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The electroactive composites based on reduced graphene oxide (RGO), poly‐o‐phenylenediamine (PPD) and heteropolyacids – H4SiW12O40nH2O (SiW) and H3[PW12O40] ⋅ nH2O (PW) was applied to a screen‐printed carbon electrode (SPCE) as a planar three‐electrode cell as the first step to creating various devices, in particular, sensors and catalysts. We studied potential use of the modified and unmodified SPCE planar electrode in determining the concentration of antitubercular antibiotic isoniazid (isonicotinic acid hydrazide C6H7N3O or INH). The best result was observed for SPCE+RGO‐PPD‐SiW. CV of normal saline with various concentrations of C6H7N3O demonstrated linear dependence of the relevant anodic peak current either in the bulk solution upon immersion of the modified electrode or in a droplet on the electrode surface. [ABSTRACT FROM AUTHOR]

The study of planar energy storage devices, characterized by low-cost, high capacity, and satisfactory flexibility, is becoming a valuable research hotspot. Graphene, monolayer sp2 hybrid carbon atoms with a large surface area, always acts as its active component, yet there is a tension between its high conductivity and ease of implementation. Although the difficult-to-assemble graphene can easily achieve planar assemblies in its highly oxidized form (GO), the undesirable conductivity, even after proper reduction, still restricts its further applications. Here, a facile "Top-down" method has been proposed to prepare the graphene planar electrode via in situ electro-exfoliation of graphite supported on a piece of laser-cutting patterned scotch tape. Detailed characterizations have been performed to study its physiochemical property evolution during electro-exfoliation. The obtained flexible graphene planar electrodes show decent energy storage performance, e.g., 40.8 mF cm−2 at a current density of 0.5 mA cm−2 and an 81% capacity retention at a current density of 8 mA cm−2 for the optimized sample G-240. Their high conductivity also makes it possible to couple them with other redox-active materials through electrodeposition to improve their performance, e.g., ferrocene-functionalized mesoporous silica film (Fc-MS), MnO2, and polyaniline (PANI). The highest capacity was achieved with the PANI functionalized sample, which achieved a 22-fold capacity increase. In a word, the versatility, practicality, and adaptability of the protocol to prepare the planar graphene electrode proposed in this work make it a potential candidate to meet the continuously growing energy storage demands. [ABSTRACT FROM AUTHOR]

The catalytic activity of particles of gold, cobalt, and a gold–cobalt binary system electrodeposited on the surface of planar carbon electrodes was found in the oxidation of glucose in a neutral medium. The amperometric response of a screen-printed electrode modified with a gold–cobalt binary system was used as an analytical signal in the determination of glucose in a sequential injection system. The linear logarithmic dependence of current on the glucose concentration was observed in the range from 5 × 10–8 to 5 × 10–2 M. The use of a screen-printed electrode modified with a gold–cobalt binary system as an amperometric detector in a sequential injection system makes it possible to selectively determine glucose in saliva in the concentration range used for medical diagnosis. [ABSTRACT FROM AUTHOR]

The goal of this research is to obtain new electrode hybrid coatings for electrochemical devices applications. Nanocomposites based on unsubstituted polyphenothiazine (PPTA) and carbon nanomaterials (CNM) were prepared for the first time. Reduced graphene oxide (RGO), single-walled and multi-walled carbon nanotubes (SWCNT and MWCNT) were used as CNM. Hybrid nanocomposites were prepared by two methods: via oxidative polymerization of PTA in the presence of CNM (CNM/PPTA-1), or from pre-synthesized polymer solution in DMF containing CNM followed by solvent removal (CNM/PPTA-2). The structure and morphology of PPTA-derived nanocomposites were studied by means of FTIR spectroscopy, X-ray diffraction, and FE-SEM. The nanocomposite composition dependence of conductivity was demonstrated. Electrochemical behavior of the electrode coatings prepared on the basis of the said polymer and CNM/PPTA nanocomposites thereof was studied by CV methods. All the samples were found to be electroactive in 1 M sulfuric acid. An addition of carbon nanomaterials was shown to improve reversibility of the electrode processes that is related to formation of nanocarbon conductive framework in the composite with a highly developed surface filled with thin layers of the polymer. CNM/PPTA nanocomposites exhibit the electrocatalytic effect to the redox behavior of ferro/ferricyanide couple in 1 M H 2 SO 4. • New electrode hybrid coatings for electrochemical devices applications. • Nanocomposites of polyphenothiazine and carbon nanomaterials were prepared for the first time. • Two method of preparation: via oxidative polymerization or from pre-synthesized polymer solution. • Nanocomposites exhibit the electrocatalytic effect in some reactions. • Easy application on the electrode surface. [ABSTRACT FROM AUTHOR]

