Yehia-Alexe Sasa-Alexandra

@inflpr.ro

Low Temperature Plasma Laboratory
National Institute for Laser Plasma and Radiation Physics

Yehia-Alexe Sasa-Alexandra


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https://researchid.co/yehia-alexesasa-alexandra

RESEARCH, TEACHING, or OTHER INTERESTS

Spectroscopy, Nuclear Energy and Engineering, Water Science and Technology, Atomic and Molecular Physics, and Optics
14

Scopus Publications

Scopus Publications

  • Calcium Phosphate–Poly(methyl methacrylate) Composite Layers Synthetized in Radio-Frequency Magnetron Sputtering Discharge
    Andreea Groza, Maria E. Hurjui, Sasa A. Yehia-Alexe, Bogdan Butoi, Silviu D. Stoica
    Polymers, 2026
    Calcium phosphate–poly(methyl-methacrylate) composite layers have been synthetized on silicon substrates in magnetron sputtering discharge by adjusting the radio-frequency power. The electron energy distribution function measured at holder substrate position shifts to lower energies when the radio-frequency power applied to the magnetron source increases from 50 to 150 W and the poly(methyl-methacrylate) molecule dissociation is augmented. The optical emission spectral analysis indicated the dynamics of the excitation and ionization processes in the Ar–calcium phosphate–poly(methyl-methacrylate) plasma mixture, as well as the dissociation patterning of the polymer molecules. The Ca I, P I, and Hα atomic lines and CaO, PO, POH, CO, CH and C2 molecular bands characteristic to the calcium phosphate and poly(methyl-methacrylate) decomposition were evidenced. At 150 W radio-frequency power a reduction in the polymer content in the composite layer volume was observed even if the α-CH3 main chain and the C=O molecular bands are still present. More C-C/C-H, C-OH/C-O-C polymeric bonds were revealed at the layer surface, indicating the formation of plasma polymers. The Ca/P ratio changes from 1.72 to 1.9 at 50 to 150 W, respectively, maintaining the amorphous structure of the layers. In this power range, the transition of layer surface morphologies from grain-like to worm-like plasma polymer characteristics is connected to an increase in plasma ion density and layer thickness.
  • Deuterium release from beryllium layers by laser induced plasma ablation and laser induced desorption coupled with quadrupole mass spectrometry
    Sasa-Alexandra Yehia-Alexe, Mihai Serbanescu, Paul Dinca, Bogdan Butoi, Maria Elena Zarif, et al.
    Spectrochimica Acta Part B Atomic Spectroscopy, 2025
  • Influence of Electron Beam Irradiation and RPMI Immersion on the Development of Magnesium-Doped Hydroxyapatite/Chitosan Composite Bioactive Layers for Biomedical Applications
    Andreea Groza, Maria E. Hurjui, Sasa A. Yehia-Alexe, Cornel Staicu, Coralia Bleotu, et al.
    Polymers, 2025
    Magnesium-doped hydroxyapatite/chitosan composite coatings produced by the radio-frequency magnetron sputtering technique were exposed to 5 MeV electron beams of 8 and 30 Gy radiation doses in a linear electron accelerator. The surfaces of unirradiated layers are smooth, while the irradiated ones exhibit nano-structures with sizes that increase from 60 nm at a 8 Gy dose to 200 nm at a 30 Gy dose. Young’s modulus and the stiffness of the layers decrease from 58.9 GPa and 10 µN/nm to 5 GPa and 2.2 µN/nm, respectively, when the radiation doses are increased from 0 to 30 Gy. These data suggest the diminishing of the contribution of the chitosan to the elasticity of the magnesium-doped hydroxyapatite/chitosan composite layers after electron beam irradiation. The biological capabilities of the coatings were assessed before and after their immersion in RPMI-1640 cell culture medium for 7 and 14 days, respectively, and further cultured with a MG63 cell line (ATCC CRL1427) in Dulbecco’s Modified Eagle Medium supplemented with fetal bovine serum, penicillin–streptomycin, and