Cathodic Grafting of Alkyl Chains onto Glassy Carbon. Easy Immobilization of Ferrocene Used as Redox Probe

摘要

ω-lodo- and α,ω-dihaloalkanes, in contact with glassy carbon (GC) polarized at potentials more negative than -1.7 V vs. Ag/AgCl, can be immobilized at the electrode surface. The process, involving the cathodic charge of the graphitized zones of GC and formation of nucleophilic sites within the superficial layers of this material, is typically carried out in an aprotic organic solvent containing tetraalkylammonium salts as electrolyte. With α,ω-dihaloalkanes, the process is completed by a nucleophilic displacement reaction towards pending C-I functions left after the grafting/consumption of the first C-I group. The reaction of negatively charged carbon with bis-(ω-iodoalkyl)ferrocenes was successfully used for immobilization of ferrocenyl groups used as an efficient redox probe. The levels of surface coverage were shown to be high, with the apparent surface concentrations of ferrocene greater than 10~(-8) mol cm~(-2). The alkylferrocene layers deposited onto carbon are chemically and electrochemically stable; these new superficial structures are expected to be suitable for the use in efficient electricity storage devices.