We have designed a novel catechol-modified electrode that could be used for bias-assisted Michael addition at the solid/liquid interface. The glassy carbon electrode was modified by the electrochemical reduction of a catechol para-substituted phenyldiazonium salt. The electrochemistry of surface-confined catechol moieties was investigated by cyclic voltammetry. The transfer coefficient and apparent surface standard electron-transfer rate constant were obtained using Laviron's theory. We demonstrate that o-quinone moieties linked to the surface remain quite reactive with nucleophilic species by Michael addition at the solid/liquid interface. To demonstrate the versatility of this procedure, 4-nitrobenzyl alcohol, (4-nitrobenzyl)amine, and a ferrocenealkylamine were chosen as nucleophile models due to their well-known redox properties. Electrochemically triggered Michael addition was validated, leading to redox headgroup-tethered surfaces.

Grafting commercial surfactants appears to be a simple way to modify electrodes and conducting interfaces, avoiding the synthesis of complex organic molecules. A new surface functionalization route is presented to build surfactant coatings with monolayer thickness grafting molecules considered as nonreactive. A monolayer of -SOCl functions (from a p-benzenesulfonyl chloride) was first electrografted. It showed a high reactivity toward weak nucleophiles commonly found on surfactant end-moieties such as hydroxyl groups (-OH), and it was used to covalently graft the following: (1) nonionic diblock oligomers (Brij or CiEj, CH + (OCHCH)OH with x = 16 and n = 23 for Brij58, x = 16 and n = 10 for Brij C10, and x = 16 and n = 2 for Brij52); (2) poly(ethylene glycol) (PEG) short chains (PEO for (OCHCH)OH with n = 9) and mixed formula. The surface modification due to these molecular coatings was investigated in terms of wetting properties and interfacial electrochemistry characteristics (charge transfer resistivity, capacity, and ions dynamics). Built on flat and transparent thin chromium films, Brij and PEO mixed coatings have been proven to be promising coatings for electrochemical biosensor application such as for stabilizing a partially tethered supported biomimetic membrane.