Nanostructured Monolayers on Carbon Substrates Prepared by Electrografting of Protected Aryldiazonium Salts

The electrogeneration of aryl radicals from protected diazonium salts combined with protection-deprotection steps was evaluated to design functional monolayers on carbon substrates with a well-controlled organization at the nanometric scale. The structure of the obtained monolayer is adjusted by varying the size of the protecting group that is introduced on the precursors (trimethylsilyl, triethylsilyl, and tri(isopropyl)silyl were tested in the present study). After deprotection, a robust ethynylaryl monolayer is obtained whatever the substituent that serves as a platform to attach other functional groups by a specific click chemistry coupling step. Electrochemical and structural analyses show that the organization of the attached monolayer is totally governed by the size of the protecting group that leaves a footprint after removal but maintains a total availability of the immobilized functional groups. Properties of the monolayer (charge transfer, permeation of molecules through the layer, density of functional groups) were examined in combination with the performances for postfunctionalization taken with an alkyl-ferrocene derivative as an example of the immobilized species.