The challenge encountered by the sensor in practical application is that the optimal working temperature is high, which will cause certain dangers in the work. Herein, we fabricated a p-p heterojunction composite LaFeO 3 /YFeO 3 planar electrode sensor for gas detection. The planar electrode sensor adopts the method of direct heating, which reduces the optimal working temperature of the sensor compared with the traditional side-heated alumina ceramic tube sensor. The optimal operating temperature of the LaFeO 3 /YFeO 3 (0.8:0.2) planar electrode sensor is 110 °C. In addition, we also performed multi-wavelength (470, 420, and 370 nm) light illumination experiments on the LaFeO 3 /YFeO 3 sensor to improve gas response. Under 370 nm light illumination, the response values of the LaFeO 3 /YFeO 3 (0.8:0.2) sensor to 30 ppm methanol, acetone, and ethanol were 166.82, 199.58, and 292.67, which were 1.19, 1.33, and 1.36 times than those in the dark. The lowest detection limits of the LaFeO 3 /YFeO 3 (0.8:0.2) sensor under 370 nm light illumination for methanol, acetone, and ethanol were 0.3, 0.8, and 0.2 ppm, respectively. Therefore, the LaFeO 3 /YFeO 3 (0.8:0.2) planar electrode sensor has the advantages of small size, low optimal operating temperature, low power consumption, high response value to volatile organic compounds gases, and high-cost performance for use in different gas environments. • The LaFeO 3 /YFeO 3 (a:b) materials were fabricated by the sol-gel method. • Gas sensor was prepared using 1.5 × 1 mm plane electrodes. • The sensors were tested under multi-wavelength light illumination. • The optimal operating temperature of LaFeO 3 /YFeO 3 (0.8:0.2) sensor was 110 °C. • Light illumination improved the sensor's response to VOCs gases. [ABSTRACT FROM AUTHOR]

Measuring electrical conductivity makes it possible to determine the concentration of dissolved ionic compounds in the water. Presented is a sensor developed for easily measuring the electrical conductivity of aqueous solutions. This sensor is comprised of two planar electrodes integrated onto a printed circuit board (PCB). PCB technology enables this sensor to be manufactured at high volumes for a modest cost. However, when the sensor is integrated into a PCB, it becomes difficult to analytically determine the influence the dimensions of the sensor's electrodes have on its measurements. In this research, a genetic algorithm was used to derive an equation predicting the behaviour of a PCB sensor with any reasonable electrode dimensions. Afterwards, the accuracy of this equation was evaluated by comparing its predictions to the measurements taken using actual sensors. [ABSTRACT FROM AUTHOR]

The aim of this study was to obtain time-resolved images of the electrical breakdown of a planar microelectrode gap along the surface of a glass substrate in atmospheric air. The obtained images revealed details of the events leading to the breakdown. First, a point light emission appeared at the cathode, indicating breakdown initiated by the field emission of electrons from the cathode under extremely high electric fields. Then, a flare-like broad light emission was generated at the anode. Finally, breakdown occurred over the entire gap by the expansion and merger of the two emissions. [ABSTRACT FROM AUTHOR]

