Corrosion Behavior of Biocompatible Stainless Steels in Physiological Medium for Non‐invasive Diagnosis of Small Fiber Neuropathies Applications

A non‐invasive device based on measurements of electrochemical skin conductance can detect small fiber neuropathy, a sweat gland dysfunction implicated in several diseases. The measurement is related to sweat composition and notably to chloride concentration. To optimize the electrode material, in vitro experiments are performed in mimetic sweat solutions. This work reports on the resistance to pitting corrosion of biocompatible stainless steels (AISI 304L, AISI 430, AISI 430T, D2205) in sweat mimicking electrolyte at pH 7 with variable chloride concentration, to determine the most sensitive material to sweat composition. AISI 430 is promising due to its high sensitivity to chloride concentration variations.     

Skin‐worn Soft Microfluidic Potentiometric Detection System

A flexible skin‐mounted microfluidic potentiometric device for simultaneous electrochemical monitoring of sodium and potassium in sweat is presented. The wearable device allows efficient natural sweat pumping to the potentiometric detection chamber, containing solid‐contact ion‐selective Na⁺ and K⁺ electrodes, during exercise activity. The fabricated microchip electrolyte‐sensing device displays good analytical performance and addresses sweat mixing and carry‐over issues of early epidermal potentiometric sensors. Such soft skin‐worn microchip platform integrates potentiometric measurement, microfluidic technologies with flexible electronics for real‐time wireless data transmission to mobile devices. The new fully integrated microfluidic electrolyte‐detection device paves the way for practical fitness and health monitoring applications.     

Electrochemical Characterization of Nickel Electrodes in Phosphate and Carbonate Electrolytes in View of Assessing a Medical Diagnostic Device for the Detection of Early Diabetes

In view of optimizing a multi‐electrode device using proprietary technology for noninvasive assessment of eccrine sweat gland activity and thus the early detection of diabetes, we thoroughly explored the electrochemical behavior of a nickel electrode in a three‐electrode set up combining a nickel counter electrode and a nickel pseudo‐reference electrode in synthetic buffered phosphate and carbonate solutions in presence of chloride, lactate and urea that mimic the composition of physiological sweat. This approach provides insight into the origin of the onset of responses measured upon the application of low voltage potential with variable amplitudes to Ni electrodes on the skin. For low voltage amplitude of ca. ΔE=0.6 V, the electrochemical reactions measured at the electrodes are those related to the oxidation of Ni leading to the formation of a passive layer, as well as the reduction of this passive layer. For voltage amplitude higher than 1 V, or current densities higher than 1 mA/cm², the breakdown of the passive layer becomes the main electrochemical anodic reaction, while its reduction and the electrolytic solution govern the cathode reactions. This brings explanation of the nonlinear current‐voltage features measured during the clinic tests. Finally, the obtained results make possible the definition of the experimental electrochemical conditions where the Ni electrodes can be renewed.     

Characterization of Electrode/Electrolyte Interface of ECIS Devices

Electric cell‐substrate impedance sensing requires low electrode/electrolyte interface impedance for effective biomedical and biophysical applications. Thus a complete understanding of physical processes involved in the formation of an electric double layer is required to design a low interface impedance device. This paper presents the numerical simulation of the impedance for the electrode/electrolyte interface of three‐electrode devices along with the practical realization for the effective workout of impedance sensing devices. The three‐electrode based impedance sensing devices along with phosphate buffered saline as electrolyte is simulated using COMSOL Multiphysics to evaluate the impedance of the electrode/electrolyte interface. Microfabrication technology is used to realize three‐electrode impedance sensing devices with diverse configuration which are used to measure the electrode/electrolyte interface impedance. The measured impedance data were then compared with the COMSOL simulated results and it is found that both the data sets fitted well with less than 5 % RSE. The results obtained from simulation and experiments indicate that the impedance due to double layer diffusion dominates in the low frequency region up to few kHz whereas electrolytic bulk resistance plays a major role in the higher frequency range. The experimental impedance data were further interpreted by electrochemical impedance spectroscopy analysis software to model the equivalent circuit of the electrochemical system.     

