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Binder free spinel Co >0.5 Mn 0.1-0.3 O 0.1-0.4 @rGO composite electrode films were fabricated via galvanostatic electrochemical deposition technique over α-Fe(110) as current collector for hybrid supercapattery. Self-designed, n-MOSFET embedded ATMega328P microcontroller assisted modules were deployed to record the chronopotentiometric as well as galvanostatic charging-discharging analysis for specific capacitance (C s) measurements. Partial, exchange as well as limiting current densities(i L) and cathodic current efficiency were estimated. Electrochemical signature was analyzed from cyclic voltammetry data. Morphology and chemical nature of the composites were scrutinized with scanning electron microscopy, X-ray photoelectron, FT-IR and Raman spectra. Indigenously designed computer simulation programs coded in Python were used to optimize the deposition parameters and to analyze the crystalline structure from XRD data. The unit cell length for the FCC crystal with an octahedral geometry was ∼ 4.28 Å. An in-depth analysis of potentiodynamic polarization as well as electrochemical impedance spectral data were carried out to scrutinize the corrosion resistance and capacitance characteristics of the composites in KOH. From the Tafel constants, E corr , I corr , R u , R CT and Z W data, it was accentuated that rGO incorporated composite films offer enhanced corrosion protection for Fe(110) substrates than their individual counterparts along with augmented specific capacitance. Estimated C s was about 1166 F.g−1 at a scan-rate of 10 mV.s−1. Impact of time-constant (τ) and current density over C s was analyzed via GCD technique and was about 1458.73 F.g−1 at 2 τ and at 0.5 A.g−1. And the corresponding specific energy and power density were about 183.23 W.h.kg−1 and 237.75 W.kg−1 respectively. These composite electrode films impregnated with rGO not only improved the specific capacitance but also imparts the sacrificial corrosion resistance over the α-Fe(110) as current collector in presence of OH−as electrolyte and can serve as a sustainable electrode material for supercapatteries. [ABSTRACT FROM AUTHOR]

Ion-selective electrodes have become the largest and most widely utilized category of electrochemical sensors since the end of the last century, marked by the introduction of solid-contact electrodes. Ongoing research in potentiometric sensors predominantly focuses on innovating new variations or emerging trends of solid contact to yield devices with improved analytical parameters. Many advanced ion selective electrodes (ISEs) have proven to be highly effective in pharmaceutical practical applications. The inherent advantages of ISEs, including their simplicity, affordability, rapid analysis, precision and accuracy, on-site monitoring, acceptable limit of detection (LOD), wide linear range, and selectivity, make them promising candidates for pharmaceutical analysis. While numerous review articles have been published in recent years, addressing topics such as membrane materials, ionophores, functional materials, and applications in various fields, there seems to be a gap in the literature when it comes to a comprehensive review summarizing the extensive utilization of various solid-contact ion-selective electrodes (SC-ISEs) in pharmaceuticals and biomedical applications, based on our current knowledge. Therefore, this review article aims to fill this gap by focusing on advancements made in the past six years in the detection capabilities of SC-ISEs within pharmaceuticals. This review article provides an overview of the traditional and modified various types of SC-ISC viz carbonaceous, metal/metal oxide, composite based, and polymer-based ISE used for pharmaceutical analysis with their detection limit, stability, recovery, and target matrix sensing. Introduction of new materials viz. MXene and other polymeric materials give new dimensions in the future to enhance the selectivity and sensitivity of ISEs. Sensors developed with ISE have extraordinary potential to reduce the LOD of different surface modifications down to the pM level. They have the ability to perform analyses directly on the sample without requiring pretreatment in diagnostic laboratories. The intent is to provide an up-to-date and thorough overview of the progress made in the development of these electrodes, enhancing performance and accessibility in this specific area of research. [ABSTRACT FROM AUTHOR]

p -Phenylenediamine (p -PDA) is a common ingredient in hair dyes, cosmetics and herbal products. The current study used graphene nanoparticles and phosphotungstic acid in a quality-by-design approach to develop and optimize a carbon-paste sensor for p -PDA. Twenty-three sensors with different compositions were tested, and the results were computationally analyzed to generate prediction models. The optimized sensor consisted of graphite, graphene, o-nitrophenyloctylether, and phosphotungstic acid in a 62.83: 4.01: 27.1: 5.34 (wt %) ratio. The optimized sensor displayed a Nernstian slope of 29.1±0.22 mV decade−1, a detection limit of 1.0×10−7 mol L−1, thermal and pH stabilities and a fast equilibration time of 10 s over ten weeks. The sensor accurately measured p -PDA concentrations within a wide linear range (1.0×10−7–1.0×10−3 mol L−1) with high sensitivity and selectivity (even over its isomers o - and m -phenylenediamine). The developed electrochemical method outperformed the commonly used high performance liquid chromatography methods in simplicity, speed, cost-effectiveness, linear range width and enabled real-time detection. The sensor's microstructure, morphology, and particle size were examined using the scanning electron microscope and energy-dispersive X-ray analysis. Spiked samples (3.60×10−3–10.8 % w/w) were analyzed for p -PDA content, including tea, henna, synthetic dye, black pepper, and cosmetics. The work provides quality control laboratories with a validated, fast, and reliable tool to support data-based decisions that can have important implications for health and safety. [ABSTRACT FROM AUTHOR]

Porous Germanium (PGe) has emerged as a promising material for applications such as substrate engineering, sensing, and energy storage, thanks to its uniquely versatile and tunable properties. The bipolar electrochemical etching (BEE) method is widely regarded as the go-to approach for producing high-quality PGe layers. However, the lack of profound understanding of BEE process limits its use to a few well-studied morphological structures, hindering the development of more complex multi-layered structures with variable morphologies. In this work, we introduce potentiometric measures of the system as a means of monitoring the BEE process. We establish a correlation between the potential response and the reactions occurring during the BEE process, as well as their evolution over time. This approach enables elucidating the importance of the passivation, and how to shape the double-layered PGe structures. These findings bring new opportunities for controllable BEE with process monitoring and fabrication of tunable PGe multilayers for advanced applications. [ABSTRACT FROM AUTHOR]

Abstract Surface functionalization of two-dimensional (2D) WO 3 nanofilms by noble metal (NM) nanoparticles (NM = Ag, Pt and Pd) was successfully achieved for the first time via combination of the atomic layer deposition (ALD) process and electrochemical deposition method. Deposited NM nanoparticles were uniformly in the particle size and homogeneously dispersed on the surface of 2D WO 3. They represented electrochemically active metal-semiconductor hybrid nanocomposites with the larger electroactive area, and consequently, substantially enhanced the electrochemical H 2 O 2 detection of the device based on functionalized 2D WO 3 nanofilms. Functionalization by Ag was found to be more efficient compared to the same functionalization by Pt and Pd nanoparticles. Particularly, Ag 200 -WO 3 nanofilms exhibited the best electrochemical performance with a high sensitivity of 282 μA mM cm−2, extremely wide linear H 2 O 2 concentrations range from 0.2 μM to 33.6 mM, a low detection limit of 0.1 μM, fast response time of 2 s and an excellent selectivity and long-term stability. Surface functionalization by NM nanoparticles approach has clearly demonstrated the great potential in the development of hybrid nanostructured electrode for various devices with enhanced electrochemical capabilities. Graphical abstract Image 1 Highlights • Wafer-scale 2D WO 3 were ALD-developed with following functionalization by NM nanoparticles. • Surface functionalization of 2D WO 3 by NM nanoparticles is done by electrochemical deposition method. • Ag amount was optimized at electrochemical deposition time of 200 s. • High sensitivity of 282 μA mM cm−2 towards H 2 O 2 detection was achieved by Ag 200 -WO 3 nanofilms. • A wide liner concentrations range of 0.2 μM–33.6 mM with low detection limit of 0.1 μM was also obtained. [ABSTRACT FROM AUTHOR]

