Vibration Region Research Articles

Determination of the Degree of Structural Heterogeneity of Kaolinites by the Decomposition of Their IR Spectra in the OH-Stretching Vibration Region

Determination of the Degree of Structural Heterogeneity of Kaolinites by the Decomposition of Their IR Spectra in the OH-Stretching Vibration Region

Conformational Geometry Matters: The Case of the Low-Melting-Point Systems of Tetrabutylammonium Triflate with Fumaric or Maleic Acid

For this article, the interaction of tetrabutylammonium trifluoromethanesulfonate (TBATFO) with either fumaric (FUM) or maleic (MAL) acid has been investigated. These acids are isomers and can be considered the trans and cis configurations of the same molecular geometry. When TBATFO is mixed with FUM, an eutectic point is obtained for a relative composition of 90-10 (molar ratio), with a melting point of ≈90 °C. If maleic acid is mixed with TBATFO, one obtains an inhomogeneous phase with the retention of a solid portion immersed in a liquid phase, even above 90 °C. DFT calculations helped to model the interaction between the components. It is suggested herein that TBATFO interacts more strongly with FUM than with MAL, due to possible interactions in two different sites for hydrogen bonding (HB) in FUM. In MAL, one of the HB sites is instead retained in the intramolecular interactions; therefore, fewer sites are available for intermolecular interactions. Infrared spectroscopy measurements have confirmed this scenario, in which the hydrogen bonds of the acid molecules are replaced by HB between the acid and the ionic couple: for both kinds of mixtures, the vibration region of the OH bonds is strongly affected by mixing. However, in the case of FUM, the vibrations of the SO3 group of the TFO anion are displaced, while they remain in practically the same frequency position in the case of MAL.

Development of chitosan-acrylic acid based hydrogels with incorporated polyaniline and plasma treatment

Hybrid hydrogels are materials that incorporate features from multicomponent systems of polymers, significantly improving their functionality and making them ideal for biomedical applications. Both natural and synthetic polymers are utilized, further enhancing their functionality. The combination of polyaniline (PANI), chitosan (CS), and acrylic acid (AA) can result in a multifunctional hybrid hydrogel that is antibacterial, hydrophilic, and salt-sensitive. A multifunctional PANI-CS-AA with varying PANI weight ratio was synthesized in this study. In addition, improving the surface of the multifunctional hydrogels by atmospheric pressure plasma (APP) treatment was also investigated. During APP treatment, the production of reactive species (e.g., OH and N2 radicals) responsible for the functionalization of the hydrogel surface was confirmed through optical emission spectroscopy. The integration of three polymer components in the synthesized hydrogels was confirmed through the presence of their mid-FTIR spectral characteristics, particularly in the AA and CS C=O, PANI quinonoid and benzenoid units, AA COO−, and the PANI aromatic and C—H vibration regions. Moreover, the hybrid hydrogels with incorporated PANI and APP treatment improved their wettability and surface free energy (SFE) characteristics. The hybrid hydrogels with 0.25 wt. % PANI and exposed to 2 min air plasma yielded the highest hydrophilicity and total SFE with values 41.27° ± 2.15° and 135.68 ± 4.72 mJ/m2, respectively. The plasma-treated 0.25PANI-2.5CS-4AA samples exhibit improved swelling response in water (Smax = 1310 ± 100; ks = 0.005) and saline media (Smax = 1280 ± 80; ks = 0.001) due to enhanced polymeric chains and affinity toward polar liquids. Synthesized hydrogels exhibited antibacterial activity, as evidenced by the zone of inhibition test. Clearing zones measured were in the range of 16–27 mm. The study developed an APP-treated tricomponent hydrogel consisting of PANI, CS, and AA that has improved hydrophilicity, salt sensitivity, and antibacterial features.

