Nanostructured Au platforms for devices based on self assembled molecular systems.

EMILIANO CORTÉS, ALDO A. RUBERT, GUILLERMO BENITEZ, PILAR CARRO, MARIA E. VELA AND ROBERTO C. SALVAREZZA.

S. C. de Bariloche

Workshop; NANOMAT 09 US-Argentina Workshop on Nanomaterials; 2009

Self-assembled monolayers (SAMs) on solid surfaces are key elements for many promising applications in the wide field of nanoscience and nanotechnology. SAMs of thiols on metals surfaces are the most popular because they can be easily prepared in gas or liquid phases forming high-quality close packed organic layers of controlled thickness and functionality. Thiols on Au surfaces have been proposed as basic units in molecular electronics, as building blocks in sensing and bio-recognition devices, in actuators, molecular motors, and biomimetic phospholipid membranes among others. However, oxidation of thiolate-Au bonds in ambient conditions and liquid environments seriously limits the fabrication of thiol-based devices. Here we demonstrate that nanostructured gold exhibits higher resistance to thiolate oxidation and increased electrochemical stability against thiolate desorption in relation to polycrystalline preferred oriented Au(111). In particular, we demonstrate that alkanethiolate SAMs on these nanostructured substrates formed by small sized columns (10-20 nm diameter, 400-500 nm in length) resist more than 6 weeks without significant thiolate oxidation. In contrast polycrystalline preferred oriented Au(111) loss 40% of the alkanethiolates as alkyldisulfides in only two weeks. The increased stability can be related to the presence of large number of defects such as adatoms, vacancies and steps where the thiolate binding energy is stronger than at terraces. The nanostructured Au is an interesting platform because can be easily prepared, it has SERS activity, and exhibits high signal/noise ratio for amperometric detection due to its large real surface area.