Electroless preparation and electrochemical behavior of a platinum-doped nickel hexacyanoferrate film–zinc modified electrode: catalytic ability of the electrode for electrooxidation of methanol

The use of a zinc substrate as an electrode and the modification of its surface by means of a thin film of platinum-doped nickel hexacyanoferrate (Pt-NiHCF) were developed. The modification conditions of the zinc surface including the electroless deposition of metallic nickel on the electrode surface from NiCl₂ solution, chemical derivatization of the deposited nickel to the NiHCF film in 0.5 M K₃[Fe(CN)₆] solution, and electrochemical penetration of metallic platinum into the modified film are described. The modified zinc electrodes prepared under optimum conditions show a well-defined redox couple due to the [Ni^IIFe^III/II(CN)₆]^1–/2– system. The effects of pH, the alkali metal cation, and the anion of the supporting electrolyte on the electrochemical characteristics of the modified electrode were studied in detail. The diffusion coefficients of hydrated alkali metal cations in the film (D), the transfer coefficient (), and the transfer rate constant for the electron (k_s) were calculated in the presence of some alkali metal cations. The electrocatalytic activity of the modified electrode for methanol oxidation was demonstrated. The stability of the modified electrode under various experimental conditions was investigated.     

One-step electrochemical synthesis of Pt–CeO2 composite thin films on a glassy carbon electrode

A Pt–CeO₂ composite thin film was prepared on a glassy carbon electrode by one-step electrochemical deposition technique. The film was constructed of Pt particles well dispersed and embedded in a porous CeO₂ substrate. The prepared Pt–CeO₂/GC electrode showed a better catalytic performance toward methanol electrooxidation compared with the bulk Pt electrode.     

Wearable electrochemical sensors for noninvasive monitoring of health—a perspective

Global problems today such as aging society and rising health costs have made preventive care and health monitoring increasingly important, so research on wearable electrochemical sensors for noninvasive monitoring of health has become very popular during the past several years. But the new technologies cannot be some dues ex machine who wrought changes overnight. Problems about fundamentals of electrochemistry under wearable conditions, software algorithms to treat signal artifacts in the real wearable detection, reliable sensors for prolonged wearable sensing in body fluid, platforms for tests of newly developed sensors, validation of test results, reproducible and standardized sampling methods, as well as clinical significance of wearable testing data still require to be addressed. The short review is not to include all important works recently published or reach any conclusion but to focus on the challenges as well as some of the promising approaches that help to overcome these challenges.     

Mediated spectroelectrochemical determination of holo-transferrin reduction potential using a flow cell with disposable screen-printed indium‑tin oxide electrode

A convenient spectroelectrochemical method for the determination of holo-transferrin reduction potential is described. All materials and accessories are commercially available and the results are in agreement with previous reports that required custom-built hardware. The method requires minimal preparation with simple sample handling, small solution volume, cost-effective electrode replacement and automated measurement. This method can easily be applied to the study of similar systems in aqueous media and might be of particular importance in the momentous field of glycomics, where large numbers of protein isoforms need to be characterized.     

What is the best definition of a liquid cluster at the molecular scale?

We investigate the ability of different cluster definitions to serve as a good reaction coordinate in molecular simulations of nucleation. In particular, the most commonly used Stillinger criterion [J. Chem. Phys. 38, 1486 (1963)] is compared with the cluster definition introduced by ten Wolde and Frenkel [J. Chem. Phys. 109, 9901 (1998)]. The accuracy of these two different cluster definitions is tested by using molecular dynamics to study the vapor-liquid nucleation of Lennard-Jones argon as a model system. We are able to compare the size of the critical cluster identified by each cluster definition with a completely model-independent value provided by the nucleation theorem, aided by a recently introduced method that accurately extracts the location of the transition state directly from the kinetics. It is found that the Stillinger definition strongly overestimates the size of small molecular clusters by up to a factor of 2. A simple change of the Stillinger radius is unable to rectify this deficiency. On the contrary, the ten Wolde-Frenkel definition, while being only slightly more elaborate than a simple Stillinger criterion, is remarkably successful in identifying the correct molecular excess of the small clusters if the parameters are chosen adequately. The method described here can also be generalized to identify a proper reaction coordinate in other activated processes.     

