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The ongoing surge in demand for sustainable energy technologies with little to no environmental impacts calls for the exploration of advanced energy storage materials. Inspiration from nature is undoubtedly a promising approach to comply with environmental legislations. Herein, we describe a facile and green electrosynthesis approach to fabricate a polydopamine (PDA) nanofilm supported on oxygen-functionalized carbon cloth (FCC). The surface functionalization of carbon cloth facilitates the PDA nanofilm adhesion and endows the as-prepared PDA-FCC electrode with excellent flexibility, good electrical conductance (22.6 mS), and outstanding wettability to the aqueous electrolyte. Owing to these merits, the PDA-FCC electrode delivers a favorable capacitance of 626 F g−1 at 1.0 A g−1 (617 mF cm−2 at 2.2 mA cm−2, and 1296 mF cm−3 at 5.3 mA cm−3), in which the catechol, amine, and imine moieties of PDA are responsible for its excellent pseudocapacitive behavior. The symmetric all-solid-state flexible PDA-FCC||PDA-FCC device covers almost the entire thermodynamic stability window of aqueous electrolytes (1.2 V), delivers a high specific energy of 11.7 W h kg−1, superb specific power of up to 6.4 kW kg−1, and excellent flexibility along with outstanding cycling stability (81% retention of the initial capacitance after 10 000 cycles). These performance characteristics are in part due to the binder-free PDA biopolymer film that adopts the inherent texture of the carbon cloth, enabling the pores to play the role of temporary ion-buffering reservoirs that facilitate effective mass transport. This new approach to fabricate electrodes from green sources is considered an important step toward environmentally-benign energy storage technologies.

High power performance with the ability to be charged in a matter of seconds have made supercapacitors the technology of choice for cutting-edge applications. However, improving the energy content of supercapacitors is necessary to contribute to the technological advancement of energy storage devices. Herein, we report the synthesis of two transition metal spinel oxide-reduced graphene oxide (rGO) nanocomposites; namely CuCo2O4-rGO and CoFe2O4-rGO. The CuCo2O4-rGO nanocomposite as a positive electrode exhibits an extremely high specific capacitance of 2064.0 F g−1 at 2 A g−1, whereas the CoFe2O4-rGO nanocomposite as a negative electrode shows a specific capacitance of 261.0 F g−1 at 2 A g−1. The asymmetric CoFe2O4-rGO//CuCo2O4-rGO device exhibits an ultrahigh specific energy of 77.2 Wh kg−1 at 953.0 W kg−1, maintains 8.3 Wh kg−1 under the outstanding specific power of 21.0 kW kg−1, and displays excellent cycling stability (96% capacitance retention after 5000 cycles). We also fabricated an asymmetric AC//CuCo2O4-rGO device (AC = activated carbon) as a control, and realized that the CoFe2O4-rGO nanocomposite not only outperforms AC in terms of specific energy, but also contributes to a higher specific power. The results indicate that these nanocomposites are promising materials for the fabrication of high performance supercapacitors.

Herein, we report the one-pot co-synthesis of a novel water-stable nickel-based metal-organic framework (Ni-MOF) with a Co-MOF, as well as the dual Ni/Co-MOF-reduced graphene oxide (rGO) nanocomposite in the same reaction vessel. Introduction of the two metal precursors along with the organic linker in the same reaction vessel guarantees in situ homogeneously distributed MOF particles in the nanoscale level that cannot be obtained by physical mixing of the MOFs synthesized individually. The Ni/Co-MOF-rGO nanocomposite demonstrates a high specific capacitance of 860 F/g at 1.0 A/g. The asymmetric activated carbon//Ni/Co-MOF-rGO device delivers specific energy of 72.8 Wh/kg at 850 W/kg, and still holds 15.1 Wh/kg under the high specific power of 42.5 kW/kg, as well as a long cycle life (91.6% capacitance retention after 6000 charge-discharge cycles at 1 A/g). Two 1.0 cm2 devices connected in series run a clock for about 2 h, and also sequentially power a blue light emitting diode (LED) for 25 min, then a green LED for 25 min, and finally a red LED for more than 140 min, demonstrating that the nanocomposite is a very promising active material for practical applications.

While the market for supercapacitors is rapidly growing due to their high power density, their low energy density compared to batteries represents a great barrier for the future of this technology. The poorly understood chemistry of electrode-electrolyte interfaces implies that there is substantial room for improvement through a careful design of the materials involved. Here we present a unique approach for improving the energy density of supercapacitors through redox additive-assisted electrocatalytic in situ regeneration of the electrode active materials. By utilizing a quinone-based redox electrolyte and a nanostructured conjugated polyaniline electrode, we continually regenerate the reactants, resulting in a redox supercapacitor having an extremely high energy density of 1091 Wh kg−1 (based on the total mass of the electrode active materials and the redox additive) and a high power density up to 196 kW kg−1. Considering the other outstanding properties of the polyaniline-naphthoquinone system, such as extreme flexibility (96% capacity retention after bending at an angle of 180° for 1000 cycles), non-flammability, and excellent cycling stability (84% capacity retention after 7000 cycles at 35 A g−1), such a well designed in situ regeneration of the electrode active materials makes this method a very promising approach towards the development of state-of-the-art energy storage devices.

Aqueous supercapacitors based on neutral solutions have the advantages of high-ionic conductivity, being environmentally friendly, safe, and low cost. However, the operating potential window for most aqueous electrolytes is far lower than that of organic electrolytes that are commonly used in commercial supercapacitors. In this work, we report on the fabrication of a wide potential window, high-energy aqueous asymmetric supercapacitor, without sacrificing power, by using a nanostructured LiMn2O4/reduced graphene oxide (LMO–rGO) nanocomposite. We synthesized the uniformly distributed LMO in the LMO–rGO nanocomposite using a co-precipitation route followed by a low-temperature hydrothermal treatment. In a three-electrode cell setup, the specific capacitance of the LMO–rGO nanocomposite electrode at 1 A/g (1.2 mA/cm2) is 268.75 F/g (258 mF/cm2), which shows a dramatic improvement over the sum of the specific capacitances of pristine LMO (162.5 F/g) and pure rGO (29.94 F/g) electrodes in their relative ratios, when used alone. This finding suggests a synergistic coupling of LMO and rGO in the nanocomposite. We also assembled the LMO–rGO nanocomposite, as the positive electrode, with activated carbon, as the negative electrode, into an asymmetric cell configuration. The device shows an ultra-wide potential window of 2.0 V in a neutral aqueous Li2SO4 electrolyte, with a maximum energy density of 29.6 Wh/kg (which approaches the commercial lead-acid batteries), power density of up to 7408 W/kg, and an excellent cycle life (5% loss after 6000 cycles). These findings confirm that an LMO–rGO nanocomposite is a promising material to meet the demands of real world energy storage.