Electrocarboxylation of Carbon Dioxide with Polycyclic Aromatic Hydrocarbons Using Ni as the Cathode

Using Ni cathode and Al sacrificial anode, the electrocarboxylation of polycyclic aromatic hydrocarbons (naphthalene, 5‐methylnaphthalene, anthracene, phenanthrene and 1H‐indene) with carbon dioxide (4 MPa) could be successfully performed in an undivided cell containing n‐Bu₄NBr‐DMF supporting electrolyte with a constant current at room temperature, affording the corresponding trans‐dicarboxylic acids in good to excellent yields (62% –90%). Among the examined cathode materials (Ni, Pt, Ag, Cu and Zn), Ni and Pt cathodes exhibited a good catalytic activity for the electrocarboxylations. In addition, the experimental results indicated that electrolytic conditions (conducting salts, electricity, CO₂ pressure and temperature) could also affect the result of the electrocarboxylation. According to the results of the electrocarboxylations and CV (cyclic voltammetry), a possible electrochemical reaction mechanism was also proposed.     

Salt‐Based Organic–Inorganic Nanocomposites: Towards A Stable Lithium Metal/Li10GeP2S12 Solid Electrolyte Interface

Solid‐state Li metal battery technology is attractive, owing to the high energy density, long lifespans, and better safety. A key obstacle in this technology is the unstable Li/solid‐state electrolyte (SSE) interface involving electrolyte reduction by Li. Herein we report a novel approach based on the use of a nanocomposite consisting of organic elastomeric salts (LiO‐(CH₂O)_n‐Li) and inorganic nanoparticle salts (LiF, ‐NSO₂‐Li, Li₂O), which serve as an interphase to protect Li₁₀GeP₂S₁₂ (LGPS), a highly conductive but reducible SSE. The nanocomposite is formed in situ on Li via the electrochemical decomposition of a liquid electrolyte, thus having excellent chemical and electrochemical stability, affinity for Li and LGPS, and limited interfacial resistance. XPS depth profiling and SEM show that the nanocomposite effectively restrained the reduction of LGPS. Stable Li electrodeposition over 3000 h and a 200 cycle life for a full cell were achieved.     

Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures

Electrical properties of thin dielectric films at the solid‐liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co‐polymeric hydrogels of polyacrylic acid co‐sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co‐planar geometry. Silane‐modified glasses were characterized by the co‐planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger . The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint‐test cell versus this co‐planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (R_s) was a spectral feature seen only by the co‐planar hydrogel cell. Thus, it can be concluded that the use of such co‐planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.     

Electrochemical Behavior of Stainless Steels for Sudomotor Dysfunction Applications

AISI 304L is used in Sudoscan^TM technology (Impeto Medical Inc.) for the early diagnosis of small fiber neuropathy caused by type‐2 diabetes or cystic fibrosis. In a recent paper, several substitute electrodes were analyzed, among which the biocompatible nickel‐free AISI 430 appeared as an interesting material. In the present work, we compare in details the electrochemical behavior of AISI 430 with respect to the reference AISI 304L, using Electrochemical Impedance Spectroscopy (EIS) in mimetic electrolytic solutions of sweat. Apart of being cheaper than AISI 304L, AISI 430 has roughly similar characteristics but is slightly more sensitive to chloride ions concentration and, according to EIS and SEM analyses, forms a thicker, more homogeneous and protective oxide layer, which makes it a convenient electrode material.     

Fabrication and characterization of SiO2/PVDF composite nanofiber‐coated PP nonwoven separators for lithium‐ion batteries

SiO₂/polyvinylidene fluoride (PVDF) composite nanofiber‐coated polypropylene (PP) nonwoven membranes were prepared by electrospinning of SiO₂/PVDF dispersions onto both sides of PP nonwovens. The goal of this study was to combine the good mechanical strength of PP nonwoven with the excellent electrochemical properties of SiO₂/PVDF composite nanofibers to obtain a new high‐performance separator. It was found that the addition of SiO₂ nanoparticles played an important role in improving the overall performance of these nanofiber‐coated nonwoven membranes. Among the membranes with various SiO₂ contents, 15% SiO₂/PVDF composite nanofiber‐coated PP nonwoven membranes provided the highest ionic conductivity of 2.6 × 10^?3 S cm^?1 after being immersed in a liquid electrolyte, 1 mol L^?1 lithium hexafluorophosphate in ethylene carbonate, dimethyl carbonate and diethyl carbonate. Compared with pure PVDF nanofiber‐coated PP nonwoven membranes, SiO₂/PVDF composite fiber‐coated PP nonwoven membranes had greater liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO₂/PVDF composite fiber‐coated PP nonwoven membrane separators were assembled into lithium/lithium iron phosphate cells and demonstrated high cell capacities and good cycling performance at room temperature. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1719–1726     

