Electrode In Presence Research Articles

Determination of silver ions in distilled water by stripping voltammetry at a Nafion-coated gold electrode in combination with quartz crystal microbalance and electrochemical impedance spectroscopy

Here, we propose a stripping voltammetric method for Ag+ ion determination in distilled water utilizing screen-printed Au electrodes coated with Nafion (Nafion/Au screen-printed electrodes). The concentration of Ag+ in pure water was determined by linear sweep voltammetry (LSV) after silver deposition on the Nafion/Au electrode. The anodic stripping peak current increased linearly with the concentration of Ag+ ion in the range from 1 ppm to 22 ppm. The LSV oxidative peak current was increased by extending the silver deposition time from 300 s to 500 s. Repetitive LSV measurements revealed satisfactory reproducibility of the Nafion/Au screen-printed electrodes. The detection mechanism was elucidated by recording mass changes of the Nafion/Au electrode with a quartz crystal microbalance (QCM), and by determining changes in the low-frequency capacitance of the Nafion/Au electrode by electrochemical impedance spectroscopy (EIS). The observed changes in mass and capacitance confirmed Ag+ accumulation and release processes at the Nafion/Au electrodes, in good agreement with stripping voltammetry. The combination of stripping voltammetry, QCM and EIS allowed a detailed characterization of the ion transfer, deposition and stripping processes at the Nafion/Au electrodes in presence of Ag+ ions. The Nafion/Au screen-printed electrode enabled voltammetric determination of low Ag+ concentrations in distilled water, without any sample pretreatment nor addition of supporting electrolyte.

Qualitative Analysis of Decision to Pursue Electrical Brain Stimulation by Patients With Drug-Resistant Epilepsy and Their Caregivers.

To understand why patients with drug-resistant epilepsy (DRE) pursue invasive electrical brain stimulation (EBS). We interviewed patients with DRE (n = 20) and their caregivers about their experiences in pursuing EBS approximately 1 year post device implant. Inductive analysis was applied to identify key motivating factors. The cohort included participants aged from teens to 50s with deep brain stimulation, vagus nerve stimulation, responsive neurostimulation, and chronic subthreshold cortical stimulation. Patients' motivations included (1) improved quality of life (2) intolerability of antiseizure medications, (3) desperation, and (4) patient-family dynamics. Both patients and caregivers described a desire to alleviate burdens of the other. Patient apprehensions about EBS focused on invasiveness and the presence of electrodes in the brain. Previous experiences with invasive monitoring and the ability to see hardware in person during clinical visits influenced patients' comfort in proceeding with EBS. Despite realistic expectations for modest and delayed benefits, patients held out hope for an exceptionally positive outcome. Our findings describe the motivations and decision-making process for patients with DRE who pursue invasive EBS. Patients balance feelings of desperation, personal goals, frustration with medication side effects, fears about surgery, and potential pressure from concerned caregivers. These factors together with the sense that patients have exhausted therapeutic alternatives may explain the limited decisional ambivalence observed in this cohort. These themes highlight opportunities for epilepsy care teams to support patient decision-making processes.

Insights into sulfur cycling contribution to nitrogen removal in sulfur autotrophic denitrification combined microbial electrochemical denitrification

In the face of increasing discharge standards, sulfur autotrophic denitrification (SAD) is gradually applied for deep nitrogen removal of electron-donor-deficient waters. However, the product sulfate induces secondary pollution in the effluent, and the proton consumption from alkalinity is detrimental to the stable operation of the system. In this study, a sulfur autotrophic denitrification coupled with microbial electrochemical denitrification system (S-MED) is proposed to reduce the addition of inorganic sulfur, alleviating nitrite accumulation, while enabling the system to self-sustain at a neutral pH. The S-MED system that was operated under the applied potential of −0.5 V achieved a nitrate removal of 97.5 ± 1.57 % and a total nitrogen removal of 90.3 ± 4.27 %, which were 14.6 % and 68.0 % higher than the SAD systems in control under the S/N molar ratio of 0.8. The nitrite accumulation rate was reduced by 69.1 % compared to SAD. The effluent sulfate concentration was also reduced to 5.8 mg/mg-N TN removal. The electrochemically active denitrifying bacterium Thiobacillus was enriched in the coupled system, and the copy numbers of functional genes of narGHI, napAB, and nirK involved in denitrification were increased. According to the microbial analysis and electrochemical characteristics, it suggested that S2- might be generated from sulfate with the presence of electrodes, enabling the cycling of sulfur, providing mobile electron carriers for denitrification, thus allowing bacteria to conduct denitrification by indirectly obtaining electrons from the electrode.