A survey on the effect of ionic liquid on electrochemical behavior and electrocatalytic activity of a phosphomolybdic acid-ionic liquid-MWCNT–modified glassy carbon electrode

Journal of Solid State Electrochemistry - The surface of a glassy carbon electrode modified with multi-walled carbon nanotubes (GCE/MWCNTs) was coated with a layer of phosphomolybdic acid (PMo12)...     

Application of atomic Hirshfeld surface analysis to intermetallic systems: is Mn in cubic CeMnNi4 a thermoelectric rattler atom?

The Mn atom in the cubic polymorph of CeMnNi(4) appears to be located in an oversized cage-like structure, and anomalously large atomic displacement parameters (ADPs) for the Mn atom indicate that it is a potential "rattler" atom. Here, multitemperature synchrotron powder X-ray diffraction data measured between 110 and 900 K are used to estimate ADPs for the Mn "guest" atom and the "host" structure atoms in cubic CeMnNi(4). The ADPs are subsequently fitted with Debye and Einstein models, giving Θ(D) = 301(2) K for the "host" structure and Θ(E) = 165(2) K for the Mn atom. This is higher than typical Einstein temperatures for rattlers in thermoelectric skutterudites and clathrates (Θ(E) = 50-80 K), indicating that the Mn atom in cubic CeMnNi(4) is more strongly bonded. In order to probe the chemical interactions of the potential Mn rattler atom, atomic Hirshfeld surface (AHS) analysis is carried out and compared with AHS analysis of well-established guest atom rattlers in archetypical skutterudites, MCoSb(3). Surprisingly, the skutterudite rattlers have more deformed AHSs than the Mn atom in cubic CeMnNi(4). This is related to the highly ionic nature of the skutterudite rattlers, which is not taken into account in the neutral spherical atom approach of the AHS. Additionally, visualization of void spaces in the two materials using the procrystal electron density shows that while the Mn atom is tightly fitting in the CeMnNi(4) structure then the La atom in the skutterudite is truly situated in an oversized cage of the host structure. Overall, we conclude that the Mn atom in cubic CeMnNi(4) cannot be coined a rattler.     

Aptamer-based electrochemical assay of 17β-estradiol using a glassy carbon electrode modified with copper sulfide nanosheets and gold nanoparticles,and applying enzyme-based signal amplification

Microchimica Acta - We have developed an electrochemical method for the determination of 17β-estradiol. A glassy carbon electrode was modified with a composite made from copper sulfide...     

Zinc oxide nanoparticles-based electrochemical sensor for the detection of nitrate ions in water with a low detection limit—a chemometric approach

We report for the first time a cyclic voltammetric nitrate sensor with a low detection limit based on the immobilization of zinc oxide nanoparticles on the surface of the platinum working electrode using chitosan membrane. Cyclic voltammetric data demonstrated that zinc oxide nanoparticles can electrochemically reduce nitrate ions to ammonium ions with high conductivity. In order to estimate electroanalytical parameters for each of the nitrate concentrations, Gaussian and Lorentzian curve fitting algorithms were performed on cyclic voltammetric data. Among them, the best analytical performance results were obtained with Gaussian calibration linear model. The zinc oxide modified platinum electrode showed a linear response to nitrate ions over a concentration range from 0.1 to 2.0 mM with a low detection limit and high sensitivity of 10 nM and 39.91 μA/cm² mM, respectively. The nitrate ion concentrations in drinking water samples were determined using Gaussian calibration linear model and the predicted, added nitrate ion concentration values showed good correlation.     

Synthetic boron-doped carbonado,a new electrode material: synthesis in C–metal–B growth systems aimed at the lowering of the synthesis temperature without loss of electrochemical activity

New electrode material—boron-doped synthetic carbonado (bulk polycrystalline diamond)—was synthesized at high pressures and high temperatures in the C–metal (Co, Ni, or Fe) –B growth systems. The metal borides were used as the growth medium-forming substances for graphite-to-diamond transformation at a temperature of ~?1300 °C and pressure of 8 GPa. For comparison, etalon carbonado-type electrode with nearly limiting concentration of boron in diamond was synthesized by subjecting the mixture of amorphous boron with graphite to much higher temperatures (2200–2500 °C) under the same pressure. Despite the lower content of boron in diamond synthesized in the presence of metal borides, these new boron-doped carbonado electrodes are not inferior to the etalon compact in their electrochemical activity, as judging by the onset potential of anodic chlorine evolution from KCl solution. The presence of metal-containing structural defects in boron-doped diamond matrix is supposed to be responsible for the somewhat enhanced catalytic activity of the electrodes. High-pressure synthesis of bulk metal-modified boron-doped diamond opens a new avenue in the development of superior functional electrode materials.     

