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Monomers of N-hydroxypyridine-2(1H)-thione were isolated in low-temperature matrices of solid normal hydrogen (n-H2). The matrix-isolated compound was irradiated with UV-B (λ = 305 nm) or UV-A (λ > 360 nm) light. Upon such irradiation, the initial form of N-hydroxypyridine-2(1H)-thione was completely consumed and converted into photoproducts. 2-Mercaptopyridine and water were identified as the main products of these photochemical transformations. Identification of photoproduced 2-mercaptopyridine is unquestionable. It is based on the identity of two sets of IR bands: (i) the bands observed in the IR spectrum recorded (in a separate experiment) for monomers of 2-mercaptopyridine trapped in an n-H2 matrix and (ii) a set of IR bands observed in the spectrum recorded after UV irradiation of N-hydroxypyridine-2(1H)-thione. It should be emphasized that the UV-induced processes, occurring for N-hydroxypyridine-2(1H)-thione isolated in an n-H2 matrix, lead to products that are significantly different from those generated from the compound trapped in solid Ar or in solid N2. [ABSTRACT FROM AUTHOR]

We describe the properties of the bacterial cellulose of various origins obtained with the help of XRD, FTIR, and dielectric spectroscopy methods. The samples were produced by Gluconacetobacter bacteria (with Іα phase content of 36%) and a symbiotic culture of bacteria and yeasts present in Kombucha fermented drink (with Іα phase content of 62%). An increase in the Іα phase concentration results in a decrease in the intensity of the low-temperature dielectric relaxation and its shift toward higher temperatures. We demonstrate that this dielectric relaxation occurs primarily due to the reorientation of the methylol groups on the surfaces of the cellulose crystallites. We also report that the concentration of the activated relaxers in Іβ cellulose allomorph exceeds that of the Іα allomorph. [ABSTRACT FROM AUTHOR]

Para-tert-butylthiacalix[4]arenimines with mono- and distally substituted functional groups have been examined in terms of their structure and spectra. The structure and H-bonds of these compounds can be studied by comparing their vibrational and NMR spectra. The spectra of several conformations of the molecules TCA1-4 were calculated. For the molecules TCA3 and TCA4, the most stable conformation is a distorted cone (DC2) with the same imine or phthalimide group orientation, consequently. The least stable conformation is pinched cone (PC). The conformations of molecules TCA2, TCA3, and TCA4 are DC1 and DC2, respectively. H-bonds in the molecules TCA1-4 alter their supramolecular properties. Ionization energy and dipole moment decrease as monosubstituted thiacalixarene (TCA1) transforms into disubstituted TCA2. In this instance, there is an increase in softness, electrophilicity, chemical potential, and electron affinity. An increase in the number of methylene groups in disubstituted thiacalixarenes from TCA4 to TCA2 is accompanied by an increase in ionization energy, electron affinity, and electrophilicity. [ABSTRACT FROM AUTHOR]

Abstract Serpentine minerals, either polymorphs or polytypes (mostly chrysotile, lizardite and antigorite), are hardly distinguished in ophiolitic serpentinites and serpentinized peridotite unless sophisticated mineralogical tools are applied. Among them, chrysotile has special chemical and structural characteristics, which can be used to identify and classify different modes, and accordingly as significant petrographic indicators of serpentinization in ophiolite sequences. Generally, chrysotile characterizes low-grade metamorphism and it occurs in massive serpentinites as well as asbestos veinlets traversing them. The present paper aims to characterize the different modes of chrysotile in serpenitinite and serpentinized peridotite from the Semail ophiolite at the Daftah area in the United Arab Emirates (UAE). The objectives include microscopic and chemical separation of three chrysotile modes; namely slip-fiber (most common), mass fiber (common) and cross-fiber (less common). The cross-fiber mode is considered a “spinning type” in sheared serpentinite with asbestos veinlets whereas the other two belong to “non-spinning type” in massive serpentinite being formed by a contact volume metasomatic process by replacement of olivine and pyroxene. Excess Mg from the transformation of ferromagnesian minerals into chrysotile, in the presence of additional SiO2, results in an association of cryptocrystalline talc with the chrysotile fibers. Differential thermal analysis (DTA) and thermogravimetry (TG) indicate that the process of thermal decomposition of chrysotile leads to the formation of olivine (forsterite). The infra-red (IR) absorption technique for end products of some selected samples appear to indicate that the spectra of the end products are similar and the absorption bands are assigned in the range of (1100–800 cm−1) and (700–200 cm−1) corresponding to Si–O and Mg–O vibration modes. Based on the findings of the present paper, the chrysotile serpentinization process is due to metasomatic replacement of peridotite during the ocean floor early episode and later an episode of ophiolite obduction. The chemical data focalize that the similarity in chemical behaviour of chrysotile veins implies that a close cogenetic relationship among three modes of chrysotile and removal of such major elements occurred during serpentinization; Mg, Fe and Si were removal in solution from the peridotite and precipitated in tension and shear fractures to form fibrous chrysotile and magnetite. Also, it can be concluded that the mode of occurrence and timing of chrysotile vein formation can be fitted according to the type of chrysotile mode. Cross-fiber type develops along tension fractures whereas mass-fiber type is finally developed via CO2 metasomatism. Finally, the slip-fiber type forms by a volume-for volume metasomatic process due to the replacement of olivine and/or pyroxene. In terms of time and tectonism, the different mode witnessed different metamorphic/metasomatic events and structures. Shear deformation is more likely connected to the formation of cross-fibers in NW- and NE-trending asbestos veins and veinlets.

