Loading...
Search for:
esfandiar--a---ali
0.143 seconds
Total 15953 records
The Growth and Characterization of Two-Dimensional Molybdenum Diselenide Crystals as Photodetectors
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
A novel optoelectronic property of two-dimensional (2D) materials suggests they can be used for high-performance photodetector design. There has been a lot of attention paid to MoS2 and Despite its higher optical absorbance, MoSe2 has received little attention. A chemical vapor deposition system was used to prepare atomically thin MoSe2 films. Our research developed a method of preparing hexagon-shaped MoSe2 photodetector on Si/SiO2 substrates in atmospheric pressure with sawtooth edges, leading to large-scale MoSe2 layers with the size of ∼ 70µm . The Raman characterization of the grown flakes indicated that they possessed high quality few layers of MoSe2 and the distance between the two...
Design and Construction of Fluorescent Confocal Microscopy Setup for Detection of Single Photon Emitters in 2d Materials
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
The main goal of this research is to detect and characterize single-photon emitters in two-dimensional hexagonal boron nitride crystal with the help of fluorescence confocal microscope and Hanbury-Brown and Twiss interferometer. The origin of single-photon radiation in this crystal is not precisely known. It seems that the transition between energy levels, which occurs due to the presence of point defects in the crystal structure of this material, in the distance between the conduction and valence bands, is the source of single-photon radiation. This material does not require low temperature for single-photon radiation, which is an important advantage for it. In a confocal microscope, the...
Study of Ion Transport from the Two-Dimensional Structure of MXene
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
Reverse electrodialysis-based membranes are one of the most promising approaches to osmotic energy production. However, conventional reverse electrodialysis membranes have high strength and insufficient mass transfer, which leads to low power density and efficiency. In recent decades, the transport of ions at the nanoscale for the manufacture of reverse electrodialysis machines has attracted much attention. Compared to conventional devices, power density and energy conversion efficiency increase dramatically due to space constraints and electrostatic interactions at the nanoscale. Lamellar nanostructures, which can be easily fabricated by stacking two-dimensional nanosheets, may be a...
Ion Transport Through Graphene Fibers
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
Nanostructured graphene based membranes demonstrated excellent capabilities in various applications in nanofiltration and energy conversion due to unique atomically smooth surfaces and adjustable pore size or interlayers spacing at Angstrom scales.In addition to graphitic surface and physical confinement on ions in Graphene-oxide (GO) laminates, surface charges on such 2D-slits provide an attractive aspects to have more channels walls interactions with ions. There are some reports on the osmotic power generation using physical confinements and electrostatic interactions between ions and GO membranes. However, the results indicated insufficient power densities (1 W=m2 ) can be achieved...
Synthesis and Investigation of Physical Properties of PVDF/Graphene Nanostructured Membranes for Molecular Sieving
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
Poly vinylidene fluoride (PVDF) as a fluorine polymer with acceptable thermal, chemical and physical property attractive create attention in membrane technology for water treatment application. However, with differential surface free energy between PVDF and water (∆G_s=30 mJ/m^2) PVDF polymer is divided as a hydrophobic materials, that is one of the basic problem for PVDF polymer. Due to its hydrophobicity the water molecules repulsion away from hydrophobic PVDF membrane surface as a spontaneous process with an entropy increasing and therefore pollutant molecules with hydrophobic functional group have tendency to adsorb onto membrane surface and dominate the boundary layer. In recent years...
Synthesis and Characterization of Graphene/Tin (IV) Sulfide (SnS₂) Hybrid Nanostructures as Anode Material for Ionic Batteries
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
In the current century, an energy storage is one of the critical and important factors affecting on human life. Rechargeable batteries, specially Lithium ion batteries (LIBs), can be considered as ideal energy storage devices including various advantages e.g. high energy and power densities. In this work, Tin IV sulfide (SnS2) and its composites, making by conductive materials e.g. Reduced Graphene Oxide (SnS2@rGO), are prepared during two different synthesis methods consisting of Hydrothermal and Hot-bath, and their properties are investigated as anode material in LIB. The structural and electrochemical analyses demonstrated that the composite sample prepared by hot-bath method exhibited...