Effect of time series on the degradation of lignin by Trametes gibbosa: Products and pathways

Lignin is the third most abundant organic resource in nature. The utilization of white-rot fungi for wood degradation effectively circumvents environmental pollution associated with chemical treatments, facilitating the benign decomposition of lignin. Trametes gibbosa is a typical white-rot fungus with rapid growth and strong wood decomposition ability. The lignin content decreased from 23.62 mg/mL to 17.05 mg/mL, which decreased by 27 % in 30 days. The activity of manganese peroxidase increased steadily by 9.44 times. The activities of laccase and lignin peroxidase had the same trend of change and reached peaks of 49.88 U/L and 10.43 U/L on the 25th day, respectively. The change in H2O2 content in vivo was opposite to its trend. For FTIR and GC–MS analysis, the fungi attacked the side chain structure of lignin phenyl propane polymer and benzene ring to crack into low molecular weight aromatic compounds. The side chains of low molecular weight aromatic compounds are oxidized, and long-chain carboxylic acids are formed. Additionally, the absorption peak in the vibration region of the benzene ring skeleton became complex, and the structure of the benzene rings changed. In the beginning, fungal growth was inhibited. Fungal autophagy was aggravated. The metal cation binding proteins of fungi were active, and the genes related to detoxification metabolism were upregulated. The newly produced compounds are related to xenobiotic metabolism. The degradation peak focused on the redox process, and the biological function was enriched in the regulation of macromolecular metabolism, lignin metabolism, and oxidoreductase activity acting on diphenols and related substances as donors. Notably, genes encoding key degradation enzymes, including lcc3, lcc4, phenol-2-monooxygenase, 3-hydroxybenzoate-6-hydroxylase, oxalate decarboxylase, and acetyl-CoA oxidase were significantly upregulated. On the 30th day, the N-glycan biosynthesis pathway was significantly enriched in glycan biosynthesis and metabolism. Weighted correlation network analysis was performed. A total of 1452 genes were clustered in the coral1 module, which were most related to lignin degradation. The genes were significantly enriched in oxidoreductase activity, peptidase activity, cell response to stimulation, signal transduction, lignin metabolism, and phenylpropane metabolism, while the rest were concentrated in glucose metabolism. In this study, the lignin degradation process and products were revealed by T. gibbosa. The molecular mechanism of lignin degradation in different stages was explored. The selection of an efficient utilization time of lignin will help to increase the degradation rate of lignin. This study provides a theoretical basis for the biofuel and biochemical production of lignin. SynopsisTrametes gibbosa degrades lignin in a pollution-free way, improving the utilization of carbon resources in an environmentally friendly spontaneous cycle. The products are the new way towards sustainable development and low-carbon technology.

Features of the defect structure of a lithium-gradient nonlinear optical single crystal LiNbO3 and their manifestation in the Raman spectra

LiNbO3 crystal with a lithium composition gradient of Li/Nb = 0.8 wt%/cm (Li0.97..1.01Nb1.03..0.99O3) were obtained. A monotonic change in the edge of the UV absorption edge is observed when scanning the surface of the gradient crystal along the growth direction. Raman spectra from different areas of studied crystal were analyzed in a wide frequency range, which includes the region of fundamental vibrations of the crystal lattice (100–900 cm−1) and the region of overtone processes (900–3000 cm−1). A compositionally homogeneous, congruent LiNbO3 crystal was used as a comparison sample. It was found that in the spectra obtained from different parts of the gradient crystal, there is a significant scatter in the frequency values of the lines corresponding to the fundamental vibrations of the crystal lattice, but at the same time, the number of lines corresponding to the fundamental vibrations of the lattice for the gradient and compositionally homogeneous LiNbO3 crystals is the same. Moreover, in the spectrum of a gradient crystal in the region of overtone processes of fundamental vibrations, significantly more lines (35 lines) are observed than in the spectrum of compositionally homogeneous crystals (15 lines). The data obtained show that the state of the defect structure of compositionally homogeneous crystals and gradient LiNbO3 crystal is significantly different. The discovered differences between the defective structure of a gradient crystal and the defective structure of a compositionally homogeneous crystal may be the reason for compensation (damping) of distortions during nonlinear optical conversion of laser radiation by a gradient crystal due to the uneven temperature distribution along the length of the crystal. In compositionally homogeneous crystals, such temperature distortions significantly limit the efficiency of nonlinear optical conversion.

