Browsing by Author "Sabrina Roguai"
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Item A simple synthesis of CuO NPs for photocatalytic applications and theirs structural and optical properties.(2021-10-24) Sabrina RoguaiIn this study, the copper nanoparticles were synthesized by simple co-precipitation method which were obtained by heating at 80°C for photocatalytic application. The microstructural characterization of the nanopowder obtained was performed using X-ray diffraction (XRD), SEM, EDS, and Infrared Spectroscopy (IR). The optical properties of nanoparticles were studied by UV-Visible spectroscopy. XRD studies demonstrated that the formation of CuO monoclinic phase and the average grain size of CuO crystallite were found to be 30 nm. The FTIR spectral analysis showed the characteristics peaks of Cu-O bond. The EDAX result indicated that there were no other elemental impurities present in the prepared CuO nanoparticles. SEM images indicate the morphology as a three-dimensional flower-like structure was successfully prepared for subsequent degradation of methylene blue (MB). With regard to the optical proprieties, the value of the bandgap energy equals 1.34 eVItem A structural and optical properties of Cu‑doped ZnO films prepared by spray pyrolysis(2020-01-09) Sabrina RoguaiPure and Cu doped ZnO films were grown by ultrasonic spray pyrolysis onto glass substrates at 450 °C for 30 min. This study aims to investigate the influence of Cu doping content [0.02–0.20] on structural, microstructural and optical properties. X-ray diffraction analysis reveals a structural disorder depending on Cu loading besides the appearance of CuO phase. The doping effectiveness is revealed by EDX analysis of the chemical composition of the films. The transmittance shows a decreasing tendency with increasing Cu concentration. The refractive indices increase, whereas the values of forbidden energy gap decrease with the increase in Cu dopant concentration.Item Elaboration, characterization and applications of SnO2, 2 %Gd-SnO2 and 2 %Gd-9 %F-SnO2 thin films for the photocatalytic degradation of MB by USP method(2022-02-17) Sabrina RoguaiIn this study, SnO2, 2 %Gd-SnO2, and 2 %Gd-9 %F-SnO2 films were grown from tin chloride solutions by the ultrasonic spray technique on ordinary microscope glass substrates heated to a fixed temperature of 450 ◦C for photocatalytic application. The microstructural characterization of the thin films obtained was performed using X-ray diffraction (XRD), SEM, EDAX, and Infrared Spectroscopy (IR). The optical properties of thin films were studied by UV–Visible spectroscopy. To examine the electrical properties, we use the four-point method, the Seebeck effect and the Mott Shottky analysis. X-ray difraction reveals the formation of the routile phase of SnO2 in all thin films with average crystallite size estimated in the range of 24–62 nm. The co-doping in (Gd-F) permitted an improvement of the thermoelectric properties of SnO2. Moreover, we have demonstrated that an increase in grain size allows toimprove the Seebeck coefficient, to increase the electrical conductivity, on the other hand the doping in (Gd), presents a decrease in the size of the crystallites, which improves the degradation of methyl blue. The UV–Visible spectra of optical transmission of the layers show that the pure, doped and codoped SnO2 films are of good quality with a transmittance of 73–83% in the visible and have an optical gap evaluated between 3.89, 3.98 and 3.99 eV respectivelyItem Gold coated vertically aligned carbon nanotubes as electrode for electrochemical capacitors(2023-05-20) Sabrina RoguaiIn this work, gold (Au) films were deposited onto vertically aligned carbon nanotubes (CNTs) by Dc magnetron sputtering method for use as super-capacitor electrodes. By so doing, we synthesize a porous Au deposit anchored on the CNTs with a high apparent surface area. The structure and microstructure studies revealed that the Au@CNTs have a porous nanostructure morphology. The porous Au/CNTs electrodes exhibit an a good areal capacitance compared to state of art Au based electrode (25.6 mF cm-2 at 5 mV.s-1) and excellent cycling stability (90% retention after 10.000 cycles) in 0.5 M H2SO4 aqueous solution. These results demonstrate the beneficial use of CNTs to fabricate a porous Au deposit with improved electrochemical energy storage. In addition, these porous structures can also be used as templates for another type of materials for electrochemical energy storageItem Gold coated vertically aligned carbon nanotubes as electrode for electrochemical capacitors(2023-05-20) Sabrina RoguaiIn this work, gold (Au) films were deposited onto vertically