Abstract An ex-situ potentiometric titrations were normally performed using an oxidation/reduction potential (ORP) electrode to monitor the electrochemically generated active electron mediators, either oxidants or reductants, in a mediator generation plant. In the present investigation, an attempt was made to monitor electron mediator [Ni1+(CN) 4 ]3- (Ni(I)) in-situ in a high electrolyte concentration (9 M KOH) during its electrochemical generation. A ring type flow cell developed using a 0.6 cm diameter electrode was tested on a standard redox couple of [Fe3+(CN) 6 ]3- (Fe(III))/[Fe2+(CN) 6 ]4- (Fe(II)) at different ratios during solution flow. The found results suggested that direct determination of an electrochemically prepared electron mediator is possible using a potentiometric method. A periodical potential change in the in-situ linear sweep voltammetry of electrogenerated Ni(I) during its electrochemical generation allowed the direct determination of electrogenerated Ni(I) by the ring type flow cell. A calibration plot derived from chemically synthesized Ni(I) using an ex-situ potentiometric titration or UV–visible spectra was used to monitor electrogenerated Ni(I) by the in-situ method. The electrochemically generated Ni(I) concentration detected in the 0–4.5 mmol/L region that followed non-Nernstian behavior. A change in the Ni(I) concentration during N 2 O removal at the scrubber column suggesting that air pollutant removal can be monitored using the in-situ flow sensor cell, once how many electron involved in the removal process. Highlights • Established a macro flow sensor for in-situ monitoring low valent metal ions during its electrogeneration. • Periodical limiting peak potential change during electrolysis favors to sense Ni(I). • A 0–5 mm Ni(I) range derived with a slope of non-Nernstian behavior. • A defined Ni(I) concentration change when N 2 O removal correlates automation is possible by in-situ sensor. [ABSTRACT FROM AUTHOR]

A new all-solid-state PVC membrane nitrate electrode was developed and nitrate ions were potentiometrically analyzed. Silver (I) bisdiethyldithiocarbamate ((C 2 H 5) 2 NCS 2) 2 Ag+) (Ag(dtc) 2) compound was used as electroactive positive charged carrier (ionophore) in the plasticized PVC membrane structure of the developed electrode. The developed nitrate selective polymeric membrane electrode (nitrate-ISE) exhibited linear potentiometric behavior in the concentration range of nitrate ions from 1.0 × 10−1 to 1.0 × 10−5 mol L−1 and the detection limit was determined as 6.71 × 10−6 mol L−1. Although nitrate-ISE has good reproducibility, the pH working range is determined to be 4 – 9. The proposed nitrate-ISE has been successfully applied for the determination of nitrate ions in different water samples and fruit juices. [ABSTRACT FROM AUTHOR]

A novel method of quantitative optical readout of potentiometric responses of ion-selective electrodes is proposed. This idea was realized in a simple self-powered bipolar electrode system, with an ion-selective pole directly connected with the second pole, where a fluorimetric signal is generated. In this way, space and time separated optical readout and sampling can be achieved. This concept was tested on a model example of a system containing potassium-selective electrode (ISE-K) with polypyrrole solid contact, connected to a zinc wire immersed in the solution. In this arrangement increase of potassium ions activity in the solution results in change of the membrane potential of ISE-K, inducing reduction of polypyrrole solid contact and corresponding oxidation of the other component - zinc. Increase of zinc ions concentration is read as increase of emission intensity. Thus, this simple system allows quantitative in situ potassium ions determination, with the fluorescence intensity being a linear function of logarithm of analyte activity in solution in turn-on mode. Moreover, due to simplicity of the system and presence of reactants in the solution phase, a quantitative correlation between electrochemical and optical behaviour was confirmed and indications for the system optimization could be proposed. [ABSTRACT FROM AUTHOR]

Design of sensors with improved parameters is still an extensive field of analytical research. A comparative study between seven types of all-solid-state ion-selective electrodes (ASS-ISEs) and coated disc ion-selective electrode (CD-ISE) was carried out. This work developed solid contact layers designed from molecular organic materials (MOMs): tetrathiafulvalene (TTF), its chloride salt (TTFCl) or tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) with or without the addition of carbon black (CB) acting as inner transducers. Intermediate layers were deposited by a solution casting on the top of glassy carbon disc electrodes and then were covered with a membrane containing tridodecylmethylammonium chloride, o-nitrophenyl octyl ether, and poly(vinyl chloride). Molecular organic conductive materials were compared with CB-MOM composites as materials responsible for transduction process in all-solid-state chloride-selective electrodes. The proposed solid contact layers were characterized by scanning electron microscopy and electrochemical methods. The intermediate layer effect on the electrodes was tested, and prepared sensors were investigated by potentiometric, chronopotentiometric and electrochemical impedance spectroscopy measurements. All the modified electrodes displayed a satisfactory performance and Nernstian electrode function for chloride in the concentration range from 10 −5  M to 10 −1  M, however the best sensitivity and detection limit were observed for the CB-TTFCl-contacted electrode. The obtained results showed that the electrodes with internal layer consisting of CB-MOM nanocomposite presented slightly more sensitive response to chloride, lower impedance and a higher capacitance than electrodes based only on various molecular organic materials. [ABSTRACT FROM AUTHOR]

In this paper, the thermodynamic activity of two lanthanide chlorides (CeCl 3 and NdCl 3 ) in molten LiCl-KCl eutectic salt measured using open circuit potentiometry has been reported. Activity coefficient of CeCl 3 was found to be strongly dependent on the concentration of CeCl 3 in a concentration window of up to 4.66 mol % CeCl 3 . The activity coefficient of NdCl 3 could not be measured due to the uncertainty in NdCl 3/ NdCl 2 molar ratio in the salt, however the thermodynamic activity was measured relative to a 5 mol% Ag∣AgCl reference electrode. The concurrent analysis of data presented in this paper along with previously published activity data for LaCl 3 and GdCl 3 demonstrates that the departure from ideal solution behavior shown by the rare earths chlorides correlates with ionic size of underlying rare earth element. The smaller the ionic size of the species under consideration, the greater its departure from ideal solution behavior. Further, using the activity data of all four rare earth chlorides, an ionic size dependent correlation was developed. Using this empirical correlation, it is possible to calculate the activity of all species from La(Z = 57) to Gd (Z = 64) for a concentration of up to 2.5 mol% rare earth chloride in LiCl-KCl molten salt at 773 K. [ABSTRACT FROM AUTHOR]

