Electrode Response Research Articles

Theoretical description of the ligand function for ionoselective electrodes reversible to metal anion complexes. 3. Modeling of the electrode response in ligand and foreign ions solutions using the multi-species approach model

A description for the ligand function of the tetrathiocyanatozincate selective electrode, has been proposed, using a multi-species approach model. This model takes into account simultaneous phase-boundary, diffusion-controlled, processes of ion exchange between tetrathiocyanatozincate, thyocyanate and foreign ions unable to form zinc complexes, as well as distribution of the neutral zinc complex between phases, partial decomposition of quaternary ammonium tetrathiocyanatozincate salt and stepwise complex formation processes in water phase. The model is based on solving the system of equations describing several interphase and intraphase equilibria, assuming that diffusion flows of all membrane and solution components at the phase boundary are stationary. It provides the adequate description of tetrathiocyanatozincate selective electrode in solutions of the ligand, foreign ions and mixed solutions of the above, and predicts the effect of zinc chloride concentration in the sample solution upon electrode function slopes, lower detection limits and selectivity coefficients.

Recent Trends in the Improvement of the Electrochemical Response of Screen-Printed Electrodes by Their Modification with Shaped Metal Nanoparticles.

Novel sensing technologies proposed must fulfill the demands of wastewater treatment plants, the food industry, and environmental control agencies: simple, fast, inexpensive, and reliable methodologies for onsite screening, monitoring, and analysis. These represent alternatives to conventional analytical methods (ICP-MS and LC-MS) that require expensive and non-portable instrumentation. This needs to be controlled by qualified technicians, resulting moreover in a long delay between sampling and high-cost analysis. Electrochemical analysis based on screen-printed electrodes (SPEs) represents an excellent miniaturized and portable alternative due to their disposable character, good reproducibility, and low-cost commercial availability. SPEs application is widely extended, which makes it important to design functionalization strategies to improve their analytical response. In this sense, different types of nanoparticles (NPs) have been used to enhance the electrochemical features of SPEs. NPs size (1–100 nm) provides them with unique optical, mechanical, electrical, and chemical properties that give the modified SPEs increased electrode surface area, increased mass-transport rate, and faster electron transfer. Recent progress in nanoscale material science has led to the creation of reproducible, customizable, and simple synthetic procedures to obtain a wide variety of shaped NPs. This mini-review attempts to present an overview of the enhancement of the electrochemical response of SPEs when NPs with different morphologies are used for their surface modification

An Elementary Kinetic Model for the LSCF and LSCF-CGO Electrodes of Solid Oxide Cells: Impact of Operating Conditions and Degradation on the Electrode Response