aligned carbon nanotubes (CNTs) by Dc magnetron sputtering method for use as super-capacitor electrodes. By so doing, we synthesize a porous Au deposit anchored on the CNTs with a high apparent surface area. The structure and microstructure studies revealed that the Au@CNTs have a porous nanostructure morphology. The porous Au/CNTs electrodes exhibit an a good areal capacitance compared to state of art Au based electrode (25.6 mF cm-2 at 5 mV.s-1) and excellent cycling stability (90% retention after 10.000 cycles) in 0.5 M H2SO4 aqueous solution. These results demonstrate the beneficial use of CNTs to fabricate a porous Au deposit with improved electrochemical energy storage. In addition, these porous structures can also be used as templates for another type of materials for electrochemical energy storage.Item Photocatalytic degradation of methylene blue using sprayed Mg diluted ZnO heterostructure thin films photocatalysts(2021-03-07) Sabrina RoguaiThe thin layers of ZnOx%/MgO [x= 30, 40 and 50 at%], were prepared by the spray pyrolysis method on glass substrates at 450 °C, then tested for methyl blue (MB) degradation under visible irradiations. The ZnOx%/MgO [x= 30,40 and 50 at%] thin films were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy and Mott-Schottky analysis. X-ray diffraction analysis revealed that the layers have a polycrystalline nature of hexagonal (wurtzite) and cubic structure. Microstructures the films were also analyzed using scanning electron. The films show a radical change in the surface morphology in accordance with the XRD results. The above analyses confirm the co-existence of a mixture of the wurtzite (ZnO) structure and cubic phase of MgO. The use of these mixed layers in the photo degradation of MB gave satisfactory results. Indeed, the photocatalytic tests showed the efficiency of Mg diluted ZnO films with the best yield in the case of 50% diluted ZO films. It was confirmed that the ZnO50%/MgO had a profound effect on reduction of band gap and photocatalytic performances.Item Roles of Cobalt Doping on Structural and Optical of ZnO Thin Films by Ultrasonic Spray Pyrolysis(2021) Sabrina RoguaiHere we report a systematic study of structural, optical, and magnetic measurements of Zn1-xCoxO (x = 0–0.22 at.%) by Ultrasound pyrolysis spray technique. The hexagonal wurtzite structure of our films is confirmed by X-ray diffraction with an average crystallite size estimated in the range of 18–30 nm. For the optical proprieties, using the Levenberg–Marquardt least squares rule, the experimental transmission measurements were perfectly adapted to the transmission data calculated by a combination of the Wemple-DiDomenico model, the absorption coefficient of an electronic transition and the Tauc-Urbach model. The concentration of the NCo absorption centers and the oscillator intensity f of the d-d transition of Co2+ ions are determined by the Smakula method. The presence of high concentrations of localized states in the thin films is responsible for the reduction in the width of optical bandgapItem Sn doping effects on the structural, microstructural, Seebeck coefficient, and photocatalytic properties of ZnO thin films(2022-04-07) Sabrina RoguaiSuccessful ZnO, SnxZn1-xO [x = 0.01 and 0.03] films were synthesized by pyrolysis on glass substrates at Ts = 450 ◦C for 1 h. Sn doping effect on structural, microstructural, Seebeck coefficient and optical characterizations were performed. It found that all films crystallize in the hexagonal würtzite structure. The success of the 1 at.% Sn doping is confirmed by the SEM images which show that the microstructure of the 1 at.% Sn doped ZnO is rather similar to that of the undoped ZnO film and shows spherical grains, by further increasing the Sn content (3 at.%), the films show a small spherical grains. Through FTIR analysis, distinct characteristic absorption peak at 449 cm− 1 for the Zn–O stretching mode with some changes in intensities. ZnO, ZnO:Sn films transmit decrease from 87 to 66% with doping content, while the bandgap energy not affected with doping. The Seebeck coefficient decreases from |188| to |110|μV/K, while the carrier concentration increases from 3.37 × 1018 and 1.00 × 1019cm− 3 with doping content. The photocatalytic activity of Zn1-xSnxO investigated by testing the degradation of methylene blue (MB)Item Sn doping effects on the structural, microstructural, Seebeck coefficient, and photocatalytic properties of ZnO thin films(2022) Sabrina RoguaiSuccessful ZnO, SnxZn1-xO [x = 0.01 and 0.03] films were synthesized by pyrolysis on glass substrates at Ts = 450 ◦C for 1 h. Sn doping effect on structural, microstructural, Seebeck coefficient and optical characterizations were performed. It found that all films crystallize in the hexagonal würtzite structure. The success of the 1 at.