STUDY OF THE ANTIOXIDANT ACTIVITY OF FLAVONOIC EXTRACT OF A MEDICINAL PLANT (CALOTROPIS PROCERA) OF AHAGGAR TAMANRASSET

Calotropis procera (family Lamiaceae) is a famous medicinal plant in the region of Hoggar Tamanrasset in southern Algeria. In this study, will have undertaken the study of the antioxidant activity of the flavonoid extract of this plant using several solvents (diethylether, ethyl acetate and N-butanol), the potential antioxidant extracts was determined on the based on their scavenging activity of the stable 1.1-Diethyl-2, hydrazylpyrryl (DPPH) free radicals. The values ​​of IC50 (mg / ml) were for the extract of 0.020 g / l, 0.014 g / l and 0.029 g / l successively for diethyl ether, ethyl acetate and N-butanol. Compared to the salts of ascorbic acid (VC) and tocopherol acid (VE) which were 0.011g / l and 0.015 g / l respectively. In addition the FRAP (Fenic antioxidant power reduction) effective acetate test on the same extract. By using VEAC (Vit E equivalent antioxidant capacity) it is found that the ethyl acetate extract has a higher reducing power than the other extracts equal to 1.115 g / l. diethyl ether 0.956g / l and n-butanol 0.987 g / l and ascorbic acid (VC) was considered a positive test with a VEAC is equal to 2.031g /

Annealing study and thermal investigation on bismuth sulfide thin films prepared by chemical bath deposition in basic medium

This is a post-peer-review, pre-copyedit version of an article published in Applied Physics A 124.2 (2018): 166. The final authenticated version is available online at: http://doi.org/10.1007/s00339-018-1584-7Bismuth sulfide thin films were prepared by chemical bath deposition using thiourea as sulfide ion source in basic medium. First, the effects of both the deposition parameters on films growth as well as the annealing effect under argon and sulfur atmosphere on as-deposited thin films were studied. The parameters were found to be influential using the Doehlert matrix experimental design methodology. Ranges for a maximum surface mass of films (3 mg cm-2) were determined. A well crystallized major phase of bismuth sulfide with stoichiometric composition was achieved at 190°C for 3 hours. The prepared thin films were characterized using Grazing Incidence X-ray diffraction (GIXRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). Second, the band gap energy value was found to be 1.5 eV. Finally, the thermal properties have been studied for the first time by means of the electropyroelectric (EPE) technique. Indeed, the thermal conductivity varied in the range of 1.20 - 0.60 W m-1 K-1 while the thermal diffusivity values increased in terms of the annealing effect ranging from 1.8 to 3.5 10-7 m2s-1This work was financially supported by the Tunisian Ministry of Higher Education and Scientific Research and by the WINCOST (ENE2016-80788-C5-2-R) project funded by the Spanish Ministry of Economy and Competitivenes

Site location of Al-dopant in ZnO lattice by exploiting the structural and optical characterisation of ZnO:Al thin films

The zinc oxide thin films, highly transparent, doped aluminium were prepared on glass substrates by the reactive chemical spray method. The incorporation nature of Al atoms in the ZnO lattice was determined by X-ray diffraction and optical analyses. Indeed, for low doping ⩽2%, the results of X-ray spectra analysis show a simultaneous reduction of lattice parameters (a and c), this variation, which follows VEGARD’s law, tends to indicate a substitution of Zn by Al. By against for doping >2% the increase in the lattice parameters thus the grain sizes, in accordance with the VEGARD’s law can be explained by occupation of the interstitial sites by Al atoms. Beyond 4%, the material tends to get disorderly and the crystallites orientation is random. The studied optical properties show that the variation of the optical gap follows a law of the x3/2 form for x < 3% (x is the aluminium atom fraction incorporated in the ZnO lattice). The granular structure is fairly visible and some local growths are disrupted. The crystallite size at low enlargement is coherent with the XRD results. Keywords: Al-doped ZnO thin films, XRD, Substitutional and interstitial sites, Band gap, SE

Вплив кристалічної об'ємної фракції на електронні властивості гідрогенізованого мікрокристалічного кремнію, дослідженого методом еліпсометрії та моделюванням мікроелектронних і фотонних структур

The main objective of the present work is to study experimentally and by simulation, using the one dimensional analysis of microelectronic and photonic structures program (AMPS-1D), the correlation between the crystalline volume fraction (Fc) and the transport properties of hydrogenated microcrystalline silicon thin films (мc-Si:H). The Fc was determined by spectroscopic ellipsometry (SE) and the electrical conductivity measurements. The мc-Si:H samples were deposited by radio-frequency magnetron sputtering technique of a crystalline silicon target, under an argon (Ar) gas mixture of 70 % of hydrogen (H2) and 30 % of Ar, at three different total pressures (2, 3 and 4 Pa) and changing substrate temperatures (25, 100, 150 and 200 °C). The dark conductivity was measured in a coplanar configuration in an optical cryostat under applied electrical field and controlling current with an electrometer. In the simulation studies of the dark conductivity using the AMPS-1D, we modelled the films as an alternation of amorphous and crystalline regions with different crystalline volume fractions Fc (from 0 to 80 %). The results evidently demonstrated that the conductivity depends on the width of the area separating amorphous and crystalline regions. We found a strong correlation between the c-Si:H films activation energy and the crystalline volume fraction where the grain size-to-thickness ratio plays a crucial role.Метою даної роботи є експериментальне і модельне дослідження кореляції між об'ємною фракцією кристалів і транспортними властивостями тонких плівок гідрогенізованого мікрокристалічного кремнію, використовуючи одновимірний аналіз програми мікроелектронних і фотонних структур (AMPS 1D). Об'ємну фракцію кристалів визначали спектроскопічною еліпсометрією і вимірюваннями елект- ропровідності. Зразки гідрогенізованого мікрокристалічного кремнію осаджували методом радіочастотного магнетронного розпилення кристалічної мішені кремнію у газовій суміші аргону і водню при трьох різних сумарних тисках (2, 3 і 4 Па) та змінюючи температуру підкладки (25, 100, 150 і 200 °С). Темна провідність вимірювалася в копланарній конфігурації в оптичному кріостаті при прикладанні електричного поля і керуючого струму. У дослідженнях темної провідності з використанням AMPS-1D ми моделювали плівки як чергування аморфних і кристалічних областей з різними кристалічними об'ємними фракціями (від 0 до 80 %). Результати показали, що провідність залежить від ширини ділянки, що розділяє аморфні та кристалічні області. Була виявлена сильна кореляція між енергією активації плівок гідрогенізованого мікрокристалічного кремнію і об'ємною часткою кристалічних речовин, де співвідношення розміру зерна до його товщини грає вирішальну роль

Optical and electrical properties of thin films grown by spray pyrolysis

International audienceno abstrac

Optical and electrical properties of Bi₂S₃ films deposited by spray pyrolysis

International audienceThin films of Bi2S3 were prepared by spray pyrolysis method. Optical constants, electrical and photoelectrical studies have been carried out on these films. The optical constants confirm that the Bi2S3 thin film has a direct band gap of 1.69 eV. The Hall Effect measurements indicate that the Bi2S3 thin films prepared by spray pyrolysis method are n-type in nature with a carrier concentration of 3.51 × 1017 cm− 3. An activated process with activation energy of 65 meV governs the conduction in these films. The photoconductivity measurement indicates the presence of continuously distributed localized gap states in this material