Bashar Lahlouh

Effects of molybdenum concentration and valence state on the structural and magnetic properties of BaFe 11.6 Mo x Zn 0.4− x O 19 hexaferrites

Barium hexaferrites BaFe11.6MoxZn0.4−xO19 (x= 0.1, 0.2, 0.4) were prepared by precipitation of the precursors using wet chemical mixture method and then sintering the dried powders at 1100 °C. The properties of the prepared samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer, and Mössbauer spectroscopy. XRD patterns revealed that all prepared samples had BaFe12O19 hexaferrite structure as a majority phase. SEM images demonstated that the samples consisted mainly of hexagonal platelet-like grains with diameters ranging from 100 to 500 nm. Mössbauer spectra revealed that Zn2+ ions occupy 4f1 sites leading to the splitting of the 12k component. However Mo6+ ions occupy 2b sites while Mo4+ prefer 4f1 and 12k sites. For the sample with x = 0.4,Mo6+ and Mo4+ ions were found to have preference for 2b and 12k sites, respectively, and to induce the development of Fe2+ ions in the hexaferrite, leading to noticeable changes in the magnetic properties of the system. The observed magnetic properties were found to be consistent with the preferential site occupation of metal ions, and the hyperfine fields derived from Mössbauer spectra of these samples.

Analytical study of thermal annealing behaviour of erbium emission in Er2O3-sol–gel silica films

Room-temperature 1535 nm band photoluminescence in ~126 nm silica films (6 at% doping), produced by spin coating an Er2O3 and tetraethylorthosilicate sol–gel formulation on silicon substrates, was studied as a function of vacuum furnace annealing (500–1050 °C). Emission is strongly enhanced for annealing near 850 °C, which is shown by modelling the temperature dependence as arising from thermally activated removal of hydroxyl ions. Suitability of such a process for silicon-based applications is discussed.

Room-temperature silicon band-edge photoluminescence enhanced by spin-coated sol–gel films

Photoluminescence is observed at room temperature from phonon-assisted band-to-band emission in Si (1.067 eV peak) using unpatterned bulk p-type silicon wafer samples that were spin-coated with Er-doped (6 at. %) silica-gel films (0.13 m) and vacuum annealed (strongest emission for ~700 C). Comparative study of annealing behavior indicates two-orders of magnitude efficiency enhancement. Emission from Er +3 ions in the silica film is used to gauge relative emission strengths. Mechanisms for inducing

Purification and biochemical characterization of photo-active membrane protein bacteriorhodopsin from Haloarcula marismortui, an extreme halophile from the Dead Sea

Bacteriorhodopsin (BR) is an exciting photo-active retinal protein with many potential industrial applications. In this study, BR from the extremely halophilic archaeon Haloarcula marismortui (HmBR) was purified successfully using aqueous two phase extraction method. Absorption spectroscopy analysis showed maximum absorption peak of HmBR retinal protein (λmax) at 415 nm. The purified HmBR was visualized by SDS-PAGE, with a subunit molecular mass of 27 kDa, and its identity was confirmed by resonance Raman spectroscopy, Fourier transform infrared spectroscopy and atomic force microscopy. The effect of pH and salt concentration on the absorption spectrum of HmBR was evaluated. Red-shifted in λmax of HmBR was recorded at acidic condition (pH 5) and HmBR showed remarkable optical activity under high salinity condition. The photoelectric activity of HmBR was evaluated by measuring the DC-voltage generated from HmBR coated on indium tin oxide (ITO) glass when light illumination was applied.