An enlarged bis-bipyridinium cyclophane-Au nanoparticle superstructure for selective electrochemical sensing applications

Highly stable electrostatically-linked superstructures of 13 nm Au-colloids have been constructed by the use of the tetracationic cyclophanes cyclobis(paraquat-p-phenylene) and cyclobis(paraquat-p-biphenylene). These architectures have been characterized by optical and electrochemical means and exhibit sensing capabilities that are shown to depend on the crosslinking cyclophane. While superstructures linked by cyclobis(paraquat-p-phenylene) sense hydroquinone derivatives and not ferrocene derivatives, those linked by the larger receptor cyclobis(paraquat-p-biphenylene) sense only the ferrocene derivatives. This high degree of selectivity is based on the topological and supramolecular fit of the analyte in the cavity of the receptor. Arrays containing both cyclophanes are shown to exhibit sensing characteristics that are dependent on the position of each cyclophane in the superstructure, possibly as a consequence of the limited porosity of the composite.