One-Pot Electrografting of Mixed Monolayers with Controlled Composition

Abstract

International audienceSurface functionalization with ultrathin layers exhibiting a highly robust interface is of paramount importance for designing materials with tailored properties or operating functions, without modifying drastically the material’s bulk structures. A fine-tuning of the surface composition obtained, for instance from binary mixed layers, is also a key issue for developing high value-added applications like efficient sensors. Herein, binary mixtures of calix[4]arene-tetra-diazonium salts generated in situ from their corresponding calix[4]tetra-anilines are electrografted to form covalently bound monolayers onto substrates for yielding versatile functionalizable molecular platforms. Wettability studies, X-ray photoelectron spectroscopy analyses, and scanning electrochemical microscopy show the formation of homogeneous mixed monolayers. The distribution of the two calixarenes on the surface is directed by their relative molar fraction in the deposition solution. The strategy allows the control of the composition of mixed monolayers in a one-step approach. Postfunctionalization of the mixed layers with ferrocene centers is performed to exemplify the benefit of a dilution procedure when functional groups are introduced at the calix[4]arene small rim. This study highlights the potential of diazonium salt electrografting as a competitive alternative to chemisorption strategies such as self-assembled monolayers of alkyl thiols in the field of surface functionalization

Controlling Redox Enzyme Orientation at Planar Electrodes

“…The interest in such modifications concerns the wide range of functional groups available that are associated to high stability over a large potential window. Formation of mixed monolayers by successive electrochemical reductions from a mixture of diazonium salts presents an added advantage towards surface functionalization [109,110]. The disadvantage is the difficulty to stop the reaction at the monolayer formation.…”

Synthesis of a Calix[4]arene‐Monodiazonium Salt for Surface Modification

“…Surface modification with calix[4]arene‐tetradiazonium salts X 4 N 4 a – c , . Inset: targeted calix[4]arene‐monodiazonium salt 1 .…”

Molecular and Biological Catalysts Coimmobilization on Electrode by Combining Diazonium Electrografting and Sequential Click Chemistry

“…For that reason, the composition of the final organic layer obtained by electrografting in a potentiostatic mode is strongly influenced by the potential applied during the deposition. It is usually observed a most important surface concentration for the species which are easy to reduce even if its concentration in the starting solution is lower ,,,…”

“…Such electrografting method is based on the electrochemical generation of highly reactive aryl radicals (concerted with the loss of N 2 ), which can bind the electrode surface resulting in the formation of an organic layer covalently attached to the substrate. The method can be applied to bind various organo‐functional groups to a wide range of substrates such as carbon, silicon and metal surfaces ,. In many cases, however, the high reactivity of the aryl radicals can lead to the formation of multilayers, which can limit or even prevent electrochemical reactions due to the insulating character of the coatings, requiring a careful control of the compacting degree of the organic layer.…”

“…The introduction of multiple organic functions onto electrode surfaces is important for a variety of applications, including surface wetting, chemical sensing, biosensing and photosynthesis. Multifunctionalized surfaces can be basically prepared by electrochemical reduction of mixtures of aryl diazonium cations,,,, but this approach suffers from several drawbacks making difficult to control the composition of the final coating. For instance, one of the first detailed works concerning the electrochemical reduction of a mixture of diazonium cations concluded that the composition of the organic layer obtained was dominated by the diazonium salt easier to reduce .…”