首页 | 本学科首页   官方微博 | 高级检索  
     


Photoswitchable Superabsorbency Based on Nanocellulose Aerogels
Authors:Marjo Kettunen  Riitta J. Silvennoinen  Nikolay Houbenov  Antti Nykänen  Janne Ruokolainen  Jani Sainio  Viljami Pore  Marianna Kemell  Mikael Ankerfors  Tom Lindström  Mikko Ritala  Robin H. A. Ras  Olli Ikkala
Affiliation:1. Molecular Materials, Department of Applied Physics and Center for New Materials, Aalto University School of Science and Technology, (previously Helsinki University of Technology), P.O. Box 15100, FIN‐00076, Espoo, Finland;2. The Surface Science Group, Department of Applied Physics, Aalto University School of Science and Technology, P.O. Box 11100, FIN‐00076, Espoo, Finland;3. Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FI‐00014, Finland;4. Innventia AB, Process and Product Innovation, P.O. Box 5604, SE‐114 86 Stockholm, Sweden
Abstract:Chemical vapor deposition of a thin titanium dioxide (TiO2) film on lightweight native nanocellulose aerogels offers a novel type of functional material that shows photoswitching between water‐superabsorbent and water‐repellent states. Cellulose nanofibrils (diameters in the range of 5–20 nm) with native crystalline internal structures are topical due to their attractive mechanical properties, and they have become relevant for applications due to the recent progress in the methods of their preparation. Highly porous, nanocellulose aerogels are here first formed by freeze‐drying from the corresponding aqueous gels. Well‐defined, nearly conformal TiO2 coatings with thicknesses of about 7 nm are prepared by chemical vapor deposition on the aerogel skeleton. Weighing shows that such TiO2‐coated aerogel specimens essentially do not absorb water upon immersion, which is also evidenced by a high contact angle for water of 140° on the surface. Upon UV illumination, they absorb water 16 times their own weight and show a vanishing contact angle on the surface, allowing them to be denoted as superabsorbents. Recovery of the original absorption and wetting properties occurs upon storage in the dark. That the cellulose nanofibrils spontaneously aggregate into porous sheets of different length scales during freeze‐drying is relevant: in the water‐repellent state they may stabilize air pockets, as evidenced by a high contact angle, in the superabsorbent state they facilitate rapid water‐spreading into the aerogel cavities by capillary effects. The TiO2‐coated nanocellulose aerogels also show photo‐oxidative decomposition, i.e., photocatalytic activity, which, in combination with the porous structure, is interesting for applications such as water purification. It is expected that the present dynamic, externally controlled, organic/inorganic aerogels will open technically relevant approaches for various applications.
Keywords:Aerogels  cellulose nanofibers  photo‐induced water absorption  stimuli‐responsive materials  photocatalysis
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号