In this work, the influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb 2+ -selective electrode (Pb 2+ -ISE) was studied. The effects of bovine serum albumin (BSA) adsorption at the surface of the ion-selective membrane combined with electrode conditioning in phosphate-buffered saline (PBS) solution was elucidated by potentiometry and electrochemical impedance spectroscopy. The adsorbed BSA at the surface of the Pb 2+ -ISE slightly lowered the detection limit but did not influence the selectivity of the Pb 2+ -ISE towards the interfering ions studied (Cu 2+ , Cd 2+ ). Conditioning of the Pb 2+ -ISE in 0.01 mol dm –3 PBS resulted in a super-Nernstian response which was related to fixation/extraction of Pb 2+ in the ion-selective membrane via precipitation of Pb 3 (PO 4 ) 2 by PO 4 3– anions present in PBS. By conditioning of the Pb 2+ -ISE in 0.01 mol dm –3 PBS + 1 mg/ml BSA it was possible to extend the linear response range of the Pb 2+ -ISE towards lower analyte concentrations. The utilization of this conditioning procedure was validated by determination of Pb 2+ concentrations down to ca 20 ppb in aqueous samples by Pb 2+ -ISEs and by comparing the results with those obtained by ICP-MS. [ABSTRACT FROM AUTHOR]

A light-addressable potentiometric sensor (LAPS) is a field-effect-based potentiometric sensor with an electrolyte/insulator/semiconductor (EIS) structure, which is able to monitor analyte concentrations of (bio-)chemical species in aqueous solutions in a spatially resolved way. Therefore, it is also an appropriate tool to record 2D-chemical images of concentration variations on the sensor surface. In the present work, two differential, LAPS-based measurement principles are introduced to determine the metabolic activity of Escherichia coli ( E. coli ) K12 and Chinese hamster ovary (CHO) cells as test microorganisms. Hereby, we focus on i) the determination of the extracellular acidification rate (ΔpH/min) after adding glucose solutions to the cell suspensions; and ii) recording the amplitude increase of the photocurrent (I ph ) related to the produced acids from E. coli K12 bacteria and CHO cells on the sensor surface by 2D-chemical imaging. For this purpose, 3D-printed multi-chamber structures were developed and mounted on the planar sensor-chip surface to define four independent compartments, enabling differential measurements with varying cell concentrations. The differential concept allows eliminating unwanted drift effects and, with the four-chamber structures, measurements on the different cell concentrations were performed simultaneously, thus reducing also the overall measuring time. [ABSTRACT FROM AUTHOR]

The robustness of nanostructured electrocatalysts is crucial for long-term highly sensitive glucose detection, but most of the current reports mainly focus on the amelioration of activity and conductivity. Herein, we designed a triple-shelled hollow architecture by decorating the Ni(OH) 2 nanocages with internal and external CuS "armors" (CuS@Ni(OH) 2 @CuS), aiming at boosting both electrocatalytic activity and the robustness of hollow nano-electrocatalysts. The fabrication process involves sulfidation, coordinated etching and precipitation, and template ion reutilization, which interact to give the designed catalyst a high degree of structural integrity. In this novel nano-system, the inner CuS composed of nanoparticles and the external CuS with nanoflake-like shape favored the support effect and intensified charge transfer/glucose adsorption, respectively, and provided a cooperative protection for Ni(OH) 2 layer to maintain high activity and long-term glucose monitoring. Theoretical calculations further confirmed that CuS significantly promoted conductivity and glucose adsorption ability of the electrocatalyst. These advantages ensured that the proposed sensor can monitor glucose over time (60 days) combined with sensitivity up to 3128.1 μA mM–1 cm–2, wide linear range (0.001–7.6 mM), low detection limit (0.08 μM), and extremely short response time (0.75 s). Overall, this hierarchical electrocatalyst will stimulate more studies for the durability of electrochemical sensors. [ABSTRACT FROM AUTHOR]

Screening highly selective ionophores from a large amount of ionophores is the principle and most realizable method to discover new ionophores used in ion-selective electrodes (ISEs). In this paper a screening method is described for ionophore-based polymeric membrane heavy metal ion-selective electrodes (IBPMHM ISEs) to determine heavy metal ions (Cu 2+ , Pb 2+ , Zn 2+ , Cd 2+ , Hg 2+ and Ag + ). The protocol uses the averaged negative logarithmic potential selectivity coefficients ( p K 5 ¯ ) of five major interfering ions as screening parameters. The specified five major interfering ion group (Group A) can enhance the screening ability of the parameter p K 5 ¯ . The molecular categories of preferred ionophores ( p K 5 ¯ >2.00) for these ISEs were as follows: Schiff bases for Cu 2+ -ISE; Schiff bases and macrocycles for Zn 2+ -ISE; calixarenes, crown ethers and macrocycles for Ag + -ISE; calixarenes, Schiff bases and crown ethers for Pb 2+ -ISE, and another group for both Cd 2+ - and Hg 2+ -ISEs. Strong interaction between the donor atoms of ionophores and the heavy metal ions follows the hard soft acids and bases rule (HSAB). This approach efficiently screens the best ionophores for these IBPMHM ISEs, and provides a new route to explore new ionophores for other ionophore-based ISEs and potentiometric sensors. [ABSTRACT FROM AUTHOR]

Electrochemical sensors and supercapacitors are two noteworthy applications of electrochemistry. Herein, we report the synthesis of SnFe 2 O 4 microcubes and Fe 2 O 3 nanorods through a facile microwave assisted technique which are employed in fabricating the electrodes for nonenzymatic hydrogen peroxide (H 2 O 2 ) sensor and supercapacitor applications. SnFe 2 O 4 microcubes exhibited an enhanced specific capacitance of 172 Fg −1 at a scan rate of 5 mVs −1 in comparison to Fe 2 O 3 nanorods (70 Fg −1 ). Furthermore, the H 2 O 2 sensing performance of the fabricated SnFe 2 O 4 electrodes through chronopotentiometry studies in 0.1 M PBS solution (at pH 7) with a wide linear range revealed a good sensitivity of 2.7 mV μM −1 μg −1 with a lowest detection limit of 41 nM at a signal-to-noise ratio of 3. These results indicate that SnFe 2 O 4 microcubes are excellent materials for the cost effective design and development of efficient supercapacitors as well as nonenzymatic sensors. [ABSTRACT FROM AUTHOR]

The solution resistivity ( R sol ) and ohmic drop (Δ E Ω ) of a three electrode high temperature electrochemical autoclave system containing a water + 11550 ppb NH 4 OH (pH (25 °C) 10) solution were analyzed in the temperature range of 25 °C to 285 °C using electrochemical impedance spectroscopy (EIS) and galvanostatic potentiometry combined with automatic current interrupt iR compensation technique. The determined values were compared with the conductivity values calculated by a pH & Conductivity Calculator software. The results showed that when the temperature of the solution is increased the magnitude of the R sol and therefore ohmic drop of the system decrease and after a defined temperature (150 °C for EIS and 180 °C for current interrupt) increase. The variations in the conductivity of the solution versus temperature calculated by the pH & Conductivity Calculator software were in more agreement with the impedance based R sol values determined in this study. While investigation of the oxygen reduction reaction on platinum versus temperature showed that exactly at 180 °C (the temperature corresponding to minimum R sol and ohmic drop values determined using the current interrupt technique) the oxygen reduction reaction reached its maximum rate and by further increasing the temperature the oxygen reduction rate decreased and the reaction mechanism switched from a mixed mass–charge transfer controlled process to a charge transfer controlled process. The experiment results revealed that the R sol values determined by the current interrupt technique are more accurate than the values obtained by EIS. [ABSTRACT FROM AUTHOR]