Fluorescently probing anaerobic digester sludge: Measuring single-cell anabolic activity in methanogens (Methanosarcina and Methanothermobacter) with deuterium-labeled Raman analysis

This study addresses the challenge of obtaining in situ information on substrate utilization rates for individual microbial species in complex microbial communities such as anaerobic digester sludge. To overcome this hurdle, a novel approach combining doubly-labelled deuterium, fluorescence in situ hybridization (FISH) and Raman microspectroscopy was developed. The method enables quantitative determination of anabolic heavy hydrogen incorporation into FISH-targeted, exemplified by methanogenic cells from the genera Methanosarcina and Methanothermobacter.The deuterium incorporation rates ascertained by Raman red-shifting of C-Hx vibrational region to C-Dx vibrations, quantified through Raman peak area ratios, were compared for different carbon sources. Methanosarcina exhibited highest kinetic rates with acetate and propionate, while Methanothermobacter demonstrated faster incorporation under acetate and methanol supplementation.This groundbreaking study demonstrates the feasibility of obtaining quantitative metabolic rate information at a single-cell level using deuterium, FISH probes, and Raman microspectroscopy.

Pressure-induced phase changes in natural fluorapophyllite-(K) studied by Raman spectroscopy

The high-pressure Raman spectra in the low-wavenumber region (50–1200 cm−1) and the hydroxyl stretching vibration region (2600–3800 cm−1) of fluorapophyllite-(K) were collected in the interval of 0.0–50.7 GPa. Experimental results show that fluorapophyllite-(K) undergoes a crystalline-crystalline phase transition from a tetragonal structure (P4/mnc) to an orthorhombic structure (Pnnm) and then amorphization under high pressure conditions. Discontinuous changes in Raman peaks in the hydroxyl vibration region (2600–3800 cm−1) and the low-wavenumber region (50–1200 cm−1) occur at different onset pressures, suggesting that the destabilization of sub-lattices in fluorapophyllite-(K) under high pressure is not synchronous; the weak interlayer H2O structural units are more prone to destabilization at lower pressures than the rigid SiO4 tetrahedral layer units. Therefore, H2O groups in fluorapophyllite-(K) serve as sensitive local probes during the pressure-induced phase transition and amorphization.

Near-Infrared Spectroscopic Study of Secondary Minerals in the Oxidation Zones of Copper-Bearing Deposits

This study measured the infrared spectra of secondary minerals in the oxidation zones of three types of copper ores: dioptase, malachite, and azurite, and assigned the peak positions of OH stretching vibrations and the origins of OH combination vibrations. Dioptase contains three types of water molecules with different orientations within its ring channels, which exhibit six kinds of OH stretching vibrations in the 3000–3600 cm−1 range; the bond length range is 2.652 to 2.887 Å. Among them, the 3443 cm−1 band shows strong near-infrared activity and combines with Si–O vibrations or OH bending vibrations in the structure, resulting in five combination vibration peaks in the 4000–5000 cm−1 range. Malachite contains two inequivalent hydroxyls in its structure, leading to two OH stretching vibrations in the high-frequency region located at 3314 and 3402 cm−1, respectively. Azurite contains only one type of hydroxyl, and thus only one characteristic OH stretching vibration is present at 3424 cm−1. The OH stretching vibrations of malachite and azurite mainly combine with [CO3]2− vibrations or OH bending vibrations, leading to six and five combination peaks in the OH combination vibration region, respectively. By analyzing the combination of peak positions at 4341 cm−1 in the near-infrared spectrum, the merged OH bending vibration at 921 cm−1 in azurite was discovered. Spectroscopic research on secondary minerals can better provide a basis for ore exploration and geological remote sensing.

