Electroanalysis
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Reference Electrode for Ionic Liquids Abstract Reference electrodes for room temperature ionic liquid (RTIL) applications were constructed that have a known and reproducible potential versus the ferrocene/ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag+ couple type, or of the second kind, based on Ag/AgCl in M+ Cl− . The former uses AgNO3 salt and the latter tetrabutylammonium chloride, Bu4 NCl, dissolved in acetonitrile which are then introduced to the ionic liquid of choice for a final concentration of 0.1 M. The reference electrodes can be easily and reproducibly constructed. An ionic contact of these reference systems with the test electrolyte was made using an asbestos fiber liquid junction. The internal compartment of the reference system was filled with the same ionic liquid as used for the electrochemical experiment. The performance of these reference electrodes was tested in selected ionic liquids using the ferrocene/ferrocenium redox couple. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized in the following ionic liquids: 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIBF4 ), 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI(CF3 SO2 )2 N), and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIPF6 ). It has been found that the formal potentials of the examined reference systems are stable over several days. There is a linear relationship for the temperature studied in the range from 25 to 60 °C.
Electroanalysis - Tập 18 Số 4 - Trang 405-409 - 2006
Electrocatalytic Reduction of Oxygen at Glassy Carbon Electrodes Coated with Diazonium‐derived Porphyrin/Metalloporphyrin Films Abstract In this study, the influence of the film structure was investigated on the electrocatalytic oxygen reduction at GC electrodes covered with porphyrin and metalloporphyrin rings via the diazonium modification method. For that purpose, primarily, tetraphenylporphyrin (TPP) films on GC electrode surfaces were prepared by electroreduction of in situ generated diazonium salts of 5‐(4‐aminophenyl)‐10,15,20‐triphenylporphyrin (APP) and 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin (TAPP) molecules. Next, the formation of metalloporphyrin films on the modified surfaces was accomplished through the complexation reactions of surface porphyrin rings with metal ions in the salt solutions containing Mn(II), Fe(III) and Co(II) ions. The resulting porphyrin and metalloporphyrin layers were identified with XPS and ICP‐MS. The electrochemical barrier properties of the films on GC surfaces were examined by cyclic voltammetry in K3 Fe(CN)6 aqueous solution. The electrocatalytic abilities of the resulting films were also investigated for the oxygen electrochemical reduction by employing cyclic voltammetry in PBS solutions saturated with oxygen. The results showed that the oxygen reduction potentials on modified GC electrodes were shifted to less negative potentials compared to that of bare GC electrode. Also, it was obtained that the oxygen reduction reaction was more effective on the GC electrodes modified with TPP rings by using TAPP molecules than those prepared by using APP molecules.
Electroanalysis - Tập 32 Số 6 - Trang 1379-1390 - 2020
A Novel Biomimetic Hydrogen Peroxide Biosensor Based on Pt Flowers‐decorated Fe<sub>3</sub>O<sub>4</sub>/Graphene Nanocomposite Abstract A sensitive and selective amperometric H2 O2 biosensor was obtained by utilizing the electrodeposition of Pt flowers on iron oxide‐reduced graphene oxide (Fe3 O4 /rGO) nanocomposite modified glassy carbon electrode (GCE). The morphology of Fe3 O4 /rGO and Pt/Fe3 O4 /rGO was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The step‐wise modification and the electrochemical characteristics of the resulting biosensor were characterized by cyclic voltammetry (CV) and chronoamperometry methods. Thanks to the fast electron transfer at the Pt/Fe3 O4 /rGO electrode interface, the developed biosensor exhibits a fast and linear amperometric response upon H2 O2 . The linear range of Pt/Fe3 O4 /rGO is 0.1∼2.4 mM (R2 =0.998), with a sensitivity of 6.875 μA/mM and a detection limit of 1.58 μM (S/N=3). In addition, the prepared biosensor also provides good anti‐interferent ability and long‐term stability due to the favorable biocompatibility of the electrode interface. The proposed sensor will become a reliable and effective tool for monitoring and sensing the H2 O2 in complicate environment.
Electroanalysis - Tập 29 Số 6 - Trang 1518-1523 - 2017
A Non‐enzymatic Hydrogen Peroxide Photoelectrochemical Sensor Based on a BiVO<sub>4</sub> Electrode Abstract In this study, a non‐enzymatic hydrogen peroxide photoelectrochemical (PEC) sensor based on nanoporous BiVO4 film electrode is fabricated by electrodeposit of nanoporous BiOI film on fluorine‐doped tin oxide glass (FTO) and subsequent conversion to BiVO4 by annealing at elevated temperature. The electrode exhibits excellent visible light photoelectrochemical activity, and H2 O2 works as a hole scavenger to react with light‐induced electron holes on the valence band of BiVO4 . Upon illumination and at applied bias potential of +0.2 V, the photocurrent density is linearly correlated to the concentration of H2 O2 . The linear determination range of H2 O2 is 9.54–764.76 μM with a corresponding correlation coefficient of 0.9997, a detection limit of 1.59 μM (S/N=3), and sensitivity of 182.6 μA mM−1 cm−2 . The optimum bias potential, most suitable film thickness, anti‐interference performance, and impedance are also explored. The sensor shows good response towards H2 O2 and displays a promising prospect for non‐enzyme PEC H2 O2 sensor.