An elementary kinetic model was developed to predict the electrochemical response of porous LSCF and LSCF-CGO electrodes. The model was validated thanks to experiments performed on symmetrical cells using a three-electrode setup. After the model calibration on polarization curves, it has been shown that the model is able to simulate accurately the experimental impedance diagram at OCP and under polarization without additional fitting. Moreover, the evolution of the electrode polarization resistance with the oxygen partial pressure is well reproduced by the model. The electrodes reaction mechanism was thoroughly analyzed and it has been shown that the transition from the bulk path to the surface path depends on the temperature, the polarization and the oxygen partial pressure. The rate-determining steps for the LSCF electrode have been identified at OCP as function of the oxygen partial pressure. Finally, a sensitivity analysis has been performed to study the impact of LSCF demixing on the electrode performances. For a given decomposition, it has been highlighted that the surface passivation would be more impacting than the decrease of the ionic conductivity. Moreover, the impact of the LSCF decomposition would be more detrimental for the electrode performances evaluated in electrolysis mode. List of symbols Roman Symbols: Surface double layer capacitance(F m−2) Double layer capacitance at the LSCF/CGO interface(F m−2) Maximum concentration of neutral oxygen atoms in LSCF(mol m−3) Vacancies concentration in LSCF(mol m−3) Vacancies concentration in LSCF at equilibrium(mol m−3) Bulk oxygen chemical diffusion coefficient in LSCF(m2 s−1) Effective diffusion for the i-th species(m2 s−1) Oxygen vancancies self-diffusion coefficient(m2 s−1) Knudsen diffusion coefficient(m2 s−1) Molecular diffusion coefficient(m2 s−1) Diffusion coefficient of the oxygen ad-ions(m2 s−1) Diffusion coefficient of the oxygen ad-atoms(m2 s−1) Diffusion coefficient of the oxygen ad-molecules(m2 s−1) Local electrode potential(V) Activation energy for the i-th species(kJ mol−1) Faraday’s constant(C mol−1) Total inlet gas flow rate(mol s−1) Hole defect in LSCF(–) Ionic current density in CGO/Electronic current density in LSCF(A m−2) Thermodynamic equilibrium constant for the i-th species(–) Forward reaction kinetic constants for R1 for the LSCF(*) or LSCF-CGO(**) electrode (*) (mol m−1 s−1) or (**) (mol m−2 s−1) Forward reaction kinetic constants for R2(m3 mol−1 s−1) Forward reaction kinetic constants for R3 for the LSCF(*) or LSCF-CGO(**) electrode (*) (m s−1) or (**) (s−1) Forward reaction kinetic constants for R4(s−1) Forward reaction kinetic constants for R5(mol2 m−1 s−1) Forward reaction kinetic constants for R6(s−1) Electrode thickness(μm) CGO Electrolyte thickness(μm) Molar mass for the i-th species(g mol−1) m Reaction order(–) Molar flux of the i-th species(mol·m−2·s−1) Oxygen atom in the LSCF lattice(–) Oxygen atom in the CGO lattice(–) Oxygen ad-ion on LSCF surface(–) Oxygen ad-atom on LSCF surface(–) Oxygen ad-molecule on LSCF surface(–) O 2 Gaseous oxygen molecule(–) Oxygen partial pressure(atm) Total pressure(atm) Mean pore radius(m) universal gas constant(J mol−1 K−1) Serial resistanceΩ cm2 Polarization resistanceΩ cm2 Adsorption site on LSCF surface(–) Specific surface area between CGO and LSCF for the LSCF(*) or LSCF-CGO(**) electrode (*) (–) or (**) (m−1) Specific surface area between LSCF and gas phase(m−1) Electrode surface(cm2) Absolute temperature(K) Fuller’s volume for the i-th species(–) Oxygen vacancy in the LSCF lattice(–) Oxygen vacancy in the CGO lattice(–) Molar fraction of species i-th species(–)Greek Symbols: Charge transfer coefficient for oxidation or reduction for the reaction Ri(–) Surface density of available sites on LSCF(mol m−2) ε X Phase volume fraction for the phase X(–) η Overpotential(V) Coverage of oxygen ions on LSCF(–) Coverage of oxygen atoms on LSCF(–) Coverage of oxygen molecules on LSCF(–) Free sites on the LSCF surface(–) Coverage rate of oxygen ions on LSCF at equilibrium(–) Coverage rate of oxygen atoms on LSCF at equilibrium(–) Coverage rate of oxygen molecules on LSCF at equilibrium(–) Free site on LSCF at equilibrium(–) Kinetic rate of chemical/electrochemical reaction (i) in the electrode(*) or at the electrolyte interface(**) (*) (mol m−3 s−1) or (**) (mol m−2 s−1) Electrochemical potential(J mol−1) Density of triple phase boundary lengths for the LSCF(*) or LSCF-CGO(**) electrode (*) (m−1) or (**) (m−2) Electronic conductivity of LSCF(S m−1) Ionic conductivity of CGO(S m−1) Effective conductivity for th i-th species(S m−1) φ i Potential(V) χ Surface electrostatic potential(V) τ X Tortuosity factor for the phase X(–)

Local Substrate Heterogeneity Influences Electrochemical Activity of TEM Grid-Supported Battery Particles.

Understanding how particle size and morphology influence ion insertion dynamics is critical for a wide range of electrochemical applications including energy storage and electrochromic smart windows. One strategy to reveal such structure–property relationships is to perform ex situ transmission electron microscopy (TEM) of nanoparticles that have been cycled on TEM grid electrodes. One drawback of this approach is that images of some particles are correlated with the electrochemical response of the entire TEM grid electrode. The lack of one-to-one electrochemical-to-structural information complicates interpretation of genuine structure/property relationships. Developing high-throughput ex situ single particle-level analytical techniques that effectively link electrochemical behavior with structural properties could accelerate the discovery of critical structure-property relationships. Here, using Li-ion insertion in WO3 nanorods as a model system, we demonstrate a correlated optically-detected electrochemistry and TEM technique that measures electrochemical behavior of via many particles simultaneously without having to make electrical contacts to single particles on the TEM grid. This correlated optical-TEM approach can link particle structure with electrochemical behavior at the single particle-level. Our measurements revealed significant electrochemical activity heterogeneity among particles. Single particle activity correlated with distinct local mechanical or electrical properties of the amorphous carbon film of the TEM grid, leading to active and inactive particles. The results are significant for correlated electrochemical/TEM imaging studies that aim to reveal structure-property relationships using single particle-level imaging and ensemble-level electrochemistry.

