In the case of ZnO-40, this unusual adsorption profile could be ascribed to the presence of a two different organization within the ‘‘flower-like’’ structure: one, ‘‘intra-petals’’, maintaining the mesoscopic organization, typical of mesoporous materials with low nanoparticle loadings and the other, ‘‘inter-petals’’, generating a heterogeneous porosity.
This second less ordered structuring would be also responsible for the asymmetric broadening of the peak toward larger pore sizes.
At a loading of 60 wt% of ZnO nanoparticles the mesoporous organization is clearly lost, with the material ZnO-60 presenting a very low surface area.