Impact of the Diazonium Grafting Control on the Interfacial Reactivity: Monolayer versus Multilayer

A very simple strategy to prepare, in two steps, a versatile and sustainable monolayer platform for on-surface chemistry is presented. The first step consists in the electroreduction of the well-known 4-nitrobenzenediazonium in the presence of a radical scavenger, leading to a covalent monolayer surface modification. Then, a dense reactive phenylamine monolayer is obtained by the full electroreduction of the nitrophenyl moieties. The platform thus obtained is available for post-functionalization with carboxyl derivatives via a usual peptide coupling. Attachment of a TEMPO unit, offering both redox and electrocatalytic properties, validates this approach and leads to high surface coverage and fast electron transfer. A comparison of the electrochemical properties of the modified surface with a classical multilayered post-functionalized one highlights important differences in terms of interfacial reactivity. The results presented here justify the interest of preparing reactive monolayer platform for molecule grafting and opens the way for simple and controlled surface chemistry without the need of synthesis.