The impact of the aqueous electrolyte co-extraction to the potentiometric response of ionophore-based ion-selective electrodes (ISEs) is studied theoretically and experimentally. A simple theoretical model is developed to describe quantitatively how co-extraction of electrolytes influences the lower and the upper detection limits of ISEs. The theory is successfully verified with valinomycin-based K + -ISE as a model system, using potentiometric, chronopotentiometric, impedance and UV–vis measurements. A special (symmetric) setup of the galvanic cell is proposed which clearly demonstrates how co-extraction from the internal solution determines the lower detection limit of ISEs. The values of the partition coefficients of potassium salts used in the study are consistent with the respective Gibbs energies of anion transfer from water to organic phase. The model also gives a hint why the slope of real ISEs is typically slightly sub-Nernstian. [ABSTRACT FROM AUTHOR]

Polyelectrolyte microcapsules have attracted great interest in drug delivery applications, and microcapsules modified with gold nanoparticles have been used in this way with triggered release when a laser can be used to remotely open shells through light-induced local heating. The electrical impedance of unmodified microcapsules has been studied due to its implications for their permeability, however, the impedance of functionalised microcapsules has not yet been investigated. Herein, the impedance of microcapsules modified with gold nanoparticles was studied for the first time. It was shown that the modification of microcapsules with gold nanoparticles leads to a much greater impedance than would be expected from the increase in the thickness caused by the presence of a layer of gold nanoparticles alone. The impedance of gold nanoparticle modified capsules was measured using scanning photo-induced impedance microscopy (SPIM), which is based on photocurrent measurements at an electrolyte-insulator-semiconductor (EIS) field-effect structure. High resolution and good sensitivity were achieved using a two-photon effect for charge carrier excitation and organic monolayer modified silicon-on-sapphire (SOS) as the SPIM substrate. SPIM allowed impedance imaging of collapsed microcapsules with unprecedented detail. SPIM images of capsules labelled with gold nanoparticles (AuNPs) showed a good agreement with the corresponding optical images, including the creases resulting from the collapse of the hollow shells. The significant increase in impedance caused by the impregnation with AuNPs was also verified by conductive Atomic Force Microscopy (C-AFM) measurements in the dry state. [ABSTRACT FROM AUTHOR]

In this work, the development of a novel enantioselective sensor is described using chiral imprinted nanoparticles as recognition elements. Imprinted nanoparticles, synthesised via precipitation polymerisation, were incorporated in a polyvinyl chloride membrane which served as the sensing element to construct a potentiometric sensor selective to the S enantiomer of the antidepressant drug citalopram (SCIT). The effect of the amount of nanoparticles, the type and quantity of plasticiser and the concentration of the internal reference solution were assessed in order to have a sensor with best sensor performance. The fabricated sensor showed Nernstian behaviour with a slope of 50.77 ± 1.32 mV decade −1 in SCIT + solutions that ranged from 2.5 × 10 −7 to 10 −3 mol L −1 . Sensor applicability to urine samples was also tested using spiked urine samples as quality control samples as well as urine collected from a volunteer who had been treated with this drug. The fabricated sensor was capable of accurately determining SCIT + with good precision (RSD 2.07–6.56%) at different concentration levels. [ABSTRACT FROM AUTHOR]

In this communication we report about an outstanding solid-state pH sensor based on amorphous nanocolumnar porous thin film electrodes. Transparent WO 3 thin films were deposited by reactive magnetron sputtering in an oblique angle configuration to enhance their porosity onto indium tin oxide (ITO) and screen printed electrodes (SPE). The potentiometric pH response of the nanoporous WO 3 -modified ITO electrode revealed a quasi-Nernstian behaviour, i.e. a linear working range from pH 1 to 12 with a slope of about −57.7 mV/pH. pH detection with this electrode was quite reproducible, displayed excellent anti-interference properties and a high stable response that remained unaltered over at least 3 months. Finally, a pH sensor was developed using nanoporous WO 3 -modified screen printed electrode (SPE) using a polypyrrole-modified Ag/AgCl electrode as internal reference electrode. This full solid state pH sensor presented a Nernstian behaviour with a slope of about −59 mV/pH and offered important analytical and operation advantages for decentralized pH measurements in different applications. [ABSTRACT FROM AUTHOR]

The time-resolved potentiometry on dual interface of two immiscible electrolyte solutions (dual ITIES) combines redox- and phase transfer-driven potential response into a single protocol, which gains a compound-specific‚ finger-print’ character: The potential transient envelope was found to show pattern specific to molecules/ions appearing at the interface. The model system is represented by water/ o –dichlorobenzene/water dual interface with aqueous stationary (reference) and mobile (sample-carrying) phase with ternary amine salt as a phase transfer agent and alternatively, phthalocyanine-based redox mediator is added to o-dichlorobenzene phase. This potentiometric system shows biomimetic features with the selectivity simply modifiable just by varying composition of liquid phase. The transient potential response was found to correlate specifically with particular composition of sample brought by mobile phase and allows recognizing redox compounds, pH and different ions without a need of specific ion selective electrode. [ABSTRACT FROM AUTHOR]

The ionophore (salph)Co(III)OAc is used here for the first time as a recognition molecule for nitrite in lipophilic membranes. The nature of the recognition process is evaluated by UV-Vis, ATR-IR and potentiometry, while the purity of the compound is confirmed by LC-MS and cyclic voltammetry. Experimental evidence suggests a replacement of the acetate ligand by nitrite. The formation constant between (salph)Co(III)OAc and NO 2 − , β∼10 8 , is estimated potentiometrically with the sandwich membrane method. The analytical parameters, LOD∼3 μM, linear range of four orders of magnitude, stability over four days, and the selectivity over chloride (log K NO2,Cl POT ∼-4.1) are similar to previous ionophores for the same ion. Undiluted urine samples were spiked with incremental concentrations of nitrite to characterize the matrix effect. Beyond the observed analytical performance, we aim here to offer a rational study to understand an unconventional charged ionophore recognition process. [ABSTRACT FROM AUTHOR]

Typical ion-selective electrodes (ISEs) used in potentiometric mode suffer from low sensitivity, determined by Nernst (Nikolsky-Eisenman) equation. This limits resolution of potentiometric analysis, ultimately leading to significant problems in determination of relatively small changes of analyte ions concentration. A novel method was proposed using a 'reversed' amperometric setup with Ag|AgCl electrode as the working electrode and an ion-selective electrode as the reference one. Advantageously, the proposed approach does not require addition of other chemicals to the sample. A change of primary ions concentration results in change of the potential of the ISE used as the reference electrode and thus in the same change of Ag|AgCl electrode potential in amperometric (potentiostatic) mode. Due to high slope of the current vs. potential dependence for silver / silver chloride electrode small changes of ISE potential will result in significant changes of the recorded current, leading to high amplification of the analytical signal towards primary ions of the ISE. Additional unique advantage of herein proposed approach is a linear dependence of the current on analyte concentration, as tested on model examples of potassium- and calcium-selective ISEs. [Display omitted] [ABSTRACT FROM AUTHOR]

