While highly ordered, alkyl self-assembled monolayers (SAMs) are known to block charge transfer between the underlying substrate and species in solution, structural alterations have allowed selective penetration of particular species. Self-assembled molecules with larger head-groups than the cross-section of the attached alkyl-tails have shown selectivity for small, hydrophobic molecules, whilst blocking hydrated ions such as [Fe(CN)6]3-(Peng Iet.al., 2001/2003). This selectivity has been touted as a simple yet powerful tool for applications such as chemical sensing.We propose and develop a new application for such SAMs: to functionalise electrodes in photogalvanic cells (PGs). PGs have been a promising branch of solar cell technology, where the processes of light absorption of a dye and charge transfer via mediating species, occur in the liquid phase. Although theoretically capable of efficient solar energy conversion, PGs have not yet attained this potential due to lack of selectivity of the electrodes with regard to electron transfer (Albery, 1982).Based on the work of Peng et.al., an adapted synthesis of 2-mercapto-3-n-octylthiophene was developed and used to form SAMs on gold electrode surfaces, which were investigated as electrodes for use in a photosynthetic reaction centre based PG system (described by Takshi et.al., 2010). We show the SAM to be selective for the electron accepting mediator (eg methyl viologen), while excluding electron donating mediators. Electrochemical techniques have been applied to assess the degree of selectivity, SAM stability, and reduction of protein-fouling.

Selective self-assembled monolayer functionalised electrodes for photogalvanic cells

246th National Meeting (2013)

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