Structural Properties Of System Research Articles

Effect of Active Phase Precursor on Structural, Textural and Catalytic Properties of the Model NiOx/CeO2 System Active in Dry Reforming of Methane

The current paper is devoted to the synthesis of ceria-supported nickel-based catalysts starting from different precursors of the nickel active phase. Thermal decomposition of metal-containing precursors, deposited onto stable supports by dry impregnation, belongs to the industrially preferred, simple ways of catalyst preparation. The synthesized series of NiOx/CeO2 catalysts have been tested in dry methane reforming (DMR), in which two greenhouse gases, i.e., CO2 and CH4, are simultaneously converted into syngas. Both reaction progress and stability of the catalyst strongly depend on nickel speciation, which in turn can be determined by the nature of the chosen precursor. Contrary to relatively many studies focused on the importance of synthetic methods and conditions on nickel speciation, the effect of precursor nature on structural, textural, and functional properties of catalytic systems has neither been discussed much nor fully understood. The main goal of this paper was to elucidate the effect of precursors on the properties of NiOx/CeO2. Consequences of the use of various nickel precursors (simple inorganic salts, organometallic complexes, and chelates) have been analyzed in detail from the viewpoint of their beneficial influence on the catalytic performance of NiOx/CeO2 system (containing 3 wt. % of Ni) tested in DMR.

Glass-Forming Ability, Chemical Durability, and Structural Properties of Lead Dioxide-Silicate Glass System

The present study aimed to test the solubility of SiO2 in a PbO2 host glass matrix. The new glass system with chemical composition xSiO2∙(100-x)∙PbO2 (in mol%) was obtained at low temperature using the melt-quenching technique. The method proposed for the characterization of the glass system includes X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), inductively coupled plasma mass spectrometry (ICP-Ms), Fourier Transform Infrared (FTIR), and Electron Spin Resonance (ESR) spectroscopy. Understanding the relationship between the oxide composition, structure, chemical durability, and thermal characteristics of obtained materials is essential for further developing the new glass crystalline material (GCM) compositions with specific desired properties.

A sub-100 nm thickness flat jet for extreme ultraviolet to soft X-ray absorption spectroscopy.

Experimental characterization of the structural, electronic and dynamic properties of dilute systems in aqueous solvents, such as nanoparticles, molecules and proteins, are nowadays an open challenge. X-ray absorption spectroscopy (XAS) is probably one of the most established approaches to this aim as it is element-specific. However, typical dilute systems of interest are often composed of light elements that require extreme-ultraviolet to soft X-ray photons. In this spectral regime, water and other solvents are rather opaque, thus demanding radical reduction of the solvent volume and removal of the liquid to minimize background absorption. Here, we present an experimental endstation designed to operate a liquid flat jet of sub-micrometre thickness in a vacuum environment compatible with extreme ultraviolet/soft XAS measurements in transmission geometry. The apparatus developed can be easily connected to synchrotron and free-electron-laser user-facility beamlines dedicated to XAS experiments. The conditions for stable generation and control of the liquid flat jet are analyzed and discussed. Preliminary soft XAS measurements on some test solutions are shown.

Transmission Electron Microscopy and Dynamic Light Scattering-Fundamental Perspective

Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) are fundamental tools in nanotechnology and materials science, providing information about the structural and dynamic properties of nanomaterials and colloidal systems. This review provides a thorough examination of TEM and DLS, beginning with a discussion of their fundamental principles. It discusses the interaction of electron beams in TEM and the dynamics of scattered light in DLS, followed by an examination of instrumentation and experimental setups, including recent advances for increased resolution and sensitivity. The article then discusses the numerous applications of TEM and DLS in nanomaterial characterization. It includes analyses of nanoparticle size, shape, morphology, and distribution, as well as research into colloidal system dynamics such as nanoparticle aggregation, diffusion, and stability. The review concludes with a forward-looking perspective on emerging trends and future directions in nanomaterial characterization. It emphasizes the potential of TEM and DLS to overcome current challenges and advance our understanding of nanoscale phenomena. Overall, this comprehensive review provides researchers and practitioners with a solid understanding of the TEM and DLS principles, methodologies, and applications, as well as valuable fundamental insights.

