Changes In Intensity Of Bands Research Articles

The interactions of pectin with TiO2 nanoparticles measured by FT-IR are confirmed in a model of the gastrointestinal tract

The presence of nanoparticle fractions (<100 nm, NPs) in the food additive TiO2 (E171) rises concerns about its potential harmful impact on human health. The knowledge about the interaction of TiO2 NPs with food components is limited to proteins or polyphenols. The present paper is the first to report on interactions between TiO2 NPs and high molecular pectins that form gels in boluses and are remain nearly intact during digestion until they reach the colon. Direct interactions were studied using Fourier Transform Infrared Spectroscopy while indirect ones were monitored by measuring the “absorption” of TiO2 using a 0.2 microfiltration membrane, during in vitro digestion in a model of the gastro-intestinal tract. The FT-IR spectra registered for pectin-TiO2 NPs solutions confirmed changes in band intensities at 1020, 1100, 1610, and 1740 cm−1, suggesting interactions taking place mainly via the COO– groups. Furthermore, the I(1020)/I(1100) ratio was decreased (C-O stretching vibrations), suggesting partial blocking of the skeletal vibrations caused by interactions between pectin and TiO2. The modelled in vitro digestions confirmed that the “availability” of Ti was reduced when TiO2 NPs were combined with pectin, as compared to TiO2 NPs “digested” alone.

High-resolution photoluminescence study on donor-acceptor pair (DAP) recombination in silicon crystals co-doped with phosphorous and gallium

Before lower purity, lower cost silicon (Si) materials, such as compensated Si, can play a role in the terawatt-level (TW) capacity of photovoltaics, a better understanding of the fundamental properties of impurities in compensated Si is essential. In this work, high-resolution photoluminescence (PL) has been used to study the charge carrier radiative recombination through Donor-Acceptor pairs (DAPs) in phosphorus (P) and gallium (Ga) co-doped Si material grown for solar cell applications. The high spectral resolution of our PL system, 0.06 meV, enables us to overcome hitherto prior issues of overlapping spectral lines, giving access to extremely fine structures associated with DA pair (DAP) recombination. Our results confirm the presence of three broad bands and a discrete line structure related to DAP luminescence. The comparison of the discrete line structure due to DAPs recombination in the PL spectra with the theoretically predicted one allows the accurate determination of the Ga ionization energy. Temperature-dependent PL is then used to understand the thermally-induced changes in the DAP luminescence. In particular, we observe that the radiative recombination channel remains active for distant DAPs up to ∼40 K, unlike that for close-range DAPs for which the radiative channel is quenched after only slight increases in the temperature range 10–25 K. Furthermore, the analysis of the temperature dependent changes in the PL intensity of the broad DAP bands up to ∼200 K is used to derive the ionization energy of P donors in compensated Si material. In light of this important information, the significance of using high resolution PL to analyse spectral features in compensated Si is demonstrated.

Effect of mechanical impact on the microstructure and IR spectra of cohesive soil

The aim of the study is to determine the correlations between mechanical impacts on clay soil samples and resulting changes in the microstructure of the samples and their IR spectra. For research, soil from a railway subgrade under construction in the Azov-Black Sea region was used. The soil was examined by traditional and modern physical methods and classified as light clay. Clay properties were modified by adding alabaster to the soil, after which the samples with different amounts of alabaster were subjected to mechanical load. A cyclic mechanical impact by the compression method was applied to a clay sample without alabaster, an equivalent to the passage of 400 freight trains along the railway track. The microstructure of samples was studied by electron microscopy which allowed determining the microstructure parameters of the fragments of samples before and after the mechanical action. Samples of clay and clay with the addition of alabaster were subjected to a semi-quantitative express analysis by IR spectroscopy, as a result of which the concentrations of minerals were determined with an accuracy of no worse than 10%. Clay and clay samples with the addition of alabaster were subjected to static uniaxial compression, after which the samples were examined by IR spectroscopy. Comparison of the results of spectral and compression studies made it possible to investigate the correlations between changes in the peak intensities of the IR spectra bands and the concentration of alabaster, as well as the strength properties of the soil.