Listeria are Gram-negative intracellular foodborne pathogens that can cause invasive infections with high mortality rates. In this work, the antibacterial activity of ten essential oils, infusion extracts, and decoction extracts of some medicinal plants was tested against Listeria monocytogenes and listeria ivanovii strains. The effects of different physical conditions including temperature, pH, sodium chloride, and some organic acids were studied. The results showed that the water extracts gave the maximum bacterial inhibition, while ethanolic extract was inactive against the tested Listeria spp. The antibiotic sensitivity of L. monocytogenes LMG10470 and L. ivanovii LMZ11352 was tested against five antibiotics including imipenem, levofloxacin, amikacin, ampicillin, and amoxicillin. Imipenem was the most effective antibiotic, resulting in inhibition zones of 40 mm and 31 mm for L. monocytogenes and L. ivanovii, respectively. When imipenem mixed with Syzygium aromaticum oil, Salvia officinalis oil, Pimpinella anisum infusion, and Mentha piperita infusion each, the water extract of Moringa oleifera leaves and seeds against LMG10470 and LMZ11352 resulted in broader antibacterial activity. The antimicrobial activity of both Pimpinella anisum and Mentha piperita plant extracts is related to a variety of bioactive compounds indicated by gas chromatography–mass spectrometry analysis of these two plant extracts. These two plant extracts seemed to contain many chemical compounds elucidated by gas chromatography–mass spectrometry (GC-MS) and infrared radiation spectra. These compounds could be classified into different chemical groups such as ethers, heterocyclic compounds, aromatic aldehydes, condensed heterocyclic compounds, ketones, alicyclic compounds, aromatics, esters, herbicides, saturated fatty acids, and unsaturated fatty acids. The use of these natural compounds seems to be a useful technological adjuvant for the control of Listeria spp. in foods. [ABSTRACT FROM AUTHOR]

A series of substituted 2-aminotetrahydroquinolinecarbonitriles have been synthesized by the three-component condensation of diaryl(hetaryl)methylidenecyclohexanones, malononitrile, and ammonium acetate. Factors responsible for the reaction selectivity and product formation pathway have been revealed. The reaction of aminoquinolinecarbonitriles with acetic anhydride under acidic conditions afforded substituted hexahydro-pyrimido[4,5-b]quinolinones. The structure of the synthesized compounds has been determined by IR and 1H and 13C NMR spectroscopy, including HSQC two-dimensional correlation technique. [ABSTRACT FROM AUTHOR]

Context: Single-wall carbon nanotubes (SWCNT) dispersed in water with the help of sodium dodecyl sulfate (SDS) surfactants exhibit a temperature dependent near infrared (NIR) exciton spectrum. Due to their biocompatibility and NIR spectrum falling within the transparent window for biological tissue, SWCNTs hold potential for sensing temperature inside cells. Here, we seek to elucidate the mechanism responsible for this temperature dependence, focusing on changes in the water coverage of the SWCNT as the surfactant structure changes with temperature. We compare optical absorption spectra in the UV–Vis-IR range and fully atomistic molecular dynamics (MD) simulations. The observed temperature dependence of the spectra for various SWCNTs may be attributed to changes in the dielectric environment and its impact on excitons. MD simulations reveal that the adsorbed SDS molecules effectively shield the SWCNT, with ~ 70% of water molecules removed from the first two adlayers; this coverage shows a modest temperature dependence. Although we are not able to directly demonstrate how this influences the NIR spectrum, this represents a potential pathway given the strong influence of the water environment on the excitons in SWCNTs. Methods: Optical absorption measurements were carried out in the UV–Vis-NIR range using a Varian Cary 5000 spectrophotometer in a temperature-controlled environment. PeakFit™ v. 4.06 was used as peak-fitting program in the spectral range 900–1400 nm (890–1380 meV) as a function of the temperature. Fully atomistic molecular dynamics simulations were conducted using the NAMD2 package. The CHARMM force field comprising two-body bond stretching, three-body angle deformation, four-body dihedral angle deformation, and nonbonded interactions (electrostatic and Lennard–Jones 6–16 potentials) was employed. [ABSTRACT FROM AUTHOR]

The present study was undertaken to extract chitin and chitosan from crab shell waste and investigate the chemical structure and antioxidant abilities by in vitro assays. Chitin was extracted, chitosan conversion was performed by chemical methods, and the yield was found to be 21%. Several active functional groups, NH primary and secondary amines, amides, and acetyl groups with different bond stretching were conformed in FT-IR spectral analysis. In the proton NMR, N-acetyl glucosamine and H-2 proton of glucosamine (GlcN) residues were identified in chitosan. The antioxidant activities were realized by dose dependent and the maximum activity was found 62, 71, and 58% in higher concentrations of DPPH, hydroxyl, and ferrous ion chelating effects. The derived chitosan is a nontoxic polymer with high chelating capability a good source for functional foods from sustainable source of marine waste. [ABSTRACT FROM AUTHOR]

The first step in comprehending the properties of Au10 clusters is understanding the lowest energy structure at low and high temperatures. Functional materials operate at finite temperatures; however, energy computations employing density functional theory (DFT) methodology are typically carried out at zero temperature, leaving many properties unexplored. This study explored the potential and free energy surface of the neutral Au10 nanocluster at a finite temperature, employing a genetic algorithm coupled with DFT and nanothermodynamics. Furthermore, we computed the thermal population and infrared Boltzmann spectrum at a finite temperature and compared it with the validated experimental data. Moreover, we performed the chemical bonding analysis using the quantum theory of atoms in molecules (QTAIM) approach and the adaptive natural density partitioning method (AdNDP) to shed light on the bonding of Au atoms in the low-energy structures. In the calculations, we take into consideration the relativistic effects through the zero-order regular approximation (ZORA), the dispersion through Grimme's dispersion with Becke–Johnson damping (D3BJ), and we employed nanothermodynamics to consider temperature contributions. Small Au clusters prefer the planar shape, and the transition from 2D to 3D could take place at atomic clusters consisting of ten atoms, which could be affected by temperature, relativistic effects, and dispersion. We analyzed the energetic ordering of structures calculated using DFT with ZORA and single-point energy calculation employing the DLPNO-CCSD(T) methodology. Our findings indicate that the planar lowest energy structure computed with DFT is not the lowest energy structure computed at the DLPN0-CCSD(T) level of theory. The computed thermal population indicates that the 2D elongated hexagon configuration strongly dominates at a temperature range of 50–800 K. Based on the thermal population, at a temperature of 100 K, the computed IR Boltzmann spectrum agrees with the experimental IR spectrum. The chemical bonding analysis on the lowest energy structure indicates that the cluster bond is due only to the electrons of the 6 s orbital, and the Au d orbitals do not participate in the bonding of this system. [ABSTRACT FROM AUTHOR]