Rate Lifting for Stochastic Process Algebra by Transition Context Augmentation

This paper presents an algorithm for determining the unknown rates in the sequential processes of a Stochastic Process Algebra (SPA) model, provided that the rates in the combined flat model are given. Such a rate lifting is useful for model reverse engineering and model repair. Technically, the algorithm works by solving systems of nonlinear equations and – if necessary – adjusting the model’s synchronisation structure, without changing its transition system. The adjustments cause an augmentation of a transition’s context and thus enable additional control over the transition rate. The complete pseudo-code of the rate lifting algorithm is included and discussed in the paper, and its practical usefulness is demonstrated by two case studies. The approach taken by the algorithm exploits some structural and behavioural properties of SPA systems, which are formulated here for the first time and could be very beneficial also in other contexts, such as compositional system verification.

Modulation of Phospholipase A2 Membrane Activity by Anti-inflammatory Drugs.

The phospholipase A2 (PLA2) superfamily consists of lipolytic enzymes that hydrolyze specific cell membrane phospholipids and have long been considered a central hub of biosynthetic pathways, where their lipid metabolites exert a variety of physiological roles. A misregulated PLA2 activity is associated with mainly inflammatory-derived pathologies and thus has shown relevant therapeutic potential. Many natural and synthetic anti-inflammatory drugs (AIDs) have been proposed as direct modulators of PLA2 activity. However, despite the specific chemical properties that these drugs share in common, little is known about the indirect modulation able to finely tune membrane structural changes at the precise lipid-binding site. Here, we use a novel experimental strategy based on differential scanning calorimetry to systematically study the structural properties of lipid membrane systems during PLA2 cleavage and under the influence of several AIDs. For a better understanding of the AIDs-membrane interaction, we present a comprehensive and comparative set of molecular dynamics (MD) simulations. Our thermodynamic results clearly demonstrate that PLA2 cleavage is hindered by those AIDs that significantly reduce the lipid membrane cooperativity, while the rest of the AIDs oppositely tend to catalyze PLA2 activity to different extents. On the other hand, our MD simulations support experimental results by providing atomistic details on the binding, insertion, and dynamics of each AID on a pure lipid system; the drug efficacy to impact membrane cooperativity is related to the lipid order perturbation. This work suggests a membrane-based mechanism of action for diverse AIDs against PLA2 activity and provides relevant clues that must be considered in its modulation.

NMR Relaxation of Gas Adsorbed in Microporous Material.

NMR relaxometry has been widely applied to characterize fluid confined in porous media because of its versatility, chemical selectivity, and noninvasive nature. Here we extend its usage to gas adsorbed in microporous materials by establishing a new quantitative model based on the molecular level NMR relaxation mechanism revealed by the molecular simulation of a prototypical adsorption system, CH4 adsorbed in ZIF-8. The model enables new NMR relaxometry-based characterization methods for thermodynamic, dynamic, and structural properties of adsorption systems, as demonstrated and validated by the experiments where the adsorption capacity and self-diffusivity of H2, CH4, and small alcohols adsorbed in ZIF-8 are deduced from the NMR relaxation data. The findings can serve for a better understanding of the composition-structure-properties relationships of a wide range of adsorption systems which is essential for the development and application of new functional microporous materials.