• A novel planar flow-through potentiometric ion sensor is presented. • A potassium ion-selective electrode is developed as proof-of-concept. • The new design allows the sample to freely flow through the sensor. • Potential applications include wearable sweat sensors. A novel planar electrode for flow-through potentiometric sensing is presented in this work. Planar and concentric potassium solid-contact ion-selective electrodes (K+-SCISEs) were designed and studied using potentiometry and electrochemical impedance spectroscopy (EIS). The K+-SCISE consisted of a neutral carrier PVC-based ion-selective membrane with valinomycin as ionophore, carbon cloth as ion-to-electron transducer, and a gold wire as electronic conductor, all incased in a polycarbonate support. The prepared electrodes showed a stable and reproducible potentiometric response. The average slopes for three identical flow-through K+-SCISEs, calibrated once per day during five days (n = 15), was 57.2 mV/decade (SD = 0.9 mV/decade). The corresponding standard potential of the electrodes during five days (n = 15) was 417 mV (SD = 3.6 mV). The water-layer test showed that the ion-selective membrane/carbon cloth interface was not subject to the formation of a water layer. The electrodes had selectivity coefficients comparable to the values obtained from the literature. The resistance of the ion-selective membrane, determined by EIS, was in the range of 45–250 MΩ for the planar electrode geometries studied in this work. [ABSTRACT FROM AUTHOR]

Abstract: Low-cost conductometric transducers have been designed and characterised with a view to their potential use as chemiresistors in mobile sensor applications. Four different geometries of transducer have been evaluated by two different measurement techniques. Devices were fabricated by etching planar gold electrodes on low-cost glass-fibre substrates (FR-4) using a standard printed circuit board (PCB) photolithography, wet etching and electroless plating method. Thin films of the P-type semiconducting polymer poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate), PEDOT-PSS, were cast onto the electrodes by spin-coating. The conducting polymer films were electrically characterised by measuring the film resistance from the underlying gold electrodes using a digital multimeter, and also by determination of the film's current–voltage transfer characteristic (I–V curve) measured with a precision laboratory 4-point probe instrument. This allowed the relative contribution of the contact resistance at the Au/PEDOT-PSS interface to be determined as a proportion of the overall measured resistance. Contact resistance is known to affect the analytical performance of chemiresistor type devices, so in this work the combined effects of electrode geometry, polymer film composition and ageing of the film on bulk film and contact resistances have been investigated. The applicability of the chemiresistor transducers for chemical sensing is demonstrated using a PEDOT-PSS thin film as an ethanol vapour sensitive coating in a simple vapour exposure test, where a reversible conductometric response was observed. Due to the simplicity, low-cost and ultra low-power requirements of these transducers, they may be particularly suited to battery powered mobile and wireless sensing applications, or to applications dependant upon energy harvesting. [Copyright &y& Elsevier]

• Zn deposition on the surface of a planar electrode is optically observed. • The deposition process is defined as relatively uniform and non-uniform sections. • Effects of current and viscosity on the range of uniform area are analyzed. • The variations of deposition thickness in different viscosities are explored. As the dendrite issue is prominent in Zn-based batteries, the regulation of Zn electrodeposition to inhibit the dendrite formation and growth is crucial. Herein, the in-situ observation of electrodeposition process on a planar electrode is performed in this work. The scenarios of operating conditions and electrolyte viscosities are investigated by adjusting charging currents and adding polymer molecules with different concentrations. It is found that the Zn electrodeposition process can be divided into uniform and non-uniform regions, and high currents and high viscosities can prolong the uniform region. Besides, with the increases of current and viscosity, the deposition Zn becomes thinner and compact in the uniform region. The mechanism is proposed as the high current can provide enough electrons which can make the deposition occur besides the deposition tips. The increase in viscosity hinders ion transport, which makes the effect of distance more obvious. Thus, using a high charging current (e.g., pulse charging) and/or an electrolyte with high viscosity are favorable for the uniform deposition of Zn. This work lays the foundation for the improvement of alkaline Zn-based batteries. The optical in-situ observation technology used here is also favorable to explore the deposition process in other electrochemical systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the first-of-its-kind electrochemical seismic sensor where, a liquid proof mass (e.g., electrolyte solution) was used as the sensing element to translate environmental vibrations into active ion imbalances between electrodes, and therefore producing electrical current outputs. Theoretical analysis and numerical simulations were conducted to confirm the feasibility of the device concept and the proposed micro seismic sensor was fabricated by conventional MEMS technologies. Device characterization based on a vibration table recorded a linear relationship between applied velocities and output voltage amplitudes with a calculated sensitivity of 274V/(m/s) (20–80Hz). The performance of the proposed micro device was compared with a commercially available macro counterpart (MET2003), indicating strong correlations of these two types of devices in response to random vibrations while the proposed micro seismic sensor was capable of producing a lower power spectrum compared to MET2003. In summary, the electrochemical micro seismic sensor developed in this study is featured with mass fabrication capabilities due to MEMS technologies, comparable performance and lower power spectrum compared to conventional electrochemical seismometers. This newly developed micro sensor can be potentially used in the field of seismology, enabling the ground motion monitoring to locate earthquakes, volcanic eruptions, and other seismic sources. [Copyright &y& Elsevier]

