Showing papers on "Cyclic voltammetry published in 2009"
TL;DR: In this article, the preparation, characterization, and electrochemical properties of reduced graphene sheet films (rGSFs), investigating especially their electrochemical behavior for several redox systems and electrocatalytic properties towards oxygen and some small molecules.
Abstract: This paper describes the preparation, characterization, and electrochemical properties of reduced graphene sheet films (rGSFs), investigating especially their electrochemical behavior for several redox systems and electrocatalytic properties towards oxygen and some small molecules. The reduced graphene sheets (rGSs) are produced in high yield by a soft chemistry route involving graphite oxidation, ultrasonic exfoliation, and chemical reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy clearly demonstrate that graphene was successfully synthesized and modified at the surface of a glassy carbon electrode. Several redox species, such as Ru(NH3)63+/2+, Fe(CN)63−/4−, Fe3+/2+ and dopamine, are used to probe the electrochemical properties of these graphene films by using the cyclic voltammetry method. The rGSFs demonstrate fast electron-transfer (ET) kinetics and possess excellent electrocatalytic activity toward oxygen reduction and certain biomolecules. In our opinion, this microstructural and electrochemical information can serve as an important benchmark for graphene-based electrode performances.
1,088 citations
TL;DR: This study shows the successful integration of paper-based microfluidics and electrochemical detection as an easy-to-use, inexpensive, and portable alternative for point of care monitoring.
Abstract: We report the first demonstration of electrochemical detection for paper-based microfluidic devices. Photolithography was used to make microfluidic channels on filter paper, and screen-printing technology was used to fabricate electrodes on the paper-based microfluidic devices. Screen-printed electrodes on paper were characterized using cyclic voltammetry to demonstrate the basic electrochemical performance of the system. The utility of our devices was then demonstrated with the determination of glucose, lactate, and uric acid in biological samples using oxidase enzyme (glucose oxidase, lactate oxidase, and uricase, respectively) reactions. Oxidase enzyme reactions produce H2O2 while decomposing their respective substrates, and therefore a single electrode type is needed for detection of multiple species. Selectivity of the working electrode for H2O2 was improved using Prussian Blue as a redox mediator. The determination of glucose, lactate, and uric acid in control serum samples was performed using chron...
1,037 citations
TL;DR: Graphene was synthesized chemically by Hummers and Offeman method and the graphene-modified electrode was applied in selective determination of dopamine with a linear range from 5μM to 200μM in a large excess of ascorbic acid as discussed by the authors.
1,018 citations
TL;DR: In this paper, the mechanism of the ethanol oxidation reaction on a palladium electrode was studied using the cyclic voltammetry method, and the Tafel slope was found to be 130mV/dec−1 at lower potentials, which suggests that the adsorption of OH− ions follows the Temkin-type isotherm on the Pd electrode.
745 citations
TL;DR: It was demonstrated that the charge-storage mechanism in manganese dioxide (MnO2)-based electrodes is mainly faradic rather than capacitive, and specific capacitances of MnO2 forms were strongly correlated with the corresponding ionic conductivities, which obviously rely on the microstructure.
Abstract: The charge-storage mechanism in manganese dioxide (MnO2)-based electrochemical supercapacitors was investigated and discussed toward prepared MnO2 microstructures. The preparation of a series of MnO2 allotropic phases was performed by following dedicated synthetic routes. The resulting compounds are classified into three groups depending on their crystal structures based on 1D channels, 2D layers, or 3D interconnected tunnels. The 1D group includes pyrolusite, ramsdellite, cryptomelane, Ni-doped todorokite (Ni-todorokite), and OMS-5. The 2D and 3D groups are composed of birnessite and spinel, respectively. The prepared MnO2 powders were characterized using X-ray diffraction, scanning electron microscopy, the Brunauer−Emmett−Teller technique, cyclic voltammetry (CV), and electrochemical impedance spectroscopy. The influence of the MnO2 microstructure on the electrochemical performance of MnO2-based electrodes is commented on through the specific surface area and the electronic and ionic conductivities. It ...
538 citations
TL;DR: In this paper, Nitrogen-containing carbon nanotubes (NCNTs) were prepared via pyrolysis of acetonitrile over cobalt catalysts at different temperatures to control the nitrogen content.
Abstract: Nitrogen-containing carbon nanotubes (NCNTs) were prepared via pyrolysis of acetonitrile over cobalt catalysts at different temperatures to control the nitrogen content. The changes in the chemical and structural properties of undoped CNTs and NCNTs were investigated using high-resolution X-ray photoelectron and Raman spectroscopy. The NCNTs prepared at 550 °C had a higher amount of pyridinic groups and edge plane exposure than the ones prepared at 750 °C. The thermal stability and transformation of these nitrogen functional groups was studied using deconvoluted XP N 1s spectra. The NCNTs show a considerably higher activity in the oxygen reduction reaction in acidic electrolyte compared with undoped CNTs as demonstrated by cyclic voltammetry, rotating disk electrode measurements, and the redox-competition mode of scanning electrochemical microscopy (RC-SECM). Particularly, the NCNT sample prepared at 550 °C exhibited the highest activity, which was about 1 order of magnitude lower than that of a commercia...