Supercapacitors (SCs), as high power density energy storage resources, have recently attracted considerable attention. Increasing the energy of supercapacitors is a key parameter to success in achieving far more demanding energy storage applications. There are two approaches to achieve this goal: the first is to widen the operating potential window, and the second is to develop emerging capacitive or pseudocapacitive materials. Polyaniline (PANI) with different morphologies, and hence different supercapacitive performances, has been considered as one of the intriguing active materials due to its high conductivity, intrinsic flexibility, and high redox active specific capacitance. In this work, we report on a simple and convenient method to synthesize PANI nanotubes with rectangular morphology. Then we synthesized PANI/reduced graphene oxide (PANI-rGO) nanocomposite via a convenient electrochemical reduction process. We investigated electrochemical performance of the electrode in the presence and absence of catechol, as a redox-additive molecule incorporated into the electrolyte, by CV, EIS and GCD methods. With incorporation of the catechol in the electrolyte the operating potential window of the electrode increased from 1.0 to 1.2 V, and its capacitance boosted about 5-fold from 429 to 1967 F/g at a current density of 1 A/g. The astonishing supercapacitive performance of the electrode is attributed to; (i) the rectangular nanotube morphology of the PANI, which provides both a better electrical conductivity and a facilitated ion transport pathway, and (ii) the synergetic effect between PANI-rGO and catechol. The electrode showed a superior long cycle life with 81% retention of the initial specific capacitance after 5000 cycles, and demonstrated an excellent rate capability with specific capacitances of 267 and 546 F/g, at a current density of 20 A/g, in the absence and presence of catechol, respectively. Furthermore, we fabricated a symmetric device using the PANI-rGO film on a flexible stainless steel substrate in the catechol-containing electrolyte. The device showed specific capacitance of 409 F/g at 1 A/g, energy density of 81.8 Wh/kg and power density of 7.7 kW/kg. These findings could be beneficial for further development of diverse energy storage devices and open up new prospects for the fabrication of high energy and power supercapacitors.

The surging interest in high performance, low-cost, and safe energy storage devices has spurred tremendous research efforts in the development of advanced electrode active materials. Herein, the in situ growth of zinc-iron layered double hydroxide (Zn-Fe LDH) on graphene aerogel (GA) substrates through a facile, one-pot hydrothermal method is reported. The strong interaction and efficient electronic coupling between LDH and graphene substantially improve interfacial charge transport properties of the resulting nanocomposite and provide more available redox active sites for faradaic reactions. An LDH-GA||Ni(OH)2 device is also fabricated that results in greatly enhanced specific capacity (187 mAh g-1 at 0.1 A g-1 ), outstanding specific energy (147 Wh kg-1 ), excellent specific power (16.7 kW kg-1 ), along with 88% capacity retention after >10 000 cycles. This approach is further extended to Ni-MH and Ni-Cd batteries to demonstrate the feasibility of compositing with graphene for boosting the energy storage performance of other well-known Ni-based batteries. In contrast to conventional Ni-based batteries, the nearly flat voltage plateau followed by a sloping potential profile of the integrated supercapacitor-battery enables it to be discharged down to 0 V without being damaged. These findings provide new prospects for the design of high-performance and affordable superbatteries based on earth-abundant elements.

Scanning electrochemical microscopy (SECM) was employed for sensitive detection of single base mismatches (SBMs) in a sandwiched dsDNA. Ferrocenecarboxylic acid (Fc), covalently conjugated to the dsDNA, was oxidized to Fc+ via the DNA-mediated charge transfer from the underlying gold substrate, and reduced back to Fc by SECM tip generated ferrocyanide. The electrocatalytic oxidation of SECM tip-generated ferrocyanide was sensitive to presence, as well as the type of SBMs. Apparent standard rate constants (k0app) values for different SBMs, both near the electrode surface and far from it, were evaluated by SECM. The method can detect SBMs independent of their position in dsDNA.

Cocaine, a powerful addictive stimulant drug, has a variety of adverse effects on the body, thus its sensitive detection is very important. Here, we report on a simple, label-free, and sensitive impedimetric sensor for determination of cocaine based on its affinity to form an inclusion complex with β-cyclodextrin (β-CD). First, we prepared nanostructured poly N-acetylaniline film via electropolymerization of its monomer on a glassy carbon electrode (PNAANI/GC), subsequently overoxidized it, and conjugated β-CD to the polymer backbone. The designed and synthesized nanostructured PNAANI film serves a dual function in the sensor: on one hand, it maintains a high effective surface area on a geometrically small electrode that significantly enhances the number of β-CD molecules immobilized on the electrode; on the other hand, it provides an upright-oriented β-CD conjugation to the polymer backbone, thus all the β-CD receptors are actively involved in responding to the target. Sensitivity of the sensor was further enhanced by preconcentration of cocaine on the modified electrode surface. We attributed the changes in the interfacial charge transfer resistance (R ct) of the electrode to cocaine concentration. Under optimized condition (pH 7.4, 5-min accumulation at an open circuit voltage), the sensor responded to cocaine concentration in the range of 100 nM–1.0 mM with a detection limit of 50 nM. Selectivity of the sensor for cocaine relative to some potential inferring compounds was also investigated, and the results were promising. The proposed approach exhibited an extended dynamic range, low detection limit, good sensitivity, and a desirable selectivity, which provides an efficient application prospect for on-field cocaine sensing.

The search for faster, safer, and more efficient energy storage systems continues to inspire researchers to develop new energy storage materials with ultrahigh performance. Mesoporous nanostructures are interesting for supercapacitors because of their high surface area, controlled porosity, and large number of active sites, which promise the utilization of the full capacitance of active materials. Herein, highly ordered mesoporous CuCo2O4 nanowires have been synthesized by nanocasting from a silica SBA-15 template. These nanowires exhibit superior pseudocapacitance of 1210 F g–1 in the initial cycles. Electroactivation of the electrode in the subsequent 250 cycles causes a significant increase in capacitance to 3080 F g–1. An asymmetric supercapacitor composed of mesoporous CuCo2O4 nanowires for the positive electrode and activated carbon for the negative electrode demonstrates an ultrahigh energy density of 42.8 Wh kg–1 with a power density of 15 kW kg–1 plus excellent cycle life. We also show that two a...