Optical, and electrical conductivity properties of ZnO and TiO2 nanoparticles scattered in PEO-PVA for electrical devices

Polyvinyl alcohol (PVA)/Polyethylene oxide (PEO) has been blended and doped with zinc oxide and titanium oxide nanoparticles. Different concentration of the prepared ZnO and TiO2 NPs make a change in PVA/PEO- ZnO/TiO2 NPs nanocomposites films improve the characterization of PVA/PEO. XRD scans show two broad peaks at about 18.8° and 21.95° for PVA/PEO blend. XRD scans show of PVA/PEO- ZnO/TiO2 NPs nanocomposites films obtain the hexagonal structure of ZnO and the anatase phase of TiO2 NPs. The addition of dopants in the PVA/PEO blend results in a reduce in degree of crystallinity compared to the pure blend. This is evident from the decrease in the crystallinity index (Xc value) from 37.25 to 22.31. This reduction in crystallinity can have implications for the material's opticla, thermal, and electrical properties, and should be considered when evaluating its suitability for specific applications. FT-IR results show changes in intensity of bands that could be assigned to the strong interaction between PVA/PEO and ZnO/TiO2 nanoparticles. The Egopt values reduced by raising laser ablation time due to unstructured defects that enhanced the density of localized states in the band gap, dropping from 4.72 eV to 3.0 eV for direct transitions and from 3.05 eV to 2.35 eV for indirect transitions. It undergoes complete decomposition at a higher temperature, resulting in a mass percentage of 45 ± 0.3 wt%. In comparison, the pure polymer blend sample has a lower mass percentage of 33 ± 0.03 wt% during the same temperature range. The fabricated system of PVA/PEO- ZnO/TiO2 NPs nanocomposites films showing improved in AC conductivity and dielectric characteristics and could be suggested in electrical applications.

Polyethylene terephthalate (PET) biodegradation by Pleurotus ostreatus and Pleurotus pulmonarius

The essential properties of polyethylene terephthalate (PET), such as chemical inertness and durability that make it a suitable material for the packaging of mineral and soft drinks, have led to it becoming a major environmental pollutant and a threat to the planet. Ecologically friendly solutions such as bioremediation are now being advocated for by scientists. This paper, therefore, seeks to explore the potential capacity of Pleurotus ostreatus and Pleurotus pulmonarius in biodegrading PET plastic on two different substrates (soil and rice straw). The substrates were combined with 5% and 10% plastic before inoculation with Pleurotus ostreatus and Pleurotus pulmonarius and then left to incubate for 2months. Biodegradation, monitored by FT-IR pointed to the formation of new peaks in the incubated plastics after 30 and 60days unlike in the control. Changes in band intensity and shifts in the wavenumbers caused by stretching of functional groups, C-H, O-H and N-H in the band region of 2898cm-1 to 3756cm-1 are confirmed indicators of successful breakdown caused by contact with P. ostreatus and P. pulmonarius. The FT-IR analysis also gave an indication of N-H stretching at 3338.04cm-1 and 3228.62cm-1 for PET flakes incubated with Pleurotus sp. Furthermore, degradation products like hydrocarbons, carboxylic acids, alcohols, esters, and ketones were also detected in the GC-MS analysis of the decomposed PET plastic after 30 and 60days. These compounds are formed due to chain scission caused by the fungal species. There was a discoloration of the PET flakes caused by an increase in carboxyl-terminated species as a result of enzymes secreted by the fungi in the process of biodegradation.

Investigating changes in the diffuse reflectance spectra of BaSO4 powders modified with SiO2 nanoparticles exposed to proton irradiation

The authors modified BaSO4 powders with SiO2 nanoparticles and studied the effect of this modification on powders’ structure and optical properties, as well as on the changes of the latter after 5 keV proton irradiation. No significant post-modification changes in structure have been observed. In the IR-spectrum, the authors have recorded the band intensity changes for SiO2, Si – O – Si, and Si–Si vibrations, as well as emerging OH group vibration band. Additionally, the authors have noted the appearance of an absorption band in the UV/vis spectra caused by intrinsic point defects in BaSO4 anionic sublattice. The energy losses induced by displacement and ionization were calculated, as were the proton free paths in the modified powder. It is shown that an increase of radiation stability is provided by solely 1.2% of the proton energy flux absorbed in the nSiO2 nanolayer contributing to the total energy loss in the entire modified powder. Two mechanisms are proposed for the processes occurring in the nSiO2/mBaSO4 system that determine the increase of its radiation stability compared with the non-modified powder.

