Covalent Sidewall Functionalization of Carbon Nanotubes by a “Formation−Degradation” Approach

Abstract

A diazonium salt-based strategy is employed to form a covalently attached multilayer of diphenyl disulfide on the surface of single-walled carbon nanotubes (SWCNTs) or multiwalled carbon nanotubes (MWCNTs). The interlayer S−S bonds are subsequently degraded reductively to produce essentially a single layer of thiophenols (or closely related derivatives) on the nanotube surface. The functionalization is achieved in what is effectively a one-pot procedure since the involved transformations are performed without intermediate workup. This “formation−degradation” modification approach is unique in the sense that it allows the generation of a thin well-defined molecular layer in spite of the involvement of highly reactive radicals in the first step. Transmission electron microscopy and thermogravimetric analyses support the approach proposed and reveal that a significant initial functionalization is achieved. In UV−vis spectroscopy, the disappearance of the Van Hove singularities of the SWCNT after the reaction is consistent with a covalent sidewall functionalization. Moreover, the resulting thin layer of thiophenols is reactive forming Au−S bonds with a macroscopic Au surface. Finally, the peripheral thiophenol groups of the MWCNT are employed as chemical linkers for anchoring gold nanoparticles and rods in a site-selective manner.

Unlocking the energy capabilities of micron-sized LiFePO4

“…It is known that when an aromatic diazonium salt (ArN 2 + X − ) is subjected to electrochemical or chemical reduction or thermal decomposition, an aryl radical (Ar · ) will form, which is reactive and is an effective agent for surface functionalization of many kinds of substrates 28 . The obtained organic layers strongly adhere to the substrates because a covalent bond is thought to form between the substrate surface and the aryl radicals 29 30 31 32 . Although most of the organic layers reported in the literatures are insulating 28 , a few of them are indeed conducting when certain diazonium precursors are used 31 33 34 .…”

Electrografting of calix[4]arenediazonium salts to form versatile robust platforms for spatially controlled surface functionalization

“…However, an undesirable counterback is the chemical inertness of these molecules, which precludes further functionalization. To remedy this problem, aryldiazonium salts bearing a pendant function masked by a protecting group exhibiting steric hinderance [28][29][30][31] and electronic shielding 29 properties have been used (Fig. 1d).…”

The Role of Aryldiazonium Chemistry in Designing Electrochemical Aptasensors for the Detection of Food Contaminants

“…Among these strategies, the most promising rely on diazonium salts bearing bulky substituents or protecting groups which can be cleaved after performing the grafting procedure. For example, the “formation–degradation” approach employs diaryl disulfide diazonium derivatives to obtain thiophenolate monolayers at various carbon surfaces, through electrochemical reduction followed by reductive cleavage of the disulfide bonds [ 170 , 171 ]. Similarly, the “protection–deprotection” approach employs diazonium salts with ethynyl substituents protected by trialkylsilyl groups, in order to obtain ethynyl-functionalized aryl monolayers after the deprotection step [ 172 , 173 , 174 ].…”