Characteristic IR Absorption Research Articles

Dinuclear gold(I) pseudohalogen complexes bridged by a ferrocenyl bisphosphine ligand: synthesis, structure, and reactivity toward isothiocyanate

Ferrocenyl bisphosphine-bridged dinuclear gold(I) complexes containing CF3COO as a pseudohalogen ligand were synthesized from the corresponding halides using CF3COOAg. The sequential treatment of gold(I) trifluoroacetates with aqueous NaN3 afforded the corresponding ferrocenyl bisphosphine-bridged dinuclear gold(I) azides. Isolated gold(I) pseudohalogen complexes were characterized through IR, NMR and X-ray crystallography. The characteristic IR absorption bands of ν(CO), ν(CF), and ν(N3) were at 1690, 1190, and 2040 cm−1, respectively, corresponding to the gold(I) trifluoroacetates and azides, verifying gold(I) pseudohalogen formation. The molecular structure of [Au2(η1-CF3CO2)2(µ-dippf)] (dippf = 1,1’-bis(diisopropylphosphino)ferrocene) through X-ray diffraction showed intermolecular Au⋅⋅⋅Au interactions with close contacts between molecules. The crystallographic images illustrate the polymeric chain of bis(phosphino)ferrocenyl gold(I) formed via intermolecular Au⋅⋅⋅Au bonds and layered packing arrays. In contrast, the molecular structures of [Au2(η1-CF3CO2)2(µ-dtbpf)] (dtbpf = 1,1’-bis(di-tert-butylphosphino)ferrocene) and Au2(N3)2(µ-dippf) showed intramolecular Au⋅⋅⋅Au aurophilic interactions, but the structures of [Au2(η1-CF3CO2)2(µ-dcpf)] (dcpf = 1,1′-bis(dicyclohexylphosphino)ferrocene) and Au2(N3)2(µ-dppf) revealed no direct interaction within the dinuclear gold(I) system. Gold(I) azides gradually react with isothiocyanates (allyl, (S)-(+)-1-phenylethyl, and benzyl) to afford the corresponding gold(I) tetrazole-thiolates [Au2X2(µ-dippf)] or [Au2X2(µ-dtbpf)] (X = S[CN4(Y)]) (Y = allyl, (S)-(+)-1-phenylethyl, and benzyl) via dipolar cycloaddition of the isothiocyanates into the Au-N3 bond.

Nanofibrous Polythiophene-SnO2 composite Films: A novel approach for Low-Temperature NO2 sensing

The SnO2-incorporated interconnected nanofibrous Polythiophene (Sn-INPTh) composite thin film was successfully synthesized using a simple chemical bath deposition method. The film was systematically studied for its NO2 gas sensing application. The chemical bonding, surface morphology, and optical properties were investigated using FT-IR, FE-SEM, EDAX, AFM, and UV–Visible spectroscopy. The effects of SnO2 incorporation on the physicochemical and NO2 sensing properties of the Sn-INPTh thin films were examined. The surface morphological study revealed the nanofibrous Polythiophene morphology, which remained intact after the incorporation of SnO2. The investigation of the chemical bonding nature clearly indicated the characteristic IR absorption bands of Polythiophene, along with the emergence of additional bands corresponding to the SnO2 nanoparticles. The Sn-INPTh thin film gas sensor demonstrated the highest selectivity for NO2 among the various oxidizing and reducing gases (NH3, SO2, H2S, NO2, CO, LPG) tested at a low working temperature of 40 ± 2˚C. All of the Sn-INPTh composite thin films exhibited enhanced NO2 sensing performance, with the highest sensitivity of 81.5% and the shortest response time of 22.66 s observed for the optimized Sn-INPTh composite thin films.

Dual-frequency comb spectroscopy studies of ionic strength effects in time-resolved ATR-SEIRAS

