Comparative Study Of Structural Properties Research Articles

Comparative Study of Structural Properties of Bulk and Aluminum Oxide Supported Ce1–xNixOy Oxides

Comparative Study of Structural Properties of Bulk and Aluminum Oxide Supported Ce1–xNixOy Oxides

A comparative study of structural properties of oleic acid coated metal nanoparticles (Co, Ni, Fe) by co-precipitation method

Metal nanoparticles of cobalt, nickel and iron were synthesized by chemical co-precipitation method using Sodium Borohydride as the reducing agent. The metallic particles were coated with oleic acid to prevent the formation of oxides on the surface layers. The structural analysis of both coated and uncoated samples were carried out using XRD technique and FTIR spectroscopy. XRD patterns of the uncoated samples showed the significant presence of oxide phases of the metallic nanoparticles while in the case of coated samples, the metallic phase was observed. A significant observation from the XRD patterns of the coated samples was the presence of a broad peak centred at 20–210 which is indicative of the graphitic structures typically observed as (002) reflections of graphite. However, the broadened peak depicted the formation of layered graphitic structures of Graphene/ nano tubes/fullerene/ nano onions. The stretching vibration of C = O and symmetric stretching vibrations of the –COO–functional group in the FTIR spectrum, indicated that the layer of oleic acid was successfully coated on the surface of MNPs. The graphitic structures of all oleic acid coated metal nanoparticles were confirmed by Raman spectroscopy. The formation of graphitic structure was the result of the catalytic action of metal nanoparticles..

A comparative Study of Structural Properties and Antacid activity of some commercial samples of Shauktika bhasma

Backgroud: Shauktika Bhasma is a traditional ayurvedic medicine which is an excellent remedy for a number of stomach disorders, hyper acidity and ulcers. It is prepared from mother pearl by subjecting the powder of mother pearl to traditional ayurvedic processes. To get a worldwide recognition to such supreme ancient medicine, it is necessary to reinvestigate it on the basis of modern analytical techniques.In the present work a comparative study of some commercial samples of Shauktika bhasma is undertaken to understand the current status of this bhasma and to explore its acid neutralization capacity using back titration method. Materials and Methods: Samples from renowned pharmacies are collected and subjected to chemical and structural investigations using analytical techniques like XRD, IR and UV. Back titration method is applied to find acid neutralizing capacity of these bhasma samples. Conclusion:The study reveals that Shauktika bhasma is chemically calcite form of calcium carbonate. Antacid activity of the samples is reported for these samples using simple titration method which is useful to estimate number of moles neutralized for a quick comparison. The antacid activity of the samples is found to be inversely proportional to the crystallite size of the bhasma.

The Effect of synthesis methods and comparative study of structural properties of micro and nano Ferrites

In this study, Mn(x)Zn(1-x)Fe2O4 ferrite samples with x=0.4 and 0.6 were synthesized using a solid-state method and co-precipitation method. In order to determine the effects of various concentrations (x) on the ferrite's structure, particle size, and crystalline phases, prepared samples were analysed using X-ray diffraction (XRD). The XRD patterns revealed that the synthesized samples display a single-phase cubic spinel structure.FTIR analysis showed for both synthesis method have absorption band in the range 400 to 1000 cm-1.SEM analysis shows extreme homogeneity of all the samples. EDX analysis was used to examine for Mn0.4Zn0.6Fe204,The prepared ferrites powders contain Mn, Zn, and Fe, as shown in both synthesis methods.In this approach, alternative synthesis routes for these ferrites are suggested in this study in order to get around some limitations of the traditional preparation method.

Comparative study of structural properties and biological activities of polysaccharides extracted from Chroogomphus rutilus by four different approaches

Extraction processes significantly alter the structural and functional properties of polysaccharides. In this study, we extracted polysaccharides from Chroogomphis rutilus fruiting bodies (designated as CRP) using four methods, including hot water, ultrasound, microwave and sequential ultrasound-microwave, and designated these polysaccharides as CRP-H, CRP-M, CRP-U and CRP-UM, respectively. All CRPs were heteropolysaccharides with semblable monosaccharide types of glucose, mannose and galactose, mainly constituted of α-d-glucopyranosyl-(1 → 4). The extraction processes significantly affected the molecular weights, monosaccharide proportions, glycosidic bond ratios, branching degrees, triple-helix conformation and surface morphology of the CRPs. Among them, CRP-UM showed the highest yield and most potent antioxidative capacity in vitro and in HL-7702 cells, but the weakest activation of immunostimulatory response in RAW264.7 cells. In contrast, CRP-H exhibited the lowest yield but strongest immunostimulatory activity. Overall, microwave extraction could be utilized as a general and practical CRP extraction approach, based on its relatively high yield and bioactivities.

