Maria Stefan

Structural Characterization Of Zinc Sulphide Thin Films By Radial Distribution Function Analysis Using X - Ray Scattering

In the present work we are interested in studies concerning the local structure of amorphous chemical bath deposited (CBD) ZnS thin films by using wide-angle X-ray scattering (WAXS) method. The effect of the thermal treatment on the amorphous ZnS thin films structure it is also evidenced. After the formulation of hypotheses on the local order of the chalcogenide system has been enounced, the radial distribution function (RDF) analysis was done and the atom coordinations were determined. The radius of the first coordination spheres was evaluated by using the correlation function g(r) resulted from the X-ray scattering measurements.

Efficient photocatalytic removal of RhB using magnetic Fe 3 O 4 –SnO 2 nanocomposites containing Sn 2+ interstitial impurities

Fe3O4–SnO2 nanocomposites with SnO2 in the reduced form (without post-annealing) were prepared. X-ray diffraction, high resolution TEM microscopy, X-Ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy and magnetization measurements were used for sample characterizations. Additionally, nitrogen adsorption–desorption isotherms and surface area measurements (BET) were made for porosity and surface area determination. Depending on the amount of SnCl2 used in preparation, tetragonal tin oxide hydroxide Sn6O4(OH)4 or SnO secondary phases were also formed in various samples. XPS analysis shows the presence of surface Sn2+ states and as well as lack, or non-detectable, interstitial tin inside SnO2 nanocrystallites. The presence of Sn2+ surface states determines important changes of both magnetic and photocatalytic properties of samples. Thus Sn2+ surface states determine, on the one hand, an increased efficiency of photocatalytic processes and, on the other hand, a significant decrease of the saturation magnetization of Fe3O4 cores. Moreover, by using ESR spin trapping technique, the generation of reactive oxygen species (·OH, O2·−) resulted by light irradiation of samples was evidenced.

Removal of Lead(II), Cadmium(II), and Arsenic(III) from Aqueous Solution Using Magnetite Nanoparticles Prepared by Green Synthesis with Box–Behnken Design

ABSTRACT Two types of magnetite (Fe3O4) nanoparticles were investigated as adsorbents for the simultaneous removal of Pb(II), Cd(II), and As(III) metal ions from aqueous solution. Magnetite nanoparticles were prepared by two synthesis procedures, both using water as solvent, and are referred to as conventional Fe3O4 nanoparticles and green Fe3O4 nanoparticles. The latter used Citrus limon (lemon) aqueous peel extract as the surfactant. Box–Behnken experimental design was used to investigate the effects of parameters such as initial concentration (20–150 mg L−1), pH (2–9), and biomass dosage (1–5 g L−1) on the removal of Pb(II), Cd(II), and As(III) ions. The optimum parameters for removal of the studied metal ions from aqueous solutions, including the initial ion concentration (20 mg L−1), pH (5.5) and adsorbent dose (5 g L−1), were determined. The pseudosecond-order model exhibited the best fit for the kinetic studies, while adsorption equilibrium isotherms were best described by Langmuir and Freundlich models. The optimum conditions were applied for the treatment wastewater. The removal efficiencies of Pb(II), Cd(II), and As(III) using the conventional and green synthesized Fe3O4 nanoparticles were 59.4 ± 4.3, 18.7 ± 1.9 and 17.5 ± 1.6, and 98.8 ± 5.6, 46.0 ± 1.3, and 48.2 ± 2.6%, respectively. These results demonstrate the potential of magnetite nanoparticles synthesized using C. limon peel extract as highly efficient adsorbents for the removal of Pb(II), Cd(II), and As(III) ions from aqueous solution.

Characterization of Cu2ZnSnS4 thin film deposited by pulse laser deposition

Thin film of Cu2ZnSnS4 (CZTS) was deposited on Si(100) substrate by Pulse Laser Deposition (PLD) technique. The deposition was done in vacuum at 450°C. The formation of CZTS kesterite structure was confirmed by using XRD diffraction and Raman spectroscopy. The morphology and the elemental distribution of the obtained film were investigated by SEM and STEM mapping. The micrograph shows a polyhedral nanograin shape densely packed and the constituent elements are homogeneous distributed in deposited thin film. The reflectance spectrum show maximum and minimum of interference which indicates that the thin film is uniform in thickness and its surface is flat. The band gap value Eg=1.5 eV was determined from reflectance and PL spectra.