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

Abstract

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 of the electroreduction of 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 through the full electroreduction of the nitrophenyl moieties. The platform thus obtained is available for post‐functionalization with carboxyl derivatives through 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 in preparing a reactive monolayer platform for molecule grafting and paves the way for simple and controlled surface chemistry without the need of synthesis.

Steric and Electronic Effects of Electrochemically Generated Aryl Radicals on Grafting of the Graphite Surface

“…[24][25][26][27][28] Another approach to suppress multi-layer formation is addition of a radical scavenger during EC reduction of aryldiazonium salts. [29][30][31] Despite these studies, two aspects remain unclear. The first one is the generality of the blocking ability of simple functional groups towards multi-layer growth if they are located at the positions which are otherwise subjected to further attack by aryl radicals.…”

“…This multilayer growth and surface grafting occur in a competitive manner, resulting in a low grafting density. On the other hand, bulky tert -butyl groups at the 3,5-positions of 2b·Cl block this dendritic growth, leading to monolayer formation with remarkably high grafting density. , Similarly, other bulky groups, such as (trialkylsilyl)­ethynyl groups and an alkoxylated calixarene scaffold, are also known to block multilayer growth. − Another approach to suppress multilayer formation is addition of a radical scavenger during EC reduction of aryldiazonium salts. − …”

Control of Potential Response to Small Biomolecules with Electrochemically Grafted Aryl-Based Monolayer in Field-Effect Transistor-Based Sensors

“…In this case, a self-assembled monolayer (SAM) with thiol groups is often utilized to functionalize an Au electrode surface, as mentioned in the above paragraph. − However, thiol-derivative SAMs are formed on noble metals such as Au but not on other materials. Also, −S–Au bond cleavage occurs under UV irradiation. , On the other hand, a method of electrografting molecules to substrates such as carbon and Au films via diazonium chemistry has been reported. − An aryl diazonium salt can form strong bonds with substrates through the electroreduction of azo groups. Such an aryl-derivative film usually forms a multilayer with a random structure by a radical reaction.…”

A post-functionalization toolbox for diazonium (electro)-grafted surfaces: review of the coupling methods

“…4). 80 On a multilayer, a similar surface coverage was found, demonstrating that the coupling only occurs at the surface of the polyphenylene-like (15% coupling yield). Importantly, the surface concentration of electroactive redox centers was found strongly dependent on the scan rate for multilayer functionalized film contrary to that obtained on controlled layer, and higher electrocatalytic performances were highlighted.…”