期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 111, 期 16, 页码 5784-5789出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1319001111
关键词
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资金
- National Research Foundation of Korea
- Korea government (Ministry of Science, ICT and Future Planning) [2013-056344]
- National Research Foundation of Korea [2011-0029541, 2013R1A6A3A03063900] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Titania, which exhibits superwetting under light illumination, has been widely used as an ideal material for environmental solution such as self-cleaning, water-air purification, and antifogging. There have been various studies to understand such superhydrophilic conversion. The origin of superwetting has not been clarified in a unified mechanism yet, which requires direct experimental investigation of the dynamic processes of water-layer growth. We report in situ measurements of the growth rate and height of the photo-adsorbed water layers by tip-based dynamic force microscopy. For nanocrystalline anatase and rutile TiO2 we observe light-induced enhancement of the rate and height, which decrease after O-2 annealing. The results lead us to confirm that the long-range attraction between water molecules and TiO2, which is mediated by delocalized electrons in the shallow traps associated with O-2 vacancies, produces photo-adsorption of water on the surface. In addition, molecular dynamics simulations clearly show that such photo-adsorbed water is critical to the zero contact angle of a water droplet spreading on it. Therefore, we conclude that this water wets water mechanism acting on the photo-adsorbed water layers is responsible for the light-induced superwetting of TiO2. Similar mechanism may be applied for better understanding of the hydrophilic conversion of doped TiO2 or other photo-catalytic oxides.
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