A sectional nonlinear wideband piezoelectric-magnetic coupled energy collector for collecting multi-directional vibrational energy

Abstract The classic vibration energy collector has functional restrictions, and it can only collect vibration energy in one or two dimensions. At the same time, it has issues with low output power in the low-frequency vibration region and a limited reaction frequency range. This research proposes a segmented nonlinear broadband piezoelectric–magnetic coupled energy collector capable of collecting vibration energy in different directions. The collector is equivalent to current state-of-the-art research in that it can collect vibration energy in three dimensions while also having a wide collection frequency and a high power density. The collection consists of a hemispherical support structure and four fundamental piezoelectric beam collision components. The rationality of the collision segmentation nonlinear principle is first clarified through theoretical calculation and analysis, and then the collision design is applied between the ends of different cantilever beams to broaden the captured energy frequency band, while parallel piezoelectric beams use a 45° tilt treatment to fully utilize the geometrical properties of the tilted beams for multidirectional energy collection. In addition, the collector introduces a magnetic coupling effect to create a bistable structure via magnetic contact. Comsol 5.6 software is used to model and simulate the planned 45° tilted beam structure, which clarifies the piezoelectric beam’s linear intrinsic frequency characteristics and multi-directional geometric aspects. To further verify the collector’s validity, a physical model is built and a vibration experiment apparatus is created. The experimental results demonstrate that the collector’s effective bandwidth range is up to 6.3 Hz under 1 g acceleration excitation, representing a 125.0% increase in bandwidth when compared to the cantilever beam with a linear array. At 14 Hz frequency, the collector produces a maximum total output power of 19.52 mW and a power density of up to 3211uW cm−3 when excitation is provided in the Z-direction.

Evaluating the impact of storage time and temperature on the stability of bioactive compounds and microbial quality in cherry syrup from the ‘Burlat’ cultivar

This study aimed to investigate the effect of storage time and temperature on the bioactive and sanitary quality of cherry syrup made from the “Burlat” cultivar cherries. The syrup was pasteurized at 70 °C for 2 min and stored at four temperatures (− 20, 4, 28, and 40 °C) for six months. The total phenolic (TPC), total flavonoid (TFC), total anthocyanin (TAC), and antioxidant activity (AA) of the syrup were monitored throughout the storage period. Results showed that there was no statistically significant loss of TPC, TFC, TAC, and AA up to 60 days of storage at − 20 °C and 4 °C (p < 0.05). However, at 28 °C and 40 °C, a significant loss was observed from 30 days of storage. ATR-FTIR analysis confirmed the degradation of syrup nutritive compounds around the vibration regions attributed mainly to proteins and phenols as a function of temperature and storage time. Microbial control revealed that no molds or yeasts were detected at any temperature treatment during the 6-month storage period. Overall, this study suggests that low temperature storage (− 20 °C) is recommended to maintain the microbiological and biochemical quality of cherry syrup. As a result, the findings from this study will prove valuable to a wide range of industries, including food, nutrition, pharmaceuticals, and therapeutics.

Structural Study of [Sc3O4(CO2)n]+ (n = 2, 3) Complexes by Infrared Photodissociation Spectroscopy and Density Functional Calculations.

The catalytic transformation of CO2 into valuable products has garnered wide interest owing to both economic and environmental benefits, in which the chemical fixation of CO2 into carbonate structures represents a crucial step that occurs on the adsorbed catalyst surfaces. Transition metal oxides with acidic and basic active sites have exhibited potential in promoting the carbonation of weakly bound CO2 molecules. Here, the interactions between CO2 molecules and the Sc3O4+ cation in the gas phase are investigated by using infrared photodissociation spectroscopy in conjunction with quantum chemical calculations. Both end-on and various carbonate-containing configurations, including center and bridge carbonate structures, have been theoretically identified for the CO2-coordinated ion-molecule complexes. Based on the comparison between the experimental spectra and simulated spectra of low-lying isomers in the CO2 antisymmetric stretching vibrational frequency region, isomers characterized by a bridge carbonate core structure are demonstrated to be the major contributors to the observed spectra. Examination of potential energy surfaces reveals lower energy barriers and simpler reaction routes for the conversion of molecularly bound CO2 into a bridge carbonate moiety, providing reasonable explanations for their prevalence in the experiments.

