Synthesis and characterization of ferracarborane–chitosan and ferracarborane–multiwalled carbon nanotube redox mediator conjugates for bioanode applications

We present the synthesis and characterization of various ferracarborane derivatives for use as electron transfer mediators in polymer-modified bioanodes. The preliminary objective is to retain the ferracarborane electron transfer mediator at the electrode interface in the polymer film, exploiting the reversible FeIII/II redox chemistry of ferracarborane sandwich complexes. Different methods of anchoring the ferracarborane in the polymer matrix have been established. The first involves covalently tethering the mediator to the polymer backbone while other methods entail the tethering of the mediator to activated multi-walled carbon nanotubes (MWCNTs). The mediator modified carbon nanotubes are then suspended in the polymer matrix. In all cases fabricated thin film electrodes were examined using cyclic voltammetry (CV). Scanning electron microscopy (SEM) images of the ferracarborane–MWCNT/chitosan films were also taken to evaluate their porosity. A comparison is made between the modes of ferracarborane mediator tethering.

Graphical abstractThe ferracarborane [Fe(3,1,2-C2B9H11)(8--3,1,2-C2B9H10] has been modified for covalent tethering to both chitosan and multiwalled carbon nanotubes and then incorporated into modified chitosan-coated glassy carbon anodes. Preliminary electrochemical experiments have established which of these two modes represents the best strategy for pursuing a polymer-modified bioanode, where the ferracarborane will act as a tethered redox mediator complex.Figure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Functionalized ferracarboranes with reversible FeIII/II redox potentials. ► Cyclic voltammagrams (CVs) and scanning electron microscopy (SEM) of polymer-modified anodes. ► Ferracarborane mediator covalently bound to activated multiwalled carbon nanotubes (MWCNTs). ► Chitosan-modified anodes incorporating the ferracarborane-MWCNT conjugate material.