Search for: impedance-spectroscopy
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    Aging effect of quantum dots on solar cells sensitized with nano-crystals of CdS and PbS

    , Article Iranian Journal of Physics Research ; Volume 14, Issue 4 , 2015 , Pages 351-360 ; 16826957 (ISSN) Borhanifar, V ; Irjizad, A ; Samadpoor, M ; Sharif University of Technology
    Isfahan University of Technology  2015
    In this research, solar cells sensitized with CdS and PbS Nanocrystalline metal sulfides, chemically grown by SILAR, were fabricated and characterized. PV experiments including I-V test in the presence of light and dark,Vocdecay, and Electrochemical impedance spectroscopy were performed on the Cells made through this method in the presence of light and dark and in the time period of 2, 3, 6 and 10 days. From these experiments, the changes in indicators including fill factor, efficiency, open-circuit voltage, short-circuit current, lifetime of electrons in nanostructured anode electrode, recombination resistance and capacitance of the anode electrode-electrolyte interface were observed. Also,... 

    On the pseudocapacitive behavior of nanostructured molybdenum oxide

    , Article Journal of Solid State Electrochemistry ; Volume 14, Issue 4 , 2010 , Pages 643-650 ; 14328488 (ISSN) Farsi, H ; Gobal, F ; Raissi, H ; Moghiminia, S ; Sharif University of Technology
    Nanostructured molybdenum oxide was potentiodynamically deposited onto a stainless steel surface from an aqueous bath by cycling the potential between 0 and -0.75 V vs. Ag/AgCl. The deposit consisted of particulates in the range of 30 to 80 nm. Electrochemical studies under galvanostatic charge/discharge and also impedance spectroscopy revealed capacitive behavior in the potential range of -0.3 to -0.55 V vs. Ag/AgCl with the value of 477 F g-1 at 0.1 mA/cm2. An equivalent circuit comprising of three parallel branches consisting of double-layer capacitance, Warburg impedance, and a constant phase element signifying pseudo-capacitance each coupled with their corresponding resistances was... 

    Reproducible electrochemical analysis of nanostructured Cu2O using a non-aqueous 3-methoxypropionitrile-based electrolyte

    , Article Electrochemistry Communications ; Volume 86 , 2018 , Pages 1-5 ; 13882481 (ISSN) Shooshtari, L ; Iraji zad, A ; Mohammadpour, R ; Sharif University of Technology
    Elsevier Inc  2018
    Cu2O is an attractive material in terms of semiconducting properties and is considered a leading candidate in all-oxide photovoltaics. Electrochemical analysis of Cu2O, including Mott-Schottky (MS) and impedance spectroscopy (IS), provides a wealth of data on charge carriers, Fermi level and interface properties. MS and IS are usually measured in aqueous solutions. However, Cu2O is easily reduced or oxidized to Cu or CuO in aqueous solutions, the layer peels off after the analysis and there is a small voltage window for the tests. In some cases, an anti-corrosive n-type barrier layer is employed on top of the bare Cu2O electrode to make the measurement possible, which could result in... 

    Investigation of Crystallization Behavior and Electrical Properties of Glass-Ceramics in the Li2O-TiO2-P2O5 System

    , M.Sc. Thesis Sharif University of Technology Mohaghegh, Elnaz (Author) ; Nemati, Ali (Supervisor) ; Eftekhari Yekta, Bijan (Supervisor) ; Banijamali, Sara (Co-Advisor)
    During the past two decades, much attention has been paid to rechargeable lithium batteries, because they have high energy density. Glass-ceramics is a category of this material, which may be of great potential as solid electrolytes.. The object of this thesis is preparation of Li2O-TiO2-P2O5 glass, glass-ceramic and investigation their electrical behavior. Prepared Samples were investigated by Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-Visible spectroscopy and Electrochemical impedance spectroscopy (EIS). In this study LiTi2(PO4)3 crystals were crystallized in a glass with the composition 45Li2O-25TiO2-30P2O5 (molar ratio). According... 