Abstract: Trends in disposable and handheld biosensors have called for miniaturized and planar electrodes in the place of conventional bulky ones. In this work, thin tin-doped indium oxide (ITO) film coated on glass were used as a based electrode in a three-electrode electrochemical system to follow some biochemical activities, such as NADH and phenol activity. The reference electrode is made on ITO layer by electro-deposition of thin nickel layer and silver layer, consecutively, followed by chlorination of silver surface by electrochemical potentiostatic method. The plain planar ITO-coated glasses were used as both counter electrode and working electrodes. Cyclic-voltammetry measurements; which follow an oxidation of 200μM nicotinamide adenine dinucleotide (NADH) in 0.1M KCl, show current peak of 8.5μA. Another case was also to follow the NADH oxidation but in competition with its coupling activity with flavin mononucleotide (FMN). In this case, cyclic-voltammetry measurements were carried out of 200μM NADH in 50mM sodium phosphate; current peak of 1.3μA was observed. [Copyright &y& Elsevier]

The analytical solutions of the non-steady-state concentrations of species at a planar microelectrode are discussed. The analytical expression of the kinetics of CE mechanism under first or pseudo-first order conditions with equal diffusion coefficients at planar electrode under non-steady-state conditions are obtained by using Homotopy perturbation method. These simple new approximate expressions are valid for all values of time and possible values of rate constants. Analytical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. Working surfaces are presented for the variation of limiting current with a homogeneous kinetic parameter and equilibrium constant. In this work we employ the Homotopy perturbation method to solve the boundary value problem. Furthermore, in this work the numerical simulation of the problem is also reported using Scilab program. The analytical results are found to be in excellent agreement with the numerical results. [ABSTRACT FROM AUTHOR]

Abstract: An electrochemical approach has been used to model and measure acetaminophen transport through a microporous polycarbonate membrane. The dynamic response of a membrane covered planar electrode system was investigated to derive a simplified middle point formula, the time at which amperometric current reaches half steady state value, that provided reliable solute diffusion coefficients. Experimental values may be noise-contaminated; when this noise is significant, the diffusion coefficient by this method needs to be refined. Here a direct simulation method with a bipartite mathematical expression for current transient was used, which fitted calculated current transients to experimental data. A best fit was reached by minimising the standard deviation between the simulated and experimental current profiles. Mathematically, the simulated curve was linear operated, i.e. shifted and stretched vertically, as well as shifted and stretched horizontally to coincide with the experimental curve. The single point formula, bipartite expression and simulation approach allowed extraction of accurate diffusion values from a previously reported approximated method. The computation approach is not only valid for membrane covered electrodes, but is suitable for other experimental set ups where a one-dimensional Fickian diffusion model is valid, for example, for axial diffusion through cylindrical geometries. [Copyright &y& Elsevier]

Abstract: The initial event in olfactory perception is the binding of odorant molecules to specific receptor proteins in the human nose. The interaction between odorant and receptor initiates olfactory signal transduction that leads to a cation influx and change in the membrane potential of the olfactory sensory neuron. In this study, a microfabricated planar electrode was used to measure the generated membrane potential in a heterologous olfactory system. Human embryonic kidney (HEK)-293 cells expressing the olfactory receptor I7 were transfected with the gustatory cyclic nucleotide gated (CNG) channel to amplify the membrane potential. A microfabricated planar electrode was used to measure the electrical responses of odorant–receptor binding. Stimulation of the olfactory receptor with its specific odorant caused an intracellular Ca2+ influx, which was quantitatively measured using a planar electrode. The extracellular field potential generated by the Ca2+ influx through the CNGgust channel of the cells was approximately 10mV. This cell-based olfactory biosensor, which uses a microfabricated planar electrode for detection, would be useful for screening specific ligands for binding to orphan olfactory receptors. [Copyright &y& Elsevier]