Forced-Vibration Characteristics of Bowtie-Shaped Honeycomb Composite Sandwich Panel with Viscoelastic Damping Layer.

The incorporation of viscoelastic layers in laminates can markedly enhance the damped dynamic characteristics. This study focuses on integrating viscoelastic layers into the composite facesheet of the bowtie-shaped honeycomb core composite sandwich panel (BHC-CSP). The homogenization of the damped BHC-CSP is performed by employing the variational asymptotic method. Based on the generalized total energy equation, the energy functional of the representative unit cell of the damped BHC-CSP is asymptotically analyzed. The warping function, derived following the principle of minimum potential energy, provides a basis for obtaining the corresponding Euler-Lagrange equation to ascertain the equivalent elastic properties of the damped BHC-CSP. Utilizing the developed two-dimensional equivalent model, the free-vibration characteristics of the damped BHC-CSP are examined across diverse boundary conditions while delving into the impact of an external viscous damping layer on the natural frequency of the damped BHC-CSP. The results reveal that intensified boundary constraints effectively diminish the effective vibration region of the damped BHC-CSP, thereby enhancing its overall stability. The introduction of a PMI foam layer proves effective in adjusting the stiffness and mass distribution of the damped BHC-CSP. Resonance characteristics are explored through frequency and time-domain analyses, highlighting the pivotal roles of the excitation position and receiver point in influencing the displacement and velocity responses. Although the stiffness is improved by incorporating a PMI foam layer, its effect on the damping performance of the damped BHC-CSP is minimal when compared to the T-SW308 foam layer.

Analysis of vibrational modes and weak interactions in terahertz spectra of γ-aminobutyric acid and its isomer L-2-aminobutyric acid

Aminobutyric acid, a non-proteinogenic amino acid, is present in the human body and influences physiological functions, exhibiting promising pharmaceutical prospects. γ-Aminobutyric Acid (GABA) and its isomer, L-2-Aminobutyric Acid (L-AABA), exhibit unique characteristic absorption peaks in the 0.6 to 2.5 THz range. To elucidate the mechanisms behind these absorption peaks, this study employed Density Functional Theory (DFT) for theoretical simulations of the crystal cell models of L-AABA and GABA, achieving terahertz spectra consistent with experimental results. Additionally, the study utilized Vibrational Mode Automatic Relevance Determination (VMARD) and Interaction Region Indicator (IRI) methodologies to interpret the vibrational modes corresponding to different absorption peaks and to detail the locations and types of intermolecular interactions within the crystals. Research indicates that the combination of terahertz time-domain spectroscopy (THz-TDS) and theoretical calculations can serve as an effective method for identifying isomers of Aminobutyric Acid and detecting intermolecular weak interactions such as hydrogen bonds within these crystals.

Coupled response of flow-induced vibration and flow-induced rotation of a circular cylinder with a triangular fairing

In this paper, a numerical simulation investigation is carried out on the coupled response of the flow-induced vibration (FIV) and flow-induced rotation (FIR) of a circular cylinder attached with a triangular fairing at a low Reynolds number of Re = 100. The primary focus is on the impact of FIR on FIV. The vibration response, hydrodynamic coefficient, vortex shedding mode, and flow field characteristics are examined for the fairings within the vibrational reduced velocity Ur range of 3–16 with shape angle of α = 45°, 60°, and 90°. The results reveal that at low Ur, all the three considered fairings have a good suppression effect on the FIV. Nevertheless, the galloping response emerges as Ur increases when α = 45° and 60°. In contrast, the vibration response of 90° fairing presents a wider lock-in region. The rotatable 2-degree of freedom (2-DoF) fairing has a better performance in the reduction of response amplitude and hydrodynamic coefficients. The 2S (two single vortices) vortex shedding mode mainly occurs in the vortex-induced vibration (VIV) region, while 2S–8S (from two to eight vortices), 2P (two pairs of vortices), 2T (two triplets of vortices), and P + T (a pair of vortices and a triple of vortices) modes emerge in the galloping branch. Moreover, four modes of wake structures are identified according to the variation of recirculation region and the migration of boundary layer separation point. Finally, the reduced regions of drag, lift, and amplitude are highlighted compared to the bare cylinder.

