Abstract
Superhydrophilic and superhydrophobic surfaces exhibit numerous industrial applications such as self-cleaning, antifogging, anti-icing, electrowetting, and photocatalysis. A surface with reversible wetting behaviors that can be controlled by external field is both scientifically and technologically of importance. Light is a major external trigger for many natural processes. We report here an intelligent remote technology based on alternative UV and near-infrared (NIR) irradiation that enables dynamical wettability tuning of ZnO wafers. Notably, NIR irradiation with a moderate power density of 500 ± 5 mW/cm2 can rapidly recover patterned ZnO from the UV-induced superhydrophilic state (<5°) to the original state (125 ± 3°) in just 2 h. We discover that the chemical environments of O 1s and Zn 2p electrons exhibit a back-and-forth shift upon UV and NIR irradiation, respectively. The NIR-promoted wettability recovery is attributed to selective actuation of vibrational overtone transitions of hydroxyl (OH) band and background absorption of water in the NIR region. Our results highlight that oxygen and water in air are two crucial factors in determining the wettability recovery process, which could be selectively activated or deactivated by remote optical sources. We expect that this discovery could help us to understand many natural processes and shed light on the design of novel devices.
Published Version
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