Electroanalysis - Tập 29 Số 1 - Trang 305-311 - 2017
Application of Nanoparticles in Electrochemical Sensors and Biosensors Abstract The unique chemical and physical properties of nanoparticles make them extremely suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Many kinds of nanoparticles, such as metal, oxide and semiconductor nanoparticles have been used for constructing electrochemical sensors and biosensors, and these nanoparticles play different roles in different sensing systems. The important functions provided by nanoparticles include the immobilization of biomolecules, the catalysis of electrochemical reactions, the enhancement of electron transfer between electrode surfaces and proteins, labeling of biomolecules and even acting as reactant. This minireview addresses recent advances in nanoparticle‐based electrochemical sensors and biosensors, and summarizes the main functions of nanoparticles in these sensor systems.
Electroanalysis - Tập 18 Số 4 - Trang 319-326 - 2006
Electrochemical Pretreatment of Pt Surface: Modification with Co/Al Layered Double Hydroxide for Analytical Applications Abstract Co/Al Layered Double Hydroxide thin films were prepared by electrodeposition on Pt electrodes previously submitted to different electrochemical pretreatments, consisting of a large number of potential cycles (Pt‐CVT) or a cathodic polarization (Pt‐CT) in a H2 SO4 solution. Their features and analytical performance for the determination of aniline and phenol were compared to those of the film deposited on a mechanically polished Pt electrode (Pt‐MT). The Pt‐MT and Pt‐CVT electrodes displayed comparable sensitivities and equal limits of detection for both analytes. The Pt‐CT showed a lower sensitivity, but a range of linear response of about 5 orders of magnitude for aniline.
Electroanalysis - Tập 24 Số 4 - Trang 857-864 - 2012
Electrochemical Sensing of DNA Using Gold Nanoparticles Abstract The electrochemical properties of gold nanoparticles (AuNPs) have led to their widespread use as DNA labels. This fact has improved the design strategies for the electrochemical detection of DNA through hybridization event monitoring. The reported DNA hybridization detection modes are based on either AuNP detection after dissolving or the direct detection of the AuNP/DNA conjugates anchored onto the genosensor surface. Various enhancement strategies have been reported so as to improve the detection limit. Most are based on catalytic deposition of silver onto AuNP. Other strategies based on the use of AuNPs as carrier/amplifier of other labels will be also revised. The developed techniques are characterized by sensitivities and specificities that enable further applications of the developed DNA sensors in several fields.
Electroanalysis - Tập 19 Số 7-8 - Trang 743-753 - 2007
Electrocatalytic Reduction of Oxygen at Multi‐Walled Carbon Nanotubes and Cobalt Porphyrin Modified Glassy Carbon Electrode Abstract The multi‐walled carbon nanotubes (MWNTs) modified glassy carbon electrode exhibited electrocatalytic activity to the reduction of oxygen in 0.1 M HAc‐NaAc (pH 3.8) buffer solution. Further modification with cobalt porphyrin film on the MWNTs by adsorption, the resulted modified electrode showed more efficient catalytic activity to O2 reduction. The reduction peak potential of O2 is shifted much more positively to 0.12 V (vs. Ag/AgCl), and the peak current is increased greatly. Cyclic voltammetry (CV), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), were used to characterize the material and the modified film on electrode surface. Electrochemical experiments gave the total number of electron transfer for oxygen reduction as about 3, which indicated a co‐exist process of 2 electrons and 4 electrons for reduction of oxygen at this modified electrode. Meanwhile, the catalytic activities of the multilayer film (MWNTs/CoTMPyP)n 2 reduction increased and the peak potential shifted to a positive direction with the increase of layer numbers.
Electroanalysis - Tập 16 Số 17 - Trang 1444-1450 - 2004
Electrocatalytic Oxidation of Methanol at Lower Potentials on Glassy Carbon Electrode Modified by Platinum and Platinum Alloys Incorporated in Poly(<i>o</i>‐Aminophenol) Film Abstract The electrocatalytic oxidation of methanol at a glassy carbon electrode modified by a thin film of poly(o ‐aminophenol) (PoAP) containing Pt, Pt‐Ru and Pt‐Sn microparticles has been investigated using cyclic voltammetry as analytical technique and 0.10 M perchloric acid as supporting electrolyte. It has been shown that the presence of PoAP film increases considerably the efficiency of deposited Pt microparticles toward the oxidation of methanol. The catalytic activity of Pt particles is further enhanced when Ru or specially Sn is co‐deposited in the polymer film. The effects of various parameters such as the thickness of polymer film, concentration of methanol, medium temperature as well as the long term stability of modified electrodes have also been investigated.
Electroanalysis - Tập 15 Số 4 - Trang 278-286 - 2003
Electrocatalytic Oxidation of Methanol on a Nickel‐Porphyrin IX Complex Modified Glassy Carbon Electrode in Alkaline Medium Abstract Electrocatalytic oxidation of methanol on a glassy carbon disc electrode modified with Ni(II)‐hematoporphyrin IX, complex and conditioned by potential recycling in a limited range (between 100 and 600 mV vs. SCE) in 0.10 M NaOH solution, abbreviated as NiOHPME(A), was studied by cyclic voltammetry in alkaline medium. The results were compared with those obtained for a NiO modified glassy carbon electrode, NiOME, prepared in similar conditions. The findings show that the NiOHP film at NiOHPME(A) behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium via Ni(III) species with the cross‐exchange reaction occurring throughout the layer at a low concentration of methanol and for a thin film of modifier. A plausible mechanism was proposed for catalytic oxidation of methanol at NiOHP modified electrode. Moreover, the effects of various parameters such as the scan rate, methanol concentration, thickness of NiOHP film and the real surface area of modified electrode on the oxidation of methanol were investigated. Finally, it has been shown that the NiOHPME(A) has a long‐term stability toward the oxidation of methanol.
Electroanalysis - Tập 16 Số 3 - Trang 199-209 - 2004
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