Rotational and Translational Dynamics of Silver and Titanium Dioxide Nanowires Suspended in Dielectric Media in Electric Fields
, Ph.D. Dissertation Sharif University of Technology ; Moshfegh, Alireza (Supervisor) ; Esfandiar, Ali (Co-Supervisor)
Abstract
Wide utilization of nanomanipulation as a promising approach in microorganisms, nanoelectromechanical systems (NEMS) and assembly of nanostructures remarks the importance of nanostructures’ motion in electric fields. Despite of many reports on manipulation and assembly of nanowires (NWs) in non-uniform and alternating electric fields by dielectrophoresis, and also rotation of NWs in rotating electric fields, there is still a lack of knowledge on rotational and translational dynamics of metallic and dielectric NWs in uniform static electric fields. In this dissertation, we study the dynamics of silver (Ag) and titanium dioxide (TiO2) NWs, with diameters and lengths in the range of 40 to 100...
Investigation of the Hybrid Structures based on Carbon Materials for Solar Steam Generation
, Ph.D. Dissertation Sharif University of Technology ; Irajizad, Azam (Supervisor) ; Esfandiar, Ali (Supervisor)
Abstract
Two-dimensional nanostructures can significantly absorb solar irradiation, due to diverse energy levels, large effective surfaces, layered and porous structures with adjustable physical and chemical properties. Mono and multilayers of graphene, as the first isolated 2D materials with special band-structure of a zero-band gap, along with impressive optical properties, tunable light interaction, and adjustable optical properties by chemical doping or structural defects, have great potential for the next generation of nanophotonic devices. So, graphene is an appropriate candidate for absorption, frequent reflection, and energy conversion of electromagnetic waves at the frequency range of the...
Synthesis and Study of Application of MXene (Ti3C2) Layered Materials in Supercapacitors
, Ph.D. Dissertation Sharif University of Technology ; Iraji Zad, Azam (Supervisor) ; Esfandiar, Ali (Supervisor)
Abstract
In recent years, MXenes, a class of 2D materials, have drawn significant interest because of their special properties and layered structures. Among the MXenes family, Ti3C2 is a promising candidate in energy storage field due to its unique electrical conductivity, hydrophilicity, surface redox reactions, excellent packing density and high volumetric capacitance. In this thesis, synthesis and supercapacitor application of Ti3C2 have been investigated. HCl and LiF solution and mild exfoliation method has been used for etching Al layers from Ti3AlC2 and MXene synthesis. To analyze the structure of this material, scanning electron microscopy, atomic force microscopy, X-ray diffraction...
Synergistic effect of reduced graphene oxide and carbon black as hybrid light absorber for efficient and antifouling texture-based solar steam generator
, Article Solar Energy ; Volume 238 , 2022 , Pages 226-237 ; 0038092X (ISSN) ; Iraji zad, A ; Esfandiar, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Efficient utilization of solar energy as the cleanest and most plentiful natural resource for drinking water is a water is as sustianble and environmental friendly approach to obviate long-standing water scarcity. Carbon-based photothermal absorbers due to broadband light absorption are very interesting in interfacial solar steam generation systems. Herein, we investigate the convenient application of reduced graphene oxide (rGO) nanosheets with carbon black (CB) nanoparticles on the cotton fabric as a flexible texture-based photothermal absorber. Polyurethane (PU) as a self-floating insulator foam was selected to manage the energy loss and preserve light converted to heat on the fabric...
The decoration of TiO2/reduced graphene oxide by Pd and Pt nanoparticles for hydrogen gas sensing
, Article International Journal of Hydrogen Energy ; Volume 37, Issue 20 , October , 2012 , Pages 15423–15432 ; Ghasemi, S. (Shahnaz) ; Irajizada, A. (Azam) ; Akhavana, O. (Omid) ; Gholami, M. R. (Mohammad Reza) ; Sharif University of Technology
2012
Abstract
Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol–gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti–C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time...