Self-assembly preparation of mesoporous hollow nanospheric manganese dioxide and its application in zinc-air battery

In this work, mesoporous manganese dioxide with novel hollow nanospheric structure was prepared by a facile, template-free self-assembly process at room temperature in a short period of time. The product was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicate that the as-prepared material has a special mesoporous hollow nanospheric morphology and a typical composition of γ-MnO₂. Polarization curve, chronoamperometry and Tafel plot tests demonstrate that this nanostructured material has high electrocatalytic activity for the reduction of dioxygen compared to commercial electrolytic MnO₂ (EMD). Electrochemical impedance spectroscopy that was analyzed by equivalent circuit shows that as-prepared MnO₂-catalysted air electrode has a small contact resistance and ohmic resistance, a low value of electrochemical polarization resistance. An all solid-state zinc-air cell has been fabricated with this material as electrocatalyst for oxygen electrode and potassium salt of cross-linked poly(acrylic acid) as an alkaline polymer gel electrolyte. The cell has a better discharge characteristic than that of the cell employing EMD at room temperature.     

A Perovskite Electrolyte That Is Stable in Moist Air for Lithium‐Ion Batteries

Solid‐oxide Li⁺ electrolytes of a rechargeable cell are generally sensitive to moisture in the air as H⁺ exchanges for the mobile Li⁺ of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell with a solid–electrolyte separator. We report a new perovskite Li⁺ solid electrolyte, Li_0.38Sr_0.44Ta_0.7Hf_0.3O_2.95F_0.05, with a lithium‐ion conductivity of σ_Li=4.8×10^?4 S cm^?1 at 25 °C that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li⁺‐conducting polymer on its surface to prevent reduction of Ta⁵⁺ is wet by metallic lithium and provides low‐impedance dendrite‐free plating/stripping of a lithium anode. It is also stable upon contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all‐solid‐state Li/LiFePO₄ cell, a Li‐S cell with a polymer‐gel cathode, and a supercapacitor.     

Exploiting Mechanistic Solvation Kinetics for Dual‐Graphite Batteries with High Power Output at Extremely Low Temperature

Improving the extremely low temperature operation of rechargeable batteries is vital to the operation of electronics in extreme environments, where systems capable of high‐rate discharge are in short supply. Herein, we demonstrate the holistic design of dual‐graphite batteries, which circumvent the sluggish ion‐desolvation process found in typical lithium‐ion batteries during discharge. These batteries were enabled by a novel electrolyte, which simultaneously provides high electrochemical stability and ionic conductivity at low temperature. The dual‐graphite cells, when compared to industry‐type graphite ∥ LiCoO₂ full‐cells demonstrated an 11 times increased capacity retention at ?60 °C for a 10 C discharge rate, indicative of the superior kinetics of the “dual‐ion” storage mechanism. These trends are further supported by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) measurements at reduced temperature. This work provides a new design strategy for extreme low‐temperature batteries.     

Design and Performance of a New Thin‐Layer Radial‐Flow Holder for a Quartz Crystal Resonator of an Electrochemical Quartz Crystal Microbalance