• DFCS allows sub-millisecond resolution of temporal processes occurring at an electrode surface. • IR transient time constants are directly proportional to the RC cell constant. • Absorption spectra line shape depends on coverage. Attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies of the potential induced desorption/adsorption of a model organic monolayer is described using a paradigm-challenging dual frequency comb spectrometer. Experimentally measured ATR-SEIRAS transients reveal that both the rates of adsorption and desorption of 4-dimethylaminopyridine (DMAP) are dependent on the ionic strength of the supporting electrolyte. The characteristic time scales of monolayer desorption are found to be directly proportional to the spectroelectrochemical cell time constant indicating that the rate of film dissolution is much faster than the RC charging of the interface. The slow response of the interfacial charging process relative to the kinetics of the film re-organization/desorption processes means that the transient is parametrically linked to the potential dependent DMAP adsorption isotherm. The transients also reveal that the line shape of the molecular IR absorption feature exhibits a temporal dependence. A Lorentzian band is seen at early stages of the desorption transient but increasingly exhibit an anomalous bimodal line-shape at longer times. The development of the anomalous line shape is more pronounced at equivalent times in higher ionic strength electrolytes. Such an effect has been modelled using effective medium theory and is explained by the fact that the fraction of organic layer in the SEIRAS active film influences the observed apparent absorption features. The observation of a coverage dependence on SEIRAS line shapes adds new complexity to previous reports that linked anomalous absorption features exclusively to the metal film morphology and metal volume fraction.

Direct Observation of the Dynamics of Ylide Solvation by Hydrogen-bond Donors Using Time-Resolved Infrared Spectroscopy.

The photoexcitation of α-diazocarbonyl compounds produces singlet carbene intermediates that react with nucleophilic solvent molecules to form ylides. The zwitterionic nature of these newly formed ylides induces rapid changes in their interactions with the surrounding solvent. Here, ultrafast time-resolved infrared absorption spectroscopy is used to study the ylide-forming reactions of singlet carbene intermediates from the 270 nm photoexcitation of ethyl diazoacetate in various solvents and the changes in the subsequent ylide–solvent interactions. The results provide direct spectroscopic observation of the competition between ylide formation and C–H insertion in reactions of the singlet carbene with nucleophilic solvent molecules. We further report the specific solvation dynamics of the tetrahydrofuran (THF)-derived ylide (with a characteristic IR absorption band at 1636 cm–1) by various hydrogen-bond donors and the coordination by lithium cations. Hydrogen-bonded ylide bands shift to a lower wavenumber by −19 cm–1 for interactions with ethanol, −14 cm–1 for chloroform, −10 cm–1 for dichloromethane, −9 cm–1 for acetonitrile or cyclohexane, and −16 cm–1 for Li+ coordination, allowing the time evolution of the ylide–solvent interactions to be tracked. The hydrogen-bonded ylide bands grow with rate coefficients that are close to the diffusional limit. We further characterize the specific interactions of ethanol with the THF-derived ylide using quantum chemical (MP2) calculations and DFT-based atom-centered density matrix propagation trajectories, which show preferential coordination to the α-carbonyl group. This coordination alters the hybridization character of the ylidic carbon atom, with the greatest change toward sp2 character found for lithium-ion coordination.

New Way of Synthesis of Few-Layer Graphene Nanosheets by the Self Propagating High-Temperature Synthesis Method from Biopolymers.

For the first time, few-layer graphene (FLG) nanosheets were synthesized by the method of self-propagating high-temperature synthesis (SHS) from biopolymers (glucose, starch, and cellulose). We suggest that biopolymers and polysaccharides, particularly starch, could be an acceptable source of native cycles for the SHS process. The carbonization of biopolymers under the conditions of the SHS process was chosen as the basic method of synthesis. Under the conditions of the SHS process, chemical reactions proceed according to a specific mechanism of nonisothermal branched-chain processes, which are characterized by the joint action of two fundamentally different process-accelerating factors—avalanche reproduction of active intermediate particles and self-heating. The method of obtaining FLG nanosheets included the thermal destruction of hydrocarbons in a mixture with an oxidizing agent. We used biopolymers as hydrocarbons and ammonium nitrate as an oxidizing agent. Thermal destruction was carried out in SHS mode, heating the mixture in a vessel up to 150–200 °C at a heating speed of 20–30 °C/min and keeping at this temperature for 15–20 min with the discharge of excess gases into the atmosphere. A combination of spectrometric research methods, supplemented by electron microscopy data, has shown that the particles of the carbonated product powder in their morphometric and physical parameters correspond to FLG nanosheets. An X-ray diffraction analysis of the indicated FLG nanosheets was carried out, which showed the absence of formations with a graphite crystal structure in the final material. The surface morphology was also studied, and the IR absorption features of FLG nanosheets were analyzed. It is shown that the developed SHS method makes it possible to obtain FLG nanosheets with linear dimensions of tens of microns and a thickness of not more than 1–5 graphene layers (several graphene layers).

