Electrografting and Controlled Surface Functionalization of Carbon Based Surfaces for Electroanalysis

Abstract

The basic concepts of electrografting on carbon surfaces are reviewed with the emphasis on the prospects of achieving robust, well‐defined compositions and structures of electrode interfaces. The surface functionalization allows tuning the interfacial properties which play an important role in various electrochemical applications, such as sensors and biosensors. Covalent attachment of organic compounds can be achieved by means of the electrochemical reduction of diazonium salts, and oxidation of amine or carboxylate. This review also demonstrates that the electrografting followed by a post‐functionalization is an interesting approach in the designs of well‐defined interface for electrochemical (bio)sensing.

Methodologies for “Wiring” Redox Proteins/Enzymes to Electrode Surfaces

“…Diazonium electrode modification is not entirely without challenges. Multilayer formation can occur when further aryl radicals attack the unsaturated bonds of the aromatic π systems of the original monolayer, resulting in carbon−carbon bonds . Alternatively, multilayers can arise from diazonium cations coupling to surface phenyl groups through azo bond formation .…”

“…Multilayer formation can occur when further aryl radicals attack the unsaturated bonds of the aromatic p systems of the originalm onolayer,r esulting in carbonÀcarbon bonds. [144,[151][152][153] Alternatively, multilayersc an arise from diazonium cations coupling to surfacep henylg roups througha zo bond formation. [144,[151][152][153] Both modes of multilayer formation can contribute to the build-up of an amorphous, organic, insulating layer on the surface of the electrode.…”

“…[144,[151][152][153] Alternatively, multilayersc an arise from diazonium cations coupling to surfacep henylg roups througha zo bond formation. [144,[151][152][153] Both modes of multilayer formation can contribute to the build-up of an amorphous, organic, insulating layer on the surface of the electrode. [144,[151][152][153] Methodologies to prevent or minimalize multilayer formation have been reported, such as the use and subsequent cleavage of bulky protecting groups, [154] sterically hindering the 3,5-positionso f the aryl diazonium salt, [155] and addition of the radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) to quenche xcess aryl radicals.…”

“…[144,[151][152][153] Both modes of multilayer formation can contribute to the build-up of an amorphous, organic, insulating layer on the surface of the electrode. [144,[151][152][153] Methodologies to prevent or minimalize multilayer formation have been reported, such as the use and subsequent cleavage of bulky protecting groups, [154] sterically hindering the 3,5-positionso f the aryl diazonium salt, [155] and addition of the radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) to quenche xcess aryl radicals. [152,153] In the contexto fb ioelectrochemistry,d iazonium electrode modifications can be used to induce protein adsorption through non-covalent interactions in as imilar manner to that achieved using unmodified PGE or SAMs on gold.…”

“…Surface functionalizations trategy [a] References a) i) R = COOH [167] ii)R= CH 2 COOH [168] iii)R= CH=CHCOOH [169] iv) R = NO 2 [69,[170][171][172]175] v) R = NH 2 [176] b) [69,[170][171][172]175] c) [69] d) [156][157][158][159] e) [156] f) [ with electrochemical reduction being used to reduce the nitro "headgroups" into the desired amine functionalities in ap ostdiazonium crosslinking step. [151,158,159] The introduction of more reactive alkyl amine groups to electrode surfaces through diazonium modification can be achieved through the use of the 4-aminoethylbenzenediazoniumc ation, [178] or phthalimide-protected alkylamine functionalities. [154] Amide bond formation strategies have been used in the fabrication of many mediator-free biosensors;E DC/NHS-activated tyrosinase was crosslinkedt oa minophenyl groups on BDD electrodes and used to detect phenolic compounds.…”