909 — Controlled-potential electrolysis at a membrane-coated electrode: Part III. Effect of the electric field in the dielectric

The theoretical model for a controlled-potential electrolysis of positive ions on a plane parallel electrode coated by a permselective dielectric, presented previously, is examined further. The problem of the coupling of the flow equations with Poisson equation is treated by different possible approximations.Further calculations for some representative cases, with particular regard to negative and positive potential drops across the dielectric, are presented and discussed.     

Silver electrodeposition from water–acetonitrile mixed solvents and mixed electrolytes in the presence of tetrabutylammonium perchlorate. Part I—electrochemical nucleation on glassy carbon electrode

Nucleation and growth of silver, electrodeposited from water–acetonitrile (CH₃CN from 0 to 100% by volume) mixed solvents on glassy carbon electrodes, was studied by means of double-sweep voltammetry, current–time transients (CTT) and scanning electron microscopy (SEM). The effects of the addition of the specifically interacting tetrabuthylammonium cation were also investigated. From voltammetries, the formal potential, the nucleation potential and the cathodic current efficiency have been evaluated as a function of the mixed solvent composition. The key role on nucleation kinetics of transferring Ag⁺ from the bulk phase to the CH₃CN-enriched electrode/solution interphase has been highlighted. CTT transients were described by a model combining instantaneous and progressive nucleation mechanisms. SEM images highlighted the effects of the presence of the organic solvent, which yields to a more regular growth, and of the quaternary ammonium salt, which exhibits grain-refining properties.     

The role and fate of female electrochemists in the Soviet Union: Ol’ga Al’fredovna Songina—a pioneer of electrochemical solid-state analysis and Yevgeniya Nikolayevna Varasova—a pioneer of polarography

Women played and still play an outstanding role in the development of electrochemistry and electroanalysis at the universities and research institutes of the former Soviet Union. This paper is focussed on the life and achievements of Ol’ga Al’fredovna Songina and her contributions to the development of solid-state electroanalysis are discussed. Yevgeniya Nikolayevna Varasova, a guest scientist who worked with Jaroslav Heyrovský in Prague from 1927 to 1930 became the pioneer of polarography in the Soviet Union. She was executed during the great purges in 1938.     

The electrochemical behavior of p-benzenediol on a self-assembled monolayers Pt electrode modified with N-(2-mercapto-1,3,4-thiadiazol-5-yl)-N′-(4-substituted-arylacetyl) urea

Two novel N-(2-mercapto-1,3,4-thiadiazol-5-yl)-N′-(4-substituted-arylacetyl) urea compounds have been synthesized, characterized by NMR and MS, and used as self-assembly reagents to form self-assembled monolayers (SAMs) on Pt electrodes. The modified electrodes were characterized by electrochemical methods. The electrochemical behavior of p-benzenediol at the SAMs electrodes was investigated. It was found that the electrochemical response to p-benzenediol is controlled by diffusion and can be electrocatalyzed to obtain more symmetrical redox peaks and higher voltammetric current response at the SAMs electrodes, with a peak separation of 80 mV. For p-benzenediol the process at the SAMs electrodes is quasi-reversible with a rate constant of 0.6742 s⁻¹. The SAMs electrodes have been used to determine p-benzenediol by differential pulse voltammetry. The peak current was linear for concentrations of p-benzenediol in the range 1×10⁻⁷−5×10⁻⁴ mol L⁻¹ and the detection limit was 4.0×10⁻⁸ mol L⁻¹. The SAMs electrodes were used to determine p-benzenediol in real photographic developer and in a synthetic waste water sample; the standard addition recovery was in the range 96.6–100.4%.      

