Search for: electrochemical-analysis
0.006 seconds
Total 43 records

    Synthesis and Study of Electron Transport through a Self-Assembled Monolayer of Thiol-End-Functionalized Tetraphenylporphyrines and Metalo-Tetraphenylporphyrines and Electrochemical Analysis of Dopamine and Ascorbic Acid with this SAMs

    , M.Sc. Thesis Sharif University of Technology Sanaei, Mahsa (Author) ; Mohammadi Boghaei, Davar (Supervisor)
    Self-Assembled Monolayer (SAM) is the first step in all surface engineering and assembly processes. It is used in sensor fabrication, memories and molecular recognition and optoelectronic devises as an active surface for patterning and chemical architecting of solid substrates. Tetraphenyl porphyrins because of their high stability and uniqe electronic and optic properties, that comes from their conjugate π electrons, easily can be used in these monolayers. Moreover they have a wide application because of their ability for coordination with metals and accepting substituents with electron donating and withdrawing properties. Electron transport through these layars which attach to the surface... 

    Voltammetric behavior and determination of trace amounts of omeprazole using an edge-plane pyrolytic graphite electrode

    , Article Iranian Journal of Pharmaceutical Research ; Volume 14, Issue 2 , Spring , 2015 , Pages 465-471 ; 17350328 (ISSN) Shahrokhian, S ; Ghalkhani, M ; Bayat, M ; Ghorbani Bidkorbeh, F ; Sharif University of Technology
    Iranian Journal of Pharmaceutical Research  2015
    The voltammetric performance of edge-plane pyrolytic graphite (EPG) electrode via adsorptive stripping voltammetry was investigated for study of the electrochemical behavior of omeprazole (OMZ) in aqueous solution. The results revealed that the oxidation of OMZ is an irreversible pH-dependent process that proceeds with the transfer of one electron and one proton in an adsorption-controlled mechanism. The determination conditions, such as the pH values of the supporting electrolyte, accumulation time and scan rate were optimized. Simplicity, high reproducibility and low detection limit (3 nM) of the electrode response as well as wide linear range (0.01 to 4.0 µM) can be stated as significant... 

    A polypyrrole-based sorptive microextraction coating for preconcentration of malathion from aquatic media

    , Article Chromatographia ; Volume 74, Issue 9-10 , 2011 , Pages 731-735 ; 00095893 (ISSN) Bagheri, H ; Aghakhani, A ; Ayazi, Z ; Khakinezhad, M ; Sharif University of Technology
    A new micro-solid phase extraction method was developed by combining solid-phase extraction and stir bar sorptive extraction to benefit from the advantages of both techniques. A polypyrrole coating was electrochemically synthesized on the surface of an already used graphite furnace, employed in electro-thermal atomic absorption spectroscopy. The cylindrical geometry of the graphite tube provided a rather huge surface area, suitable for sorptive extraction. The novel sorbent coating was examined as an extracting medium to isolate malathion. Effects of different parameters such as extraction time, salt concentration, sample volume, desorption solvent and time were investigated and optimized.... 

    Sensitive determination of dopamine in the presence of uric acid and ascorbic acid using TiO2 nanotubes modified with Pd, Pt and Au nanoparticles

    , Article Analyst ; Volume 136, Issue 11 , 2011 , Pages 2322-2329 ; 00032654 (ISSN) Mahshid, S ; Li, C ; Mahshid, S. S ; Askari, M ; Dolati, A ; Yang, L ; Luo, S ; Cai, Q ; Sharif University of Technology
    A simple modified TiO2 nanotubes electrode was fabricated by electrodeposition of Pd, Pt and Au nanoparticles. The TiO2 nanotubes electrode was prepared using the anodizing method, followed by modifying Pd nanoparticles onto the tubes surface, offering a uniform conductive surface for electrodeposition of Pt and Au. The performance of the modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The Au/Pt/Pd/TiO2 NTs modified electrode represented a high sensitivity towards individual detection of dopamine as well as simultaneous detection of dopamine and uric acid using 0.1 M phosphate buffer solution (pH 7.00) as the base solution. In both case,... 

