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Synthesis and Characterization of Supercapacitor Electrodes Based on Graphene and MnO2 Nanostructure
, M.Sc. Thesis Sharif University of Technology ; Moshfegh, Alireza (Supervisor) ; Moradlou, Omran (Co-Advisor)
Abstract
Supercapacitors represent a new class of energy storage devices that have been attracted many researchers in last few years. Graphene with unique properties such as superior electrical conductivity and large specific surface area is one of the most suitable materials in supercapacitor applications. Besides, metal oxides are being used as active compounds in supercapacitors due to their role in redox reactions. In this research, synthesis and characterization of supercapacitor electrodes based on graphene and MnO2 nanostructured materials was studied under different conditions. For this purpose, Graphene oxide (GO) was synthesized by Hummers’ method and then, it was deposited on a nickel foam...
Synthesis, Characterization and Photoelectrochemical Application of two Dimensional MoS2 and WS2 Nanosheets
, Ph.D. Dissertation Sharif University of Technology ; Zaker Moshfegh, AliReza (Supervisor) ; Moradlou, Omran (Co-Advisor)
Abstract
In this research, Synthesis, characterization and photoelectrochemical application of two dimensional MoS2 and WS2 nanosheets have been carefully investigated. And finally, based on theoritical and experimental analysis results, the mechanisms of the observed photoelectrochemical (PEC) activities were suggested.The ab initio density functional calculations about Mo1-xWxS2 monolayer deposited over a TiO2 (110) substrate revealed a shift in band position of the Mo1-xWxS2 in favor of photoelectrochemical water splitting. Moreover, increase of W concentration in Mo1-xWxS2 could improve the charge separation and increase the effective mass ratio leading to an extension of the electron–hole...
Spatial heterodyning optical CDMA technique for near-field free-space optical communication systems [electronic resource]
, Article IEEE Journal of Optical Communications and Networking ; Vol. 1, No. 5, PP. 498-511, Oct. 2009 ; Salehi, J. A ; Sharif University Of TechnologyParallel algorithm to find minimum vertex guard set in a triangulated irregular network
, Article 7th International Conference on Parallel Processing and Applied Mathematics, PPAM 2007, Gdansk, 9 September 2007 through 12 September 2007 ; Volume 4967 LNCS , 2008 , Pages 239-248 ; 03029743 (ISSN); 3540681051 (ISBN); 9783540681052 (ISBN) ; Sharif University of Technology
2008
Abstract
This paper presents a new serial algorithm for selecting a nearly minimum number of vertex-guards so that all parts of a geographical surface modeled by a TIN (Triangulated Irregular Networks) is covered. Our algorithm selects fewer guards than the best existing algorithms on the average. Based on this approach, a new coarse-grain parallel algorithm for this problem is proposed. It has been showed that the upper bound for total number of guards, selected by this algorithm, is where n is number of vertices in the TIN. Average case analysis and implementation results show that in real TINs even fewer than guards (proved upper bound of needed guards in worse-case) are selected by our serial and...
Global-best harmony search
, Article Applied Mathematics and Computation ; Volume 198, Issue 2 , 2008 , Pages 643-656 ; 00963003 (ISSN) ; Mahdavi, M ; Sharif University of Technology
2008
Abstract
Harmony search (HS) is a new meta-heuristic optimization method imitating the music improvisation process where musicians improvise their instruments' pitches searching for a perfect state of harmony. A new variant of HS, called global-best harmony search (GHS), is proposed in this paper where concepts from swarm intelligence are borrowed to enhance the performance of HS. The performance of the GHS is investigated and compared with HS and a recently developed variation of HS. The experiments conducted show that the GHS generally outperformed the other approaches when applied to ten benchmark problems. The effect of noise on the performance of the three HS variants is investigated and a...
Design and Development of Turbine Flow Meter with Colibration System
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Alireza (Supervisor)
Abstract
In this thesis, design and development of turbine flow meter for measuring of the volumetric flow rate of open channel and calibration system for it have been developed. This system has been constructed from two main sections, namely: software and hardware sections. The hardware section consists of a turbine, turbine chamber, Tachogenerator, microcontroller, and an ultrasonic sensor for measuring of channel water level. The turbine is located in exposure of water stream, and hence can be rotated in proportional to the water stream in which the value of rotation is measured by the tachogenerator, and then sent to the microcontroller, in order to calculate the velocity of water stream. At the...