Some physicochemical characteristics and elemental composition of refined sunflower oil, as well as linseed oil added to it, were investigated; linseed oil and olive oil; truffle oil and rosemary oil. Fatty acid analysis shows substantial increases in monounsaturated fatty acids with the addition of truffle and rosemary oils (up to about 78 %). With the same supplements, a significant oxidative stability over 20 hours was also observed. High concentrations of chlorophyll were found with the addition of rosemary oils and oils of linseed oil and olive oil. ß-carotene was affected three to six times in all supplements compared to the commonly refined oil. Eight elements (Mg, Cr, Mn, Zn, Ni, As, Pd and Cd) were analyzed in the studied oils, no presence of toxic elements As and Cd (< 0.02 mg kg-1), lead was up to 0.04 mg kg-1. The remaining elements vary in different concentrations depending on the additive oils used. The fluorescence spectra of the tested samples were obtained for excitation wavelengths of 380 nm, and the fluorescence maxima allowed to determine the relationship between the optical and chemical properties of the samples. In addition, infrared spectroscopic experiments (ATR and transmittance) were used to investigate the fatty acid profile of the analyzed oil samples. [ABSTRACT FROM AUTHOR]

The reaction of ZrCl4 or HfCl4 with excess 2-methylpropanoic acid when boiling under reflux has been studied. The formation of polynuclear Zr and Hf complexes of the composition M2O(i-C3H7CO2)6 during prolonged reflux of the reaction mixtures was found. The complexes are very sensitive to hydrolysis, forming hexanuclear [M6(O)4(OH)4(i-C3H7CO2)12]. The reactions have a general character for aliphatic acids and can be used as an alternative to the known methods for the synthesis of polynuclear carboxylate clusters of Group 4 metals. The crystal and molecular structures of previously undescribed {[Hf6(μ3-O)4(μ3-OH)4(i-C3H7CO2)12(H2O)]·3i-C3H7COOH} have been determined. The molecular structure is a completely asymmetric hexanuclear cluster containing six Hf(IV) atoms united by a 4:4 μ3-O/OH system of bridges, and stabilized by twelve 2-methylpropanoate ligands, eight of which are bidentate bridging, three are chelating, and one is monodentate. The crystal structure of the complex includes three independent solvating 2-methylpropanoic acid molecules. The obtained IR spectroscopy data make it possible to determine the type of complexes in the reaction mixture. The results of the study may be useful for improving the catalytic systems for ethylene oligomerization.

NaUO2(mia)3 (I) crystals (mia: monoiodacetate ion CH2ICOO−) were synthesized and studied by X-ray diffraction and IR spectroscopic analyses. Uranyl-containing complexes [UO2(mia)3]– in the structure correspond to the crystal chemical formula A(B01)3, where A = UO22+, B01 = mia. Using coordination sequences, we analyzed the features of the 3D framework, which is realized in the structure of crystals of I and contains 8 crystallographically nonequivalent U or Na atoms. A semiempirical calculation and comparison of the calculated and experimental vibration frequencies in the IR spectrum of I were performed. [ABSTRACT FROM AUTHOR]

The reaction of ZrCl4 or HfCl4 with excess 2-methylpropanoic acid when boiling under reflux has been studied. The formation of polynuclear Zr and Hf complexes of the composition M2O(i-C3H7CO2)6 during prolonged reflux of the reaction mixtures was found. The complexes are very sensitive to hydrolysis, forming hexanuclear [M6(O)4(OH)4(i-C3H7CO2)12]. The reactions have a general character for aliphatic acids and can be used as an alternative to the known methods for the synthesis of polynuclear carboxylate clusters of Group 4 metals. The crystal and molecular structures of previously undescribed {[Hf6(μ3-O)4(μ3-OH)4(i-C3H7CO2)12(H2O)]·3i-C3H7COOH} have been determined. The molecular structure is a completely asymmetric hexanuclear cluster containing six Hf(IV) atoms united by a 4:4 μ3-O/OH system of bridges, and stabilized by twelve 2-methylpropanoate ligands, eight of which are bidentate bridging, three are chelating, and one is monodentate. The crystal structure of the complex includes three independent solvating 2-methylpropanoic acid molecules. The obtained IR spectroscopy data make it possible to determine the type of complexes in the reaction mixture. The results of the study may be useful for improving the catalytic systems for ethylene oligomerization. [ABSTRACT FROM AUTHOR]

The aim of the work is to study the effect of the 3D printing process on the microstructural and hydrophilic properties of polylactic acid (PLA) samples with various model printing patterns obtained from the black filament PLA by sequentially applying polymer layers using the FDM (fused deposition modeling) method. X-ray phase analysis revealed the partial crystallization of PLA polymer chains in the printed samples, which occurs under thermal and mechanical action on the original amorphous PLA filament during 3D printing to varying degrees, depending on the geometry of the pattern and the morphology of its surface. At the same time, IR spectroscopy data indicate the preservation of all intrastructural chemical bonds of polylactide. Measured at the original installation, the values of the wetting edge angles on the surface of the printed samples are in the range φ = 50–60°, which is significantly less than the right angle. This indicates the hydrophilic properties of the whole sample's surface. At the same time, the influence of different geometries of model drawings in printed samples was found not only on the morphology of the sample's surface according to SEM data but also on its wettability. [ABSTRACT FROM AUTHOR]

