Fabrication of phase-separated multicomponent self-assembled monolayers at gold nanoparticles electrodeposited on glassy carbon electrodes

This study aims at the fabrication of ternary self-assembled monolayers (ternary SAMs) composed of three kinds of thiol molecules with different lengths and different terminal function groups via a chemisorption on different domains of Au nanoparticles electrodeposited onto glassy carbon (GC) electrodes. The composition, domain size, and the surface concentration of each thiol molecule of the phase-separated ternary SAM are shown to be controllable. That is, the functionalization of the GC electrode (through the SAMs attachment) is composed of two consecutive processes, i.e., the electrodeposition of the Au nanoparticles followed by the fabrication of the SAM of a given thiol molecule. This electrodeposition-SAM formation process was repeated three times to fabricate phase-separated ternary SAM. The ternary SAM was composed of an unreactive methyl groups terminated long chain hydrophobic n-alkylthiol (1-dodecanethiol, DDT), a reactive amino-group terminated thiol (11-amino undecanethiol, AUDT), and a reactive carboxylic acid group terminated short chain thiol (3-mercaptopropionic acid, MPA). The ternary SAM-modified GC electrode was further functionalized by confining an electroactive molecule having a redox center (i.e., aminoferrocene, AFc) via the covalent attachment to the carboxylic acid group of the MPA moiety of the ternary SAM. The molecular-level control of the structure of the SAMs formed on the different Au nanoparticles domains is a promising criterion that could be utilized to fabricate multifunctional nanoparticles-based electrodes, for example, to analyze several bioactive species. (c) 2006 The Electrochemical Society.