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Searching for new protocols aimed at the surface functionalization of TMDCs is the password for filling the gap between reactivity and versatility of 2D carbon-based networks and their inorganic counterparts. This contribution describes a straightforward but effective approach to the chemical decoration of chemically exfoliated MoS2 nanosheets with ß-hydroxyl organic pendant arms. The adopted strategy is based on the thiol-epoxide "click"reaction and generates functional hybrids with a loading of dangling organic groups directly proportional to the epoxide electrophilic character. Most importantly, this grafted methodology occurs for the first time on both phases (1T and 2H) of the model chalcogenide and provides functional samples suitable for an additional functionalization step-forward (post-derivatization).

Here we optimized the electrophoretic deposition process for the fabrication of WS2 plasmonic nanohole integrated structures. We showed how the conditions used for site-selective deposition influenced the properties of the deposited flakes. In particular, we investigated the effect of different suspension buffers used during the deposition both in the efficiency of the process and in the stability of WS2 flakes, which were deposited on an ordered arrays of plasmonic nanostructures. We observed that a proper buffer can significantly facilitate the deposition process, keeping the material stable with respect to oxidation and contamination. Moreover, the integrated plasmonic structures that can be prepared with this process can be applied to enhanced spectroscopies and for the preparation of 2D nanopores.

The heterogenation of molecular catalysts on solid supports is a viable route for the preparation of hybrid materials that combine the high selectivity and activity of homogeneous active species with the enhanced stability and recyclability imparted by the heterogeneous nature of the support. In this work we describe the covalent functionalization with ferrocene (Fc) of two graphene derivatives: graphene acid (GA), a graphene layer whose basal plane is modified with COOH groups, and graphene oxide (GO). The surface modification is performed exploiting the carbodiimide chemistry, which allows introducing up to 3.6% at. of iron in the GA-based material. Compared to GO, GA owns a superior functionalization degree, which is attributed to its controlled surface chemistry. Both Fc-modified materials are tested as catalysts in the CeH insertion of diazonium salts employing arene substrates. The materials are active, versatile and recyclable catalysts that show a catalytic performance comparable to or even better than molecular Fc, together with a 100% recyclability which does not alter the catalytic performance. The GA based hybrid catalyst results more active than that based on GO due to the presence of more extended aromatic domains that facilitate the adsorption of the reagents close to the active sites.

This Ph.D. project is aimed to discover new strategies to develop materials to utilize in the fields of Green Energy and Green Chemistry and it was directed at the application of 2D Materials in particular. This thesis is divided into five main chapters where we presented five exemplary systems in which we focused our attention on different aspects of materials design. Each chapter comprises an introduction and a conclusion section, in which we tried to go into the details of each targeted application and of the specific design strategy employed. However, at the beginning and at the end of the thesis, the reader can find an Introduction and a Conclusion section where we tried to collocate the goals and challenges of this work within a broader context of materials science and catalysis/electrocatalysis. In our studies in the Green Energy area, we focused on the use of MoS2-based materials in water splitting cathodic half-reaction in order to obtain the best possible performance in hydrogen generation in different conditions. To do that, different strategies were developed to drive the original material to adapt to specific application. In detail, in Chapter Two we investigated the design of three-dimensional MoS2 structures doped with different amount of Ni in order to activate MoS2 for the Hydrogen Evolution Reaction (HER) performed in alkaline environment, which typically hinder this reaction. We carried out an extensive structural characterization in order to establish the role of each type of active sites formed on the material in the HER activity and kinetics. In Chapter Three, we developed an electrodeposition method for preparing amorphous MoS2/Ag2S hybrid using recycled DVD as the support; this revealed as a viable opportunity to turn an abundant waste into an added-value material. After a suitable investigation to understand what kind of material was formed upon electrodeposition, MoS2/Ag2S/DVD was tested for HER in acidic medium. In Chapter Four another kind of hybrid was prepared by designing a one-pot solvothermal synthesis of MoS2(1-x)Se2x nanosheets grown on N-doped reduced Graphene Oxide (N-rGO). The goal was the control of the optoelectronic properties of the final material, since the combination of MoS2(1-x)Se2x and N-rGO allows to form p-n nanojunctions, which induce an enhancement of HER activity upon illumination with visible light. Then we used different techniques to prove what was the best Se:S ratio to optimize both the absolute performances in HER and the enhancement upon light irradiation. Regarding Green Chemistry area, we used Graphene Acid (GA) as starting material and we exploited its uniform surface functionalization to prepare materials for heterogeneous catalysis for different reactions, comparing them with the benchmark Graphene Oxide (GO), modified with the same protocol. In Chapter Five, we synthesized a heterogeneous catalyst by covalently grafting Ferrocene (Fc) moieties to –COOH surface groups of GA and GO. The resulting Fc-modified graphene derivatives have been tested as heterogeneous catalysts for the C-H insertion of aryl diazonium salts into several arene substrates. The tests revealed a strong influence of the support, which we could attribute the intrinsic properties of GA. In Chapter Six, we have grown Pd nanoparticles on GA to prepare a catalyst for Suzuki-Miyaura cross coupling reaction. We have studied the effect of surface functionalization on the nanoparticles formation process and on the derived capability on the controlling the size distribution. The catalysts were tested in Suzuki cross coupling in green conditions and we could highlight the influence of nanoparticles size on activity. Moreover, we studied the same catalysts also for boronic acid homocoupling reaction, that can provide similar final products, but in a more atom economically way.

We propose an easy and robust strategy for the versatile integration of 2D material flakes on plasmonic nanoholes by means of controlled deposition of MoS2 via electrophoretic process. The method can be applied both to simple metallic flat nanostructures and to complex 3D metallic structures both comprising nanoholes. The deposition method allows the decoration of large ordered arrays of plasmonic structures with single or few layers of MoS2. We show that the plasmonic field generated by the nanohole can interact significantly with the 2D layer, thus representing an ideal system for hybrid 2D-Material/Plasmonic investigation. The controlled and ordered integration of 2D materials on plasmonic nanostructures opens a pathway towards, for instance, enhanced light emission; strong coupling from plasmonic hybrid structures; hot electron generation; and sensors based on 2D materials., Comment: arXiv admin note: text overlap with arXiv:1806.03643