Using nanoparticles, instead of microparticles, as active electrode materials in lithium ion batteries could provide a solution to slow charging rates due to long ion diffusion pathways in conventional bulk materials. In this work, we present a new strategy for the synthesis of high purity lithium nickel manganese oxide (LiNi0.5Mn1.5O4) nanoparticles as a high-voltage cathode. A sonochemical reaction is used to synthesize nickel hydroxide and manganese dioxide nanoparticles followed by a solid-state reaction with lithium hydroxide. The product shows a single spinel phase and uniform spherical nano-particles under the appropriate calcination conditions. The LiNi0.5Mn1.5O4 exhibits a high voltage plateau at about 4.7–4.9 V in the charge/discharge process and delivers a discharge capacity of more than 140 mA h g−1 and excellent cycling performance with 99% capacity retention after 70 cycles. The synthesized nano-particles show improved electrochemical performance at high rates. This electrode delivers a power density as high as 26.1 kW kg−1 at a discharge rate of 40 C. This power performance is about one order of magnitude higher than traditional lithium ion batteries. These findings may lead to a new generation of high power lithium ion batteries that can be recharged in minutes instead of hours.

The electrochemical behavior of cytochrome c (cyt-c) that was electrostatically immobilized onto a self-assembled monolayer (SAM) of captopril (capt) on a gold electrode has been investigated. Cyclic voltammetry, scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy were employed to evaluate the blocking property of the capt SAM. SECM was used to measure the bimolecular electron transfer (ET) kinetics (kBI) between a solution-based redox probe and the immobilized protein. In addition, the tunneling ET between the immobilized protein and the underlying gold electrode was calculated. A kBI value of (5.0±0.6)×108 mol−1 cm3 s−1 for the bimolecular ET and a standard tunneling rate constant (k0) of 46.4±0.2 s−1 for the tunneling ET have been obtained.

There has been substantial recent interest in studying monolayer-protected gold clusters (MPCs) owing to their diverse applications. The present work is an electrochemical study of novel gold nanoparticles covered with a monolayer of mercapto-dodecanol ended chloro-dicyano-quinone (HS-C12O-CDQ), which was adsorbed on the electrode (CDQ-MPCs film). Our findings reveal a redox behavior for CDQ-MPCs film similar to the solution electrochemistry of dichloro-dicyano-quinone. Furthermore, a diffusion-like mechanism was found for electron transfer, which may have occurred due to proton diffusion towards or outwards the electrode through the film casted. Chronoamperometry confirmed diffusion behavior of the ET process. Finally, EIS was used to find the rate constant of ET process for the redox reaction that occurred and the contribution of MPCs in total interfacial capacitance.

MWCNTs-nanoNiO composite was used as a glassy carbon electrode modifier for construction of a novel catalase nanobiosensor for hydrogen peroxide. The immobilized catalase exhibited excellent electrocatalytic activity towards the reduction of H2O2. The resulting amperometric biosensor exhibited a linear response over a concentration range of 200 µM to 2.53 mM with a low detection limit of 19.0 µM. Electrochemical impedance measurements revealed that the modified electrode can be used for the sensitive detection of H2O2. The charge transfer resistance found to decrease significantly after enzymatic reaction of nanobiosensor with H2O2. The resulting impedance was highly sensitive to H2O2 over a linear range of 19–170 nM with a detection limit of 2.4 nM.

Nanostructured self-doped polyaniline (SDPA) is prepared from an aqueous solution of aniline and m -aminobenzoic acid using an electrochemical method onto a stainless steel electrode. This electrode employed as a positive shared electrode in the construction of a hybrid battery–supercapacitor energy storage system AC/SDPA/Zn. This hybrid system is constructed using a parallel combination of an asymmetric supercapacitor (AC/SDPA) and a secondary battery (Zn/SDPA) in a single cell configuration and same electrolyte. Different electrochemical methods including cyclic voltammetry, galvanostatic charge–discharge and rate charge–discharge studies are carried out to characterize electrochemical performances of the hybrid system. Based on the obtained results, the hybrid system shows specific capacity, specific energy, specific power and maximum power values of 215 Ah kg −1 , 204 Wh kg −1 , 863 W kg −1 and 8909 W kg −1 , respectively, at a current density of 2.5 mA cm −2 .

A double-stranded calf thymus DNA (dsDNA) was physisorbed onto a polypyrrole (PPy) nanofiber film that had been electrochemically deposited onto a Pt electrode. The surface morphology of the polymeric film was characterized using scanning electron microscopy (SEM). The electrochemical characteristics of the PPy film and the DNA deposited onto the PPy modified electrode were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Then the interaction of DNA with salicylic acid (SA) and acetylsalicylic acid (ASA), or aspirin, was studied on the electrode surface with DPV. An increase in the DPV current was observed due to the oxidation of guanine, which decreased with the increasing concentrations of the ligands. The interactions of SA and ASA with the DNA follow the saturation isotherm behavior. The binding constants of these interactions were 1.15 × 104 M for SA and 7.46 × 105 M for ASA. The numbers of binding sites of SA and ASA on DNA were approximately 0.8 and 0.6, respectively. The linear dynamic ranges of the sensors were 0.1–2 μM (r2 = 0.996) and 0.05–1 mM (r2 = 0.996) with limits of detection of 8.62 × 10−1 and 5.24 × 10−6 μM for SA and ASA, respectively.

Self-doped polyaniline (SDPA) nanofibers were deposited on platinum (Pt) electrode by reverse pulse voltammetric (RPV) method and their electrochemical performance was evaluated in an aqueous redox supercapacitor constituted as a two electrode cell in a weak acidic medium. Scanning electron micrographs clearly revealed the formation of nanofiber structures with diameters in range of 60–90 nm under optimum experimental conditions. Different electrochemical methods including galvanostatic charge–discharge (CD) experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out in order to investigate the applicability of the system as a redox supercapacitor. Based on the charge–discharge results obtained, the SDPA represented high specific capacitance, specific power and specific energy values of 480 F g−1, 436 W kg−1 and 9.40 Wh kg−1, respectively, at a current density of 5 mA cm−2. The present study introduces new nanofiber materials for electrochemical redox capacitors with advantages including low cost, long cycle-life and stable at low acidic solutions of pH 3.

