title: One pot synthesis of opposing 'rose petal' and 'lotus leaf' superhydrophobic materials with zinc oxide nanorods.
abstract: The synthesis in one pot(1) of opposing 'rose petal' and 'lotus leaf' superhydrophobic materials from commercially available superhydrophilic cloth substrates of varying texture is described for the first time. Surfaces of 'rough' textured cloth and 'smooth' textured cloth were simultaneously rendered superhydrophobic by growing zinc oxide (ZnO) nanorods by a hydrothermal process in the same chemical bath. Contact angle hysteresis and water pendant drop tests revealed strong water adhesion to ZnO microrod-treated rough cloth. The combination of water contact angle >150° and strong adhesion is indicative of the 'rose petal effect' with potential for water pinning. Smooth cloth with ZnO nanorods exhibited no adhesion to water droplets with facilitative roll-off. The combination of water contact angle >150° and weak to no adhesion with water is indicative of the 'lotus leaf effect' with potential for self-cleaning. Pendant water drop tests indicated cohesive failure of water on rough cloth coated with ZnO nanorods. Natural rose petals demonstrated adhesive failure between the petal surface and water droplet. A parsimonious explanation is presented. We also describe the development of superhydrophobic clothes without the need for special conditions or further chemical modification.
authors.affiliation: Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, PO Box 17, Postal Code 123, Al Khoud, Oman. Electronic address: myotayzar.myint@gmail.com.
authors.forename: Myo Tay Zar
authors.initials: MT
authors.lastname: Myint
authors.forename: Gabor L
authors.initials: GL
authors.lastname: Hornyak
authors.forename: Joydeep
authors.initials: J
authors.lastname: Dutta
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D013499:Surface Properties; D013784:Textiles; D014867:Water / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D014867:Water; D015034:Zinc Oxide
keywords: Cloth; Contact angle; Lotus leaf; Microrod; Nanorod; Pendant drop; Rose petal; Sliding angle; Superhydrophobic; Zinc oxide