Melatonin as a powerful bio-antioxidant for reduction of graphene oxide
, Article Journal of Materials Chemistry ; Volume 21, Issue 29 , 2011 , Pages 10907-10914 ; 09599428 (ISSN) ; Akhavan, O ; Irajizad, A ; Sharif University of Technology
2011
Abstract
Graphene is usually synthesized through deoxygenation of graphene oxide (GO) by hydrazine as the most common and one of the strongest reducing agents. But, due to the high toxicity of hydrazine, it is not a promising reductant in large-scale production of graphene. Here, for the first time, we used melatonin (MLT), as a powerful antioxidant and a biocompatible competitor of hydrazine in reduction of GO suspension. X-ray photoelectron spectroscopy (XPS), current-voltage and optical characteristics of the sheets indicated that the deoxygenation efficiency of the GO suspensions by MLT and under heating in an alkaline condition for 3 h was comparable with the efficiency obtained by hydrazine in...
Wrapping bacteria by graphene nanosheets for isolation from environment, reactivation by sonication, and inactivation by near-infrared irradiation
, Article Journal of Physical Chemistry B ; Volume 115, Issue 19 , 2011 , Pages 6279-6288 ; 15206106 (ISSN) ; Ghaderi, E ; Esfandiar, A ; Sharif University of Technology
American Chemical Society
2011
Abstract
Bioactivity of Escherichia coli bacteria (as a simple model for microorganisms) and interaction of them with the environment were controlled by their capturing within aggregated graphene nanosheets. The oxygen-containing functional groups of chemically exfoliated single-layer graphene oxide nanosheets were reduced by melatonin as a biocompatible antioxidant. While each one of the graphene (oxide) suspension and melatonin solution did not separately show any considerable inactivation effects on the bacteria, aggregation of the sheets in the melatonin-bacterial suspension resulted in trapping the bacteria within the aggregated sheets, i.e., a kind of inactivation. The bacteria trapped within...
Graphene/PbS as a novel counter electrode for quantum dot sensitized solar cells
, Article ACS Photonics ; Vol. 1, issue. 4 , March , 2014 , pp. 323-330 ; ISSN: 23304022 ; Samadpour, M ; Esfandiar, A ; Iraji Zad, A ; Sharif University of Technology
2014
Abstract
PbS nanoparticles were in situ deposited on graphene sheets by a successive ionic liquid adsorption and reaction method to prepare a graphene/PbS composite counter electrode for CdS/CdSe quantum dot sensitized solar cells (QDSCs). Under 1 sun illumination, the cells with graphene/PbS counter electrodes (CEs) show a maximum energy conversion efficiency of 2.63%, which is remarkably higher than that of those employing PbS (1.28%) or graphene (0.23%) CEs. Electrochemical impedance spectroscopy analysis shows that graphene/PbS composite counter electrodes have lower charge-transfer resistance at the interface of the CE and the polysulfide redox electrolyte, compared to those cells with PbS and...
Effect of film morphology on water oxidation enhancement in NiFeCo modified hematite photoanodes
, Article Surface and Coatings Technology ; Volume 421 , 2021 ; 02578972 (ISSN) ; Sobhkhiz Vayghan, N ; Esfandiar, A ; Dabirian, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Hematite (α-Fe2O3) is a promising candidate for water oxidation applications due to its abundance in the earth crust and its suitable bandgap. However, hematite performance is severely limited by electron-hole recombination at its interface with the electrolyte; something that can be addressed using electrocatalysts. In this report, we evaluate the influence of a ternary NiFeCo co-catalyst to enhance the water oxidation performance of hematite photoanodes. Thus, NiFeCo co-catalyst is optimized for hematite thin films with i) dense and ii) porous (nano-rod) morphologies. Both hematite films are prepared using electron beam evaporation method followed by an annealing step and NiFeCo...
Cauliflower-Like Ni/MXene-bridged fiber-shaped electrode for flexible microsupercapacitor
, Article Energy and Fuels ; Volume 36, Issue 4 , 2022 , Pages 2140-2148 ; 08870624 (ISSN) ; Iraji zad, A ; Esfandiar, A ; Asen, P ; Sharif University of Technology
American Chemical Society
2022
Abstract
Microscale, flexible, and lightweight electrodes are of interest for the generation of light and miniaturized energy storage systems such as microsupercapacitors. Wire or fiber-shaped electrodes can be considered as potential candidates for microsupercapacitor fabrication. Herein, a facile strategy for the preparation of high electrochemical performance fiber-shaped microsupercapacitors based on Ni(OH)2-Ni-Ti3C2 film on a copper wire (CW) electrode is presented. We employed a porous cauliflower-like Ni-Ti3C2 MXene film as the supporting scaffold to bridge a Ni(OH)2 active substance with a Cu wire current collector. This hierarchical structure supplies a high surface area, many electroactive...
