Charge mediators

A qualitatively new approach to the surface pretreatment of solid electrodes is their chemical modification, which means a controlled attachment of suitable redox-active molecules to the electrode surface. The anchored surface molecules act as charge mediators between the elctrode and a substance in the electrolyte. A great effort in this respect was triggered in 1975 when Miller et al. attached the optically active methylester of phenylalanine by covalent bonding to a carbon electrode via the surface oxygen functionalities (cf. Fig. 5.27). Thus prepared, so-called chiral electrode showed stereospecific reduction of 4-acetylpyridine and ethylph-enylglyoxylate (but the product actually contained only a slight excess of one enantiomer). 

The polyvalent nature of dendrimers has been investigated as vehicles for carrying multiple chelator groups to enhance signals in various imaging applications (Barthand Soloway, 1994 Yoo et al., 1999 Kobayashi et al., 2000, 2001 Sato et al., 2001). In addition, in certain chelate-dendrimer constructs, excess amines on the dendrimer surface can aid in the cellular uptake process through charge-mediated endocytosis. 

Story is much more complex, and that the functional effects of tail modifications depend not just on charge-mediated structural changes, but on the specific amino acids that are modified. 

Dye-sensitized solar cell — Dye cells are regenerative dye-sensitized photoelectrochemical cells. Its working principle for energy conversion is based upon photon absorption by a sensitizer with subsequent electron transfer from a photoexcited state of the sensitizer into the - conduction band of a - semiconductor, and from the semiconductor to external circuitry. A charge mediator, a suitable - redox couple is added to the cell - electrolyte for re-reducing the oxidized dye. The mediator is... 

Ostomel, T.A. et al.. Metal oxide surface charge mediated hemostasis, Langmuir, 23, 11233, 2007. 

Man-C4-ChoI choIesten-5-yIoxy-N-(4-((l- Cationic Charge-mediated In vivo Gene ... 

Figure 13-6. Electrocatalytic water oxidation utilizing a polymer-coated electrode as a ftmction of the Ru-red catalyst concentration confined in a Nafion membrane coated on an electrode. Applied potential 1.4 V vs. Ag-AgCl. (a) In the absence of amino acid model compound, (b) in the presence of 5.0 x 10" M p-cresol p-Cre), and (c) with toluene. The solid line is a simulated curve considering charge mediation, and the dashed lines are the calculated values without mediator. The dash-dotted curve (I) is a simulated curve in the presence of p-Cxt when and r

I X S, where posithely surfactant molecules interact with positively charged inorganic oxide precursor, through a negatively charged mediator (X ). 

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