Influence of Sm2O3/AgNPs Addition on the Properties of Lithium-Borate Glass-Ceramic System

This work reports the effect of adding Sm2O3 and silver nanoparticles, in small quantities up to 1 mol%, on the optical and structural properties of the B2O3-Li2O glass-ceramic system. The X-ray diffraction patterns of the samples show the presence of small quantities of the B2O3 crystalline phase, in addition to a major amorphous phase. Various structural units like BO3, BO4, and LiO4, present in the samples network, are responsible for the absorption bands from the FT-IR spectra. The optical spectra provided valuable information such as the identification of the observed electronic transitions, the energy gap, the refractive index, and metallization values. The luminescence data show the fact that with the addition of metallic NPs the quenching phenomenon can be observed after 0.5 mol% samarium ions. The studied systems are interesting for optical and semiconducting devices.

Development and validation of a general-purpose ReaxFF reactive force field for earth material modeling.

ReaxFF reactive force field bridges the gap between nonreactive molecular simulations and quantum mechanical calculations and has been widely applied during the past two decades. However, its application to earth materials, especially those under high T-P conditions relevant to Earth's interior, is still limited due to the lack of available parameters. Here, we present the development and validation of a ReaxFF force field containing several of the most common elements in Earth's crust, i.e., Si/Al/O/H/Na/K. The force field was trained against a large data set obtained from density functional theory (DFT) calculations, including charges, bond/angle distortion curves, equation of states, ion migration energy profiles, and condensation reaction energies. Different coordination environments were considered in the training set. The fitting results showed that the current force field can well reproduce the DFT data (the Pearson correlation coefficient, Rp, is 0.95). We validated the force field on mineral-water interfaces, hydrous melts/supercritical geofluids, and bulk crystals. It was found that the current force field performed excellently in predicting the structural, thermodynamic, and transport properties of various systems (Rp = 0.95). Moreover, possible applications and future development have been discussed. The results obtained in this study suggest that the current force field holds good promise to model a wide range of processes and thus open opportunities to advance the application of ReaxFF in earth material modeling.

Effect of high concentration of ZnO on the structural and optical properties of silicate glass system

An investigation was conducted to explore the optimum composition to fabricate a zinc silicate glass substrate for optoelectronic device applications. The composition was determined based on the empirical formula (ZnO)x-(SiO2)1-x, where x = 0.40, 0.50, 0.60 and 0.70 wt%, which was prepared by the conventional melt quenching technique. The focus is on characterizing the physical and structural aspects as well as the optical properties of the glass substrate. The physical properties of zinc silicate samples were assessed using the densitometer and their physical appearance. In addition, the materials' amorphous and glassy characteristics were verified using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. Finally, ultraviolet–visible (UV–Vis) spectroscopy and photoluminescence spectrometer were used to study the optical properties of samples. The density of the samples was observed to increase from 2805 to 3878 kg/m3 as the percentage of ZnO in the glass composition increased. X-ray diffraction analysis indicated the absence of sharp peaks in the samples containing up to 0.60 wt% of ZnO, suggesting the presence of an amorphous phase. Furthermore, the results of this study indicate that ZnO-SiO2 glass substrate samples favor direct forbidden transitions, with an increase in ZnO leading to higher absorption and consequently a lower band gap. The photoluminescence spectrum showed blue light emissions at 422 nm, associating with the variation of band gaps in the ZnO phase. Overall, from the interesting results achieved, this zinc silicate-based composite material at 0.60 wt% ZnO can be a potent candidate in optoelectronic applications, among other concentrations used in this study.

Analysis of tourism destination centrality and structural properties of tourism system: Complex network perspective

ourism has become a new way of living with the living standard development. This study analyses the tourism destination centrality and spatial patterns of the tourism system using complex network analysis. An analysis of 245 destinations in the South of Thailand has found that the network has a low network density, large average path length and low clustering coefficient. Some a small number of high-degree destinations connect to each other, while most connect to others with a low degree. The network comprises 18 subnetworks that destinations densely connect to others in the same subnetwork but sparsely connect to others in different ones. Destinations play different roles in the network based on which a centrality measure is used, degree, betweenness and closeness centrality. 31 destinations with high hub and authority centrality are the centers playing as hubs of the network. The study’s findings draw implications for the sector.

