Hydrophobic-oleophilic surfaces based on chemical modification of nanoporous alumina

Hydrophobic/oleophilic nanoporous anodic alumina substrates were fabricated by two-step anodization method following of chemical modification with 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane (FOTS). Surface morphology was characterized using a scanning electron microscopy. The influence of the topography and the pore size of the surface in the contact angle measurements with different solvents have been studied. The water repellence capacity of the nanoporous anodic alumina structure as fabricated depends on pore diameter but, there is a critical value of pore size beyond which the water contact angle decrease. After chemical modification of the surface, this effect is not observed. The porous topography of the material is not an advantage for the oleophibicity. The CA values for the non-porous surface using different solvents are lower than the structured surface.The results obtained in this study can be used to desire wettability properties. Modified NAA exhibit hydrophobicity and at the same time permeability for solvents with low surface tension.

Automated summary

Hydrophobic/oleophilic nanoporous anodic alumina substrates were fabricated using a two-step anodization method and chemically modified with 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane (FOTS). The surface morphology was characterized using scanning electron microscopy, and the influence of surface topography and pore size on contact angle measurements with different solvents was studied. The results showed that the water repellence capacity of the nanoporous structure depended on the pore diameter, but there was a critical value beyond which the water contact angle decreased. Chemical modification eliminated this effect and the porous topography did not enhance oleophilicity. Non-porous surfaces exhibited lower contact angles compared to the structured surfaces when tested with different solvents. These findings can be used to design desired wettability properties, as modified nanoporous anodic alumina exhibited hydrophobicity and permeability for solvents with low surface tension.