INVESTIGADORES
PATRITO Eduardo Martin
congresos y reuniones científicas
Título:
Formation of Surface Disulfide Bonds in Self Assembled Monolayers of alcanedithiols. Influence of the Forming Solution.
Autor/es:
C. A. CALDERÓN; F. P. COMETTO; V. A. MACAGNO; E. M. PATRITO
Lugar:
Niza
Reunión:
Congreso; The 61st Annual Meeting of the Internaternational Society of Electrochemistry; 2010
Institución organizadora:
Internaternational Society of Electrochemistry
Resumen:
a,w-alcanedithiol
self assembled monolayers (SAMs) prepared by the immersion method in millimolar
dithiol solutions have reductive desorption charges which are higher than the
charges of the corresponding monothiols
[1, 2]. We have attributed the extra reduction charge of the dithiol SAMs to the reduction of intralayer
disulfide bonds at the SAM/electrolyte interface [2]. The breakage of S-S bonds
and S-Au bonds seem to occur at the same electrode potential. The presence of
surface disulfide bonds are expected to disorder the monolayer structure and
this was confirmed by STM measurements which showed no structure on the
nanoscale [3]. Based on density functional theory calculations we predicted
that the surface concentration of disulfide bonds should decrease with the
increase in the alkyl chain length [2]. The key role of the chain length and
the preparation procedure in the surface structure and chemistry of SAMs of
dithiols on Au(111) were reported recently [4,5].
In this work we
employed reductive desorption experiments and electrochemical impedance
spectroscopy to characterize the amount of surface disulfides and the integrity
of SAMs of dithiols prepared under different experimental conditions.
The monolayer
formation was investigated in polar and apolar solvents, in the presence and
absence of O2 and using different disulfide reducing agents (TCEP,
DTT and bME) in the forming solution. All investigations were performed for
alkanedithiols of different chain lengths. Reducing agents were employed during
and after the formation of the SAM. Optimal experimental conditions were found
for the formation of dithiol SAMs with no disulfide bonds for both short and
long alkyl chains.