Abstract: This paper presents a capillary electrophoresis poly(methyl methacrylate) (PMMA) based microchip for electrochemical detection applications featuring embedded gold nanoelectrode ensemble (GNEE) working and decoupler electrodes. In fabricating the microchip, the GNEE films are pressed directly onto the metallic electrode structures using a hot embossing technique, and the microfluidic channels are then sealed using a low-temperature azeotropic solvent bonding method. The detection performance of the microchip is evaluated using dopamine and catechol analytes for illustration purposes. The experimental results show that the GNEE working electrode provides a significantly higher signal response than that obtained from a bulk gold electrode when applied to the detection of dopamine analyte. Compared to a conventional bulk palladium decoupler electrode, the GNEE decoupler electrode reduces both the amplitude of the charge current (3.5nA vs. 18.7nA) and the baseline drift at higher separation voltages. The measured baseline current drift for the microchip equipped the proposed GNEE decoupler electrode is around three times smaller than the microchip with the palladium decoupler electrode under the applied separation electric field from 40V/cm to 240V/cm. Finally, when detecting a mixture of 1mM dopamine and 1mM catechol, the calculated signal response of the microchip with a GNEE decoupler electrode is approximately five times higher than that obtained from a microchip with a bulk Pd decoupler electrode, resulting in the detection limit of 1μM for the proposed GNEE-based microchip device. Overall, the results indicate that the proposed capillary electrophoresis-electrochemical detection (CE-ED) microchip with embedded GNEE working and decoupler electrodes provides an ideal solution for sample detection in lab-on-a-chip and micro total analysis applications. [Copyright &y& Elsevier]

Abstract: This work reports on the development of a graphite–polystyrene composite electrode of planar configuration, containing silver(II) oxide and copper(II) oxide catalysts (AgO–CuO), for the measurement of electrochemical oxygen demand (EOD). Optimisation studies of the composite composition as well as conditions for its processing on planar substrates and generation of an appropriate electrochemical active area resulted in the scalable fabrication of robust composite electrodes. These were evaluated with glucose as target analyte. They showed competitive low limits of detection in a linear concentration range from 5mgL−1 to 1400mgL−1 of O2. Besides, they were stable for at least one year. The determination of EOD in wastewater samples coming from production lines of parenteral food and winemaking was successfully carried out. [Copyright &y& Elsevier]

Abstract: Present information technologies use semiconductor devices and magnetic/optical disc. However, they are all foreseen to face fundamental limitations within a decade. Therefore, superseding devices are required for the next paradigm of high performance information technologies. This paper describes prospects for single molecule devices suitable for future information processing technologies, which are expected as the most probable candidate to supersede the present semiconductor devices. The first milestone towards the realization of single molecule devices in future electronics requires quantitative evaluation of single molecule characteristics, which inevitably needs planar nano-gap electrodes between which single molecules are sandwiched, observed their structures and measured their electrical characteristics. Nano-meter electrode pattern fabrication was achieved by electron beam lithography and metal lift-off, while planarization process requires many new technologies including chemical–mechanical polishing (CMP) and wafer bonding. The detailed planarization processing technologies are described in this paper to realize nm-planar nano-scale electrodes. [Copyright &y& Elsevier]

Abstract: A photo-crosslinkable polymer mixed with bovine serum albumin was adapted to fabricate an amperometric planar l-glutamate biosensor. The characteristics of this amperometric biosensor during aging of the membrane, its reproducibility and the effects of storage conditions on the long-term stability of the biosensor were studied. The steady-state method (R.S.D.=3.69%) was more appropriate than the kinetic method (R.S.D.=7.70%) for measuring the concentration monosodium glutamate. The l-glutamate amperometric biosensor exhibited remarkable long-term stability (150 days) when maintained in a dry dark state. Most of the functional characteristics of the biosensor were restored within 5min (wet-up times) of repeated wetting and drying. The long-term stability and short wet-up times of the electrode suggests its suitability for use in the design of real time or flow injection biosensors. [Copyright &y& Elsevier]

