Investigation of synthetic methodologies for the preparation of hybrid materials as redox nano-catalysts

The nanoparticles present different properties compared to the bulk materials due to their dimension decrease. This is caused by the electron states’ confinement of the materials (quantum effect) and by the variation of the surface area (surface effect). The high surface energy can bring the nanoparticles to the aggregation that can be avoided using different types of stabilization techniques. The catalytic activity, therefore, depends not only on the metallic nanoparticle but also from the type of stabilizer. The stabilizer influences the access of reagents to the catalyst’s free sites and the outcoming of the products back in the medium of the reaction. All this controls the conversion and the selectivity of the nano-catalysts. Polymers are the most effective stabilizers thanks to the combination of steric effects due to their long chains and electronic effects due to the presence of functional groups on the macromolecules. The development of hybrid materials, combine metals and polymers in chemical processes, leads to the enhance of the catalytic performance and the reaction efficiency. The integration of polymers into metal catalysts reduces the load of the active catalytic metal making the catalyst more cost-effective. This research work is focused on the preparation of gel-like polymeric structure employed to embed gold nanoparticles. In particular, three different types of polymeric gels (based on vinyl ammine, vinyl alcohol and acrylic acid) were synthesized to obtain hydrogels and cryogels structures. Moreover, the effect of the preparation method (in-situ or ex-situ) was properly studied to obtain different types of hybrids nanomaterials. For an industrial point view, the use of gels (crosslinked systems) could be interesting for the development of fixed bed reactors. The gold nanoparticles could be regenerated after a certain time by a total combustion of the stabilizer and consequential synthesis of the new material.