    Impedance analysis of growth and morphology of electropolymerized polypyrrole nanocomposites [electronic resource]

    , Article Journal of New Materials for Electrochemical Systems ; 2014, Volume 17, Number 2 Torabi, M. (Morteza) ; Sadrnezhaad, S. K ; Sharif University of Technology
    Pure polypyrrole (PPy), PPy/Al2O3 and PPy/SiO2 nanocomposites synthesized galvanostatically using different polymerization charges. Electrochemical impedance measurements of pure polypyrrole revealed that the film thickness affected the impedance responses. The characteristic frequencies vs. film thickness that obtained using Cole-Cole plots showed that electrodeposition mechanism changed from 3D to 1D after nuclei overlapping for pure PPy. Analysis of the nanocomposites impedance spectrums revealed no changes during the film growth, i.e. deposition continues 3D even after nuclei overlapping. Scanning electron microscopy (SEM) confirmed the impedance results and showed that the morphology of... 

    The pH effects on the capacitive behavior of nanostructured molybdenum oxide

    , Article Journal of Solid State Electrochemistry ; Volume 14, Issue 4 , 2010 , Pages 681-686 ; 14328488 (ISSN) Farsi, H ; Gobal, F ; Raissi, H ; Moghiminia, S ; Sharif University of Technology
    Nanostructured molybdenum oxide having a particle size in the range of 30-80 nm was prepared by potentiodynamic electrodeposition method, and the effects of H2SO4 concentration on its capacitive behavior were studied by cyclic voltammetry, galvanostatic discharge, and electrochemical impedance spectroscopy. Poor to fair capacitive behaviors were witnessed depending on the electrolyte concentration and conditions of charge/discharge. Increasing acid concentration to 0.02 M had favorable effect, while beyond that, the effect was detrimental. Capacitance around 600 F g-1 was recorded in the potential range of 0 to -0.55 V vs. Ag/AgCl  

    The investigation of the kinetics and mechanism of hydrogen evolution reaction on tin

    , Article International Journal of Hydrogen Energy ; Volume 32, Issue 12 , 2007 , Pages 1755-1761 ; 03603199 (ISSN) Azizi, O ; Jafarian, M ; Gobal, F ; Heli, H ; Mahjani, M. G ; Sharif University of Technology
    The mechanism and kinetics of the hydrogen evolution reaction (HER) on tin electrode in 0.1 M H2SO4 solution were studied using the methods of steady-state polarization and electrochemical impedance spectroscopy. The simulation of the data obtained from these two methods, using nonlinear fitting procedure allowed us to determine the rate constants of Volmer, Heyrovsky and Tafel steps associated with the mentioned reaction. The kinetic results indicate that HER mechanism at low negative potentials is a serial combination of Volmer step and parallel Tafel and Heyrovsky steps. At high negative potentials where the hydrogen coverage reaches its limiting value, a Tafel line with the slope of -... 

    A study of hydrated nanostructured tungsten trioxide as an electroactive material for pseudocapacitors

    , Article Ionics ; Volume 19, Issue 2 , May , 2013 , Pages 287-294 ; 09477047 (ISSN) Farsi, H ; Gobal, F ; Barzgari, Z ; Sharif University of Technology
    Agglomerates of tungsten trioxide in the range of 90 nm to 1 μm are prepared by the acid precipitation method and characterized by XRD as well as scanning electron microscopy. The product when coated with platinum showed pseudocapacitance when in contact with acidic electrolyte in the potential range of 0. 1 to -0. 25 V/SCE. Capacitance in the range of 0. 014 to 0. 039 F cm-2 exhibiting moderate potential dependencies measured through both chronopotentiometry and impedance spectroscopy is presumed to be due to the insertion/de-insertion of protons into the lattice of tungsten trioxide. Equivalent circuit consisting of parallel simulators of mass transfer and capacitor charging... 

