National Institute Of Materials Physics - Romania

Electrochemical water splitting is regarded as a viable solution to future energy demands. Considering this, an innovative method to produce efficient oxygen evolution electrodes based on Co and Ni was proposed and successfully developed, where the metal atoms are intimately mixed before the calcination treatment. Electrochemical measurements demonstrated the high oxygen evolution activity and stability of the thus synthesized electrodes, EDX, and XPS revealing that the surface exhibits a remarkable oxidation resistance, allowing the active phase to better maintain its state when subjected to the aggressive positive potential required for oxygen evolution. Moreover, low electrical resistivity was recorded as a result of reduced thickness of the catalytic layer, further increasing the efficiency. These findings provide new insights into the design of durable and high-performance OER electrodes.

We report large-scale synthesis of monolayer WS2 films obtained by sulfurization of oxidized magnetron sputtered monolayer W precursors. Literature routes typically require similar to 800 degrees C, well above the 400 degrees C limit imposed by back-end-of-line (BEOL) integration. Here, using an enhanced chemical vapor deposition (CVD) approach, the magnetron sputtered ultrathin W precursor (a W monolayer film, 0.27 nm thick, which in ambient air becomes a WOx monolayer) is sulfurized at the lowest possible temperature (450 degrees C) within a microreactor, which consists of a sandwich-like structure formed by the precursor and a clean Si substrate. The obtained WS2 material has a good crystallinity and uniform morphology across the entire growth substrate, as confirmed by detailed characterization. These results highlight the versatility of the method combining magnetron sputtering and microreactor-CVD, facilitating its applications to wafer-scale synthesis of monolayer WS2, heterogeneously integrated into electronic circuits (a major objective for next-generation electronics and optoelectronics). Additionally, we investigate in detail the properties of WS2 films synthesized from a bilayer W precursor (0.43 nm thick), under the same conditions, and we calculated the frequencies of the second-order Raman scattering modes. For electrical measurements, we fabricated WS2/few-layer-graphene heterostructures, whose atomically clean interface yields reliable, low-resistance contacts. These devices exhibit resistive switching behavior, likely governed by vacancy migration, making it a promising candidate for memristive applications. Our results demonstrate that electronics-grade monolayer WS2 can be synthesized at 450 degrees C, approaching the BEOL requirement of 400 degrees C.

The main objective of this research is to get a comprehensive view on the subsurface geological data on the Esh El Mellaha area and environs, Red Sea, Egypt. This includes determining the depth and structural characteristics of the basement surface beneath the region, as well as identifying additional gravity and magnetic sources and potential structures within the sedimentary cover. To achieve this goal, Bouguer gravity and aeromagnetic data were used, processed and analyzed. Various depth estimation techniques were employed to analyze subsurface structures, each offering distinct advantages. Euler Deconvolution effectively delineates structural discontinuities and fault systems, while the Source Parameter Imaging (SPI) method improves depth accuracy through wavenumber analysis. The Analytical Signal method enhances resolution, providing detailed depth variations. Across these methods, the estimated depth ranges from 300 to 5000 m, with an average depth of approximately 2380 m, offering critical insights into the subsurface geological framework. Two-dimensional (2.5D) modeling was conducted on two selected gravity and magnetic profiles to estimate the depth, dip, density, and magnetic susceptibility of the source bodies. Additionally, three-dimensional (3D) modeling was applied to Bouguer gravity and Reduced-to-the-Pole (RTP) magnetic profiles, providing a detailed representation of the causative source structures. The results of the 3D inversion of gravity and magnetic data reveal the subsurface distribution of density and magnetic susceptibility, aiding in the identification of major geological structures. The sectional maps and 3D models illustrate the vertical and horizontal variations in subsurface formations, highlighting distinct anomaly zones that may correspond to faults and lithological changes. The obtained results indicate that the sedimentary succession thickness is ranging from 1.0 to 2.2 km, a finding corroborated by the borehole data. Positive structural features identified in these models suggest promising targets for potential hydrocarbon reservoirs.