L-glutamine. Thus, 1 µm spherical structures were developed on the surfaces of the layers exposed to a 30 Gy radiation dose and immersed for 14 days in the RPMI-1640 biological medium. The molecular structures of all the RPMI-1640 immersed samples were modified by the growth of a carbonated hydroxyapatite layer characterized by a B-type substitution, as Fourier Transform Infrared Spectroscopy revealed. The biological assay proved the increased biocompatibility of the layers kept in RPMI-1640 medium and enhanced MG63 cell attachment and proliferation. Atomic force microscopy analysis indicated the elongated fibroblastic cell morphology of MG63 cells with minor alteration at 30 Gy irradiation doses as a result of layer biocompatibility modifications.
  • THE INFLUENCE OF THE SUBSTRATE TEMPERATURE ON THE PHISICOCHEMICAL PROPERTIES OF CALCIUM PHOSPHATE LAYERS DEPOSITED BY LOW POWER RADIO-FREQUENCY MAGNETRON SPUTTERING DISCHARGE
    UPB Scientific Bulletin Series B Chemistry and Materials Science, 2025
  • Biological and Physicochemical Analysis of Sr-Doped Hydroxyapatite/Chitosan Composite Layers
    Maria Elena Zarif, Bogdan Bita, Sasa Alexandra Yehia-Alexe, Irina Negut, Gratiela Gradisteanu Pircalabioru, et al.
    Polymers, 2024
    In this work results are presented on the evaluation of HAp, HApSr, HAp_CS, and HApSr_CS layers deposited on Ti substrates regarding L929 cell viability and cytotoxicity as well as antimicrobial activity against Staphylococcus aureus, in connection with their physicochemical properties. The HAp and HApSr layers generated by radio-frequency magnetron sputtering technique were further covered with chitosan by a matrix-assisted pulsed laser evaporation technique. During the plasma depositions, the Ti substrates were heated externally by a home-made oven above 100 °C. The HApSr_CS layers generated on the unpolished Ti substrates at 100 °C and 400 °C showed the highest biocompatibility properties and antimicrobial activity against Staphylococcus aureus. The morphology of the layer surfaces, revealed by scanning electron microscopy, is dependent on substrate temperature and substrate surface roughness. The optically polished surfaces of Ti substrates revealed grain-like and microchannel structure morphologies of the layers deposited at 25 °C substrate temperature and 400 °C, respectively. Chitosan has no major influence on HAp and HApSr layer surface morphologies. X-ray photoelectron spectroscopy indicated the presence of Ca 2p3/2 peak characteristic of the HAp structure even in the case of the HApSr_CS samples generated at a 400 °C substrate temperature. Fourier transform infrared spectroscopy investigations showed shifts in the wavenumber positions of the P-O absorption bands as a function of Sr or chitosan presence in the HAp layers generated at 25, 100, and 400 °C substrate temperatures.
  • Spectral Analysis of Strontium-Doped Calcium Phosphate/Chitosan Composite Films
    Maria Elena Zarif, Bogdan Bita, Sasa Alexandra Yehia-Alexe, Irina Negut, Andreea Groza
    Polymers, 2023
    Strontium-doped calcium phosphate/chitosan films were synthetized on silicon substrates using the radio-frequency magnetron sputtering technique and the matrix-assisted pulsed laser evaporation technique. The deposition conditions associated with the radio-frequency magnetron sputtering discharge, in particular, include the high temperature at the substrate, which promotes the formation of strontium-doped tetra calcium phosphate layers. The physical and chemical processes associated with the deposition of chitosan on strontium-doped calcium phosphate layers were investigated using Fourier Transform Infrared Spectroscopy, Energy Dispersive X-ray Spectroscopy, and Scanning Electron Microscopy. Mass spectrometry coupled with laser induced ablation of the composite films proved to be a useful tool in the detection of the molecular ions characteristic to chitosan chemical structure.
