Carbon electrode diazonium

The versatility of the method is founded on the possibility of grafting a variety of functionalised aryl groups. This allows the attachment of a wide spectrum of substances[60]. In 1992, a study by Delamar and co-workers [61] demonstrated that reduction of diazonium salts at carbon surfaces resulted in a strongly attached surface layer. They attributed this to covalent bond formation between the aryl radical and the carbon surface [61,62], One electron reduction of aryl diazonium salts at carbon electrodes leads to grafting of aryl groups to the surface. Acetonitrile is often used as the modification medium. Reduction of the diazonium salt can be achieved by cyclic voltammetry or controlled potential electrolysis. The coupling reaction is favored both by the adsorption of the diazonium prior to its reduction and by the relatively positive potential of the diazonium prior to its reduction[62],... 

The electroreduction of diazonium salts, described in Figure 9.2 and extensively used to graft hydrogenases onto electrodes, also proved to be an efficient alternative method to form covalent linkages between a model compound and a carbon electrode [27]. This was applied by Darensbourg and coworkers... 

Figure 10.4 Fabrication and measurements of molecular junction formed on PPF using diazonium chemistry, (a) Cyclic voltammo-gram measured at a PPF electrode featuring an irreversible reduction peak at approximately -0.8V that corresponds to the reduction of diazonium ions with subsequent formation of a C-C with PPF. Growth of the molecular layer results in the increased blocking of electron transfer from the electrode and gradual decrease of the peak intensity (see also Chapter 6 on carbon electrode modification), (b) AFM image of the molecular layer obtained in (a), showing that film is homogeneous, and that the thickness...

Fig. 3 Covalent attachment of functionalized aryl molecules to the surface of carbon electrodes by the electroreduction of phenyl diazonium salts in nonaqueous medium.

Electrochemically assisted modification of carbon electrodes has been accomplished by oxidation of amines (80, 81) and arylacetates (82), reduction of aryl diazonium salts (83), and anodization (oxidation) in a solution with alcohols (75). Of these schemes, reduction of diazonium salts, shown in Figure 8.11, provides a particularly convenient pathway for carbon electrode modification. 

The third method makes use of radical traps it is the most general method because it can be applied to any diazonium salt. For example, on a carbon electrode. 

The electrochemical oxidation of alkyl carboxylates is the well-known Kolbe reaction that leads to dimers. When the reaction is performed on a carbon electrode, grafting of benzyl [405-406] or alkyl [407] groups is observed (Figure 3.63). The voltammograms show an irreversible peak ( 1 V/SCE) that decreases upon repetitive scanning, as seen with diazonium salts, and the grafted electrode blocks the electron transfer of Fe(CN), clearly indicating a modification of the electrode. 

ShuL G., C. A. Castro Ruiz, D. Rochefort, P. A. Brooksby, D. Belanger. Electrochemical functionalization of glassy carbon electrode by reduction of diazonium cations in protic ionic liquid. Electrochim. Acta 106, 2013 378-385. 

Cannizzo, C., M. Wagner, J.-P. Jasmin, C. Vautrin-Ul, D. Doizi, C. Lamonronx, and A. Chauss. Calix[6]arene mono-diazonium salt synthesis and covalent immobilization onto glassy carbon electrodes. Tetrahedron Lett. 55, 2014 4315-4318. 

Fig. 2 Schematic representation of a diazonium salt grafting onto a glassy carbon electrode (GCE) upon electrochemical reduction (a), followed by clicking (b) and axial ligand attachment of a phthalocyanine to the clicked electrode (c) [16], Reproduced with permission from Ref. [16], b Shows the attachment of a substituted MPc onto a screen-printed Au electrodes (SPAuE), reproduced with permission from Ref. [12], c Shows the attachment of FePc through (A) adsorption of single-walled carbon nanotubes, (B) grafting of the GCE-SWCNT by electrochemical reduction of 4-benzeneodiazonium, (C) click chemistry with 4-ethynylpyridine and ( >) axial ligation of FePc, reproduced with permission from Ref. [17]...

Kariuki, J. K. and McDermott, M. T. 2001 Formation of multilayers on glassy carbon electrodes via the reduction of diazonium salts. Langmuir 17 5947-5951. 

POG 12] POGNON G., COUGNON C., MaYILUKILA D., et al, Catechol-modified activated carbon prepared by the diazonium chemistry for application as active electrode material in electrochemical capacitoP , ACS Applied Materials Interfaces, vol. 4, pp. 3788-3796, 2012. 

A Spectracarb 2225 carbon fabric (Engineered Fibres Technologies) was used as a basis for the synthesis of an AQ-modified carbon cloth (C-AQ) electrode. This cloth was immersed into the salt of anthraquinone-1-diazonium chloride 0.5 ZnCl2 in acetone. Then, water and 50 wt% hypophosphorous acid were added. Then, the thus-modified cloth was washed by deionized water and dried at 110°C for 20 min. 

Figure 3 Some possible routes for the covalent modification of carbon surface using (A) amino, (B) diazonium, and (C) acrylacetate based compounds. (Reproduced with permission from Zen JM, Kumar AS, and Tsai DM (2003) Recent updates of chemically modified electrodes in analytical chemistry. Electroanalysis 15 1073-1087 Wiley-VCH.)...

Bahr, J.L, Yang, J., Kosynik, D.V., Bronikowski, M.J., Smalley, R.E.,andTour, J.M. (2001) Fimctionalization of carbon nanotubes by electrochemical reduction of aryl diazonium salts a bucky paper electrode. J. Am. Chem. Soc., 123, 6536-6542. 

Arias de Fuentes, O., Ferri, T., Frasconi, M., Paolini, V, and Santucci, R. (2011) Highly-ordered covalent anchoring of carbon nanotubes on electrode surfaces by diazonium salt reactions. Angew. Chem. Int. Ed., 50 (15), 3457-3461. 

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