Electrode surface coatings

The peculiar electrochemical behaviour of electrode surfaces coated with a layer of phosphatidylcholine (PC) adds a new dimension to the practical applications of this type of sensor as it enables development of electrochemical processes within a lipid layer. Redox-active amphiphiles readily... 

In MIP chronoamperometric sensors, current due to diffusion of the analyte towards the electrode surface, coated with the recognition MIP material, is measured at a constant applied potential. The MIP film used for that purpose must be sufficiently permeable in order to allow for unhindered diffusion of the analyte. The measured current is directly proportional to the concentration of the analyte and depends upon the rate of the analyte diffusion towards and, in some cases, away from the electrode surface. The analyte determination involves a preliminary step of removal of the template from the MIP film. 

Chronoamperometric transduction can be applied to electroinactive analytes as well as electroactive, which are sorbed by the MIP film and then undergo an electrochemical reaction [25]. In the latter case, the analyte should be able to diffuse freely both towards and away from the electrode surface for the current to flow. The primary requirement of chronoamperometric sensing is a linear relationship between the current measured at the constant potential and the concentration of the analyte. Moreover, the electrochemically generated species should readily diffuse away from the electrode surface coated by the sensing film. By way of example, a few representative chronoamperometric sensors based on MIPs are presented below. 

The major limitation of present fuel cells is that the rates of the electrode reactions, especially the one in which oxygen is reduced, tend to be very small, and thus so is the output current per unit of electrode surface. Coating the electrode with a suitable catalytic material is almost always necessary to obtain usable output currents, but good catalysts are mostly very expensive substances such as platinum, so that the resulting cells are too costly for most practical uses. There is no doubt that if an efficient, low-cost catalytic electrode surface... 

The pH value of aqueous suspensions should be taken at a given temperature and only after settling equilibrium has been reached, to minimize pH drift and electrode surface coating with suspended particles. Electrolyte should not be added to the external phase of the suspension to stabilize the pH, because neutral electrolytes disturb the physical stability of the suspension. 

Fig. 4 The marker oxidation at the surface of an oriented monolayer of Receptor 1 (a) oxidation of [Fe(CN)6] at the electrode surface coated with a monolayer of Receptor I in the absence of analyte anions (b) oxidation of [Fe(CN)6] is hampered by the binding of the phosphate ion to the monolayer. (From Ref [14].)...

Figure 6.10 Current—potential curves at the disk electrode (below the x-axis in each figure) and the current at the ring electrode (Pt) (above the x-axis in each figure), recorded in Oa-saturated 1.0 mol dm KOH aqueous solution at different electrode-rotating rates. Disk electrode surface coated with a layer of (A) W2C/C, (B) Ag/C, (C) Ag-W2C/C, or (D) Pt/C. Potential scan rate 5 mV s ring potential fixed at 0.474 V vs Hg/HgO, and ring collection efficiency 20%. The insets present the Koutecky—Levich p ols of the disk electrode at different potentials. (For color version of this figure, the reader is referred to the online version of this book.)...

Electrochromic devices (ECDs) consist of a two-electrode electrochemical cell. They include an ion-conducting liquid or solid electfolyte medium sandwiched between two electrode surfaces coated with organic or inorganic electrochromic materials, chosen for their electrical and optical properties. Their purpose is the generation of a variable-color system that can be changed in a controllable fashion for potential applications as displays, smart windows or in other technologies. 

Oyama and F. C. Anson, Electrostatic binding of metal complexes to electrode surfaces coated with highly charged polymeric film, J.Electrochem.Soc., 127 247 (1980). 

Herlem G et al (2001) pH sensing at Pt electrode surfaces coated with linear polyethylenimine from anodic polymerization of ethylenediamine. J Electrochem Soc 148(11) E435-E438... 

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