Tunable gain SnS2/InSe Van der waals heterostructure photodetector
, Article Micromachines ; Volume 13, Issue 12 , 2022 ; 2072666X (ISSN) ; Iraji zad, A ; Mahdavi, S. M ; Esfandiar, A ; Sharif University of Technology
MDPI
2022
Abstract
Due to the favorable properties of two-dimensional materials such as SnS2, with an energy gap in the visible light spectrum, and InSe, with high electron mobility, the combination of them can create a novel platform for electronic and optical devices. Herein, we study a tunable gain SnS2/InSe Van der Waals heterostructure photodetector. SnS2 crystals were synthesized by chemical vapor transport method and characterized using X-ray diffraction and Raman spectroscopy. The exfoliated SnS2 and InSe layers were transferred on the substrate. This photodetector presents photoresponsivity from 14 mA/W up to 740 mA/W and detectivity from 2.2 × 108 Jones up to 3.35 × 109 Jones by gate modulation from...
Photodegradation of graphene oxide sheets by TiO2 nanoparticles after a photocatalytic reduction
, Article Journal of Physical Chemistry C ; Volume 114, Issue 30 , July , 2010 , Pages 12955-12959 ; 19327447 (ISSN) ; Abdolahad, M ; Esfandiar, A ; Mohatashamifar, M ; Sharif University of Technology
2010
Abstract
TiO2 nanoparticles were physically attached to chemically synthesized single-layer graphene oxide nanosheets deposited between Au electrodes in order to investigate the electrical, chemical, and structural properties of the TiO2/graphene oxide composition exposed to UV irradiation. X-ray photoelectron spectroscopy showed that after effective photocatalytic reduction of the graphene oxide sheets by the TiO2 nanoparticles in ethanol, the carbon content of the reduced graphene oxides gradually decreased by increasing the irradiation time, while no considerable variation was detected in the reduction level of the reduced sheets. Raman spectroscopy indicated that, at first, the photocatalytic...
Synthesis of MXene/Polyaniline Composite as an Electrode Material for Supercapacitors
, M.Sc. Thesis Sharif University of Technology ; Khachatourian, Adrineh Malek (Supervisor) ; Bagheri, Reza (Supervisor) ; Esfandiar, Ali (Co-Supervisor)
Abstract
Titanium carbide MXene (Ti_3 C_2 T_x) has attracted significant research interest because of its extraordinary advantages as advanced electrode material for energy storage. In this study, 4-aminodiphenylamine functionalized Ti_3 C_2 T_x/polyaniline composite synthesized by in situ growth of PANI on 4-aminodiphenylamine functionalized Ti_3 C_2 T_x nanosheets. First, Ti_3 C_2 T_x MXene nanosheets was prepared according to the minimally intensive layer delamination (MILD) method followed by sonication. Ti_3 C_2 T_x nanosheets were modified with 4-aminodiphenylamine diazonium salt. The FTIR، FE-SEM and EDS analysis were used to characterize modified Ti_3 C_2 T_x. Finally, the Ti_3 C_2 T_x...
Enhanced Broadband Photoresponsivity of the CZTS/WSe2Heterojunction by Gate Voltage
, Article ACS Applied Electronic Materials ; Volume 4, Issue 12 , 2022 , Pages 6189-6203 ; 26376113 (ISSN) ; Vardast, S ; Esfandiar, A ; Iraji Zad, A ; Heidariramsheh, M ; Sharif University of Technology
American Chemical Society
2022
Abstract
High-performance photodetectors play critical roles in numerous photon-based applications in imaging, communication, and energy harvesting. Nowadays, heterostructures have received significant attention to extend the performance of photodetectors, with exceptionally high optical absorption and a wide absorption range. However, the enhancement factors, exact mechanism, and facile fabrication procedures are long-standing problems. Here, a heterojunction of a two-dimensional chemical vapor deposition-grown monolayer of WSe2with a Cu2ZnSnS4(CZTS) film is introduced. The CZTS film as an abundant material was synthesized in the form of nanoparticles, and it showed a great effect on the enhancement...