Browsing by Author "Dokhan, Nahed"

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Diamond-Like carbon - coated silicon nanowires as a supercapacitor electrode in an aqueous LiClO4 electrolyte
(Springer, 2021) Rachedi, Nacera; Hadjersi, Toufik; Moulai, Fatsah; Dokhan, Nahed
Silicon nanowires (SiNWs) were successfully coated by uniform, adherent, and homogenous films of diamond-like carbon(DLC) using electrophoretic method. The coating was performed in an organic dimethylsulfoxide (DMSO) solution at 70 °Cfor 60 min with an applied voltage of 150 V. The as prepared samples of SiNWs and DLC/SiNWs were characterized by ascanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Raman spectroscopytechniques. The SEM micrographics showed that the films were uniformly deposited on the whole of SiNWs surface andcomposed of compact and small spherical grains with uniform distribution. Raman spectroscopy indicates that the coating filmswere DLC in nature. These results were well confirmed by the EDX and XRD techniques. The electrochemical investigationincluding cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, showed that theelectrochemical behavior of SiNWs was clearly enhanced after coating with a DLC film. Indeed, the latter showed a specificcapacitance of 400 mF/cm2at scan rate of 5 mV/s in an aqueous 0.5 M LiClO4solution with capacitance retention of 90% after16,000 cycles. Thus, the deposition of DLC film onto silicon nanowires (SiNWs) substrate can be considered as a simple andeconomical method to fabricate a high-performance electrode for supercapacitors
Electrochemical Deposition of Hematite α-Fe2O3 Thin Films for Photo-Current Generation Application
(Pleiades Publishing, 2024) Mokhtari, S.; Bouhdjer, Lazhar; Dokhan, Nahed; Aoudjit, Lamine; Imma, H.; Omeiri, Said; Trari, Mohamed
In the field of sustainable hydrogen production, hematite (α-Fe2O3) is a promising material owing to its optical band gap and water oxidation/reduction energies. In this context, the main objective of this work is devoted to the synthesis of α-Fe2O3 by electrochemical anodization of iron sheet using two anodization voltages (20 and 30 V), followed by annealing at 450°C (1.5 h) in air. Indeed, annealing is a necessary but not sufficient condition for the hematite prepared electrochemically. Furthermore, we discuss the effect of anodizing voltage and analyze its influence on the properties of the films namely structural, morphological, optical, electrochemical and photoelectrochemical (PEC) properties. The annealed Fe2O3 sample, anodized at 30 V, demonstrates a net photocurrent density of 0.81 mA/cm2 at 0.744 VRHE in KOH (1 M). The obtained results indicate that the α-hematite thin films synthesized by anodization technique under optimized conditions is a promising photoanode in PEC cells.
Electrophoretic deposition of carbon nanofibers/Co(OH)2 nanocomposites : application for non-enzymatic glucose sensing
(Wiley-VCH Verlag, 2016) Wang, Qian; Ma, Yao; Jiang, Xin; Yang, Nianjun; Coffinier, Yannick; Belkhalfa, Hakim; Dokhan, Nahed; Li, Musen; Boukherroub, Rabah; Szunerits, Sabine
Graphene oxide chemically reduced and functionalized with KOH-PEI for efficient Cr(VI) adsorption and reduction in acidic medium
(Elsevier, 2020) Tadjenant, Y.; Dokhan, Nahed; Barras, A.; Addad, A.; Jijie, R.; Szunerits, S.; Boukherroub, R.
In this study, graphene oxide (GO), polyethyleneimine (PEI) and potassium hydroxide (KOH) were used to synthesize reduced graphene oxide (rGO/PEI-KOH) nanocomposite. The presence and grafting of PEI molecules on the reduced GO surface were assessed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analyses. The rGO/PEI-KOH nanocomposite was successfully applied for hexavalent chromium, Cr(VI), wastewater elimination. The resulting rGO/PEI-KOH adsorbent was found to be highly effective for Cr(VI) removal at low pH values and achieved a maximum capacity of experimental adsorption of 398.9 mg/g, which is one of the highest sorption capacity of most GO- and PEI-based adsorbents reported in the literature up to date. Studying the adsorption mechanism, the sorption isotherm revealed that the modified-Langmuir model was the best fit and Cr(VI) removal follows a pseudo-second-order kinetics, with the predominance of intraparticle diffusion during the first step of adsorption. XPS analysis indicated the presence of appreciable amount of Cr(III) on the adsorbent surface, which suggests that the adsorbed Cr(VI) ions were effectively reduced to Cr(III) on the rGO/PEI-KOH adsorbent surface (∼70% of the total adsorbed Cr). Cr(VI) adsorption and subsequent reduction to Cr(III) both contributed to the Cr(VI) removal. The results of the present study highlight the benefits of rGO/PEI-KOH like low cost, environmentally friendly, large toxic Cr(VI) ions adsorption capacity and its effective reduction to less-toxic Cr(III)
Hydrothermally synthesized reduced graphene Oxide-Copper sulfide nanomaterial for application as supercapacitor
(Pleiades Publishing, 2023) Mokhtari, S.; Dokhan, Nahed; Aoudjit, Lamine; Trari, Mohamed; Omeiri, Said
This work is dedicated to the synthesis of rGO-CuS (reduced graphene oxide-copper sulfide) nanocomposites through a low-cost and environmentally friendly method through a one-step hydrothermal low-temperature process without the use of surfactants. rGO was obtained by efficient reduction of GO with PEI (polyethylenimine), identified by XRD, and confirmed by FTIR, Raman, and XPS analyses. The XRD pattern shows the formation of CuS phase crystallized in a hexagonal structure, while the SEM image shows the growth of CuS nanocrystals on the rGO layer. TEM showed the formation of spherical CuS nanoparticles distributed on the rGO surface. When studying its electrochemical reaction, the synthesized nanocomposite exhibited pseudocapacitive behavior with a specific capacitance of 418 F g –1 .
