Poly(brilliant green) and poly(thionine) modified carbon nanotube coated carbon film electrodes for glucose and uric acid biosensors

Poly(brilliant green) (PBG) and poly(thionine) (PTH) films have been formed on carbon film electrodes (CFEs) modified with carbon nanotubes (CNT) by electropolymerisation using potential cycling. Voltammetric and electrochemical impedance characterisation were performed. Glucose oxidase and uricase, as model enzymes, were immobilised on top of PBG/CNT/CFE and PTH/CNT/CFE for glucose and uric acid (UA) biosensing. Amperometric determination of glucose and UA was carried out in phosphate buffer pH 7.0 at −0.20 and +0.30 V vs. SCE, respectively, and the results were compared with other similarly modified electrodes existing in the literature. An interference study and recovery measurements in natural samples were successfully performed, indicating these architectures to be good and promising biosensor platforms

Influence of alloying on the passive behaviour of steels in bicarbonate medium

http://www.sciencedirect.com/science/article/B6TWS-45626G2-3/1/2e6023fd4790b792f8a205b584e0bd0

Electrochemical corrosion of magnetron sputtered WTiN-coated mild steels in a chloride medium

The electrochemical corrosion behaviour of WTiN coatings, of composition W 31, Ti 28 and N 40 at.% sputtered on carbon steel, chromium steel and high speed steel (HSS) has been investigated and the effect of the steel heat treatment on the steel/WTiN system performance explored. Open circuit potential measurements, polarisation curves and electrochemical impedance spectroscopy were used, together with X-ray diffraction and scanning electron microscopy to characterise the corroded and uncorroded coating/substrate systems. It was found that the influence of the substrate on corrosion resistance follows the order Carbon Steel<HSS<Chromium Steel. The best performance of the chromium steel/WTiN system can be associated with the higher compactness of the protective coating, since there is strong evidence that it is inert so that electrolyte penetration through the coating defects and pores is responsible for the initiation of substrate corrosion. Heat treatment of the substrate has some influence on the corrosion of the HSS/coating system, suggesting that there may be one ideal steel treatment temperature for which the coating adhesion is higher.http://www.sciencedirect.com/science/article/B6TVV-473F2MV-S/1/91525d9a77234a2d57d1825d9d68d1b

Influence of the biological fluid on the corrosion of dental amalgam

An electrochemical study of corrosion of Tytin® dental amalgam was carried out in electrolytes similar to body fluids: artificial saliva with or without lactic acid, a polymer-containing product of the same composition as Glandosane® and in Krebs-Ringer solution. The electrochemical techniques of open circuit potential, polarisation curves, cyclic voltammetry and electrochemical impedance were employed as a function of immersion time to characterise the surface processes occurring and bring out the differences between the different solutions. The influence of pH was tested in solutions of artificial saliva with or without lactic acid. The results demonstrated the importance of the organic component on the rate of corrosion and of adsorption phenomena on the amalgam surface.http://www.sciencedirect.com/science/article/B6TWS-4CBW449-2/1/0a518cbfe9cf78ca47335cef9310f2b

Polyphenazine films as inhibitors of copper corrosion

The polyphenazines poly(brilliant cresyl blue) (PBCB), poly(Nile blue A) (PNB) and poly(safranine T) (PST) have been investigated as corrosion protection films on copper electrodes by open circuit measurements, Tafel plots and electrochemical impedance spectroscopy, complemented by scanning electron microscopy. Pure copper electrodes were initially passivated in sodium oxalate or hydrogen carbonate solutions, to inhibit copper dissolution at potentials where phenazine monomer oxidation occurs, before electropolymerisation by potential cycling. The corrosion inhibition of these films was tested in 0.10 M KCl solution. It was found that, after long immersion times, the best protection efficiency was with PNB films formed on copper passivated in sodium hydrogen carbonate solution

Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol

Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5 × 10-7 to 3.5 × 10-4 mol L-1, in 0.1 mol L-1 sulfuric acid electrolyte, as well as high sensitivity, 0.110 A mol-1 L cm-2 at the optimized flow rate. A detection limit of 7.6 × 10-8 mol L-1 and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 [mu]L and a flow rate of 2.0 mL min-1. The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0 × 10-6 and 6.0 × 10-5 mol L-1 ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis.http://www.sciencedirect.com/science/article/B6THP-4RW434G-1/1/d40a3f00a2eaccb84817b064f601d0f

Design and application of a flow cell for carbon-film based electrochemical enzyme biosensors

A flow cell has been designed for use with an electrochemical enzyme biosensor, based on low-cost carbon-film electrodes. Three types of mediators were used: cobalt and copper hexacyanoferrates and poly(neutral red) (PNR), covered with glucose oxidase (GOx) immobilised by cross-linking with glutaraldehyde in the presence of bovine serum albumin or inside a oxysilane sol-gel network. Mixtures of sol-gel precursors were made from 3-aminopropyl-triethoxysilane (APTOS) together with methyltrimethoxysilane (MTMOS), methyltriethoxysilane (MTEOS), tetraethyloxysilane (TEOS) or 3-glycidoxypropyl-trimethoxysilane (GOPMOS), and the best chosen for encapsulation. Optimisation in batch mode, using amperometric detection at fixed potential, showed the PNR-GOx modified carbon-film electrodes to be best for flow analysis for both glutaraldehyde and sol-gel enzyme immobilisation. Both types of enzyme electrode were tested under flow conditions and the reproducibility and stability of the biosensors were evaluated. The biosensors were used for fermentation monitoring of glucose in grape must and interference studies were also performed.http://www.sciencedirect.com/science/article/B6THP-4M0BH9Y-2/1/306f5db86217ea276bf808fb05c0288

Highly sensitive poly(3,4-ethylenedioxythiophene) modified electrodes by electropolymerisation in deep eutectic solvents

Deep eutectic solvents are evaluated as media for the electropolymerisation of 3,4-ethylenedioxythiophene (EDOT) for the first time. PEDOT modified glassy carbon electrodes (GCEs) were characterised by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. PEDOT modified GCEs prepared from choline chloride–urea (reline) and choline chloride–ethylene glycol (ethaline) exhibited interesting electrocatalytic and morphological characteristics. Fixed potential sensing of ascorbate at 0.0 V showed a greater electrocatalytic effect, significantly higher sensitivity and lower detection limit than at hitherto reported PEDOT modified electrodes

Status of Shock Layer Radiation Validation Studies

This paper presents a status update for the shock layer radiation validation studies conducted at NASA. A review of the present capability for the simulation and validation of shock layer radiation is presented as well as providing an overview of the data obtained from the Electric Arc Shock Tube (EAST). The paper will include details covering updated convective and radiative heating correlations, provide an overview of the development of new kinetics for Mars entry and detail some recent work calculating after-body radiation. Furthermore, the paper will highlight conditions where there is high confidence in the validation of EAST data (e.g. Earth entry for speeds greater than approximately 10 kms and for many Mars entry conditions) and where further experimental data would be highly beneficial (e.g. lower speed Earth entry around 7.5 to 10 kms and higher speed CO2 entries relevant to Venus). Nominal test conditions for both Earth and Mars are provided for future potential facility-to-facility comparisons