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    Voltammetric determination of dopamine at the surface of TiO2 nanoparticles modified carbon paste electrode

    , Article International Journal of Electrochemical Science ; Volume 5, Issue 1 , 2010 , Pages 147-157 ; 14523981 (ISSN) Mazloum-Ardakani, M ; Rajabi, H ; Beitollahi, H ; Mirjalili, B.B.F ; Akbari, A ; Taghavinia, N ; Sharif University of Technology
    2010
    Abstract
    In the present paper, the use of a novel carbon paste electrode modified by N,N'(2,3-dihydroxybenzylidene)-1,4-phenylenediamine (DHBPD) and TiO2 nanoparticles prepared by a simple and rapid method for the determination of dopamine (DA) was described. In the first part of the work, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. A linear segment was found with slope value of about 48 mV/pH in the pH range 2.0 -12.0. The apparent charge transfer rate constant (ks) and transfer coefficient (α) for electron transfer between DHBPD and TiO2 nanoparticles-carbon paste electrode were calculated. In... 

    Determination of ascorbic acid in the presence of uric acid and folic acid by a nanostructured electrochemical sensor based on a TiO2 nanoparticle carbon paste electrode

    , Article Analytical Letters ; Volume 43, Issue 16 , 2010 , Pages 2618-2630 ; 00032719 (ISSN) Mazloum Ardakani, M ; Talebi, A ; Beitollahi, H ; Naeimi, H ; Taghavinia, N ; Sharif University of Technology
    Abstract
    A carbon paste electrode (CPE), modified with novel hydroquinone/TiO2 nanoparticles, was designed and used for simultaneous determination of ascorbic acid (AA), uric acid (UA) and folic acid (FA). The magnitude of the peak current for modified TiO2-nanoparticle CPE (MTNCPE) increased sharply in the presence of ascorbic acid and was proportional to its concentration. A dynamic range of 1.0-1400.0 μM, with the detection limit of 6.4x10-7M for AA, was obtained using the DPV technique (pH=7.0). The prepared electrode was successfully applied for the determination of AA, UA, and FA in real samples  

    Simultaneous voltammetric determination of uric acid and ascorbic acid using a carbon-paste electrode modified with multi-walled carbon nanotubes/nafion and cobalt(II)-nitrosalophen

    , Article Electroanalysis ; Volume 19, Issue 21 , 2007 , Pages 2234-2242 ; 10400397 (ISSN) Shahrokhian, S ; Zare Mehrjardi, H. R ; Sharif University of Technology
    2007
    Abstract
    A composition of multiwalled carbon nanotube (MWCNT), Nafion and cobalt(II)-5-nitrosalophen (CoNSal) is applied for the modification of carbon-paste electrode (CPE). The pretreated MWCNT is well dispersed in the alcoholic solution of Nafion under the ultrasonic agitation, and the resulted suspension is used as modifier (with 10% w/w) in the matrix of the paste electrode. The prepared electrode further modified by addition of 3 wt% of CoNSal. The resulted modified electrode is used as a sensitive voltammetric sensor for simultaneous determination of uric acid (UA) and ascorbic acid (AA). The electrode showed efficient electrocatalytic activity in lowering the anodic overpotentials and... 

    Voltammetric determination of methimazole using a carbon paste electrode modified with a Schiff base complex of cobalt

    , Article Electroanalysis ; Volume 20, Issue 10 , 2008 , Pages 1061-1066 ; 10400397 (ISSN) Shahrokhian, S ; Ghalkhania, M ; Sharif University of Technology
    2008
    Abstract
    The electrochemical behavior of methimazole, as an antithyroid agent, is investigated on the surface of a carbon-paste electrode modified with a newly synthesized Schiff base complex of cobalt. The prepared modified electrode showed an efficient catalytic role in the electrochemical oxidation of methimazole, leading to remarkable decrease in oxidation overpotential and enhancement of the kinetics of the electrode reaction. The mechanism of the electrocatalytic process on the surface of the modified electrode is analyzed by obtaining the cyclic voltammograms in various potential sweep rates and pHs of the buffer solutions. The differential pulse voltammetry is applied as a very sensitive... 