530 citations
TL;DR: The theoretical mass specific capacitance (C s ) of polyaniline (PANI) is firstly estimated by combining electrical double-layer capacitance and pseudocapacitance as discussed by the authors.
525 citations
TL;DR: The results show that Co(3)O(4) nanosheets might have potential applications as electrode materials for supercapacitors and the influence of different reaction conditions on the morphology of the products has been discussed in detail.
Abstract: Flower power: Various mesoporous Co3O4 architectural structures (see figure) have been successfully prepared through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The electrochemical experiments showed that the specific capacitance of Co3O4 nanosheets was higher than that of Co3O4 microspheres in a KOH electrolyte.
Novel and complex mesoporous 2D and 3D architectures of the oxide semiconductor Co3O4, including nanosheets, nearly monodisperse microspheres that are self-assembled from nanosheets, and copper-coin-like nanosheets, have been synthesized through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The influence of different reaction conditions on the morphology of the products has been discussed in detail. The results revealed that the volume ratio of H2O and ethanolamine (EA) play a crucial role in the morphology of the precursor. The thermal decomposition of the corresponding precursor leads to the formation of the mesoporous structure. The products have been characterized by X-ray diffraction techniques, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy. The electrochemical properties of the Co3O4 electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The electrochemical experiments revealed that the specific capacitance of the Co3O4 nanosheets was higher than that of the Co3O4 microspheres in a KOH electrolyte solution (3 m). Furthermore, the Co3O4 nanosheet electrodes exhibited good rate capabilities, and maintained 93 % of the initial capacity at a current density of 5 mA cm−2 in a KOH (3 m) electrolyte solution. The results show that Co3O4 nanosheets might have potential applications as electrode materials for supercapacitors.
514 citations
TL;DR: In this article, an in situ chemical synthesis approach has been developed to prepare SnO 2 -graphene nanocomposite, which exhibited a reversible lithium storage capacity of 765 ǫ/g in the first cycle and an enhanced cyclability.
511 citations
TL;DR: In this paper, the diffusion coefficients of lithium ions (D Li + ) in nano-Si were determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT).
476 citations
TL;DR: In this article, an asymmetric supercapacitor with activated carbon (AC)-Fe3O4 nanoparticles was assembled and characterized in 6 M KOH aqueous electrolyte for the first time.
Abstract: In this study, activated carbon (AC)-Fe3O4 nanoparticles asymmetric supercapacitor cells have been assembled and characterized in 6 M KOH aqueous electrolyte for the first time. The nanostructure Fe3O4 was prepared by the microwave method. It only cost several minutes to prepare magnetite nanoparticles with average particle size of 35 nm. The electrochemical performances of the hybrid AC-Fe3O4 supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge−discharge tests. The results show that the asymmetric supercapacitor has electrochemical capacitance performance within potential range 0−1.2 V. The supercapacitor delivered a specific capacitance of 37.9 F/g at a current density of 0.5 mA/cm2. The result of cyclic characteristic test showed that it also can keep 82% of initial capacity over 500 cycles.
TL;DR: The preparation and characterization of novel hybrid materials combining a catalytic MIP, capable of oxidizing the template, catechol, with an electrically conducting polymer, and the catalytic properties of the sensor were characterized by chronoamperometry and were found to be consistent with Michaelis-Menten kinetics.
Abstract: One of the difficulties with using molecularly imprinted polymers (MIPs) and other electrically insulating materials as the recognition element in electrochemical sensors is the lack of a direct path for the conduction of electrons from the active sites to the electrode. We have sought to address this problem through the preparation and characterization of novel hybrid materials combining a catalytic MIP, capable of oxidizing the template, catechol, with an electrically conducting polymer. In this way a network of "molecular wires" assists in the conduction of electrons from the active sites within the MIP to the electrode surface. This was made possible by the design of a new monomer that combines orthogonal polymerizable functionality; comprising an aniline group and a methacrylamide. Conducting films were prepared on the surface of electrodes (Au on glass) by electropolymerization of the aniline moiety. A layer of MIP was photochemically grafted over the polyaniline, via N,N'-diethyldithiocarbamic acid benzyl ester (iniferter) activation of the methacrylamide groups. Detection of catechol by the hybrid-MIP sensor was found to be specific, and catechol oxidation was detected by cyclic voltammetry at the optimized operating conditions: potential range -0.6 V to +0.8 V (vs Ag/AgCl), scan rate 50 mV/s, PBS pH 7.4. The calibration curve for catechol was found to be linear to 144 microM, with a limit of detection of 228 nM. Catechol and dopamine were detected by the sensor, whereas analogues and potentially interfering compounds, including phenol, resorcinol, hydroquinone, serotonin, and ascorbic acid, had minimal effect (< or = 3%) on the detection of either analyte. Non-imprinted hybrid electrodes and bare gold electrodes failed to give any response to catechol at concentrations below 0.5 mM. Finally, the catalytic properties of the sensor were characterized by chronoamperometry and were found to be consistent with Michaelis-Menten kinetics.