One long term goal for biosensor development is towards implantable, long–term sensing for diagnostics, and monitoring of chronic health. The most common electrochemical sensors employ amperometric principles, although there is a fundamental challenge when trying to minimize the sensor size since the measurement current is directly proportional to the size of the working electrode. An alternative principle to amperometry for enzyme sensor is potentiometry, measuring open circuit potential (OCP). In this study, we demonstrate the size independency of an OCP based enzyme sensor focusing on direct electron transfer (DET) type– and quasi–DET–type oxidoreductases for, glucose and L–lactate, respectively. For glucose detection, we employed DET type flavin adenine dinucleotide glucose dehydrogenase, and the engineered L–lactate oxidase derived from Aerococcus viridans (AvLOx) conjugated with amine–reactive phenazine ethosulfate (arPES) was used as the quasi–DET type enzyme for the L–lactate detection. First, both enzymes were immobilized on 3 mm diameter gold disc electrode (GDE), and glucose and L–lactate were monitored based on OCP and transient potentiometric measurement, dOCP/dt. Then, L–lactate and glucose sensors were constructed using 10 µm GDEs, showing L–lactate and glucose concentration dependent OCP and dOCP/dt changes. The sensitivity was nearly equivalent for ΔOCP and dOCP/dt between the sensor using 3 mm and 10 µm GDE even though amperometric signal was entirely lost when measuring the arPES modified AvLOx on the 10 µm electrode. These results clearly demonstrate the size independency of an OCP based enzyme sensor which will be applied for the implantable and continuous monitoring system for metabolites in vivo. [ABSTRACT FROM AUTHOR]

We report on a small and simple graphene-based potentiometric sensor for the measurement of intracellular glucose concentration. A fine borosilicate glass capillary coated with graphene and subsequently immobilized with glucose oxidase (GOD) enzyme is inserted into the intracellular environment of a single human cell. The functional groups on the edge plane of graphene assist the attachment with the free amine terminals of GOD enzyme, resulting in a better immobilization. The sensor exhibits a glucose-dependent electrochemical potential against an Ag/AgCl reference microelectrode which is linear across the whole concentration range of interest (10 – 1000 μM). Glucose concentration in human fat cell measured by our graphene-based sensor is in good agreement with nuclear magnetic resonance (NMR) spectroscopy. [ABSTRACT FROM AUTHOR]

This paper describes the development of a selective lithium ion sensor based on spinel-type manganese oxide doped with gallium and anions (Ga 0.02 Mn 1.98 O 3.98 X 0.02 , where X = S 2− and F − ). Investigation was made of the influence of cationic and/or anionic doping agents on the potentiometric response of the sensor. Experimental parameters evaluated included the effect of the lithium concentration on activation of the sensor by cyclic voltammetry, the pH of the electrolyte solution, and the selectivity towards Li + compared to other alkali and alkaline-earth metal ions. There was an important influence of the unit cell size of the material on the linear range, detection limit, and selectivity of the sensor. Reduction in the size of the tunnel for insertion of the lithium in the porous structure of the oxide directly affected the potentiometric performance of the electrode. Sensor performance increased in the order: Ga 0.02 Mn 1.98 O 4 > Ga 0.02 Mn 1.98 O 3.98 S 0.02 > Ga 0.02 Mn 1.98 O 3.98 F 0.02 . The observed super-Nernstian response could be explained by a mixed potential arising from two equilibria (redox and ion exchange) in the spinel-type manganese oxide. Sensitivity and the influence of pH on the electrode response were directly related to the doping agents present in the oxide structure. [ABSTRACT FROM AUTHOR]

Earlier it was shown that surface-attached bovine serum albumin undergoes ionic strength-induced structural transition at mercury electrodes. Using constant current chronopotentiometric stripping (CPS) here we show that this electric field-driven transition is influenced also by other factors, such as temperature, current density, and particularly by the time of surface-attached protein exposure to the negative potentials. For example, 1 s exposure to –1.6 V (against Ag/AgCl/3 M KCl) results in the protein denaturation. Exposures longer than 1 s resulted in protein denaturation even at less negative potentials. On the other hand, in CPS much shorter exposure times can be used. Exposing the surface-attached protein to negative potentials for ms time intervals the protein stability can be tested at different current densities. We investigated several proteins such as bovine and human serum albumins, ovalbumin, α-macroglobulin and α-synuclein, which showed various profiles in dependence on different parameters, including time of the protein exposure to negative potentials, ionic strengths and temperature. We believe that using this approach, new methods for testing surface-attached protein stabilities in relation to the electric field effects and to other factors can be developed. [ABSTRACT FROM AUTHOR]

Highly selective and unprecedented 4-aminoquinoline-β-lactam (AQL) based electrochemical (voltammetric & potentiometric) sensors for the selective recognition of Zn (II) ions have been developed. Preliminary, the complexation behavior of AQL towards various metal ions was investigated by employing the UV-visible and fluorescence techniques. The voltammetry of AQL exhibits two anodic peaks at 0.85 V and 1.25 V which get shifted toward more positive potential (anodic shift) on addition of Zn (II) ions in the potential range of 0.40 V to 1.60 V vs Ag/Ag+ due to formation of AQL-Zn (II) complex. Voltammetric sensor exhibited linear response in the wide concentration range of 5.0 × 10 −5 to 6.0 × 10 −4 M with detection limit of 2.5 × 10 −6 M. Potentiometrically, the polyvinyl chloride based solid contact coated graphite electrode (CGE-1) showed the Nernstian slope of 28.9 mVdecade −1 in concentration range of 1.0 × 10 −1 to 1.0 × 10 −7 M with detection limit of 8.26 × 10 −8 M. The high binding constant and negative value of free energy calculated by using the Benesi-Hildebrand equation confirmed the formation of AQL-Zn (II) complex and further validated via 1 H-NMR and mass spectrometry. The developed electrochemical sensors exhibited high selectivity and reproducibility toward Zn (II) ions. The analytical utilities of proposed sensors were confirmed by the quantification of Zn (II) content in various sample matrices. [ABSTRACT FROM AUTHOR]

CO-sensing properties of potentiometric gas sensors using an anion-conducting polymer (ACP) as an electrolyte and metal oxides loaded with and without Au as electrodes (EC(MO) or EC( n Au/MO( T m)), respectively, MO: metal oxide (In 2 O 3 , ZnO or Co 3 O 4 ), n : the loading amount of Au, 0.5∼2.0 wt%, T : heat-treatment temperature, m: heat-treatment atmosphere, air or H 2 ) have been investigated in wet synthetic air (57%RH) at 30 °C. In addition, H 2 -sensing properties of these sensors have also been investigated in the same gaseous conditions, to evaluate their CO selectivity against H 2 . All of the EC(MO) sensors showed relatively small changes in electromotive force (EMF), i.e. responses, to both CO and H 2 , but the Au loading to In 2 O 3 and ZnO drastically improved the magnitude of CO response of the EC(In 2 O 3 ) and EC(ZnO) sensors, respectively. The EC( 2.0 Au/In 2 O 3 ( 400 air)) sensor showed larger CO response, faster CO response speed, excellent CO selectivity against H 2 and better long-term stability than those of the EC( 2.0 Au/ZnO( 400 air)) sensor. The influence of moisture on the CO response of the EC( 2.0 Au/In 2 O 3 ( 400 air)) sensor was almost negligible in the humidity range of 40∼100%RH. The magnitude of CO response of the EC( 2.0 Au/In 2 O 3 ( 400 air)) sensor in wet synthetic air showed a good linear relationship with CO concentration, but the CO response was largely affected by the concentration of O 2 . These results indicate that the EMF of the EC( 2.0 Au/In 2 O 3 ( 400 air)) sensor is probably determined by the mixed potential resulting from CO oxidation and O 2 reduction. The heat-treatment conditions of the 2.0 wt% Au-loaded In 2 O 3 powder largely affected the CO-sensing properties of the EC( 2.0 Au/In 2 O 3 ( T m)) sensors. Among these sensors heat-treated in various conditions, the as-fabricated EC( 2.0 Au/In 2 O 3 ( 250 H 2 )) sensor showed the most excellent CO selectivity against H 2 in their concentration range of 10∼3000 ppm. [ABSTRACT FROM AUTHOR]