Improved glucose oxidation catalytic current generation by an FAD-dependent glucose dehydrogenase-modified hydrogel electrode, in accordance with the Hofmeister effect

Herein, we describe the effect of varying anions in an electrolyte solution on current generation by a redox hydrogel electrode. The electrode surface is coated with a thin film of hydrogel matrix, consisting of an osmium (Os) redox polymer including tethered Os complexes, polymer backbone, and a redox enzyme. In this case, the enzymes employed are flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH), which catalyzes glucose oxidation, and the result was compared with that reported earlier for glucose oxidase (GOx). The hydrogel matrix facilitates efficient electron transfer from glucose to the electrode via collision of the Os complexes and thus acts as a mediator. The degree of impact of anions on current generation is characteristic of the Hofmeister series. Chaotropic anions, such as nitrate and chloride, increase and decrease the catalytic current produced by FAD-GDH and GOx hydrogel electrodes, respectively. Such anions can adsorb onto the cationic region of the FAD-GDH surface and induce a negative charge, which enhances electrostatic interactions between the enzyme and the positively charged Os polymer. Kosmotropic anions, such as sulphate and phosphate increase the catalytic current due to hydrogel shrinkage, which increases the relative concentrations of both enzyme and mediator within the hydrogel architecture due to an increase in density. High-performance electrode design depends on understanding the impact of ion identity on catalytic current responses of redox hydrogel electrodes.

Electrode response of NaFeTiO4 in aqueous supercapacitor cells

We report electrochemical performance of a calcium ferrite type NaFeTiO4 electrode for capacitor cell applications. High-resolution transmission electron microscopy results confirmed single-phase polycrystalline surface property comprising non-uniform grain distribution. X-ray photoelectron spectrum (XPS) analysis results confirmed presence of Fe3+ and Ti4+ oxidation states. The electrochemical performance of NaFeTiO4 in a three-electrode capacitor cell using different aqueous electrolytes: 1 M H2SO4, 1 M Na2SO4, and 1 M Li2SO4 confirmed superior performance only for capacitor cell with 1 M H2SO4 exhibiting typical pseudo-capacitive response in cyclic voltammetry. In contrast, the cell response of NaFeTiO4 with 1 M Na2SO4 and 1 M Li2SO4 electrolytes was electric double-layer charge (EDLC) accumulation induced capacitive effect predominantly. The electrolyte-driven distinct charge storage mechanism has been attributed to surface adsorption-induced redox action in the former whereas the EDLC response in the latter is attributed to larger size of the hydrated Na+ and Li+ ions causing charge accumulation at the interface. An excellent cyclic stability up to 10000 cycle with capacity retention up to 91% and coulombic efficiency ~ 100% has been noted @ 1 Ag−1 in 1 M H2SO4. Two electrode symmetric cell results exhibit similar pseudo-capacitive response as in three electrode cell configuration. The material delivered maximum power density ~ 18 kW/kg @ 10 Ag−1 and energy density ~ 2.55 Wh/kg @ 0.1 Ag−1 in a three-electrode-cell configuration whereas for a two-electrode cell, corresponding values are ~ 3.13 kW/kg @ 0.43Ag−1 and ~ 2.26 Wh/kg @ 0.04 Ag−1.

Silver nanoparticles/poly(L-cysteine) nanocomposite modified pencil graphite for selective electrochemical measurement of guaifenesin in real samples

A highly sensitive electrochemical sensor for the determination of guaifenesin (GF) using a modified pencil graphite electrode was developed based on silver nanoparticles/poly(L-cysteine) (AgNPs/PLcys/PGE). The obtained results showed that the electrode response was considerably enhanced during the modification process. The effective surface area of the bare and modified electrodes was determined by using the chronocoulometry method which was accompanied by an enhancement in the effective surface area at each electrode modification step. After optimization, the modified electrode displayed a linear relationship between the concentration of GF and peak current in the range of 3.0 × 10−8 to 3.0 × 10−4 M. The limit of detection was obtained 6.1 × 10−9 M. The sensor was used to measure GF in real samples such as syrup, plasma and urine. The obtained results contained suitable recoveries indicating the precise determination of GF in real samples due to the high selectivity of the sensor.