Electrochemical impedance spectroscopy (EIS) as a powerful, non-invasive and informative technique was used to obtain important information about kinetics of doping process in conducting polymers. Polypyrrole (PPy) and its derivatives can form conducting polymer films which represent excellent charge transfer behaviors during doping processes. It can also have a wide range of applications in bioelectrochemistry. In the present study the conducting polymer of α-carboxy pyrrole (α-COOH-PPy), appended onto the underlying film of PPy, was prepared by electrochemical methods and its behavior was analyzed using EIS. From highly accurate fitting of impedance results it was found that the charging mechanism is governed by the diffusion process. In addition, the impedance analyses provided values for the bulk polymer parameters including diffusion coefficient ( D ), equilibrium capacitance ( C 0 ) and diffusion resistance ( R 0 ). The surface morphology of the polymeric film was characterized using scanning electron microscopy (SEM). The film was then used to immobilize the cytochrome C (cyt- C ) and to perform its electrochemical studies. The modified cyt- C /α-COOH-PPy electrode was used for electrocatalytic reduction of H 2 O 2 in solution and its viability as a new impedimetric biosensor was examined. Based on the calibration curve obtained for the proposed impedimetric biosensor, the limit of detection and relative standard deviation were evaluated as 0.25 μmol L −1 and 7%, respectively. Finally, the prolonged stability test was performed and high stability and reproducibility of the new biosensor was confirmed.

Spectrofluorimetric studies on the binding properties of 5-(9-anthracenylmethyl)-5-aza-2,8-dithia[9],(2,9)-1,10-phenanthrolinophane (L) toward different heavy metal ions in methanol solution revealed its selective 2:1 (ligand/metal) complexation with uranyl ion. Consequently, L was used as a suitable ionophore for the preparation of new plasticized PVC membrane-selective electrodes for the determination of uranyl ion by flow injection potentiometry. The electrodes resulted in Nernstian responses for UO22+ ion over wide concentration ranges (1.0 × 10−6 to 1.0 × 10−1 M with a detection limit of 8.3 × 10−7 M for polymeric membrane electrode, PME, and 1.0 × 10−7 to 1.0 × 10−1 M with a detection limit of 7.5 × 10−8 M for coated graphite electrode, CGE). The potentiometric response is independent of the pH of test solution in the pH range 2.5–4.0. The proposed electrodes possess very good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The CGE was used in flow injection potentiometry and resulted in well defined peaks for uranyl ions with stable baseline, excellent reproducibility and very high sampling rate of 160 injections h−1. The proposed FIP system was used for the determination of trace uranyl ions in real and synthetic samples.

An electroactive self-assembled monolayer (SAM) was fabricated by covalent attachment of a novel hydroquinone-terminated dodecanethiol onto the gold surface and its electrochemical behavior was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The capability of the designed SAM in immobilization of organic molecules onto the gold surface was studied utilizing the Michael-addition as a model reaction. The results obtained from cyclic voltammetry, electrochemical impedance and grazing incidence Fourier transform infrared (GI-FTIR) spectroscopy revealed that, upon applying an anodic potential to the Au-SAM electrode system in the presence of glutathione, the electrochemically generated p-quinone participated in a Michael-addition reaction with glutathione and the corresponding Michael adduct was formed at the solid–liquid interface. The kinetic parameters were then derived for this interfacial Michael-addition reaction.

The characteristics of polyaniline/graphite composites (PANi/G) have been studied in aqueous electrolyte. PANi/G films with different graphite particle sizes were deposited on a platinum electrode by means of cyclic voltammetry. The film was employed as a positive electrode (cathode) for a Zn-PANi/G secondary battery containing 1.0 M ZnCl2 and 0.5 M NH4Cl electrolyte at pH 4.0. The cells were charged and discharged under a constant current of 0.6 mA cm −2 . The assembled battery showed an open-circuit voltage (OCV) of 1.55 V. All the batteries were discharge to a cut off voltage of 0.7 V. Maximum discharge capacity of the Zn-PANi/G battery was 142.4 Ah kg −1 with a columbic efficiency of 97–100% over at least 200 cycles. The mid-point voltage (MPV) and specific energy were 1.14 V and 162.3 Wh kg −1 , respectively. The constructed battery showed a good recycleability. The structure of these polymer films was characterized by FTIR and UV–vis spectroscopies. Electrochemical impedance spectroscopy (EIS) was used as a powerful tool for investigation of charge transfer resistance in cathode material. The scanning electron microscopy (SEM) was employed as a morphology indicator of the cathodes. © 2007 Elsevier B.V. All rights reserved.

Primary chemically formed lead dioxide (PbO 2 ) was used as positive electrode in preparation of lead–acid bipolar batteries. Chemical oxidation was carried out by both mixing and dipping methods using an optimized amount of ammonium persulfate as a suitable oxidizing agent. X-ray diffraction studies showed that the weight ratio of β-PbO 2 to α-PbO 2 is more for mixing method before electrochemical forming. The electrochemical impedance spectroscopy (EIS) was used to investigate charge transfer resistance of the lead dioxide obtained by mixing and dipping methods before and after electrochemical forming. Four types of bipolar lead–acid batteries were produced with: (1) lead substrate and conventional electroforming; (2) carbon doped polyethylene substrate with conventional electroforming; (3) carbon doped polyethylene substrate with chemical forming after curing and drying steps in oxidant bath, followed by electrochemical forming, and (4) carbon doped polyethylene substrate with primary chemical oxidation in mixing step, followed by conventional electroforming. The capacity and cycle-life tests of the prepared bipolar batteries were performed by a home-made battery tester and using the pulsed current method. The prepared batteries showed low weight, high capacity, high energy density and high power density. The first capacities of bipolar batteries of type 1–4 were found to be 152, 150, 180 and 198 mAh g −1 , respectively. The experimental results showed that the prepared 6 V bipolar batteries of type 1–4 have power density (per cell unit) of 59.7, 57.4, 78.46 and 83.30 mW g −1 (W kg −1 ), respectively.