    Synthesis and characterization of new triphenylamine-based dyes with novel anchoring groups for dye-sensitized solar cell applications

    , Article Journal of Materials Science: Materials in Electronics ; Volume 28, Issue 2 , 2017 , Pages 1859-1868 ; 09574522 (ISSN) Salimi Beni, A ; Hosseinzadeh, B ; Azari, M ; Ghahary, R ; Sharif University of Technology
    Springer New York LLC  2017
    Three new chromophores based on the triphenylamine (MM, DM, DN) with various novel electron withdrawing anchoring groups have been synthesized for use in dye-sensitized solar cells (DSSCs). The sensitizers were characterized by 1H and 13C NMR, Mass, UV–Vis, and electrochemical analysis. The HOMO and LUMO electron distributions of the sensitizers were calculated using density functional theory on a B3LYP level for geometry optimization. The DSSC device based on DM dye showed the best photovoltaic performance among MM and DN dyes: maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 98 %, short circuit current (JSC) of 4.58 mA/cm2, open circuit voltage (VOC) of... 

    Imprinted silica nanofiber formation via sol-gel-electrospinning for selective micro solid phase extraction

    , Article New Journal of Chemistry ; Volume 42, Issue 16 , 2018 , Pages 13864-13872 ; 11440546 (ISSN) Asgari, S ; Bagheri, H ; Es Haghi, A ; Sharif University of Technology
    Royal Society of Chemistry  2018
    Sol composition and ripening conditions are two important parameters in silica fiber production through the conventional sol-gel process. In the current study, silica nanofibers were successfully obtained via the electrospinning technique, and sol-gel formation occurred during this process. Based on previous reports, with the aim of increasing the selectivity, we used the molecular imprinted methodology to produce a selective medium via sol-gel electrospinning. In this process, sol-gel was formed during electrospinning and then, the backbone polymer was removed by heating. To obtain a thin layer of silica nanofibers, the influencing parameters such as backbone polymer types, imprinting time... 

    Improvement of the electrochemical performance of a nickel rich LiNi0.5Co0.2Mn0.3O2 cathode material by reduced graphene oxide/SiO2 nanoparticle double-layer coating

    , Article New Journal of Chemistry ; Volume 43, Issue 6 , 2019 , Pages 2766-2775 ; 11440546 (ISSN) Razmjoo Khollari, M. A ; Paknahad, P ; Ghorbanzadeh, M ; Sharif University of Technology
    Royal Society of Chemistry  2019
    Due to its high discharge capacity, low cost, and good safety, LiNi0.5Co0.2Mn0.3O2 (NCM 523) is regarded as a promising cathode material for the next-generation of lithium-ion batteries. However, poor cycling stability and rate capability are the main disadvantages of the NCM 523 cathode material. In this work, SiO2 single layer-coated and reduced graphene oxide (outer)/SiO2 (inner) double layer-coated NCM 523 have been prepared by a facile wet chemical method. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy results confirm that NCM 523... 

    Cycling performance of LiFePO4/graphite batteries and their degradation mechanism analysis via electrochemical and microscopic techniques

    , Article Ionics ; 2021 ; 09477047 (ISSN) Sharifi, H ; Mosallanejad, B ; Mohammadzad, M ; Hosseini Hosseinabad, S. M ; Ramakrishna, S ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    In this work, cycling-induced aging occurring in 18650-type LiFePO4/graphite full cells at different C-rates is studied extensively. The mechanism of performance degradation is investigated using a combination of electrochemical and microstructural analyses. Half-cell studies are carried out after dismantling the full cells, using fresh and cycled LiFePO4 cathode and graphite anode to independently study them. The results show that the capacity of LiFePO4 electrodes is significantly recovered. The rate of capacity fading in the discharge state considered as irreversible capacity in the graphite is higher than LiFePO4 half cells, indicating a greater degradation in the performance of this... 

