Reaction of Gold Substrates with Diazonium Salts in Acidic Solution at Open-Circuit Potential

Abstract

The reaction of gold substrates with p-nitrobenzene diazonium tetrafluoroborate (NBD) in 0.1 M H(2)SO(4) at open-circuit potential (OCP) is demonstrated to proceed by electron transfer from gold to the NBD cation. Electrochemical, atomic force microscopy, and X-ray photoelectron spectroscopy analyses reveal the formation of multilayer films with the same composition as electrografted films. The film growth characteristics (surface concentration and film thickness vs time) also follow those observed during electrografting, consistent with electron transfer from the substrate to the diazonium cation. The OCP of the gold substrate increases during the period of film growth ( approximately 60 min) and then decreases to close to its initial value. The increase corresponds to accumulation of positive charge as electrons are transferred to NBD; the discharge process is tentatively attributed to slow oxidation of adventitious impurities in the reaction solution. Films formed at OCP or by electrografting from aqueous acid solution are markedly less stable to sonication in acetonitrile than are those electrografted from acetonitrile. Increased amounts of physisorbed material in films prepared in aqueous media or bonding of aryl groups to different gold sites in the two media are tentatively proposed to account for the different stabilities.

Spontaneous adsorbed layers of 4-nitrobenzenediazonium salt on gold and glassy carbon: Local characterization by SECM and electron-transfer kinetics evaluation

“…1b). Although the formation of an adsorbed layer was recently described during the redaction of the present contribution, through the use of classical electrochemical measurements [28], our results suggest for the first time by SECM this phenomenon in acidic aqueous solution and allow a quantitative analysis as explained below. This result can also be put in prospect with those reported in a recent study related to the observation of multi-peaks during the electrochemical reduction of NBD on gold in acetonitrile solution due to its strong adsorption on the electrode [29].…”

Diazonium-Derived Aryl Films on Gold Nanoparticles: Evidence for a Carbon–Gold Covalent Bond

“…20,26 It has also been shown that metal nanoparticles can be stabilized during synthesis by a diazonium-derived layer. 23,24 It has not yet been demonstrated that diazonium salts will spontaneously adsorb to preformed gold nanoparticles (AuNPs).…”

The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies

“…15 The aryl diazonium reduction can occur either in aqueous or organic solvents, 107 and with or without an applied potential. 96,108 As depicted in Fig. 5, formation of diazoniumbased SAMs is believed to proceed via an aryl radical intermediate, where departure of N 2 leaves an unpaired electron, followed by the formation of a covalent bond between the aryl radical and a surface atom of the substrate (aryl radical route).…”