New strategy towards periodically organized polyoxometalates on HOPG for molecular electronics applications Juba Salhi , Imad Arfaoui, David Kreher, Florence Volatron Sorbonne Université, France Polyoxometalates (POMs) are widely studied for the development of new materials for molecular electronics (1-3) . Indeed, they present several interesting redox and magnetic properties (4-5) . Nevertheless, despite several attempts (6) , one key limitation is the difficulty (or impossibility in soft conditions) to organize POMs periodically at a molecular scale on a surface, isolated from each other and isolated from the substrate as well, to allow them to be addressed individually. Indeed, POMs are charged species and tend to form aggregates due to POM- POM electrostatic interactions. In order to sort out this challenge, here we present a relatively simple approach using a molecular template (7) made of an HOPG surface-confined self-assembly of triazine-based molecules. The protonation of the self-organized triazine layer in presence of an heteropolyacid allowed the non-covalent anchoring of the POMs on specific sites of the surface by electrostatic interaction. The system was characterized at different scales, from macroscopic to molecular level using various techniques. In particular, after presenting our chemical strategy, X-ray Photoemission spectroscopy (XPS), Field Electron Gun - Scanning Electron Microscopy (SEM-FEG) with X-ray Energy Dispersive spectroscopy (EDX) as well as near-field microscopies were carried on to evidence respectively the presence of the ammonium signal , and/or of the POMs on the surface, as well to image the surface at the nanometric and molecular scales.
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