Electrocatalytic oxidation and determination of norepinephrine in the presence of ascorbic and uric acids at a poly (Evans Blue)—modified glassy carbon electrode

A sensitive and selective electrochemical method for the determination of norepinephrine using a poly (Evans Blue) film-modified glassy carbon electrode was developed. The polymer film-modified electrode shows excellent electrocatalytic activity toward the oxidation of norepinephrine (NE) in phosphate buffer solution (pH 5.0). The linear range of 5.0 × 10⁻⁷–1.8 × 10⁻⁵ M and detection limit of 3.5 × 10⁻⁸ M were observed for the determination of NE in pH 5.0 phosphate buffer solutions. The interference studies showed that the modified electrode had excellent selectivity for the determination of NE in the presence of large excess of ascorbic acid (AA) and uric acid (UA). The differences of the oxidation peak potentials for NE-AA and NE-UA were about 175 and 172 mV, respectively. The resolution is large enough to determine AA, NE and UA individually. This work provides a simple and easy approach to selective detection of NE in the presence of AA and UA in physiological samples. The article is published in the original.     

High performance and stability of double perovskite-type oxide NdBa_(0.5)Ca_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ) as an oxygen electrode for reversible solid oxide electrochemical cell

In this study,we successfully synthesized double perovskite-type oxide NdBa_(0.5)Ca_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(NBCCF) using a conventional wet chemical method as the oxygen electrode for reversible solid oxide electrochemical cells (RSOCs).The polarization resistance (R_p) of the composite electrode NBCCFGd_(0.1)Ce_(0.9)O_2 (GDC) is only 0.079Ωcm~2 at 800℃under air.The single cell based on NBCCF-GDC electrode displays a peak power density of 0.941 W/cm~2 in fuel cell mode and a low R_p value of 0.134Ωcm~2.In electrolysis cell mode,the cell displays an outstanding oxygen evolution reaction (OER) activity and shows current density as high as 0.92 A/cm~2 with 50 vol%AH (Absolute Humidity) at 800℃and applied voltage of 1.3 V.Most importantly,the cell exhibits admirable durability of 60 h both in electrolysis mode and fuel cell mode with distinguished reversibility.All these results suggest that NBCCF is a promising candidate electrode for RSOC.     

Schrödinger's What is Life?—The 75th Anniversary of a Book that Inspired Biology

In his book What is Life?—The Physical Aspect of the Living Cell, Erwin Schrödinger gives a “naïve physicist's” answer to the question “how can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?” Although his book was met with criticism from some of his colleagues, it has had a large impact and has served as profound inspiration for pioneers of molecular biology as well as for later generations of both scientists and laymen.     

Simultaneous determination of germanium,arsenic, tin and antimony with total-reflection X-ray fluorescence spectrometry using the hydride generation technique for matrix separation—first steps in the development of a new application

This paper introduces a new perspective for total-reflection X-ray fluorescence analysis (TXRF), that is the simultaneous determination of Ge, As, Sn and Sb in seawater. As is well known from atomic absorption spectroscopy (AAS) and inductively coupled plasma techniques (ICP) compounds of these elements can be reduced by sodium borohydride to their hydrides and thus separated from the matrix. In this work the hydride generation is used for matrix separation in TXRF measurements. For this purpose the following procedures are considered: (1) Preconcentration of hydrides by absorption in solvents, and evaporation of some μl of this solution on the sample carrier. (2) Decomposition of hydrides in a heated thin silica tube, or at rough and/or catalytically active surfaces, e.g. in adequately prepared columns, eluting of the species by acid and evaporation of some μl of this solution on the sample carrier. (3) Decomposition of hydrides directly on the surface of a heated silica sample carrier as a thin amorphous film. (4) Combustion of hydrides in the hydrogen flame and deposition of an elemental film on the sample carrier. Basically, all four ways have been tested and the results are promising. © 1997 Elsevier Science B.V.     

CeO<Subscript>2</Subscript> nanoparticle-modified electrode as a novel electrochemical interface in the quantification of Zn<Superscript>2+ </Superscript>ions at trace level: application to real sample analysis

A simple strategy has been proposed to quantify Zn²⁺ ions using CeO₂ nanoparticle-modified glassy carbon electrode. The CeO₂ nanoparticles were prepared by sucrose-nitrate decomposition method, and it was characterized by X-ray diffraction (XRD), FT-IR, TEM, and surface area analyzer. The synthesized CeO₂ nanoparticles were used as modifier molecules as a thin film on glassy carbon electrode (GCE) in the trace level quantification of Zn²⁺ by using cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) techniques. The fabricated sensor exhibited a good analytical response towards Zn²⁺ ions. The modified electrode showed a wide linearity in the concentration range 20–380 μg L^?1 with a limit of detection 0.36 μg L^?1. The proposed electrochemical sensor was successfully applied to trace level Zn²⁺ quantification from real sample matrices.