Effect of RGO/Zn:XCd1- xS crystalline phase on solar photoactivation processes
, Article RSC Advances ; Volume 6, Issue 52 , 2016 , Pages 46282-46290 ; 20462069 (ISSN) ; Tedadi, N ; Banazadeh, A ; Naseri, N ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
A series of reduced graphene oxide/ZnxCd1-xS (RGO/ZnxCd1-xS) nanocomposites (0 < x < 1) with different ratios of Zn/Cd were synthesized via a facile hydrothermal route under optimized experimental conditions and were carefully characterized by various techniques. Because very little is known about the morphology, specific surface area, and crystal phase effects of RGO/ZnxCd1-xS crystals on their photoresponsivity, field-emission scanning electron microscopy (FE-SEM), BET surface area analysis and X-ray diffraction (XRD) data were studied to investigate their effects on photoactivity. Based on the results, a crystal phase transition from a cubic phase in RGO/Zn0.9Cd0.1S to a hexagonal...
Synthesis, Characterization and Studying of Photoelectrochemical (PEC) Properties for TNA/Ag2S Nanostructures
, M.Sc. Thesis Sharif University of Technology ; Moshfegh, Ali Reza (Supervisor) ; Moradlo, Omran (Co-Advisor)
Abstract
Free-standing TiO2 nanotube array (TNA) films were fabricated via two-step anodization of titanium sheet. The electrolyte consisted of DI water and ethylene glycol (99.9%, Merck) solution with volume ratio of 10:90, containing 0.5 M NH4F. Then, a few drops of 1M H3PO4 aquaes solution have been added to adjust pH at 5.7. The anodization process was performed at optimized applied voltage of 60 V for 200 min. Indeed it does in two-step for 50 and 150 min, and samples were sonicated of 40s between two steps. Then, to crystallize the grown structures, they were annealed in air at 500˚C for 80 minutes. Surface of TNA was modified by sequential-chemical bath deposition (S-CBD) method to fabricate...
Finding paths with minimum shared edges
, Article Journal of Combinatorial Optimization ; Volume 26, Issue 4 , 2013 , Pages 709-722 ; 13826905 (ISSN) ; Sack, J. R ; Zarrabi Zadeh, H ; Sharif University of Technology
2013
Abstract
Motivated by a security problem in geographic information systems, we study the following graph theoretical problem: given a graph G, two special nodes s and t in G, and a number k, find k paths from s to t in G so as to minimize the number of edges shared among the paths. This is a generalization of the well-known disjoint paths problem. While disjoint paths can be computed efficiently, we show that finding paths with minimum shared edges is NP-hard. Moreover, we show that it is even hard to approximate the minimum number of shared edges within a factor of 2log1-εn, for any constant ε>0. On the positive side, we show that there exists a (k-1)-approximation algorithm for the problem, using...
Finding paths with minimum shared edges
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 14 August 2011 through 16 August 2011 ; Volume 6842 LNCS , August , 2011 , Pages 567-578 ; 03029743 (ISSN) ; 9783642226847 (ISBN) ; Sack, J. R ; Zarrabi Zadeh, H ; Sharif University of Technology
2011
Abstract
Motivated by a security problem in geographic information systems, we study the following graph theoretical problem: given a graph G, two special nodes s and t in G, and a number k, find k paths from s to t in G so as to minimize the number of edges shared among the paths. This is a generalization of the well-known disjoint paths problem. While disjoint paths can be computed efficiently, we show that finding paths with minimum shared edges is NP-hard. Moreover, we show that it is even hard to approximate the minimum number of shared edges to within a factor of 2log1-εn, for any constant ε > 0. On the positive side, we show that there exists a k-approximation algorithm for the problem, using...
The first study on enhanced photoresponsivity of ZnO-TiO2 nanocomposite thin films by anodic polarization
, Article Physical Chemistry Chemical Physics ; Volume 13, Issue 10 , Feb , 2011 , Pages 4239-4242 ; 14639076 (ISSN) ; Yousefi, M ; Moradlou, O ; Moshfegh, A. Z ; Sharif University of Technology
2011
Abstract
The physical and photoelectrochemical properties of the anodized ZnO-TiO2 thin films were investigated in this study. Impedance spectroscopy revealed a decrease in charge transfer resistance and Tafel plots determined enhancement of about 200 times in the exchange current (i 0) after anodization at high positive potential. It was found from XPS analysis that after applying the potential of 5 V to the ZnO-TiO2 photoelectrode, the lattice oxygen (O2-) in the thin film is oxidized to molecular oxygen and then, cations such as Zn2+ can be solved in the basic electrolyte and passed to the solution. Moreover, according to AFM analysis it was observed that the surface of the samples has been...