Hierarchically activated porous carbon derived from zinc-based fluorine containing metal-organic framework as extremely high specific capacitance and rate performance electrode material for advanced supercapacitors

In this work, a hierarchically activated porous carbon (APC) was synthesized using fluorine-containing metal-organic framework via facile combined carbonization and KOH activation treatments. The influences of activation conditions on the surface structures and electrochemical performance of APC were systematically studied. Afterwards, the electrochemical responses of APC electrode were further assessed from the cyclic voltammetry and galvanostatic charge-discharge examinations by 6 M KOH electrolyte. The as-obtained APC electrode delivered the high specific capacitances of 540.8 and 280 F g−1 at 1 and 500 A g−1, correspondingly with superior capacitance retention of 94% after 250,000 cycles even at 100 A g−1, which is showing that its outstanding capacitance, remarkable rate capacity, and very-long cyclic life. Furthermore, the as-assembled APC-based symmetrical supercapacitor offers a superb energy density of 19 Wh kg−1 at 182 W kg−1, indicating its large-scale application. Thus, this work proposes a potential route to synthesize highly efficient porous carbon material for the future development of energy storage systems.

Influence of solid electrolyte upon the repeatability and reproducibility of all-solid-state ion-selective electrodes with inorganic insertion material paste

The effects of the solid electrolyte β”-alumina upon the electrode responses of all-solid-state ion-selective electrodes (ISEs) with the inorganic insertion material Na0.33MnO2 were examined for Na+-ISE and K+-ISE. β”-alumina was added into the Na0.33MnO2 paste as a Na+-supply source for the ion-to-electron transducer Na0.33MnO2. For K+-ISE in the absence of β”-alumina, the insertion ion from Na0.33MnO2, Na+, was not identical to the target ion, K+, in the K+-selective membrane; thus, the exchange of Na+ for K+ at the Na0.33MnO2 | selective-membrane interface caused significant potential drift of K+-ISE; however, this drift was suppressed by the addition of β”-alumina into the Na0.33MnO2 paste. The obtained potential repeatability and Eo reproducibility (± 1.0 mV) for K+-ISE were made similar to those for Na+-ISE with Na0.33MnO2; these results show that all-solid-state ISEs can be developed for various ions without changing the inorganic insertion material.

Transmission line models for evaluation of impedance response of insertion battery electrodes and cells

Physics based transmission line models (TLMs) are a convenient tool for the analysis of the impedance response of electrochemical systems – the most prominent examples being double-layer capacitors, solar cells, and batteries. TLMs can provide a good quali- and quantitative evaluation of the main transport-reaction steps occurring in a given system - at a moderate mathematical effort. This mini review focuses on the theoretical development and application of TLM schemes in porous battery electrodes and other porous battery components. After a short historical overview of the main achievements in the field, we discuss in some detail the conventional TLM based on the de Levie's original proposal. Afterwards we present a couple of upgrades that address the deficiencies of the conventional model at low frequencies in which diffusion in electrolyte phases (in porous electrode and in separator) is supposed to be observed. We compare systematically the impedance responses of several TLMs and comment on their ability to simulate the measured impedance spectra. Simplifications and limitations of the discussed models are also considered. Finally, a comparison between the proposed TLMs and the output of the well-known Newman's porous electrode model is shown.

Voltammetric sensor based on long alkyl chain tetraalkylammonium ionic liquids comprising ascorbate anion for determination of nitrite

An electrochemical sensor was fabricated utilizing ionic liquids possessing cations with long alkyl chains such as trimethyl octadecylammonium and behenyl trimethylammonium and ascorbate anion. The ionic liquids were drop-coated onto the electrode. Thin modifying layers were prepared. Cyclic voltammetric investigations revealed electrostatic interactions between the electrochemical probes and the modified surface, proving that a positive charge was established at the film surface. Hence, negatively charged species such as nitrite can be pre-concentrated on the surface of presented modified electrodes. The fabricated electrodes have been used as a voltammetric sensor for nitrite. Due to the electrostatic accumulation properties of long alkyl cation, the assay exhibits a remarkable improvement in the voltammetric response toward nitrite oxidation. The influence of pH on the electrode response was thoroughly investigated, and the mechanism of the electrode was established. The developed sensor showed a linear electrochemical response in the range 1.0–50 μM with a detection limit of 0.1 μM. The electrode revealed good storage stability, reproducibility, and anti-interference ability. The determination of nitrite performed in curing salts brought satisfactory results.Graphical abstract