Structural, electronic, and vibrational properties of phosphates LiCdPO4, NaCdPO4, RbCdPO4, CsCdPO4 are studied by density functional theory and Hartree–Fock methods using the CRYSTAL17 code in the LCAO basis set with gradient PBE, PBEsol and hybrid PBE0, PBEsol0 functionals. It is shown that the crystal structures contain infinite zigzag chains consisting of [CdO6] octahedra and [PO4] tetrahedra inside which there are alkali metal atoms. By the Gaussian broadening of normal long-wave modes IR absorption and Raman spectra are calculated. Differences in the number of spectral bands, their polarization and intensities are related to different symmetry space groups of the crystals. [ABSTRACT FROM AUTHOR]

Blends of polylactide and polybutylene adipate terephthalate of various compositions are obtained by mixing in the melt followed by pressing. The content of PBAT in the blends is 10, 20, and 30 wt %. The effect of water on film samples at a temperature of (22 ± 2)°C is studied for 270 days. After exposure, a change in morphology is detected: turbidity of the samples and the appearance of defects. The thermophysical characteristics before and after hydrolytic degradation are determined by differential scanning calorimetry. The decrease in the cold crystallization temperature in pure PLA and in a sample with a low content of PBAT (10%), as well as the disappearance of the cold crystallization peak at a content of 20 and 30 wt % of PBAT, is shown. The degree of crystallinity of PLA after exposure to water tends to increase from 0 to 16%. Changes in the chemical structure of the mixed samples are monitored by IR spectroscopy. [ABSTRACT FROM AUTHOR]

Monomers of N-hydroxypyridine-2(1H)-thione were isolated in low-temperature matrices of solid normal hydrogen (n-H2). The matrix-isolated compound was irradiated with UV-B (λ = 305 nm) or UV-A (λ > 360 nm) light. Upon such irradiation, the initial form of N-hydroxypyridine-2(1H)-thione was completely consumed and converted into photoproducts. 2-Mercaptopyridine and water were identified as the main products of these photochemical transformations. Identification of photoproduced 2-mercaptopyridine is unquestionable. It is based on the identity of two sets of IR bands: (i) the bands observed in the IR spectrum recorded (in a separate experiment) for monomers of 2-mercaptopyridine trapped in an n-H2 matrix and (ii) a set of IR bands observed in the spectrum recorded after UV irradiation of N-hydroxypyridine-2(1H)-thione. It should be emphasized that the UV-induced processes, occurring for N-hydroxypyridine-2(1H)-thione isolated in an n-H2 matrix, lead to products that are significantly different from those generated from the compound trapped in solid Ar or in solid N2.

Changes in vibrational spectra are among the most important manifestations of the interaction between transition metal dichalcogenides and nucleic acid bases (NAB). Infrared and Raman spectra were calculated using the DFT/M06-2X method for the most stable stacked and covalently bonded complexes of pyrimidine bases with MoS2. Obtained spectra were analyzed to determine the spectral markers of the interactions between the pyrimidine bases and MoS2. We found that interaction with MoS2 leads to significant changes in both frequencies and intensities of NAB vibrations. The correlation between the changes and interaction energies of the NAB molecules with MoS2 was demonstrated. In general, changes in the vibrational frequencies in complexes with covalent bonds are significantly greater than ones in stacked ones. For the bonded complexes, the most significant changes are observed for those fragments of the NAB molecules that are directly involved in the formation of the covalent bonds. Calculations predict the decrease of the IR intensity and Raman activities of the NAB molecules in the spectra of stacked complexes and their increase in the spectra of covalently bonded complexes. [ABSTRACT FROM AUTHOR]

The possibility of modifying compositions based on epoxy-urethane oligomer and epoxy resin intended to protect steel pipelines from aggressive environments is studied. Using metal stearates and other friction modifiers, it is possible to reduce the volumetric wear of the coating material by almost half. The features of the effect of these fillers on the phase structure and physical and mechanical properties of the materials under consideration, as well as the degree of stability of the main characteristics of the developed coatings in a number of chemically aggressive environments is established. [ABSTRACT FROM AUTHOR]

In this work, optical properties of silicon dioxide thin film were studied. Optical parameters were measured using an IRTracer-100 spectrophotometer (Shimadze). Thin films of silicon oxide were formed on a substrate heated in high vacuum using a magnetron shaker, their absorption, transmission and reflection spectra were obtained, absorption coefficient, refractive index, bonding and vibrations of SiO2 atoms were measured. [ABSTRACT FROM AUTHOR]

A specialized low-temperature measuring cell with a cryogenic capillary system for infrared spectral analysis of ethanol developed by the authors is presented. The use of the created low-temperature cell is possible for further studies of the low-temperature properties of both pure ethanol and mixtures with its contents, which is currently an urgent task, and the data obtained with its help can be used for ice research. Two methods of ethanol research at low temperature are presented in comparison. In the first method proposed by the authors, a specially developed low-temperature measuring cell based on a diffuse reflection prefix of the Fourier spectrometer FSM 2203 with a cryogenic capillary system is used. This system allows you to achieve the required low-temperature regime at normal atmospheric pressure. The results of the experiment are compared with the traditional method of gas-phase condensation of the test sample under low temperature conditions at the pressure P = 1.0·10–5 Torr. Infrared spectra of low molecular weight amorphous and crystalline ethanol were obtained at a temperature of 150 K at normal atmospheric pressure and in vacuum. Comparison of experimental results confirmed the operability of the new installation. In the experiments, peaks were observed in the absorption bands from 2850 to 3000 cm–1 and from 2950 to 3100 cm–1, corresponding to the valence CH vibrations of ethanol as well as in the absorption bands from 3150 to 3400 cm–1 and from 3300 to 3500 cm–1, which corresponds to the valence vibrations of OH. The results of the study showed the prospects of the proposed method and can be useful by researchers in the field of low-temperature spectroscopy at normal pressure.