The increasing demand for energy has triggered tremendous research efforts for the development of lightweight and durable energy storage devices. Herein, we report a simple, yet effective, strategy for high-performance supercapacitors by building three-dimensional pseudocapacitive CuO frameworks with highly ordered and interconnected bimodal nanopores, nanosized walls (∼4 nm) and large specific surface area of 149 m(2) g(-1). This interesting electrode structure plays a key role in providing facilitated ion transport, short ion and electron diffusion pathways and more active sites for electrochemical reactions. This electrode demonstrates excellent electrochemical performance with a specific capacitance of 431 F g(-1) (1.51 F cm(-2)) at 3.5 mA cm(-2) and retains over 70% of this capacitance when operated at an ultrafast rate of 70 mA cm(-2). When this highly ordered CuO electrode is assembled in an asymmetric cell with an activated carbon electrode, the as-fabricated device demonstrates remarkable performance with an energy density of 19.7 W h kg(-1), power density of 7 kW kg(-1), and excellent cycle life. This work presents a new platform for high-performance asymmetric supercapacitors for the next generation of portable electronics and electric vehicles.

Normal pulse voltammetric method was used to synthesize nanofibers of polyaniline (PANi) in HCl solution on a platinum electrode. The influences of the synthesis parameters, such as potential increment, pulse duration and monomer concentration on the electrochemical properties of the PANi films were investigated. Scanning electron microscopic micrographs clearly revealed the formation a nanofiber structure with average diameter in range 70–100 nm under optimum experimental conditions. The electrochemical properties of PANi films were studied with the impedance analysis, cyclic voltammetry and charge/discharge capacities. FT-IR results revealed that the PANi nanofibers were in emeraldine salt form. The film was employed as a positive electrode (cathode) for a PANi-Zn secondary battery containing 1.0 M ZnCl2 and 0.5 M NH4Cl as electrolyte. The cells were charged and discharged under a pulse current of 0.31 mA cm−2. It was found that the maximum capacity of the PANi-Zn battery is 235.60 Ah kg−1 with a columbic efficiency of 97–100% over a wide range of current density of 0.3–5.6 mA cm−2. The specific energy was 287.43 Wh kg−1 and the PANi cathode exhibited good recycleability.

Polyaniline/graphite composites (PANi/G) with different graphite particle sizes were deposited on a platinum electrode by means of cyclic voltammetry. The surface morphology of PANi/G composites were studied by using the scanning electron microscopy (SEM) and the fractal dimension concept. This work presents the utilization of the cyclic voltammetry and electrochemical impedance spectroscopy to determine the fractal dimension. The results obtained from both these methods are in good agreement indicating the reliability of the estimated fractal dimension (Df).

Chemically synthesized polyaniline doped with perchlorate ion was used as the electroactive material of the cathode in the construction of bipolar rechargeable batteries based on carbon doped polyethylene (CDPE) as a conductive substrate of the bipolar electrodes. A significant improvement in the originally poor adherence between the polymer foil and electroactive material layer of the anode was achieved by chemical pretreatment (etching) and single-sided metallization of the polymer foil with copper. A thin layer of optalloy was electroplated onto the surface of the copper-coated polymer foil to increase the battery overvoltage. A mixture of 1 wt% electrochemically synthesized optalloy, 92 wt% electrochemically synthesized zinc powder, 2 wt% MgO, 4 wt% ZnO and 1 wt% sodium carboxymethyl cellulose (CMC) was used as the anode mixture. Then, the electroactive mixture of the anode was coated onto the metallized surface of the CDPE. Graphite powder was used to coat the other side of the CDPE at 90 °C at 1 t cm−2 pressure This side was coated with a cathode mixture containing 80 wt% polyaniline powder, 18 wt% graphite powder and 2 wt% acetylene black. The battery electrolyte contained 1 M Zn(ClO4)2 and 0.5 M NH4ClO4 and 1.0 × 10−4 M Triton X-100 at pH 3.2. Both 3.2 V dry and wet bipolar batteries were constructed using a bipolar electrode and tested successfully during 200 charge–discharge cycles. The battery possessed a high capacitance of 130 mAh g−1 and close to 100% columbic efficiency. The loss of capacity during charge–discharge cycles for the wet bipolar battery was less than that for the dry bipolar battery. Self-discharge of the dry and wet batteries during a storage time of 30 days was about 0.64% and 0.45% per day, respectively. An artificial neural network (ANN) was used to model the voltage and battery available capacity (BAC) only for the dry bipolar battery at different currents and different times of discharge.

An electro-forming method was used for the preparation of nano-structured lead dioxide on lead substrate in 4.8 M H2SO4. A two electrode system composed of two similarly prepared lead electrodes was employed. A constant current was applied between two electrodes for a short time, followed by a relaxation period. A dark oxidation film of suitable stability and homogeneity was formed on the anode electrode. Different parameters including pulse height, pulse time (ton) and relaxation time (toff) were optimized. A change in morphology of lead dioxide from globular to nanofibriliar was observed when the pulse time and relaxation time varied from 0.01 to 10 and 0.1 to 5 s, respectively, at a pulse height of 25 mA cm−2. A variation in pulse height caused a variation in diameter and length of nanofibers formed at a pulsed time of 0.1 s and relaxation time of 5 s. The scanning electron microscopy (SEM) showed that lead dioxide particles obtained under these conditions have nanofibriliar morphology with an average diameter in the range between 20 and 50 nm and length of 500–1000 nm. Keywords: Electroforming, Lead dioxide, Pulsed current, Relaxation time, Nanofibriliar

Electrochemical methods were used to investigate the interaction of neutral red (NR) with double-stranded calf thymus DNA, in solution as well as using a DNA-modified glassy carbon (GC–DNA) electrode. The results were compared with those obtained from bare glassy carbon (GC) electrode. The formal potential of NR was more positive when GC-DNA electrode was used although the rate of heterogeneous electron transfer is as high as that of using GC electrode. GC-DNA electrode enables preconcentration of NR for chosen times on the electrode surface, despite the fact that the mass transfer effects in the thin DNA layer adsorbed on the surface was still observed using cyclic voltammetry and electrochemical impedance spectroscopy techniques. Parameters, such as the diffusion coefficient of NR, binding site size in base pairs and the ratio of the binding constants for the oxidized and reduced forms of the bound species were obtained. A binding isotherm for NR at GC-DNA electrode was obtained from coulometric titrations and gave an affinity constant equal to 2.76 × 104 L mol−1. From the studies of the interaction in solution, the diffusion coefficient of free and DNA-bound NR, binding constant and binding site size of the DNA–NR complex was also obtained simultaneously by non-linear fitting analysis of voltammetric data.