The electron transfer kinetics of adsorbed species derived by sampled current voltammetry

In sampled current voltammetry, a sampled current voltammogram (SCV) is constructed by performing a number of potential steps and plotting the currents taken at a specific sampling time against the corresponding step potentials. For diffusion-controlled processes, the technique produces sigmoidal current-potential curves that are easily analysed to obtain kinetic information. Here, we extend this approach to study the electron transfer kinetics of adsorbed species (Oads+ne−⇌kbkfRads) and show that the SCVs have a characteristic peak whose shape, potential and current depend on the sampling time. We also discuss the results in terms of chronocoulograms and show that the sampled charge voltacoulograms (SQVs) are also affected by kinetics. Analysis of the SCVs and SQVs is particularly useful to unravel the dependence of the electrode response on potential and time. We investigate different data treatments and show that a logarithmic SCV, a plot of ln(j) against E, is highly sensitive to the electron transfer rate constant and to the sampling time. The time dependence of the current yields ΓO0 (initial surface coverage) and E0, while the potential dependence of the current extrapolated to very short sampling times yields α and ks. This extrapolation bypasses the double layer charging distortion, provided the sampling times are selected where the current transients are free from capacitive distortion. From the analysis of the SCVs, we propose a simple protocol to derive ΓO0, E0, α and ks, from only two current transients, the only constraint being that one of the chronoamperograms must be recorded with a large overpotential, circa ±120 mV. We also propose a simpler alternative involving non-linear regression of the current transients to a single expression. The chronoamperometric approach offers advantages compared to the voltammetric methodology proposed by Laviron. 1) Capacitive distortions only affect the current transients at short times but affect the whole potential window in voltammetry. 2) The current transients can be extrapolated to very short sampling times where the backward reaction has no influence. 3) The extrapolation to very short sampling times bypasses the double layer distortion. 4) Whereas a chronoamperogram holds a wide range of timescales, the voltammetric approach requires a wide range of scan rates to distinguish the kinetic regimes. 5) The voltammetric method only yields the values of ks and α, while the chronoamperometric method also yields ΓO0 and E0. 6) Since electrochemical workstations allow shorter time scales by chronoamperometry than voltammetry, the method can assess faster electron transfer kinetics than conventional cyclic voltammetry.

Exploring multi-step glucose oxidation kinetics at GOx-functionalized nanotextured gold surfaces with differential impedimetric technique

For a few past years, we can observe the enormous growth of investigations related to ultrasensitive electrochemical sensors capable of reliable determination of important body parameters and analytes. Utilized procedures rely on standard electrochemical methods, demanding electrode polarization, and information about the initial characteristics of the working electrode. More and more complex electrode materials are characterized however their electrochemical response is not fully understood or defined, affecting data reproducibility.Herein, we propose a novel protocol utilizing dynamic electrochemical impedance spectroscopy in galvanostatic mode (g-DEIS) to verify the sensor performance. The protocol was applied to study the response of Ti-Au nanotextured electrode depending on glucose concentration changes. The g-DEIS allowed to monitor complex mechanism occurring at the electrode/electrolyte interface with the continuously dosed glucose through electric parameters derivatives in analyte content. Our studies revealed a visible increase in electrode electric heterogeneity above 1.9 mM of glucose and gold nanoparticles’ oxidation above 3.8 mM, both influencing electrode kinetics. The results were confirmed using supporting cyclic voltammetry and x-ray photoelectron spectroscopy studies. The proposed protocol’s unique features could significantly spread further application of targetable biosensors for real-time diagnostics.

Harvesting blue energy with carbon electrodes of asymmetric nanopore distributions

Extracting the Gibbs free energy from natural water salination, a.k.a. the blue energy, has attracted a long-standing, global interest. While pressure-retarded osmosis (PRO) and reverse electrodialysis (RED) are by far the most studied methods for such a purpose, the concept of using the capacitive electrode response for blue energy harvesting has been shown to offer unique advantages. Despite that porous electrodes are predominately used in capacitive methods, the role of pore properties in energy extraction remains unclear. Here we show that the distribution of the nano-sized pores in an electrode imposes a profound impact on the electrode capacitive response under a salinity gradient. Such a pore-size effect can be sufficiently strong that leads to structural changes of the electric double layer, resulting in highly efficient extraction of the Gibbs free energy. We demonstrate that a device fabricated with carbon electrodes with significantly different nanopore distributions can generate a high power density without membranes or an external charge source. • Nano-confinement induces significant structural changes of EDLs. • Electrodes with different nanopores create dissimilar responses to salinity gradients. • Gibbs free energy from mixing can be harvested with asymmetric nanopore distributions.

