National Institute Of Materials Physics - Romania

In this study, we expand the processing space of new, quantum-confined one-dimensional lepidocrocite (1DL) titania-based nanofilaments (NFs). Our previous work to date entailed reacting Ti-precursors (e.g., TiB2, TiOSO4, TiN, TiC, etc.) with the quaternary ammonium compound (quat) tetramethylammonium hydroxide (TMAH) for tens of hours under ambient pressures at temperatures ranging from 50 degrees C to 80 degrees C. Herein, we expand the list of quats that result in 1DL NFs to tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), and choline hydroxide (ChoH). We also show that tetrabutylphosphonium hydroxide (TBPH) can be used to the same end result. These quats and TBPH are less toxic than TMAH, especially Cho+, which is fully biocompatible. And, while all the quats and TBPH result in the same 1D product, their de-flocculation in various organic solvents is different. Reacting with less polar quats (e.g., TBA) and washing with less polar solvents (e.g., dichloromethane) favors the formation of porous mesostructured particles. 2D structures are favored if the opposite is chosen. Said otherwise, by the judicious choice of a quat (e.g., TPAH) and solvent (e.g., tert-butanol) combination, we produced stable 1DL colloidal suspensions in dimethyl sulfoxide, methanol, ethanol, acetonitrile, isopropyl alcohol, butanol, and acetone. This enhanced colloidal stability is critical in applications in coatings, inks, and catalytic systems where non-aqueous stable dispersions are paramount. The high band-gap energies, Eg, measured (3.8-3.9 eV) confirm quantum confinement. The Eg are also quite insensitive to d spacings between the 2D sheets. These 1DLs exhibit significant adsorption and dye (rhodamine 6G) degradation capabilities. For example, TEA-1DL colloidal suspensions adsorb 64% of the dye in the dark in about 5 min and decolorize 99% of the remaining dye within 30 min under the irradiance of one sun.

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.

Spin asymmetry is detected in clean Pt(001)-hex by spin-resolved photoelectron spectroscopy even in absence of external sample magnetization. Magnetization of the sample immediately after preparation yields a consistent remnant spin asymmetry in the direction of the applied magnetic field. The surfaces were also characterized by low energy electron diffraction, scanning tunneling microscopy and high resolution core level x-ray photoelectron spectroscopy, allowing one to quantify the surface component, attributed to the last surface layer enriched in electrons. The explanation of the spin asymmetry induced by electron accumulation into the last monolayer is sketched by using band ferromagnetism criteria. The orientation of the spin asymmetry in the nonmagnetized sample coincides with the direction of the rows of the hex reconstruction, while in the magnetized sample it is aligned with the direction of the external magnetizing field. A strong variation of the spin asymmetry as function of the binding energy near the Fermi level, whose amplitude depends also on the median emission angle, suggests a spin textured state in this energy range or the presence of a Stoner gap

A synthetic rational design of core-shell magnetic nanomaterials has garnered significant attention for their potential in photocatalysis and adsorption applications. This study presents the synthesis and characterization of a TiO2-based core-shell photocatalyst functionalized with FexOy co-catalyst for the efficient adsorption and degradation of synthetic methylene blue dye. The chemical synthesis technique involved a three-step process consisting in the preparation of TiO2 nanoparticles followed by surface nanocompartmentalization with a ferrihydrite layer exhibiting a flower-like morphology and lastly the calcination of the resulting composite at 400 degrees C to produce a magnetic core-shell nanomaterial. Comprehensive physicochemical characterization was performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultra-high-resolution transmission electron microscopy (UHR-TEM) to elucidate the structural and morphological properties of the synthesized materials. Photodegradation experiments were conducted under both UV and Visible light irradiation using methylene blue as a model contaminant. The results revealed remarkable photocatalytic performance, with nearly instantaneous adsorption of the dye onto the catalyst surface, followed by efficient photodegradation. Detailed investigations confirmed that the adsorption process occurred at an exceptionally rapid rate, which was attributed to the unique surface functionalization and nanocompartmentalized structure of the core-shell material.

