Adlayers of alkanedithiols on Au(111): effect of disulfide reducing agent

FERNANDO P. COMETTO; GUSTAVO RUANO; HUGO ASCOLANI; GUILLERMO ZAMPIERI

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2012

0743-7463

High-resolution photoemission spectroscopy is used to characterize adlayers of ethane-, hexane- and nonane-dithiol molecules grown on Au(111) surfaces by the immersion method. The use of reducing agents during and after the immersion to inhibit or eliminate S-S bonds is investigated. Our results demonstrate that immersion 24 h in millimolar dithiol ethanolic solutions gives rise to the formation of multilayers; this effect is more pronounced in the case of ethanedithiol, the shortest molecule. A post-treatment with a disulfide reducing agent is effective to produce monolayers of standing-up molecules; this effect is again more pronounced in the case of ethanedithiol. Finally, the immersion 24 h in a solution containing dithiol and the reducing agent gives an unexpected result: most molecules remain adsorbed in the lying-down configuration; in this case the almost complete suppression of the standing-up phase occurs equally with the three types of molecules, what suggests strongly that the formation of S-S bonds must be important for the lifting of the molecules.