Determination of AVELOX (Moxifloxacin Hydrochloride) Tablets In Dosage Forms Modified With Potentiometer Sensors: A Comparative Analysis

Electro-chemical sensors response characteristics of three different electrodes modified with carbon paste (CP), screen printed (SC) and Poly-vinyl chloride(PVC) were fabricated to verify the credibility of drug “AVELOX”, whose generic name is “Moxifloxacin HCl” (AV-MOXH) are traced and calculated. The sensing membranes contain AVELOX (Moxifloxacin HCL) ion association complexes with “sodium tetraphenyl borate” (NaTPB), “Phosphomolybdic acid” (PMA), and “Phosphotungstic acid” (PTA) and “Ammonium Reineckate” (RN) as electro-active materials. All the three electrodes (ICPE, IPVC and ISPE) are subjected to underneath study displays fast, viable and near-Nernstian linear responses above a relative wide-ranging concentration which varies from (1.0×10-6)molL-1 to (1.0×10-2)molL-1 of AV-MOXH at 25°C along with a mono-valent cationic slope. On the basis of calculations and presented data in the paper shows that that the IPVCs modified electrodes, have slope values measured with 7.5mg are (53.2 ± 1.5),(58.2 ± 3.9) and (51.6 ± 2.0) mV decade -1 for NaTPB, PMA and PTA ion pairing reagents respectively. For ISPE modified electrode, the observed slope values are (59.7 ± 2.0) mV decade -1 with 22mg for NaTPB ion pair, (60.1 ± 2.0)mV decade -1 with 16mg for RN ion pair and (58.9 ± 3.2)mV decade -1 with 30 mg for PTA ion pair. Whereas, the obtained value of ICPE electrode altered with 7.5mg NaTPB shows slope calculated at (58.0 ± 2.0)mV decade -1 . The sensors demonstrate good discernment of Av-MOXH from numerous inorganic and organic compounds such as glucose, sucrose, Na+, Ca+,etc. Additionally, the isothermal coefficients along by selectivity coefficients is diagnosed. The modified Screen Printed Electrode sensor appears to be highly sensitive for determination of AV-MOXH. Electrode response was set up to observe their pH dependence range (2-6) for ISPEs and IPVC electrodes and (3-7) pH range for ICPE electrode with varied range of temperature. The short response time, life time validity, recovery and all the method of validation such limit of detection and limit of quantification are estimated. This potentiometric method is suitable for determining AV-MOXH in pharmacological formulations, and the findings obtained are comparable to the “HPLC official method” in terms of agreement. As a result, the postulated potentiometric approach was verified in accordance with IUPAC guidelines.

Introducing visible-light sensitivity into photocatalytic CeO2 nanoparticles by hybrid particle preparation exploiting plasmonic properties of gold: enhanced photoelectrocatalysis exemplified for hydrogen peroxide sensing.

In this report we combine the catalytic properties of CeO2 nanoparticles with their transduction ability for photoelectrochemical sensing. This study highlights the usage of CeO2 providing catalytic activity towards H2O2, but only with a limited excitation range in the UV for the construction of a sensing system. In order to improve the photoelectrocatalysis of CeO2 nanoparticles by extending their excitation to visible light, Au/CeO2 core/shell hybrid nanoparticles have been synthesized. The hybrid nanoparticles are fixed on electrodes, allowing for the generation of photocurrents, the direction of which can be controlled by the electrode potential (without bias). The application of the hybrid nanoparticles results in an enhanced photocurrent amplitude under white light illumination as compared to the pure CeO2 nanoparticles. Wavelength-dependent measurements confirm the participation of the Au core in the signal transduction. This can be explained by improved charge carrier generation within the hybrid particles. Thus, by using a plasmonic element the photoelectochemical response of a catalytic nanoparticle (i.e. CeO2) has been spectrally extended. The effect can be exploited for sensorial hydrogen peroxide detection. Here higher photocatalytic current responses have been found for the hybrid particles fixed to gold electrodes although the catalytic reduction has been comparable for both types of nanoparticles. Thus, it can be demonstrated that Au/CeO2 core-shell nanoparticles allow the utilization of visible light for photoelectrochemical hydrogen peroxide (H2O2) detection with improved sensitivity under white light illumination or application of such particles with only visible light excitation, which is not possible for pure CeO2. With help of the layer-by-layer (LbL) technique for nanoparticle immobilization, the electrode response can be adjusted and with a 5 layers electrode a low detection limit of about 3 μM H2O2 with a linear detection range up to 2000 μM is obtained.

