National Institute Of Materials Physics - Romania

The present study investigates the influence of strontium (Sr) content on the intrinsic properties of barium strontium titanate (Ba1-xSrxTiO3, BST) which was successfully prepared by the conventional solid-state reaction with different concentrations of strontium (x = 0, 0.3, 0.5, 0.6, 0.7, 1). The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and diffuse reflectance spectroscopy, the dielectric properties being also investigated. Structural and vibrational analyses reveal a structural phase transition from tetragonal to cubic at x = 0.4, with a linear decline of the tetragonality ratio as well as a shrinkage in the unit cell volume that occur with increasing Sr content. The morphological study shows that the grain size decreases as the Sr content increases in the tetragonal phase. Yet, upon the phase transition from tetragonal to cubic, the grain size initially increases, followed by a subsequent decrease with further Sr addition. It has been found that the band gap shows a decrease as Sr content increases. The temperature dependence of the dielectric parameters reveals that the Curie temperature as well as the dielectric constant and the loss tangent are strongly affected by the addition of Sr. The activation energy derived from the dielectric response, was found to be in the range 0.685-1.065eV, suggesting the dominance of doubly ionized oxygen vacancy for conduction and relaxation mechanism. Ab initio calculations were done employing the Linear Combination of Atomic Orbitals (LCAO) method. The bandgap energy (Eg) and the structural parameters were calculated using various types of exchange-correlation functionals (PWGGA, PBE, B3LYP and PBE0). A good agreement with the experimental results is achieved using the PBE0 functional. This study contributes to a better understanding of the structure-property relationship in BaSrTiO3 and provides valuable insights for optimizing its performance in various technological applications.

The study of spectral gamma-ray logs plays a critical role in understanding the lithofacies and depositional environments of subsurface geologic formations. This research focuses on the Lam Member within the Habban oilfield, located in the Sab'atayn Basin, Yemen. By integrating spectral gamma-ray data with core analysis and other geological datasets, this study aims to provide insights into the stratigraphic distribution, mineral composition, and depositional processes of the Lam Member. Key parameters, such as thorium, uranium, and potassium concentrations, recorded from two wells were analyzed to infer sedimentary characteristics and environmental conditions. The results reveal significant lithologic heterogeneity and suggest a complex interplay of fluvial and marine depositional systems, enhancing the understanding of the basin petroleum potential. The Lam Member comprises interbedded carbonate (dolomite) and claystone with intercalated sandstone. Spectral gamma-ray results indicate that clay minerals primarily consist of mixed-layer clays, chlorite, kaolinite, and minor illite. Based on the Th/U ratio (less than 2), the depositional environment is identified as marine.

Over the past decades, extensive research has demonstrated and confirmed the antioxidant potency of polyphenols, which due to these properties, are now widely recognized for their ability to enhance cell viability. This study investigates the antioxidant capacity of seven green leafy vegetables on in vitro mouse (L929) and human (BJ) fibroblast cell lines, aiming to determine if polyphenols could aid the regeneration of connective tissue, which would be strongly beneficial in wound healing and tissue repair, a process where fibroblast thriving is essential. The antioxidant capacity of extracts was investigated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, UV-Vis spectroscopy, and amperometry, with quercetin serving as a standard. The EC50 values for the extracts were equivalent to approximately 5 mu M quercetin, derived from a concentration range of 20 to 100 mg of fresh leaves per mL. In vitro investigations revealed that all extracts, except lovage, promoted high viability (over 80%) in both cell cultures, as shown by MTS assay results and fluorescence microscopy. Additionally, Tumor Necrosis Factor (TNF)-alpha and Lipopolysaccharide (LPS) were employed as reactive oxygen species (ROS) antagonists, and the Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay was used to demonstrate the extract's scavenging activity on fibroblasts in vitro. For some extracts, a reduction in oxidative stress compared to the cells basal metabolic conditions was observed.