    Multi-walled carbon nanotube paste electrode for selective voltammetric detection of isoniazid

    , Article Microchimica Acta ; Volume 157, Issue 3-4 , 2007 , Pages 149-158 ; 00263672 (ISSN) Shahrokhian, S ; Amiri, M ; Sharif University of Technology
    2007
    Abstract
    A multi-walled carbon nanotube paste electrode (MWCPE) is prepared as an electrochemical sensor with high sensitivity and selectivity in responding to isoniazid. The electrochemical oxidation of isoniazid is investigated in buffered solution by cyclic and differential pulse voltammetry. The electrode is shown to be very effective for the detection of isoniazid in the presence of other biological reductant compounds. The electrochemical oxidation of cysteine, due to the high overvoltage, is completely stopped at the surface of MWCPE. The electrode exhibits a very good resolution between the voltammetric peak of isoniazid and the peaks of ascorbic acid (AA) and dopamine (DA). A resolution of... 

    Voltammetric studies of propylthiouracil at a carbon-paste electrode modified with cobalt(II)-4-chlorosalophen: Application to voltammetric determination in pharmaceutical and clinical preparations

    , Article Microchimica Acta ; Volume 151, Issue 1-2 , 2005 , Pages 73-79 ; 00263672 (ISSN) Shahrokhian, S ; Jannat Rezvani, M. J ; Sharif University of Technology
    2005
    Abstract
    A carbon-paste electrode chemically modified with a Schiff-base complex of cobalt (cobalt(II)-4-chlorosalophen, CoClSal) is utilized to investigate the voltammetric response of propylthiouracil (PTU). The mechanism of electrocatalytic oxidation of the compound is investigated by means of cyclic voltammetric studies applying various pHs to the buffered solutions. The modified electrode exhibits effective catalytic properties that lower the anodic overpotential and enhance the rate of electron transfer for the electrochemical oxidation of PTU. The results of the cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques showed that the modified electrode exhibits good... 

    Voltammetric monitoring of Cd (II) by nano-TiO2 modified carbon paste electrode sensitized using 1,2-bis-[o-aminophenyl thio] ethane as a new ion receptor

    , Article Sensors and Actuators, B: Chemical ; Vol. 192 , 2014 , pp. 648-657 ; ISSN: 09254005 Ramezani, S ; Ghobadi, M ; Bideh, B. N ; Sharif University of Technology
    Abstract
    The objective of the work ahead is presentation of a new carbon paste electrode (CPE) modified by TiO2 nanoparticles (TiO2NPs) and 1,2-bis-[o-aminophenyl thio] ethane (APTE) ligand as a selective cation receptor for determination of the Cd (II) ions using differential pulse anodic stripping voltammetry (DPASV). The electrode shows an excellent tendency to Cd (II) ions in presence of some interfering species. Under the optimum conditions, a linear calibration curve was obtained in the concentration range of 2.9 nM to 4.6 μM with a correlation coefficient of 0.9969 in the anodic potential of 0.54 (V vs. Ag/AgCl). The metal detection limit was 2.0 nM after 10 min preconcentration (S/N = 3). The... 

    The electrocatalytic examination of cephalosporins at carbon paste electrode modified with CoSalophen

    , Article Talanta ; Volume 71, Issue 4 , 2007 , Pages 1669-1674 ; 00399140 (ISSN) Jamasbi, E. S ; Rouhollahi, A ; Shahrokhian, S ; Haghgoo, S ; Aghajani, S ; Sharif University of Technology
    Elsevier  2007
    Abstract
    The electrocatalytic oxidation of cephalexin and cefazolin has been studied at a carbon paste electrode modified with cobalt salophen (CoSal) by cyclic voltammetry. The selectivity of the carbon paste modified with CoSal in detecting cephalexin and cefazolin was examined. To suggest the electrocatalytic mechanism for electro-oxidation of cefazolin, the electrochemical behavior of ceftriaxone was investigated which has a thiol group out of the beta lactam ring. The electrocatalytic oxidation of these antibiotics is shown to be irreversible at the CoSal modified electrode. Scan rate dependence of cefazolin, which is a sulfur-containing compound, has been examined. The results indicated that... 

