Synthesis,characterization and performance evaluation of hybrid nano materials

Resumo

The work in this thesis is focused on the design, synthesis and characterization of new hybrid nanostructured materials as well as their performance evaluation in different applications. The growing demand of novel materials with distinct and outstanding physicochemical characteristics has driven the attention to these hybrid nanomaterials, given versatile functionalities that differ from those observed in bulk and or single materials. These materials, not only integrate the intrinsic properties of its individual constituents but also exhibit additional characteristics owing to synergistic coupling effects between the dissimilar components. For instance, plasmonic metal-semiconductor hybrid nanostructures, based on titanium dioxide (TiO2) and star-shaped Au or Ag nanoparticles, can absorb light more efficiently than the bare semiconductor and hence improve its photocatalytic activity. Analogously, combining reduced graphene oxide (rGO) sheets and Fe3O4 nanoparticles for the fabrication of hybrid nanocomposites improves the electrochemical performance, as the iron oxide nanoparticles position themselves between the graphene layers to effectively suppress their agglomeration. In addition, the rGO enhances the global conductivity, favoring as well the electrochemical performance. Such outstanding characteristics allow the implementation of these hybrid nanomaterials for environmental and energy storing applications. Alternatively, the controlled aggregation of transition metal oxide nanoparticles into clusters has been studied for heat transfer applications, dispersing this kind of nanostructured systems for the preparation of nanofluids. This work has been carried out and complemented at laboratories of Universidade de Vigo.