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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International audienceElectrografting based on the reduction of diazonium salts has been conventionally performed at the laboratory scale with cyclic voltammetry using a typical three-electrode electrochemical system. However, this promising coating technique still needs simplification for industrial feasibility. In this work, we report that pulse potential deposition, using an only two-electrode system, is a powerful tool for the grafting through diazonium chemistry. Importantly, this method allows the covalent attachment of a 135 nm thick polyvinylpyridine-like polymeric film on a titanium nitride wafer of industrial dimensions (200 mm diameter) using an acidic solution of 4-nitrobenzenediazonium and vinylpyridine monomer. Success in grafting suitable polymer films with well-controlled thickness on real engineering materials, such as titanium nitride, opens the door for many novel applications in micro-electromechanical systems (MEMS)

Current surface modification chemistry of silicon nitride (Si3N4) in the fabrication of micro/nano systems (MEMS/NEMS) mainly relies on multistep chemical processes, essentially consisting of a surface pretreatment and a challenging silanization procedure. Although direct modification of Si3N4 surface has rarely been reported in the literature, here a simple surface functionalization strategy using diazonium chemistry in open air and at room temperature, which provides a practical solution to directly attach aminophenyl groups to pristine silicon nitride without altering its intrinsic properties, is described. These strongly grafted amine‐terminated groups are easily activated to become nuclei for initializing electroless nickel plating (autocatalytic nickel deposition). This electroless nickel plating of silicon nitride while avoiding the multiplicity and complexity of the process steps is ideal for its integration into a typical MEMS/NEMS process flow. In a possible integration scheme, due to its suitable properties, this nickel film serves as a conducting seed layer for the electrolytic deposition of copper to fill the microdevices, thereby avoids the use of typically employed expensive vacuum processes.

Accurate measurement of the mechanical properties of ultra-thin films with thicknesses typically below 100 nm is a challenging issue with an interest in many fields involving coating technologies, microelectronics, and MEMS. A bilayer curvature based method is developed for the simultaneous determination of the elastic mismatch strain and Young's modulus of ultra-thin films. The idea is to deposit the film or coating on very thin cantilevers in order to amplify the curvature compared to a traditional "Stoney" wafer curvature test, hence the terminology "micro-Stoney." The data reduction is based on the comparison of the curvatures obtained for different supporting layer thicknesses. The elastic mismatch strain and Young's modulus are obtained from curvature measurements of cantilevers before and after the film deposition. The data reduction scheme relies on both analytical and finite element calculations, depending on the magnitude of the curvature. The experimental validation has been performed on ultra-thin low pressure chemical vapor deposited silicon nitride films with thickness ranging between 54 and 133 nm deposited on silicon cantilevers. The technique is sensitive to the cantilever geometry, in particular, to the thickness ratio and width/thickness ratio. Therefore, the precision in the determination of the latter quantities determines the accuracy on the extracted elastic mismatch strain and elastic modulus. The method can be potentially applied to films as thin as a few nanometers.