Phytochemicals assisted green synthesis of copper oxide/cobalt oxide as efficient electrocatalyst for oxygen evolution reaction

Electrocatalytic water splitting is a promising solution to resolve the global energy crisis. Tuning the morphology and elemental composition is a crucial aspect in designing highly-efficient nanomaterials based electrocatalyst for water splitting. Herein, green synthesis using phytochemicals from aloe vera leaves extract was employed to hydrothermally synthesize copper oxide/cobalt oxide nanostructures on nickel foam. The reaction medium was performed in presence of mineralizers of different pH; hydrochloric acid (HCl), citric acid (CA), urea, diethyl amine (DEA) and sodium hydroxide (NaOH) to produce five different compositions of copper oxide/cobalt oxide on nickel foam. Based on FESEM and EDS analysis, it was verified that the plant mediated hydrothermal process yielded interesting morphologies and the elemental composition of the synthesized metal oxide nanostructures distinctly varied with effect to the different mineralizers used. Use of acidic mineralizers such as hydrochloric acid and citric acid favoured formation of copper oxide whereas basic mineralizers such as urea, diethyl amine and sodium hydroxide favoured formation of cobalt oxide. The green synthesis of metal oxide electrode in presence of urea exhibits the best OER electrocatalytic performance with an overpotential of 390 mV, and 453 mV for a current density of 50 mA cm−2 and 100 mA cm−2 respectively. The sample also exhibited sustained stability over 70 h, hence proving that the proposed electrode can serve as an efficient catalyst for electrocatalytic OER.

Electrochemical remediation of phenol contaminated kaolin under low-strength electric fields

Soil degradation is a global concern. Electrochemical remediation (ER) technology is considered an appealing strategy for soil remediation because it is a low-cost, adaptable, and effective noninvasive in situ technology. Currently, the remediation of soil characterized by fine grains, low-hydraulic permeability, heterogeneous conditions, and mixtures of contaminants is still challenging since other conventional technologies are poorly effective. ER of soil is based on the application of low potentials between a couple of electrodes which induces an electric field (E) in the contaminated field. In this work, very low values of electric field (E≤ 0.25 V cm−1) were used for the ER of contaminated kaolin. Phenol was selected as model hazardous organic compound and kaolin as model, reproducible and low buffering and low permeability clay. The effect of several factors, including the nature of the electrodes, treatment time, kind of current, the strength of the E and the nature of supporting electrolyte, on the performance of the process was investigated in detail and discussed in terms of the normalized phenol concentration and its total removal from the kaolin. Overall, the main finding is that the use of very low value of E (0.15 V cm−1) can allow to simultaneously desorb, mobilize and also in-situ degrade phenol. The highest removals of phenol up to approximately 80% and 90% from the kaolin under both direct and sinusoidal E, respectively, were reached using compact graphite as electrodes in presence of Na2SO4 into the kaolin.

Photoelectrochemical Performance of Strontium Titanium Oxynitride Photo-Activated with Cobalt Phosphate Nanoparticles for Oxidation of Alkaline Water.

Photoelectrochemical (PEC) solar water splitting is favourable for transforming solar energy into sustainable hydrogen fuel using semiconductor electrodes. Perovskite-type oxynitrides are attractive photocatalysts for this application due to their visible light absorption features and stability. Herein, strontium titanium oxynitride (STON) containing anion vacancies of SrTi(O,N)3-δ was prepared via solid phase synthesis and assembled as a photoelectrode by electrophoretic deposition, and their morphological and optical properties and PEC performance for alkaline water oxidation are investigated. Further, cobalt-phosphate (CoPi)-based co-catalyst was photo-deposited over the surface of the STON electrode to boost the PEC efficiency. A photocurrent density of ~138 μA/cm at 1.25 V versus RHE was achieved for CoPi/STON electrodes in presence of a sulfite hole scavenger which is approximately a four-fold enhancement compared to the pristine electrode. The observed PEC enrichment is mainly due to the improved kinetics of oxygen evolution because of the CoPi co-catalyst and the reduced surface recombination of the photogenerated carriers. Moreover, the CoPi modification over perovskite-type oxynitrides provides a new dimension for developing efficient and highly stable photoanodes in solar-assisted water-splitting reactions.