This study synthesized Mg-doped ZnO nanoparticles using the co-precipitation method with doping concentrations ranging from 2 % to 8 %. The structural, morphological, and optical properties of the synthesized nanoparticles were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Visible spectroscopy. XRD analysis confirmed the successful incorporation of Mg2+ ions into the ZnO lattice, evidenced by lattice parameter shifts and a significant reduction in crystallite size from 30.91 nm (pure ZnO) to 18.10 nm (6 % Mg doping). SEM images showed uniform morphology with reduced particle agglomeration at optimal doping levels, while FTIR analysis identified characteristic Zn-O and Mg-O bonding vibrations, confirming structural integrity. UV-Vis spectroscopy revealed strong absorbance in the UV region, with the band gap energy decreasing from 3.68 eV (pure ZnO) to 3.16 eV (6 % Mg doping), indicating enhanced optical properties conducive to improved photocatalytic performance. The photocatalytic activity of Mg-doped ZnO nanoparticles was evaluated by degrading Basic Fuchsin (BF) dye under UV light irradiation. The Mg-doped ZnO nanoparticles exhibited significantly enhanced photocatalytic performance compared to undoped ZnO, achieving a maximum degradation efficiency of 99.38 % at 6 % Mg doping within 100 min. Optimal photocatalytic conditions were observed at pH 6, using 0.1 g of catalyst and an initial dye concentration of 10 ppm. These enhancements were attributed to improved electron-hole pair separation and increased generation of reactive oxygen species (ROS), facilitated by the strategic incorporation of Mg. To complement the experimental findings, Density Functional Theory (DFT) simulations were performed, integrating the Conductor-like Screening Model for Realistic Solvation (COSMO-RS), Reduced Density Gradient (RDG), and Quantum Theory of Atoms in Molecules (QTAIM). The DFT analysis revealed enhanced charge separation, optimized electron transfer dynamics, and stronger adsorption interactions at Mg-doped sites, which promoted efficient ROS generation. The calculated valence band (VB) and conduction band (CB) edge potentials supported the formation of a Z-scheme heterojunction mechanism, enhancing charge separation and minimizing recombination. These theoretical insights aligned with the experimental observations, confirming that Mg doping effectively enhances photocatalytic efficiency by optimizing electronic interactions and promoting reactive surface dynamics. This integrated experimental and theoretical investigation demonstrates that Mgdoped ZnO nanoparticles exhibit superior photocatalytic properties, making them highly effective for environmental remediation applications, particularly in degrading organic pollutants in wastewater treatment. The study highlights the potential of Mg-doped ZnO as a promising photocatalyst for sustainable environmental solutions.

In this work a method in two steps for the preparation of the composites based on poly(ortho-toluidine) (POT) and the MoS2 and WS2 sheets was reported. In the first step, by ball-milling of mixtures of MoS2 and WS2 particles, the sheets of MoS2 and WS2 (MoS2: WS2) with weight ratio equal to 3:1, 1:1 and 1:3 were prepared. In the second step, the interaction in solid-state of the MoS2: WS2 samples with POT in emeraldine-base (POT-EB) and emeraldine-salt (POT-ES) was used to obtain composites of the type MoS2: WS2/POT-EB and MoS2: WS2/ POT-ES. Using X-ray diffraction (XRD), FTIR spectroscopy, Raman scattering and X-ray photoelectron spectroscopy (XPS), we demonstrate that: i) the ball-milling method can allow the preparation of the MoS2 and WS2 sheets with different stacking order, ii) the interaction of POT-EB with the MoS2: WS2 samples involves the transformation of some repeating units of the type EB into ES; and iii) the interaction of POT-ES with the MoS2: WS2 samples leads to the appearance of new positive charges onto macromolecular chains which are compensated by S2- ions. According to thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), all samples are demonstrated to be stable up to 230 degrees C. Dielectric spectroscopy data reveal a complex dependence of DC electrical conductivity on frequency, temperature, and composite concentration. We use the apparent activation energy, defined as the derivative of the logarithm of conductivity with respect to the inverse temperature. The obtained results indicate that apparent activation energy is influenced by system composition via filling factors. The electrical properties of these heterogeneous materials are described using Lichtenecker's mixing laws. For components with similar electrical properties, the effective conductivity and apparent activation energy were determined as linear combinations of the individual conductivities and activation energies, respectively, weighted by the component concentrations. Our findings align with experimental data, offering a framework for understanding conductivity and activation energy in multi-component systems.