Comparative study of structural properties of syntactic carbon foams made using different process approaches

The structural properties of syntactic carbon foams made using different process approaches were studied by scanning electron microscopy. The paper shows that foam technology has a major influence on the formation of the foam structure.

Interactions of binuclear copper(II) complexes with S-substituted thiosalicylate derivatives with some relevant biomolecules

Interactions of copper(II) complexes which contain S-alkyl derivatives of thiosalicylic acid (alkyl = methyl, ethyl, propyl and butyl; aryl = benzyl), marked as 1–5, with guanosine-5′-monophosphate (5′-GMP) and calf thymus DNA (CT-DNA) were studied. Kinetics of substitution reactions of 1–5 with 5′-GMP and CT-DNA were investigated under pseudo-first-order conditions at 310 K and pH = 7.2 in 25 mM Hepes buffer using stopped-flow method. All complexes have high affinity toward studied bio-molecules. Additionally, interactions with CT-DNA were followed by absorption spectroscopy and fluorescence quenching measurements. The results indicate that complexes bind to DNA exhibiting high binding constants (Kb = 104 M−1). During the examination of competitive reactions with ethidium bromide (EB), results showed that complexes can replace EB-bound DNA. In addition, a new crystal structure of the binuclear Cu(II) complex with S-substituted thiosalicylate derivative has been reported. In the present series of Cu(II) complexes the crystal structure is the first example of a complex comprising an S-aryl derivative of thiosalicylate ligand. Through comparative study of structural properties of six molecules from four crystal structures we examined the structural variations, potentially important for biological activity of these complexes.

Structure‐related current transport and photoluminescence in SiOxNy and SiNx based superlattices with Si nanocrystals

A comparative study of structural properties, photoluminescence and electrical conductivity of SiOxNy/SiO2, SiOxNy/Si3N4 and SiNx/Si3N4 superlattices is presented. The samples were prepared by plasma enhanced chemical vapor deposition and annealed at 1150 °C in order to produce arrays of silicon nanocrystals, with their formation being confirmed by X‐ray diffraction analysis and photoluminescence spectroscopy. Reference samples without silicon nanocrystals were also fabricated by annealing of as‐prepared films at a lower temperature (700 °C). All high temperature ‐annealed samples are characterized by similar photoluminescence spectra with the maxima in the range from 1.3 to 1.6 eV, which were attributed to Si nanocrystals. The peak position, as well as photoluminescence lifetime in the microsecond range, point to the quantum confined origin of the emission. Current‐voltage measurements revealed an increase in conductivity by several orders of magnitude for the samples with Si nanocrystals in SiNx/Si3N4 superlattices as compared to both SiOxNy/Si3N4 and SiOxNy/SiO2 films, as well as to low temperature annealed counterparts. The dependence of the conduction mechanism in superlattices on their structural properties is discussed.

Comparative study of electronic structure of cubic and hexagonal phases of Re3W as non-centrosymmetric and centrosymmetric low-TC superconductors

The comparative study of structural properties, stability and electronic structure of cubic and hexagonal phases of the intermetallic Re3W, which have attracted recently interest as non-centrosymmetric and centrosymmetric low-TC superconductors, was performed by means of the first-principles calculations. The optimized lattice constants, cell volumes, theoretical density, formation energies and cohesive energies, as well as electronic densities of states are obtained and analyzed. We have found that the lowering of TC (as going from h-Re3W with TC ∼ 9.4 K to c-Re3W with TC ∼ 7.8 K) correlates with lowering of the near-Fermi density of states (of the mixed W 5d + Re 5d type with admixtures of (Re,W) 6s, 6p states) owing to lowering of contributions of W 5d and Re 6p states. Our estimations of average electron-phonon coupling constants λ show that these phases are near to the weak coupling limit, with some growth of constant λ for h-Re3W (λ ∼ 0.60) as compared with c-Re3W (λ ∼ 0.42).

Hexagonal mesoporous titanosilicates as support for vanadium oxide—Promising catalysts for the oxidative dehydrogenation of n-butane

The comparative study of structural properties and catalytic performance of V-containing high-surface mesoporous silica and mesoporous titanosilicate materials (HMS, Ti-HMS) in oxidative dehydrogenation of n-butane (C4-ODH) was carried out. The aim of the study was to investigate effect of different titanium amount incorporated into silica support on the texture, speciation of vanadium complexes and its impact on catalytic performance. Prepared catalysts were characterized by XRF for determination of vanadium content, DTA/TG for thermal stability of matrix, XRD, SEM and N2-adsorption for study of morphology and texture, FT-IR and DR UV–vis spectroscopy for verification of successful incorporation of Ti to the matrix and H2-TPR and DR UV–vis spectroscopy for determination of vanadium complex speciation. All prepared materials were tested in n-butane ODH reaction at 460°C. We conclude that titanium was successfully incorporated into mesoporous structure, which was preserved at least up to 600°C. Catalytic activities of V-Ti-HMS catalysts were approximately four times higher than activity of V-HMS catalyst in spite of the fact that all samples exhibit the same amount of vanadium species with similar distribution. The selectivity to desired products was comparable for all catalysts. Enhanced catalytic activity of V-Ti-HMS materials allows activating of n-butane at significantly lower temperature (by 100°C) compare with V-HMS materials.