Tunable cationic distribution and structure-related magnetic and optical properties by Cr3+ substitution for Zn2+ in nanocrystalline Ni-Zn ferrites

We report a microwave-combustion synthesis and structure-related physical properties of Ni0.4Zn0.6−xCrxFe2O4 (0.0 ≤ x ≤ 0.6) nanocrystals in a study of effects by substitution among cations with different oxidation states, Cr3+ for Zn2+. High-quality nanocrystals with an average particle size of 26–33 nm and crystallite size ranged in 23–32 nm are revealed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Structural properties and cationic redistribution are studied by the XRD Rietveld analysis implying different preferences of Zn2+ and Cr3+ ions to occupy the tetrahedral and octahedral sites, respectively. Further characterization for the characteristic IR absorption bands, ionic valence states, chemical compositions and morphology have been performed by employing the Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electron dispersive X-ray spectroscopy (SEM-EDX). XPS analysis indicates partial reduction of Fe3+ to Fe2+ and further confirms the estimated cationic distribution. UV–Vis absorbance measurements indicated a gradual decrease in the optical energy gap which implies the emergence of sub-band-gap energy levels by the Cr substitution. The magnetic properties were investigated by magnetization measurements showing highly soft magnetic behavior. The values and trend of the observed magnetic moment are consistent with the theoretically calculated magnetic moment based on cationic distributions estimated from the XRD and XPS. Ni-Zn-Cr spinel nanoferrites with soft magnetic properties, magnetization up to 106 emu/g and coercivity down to 70 Oe, tunable by cationic redistribution are introduced for high-frequency power applications.

Complex Formation and Dissociation Dynamics on Amorphous Silica Surfaces.

Benzene complex formation and dissociation dynamics with silanols on the amorphous silica surfaces of nanoporous SiO2, from a benzene/carbon tetrachloride solution, were measured by the growth of off-diagonal peaks in the two-dimensional infrared (2D IR) chemical exchange spectrum of the isolated Si-OD stretch. The presence of two types of isolated silanols, termed type I and II, was revealed, with dissociation time constants of 82 and 4.0 ps, respectively. The type I silanols are associated with the main IR absorption feature in the Si-OD stretching region, while the type II silanols give rise to a broader shoulder to lower frequency. Polarization selective pump-probe (PSPP) measurements provided the vibrational lifetimes and orientational relaxation rates of the two silanols in the CCl4 (free) and benzene (complex) environments. The type II silanols constitute roughly 30% of the isolated silanol population and exhibit a substantially faster rate of vibrational relaxation, making the type I dynamics the dominant contribution to the PSPP and 2D IR signals. From the measured dissociation times, the enthalpies of formation for the two surface complexes were obtained, with the formation of the type I complex being significantly more exothermic. As the type II site is preferentially removed from the amorphous silica surface with increasing activation temperature, the results provide a reasonable explanation for the increased exothermicity of benzene adsorption on silica with increasing activation temperature in previous calorimetry experiments.

Exploration of chromophores for a VCD couplet in a spectrally transparent infrared region for biomolecules.

Interactions of two chromophores such as carbonyl groups yield a strong VCD couplet that reflects the molecular structures. The use of VCD couplets for biomacromolecular structural studies has been hampered by severe signal overlap caused by numerous functional groups that originally exist in biomacromolecules. Nitrile, isonitrile, alkyne, and azido groups show characteristic IR absorption in the 2300-2000 cm-1 region, where biomolecules do not strongly absorb. We herein examined the usefulness of these functional groups as chromophores to observe a strong VCD couplet that can be readily interpreted using theoretical calculations. Studies on a chiral binaphthyl scaffold possessing two identical chromophores showed that nitrile and isonitrile groups generate moderately-strong but complex VCD signals due to anharmonic contributions. The nature of their anharmonic VCD patterns is discussed by comparison with the VCD spectrum of a mono-chromophoric molecule and by anharmonic DFT calculations. On the other hand, through studies on diazido binaphthyl and diazido monosaccharide, we demonstrated that the azido group is more promising for structural analysis of larger molecules due to its simple, strong VCD couplet whose spectral patterns are readily predicted by harmonic DFT calculations.