A new compact holder for either 5‐ or 10‐MHz AT‐cut quartz crystal resonator of an electrochemical quartz crystal microbalance was designed, fabricated and characterized. The holder is a hydrodynamically controlled thin‐layer radial‐flow microelectrochemical cell. Its unique feature consists of (i) a micrometer‐screw adjustable distance between the movable coaxial assembly of the Ag/Ag⁺ pseudoreference electrode and the inlet capillary nozzle with respect to the metal‐film working electrode of the quartz crystal resonator, and (ii) a U‐clamp mountable resonator, easily accessible for change without using any tools. The inlet solution stream is centered axially against the working electrode. The holder performance was tested under different flow conditions. These include hydrodynamic voltammetry measurements on the Fe(CN) /Fe(CN) couple, i.e., a redox system with no mass transfer across the solution–electrode interface, as well as simultaneous chronoamperometry and chronoelectrogravimetry measurements under flow injection analysis (FIA) conditions on the Ag/Ag⁺ couple, i.e., a system with electrodeposition of a rigid metallic film. Moreover, simultaneous changes of resonant frequency and dynamic resistance were measured under FIA conditions for a glycerol solution, i.e., an electroinactive viscous medium. For the 30<F_m<180 μL min^?1 volume flow rate of solution and 50<d<250 μm nozzle‐to‐resonator distance, the holder operates in a thin‐layer radial‐flow regime at a fully developed laminar flow. For F_m=30 μL min^?1 and d=100 μm, both mass and charge conversion accompanying silver electrodeposition is appreciably high and close to 35%. Simultaneous measurements of the resonant frequency change and current‐potential or current‐time transients allowed investigations of electrochemical processes involving mass changes of rigid deposits while those of the frequency change and dynamic resistance change involve changes of viscoelastic properties of medium.     

Electrochemical characterization of hydrogels for biomimetic applications

Hydrogels are increasingly being recognized as having potential in bio‐compatible applications. In previous work, we investigated the feasibility of poly(ethylene glycol)‐dimethacrylate (PEG‐1000‐DMA) and poly(ethylene glycol)‐diacrylate (PEG‐400‐DA) polymerized using either a chemical initiator (C) or a photoinitiator (P) to encapsulate and stabilize biomimetic membranes for novel separation technologies or biosensor applications. In this paper, we have investigated the electrochemical properties of the hydrogels used for membrane encapsulation. Specifically, we studied the crosslinked hydrogels by using electrochemical impedance spectroscopy (EIS), and we demonstrated that chemically crosslinked hydrogels had lower values for the effective electrical resistance and higher values for the electrical capacitance compared with hydrogels with photoinitiated crosslinking. Transport numbers were obtained using electromotive force measurements and demonstrated that at low salt concentrations, both PEG‐400‐DA‐C and PEG‐400‐DA‐P hydrogels presented an electropositive character whereas PEG‐1000‐DMA‐P was approximately neutral and PEG‐1000‐DMA‐C showed electronegative character. Sodium transport numbers approached the bulk NaCl electrolyte value at high salt concentrations for all hydrogels, indicating screening of fixed charges in the hydrogels. The average salt diffusional permeability 〈P_s〉 and water permeability 〈P_w〉 were found to correlate with EIS results. Both PEG‐1000‐DMA‐C and PEG‐400‐DA‐C had higher 〈P_s〉 and 〈P_w〉 values than PEG‐1000‐DMA‐P and PEG‐400‐DA‐P hydrogels. In conclusion, our results show that hydrogel electrochemical properties can be controlled by the choice of polymer and type of crosslinking used and that their water and salt permeability properties are congruent with the use of hydrogels for biomimetic membrane encapsulation. Copyright © 2011 John Wiley & Sons, Ltd.     

Ferrocenylethynyl‐Terminated Azobenzenes: Synthesis,Electrochemical, and Photoisomerization Studies

Ferrocenylethynyl‐terminated derivatives 8 – 12 have been synthesized and characterized by electrochemistry and UV/Vis spectroscopy. The electrochemical and photophysical studies indicate that the electronic communication in ferrocenylethynyl‐substituted derivatives is strongly influenced by the substituted position of the ferrocenylethynyl moiety. In situ electrochemical oxidation or chemical oxidation caused a characteristically weak ligand‐to‐metal charge‐transfer (LMCT) band to appear at 700–1000 nm. Subsequent electrochemical reduction or chemical reduction recovered the most of the original curve and the color of the solution as well. Among the derivatives, compound 8 exhibits the highest cis/trans molar ratio (64:36) in the photostationary state (PSS) upon light irradiation at 365 nm. Compound 8 exhibits excellent fatigue resistance and reversibility under several repeated reversible isomerization cycles.     

