polymers to ionizing radiation and high-energy particle beams is involved in many processes – from food sterilization to radiotherapy protocols. The resulting effects, at the final stages, determine the functional, structural, and morphological alteration of the material. However, the processes responsible for cumulative chain scission, crosslinking, and reactions with the environment are often difficult to disentangle as a sequence of elementary events. Here we report a spectroscopic study – by attenuated-total reflection Fourier transform infrared spectroscopy and powder x-ray diffraction measurements, together with differential scanning calorimetry and thermogravimetric analyses – that sheds light on the very initial stages of the mechanisms involved in radiation-induced modifications of poly(lactic acid) (PLA). The results, collected on samples from biobased processes and exposed to low x-ray doses in the range of 100–103Gy after different thermal treatments, show spectroscopic evidence of the emergence of molecular unit perturbations – mainly related to methyl and carbonyl groups with the formation of C=C double bonds – with a clear-cut dependence on the polymer conformation. Understanding the mechanisms involved and the role of crystallinity provides information potentially useful for the development of PLA with a suitable radiation hardness for applications in radiotherapy.

Molecular Orientation and Energy Transfer Dynamics of a Metal Oxide Bound Self-Assembled Trilayer.

Self-assembly of molecular multilayers via metal ion linkages has become an important strategy for interfacial engineering of metalloid and metal oxide (MOx) substrates, with applications in numerous areas, including energy harvesting, catalysis, and chemical sensing. An important aspect for the rational design of these multilayers is knowledge of the molecular structure-function relationships. For example, in a multilayer composed of different chromophores in each layer, the molecular orientation of each layer, both relative to the adjacent layers and the substrate, influences the efficiency of vectorial energy and electron transfer. Here, we describe an approach using UV-vis attenuated total reflection (ATR) spectroscopy to determine the mean dipole tilt angle of chromophores in each layer in a metal ion-linked trilayer self-assembled on indium-tin oxide. To our knowledge, this is the first report demonstrating the measurement of the orientation of three different chromophores in a single assembly. The ATR approach allows the adsorption of each layer to be monitored in real-time, and any changes in the orientation of an underlying layer arising from the adsorption of an overlying layer can be detected. We also performed transient absorption spectroscopy to monitor interlayer energy transfer dynamics in order to relate structure to function. We found that near unity efficiency, sub-nanosecond energy transfer between the third and second layer was primarily dictated by the distance between the chromophores. Thus, in this case, the orientation had minimal impact at such proximity.

Acetalization of glycerol with acetone over UAV-59 catalyst: Mild reaction conditions and enhanced selectivity

The solvent-free acetalization of glycerol with acetone was investigated using as catalyst UAV-59, a Coordination Polymer based on nitrilo(trimethylphosphonic acid) and Gd3+, at 25 °C and 55 °C, with various glycerol/acetone (Gly/Ace) molar ratios. The reaction yielded solketal, a five-membered acetal, and 2,2-dimethyl-1,3-dioxan-5-ol, a six-membered acetal. UAV-59's catalytic activity was influenced by temperature, with the highest conversion (94%) achieved at 55 °C, a 1/10 Gly/Ace ratio, and 5% catalyst. The selectivity for solketal remained consistent (95–98%) across all conditions. Reaction kinetics and selectivity profiles were compared, catalyst stability was assessed, and results were benchmarked against Metal Organic Framework catalysts from the literature. The heterogeneous nature of catalysis was confirmed through leaching tests, and the catalyst's chemical features were analyzed using ATR FT-IR spectra and X-ray diffraction patterns, indicating that UAV-59's crystalline structure was preserved during the reaction.

On the effectiveness of vibrational spectroscopy to study piezoelectric polymers

In order to investigate the effectiveness of vibrational spectroscopy in the characterization of polymer piezoelectric materials, poly(vinylidene fluoride) (PVDF) samples are carefully studied. The characterizations are performed by using different Fourier transform infrared sampling techniques, i.e. transmission (FTIR), attenuated total reflectance (FTIR-ATR) and photoacoustic spectroscopy (FTIR-PAS). The attenuated total reflectance (ATR) and photoacoustic (PAS) sampling methods allow us to study the IR spectra for thick piezoelectric samples. To the best of our knowledge, it has been determined for the first time the relative fractions of the β phase, F(β), in PVDF by FTIR-PAS.

Expeditious and accurate detection of palm oil adulteration in virgin coconut oil by utilizing ATR-FTIR spectroscopy along with chemometrics and regression models

Virgin coconut oil (VCO), being one of the most treasured and healthy edible oil, is at great risk of blending with cheaper oils like palm oil (PO). Fourier transform infrared (FTIR) spectroscopy with an Attenuated total reflection (ATR) accessory was used together with multivariate chemometrics for the classification and evaluation of numerous concentrations of PO (0.5–30% v/v) in VCO. Linear Discriminant Analysis (LDA) showed a 100% correct classification for both the initial and cross-validation groups for all the subsets of PO blends. Principal components regression (PCR) and Partial least squares regression (PLS-R) calibration models were generated and compared for normal, 1st, and 2nd derivatives of the combined informational spectral domain (3010–2800 cm−1 & 1800–700 cm−1) and separate informational domains of the spectra 3010–2800 cm−1 and 1800–700 cm−1 to get the best-fitting models. Regression models for the 2nd derivatives of 1800–700 cm−1 informational spectral domain gave exquisite outcomes of prediction with immense accuracy and precision with the highest R2 of 0.998, and the root mean square error of prediction (RMSEP) of 0.375% v/v for PLS-R and R2 of 0.998 and RMSEP of 0.441% v/v for PCR respectively. The lowest detectable limit of PO in VCO was estimated as 0.5% v/v. Hence, it has been concluded that PO adulteration of up to 0.5% with VCO can be quickly determined by using ATR-FTIR spectroscopy fitted with multivariate chemometrics.