A detailed understanding of interactions between molecules and graphene is one of the key issues for tailoring the properties of graphene-based molecular devices, because the electronic and structural properties of molecular layers on surfaces are determined by intermolecular and molecule-substrate interactions. Here, we present the atomically resolved experimental measurements of the self-assembled fullerene molecules on single-layer graphene on Cu(111). Fullerene molecules form a (4 × 4) superstructure on graphene/Cu(111), revealing only single molecular orientation. We can resolve the exact adsorption site and the configuration of fullerene by means of low-temperature scanning tunnelling microscopy (LT-STM) and density functional theory (DFT) calculations. The adsorption orientation can be explained in terms of the competition between intermolecular interactions and molecule-substrate interactions, where strong Coulomb interactions among the fullerenes determine the in-plane orientation of the fullerene. Our results provide important implications for developing carbon-based organic devices using a graphene template in the future.

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Advanced oxidation processes (AOPs) involving the conjugation of H2O2 with metal oxide catalysts such as TiO2 have been studied for a long time because they enable efficient degradation of pollutants in wastewater. The combination of H2O2 and TiO2 is well known to generate oxidizing agents such as •OH and •O2 – radicals by catalytic reactions. However, the reaction mechanism for the production of these radicals is controversial. Here, we investigated the H2O2-dosed surface of rutile TiO2(110) by low-temperature scanning tunneling microscopy (LT-STM). We successfully probed the intermediate step of AOP at the single-molecule level. Ti–O–O–Ti peroxides were formed on the surface of aqueous H2O2 vapor-dosed TiO2(110), whereas H2O molecules were hardly found on the surface until the dosing concentration of H2O2 exceeded 0.04 Langmuir, although 30% aqueous H2O2 solution was used. H2O2 could be adsorbed only at the oxygen vacancy, which limited the number of Ti–O–O–Ti peroxide molecules. The formed peroxides could generate •OH radicals by further reaction with H2O molecules. Direct observation of the intermediate step of AOP upon adsorption of H2O2 molecules enabled us to understand the mechanism of the •OH radical-generating reaction.

A new photo-stimulated triboelectric generation occurring between a metal-oxide and polyimide during friction was demonstrated. The output currents of the triboelectric nanogenerator were significantly enhanced, under light illumination, up to approximately 5 times depending on the wavelength of the light, providing a new route for energy harvesting devices as well as self-powered selective photodetectors.