    Effects of Fe2O3 content on ionic conductivity of Li2O-TiO2-P2O5 glasses and glass-ceramics

    , Article Materials Chemistry and Physics ; Volume 190 , 2017 , Pages 8-16 ; 02540584 (ISSN) Mohaghegh, E ; Nemati, A ; Eftekhari Yekta, B ; Banijamali, S ; Sharif University of Technology
    Elsevier Ltd  2017
    In this study, Li2O-TiO2-P2O5-x(Fe2O3) (x = 0, 2.5, 5 and 7.5 weight part) glass and glass-ceramics were synthesized through conventional melt-quenching method and subsequently heat treatment. Glass samples were studied by UV–visible spectroscopy and crystallized samples were characterized by differential thermal analysis, X-ray diffractometry and field emission scanning electron microscopy. Besides, electrical properties were examined according to the electrochemical impedance spectroscopy techniques. Experimental optical spectra of the Fe2O3-doped glasses revealed strong UV absorption band in the range of 330–370 nm, which were attributed to the presence of Fe3+ ions. The major crystalline... 

    Over 10-b On-Chip Impedance Measurement System for High Frequency Range

    , M.Sc. Thesis Sharif University of Technology Mirjalili, Ramin (Author) ; Atarodi, Mojtaba (Supervisor) ; Mehrani, Khashayar (Supervisor)
    Diabetes is one of the most catastrophic diseases in the world. There will be an end to patients’ problems if scientists can invent the artificial pancreas, but there is no implantable sensing core available. All of the sensors used for measuring blood glucose level were based on an electrochemical sensor which will generate a glucose level dependent electric current. The chemical structure of that sensor will deny its usability for in vivo applications. By exploring several biological and electrical literatures we introduced a fully electrical method for sensing the blood glucose level by impedance measurement. In this thesis we introduced a new method for sensing the blood glucose... 

    Frequency Domain HF on-chip Impedance Spectroscope with Over 10 bit Resolution

    , M.Sc. Thesis Sharif University of Technology Bakhshiani, Mehran (Author) ; Atarodi, Mojtaba (Supervisor) ; Mehrani, Khashayar (Supervisor)
    Impedance spectroscopy is known as one of the important integrated sensing methods in micro scale Biosensors and electrochemical sensors. Recently, Impedance spectroscopy has been noticed in many micro scale applications. These micro scale applications is being developed specially in bioelectronics and biomedical. The goal of this thesis is designing an on-chip impedance spectroscope system for high frequency with 10 bits resolution via fully electrical blood glucose concentration measurement. This system extracts the blood glucose concentration data through measuring the permittivity coefficient of blood at 1 GHz frequency. In this thesis, new method for high frequency high resolution... 

    Dye and Cadmium Based Quantum dot Sensitized Solar Cells Based on TiO2 Nanostructures

    , Ph.D. Dissertation Sharif University of Technology Samadpour, Mahmoud (Author) ; Iraji Zad, Azam (Supervisor) ; Taghavinia, Nima (Supervisor)
    In this research we focus on fabrication and characterization of Dye and Cadmium based Quantum Dot Sensitized Solar Cells (QDSCs) based on TiO2 nanostructures. TiO2 nanorods were synthesized with a simple chemical method. TiO2 nanorods, TiO2 nanorod/TiO2 and ZnO nanoparticle composite structures were integrated as photoanode in dye sensitized solar cells (DSSCs). Incorporation of TiO2 nanoparticles into the bare nanorods increased the efficiency more than 45%. Monitoring electron transport properties of the cells, pointed out the crucial role of electronic structure of composite film components on the performance of cells. Suitable morphology of TiO2 nanorods, led us to use them, to make a... 

