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.