INVESTIGADORES
PATRITO Eduardo Martin
artículos
Título:
Interaction of oxidized copper surfaces with alkanethiols in organic and aqueous solvents. the mechanism of Cu2O reduction
Autor/es:
C. A. CALDERÓN; C. OJEDA; V. A. MACAGNO; P. PAREDES OLIVERA; E. M. PATRITO
Revista:
JOURNAL OF PHYSICAL CHEMISTRY C
Editorial:
AMER CHEMICAL SOC
Referencias:
Año: 2010 vol. 114 p. 3945 - 3957
ISSN:
1932-7447
Resumen:
The interaction of 1-octanethiol, 1,8-octanedithiol, 1-hexadecanethiol, and
16-mercaptohexadecanoic acid with polycrystalline copper surfaces was
investigated comparatively using forming solutions with polar (0.05 M NaOH
solution) and apolar (n-hexane) solvents. The thiol layers were formed on the
freshly chemically polished copper surface as well as on the anodically oxidized
surface. The effects of the alkanethiol chain length and terminal group on the
blocking properties of the surface were investigated. We show for the first time
that compact monolayers and multilayers can be obtained from an alkaline forming
solution. Copper oxides are completely reduced in the alkaline forming solution
for all of the thiols investigated after an immersion time of 45 min. On the
contrary, the presence of a surface oxide was always detected after the
formation of the thiol layer in the n-hexane solution. The mechanism of Cu
2O reduction by thiols was investigated by means of density
functional theory calculations. The surface reactions involve the protonation of
the surface oxygen atoms of the oxide which act as Lewis base sites. In the
alkaline electrolyte, the proton transfer involves the water molecules of the
solvent, whereas in the n-hexane solution the proton transfer involves the -SH
group of the alkanethiol. The surface reactions are not the rate limiting step
because they have very low activation energy barriers. The higher reduction rate
observed in the alkaline thiol solutions is due to the high concentration of the
reacting water molecules, whereas the lower reaction rate in the n-hexane
solutions correlates with the lower concentration of the reactant alkanethiol
molecules. © 2010 American Chemical Society.