We have developed a highly sensitive and selective potentiometric PVC-membrane sensor for lead (II) cation. A glassy carbon electrode (GCE) was modified with synthesized 1,2-Bis(N’-benzoylthioureido) benzene (BBTB) as an ionophore and reduced graphene oxide (RGO), and this material was characterized by scanning electron microscopy. The sensor shows sensitive and highly selective response to Pb(II) ion with a linear range from 6.31 × 10 −8 to 3.98 × 10 −2 M, Nernstian slope of 30.37 ± 0.62 mV per decade and a detection limit of 2.51 × 10 −8 M. The proposed sensor could be used in a pH range of 4.0–8.0. Selectivity coefficients were determined for known common cations by applying the match potential method (MPM). The sensor was successfully applied to monitor Pb(II) in raw milk and in potentiometric titration of Pb 2+ ions. The structure of BBTB ligand and its complexation with some common cations were investigated by using quantum mechanical DFT calculations. Lead (II) cation showed prominent affinity to the BBTB carrier. [ABSTRACT FROM AUTHOR]

Coordination between copper ions of varied valence, Cu 2+ and Cu + , with glycine (Gly) was investigated by an electrochemistry method named zero current potentiometry. The copper wire (CW), connected in series between two clips of working and counter electrodes of a potentiostat, and a reference electrode were immersed into buffer solution. By applying a specific linear sweep potential E app on CW according to the redox characteristic of Cu 2+ /Cu and Cu + /Cu couples, Cu + or Cu 2+ were selectively electro-generated on the CW surface. When Gly existed in buffer solution, Cu + or Cu 2+ bonded with Gly through coordination reaction, resulting in the changing of the interfacial potential at the corresponding interface. The changing of the interfacial potential was tracked by measuring zero current potential ( E zcp ) that corresponds to where circuit current I was equal to zero in the recorded I–E app curve. The thermodynamic constants of the complexation between Cu 2+ or Cu + with Gly were accordingly determined by the relationship of E zcp with Gly concentration. The results showed that Cu 2+ and Cu + were produced on the CW surface respectively by applying different range of the linear sweep potential on CW in buffer solution. With Gly concentration increasing, the recorded I–E app curves shifted negatively and zero current potential E zcp showed linear relationship with −log c (Gly) in both cases. The slopes were coincident with the corresponding theoretical values (0.030 for Cu 2+ -Gly reaction and 0.059 for Cu + -Gly reaction). Through their linearity relationships, the stability constants log β and binding ratios of complexes were calculated respectively. The obtained results showed that the proposed approach is not only simple and rapid, but also has advantages for studying the coordination equilibrium of metal ions with varied valences, especially the ions that are not stable in solution. [ABSTRACT FROM AUTHOR]

In order to image rapidly changing systems with the Scanning Electrochemical Microscope (SECM), high scan rate must be used, otherwise by the time the scan is completed, major changes in the studied system would have occured. But if the scan rate is too high, there is not enough time for the detector to reach equilibrium before the signal is recorded at a given data acquisition point, and the image will be distorted. This is a problem especially in potentiometric SECM, where the long response time of the potentiometric cell using ultramicro electrode probes imposes a limit on the maximum scan rate. In this paper we demonstrate for the first time that high scan rates combined with signal processing can be used in potentiometric SECM to keep scan time to a minimum, and still obtain high quality results by deconvoluting the raw, distorted image. A model system was studied with high scan rate, then the image was deconvoluted using the inverse of the potentiometric response function to calculate the equilibrium value for each data acquisition point from the respective observed values. [ABSTRACT FROM AUTHOR]

This work presents a novel surface Smart Polymer Antibody Material (SPAM) for Carnitine (CRT, a potential biomarker of ovarian cancer), tested for the first time as ionophore in potentiometric electrodes of unconventional configuration. The SPAM material consisted of a 3D polymeric network created by surface imprinting on graphene layers. The polymer was obtained by radical polymerization of (vinylbenzyl) trimethylammonium chloride and 4-styrenesulfonic acid (signaling the binding sites), and vinyl pivalate and ethylene glycol dimethacrylate (surroundings). Non-imprinted material (NIM) was prepared as control, by excluding the template from the procedure. These materials were then used to produce several plasticized PVC membranes, testing the relevance of including the SPAM as ionophore, and the need for a charged lipophilic additive. The membranes were casted over solid conductive supports of graphite or ITO/FTO. The effect of pH upon the potentiometric response was evaluated for different pHs (2-9) with different buffer compositions. Overall, the best performance was achieved for membranes with SPAM ionophore, having a cationic lipophilic additive and tested in HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer, pH 5.1. Better slopes were achieved when the membrane was casted on conductive glass (-57.4 mV/decade), while the best detection limits were obtained for graphite-based conductive supports (3.6 × 10 −5 mol/L). Good selectivity was observed against BSA, ascorbic acid, glucose, creatinine and urea, tested for concentrations up to their normal physiologic levels in urine. The application of the devices to the analysis of spiked samples showed recoveries ranging from 91% (± 6.8%) to 118% (± 11.2%). Overall, the combination of the SPAM sensory material with a suitable selective membrane composition and electrode design has lead to a promising tool for point-of-care applications. [ABSTRACT FROM AUTHOR]

Original assemblies were prepared for use as sensitive films of potentiometric enzyme urea sensors, and compared to identify the more efficient structure with respect to stability. These films included electrodeposited polyaniline, used as transducer, urease, used as catalyst, and biocompatible polyelectrolytes, used as a matrix to preserve the integrity of the enzyme in the sensitive film. Two kinds of assemblies were done: the first one consisted in the adsorption of urease onto a polyaniline film followed by the adsorption of a chitosan-carboxymethylpullulan multilayer film, while the second one consisted in the adsorption of a urease-chitosan multilayer film onto an electrodeposited polyaniline film. The morphological features and growth of these assemblies were characterized by scanning electron microscopy and quartz crystal microbalance, respectively. This allowed us to demonstrate that the assemblies are successfully formed onto the electrodes of the sensors. The potentiometric responses of both assemblies were then measured as a function of urea concentration using a home-made portable potentiostat. The electrochemical response of resulting sensors was fast and sensitive for both types of assemblies, but the stability in time was much better for the films obtained from alternative adsorption of urease and chitosan onto a layer of urease adsorbed over electrodeposited polyaniline. [ABSTRACT FROM AUTHOR]

