Supramolecular donor-acceptor structures via orienting predeveloped fibrillar poly(3-hexylthiophene) crystals on bared/functionalized/grafted reduced graphene oxide with novel thiophenic constituents

Reduced graphene oxide (rGO) and its derivatives functionalized with 2-thiophene acetic acid (rGO-f-TAA) and grafted with poly (3-dodecylthiophene) (rGO-g-P3DDT) and poly (3-thiophene ethanol) (rGO-g-PTEt) were prepared to design the donor-acceptor supramolecular structures based on the regioregular poly (3-hexylthiophene) (P3HT). The P3HT nanofibers, which were pre-grown in a separate system and possessed the pi-stacked P3HT backbones in the length of fibrils, were perpendicular to the rGO surface in the solution and, consequently, they inclined onto the substrate during solvent evaporation. Through this inclination, the orientation of P3HT chains changed from face-on to edge-on. In rGO-f-TAA systems, for either short (80 nm) or long (420 nm) P3HT nanofibers, the P3HT nanofibers were attached from their sides onto the rGO. The appearance of (020) and (002) spots in selected area electron diffraction (SAED) patterns proved a fixed edge-on orientation even after solvent evaporation. Functionalization of rGO surface with 2-thiophene acetic acid altered the tethering tendency of P3HT chains from the thiophenic rings to the hexyl side chains. Via grafting the rGO with P3DDT and PTEt, the tethered P3HT nanofibers were perpendicularly fixed onto its surface with a face-on orientation having (002) and (100) spots even after solvent evaporation, resulting in the conductivity range of 9.9-10.9 S/cm. The pre-developed large single crystals were also employed to construct the donor-acceptor supramolecules with edge-on oriented P3HTs. Further tethering of P3HT fibrils onto the rGO based micron sheets reflected a red-shifting and more intensified A(0-2), A(0-1), and A(0-0) peaks in the ultraviolet-visible spectra. A quenching in the photoluminescence spectra was observed in longer preparation time (18 h) based on the charge transferring from donor (P3HT) to acceptor (rGO derivatives).