Comparative study of structural properties and NOx storage-reduction behavior of Pt/Ba/CeO2 and Pt/Ba/Al2O3

Differences in the NOx storage-reduction (NSR) behavior of Pt/Ba/CeO2 and Pt/Ba/Al2O3 have been identified and traced to their different chemical and structural properties. The results show that Pt/Ba/CeO2 exhibits inferior NOx storage and, particularly, reduction (regeneration) activity compared to the Al2O3 supported catalyst. The incomplete reduction of the stored NOx-species in Pt/Ba/CeO2 seems to be caused by a faster and more profound reoxidation of Pt particles during the lean period as evidenced by in situ X-ray absorption spectroscopy. Interestingly, the reduction activity could be significantly improved by a pre-reduction step at mild conditions. Exposure of the Pt/Ba/CeO2 catalyst to reducing H2 atmosphere in the temperature range 300–500°C lead to a moderate increase of Pt particle size which beneficially influenced the regeneration activity. In contrast, pre-reduction at temperatures above 500°C was unfavorable and resulted in a severe decrease of the regeneration activity, probably due to migration of the partially reduced CeO2 onto the surface of Pt particles.

Comparative study of structural properties of trehalose water solutions by neutron diffraction, synchrotron radiation and simulation

Neutron diffraction measurements combined with H/D substitution have been performed on trehalose aqueous solutions as a function of temperature and concentration by using the SANDALS diffractometer at ISIS Facility (UK). The findings point out a high capability of trehalose to strongly affect the tetrahedral hydrogen bond network of water. The neutron diffraction results are also compared with simulation and experimental data obtained by synchrotron radiation on the phospholipid bilayer membranes (DPPC)/trehalose/H 2O ternary system.

Comparative study of structural properties and photoluminescence in InGaN layers with a high In content

Rutherford backscattering and channeling spectrometry (RBS), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM) have been used to investigate macroscopic and microscopic segregation in MOCVD grown InGaN layers. The PL peak energy and In content (measured by RBS) were mapped at a large number of distinct points on the samples. An indium concentration of 40%, the highest measured in this work, corresponds to a PL peak of 710 nm, strongly suggesting that the light-emitting regions of the sample are very indium-rich compared to the average measured by RBS. Cross-sectional TEM observations show distinctive layering of the InGaN films. The TEM study further reveals that these layers consist of amorphous pyramidal contrast features with sizes of order 10 nm. The composition of these specific contrast features is shown to be In-rich compared to the nitride matrix.

Comparative Study of Structural Properties and Photoluminescence in InGaN Layers with a High in Content

AbstractRutherford backscattering and channeling spectrometry (RBS), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM) have been used to investigate macroscopic and microscopic segregation in MOCVD grown InGaN layers. The PL peak energy and In content (measured by RBS) were mapped at a large numberof distinct points on the samples. An indium concentration of 40%, the highest measured in this work, corresponds to a PL peak of 710 nm, strongly suggesting that the lightemitting regions of the sample are very indium-rich compared to the average measured by RBS. Cross-sectional TEM observations show distinctive layering of the InGaN films. The TEM study further reveals that these layers consist of amorphous pyramidal contrast features with sizes of order 10 nm. The composition of these specific contrast features is shown to be In-rich compared to the nitride matrix.

A comparative study of structural properties of fibronectin and its 180 kDa fragment

Fibronectin from human plasma and its 180 kDa fragment which retained collagen-binding, cell-attachment and heparin-binding activities, were studied by velocity centrifugation and 1H-NMR methods. The fibronectin hydrodynamic radius strongly increased at pH 11 while the hydrodynamic properties of the fragment did not change noticeably. 1H-NMR spectroscopy also showed differences in the molecular properties of fibronectin and its 180 kDa fragment. Under physiological conditions the structure of fibronectin differs from that of its 180 kDa fragment. At pH 11 and in 4 M urea no differences in their structures are observed. It is suggested that interdomain and intersubunit interactions play an important role in maintaining the native conformation of intact fibronectin.