The chromogenic, voltammetric and potentiometric sensors based upon the novel ferrocene appended chalcone (FAC) have been developed for the selective detection of Cu (II) ions. In UV/visible measurements, the addition of Cu (II) ion into the FAC resulted in the disappearance of low energy band associated with hypsochromic shift of 30 nm of the high energy band. This perturbation in the absorption spectrum is well appreciated by naked eye inspection. The chromogenic sensor exhibited the concentration range of 3.00 × 10 −5 to 3.50 × 10 −6 M with detection limit of 6.00 × 10 −7 M. The cyclic voltammetry (CV) of FAC showed a reversible redox couple (Fe 2+ /Fe 3+ ), when scanned in between the potential range of 0.4 V to -0.2 V vs . Ag/Ag + . The CV of FAC undergoes electrochemical changes due to the formation of FAC-Cu (II) complex on addition of Cu (II) ions. The voltammetric sensor can work within the concentration range of 5.00 × 10 −5 to 4.00 × 10 −4 M with detection limit of 2.00 × 10 −6 M. The potentiometric response of polyvinylchloride (PVC) based solid contact coated graphite electrode (CGE-1) was linear within the Cu (II) ions concentration range of 1.00 × 10 −1 to 5.00 × 10 −7 M and showed near Nernstian slope of 28.5 mV/decade with the detection limit of 1.78 × 10 −7 M. No significant interference was observed from other diverse metal ions. The analytical usefulness of proposed sensors has been validated further by estimating the Cu (II) ions in various sample matrices with excellent results. [ABSTRACT FROM AUTHOR]

This paper reports on the potentiometric response characteristics of gallium electrodes coated with native or anodic oxide layers in aqueous solutions. Solid metallic gallium electrodes were prepared by cooling liquid gallium monoliths supported either on planar silicon substrates or incorporated within glass capillaries. These metallic gallium electrodes showed potentiometric pH responses with a slope of ca . -38 mV/pH in the pH range between 3 and 9. The potentials measured could originate from redox processes involving surface oxide that was formed as a result of reactions between the metallic gallium and water (and/or OH − ), as observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Similar potentiometric measurements were examined for planar and capillary-incorporated gallium electrodes that were anodized in ice-cooled aqueous H 2 SO 4 at 10 V. Although the resulting nanoporous anodic oxide-coated electrodes did not initially show potentiometric pH responses, they exhibited pH responses with a smaller response slope ( ca . -30 mV/pH; pH 3∼9) after potentiometric measurements in a solution of pH ≤ 3. This observation could be explained by the acid-induced dissolution of an oxide-based barrier layer that passivated the underlying gallium electrode. This explanation was compatible with the observation of an additional gallium oxide layer over the nanoporous anodic oxide after the potentiometric pH measurements. Interestingly, in contrast to the metallic gallium electrodes, the anodic oxide-coated electrodes exhibited potentiometric Nernstian responses to SO 4 2− at ≥ 10 −4 M, reflecting the presence of sulfate doped into the oxide during the anodization. These results provide fundamental knowledge required to design miniaturized electroanalytical probes based on gallium electrodes. [ABSTRACT FROM AUTHOR]

The effective detection of phosphate ions is very important in the fields of chemistry, biology, medicine, environment and industry. At present, the detection of phosphate ion mainly depends on molybdenum blue colorimetry. Although this method is accurate, it needs sample pretreatment, complex operation and high cost. Therefore, it is urgent to design and develop a phosphate ion sensor with high efficiency, accuracy, simple operation and real-time on-line detection. In this study, a phosphate ion sensor was designed and developed by electrochemical modification based on nickel metal electrode. Nickel electrode was specifically modified to form a phosphate of Ni on the surface of Ni electrode. The phosphate ion response of Ni-PME(Nickel-phosphate modified electrode) was evaluated in a two-electrode system. The results show that under the condition of pH 4, Ni-PME can respond to phosphate ions with a concentration of 10−5 M to 0.1 M, the response slope is −81.0 mV dec−1, and the selectivity coefficients for common anions are below −2. The response time is less than 20 s. The stability of electrode potential is very high, and the fluctuation of 24-hour continuous test potential is within ± 3 mV. The lifetime is more than 4 weeks. Compared with the traditional molybdenum blue colorimetry, Ni-PME showed good accuracy and good recovery rate. [ABSTRACT FROM AUTHOR]

Pb 2+ -ISEs were used to demonstrate a new multicalibrational approach which gives comprehensive information about the response of a potentiomeric sensor. The method was used to study and optimize the non-equilibrium response of sensors, such as obtained with solid-contact ISEs used in time dependent conditioning procedure with recovery of the low detection limit at lowest analyte concentrations. The developed method allows better handling of non-equilibrium conditions in quantitative determinations of analytes. The multicalibrational approach with time optimization showed to be superior when compared to fixed measurement time approach using Pb 2+ -ISEs at non-equilibrium in the determination of lead(II) in environmental sample. [ABSTRACT FROM AUTHOR]

The change of entropy ΔS is a distinctive characteristic of the thermal behavior of a lithium-ion cell. Usually, the change of entropy ΔS in an individual cell type or electrode material is determined by potentiometric measurements which, although precise, are time-consuming. Measurement times could be shortened by as much as a factor of 100 by using the method presented in this paper; "electrothermal impedance spectroscopy" (ETIS). Herein, the effectiveness of ETIS is demonstrated for three different forms of commercial lithium-ion cells. Interestingly enough, ΔS of all three cell types show a hysteresis behavior for cell charging and discharging, as well-known for the open circuit voltage. Furthermore, as the ETIS method offers a high SOC-resolution of ΔS this could lead to its application in cell diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the preparation of a potentiometric strip for pH monitoring in saliva samples is reported. The potentiometric strip consists of a solid contact pH-selective and of a solid-contact ionogel reference electrode prepared on a dual screen printed substrate. The screen printing protocols, i.e., type of inks and number of deposits, were adjusted to relatively improve the batch reproducibility and the stability of the pH sensor. The pH of real saliva samples was monitored using the optimised potentiometric strip, and results were validated through parallel measurements with a standard laboratory method. [Copyright &y& Elsevier]

Abstract: This work shows that the synthesis of protein plastic antibodies tailored with selected charged monomers around the binding site enhances protein binding. These charged receptor sites are placed over a neutral polymeric matrix, thus inducing a suitable orientation the protein reception to its site. This is confirmed by preparing control materials with neutral monomers and also with non-imprinted template. This concept has been applied here to Prostate Specific Antigen (PSA), the protein of choice for screening prostate cancer throughout the population, with serum levels >10ng/mL pointing out a high probability of associated cancer. Protein Imprinted Materials with charged binding sites (C/PIM) have been produced by surface imprinting over graphene layers to which the protein was first covalently attached. Vinylbenzyl(trimethylammonium chloride) and vinyl benzoate were introduced as charged monomers labelling the binding site and were allowed to self-organize around the protein. The subsequent polymerization was made by radical polymerization of vinylbenzene. Neutral PIM (N/PIM) prepared without oriented charges and non imprinted materials (NIM) obtained without template were used as controls. These materials were used to develop simple and inexpensive potentiometric sensor for PSA. They were included as ionophores in plasticized PVC membranes, and tested over electrodes of solid or liquid conductive contacts, made of conductive carbon over a syringe or of inner reference solution over micropipette tips. The electrodes with charged monomers showed a more stable and sensitive response, with an average slope of -44.2mV/decade and a detection limit of 5.8×10−11 mol/L (2ng/mL). The corresponding non-imprinted sensors showed lower sensitivity, with average slopes of -24.8mV/decade. The best sensors were successfully applied to the analysis of serum, with recoveries ranging from 96.9 to 106.1% and relative errors of 6.8%. [Copyright &y& Elsevier]