Optical coherence tomography in healthy human subjects in the setting of prolonged dark adaptation

Human studies have established that short periods of dark adaptation can induce outer retinal thinning and various band intensity changes that can be detected with Optical Coherence Tomography (OCT). Similar findings were observed in mice, including a positive correlation between the degree of outer retinal changes and dark adaptation duration. We decided to assess potential retinal structural changes following prolonged dark adaptation in humans. 40 healthy subjects without any ocular diseases participated in this study. For each subject, one eye was covered for dark adaptation for four hours, and the other eye was left uncovered as a control. Before and after the dark adaptation period, both eyes were assessed with OCT. Using the Heidelberg Spectralis system, basic statistical functions, and qualitative and quantitative analysis, we were able to compare retinal layer thicknesses and band intensities between covered (dark adapted) versus uncovered (control) eyes. Prolonged dark adaptation did not induce any significant thickness, volume, or intensity changes in the outer retina or in the inner or overall retina. These observations thus alter our current understanding of the mechanisms underlying dark adaptation’s neuroprotective effects in preventing blindness and require further study.

Factor analysis of the time series of SERS spectra reveals water arrangement and surface plasmon changes in Ag nanoparticle systems

The enhancement of Raman signals of molecules localized in the vicinity of plasmonic nanoparticles, known as surface-enhanced Raman scattering (SERS) effect, is strongly influenced by the selected excitation wavelength. The optimal excitation wavelength in SERS measurements is given by the position of the surface plasmon extinction (SPE) band of the studied system. Even a small change of the SPE band intensity, position and/or shape during the measurement may influence the SERS signal significantly. In this work, we prepared several systems of Ag nanoparticles, which were used for the demonstration how the information about SPE changes can be obtained by multivariate statistical analysis (factor analysis; FA) from SERS spectral sets, and employed in more precise and more comprehensive interpretation of the results. In non-aggregated Ag colloidal systems measured at the excitation wavelength of 445 nm, SPE band changes could be monitored by the analysis of water stretching vibration together with the vibrations in the fingerprint region. The FA of the water stretching band region was shown to provide unique information on both arrangement and disarrangement of water molecules in the vicinity of Ag NPs during the time evolution of these SERS active systems. In addition, the FA of the fingerprint region helped to monitor a rapid metalation of meso-tetrakis(N-methyl-4-pyridyl)porphine in etched SERS systems with Ag+ ions released from the NPs surface. In aggregated Ag colloidal systems measured at the excitation wavelength of 785 nm, the FA of SERS spectral sets enabled us to reveal the contribution of the 2nd electromagnetic enhancement to the overall SERS signal. The reliability of our conclusions was verified by comparing the results obtained from FA of SERS spectral sets with the data obtained from the parallel SPE measurements of the studied systems.

Modelling solute-solvent interactions in VCD spectra analysis with the micro-solvation approach.

Vibrational circular dichroism (VCD) spectroscopy has become an important part of the (stereo-)chemists' toolbox as a reliable method for the determination of absolute configurations. Being the chiroptical version of infrared spectroscopy, it has also been recognized as being very sensitive to conformational changes and intermolecular interactions. This sensitivity originates from the fact that the VCD spectra of individual conformers are often more different than their IR spectra, so that changes in conformational distributions or band positions and intensities become more pronounced. What is an advantage for studies focussing on intermolecular interactions can, however, quickly turn into a major obstacle during AC determinations: solute-solvent interactions can have a strong influence on spectral signatures and they must be accurately treated when simulating VCD and IR spectra. In this perspective, we showcase selected examples which exhibit particularly pronounced solvent effects. It is demonstrated that it is typically sufficient to model solute-solvent interactions by placing single solvent molecules near hydrogen bonding sites of the solute and subsequently use the optimized structures for spectra simulations. This micro-solvation approach works reasonably well for medium-sized, not too conformationally flexible molecules. We thus also discuss its limitations and outline the next steps that method development needs to take in order to further improve the workflows for VCD spectra predictions.