Biodegradable polymers like poly(epsilon-caprolactone) (PCL) are widely studied for their potential applications in biomedical and environmental fields. To enhance PCL's thermal, and bioactive properties, researchers have explored composite formulations with other polymers or bioactive compounds. Oleic acid (OA), a naturally occurring fatty acid, has been identified as a promising modifier. This study investigates the modification of PCL with OA using an eco-friendly catalyst to improve its functional properties. PCL was grafted with OA using Maghnite-H+, a heterogeneous solid catalyst clay activated via sulfuric acid treatment. A response surface methodology with a central composite design was applied to optimize synthesis parameters, including reaction temperature, duration, and catalyst concentration. The resulting composite was characterized using FTIR and NMR to confirm structural modifications, while its thermal stability was evaluated. Antioxidant activity was assessed using the DPPH radical scavenging assay, and antimicrobial potential was tested against various microorganisms. The PCL-OA composite exhibited enhanced antioxidant activity, with increased radical scavenging efficiency compared to unmodified PCL. Antimicrobial tests revealed strain-dependent effects, with improved inhibition observed in specific combinations of caprolactone, OA, and PCL-OA. The findings suggest that OA incorporation enhances PCL's bioactivity, making it a promising material for biomedical and packaging applications.

In this study, we detailed the fabrication and characterization of photovoltaic structures based on PTB7:ICBA (1:1, wt.%) bulk-heterojunction on optical glass substrates by spin-coating. Some samples were deposited on a flat substrate, and others were placed on a patterned substrate obtained by nano-imprinting lithography; the induced effects were analyzed. We demonstrated that using a patterned substrate enhanced the maximum output power, primarily because the short-circuit current density increased. This can be considered a direct consequence of reduced optical reflection and improved optical absorption. The topological parameters evaluated by atomic force microscopy, namely, the root mean square, Skewness, and Kurtosis, had small values of around 2 nm and 1 nm, respectively. This proves that the mixture of a conductive polymer and a fullerene derivative creates a thin film network with a high flatness degree. The samples discussed in this paper were fabricated and characterized in air; we can admit that the results are encouraging, but further optimization is needed.

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.

Amyloid beta (A(3) peptide aggregates are well-established biomarkers for Alzheimer's disease, though the complete etiology of this disorder remains elusive. Developing biointerfaces to elucidate the physiological roles of these peptides is essential. This study investigates the aggregation, fibrillation, and interaction of A(3 peptides with conductive, biocompatible nanostructured materials designed for applications involving neuronal cells. Various conductive, rigid, and flexible surfaces, both functionalized and non-functionalized with A(340 fibrils, were fabricated. These included glass substrates and poly(methyl methacrylate) electrospun fiber networks coated with gold via magnetron sputtering. The substrates were also functionalized through physical adsorption with poly-L-lysine and collagen, known to support cell proliferation, as well as with the inverse-A(340 peptide and an Amyloid Protein Non-A(3 Component, and the results were compared. The scaffolds were characterized using scanning electron microscopy, X-ray diffraction, atomic force microscopy, contact angle and electrical measurements, while their biological interactions were assessed using MTS assays, fluorescence imaging, and scanning electron microscopy. Fibroblast L929 and neuroblastoma SH-SY5Y cell lines were used as models, with results indicating an elevated cell viability, comparable to the control. The developed nanostructured surfaces are highly promising for integration into advanced neuromorphic engineering devices, as they have proven capable of maintaining their structural integrity when exposed to proteases.

Chalcogenide glasses (ChGs) are a class of amorphous materials presenting remarkable mechanical, optical, and electrical properties, making them promising candidates for advanced photonic and optoelectronic applications. With the increasing integration of artificial intelligence in modern materials design, we are able to systematically select, prepare, and optimize appropriate compositions for desired applications in a manner that was unachievable before. This study employs various machine learning models to reliably predict the refractive index at 20 degrees C using a small dataset of 541 samples extracted from the SciGlass database. The input for the algorithms consists of a selected set of physico-chemical features computed for the chemical composition of each entry. Additionally, these algorithms served as inner models for an ensemble logistic regression estimator that achieved a superior R2 value of 0.8985. SHAP feature analysis of the second-best model, CatBoostRegressor (R2 = 0.8920), revealed the importance of elemental density, atomic weight, ground state atomic gap, and fraction of p valence electrons in tuning the value of the refractive index of a chalcogenide compound.