Background/Objectives: In this paper, we report the development of the first chrome-doped hydroxyapatite in a poly (vinyl alcohol) (PVA) matrix enriched with amoxicillin for biomedical applications. The development of chromium-doped hydroxyapatite coatings in a PVA matrix enriched with amoxicillin aims to provide new biomaterials with improved physico-chemical and biological properties, making them promising candidates for biomedical applications. Methods: Through ultrasound studies, we obtained valuable information on the stability of the samples. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, metallographic microscopy (MM), and atomic force microscopy (AFM) were employed for the characterization of the samples. The biocompatibility of the CrHApAPV and CrHApAPV-Ax coatings was assessed using the MG63 human osteoblast-like cell line. To evaluate the cytotoxic potential of these coatings, the cell viability was quantified using the MTT assay after 24 h of incubation. The antibacterial activity of the coatings was evaluated with the aid of the reference strain Pseudomonas aeruginosa ATCC 27853 (P. aeruginosa). Results: The XRD patterns of CrHApAPV and CrHApAPV-Ax samples were examined to evaluate the effects of PVA and amoxicillin on the lattice parameters, unit cell volume, and average crystallite sizes. The results of the in vitro antibacterial assay demonstrated that both the CrHApAPV and CrHApAPV-Ax coatings exhibited very good antibacterial properties for all the tested time intervals. Conclusions: Our results underline the stability of the analyzed samples. Moreover, our physico-chemical and biological studies highlight that CrHApAPV and CrHApAPV-Ax coatings could be considered promising materials for biomedical uses.

This study presents an ultrasound-assisted synthesis of (3-cyclodextrin/hydroxyapatite composites to be used as green and safe auxiliaries in the tanning process. A combination of spectroscopic and non-spectroscopic techniques such as DLS (dynamic light scattering), ZP (zeta potential), XRD (X-ray diffraction), SEM (scanning electron microscopy) and ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) were used to thoroughly characterize the eight composites obtained by varying the ultrasound process parameters. While not cytotoxic, all composites had strong antibacterial action against Brevibacterium lines, Staphylococcus aureus, Escherichia coli, and Staphylococcus epidermis. All composites underwent lab-scale tanning tests, but only those exhibiting the most suitable set of tanning abilities underwent pilot-scale testing. The composites' interaction with the collagen matrix was assessed by micro-DSC (micro-differential scanning calorimetry), TG/DTG/ DTA (thermal analysis), 1H unilateral NMR (proton nuclear magnetic resonance), ATR-FTIR, in-situ temperature synchrotron-based XRD and standard tests (UNI EN ISO 3380: 2015, UNI EN ISO 2589: 2016, UNI EN ISO 105B02:2014). Thermal stability, dye penetration, thickness, colour fastness, surface appearance and microbiological protection were all improved for the leather treated with a small amount of composite added to the wet finish float. These findings demonstrate the benefits of (3-cyclodextrin/hydroxyapatite composites as safe and sustainable tanning additives.

We present a comprehensive investigation into the synthesis, phase evolution and valence state of vanadium (V) in V1_xFexO2 (x = 0 %, 0.5 %, 0.75 %, 1.0 %) compounds. Polycrystalline samples have been synthesized with solid-state reaction method, followed by thermal annealing. X-Ray Powder Diffraction (XRPD) analyzed by Le Bail method revealed the transformation from monoclinic (M1) phase (space group: P21/c) to triclinic (T) one with increasing Fe concentration. Additionally, a monoclinic (M2) phase (space group: C2/m) emerged at 1.0 % Fe doping. Temperature-dependent XRPD and diffuse reflectance measurements elucidated the phase transitions during heating cycles, showing the impact of Fe doping on the system's behavior. The construction of a complete phase diagram for the V1_xFexO2 system (x <= 1.0 %) was achieved, addressing ambiguities in the low-Fe concentration region. X-ray Photoelectron Spectroscopy (XPS) further confirmed the influence of Fe doping on the vanadium valence states, indicating an increase of V5+ sites and therefore a lattice distortion and stabilization of the triclinic phase. The metal-insulator transition temperature (TMIT) appears to be almost constant. Post-annealing led to the reinstatement of the M1 phase in all samples, and a modified phase diagram was constructed. The accompanied decrease of V5+ ions contributed to the destabilization of the T and M2 phases, favoring the thermodynamically stable M1 phase. The findings provide valuable insights into the complex phase behavior of V1_xFexO2 compounds, showcasing a significant interplay between charge redistribution, the vanadium valence state, and the oxygen defects of the system.