Heuristic Flexibble Planning
, M.Sc. Thesis Sharif University of Technology ; Ghassem-Sani, Gholamreza (Supervisor)
Abstract
Planning, as one of the major area of the artificial intelligence, has substantial applications in different science and technology fields. In the classical planning, usually some restricted assumptions are made to simplify the planning procedure. For example, for the world representation, states and actions are defined precisely; however, in the real world such information is mostly inacurate. Therefore, in order to address this inacuracy, flexible planning has been developed. In this technique, robust restrictions such as complete satisfaction of preconditions are interpreted as preferences or priority. In other words, the flexible planning aims at fulfilling planning goals with maximum...
Lateral solutions for optimizing holding costs in job shops
, Article International Journal of Advanced Manufacturing Technology ; Volume 56, Issue 1-4 , 2011 , Pages 261-272 ; 02683768 (ISSN) ; Aliahmadi, A ; Sefidkoohi, H. M ; Omran, M. M ; Sharif University of Technology
2011
Abstract
Queuing networks present as beneficial models for a category of problems emerging in modern manufacturing systems. As the optimal control problem for queuing networks in familiar to be difficult, an important topic of research during the last two decades has been the growth of difficult estimations, and the use of these estimations to control optimal controls. Flexible moderations are an important class of such estimations that have received much consideration in recent years. The central objective of this paper is to determine the utilization of flexible moderations in solving a diversity of scheduling problems. In this paper, we investigate the role of flexible moderations in solving...
Optimal Ag2S nanoparticle incorporated TiO2 nanotube array for visible water splitting
, Article RSC Advances ; Volume 4, Issue 15 , 2014 , Pages 7838-7844 ; ISSN: 20462069 ; Qorbani, M ; Moradlou, O ; Naseri, N ; Moshfegh, A. Z ; Sharif University of Technology
2014
Abstract
Free-standing TiO2 nanotube array (TNA) films were fabricated via two-step anodization of a titanium sheet. The X-ray diffraction pattern indicated amorphous TNAs were transformed into anatase after annealing the films at 500 °C in air. The surface of TNA was modified by a sequential-chemical bath deposition (S-CBD) method to fabricate Ag2S nanoparticles and forming TNA/Ag2S-n nanostructure, by varying the number of cycles (n). Based on SEM observations, the produced films consisted of vertically ordered tubular structure arrays, each with 125 nm in diameter and 4.1 μm in length containing silver sulphide nanoparticles of ∼12 nm diameter. X-Ray photoelectron spectroscopy (XPS) confirmed the...
How CdS nanoparticles can influence TiO2 nanotube arrays in solar energy applications?
, Article Applied Catalysis B: Environmental ; Volume 162 , January , 2015 , Pages 210-216 ; 09263373 (ISSN) ; Naseri, N ; Moradlou, O ; Azimirad, R ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier
2015
Abstract
In this study, titanium dioxide (TiO2) nanotube array (TNA) films are fabricated via anodization of titanium (Ti) sheet. After annealing, the films consisted of well ordered, vertically oriented TNAs of 125±6nm diameter, 38±3nm wall thickness, and 2.9±0.3μm in length. Cadmium sulfide (CdS) nanoparticles are deposited on the synthesized TNAs by sequential-chemical bath deposition (S-CBD) method with different immersion cycle (n) to produce heterogeneous TNA/CdS-n (n=10, 20 and 30) nanostructures. UV-visible absorption spectra of the samples revealed that the absorption edge of CdS modified TNAs was shifted to a higher wavelength with respect to the pure TNAs indicating band gap reduction of...
Vertically aligned ZnO@CdS nanorod heterostructures for visible light photoinactivation of bacteria
, Article Journal of Alloys and Compounds ; Vol. 590 , 2014 , pp. 507-513 ; ISSN: 09258388 ; Akhavan, O ; Moradlou, O ; Nien, Y. T ; Moshfegh, A. Z ; Sharif University of Technology
2014
Abstract
Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (Eg) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with Eg ∼2.5-2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve...