Lead-selective solvent polymeric membrane electrodes, based on some recently synthesized 9, 10-anthraquinone derivatives, are described. The electrode exhibits a good Nernstian response for Pb (II) ions over a wide concentration range of 1.0/spl times/10/sup -6/-1.0/spl times/10/sup -2/ M with a slope of 28.9 mV decade/sup -1/. The potential-pH profile of membrane based on 1-hydroxy-2-({2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}methyl)anthra-9, 10-quinone (A/sub 3/) demonstrated a lack of H/sup +/ interference within a wide pH range (1.5-6.8). The detection limit is 6.7/spl times/10/sup -7/ M. The developed sensor has a very short response time (2.0 s), and it can be used as a working electrode in a flow injection system. The lifetime of the proposed sensor is 120 days (without any considerable divergence in potentials) with good reproducibility (SD=/spl plusmn/0.1 mV). The proposed sensor revealed good selectivity for Pb (II) over a wide variety of other metal ions. It can be used as an indicator electrode in the potentiometric titration of lead ions, with EDTA, oxalate, chromate, and hydroxide ions, and in direct determination of lead in a wastewater sample.

Solution studies on the binding properties of dibenzo‐21‐crown‐7 (DB21C7) with alkali metal and ammonium ions revealed the occurrence of a selective 1:1 complexation of the ligand with Rb+ ion. Consequently, DB21C7 was used as a suitable ionophore for the preparation of novel polymeric membrane (PME) and coated graphite (CGE) Rb+‐selective electrodes. The electrodes exhibit near‐Nernstian behavior for Rb+‐ions over concentration ranges of 5.0 × 10−5 to 1.0 × 10−1 M for PME and 1.0 × 10−5 to 5.0 × 10−2 M for CGE with limits of detection of 1.5 × 10−5 M for PME and 7.1 × 10−6 M for CGE. The proposed potentiometric sensors possess response times of

Spectrofluorometric studies on the binding properties of 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthrolinephane (L) toward La3+, Sm3+, Gd3+, Yb3+, and Nd3+ in methanol solution revealed the occurrence of both 1:1 and 2:1 (ligand/metal) complexation with a stability order of Nd3+Yb3+Gd3+Sm3+La3+. Consequently, L was used as a suitable neutral ionophore for the preparation of a novel polymeric membrane-selective electrode for Nd3+ ion. The electrode exhibited a Nernstian response over a wide concentration range (1.0 x 10(-6)-1.0 x 10(-2) M) with a low limit of detection of 7.9 x 10(-7) M. The electrode possesses a fast response time of5 s and can be used for at least 9 weeks without observing any considerable deviation. The proposed electrode revealed a very good selectivity for Nd3+ over a wide variety of alkali, alkaline earth, transition, and heavy metal ions, including members of the lanthanide family other than Nd3+. The potentiometric response of the electrode is independent of the pH of test solution in the pH range 4.0-6.5. The proposed electrode was successfully applied to the recovery of Nd3+ ion from tap water samples and, also, as an indicator electrode, in potentiometric titration of neodymium(III) ions.

The interaction of neutral red (NR) with double-stranded calf thymus DNA was investigated by electrochemical methods using a DNA-modified glassy carbon (GC-DNA) electrode. The results were compared with those obtained at a bare glassy carbon (GC) electrode. The findings showed that although the kinetic of the electron transfer process remains reversible similar to that of using GC electrode, the formal potential of NR (E0′) was more positive when using GC-DNA electrode. GC-DNA electrode enables the enrichment of the concentration of NR for the chosen times on the electrode surface. The ratio of the binding constants for the oxidized and reduced forms of the bound species was obtained through comparing the formal potentials of NR obtained using the modified and bare surfaces. A binding isotherm for NR at GC-DNA electrode was obtained from coulometric titrations indicated a Langmuiran behavior for the NR adsorption on DNA layer, and gave an affinity constant equal to 2.76 × 104 l mol−1. Keywords: Calf thymus DNA, Neutral red, Interaction, DNA-modified electrode, Binding isotherm

The construction, performance characteristics, and application of polymeric membrane (PME) and coated graphite (CGE) thiocyanate-selective electrodes are reported. The electrodes were prepared by incorporating the complex [Cu(L)](NO3)2 (L=4,7-bis(3-aminopropyl)-1-thia-4,7-diazacyclononane) into a plasiticized poly(vinyl chloride) membrane. The influence of membrane composition, pH of test solution, and foreign ions were investigated. The electrodes reveal Nernstian behavior over a wide SCN− ion concentration range (1.0×10−6–1.0×10−1 M for PME and 5.0×10−7–1.0×10−2 M for CGE) and show fast dynamic response times of 15 s and lower. The proposed sensors show high selectivity towards thiocyanate over several common organic and inorganic anions. They were successfully applied to the direct determination of thiocyanate in urine and saliva of smokers and nonsmokers, and as an indicator electrode in titration of Ag+ ions with thiocyanate.

The construction and performance characteristics of thionine electrodes based on the ion-pair complex thionine-tungstophosphate and thionine-mordenite zeolite embedded in a polyvinyl chloride (PVC) matrix is described. Thionine electrode based on the ion-pair is used for the indirect determination of ascorbic acid by standard addition method.

A new dodecyl benzene sulfonate (DBS(-)) ion-selective electrode based on polyaniline is reported. The films of polyaniline doped with DBS(-) were prepared electrochemically on platinum electrodes in the solution containing 1.0x10(-3)M aniline and 7.0x10(-3)M DBS(-). The optimum potentiometric response was obtained for prepared polymeric film by passing electricity of 7.5Ccm(-2). The electrode exhibits an excellent Nernstian slope of -59.1+/-0.3mV per decade for DBS(-) ion over a wide concentration range (5.0x10(-6) to 4.1x10(-3)M) with a low detection limit (1.0x10(-6)M). The proposed electrode revealed good sensitivities for DBS(-) ion over a wide variety of other anions and can be used in the wide pH range of 5-10. It shows good stability, good reproducibility, wide range of pH independency and fast response (

Polyaniline powder of high conductivity is prepared by chemical polymerization of aniline in solutions containing 0.10 M aniline, 2 M perchloric acid and 0.15 M ammonium persulfate at 5 °C. The powder is mixed with graphite and acetylene black for obtaining high conductivity. The chemically-synthesized polyaniline doped with perchloric acid is then used as a cathode in the construction of a bipolar rechargeable battery which employs anti-acid stainless steel as a conductive substrate for a bipolar electrode. The proposed battery contains electrochemically-synthesized zinc powder as an anode material and a solution which contains 1 M Zn(ClO 4 ) 2 and 0.5 M NClO 4 and 1.0×10 −4 M Triton-X100 at pH of 3.2 as a battery electrolyte. To prevent hydrogen reduction, 1 wt.% of electrochemically-synthesized optalloy is mixed with zinc powder which contains 2 wt.% MgO, 4 wt.% ZnO and 1 wt.% sodium carboxymethyl cellulose. To investigate the effect of separator thickness on battery efficiency, three batteries are constructed with one, two and three layers of separators. Each sub-cell from the battery has an open-circuit voltage of 1.6 V. Two bipolar batteries with open-circuit voltages of 3.2 and 6.4 V are constructed and tested successfully for 100 charge–discharge cycles. The batteries have a capacity of 110 mA h g −1 and Coulombic efficiency of >90%.