La2O3-CeO2-Supported Bimetallic Cu-Ni DRM Catalysts.

The present work is focused on nickel catalysts supported on La2O3-CeO2 binary oxides without and with the addition of Cu to the active component for the dry reforming of methane (DRM). The catalysts are characterized using XRD, XRF, TPD-CO2, TPR-H2, and low-temperature N2 adsorption-desorption methods. This work shows the effect of different La:Ce ratios (1:1 and 9:1) and the Cu addition on the structural, acid base, and catalytic properties of Ni-containing systems. The binary LaCeOx oxide at a ratio of La:Ce = 1:1 is characterized by the formation of a solid solution with a fluorite structure, which is preserved upon the introduction of mono- or bimetallic particles. At La:Ce = 9:1, La2O3 segregation from the solid solution structure is observed, and the La excess determines the nature of the precursor of the active component, i.e., lanthanum nickelate. The catalysts based on LaCeOx (1:1) are prone to carbonization during 6 h spent on-stream with the formation of carbon nanotubes. The Cu addition facilitates the reduction of the Cu-Ni catalyst carbonization and increases the number of structural defects in the carbon deposition products. The lanthanum-enriched LaCeOx (9:1) support prevents the accumulation of carbon deposition products on the surface of CuNi/La2O3-CeO2 9:1, providing high DRM activity and an H2/CO ratio of 0.9.

Vibrational Spectra of Highly Anharmonic Water Clusters: Molecular Dynamics and Harmonic Analysis Revisited with Constrained Nuclear-Electronic Orbital Methods.

Vibrational spectroscopy is widely used to gain insights into structural and dynamic properties of chemical, biological, and materials systems. Thus, an efficient and accurate method to simulate vibrational spectra is desired. In this paper, we justify and employ a microcanonical molecular simulation scheme to calculate the vibrational spectra of three challenging water clusters: the neutral water dimer (H4O2), the protonated water trimer (H7O3+), and the protonated water tetramer (H9O4+). We find that with the accurate description of quantum nuclear delocalization effects through the constrained nuclear-electronic orbital framework, including vibrational mode coupling effects through molecular dynamics simulations can additionally improve the vibrational spectrum calculations. In contrast, without the quantum nuclear delocalization picture, conventional ab initio molecular dynamics may even lead to less accurate results than harmonic analysis.

Self-assembly of macrocyclic oligofurans to create novel organic nanotubes through π–π stacking: a computational study

ABSTRACT In this manuscript, the potential utility of 6CF macrocyclic oligofuran is theoretically investigated to create novel nanotubes. The energetic, electronic, structural and topological properties of π-stacked systems are examined at B3LYP/6-31 + G(d), wB97XD/6-31 + G(d) and M06-2X/6-31 + G(d) levels of theory. The findings indicate that the self-assembly of 6CF macrocyclic oligofurans can be considered to create organic nanotubes through π–π stacking. The strength and nature of π-π interactions are examined using the atoms in molecules (AIM) approach. Meaningful relationships are obtained between stability, electronic properties and the number of stacked π-conjugated macrocyclic oligofurans. The stability and polarisability of π-stacked systems are amplified by increasing number of macrocycles. Reverse behaviours are found for the values of band gap, electronic chemical potential and first ionisation energy.

First-principle study of shear deformation effect on Mg adsorption by monolayer SnS2.