Quantum Chemical Analysis of the Processes of Synthesis of Vanadium Oxide Structures on the Silica Surface

Based on a combination of quantum chemical simulation and experimental studies, the formation of vanadium oxide structures on the silica surface when sequentially treated with VOCl3 and H2O vapors was analyzed. The synthesis products were identified by IR spectroscopy. Changes in the composition and structure of the resultant surface species according to the process temperature and VOCl3 vapor pressure in the reactor were predicted by quantum chemical methods. By the example of the synthesis at 473 K in a flow-through system and study of the chemical composition and structure of the new functional groups formed on the surface, a good agreement between the experimental and calculated data was demonstrated. The results of IR spectroscopic studies of the samples synthesized were processed using quantum chemical approaches. The characteristic IR absorption band due to vibrations of the bridging bonds of vanadium atoms with the Si–O–V matrix, localized at 920–945 or 960 cm–1 depending on the structure of the surface sites, was used as the basis for identification of the surface vanadium oxide groups.

Formation and infrared spectra of monohydrogenated pyrenes 2-C16H11 and 4-C16H11 trapped in solid para-hydrogen

We recorded the IR spectra of 2-C16H11 and 4-C16H11 trapped in solid para-hydrogen (p-H2). These species were produced on the electron bombardment of p-H2 containing pyrene (C16H10) in a small proportion during matrix deposition. IR absorption features of 1-C16H11+ and 1-C16H11 in solid p-H2 were previously identified [J. Phys. Chem. Lett. 4 (2013) 1989]. Here, the irradiation of a similar matrix sample at 365 nm depleted 1-C16H11+ and 2-C16H11 and produced 1-C16H11 and 4-C16H11. In contrast, irradiation at 405 nm decreased 1-C16H11+, 2-C16H11 and 4-C16H11. The identification of the observed lines of 2-C16H11, and 4-C16H11 was supported by predictions of the vibrational wavenumbers and relative IR intensities at the B3PW91/6–311++G(2d,2p) level of theory.

Modeling the vibrational couplings of nucleobases.

Vibrational spectroscopy, in particular infrared spectroscopy, has been widely used to probe the three-dimensional structures and conformational dynamics of nucleic acids. As commonly used chromophores, the C=O and C=C stretch modes in the nucleobases exhibit distinct spectral features for different base pairing and stacking configurations. To elucidate the origin of their structural sensitivity, in this work, we develop transition charge coupling (TCC) models that allow one to efficiently calculate the interactions or couplings between the C=O and C=C chromophores based on the geometric arrangements of the nucleobases. To evaluate their performances, we apply the TCC models to DNA and RNA oligonucleotides with a variety of secondary and tertiary structures and demonstrate that the predicted couplings are in quantitative agreement with the reference values. We further elucidate how the interactions between the paired and stacked bases give rise to characteristic IR absorption peaks and show that the TCC models provide more reliable predictions of the coupling constants as compared to the transition dipole coupling scheme. The TCC models, together with our recently developed through-bond coupling constants and vibrational frequency maps, provide an effective theoretical strategy to model the vibrational Hamiltonian, and hence the vibrational spectra of nucleic acids in the base carbonyl stretch region directly from atomistic molecular simulations.

Lumefantrine Comparative Study: Single Crystal, Powder X-Ray Diffraction, Hirshfeld Surface, and Thermal Analysis

Lumefantrine is an antimalarial drug and its crystal structure is still absent in the CCDC database. The authors propose a method to obtain the single crystal of this compound and characterize it by single crystal X-ray diffraction (XRD), FTIR, and thermal analysis. Intermolecular interactions are rationalized using the Hirshfeld surface analysis. Ethanol and dichloromethane (1:1 v/v) are used to crystallize the single crystals. The compound crystallizes in the space group P21 with a = 8.7830(11) A, b = 9.4326(7) A, c = 15.8299(16) A, and β = 95.560(9)°, with two molecules in each unit cell. CIF fully simulates the PXRD results. The measured characteristic IR absorption bands belong to the pure material. The single crystal melting point is 128.6 °C (Tonset); the heat of fusion (ΔHfus) is 73.2 J/g, and the thermal degradation process starts at 219 °C, which is confirmed by two steps of the mass loss in the thermogravimetry curve. The CCDC deposit number is 1877120.