Untwining polar contributions from light-polarization dependent photovoltaic response of LuMnO3-based ferroelectric capacitors

Narrow bandgap ferroelectrics are receiving a renewed interest for photovoltaic applications aiming at exploiting new functionalities arising from bulk photovoltaic effect (BPE). We report on the photovoltaic response of vertical capacitors of ferroelectric hexagonal LuMnO3 films sandwiched between semitransparent top electrodes (Pt, Co, Ti) and a common bottom (Pt) bottom electrode. Our results show that the presence of electrodes, other than their optical transmittance, crucially determines the imprint in the ferroelectric layer and ultimately the sensitivity of short circuit current density (Jsc) to the ferroelectric polarization direction. The use of ultrathin (7 nm) Pt top electrodes allowed to obtain a large Jsc (up to 100 mA/cm2) and an open circuit voltage of Voc ≈ 0.52 V, with a responsivity of 2 × 10−3 A/W. Yet, polarization back-switching due to imprint largely washes out the dependence of Jsc on the direction of the polarization and thus, at first sight, Jsc seemingly appears to be ruled by conventional photovoltaic response. However, a pioneering analysis of the light-polarization dependent photosensitivity, allowed to disentangle for the first time, a genuine contribution of BPE from a ubiquitous Fresnel-like contribution arising from interfaced optical media.

Revealing the super capacitive performance of N-doped hierarchical porous activated carbon in aqueous, ionic liquid, and redox additive electrolytes

Supercapacitors are generally high-power devices, yet their energy is low in contrast to batteries. In the present study, the N-doped porous carbon optimized from brinjal bio-mass waste (solanum melongena) using KOH+ Urea activation confirms its ability as a supercapacitor electrode in presence of an aqueous (1 M H2SO4), ionic liquid (1-ethyl-3-methylimidazolium-tetrafluoroborate-EMIMBF4) and an improved redox additive (0.01 M Hydroquinone-HQ) electrolytes. The hierarchical porous nature of the activated brinjal bio-mass waste carbon with desired compositions and structure is analyzed using FE-SEM and HR-TEM analysis. In a two electrodes symmetric configuration, brinjal waste-derived activated carbon (BC-700) delivers a high specific capacitance of 460 F/g at 1 A/g in 1 M H2SO4 aqueous electrolyte. In ionic liquid, it delivers 133 F/g high specific capacitance with an energy of 41 Wh/kg. This outstanding electrochemical performance is due to the electrolyte-ion movement of heteroatoms into the carbon matrix resulting in high specific surface area (850 m2 g−1) and effective microporosity. The energy density of the supercapacitor device is further enriched using the novel redox additive 0.01 M Hydroquinone in H2SO4 electrolyte with a specific capacity of 888 C/g and a maximum energy density of 61 Wh/kg, which is very high compared to batteries. Outstanding cyclic stability of 77 % capacitance retention after 5000 cycles is achieved in HQ-added aqueous electrolyte. Hence, the bio-mass waste-derived activated carbon performs as an excellent low-cost material for various electrochemical applications.

Computational Design and Application of Molecularly Imprinted/MWCNT Based Electrochemical Sensor for the Determination of Silodosin

AbstractA novel molecularly imprinted polymer (MIP) based electrochemical sensor was developed for differential pulse voltammetric detection of silodosin (SLD), used for enlarged prostate (benign prostatic hyperplasia; BPH) treatment. A computational design was first applied for optimization of the molar ratio between silodosin (SLD, template): Methacrylic acid (MAA, functional monomer), based on which five polymeric ratios were prepared followed by testing the amount of crosslinker (ethylene glycol dimethacrylate (EGDMA)), imprinting and rebinding efficiency of the polymer. The ratio 1:4:20 was found to have the highest binding capacity for SLD, and thus, was used as a modifier for the development of modified carbon paste electrodes in presence of multiwalled carbon nanotubes (MWCNT). The sensor was electrochemically characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements and morphologically using SEM, TEM and BET and its performance was optimized in terms of amounts of MIP, MWCNT, pH and other electrochemical parameters. A linear response range of 1.0×10−12–1.0×10−3 M SLD with a detection limit (S/N=3) of 1.0×10−13 M was shown. Finally, the MIP‐modified carbon paste sensor was successfully used to determine SLD in pure solutions, pharmaceutical formulations and spiked serum and urine samples.