In this study, the effects of different shear deformations on the structural stability, electronic structure, and optical properties of a Mg atom adsorption system of S vacancy defect SnS2 are systematically investigated based on density functional theory. It is shown that the presence of an S-vacancy defect makes the band gap of the SnS2 system significantly smaller than that of the perfect SnS2 system, and the SnS2 system is changed from a direct band gap semiconductor to an indirect band gap semiconductor. The optimal adsorption position of a Mg atom on the S-vacancy SnS2 system is above the S atom where the adsorption energy is the largest and the system is the most stable. The density of states of the adsorption system is predominantly contributed by the S-3p and Sn-5s orbital electrons. The imposition of shear deformation leads to the introduction of certain impurity energy levels in the adsorption system, and the forbidden bandwidth near the Fermi energy level decreases. As compared to the intrinsic SnS2, the absorption and reflection peaks of adsorption systems under different shear deformation are red-shifted and appear in the ultraviolet region. This improves the utilization of the adsorption system for ultraviolet light to a great extent. The model calculations in this paper are performed using the CASTEP module of the Material Studio (MS) software based on the first principles of Density Functional Theory (DFT) (Wei et al. in Physica B 545:99-106, 2018) for plane wave artifacts. Geometrical optimization and computational procedures are used to calculate the exchange-correlation energy using the Perdew-Burke-Ernzerhof (PBE) generalized function (Perdew et al. in Phys Rev B Condens Matter 48:4978, 1993) of the generalized gradient approximation (GGA). The Monkhorst-Pack method (Monkhorst and Pack in Phys Rev B 13:5188-5192, 1976) was used to rationalize the sampling of the highly symmetric k-points in the Brillouin zone. The grid of k-points is set to be 6 × 6 × 1. The plane-wave truncation energy is set to be 400eV. The energy convergence criterion is 1.0 × 10-5eV. The residual stress of all atoms is 0.01eV/Å. A vacuum layer with a thickness of 15Å is set up in the z-direction, which ensures that the interactions of the system along the z-axis between the top and the bottom layers can be ignored during the whole simulation process. We construct a 3 × 3 × 1 SnS2 system containing 27 atoms as the computational model. The intrinsic SnS2 contains 9 Sn atoms and 18 S atoms.

Exploring a new creatininium crystalline salt with succinic acid organic counterion: Structural establishment, spectroscopic analysis and theoretical simulation

This study elucidates the structural, vibrational, and electronic properties of a novel proton-transfer system derived from creatinine and succinic acid named bis (creatininium) succinate (I). Fourier maps and geometric evaluations confirm protonation at the imine sites. Spectroscopic analyses, involving both IR and Raman techniques, were conducted, highlighting the vibrational characteristics of key functional groups. The theoretical predictions of structural parameters and vibrational frequencies align well with experimental findings. Frontier Molecular Orbital analysis emphasized the distinct localization of HOMO and LUMO, hinting at potential intramolecular charge transfers. Molecular Electrostatic Potential maps provided a visual testament to regions of electron density and scarcity, offering predictive insights into reactivity. Hirshfeld surface analysis and fingerprint plots further illuminated the intermolecular interactions within the crystal structure, underscoring the significance of hydrogen bonding in lattice cohesion. The results present a comprehensive understanding of the compound's behaviour, potentially impacting fields demanding molecular stability and specificity.

Local density dependent potentials for an underlying van der Waals equation of state: A simulation and density functional theory analysis.

There is an ever increasing use of local density dependent potentials in the mesoscale modeling of complex fluids. Questions remain, though, about the dependence of the thermodynamic and structural properties of such systems on the cutoff distance used to calculate these local densities. These questions are particularly acute when it comes to the stability and structure of the vapor/liquid interface. In this article, we consider local density dependent potentials derived from an underlying van der Waals equation of state. We use simulation and density functional theory to examine how the bulk thermodynamic and interfacial properties vary with the cutoff distance, rc, used to calculate the local densities. We show quantitatively how the simulation results for bulk thermodynamic properties and vapor-liquid equilibrium approach the van der Waals limit as rc increases and demonstrate a scaling law for the radial distribution function in the large rc limit. We show that the vapor-liquid interface is stable with a well-defined surface tension and that the interfacial density profile is oscillatory, except for temperatures close to critical. Finally, we show that in the large rc limit, the interfacial tension is proportional to rc and, therefore, unlike the bulk thermodynamic properties, does not approach a constant value as rc increases. We believe that these results give new insights into the properties of local density dependent potentials, in particular their unusual interfacial behavior, which is relevant for modeling complex fluids in soft matter.

