Oligothiophene-Graphene Ensembles

The rise of graphite exfoliation pumping up graphene’s chemistry brings significant impact towards the preparation of novel hybrid materials combining the exceptional mechanical and electronic properties of graphene sheets with those of photoinduced charge transfer from organic chromophores interacting with the carbon nanostructure. Applications including charge transfer processes demand both defect-free graphene sheets and robust chemical procedures for the chemical or supramolecular grafting of the desired organic molecules onto the sp²-honeycomb lattice of graphene. Covalent chemistry of graphene leads to strong interactions between the organic material and the graphitic skeleton, however, introduces defects at the anchoring sites, thus acting as insulators. On the other hand, when supramolecular interactions are utilized to integrate organic moieties to graphene, the resulted hybrids although may suffer from the weaker π-π interactions and the subsequent release part of the organic units to the solution, the extended aromatic lattice of graphene sheets remains intact and undisrupted, as no bond formation takes place, thus allowing for ballistic transport of charges with negligible loss of energy.

Oligothiophenes in general and terthiophenes in particular, are readily accessible organic chromophores with interesting electronic properties. The stiff skeleton of oligothiophenes and the presence of the sulfur atom generate a stable π-conjugated chain, which can interact through multiple π-π stacking forces with the sp² graphene lattice.

In this frame, the ease of oligothiophenes chemical manipulation allows the preparation of oligothiophene-graphene ensembles showing enhanced solubility in organic solvents. The latter is justified due to the insertion of alkyl groups at 3' and 4' position of the thiophenes ring. Herein, the preparation of oligothiophene-graphene ensembles will be presented, followed by their full characterization through Raman and IR spectroscopy, TEM imaging and TGA analysis. Notably, our first data from the newly formed materials, based on electronic absorption, photoluminescence and electrochemistry, indicate the interaction of the organic units and the carbon allotrope under light irradiation.

Partial financial support from GSRT/NSRF 2007-2013 through action “Postdoctoral support” project GRAPHCELL PE5(2126) is acknowledged.