Intrinsically Ru-doped suboxide TiO2nanotubes for enhanced photoelectrocatalytic H2generation
, Article Journal of Physical Chemistry C ; Volume 125, Issue 11 , 2021 , Pages 6116-6127 ; 19327447 (ISSN) ; Mohajernia, S ; Hejazi, S ; Mehdipour, H ; Naseri, N ; Moradlou, O ; Moshfegh, A. Z ; Schmuki, P ; Sharif University of Technology
American Chemical Society
2021
Abstract
In the present research, we investigate the synergistic effects of Ru-doping and Ar/H2 reduction treatment on the photoelectrochemical water splitting performance and hydrogen evolution rate of TiO2 nanotube array photoelectrodes. The Ti-Ru alloy with 0.2 at. % Ru was used to grow anodic self-organized Ru-doped TiO2 nanotube layers. An ideal synergy between Ar/H2 reduction treatment and Ru-doping results in the extended absorption toward the visible light region and improved photoelectrocatalytic activity. The black Ru-doped TiO2-x photoanode's water splitting rate improves remarkably (∼ninefold) compared to the black TiO2-x sample (∼twofold). Moreover, the black Ru-doped TiO2-x photoanode...
Controlled engineering of WS2 nanosheets-CdS nanoparticle heterojunction with enhanced photoelectrochemical activity
,
Article
Solar Energy Materials and Solar Cells
;
Volume 141
,
2015
,
Pages 260-269
;
09270248 (ISSN)
; Zhao, M
; Moradlou, O
; Samadi, M
; Sarikhani, N
; Wang, Q
; Zhang, H. L
; Moshfegh, A. Z
;
Sharif University of Technology
Elsevier
2015
Abstract
Abstract We report the well-controlled preparation of WS2 nanosheets-CdS nanoparticle heterojunction for photoelectrochemical (PEC) water splitting application. The WS2 nanosheets with an average thickness of ~5 nm and lateral dimensions of ~200 nm were synthesized via liquid phase exfoliation of bulk WS2 in water/ethanol solution, followed by deposition onto ITO substrate via electrophoretic method. CdS nanoparticles were grown via facile successive ion layer absorption and reaction (SILAR) method. Using these two well-controlled methods, CdS/WS2 /ITO and WS2 /CdS/ITO systems were fabricated. The loading of WS2 nanosheets was...
Fabrication and surface stochastic analysis of enhanced photoelectrochemical activity of a tuneable MoS2-CdS thin film heterojunction
, Article RSC Advances ; Volume 6, Issue 20 , 2016 , Pages 16711-16719 ; 20462069 (ISSN) ; Ebrahimi, M ; Zhao, M ; Moradlou, O ; Samadi, M ; Bayat, A ; Zhang, H. L ; Moshfegh, A. Z ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
A very simple and well-controlled procedure was employed to prepare CdS nanoparticle/few-layer MoS2 nanosheet/Indium tin oxide (ITO) thin film heterostructures. To tune and fabricate the CdS/MoS2(t)/ITO thin films with various surface topographies, first electrophoretic deposition (EPD) was used to deposit MoS2 nanosheets on the ITO substrate under an optimized applied potential difference (8 V) for different deposition times (t) of 30, 60, 120 and 240 s. Then, CdS nanoparticles were deposited via a successive ion layer adsorption and reaction (SILAR) technique. The highest photo-current density of 285 μA cm-2 was measured for the CdS/MoS2(60 s)/ITO sample, which was about 2.3 times higher...
Alkali metal cation incorporation in conductive TiO2 nanoflakes with improved photoelectrochemical h2 generation
, Article ChemElectroChem ; Volume 7, Issue 7 , March , 2020 , Pages 1699-1706 ; Mohajernia, S ; Hejazi, S ; Mehdipour, H ; Naseri, N ; Moradlou, O ; Liu, N ; Moshfegh, A. Z ; Schmuki, P ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
In this research, we investigate the effect of alkali metal cations including Li, Na and Cs in hydrothermal solution on the morphology, stability, and photoactivity of nanostructured TiO2 nanoflakes as a photoanode. The TiO2 nanoflakes are formed through hydrothermal treatment of Ti foil in 1.0 M LiOH, NaOH or CsOH at 100 °C for 3 h. By subsequent thermal reduction of the structure in an optimized Ar/H2 environment, conductive TiO2 nanoflakes were formed. The reduction treatment remarkably improves the photocurrent density of the TiO2 nanoflakes and has the highest impact on the sample treated in the NaOH alkali solution. For the nanoflakes produced in NaOH alkali solution, the bandgap is...