Effects of NaCl curing and subsequent fermentation with Lactobacillus sakei or Lactobacillus plantarum on protein hydrolysis and oxidation in yak jerky

The impacts of added NaCl and subsequent fermentation with Lactobacillus sakei or Lactobacillus plantarum on proteolysis and protein oxidation in yak jerky were investigated. The proteolytic activity, peptide content and free amino acid concentration displayed decline patterns as NaCl content increased from 0 to 4% (P < 0.05), while the salted jerky fermented with lactobacillus demonstrated higher proteolysis profiles than the control without starter cultures (P < 0.05), and jerky fermented with Lactobacillus sakei showed the highest proteolysis. Adding NaCl promoted protein carbonylation, sulfhydryl loss and tryptophan fluorescence quenching. Fermentation with lactobacillus, especially with Lactobacillus sakei, effectively reduced the oxidation of sarcoplasmic and myofibrillar proteins in salted jerky (P < 0.05). Electrophoretogram showed that the changes in number and intensity of protein bands were from combined action of NaCl curing and microbial fermentation. The results suggest that both of NaCl addition and subsequent fermentation influence the protein chemical properties and hence modify the relevant quality traits of yak jerky.

Sustainable Sheep Wool/Soy Protein Biocomposites for Sound Absorption

The wool fibers of the Latxa sheep breed were combined with a soy protein isolate (SPI) matrix to develop sustainable biocomposites with acoustic properties, adding value to Latxa sheep wool, which is currently considered a residue. Samples with 7, 10, 15, and 20 wt % wool were prepared by freeze drying in order to develop porous structures, as shown by SEM analysis. Additionally, XRD analysis provided the evidence of a change toward a more amorphous structure with the incorporation of wool fibers due to the interactions between the soy protein and keratin present in wool fibers, as shown by the relative intensity changes in the FTIR bands. The biocomposites were analyzed in a Kundt's tube to obtain their sound absorption coefficient at normal incidence. The results showed an acoustic absorption coefficient that well-surpassed 0.9 for frequencies above 1000 Hz. This performance is comparable to that of the conventional synthetic materials present in the market and, thus, sheep wool/SPI biocomposites are suitable to be used as acoustic absorbers in the building industry, highlighting the potential of replacing not only synthetic fibers but also synthetic polymers, with natural materials to enhance the sustainability of the building sector.

Solid-to-Liposome Conformational Transition of Phosphatidylcholine and Phosphatidylserine Probed by Atomic Force Microscopy, Infrared Spectroscopy, and Density Functional Theory Calculations.

Liposomes are emerging therapeutic formulations for site-specific delivery of chemotherapeutic drugs. The efficiency and selectivity of drug delivery by these carriers largely rely on their surface properties, shape, and size. There is a growing demand for analytical approaches that can be used for structural and morphological characterization of liposomes at the single-vesicle level. AFM-IR is a modern optical nanoscopic technique that combines the advantages of scanning probe microscopy and infrared spectroscopy. Our findings show that AFM-IR can be used to probe conformational changes in phospholipids that take place upon their assembly into liposomes. Such conclusions can be made based on the corresponding changes in intensities of the lipid vibrational bands as the molecules transition from a solid state into large unilamellar vesicles (LUVs). This spectroscopic analysis of LUV formation together with density functional theory calculations also reveals the extent to which the molecular conformation and local environment of the functional groups alter the AFM-IR spectra of phospholipids. Using melittin as a test protein, we also examined the extent to which LUVs can be used for protein internalization. We found that melittin enters LUVs nearly instantaneously, which protects it from possible structural modifications that are caused by a changing environment. This foundational work empowers AFM-IR analysis of liposomes and opens new avenues for determination of the molecular mechanisms of liposome-drug interactions.