Experiment and performance analysis of serpentine-shaped cantilever beam for pipeline vibration-based piezoelectric energy harvester prototype development

Abstract Pipelines produce vibrations during fluid or gas transportation. These vibrations are less likely to cause structural failure as they exist with a small magnitude and can be harvested into useful energy. This paper presents a study on the piezoelectric energy-harvesting method converting mechanical energy from pipeline vibration into electrical energy. The performance of the serpentine-shaped piezoelectric cantilever beam was observed to check whether the design can produce the highest output voltage within the allowable vibration region of the pipeline from 10 to 300 Hz through finite element analysis using COMSOL Multiphysics software (Supplementary Material). In addition, this study investigates the energy-harvesting potential of the proposed design under real pipeline vibration conditions through a lab vibration test. The harvested energy output is evaluated based on various vibration frequencies and amplitudes, which gives an idea of the device and its performance under different operating conditions. The experiment result shows that the energy harvester produced an open-circuit voltage of 10.28–15.45 V with 1 g of vibration acceleration. The results of this research will contribute to the development of efficient piezoelectric energy harvesters adapted for pipeline environments.

Dual coherent anti‐Stokes Raman scattering microscopy across the vibrational spectrum enabled by single pump optically synchronised oscillators and spectral focusing

AbstractCoherent anti‐Stokes Raman scattering microscopy probing two independently selectable vibrational frequencies across the vibrational spectrum is demonstrated. A one‐box femtosecond laser source provides three synchronised 100–200 fs pulses of 77 MHz repetition rate, one at a fixed wavelength of 1025 nm from an Yb oscillator and two independently tuneable ones, over 680–960 nm and 960–1300 nm, respectively, from two optically synchronised parametric oscillators. Combined with spectral focusing, the source allows addressing the fingerprint, cell silent and C–H stretch vibrational regions simultaneously, avoiding the motion artefacts seen in sequential imaging. We demonstrate the microscopy method on water/heavy water/oil emulsions, plastic beads and deuterated lipids inside cells.

Insight on Zn-Al LDH as electrocatalyst for CO2 reduction reaction: An in-situ ATR-IR study

Electrochemical reduction of CO2 (CO2RR) is expected to play a key role among the various strategies being explored to limit global warming. In this scenario, Layered Double Hydroxides (LDHs) are emerging as a promising class of electrocatalysts to replace the most used noble metals. In this work three Zn-Al LDH with different Zn2+/Al3+ ratio were synthesized and characterized by means of XRD, STEM-EDX and HR-TEM. Their suitability for CO2RR to CO was assessed by means of a custom-made three-compartment cell, showing an increase in CO selectivity by decreasing the Zn2+/Al3+ ratio. The CO2 interaction with the samples was firstly characterized by means of volumetric adsorption measurements, exhibiting an increase in capture capacity by decreasing the Zn2+/Al3+ ratio. The evolution of the samples in interaction with a CO2-saturated liquid flow was then deeply investigated by means of in-situ ATR-IR spectroscopy. The samples displayed a different evolution in the vibrational region of the carbonate-like species (1800–1200 cm−1). To better discriminate the different carbonate cyclohexane was also employed. A definitive assignment of the main IR bands of the carbonate was carried out by studying the spectral behavior of the different bands observed in the ATR-IR experiments and by comparing these results with the existing literature. Interestingly, Zn-Al 1:2 LDH, the most efficient electrocatalyst for CO2RR, is also the sole sample exhibiting a higher monodentate to total bidentate carbonates ratio, suggesting that the existence of a higher content of low coordination oxygen anions with stronger basic character can influence the final catalytic activity.

