Publications

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.

In this study, we investigate the electrochemical performance and stability of silicon thin films, deposited by magnetron sputtering, as anodes for lithium-ion batteries (LIBs). The conventional direct current magnetron sputtering and the highly ionized technique high power impulse magnetron sputtering HiPIMS, known to produce high-density thin films, were used for the purpose. Silicon films with thicknesses of 50, 75, 124, 600 and 1000 nm were prepared and the morphology, density, and electrochemical performances of the films produced using both techniques were compared. Characterization of the prepared electrodes showed that the DCMSdeposited films exhibited lower density and large grain sizes, while the HiPIMS-deposited films exhibited higher density and relatively smaller grain sizes. The electrochemical tests revealed that the DCMS-deposited electrodes exhibited discharge capacities of 800 mAh g- 1 and 406 mAh g- 1 at a current density of 5 A g- 1 for electrode thicknesses of 600 nm and 1000 nm , respectively, demonstrating their high potential for fast charging applications. Additionally, these electrodes showed remarkable initial coulombic efficiency (ICE), with the 1000 nm thick electrode achieving an ICE of 96.08 %, outperforming traditional graphite anodes, which was attributed to a larger particle size and a lower SEI resistance. Furthermore, DCMS-deposited Si electrodes showed higher resistance to plastic deformation, which enhanced capacity retention and mitigated volume expansion, demonstrating their potential for high-performance anodes.

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.