Investigation of Water-Soluble Binders for LiNi0.5Mn1.5O4-Based Full Cells

Two water-soluble binders of carboxymethyl cellulose (CMC) and sodium alginate (SA) have been studied in comparison with N-methylpyrrolidone-soluble poly(vinylidene difluoride–co-hexafluoropropylene) (PVdF-HFP) to understand their effect on the electrochemical performance of a high-voltage lithium nickel manganese oxide (LNMO) cathode. The electrochemical performance has been investigated in full cells using a Li₄Ti₅O₁₂ (LTO) anode. At room temperature, LNMO cathodes prepared with aqueous binders provided a similar electrochemical performance as those prepared with PVdF-HFP. However, at 55 °C, the full cells containing LNMO with the aqueous binders showed higher cycling stability. The results are supported by intermittent current interruption resistance measurements, wherein the electrodes with SA showed lower resistance. The surface layer formed on the electrodes after cycling has been characterized by X-ray photoelectron spectroscopy. The amount of transition metal dissolutions was comparable for all three cells. However, the amount of hydrogen fluoride (HF) content in the electrolyte cycled at 55 °C is lower in the cell with the SA binder. These results suggest that use of water-soluble binders could provide a practical and more sustainable alternative to PVdF-based binders for the fabrication of LNMO electrodes.     

High‐Activity PtRuPd/C Catalyst for Direct Dimethyl Ether Fuel Cells

Dimethyl ether (DME) has been considered as a promising alternative fuel for direct‐feed fuel cells but lack of an efficient DME oxidation electrocatalyst has remained the challenge for the commercialization of the direct DME fuel cell. The commonly studied binary PtRu catalyst shows much lower activity in DME than methanol oxidation. In this work, guided by density functional theory (DFT) calculation, a ternary carbon‐supported PtRuPd catalyst was designed and synthesized for DME electrooxidation. DFT calculations indicated that Pd in the ternary PtRuPd catalyst is capable of significantly decreasing the activation energy of the C? O and C? H bond scission during the oxidation process. As evidenced by both electrochemical measurements in an aqueous electrolyte and polymer‐electrolyte fuel cell testing, the ternary catalyst shows much higher activity (two‐fold enhancement at 0.5 V in fuel cells) than the state‐of‐the‐art binary Pt₅₀Ru₅₀/C catalyst (HiSPEC 12100).     

A Plastic–Crystal Electrolyte Interphase for All‐Solid‐State Sodium Batteries

The development of all‐solid‐state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. Comparison of solid‐state sodium cells with 1) solid electrolyte Na₃Zr₂(Si₂PO₄) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all‐solid‐state battery cells.     

以镍为阴极由二氧化碳与芳香酮电合成α-羟基羧酸

室温下,在一室电解池中,以n-Bu4NBr-DMF作电解质、镍为阴极、铝为阳极,恒电流电解二氧化碳与芳香酮（苯乙酮、对二苯甲酮、6-甲氧基-2-萘乙酮、4-甲基苯乙酮和4-甲氧基苯乙酮）,可以得到相应的α-羟基羧酸（产率56%-90%）。实验结果显示,阴极材料、芳香族酮的结构以及电解条件（如电量、底物浓度、导电盐、溶剂和二氧化碳压力等）对目标产物的产率有很大影响;反应系统中质子剂（水）的存在将导致副产物频哪醇的生成。本文还根据循环伏安实验和合成实验结果简要地讨论了反应机理。     

Detection of Aluminum Chlorohydrate Content in Antiperspirant Deodorants Using Screen‐Printed Silver Electrodes by One Drop Analysis

Aluminum chlorohydrate (Al₂(OH)₅Cl?2H₂O, ACH) is an active ingredient in many antiperspirants and deodorants formulation to reduce the body odors (mainly sweat) through interaction with apocrine sweat glands to produce insoluble aluminum hydroxide and free chloride, which then plugs the sweat gland that stops the flow of sweat to the skin's surface. We demonstrated here an one drop (50 μL) electrochemical sensing of the ACH using an in‐built three screen‐printed electrodes assembly containing Ag as working and pseudo reference and carbon as counter electrode system (AgSPE). The free Cl^? ion librated from ACH/H₂O reaction was detected at AgSPE surface at 0.072 V vs. pseudo Ag reference electrode system in pH 2 phosphate solution by Cyclic voltammetric Technique. Under optimal working condition the AgSPE shows a linear calibration plot in the window of 30–2000 ppm of ACH with sensitivity and regression values of 0.104 μA/ppm and 0.998 respectively. Calculated detection limit is 3.03 ppm. RSD values of intra‐ and interassays were 0.19% and 2.79% respectively. Finally, real sample (antiperspirant deodorant lotions) assays were successfully demonstrated with results comparable to the predicted values.