| Popis: |
The functionalization of graphene with fluorescent molecules is a challenging issue as graphene is capable of quenching the emission. To overcome this issue we proposed molecular dyads to generate, through supramolecular chemistry and non-covalent bonding of the fluorophore, long-range, robust and ordered self-assemblies on graphene-based surfaces. To prevent surface quenching the emissive component, a perylenetetracarboxylic diimide, was placed out-of-plane with respect to the surface. Since lateral interaction between closely spaced molecules can also inhibit fluorescence, we used zinc phthalocyanine / porphyrin as molecular pedestals adsorbed in the voids of a molecular nanoporous host-guest network to ensure sufficient lateral distance between the dyads and immobilize them on graphene. We first studied the dyads in solution by titrations with NMR as well as absorption and fluorescence spectroscopy to obtain information on the dyad formation before studying them on graphene based-substrates. These supramolecular arrays of the surface-anchored fluorophore were prepared in two different ways: in our first approach (called layer-by-layer) , we initially filled the pores of the host-guest template on graphene-based substrate by drop casting the zinc phthalocyanine / porphyrin pedestals and then exposed the latter to the fluorophore. In the second approach, we assembling the dyads in solution and then drop casted the latter onto the prepatterned substrate to make the dyads fill the pores. We found that when the desired conformation of the building blocks is formed in a concentrated solution, it is also formed in the diluted solution and can be transferred to the surface by drop casting the preassembled dyad. We also demonstrated that when the pedestal and the fluorophore associate in solution in a way that prevents an upright position of perylenetetracarboxylic diimide when transferred to the surface, one can still form the desired surface conformation if one follows instead the layer-by-layer approach. |