    Electrochemical determination of atorvastatin on nano-scaled polypyrrole film

    , Article Bioelectrochemistry ; Vol. 98 , 2014 , pp. 1-10 ; ISSN: 15675394 Kamalzadeh, Z ; Shahrokhian, S ; Sharif University of Technology
    Pyrrole was electro-polymerized on the surface of the glassy carbon electrode (GCE) coated with a thin film of carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG) or graphite nanopowder (GNP). Morphology, thickness, stability and loading of the polypyrrole (PPY) film were significantly affected by the structure and morphology of the sub-layer of carbon nanomaterials. Electrochemical oxidation of atorvastatin (ATOR) was investigated. Under the optimized conditions, a significant increase in the peak current (compared to other modified electrodes and bare GCE) and a negative shift in the peak potential (compared to bare GCE) were... 

    Synthesis and electrochemical characterization of sol-gel-derived RuO 2/carbon nanotube composites

    , Article Journal of Solid State Electrochemistry ; Vol. 18, Issue 4 , April , 2014 , pp. 993-1003 ; Online ISSN: 1433-0768 Kahram, M ; Asnavandi, M ; Dolati, A ; Sharif University of Technology
    Ruthenium oxide was coated on multiwalled carbon nanotubes (MWCNTs) to obtain nanocomposite electrode which has a good response to the pH. To synthesize this electrode, gold and cobalt were coated on a stainless steel 304 substrates, respectively, and then, vertically aligned carbon nanotubes were grown on the prepared substrates by chemical vapor deposition. Gold reduced activity of the stainless steel, while cobalt served as a catalyst for growth of the carbon nanotube. Ruthenium oxide was then coated on MWCNTs via sol-gel method. At last, different techniques were used to characterize the properties of synthesized electrode including scanning electron microscopy (SEM), transmission... 

    Pd-Au nanoparticle decorated carbon nanotube as a sensing layer on the surface of glassy carbon electrode for electrochemical determination of ceftazidime

    , Article Materials Science and Engineering C ; Vol. 34, issue. 1 , 2014 , pp. 318-325 ; ISSN: 09284931 Shahrokhian, S ; Salimian, R ; Rastgar, S ; Sharif University of Technology
    A simple electrodeposition method is employed to construct a thin film modifier of palladium-gold nanoparticles (Pd-AuNPs) decorated multi-walled carbon nanotube (MWCNT) on the surface of glassy carbon electrode (GCE). Morphology and property of Pd-AuNPs-MWCNT have been examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Electrochemical performance of Pd-AuNPs-MWCNT/GCE for detection of ceftazidime (CFZ) has been investigated by cyclic voltammetry (CV). This nanostructured film modified electrode effectively exhibited enhanced properties for detection of ceftazidime (CFZ). The effects of various experimental variables such as, the amount of casted MWCNT,... 

    Nickel hydroxide nanoparticles-reduced graphene oxide nanosheets film: Layer-by-layer electrochemical preparation, characterization and rifampicin sensory application

    , Article Talanta ; Vol. 119 , 2014 , pp. 156-163 ; ISSN: 00399140 Rastgar, S ; Shahrokhian, S ; Sharif University of Technology
    Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of nickel hydroxide nanoparticle-reduced graphene oxide nanosheets (Ni(OH)2-RGO) on a graphene oxide (GO) film pre-cast on a glassy carbon electrode surface. The surface morphology and nature of the nano-hybrid film (Ni(OH)2-RGO) was thoroughly characterized by scanning electron and atomic force microscopy, spectroscopy and electrochemical techniques. The modified electrode appeared as an effective electro-catalytic model for analysis of rifampicin (RIF) by using linear sweep voltammetry (LSV). The prepared modified electrode exhibited a distinctly higher activity... 

