Symmetrical thiol functionalized polyhedral oligomeric silsesquioxanes as building blocks for LB films

Abstract

The Langmuir–Blodgett (LB) method was used for depositing cubic polyhedral oligomeric silsesquioxanes (T₈POSS) onto Au, indium tin oxide (ITO) and mica supports. Three different T₈POSS were examined; two were amphiphilic and aggregated upon transfer to a solid support, while the highly symmetric POSS (termed MP₈) gave stable and reproducible Langmuir films as studied by surface pressure and transfer ratio measurements. This was attributed to the eight identical alkanethiol groups located on each of the eight corners of the cubic like skeleton. The LB films were studied by RA-FTIR, XPS, contact angle and cyclic voltammetry. These techniques revealed the formation of a permeable, yet, stable layer. The symmetric MP₈ was utilized as a bridging building block between the support and Au nanoparticles (Au-NPs). This assembly was examined by means of AFM, SEM and anodic oxidation of the nanoparticles. An average density of 1.45 × 10⁹nanoparticles cm⁻² was obtained for the deposited Au-NPs on the MP₈ layer. Furthermore, anodic stripping voltammetry was used for studying the extraction of Hg²⁺ by the MP₈ LB film.