STUDIES OF THE ELECTROCHEMICAL REMOVAL AND EFFICIENT RE-FORMATION OF A MONOLAYER OF HEXADECANETHIOL SELF-ASSEMBLED AT AN AU(111) SINGLE-CRYSTAL IN AQUEOUS-SOLUTIONS
Df. Yang et al., STUDIES OF THE ELECTROCHEMICAL REMOVAL AND EFFICIENT RE-FORMATION OF A MONOLAYER OF HEXADECANETHIOL SELF-ASSEMBLED AT AN AU(111) SINGLE-CRYSTAL IN AQUEOUS-SOLUTIONS, Langmuir, 13(2), 1997, pp. 243-249
The electrochemistry of a hexadecanethiol monolayer deposited on a Au(
111) single crystal electrode has been examined in electrolyte solutio
ns of different pH values, and it has been found that a significant fr
action of the hexadecanethiol monolayer can be electrochemically remov
ed and redeposited repetitively from the Au(111) surface. We suggest t
hat this behavior is caused by the low solubility of the reduced molec
ules which prevents their diffusion into the bulk of the solution. The
solubility of the thiol is confirmed to be a most important factor in
the oxidative redeposition process by identical experiments performed
on butanethiol and nonanethiol layers which show a decrease in the ox
idative redeposition with the increasing solubility of the thiol. Prel
iminary work suggests that surface roughness may also play a part in i
nfluencing the extent of oxidative redeposition, with smoother surface
s giving more redeposition. The reductive desorption/oxidative redepos
ition of hexadecanethiols in an aqueous solution of high pH (0.5 M KOH
) consists of two distinct processes. This is suggested to arise from
the presence of domains of thiols of different ionic permeabilities.