    Investigation of Pb/PbS a positive Schottky junction formed on conductive glass in contact with alkaline solution

    , Article Journal of Applied Physics ; Vol. 116, issue. 3 , July , 2014 ; ISSN: 00218979 Heidaripour, A ; Jafarian, M ; Gobal, F ; Mahjani, M. G ; Miandari, S ; Sharif University of Technology
    PbS on Pb thin film (Pb/PbS) was deposited on conductive glass (CG) substrate (CG/Pb/PbS) using electrochemical techniques to investigate the Schottky junction in solution. The CG/Pb/PbS electrode was investigated by different techniques based on thermionic emission theory. Electrochemical cell consisted of the CG/Pb/PbS as a working electrode in an alkaline solution showed character of the Schottky junction. Reduction and oxidation of H2O on the CG/Pb/PbS electrode were enhanced under illumination. Water photo splitting is the main process. Study of linear sweep voltammetry at around open circuit potential (OCP) allowed proposing a model based on the Schottky junction which is charged at... 

    A study on the mechanism of electrodeposition of Ni/SiC composite coatings using impedance technique

    , Article ECS Transactions ; Volume 41, Issue 44 , 2012 , Pages 47-57 ; 19385862 (ISSN) ; 9781607683452 (ISBN) Sohrabi, A ; Dolati, A ; Electrodeposition; Sensor ; Sharif University of Technology
    Ni/SiC nanocomposite coatings were electrodeposited using Watts type bath and different SiC particle size. The electrodeposition behavior of Ni/SiC nanoelectrocomposites was studied using electrochemical techniques such as impedance spectroscopy (EIS) and voltammetry. In this study it was shown that SiC particles modify the EIS diagram and voltammograms as well as surface morphology of electrodeposited layers. Experimental results showed that SiC particles not only affect the formation of intermediate species and decrease charge transfer resistance but also increase the nucleation sites for nickel electrodeposition and thus affect the microstructure of electrodeposited Ni/SiC nanocomposites.... 

    Fabrication of self-organised highly ordered titanium oxide nanotube arrays by anodic oxidation and characterisation

    , Article International Journal of Nanomanufacturing ; Volume 5, Issue 3-4 , 2010 , Pages 297-309 ; 17469392 (ISSN) Mohammadpour, R ; Ahadian, M. M ; Iraji Zad, A ; Taghavinia, N ; Dolati, A. G ; Sharif University of Technology
    Self-organised and vertically oriented titanium oxide nanotube array (TNTA) has been synthesised by potentiostat anodisation of Ti foil in fluoride-based electrolyte. By varying the anodisation voltage from 8 V to 24 V it was possible to gradually change the topologies of nanotubes. The size of TNTAs was measured using SEM images and also determined based on a non-destructive optical method. In addition, photoelectrochemical properties of nanotubular TiO2/Ti electrodes were examined by anodic photocurrent response, potentiodynamic polarisation measurements and electrochemical impedance spectroscopy. A general equivalent circuit model was proposed for photoelectrochemical system consists of... 

    Kinetics and electrocatalytic behavior of nanocrystalline CoNiFe alloy in hydrogen evolution reaction

    , Article International Journal of Hydrogen Energy ; Volume 32, Issue 12 , 2007 , Pages 1686-1693 ; 03603199 (ISSN) Jafarian, M ; Azizi, O ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
    Electrocatalytic activity of electrodeposited nanocrystalline CoNiFe alloy in hydrogen evolution reaction (HER) was studied in 1 M NaOH solution. The steady-state polarization measurement and electrochemical impedance spectroscopy were used to determine the Tafel slope, the exchange current density and the activation energy. The simulation of the data obtained from these two methods, using a nonlinear fitting procedure, allowed us to determine the surface coverage and the rate constants associated with the mentioned reaction. The ac-impedance spectra measured at various overpotentials in the HER region exhibited three semicircles in the complex plane plots. The high-frequency semicircle was... 