The aim of the work is to study the influence of the 3-D printing process with the Hercules Original printer by sequentially applying polymer layers using the FDM (Fused Deposition Modeling) method on the microstructural and hydrophilic properties of polyethylene terephthalate glycol (PETG) samples with different printing patterns. X-ray phase analysis revealed the presence of a greater ordering of amorphous PETG polymer chains in printed samples, which occurs during thermal and mechanical impact on the initial filamentous sample during 3D printing. This manifests itself in the increase of relative intensity for the main diffraction peak of the amorphous PETG polymer by an order of magnitude for all of the samples with five different print patterns. At the same time, IR spectroscopy data revealed the preservation of all intrastructural chemical bonds of the polymer both in the original thread and in printed samples. Close contact angles of about q≈50° for all printed samples, which is much smaller than the right angle q=90°, show that the surfaces of all five printed PETG samples with different patterns are hydrophilic

A hybrid quartic force field approach produces the same accuracies as non‐hybrid methods but for less than one quarter of the computational time. This method utilizes explicitly correlated coupled cluster theory at the singles and doubles level inclusive of perturbative triples (CCSD(T)‐F12b) in conjunction with a triple‐ζ basis set, core electron correlation, and scalar relativity for the harmonic terms and CCSD(T)‐F12b with a valence double‐ζ basis set for the cubic and quartic terms. There is no sacrifice in the prediction of fundamental anharmonic vibrational frequencies or vibrationally‐averaged rotational constants as compared to experiment, but the time saved is notable. Other hybrid methods are examined involving different sizes of basis sets and composite terms included or excluded. Not one is more accurate; only one is faster. F12∗ (also called F12c) is tested as well, but it has an increase in computational time for no increase in accuracy. As such, this work reports a hybrid and composite approach (F12‐TcCR+DZ) in the computation of rovibrational spectral data which can be applied to the observation of novel molecules in the gas phase in the laboratory and potentially even in astrophysical environments. [ABSTRACT FROM AUTHOR]

Cyclodextrins (CDs) constitute a class of cyclic oligosaccharides that are well recognized and largely applied in the drug delivery field, thanks to their biocompatibility, low cost, and the possibility to be derivatized in order to tune and optimize the complexation/release of the specific drug. The conformational flexibility of these systems is one of their key properties and requires a cost-effective methodology to be studied by combining the accuracy of results with the possibility of exploring a large set of conformations. In the present paper, we have explored the conformational potential energy surface of the monomers and dimers of α-, β-, and γ-cyclodextrins (i.e., 6, 7, and 8 monomeric units, respectively) by means of fast but accurate semiempirical methods, which are then refined by state-of-the-art DFT functionals. Moreover, the crystal structure is considered for a more suitable comparison with the IR spectrum experimentally recorded. Calculations are carried out in the gas phase and in water environments, applying both implicit and explicit treatments. We show that the conformation of the studied molecules changes from the gas phase to the water, even if treated implicitly, thus modifying their complexation capability. [ABSTRACT FROM AUTHOR]

The data of X-ray diffraction and IR spectroscopy of synthetic aluminosilicates of the kaolinite subgroup with different degrees of crystallinity are analyzed. The samples are obtained under hydrothermal conditions in alkaline and neutral media with different durations of synthesis. It is shown that as the synthesis time increases a gradual transition of the amorphous phase to the crystalline phase is observed, which is reflected in the IR spectra by the shift of the bands related to the oscillations of the groups in the octahedral and tetrahedral grids. The first band of stretching vibrations of hydroxyl groups at 3628 cm–1 appears after three days of hydrothermal treatment in a neutral medium, and under alkaline conditions with the same duration of treatment, two more bands are observed at 3687 and 3668 cm–1. The detected changes in the IR spectra correspond to the appearance of the characteristic X-ray reflections of halloysite according to the XRD data. Thus, IR spectroscopy can be considered as a method for a qualitative assessment of the degree of crystallinity. [ABSTRACT FROM AUTHOR]

The amount of acid retained in the SiO2–TiO2*organic acid composites obtained by the sol-gel method depends on the structure of the acid and its concentration, but largely on the oxide ratio. At an acid concentration in the composite of less than 25%, its molecules undergo chemisorption accompanied by a change in the principal absorption bands in the IR spectra; as the acid concentration increases, physical sorption becomes prevalent. With acid-imprinted composites, an increase in the ee values in the asymmetric Biginelli reaction is observed, and the best results were obtained for aromatic acid-imprinted composites with an oxide ratio of 1 : 1. [ABSTRACT FROM AUTHOR]

In this study, a novel hybrid organic-inorganic compound, 4-(ammoniummethyl)pyridinium tetracholoraobaltate(II) monohydrate, with non-centrosymmetric properties have been synthesized and characterized by several techniques of powder and single-crystal X-ray diffraction, infrared IR and UV–Visible spectroscopies, and calorimetric (DSC) and the thermogravimetric (TG) analysis. The crystallization of this hybrid compound was found in a monoclinic system with a P21 space group. Additionally, the optimized structures of cation, anion and compound by using hybrid B3LYP method with 6-311++G(d,p) and 6-31+G(d) basis sets shown good correlations with the experimental data and the complete vibrational assignments and force constants are reported for three species. The surface morphology and the micrographs were checked by the scanning electron microscopy (SEM). The UV–Visible absorption spectrum has been used to study the optical properties and the energy gap of our compound. Hirshfeld surface (HS) analysis associated matched up with 2D fingerprint plots were used to confirm the existence of intermolecular and non-covalent interactions in the compound and confirmed by several topological approaches: Quantum Theory of Atom-in-Molecules (QTAIM), reduced density gradient (RDG) and molecular electrostatic potential surface (MEP). The frontier molecular orbitals HOMO and LUMO have been investigated for chemical reactivity and kinetic stability. [ABSTRACT FROM AUTHOR]