    A study on the effects of Fex/Niy/MgO(1-x-y) catalysts on the volumetric and electrochemical hydrogen storage of multi-walled carbon nanotubes

    , Article International Journal of Hydrogen Energy ; Volume 35, Issue 1 , 2010 , Pages 231-237 ; 03603199 (ISSN) Reyhani, A ; Mortazavi, S. Z ; Zaker Moshfegh, A ; Nozad Golikand, A ; Sharif University of Technology
    The effects of various ratios of Fe/Ni/MgO and growth temperatures on yield, diameter and quality of multi-walled carbon nanotubes (MWCNTs) were studied. Thermal gravimetric analysis (TGA) confirmed that the MWCNT yield depends on Fe/Ni ratio with the following order; Fe0.5 Ni0.5 > Fe > Fe0.75 Ni0.25 > Fe0.25 Ni0.75 > Ni. The results indicated that there is an optimum temperature (940 °C) for the MWCNT growth both from quality and quantity (yield) aspects as compared to other temperatures. Moreover, the changes on Fe/Ni to MgO ratio for the MWCNT growth revealed that Fe/Ni/MgO with the ratio of 17.5/17.5/65 had the highest quality and surface area as compared to the other ratios. The... 

    Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles

    , Article Materials Science and Engineering C ; Volume 58 , 2016 , Pages 1098-1104 ; 09284931 (ISSN) Asadian, E ; Iraji Zad, A ; Shahrokhian, S ; Sharif University of Technology
    Elsevier Ltd 
    By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable... 

    Origin of apparent light-enhanced and negative capacitance in perovskite solar cells

    , Article Nature Communications ; Volume 10, Issue 1 , 2019 ; 20411723 (ISSN) Ebadi, F ; Taghavinia, N ; Mohammadpour, R ; Hagfeldt, A ; Tress, W ; Sharif University of Technology
    Nature Publishing Group  2019
    So-called negative capacitance seems to remain an obscure feature in the analysis of the frequency-dependent impedance of perovskite solar cells. It belongs to one of the puzzling peculiarities arising from the mixed ionic-electronic conductivity of this class of semiconductor. Here we show that apparently high capacitances in general (positive and negative) are not related to any capacitive feature in the sense of a corresponding charge accumulation. Instead, they are a natural consequence of slow transients mainly in forward current of the diode upon ion displacement when changing voltage. The transient current leads to a positive or negative ‘capacitance’ dependent on the sign of its... 

    Artificial neural network aided estimation of the electrochemical signals of monosaccharides on gold electrode

    , Article Carbohydrate Research ; Volume 343, Issue 8 , 2008 , Pages 1359-1365 ; 00086215 (ISSN) Gobal, F ; Sadeghpour Dilmaghani, A ; Sharif University of Technology
    Artificial neural networks were used to predict the oxidation peaks potentials of 7 monosaccharides under linear sweep voltammetry regime. Two sets of descriptors, one based on molecular properties calculated through DFT and another based on simple geometric distributions of hydroxyl groups and asymmetric carbon atoms along molecular chains, were employed to introduce the molecules to networks. Relatively, simple networks of (3,3,1) and (3,3,3,1) structures with the number of epochs not exceeding 15 through training process were capable of correctly predicting the peaks positions with R values in the range of 0.97-0.99. © 2008 Elsevier Ltd. All rights reserved  

    Optimization of solid-phase microextraction of volatile phenols in water by a polyaniline-coated Pt-fiber using experimental design

    , Article Analytica Chimica Acta ; Volume 581, Issue 1 , 2007 , Pages 71-77 ; 00032670 (ISSN) Mousavi, M ; Noroozian, E ; Jalali Heravi, M ; Mollahosseini, A ; Sharif University of Technology
    Solid-phase microextraction (SPME) coupled to gas chromatography (GC) was applied to the extraction of phenol and some of its volatile derivatives in water samples. The SPME fiber consisted of a thin layer of polyaniline, which was electrochemically coated on a fine Pt wire. The stability of the coating was such that it could be used at temperatures as high as 325 °C, without any deterioration. The effects of various parameters affecting the extraction efficiency were studied, simultaneously. From these, optimization of the extraction temperature, extraction time, coating thickness, sample pH, salt concentration and desorption time was carried out by means of a (26-2) fractional factorial... 