    Carbon paste electrode incorporating multi-walled carbon nanotube/cobalt salophen for sensitive voltammetric determination of tryptophan

    , Article Sensors and Actuators, B: Chemical ; Volume 123, Issue 2 , 2007 , Pages 942-949 ; 09254005 (ISSN) Shahrokhian, S ; Fotouhi, L ; Sharif University of Technology
    2007
    Abstract
    A modified carbon paste electrode is prepared by incorporating multi-walled carbon nanotube (MWCNT) and cobalt salophen (CoSal). A mixture of fine graphite powder with 10 wt% of MWCNT is applied for the preparation of carbon paste (by dispersing in Nujol) and finally modified with CoSal. The electrocatalytic oxidation of tryptophan (Trp) is investigated on the surface of the MWCNT/CoSal-modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Using the modified electrode, the kinetics of the electro-oxidation of Trp is considerably enhanced, by lowering the anodic overpotential through a catalytic fashion. The mechanism of electrochemical behavior of Trp at... 

    Construction of a modified carbon paste electrode based on TiO2 nanoparticles for the determination of gallic acid

    , Article Journal of Solid State Electrochemistry ; Volume 17, Issue 1 , 2013 , Pages 157-165 ; 14328488 (ISSN) Tashkhourian, J ; Nami Ana, S. F ; Hashemnia, S ; Hormozi Nezhad, M. R ; Sharif University of Technology
    2013
    Abstract
    A modified carbon paste electrode was prepared by incorporating the TiO2 nanoparticles in the carbon paste matrix. The electrochemical behavior of gallic acid (GA) is investigated on the surface of the electrode using cyclic voltammetry and differential pulse voltammetry. The surface morphology of the prepared electrode was characterized using the scanning electron microscopy. The results indicate that the electrochemical response of GA is improved significantly at the modified electrode compared with the unmodified electrode. Furthermore, the capabilities of electron transfer on these two electrodes were also investigated by electrochemical impedance spectroscopy. Under the optimized... 

    Novel nanostructure electrochemical sensor for electrocatalytic determination of norepinephrine in the presence of high concentrations of acetaminophene and folic acid

    , Article Applied Catalysis A: General ; Volume 378, Issue 2 , 2010 , Pages 195-201 ; 0926860X (ISSN) Mazloum Ardakani, M ; Beitollahi, H ; Sheikh Mohseni, M. A ; Naeimi, H ; Taghavinia, N ; Sharif University of Technology
    2010
    Abstract
    In the present paper, the use of a carbon paste electrode modified by 2,2′-[1,2 buthanediylbis (nitriloethylidyne)]-bis-hydroquinone (BH) and TiO2 nanoparticles prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of norepinephrine (NE), acetaminophene (AC) and folic acid (FA). Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of NE, AC and FA has been explored at the modified electrode. Differential pulse voltammetry (DPV) peak currents of NE, AC and FA increased linearly with their concentration at the ranges of 4.0-1100.0 μM, 12.5-500.0 μM and 200.0-3200.0 μM,... 

    Electrochemical determinations of 6-mercaptopurine on the surface of a carbon nanotube-paste electrode modified with a cobalt salophen complex

    , Article Journal of Solid State Electrochemistry ; Volume 16, Issue 4 , April , 2012 , Pages 1643-1650 ; 14328488 (ISSN) Shahrokhian, S ; Ghorbani Bidkorbeh, F ; Mohammadi, A ; Dinarvand, R ; Sharif University of Technology
    2012
    Abstract
    A mixture of multi-walled carbon nanotube/graphite paste electrode modified with a salophen complex of cobalt was prepared and was applied for the study of the electrochemical behavior of 6-mercaptopurine (MP) using cyclic and differential pulse voltammetry (DPV). An excellent electrocatalytic activity toward the oxidation of MP was achieved, which led to a considerable lowering in the anodic overpotential and remarkable increase in the response sensitivity in comparison with unmodified electrode. Utilizing DPV method, a linear dynamic range of 1-100 μM with detection limit of 0.1 μM was obtained in phosphate buffer of pH 3.0. The electrochemical detection system was very stable, and the... 