  • Considerations on hydrogen isotopes release from thin films by laser induced ablation and laser induced desorption techniques
    Sasa-Alexandra Yehia-Alexe, Andreea Groza, Mihai Serbanescu, Maria Elena Zarif, Bogdan Bita, et al.
    Spectrochimica Acta Part B Atomic Spectroscopy, 2023
  • Corrigendum to “Laser ablation of a solid target in liquid medium for beryllium nanoparticles synthesis” [Nucl. Mater. Energy 31 (2022) 101160](S2352179122000473)(10.1016/j.nme.2022.101160)
    Saşa-Alexandra Yehia, Lavinia Gabriela Carpen, Flavian Stokker-Cheregi, Corneliu Poroşnicu, Veronica Sătulu, et al.
    Nuclear Materials and Energy, 2023
  • Calcium Phosphates–Chitosan Composite Layers Obtained by Combining Radio-Frequency Magnetron Sputtering and Matrix-Assisted Pulsed Laser Evaporation Techniques
    Maria Elena Zarif, Sasa Alexandra Yehia-Alexe, Bogdan Bita, Irina Negut, Claudiu Locovei, et al.
    Polymers, 2022
    In this work, we report the synthesis of calcium phosphate–chitosan composite layers. Calcium phosphate layers were deposited on titanium substrates by radio-frequency magnetron sputtering technique by varying the substrate temperature from room temperature (25 °C) up to 100 and 300 °C. Further, chitosan was deposited by matrix-assisted pulsed laser evaporation technique on the calcium phosphate layers. The temperature at the substrate during the deposition process of calcium phosphate layers plays an important role in the embedding of chitosan, as scanning electron microscopy analysis showed. The degree of chitosan incorporation into the calcium phosphate layers significantly influence the physico-chemical properties and the adherence strength of the resulted layers to the substrates. For example, the decreases of Ca/P ratio at the addition of chitosan suggests that a calcium deficient hydroxyapatite structure is formed when the CaP layers are generated on Ti substrates kept at room temperature during the deposition process. The Fourier transform infrared spectroscopy analysis of the samples suggest that the PO43−/CO32− substitution is possible. The X-ray diffraction spectra indicated that the crystalline structure of the calcium phosphate layers obtained at the 300 °C substrate temperature is disturbed by the addition of chitosan. The adherence strength of the composite layers to the titanium substrates is diminished after the chitosan deposition. However, no complete exfoliation of the layers was observed.
  • Laser ablation of a solid target in liquid medium for beryllium nanoparticles synthesis
    Sașa-Alexandra Yehia, Lavinia Gabriela Carpen, Flavian Stokker-Cheregi, Corneliu Poroșnicu, Veronica Sătulu, et al.
    Nuclear Materials and Energy, 2022
  • Organophosphorus toxic compounds degradation in aqueous solutions using single filament dielectric barrier discharge plasma jet source
    Sașa-Alexandra Yehia, Nicoleta Petrea, Nicoleta Grigoriu, Sorin Vizireanu, Maria Elena Zarif, et al.
    Journal of Water Process Engineering, 2022
  • Atmospheric pressure plasma activation of hydroxyapatite to improve fluoride incorporation and modulate bacterial biofilm
    Maria Elena Zarif, Sașa Alexandra Yehia, Bogdan Biță, Veronica Sătulu, Sorin Vizireanu, et al.
    International Journal of Molecular Sciences, 2021
  • Development and Optimization of Single Filament Plasma Jets for Wastewater Decontamination
    S. A. Yehia, M. E. Zarif, B. I. Bita, M. Teodorescu, L. G. Carpen, et al.
    Plasma Chemistry and Plasma Processing, 2020
  • On the Structural, Morphological, and Electrical Properties of Carbon Nanowalls Obtained by Plasma-Enhanced Chemical Vapor Deposition
    Bogdan Bita, Sorin Vizireanu, Daniel Stoica, Valentin Ion, Sasa Yehia, et al.
    Journal of Nanomaterials, 2020