Photocatalytic nanocomposite based on pyrene functionalized reduced graphene oxide in situ decorated with TiO2 nanorods

Hybrid nanocomposites based on 1-pyrene carboxylic acid (PCA) functionalized High Porous Reduced Graphene Oxide (HPRGO) sheets, decorated with oleic acid (OLEA)-coated TiO₂ nanocrystals (NCs), have been obtained by means of an in situ colloidal route, starting from titanium isopropoxide (TTIP) precursor, in presence of OLEA surfactant and trimethylamino-N-oxide dihydrate (TMAO) base catalyst. The effect of the synthesis parameters, namely the PCA-HPRGO:TTIP w/w and the OLEA:TTIP molar ratio, on the morphological, spectroscopic and structural properties of the nanocomposites, has been explored, to achieve highly crystalline TiO₂ nanostructures, with a reproducible control on morphology and crystalline phase (anatase). The TiO₂ NCs have been found to effectively heteronucleate and grow onto the –COOH groups of the PCA molecules anchoring onto the HPRGO basal plane by aromatic π-π stacking interactions. The OLEA ligand coordinating their surface endows the nanocomposites with dispersibility in organic solvents, with a morphology dictated by the PCA coordinating sites, OLEA, and the mode of the TMAO supply to the reaction mixture. A significantly higher coating density has been found for the TiO₂ in nanorods (NRs) morphology, which organize in a uniform and high packed layout onto the PCA-HPRGO basal plane. The TiO₂ NRs decorated PCA-HPRGO nanocomposites (TiO₂ NRs/PCA-HPRGO) have been tested as photocatalysts for the degradation of methyl red (MR) and nalidixic acid (NA) under UV- and solar-light irradiation. Their photocatalytic activity has been evaluated against TiO₂ reference and commercial nanostructures and discussed in terms of electronic level alignment between the hybrid nanostructure components, considering the role of the PCA anchoring molecule at the interphase.