Tunable superoleophobicity via harnessing the surface chemistry of UV responsive titania coatingsElectronic supplementary information (ESI) available: ESI Fig. S1 shows the thickness of the spray coated titania film on smooth Si substrate, Fig. S2 shows the topography of the spin coated titania on Si substrate, Fig. S3 shows the oleophobicity of the spin coated substrate . Fig. S4 shows the effect of surface tension of liquid on contact angle. Movie S1.Avi demonstrates the superoleophobicity of

• Main Authors: Barman, Jitesh, Majumder, Sumit Kumar, Roy, Pritam Kumar, Khare, Krishnacharya
• Format: Journal Article
• Published: 10.04.2018
• ISSN: 2046-2069
• DOI: 10.1039/c8ra01458b

Superoleophobic surfaces exhibiting tunable wettability are prepared by the combination of simple spray coating of Ultra Violet (UV) responsive titania nanoparticles and a low surface energy coating of a self-assembled monolayer (SAM) of 1 H ,1 H ,2 H ,2 H -perflurodecyltrichlorosilane (PFDTS). Spray coating creates random micron-sized roughness with reentrant geometry, a necessary requirement for the superoleophobic surface, and a porous network at the nanometer size level, confirmed by the field emission scanning electron microscope (FE-SEM) images. By employing the rough surface and a low surface energy monolayer, the substrates possess superhydrophobicity with a water ( γ = 72 mN m −1 ) contact angle of 163° and superoleophobicity with a decane ( γ = 23 mN m −1 ) contact angle of 144°. Wettability of these surfaces is completely reversed to the superoleophilic state upon 6 h of UV irradiation. A quantitative X-ray photoelectron spectroscopy (XPS) analysis has confirmed the mechanism of decomposition of PFDTS molecules on the superoleophilic surfaces via interaction with the defect Ti 3+ states of titania upon UV exposure. Furthermore, the superoleophobicity is restored to complete the transition cycle by changing the surface chemistry of the UV exposed surface via annealing and regrafting of the PFDTS monolayer. Superoleophobic surface with tunable oil wettability is presented by controlling the surface chemistry via exploiting the photocatalytic activity of the titania nanoparticles under UV and regrafting of the same surface.