    Hybrid supercapacitors constructed from double-shelled cobalt-zinc sulfide/copper oxide nanoarrays and ferrous sulfide/graphene oxide nanostructures

    , Article Journal of Colloid and Interface Science ; Volume 585 , 2021 , Pages 750-763 ; 00219797 (ISSN) Shahi, M ; Hekmat, F ; Shahrokhian, S ; Sharif University of Technology
    Academic Press Inc  2021
    Evolution of renewable energies in the era of the modernized world has been strongly tied up to the incessant development of high-performance energy storage systems benefiting from both high energy and power densities. In the present work, binder-free positive electrodes are fabricated via a facile electrochemical deposition route in which copper oxide nanorods (CuO NRs) directly grown onto the copper foam (CF) are decorated with bimetallic cobalt-zinc sulfide nanoarrays (Co-Zn-S NAs). The fabricated Co-Zn-S@CuO-CFs represent promising specific capacity of 317.03 C.g−1 at 1.76 A.g−1, along with superior cyclic stability (113% retention after 4500 cycles). Negative electrodes were further... 

    Preparation of novel and highly active magnetic ternary structures (metal-organic framework/cobalt ferrite/graphene oxide) for effective visible-light-driven photocatalytic and photo-fenton-like degradation of organic contaminants

    , Article Journal of Colloid and Interface Science ; Volume 602 , 2021 , Pages 73-94 ; 00219797 (ISSN) Bagherzadeh, B ; Kazemeini, M ; Mahmoodi, N. M ; Sharif University of Technology
    Academic Press Inc  2021
    Herein, MIL-101(Fe), CoFe2O4, novel binary (MIL-101(Fe)/CoFe2O4, MIL-101(Fe)/GO and CoFe2O4/GO), and ternary (MIL-101(Fe)/CoFe2O4/(3%)GO and MIL-101(Fe)/CoFe2O4/(7%)GO) magnetic composites based upon the MIL-101(Fe) were synthesized. The XRD, FESEM, TEM, EDX, BET-BJH, FTIR, VSM, DRS, PL, EIS and other electrochemical analyses were applied to characterize samples. The MIL/CoFe2O4/(3%)GO demonstrated the best performance compared to other samples for visible light photocatalytic and photo-Fenton-like degradation of Direct Red 23 (DtR-23), Reactive Red 198 (ReR-198) dyes as well as Tetracycline Hydrochloride (TC-H) antibiotic. Degradation of dyes using the ternary composite after 70 min of... 

    A novel enzyme based biosensor for catechol detection in water samples using artificial neural network

    , Article Biochemical Engineering Journal ; Volume 128 , 2017 , Pages 1-11 ; 1369703X (ISSN) Maleki, N ; Kashanian, S ; Maleki, E ; Nazari, M ; Sharif University of Technology
    Elsevier B.V  2017
    Biosensors could be used as digital devices to measure the sample infield. Consequently, computational programming along with experimental achievements are required. In this study, a novel biosensor/artificial neural network (ANN) integrated system was developed. Poly (3,4-ethylenedioxy-thiophene)(PEDOT), graphene oxide nano-sheets (GONs) and laccase (Lac) were used to construct a biosensor. The simple and one-pot process was accomplished by electropolymerizing 3,4-ethylenedioxy-thiophene (EDOT) along with GONs and Lac as dopants on glassy carbon electrode. Scanning electron microscopy (SEM) and electrochemical characterization were conducted to confirm successful enzyme entrapment. The...