Redox-active self-assembled monolayers (SAMs) provide an excellent platform for investigating electron transfer kinetics. Using a well-defined bridge, a redox center can be positioned at a fixed ...distance from the electrode and electron transfer kinetics probed using a variety of electrochemical techniques. Cyclic voltammetry, AC voltammetry, electrochemical impedance spectroscopy, and chronoamperometry are most commonly used to determine the rate of electron transfer of redox-activated SAMs. A variety of redox species have been attached to SAMs, and include transition metal complexes (e.g., ferrocene, ruthenium pentaammine, osmium bisbipyridine, metal clusters) and organic molecules (e.g., galvinol, C
60). SAMs offer an ideal environment to study the outer-sphere interactions of redox species. The composition and integrity of the monolayer and the electrode material influence the electron transfer kinetics and can be investigated using electrochemical methods. Theoretical models have been developed for investigating SAM structure. This review discusses methods and monolayer compositions for electrochemical measurements of redox-active SAMs.
•Green and multifunctional composite film using mussel adhesive protein and graphene.•Mefp-1/graphene film provides enhanced corrosion protection for carbon steel.•Corrosion protection is due to ...interaction between graphene, Mefp-1 and Fe(III).•Graphene film shows good adhesion, lubricity and wear resistance.
A new strategy was proposed to prepare a composite film using mussel adhesive protein Mefp-1 and graphene to achieve corrosion protection and surface lubrication on carbon steel. The dispersibility of graphene in Mefp-1 solution was firstly investigated and deposition methods of Mefp-1/graphene film were proposed. In-situ confocal Raman micro-spectroscopy and electrochemical impedance spectroscopy measurements were utilized to study the corrosion inhibition effect in NaCl solution. Friction tests were conducted to study the tribological properties. Results show that the Mefp-1/graphene film exhibits strong adhesion to carbon steel, provides improved corrosion- and wear-resistance, and a significantly increased lubricity on carbon steel.
•Graphene oxide (GO) is modified by urea-formaldehyde (UF) resin via in situ polycondensation.•UF resin can perform its superior compatibility with epoxy resin to remain modified GO sheets highly ...dispersed in polymer matrix.•The modified GO sheets can significantly reinforce the anticorrosion property of epoxy coatings on carbon steel substrate.
A new type of modified graphene oxide (GO) coating was prepared by anchoring a prepolymer of urea–formaldehyde (UF) resin onto GO sheets through in situ polycondensation. The modified GO sheets were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction experiment, Fourier transforms infrared spectroscopy, sedimentation test, and electrochemical impedance spectroscopy. One major finding was that the superior compatibility of UF resin with epoxy resin retained the high dispersion of modified GO sheets in polymer matrix. Results further revealed that the modified GO sheets significantly reinforced the corrosion protection property of epoxy coatings on carbon steel substrate.
Quality control in the production of automotive Li-ion cells is essential for both safety and economic reasons. At present, as part of the production process, it is common practice to store Li-ion ...cells for up to two weeks to analyze self-discharge performance and to subject sample cells to months of cycling to assess lifetime performance. This paper presents a new state-of-the-art nondestructive testing technique for automotive scale, Li-ion batteries. Importantly, the test can discriminate between viable and nonviable cells in less than one minute. This is significantly quicker than many industrially applied techniques. The proposed method, developed in partnership with three independent original equipment manufacturer automotive Li-ion cell manufacturers, uses empirical data gathered off-line for benchmarking cell response followed by a unique targeting process to reduce the test time to a level compatible with industrial manufacturing processes. The technique used is a targeted form of electrochemical impedance spectroscopy (EIS) using a commercially available potentiostat with EIS capability. The novel aspect of the research is the treatment of off-line empirical data, the construction of an empirical library database, and the development of a reliable and robust in-line test procedure. For reasons of commercial sensitivity, no knowledge of the underlying chemistry of the cells is available for use. This demonstrates the functionality of the proposed method across a range of different cell technologies and its applicability to multiple battery technologies.
Human norovirus is one of the potential foodborne pathogens causing acute gastroenteritis, diarrhea, and food poisoning. For norovirus detection, we developed the norovirus specifically capturable ...peptides functionalized gold nanoparticles (AuNP) decorated tungsten disulfide nanoflower (WS2NF/AuNP). Based on the 3D-structured WS2NF acting as a supporting material, AuNP were immobilized on its surface to assist the conductivity of WS2NF and provide effective immobilization sites for bioreceptors. Since norovirus is composed of protein that functions as an insulant, as the virus bind with WS2NF/AuNP, the impedance is elevated by hindering the charge transfer between the working electrode and redox species (Fe(CN)63-/4-). The prepared nano-bio hybrid sensor was assessed by electrochemical impedance spectroscopic technique with spiked samples and deliberately infected oyster samples, respectively. In the case of the former, the electrochemical sensor represents a low detection limit (2.37 copies/mL) with a detection range from negative control to 104 copies/mL, and it was shown a detection limit of 6.21 copies/mL even in the oyster samples. Besides, when it applies to the different types of viruses such as rotavirus and dengue virus to verify the selectivity of this system, there were no effective signals except the norovirus. Therefore, it revealed that combining WS2NF and AuNP enhances electrochemical activity and stability via mutual synergetic effects.
