title: A fast and effective approach for reversible wetting-dewetting transitions on ZnO nanowires.
abstract: Here, we demonstrate a facile approach for the preparation of ZnO nanowires (NWs) with tunable surface wettability that can be manipulated reversibly in a controlled manner from a superhydrophilic state to a superhydrophobic state. The as-synthesized ZnO NWs obtained by a chemical vapor deposition method are superhydrophilic with a contact angle (CA) value of ~0°. After H2gas annealing at 300 °C for 90 minutes, ZnO NWs display superhydrophobic behavior with a roll-off angle less than 5°. However, O2gas annealing converts these superhydrophobic ZnO NWs into a superhydrophilic state. For switching from superhydrophobic to superhydrophilic state and vice versa in cyclic manner, H2and O2gas annealing treatment was used, respectively. A model based on density functional theory indicates that the oxygen-related defects are responsible for CA switching. The water resistant properties of the ZnO NWs coating is found to be durable and can be applied to a variety of substrates including glass, metals, semiconductors, paper and even flexible polymers.
authors.affiliation: Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016, India.
authors.forename: Kavita
authors.initials: K
authors.lastname: Yadav
authors.affiliation: Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016, India.
authors.forename: B R
authors.initials: BR
authors.lastname: Mehta
authors.affiliation: Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016, India.
authors.forename: Saswata
authors.initials: S
authors.lastname: Bhattacharya
authors.affiliation: Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016, India.
authors.forename: J P
authors.initials: JP
authors.lastname: Singh