Exchange biasing of oxide-DMSs (dilute magnetic semiconductors) in exchange bias nanostructures, which are essential for use in spin-based electronic devices, presents a challenge because, in the available literature, exchange coupling typically occurs between secondary phases, with oxide-DMS not being involved. The experimental results presented in this study are consistent with the participation of Fe-doped ZnO (oxide-DMS) as a ferromagnetic (FM) component in the exchange bias (EB) of the ZnFeO system. The study was conducted on ZnFeO nanostructured systems with a 2 at% iron concentration, which were processed by the decomposition of Zn-Fe-propionates and annealing in an Ar-5%H-2 atmosphere at temperatures between 480 degrees C and 510 degrees C and times between 60 min and 100 min. The magnetization investigations support the coexistence of an FM phase with a Curie temperature above 300 K, an antiferromagnetic phase with a Neel transition, T-N, at about 200 K and a disordered spin-glass-like phase with a transition, T-SG, at about 50 K. All samples show the EB effect, characterised by a high EB blocking temperature, T-B approximate to 200 K, and/or a low EB blocking temperature, T-B approximate to 50 K. The analysis of experimental data provides evidence for the exchange biasing of Fe-ZnO (oxide-DMS) by the FeO (AFM) phase and/or SG phase. The exchange-biasing of Fe-ZnO oxide-DMS is promising for developing new materials (e.g., FM electrodes) to improve the efficiency of injecting highly spin-polarised currents in spintronic devices and to increase the device operating temperature.

In this study, thin films of copper oxide (CuO) were deposited on indium-doped tin oxide (ITO) layers supported on glass substrates using a simple and low-cost home-made pneumatic spray technique at 350 degrees C for different deposition times (5 min, 10 min, 15 min, 20 min). Copper chloride (CuCl22H(2)O) was used as copper source at a concentration of 0.05 mol/l. X-ray diffraction patterns revealed that the films were polycrystalline with a monoclinic structure in the preferred directions (111) and (-111). Increasing the deposition time led to an increase in grain size from 11.85 to 14.73 nm. Surface analysis by scanning electron microscopy revealed improved uniformity and horizontal growth of the CuO films with increasing roughness at a deposition time of 20 min. UV-Visible measurements showed a decrease in transmittance from 73 to 47% for the wavelength range (300-1100 nm) with increasing deposition time, accompanied by a decrease in the reflectance of the films. The energy gap (Eg) decreased from 2.17 to 2.44 eV, while the Urbach energy increased with increasing spray time from 0.145 to 0.33 eV. The prepared films had absorption coefficients greater than 5 x 10(4) cm(-1) in the visible range, which diminished in the near-infrared range. The refractive index ranged between 2.01 and 3.00, whereas the dielectric constant (epsilon(r)) increased from 3.65 to 9.17.

This study examines the impact of shale volume (Vsh) and clay mineral distribution on the petrophysical properties and reservoir quality of the Matulla Formation in the Gulf of Suez, a critical factor in global hydrocarbon exploration and production. Understanding how shale affects porosity, permeability, and fluid saturation enhances reservoir characterization, optimizing recovery techniques such as hydraulic fracturing and sustainable resource management. The evaluation process involved calculating shale volume using the neutron-density method, with values ranging from 1.9% to 11% across four wells (GS323-1, GS323-2A, GS323-3, GS323-4A). Clay minerals have been identified through Potassium-Thorium (K-Th) cross-plot include chlorite, illite, kaolinite, montmorillonite, and mixed-layer clays. Montmorillonite and chlorite negatively impact porosity and permeability, while kaolinite and illite improve hydrocarbon retention. Shale distribution analysis using the Thomas and Stieber model showed both laminated and dispersed forms, where laminated shales had minimal blockage, and dispersed clays significantly reduced the reservoir quality. Results reveal that wells with low Vsh (GS323-1 and GS323-4A) which ranges from 1.5 to 2% exhibit excellent reservoir quality, with high porosity (14%), high permeability (317-320.7 mD), and low water saturation (32-44%). Moderate Vsh wells (GS323-2A) show reduced porosity (13%), permeability (220 mD), and increased water saturation (46%), reflecting good but diminished quality. High Vsh well (GS323-3) display lower porosity (12%), permeability (140 mD), and moderate water saturation (37%), indicating challenges in fluid flow. This study highlights the need for tailored strategies to mitigate high shale content and swelling clays, offering valuable insights into optimizing hydrocarbon exploration and production in shale-influenced reservoirs worldwide.

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.

This work investigates photoactive inorganic powders (SiO2, IrSiO2, and IrO2/IrSiO2) and their derivatives modified with metallated porphyrin, focusing on their ability to generate reactive oxygen species (ROS) under visible light exposure. The core material, SiO2, exhibits a tubular morphology and a high density of optically active defects. Modifiers such as metallic and iridium oxide nanoparticles, along with porphyrin, are employed to enhance light absorption and the generation of singlet oxygen (O-1(2)) for potential biomedical applications. The time-dependent photogeneration of singlet oxygen is monitored using a Singlet Oxygen Green Sensor (SOSG), and its reactivity is evaluated in relation to DL alpha-Tocopherol through a spectrofluorimetric analysis. The photoactive materials, both before and after porphyrin modification, are characterized using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), UV-Vis Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), N-2 adsorption-desorption measurements, and zeta potential measurements.