    Impedance spectroscopy study of aluminum electrocrystallization from basic molten salt (AlCl3-NaCl-KCl)

    , Article Electrochimica Acta ; Volume 52, Issue 17 , 2007 , Pages 5437-5443 ; 00134686 (ISSN) Jafarian, M ; Gobal, F ; Danaee, I ; Mahjani, M. G ; Sharif University of Technology
    Aluminum electrocrystallization is studied by means of electrochemical impedance spectroscopy (EIS). A model based on random birth and deterministic growth of monolayers is proposed, in which the edges are assumed to follow a propagation law. The high frequency impedance data show charge transfer reaction of AlCl4- reduction while the low frequency features signifies the growth mode of deposits. The inductive response observed in the course of polycrystalline deposition reflects the activation of electrode area while a capacitive loop appears in regular growth. Parameters of impedance model in this system can be calculated from the fitting of experimental data to the Faradaic impedance... 

    Circuit realization of a tilted Dirac cone: Platform for fabrication of curved spacetime geometry on a chip

    , Article Physical Review B ; Volume 104, Issue 24 , 2021 ; 24699950 (ISSN) Motavassal, A ; Jafari, S. A ; Sharif University of Technology
    American Physical Society  2021
    We present an LC circuit model that supports a tilted “Dirac cone” in its spectrum. The tilt of the Dirac cone is specified by the parameters of the model consisting of mutual inductance between the neighboring sites and a capacitance C0 at every lattice site. These parameters can be completely measured by impedance spectroscopy. Given that a tilted Dirac cone can be described by a background spacetime metric, the impedance spectroscopy can perfectly provide (local) information about the metric of the spacetime. Nonuniform spatial dependence of the mutual inductance or capacitance induces a nontrivial geometrical structure on the emergent spacetime. Our work extends the range of usefulness... 

    A comparative investigation of the electrocatalytic oxidation of methanol on poly-NiTCPP and poly-TCPP/Ni modified glassy carbon electrodes

    , Article Journal of Electroanalytical Chemistry ; Volume 663, Issue 1 , December , 2011 , Pages 14-23 ; 15726657 (ISSN) Jafarian, M ; Haghighatbin, M. A ; Gobal, F ; Mahjani, M. G ; Rayati, S ; Sharif University of Technology
    Electro-oxidation of methanol in alkaline solution at a glassy carbon electrode electrochemically modified by a conductive polymeric meso-tetra(4-carboxyphenyl)porphyrinato nickel(II), abbreviated as poly-NiTCPP and also meso-tetra(4-carboxyphenyl)porphyrin with incorporated nickel(II) cations, abbreviated as, poly-TCPP/Ni, were investigated and compared. Both films were prepared by oxidative electro-polymerization of complexes by repetitive cyclic voltammetry (RCV) in 0.1 M NaOH aqueous solution. The electrochemical properties and behaviors and also kinetic values of both films have been characterized and compared using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical... 

    The influence of pulse plating parameters on the electrocodeposition of Ni-TiO2 nanocomposite single layer and multilayer structures on copper substrates

    , Article Surface and Coatings Technology ; Volume 262 , 2015 , Pages 173-183 ; 02578972 (ISSN) Mohajeri, S ; Dolati, A ; Ghorbani, M ; Sharif University of Technology
    Elsevier  2015
    The electrocodeposition of Ni-TiO2 nanocomposite single layers and Ni-TiO2/TiO2 multilayers from a Watts bath containing a TiO2 sol on copper substrates was investigated by different deposition techniques. Compared with direct current (DC) deposition, both pulse plating (PP) and pulse reverse plating (PRP) facilitated higher incorporations of TiO2 nanoparticles. Morphological studies conducted by scanning electron microscopy and field emission scanning electron microscopy revealed that the microstructure of the Ni-TiO2 nanocomposite coatings are affected both by pulse potentials and durations, indicating that higher incorporations of TiO2 nanoparticles refine the microstructure. The results...