TL;DR: In this paper, Boron and nitrogen co-doped porous carbons (BNCs) were prepared through a facile procedure using citric acid, boric acid and nitrogen as precursors, respectively.
TL;DR: In this article, a Pd-Ag/C catalyst was prepared using co-reduction method and physicochemical characterization results revealed that alloy nanoparticles with face-centered cubic structure were successfully formed.
Abstract: Carbon supported Pd–Ag/C catalyst was prepared using co-reduction method. Physicochemical characterization results revealed that alloy nanoparticles with face-centered cubic structure were successfully formed. The electrochemical studies for ethanol oxidation in alkaline media were performed with cyclic voltammetry, linear sweep voltammetry and chronoamperometry methods. The results showed that Pd–Ag/C exhibited an excellent activity, enhanced CO tolerance and better stability than Pt/C and Pd/C, making it a promising anodic catalyst for alkaline direct ethanol fuel cell.
TL;DR: Graphene-ZnO composite film was synthesized for its potential application in supercapacitors as discussed by the authors, which exhibited an enhanced capacitive behavior with better reversible charging/discharging ability and higher capacitance values.
TL;DR: In this paper, a single-metal redox flow battery employing chromium(III) acetylacetonate in tetraethylammonium tetrafluoroborate and acetonitrile has been investigated using electrochemical techniques.
TL;DR: The results obtained during the early stages of aptamer-based sensor development are presented, utilizing a model system of human alpha thrombin interacting with a thiolated DNA aptamer, immobilized on gold electrodes, took place in the presence of iron ferrocyanides.
Abstract: Electrochemical impedance spectroscopy (EIS) measurement, performed in the presence of a redox agent, is a convenient method to measure molecular interactions of electrochemically inactive compounds taking place on the electrode surface. High sensitivity of the method, being highly advantageous, can be also associated with nonspecific impedance changes that could be easily mistaken for specific interactions. Therefore, it is necessary to be aware of all possible causes and perform parallel control experiments to rule them out. We present the results obtained during the early stages of aptamer-based sensor development, utilizing a model system of human alpha thrombin interacting with a thiolated DNA aptamer, immobilized on gold electrodes. EIS measurements took place in the presence of iron ferrocyanides. In addition to known method limitations, that is, inability to discriminate between specific and nonspecific binding (both causing impedance increase), we have found other factors leading to nonspecific impedance changes, such as: (i) initial electrode contamination; (ii) repetitive measurements; (iii) additional cyclic voltammetry (CV) or differential pulse voltammetry (DPV) measurements; and (iv) additional incubations in the buffer between measurements, which have never been discussed before. We suggest ways to overcome the method limitations.
TL;DR: An amperometric glucose biosensor based on the direct electron transfer of glucose oxidase (GOx) was developed by electrochemically entrapping GOx onto the inner wall of highly ordered polyaniline nanotubes (nanoPANi), which was synthesized using anodic aluminum oxide (AAO) membrane as a template.
Abstract: An amperometric glucose biosensor based on the direct electron transfer of glucose oxidase (GOx) was developed by electrochemically entrapping GOx onto the inner wall of highly ordered polyaniline nanotubes (nanoPANi), which was synthesized using anodic aluminum oxide (AAO) membrane as a template. The cyclic voltammetric results indicated that GOx immobilized on the nanoPANi underwent direct electron transfer reaction, and the cyclic voltammogram displayed a pair of well-defined and nearly symmetric redox peaks with a formal potential of -405 +/- 5 mV and an apparent electron transfer rate constant of 5.8 +/- 1.6 s(-1). The biosensor had good electrocatalytic activity toward oxidation of glucose and exhibited a rapid response (approximately 3 s), a low detection limit (0.3 +/- 0.1 microM), a useful linear range (0.01-5.5 mM), high sensitivity (97.18 +/- 4.62 microA mM(-1) cm(-2)), higher biological affinity (the apparent Michaelis-Mentan constant was estimated to be 2.37 +/- 0.5 mM) as well as good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, uric acid, and 4-acetamidophenol, did not cause any interference due to the use of a low detection potential (-0.3 V vs SCE). The biosensor can also be used for quantification of the concentration of glucose in real clinical samples.