Composite resins impregnated by different organophosphorus extractants were developed and used for the extraction chromatography recovery of rare earth elements from nitrate-based leachate of NdFeB permanent magnets. The influence of different factors on recovery of Nd(III) and Fe(III), as the most difficult to separate elements, by developed resins was studied. The influence of extractant structure, the composition of feed solutions, and concentrations of HNO3 and NH4NO3 on the recovery of Fe(III) and Nd(III) by prepared resins were considered. The best recovery of Nd(III) was shown by resin impregnated with N,N-dioctyl (diphenylphosphoryl) acetamide. For this material, sorption characteristics (values of the distribution coefficient, capacity, and the Nd(III)/Fe(III) separation factor) were obtained, and the reproducibility of the loading–stripping process was evaluated. This resin and its precursors were characterized by IR spectroscopy. It was found that the developed resin is more efficient for Nd(III) recovery than resin impregnated with TODGA. An effective approach to the Nd(III)/Fe(III) separation with developed resin in nitrate solution was proposed. This approach was used for recovery of Pr(III), Nd(III), and Dy(III) from the nitrate-based leachate of NdFeB magnets by the developed resin. The final product contained 99.6% of rare earths. [ABSTRACT FROM AUTHOR]

We investigated the performance of the computationally effective GFN2-xTB approach in molecular dynamics (MD) simulations of liquid electrolytes for lithium/sodium batteries. The studied systems were LiTFSI and NaTFSI solutions in ethylene carbonate or fluoroethylene carbonate and the neat solvents. We focused on the structure of the electrolytes and on the manifestations of ion–solvent interactions in the vibrational spectra. The IR spectra were calculated from MD trajectories as Fourier transforms of the dipole moment. The results were compared to the data obtained from ab initio MD. The spectral shifts of the carbonyl stretching mode calculated from the GFN2-xTB simulations were in satisfactory agreement with the ab initio MD data and the experimental results for similar systems. The performance in the region of molecular ring vibrations was significantly worse. We also found some differences in structural data, suggesting that the GFN2-xTB overestimates interactions of Me ions with TFSI anions and Na+ binding to solvent molecules. We conclude that the GFN2-xTB method is an alternative worth considering for MD simulations of liquids, but it requires testing of its applicability for new systems. [ABSTRACT FROM AUTHOR]

A series of 6-Hetero aryl-5-hexene-2, 4-diones (1a-b) and their Cu (II) complexes (1c-d) of ML2 stoichiometry were synthesized by condensation of heterocyclic aldehydes with acetyl acetone through boric anhydride mediated mechanism. Boric anhydride act by blocking the medial methylene group of acetyl acetone and provides a new pathway other than facile Knoevenagel condensation. All the final structures were assigned on the basis of IR, ¹H NMR and mass spectra analysis. The test compounds were studied for short term in vitro cytotoxicity using Dalton's Lymphoma Ascites cell lines (DLA). The compound code 1C and 1D found to show significant cytotoxic action. [ABSTRACT FROM AUTHOR]

A series of rhenium compounds with the octahedral cluster core {Re6S8-xBrx} (x = 0–4): with molecular and polymeric structure were obtained. In these compounds the cluster core composition varies monotonically, the geometry of the cluster and the rhenium coordination polyhedron are retained unchanged, while the symmetry of the cluster changes. The vibrational spectra (Raman and IR) were recorded and analyzed for compounds with all possible S/Br ratios in the cluster core. The group vibrations of clusters were attributed with the use of DFT calculations of vibrational spectra. It is shown that the set of main characteristic bands is retained in both ionic and polymeric compounds regardless of the composition and the symmetry of the cluster core while the observed vibration frequencies of these bands depend on the S/Br ratio in the cluster core. In particular, the group Re–S stretching vibrations (A1g(S8) and T2g(S8) modes) shifted to higher frequencies with the increase in the number of Br atoms in the cluster. The difference in the connectivity in polymeric compounds leads to an increase in the number of bands in the spectra and to the disappearance of the A1g(Br) modes. [ABSTRACT FROM AUTHOR]

This work is devoted to the synthesis of polyurethane elastomers based on oligoetherurethane diepoxides, as well as to the study of the correlation of their physical and mechanical properties with the phase and supramolecular structure. When synthesizing such elastomers via the stage of epoxyurethane oligomers, the conditions for efficient control of the phase structure are provided by using various diisocyanates and hardeners. The approaches used, and the results obtained are of practical importance, especially in the field of materials science of frost-resistant polymers. [ABSTRACT FROM AUTHOR]

The effect of primary amino acid sequence in recombinant spidroins on their spatial organization is crucial for the fabrication of artificial fibers and fibrous materials. This study focuses on the rheological properties of aqueous and alcoholic solutions of recombinant analogs of natural spidroins (rS1/9 and rS2/12), as well as the structure of their films and nanofibrous materials. Non-Newtonian flow behavior of aqueous solutions of these proteins was observed at certain concentrations in contrast to their solutions in hexafluoroisopropanol. The secondary structure of recombinant spidroins was addressed by IR spectroscopy, whereas their self-organization in various solvents was studied by AFM and cryo-TEM. The influence of the solvent on the structure and properties of the films and nanofibrous materials produced by electrospinning has been established. [ABSTRACT FROM AUTHOR]

