A rapid and eco-friendly route to synthesize graphene-doped silica nanohybrids

In the present study, the possibility to synthesize graphene oxide (GO)-based nanohybrids with pure and O₂-doped silica nanoparticles by a rapid and easy hydrothermal process has been explored. The nanohybrids were prepared by varying the type of silica nanoparticles (average diameter 7 nm or 40 nm) and the silica/GO weight ratio. All the materials were fully characterized by spectroscopic and morphological techniques. The experimental results revealed that it is possible to tune the characteristics of the obtained nanohybrids, such as morphology and amount of ester/ether linkages upon varying the preparation parameters, together with the nanosilica's typology and the silica to GO ratio. By Fischer esterification it was possible to achieve GO-silica nanohybrid lamellae to be then reduced into nanostructured films by a hydrothermal process. These latter materials show a "lasagna-like" structure in which it is possible to observe fully exfoliated (and partially reduced) GO lamellae intercalated by silica nanoparticles agglomerates. The extension of silica layers, film morphology and structure, degree of functionalization, and thermal stability are strongly affected by the type of silica. Furthermore, after the hydrothermal treatment, the nanohybrids were found to be insoluble in water.