    Selective voltammetric determination of d-penicillamine in the presence of tryptophan at a modified carbon paste electrode incorporating TiO2 nanoparticles and quinizarine

    , Article Journal of Electroanalytical Chemistry ; Volume 644, Issue 1 , Jan , 2010 , Pages 1-6 ; 15726657 (ISSN) Mazloum Ardakani, M ; Beitollahi, H ; Taleat, Z ; Naeimi, H ; Taghavinia, N ; Sharif University of Technology
    2010
    Abstract
    A carbon paste electrode (CPE) chemically modified with TiO2 nanoparticles and quinizarine (QZ) was used as a selective electrochemical sensor for the simultaneous determination of minor amounts of d-penicillamine (D-PA) and tryptophan (Trp). This modified electrode showed very efficient electrocatalytic activity for anodic oxidation of both d-PA and Trp. Substantial decreases of anodic overpotentials for both compounds made this analysis possible. Results of square wave voltammetry (SWV) using this modified electrode showed two well-resolved anodic waves for the oxidation of d-PA and Trp, which makes the simultaneous determination of both compounds possible. The peak potential for the... 

    Modification of carbon paste with congo red supported on multi-walled carbon nanotube for voltammetric determination of uric acid in the presence of ascorbic acid

    , Article Journal of Solid State Electrochemistry ; Volume 13, Issue 10 , 2009 , Pages 1567-1575 ; 14328488 (ISSN) Shahrokhian, S ; Zare Mehrjardi, H. R ; Khajehsharifi, H ; Sharif University of Technology
    2009
    Abstract
    A chemically modified carbon-paste electrode (CPE) is prepared by incorporating congo red (CR) immobilized on multi-walled carbon nanotube (MWCNT). The results show that CR is effectively immobilized on the surface of MWCNT under the ultrasonic agitation in aqueous solution and further incorporating the nafion. The prepared electrode, due to the electrostatic repulsions between the CR and ascorbate anion, is capable to mask the response of the ascorbic acid (AA) completely and provide an effective method for the detection of minor amounts of uric acid (UA) in the presence of high concentrations of AA. On the other hand, an increase in the microscopic area of the electrode by addition of... 

    Fabrication of modified TiO 2 nanoparticle carbon paste electrode for simultaneous determination of dopamine, uric acid, and l-cysteine

    , Article Journal of Solid State Electrochemistry ; Volume 13, Issue 9 , 2009 , Pages 1433-1440 ; 14328488 (ISSN) Mazloum Ardakani, M ; Talebi, A ; Naeimi, H ; Nejati Barzoky, M ; Taghavinia, N ; Sharif University of Technology
    2009
    Abstract
    A carbon paste electrode, modified with 2, 2″-[1,7- hepthandiylbis(nitriloethylidyne)]-bis-hydroquinone and TiO 2 nanoparticles, was used for the simultaneous determination of dopamine (DA), uric acid (UA), and l-cysteine. The study was carried out by using cyclic voltammetry, chronoamperometry, and square wave voltammetry (SWV) techniques. Some kinetic parameters such as the electron transfer coefficient (α) and heterogeneous rate constant (k s) were also determined for the DA oxidation. A dynamic range of 8.0-1400 μM, with the detection limit of 8.4∈×∈10 -7 M for DA, was obtained using SWV (pH∈=∈7.0). The prepared electrode was successfully applied for the determination of DA, UA, and... 

    Silver nanoparticles modified carbon nanotube paste electrode for simultaneous determination of dopamine and ascorbic acid

    , Article Journal of Electroanalytical Chemistry ; Volume 633, Issue 1 , 2009 , Pages 85-91 ; 15726657 (ISSN) Tashkhourian, J ; Hormozi Nezhad, M. R ; Khodavesi, J ; Javadi, S ; Sharif University of Technology
    Elsevier  2009
    Abstract
    A novel modified carbon-paste electrode was employed for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) with good selectivity and high sensitivity. Silver nanoparticle and carbon nanotube modified carbon-paste electrode (Ag/CNT-CPE) displayed excellent electrochemical catalytic activities towards dopamine (DA) and ascorbic acid (AA). The oxidation overpotentials of DA and AA were decreased significantly compared with those obtained at the bare CPE. Differential pulse voltammetry was used for the simultaneous determination of DA and AA. The peak separation between DA and AA was 67 mV. The calibration curves for DA and AA were obtained in the range of 8.0 × 10-7-6.4 ×... 

