Surface chemistry is the topic of this tutorial review. It describes the electrochemical reduction of aryl diazonium salts on carbon, silicon or metals which leads to the formation of an aromatic organic layer covalently bonded to the surface. The method which permits such a modification is set forth. The proof for the existence of the organic layer is brought forward. The grafting mechanism and the covalent bonding between the surface and the aryl group are discussed. The formation of mono or multilayers depending on the experimental conditions is rationalized. Finally some examples of the possible uses of this reaction are given.

Many applications of polymers require the functionalisation of their surface for use in sensors, composite materials, membranes, microfluidic and biomedical devices and many others.

This review is divided into two parts; the first one summarizes the main features of surface modification by diazonium salts with a focus on most recent advances, while the second part deals with diazonium-based biosensors including small molecules of biological interest, proteins, and nucleic acids.

A common strategy to enhance the fibre-to-matrix adhesion of carbon fibres is to increase the surface polarity using extensive and harsh oxidation techniques. In this work, we use a novel and scalable strategy to significantly increase the hydrophobicity of carbon fibres without any sacrifice in the fibres' physical properties and demonstrate simultaneous increases to the fibre-to-matrix adhesion (59–216%). These findings contradict the commonly accepted paradigm of high fibre polarity correlating to increased interfacial adhesion. We demonstrate the ability to covalently modify the surface of carbon fibres through electrochemical reduction of nitroaryldiazonium salts to generate perfluorinated alkyl radicals. Surface modification was confirmed by XPS, ATRIR, and TEM. The surfaces produced are highly hydrophobic, though this may be mitigated through the reduction of nitro groups to amines, or increased through the accumulative effects of perfluoroalkyl chains and nitro groups (WCA ranges from 99.9 ± 0.4° up to 135.5 ± 0.2°, versus pristine fibre 98.4 ± 0.6°). Hydrophobic fibres functionalized only with perfluoroalkyl groups were stable to both acidic (pH 1) and basic (pH 12) environments. All surface chemistries demonstrated comparable or improved interfacial shear strength and these results correlated well with calculated values of interfacial shear stress, determined via molecular dynamics simulations.