Applied Surface Science 363 (2016) 346–355 Contents lists available at ScienceDirect Applied Surface Science journal h om epa ge: www.elsevier.com/locate/apsusc Developing superhydrophobic and oleophobic nanostructure by a facile chemical transformation of zirconium hydroxide surface Arundhati Sengupta, Satya Narayan Malik, D. Bahadur ∗ Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India a r t i c l e i n f o Article history: Received 1 September 2015 Received in revised form 30 November 2015 Accepted 5 December 2015 Available online 11 December 2015 Keywords: Superhydrophobicity Oleophobicity Surface functionalization Nanostructure Self-cleaning Chemical synthesis a b s t r a c t Stable hydro/oleo-phobic and superhydrophobic nanopowders, useful for self-cleaning applications, are synthesized at room temperature by modifying Zr(OH) 4 ·nH 2 O with a very low surface-energy molecule—1H,1H,2H,2H-perfluorododecyltrichlorosilane whose long chain { (CH 2 ) 2 (CF 2 ) 9 CF 3 moiety (PFD)} serves as surface-protrusion. The PFD-content is varied over 3.6–18.7 wt% in optimizing a hydrophilic to hydro/oleo-phobic or even to superhydrophobic transformation. Two halos in the X-ray diffraction pattern of amorphous Zr(OH) 4 ·nH 2 O are accompanied by a peak at 2 = 18.0 ◦ which grows in intensity progressively as the PFD-content increases from 5.2 to 18.7 wt%. The peak corresponds to CF 2 CF 2 crystalline order (10–20 nm) at the PFD-functionalized surface. The microstructure shows Zr(OH) 4 ·nH 2 O as a cloud-like phase, bonded to plate-like sheaths (PFD moiety). The C F stretching bands at 1150 and 1210 cm -1 grow in intensity relative to that of O H stretching at 3460 cm -1 in proportion to the PFD-content. An 18.7 wt% PFD-functionalized sample exhibits a high contact angle CA = 153 ◦ for water (contact angle hysteresis = 4 ◦ and roll-off angle <4 ◦ ), together with CA = 132 ◦ for glycerol, CA = 130 ◦ for diethylene glycol, and CA = 113 ◦ for n-hexadecane, supporting good superhydrophobicity and oleo- phobicity. Surface-energy reduction due to PFD moiety together with an optimal spacing between the surface-protrusions explains the water/organic liquid repellency. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Wettability transformation of a hydrophilic material (having water contact angle WCA < 90 ◦ ) such as metal oxide/hydroxide into a hydrophobic (WCA > 90 ◦ ) or oleophobic (organic liquid contact angle OCA > 90 ◦ ) or even a superhydrophobic {WCA > 150 ◦ , with contact angle hysteresis (CAH) and roll-off angle value <10 ◦ } one has been extensively explored recently [1–6]. Some of the applica- tions of superhydrophobic materials include self-cleaning textiles, automobile windshields, optical windows [7–9], anti-fouling paints for marine applications [10], anti-icing antennas, wind turbine blades, overhead transmission lines [9,11], antibacterial surfaces for healthcare applications [12], corrosion prevention in aqueous environment [13], and reduction of fluidic drag in microfluidic devices [14]. Oleophobic materials specifically exhibit excellent self-cleaning and anti-fouling capability, useful to avoid finger- prints and food stains on textiles, or any damage due to oil-spillage in industries [15,16]. It can be assimilated from the various water- repelling phenomena observed in nature [17–20] that fabrication ∗ Corresponding author. E-mail address: dhirenb@iitb.ac.in (D. Bahadur). of a superhydrophobic surface involves (i) creation of an optimum surface roughness which causes the static WCA to increase, but at the same time does not make the water drop difficult to roll off [17] and (ii) modification of the surface with low surface-energy molecules such as silicones, fluorocarbons or paraffinic hydrocar- bons [7,20]. It has been shown that protruding (e.g., overhang) structures on an intrinsically hydrophilic surface can increase its WCA to more than 150 ◦ as the water drop forms a stable con- vex interface inhibiting its entry into the surface micro-texture by capillary force [19,21]. Such a surface when modified with low surface-energy molecules can even lead to superoleophobicity along with superhydrophobicity [22,23]. Of the various well-known methods for synthesis of hydropho- bic and oleophobic, i.e., amphiphobic, or even superhydrophobic surfaces, top-down ones (such as lithography, templation and plasma-treatment [14,18,24–26]) are costly and cumbersome. Bottom-up methods involving self-assembly/organization such as layer by layer deposition and colloid assembly [27–29] allow a precise control of microstructure, but require rigorous experimen- tal conditions and may be slow. Chemical methods which involve a liquid phase, such as hydrothermal, precipitation, and grafting [30–32], can be used to easily obtain high yields of the prod- uct with suitably tailored microstructure as per the precursor http://dx.doi.org/10.1016/j.apsusc.2015.12.047 0169-4332/© 2015 Elsevier B.V. All rights reserved.