Electrografting of Sterically Bulky Tetramethylaniline Groups on Glassy Carbon Electrodes through Aryldiazonium Chemistry: Reasons for the Formation of Multilayers

Abstract

Within the field of electrografting with aryldiazonium cations, there are various methods available to graft a monolayer of organic groups onto electrode surfaces. One of these relies on the presence of steric groups or constraints on the aryldiazonium cation itself, which prevent multilayers from being formed by blocking access of the free aryl carbons on the grafted layer to the diazonium cations. Here, we investigate the nature of the layer formed from the electrochemical reduction of bulky 2,3,5,6‐tetramethylaniline monodiazonium cations on glassy carbon (GC) electrodes, to form 2,3,5,6‐tetramethylaniline‐modified GC (GC−TMA), which was subsequently characterized by atomic force microscopy scratching, cyclic voltammetry, electrochemical impedance spectroscopy, and X‐ray photoelectron spectroscopy. Despite the bulky structure of the TMA group, GC−TMA was found to exhibit sparse multilayers, owing to the ability of the precursor to undergo its own electropolymerization under the experimental conditions used.

Polyaniline nanowire arrays generated through oriented mesoporous silica films: effect of pore size and spectroelectrochemical response

“…2B 2 ), showing their characteristic irreversible oxidation signal around +1.0 V, 60,64 and an additional smaller one at lower potential values originating most probably from free oligomers. 65,66 Electrografting can also be performed potentiostatically, at −0.2 V for 1 min, as previously optimized. 60…”

“…First, a mesoporous silica lm made of vertically aligned hexagonally-packed nanochannels was generated by the nowadays well established EASA method, 27 involving the application of a cathodic potential likely to induce the self-assembly of cationic surfactants onto the electrode surface and concomitant gelication of the sol solution upon electrochemically triggered pH increase, leading to the growth of a silica mesopore channels network oriented perpendicularly to the underlying support. In a second step, aminophenyl groups were electrograed onto the ITO surface areas located at the bottom of the nanochannels, by reduction of the corresponding monodiazonium cations generated in situ, 60,64,65 via a mechanism given in the le bottom part of Fig. 2A.…”

“…2B 2 ), showing their characteristic irreversible oxidation signal around +1.0 V, 60,64 and an additional smaller one at lower potential values originating most probably from free oligomers. 65,66 Electrograing can also be performed potentiostatically, at À0.2 V for 1 min, as previously optimized. 60 In a third step, PANI electropolymerization was performed in an aniline solution (in H 2 SO 4 medium) and CV was used to follow the process (Fig.…”

Covalent grafting of aryls to modulate the electrical properties of phthalocyanine-based heterostructures: Application to ammonia sensing

“…The reduction peak of different aryldiazoniums varies between ca. -0.5 V and -0.65 V, which is attributed to the electronic and steric effects of the substituents present in the benzene ring [3,44]. The subsequent potential sweeps reveal progressive decrease in the reduction current intensity, indicating the passivation of the electrode surface because of coating of the organic film.…”

“…Owing to the advantages of performing electrografting directly on the electrode, this method has been exploited in multitude of application areas, such as sensors [13,14], catalysis [15,16], energy conversion and storage [17,18] and molecular electronics [19,20]. Some of these applications sought the growth of a monolayer of organic film, employing different strategies, among which those based on the control of charges consumed [21], use of bulky substituents [22,23] in the precursor aryldiazonium salt and employing radical scavenger [24], are worth mentioning. However, in some application areas, for instance in the field of chemical sensors where electrografted layer is used as a sensing material, there is always a trade-off between the fast charge transport (imparted by the thin functionalized layer) and high density of specific interaction sites (contained in a thick layer).…”