Design of EQCM-MIP sensing matrix for highly specific and sensitive detection of thyroglobulin

In this paper an electrochemical quartz crystal microbalance (EQCM)-MIP sensor for thyroglobulin had been developed by using 4-aminothiophenol (4-ATP) - methacrylic acid (MAA)- reduced graphene oxide (RGO) composite as a polymeric format for the first time. Thyroglobulin plays a central role in the biology of thyroid as active and exclusive support for thyroid hormone synthesis and storage. Measurement of serum thyroglobulin is primarily used to detect recurrence of follicular thyroid cancer following total thyroidectomy and radioactive iodine ablation. The MIP sensor was developed by electodeposition of 4-ATP-MAA-RGO composite on EQCM electrode in presence of template thyroglobulin. Due to the location of imprinted sites on the surface and high specific surface area, analyte molecules have good accessibility and high binding affinity to template molecules thus yielding a highly sensitive and efficient signal. The limit of detection of 0.02 ng/mL, without any crossreactivity and matrix effect indicates high sensitivity and selectivity for thyroglobulin. The sensor was appreciably selective to thyroglobulin in presence of probable interferents. The relative standard deviation for determination was 4.23%. Based on speediness and sensitivity, the sensor is reusable and shows a great improvement in selectivity and adsorption capacity over other sensors.

Conversion of carbon dioxide to value added products through anaerobic fermentation and electro fermentation: A comparative approach

Increasing carbon footprint alters the carbon balance in nature, thereby worsening global climate change. The conversion of carbon dioxide (CO 2 ) into value-added products through biological routes is the pathway of the future because of its ecological and sustainable character. The present study evaluated the conversion of CO 2 into short-chain fatty acids (SCFA)/volatile fatty acids (VFA) and methane using four experimental conditions (R1-R4). The experimental conditions are R1 was an anaerobic fermenter (AF) operated as control, R2 consisted of an AF with electrodes operated in open circuit, R3 was an AF with electrodes operated in a closed circuit with 100 Ω as load and R4 was an electro-fermentation reactor with an applied cathodic potential of −0.8 V vs. Ag/AgCl. The results were assessed in terms of production of SCFA, methane, current density and inorganic carbon reduction. Electro-fermentation (R4) setup achieved the highest production of SCFA (2050 mg/L) and methane (41.2 mL/day) compared to other reactors. R3 reported 1800 mg/L and 24 mL/day, R2 reported 1560 mg/L and 15 mL/day and R1 reported 1430 mg/L and 10 mL/day of methane and SCFA production. The study-inferred that electro-fermentation could effectively catalyse the biochemical reactions and enhance the conversion of CO 2 to organic compounds in a sustainable manner. • Presence of electrode in the anaerobic fermentation enhanced the yield of carboxylic acids and biofuels. • The redox conditions are balanced in the microbial catalysed systems than the conventional anaerobic fermentations. • Enriched microbes showed different yield based on the operational conditions. • Electrofermentation is an effective processes to convert CO 2 to Value added products.

Application of a transition metal oxide/carbon-based nanocomposite for designing a molecularly imprinted poly (l-cysteine) electrochemical sensor for curcumin

In this study an electrochemical sensor was fabricated for detection of curcumin, as a functional herbal food, using molecularly imprinted polymer and highly conductive transition metal oxide/carbon-based nanocomposite. In this way, CuCo2O4/nitrogen-doped carbon nanotubes/phosphorus-doped graphene oxide nanocomposite was dropped on the electrode. This nanocomposite synergically possesses conductivity features of copper and phosphorus-doping sites, specific surface area of carbon nanotubes, and carbons Fermi level of graphene oxide. In the following, l-Cystein electropolymerized on the electrode in presence of curcumin. The sensor was produced by removing curcumin from poly (L- cystein) matrix. The sensor was successfully used for detection of curcumin in the ranges of 0.1–1 µmol L-1 and 1–30 µmol L-1, with acceptable detection limit (30 nmol L-1). Finally, the proposed method was used for detection of curcumin in serum samples with recoveries of 80–110.87%. The results demonstrated that aforementioned method can be used for detection of curcumin in biological samples.