TL;DR: In this paper, the peak-current potential-differences obtained from cyclic voltammetry and charge transfer resistance obtained from electrochemical impedance spectroscopy were used to characterize surface cleanliness.
TL;DR: Results in this study suggest that electrospun CuO-NFs is a promising 1-D nanomaterial for further design and microfabrication of bioelectrochemical nanodevices for glucose determination.
TL;DR: In this paper, carbon-supported cobalt polypyrrole (Co-PPy/C) catalysts synthesized using a chemical method of polymerization synthesis were characterized using electrochemical techniques such as cyclic voltammetry (CV), rotating disk electrode (RDE), as well as rotating ring disk electrodes (RRDE) to quantitatively obtain the oxygen reduction reaction (ORR) kinetic constants and the reaction mechanisms.
TL;DR: In this article, a simple hydrothermal method has been used to fabricate sea urchin shaped α-MnO2 without using any template and surfactant, and the resulting 3D clewlike e-mno2 nanostructures have a specific capacitance of 120 F g−1 and lower charge-transfer resistance.
Abstract: A simple hydrothermal method has been used to fabricate sea urchin shaped α-MnO2 without using any template and surfactant. When other conditions were kept the same and Al3+ exists in the solution, the product is α-MnO2 nanorods clusters; when Al3+ was substituted by Fe3+ in the solution, the phase of the products was transformed from α-MnO2 to e-MnO2; relatively, the morphology of the product was changed from urchinlike clusters to 3D clewlike. The sea urchin shaped α-MnO2 and α-MnO2 nanorods clusters consist of radially grown single crystalline MnO2 nanorods of ca. 30−40 nm in diameter and ca. 0.87−1.2 μm in length. The 3D clewlike e-MnO2 nanostructures are composed of nanosheets with a thickness of about 17 nm. The electrochemical properties of the prepared MnO2 materials were studied using cyclic voltammetry (CV) and ac impedance measurements in aqueous electrolyte. 3D clewlike e-MnO2 nanostructures have a specific capacitance of 120 F g−1 and lower charge-transfer resistance. The results indicate tha...
TL;DR: In this paper, structural and morphological characterizations of SnO 2 and PANI/SnO 2 were carried out using power X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM).
TL;DR: In this article, ZnO nanorod arrays with dandelion-like morphology were directly grown on copper substrates by a hydrothermal synthesis process at 80°C. X-ray diffraction, scanning electron microscopy, galvanostatic discharge charge, and cyclic voltammetry were employed to characterize the structure and electrochemical property of the arrays.
TL;DR: In this paper, a simple method for electrochemical synthesis of acetaminophen's dimer is described, based on related mechanism, the observed homogeneous rate constants (k obs ) of hydrolysis, hydroxylation and dimerization reactions were estimated by comparing the experimental cyclic voltammetric responses with the digital-simulated results.
TL;DR: In this article, a non-enzymatic voltammetric and amperometric detection of glucose using a gold nanowire array electrode was performed by cyclic and differential-pulse voltammetry.
Abstract: The non-enzymatic voltammetric and amperometric detection of glucose using a gold nanowire array electrode is described. The voltammetric detection of glucose was performed by cyclic and differential-pulse voltammetry. The detection of glucose by partial and direct oxidation of glucose during the anodic and cathodic potential sweeps was shown in cyclic voltammetry. An unusual decrease in overpotential for partial oxidation of glucose on a Au NW array electrode was observed. A linear differential-pulse voltammetric response for partial oxidation of glucose was observed up to a glucose concentration of at least 20 mM with a sensitivity of 41.9 μA mM−1 cm−2 and detection limit below 30 μM (signal-to-noise ratio of 3) for glucose oxidation at low potentials, where the influence of possible intermediates can be avoided. The amperometric response was also linear up to a glucose concentration of 10 mM with a sensitivity of 309.0 μA mM−1 cm−2. The wide dynamic range and high sensitivity, selectivity and stability, as well as good biocompatibility of the Au NW electrode make it promising for the fabrication of non-enzymatic glucose sensors.
TL;DR: In this paper, multi-walled carbon nanotube (MWCNT)/polyaniline (PANI) composite films were prepared by in-situ electrochemical polymerization of an aniline solution containing different MWCNT contents.
TL;DR: Using porous cuprous oxide (Cu 2 O) microcubes, a simple non-enzymatic amperometric sensor for the detection of H 2 O 2 and glucose has been fabricated.
TL;DR: In this paper, cobalt hydroxide nano-flakes are successfully synthesized by a facile chemical precipitation method and a maximum specific capacitance of 735 F ǫg −1 can be achieved in 2 M aqueous KOH with the potential range from −0.2 to 0.4 V (vs. SCE) in a half-cell setup configuration for the Co(OH) 2 electrode, suggesting its potential application in electrochemical capacitors.