Antifogging and anti-frosting coatings by Dip-layer-by-layer self-assembly of just triple-layer oppositely charged nanoparticles

Transparent stable antifogging (AF) and anti-frosting (AFR) coatings were fabricated via layer-by-layer dip coating self-assembly (Dip-LbL self-assembly) of just triple-layer oppositely charged nanoparticles (NPs) followed by calcination. The nanoparticles we prepared naturally carried a certain electrical charge. The positively charged NPs (ZrO2 or TiO2) and the negatively charged SiO2 NPs were bound firmly together via electrostatic interaction. Morphologies and structures were observed by transmission and scanning electron microscopy. Transparency was examined using an optical clarity test and a UV-Vis transmittance test. AF/Superhydrophilic and AFR properties were studied using a water contact angle test, a constant temperature (100 °C) AF test, an AFR test and an aspirating test. Mechanical stabilities were investigated using a water-bath shaking test, an ultrasonic test and a pencil hardness test. The results showed that the TiO2/SiO2/ZrO2, ZrO2/SiO2/TiO2 and SiO2/ZrO2/SiO2 coatings with the 3D micro- and nanometer-scale hierarchical structure on the surface had excellent AF and AFR properties, and presented high mechanical stability and durability. The high availability of the materials and the simplicity of this method for the coating preparation might make the low-cost, non-toxic and eco-friendly AF and AFR coatings potentially useful in optical and display devices.