Effects of soybean β-conglycinin subunits composition on its emulsifying properties and the mechanism

In the soybean β-conglycinin system, subunit composition has an important influence on its emulsification properties. To elucidate the mechanism of subunit action in the emulsification process, the separated and purified β-subunit and the mixture α- and α′-subunits (referred to αα′-subunit) were remixed in varying proportions, and then the physicochemical properties and structural properties of the subunit emulsifying system were characterized. The results demonstrated that when the ratio of αα'-subunit to β-subunit was 5:5, the subunit aqueous dispersion system exhibited a minimum particle size of 47.58 nm, a maximum solubility of 87.21%, and the emulsification stability and emulsification activity were also optimal. Scanning electron microscope (SEM) images revealed excellent cross-linking between αα′-subunit and β-subunit, forming a protein network structure that provided a structural basis for its emulsification. The emulsion with a subunit ratio of 5:5 exhibited the highest fraction of interfacial protein adsorption of 23.43% and the largest interfacial protein concentration of 11.79 mg/m2. Inter-subunit adsorption and emulsion formation were primarily driven by hydrophobic interactions, with the β-subunit exhibiting a higher affinity for adsorption than the αα′-subunit. The action mechanism of the subunits in the emulsion formation was proposed as a “three-stage” process, including establishing an initial weak protein network structure within the aqueous dispersion, followed by developing an emulsion interface layer and ultimately culminating in forming an emulsion gel network structure. Elucidating the emulsifying mechanism at the subunit level is crucial for enhancing the theoretical framework of soybean protein emulsification.

Magnetic properties of B doped Mn-Ga-C based alloys

We present results on the structural and magnetic properties of the B-doped Mn60Ga20C20-xBx system with x = 0, 1, 2, 3, 4 and 5. A ball milling technique followed by pressing the components, and annealing under an ultra-high purity argon atmosphere for 2 h was employed to fabricate the samples. According to the XRD diffraction data, all samples can be described as single-phase compounds (i.e., the Mn3Ga cubic phase in the Pm–3 m space group) where impurity phases did not exceed 5 %. The compounds with x < 5 show similar physical behaviors as the parent, Mn3Ga2C2, which can be generally characterized by a low temperature transition from low to high magnetization states. High boron concentrations were found to completely suppress the antiferromagnetic state. The (x-TC) phase diagram at 10 K has been constructed and discussed. The magnetocaloric measurements result in magnetic entropy changes of 3.0 Jkg-1k−1 at 5 T and ΔTad by direct measurement of about 0.8 K at 1.8 T.

Molecular dynamics study of the mechanical properties of drug loaded model systems: A comparison of a polymersome with a bilayer.

In this work we implement a new methodology to study structural and mechanical properties of systems having spherical and planar symmetries throughout Molecular Dynamics simulations. This methodology is applied here to a drug delivery system based in polymersomes, as an example. The chosen model drug was the local anesthetic prilocaine due to previous parameterization within the used coarse grain scheme. In our approach, mass density profiles (MDPs) are used to obtain key structural parameters of the systems, and pressure profiles are used to estimate the curvature elastic parameters. The calculation of pressure profiles and radial MPDs required the development of specific methods, which were implemented in an in-house built version of the GROMACS 2018 code. The methodology presented in this work is applied to characterize poly(ethylene oxide)-poly(butadiene) polymersomes and bilayers loaded with the model drug prilocaine. Our results show that structural properties of the polymersome membrane could be obtained from bilayer simulations, with significantly lower computational cost compared to whole polymersome simulations, but the bilayer simulations are insufficient to get insights on their mechanical aspects, since the elastic parameters are canceled out for the complete bilayer (as consequence of the symmetry). The simulations of entire polymersomes, although more complex, offer a complementary approach to get insights on the mechanical behavior of the systems.