IR spectra of entrance and exit channels of methane and radical oxygen reaction are predicted in the ground state energy. Ab initio calculations at perturbation theory (MP2) with Dunning correction-consistent basis set (aug-cc-pVDZ) have been used. The calculations predicted structures, vibrational frequencies and potential energy surface. Three van der Waals minima from three adiabatic potential energy surfaces have been predicted in entrance and exit channels. Vibration frequency of 3209 cm-1 and 3212 cm-1 of C-H stretching in entrance structures are predicted while O-H vibrational frequency is predicted to be at 3673 cm-1 in the other channel. The lowest energy structure in entrance channel has - 0.18 kJ/ mol minimum energy. [ABSTRACT FROM AUTHOR]

It is established that the fractions of the characteristic intensities of OH group vibrations attributed to intramolecular H-bonds of O3–H···O5 and O2–H···O6 types and intermolecular H-bonds of O6–H···O3 type of air-dried samples are 0.12, 0.1, and 0.2 for UAM-100 membrane and 0.12, 0.1, and 0.19 for UAM-50 membrane. It is shown that the characteristic intensity of the ν(OH) absorption band grows from 9.55 to 10.3 in a working sample of the UAM-100 membrane and a drop in the symmetry index to 0.75 was explained by the oxidation of aldehyde groups at C1 pyranose ring to the carboxyl (–COOH). It is proved that the fractions of intermolecular bonds of О6–Н···О3 and intramolecular H-bonds of O3–H···O5 and O2–H···O6 are 0.15, 0.09, and 0.13 that indicates not only the structural rearrangement of the hydrogen bond system but also possibly the formation of weak hydrogen bonds between hydroxyl groups of pyranose rings and molecules of the sedimentary layer. [ABSTRACT FROM AUTHOR]

Infrared spectra (IR) in the O-H stretching region were recorded for natural tourmalines from the magmatic and magmatic-hydrothermal systems of Moslavačka Gora (Croatia). Samples of disseminated tourmaline (schorl) representing magmatic products were collected from leucogranite. Nodular tourmaline (intermediate members of the schorl-dravite series) from twomica granite represents a magmatic-hydrothermal mineral related to the final stage of granite crystallization. IR spectra of the typically disseminated tourmaline show four sharp O-H stretching bands: 3643, 3633, 3550, and 3484 cm–1, while typical nodular tourmaline shows spectra with asymmetric and relatively broad O-H stretching bands on 3635 and 3554 cm–1 with shoulders at the higher and lower wavenumber side. The broadening in the lower wavenumber region of nodular tourmaline compared to disseminated tourmaline indicates a higher water content in the nodular type. At the same time, the observed shifts between the corresponding bands can be explained by the shortening of the O-H1 and O-H3 distances, which can be attributed to different genetic and/or evolutionary processes. According to the models applicable to the Moslavačka Gora, disseminated tourmaline from the leucogranite can be considered a typical magmatic (pegmatitic) product and a standard accessory phase of the leucogranite. The origin of nodular tourmaline, which was the last mineral to crystallize in the evolved Late Cretaceous granitic system of Moslavačka Gora, is attributed to the interaction of a fluid phase from the residual granitic melt with the fluid originating from the wall-rock in the low-pressure crustal setting, which was accompanied by relatively rapid cooling. This interaction resulted in an increased dravite content of the nodular tourmaline and is reflected in the observed IR spectral features.

Reaction of Ni(NCS)2 with 3-methylpyridine in water leads to the formation of crystals of the title compound, [Ni(NCS)2(C6H7N)4]. All of them are of poor quality and non-merohedrally twinned but a refinement using data in HKLF-5 format leads to a reasonable structure model and reliability factors. The crystal structure of the title compound consists of discrete complexes, in which the nickel cations are sixfold coordinated by two terminal N-bonded thiocyanate anions and four 3-methylpyridine ligands within slightly distorted octahedra. One of the 3-methylpyridine ligands is disordered and was refined using a split model. The discrete complexes are arranged into layers. X-ray powder diffraction proves that pure samples have been obtained, and in the IR spectrum, the CN stretching vibration is observed at 2072 cm−1, in agreement with the presence of only terminally coordinated thiocyanate anions. Comparing the calculated powder pattern with those of the residues obtained by solvent removal from several solvates already reported in the literature proves that, in each case, this crystalline phase is formed. Assessing the crystal structures of the solvates in comparison with that of the ansolvate reveals some similarities.

Decorticated ramie fiber (Variety R-1449) was degummed using different systems, namely, individual alkali, mix alkali, enzyme, mix enzyme, and peracetic acid to the optimal level of residual gum content. Further, the optimal degummed samples of various systems have been characterized through IR analysis, DSC thermographs, scanning electron microscopes, tensile properties etc. The chemical constituents of degummed samples of various systems at optimal level along with untreated decorticated ramie fiber have been determined and compared. Study suggests the use of new eco-friendly peracetic acid is best degumming method for decorticated ramie followed by synergetic effect of alkalis.

This work aims to measure the role of zinc as an essential micronutrient for algal growth and the effect of using different concentrations of this heavy metal on growth and essential metabolites of Dunaliella tertiolecta. The EC50 obtained was around 15 mg/l. The results obtained proved that lower concentrations of the element increased growth and the content of the measured metabolites (photosynthesis pigments, fatty acids, and protein) but with different responses. The increase in content of these metabolic products with low concentrations of the tested heavy metal may be attributed to inhibition to these metabolites' export out of cells by heavy metals. The obtained infrared peaks of the major cell constituents of the treated cells revealed the emergence of new peaks and the removal of others, indicating changes in cell constituents due to changing zinc concentrations. [ABSTRACT FROM AUTHOR]