% Sn doping is confirmed by the SEM images which show that the microstructure of the 1 at.% Sn doped ZnO is rather similar to that of the undoped ZnO film and shows spherical grains, by further increasing the Sn content (3 at.%), the films show a small spherical grains. Through FTIR analysis, distinct characteristic absorption peak at 449 cm− 1 for the Zn–O stretching mode with some changes in intensities. ZnO, ZnO:Sn films transmit decrease from 87 to 66% with doping content, while the bandgap energy not affected with doping. The Seebeck coefficient decreases from |188| to |110|μV/K, while the carrier concentration increases from 3.37 × 1018 and 1.00 × 1019cm− 3 with doping content. The photocatalytic activity of Zn1-xSnxO investigated by testing the degradation of methylene blue (MB)Item Structural, microstructural, and optical properties of ZnO thin films prepared by spray pyrolysis(2022-06-15) Sabrina RoguaiThe thin films of zinc oxide were deposited by the ultrasonic spray technique on glass substrates. Our interest consists in the study of structural and microstructural properties. The X-ray diffraction analysis of the samples shows that the thin films crystallize in the hexagonal structure of the Wurtzite type. With a preferential orientation along the c-axis perpendicular to the substrate surface. The average size of the crystallites of the order of 49 nm. The microstructures/nanostructures of thin films are characterized by the presence of nano pedals. The chemical composition of the films was analyzed by EDS which revealed the formation of the ZnO phase. The synthesized layers showed a transmittance value of 90%. The optical band gap and the refractive index values are in good accordance with available studies in the literature.Item Synthesis and evaluation of the structural, microstructural, optical and magnetic properties of Zn1−xCoxO thin films grown onto glass substrate by ultrasonic spray pyrolysis(2019-10-29) Sabrina RoguaiUltrasound pyrolysis spray technique is used to prepare single-phase thin films of Zn1−xCoxO (x=0–22 at.%). The hexagonal wurtzite structure of the films is confirmed by X-ray diffraction with an average crystallite size estimated in the range of 18–30 nm. The compound structure and stoichiometry of the films are further characterized by energy-dispersive spectroscopy (EDAX). The spectrum analysis agreement great chords between the expected and measured Co atomic content in the films indicating an effective doping. The results also reveal a high solubility of Co into ZnO solid solution at about 14 at.%. For the optical proprieties, the bandgap energy decreases due to the presence of high concentrations of localized states in the thin films. The photoluminescence spectra of all the samples exhibited a broad emission in the visible range. In addition, the magnetic properties of Zn1−xCoxO thin films are found to be strongly influenced by Co dopingItem Thermodynamique, cours & exercice corrigés(Éditions universitaires européennes, 2021-10-29) Sabrina Roguai/Item ZnO and La-doped ZnO films by USP method and their characterizations for ultraviolet photodetectors and photocatalysis applications(2021-09-04) Sabrina RoguaiIn this study, ZnO, Zn1-xLaxO [2, 5, 10, 15 at.%] thin films were grown on glass substrates using the spraypyrolysis technique, to investigate the effect of doping on the structural, morphological, thermoelectric and optical properties of the layers, Also the samples were tested as UV photodetectors and photocatalyst for MB degradation. Firstly, diffraction patterns showed a hexagonal structure, with preferential grain orientation along the (002) direction, for pure ZnO and 2%La_ZnO layers, and at 5 at.% the preferential orientation changes, and crystallite sizes range from 10 nm to 19 nm. However, SEM images reveal that the ZnO and 2%La_ZnO layers are nanorods distributed over their surfaces, and the other 5%LZO, 10%LZO and 15%LZO layers characterized by nanocrystals were hexagonal prisms. The UV–visible analysis of the prepared layers shows high transparency (80–90%) in the visible range, with a constant optical gap of 3.26 eV. Thermoelectric measurements show that the ZnO and LZO layers are non-degenerate, with a maximum charge concentration of 9.18 × 1017 cm− 3 for the 15% LZO films. The thin films show an ability for UV detection, while the 5%La_ZnO layers remain the best for UV photodetection with a good sensitivity (5.07) compared with the other layers. In terms of methyl blue degradation, the 5%La_ZnO thin films had a better degradation of 95%.