IRG-II Highlight
All-in-one” self-cleaning, anti-reflection coatings from nanoparticles
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Top: drops of water sitting on a transparent polymer/nanoparticle coating with anti-reflection and water-shedding properties (less reflective right side of glass slide is coated). Bottom: Schematic of the simple water-based process used to fabricate thin film coatings containing in this case only nanoparticles of glass (SiO2) and titanium dioxide (TiO2). The rapidly developing field of nanomaterials chemistry allows a wealth of nanoparticles to be synthesized with designed properties. However, putting these nanoparticles together into useful and practical structures such as thin film coatings remains a significant challenge. Members of IRG-II of the MIT MRSEC have recently developed facile, water-based processing techniques that allow nanoparticles of opposite charge (or polymer/nanoparticle combinations) to be assembled reliably and reproducibly into robust, conformal, ultra thin film coatings with a variety of interesting properties (Lee et al., Nano Letters 6, 2305, 2006).
The coatings suppress the reflection of light dramatically so that light transmission through a glass lens can approach 100%. Water droplets can either spread instantaneously into thin sheets or roll off the surface depending on the choice of final chemical treatment. In the former case, anti-fogging properties are imparted to the surface whereas in the latter, a self-cleaning effect is realized. When created with titanium dioxide nanoparticles (TiO2), these coatings also exhibit light activated self-cleaning characteristics. The favorable combination of antireflection, antifogging and self-cleaning properties makes these “All-in-One” coatings attractive for a variety of applications, including coatings on automobile windshields, mirrors, windows in high-rise buildings, green houses and solar cell panels.