The limitations of visual inspection and interpretation of Infrared (IR) spectra from either laboratories or astronomical observations to cover a wide range of molecular types motivated us to apply a mathematical approach via a matching method called spectra similarity to identify the carriers of UIE bands in a sample of astronomical objects. The reliability of such a purely mathematical approach in targeting the correct molecular structures was tested by applying two sets of experimental IR spectra against the large pool of theoretical IR databases composed of 300,000 organic, organometallic, and, inorganic molecules. Spectra similarity calculations show that the second-row elements C, H, N, and O dominate the elemental composition of HD 44179, M 82, NGC 7023, NGC 7027, and Orion bar. In addition, the signatures of third-row elements S and Si were also identified. Our preliminary results confirm the signatures of complex organic molecules in interstellar environments. These are composed of benzene rings, five-membered rings, and side chain aliphatic groups in the cited astronomical sources. In some cases, the similarity approach suggested the fully aliphatic structures as the origin of UIE carriers. [ABSTRACT FROM AUTHOR]

Dibromomethane decomposes into ozone destroying bromine free radicals under sunlight radiation, which seriously endangers the natural environment and human health. It is necessary to study the degradation of Dibromomethane. The physical properties of Dibromomethane including total energy, bond length, electric dipole moment, energy level, energy gap, infrared spectrum under different external electric fields（0 ～ 0.025 a. u.） are studied by using density functional theory at the B3 LYP/6-311 G（d, p） basis set level. The effect of external electric field on molecular excited states is studied by using time-dependent density functional theory at the same basis set level. The potential energy curves of two C-Br bonds under external electric field are scanned separately, and it is found that when the external electric field intensities are 0.025 a.u. and 0.04 a.u., both the C-Br bonds are broken in turn and gradually dissociated. The results provide an important reference for the electric field degradation of Dibromomethane and hence for environmental protection. [ABSTRACT FROM AUTHOR]

Nanocomposites based on aqueous polyurethane latex and graphene oxide have been synthesized and characterized. The structure and composition of the nanocomposites were studied using elemental analysis, optical microscopy, IR spectroscopy, DSC, and thermogravimetry. The nanocomposites showed higher thermal stability and increased mechanical strength compared to those of the original polymer. It has been established that the Young's modulus of latex films after the introduction of 2 wt % graphene oxide increased by a factor of almost 6. In this case, the fracture stress decreased only slightly by 10–15%. The influence of the particle size of graphene oxide on the mechanical properties of the composites was found, namely: composites with larger particles of graphene oxide had a higher Young's modulus, and their relative elongation at break decreased. [ABSTRACT FROM AUTHOR]

Degradation of polylactide (PLA)— polybutylene adipate terephthalate (PBAT) mixtures under the action of UV radiation (λ= 254 and 365 nm) was investigated. It is established that polybutylene adipate terephthalate slows down the PLA degradation without changing its mechanism. After photodegradation, the PLA glass transition temperature shifts to higher values, while its melting point decreases by 3.6–5.0 °C (λ = 254 nm). The crystallinity degree of PLA is reduced by no more than 5% after exposure to UV radiation at both wavelengths. After UV radiation at both wavelengths, intensities of characteristic IR bands of both components change substantially. The mechanical properties of mixtures of all studied compositions deteriorate after irradiation with light with λ = 254 nm for 50 h, and more significant deterioration is observed for samples with a predominance of PLA. [ABSTRACT FROM AUTHOR]

Based on chitosan and the newly synthesized fluoroquinoline compound 5-dimethylaminomethyl-7-(2,2,2-trifluoro-1-hydroxy-1-trifluoromethyl-ethyl)quinolin-8-ol, a new composite has been obtained. A comparative analysis of its antimicrobial activity with other chitosan composites containing antibiotics, such as tetracycline, vancomycin, and ciprofloxacin, used in modern medicine has been carried out. The high efficiency of 5-dimethylaminomethyl-7-(2,2,2-trifluoro-1-hydroxy-1-trifluoromethyl-ethyl)quinolin-8-ol in inhibiting the growth of Staphylococcus aureus has been demonstrated. The possibility of obtaining chitosan nanoparticles doped with the new composite has been established for their application as an "intelligent" coating for heart valve bioprostheses, including those obtained with the use of carbonic acid. An approach has been found that makes it possible to form a hybrid biomatrix based on glutaraldehyde-stabilized xenogenic pericardium with a covalently attached polymeric "screen" made from chitosan nanoparticles as nano(micro)containers with antimicrobial agents. Stable chitosan nanoparticles doped with the new composite have been synthesized by ion gelation, which is confirmed by a high zeta potential (|ζ| ~ 45 mV). Using high-resolution microscopy, an ultrathin coating of spherical polymer nanoparticles (~70 nm) with high adhesion to collagen fibrils has been identified. The possibility of implementing a "smart" antimicrobial response of this biocoating induced by a change in the pH of the medium due to variation in conformation (unwinding) of polymeric chitosan nanoparticles and the release of cidal agents in the case of pathogen growth on its surface is shown. [ABSTRACT FROM AUTHOR]

For many solids operating under irradiation conditions, the study of their behavior at the neutron irradiation is of importance. Herein, the influence of neutron irradiation conditions on the infrared (IR) absorption spectra of LiF crystals containing different amounts of hydroxyl and metallic impurities is considered. The investigations are carried out for discovering new peculiarities under the extreme irradiation conditions of LiF--being a very important material for practical applications. In the crystals with OH- impurity after the action of neutron irradiation, quite clear bands are appeared in the region of 1900-2200 cm-1. The delivered doses vary from 1014 to 3 x 1017nnvt. LiF crystals are investigated by differing both in qualitative and quantitative contents of OH- ions. With the increase in irradiation dose, the maximum IR absorption of all investigated groups of crystals shifts to the region of low energies. The appearance of a new band in the IR spectrum and its shift as a function of dose is associated with the radiolysis of OH- molecule. [ABSTRACT FROM AUTHOR]