In this study, we developed a ternary nanocomposite using graphene oxide (GO), multiwalled carbon nanotubes (MWCNTs), and tungsten trioxide (WO3), nanostructures, synthesized via a straightforward chemical process with ultrasound assistance. The initial composition was GO/MWCNT, later combined with WO3 to form the GO/ MWCNT: WO3 (25/25:50) structure. Characterization was performed using X-ray diffraction, which revealed the multiphase nature of the WO3 nanostructures. Scanning Electron Microscopy showed the one-dimensional CNTs interwoven with graphene oxide sheets decorated with densely populated WO3 nanopetals. Fourier transform infrared and Raman spectroscopy confirmed the chemical composition of the system. The photocatalytic degradation of Rhodamine-B in water under visible light irradiation was significantly enhanced using the GO/

Ag8SnS6 (ATS) nanoparticles, with a band gap of 1.35 eV, which is located exactly at the Schockley-Queisser optimal value for a single-junction solar cell, were utilized as a photoabsorber component in solid state photovoltaic devices. The as-made particles were capped with long aliphatic chains of oleic acid and oleylamine. After surface functionalization of the shorter and extremely basic formamidinium cations, an increase of the absorption coefficient throughout the visible spectrum range was observed. The ligand exchange led also to a slight increase of the band gap, by a value of 0.05 eV. XRD, XPS, UPS, diffuse reflectance, TEM and EDX characterization studies revealed the structure of the nanoparticles and finally proof-of-concept thin film solar cells were fabricated. A maximum photoconversion efficiency of 0.22% was achieved for the as-made particles.

The present paper evidences the beneficial effect that the combination of Pt with WO3 and silicotungstic acid (STA) brings to the methanol oxidation electroactivity. To avoid substrate interferences boron doped diamond (BDD) was used as the electrocatalysts support. SEM measurements have shown that the use of a STA/WO3/BDD substrate allows the electrodeposition of smaller Pt clusters, exhibiting better dispersion, higher homogeneity in terms of size and enhanced electrochemically active surface area. Cyclic voltammetry, polarization and EIS experiments demonstrated than STA addition on the WO3/BDD support induces to the deposited Pt higher activity and improved resistance to fouling during methanol anodic oxidation. Based on the XPS results such behavior was tentatively ascribed to the higher surface concentration of Pt(OH)2 species and adsorbed water that STA presence enables, which may assist in the oxidative desorption of reaction intermediates.

We investigate the second-order Floquet topological (SOFT) phase transitions, from the perspective of spatial symmetries. In this respect, we consider a generic honeycomb lattice Floquet topological insulator (FTI), realized by circularly polarized light irradiation, in the presence of spin-orbit coupling (Kane-Mele model). We find that our studied FTI presents chiral symmetry on a preferential direction in Fourier space, the same property that protects the topological phases in the Su-Schrieffer-Heeger (SSH) model. Thus we were allowed to characterize the SOFT phases in terms of mirror-graded winding numbers (Zak phase). Moreover, our model exhibits C2 and C3 symmetry in Fourier space, a property which lead us to investigate two finite structures having the aforementioned symmetries, namely, rhombic and triangular shapes. Indeed, we find that both of them undergo SOFT phase transitions, characterized by the appearance of 0D corner states symmetrically localized over the whole sheet. Finally, we investigate the C2 and C3 symmetry breaking. Interestingly, we reveal that the corner states are not destroyed, but localize at preferential corners instead, giving rise to a corner polarization.