•Flower-shaped WS2 (WS2NF) synthesized for electrochemical sensing.•The surface of WS2NF decorated with gold nanoparticles (AuNPs).•Norovirus-specific binding peptide on the WS2NF/AuNPs.•Low detection limit in spiked (2.37 copies/mL) and oyster samples (6.21 copies/mL).•Selective response within 60 min compared with other viruses.
The aim of this work is to fabricate polyindole (PIn) electrode electrochemically onto a graphite sheet substrate as a supercapacitor electrode. Structural, morphological and electrochemical ...properties of the prepared supercapacitor electrodes were studied and discussed. The electrochemical properties included cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), and electrochemical impedance spectroscopy (EIS) for PIn supercapacitor electrode were investigated. The scanning electron micrographs of PIn film deposited at I V and 300 s exhibited uniform and homogenous surface that contains both dense region and porous structure. The obtained results indicated that PIn supercapacitor electrode possesses high specific capacitance of 1308.60 F/g, and cycle life retention of 130% after 850 repetitive cycle. Notably, this electrode produced high energy and power densities of 356.22 Wh/kg and 700.91 W/kg.
The present work investigates the influence of Mn on the electrochemical corrosion and passivation behaviors of CoFeNiMnCr high-entropy alloys in a 0.1 M H2SO4 solution. Potentiodynamic polarization ...and electrochemical impedance spectroscopy (EIS) results showed that the addition of Mn caused a marked difference in the active dissolution regions and active-passive transition regions. It was deduced from EIS and the potential decay results that the alloyed Mn suppressed the passivation processes and increased the chemical dissolution rate of the passive films. By contrast, the alloyed Mn did not affect the protective properties of the passive films of the alloys. Surface analysis indicated that Mn addition had little influence on the composition and thickness of the passive films. Thus the passivation current densities and transpassive potentials of the CoFeNiMnCr high-entropy alloy remained almost unchanged with the addition of Mn.
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•The addition of Mn degrades general corrosion resistance of CoFeNiMnCr high entropy alloys.•The detrimental effects of Mn were caused by suppression of adsorption of oxygen or OH− and degrade the film stability.•The alloyed Mn does not affect the protective properties of passive film.
•The steel substrate was treated by a covalently modified amino functionalized graphene oxide (fGO) film.•Deposition of fGO film at the interface of steel and epoxy could effectively improve the ...adhesion strength and corrosion protection properties.•More stable and stronger interfacial bonds was obtained when treating the interface by fGO film.
This study introduces a novel surface treatment approach of steel substrate by covalent modification of graphene oxide (fGO) nanosheets with 3-aminopropyltriethoxysilane to improve the adhesion and corrosion protection properties of an epoxy coating. The effect of fGO film on the epoxy coating performance was studied by field-emission scanning electron microscopy (FE-SEM), X-Ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), Pull-off adhesion, salt spray and cathodic delamination tests. Results revealed that deposition of fGO film on steel surface can effectively improve the adhesion strength and corrosion protection properties and reduce the cathodic delamination rate of the epoxy coating.
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•A potential resolved in-situ electrochemical impedance technique was built.•The solid electrolyte interface layer still be formed and decomposed after long cycle.•The contribution of ...the interface layer compounds to impedance was distinguished.
An understanding of the formation and evolution of the solid electrolyte interface (SEI) layer is still a challenge for lithium ion batteries due to its complexity and non-uniformity. Herein, an in-situ electrochemical technique, named potential resolved in-situ electrochemical impedance spectroscopy (PRIs-EIS), have developed to correlate the Nyquist and Bode plot changes with the voltammetric scan, which is then used to determine the correspondence between circuit components and SEI layer composition. Moreover, the formation and re-oxidation of organic compounds in the SEI layer are studied in conjunction with the electrochemical quartz crystal microbalance characteristics. In particular, it is shown that more inorganic compounds accumulate in the SEI layer as the cycle continues, repairing the pore structure, but decreasing the toughness of the SEI layer. The PRIs-EIS technique is shown to be a powerful, useful and cost-effective tool to illuminate the interfacial reaction mechanism, and the results from this technique aid in the evaluation and design of electrolyte systems.
Chronobiology is defined as the temporal fluctuations occurring in the human physiology due to the circadian cycle. These fluctuations are good indicators of the functioning of the ...Hypothalamic-Pituitary-Adrenal axis (HPA axis) and can be tracked by using biomarkers: cortisol and DHEA. Low volume tracking systems will be beneficial for patients exposed to chronic stress, patients suffering from endocrine conditions manifested by circadian disruption and act as a lifestyle monitoring tool. The sensor system demonstrated in this work was an affinity-based system, characterized using EIS (Electrochemical Impedance Spectroscopy).The sensor can detect cortisol and DHEA in the physiologically relevant ranges
i.e.
8-200 ng ml
−1
and 2-131 ng ml
−1
respectively. Thus, the senor is a non-invasive, label free, cost-effective solution for tracking chronobiology for circadian diagnostics.
The work demonstrates the development of a chronobiology tracking system using an affinity-based electrochemical detection modality. This serpentine electrode based system is non-invasive, label free, and economical enabling passive sweat tracking.
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