    DFT and experimental study of the host-guest interactions effect on the structure, properties, and electro-catalytic activities of N 2O 2-Ni(II) schiff-base complexes incorporated into zeolite

    , Article Journal of Physical Chemistry C ; Volume 116, Issue 34 , 2012 , Pages 18518-18532 ; 19327447 (ISSN) Jafarian, M ; Rashvand Avei, M ; Khakali, M ; Gobal, F ; Rayati, S ; Mahjani, M. G ; Sharif University of Technology
    2012
    Abstract
    Ni II-(N,N′-bis(2,4-dihydroxyacetophenone)-2, 2-dimethylpropandiimine (Ni II{salnptn(4-OH) 2}) complex has been encapsulated within the supercage of zeolite-NaY by reacting Ni 2+-exchanged NaY with the flexible Schiff-base ligand that diffuses into the cavities. The encapsulated complex is characterized by EDX, scanning electron microscopy, powder X-ray diffraction, FT-IR, and cyclic voltammetry studies. Density functional calculation is being carried out on both the free nickel Schiff-base complex and that encapsulated in NaY zeolite to investigate changes in structural parameters, energies of the HOMO and LUMO, and absolute hardness and softness. Electrochemical properties of the NaY... 

    Simultaneous voltammetric determination of ascorbic acid, acetaminophen and isoniazid using thionine immobilized multi-walled carbon nanotube modified carbon paste electrode

    , Article Electrochimica Acta ; Volume 55, Issue 3 , 2010 , Pages 666-672 ; 00134686 (ISSN) Shahrokhian, S ; Asadian, E ; Sharif University of Technology
    2010
    Abstract
    A carbon paste electrode (CPE) modified with thionine immobilized on multi-walled carbon nanotube (MWCNT), was prepared for simultaneous determination of ascorbic acid (AA) and acetaminophen (AC) in the presence of isoniazid (INZ). The electrochemical response characteristics of the modified electrode toward AA, AC and INZ were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic role for the electro-oxidation of AA and AC, leading to a remarkable peak resolution (∼303 mV) for two compounds. On the other hand, the presence of INZ, which is considered as important drug interference for AC, does not affect the voltammetric responses... 

    Application of carbon-paste electrode modified with iron phthalocyanine for voltammetric determination of epinephrine in the presence of ascorbic acid and uric acid

    , Article Sensors and Actuators, B: Chemical ; Volume 137, Issue 2 , 2009 , Pages 669-675 ; 09254005 (ISSN) Shahrokhian, S ; Ghalkhani, M ; Amini, M. K ; Sharif University of Technology
    2009
    Abstract
    A carbon-paste electrode (CPE) modified with iron(II) phthalocyanine was used for the sensitive voltammetric determination of epinephrine (EN). The electrochemical response characteristics of the modified electrode toward EN, ascorbic acid (AA) and uric acid (UA) were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results show an efficient catalytic activity of the electrode for the electro-oxidation of EN, which leads to improvement of reversibility of the electrode response and lowering its overpotential by more than 100 mV. The effect of pH and potential sweep rate on the mechanism of the electrode process was investigated. The modified electrode exhibits an... 

    Electrocatalytic oxidation and nanomolar determination of guanine at the surface of a molybdenum (VI) complex-TiO2 nanoparticle modified carbon paste electrode

    , Article Journal of Electroanalytical Chemistry ; Volume 624, Issue 1-2 , 2008 , Pages 73-78 ; 15726657 (ISSN) Mazloum Ardakani, M ; Taleat, Z ; Beitollahi, H ; Salavati Niasari, M ; Mirjalili, B. B. F ; Taghavinia, N ; Sharif University of Technology
    Elsevier  2008
    Abstract
    A modified carbon paste electrode was prepared by incorporating TiO2 nanoparticles with bis[bis(salicylidene-1,4-phenylenediamine)molybdenum(VI)]. A mixture of fine graphite powder with 4 wt% of TiO2 nanoparticles was applied for the preparation of the carbon paste (by dispersing in paraffin) and finally modified with a molybdenum (VI) complex. The electrocatalytic oxidation of guanine (G) was investigated on the surface of the molybdenum (VI) complex-TiO2 nanoparticle modified carbon paste electrode (MCTNMCPE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CHA) and chronocoloumetry (CHC). Using the modified electrode, the kinetics of G...