Evaluation of DNA damage induced by acesulfame potassium: spectroscopic, molecular modeling simulations and toxicity studies

Acesulfame potassium (Ace-K) is a widely used artificial sweetener that has been reported to interact with DNA and cause important genetic damage. However, the type of interaction mechanism is unknown. This study provides an approach to understanding the in vitro mechanism of Ace-K interaction with Ct-DNA using spectroscopic methods combined with molecular simulations. The hypochromic effect as obtained from UV–Vis spectra indicated the formation of the DNA-Ace-K complex in the minor groove. Further evidence for groove binding mode comes from the decrease in Hoechst-DNA fluorescence caused by increasing Ace-K concentrations, alongside no detectable change in MB-DNA emission band intensity. A negative value of ΔH and ΔS represents the hydrogen bonds and van der Waals forces between Ace-K and DNA. Based on the molecular docking, Ace-K was located between the guanine10 and 16 in DNA minor groove and stabilized by two hydrogen bonds and one π-Sulfur interaction. In vitro cell culture results showed that about 5 mg/mL of Ace-K caused the death of 85% of HUVEC cells after 48 h. Communicated by Ramaswamy H. Sarma

FT-IR Method Limitations for β-Glucan Analysis.

β-glucans are known as biological response modifiers. However, different sources can result in structural differences and as a result differences in their biological activity. The hot water extraction method allows to obtain, high molecular weight β-glucans without altering their structure by using strong chemicals, such as alkalis or acids. Analysis of β-glucans by FT-IR and NMR spectroscopy in solid state is superior to analysis in solution as it allows researchers to study the preserved structure of the extracted polysaccharides. FT-IR spectroscopy was used in this study to make side-by-side comparison analysis of hot water extracted β-glucans from different yeast sources. NMR spectroscopy was used to confirm findings made by FT-IR spectroscopy. Extracted β-glucans exhibit characteristic structure of β-1,3/1,6-linked glucans with noticeable levels of proteins, possibly in a form of oligopeptides, chitin and other impurities. β-glucans obtained from C. guilliermondii, P. pastoris and S. pastorianus exhibited higher protein content. Differences in mannan, chitin and α-glucan content were also observed; however, the species-specific structure of obtained β-glucans could not be confirmed without additional studies. Structural analysis of high molecular weight β-glucans in solid state by FT-IR spectroscopy is difficult or limited due to band intensity changes and overlapping originating from different molecules.

Impact of different extraction conditions on yield, physicochemical and functional characteristics of gelatin from Labeo rohita swim bladder.

Influences of different extraction temperatures (50, 60, and 70°C) and time (3, 6, and 9h) on yield, physicochemical, and functional properties of gelatin from swim bladder (SBG) of rohu (Labeo rohita) were investigated. Gelatin extracted at 60°C (G60-9h), and 70°C (G70-9h) temperature for 9h showed highest gelatin yield 54.91g/100g, protein (92.35g/100g), and hydroxyproline (77.50mg/g) content (P < 0.05) compared to other counterparts. All extracted gelatin showed major protein components as α-, β-, and γ-chain with slight changes in band intensity. FTIR spectra showed significant loss of molecular order of triple-helix as temperature and time increased. Furthermore, G60-9h exhibited higher emulsion, foaming, and gel strength than G70-9h, and G50-9h, respectively (P < 0.05). Therefore, G60-9h could be appropriate conditions for the extraction of SBG with better yield, physicochemical, and functional properties.