Lumefantrine comparative study: single crystal, powder X-ray diffraction, Hirshfeld surface, and thermal analysis

Lumefantrine is an antimalarial drug and its crystal structure is still absent in the CCDC database. The authors propose a method to obtain the single crystal of this compound and characterize it by single crystal X-ray diffraction (XRD), FTIR, and thermal analysis. Intermolecular interactions are rationalized using the Hirshfeld surface analysis. Ethanol and dichloromethane (1:1 v/v) are used to crystallize the single crystals. The compound crystallizes in the space group P21 with a = 8.7830(11) Å, b = 9.4326(7) Å, c = 15.8299(16) Å, and β = 95.560(9)°, with two molecules in each unit cell. CIF fully simulates the PXRD results. The measured characteristic IR absorption bands belong to the pure material. The single crystal melting point is 128.6 °C (Tonset); the heat of fusion (ΔHfus) is 73.2 J/g, and the thermal degradation process starts at 219 °C, which is confirmed by two steps of the mass loss in the thermogravimetry curve. The CCDC deposit number is 1877120.

Physico-chemical characterization of the blooming of Irganox 1076® antioxidant onto the surface of a silane-crosslinked polyethylene

This study aims at investigating the blooming of Irganox 1076® onto the surface of a silane-crosslinked polyethylene. Preliminary studies on the commercial Irganox 1076® powder enabled to identify its crystalline structure and determine its main physico-chemical properties (characteristic IR absorption bands, melting properties, etc.). Then, the behaviour of Irganox 1076® in silane-grafted polyethylene was studied. Several films containing a concentration of Irganox 1076® ranged between 0.1 wt% and 2.1 wt% were characterized with FTIR spectroscopy and DSC. A peculiar attention was paid to the phase separation within the polymer bulk and the blooming of the antioxidant onto the polymer film surface. Then, this methodology was transposed to an industrial silane-crosslinked polyethylene containing at least 1 wt% of Irganox 1076® as in-service protective antioxidant. For this latter, optical microscopy was of great help for monitoring the blooming of Irganox 1076® onto the polymer film surface. In addition, the polymorphism phenomenon of Irganox 1076® was revealed by FTIR spectroscopy and DSC after thermal treatment at 70 °C under vacuum.

Synthesis and Transport and Ionophoric Properties of α,ω-Diphosphorylated Azapodands: XII. Membrane Transport of Organic Acids by Diphosphorylated Diamines and Diazapodands

Membrane transport of mono- and polyfunctional carboxylic acids mediated by phosphorylated diamines has been studied. The structure of complexes transferred through the membrane has been discussed; in some cases, a relation has been found between the efficiency of membrane transport of organic acid substrates and the structure of membrane carriers and their complexes with the acids. A correlation between the transmembrane flow and shift of some characteristic IR absorption bands (as well as change of their intensity) of the substrate–carrier complexes in comparison to the corresponding substrates and carriers has been estimated.

Selective Chemical Enhancement via Graphene Oxide in Infrared Attenuated Total Reflection Spectroscopy

Graphene oxide (GO) as a readily prepared graphene derivative comprises negatively charged oxygenated functional groups, and a mixture of sp2 and sp3 carbon domains. In comparison with hydrophobic graphene, GO is characterized by superior water dispersibility, and may noncovalently interact with a significantly wider range of molecules. Taking advantage of GO and infrared attenuated total reflection spectroscopy (IR-ATR), an efficient strategy enabling unprecedented absorption signal amplification via chemical enhancement of various molecular species in aqueous environment was demonstrated in this study. The evolution of selectively enhanced molecular fingerprints across the entire mid-infrared spectral range was in situ monitored in real time, while retaining the characteristic molecular IR absorptions, and confirms the utility of GO as a suitable and versatile material in surface-enhanced infrared absorption spectroscopy (SEIRA) scenarios.

Hematite-catalysed scorodite formation as a novel arsenic immobilisation strategy under ambient conditions

Scorodite is an important mineral not only for arsenic (As) removal from industrial wastewaters but also in the mobility and final fate of As in waste rocks, contaminated soils and sediments, and mine tailings. Because of the mineral's high As-loading capacity and stability, numerous studies have been done to understand its formation. Unfortunately, most of these studies were limited to elevated temperatures (>70 °C), so the processes involved in scorodite formation under ambient conditions remain unclear. This study provides evidence of the catalytic effects of hematite on the formation of scorodite at 25 °C in a pyrite-rich natural geologic material. Scorodite peaks were detected in the XRD patterns of the leaching residues with and without hematite, but those in the former were stronger and more pronounced than the latter. These results suggest that the formation of scorodite was catalysed by hematite, a generalisation that is further supported by strong characteristic IR absorption bands of scorodite at 819 cm–1 (As–O bending vibration), 785 and 725 cm–1 (As–O stretching vibrations), and 2990 cm−1 (OH-vibration) as well as the distinct XPS binding energies of Fe(III)–As (709.7 eV), As(V)–O (44.8, 44.31 and 43.7 eV), O2− (530.5 eV) and coordinated water (531.3 eV) in scorodite. This phenomenon could be attributed to three possible mechanisms: (1) more rapid precipitation promoted by the “seeding” effect of hematite particles, (2) additional supply of Fe3+ from hematite dissolution under acidic conditions, and (3) enhanced oxidations of Fe2+ to Fe3+ and As(III) to As(V) on the surface of hematite.

