We report the hydrothermal synthesis of graphene (GNP)-TiO2 nanoparticle (NP) hybrids using COOH and NH2 functionalized GNP as shape controller. Anatase was the only TiO2 crystalline phase nucleated on the functionalized GNP, whereas traces of rutile were detected on unfunctionalized GNP. X-Ray Photoelectron spectroscopy (XPS) showed C-Ti bonds on all hybrids, thus confirming heterogeneous nucleation. GNP functionalization induced the nucleation of TiO2 NPs with specific shape and crystalline facets exposed. COOH functionalization directed the synthesis of anatase truncated bipyramids, bonded to graphene sheets via the {101} facets, while NH2 functionalization induced the formation of belted truncated bipyramids, bonded to graphene via the {100} facets. Belted trunc ated bipyramids formed on unfuctionalized GNP too, however the NPs were more irregular and rounded. These effects were ascribed to pH variations in the proximity of the functionalized GNP sheets, due to the high density of COOH or NH 2 groups. Because of the different reactivity of anatase {100} and {101} crystalline facets, we hypothesize that the hybrid materials will behave differently as photocatalysts, and that the COOH-GNP-TiO2 hybrids will be better photocatalysts for water splitting and H2 production .

Composites of tin nanoparticles (Sn NP) and graphene are candidate materials for high capacity and mechanically stable negative electrodes in rechargeable Li ion batteries. A uniform dispersion of Sn NP with controlled size is necessary to obtain high electrochemical performance. We show that the nucleation of Sn particles on highly ordered pyrolitic graphite (HOPG) from solution can be controlled by functionalizing the HOPG surface by aryl groups prior to Sn deposition. On the contrary, we observe heterogeneous deposition of micrometer sized Sn islands on HOPG subjected to oxidation prior to deposition in the same conditions. We demonstrate that functional groups act as nucleation sites for Sn NP nucleation, and that homogeneous nucleation of small particles can be achieved by combining surface functionalization with diazonium chemistry and appropriate stabilizers in solution.

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Current research directions with the aim of extending the applications of titanium nitride (TiN) in areas of microelectronics, electrocatalysis, biosensors etc. require identifying new and efficient methods to modify this durable material with desired organic functionalities. We have clearly demonstrated in this work that diazonium chemistry can be considered for surface modification of titanium nitride. Indeed, a near-monolayer of aminophenylene has been reported to be spontaneously grafted onto the TiN surface by simple immersion of the substrates into an acidic solution of the corresponding diazonium cations. X-ray photoelectron spectroscopy measurements strongly suggested a covalent coating of aminophenyl groups on titanium nitride. Surface functionalization with aminophenylene layers was also investigated in presence of hypophosphorous acid and iron powder. Effect of these homogeneous and heterogeneous reducing agents with respect to the formation of aryl layers at different thicknesses was discussed in detail on the basis of conventional hemolytic dediazoniation mechanism in combination with the XPS results.The reduction of diazonium cations can be achieved by different ways such as electrochemical reduction, ultrasonication, photochemistry, microwave heating etc.

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