Associative and Proton Transfer Effects on the Voltammetric Behaviour of Chemically Grafted Films Bearing Nitrophenyl Groups

Abstract

The spontaneous decomposition of 4‐nitrophenyldiazonium tetrafluoroborate in acetonitrile solution was used to modify glassy carbon electrodes with films bearing nitrophenyl groups. The modification procedure was performed by dipping non‐connected electrodes into the nitrophenyldiazonium solution. When these modified electrodes were analyzed by cyclic voltammetry in acetonitrile containing traces of water over a wide potential scale, only one reduction wave and two oxidation peaks were observed, which is atypical considering the reversible behaviour of the reduction of nitrobenzene in acetonitrile, however in acetonitrile containing a lower concentration of water, two consecutive reduction waves appear in the same potential scale. The difference between both behaviours is consistent with the presence of water trapped into the film structure, which promotes electron and proton transfer reactions that yield nitrosobenzene as product in surface. The trapping of water inside the film structure is justified by the capability of the nitrophenyl groups to interact with water by surface hydrogen bonding interactions.

Role of the Supporting Electrolyte Ions and Additives on the Electron Transport Properties of Electrografted Films Bearing Ferrocenyl Moieties

“…The possibility to achieve or to be close to the ideal behavior seems to be dependent on how the molecules that are contained into the grafted film are reduced or oxidized. For example, for nitrophenyl groups electrografted on carbon electrodes, the voltametric reduction pattern can be easily influenced by ion‐pairing, hydrogen bonding and/or proton transfer processes with traces of water contained in the solvent (most commonly, acetonitrile) [50] . Contrary, when the grafted film bears ferrocene molecules, their oxidation is less prone to exert this kind of interactions, which give rise to a voltammetric behavior with more ideal features [16,37–44] .…”

Electrode modification by diazonium chemistry : studies on the effect of steric bulk on film thickness, and modified activated carbon cloths for energy storage

“…Although there is no universal rule for the minimum number of CV cycles required for electrografting to be deemed "complete", a common recommendation is to perform CV up until the diazonium reduction peak is no longer visible on the last cycle, as explained in the previous Section. As for scan rate, in most cases involving electrografting onto planar surfaces such as GC, the scan rate is set at a value between 50 and 100 mV s -1 , [43][44][45] with 100 mV s -1 being the most common (deviations away from this range are rare).…”