Non-enzymatic electrochemical detection of glucose with and without the presence of insulin using rGO/ZnO
(2020) Belkhalfa, Hakim; Bendjerad, Adel; Dokhan, Nahed; Lahmar, Abdelilah; Rahmani, Salima
In the present work, the combination of the electrophoretic deposition of ZnO nanostructures with size not exceeding 50 nm, and the reduced graphene oxide (rGO) on gold electrodes was performed to study the non-enzymatic electrochemical detection of glucose. The effect of insulin insertion on glucose detection and regulation was studied and the electrochemical responses were compared with and without this molecule. The results showed that the GO/insulin/ZnO electrode is much more sensitive for the glucose detection, in addition to its ability to drop the insulin protein hormone under a negative voltage. That bears interest as dual function sensor for detection and regulation of glucose.
Oxygen and carbon distribution in 80Kg multicrystalline silicon ingot
(Springer, 2019) Kerkar, Fouad; Kheloufi, Abdelkrim; Dokhan, Nahed; Ouadjaout, Djamel; Belhousse, Samia; Medjahed, Sidali; Meribai, Nadjib; Laib, Karim
Perpendicular weak permanent magnetic field effect on the electrodeposited nanostructured ZnO film and its kinetic corrosion behavior
(Springer, 2019) Taleb, Samia; Dokhan, Nahed; Zazi, Nacer; Chopart, Jean-Paul
In this work the effect of the permanent weak magnetic field on the electrodeposited ZnO nanostructured film on the ITO substrate elaborated under –0.5 and –0.8 V was studied. The deposits have been characterized by SEM, EDX, and electrochemical tests. The obtained results showed the increase of crystallites dimension in the presence of magnetic field under –0.5 V, and the decrease of the number of large crystallites of ZnO deposits under potential deposition equal to –0.8 V. The deposition under weak magnetic field change the current deposition, the open circuit potential (OCP), the polarization curve parameters after one week of corrosion and crystallographic parameters
Reduction of 4-Nitrophenol and Adsorption of Rhodamine B Using Reduced Graphene Oxide-Copper Sulfide Nanomaterial
(Pleiades Publishing, 2024) Mokhtari, S.; Aoudjit, Lamine; Ben Hariz, S. Habi; Dokhan, Nahed; Trari, Mohamed
Polyethylene imine (PEI) is used as an effective chemical agent for the reduction of graphene oxide (GO) to reduced graphene oxide (rGO). It is water-soluble, stable and cost-effective, and the reaction condition is easily achievable. The rGO nanocomposite are decorated with CuS nanoparticles by a single-step hydrothermal method. GO is assisted by precursors of Cu2+ and S2– in well-defined ratios. Several analysis methods are used such as UV–Vis, FTIR, XRD with SEM coupled with EDS to develop the structure and morphology of synthesized rGO-CuS nanocomposites. GO is assisted by Cu2+ and S2– precursors in well-defined ratios. Several analysis methods are used such as UV–Vis spectrophotometry, FTIR spectroscopy, X‑ray diffraction (XRD) and scanning electron microscopy (SEM) for the structural and morphological characterizations of the synthesized rGO-CuS nanocomposites. The structural and optical properties are discussed and the results obtained are compared to the literature. The prepared material has been tested in various applications, it is used as a Calisher for the reduction of 4-nitrophenol to 4-aminophenol and the degradation of Rhodamine B (Rh B).
Slow dynamics in semiconductor multi-longitudinal-mode laser transients governed by a master mode
(2012) Dokhan, Nahed; Puccioni, G.P.; Lippi, G. L
We examine the response to the sudden switch of the pump parameter in a multimode semiconductor laser with intensity coupling on a model whose validity has been successfully compared to experimental results. We find the existence of a very slow modal evolution governed by a master mode, which reaches its steady state on a time scale that is a couple of orders of magnitude longer than that of the total intensity. The practical consequences for applications are examined, such as the temporal evolution of the spectral width of the laser emission and the time at which its steady state is attained. Issues related to modeling choices, such as the number of modes and their placement with respect to line center, are discussed