INCREASING THE COST-EFFECTIVENESS OF IN VITRO RESEARCH THROUGH THE USE OF TITANIUM IN THE DEVICE FOR MEASURING THE ELECTRICAL PARAMETERS OF CELLS

Currently, various methods are used to assess the biocompatibility of materials. After an in-depth and detailed review of the literature, the method used in the research was selected. As part of the experiments, a method based on the analysis of the values ​​of electrical parameters of cell cultures measured in the presence of electrodes was used. The electrode is a structure made of a thin layer of metallization. It measures the change in resistance, impedance and capacity of a mixture of cells and the substance in which they are grown. The plate containing the electrode assembly is called the measurement matrix. Currently, commercially used test matrices are made of gold or platinum. However, their high price means that large-scale research is significantly limited. In order to increase the access to the widespread use of this method, it was decided that it was necessary to use cheaper materials, reducing the necessary costs of conducting experiments. Considering this, an attempt was made to use a different conductive material to build matrices compatible with the ECIS® Z-Theta measurement system. Their use would enable in vitro research on living cells. In the presented work, titanium was used as a material that may turn out to be an alternative to the materials currently used. Its application to the production of matrices will allow to study the influence of this metal on the behavior of cells.

Electrosynthesis and characterization of copper dicyanamide materials

X-ray diffraction and infrared reflection spectroscopy data have confirmed the electrosynthesis of copper dicyanamide films by cyclic voltammetry and potentiostatic electrolysis. An insoluble Cu(I)dca film can be synthesized on a gold or copper electrode by the reduction of Cu(II) or oxidation of Cu(0) in aqueous or methanolic solutions containing dicyanamide ions. By resorting to the use of the ruthenium hexaammine redox probe the Cu(I)dca film was shown to be electronically conductive although the deposition rate decreases when the film formation proceeds.Depending on the applied potential, not only Cu(I)dca but also Cu(II)dca can be formed by oxidation of a copper electrode in presence of dicyanamide ions dissolved in methanol. The powder obtained by electrolysis at 1 V vs Hg/Hg2SO4 made essentially of Cu(II)dca presents a specific surface area of (183 ± 59) m2/g. This material can adsorb preferentially methyl orange and Congo red dyes compared to methylene blue whereas no marked difference is obtained between CO and CO2 adsorption.

Electrocatalytic Hydrogenation of Phenol on Pt Under pH-Dependent Open Circuit Potential

Hydrogenation of organic molecules requires sequential addition of two H atoms to the substrate. So far, two pathways have been identified for this reaction on transition metal particles in water: conventional hydrogenation (CH) and proton coupled electron transfer (PCET). Typically, CH takes place in thermocatalytic hydrogenation (TCH) in which organic substrate reacts with adsorbed H atom on the surface of transition metal (Rxn. 1). PCET is a classic pathway occurring in electrocatalytic hydrogenation (ECH) by the simultaneous or sequential attack of hydronium ions with electrons to organic substrate on an electrode under a negative overpotential (Rxn. 2).Phenol* + H*→ H-Phenol* + * (CH) Rxn. 1Phenol* + H+ + e-→ H-Phenol* (PCET) Rxn. 2In water, a metal particle itself is a hydrogen electrode in presence of H2 and at a certain pH, having a so-called open circuit potential (OCP). In this work, we will use the hydrogenation reaction of phenol on Pt to explore whether the OCP on a transition metal can induce a PCET pathway, in particular at which conditions PCET overtakes CH pathway at OCP.Figure 1(a) shows the turnover frequency of phenol hydrogenation catalyzed by carbon nanotube (CNT) supported Pt catalyst under different pH. The turnover frequency shows a clear increasing trend, growing by an order of magnitude as pH decreasing from 5.3 to 2. In order to determine the reaction pathway, kinetic experiments were designed based on the difference between two pathways. The H atom added to phenol molecule in CH pathway (Rxn. 1) is from dissociative adsorption of gaseous H2, whereas that in PCET pathway is from hydronium ions in water (Rxn. 2). If the reaction undergoes the CH pathway, a kinetic isotope effect (KIE) would be observed when changing reductant from H2 to D2; whereas if PCET pathway dominates, a KIE would be observed via replacing H2O by D2O. Figure 1(b) shows that the dominated pathway is CH under pH 5.3, a KIE of kH2/kD2 was obtained when changing between H2 and D2, while the dominated route under pH 2 shown in Figure 1(c) is PCET due to KIE of kH2O/kD2O when changing between H2O and D2O. The mentioned results reveal that both CH and PCET pathways participate in phenol hydrogenation, with the dominated route transforming from CH to PCET as pH decreasing. It should be noted that all the reactions were carried out in absence of over potential, that only OCP drove the PCET pathway.In conclusion, hydrogenation rate of phenol is greatly enhanced by decreasing pH in water. Two reaction routes, CH and PCET, are turned out to be involved in the reaction. As pH decreasing from 5.3 to 2, the main reaction pathway shifts from CH to PCET. The reaction rate of PCET is promoted by decrease of pH because of the largely increased hydronium ion concentration. These results demonstrate that an electrocatalytic hydrogenation reaction can still occur under OCP. Figure 1. TOFs of phenol hydrogenation at 313-333 K with 10 bar H2 on 1 wt% Pt/CNT (5 mg) in 100 mL H2O (0.106 M phenol) plotted as a function of pH (a). Comparison of TOF of phenol hydrogenation in H2O-H2, H2O-D2, D2O-H2, D2O-D2 on 1 wt% Pt/CNT (50 mg) under pH 5.3 (no HClO4) (b) and 1 wt% Pt/CNT (10 mg) under pH 2 (HClO4) (c),10 bar H2 or D2, 30 mL H2O or D2O, 313 K, 0.106 M phenol. Figure 1