Abstract: Twenty years has passed since the first discovery of microRNA (miRNA) lin-4 in Caenorhabditis elegans. Over the last decade, the study of miRNA biology has attracted tremendous attention. Increasing evidence has demonstrated that miRNA dysregulation could lead to a large number of genetic diseases and miRNA expressions are closely associated with the pathogenesis of most human malignancies. Recent studies have further suggested that miRNA expression profiles may serve as reliable biomarkers for cancer diagnosis, prognosis, and therapy. This provides powerful impetus and a growing demand for researchers to develop a simple analytical methodology which will allow an accurate, sensitive, selective, and cost effective miRNA analysis at point-of-care. In this regard, electrochemical methods offer many attractive characteristics and could play a leading role in future miRNA detection and quantification. This review revisits the discovery of miRNA, examines the possibility of miRNA biomarkers, discusses the conventional methods and emerging techniques for miRNA detection and quantification, and postulates future prospects in connection to electrochemical detection and quantification of miRNAs. It is hoped that this review will open new perspectives toward the development of new and novel electrochemical strategies for miRNA detection and quantification. [Copyright &y& Elsevier]

Abstract: The present review focuses on electrochemical methods for ascorbic acid assessment. The occurence, role, biological importance of vitamin C, as well as the non-electrochemical methods for its assessment are firstly reviewed. The electrochemical behavior of ascorbic acid is then illustrated, followed by a description of the potentiometric, voltammetric and amperometric methods for vitamin C content estimation in various media. Different methods for the development of electrochemical sensors are reviewed, from unmodified electrodes to different composites incorporating carbon nanotubes, ionic liquids or various mediators. From this perspective, the interaction between the functional groups of the sensor's material and the analyte molecule is discussed, as it is essential for the analytical characteristics obtained. The analytical performances of the potentiometric, voltammetric or amperometric chemical and biochemical sensors (linear range of analytical response, sensitivity, precision, stability, response time etc) are highlightened. The numerous applications of ascorbic acid electrochemical sensors in fields like food, pharmaceutical or clinical analysis, where vitamin C represents a key analyte, are also presented. [Copyright &y& Elsevier]

Highlight: [•] Highly ordered poly(aniline boronic acid) (PABA) nanotubes were firstly fabricated. [•] The synthesized polymer had a porous structure with small diameters and high surface. [•] The response of PABA nanotubes modified electrode to saccharide bonding was enhanced. [•] The nonenzymatic sensor showed high sensitivity and fast response. [Copyright &y& Elsevier]

Abstract: To obtain high quality images in scanning probe microscopy (SPM), a certain amount of scanning time is required, depending on the number of sampling points, and the scanning speed. Usually, there is a compromise between scanning speed and image quality. This is most critical in the potentiometric scanning electrochemical microscopy (SECM), which is severely limited by the relatively long response time of the ultramicro-electrode probes. That is, scanning speed can be increased only at the expense of image quality. In a great majority of the SECM studies, the subjects are circularly symmetric systems. In this paper, we present a method to increase SECM imaging speed of such systems, while improving image quality at the same time. It is achieved by using new, polar coordinate-based scanning patterns, exploiting the symmetry of the studied system, and using imaging time more economically. This technique, combined with our previously reported simplex algorithm for automatic target location, significantly improves the imaging of circularly symmetric targets. Numerical simulations and SECM scans using the traditional, and the new scanning algorithms have been performed. The resulting images have been compared with the expected, ideal image. [Copyright &y& Elsevier]

Abstract: Presented work proofs usability of polyaniline (PANI) as a receptor for potentiometric detection of salicylates. The potentiometric selectivity of PANI-coated membranes based on tridodecylmethylammonium chloride (TDDMACl) towards salicylate is at least as good as the selectivity of membranes based on “conventional” specific supramolecular receptor systems such as Sn(IV) and Al(III) phthalocyanates. X-ray diffraction (XRD) and electric impedance spectroscopy (EIS) techniques are used to insight into the phenomena leading to improvement of salicylate-selectivity of PANI. These studies reveal the relative role of sodium chloride during the PANI polymerization that leads to preparing of partially crystalline polymer and decreasing of the “bulk” resistance of membrane. The “bulk” resistance change is attributed to introduction of the electronic conductivity into the system PANI/Salicylate. Determination of acetylsalicylate in pharmaceutical preparations with recovery at about 98–100% is reported. Additionally, the ability to detect (0.11± 0.01)×10−3 M of salicylate present in a synthetic serum sample is demonstrated. [Copyright &y& Elsevier]

Abstract: In this work, two different redox-sensitive glass materials have been fabricated for the development of a production friendly redox electrode. The specific glass targets have been prepared by glass pouring process. The transducer structure is fabricated via conventional silicon-based semiconductor technology. The glass bulk material was deposited for the first time by means of pulsed laser deposition process into the thin-film state on the sensor structures. The fabricated sensors have been physically and electrochemically characterized by X-ray photoelectron spectroscopy, determination of expansion coefficient, impedance and potentiometric measurements. [Copyright &y& Elsevier]

Highlights: [•] A new concept in ion sensing was demonstrated using fluoride-effector bifunctional Na+ selective electrodes (Na-ISEs). [•] Potentiometric responses of Na-ISEs were found to depend largely on membrane resistances (R m ) varied with concentrations of fluoride ions. [•] A potentiometric sensor for sodium ion and an impedimetric sensor for fluoride ion can be fabricated. [Copyright &y& Elsevier]

Abstract: Dynamic electrochemistry of adsorbed proteins, often termed protein film electrochemistry (PFE), is widely used for the characterisation of redox proteins. The method provides a powerful alternative to spectroscopic studies that interrogate protein solutions. The reduction potential and electron stoichiometry of redox couples can be defined. The rates of catalytic redox transformations can also be quantified. Often it is considered that the behaviour of the adsorbed protein should match that displayed in solution studies if it is to be relevant to understanding the biological role of the protein. However, the environment of the protein in PFE is fundamentally different from that when it is freely diffusing in solution. As a consequence different behaviours may be expected. This raises the question, which approach is more relevant when aiming to provide insight into the cellular role of the protein? We consider this question here taking as an example the properties of a penta-heme cytochrome NrfB from Escherichia coli. The redox properties of NrfB containing solutions were presented previously (Clarke et al., Journal of Biological Chemistry (2004)). Here we present PFE of NrfB adsorbed on graphite and optically transparent mesoporous, nanocrystalline SnO2 electrodes. [Copyright &y& Elsevier]

Abstract: The electrochemical formation of Dy–Ni alloys was investigated in a molten NaCl–KCl–DyCl3 (0.50mol%) system at 973K. Cyclic voltammetry and open-circuit potentiometry at a Ni electrode indicated the formation of several Dy–Ni alloy phases. Alloy samples were prepared by one- or two-step potentiostatic electrolysis of a Ni plate electrode at various potentials. Scanning electron microscopy observations and X-ray diffraction measurements confirmed the formation of DyNi2, DyNi3, Dy2Ni7, and DyNi5. The formation reactions of the Dy–Ni alloys and the corresponding potentials were determined, and the optimum electrolysis conditions for the separation of Nd and Dy from molten salts containing both Nd(III) and Dy(III) ions are discussed. [Copyright &y& Elsevier]