Multi-Ion-Sensing Emulator and Multivariate Calibration Optimization by Machine Learning Models

One paramount challenge in multi-ion-sensing arises from ion interference that degrades the accuracy of sensor calibration. Machine learning models are here proposed to optimize such multivariate calibration. However, the acquisition of big experimental data is time and resource consuming in practice, necessitating new paradigms and efficient models for these data-limited frameworks. Therefore, a novel approach is presented in this work, where a multi-ion-sensing emulator is designed to explain the response of an ion-sensing array in a mixed-ion environment. A case study is performed emulating the concurrent monitoring of sodium, potassium, lithium, and lead ions, in a medium representative of sweat samples. These analytes are relevant examples of sweat ion-sensing applications for physiology, therapeutic drug monitoring, and heavy metal contamination. It is demonstrated that calibration datasets output by the emulator explain accurately the experimental response of polymeric solid-contact ion-selective electrodes, where root-mean-squared error of 1.37, 1.44, 1.78, 2 mV are obtained, respectively, for Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , Pb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> sensor calibration in artificial sweat. Besides, synthetic datasets of custom size are generated to train, validate, and evaluate different types of multivariate regressors. A Multi-Output Support Vector Regressor (M-SVR) is proposed as a compact, accurate, robust, and efficient multivariate calibration model. It features 13.22% normalized root mean squares, and 20.29% mean root squares improvement compared to a simple linear regression model. It is an unbiased estimator for medium to large datasets, and its average generalization error is of 3.22%. Besides, M-SVR models have a lower computational complexity than single-output SVR or neural network models, making them a suitable solution for memory and energy-constrained edge devices used for continuous and real-time multi-ion monitoring.

Potentiometric determination of finsatride by novel ion selective electrodes

In this research, five ion selective electrodes for finsatride drug were successfully prepared including: coated wire electrode (CWE), coated graphite electrode (CGE), carbon paste electrode (CPE), carbon paste-carbon nanotube electrode (CPCNT) and carbon paste-nanosilica electrode (CPNS) depending on the formation of finsatride-TPB complex. Furthermore, the Nernastain response was studied by determination of slope and detection limit with the study pH effect on the response for finsatride electrodes and response time. However, the selectivity was calculated with applied the potentiometric method which including: direct, standard addition method and potentiometric titration for pure and pharmaceutical formulation of finsatride. The RSD was 2.82, 1.52, 2.04, 2.27, 1.84, respectively. And the 6.350 × 10-7, 7.449 × 10-8, 6.334 × 10-6, 5.316 × 10-6 and 5.433 × 10-6 M, respectively.

Estimation of temperature effect on PVC-based ciprofloxacin selective electrode response

Estimation of temperature effect on PVC-based ciprofloxacin selective electrode response

Eco-friendly modified carbon paste electrode by Bigarreau Burlat kernel shells for simultaneous trace detection of cadmium, lead, and copper

Bigarreau Burlat kernel shell was valorized as an eco-friendly modifier of carbon paste electrode (BBKS-CPE) for simultaneous trace detection of Cd 2+ , Pb 2+ and Cu 2+ ions. The electrochemical investigation by cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) revels an enhancement in the detection current intensity after the electrode modification. After calibration, the obtained detection limits are 9.56 ppb for Cd 2+ , 8.48 ppb for Pb 2+ and 9.77 ppb for Cu 2+ under the following optimal conditions: modifier granulometry between 180 and 125 µm, pH= 6, 10% of modifier ratio, acetate buffer as supporting electrolyte, -2 V and 130 s as an accumulation potential and time, respectively. The manufactured electrode exhibited good selectivity and sensitivity towards these ions even in the presence of interferences. This electrode was applied to tap water, seawater and industrial wastewater, good detection limits were achieved. Good recovery was found by comparing the modified electrode response with ICP technique.