Characterization of interactive force acting on colloidal particles near an electrode in presence of a high-frequency (>10 kHz) AC electric field using particle diffusometry

Colloidal particles like polystyrene beads and metallic micro and nanoparticles are known to assemble in crystal-like structures near an electrode surface under both DC and AC electric fields. Various studies have shown that this self-assembly is governed by a balance between an attractive electrohydrodynamic (EHD) force and an induced dipole-dipole repulsion (Trau et al., 1997). The EHD force originates from electrolyte flow caused by interaction between the electric field and the polarized double layers of both the particles and the electrode surface. The particles are found to either aggregate or repel from each other on application of electric field depending on the mobility of the ions in the electrolyte (Woehl et al., 2014). The particle motion in the electrode plane is studied well under various conditions however, not as many references are available in the literature that discuss the effects of the AC electric field on their out-of-plane motion, especially at high frequencies (>10 kHz). Haughey and Earnshaw (1998), and Fagan et al. (2005) have studied the particle motion perpendicular to the electrode plane and their average height from the electrode mostly in presence of DC or low frequency AC (<1 kHz) electric field. However, these studies do not provide enough insight towards the effects of high frequency (>10 kHz) electric field on the particles’ motion perpendicular to the electrode plane.

Unveiling the performance metrics for supercapacitor electrodes with adsorbed redox additives

• Demonstration of how to obtain the capacity of supercapacitor electrodes with adsorbed redox additives; • Surface excess is obtained by cyclic voltammetry and utilized for acquiring the pure Methylene Blue capacity; • The explored approach offers an easy and coherent way to report the capacity of supercapacitor electrodes with adsorbed redox additives; • The obtained capacity of adsorbed MB is around 45 mAh g-1, in agreement among the employed methods. In recent years, the use of supercapacitors with redox additives has been widely explored with the aim of maximizing energy density. However, the inclusion of such additives increases the complexity of the charge storage mechanisms, requiring more attention in quantifying performance parameters. Specific electrode capacities and capacitances are one of the most reported parameters and have been often overestimated or misinterpreted in relation to each other. Here, we evaluate these parameters considering the surface excess ( Γ * ) of redox additives adsorbed on electrode, which is obtained by current contribution separation from cyclic voltammetry (CV) measurements. Activated glassy carbon (AGC) electrodes in absence and presence of adsorbed methylene blue (MB) are studied by CV, chronopotentiometry and electrochemical impedance spectroscopy. The gravimetric normalization is obtained by means of Γ * and reveals specific capacity of 41.2±1.9 mAh g −1 , around half of the theoretical for MB in 1e − -process. Finally, a comprehensive electrochemical discussion is done to assist the researcher community to improve performance metrics in supercapacitor electrodes in the presence of redox additives.