DL-3-Aminoisobutyric acid: vibrational, NBO and AIM analysis of N–H⋯O bonded-zwitterionic dimer model

A zwitterionic dimer model constructed of inter-molecular –N–H⋯O bonding has been proposed for the solid sample of DL-3-Aminoisobutyric acid consistent with IR absorption and Raman spectral features measured in the 3500–400/50 cm−1. This zwitterionic dimer model in water as solvent has been computed at B3LYP/6–311++G(d,p) and B3LYP-D3/6–311++G(d,p) levels including Grimme's dispersion correction associated with the –N–H⋯O interaction and SCRF-SMD method. Of the several possible monomer and dimer conformational structures, the most stable dimer constructed of two zwitterion monomer units has produced vibrational modes due to the –NH3+ cation and –CO2‾ anion involved in the –N–H⋯O bonding in fair agreement with the observed broad but composite IR modal features near the 3500–2000 cm−1. Except for the frequency of asymmetric stretching mode of the –NH3+ cation, its symmetric and bending modes agree with the observed values. As for the –CO2‾ anion, the frequencies of all of its modes are in good agreement with the experiment. Natural bond orbital (NBO), molecular electrostatic potential (MEP), atoms-in-molecules (AIM) and non-covalent interaction (NCI) analyses have been used to understand electronic characterization of the –N–H⋯O bonding.

Structural and magnetic studies on Co-Zn nanoferrite synthesized via sol-gel and combustion methods

Abstract Co–Zn nanocrystalline ferrites with chemical composition Co0:5Zn0:5Fe2O4 were synthesized by sol-gel and combustion methods. The sol-gel method was carried out in two ways, i.e. based on chelating agents PVA and PEG of high and low molecular weights. In auto-combustion method, the ratio of citric acid to metal nitrate was taken as 1:1, while in sol-gel method the chelating agents were taken based on oxygen balance. All the three samples were studied by thermogravimetric and differential thermal analysis for the identification of phase formation and ferritization temperature. The synthesized samples were characterized by powder X-ray diffraction and FT-IR spectroscopy without any thermal treatment. The measured lattice constants and observed characteristic IR absorption bands of the three samples are in good agreement with the reported values showing the formation of a cubic spinel structure. The crystallite sizes of all samples were determined using high intensity peaks and W-H plot. Size-Strain Plot method was also implemented since two of the samples showed low crystallite sizes. The least crystallite size (5.5 nm) was observed for the sample CZVP while the highest (23.8 nm) was observed for the sample CZCA. Cation distribution was proposed based on calculated and observed intensity ratios of selected planes from X ray diffraction data. All structural parameters were presented using experimental lattice constant and oxygen positional parameter, and they correlated with FT-IR results. Magnetic measurements were carried out using vibrating sample magnetometer at room temperature to obtain the characteristic parameters such as saturation magnetization, coercivity, remanence, squareness ratio and Bohr magnetons. Among all, the sample synthesized via citric acid autocombustion method displayed a remarkably higher magnetization of 53 emu/g and the remaining two samples displayed low magnetization values owing to their smaller crystallite sizes.

Experimental and Simulation Research of Spatial Distribution of Carbonyl Groups in γ-Irradiated Polyethylene

The dependence of the optical density in the peak of the characteristic IR absorption band of carbonyl groups on the thickness of polyethylene films irradiated with 60Co gamma quanta is experimentally determined. A method for calculating the distribution of CO groups relative to the frontal surfaces of the samples is proposed and justified. The calculated curves are discussed in terms of the generally accepted model of diffusion-controlled oxidation of polymers under the action of high energy radiation. Based on the data obtained, the conditions for the radiation modification of polymers are found, which make it possible to minimize the destructive effects of oxidation.