A highly selective membrane electrode for the determination of ultratrace amounts of lead was prepared. The PVC membrane electrode based on 2-(2-ethanoloxymethyl)-1-hydroxy-9,10-anthraquinone (AQ), directly coated on graphite, exhibits a good Nernstian response for Pb(II) ions over a very wide concentration range (1.0×10−7–1.0×10−2 M) with a limit of detection of 8.0×10−8 M. It has a fast response time of ca. 10 s and can be used over a period 2 months with good reproducibility (SD=±0.2 mV). The electrode revealed a very good selectivity respect to common alkali, alkaline earth, transition and heavy metal ions and could be used in the pH range of 3.5–6.8. It was used as an indicator electrode in potentiometric titration of lead ions with chromate and oxalate, and in indirect determination of lead in spring water samples.

A new graphite coated electrode for the determination of Pb(2+) based on a recently synthesized ionophore 1-hydroxy-2-{2-[2-(2-hydroxy-ethoxy)-ethoxy]-ethoxy methyl}-anthracene-9,10-dione (L) has been developed. The electrode was used in flow injection potentiometry by a home-made flow cell. Under both the batch and flow conditions, the electrode revealed a near Nernstian response over a wide lead ion concentration range (10(-6) to 10(-1) M) and very low limit of detection. In flow injection potentiometry, excellent reproducibility (RSD%=0.49%), very high sampling rate (170 injections h(-1)) and stable baseline was observed in the presence of 10(-3) M KCl as ionic strength adjuster. The electrode showed high sensitivity and good selectivity for Pb(2+) over a wide variety of alkali, alkali earth and transition metal ions and the electrode can be used for at least 3 months without any considerable change in potential response. The proposed sensor was successfully applied to the direct determination of lead in real samples and also used for the titrimetric determination of phosphate ions by both batch and flow injection potentiometry.

New polymeric membrane (PME) and coated graphite (CGE) samarium(III)-selective electrodes were prepared based on isopropyl 2-[(isopropoxycarbothioyl) disulfanyl]ethanethioate as a suitable neutral ionophore. The electrodes exhibit Nernstian slopes for Sm 3+ ions over wide concentration ranges (1.0×10 −5 to 1.0×10 −1 M for PME and 1.0×10 −6 to 1.0×10 −1 M for CGE). The PME and CGE have limits of detection of 3.1×10 −6 and 5.0×10 −7 M, respectively, and response times of about 20 s. The potentiometric responses are independent of the pH of the test solution in the pH range 4.0–7.0. The proposed electrodes revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The electrodes were successfully applied to the recovery of Sm 3+ ion from tap water samples and also, as an indicator electrode, in potentiometric titration of samarium(III) ions.

A new coated ion-selective electrode for the determination of trace vanadyl ions (VO 2+ ) by flow injection potentiometry (FIP) with a home-made flow cell has been developed. The PVC-based membrane was coated on a graphite electrode with an effective area of 4.90 mm 2 . The optimum membrane contains 5 wt.% 1,8-diaminonaphtalene as ionophore, 35 wt.% plasticizer 2-nitrophenyl octyl ether, 55 wt.% PVC and 5 wt.% additive potassium tetrakis ( p -chlorophenyl) borate. The electrode in flow injection potentiometry resulted in well defined peaks for vanadyl ions with a very high sampling rate (180 injections/h). Linear calibration was obtained from 1.14×10 −7 to 1.14×10 −1 M vanadyl ions, with a slope of 28.3±0.3 mV per decade change in vanadyl concentration, and very low detection limit of 1.14×10 −7 M and the electrode can be used for at least 1 months without any considerable change in potential response. Selectivity coefficients for several ions were obtained by the matched potential method with respect VO 2+ ions. The flow cell is simple to construct and free from memory effect problems over long periods of use. The sensor was used for the recovery of trace VO 2+ ions from tap water and the determination of VO 2+ in synthetic sample.

A supported liquid and a poly(vinyl chloride) (PVC)-based membrane selective for dodecylsulfate (DS−) ion are described. The active element is a membrane containing a dissolved ion association complex of DS− with cetylpyridinium (CP+) cation. The supported liquid membrane electrode (acetophenone as solvent) showed a Nernstian response towards the DS− anion over the concentration range of sodium dodecylsulfate (SDS) from 8.3×10−3 to 1.0×10−6 mol dm−3 at 25 °C. The proposed electrode also showed a super-Nernstian potential response (108±2 mV decade−1) at low concentrations (1.0×10−9 to 1.0×10−6 mol dm−3). Moreover, this electrode showed good selectivity and precision (R.S.D.⩽2.0%), and was usable within the pH range 4.0–6.8. The proposed electrode revealed a lower limit of detection of 6.3×10−7 mol dm−3 and improved selectivity in comparison with the some previously reported DS− ion selective electrodes. The isothermal temperature coefficient of this electrode amounted to −0.001 V °C−1. The liquid membrane electrode may find application in the direct determination of SDS by the standard addition method at pH 5.0, and in the physicochemical studies of surfactant solutions.

Three different recently synthesized aza-thioether crowns containing a 1,10-phenanthroline sub-unit (L1–L3) and a corresponding acyclic ligand (L4) were studied to characterize their abilities as silver ion ionophores in PVC-membrane electrodes. Novel conventional silver-selective electrodes with internal reference solution (CONISE) and coated graphite-solid contact electrodes (SCISE) were prepared based on one of the 15-membered crowns containing two donating S atoms and two phenanthroline-N atoms (L1). The electrodes reveal a Nernstian behavior over wide Ag+ ion concentration ranges (1.0×10−5−1.0×10−1 M for CONISE and 5.0×10−8−4.0×10−2 M for SCISE) and very low limits of detection (8.0×10−6 M for CONISE and 3.0×10−8 M for SCISE). The potentiometric response is independent from pH of the solution in the pH range 3.0–8.0. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations. The electrodes can be used for at least 2 months (for CONISE) and 4 months for (SCISE) without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of Ag+ ion and in the determination of silver in photographic emulsions and in radiographic and photographic films.