Temperature abetted synthesis of novel magnesium stannate nanoparticles assisted for nanomolar level detection of hazardous flavonoid in biological samples

Fabrication of temperature-influenced nanoparticles over the superficial region of glassy carbon electrode (GCE) stimulates the electrocatalytic activity owing to their morphology, defective sites, and higher active surface area, etc. In this regard, we have fabricated annealed magnesium stannate nanoparticles (Mg2SnO4 NPs) on GCE for nanomolar level detection of hazardous flavoring and pharmaceutical compound Rutin (RT). To analyze the impact of temperature, we have compared annealed Mg2SnO4 NPs with unannealed magnesium stannate hydrate (MgSnO3·3H2O) particles. The physicochemical properties of synthesized materials were characterized with different microscopic and spectroscopic techniques. From these studies, annealed Mg2SnO4 NPs formed purely without any flith and existence of water molecules as compared to unannealed MgSnO3·3H2O. Moreover as fabricated, Mg2SnO4 NPs/GCE outcomes with higher redox behavior compared to other electrodes in presence of RT at optimized working buffer (pH = 7.0). Interestingly, the electrode successfully established a dual wider linear response (0.062–34.8 & 34.8–346.8 µM) with a nanomolar detection limit (1 nM) and higher sensitivity. The practicability analysis of the proposed sensor also affords excellent selectivity, reproducibility, repeatability, reversibility, and storage stability. Furthermore, the real sample analysis was carried out in blood and orange samples fallout with better recovery results.

Electron transfer studies of a conventional redox probe in human sweat and saliva bio-mimicking conditions

Modern day hospital treatments aim at developing electrochemical biosensors for early diagnosis of diseases using unconventional human bio-fluids like sweat and saliva by monitoring the electron transfer reactions of target analytes. Such kinds of health care diagnostics primarily avoid the usage of human blood and urine samples. In this context, here we have investigated the electron transfer reaction of a well-known and commonly used redox probe namely, potassium ferro/ferri cyanide by employing artificially simulated bio-mimics of human sweat and saliva as unconventional electrolytes. Typically, electron transfer characteristics of the redox couple, [Fe(CN)6]3−/4− are investigated using electrochemical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. Many different kinetic parameters are determined and compared with the conventional system. In addition, such electron transfer reactions have also been studied using a lyotropic liquid crystalline phase comprising of Triton X-100 and water in which the aqueous phase is replaced with either human sweat or saliva bio-mimics. From these studies, we find out the electron transfer reaction of [Fe(CN)6]3−/4− redox couple is completely diffusion controlled on both Au and Pt disc shaped electrodes in presence of sweat and saliva bio-mimic solutions. Moreover, the reaction is partially blocked by the presence of lyotropic liquid crystalline phase consisting of sweat and saliva bio-mimics indicating the predominant charge transfer controlled process for the redox probe. However, the rate constant values associated with the electron transfer reaction are drastically reduced in presence of liquid crystalline phase. These studies are essentially carried out to assess the effect of sweat and saliva on the electrochemistry of Fe2+/3+ redox couple.

A three-dimensional model of streamer discharges in unsteady airflow

A 3D fluid model has been developed to simulate streamer discharges in unsteady airflow. The model couples the drift–diffusion equation for charged particles, the Navier–Stokes equations for air, the Poisson’s equation for the electric field, and the Helmholtz equation for photoionization. It allows us to study electrical discharges at different timescales defined by light and heavy particles and to investigate the effects of unsteady airflow. The model treats the time integration in an implicit manner to allow longer time steps, which makes the simulation of long-duration discharges feasible. Moreover, the model uses an unstructured mesh allowing the calculation around solid bodies with complex geometries, and uses adaptive mesh refinement to lower the computation time. The validity and accuracy of the model has been verified by comparing its results with published results, which compares simulations in steady air from six different streamer codes. Our results are consistent and among the most accurate in terms of charge conservation. In order to investigate the influence of wind on streamer discharges, we present results from simulation of a long-duration discharge, in which two successive positive streamers are initiated from a positive polarity electrode in presence of a transverse airflow. This simulation shows that the impact of airflow on positive streamers is driven by the ions, and therefore the airflow effects are seen in ions timescale. Interestingly, we observe that the positive streamer channel, while tilting in the direction of the wind, remains attached to the surface of the electrode. The subsequent positive streamer emerges from the charges remaining from the initial streamer, which have been moved over the electrode surface toward the trailing edge. This mechanism shows and explains the clear tilting of the successive positive streamers in the direction of the wind.