Uncovering strong π-metal interactions on Ag and Au nanosurfaces under ambient conditions via in-situ surface-enhanced Raman spectroscopy

Uncovering strong π-metal interactions on Ag and Au nanosurfaces under ambient conditions via in-situ surface-enhanced Raman spectroscopy

Spectroscopic investigation of tau protein conformational changes by static magnetic field exposure

Electromagnetic fields taint the molecular environment of proteins and induce changes in the central nervous system. This research applied Fourier transform infrared spectroscopic analysis to investigate the effects of static magnetic fields on tau protein in neurological disorders. It explores the conformational changes of tau protein and highlights its’ potential application as a pathological biomarker for early detection and therapeutic interventions. The results indicate that tau protein is susceptible to magnetic field exposure in the amide B, fingerprint, and amide regions (IV-VI). Changes in peak positions and band intensities were identified and delineated as the outcome effect of magnetic forces on molecular vibrations. Magnetic forces may affect the microtubule structure of the tau protein, leading to protein aggregation. These results indicate the potential application of FTIR spectroscopy for the early detection and classification of degenerative diseases through spectrum analysis. Different magnetic fields can be used as spontaneous therapeutic procedures to induce changes in the molecular environment of proteins.

Structural evolution of La-modified AgNbO3 lead-free ceramics: Perspective from octahedral tilting and tolerance factor

Systematic studies on the structural and microstructural properties as a function of the lanthanum concentration have been performed in AgNbO3-based lead-free ceramics, which were synthesized via the conventional solid-state reaction process. The structural analysis has been carried out at room temperature by the X-ray diffraction technique as well as Raman spectroscopy. A single-phase orthorhombic polycrystalline perovskite structure, without undesired phases, has been confirmed for all studied compositions. Structural distortions, which have been associated with the doping concentration, have been investigated through Rietveld refinement and Raman results. The La3+ ion concentration has also shown an important influence on the Raman spectra, showing a wavenumber shift and a dramatic change in absolute intensity of several bands with the increase of the lanthanum dopant. With a further inclusion of the doping element, a change in the local structural properties is revealed, detecting additional bands in the 90–93 cm−1 and 570−758 cm−1 ranges of Raman spectra. The microstructure is strongly influenced by the additive content, revealing a decrease in grain-size as the La-content increases.

Anisotropic 3D columnar micro-film coating for applications in infrared and visible spectral ranges

Polarisation analysis of thin (∼1μm) SiO2 films deposited via evaporation at a glancing angle of 70°to the normal on resist pillar arrays was carried out using synchrotron-based Fourier transform infrared (s-FTIR) microspectroscopy in reflection mode. Changes in intensity of absorption bands were observed to follow the angular dependence of ∼cos2θ, consistent with the absorption anisotropy. The strongest absorption was found to be the sharp Si–O–Si stretching vibrational mode at 1040 ± 20 cm−1, which can be used for sensor applications, as well as radiative cooling in the atmospheric transparency window, within the range of 8-13μm (i.e. 1250-769 cm−1). Anisotropy of IR absorbance is correlated with retardance/birefringence of the same patterns in the visible spectral range. Larger period patterns of 3D columnar SiO2 films of ∼1μm in thickness deposited on polymer/resist pillar arrays provide the possibility to control anisotropy of the form-birefringent 3D columnar films.

Investigation of the Interface of Y3Fe5O12/Gd3Ga5O12 Structure Obtained by the Liquid Phase Epitaxy

AbstractThe changes in the optical, structural, mechanical properties, and chemical composition of Y3Fe5O12/Gd3Ga5O12 (YIG/GGG) single crystal structures grown by liquid phase epitaxy, particularly at the interface between the film (Y3Fe5O12) and the substrate (Gd3Ga5O12), are studied. Different complementary techniques, including optical microscopy, local spectrophotometry, electron probe microanalysis, micro‐Raman spectroscopy, and nanohardness analysis are used. The main finding of the study is an experimental approach, in which the probe of the measuring device (light beam, electron beam, nanoindenter) is directed to the surface of the studied sample in a direction perpendicular to the direction of structure growth, and the surface is scanned along this direction. It allows to obtain the profiles of changes in refractive properties, nanohardness, optical absorption, chemical composition, and intensity of phonon spectrum bands at the transition from the GGG to YIG. It is established that the lengths of the scanning intervals, at which the changes of various properties of a specimen occur, differ significantly. The obtained results are affected by the size of the probes and by the sensitivities of both the particular measuring method and the particular physical property of the material to changes in the chemical composition and crystalline structure of the sample.