Covalent modification of glassy carbon surface with organic redox probes through diamine linkers using electrochemical and solid-phase synthesis methodologies

Various mono-Boc-protected diamines have been covalently grafted to glassy carbon electrodes by electrochemical oxidation of the free amine. After deprotection of the Boc group, anthraquinone and nitrobenzene probes were coupled to the linkers using solid-phase coupling reactions. X-Ray photoelectron spectroscopy and cyclic voltammetry were used to monitor the coupling efficiency, effect of linker length on the surface coverage and electron transfer between the attached redox probes and electrode. The anthraquinone surface coverage was found to decrease as the chain length of alkyl diamine linker increased and the electron transfer kinetics were found to be faster for the lower coverages and the longer, more flexible linkers. In the case of nitrobenzene, there was only a slightly change in coverage with increasing linker length. This electrochemical attachment of protected diamine linkers followed by solid-phase coupling provides a very versatile methodology for attaching a wide range of molecular architectures onto glassy carbon surfaces.