Investigation of the Effects of Vortex Isolation Plates with Different Opening Ratios and Sizes on Vortex-Induced Vibration

Twin-box girders are a good option for long-span cable-bearing bridges due to their excellent stability. Nonetheless, the girder’s slots may generate vortex-induced vibrations (VIVs). Fortunately, appropriate aerodynamic measures can effectively suppress the VIVs in twin-box girders while reducing costs. To examine the effects of vortex isolation plates with varying aperture diameters and opening ratios on the VIVs, a segment model wind tunnel test was conducted. The results demonstrated that a reduction in the opening ratio improved the performance under heaving VIVs, but there was no discernible trend under torsional vibrations. It was also discovered that the opening size significantly influences the length of the lock-in region of torsional vibrations. Furthermore, heaving VIVs have a substantial correlation with both of the girder’s boxes, while torsional vibrations are mostly connected with the downstream section.

Application of Acid Activated Ouw’s Natural Clay (ONC) on Adsorption of Methylene Blue Dye

The application of natural clay as an adsorbent has been widely used. This is supported by the porous surface texture of the clay. However, some treatments are needed to remove impurities in natural clay before using it as an adsorbent. The common effort is to activate it with acid. This research studied the effect of hydrochloric acid concentration on the adsorption capacity of methylene blue dye. The concentrations of hydrochloric acid used were 2, 3, and 4 M. Characterization was carried out with IR, XRD, and SEM-EDX spectroscopy to see the differences in ONC characters before and after adding hydrochloric acid. The characterization results showed that ONC contained montmorillonite and quartz, and an increase in base distance was directly proportional to the increase in the concentration of hydrochloric acid used. High concentrations of hydrochloric acid caused excessive dealumination and deionization. The dealumination process was supported by IR data where there was a shift in wavenumber in the Al-O stretching vibration region from 796 cm–1 to 794 cm–1; the sharper the vibration in the Si-O region (488-468 cm–1); there was also an increase in the Si/Al ratio of pure ONC from 1.7497 to 2.2970 for 3 M ONC-HCl. The concentration of hydrochloric acid did not significantly affect the capacity of ONC as an adsorbent for methylene blue. The adsorption capacity of pure ONC obtained was 4.97215 mg/g, while for ONC-HCl 3 M was 4.97746 mg/g.

INVESTIGATION OF SOLVATION IN LITHIUM PERCHLORATE -PROPYLENE CARBONATE-DIMETHYL CARBONATE SYSTEM BY RAMAN SPECTROSCOPY

The difference of solvent properties can significantly affect the solvation phenomena in individual and, especially, in mixed solutions. In particular, it can be assumed that in mixed solvents, i.e. in systems with intermediate dielectric permittivity (mixtures of linear and cyclic carbonic acid esters), cations will bind molecules of linear esters more strongly and bind molecules of cyclic esters more weakly than it takes place in individual solvents. In the present work the Raman spectra of lithium perchlorate solvents in propylene carbonate (PC), dimethyl carbonate (DMC) and their mixture in a wide range of salt concentrations are studied. It is shown that the solvation effects of the cation are clearly traced in the region of symmetric ring vibrations (~690-730 cm-1) of propylene carbonate and in the region of deformation vibrations of CCA (~520 cm-1) of dimethyl carbonate. These effects are also evident in the mixed solvent. The so-called method of differential spectroscopy was used to judge the structural changes of mixed-solvent systems. It consisted in constructing spectra of lithium salt solutions in mixed solvents, additive sum of spectra of lithium salt solutions in PC and DMC, as well as their difference (differential spectra). The analysis of differential spectra allows us to conclude that in systems with mixed solvent there is a weakening of interaction of propylene carbonate molecules with ions, and there is a preferential solvation of cations and anions by dimethyl carbonate molecules. Also, unlike propylene carbonate, dimethyl carbonate solvates perchlorate ions, which follows from the line contour changes in the region of CH3-group vibrations (2970 cm-1) solvation of anions is also observed in the mixed solvent. For citation: Rabadanov K.Sh., Gafurov M.M., Akhmedov M.A., Rabadanova D.I., Magomedova A.G. Investigation of solvation in lithium perchlorate -propylene carbonate-dimethyl carbonate system by raman spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 36-42. DOI: 10.6060/ivkkt.20246705.6967.