Highlight: AllinOne SelfCleaning, AntiReflection Coatings from Nanoparticles

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Highlight All-in-One Self-Cleaning,
Anti-Reflection Coatings from Nanoparticles
R. Cohen (MIT) and M. Rubner (MIT) This work was
supported primarily by the MRSEC Program of the
National Science Foundation under award number
DMR-0213282.
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.
Figure. 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).