A new calix[4]arene derivative [25-(3-bromo-propyloxy)-5,11,-17,23-tetrakis(tert-butyl)-26,27,28-tris(1-propyloxy) calix[4]arene] (BTC) in the 1,3-alternate conformation was tested as a cesium-selective ionophore plasticized PVC membrane electrode. The resulting electrode showed a Nernstian behavior for Cs+ ion over a wide concentration range (1.0 × 10−6–1.0 × 10−1 M). The selectivity coefficients for cesium with respect to alkali, alkaline earth, ammonium and some transition metal ions, were determined. A relatively high Cs+/Rb+ selectivity was observed, the selectivity coefficient being ca. 10−2. Effects of membrane composition and pH of test solution on the potential response of the electrode were also discussed. The proposed electrode revealed a lower limit of detection (2.1 × 10−7 M) and improved Cs+/Rb+ selectivity in comparison with the previously reported Cs+ ion selective electrodes.

A PVC membrane electrode for aluminum(III) ions based on Furil (ethan dione, di-(2-furyl)) as neutral carrier was prepared. The electrode exhibits a near Nernstian response for Al3+ ions over a wide concentration range (1.0×10−6 to 1.0×10−2 mol dm−3) with a limit of detection 1.3×10−7 mol dm−3. It has a relatively fast response time and can be used for at least 2 months without any considerable divergence in potentials. The proposed membrane electrode revealed very good selectivity for Al3+ ions over a wide variety of other cations and could be used in acidic media. It was used as an indicator electrode in potentiometric titration of aluminum ions.

A sensitive and selective method for the determination of lead(II) with a 1,4-bis(prop-2′-enyloxy)-9,10-anthraquinone (AQ) modified carbon paste electrode has been developed. The method is based on non-electrolytic preconcentration via complex formation with modifier, followed by an accumulation period with a negative potential (−1.5 V), and then by a proper anodic stripping. The analytical performance was evaluated with respect to the quantity of modifier in the paste, concentration of electrolyte solution, preconcentration time, lead(II) concentration, and other variables. A linear calibration graph was obtained in the concentration range 2.00×10 −9 –1.06×10 −5 M Pb(II) ( n =21, r =0.9999) with 30 s preconcentration time. The detection limit was found to be 1×10 −9 M. For eight preconcentration/determination cycles, the differential pulse voltammetric response was reproduced with 5.0 and 3.7% relative standard deviations at 2.00×10 −8 and 2.00×10 −6 M Pb(II), respectively. Rapid and convenient renewal of electrode surface allows the use of a single modified electrode surface in multiple analytical determinations over several weeks. Many coexisting metal ions had little or no effect on the determination of lead(II). The developed method was applied to lead determination in waste waters.

The preparation and aqueous electrochemistry of carbon paste electrodes modified by some amino-substituted 9,10-anthraquinones are reported. In all cases, the reduction processes studied by cyclic voltammetry reveal a quasi-reversible behavior. The half-wave potentials were calculated as a function of the solution pH and from the resulting potential-pH plots the formal potentials and pKa′ values of different redox and acid-base couples involved at various pH ranges were evaluated. The diffusion coefficients of different anthraquinone derivatives used in paraffin oil were calculated by chronoamperometry.

A PVC membrane lead(II) ion-selective electrode has been constructed using 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBzDA18C6) as membrane carrier. The sensor shows a Nernstian response for Pb(II) ions over a wide concentration range (5.0×10−5 to 1.0×10−2 M). It has a fast response time and can be used for more than 10 months without any considerable divergence in potentials. The proposed sensor exhibits comparatively good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions. It was employed as an indicator electrode in potentiometric titration of EDTA with lead ions and used for direct determination of lead in waste water.

The preparation and electrochemical characterization of glassy carbon electrodes modified by four recently synthesized 1,4-dihydroxy-9,10-anthraquinone derivatives are reported. The anthraquinones used were strongly and irreversibly adsorbed on the preanodized glassy carbon electrodes. The electrochemical behavior and stability of the modified electrodes were studied by cyclic voltammetry at different acidic and basic aqueous solutions, and pH of 6—7 was chosen as the optimum working pH. The adsorbed anthraquinone derivatives showed excellent electrocatalytic ability for the reduction of O2 to H2O2 with overpotentials of from 560 to 650 mV lower than that of a plain glassy carbon electrode. The heterogeneous rate constants for the reduction of O2 at the surface of the modified electrodes were determined by rotating-disk electrode voltammetry using the Koutecky–Levich plots. The apparent diffusion coefficient of O2 in buffered aqueous O2-saturated solutions was also estimated.

A PVC membrane nickel(II) ion-selective electrode was constructed using 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBzDA18C6) as a neutral carrier. The sensor exhibits a Nernstian response for Ni(II) ions over a wide concentration range (5.5×10−3–2.0×10−5 M). It has a relatively fast response, time and can be used for at least 6 weeks without any considerable divergence in potentials. The proposed sensor revealed relatively good selectivity for Ni(II) over a wide variety of other metal ions, and could be used in a pH range of 4.0–8.0. It was used as an indicator electrode in potentiometric titration of nickel ions.

A surface modification procedure for the creation of self-assembled monolayers (SAMs) that can be used as a scaffold for double-stranded DNA (dsDNA) incorporation onto the gold surfaces is described. The SAMs of an azidohexane thiol derivative were prepared on the Au electrode and then used for the immobilization of dsDNA. The electrochemical characteristics of dsDNA onto the SAM-modified gold electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy, and the surface concentration of dsDNA onto the SAMs surface was estimated. The interaction of dsDNA with the anticancer drug, taxol (paclitaxel), was also studied on the surface of DNA/SAM/Au electrode. The observed decrease in the guanine oxidation peak current was used to monitor the interaction of taxol with DNA. The resulting Langmuir isotherm for taxol binding to DNA at the modified electrode was used to evaluate the binding constant of taxol-DNA. The results obtained supported the groove binding interaction of taxol with DNA. The modified electrode was used as a sensitive sensor for quantification of taxol in human serum sample.