Abstract: A new method for the fabrication of a planar silver/silver chloride reference electrode for electrochemical detection is described. The film microelectrode was directly fabricated on the surface of a glass slide through a combination of electroless deposition and electroplating. Thickness of the electrode film could be easily controlled by setting the repetition times of the deposition. The whole process can be operated in ordinary chemistry laboratory at a low cost, which makes it possible for the development of disposable devices. The electrode potential showed extreme stability in 3mol/L KCl and water during the tested period of 14 and 10 days, respectively. pH does not have a significant effect on the performance of the electrode. In both potentiometric and amperometric applications, the film Ag/AgCl electrode demonstrated to be a good reference for electroanalysis with its performance comparable to that of commercial reference electrode and the electrodes fabricated from different batches showed good reproducibility. [Copyright &y& Elsevier]

Real-time detection of bioparticles is of great importance in deterring infectious diseases and bioterrorism. For bioparticle solutions with concentrations at an infectious level, culturing is typically used to increase the particle concentration to a detectable level, which is time consuming and often unfeasible under field conditions. Therefore, a real-time particle concentration technique is in demand to bridge the gap between the detectable level and infectious level of bacterial solutions. This paper describes a novel electrokinetic method that can potentially concentrate particles in real time. By studying surface flows on planar electrode pairs, two distinct ac electro-osmosis (ACEO) flows have been identified which are due, respectively, to capacitive and Faradaic charging of electrode double layers. Biased ACEO, combining dc bias with ac signals, breaks the symmetry of electrode charging, leading to asymmetric surface flows and a variety of directed surface flows that can concentrate, manipulate, and transport particles. Surface flows of opposite directions on planar electrodes produce stagnation lines that function as long-range particle traps and lead to net flows for micropumping. The device fabrication and operation are simple and compatible with integrated circuit technology [ABSTRACT FROM PUBLISHER]

The voltammetric response of metal complex systems with various labilities is analyzed by rigorous numerical simulation with the Finite Element Method of the time-dependent concentration profiles of the different species. The ensuing exact fluxes and the corresponding currents are compared to those derived from the Koutecky´–Koryta (KK) approximation which assumes a discontinuous transition in the concentration profiles from non-labile to labile behavior. The results indicate a relatively far-reaching correctness of the KK approximation in the complete kinetic range from non-labile to labile complexes, as long as the kinetic flux is computed from the effective concentration of the complex in the reaction layer. Some approximate analytical expressions for this concentration are provided. The KK approximation is shown to be applicable for any metal-to-ligand ratio, provided that the thickness of the reaction layer is expressed in terms of the ligand concentration at the electrode surface. [Copyright &y& Elsevier]

Experiments are performed, which investigated the performance of a planar thermionic converter with molybdenum electrodes and 0.5 mm inter-electrode gap for low temperature, energy conversion applications. Results confirmed that for TE<1773 K, the performance of the converter is superior to that with a tungsten emitter, when operated at near same conditions. The largest difference occurred at TE∼1600 K and TC∼1000 K, at which the maximum electric power density (3.0 We/cm2) is 70% higher than that of the converter with a W emitter, at more than double the output voltage (0.43 V vs. 0.21 V) and at lower cesium pressure (∼105 Pa vs. 245 Pa). At TE=1700 K, TC=1000 K and TE=1600 K, TC=800 K, respectively, the maximum electric power density of the present converter is 25% and 50% higher and occurred consistently at lower cesium pressure and higher output voltage. At TE=1673 K and TC=973 K, an electric power density of ∼3.22 We/cm2 is measured at 0.49 V, PCs=241 Pa, and an estimated conversion efficiency of 12.4%. For the same electrode temperatures, however, the estimated peak efficiency of 15.1% occurred at a significantly lower PCs (140 Pa), at which the measured electric power density=2.27 W/cm2. [Copyright &y& Elsevier]